JP3807715B2 - Rotary valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotary valve used in a power steering apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a rotary valve used in a power steering apparatus is composed of, for example, a rotor valve member V1 and a sleeve valve member V2 that are fitted so as to be relatively rotatable with each other as shown in FIG. By relative rotation, the orifice F formed between the two valve members is controlled to control the supply pressure to the power cylinder P, and the return fluid from the power cylinder P is discharged through the plurality of discharge holes R. I try to let them.
[0003]
[Problems to be solved by the invention]
FIG. 6 shows assist characteristics of the conventional servo valve. As can be seen in this figure, the assist force gradually increases by applying manual torque, but in reality, a slight hysteresis is applied to the reference characteristic L due to the sliding resistance of the bearings and oil seals constituting the power steering device. For example, it changes like a characteristic La slightly shifted outward when the steering wheel is cut, and changes like a characteristic Lb slightly shifted inward when the handle is returned.
However, according to the conventional servo valve, the characteristics are almost the same at the time of steering both when the steering wheel is turned and when the steering wheel is returned, and the width of the hysteresis H is small. In such a conventional assist characteristic, the power assist force is greatly reduced at the moment of returning the steering wheel, so that the vehicle is steered quickly following this, and the steering stability is not sufficient as a driver's steering feeling.
[0004]
[Means for Solving the Problems]
The present invention has been made in order to solve the above-mentioned problems, and the invention according to claim 1 comprises a sleeve valve member and a rotor valve member which are fitted so as to be relatively rotatable with each other. by, in the servo valve so as to be discharged through the four discharge holes respectively communicating return fluid to the plurality of grooves and the groove from by controlling the supply pressure to the power cylinder and the power cylinder, the Among the four discharge holes, the two discharge holes adjacent to each other are different in opening area from the other two discharge holes .
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example in which a rotary valve according to a reference example of the present invention is applied to a rack and pinion type power steering apparatus. Reference numeral 10 denotes a gear housing that forms a main body of the power steering apparatus. The pinion shaft 11 is rotatably supported by bearings 12 and 13 at both ends, and meshes with rack teeth 15 of a rack shaft 14 that can slide in a direction intersecting with the bearings. A piston 17 (see FIG. 2) of a power cylinder 16 that assists handle torque is operatively connected to the rack shaft 14.
[0007]
A valve housing 18 is fixed to the gear housing 10, and a rotary valve 20 of the present invention is accommodated in a valve hole of the valve housing 18. The rotary valve 20 includes a sleeve valve member 21 and a rotor valve member 22 that are rotatable relative to each other about the axis of the pinion shaft 11. The sleeve valve member 21 is connected to the pinion shaft 11 by a connecting pin 23. The rotor valve member 22 is formed on a control shaft 24 connected to the steering wheel, and the control shaft 24 is flexibly connected to the pinion shaft 11 via a torsion bar 25.
[0008]
As shown in FIG. 2, a plurality of (eight in the embodiment) concave grooves 27 are formed on the inner periphery of the sleeve valve member 21, and a land portion 28 is formed between each of the concave grooves 27. Yes. A plurality of land portions 35 corresponding to the respective concave grooves 27 of the sleeve valve member 21 are formed on the outer periphery of the rotor valve member 22, and concave grooves 36 are formed between the land portions 35.
[0009]
A supply hole 29 is opened in one jump of the land portion 28 of the sleeve valve member 21, and the supply hole 29 communicates with a supply port 30 communicating with the supply pump. A pair of distribution holes 31 and 32 are opened in the concave grooves 27 and 27 provided on both sides of the land portion 28, and the pair of distribution holes 31 and 32 are formed in the left and right chambers 16 a and 16 b of the power cylinder 16. It communicates with the supply / discharge ports 33 and 34 that communicate with each other.
[0010]
Further, out of the concave grooves 36 of the rotor valve member 22, discharge grooves 37 a, 37 b, 37 c, 37 d are opened in the single concave groove 36, and these discharge holes 37 a, 37 b, 37 c, 37 d are connected to the rotor valve member 22. It communicates with the reservoir via a passage 38 formed between the torsion bar 25, a through hole 39 and a discharge port 40.
[0011]
In the servo valve having such a configuration, in the reference example of the present invention, among the plurality of discharge holes 37a, 37b, 37c, and 37d that are respectively opened in the concave groove 36, the discharge hole 37c is at least the other that faces in the radial direction. The opening area is smaller than the discharge holes 37a, 37b, and 37d. Accordingly, the groove 36 communicating with the small diameter discharge hole 37c and the groove 36 communicating with the large diameter discharge hole 37a generate different sizes of fluid pressure (back pressure) in the groove 36. As a result, the rotor The valve member 22 is pressed in the radial direction.
[0012]
Next, the operation of the servo valve in the above configuration, FIGS. 1 and 2, will be described with reference to 4. In the neutral state of both valve members 21, 22, the pressure fluid supplied to the supply port 30 is discharged from the supply hole 29 opened in the land portion 28 through the discharge holes 37 a, 37 b, 37 d with almost no resistance. The pressure difference is not generated in the left and right chambers 16a and 16b of the power cylinder 16.
[0013]
However, when the rotor valve member 22 is rotated clockwise with respect to the sleeve valve member 21 by the turning operation of the handle, the orifice formed between the valve members is throttled. As a result, the supply port 30 and the supply hole are supplied from the pump. 29, the fluid pressure of the pressure fluid supplied to the concave groove 36 is increased, and this increased fluid pressure is introduced into the right chamber 16b of the power cylinder 16 through the concave groove 27 and the distribution port 32, and The pressure fluid in the left chamber 16a of the power cylinder 16 is discharged to the reservoir through the distribution port 31, the concave groove 36, the discharge holes 37a, 37b, 37c, 37d, the passage 38, the through hole 39, and the discharge port 40.
