JPH09303307A - Control device of hydraulic cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of a hydraulic cylinder capable of drive- control of a working part of the hydraulic cylinder in the arbitrary axial direction with excellent accuracy with simple constitution. SOLUTION: Individual solenoid valves 11, 12 are arranged to forward and rear cylinder chambers 7, 8 of a pneumatic cylinder 1, and the pumping volume of the compressed air to the cylinder chambers 7, 8 is individually controlled. The solenoid valves 11, 12 are drive-controlled while the axial direction of a piston rod 3 is detected, and the pneumatic pressure of the cylinder chambers 7, 8 is also controlled with the original pressure of a pneumatic pressure supply source 10 as a control parameter, and the speed when the piston rod 3 is advanced/retracted and the stop position can be precisely controlled with excellent accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a fluid pressure cylinder, and more specifically, it detects the position of a piston of a fluid pressure cylinder and determines the piston rod or slider, which is the operating portion, in an arbitrary axial direction. The present invention relates to a control technique for controlling driving to a position.

[0002]

2. Description of the Related Art A fluid pressure cylinder device is widely used in all industrial fields by taking advantage of the characteristics of fluid pressure of its working fluid. For example, a general structure of a pneumatic cylinder device is that the supply / exhaust amount of compressed air to / from the front and rear cylinder chambers of the pneumatic cylinder is controlled by the switching operation of a directional control valve arranged in the pneumatic circuit, which causes the piston rod to project and retract. It is configured to enter and make a linear reciprocating motion.

[0003]

By the way, in the conventional pneumatic cylinder device, since the amount of compressed air supplied to and exhausted from the front and rear cylinder chambers is controlled by a single directional control valve, the linear reciprocation is performed. The motion is limited to a simple linear motion in which the piston rod projects or retracts over the entire working stroke, that is, when it stops at the stroke end of the working stroke, and the piston rod moves at any point in the working stroke. It was not possible to stop at the intermediate position in the axial direction.

This is largely due to the characteristics of the compressed air which is the working fluid, that is, since the air has the properties of compression and expansion, there is unevenness in the projecting / retracting movement of the piston rod, and the precise This is because speed control is difficult and precise positioning is difficult.

Therefore, when it is desired to stop the piston rod at the axial intermediate position of the entire working stroke in the target equipment, a plurality of pneumatic cylinders having the above-mentioned configuration are combined in series to each pneumatic cylinder. The operation stroke of each pneumatic cylinder is set to the above-mentioned total stroke, so that the stroke end of the working stroke of each pneumatic cylinder is set to the intermediate position in the axial direction, in other words, the intermediate position in the axial direction to be stopped. The method of combining the same number of pneumatic cylinders was adopted.

However, with such a configuration, there is a problem in that the apparatus as a whole becomes complicated and large, and the apparatus cost increases significantly.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to make a working portion of a fluid pressure cylinder highly accurate in an arbitrary axial direction with a small size, a light weight and a simple structure. It is an object of the present invention to provide a control device that can drive and control a position.

[0008]

In order to achieve the above object, a control device for a fluid pressure cylinder according to the present invention comprises a first solenoid valve for controlling a flow of a working fluid to a rear cylinder chamber of the fluid pressure cylinder, A second solenoid valve for controlling the flow of the working fluid to the front cylinder chamber of the fluid pressure cylinder;
A position detection sensor that detects the axial position of the working portion of the fluid pressure cylinder, a first fluid pressure detection sensor that detects the fluid pressure in the rear cylinder chamber of the fluid pressure cylinder, and a front cylinder of the fluid pressure cylinder. A second fluid pressure detection sensor for detecting the fluid pressure in the room, a source pressure detection sensor for detecting the fluid pressure of the fluid pressure supply source, the position detection sensor, the first and second fluid pressure detection sensors, and the above It is characterized by comprising a control unit for driving and controlling the first and second electromagnetic valves according to a detection signal from the source pressure detection sensor.

In a preferred embodiment, the control section is
The first and second solenoid valves are drive-controlled while adjusting the fluid pressures in the front and rear cylinder chambers of the fluid pressure cylinder in accordance with the magnitude and fluctuation of the fluid pressure of the fluid pressure supply source. It is configured to control the advancing / retreating speed and the axial position of the actuator.

