Proportional valve control device and proportional valve control method

Abstract

To provide a proportional valve control device that can improve the accuracy of flow control, and a proportional valve control method.SOLUTION: A proportional valve control device 57 sets the valve opening degree of a valve part by controlling a coil 8 in a balance type proportional valve 1. The proportional valve control device 57 comprises a driving unit 58 for applying a pulse voltage Vpl to the coil 8, and driving a plunger, and a control unit 59 for controlling the valve opening degree of the valve part. The control unit 59 applies the pulse voltage Vpl having amplitude corresponding to a command value Vin for the valve opening degree to the coil 8 from the driving unit 58, passes a current corresponding to the pulse voltage Vpl through the coil 8, and controls the valve opening degree of the valve part.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a proportional valve control device and a proportional valve control method.

Background Art

[0002] As disclosed in Patent Document 1, an electromagnetic proportional control valve that controls flow rate and pressure using a solenoid is well-known. In Patent Document 1, a problem has been raised regarding the hysteresis that occurs between the excitation current of the solenoid and the displacement position of the spool. Hysteresis generally refers to a phenomenon in which the displacement position of the spool is different even with the same excitation current.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, hysteresis hinders accurate control of the flow rate. Therefore, development of a technology that enables more accurate flow rate control by further reducing hysteresis has been desired. An object of the present invention is to provide a proportional valve control device and a proportional valve control method that can improve the accuracy of flow rate control.

Means for Solving the Problems

[0005] A proportional valve control device for solving the above problem is a device for setting the valve opening degree of a valve by controlling the coil in a balanced proportional valve in which the pressure acting on a plunger that moves to open and close the valve based on the magnetomotive force of a coil and the elastic force of an elastic part and the pressure acting on the valve part are set to the same pressure, the device comprising: a drive unit that drives the plunger by applying a pulse voltage to the coil; and a control unit that applies the pulse voltage having an amplitude corresponding to a command value of the valve opening degree from the drive unit to the coil, and controls the valve opening degree of the valve part by flowing a current corresponding to the pulse voltage through the coil.

[0006] A proportional valve control method for solving the above problem is a balanced proportional valve in which the pressure acting on a plunger that moves to open and close the valve based on the magnetomotive force of a coil and the elastic force of an elastic part, and the pressure acting on the valve part are set to the same pressure, and the method for setting the valve opening degree of the valve part by controlling the coil, wherein a drive unit that drives the plunger by applying a voltage to the coil applies a pulse voltage having an amplitude corresponding to a command value for the valve opening degree to the coil, thereby causing a current corresponding to the pulse voltage to flow through the coil and controlling the valve opening degree of the valve part. [Effects of the Invention]

[0007] This invention can improve the accuracy of flow control in proportional valves. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of a proportional valve in one embodiment. [Figure 2] This is a side view of the plug. [Figure 3] This is a cross-sectional view of a proportional valve in the closed state. [Figure 4] This is a curve diagram showing the change in flow rate with respect to current. [Figure 5] This waveform diagram shows the specific values ​​of the pulse voltages and the current flowing through each pulse voltage. [Figure 6] This is an electrical diagram of a proportional valve control device. [Figure 7]This is a waveform diagram of the pulse voltage used to explain the amplitude. [Figure 8] This is a waveform diagram showing the time variation of a pulse voltage. [Figure 9] This flowchart shows the control flow for a proportional valve. [Figure 10] This is a graph showing the change in fluid flow rate at various pressures. [Figure 11] This waveform diagram shows an alternative method for determining pulse voltage. [Modes for carrying out the invention]

[0009] An embodiment of this disclosure is described below. (Proportional valve 1) As shown in Figure 1, the proportional valve 1 comprises a valve section 2 that switches the fluid flow path and a solenoid 3 that drives the valve section 2. The valve section 2 and the solenoid 3 are integrally mounted by a mounting structure (not shown) using, for example, bolts or screws. The housing 4 of the proportional valve 1 has, for example, a frame 5 for the solenoid 3 and a body 6 for the valve section 2. The proportional valve 1 is an electromagnetic proportional valve in which the opening and closing of the valve section 2 is electromagnetically switched by the solenoid 3. The fluid is, for example, positive-pressure air.

[0010] (Solenoid 3) As shown in Figure 1, the solenoid 3 has a coil 8, a stator 9, and a plunger 10. The coil 8, stator 9, and plunger 10 are housed inside a frame 5. The coil 8 is wound multiple times around a cylindrical bobbin 11. The coil 8 is shielded by a first magnetic frame 12 and a second magnetic frame 13 made of magnetic material. The bobbin 11 has a hole 14 that extends along the axial direction of the coil 8 (the X-axis direction in Figure 1).

