JP3034195B2 - Hydraulic circuit of work machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for a working machine such as a mini shovel having a spare actuator selectively disposed when necessary in addition to a permanent actuator such as a left and right running motor.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing an example of a hydraulic circuit of a conventional working machine of this type, and FIG. 4 is a side view showing a working machine, that is, a mini shovel provided with the hydraulic circuit shown in FIG. The conventional hydraulic circuit shown in FIG.
A first hydraulic pump 2 driven by the engine 1;
And the second hydraulic pump 3, and these hydraulic pumps 2, 3
Actuators driven by pressure oil discharged from the cylinder, for example, a cylinder 4 for the earth discharging plate, a turning motor 5, a left running motor 6, an arm cylinder 7, a spare actuator 8, a bucket cylinder 9, a swing cylinder 10, a boom cylinder 11. , A right running motor 12.

[0003] The above-mentioned earthing plate cylinder 4 controls the raising and lowering operation of the earthing plate 32 shown in FIG. 4, and the left running motor 6 and the right running motor 12 control the running of a pair of crawler belts, that is, the running body 30. The swing motor 5 controls the swing of a main body having a driver's seat disposed on the traveling body 30, that is, the swing body 31, the boom cylinder 11 controls the vertical rotation of the boom 33, and the arm cylinder 7 controls the arm cylinder 7. The bucket cylinder 9 controls the pivoting operation of the bucket 35 in the vertical direction. The boom cylinder 11, the arm cylinder 7, and the bucket cylinder 9 constitute a front actuator, and the swing cylinder 10 includes the boom 33, the arm 3
4. Control the horizontal swing operation of the front including the bucket 35.

[0004] Of the actuators described above, the cylinder 4 for the earthing plate, the turning motor 5, the left running motor 6, the arm cylinder 7, the bucket cylinder 9, and the swing cylinder 1
0, the boom cylinder 11, and the right running motor 12 are permanent actuators. The spare actuator 8 is an actuator different from the permanently installed actuator, and is selectively disposed when necessary, and is, for example, a motor provided in a mower.

As shown in FIG. 3, a discharge pipe of the first hydraulic pump 2 controls a drive of a directional control valve for controlling the driving of the cylinder 4 and a drive of a swing motor 5. A direction switching valve, a left traveling direction switching valve 13 for controlling the driving of the left traveling motor 6, a direction switching valve for controlling the driving of the arm cylinder 7, and a preliminary direction switching valve 15 for controlling the driving of the preliminary actuator 8 are provided. It is connected.

A right traveling direction switching valve 1 for controlling driving of a right traveling motor 12 is provided in a discharge line of the second hydraulic pump 3.
4, a directional control valve for controlling the driving of the boom cylinder 11,
A direction switching valve for controlling the driving of the swing cylinder 10 and a direction switching valve for controlling the driving of the bucket cylinder 9 are connected, and a direction switching valve for controlling the driving of the above-described arm cylinder 7 via the merging line 20. And a spare directional control valve 15 for controlling the drive of the spare actuator 8. That is, the pressure oil of the first hydraulic pump 2 and the pressure oil of the second hydraulic pump 3 can be supplied to the arm cylinder 7 and the spare actuator 8 via the merging line 20. .

A communication line 16 is provided for connecting an input port of the left-direction switching valve 13 and an input port of the right-direction switching valve 14. A communication / shutoff switching valve 17 for holding the path 16 in a communication state or a cutoff state is provided. The drive unit of the communication / shutoff switching valve 17 detects a switching operation from a neutral position such as a directional switching valve for the boom cylinder 11 and the arm cylinder 10, and switches the communication / shutoff switching valve to a state in which the communication line 16 is communicated. Signal line 19 for guiding the signal pressure for switching 17
Is connected. The signal pressure in the signal line 19 is provided by the pilot hydraulic pressure source 18.

