JP2647471B2 - Hydraulic drive for civil and construction machinery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention is provided for a civil engineering or construction machine such as a hydraulic shovel, and is provided with a variable displacement hydraulic pump for maintaining a constant differential pressure between a pump pressure and an actuator load pressure. The present invention relates to a hydraulic drive device including a load sensing system for controlling a displacement.

<Prior Art> FIG. 18 is a circuit diagram showing a schematic configuration of a conventional hydraulic drive device of this kind for a civil engineering / construction machine. The hydraulic drive device includes a variable displacement hydraulic pump 1, an actuator driven by hydraulic oil discharged from the hydraulic pump 1, for example, a hydraulic cylinder 2, and a flow of hydraulic oil supplied from the hydraulic pump 1 to the hydraulic cylinder 2. , A control actuator 4 for controlling the displacement of the variable displacement hydraulic pump 1, and a flow control means for controlling the drive of the control actuator 4, for example, a flow regulating valve 5. . A spring 7 that urges the flow control valve 5 to switch to the left position in the drawing is provided on one drive unit 6 of the flow control valve 5.
Is provided. Also, the actuator load pressure, that is, the hydraulic cylinder 2
Of the other driving unit 9 which is opposed to the driving unit 6
, A pump pressure, that is, a discharge pressure of the variable displacement hydraulic pump 1 is guided through a pipe 10.

In the hydraulic drive device configured as described above,
When the directional control valve 3 is neutral as shown in FIG. 18, the pipe 8 communicates with the tank 11, and the discharge pressure of the hydraulic pump 1 is guided to the other drive unit 9 of the flow control valve 5 via the pipe 10. The flow control valve 5 is switched to the right position in FIG. 18 against the force of the spring 7. Therefore, the control actuator 4
The head side chamber 12 communicates with the tank 11 while the head side chamber 12
The discharge pressure of the hydraulic pump 1 is led to 13, and the piston rod 14 of the control actuator 4 moves to the left in FIG. 18, whereby the displacement of the hydraulic pump 1 is minimized and the hydraulic pump 1 is discharged from the hydraulic pump 1. Is maintained at a minimum flow rate.

When the directional control valve 3 is switched to one of the left and right switching positions for the purpose of driving the hydraulic cylinder 2 from such a state, the pressure oil of the hydraulic pump 1 The hydraulic cylinder 2 is supplied to the cylinder 2 and expands or contracts. At this time, the load pressure of the hydraulic cylinder 2 is guided to one drive unit 6 of the flow control valve 5 via the pipe 8, and the flow control valve 5 18 is switched to the left position in FIG. 18 against the pump pressure by the load pressure and the force of the spring 7. As a result, the discharge pipe 15 of the hydraulic pump 1 is connected to the head side chamber 12 and the rod side chamber 12 of the control actuator 4.
The pump pressure is applied to both the head side chamber 13 and the head side chamber 13. At this time, due to the difference between the pressure receiving area on the head side of the piston rod 14 and the pressure receiving area on the rod side, the control piston 4 moves to the right in FIG.
Thereby, the displacement of the hydraulic pump 1 increases. Then, a difference between the pump pressure and the load pressure applied to the driving units 9 and 6 of the flow regulating valve 5, that is, the maximum flow rate at which the load sensing differential pressure and the pressure by the spring 7 are balanced is discharged from the hydraulic pump 1, The hydraulic cylinder 2 operates at the maximum flow rate.

<Problems to be Solved by the Invention> By the way, civil engineering / equipment provided with the above-described hydraulic drive device
Construction machinery may be used during the winter months or in cold climates. In such a case, the temperature of the pressure oil discharged from the hydraulic pump 1 decreases, and the viscosity of the pressure oil increases with the temperature drop. When such a situation is reached, the pressure loss in the pipe connecting the hydraulic pump 1 and the directional control valve 3 increases as shown in FIG. At this time, the control actuator 4 is controlled by the load sensing differential pressure acting on the flow control valve 5 and the pressure of the spring 7 so that the flow discharged from the hydraulic pump 1 is reduced, and the same pressure loss as at normal temperature is generated. The flow control valve 5 and the control actuator 4 operate to maintain the flow rate.

Therefore, in this conventional hydraulic drive device, when the oil temperature decreases, even if the directional control valve 3 is operated at full stroke, the desired maximum flow rate is not supplied to the hydraulic cylinder 2; The flow rate discharged from the hydraulic pump 1 is smaller than that at normal temperature, and therefore, the efficiency of the work performed via the hydraulic cylinder 2 is reduced due to such a decrease in the oil temperature, and the oil film is cut. As a result, the equipment may be damaged, or the warm-up operation for warming the entire circuit may take a long time.

SUMMARY OF THE INVENTION 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 for a civil engineering / construction machine capable of providing an actuator with a flow rate equal to that at normal temperature even when the hydraulic pressure is lowered. Is to provide.

