JPS6310031B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device for a vehicle.

2. Description of the Related Art In order to reduce fatigue associated with steering operations in automobiles, power steering devices are known that use hydraulic pressure to power assist steering operations.

This power steering device generally has a problem in that it has a complicated structure, poor productivity, and is expensive.

The present invention was proposed in order to solve this problem, and an object of the present invention is to obtain a power steering device that is equipped with a conical rotary valve and has excellent productivity.

Therefore, in the present invention, there is a stub shaft to which input rotation is transmitted, a worm shaft that is screwed into a piston connected to the stub shaft via a torsion bar, and a worm shaft that is switched based on the rotational phase of both shafts, so that the left and right sides of the piston are switched. In a power steering device equipped with a control valve that selectively supplies pressure oil to a cylinder chamber, the control valve is composed of a valve rotor and a valve sleeve that are coupled to either a stub shaft or a worm shaft, and The rotating sliding contact surface forms a conical surface centered on the rotation axis, and the groove bottom of the groove portion formed on these conical surfaces is approximately parallel to the rotation axis, and is connected to either the valve rotor or the sleeve. A thrust bearing was interposed between the base end of the wormshaft and the valve housing.

Embodiments of the present invention will be described below based on the drawings.

As shown in FIGS. 1 and 2, the housing 1 includes a cylinder housing 1A and a valve housing 1B.
It consists of

A stub shaft 3 connected to a steering wheel is rotatably supported by a bearing 2 in the valve housing 1B.

A torsion bar 5 coupled with a pin 4 is coaxially disposed at the tip of the stub shaft 3. This torsion bar 5 is inserted into a hollow wormshaft 6, and its tip is connected to the wormshaft 6 by a pin 7.

Therefore, when a rotational input is applied to the stub shaft 3, the wormshaft 6 rotates in the same direction via the torsion bar 5.

A thread groove 8 is formed on the outer periphery of the wormshaft 6, and a thread groove 12 of the same pitch is also formed in a through hole 11 that passes through the center of a piston 10 that is slidably housed in the cylinder housing 1A. It is formed.

The wormshaft 6 is inserted into the through hole 11, and a large number of balls 13 are continuously arranged between the thread grooves 8 and 12.

This allows the ball screw assembly 14
The piston 10 moves left and right as the worm shaft 6 rotates.

Cylinder chambers 15A and 1 are provided on the left and right sides of the piston 10.
5B is divided into cylinder chambers 15A and 1.
The movement of the piston 10 is assisted by pressure oil selectively supplied to 5B.

A rack 16 is carved into the side surface of the piston 10, and the pinion 1 of the sector shaft 17 is connected to this rack.
7A is engaged.

The sector shaft 17 is connected to a steering link (not shown) and controls the direction of the steering wheels of the vehicle.

Therefore, when the steering wheel is operated and the worm shaft 6 is rotated while the torsion bar 5 is twisted by the stub shaft 3, the piston 10 moves in the axial direction corresponding to the direction of rotation, and the pinion 17A that engages with the rack 16 is moved. It can be driven to change the direction of the vehicle's steering wheels.

In order to reduce this steering operation force, pressure oil is sent into the cylinder chamber 15A or 15B to power assist the movement of the piston 10.

A rotary control valve 18 for controlling the supply of pressure oil is disposed inside the valve housing 1B.

An inner race 21 of a thrust bearing 20 is formed at the base end of the wormshaft 6 on which a thrust reaction force acts when the piston 10 moves, and a ring-shaped outer race 24 is fitted on the outside of the inner race 21 so as to sandwich a steel ball 22 therebetween. .

Note that the retainer 25 prevents the steel balls 22 from coming off.

The thrust bearing 20 thus integrally constructed at the base end of the wormshaft 6 is attached to the boss hole 27 of the valve housing 1B via the race retaining ring 26.

Next, the valve sleeve 30 of the control valve 18 is fitted into the flange 28 at the base end of the wormshaft 6, and is prevented from rotating by a pin 31.

Therefore, the valve sleeve 30 rotates at the same time as the wormshaft 6.

On the other hand, a valve rotor 32 disposed on the inner surface of the valve sleeve 30 is commonly connected to the stub shaft 3 and the torsion bar 5 by a pin 4 that connects them.

