JPH0147348B2 - - 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. By supplying pressure oil to the steering link, the direction of the wheels is changed by comparing the rotation of the input shaft with 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 it can be operated even if hydraulic assist force cannot be obtained due to a failure of the hydraulic system. are mechanically interconnected.

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 that always provides optimal control force, the structure of the control valve has to be even more elaborate, which makes maintainability and safety poor and expensive. There was a drawback.

On the other hand, control to obtain the optimum steering force according to various driving conditions will be increasingly required from the perspective of pursuing comfort and safety in automobiles, and this is why microcomputers are being used. The present applicant has proposed a power steering device in Japanese Patent Application No. 56-19196, which allows optimum steering force to be obtained at all times under all driving conditions.

This will be explained based on FIG. 1. An input shaft 2 connected to a handle 1 is connected to a piston 4 of a power cylinder 3 as a hydraulic actuator.

In this case, the piston 4 is connected to the input shaft 2 via a pole/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 is engaged with the 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, oil chambers 8A and 8B separated on both sides of the piston 4 are provided with
Pressure oil is selectively controlled and supplied from the pump P by the PS control valve 9.

The control valve 9 is an electromagnetic valve whose operation is controlled by a microcomputer 10 to which the rotational direction, rotational force, or rotational speed of the input shaft 2 is input, and 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 rotational force and direction of rotation by detecting 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, thereby controlling the amount of pressure oil sent to the left and right oil chambers 8A and 8B of the power cylinder 3.

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 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 detected by the pick-up 12. input to the microcomputer 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 this value, 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 the tank T side.) In this case, when the vehicle speed is low and the wheel turning resistance is large, the load sensor 1
1 detects that the torsion angle of the input shaft 2 is large, so it increases the hydraulic pressure supplied to the power cylinder 3, and when the handle rotation speed is high, the amount of pressure oil sent increases accordingly. The microcomputer 10 controls the output value so that the amount of switching of the control valve 9 increases as the output voltage increases.

As a result, the operation to move the piston 4 using the input shaft 2 is assisted by the hydraulic pressure in the oil chamber 8A or 8B corresponding to the operating load, so the handle operation is light and easy with an appropriate operating feel. can be done.

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 state via the microcomputer 10, and the supply of pressure oil to the power cylinder 3 is thereby stopped.

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.

By the way, with this power steering device,
The PS control valve 9 can be installed freely, but since it was installed independently from other parts, there were problems with the actual equipment, such as long piping and the need for mounting methods on the vehicle body.

The present invention solves such problems, namely PS
The purpose is to simplify control valve piping, improve installation ease, and at the same time achieve weight reduction.

The present invention fixes the valve housing of the electromagnetic PS control valve to the body of the hydraulic pump or the flow control valve body, and connects the hydraulic passages inside the housing to form hydraulic piping that connects the pump and the control valve. It is designed to be simplified and to save time and effort in installing the control valve.

Hereinafter, embodiments will be described based on the drawings.

In FIGS. 2 and 3, 20 is a hydraulic pump that supplies pressure oil to the power cylinder 3, and the discharge oil is sent to the power cylinder 3 via a PS control valve 22 while controlling the flow rate with a flow control valve 21. The returned oil is returned to the reservoir 23 and sucked into the hydraulic pump 20 again.

The reservoir 23 is integrally attached to the upper part of the hydraulic pump 20, and the flow control valve 21
A valve body 25 is integrally formed in a part of the pump body 24 by casting or the like.

A housing 26 of an electromagnetic PS control valve 22 controlled by the microcomputer 10 is fixed to the valve body 25 by a hollow bolt 28 having a discharge passage 27 from the flow control valve 21 inside.

Additionally, a reservoir 23 formed in the housing 26
A return pipe 31 of the reservoir 23 is inserted into the torsion passage 30 through a seal 32 from the same axis as the hollow bolt 28 .

A valve spool 33 is slidably inserted into the valve housing 26, and a solenoid 35 to which a control output from the microcomputer 10 is applied is connected to an end of the spool 33. Therefore, by energizing the solenoid 35, the valve spool 3
3 is displaced, and the oil chamber 8A or 8 of the power cylinder 3
Actuation port (passage) 37 or 38 connected to B
and a pump port 3 connected to the discharge passage 27.
6 or a tank port 39 connected to the return passage 30.

