JPH0352273Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a hydraulic circuit for a hydraulic excavator.

A conventional example of a hydraulic excavator and its hydraulic circuit will be explained with reference to Figs. 1 and 2. In Fig. 1, a is a bucket, b is an arm, c is a boom, d is a rotating structure,
In the figure, 1 is one operating valve for traveling, 2 is an operating valve for the swing motor, 3 is an operating valve for the arm, 4 is the other operating valve for traveling, 5 is the operating valve for the bucket, 6 is the operating valve for the boom, B is one control valve that includes each of the operating valves 1, 2, and 3, A is the other control valve that includes each of the operating valves 4, 5, and 6, and 7 is a logic valve.
0 is the boom cylinder, 10a is the piston side of the boom cylinder 10, and 10b is the boom cylinder 1
0 on the piston rod side, 10c on the lifting (extension) passage communicating with the piston side 10a of the boom cylinder 10, 11 on the arm cylinder, 13 and 14 on the pump, 15 on the check valve, 15a on the throttle, 17
is a swing motor, 21 is a signal passage, and 28 in FIG. 1 is a bucket cylinder. need to be operated. At this time, by pushing the boom operation valve 6 (extending the boom cylinder 6), the signal passage 21 communicates with the tank side passage, the logic valve 7 opens, and the swing operation valve 2 opens on the piston side of the boom cylinder 10. It is connected in parallel to a lifting (extension) passage 10c that communicates with 10a.
Therefore, the boom cylinder 10 is under relatively high pressure.
The swing motor 17 is driven by the lifting pressure. Furthermore, since the arm operation valve 3 in the control valve B is connected in tandem with the swing motor operation valve 2, pressure oil from the pump 14 is not supplied to the arm cylinder 11, but the pump 1
3 is supplied through the check valve 15 and throttle 15a on the upstream side of the control valve A. The case in which the swing motor 17, arm cylinder 11, and boom cylinder 10 are operated simultaneously during actual work is explained using the power shovel body shown in Fig. 1. Excavated soil is piled up in a bucket a, and the boom cylinder 10 is extended. , lift arm b, boom c and bucket a, and at the same time turn the swing motor 1
7 to extend or contract the arm cylinder 11 while moving the bucket truck a closer to the dump truck in a predetermined position, actuating the arm b, and moving the bucket truck a closer to the dump truck in a predetermined position.
It exists during the process of correcting the position of. Hereinafter, this work will be referred to as dump truck loading work. In this dump loading work, the boom cylinder 10
Focusing on the extension stroke of the power shovel and the drive stroke of the swing motor 17, the swing motor 17 is driven by relatively high boom cylinder lifting pressure, so the drive shaft torque is large and the power shovel swing structure d
The acceleration torque of d also increases, and the rotational speed of the rotating body d increases. In addition, by opening the logic valve 7 connected in parallel to the operating valve 2 for the swing motor,
Pressure oil from the pump 14 is supplied to the boom cylinder 10, and pressure oil from the pump 13 is supplied to the check valve 15 connected in parallel to the boom operation valve 6.
Most of the pressure oil flows into the arm cylinder 11 through the throttle 15a (to the arm cylinder 11, which has relatively low pressure due to aerial work), and from the boom operation valve 6 to the boom cylinder 10 on the relatively high pressure side. As the supply becomes smaller, the extension speed of the boom cylinder 10 becomes slower. The relationship between the turning angle θ and the amount of extension of the boom cylinder 10 at this time is shown in FIG. 3. Since the change in the turning angle θ is large relative to the amount of extension of the boom cylinder 10, when loading a dump truck, the bucket a turns before it clears the height of the loading platform, causing problems such as colliding with the side of the dump truck. The problem was that it was easy to occur.

This proposal addresses the above-mentioned problem, and the pressure oil from one pump 14 is transferred to one control valve B.
The pressure oil from the other pump 13 is supplied to and discharged from the swing motor 17 and the arm cylinder 11 through the swing operation valve 2 and the arm operation valve 3 connected to the tandem circuit of the control valve A, and the pressure oil from the other pump 13 is used for the boom of the other control valve A. The pressure oil from the one pump 14 is supplied to and discharged from the boom cylinder 10 via the operation valve 6, and the pressure oil from the one pump 14 is supplied to the boom cylinder 10 through the other pump 13.
In the hydraulic circuit of the hydraulic excavator, in which pressure oil is supplied and discharged from the arm cylinder 11 to and from the arm cylinder 11, when the boom cylinder 10 is lifted, the swing motor 17 and the arm cylinder 11
The switching circuit 27 is connected to the discharge side of the one pump 14 via the logic valve 12, and the switching circuit 27 is connected to the discharge side of the other pump 14 via the selector valve 18. The hydraulic circuit of the hydraulic excavator is connected to the discharge side of the pump 13, and its purpose is to prevent the bucket from turning before it exceeds the height of the loading platform during loading into a dump truck. The object of the present invention is to provide an improved hydraulic circuit for a hydraulic excavator that can eliminate the problem of collision with the side of a dump truck.

