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eS4500i: Highly Integrated Electric Drive Unit for Multiple Applications

Marco Silvestri, Chief Engineer, Dana Incorporated

Across all our actions, we never lose sight of a guiding vision toward a zeroemissions future. This has powered our first-mover advantage in electrification.

At Dana, we strategically invest in technical competence − designing, engineering, and manufacturing the components of a complete e-Propulsion system in-house. These innovations include efficient EV systems and new electrodynamic products like motors, inverters, controls and software, battery cooling systems, and metallic bipolar plates for fuel cell applications.

The legislation for pollutants and emissions is driving OEMs to design their reduction programs to align with aggressive timelines — accelerating the adoption of electrification. These mandates, coupled with corporate commitments from OEMs, will significantly increase the demand for electrified vehicle architectures, the main components of a Battery Electric Vehicle.

Dana’s solution is the Spicer® Electrified eS4500i e-Drive Unit − a highly versatile 3-in-1 electric drive unit (EDU) that converts the stored electrical energy from the battery into mechanical power to the wheels.

eS4500i Platform

Utilizing competencies from Dana’s global network of technology centers, the highly integrated eS4500i comprises an inverter, motor, one-speed geartrain, open differential, and optional park-lock.

The thinking behind the eS4500i was really to provide more than a single EDU. What was needed was a versatile platform offering multiple ratios and integrated design of motor and gearbox while also taking into consideration efficiency, optimized packaging space, and lower weight.

To cover multiple applications, five different ratios were designed (macrogeometry) with the same center distances, same gear width, and similar envelopes diameters also recombining the same gears to reach five different ratios.

In this way, with a unique design of the housing and bearings, the eS4500i can host five different gear-trains to be able to match different vehicle requirements in terms of maximum torque and speed. From figure 2, it’s appreciable the spread of torque and speed that the system can cover with the five different ratios options. A limitation of around 4,500 Nm (as max nominal output torque value) has been decided for ratio 15.1 and 13.1 because of match with other Dana products but useful in case of demanding vehicle gradeability and high continuous torque.

Highly Integrated Layout

The design of the gearbox and the motor was improved by integrating the components as much as possible to provide a light, compact, and power-dense EDU.

For the eS4500i, it has been decided to have a highly integrated design between the motor and gearbox to save weight and to improve the power density.

Only three housings compose the structure of the EDU and shape two separate environments: a dry one for the motor and a wet one for the oil-lubricated gearbox.

Referring to figure 3, from right to left:

The motor back-case supports the rear motor bearing and becomes the seat for the stator and the internal side of the motor cooling jacket. The helical cooling path is made by die-cast molding for manufacturing efficiency.

A carrier housing supports the front motor bearing and becomes one of two gearbox housings as well as the external side of the motor cooling jacket to complete the sealed channel.

The cover housing enclosures the gearbox components.

One of the main characteristics of the highly integrated layout is the over-hanged pinion gear directly mounted on the head of the rotor shaft. Between the pinion gear and the motor front bearing, there is a parking gear.

The layout is completed by an intermediate shaft and an open differential, both supported by taper roller bearings.

This new layout reduces the interfaces between the gearbox and the motor to achieve a precise axial centering of the gearbox with the output shaft of the motor. This also allowed a significant reduction of components like having only two bearings on the input axis, a reduction of the number of housings and a significant a reduction of fasteners.

The EDU is completed by the inverter that is direct-mounted on top of the motor with the high voltage connections passing through the back housing.

The park-lock adds another degree of flexibility because it can be added or removed on customer request. This park-lock option is already patented and in series production, with a mechanism layout now upgraded with a new smart actuator.

Motor and Inverter

The eS4500i is powered by a propulsion system composed of an asynchronous dry 450V motor and with a Dana 2nd generation directmounted inverter.

The propulsion system is cooled by water-glycol and the theoretical performance curves are shown in fig. 5 at 65°C coolant temperature.

Since this propulsion system is for a medium voltage (450V) application, Dana decided to use the latest IGBT module technology for this inverter over the newer SiC MOSFET technology. This allows the use of our proprietary Reflex gate driver technology to achieve the most cost-effective solution for this voltage range.

Conclusion

As a Tier 1 supplier, Dana offers its new eS4500i EDU, an off-the-shelf solution on the path to electrification, with a compact and light package for a wide range of applications.

The eS4500i is equipped with the well-known Dana differential from a robust off-road heritage, with an optional park lock system.

Dana is offering its all-new configurable off-the-shelf eS4500i EDU to a multitude of segments and applications. This work is the result from the synergy between the different technical centers and other global Dana branches, putting together different competencies. With its power density, reliability, and cost competitiveness, this product will contribute to our customers’ success on the path to electrification.

JJE 2-Speed Electric Beam Axle for Medium Duty Truck

Ping Yu, CEO, Chief Engineer, Founder, Jing-Jin Electric
Dr. Yang Cao, Transmission Senior Supervisor, Jing-Jin Electric

The electrification of medium duty truck grows rapidly. JJE’s newest electric beam axle family can cover up to 11T (or class 6 in North America) trucks, including single-speed and  2-speed systems. Multiple advanced technologies are integrated into the electric beam system, such as bi-stable electromagnetic bi-directional shifting clutch, bi-stable eLocker, linear park lock system, and active cooling and lubrication. These functions’ control is all in the electric beam axle’s inverter, which is mounted on the axle. 800V, high power hairpin motor and SiC inverter are used to produce strong capacity, and high efficiency across wide operating range.

The 2-speed axle features a high efficiency hair-pin electric motor, a 400kW SiC inverter with “safe towing” feature, electro-magnetic shifted 2-speed gearbox, with neutral position that also serves as a disconnect, bi-stable differential eLocker, linear park lock system. With 2-speed gearbox, the beam axle’s wheel-end torque is up to 15,000Nm, and the maximum vehicle speed is over 160km/h. Integrated design for motor and gearbox reduces the axial length of the system.

JJE’s 2-speed beam axle features high performance and high output speed, with little power degradation at high speed. Its efficiency is high over a wide speed range – especially in comparison to a single speed axle thanks to the 2-speed gearbox.

Fig. 2 JJE Electric Beam at the Rear of a Truck Demonstrator

Fig. 3 JJE 2-speed Electric Beam Performance

Electric Motor

JJE has a mature hairpin motor designs to cover performance requirement of wide range of vehicles. For this electric beam axle system, the electric motor’s peak power reaches 420kW at 650Vdc, with 97.4% maximum efficiency, and over 90% of the efficiency map is above 88%. The water-oil combined cooling allows the electric motor to produce high continuous power.

2-speed Gearbox

The 2-speed gearbox provides high launch torque, high vehicle speed and high efficiency over broad duty conditions, and helps contain motor’s top speed for better reliability and durability. It also broadens high efficiency operating range, and significantly reduces thermal loading in the system at high speed. A 2-way, bi-stable electromagnetic clutch is used for shifting between 1st gear and 2nd gear, with neutral position. The neutral position is a natural “disconnect”. Combining this rear axle with neutral with a constantly powered front eAxle, the vehicle efficiency can be improved. JJE’s patented DirectFluxTM Bi-stable eLocker enhances functional safety of the locker and eliminate the power consumption. Proven park lock system is implemented on the motor shaft, or the “lowest torque” point of the system. An oil pump provides active oil lubrication, which allows low oil level in the gearbox, reduces gear churning loss.

