JPH0253269B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device for an automobile that uses hydraulic pressure to reduce steering force.

A normal power steering device has a control valve that mechanically detects the rotation of the input shaft connected to the steering wheel and switches the control valve, and the switching operation of this control valve selectively controls the power cylinder installed at the tip of the input shaft. Pressure oil is supplied to the steering link to change the direction of the wheels in proportion to the rotation of the input shaft.

Especially in automobile power steering devices,
To ensure safety, the tip of the input shaft is connected to the piston of the power cylinder via a ball screw assembly so that the input shaft can be operated even if hydraulic assist force cannot be obtained due to a failure in the hydraulic system. They are mechanically linked.

By the way, the control valve that controls the direction of the pressure oil sent to the power cylinder by the rotation of the input shaft is linked to the movement of the input shaft as well as the actual movement of the piston on the output side, and is now subject to feedback control. Because of this, there are significant restrictions on its installation, and its placement is usually limited to areas where the input shaft connects to the power cylinder. In addition, in order to perform such mechanical feedback control, the structure of the control valve is extremely complex, and in particular, the hydraulic pressure is controlled in response to the ground resistance of the wheels, which changes depending on the traveling speed.
In a speed-sensitive power steering system designed to always provide optimal maneuverability, the structure of the control valve has to become even more elaborate, making maintenance difficult and expensive. There was a drawback.

On the other hand, from the viewpoint of pursuing comfort and safety of automobiles, there will be a stronger demand for control so as to obtain optimum maneuverability according to various driving conditions.

The present invention was proposed to solve these technical problems, and provides a power steering device that utilizes a microcomputer to ensure optimal maneuverability under all driving conditions. .

The present invention will be explained below based on illustrated embodiments.

An input shaft 2 connected to a handle 1 is connected to a piston 4 of a power cylinder 3 as a hydraulic actuator.
linked to.

In this case, the piston 4 is linked to the input shaft 2 via a ball screw assembly (not shown), and the piston 4 slides inside the cylinder 3 depending on the rotational direction and speed of the input shaft 2.

A rack 5 is provided on the side of the piston 4.
A sector gear 6 meshes with this rack 5, and as the piston 4 moves, a steering link (not shown) is driven via a pitman arm 7 which is interlocked with the sector gear 6.

The piston 4 moves due to the input rotation of the input shaft 2, and in order to assist this movement with hydraulic pressure, a control valve 9 applies pressure from the pump P to the oil chambers 8A and 8B, which are separated on both sides of the piston 4. Oil is supplied in a selectively controlled manner.

The operation of this control valve 9 is controlled by a microcomputer 10 to which the rotational direction, rotational force, or rotational speed of the input shaft 2 is input, and at the same time, the control load on the output side is fed back.

Here, reference numeral 11 denotes a load sensor attached to the input shaft 2, which is composed of a strain gauge or the like that detects the steering torque (input torque) and rotation direction by detecting the twist of the input shaft 2. 12 is a magnetic pickup for similarly detecting the rotational speed of the input shaft 2.

These detection signals are then amplified and
Input interface 1 with signal waveform processing function
4 to the arithmetic control section 15 of the microcomputer 10.

The calculation control unit (CPU) 15 performs calculations based on these inputs, selects the stored value from the storage unit (ROM) 16 in which optimal values corresponding to the operating conditions are stored in advance, and outputs the stored value to the output interface 17.
The signal is output to the control valve 9 via the control valve 9.

The control valve 9 is composed of a solenoid valve, and the switching direction and switching amount are controlled based on an input signal, and the amount of pressure oil sent to the left and right oil chambers 8A and 8B of the power cylinder 3 is controlled.

Next, it will be explained in more detail, including its effects.

When operating the handle 1 to rotate the input shaft 2 in either direction, a reaction force proportional to the operating load applied to the piston 4 of the power cylinder 3 is generated on the input shaft 2, so this is used as the operating force for operating the handle. This operating force (rotational force and direction of rotation) is detected by the load sensor 11 attached to the input shaft 2, and at the same time, the input rotational speed is determined from the output of the pickup 12 and transmitted to the microcontroller. input into the computer 10.

