JPH09165798A - Hydraulic circuit for working machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic circuit which is capable of achieving a combined operation where an arm is operated at a high speed while a boom is operated at a low speed even with both of a directional control valve for arm operation and a directional control valve for boom operation operated at a full control input. SOLUTION: A directional control valve 7a for arm operation connected to a first oil-hydraulic pump 2 for controlling an arm cylinder 7, a directional control valve 11a for boom operation connected to a second oil hydraulic pump 3 for controlling a boom cylinder 11 are provided. A connecting line 26 connecting the upstream side of the directional control valve 11a for boom operation and an input port of the directional control valve 7a for arm operation is provided. A check valve 28 provided at the connecting line 26 on a point between a throttle valve 27a provided at the connecting line 26 and the input port of the directional control valve 7a for arm operation and allows oil to flow in the direction from the throttle valve 27 to the input port of the directional control valve 7a for arm operation while checking the oil flowing in the reverse direction is provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a boom cylinder,
The present invention relates to a hydraulic circuit of a work machine such as a mini excavator that has an arm cylinder and is capable of performing horizontal pull-in excavation work in which, in addition to normal excavation work, the tip of an arm is moved horizontally to perform excavation work.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a first example of a hydraulic circuit of a conventional working machine of this type, and FIG. 4 is a side view showing a working machine, that is, a mini excavator provided with the hydraulic circuit shown in FIG. Is. The conventional hydraulic circuit shown in FIG.
And a first hydraulic pump 2, a second hydraulic pump 3, and a third hydraulic pump 3a driven by the engine 1.
And a plurality of actuators driven by the pressure oil discharged from these hydraulic pumps 2, 3, 3a, for example, an earth plate cylinder 4, a turning motor 5, a left traveling motor 6, an arm cylinder 7, a bucket cylinder 9, a swing. Cylinder 1
0, a boom cylinder 11, and a right traveling motor 12.

The above-mentioned soil discharging plate cylinder 4 controls the raising / lowering operation of the soil discharging plate 32 shown in FIG. 4, and the left traveling motor 6 and the right traveling motor 12 control the traveling of a pair of crawler tracks, that is, the traveling body 30, The swing motor 5 controls the swing of the main body having the driver's seat arranged on the traveling body 30, that is, the swing body 31, the boom cylinder 11 controls the vertical swing movement of the boom 33, and the arm cylinder 7 is the arm. The bucket cylinder 9 controls the vertical rotation operation of the bucket 35. Further, the boom cylinder 11, the arm cylinder 7, and the bucket cylinder 9 described above constitute a front actuator, and the swing cylinder 10 includes the boom 33 and the arm 3.
4. Control the swinging movement of the front of the bucket 35 in the horizontal direction.

Further, as shown in FIG. 3, a left traveling motor 6 is provided on the bypass line communicating with the first hydraulic pump 2.
Driving direction control valve 6a for controlling the drive of the vehicle, an arm direction control valve 7a for controlling the drive of the arm cylinder 7, and a spare direction control valve for controlling a spare actuator that drives a special actuator that is mounted only when necessary. 8
a is connected. Further, in the center bypass line of the second hydraulic pump 3, a right traveling directional control valve 12a that controls the drive of the right traveling motor 12, a boom directional control valve 11a that controls the drive of the boom cylinder 11, and a swing cylinder 10 are provided. Swing directional control valve 10 for controlling the drive of the
a, a bucket direction switching valve 9a for controlling the drive of the bucket cylinder 9 is connected. Further, in the center bypass line of the third hydraulic pump 3a, there are an earth-discharging-plate directional switching valve 4a for controlling the drive of the earth-discharging-plate cylinder 4 and a turning direction switching valve 5a for controlling the driving of the turning motor 5. It is connected.

Among the operations performed in the conventional hydraulic circuit, for example, in the case of excavation work by combined arm / boom operation, the corresponding arm directional control valve 7a and boom directional control valve 11a are switched. As a result, the pressure oil of the second hydraulic pump 3 is supplied to the boom cylinder 11 via the boom direction switching valve 11a, and the first hydraulic pump 2
Is supplied to the arm cylinder 7 via the arm direction switching valve 7a, and the boom 33 and the arm 34 shown in FIG.
Can be rotated to perform a desired arm / boom combined operation, and excavation work of earth and sand can be performed.

