JPS59190054A - Power steering - Google Patents

Abstract

PURPOSE:To prevent self-excited vibrations in a valve piston from accurring, by connecting a pair of sub-reaction chambers installed at both sides of the valve piston, while setting up a fixed orifice in a circuit which is provided with a variable orifice adjusting the opening according to a car speed. CONSTITUTION:Each of sub-reaction chambers 20 and 21 is formed at both sides of a valve piston 13. Both these sub-reaction chambers 20 and 21 are interconnected with each other via a circuit 35 being provided with a variable orifice 34 which responds to a car speed and is set so as to make its opening smaller in proportion to an increase in the car speed. And, a fixed orifice 36 is set up on the circuit 35 in front and in the rear of the variable orifice 34. Therefore, in time of low-speed running, if opening of the variable orifice 34 grows large, a flow of oil is regulated by the fixed orifice 36 and a pressure differential at both sides of the valve piston 13 is moderately given so that self-excited vibrations in the valve piston 13 is thus prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device that can change steering force according to vehicle speed.

The power steering device has a configuration in which a power piston is incorporated into a manual steering mechanism that engages a sector shaft, and the movement of a worm shaft interlocked with a steering wheel is assisted by hydraulic pressure acting on the power piston. There is. Therefore, the power steering device enables light and quick steering of the vehicle due to the above configuration, but simply reducing the steering effort will, on the other hand, lead to more steering phenomena than necessary at high speeds, giving the driver a sense of anxiety. give.

For this reason, at high speeds, increasing the reaction force against the steering wheel and increasing the steering force will make the vehicle run more comfortably.Therefore, power steering devices that change the steering force in response to vehicle speed have been proposed. There is.

One of the conventionally proposed steering devices of this type is to provide a secondary reaction force chamber on both sides of a valve piston, communicate the secondary reaction force chamber with the main reaction force chamber via an orifice, and The reaction force chamber is made conductive by a circuit with a variable orifice, and the variable orifice is closed at high speeds, and a pressure corresponding to the pump pressure is introduced into one sub-reaction force chamber to increase the reaction force on the valve piston. It incorporates a control valve device. However, in this conventionally proposed device, the pressure difference between both ends of the control valve is reduced at low speeds.
The damping effect of the valve is small, and therefore valve vibration is likely to occur.

An object of the present invention is to provide a power steering device in which self-excited vibration does not occur in the valve piston by providing a fixed orifice in the conventional variable orifice circuit.

In order to achieve this object, the present invention includes a worm shaft that interlocks with a steering wheel of a vehicle, and engages with the worm shaft via a steering nut.
A power piston that slides along the worm shaft, a sector shaft that engages with a rack of the power piston and interlocks with a link mechanism that changes direction of the vehicle, and a sector shaft that is incorporated in the power piston and that is connected to the steering nut. The control valve device includes a control valve device actuated by a valve pin fixed to the control valve device, and the control valve device includes a valve piston having a pair of main reaction force chambers therein, and a control valve device provided on both sides of the valve piston. The sub-reaction chambers are connected to the main reaction chamber through orifices, and the sub-reaction chambers on both sides have variable openings that change in response to vehicle speed. In a power steering device connected by a circuit provided with an orifice, a fixed orifice is disposed on the circuit provided with the variable orifice, and when the vehicle is to turn right, for example, the steering When the wheel is turned to the right, the worm shaft and steering nut rotate to the right at the same time.

Rotation of the steering nut to the right rotates the valve pin integrated with it to the right, which operates the valve piston in the control valve device to the right, supplies hydraulic pressure to the right cylinder chamber, and moves the valve pin along the worm shaft of the power piston to the left. assisting the movement and reducing the movement of the sector shaft that engages the power piston.

On the other hand, if oil escapes from the secondary reaction force chamber into a circuit with a variable orifice, and if there is no fixed orifice and the diameter of the variable orifice is large, the differential pressure on both sides of the valve piston becomes extremely small, and the resistance force acting on the valve piston increases. Because it is small,
When vibrations from the steering wheel act on the valve piston, self-excited vibrations tend to occur.

