JPH059572Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a relief valve provided between a pair of supply/discharge passages connecting a switching valve and a fluid motor.

BACKGROUND ART Conventionally, a relief valve 5 is provided between a pair of supply and discharge passages 3 and 4 that connect a switching valve 1 and a fluid motor 2.
For example, the one described in Japanese Utility Model Application Publication No. 60-38901 is known. As shown in FIG. 2, this includes a casing 7 having a spool chamber 6, and a spool 10 housed in the spool chamber 6 and having a small diameter portion 8 and a large diameter portion 9.
and the spool 10 provided in the casing 7.
a spring 11 that urges the
and a small diameter part 8 and a large diameter part 9 provided in the casing 7.
A first passage 13 that guides the fluid pressure of one supply/discharge passage 3 to the stepped surface 12 between the two, and a second passage 13 that is provided in the casing 7 and guides the fluid pressure of the other supply/discharge passage 4 to the end face 14 of the small diameter portion 8. a passage 15; and a high-pressure passage 18 that guides high-pressure fluid from the supply and discharge passages 3 and 4 taken out at the counterbalance valve 16 to the end surface 17 of the large diameter portion 9 when the switching valve 1 is in the flow position. It is something that

Problems to be solved by the invention However, in the past, the spring 1
In order to make the relief valve 5 compact through the miniaturization of 1, the pressure receiving area, specifically the area of the end face 14 of the small diameter part 8 and the area of the step surface 12 between the small diameter part 8 and the large diameter part 9, are made as small as possible. That is, the diameters of the small diameter part 8 and the large diameter part 9 are made small, but in this case, the outer circumferential length of the large diameter part 9 is shortened, and the fluid flows between the first passage 13 and the second passage 15. There is a problem in that the area of the flow path when relieving the gap becomes narrow, and as a result, the performance of the relief valve deteriorates. Furthermore, since the small diameter portion 8 and the large diameter portion 9 have small diameters, there is a problem in that processing costs will be high if it is attempted to process these with high precision.

The purpose of this invention is to provide a relief valve which can increase the flow passage area during relief while reducing the size of the spring, and which can be manufactured with high precision at low cost.

Means for Solving the Problems Such an objective consists of a casing having a spool chamber, a casing having a small diameter in the axial direction, and a casing having a spool chamber.
A spool in which a medium diameter land and a large diameter land are sequentially formed, a spring housed in a casing and biasing the spool toward the small diameter land side, and a first spring provided in the casing and formed between the small diameter land and the medium diameter land. a first passage that guides the fluid pressure of one supply/discharge passage into the chamber; and a second passage that guides the fluid pressure of the other supply/discharge passage to a second chamber provided in the casing and formed between the medium and large diameter lands. , when a high-pressure fluid higher than the set pressure is introduced into the first chamber or the second chamber, the difference in cross-sectional area between the small diameter land and the medium diameter land or the cross-sectional area difference between the medium diameter land and the large diameter land is defined as a pressure receiving area, This can be achieved by a relief valve that moves the spool toward the large-diameter land against the spring, thereby communicating the first passage and the second passage, which have been cut off from each other by the medium-diameter land.

Operation When the switching valve is switched from the flow position to the neutral position, the fluid motor rotates inertia, so that one or the other supply/discharge passage may reach a high pressure higher than the set pressure. At this time, the high pressure fluid flows through the first passage or the second passage.
It is led to the first or second chamber through the passage,
Since the relief valve no longer receives fluid pressure from the supply/discharge passage on the high pressure side, the spool receives the fluid force of the high pressure fluid and moves toward the large diameter land while opposing the spring. The fluid force at this time is a value obtained by multiplying the cross-sectional area difference between the small-diameter land and the medium-diameter land or the cross-sectional area difference between the medium-diameter land and the large-diameter land, respectively, by the pressure of the high-pressure fluid. In this way, in this invention, the difference in cross-sectional area between the two lands is used as the pressure-receiving area, so even if the diameter of the small, medium, or large diameter land itself, that is, the diameter of the spool, is increased, the difference in diameter between the two lands can be made small. If this is done, the fluid force acting on the spool can be reduced, and as a result, the spring can be made smaller and the spool can be made larger in diameter. Therefore, the area of the flow path between the first and second passages communicating with each other can be increased by the movement of the spool, and high-precision machining of the spool becomes easy and inexpensive.

Embodiment Hereinafter, an embodiment of this invention will be described based on the drawings.

