JPH0547503U - Hydraulic circuit - Google Patents

Abstract

(57) [Summary] [Purpose] When the cutoff valve is in the unload state, the check valve does not operate suddenly and the hydraulic shock does not occur on the work machine actuator side at the moment of unloading. [Structure] The discharge side of the first hydraulic pump 16 is connected to the working machine actuator by the operation valve 1, the unload valve 21 is provided on the discharge side of the second hydraulic pump 39, and the inlet side of the unload valve 21 is a check valve. It is connected to the discharge side of the first hydraulic pump 16 via 31 and the throttle 25. [Effect] When the discharge pressure oil of the second hydraulic pump 39 is supported by the first hydraulic pump 16 side, the second hydraulic pump 39
When the cut-off valve 21 is unloaded, the discharge flow rate of the throttle valve 25 is increased by the passage resistance of the throttle 25, and the check valve 31 is activated when the flow rate of the throttle valve 25 decreases and becomes equal to or lower than the opening pressure of the check valve 31. Therefore, the discharge pressure of the first hydraulic pump 16 does not decrease at the moment of unloading, and the hydraulic shock does not occur on the working machine actuator side.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a hydraulic circuit of a construction machine such as a wheel loader and a dump truck.

[0002]

[Prior Art]

 In construction machines equipped with actuators for work machines such as boom cylinders and arm cylinders, and steering cylinders, pressure oil can be supplied to the work machine actuators from multiple hydraulic pumps to supply a large flow rate to the work machine actuators, resulting in an operating speed. A hydraulic circuit that speeds up is known. In the aforementioned hydraulic circuit, when the discharge pressure oil of multiple hydraulic pumps is supplied to the work machine actuator at high load, the pressure of the discharge pressure oil exceeds the set pressure of the relief valve and the driving horsepower of multiple hydraulic pumps is output to the engine. Since the engine will stop as described above, a cut-off valve is provided to allow the pressure oil discharged from one hydraulic pump to flow into the tank and put it in an unloading state to prevent the engine from stopping.

[0003]

[Problems to be solved by the device]

 With such a hydraulic circuit, a hydraulic shock is generated in the pressure on the actuator side for the work machine at the moment when the cut-off valve is in the unloading state, and this hydraulic shock causes vibration to the entire vehicle body, causing operator discomfort. It may be applied or the work equipment such as a bucket may vibrate and spill the earth and sand. In other words, the cutoff valve is in an unloading state while the pressure oil discharged from two hydraulic pumps is being combined and supplied to the work machine actuator, and only the pressure oil discharged from one hydraulic pump is the work machine actuator. The pump power momentarily decreases until the confluence check valve is received at the moment when it is supplied to the cylinder, which causes the hydraulic shock described above.

Therefore, an object of the present invention is to provide a hydraulic circuit capable of solving the above problems.

[0005]

[Means for Solving the Problems]

 The discharge side of the first hydraulic pump 16 is connected and controlled by the operation valve 1 to the working machine actuator, the cutoff valve 21 is provided on the discharge side of the second hydraulic pump 39, and the check valve 31 is provided at the inlet side of the cutoff valve 21. And a hydraulic circuit connected to the discharge side of the first hydraulic pump 16 via a throttle 25.

[0006]

[Work]

 When the discharge pressure oil of the second hydraulic pump 39 is being supported to the first hydraulic pump 16 side, the discharge pressure of the second hydraulic pump 39 becomes higher than the discharge pressure of the first hydraulic pump 16 by the passage resistance of the throttle 25, When the cutoff valve 21 is in the unloading state, the discharge pressure of the second hydraulic pump 39 decreases according to the unloading flow rate and decreases as the passing flow rate of the throttle 25 decreases, and is equal to or lower than the discharge pressure of the first hydraulic pump 16. That is, when the cutoff valve 21 is unloaded because the check valve 31 does not suddenly operate due to the receipt of the check valve 31 when the opening pressure of the check valve 11 falls below the opening pressure, the first hydraulic pump 16 The discharge pressure of will not drop for a moment and hydraulic shock will not occur on the work implement actuator side.