[0011] The first magnetic frame 12 is formed, for example, in a substantially cylindrical shape with both ends open and covers the bobbin 11 from the circumferential direction. The second magnetic frame 13 is attached to one opening 15 of the first magnetic frame 12 so as to cover the end portion of the bobbin 11. A seal portion 16 for sealing the gap between the bobbin 11 and the second magnetic frame 13 is attached.

[0012] The stator 9 is attached to the end portion of the hole 14 so as to close the hole 14 of the bobbin 11. The stator 9 has a screwing portion 17 formed at the end portion screwed to a screwed portion 18 formed in the other opening of the first magnetic frame 12. The screwing portion 17 is, for example, an internal thread. The screwed portion 18 is, for example, an external thread.

[0013] The plunger 10 is accommodated in both the hole 14 of the bobbin 11 and the hole 19 of the second magnetic frame 13 so as to be reciprocally movable along the axial direction (X-axis direction in FIG. 1) of the holes 14 and 19. The plunger 10 is arranged coaxially with the stator 9. The tip of the plunger 10 projects a predetermined amount from the hole 19 of the second magnetic frame 13 toward the valve portion 2.

[0014] The solenoid 3 includes an elastic portion 20 that moves the plunger 10 in a direction away from the stator 9 (arrow +X direction in FIG. 1). The elastic portion 20 is, for example, a spring (such as a conical spring). One end of the elastic portion 20 is supported, for example, on the end face of the first magnetic frame 12. The other end of the elastic portion 20 is supported, for example, on the projection 21 at the tip of the plunger 10.

[0015] (Valve portion 2) As shown in FIG. 1, the body 6 has a first hole 23 that houses the tip of the plunger 10 and a second hole 24 arranged coaxially with the first hole 23. The body 6 is formed of, for example, a non-magnetic material. A seal portion 25 for sealing the gap is provided between the body 6 and the first magnetic frame 12. The seal portion 25 is, for example, an O-ring. The body 6 has a supply port 26 for supplying fluid to the inside of the proportional valve 1 and an output port 27 for outputting fluid from the proportional valve 1.

[0016] The valve portion 2 includes a valve 28 whose valve opening degree is set by a solenoid 3. The valve portion 2 includes a plug 29 fitted into the second hole 24. From the approximate center to the tip of the valve 28 is accommodated in the first hole 23. From the approximate center to the base end of the valve 28 is accommodated in a space 30 provided in the plug 29. The base end of the second hole 24 is sealed by the plug 29.

[0017] The valve 28 is, for example, a poppet valve that moves in a direction perpendicular to the valve seat 31 (the X-axis direction in FIG. 1). In the case of this example, the valve seat 31 is, for example, the tip of the plug 29. Therefore, the valve seat 31 is formed in the circumferential direction along the opening of the plug 29. The valve 28 has an opening / closing portion 32 for opening and closing the valve seat 31. The opening / closing portion 32 is formed in the circumferential direction along, for example, the circumference around the axis of the valve 28. The poppet-type valve 28 linearly moves in a perpendicular direction by the drive of the solenoid 3.

[0018] The valve 28 has a columnar valve rod 34 that serves as the main body of the valve 28. The opening / closing portion 32 is formed at a position near the tip of the valve rod 34 and is accommodated in the second hole 24. The opening / closing portion 32 has a projecting seat 35 formed on the outer peripheral surface of the valve rod 34 and a valve body 36 attached to the seat 35. The valve body 36 is formed in an annular shape in the circumferential direction of the valve rod 34.

[0019] The valve rod 34 has a sliding portion 37 slidably accommodated in the space 30 of the plug 29. The sliding portion 37 is arranged at a position near the base end of the valve rod 34. The sliding portion 37 is formed in a shape, so-called, flange shape formed in the circumferential direction of the outer peripheral surface of the valve rod 34. A seal portion 38 for sealing the gap is provided between the plug 29 and the sliding portion 37. The seal portion 38 is, for example, an O-ring. When the valve 28 linearly moves in the axial direction (the X-axis direction in FIG. 1), the seal portion 38 slides on the inner peripheral surface of the space 30 of the plug 29.

[0020] The tip of the valve 28 is supported so as to be relatively movable in the axial direction (X-axis direction in Figure 1) by a stepped support portion 39 provided at the boundary between the first hole 23 and the second hole 24. The base end of the valve 28 is supported so as to be relatively movable in the axial direction (X-axis direction in Figure 1) by a sliding portion 37 provided at the inner circumferential surface of the space 30 of the plug 29.

