JPH084705A - Oil pressure driving circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a hydraulic drive circuit that can achieve good control of the actuator supply flow rate during fine operation. [Structure] Branch pipes 21A and 22A connected to the main pipes 11 and 12 between the flow rate adjusting valve 103 and the hydraulic cylinder 4.
And variable adjusting valves 201 and 202 provided in the branch pipes 21A and 22A, and these variable adjusting valves 201 and 20.
2 is provided, and the valve control device 105 includes a flow rate command value output from the flow rate command means,
When the flow rate command value is smaller than the reference value, the reference value is selected as the target flow rate command value by comparing with the reference value set corresponding to the load flow rate in the detectable range guaranteed in the performance of the flowmeter 101. The external command means 210 controls the variable adjustment valves 201 and 202 according to the magnitude of the flow rate command value when the flow rate command value is smaller than the reference value. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided in an industrial machine such as a construction machine including a hydraulic excavator, and each of a plurality of actuators can obtain only a required flow rate with a minimum required pressure loss, and a small amount of pressure loss. The present invention relates to a hydraulic drive circuit capable of ensuring good control accuracy during operation.

[0002]

2. Description of the Related Art As an example of a conventional hydraulic drive circuit in which each of a plurality of actuators can obtain only a required flow rate with a necessary minimum pressure loss, an international publication number WO /
There is a conventional technique shown in 16285.

FIG. 8 is a circuit diagram showing this conventional technique.
In the conventional technique shown in FIG. 8, a variable displacement hydraulic pump 3 driven by a prime mover (not shown), a plurality of actuators connected in parallel to the hydraulic pump 3, for example, a hydraulic cylinder 4 included in the first actuator circuit 1, Second
Hydraulic cylinder 5 included in the actuator circuit 2 of
A flow rate adjusting valve 103 which is arranged between the hydraulic pump 3 and the hydraulic cylinder 4 and controls the drive of the hydraulic cylinder 4, and a flow rate which is arranged between the hydraulic pump 3 and the hydraulic cylinder 5 and controls the drive of the hydraulic cylinder 5. A flow meter 1 for detecting the load flow rate adjusted by the adjustment valve 104 and the flow rate adjustment valve 103.
01 and a flow meter 102 for detecting the load flow rate adjusted by the flow rate adjusting valve 104. The flow rate adjusting valves 103 and 104 described above are electromagnetic proportional valves and have a direction switching function.

Further, in correspondence with the hydraulic cylinder 5, there is provided a flow rate command means comprising an operation lever 6 for outputting a flow rate command value for driving the hydraulic cylinder 4 and a potentiometer 107, and the hydraulic cylinder 5. A flow rate command means provided with an operation lever 7 for outputting a flow rate command value for driving the hydraulic cylinder 5 and a potentiometer 108, and a flow rate command value and a flow meter output from the potentiometer 107 when the operation lever 6 is operated. 101
Based on the load flow rate output from the flow rate adjustment valve 103
Of the valve control device 105 for controlling the drive of the flow rate control valve 104 and the drive of the flow rate control valve 104 based on the flow rate command value output from the potentiometer 108 and the load flow rate output from the flow meter 102 in accordance with the operation of the operation lever 7. Valve control device 1
06, the flow rate command value given in relation to each of the hydraulic cylinders 4 and 5, and the sum of the respective deviations of the load flow rates detected by the flowmeters 101 and 102, the tilting of the hydraulic pump 3 is performed. Operate the regulator 109 to decide,
Pump tilting control device 1 for controlling the discharge amount of the hydraulic pump 3
10 is provided.

Flow control of the actuator circuit in this prior art, for example, the first actuator circuit 1 is performed as follows.

That is, in order to make the load flow rate supplied to the hydraulic cylinder 4 follow the flow rate command value output from the potentiometer 107 according to the operation amount of the operation lever 6, the valve control device 105 is made to have the above-mentioned flow rate command value. Flow meter 10
The load flow rate detected in 1 is taken in, and the deviation between the flow rate command value and the load flow rate is calculated. If this deviation is positive, the load flow rate is insufficient with respect to the flow rate command value, and the valve control device 105 causes the drive unit of the flow rate adjustment valve 103 to
It outputs a signal to increase the valve opening. On the contrary, if the deviation is negative, the load flow rate is excessive with respect to the flow rate command value, and the valve control device 105 outputs a signal for reducing the valve opening degree to the drive unit of the flow rate adjusting valve 103. . In this way, the load flow rate can be made to follow the flow rate command value.

The flow rate control of the second actuator circuit 2 is similarly performed. Then, the pump displacement control device 110 takes in the deviations obtained by the valve control devices 105 and 106, and outputs a drive signal to the regulator 109 so that the sum of these deviations is always zero.

