JPH032465Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a power steering device for a vehicle that increases hydraulic reaction force in a high speed range.

To reduce the steering force of the vehicle,
In the case of a power steering device that uses hydraulic power to assist, the steering wheel may become too light, especially when turning resistance is reduced, such as at high speeds, resulting in unstable steering.

In order to prevent such problems, there is a device that improves stability by increasing the hydraulic reaction force of a control valve that is switched by handle operation and sending pressure oil to the power cylinder at high speeds, for example. 128799
This method has been proposed by the present applicant as a reference to Publication No. 1-13665.

This increases the hydraulic pressure in the reaction chamber at the end of the control valve's spool at high speeds to provide resistance to valve switching, but the structure for switching the hydraulic pressure in the reaction chamber is complex, especially when using a planetary gear system. The disadvantage of the steering system was that it was difficult to adapt.

It is an object of the present invention to provide a power steering device that can solve these problems and reliably provide an appropriate steering feel in a high speed range.

Hereinafter, embodiments of the present invention will be described based on the drawings.

As shown in FIGS. 1 and 2, a stub shaft 1 connected to the handle side for input rotation is connected to a screw shaft 3 via a torsion bar 2. As shown in FIGS.

A thread groove is cut on the outer periphery of the screw shaft 3, and is screwed into a thread groove on the inner periphery of the piston 4 via a ball.

The piston 4 defines the inside of the housing 5 into two oil chambers 6A and 6B, and a sector gear 8 connected to a steering link meshes with a rack 7 formed on the side surface of the piston 4.

Therefore, when the stub shaft 1 rotates and rotates the screw shaft 3 while twisting the torsion bar 2, feed is applied to the piston 4, and the sector gear 8 rotates via the rack 7, changing the direction of the wheel. .

In order to hydraulically power assist the movement of the piston 4 at this time, pressure oil is selectively fed into the oil chambers 6A and 6B via the control valve 10.

The control valve 10 is switched via a planetary gear 11, which is connected to a planetary gear 13 supported by a carrier 12 connected to the stub shaft 1.
and sun gear 1 connected to screw shaft 3.
5 and a ring gear 16, the ring gear 1
A pin 17 implanted on the outer periphery of the control valve 10 is interlocked with a spool 20 of the control valve 10. Therefore, when the stub shaft 1 rotates, the planet gear 13 revolves, causing the ring gear 16 to rotate slightly since the load side sun gear 15 is stationary. As a result, the spool 20 is displaced and switched from side to side, and pressure oil from the control valve 10 is fed into the oil chamber 6A or 6B to provide power assist.

As a result, when the screw shaft 3 starts to rotate, the sun gear 15 rotates, so the ring gear 1
6 remains stationary at the valve switching position, and the control valve 10 remains switched as long as there is input rotation. When the input stops, the planet gear 13 comes to rest, so the rotation of the sun gear 15 returns the ring gear 16, returning the control valve 10 to neutral.

Note that 21 is a torsion bar whose base end is fixed to the valve housing 22, and applies valve switching pressure. Reaction force chambers 23A, 23B are formed at both ends of the spool 20 of the control valve 10, and these reaction force chambers 23A, 23B are communicated with each other by a switching valve 25, and are connected to the oil chambers 6A, 23B of the power cylinder 14.
It may be selectively connected to 6B.

The switching valve 25 is connected to branch passages 26A, 26B from the middle of each operating port A, B (communicating with the oil chambers 6A, 6B) of the control valve 10, and the reaction force chamber 23.
It has a spool 30 that selectively switches connection to the passages 27A and 27B connected to the passages 27A and 23B, and this spool 30 is displaced via a solenoid 31. The solenoid 31 is excited by a signal from a vehicle speed sensor 32 that detects the speed of the vehicle at a predetermined vehicle speed or higher via a controller 33, and switches the spool 30 (the state shown in FIGS. 2 to 3).

In other words, in the low and medium vehicle speed range, the passages 27A and 27
B are communicated with each other to keep the reaction force chambers 23A and 23B at the same pressure, and in the high speed range, high pressure is supplied to the reaction force chambers 23A and 23B on the side opposite to switching of the spool 20 (A, B). are communicated with each other to counteract the displacement of the spool 20 with hydraulic pressure.

In the figure, 35 is a high pressure port of the control valve 10;
6 is a low pressure (drain) port, 37 is a neutral return spring, and 38 is a spring receiver.

Therefore, in the low and medium speed range, the switching valve 25
is in the state shown in Fig. 2, and the reaction force chambers 23A and 23B are kept at the same pressure.

Therefore, the hydraulic reaction forces acting on the ends of the spool 20 cancel each other out, and therefore, when the control valve 10 is switched, only the reaction force from the torsion bars 21 and 3 is applied, and the steering wheel side is burdened with steering. A moderate reaction force is transmitted that does not become .

On the other hand, when the switching valve 25 is switched in a high speed range as shown in FIG. The pressure in the reaction force chamber 23B or 23A becomes low, and hydraulic pressure acts to push back the spool 20 that is about to be switched.

As a result, heavy steering force is fed back to the steering wheel at high speeds, preventing excessive steering.

The relationship between this steering force and output is shown in the fourth section.
In the low-to-medium speed range, a large power assist force can be obtained with a small amount of steering force, allowing for nimble steering operation, and in the high-speed range, hydraulic steering reaction force is applied to provide a sure response.

As described above, according to the present invention, it is possible to switch the hydraulic pressure to the reaction force chambers at both ends of the spool in the low speed range and the high speed range, and to reliably move the hydraulic reaction force in the high speed range, improving maneuverability. It is measured.

Moreover, it is structurally simple and can reduce cost increase.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the embodiment of the present invention, and Fig. 2 is a cross-sectional view of the embodiment of the present invention.
3 is a diagram illustrating the operation of the switching valve, and FIG. 4 is a characteristic diagram of the present invention. 1... Stub shaft, 3... Screw shaft, 4... Piston, 10... Control valve, 1
1... Planetary gear, 14... Power cylinder, 20
...Spool, 23A, 23B...Reaction force chamber, 25
...Switching valve, 30...Spool, 31...Solenoid, 32...Vehicle speed sensor.

Claims (1)

[Scope of utility model registration request] A control valve spool is connected via a pin to the ring gear of the planetary gear, which has a planet gear on the input side and a sun gear on the output side, and pressurized oil is supplied to the power cylinder via the control valve, which switches based on the input rotation of the handle. In a power steering device that selectively feeds the power, reaction force chambers are formed at both ends of the spool, and a switching valve that switches in response to vehicle speed is provided, and the switching valve switches both reaction chambers interchangeably in a low speed range. A power steering device characterized in that it is configured to introduce pressure oil from an operating port into a reaction force chamber that communicates with the spool and opposes displacement of the spool in a high-speed range.