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Carbon neutrality has become a significant target. One essential parameter regarding energy consumption and emissions is the mass of vehicles. Lightweight design improves the result of vehicle life cycle assessment (LCA), increases efficiency, and can be a step towards sustainability and CO2 neutrality. Weight reduction through structural optimization is a challenging task. Typical design development procedures have to be overcome. Instead of just a facelift or the creation of a derivative of the predecessor design, completely alternative design creation methods have to be applied. Automated structural optimization is one tool for exploring completely new design approaches. Different methods are available and weight reduction is the focus of topology optimization. This paper describes a fatigue life homogenization method that enables the weight reduction of vehicle parts. The applied CAE process combines fatigue life prediction and topology optimization.

In recent years, swift changes in market demands toward achieving carbon neutrality have driven significant developments within the automotive industry. Consequently, employing computer simulations in the early stages of vehicle development has become imperative for a comprehensive understanding of performance characteristics. Of particular importance is the cooling performance of vehicles, which plays a vital role in ensuring safety and overall performance. It is crucial to predict optimal cooling performance, particularly about the heat generated by the powertrain during the initial phases of vehicle development. However, the utilization of thermal analysis models for assessing vehicle cooling performance demands substantial computational resources, rendering them less practical for evaluating performance associated with design changes in the planning phase.

Internal combustion engines will play an important role in the coming decades, even considering targets of carbon neutrality for a sustainable future. This will be especially true in regions where pure electrified vehicle implementation is not yet practical, or for long-range heavy load transportation purposes, even in regions where BEV infrastructure is well established. HEV/PHEV’s importance and contribution to CO2 emission reduction together with carbon neutral fuels such as hydrogen, e-fuel and biomass fuel etc. will remain crucial regardless of region/transport sectors. In this respect, brake thermal efficiency improvements by friction reduction needs further investigation. This is especially so with the crankshaft bearings’ lubrication system, which can provide as much as 40% of the total mechanical losses in some cases. It is a well-established fact, that plain bearings require a minimum oil flow volume to maintain their real function rather than oil pressure.

Contribution to carbon neutrality is one of the most important challenges for the automotive industry. Though CO2 emission has been reduced through electrification, internal combustion engines equipped in vehicles such as Hybrid Electric Vehicle (HEV) and Plug-in Hybrid Electric Vehicle (PHEV) are still necessary for the foreseeable future, and continuous efforts to improve fuel economy are demanded. To improve powertrain thermal efficiency, direct-injection turbocharged gasoline engines have been widely utilized in recent years. Super lean-burn combustion engine has been being researched as the next generation of turbocharged gasoline engines. It is known that an increase of the boost pressure causes deposit formation, which decrease the turbocharger efficiency, in the turbocharger compressor housing. To avoid the efficiency loss due to deposit, air temperature at compressor outlet has to be limited low.

Toyota has launched a new BEV which incorporates our newest evolutions in BEV powertrain systems and vehicle platform innovations. The new BEV uses newly developed large format battery cells, which, in addition to achieving our key performance and safety targets, also incorporates new technologies resulting in improved battery energy density and a reduction in battery deterioration. For the BEV battery cooling, to enhance safety, the cooling plate and the battery cells are separated by a chamber structure. The battery pack also incorporates a newly developed high resistance coolant with low conductivity. The new BEV improves system efficiency by leveraging some technologies that were originally developed for HEV and developing new systems. For example, radiant heating and a newly developed heat pump system improve EV driving range. This presentation will introduce our new battery technologies and discuss our new BEV system.

Recently, electric-powered vehicle such as HV, PHV, EV and FCV has been highly demanded and getting attention due to the increase of environmental-consciousness. Also, environmental regulations are getting more and more strict in many countries and regions. Then, environmental friendly vehicle is needed to be spread more and more than ever. As it is found in “TOYOTA Environmental challenge 2050”, Toyota will rapidly increase the number of new car sales of electric-powered vehicle towards 2050. This paper covers the rear wheel drive Q710 electric drive transaxle for 2nd generation MIRAI FCV. Toyota developed the transaxle for FCV (rear mounted) and for EV (front mounted) simultaneously and achieved coexistence of vehicle mountability and commonization of majority of the parts. This paper describes the hardware feature and the detailed technology which was adopted to Q710.

In Toyota’s 2nd generation FCV, an electric turbo-type air compressor has been adopted for downsizing and cost reduction. Automotive Fuel Cell applications present several challenges for implementing a turbo-type air compressor. When operating a fuel cell in high-temperature or high-altitude locations, the FC stack must be pressurized to prevent dry-up. The flow rate vs pressure conditions that the FC must pass through or in some cases operate at are typically within the surge region of a turbo-type air compressor. Additionally, Toyota requires quick air transient response (< 1 sec) for power generation, energy management, and FC dry-up prevention. If the turbo-type air compressor is not precisely controlled during quick transients, it can easily enter the surge region.

