JP3808808B2 - Cylinder operation control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cylinder operation control device that performs operation control of a fluid pressure cylinder.
[0002]
[Prior art]
Fluid pressure cylinders such as hydraulic cylinders are used as hoisting cylinders for hoisting a boom of an aerial work vehicle or a crane vehicle, for example. FIG. 5 shows a specific conventional example of the operation control device for the hoisting cylinder. In this device, when the operator tilts the hoisting operation lever 10a for the hoisting operation of the boom, the operation to the controller 40 is performed. A signal is sent out. A control signal corresponding to the operation signal is sent from the controller 40 to the electromagnetic actuation control type raising / lowering cylinder control valve 22, and the rod-side oil chamber 6 b of the raising / lowering cylinder 6 through the rod-side oil path 52 and the bottom-side oil path 53. And the supply / discharge of the oil to the bottom side oil chamber 6a is controlled, and the expansion / contraction operation control is performed.
[0003]
When the hoisting operation lever 10a is returned to the neutral position, the spool of the hoisting cylinder control valve 22 moves to the neutral position (the position shown in the figure), and the hydraulic oil is discharged to the rod side oil chamber 6b and the bottom side oil chamber 6a. Stops, and the operation of the hoisting cylinder 6 is stopped. At this time, the hydraulic cylinder 6 holds the boom at a predetermined undulation angle position, and the load from the boom is applied to the hydraulic cylinder, so that the hydraulic oil in the bottom side oil chamber 6b and the bottom side oil passage 53 is used. The hydraulic pressure corresponding to this load is generated. Here, since the hoisting cylinder control valve 22 is configured to perform hydraulic oil supply / exhaust oil path switching control by moving the spool, even when the spool is in the neutral position, some oil leakage occurs from the outer periphery of the spool. In this state, the hoisting cylinder 6 is gently contracted, and the boom is gradually lowered.
[0004]
Therefore, in order to prevent such oil leakage and prevent the boom cylinder 6 from falling over due to the contraction operation, the bottom oil passage from the bottom oil chamber 6a of the hoisting cylinder 6 to the hoisting cylinder control valve 22 is conventionally used. A counter balance valve 31 is disposed in the ring 53. Furthermore, a pilot check valve 39 is arranged in series as a double safety device so that the hydraulic oil can be prevented from leaking even when the spool of the counter balance valve 31 is clogged with dust or the like, causing malfunction. Has been. The counter balance valve 31 has good operating performance but high cost. Therefore, the counter balance valve 31 is combined with a low-cost pilot check valve 39 with a simple configuration as a double safety device. As a result, the counter balance valve 31 prevents the escape of the lowering operation as well as the counter balance function to reliably prevent the hydraulic oil from leaking, and the pilot check valve 39 serves as a backup in case of malfunction.
[0005]
The counter balance valve 31 includes a direct acting control valve 31b and a check valve 31c. The direct acting control valve 31b is opened and closed in response to a pilot pressure introduced from a pilot oil passage 31a connected to the rod-side oil passage 52. Specifically, it is closed when the pilot pressure is lower than a predetermined pressure, and is released when the pilot pressure is higher than the predetermined pressure. The check valve 31c is disposed in the bypass oil passage 54 that bypasses the direct acting control valve 31b, and allows only the flow in the direction in which the hydraulic oil is supplied to the bottom side oil chamber 6a. The direct acting control valve 31b has a dull response so that the spool slowly moves with respect to fluctuations in the pilot pressure in order to suppress sudden fluctuations in the flow rate and pressure of the pressure oil caused by the movement of the spool. It is
[0006]
The pilot check valve 39 includes a check valve 39b that allows only a flow in the direction in which the hydraulic oil is supplied to the bottom-side oil chamber 6a, and a pilot oil passage 39a that is connected to the rod-side oil passage 52. The check valve 39b is opened when the pilot pressure derived from the pressure exceeds a predetermined pressure. Since the pilot check valve 39 has a relatively low cost and simple structure as described above, the responsiveness cannot be adjusted unlike the counter balance valve 31, and is sensitive to fluctuations in the pilot pressure. Opened and closed.