In the present invention, a fixed orifice is arranged on the circuit, so even if the variable orifice opening is large and oil tries to escape, this oil is regulated by the diameter of the fixed orifice, and no extra movement will flow. Since the difference between the opposite sides of the piston is appropriately strengthened, self-excited vibration of the valve piston can be prevented. Note that although it is possible to limit the opening degree of the variable orifice, in this case, the characteristics change depending on the processing accuracy of the variable orifice. The present invention allows the purpose of preventing self-excited vibration to be easily achieved through a simple structure in which a fixed orifice is provided that facilitates machining accuracy.

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 2 and 3 each show a different embodiment, and each A in FIG.
-A sectional view. In the figure, l denotes a power steering device, which has a worm shaft 3 rotatably supported at both ends of a housing 2 and a sector shaft 5 that engages with a rack of a power piston 4.

Further, one end of the worm shaft 3 is interlocked with a steering wheel (not shown), the sector shaft 5 is interlocked with a link mechanism (not shown) that changes the direction of the wheel, and the worm shaft 3 is supported at both ends within the power piston 4 by thrust bearings 6. The worm shaft 8 is engaged with the worm shaft 8 via a steering nut 7 and a pawl that restrict the movement in the axial direction. Therefore, the steering nut 7 can only rotate within the power piston.

A valve pin 8 is fixed to the steering link neck 1 and 7, and the tip of the valve pin 8 is inserted into the center of a control pulse '7' device 9 incorporated in the power piston 4. The control valve device 9 supplies hydraulic pressure to either the right cylinder chamber IO or the left cylinder chamber 11 partitioned by the power piston 4 in the housing 2, depending on the steering direction, and the worm shaft 8 of the power piston Φ. It works to encourage movement along the lines.

That is, the control valve device 9 is housed in a cylinder 2 as shown in FIG. 2, and includes a valve piston 18 having a hole in the center thereof into which the tip of the valve pin 8 is inserted. The valve piston (3) has a pair of bores (14, (5) open at one end on its left and right sides, and a reaction force piston (16.17) fixed to the power piston (4) inside the bore (14.15) is a main reaction force. Furthermore, on both sides of the cylinder 12, which are inserted so as to form the force chambers 18, 19, auxiliary reaction chambers 20.21 are formed, which have a larger pressure acting area than the main reaction force chamber. Additionally, a pair of annular grooves 22.2 are formed on the outer peripheral wall of the valve piston 18.
8, one of the annular grooves 22 communicates with the right cylinder chamber 10, and the other annular groove 28 communicates with the left cylinder chamber 11.

Pairs of annular grooves 24, 25, 26, and 27 are formed on the left and right sides of the inner circumferential wall of the cylinder 12, respectively, with the grooves 24, 26 communicating with the oil pump 28, and the grooves 25, 27 communicating with the oil reservoir 29. let The main reaction chamber 18.19 connects the annular groove 22 of the valve pin 18 via an orifice 80.81.
．． 23, and the auxiliary reaction force chambers 20 and 21 communicate with the reaction force piston 1.
6.17 respectively communicate with the auxiliary reaction chambers 20.21 via orifices 82.33.

Further, the sub-reaction force chambers 20 and 21 communicate with each other via a circuit 35 incorporating a variable orifice 34.

The variable orifice 84 changes its opening degree in response to vehicle speed, and is designed to be open at low speeds and closed at high speeds. 86 and 86 are fixed orifices provided on the circuit 35 before and after the variable orifice 34. The fixed orifice 86 may be provided on both sides of the variable orifice 84, or may be provided on only one side of the variable orifice 84. Fixed orifice 86 at a diameter of
If the diameter is larger than , it will not work effectively and the fixed orifice 86
Only those with a diameter smaller than or equal to the diameter will work effectively. That is, the fixed orifice 36 is responsible for the upper limit, and the eight variable orifices are responsible for the lower limit.

Next, the operation will be explained. When the vehicle is running at low speed, the variable orifice 34 is open, and the pressures in both side reaction chambers 20, 21 are equal. When the valve piston 18 moves to the right, the groove 22 of the piston 18 becomes electrically conductive with the groove 24 of the cylinder 12, and the oil well from the pump 28 is supplied to the right cylinder chamber 10, assisting the movement of the power piston 4. O On the other hand, the groove 28 of the valve piston 18 is
The left cylinder chamber 11 is electrically connected to the oil reservoir 29 and is not subjected to hydraulic action. Note that the groove 25,
26 is closed by the land of the valve piston 13. Further, pressure from the pump 28 is supplied to the main reaction force chamber 18 and the sub reaction force chamber 20 via the orifices 30 and 82.