[0021] As shown in Figure 2, the plug 29 has a recess 40 formed by recessing a predetermined amount from its outer surface. The recess 40 is formed in the circumferential direction of the outer surface of the plug 29. The plug 29 has a hole 41 that connects the internal space 30 to the supply port 26. The hole 41 is formed in the recess 40 of the plug 29. Multiple holes 41 are formed at predetermined intervals in the circumferential direction of the recess 40.

[0022] The plug 29 is fitted with a pair of sealing portions 42 on both sides of the recess 40 to seal the gap between the plug 29 and the body 6. The sealing portions 42 are, for example, O-rings. The plug 29 is attached to the body 6 by screwing a threaded portion 43, provided at its base end, into a threaded portion 44 formed in the second hole 24 of the body 6. The threaded portion 43 is, for example, a male thread. The threaded portion 44 is, for example, a female thread.

[0023] As shown in Figure 1, the plug 29 has a manual operating shaft 46 for manually operating the valve 28. The manual operating shaft 46 is mounted in a through hole 47 formed at the end of the plug 29. A sealing portion 48 is provided between the manual operating shaft 46 and the through hole 47 to seal the gap.

[0024] The proportional valve 1 includes a valve chamber 49 which is opened and closed by a valve 28. In this example, the valve chamber 49 is a region enclosed by, for example, the inner surface of the body 6, the valve 28, and the inner surface of the plug 29. The valve chamber 49 is in communication with a supply port 26 for taking in fluid. The gap between the valve 28 and the plug 29 in the valve chamber 49 is sealed by a seal portion 38. The gap between the body 6 and the plug 29 in the valve chamber 49 is sealed by a seal portion 42. The valve 28 is in an open state when the opening / closing portion 32 moves away from the valve seat 31, and in a closed state when the opening / closing portion 32 contacts the valve seat 31.

[0025] (Electrical circuit 51 of proportional valve 1) As shown in Figure 1, the proportional valve 1 includes an electrical circuit 51 that supplies current to the solenoid 3. The electrical circuit 51 has a circuit board 52 on which various elements are mounted. The circuit board 52 is enclosed by a case 53 attached to the housing 4. The case 53 is provided with a connector 54 for electrically connecting the electrical circuit 51 to the outside. The proportional valve 1 is set to a valve opening degree corresponding to the magnitude of the current flowing from the electrical circuit 51 to the solenoid 3.

[0026] (Balanced proportional valve 1) As shown in Figure 1, the proportional valve 1 is a balanced type in which the pressure acting on the valve section 2 and the pressure acting on the solenoid 3 are equal. When the proportional valve 1 is operating, the fluid pressure in the valve chamber 49 acts on the opening / closing section 32 of the valve 28 and the sliding section 37 of the valve 28. In the case of the balanced proportional valve 1, the area of ​​the valve 28 that receives the fluid pressure at the opening / closing section 32 and the area of ​​the valve 28 that receives the fluid pressure at the sliding section 37 are the same. Therefore, the pressure received at the opening / closing section 32 and the pressure received at the sliding section 37 cancel each other out. In this way, when the pressure acting on the plunger 10 and the pressure acting on the valve section 2 are set to be equal, no differential pressure occurs between the plunger 10 and the valve 28.

[0027] In the case of a balanced proportional valve 1, when current flows through the solenoid 3, the timing of valve opening is consistent regardless of the fluid pressure. That is, the characteristic change between flow rate and current takes the form of a waveform where the valve opening timing is consistent. Thus, in the case of a balanced type, the waveform change that causes the valve opening timing to change in response to fluid pressure is avoided. Note that the characteristic change between flow rate and current takes the form of a waveform where the slope becomes steeper as the pressure increases.

[0028] (Opening and closing operation of proportional valve 1) As shown in Figure 1, when the coil 8 is energized, the plunger 10 is attracted by the coil 8 and moves linearly away from the valve 28 (in the direction of the arrow X in Figure 1), against the elastic force of the elastic part 20. At this time, the opening / closing part 32 of the valve 28 moves away from the valve seat 31. The valve 28 is then positioned according to the current flowing through the coil 8. Therefore, the valve 28 takes an opening degree corresponding to the current flowing through the coil 8.

[0029] On the other hand, as shown in Figure 3, when the coil 8 is not energized, the plunger 10 moves linearly toward the valve 28 (in the direction of the arrow +X in Figure 3) due to the elastic force of the elastic part 20. At this time, the opening / closing part 32 of the valve 28 comes into contact with the valve seat 31. Therefore, the valve 28 becomes closed.