Quietness is one of the most important characteristics for Hybrid Electric Vehicle quality. Reduction of the rattle noise caused by the torque fluctuation of an internal combustion engine can contribute to get a customer satisfaction. Toyota Hybrid System(THS) also has same requirement. Especially, the rattle noise during idling may happen discontinuously despite of periodical engine combustion excitation. It is necessary to study the mechanism and reduce the rattle noise. At lower engine torque range, decreasing the torsional damper’s stiffness can improve this condition as the manual transaxle done. However, the rattle noise can occur easily in conditions of relatively large torque spike inputs to the torsional system, such as the engine start/stop function of THS using the motor/generator in the transaxle.

This paper describes the development of a simplified fracture finite element (FE) model for resistance spot welds (RSW) of ultra-high-strength steel (UHSS) that can be incorporated into large-scale vehicle FE model. It is known that the RSW of UHSS generates two types of fracture modes: heat-affected zone (HAZ) and nugget zone fractures. Lap shear and peeling coupon tests using UHSS sheets found that the different RSW fracture modes occurred at different nugget diameters. To analyze this phenomenon, detailed simulated coupon tests were carried out using solid hexahedral elements. The analytical results revealed that RSW fractures are defined by both the application of plastic strain on the elements and the stress triaxiality state of the elements. A detailed model incorporating a new fracture criteria model recreated the different UHSS RSW fracture modes and achieved a close correlation with the coupon test results.

1 In order to reduce the size and weight of the hybrid motor, improving motor cooling performance is essential. Therefore, we have been working on the development. This paper will explain the development of cooling technology TOYOTA has been working on, specifically the evolution of the hybrid motor cooling system and structure from the 1st generation Prius to the current model.

The knock-suppression effectiveness of exhaust-gas recirculation (EGR) can vary between implementations that take EGR gases after the three-way catalyst and those that use pre-catalyst EGR gases. A main difference between pre-and post-catalyst EGR gases is the level of trace species like NO, UHC, CO and H2. To quantify the role of NO, this experiment-based study employs NO-seeding in the intake tract for select combinations of fuel types and compression ratios, using simulated post-catalyst EGR gases as the diluent. The four investigated gasoline fuels share a common RON of 98, but vary in octane sensitivity and composition. To enable probing effects of near-zero NO levels, a skip-firing operating strategy is developed whereby the residual gases, which contain trace species like NO, are purged from the combustion chamber. Overall, the effects of NO-seeding on knock are consistent with the differences in knock limits for preand post-catalyst EGR gases.

This paper presents the thermal management of a hybrid vehicle (HV) using a heat pump system in cold weather. One advantage of an HV is the high efficiency of the vehicle system provided by the coupling and optimal control of an electric motor and an engine. However, in a conventional HV, fuel economy degradation is observed in cold weather because delivering heat to the passenger cabin using the engine results in a reduced efficiency of the vehicle system. In this study, a heat pump, combined with an engine, was used for thermal management to decrease fuel economy degradation. The heat pump is equipped with an electrically driven compressor that pumps ambient heat into a water-cooled condenser. The heat generated by the engine and the heat pump is delivered to the engine and the passenger cabin because the engine needs to warm up quickly to reduce emissions and the cabin needs heat to provide thermal comfort.

The quantity of heavy components in fuel is increasing as automotive fuels diversify, and engine oil formulations are becoming more complex. These trends result in the formation of larger amounts of carbon deposits as reaction byproducts during combustion, potentially worsening the susceptibility of the engine to knock [1]. The research described in this paper aimed to identify the mechanism that causes knocking to deteriorate due to carbon deposits in low to medium engine load ranges, which are mainly used when the vehicle drives off and accelerates. With this objective, the cylinder temperature and pressure with and without deposits were measured, and it was found that knocking deteriorates in a certain range of ignition timing.

Plugin hybrid electric vehicles (PHEVs) have several attractive features in terms of reduction of greenhouse gas (GHG) emissions. Compared to conventional vehicles (CVs) that only have an internal combustion engine (ICE), PHEVs have better energy efficiency like regular hybrids (HEVs), allow for electrifying an appreciable portion of traveled miles, and have no range anxiety issues like battery-only electric vehicles (BEVs). However, in terms of criteria emissions (e.g., NOx, NMOG, HC), it is unclear if PHEVs are any better than HEVs or CVs. Unlike GHG emissions, criteria emissions are not continuously emitted in proportional quantities to fossil fuel consumption. Rather, the amount and type of criteria emissions is a rather complex function of many factors, including type of fuel, ICE temperature, speed and torque, catalyst temperature, as well as the ICE controls (e.g., fuel-to-air ratio, valve and ignition timing).