That is, one end of the pin 4 is inserted into an axially extending groove 33 formed on the inner periphery of the valve rotor 32, so that the valve rotor 32 and the stub shaft 3 rotate at the same time.

By the way, one of the major features of the present invention is that the rotating sliding contact surface between the valve sleeve 30 and the valve rotor 32 of the control valve 18 is
It is formed into a conical surface with the axis of the stub shaft 3 as the rotation center.

A plurality of groove portions 34 extending in the axial direction are formed on the outer circumferential conical slope of the valve rotor 32 at equal intervals on the circumference, and land portions 35 are formed between the groove portions 34 .

The groove bottom of the groove portion 34 is formed approximately parallel to the rotation center line, and therefore the depth of the groove is equal to the rotor 3.
As the cone diameter of No. 2 becomes smaller, the groove becomes shallower, and the bottom surface of the groove directly intersects with the cone slope.

By forming the valve rotor 32 in this way, it is possible to integrally mold the valve rotor 32 by cutting it in the axial direction without using a split die using precision casting, forging, or sintered metal. In the same manner, a groove portion 36 is formed on the inner conical slope of the valve sleeve 30.

Of course, the groove depth of the groove portions 36 changes continuously in the axial direction, and the groove portions 36 are arranged at equal intervals in the circumferential direction corresponding to the land portions 35 of the rotor 32.

By configuring the valve sleeve 30 and the valve rotor 32 in this way, it is possible to integrally mold them using precision casting, forging, or sintered metal, and in particular, by punching in the axial direction, burrs from the mating surfaces peculiar to split molds can be eliminated. This has the advantage that no subsequent machining is required.

Next, as is clear from FIG. 2, passages 38 communicating with the central through hole 37 are formed in every other groove part 34B of the groove parts 34A and 34B of the valve rotor 32, and the passages 38 communicate with the central through hole 37. It communicates with a space 39 with the outer surface of the stub shaft 3.

This space 39 communicates with the low pressure tank side.

Note that the stepped portion 37A of the central through hole 37 has a flange portion 40 formed in the middle of the stub shaft 3.
are in contact with each other, and receive a thrust force acting on the valve rotor 32 in the right direction in the figure.

In this embodiment, the groove portions 36 of the valve sleeve 30 include six groove portions 36A and 36B, and every other groove portion is connected to the cylinder chambers 15A and 1, respectively.
Passages 42 and 43 are formed through the valve sleeve 30 for communication with the valve sleeve 30.

Two annular grooves 44 and 45 are formed in the valve housing 1B at the outer periphery of the sleeve 30,
One annular groove 44 is connected to a pump port 46 and pump discharge oil is guided thereto, and the other annular groove 45
communicates with the cylinder chamber 15A through passages 47 formed in the housings 1B and 1A.

The annular groove 45 is always connected to the passage 42 of the groove portion 36A, and the annular groove 44 is connected to the passage 47 that opens to the land portion 41 between the grooves 36 of the valve sleeve 30. is in constant communication.

Note that the passage 43 of the groove portion 36B communicates with an annular space 48 formed between the end surface of the valve sleeve 30 and the valve housing 1B.
8 further communicates with the cylinder chamber 15B on the left side in the figure through a gap between the thrust bearings 20.

Therefore, the pressure oil supplied to the annular groove 44 is
In the neutral state of the control valve 18, the passage 4
7, the valve sleeve 30 passes through the groove portion 34A of the valve rotor 32 and communicates therewith in common.
The flow is divided into two groove parts 36A and 36B,
Furthermore, the rotor groove portion 34 communicates with the tank side.
B flows out into the passage 38.

At this time, the groove portions 36A and 3 which communicate with the left and right cylinder chambers 15A and 15B of the piston 10 are
6B is maintained at the same pressure, the hydraulic pressure on the piston 10 remains balanced.

On the other hand, if, for example, the valve rotor 32 rotates relative to the valve sleeve 30 in the clockwise direction in FIG.
4A communicates with the sleeve groove portion 36A, and on the other hand, the rotor groove portion 34B on the low pressure side communicates with the sleeve groove portion 36B. Therefore, pressure oil is sent to the left cylinder chamber 15A in FIG. The other cylinder chamber 15B is opened toward the tank, thereby disrupting the hydraulic balance regarding the piston 10 and causing the piston 10 to move to the right.