[0030] (Hysteresis of proportional valve 1) As shown in Figure 4, the proportional valve 1 sets the valve opening by adjusting the amount of movement of the plunger 10 in accordance with the current flowing through the coil 8. However, due to the sliding resistance (frictional resistance) of the plunger 10, a loss occurs in the direction of movement. Therefore, when the valve 28 starts to move from a fully closed state to an open state, or from a fully open state to a closed state, a delay occurs in the start of movement due to the loss of sliding resistance. Thus, hysteresis occurs in the proportional valve 1 when controlling the valve opening.

[0031] When hysteresis occurs, even with the same current, a difference (hyperradii) in flow rate will occur between the fully closed → open operation and the fully open → closed operation. In particular, the hyperradii is small at the beginning and end of valve opening and large near the center of valve opening. When controlling the valve opening degree, if such hyperradii (hysteresis) occurs, the accuracy of the control will decrease, so countermeasures are necessary.

[0032] (Proportional valve control device 57) As shown in Figure 6, the proportional valve 1 includes a proportional valve control device 57 that controls the operation of the proportional valve 1. In a balanced proportional valve 1, the proportional valve control device 57 sets the valve opening degree of the valve section 2 by controlling the coil 8. The proportional valve control device 57 includes a drive unit 58 that drives the plunger 10 by applying a pulse voltage Vpl to the coil 8, and a control unit 59 that controls the valve opening degree of the valve section 2 via the drive unit 58. The drive unit 58 and the control unit 59 are composed of various elements mounted on a circuit board 52 of the electrical circuit 51, for example.

[0033] (Circuit configuration of proportional valve control device 57) As shown in Figure 6, the drive unit 58 includes a regulator 60 that outputs a constant voltage and a voltage divider circuit 61 for adjusting the output of the regulator 60. The regulator 60 is, for example, a step-up / step-down regulator. The regulator 60 has an input terminal 60a, an output terminal 60b, a feedback terminal 60c, and a ground terminal 60d. The input terminal 60a is connected to the main power terminal 62. The main power supply voltage Vcc is applied to the main power terminal 62. The output terminal 60b is connected to the coil 8 and the voltage divider circuit 61. The feedback terminal 60c is connected to the midpoint 63 of the voltage divider circuit 61.

[0034] The voltage divider circuit 61 includes a constant resistor 65 having a constant resistance value and a variable resistor 66 whose resistance value can be varied by a control signal Vs from the control unit 59. The variable resistor 66 is, for example, a digital potentiometer whose resistance value can be varied by a digital signal control Vs. A digital potentiometer is, for example, a digital variable resistor whose resistance value can be changed by a digital signal.

[0035] The control unit 59 is composed of, for example, an MPU (Micro Processing Unit) and various memories. The control unit 59 has, for example, a first input terminal 59a, a second input terminal 59b, a third input terminal 59c, a first output terminal 59d, a second output terminal 59e, and a ground terminal 59f. The first input terminal 59a is connected to the midpoint 68 of a resistor R1 connected to the main power terminal 62 and a diode D1 connected to the power terminal 67. A predetermined voltage Vout1, lower than the power supply voltage Vcc, is applied to the power terminal 67. The first input terminal 59a is a terminal for checking whether or not power is supplied to the control unit 59.

[0036] The second input terminal 59b is connected to the midpoint 70 between the power supply terminal 67 and the voltage conversion circuit 69. The voltage conversion circuit 69 is, for example, a three-terminal regulator. The voltage conversion circuit 69 converts the power supply voltage Vcc of the main power supply terminal 62 into a constant drive voltage Va for driving the control unit 59 and outputs it to the control unit 59. The second input terminal 59b is a terminal for inputting the drive voltage Va from the voltage conversion circuit 69.

[0037] The third input terminal 59c is connected to the flow rate setting terminal 71, which is set to a voltage corresponding to the user's target flow rate. The third input terminal 59c is a terminal for inputting the flow rate command value Vin from the flow rate setting terminal 71. The command value Vin is the voltage of the flow rate setting terminal 71, that is, the voltage value corresponding to the user's target flow rate.

[0038] The first output terminal 59d is connected to the variable resistor 66 of the voltage divider circuit 61. The first output terminal 59d adjusts the resistance value of the variable resistor 66 by outputting a control signal Vs to the variable resistor 66 that corresponds to the flow rate set by the user. The control signal Vs is, for example, a digital voltage signal for controlling the resistance value of the digital potentiometer, which is the variable resistor 66.

