JP2889250B2 - Hydraulic drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention is provided in a hydraulic machine such as a hydraulic shovel, and is capable of simultaneously driving a plurality of actuators by hydraulic oil discharged from a hydraulic pump. Related to the device.

<Prior Art> FIG. 6 is a circuit diagram showing an example of a conventional hydraulic drive device. This hydraulic drive device is applied to, for example, a hydraulic shovel, and includes a plurality of actuators, for example, an arm cylinder 2 and a bucket cylinder 3 for a variable displacement hydraulic pump.
The flow control valve with pressure compensation for controlling the flow of the pressure oil supplied to the arm cylinder 2, that is, the direction control valve 4 for the arm and the pressure of the pressure oil guided to the direction control valve 4 for the arm Pressure compensating valve 6 for compensating for constant pressure
And a flow control valve with pressure compensation between the hydraulic pump 1 and the bucket cylinder 3 for controlling the flow of pressure oil supplied to the bucket cylinder 3, that is, a directional control valve for the bucket. 5 and a combination of a pressure compensating valve 7 for compensating the pressure of the pressure oil guided to the bucket direction control valve 5 to be constant. In addition, springs 8 and 9 for applying a predetermined force for operating the pressure compensating valves 6 and 7 to open are provided in one drive unit of each of the pressure compensating valves 6 and 7. Further, a control actuator 10 for controlling the displacement of the hydraulic pump 1 and a flow regulating valve 11 for controlling the drive of the control actuator 10 are provided. The pilot chamber of the flow control valve 11 is connected to the discharge line 13 of the hydraulic pump 1 via a line 14, and the spring chamber of the flow control valve 11 is connected to the lines connected to the directional control valves 4 and 5. The shuttle valve 15 is communicated via a line 16. The pressure of the hydraulic oil discharged from the hydraulic pump 1 is always set to be larger than the maximum load pressure of the load pressures generated by driving the cylinders 2 and 3.

Although not shown, a prime mover for driving the hydraulic pump 1, an operating device for instructing driving of the arm cylinder 2 and the bucket cylinder 3, a target rotational speed setting device for setting a target rotational speed of the prime mover, and a target rotational speed of the prime mover And a control device for performing switching control of the above-mentioned flow control valve with pressure compensation in accordance with the operation of the operating device, and a boom cylinder, a swing motor, a left and right running motor, and the like. ing.

In the case of the hydraulic drive device configured as described above, if the directional control valve 4 for the arm and the directional control valve 5 for the bucket are switched, the hydraulic pump 1 is switched with the switching of the directional control valves 4 and 5. Pressure oil is supplied to the arm cylinder 2 and the bucket cylinder 3 so that each of the arm cylinder 2 and the bucket cylinder 3 can perform a single expansion / contraction operation or a combined expansion / contraction operation.

<Problems to be solved by the invention> By the way, in the conventional hydraulic drive device described above,
The displacement of the hydraulic pump 1 changes at a constant rate in accordance with the change in the rotation speed of the prime mover, and accordingly, the flow rate passing through the directional control valve 4 for the arm and the directional control valve 5 for the bucket changes at a constant rate. I do. In this case, as shown in FIG.
The relationship between the directional control valve stroke of the directional control valve 4 for the arm and the flow rate passing through the directional control valve when the prime mover is at the maximum rotational speed A is tentatively indicated by a characteristic line 100. The relationship between the directional control valve stroke and the flow rate that can pass through the directional control valve is shown by a characteristic line 102, and the directional control of the arm directional control valve 4 is performed in a state where the rotational speed of the motor is reduced to a predetermined rotational speed B. Assuming that the relationship between the valve stroke and the flow rate that can pass through the directional control valve is as shown by a characteristic line 101, the state in which the combined drive of the arm cylinder 2 and the bucket cylinder 3 is performed at the maximum rotation speed A of the prime mover. When performing another operation while reducing the maximum rotation speed of the prime mover to B, the relationship between the directional control valve stroke and the flow rate that can pass through the directional control valve depends on the characteristic line 100 for the directional control valve 4 for the arm. Although it changes to 101, the directional control valve 5 for the bucket remains unchanged on the characteristic line 102. That is, while the flowable amount of the directional control valve 4 for the arm changes greatly, the passage of the directional control valve 5 for the bucket does not change. Since the allowable flow rate does not change, the operational feeling received by the operator is poor and the operability is reduced.