Further, in the mini excavator as shown in FIG. 4, in addition to the normal excavation work described above, a horizontal pull-in excavation work in which the tip of the arm 34 is moved horizontally to perform excavation may be carried out. is there. In this horizontal pull-in excavation work, the combined operation of the arm and boom is performed.
At this time, the raising speed of the boom 33 is slower than the retracting speed of the arm 34, so that the boom direction switching valve 1
Hold the boom lever that switches 1a to the half lever (the operation amount that is smaller than the full operation amount), and set the boom cylinder 11
The flow rate to be supplied to the armature is made smaller than that at the time of the normal excavation described above, whereby a fine operation for matching and moving the arm 34 and the boom 33 is performed.

FIG. 5 shows a second hydraulic circuit of a conventional working machine.
FIG. 4 is a circuit diagram showing an example of the embodiment. The second conventional example shown in FIG. 5 includes a first hydraulic pump 2 and a second hydraulic pump 3, and, like the first conventional example shown in FIG. 3,
Excavation plate cylinder 4, turning motor 5, left traveling motor 6,
The arm cylinder 7, the bucket cylinder 9, the swing cylinder 10, the boom cylinder 11, and the right traveling motor 12 are provided.

As shown in FIG. 5, on the center bypass line communicating with the first hydraulic pump 2, the earth shunt directional control valve 4a, the turning directional control valve 5a, the left traveling directional control valve 6a, The arm directional control valve 7a and the standby directional control valve 8a are connected. The center bypass line of the second hydraulic pump 3 is connected to the right traveling directional switching valve 12a, the boom directional switching valve 11a, the swing directional switching valve 10a, and the bucket directional switching valve 9a, and is connected to the merging conduit. The arm directional control valve 7a and the standby directional control valve 8a are connected via 21. That is, the pressure oil of the first hydraulic pump 2 and the pressure oil of the second hydraulic pump 3 can be merged and supplied to the arm direction switching valve 7 a via the merge conduit 21.

In the second conventional example, for example, in the case of excavation work by combined arm / boom operation, the corresponding arm directional control valve 7a and boom directional control valve 11a.
By switching the full operation amount, the supply of pressure oil from the second hydraulic pump 3 to the merging conduit 21 is blocked. Therefore, the pressure oil of the second hydraulic pump 3 is transferred to the boom directional control valve 1
1a is supplied to the boom cylinder 11, the pressure oil of the first hydraulic pump 2 is supplied to the arm cylinder 7 via the arm directional switching valve 7a, and a desired arm / boom combined operation is performed to remove soil and sand. Excavation work can be performed.

Further, when the arm is operated independently, by switching the arm directional control valve 7a, the pressure oil of the first hydraulic pump 2 is supplied to the arm directional control valve 7a.
The pressure oil of the second hydraulic pump 3 is supplied to the arm directional control valve 7a via the merging conduit 21. That is, the combined pressure oils of the first and second hydraulic pumps 2 and 3 are supplied to the arm cylinder 7 via the arm direction switching valve 7a, and the operating speed of the arm cylinder 7 is increased to increase the arm speed. 34
The working speed of can be increased.

Further, when performing the horizontal pull-in excavation work as described above, in order to slow the raising speed of the boom 33 relative to the pull-in speed of the arm 34, the boom direction switching valve 11a is switched. It is necessary to keep the lever for a half lever and perform a fine operation to reduce the flow rate supplied to the boom cylinder 11 as compared with the above-described normal excavation.

[0012]

In the first conventional example shown in FIG. 3 described above, the boom direction switching valve 11 is used in the combined operation of the arm and the boom in the horizontal pulling and excavating work.
The half lever is used as the boom lever that switches a, the flow rate supplied from the second hydraulic pump to the boom cylinder 11 is made smaller than that during normal excavation, and the remaining pressure oil of the second hydraulic pump 3 is discarded in the tank. It is like this. Therefore, in the first example of the related art, there is a problem in that the energy loss becomes large and uneconomical.