[0008] Among the operations performed in this conventional hydraulic circuit, for example, in the case of traveling alone, the left traveling direction switching valve 13 and the right traveling direction switching valve 14 are respectively switched, and the first hydraulic pump 2 is switched. Pressure oil is left direction switching valve 1
3, the hydraulic fluid of the second hydraulic pump 3 is supplied to the right traveling motor 12 via the right traveling direction switching valve 14, and the left traveling motor 6 and the right traveling motor 12 When driven, the traveling body 30 shown in FIG. 4 is driven to perform a desired traveling independent operation.

For example, in the case of a combined arm and bucket operation, by switching the corresponding directional control valve,
The pressure oil of the second hydraulic pump 3 is supplied to the bucket cylinder 9, the pressure oil of the first hydraulic pump 2 is supplied to the arm cylinder 7, and the arm 34 and the bucket 35 shown in FIG. Arm and bucket combined operation
Excavation work of earth and sand can be performed.

Further, for example, in the case of a combined traveling and arm operation, the direction switching valve 13 for the left traveling and the direction switching valve 14 for the right traveling are switched, and the direction switching valve related to the arm cylinder 7 is switched. A signal pressure is generated in the signal line 19 in accordance with the switching operation of the direction switching valve related to the arm cylinder 7, and this signal pressure is supplied to the drive unit of the communication / cutoff switching valve 17. As a result, the communication pipe 16 is in a communicating state, and the upstream sides of the left and right traveling direction switching valves 13 and 14 are connected via the communication pipe 16. For this reason, the pressure oil of the first and second hydraulic pumps 2 and 3 is supplied to the left and right traveling direction switching valves 13 and 14 and the direction switching valve related to the arm cylinder 7 via the communication line 16, Further, it is supplied to the left and right traveling motors 6 and 12 and the arm cylinder 7. Thus, combined driving of the straight traveling operation and the arm cylinder 7 can be performed.

Then, when the operation of the spare actuator 8 is required, that is, at the time of mowing, the bucket 35 shown in FIG. 4 is removed, and a mowing machine is attached to the tip of the arm 34 instead. When only the spare directional control valve 15 shown in FIG. 3 is switched in the state where the mower is mounted in this way, the hydraulic oil of the first hydraulic pump 2 is supplied to the spare directional switch valve 15 and merged. Pipe line 2
0, the hydraulic oil of the second hydraulic pump 3 is supplied to the auxiliary directional switching valve 15, and the auxiliary actuator 8 is driven by the merging of the hydraulic oils of the first and second hydraulic pumps 2, 3. Then, the mowing machine operates to perform a desired mowing operation.

[0012]

However, in the prior art shown in FIG. 3, a spare directional control valve 15 is provided in tandem downstream of the left traveling directional switching valve 13 and the right traveling directional switching valve 14, respectively. Because of the connection, when the left and right traveling direction switching valves 13 and 14 are simultaneously switched to the full stroke and the vehicle travels straight, the pressure oil does not flow through the spare direction switching valve 15. Therefore, the mowing machine cannot be operated while traveling straight, and it is difficult to expect improvement in efficiency of mowing work.

In the above prior art, a motor of a mower is given as an example of the spare actuator 8, but the spare actuator 8 is not limited to such a motor.
For example, a hydraulic cylinder or the like of a crusher may be used. In any case, in the above-described conventional technology, there is a problem that it is difficult to perform combined driving of the left and right traveling motors and the spare actuator 8, and it is difficult to improve efficiency of a specific operation performed in accordance with the operation of the spare actuator 8. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances in the prior art, and has as its object to provide a hydraulic circuit of a working machine capable of realizing combined driving of a left-right traveling motor and a spare actuator. It is in.

