阅读说明：本技术 流体压力执行器的动作量检测装置 (Device for detecting amount of movement of fluid pressure actuator ) 是由 近藤健元 于 2019-12-18 设计创作，主要内容包括：本公开涉及一种流体压力执行器的动作量检测装置。本发明的流体压力执行器的动作量检测装置检测流体压力执行器的活塞的位置,所述流体压力执行器具有内部被活塞划分为第一压力作用室和第二压力作用室的双作用缸,该流体压力执行器的动作量检测装置具有：第一压力变换器,其检测第一压力作用室的压力值；第二压力变换器,其检测第二压力作用室的压力值；以及控制部,其具有根据第一压力变换器或第二压力变换器检测到的压力值来算出活塞的移动量的活塞位置检测程序。该流体压力执行器的动作量检测装置不会制约流体压力执行器的形状、可以提高设备设计的自由度而且价格低廉。(The present disclosure relates to an operation amount detection device for a fluid pressure actuator. A motion amount detection device of a fluid pressure actuator according to the present invention detects a position of a piston of the fluid pressure actuator having a double acting cylinder whose interior is divided into a first pressure acting chamber and a second pressure acting chamber by the piston, the motion amount detection device of the fluid pressure actuator comprising: a first pressure transducer that detects a pressure value of the first pressure acting chamber; a second pressure transducer that detects a pressure value of the second pressure acting chamber; and a control unit having a piston position detection program for calculating the amount of movement of the piston from the pressure value detected by the first pressure transducer or the second pressure transducer. The device for detecting the amount of motion of a fluid pressure actuator does not restrict the shape of the fluid pressure actuator, can improve the degree of freedom in designing the device, and is inexpensive.)

1. A device for detecting an amount of actuation of a fluid pressure actuator that detects a position of a piston of the fluid pressure actuator, the fluid pressure actuator having a double acting cylinder whose interior is divided by the piston into a first pressure acting chamber and a second pressure acting chamber, and moving the piston by flowing fluid into and out of the first pressure acting chamber or the second pressure acting chamber, the device comprising:

a pressure detector that detects a pressure value of the first pressure acting chamber or the second pressure acting chamber; and

and a control unit having a piston position detection program for calculating a movement amount of the piston as an operation amount of the fluid pressure actuator based on the pressure value detected by the pressure detector.

2. The device for detecting the operation amount of a fluid pressure actuator according to claim 1, wherein the fluid pressure actuator is subjected to an intake throttle control for adjusting the flow rate of the fluid flowing into the first pressure acting chamber or the second pressure acting chamber to control the moving speed of the piston, and the control unit calculates the moving amount of the piston from the pressure value on the side of the first pressure acting chamber and the second pressure acting chamber into which the fluid flows, based on the piston position detection program.

3. The device for detecting the operation amount of a fluid pressure actuator according to claim 1, wherein the fluid pressure actuator performs an exhaust throttle control for controlling the movement speed of the piston by adjusting the flow rate of the fluid flowing out from the first pressure acting chamber or the second pressure acting chamber, and the control unit calculates the movement amount of the piston from the pressure value of the side of the first pressure acting chamber and the second pressure acting chamber from which the fluid flows out, based on the piston position detection program.

4. The device for detecting the operation amount of the fluid pressure actuator according to any one of claims 1 to 3, wherein the control unit calculates a variation in the pressure value with the passage of time of the pressure value of the first pressure working chamber or the second pressure working chamber detected by the pressure detector based on the piston position detection program, and converts the variation in the pressure value into the movement amount of the piston based on a predetermined correction value stored in advance in a storage unit provided in the control unit, thereby calculating the movement amount of the piston.

5. The apparatus for detecting the amount of motion of a fluid pressure actuator according to claim 4, wherein the correction value includes a first correction value determined by an inner diameter of the double acting cylinder and a stroke and a moving time of the piston, and a second correction value determined by a ratio of a prescribed stroke of the piston to a second correction pressure value determined by the inner diameter of the double acting cylinder,

the first correction value is a value obtained by subtracting a difference between a pressure value at a movement start time point of the piston and a pressure value at a movement completion time point of the piston when the piston having the predetermined stroke is operated for the predetermined movement time from the second correction pressure value, the first correction value being a value obtained by setting a movement start time point of the piston to zero and increasing the pressure value in proportion to a time lapse until a first correction pressure value at a movement completion time point of the piston, the control unit calculates a variation amount of the pressure value with the time lapse based on the pressure value at the movement start time point of the piston detected by the pressure detector based on the pressure value of the first pressure operation chamber or the second pressure operation chamber detected by the pressure detector based on the piston position detection program, and calculating a sum of the first correction value and the variation of the pressure value for each time, and multiplying the calculated sum by the second correction value to thereby calculate the movement amount of the piston.

6. The device for detecting an amount of actuation of a fluid pressure actuator according to any one of claims 1 to 3, wherein the fluid pressure actuator has:

a first pipe leading to the first pressure acting chamber for flowing a fluid in or out; and

a second pipe leading to the second pressure acting chamber for flowing in or out of the fluid;

the pressure detectors are respectively arranged on the first pipeline and the second pipeline.

7. The device for detecting an amount of actuation of a fluid pressure actuator according to claim 4, wherein the fluid pressure actuator has: a first pipe leading to the first pressure acting chamber for flowing a fluid in or out; and a second conduit leading to the second pressure-acting chamber, for flowing a fluid into or out of the second pressure-acting chamber; the pressure detectors are respectively arranged on the first pipeline and the second pipeline.

8. The device for detecting an amount of actuation of a fluid pressure actuator according to claim 5, wherein the fluid pressure actuator has: a first pipe leading to the first pressure acting chamber for flowing a fluid in or out; and a second conduit leading to the second pressure-acting chamber, for flowing a fluid into or out of the second pressure-acting chamber; the pressure detectors are respectively arranged on the first pipeline and the second pipeline.

Technical Field

The present invention relates to the field of detection devices, and more particularly, to a device for detecting the amount of actuation of a fluid pressure actuator having a double acting cylinder whose interior is divided by a piston into a first pressure acting chamber and a second pressure acting chamber, and moving the piston by flowing fluid into and out of the first pressure acting chamber or the second pressure acting chamber.

Background

For example, a fluid pressure actuator having a double acting cylinder is used for controlling a robot arm and a gas claw used in a food factory or the like.

The interior of the double acting cylinder is divided by the piston into a first pressure acting chamber and a second pressure acting chamber, and one end of a pipe for performing intake or exhaust of compressed air is connected to each of the first pressure acting chamber and the second pressure acting chamber. The other end of the pipe is connected to a compressed air supply source via a switching valve, and the switching valve switches between intake air to the first pressure acting chamber and intake air to the second pressure acting chamber, whereby the piston reciprocates in the cylinder.

In the double acting cylinder as described above, an operation of detecting the position of the piston by the magnetostrictive sensor as disclosed in patent document 1 is performed.

For example, a permanent magnet is incorporated in the piston, and a magnetostrictive wire is disposed on the outer circumferential surface of the cylinder tube of the double acting cylinder in the axial direction. When a current pulse is applied to the magnetostrictive wire, a magnetic field in the circumferential direction is generated over the entire axial region, and when the permanent magnet mounted in the piston approaches the magnetic field, a resultant magnetic field of the permanent magnet and the magnetic field in the circumferential direction of the magnetostrictive sensor is generated, and torsional deformation is generated in a portion of the magnetostrictive wire where the resultant magnetic field is generated. The resulting torsional deformation propagates on the magnetostrictive line in the form of vibrations, and therefore, by measuring the propagation time, the position of the permanent magnet can be detected, and thus the position of the piston equipped with the permanent magnet can be detected.

Disclosure of Invention

However, the above-described prior art has the following problems.

