JPH0248764B2 - EKIATSUKAIRO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention improves the combined operability of each actuator and the fine operability of the boom and arm, and also increases the speed of the actuator except for turning, and minimizes the pump discharge flow rate under no load. The present invention relates to a hydraulic circuit that can control the pump discharge flow rate according to the amount of movement of an operating lever, and can easily utilize a reserve valve by using a logic valve.

Conventionally, in hydraulic circuits, when connecting multiple actuators to a hydraulic pump, there are two methods: parallel connection and tandem (series) connection.The parallel connection method allows for combined operation of actuators, but it requires a light load. Pressure oil tends to flow toward the actuator on the low pressure side, making stable operation impossible. Furthermore, when using the tandem (series) connection method, when the actuator on the upstream side is actuated, the actuator on the downstream side cannot be actuated, so that combined operation is insufficient. Furthermore, although some conventional hydraulic pressure circuits have a speed increasing function, only a very limited number of hydraulic circuits can speed up, and there is no speed increasing circuit like the present invention. Furthermore,
The operating speed of the arm and boom changes depending on the work content, and conventional hydraulic circuits are insufficiently responsive to this, making it particularly difficult to perform delicate operations. Furthermore, there is no system that can control the discharge flow rate of a hydraulic pump under no load to the minimum level using a simple and inexpensive mechanism, or control the pump discharge flow rate by moving an operating lever.

The present invention has been made to correct the above-mentioned problems, and is designed so that the first pressure fluid supply pipe 2 communicating with the first pump 1 can supply pressure fluid to a predetermined actuator in a non-neutral state. A plurality of center bypass type switching valves 3, 8, and 11 are sequentially connected in tandem from the upstream side to the downstream side, and a required switching valve 8 is connected among the switching valves 8, 11 other than the switching valve 3 on the most upstream side. , 11 are connected in parallel, a logic valve 14 is connected to the downstream end of the first pressure fluid supply pipe 2, and the plurality of switching valves 3, connected to the first pressure fluid supply pipe 2,
Pilot switching valves 5, 10, 13 are installed at 8 and 11, respectively.
and a second pump 20 connected to the second pump 20.
A plurality of center-bypass type switching valves 22, 25, 2 are provided in the pressure fluid supply pipe 21 of the system, which is capable of supplying pressure fluid to a predetermined actuator in a non-neutral state.
8 are sequentially connected in tandem from the upstream side to the downstream side, and the switching valves 2 other than the switching valve 22 on the most upstream side
Of the switching valves 5 and 28, required switching valves 25 and 28 are connected in parallel, and pilot switching valves 24, 27 and 29 are connected to the plurality of switching valves 22, 25 and 28 connected to the second pressure liquid supply pipe 21, respectively. The third
A third pressure liquid supply pipe 41 communicating with the pump 40 of
A plurality of center bypass type switching valves 42 and 45, which are capable of supplying pressure fluid to a predetermined actuator in a non-neutral state, are sequentially connected in tandem from the upstream side to the downstream side, and the third pilot switching valves 44 and 46 are interlocked with the plurality of switching valves 42 and 45 connected to the pressure fluid supply pipe 41, respectively;
The first pressure liquid supply pipe 2 and the second pressure liquid supply pipe 21
are connected by a connecting pipe 30 on the upstream side of the most upstream switching valve 3, 22 connected to the dual pressure liquid supply pipes 2, 21, and the downstream end of the third pressure liquid supply pipe 41 is connected to the first A pilot switching valve 5 connected downstream of the switching valve 3 on the most upstream side of the pressure fluid supply pipe 2 and interlocked with the switching valve 3 on the most upstream side of the first pressure fluid supply pipe 2.
A switching operation means for switching the pilot switching valve 5 is connected to the switching operation means, and a shutoff valve 7 whose spool end is brought into contact with a guide portion provided in the switching operation means so as to be able to switch freely is disposed. The pilot pipe 17 connected to the signal port b1 of the valve 14 is connected to the switching valve 18 for speed increase, and the pilot pipe 19 branched from the pilot pipe 17 is connected to the shutoff valve 7 to supply the first pressure fluid. The upstream side of the logic valve 14 of the pipe 2 and the middle part of the connecting pipe 30 are communicated by a pressure liquid supply pipe 33, and the first pilot pipe 49 and the second pilot pipe 50 are connected to the pilot pump 48 in parallel, First pilot tube 46
, the switching valves 11, 8, of the first pressure liquid supply pipe 2,
Pilot switching valves 13, 10, 5 linked to 3
The end of the first pilot pipe 49 is connected to a regulator 51 that adjusts the swash plate tilt angle θ of the first pump 1, and the switching valves 3, 8, Among the pilot switching valves 5, 10, and 13 linked to the pilot pipe 11, the third pilot pipe 49' is branched from the first pilot pipe 49 on the downstream side of the pilot switching valve 5 which is the most downstream of the pilot pipe 49. and the pilot tube 4
9′ is the switching valve 45, 4 of the third pressure liquid supply pipe 41.
The end of the third pilot pipe 49' is connected to a regulator 53 that adjusts the swash plate tilting angle θ of the third pump 40, and pilot tube 5
0 is the switching valve 28, 2 of the second pressure liquid supply pipe 21.
Pilot switching valve 29, 2 linked to 5, 22
7, 24, and the second pilot pipe 50
It is characterized in that the end of the pump is connected to a regulator 52 that adjusts the tilt angle θ of the swash plate of the second pump 20.