<Means for Solving the Problems> In order to achieve this object, the present invention provides a variable displacement hydraulic pump, an actuator driven by pressure oil discharged from the variable displacement hydraulic pump, and the variable displacement hydraulic pump. A direction control valve for controlling the flow of pressure oil supplied from the actuator to the actuator, a control actuator for controlling the displacement of the variable displacement hydraulic pump, and a flow control means for controlling the drive of the control actuator, A variable displacement hydraulic pump for a civil engineering and construction machine hydraulic drive device that controls a displacement of a variable displacement hydraulic pump via a flow control means and a control actuator so as to keep a differential pressure between a pump pressure and an actuator load pressure constant. The target value of the differential pressure between the pump pressure and the actuator load pressure is increased according to the temperature decrease of the pressure oil discharged from the A differential pressure target value changing means for changing the target pressure is provided.

<Operation> Since the present invention has a configuration in which the differential pressure target value changing means is provided as described above, when the oil temperature decreases, the differential pressure target value changing means operates, and the pump pressure and the actuator load pressure are changed. The target value of the differential pressure is larger than before, and as a result, a larger flow rate than at room temperature is discharged from the variable displacement hydraulic pump, and the increase in pressure loss in the pipeline due to the decrease in temperature is caused by this large flow rate. Therefore, even when the hydraulic pressure is lowered, the same flow rate as at normal temperature can be supplied to the actuator.

<Example> Hereinafter, a hydraulic drive device of a civil engineering / construction machine according to 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.

The first embodiment shown in FIG. 1 is drawn in correspondence with FIG. 18 described above, and has a variable displacement hydraulic pump 1 and an actuator such as a hydraulic cylinder 2 which are equivalent to those shown in FIG. Control valve 3, head side chamber 12 and rod side chamber
13, a flow control means for controlling the driving of the control actuator 4, for example, a flow control valve 5 having driving units 6 and 9, a spring 7 for urging the flow control valve 5, and a hydraulic cylinder 2. A pipe 8 for guiding the load pressure to the drive section 6 of the flow control valve 5, a pipe 10 for guiding the pump pressure to the drive section 9 of the flow control valve 5 via the discharge pipe 15 of the hydraulic pump 1,
And a tank 11.

In the first embodiment, the variable displacement hydraulic pump 1
Differential pressure target value changing means for changing the target value of the differential pressure between the pump pressure and the load pressure of the hydraulic cylinder 2 so as to increase as compared with that according to the temperature decrease of the pressure oil discharged from Displacement volume changing means for forcibly changing the displacement volume of the variable displacement hydraulic pump 1 in accordance with the temperature drop of the pressurized oil, and the displacement volume changing device is, for example, sucked into the hydraulic pump 1. Oil temperature sensor 16 for detecting the temperature of the pressure oil to be supplied, and a control force for applying a control force corresponding to a signal output from the oil temperature sensor 16 to the drive unit 6 of the flow regulating valve 5 on the side where the spring 7 is provided. Means 17
Is included. The control force applying means 17 described above
Actuator 18 having a plunger capable of energizing drive unit 6 of flow regulating valve 5, and control device for controlling the drive of actuator 18
19 is included.

As shown in FIG. 2, the control device 19 includes an input unit 20 for inputting a signal output from the oil temperature sensor 16, a storage unit 21 for storing in advance the relationship between the pressure oil temperature θ and the control force F,
The control force F depends on the oil temperature detected by the oil temperature sensor 16.
And an output unit 23 that outputs a drive signal corresponding to the control force F obtained by the arithmetic unit 22 to the above-described operating body 18.
It has.

The relationship between the pressure oil temperature θ and the control force F stored in the storage unit 21 of the control device 19 described above is, for example, as shown in FIG. Characteristic line 24 indicating the pressure loss of
A hatched region 26 sandwiched between a characteristic line 25 indicating the initial set force of the spring 7 for biasing
That is, the relationship is such that the control force F increases as the hydraulic oil temperature θ decreases. For example, when the hydraulic temperature θ is θ1, the control force F
It is the relationship that becomes F1.

In the first embodiment configured as described above, the processing shown in FIG. 4 is performed by the control device 19 according to the signal output from the oil temperature sensor 16.

That is, first, as shown in step S1, the oil temperature sensor
The signal output from 16, that is, the pressure oil temperature θ
The data is read into the calculation unit 22 via the input unit 20 of 19. Next, the procedure proceeds to step S2, where the calculation unit 22 reads the relationship shown in FIG. 3 stored in the storage unit 21 and performs a calculation for obtaining the control force F corresponding to the above-described pressure oil temperature θ. Next, the procedure proceeds to step S3, where a drive signal corresponding to the control force F determined in step S2 is output from the output unit 23 to the operating body 18.

As a result, the force of the spring 7 and the control force F by the operating body 18 are given to the drive unit 6 of the flow regulating valve 5. The magnitude of the control force F applied to the drive unit 6 of the flow control valve 5 corresponding to the hydraulic oil temperature θ corresponds to the magnitude of the pressure loss in the pipeline at the hydraulic oil temperature θ. Therefore, when the temperature of the pressure oil decreases, the control force F increases, so that the flow control valve 5
Is forcibly switched to the left position side in FIG. 1, and accordingly, the piston rod 14 of the control actuator 4 tends to move rightward, so that the displacement of the hydraulic pump 1 is forcibly compared with that at normal temperature. Is controlled so as to largely change.