[0007]
In the operation control apparatus configured as described above, the tilting operation of the hoisting operation lever 10a is performed as described above, and the spool of the hoisting cylinder control valve 22 is moved to the left side in the drawing, and the working oil is supplied to the rod side oil passage 52. When the bottom side oil passage 53 is connected to the tank 20 side, the oil pressure in the rod side oil passage 52 rises. The oil pressure in the rod side oil passage 52 acts as a pilot pressure on the counter balance valve 31 and the pilot check valve 39 via the pilot oil passages 31a and 39a, and the pilot pressure rises so that the counter balance valve 31 and the pilot check valve are increased. 39 is opened. As a result, the hydraulic oil is supplied to the rod-side oil chamber 6b and the hydraulic oil is discharged from the bottom-side oil chamber 6a to the tank 20, the hoisting cylinder 6 is reduced, and the boom is lowered. On the other hand, when the spool of the hoisting cylinder control valve 22 is moved to the right side in the drawing to supply hydraulic oil to the bottom side oil passage 53 and the rod side oil passage 52 is connected to the tank 20 side, the pilot check valve 39 and the check valve By the action of 31c, the hydraulic oil is supplied to the bottom side oil chamber 6a and the hydraulic oil is discharged from the rod side oil chamber 6b, the hoisting cylinder 6 is extended, and the boom is raised.
[0008]
When the hoisting operation lever 10a is returned to the neutral position, the spool of the hoisting cylinder control valve 22 is moved to the neutral position, and the rod side oil passage 52 and the bottom side oil passage 53 are closed here. As a result, the hydraulic pressure in the rod-side oil passage 52 is lowered and the pilot pressure is lowered, so that the undulating cylinder counterbalance valve 31 and the pilot check valve 39 are closed to prevent the hydraulic oil from being discharged from the bottom-side oil chamber 6a. The expansion and contraction operation of the hydraulic cylinder 6 is surely stopped.
[0009]
[Problems to be solved by the invention]
By the way, when the hoisting operation lever 10a is positioned at the neutral position and the telescopic operation of the hoisting cylinder 6 is stopped in this way, the direct acting control valve 31b is slow in response to fluctuations in the pilot pressure. However, the pilot check valve 39 is suddenly closed in response to the fluctuation of the pilot pressure. For this reason, for example, when the hoisting operation lever 10a is returned to the neutral position from the state in which the hoisting cylinder 6 is contracted and the boom is tilted, and the boom tilting motion is stopped, the pilot check valve 39 is counterbalanced. The valve 31 is suddenly closed before the valve 31. When the pilot check valve 39 is suddenly closed in this way, the internal pressure of the rod-side oil passage 52 as well as the bottom-side oil passage 53 suddenly increases due to the gravity and inertia force from the boom side acting on the hoisting cylinder 6. As a result, the pilot pressure rapidly rises and the pilot check valve 39 is opened again. However, since the spool of the hoisting cylinder control valve 22 is in the neutral position, the pilot pressure decreases again, and the pilot check valve 39 is immediately closed again. Thus, there is a problem that a phenomenon (chattering phenomenon) in which the pilot check valve 39 is repeatedly opened and closed in a short time occurs when the boom collapse movement is stopped.
[0010]
Furthermore, such a sudden opening / closing operation of the check valve 39b causes an oil hammer phenomenon (oil hammer phenomenon) in the oil passage or a phenomenon in which the hoisting cylinder 6 operates intermittently or vibrates. There is a problem that the boom vibrates. Further, when the check valve 39b is opened and closed in this manner, intermittent hydraulic oil outflow occurs, and a stepping phenomenon occurs in which the boom itself is slightly lowered while vibrating. Due to such boom vibration and stepping phenomenon, In addition, there is a problem that uncomfortable feeling is given to an operator who is on the workbench at the end of the boom.
[0011]
Further, when dust or the like is generated in the hoisting cylinder control valve 22 that controls the supply and discharge of the pressure oil to the hoisting cylinder 6, the operator can stop the boom overturning operation, but the operation to the rod side oil passage 52 is stopped. Pressure oil supply may not stop. Then, since the pilot pressure does not drop, the hoisting cylinder counterbalance valve 31 and the pilot check valve 39 remain open, and there is a possibility that the shrinking operation of the hoisting cylinder 6 does not stop.
[0012]
The present invention has been made in view of such a problem, and provides a cylinder operation control device configured to be able to reliably hold the operation stop state of the hydraulic cylinder and to smoothly stop the operation. Objective. Another object of the present invention is to provide a cylinder operation control device excellent in safety that can securely stop a boom even if a cylinder control valve fails.