Further, in the above-mentioned second example shown in FIG. 5,
In order to perform fine operation in horizontal pull-in excavation work,
If the boom lever is kept at the half lever, the boom directional control valve 11a cannot be closed completely. As a result, a part of the pressure oil of the second hydraulic pump 3 merges with the pressure oil of the first hydraulic pump 2 through the center bypass line and the merging pipe line 21 which are continuous with the second hydraulic pump 3 and the arm. It is supplied to the direction switching valve 7a. That is, the arm cylinder 7 is driven by the pressure oil merged by the first and second hydraulic pumps 2, 3. Therefore, even if the operation amount of the boom lever is slightly changed, the flow rate supplied to the arm cylinder 7 via the arm direction switching valve 7a is changed, and the arm cylinder 7 is changed.
The operating speed of, that is, the working speed of the arm 34 suddenly changes. Therefore, there is a problem in that this horizontal pull-in excavation work becomes difficult and the work accuracy is likely to deteriorate.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and its object is to perform an arm / boom combined operation for making the working speed of the arm relatively high and the working speed of the boom relatively slow. Another object of the present invention is to provide a hydraulic circuit for a working machine that can be realized by setting the operation amounts of the arm directional control valve and the boom directional control valve to full operation amounts.

[0015]

In order to achieve the above object, the present invention provides a first and a second hydraulic pump, an arm cylinder and a boom cylinder, and a center bypass line connected to the first hydraulic pump. And a pressure control valve for controlling the flow of pressure oil supplied to the arm cylinder and a center bypass line connected to the second hydraulic pump, the pressure oil supplied to the boom cylinder. Equipped with a directional control valve for the boom to control the flow of
In a hydraulic circuit of a working machine capable of combined arm / boom operation, a connection conduit for connecting an upstream portion of the boom directional control valve and an input port of the arm directional control valve is provided, and the connection conduit is also provided. The throttle means provided on the connecting pipe line portion located between the throttle means and the input port of the arm directional control valve, and from the throttle means side to the input port direction of the arm directional control valve. And a check valve that allows the oil flow to and from preventing the oil flow in the opposite direction.

According to the present invention, when the boom working speed is desired to be relatively high as in the case of normal excavation work, for example, the throttle amount of the throttle means is increased in advance and the opening area thereof is set smaller. Just keep it. It is empirically known that in normal excavation work and horizontal pull-in excavation work to be described later, the load pressure on the arm side is generally lower than the load pressure on the boom side. Therefore, in the above-described state, when the arm directional control valve and the boom directional control valve are switched by full operation amounts, the pressure oil of the first hydraulic pump is supplied to the arm directional control valve and the second hydraulic pump. A considerable amount of the pressure oil of the second hydraulic pump is supplied to the boom cylinder via the direction switching valve for the boom, and the remaining amount of the pressure oil of the second hydraulic pump, that is, a relatively small flow rate, is supplied to the connection conduit, the throttle means, and the reverse. It is supplied to the arm directional control valve via the stop valve. That is, in the arm cylinder, a combined flow rate of the pressure oil of the first hydraulic pump and a relatively small flow rate of a part of the pressure oil of the second hydraulic pump corresponding to the small opening area of the throttle means is joined. Is supplied. By this operation, the operating speed of each of the arm cylinder and the boom cylinder can be made relatively high, and a composite operation can be performed in which each of the arm and the boom is driven at a relatively high working speed suitable for normal excavation work.

Unlike the normal excavation work described above, an arm / boom in which the work speed of the arm is made relatively high and the work speed of the boom is made slower than in the normal excavation work, as in the horizontal pull-in excavation work. When performing a combined operation, the amount of throttle of the throttle means may be reduced in advance and the opening area thereof may be set to be larger than in the case of the normal excavation work described above. In this state, when the arm directional control valve and the boom directional control valve are switched by full operation amounts, the pressure oil of the first hydraulic pump is supplied to the arm directional control valve, and the pressure oil of the second hydraulic pump is supplied. A part of the flow rate is supplied to the boom cylinder via the boom directional control valve, and a considerable amount of pressure oil of the second hydraulic pump, A larger flow rate than in the case of the normal excavation work described above is supplied to the arm directional control valve via the connection conduit, the throttle means, and the check valve. That is, in the arm cylinder, the combined flow rate of the pressure oil of the first hydraulic pump and a relatively large amount of the pressure oil of the second hydraulic pump, which is a relatively large flow rate corresponding to the large opening area of the throttle means. Is supplied. By this operation, the operating speed of the arm cylinder can be made relatively high, the operating speed of the boom cylinder can be made relatively low, and a combined operation suitable for horizontal retraction work in which the arm is moved fast and the boom is moved slowly can be performed.

As described above, according to the present invention, the throttling amount of the throttling means of the connection conduit is taken into consideration, so that even if both the arm directional control valve and the boom directional control valve are switched to full operating amounts, the arm It is possible to realize an arm / boom combined operation in which the work speed is relatively high and the boom work speed is relatively slow.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a hydraulic circuit for a working machine according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a first embodiment of a hydraulic circuit for a working machine according to the present invention.

