JPH11236903A - Hydraulic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize a waste of energy, and provide a hydraulic device which uses a pressure compensating valve having a suitable responsivenessand a hydraulic device which is fit to a hydraulic circle preventing a traveling curve. SOLUTION: A C (D) pressure compensating valve 91 (91') is provided with a check valve part 93 (93') and pressure reducing valve part 95 (95'). The pressure reducing valve part 95 (95') receives pressure from a C (D) load pressure circuit 89 (89') of a C (D) operating valve 81 (81') as a pilot pressure, and reduce an output pressure of a throttle valve so as to produce an output to a CD load pressure circuit 97 (97') and 126. At this time, if the operating valve 81 (81') is in a neutral state, the C (D) load pressure circuit 89 (89') is made to have a lower pressure than the CD load pressure circuit 97 (97') and 126, and the pressure of a back pressure drain circuit 27-6 is applied to both circuits, thus reducing an unexpected consumption of pressure oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic device, such as a hydraulic device for a hydraulic shovel, having a plurality of actuators and compensating for supply hydraulic pressure in accordance with the load pressure of each actuator.

[0002]

2. Description of the Related Art The prior art will be described using a hydraulic device of a hydraulic shovel as an example. The hydraulic shovel has left and right traveling motors and working machine actuators such as a boom cylinder and a bucket cylinder that drive the shovel. In this hydraulic device, there is a type that performs so-called pressure compensation that performs flow distribution according to the operation amount of an operation valve regardless of the load pressure of each actuator.

A conventional pressure compensating valve includes a check valve unit for supplying pump discharge pressure oil to an operation valve, and a pressure reducing valve unit for reducing and outputting the pump discharge pressure oil in accordance with the load pressure of an actuator. There was something that became. The pressure reducing valve reduces the pump discharge pressure by applying the load pressure of the actuator to the load pressure detection port, and outputs the signal pressure to the load pressure circuit. Further, the pressure of the load pressure circuit acts to shut off the output of the pressure reducing valve.

When this pressure compensating valve is applied to a hydraulic device having a plurality of actuators, a load pressure circuit for introducing the maximum pressure out of the output pressures is constructed by connecting the output sides of the pressure reducing valves. Was. The pressure of the load pressure circuit is
At the same time, by defining the set pressures of all the pressure compensating valves, the pressure compensating valves operate so as to maintain a constant differential pressure between the upstream side and the downstream side of the operation valve connected to each pressure compensating valve.

[0005] The pressure of the load pressure circuit is introduced into a pump discharge amount control circuit, and the pump discharge amount is controlled so as to keep the pump discharge pressure and the pressure difference between the load pressure circuit constant. At this time, the load pressure circuit is always in communication with the tank via the throttle. Therefore, in the case of the conventional configuration, when all the operation valves are set to neutral, all the pressure reducing valve units of the load pressure circuit stop outputting the signal, so that the tank pressure becomes the pressure via the throttle.

By the way, the pressure acting on the load pressure detection port which regulates the output pressure of the pressure reducing valve is connected to the return side hydraulic oil circuit of the actuator in order to prevent the load pressure of the actuator from remaining when the operation valve is stopped. I was This circuit is a circuit that is boosted by a back pressure check valve that defines a back pressure.

[0007]

In the conventional configuration, when all the operation valves are in the neutral state, the following occurs. That is, the pressure increased by the back pressure check valve acts on the load pressure detection port acting on the pressure reducing valve, and the pressure of the load pressure detection port is the tank pressure. Therefore, the pressure reducing valve always outputs some pressure oil.

As described above, the pump discharges pressure oil that is higher than the load pressure by a constant differential pressure. Therefore, even if all the operation valves are neutral, the pressure oil from the pressure reducing valve continues to be output, indicating that energy is consumed even when the operation valves are neutral. It also shows that the set pressure itself of the pressure compensating valve deviates from the target pressure. When operating the operating valves from the neutral state of all operating valves, the response of the pump discharge pressure becomes too fast,
Alternatively, the opening of the check valve portion of the pressure compensating valve may be too fast.

Consider a case in which a hydraulic excavator has the following hydraulic device configuration. That is, two pump discharge ports are provided, and one discharge port is connected to a right traveling motor and a work implement actuator, and the other discharge port is connected to a left traveling motor. A pressure oil supply path to the work machine actuator is connected via a throttle. Further, a merging / dividing valve is provided so that the two pump discharge pressure oils and the load pressure circuit can be merged and separated. Further, a hydraulic device provided with a throttling circuit for connecting a load pressure circuit to which a work machine actuator is connected to a tank via a throttling device is provided.

At this time, when the pressure of the load pressure circuit is increased by the back pressure check valve while the branching valve is kept in the separated state, the pressure oil of the load pressure circuit flows out of the throttle discarding circuit, and the pressure compensating valve of the right traveling motor. And the set pressure of the pressure compensating valve of the left traveling motor are different. Therefore, in this state, even if the same flow rate command is given to the left and right traveling motors by the pilot operation valve or the like and the vehicle travels straight, the actual flow rate is different and the traveling curve occurs.

SUMMARY OF THE INVENTION The present invention provides a hydraulic device using a pressure compensating valve having an appropriate responsiveness and minimizing waste of energy, and a hydraulic device suitable for a hydraulic circuit for preventing running bending. With the goal.

