JP2548204Y2 - Hydraulic drive - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive for a construction machine or the like, and more particularly to an improvement of a hydraulic drive for improving the combined operability of an actuator of this kind.

[0002]

2. Description of the Related Art Generally, in a hydraulic drive system comprising a plurality of control valves connected in parallel, when an actuator is operated in a combined manner, pressure oil flows only into a light-load-side actuator. Either a fixed throttle is provided on the light-load-side actuator, or a shunt compensation valve is provided for each control valve. However, in the former case, there is a drawback that the energy loss is impaired due to the pressure loss due to the fixed throttle, while the latter case requires a special shunt compensating valve, which complicates the structure and increases the price.

[0003] The applicant of the present invention has previously developed a new technique for solving these drawbacks and has filed an application for registration of a utility model (Japanese Utility Model Publication No. 2-10802). Hereinafter, this conventional technique will be briefly described.

In FIG. 2, a hydraulic drive system comprising a plurality of control valves is provided with a plurality of (in this case, two) control valves 12 and 14 in which pressure oil discharged from a pump 10 is arranged in parallel. 16 and 18, and the return oil is discharged to the tank 20. When the control valves 12 and 14 are in the neutral state (the state shown in the figure)
, The discharge pressure oil is directly discharged to the tank 20. Also,
Each control valve 12, 14 operates a corresponding pilot valve 22, 24 to apply a pilot pressure from a pilot pump 26 via a respective pilot line 28, 30 and 32, 34, thereby providing a neutral position as shown. The position is switched to the left or right. However,
In this prior art, the light load side actuator 16
A pilot line 28 for switching the control valve 12 to lower the load 17
A pressure reducing valve 36 is provided thereon, and a cylinder 40 for applying a spring pressure to a valve body 38 of the pressure reducing valve 36 is provided with a pilot pressure for switching the control valve 14 of the high-load-side actuator 18, that is, both actuator lines 32 and 34. The pilot pressure 44 detected via the shuttle valve 42 in any one of them is applied. It is needless to say that the same pressure reducing valve as described above can be provided for the other pilot line 30 of the light load side actuator 16 as necessary.

Accordingly, in such a prior art arrangement, when the combined operation of the two actuators, control valve 14 corresponding to the high load side actuator 18 is being fully switched open, corresponding to the light load actuator 16 control valve 12 is completely not switched and is maintained in the middle of the metering state. As described above, the pressure oil for the light-load-side actuator 16 is throttled, so that the pressure oil is also supplied to the high-load-side actuator 18, and a combined operation is achieved.

As described above, according to the prior art, since a fixed throttle is not required for the light-load-side actuator, no energy loss occurs in the light-load-side actuator, and a special shunt compensation is provided for each control valve. Since no valve is required, the structure is simplified and the cost is reduced.

[0007]

However, the complex operability achieved by the above conventional technique still has the following problems.

That is, at the time of the combined operation in the prior art, the control valve corresponding to the light-load-side actuator is throttled to the metering state, so that the pump discharge pressure increases and the high-load-side actuator is also driven. However, at this time, since the discharge flow rate of the pump is not controlled, the distributed supply amount to each actuator is actually unstable, and as a result, combined operability cannot be reliably achieved. In this prior art, since the pump discharge pressure oil is bypassed in the metering state of the control valve irrespective of a single operation or a combined operation, there is a problem that the efficiency of the entire apparatus is reduced.

Therefore, the purpose of the present invention is to reduce the load
Multiple different actuators can be connected to a common variable displacement pump
Operation by multiple control valves connected in parallel to
When working, the discharge rate of the variable displacement pump is
The differential pressure between the discharge pressure and the actuator load pressure becomes constant
Control in the light load side actuator and
Oil supply to the high-load actuator
An object of the present invention is to provide a hydraulic drive device that can stabilize and secure complex operability and improve the efficiency of the device.

