JPH08260524A - Hydraulic circuit for hydraulic shovel - Google Patents

Abstract

PURPOSE: To improve operability by receiving the operation signal when hydraulic pilot valves for revolving and for working machine are simultaneously operated, and closing the check valve of a pipeline for connecting the hydraulic pilot valve to a working machine dlrectional control valve. CONSTITUTION: When a rotating operation lever 28 is operated, the pilot pressure from a hydraulic pilot valve 28A switches a directional control valve 15 to a position (b). When an arm operating lever 26 is operated, the pilot pressure from a hydraulic pilot valve 26A switches a directional control valve 17 to the position (b). A control device 41 judges the simultaneous operation of revolving and an arm from the signals consisting of each pilot pressure, and switches a directional control valve 34 to a position (a). The pilot pressure from a pilot pump 36 switches a directional control valve 36 to the position (a), and the pilot pressure from a pilot pump 40 closes a check valve 11a. Further, the pressure oil from a hydraulic pump 2 is preferentially carried to a motor 20 to rotate it right, and the pressure oil is also carried to an arm cylinder 22 to extend it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turning priority circuit used for construction machines such as hydraulic excavators.

[0002]

2. Description of the Related Art First, a hydraulic excavator will be described with reference to FIG. The lower traveling body 51 of the hydraulic excavator 50 can travel freely by driving a traveling motor (not shown). An upper revolving structure 52 that can be revolved by driving a revolving motor (not shown) is provided above the lower traveling structure 51. The working machine 60 is mounted on the upper swing body 52, and the boom 53 of the working machine 60 is attached to a bracket on the upper swing body 52 (not shown). The boom 53 is vertically swingable by driving a boom cylinder 54. An arm 55 is attached to the tip of the boom 53,
The arm 55 is vertically swingable by driving an arm cylinder 56. A bucket 57 is attached to the tip of the arm 55, and the bucket cylinder 5
8 and one end of the tilt lever 59a and the link 59
One end of b is connected together, the other end of this tilt lever 59a is connected to the arm 55, and the other end of the link 59b is connected to the bucket 57. The working machine 60 includes a boom 53, an arm 55, a bucket 57, a plurality of hydraulic cylinders 54, 5.
6, 58, a tilt lever 59a, and a link 59b, and is used for excavating earth and sand.

Next, a hydraulic circuit of a conventional hydraulic excavator will be described with reference to FIG. The operation pilot circuit of each operation valve 70, 80 is omitted. The variable displacement hydraulic pumps 47, 48, 49 (hereinafter referred to as hydraulic pumps) are driven by the engine 1. The hydraulic pump 47 is connected to the four-way operation valve 70. The hydraulic pump 48 is connected to the four-way operation valve 80. The right traveling valve 60 is the right traveling motor 8
It is connected to 1. The left travel valve 68 is connected to the left travel motor 82. The first boom valve 61 and the second boom valve 65 are connected to the boom cylinder 54. First bucket valve 6
The second and second bucket valves 67 are connected to the bucket cylinder 58. The first arm valve 63 and the second arm valve 66 are connected to the arm cylinder 56. The hydraulic pump 49 is independently connected to the swing motor 83 via the swing valve 64.

As shown in FIG. 4, the hydraulic excavator 50 is affected by a boom (arm) drive when the swing motor 83 and the boom cylinder 54 or the swing motor 83 and the arm cylinder 56 are simultaneously rotated and other cylinders are operated simultaneously. Instead, the swing motor is independently driven to improve simultaneous operability.

[0005]

However, in the hydraulic circuit as shown in FIG. 4, there is a problem that the cost is increased because pressure oil is supplied to the swing motor 83 from the independent swing pump 49. On the other hand, in order to reduce the cost, it is considered to use a hydraulic pump for driving a swing motor and a hydraulic pump for driving a working machine (boom, arm, bucket) cylinder. However, if there is a large difference in load pressure when the swing motor and the working machine cylinder are simultaneously operated, there is a problem in that simultaneous operability is poor because oil flows toward the lower load pressure.

