JPH05332316A - Control circuit for cylinder - Google Patents

Abstract

PURPOSE:To prevent a phenomenon occurring with the high-speed tendency of the working speed of a construction machine, that is to say, a boom vibration resulting from a slight repeated telescopic motion caused by a cylinder not stopping instantly even after the stoppage of operation in the case where the operation of a boom turning up and down cylinder is stopped. CONSTITUTION:When the telescopic operation of a cylinder 1 is stopped, pressure fluctuation caused by the inertia force of a boom 2 in the cylinder 1 is detected, and pressure oil is supplied in a direction where the pressure fluctuation caused by the inertia force is diminished for early stopping the telescopic motion of the cylinder 1 occurring at the time of stopping the operation of the cylinder 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder control circuit for coping with speeding up of work in a construction machine such as a hydraulic excavator in which a boom is directly driven by a cylinder.

[0002]

2. Description of the Related Art In construction machines such as hydraulic excavators, the cylinder speed has been increased in order to improve the work efficiency, but in the boom / elevation cylinder with a large inertia load, the work speed increases as When work is stopped, due to the inertial force of the boom and the compressibility of hydraulic oil, the cylinder repeatedly expands and contracts slightly, and as a result, the boom vibrates, which hinders the efficiency of work requiring precision. found.

In the past, since the operating speed of each actuator was not so high, the inertial force at the time of stop was not so great, the existence of the above problems was not so noticeable, and a technique for solving them was not developed. ..

However, in recent years, there has been a call for improvement in work efficiency of construction machines, and there is a tendency to increase the operating speed of each actuator. As a result, a boom drive cylinder having a large inertia, even after the operation is stopped, is slightly increased. The phenomenon of repeated expansion and contraction appeared and became a problem.

[0005]

The present invention has been made to solve the above problems, but
In order to clarify this problem, first, the location of the problem will be specifically explained. In general, a pressure change in a container such as a hydraulic cylinder due to a change in volume of the container is expressed by the following equation. ΔP = ΔV / β × V Equation 1 where ΔP; pressure change amount β; compression rate V; container volume ΔV; volume change amount

Considering the movement of the cylinder 1 in the state shown in the figure, in the operation neutral state, the rod side 1a in the cylinder 1 is in an unloaded state, and the holding pressure of the boom 2 acts on the bottom side 1b.

During the boom raising operation, the rod side 1a in the cylinder 1 is in an unloaded state, and the driving pressure (> holding pressure) acts on the bottom side 1b.

-1 Immediately after the operation is stopped, the boom 2 tries to further rise due to the inertial force. However, at this time, there is no force (pressure) for stopping the movement of the boom 2 on the rod side 1a, so that the boom 2 rises. Along with this, 1) The volume on the rod side 1a decreases and the pressure increases.
(See Formula 1) When this pressure becomes equal to the inertial force of the boom 2, the boom 2
Will stop. 2) The bottom side 1b extends the cylinder 1 (increased volume)
The pressure decreases in inverse proportion to. (See Formula 1) 3) As a result, the boom 2 is temporarily stopped.

-2 With the boom 2 temporarily stopped,
This time, there is no force (pressure) to support the boom 2 on the bottom side 1b, so the boom 2 is lowered. Along with this, 4) The volume on the bottom side 1b decreases and the pressure increases. Even when this pressure reaches the holding pressure, it is further lowered by the inertial force of the boom 2, and the pressure finally becomes equal to the inertial force, and finally stops. 5) At this time, the pressure on the rod side 1a decreases in inverse proportion to the contraction (increase in volume) of the cylinder 1.

-3 While the boom 2 is once stopped again, 6) Since the pressure on the bottom side 1b is equal to or higher than the holding pressure, this pressure causes the cylinder to extend (volume increases) and the boom 2 to rise. To do. 7) Accordingly, even if the pressure on the bottom side 1b is reduced to the holding pressure, the state returns to -1, and the above 1) to 7) are repeated, and the expansion and contraction eventually converge due to energy loss during that period. Stop.

A similar phenomenon occurs even after the boom is stopped to be lowered, and the cylinder 1 sequentially converges and stops while repeatedly expanding and contracting.

As described above, when the cylinder 1 is expanded and contracted to move the boom 2 up and down and the operation is stopped, the cylinder 1 does not stop immediately after the stop operation, but stops after repeating a small expansion and contraction. Although a phenomenon occurs, if the expansion and contraction speed of the cylinder 1 is slow, accurate work is not required, and the compression rate of the hydraulic oil is the theoretical value, this phenomenon does not cause much trouble.

However, when the work speeds up, the expansion / contraction speed of the cylinder 1 increases, and the work with high accuracy is required, and when the chances of air bubbles in the working oil increase accordingly, the work oil is contained in the working oil. Due to the small amount of air bubbles, the compressibility becomes large in a low pressure state, and the above phenomenon becomes apparent, which has become a problem as a factor that hinders the speeding up of work and the improvement in accuracy.

