JPH04210102A - Oil-hydraulic circuit - Google Patents

Abstract

PURPOSE:To reduce the cost by furnishing a pressure compensation valve with an internal load pressure sensing circuit, connecting this sensing circuit to a load pressure lead-in path, and providing possibility of sending the load pressure from the inlet side of the compensation valve. CONSTITUTION:A pressure compensation valve 18 is pushed by the pressure oil of No.1 pressure receiving part 19 and the force of a spring 20 into the shut position A and pushed by the pressure oil of No.2 pressure receiving part 21 into the communicative position B. This No.2 pressure receiving part 21 is connected with the inlet to the compensation valve 18 to supply the inlet side pressure, while the No.1 pressure receiving part 19 is connected to a main load pressure lead-in path 23 via a load pressure lead-in path 22, to supply the highest load pressure. An internal load pressure sensing circuit 50 is composed of a passage 53 leading from the internal inlet side of the pressure compensation valve 18 to its internal outlet side, another passage 54 connected to the middle between No.1 throttle 51 and No.2 throttle 52 in the first named passage 53, and a check valve 55 installed in the later named passage 54.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic circuit that supplies pressure oil discharged from one hydraulic pump to a plurality of hydraulic actuators.

[Conventional technology]

In order to supply pressure oil discharged from one hydraulic pump to multiple hydraulic actuators, it is sufficient to provide multiple operating valves in the discharge path of the hydraulic pump and supply pressure oil to each hydraulic actuator by switching the operating valves. However, in this case, when pressure oil is supplied to a plurality of hydraulic actuators at the same time, pressure oil is supplied only to the hydraulic actuators with a small load, and no pressure oil is supplied to the hydraulic actuators with a large load.

As a hydraulic circuit to solve this problem, for example,
The method shown in Japanese Patent No. 49405 has been proposed.

Such a hydraulic circuit is schematically shown in FIG.

That is, a plurality of operation valves 2 are provided in the discharge path 1a of the hydraulic pump 1, and pressure compensation valves 5 are provided in the circuits 4 connecting each operation valve 2 and each hydraulic actuator 3, and the pressure in each circuit 4, that is, the load The highest pressure in the pressure is detected by the check valve 6, and the detected load pressure is applied to each pressure compensation valve 5.
When the pressure on the outlet side of each operating valve 2 is equalized and each operating valve 2 is operated simultaneously, each hydraulic actuator is divided at a flow division ratio proportional to the opening area of each operating valve. 3 to be able to supply pressure oil.

[Problem to be solved by the invention]

With such a hydraulic circuit, the function of the pressure compensating valve 5 makes it possible to distribute the flow rate in proportion to the opening area of the operating valve 2, regardless of the magnitude of the load on each hydraulic actuator 3. It can be supplied to each hydraulic actuator 3 in proportion to the amount of operation of the operation valve 2.

However, by detecting and comparing the negative 6j pressure of the hydraulic actuator 3 from the outlet side of the pressure compensating valve 5, the highest pressure is introduced into the pressure receiving part 5a that increases the set pressure of the pressure compensating valve 5. The resulting pressure P is no lower than the inlet side pressure P by the pressure loss when flowing through the pressure compensating valve 5, and the flow rate flowing through the pressure compensating valve 5 becomes an error by the pressure loss, resulting in a flow rate distribution error. .

In other words, the flow mQ flowing through the pressure compensation valve 5 on the low load pressure side
1. Flow flowing through the pressure compensation valve 5 on the high load pressure side Q
2 is g2-ca2'%τ〒7 However, C is a constant, al, al are the operating valve opening area, Pl
is the discharge pressure of the hydraulic pump, and the error is the pressure loss (p, -p,) of the pressure compensating valve 5.

Note that the above problem can be solved by detecting the load pressure from the inlet side of the pressure compensation valve 5, but the same pressure P2 acts on the set pressure high side pressure receiving part and the set pressure low side pressure receiving part of the pressure compensation valve 5. Therefore, the pressure compensation valve 5 is closed due to the spring 7, and pressure oil is no longer supplied to the hydraulic actuator 3.

