JPH06280804A - Load pressure relief valve - Google Patents

Abstract

PURPOSE:To cause a load relief valve to make relief action slowly after load pressure rises to a set pressure. CONSTITUTION:An open/close poppet 35 is provided on an inlet port 36 communicating with a load pressure introduction passage 8 and on an outlet port 37 communicating with a tank passage 56 while the open/close poppet 35 is in a closed position by a spring 38 and in an open position by the pressure of a pressure imposed portion 39 and the pressure imposed portion 39 is communicated with the load pressure introduction passage 8 through a small hole 49 causing the pressure of the pressure imposed portion 39 to rise slowly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load pressure relief valve used in a hydraulic circuit for supplying hydraulic oil discharged from a hydraulic pump to a plurality of actuators by a plurality of closed center type operation valves.

[0002]

2. Description of the Related Art As shown in FIG. 1, a plurality of closed center type operation valves 2 are arranged in a discharge passage 1a of a hydraulic pump 1, and a pressure compensating valve 5 is connected to a connection circuit 4 between the operation valve 2 and an actuator 3. Is provided, the maximum pressure in the load pressure of each actuator 4 is detected by the shuttle valve 6, and the load pressure is supplied to the spring chamber 5a of each pressure compensating valve 5 to obtain a set pressure corresponding to the load pressure. It has been known.

With such a hydraulic circuit, a plurality of operating valves 2
The pressure compensating valve 5 is set by the maximum pressure among the load pressures of the plurality of actuators 3 when they are simultaneously operated. it can.

In such a hydraulic circuit, an unload valve 7 is provided in the discharge passage 1a of the hydraulic pump 1 and a relief valve 9 is provided in the load pressure introducing passage 8 so that the unload valve 7 is placed below the load pressure P _LS. When the pump discharge pressure P ₁ becomes higher than the set pressure, unloading is performed, and when the load pressure P _LS of the load pressure introducing passage 8 becomes equal to or higher than the set pressure of the relief valve 9, the relief valve 9 is operated to perform the relief operation. _When a part of the _LS flows out into the tank and the load pressure P _LS decreases and the differential pressure from the pump discharge pressure P ₁ becomes equal to or higher than the set pressure, the unload valve 7 unloads and the pump discharge pressure P ₁ increases. It is proposed that a part of it can flow out to the tank to limit the maximum pump discharge pressure.

[0005]

As shown in FIG. 2, the relief valve 9 described above is provided with a poppet 13 for communicating and blocking the inlet port 11 and the outlet port 12 in the valve body 10, and the poppet 13 is blocked by the spring 14. When the pressure in the inlet port 11 exceeds the set pressure, the poppet 13 is pushed to the communicating position so that the inlet port 11 and the outlet port 12 communicate with each other, and the inlet port 11 communicates with the load pressure introducing passage 8. However, the outlet port 11 communicates with the tank passage 15.

In FIG. 2, reference numeral 16 is a main valve of the unload valve 7, and the main valve 16 is a main spring 17.
And the inlet port pressure (load pressure P _LS ) of the relief valve 9 pushes the pump port 18 and the tank port 19 in a blocking direction, and the pressure of the pump port 18 (pump discharge pressure P ₁ ) pushes in the communicating direction. The pump port 18 is connected to the discharge passage 1 a of the hydraulic pump 1, and the tank port 19 communicates with the tank passage 15.

In the case of the relief valve described above, the inlet port 1
Part sets the load pressure P _LS from flowing out to the tank passage 15 from the outlet port 12 pressure of the load pressure P _LS that has flowed into the 1 becomes higher than the set pressure increased poppet 13 is pushed load pressure P _LS Can be maintained at However, the load pressure P _LS is
As shown in, the swash plate angle is controlled by acting on the pressure receiving portion 21a of the control valve 21 that controls the angle of the swash plate 20 of the hydraulic pump 1. Therefore, when the load pressure P _LS suddenly decreases, the swash plate angle changes. Sudden change, the discharge amount of the hydraulic pump 1 changes rapidly, the flow rate to the actuator 3 also changes rapidly, the actuator operating speed changes rapidly, and the operability deteriorates.