Also, in the case of a hydraulic shovel provided with this hydraulic drive device, shaping work or the like for flattening the ground or the like is often performed. The actuator may be finely operated. At the time of this fine operation, the rotation speed of the prime mover is reduced, the displacement of the hydraulic pump 1 is reduced, the flowable amount of the directional control valve is reduced, and the flow supplied to the actuator is reduced. However, as described above, the allowable flow rate of the directional control valve changes at a constant rate in accordance with the change in the rotation speed of the prime mover. Therefore, the speed of the actuator tends to be higher than the speed intended by the operator during the fine operation in the related art, and this fine operation is likely to be difficult. Had a problem with operability in another sense.

The present invention has been made in view of the above-described circumstances in the related art, and has as its object to provide a hydraulic drive device capable of supplying a flow rate suitable for performing an operation to an actuator according to the type of the operation. It is in.

<Means for Solving the Problems> In order to achieve this object, the present invention provides a prime mover, a hydraulic pump driven in accordance with the rotation of the prime mover, and a hydraulic oil discharged from the hydraulic pump. An actuator, a flow control valve with pressure compensation for controlling the flow of pressure oil supplied from the hydraulic pump to the actuator, an operating device for instructing driving of the actuator, and a target speed setting device for setting a target speed of the prime mover. , A target rotational speed detecting device for detecting a target rotational speed of a prime mover, and a control device for performing switching control of a flow control valve with pressure compensation in accordance with operation by an operating device; Limiting means for limiting the maximum flow rate that can pass through the flow control valve with pressure compensation in accordance with a predetermined functional relationship in accordance with the target rotation speed detected at With
The target rotational speed setting device has a first set point capable of providing a first rotational speed lower than the maximum rotational speed of the prime mover, and the restricting means controls the flow control with pressure compensation in association with the first set point. A signal that limits the maximum stroke of the valve to a first maximum stroke smaller than the maximum stroke corresponding to the maximum rotation speed can be output, and the first maximum stroke is the first maximum stroke. And a maximum stroke corresponding to the maximum rotation speed is larger than a ratio between the first rotation speed and the maximum rotation speed.

<Operation> Since the present invention is configured as described above, the type of work, for example, a normal excavation work that maximizes the capacity of a hydraulic shovel, excavation of earth and sand with emphasis on saving fuel consumption, and the like. Excavation work or work that requires fine operation.The maximum flow rate that can be passed through the flow control valve with pressure compensation suitable for these types of work is set in advance in relation to the target rotation speed of the prime mover. The limiting means may limit the maximum flow rate of the pressure-compensated flow control valve corresponding to the above-described relationship in accordance with the target rotation speed detected by the target rotation speed setting device, whereby the type of work is performed. Accordingly, a flow rate suitable for performing the work can be supplied to the corresponding actuator via the corresponding flow control valve with pressure compensation.

<Example> Hereinafter, a hydraulic drive device of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing a schematic configuration of a first embodiment of the present invention, which is provided, for example, in a hydraulic shovel. In FIG. 1, the same components as those shown in FIG. 6 indicate the same components. That is, this first
6, the variable displacement hydraulic pump 1, a plurality of actuators such as the arm cylinder 2, the bucket cylinder 3 and the like, and the arm directional control valve 4 are provided in the same manner as shown in FIG. A flow control valve with pressure compensation comprising a combination of a pressure compensating valve 6 with a spring 8, a combination of a bucket directional control valve 5 and a pressure compensating valve with a spring 9, and a control actuator 1 for controlling the displacement of the hydraulic pump 1.
0, a flow regulating valve 11 and the like. Further, the first embodiment includes a prime mover 18 for driving the hydraulic pump 1, a target rotational speed setting device 19 for setting a target rotational speed of the prime mover 18,
Target speed detector 18 for detecting the target speed of the prime mover 18
a, and an operating device 21a for commanding driving of the arm cylinder 2 and the bucket cylinder 3.