Next, the hydraulic circuit of the hydraulic excavator of the present invention will be explained with reference to an embodiment shown in FIG. 5 is a travel operating valve; 5 is a bucket operating valve; 6 is a boom operating valve; B is one control valve including each of the above operating valves 1, 2, and 3;
is the other control valve including each of the operation valves 4, 5, and 6, 7, 8, and 9 are logic valves, 10 is a boom cylinder, 10a is the piston side of the boom cylinder, 10b is the piston rod side of the boom cylinder 10, 10c is a lifting (extension) passage communicating with the piston side 10a of the boom cylinder 10; 11;
is the arm cylinder, 12 is the logic valve, 13,1
4 is the pump, 15 is the check valve, 15a is the throttle,
16 is a check valve, 17 is a swing motor, 18 is a selector valve, 19, 20, 21, 22 is a signal path,
23, 24, 25, 26 are check valves, 27 is a switching circuit, 28 is a bucket cylinder, 29 is an upstream passage of the logic valve 9, and the pump 13 includes operating valves 4, 5, 6, logic valve 9, and a selector valve. The pump 14 supplies pressure oil to the control valve A, which has a passage connecting the 18 check valves 15, 25, 26, Pressure oil is supplied to control valve B, which has a connected passage. The arm operation valve 3 is connected to the arm cylinder 11 and also to a signal path 19 for controlling the opening and closing of the logic valve 9. Further, the swing operation valve 2 is connected to a swing motor 17. The boom operation valve 6 is connected to the boom cylinder 10, and signal passages 20, 2 which control the opening and closing of the logic valves 8, 7, 12 and the selector valve 18 are connected to the boom cylinder 10.
It is also connected to 1 and 22. Further, the bucket operation valve 5 is connected to the bucket cylinder 28. The logic valve 7 is also connected to a piston-side pressure chamber 10a of the boom cylinder 10 via a check valve 16 and a passage 10c. The logic valve 12 is connected to a passage (switching circuit) 27 via a check valve 23, the selector valve 18 is connected to a check valve 15 via a throttle 15a, and the upstream passage 29 of the logic valve 9 is connected to a passage (switching circuit) 27 via a check valve 26. They are connected to each other.

Next, the operation of the hydraulic circuit of the hydraulic excavator will be explained. When the swing operating valve 2 is switched in an attempt to drive the swing motor 17, the arm operating valve 3 on the downstream side is not supplied with pressure oil from the bypass passage 30 because it is connected in tandem with the swing operating valve 2. When the arm operation valve 3 is switched in an attempt to operate the arm cylinder 11 at the same time, pressure oil is not supplied from the passage 30 due to the tandem connection as described above, but the signal passage 19 is blocked, so the logic valve 9 closes, pressure oil from pump 13 flows into passage 2.
9 and selector valve 18 to each check valve 26,1
It is supplied to the arm operation valve 3 through the 5 passage 27, and the arm cylinder 11 is operated.
At the same time, when switching the bucket operation valve 5 in an attempt to operate the bucket cylinder 28,
Pressure oil is no longer supplied from the passage 29 to the passage 27, but the flow from the selector valve 18 to the throttle 15a and the check valve 1
There is a supply of pressure oil via 5 passages 27. In other words, the bucket cylinder 28 is connected to the bucket operation valve 5, and the arm cylinder 11 is connected to the selector valve 18.
The pressure oil of the pump 13 is distributed from the swivel operation valve 2 to the swivel motor 17, and the pressure oil of the pump 14 is supplied to the swing motor 17 from the swivel operation valve 2. In this way, the load fluctuations of the arm cylinder 11 and the bucket cylinder 28 are reduced to the swing motor 17.
When excavating with a bucket a using the arm cylinder 11 and the bucket cylinder 28 of a power shovel, the side of the bucket a is pressed against the side of the excavation section by the driving force of the swing motor 17 to flatten the surface. This makes it possible to obtain a finished surface. Further, when the excavation work is finished and the move is to proceed to the loading process, a three-linked operation is performed in which the swing motor 17 is driven, the boom cylinder 10 is extended, and the arm cylinder 11 is extended or contracted (dump loading work). At this time, operation valves 2, 3, 6
Switch at the same time. On the control valve B side, since the arm operation valve 3 is tandemly connected to the swing operation valve 2, pressure oil is not supplied from the passage 30 to the arm operation valve 3. On the control valve A side, the boom operation valve 6 is switched to a function 6a that supplies pressure oil to the extension side of the boom cylinder 10 and a pilot part function 6b. Therefore,
Since the signal passage 20 of the logic valve 8 is closed, the signal passage 21 of the logic valve 7 is opened, and the signal passage 22 of the logic valve 12 and the selector valve 18 is opened, the logic valve 8 is closed, the logic valves 7 and 12 are opened, and the selector Valve 18 is in closed position 18a. In this state, the passage 30 and the boom operation valve 6 are switched,
Since the passage 29 and the selector valve 18 are closed, pressure oil is not supplied to the arm operation valve 3 from these passages, but since the logic valve 12 is opened, the pump 14 is not supplied.
A part of the pressure oil is supplied to the arm operating valve 3 via the check valve 23 and the passage 27. At this time, the swing operation valve 2 of the swing motor 17 and the arm cylinder 1
The first arm operation valve 3 is connected in parallel through a logic valve 12, a check valve 23, and a passage 27. On the other hand, since the selector valve 18 is in the closed state, all of the pressure oil from the pump 13 is supplied from the boom operation valve 6 to the boom cylinder 10. Also, since the logic valve 7 is open, the pump 14
A part of the pressure oil from the check valve 16 can be supplied to the boom cylinder 10 through the passage 10c of the check valve 16. Thus, in the above case, all of the pressure oil from the pump 13 is supplied to the boom cylinder 10. In addition, the discharge side of the pump 14 has an operation valve 2 and a logic valve 1.
By opening 2, 7, etc., it becomes possible to connect the swing motor 17 to the arm cylinder 11 and the boom cylinder 10 in parallel, and to supply pressure oil to these.

