JPH058323Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control circuit for controlling the operating speed of an arm in a hydraulic excavator.

[Conventional technology]

Conventionally, as a control circuit for a hydraulic cylinder, one of the two pipes connected to the oil chambers on the rod side and the head side of the hydraulic cylinder, for example, the pipe that becomes the discharge side from the hydraulic cylinder to the tank when reducing the load. A so-called slow return check valve is installed in the conduit connected to the rod side oil chamber, in which a check valve that only allows oil to flow into the hydraulic cylinder side (forward flow) and prevents its reverse flow, and a throttle are connected in parallel. something is known.

[The problem that the idea aims to solve]

According to the conventional circuit described above, when the directional control valve is switched and the discharge oil of the hydraulic pump is supplied to the head side oil chamber of the hydraulic cylinder to reduce the load, the hydraulic oil is discharged from the rod side oil chamber of the hydraulic cylinder. By restricting the discharge flow rate by the throttle, the influence of the load's own weight can be reduced, and the operating speed in the direction of lowering the load can be stabilized. However, since the hydraulic oil flowing out from the rod side oil chamber is always throttled by the throttle, the operating speed in the direction of lowering the load is almost constant, and even if the spool opening of the directional control valve is adjusted, the operating speed remains constant. It is difficult to change significantly.

By the way, when using a hydraulic excavator, it is required to work in a low speed range by slowing down the operating speed of the hydraulic cylinder for the arm, especially the operating speed of arm pulling, during ground leveling work, and to be able to perform delicate speed control in that low speed range. When excavating, it is necessary to operate the arm hydraulic cylinder in a high speed range and shorten the arm operation cycle time as much as possible. However, with the above conventional slow return check valve, the operating speed of the arm pull is constant, and it is difficult to arbitrarily and significantly change the operating speed of the arm pull, so it is difficult to perform the above-mentioned land leveling work. It has been difficult to satisfy all requirements for excavation work, river excavation work, and other work.

It is known that the above-mentioned diaphragm is a variable diaphragm, and the opening degree of the diaphragm can be adjusted. However, it is difficult to significantly change the operating speed between a high speed range and a low speed range only by adjusting the variable throttle.

In view of these points, the present invention allows the operating speed of the hydraulic cylinder for the arm to be significantly changed with a simple circuit configuration, and is suitable for land leveling work that requires delicate speed control in the low speed range when working with a hydraulic excavator. We also provide arm operating speed control circuits for hydraulic excavators that can efficiently carry out excavation work on rivers and other various types of work that require speed control in high-speed ranges, in optimal conditions depending on the work. It is something to do.

[Means for solving problems]

The present invention is a hydraulic excavator in which a boom, an arm, and a bucket are installed at the front of the vehicle body so that they can rotate freely using hydraulic cylinders. An arm directional control valve consisting of a neutral block type three-position switching valve that controls the rotation of the arm by controlling the flow direction and flow rate of pressure oil to the cylinder is provided, and the arm directional control valve and the arm hydraulic pressure are Of the two pressure oil supply and discharge pipes connecting the cylinder, a logic valve is connected in the middle of the pipe from which oil is discharged from the arm hydraulic cylinder when the arm is rotated in the pulling direction. That's what it is,
The logic valve includes a valve body having a first passage and a second passage, a poppet slidably inserted into the intersection of the first passage and the second passage within the valve body, and a poppet whose tip is connected to the first passage. a spring that presses against a valve seat provided on the side and biases the valve in the valve closing direction; the first passage of the logic valve is connected to a conduit on the arm directional control valve side, and the second passage is connected to the arm hydraulic cylinder side. An electromagnetic switching valve is provided between the pilot passage taken out from the second passage of the logic valve and the pilot passage taken out from the spring chamber on the back of the poppet. a first control position that guides pressure in the passageway to the spring chamber to bias the poppet in the valve-closing direction, thereby allowing forward flow of oil from the first passageway to the second passageway and preventing backflow thereof; The spring chamber is configured to communicate with the tank and can be freely switched to a second control position that allows both forward flow and reverse flow, and furthermore, a first passage and a second passage are provided in the valve body of the logic valve. The device is characterized in that a bypass passage is provided that is communicated at all times, and that this bypass passage is provided with a restriction.

