JP2007278514A - Control method for flow control valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method for a flow control valve attaining flow control of high accuracy by reducing the individual difference of valve opening caused by the mounting accuracy of a detecting means. <P>SOLUTION: In this control method for the flow control valve 1, a detecting means 25 is provided for detecting the arrival of a piston 22 to close the valve from the state of the detecting means being turned OFF from ON or turned ON from OFF, and the difference between an operation signal when the detecting means 25 is turned OFF from ON or turned ON from OFF, and an operation signal value corresponding to the reference origin is set as an individual difference value to compensate a reference curve with the individual difference value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control method for a flow control valve that shifts to an open state when the pressure of compressed air resists the biasing force of a spring.

Conventionally, a flow control valve has been used to supply a chemical solution to a semiconductor manufacturing apparatus. In Japanese Patent Application No. 2001-274467, the present applicant has proposed a flow rate control valve capable of performing flow rate adjustment by remote control with high accuracy. FIG. 5 shows a cross-sectional view of the flow control valve 100.
The flow control valve 100 includes an underbody 27, a cylinder 23 fixed above the underbody 27, a housing 14 fixed above the cylinder 23, and a motor mounted on the housing 14 via a cover 12. 11 and the entire outer shape. Here, a stepping motor is employed as the motor 11.

  In the underbody 27, an input port 51 is formed on the left side in the drawing, an output port 52 is formed on the right side in the drawing, and an annular valve seat 54 is formed in the center. In addition, a substantially cylindrical piston 22 is slidable in the axial direction and is hermetically fitted in the cylinder 23. A pilot chamber 55 is defined by the lower surface of the piston 22 and the inner surface of the cylinder 23, and an operation port 53 formed in the cylinder 23 communicates with the pilot chamber 55. Further, a diaphragm 24 as a valve body is attached to the lower end of the piston 22, and the periphery of the diaphragm 24 is sandwiched between the underbody 27 and the cylinder 23. When the diaphragm 24 moves as the piston 22 moves up and down and comes into close contact with or separates from the valve seat 54, the input port 51 and the output port 52 are blocked or communicated.

  In addition, a return spring 20 that urges the piston 22 downward in the figure is mounted inside the substantially cylindrical housing 14. Further, a screw 16 screwed with a nut 19 as an abutting member is provided, and a return spring 21 is mounted between the nut 19 and the piston 22 in order to prevent backlash in the thrust direction of the nut 19 with respect to the screw 16. ing. The screw 16 is coupled to the shaft 56 by the coupling 13, and the rotation of the motor 11 provided on the upper portion of the housing 14 is transmitted to the screw 16 through the gear box 15 and the shaft 56. Further, in the flow control valve 100, an electropneumatic regulator unit 31 is attached to an operation port 53 formed in the cylinder 23. The electropneumatic regulator unit 31 operates a normally-closed intake proportional valve 32 and a normally-closed exhaust proportional valve 33 via a control board 35, and also includes a manually operated needle valve 34.

  In the flow control valve 100, the air pressure in the pilot chamber 55 is controlled by the electropneumatic regulator unit 31 through the operation port 53. The electropneumatic regulator unit 31 adjusts the air pressure in the pilot chamber 55 in response to the input electric signal, and moves the piston 22 upward in the figure against the return spring 20 by the increase in the air pressure. As a result, the diaphragm 24 is separated from the valve seat 54 and the flow control valve 100 is opened. Since the moved piston 22 is stopped when its upper surface comes into contact with the nut 19, the valve opening stop position, which is the position of the diaphragm 24, is defined by the stop position of the nut 19. The nut 19 is moved up and down by the rotation of the motor 11 transmitted to the screw 16.

  Conventionally, in the flow control valve 100, the electropneumatic regulator unit 31 and the motor 11 are operated by a controller (not shown) corresponding to the valve opening stop position and the valve opening operation time specified by the user. Here, the valve opening stop position is the stop position of the piston 22 by the nut 19 as described above, and the motor 11 is rotated to adjust the position of the nut 19 to the designated stop position. By controlling the motor 11 as a stepping motor according to the number of steps, the stop position of the nut 19 can be controlled with high accuracy.

  Further, the valve opening operation time is instructed by the user, and after the user instructs the valve opening operation in the valve closed state, the piston 22 is brought into contact with the nut 19 within the time to reach the valve opening stop position. It is something to be made. A controller (not shown) operates the electropneumatic regulator unit 31 to increase the air pressure in the pilot chamber 55 so that the piston 22 moves to the valve opening stop position within the valve opening operation time. In a semiconductor manufacturing process or the like, a faster valve opening operation is not better, and it is desired to gradually open the valve within a specified valve opening operation time and gradually increase the flow rate.

  Therefore, a controller (not shown) increases the air pressure at a constant rate per unit time so that the air pressure in the pilot chamber 55 becomes the maximum air pressure at the end of the valve opening operation time. Here, the maximum air pressure is the air pressure in the pilot chamber 55 for moving the piston 22 to the maximum valve opening stop position determined by the tip position of the screw 16. An example of the relationship between the time from the instruction to open the valve and the air pressure in the pilot chamber 55 is shown in FIG. The example of FIG. 6 shows a case where the valve opening operation time is 2 seconds and the maximum air pressure is 0.3 MPa. As shown in FIG. 6, the air pressure in the pilot chamber 55 is increased at a constant rate during 2 seconds of the valve opening operation time so that the maximum air pressure becomes 0.3 MPa at the end of 2 seconds.

  However, in the flow control valve 100, a controller (not shown) outputs an operation signal for operating the motor 11 in order to stop the nut 19 at a predetermined stop position. At this time, when the origin that is the reference position of the motor 11 or the nut 19 is detected by a detecting means such as a sensor, the operation of the motor 11 by a controller (not shown) is performed with reference to the origin. Therefore, if there is a variation in the mounting accuracy of sensors or the like, individual differences due to individual valves occur in the relationship between the operation signal output by a controller (not shown) and the stop position of the nut 19. However, since it is very difficult to improve the mounting accuracy of the sensor in assembly work, there is a problem that it is very difficult to reduce individual differences of valves.