In the first embodiment configured as described above, when the temperature of the hydraulic pressure is lowered as described above, the resultant force of the force of the spring 7 and the control force F by the operating body 18 is applied to the drive unit 6 of the flow control valve 5. As a result, the target value of the differential pressure between the pump pressure and the load pressure of the hydraulic cylinder 2 is increased, that is, the displacement of the hydraulic pump 1 is changed to be forcibly increased, and thus the flow rate is larger than that at normal temperature. Is discharged from the hydraulic pump 1, and the pressure loss in the pipeline is absorbed by the large flow rate, so that the flow rate equivalent to that at normal temperature can be supplied to the hydraulic cylinder 2 through the directional control valve 3. Therefore, the maximum flow rate equal to the maximum flow rate supplied to the hydraulic cylinder 2 when the directional control valve 3 is operated at full temperature at normal temperature can be supplied to the hydraulic cylinder 2 when the hydraulic pressure decreases, and the temperature of the hydraulic oil decreases. Also, a constant operating speed of the hydraulic cylinder 2 can be obtained at all times, and a reduction in work efficiency can be prevented. Further, even when the temperature of the hydraulic oil is lowered, a constant flow rate is maintained at the hydraulic cylinder 2.
The oil film is not supplied, so that the oil film does not break, and therefore, the damage of the equipment due to such oil film break can be prevented. In addition, when the temperature of the pressure oil drops, a larger flow rate flows through the circuit than before, so that a warm-up operation for warming the entire circuit can be performed in a short time.

FIG. 5 is a circuit diagram showing a schematic configuration of the second embodiment of the present invention.

In the second embodiment, the force of the spring 7 for urging the driving portion of the flow control valve 5 is set to be larger than the force of the spring 7 in the first embodiment described above. The control force F is applied to the drive unit 9 of the flow control valve 5 via the control valve F. The relationship between the pressure oil temperature θ and the control force F stored in the storage unit 21 of the control device 19 is as shown in FIG.
The relationship is represented by a hatched area 26 sandwiched between a characteristic line 25 indicating the initial set force of the spring 7 and a characteristic line 24 indicating the pressure loss of the pipeline.

In the second embodiment configured as described above, when the temperature of the pressure oil drops, a smaller control force is applied to the drive unit 9 of the flow control valve 5 than at normal temperature. Is forcibly switched to the left position side, whereby the differential pressure target value is increased as in the first embodiment, that is, the displacement of the hydraulic pump 1 is controlled so as to be forcibly changed to a large value. The same operation and effect as those of the first embodiment are obtained.

FIG. 7 is a circuit diagram showing a schematic configuration of the third embodiment of the present invention.

In the third embodiment, the flow rate control means for controlling the drive of the control actuator 4 for controlling the displacement of the hydraulic pump 1 supplies a constant pressure, and the hydraulic pressure communicated to the rod side chamber 13 of the control actuator 4. The electromagnetic switching valve 28, which is connected to the power source 27 and the hydraulic pressure source 27, and is connected to the head side chamber 12 and the rod side chamber 13 of the control actuator 4, and communicates with the tank 11 and the electromagnetic switching valve 28. And the head side chamber 12 of the control actuator 4
The control force applying means is constituted by an oil temperature sensor 16 and a differential pressure Δ between the pump pressure and the actuator load pressure, that is, the load pressure of the hydraulic cylinder 2.
A differential pressure sensor 30 for detecting a P _LS, are constituted by One Manzanillo a control device 31.

The above-described control device 31 has an input unit for inputting each of the signals output from the above-described oil temperature sensor 16 and the differential pressure sensor 30, an oil temperature, that is, a pressure oil temperature θ, and a target differential pressure, that is, a differential pressure target value ΔP. , A target differential pressure corresponding to the oil temperature detected by the oil temperature sensor 16, that is, a differential pressure target value ΔP is calculated, and the differential pressure ΔP _LS detected by the differential pressure sensor 30 is calculated. And a calculation unit for calculating the pressure difference between the pressure difference and the differential pressure target value ΔP, and an output unit for outputting a drive signal corresponding to the pressure difference obtained by the calculation unit to each of the electromagnetic switching valves 28 and 29. is there.

The storage unit of the control device 31 stores, for example, the relationship between the pressure oil temperature θ and the target differential pressure value ΔP shown in FIG. 8, that is, the target differential pressure value ΔP as the pressure oil temperature θ decreases. The relationship that increases is stored, and the characteristic line 32 is set to a relationship corresponding to the relationship between the pressure oil temperature θ and the control pressure loss shown in FIG. 19 described above.

In the third embodiment configured as described above, the processing shown in FIG. 9 is performed by the control device 31 in accordance with the signals output from the oil temperature sensor 16 and the differential pressure sensor 30.

