JPS646986B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an energy-saving type power steering (POWER ASSIST) device that can change steering assistance in response to engine rotation or vehicle speed.

Generally, in power steering devices,
When the vehicle is stopped or running at low speeds, the supply of power fluid to the power cylinder (actuator) is increased to increase steering assistance to the steering wheel, and when the vehicle is running at high speeds, the supply of power fluid is decreased to assist steering wheel steering. It is well known that it is desirable to improve running stability by reducing .

Therefore, conventionally, in order to obtain the above-mentioned characteristics in a power steering device, for example,
As described in No. 54-9774, an electromagnetic clutch is used to control the drive of an oil pump that supplies power fluid using engine rotation, and for example, a large rotation angle is given to the steering wheel when stopped or when driving at low speed. Taking this into consideration, there is a power steering device that operates an electromagnetic clutch to provide steering assist force when the rotation angle of the steering wheel exceeds a predetermined value. However, in this type of conventional device, the effect of the steering assist force is determined by the rotation angle of the steering wheel, so when the vehicle is traveling at a relatively high speed, the steering wheel is suddenly steered near the planned rotation angle. The instability may lead to an extremely dangerous situation.

Furthermore, as described in Japanese Patent Application Laid-Open No. 54-111707, there is a type that uses an electromagnetic bypass valve to control the supply of power fluid from the oil pump to the power cylinder, or a type that controls the flow rate according to the vehicle running condition. In a type of power steering device that is regulated by a valve, when driving at high speeds, most of the oil pumped up by the oil pump, which continuously rotates at high speed in proportion to the engine rotation, is continuously returned to the oil tank, resulting in substantial Despite not doing much work,
Since engine consumption is large, this goes against the current demands for energy conservation.

In addition, recently, as part of energy-saving measures, there has been a trend to lower the engine speed during idling and at the same time to increase the maximum rotation range in order to make the engine smaller and lighter. In this case, the steering assist force is insufficient when power steering is most needed, such as when turning off the vehicle, parking in a garage, or driving at very low speeds.If the pump discharge amount is increased at low speeds, the engine will overdischarge in the high speed range of the engine, resulting in significant energy consumption. There are some inconveniences such as

The present invention provides an energy-saving type power steering device that is an improvement over the conventional power steering device as described above and is capable of changing the steering assist force by changing the oil pump rotation speed in response to vehicle speed steering. It is intended to.

The invention will be explained below with reference to illustrated embodiments.

FIG. 1 shows the configuration of an embodiment of the power steering device of the present invention. Steering
The wheel 1 is connected to an actuator 4 via a control valve 2 and a steering gear 3, and the actuator 4 and communication valve 5 are connected to an oil pump 6 via the control valve 2 by lines A and B. . The control valve 2 controls the amount and direction of power fluid supplied from the oil pump 6 to the actuator 4 in accordance with the steering of the steering wheel 1. The communication valve 5 has a valve body actuated by a pilot line C that transmits the pressure of oil supplied by the rotation of the oil pump 6, and is connected to the supply line A of the actuator 4,
By closing the bypass oil passage between B and thereby providing a power steering condition, when the oil pump 6 is rotating at an extremely low speed or has stopped,
A bypass oil passage between oil supply lines A and B is opened to eliminate steering assistance and provide a manual steering condition. The rotating shaft of the engine 7 is connected to the oil pump 6 via an electromagnetic clutch 8 having linear transmission characteristics.

A steering sensor 9 is also attached to the steering wheel 1, and this sensor is constituted by, for example, a small DC generator, and outputs an electric signal in accordance with the steering of the steering wheel 1. An engine rotation sensor 10 attached to the engine 7 outputs an electrical signal corresponding to the engine rotation speed by detecting, for example, an ignition pulse or integrating the pulse and converting it into an analog signal. Further, a vehicle speed sensor 12 detects the rotation of a wire/cable of a vehicle speedometer connected to the transmission gear 11, and outputs an electrical signal corresponding to the vehicle speed.

The electronic control circuit (not shown)
The output signals of the sensor 9, engine rotation sensor 10, and vehicle speed sensor 12 are input to the operating device 13, and when the steering wheel 1 rotates and the output signal of the steering sensor 9 is input, the engine rotation It is configured to amplify the AND amount of the output signal of the sensor 10 and the output signal of the vehicle speed sensor 12 and apply it to the electromagnetic clutch 8. Therefore, since the electromagnetic clutch 8 has a vehicle speed sensitive characteristic and also has a linear transfer characteristic, the excitation current of the solenoid coil of the electromagnetic clutch 8 is maximized when the vehicle speed is zero.
The rotation of the engine 7 is transmitted to the oil pump 6 without slipping, and the excitation current is variably reduced as the vehicle speed increases, thereby increasing the slippage. In this way, by electrically varying the degree of slip transmission by adjusting the magnetic field generated by the solenoid coil of the electromagnetic clutch 8, it is possible to obtain a steering assist force that changes with the vehicle speed. In the illustrated embodiment, the steering sensor 9 operates the electromagnetic clutch 8 with a preset transmission amount only during steering to drive the oil pump 6, but the detection signals from the vehicle speed sensor 12 and the engine rotation sensor 10 The oil pump 6 may be driven by operating the electromagnetic clutch 8 while continuing the transmission amount variable setting range. Further, the discharge amount of the oil pump 6 can be easily controlled by operating the electromagnetic clutch 8 only by the variable transmission amount of the detection signal from the engine rotation sensor 10. Furthermore, the illustrated embodiment is provided with a communication valve 5 that bypasses both chambers of the actuator 4 to avoid oil passage resistance during steering when the oil pump 6 rotates at an extremely low speed or has stopped and is not assisted.・Slight increase in steering torque in the manual range where pump 6 does not assist steering and mechanical strength of control valve 2 (torsion bar)
If this is taken into consideration, it is not necessary to use the communication valve.
As an electromagnetic clutch with linear transfer characteristics,
Specifically, a powder clutch uses magnetic iron powder and torque is transmitted by the coupling force between the magnetic iron powder and the frictional force between the magnetic iron powder and the operating surface in an excited state, or a mechanical clutch. A hysteresis clutch, etc., in which non-contact connection is performed purely electromagnetically without using frictional force, can be considered.

