JP3403535B2 - Control equipment for construction machinery - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for construction machines such as hydraulic excavators, and more particularly to controlling the maximum drive pressure of an actuator in accordance with a switching operation of a flow rate control valve having a bleed-off throttle. The present invention relates to a control device for a construction machine capable of performing.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram showing a conventional controller for a construction machine. This prior art is, for example, a control device provided in a hydraulic excavator, and as shown in FIG. 5, a prime mover 1, a main pump driven by the prime mover 1, that is, a variable displacement hydraulic pump 3, and a pilot pump 1.
16, a pump regulator 2 for controlling the discharge flow rate of the hydraulic pump 3, an unload valve 11 connected to the discharge pipe line 101 of the hydraulic pump 3, and a main relief valve 10.

Further, actuators such as a boom cylinder 81, an arm cylinder 82, and a swing motor 83 are arranged in parallel with the hydraulic pump 3, that is, in parallel with the discharge pipe line 101. A hydraulic excavator usually has a bucket cylinder, a left and right traveling motor, and the like as other actuators, but these actuators are omitted in the drawing for simplification of description.

The boom cylinder 81, the main cylinders 81A, 81B connecting the hydraulic pump 3, the boom cylinder 81, the arm cylinder 82, and the swing motor 83, respectively, are connected to the boom cylinder 81,
Flow control valves 41, 42, 4 for controlling the flow of pressure oil supplied to the arm cylinder 82 and the swing motor 83, respectively.
3 are arranged. The flow rate control valve 41 is, for example, a pilot-operated type flow rate control valve, and has springs 41I and 41 at both ends.
In addition to H, the meter-in diaphragm 41A, the meter-out diaphragm 41C, and the meter-in diaphragm 41
A, bleed-off throttle 4 provided in a bleed-off pipe 81C connecting the respective downstreams of the meter-out throttle 41C
Built-in 1B. Similarly, the flow control valves 42 and 43
Is a pilot-operated flow control valve having springs 42I and 42H and springs 43I and 43H at both ends, and meter-in throttles 42A and 43A, meter-out throttles 42C and 43C, and a bleed-off throttle 42.
B and 43B are built in. The flow control valves 41, 4
Each of the return passages 2 and 43 and the tank are connected by a tank communication pipe 100. Therefore, the bleed-off conduit 81C and the like described above are also substantially connected to the tank communication conduit 100.

Each of the flow rate control valves 41, 42, 43 described above is switched and operated by pilot pressures 91A, 92A, 93A output from pilot operation valves 91, 92, 93. These pilot operated valves 91, 92,
The pressure oil from the above-described pilot pump 116, which is defined by the pilot relief valve 119, is supplied to 93 via the pilot pipe line 117.

Further, the above-mentioned flow rate control valves 41, 42, 4
Load pressure detection pipe lines 61, 62, 63 for detecting the load pressures of the boom cylinder 81, the arm cylinder 82, and the swing motor 83 are connected to each of the three. The maximum load pressure Lmax of the load pressures detected by these load pressure detection pipe lines 61, 62, 63 is given to one pilot chamber of the pump regulator 2 via the maximum load pressure detection pipe line 7. The pump discharge pressure Pd detected via the pump discharge pressure detection conduit 5 is applied to the other pilot chamber of the pump regulator 2. That is, the pump regulator 2 has the pump discharge pressure Pd and the maximum load pressure Lm.
It is controlled by a load sensing differential pressure which is a differential pressure with respect to ax, and this load sensing differential pressure is constant (target differential pressure ΔP
The discharge amount of the hydraulic pump 3 is determined so as to be _LS ).

In this conventional technique, the flow rates supplied to the boom cylinder 81, the arm cylinder 82, and the swing motor 83 are basically not influenced by the fluctuations in the load pressures of the other actuators, and the flow rates of their own are eliminated. Control valves 41, 4
It is determined based on the opening areas of 2,43. As a result, a load sensing system capable of performing a combined operation of the boom cylinder 81, the arm cylinder 82 and the like is formed.