In the control device of the present invention, separate and independent solenoid valves are respectively arranged for the rear cylinder chamber and the front cylinder chamber of the fluid pressure cylinder, so that the amount of compressed air supplied to and exhausted from the front and rear cylinder chambers can be increased and decreased. Since it is configured to be controlled individually, it is possible to adjust the fluid pressures in the front and rear cylinder chambers by drivingly controlling the solenoid valve while detecting the axial position of the working portion of the fluid pressure cylinder, for example, the piston rod. Thus, the piston rod is drive-controlled to an arbitrary axial position.

In this case, since the fluid pressures of the front and rear cylinder chambers are controlled and this control is performed according to the detection result of the fluid pressure of the fluid pressure supply source, that is, the original pressure, when the fluid pressure cylinder device is installed. The initial setting of the controller in
The number of control parameters to be input is small and it is simple and easy, and the specifications of the fluid pressure cylinder to be applied are not limited. In addition, it is possible to control the fluid pressure in the cylinder chamber that is suitable for the magnitude (capacity) of the source pressure, and the piston rod drive control can be performed with high accuracy without causing an error in spite of fluctuations in the source pressure. Done.

That is, the above pneumatic cylinder device is so-called electro-pneumatic control in which the control of the pneumatic circuit thereof is processed by an electric signal. The control of was only to control the flow rate.
Therefore, at the time of initial setting of the control device at the time of installation of the pneumatic cylinder device, in order to allow the projecting and retracting operation of the piston rod to be performed smoothly and stably,
It is necessary to input and set a large number of various control parameters such as the load to be operated, the air pressure (source pressure) of the air pressure supply source, the inner diameter and length of the cylinder tube, etc. Many were complicated and took a long time.

Not only that, even if the initial setting is perfectly performed in this way, in the conventional method of simply controlling the flow rate of the compressed air, if the source pressure fluctuates, the movement of the piston rod becomes extremely large. It became an unstable state, and an error was likely to occur in its drive control, and precise and high-precision control could not be performed.

On the other hand, as in the present invention, the control of the supply / exhaust amount for both the front and rear cylinder chambers is performed by detecting the original pressure in addition to the fluid pressures in the front and rear cylinder chambers. The control parameters to be input at the time of initial setting need only be the minimum necessary basic parameters, and the control device itself then performs control while detecting the fluid pressure and the original pressure during actual operation. Therefore, the above-mentioned initial setting is easy with few control parameters to be input, and in spite of the fluctuation of the original pressure, the projecting and retracting operation of the piston rod is smoothly and stably performed, and an error is hard to occur.

[0015]

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

FIG. 1 shows a fluid pressure cylinder device according to the present invention. Specifically, this fluid pressure cylinder device is a pneumatic cylinder device utilizing air pressure as fluid pressure, and is of a double-acting rod type which is an actuator. Pneumatic cylinder 1 and control device 2 that drives and controls this pneumatic cylinder 1.
Is provided as a main part, and the piston rod 3, which is the operating part of the pneumatic cylinder 1, is driven and controlled to an arbitrary axial position.

Since the basic structure of the pneumatic cylinder 1 is well known in the art, a detailed description thereof will be omitted. However, due to the relationship with the position detection sensor 13 of the control device 2 described later, the cylinder tube 4 is made of aluminum alloy or the like. The piston 5 is made of a magnetic material while being made of a non-magnetic material such as brass. As a concrete structure of the piston 5, a permanent magnet 6 is integrally incorporated in the non-magnetic piston 5 as shown in the figure, or the piston 5 itself is formed of a permanent magnet.

Further, the inside of the cylinder tube 4 is divided into a rear cylinder chamber 7 and a front cylinder chamber 8 by a piston 5, and these cylinder chambers 7 and 8 are respectively connected via supply / discharge ports 7a and 8a. It is connected to the pneumatic circuit 9.

The air pressure circuit 9 supplies an air pressure supply source 10 as a fluid pressure supply source for sucking atmospheric air to produce compressed air, and the compressed air supplied from the air pressure supply source 10 to the pneumatic cylinder 1. The first and second solenoid valves 11 and 12 are configured as main parts. The specific structure of the air pressure supply source 10 is well known in the art, and includes an air compressor, a cooler, an air tank, and the like.

The control device 2 includes a position detection sensor 13 for detecting the axial positions of the first and second solenoid valves 11 and 12 provided in the pneumatic circuit 9 and the piston rod 3,
The first and second air pressure detection sensors 14 and 15 that detect the air pressure in the cylinder chambers 7 and 8, the source pressure detection sensor 16 that detects the air pressure of the air pressure supply source 10, the controller 17 as a control unit, and the like. It is composed as the main part.