  In particular, this problem becomes important when the flow control valve 100 is used in open loop control. A general method of using the flow rate control valve 100 is feedback control performed by feeding back flow rate data. However, for example, when the fluid outflow time is short, feedback control becomes difficult due to a problem of responsiveness. In such a case, it is used in open loop control, and the motor 11 is operated only by an operation signal output by a controller (not shown). Accordingly, in this case, the individual difference in the origin position becomes the individual difference in the stop position of the nut 19 as it is, and is directly connected to the individual difference in the valve opening. Therefore, in particular, it is desirable that the individual difference in the origin position is small.

  Accordingly, the present invention has been made to solve the above-described problems, and a flow rate control valve that enables highly accurate flow rate control by reducing individual differences in valve opening due to mounting accuracy of detection means. It is an object to provide a control method.

The invention according to claim 1, which has been made to solve the above-described problem, is the compression provided to the pilot chamber while the valve body provided at the tip of the piston is brought into close contact with the valve seat by the biasing force of the spring. By moving the piston with the pressure of air, the valve body is separated from the valve seat to be in an open state, and further, the rotation of the motor is converted into linear movement of the contact member by the deceleration conversion means, Based on a reference curve indicating the relationship between the stop position of the contact member and the operation signal, the motor is operated so that the contact member moves to the stop position and is stopped, and the piston hits the contact member. In the control method of the flow rate control valve in which the valve opening stop position of the valve body is determined and the flow rate of the fluid is adjusted, whether the piston has reached the valve closing state from on to off or off. Detection means is provided to detect when turned on, and the difference between the operation signal value when the detection means is turned from on to off or from off to on and the operation signal value corresponding to the reference origin is an individual difference value. The reference curve is compensated by the individual difference value.
The invention according to claim 2 is characterized in that, in the method for controlling a flow rate control valve according to claim 1, the flow rate control valve is used by open loop control.

  That is, in the flow rate control valve controlled by the control method of the present invention, the detection means detects that the piston has reached the valve closing. Further, the operation signal value when the detection means is turned off from on or turned off to on can be obtained as an individual difference value by comparing with the operation signal value corresponding to the reference origin. If the reference curve is corrected by the individual difference value, the relationship between the stop position of the contact member and the operation signal is determined based on the corrected reference curve. Therefore, the individual difference due to the error in the attachment position of the detection means can be compensated by the individual difference value. Thereby, the error by the individual difference of a flow control valve is reduced, and highly accurate flow control is attained. Furthermore, individual differences due to variations in spring set load can be compensated. The fluid outflow time is short, feedback control is difficult due to responsiveness problems, and this is particularly effective when open loop control is performed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. A cross-sectional view of a flow control valve 1 controlled by the control method of the present embodiment is shown in FIG. The control method of the present invention is a method of controlling the flow control valve 1 described in the section of the prior art by a controller (not shown). The flow control valve 1 is obtained by attaching an origin switch 25 and an adjustment limit point switch 26 to the flow control valve 100 described in the prior art. Since other parts are the same as those of the flow control valve 100, description thereof is omitted here.

  As shown in FIG. 1, two detection elements 19 a and 19 b are provided on the upper surface of the nut 19, and extend upward through a hole provided in the housing 14. In the housing 14, an origin switch 25 and an adjustment limit point switch 26 are provided on both sides of the coupling 13. The origin switch 25 and the adjustment limit point switch 26 are both optical switches, and as shown in FIG. 2, the light is blocked by the tips of the detected elements 19a and 19b, so that the position of the nut 19 is detected. The

  The storage device of the controller (not shown) stores the relationship between the air pressure in the pilot chamber 55 and the stroke of the piston 22 in the flow control valve 1 as shown in FIG. The numerical value displayed in this graph is an example, but is determined by the configuration of the return springs 20, 21 and the like, and is a relationship inherent to the flow control valve 1, and is stored in advance in a storage device of a controller (not shown). I can leave it to you. In the flow control valve 1, when the air pressure in the pilot chamber 55 becomes 0.16 MPa or more, the piston 22 starts to move against the urging force of the return springs 20 and 21. Therefore, in this flow control valve 1, the immobility limit pressure that is the pressure immediately before the piston 22 moves is 0.15 MPa.

  Further, when the flow control valve 1 is operated, the user instructs the valve opening stop position and the valve opening operation time. A controller (not shown) calculates the valve opening air pressure, which is the minimum air pressure for opening the valve to the indicated valve opening stop position, from the relationship between the air pressure in the pilot chamber 55 stored in the storage device and the stroke of the piston 22. calculate. Further, a target air pressure is set to a pressure obtained by adding 0.01 MPa in order to obtain a stable valve open state. For example, as shown in FIG. 7, at the valve opening stop position of 1.4 mm, the valve opening air pressure is 0.21 MPa and the target air pressure is 0.22 MPa. At the valve opening stop position of 2.6 mm, the valve opening air pressure is 0.25 MPa and the target air pressure is 0.26 MPa.

  Next, a controller (not shown) increases the air pressure in the pilot chamber 55 at a constant rate from the immobility limit pressure, and calculates the increase rate of the air pressure in order to reach the target air pressure within the valve opening operation time specified by the user. . That is, (air pressure increase amount per unit time) = (target air pressure−immobility limit pressure) / (valve opening operation time).

  Further, in the control method for the flow control valve 1 of the present embodiment, before starting the valve opening operation, the controller (not shown) operates the motor 11 to move the nut 19 to the valve opening stop position instructed by the user. Let In this flow control valve 1, since the motor 11 is a stepping motor, a controller (not shown) can precisely operate the motor 11 by inputting a pulse corresponding to the number of rotation steps to the motor 11. The rotation of the motor 11 is decelerated by the gear box 15 and transmitted as the rotation of the screw 16 via the shaft 56 and the coupling 13. Since rotation of the screw 16 is converted into linear movement of the nut 19 in the axial direction, a controller (not shown) can operate the position of the nut 19 by the number of rotation steps of the motor 11.

