JPH0359281B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides a control device for a hydraulic circuit that has a switching valve between a variable displacement pump and an actuator and controls the speed of the actuator according to the discharge flow rate of the pump. Regarding.

[Background of the invention]

In recent years, in order to achieve energy savings or higher functionality of hydraulic circuits, hydraulic circuits have been proposed in which the speed of a hydraulic actuator is controlled in accordance with the discharge flow rate of a hydraulic pump.

FIG. 1 is a circuit diagram showing the basic configuration of a control device for a hydraulic circuit of this type, and FIG. 2 is a block diagram showing an example of control means included in the control device shown in FIG. In Fig. 1, 1 is a variable displacement pump;
a is a discharge rate variable mechanism of a variable displacement pump, such as a swash plate; 2 is a regulator that drives the swash plate 1a; 3
4 is a displacement meter that detects the position of the swash plate 1a, 4 is an actuator such as a cylinder driven by pressure oil supplied from the variable displacement pump 1, 5 is the load on the cylinder 4, and 6 is the variable displacement pump 1 and the cylinder 4.
This is a switching valve that is interposed between the variable displacement pump 1 and the cylinder 4 to connect and disconnect the flow of pressure oil supplied from the variable displacement pump 1 to the cylinder 4. Reference numeral 7 designates a control lever that instructs the discharge amount of the variable displacement pump 1, that is, the speed of the cylinder 4, and 8 a control device, which controls the swash plate tilting amount Y from the displacement meter 3 and the control lever 7. Operation amount of X _L
and outputs a control signal to the regulator 2 and a switching signal to the switching valve 6.

As shown in FIG. 2, the aforementioned control device 8 is composed of, for example, a microcomputer, and includes a multiplexer 8 that inputs analog signals from the displacement meter 3 and the operating lever 7, and switches and outputs them.
a, an A/D converter 8b that converts analog signals into digital signals, a central processing unit (CPU) 8c that performs various controls and arithmetic processing, and a ROM memory that stores programs for operating procedures and predetermined functional relationships. 8d, a RAM memory 8e that temporarily stores data during calculation, and an output device 8f that outputs the control contents obtained by the calculation to the regulator 2 or the switching valve 6.

3 and 4 are flowcharts illustrating the operation procedure stored in the ROM memory 8d in the control device 8 described above. FIG. 3 shows the overall procedure, and FIG. 4 shows the step S in FIG. -8 is shown in detail.

In FIG. 3, first, as shown in step S-1, after the multiplexer 8a of the control device 8 is switched, the operating amount X _L of the operating lever 7 and the output of the displacement meter 3 are transmitted via the A/D converter 8b. The swash plate tilting amount Y is read into the central processing unit 8c. Next, as shown in step S-2, the central processing unit 8c determines whether the manipulated variable X _L is within the neutral range (A'≦ _XL ≦A) in which the cylinder 4 is stopped. At this time, if it is determined that the manipulated variable X _L is within the neutral range, the process moves to step S-3.
In step S-3, an OFF signal is output from the central processing unit 8c to the switching valve 6 via the output device 8f.
This keeps the switching valve 6 in the closed state shown in FIG. Next, as shown in step S-4, the central processing unit 8c performs processing to set the discharge amount command value X to zero.

Further, if it is determined in step S-2 that the manipulated variable X _L is not within the neutral range, step S-2 is performed.
-5, an ON signal is output from the central processing unit 8c to the switching valve 6 via the output device 8f, thereby switching the switching valve 6 from the state shown in FIG. 1 to the right.
It becomes open. Next, as shown in step S-6, the central processing unit 8c determines the discharge amount of the variable displacement pump 1 from the functional relationship between the operation amount X _L of the operating lever 7 and the discharge amount command value X stored in the ROM memory 8d. A process of converting the command value X into a target discharge amount _X0 corresponding to the manipulated variable X _L is performed, and step S
-7, this X=X ₀ is set in the RAM memory 8e. Then, step S-4 and step S-
After step 7, the process moves to step S-8, where the discharge amount of the variable displacement pump 1 is controlled according to the discharge amount command value X, and the process returns to the start.

