JPH094605A - Control device for hydraulic actuator - Google Patents

Abstract

PURPOSE: To constantly maintain operable range where cylinder flow rate varies with respect to the operation of a control valve regardless of the pump discharge flow rate. CONSTITUTION: Provided hereof is a flow control valve 11 for controlling supply flow rate to a huydraulic cylinder 3 correspondingly to the operating quantity of a control valve 4 and the discharge rate of a pump 2 and it is contrived so that the flow gain of the flow control valve 11 by a controller 10 may be less the less the pump discharge flow rate 11 is by the lowering of the engine speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic actuator control device for controlling the operation of a hydraulic actuator in a hydraulic working machine such as a hydraulic excavator.

[0002]

2. Description of the Related Art Conventionally, as a control device of this type, a control device having a structure shown in FIG. 4 has been generally used. This will be described briefly. In the figure, a hydraulic cylinder is shown as the hydraulic actuator, and only the extension operation of the cylinder is controlled for the sake of clarity.

Reference numeral 1 is an engine, 2 is a hydraulic pump driven by the engine 1, and a control valve (in the figure, an internal valve) is provided between the hydraulic pump 2 and the hydraulic cylinder 3 for controlling the operating direction and speed of the cylinder 3. Only the passages are schematically shown) 4. 5 is a relief valve.

The control valve 4 has a meter-in passage 4a for communicating the pump circuit with the head-side oil chamber 3a of the cylinder 3, a tank passage 4b for communicating the rod-side oil chamber 3b of the cylinder 3 with the tank T, and a pump. A bleed-off passage 4c for communicating the circuit with the tank T is provided,
Meter-in passage 4a by operating a remote control valve (not shown)
And the opening area of the bleed-off passage 4a (flow rate of oil) are changed simultaneously and in opposite directions to control the pump discharge pressure.

That is, when the control valve 4 is operated in the cylinder operating direction, the opening area of the meter-in passage 4a increases and the meter-in flow rate (flow rate supplied to the cylinder 3) increases, while the escape path for the oil to the tank T is increased. The opening area of the bleed-off passage 4c is reduced, the bleed-off flow rate is reduced, and the cylinder 3 is extended.

Further, when the head side pressure of the cylinder 3 changes due to a change in load during work, the flow rate into the cylinder 3 changes, which changes the bleed-off flow rate, which changes the pump pressure. For example, when the load increases and the cylinder head side pressure increases, the cylinder inflow flow rate decreases, the bleed-off flow rate increases correspondingly, the inlet pressure of the bleed-off passage 4c increases, and the pump discharge pressure also increases.

In this way, the pump pressure is controlled according to the load fluctuation, and the operation of the cylinder 3 is maintained.

[0008]

The speed control of the cylinder 3 is usually carried out by adjusting the operation amount of the control valve 4, but when it is desired to lower the maximum speed of the cylinder 3 such as when performing a low speed fine operation. In order to reduce the pump discharge flow rate, the rotation speed of the engine is reduced.

However, in this case, according to the conventional control device, as shown in FIG. 5, in the entire operation range S of the control valve 4, the cylinder flow rate (cylinder speed) changes in response to the valve operation. Since the manipulatable range S1 is narrowed and the dead zone S2 in which the cylinder speed does not change in response to the valve operation is widened, there is a drawback that operability is poor and control is likely to be inaccurate.

Therefore, the present invention provides a control device for a hydraulic actuator capable of keeping the operable range of the control valve substantially constant regardless of changes in the pump discharge flow rate.

[0011]

According to a first aspect of the present invention, an operation of a hydraulic pump driven by an engine and a hydraulic actuator driven by pressure oil from the hydraulic pump is controlled. In a control device for a hydraulic actuator provided with a control valve, a flow control valve for controlling a supply flow rate to the actuator is provided in a pump circuit, and valve operation amount detecting means for detecting an operation amount of the control valve, Pump flow rate detecting means for detecting the discharge flow rate of the hydraulic pump, which is determined by the rotational speed of the engine, and a change in the flow rate passing through the flow rate control valve with respect to the valve operation quantity, based on the valve operation amount and the pump discharge flow rate detected by these detection means. The flow rate gain, which is the degree of Depending on the pump delivery rate in Kunar so those formed by a control means for outputting to calculate the instruction flow to the flow control valve.

According to a second aspect of the present invention, in the configuration of the first aspect, a speed sensor for detecting the rotational speed of the engine is used as the pump flow rate detecting means.

According to a third aspect of the present invention, in the structure of the first or second aspect, the control valve is provided with a bleed-off passage that opens in a predetermined operation range in the operating position direction to communicate the pump circuit with the tank. And the control means
In the operation range where the bleed-off passage is opened in the entire operation range of the control valve, the flow rate gain of the flow rate control valve is kept constant.

