电动马达驱动泵控制的液压动力转向系统的发展外文翻译.doc

外文翻译原文Development of Controlled Electric Motor-Driven Pump Type Hydraulic Power Steering SystemY. Obata Y. Teramae K. YamamotoWithin 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 motor1. IntroductionFrom 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 followsEurope:Introduction of carbon taxation in each countryJapan:Regulation of fuel consumption since 2000U.S.A.:Intensification of CAFE (Corporate Average Fuel Economy) regulation, activity of EPA(Environmental Protection Agency) and ARB(Air Resources Board) On todays vehicles driven by gasoline engine or diesel engine, a hydraulic power steering (called hereafter NPS) 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 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 electric pump) type hydraulic power steering system (called hereafter H-EPS).2. Outlines of Electric Motor-Driven Pump Type Hydraulic Power Steering System (H-EPS)2. 1 Second Generation H-EPSSince 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 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-EPSAn example of structure of this system is shown in Fig. 2.In this system, its steering gear is the same as for the normal hydraulic power steering, while a source of hydraulic pressure is changed to a pump driven by a brushless DC motor powered from a battery. Accordingly this system comes to beable to provide a steering feel as smooth as the conventional normal hydraulic power steering system.In addition, this system aims at supplying required amount of oil to its steering gear more precisely and rapidly by means of a combination of a steering angle sensor and a brushless motor, for contributing to energy saving much more than that of the conventional second generation type.2. 3 Structure of Electric Pump ModuleThis structure, which is represented by a modularization of a brushless motor, controller, gear pump and reservoir, has a flexibility in packaging on vehicle regardless of its location. In addition, arrangement of the controller between the pump and motor has come to reduce an exothermal energy of different electronic components in the controller and motor under cooling effect of oil in a pump body.Cost reduction also has been tried by decreasing the number of components in this module at the transition from the 2nd generation type to the 3rd generation type.For pump itself, a pressure-balanced type gear pump has been adopted since the 1 st generation module and its efficiency has been much better than that of a conventional vane pump. Figure 3 shows a model diagram of the gear pump for this module.The operational principle of this pump is identical to that of normal gear pumps, wherein hydraulic oil is sucked through its suction port and introduced into teeth-spaces of its gears when its driving and driven pinions are driven by a motor, and then carried continuously toward its discharge side. As shown in Fig. 3, this pump is remarkably characterized by a function as bearing of its side plate enabling both the pinions to be floated for a limitation to the minimum level of bearing friction. In addition, a high pressure leaked oil circuit as formed in a groove of the bearing portion can serve as a lubrication for prevention of an increasing wear on the portion. And an introduction of high pressure oil into the rear side of the side plate allows the rear side to counterbalance in pressure the tooth side, so that a constant thrust force can be designed to be always applied on such side faces in a range from low pressure to high pressure.Such structure as mentioned above has come to enable this pump not only to have an efficiency much higher than that of the vane pump as shown in Fig. 4, but also to realize the downsizing and energy saving.2. 