In the prior art shown in FIG. 8, by controlling the supply flow rates of the hydraulic cylinders 4 and 5 in this way, it is possible to obtain only the necessary flow rate by the hydraulic cylinders 4 and 5 with the minimum necessary pressure loss. It is possible to improve energy efficiency.

[0009]

By the way, in general, the flowmeters 101 and 102 are limited in the guaranteed detectable range. For example, in a hydraulic excavator equipped with 1
Detection values in the range of 15 liters to 350 liters per minute are guaranteed. However, the hydraulic cylinder 4
To the hydraulic cylinder 4 and the like, that is, at the time of a fine operation, the flow rate supplied to the hydraulic cylinder 4 and the like, that is, the load flow rate detected by the flowmeter 101 and the like, It may be smaller than the guaranteed detectable range mentioned above. For example, 10 per minute
It can be about a liter.

Therefore, in the above-described conventional technique shown in FIG. 8, there is a possibility that a load flow rate including an error may be detected during a fine operation. When such a load flow rate including an error is detected, the flow rate control accuracy is increased. Deteriorates, and hydraulic cylinder 4
However, there is a problem that the operability of the actuator is deteriorated.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and its object is to reduce the actuator supply flow rate during a fine operation such that the load flow rate becomes smaller than the load flow rate detectable by the flow meter. An object of the present invention is to provide a hydraulic drive circuit that can achieve good control.

[0012]

In order to achieve this object, the invention described in claim 1 of the present invention is shown in FIGS.
The configuration is as follows, corresponding to the embodiment shown in FIG. First, as a prerequisite technique, a variable displacement hydraulic pump 3 driven by a prime mover, and the variable displacement hydraulic pump 3
A plurality of actuators connected in parallel to the hydraulic cylinders 4 and 5, and a flow rate adjustment provided between the hydraulic pump 3 and the actuators such as hydraulic cylinders 4 and 5 and provided corresponding to the hydraulic cylinders 4 and 5, respectively. Valve 10
3, 104 and flow meters 101, 10 for detecting load flow rates adjusted by these flow rate adjusting valves 103, 104.
2 and operation levers 6 and 7 provided corresponding to each of the hydraulic cylinders 4 and 5 and outputting a flow rate command value for driving the corresponding hydraulic cylinders 4 and 5, and a potentiometer 10.
7, 108, a flow rate commanding means, a flow rate command value output from the flow rate commanding means, and a flow meter 10.
A valve control device 1 for controlling the drive of the flow rate adjusting valves 103, 104 based on the load flow rate detected by
05, 106, and the tilt of the hydraulic pump 3 is operated based on the sum of the deviations between the flow rate command values given in relation to the hydraulic cylinders 4, 5 and the load flow rate detected by the flowmeters 101, 102. And a pump tilting control device 110 for controlling the discharge flow rate.

In particular, the main pipe lines 11, 12, between the flow rate adjusting valves 103, 104 and a predetermined actuator included in the plurality of actuators, for example, hydraulic cylinders 4, 5,
Branch pipes 21A, 22A, 23 connected to 13, 14
A, 24A and these branch lines 21A, 22A, 23
A, 24A, variable adjusting valve 201, which can secondarily control the flow rate controlled by the flow rate adjusting valves 103, 104,
202, 203, 204 and their variable control valves 20
1, 202, 203 and 204, and external command means 210 and 211 for outputting drive signals, and the valve control devices 105 and 106 have load flow rates within a detectable range that are guaranteed in terms of the performance of the flow meters 101 and 102. Is set as a reference value, and the flow rate command value output from the flow rate commanding means composed of the combination of the operation levers 6, 7 and the potentiometers 107, 108 is compared with the reference value set by the setting means 105d. When the flow rate command value is smaller than the reference value, the target command value selecting means 105a for selecting the reference value as the target flow rate command value is included, and the target command value output from the target command value selecting means 105a and the flowmeter 101, 1
A drive signal based on the load flow rate detected in 02 is output as a signal for driving the flow rate adjusting valves 103 and 104, and when the external command means 210 and 211 have the flow rate command value smaller than the reference value. , The variable control valves 201, 202, 20 according to the magnitude of the flow rate command value.
The configuration is such that a drive signal for driving to open 3,204 is output.