[0015]

In order to achieve the above object, the invention according to claim 1 of the present invention comprises a hydraulic pump, a left traveling motor driven by hydraulic oil discharged from the hydraulic pump, and a right traveling motor. A drive motor and an actuator that is driven by pressure oil discharged from the hydraulic pump and is different from a permanently installed actuator, and controls the drive of the left travel motor and a spare actuator that is selectively disposed when necessary. A left traveling direction switching valve, a right traveling direction switching valve for controlling the driving of the right traveling motor, and a left traveling direction switching valve, and at least one downstream of the right traveling direction switching valve, The spare directional control valve for controlling the drive of the spare actuator is connected to the input port of the left traveling directional switching valve and the input port of the right traveling directional switching valve. In the hydraulic circuit of a working machine, the communication circuit includes a communication pipe provided in the communication pipe and a communication / shut-off switching valve for holding the communication pipe in one of a communication state and a cutoff state. A connecting pipe line for connecting the switching valve to at least one of the left traveling direction switching valve and the right traveling direction switching valve is provided, and the communication / cutoff switching valve is provided so as to interlock with the spare direction switching valve. A throttle means provided in the connection pipe; and a connection pipe portion provided between the throttle means and an input port of the spare direction switching valve. A check valve is provided to allow the flow of oil toward the input port of the switching valve and to block the flow of oil in the opposite direction.

According to the first aspect of the invention, when the left traveling direction switching valve, the right traveling direction switching valve, and the preliminary direction switching valve are simultaneously operated in the combined driving of the left and right traveling motors and the preliminary actuator, The communication / shutoff switching valve is switched in conjunction with the direction switching valve so as to maintain the communication conduit in the communicating state. Therefore, the input port of the left traveling direction switching valve and the input port of the right traveling direction switching valve communicate with each other through the communication conduit. Thus, the pressure oil of the hydraulic pump is supplied to the left traveling motor and the right traveling motor via the left traveling direction switching valve, the right traveling direction switching valve, and the communication pipeline. Further, a part of the pressure oil of the hydraulic pump is supplied to a connection pipe for connecting the spare direction switching valve and the corresponding traveling direction switching valve in parallel, and the throttle means and the check valve of the connection pipe are used for the connection. It is supplied to the spare direction switching valve and further supplied to the spare actuator. That is, the pressure oil of the hydraulic pump is supplied to the left traveling motor, the right traveling motor, and the spare actuator. As a result, combined driving of the straight traveling operation and the standby actuator can be performed.

In addition, when the load pressure of the spare actuator is lower than the load pressure of the left and right traveling motors in such combined driving, too much pressure oil flows to the spare actuator side by the throttle means provided in the connection conduit. And the desired flow rate to the left and right traveling motors is compensated.

In addition, the backflow of the pressure oil from the auxiliary actuator side to the left and right traveling motors during the combined driving is prevented by the check valve provided in the connection pipe, and these left and right traveling motors have unexpected abnormalities. Operation does not occur.

According to a second aspect of the present invention, in the above-mentioned first aspect, the hydraulic pump is a first hydraulic pump.
, The left traveling direction switching valve is connected to the discharge line of the first hydraulic pump, and the right traveling direction is connected to the discharge line of the second hydraulic pump. A switching valve is connected, and a downstream side of the left traveling direction switching valve and a downstream side of the right traveling direction switching valve are communicated with each other, so that the hydraulic oil merges with the first hydraulic pump and the second hydraulic pump. A state in which a connection pipe is provided to enable the connection, the spare directional switching valve is provided downstream of the combined pipe, a switching operation from a neutral position of the spare directional switching valve is detected, and the communication pipe is communicated. The signal pressure for switching the communication / cutoff switching valve is
A signal line leading to the drive unit of the communication / cutoff switching valve is provided, and the connection line is connected to the communication line.

According to the second aspect of the invention, in particular, when the vehicle is traveling alone, the pressure oil of the first hydraulic pump is supplied to the left traveling motor via the left traveling direction switching valve, and the pressure of the second hydraulic pump is increased. The oil is supplied to the right traveling motor via the right traveling direction switching valve, and the desired traveling alone drive can be performed.

Further, when the spare actuator is driven alone, the hydraulic oil of the first and second hydraulic pumps joined via the joining pipe is supplied to the spare actuator. That is, the spare actuator can be driven by the combined flow rate of the first and second hydraulic pumps.