[0013]

The hydraulic apparatus according to the present invention comprises a C pressure compensating valve 91 connected to a pump 21.
And a C circuit including a C operating valve 81 connected downstream of the C pressure compensating valve 91 and a C actuator 65 connected downstream of the C operating valve 81; D pressure compensating valve 91 ', a D operating valve 81' connected downstream of the D pressure compensating valve 91 ', and a D operating valve 8
And a D circuit having a D actuator 65 'connected downstream of 1'. The C and D pressure compensating valves 91,
Reference numeral 91 'denotes a check valve unit for supplying the discharge pressure oil of the pump 21 to the C and D operation valves 81 and 81', and the pump 21 according to the load pressure of the C and D actuators 65 and 65 '. A pressure reducing valve for reducing the pressure of the discharge pressure oil and outputting the reduced pressure. It has a CD load pressure circuit for introducing the maximum pressure out of the output pressures of the pressure reducing valves of the C and D pressure compensating valves 91 and 91 '. The pressure reducing valve section has a discharge pressure oil detecting port of the pump 21 and a load pressure detecting port of an actuator connected to each pressure compensating valve. The output pressure of the pressure reducing valve section is increased by the pressure of the discharge pressure oil detection port and the load pressure detection port, and the output pressure is reduced by the pressure of the CD load pressure circuit and the pressure upstream of the operation valve. The CD load pressure circuit communicates with the tank via a throttle, and the C and D operation valves 81,
When 81 'is neutral, the CD load pressure circuit becomes the pressure of the return pressure oil of the C and D actuators 65 and 65' defined by the back pressure check valve 29, and the load pressure detection port of the pressure reducing valve section. A pressure defined by the back pressure check valve 29 is applied to the pressure sensor.

C (D) The pressure of the load pressure circuits 89, 89 'acting as pilot pressures on the pressure reducing valve portions 95, 95' of the pressure compensating valve 91 (91 ') is the output pressure (CD load pressure circuit 97 (91)). 97 'and 126. The pressure reducing valve portion 95 (95') is closed by the spring force acting in the closing direction and no flow of pressure oil occurs, so that unintended pressure oil consumption can be reduced. Further, since a pressure for operating the actuator is not applied in advance, it is possible to prevent a situation where a sudden operation is given.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a circuit diagram of a hydraulic device of the hydraulic shovel according to one embodiment of the present invention. First, an outline of the hydraulic circuit of this example will be described with reference to FIG.

(1) Outline of Circuit This hydraulic circuit has a circuit subdivided into the following. Left traveling circuit (A circuit): a circuit for driving the traveling motor on the left side of the excavator. The configuration of this circuit is as follows. At the time of split flow, a first discharge port (first pump) 21-1 of a two-flow-way type swash plate type piston pump 21 (hereinafter simply referred to as a pump 21) communicates with the junction valve 201. The junction valve 201 communicates with the check valve section 253 of the A pressure compensating valve 251 via the A discharge path 221. The check valve portion 253 is connected to a left traveling hydraulic motor (A actuator) 235 via an A operation valve 241. In addition, it communicates with a pump control circuit via a pump control discharge path pressure circuit 307. The two-flow-way swash plate piston pump is also called a double discharge flow type or a split type.

Right traveling circuit (B circuit): a circuit for driving the traveling motor on the right side of the hydraulic shovel. The configuration of this circuit is as follows. At the time of branch flow, the second
The discharge port (second pump) 21-2 communicates with the junction valve 201. B via the downstream pipe 31 of the merge / shunt valve 201
It communicates with the check valve part 173 of the pressure compensating valve 171. The check valve portion 173 is connected to a right traveling hydraulic motor (B actuator) 155 via a B operation valve 161. At the time of merging, the first discharge port of the pump 21 (first pump)
Reference numeral 21-1 communicates with a second discharge port (second pump) 21-2 via a merging / splitting valve 201. The merging / dividing valve 201 outputs the merged pump pressure oil to a pump control circuit described later via a pump control discharge pressure circuit 307.

Work machine circuits (C and D circuits): circuits for driving work machine actuators such as a boom cylinder and an arm cylinder of a hydraulic shovel. The configuration of this circuit is as follows. Although only two cylinders 65 and 65 'are shown in the figure, there are actually a plurality of similar cylinders and a plurality of hydraulic circuits for driving them. Circuit C: The second discharge port (second pump) 21-2 of the pump 21 communicates with the merge / shunt valve 201 at the time of branching. Downstream pipe line 31 and C discharge path 37 of merge / shunt valve 201
Through the throttle valve portion 113 of the throttle valve 111. The throttle valve section 113 communicates with the check valve section 93 of the C pressure compensating valve 91 of the working machine pressure oil supply circuit 46. Check valve part 93
Is connected to the working machine cylinder (C actuator) 65 via the C operation valve 81 of the C operation valve circuit 87.

Circuit D: At the time of branching, the second discharge port (second pump) 21-2 of the pump 21 is connected to the merging / dividing valve 201.
Communicate with It communicates with the throttle valve portion 113 of the throttle valve 111 via the downstream pipe line 31 of the junction valve 201 and the C discharge path 37. The throttle valve section 113 communicates with the check valve section 93 'of the D pressure compensating valve 91' of the working machine pressure oil supply circuit 46. The check valve section 93 'is a D operation valve 81' of the D operation valve circuit 87 '.
Is connected to the working machine cylinder (D actuator) 65 '.

Back pressure drain circuit: Reference numeral 27 denotes a back pressure drain circuit. A back pressure check valve 29 is provided at an end (lower end in the figure) of the back pressure drain circuit 27.

Non-pressure drain circuit: 131-1 to 1
31-5 shows a non-pressure drain circuit. This circuit is open to the pressure oil tank 131.

CD load pressure circuit (signal pressure circuit based on work machine load pressure): C load pressure circuit 89 and D load pressure circuit 89 ′
Are applied with the load pressures of the C and D actuators, respectively.
Reference numerals 97, 121, 123, 125, 126, 127
Is a CD load pressure circuit. The pressure of the CD load pressure circuit is
The pressure (load sensing pressure, LS) determined by the maximum load pressure among the work implement actuators in this circuit
Pressure).

