JP3165048B2 - Hydraulic excavator control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of a control circuit for a hydraulic shovel. More specifically, the present invention belongs to the technical field of a hydraulic circuit in which operation characteristics and the like in operations such as horizontal pulling of a hydraulic shovel are improved.

[0002]

2. Description of the Related Art Conventionally, when performing operations such as horizontal pulling with a hydraulic shovel, a hydraulic control circuit has been devised so that an operator can smoothly perform these operations. FIG. 3 is a view showing the entire hydraulic excavator for explaining the horizontal pulling operation. 3A shows the position of the arm and the boom before the start of the horizontal pull, and FIG. 3B shows the position of the arm and the boom after the horizontal pull. In these figures, an upper swing body 26 is provided on a traveling vehicle 25. A boom 27 is rotatably provided at an appropriate position in front of the upper swing body 26, and an arm 28 and a bucket 29 are sequentially and rotatably connected to a distal end of the boom 27. The rotation angle and speed of the boom 27, the arm 28, and the bucket 29 are controlled by the boom cylinder 19, the arm cylinder 8, and the bucket cylinder 30, respectively.

FIG. 4 shows a conventional control circuit (hereinafter referred to as conventional circuit 1).
FIG. In FIG. 4, the first hydraulic pump 1 is connected to a left input port of an arm cylinder switching valve 3 by a center oil passage 2, and the left output port is connected to an oil tank 5 via a throttle valve 4. The first hydraulic pump 1 is connected to the central input port of the switching valve 3 via a check valve 7 via a branch path 6 from the center oil path 2, and the central output port is connected to the extension port 8 a of the arm cylinder 8. It is connected. The reduction port 8b of the arm cylinder 8 is connected to the right output port of the switching valve 3, and the right input port is connected to the oil tank.

The second hydraulic pump 11 is connected to a left input port of a boom cylinder switching valve 13 by a center oil passage 12, and the left output port is connected to a junction switching valve 14, a throttle 15 and an oil tank 16 in order. ing. The right pilot port of the junction switching valve 14 is connected so as to operate with the arm pilot pressure, and when the arm pilot pressure acts, the oil passage of the input / output port of the junction switching valve 14 is shut off. The branch circuit 17 from the center oil passage 12
Thereby, the second hydraulic pump 11 is connected to the central input port of the switching valve 13 via the check valve 17, and the central output port is connected to the extension side port 19 a of the boom cylinder 19. Reduction port 19 of boom cylinder 19
b is connected to the right output port of the switching valve 13, and the right input port is connected to the oil tank.

The first branch oil passage 21 branches off from the center oil passage 12 downstream of the left output port of the boom cylinder switching valve 13, and the check valve 7 of the branch oil passage 6 passes through a check valve 22.
To form a combined oil passage 21a. Further, the second branch oil passage 23 branches from the downstream of the second hydraulic pump 11, and merges with the check valve 7 on the branch oil passage 6 via the check valve 24 and the throttle 25.

Hereinafter, a horizontal pulling operation of the hydraulic excavator will be described with reference to FIGS. To perform the horizontal pulling operation with the hydraulic excavator, the tip of the bucket 29 is moved in the direction of the arrow in the drawing from the state of FIG. 3A to the state of FIG. 3B while simultaneously operating the boom 27, the arm 28, and the bucket 29. . That is, the rotation operation of the bucket is performed while the arm closing operation and the boom raising operation can be performed simultaneously.

First, in the initial stage of the horizontal pulling operation, the bucket 29 is located farthest from the revolving body 26, and the horizontal pulling operation is performed from here by closing the arm 28 (extending the arm cylinder 46). In this case bucket 2
9, the downward movement of the boom 27 must be performed at a high speed.

Next, in an intermediate stage, that is, in a state where the bucket is drawn to some extent, the downward speed of the bucket decreases. Therefore, the amount of operation of raising the boom is also small, and the operation of raising the boom requires a delicate operation. For this reason,
Fluctuations in the supply / inflow of the supply oil amount to the raising-side input port 19a of the boom cylinder 19 frequently occur. Further, since the opening area of the right intermediate port of the direction switching valve 13 is larger than the opening area of the central left input / output port, the oil pressure of the supply oil becomes oscillating. This causes the boom to vibrate, giving the operator a "fluffy feeling".