[0014]
When the rotor valve member 22 is rotated counterclockwise with respect to the sleeve valve member 21 by the return operation of the handle from this state, the orifice formed between the valve members is throttled, and as a result, the supply port 30 is supplied from the pump. The fluid pressure of the pressure fluid supplied to the concave groove 36 through the supply hole 29 rises, and this increased fluid pressure is introduced into the left chamber 16 a of the power cylinder 16 through the concave groove 27 and the distribution port 31. The pressure fluid in the right chamber 16b of the power cylinder 16 is discharged to the reservoir through the distribution port 32, the concave groove 36, the discharge holes 37a, 37b, 37c, 37d, the passage 38, the through hole 39, and the discharge port 40. The
[0015]
At the time of such steering, in the servo valve of the reference example of the present invention, as shown in FIG. 4 , when the steering wheel is turned, the characteristic La changes to the reference characteristic L when the steering wheel is cut, and when the steering wheel is returned, the reference characteristic is changed. It changes like a characteristic Lb shifted inward with respect to L.
[0016]
However, in the servo valve according to the reference example of the present invention, one of the plurality of discharge holes 37a, 37b, 37c, and 37d has an opening area at least with respect to the other discharge hole 37a facing in the radial direction. Therefore, the generated pressure is unbalanced in the concave groove 36 communicating with the discharge hole 37a having a large opening area and the concave groove 36 communicating with the discharge hole 37c having a small opening area. The rotor valve member 22 is pressed in the radial direction, and a frictional force is generated between the rotor valve member 22 and the sleeve valve member 21.
[0017]
In the reference example of the present invention , due to the action of the frictional force, the shift amount in both the inner and outer directions in FIG. 4 , that is, the width of the hysteresis H, becomes larger, and thus the power assist force with respect to the steering force gradually decreases at the moment of returning the steering wheel. As a result, the vehicle is gently returned and steered, and the driver can obtain a stable steering feeling.
[0018]
Figure 3 is an embodiment of the present invention. In this embodiment , among the plurality of discharge holes 37a, 37b, 37c, 37d, the opening area of two discharge holes 37c, 37d adjacent to each other is made smaller than the opening area of the other discharge holes 37a, 37b. Therefore, in the two concave grooves 36 where the discharge holes 37c and 37d are opened, a larger fluid pressure is generated than in the other concave grooves 36 opposed to the radial grooves 36, so that the rotor member 22 is pressed in a larger radial direction. Force can be applied. As a result, the width of the assist characteristic hysteresis H when the steering wheel is turned and when the steering wheel is returned is further increased. As a result, the power assist force with respect to the steering force gradually decreases at the moment when the steering wheel is returned. The driver is steered back, and the driver can obtain a more stable steering feeling.
[0019]
【The invention's effect】
As described above, since the opening areas of the plurality of discharge holes are made different from those of the other discharge holes opposed in the radial direction, a differential pressure corresponding to the difference in the diameter of the discharge holes is generated between the concave grooves facing each other. The differential pressure acts as a pressing force against the spool valve member, and as a result, the sleeve valve member is pressed in the radial direction, and a frictional force is generated between the sleeve valve member and the sleeve valve member. This frictional force makes it possible to increase the width of the hysteresis of the characteristics when the handle is turned and when the handle is returned, and as a result, the power assist force with respect to the steering force gradually decreases at the moment of returning the handle. The vehicle is steered back more gently, and the driver has an advantage of obtaining a more stable steering feeling.
[0020]
Moreover in the present invention, by difference the opening area of the exhaust Deana, because it so as to exert a pressing force in the radial direction to the rotor valve member, also special equipment other than to have the opening area difference of the discharge hole must In addition, the necessary assist characteristics can be obtained with a simple configuration, and the opening area is selectively used depending on the target vehicle, so that the assist characteristics matching the target vehicle can be easily tuned.
[0021]
Further, among the four discharge holes, two adjacent discharge holes have different opening areas from the other two discharge holes, so that a larger fluid pressure is applied to the rotor valve member . As a result, the hysteresis of the assist characteristic at the time of turning the steering wheel and returning the steering wheel becomes larger, and as a result, the power assist force with respect to the steering force gradually decreases at the moment of returning the steering wheel, and the vehicle becomes more gentle. The driver is steered back, and the driver can obtain a more stable steering feeling.
[Brief description of the drawings]
FIG. 1 is a sectional view of a power steering apparatus provided with a servo valve according to a reference example of the present invention.
FIG. 2 is a sectional view of a servo valve according to a reference example of the present invention.
FIG. 4 is a characteristic diagram showing a relationship between steering torque and assist force according to a reference example of the present invention.
FIG. 3 is a diagram showing an embodiment of the present invention.
FIG. 5 is a cross-sectional view corresponding to FIG. 2 showing a conventional example.
FIG. 6 is a characteristic diagram showing a relationship between conventional steering torque and assist force.

Claims (1)

It consists of a sleeve valve member and a rotor valve member that are fitted so as to be rotatable relative to each other. By rotating both the valve members relative to each other, the supply pressure to the power cylinder is controlled and the return fluid from the power cylinder is made into a plurality of concave grooves. In addition, in the servo valve adapted to discharge through the four discharge holes respectively communicating with the concave grooves, the two discharge holes adjacent to each other among the four discharge holes are opened with respect to the other two discharge holes. Servo valve characterized by different .

Images