JPH01141203A - Hydraulic driving device - Google Patents

Abstract

PURPOSE:To improve the working efficiency and achieve energy economization by installing an unloading valve and setting the following value to zero: the total demanded flow rate of the flow rate control valves permitting pressure compensation-(max. flow rate of a variable capacity hydraulic pump-flow rate of the unloading valve). CONSTITUTION:An unloading valve 8 is installed on the discharge side of a variable capacity hydraulic pump 2, and the discharge flow rate of the variable capacity hydraulic pump 2 is controlled so that the following value becomes nearly zero: the total demanded flow rate of the flow rate control valves 6a and 6b permitting pressure Compensation-(max. flow rate of the variable capacity hydraulic pump-flow rate of the unloading valve 8). Therefore, independently of the magnitude of the load applied onto each actuator 7a, 7b, the pump flow rate nearly equal to the demanded flow rate of the flow rate control valves 6a and 6b permitting pressure compensation can be supplied. Therefore, the desired complex operation can be executed, and the working efficiency can be improved, and the energy economization can be achieved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention applies to hydraulic pressure of hydraulic excavators, etc. ! Concerning a hydraulic drive device that can be used in acupuncture.

<Prior Art> FIG. 9 is a circuit diagram showing an example of this type of conventional hydraulic drive device.

This hydraulic drive device includes a prime mover, that is, an engine 1, a variable displacement hydraulic pump 2 driven by the engine,
A regulator 40 that controls the displacement of the hydraulic pump 2, that is, a tilt angle, and a plurality of actuators 7a, 7 driven by pressure oil discharged from the hydraulic pump 2.
A pressure-compensated flow control valve and a hydraulic pump consisting of a pressure-compensated flow control valve that controls the flow of pressure oil supplied from the hydraulic pump 2 to the actuator 7a, that is, a pressure-compensated valve 31a and a flow control valve 30a. A flow control valve with pressure compensation that controls the flow of pressure oil supplied from 2 to the actuator 7b, that is, a flow control valve with pressure compensation consisting of a combination of a pressure compensation valve 31b and a flow control valve 30b, a flow control valve 30a, A shuttle valve 44 interposed in a conduit 43 connected to each of the pumps 30b, a conduit 42 connecting the shuttle valve 44 and the regulator 40, and a discharge conduit of the hydraulic pump 2 and the regulator 40 communicating with each other. A conduit 41 is provided.

In this hydraulic drive device, a hydraulic pump 2 is driven by an engine 1, and pressure oil discharged from the hydraulic pump 2 is supplied to actuators 7a and 7b by switching flow rate control valves 30a and 3Qb according to a command from an operating device (not shown). is,
As a result, the driving bodies associated with the actuators 7a and 7b are activated, and, for example, in the case of a hydraulic excavator, operations such as traveling, turning, and digging are performed. Then, the regulator 40 detects the pressure in the pipe line 41 and changes the tilt angle of the hydraulic pump 2, so as not to exceed the horsepower curve 23 of the engine 1, as shown by the PQ left curve 4 in FIG. In addition, a so-called load sensing system is configured to change the tilting angle of the hydraulic pump 2 so that the pressure difference between the pressure in the pipe line 41 and the pressure in the pipe line 42 becomes a predetermined value ΔP. In addition, in FIG. 10, 25 indicates a characteristic line at the time of relief cutoff.

<Problems to be Solved by the Invention> By the way, the conventional hydraulic drive device described above has the following problems. That is, (1) switching the flow rate control valves 30a, 30b to actuators 7a, 7b;
When trying to move the flow rate control valves 30a, 30
The total value of the required flow rate of b is the maximum flow rate Qma of the hydraulic pump 2
When x is exceeded, pressure oil flows to an actuator with a small load, for example, the actuator 7a. For this reason, it may not be possible to achieve the desired combined operation.For example, when moving the boom cylinder, arm cylinder, or packet cylinder, which are the actuators that drive the boom, arm, or packet of a hydraulic excavator, pressure oil is supplied to the boom cylinder. The boom may not move. In particular, when the engine output is not very large, the flow rate Q is reduced when the pressure P of the pump 2 is high, as shown in FIG.
The load on the engine 1 is prevented from exceeding a horsepower curve 23. Therefore, since the flow rate Q decreases, the difficulty of the combined operation becomes more pronounced.

