Pressure control device

Abstract

This pressure control device has a device body provided with an input port through which gas is input, an output port through which gas is output, and an exhaust port through which gas is discharged. The pressure control device has: an air supply valve connected to the input port via an input flow path; an exhaust valve connected to the exhaust port via an exhaust flow path; and a control board unit that performs feedback control of the air supply valve and the exhaust valve. The pressure control device has a communication port that is communicably connected to the control board unit and receives a switching signal transmitted from an external device. The control board unit selects, on the basis of the switching signal, an execution parameter from among a plurality of parameters stored in a memory. The control board unit executes feedback control of the air supply valve and the exhaust valve on the basis of the execution parameter.

Description

Pressure control device

[0001] The present disclosure relates to a pressure control device.

[0002] In order to control the pressure of a gas supplied to a compressed fluid device such as an air cylinder or an air gripper (hereinafter referred to as a pneumatic device), a pressure control device called an electro-pneumatic regulator has been proposed (see Patent Document 1). By controlling the gas pressure using such a pressure control device, a pneumatic device incorporated in equipment such as production equipment can be operated.

[0003] Japanese Patent Application Laid-Open No. 2022-37588

[0004] By the way, in order to appropriately operate a pneumatic device provided in equipment, it is important to quickly feedback-control the pressure of the gas supplied from the pressure control device to the pneumatic device toward the target pressure. For this reason, when constructing equipment equipped with a pneumatic device, it was necessary to adjust the control parameters of the feedback control stored in the pressure control device according to the volume of the pneumatic device, the length of the piping, etc. That is, it was necessary to adjust the parameters of the feedback control stored in the memory of the pressure control device and adapt the control characteristics of the pressure control device to the equipment.

[0005] However, the control characteristics of the pressure control device required from the equipment side are not limited to one control characteristic. For example, as a situation where a plurality of control characteristics are required, a situation can be considered where the control characteristics required during pressure increase and the control characteristics required during pressure decrease are different from each other. Also, in equipment that switches and uses a plurality of pneumatic devices, a situation where different control characteristics are required for each pneumatic device used can be considered. In order to cope with these situations, it is required to switch the control characteristics of the pressure control device.

[0006] According to this disclosure, a pressure control device has a main body that includes an input port into which gas is input, an output port out which gas is output, and an exhaust port out which gas is discharged. The pressure control device includes an air supply valve connected to the input port via an input flow path, an exhaust valve connected to the exhaust port via an exhaust flow path, and a control board that provides feedback control of the air supply valve and the exhaust valve. The pressure control device has a communication port that is communicably connected to the control board and receives switching signals transmitted from an external device. Based on the switching signals, the control board selects execution parameters from a plurality of parameters stored in memory. Based on the execution parameters, the control board performs feedback control of the air supply valve and the exhaust valve.

[0007] According to the technology of this disclosure, the control board of the pressure control device selects execution parameters from a plurality of parameters based on a switching signal transmitted from an external device, and performs feedback control of the air supply valve and exhaust valve based on the execution parameters. This makes it possible to switch the control characteristics of the pressure control device.

[0008] Figure 1 shows a pressure control device according to one embodiment of the present disclosure. Figure 2 is a cross-sectional view showing the pressure control device along line II-II in Figure 1. Figure 3A is an enlarged view showing a portion of the air supply valve and exhaust valve. Figure 3B is an enlarged view showing a portion of the air supply valve and exhaust valve. Figure 4 shows an example of the configuration of an internal controller. Figure 5 shows an example of the configuration of a group of controllers. Figure 6 shows an example of control characteristics obtained by a parameter set. Figure 7 shows equipment incorporating the pressure control device. Figure 8 is a timing chart showing an example of the control status of the pressure control device. Figure 9 is a timing chart showing an example of the control status of the pressure control device. Figure 10 shows equipment incorporating the pressure control device. Figure 11 is a timing chart showing an example of the control status of the pressure control device. Figure 12 shows an example of the dead zone of the air supply valve and exhaust valve. Figure 13 shows a pressure control device according to another embodiment of the present disclosure. Figure 14 shows a pressure control device according to another embodiment of the present disclosure. Figure 15 shows a pressure control device as a modified example.

[0009] Embodiments of this disclosure will be described in detail below with reference to the drawings. In the following description, identical or substantially identical components and elements will be denoted by the same reference numerals, and repeated descriptions will be omitted.

[0010] <First Embodiment> <Pressure Control Device> Figure 1 is a diagram showing a pressure control device 10 according to one embodiment of the present invention. Figure 2 is a cross-sectional view showing the pressure control device 10 along the line II-II in Figure 1. As shown in Figures 1 and 2, the pressure control device 10 has a device body 13 consisting of a flow path block 11 and a housing 12. As shown in Figure 2, the flow path block 11 has an input port 14, an output port 15 and an exhaust port 16. The flow path block 11 also has an input flow path 20 communicating with the input port 14, an output flow path 21 communicating with the output port 15 and an exhaust flow path 22 communicating with the exhaust port 16. Furthermore, the flow path block 11 has connecting flow paths 21a and 21b communicating with the output flow path 21 and a sensor flow path 23 branching off from the output flow path 21.

[0011] A fitting 25 for connecting an air tube 24 is attached to the input port 14, and a fitting 27 for connecting an air tube 26 is attached to the output port 15. In addition, a female thread 16a for connecting a muffler 84, which will be described later, is formed in the exhaust port 16. This pressure control device 10 controls the pressure of the air (gas) flowing from the input port 14 to the output port 15 based on voltage signals, current signals, etc., input from an external controller 82, which will be described later. This pressure control device 10 is also called an electro-pneumatic regulator. The input port 14 is a port to which air is supplied from a pressure supply source 83, which will be described later, and is also called an air supply port.

[0012] <Air Intake Valve and Exhaust Valve> As shown in Figure 2, the pressure control device 10 has an air intake valve 30 and an exhaust valve 40 provided in the flow path block 11 of the device body 13. The air intake valve 30 is connected to the input flow path 20 of the flow path block 11, and the exhaust valve 40 is connected to the exhaust flow path 22 of the flow path block 11. The air intake valve 30 and the exhaust valve 40 are also connected to each other via connecting flow paths 21a and 21b of the flow path block 11.

