JPH0263964A - Control valve for power steering - Google Patents

Abstract

PURPOSE:To eliminate any unbalance of steering resistance by making initial throttle opening in a part of the piston rod nonconnective side in throttle parts of a hydraulic passage leading to two chambers partitioned by a piston of a one-side push type power cylinder larger than that of others. CONSTITUTION:A control valve 4 consists of a rotor 20 at the side of a steering shaft 2 and a sleeve 21 at the side of a pinion shaft 3. A pinion 3a is engaged with a piston rod 6. Hydraulic pressure out of an oil pump is transmitted to an oil chamber 5a at the piston rod nonconnective side by way of a throttle part OA installed between the sleeve 21 and the rotor 20 while transmitted to an oil chamber 5b at the piston connective side by way of another throttle part OB, respectively. Initial opening A of the throttle part OA is larger than initial opening B of the throttle part OB. Consequently, any unbalance in symmetrical steering resistance differences as far as a position for a sectional area of the piston rod is offset, thus this unbalance is eliminated with a small-sized device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a power steering control valve, and particularly to a power steering control valve using a single-push type power cylinder.

[Prior art and its problems]

-C, the power steering that supplements part of the steering force of the steering wheel uses a power cylinder operated by hydraulic pressure from a hydraulic source, and a control valve that selectively switches the hydraulic pressure from the hydraulic source to two oil chambers of the power cylinder. It is made up of.

There are two types of power cylinders: a double push type, in which piston rods are connected to both sides of the piston, and these piston rods are connected to the left and right wheels via tie ports, doors, etc.; There are two types of power cylinders: a single-push type in which the rod is connected to the left and right wheels via a link mechanism, and the single-push type power cylinder has the advantage of being smaller in size compared to the double-push type.

FIG. 1 shows an example of power steering using a single-push type power cylinder, in which a control pulp 4 is interposed between a steering shaft 2 connected to a handle 1 and a pinion shaft 3. A pinion 3a is formed at the tip of the pinion shaft 3.
a meshes with a bulge 6a provided on the piston rod 6 of the power cylinder 5. One end of the piston rod 6 is connected to a piston 7, and the other end is connected to an arm 9a of a steering knuckle 9 via a rod 8.

The steering knuckle 9 can swing around a fulcrum 9b pivotally mounted on the vehicle body, and swings left and right as the piston rod 6 moves in the axial direction, and the steering knuckle 9 swings from side to side as the piston rod 6 moves in the axial direction. It is designed to steer a .13.

In the case of the single-push type power cylinder 5 as described above, the pressure-receiving areas on both sides of the piston 7 are unbalanced by the cross-sectional area of the piston rod 6, so the steering resistance of the handlebar 1 increases when turning to the right and when turning to the left. The problem is that they are different. In order to solve this problem, conventional methods have been to increase the cylinder diameter of the power cylinder 5 to such an extent that the cross-sectional area of the piston rod 6 can be ignored, or to move the piston rod 6 degrees opposite the piston rod 6 as shown by the broken line in Figure 1. A method is being considered in which the cross-sectional area of the piston rod is offset on the left and right sides by extending the piston rod to the left and right sides. However, the former case has the disadvantage that the power cylinder 5 becomes large, and in the latter case, when turning right, the piston rod 6'' shown by the broken line protrudes to the vicinity of the bumper 14, and even in the event of a minor collision, the steering gear mechanism could be damaged. In particular, in vehicles with small front spaces, such as cab-over vehicles and light vehicles, there is a high possibility that the steering gear mechanism will be damaged in the event of a collision.

[Purpose of the invention]

The present invention has been made in view of the above problems, and its purpose is to provide a control valve for a power cylinder that can reduce or eliminate the unbalance of steering resistance between the right and left sides of the steering wheel without changing the shape of the power cylinder. It's about doing.

[Structure of the invention]

In order to achieve the above object, the present invention provides a control valve that supplies hydraulic pressure to a single-push power cylinder, an input port to which hydraulic pressure is supplied from a hydraulic source, and an output port connected to both chambers of the power cylinder. and a drain port for draining the hydraulic pressure from both chambers, and a throttle part whose opening degree is variable depending on the steering force between the input port and each output port. The initial opening degree of the throttle part communicating with the oil chamber is made larger than the initial opening degree of the throttle part communicating with the oil chamber on the side where the piston rod is not connected.