Further, when the left traveling direction switching valve, the right traveling direction switching valve, and the preliminary direction switching valve are simultaneously operated in the combined driving of the left and right traveling motors and the preliminary actuator, the signal pressure guided through the signal line is increased. As a result, the communication / shutoff switching valve is switched, and the communication line is brought into the communication state. Therefore,
The pressurized oil of the first and second hydraulic pumps is supplied to the left-right traveling direction switching valve, is guided from the connecting pipe to the connecting pipe, and is supplied to the spare direction switching valve. Thus, in the same manner as described in the first aspect of the present invention, the hydraulic oil of the first and second hydraulic pumps is supplied to the left and right traveling motors and the spare actuator, and the traveling straight ahead operation and the spare Combined driving with an actuator can be performed.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the throttle means provided in the connection conduit is constituted by a throttle valve.

According to the third aspect of the present invention, since a relatively simple throttle valve which is generally available is provided, it is easy to manufacture the hydraulic circuit.

According to a fourth aspect of the present invention, in the third aspect, the throttle valve is constituted by a variable throttle valve.

According to the fourth aspect of the present invention, by adjusting the opening degree of the variable throttle valve, the flow rate in a well-balanced state considering the magnitude of the load pressure of the spare actuator and the magnitude of the load pressure of the left and right traveling motors. A spare actuator,
It can be supplied to each of the left and right traveling motors.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic circuit for a working machine according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a first embodiment of a hydraulic circuit of a working machine according to the present invention.

FIG. 1 is drawn corresponding to the hydraulic circuit shown in FIG. That is, the first
Is also provided, for example, in a mini-excavator, and includes an engine 1, a hydraulic pump driven by the engine 1, for example, a first hydraulic pump 2, a second hydraulic pump 3, and a hydraulic pump 2 , 3, a plurality of actuators driven by the pressure oil discharged from the cylinders, for example, a cylinder 4 for the earthing plate, a turning motor 5, a left running motor 6, an arm cylinder 7, a spare actuator 8, a bucket cylinder 9, a swing cylinder 10, a boom Cylinder 1
1, a right running motor 12.

Of the actuators described above, the cylinder 4 for the earthing plate, the turning motor 5, the left running motor 6, the arm cylinder 7, the bucket cylinder 9, the swing cylinder 1
0, the boom cylinder 11, and the right running motor 12 are permanent actuators as described above. The spare actuator 8 is an actuator different from the permanently installed actuator, and is selectively disposed when necessary, and is, for example, a motor provided in a mower.

In the discharge line of the first hydraulic pump 2, there are provided a directional control valve for controlling the driving of the above-described earthing plate cylinder 4, a directional switching valve for controlling the driving of the swing motor 5, and a left running motor. 6 directional control valve 1 for driving the left
3. A direction switching valve for controlling the driving of the arm cylinder 7 and a spare direction switching valve 15 for controlling the driving of the spare actuator 8 are connected.

A right traveling direction switching valve 1 for controlling driving of a right traveling motor 12 is provided in a discharge line of the second hydraulic pump 3.
4, a directional control valve for controlling the driving of the boom cylinder 11,
A direction switching valve for controlling the driving of the swing cylinder 10 and a direction switching valve for controlling the driving of the bucket cylinder 9 are connected, and a direction switching valve for controlling the driving of the above-described arm cylinder 7 via the merging line 20. And a spare directional control valve 15 for controlling the drive of the spare actuator 8. That is, the pressure oil of the first hydraulic pump 2 and the pressure oil of the second hydraulic pump 3 can be supplied to the arm cylinder 7 and the spare actuator 8 via the merging line 20. .

Further, there is provided a communication line 16 for connecting an input port of the left-direction switching valve 13 and an input port of the right-direction switching valve 14, and the communication line 16 is provided in the middle of the communication line 16. A communication / shutoff switching valve 17 for holding the path 16 in a communication state or a cutoff state is provided. The drive unit of the communication / cutoff switching valve 17 includes a directional switching valve related to the boom cylinder 11 and the arm cylinder 10 and a spare directional switching valve 15.
Switching operation from the neutral position, etc.
A signal line 19 for guiding the signal pressure for switching the communication / shutoff switching valve 17 to a state in which the
Is connected. The signal pressure in the signal line 19 is provided by the pilot hydraulic pressure source 18. The above configuration is the same as that shown in FIG.