Since the magnetostrictive sensor is provided with a rod-shaped magnetostrictive wire, it is difficult to attach the magnetostrictive sensor to a fluid pressure actuator that does not perform linear motion, such as a robot arm, and the like, and the shape of the fluid pressure actuator is restricted by the shape of the magnetostrictive sensor, which impairs the degree of freedom in designing devices, such as a robot arm and a gas claw, used in a food factory, for example.

Further, since the length of the magnetostrictive wire must be set to a length that matches the operating stroke of the piston of the fluid pressure actuator, when a plurality of fluid pressure actuators having different strokes are used, it is necessary to prepare a magnetostrictive wire that matches each stroke, which may increase the manufacturing cost.

The present invention has been made to solve the above-described problems, and an object thereof is to provide an inexpensive operation amount detection device for a fluid pressure actuator, which can improve the degree of freedom in designing the device without restricting the shape of the fluid pressure actuator.

In order to solve the above problems, the actuator operation detection device according to the present invention has the following configuration.

(1) An operation amount detection device for a fluid pressure actuator that detects a position of a piston of the fluid pressure actuator, the fluid pressure actuator having the piston and a double acting cylinder whose interior is divided into a first pressure acting chamber and a second pressure acting chamber by the piston, and moving the piston by flowing a fluid into and out of the first pressure acting chamber or the second pressure acting chamber, the operation amount detection device for the fluid pressure actuator comprising: a pressure detector that detects a pressure value of the first pressure acting chamber or the second pressure acting chamber; and a control unit having a piston position detection program for calculating a movement amount of the piston as an operation amount of the fluid pressure actuator based on the pressure value detected by the pressure detector.

(2) The device for detecting an amount of actuation of a fluid pressure actuator according to (1), wherein the fluid pressure actuator is controlled by an intake throttle (Meter-in), that is, by adjusting a flow rate of the fluid flowing into the first pressure acting chamber or the second pressure acting chamber, thereby controlling a moving speed of the piston, and the control unit calculates the amount of movement of the piston from a pressure value on a side of the first pressure acting chamber and the second pressure acting chamber into which the fluid flows, based on a piston position detection program.

(3) The device for detecting an operation amount of a fluid pressure actuator according to (1), wherein the control unit performs Meter-out control for controlling a moving speed of the piston by adjusting a flow rate of the fluid flowing out of the first pressure acting chamber or the second pressure acting chamber of the fluid pressure actuator, and the control unit calculates the moving amount of the piston from a pressure value of the side of the first pressure acting chamber or the second pressure acting chamber from which the fluid flows out, based on the piston position detection program.

(4) The device for detecting an amount of actuation of a fluid pressure actuator according to any one of (1) to (3), wherein the control unit calculates an amount of variation in the pressure value with time of the pressure value of the first pressure acting chamber or the second pressure acting chamber detected by the pressure detector based on the piston position detection program, and calculates the amount of movement of the piston by converting the amount of variation in the pressure value into the amount of movement of the piston based on a predetermined correction value stored in advance in a storage unit provided in the control unit.

(5) The device for detecting an amount of actuation of a fluid pressure actuator according to (4), wherein the correction value includes a first correction value determined by an inner diameter of the double acting cylinder and a stroke and a movement time of the piston, and a second correction value determined by a ratio of a predetermined stroke of the piston to a second correction pressure value determined by the inner diameter of the double acting cylinder, the first correction value is a pressure value obtained by setting a movement start time point of the piston to zero and increasing the value in proportion to a lapse of time until the first correction pressure value at a movement completion time point of the piston, the first correction pressure value is a value obtained by subtracting a difference between a pressure value at the movement start time point of the piston and a pressure value at the movement completion time point of the piston in the first pressure acting chamber or the second pressure acting chamber when the piston having the predetermined stroke is actuated for the predetermined movement time from the second correction pressure value, the control unit calculates a displacement amount of the piston by calculating a variation amount of the pressure value with time based on the pressure value at the time point of starting the movement of the piston based on the pressure value of the first pressure acting chamber or the second pressure acting chamber detected by the pressure detector based on the piston position detection program, calculating a sum of a first correction value and the variation amount of the pressure value for the corresponding time, and multiplying the calculated sum by a second correction value.

(6) The device for detecting an amount of actuation of a fluid pressure actuator according to any one of (1) to (5), wherein the fluid pressure actuator has: a first pipe leading to the first pressure acting chamber for flowing in or out a fluid; and a second conduit leading to the second pressure-acting chamber, for flowing the fluid in or out; the pressure detectors are respectively arranged on the first pipeline and the second pipeline.

ADVANTAGEOUS EFFECTS OF INVENTION

With the above configuration, the actuator operation detection device according to the present invention has the following operations and effects.

With the configuration of (1), the operation amount detection device of the fluid pressure actuator can be manufactured at low cost without restricting the shape of the fluid pressure actuator and with a high degree of freedom in equipment design.

That is, since the control unit can calculate the piston position from the pressure value of the first pressure acting chamber or the second pressure acting chamber detected by the pressure detector by executing the piston position detection program, it is not necessary to use a special sensor for detecting the piston position, as in the case where, for example, a magnetostrictive sensor is mounted on a fluid pressure actuator. Since the use of a sensor is not required, the shape of the fluid pressure actuator is not restricted by the shape of the sensor, and the degree of freedom in designing equipment such as a robot arm and a gas claw used in a food factory is improved.

Further, the pressure detector is versatile, and even when a plurality of fluid pressure actuators having different strokes are used, it is not necessary to prepare a plurality of magnetostrictive sensors corresponding to the strokes of the respective fluid pressure actuators, unlike the magnetostrictive sensor, and there is no fear of an increase in manufacturing cost.

With the above configurations (2) and (3), when the intake throttle control is performed or the exhaust throttle control is performed in the fluid pressure actuator, the position of the piston can be calculated from the pressure value of the first pressure acting chamber or the second pressure acting chamber. In both cases of performing the intake throttle control and the exhaust throttle control, the intake throttle control and the exhaust throttle control can be used separately and independently in consideration of their characteristics as long as the piston position can be detected, and therefore, the degree of freedom in designing equipment such as a robot arm and a gas claw used in a food factory, for example, is improved.

Here, in order to detect the piston position, it is necessary to detect the pressure value on the side where the flow rate of the fluid flowing into or out of the first pressure acting chamber or the second pressure acting chamber is controlled, in both the case where the intake throttle control is performed and the case where the exhaust throttle control is performed. The reason for this is described below.

The reason for this is that, in the case of the intake throttle control, the pressure value of the side of the first pressure acting chamber and the second pressure acting chamber into which the fluid flows is controlled by adjusting the flow rate of the fluid flowing into the first pressure acting chamber or the second pressure acting chamber. In addition, in the case of the exhaust throttle control, the pressure value on the side from which the fluid flows out of the first pressure acting chamber and the second pressure acting chamber is controlled by adjusting the flow rate of the fluid flowing out of the first pressure acting chamber or the second pressure acting chamber. Since the moving speed of the piston is controlled by controlling the pressure value, the position of the piston can be detected with high accuracy by detecting the pressure value on the side to be controlled among the pressure values of the first pressure operation chamber or the second pressure operation chamber and calculating the piston position.

With the above configurations (4) and (5), the amount of movement of the piston can be detected with high accuracy using the pressure value of the first pressure acting chamber or the second pressure acting chamber. Conventionally, it has been considered that there is a certain relationship between the pressure value of the first pressure acting chamber or the second pressure acting chamber and the position of the piston, but it has not been considered that the position of the piston can be detected with high accuracy by using the pressure value. In this context, the applicant of the present invention has derived experimentally the following facts: as described above, the pressure value of the first pressure acting chamber or the second pressure acting chamber is converted based on the correction value, and the piston position can be detected with high accuracy using the value obtained by the conversion.

By performing the conversion as described above, it is possible to prevent the occurrence of a delay in information processing of a CPU incorporated in the operation amount detection device of the fluid pressure actuator.