[0039] The voltage divider circuit 61 outputs a regulator adjustment voltage Vr corresponding to the resistance value of the variable resistor 66 from the midpoint 63 to the feedback terminal 60c of the regulator 60. The regulator 60 outputs a voltage corresponding to the regulator adjustment voltage Vr input to the feedback terminal 60c. The voltage output of the regulator 60 decreases when the voltage at the feedback terminal 60c is lower than the midpoint 63, and increases when the voltage at the feedback terminal 60c is higher than the midpoint 63. In this way, the regulator 60 outputs a pulse voltage Vpl with a waveform corresponding to the regulator adjustment voltage Vr input from the voltage divider circuit 61 to the coil 8. As a result, a current corresponding to the pulse voltage Vpl flows through the coil 8. Therefore, the valve opening degree of the valve section 2 is set to an opening degree corresponding to the pulse voltage Vpl.

[0040] The second output terminal 59e is connected to a switching circuit 72 located on the wiring path of the coil 8. In this example, the switching circuit 72 is, for example, an on / off switching circuit using a photocoupler. The second output terminal 59e outputs an on / off switching signal Vt to the switching circuit 72 to switch between on and off, thereby switching between supplying voltage to the proportional valve 1 and cutting off the voltage.

[0041] (Characteristics of the operation of the control unit 59) As shown in Figure 5, the control unit 59 applies a pulse voltage Vpl having an amplitude Ax corresponding to the command value Vin of the valve opening degree from the drive unit 58 to the coil 8, and controls the valve opening degree of the valve unit 2 by flowing a current corresponding to the pulse voltage Vpl through the coil 8. Specifically, the control unit 59 controls the amplitude Ax by switching the resistance value of the variable resistor 66 based on the command value Vin. In this example, the control unit 59 adjusts the pulse voltage Vpl, which is the output of the regulator 60, by adjusting the resistance value of the digital potentiometer.

[0042] The control unit 59 causes the drive unit 58 to output a pulse voltage Vpl that corresponds to the phenomenon (hysteresis) in which the valve opening differs depending on whether the valve opening is increased or decreased, even with the same current. In this example, the amplitude Ax of the pulse voltage Vpl is set to be small when the valve section 2 is near fully closed and fully open, and large when the valve opening is near the middle.

[0043] As shown in Figure 7, the current flowing through coil 8 is determined, for example, by the bottom Bt of the amplitude Ax, the peak Pk of the amplitude Ax, and the difference between bottom Bt and peak Pk. The current flowing through coil 8 increases, for example, as bottom Bt and peak Pk are increased. Also, the current flowing through coil 8 decreases when both bottom Bt and peak Pk are relatively low values, and increases when both bottom Bt and peak Pk are relatively high values.

[0044] As shown in Figure 5, the control unit 59 changes the amplitude Ax by fixing one of the bottom Bt and peak Pk of the amplitude Ax and making the other variable. In this example, when the pulse voltage Vpl applied to the coil 8 is less than the median of the power supply voltage Vcc, the current is adjusted by fixing the bottom Bt and increasing the peak Pk. On the other hand, when the pulse voltage Vpl applied to the coil 8 is equal to or greater than the median of the power supply voltage Vcc, the current is adjusted by fixing the peak Pk and increasing the bottom Bt.

[0045] As shown in Figure 8, the pulse voltage Vpl has a constant period regardless of its amplitude Ax. Thus, the pulse voltage Vpl is a periodic signal in which the amplitude Ax changes with a constant period. The control unit 59 controls the opening degree of the proportional valve 1 by applying the pulse voltage Vpl, in which the amplitude Ax changes with a constant period, from the regulator 60 to the coil 8.

[0046] Next, the operation of the proportional valve control device 57 (proportional valve control method) of this embodiment will be described. (Control flow of proportional valve 1) Figure 9 is a flowchart of the operations performed by the control unit 59 during flow rate adjustment. For example, when the user's target flow rate is set at the flow rate setting terminal 71, the control unit 59 starts processing when it receives a command value Vin based on that setting at the third input terminal 59c.

[0047] In step 101, the control unit 59 converts the input command value Vin into a voltage value to be applied to the coil 8. If the power supply voltage Vcc is, for example, "12V", the command value Vin is converted to a value between "0V and 12V".

[0048] In step 102, the control unit 59 determines whether the converted voltage value is less than a predetermined voltage value for switching the control content. In this example, the power supply voltage Vcc is "12V", and the control content is switched at its median value of "6V", so it is determined whether the converted voltage value is less than 6V.

[0049] If the converted voltage value is determined to be less than 6V in step 102, proceed to step 103. If the converted voltage value is determined to be 6V or greater in step 102, proceed to step 112.