That is, first, as shown in step S1, the differential pressure sensor
Signal output from the signal and an oil temperature sensor 16 is output from 30 is read into the arithmetic unit as the respective difference pressure detection value [Delta] P _LS and the pressure oil temperature through the input unit of the control device 31 theta. Next, the procedure proceeds to step S2, where the arithmetic unit reads the relationship shown in FIG. 8 stored in the storage unit and performs an arithmetic operation to obtain a differential pressure target value ΔP corresponding to the pressure oil temperature θ. Next, the process proceeds to step S3, where it is determined whether the differential pressure detection value ΔP _LS is equal to the differential pressure target value ΔP. If this determination is not satisfied, the procedure moves to step S4. In this step S4, it is determined whether or not the detected differential pressure value ΔP _1S is larger than the target differential pressure value ΔP. If this determination is satisfied, the flow rate is too large,
Move on to step S5. In this step S5, the electromagnetic switching valve is
A signal for turning off the 28 and a signal for turning on the electromagnetic switching valve 29 are output. As a result, the electromagnetic switching valve 28 shown in FIG. 7 is held in the closed position shown in FIG. 7, the electromagnetic switching valve 29 is switched to the communication position, and the pressure oil of the hydraulic power source 27 is supplied to the rod side chamber of the control actuator 4. The pressure oil supplied to the head side chamber 12 is returned to the tank 11 via the electromagnetic switching valve 29, and the piston rod 14 moves leftward in the figure. Therefore, the displacement of the hydraulic pump 1 is controlled to be small, and the flow rate is small.

If the determination in step S4 in FIG. 9 is not satisfied, the flow rate is too small, and the process proceeds to step S6. In step S6, the electromagnetic switching valve is output from the output unit of the control device 31.
A signal is output to turn on 28 and turn off the electromagnetic switching valve 29.
As a result, the electromagnetic switching valve 28 shown in FIG. 7 is switched to the communicating position, the electromagnetic switching valve 29 is held at the shearing position shown in FIG. 7, and the pressure oil of the hydraulic power source 27 is supplied to the rod side chamber of the control actuator 4. 13 and the head side chamber 12 are supplied. Accordingly, the piston rod 14 moves to the right in FIG. 7 due to the pressure receiving area difference between the rod side and the head side, and is controlled so as to increase the displacement, thereby increasing the flow rate.

Further, when the above determination in the step S3 of FIG. 9 is satisfied, that is, when the differential pressure detection value ΔP _LS is equal to the differential pressure target value ΔP
If it is equal to, the process returns to the beginning, that is, both the electromagnetic switching valves 28 and 29 are held in the disengaged and disconnected positions, the displacement at that time is maintained, and the appropriate flow rate is supplied to the hydraulic cylinder 2. Supplied.

In the third embodiment configured as described above, the storage unit of the control device 31 stores in advance the differential pressure target value ΔP that increases as the hydraulic oil temperature θ decreases, and this differential pressure target value ΔP
Since the rate of increase in the pressure oil is approximated to the rate of pressure loss in the pipeline that increases with a decrease in the pressure oil temperature, when the directional control valve 3 is in the full stroke state, the decrease in the pressure oil temperature θ Regardless, a constant maximum flow rate can be supplied to the hydraulic cylinder 2, and the same operational effects as those of the first and second embodiments can be obtained.

FIG. 10 is a circuit diagram showing a schematic configuration of a fourth embodiment of the present invention.

In FIG. 10, an unload valve 33 for discharging a small flow rate to the tank 11 is provided to protect the circuit when the directional control valve 3 is neutral. Generally, the set differential pressure of the unload valve 33 tends to increase as the unload flow rate shown in FIG. 11 increases.

In the fourth embodiment shown in FIG. 10, the drive unit 6 of the flow rate regulating valve 5 is configured to be able to be given a force by the spring 7 and a force by the operating body 18 of the control force adding means 17. The relationship between the pressure oil temperature θ shown by, for example, a solid line in FIG. 12, and the differential pressure target value between the pump pressure and the load pressure of the hydraulic cylinder 2, that is, the differential pressure target value ΔP is stored in the storage unit of the control device 19. Let me do it. In FIG. 12, a characteristic line indicated by a chain line
34a exemplifies the set differential pressure of the unload valve 33, and the characteristic line 35 shown by a solid line is based on the pressure oil temperature θ2 at which the circuit needs to be warmed up, and the pressure oil temperature θ is smaller than θ2 In this case, the differential pressure target value ΔP becomes larger than the set differential pressure of the unload valve 33, and when the hydraulic oil temperature θ is larger than θ2, the differential pressure target value ΔP becomes smaller than the set differential pressure of the unload valve 33. ing.

Further, in the fourth embodiment, as shown in FIG. 10, for example, a selection device 37 for selecting whether or not to perform a warm-up operation is provided, and the warm-up operation is selected by the selection device 34. When this is done, the warm-up signal is output to the control device 19.