As a device for detecting the position of the piston without using the magnetostrictive sensor, the present applicant has proposed an actuation amount detection device of a fluid pressure actuator of japanese patent application publication 2019-100512. In this device, the amount of change in the speed of the piston is calculated by differentiating the amount of change in the pressure value of the first pressure operation chamber or the pressure value of the second pressure operation chamber, and the amount of movement of the piston is calculated by integrating the amount of change in the speed.

However, since the amount of change in the pressure value accompanying the movement of the piston is relatively small, there is a possibility that the calculation accuracy may be deteriorated due to noise, and therefore, the actual calculation process requires the movement averaging filter process, and there is a possibility that the CPU incorporated in the operation amount detection device of the fluid pressure actuator may cause a processing delay.

Therefore, if the pressure value can be converted to the movement amount of the piston by only addition, division, or multiplication using the correction value stored in advance as in the present invention, the influence of disturbance noise is not easily received, and delay in information processing of the CPU due to filter processing that has conventionally occurred can be prevented.

With the above configuration (6), the degree of freedom of the arrangement position of the pressure detector is high, and the degree of freedom of the apparatus design is improved.

That is, according to the pascal principle, the pressure applied to the inner wall of the first pressure acting chamber and the inner wall of the first pipe leading to the first pressure acting chamber is uniform, and the pressure applied to the inner wall of the second pressure acting chamber and the inner wall of the second pipe leading to the second pressure acting chamber is uniform. Therefore, the pressure detector provided in the first pipe leading to the first pressure acting chamber can detect the pressure value of the first pressure acting chamber regardless of the length of the first pipe, and the pressure detector provided in the second pipe leading to the second pressure acting chamber can detect the pressure value of the second pressure acting chamber regardless of the length of the second pipe. Therefore, the pressure detector does not need to be disposed in the vicinity of the fluid pressure actuator, and therefore, the degree of freedom in disposing the pressure detector is high, and the degree of freedom in designing the apparatus is improved.

Additional features and advantages of the disclosure will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure. In the drawings:

fig. 1 is a circuit diagram of a fluid pressure actuator monitoring system using a motion amount detection device of a fluid pressure actuator.

Fig. 2 is a block diagram showing a control configuration of the operation amount detection device of the fluid pressure actuator.

Fig. 3 is a diagram showing a method of determining the first correction value in the case where the exhaust throttle control is performed.

Fig. 4 is a diagram showing a method of converting the amount of fluctuation of the pressure value on the exhaust side in the first pressure operation chamber or the second pressure operation chamber into the amount of movement of the piston.

Fig. 5 is a reference diagram showing the amount of movement of the piston when an abnormality occurs in the driving of the piston.

Fig. 6 is a diagram showing a method of determining the first correction value in the case where the intake air throttle control is performed.

Fig. 7 is a diagram showing a method of converting the amount of fluctuation of the pressure value on the intake side in the first pressure acting chamber or the second pressure acting chamber into the amount of movement of the piston.

Fig. 8 is a diagram showing a modification of the circuit diagram of the fluid pressure actuator monitoring system.

Description of the reference numerals

10 fluid pressure actuator

20 device for detecting motion amount of fluid pressure actuator

101 double acting cylinder

102 piston

103 first pressure acting chamber

104 second pressure acting chamber

201 control part

202 first pressure transducer

203 second pressure transducer

2012a piston position detecting program

Detailed Description

An embodiment of an operation amount detection device 20 for a fluid pressure actuator (hereinafter also simply referred to as "operation amount detection device") according to the present invention will be described in detail below with reference to the drawings.

Fig. 1 is a circuit diagram of a fluid pressure actuator monitoring system 1 using a fluid pressure actuator operation amount detection device 20. The operation amount detection device 20 of the fluid pressure actuator functions as a device for detecting the position of a piston 102 slidably held inside a double acting cylinder 101 constituting the fluid pressure actuator 10 in the double acting cylinder 101.

The interior of the double acting cylinder 101 is divided by a piston 102 into a first pressure acting chamber 103 and a second pressure acting chamber 104. An operating rod 105 is connected to a second pressure chamber side end surface (second end surface) 102b of the piston 102, and the operating rod 105 extends to the outside of the double acting cylinder 101 through an insertion hole of a second pressure chamber side inner wall surface (second inner wall surface) 101b of the double acting cylinder 101.

One end of a first pipe 11 for introducing or discharging compressed air is connected to the first pressure acting chamber 103, and the other end of the first pipe 11 is connected to a first connection port 131 of the switching valve 13.

One end of a second pipe 12 for introducing or discharging compressed air is connected to the second pressure acting chamber 104, and the other end of the second pipe 12 is connected to a second connection port 132 of the switching valve 13.

The first duct 11 is provided with a flow rate adjuster 14A including a check valve 141A and a flow rate adjustment valve 142A, and the second duct 12 is provided with a flow rate adjuster 14B including a check valve 141B and a flow rate adjustment valve 142B.

The switching valve 13 has an input port 133 to which compressed air is input, one end of the intake duct 15 is connected to the input port 133, and the other end of the intake duct 15 is connected to the compressed air supply source 16.

The switching valve 13 is a two-solenoid type solenoid valve, and drives an internal valve body (not shown) by applying an electric signal from the outside to the solenoids 134A and 134B.

When an electric signal is applied to the solenoid 134A, the spool of the switching valve 13 is attracted to the solenoid 134A side, the input port 133 communicates with the first connection port 131, and the second connection port 132 is opened to the outside.

The input port 133 communicates with the first connection port 131 so that the compressed air supplied from the compressed air supply source 16 is input from the input port 133 to the switching valve 13 and is output from the first connection port 131. The compressed air output from the first connection port 131 is fed to the first pressure acting chamber 103 of the double acting cylinder 101 through the first piping 11.

By supplying the compressed air to the first pressure operation chamber 103, the pressure inside the first pressure operation chamber 103 rises, the first pressure operation chamber side end surface (first end surface) 102a of the piston 102 is pressed, and the piston 102 moves in the forward direction (rightward in fig. 1). While the piston 102 is moving in the forward direction, the exhaust of the second pressure acting chamber 104 is started, and the compressed air previously fed to the second pressure acting chamber 104 is discharged to the outside via the second duct 12, the second connection port 132, the switching valve 13, and the muffler 17B.

On the other hand, when an electric signal is applied to the solenoid 134B, the spool of the switching valve 13 is attracted to the solenoid 134B side, the input port 133 communicates with the second connection port 132, and the first connection port 131 is opened to the outside.

The input port 133 communicates with the second connection port 132 so that the compressed air supplied from the compressed air supply source 16 is input from the input port 133 to the switching valve 13 and is output from the second connection port 132. The compressed air output from the second connection port 132 is fed to the second pressure acting chamber 104 of the double acting cylinder 101 through the second pipe 12.

By feeding the compressed air to the second pressure operation chamber 104, the pressure inside the second pressure operation chamber 104 rises, the second end surface 102b of the piston 102 is pressed, and the piston 102 moves in the retreating direction (leftward in fig. 1). While the piston 102 moves in the retracting direction, the exhaust of the first pressure acting chamber 103 starts, and the compressed air previously fed to the first pressure acting chamber 103 is discharged to the outside via the first duct 11, the first connection port 131, the switching valve 13, and the muffler 17A.

As described above, by driving the spool by energizing the solenoid 134A or the solenoid 134B of the switching valve 13, the feeding of the compressed air into the first pressure acting chamber 103 and the feeding of the compressed air into the second pressure acting chamber 104 can be switched, and by repeating this switching, the piston 102 can be reciprocated. Then, the operating rod 105 connected to the second end surface 102b of the piston 102 reciprocates as the piston 102 reciprocates.

The control of the operating speed of the reciprocating motion of the piston 102 is performed by adjusting the flow rate of the compressed air in the flow rate adjuster 14A or the flow rate adjuster 14B.