BCD load pressure circuit (right running motor, C
Signal pressure circuit by D load pressure circuit): Right running load pressure circuit 1
The load pressure of the right running motor 155 acts on 63.
Reference numerals 141, 145, 147, 177, 181, 18
3, 185 and 187 are BCD load pressure circuits. The load pressure unit 175 reduces the load pressure of the right traveling motor 155 and outputs the reduced load pressure. The pressure of the BCD load pressure circuit 147 is the higher pressure of the load pressure of the right running motor 155 and the output pressure of the work equipment load pressure extraction pilot pressure reducing valve 143 determined by the pressure of the CD load pressure circuit 126.

A load pressure circuit (signal pressure circuit by left traveling motor): A load pressure circuit 243 includes left traveling motor 23
A load pressure of 5 is acting. Symbols 203, 205, 20
The straight lines indicated by 7, 209, and 211 are the left running (A) load pressure circuits. The load pressure of the left traveling motor 235 is extracted into the load pressure circuit at the time of separation. At the time of merging, the maximum load pressure of all actuators is extracted.

Equalizing circuit: 179, 25
The straight lines indicated by 7, 265 are the left and right traveling motors 235, 1
55 equalizing circuits. This equalizing circuit
This is a circuit for equalizing the flow rate to the left and right traveling motors 235 and 155. This is because, even with the same flow rate command value, the actual flow rate may be different between the left and right due to individual differences between motors and the length of the pipeline. It should be noted that a difference in flow rate is required during turning. For this, the pipe diameter and the throttle 180,
258 is determined by design.

(2) Pump The pump 21 is a two-flowway type swash plate type variable displacement pump. The pump 21 is driven to rotate by an engine (not shown). The amount of oil discharged from the pump is changed by adjusting the angle of the swash plate. The swash plate angle is controlled by a pump swash plate control circuit (known in the art, not shown) that receives the LS pressure and the pump discharge pressure as inputs so as to keep the differential pressure constant. The pump 21 has a plurality of axial pistons in one cylinder block.
-1 and 21-2. The same amount of pressure oil is discharged from both discharge ports.

(3) Merging / Joining Valve FIG. 3 is a diagram showing details of the merging / joining valve. (A) is a separation state, (b) is a merging state. First, each port will be described. The F port is connected to a downstream pipe 31 which is a pump pressure supply path to the right traveling / working machine. The G port is connected to a B discharge passage 23 from the second pump discharge port. The K port is connected to an A discharge path 221 that travels to the left. The L port is an A discharge passage 25 from the first pump discharge port.
It is connected to the. Pressure oil from the pump 21 is supplied to each actuator through these ports and the discharge path.

In the separated state (a), the FG port communicates and the KL port communicates. Thereby, one pump discharge port of the pump 21 (first pump)
All of the pressure oil discharged from 21-1 is sent from the A discharge path 25 to the A discharge path 221 and supplied to the left traveling hydraulic motor. On the other hand, the entire amount of pressure oil discharged from the other pump discharge port (second pump) 21-2 of the pump 21 is sent from the B discharge path 23 to the downstream pipe line 31 of the junction valve 201,
It is supplied to the right running motor 155. As will be described in detail later, when the work machine cylinder is not used,
01 is in this separated state.

In the merged state of (b), four ports F,
G, K and L are all in communication with each other. Therefore, the pressure oil from the first pump discharge port and the pressure oil from the second pump discharge port merge once, and then the left traveling motor 23
5, the right running motor 155 and the working machine cylinder. It is the role of each pressure compensating valve and throttle valve, and the load pressure circuit connecting them, that makes the distribution of pressure oil desirable.

The M port is connected to the circuit 315. The circuit 315 is connected to the maximum pump discharge pressure selection circuit 300 including the check valves 303, 311 and the like.
The maximum pump discharge pressure selection circuit 300 has a circuit 301 branched from the downstream pipe 31, a check valve 303 connected to the circuit 301, and a circuit 305 connected to the check valve 303. The selection circuit 300 includes a circuit 313 branched from the first discharge path 25, a check valve 311 connected to the circuit 313, and a circuit 309 connected to the check valve 311. Circuits 305, 309 and 31
5 is connected. Each check valve 303, 311
Although the pressure oil from the downstream pipe line 31 and the direction of the A discharge path 25 passes, the pressure oil in the opposite direction does not pass. Therefore, the circuits 305, 309, 315 between the check valves 303 and 311
, The higher pressure of the A discharge path 25 and the downstream pipe line 31 is introduced. The circuits 305, 309, 315
Is connected to a discharge path pressure circuit 307 for pump control.
Is connected. The circuit 307 supplies a pump discharge path pressure as a pilot pressure to a circuit (not shown) for controlling a swash plate angle of the pump 21.

The M port is in communication with the H port via the throttle 321 in the separated state shown in FIG. Since the H port is connected to the pump control load pressure circuit 202, a higher pump discharge path pressure is applied to the load pressure circuit 202. On the other hand, in the merging state shown in FIG.
The ports communicate with the F, K, L, and M ports. In the merged state, the pressure in the A discharge passage 221 and the pressure in the downstream pipe 31 are the same. The pressure is output to the discharge path pressure circuit 307 for pump control.

The H port is connected to the pump control load pressure circuit 20.
2 are connected. S port is a right running / working machine (B
CD) is connected to the load pressure circuit 187. In the load pressure circuit 187, the highest pressure among the load pressures of the right traveling motor 155 and each working machine cylinder is extracted. The R port is connected to the left traveling (A) load pressure circuit 203. The N port is connected to the non-pressure drain circuit 131-3.

In the separated state shown in FIG. 3A, the H port is connected to the M port via the throttle 321 as described above, and the higher discharge path pressure is applied to the load pressure circuit 2 for pump control.
02 is introduced. The N port communicates with the S port via the aperture 323. Therefore, the BCD load pressure circuit 1
The pressure oil in 87 communicates with the non-pressure drain circuit 131-3 via a throttle. The R port is closed.