In the fourth embodiment having such a configuration, the fourth embodiment
The processing shown in FIG. 13 is performed. That is, as shown in step S1 in FIG. 13, the arithmetic unit of the control device 19 determines whether or not a warm-up signal is input. If this determination is not satisfied, for example, it is obvious that the temperature of the pressure oil will not drop at normal temperature, for example, and the process returns to the beginning. In this case, since no drive signal is output to the operating body 18, the force applied to the drive unit 6 of the flow control valve 5 is only the force of the spring 7, and thus the drive units 9, 6 of the flow control valve 5 are provided. The differential pressure acting on, for example, in FIG.
This corresponds to the characteristic line 35 when the pressure oil temperature θ is larger than θ2.

Then, when the selection device 34 is operated and the warm-up signal is input, the warm-up operation is intended,
Move on to step S2. In step S2, the signal from the oil temperature sensor 16
That is, the pressure oil temperature θ is read into the calculation unit. Then step S3
Move on to In step S3, the relationship indicated by the characteristic line 35 in FIG. 12 stored in the storage unit is read, and when the pressure oil temperature θ is smaller than θ2, the differential pressure target value that becomes larger than the set differential pressure of the unload valve 33 When the pressure oil temperature θ is larger than θ2, a target differential pressure value ΔP that becomes smaller than the set differential pressure of the unload valve 33 is obtained. Then, proceed to step S4,
The driving signal is selectively output to the operating body 18 in accordance with the differential pressure target value ΔP obtained in the step (1).

In this case, when the pressure oil temperature θ is smaller than θ2, a drive signal is given to the operating body 18 to operate the operating body 18, and a control force by the operating body 18 is applied to the drive section 6 of the flow rate regulating valve 5. . When the pressure oil temperature θ is larger than θ2, the drive signal for operating the operating body 18 is not output, that is, the driving force of the operating body 18 is not applied to the drive unit 6 of the flow rate regulating valve 5. That is, when the pressure oil temperature θ is larger than θ2, as in the case where the selection device 34 is not operated, only the weak force of the spring 7 is applied to the drive unit 6 of the flow regulating valve 5, and the pressure oil temperature θ
Is smaller than θ2, a large force of the control force by the spring 7 and the operating body 18, that is, the driving unit 9 of the flow regulating valve 5,
6 shows a differential pressure target value Δ larger than the set differential pressure of the unload valve 33.
A large force that can generate P is applied to the drive unit 6 of the flow control valve 5.

In the fourth embodiment having such a configuration, when the selection device 34 is operated and the pressure oil temperature θ is lower than the temperature θ2 at which the warm-up operation is considered to be necessary, The flow control valve 5 is forcibly switched to the left position in FIG. 10, and the differential pressure target value Δ is set in the same manner as in the first to third embodiments.
P is increased, that is, the displacement of the hydraulic pump 1 is controlled to be greatly changed, and a larger flow rate is discharged from the hydraulic pump 1 than at normal temperature, whereby the flow rate equivalent to that at normal temperature is reduced by the hydraulic cylinder 2. To the first to third
The same effect as that of the embodiment can be obtained.

In the fourth embodiment, as shown by the characteristic line 35 in FIG. 12, the temperature θ of the pressure oil which is considered to require a warm-up operation
2, the operating member 18 is controlled ON-OFF. However, the pressure oil temperature θ and the differential pressure target value ΔP continuously change as indicated by a characteristic line 36 shown by a broken line in FIG. The relationship between the control device
The control unit 19 may store the control force in accordance with the characteristic line 36 to the drive unit 6 of the flow control valve 5 via the operating body 18. In this case, the flow rate increases due to the forcible change of the displacement volume due to the decrease in the pressure oil temperature θ, and the increase in the flow rate causes the unload valve 33 to move as shown in FIG.
Pressure rises slightly. Accordingly, when the pressure oil temperature θ is slightly lower than θ2 in FIG. 12 and the differential pressure target value ΔP slightly exceeds the set differential pressure 34 of the unload valve 33,
The balance is achieved at the point where the differential pressure target value ΔP and the set differential pressure of the unload valve 33 become equal. Even when the pressure oil temperature θ is smaller than θ2, the flow control valve 5 is switched to the left position in FIG.
The same effect as described above is achieved. Further, the flow rate is gradually switched as compared with the case where the flow control valve 5 is switched ON / OFF, so that the flow rate discharged from the hydraulic pump 1 also gradually increases, which contributes to the safety protection of the circuit.

FIG. 14 is a circuit diagram showing a schematic configuration of a fifth embodiment of the present invention, and FIG. 15 is a circuit diagram showing a schematic configuration of a sixth embodiment of the present invention.

The fifth embodiment shown in FIG. 14 differs from the second embodiment shown in FIG. 5 in that an unload valve 33 and a selector 34 are provided, and the sixth embodiment shown in FIG. Is the unload valve 33 in the third embodiment shown in FIG.
A control device 19 according to the fifth embodiment and a control device 31 according to the sixth embodiment are provided.
Each of the storage sections stores the relationship between the hydraulic oil temperature θ and the control force F or the differential pressure target value ΔP as shown in FIG.

