JP3046120B2 - Relief valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relief valve provided in a hydraulic circuit or the like. More specifically, the present invention relates to an improvement of a pilot operated relief valve having a shockless function suitable for equipping a hydraulic circuit including a brake circuit.

[0002]

2. Description of the Related Art In general, when a surge pressure is generated in a relief valve, a time delay from the generation of the surge pressure until the control is stabilized, that is, an operation delay occurs. Therefore, it is considered that it is absolutely necessary to reduce the surge pressure in order to improve the characteristics of the relief valve. The direct acting relief valve shown in FIG. 9 is conventionally known as a device for cutting surge pressure. The direct-acting relief valve includes first and second outflow / inflow ports 2 and 3
And the bore 4 is formed. And
One end of the bore 4 is closed with a plug 5 , and one end of a sleeve 6 is fitted to the plug 5 . The other end of the sleeve 6 is attached to a tubular sheet member 7.

Further, an annular projection 8 is formed in the bore 4, and a space is secured on the plug 5 side with the projection 8 as a boundary.
A free piston 9 is provided in this space. The free piston 9 is formed in a ring shape, and the inside thereof is in contact with the sleeve 6 and the outside is in contact with the bore 4. By providing the free piston 9 in this manner, the first and second oil chambers 10 and 11 are partitioned above and below the piston 9. The second oil chamber 11 is communicated with the second inflow / outflow port 3 via a passage 12 formed between the annular protrusion 8 and the sleeve 6.

[0004] A valve member 13 is provided in the sleeve 6, and a shaft portion 13 a of the valve member 13 is attached to the sleeve 6.
Slidably with respect to the poppet 13
b contacts the sheet portion 14 of the sheet member 7,
I try to get away from it. By inserting the shaft portion 13a of the valve member 13 into the sleeve 6, a spring chamber 15 is formed in the sleeve 6 on the plug 5 side.

The tip of the shaft portion 13a of the valve member 13 projects into the spring chamber 15, and a spring receiver 16 is placed over the projecting end. This spring receiver 1
A spring 17 is interposed between the plug 6 and the plug 5,
Normally, the poppet portion 13b is pressed against the sheet portion 14. The spring chamber 15 communicates with the first oil chamber 10 via a small hole 18 formed in the sleeve 6. Further, the valve member 13 has a communication hole 19 formed at the axial center thereof, and an orifice 20 formed in the communication hole 19. In addition, the seat portion 1
4 of the diameter D _1, is to reduce the diameter D ₂ of the shaft portion 13a of the valve member 13.

Next, the operation of the conventional direct acting relief valve will be described. Now, when the second outflow / inflow port 3 side is maintained at a high pressure and the first inflow / outflow port 2 side is maintained at a low pressure, the pressure on the outflow / inflow port 3 side acts on the second oil chamber 11 and the free piston 9 is moved to the position shown in the figure. Push it up. And the valve member 13 is
Due to the area difference between the spring 17 and the diameters D ₁ and D ₂ , the poppet portion 13 b maintains a state in which the poppet portion 13 b is pressed against the seat portion 14.

When the pressure on the first inflow / outflow port 2 side becomes high and the pressure on the second inflow / outflow port 3 side becomes low from the above state, the free piston is first operated by the pressure action on the first inflow / outflow port 2 side at that time. 9 moves. When the free piston 9 moves, a differential pressure is generated around the orifice 20.
The valve member 13 moves against the spring 17 and quickly opens the seat portion 14. The surge pressure can be cut by opening the seat portion 14 quickly. Further, after the free piston 9 has moved , the difference between the cross-sectional areas due to the diameters D ₁ and D ₂ and the spring force of the spring 17 are used.
Thus, the opening of the seat portion 14 is determined.

[0008]

In the above-mentioned conventional apparatus, the surge pressure can be cut. However, since it is a direct-acting type, there is a problem that its override characteristics are not good. In order to improve the override characteristics, a pilot-operated relief valve may be used.However, since the pilot-operated relief valve has a complicated structure, the free-piston relief valve can be easily formed like a direct acting relief valve. Could not be established. For this reason, conventionally, there has been a problem that a relief valve that can simultaneously solve two problems such as improving surge characteristics while preventing surge of operation by cutting surge pressure cannot be used.