[0013]
[Means for Solving the Problems]
In order to achieve this object, a cylinder operation control device of the present invention includes a double-acting fluid pressure cylinder (for example, an undulating cylinder 6 in the embodiment of the present invention) that is expanded and contracted by supplying and discharging a working fluid, and the fluid. The cylinder control valve (for example, the undulating cylinder control valve 22 in the embodiment of the present invention) that controls the supply and discharge of the working fluid by moving the spool, and the supply and discharge of the working fluid to and from the pressure cylinder, An operation device (for example, a hoisting operation lever 10a in the embodiment of the present invention) that sends an operation signal according to an external operation for controlling the operation, and an operation signal received from the operation device in accordance with the operation of the operation device a controller for controlling the operation of the cylinder control valve Te (e.g., the controller 40 in the embodiment of the present invention), a one of the oil chambers of the hydraulic cylinder A second flow path that is disposed in a first flow path that connects the Linda control valve (for example, the bottom oil path 53 in the embodiment of the present invention) and that connects the other oil chamber of the fluid pressure cylinder and the cylinder control valve. (For example, a counter balance valve (for example, the counter balance valve 31 in the embodiment of the present invention ) that is opened and closed under the pressure of the rod side oil passage 52 in the embodiment of the present invention, and a counter balance in the first flow path. An electromagnetic check valve (for example, the electromagnetic check valve 35 in the embodiment of the present invention) that is arranged in series on the downstream side of the valve and that is controlled to be opened and closed by the controller is configured. When the operation signal is received, the control to open the electromagnetic check valve is performed, and when the operation signal from the operation device is stopped Performs control to closing operation of the electromagnetic check valve at a time delay of the constant time.
[0014]
According to such a cylinder operation control device, the controller immediately opens the electromagnetic check valve when the operating device is operated to operate the fluid pressure cylinder, but when the operating device is operated to stop, the controller In order to close the electromagnetic check valve with a delay, the electromagnetic check valve is closed after completion of the closing operation of the hoisting cylinder control valve and the counter balance valve. For this reason, when the operation is stopped, the fluid discharge oil passage from the fluid pressure cylinder is gently closed by the undulating cylinder control valve and the counter balance valve, and the chattering phenomenon, the oil hammer phenomenon, and the stepped operation phenomenon described above are generated. It can be suppressed. Even when a malfunction occurs that causes the hydraulic cylinder control valve to open, the electromagnetic check valve is closed as long as the operating device is stopped. can do.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. An aerial work vehicle 1 using the cylinder operation control device of the present invention is shown in FIG. The aerial work vehicle 1 is capable of traveling with front and rear wheels 3a and 3b, and is configured based on a truck vehicle having a driving cabin 2a at the front. On the vehicle body 2 of the truck vehicle, there is disposed a turntable 4 that is driven by a turn motor 14 (see FIG. 3) and configured to be able to turn horizontally. A base 5 is pivotally connected to the swivel 4 and a boom 5 is attached. The boom 5 is moved up and down by a hoisting cylinder 6. The boom 5 is configured such that a proximal boom 5a, an intermediate boom 5b, and a distal boom 5c are combined in a nested manner, and can be expanded and contracted by a built-in telescopic cylinder 7.
[0016]
The tip boom 5c has a boom head 5d at the tip, and is pivotally connected to the boom head 5d and attached to the support member 8 so as to be swingable up and down. The support member 8 has a vertical post portion (not shown), and swinging control of the support member 8 is performed by a leveling cylinder (not shown) disposed between the boom head 5d and the support member 8. Regardless of whether the boom 5 is raised or lowered, the support member 8 is controlled to swing so that the vertical post portion always extends vertically. In this manner, the work table 9 is attached to the vertical post portion which is always held vertically so as to be able to swing horizontally (swing freely), and the work table 9 is always held horizontally regardless of the undulation of the boom 5.
[0017]
An operation device 10 for operating the operation of the boom 5 and the like is provided at the rear part of the work table 9 and the vehicle body 2. In addition, outriggers 11 that are extendable downward are provided at four locations on the front, rear, left, and right of the vehicle body 2, and when performing work at a high place, the outrigger operation levers disposed on the rear portion of the vehicle body 2 as shown in the figure. The vehicle body 2 can be lifted and supported by operating the outrigger cylinder 13 downward by operating 12.