In order to prevent this fluffy feeling, a second
A part of the supply amount from the hydraulic pump 11 may be directly released to the arm side to reduce the change in the supply oil amount to the raising port 19a of the boom cylinder 19. For this reason, in the conventional circuit described above, the second branch oil passage 23 that supplies a part of the pressure oil from the second hydraulic pump 11 to the arm side via the throttle 25 is provided. That is, when both the arm and the boom are operated at the same time in the conventional circuit 1, a part of the pressure oil from the second hydraulic pump 11 passes through the second branch oil passage 23 to the junction oil passage 2
1a, the moving speed of the arm cylinder 19 is increased. In addition, the moving speed of the boom cylinder is reduced by the pressure oil flowing through the second branch oil passage 23. In the initial stage of the horizontal pulling operation, the boom cylinder 19
Is supplied from the second hydraulic pump 11 and the input / output oil passage on the left side of the switching valve 13 is shut off, so that the speed increase via the first branch oil passage 21 does not occur.

As can be seen from the above description, the conventional circuit 1
Then, when the arm and the boom are simultaneously operated, the pressure oil from the second hydraulic pump 11 flows to the arm cylinder 8 via the throttle 25. By the action of the throttle 25, the movement speed of the boom cylinder is suppressed, and the "fluffiness" of the boom which occurs when performing the horizontal pulling operation of the hydraulic excavator is prevented, and the movement speed of the arm is increased.

However, the stop 25 is a fixed stop. Therefore, when the resistance of the throttle 25 is small, the pressure oil from the second hydraulic pump 11 flows into the low-pressure arm cylinder side during the full operation of the horizontal pull, and the boom does not rise and only the arm moves at high speed. The disadvantage is that the bucket cuts into the ground. If an operation of narrowing the opening of the arm cylinder switching valve 3 is performed in order to prevent this, there is a disadvantage that the moving speed of the arm is reduced and the working efficiency cannot be improved. When the resistance of the diaphragm 25 is increased, the moving speed of the boom is increased, but the gain is large, so that a “fluffy feeling” occurs in the boom operation,
The so-called “breathing” phenomenon of instantaneous stop or deceleration of the arm due to insufficient supply of pressurized oil to the arm cylinder causes inconvenience that operability is deteriorated.

FIG. 5 is a diagram showing another conventional control circuit (hereinafter referred to as conventional circuit 2). In FIG. 5, a switching type throttle valve 31 is used instead of the fixed throttle 25. The pilot port 31b on the communication side (throttle valve side) is connected to the pilot output oil passage of the arm remote control valve 33 via the shuttle valve 34, and the spool on the closed side is pressed by a spring 31c. Therefore, when the arm pilot pressure becomes equal to or higher than the predetermined pressure, the pressure oil of the hydraulic pump 11 is supplied to the arm cylinder switching valve 3 through the throttle 31 a of the switching valve 31.

As a result, even in the initial stage of the horizontal pulling operation, if the arm pilot pressure becomes equal to or higher than the predetermined pressure, the hydraulic oil from the hydraulic pump 11 flows out to the low-pressure arm through the throttle 31a, and the bucket bites. The inconvenience that it occurs. In order to prevent this, it is necessary to considerably narrow the opening of the arm cylinder switching valve 3, and as a result, the floor moat speed cannot be increased. Also,
If the aperture of the diaphragm 31a is reduced, the gain of the boom increases, and there is a disadvantage that the fluffy feeling of the boom cannot be eliminated.