Further, when the operation valve 2 is set to the neutral position, the holding pressure of the hydraulic actuator 3 is supplied from the check valve 6 to the capacity control unit 8 of the hydraulic pump 1, and the hydraulic pump 1 is adjusted to match the holding pressure.
Since the capacity of the hydraulic pump 1 increases in an attempt to increase the discharge pressure of the hydraulic pump 1, the driving horsepower of the hydraulic pump 1 is wasted. Therefore, if the circuit that introduces the load pressure into the capacity control section is connected to the tank via the throttle 9 to prevent the capacity of the hydraulic pump 1 from increasing, the holding pressure will flow to the tank via the throttle 9, so the hydraulic actuator's natural The drop becomes so large that it becomes impossible to hold the hydraulic actuator.

Therefore, in the conventional hydraulic circuit, a counterbalance valve is provided to prevent the holding pressure of the hydraulic actuator 3 from flowing into the check valve 6, which increases the complexity of the circuit and the number of parts, which increases the cost.

Therefore, an object of the present invention is to provide a hydraulic circuit that can solve the above-mentioned problems.

[Means and effects for solving the problem] In the pressure compensation valve,
An internal load pressure detection circuit is provided to detect the intermediate pressure between the internal inlet side pressure and the internal outlet side pressure, and this internal load pressure detection circuit is connected to the load pressure introduction path, so that the internal pressure is detected from the inlet side of the pressure compensation valve. It is designed to detect load pressure.

〔Example〕

As shown in FIG. 1, the hydraulic pump 10 is a variable displacement hydraulic pump in which the displacement, that is, the discharge flow rate per rotation, is changed by changing the angle of the swash plate 11. The small diameter piston 13 tilts in the capacity decreasing direction, and the small diameter piston 13 tilts in the capacity increasing direction.

The pressure receiving chamber 12g of the large diameter piston 12 is communicated with and cut off from the discharge passage 10g of the hydraulic pump 10 by a switching valve 14, and the pressure receiving chamber 13g of the small diameter piston 13 is connected to the discharge passage 10a.

A plurality of operation valves 15 are provided in the discharge passage 10a of the hydraulic pump 10, and a pressure compensation valve 18 is provided in a circuit 17 connecting each operation valve 15 and the hydraulic actuator 16. is pushed towards the blocking position A by the pressure oil of the first pressure receiving part 19 and the spring force of the spring 20, and is pushed towards the communicating position B by the pressure oil of the second pressure receiving part 2N,
The second pressure receiving part 21 is connected to the inlet side of the pressure compensating valve 18 and is supplied with the inlet side pressure, and the first pressure receiving part 19 is connected to the main load pressure introducing path 23 via the load pressure introduction path 22 and is connected to the main load pressure introduction path 23 for the highest load. pressure is supplied.

A load check valve 24 is provided on the outlet side of the pressure compensation valve 18 in the circuit 17, and the load check valve 24 is opened by the pressure on the outlet side of the pressure compensation valve 18.

The load check valve 24 and the hydraulic actuator 16 in the circuit 17 are connected to a drain passage 27 via a safety valve 25 and a suction valve 26, and the drain passage 27 is connected to a tank 28.

The switching valve 14 is pushed to the supply position C by the pressure in the discharge passage 10a, that is, the discharge pressure P1 of the hydraulic pump 10, and the spring 29
is pushed to the drain position &D by the spring force and the load pressure PLS acting on the pressure receiving part 14a, and the discharge pressure P1 and the load pressure PLS
When the pressure difference (P + PLS) PLS becomes higher than the spring force of the spring 29, the large diameter piston 1 is pushed to the supply position C.
The swash plate 11 is tilted in the capacity reduction direction by supplying the discharge pressure P1 to the pressure receiving chamber 12a of No. 2, and when the pressure difference ΔPLS becomes lower than the spring force of the spring 29, the switching valve 14 is pushed to the drain position iD and the swash plate 11 is tilted in the capacity reduction direction. The pressure oil in the pressure receiving chamber 12a of the diameter piston 12 flows out to the tank side, and the swash plate 11 is tilted in the direction of increasing the capacity.