[Effect]

According to the above configuration, if the electromagnetic switching valve is held in the first control position, the oil discharged from the arm hydraulic cylinder will not flow backward through the logic valve, but will flow through the bypass passage to the arm directional control valve side. As a result, the discharge flow rate is restricted by the throttle, and the arm operation in the low speed range can be performed with high precision.
Also, when the electromagnetic switching valve is switched to the second control position,
The oil discharged from the arm hydraulic cylinder smoothly flows back through the logic valve and flows out to the arm directional control valve side without being subjected to the throttling action of the bypass passage, allowing work to be performed efficiently in the high-speed range. In other words, by switching the switching valve, the work speed can be changed significantly, such as working in a low speed range or working in a high speed range.
Efficiently perform both land leveling work, which requires delicate speed control at low speeds, river excavation work, and other various tasks, which require speed control at high speeds, in the optimal state according to the work content. Can perform well.

〔Example〕

FIG. 1 shows an embodiment of a logic valve used in the control circuit of the present invention. In the figure, 1 is a logic valve, and a first
A poppet 6 is slidably disposed via a sleeve 5 at the intersection of the passage 3 and a second passage 4 provided on the outlet side, and a valve seat 7 is provided with the tip of the poppet 6 on the first passage 3 side. It is biased by a spring 8 so as to be pressed against it.

In the above logic valve 1, in this embodiment,
In particular, a bypass passage 9 is provided between the first passage 3 and the second passage 4 to constantly communicate the two passages, and a valve body 11 having a throttle hole 10 is replaceably installed in the bypass passage 9. The pilot port 12 communicates with the spring chamber on the back of the poppet 6, and the second
An electromagnetic switching valve 16 is connected to a pilot port 13 communicating with the passage 4 via pilot pipes 14 and 15.

The electromagnetic switching valve 16 has a first control position 16a that guides the pressure in the second passage 4 to the back of the poppet 6 and a second control position that communicates the back of the poppet 6 with the tank 17 by operating a switch installed in the driver's cab or the like. control position 16
It is provided so that it can be freely switched between 18 is a plug. Note that this electromagnetic switching valve 16 is switched by operating a switch installed in the operator's cab, etc., and is installed between the pilot pipes 14 and 15, so it is small and has a small capacity. can be used.

According to the above configuration, the following control can be performed by switching the electromagnetic switching valve 16.

A When the electromagnetic switching valve 16 is in the first control position 16a, the flow from the first passage 3 to the second passage 4 (forward flow) is freely allowed, but the flow from the second passage 4 to the first passage 3 is allowed. (backflow), with the poppet 6 closed by the pilot pressure from the second passage 4,
It passes only through the throttle hole 10, and the flow rate of the reverse flow is throttled.

B When the electromagnetic switching valve 16 is switched to the second control position 16b, the flow (forward flow) from the first passage 3 to the second passage 4 is freely allowed, the back side of the poppet 6 is communicated with the tank 17, and the second Flow (backflow) from the passage 4 to the first passage 3 is also freely allowed.

That is, for forward flow, the solenoid switching valve 16 is freely allowed in any position, but for reverse flow, the switching valve 16 is set to the first control position 16a.
When the flow rate is at the second control position 16b, the flow rate passing through the throttle hole 10 is controlled to be restricted, and when the control position is at the second control position 16b, the backflow is freely allowed. In other words, two types of control are possible for backflow. In this case, by replacing the valve body 11 and changing the opening area of the throttle hole 10, the amount of throttle at the time of backflow can be arbitrarily set.

In addition, as shown in FIG.
If the valve element 11' having a diameter of 0' is mounted so as to be adjustable in its position in the axial direction, and the opening area of the variable throttle part 10' can be adjusted from the outside, the switching valve 16 can be
The amount of throttling for backflow at the control position 16a can be easily and arbitrarily changed, and the control range can be expanded to further enhance the utility value. The shape of the variable throttle portion 10' is not limited to an inclined surface, but may be an inclined groove, and the throttle effect may be adjusted by adjusting the position or rotation of the valve body 11' in the axial direction.