In the merged state shown in FIG. 3B, the H port, the S port, and the R port communicate with each other. Therefore, the BCD load pressure circuit 187 and the left running load pressure circuit 20
3 is connected to these load pressure circuits, and the highest pressure among the load pressures of the two traveling motors and the working machine cylinders is extracted. Then, the pressure is applied to the pump control load pressure circuit 202. That is, in the merged state, the pressure compensating valve of each traveling motor and the throttle valve for the working machine circuit are set to the highest pressure among the load pressures of all the actuators. N port is closed.

The U port, which is the pilot port on the left side of FIG. 3B of the junction valve 201, is connected to the back pressure drain circuit 27-.
13 is connected. Further, a spring 317 is provided so that the spool of the junction valve 201 is set to the junction position side. U
Due to the back pressure of the port circuit 27-13 and the spring 317, when all the actuators in the hydraulic system are not used, the junction valve 201 is at the junction position.

A V port (pressure receiving port), which is a pilot port on the right side of FIG. 3A of the valve 201, is connected to a pilot pressure circuit 263 from the merge / shunt valve switching valve.
The junction valve 201 is at the junction position in the normal state, and is in the separated state when the pilot pressure is applied to the pressure receiving port 263. Note that, although the details will be described later, the junction valve switching valve 261 operates using the pressure of the work machine load pressure circuit 123 as the pilot pressure, and when the work machine cylinder is used, the junction valve 201 is set to the merge position. The rest is at the separation position.

(4) Traveling (A, B) Pressure compensating valve 251,
171 Both pressure compensating valves of the A and B circuits have the same structure and operation, and will be described together. FIG. 4 is a detailed circuit diagram of the traveling pressure compensating valve. FIG. 6 is a detailed circuit diagram of the traveling pressure compensating valve and the traveling motor operating valve. Pressure compensating valve 251 (171)
Are the check valve part 253 (173) and the load pressure part 255
(175) and a rod 254 (174) connecting both parts.

In the check valve section 253 (173), the G port is connected to the discharge path 221 (33) from the pump, and the F port is connected to the discharge path 223 (35) to each traveling motor operation valve. ing. By a mechanism described later, the pump pressure PP of the discharge path 221 (33) from the pump is reduced and output to the discharge path 223 (35) to the operation valve. When the pressure of the outlet circuit 223 (35) of the operation valve is higher than the pressure of the discharge passage 221 (33) from the pump, the check valve portion 253 (173) is closed to prevent the backflow of the pressure oil. It also serves as a load check valve to prevent.
The pump pressure PP of the discharge passage 221 (33) acts on the pilot port H of the check valve 253 (173), and the check valve 253 (173) moves in the communicating direction. The pilot port S of the check valve portion 253 (173) is connected to the downstream discharge passage 223 (3) of the check valve portion 253 (173).
The output pressure PPA of 5) is applied.

The load pressure section 255 (175) is composed of K, L, M
3 ports. The K port is connected to a load pressure circuit 243 (163) for introducing the load pressure of the traveling motor. The L port is connected to the equalizing circuit 257 (179). The M port is a load pressure circuit 211 (177)
It is connected to the. The traveling motor load pressure PLS from the load pressure circuit 243 (163) is applied to the pilot port R of the load pressure unit 255 (175). Load pressure part 2
The load pressure PLSMAX from the load pressure circuit 211 (177) is applied to the pilot port S at 55 (175). At the time of merging, the load pressure circuit 211 (177)
Is the highest load pressure PL of each actuator.
SMAX is applied. Further, the load pressure unit 255 (17
5) Spring 255 for pushing in the blocking direction (toward the left position in the figure)
a is also provided.

The pressure compensating valve 251 (171) operates so that the pressure of each part is balanced as in the following equation. The spring force is ignored. PP-PLSMAX = PPA-PLS Therefore: PPA = PP− (PLSMAX−PLS) That is, the upstream pressure of the operation valve 241 is set to the maximum load pressure PLS.
In order to reduce and balance the pump pressure PP by a pressure obtained by subtracting the load pressure PLS of each actuator from MAX, the flow rate passing through the check valve unit 253 is reduced and output to each operation valve.

Therefore, the pump pressure P at each operating valve
The difference between PA and the output pressure (load pressure) PLS is as follows. PPA-PLS = PP- (PLSMAX-PLS) -PLS = PP-PLSMAX Here, PP and PLSMAX are the same throughout the hydraulic circuit when the merge / shunt valve is in the merged state. Therefore, the differential pressure PPA-PLS at each operation valve is the same for each actuator operation valve. As a result, each actuator
Despite the difference between the load pressures, pressure oil is supplied according to the opening degree (opening area) of each operation valve. Each of the operation valves is manually operated by the operator including the opening degree, but the operation of the pressure compensating valve causes each actuator to respond to the opening degree determined by the operator regardless of the magnitude of the load pressure of the actuator. The amount of oil is sent and the actuator indicates the movement as intended by the operator.

The operation of the load pressure unit 255 (175) will be described. When PLS is greater than PLSMAX, that is, when the load pressure PLS of the actuator is to be the maximum load pressure, the load pressure unit 255 (175) is at the left position in FIG. 4, and the K and M ports communicate with each other. , Load pressure circuit 2
11 (177), the actuator load pressure is extracted. On the other hand, in the case opposite to the above (PLS <PLSMAX),
The load pressure part 255 (175) is at the right position in FIG. Then, the load pressure circuit 243 (163) and the load pressure circuit 211
(177) is cut off. The K port and the L port are always in communication, and the load pressure circuit 243 (163) and the equalizing circuit 257 (179) are always in communication via the throttles 180 and 258.

