JPH08119126A - Power steering device - Google Patents

Abstract

PURPOSE: To make cavitation hardly occur and reduce a fluid sound. CONSTITUTION: A worm shaft and a stub shaft are laid on the same axial line and jointed to each other via a torsion bar, so as to be capable of relative rotation at the preset angle. Furthermore, a valve sleeve 32 is formed on the internal surface of the worm shaft and coupled to the external surface of a valve rotor jointed to the stub shaft, thereby forming a rotary valve. Also, three return holes 50 are formed on the sleeve 32 at peripherally equal intervals, and return oil from the rotary valve is circulated to an oil tank via the holes 50. In this case, each of the holes 50 is formed out of two small round holes 50a and 50a adjacent to each other in a circumferential direction, or a circumferential slot. According to this construction, the flow passage area of each hole 50 becomes large. As a result, a flow velocity drops and a flow is facilitated, thereby making cavitation hardly occur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering apparatus, and more particularly to a power steering apparatus for controlling the supply and discharge of hydraulic oil via a rotary type control valve.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a conventional integral type power steering apparatus, which is slidably fitted in a cylinder portion 4 of a gear housing 2 to form two pressure chambers in the cylinder 4. A partitioning piston 6, a sector gear 14 that meshes with a rack 12 formed on the side surface of the piston 6, and a worm shaft (output shaft) screwed through a ball screw that circulates a large number of balls around the shaft center of the piston 6. ) 22, a stub shaft (input shaft) 26 arranged on the same axis as the worm shaft 22 and connected by a torsion bar 28 to allow relative rotation at a predetermined angle, and a large-diameter cylinder at the end of the worm shaft 22. Valve sleeve (outer valve) 32 formed on the inner peripheral surface of the portion and a valve rotor (inner bar) connected to the outer surface of the stub shaft 26 via a pin 34. And a rotary type of control valve 38 consisting of blanking) 36.

In the integral type power steering apparatus having the above structure, the stub shaft 26 and the worm shaft 22 (that is, the valve rotor 36 and the valve sleeve 32 that rotate integrally with them) by operating a steering handle (not shown).
When the and are rotated relative to each other, the pressure oil discharged from the oil pump enters the rotary valve 38 through the pump port formed in the valve housing 24, and is distributed and introduced into one chamber of the cylinder 4. At the same time, the hydraulic oil in the other chamber passes through the control valve 38,
Radial return hole 33 formed in valve sleeve 32
After flowing out into the annular space 40 between the outer peripheral surface of the stub shaft 26 and the inner peripheral surface of the valve housing 24 via the, the tank port 42 of the valve housing 24 returns to the oil tank, The piston 6 is operated by the pressure difference between the two chambers of the cylinder 4 to generate a steering assist force.

[0004]

The above-mentioned valve sleeve 3
As shown in FIGS. 7 and 8, the return holes 33 to the oil tank formed in 2 are formed as a single round hole at a plurality of places (three places in this example) at equal intervals in the circumferential direction. There is. When the oil flows out into the annular space 40 through the single small-diameter round hole formed in each part as described above, the flow velocity is high and the flow is rapidly bent, so that the cavitation is reduced. There is a problem that it is easy to generate and the fluid noise is loud.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a power steering apparatus capable of suppressing the occurrence of cavitation and reducing fluid noise.

[0006]

A power steering apparatus according to the present invention includes an input shaft that is rotated by operating a steering handle,
An output shaft that is arranged on the same axis as this input shaft and is connected via a torsion bar and is relatively rotatable, and an inner valve that is provided on the outer periphery of the input shaft and that rotates integrally with the output shaft It has a rotary type control valve consisting of an outer valve formed,
The control valve is operated by rotating the steering wheel to supply the pressure oil discharged from the main pump to one chamber of the cylinder, and to recirculate the hydraulic oil in the other chamber to the tank. The steering assist force is generated by the control valve, and the hydraulic oil flowing back from the control valve to the oil tank is returned to the outer valve through return holes formed at a plurality of positions at equal intervals in the circumferential direction. In particular, the opening areas of the return holes formed in the respective outer valves are enlarged in the circumferential direction.