[0007]

【Example】

 As shown in FIG. 1, the operation valve 1 has a valve body 2 provided with a first spool 3 and a second spool 4, and has a boom valve 5 and a bucket valve 6. Third and fourth actuator ports 7, 8, 9, 10 and a pump port 11 and a tank port 12 are formed, and the connecting surface 2a of the valve body 2 has first, second and third connecting ports 12, 13, 14 is formed, the first and second actuator ports 7 and 8 are connected to the output side of the boom valve 5, the third and fourth actuators 9 and 10 are connected to the main force side of the bucket valve 6, and the pump port Reference numeral 11 is an inlet passage 15 connected to the inlet port 6a of the bucket valve 6 and connected to the discharge side of the first hydraulic pump 16, and the tank port 12 is connected to the drain passage 17 and connected to the tank 18. is there. The first connecting port 12 is connected to the inlet passage 15, the second connecting port 13 is connected to the drain passage 17, the third connecting port 14 is connected to the neutral passage 19, and the neutral passage 19 is connected to the bucket valve 6. The boom valve 5 is connected to the drain passage 17 via the neutral ports 6b and 5b, and is also connected to the inlet port 5a of the boom valve 5 via the check 20. The cut-off valve 21 has a valve body 22 provided with first and second relief valves 23 and 24. A pump port 26 is formed in the valve body 22 and is connected to the connecting surface 2a of the valve body 2 of the operation valve 1. The first, second, and third connection ports 27, 28, and 29 are formed on the connecting surface 22a, and the first connection port 27 and the third connection port 29 communicate with each other through the communication passage 30, and the pump port 26 A first passage 32 having a check valve 31 and a throttle 25 is connected to the communication passage 30 and is connected to an inlet port 23a of the first relief valve 23, and an outlet port 23b thereof is a drain passage 33 to a second connection port 28. Connected, the inlet port 24a of the second relief valve 24 is connected to the pump port 26 by the second passage 36 having the first and second throttles 34, 35, and its outlet port 24b is drained by the third passage 37. Connected to the passage 33, the second relief valve 24 is pushed in the communicating direction by the pressure of the communicating passage 30 and in the closing direction by the spring force and the outlet pressure, and the pump port 26 is in the second hydraulic pump 39. It is connected to the discharge side of.

Next, the operation will be described. Since the supply pressure is low when the load on the boom cylinder 40 and the bucket cylinder 41 is small, the discharge pressure oil from the first and second hydraulic pumps 16 and 39 cannot be discharged without the relief operation of the first and second relief valves 23 and 24. Can be merged and supplied to each cylinder. At this time, the support pressure of the second hydraulic pump 39 becomes the pressure of the first hydraulic pump 16 plus the resistance pressure of the throttle 25 due to the throttle 25, and the pressure of the second hydraulic pump 39 is higher than the pressure of the first hydraulic pump 16. Become. Since the supply pressure is high when the load on the boom cylinder 40 and the bucket cylinder 41 is large, the second relief valve 24 is pushed to the communicating position, and the pressure oil in the second passage 36 flows out to the tank 18 at a small flow rate. Due to the flow of the flow rate, a differential pressure is generated before and after the second throttle 35, and when the differential pressure becomes equal to or higher than the valve opening pressure by the spring 23c, the first relief valve 23 becomes the communicating position and the discharge pressure oil of the second hydraulic pump 39 is discharged. The drain passage 33, the second connection port 28, the second connection port 13 of the valve body 2, the drain passage 17, and the tank port 12 flow into the tank 18 and the unload valve 21 enters the unload state, and the first hydraulic pump 16 It is possible to prevent the discharge pressure oil from being supplied to each cylinder and stopping the engine that drives each hydraulic pump. The operation of the unload valve 21 described above is slowed by the damper throttle 23d, and the unload flow rate does not increase sharply, and the support flow rate of the second hydraulic pump 39 also decreases as the unload flow rate increases. Therefore, the throttle resistance of the throttle 25 of the first passage 32 decreases, and the check valve 31 receives only when the passage resistance becomes equal to or lower than the opening pressure of the check valve 31, so that the discharge flow rate of the second hydraulic pump 39 is reduced. To load. As described above, since the check valve 31 does not suddenly receive (operate) when it is in the unloading state, the pressure on the first hydraulic pump 16 side does not drop for a moment and the hydraulic shock does not occur. That is, without the throttle 25, the pressure on the first hydraulic pump 16 side is unloaded and the pressure is instantaneously reduced when the check valve 31 has the same front-rear pressure and is in the unloading state. When the cut-off valve 22 is unnecessary, the discharge sides of the first and second hydraulic pumps 16 and 39 are connected to the first and third connection ports 12 and 14 formed in the valve body 2 of the operation valve 1, It suffices if the second connection port 13 is closed with a plug, and the cutoff valve 22 can be retrofitted or removed as required.

