JPH08277805A - Valve device and cylinder driving device using the same - Google Patents

Abstract

PURPOSE: To adjustably change pressure to optimize the pressure in a cylinder according to the use by providing a pressure applying means and pressure reducing means in a valve device. CONSTITUTION: When addition pressure acts on an addition pressure inlet 45a, a diaphragm 46 and movable body 39 are depressed to close an opening of a nozzle hole 43 with a flapper 44. Thus, a diaphragm 33 under the balanced condition is pushed downward by the back pressure in the nozzle hole 43 to open a communicating path 27 and supply compressed air to an output port 26. The compressed air acts to lift the diaphragm 33, resulting in setting the diaphragm 33 to the balanced condition with the back pressure of the nozzle hole 43 to the pressure of the addition pressure added to the set pressure and the pressure acting on the output port. Thus, the pressure in a cylinder 11 is held at the pressure of the addition pressure added to the set pressure. Also, when a subtraction pressure part acts on a subtraction pressure part, the pressure in the cylinder is the set pressure subtracted by the subtraction pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve device and a cylinder driving device for controlling the pressure in a cylinder.

[0002]

2. Description of the Related Art A lot of control machines for performing various controls using compressed air are provided in automobile production lines and the like. Such a control machine is provided with a cylinder and a cylinder drive device for driving the cylinder.

The cylinder is constructed so that a rod is slidably provided in a cylinder tube, and air pipes are connected to both the head side chamber and the rod side chamber of the cylinder tube. The cylinder driving device is composed of the circuit shown in FIG. The circuit is connected via a filter 1 to an air pipe connected to a factory air source (not shown), and an electromagnetic switching valve 3 is connected to the output side of the filter 1 via a regulator 2. The electromagnetic switching valve 3 is connected to the head side of the cylinder 4 via a check valve 5 and a flow rate control valve 6, respectively, and performs a port switching operation based on a command from the control unit 7 to prevent air from flowing into the cylinder 4. It is possible to supply and discharge.

[0004]

However, in the cylinder drive device having the above-mentioned structure, since the compressed air of a constant pressure is simply supplied to the cylinder, a constant thrust force is applied to the object. . Therefore, inconvenience may occur depending on the application.

For example, there is a case where a stationary object which is easily damaged is to be moved at a low speed or a constant speed. In this case, the object has the highest load when moving from the stationary state to the moving state,
The load is small in the moving state (see FIG. 6). This is because the frictional force between the object and, for example, the floor surface and the sliding resistance between the rod and the cylinder tube become maximum at the start of movement. Therefore, in order to move an object, it is necessary to first apply a pressure slightly higher than this in consideration of static friction force and the like. However, once the object starts to move, the load becomes small. Therefore, if the pressure at the start of movement continues to be applied to the cylinder even after the object starts moving (see FIG. 5), the object will be accelerated and the speed will be low or constant. Cannot be done (see FIG. 7).

The present invention has been made in view of the above circumstances, and an object thereof is to provide a valve device and a cylinder drive device capable of changing the pressure in the cylinder to an optimum state according to the application. And in addition,
Another object is to provide a cylinder drive device capable of moving an object at a low speed or at a constant speed.

[0007]

In order to achieve the above object, the valve device of the present invention is provided between a cylinder and a working fluid supply means for supplying a working fluid to the cylinder. In a valve device for controlling the internal pressure, a set pressure input section is provided, and the set pressure acting on this is compared with the pressure in the cylinder. If the set pressure is lower, the working fluid in the cylinder is discharged. A pressure control unit having a discharge operation unit and a supply operation unit for supplying the working fluid from the working fluid supply unit into the cylinder if the set pressure is higher, and an additional pressure input unit are provided and operate here. The pressurizing means for forcibly performing the supply operation in the supply operation unit until the added pressure and the pressure in the cylinder are balanced, and the subtraction pressure input unit are provided to balance the subtraction pressure acting on this and the pressure in the cylinder. Drain until Forced to perform discharge operation to the operation unit characterized in that it comprises a pressure reducing means (the invention of claim 1).