For example, when loading the excavated earth and sand by the hydraulic excavator into the dump sill, simultaneous operation of turning and boom raising is performed. At this time, if the turning speed is slow, the boom rises quickly, so the operator slows the boom raising speed. There is a problem that the lever operation is performed as described above and the operation becomes complicated.

The present invention has been made by paying attention to the above-mentioned conventional problems. When the turning and boom of the hydraulic excavator are simultaneously operated, the turning is preferentially driven, and the simultaneous operability of the turning and the boom is also provided. An object of the present invention is to provide a hydraulic circuit for a hydraulic excavator that is also improved.

[0008]

In order to achieve the above object, a hydraulic circuit of a first hydraulic excavator according to the present invention comprises a hydraulic pump 2 driven by an engine 1 and pilot pumps 29, 36, 39 ,. 44, the turning actuator 20 and the working machine actuators 21, 22, 23
Directional control valve 15 for receiving turning pressure oil from the hydraulic pump 2 in parallel and directional control valves 16, 17 for working machine,
18. A hydraulic circuit of a hydraulic excavator comprising a hydraulic pilot valve 28A for turning and a hydraulic pilot valve 25A, 26A, 27A for working machine for switching the directional control valves 15, 16, 17, 18 and 18, A first conduit 3 that connects the pump 2 and the work machine direction switching valves 16, 17, 18
Pilot type check valve 5 provided on c, 5, 8 and 11
a, 8a, 11a, 45a and the first conduit 3c,
Second pipelines 3b, 4, 7, provided in parallel with 5, 8, 11
10 throttles 4a, 7a, 10a, 45b, check valves 4b, 7b, 10b, 45c, turning hydraulic pilot valve 28A, and working machine hydraulic pilot valves 25A, 26.
Outputs a command signal for closing the pilot type check valves 5a, 8a, 11a, 45a provided on the first pipelines 3c, 5, 8, 11 in response to an operation signal when A and 27A are simultaneously operated. The control device 41 is provided.

The hydraulic circuit of the second hydraulic excavator according to the present invention supplies hydraulic oil to the hydraulic pump 2 driven by the engine 1, the pilot pumps 29, 36, 39, 44 and the actuators 20, 21. A hydraulic circuit of a hydraulic excavator including a turning directional control valve 15 and a boom directional control valve 16 received in parallel from the hydraulic pump 2, and hydraulic pilot valves 27A, 28A for switching the directional control valves 15, 16. Pilot type check valves 5a and 45a provided on the first pipelines 3c and 5 for connecting the hydraulic pump 2 and the boom direction switching valve 16, and the first pipeline 3
A diaphragm 4 is provided on the second conduits 3b and 4 provided in parallel with the c and 5.
a, 45b and check valves 4b, 45c, and the pilot type check valve 5 provided on the first pipelines 3c, 5 in response to the ON signal from the switching means 42 for selecting the turning priority.
a, 45a for outputting a command signal for closing operation
It is equipped with (41).

In the above structure, the turning hydraulic pilot valve 28A and the working machine hydraulic pilot valves 25A, 2
6A and 27A are simultaneously operated to output a command signal to the electromagnetic switching valves 34, 37 and 43 to open the electromagnetic switching valves 34, 37 and 43, and the pilot pump Pilot pressure from 36, 39, 44 is applied to pilot type check valves 5a, 8a, 11a, 45a provided on the first pipelines 3c, 5, 8, 11 via electromagnetic switching valves 34, 37, 43. In addition, the control device 41 that outputs a command signal for the closing operation is provided.

[0011]

According to the above construction, when the swing motor and the working machine (boom, arm, bucket) cylinder are simultaneously operated, the pressure oil is preferentially supplied to the swing motor, and the working machine (boom, arm, bucket) is supplied. Since the pressure oil supply to the cylinder is restricted, simultaneous operability of the swing motor and the working machine cylinder is improved. In this case, the throttle diameter of the second pipeline for supplying the pressure oil to the working machine side cylinder is set so as to match with the amount of the pressure oil supply to the swing motor side. Further, the throttle may be a variable throttle to change the opening amount according to the operation amount of the work implement operating lever to supply the pressure oil to the cylinder on the work implement side.