(5) Pressure for work (CD actuator) machine
The pressure compensating valve 91C and the pressure compensating valve of the D circuit have the same structure and operation, and will be described together. FIG. 1 shows a pressure compensating valve 91 (9
The details around the preload section of 1 ′) are shown. The work machine pressure compensating valve 91 (91 ') is a rod 94 (94') connecting the check valve section 93 (93 '), the pressure reducing valve section 95 (95'), and both sections.
Is provided.

The check valve 93 (93 ')
The (R ') port is connected to the working machine pressure oil supply circuit 46 (46') from the pump 21, and the Q (Q ') port is connected to the circuit 87 (81) to the C (D) operating valve 81 (81'). 87 ')
It is connected to the. The S (S ') and T (T') ports are pilot ports.

The pump pressure PPR of the working machine pressure oil supply circuit 46 (46 ') acts on the S (S') port, and the check valve portion 93 (93 ') moves in the communicating direction. The output pressure PPA of the circuit 87 (87 ') is applied to the T (T') port.

X, Y, Z, W
It has four ports (X ', Y', Z ', W'). X
The (X ') port is connected to the working machine pressure oil supply circuit 46 (46'). The Y (Y ') port is connected to the circuit 87 (8
7 '). The W (W ') port is connected to CD load pressure circuits 97 (97') and 126. Z
The (Z ') port is a pilot port to which the traveling motor load pressure PLS' from the CD load pressure circuits 97 (97 ') and 126 is applied.

The working machine pressure compensating valve 91 (91 ') basically has the same function as the above-mentioned traveling pressure compensating valves 251 and 171. However, they differ in the following points. The discharge passage 46 (46 ') for supplying the pump pressure is once throttled by the working machine circuit throttle valve 111 (this detailed description will be made in conjunction with the description of the throttle valve 111 described later).

The pressure reducing valve section 95 (95 ′) is connected to the C (D) load pressure circuit 89 (8) of the C (D) operating valve 81 (81 ′).
9 ′) is received as pilot pressure and the throttle valve 11
The output pressure (pressure of the working machine pressure oil supply circuit 46 (46 ')) is reduced to reduce the CD load pressure circuits 97 (97') and 12 (1).
6 is output.

At this time, the C (D) operation valve 81 (81 ')
Is neutral, the C (D) load pressure circuit 89 (8
9 ') is set to a pressure lower than that of the CD load pressure circuits 97 (97') and 126, and a back pressure drain circuit 27-
A pressure of 6 is applied. Therefore, the pressure reducing valve section 95 (9
5 ') is closed. This reduces unintended consumption of pressure oil.

(6) Traveling Motor (A, B) Operation Valve 24
The structure and operation of both operation valves 1 and 161 are the same, and will be described simultaneously.
FIG. 5 is an enlarged view showing one position (the right position in FIG. 2) of the traveling motor operation valve.

The E and H ports of the operating valve are connected to the circuits 231 (151), 23 to the traveling motor 235 (155).
3 (153). The F port and the G port are connected to the communication path 351. K port and N port are back pressure drain circuits 27-17 (5), 27
-19 (7). The L port is connected to the discharge path 223 (35) on the pressure compensation valve outlet side. The M port is connected to a load pressure circuit 243 (163) to the pressure compensating valve.

In the position shown in FIG. 5, the L port communicates with the G port via the variable aperture 353. The E port is in communication with the F port, and the F port is in communication with the G port. Therefore, the traveling motor circuit 231 (151)
, Pressure oil from the discharge path 223 (35) is sent. H
The port is connected to one of the traveling motor circuits 233 (153) and communicates with the N port. Therefore, the return oil from the traveling motor circuit 233 (153) is sent to the back pressure drain circuit 27-19 (7). As a result, the traveling motor 235 (155) rotates in the forward or backward direction by switching the operation valve.

The G port communicates with the M port connected to the load pressure circuit 243 (163). Therefore, the pressure of the load pressure circuit 243 is the load pressure of the traveling motor 235 (155). Variable aperture 35 between L port and G port
Numeral 3 changes the opening according to the operation of the operator.

At a position on the left side of the traveling motor operation valve 241 (161), as shown in FIG.
The direction of the pressure oil supplied to 5) and the return pressure oil from the motor are reversed, and the rotation of the motor 235 (155) is reversed.
In the neutral position of the travel motor operation valve 241 (161), the travel motor circuits 231 (151) and 233 (153) are connected to the back pressure drain circuits 27-17 (27-5) and 27-19.
(27-7). On the other hand, the discharge path 223 (35)
Is closed. Further, the load pressure circuit 243 (163) is also closed.

(7) Working Machine (C, D) Operating Valve 81 The working machine operating valve 81 is the same as the travel motor operating valves 241 and 161 except for the following points. The work machine circuits 61 and 63 are closed at the neutral position. In addition, the circuit including the check valves 68 and 69 connected to the work machine circuits 61 and 63 includes the work machine circuits 61 and 63 which function as blow valves when the pressure drops below the back pressure check valve.
This is for replenishing oil from the back pressure drain circuit.

The operation is performed by the pilot pressure from the pilot pressure circuits 83 and 85. The pilot pressure circuits 83 and 85 are connected to a manually operated valve operated by an operator.

(8) Pilot pressure reduction for extracting work machine load pressure
Valve 143 Discharge path (C discharge path) 37 for supplying pressure oil to C and D circuits
Are connected to discharge paths 39 and 43. A pilot pressure reducing valve 143 is connected to the discharge path 43. The output side of the pressure reducing valve 143 is connected to BCD load pressure circuits (right running / work equipment load pressure circuits) 145 and 147. Further, CD load pressure circuits (work equipment load pressure circuits) 125 and 126 are connected to the pressure reducing valve 143 as pilot pressure.

The pressure reducing valve 143 reduces the pressure in the discharge passage 43 to substantially the same pressure as the pilot pressure of the CD load pressure circuit 126, and outputs the pressure to the BCD load pressure circuit 147. That is, a signal pressure equivalent to that of the CD load pressure circuit 126 is output to the BCD load pressure circuit 147. The CD load pressure circuit 126
When the pressure of the BCD load pressure circuit 147 is higher, the valve is closed.