Further, the cylinder drive device of the present invention comprises a working fluid supply means for supplying a working fluid to the cylinder, and the cylinder fluid for displacing the rod in the cylinder by the working fluid to move the object. In the device,
The valve device is provided between the working fluid supply means and the cylinder, and the set pressure input part of the valve device has a set pressure for applying a set pressure for controlling the pressure in the cylinder to the set pressure input part. A supply means is connected to the addition pressure input section of the valve device, and an addition pressure supply means for applying an addition pressure for increasing the pressure in the cylinder to the addition pressure input section is connected to the addition pressure input section of the valve device. The section is characterized in that a subtraction pressure supply means for applying a subtraction pressure for reducing the pressure in the cylinder is connected to the subtraction pressure input section (the invention of claim 2).

The additional pressure acting on the additional pressure input portion is a pressure corresponding to the maximum load acting on the movement of the object, and acts on the additional pressure input portion when the object is stationary and on the subtraction pressure input portion. The pressure is a pressure for reducing the moving speed of the object, and may be applied to the subtraction pressure input section when the object moves (the invention of claim 3).

[0010]

According to the first and second aspects of the present invention, if the set pressure acting on the set pressure input portion is higher than the pressure in the cylinder, the working fluid is supplied into the cylinder to increase the pressure in the cylinder. To be If the set pressure acting on the set pressure input portion is lower than the pressure in the cylinder, the working fluid in the cylinder is discharged and the pressure is lowered. That is, the pressure in the cylinder is determined by the set pressure and is always equal to the set pressure.

On the other hand, when the additional pressure acts on the additional pressure input section, the working fluid is further supplied into the cylinder.
That is, the pressure in the cylinder is further increased by the added pressure to the pressure determined by the set pressure. When the subtraction pressure acts on the subtraction pressure input section, the working fluid in the cylinder is discharged. That is, the pressure in the cylinder is reduced by the subtracted pressure from the pressure determined by the set pressure.

According to the third aspect of the invention, the additional pressure corresponding to the load required to move the object acts on the additional pressure input section of the valve device until the object changes from the stationary state to the moving state. . That is, the pressure obtained by adding the additional pressure to the set pressure acts in the cylinder. As a result, high pressure can be applied only when the movement of the object starts,
Since there is no more pressure than necessary in the cylinder after the load is reduced, the object moves at a constant speed. Further, as the object starts to move, the subtraction pressure acts on the subtraction pressure input section of the valve device. That is, a pressure obtained by reducing the set pressure by the subtracted pressure acts on the cylinder. As a result, the moving speed of the object is reduced.

[0013]

As described above, according to the first and second aspects of the present invention, by providing the pressurizing means and the depressurizing means in the valve device, it is possible to increase and decrease the pressure. The pressure can be changed so as to be in an optimum state according to the application.

According to the third aspect of the present invention, the pressure in the cylinder can be increased only when the movement of the object is started, and the pressure in the cylinder can be reduced when the movement starts. Therefore, the pressure in the cylinder is moved. The effect is that it can be changed according to the load acting on the object, and the object can be moved at a low speed or at a constant speed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the cylinder drive device of the present invention will be described below with reference to FIGS. <Cylinder> First, as shown in FIG. 1, the cylinder 11 driven by the cylinder drive device of the present embodiment is constituted by a rod 13 slidably provided in a cylinder tube 12, and the cylinder tube Air inlets and outlets 12a and 12b are provided in both the head chamber side and the rod chamber side of the chamber 12.
Is provided. When compressed air is supplied to the air inlet / outlet 12a provided on the rod chamber side, the rod 13
Slides forward, and when compressed air is supplied to the air inlet / outlet 12b provided on the head chamber side, the rod 13 slides backward. Also, the cylinder 11
In front of, the limit switches 14 and 15 are installed at the front and rear positions corresponding to the moving area of the object, so that the switches 14 and 15 are turned on when the object moves to the front and rear positions. Has become.

<Operating Valve (Valve Device)> Next, an operating valve corresponding to the valve device of the present invention used in the cylinder drive device of the present embodiment will be described with reference to FIG. The operate valve 21 includes a box-shaped pressure control unit 22 formed substantially in the center, and
A cylindrical addition pressure supply unit 23 and a subtraction pressure supply unit 24 are coaxially connected to each other on the upper and lower sides thereof.