Fig. 1 is a circuit for controlling the operating speed of the piston 102 (hereinafter referred to as exhaust throttle control) by adjusting the flow rate of compressed air discharged from the first pressure acting chamber 103 or the second pressure acting chamber 104 when the piston 102 is driven.

Specifically, the check valves 141A and 141B of the flow rate control units 14A and 14B allow the compressed air to flow only in one direction from the switching valve 13 side to the fluid pressure actuator 10 side, and the flow of the compressed air in the opposite direction is blocked by a valve body (not shown).

For example, in the case where compressed air is to be fed from the first pipe 11 to the first pressure-acting chamber 103, since the check valve 141A of the flow rate adjustment portion 14A on the first pipe 11 permits the flow of the compressed air to the first pressure-acting chamber 103, the compressed air is fed to the first pressure-acting chamber 103. As the compressed air is fed to the first pressure acting chamber 103, the piston 102 moves, and the compressed air is discharged from the second pressure acting chamber 104 to the second pipe 12. At this time, the check valve 141B of the flow rate adjuster 14B in the second duct 12 blocks the compressed air discharged from the second pressure acting chamber 104, and therefore the compressed air passes through the flow rate adjustment valve 142B. Therefore, by adjusting the throttle degree of the flow rate adjustment valve 142B, the flow rate of the compressed air is restricted according to the valve opening degree, and the moving speed of the piston 102 is controlled.

Conversely, in the case where the compressed air is to be fed from the second pipe 12 to the second pressure acting chamber 104, the compressed air is fed to the second pressure acting chamber 104 because the check valve 141B of the flow rate adjuster 14B on the second pipe 12 permits the flow of the compressed air to the second pressure acting chamber 104. As the compressed air is fed to the second pressure acting chamber 104, the piston 102 moves, and the compressed air is discharged from the first pressure acting chamber 103 to the first pipe 11. At this time, the check valve 141A of the flow rate adjuster 14A in the first duct 11 blocks the compressed air discharged from the first pressure acting chamber 103, and therefore the compressed air passes through the flow rate adjustment valve 142A. Therefore, by adjusting the throttle degree of the flow rate adjustment valve 142A, the flow rate of the compressed air is restricted according to the valve opening degree, and the moving speed of the piston 102 is controlled.

An operation amount detecting device 20 of the fluid pressure actuator for detecting the position of the piston 102 in the double acting cylinder 101 (that is, the operation amount of the fluid pressure actuator 10) is connected to the first pipe line 11 and the second pipe line 12 and between the flow rate adjusting portions 14A and 14B and the fluid pressure actuator 10.

Fig. 2 is a block diagram showing the configuration of the operation amount detection device 20 of the fluid pressure actuator. The operation amount detection device 20 includes a control unit 201, a first pressure transducer 202 and a second pressure transducer 203 as pressure detectors, an AD conversion unit 204, a display unit 205, a setting unit 206, a storage unit 207, a signal circuit 208, and a communication circuit 209. Further, the controller 201 includes a CPU 2011 and a memory 2012, and the memory 2012 stores a piston position detection program 2012a for calculating the movement amount of the piston 102 in the double acting cylinder 101.

The first pressure transducer 202 is connected to the first pipe 11, and detects a pressure value of the first pipe 11. The second pressure transducer 203 is connected to the second pipe 12, and detects a pressure value of the second pipe 12. According to the pascal principle, the pressure applied to the inner wall of the first pressure acting chamber 103 is uniform with the pressure applied to the inner wall of the first pipe 11 leading to the first pressure acting chamber 103, and the pressure applied to the inner wall of the second pressure acting chamber 104 is uniform with the pressure applied to the inner wall of the second pipe 12 leading to the second pressure acting chamber 104. Therefore, the pressure values detected in the first duct 11 and the second duct 12 are the same as those detected in the first pressure operation chamber 103 and the second pressure operation chamber 104. In addition, the first pressure transducer 202 and the second pressure transducer 203 can detect the pressure values of the first pressure operation chamber 103 and the second pressure operation chamber 104 regardless of the lengths of the first pipe 11 and the second pipe 12. Therefore, the first pressure transducer 202 and the second pressure transducer 203 do not need to be disposed in the vicinity of the fluid pressure actuator 10, and therefore the degree of freedom in disposing the first pressure transducer 202 and the second pressure transducer 203 is high, and the degree of freedom in designing the apparatus is improved.

The first pressure transducer 202 and the second pressure transducer 203 are connected to the control unit 201 via an AD converter 204.

The pressure values detected by the first pressure transducer 202 and the second pressure transducer 203 are converted into electric signals and output. Since the electric signal is an analog signal, the electric signal is converted into a digital signal by the AD converter 204 and then output to the controller 201.

When the pressure value is input to the control unit 201, the CPU 2011 reads out and executes the piston position detection program 2012a from the memory 2012, thereby calculating the movement amount of the piston 102 in the double acting cylinder 101 based on the input pressure value.

The display 205, the setting unit 206, the storage 207, the signal circuit 208, and the communication circuit 209 are connected to the control unit 201, a predetermined correction value (described in detail later) for calculating the movement amount of the piston 102 using the pressure value is stored in the storage 207 in advance, and the CPU 2011 reads the predetermined correction value from the storage 207 when calculating the movement amount of the piston 102 using the pressure value. The predetermined correction value is determined based on the inner diameter of the double acting cylinder 101 and the stroke and movement time (operation cycle) of the piston 102, and information on the inner diameter of the double acting cylinder 101 and the stroke and movement time of the piston 102 is input by the operator via the setting unit 206, and thus the correction value corresponding to the input information is selected and used for calculating the movement amount of the piston 102 when the piston position detection program 2012a is executed. The storage unit 207 may be built in the control unit 201.

The display unit 205 can display the amount of movement of the piston 102 calculated by the CPU 2011, the contents of the first pressure chamber side inner wall surface (first inner wall surface) 101a or the second inner wall surface 101b in which the driven piston 102 has reached the interior of the double acting cylinder 101, and the like. Further, the contents input by the setting unit 206, the contents displayed on the display unit 205, the waveform data of the movement amount of the piston 102, and the like may be output to the outside through the communication circuit 209.

The signal circuit 208 transmits and receives signals to and from the outside of the operation amount detection device 20. For example, the signal circuit 208 receives a trigger signal for starting or stopping the fluid pressure actuator 10 from the outside, and thereby the control unit 201 controls the start and stop of the introduction of the waveform data of the movement amount of the piston 102. When the operator specifies the amount of movement of piston 102 in advance, the operator may be notified by outputting a signal to the outside when piston 102 to be driven has reached the specified amount of movement.

Next, a method of calculating the movement amount of the piston 102 from the pressure value of the first pressure acting chamber 103 or the second pressure acting chamber 104 will be described with reference to fig. 3 and 4.

In fig. 3 and 4, time t0 is a time point at which the compressed air starts to be fed from the compressed air supply source 16, time t1 is a time point at which the piston 102 starts to move, and time t2 is a time point at which the piston 102 finishes moving by reaching the first inner wall surface 101a or the second inner wall surface 101b of the double acting cylinder 101.

In the present embodiment, the exhaust throttle control is performed, and the movement amount of the piston 102 is calculated by converting the pressure value on the exhaust side of the first pressure acting chamber 103 and the second pressure acting chamber 104 into the movement amount based on a predetermined correction value stored in advance in the storage unit 207.

Here, the predetermined correction value refers to a first correction value CV11 determined by the inner diameter of the double acting cylinder 101, the stroke and the moving time of the piston 102, and a second correction value CV12 described later. The first correction value CV11 and the second correction value CV12 are stored in the storage unit 207 in advance, and are read out and used for calculation when the piston position detection program 2012a is executed.

First, the first correction value CV11 will be explained.

The first correction value CV11 is a pressure value, and as shown in fig. 3(b), is a value that increases in proportion to the passage of time from the time point t1 at which the movement of the piston 102 is started to the first correction pressure value CP11 at the time point t2 at which the movement of the piston 102 is completed, to 0 MPa.