In FIG. 1, 21 is a switching valve connected to a fluid pump 22 and a tank 23, and this switching valve 21 and a fluid motor 24 for driving a crawler vehicle are connected to a pair of supply/discharge passages 25, which are bifurcated in the middle. 2
6. These supply and discharge passages 25,
Check valves 27, 28 and a counterbalance valve 29 are interposed in the flow dividing portion 26. The supply/discharge passages 25 and 26 between the counterbalance valve 29 and the fluid motor 24 are connected to a relief valve 30.
are communicated by a passage 41 provided in the middle. The relief valve 30 has a casing 33 consisting of a body 31 and a cap 32 screwed into the body 31, and a spool chamber 34 is formed within the body 31. A spool 35 is housed in the spool chamber 34 and is movable in the axial direction. Three types of lands are formed on the spool 35, namely, a small diameter land 36, a medium diameter land 37, and a large diameter land 38. These small, medium, and large diameter lands 36, 37, and 38 are sequentially arranged apart from each other in the axial direction from one end of the spool 35 toward the other end, and as a result, the small diameter land 36 and the medium diameter land 37 are In between is the first chamber 39, and
Between the medium diameter land 37 and the large diameter land 38, there is a second
A chamber 40 is formed. Then, the medium diameter land 3
7 has a slightly larger diameter than the small diameter land 36, and the large diameter land 38 has a slightly larger diameter than the medium diameter land 37. Here, the medium diameter land 37
The difference in cross-sectional area between the large-diameter land 38 and the small-diameter land 36 and the cross-sectional area difference between the large-diameter land 38 and the medium-diameter land 37 are the pressure-receiving areas, but in this embodiment, both cross-sectional area differences have the same value. A first passage 43 is formed in the body 31 and communicates with one of the supply and discharge passages 25, and this first passage 43 transfers the fluid pressure in the supply and discharge passage 25 to the first chamber 39.
lead to. A second passage 44 is formed in the body 31 and communicates with the other supply/discharge passage 26 , and this second passage 44 guides the fluid pressure in the supply/discharge passage 26 to the second chamber 40 . And usually medium diameter land 37
and the spool chamber 34 between the first and second passages 43 and 44.
The inner surfaces of the first passage 43 and the second passage 44 are overlapped, and the first passage 43 and the second passage 44 are cut off. A receiver 47 is engaged with a flange 46 formed at the other end of the spool 35, and a spring chamber 49 for housing a spring 48 is formed within the cap 32. The spring 48 is interposed between the receiver 47 and the bottom surface of the spring chamber 49,
This spring 48 urges the spool 35 toward the small diameter land 36 side. Reference numeral 51 denotes a high-pressure passage into which the high-pressure fluid selected from the supply and discharge passages 25 and 26 flows by the counterbalance valve 29, and the high-pressure fluid in this high-pressure passage 51 flows through the third passage 52 formed in the body 31. and is guided to the spring chamber 49. 53 is a through hole formed in the spool 35, and this through hole 53 connects the spring chamber 49 and the spool chamber 3 located on one end side of the spool 35.
4.

Next, the operation of one embodiment of this invention will be explained.