The operation valve 15 is operated in a direction in which the opening area increases in proportion to the pilot pressure oil from the pilot control valve 30,
The pilot pressure oil is proportional to the operating stroke of the lever 30a.

That is, the pilot control valve 30 includes a plurality of pressure reducing parts 32 that output pressure oil discharged from the pilot hydraulic pump 31 in proportion to the operating stroke of the lever 30a, and the output side of the pressure reducing part 32 is connected to the pressure receiving part of the operating valve 15. 15a, and when the lever 30a is operated to output pressure oil from one pressure reducing part 32, the operating valve 15 moves from the neutral position N to the first or second pressure oil supply position 1. II, and the switching stroke is proportional to the pilot pressure oil from the pressure reducing section 32.

The operation valve 15 has first and second pump ports 33 and 34, first and second tank boats 35 and 36, first and second actuator boats 38 and 39, and first and second auxiliary ports 40.
．． 41, the first and second pump boats 33 and 34 are connected to the discharge path 10a of the hydraulic pump 10, the 1φ second tank ports 35 and 36 are connected to the drain path 27, and the first and second actuators The boats 38, 39 are connected to the inlet side of each pressure compensating valve 18, and the second auxiliary port 40.
41 is a short circuit path 42 connected to the outlet side of the load check valve 24 in the circuit 17.

When the operation valve 15 is in the neutral position N, each boat is shut off, and when it is in the first pressure oil supply position I, the first pump port 33 and the first actuator 38 are in communication, and the second auxiliary port 41 is connected to the second tank boat. 36, and when in the second pressure oil supply position H, the second pump port 34 and the second actuator port 39 communicate, and the TSlSl auxiliary port 40
communicates with the first tank port 35, and the operation valve 15 is a closed center type three-position switching valve.

An unload valve 4 is provided in the discharge passage 10a of the hydraulic pump 10.
3 is provided, and this unload valve 43 is configured to unload when the pressure difference (Pl-P) ΔPLS between the discharge pressure P and the load pressure PLS exceeds the set pressure,
When LS is large, it opens to release the oil discharged from the hydraulic pump 10 into the tank to reduce the peak pressure of the discharge pressure P1, and when each operating valve 15 is at the neutral position, the oil discharged from the hydraulic pump 1° is transferred to the tank. It's Nishide.

The pressure compensating valve 18 has the pressure of the first pressure receiving part 19 + the spring 20
It moves from the cutoff position A toward the communication position B in proportion to the difference between the spring force of An intermediate pressure is detected and introduced into the load pressure introduction path 22.

The internal load pressure detection circuit 50 has first and second throttles 51.5
2, a passage 53 communicating the internal inlet side and the internal outlet side of the pressure compensation valve 18, and a first throttle 5 in the passage 53.
It consists of a passage 54 connected between the first and second throttles 52 and a check valve 55 provided in the passage 54.

That is, as shown in FIG. 2, the pressure compensating valve 18 has a poppet 63 slidably inserted into the valve body 60 for communicating and blocking the inlet port 61 and the outlet port 62, and the poppet 63 is moved in the blocking direction by the spring 20. The seat surface 64 is pressed against the valve seat 65, and the poppet 63 is provided with first and second pores 66.6 that communicate the front end surface 63a and the front end of the seat surface 64.
7 and has first and second apertures 51,52.
3, the confluence of the first and second pores 66 and 67 communicates with a spring chamber 69, that is, the first pressure receiving part 19, through a through hole 68, and a check valve 55 is provided in the through hole 68.

Next, the operation will be explained.