FIG. 1 is drawn corresponding to the hydraulic circuit shown in FIG. That is, the first shown in FIG.
The embodiment of the present invention is also provided in, for example, a mini excavator, and includes an engine 1, a first hydraulic pump 2, a second hydraulic pump 3, and a third hydraulic pump 3a, a cylinder 4 for a dump plate, and a swing. A motor 5, a left traveling motor 6, an arm cylinder 7, a bucket cylinder 9, a swing cylinder 10, a boom cylinder 11, and a right traveling motor 12 are provided.

Further, on the bypass line communicating with the first hydraulic pump 2, a left traveling directional control valve 6a, an arm directional control valve 7a, and a standby directional control valve 8a are connected. Further, to the center bypass line of the second hydraulic pump 3, a right traveling directional control valve 12a, a boom directional control valve 11a, a swing directional control valve 10a, and a bucket directional control valve 9a are connected. Further, an earth discharging plate directional switching valve 4a and a turning directional switching valve 5a are connected to the center bypass line of the third hydraulic pump 3a. The above configuration is equivalent to that shown in FIG.

In the first embodiment, in particular, the connecting conduit 26 connecting the upstream portion of the boom directional control valve 11a and the input port of the arm directional control valve 7a downstream of the load check valve 25. And a throttle means provided in the connection conduit 26, for example, a throttle valve 27, and a connection conduit 26 portion located between the throttle valve 27 and the input port of the arm directional control valve 7a. A check valve 28 is provided which allows the oil flow from the throttle valve 27 toward the input port of the arm direction switching valve 7a and blocks the oil flow in the opposite direction.

In the first embodiment, when it is desired to make the boom work speed relatively high as in the case of normal excavation work, for example, the throttle amount of the throttle valve 27 is increased in advance and the opening area thereof is decreased. You can set it to. It is empirically known that in normal excavation work and horizontal pull-in excavation work to be described later, the load pressure on the arm side is generally lower than the load pressure on the boom side. Therefore, in the above state, when the arm lever for operating the arm direction switching valve 7a and the boom lever for operating the boom direction switching valve 11a are switched to the full lever (full operation amount), respectively, the first hydraulic pressure is changed. The pressure oil of the pump 2 is supplied to the arm directional control valve 7a. A considerable amount of the pressure oil of the second hydraulic pump 3 is supplied to the boom cylinder 11 via the boom direction switching valve 11a. In addition, the remaining amount of the pressure oil of the second hydraulic pump 3 that is not supplied to the boom cylinder 11, that is, a relatively small flow rate, changes the direction of the arm by way of the connection pipe line 26, the throttle valve 27, and the check valve 28. It is supplied to the valve 7a. That is, in the arm cylinder 7, the pressure oil of the first hydraulic pump 2 and a part of the pressure oil of the second hydraulic pump 3 have a relatively small flow rate corresponding to the small opening area of the throttle valve 27. The combined flow rate is supplied. Thereby, the arm cylinder 7 and the boom cylinder 1
It is possible to carry out a combined operation in which the operating speed of each of the two is relatively high, and each of the arm and the boom is driven at a relatively high operating speed compatible with a normal excavation operation.

Unlike the normal excavation work described above, an arm / boom in which the work speed of the arm is relatively high and the work speed of the boom is slower than that of the normal excavation work as in the horizontal pull-in excavation work. When performing the combined operation, the throttle amount of the throttle valve 27 may be made small in advance so that the opening area thereof is set to be larger than that in the case of the normal excavation work described above. In this state,
When the arm lever and the boom lever are respectively switched to full levers, the pressure oil of the first hydraulic pump 2 is supplied to the arm direction switching valve 7a. A part of the pressure oil of the second hydraulic pump 3, that is, a flow rate smaller than that in the case of the normal excavation work described above, is supplied to the boom cylinder 11 via the boom direction switching valve 11a. Further, a considerable amount of the pressure oil of the second hydraulic pump 3, that is, a flow rate larger than that in the case of the above-described normal excavation work, is switched to the arm direction via the connection conduit 26, the throttle valve 27, and the check valve 28. It is supplied to the valve 7a. That is, in the arm cylinder 11, the pressure oil of the first hydraulic pump 2 and a considerable amount of the pressure oil of the second hydraulic pump 3 merge with a relatively large flow rate corresponding to a large opening area of the throttle valve 27. The supplied flow rate is supplied. By this operation, the operating speed of the arm cylinder 7 is made relatively high,
The operation speed of the boom cylinder 11 can be made relatively slow, and the arm can be retracted quickly, and the combined operation suitable for horizontal retracting excavation work in which the boom is slowly raised can be performed.