The discharge amount control in step S-8 described above is performed in the fourth step.
The procedure is shown in the figure. That is, as shown in step S-81, the central processing unit 8c performs a calculation to subtract the swash plate tilting amount Y from the discharge amount command value X (=0,=X ₀ ) to calculate the deviation ΔY. Proceeding to step S-82, the sign of the ΔY is determined. At this time, if it is determined that ΔY is - (negative value), the process moves to step S-83, and in this step S-83, the central processing unit 8c outputs the output device 8.
A control signal for moving the swash plate 1a in one direction is output to the regulator 2 via f. If it is determined in step S-82 that ΔY is 0, the process moves to step S-84. Here, ΔY=0 means that the discharge amount command value X and the swash plate tilting amount Y match.
A control signal is output to stop the swash plate 1a.
Furthermore, if it is determined in step S-82 that ΔY is + (positive value), the process proceeds to step S-82.
85, and in this step S-85 the central processing unit 8
swash plate 1 from c to regulator 2 via output device 8f.
A control signal that moves a in the + direction is output. In the above procedure, steps S-1 to S-8 are always repeated to control the hydraulic circuit shown in FIG.

Conventionally, the hydraulic circuit control device configured as described above has had the following problems. That is, generally, in the variable displacement pump 1, as shown in FIG. 1, there is a flow rate qlt that leaks from the discharge port (not shown) of the pump 1 to the tank, and a flow rate qli that leaks from the discharge port to the suction port. Therefore, if this hydraulic circuit is applied, for example, to a circuit that operates the boom of a hydraulic excavator (corresponding to load 5), the pressure in the circuit will increase due to the boom load being applied to cylinder 4, and the leakage flow rate qlt will increase. , qli both grow larger. In such a situation, if you slightly operate the operating lever 7 to move the cylinder 4 slightly and try to stop it, the discharge amount command value
The cylinder 4 is actuated by the leakage flow rate qlt+qli at a point where the amount of discharge from the variable displacement pump 1 is almost 0.

For this reason, even though the operating lever 7 is moved to raise the cylinder 4 slightly, the cylinder 4 may drop to the verge of stopping, or even if the cylinder 4 is lowered only slightly, leakage may occur. This will cause the cylinder 4 to drop by an amount corresponding to the flow rate qlt + qli, and even if you try to stop the cylinder 4 without a shock, the cylinder 4 will drop at the speed of the leakage flow rate qlt + qli.
Since the switching valve 6 is closed while the cylinder is operating, the speed of the cylinder 4 suddenly changes, causing a shock.

In this way, in the conventional hydraulic circuit control device, when the cylinder 4 is at a speed lower than that corresponding to the leakage flow rate,
There was a problem that the speed could not be controlled and fine controllability was poor. Such defects in fine operability are also a problem from the standpoint of protecting the safety of workers working on various hydraulic machines to which the above-mentioned hydraulic circuit control device is applied.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic circuit control device that eliminates the above-mentioned drawbacks of the prior art and eliminates the unnecessary operation and shock of the actuator corresponding to the leakage flow rate of the variable displacement pump when the fine operation is stopped. .

[Summary of the invention]

In order to achieve this object, the present invention provides a variable displacement pump, an actuator driven by the variable displacement pump, and an actuator that is interposed between the variable displacement pump and the actuator so that the actuator can be moved from the variable displacement pump to the actuator. In a hydraulic circuit having a switching valve that connects and disconnects the flow of pressure oil supplied to the hydraulic circuit,
A control means for controlling the switching valve to be closed when the actuator is not operated and to open the switching valve when the actuator is to be operated, and for controlling the discharge flow rate of the variable displacement pump; and a control means connected to the control means. In the control device for a hydraulic circuit, the control means is configured to control a hydraulic circuit according to a preset method when the amount of operation of the operating lever returns from a range instructing the operation of the actuator to a range instructing the actuator to stop. The first discharge amount command value of the variable displacement pump is added or subtracted from the neutral discharge amount command value of the variable displacement pump according to the load direction of the actuator to obtain a second discharge amount command value, and this second The discharge flow rate of the variable displacement pump is controlled according to the discharge rate command value, and the switching valve is controlled to close when the discharge flow rate of the variable displacement pump matches the second discharge rate command value. shall be.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 is an explanatory diagram showing an example of a metering table used in the hydraulic circuit control device of the present invention, in which the horizontal axis represents the operation amount X _L of the operating lever 7, and the vertical axis represents the target value that determines the cylinder speed. A discharge amount of X ₀ is set. In FIG. 5, F specifies a neutral range that forms a region where the speed of the cylinder 4 is not controlled by the operating lever 7, and A and A' specify predetermined values set in advance, that is, the range of the neutral range F. In the neutral range F, the discharge amount of the variable displacement pump is always 0.