Therefore, the switching valves 3, 8, 11, 22, 25, 2
8, 42, and 45 to the neutral state, and the switching valve 1
When the pumps 1, 20, 40 and the pilot pump 48 are driven with the valves 8 in communication, the pressure fluid from the pump 1 is transferred to the switching valves 3, 8, 11 and the logic valve 1.
The pressure liquid from the pump 20 flows to the tank via the switching valves 22, 25, 28, and the pressure liquid from the pump 40 flows to the tank via the switching valves 42, 45.
The pressure liquid from the pilot pump 48 flows from the pilot pipe 49 to the regulator 51 of the pump 1 via the pilot switching valves 13, 10, 5, and from the pilot pipes 49, 4 to the upstream side of the switching valve 8.
9' to pilot switching valves 13, 10, 5, 46,
44 to the regulator 53 of the pump 40,
Furthermore, the pilot switching valve 2 is connected from the pilot pipe 50.
9, 27, 24, respectively, on the regulator 52 of the pump 20, so that each pump 1, 2
The swash plate tilt angle θ of 0 and 40 is the minimum, and each pump 1, 20, and 40 is operated with the minimum load.

Any of switching valves 3, 8, and 11, switching valve 2
Any of 2, 25, 28, switching valve 42, 4
When any one of the switching valves 5, 10, and 5 is switched to a non-neutral state, the pilot switching valves 5, 10,
13, pilot switching valve 24, 2
Either of 7 or 29, pilot switching valve 4
Either one of pumps 4 and 46 is shut off, and the hydraulic pressure acting on the regulators 51, 52, 53 decreases, causing the swash plate tilt angle θ to increase, and the pressure from each pump 1, 20, 40 to decrease. Discharge amount increases.

If any of the switching valves 3, 8, and 11 is switched to a non-neutral state while the switching valve 18 is maintained in the communicating state, the pressure fluid from the pump 1 is transferred from the switching valve 3, 8, or 11 in the non-neutral state. It is supplied to a predetermined actuator. When the switching valve 3 is placed in a neutral state and the switching valves 8 and 11 are switched to a non-neutral state, pressure fluid is supplied from both switching valves 8 and 11 to a predetermined actuator.

When any one of the switching valves 22, 25, and 28 is switched to a non-neutral state, the pressure fluid from the pump 20 is transferred to the switching valve 22, 25, or 28 in the non-neutral state.
is supplied to a predetermined actuator. When the switching valve 22 is placed in the neutral state and the switching valves 25 and 28 are switched to the non-neutral state, pressure fluid is supplied from both the switching valves 25 and 28 to a predetermined actuator.