The target rotation speed setting device 19 described above is, for example, a normal operation point provided corresponding to a normal excavation operation for maximizing the capacity, and corresponds to an excavation operation for excavating earth and sand while emphasizing fuel saving. A first set point capable of providing a first rotation speed NE lower than the maximum rotation speed Nmax of the prime mover 18, a work requiring fine operation, such as a shaping work, and a first rotation speed Second rotation speed even lower than NE
It has a second set point that can give NL. The target rotation speed setting device 19 is connected to the target rotation speed setting device.
The above normal working point set to 19, the first set point, the second
And a selection device 20 that can select any one of the set points.

The control device 21 selectively outputs signals a, b, c, and d for controlling the switching of the directional control valve 4 for the arm and the directional control valve 5 for the bucket according to the signal output from the operating device 21a. This control device 21 is provided with an input unit.
21b, an output unit 21c, a calculation unit 21d, and a storage unit 21e, and the above-described arm direction control valve 4 and bucket direction control according to the target rotation speed detected by the target rotation speed detection device 18a. The storage unit 21 of the control device 21 includes limiting means for limiting the maximum flow rate that can pass through the flow control valve with pressure compensation such as the valve 5 according to a predetermined functional relationship.
For example, the function relation shown in FIG. 2 is stored in e in advance.

FIG. 2 shows the maximum stroke Sm of the directional control valves 4 and 5.
a indicates the relationship between ax and the target rotation speed No of the prime mover 18. The point P corresponds to, for example, the above-mentioned normal working point for maximizing the capacity, and the target rotation speed No of the prime mover 18 is the highest. When the rotational speed is Nmax, the maximum stroke Smax of the arm directional control valve 4 and the bucket directional control valve 5 is determined in manufacturing.
Satisfies the relationship of 100%. Point E is a point corresponding to the above-described first set point at which fuel economy is emphasized, and when the target rotation speed No of the prime mover 18 is the first rotation speed NE lower than the maximum rotation speed Nmax, The maximum stroke Smax of the arm directional control valve 4 corresponds to the maximum rotation speed Nmax described above.
The relationship that the first maximum stroke SE is smaller than the 0% maximum stroke Smax is satisfied. In particular, the ratio of the first maximum stroke SE to the 100% maximum stroke Smax corresponding to the maximum rotation speed Nmax is the ratio between the first rotation speed NE and the maximum rotation speed Nmax. It is set to be larger than the ratio. In this case, the maximum stroke Smax of the bucket directional control valve 5 is, for example, 100%.
Is determined in advance to be the maximum stroke.
The point L is a point corresponding to the above-mentioned second set point related to the shaping operation, and when the target rotational speed No of the prime mover 18 is the second rotational speed NL which is still lower than the first rotational speed NE. , The maximum stroke Smax of the bucket directional control valve 5 is equal to the first stroke described above.
Satisfies the relationship that the second maximum stroke SL is smaller than the maximum stroke SE. In particular, the ratio of the second maximum stroke SL to the 100% maximum stroke Smax corresponding to the maximum rotation speed Nmax is the ratio between the second rotation speed NL and the maximum rotation speed Nmax. It is set to be smaller than the ratio. In this case, the maximum stroke Smax of the arm direction control valve 4 is, for example, 100%.
Is determined in advance to be the maximum stroke.

