JPS6025855A - Power steering device - Google Patents

Abstract

PURPOSE:To enable to easily control the characteristic of power assisting force without developing over-discharging of battery and large power loss by a method wherein an engine-driven pump is used during low speed running, while motor-operated pump is used during high speed running. CONSTITUTION:A controller 32 is connected to an electromagnetic clutch 25 and an electric motor 27 and controls the operations of the electromagnetic clutch 25 and of the electric motor 27 by a signal sent from a vehicular speed sensor 33. The controller 32 processes the signal sent from the vehicular speed sensor 33 so that an ''ON'' signal is issued to the electromagnetic clutch 25 when a vehicle runs at low speed and an ''OFF'' signal is issued to the electromagnetic clutch 25 and at the same time an ''ON'' signal is issued to the electric motor 27 when the vehicle runs at high speed.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a power steering device.

(Prior art) Steer 1J is used as a power steering device for automobiles.
A vehicle speed sensitive type vehicle has been known in which the amount of pressure oil supplied to a power cylinder that assists the steering force of the engine is reduced in accordance with an increase in vehicle speed, thereby reducing the power assist force.

In the power steering system mentioned above, it is common practice to supply pressurized oil to the power cylinder using an engine-driven oil pump, but in order to reduce the power assist force during high-speed driving, a large amount of excess pressure is It is necessary to drain the oil using a valve inside the pump, which causes a large loss in terms of power.

On the other hand, there is an idea of supplying pressure oil to the power cylinder with an electric motor-driven oil pump, but in low-speed driving conditions where a large power assist force is required,
In order to increase the rotational speed of the electric motor, a large amount of electric power is required, and since the amount of power generated by the generator is small in this low-speed driving state, there is a need to increase the capacity of the battery.

On the other hand, there is a proposal to use multiple engine-driven oil pumps and use these pumps depending on the power steering load, as disclosed in Japanese Patent Application Laid-Open No. 56-727560 (1986-727560). In this case, it is necessary to reduce the amount of pressure oil supplied with predetermined characteristics, making it difficult to set the characteristics of the oil pump and making it impossible to control the pressure oil supply lid sufficiently.

(Object of the invention) The present invention supplies pressure oil to the power cylinder by using an oil pump driven by an engine and an oil pump driven by an electric motor. By operating the pump and operating the electric pump in high-speed driving conditions,
By making full use of the characteristics of both pumps, it is possible to easily control the amount of pressure oil supplied.

(Structure of the Invention) A power steering device according to the present invention includes a power cylinder that assists steering force, an engine-driven pump that is driven by an engine and supplies pressure oil to the power cylinder, and a power steering device that is driven by an electric motor to provide power. It includes an electric pump that supplies pressurized oil to the cylinders, a driving condition sensor that detects the driving condition of the vehicle, and a controller that receives signals from the driving condition sensor and issues operating commands for the engine-driven pump and the electric pump.

The controller processes the signal from the driving condition sensor so that the engine-driven pump operates only when the vehicle is running at low speed, and processes the signal from the driving condition sensor so that the electric pump operates with predetermined characteristics depending on the driving condition when the vehicle is running at high speed. The device is configured to process the signal of the condition sensor.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In the power steering device 1 shown in FIG. 1, 2 is a steering wheel, 3 is a left and right wheel constituting the front wheels of an automobile; It is.

In this steering linkage 4, 5 is a steering shaft whose upper end is connected to the steering wheel 2, 6 is an intermediate shaft, and 7 is a lower shaft, in which a pinion 8 at the lower end of the lower shaft 7 meshes with a rack 10 of a rack shaft 9. Both ends of the shaft 9 are connected via tie rods 11 to knuckle arms 12 that support the wheels 6.

A power cylinder 13 that assists the steering force of the steering wheel 2 is attached to the rack shaft 9. The power cylinder 16 includes a piston 1 fixed to a rack shaft 9.
4 into a first chamber 15 and a second chamber 16. This first room 15 and the 1st! The chamber 16 communicates with a gear control valve 17 attached to the lower shaft 7 through oil passages 18 and 19.

The upstream side of the pressure oil supply path 20 connected to the gear control valve 17 is the first supply line w! It branches into r21 and a second delivery route 22. An oil pump driven by an engine 26 via a transmission belt 24 and an electromagnetic clutch 25, that is, an engine-driven pump 26, is connected to the first supply path 21, and an oil pump 26 is connected to the second supply path 22, which is driven by an electric motor 27. An oil pump, ie, an electric pump 28, is connected. A check valve 29,30 is arranged in each of the two supply channels 21,22. Further, a return passage 61 extends from the gear control valve 17.