  Here, the gear box 15 and the deceleration conversion means such as between the screw 16 and the nut 19 have backlash. Even if the motor 11 is precisely operated, an error due to backlash occurs in the position of the nut 19. To do. The backlash is substantially the same regardless of the rotation direction of the motor 11, and can be canceled by always rotating the motor 11 in the same predetermined rotation direction before stopping the motor 11. Therefore, when the rotation direction of the motor 11 for moving the nut 19 to the designated valve opening stop position is the reverse direction of the predetermined direction, the motor 11 is rotated excessively and the nut 19 is stopped at the stop position. , And then, it is rotated in a predetermined direction by the number of extra rotated steps. The number of extra rotation steps is sufficiently larger than the rotation amount of the motor 11 in which the nut 19 does not move even if the motor 11 is rotated by backlash, and is not shown as a unique value depending on the configuration of the flow control valve 1. Remember me.

  For example, assuming that the backlash of the flow control valve 1 is about 50 steps, the controller storage unit (not shown) stores 100 steps as the rotation amount for canceling the backlash. Moreover, the normal rotation of the direction which increases the step number of the motor 11 as a predetermined rotation direction is set. From these, if the movement direction for moving the nut 19 to the valve opening stop position is the normal rotation direction of the motor 11, the controller (not shown) sends pulses to the motor 11 for the number of steps corresponding to the movement distance of the nut 19. Output. On the other hand, if the movement direction for moving the nut 19 to the valve opening stop position is the reverse rotation direction of the motor 11, the controller (not shown) has the number of steps according to the movement distance of the nut 19 +100 for canceling backlash. A reverse rotation direction pulse for the step is output to the motor 11. Then, 100-step forward rotation direction pulses are output.

  For example, when the nut 19 located at the 1000 step position in the number of steps of the motor 11 is moved to the 2000 step position, a controller (not shown) outputs a pulse for 1000 forward rotations to the motor 11, and the motor 11 is equivalent to 1000 steps. Rotate forward and stop. On the other hand, when the nut 19 located at the 2000 step position is moved to the 1000 step position, a controller (not shown) outputs a pulse corresponding to 1100 steps of reverse rotation 100 steps beyond the movement amount to the motor 11. Therefore, the motor 11 rotates in reverse for 1100 steps, and backlash for about 50 steps is included therein. Thereafter, a controller (not shown) outputs pulses for 100 steps of forward rotation to the motor 11. For this reason, the motor 11 rotates forward for 100 steps, of which about 50 steps of backlash are included. These two backlashes for 50 pulses are canceled out because they are in opposite directions. As a result, there is no error due to backlash in both the forward rotation and the reverse rotation, and the position of the nut 19 can be precisely controlled. Therefore, the valve opening stop position is precisely controlled.

  Next, the valve opening operation of the flow control valve 1 will be described. FIG. 3 is a graph showing a change in air pressure in the pilot chamber 55 operated by the control method embodying the present invention. In the control method of the flow control valve 1 of the present embodiment, a controller (not shown) operates the electropneumatic regulator unit 31 together with an instruction to start the valve opening operation by the user, and the air pressure in the pilot chamber 55 is reduced to the immobility limit pressure. Raise. Here, since the immobility limit pressure is 0.15 MPa, a controller (not shown) inputs an electric signal corresponding to the air pressure of 0.15 MPa in the pilot chamber 55 to the electropneumatic regulator unit 31.

  Subsequently, the electrical signal input to the electropneumatic regulator unit 31 is increased at a rate corresponding to the air pressure increase per unit time calculated in advance. FIG. 3 shows a graph 61 showing a change in air pressure in the pilot chamber 55 when the valve opening operation time is 2 seconds and the valve opening stop position is 2.6 mm, and the valve opening operation position is 1.4 mm when the valve opening operation time is 2 seconds. The graph 62 showing the change of the air pressure of the pilot chamber 55 in the case is shown. As shown in FIG. 3, when the valve opening operation time is 2 seconds and the valve opening stop position is 2.6 mm, the pilot chamber 55 is raised from the stationary limit pressure of 0.15 MPa to the target air pressure of 0.26 MPa within 2 seconds. In addition, a controller (not shown) changes an electric signal input to the electropneumatic regulator unit 31.

  In the flow control valve 1, the piston 22 moves when the pressure in the pilot chamber 55 ranges from (immobility limit pressure + 0.01 MPa) to valve opening air pressure. For example, at the valve opening stop position of 2.6 mm, the range of 0.16 to 0.25 MPa is the pressure at which the piston 22 can move. On the other hand, according to the control method of the flow control valve 1, as shown in the graph 61 of FIG. 3, the air pressure in the pilot chamber 55 is first raised to 0.16 MPa and then slowly increased over the valve opening operation time. Therefore, since the piston 22 can be actually moved to 0.16 MPa in a very short time after an instruction to start the valve opening operation by the user, the rise of the valve opening operation is accelerated. Further, the time when the diaphragm 24 moves together with the piston 22 and the flow rate of the control fluid is changed is time TC as shown in FIG. Compared to the time TA as shown in FIG. 6 in the prior art, the time during which the piston 22 and the diaphragm 24 are actually moving out of the valve opening operation time of 2 seconds becomes longer, and the flow rate of the control fluid is further increased. It could be increased slowly. Further, when the valve opening stop position is 1.4 mm, the time TD is compared with the conventional time TB, which is more effective.

  Further, in the flow control valve 1 of the present embodiment, an origin switch 25 and an adjustment limit point switch 26 are provided in order to detect the origin position and the adjustment limit point, which are the upper and lower limit positions of the movement range of the nut 19. (See FIG. 1). When returning the nut 19 to the origin (or adjustment limit point), the motor 11 is rotated and the origin position (or adjustment limit) detected by this origin switch 25 (or adjustment limit point switch 26). Move to (point position). At this time, the backlash is canceled by rotating the nut 19 in a predetermined direction as in the case of moving the nut 19 to the valve opening stop position. Alternatively, if the switch has a hysteresis, the hysteresis is also canceled at the same time.