Since the optimal value corresponding to the input signal is set in advance in the storage unit 16, the arithmetic control unit 15 reads it out, performs predetermined signal waveform processing and amplification at the output interface 17, and then outputs the control valve 9. Enter.

Therefore, the control valve 9 sends the required amount of pressure oil to the oil chamber 8A or 8B of the power cylinder 3 in proportion to the magnitude and direction of the handle operating force (at this time, the other oil chamber 8A, 8B is (connected to tank T side). In this case, when the vehicle speed is low and the steering resistance of the wheels is large, the load sensor 11 detects that the torsional torque of the input shaft 2 is large, so it increases the oil pressure supplied to the power cylinder 3 and also reduces the steering wheel rotation speed. When it's fast,
Correspondingly, the microcomputer 10 controls the output value so that the switching amount of the control valve 9 increases to increase the amount of pressure oil fed.

As a result, the operation of moving the piston 4 using the input shaft 2 is assisted by the hydraulic pressure of the oil chamber 8A or 8B corresponding to the operating load.
The steering wheel can be operated easily and with an appropriate steering feel.

On the other hand, when the handle 1 is fixed, the reaction force that tries to twist the input shaft 2 according to the operating load decreases, so the output value of the load sensor 11 becomes smaller, and the control valve 9 is moved to the neutral position accordingly. The power cylinder 3 is returned to the original state via the microcomputer 10, thereby stopping the supply of pressure oil to the power cylinder 3.

In other words, feedback input can be obtained at the same time, and when the input shaft 2 stops, the power cylinder 3 also stops operating, and the wheels are held at that switching angle.

At this time, the handle 1 is connected via the input shaft 2.
If the acting force that tries to return the wheel to its original state acts as a resistance reaction force from the wheels, if the handle 1 is kept stationary, the load sensor 11 will detect this reaction force, and this will be controlled via the microcomputer 10. The feedback is fed back to the valve 9, and the hydraulic pressure of the power cylinder 3 is increased to maintain balance and prevent the handle 1 from turning due to the steering reaction force from the wheels.

Incidentally, in this embodiment, signals from the load sensor 11 and the rotation speed pickup 12 are used as control inputs, but the same control can be performed even if the load applied to the pitman arm 7 is detected by a load sensor.

In addition, as inputs to the microcomputer 10, multiple signals such as vehicle speed, which is a function of steering resistance, and vehicle weight (for example, tire pressure) are detected and used as additional signals, and the power assist force is relatively weakened during high-speed driving. It is also possible to strengthen the operating feeling of the steering wheel 1 and improve steering stability, or to strengthen the power assist force when the weight of the vehicle is large, and to reduce the steering force.

As described above, according to the present invention, it is possible to perform power assist so that optimum maneuverability can be obtained according to the driving conditions at the time, such as the steering torque (input torque) of the steering wheel and additionally the steering wheel operation speed. We can provide a power steering system with excellent safety and steering feel.

In addition, the control valve can have a simple structure and can be installed separately from the input shaft, so there are no restrictions on installation space.
Maintenance and maintainability will also be improved.

As for microcomputers, the cost burden is extremely low if one used for engine control installed in a vehicle is used, and the types of microcomputers include digital, analog, and hybrid types. The method to be used can be arbitrarily selected.

[Brief explanation of drawings]

The drawings are schematic configuration diagrams of the present invention. 2...Input shaft, 3...Power cylinder, 4...
Piston, 7... Piston arm, 8A, 8B
...Oil chamber, 9...Control valve, 10...
Microcomputer, 11...Load cell, 1
2... Rotation speed pickup, 15... Arithmetic control unit (CPU), 16... Memory unit (ROM).

Claims (1)

[Scope of Claims] 1. A hydraulic actuator that interlocks with an input shaft connected to a handle, means for detecting at least the steering torque transmitted to the input shaft and the rotational direction of the input shaft, and an optimal control system based on the detected values. A power steering device comprising: a microcomputer that calculates a value; and a control valve that switches according to the output of the microcomputer to control pressure oil supplied to a hydraulic actuator. 2. The power steering device according to claim 1, wherein the steering torque and rotation direction detecting means is a load sensor attached to the input shaft and detecting torsional torque.