When either of the switching valves 42, 45 is switched to a non-neutral state, the pressure fluid from the pump 40 is supplied to a predetermined actuator from the switching valve 42 or 45 in the non-neutral state. The systems of each pump 1, 20, and 40 can be operated independently, regardless of the systems of other pumps, and combined operation is possible.

When the switching valves 42 and 45 are in the neutral state, the pressure fluid from the pump 40 is supplied from the pressure fluid supply pipe 41 to the pressure fluid supply pipe 2, so the switching valve 3 is switched to a non-neutral state. The switching valves 8 and 11 can also be operated, and combined operation of the actuator operated by the pressure fluid from the switching valve 3 and the actuator operated by the pressure fluid from the switching valve 8 or 11 is possible.

When both the switching valves 3 and 22 are switched to a non-neutral state, the switching of the switching valve 3 switches the shutoff valve 7, and the pilot pipe 19 is shut off. Therefore,
When the switching valve 18 is switched and shut off, the logic valve 14
is closed, and the pressure fluid from the pressure fluid supply pipe 2 no longer flows through the logic valve 14. For this reason, the switching valve 4
2 and 45 are in the neutral state, the pressure fluid from the pump 40 enters the connection pipe 30 through the pressure fluid supply pipes 41, 2, and 33, and half of the pressure fluid flows into the pressure fluid from the pump 1 or the pump. The pressure liquid from 20 joins with the pressure liquid supply pipes 2 and 21, respectively. For this reason, the switching valve 3,
The flow rate of the pressurized liquid sent from 22 to each predetermined actuator increases, and the predetermined actuator is driven at high speed.

When the switching valves 3, 42, and 45 are in the neutral state, if the switching valve 8 or 11 is switched to the non-neutral state,
In addition to the pressure fluid from the pump 1, the pressure fluid from the pump 40 is supplied to an actuator operated by the pressure fluid from the switching valve 8 or 11, and the actuator is operated at an increased speed.

Each switching valve 3, 8, 11, 22, 25, 28, 4
2, 45, each pilot switching valve 5, 10, 13, 24, 27, 29, 4
4 and 46 are also switched by an amount corresponding to the switching amount of each switching valve, and the swash plate tilting angle θ of each pump 1, 20, and 40 is an angle corresponding to the pilot pressure, and the discharge from pumps 1, 20, and 40 is The amount of pressurized liquid that is applied corresponds to the swash plate tilt angle θ. For this reason, pump discharge amount control is performed, and each actuator is controlled steplessly from the maximum speed to the minimum speed.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example in which the hydraulic circuit of the present invention is applied to a hydraulic shovel.

A right travel switching valve 3 which can be switched in conjunction with a pilot switching valve 5 by an operating lever 4 is connected to the pressure oil supply pipe 2 connected to the first pump 1. A switching bracket 6, which is a switching operation means, is attached, and the spool end of the shutoff valve 7 is brought into contact with the concave guide portion of the switching bracket 6 so as to be able to switch freely. Further, downstream of the right travel switching valve 3 of the pressure oil supply pipe 2, there is a bucket switching valve 8 which can be switched in conjunction with the pilot switching valve 10 by the operating lever 9, and a pilot switching valve 13 by the operating lever 12. The first boom switching valves 11 which can be switched in conjunction with the first boom switching valve 11 are sequentially connected in tandem, and the bucket switching valve 8 and the first boom switching valve 11 are connected in parallel. The right travel switching valve 3 is connected in tandem to a bucket switching valve 8 and a first boom switching valve 11.

A first logic valve 14 is provided downstream of the first boom switching valve 11 of the pressure oil supply pipe 2, and the outlet _a1 of the logic valve 14 is connected to the tank 16 via a return pipe 15.
The signal port b ₁ is connected to the travel speed increase selector valve 18 via the pilot pipe 17 so that the oil that has passed through the travel speed increase selector valve 18 can be returned to the tank 16. The pipe 19 is branched so that oil from the pilot pipe 19 passing through the shutoff valve 7 can be returned to the tank 16.