  Specifically, for example, a case where the origin of the nut 19 is detected will be described. When the predetermined direction of rotation of the motor 11 is a direction in which the nut 19 is brought closer to the origin, the nut 19 approaches the origin by the rotation of the motor 11 in a predetermined direction, and stops when the origin switch 25 is turned on. On the other hand, when the predetermined direction of rotation of the motor 11 is a direction in which the nut 19 is moved away from the origin, the nut 19 approaches the origin by the reverse rotation of the motor 11 in the predetermined direction, and the origin switch 25 is turned on. The motor 11 is reversed, the motor 11 is rotated in a predetermined direction, and is stopped when the origin switch 25 is turned off.

  As a result, the origin (or adjustment limit point) of the motor 11 can be detected, and errors due to backlash and hysteresis of the detection switch can be detected even when the nut 19 is moved to the origin position (or adjustment limit point position). Does not occur. In addition, when the flow control valve 1 is used, if it is detected that the position of the nut 19 has reached the origin or the adjustment limit point, or if it is instructed to move beyond the origin or the adjustment limit point, a controller (not shown) Displays a warning to the user and does not move further.

  Furthermore, in the control method of the flow rate control valve 1 of the present embodiment, a stepping motor is used as the motor 11, and this generates a relatively large amount of heat when energized. Therefore, after stopping the nut 19 at a desired stop position, a controller (not shown) cuts off the energization of the motor 11. This prevents the liquid temperature of the control fluid from rising.

  Furthermore, in the control method of the flow control valve 1 of the present embodiment, in order to operate the motor 11, an operation signal such as a pulse is transmitted by a controller (not shown). The motor 11 is operated by this operation signal, and as a result, the nut 19 moves and stops. If the air pressure in the pilot chamber 55 is increased by the electropneumatic regulator unit 31, the piston 22 is brought into contact with the nut 19, so the stop position of the nut 19 corresponds to the opening of the valve. The relationship between the opening of the valve and the operation signal to the motor 11 is shown in FIG.

  The origin corresponding to the reference position of the motor 11 is detected by the origin switch 25, and it is inevitable that some individual differences occur due to the mounting accuracy of the origin switch 25. When the attachment position of the origin switch 25 is the reference position, the relationship between the operation signal and the valve opening is a reference curve L1 indicated by a solid line in FIG. On the other hand, when the origin position of the motor 11 is shifted due to the accuracy of the attachment position of the origin switch 25, the sample curves L2 and L3 shown in FIG. The individual difference values k1 and k2 are obtained by measuring the difference between the sample curves L2 and L3 and the reference curve L1. This deviation is caused by a deviation in the mounting position of the origin switch 25, and the amount of increase in the opening of the valve with respect to the operation signal (slope of the graph) is the same for any flow control valve 1.

  When each flow control valve 1 is controlled, the individual difference values k1 and k2 measured with respect to the reference operation signal are adjusted. When the valve is opened even with an operation signal that is smaller than the reference value when the installation position of the origin switch 25 is slightly above as shown in the sample curve L2, the operation is performed according to operation signal = (reference operation signal−individual difference value k1). . Also, as shown in the sample curve L3, when the valve is not opened unless the operation position of the origin switch 25 is slightly lower and the operation signal is larger than the reference value, the operation signal = (reference operation signal + individual difference value k2). Operate by. By specifying these individual difference values k1 and k2 in the respective flow control valves 1 with signs, it is possible to perform control with reduced individual differences. In particular, even when used in open loop control, highly accurate flow rate control can be performed.

  As described above in detail, according to the control method of the flow control valve 1 of the present embodiment, the piston 22 is moved by the pressure of the compressed air supplied into the pilot chamber 55 by operating the electropneumatic regulator unit 31. With respect to the flow control valve 1 that opens the valve, the pressure of compressed air supplied into the pilot chamber 55 is adjusted at the start of the valve opening operation so that the inside of the pilot chamber 55 becomes the stationary limit pressure. The regulator unit 31 is operated. This immobility limit pressure is the air pressure immediately before the piston 22 moves against the urging force of the return spring 20, so that the piston 22 does not move as it is, but if the air pressure rises even slightly, the piston 22 immediately Start moving to. Subsequently, the air pressure in the pilot chamber 55 is increased, and the electropneumatic regulator unit 31 is operated so that the piston 22 reaches the desired valve opening stop position during the desired valve opening operation time. Accordingly, the movement of the piston 22 and the diaphragm 24 can be started in a very short time from the start of the valve opening operation, and the valve opening stop position can be reached immediately before the end of the valve opening operation time. Most of the time can be the time during which the diaphragm 24 is actually moving. As a result, the rise of the valve opening operation is fast, and the time during which the piston 22 and the diaphragm 24 are actually moving can be increased during the valve opening operation time, so that the reliability of the flow rate control can be improved. .

  Further, in the flow control valve 1 controlled by the control method of the present embodiment, the motor 11 is operated to move the nut 19 to the stop position, and the valve 22 stop position is determined by the piston 22 abutting against the nut 19. The Therefore, when the rotation direction of the motor 11 for moving the nut 19 to the stop position is a predetermined direction, the motor 11 is rotated in a predetermined direction to stop the nut 19 at the stop position. Rotate in the direction and then stop. On the other hand, when the rotation direction of the motor for moving the nut 19 to the stop position is the reverse direction of the predetermined direction, the motor 11 is rotated in the reverse direction so that the nut 19 passes the stop position. Is rotated in a predetermined direction to stop the nut 19 at the stop position. Therefore, when the motor 11 is stopped, the motor 11 rotates in a predetermined direction and then stops. Therefore, in any case, since the motor 11 is rotated after being rotated in a predetermined direction, the backlash due to the change in the rotation direction is canceled, and the nut 19 can be accurately positioned without any error due to the backlash. As a result, the influence of backlash is reduced and high-precision flow rate control is possible.