An object of the present invention is to solve this problem, and when the operation of the boom / elevation cylinder is stopped, the cylinder does not immediately stop due to the action of inertial force. An object of the present invention is to provide a hydraulic control circuit capable of avoiding a phenomenon in which the boom repeatedly vibrates and vibrates.

[0015]

The present invention provides a means for solving the above-mentioned problems, in which pressure oil from a hydraulic pump 3 is transferred to a cylinder 1 via a hydraulic pilot type directional control valve 4. In the hydraulic circuit of the construction machine, which is configured to feed the rod 2a to the rod side 1a or the bottom side 1b to raise and lower the boom 2, the pressure in the cylinder 1 generated by the inertial force of the boom 2 when the expansion and contraction operation of the cylinder 1 is stopped. A cylinder 1 that detects a change and supplies pressure oil in a direction to reduce the change in pressure due to the inertial force, and that is generated when the operation is stopped
The invention is directed to a hydraulic control circuit characterized in that the expansion and contraction of the valve are converged at an early stage.

[0016]

When the cylinder 1 for raising and lowering the boom 2 is stopped from supplying pressure oil to the rod side 1a or the bottom side 1b and the expansion and contraction of the cylinder 1 is stopped, the inertia force of the boom 2 causes the pressure in the cylinder 1 to increase. Change occurs, cylinder 1
Tries to repeat the minute expansion and contraction immediately without stopping, but according to the present invention, the pressure change in the cylinder 1 caused by the inertial force of the boom 2 is detected by an appropriate detecting means, and the pressure change due to the inertial force is detected. Since the pressure oil is supplied in such a direction as to reduce the force, the expansion and contraction of the cylinder 1 can be converged at an early stage, the vibration of the boom 2 can be prevented, and the work can be speeded up and the accuracy can be improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, reference numeral 1 is a cylinder for raising and lowering a boom 2, and the boom 2 can be raised and lowered by supplying pressure oil to its rod side 1a or bottom side 1b.

Reference numeral 3 denotes a negative control (hereinafter abbreviated as negative control) hydraulic pump, the discharge side 3a of which is connected to a rod side 1a or a bottom side 1b of the cylinder 1 via a hydraulic pilot type directional control valve 4. The pressure oil can be selectively supplied, and in the neutral state (state shown in the drawing), the pressure oil is communicated with the tank T via the negative bypass throttle 5 via the center bypass.

Reference numeral 6 denotes a pilot operated valve, which can be switched between neutral, boom up, and boom down by operating an operation lever (not shown). 7 is a pilot pump. Since the above is known in the related art, the description of the operation is omitted.

Reference numeral 8 is a pressure sensor, the input side of which is connected to the hydraulic oil line 1b 'on the bottom side 1b of the cylinder 1 and the output side of which is connected to the controller 9. 10 is a pressure switch connected to the controller 9,
It is inserted between the pilot lines 6a and 6b and turned on / off depending on the presence or absence of the pilot pressure.

Reference numeral 11 denotes an electromagnetic switching valve, which is provided between the hydraulic pump 3 and the rod-side hydraulic oil line 1a 'and the bottom-side hydraulic oil line 1b' of the cylinder 1, and the directional switching valve 4 is provided.
And a bottom side hydraulic oil line at the position A where the line 3b branched from the discharge side line 3a of the hydraulic pump 3 is connected to the rod side hydraulic oil line 1a ′ by the output signal of the controller 9 and the bottom side hydraulic oil line. It can be switched to a position B communicating with 1b '. Reference numeral 12 is a check valve inserted in the branch line 3b.

The controller 9 includes the pressure switch 10
When the pressure sensor 8 is turned on, it does not operate, and when it is turned off, it operates by the output signal of the pressure sensor 8 and when the pressure sensor 8 detects a value larger than the reference pressure (for example, boom holding pressure). The electromagnetic switching valve 11 is switched to the position A, and when it detects a small value, it is switched to the position B, and is controlled to return to the neutral position after a lapse of a certain time.

While the pilot valve 6 is operated and the direction switching valve 4 is switched to the operating position, the boom 2 is raised and lowered,
Since the pressure switch 10 is maintained in the ON state by the pilot pressure of the pilot line 6a or 6b, the controller 9 does not operate and the electromagnetic switching valve 11 is held at the neutral position. Therefore, it is possible to perform a normal boom / fall operation.

When the pilot valve is returned to the neutral position and the direction switching valve 4 is returned to the neutral position as shown in the drawing, the negative control throttle for generating the signal pressure for the negative control is provided downstream of the center bypass of the direction switching valve 4. 5, the surge pressure is generated in the discharge line 3a of the hydraulic pump 3 and its branch line 3b. On the other hand, since the pilot pressures in the pilot lines 6a and 6b disappear, the pressure switch 10 is turned off, and the controller 9 is activated by the output of the pressure sensor 8.

