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In Japan, from the viewpoint of ozone layer protection, specified CFCs (Chlorofluorocarbons) phase-out started in 1992 and completed by 1995. HFC-134a (Hydro fluorocarbon-134a) is now dominant in the market. HFC-134a, the replacement, has zero ozone depleting potential, while it still has a higher global warming potential (GWP = 1430). In this paper, efforts of DENSO and the Japanese industry from aspects of refrigerant emission reduction and energy efficiency improvement are introduced.

We have developed a novel wafer process for capacitive sensing accelerometer using surface Micro Electrical Mechanical Systems (MEMS) technology and successfully applied to the fabrication process. Our new process combines with a single crystal SOI (Si on Insulator) wafer, high aspect ratio silicon etching and newly developed anhydrous HF/Alcohol etch process of silicon oxides. Although wet conditions such as HF/water etch occurs stiction of mobile structure, our anhydrous HF/Alcohol etch process technology occurs no stiction of mobile structures, because of gas phase (dry) process. In our process, we have achieved smaller-sized sensor chip compared to our conventional 2 axes accelerometer.

In a conventional soldering process, solvents, such as chlorofluorocarbons (CFCs), have been necessary to remove the flux-residue after soldering. A new CFC-free fluxless soldering process has been developed to obtain high sealing ability even in a small soldering area. This new process utilizes a reducing atmosphere with an appropriate load and assembly orientation to solder the parts. Under this fluxless condition, it is found that appropriate loading and good solder-wettability of the upper part increase the wettability of the lower part.

Increasing electric loads in a vehicle causes over-discharge of a battery and drag torque due to an alternator. This paper gives a system concept of vehicle electric power flow management to solve these issues. Its primary function includes preserving electricity in a battery, stabilizing electric bus voltage, interfacing with vehicle torque control system, and improving fuel economy. The key point to realize such a system is a unified structure. It offers ‘Plug and Play’ function for electric power management components. Newly developed Vehicle Electric Power Flow Management System (VEF ) totally controls electric power flow in a vehicle. VEF contains an Electric Power Manager and its functional sub-systems, and controls them with the key parameter ‘electric power’. The sub-system includes Generation, Storage, Conversion, and Distribution to the loads.

We have achieved significant weight reduction for the MS (Multi-Tank Super Slim Structure) Evaporator (1)currently in production at DENSO CORPORATION. The evaporator of HVAC unit, located in the instrument panel, is a component of the aluminum heat exchanger used in automotive air conditioners. The new evaporator uses thinner quad-layer sheet material, thanks to optimization of the electrical potential among its outer filler metal, intermediate anodic layer and core. The evaporator is thus lighter than conventional evaporators, but retains equivalent corrosion resistance.

In conventional automobile designs, a radiator and a condenser are typically configured and mounted independently of each other. We have developed a smaller and more powerful cooling module by integrating these two products into one piece. The new cooling module has been designed to share the fin material and to have an insulating slit and other means for effective prevention of heat loss that occurs due to thermal conduction between the radiator and the condenser1). In addition, as one of the key techniques for integrating fins, we studied thermal spraying of brazing filler to the tube material and were able to achieve a practical-level cooling module through use of high-performance fins, contributing largely to the efforts to create a more compact, higher performance cooling module.

As automobiles become quieter, wiper operation noise becomes more noticeable. Squeal noise is one type of wiper operation noise. It is a high-frequency self-excited vibration that is easily generated before and after the wiper reverses direction. In analyzing this vibration, squeal noise was observed using a rotary disk system. Then FEM was applied to deduce an equation of motion that reflects the observation results. The equation suggests material and configuration approaches toward reducing squeal noise. Potential measures include improvement in the blade damping coefficient, reduction in the coefficient of friction by surface treatment, and an increase in neck thickness, etc. Implementation of these measures reduced squeal noise.

Carbon brushes for automotive starters are used under severe conditions of high electric current density, high contact pressure and high sliding velocity. Therefore lead has traditionally been added to brushes to improve performance and durability. Lead is an environmental hazardous substance. In the EU, the law prohibits adding lead to brushes for electric motors which is installed on new automobiles in and after January 2005. In order to develop the lead free carbon brush for starters, we analyzed the effect and selected substitutive substance of lead. Adding lead to the brush reduces the electric resistance increase of the brush in high-temperature and high-humidity atmosphere and in high-temperature atmosphere. Furthermore lead reduces the wear amount of brush. We developed the lead free brush surpassing the lead addition brush in performance and durability by addition of lead alternatives silver and zinc.

We have developed a novel capacitive acceleration sensor fabrication process by applying surface MEMS (Micro Electro-Mechanical System) technology and successfully introduced this process for volume production of a new super slim sensor. The new process uses the ICP-RIE(Inductively Coupled Plasma - Reactive Ion Etching) technology to etch single crystal SOI(Si on Insulator wafers. In this technology, vertical Si etching is followed by, lateral etching along the buried oxide to release the movable electrode. Because of a dry process, the new process does not cause the movable structures to stick to each other. Our process uses only three masks and reduces the sensor chip size to a half that of our conventional capacitive acceleration sensors.