[0050] In step 103, the control unit 59 sets the bottom Bt and peak Pk of the pulse voltage Vpl applied to the coil 8. If the converted voltage value is less than 6V, the control unit 59 sets the bottom Bt to "0[V]" and the peak Pk to "Y=aX[V]". Herein, "a" is a correction coefficient. The correction coefficient "a" is, for example, an experimental coefficient calculated from the hysteresis of the proportional valve 1. "X" is the target flow rate set by the user, i.e., the voltage converted value of the command value Vin. The correction coefficient "a" is, for example, a variable value that takes a value corresponding to the voltage converted value of the command value Vin.

[0051] In step 104, the control unit 59 determines whether the peak Pk is less than the maximum value of the power supply voltage Vcc (in this example, less than 12[V]). In step 105, if the peak Pk is less than the voltage value of the power supply voltage Vcc, the process proceeds to step 106. In step 105, if the peak Pk is equal to or greater than the maximum value of the power supply voltage Vcc, the process proceeds to step 110.

[0052] In step 105, the control unit 59 determines the combination of the bottom Bt and peak Pk of the pulse voltage Vpl to be "0[V]" for the bottom Bt and "Y=aX[V]" for the peak Pk.

[0053] In step 106, the control unit 59 outputs a pulse voltage Vpl to the coil 8 that has a bottom Bt and peak Pk set in step 105. In step 107, the control unit 59, as processing the output of the pulse voltage Vpl, first outputs a control signal Vs corresponding to the bottom Bt determined in step 105 to the variable resistor 66, thereby setting the resistance value of the variable resistor 66 to a value that allows 0[V] to be output from the regulator 60 to the coil 8 for a predetermined time. As a result, 0[V] is output from the regulator 60 to the coil 8 for a predetermined time.

[0054] In step 108, the control unit 59 then processes the output of the pulse voltage Vpl by outputting a control signal Vs corresponding to the peak Pk determined in step 105 to the variable resistor 66, thereby setting the resistance value of the variable resistor 66 to a value that allows the regulator 60 to output Y=aX[V] to the coil 8 for a predetermined time. As a result, Y=aX[V] is output from the regulator 60 to the coil 8 for a predetermined time.

[0055] Then, in step 109, a pulse voltage Vpl of a constant period is applied to the coil 8 by repeating the processes of steps 107 and 108 described above. As a result, a current based on the combination of bottom Bt and peak Pk set in step 105 flows through the coil 8, and consequently, the valve 28 opens to an opening degree corresponding to this current.

[0056] If the process proceeds to step 110, the control unit 59 determines the combination of the bottom Bt and peak Pk of the pulse voltage Vpl to be "0[V]" for the bottom Bt and "12[V]" for the peak Pk.

[0057] Then, in step 111, the control unit 59 adjusts the variable resistor 66 by the control signal Vs so that 0[V] and 12[V] are alternately applied from the regulator 60 to the coil 8. As a result, a current based on the bottom Bt and peak Pk combination set in step 110 flows through the coil 8, and consequently, the valve 28 opens to an opening degree corresponding to this current.

[0058] If the process proceeds to step 112, the control unit 59 sets the bottom Bt to "Y=a(X-6)0[V]" and the peak Pk to "12[V]". In step 113, the control unit 59 determines whether the bottom Bt is less than the maximum value of the power supply voltage Vcc (in this example, less than 12V). If the bottom Bt is less than the maximum value of the power supply voltage Vcc in step 113, the process proceeds to step 114. If the bottom Bt is greater than or equal to the maximum value of the power supply voltage Vcc in step 113, the process proceeds to step 116.

[0059] In step 114, the control unit 59 determines the combination of the bottom Bt and peak Pk of the pulse voltage Vpl to be "Y=a(X-6)[V]" for the bottom Bt and "12[V]" for the peak Pk.

[0060] Then, in step 115, the control unit 59 adjusts the variable resistor 66 by the control signal Vs so that Y=a(X-6)[V] and 12[V] are alternately applied from the regulator 60 to the coil 8. As a result, a current based on the combination of bottom Bt and peak Pk set in step 114 flows through the coil 8, and consequently, the valve 28 opens to an opening degree corresponding to this current.

[0061] If the process proceeds to step 116, the control unit 59 determines the combination of bottom Bt and peak Pk of the pulse voltage Vpl to be "12[V]" for both bottom Bt and peak Pk.