[0013] The flow path block 11 has a mounting recess 31 for mounting an air supply valve 30 and a mounting recess 41 for mounting an exhaust valve 40. A valve seat 32 attached to the open end of a connecting flow path 21a extending from the output flow path 21 is positioned in the mounting recess 31 of the flow path block 11, and the end of the input flow path 20 is open. A valve seat 42 attached to the open end of an exhaust flow path 22 is positioned in the mounting recess 41 of the flow path block 11, and the end of a connecting flow path 21b extending from the output flow path 21 is open.

[0014] Figures 3A and 3B are enlarged views showing parts of the air intake valve 30 and the exhaust valve 40. As shown in Figure 3A, the air intake valve 30 includes a coil 34 wound around a bobbin 33, a fixed core 35 fixed inside the bobbin 33, and a movable core 36 movably provided inside the bobbin 33. The movable core 36 is equipped with a valve body 37 facing the valve seat 32. The air intake valve 30 also has a spring 38 that biases the movable core 36 toward the valve seat 32.

[0015] As shown in Figure 3A, when the power supply to the coil 34 of the air supply valve 30 is cut off, the movable core 36 is pushed by the spring 38 and moves in the direction of arrow Da1, and the valve body 37 of the movable core 36 comes into contact with the valve seat 32, closing the connecting passage 21a, i.e., the output passage 21. On the other hand, as shown in Figure 3B, when power is supplied to the coil 34 of the air supply valve 30, the movable core 36 is attracted to the fixed core 35 and moves in the direction of arrow Db1, and the valve body 37 of the movable core 36 moves away from the valve seat 32, opening the connecting passage 21a, i.e., the output passage 21.

[0016] In other words, the air supply valve 30, which is an on / off valve, operates in a connected state when the coil is energized, connecting the input flow path 20 and the output flow path 21, while operating in a blocked state when the coil is not energized, blocking the input flow path 20 and the output flow path 21. By controlling the air supply valve 30 to the connected state, air flows from the input flow path 20 to the output flow path 21, thereby increasing the pressure of the air discharged from the output flow path 21.

[0017] As shown in Figure 3A, the exhaust valve 40 includes a coil 44 wound around a bobbin 43, a fixed core 45 fixed inside the bobbin 43, and a movable core 46 movably provided inside the bobbin 43. The movable core 46 is equipped with a valve body 47 facing the valve seat 42. The exhaust valve 40 also has a spring 48 that biases the movable core 46 toward the valve seat 42.

[0018] As shown in Figure 3A, when the power supply to the coil 44 of the exhaust valve 40 is cut off, the movable core 46 is pushed by the spring 48 and moves in the direction of arrow Da2, and the valve body 47 of the movable core 46 comes into contact with the valve seat 42 and closes the exhaust passage 22. On the other hand, as shown in Figure 3B, when power is supplied to the coil 44 of the exhaust valve 40, the movable core 46 is attracted to the fixed core 45 and moves in the direction of arrow Db2, and the valve body 47 of the movable core 46 moves away from the valve seat 42 and opens the exhaust passage 22.

[0019] In other words, the exhaust valve 40, which is an on / off valve, operates in a connected state when the coil is energized, connecting the output passage 21 and the exhaust passage 22, while operating in a blocked state when the coil is not energized, blocking the output passage 21 and the exhaust passage 22. By controlling the exhaust valve 40 to the connected state, air flows from the output passage 21 to the exhaust passage 22, thereby reducing the pressure of the air discharged from the output passage 21.

[0020] <Internal Controller> As shown in Figure 2, the pressure control device 10 has an internal controller (control board section) 50 provided in the housing 12 of the device body 13. The internal controller 50 has a printed circuit board 51 mounted inside the housing 12, a microcontroller 52 mounted on the printed circuit board 51, an external memory 53 mounted on the printed circuit board 51, and various elements 54 mounted on the printed circuit board 51. The internal controller 50 is also connected to the coil 34 of the air supply valve 30 via a power supply line 55 and to the coil 44 of the exhaust valve 40 via a power supply line 56.

[0021] A pressure sensor 61 is connected to the internal controller 50 via a communication line 60. The pressure sensor 61, which is attached to the open end of the sensor flow path 23, has a pressure-receiving part 62 that is exposed to the sensor flow path 23. A communication port 64 is also connected to the internal controller 50 via a communication line 63. An external controller (external device) 82, which will be described later, can be connected to the communication port 64, which is provided in the housing 12 of the main body of the device 13, in a communication manner. The communication line 63 connected to the communication port 64 is composed of multiple wires, including power lines and communication lines.

[0022] Figure 4 shows an example of the configuration of the internal controller 50. As shown in Figure 4, the internal controller 50 receives a signal (target pressure signal) indicating the target pressure value P1, which is the control target, from the external controller 82 via the A / D converter 70. The internal controller 50 also receives a signal indicating the measured pressure value P2, which is the control result, from the pressure sensor 61 via the A / D converter 71. Furthermore, the internal controller 50 receives a switching signal S1 for selecting a parameter set, which will be described later, from the external controller 82 via the A / D converter 70.

[0023] The internal controller 50 performs PID control, or feedback control, of the air supply valve 30 and exhaust valve 40 to converge the measured pressure value P2 toward the target pressure value P1. The internal controller 50 includes a selector 72, a controller group 73, PWM conversion circuits 74 and 75, and drive circuits 76 and 77. The controller group 73 of the internal controller 50 is composed of three PID controllers 73H, 73M, and 73L. In the illustrated example, the controller group 73 is composed of three PID controllers 73H, 73M, and 73L, but it is not limited to this, and the controller group 73 may be composed of two PID controllers, or four or more PID controllers.

[0024] The selector 72 of the internal controller 50 selects the PID controller to be used from the PID controllers 73H, 73M, and 73L of the controller group 73 based on the switching signal S1 transmitted from the external controller 82. For example, when PID controller 73H is selected by the selector 72, PID controller 73H performs PID control based on the deviation e between the target pressure value P1 and the measured pressure value P2, and outputs the control amount calculated through PID control to the PWM conversion circuits 74 and 75. The PWM conversion circuit 74 calculates a pulse signal to be used for PWM control of the air supply valve 30 based on the control amount and outputs this pulse signal to the drive circuit 76. The drive circuit 76 then controls the energization state of the air supply valve 30 based on the pulse signal. Similarly, the PWM conversion circuit 75 calculates a pulse signal to be used for PWM control of the exhaust valve 40 based on the control amount and outputs this pulse signal to the drive circuit 77. The drive circuit 77 then controls the energization state of the exhaust valve 40 based on the pulse signal.