A left travel switching valve 22 which can be switched in conjunction with a pilot switching valve 24 by an operating lever 23 is connected to the pressure oil supply pipe 21 connected to the second pump 20, and the pressure oil supply pipe 21 is switched for left travel. Downstream of the valve 22, there is a first arm switching valve 25 which can be switched in conjunction with a pilot switching valve 27 by an operating lever 26, and a first arm switching valve 25 which can be switched in conjunction with a pilot switching valve 29 by an operating lever 12. The two boom switching valves 28 are sequentially connected in tandem, and the first arm switching valve 25 and the second boom switching valve 28 are connected in parallel. The left travel switching valve 22 is connected in tandem to a first arm switching valve 25 and a second boom switching valve 28.

A portion of the pressure oil supply pipe 2 upstream of the right-hand travel switching valve 3 and a portion of the pressure oil supply pipe 21 upstream of the left-hand travel changeover valve 22 are connected by a connecting pipe 30 equipped with check valves 31 and 32. Then, the pressure oil supply pipe 33 branched from the part of the pressure oil supply pipe 2 between the first boom switching valve 11 and the first logic valve 15 is connected to the check valves 31 and 32 of the connecting pipe 30. Connect to the part between.

Second boom switching valve 28 of the pressure oil supply pipe 21
A second logic valve 34 is provided downstream of the logic valve 34, and the outlet _a2 of the logic valve 34 is connected to the tank 16 via the return pipe 35. The pressure oil supply pipe 36 branched from the part between the logic valve 34 and the second logic valve 34 is connected to a spare switching valve 37 that can be operated in conjunction with the shutoff valve 38, and the signal port b of the second logic valve 34 is connected. ₂ is connected to the shutoff valve 38 via the pilot pipe 39, so that pressure oil can be supplied from the switching valve 37 to an actuator (not shown), and when the actuator is not in operation, the oil can be returned to the tank 16, and the shutoff valve 38 is connected to the shutoff valve 38. Oil passing through valve 38 can also be returned to tank 16. Further, the operating lever 12 for operating the first boom switching valve 11, the second boom switching valve 28, etc. is designed so that the second boom switching valve 28 side is switched after the first boom switching valve 11 side is switched. There is.
To explain this in detail with reference to FIG. 2, one end of the reach rod 68 is pivotally connected with a pin to the lower end of the operating lever 12 which is swingably supported on the bracket 67.
A shaft 70 is rotatably mounted on a bearing 69 arranged at a required position.
A link 7 is fixed to one end of a shaft 70.
1 to the reach rod 68 by a pin. Also, links 72 and 73 are fixed at required positions in the longitudinal direction of the shaft 70, and the pilot switching valve 1 is attached to the lower end of the link 72.
The rod 74 connected to the spool of the pilot switching valve 29 is provided with a long hole 76, and the link 73 is pin-mounted to the long hole 76. After the rod 75 moves, the rod 75 should move.

To the pressure oil supply pipe 41 connected to the third pump 40,
The swing switching valve 42 which can be switched in conjunction with the pilot switching valve 44 by the operating lever 43 and the second arm switching valve 45 which can be switched in conjunction with the pilot switching valve 46 by the operating lever 26 are rotated. A check valve 47 is provided downstream of the second arm switching valve 45 of the pressure oil supply pipe 41, and the downstream end of the pressure oil supply pipe 41 is Oil supply pipe 2
It is connected to the part between the right travel switching valve 3 and the bucket seat switching valve 8. Further, the operating lever 26 for operating the first arm switching valve 25, the second arm switching valve 45, etc. is such that the second arm switching valve 45 side is switched after the first arm switching valve 25 side is switched. ing. To explain this in detail with reference to FIG. 3, one end of a reach rod 78 is pivotally connected with a pin to the lower end of the operating lever 26 which is swingably supported on a bracket 77, and is rotatably mounted on a bearing 79 disposed at a predetermined position. A shaft 80 is pivotally supported, and a link 81 fixed to one end of the shaft 80 is pivotally connected to the reach rod 78 with a pin. Further, links 82 and 83 are fixed at required positions in the longitudinal direction of the shaft 80, and a rod 84 connected to the spool of the pilot switching valve 27 is pivotally connected to the lower end of the link 82 by a pin. A long hole 86 is provided in the rod 85, and the link 83 is pivotally connected to the long hole 86,
After the rod 84 moves, the rod 85 should move.