(When the operation valve 15 is in the neutral position) As shown in Fig. 1, the discharge passage 10a of the hydraulic pump 10 is blocked by the operation valve 15, and the pressure oil discharged from the hydraulic pump 10 comes to a dead end, but the main load pressure is introduced. Since the pressure in the passage 23 is zero, the angle of the swash plate 11, that is, the discharge amount of the hydraulic pump 10 is reduced by the switching valve 14, and the discharge pressure P becomes a low pressure commensurate with the spring 29 of the switching valve 14. At this time, hydraulic pump 1
When the discharged oil of 0 becomes surplus, the discharge pressure P tries to rise, but the unload valve 43 opens and the discharged oil flows to the unload valve 4.
Escape from 3 to the tank.

At this time, the pressure compensating valve 18 is held at the shutoff position A by the spring 20, and the holding pressure ph of the hydraulic actuator 16 is held by the pressure compensating valve 18, and the operating valve 1
5, the natural fall of the hydraulic actuator 16 is very small.

In FIG. 1, the load check valve 24 is designed to prevent the holding pressure from flowing into the outlet side of the pressure compensating valve 18, and opens when the outlet pressure of the pressure compensating valve 18 exceeds the holding pressure.

(When one operation valve 15 is set to the first pressure oil supply position I)・
...Refer to Fig. 3■ When the lever 30a of the pilot control valve 30 is operated to output pressure oil from the pressure reducing part 32 and the pressure oil is supplied to the pressure receiving part 15a of the operating valve 15, the operating valve 15 moves from the neutral position N. 1st
Switched to pressure oil supply position I.

Thereby, the discharge pressure oil of the hydraulic pump 10 is supplied from the first pump port 33 to the inlet side of the pressure compensation valve 18 via the first actuator boat 38, and at the same time, the second pressure receiving part 21 of the pressure compensation valve 18 is supplied to the inlet side of the pressure compensation valve 18. , the pressure compensation valve 18 is pushed toward the communication position B.

When the pressure compensation valve 13 is pushed to the communication position B, the hydraulic pump 1
The discharge pressure oil of 0 is the first throttle 51 of the internal load pressure detection path 50,
It flows into the load pressure introduction path 22 from the passage 54 and the check valve 55 and acts on the first pressure receiving part 19 of the pressure compensation valve 18, and at the same time acts on the pressure receiving part 14a of the control valve 14 from the main load pressure introduction path 23 as pilot pressure. .

■Discharge pressure P of the hydraulic pump 10 in the above-mentioned state.

is lower than the holding pressure Ph, the pressure oil discharged from the hydraulic pump 10 does not flow to the hydraulic actuator 16, so the passage 53
The pressure in the load pressure introduction path 22 and the pressure on the inlet side of the pressure compensating valve 18 become equal, and the pressure compensating valve 18 is pushed to the shutoff position A by the spring force of the spring 20. Eventually, the passage 54 of the pressure compensation valve 1B opens slightly, and a pressure slightly lower than the discharge pressure P1 is introduced into the load pressure introduction passage 22.
This is a position where the load pressure applied to the pressure receiving part 19 is balanced.

For this reason, the discharge pressure P of the hydraulic pump 10 increases due to the operation of the switching valve 14, and accordingly, the pressure compensation valve 18 becomes the communication position B, and the pressure in the load pressure introduction path 22, that is, the load pressure PLS also increases. , the control valve 14 has its load pressure pts
is pushed from the supply position C to the drain position iD, which communicates with the pressure receiving chamber 12a of the large diameter piston 12 or the drain, and the swash plate 11 is tilted in the direction of increasing the capacity by the small diameter piston 13 to increase the discharge pressure P1.
further increases, and by repeating this operation, the discharge pressure P1 of the hydraulic pump 10 gradually increases.

■As mentioned above, the discharge pressure P of the hydraulic pump 10.

rises to the holding pressure of the hydraulic actuator 16,
The load check valve 24 opens at that pressure and the pressure compensation valve 18
The outlet side pressure oil is supplied to the hydraulic actuator 16.