Further, since the bleed-off throttles 41B, 42B and 43B are built in the flow control valves 41, 42 and 43, the pilot operated valves 91, 92 and 93 are provided.
The maximum drive pressure of each actuator can be controlled according to the operation amount of.

For example, in the boom cylinder 81, the opening area of the meter-in throttle 41A of the flow control valve 41 is A1, the opening area of the bleed-off throttle 41B of the flow control valve 41 is B1, the load sensing target differential pressure. As described above, ΔP _LS , the flow rate coefficient of pressure oil including viscosity and gravity is C, and the meter-in throttle 4 of the flow rate control valve 41 from the hydraulic pump 3.
The flow rate of meter-in supplied to 1A is Q _A1 , the bleed-off flow rate flowing into the tank through the bleed-off throttle 41B of the flow control valve 41 and the bleed-off conduit 81C is Q _B1 , and the load pressure of the boom cylinder 81 is P. _L1 , ・ Assuming that the flow rate supplied to the boom cylinder 81 is Q _I1 , Q _A1 = C · A1√ (ΔP _LS ) Q _B1 = C ・ B1√ (ΔP _L1 ) Q _I1 = Q _A1 −Q _B1 = C ・A1√ (ΔP _LS ) -C ・ B1√
The expression of (ΔP _L1 ) is established.

As shown in FIG. 6, the relationship between the operation amount of the flow control valve 41 and the opening area A1 of the meter-in throttle 41A is such that the opening area increases as the operation amount increases, and becomes the maximum at the full operation position. The relationship between the operation amount of the flow control valve 41 and the opening area B1 of the bleed-off throttle 41B is as follows.
As shown in FIG. 7, the opening area decreases as the operation amount increases, and the opening area is zero at the full operation position, that is, the bleed-off flow rate is zero.

The drive pressure of the boom cylinder 81 is manipulated as shown in FIG. 8 by operating the flow control valve 41 so as to balance the meter-in flow rate Q _A1 and the bleed-off flow rate Q _B1 shown in the above equation. It increases with an increase in the amount and reaches the maximum drive pressure at the full operating position, which can be controlled by the operator.

The above equations and the relationships shown in FIGS. 6, 7 and 8 hold for other actuators such as the arm cylinder 82.

As described above, in the conventional technique shown in FIG.
By incorporating the bleed-off throttles 41B, 42B, 43B in the flow control valves 41, 42, 43, respectively,
The drive pressures of the boom cylinder 81, the arm cylinder 82, the turning motor 83, etc. can also be controlled by operating the pilot valves 91, 92, 93, etc., and a fine operation (half operation) for slowly turning a swinging body having a large inertia and an inertia It is possible to realize a fine operation (half operation) that does not cause a large boom vibration, and along with this, improve the work accuracy of the hanging work performed through the revolving structure and perform the boom rotation. Good workability can be obtained such as improvement in work accuracy of excavation work.

Known techniques corresponding to this type of construction machine control device are Japanese Patent Laid-Open Nos. 61-88002, 1-274866, and 3-524.
There is one described in Japanese Patent Publication No. 02.

[0015]

In the prior art shown in FIG. 5 described above, the dischargeable flow rate of the hydraulic pump 3 and the required flow rate during the combined operation of the actuators such as the boom cylinder 81, the arm cylinder 82, and the swing motor are shown. connection of,
Also, there is a problem associated with a combined operation of fine operation (half operation) and full operation.

In the combined operation of the two actuators, for example, the boom cylinder 81 and the arm cylinder 82, when both are fine operations (half operation), the required flow rate of these boom cylinder 81 and arm cylinder 82 is small, Therefore, the dischargeable flow rate of the hydraulic pump 3 is usually larger than the actuator required flow rate, and good fine operability (half operability) can be secured.