[0014]

Since the present invention has the above-described structure, for example, the discharge flow rate of the variable displacement hydraulic pump 3 is relatively large, and the operating speed of the actuators, that is, the hydraulic cylinders 4 and 5 is set to a relatively high operating speed. At the time of operation, the flow rate command value output from the flow rate command means including the combination of the operation levers 6 and 7 and the potentiometers 107 and 108 is set in the valve control devices 105 and 106.
It becomes larger than the reference value of 5a. The flow rate command value at this time corresponds to the detectable load flow rate guaranteed in the performance of the flowmeters 101 and 102. Therefore, there is no concern that the load flow rate detected by the flowmeters 101 and 102 will cause an error, and the flow rate command value and the flowmeters 101 and 102 will be the same as in the conventional case.
The drive of the flow rate adjusting valves 103 and 104 is controlled by signals output from the valve control devices 105 and 106 based on the load flow rate detected by the hydraulic cylinder 4,
The flow rate supplied to 5 can be well controlled.

Further, the discharge flow rate of the hydraulic pump 3 is small,
During fine operation in which the operating speed of the hydraulic cylinders 4 and 5 becomes slow, the flow rate command value output from the above-mentioned flow rate commanding means is
Setting means 105d included in the valve control devices 105 and 106
The situation will be smaller than the standard value of. In such a case, the reference value is selected as the target flow rate command value by the target command value selection means 105a included in the valve control devices 105 and 106. This target flow rate command value is used by the flowmeter 10
1 and 102 correspond to the detectable load flow rate that is guaranteed in terms of performance, and the load flow rate that is actually detected by the flow meters 101 and 102 is also within the detectable range that is guaranteed by these flow meters 101 and 102. It becomes a value. Therefore, the signal output from the valve control devices 105 and 106 based on the target flow rate command value and the load flow rate detected by the flow meters 101 and 102 does not correspond to the flow rate command value output from the flow rate commanding means. The flow rate adjusting valves 103 and 104 can be controlled so as not to cause an error. At this time, at the same time, the external control means 210, 211 adjust the variable control valves 201, 202, 203, 2 according to the magnitude of the flow rate command value.
Appropriate one of 04 is opened and the flow control valve 10
A part of the flow rate from 3, 104 to the corresponding one of the main pipelines 11, 12, 13, and 14 flows out through the corresponding one of the variable control valves 201, 202, 203, and 204 described above. . Therefore, the hydraulic cylinders 4, 5
The flow rate can be controlled in accordance with the flow rate command value output from the above-mentioned flow rate commanding means so that the flow rate can be reduced, and good flow rate control can be realized even during such fine operation.

[0016]

Embodiments of the hydraulic drive circuit of the present invention will be described below with reference to the drawings. 1 is a circuit diagram showing an embodiment of a hydraulic drive circuit corresponding to claims 1, 2 and 3 of the present invention, and FIG. 2 is a block diagram showing the configuration of a valve control device provided in the embodiment shown in FIG. FIG. 3 is a block diagram showing the configuration of the external command means provided in the embodiment shown in FIG. 1, and FIGS. 4, 5, and 6 are diagrams showing the characteristics obtained in the embodiment shown in FIG.

FIG. 1 shows a hydraulic drive circuit applied to a hydraulic excavator, for example, and is drawn corresponding to FIG. 8 described above. Therefore, in FIG. 1, the same components as those shown in FIG. 8 described above are designated by the same reference numerals.

That is, even in this embodiment shown in FIG. 1, a variable displacement hydraulic pump 3 driven by a prime mover (not shown) and a plurality of actuators connected in parallel to the hydraulic pump 3, for example, a first actuator circuit. A hydraulic cylinder 4 such as a boom cylinder included in 1 and a hydraulic cylinder 5 such as an arm cylinder included in the second actuator circuit 2 are arranged between the hydraulic pump 3 and the hydraulic cylinder 4 to drive the hydraulic cylinder 4. A flow rate adjusting valve 103 composed of an electromagnetic proportional valve for controlling, a flow rate adjusting valve 104 arranged between the hydraulic pump 3 and the hydraulic cylinder 5, and composed of an electromagnetic proportional valve for controlling the drive of the hydraulic cylinder 5, The flow meter 101 that detects the load flow rate adjusted by the adjustment valve 103 and outputs an electric signal, and the negative flow meter that is adjusted by the flow rate adjustment valve 104. Detecting a flow rate and a flow meter 102 for outputting an electric signal.

Further, corresponding to the hydraulic cylinder 5, there is provided a flow rate command means comprising an operation lever 6 for outputting a flow rate command value for driving the hydraulic cylinder 4 and a potentiometer 107, and the hydraulic cylinder 5. A flow rate command means provided with an operation lever 7 for outputting a flow rate command value for driving the hydraulic cylinder 5 and a potentiometer 108, and a flow rate command value and a flow meter output from the potentiometer 107 when the operation lever 6 is operated. 101
Based on the load flow rate output from the flow rate adjustment valve 103
The valve control device 105 including a personal computer and the like, and the flow rate command value output from the potentiometer 108 in accordance with the operation of the operation lever 7 and the flow meter 1
Flow control valve 1 based on the load flow rate output from 02
04, controlling the drive of 04, the flow rate command value given in relation to each of the valve control device 106 including a personal computer and the hydraulic cylinders 4 and 5, and the flowmeters 101 and 1.
Based on the total deviation from the load flow rate detected in 02,
A pump tilt control device 110 that operates a regulator 109 that determines tilting of the hydraulic pump 3 and controls the discharge amount of the hydraulic pump 3 is provided.