[0014]

According to the above structure, the flow gain of the flow control valve changes according to the pump discharge flow rate, and as the pump discharge amount decreases due to the decrease in engine speed, the flow gain of the flow control valve decreases and the valve operation amount decreases. The degree of change in the actuator flow rate with respect to is moderate.

As a result, the manipulable range can be kept substantially constant regardless of the change in the pump discharge flow rate.

In this case, according to the second aspect of the invention, since the pump discharge flow rate is detected by the speed sensor through the engine rotation speed, the sensor is simpler than the case where the pump discharge flow rate is directly detected by the flow meter. The cost is low.

By the way, including the conventional device shown in FIG.
When the actuator is controlled by the control valve provided with the bleed-off passage, the actuator flow rate and the bleed-off flow rate vary due to the load variation in the operation range where the bleed-off passage is open.

That is, when the load increases, the actuator flow rate decreases and the bleed-off flow rate increases.

Therefore, if the flow rate gain is reduced in the low flow rate range as described above with the bleed-off passage open, there is a risk that the actuator flow rate will be insufficient and the actuator will be difficult or impossible to operate. is there.

In this respect, according to the third aspect of the invention, when the bleed-off passage is open, the flow rate gain is kept constant regardless of the change in the pump discharge flow rate. Since the pressure oil is supplied with the same gain as in the large amount state, it is unlikely that the actuator flow rate becomes insufficient.

[0021]

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

In FIG. 1, the same parts as those in FIG. 4 are designated by the same reference numerals, and the duplicated description thereof will be omitted.

In FIG. 1, 6 is a control valve 4
The pilot pressure of the remote control valve 6 (the operation amount of the control valve 6, hereinafter referred to as the valve operation amount) is detected by the pressure sensor 7 by a remote control valve that supplies a pilot pressure to the valve 4 and operates the valve 4 by switching.

Reference numeral 8 denotes a speed setter for setting the rotation speed of the engine 1 by operating a lever. The set rotation speed of the engine 1 (indirectly, pump discharge flow rate) is detected by a speed sensor 9 and detected. The engine rotation speed and the valve operation amount are input to the controller 10.

On the other hand, the cylinder 3 is provided between the hydraulic pump 2 driven by the engine 1 and the control valve 6.
An electromagnetic proportional type flow control valve 11 for controlling the amount of pressure oil supplied to the control valve is provided, and the opening degree of the flow control valve 11, that is, the passing flow rate (hereinafter referred to as the control valve passing flow rate) is controlled by a control signal i from the controller 10. The size is controlled.

FIG. 2 shows the operation amount of the control valve 4,
The relationship between the meter-in, tank, and bleed-off passages 4a, 4b, and 4c of the valve 4 and the opening area of the valve 4 is shown. , Bleed-off operation area) Sb is opened, and this bleed-off operation area Sb
Thus, the pump pressure control action according to the load variation as described above is performed.

The controller 10 includes a flow rate gain calculator 1
2 and the output unit 13.

Based on the detected valve operation amount and engine rotation speed, the flow rate gain calculation unit 12 changes the flow rate so that the flow rate gain, which is the degree of change in the cylinder flow rate with respect to the valve operation amount, changes according to the engine rotation speed. The command flow rate for the control valve 11 is calculated, and this is output as the control signal i from the output unit 13 to the flow control valve 11.

That is, as shown in FIG.
The rotational speed of is divided into a low speed region, a medium speed region and a high speed region, and the flow rate gain is minimized in the low speed region where the pump discharge flow rate decreases.

In this way, in the low speed range (small flow rate range), the degree of change in the cylinder flow rate with respect to the valve operation amount becomes gentle, and the cylinder flow rate can be changed in such a wide valve operation range.

Therefore, when an operation for reducing the engine speed (pump discharge flow rate) is performed in order to reduce the maximum speed of the cylinder 3, as is apparent from the comparison between FIGS. 3 and 5, the flow rate gain is constant. Compared with the conventional device, the operable range S1 of the control valve 4 can be kept substantially the same as the medium speed range and the high speed range. In other words, operable area S
1 can be kept almost constant regardless of the change in the pump discharge flow rate.

In this case, if the flow rate gain is reduced in the low speed range even in the bleed-off operation range Sb in which the bleed-off passage 4c of the control valve 4 is open, the cylinder flow rate becomes insufficient especially when the load increases, and the operation of the cylinder 3 becomes difficult or It may be impossible.