In the first embodiment, in particular, a pipe line for connecting the spare direction switching valve 15 and at least one of the left traveling direction switching valve 13 and the right traveling direction switching valve 14 in parallel, for example, A connection pipe line 22 for connecting the input port of the spare directional control valve 15 to the communication pipe line 16 is provided. Further, a throttle means, for example, a throttle valve 23 is provided in the connection pipe line 22. Further, a connection line 22 located between the throttle valve 23 and the input port of the spare direction switching valve 15 is provided.
The portion is provided with a check valve 24 that allows the flow of oil from the communication line 16 toward the input port of the spare direction switching valve 15 and blocks the flow of oil in the opposite direction.

Among the operations performed in the first embodiment configured as described above, the traveling alone operation, the combined arm / bucket operation, the combined traveling / arm operation, the independent operation of the mower by the operation of the spare actuator 8, and the like are described. Are the same as those in the hydraulic circuit shown in FIG.

Then, the combined operation of the traveling and mowing machine, that is, the left and right traveling motors 6, 12 and the spare actuator 8
The following operation is performed in the case of the combined driving.

That is, when the left traveling direction switching valve 13, the right traveling direction switching valve 14, and the spare direction switching valve 15 are simultaneously switched, the communication / cutoff switching valve 17 is activated by the signal pressure guided through the signal line 19. Is switched to the communication line 16
Becomes a communication state. Accordingly, the input port of the left traveling direction switching valve 13 and the input port of the right traveling direction switching valve 14 communicate with each other through the communication conduit 16. Thereby, the first,
The pressure oil of the second hydraulic pumps 2 and 3 is supplied to the left traveling direction switching valve 1
3. While being supplied to the right traveling direction switching valve 14, a part thereof is supplied to the communication pipe 16. This connecting line 16
Is supplied to the connecting line 22 and is supplied to the spare direction switching valve 15 via the throttle valve 23 and the check valve 24 of the connecting line 22, and further, the spare actuator, that is, the motor of the mower. Supplied to That is, the first
The pressure oil of the second hydraulic pumps 2 and 3 is supplied to the left traveling direction switching valve 1.
3. Direction switching valve 14 for right traveling and direction switching valve 15 for standby
, Whereby a combined operation of the straight traveling operation and the driving of the mower can be performed.

In such combined driving, there is a concern that the load pressure of the spare actuator 8 will be lower than the load pressure of the left and right traveling motors 6 and 12. The throttle valve 23 provided prevents excessive flow of pressure oil to the spare actuator 8 side, secures a desired flow rate to the left and right traveling motors 6 and 12, and performs a combined operation of the straight traveling operation and the driving of the mower. be able to.

Also, during such combined driving, the backflow of pressure oil from the auxiliary actuator 8 side to the left and right traveling motors 6 and 12 is prevented by the check valve 24 provided in the connection line 16. Unexpected abnormal operation of the left and right traveling motors 6, 12 during combined driving does not occur.

In the first embodiment configured as described above,
As described above, the hydraulic oil of the first and second hydraulic pumps 2 and 3 is supplied to both the left and right traveling motors 6 and 12 and the spare actuator 8, and the left and right traveling motors 6 and 12 and the spare actuator 8 are supplied. In the mowing operation by the mowing machine, the mowing operation can be performed while the mower is running, and the mowing operation can be performed efficiently.

Also, since the hydraulic pump only has two hydraulic pumps, ie, first and second hydraulic pumps 2 and 3,
The engine horsepower can be suppressed to the same extent as that shown in FIG.

Further, it is only necessary to add the connecting line 16, the throttle valve 23 and the check valve 24 to the hydraulic circuit shown in FIG. 3 described above, and the circuit can be easily manufactured.