The hollow bolt 28 passes through the valve housing 26 from a direction perpendicular to the axis of the valve spool 33 and is screwed into the valve body 25. They communicate via an annular groove 40 on the outer periphery.

Hollow bolts 2 are located on both sides of this annular groove 40.
8 are fitted with seals 41 and 42.

Therefore, by connecting the PS control valve 22 to the valve body 25 of the flow control valve 21 with the hollow bolt 28 in this way, the installation of the PS control valve 22 is simplified, and the flow control valve 2
The oil discharged from 1 is directly transferred to the valve housing 26.
The return oil is guided to the PS control valve 22 via the internal passage 36 of the PS control valve 22, and at the same time, the return oil is returned to the reservoir 23 via the passage 30, so there is no need for piping to connect these parts.

Note that the PS control valve 22 is operated by the output of the microcomputer 10 in the same way as the control valve 9 in FIG. Obtaining is the same as in Figure 1.

FIG. 4 shows a rack-and-pinion type power steering actuator.

In this case, said working ports 37 and 38 are connected to ports 44 and 45 of cylinder 43, respectively.

Rod 47 of internal piston 46 of cylinder 43
Both protruding ends 47A and 47B are respectively connected to the wheel side, and a rack (not shown) is cut in the middle thereof, and meshes with a pinion (not shown) of the input shaft 2.

Therefore, the piston 46 is moved to either side by hydraulic pressure supplied from the operating ports 37, 38, and the piston rod 47 is displaced to change the direction of the wheel.

In this case, even if hydraulic assist cannot be obtained, such as when a hydraulic power source fails, the rack can be displaced via the pinion by rotation of the input shaft 2, and the direction of the wheels can be changed.

In the above embodiment, the solenoid 35 may be of a push-pull type at two locations at both ends, in addition to the proportional type. As described above, according to the present invention, the PS control valve is configured to be fastened to the pump body side, such as a hydraulic pump body or the valve body of a flow control valve, via bolts, and the oil passage between the valve body and the control valve is connected in the coupled state. Since they are connected, the piping structure of the PS control valve is simplified and its mounting bracket is not required at all, making it possible to reduce the size and weight of the entire power steering device.

In particular, in the present invention, the control valve is fastened to the pump body side via a hollow bolt having a passage that communicates the discharge passage on the pump body side with a port in the control valve. There is an advantage that the passage configuration can be streamlined to the maximum extent and the size of the control valve can be minimized.

Furthermore, the present invention has a structure in which the bolt that connects the control valve to the pump body side is screwed into the discharge passage, so it is characterized in that it can be made smaller and lighter without significantly changing the structure of the conventional pump body etc. .

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a conventional device, Fig. 2 is a cross-sectional view centered on the control valve portion, which is the main part of the present invention, Fig. 3 is a cross-sectional view taken along the line A-A, and Fig. 4
The figure is a sectional view showing another example of the hydraulic actuator. 2...Input shaft, 3...Power cylinder, 10...
...Microcomputer, 11...Load cell,
12... Rotation speed pickup, 20... Hydraulic pump, 21... Flow control valve, 22...
...PS control valve, 23...reservoir,
24...Pump body, 25...Valve body,
26...Valve housing, 27...Discharge passage,
28...Hollow bolt, 30...Return passage, 31...
...Return pipe, 33...Valve spool, 3
5... Solenoid.

Claims (1)

[Claims] 1 A hydraulic actuator that interlocks with the input shaft connected to the handle, a means for detecting at least the load transmitted to the input shaft and its rotational direction, a microcomputer that calculates the optimum steering value based on the detected values, and a microcomputer that calculates the optimum steering value based on the detected values. In a power steering device equipped with an electromagnetic control valve that is switched by the output of a computer to control the hydraulic pressure from a hydraulic pump that is supplied to a hydraulic actuator, the control valve is connected to a discharge passage on the side of the pump body through a bolt. The power steering device is configured such that it can be attached and detached, and the bolt has a hollow structure having a passage that communicates the discharge passage with a port in the control valve when the control valve is fastened to the pump body side. .