As shown in FIG. 2, the first valve 32 may be connected to the discharge channel of the first hydraulic pump 16 by a pipe 32 while the operation valve 1 and the cutoff valve 21 are provided as separate bodies. The throttle 25 provided in the passage 32 may be provided in the pipe 32.

FIG. 3 shows a specific structure, and a plug 45 having a fine hole 44 is provided in the oil hole 43 forming the first passage 32 of the valve body 22 of the cutoff valve 21 to form a throttle 25. The check valve 31 has a structure in which a valve 46 is pressed against a valve seat 48 by a spring 47.

FIG. 4 shows a check valve 31 having a throttle 25. A small-diameter projection 49 is integrally formed on the valve 46 to form a gap with the inlet port 50. The pressure oil flows through the gap between the inlet port 50 and the small diameter protrusion 49 when the valve 46 is pushed open against the spring 47 by the pressure. The area of the diaphragm 25 at this time is (D ² −d ² ) × π / 4. However, D is the inner diameter of the inlet port 50, and d is the outer diameter of the small diameter protrusion 49.

[0012]

[Effect of the device]

 When the discharge pressure oil of the second hydraulic pump 39 is being supported to the first hydraulic pump 16 side, the discharge pressure of the second hydraulic pump 39 becomes higher than the discharge pressure of the first hydraulic pump 16 by the passage resistance of the throttle 25, When the cutoff valve 21 is in the unloading state, the discharge pressure of the second hydraulic pump 39 decreases according to the unloading flow rate and decreases as the passing flow rate of the throttle 25 decreases, and is equal to or lower than the discharge pressure of the first hydraulic pump 16. That is, when the cutoff valve 21 is unloaded because the check valve 31 does not suddenly operate due to the receipt of the check valve 31 when the opening pressure of the check valve 11 falls below the opening pressure, the first hydraulic pump 16 The discharge pressure of will not drop for a moment and hydraulic shock will not occur on the work implement actuator side.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view showing a first embodiment of the present invention.

FIG. 2 is a schematic structural explanatory view showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a specific example of the present invention.

FIG. 4 is a sectional view of a check valve.

[Explanation of symbols]

1 ... Operating valve, 2 ... valve body, 11 ... honp port, 12 ...
First connection port, 13 ... Second connection port, 14 ... Third connection port, 15 ... Inlet passage, 16 ... First hydraulic pump, 1
7 ... Drain passage, 19 ... Neutral passage, 20 ... Cut-off valve, 21 ... Valve body, 25 ... Restrictor, 26 ... Second pump port, 27 ... First connection port, 28 ... Second connection port, 29 ... Third Connection port, 30 ... Communication passage, 31 ... Check valve, 33 ... Drain passage, 39 ... Second hydraulic pump.

Claims (1)

[Scope of utility model registration request] 1. The operation valve 1 is provided on the discharge side of the first hydraulic pump 16.
And the cutoff valve 21 is provided on the discharge side of the second hydraulic pump 39.
A hydraulic circuit characterized in that an inlet side of the cutoff valve 21 is connected to a discharge side of the first hydraulic pump 16 via a check valve 31 and a throttle 25.