However, since the auxiliary reaction force chambers 20 and 2] are electrically connected and have approximately equal pressure, a reaction force corresponding to the differential pressure between the main reaction force chambers 18 and 19 acts on the valve piston 13.

- When the blade is at high speed, the variable orifice 34I of the circuit 35 is closed and the secondary reaction force chambers 20.21 are in a non-conducting relationship.

When the valve piston 13 is moved to the right by the valve pin 8 in this state, the hydraulic pressure from the pump 28 is supplied to the right cylinder chamber lO through the groove 22 as described above, and the left cylinder chamber 11 is supplied to the oil reservoir through the groove 28. It communicates with 29.

In this way, the movement of the power piston hand can be assisted, but since the hydraulic pressure from the pump 28 is supplied to the main reaction force chamber 18 and the auxiliary reaction force chamber 20 through the orifice 30.82, the reaction from the main reaction force chamber 18 is reduced. In addition to the force, the valve piston 13 receives a reaction force from the auxiliary reaction force chamber 20 that acts on the end surface of the valve piston 18. That is, the steering wheel is made heavier at high speeds than at low speeds.

In addition, although the case where the valve piston 18 was moved to the right was shown above, it can be easily understood that the same effect can be obtained even if the valve piston 18 is moved to the left.

FIG. 3 shows another embodiment, in which four annular grooves 2, 25, 26, and 27 are formed in the cylinder 12 in FIG. annular groove 3
The annular groove 87 is connected to the left cylinder chamber 11 by a circuit 40, and the annular grooves 38, 39 are connected to the right cylinder chamber IO by circuits 41 and 42, respectively. It will be communicated to. Further, the annular groove 37 communicates with the main reaction force chamber 19 through an orifice 43 , and the annular groove 88 communicates with the main reaction force chamber 18 through an orifice 44 .

When the valve piston 18 moves to the right, the annular groove 22 communicating with the pump 28 communicates with the right cylinder chamber 10 via the annular groove 88, and the annular groove 28 communicating with the reservoir 29 communicates with the left cylinder chamber 10 via the annular groove 87. It communicates with the cylinder chamber 11. Moreover, when the valve screws 1 to 18 move to the left, this communication is reversed. However, the embodiment shown in FIG. 8 is similar to the embodiment shown in FIG. 2 in terms of operation and effect.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a power steering device showing an embodiment of the present invention, and FIGS. 2 and 3 are sectional views taken along line A-A in FIG. 1, respectively, showing an optical embodiment. Explanation of the main parts of the diagram ■... Power steering device 8... Worm shaft 4
...Power piston 5...Sector shaft 7...
・Steering nut] -1...Left cylinder chamber ■2...Cylinder 18
... Valve piston 16°] 7 ... Reaction force piston 18, 19 ... Main reaction force chamber 20.2] ・
・・Sub-reaction force chamber 22゜23゜24゜25゜26゜27
... Annular groove 28 ... Oil pump 29 ... Oil reservoir 80, 81 ... Orifice 82.8
8... Orifice 34... Variable orifice 3
5...Circuit 86...Fixed orifice Fig. 6

Claims (1)

[Claims] A worm shaft that is interlocked with a steering wheel of a vehicle, which engages with the worm shaft through a steering nut, and which is engaged with a rack of a warp piston by a power screw that slides along the worm shaft. , a sector shaft interlocking with a link mechanism for changing the direction of the vehicle, and a control valve device incorporated in the power piston and operated by a valve pin fixed to the steering nut,
The control valve device has a valve piston having a pair of main reaction chambers therein, and a pair of auxiliary reaction chambers provided on both sides of the valve piston, and the auxiliary reaction chambers are connected to the main reaction chambers through an orifice. In the power steering device, the variable orifice is provided in a power steering device in which the secondary reaction chambers on both sides are connected by a circuit having a variable orifice that changes the opening degree in response to the vehicle speed, and the auxiliary reaction chambers on both sides are connected to each other by a circuit that is in communication with the main reaction force chamber. A power steering device characterized by having a fixed orifice arranged on a circuit.