Further, when the turning priority switching means is turned ON, the pressure oil is preferentially supplied to the turning motor and the supply of the pressure oil to the boom cylinder is restricted when the turning and boom raising operations are simultaneously performed. May be.

By the way, hydraulic excavators perform various operations. For example, in the case of excavation work, the boom and arm or the arm and bucket are operated simultaneously, and when the excavated earth and sand are loaded into the dump sill, simultaneous operation of turning and boom raising is performed, but at this time the turning speed is slow. Since the boom rises quickly, the operator operates the lever so as to slow down the boom raising speed, which complicates the operation.Therefore, according to the hydraulic circuit of the present invention, when the swing and the working machine are simultaneously operated, the swing should not be performed. Since the pressure oil is preferentially supplied and the pressure oil supply to the working machine is restricted, simultaneous operability is improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the hydraulic circuit of the first hydraulic excavator according to the present invention will be described in detail below with reference to FIG. Variable displacement hydraulic pump (hereinafter referred to as hydraulic pump) 2 driven by the engine 1 and pilot pumps 29, 36, 3
It is equipped with 9,40. Discharge line 3 of this hydraulic pump 2
Is connected to the first directional control valve (for turning) 15. A pipe line 4 and a pipe line 5 further branched from a pipe line 3a branched from the discharge pipe line 3 are connected, and the pipe line 4 and the pipe line 5 are connected to a pipe line 6. This conduit 6 and the second directional control valve (for boom)
Connected with. A pipe line 7 and a pipe line 8 which are further branched from the branch pipe line 3a are connected, and the pipe line 7 and the pipe line 8 are connected to a pipe line 9. This conduit 9 is connected to the third directional control valve (for arm). Further, the pipeline 10 and the pipeline 11 that branch further from the branch pipeline 3 a are connected, and the pipeline 10 and the pipeline 11 are connected to the pipeline 12. The conduit 12 is connected to the fourth directional control valve (for bucket).

A throttle 4a and a check valve 4b are provided on the branch pipe line 4, and a pilot type check valve 5a which is closed by pilot pressure is provided on the branch pipe line 5. A restrictor 7a and a check valve 7b are provided on the branch pipe line 7,
A pilot-type check valve 8a that is closed by pilot pressure is provided above. A throttle 10a and a check valve 10b are provided on the branch pipeline 10, and a check valve 11a that is closed by pilot pressure is provided on the branch pipeline 11.

The first directional control valve 15 is provided with conduits 20a, 2
It is connected to the turning motor 20 via 0b. The second
The direction switching valve 16 is connected to the boom cylinder 21 via pipe lines 21a and 21b. The third directional control valve 17 is connected to the arm cylinder 22 via conduits 22a and 22b. The fourth directional control valve 18 is provided with pipes 23a, 23.
It is connected to the bucket cylinder 23 via b.

Next, the pilot pump 29 is connected to the hydraulic pilot valves 25A, 26A, 27A and 28A. This hydraulic pilot valve 25A, 26A, 27A, 2
8A and the operating levers 25, 26, 27, 28 are attached so as to interlock with each other, and the pilot pressure is output from the hydraulic pilot valve according to the operation amount of the operating lever. The hydraulic pilot valve 28A is connected to the operating portions 15a and 15b of the first directional control valve 15 via pilot conduits 28a and 28b. The hydraulic pilot valve 27A is connected to the operating portions 16a, 16b of the second directional control valve 16 via pilot conduits 27a, 27b.
The hydraulic pilot valve 26A includes a pilot line 26a,
26b via the operation portion 17a, 1 of the third directional control valve 17
It is connected to 7b. The hydraulic pilot valve 25A is connected to the fourth directional control valve 1 via pilot lines 25a and 25b.
8 operation units 18a and 18b are connected.