SiC Inverter

The electric beam axle has an 850V SiC inverter integrated on it, with functional safety level up to ASIL D. Multiple functions − such as motor control, differential locker control, 2-speed transmission control, park lock control − are integrated in the inverter, taking advantage of inverter’s high functional safety control platform. With backup power supply, the inverter enables “safe towing”, a feature highly desired by customers. It is a critical safety redundancy in the event of 12V power supply loss.

DirectFluxTM Bi-stable Electromagnetic Clutch

Patented bi-stable electromagnetic clutch is JJE’s one of the most advanced technologies. It is used for gears shifting and locking the differential in the electric beam axle system. This technology has been successfully used as a differential locker in JJE’s 300kW SiC EDM and as a disconnect in JJE’s new AWD EDM.

DirectFluxTM electromagnetic clutch takes advantages of its innovative magnetic circuit design. Compared to the more conventional reluctance flux magnetic circuit design, the DirectFluxTM design greatly reduces flux leakage, and therefore utilizes magnetic flux more effectively to generate force. However, the conventional reluctance flux design cannot avoid magnetization of parts near flux circuit, or “flux leakage”, which causes less effective utilization of magnetic flux. As a result, DirectFlux acts 2-3 times faster than a reluctance flux design.

The bi-stable clutch is inherently fail-safe as it won’t change state in the event of loss of power. This feature gives bi-stable clutch a higher safety level than mono-stable clutch. For differential locker, it will prevent sudden locker release due to the loss of power or control failure. For transmission shift, it will prevent gear unexpected back to neutral which will lead the vehicle loss of traction. On energy consumption side, the bi-stable clutch’s feature of “zero holding current” eliminates holding current and in turn achieves zero power consumption.

In the development stage of an electromagnetic clutch, a software platform based on several simulation tools is built for more precise simulation result. This platform covers signal, electric, electromagnetic, and mechanical aspects. It addresses almost every detail, including software control, PCB layout, electromagnetic transient simulations, multi-body dynamic simulations, and strength. It provides strong support to the clutch’s development.

Electric beam axles are designed for pickup trucks, light duty trucks, or medium trucks. As the beam axles get electrified, a lot of traditional technologies no longer fit. JJE takes advantage of its knowledge in electric drive, strong R&D capabilities on motor, inverter, transmission and clutches and expertise in system integration, creating the 2-speed electric beam axle for the large medium truck segment.

Overcoming Challenges to High-Speed Electric Motors

Craig Renneker, Vice President Innovation, AAM

While the EV growth rate remains uncertain, there is little doubt that the use of automotive electric drive units must drastically increase to meet global climate objectives. This requires mass market acceptance across the full range of vehicles − size and price. A major enabler to reaching more customers is to reduce the cost, size and mass of Electric Drive Units (EDUs), as well as the quantity of natural resources required in manufacturing.

The power produced by an EDU is a product of its torque and rotational speed. Increasing the rotational speed enables power to be achieved at a lower torque. Simply put, spinning the motor faster reduces its size, mass and cost (Figure 1). The result: fewer costly materials are required, such as copper windings, magnetic steel and, in some cases, rare-earth magnets.

Traditional electric motors rarely spin to 20,000 rpm. Exceeding this level requires careful motor, gearbox and inverter design. This article discusses the approach AAM is taking to overcome various design obstacles to enable speeds up to 30,000 rpm – the speed needed to make a real impact in clean mobility and customer acceptance of EVs.

The Integrated Approach

An accessible EDU with a 30,000 rpm motor requires an integrated motor, gearbox and inverter. Each area presents specific challenges to execution and opportunities for new designs:

• Motor: pole count, rotor centrifugal forces, cooling, sealing and bearings
• Gearbox: pitch line velocity of the gear teeth
• Inverter: Switching losses

The Motor

Most electric motors employ stators with 3-phase copper windings driven by sinusoidal alternating current. As the frequency of these sinusoidal currents increase, parasitic power losses in both the magnetic steel laminations and copper conductors increases. These are commonly called iron and copper AC losses. The required frequency for a 3-phase motor is determined by the motor pole count and rotational speed. Most motors today are 8-pole designs with interior permanent magnets. AAM uses a 4-pole architecture which requires half the sinusoidal current frequency of an 8-pole design. This significantly reduces iron and copper AC losses. (Figure 2)

Reducing the diameter of the rotor enables higher speeds. Fortunately, higher-speed motors require less torque for a given power level, allowing a smaller diameter. As an example, the tangential speed of an 87 mm OD rotor at 24,000 rpm is lower than a much larger rotor spinning at 15,000 rpm (Figure 3). Using stress analysis of the lamination and magnet geometry, high speeds can be attained.

Smaller, fast turning motors have basic geometric challenges in removing heat. To effectively remove this heat AAM uses forced oil cooling of both the stator and rotor. A series of stamped holes in the stator laminations are arranged to form helical cooling passages around the copper windings. Oil is also pumped into the hollow rotor shaft with special heat sink features to increase surface cooling. This method reduces the heat generated in both the stator and rotor without the need for a glycol-cooled motor jacket.

AAM is employing a completely different approach to cooling highspeed rotors. Instead of pumping glycol coolant through the hollow center of the rotor requiring radial lip seals, AAM is cooling the stator, rotor and inverter with the same low-viscosity oil used to lubricate the gears and bearings. With this arrangement, no sealing is required between the rotor and gearbox elements.

In most EDUs, a simple 2-stage helical-gear reduction is used to step motor speed down to the vehicle wheel speed. The pressure angle of the gear teeth generates a radial load proportional to gear torque that must be carried by bearings on the rotor axis. With a typical singlemesh, 2-stage helical gear reduction, bearing capability limits motor speeds to 20,000 rpm. AAM uses a dual-layshaft gearbox arrangement to balance these gear separation loads, which enables traditional small bearings to be used. (Figure 4).

Gearbox

Higher motor speeds require higher gear ratios to maintain normal wheel speeds. Any ratio can be accommodated with enough successive reduction stages. However, each additional stage adds cost, mass, package space and parasitic loss to the gearbox. Typical low-speed drive units employ a 2-stage reduction. As such, it is desirable for a high-speed motor to avoid the penalty of adding a third reduction stage. The critical enabler for high ratio (up to 22:1) is keeping the first stage drive gear very small. By keeping the motor off the wheel axis AAM enables the rotor shaft drive gear pitch diameter to be very small to provide a large reduction in the first stage and reduce pitch line velocity (Figure 5)

Inverter

The inverter converts DC battery voltage into multi-phase AC that drives the stator of the electric motor. The frequency of the required sinusoidal current is directly proportional to the  motor’s rotational speed and its number of magnetic poles. The inverter induces this sinusoidal AC to flow in the stator windings using pulse-width modulation (PWM) of the battery voltage (Figure 6). Pulse-width modulation involves solidstate switching devices that can turn on and off very quickly. Each on/off cycle results in a small amount of energy being lost within the switching device. As such, higher sinusoidal frequencies require faster switching, which increases inverter losses.

AAM’s 4-pole motor design operates at half the sinusoidal frequency of a traditional 8-pole motor. This enables the motor to spin at twice the speed with equivalent inverter switching losses.

Conclusion

AAM continues to push the limits of electric motor speed in EDUs. The company has several demonstration vehicles and one pre-production application running at 24,000 rpm, with an additional development unit producing 30,000 rpm. These designs can be produced at low cost in high volume using practical engineering solutions overcoming previously perceived limiting factors. These designs can enable the growth of EDUs into a wide variety of vehicle applications, thus creating a broader impact on carbon reduction and clean transportation. Innovations at AAM are creating efficiencies for our customers, satisfaction for consumers and an increased opportunity to positively impact our environment.