[0014]

As described above,
In the conventional circuit 1, since the diaphragm 25 is a fixed diaphragm, it is not possible to simultaneously improve the work efficiency and prevent the "fluffy feeling" in the horizontal drawing operation. Further, in the conventional circuit 2, in the initial stage of the horizontal pulling operation, the throttle 31a communicates as soon as the pilot oil pressure becomes equal to or higher than the predetermined pressure, thereby simultaneously improving the work efficiency and preventing the "fluffy feeling" in the horizontal pulling work. I couldn't do that. Therefore, the present invention solves the problems of the above-described conventional control circuit, and provides a control circuit that prevents the digging of the bucket and the fluffy feeling of the boom during the horizontal pulling of the hydraulic shovel and improves the working efficiency of the horizontal pulling. It is intended to be.

[0015]

According to a first aspect of the present invention, there is provided a control circuit for connecting an arm cylinder to an oil passage of a first hydraulic pump via an arm switching valve,
A boom cylinder is connected to an oil passage of the hydraulic pump via a boom switching valve, and a first oil passage is provided from a center oil passage downstream of the boom switching valve.
A branch oil passage is provided to join the input oil passage of the arm switching valve, and a second branch oil passage is provided from the downstream of the second pump to join the merge oil passage, and a throttle valve is connected to the second branch oil passage. In the control circuit of the inserted hydraulic excavator, the throttle valve is a switching throttle valve or a variable throttle valve, and the throttle valve is controlled so that the opening degree increases as the arm negative pressure increases.

In this control circuit, when the boom remote control valve and the arm remote control valve are operated together, pressure oil from the second hydraulic pump is supplied to the boom cylinder and the arm cylinder is also supplied from the first hydraulic pump. Pressure oil is supplied. Further, the pressure oil of the second hydraulic pump is supplied to the arm cylinder from the second branch oil passage, and the supply amount is controlled by negative pressure acting on the arm cylinder. As the negative pressure increases, the supply amount increases. Become.

According to a second aspect of the present invention, in the control circuit according to the first aspect, the switching throttle valve restricts an oil passage when a pilot pressure is low, and the switching throttle valve has a hydraulic pressure which is higher than a predetermined pressure. The switching valve is fully opened, and the hydraulic pressure of the merged oil passage is applied to the pilot port of the switching throttle valve. In this control circuit, the junction oil passage and the pilot port of the switching throttle valve are connected, and the oil pressure of the junction oil passage acts on the pilot port. The oil pressure in the junction oil passage is substantially equal to the back pressure of the arm cylinder, and the opening of the switching throttle valve increases as the arm negative pressure increases.

Further, in the control circuit according to a third aspect of the present invention, in the circuit according to the first aspect, a pilot pressure of an arm pilot port is applied to a pilot port of the variable throttle valve to switch to a communication state by the arm pilot pressure. Instead, the opening degree increases as the arm load pressure increases. In this control circuit, the pilot port of the variable throttle valve is connected to the pilot output port of the arm remote control valve, and is switched to the communication state by the arm pilot pressure. When the arm load increases, the opening of the variable throttle valve also increases.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 1 shows a configuration of a control circuit according to a first embodiment of the present invention. Hereinafter, the elements already described in the related art (FIGS. 4 and 5) will be assigned the same reference numerals and detailed description thereof will be omitted. In FIG. 1, the first hydraulic pump 1 is connected to an arm cylinder 8 via an arm switching valve 3, and the second hydraulic pump 11 is connected to a boom cylinder 19 via a boom switching valve 13. A first branch circuit 21 branches from the center oil passage 12 downstream of the boom switching valve 13 and joins the input oil passage 6 of the arm switching valve 3 via the shuttle valve 22. The pressure oil flow rate of the merging oil passage 21 a is determined by the merging switching valve 1 provided downstream of the center oil passage 12.
4.

The second branch oil passage 23 branches from the downstream of the second hydraulic pump 11 and is connected to the merge oil passage 21a. A check valve 24 and a switching throttle valve 40 are provided on the second branch oil passage 23.
Is inserted. The pilot port 40a of the switching throttle valve 40 is connected to the junction oil passage 21a by an oil passage 41. When the pilot pressure is low, the switching throttle valve 40
In this state, the oil passage between the input and output ports is narrowed, and when the pilot pressure becomes equal to or higher than a predetermined pressure, the state becomes the state b, whereby the oil passage between the input and output ports is fully opened.