[Effect]

That is, between the input port of the control valve and the output port leading to both oil chambers of the power cylinder, there is a constriction formed by the gap between the pulp body and the valve body, and the opening degree of this constriction is determined by By changing according to the magnitude of the steering force, the oil pressure supplied to the oil chamber of the power cylinder changes. Conventionally, the initial opening degree of this throttle part, that is, the opening degree when not steering, is the same when turning right and when turning to the right.
When the steering wheel is turned with the same steering force, the same oil pressure is supplied to both oil chambers of the power cylinder. Therefore, in the case of conventional single-push type power cylinders, there was a left-right unbalance in the actuation force of the piston, but in the present invention, the initial opening of the throttle part leading to the oil chamber on the piston rod connection side is By making the initial opening of the throttle part that leads to the oil chamber on the side where the piston rod is not connected, even if the steering wheel is turned with the same steering force, the oil chamber on the side where the piston rod is connected will not be connected to the oil chamber on the side where the piston rod is not connected. Higher oil pressure is supplied. Therefore, the unbalance in the pressure receiving area can be eliminated by adjusting the supplied hydraulic pressure, and the unbalance in the steering resistance can be eliminated without increasing the cylinder diameter of the power cylinder or extending the piston rod.

〔Example〕

2 and 3 show the internal structure of the control valve 4 shown in FIG. The rotor 20 is composed of a rotor 20 and a sleeve 21 that is integrally provided on the pinion shaft 3, and the rotor 20 can slide inside the sleeve 21. The rotor 20 and sleeve 21 are connected via a torsion bar 22 so that they can be twisted relative to each other.

A plurality of lands 20a, 20b, 20c are formed on the circumferential surface of the rotor 20, as shown in FIG. An input port 24 to which hydraulic pressure is supplied from, and drain ports 26 and 27 from which oil is drained to the oil tank 25 are formed. In addition, the input port 24 and the drain port 26, 27 of the sleeve 21
An output port 28 communicating with the oil chamber 5b (see FIG. 1) on the piston rod non-coupling side of the power cylinder 5 and an output port 29 communicating with the oil chamber 5a on the piston rod coupling side are formed at an intermediate position between the two. ing.

In the oil passage leading from the input port 24 to the output port 29, a throttle portion OA defined by the gap A between the land 20a and the inner peripheral surface of the sleeve 21 is provided.
Similarly, there is a gap B in the oil passage leading from 4 to the output port 28.
A constriction section 08 given by is provided. The initial opening degree A of the throttle part OA is the initial opening degree B of the throttle part 08.
is set larger. Note that the initial opening degree refers to the opening degree of the throttle portion in a state where no steering force is acting on the handle l.

Here, the operation of the power steering having the above configuration will be explained.

First, when the vehicle is traveling straight, no steering force is acting on the handlebar 1, so the rotor 20 and sleeve 21 of the control valve 4 are in the position shown in FIG. 3.

Therefore, the oil pressure in both chambers 5a, 5b of the power cylinder 5 is drained through the drain ports 26, 27.

Now, if you turn the steering wheel l to the right, the steering force will be transferred to the steering shaft 2. The signal is transmitted to the pinion 3a via the piston shaft 3, and the pinion 3a operates the piston rod 6 provided with the rack 6a in the upper right direction in FIG. Since the steering knuckle 9 swings clockwise about the fulcrum 9b in conjunction with the piston rotation, the left and right wheels 12 and 13 are steered to the right.

When a steering force is applied to the above-mentioned handle l, the ground resistance of the wheels 12.13 acts on the pinion 3a, so the pinion shaft 3 does not rotate together with the steering shaft 2, but due to the torsion bar 22, it responds to the steering force. It follows the rotation while causing a ↑backward movement. Due to this tearing, relative rotation occurs between the rotor 20 and the sleeve 21 in FIG. 3, the opening degree of the throttle part O' increases, and the opening degree of the throttle part O8 becomes fully closed or becomes small.