In particular, in this embodiment, the flow rate adjusting valve 1
03 and the hydraulic cylinder 4 to selectively form a meter-in side conduit and a meter-out side conduit 1
Branch points 21 and 22 are provided at 1 and 12, respectively, and a branch pipeline 21A that connects the branch point 21 and the tank 10 and a branch pipeline 22A that connects the branch point 22 and the tank 10 are provided. A variable adjusting valve 201 including an electromagnetic switching valve capable of secondarily controlling the flow rate controlled by the flow rate adjusting valve 103 is provided in the branch pipeline 21A, and the flow adjusting valve 103 controls the branch pipeline 22A. A variable adjusting valve 202 is provided which is an electromagnetic switching valve capable of secondarily controlling the generated flow rate. These variable control valves 201 and 202 are set to a normally closed type. Similarly, branch points 23 and 24 are provided on the main pipelines 13 and 14 which are located between the flow rate adjusting valve 104 and the hydraulic cylinder 5 and selectively form the meter-in side pipeline and the meter-out side pipeline, respectively. A branch pipeline 23A that connects the branch point 23 and the tank 10 and a branch pipeline 24A that connects the branch point 24 and the tank 10 are provided. Branch line 23A
Is provided with a variable adjustment valve 203 composed of an electromagnetic switching valve capable of secondarily controlling the flow rate controlled by the flow rate adjustment valve 104, and the branch pipe line 24A is provided with the flow rate controlled by the flow rate adjustment valve 104. A variable control valve 204 is provided which is a secondary controllable electromagnetic switching valve. These variable control valves 203,
204 is a normally closed type.

Further, the valve control device 105 for controlling the drive of the variable adjustment valve 103, as shown in FIG.
The load flow rate within the detectable range that is guaranteed in terms of the performance of the reference value Qse, for example, a value slightly larger than the detectable lower limit value.
The setting means 105d set as t is compared with the flow rate command value Qref output from the potentiometer 107 according to the operation of the operation lever 6 and the reference value Qset set by the setting means 105d, and the target is determined according to the comparison result. Target command value selection means 105a for selecting the flow command value QR,
The target flow rate command value QR output from the target command value selection means 105a is assigned a (+) sign, the load flow rate QL output from the flowmeter 101 is assigned a (-) sign, and these are added. The drive signal corresponding to the value obtained by the unit 105b and the addition unit 105b is calculated, and is supplied to the drive unit A located on the left side of the flow rate adjusting valve 103 in FIG. 1 or to the right side of the flow rate adjusting valve 103 in FIG. It is configured to include a computing unit 105c that selectively outputs to the drive unit B located.
The target command value selection unit 105a described above uses the flow command value Qref as the target flow command value QR when the flow command value Qref output from the potentiometer 107 is greater than or equal to the reference value Qset set by the setting unit 105d.
Is selected and the flow rate command value Qref is smaller than the reference value Qset, the reference value Qs is set as the target flow rate command value QR.
Select et. The valve control device 106 also has the same configuration as that shown in FIG.

Further, the external command means 210 for controlling the drive of the variable adjusting valves 201, 202 and the variable adjusting valves 203, 2
The external command means 211 for controlling the driving of the flow control unit 04, and these external command means 210, 211, depending on the magnitude of the flow rate command value Qref, when the above-mentioned flow rate command value Qref is smaller than the reference value Qset. And outputs a drive signal for driving the corresponding variable control valve 201, 202, 203, 204 to open. For example, the variable adjustment valve 20
As shown in FIG. 3, the external command means 210 for controlling the drive of the motors 1, 202 sets a load flow rate within the detectable range guaranteed in the performance of the flowmeter 101, for example, a value slightly larger than the lower limit value that can be detected. Setting means 105c for setting as the reference value Qset (the setting means 10 of the valve control device 105 described above
5d) and the flow rate command value Qref output from the potentiometer 107 is smaller than the reference value Qset, an opening factor corresponding to the magnitude of the flow rate command value Qref, for example, an opening ratio α (0 ≦ α Opening degree selecting means 210 for outputting ≦ 1, α = 0 when fully closed, and α = 1 when fully opened)
a and a calculation unit 210b that calculates a drive signal corresponding to the opening ratio α output from the opening selection unit 210a and outputs the calculated drive signal to the drive unit of the variable adjustment valve 201 or the drive unit of the variable adjustment valve 202. It is configured to include. As shown in FIG. 3, when the flow rate command value Qref is larger than the reference value Qset, the opening degree selecting means 210a described above has an opening degree ratio α for keeping both the variable adjustment valves 201 and 202 in the closed state.
(= 0) is selected, and the flow rate command value Qref is the reference value Qse.
When it is smaller than t, the functional relationship for selecting the opening ratio α that increases inversely proportionally as the flow rate command value Qref decreases, that is, the opening ratio α that increases the opening amount of only one of the variable control valves 201 and 202. However, it is set in advance. The external command means 211 for controlling the drive of the variable adjustment valves 203 and 204 is also the external command means 210 described above.
It has the same configuration as.