  Further, the stop positions of the nut 19 include origins and adjustment limit points located at both ends of the movable range, and the motor 11 is rotated and stopped in a predetermined direction by the same control method. As a result, when the nut 19 is stopped at the origin or the adjustment limit point, an error due to backlash can be eliminated. Further, if the origin switch 25 or the adjustment limit point switch 26 is provided to detect the origin and the adjustment limit point, it is possible to accurately detect that the contact member has reached the position. On the other hand, when the origin switch 25 or the adjustment limit point switch 26 is provided, a hysteresis occurs between these switches. Even at this point, it is effective to stop the motor 11 by rotating it in a predetermined direction. That is, if the movement of the nut 19 to the origin or the adjustment limit point is a rotation of the motor 11 in a predetermined direction, the motor 11 is stopped when the origin switch 25 or the adjustment limit point switch 26 detects the nut 19. Alternatively, if the motor 11 rotates in the reverse direction in a predetermined direction, when the origin switch 25 or the adjustment limit point switch 26 detects the nut 19, the motor 11 is rotated in the reverse direction (that is, the predetermined direction). When the switch 25 or the adjustment limit point switch 26 no longer detects the nut 19, the motor 11 is stopped. Thus, by rotating the motor 11 in a predetermined direction and stopping it, the hysteresis of the detection means can be canceled out. Further, after the nut 19 is stopped at the stop position, the energization to the motor 11 is interrupted, so that the motor 11 can be prevented from generating heat and the control fluid can be prevented from rising in temperature.

  Furthermore, in the flow control valve 1 controlled by the control method of the present embodiment, the origin switch 25 detects that the nut 19 has reached the origin. Further, the operation signal value when the origin switch 25 detects the nut 19 can be compared with the operation signal value corresponding to the reference origin to obtain individual difference values k1 and k2. If the reference curve L1 is compensated by the individual difference value, the relationship between the stop position of the nut 19 and the operation signal is determined based on the compensated reference curve. Accordingly, individual differences due to errors in the attachment position of the origin switch 25 can be compensated by the individual difference values k1 and k2. Thereby, the error by the individual difference of the flow control valve 1 is reduced, and highly accurate flow control is possible. The fluid outflow time is short, feedback control is difficult due to responsiveness problems, and this is particularly effective when open loop control is performed.

  Further, FIG. 8 shows a cross-sectional view of the flow control valve 1 controlled by the control method of the embodiment different from the above. The control method of the present invention is a method of controlling the flow control valve 1 described in the section of the prior art by a controller (not shown). The flow control valve 1 is obtained by attaching an origin switch 25 and an adjustment limit point switch 26 to the flow control valve 100 described in the prior art. Since other parts are the same as those of the flow control valve 100, description thereof is omitted here.

As shown in FIG. 8, two detection elements 19 a and 19 b are provided on the top surface of the nut 19, and extend upward through a hole provided in the housing 14. In the housing 14, an origin switch 25 and an adjustment limit point switch 26 are provided on both sides of the coupling 13. The origin switch 25 and the adjustment limit point switch 26 are both optical switches. As shown in FIG. 9, the light is blocked by the tip portions of the detected elements 19a and 19b, so that the position of the nut 19 is detected. The This origin switch 25 corresponds to the detecting means described in claim 1.
In addition, the to-be-detected child 19a does not take the structure which leaves | separates below the origin switch 25. FIG.

  The storage device of the controller (not shown) stores the relationship between the air pressure in the pilot chamber 55 and the stroke of the piston 22 in the flow control valve 1 as shown in FIG. The numerical value displayed in this graph is an example, but is determined by the configuration of the return springs 20, 21 and the like, and is a relationship inherent to the flow control valve 1, and is stored in advance in a storage device of a controller (not shown). I can leave it to you. In the flow control valve 1, when the air pressure in the pilot chamber 55 becomes 0.16 MPa or more, the piston 22 starts to move against the urging force of the return springs 20 and 21. Therefore, in this flow control valve 1, the immobility limit pressure that is the pressure immediately before the piston 22 moves is 0.15 MPa.

  Further, when the flow control valve 1 is operated, the user instructs the valve opening stop position and the valve opening operation time. A controller (not shown) calculates the valve opening air pressure, which is the minimum air pressure for opening the valve to the indicated valve opening stop position, from the relationship between the air pressure in the pilot chamber 55 stored in the storage device and the stroke of the piston 22. calculate. Further, a target air pressure is set to a pressure obtained by adding 0.01 MPa in order to obtain a stable valve open state. For example, as shown in FIG. 7, at the valve opening stop position of 1.4 mm, the valve opening air pressure is 0.21 MPa and the target air pressure is 0.22 MPa. At the valve opening stop position of 2.6 mm, the valve opening air pressure is 0.25 MPa and the target air pressure is 0.26 MPa.

  Next, a controller (not shown) increases the air pressure in the pilot chamber 55 at a constant rate from the immobility limit pressure, and calculates the increase rate of the air pressure in order to reach the target air pressure within the valve opening operation time specified by the user. . That is, (air pressure increase amount per unit time) = (target air pressure−immobility limit pressure) / (valve opening operation time).

  Further, in the control method for the flow control valve 1 of the present embodiment, before starting the valve opening operation, the controller (not shown) operates the motor 11 to move the nut 19 to the valve opening stop position instructed by the user. Let In this flow control valve 1, since the motor 11 is a stepping motor, a controller (not shown) can precisely operate the motor 11 by inputting a pulse corresponding to the number of rotation steps to the motor 11. The rotation of the motor 11 is decelerated by the gear box 15 and transmitted as the rotation of the screw 16 via the shaft 56 and the coupling 13. Since rotation of the screw 16 is converted into linear movement of the nut 19 in the axial direction, a controller (not shown) can operate the position of the nut 19 by the number of rotation steps of the motor 11.

  Here, the gear box 15 and the deceleration conversion means such as between the screw 16 and the nut 19 have backlash. Even if the motor 11 is precisely operated, an error due to backlash occurs in the position of the nut 19. To do. The backlash is substantially the same regardless of the rotation direction of the motor 11, and can be canceled by always rotating the motor 11 in the same predetermined rotation direction before stopping the motor 11. Therefore, when the rotation direction of the motor 11 for moving the nut 19 to the designated valve opening stop position is the reverse direction of the predetermined direction, the motor 11 is rotated excessively and the nut 19 is stopped at the stop position. , And then, it is rotated in a predetermined direction by the number of extra rotated steps. The number of extra rotation steps is sufficiently larger than the rotation amount of the motor 11 in which the nut 19 does not move even if the motor 11 is rotated by backlash, and is not shown as a unique value depending on the configuration of the flow control valve 1. Remember me.