However, when a complex operation in which some of the actuators are to be fully operated and some of which are to be finely operated (half operation) is performed, for example, during excavation work, the arm cylinder 82 that has a high load pressure is used. Boom cylinder 8 with full operation and relatively low load pressure
When a complex operation of performing fine operation (half operation) of 1 is performed, the actuator required flow rate may become larger than the dischargeable flow rate of the hydraulic pump 3.
In such a case, the dischargeable flow rate of the hydraulic pump is relatively high in spite of the situation where the flow rate discharged from the hydraulic pump 3 has already been wasted by the bleed-off flow rate due to the fine operation of the boom cylinder 81. Since it will be insufficient, the supply flow rate to the arm cylinder 81, which is on the high load pressure side in particular, decreases, and the operating speed of this arm cylinder 81 decreases, which leads to a decrease in work efficiency.

Such a phenomenon occurs when the boom cylinder 81 is fully operated so as to raise the boom and the combined operation of finely operating the arm cylinder 82 to slightly move the arm is performed. The flow rate to the boom cylinder 81 forming the high load pressure side decreases, and the work efficiency decreases due to the decrease in the boom lift amount.

As described above, in the prior art shown in FIG. 5, it is unavoidable for the drive pressure control in the combined operation of the fully operated actuator and the finely operated (half operated) actuator, but the fine operation is unavoidable. The amount of bleed-off flow was discarded in the tank due to the above, and on the other hand, there was a problem in that the supply flow rate to the fully operated actuator, which is on the high load side, became insufficient, resulting in a decrease in work efficiency.

The present invention has been made in view of the above-mentioned actual situation in the prior art, and an object thereof is to perform a fine operation in a combined operation of an actuator to be fully operated and an actuator to be finely operated (half operation). It is an object of the present invention to provide a control device for a construction machine capable of reducing the bleed-off flow rate.

[0021]

To achieve this object, the invention according to claim 1 of the present invention provides a prime mover, a main hydraulic pump driven by the prime mover, and a pressure discharged from the main hydraulic pump. A plurality of actuators driven by oil, and a flow rate control that is provided corresponding to each of these actuators, controls the flow of pressure oil supplied from the main hydraulic pump to the actuators, and has an internal bleed-off throttle In a control device for a construction machine, which is provided with a valve, and is capable of controlling the maximum drive pressure of the actuator according to a switching operation of these flow control valves,
A bleed-off control valve for changing the opening area to a small value in accordance with an increase in the operation amount of the actuator is provided in a pipe line connecting the bleed-off throttle and the tank.

[0022]

In the invention according to claim 1 of the present invention, since it has the above-mentioned configuration, an actuator that is fully operated,
When a combined operation with a finely operated (half-operated) actuator is performed, the bleed-off throttle of the flow control valve for the fully-operated actuator that maximizes the operation amount has an opening area of zero and the bleed-off There is no bleed-off flow from the throttle to the tank. This point is the same as the conventional technique.

At this time, the opening area of the bleed-off control valve changes to a small value as the operation amount of the fully operated actuator becomes maximum. As a result, the bleed-off throttle built in the flow rate control valve for the finely operated actuator is held in a predetermined opening area, and the drive pressure of the actuator for the fine operation can be controlled, and The bleed-off flow rate flowing from the bleed-off throttle of the actuator to the tank is regulated by the bleed-off control valve having a small opening area.

Therefore, in the combined operation of the fully operated actuator and the finely operated (half operated) actuator, when the required flow rate of the actuator becomes larger than the dischargeable flow rate of the hydraulic pump, the bleed-off control valve The bleed-off flow rate flowing from each flow rate control valve to the tank is reduced by driving, and the supply flow rate to the actuator, especially the fully operated actuator on the high load side, is reduced from that of the conventional technology according to the reduced flow rate. Can also be increased.