In the first embodiment configured as described above, for example, when the normal operation point is selected by the selection device 20 with the intention of performing the excavation operation with the maximum capacity, the target rotation speed setting device 19 In response, the target rotational speed No of the prime mover 18 is set to the maximum rotational speed Nmax, and the prime mover 18 is driven at the maximum rotational speed Nmax to drive the hydraulic pump 1. In this state, when the operating device 21a is operated to drive the arm cylinder 2 and the bucket cylinder 3, for example, the processing shown in FIG. 3 is performed by the control device 21, that is, first, the processing shown in FIG. As shown in step S1, a command signal (signal value T1) for driving the directional control valve 4 for the arm, a command signal (signal value T2) for driving the directional control valve 5 for the bucket, and the target rotation output from the operating device 21a. Target number of rotations output from number detector 18a
= Nmax is input to the calculation unit 21d via the input unit 21b of the control device 21. Next, proceeding to step S2, the arithmetic unit 21d stores the data in the storage unit 2
1e is read out from the relationship shown in FIG.
A calculation is performed to find the maximum stroke Smax corresponding to the 18 target rotation speed No. Now, since No = Nmax, the maximum stroke Smax of the direction control valves 4 and 5 is obtained as the maximum stroke Smax having an opening of 100%. Next, the procedure proceeds to step S3 in FIG. 3, in which a calculation section 21d calculates a control value X1 for driving the arm directional control valve 4 and a control value X2 for driving the bucket directional control valve 5. now,
Since the maximum stroke Smax is 100%, X1 = T1 · (100/100) = T1 X2 = T2 · (100/100) = T2.

Next, proceeding to step S4 in FIG. 3, the control signal a or b having the control value X1 is output to the drive section of the arm direction control valve 4 via the output section 21c, and the control signal c or the control signal X having the control value X2 is output. d is output to the drive unit of the bucket directional control valve 5 via the output unit 21c. Thereby, the directional control valve 4 for the arm and the directional control valve 5 for the bucket are
The directional control valves 4 and 5 are driven in accordance with the command amount of a, that is, the signal values X1 and X2. The maximum flow rate is appropriately divided and supplied to the arm cylinder 2 and the bucket cylinder 3 by the action of the pressure compensating valves 6 and 7 so that the operating speed of the arm cylinder 2 and the bucket cylinder 3 can be maximized. It is in a state, and it is possible to perform a desired excavation work that makes full use of the capacity.

Further, for example, when the first set point is selected by the selection device 20 with the intention of performing excavation work with an emphasis on fuel efficiency, the target rotation speed setting device 19 responds and the target rotation speed No.
Is set to the first rotation speed NE lower than the maximum rotation speed Nmax, and the prime mover 18 is driven at the first rotation speed NE and the flow rate discharged from the hydraulic pump 1 is slightly smaller than when the maximum rotation speed Nmax. . In this state, when the operating device 21a is operated to drive, for example, the arm cylinder 2 and the bucket cylinder 3, the processing section 21d of the control device 21 performs the processing shown in steps S2 and S3 in FIG. It is. However, in this case, since No = NE (<Nmax), the maximum stroke Smax of the directional control valve 4 for the arm is SE slightly smaller than 100% as shown in FIG. The maximum stroke Smax of the valve 5 is 10 as described above.
Therefore, the control value X1 for the directional control valve 4 for the arm and the control value X2 for the directional control valve 5 for the bucket are X1 = T1 · (SE / 100) X2 = T2 · ( 100/100) = T2.

Then, control signals a, b, and c or d having these control values X1 and X2 are output to the drive units of the directional control valve 4 for the arm and the directional control valve 5 for the bucket. As a result, the maximum stroke Smax of the arm directional control valve 4
Is limited to the first maximum stroke SE, the bucket directional control valve 5 can be driven at the maximum stroke Smax of 100%, the flow rate corresponding to the slightly limited stroke is supplied to the arm cylinder 2, and fuel efficiency is emphasized. Excavation work can be realized. In this case, the first maximum stroke SE is 100 corresponding to the first maximum stroke SE and the maximum rotational speed Nmax.
% Of the maximum stroke Smax, which satisfies the relation that the ratio between the first rotation speed NE and the maximum rotation speed Nmax is larger than the ratio between the first rotation speed NE and the maximum rotation speed Nmax. Larger stroke than
That is, a larger flow rate can be supplied, and the characteristic line 10 in FIG.
As shown by 4, a large flow rate can be supplied to the arm cylinder 2 as compared with the characteristic line 101 in the related art. That is,
Excavation in which the prime mover 18 is reduced to the first rotational speed NE from a state in which the prime mover 18 is set to the maximum rotational speed Nmax for the purpose of a combined drive of the arm cylinder 2 and the bucket cylinder 3 to emphasize fuel efficiency. When the operation is changed to the operation, as shown in FIG.
To the characteristic line 104, the flow rate slightly decreases, and the operating speed of the arm cylinder 2 decreases.
The amount of change is much smaller than the amount of change in the prior art exemplified in FIG. 1, and therefore, a situation that causes an uncomfortable feeling in the operation feeling of the operator is not caused, and good operability can be secured.