Interview with Thorsten Jablonski, Head of Technical Development and Product Management – Volkswagen Group Components

“In E-Mobility, Performance doesn’t have to be Expensive.”

How do you make e-mobility more affordable? At the CTI Symposium Berlin in December 2023, we caught up with Thorsten Jablonski, Head of Development & Product Management Volkswagen Group Components. As he sees it, there are several levers: for example battery technology, electric drives, and leaner processes in development and production.

On the product side, what key levers can make BEVs affordable for people who find them too expensive?

The biggest cost driver for electric cars is still the battery. Fast charging tech costs money, and so does battery capacity. Volkswagen has to focus on customers’ priorities. Is this a second vehicle that you can charge slowly at home, but which has a high range? Or are 200 kilometers of range enough? Another big cost factor is cell chemistry. With electric powertrains, it’s all about simplification. With electric drives, you can dial some of the requirements down a bit, for example how quickly the interior heats up. So it’s simplification and the battery system. For me, those are the two levers for building an electric car in an affordable price range.

What are you doing in the field of batteries?

Volkswagen develops and produces its own battery systems, and also assembles them. It started with the E-Golf and also the systems for the E-Up were produced in-house. The only components which were bought are the battery cells and the modules. In the future, the modules will gradually disappear and the cells will increasingly migrate into the vehicle. Today Volkswagen also develops the battery management software and battery system in-house and assembles them at its own factories, sometimes via third-party manufacturers. But the development is always 100 percent Volkswagen.

Depending on the brand and segment, you might also want to scale the electric drives. How do you reduce variance there?

In electromobility, performance doesn’t have to be expensive. The cost difference between 100 and 400 kW doesn’t have to be that big. The key is a concept for scaling performance neatly, in a modular system. That means all drives can be manufactured on the same production lines. It takes a lot of brainpower to avoid compromising on the costs of drives, which need to be affordable. The modular system achieves best-in-class scores in many areas. All that calls for a lot of discipline, and a great deal of engineering skill.

Charging options are the make-or-break factor for BEV acceptance. What is Volkswagen doing to improve public charging infrastructures?

Within the Group, the Elli brand is responsible specifically for this purpose. With Elli we are offering one of the the largest charging networks in Europe and are giving access to more than 620,000 charging points. And through Electrify America Volkswagen has built up the most powerful open hyper-fast charging network in the United States and Canada.

Another factor with range is thermal management. How can that be made more efficient?

If you look at the total number of hoses in there today, it’s enormous. It`s called the ‘snake pit’. All those connecting hoses will disappear in the future; everything will be combined in a single module. You can even replace hardware with software. That improves your cost efficiency, and also your energy efficiency. But you have to think holistically, throughout the whole electric powertrain. That’s one key reason why we focus on the entire powertrain.

Which areas will Volkswagen withdraw from, in favor of electric drives?

Everything about electric powertrains will be kept, including the chassis that were designed for them. But components that are costly and not sustainable will be skipped. For example, the development and production of shock absorbers.

What will remain apart from BEVs? In China, P1/P3-xHEVs are still selling. Do you see any future in Europe for solutions like these?

Often markets depend on legislation. In China, plug-in hybrids grew their market share from one or two to thirty percent. Some Chinese manufacturers decided to back PHEVs – and then they got subsidized. If Volkswagen starts selling systems like that now in China, I believe that those incentives will soon be scrapped. As for Europe or Germany, if biofuels are not accepted as sustainable and there is no funding, plug-in hybrids will not gain a huge market share. Germany and Europe are concentrating on electric cars now because they want to get one technology established first.

Interview | Gernot Goppelt

A Game-Changing Solution for OEMs and Tier 1 Suppliers:

Pressure Equalization Element Protects Transmissions During Water Crossings

Volker Buchmann, Business Development Manager, Konzelmann

In a world where extreme weather conditions and waterrelated challenges have become commonplace, the automotive industry faces a pivotal question: How can we equip vehicles for water crossings efficiently while saving time and resources? The answer lies in a groundbreaking innovation that is poised to revolutionize how we approach water crossings and offers OEMs and Tier 1 suppliers a transformative advantage.

Safeguarding against the elements

Throughout this past summer, extreme weather conditions occurred all over the world, with extraordinarily strong rainfalls accompanied by heavy thunderstorms and an increased risk of flash floods. When tunnels or underpasses are flooded due to continuous rain, there are often only two options: detour or wade through. Vehicle drivers tend to overestimate their vehicle‘s ability to cross water. In these situations, water or mud can quickly infiltrate the transmission resulting in a failure that only a towing service and costly repairs can resolve.

While vehicles usually are equipped with a hose construction to manage water crossings, there was no simple technical solution for wading through water. Until now. The newly designed Pressure Equalization Element (PEE), directly integrated into the transmission, prevents both positive as well as negative pressure within closed housings in electric axes and differentials, promising new perspectives for reducing product costs and time to market.

Hose construction: elaborate and costly

As mentioned, to prevent water from entering, a hose is connected directly to the transmission, providing ventilation during pressure variations. Although the hose construction is suitable for water crossings and is installed as standard, it is considered elaborate in design, resulting in time and cost-intensive assembly. Currently, there is a lack of a simple technical solution for water crossings.

The solution to this challenge is the Pressure Equalization Element (PEE), a pioneering innovation designed to fit directly into the transmission housing. The PEE houses an internal pressure-regulating valve that swiftly balances pressure differentials, safeguarding the ventilation space against contamination and the intrusion of liquids. Operating at 70 mbar, equaling a water column of 70 cm, the valve withstands exposure to gearbox oil aerosols, typical vehicle substances, and environmental materials.

Konzelmann’s Pressure Equalization Element protects the system seals from damage due to positive or negative pressure. Source: Konzelmann GmbH

A membrane that defies liquids and contaminants

In contrast to a conventional hose system, the PEE is securely integrated within the electric axle housing.The pressure equalization valve, designed to prevent positive pressure, allows escaping gas to exit through a lateral opening in the housing while permitting air to flow in during a negative pressure situation in the housing. This air passes through an air-permeable yet waterproof Ventikon membrane. This membrane is capable of withstanding a water column of 30 meters, effectively blocking liquids as well as contaminants, safeguarding the electric axle against foreign objects.

At a defined negative pressure, the valve opens, enabling air to flow in to equalize the pressure difference. The PEE‘s membrane is thoughtfully shielded, preventing it from being coated with spray oil. Furthermore, a labyrinth-like oil separator, positioned between the valve and the electric axle‘s interior, shields the valve from direct contact with splashing oil.

Simulating real-world performance

Konzelmann, in collaboration with an OEM and a Tier 1 supplier deeply involved in transmission and differential development, has conducted in-depth analysis and established testing parameters for a dedicated testing environment. This in-house testing platform enables accurate simulation of transmission behaviour, allowing precise customization of the pressure equalization valve to meet the unique requirements of each manufacturer.

The testing setup mirrors the oil and air volumes within a transmission housing, ensuring a comprehensive evaluation of the system‘s performance throughout its lifespan. Information from the transmission manufacturer regarding residual air content in the transmission guides the testing process. The artificial transmission is then filled with the manufacturer‘s original transmission oil and subjected to controlled heating, creating positive pressure and pressure equalization. When the oil and air cool, a vacuum or negative pressure forms, drawing in outside air through the membrane. This testing approach has already successfully simulated 8,000 kilometers of test drives.

