DENSO Corporation has developed four new components for hybrid vehicles: a hybrid control computer; a new battery-monitoring unit; a DC-DC converter, and an electric compressor for air conditioning systems. All are smaller and lighter than conventional components, but meet the increasing needs of the growing number of larger hybrid vehicles.
Toyota uses the new Denso elements in its Lexus Rx400h (Harrier in Japan) and Toyota Highlander Hybrid (Kluger in Japan).
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 takes over the tasks of monitoring the battery’s voltage, current and temperature. 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% smaller than a conventional DC-DC converter, but delivers 20% more output—120 amperes from 100 amperes—allowing it to respond to the power needs of larger vehicles. DENSO adopted a new circuit control technology to reduce energy loss in the DC-DC converter,allowing it to size the unit. 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%, contributing to the 10% converter size reduction.
Electric Compressor. The electric compressor, jointly developed with Toyota Industries Corporation, is the first to incorporate an inverter that drives the built-in motor. This structure reduces the compressor size by approximately 60% 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 segment conductor wiring method, developed for alternators in 2000, reduced the size of the built-in motor.