Pipe line 2 branched from the pilot pipe line 25a and the pilot pipe line 25b of the hydraulic pilot valve 25A.
5c is connected to the oil pressure sensor 30, and a signal from this oil pressure sensor 30 is input to the control device 41. A hydraulic pressure sensor 31 is connected to a hydraulic pressure pipe 31a of the hydraulic pressure pilot valve 26A, and a hydraulic pressure sensor 31 is connected to a hydraulic pressure pipe 31c that branches off from the hydraulic pressure pilot valve 26a and a signal is output from the hydraulic pressure sensor 31 to a control device 41. A hydraulic pressure sensor 32 is connected to a hydraulic pipe 32c that branches from the pilot hydraulic pipe 27a and the pilot hydraulic pipe 27b of the hydraulic pilot valve 27A.
The signal from is input to the control device 41. A hydraulic pressure sensor 33 is connected to a hydraulic pipeline 33c that branches from the pilot hydraulic pipeline 28a and the pilot hydraulic pipeline 28b of the hydraulic pilot valve 28A, and a signal from the hydraulic hydraulic sensor 33 is supplied to the control device 41.
Are typing in. The turning priority changeover switch 42 is connected to the control device 41.

The control device 41 is connected to an electromagnetic switching valve 34, and this electromagnetic switching valve 34 is connected to a pilot pump 36, and a hydraulic switching valve 35 is connected via a conduit 34a.
Connected with. The hydraulic switching valve 35 is connected to the pilot pump 40. The hydraulic switching valve 35 is provided in the conduit 3
It is connected to the pilot type check valve 11a via 5a and is connected to the pilot type check valve 8a via a line 35b. The control device 41 is connected to the electromagnetic switching valve 37, which is connected to the pilot pump 39 and also to the hydraulic switching valve 38 via the conduit 37a. The hydraulic switching valve 38 is connected to the pilot pump 40 and is also connected to the pilot type check valve 5a via the pipe line 38a.

Next, the operation will be described. First, the simultaneous operation of turning and arm excavation will be described. When the turning operation lever 28 is operated forward, the hydraulic pilot valve 28A
The pilot pressure output from the valve acts on the operating portion 15a of the first directional control valve 15 via the conduit 28a, and switches the first directional control valve 15 to the b position. On the other hand, when the arm operating lever 26 is operated in the forward direction, the pilot pressure output from the hydraulic pilot valve 26A acts on the operating portion 17a of the third directional control valve 17 via the conduit 26a, and the first directional control valve 17 is operated. To the b position.

At this time, the pilot pressure output from the hydraulic pilot valve 26A passes through the pipe line 26c and the hydraulic pressure sensor 31.
The pilot pressure output from the hydraulic pilot valve 28A is input to the control device 41 via the hydraulic pressure sensor 33 through the pipe line 28c while the signal is input to the control device 41 via the hydraulic pressure sensor 33. As a result, the control device 41 determines that the swing and the arm are simultaneously operated, and sends a command signal to the electromagnetic switching valve 34. Therefore, the electromagnetic switching valve 34 is switched to the a position,
The pilot pressure discharged from the pilot pump 36 acts on the hydraulic switching valve 35 via the pipe line 34a. This hydraulic switching valve 35 is switched to the a position, and the pilot pump 4
The pilot pressure discharged from 0 acts on the check valve 11a via the pipe 35b branched from the pipe 35a to close the check valve 8a.

Therefore, the pressure oil discharged from the hydraulic pump 2 preferentially flows into the turning motor 20 from the pipe 20a through the position b of the first directional control valve 17 and rotates clockwise. At the same time, the pressure oil discharged from the hydraulic pump 2 passes from the discharge pipeline 3 to the branch pipeline 3a, and from the branch pipeline 7 to the throttle 7a.
Flows into. The pressure oil that has passed through this throttle 7a is checked valve 7
The arm cylinder 22 extends from b via the conduit 9 through the position b of the third directional control valve 17 into the bottom chamber of the arm cylinder 22 from the conduit 22a. As a result, during simultaneous operation of turning and arm excavation, the turning is preferentially driven to stabilize the rotation speed, and the arm excavation speed is throttled so as not to become faster, so simultaneous operation of turning and arm excavation is improved. .