[0025] As shown in Figure 2, the internal controller 50 has a microcontroller 52 equipped with a processor 57 and main memory 58. The main memory 58 stores a control program for executing PID control and the parameter sets PH, PM, and PL, which will be described later. By having the processor 57 execute this control program, the controller group 73 of the internal controller 50 shown in Figure 4 can be made to function, and PID control of the air supply valve 30 and exhaust valve 40 can be performed.

[0026] Figure 5 shows an example configuration of the controller group 73. As shown in Figure 5, the controller group 73 includes a PID controller 73H consisting of a high-sensitivity parameter set PH, a PID controller 73M consisting of a medium-sensitivity parameter set PM, and a PID controller 73L consisting of a low-sensitivity parameter set PL. Parameter set PH includes a proportional gain KpH for proportional operation, an integral gain KiH for integral operation, and a differential gain KdH for differential operation. Parameter set PM includes a proportional gain KpM, an integral gain KiM, and a differential gain KdM. Furthermore, parameter set PL includes a proportional gain KpL, an integral gain KiL, and a differential gain KdL. Thus, the control program stored in the main memory 58 includes multiple parameter sets PH, PM, and PL.

[0027] Figure 6 shows an example of control characteristics obtained by parameter sets PH, PM, and PL. In Figure 6, the symbols P2H, P2M, and P2L are assigned to the measured pressure values ​​to distinguish between multiple measured pressure values ​​P2. As shown by the solid line in Figure 6, the high-sensitivity parameter set PH of the PID controller 73H has the proportional gain KpH, integral gain KiH, and differential gain KdH set so that the rise time of the measured pressure value P2H is fast.

[0028] As shown by the dashed line in Figure 6, the parameter set PM for the medium sensitivity of the PID controller 73M is set such that the rise time of the measured pressure value P2M is slower than that of the measured pressure value P2H, with proportional gain KpM, integral gain KiM, and differential gain KdM configured accordingly. Furthermore, as shown by the double dashed line, the parameter set PL for the low sensitivity of the PID controller 73L is set such that the rise time of the measured pressure value P2L is slower than that of the measured pressure value P2M, with proportional gain KpL, integral gain KiL, and differential gain KdL configured accordingly.

[0029] <Equipment Example 1> Equipment 80 into which the pressure control device 10 is incorporated will be described. Figure 7 is a diagram showing equipment 80 into which the pressure control device 10 is incorporated. As shown in Figure 7, equipment 80 has a pressure control device 10, an air hand 81 and an external controller 82. A pressure supply source 83 such as an air compressor or air tank is connected to the input port 14 of the pressure control device 10 via an air tube 24. A muffler 84 is connected to the exhaust port 16 of the pressure control device 10. Furthermore, the pneumatic chamber 81a of the air hand 81 is connected to the output port 15 of the pressure control device 10 via an air tube 26. The air hand 81 connected to the pressure control device 10 is a pneumatic actuator used for holding and moving a workpiece W.

[0030] An external controller 82 is connected to the communication port 64 of the pressure control device 10 via a communication cable 85. For example, a programmable logic controller (PLC) can be used as the external controller 82. The external controller 82 controls the air pressure supplied to the air hand 81 by transmitting a signal of a target pressure value P1 to the pressure control device 10, and also transmits a switching signal S1 to select parameter sets PH, PM, and PL, according to a predetermined control program. The external controller 82 includes, for example, a microcontroller (not shown) incorporating a processor and memory, an output circuit (not shown) that outputs signals to the internal controller 50, and a power supply circuit (not shown) that supplies power to the internal controller 50.

[0031] <Control Status of Pressure Control Device 1> Figure 8 is a timing chart showing an example of the control status of the pressure control device 10. Figure 8 shows the situation when the external controller 82 raises the target pressure value P1 from "0" to "PA" and holds it there, and then lowers the target pressure value P1 from "PA" to "0". The external controller 82 transmits a signal indicating the target pressure value P1 to the internal controller 50, but in the following explanation, it will be written as the external controller 82 transmits the target pressure value P1 to the internal controller 50. Also, the switching signal S1 shown in Figure 8 is a voltage signal that can be switched in three stages.

[0032] As shown in Figure 8, at time t1, the external controller 82 transmits "0" as the target pressure value P1 to the internal controller 50 (symbol a1), and also transmits "V1" as the switching signal S1 (symbol b1). Upon receiving "V1" as the switching signal S1, the internal controller 50 selects parameter set PH as the execution parameter set from among the multiple parameter sets PH, PM, and PL (symbol c1). In other words, the internal controller 50 selects the highly sensitive PID controller 73H from the controller group 73.

[0033] At time t2, the external controller 82 transmits "PA" as the target pressure value P1 to the internal controller 50 (symbol a2). Upon receiving "PA" as the target pressure value P1, the internal controller 50 performs PID control of the air supply valve 30 and the exhaust valve 40 to converge the measured pressure value P2 to "PA". At this time, the internal controller 50 performs PID control using a highly sensitive PID controller 73H, which allows the measured pressure value P2 to rapidly increase toward "PA" (symbol d1).

[0034] At time t3, the external controller 82 transmits "PA" as the target pressure value P1 (symbol a3) and "V2" as the switching signal S1 (symbol b2). Upon receiving "V2" as the switching signal S1, the internal controller 50 selects parameter set PM as the execution parameter set from among the multiple parameter sets PH, PM, and PL (symbol c2). In other words, the internal controller 50 selects the medium-sensitivity PID controller 73M from the controller group 73. As a result, the internal controller 50 can perform PID control using the medium-sensitivity PID controller 73M and accurately maintain the measured pressure value P2 at "PA" (symbol d2).

[0035] At time t4, the external controller 82 transmits "0" as the target pressure value P1 to the internal controller 50 (symbol a4), and also transmits "V3" as the switching signal S1 (symbol b3). Upon receiving "V3" as the switching signal S1, the internal controller 50 selects parameter set PL as the execution parameter set from among the multiple parameter sets PH, PM, and PL (symbol c3). In other words, the internal controller 50 selects the low-sensitivity PID controller 73L from the controller group 73. As a result, the internal controller 50 can perform PID control using the low-sensitivity PID controller 73L, and can gradually decrease the measured pressure value P2 toward "0" (symbol d3).