Therefore, in the bleed-off operation range Sb, the flow rate gain is kept constant regardless of the change in the engine rotation speed.

As a result, oil is supplied to the cylinder 3 with the same gain as in the medium and high speed regions even in the low speed region, so that the situation in which the cylinder flow rate becomes insufficient does not occur easily.

Other Embodiments (1) In the above embodiment, the rotational speed of the engine 1 is detected by the speed sensor 9, but the speed setting signal output from the speed setter 8 to the engine 1 is detected. Good.

(2) Instead of indirectly detecting the pump discharge flow rate through the rotational speed of the engine 1 as described above,
The pump discharge flow rate may be directly detected by a flow meter.
However, it is easier to detect the rotation speed of the engine 1 as a sensor, and the cost is lower.

(3) In the above embodiment, the pilot pressure sent from the remote control valve 6 to the control valve 4 is detected as the valve operation amount, but the lever operation amount of the remote control valve 6 or the actual control valve 4 is detected. The working stroke may be detected.

(4) In the above embodiment, the hydraulic cylinder 3 is taken as an example of the hydraulic actuator to be controlled.
The present invention can be applied to a hydraulic motor in the same manner as above.

(5) In the above embodiment, the control device using the control valve 4 provided with the bleed-off passage 4c is taken as an example, but the invention of claims 1 and 2 does not have this bleed-off passage 4c. It can also be applied to a control device using a control valve.

[0040]

As described above, according to the present invention, a flow rate control valve for controlling the supply flow rate to the actuator according to the operation amount of the control valve and the pump discharge flow rate is provided, and the control means controls the flow rate control valve. Since the flow rate gain is reduced as the pump discharge flow rate decreases due to the decrease in the engine rotation speed, the degree of change in the actuator flow rate with respect to the operation amount of the control valve becomes gentle in this low flow rate range.

As a result, the manipulatable region can be kept substantially constant regardless of the change in the pump discharge flow rate, so that the operability is improved and accurate control can be performed.

In this case, according to the invention of claim 2, since the pump discharge flow rate is detected by the speed sensor through the engine rotation speed, the sensor is simple as compared with the case where the pump discharge flow rate is directly detected by the flow meter. The cost is low.

Further, according to the invention of claim 3, in the control device in which the bleed-off passage is provided in the control valve, the flow rate gain is kept constant regardless of the change in the pump discharge flow rate when the bleed-off passage is open. Since the pressure oil is supplied with the same gain as when the pump discharge flow rate is low even when the pump discharge flow rate is high, it is less likely that the actuator flow rate will be insufficient, which is an adverse effect of reducing the flow rate gain in the low flow rate range. Become.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a relationship between an operation amount of a control valve used in the device and an opening area of each internal passage.

FIG. 3 is a diagram showing a relationship between a valve operation amount and a cylinder flow rate.

FIG. 4 is an overall configuration diagram showing a conventional device.

FIG. 5 is a diagram showing a relationship between a valve operation amount and a cylinder flow rate in the same device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 engine 2 hydraulic pump 3 hydraulic cylinder as hydraulic actuator 4 control valve 4c bleed-off passage of the valve 7 pressure sensor as valve operation amount detection means 9 speed sensor for detecting engine rotation speed 10 controller as control means 12 controller Flow gain calculation part 13 of the same output part 11 Flow control valve

Claims (3)

[Claims] 1. A control device for a hydraulic actuator, wherein a control valve for controlling the operation of the hydraulic pump driven by the engine and the hydraulic actuator driven by the pressure oil from the hydraulic pump is provided. In, the pump circuit is provided with a flow control valve for controlling the supply flow rate to the actuator,
Further, valve operation amount detection means for detecting the operation amount of the control valve, pump flow rate detection means for detecting the discharge flow rate of the hydraulic pump determined by the rotation speed of the engine, and valve operation amount detected by the both detection means. Based on the pump discharge flow rate, the command flow rate for the flow rate control valve is adjusted according to the pump discharge flow rate so that the flow rate gain, which is the degree of change in the flow rate passing through the flow rate control valve with respect to the valve operation amount, decreases as the pump discharge flow rate decreases. A control device for a hydraulic actuator, comprising a control means for calculating and outputting. 2. The control device for a hydraulic actuator according to claim 1, wherein a speed sensor for detecting a rotation speed of the engine is used as the pump flow rate detecting means. 3. The control valve is provided with a bleed-off passage that opens in a predetermined operating range in the direction of the operating position to communicate the pump circuit with the tank, and the control means is within the entire operating range of the control valve. 3. The hydraulic actuator control device according to claim 1, wherein the flow rate gain of the flow rate control valve is kept constant in an operation range where the bleed-off passage is opened.