JPH09158903A - Flow control device for hydraulic actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify structures of device total unit constitution and a pressure compensating flow control valve fixedly controlling a differential pressure before/after the control valve, and cope with each control valve of hydraulic pilot type, manually switching type and electromagnetic switching type. SOLUTION: A throttle 11 is provided in a load pressure introducing pipe line 10 introducing a load pressure to a pressure compensating flow control valve 6, a solenoid proportional relief valve 12 is provided branching from the load pressure introducing pipe line 10 in an outlet side of this throttle 11, and a preset pressure of this relief valve 12 is changed, so as to change a differential pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic actuator flow rate control device for controlling a flow rate supplied to a hydraulic actuator such as a hydraulic cylinder or a hydraulic motor.

[0002]

2. Description of the Related Art Conventionally, in a construction machine such as a hydraulic crane or a hydraulic excavator, as shown in FIG.
And a hydraulic actuator (here, a hydraulic cylinder is shown) 2 having the pump 1 as a hydraulic source, a throttle operated by, for example, a remote control valve 3 (4 is an operating lever of this remote control valve 3). In general, a hydraulic pilot type control valve 5 with 5a is provided, and the control valve 5 controls the operating direction and speed of the actuator 2. T is a tank.

Further, assuming such a circuit configuration,
A pressure compensation type flow rate control valve 6 is provided in the discharge circuit of the pump 1, and by the control valve 6, the inlet pressure (inlet pressure of the throttle 5a) P1 of the control valve 5 and the outlet pressure (outlet pressure of the throttle 5a = actuator load pressure). ) A flow rate control that keeps the difference between P2 and thereby keeps the corresponding relationship between the lever operation amount of the remote control valve 3 and the actuator flow rate constant regardless of the fluctuation of the load pressure, that is, so-called load sensing control (constant differential pressure control). Devices are known.

In this known load sensing type flow control device, one pressure port 6a of the pressure compensation type flow control valve 6 has an inlet pressure P1 of the throttle 5a and the other pressure port (load pressure port) 6b has a load pressure P2. And the basic pressure K generated by the spring 6c, the difference between the valve inlet pressure and the load pressure (differential pressure ΔP = P1−P2 = K) is kept constant.

In this way, Q: flow rate through the control valve 5 (actuator flow rate) A: passage area of the control valve 5 ΔP: differential pressure C: flow coefficient,

[0006]

## EQU1 ## Since Q = CA√ΔP, the differential pressure ΔP is kept constant, so that the actuator flow rate Q is kept constant.

On the other hand, in such a device, there is a demand to change the correspondence between the lever operation amount and the actuator flow rate in the following cases.

(A) In a crane, for example, when the suspension load amount is large, it is desired to reduce the actuator flow rate with respect to the lever operation amount to prevent a sudden change in speed.

(B) In hydraulic excavators and cranes,
When the engine speed that drives the hydraulic pump is high, the pump discharge flow rate is also large, so the actuator flow rate can be proportionally changed over the entire stroke of the lever operation as shown by the solid line in FIG. When the value becomes lower, the pump discharge flow rate also decreases, so that the actuator flow rate reaches the upper limit in the intermediate stroke of the lever operation as shown by the broken line in FIG. 5, and the actuator flow rate does not change in the remaining strokes, resulting in poor operability. .

Therefore, as shown in FIG. 6, it is desired to change the characteristics of the lever operation amount / actuator flow rate according to the engine speed (high speed, low speed).

Conventionally, as means for coping with such a demand, (i) as shown in FIG. 3, an auxiliary pressure port 6d is separately provided in the flow control valve 6, and this auxiliary pressure port 6d is supplied from an auxiliary hydraulic pressure source 7. A configuration in which the hydraulic pressure is reduced by the electromagnetic proportional pressure reducing valve 8 and introduced (see Japanese Patent Laid-Open No. 2-118203), (i
i) As shown in FIG. 4, an electromagnetic proportional pressure reducing valve 9 is provided on both pilot lines connecting the remote control valve 3 and the pilot ports on both sides of the control valve 5 to reduce the pilot pressure from the remote control valve 3 to control the control valve. No. 5 pilot port (JP-A-4-13150)
No. 5) is publicly known.

[0012]

However, in the above (i)
According to the auxiliary pressure introducing method, the flow control valve 6 must be provided with another auxiliary pressure port 6d, which complicates the structure of the control valve 6. In addition, another hydraulic source (auxiliary hydraulic source) 7
Is required.