The first and second solenoid valves 11 and 12 control the flow of compressed air to both cylinder chambers 7 and 8 of the pneumatic cylinder 1, and are electrically connected to the controller 17. In the illustrated example, pilot type three-position solenoid valves are used as these solenoid valves 11 and 12.

Although the specific structure of the solenoid valves 11 and 12 is not shown, it is composed of, for example, two pilot valves (solenoid valves) and a main valve, and the main valve is switched by the ON / OFF control of the pilot valve. Is configured. The main valve switching position is a supply position where the cylinder chambers 7 and 8 of the pneumatic cylinder 1 communicate with the pneumatic supply source 10, and
There are three positions, a closed position that blocks communication with the cylinder chambers 7 and 8 and a discharge position that communicates the cylinder chambers 7 and 8 with a discharge port 19. Although not shown, the two solenoid valves 11 and 12 have an integrated one-block structure in order to make the structure compact and simple, but of course, separate structures may be used.

The position detection sensor 13 is the pneumatic cylinder 1
Is for detecting the axial position of the piston rod 3, and specifically, the permanent magnet 6 provided in the piston 5 described above.
A magnetostrictive linear displacement sensor for detecting the axial position of the is used.

The magnetostrictive linear displacement sensor 13 has a linear probe 13a as its detecting portion and is electrically connected to the controller 17 via a gate array 25. The probe 13a is a linear rod having a magnetostrictive wire made of a ferromagnetic material as a constituent element, and is attached to the outer periphery of the cylinder tube 4 of the pneumatic cylinder 1 so as to extend in the axial direction and the axial position of the permanent magnet 6. Is detected and the detected signal is electrically processed by the gate array 25 and then sent to the controller 17.

The basic operating principle of the magnetostrictive linear displacement sensor 13 will be described below with reference to FIG. First, when a current pulse in the direction of arrow A is applied to the magnetostrictive line of the probe 13a from the starting end side thereof, a magnetic field in the circumferential direction as shown in the figure is generated on this magnetostrictive line. On the other hand, the permanent magnet 6 of the piston 5 is arranged with respect to the magnetostrictive line as shown in the drawing, and an axial magnetic field as shown in the drawing is applied to the portion of the permanent magnet 6. When the permanent magnet 6 approaches the magnetostrictive line, an oblique magnetic field as shown by a dotted line is generated in the axial magnetic field, and for this reason, the permanent magnet 6 on the magnetostrictive line.
Torsional strain occurs at the position of (the phenomenon of Wiedemann
Effect). Since this torsional strain is a kind of ultrasonic vibration, it propagates on the magnetostrictive line which is a metal at the speed of sound, and by measuring the propagation time from the position of the permanent magnet 6 of this ultrasonic wave to the beginning of the magnetostrictive line, The axial position of the piston 5 is detected.

First and second air pressure detection sensors 14,
Reference numeral 15 is for detecting the air pressure in the front and rear cylinder chambers 7 and 8 of the pneumatic cylinder 1, and specifically, the first and second cylinder chambers.
It is incorporated into the solenoid valves 11 and 12 and is electrically connected to the controller 17. The first and second air pressure detection sensors 14 and 15 detect the air pressures flowing through the first and second electromagnetic valves 11 and 12, and indirectly detect the air pressures in the cylinder chambers 7 and 8 from the air pressures. It is configured to detect, and the detection signal is sent to the controller 17.

The source pressure detection sensor 16 is the air pressure supply source 10.
The air pressure is detected, and specifically, it is arranged at the supply port of the air pressure supply source 10, for example, at the air supply port portion of the air tank, and is electrically connected to the controller 17. The source pressure detection sensor 16 detects the air pressure of the compressed air accumulated in the air tank, and the detection signal is sent to the controller 17.

The controller 17 drives and controls the first and second solenoid valves 11 and 12 in conjunction with each other.
Specifically, it is a controller composed of a microcomputer including a CPU, a ROM, a RAM and an I / O port. As described above, the controller 17 includes the position detection sensor 13, the air pressure detection sensor 14, and the position detection sensor 13 in addition to the first and second solenoid valves 11 and 12.
15 and the source pressure detection sensor 16 are electrically connected.