[0018]
Next, with reference to FIG. 3, the operation control of the hydraulic actuators (the hoisting cylinder 6, the telescopic cylinder 7, the turning motor 14, and the outrigger cylinder 13) will be described. These hydraulic actuators 6, 7, 14, and 13 control the oil in the tank 20 supplied from the hydraulic pump 21 (the hoisting cylinder control valve 22, the telescopic cylinder control valve 23, the swing motor control valve 24, and the outrigger cylinder control valve). 25), the operation is controlled by controlling the supply and discharge. In FIG. 3, the oil passage is indicated by a solid line, and the electrical connection is indicated by a broken line.
[0019]
Of these four control valves, three (hydraulic cylinder) control valves 22, 23, 25 have port A connected to the bottom side oil chambers 6a, 7a, 13a of each hydraulic cylinder, as shown in the figure, and port B, This is a 4 port 3 position switching valve connected to the rod side oil chambers 6b, 7b, 13b. The pressure in the bottom side oil chamber is secured between the bottom side oil chambers 6a, 7a, 13a and the port A so that the hydraulic cylinder does not operate due to an external force such as the weight of the hydraulic cylinders 6, 7, 13 or the load of the boom 5. Counter balance valve (relief cylinder counter balance valve 31, telescopic cylinder counter balance valve 32 and outrigger cylinder counter balance valve 33) and electromagnetic check valve (relief cylinder electromagnetic check valve 35, telescopic cylinder electromagnetic check valve 36 and outrigger cylinder electromagnetic) A check valve 37) is provided. Note that the swing motor control valve 24 (four-port three-position switching valve) that controls the swing motor 14 is connected to the port of the swing motor 14 in which port A and port B correspond to right rotation and left rotation, respectively.
[0020]
The controller 40 electrically controls the four control valves 22 to 25 and the three electromagnetic check valves 35 to 37. In the controller 40, a hoisting operation control unit 41 that controls the hoisting cylinder 6, a telescopic operation control unit 42 that controls the telescopic cylinder 7, a swing operation control unit 43 that controls the swing motor 14, and an outrigger cylinder 13 are controlled. And an outrigger control unit 44. These control units 41 to 44 receive operation signals from the operation device 10 installed on the work table 9 and behind the vehicle body 2 and the outrigger operation lever 12 installed behind the vehicle body 2, and are necessary for the operation. Send control signals to the respective control valves and electromagnetic check valves.
[0021]
The operating device 10 includes a hoisting operation lever 10a for operating the hoisting operation of the boom 5, an extendable operation lever 10b for operating the telescopic operation, and a turning operation lever 10c for operating the turning operation of the swivel 4 as shown in the figure. It is also configured to have a workbench swing lever or the like that does not work.
[0022]
Next, regarding the hydraulic cylinder operation control device that controls the operation of the hydraulic cylinders 6, 7, and 13 by the action of the counter balance valve and the electromagnetic check valve, the hydraulic pressure related to the control of the undulating cylinder 6 shown in the upper part of FIG. The cylinder operation control device 60 will be described in detail with reference to FIG. In FIG. 1, as in FIG. 3, the oil passage is indicated by a solid line and the electrical connection is indicated by a broken line.
[0023]
As shown in FIG. 1, the hydraulic cylinder operation control device 60 includes a rod-side oil passage 52 connecting the rod-side oil chamber 6 b of the hoisting cylinder 6 and the hoisting cylinder control valve 22, and a bottom-side oil chamber 6 a of the hoisting cylinder 6 and the hoisting. There are three oil passages: a bottom-side oil passage 53 connecting the cylinder control valve 22 and a pilot oil passage 31 a connected to the rod-side oil passage 52. As already described, in the middle of the bottom side oil passage 53, there are the undulating cylinder counterbalance valve 31 and the undulating cylinder electromagnetic check valve 35, and when these two hold the undulating cylinder 6, the bottom side Oil leakage from the oil chamber 6a is prevented.