In the embodiment thus constructed,
For example, in a normal operation in which the discharge flow rate of the hydraulic pump 3 supplied to the first actuator circuit 1 is relatively increased and the operating speed of the hydraulic cylinder 4 is set to a high operating speed,
When the operation lever 6 is operated, the flow command value Qref is output from the potentiometer 107 to the valve control device 105 according to the operation amount. In the target command value selection means 105a of the valve control device 105 shown in FIG. 2, the reference value Qset set in the setting means 105d along with the input of the flow rate command value Qref is read, and the input flow rate command value Qref and the reference value Qset. Compare with. In this case, since the operation lever 6 is operated normally, the operation amount is large and the flow rate command value Qref is larger than the reference value Qset. Therefore, the flow rate command value Qref is set as the target flow rate command value QR. Selected as is. The flow rate command value Qref at this time corresponds to the detectable load flow rate guaranteed in the performance of the flowmeter 101. As a result, there is no concern that the load flow rate detected by the flow meter 101 will have an error. The target flow rate command value QR (= flow rate command value Qref) selected by the target command value selecting means 105a as described above,
The deviation from the load flow rate QL detected by the flow meter 101 is calculated by the adder 105b, and the driving signal corresponding to the deviation thus calculated is calculated by the calculation means 105c.
The drive unit A (the drive unit on the left side in FIG. 1) of the variable adjustment valve 103 or the drive unit B corresponding to the operating direction of the operating lever 6.
(Drive unit on the right side of FIG. 1). As a result, the variable adjustment valve 103 is switched by the stroke amount corresponding to the operation amount of the operation lever 6, and the main pipe line 11 and the main pipe line 1 are passed through the variable adjustment valve 103 in which the discharge flow rate of the hydraulic pump 3 is opened.
It is supplied to either of the two.

At the same time, the flow rate command value Qref output from the potentiometer 107 according to the operation of the operation lever 6 is input to the external command means 210. The opening selection means 210a shown in FIG. 3 uses the flow rate command value Qref.
The reference value Qset set in the setting means 210c according to the input of is read, and the opening ratio α is selected. In this case, as described above, since the operation lever 6 is normally operated, the operation amount is large, the flow rate command value Qref is larger than the reference value Qset, and the opening ratio α = 0 is selected. It In the calculation means 210b, the variable adjustment valve corresponding to the operation direction of the operation lever 6 based on the opening ratio α (when the operation lever 6 is the operation direction for switching the flow rate adjustment valve 103 to the left position in FIG. 1, the variable adjustment valve 201). , Operating lever 6
1 calculates the drive signal for driving the variable adjusting valve 202) when the flow adjusting valve 103 is in the operation direction for switching to the right position in FIG. 1, but since α = 0 now, the corresponding variable adjusting valve is in the closed state. Kept in. The variable adjustment valve that does not correspond to the operation direction of the operation lever 6 is kept closed. Therefore, in the present case, the branch pipelines 21A, 22A
Both of them are kept in the cutoff state, and the flow rate that has passed through the flow rate adjusting valve 103 is supplied to the hydraulic cylinder 4 as it is.
In this way, the flow rate supplied to the hydraulic cylinder 4 is controlled well in accordance with the flow rate command value Qref output from the potentiometer 107 in accordance with the operation of the operation lever 6, as in the prior art shown in FIG. 8 described above. can do.