FIG. 6 is a characteristic diagram showing the relationship between the amount of tilting of the swash plate and the cylinder speed, which is generally seen in this type of hydraulic circuit. The cylinder speed v _c is taken. In FIG. 6, + and - on the horizontal axis indicating the amount of swash plate tilting indicate the tilting direction of the swash plate 1a of the variable displacement pump 1, and + and - on the vertical axis indicating the cylinder speed indicate the operating direction of the cylinder 4. The solid line indicates that cylinder 4 is under load 5.
The broken line in the state in which the cylinder 4 is supporting the cylinder 4 shows the characteristics in a state in which the cylinder 4 is driven by a load, for example, in a state in which an object is suspended by the cylinder 4.
As can be seen from the solid line in Fig. 6, cylinder 4
is supporting the load 5, when the swash plate tilting amount Y of the variable displacement pump 1 is 0, the cylinder speed v _c becomes a negative value due to the leakage flow rate qlt + qli, and the discharge amount of the variable displacement pump 1 becomes the leakage flow rate qlt + qli. The cylinder speed v _c becomes 0 at the swash plate tilt amount X ₁ at the matching point. Further, as can be seen from the broken line in FIG. 6, when the cylinder 4 is driven by the load 5, when the swash plate tilting amount Y is 0, the cylinder speed v _c becomes a + value, and the discharge amount of the variable displacement pump 1 is the leakage flow rate qlt+
The cylinder speed v _c becomes 0 at the swash plate tilt amount -X ₁ at the point corresponding to qli.

7 is a circuit diagram showing the configuration of a control device for a hydraulic circuit according to the present invention, FIG. 8 is a block diagram showing an example of control means provided in the control device shown in FIG. 7, and FIG. Parts corresponding to are given the same reference numerals.

In FIG. 7, reference numeral 9 denotes a load direction detector whose piston moves in the left and right directions in the figure according to the level of pressure in the head side circuit and rod side circuit of the cylinder 4, and 10 and 11 denote pistons of the load direction detector 9. A switch 80, such as a proximity switch, which outputs a signal in response to the movement of the switch 80 is a control device. Among these two proximity switches 10 and 11, one proximity switch 10 is activated when the head side of the cylinder 4 is under high pressure.
The other proximity switch 11 is turned ON when the rod side of the cylinder 4 is under high pressure. When both the head side and rod side circuits of the cylinder 4 have equal low pressure, the piston of the load direction detector 9 is kept at the neutral position shown by the spring, and both the proximity switches 10 and 11 are turned OFF.

The control device 80 is configured as shown in FIG. 8, and an input device 8g for inputting the states of both proximity switches 10 and 11 is added to the control device 8 shown in FIG. 2 described above. The rest of the structure is the same as that shown in FIG. 2. That is, the control device 80
For example, the multiplexer 8a, A/D converter 8b, central processing unit (CPU) 8c, ROM memory 8d, RAM memory 8e, output device 8f, input device 8
It is composed of g.

The control in the embodiment shown in FIG. 7 described above is as follows:
For example, this is carried out according to the procedure shown in the flowchart of FIG. In this flowchart,
Each step is designated by a symbol S-100, S-101, . Further, this flowchart also constantly rotates between steps S-100 to S-8, similar to the flowchart shown in FIG. 3 described above.

Next, the control device 80 described above based on FIG.
The operating procedure will be explained. First, as shown in step S-100, multiplexer 8a is switched,
The amount of operation of the operating lever 7 is determined via the A/D converter 8b.
X _L and the swash plate tilt amount Y of the displacement meter 3 are read.
Next, as shown in step S-101, the central processing unit 8c selects the variable displacement pump 1 corresponding to the operating amount X _L of the operating lever 7 from the metering table (see FIG. 5) stored in the ROM memory 8d. A process of reading out the target discharge amount X ₀ is performed. Next, the process moves to step S-102, where the central processing unit 8c determines whether the manipulated variable X _L is within the neutral range F, that is, whether the manipulated variable X _L is within the range of a predetermined amount A'-A. At this time, if it is determined that the manipulated variable X _L is not within the neutral range F, that is, if the manipulated variable X _L from the operating lever 7 is a command to drive the cylinder 4, the process moves to step S103, and the central processing unit 8c Turns ON to switching valve 6 via output device 8f
A signal is output, which opens the switching valve 6 and connects the variable displacement pump 1 and the cylinder 4. Next, in step S-104, the discharge amount command value X of the variable displacement pump 1 is set to the previous target discharge amount _X0 , and the process moves to the discharge amount control in step S-8.