[0024]
The hoisting cylinder counter balance valve 31 includes a direct acting control valve 31b and a check valve 31c. The direct-acting control valve 31b is positioned at a closed position where the spool is seated on the seat surface when the pilot pressure guided from the holding pilot oil passage 31a connected to the rod-side oil passage 52 is lower than a predetermined pressure. Blocks the flow of hydraulic oil in the discharge direction. On the other hand, when the pilot pressure becomes higher than the predetermined pressure, the spool opens (moves to the left in FIG. 1), opens the bottom side oil passage 53 at this portion, and flows the hydraulic oil through the direct acting control valve 31b. Allow. The check valve 31c is disposed in a bypass hydraulic line 54 that bypasses the direct acting control valve 31b, and allows the flow of hydraulic oil in the supply direction to the bottom side oil chamber 6a and prevents the flow in the discharge direction. The direct acting control valve 31b has a low operating response of the spool with respect to fluctuations in the pilot pressure by, for example, providing a throttle in the pilot oil passage in order to suppress the occurrence of the chattering phenomenon described above. Even if the pressure changes suddenly, it is configured so as to close gently.
[0025]
The hoisting cylinder electromagnetic check valve 35 is a two-port, two-position electromagnetic switching check valve, and, as schematically shown in FIG. 1, is a direct connection position 35b through which the bottom side oil passage 53 is communicated by excitation control of the solenoid 35a. And control which selectively switches to the non-return connection position 35c which blocks | prevents only the discharge | emission of the hydraulic oil from the bottom side oil chamber 6a is performed. The electromagnetic check valve 35 may have a configuration using electromagnetic force instead of the pilot hydraulic pressure of the conventional hydraulic pilot check valve 35 shown in FIG. The electromagnetic check valve 35 is pushed by the spring 35d when the solenoid 35a is not excited and is positioned at the check connection position 35c. When the solenoid check valve 35 is excited, the exciting force acts against the pressing force of the spring 35d. It is located at the direct connection position 35b. This excitation is performed by a control signal (current) sent from the undulation operation control unit 41 in the controller 40.
[0026]
Next, with reference to FIG. 4, the operation of the hydraulic cylinder operation control device 60 having the above-described configuration will be described by taking as an example the case where the boom 5 is operated to fall down. This figure shows changes over time in the lever operation (operation of the hoisting operation lever 10a), the on / off operation of the electromagnetic check valve 35, and the counter balance valve 31, and the open / close operation.
[0027]
When the operator tilts the hoisting operation lever 10a to the tilting operation side at time ta, a tilting operation signal is sent to the hoisting operation control unit 41 in the controller 40. Upon receiving the operation signal, the hoisting operation control unit 41 sends a control signal to the electromagnetic check valve 35 to excite the solenoid 35a to place the hoisting cylinder electromagnetic check valve 35 at the direct connection position 35b and open it. . At the same time, a control signal is sent to the hoisting cylinder control valve 22 to reduce the position (in FIG. 1, the spool is moved to the left to connect the pump port P to the port B and connect the port A to the tank port T. The hydraulic oil from the pump 21 is supplied to the rod-side oil chamber 6b to the rod-side oil chamber 6b of the hoisting cylinder 6 through the rod-side oil passage 52, and the control valve 22 in the bottom-side oil passage 53 is provided. The part connected to is connected to the tank T side.
[0028]
At this time, since the counter balance valve 31 closes the oil passages 53, the internal pressure of the rod-side oil passage 52 and the rod-side oil chamber 6b rises, and the rod-side holding pilot oil passage 31a extends from the rod-side oil passage 52. As a result, the pilot pressure introduced through the valve increases, and the direct acting control valve 31b constituting the counter balance valve 31 is opened. As a result, the hydraulic oil from the pump 21 flows into the rod side oil chamber 6b, the hydraulic oil in the bottom side oil chamber 6a is discharged to the tank 20, the hoisting cylinder 6 is contracted, and the boom 5 falls down. .
[0029]
Next, when the operator returns the tilt of the hoisting operation lever 10a to the neutral position at time tb, the hoisting operation control unit 41 sends a control signal to the hoisting cylinder control valve 22, and the spool of the hoisting cylinder control valve 22 is moved to the neutral position. To stop the supply of hydraulic oil. Then, the pressure in the rod side oil passage 52 is lowered, the pilot pressure acting on the counter balance valve 31 via the pilot oil passage 31a is also lowered, the direct acting control valve 31b is closed, and the boom 5 is moved down. Stops. However, as described above, in the counter balance valve 31, the direct acting control valve 31b is configured to respond gently to changes in the pilot pressure, and the direct acting control valve 31b is configured as shown in FIG. During the period from time tb to time tc, the boom 5 can be closed slowly and the boom 5 can be stopped without causing chattering or the like.