Therefore, the discharge oil pressure of the oil pump 23 is
9 to the oil chamber 5a of the power cylinder 5, and the oil pressure in the oil chamber 5b is drained through ports 28, 26. As a result, the operating force of the piston 7 connected to the piston 7 is amplified in the upper right direction in FIG. It can be steered to the right.

When the handle l is turned to the left, the operation is the opposite to that described above, so a description thereof will be omitted.

In the above operation, the throttle portion 0. The initial opening degree A is set to 0. Since the opening degree is larger than the initial opening degree B, even if the relative rotation angle between the rotor 20 and the sleeve 21 is the same when turning to the right and when turning to the left (in other words, even if the steering force is the same), the opening degree of the throttle part oA is This is larger than the opening degree of the throttle portion 0°, and the oil flow rate to the oil chamber 5a is greater than that to the oil chamber 5b. Therefore, as shown in FIG. 4, even if the steering force F is the same when turning to the right and turning to the left, the oil pressure PA supplied to the oil chamber 5a becomes higher than the oil pressure P supplied to the oil chamber 5b. This unbalance in the supplied hydraulic pressure offsets the unbalance in the pressure receiving areas of the oil chambers 5a and 5b, and when the steering wheel 1 is steered left and right, the unbalance in steering resistance can be reduced or eliminated.

FIG. 5 shows a second embodiment of the control valve of the present invention, which is constructed as a spool type. Spool 3
0 is operated integrally with the steering shaft, and the valve body 31 follows the spool 30. In the neutral state, the initial opening degree A of the throttle portion OA located between the input port 24 and the output port 29 to the oil chamber 5a is located between the input port 24 and the output port 28 to the oil chamber 5a. Also in the case of this embodiment, which is larger than the initial opening degree B of the throttle part OI, the oil pressure PA output from the output port 29 is higher than the oil pressure P output from the output port 28, and the oil chamber 5a,
By offsetting the unbalance of the pressure receiving area of 5b, the unbalance of steering resistance can be reduced or eliminated.

In each of the above embodiments, a case has been shown in which the steering force of the steering shaft is transmitted to the piston rod via the rack and pinion mechanism, but the steering force may be transmitted using other mechanisms.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, the initial opening of the throttle part communicating with the oil chamber on the side where the piston rod of the power cylinder is not connected is set to Since it is made larger, when the steering wheel is turned to the left or right with the same steering force, a higher hydraulic pressure is supplied to the oil chamber on the side where the piston rod is connected than the oil chamber on the side where the piston rod is not connected. In this way, the unbalance in the pressure-receiving area of the power cylinder can be resolved by adjusting the supply oil pressure, so the unbalance in steering resistance can be resolved without increasing the cylinder diameter of the power cylinder or extending the piston rod. .

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a vehicle equipped with power steering, which is the premise of the present invention, Fig. 2 is a sectional view of a control valve, and Fig. 3 is an enlarged view of the line ■-■ in Fig. 2 showing the main parts of the present invention. 4 is a characteristic diagram showing the relationship between the hydraulic pressure supplied to each chamber of the power cylinder and the steering force, and FIG. 5 is a sectional view of another embodiment of the present invention. 4... Control valve, 5... Power cylinder, 5a, 5b... Oil chamber, 6... Piston rod, 7
...Piston, 20...Rotor, 21...Sleeve, 23...Oil pump, 24...Input port,
26.27... Drain port, 28゜29... Output port, OA, Os... Throttle section. Applicant Daihatsu Motor Co., Ltd. Agent Patent Attorney Hidetaka Tsutsui Figure 1 Figure 4 G1 Figure 2 Figure 3 Figure 5 S

Claims (1)

[Claims] In a power steering system comprising a single-push type power cylinder in which a piston rod is connected to one side of the piston, and a control valve that selectively supplies hydraulic pressure to two oil chambers partitioned by the piston. , The above control valve has an input port to which hydraulic pressure is supplied from a hydraulic source, an output port connected to both chambers of the power cylinder, a drain port to drain the hydraulic pressure from both chambers, and an input port and each A throttle section is provided between the output port and the opening degree of which is variable depending on the steering force, and the initial opening degree of the throttle section that communicates with the oil chamber on the side where the piston rod of the power cylinder is connected is set to the oil chamber on the side where the piston rod is not connected. A power steering control valve characterized by having a larger opening than the initial opening of the throttle section leading to.