When a composite operation is performed between actuators that are finely operated (half operation), the bleed-off throttles incorporated in the respective flow rate control valves are held in a predetermined opening area, and the operation of each actuator is performed. Due to the small amount, the opening area of the bleed-off control valve is also maintained at a slightly opened predetermined opening area.

Therefore, as in the prior art, a predetermined bleed-off flow rate flows from the bleed-off throttle of the flow control valve for each actuator to the tank through the bleed-off control valve, and the drive pressure of these actuators is controlled. it can.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a control device for a construction machine according to the present invention will be described below with reference to the drawings. FIG. 1 shows claim 1 of the present invention.
2 and 4 are circuit diagrams showing a first embodiment corresponding to FIGS.
FIG. 3 is a diagram showing characteristics of a bleed-off control valve provided in the first embodiment shown in FIG. 1.

FIG. 1 is drawn corresponding to FIG. 5 described above, and shows a control device provided in, for example, a hydraulic excavator. Also, in FIG. 1, the same components as those shown in FIG. 5 described above are designated by the same reference numerals.

That is, also in the first embodiment shown in FIG. 1, a prime mover 1, a main pump driven by the prime mover 1, ie, a variable displacement hydraulic pump 3, a pilot pump 116, and a pump regulator 2. , An unloading valve 11 connected to the discharge line 101 of the hydraulic pump 3,
And a main relief valve 10, and the boom cylinder 81 and the arm cylinder 8 are provided in parallel with the hydraulic pump 3.
2. An actuator such as a turning motor 83 is arranged. Bucket cylinder forming another actuator,
The left and right traveling motors and the like are omitted from the drawing for the sake of simplicity.

Further, the hydraulic pump 3 and the boom cylinder 8
A flow control valve for controlling the flow of pressure oil supplied to each of the boom cylinder 81, the arm cylinder 82, and the swing motor 83 in the main pipe lines 81A and 81B that connect the arm cylinder 82, the swing motor 83, and the like. 41,4
2 and 43 are arranged. Flow control valves 41, 42, 43
Is, for example, a pilot-operated flow control valve, and has springs 41I, 41H, springs 42I, 42H at both ends, respectively.
The springs 43I and 43H are provided, and the meter-in diaphragms 41A, 42A, 43A, and the meter-out diaphragms 41C, 4C are provided.
2C, 43C and bleed-off conduits 81C, 82,
Bleed-off diaphragms 41B, 42B, 43 provided at 83C
Built-in B.

The flow rate control valves 41, 42, 43 described above are switched by pilot pressures 91A, 92A, 93A output from the pilot operation valves 91, 92, 93, respectively. Is
The pressure oil from the pilot pump 116 defined by the pilot relief valve 119 is supplied to the pilot line 117.
Is supplied via.

Further, each of the flow rate control valves 41, 42, 43 has a boom cylinder 81, an arm cylinder 82,
Load pressure detection pipe lines 61, 62, 63 for detecting the respective load pressures of the swing motor 83 are connected. The maximum load pressure Lmax among the load pressures detected by the load pressure detection pipe lines 61, 62, 63 is given to one pilot chamber of the pump regulator 2 via the maximum load pressure detection pipe line 7, and this pump regulator In the other pilot chamber of No. 2, the pump discharge pressure P detected via the pump discharge pressure detection pipe line 5 is detected.
d is given, and the pump regulator 2 is controlled by the load sensing differential pressure which is the differential pressure between the pump discharge pressure Pd and the maximum load pressure Lmax, so that this load sensing differential pressure becomes constant (target differential pressure ΔP _LS ). In addition, the discharge amount of the hydraulic pump 3 is determined. The above configuration is equivalent to that shown in FIG. 5 described above.