As described above, in the first embodiment, the setting of the throttle amount of the throttle valve 27 of the connecting conduit 26 is considered according to the type of work, so that the arm directional control valve 7a,
Even when both the boom direction switching valves 11a are switched to full operation amounts, the arm working speed can be made relatively high and the boom working speed can be made relatively slow, and horizontal pulling excavation work can be realized. it can. Therefore, in the combined operation of the arm and boom in this horizontal pull-in excavation work, it is not necessary to keep the boom lever for switching the boom direction switching valve 11a at the half lever, so that the pressure oil of the second hydraulic pump 3 is transferred to the tank. Never throw away
Therefore, it is economical with less energy loss.

Further, during the horizontal pull-in excavation work, the boom lever may be held at the full lever like the arm lever. Therefore, during the horizontal pull-in excavation work, the operation amount of the boom lever changes. There is little concern, and there is no sudden change in the working speed of the arm 34 due to the change in the flow rate supplied to the arm cylinder 7 via the arm directional switching valve 7a. It becomes easy and high working accuracy can be obtained.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. In the second embodiment, the diaphragm means arranged in the connection conduit 26 is constituted by the variable diaphragm 27a. Other configurations are the same as those of the first embodiment shown in FIG. 1 described above.

In the second embodiment, adjustment of the throttle amount of the variable throttle is easy, and the arm cylinder 7 and the boom cylinder 11 suitable for various work modes including normal excavation work and horizontal pull-in excavation work. The relationship of the operating speed can be easily obtained, and a change from one specific work such as a normal excavation work to another specific work such as a horizontal pull-in work can be performed in a short time.

[0029]

According to the present invention, the arm / boom combined operation for making the arm working speed relatively fast and the boom working speed relatively slow can be performed by operating the arm directional switching valve and the boom directional switching valve. It can also be realized by setting the amount to the full operation amount.Therefore, it is not necessary to maintain the boom directional control valve at the half operation amount in the combined operation of the arm and boom in the horizontal pull-in excavation work.
During this horizontal pull-in excavation work, the pressure oil of the second hydraulic pump is not thrown into the tank, and the energy loss is smaller than in the conventional case, which is economical. Further, during horizontal pull-in excavation work, the boom directional control valve only needs to be kept at the full operation amount, so during such horizontal pull-in excavation work,
There is almost no concern that the operation amount of the boom directional control valve will change, and the change in the flow rate of the arm cylinder will not cause a sudden change in the working speed of the arm. It becomes easy to carry out, and it is possible to obtain higher working accuracy than in the past.

[Brief description of the drawings]

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

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

FIG. 3 is a circuit diagram showing a first example of a hydraulic circuit of a conventional work machine.

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

FIG. 5 is a circuit diagram showing a second conventional example.

[Explanation of symbols]

 2 1st hydraulic pump 3 2nd hydraulic pump 7 Arm cylinder 7a Arm directional switching valve 11 Boom cylinder 11a Boom directional switching valve 26 Connection line 27 Throttle valve (throttle means) 27a Variable throttle (throttle means) 28 Reverse Stop valve

Claims (3)

[Claims] 1. A first and a second hydraulic pump, an arm cylinder and a boom cylinder, and a center bypass line which is connected to the first hydraulic pump, and which distributes a flow of pressure oil supplied to the arm cylinder. An arm directional control valve that is arranged on a center bypass line that is connected to the second hydraulic pump and that controls the flow of pressure oil supplied to the boom cylinder; In a hydraulic circuit of a work machine capable of combined boom operation, a connection pipe for connecting an upstream portion of the boom directional control valve and an input port of the arm directional control valve is provided and provided in the connection pipeline. And a throttle means provided in the connecting conduit portion located between the throttle means and the input port of the directional control valve for arm, and the throttle means from the throttle means side. A hydraulic circuit for a working machine, comprising: a check valve that allows the flow of oil in the direction of the input port of the directional control valve for the boom and blocks the flow of oil in the opposite direction. 2. The hydraulic circuit for a working machine according to claim 1, wherein the throttle means is a throttle valve. 3. The hydraulic circuit for a working machine according to claim 1, wherein the throttle means is a variable throttle.