Further, for example, the first actuator circuit 1
When the operation lever 6 is operated during a fine operation such that the discharge flow rate of the hydraulic pump 3 supplied to the cylinder is relatively small and the operation speed of the hydraulic cylinder 4 is set to a low operation speed, the potentiometer 107 is operated according to the operation amount. As described above, the flow rate command value Qref is output to the valve control device 105. The target command value selection means 105a of the valve control device 105 shown in FIG. 2 reads the reference value Qset along with the input of the flow rate command value Qref, and compares the input flow rate command value Qref with the reference value Qset. In this case, since the operation lever 6 is operated in accordance with the fine operation, the operation amount is small and the flow rate command value Qref becomes smaller than the reference value Qset. At this time, as the target flow rate command value QR, the reference value Qset, which is a relatively small value in the range that does not cause an error, is selected. As a result, the target flow rate command value QR is the flow rate command value Qre based on the operation of the operation lever 6.
Although it does not correspond to f, the load flow rate QL itself detected by the flow meter 101 may not include an error. Then, as described above, the target command value selection means 105
Target flow rate command value QR (= reference value Qse selected in a)
The deviation between t) and the load flow rate QL detected by the flow meter 101 is obtained by the addition unit 105b, and a drive signal corresponding to the thus obtained deviation is calculated by the calculation means 105c, and the operation lever 6 of the operation lever 6 is calculated. It is output to, for example, the drive unit A (the drive unit on the left side in FIG. 1) of the variable adjustment valve 103 in accordance with the operation direction. As a result, the variable adjustment valve 103 moves the operation lever 6
The stroke amount corresponding to the operation amount of is slightly switched to the left side of FIG. Therefore, as described above, the discharge flow rate of the hydraulic pump 3 is variable with the opening amount limited so as to pass only the load flow rate QL corresponding to the reference value Qset (the flow rate higher than the load flow rate corresponding to the flow rate command value Qref). It is supplied to the main pipe line 11 via the adjusting valve 103.

At the same time, as described above, the flow rate command value Qref output from the potentiometer 107 according to the operation of the operation lever 6 is input to the external command means 210. The opening degree selection means 210a shown in FIG. 3 reads the reference value Qset along with the input of the flow rate command value Qref, and selects the opening degree ratio α. In this case, the operation amount is small because the operation lever 6 is operated in accordance with the fine operation, the flow rate command value Qref is smaller than the reference value Qset, and the opening ratio α (0 <α ≦ 1) is selected. To be done. The calculation means 210b calculates a drive signal for driving the variable adjustment valve 201 corresponding to the operation direction of the operation lever 6 based on the selected opening ratio α. The variable adjustment valve 202, which does not correspond to the operation direction of the operation lever 6, remains in the closed state. Therefore, in this case, the branch line 21A
Is brought into a communication state via the variable adjustment valve 201, and the other branch pipe line 22A is kept in a shut-off state. Therefore, a part of the flow rate that has passed through the flow rate adjusting valve 103 and flown into the main pipeline 11 flows out to the tank 10 through the branch pipeline 21A, and the flow rate to the hydraulic cylinder 4 is less than the flow rate that has passed through the flow rate regulating valve 103. Is supplied. In this way, even during the fine operation, the flow rate flowing to the hydraulic cylinder 4 can be well controlled according to the flow rate command value Qref output from the potentiometer 107 in accordance with the operation of the operation lever 6.

The variable control valve 201 is operated as described above.
The flow rate adjusted by, that is, the flow rate Qb flowing out into the tank 10 via the branch pipe line 21A can be expressed by the following equation:

Here, C is a flow coefficient, Ab is the opening degree of the variable adjustment valve 201, and PL is a differential pressure between the upstream pressure and the downstream pressure of the variable adjustment valve 201. Since the pressure on the downstream side of the variable adjustment valve 201 is the tank pressure, PL is substantially the pressure on the upstream side of the variable adjustment valve 201, that is, the load pressure on the meter-in side of the flow rate adjustment valve 103.

A when PL is used as a parameter
The relationship between b and Qb is as shown in FIG. Load pressure P
When L takes a certain value, the opening degree Ab of the variable control valve 201
Is proportional to the flow rate Qb adjusted by the variable adjustment valve 201, and the flow rate Qb is uniquely determined with respect to the opening Ab of the variable adjustment valve 201. This is the opening Ab to the load pressure P.
The desired flow rate Qb can be adjusted by adjusting it according to L.
It means that you can miss it. That is, the flow rate supplied to the hydraulic cylinder 4 can be controlled as a difference between the reference value Qset adjusted by the flow rate adjustment valve 103 and the flow rate Qb adjusted by the variable adjustment valve 201 corresponding to the flow rate command value Qref. it can.