[0007]

In the power steering apparatus according to the present invention, the oil flowing back from the inside of the control valve to the oil tank through the return hole formed in the outer valve has a return hole enlarged in the circumferential direction as compared with the conventional one. Since it flows through, the flow area is slow due to the large passage area, and when it flows out from the return hole to the annular space on the outlet side, it easily flows along the annular surface, so the oil flow is smooth. Therefore, cavitation is less likely to occur, and therefore, the fluid noise generated due to cavitation is reduced.

[0008]

The present invention will be described below with reference to the illustrated embodiments.
1 is a longitudinal sectional view of an integral type power steering apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1,
FIG. 3 is a front view of a worm shaft used in the power steering apparatus. Cylinder part 4 of gear housing 2
A piston 6 is slidably fitted therein, and divides the inside of the cylinder portion 4 into two pressure chambers 8 and 10. A rack 12 is formed on one side surface (the lower surface side in FIG. 1) of the piston 6, and the rack 12 is integrally provided on a sector shaft connected to a steering wheel (not shown) via a link mechanism. The sector gear 14 engaged with the piston 6
The sector gear 14 rotates forward and backward in accordance with the reciprocating movement of the.

A ball screw groove 18 is screwed into the hole 16 of the shaft core of the piston 6, and a worm shaft (output shaft) 22 is screwed through a large number of balls 20 accommodated in the ball screw groove 18. Have been combined. Worm shaft 2
One end of 2 (right side of FIG. 1) has a large-diameter cylindrical shape,
The outer peripheral surface of the large-diameter cylindrical portion is slidably fitted to the inner surface of the valve housing 24 fixed to the end of the gear housing 2. An inner race 25a of a ball bearing 25 is provided at the tip of the large-diameter cylindrical portion of the worm shaft 22, and the step portion inside the valve housing 24 and the plug 2 screwed into the valve housing 24 are provided.
Between the outer race 25b fixed between 7 and
Many balls 25 held by cage bearings 25c
d is held to rotatably support the worm shaft 22. An end of a stub shaft (input shaft) 26 that is rotated by a steering handle (not shown) is fitted into the large-diameter cylindrical portion of the worm shaft 22, and a bearing 29 and a plug 27 arranged inside the worm shaft 22 are fitted. It is rotatably supported by the inner bearing 30. The worm shaft 22 and the stub shaft 26 are connected to each other by a torsion bar 28 inserted in the holes of their respective axial cores, and relative rotation of a predetermined angle is allowed.

A valve sleeve (outer valve) 32 is formed on the inner peripheral surface of the large-diameter cylindrical portion of the worm shaft 22. On the other hand, a valve rotor (inner valve) 36 is fitted on the outer peripheral surface of the stub shaft 26 and is connected by a pin 34 so as to rotate integrally. The valve sleeve 32 and the valve rotor 36 constitute a rotary type control valve 38. A plurality of (six in this embodiment) valve grooves 32a extending in the axial direction are formed on the inner peripheral surface of the valve sleeve 32 at equal intervals in the circumferential direction, and the valve sleeve 32 is formed on the outer peripheral surface of the valve rotor 36. Similarly, a plurality of (six) valve grooves 36a extending in the axial direction are formed at equal intervals in the circumferential direction. In the neutral state of the rotary valve 38, the valve groove 32a of the valve sleeve 32 and the valve rotor 36 are formed.
The worm shaft 22 and the stub shaft 26 are connected such that the valve grooves 36a of the worm shaft are alternately located. In this embodiment, the valve grooves 32a and 36a formed in the valve sleeve 32 and the valve rotor 36 are used.
The number of each is 6, but it is not limited to 6 and may be an even number such as 8.

