JPH0425571Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a relief valve, and particularly to a relief valve that relieves the peak pressure that occurs when the valve changes from a non-operating state to an operating state due to an increase in pressure in a circuit. Regarding relief valves.

[Prior Art] An example of a conventional relief valve will be described with reference to FIG. The housing 1 is provided with an annular chamber 4 and a circular hole 5 connected to an inlet passage 2 and an outlet passage 3 in the axial direction from the left side. The circular hole 5 is provided with a poppet 6 which is slidable and has an aperture 6A at its tip (left end).
The tip side slope of the poppet 6 engages and disengages from the seat 7 fitted in the inlet passage 2, and the inlet passage 2 is connected to the outlet passage 3.
It is designed to open and close against each other. The rear end of the poppet 6 and the rear end of the piston 8 slidably inserted into the inner hole of the poppet 6 are in contact with one end of springs 9 and 10, respectively, and the other end is in contact with a cap 11 fixed to the right end of the housing 1. Therefore, the poppet 6 and piston 8 are always pressed to the left. The strength of the spring 9 is stronger than that of the spring 10, and 12 is a stopper that restricts the retraction limit of the piston 8, and is screwed into the cap 11, and 13 and 14 are gaskets.

In such a configuration, when pressure fluid flows into the inlet passage 2, the fluid first passes through the throttle 6A and presses the front surface of the piston 8, causing the piston 8 to retreat and collide with the stopper 12 to stop. Next, when the piston 8 stops, the pressure in the inlet passage 2 increases, and when the pressing force of the poppet 6 becomes greater than the strength of the spring 9, the poppet 6 retreats and the pressure in the inlet passage 2 increases.
and the outlet passage 3 are communicated or relieved.

Therefore, even with such a configuration, it is possible to reduce the peak when the relief valve transitions from the non-operating state to the operating state. However, in this method, the spring 10 that presses the piston 8 cannot have a large spring force due to space constraints, and the aperture 6A
It is impossible to make it too small due to machining constraints, and a sufficient squeezing effect cannot be obtained.Furthermore, the spring force of the spring 9 pressing the poppet 6 is large, so at the start of relief, Only the piston 8 moves with low pressure and reaches its stroke limit in a short time. For this reason, although the peak pressure was reduced, there was a problem that it could not be completely eliminated. Furthermore, at the beginning of the relief, the piston 8 retreats and the stopper 1
In order for the poppet 6 to move and open the passage after stopping at step 2, the fluid inside the poppet 6 must be discharged against the flow through the throttle 6A to the high pressure side of the inlet passage 2. Since the pressures are approximately the same, this discharge takes time and there is a drawback that there is a delay in the start of relief. In addition, the poppet 6 and the piston, which are separate parts, are provided inside the poppet 6, and two types of springs are used, one for the poppet and the other for the piston, resulting in high costs.

[Purpose of the invention] The present invention eliminates these drawbacks, and its purpose is to provide a low-cost relief valve that sufficiently relieves the peak pressure that occurs when transitioning from a non-operating state to an operating state. be.

[Main points of the invention] The relief valve of the invention includes a housing provided with an annular chamber that communicates with an inlet passage and an outlet passage, and a seat that is attached to the housing and has one side open to the annular chamber and communicates with the inlet passage. A sleeve that is fixed by one side, a poppet that is slidably inserted into the sleeve and engages and disengages from the seat and forms a rod on one side, and a pair of poppets that are closed in the middle and are provided in the axial direction of the poppet. a passage provided in the rod of the poppet, a piston slidably inserted into the outer periphery of the poppet rod and the inner periphery of the sleeve, and a piston provided between the piston and the poppet to push them apart from each other. It is characterized by consisting of a spring.

[Embodiment of the invention] Hereinafter, FIG. 1 showing an embodiment of the invention will be described. An annular chamber 22 located approximately at the center of the housing 21 is provided with an inlet passage 23 to the left in the figure and an outlet passage 24 at the bottom. On the left side of the housing 21, there is a sleeve 25 between which the packing 2 is inserted.
6, and a sheet 27 having an inner hole communicating with the inlet passage 23 is fixed by its tip. A poppet 28 is slidably inserted into the sleeve 25. The poppet 28 has a sloped end and opens and closes the inlet passage 23 and the outlet passage 24 by engaging and disengaging the slope with the seat 27.