In the first embodiment, a relatively simple throttle valve 23, which is generally available, is provided as a throttle means provided in the connection line 22, so that the circuit can be easily manufactured in this respect as well.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. In the second embodiment, a variable throttle valve 25 is provided as a throttle valve provided in the connection pipeline 22. Other configurations are the same as those of the first embodiment shown in FIG.

In the second embodiment configured as described above,
By adjusting the opening degree of the variable throttle valve 25, the flow rate in a well-balanced state in consideration of the magnitude of the load pressure of the spare actuator 8 and the magnitude of the load pressure of the left and right traveling motors 6 and 12 can be adjusted. Left and right running motor 6,
12 can be supplied to each of them, and a more accurate combined operation of the straight traveling operation and the driving of the mower can be performed. In addition, a working machine whose load pressure is higher than the load pressure when the mower is driven, for example, a case where a crusher is mounted in place of a bucket and the spare actuator 8 is a hydraulic cylinder built in the crusher, etc. In this case, the opening degree of the variable throttle valve 25 is adjusted to be slightly open compared to the case where a mowing machine is provided, and the preliminary directional control valve 1
It is sufficient that the oil can easily flow in five directions, and thus, even when a crusher or the like having a relatively high load pressure is provided, the combined driving of the left and right traveling motors 6, 12 and the spare actuator 8 can be performed. Therefore, the efficiency of the specific operation can be improved.

In each of the above embodiments, the connecting pipe 22
Is connected to the communication line 16, but instead of connecting the connection line 22 to the communication line 16 in this manner, a spare port is connected to at least one of the input ports of the left and right traveling direction switching valves 13 and 14. The connection pipe line 22 connected to the input port of the directional control valve 15 is connected to the directional control valves 13 and 14 for traveling left and right.
May be connected in parallel with the spare direction switching valve 15. For example, the connection pipeline 22 shown in FIG. 1 may be connected to the input port of the right traveling direction switching valve 14 without being connected to the communication pipeline 16.

Even with this configuration, the first and second hydraulic pumps 2 and 2 are connected to the left and right traveling direction switching valves 13 and 14 through the communication pipe 16 during combined driving of the straight traveling operation and the driving of the mower. 3 is supplied, the left and right traveling motors 6 and 12 can be driven to drive straight ahead, and a part of the pressure oil of the first and second hydraulic pumps 2 and 3 is connected to the connection pipeline 22. Is supplied to the spare direction switching valve 15 via the auxiliary actuator 8 so that the spare actuator 8 can be driven at the same time.

In each of the above embodiments, the merging pipe 20
Is supplied to the standby actuator 8 through the first and second hydraulic pumps 2 and 3 via the circulating fluid. However, such a junction line 20 is not provided, and for example, a standby direction switching valve 15 may be connected only to the first hydraulic pump 2 side, and when the auxiliary actuator 8 is driven alone, the auxiliary actuator 8 may be driven only by the pressure oil from the first hydraulic pump 2.

Further, in each of the above embodiments, the connection pipe 22
Is provided with a throttle valve 23 or a variable throttle valve 25 as the throttle means provided in the throttle valve 2.
Instead of providing the 3 or the variable throttle valve 25, for example, a configuration may be adopted in which the pipe diameter of a part of the connection pipe line 22 is set smaller than the pipe diameter of the other part.

[0049]

According to the first to fourth aspects of the present invention, combined driving of the left and right traveling motors and the spare actuator can be realized, and the specific operation performed via the driving of the spare actuator can be realized. In addition, the specific work can be performed while traveling straight, and the corresponding specific work can be performed more efficiently than in the past. In particular, according to the second aspect of the present invention, since only two hydraulic pumps are provided, the engine horsepower can be suppressed to the same level as the conventional hydraulic circuit of the two pumps. On the other hand, it is only necessary to add a connection pipe, a throttle means, and a check valve, and the circuit can be easily manufactured.

According to the third aspect of the present invention,
Since a relatively simple throttle valve, which is generally available, is provided as the throttle means provided in the connection conduit, the circuit can be easily manufactured.