The valve grooves 32a formed in the valve sleeve 32 are alternately provided with passages 32c passing through the inside of the valve sleeve 32 and passages 24a inside the valve housing 24.
And the like, and is connected to the pressure chamber 8 on the left side of the cylinder 4 and to the pressure chamber 10 on the right side of the cylinder 4 via a passage 32d passing through the inside of the valve sleeve 32. On the other hand, every other valve groove 36a formed in the valve rotor 36 has a radial passage 32b formed in the land of the valve sleeve 32 facing each other and the valve housing 2
It is connected to an oil pump (not shown) through a pump port formed in 4. Further, each valve groove 36a positioned in the middle of the three valve grooves 36a connected to the oil pump of the valve rotor 36 has a radial return hole 50 formed in the land of the valve sleeve 32 facing the valve groove 36a. And an annular space 40 between the outer peripheral surface of the valve sleeve 32 and the inner peripheral surface of the valve housing 24 and the tank port 4 provided in the valve housing 24.
It is connected to an oil tank (not shown) via 2 or the like.

At the neutral position of the rotary valve 38,
The pressure oil discharged from the oil pump enters the pump side valve groove 36a of the valve rotor 36 through the pump port of the valve housing 24, the radial passage 32b formed in the valve sleeve 32, and the like, and the pump side valve groove 36a.
Valve groove 32 of valve sleeve 32 located on both sides of a
through a, into the valve groove 36a on the other tank side of the valve rotor 36, and from the return hole 50 formed in the valve sleeve 32 facing the valve groove 36a on the tank side, through the annular space 40 and the tank port 42. To return to the oil tank.

When the stub shaft 26 rotates in either direction by the operation of the steering wheel and the valve rotor 36 and the valve sleeve 32 rotate relative to each other, the pressure oil discharged from the oil pump is transferred to the valve rotor. After entering the pump side valve groove 36a formed in 36, the pressure chamber 8 of the cylinder 4 or the pressure chamber 8 of the cylinder 4 is passed through one valve groove 32a of the grooves 32a of the valve sleeve 32 facing both sides of the pump side valve groove 36a. The hydraulic oil introduced into the other pressure chamber 10 or 8 enters the tank side valve groove 36a of the valve rotor 36 from the other valve groove 32a of the valve sleeve 32, and further, the return hole 50 of the valve sleeve 32 facing each other. To return to the oil tank.

In the power steering apparatus according to the present embodiment, the radial return hole 50 formed through the inside and the outside is formed in the large-diameter cylindrical portion of the worm shaft 22 provided with the valve sleeve 32. As shown in FIG. 2 and FIG. 3, three return holes 50 are formed at equal intervals in the circumferential direction, and the return holes 50 at each of the points are composed of two circular holes 50a and 50b adjacent to each other in the circumferential direction. ing. Therefore, for example, if each of the round holes 50a and 50b has the same diameter as the single round hole provided in the power steering apparatus having the above-described conventional structure, the passage area is doubled as a whole. When the passage area of the return hole 50 increases in this way, the rotary valve 3
Since the flow velocity of the oil flowing back from the oil tank 8 to the oil tank becomes slower and the flow becomes smoother, cavitation is less likely to occur and the fluid noise is reduced. Further, when a plurality of holes are arranged in the axial direction, the entire power steering apparatus becomes large in the axial direction, but since they are arranged in the circumferential direction, the same size as the conventional one can provide an excellent effect. be able to.

In this embodiment, two sets of two round holes 50a and 50b are provided on the circumference of the worm shaft 22, but the number is not limited to three, and the valve sleeve 32 and the valve rotor are not limited to three. 36 valve grooves 32a, 36
When the number of a is eight, it is determined by the number of equal valve grooves 32a and 36a in which four return holes 50 are provided. Further, the number of round holes 50a and 50b at each location is not limited to two, and may be three or more. In addition, return hole 5
The shape of each hole of 0 is not limited to a circular shape, and may be other shapes. Further, the diameters of the round holes 50a and 50b do not have to be the same as those of the conventional round holes, and can be appropriately determined.