4 Pulsation of PumpFigure 5 shows a comparison of pulsation value without steering operation on a vehicle idling condition between with this electric pump and with an engine-driven pump. When an engine is being idled, the electric pump is in a standby control mode so that its discharge flow rate is at low level. Accordingly this pump can produce a pulsation lower than the engine-driven pump so that the former has an advantage over the latter for pump Goo (groaning) noise. In addition, reduction of abnormal noise gets easier on the former than on the latter. As for piping, a smaller pulsation would lead to a smaller vibration, thus allowing a simplification of piping structure by, for an example, a disuse of flexible tube as well as a simplification of clamp-like piping fitting, and a consequent cost reduction expected.3. Outlines of motor Control for H-EPSControl of H-EPS system consists in optimizing the control of a motor as a power source in connection with a hydraulic pump. As shown in Fig. 6, a controller is allowed to set a target value of motor revolution speed according to signals from a steering angle sensor and a vehicle speed sensor. For adaptation of a motor revolution speed to its target value, a signal from a motor revolution sensor (Hall element sensor) is fed back to loop control circuit so that an appropriated revolution can be transmitted to the hydraulic pump for realization of optimal steering feel. The following is a description of this control.In order for further improvement in responsiveness and energy saving of the above-mentioned standby control, a Stop & Go control has been developed by application of a low-inertia brushless motor excellent in starting property and a steering angle sensor as an external sensor.The Stop & Go control has basically the same principle as the standby control, that is, consisting in stopping the motor at no steering operation such as straight ahead driving and vehicle stopping and then ramping up the motor promptly from its stop status to its target revolution speed once steering operation begins, by calculation of a steering speed from an output signal of the steering angle sensor followed by instantaneous definition of a motor revolution speed suitable to generation of an optimal assistance force.In this control, a lower oil flow rate at no steering operation can restrict an oil temperature increase, so that no oil cooler comes to be required.The following controls are adopted in this Stop & Go control: Steering speed control: Correction by variation of motor revolution speed as a function of steering speed is made in order for oil flow into hydraulic valve to be keep constant. Figure 7 shows a control of motor revolution speed as a function of steering speed.Motor starting control: By a variation of motor starting voltage as a function of steering speed, a motor can be gradually started at an extremely low steering speed while instantaneously started at a high steering speed. Figure 8 shows a control chart of motor starting voltage as a function of steering speed.3 Vehicle speed control: Fig. 9 shows a control chart of motor revolution speed vs vehicle speed.The power steering system allows a steering effort to become lighter at low vehicle speed and heavier at high vehicle speed for stability in steering, by a control of motor revolution speed, for the propose of providing a good steeringfeel .4. Evaluation Result of H-EPS4. 1 Basic Performance of Electric PumpCharacteristics of flow rate vs pressure, of motor revolution speed vs pressure and of motor current vs pressure are shown in Fig. 10. Figure 11 shows representative characteristics of motor revolution vs steering speed, of motor current vs steering speed and of flow rate vs steering speed, at a vehicle speed of 20km/h. Figure 12 shows characteristics of vehicle speed vs flow rate and of vehicle speed-vs motor current.4. 2 Starting Characteristic of Electric Pump at Low TemperatureAgainst a concern about discharge inferiority at low temperature to conventional engine-driven hydraulic pump, the electric pump adopts not only a gear pump capable of discharge even at low revolution speed, but also a control enabling a motor to achieve its full running at low temperature by means of a temperature sensor.Figure 13 shows characteristics of flow rate/current as a function of time at-40 C.4. 3 Bench Test Result of Evaluation of Fuel ConsumptionAs shown in Fig. 14, the same simulation system as on vehicle configuration was built up on bench for fuel consumption measurement and an energy as consumed by the electric pump and by the engine一driven hydraulic pump respectively was measured thereon. Figure 15 shows the result of such measurement. Consuming an energy half as much as the 2nd generation electric pump and also 20% max. as much as the engine-driven hydraulic pump, the 3rd generation electric pump was proved to provide a large energy saving effect.4. 