The relationship between the opening Ab and the load pressure PL when the flow rate Qb is used as a parameter is shown in FIG. 5, and the opening Ab and the load pressure PL are uniquely determined for a certain flow rate Qb. As for the relationship, the load pressure PL decreases as the opening Ab increases, and conversely, the load pressure PL increases as the opening Ab decreases. This is
Considering the relationship (inverse proportional relationship) between the flow rate command value Qref and the opening ratio α shown in FIG. 3, as shown in FIG. 6, the load pressure PL also increases as the flow rate command value Qref increases, and conversely. As the flow rate command value Qref decreases, the load pressure PL also decreases. Thus, for example, the sudden rise of the load pressure PL which becomes a problem at the time of starting the hydraulic cylinder 4 is controlled by controlling the flow rate command value Qref, that is, by appropriately considering the operation amount when the operation lever 6 is operated. It can be resolved.

As described above, the flow rate command value Qr during fine operation
Even if ef falls outside the detectable range of the flow meter 101, the flow rate supplied to the hydraulic cylinder 3 can be controlled by controlling the variable adjustment valve 201 independently of the flow rate adjustment valve 103.

In the above description, the case where the flow rate adjusting valve 103 is switched to the left position in FIG. 1 has been described as an example, but the same applies when the flow rate adjusting valve 103 is switched to the right position in FIG. During operation, potentiometer 107
The opening degree of the variable adjustment valve 202 is controlled according to the flow rate command value Qref output from the variable adjustment valve 201, the variable adjustment valve 201 is held in a closed state, and a part of the flow rate introduced to the main pipeline 12 is branched by the branch pipeline 22A. It is possible to satisfactorily control the flow rate that is released to the tank 10 via the above and is supplied to the hydraulic cylinder 4.

When operating the operating lever 7 to control the drive of the hydraulic cylinder 5, the supply flow rate to the hydraulic cylinder 5 during fine operation can be controlled well in the same manner as described above.

As described above, in the present embodiment, the flow rate control of the hydraulic cylinders 4 and 5 at the time of a fine operation such that the load flow rate is smaller than the load flow rate detectable by the flowmeters 101 and 102 is also excellent. Therefore, it is possible to improve the operability of the hydraulic cylinders 4 and 5 at the time of such fine operation, and it is possible to perform the work accompanying the operation of the hydraulic cylinders 4 and 5 with high accuracy.

In the above embodiment, for the sake of simplification of description, only the two hydraulic cylinders 4 and 5 are given as the plurality of actuators, but other hydraulic cylinders or hydraulic motors may be provided. Even in such a case, the same effect can be obtained by providing the corresponding actuator circuit with the same configuration as described above.

FIG. 7 is a circuit diagram showing the essential parts of another embodiment of the hydraulic drive circuit according to claim 4 of the present invention. In another embodiment shown in FIG. 7, branch pipes 25A and 26A are connected at one end to branch points 25 and 26 of main pipe lines 11 and 12 that connect the flow rate adjusting valve 103 and the hydraulic cylinder 4, respectively. is there. The other ends of these branch pipelines 25A and 26A are
The pressure oil on the larger side of the pressure oil guided to the branch pipelines 25A and 26A is connected by a priority valve 220 that selectively outputs it. Further, a return conduit 15 that connects the priority valve 220 and the tank 10 is provided, and the return conduit 15 is provided with a variable adjustment valve 201A that operates according to the drive signal output from the external command means 210 described above. There is. In another embodiment configured in this manner also, at the time of fine operation, by the drive signal output from the external command means 210 according to the flow rate command value Qref output from the potentiometer 107,
The variable adjusting valve 210A is opened slightly, and the main pipe lines 11, 1
A part of the pressure oil guided to the main pipe line forming the meter-in side of 2 is escaped to the tank 10 through the priority valve 220 and the return pipe line 15 by the flow rate corresponding to the above-mentioned flow rate command value Qref. The flow rate supplied to the hydraulic cylinder 4 can be controlled well. The embodiment shown in FIG. 7 has the same effect as that of the embodiment shown in FIG. 1 described above, and the number of variable adjustment valves that are electromagnetic switching valves can be halved, so that the manufacturing cost is relatively low. be able to.

[0037]

Since the hydraulic drive circuit according to claim 1 of the present invention is configured as described above, the actuator at the time of fine operation is such that the load flow rate becomes smaller than the load flow rate detectable by the flow meter. The control of the supply flow rate can also be realized satisfactorily, which can improve the operability of the actuator at the time of fine operation compared to the past, and the work accompanying the operation of the actuator at the time of such fine operation can be performed accurately. It can be done.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a hydraulic drive circuit corresponding to claims 1, 2, and 3 of the present invention.

FIG. 2 is a block diagram showing a configuration of a valve control device provided in the embodiment shown in FIG.

FIG. 3 is a block diagram showing a configuration of external command means provided in the embodiment shown in FIG.

FIG. 4 is a diagram showing characteristics obtained in the embodiment shown in FIG.

FIG. 5 is a diagram showing characteristics obtained in the embodiment shown in FIG.