Furthermore, if it is determined in step S-102 that the manipulated variable X _L is within the neutral range F, the process moves to step S-105, where it is determined in the central processing unit 8c whether the switching valve 6 was previously turned on. be done. At this time, if the switching valve 6 was OFF last time, step S
-106, from the central processing unit 8c to the output device 8f
An OFF signal is output to the switching valve 6 via the switching valve 6, and the switching valve 6 is kept in the closed state. Next step S-107
As shown in , the discharge amount command value
The setting is made to be X ₀ , and the process moves to step S-8, discharge amount control. In this embodiment, since the discharge amount command value X ₀ of the variable displacement pump 1 in the neutral state is X ₀ =0 as shown in FIG. 5, the setting of X = 0 is performed in step S-107. .

In step S-105, the previous switching valve 6
When it is ON, it means that the operating amount X _L of the operating lever 7 has returned from the range that instructs the operation of the cylinder 4 to the range that instructs the cylinder 4 to stop, and immediately proceeds to step S-
108, close proximity switch 1 on central processing unit 8c
The load direction of the cylinder 4 is determined from the output signals of 0 and 11. When the proximity switch 10 is ON, the cylinder 4 supports the load 5 as shown in Fig. 7, and the head side of the cylinder 4 is under high pressure. As shown above, the cylinder speed v _c becomes 0 when the swash plate tilt amount Y
is X ₁ (first discharge amount command value). Therefore, the process moves to step S-111, where the central processing unit 8c sets the second ejection amount command value X to X ₀ +|X ₁ |. In this case, since the discharge amount command value X ₀ is 0 as described above, X=+|X ₁ |. Next, as shown in step S-112, the central processing unit 8c determines whether the swash plate tilt amount Y matches the discharge amount command value X.

In addition, in step S-108, the proximity switch 11 is turned ON when the cylinder 4 is driven by the load 5 and the rod side of the cylinder 4 is under high pressure, and in this case, it is indicated by the broken line in FIG. As shown above, the cylinder speed v _c becomes 0 when the swash plate tilting amount Y is _-X1 . Therefore, step S-109
Then, the central processing unit 8c sets the second discharge amount command value X as X ₀ −|X ₁ |, that is, in this embodiment, X=X ₀ (=0) −|X ₁ |=−|X ₁ | Settings are made, and then the process moves to step S-112.

In addition, in step S-108, both proximity switches 10 and 11 are turned OFF on cylinder 4.
In this case, the process moves to step S-110, and the central processing unit 8c sets the second discharge amount command value X to X ₀ +0× _| Since X ₀ = 0, X=
Setting to 0 is performed, and then step S-
Move to 112.

In step S-112, it is determined whether the swash plate tilt amount Y matches the second discharge amount command value X as described above. If it is determined that Y≠X, that is, the swash plate tilting amount Y does not match the discharge amount command value X, the step The process moves to step S-113, the switching valve 6 is kept in the ON state, and the process moves to step S-8. Further, in step S-112, if it is determined that Y=X, that is, the swash plate tilting amount Y matches the discharge amount command value X, the process moves to step S-114.
An OFF signal is output to the switching valve 6, and the connection between the variable displacement pump 1 and the cylinder 4 is cut off. Next, the process moves to step S-115, where the discharge amount command value X is set to be the discharge amount command value X ₀ when the variable displacement pump 1 is in neutral.
That is, in this embodiment, the setting is made so that X=0, and the process moves to step S-8.