[0036] In this way, by switching the parameter sets PH, PM, and PL, the control characteristics of the pressure control device 10 can be switched, allowing the pressure control device 10 to be appropriately controlled in accordance with the requirements from the equipment 80. In other words, the internal controller 50 selects execution parameters from a plurality of parameters constituting the parameter sets PH, PM, and PL, and performs feedback control based on these execution parameters. This allows the control characteristics of the pressure control device 10 to be switched, enabling the pressure control device 10 to be appropriately controlled in accordance with the requirements from the equipment 80. That is, as shown in Figure 8, even if the control characteristics required by the air hand 81 during the process of increasing the air pressure differ from those required by the air hand 81 during the process of decreasing the air pressure, the pressure control device 10 can be appropriately controlled.

[0037] Furthermore, the internal controller 50 does not determine the switching of parameter sets PH, PM, and PL on its own, but rather switches the parameter sets PH, PM, and PL based on the switching signal S1 from the external controller 82. This allows the control characteristics of the pressure control device 10 to be switched without delay in response to changes in the target pressure value P1. For example, if the internal controller 50 were to determine the switching of control characteristics on its own based on changes in the target pressure value P1, it would be a factor that delays the switching of control characteristics in response to changes in the target pressure value P1. In contrast, the internal controller 50 of this disclosure switches control characteristics based on the switching signal S1 from the external controller 82, making it possible to switch control characteristics without delay in response to changes in the target pressure value P1.

[0038] In the above explanation, a voltage signal that can be switched in three stages is used as the switching signal S1, but it is not limited to this. For example, as shown by the symbol α in Figure 8, two switching signals Sa1 and Sb1 transmitted from the external controller 82 may be used in combination. For example, as shown at time t1, if the switching signal Sa1 is "Low" (symbol e1) and the switching signal Sb1 is "Low" (symbol f1), the internal controller 50 selects parameter set PH (symbol c1). Also, as shown at time t3, if the switching signal Sa1 is "High" (symbol e2) and the switching signal Sb1 is "Low" (symbol f2), the internal controller 50 selects parameter set PM (symbol c2). Furthermore, as shown at time t4, if the switching signal Sa1 is "Low" (symbol e3) and the switching signal Sb1 is "High" (symbol f3), the internal controller 50 selects parameter set PL (symbol c3).

[0039] <Control Status of Pressure Control Device 2> Figure 9 is a timing chart showing an example of the control status of the pressure control device 10. Figure 9 shows the situation when the external controller 82 raises the target pressure value P1 from "0" through "PB" to "PC", and then lowers the target pressure value P1 from "PC" to "0".

[0040] As shown in Figure 9, at time t1, the external controller 82 transmits "0" as the target pressure value P1 to the internal controller 50 (symbol a1), and also transmits "V1" as the switching signal S1 (symbol b1). Upon receiving "V1" as the switching signal S1, the internal controller 50 selects parameter set PH as the execution parameter set from among the multiple parameter sets PH, PM, and PL (symbol c1). In other words, the internal controller 50 selects the highly sensitive PID controller 73H from the controller group 73.

[0041] At time t2, the external controller 82 transmits "PB" as the target pressure value P1 to the internal controller 50 (symbol a2). Upon receiving "PB" as the target pressure value P1, the internal controller 50 performs PID control of the air supply valve 30 and the exhaust valve 40 to converge the measured pressure value P2 to "PB". At this time, the internal controller 50 performs PID control using a highly sensitive PID controller 73H, which allows the measured pressure value P2 to rapidly increase toward "PB" (symbol d1).

[0042] At time t3, after a predetermined time Ta has elapsed from time t2, the external controller 82 transmits a switching signal S1 to the internal controller 50, switching from "V1" to "V3" (symbol b2). Upon receiving "V3" as the switching signal S1, the internal controller 50 selects parameter set PL as the execution parameter set from among the multiple parameter sets PH, PM, and PL (symbol c2). In other words, in the process of converging the measured pressure value P2 to "PB", the internal controller 50 switches from the high-sensitivity PID controller 73H to the low-sensitivity PID controller 73L.

[0043] As a result, when the measured pressure value P2 reaches "PB", PID control can be executed using the low-sensitivity PID controller 73L, allowing the measured pressure value P2 to gradually converge to "PB". In other words, the measured pressure value P2 can converge to "PB" while suppressing overshoot as indicated by the symbol Xa. The timing of switching to the low-sensitivity PID controller 73L after the target pressure value P1 has risen, i.e., the elapsed time Ta from time t2, is determined by experiments or simulations.

[0044] After that, at time t4, "V1" is transmitted from the external controller 82 to the internal controller 50 as the switching signal S1 (reference sign b3). The internal controller 50 that has received "V1" as the switching signal S1 selects the parameter set PH as the execution parameter set from the plurality of parameter sets PH, PM, and PL (reference sign c3). That is, the internal controller 50 switches from the low-sensitivity PID controller 73L to the high-sensitivity PID controller 73H while the measured pressure value P2 is converging to "PB".

[0045] At time t5, "PC" is transmitted from the external controller 82 to the internal controller 50 as the target pressure value P1 (reference sign a3). The internal controller 50 that has received "PC" as the target pressure value P1 executes PID control of the air supply valve 30 and the exhaust valve 40 so as to converge the measured pressure value P2 to "PC". At this time, since the internal controller 50 executes PID control using the high-sensitivity PID controller 73H, the measured pressure value P2 can be rapidly increased toward "PC" (reference sign d3).

[0046] At time t6 when a predetermined time Tb has elapsed from time t5, the switching signal S1 is switched from "V1" to "V3" and transmitted from the external controller 82 to the internal controller 50 (reference sign b4). The internal controller 50 that has received "V3" as the switching signal S1 selects the parameter set PL as the execution parameter set from the plurality of parameter sets PH, PM, and PL (reference sign c4). That is, the internal controller 50 switches from the high-sensitivity PID controller 73H to the low-sensitivity PID controller 73L in the process of converging the measured pressure value P2 to "PC".

[0047] As a result, when the measured pressure value P2 reaches "PC", PID control can be executed using the low-sensitivity PID controller 73L, and the measured pressure value P2 can be gently converged to "PC". That is, the overshoot as indicated by the symbol Xb can be suppressed while the measured pressure value P2 is converged to "PC". Note that the timing for switching to the low-sensitivity PID controller 73L after starting the target pressure value P1, that is, the elapsed time Tb from time t5, is determined by experiments, simulations, etc.