  For example, assuming that the backlash of the flow control valve 1 is about 50 steps, the controller storage unit (not shown) stores 100 steps as the rotation amount for canceling the backlash. Moreover, the normal rotation of the direction which increases the step number of the motor 11 as a predetermined rotation direction is set. From these, if the movement direction for moving the nut 19 to the valve opening stop position is the forward rotation direction of the motor 11 (the direction in which the nut 19 is moved upward), the controller (not shown) can respond to the movement distance of the nut 19. Pulses corresponding to the number of steps are output to the motor 11. On the other hand, if the moving direction for moving the nut 19 to the valve opening stop position is the reverse rotation direction of the motor 11 (the direction in which the nut 19 is moved downward), the controller (not shown) corresponds to the moving distance of the nut 19. The number of steps plus a reverse rotation direction pulse for 100 steps for canceling backlash is output to the motor 11. Then, 100-step forward rotation direction pulses are output.

  For example, when the nut 19 located at the 1000 step position in the number of steps of the motor 11 is moved to the 2000 step position, a controller (not shown) outputs a pulse for 1000 forward rotations to the motor 11, and the motor 11 is equivalent to 1000 steps. Rotate forward and stop. On the other hand, when the nut 19 located at the 2000 step position is moved to the 1000 step position, a controller (not shown) outputs a pulse corresponding to 1100 steps of reverse rotation 100 steps beyond the movement amount to the motor 11. Therefore, the motor 11 rotates in reverse for 1100 steps, and backlash for about 50 steps is included therein. Thereafter, a controller (not shown) outputs pulses for 100 steps of forward rotation to the motor 11. For this reason, the motor 11 rotates forward for 100 steps, of which about 50 steps of backlash are included. These two backlashes for 50 pulses are canceled out because they are in opposite directions. As a result, there is no error due to backlash in both the forward rotation and the reverse rotation, and the position of the nut 19 can be precisely controlled. Therefore, the valve opening stop position is precisely controlled.

  Next, the valve opening operation of the flow control valve 1 will be described. FIG. 10 is a graph showing a change in air pressure in the pilot chamber 55 operated by the control method embodying the present invention. In the control method of the flow control valve 1 of the present embodiment, a controller (not shown) operates the electropneumatic regulator unit 31 together with an instruction to start the valve opening operation by the user, and the air pressure in the pilot chamber 55 is reduced to the immobility limit pressure. Raise. Here, since the immobility limit pressure is 0.15 MPa, a controller (not shown) inputs an electric signal corresponding to the air pressure of 0.15 MPa in the pilot chamber 55 to the electropneumatic regulator unit 31.

  Subsequently, the electrical signal input to the electropneumatic regulator unit 31 is increased at a rate corresponding to the air pressure increase per unit time calculated in advance. FIG. 10 shows a graph 61 showing a change in air pressure in the pilot chamber 55 when the valve opening operation time is 2 seconds and the valve opening stop position is 2.6 mm, and the valve opening stop position is 1.4 mm when the valve opening operation time is 2 seconds. The graph 62 showing the change of the air pressure of the pilot chamber 55 in the case is shown. As shown in FIG. 10, when the valve opening operation time is 2 seconds and the valve opening stop position is 2.6 mm, the pilot chamber 55 is raised from the stationary limit pressure 0.15 MPa to the target air pressure 0.26 MPa within 2 seconds. In addition, a controller (not shown) changes an electric signal input to the electropneumatic regulator unit 31.

  In the flow control valve 1, the piston 22 moves when the pressure in the pilot chamber 55 ranges from (immobility limit pressure + 0.01 MPa) to valve opening air pressure. For example, at the valve opening stop position of 2.6 mm, the range of 0.16 to 0.25 MPa is the pressure at which the piston 22 can move. On the other hand, according to the control method of the flow control valve 1, as shown in the graph 61 of FIG. 10, the air pressure in the pilot chamber 55 is first raised to 0.16 MPa and then slowly increased over the valve opening operation time. Therefore, since the piston 22 can be actually moved to 0.16 MPa in a very short time after an instruction to start the valve opening operation by the user, the rise of the valve opening operation is accelerated. Further, the time when the diaphragm 24 moves together with the piston 22 and the flow rate of the control fluid is changed is time TC as shown in FIG. Compared to the time TA as shown in FIG. 6 in the prior art, the time during which the piston 22 and the diaphragm 24 are actually moving out of the valve opening operation time of 2 seconds becomes longer, and the flow rate of the control fluid is further increased. It could be increased slowly. Further, when the valve opening stop position is 1.4 mm, the time TD is compared with the conventional time TB, which is more effective.

  Further, in the flow control valve 1 of the present embodiment, an origin switch 25 and an adjustment limit point switch 26 are provided in order to detect the origin position and the adjustment limit point, which are the upper and lower limit positions of the movement range of the nut 19. (See FIG. 8). When returning the nut 19 to the origin (or adjustment limit point), the motor 11 is rotated and the origin position (or adjustment limit) detected by this origin switch 25 (or adjustment limit point switch 26). Move to (point position). In particular, when the nut 19 is returned to the origin, the backlash is canceled by rotating the nut 19 in a predetermined direction as in the case of moving the nut 19 to the valve opening stop position. If there is a hysteresis in the switch, the hysteresis is also canceled at the same time.

Specifically, a case where the origin of the nut 19 is detected will be described. As shown in FIG. 15A, when the origin switch 25 is OFF, the motor 11 is rotated in a direction to move the nut 19 downward, and when the origin switch 25 is turned ON, backlash is generated. In order to cancel the rotation, the motor 11 is rotated in the direction in which the nut 19 is moved downward by an additional 100 steps. Thereafter, the motor 11 is rotated in the direction in which the nut 19 is moved upward, and is stopped when the origin switch 25 is turned off.
As shown in FIG. 15B, when the origin switch 25 is ON, first, the motor 11 is moved in a direction to move the nut 19 downward for 100 steps to cancel backlash. Rotate. Thereafter, the motor 11 is rotated in the direction in which the nut 19 is moved upward, and is stopped when the origin switch 25 is turned off.
A case where the adjustment limit point of the nut 19 is detected will be described. The rotation of the motor 11 causes the nut 19 to approach the adjustment limit point and stops when the adjustment limit point switch 26 is turned on.