[0062] Then, in step 117, the control unit 59 adjusts the variable resistor 66 by the control signal Vs so that 12[V] is constantly applied from the regulator 60 to the coil 8. As a result, a current based on the combination of bottom Bt and peak Pk set in step 117 flows through the coil 8, and consequently, the valve 28 opens to an opening degree corresponding to this current.

[0063] (Advantages of proportional valve control in this example) As shown in Figure 8, the voltage applied to the coil 8 from the regulator 60 to supply current to the coil 8 is a pulse voltage Vpl that repeatedly switches on and off at a predetermined period. This makes it possible to generate minute vibrations when the plunger 10 moves, thereby reducing the sliding resistance (frictional resistance) generated in the plunger 10. Therefore, it is possible to keep the flow rate difference between when the valve 28 is open and when it is closed, so-called hysteresis, to a minimum.

[0064] In particular, as shown in Figure 5, the pulse voltage Vpl in this example is set so that the amplitude Ax increases as the hysteresis during opening and closing of valve 28 increases. Specifically, the amplitude Ax is increased as the movement range of plunger 10 approaches the intermediate position. Therefore, in the region where the hysteresis is large, the amount of micro-vibration of plunger 10 increases, making it possible to suppress the hysteresis accordingly. Thus, it becomes possible to control the flow rate of proportional valve 1 with high precision.

[0065] Figure 10 shows the fluid flow rate change curves L at pressures of "Pa", "Pb", and "Pc". In Figure 10, the flow rate change curve L at a pressure of Pa (>Pb) is "L1", the flow rate change curve L at a pressure of Pb (>Pc) is "L2", and the flow rate change curve L at a pressure of Pc is "L3". In this example, it can be seen that the hysteresis is kept small at all pressures from "Pa" to "Pc". Therefore, it can be seen that the hysteresis can be kept small even when the fluid pressure changes.

[0066] (Effects of the embodiment) According to the configuration of the above embodiment, the following effects can be obtained. (1) The proportional valve 1 is a balanced type in which the pressure acting on the plunger 10, which moves based on the magnetomotive force of the coil 8 and the elastic force of the elastic part 20 to open and close the valve section 2, and the pressure acting on the valve section 2 are set to be the same. The proportional valve control device 57 sets the valve opening degree of the valve section 2 by controlling the coil 8 in the balanced type proportional valve 1. The proportional valve control device 57 comprises a drive unit 58 that drives the plunger 10 by applying a pulse voltage Vpl to the coil 8, and a control unit 59 that controls the valve opening degree of the valve section 2. The control unit 59 applies a pulse voltage Vpl having an amplitude Ax corresponding to the command value Vin of the valve opening degree from the drive unit 58 to the coil 8, and controls the valve opening degree of the valve section 2 by flowing a current corresponding to the pulse voltage Vpl through the coil 8.

[0067] In this configuration, a pulse voltage Vpl having an amplitude Ax corresponding to the valve opening is applied to the coil 8 to open and close the valve 28, making it possible to generate minute vibrations in the plunger 10 corresponding to the valve opening. This makes it possible to suppress the effect of sliding resistance when the plunger 10 moves. Therefore, the accuracy of flow control can be improved.

[0068] (2) The pulse voltage Vpl has a constant period regardless of the amplitude Ax. With this configuration, since it is only necessary to apply the pulse voltage Vpl at a constant period, simple control is required. (3) The control unit 59 outputs a pulse voltage Vpl to the drive unit 58 that corresponds to the phenomenon in which the valve opening differs when the valve opening is increased and when the valve opening is decreased, even with the same current. With this configuration, the phenomenon of hysteresis, which is the phenomenon in which the valve opening differs between when the valve is open and when it is closed, even with the same current value, can be suppressed.

[0069] (4) The amplitude Ax is set to be small when the valve section 2 is near fully closed and near fully open, and large when the valve opening is near the middle. This configuration can suitably address the phenomenon in which the sliding resistance becomes large when the plunger 10 is located near the middle of the valve opening.

[0070] (5) The drive unit 58 includes a regulator 60 that outputs a constant voltage and a voltage divider circuit 61 for adjusting the output of the regulator 60. The voltage divider circuit 61 includes a constant resistor 65 having a constant resistance value and a variable resistor 66 whose resistance value can be changed by a control signal Vs from the control unit 59. The control unit 59 controls the amplitude Ax by switching the resistance value of the variable resistor 66 based on the command value Vin. With this configuration, the drive unit 58 can be made into a simple configuration using the regulator 60 and the voltage divider circuit 61. In addition, the amplitude Ax of the pulse voltage Vpl can be changed by simple control of switching the resistance value of the variable resistor 66 of the voltage divider circuit 61.