For this reason, in the past, there were problems in terms of multiple operations, and no improvement in work efficiency could be expected.

(2) The pressure difference between the discharge pressures of the pipe line 42 and the pump 2 shown in FIG. 9 is always controlled to a constant pressure ΔP, and since a pressure loss of this ΔP always occurs during operation, the pressure loss is large. If an attempt is made to reduce ΔP, if the resistance of the pipeline from the discharge port of the pump 2 to the flow rate control valves 30a, 30b is large, the loss will increase even when these flow rate control valves 30a, 30b are fully opened. 62 or more, the pump 2 is controlled to reduce the flow rate so that the pressure loss becomes ΔP. Therefore, the driving speed of the actuators 7a, 7b tends to decrease.
This is even more noticeable when the structure of b is multiplexed. In the case of multiple series, the flow rate control valve 30a from the discharge port of the pump 2,
30b to the inlet of each flow control valve 30a, 3.
Since ΔP is different for each 0b, the speed of the actuators 7a and 7b will not be achieved unless ΔP is set in accordance with the most downstream flow control valve with a large pressure loss, so ΔP is set relatively large. Therefore, when operating the upstream flow control valve, losses increase.

In addition, the setting of ΔP must be determined by taking into account various errors in pressure loss. Errors, etc. Therefore, in order to ensure the predetermined speed of the actuators 7a and 7b,
Since ΔP is determined by considering all of these errors, ΔP must be set quite high as a result.

For this reason, in the past, heat generation corresponding to ΔP is generated, the durability of the equipment is likely to deteriorate, and there is also a large amount of energy loss, and no improvement in fuel efficiency can be expected, resulting in problems in terms of economic efficiency.

■ Since the drive control of the regulator 40 of the pump 2 is performed by pressure feedback, the setting of the tilting angle tends to become unstable. Therefore, the speed of operation to change the tilting angle is slowed down to stabilize the entire system. However, this deteriorates the followability when the actuators 7a, 7b are driven by the operation of the operating device, making it difficult to expect improvement in operability and increasing operator fatigue.

■ This conventional hydraulic drive device includes an actuator 7a,
When the operating device that commands the drive of the pump 7b is in the neutral state, the tilt angle of the pump 2 becomes 0, so a device (not shown) for cooling the entire device is required, leading to an increase in manufacturing costs. .

The present invention has been made in view of the actual situation in the prior art described above, and its purpose is to improve complex operability, reduce pressure loss, and improve followability of actuator drive to operation of the operating device. Moreover, it is an object of the present invention to provide a hydraulic drive device that does not require a cooling device.

Means for Solving the Problems In order to achieve this object, the present invention provides a prime mover, a variable displacement hydraulic pump driven by the prime mover, a regulator that controls the displacement of the variable displacement hydraulic pump, In a hydraulic drive device equipped with a pressure-compensated flow control valve that controls the flow of pressure oil supplied from a variable displacement hydraulic pump to an actuator, switching control of an unload valve and a pressure-compensated flow control valve and drive of a regulator are provided. and a control device for controlling the total required flow rate of the pressure-compensated flow control valve - (maximum flow rate of the variable displacement hydraulic pump - flow rate of the unload valve) to approximately O. This is a configuration that includes.

Effect> Since the present invention is configured as described above, regardless of the magnitude of the load applied to each actuator,
A pump flow rate approximately equal to the flow rate required by the pressure compensated flow control valve can be supplied, and therefore the desired combined operation can be performed.

In addition, when controlling the regulator, there is no need to consider a constant pressure ΔP as in the conventional method, so pressure loss can be reduced as much as possible.In addition, the regulator can be controlled by so-called feedforward without relying on feedback of this ΔP. Since this becomes possible, it is possible to improve the followability of the actuator drive corresponding to the operation of the operating device.