Pilot pump 48 and pilot pipes 49,5
0 are connected in parallel, and the pilot pressure is supplied from the pilot pipe 49 to the pilot switching valves 13, 10, 5, 4.
6, 44 through the first pump 1 and the third pump 4
0 to the regulators 51, 53, the swash plate tilting angle θ of the first pump 1 and the third pump 40 is minimized, and the pilot switching valves 13, 10, 5, 4 are
By switching and shutting off either one of the pumps 6 and 44, the swash plate tilting angle θ of the first pump 1 and the third pump 40 can be maximized by the regulators 51 and 53. Pilot switching valves 29, 27, 2
4 to the regulator 52 of the second pump 20 to minimize the swash plate tilting angle θ of the second pump 20, and by switching and shutting off any one of the pilot switching valves 29, 27, and 24, the second pump The configuration is such that the tilt angle θ of the swash plate 20 can be maximized.

In the figure, 54 is a right travel motor that can be driven by pressure oil sent from the right travel switching valve 3 through the rotary joint 56, and 55 is a right travel motor that is driven from the right travel switching valve 22 to the rotary joint 5.
6 is a left travel motor that can be driven by pressure oil sent from the bucket switching valve 8; 57 is a bucket cylinder that can be moved forward and backward by pressure oil sent from the bucket switching valve 8; A boom cylinder 59 can be moved forward and backward by pressure oil sent from the switching valve 11 for the first boom and the switching valve 28 for the second boom. An arm cylinder that can be moved forward and backward by the supplied pressure oil; 60 is a flow control valve provided in each circuit that sends oil to the bucket cylinder 57, boom cylinder 58, and arm cylinder 59; 61 is a return pipe; 15 is a cooler, 62 is the same thermovalve, 63 is a suction pipe to each pump, 64 and 65 are relief valves for circuit protection, and 66 is a swing motor.

Next, the effects of the present invention will be explained in different cases.

() for compound operations.

When the operation is performed with each operating lever in the neutral state as shown in the figure, pressure is applied below the first logic valve 14 by pressure oil from the first pump 1 and the third pump 40, and pressure from the second pump 20 is applied. Oil applies pressure below the second logic valve 34,
On the other hand, the return pipe 15 and the pilot pipe 17 are connected to the tank 1.
6, the first logic valve 14
Since the return pipe ₃₅ communicates with the tank 16, the outlet _a2 of the second logic valve 34 is open. Therefore, the pressure oil discharged from the first pump 1 flows through the pressure oil supply pipe 2 to the tank 16 from the outlet _a1 of the first logic valve 14, and the pressure oil discharged from the second pump 20 is supplied to the tank 16. The pressure oil flows into the tank 6 from the outlet a ₂ of the second logic valve 34 via the pipe 21, and the pressure oil discharged from the third pump 40 flows into the pressure oil supply pipe 2 from the pressure oil supply pipe 41, and is then It flows together with the pressure oil through the pressure oil supply pipe 2 and the outlet a ₁ of the first logic valve 14 to the tank 16 .

Also, pilot pressure is transferred from the pilot pump 48 to the pilot pipe 49 and the pilot switching valve 1.
3, 10, 5, 46, 44 to the regulators 51, 5 of the first pump 1 and the third pump 40.
3, and is also connected to the regulator 52 of the second pump 20 through the pilot pipe 50 and the pilot switching valves 29, 27, and 24. For this reason, the tilting angle θ of the swash plate of each pump is controlled to be the minimum, so the load on the pump is minimized, and energy saving can be achieved.

If the hydraulic shovel is to be moved forward or backward at low speed, the operating lever 4 is used to switch the right travel switching valve 3, and the operating lever 23 is also used to switch the left travel switching valve 22. At this time, the pilot switching valve 5 is switched by switching the right running switching valve 3, and the left running switching valve 22 is switched.
Since the pilot switching valve 24 is switched by switching, the pilot pressure from the pilot pump 48 is controlled by the regulators 51, 53, 53 of the first pump 1, third pump 40, and second pump 20.
52, and therefore the tilting angle θ of the swash plate
becomes the maximum, and the discharge amount from each pump also becomes the maximum.