Particularly in this first embodiment, the flow control valve 4
The bleed-off pipes 81C, 82, 83C built in 1, 42, 43 are respectively provided with check valves 45, 46, 4
7 to the bleed-off connection line 111. Each of the check valves 45, 46, 47 allows the flow of the pressure oil from the bleed-off connecting lines 81C, 82, 83C to the bleed-off connecting line 111, and allows the bleed-off connecting line 111 to bleed-off connecting line 81C, 82,83
The arrangement is such that backflow of pressure oil to C is prevented. Also,
A bleed-off control valve 112 that can change the opening area from a predetermined maximum opening to zero is provided in the pipeline connecting the downstream side of the bleed-off connection pipeline 111 and the tank.
In the neutral state, the bleed-off control valve 112 holds the position where it is maximized by the force of the spring.

The pilot operated valves 91, 92, 9
3 pilot pressure 91A, 92A, 93A
Valve 120 for detecting the maximum pilot pressure of the
And a maximum pilot pressure detection conduit 115 for guiding the maximum pilot pressure taken out by the shuttle valve 120 to the pilot chamber of the bleed-off control valve 112 described above.

The bleed-off control valve 112 described above is shown in FIG.
When the pilot pressure guided by the maximum pilot pressure detection conduit 115 has a small constant value, as in the case where all of the pilot operated valves 91, 92, 93 are kept neutral, as shown in FIG. When the pilot operation valves 91, 92, and 93 are slightly operated (half operation), the opening area is gradually changed to a small opening area according to the operation amount of the pilot operation valves 91, 92, and 93, and the pilot operation valve is operated. For example, when at least one of the valves 91, 92, 93 is fully operated, it is preset so as to be held in a closed state where the opening area is zero.

In the first embodiment constructed as described above, in the case of a combined operation of actuators for fine operation (half operation), for example, a combined operation of a boom cylinder 81 for fine operation and an arm cylinder 82 for fine operation, , Pilot pressure 91A, 9 output from the pilot operated valves 91, 92
Both 2A are relatively small, and therefore their relatively small pilot pressure is guided by the maximum pilot pressure detection line 115 and is provided to the pilot chamber of the bleed-off control valve. As a result, as shown in FIG. 2, the bleed-off control valve 112 is held in the half open state.

On the other hand, the pilot operated valve 9 described above
The flow rate control valves 41, 42 are switched according to the pilot pressures 91A, 92A output from the motors 1, 92, as shown in FIG.
As shown in FIG. 7, each meter-in diaphragm 41A, 4A
2A and the bleed-off diaphragms 41B and 42B are also held in the half-opened state.

The pressure oil discharged from the hydraulic pump 3 is supplied to the discharge pipe 101 and the meter-in throttle 4 of the flow control valves 41 and 42.
Boom cylinder 8 through 1A, 42A, main pipe 81A, etc.
1. The return oil supplied to each of the arm cylinders 82 is returned to the tank through the meter-out throttles 41C and 42C of the flow rate control valves 41 and 42 such as the main pipe 81B. Further, the meter-in throttles 41A, 4 of the flow control valves 41, 42
A part of the pressure oil on the downstream side of 2A is part of the flow control valves 41, 42.
A bleed-off flow rate is returned to the tank via the bleed-off throttles 41B and 42B, the check valves 45 and 46, the bleed-off connection conduit 111, and the bleed-off control valve 112 which are built into the tank.

In such a combined operation of the actuators between the fine operations, the required flow rate of the actuator is relatively small, and therefore, the dischargeable flow rate of the hydraulic pump 3 is usually larger than the required flow rate of the actuator, and the bleed-off flow rate is large. However, the boom cylinder 81 and the arm cylinder 82 are supplied with a relatively small flow rate corresponding to the opening areas of the meter-in throttles 41A and 42A of the flow rate control valves 41 and 42. Can be operated at speed,
Further, by generating the bleed-off flow rate, the boom cylinder 81 and the arm cylinder 82 can be controlled to the relatively small drive pressure shown in FIG. 8 described above.