In particular, according to the fourth aspect of the invention,
By adjusting the opening degree of the variable throttle, a well-balanced flow rate considering the magnitude of the load pressure of the spare actuator and the magnitude of the load pressure of the left and right traveling motors is supplied to each of the spare actuator and the left and right traveling motors. Thus, the combined operation of the straight traveling operation and the driving of the working machine related to the standby actuator can be performed with higher accuracy.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a hydraulic circuit of a working machine according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram illustrating an example of a hydraulic circuit of a conventional working machine.

4 is a side view showing a work machine provided with the hydraulic circuit shown in FIG.

[Explanation of symbols]

 2 First hydraulic pump 3 Second hydraulic pump 6 Left traveling motor 8 Preliminary actuator 12 Right traveling motor 13 Left traveling direction switching valve 14 Right traveling direction switching valve 15 Preparatory direction switching valve 16 Communication line 17 Communication Shut-off switching valve 19 Signal line 20 Merging line 21 Load check valve 22 Connection line 23 Throttle valve 24 Check valve 25 Variable throttle valve 30 Traveling body

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-5531 (JP, A) JP-A-2-164939 (JP, A) JP-A-5-287775 (JP, A) 106602 (JP, U) Japanese Utility Model 4-22555 (JP, U) Japanese Utility Model 57-124603 (JP, U) Japanese Utility Model 56-158503 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) E02F 9/22 F15B 11/02 F15B 11/17

Claims (4)

(57) [Claims] 1. A hydraulic pump, a left traveling motor and a right traveling motor driven by hydraulic oil discharged from the hydraulic pump, and different from a permanent actuator driven by hydraulic oil discharged from the hydraulic pump. An actuator, a spare actuator selectively disposed when necessary, a left traveling direction switching valve for controlling driving of the left traveling motor, and a right traveling direction switching valve for controlling driving of the right traveling motor. A standby direction switching valve disposed downstream of at least one of the left traveling direction switching valve and the right traveling direction switching valve to control driving of the preliminary actuator; and A communication pipe for connecting the input port of the right traveling direction switching valve to the input port of the right traveling direction valve, and a communication state and a cutoff of the communication pipe provided in the communication pipe. In a hydraulic circuit of a work machine having a communication / shutoff switching valve for holding in either of the states, the spare directional switching valve and at least one of the left traveling directional switching valve and the right traveling directional switching valve are provided. A connecting pipe for parallel connection is provided, and the communication / shutoff switching valve is provided so as to interlock with the spare direction switching valve. A throttle means provided in the connection pipe, and the throttle means and the spare direction switching are provided. It is provided in the connection line portion located between the valve and the input port, and allows the flow of oil from the throttle means toward the input port of the spare directional control valve, and allows the oil to flow in the opposite direction. A hydraulic circuit for a working machine, comprising: a check valve for preventing flow. 2. The hydraulic pump according to claim 1, wherein the hydraulic pump includes a first hydraulic pump and a second hydraulic pump, and the left traveling direction switching valve is connected to a discharge line of the first hydraulic pump. The right traveling direction switching valve is connected to a discharge pipe of a hydraulic pump, and the downstream of the left traveling direction switching valve and the downstream of the right traveling direction switching valve are communicated with each other to connect the first hydraulic pump to the first hydraulic pump. A merging pipe for allowing the pressure oil to merge with the second hydraulic pump; a spare directional switching valve provided downstream of the merging pipe; and a switching operation from a neutral position of the spare directional switching valve And a signal line for guiding a signal pressure for switching the communication / shutoff switching valve to a state in which the communication line is communicated to a drive unit of the communication / shutoff switching valve is provided. The work according to claim 1, wherein the work is connected to a pipe. Hydraulic circuit of 械. 3. The hydraulic circuit for a working machine according to claim 1, wherein said throttle means is a throttle valve. 4. The hydraulic circuit according to claim 3, wherein the throttle valve is a variable throttle valve.