An input port 25 to which an input pressure supply device 62, which will be described later, is connected and an output port 26 which is connected to the cylinder 11 via an electromagnetic switching valve 73, which will be described later, face each other on the left and right side surfaces of the pressure control section 22. The input port 25 and the output port 26 are connected to each other via a communication path 27. An air supply valve 28 that can slide up and down is provided in the communication path 27, and the communication path 27 can be opened and closed by the air supply valve 28. The air supply valve 28 is constantly urged by the spring 31 to close the communication path 27.

Further, a through hole 28a is formed in the axial center of the air supply valve 28 so as to vertically penetrate therethrough.
Exhaust port 29 provided below the output port 2
6 is communicated with the through hole 28a. An exhaust valve 30 having a rod shape as a whole is inserted in the through hole 28a so as to be vertically slidable. Further, the exhaust valve 30 has a diameter larger than that of the upper portion of the through hole 28a, so that the through hole 28a can be opened and closed. When the exhaust valve 30 slides downward, the air supply valve 28 is pushed down to open the communication passage 27 while the through hole 28a is closed, and when the exhaust valve 30 slides upward, the air supply valve 28 is returned to the original state by the spring 31. Returning to the state, the communication path 27 is closed, but the through hole 28a is opened.

A first valve chamber 32 is formed above the exhaust valve 30, and the inside of the first valve chamber 32 is vertically divided by a diaphragm 33. The upper end of the exhaust valve 30 extends into the first valve chamber 32 and is connected to the center of the diaphragm 33. Therefore, when the diaphragm 33 is displaced up and down, the exhaust valve 30 slides up and down. The chamber below the first valve chamber 32 and the output port 26 are connected to the return passage 3
4, the pressure acting on the output port 26 acts on the diaphragm 33 via the return passage 34.

Further, a second valve chamber 35 is formed above the first valve chamber 32, and three diaphragms 36, 3 are formed.
7, 38 are arranged at predetermined intervals in the vertical direction, and the second valve chamber 35
The interior is divided into a total of 4 rooms, one above the other. The movable body 39 to which the diaphragms 36, 37 and 38 are attached is urged by springs 40 and 41 from both upper and lower sides,
It is always held in the second valve chamber 35 in a neutral state.
Further, the diaphragm 3 mounted in the second valve chamber 35
Of the 6, 37, 38, the set pressure supply chamber 4 formed by the upper diaphragm 36 and the central diaphragm 37.
2, a set pressure input port 42a to which a set pressure supply device 63 described later is connected is formed on the right side surface. Further, a nozzle hole 43 is formed from the upper part of the first valve chamber 32 to the lower part of the second valve chamber 35. The upper end of the nozzle hole 43 has a slightly large diameter, and can be opened and closed by a flapper 44. That is, when the set pressure acts on the set pressure input port 42a, the movable body 39 slides downward and pushes down the flapper 44, so that the nozzle hole 43 is closed by the flapper 44.

On the other hand, the added pressure supply unit 23 is provided with an added pressure supply chamber 45, and an added pressure input port 45a to which an added pressure supply device 64, which will be described later, is connected is formed on the upper surface thereof, and the inside is It is partitioned by the diaphragm 46. An operating rod 47 extending downward is attached to the diaphragm 46.
Are integrally connected, and the lower end portion of the operating rod 47 is connected to the movable body 39. That is, the additional pressure input port 45a
When the additional pressure acts on the diaphragm 46 and the diaphragm 46 is displaced downward, the movable body 39 slides downward.
Therefore, the movable body 39 is slid downward not only by the set pressure acting on the set pressure input port 42a but also by the added pressure acting on the added pressure input port 45a.

Further, the subtraction pressure supply section 24 is provided with a subtraction pressure supply chamber 48, and a subtraction pressure input port 48a to which a subtraction pressure supply device 65, which will be described later, is connected is formed on the lower surface thereof, and the inside thereof is It is partitioned by the diaphragm 49. The diaphragm 49 has an operating rod 50 extending upward.
Is connected to the lower end of the exhaust valve 30 through the through hole 28a. That is,
When the diaphragm 49 is displaced upward by the subtractive pressure acting on the subtractive pressure input port 48a, the exhaust valve 30 is pushed upward. Therefore, the subtraction pressure input port 48a
When a subtractive pressure acts on the output port 26, the output port 26 and the exhaust port 29 are communicated with each other.

<Cylinder Drive Unit> Next, the cylinder drive unit will be described with reference to FIG. The cylinder driving device is connected to an air pipe connected to a factory air source (not shown) via a filter 61, and the output side of the filter 61 is branched into four, and an input pressure supply device 62 is provided for each. The setting pressure supply device 63, the addition pressure supply device 64, and the subtraction pressure supply device 65 are connected.