In addition, since the regulator can be controlled so that the pump tilt angle is the minimum tilt angle Qmin that is not 0 even in the neutral state, the flow of pressure oil can be maintained and a device for cooling the entire device is not required. .

<Example> Hereinafter, the hydraulic drive device of the present invention will be explained based on the drawings.

Figures 1 to 8 are explanatory diagrams showing one embodiment of the present invention. Figure 1 is a circuit diagram showing the outline of the overall configuration, and Figure 2 (a) is a flow rate with pressure compensation provided in this embodiment. Diagram showing the control valve,
Fig. 2(b) is a diagram showing the unloading valve provided in this embodiment, Fig. 3(a), (b), and Fig. 4(a), (b).
, and FIG. 6 are diagrams respectively showing the contents of the setting means included in the control device provided in this embodiment, FIG. 7 is a flowchart showing the processing procedure in the control device provided in this embodiment, and FIG. It is a characteristic diagram showing the relationship between the lever stroke and the flow rate flowing into the actuator obtained in the example.

As shown in FIG. 1, in this embodiment as well, the prime mover, that is, the engine
, a variable displacement hydraulic pump 2 driven by this engine 1, a regulator 3 that controls the displacement or tilt angle of this hydraulic pump 2, and a plurality of actuators 7a driven by pressure oil discharged from the hydraulic pump 2.
, 7b and the actuators 7a, 7b from the hydraulic pump 2
Pressure supplement 1δ that controls the flow of pressure oil supplied to each
The flow rate control valve 6a, 6b includes a pressure compensation valve 6a, 6b which is a combination of a pressure compensation valve 31 and a flow rate control valve 30 as shown in FIG. 2(a).

In addition, in this embodiment, an operating device that commands the drive of the actuators 7a and 7b, that is, an operating device with operating levers a and llb, an unload valve that releases a predetermined amount of the pressure oil discharged from the pump 2 into the tank, In other words, Figure 2 (
The unload valve 8 illustrated in b), the tilt angle sensor 4 that detects the tilt angle of the pump 2, the rotation speed sensor 5 that detects the rotation speed of the engine 1, and the pressure oil discharged from the pump 2. A pressure sensor 9 for detecting pressure is provided, as well as a drive unit for the aforementioned pressure-compensated flow control valves 6a and 6b, a regulator 3, a drive unit with operating levers a and b, a drive unit for the unload valve 8, and a tilt angle sensor. 4. The rotation speed sensor 5 and the pressure sensor 9 are connected to each other, and a control device 10 is provided which controls the drive of the regulator 3, the flow control valves with pressure compensation 6a and 6b, and the unload valve 8. There is. This control device 10 has storage, calculation, and logical judgment functions, and includes various setting means, calculation means, discrimination means, and output means.

The above-mentioned setting means include means for setting the pump minimum flow iQmin, means for setting a constant flow rate Δq almost equal to 0, and means for setting the pressure P of the pressure oil discharged from the pump 2 and the pump 2.
In addition to the setting means for presetting the relationship between the maximum tilt angle θ(P) and the maximum tilt angle θ(P), as shown in FIGS. A setting means for presetting the relationship between the required flow rates qa and qb of the control valves 6a and 6b, and a lever stroke xa of the operating levers a and llb, as shown in FIGS. 4(a) and 4(b).
,
As shown in FIGS. (a) and (b), there is a setting means for setting the relationship between the target strokes Sa, sb of the control valves 6a, 6b and the target flow rates qao, qbo, and as shown in FIG. setting means for setting the relationship with fir q A.