Thus, the CD load pressure circuit 126 and the BCD load pressure circuit 147 can be completely separated.

(9) Work Machine Pressure Oil Supply Path Throttle Valve 111 FIG. 7 is a diagram showing details of the throttle valve 111 provided in the work machine pressure oil path and its periphery. The throttle valve 111 includes a check valve unit 113 and a throttle valve unit 115. The check valve unit 113 has an input-side E port and an output-side F port as main ports for supplying a flow rate to the working machine, and a G port and an H port as pilot ports. The F port is connected to the discharge path 45 of the working machine. The E port is connected to the work machine circuit 46. G port is discharge path 45
Pressure PP (pump discharge pressure). The work port circuit pressure PPR on the output side of the check valve unit 113 is applied to the H port.

The throttle valve section 115 has an S port, a J port and a K port as main ports, and an L port and an M port as pilot ports. The K port is connected to the discharge path 41. The S port is connected to the CD load pressure circuits 121 and 126. The J port is connected to the CD load pressure circuit 123 that outputs pressure to the merge / shunt valve switching pilot valve 261. The working port load pressure of the CD load pressure circuit 121 (the highest load pressure among a plurality of working machine actuators) PLS 'is applied to the L port. The M port is connected to the BCD load pressure circuits 141 and 147, and the maximum load pressure PLSMAX is applied.

The throttle valve 111 operates so as to maintain the pressure balance as shown in the following equation. The spring force is ignored. PP-PLSMAX = PPR-PLS 'Therefore: PPR = PP− (PLSMAX−PLS ′) That is, the upstream pressure of the operation valve 241 is set to the maximum load pressure PLS.
Maximum load pressure PLS 'of work equipment actuator from MAX
In order to reduce and balance the pump pressure PP by the pressure obtained by subtracting the flow rate, the flow rate passing through the check valve section 253 is reduced and output to the working machine pressure oil supply circuit 46.

On the other hand, in the C pressure compensating valve 91, pressure compensation represented by the following equation is performed as described above. PPR is the pressure compensating valve upstream circuit pressure = the throttle valve downstream circuit pressure. PLS is the load pressure of the C actuator. PPA is the pressure on the downstream side of the C pressure compensating valve and is the input pressure to the work implement operating valve. PLS 'is the pressure of the CD load pressure circuit. PPR-PLS '= PPA-PLS When the expression in the preceding paragraph is substituted into PPR, the following is obtained. PP- (PLSMAX-PLS ') + PLS = PPA +
PLS 'From now on: PPA-PLS = PP-PLSMAX

This means that the pressure compensating operation for each work machine is performed by each work machine pressure compensating valve 91 through the throttle valve 111. On the other hand, the pressure compensation operation of the traveling motor is performed only by each of the pressure compensation valves 251 and 171 alone. This is because the load pressure circuit is divided and the load pressure signal on the working machine side is output independently.

The circuit symbol of the check valve unit 113 of the throttle valve 111 will be described. Here, two independent functions are shown at the same time. Flow control for pressure balance is performed at the left end and the right end. Compensates for oil leaks when the work equipment is neutral at the left and middle positions. The check valve portion 113 of the throttle valve 111 is also provided with a check valve portion 93 of the pressure compensating valve 91 as described above.
The work machine circuit 46 is provided with a check function for preventing backflow.

Next, the throttle valve portion 115 of the throttle valve 111 will be described. On the circuit symbol, the left end position is the KJ port communication and the S port closed position. At this position, the pressure oil in the pump discharge path 41 connected to the downstream pipe 31 of the merge / shunt valve 201 flows from the K port to the J port and to the merge / shunt switch circuit 123. The pump discharge path pressure is applied to the pilot port of the merge / shunt valve switching valve 261. Thereby, the junction valve 2
01 switches to a merge (details will be described later).

The position of the throttle valve 111 at the right end in FIG. 7 is K port closed and SJ port communication. In this position, the CD
The pressure oil of the load pressure circuit is applied from the circuit 126 through the S port, the J port, and the circuit 123 to the pilot port of the junction valve switching valve 261. At this time, the load pressure of the working machine is zero. Since the pressure at the pilot port of the junction valve switching valve 261 becomes zero, the junction valve is at the separation position. Here, when the work machine is used, a pressure corresponding to the load is generated in the CD load pressure circuit 126. This pressure is applied to the junction valve switching valve 261 through the circuit 123, and the junction valve 201 is quickly switched to the junction position.

Here, only after the throttle valve 111 is switched to the left end position in FIG.
Assume that a throttle valve is supplied with a logic pilot pressure. The case where the right end in FIG. 7 of the throttle valve 111 is fully closed is shown. When the left and right traveling motors have already been driven at the same flow rate (straight traveling), the operation valve 81 or 81 'is operated to issue an operation instruction to the C or D actuator 65 or 65'. At this time, first, the operation valve 81 or 81 '
Switches to the communication position. Thereafter, a load pressure is applied to the C or D actuator 65 or 65 '. The pressure oil is output from the pressure reducing valve portion 95 or 95 ′ of the pressure compensating valve to the CD load pressure circuit 126 by the load pressure of the actuator.
Pressure oil is supplied to the discharge amount control means of the pump 21 using the output pressure oil as a signal pressure to increase the discharge amount of the pump 21-2. Thereafter, the pump discharge amount increases, and the pressure of the B discharge passage 23 and the pressure of the downstream pipe line 31 of the junction valve 201 which is still shut off increase. Here, since the pump discharge amount control means is a single pump 21-1 and pump 21-2, the same flow rate as that of the downstream pipe 31 is supplied to the pipe 221 as well. The downstream conduit 31 supplies flow to the right travel motor 155 and the C or D actuator 65 or 65 ', and the conduit 21 supplies flow to the left travel motor 235.
Then, since the required flow rates of the left and right traveling motors 235 and 155 are the same, a flow rate difference is inevitably generated to cause traveling bending.