By switching between the right travel switching valve 3 and the left travel switching valve 22, the pressure oil sent from the first pump 1 is blocked by the right travel switching valve 3 and enters the right travel circuit, and is then transferred to the second pump 20. The pressure oil sent from the hydraulic excavator is blocked by the left travel switching valve 22 and enters the left travel circuit, and the left and right travel motors 55 and 54 are driven to move the hydraulic shovel forward. When the right travel selector valve 3 is switched, the pilot selector valve 5 and the shutoff valve 7 are also switched and shut off, but unless the travel speed increase selector valve 18 is operated, the first logic valve 14 remains open and the exit is closed. _a1 and tank 16 are in communication.

When turning during forward and backward travel at low speed, the turning switching valve 42 is switched by the operating lever 43, pressure oil from the third pump 40 is sent to the turning circuit, and the turning motor 66 is driven. Since the system of the third pump 40 is a tandem connection circuit, the turning can be driven independently from the traveling circuit, and problems of conventional circuits such as traveling and meandering are eliminated.

In the case of combined operation of running and turning, the first and third
On the pump side, the pilot pressure from the pilot pump 48 is cut off at the pilot switching valve 5, but in the case of single swing operation, the pilot pressure is cut off at the pilot switching valve 44.

Swing switching valve 42 and second arm switching valve 4
5 is not switched, the third pump 40
The pressure oil from the pressure oil supply pipe 41 to the pressure oil supply pipe 2
Therefore, even if the right travel switching valve 3 is switched, the bucket switching valve 8 and the first boom switching valve 11 can be operated. Combined operations are possible independently for the running circuit.

When the left travel switching valve 22 is switched, the pressure oil from the second pump 20 is blocked by the left travel switching valve 22, but arm operation is performed by switching the second arm switching valve 45 using the operating lever 26. Pressure oil is supplied from the third pump 40, and the arm can be operated independently of the travel circuit. In addition, when the swing drive is performed without switching the traveling switching valves 3 and 22, the pressure oil from the third pump 40 is used only for swinging by switching the swing switching valve 42, and therefore does not flow downstream. but,
Since the other actuators can be operated with pressure oil from the first pump 1 and the second pump 20,
Problems caused by conventional circuits when performing multiple operations are resolved.

As described above, in the hydraulic circuit of the present invention, various complex operations can be performed independently.

() In case of speed increase operation Speed increase operation is possible when the swing switching valve 42 cannot be switched.

When increasing the speed of the arm, firstly switch the first arm switching valve 25 and then switch the second arm switching valve 45 using the operating lever 26, so that in addition to the pressure oil from the second pump 20, the third arm Since the pressure oil from the pump 40 is sent to the arm operation circuit, the arm cylinder 59 is operated at increased speed. In the case of this arm speed increasing operation, it is possible to run to the right or perform a combined operation with a bucket or boom independently.

When increasing the speed of the bucket, by switching the bucket switching valve 8 using the operating lever 9, pressure oil from the first pump 1 is supplied to the bucket operation circuit, and pressure oil from the third pump 40 is also supplied. The bucket cylinder 57 is operated at an increased speed in order to send this to the bucket operation circuit. In the case of this bucket speed increasing operation, left-hand travel or combined operation with the arm can be performed independently.

When increasing the speed of the boom, by switching the first boom switching valve 11 and then switching the second boom switching valve 28 using the operating lever 12, in addition to the pressure oil from the first pump 1, Since the pressure oil from the second pump 20 is sent to the boom operation circuit, the boom cylinder 58 is operated at increased speed. In the case of this boom speed increasing operation, a combined operation with turning can be performed independently.