FIGS. 4 and 5 are a cross-sectional view of the worm shaft 122 of the power steering apparatus according to the second embodiment, similar to FIG. 2, and a view showing the entire worm shaft 122, and other parts. Since it has the same configuration as that of the first embodiment, illustration and description thereof will be omitted. In this embodiment, similar to the first embodiment, the valve sleeve 13
Radial return holes 150 for circulating the hydraulic oil from the rotary valve 38 to the oil tank are provided at three circumferential positions of 2.
However, each of the return holes 150 at each location is composed of a single elongated hole whose length is enlarged in the circumferential direction. In this embodiment as well, the effect of suppressing the generation of cavitation and reducing the fluid noise can be achieved as in the case of the above-described embodiment, but in particular, the return hole 150 is a single elongated hole having a large cross-sectional area. Therefore, when the hydraulic oil flows out of the return hole 150 into the annular space 40 between the inner peripheral surface of the valve housing 24 and the outer peripheral surface of the worm shaft 122, the flow is bent smoothly and cavitation is further reduced. It becomes difficult to generate, and the fluid noise can be effectively reduced.

In each of the above embodiments, the valve rotor 3
6 directly from the tank side valve groove 36a of the valve sleeve 3
The oil is returned to the oil tank through the two return holes 50 and 150 and the annular space 40. However, the structure is not limited to this, and the valve groove on the tank side of the valve rotor may be
The structure of the present invention is similarly applied to a structure in which the oil is once introduced into the space inside the valve rotor and then returned to the oil tank through another radial passage formed in the valve rotor and the return hole of the valve sleeve. Can be applied.

[0018]

As described above, according to the present invention, the control valve including the inner valve integrated with the input shaft and the outer valve integrated with the output shaft is provided, and the return oil from the control valve is supplied to the outer valve. The opening area of the return holes of each part formed on the outer valve of the power steering device in which the oil is returned to the oil tank through the return holes formed at a plurality of positions at equal intervals in the circumferential direction on the valve in the circumferential direction. Since the passage area of the hydraulic oil is expanded, the flow velocity is slowed down, and the flow is easy along the space discharged from the return hole, and the flow is smoothed so that cavitation is less likely to occur and fluid noise is reduced. Can be reduced.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a power steering apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a front view of a worm shaft that constitutes the power steering apparatus.

FIG. 4 is a sectional view of a position corresponding to FIG. 2 of the second embodiment.

FIG. 5 is a front view of a worm shaft that constitutes a power steering apparatus according to a second embodiment.

FIG. 6 is a vertical cross-sectional view showing a main part of a conventional power steering apparatus.

7 is a sectional view taken along the line BB of FIG.

FIG. 8 is a front view of a worm shaft that constitutes a conventional power steering apparatus.

[Explanation of symbols]

 4 Cylinder 8 Cylinder One Chamber 10 Cylinder One Chamber 22 Output Shaft (Worm Shaft) 26 Input Shaft (Stub Shaft Shaft) 32 Outer Valve (Valve Sleeve) 36 Inner Valve (Valve Rotor) 38 Control Valve 50 Return Hole

Claims (3)

[Claims] 1. An input shaft which is rotated by operating a steering handle, an output shaft which is arranged on the same axis as the input shaft and is relatively rotatable, and an inner valve which is provided on the outer periphery of the input shaft and integrally rotates. It is equipped with a control valve consisting of an outer valve formed on the inner surface of the output shaft.The control valve is operated by rotating the steering wheel, and the pressure oil discharged from the main pump is supplied to one chamber of the cylinder for steering. While generating auxiliary power,
In the power steering device, the hydraulic oil that returns from the control valve to the oil tank is returned to the outer valve through return holes formed at a plurality of locations at equal intervals in the circumferential direction. A power steering apparatus, wherein the opening area of each return hole is enlarged in the circumferential direction. 2. The return hole at each of the points is formed by a plurality of holes that are circumferentially adjacent to each other.
The power steering apparatus according to. 3. The power steering apparatus according to claim 1, wherein the return holes at the respective points are elongated holes that are enlarged in the circumferential direction.