Next, a specific example in which the above circuit is used in an arm circuit of a hydraulic excavator will be described.

FIG. 4 shows an example of a hydraulic excavator, which includes a traveling body 20, a revolving body 21, a boom 23 that is lifted up and down by a boom hydraulic cylinder 22, and an arm hydraulic cylinder 24.
The arm 25 is rotated by the arm 25, and the bucket 27 is rotated by the bucket hydraulic cylinder 26.
It is equipped with.

FIG. 3 shows a control circuit in which the control circuit shown in FIG. 1 is incorporated into the control circuit for the arm hydraulic cylinder 24 of the hydraulic excavator shown in FIG. 4. In FIG. That is, this control circuit is configured so that the oil discharged from the hydraulic pump 28 can be supplied to the rod-side oil chamber 24a and the head-side oil chamber 24b of the arm hydraulic cylinder 24 by switching the arm directional control valve 29. ,and,
Pipe line 3 connected to each oil chamber 24a, 24b
A control circuit shown in FIG. 1 is provided in the pipe line 30, which is the discharge side from the cylinder when the arm is pulled. In this case, the first passage 3 of the logic valve 1 is connected to the directional control valve 29 side, and the second passage 4 is connected to the hydraulic cylinder 24 side.

According to the above control circuit, when it is desired to perform arm pulling work in a low speed range, such as when leveling the ground, the electromagnetic switching valve 16 is moved to the first control position 16a shown in the figure.
Keep it in.

In this state, when the arm directional control valve 29 is switched to the lower position in the figure, the oil discharged from the hydraulic pump 28 is guided to the head side oil chamber 24b of the hydraulic cylinder 24,
The hydraulic cylinder 24 is extended and the arm 25 shown in FIG. 4 is rotated clockwise to perform an arm pulling operation. At this time, the poppet 6 of the logic valve 1 is closed by the pressure of the oil discharged from the rod side oil chamber 24a of the hydraulic cylinder 24, and the oil discharged from the rod side oil chamber 24a flows through the throttle hole of the bypass passage 9. 10, and the discharge flow rate is restricted. For this reason, the hydraulic cylinder 2
The maximum speed of extension speed No. 4 is controlled to be slow, and the arm pulling work is performed smoothly in a low speed range suitable for ground leveling work.

Next, when it is desired to perform arm pulling work in a high-speed range, such as excavation work in a river, the switching valve 16 is switched to the second control position 16b.

In this state, when the arm directional control valve 29 is switched to the lower position in the drawing, the hydraulic pump 28
The discharged oil is led to the head side oil chamber 24b of the hydraulic cylinder 24, and the hydraulic cylinder 24 is extended to perform the arm pulling operation. At this time, the spring chamber on the back side of the poppet 6 is communicated with the tank 17. Therefore, the oil discharged from the rod-side oil chamber 24a of the hydraulic cylinder 24 flows not only through the throttle hole 10 of the bypass passage 9 but also from the second passage 4 of the logic valve 1 to the first passage 3 while opening the poppet 6. leak. Therefore, compared to the case of the above-mentioned ground leveling work, the throttling effect on the oil discharged from the rod side oil chamber 24a is small, the discharge flow rate is increased, and the upper limit value of the extension speed of the hydraulic cylinder 24, that is, the operating speed of arm pulling is increased. . This makes it possible to work in a high-speed range and shorten the work cycle time.

In addition, in each of the above operations, the spool opening degree is adjusted by operating the lever of the arm directional control valve 29, and the head side oil chamber 2 of the arm hydraulic cylinder 24 is adjusted.
By adjusting the amount of oil supplied to the rod side oil chamber 4b and the discharge flow rate from the rod side oil chamber 24a to the tank, the extension speed of the arm hydraulic cylinder 24, that is, the arm pulling operation speed can be controlled by adjusting the opening area of the throttle hole 10 or the poppet 6. can be controlled arbitrarily within the upper limit determined by Particularly, when working in a low speed range such as when leveling the ground, detailed control is possible by operating the lever of the arm directional control valve 29.

By simply switching the electromagnetic switching valve 16 in this way,
Work in low speed ranges that require delicate control such as land leveling work, work in high speed ranges that require fast cycle times such as river excavation work, and various other types of work. Each can be done efficiently and at a speed appropriate to the content.