Moreover, as the above-mentioned calculation means, each control valve 6a, 6b
a first calculating means for calculating the total required flow rate of the control valves 6a and 6b, that is, the valve total required flow fmqv from the required flow rates qa and qb, and a maximum tilting means corresponding to the pump pressure detected by the pressure sensor 9. A second calculating means calculates the angle θ(P) and calculates the pump maximum flow iQmin from this maximum tilt angle θ(P) and the engine speed N, and each amplifier related to the control valves 6a and 6b. A third calculation means calculates the flow rate of the unload valve 8, that is, the total unload flow rate QA, from the load flow rates CIAa and QAb, and the valve total required flow rate qv-(pump maximum flow rate Qmax-total unload flow rate jtqA). The fourth calculation means for calculating and the target valve total flow rate qvo=
Pump maximum flow rate Qmax - total unload flow rate qA + Δ
a fifth calculating means for calculating q, a sixth calculating means for calculating valve total required flow rate qv-pump minimum flow rate Qmin, and target pump flow rate Q=valve total required flow rate iqv + total unload flow rate qA- Seventh step to calculate Δq
and an eighth calculation means for determining the target pump tilt angle θ from the target pump flow rate Q and the engine speed N.

Further, the above-mentioned discriminating means determines the valve total required flow rate qv-
(Pump maximum flow rate Qmax - total unload flow rate QA)
a first determining means for determining whether the value of is equal to or greater than the above-mentioned 69;
and second determining means for determining whether in is 69 or more.

The output means described above includes a first output section that outputs signals corresponding to the target strokes sa and sb that drive the flow control valves 6a and 6b, and a signal that outputs signals corresponding to the target stroke SA that drives the unload valve 8. a second output section that outputs the target pump tilt angle θ, and a third output section that outputs the target pump tilt angle θ to the regulator 3.
and an output section.

The above-described respective setting means, first to eighth calculation means, first and second determination means, and output means determine the valve total required flow fiqv-(maximum flow rate Qm of the variable displacement hydraulic pump 2).
Means are provided for controlling the value of ax-total unload flow rate QA) to approximately zero.

In the embodiment configured in this way, the engine 1
Hydraulic pump 2 is driven by the drive of
, llb, the flow rate control valves 6a, 6b with pressure compensation are operated.
is switched, and the pressure oil from pump 2 is transferred to actuator 7.
a, 7b, these actuators 7a, 7
b is activated, and the drive bodies associated with these actuators 7a and 7b are driven to perform various movements and operations, for example, when this embodiment is installed in a hydraulic excavator, operations such as traveling, turning, and excavation. Work etc. are carried out.

During this time, the control device 10 performs the processing illustrated in FIG. 7. That is, first, step S
As shown in 50, the strokes xa and xb of the operating levers a and llb, the pump pressure P detected by the pressure sensor 9, and the engine rotation speed N detected by the rotation speed sensor 5 are read.

Next, the process moves to step S51, and the required flows -uqa, qb of the control valves 6a, 6b according to the respective lever strokes xa, xb of the operating levers a and b are calculated as shown in FIGS. 3(a) and 3(b).
Based on this, the first calculation means calculates the valve total required flow rate qv=required flow rate qa of the control valve 6a.
The required flow rate qb of the control valve 6b is calculated.

Next, the process moves to step 52, where the maximum tilt angle θ(P) corresponding to the pump pressure detected by the pressure sensor 9 is determined, and the second The calculation means calculates the pump maximum flow iLQmax=
The maximum tilt angle θ(P)×engine speed N is calculated.

Next, the process moves to step S53, and the control valves 6a and 6b are adjusted according to the lever strokes xa and xb of the operating levers a and b.
The respective unload flow rates CIAa and qAb are shown in Figure 4 (
A) and (b) are obtained, and based on this, the third calculation means calculates the total unload flow ff1qA=control valve 6
The unload flow rate qAa related to a and the unload flow rate qAb related to the control valve 6b are calculated.

Next, the process moves to step S54, where the fourth calculation means calculates the valve total required flow Jiqv-(pump maximum flow rate Qmax-total unload flow rate qA), and the first determination means calculates the value obtained by this calculation means. is 69 or more. When this determination is satisfied, the valve total required flow ff1qv is larger than the pump maximum flow Qmax, and the process moves to step S55.

In step S55, the target pump flow IQ is set to the pump maximum fLit.
A process of selecting Qmax is performed.

Next, the process moves to step S56, and the fifth calculation means calculates the following: target valve total flow rate qvo=pump maximum flow rate Qmax-total unload flow rate qA+Δq, and the process moves to step S57.