[0010]

In order to achieve the above object,
Therefore, the hydraulic drive device according to the present invention includes a plurality of multiple control valves (12, 14 ) connected in parallel to a common variable displacement pump (10) and controlling a plurality of actuators (16, 18) having different loads, respectively. made), the respective control valve is energized the spool center spring, in a configuration with the hydraulic drive device comprising to adjust the spool stroke by the pilot pressure, wherein the control valves (12, 14) is closed center Detecting the load pressure of the actuators (16, 18) respectively
The load pressure detection line (50, 52) provided, each control valve (1
Pressure reducing valve (36a, 36) on pilot line (28,34)
b) is provided , and the discharge pressure oil from the variable displacement pump (10) is
When passing through the control valves (12, 14),
Actuators generated by the throttles (13, 15)
Shuttle valve for comparing the load pressure of (42a) provided, the shuttling
Of the maximum load pressure detected by either valve (42a).
Select this and control the discharge flow rate of the variable displacement pump (10)
Means (56), controlling the discharge flow rate of the variable displacement pump (10) so that the differential pressure between the pump discharge pressure and the actuator load pressure becomes constant, and further controlling the control valve of the light load side actuator. provided on a pilot line to switch
The pressure reducing valve, characterized by configured to control the pilot pressure for switching the control valve of the high-load side actuator.

In this case, the pressure reducing valves (36a, 36b) are
A body that applies spring pressure to the body (38a, 38b) and this valve body
(40a, 40b) and the light load side actuator (16
Or 18) corresponding to the control valve (12 or 14)
Reducing valve (3) connected to pilot line (28 or 34)
High load on cylinder (40a or 40b) of 6a or 36b)
Control valve (14) to control the side actuator (18 or 16)
Or 12) corresponding pilot lines (32 and 34 or
28 and 30)
Is detected by the shuttle valve (42c or 42b) and
Applied via the set pressure signal line (62 or 60)
The control valve (12 or 14) can be configured to maintain a metering state .

[0012]

According to the hydraulic drive of the present invention, the negative
Multiple actuators with different loads can be
In the case of operating multiple <br/> case by a plurality of multiple-control valve connected in parallel to the pump, the control valve corresponding to a light load side actuator is squeezed, high load the pump discharge pressure is increased The side actuator is also driven. At this time , the variable displacement pump is controlled so that its discharge flow rate is constant such that the differential pressure between the pump discharge pressure and the actuator load pressure is constant, that is, corresponding to the actuator load pressure. . Therefore, the pressurized oil distribution supply quantity for both the actuators is stabilized, the operability in the combined operation is ensured, and can also improve the efficiency of the device.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the hydraulic drive device according to the present invention will be described in detail with reference to the accompanying drawings.
For convenience of description, the same components as those of the conventional configuration shown in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, first, the overall configuration of the hydraulic drive device of the present invention is the same as the conventional device shown in FIG.
Therefore, to briefly explain the whole apparatus again, the pilot pressure from the pilot pump 26 is applied to the pilot lines 28, 30 or 32, 34 via the pilot valves 22, 24 to operate the control valves 12, 14. By doing so, the hydraulic pressure discharged from the pump 10 is supplied to the actuators 16 and 18, respectively, and the return oil is discharged to the tank 20, whereby the actuator is driven. In this embodiment, the two actuators 16 and 18 each have a load 1
The ascent and descent are carried out while suspending or supporting 7, 19, and when the descent is performed, the load becomes light.

In the present invention, however, the control valve 12,
14 is a closed center type pump
10 is configured as a variable displacement type, and control valves 12, 14
A predetermined pressure reducing valve 36 is provided on pilot lines 28 and 34 of
a and 36b are provided. That is, the control valve 12,
14 is configured as a closed center as shown in the figure, and its respective actuators 16, 1
Eight load pressure detection lines 50 and 52 are provided. Then, the highest load pressure in these load pressure detection lines 50 and 52 is selected via the shuttle valve 42a, and the signal
Discharge flow rate control hand of the variable displacement pump 10 via an in-54
It is configured to be applied to the stage 56. Incidentally, the in <br/> pump 10, the pump discharge pressure via the hydraulic line 58 is also applied.