When the turning operation lever 28 is operated backward, the pilot pressure output from the hydraulic pilot valve 28A acts on the operating portion 15b of the first directional control valve 15 via the conduit 28b, and the first direction The switching valve 15 is switched to the a position. As a result, the pressure oil discharged from the hydraulic pump 2 flows into the swing motor 20 from the pipe line 20b and rotates counterclockwise. When the arm levers are simultaneously moved backward, the check valve 8a is closed as described above. , The third direction switching valve 17 is switched to the a position, and the pressure oil from the hydraulic pump 2 flows from the discharge pipe line 3 through the branch pipe line 3a and further flows into the throttle 7a from the branched pipe line 7. The pressure oil that has passed through the throttle 7a is sent from the check valve 7b through the pipe 9 to the third directional control valve 1
7 to the arm cylinder 22 from the conduit 22b through the position a.
And the arm cylinder 22 is shortened. Also in this case, the turning is preferentially driven to stabilize the rotation speed, and the arm dump speed is throttled so as not to become fast, so that the simultaneous operability of the turning and the arm dump is improved.

Further, the simultaneous operation of the swing and the bucket is the same as that of the above-mentioned simultaneous operation of the swing and the arm, and a detailed description thereof will be omitted. However, when the simultaneous operation of the swing and the bucket is performed, the hydraulic pressure is applied. The check valve 11a provided in the pipe line 11 that connects the pump 2 and the fourth directional control valve 18 is closed, and the pressure oil discharged from the hydraulic pump 2 is the check valve that passes through the throttle 10a from the pipe line 10. 10b through the pipe 12 and the fourth directional control valve 18 through the pipes 23a, 23b.
Flows into the bucket cylinder 23 and expands and contracts the bucket cylinder 23. In this case as well, the turning is preferentially driven to stabilize the rotation speed, and the bucket speed is throttled so as not to increase, so that the simultaneous operability of the turning and the bucket is improved.

Next, simultaneous turning and boom operation will be described. First, the turning priority switch 42 is turned on, and a signal is input to the control device 41. When the turning lever 28A is operated in the forward direction, it acts on the operating portion 15a of the first directional control valve 15 in the same manner as described above, and switches the first directional control valve 15 to the b position. On the other hand, when the boom operation lever 27 is operated in the forward direction, the pilot pressure output from the hydraulic pilot valve 27A is applied to the operation portion 1 of the second directional control valve 16 via the pipe line 27a.
6a to switch the second directional control valve 16 to the b position.

At this time, the pilot pressure output from the hydraulic pilot valve 27A passes through the conduit 27c and the hydraulic sensor 32.
The pilot pressure output from the hydraulic pilot valve 28A is input to the control device 41 via the hydraulic pressure sensor 33 through the pipe line 28c while the signal is input to the control device 41 via the hydraulic pressure sensor 33. As a result, the control device 41 determines the simultaneous operation of the swing and the boom, and sends a command signal to the electromagnetic switching valve 37. Therefore, the electromagnetic switching valve 37 switches to the a position,
The pilot pressure discharged from the pilot pump 39 acts on the hydraulic switching valve 38 via the conduit 37a. This hydraulic switching valve 38 is switched to the a position, and the pilot pump 4
The pilot pressure discharged from 0 acts on the check valve 5a via the pipe 38a, and closes the check valve 5a.

Therefore, the pressure oil discharged from the hydraulic pump 2 preferentially flows into the turning motor 20 from the pipe 20a through the position b of the first directional control valve 17 and rotates clockwise. At the same time, the pressure oil discharged from the hydraulic pump 2 passes from the discharge pipeline 3 to the branch pipeline 3a, and from the branch pipeline 4 to the throttle 4a.
Flows into. The pressure oil that has passed through the throttle 4a is checked by the check valve 4
From the b side through the b path 6 through the b position of the second directional control valve 16 to the bottom chamber of the boom cylinder 21 from the baffle 21a, the boom cylinder 22 extends. As a result, during simultaneous operation of turning and boom raising, the turning is preferentially driven to stabilize the rotation speed, and the boom raising speed is throttled so as not to become fast, so simultaneous operability of turning and boom raising is improved. .