Further, for example, when the second set point is selected by the selection device 20 with the intention of performing a shaping operation requiring fine operation, the target rotation speed setting device 19 responds and the target rotation speed No.
Is set to a second rotation speed NL lower than the first rotation speed NE, and the prime mover 18 is driven at the second rotation speed NL to drive the hydraulic pump 1.
Is smaller than that at the first rotation speed Nmax. In this state, when the operating device 21a is operated to drive the arm cylinder 2 and the bucket cylinder 3, for example, the arithmetic unit 2 of the control device 21 is operated.
In 1d, the processes shown in steps S2 and S3 in FIG. 3 are performed.
However, in this case, since No = NL (<NE <Nmax), the maximum stroke Smax of the bucket directional control valve 5 is determined.
Is an even smaller SL than SE, as shown in FIG.
On the other hand, the maximum stroke Smax of the arm directional control valve 4 is 100% as described above. Therefore, the control value X1 for the arm directional control valve 4 and the control value X2 for the bucket directional control valve 5 are controlled. X1 = T1T (100/100) = T1 X2 = T2 ・ (SL / 100), respectively.

Then, the control signals a or b and c or d having these control values X1 and X2 are transmitted to the arm direction control valve 4,
It is output to the driving section of the bucket direction control valve 5. Thereby, the maximum stroke Smax of the bucket and the direction control valve 5 is limited to the second maximum stroke SL, and the direction control valve 4 for the arm can be driven at the maximum stroke Smax of 100%.
The bucket cylinder 3 is supplied with a flow rate corresponding to a sufficiently limited stroke, and has a very gentle operation speed, while the arm cylinder 2 has a relatively high operation speed, and a desired operation efficiency is ensured while securing excellent work efficiency. Can be realized. In this case, the second maximum stroke SL is 100 corresponding to the second maximum stroke SL and the maximum rotation speed Nmax.
% Of the maximum stroke Smax, which satisfies the relationship that the ratio between the second rotational speed NL and the maximum rotational speed Nmax is smaller than the ratio between the second rotational speed NL and the maximum rotational speed Nmax. Smaller stroke than
That is, the flow rate can be limited to a smaller value, and the characteristic line 10 in FIG.
As shown by 5, it is possible to supply a smaller flow rate to the arm cylinder 2 as compared with the characteristic line 103 in the prior art, and to drive the arm cylinder 2 at a low speed.

As described above, in the first embodiment, the selecting device 20 selects one of the normal working point, the first set point, and the second set point to maximize the capacity. It is possible to realize the supply of a flow rate suitable for the normal excavation work that is utilized, the excavation work that emphasizes fuel efficiency, and the shaping work that requires fine operation. In addition, excellent operability is obtained without giving the operator a sense of operation at all.

4 and 5 are explanatory views showing a second embodiment of the present invention. FIG. 4 is a circuit diagram showing a schematic configuration, and FIG. 5 is an enlarged sectional view showing a portion A in FIG. .

This second embodiment shown in FIG. 4 is arranged between a variable displacement hydraulic pump 1 and an arm cylinder 2 and a bucket cylinder 3 to reduce the amount of oil supplied to the arm cylinder 2 and the bucket cylinder 3. A flow control valve 22 with pressure compensation for controlling the flow ratio of the arm cylinder 2 and the bucket cylinder 3 so as not to be substantially changed by the change and the change of the load pressure.
Each of 23 has a plurality of main valves including a main valve arranged in a meter-in circuit, as described later, forms a maximum throttle state when these main valves are closed, and the opening degree of the main valve is large. It is composed of a variable throttle that reduces the throttle amount as much as possible, and a logic valve having a pilot valve that operates the variable throttle and the main valve. A variable throttle member for controlling the operation is provided. Other configurations are the same as those of the first embodiment.