That is, the swash plate 20 is tilted in the small angle direction by the large piston 22 and tilted in the large angle direction by the small piston 23, and the control valve 21 receives the load pressure P _LS acting on the pressure receiving portion 21a. When the height becomes higher, the large piston 22 communicates with the tank, so that the angle of the swash plate 20 becomes smaller and the discharge amount of the hydraulic pump 1 decreases.

Since the main valve 16 of the unloading valve 7 is held in the shut-off position by the spring force of the main spring 17, the pump discharge pressure P ₁ is a pressure that matches the spring force of the main spring 17 rather than the load pressure P _LS. When the pressure difference between the pump discharge pressure P ₁ and the load pressure P _LS becomes higher than that, the main valve 16 is pushed to the communicating position against the main spring 17 to transfer the pressure oil of the pump port 18 to the tank port 19 Spilled into
As a result, the pump discharge pressure P ₁ is always maintained higher than the load pressure P _LS by the set pressure.

An object of the present invention is to provide a load pressure relief valve capable of solving the above-mentioned problems.

[0011]

A poppet 35 for opening and closing an inlet port 36 communicating with a load pressure introducing passage 8 and an outlet port 37 communicating with a tank is held in a closed position by a spring 38, and a pressure receiving portion 39 of the poppet 35. A load pressure relief valve having an open position by a pressure acting on the pressure receiving portion 39 and communicating with the load pressure introducing passage 8 through a throttle.

[0012]

[Operation] Since the load pressure of the load pressure introducing path 8 slowly rises by the throttle and acts on the pressure receiving portion 39 of the poppet 35, the poppet 35 slowly rises with a slight time delay after the load pressure rises to the set pressure. When the load pressure in the load pressure introducing passage 8 rises to the set pressure, the load pressure does not suddenly decrease but slowly decreases over time.

[0013]

[Example] As shown in FIG. 3, the shaft hole 3 of the valve body 30 is
1, the sleeve 33 is fitted and inserted, the poppet mounting body 34 is fitted inside one end of the sleeve 33, and the poppet 35 is fitted into the poppet mounting body 34 to open and close the inlet port 36 and the outlet port 37. The poppet 35 is held in the closed position by the spring 38, and is pushed to the open position against the spring 38 by the pressure acting on the pressure receiving portion 39.

Next, the details of each part will be described. A large diameter hole 40 on one side and an intermediate small diameter hole 4 are provided at the axis of the poppet mounting body 34.
1, the large hole 42 on the other side is continuously formed, and the poppet 35
The small-diameter portion 43 is fitted into the intermediate small-diameter hole 41, the large-diameter portion 44 is inserted into the other-side large-diameter hole 42, and is pushed by the spring 38, so that the conical seat portion 45 becomes the seat seat 46 of the poppet attachment body 34. It is crimped to.

A piston 47 is fitted in the one-side large-diameter hole 40, and an end face of the piston 47 is formed with a recess 48 facing the tip surface of the small-diameter portion 43 of the poppet 35, that is, the pressure receiving portion 39. Reference numeral 48 denotes a small hole 49 serving as a diaphragm and a plurality of radially facing holes 50 that open into an annular groove 51 formed on the outer peripheral surface.
The port 53 is opened through an annular gap 52 which is a clearance filter formed between the port 5 and the outer peripheral surface.
3 is opened to the port 54 of the sleeve 33 together with the inlet port 36, and the port 54 communicates with the load pressure introducing passage 8 so that the load pressure of the load pressure introducing passage 8 flows into the inlet port 36 and the port 53. is there. The size of the annular gap 52 is larger than the diameter of the pore 49, and the opening area of the entire annular gap 52 is larger than the area of the pore 49.

