JPH0556434B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a pilot check valve with decompression that has a pressure relief function during backflow by pilot operation.

(Prior Art) FIG. 4 shows a conventional pilot check valve DV with decompression. As shown in the figure, when the pressure oil flows in the forward direction from the inlet port 32 side formed in the valve body 31 to the outlet port 33 side, the pilot check valve DV with decompression always flows in the opposite direction. A smaller decompression poppet 36 is housed in the housing chamber 35 of the main poppet 34, which is provided to prevent the flow of the main poppet 34.
It has a heavy poppet structure. When the poppet is opened by the pilot piston 37 in order to cause the pressure oil to flow back (return to the tank), the decompression poppet 36 in the poppet 34 is opened prior to the opening operation of the main poppet 34. As a result, the high-pressure oil in the storage chamber 35 is gradually released to the inlet side, suppressing a sudden change in pressure when the poppet is opened, and preventing impact. In the figure, numeral 38 is a push spring that presses the decompression poppet 36 and the main poppet 34 against the seat, numeral 39 is a pilot port for the pilot piston 36, and numeral 40 is a drain port.

(Problems to be Solved by the Invention) By the way, in an actual hydraulic circuit incorporating the pilot check valve DV with decompression having the structure described above, the flow rate of pressure oil is not controlled in the inlet port side pipe. In some cases, a controlling throttle valve or the like is installed. For example, as shown in FIG. 3, in the operating circuit of a lift cylinder 15 in a forklift, an electromagnetic switching valve 17 with a throttle valve 16 is provided in a conduit 18 on the inlet port side to control the lifting speed. It is being However, when such a throttle valve 16 exists, back pressure is generated on the inlet port side (primary side) when the switching valve 17 is switched to the lowering side to lower the lift cylinder 15 and conduction is established to the tank T. However, due to this back pressure, when the pilot piston 37 operates to open the poppet, the internal pressure of the accommodation chamber 35 in the main poppet 34 cannot be lowered below the pressure on the inlet port side.
As a result, a problem arises in that a large pilot pressure is required to operate the pilot piston 37.

SUMMARY OF THE INVENTION The technical problem to be solved by the present invention is to perform the depressurizing action of a pilot check valve with decompression using a drain pipe.

(Means for Solving the Problems) The technical means for solving the above problems is to use a rod tip of a pilot piston that opens and closes a main poppet and a decompression poppet that is concentrically housed in the main poppet. The small diameter portion is formed in a stepped shape from the large diameter portion, and the small diameter portion of the rod is slidably and closely inserted into the cylindrical hole of the main poppet so as to face the tip of the decompression poppet so that it can come into contact with it, Furthermore, a passage is formed in the rod to communicate the accommodation chamber of the decompression poppet with the drain port of the pilot piston when the decompression poppet is pushed open.

(Function) When pilot pressure is applied to the pilot piston, first the tip of the small diameter part of the rod in the pilot piston pushes the decompression poppet to open it, so the accommodation chamber of the decompression poppet passes through the passage of the rod to the pilot piston. It communicates with the drain port of the piston, and the high pressure oil in the storage chamber is gradually released. Then, when the pressure inside the storage chamber decreases, the large diameter portion of the rod pushes the main poppet to open it, and the high pressure oil on the outlet side flows to the inlet port side.

(Example) Hereinafter, an example of the present invention will be specifically described based on the drawings. Figure 1 shows a pilot check valve DV with decompression. In the figure, 1 is the valve body, and on one side (right side in the figure) is a flow of high-pressure oil from the inlet port 2 side to the outlet port 3 side. A main poppet 4 is slidably incorporated in the main poppet 4 to allow the flow of water and to prevent the reverse flow.
A decompression poppet 6 for releasing pressure is housed in a cylindrical housing chamber 5 formed in the cylindrical hole. In addition, a small-diameter cylindrical hole 7 communicating with the accommodation chamber 5 is formed concentrically with the accommodation chamber 5 on one side (left side in the figure) of the main poppet 4, and the outlet port 3 and the accommodation chamber 5 are communicated with each other on the outer periphery. A small hole 8 is formed.

The decompression poppet 6 is normally pressed against the seat by a pressure spring 9 so as to cut off communication between the storage chamber 5 and the cylindrical hole 7, and the main poppet 4
is pressed against the seat via the decompression poppet 6 so as to cut off communication between the outlet port 3 and the inlet port 2.

On the other hand, a pilot piston 10 for poppet operation is slidably built into the other side of the valve body 1 (on the left side in the figure) so as to coaxially oppose the poppets 4 and 6.
A pilot port 11 is formed on one side (left side in the figure), and a drain port 12 is formed on the other side. Further, the rod 13 of the pilot piston 10 extends slidably and closely through the wall 1a between the drain port 12 and the inlet port 2 to the poppet side, and its tip side is formed to have a small diameter. has been done.