Now, assuming that the switching valve 21 is in the flow position, for example, the parallel flow position, the high pressure fluid discharged from the fluid pump 22 passes through the supply and discharge passage 25 to the fluid motor 24.
On the other hand, the low pressure fluid flowing out from the fluid motor 24 is returned to the tank 23 through the supply/discharge passage 26 . At this time, the high pressure fluid in the supply/discharge passage 25 is
Since the counterbalance valve 29 is switched to the switching position A, the air is selected and taken out by the counterbalance valve 29 and flows into the spring chamber 49 . Therefore, the spool 35 is moved to the small diameter land 36 by the total force of this fluid force and the elastic force of the spring 48.
It is urged to the side and stopped. At this time, the first passage 43 and the second passage 44 are blocked by the medium diameter land 37, and the relief valve 30 is closed.
Next, when the switching valve 21 is switched to the neutral position,
Since the supply and discharge passages 25 and 26 have equal pressure, the spool 35 no longer receives the fluid pressure of the high-pressure fluid as described above, and the relief valve 30 is released from the fluid lock. At this time, the supply of high-pressure fluid to the fluid motor 24 is also stopped, but since the fluid motor 24 continues to rotate due to inertia, fluid is discharged from the fluid motor 24 into the supply/discharge passage 26 . Internal pressure increases. Therefore, back pressure acts on the fluid motor 24, and fluid braking force is applied to the fluid motor 24. Here, the supply/discharge passage 26, the second
When the internal pressure of the chamber 40 becomes higher than the set pressure, a value (fluid force) obtained by multiplying the cross-sectional area difference (pressure receiving area) between the large-diameter land 38 and the medium-diameter land 37 by the high pressure increases the elastic force of the spring 48. Spool 35 to exceed
moves toward the large diameter land 38 against the spring 48. As a result, the medium diameter land 37 separates from the inner surface of the spool chamber 34 between the first and second passages 43 and 44, the relief valve 30 opens, and the supply/discharge passage 25 and the supply/discharge passage 26 are connected to the passage 41, the first, second passage 43,
44. As a result, the supply/discharge passage 2
The high-pressure fluid in 6 is released to the supply/discharge passage 25, and the fluid circuit is protected from abnormally high pressure. On the other hand, switching valve 2
1 is switched from the cross-flow position to the neutral position, it operates in the same manner as described above, but in this case, the difference in cross-sectional area between the medium-diameter land 37 and the small-diameter land 36 becomes the pressure-receiving area, and the high-pressure fluid is not supplied. The water is discharged from the exhaust passage 25 to the supply/discharge passage 26. In this way, the difference in cross-sectional area between the two lands, that is, the small-diameter land 36 and the medium-diameter land 37, and the medium-diameter land 37 and the large-diameter land 38, is defined as the pressure-receiving area.
Even if the diameters of 37 and 38 are increased, if the difference in diameter between the two lands is made smaller, the spool 35
It is also possible to reduce the fluid force acting on the spring 48 and the spool 35.
It is possible to increase the diameter of the For this reason, the relief valve 3
The first and second passages 43 when 0 is open,
The flow path area between 44 can be widened, and
High-precision machining of the spool 35 is also facilitated, and the machining cost can also be reduced.

Effects of the Invention As explained above, according to this invention, it is possible to increase the diameter of the spool while reducing the fluid force applied from the spool to the spring.
As a result, the flow path area during relief can be increased, high-precision machining is easy and inexpensive, and the spring can also be made smaller, so the relief valve can be made more compact.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view, partially represented by symbols, showing an embodiment of this invention, and Fig. 2 is a cross-sectional view, partially represented by symbols, showing a fluid circuit including a conventional relief valve. be. 21...Switching valve, 24...Fluid motor, 25,
26... Supply/discharge passage, 30... Relief valve, 33...
...Casing, 34...Spool chamber, 35...Spool, 36...Small diameter land, 37...Medium diameter land, 38...Large diameter land, 39...1st chamber, 40
...Second chamber, 43...First passage, 44...Second passage, 48...Spring.

Claims (1)

[Scope of utility model registration request] The switching valve 21 is provided between a pair of supply/discharge passages 25 and 26 connecting the switching valve 21 and the fluid motor 24.
When in the flow position, it receives fluid pressure from the supply and discharge passage on the high pressure side and closes, and the switching valve 21 is switched to the neutral position so that it no longer receives fluid pressure from the supply and discharge passage on the high pressure side, and the fluid In the relief valve 30, which opens when the motor 24 rotates inertia and one of the supply/discharge passages reaches a high pressure equal to or higher than the set pressure, the relief valve 30 releases high-pressure fluid higher than the set pressure to the remaining supply/discharge passages. A casing 33 having a chamber 34, a spool 35 housed in the spool chamber 34 and having a small-diameter land 36, a medium-diameter land 37, and a large-diameter land 38 sequentially formed in the axial direction; Spring 4 biasing toward the small diameter land 36 side
8 and a small diameter land 36 provided on the casing 33.
A first chamber 39 formed between the land 37 and the medium diameter land 37
A first passage 43 that guides the fluid pressure of one of the supply and discharge passages to
and a second passage 44 that guides the fluid pressure of the other supply/discharge passage to a second chamber 40 provided in the casing 33 and formed between the medium-diameter land 37 and the large-diameter land 38;
The high-pressure fluid having the set pressure or more flows into the first chamber 39.
Or when guided to the second chamber 40, the small diameter land 3
6 and the medium-diameter land 37 or the cross-sectional area difference between the medium-diameter land 37 and the large-diameter land 38 as the pressure-receiving area, the spool 35 is moved toward the large-diameter land 38 side against the spring 48, and this As a result, the first
A relief valve 30 characterized in that a passage 43 and a second passage 44 are communicated with each other.