That is, the flow control valve 22 with pressure compensation disposed on the arm cylinder 2 side in the second embodiment has two main valves 50 and 51 on the meter-in circuit side and another two main valves 50 and 51 on the meter-out circuit side. Main valves 52 and 53, these four main valves
Each of 50, 51, 52, 53 has a slit 54, 55, 56, 57 that forms a variable aperture, and these slits 54, 55,
Each of the main valves 50, 51, 52, 53 including 56, 57 opens in proportion to the amount of operation of the pilot valves 58, 59, 60, 61. Further, between the main valve 50 and the pilot valve 58, the main valve 51 and the pilot valve are provided.
Between 59 and 59, a variable throttle member 62 having a pressure compensation function,
63 is arranged.

Similarly, the flow control valve 23 with pressure compensation disposed on the side of the bucket cylinder 3 has two main valves 64 on the meter-in circuit side.
65 and another two main valves 66 and 67 on the meter-out circuit side.
And each of these main valves 64, 65, 66, 67 has:
Main valves 64, 65, 66, including slits 68, 69, 70, 71 forming variable throttles, including these slits 68, 69, 70, 71;
Pilot valves 72, 73, 74, 75 are provided corresponding to 67. Further, between the main valve 64 and the pilot valve 72, and between the main valve 65 and the pilot valve 73, variable throttle members 76 and 77 forming the above-mentioned valve body are arranged.

FIG. 5 shows part A near the main valve 50 of the flow control valve 22 with pressure compensation disposed on the side of the arm cylinder 2 described above. In FIG. Pilot valve. A slit 54 is formed on the peripheral side of the main valve 50. Shown upper end face of the main valve 50 described above, the stepped portion of the lower side in the figure to form a pressure receiving portion Ac which receives the back pressure P _B that acts on the main valve 50 forms a pressure receiving portion for receiving a pump pressure Pb.

The above-described variable throttle member 62 is provided in a pilot line of the pilot valve 58, that is, between the main valve 50 and the pilot valve 58. The variable throttle member 62 includes a main valve 50
A pressure receiving portion ac which receives the back pressure P _B, the maximum load pressure of the circuit Pama
It has a pressure receiving portion aa that receives x as a control pressure, and a pressure receiving portion as that receives the pump pressure Pb.

Then, they are contacted through the passage 81 and the pressure receiving chamber 80 of the control chamber 79 and the variable throttle member 62 for receiving the back pressure P _B of the main valve 50.
This passage 81 is a passage that leads to the variable throttle member 62 the back pressure P _B of the main valve 50. Further, the pump port 82 and the pressure receiving chamber 83 of the variable throttle member 62 are connected via a passage 84. This passage
84 guides the pump pressure Pb to the variable throttle member 62 so as to operate in a direction in which the variable throttle member 62 closes. The passage 78 for guiding the maximum load pressure Pamax of the circuit as a control pressure guides the maximum load pressure Pamax to the pressure receiving chamber 78a of the variable throttle member 62 so that the variable throttle member 62 operates in the closing direction. Further, an inlet portion 85 of the pilot valve 58 and a pressure receiving chamber 86 of the variable throttle member 62 are connected via a passage 87. The passage 87 guides the inlet pressure Pz of the pilot valve 58 to the variable throttle member 62 so that the variable throttle member 62 operates in the closing direction. In addition,
The outlet 88 of the pilot valve 58 and the outflow port 89 are connected by a passage 90. Then, a spring 80a for applying a preset force to oppose the maximum load pressure Pamax is provided in the pressure receiving chamber 8.
Set to 0. Main valve 51 of the flow control valve 22 with pressure compensation, and main valve 6 of the flow control valve 23 with pressure compensation on the bucket cylinder 3 side
The parts 4 and 65 also have the same configuration as that shown in FIG. 5, and each of the variable throttle members 63, 76 and 77 has a spring 80
The configuration includes b, 80c, and 80d.