The first correction value CV11 is obtained as follows.

A pressure value waveform P11 of a pressure acting chamber on the side from which compressed air is discharged by driving of the piston 102, out of the first pressure acting chamber 103 and the second pressure acting chamber 104, in a case where the piston 102 having a predetermined stroke is operated for a predetermined moving time is detected.

After the pressure value waveform P11 is detected, a difference Δ P11 between the pressure value at the time point t1 and the pressure value at the time point t2 is calculated.

Then, the difference Δ P11 is subtracted from the second corrected pressure value CP12 stored in advance in the storage unit 207, and the first corrected pressure value CP11 is calculated. The second corrected pressure value CP12 is a value determined by the inner diameter (cylinder diameter) of the double acting cylinder 101, and is a value experimentally derived by the applicant of the present invention. For example, the cylinder diameter of 25mm is 0.35MPa, and a different value is set for each cylinder diameter. Then, the operator inputs the cylinder diameter of the fluid pressure actuator 10 to be used through the setting unit 206, and reads and calculates the second corrected pressure value CP12 corresponding to the input cylinder diameter.

The calculated first corrected pressure value CP11 is set as a pressure value at the time point t2, and a value that increases in proportion to the passage of time from 0MPa at the time point t1 to the first corrected pressure value CP11 at the time point t2 becomes the first correction value CV 11. Here, since the first correction value CV11 changes with time from the time point t1, the first correction value CV11 at a predetermined time after the time point t1 is defined as Δ CV 11.

Next, the second correction value CV12 will be described.

The second correction value CV12 is a value determined by the ratio of the stroke of the piston 102 to the second correction pressure value CP12 determined by the inner diameter of the double acting cylinder 101.

The operator inputs the cylinder diameter of the used fluid pressure actuator 10 and the stroke of the piston 102 through the setting unit 206, calculates a second correction value CV12 corresponding to the input cylinder diameter and the stroke of the piston 102, and stores the second correction value CV12 in the storage unit 207.

Next, how to convert the pressure value of the first pressure operation chamber 103 or the second pressure operation chamber 104 into the movement amount of the piston 102 will be described.

The pressure value waveform P11 shown in fig. 4(a) is a waveform of a pressure value on the side where air is exhausted from the first pressure acting chamber 103 or the second pressure acting chamber 104 of the fluid pressure actuator 10 that operates in the same stroke and movement time as the predetermined stroke and movement time for which the first correction value CV11 and the second correction value CV12 are obtained.

First, as shown in fig. 4(a), a fluctuation amount Δ P111 of the pressure value which fluctuates with the lapse of time is calculated with reference to the pressure value P1 at time t 1.

The fluctuation amount Δ P111 when the value indicated by the pressure value waveform P11 exceeds the pressure value P1 is a positive value, and the fluctuation amount Δ P111 when the value is below the pressure value P1 is a negative value.

Next, the first correction value CV11 obtained in advance is read from the storage unit 207, and as shown in fig. 4(b), the variation Δ P111 of the pressure value waveform P11 for the corresponding time is added to Δ CV11 for a predetermined time, to obtain a pressure value waveform P12 (for example, the value of Δ CV11 after 10 seconds of t1 is added to the value of Δ P111 after 10 seconds of t 1).

When Δ P111 is a positive value, the value indicated by the pressure value waveform P12 exceeds the first correction value CV11, and when Δ P111 is a negative value, the value indicated by the pressure value waveform P12 is lower than the first correction value CV 11.

Finally, the pressure value is converted from units MPa to units mm of movement. The second correction value CV12 obtained in advance is read from the storage unit 207, and the pressure value waveform P12 is multiplied by the second correction value CV12, thereby converting the result into the movement amount PD11 of the piston 102 shown in fig. 4 (c). For example, a value obtained by multiplying the maximum pressure value P2 in fig. 4(b) by the second correction value CV12 is a value converted into the amount of movement of the piston 102.

The following explains why the pressure value of the first pressure operation chamber 103 or the second pressure operation chamber 104 can be thus converted into the amount of movement of the piston 102.

First, the rate of change (dP/dt) in the pressure value represented by the pressure value waveform P11 is expressed by the following expression 1.

(formula 1)

(formula 2)

(formula 3)

Here, "M" means the mass (kg) of the compressed air, "R" means the gas constant, "T" means the temperature (K), "P" means the pressure value (Pa) of the first pressure acting chamber 103 or the second pressure acting chamber 104, "V" means the volume (M) of the first pressure acting chamber 103 or the second pressure acting chamber 104³) "A" means the pressing area (m) of the piston 102²) "L" means the stroke (m) of the piston 102, and "Y" means the amount of movement (m) of the piston 102.

Equation 1 is obtained by substituting equation 3 obtained by time-differentiating both sides of a (L-Y) indicating the relationship between the amount of movement of the piston 102 and the volume of the pressure acting chamber into equation 2 obtained by time-differentiating both sides of the gas state equation M ═ PV/RT, and equation 1 shows that the first term on the right side of equation 1 ("(-RT/V) × (dM/dt)") has a negative value and that the pressure value on the exhaust side of the first pressure acting chamber 103 or the second pressure acting chamber 104 tends to decrease as the exhaust advances, and for example, the pressure value P1 at time t1 is a value that decreases as indicated by a broken line in fig. 4 (a).

On the other hand, the second term on the right side of equation 1 ("(P/V) × a × (dY/dt)") has a positive value, and represents that the pressure value tends to increase as the piston 102 moves because the space of the pressure acting chamber on the exhaust side of the first pressure acting chamber 103 or the second pressure acting chamber 104 is compressed.

The conversion from the pressure value waveform P11 to the pressure value waveform P12 by the first correction value CV11 has a meaning of correcting the slope of the pressure value waveform P11, and the first term on the right side of the equation 1, which is the pressure value to be lowered as the exhaust gas advances, is cancelled by correcting the slope of the pressure value waveform P11. Then, the rate of change in pressure value (dP/dt) is expressed as shown in the following equation 4.

(formula 4)

The right side of equation 4 can be said to be represented by the time differential value of the movement amount Y of the piston 102 and its coefficient, meaning that the value obtained by multiplying the time differential value of the movement amount Y of the piston 102 by the coefficient is equal to the time differential value of the pressure value P.

If the coefficient is regarded as corresponding to the reciprocal of the second correction value CV12, the pressure value waveform P12 converted from the pressure value waveform P11 is converted into the movement amount PD11 of the piston 102 shown in fig. 4(c) by multiplying the second correction value CV12 as described above.

The waveform of the movement amount PD11 calculated as described above is substantially the same as the waveform D11 indicating the movement amount of the piston 102 driven at the same stroke and the same movement time by the magnetostrictive sensor between the time point t1 and the time point t 2.

From this, it is found that the position of the piston 102 can be detected using the pressure value of the first pressure operation chamber 103 detected by the first pressure transducer 202 or the pressure value of the second pressure operation chamber 104 detected by the second pressure transducer 203, without using a magnetostrictive sensor as in the related art. Since the magnetostrictive sensor is not used, the shape of the fluid pressure actuator 10 is not restricted by the shape of the magnetostrictive sensor as in the conventional art, and the degree of freedom in designing equipment such as a robot arm and a gas claw used in a food factory is improved.

Further, the first pressure transducer 202 and the second pressure transducer 203 have versatility, and even when a plurality of fluid pressure actuators 10 having different strokes are used, it is not necessary to prepare a plurality of magnetostrictive sensors that match the strokes of the respective fluid pressure actuators 10, unlike the magnetostrictive sensors, and there is no fear of an increase in manufacturing cost.

Further, if the pressure value can be converted to the movement amount of the piston 102 by only addition, division, or multiplication of the pressure value using the first correction value CV11 and the second correction value CV12 stored in advance, the influence of disturbance noise is less likely to be received, and delay in information processing of the CPU 2011 due to filter processing that has conventionally occurred can be prevented.