In step S-8, as described above, the discharge amount is controlled according to the procedure shown in FIG. 4, and the regulator 2 controls the discharge flow rate of the variable displacement pump 1 according to the discharge amount command value X, and starts Return to

In one embodiment configured in this way,
When the operating amount X _L of the operating lever 7 returns from the range that instructs the operation of the cylinder 4 to the range that instructs it to stop, if the head side of the cylinder 4 is loaded in the direction of high pressure, the discharge amount command value After setting the swash plate tilting amount Y ( ₌ If so, set the discharge amount command value X to −X ₁
After that, the switching valve 6 is closed, and if the load direction of the cylinder 4 is neutral, the leakage flow rate of the variable displacement pump 1 is
Since the cylinder 4 does not move due to qlt+qli, the discharge amount command value X can be set to 0 and the switching valve 6 can be closed. Therefore, unnecessary movements and shocks of the cylinder 4 due to the influence of the leakage flow rate qlt+qli can be alleviated, and a stopping operation can be realized by finely operating the cylinder 4 according to the operating amount _XL of the operating lever 7.

In the above embodiment, the swash plate 1a of the variable displacement pump 1 is in the neutral position when the discharge amount command value X ₀ is 0, but the tilting of the variable displacement pump 1 is commanded to 0 (neutral). The discharge amount command value X ₀ does not necessarily have to be 0. For example, if the displacement meter 3 outputs a signal that is not 0 when the swash plate 1a is in the neutral position, the variable displacement pump 1 is in the neutral position when X ₀ ≠ 0. becomes.

Further, in the above embodiment, the piston 9 and the proximity switches 10, 11 are used as a means for detecting the load direction of the actuator (cylinder) 4, but this load direction detection means is not limited to the above embodiment. For example, a pair of pressure detectors may be provided to detect the pressures of both ports of the variable displacement pump 1, and the load direction of the actuator may be detected based on the states of both pressure detectors.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to prevent unnecessary operation or shock of the actuator corresponding to the leakage flow rate of the variable displacement pump when the fine operation is stopped.
Therefore, it is possible to prevent the actuator from operating unintentionally by the operator who operates the actuator.
It can contribute to worker safety.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing the basic configuration of a conventional hydraulic circuit control device, Fig. 2 is a block diagram showing an example of control means constituting the hydraulic circuit control device shown in Fig. 1, and Fig. 3 is a conventional hydraulic circuit control device. FIG. 4 is a flowchart illustrating the control means in the hydraulic circuit control device of the present invention; FIG. 4 is a flowchart illustrating step S-8 of the flowchart shown in FIG. 3 in detail; FIG. FIG. 6 is a characteristic diagram showing the swash plate tilting amount-cylinder speed characteristic commonly seen in the hydraulic circuit to which the present invention is applied, and FIG. 7 is a characteristic diagram showing the metering table used in the present invention. Circuit diagram showing the configuration of the control device of the hydraulic circuit, No. 8
The figure is a block diagram showing an example of the control means constituting the control device for the hydraulic circuit shown in FIG. 7, and FIG.
2 is a flowchart illustrating a control means in the control device for the hydraulic circuit shown in the figure. DESCRIPTION OF SYMBOLS 1... Variable displacement pump, 1a... Swash plate, 2... Regulator, 3... Displacement meter, 4... Cylinder (actuator), 5... Load, 6... Switching valve, 7... Operating lever,
9... Load direction detector, 10, 11... Proximity switch, 80... Control device.

Claims (1)

[Claims] 1 a variable displacement pump, an actuator driven by the variable displacement pump, and a variable displacement pump interposed between the variable displacement pump and the actuator,
In a hydraulic circuit having a switching valve that connects and disconnects the flow of pressure oil supplied from a variable displacement pump to an actuator, the switching valve is closed when the actuator is not operated, and is opened when the actuator is operated. In the hydraulic circuit control device, the control device includes a control means for controlling the discharge flow rate of the variable displacement pump, and an operation lever connected to the control means, wherein the control means controls the discharge flow rate of the variable displacement pump. When the operation amount returns from the range that instructs the operation of the actuator to the range that instructs it to stop, the preset first discharge amount command value of the variable displacement pump is changed according to the load direction of the actuator. A second discharge amount command value is obtained by adding or subtracting from the discharge amount command value at neutral time, and the discharge flow rate of the variable displacement pump is controlled according to this second discharge amount command value, and the discharge amount of the variable displacement pump is controlled. A control device for a hydraulic circuit, characterized in that the switching valve is controlled to be closed when the flow rate matches a second discharge amount command value.