4 Result of Evaluation of Responsiveness on Vehicle.Figure 16 shows the result of responsiveness measurement (at steering in a parking condition) for an electric pump and an engine-driven pump, which were respectively installed on vehicles with the same front axle load. As the electric pump is equipped with a standby control capable of setting a pump revolution speed enough for the minimum responsiveness so as to reduce any extra discharge flow, it comes to have a responsiveness lower than the engine-driven pump. However, some set value of parameters could allow it to provide a responsiveness equivalent to that for the engine-driven pump, in other words, it comes to have an advantage in defining a condition in favor of both the energy saving effect and the responsiveness.4. 5 Reliability Test for H-EPSFor reliability, an electric pump has been subjected to various tests under every on-vehicle condition such as steering conditions and environmental conditions and it has already been proved to have a reliability equivalent to that for the engine-driven pump.H-EPS systemPerformance test at low temperatureRotational input endurance testTemperature rise property test and othersElectric pumpLow temperature parking condition steering testHigh temperature parking condition steering testLow vehicle speed driving test (with steering operation)High vehicle speed straight-ahead driving test High temperature operation endurance testHeat shock testTransient voltage test and others5. ConclusionWithin a frame of our engagement in development of energy saving type power steering systems designated as ecological products, we have achieved the mass production of electric motor driven pump type hydraulic power steeringsystem (H-EPS), which not only has been remarkably improved in terms of fuel economy in relation to the conventional normal hydraulic power steering system, but also targets small passenger car. However in response to a request for installation of this H-EPS system on even small track and medium-class passenger car, the relevant motor needs to be powered up. In this case, electric current would come to be largely consumed in such system if 12V battery is applied, so that the connectors, harness, battery and alternator could be largely loaded. That is the reason why a system applicable at high voltage such as 42V (expected to be international standard instead of 12V) needs to be developed immediately. In this line, we would like to direct our efforts hereafter towards a development of energy saving type power steering systems applicable at high voltage.外文翻译电动马达驱动泵控制的液压动力转向系统的发展Y. Obata Y. Teramae K. Yamamoto在生态动力转向系统的发展框架内，我们已经完成了一个电动马达驱动泵液压动力转向系统的发展，它不是传统的有刷电机，而是无刷电机ECU的控制，并且取得了进一步的节能装备。下面介绍了该系统的内容。关键词：节能、液压动力转向、无刷电机1 介绍从近期全球生态问题和改善燃油消耗和废气来看，如日本汽车氮氧化物排放的法律法规问题已成为世界各地的重要问题。每个国家往往对环保法规和税费列举如下：欧洲：每个国家的碳排放税简介日本：自2000年以来燃料消耗的规例美国：集约化的CAFE（企业平均燃油经济性）规例，有活力的EPA（环境保护局）和ARB（空气资源委员会）在今天的汽油或柴油驱动的发动机车辆，液压动力转向系统的动力源一般来自于安装的发动机驱动的液压泵。在此动力转向系统中，液压泵与上述发动机按一定比例的转速旋转，并常在高转速下运行，即使车辆在高速行驶时没有转向操作与直线前进，也都必需电力援助，所以它总是消耗浪费能源。这就是说，这样的动力转向系统所消耗的能量，约为所有的汽车燃料消耗量的3。因此，这样的动力转向系统的节能要求会更多。事实上，传统发动机驱动的液压泵已经受了不同的试验，如在低流量和较高的压力下的应用，还有节能的实施。然而，这些试验的施加对结果的影响并不剧烈，不过对一定程度上的燃油的经济性有限制。在进一步对燃油经济性的要求下，我们已经开发了一种节能型动力转向系统，它就是液压动力转向系统，它包含一个被独立的发动机作为电动马达驱动的泵，因此大幅燃料的经济性可以实现。以下是对这电动马达驱动泵（以下简称“电动泵”）液压动力转向系统的说明。2 电动马达驱动泵液压动力转向系统的轮廓2.1 第二代的电动马达驱动泵液压动力转向系统自1989年以来，我们已经在法国生产出了由高效率的齿轮泵构成的电动泵（第一代，不带控制器），自1998年以来，我们已经生产出了其中同一类型的（第二代）配备有刷直流电动机的泵，它的转速由一个遥控器控制。这种类型的泵不使用外部传感器，但它的电机的内部电路的电流检测的结果来自于电机控制器的电流变化的计算。此方法适合转向条件下的判断和电机驱动电压的变化来控制电机转速。它的结果是可实现节能高效与低成本控制器来控制电动泵。这种控制方法，包括在没有转向操作（待机模式）时降低电机转速和增加任何转向操作时需要动力转向系统运作（功耗模式）。从待机模式到功耗模式的过渡，实现了电机转速控制量的功能和转向操作下当压力上升时的电机电流变化率情况。然而，这种方法可提供在模式转变下的低响应，会使转向感觉很容易恶化，所以应该有一些解决方案被提出，如电机转速较高时应该采取待机模式。如果不是这样的话，这种方法对于节约能源的贡献就很小了。在要求响应比第二代电动泵更好的和进一步把节能作为目标的系统要求下，我们已经开发出第三代电动泵，它集成了直流无刷电机和控制器。自2001年春季以来该泵已配备了由1.4升到2.0升的307型（继承了306型）变压吸附器。2.2 第三代的电动马达驱动泵液压动力转向系统的结构该系统的一个结构例子如图 2。在这个系统中，其转向器与通常的液压动力转向相同，不同的是该系统由电池供电的无刷直流电电机驱动泵来作为液压源。因此，本系统能够提供一个像传统的液压动力转向系统那样顺利转向的感觉。此外，该系统旨在提供所需的石油量的转向器，以达到更准确和迅速的转向角传感器和无刷电机相结合的方式，它在促进节能方面比传统的第二代类型做了更多的贡献。2.3 电泵模块结构这种结构被一个无刷电机的模块化，控制器，齿轮泵和水库表示，无论其在何位置都保证了车辆包装的灵活性。此外，安排控制器在泵和电机之间，以减少在泵体下控制器和电机在不同的电子元件放出能量时油的冷却效果。从第二代类型到第三代类型的过渡时期一直在试图通过减少此模块中的元件数量来降低成本。对于压力平衡式齿轮泵本身而言，自从其第一代模型以来，其效率已经比传统叶片泵好很多了。图3显示了此模型的齿轮泵的模型图。这种泵的工作原理与通常的齿轮泵是相同的，其中液压油通过其吸入口被吸入，并在运作和电动机驱动齿轮转动时引入其齿轮空间，然后在排出端连续进行。正如图3所示，该泵的显著特点是通过其侧面板使两个齿轮轴承摩擦在最低水平，以达到限制轴承浮动的功能。此外，高压泄漏油路中形成轴承部分的凹槽以提高磨损增加部分的润滑。高压油被引入到侧板背面以达到后侧齿侧压力的平衡，这样一个恒定的推力可以始终适用于变动于低压到高压范围等方面。正如图4所示的叶片泵，上述的这种结构已经用于此泵，它不仅能实现很高的效率，而且还实现了裁员和节约能源。2.4 泵的脉动图5显示了车辆在没有转向操作空转状况下与泵在一个发动机驱动泵状况下脉动值的比较