Therefore, according to such a configuration, the discharge flow rate of the pump 10 is controlled to a flow rate at which the differential pressure between the discharge pressure of the pump 10 and the maximum load pressure becomes constant. Further, the differential pressure, discharge pressure oil from the pump 10,
When passing through the control valves 12 and 14, they are generated by throttles 13 and 15 provided therein. Next, the pilot lines 28, 34 of the control valves 12 , 14
Pressure reducing valves 36a and 36b are provided on (a pilot line for operating the control valves 12 and 14 in the direction of lowering the loads 17 and 19 with respect to the actuators 16 and 18). The pressure reducing valves 36a and 36b are
The configuration is basically the same as that of the conventional technology. That is,
The pressure reducing valves 36a and 36b are composed of valve bodies 38a and 38b and cylinders 40a and 40b for applying spring pressure to the valve bodies.
And controls the light load side actuator
Pilot line corresponding to control valve 12 or 14
Pressure reducing valve 36a or 36b connected to 28 or 34
The other (high load side) air cylinders 40a and 40b
Actuator in <br/> pressure of the pilot line 32 and 34 or 28 and 30 corresponding to the control valve 14 or 12 to control, either pressure respectively, are detected shuttle valve 42c, the 42b pilot Pressure signal line
It is configured to be applied through the terminals 62 and 60 . The operation of the pressure reducing valves 36a and 36b is the same as that of the above-described conventional technique, and is as described as the next overall operation.

Therefore, the overall operation, that is, the operation of the hydraulic drive device of the present invention will be described. If the pilot valve 24 is operated to apply a pilot pressure to, for example, the pilot line 34, the control valve 14 moves rightward in the drawing, and the discharge oil from the variable displacement pump 10 is supplied to the piston side chamber of the actuator 18. , Actuator 18
Are driven independently. By the way, in this case, since the load 19 is lowered, the load is light, the discharge pressure of the variable displacement pump 10 is maintained at a relatively low pressure, and the discharge flow rate is the differential pressure of the throttle 15 as described above. The flow rate is controlled so as to be constant, that is, irrespective of the load pressure, in accordance with the operation amount of the control valve 14 (the opening degree of the throttle 15). Since no pressure is generated in the pilot pressure signal line 60, the pressure reducing valve 36b does not operate.

Next, in this state, when the pilot valve 22 is also operated to apply a pilot pressure to, for example, the pilot line 30, the control valve 12 moves rightward in the drawing, and the pressure oil flows to the piston side chamber of the actuator 16. The load 17 is supplied, and the load 17 rises. However, at this time, the actuator 16
Is high load, the pilot pressure in the pilot line 30 acts on the cylinder 40b via the shuttle valve 42b and the signal line 60 to reduce the secondary pressure of the pressure reducing valve 36b and open the control valve 14. Decrease the degree. As a result, the pump discharge pressure rises and the high load side actuator 16 is also driven. At this time, the discharge flow rate of the variable displacement pump 10 depends on the load pressure of the high load side actuator 16 detected by the load pressure detection line 50. Is applied to the discharge flow rate control unit 56 via the shuttle valve 42a and the signal line 54, so that the flow rate is controlled to a flow rate corresponding to the high load pressure. Regardless of the load pressure at 18, the flow rate is controlled to correspond to the opening of the control valve 14. Therefore, the high-load-side actuator 16 is reliably and stably driven with the surplus oil amount obtained by subtracting the distribution flow rate to the light-load-side actuator 18 from the total discharge flow rate of the pump.

As described above, according to the present invention, the composite operability of the actuator can be reliably achieved with a relatively simple configuration, and the device efficiency can be improved. The operation of the pressure reducing valve 36a in the same manner can be easily analogized, and the description thereof will be omitted.

While the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various design changes can be made without departing from the spirit of the present invention. . Further, in the above-described embodiment, the case where two actuators are used has been described. However, it is needless to say that the same can be applied to a case where three or more actuators are used.