Further, according to the piston position detection program 2012a, even when an abnormality occurs in the driving of the piston 102, such as an excessive friction force between the piston 102 and the inner surface of the double acting cylinder 101 during the driving of the piston 102 or the operating rod 105 connected to the piston 102 hitting an obstacle, the position of the piston 102 can be accurately detected.

For example, fig. 5 is a graph showing the experimental results obtained by the applicant of the present invention. Waveform D12 represents the following: in the case where the piston 102 moves from the first inner wall surface 101a toward the second inner wall surface 101b, that is, the operation rod 105 is driven in the direction protruding from the double acting cylinder 101, the operation rod 105 is intentionally made to collide against an obstacle at a time point t3 between a time point t1 when the piston 102 starts driving and a time point t2 when the piston 102 completes driving. At the time point t3, the operating rod 105 hits an obstacle and the moving speed of the piston 102 decreases, and therefore, the slope of the waveform D12 after the time point t3 is gentler than that before the time point t 3.

In contrast, the waveform PD12 shown in fig. 5 is a waveform obtained by converting the amount of fluctuation in the pressure value of the second pressure acting chamber 104 detected simultaneously with the detection of the waveform D12 into the amount of movement of the piston 102 based on the first correction value CV11 and the second correction value CV 12. It was found that the waveform PD12 exhibited substantially the same behavior as the waveform D12. Therefore, according to the piston position detection program 2012a, the position of the piston 102 can be accurately detected not only when the piston 102 is normally driven but also when an abnormality occurs in the driving thereof.

In the case of performing the exhaust throttle control, the flow rate adjusting portions 14A and 14B need not be disposed between the operation amount detecting device 20 and the switching valve 13. As shown in fig. 8, the muffler 17A, 17B may be disposed between the switching valve 13. Even with this arrangement, the flow rate of the compressed air discharged from the first pressure acting chamber 103 or the second pressure acting chamber 104 can be adjusted.

Although the case of performing the exhaust throttling control of the fluid pressure actuator 10 has been described above, the movement amount of the piston 102 can be calculated similarly also in the case of performing the control of the operating speed of the piston 102 by adjusting the flow rate of the compressed air fed to the first pressure acting chamber 103 or the second pressure acting chamber 104 (hereinafter, referred to as intake throttling control) using the fluid pressure actuator monitoring system shown in fig. 1.

In the case of performing the intake air throttle control, the check valves 141A and 141B of the flow rate adjustment portions 14A and 14B can flow the compressed air only in one direction from the fluid pressure actuator 10 side to the switching valve 13 side, and the flow of the compressed air in the opposite direction is blocked by the valve body (not shown).

For example, when compressed air is to be fed from the first pipe 11 to the first pressure acting chamber 103, the check valve 141A of the flow rate adjuster 14A in the first pipe 11 blocks the flow of the compressed air to the first pressure acting chamber 103, and therefore the compressed air is fed to the first pressure acting chamber 103 through the flow rate adjustment valve 142A. Therefore, by adjusting the throttle degree of the flow rate adjustment valve 142A, the flow rate of the compressed air is restricted according to the valve opening degree, and the moving speed of the piston 102 is controlled. As the compressed air is fed to the first pressure acting chamber 103, the piston 102 moves, and the compressed air is discharged from the second pressure acting chamber 104 to the second pipe 12. At this time, the check valve 141B of the flow rate adjuster 14B on the second pipe 12 allows the flow of the compressed air to the switching valve 13.

Conversely, when compressed air is to be fed from the second pipe 12 to the second pressure acting chamber 104, the flow of the compressed air to the second pressure acting chamber 104 is blocked by the check valve 141B of the flow rate adjuster 14B in the second pipe 12, and therefore the compressed air is fed to the second pressure acting chamber 104 through the flow rate adjustment valve 142B. Therefore, by adjusting the throttle degree of the flow rate adjustment valve 142B, the flow rate of the compressed air is restricted according to the valve opening degree, and the moving speed of the piston 102 is controlled. As the compressed air is fed to the second pressure acting chamber 104, the piston 102 moves, and the compressed air is discharged from the first pressure acting chamber 103 to the first pipe 11. At this time, the check valve 141A of the flow rate adjusting portion 14A on the first pipe 11 allows the flow of the compressed air to the switching valve 13.

The other circuit configurations and the configuration of the operation amount detection device 20 of the fluid pressure actuator are the same as those in the case of the exhaust throttle control shown in fig. 1.

Next, a method of calculating the movement amount of the piston 102 from the pressure value of the first pressure acting chamber 103 or the second pressure acting chamber 104 will be described with reference to fig. 6 and 7.

In fig. 6 and 7, time t0 is a time point at which the compressed air starts to be fed from the compressed air supply source 16, time t1 is a time point at which the piston 102 starts to move, and time t2 is a time point at which the piston 102 finishes moving by reaching the first inner wall surface 101a or the second inner wall surface 101b of the double acting cylinder 101.

In the case of performing the intake air throttle control, the amount of movement of the piston 102 is calculated by converting the pressure value on the intake air side of the first pressure acting chamber 103 and the second pressure acting chamber 104 into the amount of movement based on a predetermined correction value stored in advance in the storage unit 207.

Here, the predetermined correction value refers to a first correction value CV21 determined by the inner diameter of the double acting cylinder 101, the stroke and the moving time of the piston 102, and a second correction value CV22 described later.

The first correction value CV21 and the second correction value CV22 are stored in the storage unit 207 in advance, and are read out and used for calculation when the piston position detection program 2012a is executed.

First, the first correction value CV21 will be explained.

The first correction value CV21 is a pressure value, and as shown in fig. 6(b), is a value that increases in proportion to the passage of time from the time point t1 at which the movement of the piston 102 is started to the first correction pressure value CP21 at the time point t2 at which the movement of the piston 102 is completed, to 0 MPa.

The first correction value CV21 is obtained as follows.

A pressure value waveform P21 of a pressure acting chamber on the side to which compressed air is fed by driving of the piston 102, out of the first pressure acting chamber 103 and the second pressure acting chamber 104, in a case where the piston 102 having a predetermined stroke is operated for a predetermined moving time is detected.

After the pressure value waveform P21 is detected, a difference Δ P21 between the pressure value at the time point t1 and the pressure value at the time point t2 is calculated (refer to fig. 6 (a)).

Then, the difference Δ P21 is subtracted from the second corrected pressure value CP22 stored in advance in the storage unit 207, and the first corrected pressure value CP21 is calculated. The second corrected pressure value CP22 is a value determined by the inner diameter of the double acting cylinder 101 and is a value experimentally derived by the applicant of the present invention. For example, ifThe cylinder diameter of (2) is 0.35MPa, and different values are set for each cylinder diameter. Then, the operator inputs the cylinder diameter of the fluid pressure actuator 10 to be used through the setting unit 206, and reads and calculates the second corrected pressure value CP22 corresponding to the input cylinder diameter.

The calculated first corrected pressure value CP21 is set as a pressure value at the time point t2, and a value that increases in proportion to the passage of time from 0MPa at the time point t1 to the first corrected pressure value CP21 at the time point t2 becomes the first correction value CV 21. Here, since the first correction value CV21 changes with time from the time point t1, the first correction value CV21 at a predetermined time after the time point t1 is defined as Δ CV 21.

Next, the second correction value CV22 will be described.

The second correction value CV22 is a value determined by the ratio of the stroke of the piston 102 to the second correction pressure value CP22 determined by the inner diameter of the double acting cylinder 101.

The operator inputs the cylinder diameter of the used fluid pressure actuator 10 and the stroke of the piston 102 through the setting unit 206, calculates a second correction value CV22 corresponding to the input cylinder diameter and the stroke of the piston 102, and stores the second correction value CV22 in the storage unit 207.

Next, how to convert the pressure value of the first pressure operation chamber 103 or the second pressure operation chamber 104 into the movement amount of the piston 102 will be described.