As described above, the hydraulic circuit of the hydraulic excavator of the present invention includes a switching circuit 27 that connects the swing motor 17 and the arm cylinder 11 in parallel when the boom cylinder 10 is lifted. The switch circuit 27 is connected to the discharge side of one pump 14 via the selector valve 18, and the logic valve 12 is opened when the boom cylinder 10 is extended. Then, the swing operation valve 2 and the arm operation valve 3 are connected in parallel by the switching circuit 27, and at the same time, the selector valve 18 is closed.
The above-mentioned parallel passage with throttle is closed and pressure oil is supplied only through the tandem passage 29 downstream of the boom operation valve 6 to give priority operation to the boom arm, so that the extension amount of the boom cylinder and the turning angle θ are The relationship can be made as shown in FIG. 3(), and the conventional problems (see FIG. 3()) can be solved.

In addition, in this proposal, the target actuator for swing and tandem/parallel switching is only the arm cylinder, so the signal pressure for swing and tandem/parallel switching can be obtained by opening and closing the pilot function 6b of the boom spool 6. Since only the self-pressure signal is used, the configuration can be simplified.

Tamming, which switches from tandem to parallel, is performed only when the boom cylinder is extended, resulting in good operability.

The tandem and parallel switching devices are achieved by opening one logic valve 12 through the passage 27 to the tandem passage, which not only simplifies the configuration but also ensures stable operation without oscillation. It is.

[Brief explanation of the drawing]

Fig. 1 is a side view schematically showing a hydraulic excavator, Fig. 2 is a conventional hydraulic circuit of the hydraulic excavator, and Fig. 3 is a diagram showing the relationship between the extension amount of the boom cylinder and the swing angle in the conventional and proposed hydraulic circuits. Explanatory diagram showing, No. 4
The figure is a hydraulic circuit diagram showing an embodiment of the hydraulic circuit of a hydraulic excavator according to the present invention. 2...Swivel operation valve, 3...Arm operation valve,
6...Boom operation valve, 10...Boom cylinder, 11...Arm cylinder, 12...Logic valve, 13...Other pump, 14...One pump, 17...Swivel motor, 18...Selector valve,
27...Switching circuit, A...other control valve, B...one control valve.

Claims (1)

[Scope of utility model registration request] Pressure oil from one of the pumps 14 passes through the swing operation valve 2 and the arm operation valve 3 connected to the tandem circuit of one control valve B to the swing motor 17,
The pressure oil from the other pump 13 is supplied to and discharged from the boom cylinder 10 through the boom operation valve 6 of the other control valve A, and the pressure oil from the one pump 14 is supplied to and discharged from the arm cylinder 11. Oil is supplied to the boom cylinder 10, and pressure oil from the other pump 13 is supplied to the arm cylinder 11.
In the hydraulic circuits of the hydraulic excavators that are supplied and discharged respectively, a switching circuit 27 is provided for connecting the swing motor 17 and the arm cylinder 11 in parallel when the boom cylinder 10 is lifted. Hydraulic pressure of a hydraulic excavator characterized in that the hydraulic excavator is connected to the discharge side of the one pump 14 via the logic valve 12, and the switching circuit 27 is connected to the discharge side of the other pump 13 via the selector valve 18. circuit.