The Konzelmann endurance test stand for load spectra of oil temperatures of up to 120 °Celsius

A consultative approach

Thus, for the first time, a valve has been developed that optimally functions during the critical phase of water crossings, ensuring that the membrane remains unclogged with oil. All gearboxes available on the market can be tested in advance and manufacturers can be advised optimally.

This groundbreaking product innovation is adaptable to all vehicle types and drivetrains, even within mobile systems. It is characterized by its minimal installation requirements and space-efficient design. The precisely defined ventilation and exhaust mechanism guarantees optimal pressure management within transmissions and other systems. Additionally, the Pressure Equalization Element offers a distinct production advantage over conventional hose constructions: It enables vehicle rotation on the production line even after the transmission/e-axle unit has been filled with oil.

Currently, the product is already undergoing testing with an OEM, with production scheduled for 2024.

About Konzelmann

Konzelmann GmbH, headquartered in Löchgau between Stuttgart and Heilbronn in south-western Germany, develops and produces high-quality plastic injection molding products. For more than 60 years now, Konzelmann has planned, developed, and manufactured high-precision components and complex assemblies made of polymeric materials for the medical, automotive and industrial sectors. Their extensive experience has made them a market leader in the fields of highly specialized technical applications. Furthermore, Konzelmann has a global presence, with representatives in Detroit/USA, Seoul/Korea and New Delhi/India.

More information: https://www.konzelmann.com/en/expertise

JTEKT Ultra Compact Products for Further eAxle Improvement

Makoto NISHIJI, Chief Engineer Driveline CE Dep’t, Automotive Business Unit, JTEKT Corporation

JTEKT contribution for e-Drive system

The automotive industry is developing technologies to respond to the once-in-a-century transformation for realizing a carbon-neutral, recycling-oriented, safe and comfortable society. As the powertrains of automobiles become electrified, the requirements for the e-motor based driveline systems and units that handle the vehicle movement are changing significantly. To take this evolution to an even higher level, reliability and cost reduction are essential, but it is also important to address improvements such as better power consumption (loss reduction, weight reduction, efficient regenerative braking), mountability (size reduction), low NV, and added values (4WD function, Torque control devices, etc.). To achieve this, JTEKT is conducting technological development for e-Drive system by several units/components aiming for “No.1 & Only One” in each field. (Fig. 1)

eAxle improvement by JTEKT Ultra Compact products

Following to the strong demand for higher power density eAxle in future, JTEKT has developed “Ultra Compact” product series, covering Differential (JUCD), Ball Bearing (JUCB) and Conductive Ball Bearing (JUEB), Oil Seal (JUCS) for eAxle size and weight reduction.

Figure 2: Co-Axial eAxle with JTEKT Ultra Compact products

Fig. 2 shows application example for 150kW class Co-Axial stepped pinion reducer eAxle. Co-Axial eAxle has advantage for packaging in height and front-rear axial length, therefore higher power density compared with traditional 3-Axis parallel offset reducer eAxle, but the eAxle width remains wide because of side-by-side e-motor, reducer, and differential layout. By introducing JTEKT Ultra Compact products, we estimate -70mm width and -7kg weight reduction from typical Co-Axial eAxle arrangement, therefore we can contribute eAxle power density improvement furthermore.

JUCB® Features and Advantages: Compact and High-speed performance

The most important requirement for bearings due to the shift to BEVs is higher rotational speed. In some cases, the maximum rotational speed ratio between the conventional power source, the engine, and the motor can exceed more than three times. The problem is the deformation of the cage due to centrifugal force. With a typical resin cage, when the limit speed is exceeded, the cage pockets deform due to centrifugal force, causing interference with the rolling elements, and the increased rotational resistance causes abnormal heat generation, leading to seizure.

JTEKT has developed a combination cage concept that can minimize deformation. Two resin parts of the same shape are combined to create a structure that suppresses deformation of each other, ensuring cage strength. Furthermore, in order to downsize, JTEKT have developed a bearing, JUCB® (JTEKT Ultra Compact Bearing®), which reduces the bearing width to almost the ball diameter size by minimizing the cage width (Fig. 3).

Figure 3: JUCB® (JTEKT Ultra Compact Baring®)

By optimizing the cage mold and that conditions, JTEKT achieved high-speed rotation of over 2 million dm-n (bearing high-speed performance index: multiplication of ball pitch diameter (dm) and rotational speed) under oil lubrication.

UEB® Features and Advantages: Compact and Conductivity

In bearings used in motors (especially driven by inverters), a potential difference may act between the inner and outer rings of the bearing due to magnetic flux imbalance inside the motor. Sparks (electrolytic corrosion) are generated at the contact between the rolling elements and the raceway due to this potential difference, which is known to cause washboard-like damage to the raceway. Conventional technology has taken measures to insulate bearings, such as using ceramic balls as insulators and forming an insulating coating on the outer ring surface. In addition, measures have been put into practical use to bypass the potential between the tracks other than the bearings using a separate circuit parallel to the track. JTEKT has developed JUEB® (JTEKT Ultra Earth Bearing®), which uses a conductive material in the seal to bypass the current path to the seal and avoid electrolytic corrosion on the bearing raceway. JUEB will provide a compact bearing with a conductive mechanism, contributing to improving the reliability of eAxle. (Fig. 4).

JUCS® Features and Advantages: Compact and Sealability

The oil seal installed at the connection between the differential and the drive shaft must be able to prevent oil leakage from the inside and contamination from the outside. If the seal  width is shortened to make the seal smaller, the lip length will also become shorter, and if the conventional design is used, the ability to follow eccentricity to the shaft will decrease. In addition, the rubber will become hard at low temperatures, worsening the ability to follow the eccentricity. As a result, there was a problem that oil leaks were more likely to occur.

We have developed an acrylic rubber material with improved low-temperature properties and have improved its ability to follow eccentricity at low temperatures by optimizing the tension force composition ratio (rubber, spring). The acrylic rubber also has improved elasticity and can maintain the same oil retention capacity as conventional products. As a result, the JUCS® (JTEKT Ultra Compact Sael®) makes it possible to shorten the seal in the axial direction, contributing to the miniaturization of e-axles. (Fig. 5).

JUCD® Features and Advantages: High torque density and safety performance

Compared to typical bevel gear type open differential, JUCD® (JTEKT Ultra Compact Diff®) has an increased gear mesh quantity and wider gear mesh width at larger gear mesh diameter between planet gear (PG) and side gear (SG). This is possible by using small diameter parallel axis planet gears which are directly supported by the housing bore similar with journal bearing structure. As a result, JUCD has higher torque density (= strength/volume) than typical open diff. Required differential gearing functional volume for JUCD will be less than half compared with open diff. for the same strength. (Fig. 6)

Figure 6: JUCD® (JTEKT Ultra Compact Diff.®

PG outer diameter – HSG bore direct contact structure generate torque sensing limited slip diff effect, which brings vehicle performance improvement advantages for safe and confident drive under daily various driving situations. This LSD function works not only drive mode, but also coast mode or even regenerating braking mode, therefore it will bring potentially better power consumption for BEV in real world by minimizing wheel slip/spin situation and friction brake activation.

Planetary Carrier integrated JUCD

In case of Co-Axial stepped pinion reducer, planetary carrier and differential housing will have same rotational speed, therefore it is possible to integrate those two functions into one housing, but typical open diff. bevel gear will be located at the side of planetary carrier in to avoid radial dimensional interferences and maintain assembly possibility of the differential components into one-piece housing thru its window. (Fig. 2)

JUCD can reduce differential radial and axial dimension significantly keeping the same required strength. By using this advantage, it is possible to locate the differential well inside of the planetary reduction gearing for reducer width improvement by full axial overlap.

On top of JUCD, JUCB and JUCS could be also integrated into the reducer for further width/weight improvement not only for reducer, but also for eAxle, and even vehicle level. (Fig. 7)

Figure 7: Planetary carrier integrated JUCD in eAxle reducer

Cylindrical JUCD housing together with the same number of differential PG set and reducer stepped pinion gear set reduce planetary carrier stress variation at each stepped pinion support during torque transfer situation. This is also interesting advantage to minimize tooth contact variation of the stepped pinion set, so that it will be easier to define common and optimum tooth micro geometry for the reducer gearing for low NV, and better durability.

https://www.jtekt.co.jp/e/news/

eFluid Formulation Balance & Challenges in Electrified Commercial Vehicles

Andrew Wood, Driveline Fluids Technologist, Infineum UK Ltd
Calum Sugden, Driveline Fluids Technologist, Infineum UK Ltd

The transportation industry is working to decarbonise, and commercial vehicle manufacturers are exploring a range of low and zero carbon propulsion options, including electrification. New opportunities to formulate tailored driveline eFluids are emerging, as the electrified truck and bus market develops.

The evolving electric drive architectures used in this vehicle segment have specific protection and performance needs.

Full battery electric propulsion is one option commercial vehicle Original Equipment Manufacturers (OEMs) are exploring.

In 2021 it was estimated that just over 4% of the combined global bus and truck fleet was fully electric. Looking ahead, as the pressure to decarbonise intensifies, forecasters suggest that by 2029 some 10% of commercial vehicles rolling off the production line will be electric, with the majority produced in China, and small volumes coming from Europe and North America (see visual 1).

However, more detailed data suggests a faster electrification rate in buses compared to heavy-duty trucks.

Shorter trips and return to base operations where charging can be done overnight, plus local government measures to reduce air pollution in city centres, makes the transition less difficult for buses (see visual 2).

As the hardware evolves, we can expect to see three key drive systems in the market − central drive, integrated eAxle and distributed wheel/ specific hub motors.

Two separate fluids are typically used (one to cool the motor and another to protect the gears), because the position of the motor and gear type means it is challenging currently for one fluid to meet all the requirements of these systems.

Fluid requirements

In addition, it is challenging to deliver sufficient hardware protection in these fully electric models with the conventional automatic transmission fluids (ATF) and axle oils used today (see visual 3).

Next generation eFluids will need to deliver not only traditional transmission fluid properties but also new eFluid requirements including improved heat transfer, better materials compatibility, and higher volume resistivit (see visual 4).

Heat transfer for eMotor cooling

Cooling electric motors is recognised as a critical function of electric vehicle transmission fluids. Infineum has carried out extensive assessments to determine the most important properties of eFluids for heat transfer.

While the impact of viscosity and additive technology have been key focal points during tests carried out in different motor configurations, attention has also been directed towards the effect of operating conditions such as flow rate and motor torque.

Heat generation tests revealed that low viscosity fluids offer significant performance benefits versus higher viscosity formulations – delaying derating of stator windings and showing lower steady state temperatures.

However, when moving to lower viscosity lubricants, cooling benefits provided need balancing by an additive technology which also delivers sufficient wear protection.

Materials compatibility

eMotors introduce a wide range of materials into the drivetrain including insulating material, copper wire and connections, aluminium, plastics, and sealants. Many OEMs consider copper compatibility to be one of the most important design parameters for eFluids, because electronic circuit boards are increasingly in contact with or immersed in oil, so full compatibility is required.

The ASTM D130 procedure is one of the most common methods used to study the impact of copper corrosion. But now, newer methods, including energised circuit board tests that involve the passage of an electric current, are also being used to better understand copper corrosion.

In addition, thermal shock testing is a useful way to evaluate compatibility with other materials including varnished wire and a range of insulation materials under extreme thermal cycling conditions (see visual 5).

Using these tests, Infineum’s eFluid and eMotor cooling fluid have shown outstanding motor material compatibility performance.

Electrical properties

The issue of electrical compatibility overarches all electric vehicle developments. The power electronics operate at hundreds of volts, which means the fluid needs to provide enough resistivity to avoid any current leakage and/or shortcuts.

However, if the fluid is completely insulating, it can lead to static charge buildup which can damage the equipment due to arcing phenomena. eFluids designed with optimal resistivity can help OEMs to reduce the size of the motor and casing, which means less material use, lower production costs, and enables the use of even higher voltages.

In our view, it is important to tailor eFluid formulations for commercial vehicles to ensure they deliver the right balance of performance to meet individual customer needs.

eFluids need to provide both high gear scuffing and high-volume resistivity performance, making a tailored eFluid a good fit for use in these applications (see visual 6).

Conclusion

A careful balance of additive components and base stock is needed to create tailored eFluids that deliver the required cooling, electrical performance and materials compatibility electric commercial vehicles require. But, at the same time, these complex fluids must also meet gear and bearing durability, aeration and efficiency requirements.

Infineum eFluids have demonstrated improvements in electrical performance, material compatibility and motor cooling efficiency via modelling, novel test methods, eMotor rig testing and field trials in electrified applications. As we look to a future where transmission oils in commercial vehicles will be replaced by advanced eFluids, Infineum is ready with tailored solutions that are aligned with evolving hardware designs.

Visit the Infineum exhibition stand at CTI Berlin to speak to our experts.

The Powertrain as an Intelligent System

The automotive world is changing, and the CTI Symposium is helping to drive the transformation. Where will the boundaries of powertrains lie in future? While powertrains will still be centre stage of the Symposium, the scope will expand. Artificial intelligence will play a growing role, and so will the provision of energy sources.

The 22^nd CTI Symposium 2023 in Berlin (5 – 6 December) began with an important announcement, as Prof. Ferit Küçükay handed over his role as chairperson to Prof. Malte Jaensch. Jaensch’s primary role is Chair of Sustainable Mobile Powertrain at the Technical University of Munich. Professor Küçükay will stay with the Symposium in the role of Founding Chairman. Malte Jaensch justifiably praised his predecessor’s work for CTI as a “lifetime achievement.”

For nearly 25 years, Professor Küçükay shaped the themes of the CTI Symposium, and oversaw a number of paradigm shifts along the way. It all began in late 2000, just after Professor Küçükay became head of the Institute of Automotive Engineering at the TU Braunschweig. One day, he took a call from Sylvia Zenzinger, now the symposium’s conference director. Would he be interested in chairing a new congress on vehicle drives? Küçükay agreed right away.

Since then, both the Symposium’s topics and its tagline have evolved steadily. In 2010, hybrid and electric drives were added to the programme and tagline. Recently, “Automotive Drivetrains, Intelligent, Electrified” has reflected the growing importance of electrification. Today, the CTI Symposium is a major international event, with presentations held exclusively in English.

This December, the Symposium changed its tagline to “Automotive Powertrain Systems”. This reflects two current developments: Firstly, that electrification is now a perfectly normal powertrain topic; secondly, that adopting a system view is crucial when developing vehicle drives.

The BEV for Everybody

As Professor Malte Jaensch specified in his opening speech, we need to consider the powertrain as a system and understand how all the individual components work. That starts with electric motors, gearboxes for elctric drives, inverters and batteries – and extends right up to the overall vehicle and, of course, the consumers’ wishes.

With BEVs, another question is how to make them affordable for everyone. In Berlin, this was the focus of the Executive Discussion “The BEV for Everybody”, with participants Karsten Bennewitz, Volkswagen, Marcus Lott, Opel, Prof. Maximilian Fichtner, Helmholtz Institute Ulm, and David Green from Lynk.

The first question was, “When will BEVs dominate the vehicle market?” Using their voting app, the majority of audience members said it would be when cost parity was achieved with other drive types. In second place came adequate infrastructure, followed by sufficient range and/or faster charging times.

On costs, Bennewitz agreed that we need to approach cost parity, but said Germany already had an adequate charging infrastructure, with high numbers of fast charging stations. He cited fun-to-drive as a further important factor for winning over consumers to BEV. From an OEM perspective, he does not foresee an immediate switch to BEV, saying markets such as India had totally different requirements.

Marcus Lott took a similar view. He said combustion engines are still needed for other markets, but PSA and Opel have started their electric transformation process early on, driven by legislation. If legislation were to develop less stringently in Europe, reverting to conventional drives would not pose a problem. That said, consumers who switch to BEV “never go back”. As for costs, the competition in China is making us “fit and lean”.

David Green, from the Geely subsidiary Lynk, said other forms of ownership were a way to reduce costs. Lynk’s offering includes a subscription model that could be canceled at any time, but also a rental model that increases vehicle use times, and thus distributes costs more effectively over the life cycle. Unlike Bennewitz, Green thinks charging options could be improved, noting that ‘BEV for Everybody’ would not work if you lived in an apartment in Munich, or any other urban area with poor charging availability.

For Professor Fichtner, a battery expert at the Helmholtz Institute, the main lever for making BEVs affordable is new battery technology. In future, he said, charging times of ten minutes for a range of 700 km would be possible. In addition, cost issues should be bundled with other issues: whereas batteries can be recycled, fossil fuels are “gone” once you burn them.

The discussion may have been a starting point for further questions in the future. One may be: How can we make make used BEVs more attractive, for example through more hardware and software update abilities?

The advent of new battery technologies

But back to batteries for now: Prof. Fichtner examined batteries more closely in his plenary speech, “Recent trends in battery research and development”. Given the growth of e-mobility, he said, Europe would need a production capacity of around 1 TWh in 2030, compared to just 21 kWh in 2020. On the other hand, we need higher numbers of sustainable batteries, and hence new raw materials. On the cathode side, these would lithium iron phosphate (LiFePO₄), lithium manganese oxide (LiNi_3/4Mn₁/4O₂) and nickel manganese (LiMnO₂), all without cobalt. New anode materials were also expected, such as silicon carbon composites. These would enable 40% more energy content at cell level, putting them on a par with solid-state batteries – a technology he said has had a great future for a long time, but one that might not materialize.

In future, sodium batteries would enable batteries that required no critical raw materials. And generally, lithium, nickel, cobalt, graphite and copper could be replaced by sodium, iron, magnesium, hard carbon and aluminum. Since some new developments would mean reduced energy density, Fichtner advocates close collaboration between chemists and engineers in order to optimize battery weight and packaging at the construction level. He cited CATL’s cell-to-pack process as an example.

Battery topics were also discussed intensively in the Deep Dive sessions. Presentations by TotalEnergies and Valeo covered cooling aspects, while APL reported on “Mastering Thermal Runaway” and Marelli dealt with wireless battery management systems.

Remarkable progress in e-motors and e-drives

As to future electric drives, Jörg Gindele from Magna Powertrain talked about the companies next gen e-drive portfolio. He said system efficiency of the new development is 93% (motor efficiency 96.3%), namely in WLTC and with additional highway components – so basically, in real life operation.

The high system-level efficiency is due to the significantly expanded sweet spot, Gindele said. This also helped for what Magna calls the ‘complementary operation’ of the front and rear axle drives. Basically, this means the gear ratio of the front primary drive can be made longer, and hence more efficient, while the secondary (rear) drive, which can be activated at will, can be configured for performance.

A few design features: The drive is so compact that it can tilt 90 degrees and be used on either the front or rear axle. To optimize motor costs, the magnets are fixed by mechanical means only, using flaps. The active fluid control system uses a pump actuator taken from transmission technology. Since its direction of rotation is reversible, the oil flow can, for example, be distributed between the motor shaft and the winding heads. An HV Embedding process reduces shift losses, while Optimized Pulse Patterns smooth out the drive’s pulse – and hence vibration – behavior.

Gindele concluded with an outlook for further goals in tomorrow’s drives. These included new magnet-free motor concepts, the elimination of rare earths, GaN architectures for both 800 and 400 V, and further digitalization, for example the Digital Energy Twin, to improve range prediction.

His speech is just one example for the lively development activitiy in the e-drive field. In Berlin, no fewer than three Deep Dive sessions with over 14 presentations were dedicated to e-motors and e-drives. Just a few examples:

Volkswagen presented their new electric MEB platform in detail. Great wall introduced the e-drive architecture of their ORA Lightning Cat. DeepDrive talked about the advantes of the radial-flux electric machines. New e-motor technologies and approaches were presented by ZF, Infimotion, BorgWarner, Dana and Valeo. American Axle discussed solutions for high-speed e-motors, Valeo talked about optimizing e-drive efficiency. AVL List presented their development process for an e-drive system, and Hofer Powertrain several torque vectoring solutions for unique markets.

This short list shows how manifold the e-drive topic is and there is much more to come and discuss on upcoming CTI symposia.

How are OEMs electrifying?

Volkswagen, Mercedes-Benz and Opel gave insights into their plans for further electrification.

In his plenary speech, Thorsten Jablonski showed how the Volkswagen Components Group was transforming itself into an Electric Powertrain Supplier. Until recently, the group and its 69,000 employees manufactured transmissions, combustion engines and more. Today, it’s becoming an electric drive supplier with a holistic perspective that includes e-drives, inverters, batteries and thermal management, as well as their system integration. In future, Jablonski said, the SSP platform (Scalable Systems Platform) would be used in a scalable manner for all Group brands and segments. His comments on scalable battery technology were equally interesting: At its Powerco subsidiary in Salzgitter, Volkswagen is planning different cell chemistries for different vehicle segments: iron phosphate for the entry level, high manganese for the mass market, and increased silicon content as a best-in-class application.

Konstantin Neiß, Mercedes-Benz, began his plenary speech by reiterating his company’s commitment to becoming CO₂-neutral by 2039. He said Mercedes was also investing in transforming its Stuttgart plant for more electrification, with a focus on batteries and e-drives. This includes small series production of Li-ion cells, though Mercedes plans to buy in more from various sources. Neiß also mentioned the acquisition of Yasa, which will produce performance electric motors at its Berlin factory. In 2025, Mercedes plans to launch its first ‘electric first’ platform (MMA), for which combustion engines are just one of several options. Neiß then showed a vehicle based on this MMA platform: the Concept CLA Class. He put the powertrain overall efficiency at 93%, with an energy consumption as low as 12 kWh per 100 km. The range would be 750 km (WLTC), and 400 km of range could be ‘refueled’ in 15 minutes. The speaker then touched briefly on the Vision One-Eleven vehicle, which features axial flux machines by Yasa. The advantages of this design: very short, very good continuous performance, and low weight.

In his plenary speech, Marcus Lott, Opel, talked about the “BEV for Everybody” that Opel and its parent company Stellantis are striving for. From 2024, Opel wants to offer at least one BEV in every vehicle series; from 2025 on, every new launch would be a BEV. In future, Opel would have access to four Stellantis platforms with ranges of 500 to 800 km. The group was pursuing a circular strategy for batteries, including a ‘second life’ and materials recycling. Lott noted that Opel has also offered an FCEV transporter – the Vivaro-e Hydrogen – since 2021. The design is interesting: a 45 kW fuel cell stack, and a battery and electric drive with a maximum output of 100 kW each. At 10.5 kWh, the battery is fairly large and provides around 50 km of electric driving; the total range is 400 km. Opel describe this as a “mid-power concept” with an optimal balance of customer benefits. In 2023, Lott said, Europe had over 150 700-bar gas stations; by the end of 2025, that should rise to more than 450. According to the EU AFIR (EU Alternative Fuels Infrastructure Regulation), from 2030 on filling stations of this type will be mandatory every 200 km, plus an additional station at every urban node.

Heavy commercial vehicles have diverse requirements

Requirements in the heavy commercial vehicle segment are different from those for passenger cars, as the Expert Discussion “Who Will Take the Heavy-Duty Vehicle Volume – FCEV, Green ICE or BEV?” confirmed. The participants were Gernot Graf, AVL, Michael Himmen, Hydrogenics, Loek van Seeters, DAF, and Götz von Esebeck, Traton.

Right at the start, audience members were able to cast their app votes in response to the question: “Which drive concept will take the volume in heavy-duty vehicles in the long run?” Multiple answers were permitted. Overall, 47% said BEV, 45% FCEV, 31% H₂ combustion, 22% e-fuels, 18% HEV and 14% diesel engines. This showed just how diverse the possible solutions are considered to be.

This diversity was reflected in the views of the discussion participants. Gernot Graf argued in favor of hydrogen for both FCEVs and combustion engines, saying fuel cell had an efficiency of around 50%, a combustion engine slightly more. He said, it all depends on the application: Above a certain performance threshold, you need a combustion engine with its better power-to-weight ratio. Fuel cell are better under partial load, combustion engines at high and full load.

Götz von Esebeck was sure that BEV would dominate in terms of volume. In the transport business, he said, TCO is king, and electricity weill be the cheapest option in future. He even sees opportunities for BEV on long hauls, especially since fast charging were not an issue for the large batteries involved. Of course, the infrastructure would need to be built first.

For Michael Himmen there is no “super answer for all”. Fuel cell would come; there is a “momentum”, he said, as the industry has special requirements in terms of weight and distance. Transporting goods from Poland to Spain, for example, would remain challenging for a long time to come. Markets like India would still need ICEs for many years, due to the lack of infrastructure. Interestingly, Himmen also sees fuel cell mainly for stationary applications. He said Hydrogenics and its parent company Cummins were covering this aspect as well.

In the discussion and the plenary speech he gave earlier, Loek van Seeters spoke in favor of developing all drive options, then seeing which prevailed. After all, new technologies needed a certain ramp-up time. Today we still needed diesel engines; drives that used no fossil fuels would not arrive around 2040 – but DAF is committed to developing them. In his talk, the speaker presented the manufacturer’s range of drives for commercial vehicles. Besides conventional drives, this includes hybrid drives, purely electric tractors and, as of 2021, a tractor with a hydrogen combustion engine. But in order to achieve the EU goal of reducing CO₂ emissions from electrically powered trucks and buses by 45% by 2030, he said a lot more would have to happen. Per year, 42 TWh – the equivalent of 17 million households or 11 nuclear power plants – would have to be upgraded. We also needed 280,000 charging stations and 50,000 public charging stations; the rollout is still progressing far too slowly, he said.

AI – the 5^th revolution?

Another topic is currently growing at breakneck speed: artificial intelligence. The catalyst here may have been ChatGPT, the AI tool that is already being used for automated text creation.

In Berlin, Hamidreza Hosseini, CEO of Ecodynamics GmbH, gave a highly anticipated speech entitled: “GenAI, & ChatGPT’s Impact on Future Automotive Development and Engineering”. Hosseini described and demonstrated how generative AI can also change processes in the automotive industry. GenAI can generate new content by processing patterns drawn from training data; ChatGPT, now familiar to many people, is just one part of it.

Hosseini also pointed out that ethical issues are involved, and that systemic transparency is a prerequisite for using AI tools of this kind. But what stuck most in listeners’ minds was the message that artificial intelligence could change work processes in the automotive industry very quickly. Hosseini spoke of a 5^th industrial revolution, adding that others could follow. In 50 to 60 years’ time, the “merging of humans and machines” could be next.

The CTI symposium helps shaping the transition

What were the key learnings from the CTI Symposium Berlin? Summing up, chairperson Prof. Malte Jaensch mentioned several points. Firstly, it’s becoming more and more important to see the powertrain as a system – a development that is reflected in the new symposium tagline “Automotive Powertrain Systems”. Secondly, there is no such thing as “one size fits all”. Instead, we need to strike the optimal balance between sustainability, development, production, cost, efficiency and more besides.

Thirdly, as the conference showed, drive options for heavy-duty vehicles were more varied than for passenger cars. All the same, it was important for passenger car and heavy-duty developers to exchange ideas at the CTI Symposium, and to learn from each other across functional and product boundaries.

In general – and despite the importance of overall systems – powertrains would always be at the heart of the CTI symposium, Jaensch added. That said, there would be changes. The topic of AI in automotive engineering could – and probably will – be accompanied by a growing number of lectures and discussions. Jaensch said we should see this as an opportunity, not a threat.

He also mentioned the topic of “Energy Formability,” which essentially places the system idea in a larger context. Powertrains alone could not be “green”; instead, we must consider drives, mobility and energy together as a whole. This included topics such as bidirectional charging, vehicle-to-x or “second life of batteries”, which could likewise become symposium topics in future.

The next CTI Symposium Berlin is scheduled for 3 – 4 December 2024. The next US symposium takes place much earlier (15 – 16 May 2024, in Novi near Detroit), and we warmly invite you to attend.

Report: Gernot Goppelt

Unlocking the Key to Seamless EV Driveline Disconnects

John Jennings, Director of Innovation and eMobility, Amsted Automotive

The future of vehicle propulsion is not simply a trending topic. It’s a global reckoning, as well as a global opportunity for revolutionary advances in powertrain and driveline technologies. Next-generation technology is at the forefront, and leading the way is Amsted Automotive with its Dynamic Controllable Clutch (DCC), an Electro-Mechanical E-axle Disconnect system for EVs.

As you read in every issue of CTI Magazine, Electric Vehicles (EV) drivetrain systems are being redefined—creating next-generation propulsion systems—as the EV market grows rapidly. The first EV propulsion systems simply replaced ICE powertrains with electric motors and battery systems. This next generation of EV propulsion systems will need to be further optimized for function, efficiency, range and cost as the EV market scales up. This includes the need for new solutions to facilitate seamless eAWD disconnect with the ability to quickly and reliably shift between disconnected, forward propulsion, and regen or reverse modes. Design flexibility is also required for adaptability at multiple locations between the eMachine and wheels.

In addition to disconnects, next generation EV drivetrains will also require more sophisticated solutions for electronic park-lock, hill-hold and multi-speed shifting, combining the functions of historical ICE transmissions and drivelines. These technologies can be applied to EV passenger cars, light truck and commercial vehicles.

Means, an Amsted Automotive division, has developed controllable disconnect clutch and actuation technology with full disconnect and locking functions, plus the additional functionality for controlled bidirectional one-way-clutch operation. This technology, when applied to EV drivetrains, can provide novel and flexible system solutions for EV disconnects for both eAWD and primary electric drive unit (EDU) applications. The control and flexibility of this technology can also enable the same disconnect function and advantages for the primary EDU. Additional capability can also be combined with multi- speed shift functions, hill-hold and park-lock features to create novel multi-functional clutch solutions for the next generation of EV drivetrains. The first Means base disconnect for EV application was launched into production in 2021.

The Dawn of New Technology for EV Drivetrains

Market growth for EVs is exploding at a remarkable pace. Yet there’s a significant challenge: OEMs and Tier 1 Automotive Suppliers − both established and new − may not have the capabilities to develop next-generation technology required for electrification. Simply put, traditional ICE drivetrains and electric drivetrains are not the same. Without this ability to adapt to the unique requirements of EV powertrain systems, there may be missed opportunities for new success within the transportation sector.

As emerging products for EV propulsion systems continue to be redefined and reinvented, Amsted Automotive is the leader in the solutions for EV drivetrains, optimizing for function, efficiency, range, and cost, as well as to meet emissions standards and other electrification targets. Means Industries, an Amsted Automotive company, has developed a novel multifunctional clutch technology that’s revolutionizing electrification in a very short time: Dynamic Controllable Clutch (DCC) and Electro- Mechanical E-axle Disconnect Solutions.

Design and engineering expertise, as well as agile capabilities in advanced metal-forming and powder metal manufacturing with electro-mechanical clutch design capabilities for electrified propulsion solutions, have put Amsted Automotive at the forefront of advanced EV drivetrain technology worldwide.

ICE AWD Architecture

A typical ICE AWD architecture based on a front- wheel-drive platform includes an engine, a power- takeoff unit (PTU) in the transaxle and a rear-drive unit (RDU) with a coupler. The system has a disconnect in both the PTU and RDU.

This configuration has parasitic losses created by hypoid gear meshing in both the PTU and RDU, fluid churning, bearing and seal drag, and spin loss of the propshaft. In addition to parasitic losses, there are challenges with seamless disconnect and reconnect of the RDU while the vehicle is in motion. The system must match rear-wheel speed with the ICE powertrain.

There is high inertial torque of the RDU. There are also challenges with cold-weather drag, block shift, and shift interruption with dog clutches and limitations on shift engagement time. Finally, by design, disconnect function must be contained in both the PTU and RDU, which poses challenges with packaging.

EV AWD Architecture

EV powertrains provide an opportunity to rethink the traditional AWD architecture. Without the need to physically connect the front and rear drive axles, parasitic losses can be significantly reduced, and packaging issue are simplified. EVs have a dedicated eMotor for each axle, or in some cases a dedicated eMotor for each wheel. This enables the eMotor to control the power and speed directly for each axle, and therefore it can also be used to manage the synchronization and speed-matching for the AWD disconnect & re-connect.

Advantages include flexible package locations for EV drivetrains and intelligent energy management to optimize driving range. The challenges in an EV AWD architecture are NVH − EVs do not mask NVH like ICE powertrains do − and managing AWD regenerative braking mode. All of this creates opportunity for new approaches to disconnect systems that cannot be accomplished with ICE AWD architectures.

The New EV AWD Disconnect Solution

At the 2018 CTI Symposium in Berlin, Means Industries redefined propulsion system design by introducing two game-changing technologies.

The Electronic Controllable Mechanical Diode (eCMD) is a static, electrically actuated concept that offered the benefits of latching in state without a constant power supply. Hydraulic control was eliminated as were the associated costs and complexities. Power would be consumed only during state transition, thereby reducing energy consumption.

The other new device was DCC. This was a level of advanced technology never before seen in electrified vehicles. Using electric actuation, DCC creates substantial packaging and system efficiencies by eliminating complex hydraulic systems. The dynamic controllable clutch technology coupled with electromagnetic actuation technology can be utilized in single or multi-speed gearboxes for markedly improved EV powertrain efficiencies. There was no need for more packaging space.

The DCC system offers fast, smooth shifting that is managed by eMotor controls, with mechanical engagement always available for eMotor speed matching. It is also very reliable; no blocked shifts. There are no friction elements during a mechanical engagement, with a bistable magnetic latch (on/off) to eliminate power consumption while in-state.

Next-Gen EV Disconnect with One-Way Clutch Functionality

In order to enable faster AWD vehicle system disconnect shift time,the next generation EV disconnect includes another Amsted Automotive innovation: integrated one-way-clutch (OWC) functionality. This is easy to conceptualize by considering a bicycle. With power applied (pedaling), the one-way clutch transmits torque to the wheel. When power is off (coasting and not pedaling), the one-way clutch overruns or freewheels. When power is reapplied (pedaling again), the pedals ramps up to match the wheel speed and then transmits torque again to the wheel.

Means developed an integrated controllable bi- directional one-way clutch which enables Reverse and regenerative braking. The system also includes a passive one-way clutch for forward driving operation. In freewheel mode, both clutches are disengaged.

Under power traveling forward, the passive one-way clutch engages to transmit torque to the wheels. When Reverse or regenerative braking mode are required, the controllable one-way clutch is engaged along with the passive one-way clutch.

In the forward propulsion direction, the disconnect and re-connect are automatic and is simply controlled by powering the propulsion motor on and off, just like described in the bicycle analogy.

This technology provides fast shift times − 17 millisecond pre-engagement shifts − for Reverse and regenerative braking. The system is based on proven production technology and is reliable. It eliminates the possibility of blocked shifts or rejected shifts. Mechanical engagement is always available for speed matching the eMotor. It offers the opportunity for flexible EV drivetrain packaging locations by providing modular style and integrated solutions.

And it can improve the efficiency of AWD EVs by as much as 5–10% on the highway because there are no friction elements and the magnetic latching for on/off states doesn’t require any power consumption to remain in state.

The Next Generation is Here Now

With the accelerated push to rapidly grow the EV market, there may be more innovations in powertrain being developed today than any other time in history. One of the key technologies developed by Means Industries for this market presents great opportunity to solve the issue of seamless eAWD disconnects in EV powertrains and provide much more. The design provides the ability to quickly and reliably shift between disconnected, forward propulsion, and regen or reverse modes. However, the design also enables flexibility for adaptability at multiple locations between the eMachine and wheels. Beyond the driving functions of an eAxle disconnect, the system also enables responsibilities previously provided by traditional ICE transmissions and drivelines such as park-lock, hill-hold and multispeed shifting. The next generation of EV powertrain systems is here today.

Who is Amsted Automotive?

Amsted Industries is a diversified designer and manufacturer of cutting-edge industrial solutions serving the railroad, vehicular and construction markets with a global footprint spanning 66 facilities in 10 countries across 6 continents, with more than 19,000 employees and approximately $4B in annual revenue.

Amsted Automotive was formed in 2021 − bringing together two of its century-old, core Tier 1 and Tier 2 automotive supply business units − Means Industries and Burgess Norton, to form a new and innovative technology team. SMW Manufacturing was added to the group in 2021. The integration provides an expanded global presence with 16 facilities in North America, Asia and Europe to serve global automakers with a robust manufacturing footprint producing more than 100 million components and assemblies annually.

This group combines design and engineering expertise, strategically aligned to be a nimble leader in advanced metal-forming including powder metal manufacturing with electro-mechanical clutch design capabilities for electrified propulsion solutions, building on integral roles in global advanced automatic transmissions designed in North America, Europe, and Asia