Moreover, if the valve rotor 32 rotates in the opposite counterclockwise direction, the pressure in the sleeve groove part 36A becomes low and the pressure in 36B becomes high, so the piston 10 starts moving to the left in the figure. be.

Such a hydraulic differential force to the piston 10 is generated in conjunction with the steering operation.

In other words, as mentioned above, when input rotation is applied to the stub shaft 3 due to steering operation, this is transmitted to the wormshaft 6. At this time, the steering load is transferred to the wormshaft 6 side via the piston 10 and the sector shaft (proportional to the turning resistance of the steering wheels), the rotation of the stub shaft 3 first causes the torsion bar 5 to
It is twisted according to the load.

At that point, the wormshaft 6 is still not moving, so the valve rotor 32 connected to the stub shaft 3 causes a rotational displacement with respect to the valve sleeve 30 connected to the wormshaft 6. Piston 1 in steps
A hydraulic pressure difference occurs between the left and right sides of 0, and the piston 10 begins to move.

This allows the wormshaft 6 to rotate in the same direction as the stub shaft 3 while maintaining the initial rotational phase difference, and in this way, as long as the input rotation continues, the control valve 18
is maintained in the switched state, allowing for light steering operation while receiving hydraulic assistance.

When the input rotation of the stub shaft 3 stops, the control valve 18 returns to the neutral state and holds the piston 10 at that position when the worm shaft 6 further rotates in the same direction by the torsional phase of the torsion bar 5. .

In this way, hydraulic pressure is applied in conjunction with steering operations, making it possible to perform very light steering operations.

By the way, in the present invention, the control valve 1
8 has a conical sliding surface, a thrust force to the left in FIG. 1 acts on the valve sleeve 30, and a thrust force to the right acts on the valve rotor 32. It can be received by the thrust bearing 20 and the flange portion 40 of the stub shaft 3, and an oil seal 5 is provided on the rotating sliding surface.
By providing 0, leakage of hydraulic oil can be prevented.

Thrust bearing 20 is wormshaft 6
Since a part of the inner race 21 is used as the inner race 21 and is formed integrally with the inner race 21, the structure can be simplified.

Note that the positioning of the control valve 18 is as follows:
For example, this can be done using only the flange portion 40 of the stub shaft 3, and there is no need to position both ends as in a normal rotary valve.

Note that this flange portion 40 may be of a snap-spring type, or a ring member separate from the stub shaft 3 may be screwed together, especially in the latter case, the valve clearance of the rotary valve 18 (valve sleeve 30 and rotor 32) can be easily adjusted, and assembly efficiency during production can be improved.

Since it is sufficient that the valve rotor 32 and the valve sleeve 30 have a relative rotational phase by steering operation, the attachments to the stub shaft 3 and the worm shaft 6 may be reversed.

Further, the present invention reduces the overall cost of the power steering device by reducing the control valve 18.
Because of the high productivity of the thrust bearing 20, it is possible to reduce the cost, and it also has the advantage of improving assembly efficiency.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the present invention, and FIG. 2 is a sectional view taken along the line -- in FIG. 1...Housing, 3...Stubshaft, 5
...Torsion bar, 6...Wormshaft,
10... Piston, 15A, 15B... Cylinder chamber, 17... Sector shaft, 18... Control valve, 20... Thrust bearing, 3
0... Valve sleeve, 32... Valve rotor.

Claims (1)

[Claims] 1. A stub shaft to which input rotation is transmitted, a worm shaft that screws into a piston connected to the worm shaft via a torsion bar, and switches based on the rotational phase of both shafts to selectively apply input rotation to the left and right cylinder chambers of the piston. In a power steering device equipped with a control valve that supplies pressure oil to a worm shaft, the control valve is composed of a valve rotor and a valve sleeve that are connected to either the stub shaft or the worm shaft, and the rotating sliding surfaces of both are connected to the stub shaft or the worm shaft. The groove portions formed in these conical surfaces form conical surfaces centered on the rotation axis, and the groove bottoms are approximately parallel to the rotation axis, while the worm shaft is connected to either the valve rotor or the sleeve. A power steering device characterized in that a thrust bearing is interposed between the base end of the valve housing and the valve housing.