As a result, the internal load pressure detection circuit 50 of the pressure compensation valve 18
Pressure oil flows through a passage 53 in the passage 53, and a pressure between the inlet side pressure and the outlet side pressure of the pressure compensating valve 18 is introduced into a passage 54 connected between the first throttle 51 and the second throttle 52, and the pressure is Since the load pressure pts is supplied from the load pressure introduction path 22 to the first pressure receiving part 19 of the pressure compensation valve 18, the pressure in the first pressure receiving part 19 of the pressure compensation valve 18 becomes lower than the pressure in the second pressure receiving part 21. A differential pressure is generated, the pressure compensation valve 18 is pushed toward the communication position B, and the flow rate passing through the pressure compensation valve 18 increases.
As a result, the flow rate flowing through the passage 53 also increases, and the pressure difference between the first throttle 51 and the second throttle 52 increases, so the difference between the load pressure pts of the load pressure introduction passage 22 and the pressure on the inlet side of the pressure compensating valve 8 The pressure also increases, and the pressure compensating valve 18 is further pushed toward the communication position B, so that the pressure compensating valve 18 becomes a set pressure corresponding to the load pressure PLs.

The return port from the hydraulic actuator 16 is a short circuit path 42
, the second auxiliary port 41 and the second tank port 36 into the drain passage 27 .

(Flow rate supplied to the hydraulic actuator 16) The pressure difference ΔPLS between the discharge pressure P of the hydraulic pump 10 and the load pressure PLS is the difference between the discharge side of the hydraulic pump 10 and the pump port 1 of the operation valve 15.
・Pressure loss due to line resistance of the piping connecting the control valve 1
5, the pressure loss in the main passage 15b, the first throttle 51 of the passage 53
It is determined by the pressure loss due to

Here, the pressure loss due to the resistance of the first pipe is ignored since it is small, and the pressure loss of other pipes is similarly ignored, and the discharge pressure Pl
, the main passage 15° outlet pressure of the operating valve 15 is P 2 , the passage 5
The outlet pressure of the first throttle 51 of No. 3 is P3, and the outlet pressure of the load check valve 25 is P4. Note that the outlet pressure P of the first throttle 51 of the passage 53 becomes the load pressure pts.

Let A be the opening area of the main passage 15b of the operation valve 15, that is, the opening area of the first pump port 33 and the first actuator port 38.

In this state, the pressure difference △PL5 is caused by the spring 29 of the switching valve 14.
If the spring force is too small, the switching valve 14 will be in the drain position as described above, the angle of the swash plate 11 will increase, and the discharge amount of the hydraulic pump 10 will increase.

As a result, the main passage 15 of the operation valve 15. As the flow rate increases, the pressure difference △PL increases, and the pressure difference △pt
When s increases more than the spring force of the spring 29, the switching valve 14 becomes the supply position C, and the discharge amount of the hydraulic pump 10 decreases as described above.

That is, the switching valve 14 has a pressure difference ΔPLSX pressure receiving part 14.
The pressure receiving area - the spring force of the spring 29 is balanced so that the discharge amount of the hydraulic pump 10 is equal to the pressure difference △PLS of the spring 29.
The spring force is controlled to a value commensurate with the spring force.

In the above state, the flow ff1Q flowing into the hydraulic actuator 16 is Q = CA (ET'V; ・CA J7T"1Blue-・
It is expressed as CA PH-h )+(Pl-PI). However, C is a constant, and A is the main passage 15 of the operating valve 15. opening area.

In this way, the flow ff1Q flowing to the hydraulic actuator 6
is not Q-cA(P";"-τ17 but Q-CA
°(Pl P2 ) + (P2 Pg ), so the main passage 15 of the operating valve 15. Although only the term (P2 P3) causes an error without being completely proportional to the opening area of This will ensure the required flow rate.

- As an example, the numerical values for each pressure are shown below.