  As a result, the origin (or adjustment limit point) of the motor 11 can be detected, and errors due to backlash and detection switch hysteresis do not occur even when the nut 19 is moved to the origin position. In addition, when the flow control valve 1 is used, if it is detected that the position of the nut 19 has reached the origin or the adjustment limit point, or if it is instructed to move beyond the origin or the adjustment limit point, a controller (not shown) Displays a warning to the user and does not move further.

  Furthermore, in the control method of the flow rate control valve 1 of the present embodiment, a stepping motor is used as the motor 11, and this generates a relatively large amount of heat when energized. Therefore, after stopping the nut 19 at a desired stop position, a controller (not shown) cuts off the energization of the motor 11. This prevents the liquid temperature of the control fluid from rising.

  Furthermore, in the control method of the flow control valve 1 of the present embodiment, in order to operate the motor 11, an operation signal such as a pulse is transmitted by a controller (not shown). The motor 11 is operated by this operation signal, and as a result, the nut 19 moves and stops. If the air pressure in the pilot chamber 55 is increased by the electropneumatic regulator unit 31, the piston 22 is brought into contact with the nut 19, so the stop position of the nut 19 corresponds to the opening of the valve. The relationship between the opening of the valve and the operation signal to the electropneumatic regulator unit 31 is shown in FIG.

  It is inevitable that some individual differences occur between the operation signal and the opening of the valve due to variations in the load of the return spring 20 or the like. The relationship between the operation signal and the opening of the valve is a reference straight line L1 indicated by a solid line in FIG. On the other hand, for example, sample curves L2 and L3 shown in FIG. The differences between the sample curves L2 and L3 and the reference curve L1 are measured to obtain individual differences k1 and k2. In many cases, this deviation is greatly affected by variations in the load of the return spring 20, and the amount of increase in the valve opening relative to the operation signal (slope of the graph) is the amount of increase in the valve opening relative to the operation signal (slope of the graph). Is the same for any flow control valve 1.

  When each flow control valve 1 is controlled, the individual difference values k1 and k2 measured with respect to the reference operation signal are adjusted. When the set load of the return spring 20 is slightly small and the valve is opened even with an operation signal smaller than the reference value as in the sample curve L2, the operation is performed according to operation signal = (reference operation signal−individual difference value k1). Also, as in the sample curve L3, when the set load of the return spring 20 is slightly large and the valve does not open unless the operation signal is larger than the reference value, the operation signal = (reference operation signal + individual difference value k2). Manipulate. By specifying these individual difference values k1 and k2 in the respective flow control valves 1 with signs, it is possible to perform control with reduced individual differences. In particular, even when used in open loop control, highly accurate flow rate control can be performed.

  As described above in detail, according to the control method of the flow control valve 1 of the present embodiment, the piston 22 is moved by the pressure of the compressed air supplied into the pilot chamber 55 by operating the electropneumatic regulator unit 31. With respect to the flow control valve 1 that opens the valve, the pressure of compressed air supplied into the pilot chamber 55 is adjusted at the start of the valve opening operation so that the inside of the pilot chamber 55 becomes the stationary limit pressure. The regulator unit 31 is operated. This immobility limit pressure is the air pressure immediately before the piston 22 moves against the urging force of the return spring 20, so that the piston 22 does not move as it is, but if the air pressure rises even slightly, the piston 22 immediately Start moving to. Subsequently, the air pressure in the pilot chamber 55 is increased, and the electropneumatic regulator unit 31 is operated so that the piston 22 reaches the desired valve opening stop position during the desired valve opening operation time. Accordingly, the movement of the piston 22 and the diaphragm 24 can be started in a very short time from the start of the valve opening operation, and the valve opening stop position can be reached immediately before the end of the valve opening operation time. Most of the time can be the time during which the diaphragm 24 is actually moving. As a result, the rise of the valve opening operation is fast, and the time during which the piston 22 and the diaphragm 24 are actually moving can be increased during the valve opening operation time, so that the reliability of the flow rate control can be improved. .

  Further, in the flow control valve 1 controlled by the control method of the present embodiment, the motor 11 is operated to move the nut 19 to the stop position, and the valve 22 stop position is determined by the piston 22 abutting against the nut 19. The Therefore, when the rotation direction of the motor 11 for moving the nut 19 to the stop position is a direction in which the nut 19 is moved upward, the nut 11 is stopped at the stop position by rotating the motor 11 in this direction. When stopping, the motor rotates in this direction and then stops. On the other hand, when the rotation direction of the motor for moving the nut 19 to the stop position is the direction in which the nut 19 is moved downward, the motor 11 is rotated in this direction so that the nut 19 passes the stop position. Since the motor 11 is rotated in a direction opposite to the direction and the nut 19 is stopped at the stop position, the motor 11 is stopped after rotating in the direction opposite to the direction when stopping. Accordingly, in any case, since the motor 11 is rotated after being rotated in a predetermined direction (the direction in which the nut 19 is moved upward), the backlash due to the change in the rotation direction is canceled, and the error due to the backlash is eliminated. Thus, the nut 19 can be accurately positioned. As a result, the influence of backlash is reduced and high-precision flow rate control is possible.

  In addition, the stop positions of the nut 19 include origins located at both ends of the movable range, and the motor 11 is rotated and stopped in a predetermined direction by the same control method. As a result, when the nut 19 is stopped at the origin, errors due to backlash can be similarly eliminated. Further, if the origin switch 25 or the adjustment limit point switch 26 is provided to detect the origin and the adjustment limit point, it is possible to accurately detect that the contact member has reached the position. On the other hand, when the origin switch 25 is provided, a hysteresis of the switch occurs. However, it is also effective to stop the motor 11 by rotating it in a predetermined direction (direction in which the nut 19 is moved upward). That is, if the movement of the nut 19 to the origin is the rotation of the motor 11 in a predetermined direction (the direction in which the nut 19 is moved upward), the motor 11 is stopped when the origin switch 25 no longer detects the nut 19. To do. Alternatively, if the motor 11 rotates in a direction opposite to a predetermined direction (a direction in which the nut 19 is moved up) (a direction in which the nut 19 is moved down), the motor 11 is moved after the origin switch 25 detects the nut 19. When the motor 11 rotates by a predetermined amount, the rotation of the motor 11 is reversed, and the motor 11 is stopped when the origin switch 25 stops detecting the nut 19. Thus, by rotating and stopping the motor 11 in a predetermined direction (direction in which the nut 19 is moved upward), it is possible to cancel the hysteresis of the detection means. Further, after the nut 19 is stopped at the stop position, the energization to the motor 11 is interrupted, so that the motor 11 can be prevented from generating heat and the control fluid can be prevented from rising in temperature.