A lot of electric components have been installed in a vehicle today for comfort, safety and environment. This tendency is said to be continued in the future. Therefore, additional power supplies such as exhaust gas electricity generation system and thermal electricity generation system have been developed in the world to supply additional electricity as well as an enlargement of an alternator. However, if these new electricity supply systems are installed in a present electric power system that is controlled based on a voltage feedback, each supply system cannot be controlled effectively, because it is difficult to control output power of each system independently. An electric power based control system, Vehicle Electric power Flow management system (VEF), has been developed to avoid this problem. Sum of required electric power is calculated based on electric loads power and battery charging power. This required power is allocated to each power supply system.

Through the years, aluminum automotive heat exchangers have been developed in order to have a high performance and a light weight. Therefore, the thickness of the aluminum sheets for the application has been reduced. As the brazeability declines with the reduction in thickness, fins having a thickness under 80μm may be difficult to secure a good brazeability. Therefore, we studied the brazeability to determine the limit of thickness using clad fins from 40 to 80μm. The fillet volume formed at the joints of the fin and tube decreased with the decreasing fin thickness and the Si content in both the filler metals and the core alloys. The suitable range of Si content in the filler metals and the core alloys to obtain a good brazeability decreased with the decreasing fin thickness. When the fins were thinner than the critical values, it was impossible to have a good brazeability.

In general, automatic braking uses an electric stability control (ESC) hydraulic unit that can automatically increase the hydraulic pressure in the wheel cylinder (hereinafter called wheel pressure), independent of the driver’s braking operation. The hydraulic unit should have sufficient pressure response to apply autonomous emergency braking (AEB). It was necessary for the hydraulic unit to have a high flow rate for the pressure response. To satisfy the performance requirements of the AEB, a brushless motor, which has a high maximum rotational speed and good response, is adopted for the hydraulic unit. Furthermore, sensorless control, which does not require a rotation angle sensor, has been developed so that the motor size can be small and common to conventional units. The developed sensorless control can switch the driving methods in three states: pre-rotation, low speed, and high speed.

Recently, automotive semiconductor devices need miniaturization. One of the most important technologies is the package which encapsulates devices. In addition, the outer shape of the package is needed to change according to the mounted space. Conventional devices are mounted in the case, and encapsulated with potting resin. However this package structure is difficult to miniaturize because the case size limit. This report describes the development of the packaging technology for miniature and particular outer shape. The devices are set in the cavity and molded to one package. The three-dimension flow simulation is applied to analyze the flow in the cavity. The results of simulation correspond with experimental results. The cavity structure and the mold resin can be optimized by the simulation.

Having a light weight, a good heat conductivity and a good brazability, aluminum alloy is widely used for automotive heat exchanger systems. The major problem with Aluminum is perforation of the tube by pitting corrosion and corrosion protection is necessary in the field. In radiator and condenser systems using the the Nocolok brazing process given good corrosion resistance using cathodic protection with sacrificial anode made of Zn-sprayed onto tube or low corrosion potential fins etc. On the other hand, in drawn-cup type evaporators, that are fabricated from brazing sheet tubes in vacuum brazing method and then covered low electro-conductive drain water film in operation, the effect of cathodic protection by the anode fin is limited to a very small area. Therefore, this has been studied to improve self-corrosion resistance of the core in the brazing sheet tube.

Toyota Motor Corporation has developed a new battery electric vehicle (BEV) on the dedicated e-TNGA platform for BEVs, which was designed to lower the center of gravity of the vehicle and increase body stiffness. In addition to a full-time 4WD system, another feature of this new BEV is its pleasurable driving experience. A new inverter drive unit was developed for this system. Unlike the previous inverter, the advantage of the new inverter is that it is small enough to be mounted inside the transaxle housing, thereby contributing to the availability of interior and luggage space. The temperature rise of the power semiconductors in the inverter was reduced considerably by the development of a new power semiconductor for BEVs. This enables a parallel layout of two power semiconductors instead of three. The components of the inverter were also downsized. A coreless current sensor was adopted, and capacitors were developed with significantly lower capacitance.

Reducing vehicle CO2 emissions is an important measure to help address global warming. To reduce CO2 emissions on a global basis, Toyota Motor Corporation is taking a multi-pathway approach that involves the introduction of the optimal powertrains according to the circumstances of each region, including hybrid electric (HEVs) and plug-in hybrid electric vehicles (PHEVs), as well as battery electric vehicles (BEVs). This report describes the development of a new PHEV system for the Toyota Prius. This system features a traction battery pack structure, transaxle, and power control unit (PCU) with boost converter, which were newly developed based on the 2.0-liter HEV system. As a result, the battery capacity was increased by 1.5 times compared to the previous model with almost the same battery pack size. Transmission efficiency was also improved, extending the distance that the Prius can be driven as an EV by 70%.