JPH018456Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a power steering device equipped with a flapper type control valve. The purpose is to prevent uneven flow and thereby make cavitation less likely to occur.

Generally, in a power steering system equipped with a flapper type control valve, the flapper valve is rotatably housed in a valve body that forms an outflow nozzle, and the valve seat provided on the flapper valve is operated by relative rotation between the valve body and the flapper valve. The outflow nozzle is opened and closed to generate the required pressure in the power cylinder.

In this kind of flapper type control valve, as shown in FIG. 1A, when the flapper valve 2 is rotated by the maximum angle θ within the valve body 1, the valve is attached to the side wall 5 of the valve body 1 which opens the outflow nozzle 4. The end face of the valve seat 3 is inclined so that the end face of the seat 3 comes into contact with the face and closes the outflow nozzle 4. Therefore, in the angular range from the neutral position of the flapper valve 2 to just before the valve seat 3 abuts the side wall 5, the valve seat 3 and the side wall 5 move as shown in FIG. 1B.
The gap between the inner gap δ1 and the outer gap δ
2 is always larger, and since the valve seat 3 and the outflow nozzle 4 are almost concentric, the pressure fluid flowing out from the outflow nozzle 4 flows toward the outside where the gap is larger, and cavitation occurs in this part. This causes a squeezing sound.

The present invention was developed in view of the above-mentioned problems, and is intended to prevent cavitation by allowing pressure fluid to flow uniformly over the circumference from the outflow nozzle regardless of the size of the gap.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 2 shows a power steering device, in which a power cylinder 11 fitted with a piston 10 is provided on one side,
The other side is provided with a valve housing 13 housing a flapper type control valve 12 for controlling the pressure fluid supplied to the power cylinder 11. A rack 14 is carved on a portion of the circumference of the piston 10, and the rack 14 meshes with a sector gear 16 of a cross shaft 15 connected to a steering wheel via a link mechanism. Further, a screw shaft 18 is screwed onto the piston 10 via a ball 17, and a main valve member 2 to which a sleeve valve member 19 to be fitted into the valve housing 13 is fitted and fixed is attached to one end of the screw shaft 18.
0 (see FIGS. 3 and 4) is integrally formed.

A valve chamber having side walls facing each other is formed in the main valve member 20 in the axial direction. It is sealed and separated into 25 and 26. On both side walls 25a of one valve chamber 25, a pair of distribution nozzles 27, 2 are provided as shown in FIG.
8 are opened to face each other, and this valve chamber 25 is communicated with a supply port 29. In addition, a pair of outflow nozzles 31 and 32 are opened to face each other on both side walls 26a of the other valve chamber 26, as shown in FIG. 4, and this valve chamber 26 is communicated with a discharge port 35. One valve chamber 25 accommodates a first flapper valve 37 with circular valve seats 33 attached on both sides for controlling opening and closing of the distribution nozzles 27, 28, and the other valve chamber 26 accommodates the outflow nozzles 31, 28. A second flapper valve 38 with circular valve seats 34 attached on both sides for controlling the opening and closing of the flapper valve 32 is housed, and these flapper valves 37 and 38 are connected to the first flapper valve 3 in order to obtain an appropriate steering reaction force during steering.
The rotation radius of the second flapper valve 38 is configured to be larger than the rotation radius of the second flapper valve 7. The first and second flapper valves 37, 38 are integrally formed with a steering shaft 39 rotatably supported on a bearing member, and this steering shaft 39 is connected to a steering handle via a joint (not shown) and a handle shaft. . A torsion bar 40 is inserted through the centers of the screw shaft 18, the first and second flapper valves 37, 38, and the steering shaft 39, and both ends of the torsion bar 40 are connected to the screw shaft 1.
8 and a steering shaft 39, respectively.

Said distribution nozzles 27, 28 and outflow nozzle 3
1 and 32, one of the distribution nozzles 27 and one of the outflow nozzles 31 communicate with an annular groove 43 formed in the sleeve valve member 19 through communication passages 41 and 42, and from this annular groove 43 through a passage 44. It communicates with the left chamber 11a of the power cylinder 11, and the other distribution nozzle 28 and the other outlet nozzle 32 communicate with each other through communication passages 45 and 46, and the screw shaft 1
The right chamber 11b of the power cylinder 11 is communicated with the right chamber 11b of the power cylinder 11 through a passage 47 formed at one end of the power cylinder 8.