When performing a speed increase operation for longitudinal travel, both the right travel switching valve 3 and the left travel switching valve 22 are switched. By switching the right travel switching valve 3, the cutoff valve 7 is switched, and the pilot pipe 19 is cut off from the tank 16. Therefore, traveling speed increase switching valve 1
8 to shut off the pilot pipe 17 and tank 16, the first logic valve 14 is closed and the communication between the pressure oil supply pipe 2 and the tank 16 is closed.
The pressure oil from the third pump 40 is supplied to the pressure oil supply pipe 41,
2 and 33, and enters the connecting pipe 30 via the check valves 31 and 32, and 1/2 of each is connected to the pressure oil from the first pump 20 or the pressure oil from the second pump 20 and the pressure oil supply pipe 2. , 21, respectively, and enter the left and right travel circuits to drive the travel motors 55,
54 is driven. This causes the hydraulic shovel to travel at increased speed.

() For fine operation of the arm and boom.

Fine operation of the arm can be performed by appropriately switching the switching valves 25 and 45 using the operation lever 26, and fine operation of the boom can be performed using the operation lever 1.
This can be done by appropriately switching the switching valves 11 and 28 using the switch 2.

() When controlling the pump discharge amount to the minimum when no load is applied.

This is omitted since it is explained in detail in the explanation for the case where the operating lever in parentheses is in the neutral position.

() When controlling the pump discharge amount according to the amount of movement of the operating lever.

Each operating lever 4, 9, 12, 23, 26, 4
If any one of the valves 3 is moved by an appropriate amount without completely switching, each switching valve and each pilot switching valve are switched according to the amount of movement. Therefore, the tilt angle θ of the swash plate of the first to third pumps 1, 20, 40 also becomes an angle corresponding to the pilot pressure, and the amount of pressure oil discharged from the first to third pumps 1, 20, 40 becomes an angle corresponding to the pilot pressure. The amount corresponds to the plate tilt angle θ. Therefore, the pump discharge amount can be controlled in accordance with the amount of movement of the operating lever, and the speed of each actuator can be controlled steplessly from the maximum speed to the minimum speed.

() When operating the spare switching valve 37.

By switching the switching valve 37, the shutoff valve 38 is also switched, and the pilot pipe 39 and the tank 16 are shut off, so the second logic valve 3
4 is closed, thereby blocking the communication between the pressure oil supply pipe 21 and the tank 16, and the pressure oil from the second pump 20 is sent from the pressure oil supply pipes 21 and 36 to the other actuator via the switching valve 37.

In the embodiments of the present invention, the case where the hydraulic circuit is used in a hydraulic excavator has been explained, but it can be used not only in a hydraulic excavator but also in various other things, and within the scope of the gist of the present invention. It goes without saying that various changes may be made within this document.

Since the hydraulic circuit of the present invention has the above-mentioned configuration, it improves the combined operation of each actuator, and facilitates speed increase operation, fine operation, and pump discharge amount control, and the circuit configuration using logic valves makes it extremely It can be simplified, and furthermore, the pump discharge amount can be minimized during no-load operation, contributing to energy saving, and various other excellent effects can be achieved.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram of a hydraulic excavator showing an example of the hydraulic circuit of the present invention, and FIGS.
FIG. 3 is an explanatory diagram of a portion of an operating lever for simultaneously switching a plurality of pilot switching valves used in the hydraulic circuit shown in the figure. In the figure, 1 is the first pump, 2, 21, 33, 36,
41 is a pressure oil supply pipe, 3 is a right-hand travel switching valve, 5, 1
0, 13, 24, 27, 29, 44, 46 are pilot switching valves, 7, 38 are shutoff valves, 8 is a bucket switching valve, 11 is a first boom switching valve, 14, 3
4 is a logic valve, 17, 19, 39, 49, 4
9', 50 are pilot pipes, 18 is a traveling speed increasing switching valve, 20 is a second pump, 22 is a left traveling switching valve,
25 is a switching valve for the first arm, 28 is a switching valve for the second boom, 30 is a connecting pipe, 40 is a third pump, 42
45 is the switching valve for the swing, 45 is the switching valve for the second arm, and 4 is the switching valve for the second arm.
8 is a pilot pump, and 51, 52, 53 are regulators.