The pressure value waveform P21 shown in fig. 7(a) is a waveform of a pressure value on the side where air intake is performed, among the first pressure acting chamber 103 and the second pressure acting chamber 104 of the fluid pressure actuator 10 that operates with a stroke and a moving time that are the same as the predetermined stroke and the predetermined moving time for which the first correction value CV21 and the second correction value CV22 are obtained.

First, as shown in fig. 7(a), a fluctuation amount Δ P211 of the pressure value that fluctuates with the passage of time is calculated with reference to the pressure value P3 at time t 1.

The fluctuation amount Δ P211 exceeding the pressure value P3 shown in the pressure value waveform P21 is a positive value, and the fluctuation amount Δ P211 falling below the pressure value P3 is a negative value.

Next, the first correction value CV21 obtained in advance is read from the storage unit 207, and as shown in fig. 7(b), the fluctuation amount Δ P211 of the pressure value for a predetermined time is added to Δ CV21, and the pressure value waveform P22 is obtained (for example, the value of Δ CV21 after 10 seconds of t1 is added to Δ P211 after 10 seconds of t 1). Here, the difference from the case of performing the exhaust throttle control is that the value indicated by the pressure value waveform P22 becomes a value exceeding the first correction value CV21 when Δ P211 is a negative value; when Δ P211 is a positive value, it becomes a value lower than the first correction value CV 21. The reason is that, as shown in equation 5 described later, the polarity of the increase and decrease in pressure accompanying the movement of the piston 102 is different from equation 1 in the case of performing the exhaust throttle control.

Finally, the pressure value is converted from MPa to mm. The second correction value CV22 obtained in advance is read from the storage unit 207, and the pressure value waveform P22 is multiplied by the second correction value CV22, thereby converting the result into the movement amount PD21 of the piston 102 shown in fig. 7 (c). For example, a value obtained by multiplying the pressure value P4 at the time point t2 in fig. 7(b) by the second correction value CV22 is a value converted into the amount of movement of the piston 102.

The following explains why the pressure value of the first pressure operation chamber 103 or the second pressure operation chamber 104 can be thus converted into the amount of movement of the piston 102.

First, the rate of change in pressure value (dP/dt) shown by the pressure value waveform P21 is expressed by the following expression 5.

(formula 5)

The method of deriving equation 5 is the same as equation 1, but the polarity of the increase and decrease in pressure accompanying the movement of the piston 102, that is, the sign of each item shown on the right side, is different from equation 1 in the case of performing the exhaust throttle control.

That is, the first term on the right side of equation 5 ("(RT/V) × (dM/dt)") is a positive value, and represents that the pressure value on the intake side of the first pressure operation chamber 103 or the second pressure operation chamber 104 is going to rise with the intake of the first pressure operation chamber 103 or the second pressure operation chamber 104, and for example, refers to a value that rises from the pressure value P3 at time t1 as indicated by a broken line in fig. 7 (a).

On the other hand, the second term ("P/V) × a × (dY/dt)") on the right side of equation 5 has a negative value, and represents that the pressure value is to be decreased as the piston 102 moves and the space of the pressure acting chamber on the intake side of the first pressure acting chamber 103 or the second pressure acting chamber 104 expands.

The conversion from the pressure value waveform P21 to the pressure value waveform P22 by the first correction value CV21 has a meaning of correcting the slope of the pressure value waveform P21, and the first term on the right side of equation 5, which is the pressure value to be raised as the intake air advances, is cancelled by correcting the slope of the pressure value waveform P21. Then, the rate of change in the pressure value (dP/dt) is assumed to be expressed by the above equation 4.

The right side of equation 4 can be said to be represented by the time differential value of the movement amount Y of the piston 102 and its coefficient, meaning that the value obtained by multiplying the time differential value of the movement amount Y of the piston 102 by the coefficient is equal to the time differential value of the pressure value P.

If the coefficient is regarded as corresponding to the second correction value CV22, the pressure value waveform P22 converted from the pressure value waveform P21 is converted into the movement amount PD21 of the piston 102 shown in fig. 7(c) by multiplying the second correction value CV22 as described above.

The waveform of the thus calculated movement amount PD21 is substantially the same as the waveform D21 indicating the movement amount of the piston 102 driven at the same stroke and the same movement time by the magnetostrictive sensor between the time point t1 and the time point t 2.

Therefore, even when the intake throttle control is performed, the position of the piston 102 can be detected without using a magnetostrictive sensor as in the related art. Since the position of the piston 102 can be detected both when the intake throttle control is performed and when the exhaust throttle control is performed, the intake throttle control and the exhaust throttle control can be used independently and separately in consideration of their characteristics, and therefore, the degree of freedom in designing equipment such as a robot arm and a gas claw used in a food factory is improved.

Here, in order to detect the position of the piston 102, it is necessary to detect the pressure value on the side where the flow rate of the fluid flowing into or out of the first pressure acting chamber 103 or the second pressure acting chamber 104 is controlled, in both the case of performing the intake throttle control and the case of performing the exhaust throttle control. The reason for this is described below.

This is because, in the case of the intake throttle control, the pressure value of the first pressure acting chamber 103 and the second pressure acting chamber 104 on the side where the fluid flows in is controlled by adjusting the flow rate of the fluid flowing into the first pressure acting chamber 103 or the second pressure acting chamber 104. In the case of the exhaust throttle control, the pressure value on the side of the first pressure acting chamber 103 and the second pressure acting chamber 104 from which the fluid flows out is controlled by adjusting the flow rate of the fluid flowing out from the first pressure acting chamber 103 or the second pressure acting chamber 104. Since the moving speed of the piston 102 is controlled by controlling the pressure value, the position of the piston 102 can be detected with high accuracy by detecting the pressure value on the side to be controlled among the pressure values of the first pressure operation chamber 103 and the second pressure operation chamber 104 and calculating the position of the piston 102.

Further, according to the piston position detection program 2012a, as in the case of performing the exhaust throttle control, even when an abnormality occurs in the driving of the piston 102, such as an excessive friction force between the piston 102 and the inner surface of the double acting cylinder 101 during the driving of the piston 102 or the operating rod 105 connected to the piston 102 hitting an obstacle, the position of the piston 102 can be accurately detected.

(1) As described above, according to the actuator operation detection device 20 of the present embodiment, which detects the position of the piston 102 of the fluid pressure actuator 10, the fluid pressure actuator 10 includes the piston 102 and the double acting cylinder 101 having the interior divided into the first pressure acting chamber 103 and the second pressure acting chamber 104 by the piston 102, and moves the piston 102 by flowing in and out of the fluid in the first pressure acting chamber 103 or the second pressure acting chamber 104, the operation amount detection device 20 includes: a first pressure transducer 202 that detects a pressure value of the first pressure apply chamber 103; a second pressure transducer 203 that detects a pressure value of the second pressure acting chamber 104; and a control unit 201 having a piston position detection program 2012a for calculating the movement amount of the piston 102 as the operation amount of the fluid pressure actuator based on the pressure value detected by the first pressure transducer 202 or the second pressure transducer 203. This makes it possible to provide the low-cost apparatus 20 for detecting the amount of actuation of the fluid pressure actuator, which can improve the degree of freedom in designing the apparatus without restricting the shape of the fluid pressure actuator 10.

That is, since the control unit 201 can calculate the position of the piston 102 from the pressure value of the first pressure acting chamber 103 or the second pressure acting chamber 104 detected by the first pressure transducer 202 or the second pressure transducer 203 by executing the piston position detection program 2012a, it is not necessary to use a special sensor for detecting the position of the piston 102, as in the case where, for example, a magnetostrictive sensor is mounted on the fluid pressure actuator 10. Since no sensor is used, the shape of the fluid pressure actuator 10 is not restricted by the shape of the sensor, and the degree of freedom in designing equipment such as a robot arm and a gas claw used in a food factory is improved.