[0048] After that, at time t7, "V1" is transmitted from the external controller 82 to the internal controller 50 as the switching signal S1 (symbol b5). The internal controller 50 that has received "V1" as the switching signal S1 selects the parameter set PH as the execution parameter set from the plurality of parameter sets PH, PM, PL (symbol c5). That is, the internal controller 50 switches from the low-sensitivity PID controller 73L to the high-sensitivity PID controller 73H under the condition that the measured pressure value P2 has converged to "PB". At time t8, "0" is transmitted from the external controller 82 to the internal controller 50 as the target pressure value P1 (symbol a4). As a result, the internal controller 50 executes PID control using the high-sensitivity PID controller 73H, and rapidly decreases the measured pressure value P2 toward "0" (symbol d5).

[0049] As explained with reference to Figure 9, the internal controller 50 switches from a high-sensitivity PID controller 73H to a low-sensitivity PID controller 73L during the process of converging the measured pressure value P2 to the target pressure value P1. This allows the measured pressure value P2 to quickly converge to the target pressure value P1 while suppressing overshoot of the measured pressure value P2. In other words, the internal controller 50 of this disclosure performs PID control based on the target pressure value P1 transmitted from the external controller 82, and switches the parameter sets PH, PM, and PL based on the switching signal S1 transmitted from the external controller 82. That is, since the internal controller 50 performs PID control and switches control characteristics based on the target pressure value P1 and switching signal S1 transmitted from the external controller 82, it is possible to switch the control characteristics at a timing before the measured pressure value P2 converges to the target pressure value P1.

[0050] <Equipment Example 2> Figure 10 shows equipment 90 incorporating a pressure control device 10. As shown in Figure 10, equipment 90 includes a pressure control device 10, a small air hand 91, a large air hand 92, and an external controller 82. The volume of the pneumatic chamber 91a of the small air hand 91 is designed to be smaller than the volume of the pneumatic chamber 92a of the large air hand 92. A hand changer 93 is connected to the output port 15 of the pressure control device 10 via an air tube 26. The hand changer 93, which is attached to the robot arm 94, can move to the installation position of the small air hand 91 to attach and detach the small air hand 91, and can move to the installation position of the large air hand 92 to attach and detach the large air hand 92.

[0051] In other words, the situation in which a small air hand 91 is attached to the hand changer 93 is the situation in which a small volume pneumatic chamber 91a is connected to the pressure control device 10. On the other hand, the situation in which a large air hand 92 is attached to the hand changer 93 is the situation in which a large volume pneumatic chamber 92a is connected to the pressure control device 10. That is, the secondary volume connected to the output port 15 of the pressure control device 10 changes depending on the connection status of the air hands 91 and 92 to the hand changer 93.

[0052] <Control Status of Pressure Control Device 3> The control status of the pressure control device 10 installed in the equipment 90 will be explained. Figure 11 is a timing chart showing an example of the control status of the pressure control device 10. Figure 11 shows the situation when the external controller 82 raises the target pressure value P1 from "0" to "PD" and then lowers the target pressure value P1 from "PD" to "0" with the large air hand 92 attached to the hand changer 93. Also, Figure 11 shows the situation when the external controller 82 raises the target pressure value P1 from "0" to "PD" and then lowers the target pressure value P1 from "PD" to "0" with the small air hand 91 attached to the hand changer 93.

[0053] As shown in Figure 11, at time t1, the large air hand 92 is attached to the hand changer 93 (reference numeral a1). In this state, the external controller 82 transmits a switching signal S1, "V1", to the internal controller 50 (reference numeral b1). Upon receiving the switching signal S1, "V1", the internal controller 50 selects parameter set PH as the execution parameter set from among the multiple parameter sets PH, PM, and PL (reference numeral c1). In other words, the internal controller 50 selects the highly sensitive PID controller 73H from the controller group 73.

[0054] At time t2, the external controller 82 transmits "PD" as the target pressure value P1 to the internal controller 50 (symbol d1). Upon receiving "PD" as the target pressure value P1, the internal controller 50 performs PID control of the air supply valve 30 and the exhaust valve 40 to converge the measured pressure value P2 to "PD". At this time, since the internal controller 50 performs PID control using a highly sensitive PID controller 73H, it can quickly supply air to the large volume air pressure chamber 92a and appropriately raise the measured pressure value P2 toward "PD" (symbol e1).

[0055] At time t3, the external controller 82 transmits "0" as the target pressure value P1 to the internal controller 50 (symbol d2). Upon receiving "0" as the target pressure value P1, the internal controller 50 performs PID control of the air supply valve 30 and the exhaust valve 40 to converge the measured pressure value P2 to "0". At this time, since the internal controller 50 performs PID control using a highly sensitive PID controller 73H, it is possible to quickly discharge air from the large volume air pressure chamber 92a and appropriately reduce the measured pressure value P2 toward "0" (symbol e2).

[0056] At time t4, the large air hand 92 is removed from the hand changer 93, and the small air hand 91 is attached to the hand changer 93 (symbol a2). At this time, the external controller 82 transmits a switching signal S1 to the internal controller 50, switching from "V1" to "V3" (symbol b2). Upon receiving "V3" as the switching signal S1, the internal controller 50 selects parameter set PL as the execution parameter set from among the multiple parameter sets PH, PM, and PL (symbol c2). In other words, the internal controller 50 selects the low-sensitivity PID controller 73L from the controller group 73.

[0057] At time t5, the external controller 82 transmits "PD" as the target pressure value P1 to the internal controller 50 (symbol d3). Upon receiving "PD" as the target pressure value P1, the internal controller 50 performs PID control of the air supply valve 30 and the exhaust valve 40 to converge the measured pressure value P2 to "PD". At this time, since the internal controller 50 performs PID control using a low-sensitivity PID controller 73L, it is possible to supply air to the small volume air pressure chamber 91a gradually and appropriately increase the measured pressure value P2 toward "PD" (symbol e3).

[0058] At time t6, the external controller 82 transmits "0" as the target pressure value P1 to the internal controller 50 (symbol d4). Upon receiving "0" as the target pressure value P1, the internal controller 50 performs PID control of the air supply valve 30 and the exhaust valve 40 to converge the measured pressure value P2 to "0". At this time, since the internal controller 50 performs PID control using a low-sensitivity PID controller 73L, it is possible to gradually discharge air from the small volume air pressure chamber 91a and appropriately reduce the measured pressure value P2 toward "0" (symbol e4).