However, in the throttle valve 111 of the present embodiment, the junction valve 201 is brought into a merged state before the discharge flow rate of the pump 21 is increased by the operation of the C or D actuator 65 or 65 '. Nothing. As described above, since switching is not performed unnecessarily early, energy loss can be avoided.

In the actual circuit design, the CD load pressure circuit 126 is always connected to the merging / shunting valve switching circuit 123 so that the pump discharge path 41 is maintained even after the throttle valve 111 is switched.
May not be introduced into the merge / shunt valve switching circuit 123. However, since the load fluctuates, it is better to use the circuit of this example in order to stably maintain the position of the diverging / joining valve 201.

(10) CD Load Pressure Circuit Next, the CD load pressure circuit will be described. As shown in FIG. 2, the CD load pressure circuit includes circuits 97, 122, 125,
126, 127, 97 'and the like. Circuits 97, 97 '
Is connected to the pilot ports of the pressure reducing valves 95, 95 'of the C and D working machine pressure compensating valves 91, 91'. In the same part, the working machine pressure oil supply circuits 46, 4
The pressure at 6 'is reduced and output to the CD load pressure circuit.
Circuits 126, 122, 127 and the like are connected to the circuit 97. The circuit 127 is connected to the non-pressure drain circuit 131-1 via the diaphragm 129 to form a diaphragm discard circuit. The circuit 126 is a circuit for extracting the LS pressure due to the largest load pressure among the load pressures of the respective working machine actuators by connecting the circuits 97 and 97 '. A back pressure drain circuit 27-6 is connected to an end of the CD load pressure circuit 126 on the traveling circuit side via a check valve 128. Check valve 128 passes pressure oil from back pressure drain circuit 27-6 to CD load pressure circuit 126, and vice versa.

From the CD load pressure circuit 122, the circuit 12
5, 121 and the pilot pressure circuit 120 are branched.
The circuit 125 is connected to a pilot port of the pressure reducing valve 143. The circuit 121 and the pilot pressure circuit are connected to the throttle valve 111. These operations are as described above.

(11) BCD Load Pressure Circuit The right running load pressure circuit is a circuit 141, 145, 147, 1
77, 181, 183, 185, etc. The circuit 141 supplies a pilot pressure to the throttle valve section 115 of the throttle valve 111. The circuits 145, 147, and 177 are in communication. In these circuits, the output pressure from the pressure reducing valve 143 or the output pressure from the right traveling pressure compensating valve 171 becomes the higher one. That is, the circuit 147 is a circuit of a pressure corresponding to the highest pressure among the load pressures of the work implement actuator and the right traveling motor.

The circuit 147 is connected to the circuits 181 and 183. The circuit 181 is connected to the non-pressure drain circuit 131-1 via the diaphragm 182 to form a diaphragm discarding circuit. The circuit 183 is connected via the circuit 187 to the junction valve 201.
Connected to When the merging / diverting valve 201 enters the merging state, B
CD load pressure circuits 183 and 147 and A load pressure circuit 203,
207 and 211 communicate. As a result, a pressure corresponding to the highest pressure among the load pressures of the actuators of the left running, the right running, and the working machine is introduced into these circuits.

(12) A Load Pressure Circuit The A load pressure circuit includes circuits 203, 205, 207, and 20.
9, 211, etc. The circuit 209 is connected to the non-pressure drain circuit 131-5 via the restrictor 210 to form a restricting circuit. The circuit 211 is connected to the right traveling pressure compensating valve 251. These A load pressure circuits 211 and the like include
The load pressure of the left running motor 235 is introduced in the separated state, and the signal pressure corresponding to the maximum load pressure of all the actuators is introduced in the merged state as described above. When all the actuators are neutral, the BCD load pressure circuit 14
7. Since the pressure of the A load pressure circuit 211 and the like is connected to the non-pressure drain circuit via the throttling circuit, it becomes almost zero.

(13) Equalizing Circuit The equalizing circuit includes an output circuit 257 of the load pressure unit 255 of the left traveling pressure compensating valve 251 and a right traveling pressure compensating valve 171.
The circuit 179 output from the load pressure unit 175 of the
0 and 258. This equalizing circuit includes the equalizing circuits 179, 257,
As in the case of H.265, the flow rate difference due to the individual difference of the motor and the difference in the pipe length is absorbed and made uniform. When driving the left traveling motor 235, the load pressure of the left traveling motor 235 acts on the circuit 257 on the left traveling side. When the right traveling motor 155 is operated, the load pressure of the right traveling motor 155 acts on the circuit 179 on the right traveling side.

The pressure of the equalizing circuit passes through the circuit 265, the diverging valve switching valve 261, and the circuit 263, and passes through the diverting valve 20.
1 pilot port. When pressure is applied to the port, the merge / shunt valve 201 switches to separation. By using the equalizing circuit pressure as the separation pilot pressure of the merge / shunt valve switching valve 261 in this manner, the circuit can be configured most simply. It should be noted that the merging / dividing valve 201 is merging in the normal state.

(14) Combining / junction valve switching valve The switching valve 261 is a valve for switching between the output of equalization in the pilot pressure circuit 263 to the combining / junction valve 201 and the tank pressure. That is, when the valve 261 is at the upper position in FIG. 2, the pressure oil in the circuit 263 is drained to the back pressure drain circuit 27-11. On the other hand, when the valve 261 is at the lower position in the figure, the circuit 26
3, the output pressure of the equalizing circuit 265 is introduced. The logic pilot pressure for switching the position of the switching valve 261 is introduced from a circuit 123 from the throttle valve 111. Circuit 1
23 is when the throttle valve 111 is at the left end position in the figure, that is, when the C or D actuator is operating,
It communicates with the discharge path 41 from the pump 21. On the other hand, when the throttle valve 111 is at the right end position in FIG.
It communicates with the CD load pressure circuits 121, 126. The effect of this is as described above in the description of the throttle valve.