In step S57, based on the target total flow 1qvo obtained in step S56, the target flows ff1qao, qbo of each flow rate control valve 6a, 6b are determined as qao=Ka-qvo, qb.
A process of selecting o=Kb-qbo is performed. Here, there is a relationship of K a + K b = 1.

Next, the process moves to step S58, and based on the target flow rates qao and qbo of the control valves 6a and 6b, the target strokes sa and sb of the control valves 6a and 6b are selected as shown in FIG. Signals corresponding to these target strokes sa, sb are transmitted from the first output section of the output means to the control valves 6a, 6b.
output to the drive unit. As a result, the control valves 6a, 6b are driven by strokes corresponding to the target strokes sa, sb.

Next, the process moves to step S59, where a target stroke sA of the unload valve 8 is selected as shown in FIG. It is output from the output section to the drive section of the unload valve 8. As a result, the unload valve 8 is driven by a stroke corresponding to the target stroke sa.

Next, the process moves to step S60, and the eighth calculation means performs a calculation to determine the target tilting angle θ from the target pump flow rate JitQ and the engine speed N, θ=Q/N, and calculates the target tilting angle θ corresponding to the target tilting angle θ. A signal is outputted to the regulator 3 from the third output section of the output means. Thereby, the regulator 3 controls the tilting angle to correspond to the target tilting angle θ.

After the process in step S60, the process returns to the beginning.

In addition, if the determination in step S54 described above is not satisfied, the pump maximum flow rate Qm is determined for the valve total required flow rate qv.
If there is room for ax, the process moves to step S61.

In step S61, the pump minimum flow i set by the setting means is
Based on Qmin, it is determined by the sixth calculation means whether the valve total required flow rate qv-pump minimum flow rate Qmin is 69 or more. When this determination is satisfied, the valve total required flow rate qv is larger than the pump minimum flow rate Qmin, and the process moves to step S62.

In step S62, the seventh calculation means calculates the target pump flow rate Q.
=Valve total required flow rate qv + total unload flow rate i Q
Calculate A-Δq.

Next, the process moves to step 363, and the target flow rates qao and qbo of the respective flow rate control valves 6a and 6b are changed to the required flows: iqa and qb shown in FIGS. 3(a) and 3(b), that is, qao=qa, q.
The process of selecting bo=qb is performed, and then the process moves to step 358 described above, the process of steps S58, 59, and 60 described above is performed, and the process returns to the beginning.

In addition, if the determination in step S61 described above is not satisfied, the total pulp required flow jiqv is equal to the pump minimum flow rate Qmin.
In this case, the process moves to step S64.

In step S64, a process is performed to select the target pump flow rate Q to be the minimum pump flow rate Qmin, and then the process moves to the above-mentioned step 363, processes in steps S63, 58, 59, and 60 are performed, and the process returns to the beginning.

FIG. 8 shows the characteristics obtained by the processing in the control device 10 described above, the lever stroke x of the control lever a.
It shows the relationship between a and the flow rate flowing to the actuator 7a. In the figure, 20 is a characteristic line indicating the required flow rate of the control valve 6a, 21 is a characteristic line indicating the pump flow rate, and 22 is a characteristic line indicating the unloading flow rate. The area 70 corresponds to the flow from step s54 to S55.56.57.58.59.6o in FIG. 7, and the area 71 corresponds to the flow from step S54 to S61.
62.63.58.59.6o,
The area 72 includes steps S54 to S61.64.63.58.
59.60.

In the embodiment configured in this way, as is clear from the characteristic line shown in FIG.
Regardless of the magnitude of the load applied to the pump, it is possible to supply a pump flow rate approximately equal to the flow rate required by the control valves 6a and 6b, and therefore,
Desired multiple operations can be realized and excellent work efficiency can be ensured.

In addition, when controlling the regulator 3, there is no consideration of a constant pressure ΔP as in the past, so pressure loss can be reduced as much as possible, heat generation can be suppressed, and the durability of the equipment can be improved. , it is possible to reduce energy loss and improve fuel efficiency.