Further, in this conventional relief valve, the free piston 9 cannot be returned to the original position shown in the drawing unless the pressure on the side of the second inflow / outflow port 3 increases. if,
If the free piston 9 is stopped at the position opposite to the original position shown in the drawing, there is a problem that the function of cutting the surge pressure is not exhibited at all. SUMMARY OF THE INVENTION It is an object of the present invention to provide a relief valve in which a free piston is always returned to an original position while a free piston is easily provided in a pilot operated type relief valve.

[0010]

According to the present invention, a sleeve is provided in a casing in which first and second inflow / outflow ports are formed, and a cylindrical valve member is slidably provided inside the sleeve. An orifice is formed in the hollow portion of the first member, and a pilot seat member is slidably fitted to the outside of the sleeve, and a first valve closing force is applied to the valve member between the valve member and the pilot seat member. With a spring interposed,
Moreover, a second spring is provided for opening and closing the pilot seat of the pilot seat member with the pilot poppet, and for applying a force in a direction of pressing the pilot seat to the pilot seat. The orifice is made larger than the spring force of the first spring, the orifice communicates with the pilot seat through the hollow portion of the valve member, and the fluid that has passed through the pilot seat passes through a gap formed around the pilot seat member. This is characterized in that it is configured to communicate with the second inflow / outflow port.

[0011]

According to the present invention, the valve member is closed by the action of the first and second springs when no pressure is generated in any of the first and second outflow / inflow ports. When the pressure of the first inflow / outflow port rises from this state, the pilot action causes the pilot seat member and the pilot poppet to move together as a unit against the second spring. By the volume change when the pilot seat member moves, the valve member can be opened and the surge pressure in the circuit can be cut.

The pressure at the first inflow / outflow port is equal to the second pressure.
When the pressure exceeds the set pressure of the pilot poppet determined by the spring, the pilot poppet opens. When the pilot poppet opens, the fluid at the first outflow / inflow port flows out of the second outflow port from the orifice formed in the valve member, through the pilot seat and the passage formed around the pilot seat member. When the flow passing through the orifice is generated as described above, a differential pressure is generated before and after the flow, and the valve member is opened by the action of the differential pressure.

[0013]

According to the relief valve of the present invention, a mechanism for cutting the surge pressure can be adopted also in the pilot operated type, so that the surge pressure is cut and the operation delay is prevented while improving the override characteristics. it can. That is, the improvement of both characteristics, which could not be achieved conventionally, can be achieved at the same time. Further, since the pilot seat member can be returned to the original position by the spring force of the second spring even if the pressure on the second inflow / outflow port side does not rise, the surge pressure can be reliably cut in any situation. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment shown in FIG.
A first inflow / outflow port 22 and a second inflow / outflow port 23 are formed at the same time, and a bore 24 is formed in the axial direction.
The bore 24 has one end communicating with the first inflow / outflow port 22 and the other end opened to the end of the casing 21. A plug 25 is fitted in the opened portion to cover the bore 24. Further, the bore 24 has a large-diameter portion 24a on the plug 25 side and a small-diameter portion 24b on the first outflow port 22 side with the step portion 26 as a boundary.

A sleeve 27 is fitted into the small diameter portion 24b, and one end of the sleeve 27 is projected toward the large diameter portion 24a. While a main sheet 28 is formed in the hollow portion of the sleeve 27, the main sheet 28 is shown in FIG.
, A communication hole 29 is formed at the upper side. This communication hole 29 is always in communication with the second inflow / outflow port 23. A valve member 30 is slidably provided above the main seat 28 in a hollow portion of the sleeve 27. The valve member 30 is formed in a cylindrical shape except for the poppet portion 30 a, and a hollow portion thereof is used as a relay chamber 31. An orifice 32 is formed in the poppet portion 30a, and the relay chamber 31 and the first inflow / outflow port 22 are communicated through the orifice 32.