Also in the fifth and sixth embodiments configured as described above, when the selecting device 34 is operated and the hydraulic oil temperature θ is lower than θ2, the differential pressure target value increases more than before.
That is, the displacement of the hydraulic pump 1 is forcibly changed to be large, and the same effect as that of the above-described fourth embodiment is obtained.

FIG. 16 is a circuit diagram showing a schematic configuration of the seventh embodiment of the present invention.

The seventh embodiment includes an unload valve 37 interposed between the discharge pipe line 15 of the hydraulic pump 1 and the tank 11, and a directional control valve.
A conduit 41 that connects the secondary side of the throttle valve 39 incorporated in 38 and the spring chamber 40 of the flow regulating valve 39a, and is interposed in the conduit 41 to prevent backflow in the direction of the throttle valve 39. A check valve 42 and a minute relief valve 43 that allows a minute amount of pressurized oil flowing through a portion of a pipe 41 communicating the check valve 42 and the spring chamber 40 to flow out to the tank 11.
And a throttle valve 44 interposed in the pipeline 41, and disposed between the throttle valve 44 and the spring chamber 40 to maintain a predetermined pressure in a pipeline between the throttle valve 44 and the spring chamber 40. A relief valve 45 is provided. Further, a pipe connecting the pilot chamber 46 of the flow control valve 39a to the primary side of the throttle valve 39 built in the direction control valve 38.
47 and.

Then, a differential pressure target value changing means for changing the target value of the differential pressure between the pump pressure and the load pressure of the hydraulic cylinder 2 so as to increase the same, for example, a displacement volume changing means for changing the displacement of the hydraulic pump 1 is provided by a hydraulic pump. A resistance element provided in the discharge pipe 15, for example, a throttle valve 48, and control force adding means 49 for applying a control force corresponding to a differential pressure across the throttle valve 48 to the drive unit of the flow rate adjustment valve 39 a, that is, the spring chamber 40. It is constituted by. The above-described control force adding means 49 includes, for example, a flow control valve 39a.
, That is, an actuator 52 having an operating portion 51 connected to the spring 50, for example, a set force control means for controlling the set force of the spring 50 of the spring chamber 40.
A chamber 53 located on the spring chamber 40 side of the actuator 52 is connected to a pipe 47 via a pipe 54, and a chamber 55 of the actuator 52 opposite to the chamber 53 is connected via a pipe 56. The upstream side of the throttle valve 48 is communicated.

In the seventh embodiment constructed as described above, when the directional control valve 38 is in the neutral position and the hydraulic pump 1 is driven, the discharge line 15 and the line 41 of the hydraulic pump 1 are cut off. And communicates with the tank 11 via a minute relief valve 43 in a conduit 41. Also, the pressure oil discharged from the hydraulic pump 1
It is led to the pilot chamber 46 of the flow control valve 39a via 47,
The tank pressure is led to the spring chamber 40 via the throttle valve 44. 16 is switched to the left position in FIG. 16, the piston rod 14 of the control actuator 4 moves leftward in the figure due to the pressure receiving area difference between the head side and the rod side, and the displacement of the hydraulic pump 1 is reduced to the minimum tilt position. , And the minimum flow rate is discharged from the hydraulic pump 1 and unloaded.

In such a state, when the directional control valve 38 is switched to one of the left and right switching positions with the intention of driving the hydraulic cylinder 2, the secondary side of the throttle valve 39 of the directional control valve 38 communicates with the pipeline 41. From there, a gradually increasing pressure is guided to the spring chamber 40 of the flow regulating valve 39a via the throttle valve 44. When the combined force of the force due to the rising pressure and the force of the spring 50 of the spring chamber 40 becomes larger than the force on the pilot chamber 46 side, that is, the force due to the pump pressure, the flow regulating valve 39a is gradually switched to the right position, The head side chamber 12 of the control actuator 4 is a tank 11
And its piston rod 14 moves to the right in the figure,
The displacement of the hydraulic pump 1 increases, and a large flow rate is supplied to the hydraulic cylinder 2 via the direction control valve 38, and the hydraulic cylinder 2 is driven. In the hydraulic pump 1, the pressure difference between the pilot chamber 46 of the flow control valve 39a and the spring chamber 40
Attempt to deliver flow until it is equal to the set pressure due to zero. This pressure difference corresponds to the pressure loss of the throttle valve 39 of the direction control valve 38. When the opening area of the throttle valve 39 is gradually increased in accordance with the opening of the direction control valve 38, the pump flow rate is also gradually increased in accordance with the opening, and metering is obtained.