[0021]

As described above, the hydraulic drive device according to the present invention comprises a plurality of multiple control valves which are connected in parallel to a common variable displacement pump and respectively control a plurality of actuators having different loads. wherein each control valve is energized the spool center spring, in a hydraulic drive system comprising configured to adjust the spool stroke by the pilot pressure, wherein the control valve is a load of each actuator configured to closed center Negative detecting pressure
A load pressure detection line is provided , and a pilot line
A pressure reducing valve is provided on the pump to control the discharge pressure from the variable displacement pump.
As oil passes through each of the control valves,
Comparison of actuator load pressures generated by different throttles
A shuttle valve that detects the
Select one of the maximum load pressures and set it to the variable
Is applied to the discharge flow rate control means of the amount pump, a control valve of the discharge flow rate of the variable displacement pump is controlled so that the differential pressure between the pump delivery pressure and the actuator load pressure is constant, further light load side actuator the pressure reducing valve provided on a pilot line for switching, by <br/> be configured to control the pilot pressure for switching the control valve of the high-load side actuator, Oite during the combined operation of the actuators, for controlling the light load side actuator Control valve is throttled and variable
By the discharge pressure of the displacement pump rises, it reaches the also drives the high-load side actuator, this time the pump
Discharge flow rate of is controlled to a constant flow rate corresponding to the load pressure of the actuator, and the pump pressure oil of the constant flow rate,
For light load actuator is supplied at a flow rate corresponding to the opening degree of the control valve, also for high-load side actuator is supplied at a flow rate of the remainder. Thus, this ensures that a combined operation is achieved , and the efficiency of the device is also improved, and its practical effect is extremely large.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a hydraulic drive device according to the present invention.

FIG. 2 is a hydraulic circuit diagram showing a configuration of a conventional hydraulic drive device.

[Explanation of symbols]

Reference Signs List 10 Variable displacement pump 12, 14 Control valve (closed center type) 13, 15 Restrictor 16, 18 Actuator 17, 19 Load 20 Tank 22, 24 Pilot valve 26 Pilot pump 28, 30 Pilot line 32, 34 Pilot line 36a, 36b Valve 38a, 38b Valve body 40a, 40b Cylinder 42a, 42b, 42c Shuttle valve 50, 52 Load pressure detection line 54 Maximum load pressure signal line 56 Discharge flow control means 58 Hydraulic line 60, 62 Pilot pressure signal line

Claims (2)

(57) [Scope of request for utility model registration] A plurality of actuators (16, 1 ) connected in parallel to a common variable displacement pump (10) and having different loads, respectively.
Becomes 8) from a plurality of multiple-control valve for controlling respectively (12, 14), wherein each control valve is energized the spool center a spring, hydraulic pressure becomes configured to adjust the spool stroke by the pilot pressure In the driving device, each of the control valves (12, 14) is configured as a closed center type.
Negative for detecting the load pressure of the actuator (16, 18), respectively
A load pressure detection line (50, 52) is provided , and each control valve (12, 14)
Reducing valves (36a, 36b) on pilot lines (28, 34)
The pressure oil discharged from the variable displacement pump (10)
When passing through the control valves (12, 14)
(13, 15)
Comparison shuttle valve (42a) is provided, the shuttle valve (42
a) Select one of the maximum load pressures detected in
This is used to control the discharge flow rate of the variable displacement pump (10) (5
6) to control the discharge flow rate of the variable displacement pump (10) so that the differential pressure between the pump discharge pressure and the actuator load pressure becomes constant, and further switch the control valve of the light load side actuator. Pressure reducing valve installed on line
A hydraulic drive device, characterized in that configured to control the pilot pressure for switching the control valve of the high-load side actuator. 2. The pressure reducing valve (36a, 36b) includes a valve body (38a, 38b).
And a cylinder that applies spring pressure to the valve body (40a, 40b)
And the light load side actuator (16 or 18)
The pilot valve corresponding to the control valve (12 or 14) to be controlled
Pressure reducing valve (36a or 36b) connected to IN (28 or 34)
Actuator for high load side for cylinder (40a or 40b)
Control valve (14 or 12) that controls the motor (18 or 16)
Corresponding pilot line (32 and 34 or 28 and 30)
One of the two pressures is the shuttle
Pilot pressure signal detected by valve (42c or 42b)
(62 or 60) and the control valve (12
2. The hydraulic drive device according to claim 1, wherein the hydraulic drive device is configured to maintain the metering state .