Further, the pressure transducer is versatile, and even when a plurality of fluid pressure actuators 10 having different strokes are used, it is not necessary to prepare a plurality of magnetostrictive sensors corresponding to the strokes of the respective fluid pressure actuators, unlike the magnetostrictive sensors, and there is no fear of an increase in manufacturing cost.

(2) The device 20 for detecting the operation amount of a fluid pressure actuator according to (1), in which the fluid pressure actuator 10 is subjected to an intake throttle control, that is, the moving speed of the piston 102 is controlled by adjusting the flow rate of the fluid flowing into the first pressure acting chamber 103 or the second pressure acting chamber 104, and the controller 201 calculates the moving amount of the piston 102 from the pressure value on the side of the first pressure acting chamber 103 and the second pressure acting chamber 104 into which the fluid flows, based on the piston position detection program 2012 a. Alternatively, (3) the controller 201 controls the moving speed of the piston 102 by adjusting the flow rate of the fluid flowing out of the first pressure acting chamber 103 or the second pressure acting chamber 104 of the fluid pressure actuator 10, and the controller 201 calculates the moving amount of the piston 102 from the pressure value on the side from which the fluid is discharged out of the first pressure acting chamber 103 and the second pressure acting chamber 104 based on the piston position detection program 2012 a. Thus, when the intake air throttle control or the exhaust air throttle control is performed by the fluid pressure actuator 10, the position of the piston 102 can be calculated from the pressure value of the first pressure acting chamber 103 or the second pressure acting chamber 104. In both cases of performing the intake throttle control and the exhaust throttle control, the intake throttle control and the exhaust throttle control can be used separately and independently in consideration of their characteristics as long as the position of the piston 102 can be detected, and therefore, the degree of freedom in designing equipment such as a robot arm and a gas claw used in a food factory, for example, is improved.

Here, in order to detect the position of the piston 102, it is necessary to detect the pressure value on the side where the flow rate of the fluid flowing into or out of the first pressure acting chamber 103 or the second pressure acting chamber 104 is controlled, in both the case of performing the intake throttle control and the case of performing the exhaust throttle control. The reason for this is described below.

This is because, in the case of the intake throttle control, the pressure value of the first pressure acting chamber 103 and the second pressure acting chamber 104 on the side where the fluid flows in is controlled by adjusting the flow rate of the fluid flowing into the first pressure acting chamber 103 or the second pressure acting chamber 104. In the case of the exhaust throttle control, the pressure value on the side of the first pressure acting chamber 103 and the second pressure acting chamber 104 from which the fluid flows out is controlled by adjusting the flow rate of the fluid flowing out from the first pressure acting chamber 103 or the second pressure acting chamber 104. Since the moving speed of the piston 102 is controlled by controlling the pressure value, the position of the piston 102 can be detected with high accuracy by detecting the pressure value on the side to be controlled among the pressure values of the first pressure operation chamber 103 and the second pressure operation chamber 104 and calculating the position of the piston 102.

(4) The device 20 for detecting the amount of movement of a fluid pressure actuator according to any one of (1) to (3), wherein the controller 201 calculates the amount of change in the pressure value with the elapse of time of the pressure value of the first pressure working chamber 103 or the second pressure working chamber 104 detected by the first pressure transducer 202 or the second pressure transducer 203 based on the piston position detection program 2012a, and calculates the amount of movement of the piston 102 by converting the amount of change in the pressure value into the amount of movement of the piston 102 based on a predetermined correction value stored in advance in the memory 207 provided in the controller 201. (5) The correction values include first correction values CV11 and CV21 determined by the inner diameter of the double acting cylinder 101 and the stroke and movement time of the piston 102, and second correction values CV12 and CV22 determined by the ratio of the predetermined stroke of the piston 102 to the second correction pressure values CP12 and CP22 determined by the inner diameter of the double acting cylinder 101. The first correction values CV11 and CV21 are pressure values that increase in proportion to the passage of time from the time point when the movement of the piston 102 starts to zero to the time point when the movement of the piston 102 completes to the first correction pressure values CP11 and CP 21. The first corrected pressure values CP11 and CP21 are values obtained by subtracting, from the second corrected pressure values CP12 and CP22, a difference between a pressure value at the time point of starting movement of the piston 102 in the first pressure working chamber 103 or the second pressure working chamber 104 and a pressure value at the time point of completion of movement of the piston 102 when the piston 102 having a predetermined stroke is operated for a predetermined movement time. The control unit 201 calculates the amount of movement of the piston 102 by calculating the amounts of variation Δ P111, Δ P211 of the pressure values with the elapse of time based on the pressure values of the first pressure working chamber 103 or the second pressure working chamber 104 detected by the first pressure transducer 202 and the second pressure transducer 203 based on the piston position detection program 2012a and the pressure value at the time point of the start of movement of the piston 102, calculating the sum of the first correction values CV11, CV21 and the amounts of variation Δ P111, Δ P211 of the pressure values for the corresponding time, and multiplying the calculated sum by the second correction values CV12, CV 22. With the above configuration, the amount of movement of the piston 102 can be detected with high accuracy using the pressure value of the first pressure acting chamber 103 or the second pressure acting chamber 104. It has been conventionally thought that there is some relationship between the pressure value of the first pressure acting chamber 103 or the second pressure acting chamber 104 and the position of the piston 102, but it has not been considered that the position of the piston 102 can be detected with high accuracy using the pressure value. In this context, the applicant of the present invention has derived experimentally the following facts: as described above, the pressure value of the first pressure acting chamber 103 or the second pressure acting chamber 104 is converted based on the correction value, and the position of the piston 102 can be detected with high accuracy using the value obtained by the conversion.

Further, if the pressure value can be converted to the movement amount of the piston 102 by only addition, division, or multiplication of the pressure value using the correction value stored in advance, the influence of disturbance noise is less likely to be received, and delay in information processing by the CPU 2011 due to filter processing that has conventionally occurred can be prevented.

(6) The device 20 for detecting an amount of actuation of a fluid pressure actuator according to any one of (1) to (5), wherein the fluid pressure actuator 10 has: a first pipe 11 leading to the first pressure acting chamber 103 for flowing a fluid in or out; and a second conduit 12 leading to the second pressure acting chamber 104 for flowing a fluid in or out; the first pressure transducer 202 and the second pressure transducer 203 are disposed on the first pipe 11 and the second pipe 12, respectively. This increases the degree of freedom in the arrangement positions of the first pressure transducer 202 and the second pressure transducer 203, and improves the degree of freedom in the design of the apparatus.

That is, according to the pascal principle, the pressure applied to the inner wall of the first pressure acting chamber 103 and the inner wall of the first pipe 11 leading to the first pressure acting chamber 103 is uniform, and the pressure applied to the inner wall of the second pressure acting chamber 104 and the inner wall of the second pipe 12 leading to the second pressure acting chamber 104 is uniform. Thus, the first pressure transducer 202 disposed in the first pipe 11 leading to the first pressure acting chamber 103 can detect the pressure value of the first pressure acting chamber 103 regardless of the length of the first pipe 11, and the second pressure transducer 203 disposed in the second pipe 12 leading to the second pressure acting chamber 104 can detect the pressure value of the second pressure acting chamber 104 regardless of the length of the second pipe 12. Therefore, the first pressure transducer 202 and the second pressure transducer 203 do not need to be disposed in the vicinity of the fluid pressure actuator 10, and therefore the degree of freedom in disposing the first pressure transducer 202 and the second pressure transducer 203 is high, and the degree of freedom in designing the apparatus is improved.

The present embodiment is merely an example, and the present invention is not limited to the embodiment. Therefore, it is needless to say that various improvements and modifications can be made to the present invention without departing from the scope of the invention.

For example, in the present embodiment, the fluid pressure actuator 10 is exemplified by a pneumatic actuator that operates by compressed air, but may be a hydraulic actuator. Further, the fluid pressure actuator 10 does not necessarily have the operating rod 105, and may be applied to an actuator having a double acting cylinder such as a parallel hand.