In the illustrated embodiment, the arithmetic processing unit (CPU) 17a of the controller 17 digitally processes the detection signal of the position detection sensor 13 processed by the gate array 25 and the A / D conversion unit 17b. The detection signals from the air pressure detection sensors 14 and 15 and the original pressure detection sensor 16 are input.

Then, the arithmetic processing unit 17a performs arithmetic processing based on the arithmetic expression of the arithmetic expression setting unit 17c for each of the detection signals according to the control program stored in the memory, and at the same time, the arithmetic result, that is, the actual result. A control signal is output through the output units 17e and 17f so as to match the actual value with the target value by performing a comparison operation between the target value and the target value preset by the target value setting unit 17d. To the solenoid valves 11 and 12.

That is, the controller 17 controls the air pressure in both the front and rear cylinder chambers 7, 8 of the pneumatic cylinder 1 in accordance with the magnitude and fluctuation of the air pressure (source pressure) of the air pressure supply source 10 while controlling the piston rod 3 The first and second solenoid valves 11 and 12 are drive-controlled so as to control the forward / backward speed and the axial position.

In this case, the first and second solenoid valves 11,
The air pressure in both the front and rear cylinder chambers 7 and 8 of the pneumatic cylinder 1 is adjusted by repeatedly performing ON-OFF control of 12. In other words, the air pressure in the front and rear cylinder chambers 7 and 8 is adjusted by controlling the solenoid valves 11 and 12 to open and close with a proper pulse width or cycle (fully open or fully closed), that is, by controlling the pulse width. The compressed air is intermittently supplied to and exhausted from the cylinder chambers 7 and 8. With such a configuration, the response speed of the pneumatic cylinder 1 to the control signal from the control device 2 is fast, and accurate drive control without delay is secured.

In the pneumatic cylinder device configured as described above, the compressed air from the pneumatic pressure supply source 10 is transferred to the front and rear cylinders of the pneumatic cylinder 1 by the first and second solenoid valves 11 and 12 of the control device 2. The piston rod 3 is moved forward / backward along a preset speed path (acceleration → constant speed → deceleration), and is stopped at an arbitrary axial position, by supplying / exhausting air to / from the chambers 7 and 8 as appropriate.

In this case, separate and independent solenoid valves 11 and 12 are provided for the front and rear cylinder chambers 7 and 8 of the pneumatic cylinder 1, respectively, so that the supply and exhaust amounts of compressed air to and from the front and rear cylinder chambers 7 and 8 are increased. Since it is configured to be controlled individually, while detecting the axial position of the piston rod 3,
By controlling the solenoid valves 11 and 12 by driving to adjust the air pressures in the front and rear cylinder chambers 7 and 8, the speed control and stop position control of the piston rod 3 at the time of advancing and retreating can be performed with high accuracy and precision. You can

Further, when adjusting the air pressures of the front and rear cylinder chambers 7 and 8, the fluid pressure of the air pressure supply source 10, that is, the original pressure is also detected as a control parameter, so that the control device 2 when the pneumatic cylinder device is installed is used. The initial setting is
The number of control parameters to be input is small and easy, and the specifications of the pneumatic cylinder 1 to be applied are not limited. Further, it is possible to control the air pressure in the cylinder chambers 7 and 8 suitable for the magnitude (capacity) of the source pressure, and the drive control of the piston rod 3 is high without causing an error despite the variation of the source pressure. It is done with precision and precision.

That is, the pneumatic cylinder device is so-called electro-pneumatic control in which the control of the pneumatic circuit 9 is processed by an electric signal. In the conventional pneumatic cylinder device of the same type, the cylinder chambers for the front and rear of the pneumatic cylinder are provided. The control of the supply / exhaust amount was merely to control the flow rate. Therefore, at the time of initial setting of the control device at the time of installation of the pneumatic cylinder, in order to allow the projecting and retracting operation of the piston rod to be performed smoothly and stably, the load to be operated and the air pressure of the air pressure supply source ( It is necessary to input and set a large number of various control parameters such as the magnitude of the original pressure), the inner diameter and the length of the cylinder tube, and the initial setting work requires a lot of man-hours and requires a long time.

Not only that, even if the initial setting is perfected as described above, in the method of simply controlling the flow rate of the compressed air, if the source pressure fluctuates, the movement of the piston rod becomes extremely unsatisfactory. In a stable state, an error occurred in the drive control, and high precision control could not be performed.