Claims (1)

[Claims] 1 A plurality of center bypass type switching valves 3, 8, which are capable of supplying pressure liquid to a predetermined actuator in a non-neutral state, are connected to a first pressure liquid supply pipe 2 communicating with the first pump 1. 11 are sequentially connected in tandem from the upstream side to the downstream side, and the required switching valves 8, 11 other than the switching valve 3 on the most upstream side are connected in parallel, and the first pressure liquid supply pipe 2, the plurality of switching valves 3 connected to the first pressure liquid supply pipe 2,
Pilot switching valves 5, 10, 13 are installed at 8 and 11, respectively.
and a second pump 20 connected to the second pump 20.
A plurality of center-bypass type switching valves 22, 25, 2 are provided in the pressure fluid supply pipe 21 of the system, which is capable of supplying pressure fluid to a predetermined actuator in a non-neutral state.
8 are sequentially connected in tandem from the upstream side to the downstream side, and the switching valves 2 other than the switching valve 22 on the most upstream side
Of the switching valves 5 and 28, required switching valves 25 and 28 are connected in parallel, and pilot switching valves 24, 27 and 29 are connected to the plurality of switching valves 22, 25 and 28 connected to the second pressure liquid supply pipe 21, respectively. The third
A third pressure liquid supply pipe 41 communicating with the pump 40 of
A plurality of center bypass type switching valves 42 and 45, which are capable of supplying pressure fluid to a predetermined actuator in a non-neutral state, are sequentially connected in tandem from the upstream side to the downstream side, and the third pilot switching valves 44 and 46 are interlocked with the plurality of switching valves 42 and 45 connected to the pressure fluid supply pipe 41, respectively;
The first pressure liquid supply pipe 2 and the second pressure liquid supply pipe 21
are connected by a connecting pipe 30 on the upstream side of the most upstream switching valve 3, 22 connected to the dual pressure liquid supply pipes 2, 21, and the downstream end of the third pressure liquid supply pipe 41 is connected to the first A pilot switching valve 5 connected downstream of the switching valve 3 on the most upstream side of the pressure fluid supply pipe 2 and interlocked with the switching valve 3 on the most upstream side of the first pressure fluid supply pipe 2.
A switching operation means for switching the pilot switching valve 5 is connected to the switching operation means, and a shutoff valve 7 whose spool end is brought into contact with a guide portion provided in the switching operation means so as to be able to switch freely is disposed. The pilot pipe 17 connected to the signal port b1 of the valve 14 is connected to the switching valve 18 for speed increase, and the pilot pipe 19 branched from the pilot pipe 17 is connected to the shutoff valve 7 to supply the first pressure fluid. The upstream side of the logic valve 14 of the pipe 2 and the middle part of the connecting pipe 30 are communicated by a pressure liquid supply pipe 33, and the first pilot pipe 49 and the second pilot pipe 50 are connected to the pilot pump 48 in parallel, First pilot tube 49
, the switching valves 11, 8, of the first pressure liquid supply pipe 2,
Pilot switching valves 13, 10, 5 linked to 3
The end of the first pilot pipe 49 is connected to a regulator 51 that adjusts the swash plate tilt angle θ of the first pump 1, and the switching valves 3, 8, Among the pilot switching valves 5, 10, and 13 linked to the pilot pipe 11, the third pilot pipe 49' is branched from the first pilot pipe 49 on the downstream side of the pilot switching valve 5 which is the most downstream of the pilot pipe 49. and the pilot tube 4
9′ is the switching valve 45, 4 of the third pressure liquid supply pipe 41.
The end of the third pilot pipe 49' is connected to a regulator 53 that adjusts the swash plate tilting angle θ of the third pump 40, and pilot tube 5
0 is the switching valve 28, 2 of the second pressure liquid supply pipe 21.
Pilot switching valve 29, 2 linked to 5, 22
7, 24, and the second pilot pipe 50
A hydraulic circuit characterized in that an end of the hydraulic circuit is connected to a regulator 52 that adjusts a swash plate tilt angle θ of the second pump 20.