Further, for example, when a combined operation of a fully operated actuator and a finely operated (half operated) actuator is carried out, for example, during excavation work, the arm cylinder 82, which has a high load pressure, is fully operated and the load pressures are compared. When a complex operation such as a fine operation of the boom cylinder 81, which is extremely low, is performed, the actuator required flow rate may be larger than the dischargeable flow rate of the hydraulic pump 3. In the first embodiment, the following operation is performed during such a combined operation of full operation and fine operation.

That is, by finely operating the pilot operating valve 91 and fully operating the pilot operating valve 92,
A relatively small pilot pressure 91A is applied to the flow rate control valve 41, the flow rate control valve 41 is half-stroke switched, and the meter-in throttle 41A and the bleed-off throttle 41B are each held in a half-opened opening area. The pilot pressure 92A is applied to the flow rate control valve 42, the flow rate control valve 42 is subjected to full stroke switching operation, the meter-in throttle 42A is held at the maximum opening area, and the bleed-off throttle 42B is held at zero opening area.

On the other hand, the larger pilot pressure of the pilot pressure 91A of the pilot operation valve 91 and the pilot pressure 92A of the pilot operation valve 92, that is, the pilot pressure 92A is taken out via the shuttle valve 120, and the maximum pilot pressure is obtained. It is given to the pilot chamber of the bleed-off control valve 112 via the pressure detection pipe line 115. At this time, the bleed-off control valve 112 has the relationship shown in FIG.
Large pilot pressure 92A output with full operation
The opening area is switched to zero corresponding to

Therefore, the boom cylinder 81 can be finely controlled by controlling the flow control valve 41, and the bleed-off control valve 112 is closed even though the bleed-off throttle 41B of the flow control valve 41 is open. As a result, the bleed-off flow rate from the bleed-off throttle 41B to the tank does not occur, and the flow rate corresponding to the bleed-off flow rate is increased especially to the fully operated arm cylinder 82 forming the high load pressure side. Supplied as a minute. As a result, it is possible to suppress a decrease in the operating speed of the arm cylinder 82.

As described above, in the first embodiment, the actuator having the control function of the driving pressure of the actuator at the time of the fine operation as in the prior art and having the full operation and the fine operation (half operation) coexist. In the combined operation of the above, when the actuator required flow rate becomes larger than the dischargeable flow rate of the hydraulic pump 3, the bleed-off control valve 112 is switched so as to change the opening area to zero in accordance with the full operation of the actuator. Therefore, the bleed-off flow rate can be eliminated and the flow rate corresponding to the bleed-off flow rate can be increased to the actuator on the high load side, improving work efficiency during combined operation of actuators that include both full operation and fine operation. Can be made.

In the first embodiment described above, the bleed-off control valve 112 having an opening area of zero is provided in the combined operation of the fine operation of the boom cylinder 81 and the full operation of the arm cylinder 82. As shown, although the opening area gradually decreases as the operation amount of the actuator increases, the bleed-off control valve 113 may be provided so that the small opening area is secured even when the actuator is fully operated. . Such a bleed-off control valve 1
Even when the number 13 is provided, it is possible to reduce the bleed-off flow rate to the tank during the combined operation of the actuator in which the fine operation and the full operation are mixed, and the flow rate corresponding to the reduced flow rate can be applied to the actuator on the high load side. Can be utilized for increasing the amount of the actuator, and the work efficiency at the time of compound operation of the actuator in which full operation and fine operation are mixed can be improved as in the first embodiment described above.