When the turning operation lever 28 is operated in the rearward direction, the turning motor 20 is rotated counterclockwise as described above. Detailed description is omitted here. When the boom operation lever 27 is operated backward, the pilot pressure output from the hydraulic pilot valve 27A is transferred to the second directional control valve 16 via the pipe line 27b.
It acts on the operating portion 16b of the
The pressure oil that is switched to the position and discharged from the hydraulic pump 2 is in the line 3
Through the branch conduit 3a, and then into the throttle 4a from the branching conduit 4. The pressure oil that has passed through the throttle 4a flows from the check valve 4b through the line 6 through the position a of the second directional control valve 16 into the head chamber of the boom cylinder 21 through the line 21b, and the boom cylinder 22 is shortened. To do. In this way, simultaneous operability of turning and boom lowering can be achieved.

Next, the hydraulic circuit of the second hydraulic excavator according to the present invention will be described in detail with reference to FIG. It is to be noted that the components denoted by the same reference numerals as those in FIG. The discharge line 3 of the hydraulic pump 2 is connected to the first directional control valve (for turning) 15. It connects with the pipeline 3a branched from this discharge pipeline 3, and connects with the pipeline 3b and the pipeline 3c which branch further from this pipeline 3a. A variable diaphragm 45b is provided on this branch line 3b. A check valve 45c is provided on the downstream side of the variable throttle 45b. The conduit 3b is connected to the second directional control valve (for boom) 16 via the conduit 3e and the conduit 3f. The conduit 3e is connected to the conduit 3i and the third directional control valve (for arm) 17 through the conduit 3h. Further, from pipeline 3h through pipeline 3k, pipeline 3
1 and the fourth directional control valve (for bucket) 18 are connected.

A pilot type check valve 45a is provided on the branch line 3a to the line 3c. The conduit 3d on the downstream side of the pilot type check valve 45a is the conduit 3
It is connected to the second directional control valve (for boom) 16 via f. The conduit 3d is connected to the conduit 3i and the third directional control valve (for arm) 17 through the conduit 3g. The pipe 3g is connected to the fourth directional control valve (for bucket) 18 through the pipe 3j and the pipe 3l.

The control device 41 is connected to the electromagnetic switching valve 43. This electromagnetic switching valve 43 is a pilot pump 44.
It is also connected to the pilot type check valve 45a through the pilot pipe line 43a.

Next, the operation will be described. First, in the case of operating the turning and boom simultaneously, the turning priority switch 42 is turned on and a signal is input to the control device 41. When the swivel lever 28 is operated in the forward direction, the pilot pressure output from the hydraulic pilot valve 28A acts on the operating portion 15a of the first directional control valve 15 to switch the first directional control valve 15 to the b position. On the other hand, when the boom operating lever 27 is operated in the forward direction, the pilot pressure output from the hydraulic pilot valve 27A acts on the operating portion 16a of the second directional control valve 16 to switch the second directional control valve 16 to the b position.

At this time, the pilot pressure output from the hydraulic pilot valve 27A passes through the conduit 27c and the hydraulic sensor 32.
The pilot pressure output from the hydraulic pilot valve 28A is input to the control device 41 via the hydraulic pressure sensor 33 through the pipe line 28c while the signal is input to the control device 41 via the hydraulic pressure sensor 33. As a result, the control device 41 determines the simultaneous operation of turning and boom, and sends a command signal to the electromagnetic switching valve 43. Therefore, the electromagnetic switching valve 43 switches to the a position,
The pilot pressure discharged from the pilot pump 44 acts on the pilot type check valve 45a via the pipe 43a, and the pilot type check valve 45a is closed.

Therefore, the pressure oil discharged from the hydraulic pump 2 preferentially flows into the turning motor 20 from the pipe 20a through the position b of the first direction switching valve 15 and rotates clockwise. At the same time, the pressure oil discharged from the hydraulic pump 2 flows from the discharge conduit 3 through the branch conduit 3a and into the variable throttle 45b from the further branched conduit 3b. The variable aperture 45b is adapted to open and close according to the operation amount of the work machine levers 25, 26, 27. The pressure oil that has passed through the variable throttle 45b flows from the check valve 45c through the pipe 3e, the pipe 3f, the position b of the second directional control valve 16 and the pipe 21a into the bottom chamber of the boom cylinder 21. Then, the boom cylinder 22 extends. As a result, during simultaneous operation of turning and boom raising, the turning is preferentially driven to stabilize the rotation speed, and the boom raising speed is throttled so as not to become fast, so simultaneous operability of turning and boom raising is improved. .