[0030]
In this way, the hoisting operation control unit 41 performs control to stop the supply of hydraulic oil by moving the hoisting cylinder control valve 22 to the neutral position when the hoisting operation lever 10a is returned to the neutral position. The valve 35 is controlled to be closed after a delay time T. This delay time T can be arbitrarily set in advance, and as shown in FIG. 4, the undulating cylinder electromagnetic check valve 35 is also closed at the time tc when the undulating cylinder counter balance valve 31 is completely closed. Has been.
[0031]
By setting the delay time T in this way, after the slow closing operation of the direct acting control valve 31b in the counter balance valve 31 is completed, the hoisting cylinder electromagnetic check valve 35 is closed, and chattering phenomenon, oil hammer phenomenon Thus, the stepping phenomenon or the like does not occur, and the boom 5 can be smoothly stopped from falling down.
[0032]
Further, according to the hydraulic cylinder operation control device 60 configured in this way, even if an operation failure occurs such that the spool remains in the open position due to dust or the like in the hoisting cylinder operation valve 22, Since the hoisting operation control unit 41 closes the electromagnetic check valve 35 as long as the hoisting operation lever 10a is in the neutral position, the boom 5 can be stopped and held.
[0033]
In the above description of the embodiment, the stop of the boom overturning motion at the aerial work vehicle 1 has been described. However, the oil control device of the present invention is not limited to the boom overturning motion, and the contraction of the telescopic cylinder 7 is reduced. A similar device can be applied to an oil passage that stops operation or stops operation of the outrigger cylinder 13.
[0034]
【The invention's effect】
As described above, according to the present invention, when the operating device is operated to operate the fluid pressure cylinder, the electromagnetic check valve is opened immediately, but when the operating device is operated to stop, there is a time delay. In this case, the electromagnetic check valve is closed so that the electromagnetic check valve is closed after the counter balance valve is closed. This fluid discharge oil passage is gently closed by the counter balance valve, and the occurrence of chattering phenomenon, oil hammer phenomenon and stepped operation phenomenon can be surely suppressed. Even when a malfunction occurs that causes the hydraulic cylinder control valve to open, the electromagnetic check valve is closed as long as the operating device is stopped. can do.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a cylinder operation control device according to the present invention.
FIG. 2 is a perspective view showing an aerial work vehicle to which a cylinder operation control device according to the present invention is applied.
FIG. 3 is a block diagram illustrating control of an actuator used in the aerial work vehicle.
FIG. 4 is a timing chart illustrating the operation of the cylinder operation control device according to the present invention.
FIG. 5 is a block diagram illustrating a conventional cylinder operation control device.
[Explanation of symbols]
6 Rolling cylinder (fluid pressure cylinder)
10a Hoisting control lever 31 Hoisting cylinder counter balance valve 35 Hoisting cylinder electromagnetic check valve 40 Controller 41 Hoisting operation control unit 52 Rod side oil passage (second passage)
53 Bottom side oil passage (first passage)
60 Hydraulic cylinder operation control device (Cylinder operation control device)

Claims (1)

A double-acting fluid pressure cylinder that expands and contracts by supplying and discharging working fluid;
A cylinder control valve that performs supply / discharge oil path switching control of the working fluid by moving the spool , and supply / discharge of the working fluid to and from the fluid pressure cylinder;
An operating device for sending an operation signal according to an external operation for controlling the operation of the fluid pressure cylinder;
A controller that controls the operation of the cylinder control valve in response to an operation of the operating device in response to the operation signal from the operating device;
Pressure in a second flow path that is disposed in a first flow path that connects one oil chamber of the fluid pressure cylinder and the cylinder control valve, and that connects the other oil chamber of the fluid pressure cylinder and the cylinder control valve. Counter balance valve that is opened and closed in response to
An electromagnetic check valve that is arranged in series downstream of the counter balance valve in the first flow path and is controlled to be opened and closed by the controller;
When the controller receives the operation signal from the operation device, the controller performs control to open the electromagnetic check valve, and when the operation signal from the operation device is stopped, the electromagnetic signal is delayed with a predetermined time. Cylinder operation control device that performs control to close the type check valve.

Images