A pilot seat member 33 is slidably fitted to the end of the sleeve 27 projecting toward the large diameter portion 24a of the bore 24. The pilot seat member 33 has an inverted concave cross section and includes a ceiling portion 33a and a tubular portion 33b, and an annular guide piece 33c protrudes from the ceiling portion 33a. The guide piece 33c faces the inside of the cylindrical portion 25a of the plug 25. The cylindrical portion 33b is fitted to the sleeve 27, and a gap 34 is formed between the cylindrical portion 33b and the large diameter portion 24a. This gap 34
Communicates with the second inflow / outflow port 23 through a passage 35 formed between the sleeve 27 and the step portion 26.

The ceiling portion 33a of the pilot seat member 33
A first spring 36 is interposed between the poppet portion 30a of the valve member 30 and the poppet portion 30a closes the main seat 28 at the normal position shown in the drawing by the action of the first spring 36. When the same pressure acts on the main sheet 28 side and the relay chamber 31 side, the poppet 30a closes the main sheet 28.

A pilot seat 37 is formed on the ceiling 33a.
7 is configured to be opened and closed by a pilot poppet 38. A second spring 39 is made to act on the pilot poppet 38, and usually, by the action of the second spring,
The pilot seat 37 is closed by a pilot poppet 38. And this second spring 3
9 has an adjusting piston 40 for adjusting the spring force.
The initial load of the second spring 39 can be adjusted by moving the adjustment piston 40 with the bolt 41. However, the spring force of the second spring 39 is larger than the spring force of the first spring 36.

Next, the operation of this embodiment will be described. If the pressures of the first and second outflow / inflow ports 22 and 23 are not increased, the pilot poppet 38, the pilot seat member 33 and the valve member 30 are integrally formed by the first and second springs 36 and 39. While popping, the poppet part 30a is pressed against the main sheet 28 to keep it closed. When the pressure on the first inflow / outflow port 22 side becomes high in this state, the pressure is transmitted to the relay chamber 31 via the orifice 32. At this time, if the pressure in the relay chamber 31 is equal to or less than the set pressure specified by the second spring 39, the pilot poppet 38 presses against the pilot seat 37 and keeps it closed.

However, since the pressure receiving surface of the pilot seat member 33 to which the pressure of the relay chamber 31 acts is sufficiently larger than the pressure receiving surface of the pilot poppet 38, the pilot seat member 33 is pressed by the pressure action on the first inflow / outflow port 22 side. Member 33
With the pilot poppet 38 and the second spring 3
Move against 9

[0021] If only the pilot seat member 33 as described above moves, although the volume of the relay chamber 31 is enlarged as a matter of course, the expansion change of the volume, first inflow and outflow
Port fluid is passed through orifice 32 of valve member 30
The valve member is supplied by the differential pressure across the orifice,
And the surge pressure generated on the first outflow / inflow port 22 side can be cut. Free piston jumps with plug
When it stops, the shock-less operation of this relief valve
The first stage will be completed. In this state, when the pressure on the first inflow / outflow port 22 side further increases and becomes equal to or higher than the pressure set by the second spring 39, the pilot poppet 38 opens the pilot seat 37. As a result, the fluid on the first inflow / outflow port 22 side is changed to the orifice 32 →
Relay room 31 → pilot seat 37 → small hole 42 formed in guide piece 33 c → gap 34 → flows out to second inflow / outflow port 23 via passage 35.

In this manner, the position where the differential pressure across the orifice 32, the force of the first spring 36, and the fluid axial force are balanced.
The opening of the main seat 28 is determined by the position. Therefore, the fluid on the first inflow / outflow port 22 side flows out to the second inflow / outflow port 23 side, which is on the low pressure side. And the first outflow / inflow port 2
When the pressure on the second side drops to a low pressure, each member returns to the original position shown in the drawing by the action of the first and second springs 36 and 39.
In the original position shown in the drawing, when the pressure on the second inflow / outflow port 23 side becomes high, the pressure acts on the pilot poppet 38, but since the pilot poppet 38 has an area difference corresponding to the pressure contact with the pilot seat 37, , The pilot poppet 38 keeps the pilot seat 37 closed.

According to the relief valve of the first embodiment as described above, even if the pressure at the first inflow / outflow port 22 rises sharply, the pilot seat member 33 can move to cut the surge pressure. . Since the surge pressure is cut by moving the pilot seat member 33 in this manner, a pilot-operated relief valve can be easily handled. Therefore, the surge pressure can be further reduced while utilizing the good override characteristic which is a feature of the pilot operation type.