FIG. 4 is a circuit diagram showing a second embodiment corresponding to claims 1 to 5 of the present invention. In this second embodiment, two variable displacement hydraulic pumps 3 are used as main hydraulic pumps.
A and 3B are provided, and the discharge line 10 of the hydraulic pump 3A is provided.
An actuator such as a boom cylinder 81 and an arm cylinder 82 is connected in parallel to 1A, and an actuator such as a swing motor 83 and a traveling motor 84 is connected in parallel to the discharge pipe line 101B of the hydraulic pump 3B. The flow control valve 44 for controlling the traveling motor 84 is also the other flow control valves 41, 42,
It is a pilot operated flow control valve similar to 43,
With springs 44I and 44H at both ends,
It incorporates a meter-in diaphragm 44A, a meter-out diaphragm 44C, a bleed-off conduit 84C, and a bleed-off diaphragm 44B. Load pressure detection conduits 61, 62, 63, 64 are connected to the flow rate control valves 41, 42, 43, 44, respectively, and the maximum load pressure Lm of these load pressures is Lm.
ax is connected to the hydraulic pump 3A via the maximum load pressure detection line 7.
Is supplied to one pilot chamber of the pump regulator 2A that controls the discharge amount of the hydraulic pump 3B and one pilot chamber of the pump regulator 2B that controls the discharge amount of the hydraulic pump 3B. The pump discharge pressure Pd is applied to the other pilot chamber of each of the pump regulators 2A and 2B via the pump discharge pressure detection lines 5A and 5B. That is, also in the second embodiment, the load sensing control is executed according to the differential pressure between the pump discharge pressure Pd and the maximum load pressure Lmax.

Bleed-off conduit 81C in which the bleed-off throttle 41B of the flow control valve 41 for controlling the boom cylinder 81 is arranged, and bleed-off in which the bleed-off throttle 42B of the flow control valve 42 for controlling the arm cylinder 82 is arranged. The conduit 82C is a check valve 45, 46, respectively.
Is connected to the bleed-off connection pipe line 111A via. Further, a bleed-off pipe 83C in which the bleed-off throttle 43B of the flow control valve 43 for controlling the swing motor 83 is arranged, and a bleed-off pipe in which the bleed-off throttle 44B of the flow control valve 44 for controlling the traveling motor 84 is arranged. The line 84C is connected to the bleed-off connection line 111B via check valves 47 and 48, respectively. Further, the bleed-off connection conduit 111A and the bleed-off connection conduit 111B are connected to the tank via the bleed-off connection conduit 111C. This bleed-off connection line 11
The bleed-off control valve 112 is arranged at 1C. Pilot pressures 91A, 92A, 93 output in accordance with the operation of pilot operation valves 91, 92, 93, 94 for switching the flow control valves 41, 42, 43, 44 respectively.
The maximum pilot pressure of A and 94A is taken out through the shuttle valve 120 and is given to the pilot chamber of the bleed-off control valve 112 through the maximum pilot pressure detection pipe line 115. Other configurations are the same as those in the first embodiment described above.

Also in the second embodiment constructed as above, when any one of the pilot operated valves 91, 92, 93 and 94 is only slightly operated, the bleed-off control valve 112 is in a half-open state and the bleed-off flow rate. Flow into the tank, and the desired fine operation can be performed.
During a combined operation in which any one of 1, 92, 93, and 94 is finely operated and at least the other one is fully operated, the bleed-off control valve 112 is fully closed and the bleed-off flow rate disappears. It is possible to increase and supply a flow rate corresponding to the above to the fully operated high load pressure actuator, and it is possible to improve the work efficiency as in the first embodiment.

In the first and second embodiments, the discharge amounts of the hydraulic pumps 3, 3A, 3B are controlled by the load sensing differential pressure between the pump discharge pressure Pd and the maximum load pressure Lmax. However, this pump control does not have to be based on the load sensing system, and may be configured by, for example, control for increasing the pump discharge amount according to the operation amount of the pilot operated valves 91 to 94, that is, positive control.

Further, in the above embodiment, the bleed-off throttles 41B to 44B are provided in all the flow rate control valves 41 to 44, but the bleed-off throttles may be selectively provided according to the type of actuator. .

Further, in the above embodiment, one bleed-off control valve 112 is provided for all the actuators, but one bleed-off control valve 112 may be provided for one actuator. The bleed-off control valve 112 may be separately provided for each of the plurality of actuators.