On the other hand, according to the pilot pressure reducing system of (ii), the control valve 5 is limited to the hydraulic pilot type and cannot be applied to the manual switching type and the electromagnetic switching type. Further, since the electromagnetic proportional pressure reducing valve 9 is required for the pilot lines on both sides, the cost becomes high.

Therefore, according to the present invention, the structure of the flow control valve and the configuration of the entire apparatus are simple, and the flow control of the hydraulic actuator is applicable to each control valve of the hydraulic pilot type, manual switching type and electromagnetic switching type. A device is provided.

[0015]

According to a first aspect of the present invention, there is provided a hydraulic actuator, a hydraulic pump as a hydraulic source of the hydraulic actuator, and an operation of the actuator provided between the hydraulic pump and the hydraulic actuator. Flow rate of a hydraulic actuator equipped with a control valve for controlling the control valve, an operating means for operating the control valve, and a pressure compensation type flow control valve for setting a difference between the load pressure which is the inlet pressure and the outlet pressure of the control valve. In the control device, a throttle is provided in the load pressure introducing pipe that introduces the load pressure into the load pressure port of the flow control valve, and the outlet side of the throttle is branched from the load pressure introducing pipe to provide a variable relief. A valve is provided.

In this structure, the pressure introduced into the load pressure port of the pressure compensation type flow control valve can be changed by changing the set pressure of the variable relief valve, thereby changing the differential pressure and operating means ( Operation amount /
The characteristics of the actuator flow rate can be changed.

According to a second aspect of the present invention, in the structure of the first aspect, a hydraulic actuator circuit including a hydraulic actuator and a control valve is connected in parallel to one hydraulic pump, and a discharge line and a tank of this hydraulic pump are connected. A pressure compensating type flow control valve is provided in the bypass pipe to be connected, and the load pressure introducing pipes of the respective hydraulic actuator circuits are joined via the high pressure selecting means and connected to the load pressure port of the flow control valve. A throttle is provided in the pipeline, and a variable relief valve is provided on the outlet side of the throttle branching from the merging pipeline.

According to this structure, in the method of driving a plurality of actuators by one pump, when each actuator is operated independently, the load pressure of the operated actuator is introduced into the merging conduit via the high pressure selecting means and the throttle. It is introduced into the load pressure port of the flow control valve.

Here, by changing the set pressure of the variable relief valve, the pressure introduced into the load pressure port can be changed to change the differential pressure, and the characteristics of the operation amount of the operation means / actuator flow rate can be changed. .

According to a third aspect of the invention, in the structure of the first or second aspect, an electromagnetic proportional relief valve is used as the variable relief valve, and a load pressure sensor for detecting a load pressure,
The electromagnetic proportional relief based on the characteristic selecting means for selecting the characteristic of the actuator flow rate with respect to the operation amount of the operating means from a plurality of, the load pressure detected by the load pressure sensor, and the characteristic selected by the characteristic selecting means. And a controller for controlling the set pressure of the valve.

According to this structure, the differential pressure control in the inventions of claims 1 and 2 is automatically performed by the controller based on the selected characteristic and the load pressure.

According to the structure of each of the above claims, it is unnecessary to provide the pressure compensation type flow control valve with another auxiliary pressure port or another auxiliary hydraulic pressure source.

Further, it can be applied to each control valve of hydraulic pilot type, manual switching type and electromagnetic switching type.

[0024]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIGS.

In the following embodiments, the same parts as those in FIGS. 3 and 4 are designated by the same reference numerals, and the duplicated description thereof will be omitted.

First Embodiment (see FIG. 1) The first embodiment shows a case where it is applied to a system in which one pump drives one actuator.

Load pressure port 6 of pressure compensation type flow control valve 6
A throttle 11 is provided in the load pressure introducing pipe line 10 for introducing the load pressure into b.

An electromagnetic proportional relief valve (hereinafter referred to as proportional relief valve) 12 is provided on the outlet side of the throttle 11 as a variable relief valve that branches from the load pressure introducing pipe 10 and is connected to the tank T. The set pressure Pi of the proportional relief valve 12 is applied to the load pressure port 6b of the flow control valve 6.

The set pressure Pi of the proportional relief valve 12 is controlled by the controller 13.

The controller 13 has the characteristics of the operation amount / actuator flow rate of the remote control valve operating lever 4 selected by the characteristic selecting means 14 and the load pressure introducing conduit 10.
A load pressure signal is input from a load pressure sensor (pressure sensor) 15 provided in the.