[0059] In this way, by switching the parameter sets PH, PM, and PL, the control characteristics of the pressure control device 10 can be switched, so that the pressure control device 10 can be appropriately controlled even when the secondary volume of the pressure control device 10 changes. In other words, when a small air hand 91 is attached to the hand changer 93 and PID control is performed using a high-sensitivity PID controller 73H, there is a risk of hunting occurring in the measured pressure value P2, as shown by the symbol Xc in Figure 11. In contrast, in the technology of this disclosure, the control characteristics can be switched according to the secondary volume of the pressure control device 10, so that the occurrence of hunting can be suppressed and the measured pressure value P2 can be appropriately controlled.

[0060] <Bias Values> In the above explanation, the parameter sets PH, PM, and PL are composed of proportional gains KpH, KpM, and KpL, integral gains KiH, KiM, and KiL, and differential gains KdH, KdM, and KdL, but are not limited to this. For example, bias values ​​(dead zone adjustment values) for offsetting (adjusting) the dead zones of the intake valve 30 and exhaust valve 40 may be included in the parameter sets PH, PM, and PL.

[0061] As described above, the PID controllers 73H, 73M, and 73L perform PID control based on the deviation e between the target pressure value P1 and the measured pressure value P2, and output the control amount (hereinafter referred to as the target valve opening) calculated through PID control to the PWM conversion circuits 74 and 75. The PWM conversion circuit 74 calculates the pulse signal (hereinafter referred to as the duty cycle) used for PWM control of the air supply valve 30 based on the target valve opening, and outputs this duty cycle to the drive circuit 76. Similarly, the PWM conversion circuit 75 calculates the duty cycle used for PWM control of the exhaust valve 40 based on the target valve opening, and outputs this duty cycle to the drive circuit 77.

[0062] Figure 12 shows an example of the dead zone of the intake valve 30 and exhaust valve 40. As shown by the characteristic line La1 in Figure 12, frictional force and spring force from springs 38 and 48 act on the movable iron cores 36 and 46 of the intake valve 30 and exhaust valve 40, making it difficult to operate the movable iron cores 36 and 46 in the low duty cycle region. In other words, the intake valve 30 and exhaust valve 40 have a dead zone in the low duty cycle region where it is difficult to change the actual valve opening. Thus, in the low duty cycle region, i.e., the region with a small deviation e, the intake valve 30 and exhaust valve 40 enter the dead zone, making it difficult to quickly converge the measured pressure value P2 to the target pressure value P1. For this reason, the main memory 58 of the internal controller 50 sometimes stores a bias value (dead zone adjustment value) for adjusting the dead zone of the intake valve 30 and exhaust valve 40 as one of the parameters for feedback control.

[0063] The characteristic curve La2 shown in Figure 12 represents the relationship between the duty cycle after bias adjustment and the actual valve opening. In other words, as shown by the characteristic curve La2 in Figure 12, by offsetting the duty cycle corresponding to the deviation e with the bias value Bi, the dead zone of the intake valve 30 and exhaust valve 40 can be narrowed by the amount of the bias value Bi. By narrowing the dead zone using the bias value Bi in this way, the duty cycle can be set higher even in regions where the duty cycle is inherently low (regions with small deviation e). This allows the intake valve 30 and exhaust valve 40 to be removed from the dead zone, enabling them to operate appropriately and improving their controllability. Note that the bias values ​​Bi used for both the intake valve 30 and exhaust valve 40 may be the same, or they may be different. Furthermore, the bias value Bi can be set to eliminate the dead zone, or it can be set to intentionally leave a dead zone.

[0064] Even when the aforementioned parameter sets PH, PM, and PL include a bias value Bi for adjusting the dead zone, the control characteristics of the pressure control device 10 can be switched by switching the parameter sets PH, PM, and PL. In other words, by including a bias value Bi of a different value for each parameter set PH, PM, and PL, the control characteristics of the pressure control device 10 can be switched by switching the parameter sets PH, PM, and PL.

[0065] In the explanation above, the parameter set includes proportional gain, integral gain, differential gain, and bias value, but it is not limited to these. For example, the parameter set may include only the proportional gain, or only the bias value. In other words, the parameter set only needs to include at least one of the proportional gain, integral gain, differential gain, and bias value.

[0066] <Second Embodiment> In the above description, the internal controller 50 selects an execution parameter set from a plurality of parameter sets PH, PM, PL based on the switching signal S1, and performs feedback control of the air supply valve 30 and exhaust valve 40 based on the execution parameter set, but is not limited to this. For example, the internal controller 50 may select an execution parameter from a plurality of parameters based on the switching signal S1, and perform feedback control of the air supply valve 30 and exhaust valve 40 based on the execution parameter.

[0067] Figure 13 shows a pressure control device 100 according to another embodiment of the present disclosure. In Figure 13, components and elements similar to those shown in Figure 4 are denoted by the same reference numerals and their descriptions are omitted. As shown in Figure 13, the pressure control device 100 has an internal controller (control board unit) 101. The internal controller 101 performs PID control, or feedback control, of the air supply valve 30 and the exhaust valve 40 so as to converge the measured pressure value P2 toward a target pressure value P1. The internal controller 101 has a parameter selection circuit 102, a PID controller 103, PWM conversion circuits 74, 75, and drive circuits 76, 77.

[0068] As shown in Figure 2 above, the internal controller 101 has a microcontroller 52 equipped with a processor 57 and a main memory 58. The main memory 58 stores a control program for executing PID control and parameters described later. By having the processor 57 execute this control program, the parameter selection circuit 102 and PID controller 103 of the internal controller 101 shown in Figure 13 can be made to function, and PID control of the air supply valve 30 and exhaust valve 40 can be performed.

[0069] The parameter selection circuit 102 of the internal controller 101 selects execution parameters from a plurality of parameters Kp, Ki, Kd, ​​and Bi based on a switching signal S1 transmitted from the external controller 82. The main memory 58 stores a plurality of proportional gains Kp, a plurality of integral gains Ki, a plurality of differential gains Kd, and a plurality of bias values ​​(dead zone adjustment values) Bi as parameters for feedback control. That is, the parameter selection circuit 102 selects one of the proportional gains Kp, one of the integral gains Ki, one of the differential gains Kd, and one of the bias values ​​Bi as execution parameters based on the switching signal S1. The parameter selection circuit 102 then transmits the selected execution parameters to the PID controller 103, and the PID controller 103 performs PID control based on the execution parameters and the deviation e.