FIG. 6 is a diagram showing characteristics obtained in the embodiment shown in FIG.

FIG. 7 is a circuit diagram showing a main part of another embodiment of the hydraulic drive circuit according to claim 4 of the present invention.

FIG. 8 is a circuit diagram showing a conventional hydraulic drive circuit.

[Explanation of symbols]

 1 First Actuator Circuit 2 Second Actuator Circuit 3 Variable Displacement Hydraulic Pump 4 Hydraulic Cylinder (Actuator) 5 Hydraulic Cylinder (Actuator) 6 Operation Lever (Flow Rate Command Means) 7 Operation Lever (Flow Rate Command Means) 10 Tank 11 Main Pipe Line 12 main pipeline 13 main pipeline 14 main pipeline 15 return pipeline 21 branching point 21A branch pipeline 22 branching point 22A branch pipeline 23 branching point 23A branch pipeline 24 branching point 24A branch pipeline 25 branching point 25A branch pipeline 26 branching Point 26A Branch pipe 101 Flow meter 102 Flow meter 103 Flow rate adjustment valve 104 Flow rate adjustment valve 105 Valve control device 105a Target command value selection means 105b Addition section 105c Calculation means 105d Setting means 106 Valve control apparatus 107 Potentiometer (flow rate command means) 108 Potentiometer (Flow rate commanding means) 109 Regulator 110 Pump tilt control device 201 Variable adjusting valve 201A Variable adjusting valve 202 Variable adjusting valve 203 Variable adjusting valve 204 Variable adjusting valve 210 External commanding means 210a Opening selecting means 210b Arithmetic means 210c Setting means 211 External Commanding means 220 Priority valve

Claims (4)

[Claims] 1. A variable displacement hydraulic pump driven by a prime mover, a plurality of actuators connected in parallel to the variable displacement hydraulic pump, and a plurality of actuators arranged between the variable displacement hydraulic pump and the actuator. Corresponding to each of the above-mentioned actuators, and a flow rate command value for driving the corresponding actuator is output. For controlling the drive of the flow rate adjusting valve based on the flow rate command value output from the flow rate commanding means and the load flow rate detected by the flow meter, and the actuator. Based on the sum of the deviations of the flow rate command value given in relation to the load flow rate detected by the flow meter. A hydraulic drive circuit having a pump displacement control device for controlling the displacement of the variable displacement hydraulic pump to control the discharge flow rate, wherein the flow rate control valve and a predetermined actuator included in the plurality of actuators are connected to each other. A branch pipe connected to the main pipe, a variable adjustment valve provided in the branch pipe and capable of secondarily controlling the flow rate controlled by the flow rate adjustment valve, and a drive signal for driving the variable adjustment valve. And an external command means for outputting the flow rate output from the flow rate command means, wherein the valve control device sets the load flow rate within a detectable range guaranteed by the performance of the flow meter as a reference value. A target command value selecting means for comparing the command value with the reference value set by the setting means and selecting the reference value as the target flow rate command value when the flow rate command value is smaller than the reference value. Look, a drive signal based on the load flow rate detected by the target command value and the flowmeter output from the target command value selecting means,
While outputting as a signal for driving the flow rate control valve, the external command means opens the variable control valve according to the magnitude of the flow rate command value when the flow rate command value is smaller than the reference value. A hydraulic drive circuit comprising means for outputting a drive signal for driving. 2. The setting means for setting the flow rate in the detectable range guaranteed by the performance of the flow meter as a reference value by the external command means, and the flow rate command value output from the flow rate command means for the setting means. When it is smaller than the reference value set in step 1, the opening degree selecting means for outputting the opening degree element according to the flow rate command value is included, and the drive signal corresponding to the opening degree element selected by the opening degree selecting means is output. The hydraulic drive circuit according to claim 1, wherein the hydraulic drive circuit outputs the variable control valve as a signal for driving the variable control valve. 3. The branch pipe in each of a main pipeline between the meter-in side of the flow rate adjusting valve and the predetermined actuator and a main pipeline between the meter-out side of the flow rate adjusting valve and the predetermined actuator. 3. The hydraulic drive circuit according to claim 1, wherein the variable regulating valve is provided in each of the branch pipe lines while connecting the lines. 4. A main pipe line between the meter-in side of the flow rate adjusting valve and the predetermined actuator, and a main pipe line between the meter-out side of the flow rate adjusting valve and the predetermined actuator, respectively. The above branch pipes, a priority valve that connects these branch pipes, and selectively outputs the pressure oil on the larger side of the pressure oil that is guided to these branch pipes; The hydraulic drive circuit according to claim 1 or 2, further comprising: a return pipeline for returning the pressure oil to the tank, and the variable adjustment valve provided in the return pipeline.