In the second embodiment constructed as described above, for example, when the pilot valve 58 shown in FIG. 5 is not operated,
The pump pressure Pb of the pump port 82 is controlled by the maximum load pressure Pamax acting on the spring chamber of the flow regulating valve 11.
10 is determined by the displacement of
Is set in advance by operation setting means such as a spring of the flow control valve 11 so as to always be higher than the maximum load pressure Pamax. Further, as described above, the urging force of the spring 80a acts as a response to the differential pressure between the arm cylinder 2 and the bucket cylinder 3, whereby the maximum load pressure Pamax that overcomes the irregular force of the spring 80a, that is, the differential pressure While no pressure is generated between the arm cylinder 2 and the bucket cylinder 3, the throttle portion of the variable throttle member 62 is kept open as shown in FIG. 79
Become conductive. In this state, the throttle function of the variable throttle member 62 is stopped, and the main valves 52 and 53 of the flow control valve with pressure compensation 22 shown in FIG.
The 23 main valves 66 and 67 are always in such a state because they do not have a variable throttle member.

A structure capable of forming such a state, that is, a structure in which the variable throttle members 62, 63, 76, and 77 are removed from the circuit shown in FIG. 4, is already known from Japanese Patent Application Publication No. 58-501781. . In such a structure, for example, as shown in FIG. 5, if the variable throttle member 62 is not provided, the main valve 50 moves up and down with the operation of the pilot valve 58, and the flow rate of the pilot and the passage of the slit 54 Main valve at a position where flow is balanced
If the pressure of the pump port 82 is assumed to be constant, the flow rate proportional to the card of the pilot valve 58 can be controlled from the pump port 82 to the outlet port 89.
Can be drained.

4, the variable throttle member 6 is actuated by the biasing force of the springs 80a, 80b, 80c, 80d as described above.
In a state where the throttle functions of 2, 63, 76 and 77 are stopped, for example, the pilot valves 58 and 60 are operated to drive the arm cylinder 2, and the pilot valves 72 and 74 are driven to drive the bucket cylinder 3. When the combined operation of the arm and the bucket is to be performed, on the arm cylinder 2 side, the hydraulic oil of the hydraulic pump 1 passes through the main valve 50 and the arm cylinder 2 along with the operation of the pilot valves 58 and 60. The pressure oil on the head side is guided to the tank via the main valve 52, and the arm cylinder 2 operates in the contracting direction. Also,
Similarly, the bucket cylinder 3 contracts with the operation of the pilot valves 72 and 74 on the bucket cylinder 3 side. Then, the maximum load pressure Pamax of the circuit is guided to the spring chamber of the flow control valve 11, and the control actuator 10 is actuated accordingly, and the amount of tilting of the hydraulic pump 1 is reduced by the combination of the arm cylinder 2 and the bucket cylinder 3. The tilt amount is controlled to be suitable for driving.

Also in the second embodiment constructed as described above, the pressure oil discharged from the hydraulic pump 1 is divided through the flow control valves 22 and 23 with pressure compensation, which are composed of logic valves, so that the arm cylinder 2 and the bucket are separated. It can be supplied to the cylinder 3 to perform these combined drives, and has the same target rotation speed detection device 18a, target rotation speed setting device 19, selection device 20, operating device 21a, and control device 21 as those of the first embodiment. The pilot valves 58, 59, 60, 61, 72, 7 are respectively controlled by control signals a, b, c, d, e, f, g, h output from the control device 21.
3, 74, and 75 are selectively driven, and the corresponding pilot valves 58, 59, 60, 61, and 7, depending on the type of work.
Since the operation amount of any one of 2, 73, 74, and 75 is appropriately restricted, a suitable flow rate according to the type of work is set to the arm cylinder 2, the bucket cylinder, and the like, as in the first embodiment. 3 and therefore, the second embodiment also has the same effect as the first embodiment.

In the above embodiment, the arm cylinder 2 and the bucket cylinder 3 have been described as examples of actuators. However, the present invention is not limited to this, and includes a boom cylinder, a swing motor, and a travel motor. Of course, it is good.