On the other hand, in the above-described embodiment of the present invention, the supply / exhaust amounts of the front and rear cylinder chambers 7, 8 are controlled by detecting the air pressure and the original pressure of the front and rear cylinder chambers 7, 8. With the configuration, the control parameters to be input at the time of the initial setting need only be basic, and the control device 2 itself performs control while detecting the air pressure and the original pressure during the actual operation, that is, the original The ON-OFF time of the first and second solenoid valves 11 and 12 is controlled according to the pressure. Therefore, the above-mentioned initial setting is easy because there are few control parameters to be input, and in spite of the fluctuation of the source pressure, the projecting / withdrawing operation of the piston rod 3 is smoothly and stably performed, and an error is hard to occur. Accurate and precise control can be performed with high accuracy.

The above-described embodiment merely shows a preferred specific example of the present invention, and the present invention is not limited to this, and the design can be appropriately changed within the range.

For example, the pneumatic cylinder 1 as an actuator is not limited to the illustrated embodiment, and conventional pneumatic cylinders of various specifications and types (rod type, rodless type) can be used as appropriate.

Further, the solenoid valve 1 in the illustrated embodiment
Pilot type 3-position solenoid valves are used as 1 and 12, but similar functions (supply of air to cylinder chambers 7 and 8,
The structure is not limited to the illustrated structure as long as it has a communication block, an exhaust gas, etc., and the target pneumatic cylinder 1
The design can be changed as appropriate according to the specifications and uses.

Further, in the illustrated embodiment, the air pressure detection sensor 14 is used for the purpose of making the control device 2 as a unit structure independent of the air pressure cylinder 1 and widely applicable to air pressure cylinders of all kinds and sizes. ，
15 detects the air pressure flowing through the solenoid valves 11 and 12,
The air pressure in the front and rear cylinder chambers 7 and 8 of the pneumatic cylinder 1 is indirectly detected, but of course, the air pressure in the front and rear cylinder chambers 7 and 8 is directly detected to achieve higher accuracy. It is also possible to ensure control.

Further, the position detecting sensor 13 may be any other type of sensor as long as it has the same function as the magnetostrictive position detecting sensor shown in the figure.
As an example, a magnetoresistive element such as a Hall element or an MR element may be used as the probe 13a of the magnetostrictive linear displacement sensor 13 described above.
Similarly to the above, it is possible to adopt a configuration in which a large number of linearly and continuously arranged in the axial direction on the outer circumference of the cylinder tube 4 of the pneumatic cylinder 1 to detect the axial position of the permanent magnet 6 of the piston 5.

The pneumatic cylinder device according to the present invention is used not only for its original purpose of utilizing the forward / backward movement of the piston rod 3 of the pneumatic cylinder 1, but also for detecting the air pressure in the front and rear cylinder chambers 7, 8 of the pneumatic cylinder 1. Since the control method is adopted, as an example, application as a pressure adjusting device as shown in FIG. 3 is also possible.

That is, this pressure adjusting device is provided with the roll 5
It is a tension controller for adjusting the tension applied to the cloth body 51 when the cloth body 51 having a wider width than 0 is wound or pulled out. This tension controller is
A configuration in which two pneumatic cylinder devices are combined, and bearings 52 and 53 that support the spindle 50a of the roll 50 are respectively supported by the piston rods 3 of the pneumatic cylinders 1a and 1b with a predetermined pressing force. It is said that.

As a result of the tension acting on the cloth 51 being different in the width direction, the both ends of the support shaft 50a of the roll 50 are deviated, and the air pressures in the cylinder chambers 7, 8 of the pneumatic cylinders 1a, 1b are balanced. When the relative deviation of the piston rods is relatively lost, the projecting and retracting amounts of the piston rods 3, 3 are adjusted so as to restore this balance, and the bias of the tension is corrected.

Further, the fluid pressure cylinder as the actuator is not particularly limited, and the present invention can be applied to not only the pneumatic cylinder 1 as in the illustrated embodiment but also a hydraulic cylinder using hydraulic pressure as a working fluid.

[0048]

As described in detail above, according to the present invention,
Separate and independent solenoid valves are provided for the rear cylinder chamber and the front cylinder chamber of the fluid pressure cylinder, respectively, so that the amount of compressed air supplied to and discharged from the front and rear cylinder chambers is individually controlled. It is possible to perform speed control and stop position control at the time of advancing and retreating an operating part such as a piston rod with high accuracy and precision.