The input pressure supply device 62 comprises a regulator 66 for outputting a constant pressure and is connected to the input port 25 of the operate valve 21. The set pressure supply device 63 includes a regulator 67 for outputting a predetermined pressure and a solenoid valve 68. The output port of the regulator 67 is connected to the set pressure input port 42a of the operate valve 21 via the solenoid valve 68. It is connected. That is, when the solenoid operates, a predetermined set pressure acts on the set pressure input port 42a of the operate valve 21.

The additional pressure supply device 64 includes a regulator 69.
And a solenoid valve 70. The regulator 69 outputs a constant pressure set according to the static frictional force of the object to be worked and the sliding resistance at the time of starting the rod 13 and the cylinder tube 12 in the cylinder 11. And regulator 6
The output port 9 is connected to the additional pressure input port 45 a of the operate valve 21 via the solenoid valve 70. That is, when the solenoid operates, the additional pressure according to the static friction force or the like acts on the additional pressure input port 45a of the operate valve 21.

The subtraction pressure supply device 65 is also the addition pressure supply device 6.
4, the regulator 71 and the solenoid valve 72 are provided. The regulator 71 outputs a constant pressure for reducing the moving speed of the object. The output port of the regulator 71 is connected to the subtraction pressure input port 48a of the operate valve 21 via the solenoid valve 72. That is, when the solenoid is operated, a predetermined subtraction pressure acts on the subtraction pressure input port 48a of the operating valve 21.

The relationship between the set pressure and the addition pressure and the subtraction pressure will be described. First, the target thrust force for moving the object at a low speed and a constant speed is determined from the load curve acting on the object in FIG. Is a pressure set higher than the target thrust (curve shown by line A in FIG. 3), and the added pressure is such that the value obtained by adding the added pressure to the set pressure is the thrust required to start the object. The pressure (curve shown by the line B in FIG. 3) is set only at the starting point of the object, and the subtraction pressure is the value obtained by subtracting the subtraction pressure from the set pressure and the thrust required to obtain the target speed. The pressure set to
Curve indicated by C line), which acts during movement of the object.

On the other hand, an electromagnetic switching valve 73 is connected to the output port of the operating valve 21, and one of the output ports is provided on the rod chamber side of the cylinder 11 via a check valve 74. Air door 12a
It is connected to the. The other output port is connected via a check valve 75 to an air inlet / outlet port 12b provided on the head chamber side of the cylinder 11. That is, normally, the output port of the operate valve 21 is connected to the air inlet / outlet port 12b provided on the rod chamber side of the cylinder 11, and when the solenoid is operated, the output port of the operate valve 21 is provided on the head chamber side of the cylinder 11. It is adapted to be connected to the air inlet / outlet port 12a. The flow control valve 7 is arranged in parallel with each check valve 74, 75.
6 and 77 are connected so that the back pressure in the cylinder 11 is adjusted.

<Operation of this Embodiment> Next, the operation of this embodiment will be described. First, the operation of the operate valve 21 will be described. When a predetermined set pressure acts on the set pressure input port 42a, the movable body 39 is pushed down together with the diaphragm 37. Then, since the nozzle hole 43 is closed by the flapper 44, the diaphragm 33 is pushed down by the back pressure from the nozzle hole 43. As a result, the exhaust valve 30 slides downward, the through hole 28a that connects the output port 26 and the exhaust port 29 is closed, and
The air supply valve 28 is pushed down so that the input port 25 and the output port 26 are communicated with each other via the communication path 27. Therefore, the compressed air supplied from the input pressure supply device 62 is supplied from the input port 25 to the output port 26, and the pressure in the cylinder 11 is increased.

On the other hand, the input port 25 to the output port 26
The compressed air supplied to the first valve chamber 32 is also supplied to the first valve chamber 32 through the return passage 34, and acts to push up the diaphragm 33. At this time, the pressure at the output port 26 (the cylinder 11
When the internal pressure) becomes high, the diaphragm 33 is pushed upward against the back pressure caused by closing the nozzle hole 43. As a result, the spring 31 pushes up the air supply valve 28 to close the communication path 27, the through hole 28a is opened, and the compressed air of the output port 26 is exhausted from the exhaust port 29, so that the pressure of the output port 26 (cylinder The pressure in 11) decreases. Therefore, the diaphragm 33
Is always balanced by the back pressure of the nozzle hole 43 and the pressure acting on the output port 26, and the pressure in the cylinder 11 is maintained at a pressure equal to the set pressure.