Here, the valve seat 34 attached to the second flapper valve 38 is in a state where the valve seat 34 is in surface contact with the side wall 26a as shown in FIG. 5A.
is arranged such that its center is offset radially outwardly by a small amount e with respect to the center of the outlet nozzles 31, 32. This causes the valve seat 34 to connect to the outflow nozzle 31,
32 is closed, even if the outer gap δ2 is larger than the inner gap δ1 between the valve seat 34 and the side wall 26a, on the outside where the gap is large, from the center of the outflow nozzles 31 and 32 to the outer periphery of the valve seat 34. On the inside where the gap is small, the distance from the center of the outflow nozzles 31, 32 to the outer periphery of the valve seat 34 becomes shorter, and as a result, as shown in FIG. The aperture length l1 between the side wall 26a and the side wall 26a becomes longer, and the flow path resistance increases.
Conversely, on the inside, the aperture length l2 becomes shorter and the flow path resistance decreases.

Since the power steering system of the present invention is constructed as described above, when the steering handle is in the neutral state, the first and second flapper valves 37 and 38 are closed as shown in FIGS. 3 and 4. is held in a neutral position within the valve chambers 25, 26, thereby allowing the supply port 29
The pressure fluid supplied to the valve chamber 25 is equally distributed to the distribution nozzles 27 and 28, and this distributed flow is discharged from the outlet 35 via the valve chamber 26 from the outflow nozzles 31 and 32, so that the power The pressure fluid in the left and right chambers 11a and 11b of the cylinder 11 does not increase in pressure, and the steering wheels maintain a neutral state.

However, when the steering handle is rotated, for example, to the left, the first and second flapper valves 37 and 38 cause one of the distribution nozzles 28 and the outflow nozzle 31
is closed and the other distribution nozzle 27 and outlet nozzle 32 are opened. As a result, the pressure fluid supplied to the valve chamber 25 is distributed only to the distribution nozzle 27 and sent under pressure to the outflow nozzle 31, but since the amount of outflow from this outflow nozzle 31 is restricted, the pressure increases, and this pressure increase The pressure fluid is in the cylinder left ventricle 1.
1a, the piston 10 presses to the right,
The fluid in the cylinder right chamber 11b is discharged through the outflow nozzle 32.

At this time, the pressure fluid whose outflow is restricted from the outflow nozzle 31 flows out at high speed into the low-pressure valve chamber 26 through a small gap between the valve seat 34 of the second flapper valve 38 and the side wall 26a. Moreover, the flow is biased toward the outside of the valve seat 34 with a large gap, but the valve seat 34 of the second flapper valve 38 is disposed radially outward with respect to the center of the outflow nozzle 31. Therefore, the flow path resistance at the constricted portion with a large gap increases. Therefore, the pressure fluid flows through the valve seat 34 with a large gap.
It is possible to prevent the flow from being biased toward the outside of the valve seat 34, and it is distributed almost evenly over the circumference of the valve seat 34, making it difficult for cavitation to occur, thereby making it possible to prevent the generation of squeezing noise.

As described above, in the present invention, in the part where there is a large gap between the valve seat and the side wall that opens and closes the outflow nozzle, the length of the aperture formed between the valve seat and the side wall is
Since the gap is longer than the small part of the gap, it is possible to prevent the pressure fluid flowing out from the outflow nozzle from flowing toward the large gap side, and the flow of the pressure fluid can be almost evenly distributed. Therefore, cavitation is less likely to occur, and the effect of preventing the generation of squeezing noise can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a conventional flapper type control valve, Fig. 2 is a sectional view of a power steering device showing an embodiment of the present invention, and Figs. 3 and 4 are -
5 is a cross-sectional view of a flapper type control valve which is a main part of the present invention. DESCRIPTION OF SYMBOLS 11...Power cylinder, 12...Flapper type control valve, 13...Valve housing, 20...Main valve member, 27, 28...Distribution nozzle, 31, 32...
Outflow nozzle, 33, 34... Valve seat, 37, 38...
...Fratsupaben.

Claims (1)

[Scope of utility model registration request] A flapper-type control valve comprising a main valve member having a side wall opening an outflow nozzle for pressurized fluid, and a flapper valve that is housed in the main valve member so as to be relatively rotatable and is provided with a valve seat that opens and closes the outflow nozzle. In a power steering device that selectively supplies pressurized fluid to the left and right chambers of a power cylinder, in a portion where there is a large gap between the valve seat and the side wall that opens and closes the outflow nozzle, there is a gap between the valve seat and the side wall. A power steering device in which the length of the aperture formed is longer than the small part of the gap.