A controller 62 is connected to the electromagnetic clutch 25 and the electric motor 27, and the controller 62 controls the operation of the electromagnetic clutch 25 and the electric motor 27 based on a signal from a vehicle speed sensor 66. In FIG. 1, 64 is a battery.

In the above configuration, the gear control valve 17 directs the pressure oil supply direction to the oil path 18 in accordance with the steering direction of the steering wheel 2.
and the oil passage 19, and the first chamber 15 of the power cylinder 16
Alternatively, pressure oil is supplied to the second chamber 16, thereby assisting the steering force of the steering wheel 2. The flow of pressure oil is indicated by arrows along each oil path in the figure.

Next, to explain the characteristics of the controller 62, the controller 62 processes the signal from the vehicle speed sensor 66, issues an ON signal to the electromagnetic clutch 25 when the vehicle is running at low speed, and issues an ON signal to the electromagnetic clutch 25 when the vehicle is running at high speed.
It has a function of emitting an off signal to the electric motor 27 and also emitting an @ sign with a predetermined output characteristic to the electric motor 27. The output characteristics of the controller 62 in this high-speed running state are shown in FIG.

That is, the controller 62 passes a high current to the electric motor 27 when the vehicle enters a high-speed running state exceeding the set vehicle speed v□, and gradually decreases the magnitude of the current I to the electric motor 27 as the vehicle speed increases, thereby achieving the set speed. When the vehicle speed reaches V1, a constant current ■1 is applied to the electric motor 27 from then on.

Therefore, the engine-driven pump 26 and the electric pump 27
The characteristics of the amount of pressure oil supplied to the power cylinder 16 when used in combination with the above are shown in FIG. In this case, the engine-driven pump 26 is equipped with a valve that drains pressure oil exceeding a set oil amount, and the upper limit of the pressure oil supply amount q is made constant depending on the characteristics of the valve. In addition, the electric pump 28
The output characteristics of the controller 62 are set so that the maximum amount of pressure oil supplied by the engine-driven pump 26 is equal to the amount of pressure oil supplied by the engine-driven pump 26. The amount of pressurized oil supplied in the high-speed running state decreases as the vehicle speed increases in proportion to the output characteristics of the controller 62 shown in FIG.

Therefore, the steering torque of the steering wheel 2 remains approximately constant regardless of the vehicle speed.

In the above embodiment, the electric pump 28 is connected to the vehicle speed sensor 3.
I tried to control it with the signal from steering wheel 6, but the steering wheel 2
A steering sensor that detects the steering speed of the vehicle is connected to the controller separately, and in addition to being controlled by the signal from the vehicle speed sensor 63, the pressure oil supply amount of the electric pump 28 is controlled by the signal from the steering sensor as the steering speed increases. It is said that control is performed to perform an increase correction as shown in the characteristic indicated by the chain line in FIG. 3, so that the steering torque remains constant regardless of the magnitude of the steering speed.

Further, in detecting the running state of the vehicle, an engine rotation sensor that detects the engine rotation speed or a transmission gear position detection sensor may be used in addition to the vehicle speed sensor.

Furthermore, a hydraulic clutch may be used as the clutch for controlling on/off of the engine-driven pump 26.

(Effects of the Invention) The present invention uses an engine-driven pump when running at low speeds, which requires a large amount of pressure oil supply, and uses an electric pump, especially when running at high speeds, which requires controlling the amount of pressure oil supplied according to the running conditions. The characteristics of the 7NIL power assist force can be controlled relatively easily without causing over-discharge of the bar or large loss of power.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the present invention, and Fig. 1 shows the overall configuration of the lower steering device, Fig. 2 shows the output characteristics of the controller in high-speed running conditions, and Fig. 3 shows the vehicle speed and pressure oil supply. FIG. 3 is a characteristic diagram showing the relationship between quantities. 1...Power steering device, 2...
・Steering link, 3...Wheel, 13...
・Power cylinder, 20...liM! y, 62
...Controller, 66...Vehicle speed sensor

Claims (1)

[Claims] (11) A power cylinder that assists the steering force, an engine-driven pump that is driven by the engine and supplies pressure oil to the power cylinder, and an electric pump that is driven by an electric motor and supplies pressure oil to the power cylinder.
A driving condition sensor detects the driving condition of the vehicle, and receives signals from the driving condition sensor, issues an operation command to the engine-driven pump in low-speed driving conditions, issues a stop command to the engine-driven pump in high-speed driving conditions, and also issues an operation command to the engine-driven pump in high-speed driving conditions. An operating command is set to reduce the amount of pressurized oil supplied as the vehicle transitions to high-speed driving.