In the above state, the additional pressure is applied to the additional pressure input port 45a. Then, since the diaphragm 46 is pushed down and the movable body 39 is also pushed down, the opening of the nozzle hole 43 is closed by the flapper 44. As a result, the diaphragm 33 in the equilibrium state is replaced by the nozzle hole 4
It is pushed down by the back pressure of 3 to open the communication path 27 and supply compressed air to the output port 26. Then, similarly to the above, the compressed air acts to push up the diaphragm 33, and eventually the diaphragm 33 is driven by the back pressure of the nozzle hole 43 and the pressure acting on the output port 26 in that case with respect to the pressure obtained by adding the added pressure to the set pressure. Is in equilibrium. Therefore, the pressure in the cylinder 11 is maintained at the pressure obtained by adding the added pressure to the set pressure.

Further, in the above state where the set pressure is applied to the set pressure input port 42a, the subtraction pressure is applied to the subtraction pressure input port 48a. Then, the diaphragm 49 is pushed up and the exhaust valve 30 is pushed up, so that the through hole 28a is opened and the compressed air of the output port 26 is exhausted from the exhaust port 29. As a result, the pressure acting on the output port 26 becomes lower than the set pressure, and the diaphragm 33 is balanced by the back pressure of the nozzle hole 43 with respect to the set pressure and the pressure acting on the output port 26 in that case plus the subtractive pressure. To be in a state. Therefore, the pressure in the cylinder 11 is maintained at the pressure obtained by reducing the subtraction pressure from the set pressure.

Next, the operation of the cylinder drive device will be described with reference to FIG. First, solenoid valve 6
8, 70 and the solenoid in the electromagnetic switching valve 73 are operated. Then, the set pressure input port 4 of the operating valve 21
A predetermined set pressure acts on 2a (curve shown by line A in FIG. 3), and a load necessary to move the object (static friction force of the object and rod 1) is applied to the additional pressure input port 45a.
3 and a value considering the maximum sliding resistance force between the cylinder tube 12) (the curve indicated by the line B in FIG. 3). Therefore, the output port 2 of the operating valve 21
A pressure obtained by adding an additional pressure to the set pressure is output to 6, and compressed air is supplied to the air inlet / outlet 12a provided on the rod chamber side of the cylinder 11 via the electromagnetic switching valve 73.

Then, the rod 13 is pushed forward and the object starts to move. When the limit switch 14 is turned off, the solenoid of the solenoid valve 70 is turned off and the solenoid valve 72
The solenoid of is activated. As a result, the additional pressure input port 4
The added pressure acting on 5a decreases and the subtracted pressure begins to act on the subtracted pressure input port 48a (curve shown by line C in FIG. 3). Therefore, the output port 2 of the operating valve 21
A pressure obtained by reducing the subtraction pressure from the set pressure is output to 6, and the object moves at a low speed. Then, when the limit switch 15 is turned on, the solenoids in the solenoid valves 68 and 72 are turned off and the object stops. The curve indicated by the D line in FIG. 3 is the thrust of the rod 13 that actually acts on the object, and this is almost the same as the target thrust for obtaining a low speed and a constant speed. In addition, E in FIG.
The curve indicated by the line is a value obtained by adding the set pressure (the curve indicated by the line A) and the added pressure (the curve indicated by the line B) in the figure, and the curve indicated by the line F in the figure indicates the back pressure from the cylinder 11. Show.

In order to move the object in the opposite direction to the above, the solenoid in the electromagnetic switching valve 73 is turned off, and compressed air is supplied to the air inlet / outlet port 12b provided on the head chamber side of the cylinder 11 by the same procedure as above. Just supply it.

As described above, according to this embodiment, the pressure in the cylinder 11 can be increased only when the movement of the object is started, and the pressure in the cylinder 11 can be reduced when the movement is started. The internal pressure changes according to the load applied to the object, and the low speed or constant speed can be obtained. Also, depending on the application
In advance, the switching timing of each solenoid valve etc. and the added pressure,
By setting the subtraction pressure or the like, the pressure in the cylinder 11 can be changed so as to be in an optimum state according to the application, and thus the rod 13 can be moved in a predetermined manner according to the application.