The holding pressure ph of the hydraulic actuator 16 is 150 kg /
c-, when the spring set of the control valve 14 has a pressure difference Δpts of 20 kg/c-, P + -173 kg/cd, P2-156 kg/
cd.

P3 - 153kg/cd, P4 = 150kg/c (holding pressure).

(When supplying pressure oil to a plurality of hydraulic actuators 16) From the state where pressure oil is being supplied to the left hydraulic actuator 16 shown in FIG. 3 described above, to the right hydraulic actuator 16 as shown in FIG. The operation when supplying pressure oil will be explained. Note that the holding pressure of the right hydraulic actuator 16 is 200) cg/c.

When the right operation valve 15 is switched to the first pressure oil supply position l in the same manner as described above, the pressure oil discharged from the hydraulic pump 10 is pressure compensated from the first pump port 33, the main passage 15b, and the first actuator boat 38. Flows to the inlet side of the valve 18, and the discharge pressure P at that time.

is 173 kg/c-, so the load pressure pts (153 kg/c-) acting on the first pressure receiving part 19 of the right pressure compensation valve 18 is
Although it is pushed to the communication position B higher than g/cJ3, the outlet pressure is lower than the holding pressure (200 kg/cd), so the discharge pressure oil of the hydraulic pump 10 becomes a dead end.

As a result, the discharge pressure P of the hydraulic pump 1 enters the main load pressure introduction passage 23 from the load pressure introduction passage 22 through the passages 53 and 54 of the pressure compensation valve 18 on the right side and the check valve 55, and the discharge pressure P enters the main load pressure introduction passage 23 from the load pressure introduction passage 22. Since the pressure PL5 acts on the pressure receiving part 14a of the switching valve 14 and sets it to the drain position, the above-mentioned pressure increase process starts again, and the discharge pressure P1 of the hydraulic pump 10 reaches the holding pressure of the right hydraulic actuator 16 of 200 kg/cli. When the holding pressure increases to 200 kg/c- or higher, the discharge pressure of the hydraulic pump 10 is supplied to the right hydraulic actuator 16 in the same manner as in the above-described single operation.

Each pressure when the right hydraulic actuator 16 is operating is as follows.

The discharge pressure P1 of the hydraulic pump 10 is 223 kg/cd, and the main passage 15 of the operating valve 15 is 223 kg/cd. The outlet pressure P is 206 kg
/ cd, first throttle 51 outlet side pressure Pa of passage 53
(Load pressure PLS) is 203 kg/c-.

At this time, the left hydraulic actuator 16 operates as follows.

The first pressure receiving part 19 of the left pressure compensation valve 18 has a weight of 153 kg.
Since a load pressure of /c- was acting, the right hydraulic actuator 16 operates to reduce the load pressure P Ls-2.
03kg/e- from the check valve 42 to the main load pressure introduction path 2
3. When the load pressure acts on the first pressure receiving part 19 through the load pressure introduction path 22 and rises, and the load pressure pts of the first pressure receiving part 19 exceeds the pressure of the second pressure receiving part 21 (P 2 - 156 kg/cd). The pressure compensating valve 18 is in the blocking position i! A, the opening is narrowed, and as a result, the pressure on the inlet side of the pressure compensating valve 18, that is, the main passage 15. of the operating valve 15. Balance occurs when the outlet pressure P2 increases and reaches the load pressure pL, -203) cg/c- on the right side.

That is, the pressure in the first pressure receiving part 19 of the left pressure compensation valve 18 rises to the load pressure PLs-203 kg/c- corresponding to the holding pressure of the right hydraulic actuator 16, and as the pressure rises, the pressure in the first pressure receiving part 19 of the pressure compensation valve 18 on the inlet side of the pressure compensation valve 18 increases. The pressure also increases and balances at the load pressure PLS203 kg/C-.

As a result, the outlet pressure P2 of the main passage 15° of the left operation valve 15 becomes 203 kg/c-, the load check valve outlet pressure P4 becomes 15.0 kg/c-, and the outlet pressure P3 of the first restrictor 51 of the passage 53 becomes 203 kg/c-. becomes 176.5 kg/C-.