[0070] In this way, the internal controller 101 selects execution parameters from a plurality of parameters based on the switching signal S1, and performs feedback control of the air supply valve 30 and exhaust valve 40 based on the execution parameters. As a result, the control characteristics of the pressure control device 100 can be switched using the execution parameters, so that the pressure control device 100 can be appropriately controlled in accordance with the requirements from the equipment side. Moreover, the internal controller 101 does not decide on the switching of parameters Kp, Ki, Kd, ​​and Bi on its own, but switches the parameters Kp, Ki, Kd, ​​and Bi based on the switching signal S1 from the external controller 82. As a result, the control characteristics of the pressure control device 100 can be switched without delay in response to changes in the target pressure value P1.

[0071] In the explanation above, multiple parameters include proportional gain, integral gain, differential gain, and bias value, but this is not the only way to define them. For example, multiple parameters may include only the proportional gain, or only the bias value. In other words, multiple parameters only need to include at least one of the proportional gain, integral gain, differential gain, and bias value.

[0072] <Third Embodiment> The pressure control device 10 shown in Figures 2 and 5 directly controls the air pressure using an air supply valve 30 and an exhaust valve 40, but is not limited to this, and the air pressure may be indirectly controlled using the air supply valve 30 and the exhaust valve 40. In other words, it is not limited to a direct-acting pressure control device 10, and the technology of this disclosure may also be applied to a pilot-operated pressure control device. Here, Figure 14 shows a pressure control device 201 according to another embodiment of this disclosure. In Figure 14, components and elements similar to those shown in Figure 7 are denoted by the same reference numerals and their descriptions are omitted.

[0073] As shown in Figure 14, the main body 202 of the pressure control device 201 has an input port 203, an output port 204, an exhaust port 205, and an exhaust port 206. The main body 202 has an input flow path 210 that communicates with the input port 203, and a branch flow path (input flow path) 210a that branches off from the input flow path 210. The main body 202 also has an output flow path 211 that communicates with the output port 204, and a sensor flow path 212 that branches off from the output flow path 211. Furthermore, the main body 202 has an exhaust flow path 213 that communicates with the exhaust port 205, and an exhaust flow path 214 that communicates with the exhaust port 206.

[0074] The main body 202 of the pressure control device 201 has a main valve 220 positioned between the input passage 210 and the output passage 211 to control the communication state of the input passage 210, the output passage 211, and the exhaust passage 213. This main valve 220 has a diaphragm (not shown) that controls the communication state of the input passage 210, the output passage 211, and the exhaust passage 213, and a pilot chamber 221 partitioned on one side of the diaphragm. By increasing the pressure of the air supplied to the pilot chamber 221, the input passage 210 and the output passage 211 can be connected via the main valve 220. On the other hand, by decreasing the pressure of the air supplied to the pilot chamber 221, the output passage 211 and the exhaust passage 213 can be connected via the main valve 220.

[0075] To control the main valve 220, the pressure control device 201 has an air supply valve 30 and an exhaust valve 40. The air supply valve 30 is located between the branch passage 210a and the connecting passage 215, and the exhaust valve 40 is located between the connecting passage 215 and the exhaust passage 214. In other words, the air supply valve 30 is connected to the input port 203 via the input passage 210 and the branch passage 210a, and the exhaust valve 40 is connected to the exhaust port 206 via the exhaust passage 214. In addition, a pilot passage 216 extending from the pilot chamber 221 is connected to the connecting passage 215 that connects the air supply valve 30 and the exhaust valve 40. In other words, the connecting passage 215 that connects the air supply valve 30 and the exhaust valve 40 is in communication with the pilot chamber 221 that operates the main valve 220.

[0076] By controlling the air supply valve 30 to a connected state, air flows from the branch passage 210a to the connecting passage 215, thereby increasing the pressure of the air supplied from the pilot passage 216 to the pilot chamber 221. On the other hand, by controlling the exhaust valve 40 to a connected state, air flows from the connecting passage 215 to the exhaust passage 214, thereby decreasing the pressure of the air supplied from the pilot passage 216 to the pilot chamber 221. In other words, by controlling the air supply valve 30 and the exhaust valve 40, the pressure of the air supplied to the pilot chamber 221 can be controlled, and the main valve 220 can be controlled.

[0077] The main unit 202 of the pressure control device 201 has an internal controller 50 that performs PID control of the air supply valve 30 and the exhaust valve 40. As described above, the internal controller 50 selects an execution parameter set from the parameter sets PH, PM, and PL based on the switching signal S1 transmitted from the external controller 82, and performs feedback control of the air supply valve 30 and the exhaust valve 40 based on the execution parameter set. In other words, the internal controller 50 selects an execution parameter from a plurality of parameters that make up the parameter sets PH, PM, and PL, and performs feedback control based on this execution parameter. As a result, the control characteristics of the pressure control device 201 can be switched, similar to the pressure control device 10 described above, so that the pressure control device 201 can be appropriately controlled according to the requirements of the equipment. In addition, similar to the internal controller 101 shown in Figure 13, the internal controller 50 may select any of the proportional gain Kp, any of the integral gain Ki, any of the differential gain Kd, and any of the bias value Bi as the execution parameter based on the switching signal S1.

[0078] <Modifications> This disclosure is not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the gist of the invention. For example, in the examples shown in Figures 1, 2 and 7, the pressure control device 10 has one communication port 64 for receiving a switching signal S1 and a target pressure value P1, but it is not limited to this. Here, Figure 15 shows a pressure control device 230 as a modification. As shown in Figure 15, the pressure control device 230 has a communication port 64 for receiving a target pressure value P1 and a communication port 231 for receiving a switching signal S1. In this way, even if a dedicated communication port 231 for receiving the switching signal S1 is provided, it can be made to function in the same way as the pressure control device 10 described above. Also, in the example shown in Figure 15, the communication port 231 is provided on the upper surface 12a of the housing 12, but the installation position of the communication port 231 is not limited to the upper surface 12a. For example, as shown by the arrow β in Figure 15, the communication port 231 for receiving the switching signal S1 may be provided on the side surface 12b of the housing 12.