(15) Operation of the whole circuit at the time of separation
If only 35 and 155 are used,
1 is a separation state. Then, the pressure oil is separately sent from the respective pumps of the pump 21 to the left running and the right running. At this time, the pump pressure is output from the shunt valve 201 to the pump swash plate control signal pressure circuit 202. A swash plate angle control device (not shown) acts to keep the differential pressure between the discharge pressure and the signal pressure constant. Therefore, the swash plate is at the most inclined position, and the pump discharge amount is maximized.

(16) Operation of the whole circuit at the time of merging When the C or D actuator 65 or 65 ′ is used, the logic pilot pressure is applied to the merging / diverging switching valve 261 through the above-mentioned circuit 123, The pilot line 263 communicates with the tank. Therefore, the merging valve 201 is at the merging position on the left side of the drawing, which is the normal position. In this case, the pressure oil discharged from the two discharge ports 21-1 and 21-2 of the pump 21 is merged by the merge / separate valve 201, and the left and right traveling motors 235 and 155 and the C and the D actuators 65 and 65 'have the required flow rate. Will be distributed accordingly.

Further, A load pressure circuits 203 and 211 and B
The CD load pressure circuits 187 and 147 also join. The pressure in these lines is the highest of the A load pressure circuit and the BCD load pressure circuit. Then, the pressure compensating valve of each actuator and the throttle valve of the working machine circuit perform the above-described pressure compensating action, and each actuator is supplied with pressure oil according to the opening degree of each operating valve regardless of the level of the load pressure. You.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing details around a precompression section of a pressure compensating valve for a working machine according to one embodiment of the present invention.

FIG. 2 is a circuit diagram of a hydraulic device of the hydraulic shovel according to one embodiment of the present invention.

FIG. 3 is a circuit diagram showing details of a merge / shunt valve. (A) is a separation state, (b) is a merging state.

FIG. 4 is a circuit diagram showing details of a traveling pressure compensating valve.

FIG. 5 is a circuit diagram showing details of a position on the right side in FIG. 2 of the travel motor operation valve.

FIG. 6 shows details of a circuit around a traveling pressure compensating valve and a traveling operation valve.

FIG. 7 is a circuit diagram showing details of a working machine circuit throttle valve and its surroundings.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 21 Pump 23 B discharge path 25 A discharge path 27 Back pressure drain circuit 29 Back pressure check valve 31 Downstream line 37 C discharge path 65, 65 'Work machine cylinder (C, D actuator) 68, 69 Check valve 81, 81 ′ Work machine (C, D) operation valve 83, 85 Pilot pressure circuit 89, 89 ′ Work machine (C, D) load pressure circuit 91, 91 ′ Work machine (C, D) pressure compensation valve 93, 93 ′ Check valve Part 94, 94 'Rod 95, 95' Pressure reducing valve part 111 Work machine circuit throttle valve 113 Check valve part 115 Throttle valve part 116 Check valve 120 Pilot pressure circuit 97, 97 ', 121, 122, 125, 126, 12
7 CD load pressure circuit 123 Merging / shunt valve switching circuit 128 Check valve 129 Restrictor 131 Non-pressure drain circuit 141, 145, 147, 177, 181, 183, 1
85,187 BCD load pressure circuit 143 Pilot pressure reducing valve 155 Right traveling hydraulic motor (B actuator) 161 Right traveling (B) operating valve 163 Right traveling load pressure circuit 171 Right traveling (B) pressure compensating valve 173 Pressure reducing valve section 175 Load pressure Part 179, 257, 265 Equalizing circuit 180, 182, 210, 258 Restrictor 201 Merging / shunting valve 202 Pump control signal pressure circuit 203, 205, 207, 209, 211 A load pressure circuit 218, 219 Unload valve 221 A discharge path 231 233 Left traveling circuit 235 Left traveling hydraulic motor (A actuator) 241 Left traveling (A) operating valve 243 Left traveling load pressure circuit 251 Left traveling (A) pressure compensating valve 253 Check valve section 255 Load pressure section 261 Combined flow switching Pilot valve 263 Pilot pressure circuit

Claims (1)

[Claims] 1. C pressure compensating valve 9 connected to a pump 21
1, a C circuit including a C operating valve 81 connected downstream of the C pressure compensating valve 91, and a C actuator 65 connected downstream of the C operating valve 81; D pressure compensating valve 91 '
D operation valve 81 'connected downstream of pressure compensating valve 91'
And a D circuit having a D actuator 65 'connected downstream of the D operation valve 81'. The C and D pressure compensating valves 91 and 91 'are respectively C and D
A check valve unit for supplying the discharge pressure oil of the pump 21 to the operation valves 81 and 81 ';
A pressure reducing valve for reducing the pressure of the oil discharged from the pump 21 in accordance with the load pressure of the pump 65 'and outputting the reduced pressure oil. A CD load pressure circuit for introducing pressure; the pressure reducing valve section has a discharge pressure oil detection port of the pump 21 and a load pressure detection port of an actuator connected to each pressure compensating valve; The output pressure of the pressure reducing valve section is increased by the pressure of the load pressure detection port, and the output pressure is reduced by the pressure of the CD load pressure circuit and the pressure on the upstream side of the operation valve. When the C and D operation valves 81 and 81 ′ are in neutral, the CD
The load pressure circuit becomes the pressure of the return side hydraulic oil of the C and D actuators 65 and 65 'defined by the back pressure check valve 29, and is connected to the load pressure detection port of the pressure reducing valve section by the back pressure check valve 29. A hydraulic device characterized by applying a specified pressure.