This outlet pressure P3 becomes a load pressure, but since it is lower than the load pressure Pts=203 kg/C- of the right hydraulic actuator 16, it is not supplied to the first pressure receiving part 19 of the pressure compensation valve 18 due to the action of the check valve 55.

That is, the load pressure PLFt corresponding to the holding pressure of each hydraulic actuator 16 is determined by the load pressure detection boat 37 of each operation valve 15.
However, since the highest load pressure is introduced into the load pressure introduction path 23 by the check valve 55, each pressure compensation valve 1
The highest load pressure is supplied to the first pressure receiving part 19 of No. 8, and each pressure compensating valve 18 has a set pressure corresponding to the highest load pressure.
The discharge pressure oil of the hydraulic pump 10 can be supplied in proportion to the opening degree of the hydraulic pump 10.

The flow rate when the left and right hydraulic actuators 16 are operating simultaneously is as follows.

The discharge amount of the hydraulic pump 10 is Q, the flow rate to the hydraulic actuator 16 on the low pressure side (left side) is Qs, and the high pressure side (right side)
If the flow rate to the hydraulic actuator 16 is Ql, then Q = Q1 + Q2 Ql - CAIXJ lower] = 777 Ql - CA2 x p, -p〒, P + -223kg/c, P2 - 203k
g/cd, P5 = 206 kg/cd, so Q+-CA, x, , r.

Q2=CA2X7cho7 becomes.

Here, the opening area A of the main passage 15a of the left and right operation valves 15 is
,, Even if A2 is the same, the values of the respective pressures described above do not change, so the flow rate ratio between the left and right sides becomes 8%, which becomes a flow rate distribution error.

On the other hand, when the load pressure PLs is introduced from the outlet side of the pressure compensation valve 18 as in the prior art, the pressure loss of the pressure compensation valve 18 in the high pressure side (right side) hydraulic actuator 16 is p5-p, m206kg/c. sea 200 kg/
Since cd = 6 kg/cd, the flow ff1Q2 of the right hydraulic actuator 16 is Ql - CA2
()0-6-CA2

Next, a modification will be explained.

As shown in FIG. 5, a bypass path 70 is connected to the main load pressure introduction path 23.
This bypass passage 70 is connected to the tank 7 via a throttle 71.
It is connected to 2.

In this way, when each operation valve 15 is set to the neutral position N, the pressure in the main load pressure introduction path 23 will decrease quickly, and the control valve 1
The load pressure acting on the hydraulic pump 10 quickly becomes zero and the hydraulic pump 10
Since the discharge pressure P1 of the hydraulic pump 10 decreases quickly, the driving load on the hydraulic pump 10 can be immediately reduced, and the residual load noise of the hydraulic pump can be reduced.

As shown in FIG. 6, the bypass passage 70 is connected to the discharge passage of the pilot hydraulic pump 31 of the pilot control valve 30.

Even in this case, the same function as described above is achieved.

As shown in FIG. 7, the bypass passage 70 is connected to and disconnected from the tank 72 by the unload valve 43, and when the unload valve 43 is switched from the shut-off position E to the communication position F, the bypass passage 70 is opened to the throttle 72. It communicates with the tank 72 through the.

With such a configuration, the operating valve 15 is moved from the neutral position N to the first
Or, when operated to the second pressure oil supply position I or ■, the differential pressure between the discharge pressure P of the hydraulic pump 10 and the load pressure pts becomes smaller than the spring force of the spring 43a of the unload valve 43, so the unload valve 43 The communication position F becomes the cutoff position E, and the load pressure introduction path 23 does not communicate with the tank 72 via the bypass path 70, so responsiveness is ensured, and the operation valve 15 is moved from the first or second pressure oil supply position I or ■ to the neutral position. When operated to position N, the unloading valve 43 changes from the blocking position E to the communicating position F, and the main load pressure introduction path 23 passes through the throttle 73 and is connected to the tank 72.
Since the load pressure is communicated with the valve, the load pressure decreases quickly, and the ribbon pressure decreases quickly, so there is no discomfort.