  Furthermore, in the flow control valve 1 controlled by the control method of the present embodiment, the origin switch 25 detects that the nut 19 has reached the origin. Further, the operation signal value when the origin switch 25 detects the nut 19 can be compared with the operation signal value corresponding to the reference origin to obtain individual difference values k1 and k2. If the reference curve L1 is compensated by the individual difference value, the relationship between the stop position of the nut 19 and the operation signal is determined based on the compensated reference curve. Therefore, individual differences due to variations in spring set loads can be compensated by the individual difference values k1 and k2. Thereby, the error by the individual difference of the flow control valve 1 is reduced, and highly accurate flow control is possible. The fluid outflow time is short, feedback control is difficult due to responsiveness problems, and this is particularly effective when open loop control is performed.

  Further, since the motor 11 of the flow control valve 1 of the present embodiment is two-phase excitation, there are two coils V1 and V2 as shown in FIG. 12, and the current flowing through these coils V1 and V2 According to the directions r1, r2, r3, and r4, the phase can be divided into four combinations as shown in FIG. That is, the motor 11 can be rotated by continuously changing the phase in the order of r1r3 → r1r4 → r2r4 → r2r3 → r1r3 →... When operating, two phases are shifted according to the direction of rotation. Therefore, a controller (not shown) can grasp where the stop position of the nut 19 is with respect to the origin based on the number of steps and the phase. In this respect, the number of steps and the phase are stored in the storage device of the controller (not shown), and even when the power is turned on again, as shown in FIG. You can see if it is in the position.

  Further, when returning the nut 19 to the origin, a controller (not shown) counts the number of steps when rotating the motor 11, and warns the user when the counted number of steps exceeds a predetermined value. And the rotation of the motor 11 is stopped (for example, d to e in FIG. 15B correspond).

  Further, in the control method of the flow control valve 1 of the present embodiment, the number of steps and the phase are stored in the storage device of the controller (not shown), and the stop position of the nut 19 is maintained even when the power is turned on again. It is possible to grasp which position is relative to the origin. Therefore, even when the power is turned on again, the motor 11 can be operated so as to stop the nut 19 at the stop position. Therefore, the valve 19 of the nut 19 and the piston 22 and the diaphragm 24 are stopped open beyond the movable range. Nothing happens to move the position. Further, since the phase of the controller (not shown) when the power is turned on and the phase of the motor 11 are the same, the motor 11 does not operate up to the phase when the controller (not shown) is turned on.

  Further, in the control method of the flow control valve 1 of the present embodiment, when the nut 19 is returned to the origin, the motor 11 is rotated and moved to the origin position detected by ON / OFF of the origin switch 25. To do. In this regard, a controller (not shown) counts the number of steps when the motor 11 is rotated. When the counted number of steps exceeds a predetermined value, a warning is displayed to the user and the motor 11 The rotation is stopped (from d to e in FIG. 15B). Therefore, even if the origin switch 25 does not function, the rotation of the motor 11 can be automatically stopped.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning.

It is sectional drawing which showed the flow control valve of this invention. It is the figure which showed the origin switch part. It is the graph which showed the change of the air pressure of the pilot chamber by the control method of the flow control valve of this invention. It is the graph which showed the relationship between the operation signal by the control method of the flow control valve of this invention, and the opening degree of a valve. It is sectional drawing which showed the conventional flow control valve. It is the graph which showed the change of the air pressure of the pilot chamber by the control method of the conventional flow control valve. It is the graph which showed the characteristic of the flow control valve. It is sectional drawing which showed the flow control valve of this invention. It is the figure which showed the origin switch part. It is the graph which showed the change of the air pressure of the pilot chamber by the control method of the flow control valve of this invention. It is the graph which showed the relationship between the operation signal by the control method of the flow control valve of this invention, and the opening degree of a valve. It is the schematic which showed the structure of the motor of the flow control valve of this invention. It is the figure which showed the combination of the phase of the motor of the flow control valve of this invention. In the flow control valve of this invention, when power is turned on again, it is the conceptual diagram which showed grasping | ascertaining the position which the stop position of a nut is with respect to the origin. In the control valve of this invention, it is the figure explaining the movement (rotation of a motor) of a nut at the time of the origin return of a nut.

Explanation of symbols

1 Flow Control Valve 11 Motor 19 Nut 20 Return Spring 22 Piston 24 Diaphragm 25 Origin Switch 26 Adjustment Limit Point Switch 31 Electropneumatic Regulator Portion 54 Valve Seat 55 Pilot Chamber

Claims (2)

A valve body provided at the tip of the piston is brought into a closed state in close contact with the valve seat by the urging force of a spring, while the piston is moved by the pressure of compressed air supplied into a pilot chamber so that the valve body is moved to the valve Based on a reference curve indicating the relationship between the stop position of the abutting member and the operation signal, the motor is converted into a linear movement of the abutting member by the deceleration conversion means. Then, the motor is operated so that the contact member moves to the stop position and is stopped, and the valve opening stop position of the valve body is determined by the piston abutting against the contact member, and the flow rate of the fluid In the control method of the flow control valve for adjusting
A detecting means for detecting that the piston has reached the valve closing state by turning off from on or turning on from off;
The difference between the operation signal value when the detection means is turned off from on or turned off and turned on and the operation signal value corresponding to the reference origin is an individual difference value,
A control method of a flow control valve, wherein the reference curve is compensated by the individual difference value. In the control method of the flow control valve according to claim 1,
A control method for a flow control valve, wherein the flow control valve is used by open loop control.

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