The first embodiment operates as follows in the horizontal pulling operation by the above configuration. That is, in the initial stage of the operation, the arm closing operation and the boom raising operation are performed simultaneously, and the extending operation of the arm cylinder 8 and the boom cylinder 1 are performed.
9 is performed. However, in the initial stage, the load on the arm is small, so that the back pressure of the arm cylinder 8 is low, and the oil pressure of the joining oil passage 21a does not increase. Therefore, the switching valve 40
Only low oil pressure acts on the pilot port 40a of
The switching throttle valve 40 is in the state a, and most of the pressure oil from the second hydraulic pump 11 flows into the boom cylinder 19 via the boom switching valve 13. As a result, the boom rises well,
There is no inconvenience such as the bucket 29 digging into the ground.

Next, at an intermediate stage of the operation, the load on the arm gradually increases. Further, at this stage, the arm 28 rotates, but the downward speed of the bucket 29 is low, and the boom raising speed may be low. The back pressure of the arm cylinder 8 increases due to an increase in the load on the arm, and the switching throttle valve 40
Transition from state to state b. For this reason, the second branch oil passage 2
3, the flow resistance decreases, and most of the pressure oil from the second hydraulic pump flows into the input port 8a of the arm cylinder 8 through the second branch oil passage 23. Therefore, the speed of the arm is increased, the work efficiency of the arm operation is improved, and the phenomenon of breathing does not occur. On the other hand, the boom cylinder cylinder 19
Since the flow rate of the pressure oil flowing into the boom decreases and the gain of the boom decreases, the boom operation does not feel fluffy.

As described above, in the first embodiment, when the hydraulic excavator is pulled horizontally, the prevention of the bite of the bucket, the fluffy feeling of the boom, and the breathing phenomenon are prevented, and the operability is improved. In addition, by accelerating the arm speed, the speed of the horizontal pulling operation is increased, and the work efficiency is improved. This effect is not limited to the horizontal pulling work. For example, when a high load is applied to the arm in excavation work or the like, the shortage of oil supply to the arm cylinder can be compensated, the required arm speed can be secured, and operability and work The efficiency is improved.
Further, since the switching throttle valve 40 is fully opened and the oil pressure loss is reduced, there is also an effect that the energy efficiency is improved.

<Embodiment 2> FIG. 2 shows a configuration of a control circuit according to Embodiment 2 of the present invention. Hereinafter, the elements already described in the related art (FIGS. 4 and 5) and the first embodiment are denoted by the same reference numerals, and detailed description is omitted. In FIG. 2, the first hydraulic pump 1 is connected to an arm cylinder 8 via an arm switching valve 3, and the second hydraulic pump 11 is connected to a boom cylinder 19 via a boom switching valve 13. The arm switching valve 3 and the boom switching valve 13 are operated by an arm remote control valve 33 and a boom remote control valve 32, respectively.

The first branch circuit 21 branches from the center oil passage 12 of the second hydraulic pump 11 from the downstream of the boom switching valve 13 and joins the input oil passage 6 of the arm switching valve 3 via the check valve 22. I have. Further, a second branch oil passage 23 branches from the downstream of the second hydraulic pump 11 and is connected to a merge oil passage 21a. Check valve 2 on second branch oil passage 23
4 and a variable throttle valve 43 are interposed. Variable throttle valve 43
The pilot port 43a is connected to the arm remote control valve via the shuttle valve 34 by an oil passage 44. The variable throttle valve 43 is configured to be switched to the communicating state (b) by the arm pilot pressure and to have a larger opening degree (opening area) as the pressure after passage, that is, the arm load pressure increases.