The controller 13 uses the load pressure sensor 1
Load pressure P2 detected by 5 and the characteristic selection means 14
The set pressure Pi of the proportional relief valve 12 is calculated based on the lever operation amount / actuator flow rate characteristic selected by, and a command signal corresponding to the set pressure Pi is output to the proportional relief valve 12.

The operation of this point will be described in detail below. here,
By the characteristic selection means 14, the lever operation amount / actuator flow rate characteristic is a normal characteristic in which the load pressure P2 is directly input to the load pressure port 6b of the flow control valve 6, and a pressure lower than the load pressure is input to the load pressure port 6b. As an example, a case will be described in which it is possible to select from two characteristics of reducing the actuator flow rate with respect to the lever operation amount.

(I) When normal characteristics are selected In this case, the set pressure Pi of the proportional relief valve 12 is maximum, that is, equal to the load pressure P2.

Therefore, the valve inlet pressure P1, the load pressure P2,
The relationship of the basic pressure K (constant) by the spring 6c of the flow control valve 6 is

[0035]

[Equation 2] P1 = P2 + K

[0036]

P1−P2 = K That is, the differential pressure ΔP before and after the throttle of the control valve 5
= P1-P2 = K, if the passage area A of the control valve 5 by lever operation is determined, the actuator flow rate Q is

[0037]

## EQU4 ## Q = CA√ΔP = constant.

(II) When the weight loss characteristic is selected: The load pressure signal from the load pressure sensor 15 is sent to the controller 13
Pressure P lower than the load pressure P2 by a predetermined value
i is calculated as the relief valve set pressure.

That is,

[0040]

## EQU00005 ## P1 = Pi (<P2) + K, and the differential pressure .DELTA.P 'of the control valve 5 is

[0041]

ΔP '= P1-P2 = Pi + K-P2 = (Pi
Since −P2 + K) <K, the actuator flow rate Q ′ at this time is

[0042]

## EQU7 ## Q '= (CA√ΔP') <(CA√ΔP) and Q '<Q, and the actuator flow rate is reduced as compared with the case of the normal characteristic.

Thus, for example, as shown in FIG. 6, when the engine speed is high, the rate of increase of the actuator flow rate with respect to the lever operation amount is increased, and when the engine speed is low, the increase of the actuator flow rate with respect to the lever operation amount is increased. It is possible to change the lever operation amount / actuator flow rate characteristic by reducing the rate.

Second Embodiment (Refer to FIG. 2) This embodiment shows a case in which one pump is used to drive a plurality of actuators.

Only differences from the first embodiment will be described.

A first hydraulic actuator (hydraulic cylinder) 2A and a first control valve 5 for controlling the same.
A first hydraulic actuator circuit C1 including A, a second hydraulic actuator (hydraulic motor) 2B, and a second hydraulic actuator circuit C2 including a second control valve 5B for controlling the second hydraulic actuator C2 are one hydraulic pump. It is connected in parallel to one discharge circuit.

Further, the bypass line 16 connected to the tank T is connected to the pump discharge circuit, and the pressure compensation type flow control valve 6 is connected to the bypass line 16 as opposed to the first embodiment.
Basically, it is provided so as to be held at the block position.

On the other hand, the load pressure introducing conduits 10A and 10B of both actuator circuits C1 and C2 join together via a shuttle valve 17 as a high pressure selecting means, and the joining conduit 10C.
Is connected to the load pressure port 6b of the flow control valve 6.

A constriction 11 is provided in the confluent conduit 10C, and a proportional relief valve 12 is connected to the outlet side of the constricted conduit 11 branching from the confluent conduit 10C.

In FIG. 2, the remote control valve for individually operating both control valves 5A and 5B, the controller for calculating and instructing the set pressure of the proportional relief valve 12 and the characteristic selecting means are omitted.

According to this structure, both actuators 2
When one of A and 2B is independently operated, the load pressure P2 of the operated actuator is selected by the shuttle valve 17 and introduced into the merging conduit 10C.

Then, the selected characteristic and this load pressure P2
The set pressure Pi is calculated by the controller based on and, and the set pressure Pi is applied to the load pressure port 6b of the flow control valve 6.

As a result, similar to the first embodiment, the constant differential pressure is controlled by the flow control valve 6, and the differential pressure is changed by the characteristic selection to change the lever operation amount / actuator flow rate characteristic. .

This configuration can also be applied to a system in which one pump drives three or more actuators.

In both of the above embodiments, the case where the control valve 5 (5A, 5B) is the hydraulic pilot type is shown as an example. However, the present invention uses the manual switching type or electromagnetic switching type control valve. Can also be applied to.