In addition, since the control of the regulator 3 is not based on feedback of a constant pressure ΔP as in the conventional case but is based on feedforward control, the followability of the actuators 7a and 7b drive to the operation of the operating levers a and llb is improved. This improves operability and reduces operator fatigue.

In addition, even in the neutral state, the tilting angle of the pump 2 is not 0, but is controlled to maintain the minimum tilting angle Qmin, so pressure oil can be constantly flowing, and this allows special No equipment is required, and a rise in production costs associated with this can be prevented.

<Effects of the Invention> Since the hydraulic drive device of the present invention is configured as described above, it is possible to improve the combined operability compared to the conventional one.
Therefore, work efficiency can be improved, and pressure loss can be reduced compared to conventional methods, thereby suppressing heat generation and improving the durability of equipment, as well as reducing fuel consumption by suppressing energy loss. In addition, it is possible to improve the ability of the actuator drive to follow the operation of the operating device compared to the conventional method, thereby improving operability and suppressing operator fatigue. ,Also,
A special ring device is not required, and therefore, a rise in manufacturing costs can be suppressed.

[Brief explanation of the drawing]

1 to 8 are explanatory diagrams showing one embodiment of the hydraulic drive device of the present invention, FIG. 1 is a circuit diagram showing an outline of the overall configuration, and FIG. 2(a) is an explanatory diagram showing an embodiment of the hydraulic drive device of the present invention. FIG. 2(b) is a diagram showing a flow control valve with pressure compensation, FIG. 2(b) is a diagram showing an unloading valve provided in this embodiment, FIG. 3(a), (b), FIG. ), FIGS. 5(a), (b), and 6 are diagrams each showing the contents of the setting means included in the control device provided in this embodiment, and FIG. 7 is a diagram showing the contents of the setting means included in the control device provided in this embodiment, and FIG. FIG. 8 is a characteristic diagram showing an example of the relationship between the lever stroke and the flow rate flowing to the actuator obtained in this embodiment. FIG. 9 is a circuit diagram showing a conventional hydraulic drive device. FIG. 10 is an explanatory diagram showing the relationship between the PQ right curve prime mover and the horsepower curve. 1...Engine (prime mover), 2...Variable capacity basin hydraulic pump, 3...Regulator, 4...
......Tilt angle sensor, 5...Rotation speed sensor, 6a, 6b...Flow rate control valve with pressure compensation, 7a
, 7b...actuator, 8...unload valve, 9...pressure sensor, 10...
...control device, lla, llb...operation lever (operation device). Figure 1 Figure 2 Cσ (b) Figure 3 (0) (tν(0)
(b) Figure 6 @ 椴xIro-75', a Figure 8

Claims (1)

[Claims] 1) A prime mover, a variable displacement hydraulic pump driven by the prime mover, a regulator that controls the displacement of the variable displacement hydraulic pump, and a pressurized oil discharged from the variable displacement hydraulic pump. A hydraulic drive device comprising an actuator that is driven by the actuator, and a flow control valve with pressure compensation that controls the flow of pressure oil supplied to the actuator from a variable displacement hydraulic pump, the unload valve and the flow control valve with pressure compensation. and a control device that performs valve switching control and drive control of the regulator, and this control device controls the total required flow rate of the pressure compensated flow control valve - (maximum flow rate of the variable displacement hydraulic pump - the unload valve). 1. A hydraulic drive device comprising means for controlling a value of the flow rate (flow rate) to approximately 0. (2) The control means sets the target pump flow rate when the total required flow rate of the pressure compensated flow control valve does not exceed the maximum flow rate of the variable displacement hydraulic pump, which is set according to the horsepower limited by the prime mover. means for selecting the pressure so as to be approximately equal to the total required flow rate of the compensated flow control valves + the flow rate of the unloading valve, and a means for selecting the pressure so that the total required flow rate of the pressure compensated flow control valves exceeds the maximum flow rate of the variable displacement hydraulic pump; and means for selecting the target total flow rate of the pressure-compensated flow control valve so as to be approximately equal to the maximum flow rate of the variable displacement hydraulic pump + the flow rate of the unload valve. 1) Hydraulic drive device as described in item 1).