外文翻译原文
Development of Controlled Electric Motor-Driven Pump
Type Hydraulic Power Steering System
Y. Obata Y. Teramae K. Yamamoto
Within a frame of development of ecological power steering systems, we have completed the development of an electric motor-driven pump type hydraulic power steering system,equipped with not conventional brushed motor but brushless motor controlled by ECU, which has achieved a further energy saving. The following describes the content of this system.
key words: energy saving,hydraulic power steering, brushless motor
1. Introduction
From a viewpoint of recent global ecological problems, an improvement of fuel consumption and exhaust gas regulations such as the Japanese Automobile NOx law have been coming to be world wide important issues.
Regulations and taxations that each country tends to impose for environmental protection are enumerated as follows
①Europe:Introduction of carbon taxation in each country ②Japan:Regulation of fuel consumption since 2000
③U.S.A.:Intensification of CAFE (Corporate Average Fuel Economy) regulation, activity of EPA(Environmental Protection Agency) and ARB(Air Resources Board)
On today's vehicles driven by gasoline engine or diesel engine, a hydraulic power steering (called hereafter \of which the power source is an engine-driven hydraulic pump is generally mounted.
In this power steering system, a hydraulic pump as mentioned above is rotated in proportion with a revolution speed of engine and runs at high
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revolution speed even during a straight-ahead and high-vehicle speed driving with no steering operation, regardless of a necessity for power assistance, so that it always consumes a wasteful energy. It is said that an energy consumed by such power steering system represents approximately 3% of all the vehicle fuel consumption. Therefore, a request for energy saving in such power steering system would be more and more intensified hereafter.
In fact, the conventional engine-driven hydraulic pumps have been subjected to different trials such as an application of lower flow rate with higher pressure and an implementation of energy saving. However these trials have exerted an effect not drastic but limited to certain extent on the fuel economy. In response to a request for further fuel economy, we have developed an energy saving type power steering system that is a hydraulic power steering system, but comprising a pump driven by an electric motor as a power source independent of engine, so that a drastic fuel economy can be realized.
The following is a description of this electric motor-driven pump (called hereafter \\
2. Outlines of Electric Motor-Driven Pump Type Hydraulic Power Steering System (H-EPS)
2. 1 Second Generation H-EPS
Since 1989 we have produced in France an electric pump (First generation type, without a controller) constituted by high efficiency gear pump, and since 1998 we have produced therein a pump of the same kind (Second generation type) equipped with a brushed DC motor having its revolution speed controlled by a remote controller. This type does not use an external sensor, but a motor current detection circuit inside of the controller for calculation of motor current variation. This method allows a judgment of steering condition and a control of motor revolution speed by a variation of motor driving voltage. As a result, an energy saving can be realized by an efficient control of electric pump module
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with a low cost type controller.
This control method consists of lowering the motor revolution speed during no steering operation (standby mode) and increasing it when any steering operation requires power assistance (power mode) for the power steering system operation. Transition from the standby mode to the power mode is realized by controlling the motor revolution speed as a function of the amount and rate of a motor current variation under given pressure rise at steering operation. However this method could provide a low responsiveness at the mode transition and make steering feeling easily worse, so that some solution should be taken such as a higher motor revolution speed at standby mode. If not, this method would contribute a little to energy saving.
As a system having a responsiveness better than that for the second generation electric pump and targeting further energy saving, we have developed the third generation electric pump which integrates a brushless DC motor and a controller. This pump has been equipped with the 1.4 L to 2.0 L of PSA 307 vehicles (succession to 306) since spring, 2001.
2. 2 Structure of Third Generation H-EPS
An example of structure of this system is shown in Fig. 2.
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