Next, the operation of the load pressure relief valve will be described.
In the circuit shown in FIG. 1, the operating valve 2 is switched to supply pressure oil to the actuator 3 to operate the actuator 3, and when the external load of the actuator 3 increases, the load pressure P _LS rises and the load pressure P _LS increases. Is a port 54, a port 53, an annular gap 52, an annular groove 5 from the load pressure introducing passage 8.
1, the holes 50, and the pores 49 flow into the concave portion 48 and act on the pressure receiving portion 39 of the poppet 35. When the load pressure P _LS becomes higher than the set pressure of the load pressure relief valve, the poppet 35 is pushed against the spring 48, the seat portion 45 is separated from the seat seat 46, and the inlet port 36 and the outlet port 37 communicate with each other. As a result, part of the load pressure P _LS becomes
The load pressure P _LS is maintained at the set pressure by flowing out (that is, the relief operation) from the outlet port 37 and the port 55 into the tank passage 56.

However, during the relief operation described above, the pressure in the recess 48 is slowly changed by the pores 49, and the load pressure P _LS acting on the pressure receiving portion 39 of the poppet 35 is slowly changed, so that the load pressure P _{LS of the} poppet 35 is changed. After the pressure has risen to the set pressure, the valve is slowly pushed in the opening direction with a slight time delay to perform a relief operation. Therefore, the load pressure in the load pressure introducing passage 8 is slowly decreased, the angle of the swash plate 20 is slowly changed, the discharge amount of the hydraulic pump 1 is not rapidly changed, and the flow rate to the actuator 3 is slowly changed. The operability is improved because the operating speed does not change drastically.

Further, when the load pressure P _LS flows through the annular gap 52, the foreign matter in the oil is removed, the foreign matter in the oil does not flow into the pores 49, and the pores 49 are clogged. It is possible to correctly increase the load pressure acting on the pressure receiving portion 39 of the poppet 35 with a set time difference.

In FIG. 3, a main valve 60 is fitted to the tip of the sleeve 33, and the main valve 60 is held by a main spring 63 at a position where the pump port 61 and the tank port 62 are closed, and its spring chamber 64 is The load pressure P _LS flows into the annular groove 51 through the fine holes 65 formed in the piston 47, and the pump discharge pressure flowing into the pump port 61 is higher than the load pressure P _LS by a pressure commensurate with the main spring 63. Then, the main valve 60 is pushed to connect the pump port 61 to the tank port 62, thereby forming an unload valve for maintaining the pump discharge pressure P ₁ at a pressure slightly higher than the load pressure P _LS . .

[0020]

Since the load pressure of the load pressure introducing passage 8 gradually increases by the throttle and acts on the pressure receiving portion 39 of the poppet 35, the poppet 35 has a slight time delay after the load pressure rises to the set pressure. It operates slowly in the opening direction, and even if the load pressure in the load pressure introducing passage 8 rises to the set pressure, it does not drop sharply but slowly drops over time. Therefore, when the discharge amount of the hydraulic pump 1 is controlled by the load pressure of the load pressure introducing passage 8, the load pressure does not change rapidly and the discharge amount of the hydraulic pump 1 does not change rapidly. The operating speed of the actuator that operates with the discharge pressure oil is not suddenly changed, and the operability is improved.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram using a closed center type operation valve.

FIG. 2 is a sectional view showing an example of a load pressure relief valve.

FIG. 3 is a sectional view of a load pressure relief valve showing an embodiment of the present invention.

[Explanation of symbols]

1 ... hydraulic pump, 2 ... operation valve, 3 ... actuator, 5
... Pressure compensating valve, 9 ... Load pressure relief valve, 8 ... Load pressure introducing passage, 35 ... Poppet, 36 ... Inlet port, 37 ... Outlet port, 39 ... Pressure receiving part, 49 ... Pore, 52 ... Annular gap.

Claims (2)

[Claims] 1. An inlet port 3 communicating with a load pressure introducing passage 8.
6, the poppet 35 that opens and closes the outlet port 37 that communicates with the tank is held in a closed position by a spring 38, and is opened by the pressure acting on the pressure receiving portion 39 of the poppet 35. A load pressure relief valve characterized by communicating with the introduction passage 8. 2. The load pressure introducing passage 8 is communicated with the pressure receiving portion 39 via a throttle and a clearance filter.
Load pressure relief valve described.