When controlling the fluid pressure in both the front and rear cylinder chambers, the fluid pressure of the fluid pressure supply source, that is, the original pressure is also detected as a control parameter. The initial setting of the device is easy with few control parameters to be input, and is not limited by the specifications of the fluid pressure cylinder to be applied, and is highly versatile.

Further, by detecting the source pressure of the fluid pressure supply source as a control parameter, the magnitude (capacity) of the source pressure can be obtained.
It is possible to control the fluid pressure in the cylinder chamber suitable for the above, and despite the fluctuation of the original pressure, the drive control of the piston rod does not cause an error, and in combination with the above effect, more precise control is possible. It will be possible.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing an overall configuration of a pneumatic cylinder device according to the present invention.

FIG. 2 is a perspective view for explaining an operating principle of a magnetostrictive linear displacement sensor of a control device in the pneumatic cylinder device.

FIG. 3 is a schematic plan view showing an application example of the pneumatic cylinder device.

[Explanation of symbols]

1 Pneumatic Cylinder (Fluid Cylinder) 2 Control Device 3 Piston Rod (Operating Part) 4 Cylinder Tube 5 Piston 6 Permanent Magnet 7 Rear Cylinder Chamber 8 Front Cylinder Chamber 9 Pneumatic Circuit 10 Air Pressure Supply Source (Operating Pressure Supply Source) 11, 12 Solenoid valve 13 Magnetostrictive linear displacement sensor (position detection sensor) 14, 15 Air pressure detection sensor (fluid pressure detection sensor) 16 Source pressure detection sensor 17 Controller (control unit)

Claims (7)

[Claims] 1. A device for driving and controlling an operating portion of a fluid pressure cylinder to an arbitrary axial position, the first solenoid valve controlling a flow of a working fluid to a rear cylinder chamber of the fluid pressure cylinder, A second solenoid valve for controlling the flow of the working fluid to the front cylinder chamber of the fluid pressure cylinder, a position detection sensor for detecting the axial position of the working portion, and a fluid pressure in the rear cylinder chamber of the fluid pressure cylinder. A first fluid pressure detection sensor, a second fluid pressure detection sensor that detects a fluid pressure in the front cylinder chamber of the fluid pressure cylinder, and a source pressure detection sensor that detects a fluid pressure of a fluid pressure supply source. A position detection sensor, the first and second fluid pressure detection sensors, and a control unit that drives and controls the first and second solenoid valves according to detection signals from the source pressure detection sensor. Control device for a fluid pressure cylinder, characterized by comprising Te. 2. The first and second control units adjust the fluid pressures in the front and rear cylinder chambers of the fluid pressure cylinder in accordance with the magnitude and fluctuation of the fluid pressure of the fluid pressure supply source. The control device for the fluid pressure cylinder according to claim 1, wherein the solenoid valve is driven and controlled to control the advancing / retreating speed and the axial position of the actuating portion. 3. The control unit is configured to adjust the fluid pressure in both front and rear cylinder chambers of the fluid pressure cylinder by repeatedly performing ON-OFF control of the first and second solenoid valves. The control device for a fluid pressure cylinder according to claim 1 or 2, wherein: 4. The control unit is configured to control the ON-OFF time of the first and second solenoid valves according to the magnitude and fluctuation of the fluid pressure of the fluid pressure supply source. The control device for the fluid pressure cylinder according to claim 3, wherein: 5. The first and second solenoid valves are closed so as to block communication between a supply position for communicating the cylinder chamber of the fluid pressure cylinder with the fluid pressure supply source and communication with the cylinder chamber of the fluid pressure cylinder. 5. A pilot-type three-position solenoid valve that switches between three positions, a position and a discharge position where the cylinder chamber of the fluid pressure cylinder communicates with a discharge port, and is a pilot-type three-position solenoid valve. A control device for the fluid pressure cylinder described. 6. The position detection sensor is a magnetostrictive linear displacement sensor that detects an axial position of a permanent magnet provided on a piston of the fluid pressure cylinder, and a probe of the magnetostrictive linear displacement sensor is the fluid displacement sensor. The control device for the fluid pressure cylinder according to claim 1, wherein the control device is attached to the outer circumference of the cylinder tube of the pressure cylinder so as to extend in the axial direction. 7. The first and second fluid pressure detection sensors indirectly detect the fluid pressures in the front and rear cylinder chambers of the fluid pressure cylinder from the fluid pressures flowing in the first and second solenoid valves, respectively. The control device for a fluid pressure cylinder according to claim 1, wherein the control device is configured to: