Transformation of the Automobile and Supplier Industry
Markets and Analysis
OEM Panel: “What´s coming next?“
Supplier Panel: “How deal with the Supply Chain, Sustainability & Accessibility Requirements and Challenges“
University Panel “EV Technologies of the Future – University Projects & Perspectives”
Deep Dive Sessions on Passenger Cars and Commercial Vehicles
Latest EV and HEV Propulsion Technology
E-Drives, E-Motors
EDU Components
Power Electronics
Thermal Management
Battery Technologies
Lubrication
Development Tools
The Expert Summit for a Sustainable Future Mobility
Only together we can create a sustainable future mobility. CO2 reduction is critical for automotive drivetrain. Here the battery electric drive using renewable energy is the focus. What can we do to increase efficiency and reliability, reduce cost and at the same time reduce the upstream CO2?
At CTI SYMPOSIUM the automotive industry discusses the challenges it faces and promising strategies. Latest solutions in the fields of electric drives, power electronics, battery systems, e-machines as well as the manufacturing of these components and supply chain improvements are presented. For the bigger picture market and consumer research results as well as infrastructure related topics supplement the exchange of expertise.
CTI SYMPOSIA drive the progress in individual and commercial automotive transportation. Manufacturer, suppliers and institutions are showing how to master the demanding challenges.
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 […]
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.
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 […]
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.
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 […]
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.