Then, when the pressure oil temperature θ decreases, the differential pressure across the throttle valve 48 increases, and a large pressure is guided to the chamber 55 of the actuator 52 via the conduit 56. As a result, the operating portion 51 moves to the left in FIG. 16 against the force of the spring in the chamber 53,
The setting force of the spring 50 of the spring chamber 40 of the flow regulating valve 39a is greatly changed. Along with this, the flow control valve 39a is switched to the right position in FIG. 16, and the head side chamber 12 of the control actuator 4 communicates with the tank 11. Accordingly, the pump pressure guided to the rod side chamber 13 of the control actuator 4 moves the piston rod 14 of the control actuator 4 rightward in FIG. 16 to increase the differential pressure target value. The displacement of the pump 1 is controlled so as to be forcibly changed greatly, and a larger flow rate is supplied from the hydraulic pump 1 than at normal temperature. Therefore, the pressure loss in the pipeline caused by the decrease in the hydraulic pressure is absorbed to control the direction. A flow rate equivalent to that at normal temperature is supplied to the hydraulic cylinder 2 via the valve 38, and the same effect as in the above-described fourth to sixth embodiments is achieved.

FIG. 17 is a circuit diagram showing a schematic configuration of the eighth embodiment of the present invention.

In the eighth embodiment, a pilot pump 56a driven in synchronization with the hydraulic pump 1 is provided, and a throttle valve 58 is provided in a discharge pipe 57 of the pilot pump 56a. Is connected to the chamber 55 of the actuator 52 via the pipe 59, and the downstream side is connected to the actuator via the pipe 60.
Called room 55 in 52. Other structures are almost the same as those of the seventh embodiment shown in FIG.

In the eighth embodiment, the differential pressure across the throttle valve 58 increases with a decrease in the pressure oil temperature θ, and a large pressure is guided to the chamber 55 of the actuator 52 via the pipe 59, and as a result, 17 moves to the left in FIG. 17, the flow control valve 39a is switched to the right position in FIG. 17 via the spring 50, and the piston rod 14 of the control actuator 4 moves to the right in FIG. Then, the target value of the differential pressure increases, that is, the hydraulic pump 1
The displacement is controlled so as to be forcibly changed greatly, and an effect equivalent to that of the above-described seventh embodiment is obtained.

In each of the above-described seventh embodiment shown in FIG. 16 and the sixth embodiment shown in FIG.
Although each of the 58 is provided, a configuration in which the pipe diameter of a part of the managements 15 and 57 is reduced may be used instead. Even in this case, the same effect can be obtained.

<Effect of the Invention> Since the hydraulic drive device for civil engineering and construction machinery of the present invention is configured as described above, it is possible to supply a flow rate equal to the normal temperature to the actuator even when the oil noise is reduced, and therefore, This has the effect of preventing a decrease in work efficiency due to a decrease in oil temperature, preventing damage to equipment due to breakage of an oil film due to a decrease in oil temperature, and enabling a warm-up operation to be performed in a shorter time than before.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a hydraulic drive system for a civil engineering and construction machine according to the present invention.
FIG. 2 is a circuit diagram showing a schematic configuration of an embodiment of the present invention; FIG. 2 is a diagram showing a configuration of a control device provided in the first embodiment shown in FIG. 1;
FIG. 3 is a diagram showing a relationship between the pressure oil temperature and the control force stored in a storage unit of the control device provided in the first embodiment, and FIG. 4 is a processing content in the control device provided in the first embodiment. FIG. 5 is a circuit diagram showing a schematic configuration of a second embodiment of the present invention, and FIG. 6 is stored in a storage section of a control device provided in the second embodiment shown in FIG. FIG. 7 is a diagram showing the relationship between the pressure oil temperature and the control force, FIG. 7 is a circuit diagram showing a schematic configuration of a third embodiment of the present invention, and FIG. 8 is provided for the third embodiment shown in FIG. FIG. 9 is a diagram showing a relationship between a pressure oil temperature and a differential pressure target value stored in a storage unit of the control device, FIG. 9 is a flowchart showing processing contents in the control device provided in the third embodiment, and FIG. FIG. 11 is a circuit diagram showing a schematic configuration of a fourth embodiment of the present invention. FIG. 11 is a circuit diagram showing an antenna provided in the fourth embodiment shown in FIG. FIG. 12 is a diagram showing characteristics of a pressure valve, FIG. 12 is a diagram showing a relationship between a pressure oil temperature and a differential pressure target value stored in a storage unit of a control device provided in the fourth embodiment, and FIG. FIG. 14 is a flowchart showing the processing contents in the control unit provided in the fourth embodiment, FIG. 14 is a circuit diagram showing a schematic configuration of a fifth embodiment of the present invention, and FIG. 15 is a circuit diagram showing a sixth embodiment of the present invention. FIG. 16 is a circuit diagram showing a schematic configuration of the seventh embodiment of the present invention, FIG. 17 is a circuit diagram showing a schematic configuration of the eighth embodiment of the present invention, and FIG. Is a circuit diagram showing a schematic configuration of a conventional hydraulic drive device for civil engineering and construction machinery, and FIG.
FIG. 19 is a view showing a relationship between a pressure oil temperature and a pressure loss in a pipeline in the hydraulic drive device shown in FIG. 18. DESCRIPTION OF SYMBOLS 1 ... Variable displacement hydraulic pump, 2 ... Hydraulic cylinder (actuator), 3 ... Directional control valve, 4 ... Actuator for control, 5 ... Flow control valve, 6, 9 ... Drive section, 7 ...
… Spring, 8,10… Pipe line, 11… Tank, 12… Head side chamber, 13… Rod side chamber, 14… Piston rod, 15…
... Discharge pipeline, 16 ... Oil temperature sensor, 17 ... Control force adding means, 18 ... Working body, 19 ... Control device, 20 ... Input unit, 21
... Storage unit, 22 ... Calculation unit, 23 ... Output unit, 27 ... Hydraulic source, 28, 29 ... Solenoid switching valve, 30 ... Differential pressure sensor, 31 ...
Control device, 33, 37 ... unload valve, 34 ... selection device,
38: Directional control valve, 39: Throttle valve, 39a: Flow control valve, 40: Spring chamber, 46: Pilot chamber, 48: Throttle valve (resistance element), 49: Control force applying means 50 …… Spring, 51
… Actuator, 52… Actuator, 56a… Pilot pump, 58… Throttle valve.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masakazu Haga 650, Kandamachi, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura Plant (56) References JP-A-61-189350 (JP, A) JP-A-57 −9302 (JP, A)