〔Effect of the invention〕

Since the intermediate pressure between the inlet side pressure and the outlet side pressure of the pressure compensation valve 18 is supplied to the first pressure receiving part 19 that pushes the pressure compensation valve 18 in the blocking direction, the error in the passing flow m due to the pressure loss of the pressure compensation valve 18 is reduced. This reduces errors in flow rate distribution to the plurality of hydraulic actuators 16, and the pressure on the outlet side of the operating valve 15 supplied to the second pressure receiving section 21 that pushes the pressure compensating valve 18 in the communication direction is lower than that of the first pressure receiving section. As the pressure supplied to the valve 19 becomes lower, the pressure compensating valve 18 operates in the communication direction and can perform a pressure compensating operation.

Moreover, when the operation valve 15 is set to the neutral position, the pressure compensation valve 1
8 is held at the cutoff position A by the spring force of the spring 20, and the holding pressure of the hydraulic actuator 16 is maintained at the main load pressure introduction path 2.
3, when controlling the capacity of the hydraulic pump 10 using the load pressure of the main load pressure introduction path 23, the capacity of the hydraulic pump 10 does not increase due to the holding pressure, and the pressure compensating valve 18 There is no need to provide a counterbalance valve in the circuit connecting the outlet side and the hydraulic actuator 16, which not only simplifies the hydraulic circuit, but also reduces the number of parts and reduces costs.

Further, since the load pressure is detected by the internal load pressure detection circuit 50 of the pressure compensation valve 18, the load pressure detection circuit is simplified.

Further, since the internal load pressure detection circuit 50 of each pressure compensation valve 18 is connected to the load pressure introduction path 22 through the check valve 55,
When a plurality of operation valves 15 are operated simultaneously, the highest load pressure is introduced into the load pressure introduction path 22, and the flow rate can be distributed to each hydraulic actuator 16.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing a first embodiment of the present invention, FIG. 2 is a sectional view of a pressure compensation valve, FIGS. 3 and 4 are operation explanatory diagrams,
FIG. 5, FIG. 6, and FIG. 7 are hydraulic circuit diagrams showing the second, third, and fourth embodiments, and FIG. 8 is a conventional schematic explanatory diagram. 10 is a hydraulic pump, 15 is an operation valve, 16 is a hydraulic actuator, 18 is a pressure compensation valve, 19 is a first pressure receiving part, 20 is a spring, 21 is a second pressure receiving part, 23 is a load pressure introduction path, 23 is the main load Pressure introduction path; 50 is an internal load pressure detection circuit; 51.
52 is a first and second throttle, 53 and 54 are passages, and 55 is a check valve.

Claims (1)

[Claims] A plurality of operation valves 15 are provided in the discharge path 10a of the hydraulic pump 10, and a pressure compensation valve 18 is provided in the connection circuit between each operation valve 15 and each hydraulic actuator 16.
8 is set at the highest load pressure of each hydraulic actuator 16, a first pressure receiving part 19 that pushes the pressure compensating valve 18 toward the cutoff position A is connected to the load pressure introduction path 22, These load pressure introduction paths 22 are connected through a main load pressure introduction path 23, and a second pressure receiving part 21 that pushes the pressure compensation valve 18 toward the communication position B is connected to the outlet side of the operation valve 15, and the pressure compensation valve 18, a passage 53 having a first throttle 51 and a second throttle 52 and communicating the internal inlet side and the internal outlet side, and a check valve connected between the first throttle 51 and the second throttle 52 in this passage 53. 5. A hydraulic circuit characterized in that an internal load pressure detection circuit 50 comprising a passage 54 having a diameter 55 is provided, and the passage 54 is connected to the load pressure introduction passage 22.