Further, in the above embodiment, the lever operation amount /
Although the characteristic of the actuator flow rate is selected from the normal characteristic and one reduction characteristic in which the actuator flow rate with respect to the lever operation amount decreases more than this, the reduction characteristic may be set in a plurality of ways.

On the other hand, the variable relief valve is not limited to the electromagnetic proportional type mentioned in the above embodiment, but a hydraulic pilot type variable relief valve whose set pressure changes according to the hydraulic pilot pressure may be used.

Alternatively, a manual variable relief valve for manually changing the set pressure can be used. In this case, the characteristic selection / selection unit 14 and the controller 13 are unnecessary.

[0059]

As described above, according to the present invention, the pressure compensating type flow control valve for performing the constant differential pressure control is provided with a throttle in the load pressure introducing pipe for introducing the load pressure, and the outlet side of the throttle is provided with:
Since a variable relief valve is provided by branching from the load pressure introducing pipe and the differential pressure is changed by changing the set pressure of this variable relief valve, another auxiliary pressure port is provided in the pressure compensation type flow control valve. There is no need to provide another auxiliary hydraulic power source.

Therefore, the structure of the flow control valve is simpler than that of the conventional auxiliary pressure introducing system shown in FIG. Further, unlike the pilot pressure reducing system shown in FIG. 4, since only one variable relief valve and throttle need be provided, the overall structure of the device is simplified and the device cost is low.

Moreover, not only the hydraulic pilot type control valve but also a manual switching type and an electromagnetic switching type control valve can be applied, and the versatility is enhanced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a control device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a control device according to a second embodiment of the present invention with a part thereof omitted.

FIG. 3 is an overall configuration diagram of a control device that adopts a conventional auxiliary pressure introduction method.

FIG. 4 is an overall configuration diagram of a control device that adopts a conventional pilot pressure reducing system.

FIG. 5 is a diagram showing a lever operation amount / actuator flow rate characteristic for explaining the purpose of changing the differential pressure.

FIG. 6 is a diagram showing a lever operation amount / actuator flow rate characteristic obtained by changing a differential pressure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 hydraulic pump 2 hydraulic actuator 5 control valve 3 remote control valve as operating means for control valve 4 operating lever of remote control valve 6 pressure compensation type flow control valve 10, 10A, 10B load pressure introducing pipe 11 throttle 12 as variable relief valve Electromagnetic proportional relief valve 13 Controller 14 Characteristic selection means 15 Load pressure sensor 2A, 2B Hydraulic actuator 10A, 10B Load pressure introduction pipeline 17 Shuttle valve as high pressure selection means 10C Confluence pipeline

Claims (3)

[Claims] 1. A hydraulic actuator, a hydraulic pump as a hydraulic source of the hydraulic actuator, a control valve provided between the hydraulic pump and the hydraulic actuator to control the operation of the actuator, and the control valve. In a flow control device for a hydraulic actuator, which comprises an operating means for operating and a pressure compensation type flow control valve for setting a difference between an inlet pressure and a load pressure which is an outlet pressure of the control valve, the load pressure is controlled by the flow control device. The load pressure introducing pipe introduced into the load pressure port of the valve is provided with a throttle, and the outlet side of the throttle is provided with a variable relief valve branched from the load pressure introducing pipe. Flow control device for hydraulic actuator. 2. The flow rate control device for a hydraulic actuator according to claim 1, wherein a hydraulic actuator circuit including a hydraulic actuator and a control valve is connected in parallel to one hydraulic pump, and a discharge line and a tank of the hydraulic pump are connected. A pressure compensation type flow rate control valve is provided in the bypass line connecting the flow rate control valves, and the load pressure introducing lines of the respective hydraulic actuator circuits merge through the high pressure selecting means and are connected to the load pressure port of the flow rate control valve. A flow control device for a hydraulic actuator, characterized in that a converging pipe line is provided with a throttle, and a variable relief valve is provided on the outlet side of the constriction so as to branch from the converging pipe line. 3. An electromagnetic proportional relief valve is used as the variable relief valve, and a load pressure sensor for detecting a load pressure, and a characteristic selecting means for selecting a characteristic of an actuator flow rate with respect to an operation amount of an operating means from a plurality of. 3. A controller for controlling the set pressure of the electromagnetic proportional relief valve based on the load pressure detected by the load pressure sensor and the characteristic selected by the characteristic selecting means. A flow control device for the hydraulic actuator described.