Claims (11)

(57) [Claims] 1. A variable displacement hydraulic pump, an actuator driven by pressure oil discharged from the variable displacement hydraulic pump, and a direction for controlling a flow of pressure oil supplied from the variable displacement hydraulic pump to the actuator. A control valve, a control actuator for controlling the displacement of the variable displacement hydraulic pump, and a flow control means for controlling the drive of the control actuator; and maintaining a constant pressure difference between the pump pressure and the actuator load pressure. As described above, in a hydraulic drive device of a civil engineering / construction machine for controlling the displacement of the variable displacement hydraulic pump via the flow rate control means and the control actuator, the temperature of the pressure oil discharged from the variable displacement hydraulic pump is controlled according to the temperature drop. Differential pressure target value changing means for changing the target value of the differential pressure between the pump pressure and the actuator load pressure so as to increase. The hydraulic drive system for civil engineering and construction machine, characterized in that provided. 2. The variable displacement hydraulic pump according to claim 1, wherein said differential pressure target value changing means is a displacement volume changing means for forcibly increasing a displacement of said variable displacement hydraulic pump. Hydraulic drive for civil and construction machinery. 3. The flow rate control means comprises a flow rate regulating valve, and the differential pressure target value changing means responds to an oil temperature sensor for detecting the temperature of the pressure oil and a signal output from the oil temperature sensor. The hydraulic drive system for civil engineering and construction machinery according to claim 1 or 2, further comprising control force applying means for applying a control force to a drive unit of the flow control valve. 4. The hydraulic drive device for civil engineering and construction machinery according to claim 3, further comprising an unload valve for releasing a predetermined amount of pressure oil discharged from the variable displacement hydraulic pump to a tank. 5. The apparatus according to claim 1, wherein the flow rate control means includes an electromagnetic switching valve for controlling the driving of the control actuator, and the differential pressure target value changing means includes an oil temperature sensor for detecting a temperature of the pressure oil, and a pump pressure sensor. Pressure sensor that detects the pressure difference between the oil pressure and the actuator load pressure, and an input unit that inputs each of the oil temperature sensor and the signal output from the pressure difference sensor.The relationship between the oil temperature and the target differential pressure is stored in advance. A storage unit that calculates a target differential pressure corresponding to the oil temperature detected by the oil temperature sensor, and calculates a pressure difference between the differential pressure detected by the differential pressure sensor and the target differential pressure. The civil engineering apparatus according to claim 1, further comprising: a control unit having an output unit that outputs a drive signal corresponding to the pressure difference obtained by the arithmetic unit to the electromagnetic switching valve.・ Hydraulic drive for construction machinery. 6. A hydraulic drive system for civil engineering and construction machinery according to claim 5, further comprising an unload valve for releasing a predetermined amount of pressure oil discharged from said variable displacement hydraulic pump to a tank. 7. The flow rate control means comprises a flow rate control valve, and the differential pressure target value changing means provides a resistance element provided in a pipeline and a control force according to a differential pressure across the resistance element. The hydraulic drive system for civil engineering and construction machinery according to claim 1 or 2, further comprising a control force applying means for applying the control force to the drive unit. 8. The civil engineering / construction machine according to claim 7, wherein said control force applying means is a set force control means for controlling a set force of a spring for urging said flow regulating valve. Hydraulic drive. 9. The hydraulic drive device for civil engineering and construction machinery according to claim 7, wherein the pipeline in which the resistance element is provided is a discharge pipeline of the variable displacement hydraulic pump. 10. A pilot pump which is driven in synchronization with said variable displacement hydraulic pump, and wherein a pipe in which said resistance element is provided is a discharge pipe of said pilot pump. Hydraulic drive for civil engineering and construction machinery as described. 11. The hydraulic drive system for civil engineering and construction machinery according to claim 7, wherein said resistance element is a throttle valve.