That is, the rod 1 of the pilot piston 10
3 is formed in two stages from a small diameter part 13a and a large diameter part 13b, and the small diameter part 13a is slidably and tightly inserted into the cylindrical hole 7 of the main poppet 4, and the end face of the small diameter part 13b is The decompression poppet 6 can be pushed by the decompression poppet 6, and the main poppet 4 can be pushed by the stepped end face of the large diameter portion 13b.
Further, a through hole 14 is formed in the rod 13 in the axial direction, and one end of the through hole 14 communicates with the cylindrical hole 7 of the main poppet 4, and the other end communicates with the drain port 12. Note that a through hole 14 is formed at the tip of the rod 13 when it comes into contact with the decompression poppet 6.
A U-shaped metal fitting 14a is fixed to prevent the closure.

FIG. 3 illustrates a case where the pilot check valve DV with decompression configured as described above is incorporated into the operating circuit of the lift cylinder 15 in a forklift. As shown in the figure, the pilot check valve DV with decompression is disposed in the piping between the lift cylinder 15 and an electromagnetic switching valve 17 with a throttle valve 16 that controls the supply and discharge of pressure oil to and from the lift cylinder 15. Inlet port 2 is pipe line 1 on the electromagnetic switching valve 17 side
8 and outlet port 3 is connected to lift cylinder 1.
It is connected to the conduit 19 on the 5 side. The pilot port 11 of the pilot check valve DV is connected to a pump P1 for generating pilot pressure via a pilot pipe line 20, and the drain port 12 is connected to a pump P1 for generating pilot pressure.
is connected to the tank T by a drain pipe 21. In FIG. 3, P is a hydraulic pump for driving the lift cylinder, and 22 and 23 are relief valves.

This embodiment is configured as described above,
As shown in FIG. 3, when the electromagnetic switching valve 17 is held in the neutral position, the pilot line 20 is blocked, and therefore the pilot check valve DV with decompression is held in the state shown in FIG. 1. has been done.

In this state, when the electromagnetic switching valve 17 is switched to the upward side a, the high pressure oil discharged from the hydraulic pump P flows into the inlet port 2 of the pilot check valve DV via the electromagnetic switching valve 17. , flows toward the outlet port 3 while pushing the main poppet 4 and the decompression poppet 6 open against the push spring 9, flows into the lift cylinder 15 through the conduit 19, and lifts the lift cylinder 15. let

Therefore, in order to lower the lift cylinder 15,
When the electromagnetic switching valve 17 is switched to the downward side b, the pilot line 20 is communicated with the pump P1.
Since the pilot pressure from
The small diameter portion 13a of the decompression poppet 6
Push open against the pushing spring 9 to open the storage chamber 5 and the cylindrical hole 7.
are communicated. Therefore, the high pressure oil in the storage chamber 5 is discharged from the cylinder hole 7 through the through hole 14 of the rod 13 to the drain port 12 side of the pilot piston 10, and the pressure in the storage chamber 5 is reduced.

Subsequently, the stepped end surface of the large diameter portion 13b of the rod 13 comes into contact with the main poppet 4, and pushes it together with the decompression poppet 6 against the push spring 9, but at this time, the pressure inside the storage chamber 5 increases. Since the main poppet 4 is lowered, the main poppet 4 is opened with a lower pilot pressure. As a result, the outlet port 3 and the inlet port 2 are communicated with each other, the high pressure oil on the outlet side returns to the tank T, and the lift cylinder 15 is lowered.

Although this embodiment has been described as a case where the pilot check valve with decompression is incorporated into the operating circuit of the lift cylinder 15 for a forklift, its application is not limited to this. It is effective if the circuit has a valve such as a throttle valve inserted on the return side of the connected pipe line to regulate the flow rate.

(Effects of the Invention) As described in detail above, according to the pilot check valve with decompression of the present invention, by communicating the storage chamber of the decompression poppet with the drain pipe during the pressure relief operation, the storage chamber is The main poppet can be opened by the pilot piston with a small operating force by reducing the pressure of the main poppet.This allows the pilot piston to be made smaller and provides a stable pressure relief effect.
The pilot check valve with decompression of the present invention is particularly effective when incorporated into a hydraulic circuit in which back pressure is generated on the return side of a conduit connected to an inlet port.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the pilot check valve with decompression according to the present invention, Fig. 2 is a sectional view showing the opening operation by the pilot piston, and Fig. 3 is a sectional view of the pilot check valve with decompression. Hydraulic circuit diagram of an example of incorporating this into the lift cylinder operating circuit of a forklift.
FIG. 4 is a sectional view showing a conventional pilot check valve with decompression. DESCRIPTION OF SYMBOLS 1...Valve body, 2...Inlet port, 3...Outlet port, 4...Main poppet, 5...Accommodation chamber, 6...
... Decompression poppet, 7 ... Cylindrical hole, 9
...Press spring, 10...Pilot piston, 1
1... Rod, 14... Cylindrical hole.

Claims (1)

[Claims] 1. The tip of the rod of the pilot piston that opens and closes the main poppet and the decompression poppet concentrically housed in the accommodation chamber formed in the main poppet is formed into a stepped shape with a small diameter part and a large diameter part, The small diameter portion of the rod is slidably and tightly inserted into the cylindrical hole of the main poppet so as to be able to come into contact with the tip of the decompression poppet, and the rod further includes the housing when the decompression poppet is pushed open. A pilot check valve with decompression that has a through hole that communicates a chamber with a drain port of a pilot piston.