FIG. 2 is an example diagram showing the vehicle speed/pump rotation speed characteristics of the power steering device according to the present invention, in which a1 is the constant rotation range of the oil pump, a2 is the damping rotation range of the oil pump, and b is the vehicle rotation speed characteristic. The sensitive linear damping rotation characteristics are respectively shown, and D represents the operating point of the communication valve. Furthermore, FIG. 3 is an example diagram showing vehicle speed/pump rotation speed characteristics to explain the energy saving effect of the power steering device of the present invention, where c1 is the oil pump rotation range during steering operation, and c2 is the oil pump rotation speed range during steering operation. C3 indicates the oil pump stop range when the steering wheel is not operated, and c3 indicates the extremely low-speed warming/up rotation range of the oil pump when the steering wheel is not being operated, and the amount of oil discharged from the oil pump is reduced when power steering is not required. Or it can be understood that it will stop. Additionally, the communication valve operates in the high speed range at point D', bypassing both chambers of the actuator and providing manual steering.

Figure 4 shows the discharge characteristics of an oil pump used in a conventional power steering system in which the supply of power fluid from the oil pump to the power cylinder is adjusted by a flow control valve depending on the vehicle's running conditions. is a diagram comparing the discharge characteristics of the oil pump of the present invention, d1 is the apparent discharge characteristic of the oil pump, and d2 is the discharge characteristic of a general oil pump when no vehicle speed sensitive characteristic is added (this state (in which unnecessary pumped oil is returned to the tank by a flow control valve), e is the discharge characteristic of the oil pump according to the present invention. Therefore, in FIG. 4, the area is the ineffective oil pumping area, and according to the present invention, by operating the electromagnetic clutch having a linear transmission characteristic near point P, oil can be efficiently pumped within the effective oil pumping area. The pump can be operated.

In the embodiment shown in FIG. 1, the electromagnetic clutch 8 is shown to be directly connected to the oil pump 6, but a transmission that increases the rotation speed of the oil pump may be interposed, thereby reducing the Even if an oil pump with a smaller and lighter discharge capacity is used, sufficient steering assist force can be obtained during idling at a low engine speed or when driving at an extremely low speed.

As detailed above, according to the present invention, ON/
Unlike OFF control, a variable steering assist power steering effect is obtained according to the vehicle speed setting, so the driver does not feel any discomfort when steering.
The interlocking operation of the communication valve has the effect of smoothing the transition between the steering wheel and the steering wheel, thereby making it possible to stabilize the steering of the steering wheel.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, FIGS. 2 and 3 are vehicle speed/pump rotation speed characteristic diagrams in the device shown in FIG. 1, and FIG. 4 is a diagram showing the present invention. Pump rotation speed/pump discharge amount characteristic diagrams are shown for comparison between the invention and the conventional device. (Explanation of symbols), 1: Steering wheel,
2: Control valve, 3: Steering gear, 4: Actuator, 5: Communication valve, 6: Oil pump, 7: Engine, 8: Electromagnetic clutch,
9: Steering sensor, 10: Engine rotation sensor, 11: Mission gear, 12: Vehicle speed sensor, 13: Operating device.

Claims (1)

[Scope of Claims] 1. A power steering device for a vehicle that assists steering by controlling an oil path of a control valve in response to steering of a steering wheel and supplying fluid discharged from an oil pump to an actuator, comprising: a vehicle engine; an electromagnetic clutch that is driven by the rotation of the vehicle engine and transmits the rotation to the oil pump; and a control device that is electrically connected to the electromagnetic clutch and controls the amount of rotation of the vehicle engine transmitted to the oil pump. (b) applying an excitation current to the electromagnetic clutch in response to a vehicle speed detection signal obtained by detecting the vehicle speed and a rotation detection signal obtained by detecting the rotation of the engine; When the vehicle speed is zero, the excitation current is maximized to transmit the rotation of the engine to the oil pump without slipping, and as the vehicle speed increases, the excitation current is variably decreased to increase slippage, thereby increasing the vehicle speed. (b) A preset auxiliary excitation current is always applied to the electromagnetic clutch in order to obtain a steering assist preparation state by rotating the oil pump at a low speed in advance. , when the steering wheel is operated, the excitation current is superimposed on the auxiliary excitation current to drive the electromagnetic clutch in response to a steering detection signal obtained by detecting a steering force or a steering angle. The power steering device characterized in that it is configured as follows. 2. The actuator is provided with a communication valve that bypasses both chambers of the actuator when the oil pump is rotating at a low speed or is stopped, so that a manual steering state is achieved in which steering is not substantially assisted. A power steering device according to claim 1.