In the first embodiment, the strokes of the directional control valve 4 for the arm and the directional control valve 5 for the bucket are limited by the restricting means. In the second embodiment, the pilot valve 58,
Although it is configured such that the operation amounts of 59, 60, 61, 72, 73, 74, and 75 can be limited, the present invention is not limited to this, and the limiting means changes the gain for the stroke of the directional control valves 4 and 5. Or pilot valves 58, 59, 60, 61, 72, 73, 7
It may be constituted by means for changing the gain for the operation amount of 4, 75.

<Effect of the Invention> Since the hydraulic drive device of the present invention is configured as described above, it is possible to supply a flow rate suitable for performing the work to the actuator in accordance with the type of work, and therefore, to combine the actuators. There is an effect that operability including operability and fine operability can be improved as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a schematic configuration of a first embodiment of a hydraulic drive device according to the present invention, and FIG. 2 is preset in a storage section of a control device provided in the first embodiment shown in FIG. FIG. 3 is a flowchart showing a processing procedure in a control device provided in the first embodiment shown in FIG. 1, and FIG. 4 is a second embodiment of the hydraulic drive device of the present invention. FIG. 5 is an enlarged sectional view showing a portion A in FIG. 4, FIG. 6 is a circuit diagram showing an example of a conventional hydraulic drive device, and FIG. 7 explains a conventional problem. FIG. 1 ... variable displacement hydraulic pump, 2 ... arm cylinder, 3
... bucket cylinder, 4 ... directional control valve for arm, 5
… Bucket directional control valve, 6, 7… pressure compensating valve, 10
…… Control actuator, 11 …… Flow control valve, 18 ……
Prime mover 18a target rotational speed detecting device 19 target rotational speed setting device 20 selecting device 21 control device 21a
… Operating device, 22, 23 …… Flow control valve with pressure compensation.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-186004 (JP, A) JP-A-61-191504 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F15B 11/00-11/04 F02D 29/04 E02F 3/43

Claims (3)

(57) [Claims] A motor, a hydraulic pump driven in accordance with the rotation of the motor, an actuator driven by hydraulic oil discharged from the hydraulic pump, and a hydraulic oil supplied from the hydraulic pump to the actuator. A flow control valve with pressure compensation for controlling the flow of the motor, an operating device for instructing the drive of the actuator, a target speed setting device for setting a target speed of the prime mover, and a target for detecting a target speed of the prime mover A target rotational speed detected by the target rotational speed detecting device in a hydraulic drive device including a rotational speed detecting device and a control device that performs switching control of the flow control valve with pressure compensation in accordance with operation by the operating device; A limiting means for limiting the maximum flow rate which can be passed through the flow control valve with pressure compensation in accordance with a predetermined functional relationship, The speed setting device has a first set point capable of providing a first speed lower than the maximum speed of the prime mover, and the restricting means has a pressure compensating flow control valve associated with the first set point. Can be output to limit the maximum stroke of the first maximum stroke to a first maximum stroke smaller than the maximum stroke corresponding to the maximum rotation speed, and the first maximum stroke is equal to the first maximum stroke. A hydraulic drive device, wherein a ratio of a maximum stroke corresponding to the maximum rotation speed is larger than a ratio of the first rotation speed to the maximum rotation speed. 2. The apparatus according to claim 1, wherein the target rotation speed setting device has a second set point capable of providing a second rotation speed lower than the first rotation speed, and the control means relates to the second set point. Thus, it is possible to output a signal for limiting the maximum stroke of the flow control valve with pressure compensation to a second maximum stroke smaller than the first maximum stroke, and the second maximum stroke is controlled by the second maximum stroke. 2. The hydraulic drive according to claim 1, wherein the ratio between the maximum stroke and the maximum stroke corresponding to the maximum rotation speed is smaller than the ratio between the second rotation speed and the maximum rotation speed. apparatus. 3. A device for selecting one of a plurality of set points including a first set point and a second set point set in the target rotational speed setting device, wherein: 2)
The hydraulic drive as described.