The right side of the poppet 28 is formed into a rod 28A, and the rod 28A is provided with passages 28B and C which are closed in the middle.
8D and E through an annular groove 28F. A slidable piston 29 is inserted between the right end of the rod 28A and the middle of the sleeve 25, and a spring 30 is provided between the piston 29 and the poppet 28. Due to the pressing force of the spring 30, the piston 29 attaches the seal 31 to the right end of the housing 21.
The poppet 28 is always in contact with the cap 32 which is screwed onto the seat 2.
7 is always engaged. Note that hole 2 of sleeve 25
5A is the entrance passage 23 when the poppet 28 is retracted.
is a hole through which fluid flows out into the outlet passage 24, and the hole 2
Reference numeral 5B designates a hole through which fluid in a portion of the sleeve 25 surrounded by the poppet 28 and the piston 29 flows out into the annular chamber 22 when the piston 29 moves forward.

Next, the operation of the above-mentioned embodiment will be explained by taking as an example a case where the present relief valve is provided in a non-drive side connection circuit of a motor driving an inertial load. When the switching valve of the currently rotating motor is set to neutral, the non-drive side connection circuit is suddenly closed, and the fluid pressure in the inlet passage 23 increases rapidly. At this time, the poppet 28 quickly retreats with a low pressure since the initial pressing force of the spring 30 is weak. At the same time, the pressure fluid acts on the right end surface of the piston 29 through the passage 28B, the C/restriction 28D and the E/annular groove 28F of the poppet 28.

The pressurized fluid in the inlet passage 23 flows into the outlet passage 24 when the poppet 28 quickly retreats, so even if the fluid flows extremely rapidly, the piston 29 opens at a low pressure. The pressing force of this is increased by compressing it. At this time, the piston 29
The flow rate of the pressure fluid that moves the piston to the left is limited by the throttles 28D and E in the middle, and the piston 29 moves slowly to the left.The pressing force of the spring 30 is gradually increased, and when the piston 29 reaches its stroke limit, the spring The pressing force of 30 is the maximum and this value becomes the required set pressure. At this time, the poppet 28 moves back and the oil chamber 33 at the right end of the rod 28A is compressed, but since the piston 29 moves immediately, it does not take time for the oil in the poppet chamber to be drained unlike the conventional example. Poppet 2 can therefore be removed without creating a peak pressure.
8 is retracted by the required amount at the set pressure, and the inlet passage 23
and the outlet passage 24 for relief.

[Effect of the invention] As explained above, in the relief valve of the present invention, when the fluid pressure in the inlet passage increases, the poppet immediately retreats to connect the inlet passage and the outlet passage, and in response to this pressure, the piston moves forward, but the fluid flowing into the rear surface of the piston has a restriction in the middle, so the piston moves forward slowly. Therefore, the pressing force of the spring that presses the poppet against the seat gradually increases, and eventually when the piston reaches its stroke limit, the spring's pressing force reaches its maximum and the fluid in the inlet passage reaches the necessary relief pressure. Since the peak pressure is relieved without delay to the outlet passage, the peak pressure is sufficiently relieved. Furthermore, since there is only one spring, the number of parts is reduced, which also has the advantage of lowering costs.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional example. 21... Housing, 22... Annular chamber, 23...
...Inlet passage, 24...Outlet passage, 25...Sleeve, 27...Seat, 28...Poppet, 28A
... Rod, 28B, C... Passage, 28D, E...
...Aperture, 28F...Annular groove, 29...Piston,
30...Spring.

Claims (1)

[Scope of utility model registration request] A housing provided with an annular chamber communicating with an inlet passage and an outlet passage, and a sleeve attached to the housing and having one side thereof open to the annular chamber and fixing a sheet communicating with the inlet passage by one side thereof. a poppet that is slidably inserted into the sleeve and engages and disengages from the seat and forms a rod on one side; a pair of passages that are closed in the middle and are provided in the axial direction of the poppet; a piston slidably inserted into the outer periphery of the rod of the poppet and the inner periphery of the sleeve; A relief valve consisting of a spring provided between the poppets and pushing them apart from each other.