Next, when the turning operation lever 28 and the boom operation lever 27 are operated in the backward direction, the first directional control valve 15 and the second directional control valve 16 are switched to the a position, contrary to the above. The pilot pressure output from the hydraulic pilot valves 27A and 28A is input to the control device 41 via the oil sensors 32 and 33. As a result, the control device 41 determines the simultaneous operation of turning and boom, and sends a command signal to the electromagnetic switching valve 43. Therefore, the electromagnetic switching valve 43 is switched to the a position, the pilot pressure discharged from the pilot pump 44 acts on the pilot type check valve 45a via the pipe line 43a, and the pilot type check valve 45a is closed. The pressure oil discharged from the hydraulic pump 2 passes from the pipe line 3 through the branch pipe line 3a, and from the further branched pipe line 3b.
Flows into 5b. The pressure oil that has passed through the variable throttle 45b flows from the check valve 45c through the conduit 3e, the conduit 3f, the position a of the second directional control valve 16 and the conduit 21b into the head chamber of the boom cylinder 21. Then, the boom cylinder 22 is shortened, and the pressure oil discharged from the hydraulic pump 2 flows from the conduit 3 to the turning motor 20 from the conduit 20b through the position a of the first directional control valve 15 and rotates counterclockwise. As a result, during simultaneous operation of turning and boom lowering, the turning is preferentially driven to stabilize the rotation speed, and the boom lowering speed is throttled so as not to become faster, so simultaneous operability of turning and boom lowering is improved. .

As described above, according to the first and second hydraulic circuits of the present invention, the swivel is prioritized in various simultaneous operations such as simultaneous operation of the swing and boom, or simultaneous operation of the swing and arm. While driving, pressure oil is supplied to different actuators such as booms and arms through throttles. In the above-mentioned first hydraulic circuit, a fixed throttle is provided for each pressure oil supply pipe line such as the boom and arm. The fixed throttle diameter is set to an optimum diameter for the boom and arm.

Further, in the second hydraulic circuit, a variable throttle is provided in the pressure oil supply pipe line that communicates commonly with the boom and the arm, and this variable throttle corresponds to the operation amount of the operating lever of the boom and the arm. Since the diaphragm diameter can be varied, the work speed of the boom and arm can be adjusted according to various work. Because of this, it is possible to improve the simultaneous operability of the swing and the boom or arm while driving the swing with priority.

Although the ON signal of the turning priority switch and the operation signal of the operating lever (the signal output from the hydraulic pressure sensor) are input to the control device to judge whether the turning and the working machine are simultaneously operated, the turning priority is given. The turning operation and the simultaneous operation of the working machine may be determined by the ON operation of only the switch. Alternatively, the simultaneous operation may be determined when the turning and operation signals of the operating lever of the working machine are input to the control device without using the turning priority switch.

[0039]

As described above, according to the hydraulic circuit of the hydraulic excavator according to the present invention, when the swing motor and the working machine (boom, arm, bucket) cylinder are simultaneously operated, the pressure oil to the swing motor is prioritized. Since the pressure oil is supplied to the work machine (boom, arm, bucket) cylinders, the simultaneous operation of the swing motor and the work machine cylinder is improved, and the workability is improved.

Further, when the swing and the boom are simultaneously operated, the swing priority changeover switch is turned on to preferentially supply the pressure oil to the swing motor and throttle the supply of the pressure oil to the boom cylinder. From this, the operator can arbitrarily select the turning priority.

Further, when the swing motor and the working machine cylinder are simultaneously operated, the swing motor is driven with priority, and the pressure oil to the working machine cylinder is supplied through the variable throttle. Since the diaphragm diameter can be changed according to the amount of operation of the operation lever, the work speed of the boom, arm, etc. can be adjusted according to various works, improving workability.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a first hydraulic excavator according to the present invention.

