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DENSO Develops Smaller, Lighter Components for Large Hybrid Vehicles
Date: 04/07/2005

Tokyo - DENSO Corporation has developed four new components for hybrid vehicles: a hybrid control computer; a battery-monitoring unit; a DC-DC converter, and an electric compressor for air conditioning systems. All are smaller and lighter than conventional components, but still able to meet the needs of today's larger hybrid vehicles.

In March, Toyota Harrier hybrid and Kluger hybrid vehicles with these components installed were launched in Japan. This month, the components will be introduced in the United States on the Lexus RX400h and Toyota Highlander hybrid.

Hybrid Control Computer
The hybrid control computer, developed jointly with Toyota Motor Corporation, integrates such control functions as hybrid system control, engine control, and battery control into one unit. The hybrid control computer enables a significant size reduction of the control units.

Battery-Monitoring Unit
The new battery-monitoring unit monitors the main battery's condition including voltage, current and temperature, which traditionally were performed by the battery ECU. The battery-monitoring unit was designed separately from the hybrid control computer, because the battery-monitoring unit needs to be installed close to the main battery.

DC-DC Converter
DENSO's newly developed DC-DC converter is approximately 10 percent smaller than a conventional DC-DC converter, but its increased output current from 100 amperes to 120 amperes is able to respond to the electric power needs of larger vehicles. DENSO achieved the increased output current by adopting a new circuit control technology to reduce energy loss in the DC-DC converter. To handle the increased output current, DENSO improved the converter's power elements by changing the mounting method from soldering to welding. Customized integrated circuits reduce the area of the converter's circuit board by approximately 40 percent, contributing to the 10 percent converter size reduction.

Electric Compressor
The electric compressor, jointly developed with Toyota Industries Corporation, is the first in the world to incorporate an inverter that drives the built-in motor. This structure reduces the compressor size by approximately 60 percent compared with a conventional electric compressor and inverter (when they are assumed to provide the same output). DENSO miniaturized the inverter by using simplified circuits and a higher-density mounting with three-dimensional wirings.

It is difficult to integrate the conventional compressor and inverter, because the conventional inverter is cooled by the engine's coolant system. To solve this problem, DENSO developed a new cooling method using air conditioning refrigerant in the compressor, allowing the integration of the electric compressor and the inverter. DENSO's unique segment conductor wiring method, which was developed for alternators in 2000, reduced the size of the built-in motor.

"DENSO has been providing components for hybrid vehicles since 1997 when the Toyota Prius was first introduced to the market," said Hiromi Tokuda, managing officer responsible for Powertrain Control Systems Business Group at DENSO Corporation. "Using our experience and expertise, DENSO will continue to develop new technologies and products for hybrid vehicles and contribute to vehicles that are less harmful to the environment."
DENSO Corporation, headquartered in Kariya, Aichi prefecture, Japan, is a leading global supplier of advanced technology, systems and components. Its customers include all the world's major carmakers. Worldwide, the company employs 95,000 people in 31 countries and regions, including Japan. Consolidated global sales for the fiscal year ended March 31, 2004 totaled US$24.2 billion. DENSO common stock is traded on the Tokyo, Osaka and Nagoya stock exchanges. For more information, go to

Battery-Monitoring Unit

DC-DC Converter



Sadayoshi Yokoyama
+81 566-25-5594

Toshiko Watanabe
+81 566-25-7889