[0052]

Since the present invention has the above-described structure, the bleed-off flow rate to the tank can be reduced during the combined operation of the actuator in which the fine operation and the full operation are mixed, and the flow rate can be reduced. A corresponding flow rate can be utilized for increasing the amount of the actuator, and thus work efficiency can be improved as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a control device for a construction machine according to the present invention.

FIG. 2 is a diagram showing characteristics of a bleed-off control valve provided in the first embodiment shown in FIG.

FIG. 3 is a diagram showing another example of a bleed-off control valve.

FIG. 4 is a circuit diagram showing a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a control device for a conventional construction machine.

FIG. 6 is a diagram showing characteristics of a meter-in throttle provided in a flow control valve provided in the control device for the conventional construction machine shown in FIG.

FIG. 7 is a diagram showing characteristics of a bleed-off throttle provided in a flow control valve provided in the control device for the conventional construction machine shown in FIG.

FIG. 8 is a diagram showing pressure control characteristics obtained by the control device for the conventional construction machine shown in FIG.

[Explanation of symbols]

1 prime mover 2 pump regulator 3 Variable displacement hydraulic pump 3A variable displacement hydraulic pump 3B variable displacement hydraulic pump 41 Flow control valve 41A meter-in diaphragm 41B bleed-off diaphragm 42 Flow control valve 42A meter-in diaphragm 42B bleed-off diaphragm 43 Flow control valve 43A meter-in diaphragm 43B Bleed-off diaphragm 44 Flow control valve 44A meter-in diaphragm 44B bleed-off diaphragm 45 check valve 46 check valve 47 check valve 48 check valve 81 Boom cylinder (actuator) 81A Main pipeline 81B Main pipeline 81C bleed-off conduit 82 Arm cylinder (actuator) 82C bleed-off conduit 83 Swing motor (actuator) 83C bleed-off conduit 84 Traveling motor (actuator) 84C bleed-off conduit 91 Pilot operated valve 91A Pilot pressure 92 Pilot operated valve 92A Pilot pressure 93 Pilot operated valve 93A Pilot pressure 94 Pilot operated valve 94A Pilot pressure 101 discharge line 101A discharge line 101B discharge line 111 Bleed-off connection line 111A bleed-off connection line 111B bleed-off connection line 111C bleed-off connection line 112 Bleed-off control valve 113 Bleed-off control valve 115 Maximum pilot pressure detection line 116 Pilot pump 117 Pilot line 120 shuttle valve

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Claims (5)

(57) [Claims] 1. A prime mover, a main hydraulic pump driven by the prime mover, a plurality of actuators driven by pressure oil discharged from the main hydraulic pump, and a plurality of actuators provided corresponding to each of the actuators. While controlling the flow of pressure oil supplied from the hydraulic pump to the actuator, a flow control valve having a bleed-off throttle inside is provided, and the maximum drive pressure of the actuator is changed according to the switching operation of these flow control valves. In a controllable control device for a construction machine, a bleed-off control valve for changing the opening area to a small value is provided in a pipe line connecting the bleed-off throttle and the tank in accordance with an increase in the operation amount of the actuator. A control device for construction machinery. 2. A bleed-off connection pipe communicating with a plurality of bleed-off throttles of the flow control valve is provided, and the bleed-off control valve is arranged downstream of the bleed-off connection pipe. The control device for a construction machine according to claim 1. 3. The construction machine control device according to claim 1, wherein the main hydraulic pump comprises a plurality of hydraulic pumps. 4. The flow control valve comprises a pilot-operated flow control valve, is equipped with a pilot control valve for switching operation of these flow control valves, and controls the pilot pressure output from these pilot control valves. The control device for a construction machine according to any one of claims 1 to 3, further comprising: a maximum pilot pressure detection pipe line that guides a maximum pilot pressure as a drive signal for the bleed-off control valve. 5. The construction machine control device according to claim 1, wherein the construction machine is a hydraulic excavator.