At this time, the pressure sensor 8 detects a pressure change in the cylinder 1 caused by the inertial force of the boom 2, and when a value larger than a reference pressure (for example, a boom holding pressure) is detected, the electromagnetic switching valve 11 is moved to the position. Controller 9 to switch to position B when a small value is detected in A
The controller 9 switches the electromagnetic switching valve 11 to the position A or the position B in accordance with the signal, and controls so as to return to the neutral position after a certain period of time.

When the pressure sensor 8 senses a value larger than the reference pressure and the electromagnetic switching valve 11 is switched to the position A,
The surge pressure generated in the branch line 3b causes the rod side 1
a to the position B in the same manner by sensing a small value.
Is supplied to the bottom side 1b when it is switched to, and in any case, since the pressure oil is supplied in the direction in which the change in the pressure generated in the cylinder 1 by the inertial force of the boom 2 is attenuated, the expansion and contraction of the cylinder 1 is performed. Can be quickly converged,
It is possible to prevent vibration of the boom 2 to speed up work and improve accuracy.

[0027]

According to the present invention, when the expansion / contraction of the cylinder 1 for raising and lowering the boom 2 is stopped, the pressure change in the cylinder 1 caused by the inertial force of the boom 2 is detected, and the pressure due to the inertial force is detected. By supplying the pressure oil in the direction of canceling the change of, the expansion and contraction of the cylinder 1 that occurs when the operation is stopped can be quickly converged. Therefore, when the operation of the boom / elevation cylinder is stopped, the force of inertia is applied. It is possible to avoid a phenomenon in which the cylinder does not stop immediately and expands and contracts slightly, and the boom vibrates, so that the vibration of the boom 2 is prevented and the work can be speeded up and accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1 Cylinder 1a Cylinder 1 Rod Side 1b Cylinder 1 Bottom Side 2 Boom 3 Hydraulic Pump 4 Directional Switching Valve 5 Negative Control Throttle 6 Pilot Valve 6a, 6b Pilot Line 7 Pilot Pump 8 Pressure Sensor 9 Controller 10 Pressure Switch 11 Electromagnetic Switching Valve

Claims (4)

[Claims] 1. The hydraulic fluid from the hydraulic pump (3) is sent to the rod side (1a) or the bottom side (1b) of the cylinder (1) via the hydraulic pilot type directional control valve (4), and the boom ( 2) In the hydraulic circuit of the construction machine in which the cylinder is raised, the pressure change in the cylinder (1) caused by the inertial force of the boom (2) is detected when the expansion and contraction operation of the cylinder (1) is stopped.
A hydraulic control circuit characterized in that pressure oil is supplied in a direction to reduce a change in pressure due to the inertial force, so that expansion and contraction of the cylinder (1) which occurs when the operation is stopped is quickly converged. 2. The hydraulic fluid from the hydraulic pump (3) is sent to the rod side (1a) or the bottom side (1b) of the cylinder (1) via the hydraulic pilot type directional control valve (4), and the boom ( 2) In a hydraulic circuit of a construction machine that raises and lowers the pressure sensor that detects the pressure change in the cylinder (1) caused by the inertial force of the boom (2) when the expansion and contraction operation of the cylinder (1) is stopped. An electromagnetic switching valve equipped with (8) and controlled by the controller (9) according to the output signal of the pressure sensor (8).
Cylinder (1) that is generated when the operation is stopped by supplying pressure oil through the (11) in a direction that reduces the pressure change due to the inertial force.
A hydraulic control circuit characterized by quickly converging the expansion and contraction of the. 3. The hydraulic fluid from the hydraulic pump (3) is sent to the rod side (1a) or the bottom side (1b) of the cylinder (1) via the hydraulic pilot type directional control valve (4), and the boom ( 2) In a hydraulic circuit of a construction machine that raises and lowers the pressure sensor that detects the pressure change in the cylinder (1) caused by the inertial force of the boom (2) when the expansion and contraction operation of the cylinder (1) is stopped. The pressure sensor (8) has an input side on the bottom side (1b) of the cylinder (1) and an output side on the controller.
The controller (9) is connected to (9), and the controller (9) is on the rod side (1a) when the detected value of the pressure sensor (8) is higher than the preset reference value, and on the bottom side (1b) when it is low. , The electromagnetic switching valve (11) is switched to supply pressure oil for a certain time respectively, and the pressure oil is supplied in a direction to reduce the change in pressure due to the inertial force, and the expansion and contraction of the cylinder (1) that occurs when the operation is stopped. A hydraulic control circuit characterized by early convergence. 4. A pressure switch (10) is inserted between the left and right pilot lines (6a) (6b) of the hydraulic pilot type directional control valve (4), and the pressure switch (10) is turned on by pilot pressure. The hydraulic control circuit according to claim 2 or 3, wherein the controller (9) does not operate during the period, and the controller (9) can be operated only while the pilot pressure disappears and the pressure switch (10) is turned off.