Further, the pilot seat member 33 corresponding to the conventional free piston 9 is forcibly returned to the original position in the normal state by the action of the second spring 39. There is no problem that the position is not fixed. Further, in the first embodiment, since the gap 34 is formed between the pilot seat member 33 and the large diameter portion 24a, the degree of freedom in the diameter direction of the pilot seat member 33, that is, the large diameter portion of the bore 24, The space between the pilot seat member 33 and the seat 24a can be maintained. Since the degree of freedom in the diametric direction of the pilot seat member 33 can be maintained in this way, even if the axes of the bore 24, the pilot seat member 33, and the sleeve 27 are not so accurate, they do not hinder the assembly thereof. . However, in the conventional case shown in FIG.
Since the diametrical relationship among the bore 4, the free piston 9, the sleeve 6, and the seat member 7 is fixed, if the centers of the bores 4, the free piston 9, the sleeve 6, and the seat member 7 do not exactly match, the assembly cannot be performed. Therefore, in the case of the related art, there is a problem that the processing accuracy of each of the above-described components must be increased, but the first embodiment does not have such a problem at all.

The second embodiment shown in FIG. 2 is the same as the first embodiment except that the adjustment piston 40 and the bolt 41 of the first embodiment are omitted. The third embodiment shown in FIG. 3 is the same as the first embodiment except that the sleeve 27 is fixed with bolts 43. The fourth embodiment shown in FIG.
3c corresponds to the outside of the cylindrical portion 25a of the plug 25, and the other portions are the same as in the first embodiment.

The fifth embodiment shown in FIG. 5 is similar to the first embodiment except that the guide piece 33c of the pilot seat member 33 is separated from the plug 25. In the sixth embodiment shown in FIG. 6, the guide piece 33c of the pilot seat member 33 as in the first embodiment is omitted, and the small hole 42 is formed in the projection 25b formed below the plug 25. The seventh embodiment shown in FIG. 7 is similar to the first embodiment except that the small holes 42 are formed directly in the pilot seat member 33. In the eighth embodiment shown in FIG. 8, the valve member 30 is formed in a cylindrical shape, and the opening to the second inflow / outflow port 23 is determined by opening and closing the port 44 and the communication hole 29. This is the same as the seventh embodiment.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment.

FIG. 2 is a sectional view of a second embodiment.

FIG. 3 is a sectional view of a third embodiment.

FIG. 4 is a sectional view of a fourth embodiment.

FIG. 5 is a sectional view of a fifth embodiment.

FIG. 6 is a sectional view of a sixth embodiment.

FIG. 7 is a sectional view of a seventh embodiment.

FIG. 8 is a sectional view of an eighth embodiment.

FIG. 9 is a cross-sectional view of a conventional relief valve.

[Sign]

 Reference Signs List 21 casing 22 first inflow / outflow port 23 second inflow / outflow port 27 sleeve 30 valve member 32 orifice 33 pilot seat member 34 gap 36 first spring 39 second spring

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-207585 (JP, A) JP-A-57-208371 (JP, A) JP-A-64-12183 (JP, A) 97768 (JP, U) JP 3-79593 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16K 17/00-17/30 F16K 31/12-31/165

Claims (1)

(57) [Claims] A sleeve is provided in a casing having first and second inflow / outflow ports, and a cylindrical valve member is slidably provided inside the sleeve, and an orifice is formed in a hollow portion of the valve member. A first seat for slidably fitting a pilot seat member to the outside of the sleeve, and applying a force in a valve closing direction to the valve member between the valve member and the pilot seat member;
A second spring for interposing a spring, opening and closing the pilot seat of the pilot seat member with a pilot poppet, and applying a force in a direction of pressing against the pilot seat to the pilot poppet is provided. The spring force is made larger than the spring force of the first spring, and the orifice communicates with the pilot seat via the hollow portion of the valve member, and the fluid passing through the pilot seat flows around the pilot seat member. The second through the formed gap
A relief valve configured to communicate with the inflow / outflow port.