The second embodiment operates as follows in the horizontal pulling operation by the above configuration. That is, in the initial stage of the operation, the extension operation of the arm cylinder 8 and the extension operation of the boom cylinder 19 are performed. However, since the load on the arm is small in the initial stage, the pilot output pressure of the arm remote control valve 33 is low. Therefore, the oil passage between the input and output ports of the variable throttle valve 43 is closed or the throttle is large, and most of the hydraulic oil from the second hydraulic pump 11 is supplied to the boom switching valve 13.
Through the boom cylinder 19. As a result, the boom rises well, and there is no inconvenience such as the bucket 29 digging into the ground.

Next, at the intermediate stage of the operation, the variable throttle 43 is switched from the closed state (a) to the communicating state (b) due to the rise of the arm pilot pressure, and the load on the arm is gradually increased. The opening degree of the throttle of the variable throttle valve 43 is increased by the pressure after passing through the variable throttle valve 43, and the flow resistance of the second branch oil passage is reduced. Therefore, most of the pressure oil from the second hydraulic pump flows into the input port 8 a of the arm cylinder 8 through the second branch oil passage 23. Therefore, the speed of the arm is increased, the work efficiency of the arm operation is improved, and the phenomenon of breathing does not occur. On the other hand, the flow rate of the pressure oil flowing into the boom cylinder cylinder 19 decreases, and the gain of the boom decreases, so that the boom operation does not feel fluffy.

Therefore, in the second embodiment, the first embodiment
The same effect can be obtained. As described above, the embodiment of the present invention,
Although the embodiment has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and any change in the design without departing from the spirit of the invention is included in the invention. For example, the pilot port of the arm remote control valve may be connected to the pilot port of the switching throttle valve 40, or the pilot port of the variable throttle valve 43 may be connected to the junction oil passage 21a. (Claim 1).

[0029]

As described above, according to the structure of the present invention, it is possible to prevent the bucket from biting and the fluffy feeling of the boom in the work such as horizontal pulling, and at the same time to increase the speed of horizontal pulling. There is an effect that it can be achieved. Furthermore, since the throttle resistance is reduced when the arm load is large, there is an effect that energy loss due to pressure loss can be reduced.

[Brief description of the drawings]

FIG. 1 shows a configuration of a first embodiment of the present invention.

FIG. 2 shows a configuration of Embodiment 2 of the present invention.

FIGS. 3A and 3B are diagrams for explaining a horizontal pulling operation.

FIG. 4 is a diagram showing a configuration of a conventional circuit 1.

FIG. 5 is a diagram showing a configuration of a conventional circuit 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st hydraulic pump 2, 12 Center oil path 3 Arm cylinder switching valve 8 Arm cylinder 11 2nd hydraulic pump 13 Boom cylinder switching valve 14 Merging switching valve 19 Boom cylinder 21 1st branch oil path 21a Merging oil path 23 Second branch Oil passage 25 Fixed throttle 31 Switching throttle valve 32 Boom remote control valve 33 Arm remote control valve 40 Switching throttle valve 43 Variable throttle valve

Claims (3)

(57) [Claims] An arm cylinder connected to an oil passage of a first hydraulic pump via an arm switching valve, a boom cylinder connected to an oil passage of a second hydraulic pump via a boom switching valve, and downstream of the boom switching valve. A first branch oil passage is provided from the center oil passage of the second pump to be joined to the input oil passage of the arm switching valve, and a second branch oil passage is provided from the downstream of the second pump to be joined to the merged oil passage. In a control circuit of a hydraulic shovel in which a throttle valve is inserted in a branch oil passage, the throttle valve is a switching throttle valve or a variable throttle valve, and the throttle valve is controlled such that the opening increases as the arm load pressure increases. A hydraulic excavator control circuit. 2. The switching throttle valve, wherein the oil passage is throttled when the pilot pressure is low, and is fully opened when the pilot pressure becomes equal to or higher than a predetermined pressure. The hydraulic excavator control circuit according to claim 1, wherein the hydraulic pressure of the oil passage is applied. 3. The method according to claim 1, wherein a pilot pressure of an arm pilot port is applied to a pilot port of the variable throttle valve to switch to a communication state by the arm pilot pressure, and that the opening increases as the arm load pressure increases. The hydraulic shovel control circuit according to claim 1, wherein