FIG. 2 is a hydraulic circuit diagram of a second hydraulic excavator according to the present invention.

FIG. 3 is a side view of the hydraulic excavator.

FIG. 4 is a hydraulic circuit of a conventional hydraulic excavator.

[Explanation of symbols]

2 ... hydraulic pump, 4a, 7a, 10a ... throttle, 4b, 7
b, 10b, 45c ... Check valve, 5a, 8a, 11
a, 45a ... Pilot type check valve, 15, 16, 1
7, 18 ... Direction switching valve, 20 ... Slewing motor, 21 ... Boom cylinder, 22 ... Arm cylinder, 23 ... Bucket cylinder, 25, 26, 27, 28 ... Operating lever, 25
A, 26A, 27A, 28A ... Hydraulic pilot valve, 3
0, 31, 32, 33 ... Oil pressure sensor, 36, 39 ... Electromagnetic switching valve, 35, 38 ... Hydraulic switching valve, 29, 36, 3
9, 40 ... Pilot pump, 41 ... Control device, 42 ...
Turn priority changeover switch, 45b ... Variable diaphragm.

Claims (3)

[Claims] 1. A hydraulic pump (2) driven by an engine (1), a pilot pump (29, 36, 39, 44), a swing actuator (20) and a working machine actuator (21,
(22, 23) receives the pressure oil supplied in parallel from the hydraulic pump (2) and the directional control valve (15) for turning and the directional control valve (16,
17,18), and a hydraulic excavator equipped with a turning hydraulic pilot valve (28A) for switching the directional control valves (15,16,17,18) and a working machine hydraulic pilot valve (25A, 26A, 27A). In the hydraulic circuit of, the hydraulic pump (2) and the working machine directional control valve (1
6,17,18) and the pilot type check valve (5a, 8a, 11a, 45a) provided on the first conduit (3c, 5,8,11) and this first
The second pipeline (3b, 4,7,7) installed in parallel with the pipeline (3c, 5,8,11) of
10) Throttle up (4a, 7a, 10a, 45b) and check valve (4b, 7b, 10b
b, 45c) and the hydraulic pilot valve for turning (28A) and the hydraulic pilot valve for working machine (25A, 26A, 27A) at the same time, the first pipeline (3c, 5, 8, 11) A hydraulic circuit for a hydraulic excavator, comprising: a control device (41) that outputs a command signal for closing the pilot-type check valves (5a, 8a, 11a, 45a) provided above. 2. A hydraulic pump (2) driven by an engine (1), a pilot pump (29, 39, 40), and pressure oil supplied to each actuator (20, 21) from the hydraulic pump (2). Hydraulic circuit of a hydraulic excavator equipped with a turning directional control valve (15) and a boom directional control valve (16) that are received in parallel, and a hydraulic pilot valve (27A, 28A) that switches the directional control valve (15, 16). At the hydraulic pump (2) and the directional control valve for the boom
(16), the pilot type check valve (5a, 45a) provided on the first conduit (3c, 5) and the second conduit provided in parallel with the first conduit (3c, 5) Switching means (42) for selecting turning priority by providing throttles (4a, 45b) and check valves (4b, 45c) on the pipelines (3b, 4) of
A control device (41) for outputting a command signal for closing the pilot type check valve (5a, 45a) provided on the first pipeline (3c, 5) in response to an ON signal from The hydraulic circuit of the hydraulic excavator. 3. The turning hydraulic pilot valve (28A),
A command signal is output to the electromagnetic switching valve (34, 37, 43) in response to the signal when the hydraulic pilot valve for work equipment (25A, 26A, 27A) is operated simultaneously, and this electromagnetic switching valve (34, 37,43) and the pilot pressure from the pilot pump (36,39,44) is passed through the electromagnetic switching valve (34,37,44) to the first
Pilot operated check valve (5c) provided on the pipeline (3c, 5,8,11)
The hydraulic circuit for a hydraulic excavator according to claim 1 or 2, further comprising a control device (41) that outputs a command signal for closing operation in addition to (a, 8a, 11a, 45a).