[0079] In the example shown in Figure 4, the controller group 73 is composed of three PID controllers 73H, 73M, and 73L, but it is not limited to this. The controller group 73 may be composed of two PID controllers, or four or more PID controllers. In other words, two parameter sets may be stored in the main memory 58, or four or more parameter sets may be stored in the main memory 58. Furthermore, in the above description, PID control is performed as feedback control, but it is not limited to this. P control, PI control, or PD control may be performed as feedback control.

[0080] As shown in Figure 5, the proportional gains KpH, KpM, and KpL of the parameter sets PH, PM, and PL may all have different values, or some or all of them may have the same value. Similarly, the integral gains KiH, KiM, and KiL of the parameter sets PH, PM, and PL may all have different values, or some or all of them may have the same value. Furthermore, the differential gains KdH, KdM, and KdL of the parameter sets PH, PM, and PL may all have different values, or some or all of them may have the same value.

[0081] In the above description, multiple parameter sets PH, PM, PL, or multiple parameters Kp, Ki, Kd, ​​Bi are stored in the main memory 58 of the microcontroller 52, but this is not limited to this. For example, multiple parameter sets PH, PM, PL may be stored in the external memory 53 of the internal controller 50, or multiple parameters Kp, Ki, Kd, ​​Bi may be stored in the external memory 53 of the internal controller 50. Furthermore, multiple parameter sets PH, PM, PL and multiple parameters Kp, Ki, Kd, ​​Bi may be pre-set at the factory shipment stage of the pressure control devices 10, 100, 201, 230, or the user may set them to arbitrary values ​​using an external controller 82 or the like after the pressure control devices 10, 100, 201, 230 have been shipped from the factory. In the above description, voltage signals are used as switching signals S1, Sa1, Sb1, but this is not limited to this, and pulse signals or serial signals may be used as switching signals.

[0082] In the above description, the internal controller 50 is configured using a microcontroller 52, but it is not limited to this, and the internal controller 50 may also be configured using an analog circuit consisting of elements such as operational amplifiers. In the above description, the air pressure in the output flow paths 21 and 211 is controlled by performing PWM control on the air supply valve 30 and the exhaust valve 40, but it is not limited to this. For example, the air supply valve 30 and the exhaust valve 40 may be configured using flow control valves. As a flow control valve, it is possible to use a flow control valve that can adjust the opening degree of the valve body by controlling the current value and the voltage value supplied to the coil. Alternatively, it is possible to use a piezo-type flow control valve that can adjust the opening degree of the valve body using a piezoelectric element.

[0083] In the illustrated example, a muffler 84 is attached to the exhaust port 16, but this is not limited to this, and an air tube or the like may be connected to the exhaust port 16. In the illustrated example, a pressure sensor 61 incorporated into the pressure control devices 10, 100, and 201 is used, but this is not limited to this, and a pressure sensor provided separately from the pressure control devices 10, 100, 201, and 230 may be used. In the examples shown in Figures 7 and 14, an air hand 81 is connected to the pressure control devices 10 and 201, but this is not limited to this. For example, in addition to using the pressure control devices 10, 100, 201, and 230 with an air hand connected, an air cylinder, an air motor, a chemical supply tank, a pilot-operated valve, a process chamber, etc. may also be connected and used. In the above description, the pressure control devices 10, 100, 201, and 230 control the pressure of air, which is a gas, but this is not limited to this, and the pressure control devices 10, 100, 201, and 230 may also control the pressure of gases other than air.

[0084] 10... Pressure control device, 13... Device body, 14... Input port, 15... Output port, 16... Exhaust port, 20... Input flow path, 21... Output flow path, 21a, 21b... Connection flow path, 22... Exhaust flow path, 30... Intake valve, 40... Exhaust valve, 50... Internal controller (control board), 58... Main memory (memory), 64... Communication port, 82... External controller (external device), 100... Pressure control device, 101... Internal controller (control board), 201... Pressure control device, 202... Device body, 203... Input port, 204... Output port, 206... Exhaust 210...Input channel, 210a...Branch channel (input channel), 211...Output channel, 214...Exhaust channel, 215...Connection channel, 220...Main valve, 221...Pilot chamber, 230...Pressure control device, 231...Communication port, S1, Sa1, Sb1...Switching signals, PH, PM, PL...Parameter set, Kp, KpH, KpM, KpL...Proportional gain (parameter), Ki, KiH, KiM, KiL...Integral gain (parameter), Kd, ​​KdH, KdM, KdL...Differential gain (parameter), Bi...Bias value (dead zone adjustment value, parameter)

Claims

1. A pressure control device for controlling the pressure of a gas, comprising: a device body having an input port into which gas is input, an output port out which gas is output, and an exhaust port out which gas is discharged; an air supply valve provided on the device body and connected to the input port via an input flow path; an exhaust valve provided on the device body and connected to the exhaust port via an exhaust flow path; a control board unit provided on the device body for feedback control of the air supply valve and the exhaust valve; and a communication port communicably connected to the control board unit and for receiving switching signals transmitted from an external device, wherein the control board unit selects execution parameters from a plurality of parameters stored in memory based on the switching signals, and performs feedback control of the air supply valve and the exhaust valve based on the execution parameters.

2. A pressure control device according to claim 1, wherein the control board unit performs feedback control of the air supply valve and the exhaust valve based on a target pressure signal transmitted from the external device.

3. A pressure control device according to claim 1, wherein the plurality of parameters include at least one of a proportional gain, an integral gain, a differential gain, and a dead zone adjustment value.

4. A pressure control device according to claim 1, wherein the control board unit selects an execution parameter set from a plurality of parameter sets consisting of a plurality of parameters based on the switching signal, and performs feedback control of the air supply valve and the exhaust valve based on the execution parameter set.

5. A pressure control device according to claim 4, wherein the parameter set includes at least one of a proportional gain, an integral gain, a differential gain, and a dead zone adjustment value.

6. A pressure control device according to claim 1, wherein the device body comprises an output flow path communicating with the output port, and a connecting flow path connecting the air supply valve and the exhaust valve to each other, and the output flow path and the connecting flow path are in communication with each other.

7. A pressure control device according to claim 1, wherein the device body comprises: an output flow path communicating with the output port; a connecting flow path connecting the air supply valve and the exhaust valve to each other; and a main valve provided between the input flow path and the output flow path for controlling the communication state between the input flow path and the output flow path, wherein the connecting flow path communicates with the pilot chamber of the main valve.

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