The present invention is not limited to the above embodiments, but can be modified and implemented as follows, for example, and these embodiments also belong to the technical scope of the present invention. (1) In the above embodiment, the subtraction pressure acting on the subtraction pressure input port 48a is for decelerating the moving speed of the object and is a constant pressure. However, by providing a flow control valve or the like,
It may be variable. Thereby, the moving speed of the object can be changed according to the application. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an entire embodiment.

FIG. 2 is a cross-sectional view showing a valve device.

FIG. 3 is a graph showing changes in pressure in each element.

FIG. 4 is a circuit diagram showing a conventional cylinder drive device.

FIG. 5 is a graph showing a conventional pressure change in a cylinder.

FIG. 6 is a graph showing changes in the load applied to a conventional object.

FIG. 7 is a graph showing a change in speed of an object in the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Cylinder 21 ... Operate valve (valve device) 22 ... Pressure control part (pressure control means) 23 ... Addition pressure supply part (pressurization means) 24 ... Subtraction pressure supply part (pressure reduction means) 28 ... Air supply valve (supply operation) 30) Exhaust valve (discharging operation part) 42a ... Set pressure input port (set pressure input part) 45a ... Addition pressure input port (addition pressure input part) 48a ... Subtraction pressure input port (subtraction pressure input part) 62 ... Input Pressure supply device (compressed air supply means) 63 ... Set pressure supply device (set pressure supply means) 64 ... Addition pressure supply device (addition pressure supply means) 65 ... Subtraction pressure supply device (subtraction pressure supply means)

Claims (3)

[Claims] 1. A cylinder provided between a cylinder and a working fluid supply means for supplying a working fluid to the cylinder,
In the valve device for controlling the pressure in the cylinder, a set pressure input unit is provided, and the set pressure acting on this is compared with the pressure in the cylinder. If the set pressure is lower, the operation in the cylinder is performed. Pressure control means having a discharge operation part for discharging the working fluid, and a supply operation part for supplying the working fluid from the working fluid supply means into the cylinder if the set pressure is higher, and an additional pressure input And a subtraction pressure input section for operating the supply operation section forcibly performing the supply operation until the added pressure acting on the section and the pressure in the cylinder are balanced. A valve device comprising: a depressurizing unit for forcibly performing the discharging operation of the discharging operation unit until the subtraction pressure and the pressure in the cylinder are balanced. 2. A cylinder drive device comprising a working fluid supply means for supplying a working fluid to a cylinder, wherein the working fluid displaces a rod in the cylinder to move an object. A valve device is provided between the supply means and the cylinder, and the set pressure input part of the valve device supplies a set pressure for controlling the pressure in the cylinder to the set pressure input part. Means is connected to the additional pressure input section of the valve device, and an additional pressure supply means for applying an additional pressure for pressurizing the pressure in the cylinder to the additional pressure input section is connected to the additional pressure input section of the valve device. The pressure input unit is connected to a subtraction pressure supply unit that applies a subtraction pressure for reducing the pressure in the cylinder to the subtraction pressure input unit, and the valve device includes: A pressure input unit is provided, and a set pressure acting on the pressure input unit is compared with a pressure in the cylinder. If the set pressure is lower, a discharge operation unit for discharging the working fluid in the cylinder; and the set pressure. Is higher, pressure control means having a supply operation part for supplying the working fluid from the working fluid supply means into the cylinder, and an additional pressure input part are provided, and the additional pressure acting on the cylinder and the cylinder Until the pressure in the cylinder balances, the pressurizing means for forcibly performing the supply operation in the supply operation unit and the subtraction pressure input unit are provided, and until the subtraction pressure acting on this and the pressure in the cylinder balance. A cylinder drive device, comprising: a depressurizing unit forcibly causing the discharging operation unit to perform a discharging operation. 3. The added pressure acting on the added pressure input section is a pressure according to the maximum load acting when the object moves, and acts on the added pressure input section when the object is stationary and the subtracted pressure The cylinder drive device according to claim 2, wherein the subtraction pressure acting on the input unit is a pressure for reducing the moving speed of the object, and acts on the subtraction pressure input unit when the object moves.