In addition, if a bypass passage 9 with a variable throttle is installed in the logic valve 1 as shown in Fig. 2 in the arm circuit described above, the variable Aperture 10'
By adjusting the amount of throttle, the upper limit of the arm pulling speed can be set arbitrarily and steplessly.
You can work at the optimal speed range according to the task.

[Effect of idea]

As described above, according to the present invention, by simply switching the electromagnetic switching valve, the maximum value of the flow rate in the reverse flow direction can be set to two states, one in which the throttling effect of the bypass passage, which is arbitrarily set in advance, is exerted and the other in which it is not exerted. The type can be arbitrarily selected, and the operating speed in the arm pulling direction by the arm hydraulic cylinder can be significantly changed between a low speed range and a high speed range.

When working in a low speed range, such as during ground leveling work with a hydraulic excavator, the above-mentioned throttling effect can be used to perform delicate speed control and work smoothly.
Further, when working in a high-speed region such as excavating in a river, the work speed can be increased without exerting the above-mentioned throttling effect, and work efficiency can be greatly improved. Moreover, in each of the above operations, the discharge flow rate from the arm hydraulic cylinder to the tank can be easily adjusted by controlling the flow rate with the directional control valve within the range of the maximum value of the flow rate in the reverse flow direction. Each type of work, from high-speed to high-speed, can be carried out efficiently under optimal conditions according to the content of each work.

Furthermore, the above control can be achieved with a simple circuit such as providing a bypass passage with a restriction in a commercially available logic valve and adding an electromagnetic switching valve. Since it is installed in the conduit, it can be small and small in capacity, can be implemented very simply and at low cost, and has excellent controllability and practicality.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a logic valve showing an embodiment of the present invention and an explanatory diagram of the main part of the circuit in which a switching valve is combined;
The drawings are a diagram corresponding to FIG. 1 showing another embodiment, FIG. 3 is a hydraulic circuit diagram showing an embodiment of the present invention, and FIG. 4 is a side view showing an example of a hydraulic excavator. 1...Logic valve, 2...Valve body, 3...First
Passage, 4...Second aisle, 6...Poppet, 8...
Spring, 9... Bypass passage, 10... Throttle hole, 1
0'...Variable throttle part, 11, 11'...Valve body, 1
2, 13...Pilot port, 16...Switching valve, 16a...First control position, 16b...Second control position, 17...Tank.

Claims (1)

[Scope of utility model registration request] In a hydraulic excavator, a boom, an arm, and a bucket are installed at the front of the vehicle body so that they can rotate freely using hydraulic cylinders. An arm directional control valve consisting of a neutral block three-position switching valve that controls the rotation of the arm by controlling the direction and flow rate of oil flow is provided, and the arm directional control valve is connected to the arm hydraulic cylinder. Of the two pressure oil supply and drainage pipes,
A logic valve is connected to the middle of the pipe that is the discharge side of the oil from the arm hydraulic cylinder when the arm is rotated in the pulling direction, and the logic valve is connected to the first passage and the second passage. a poppet slidably inserted into the intersection of the first passage and the second passage within the valve body, and a valve closing direction in which the tip of the poppet comes into pressure contact with a valve seat provided on the first passage side. and a spring biasing the first logic valve.
The passage is connected to the pipe line on the side of the arm directional control valve, and the second
The passages are connected to the pipes on the arm hydraulic cylinder side, and an electromagnetic switching valve is provided between the pilot passage taken out from the second passage of the logic valve and the pilot passage taken out from the spring chamber on the back of the poppet. The electromagnetic switching valve allows the forward flow of oil from the first passage to the second passage and prevents the reverse flow by guiding the pressure of the second passage to the spring chamber and biasing the poppet in the valve closing direction. a first control position to
The spring chamber is configured to communicate with the tank and can be freely switched to a second control position that allows both forward flow and reverse flow, and the valve body of the logic valve further includes a first passage and a second passage. 1. An operating speed control circuit for an arm in a hydraulic excavator, characterized in that a bypass passage is provided for constant communication between the arms, and a throttle is provided in the bypass passage.