Methylcyclopentadienyl manganese tricarbonyl (MMT) is used as an octane-enhancing metallic additive for unleaded gasoline which can prevent engine knock by proactive reaction with the hydrocarbon free radicals before starting the auto-ignition of hydrocarbons. However it has been pointed out that MMT causes automotive catalysts clogging and spark plug severely fouling. Therefore, many countries have fuel standards that prohibit or limit the usage of MMT. Nevertheless, some countries still use MMT as there are no restrictions imposed by fuel standards. As mentioned in several papers, metallic additives of engine oil such as calcium cause an abnormal combustion phenomenon called low-speed pre-ignition (LSPI) in turbocharged spark ignition engines. In contrast, the effect of metallic additives of gasoline such as MMT on LSPI has not been studied.

Over the past decades, the automotive industry has made significant efforts to improve engine fuel economy by reducing mechanical friction. Reducing friction under cold conditions is becoming more important in hybrid vehicle (HV) and plug-in hybrid vehicle (PHV) systems due to the lower oil temperatures of these systems, which results in higher friction loss. To help resolve this issue, a new internal gear fully variable discharge oil pump (F-VDOP) was developed. This new oil pump can control the oil pressure freely over a temperature range from -10°C to hot conditions. At 20°C, this pump lowers the minimum main gallery pressure to 100 kPa, thereby achieving a friction reduction effect of 1.4 Nm. The developed oil pump achieves a pressure response time constant of 0.17 seconds when changing the oil pressure from 120 kPa to 200 kPa at a temperature of 20°C and an engine speed of 1,600 rpm.

The renewed platform of the upcoming flagship front-engine, rear-wheel drive (FR) vehicles demands high levels of driving performance, fuel efficiency and noise-vibration performance. The newly developed driveline system must balance these conflicting performance attributes by adopting new technologies. This article focuses on several technologies that were needed in order to meet the demand for noise-vibration performance and fuel efficiency. For noise-vibration performance, this article will focus on propeller shaft low frequency noise (booming noise). This noise level is determined by the propeller shaft’s excitation force and the sensitivity of differential mounting system. In regards to the propeller shaft’s excitation force, the contribution of the axial excitation force was clarified. This excitation force was decreased by adopting a double offset joint (DOJ) as the propeller shaft’s second joint and low stiffness rubber couplings as the first and third joints.

Torque loss reduction at differential gear unit is important to improve the fuel economy of automobiles. One effective way is to decrease the viscosity of lubricants as it results in less churning loss. However, this option creates a higher potential for thin oil films, which could damage the mechanical parts. At tapered roller bearings, in particular, wear at the large end face of rollers and its counterpart, known as bearing bottom wear is one of major failure modes. To understand the wear mechanism, wear at the rolling contact surface of rollers and its counterpart, known as bearing side wear, was also observed to confirm the wear impact on the tapered roller bearings. Because gear oils are also required to avoid seizure under extreme pressure, the combination of a phosphorus anti-wear agent and a sulfurous extreme pressure agent are formulated.

Conventional CFD-based shape optimization technology that uses parametric shape modification and optimal solutions searching algorithms has the two problems: (1) outcome of optimized shapes depend on the selection of design parameters made by the designer, and (2) high computational costs. To resolve those problems, two innovative inverse analysis technologies based on the Adjoint Method were developed in previous study: surface geometry deformation sensitivity analysis to identify the locations to be modified, and topology optimization to generate an optimal shape for maximizing the cost function in the constrained design space. However, these technologies are only applicable to steady flows. Since most flows in a vehicle (such as engine in-cylinder flow) are transient, a practical technology for surface geometry sensitivity analysis has been developed based on the Transient Adjoint Method.

A new concept of an electromagnetic torque converter for hybrid electric vehicles is proposed. The electromagnetic torque converter, which is an electric system comprised of a set of double rotors and a stator, works as a high-efficiency transmission in the driving conditions of low gear ratio including a vehicle moving-off and as a starting device for an internal combustion engine. Moreover, it can be used for an electric vehicle driving as well as for a regenerative braking. In this concept, a high-efficiency drivetrain system for hybrid electric vehicles is constructed by replacing a fluid-type torque converter with the electromagnetic torque converter in the automatic transmission of a conventional vehicle. In this paper, we present the newly developed electromagnetic torque converter with a compact structure that enables mounting on a vehicle, and we evaluate its transmission efficiency by experiment.