[0071] (6) The variable resistor 66 is a digital potentiometer whose resistance value can be varied by a digital control signal Vs. With this configuration, the resistance value of the variable resistor 66 can be easily adjusted by the digital signal output from the control unit 59.

[0072] (7) The control unit 59 changes the amplitude Ax by fixing one of the bottom Bt and peak Pk of the amplitude Ax as a fixed value and making the other variable. With this configuration, the amplitude Ax of the pulse voltage Vpl can be easily set.

[0073] (Other embodiments) This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0074] As shown in Figure 11, the control unit 59 may change the amplitude Ax by processing both the bottom Bt and peak Pk of the amplitude Ax to be variable. This configuration makes it possible to diversify the method of determining the amplitude Ax of the pulse voltage Vpl, which is advantageous for setting the optimal amplitude Ax.

[0075] The drive unit 58 is not limited to being composed of a regulator 60 and a voltage divider circuit 61. For example, the drive unit 58 may be composed of an IC or the like whose output voltage changes based on a control signal Vs.

[0076] • Variable resistor 66 is not limited to a digital potentiometer; a mechanical variable resistor may also be used. The pulse voltage Vpl is not limited to signals with a constant period; it can also be a signal with a changing period.

[0077] Valve 28 is not limited to a poppet valve; for example, it may be a spool valve. The proportional valve 1 is not limited to a two-port type having, for example, a supply port 26 and an output port 27, but may also be a three-port type having an exhaust port in addition to these.

[0078] • Proportional valve 1 can be applied, for example, to factory automation (FA) equipment and medical devices. Furthermore, proportional valve 1 may be used in fluid control devices for the food industry, heating devices for packaging chemicals, and gas control devices related to semiconductor manufacturing.

[0079] The control unit 59 may be composed of [1] one or more processors operating according to a computer program (software), or [2] a combination of such processors and one or more dedicated hardware circuits, such as application-specific integrated circuits (ASICs), that perform at least some of the various processes. The processor includes a CPU and memory such as RAM and ROM, and the memory stores program code or instructions configured to cause the CPU to perform the processes. The memory (computer-readable medium) includes any available medium that can be accessed by a general-purpose or dedicated computer. Alternatively, instead of a computer including the above-mentioned processor, a processing circuit composed of one or more dedicated hardware circuits that perform all of the various processes may be used.

[0080] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the scope of equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or less of those elements, fall within the scope and concept of this disclosure. [Explanation of Symbols]

[0081] 1...Proportional valve, 2...Valve section, 8...Coil, 10...Plunger, 20...Elastic section, 57...Proportional valve control device, 58...Drive unit, 59...Control unit, 60...Regulator, 61...Voltage divider circuit, 65...Constant resistor, 66...Variable resistor, Vpl...Pulse voltage, Vin...Command value, Ax...Amplitude, Vs...Control signal, Bt...Bottom, Pk...Peak.

Claims

1. In a balanced proportional valve in which the pressure acting on a plunger that moves to open and close the valve section based on the magnetomotive force of a coil and the elastic force of an elastic part, and the pressure acting on the valve section are set to be the same, a proportional valve control device that sets the valve opening degree of the valve section by controlling the coil, A drive unit that applies a pulse voltage to the coil to drive the plunger, The system includes a control unit that applies a pulse voltage having an amplitude corresponding to a command value for the valve opening degree from the drive unit to the coil, and controls the valve opening degree of the valve by flowing a current corresponding to the pulse voltage through the coil, A proportional valve control device, wherein the control unit is set to make the difference between the bottom and peak of the amplitude of the pulse voltage larger when the valve is near the middle of the valve opening than when the valve is near the fully closed or fully open position.

2. The proportional valve control device according to claim 1, wherein the pulse voltage has a constant period regardless of the amplitude.

3. The proportional valve control device according to claim 1, wherein the control unit causes the drive unit to output a pulse voltage corresponding to the phenomenon in which the valve opening differs when the valve opening is increased and when the valve opening is decreased, even with the same current.

4. The drive unit comprises a regulator that outputs a constant voltage and a voltage divider circuit for adjusting the output of the regulator. The voltage divider circuit comprises a constant resistor having a constant resistance value and a variable resistor whose resistance value can be varied by a control signal from the control unit. The proportional valve control device according to claim 1, wherein the control unit controls the amplitude by switching the resistance value of the variable resistor based on the command value.

5. The proportional valve control device according to claim 4, wherein the variable resistor is a digital potentiometer whose resistance value can be varied by the control signal, which is a digital signal.

6. In a balanced proportional valve in which the pressure acting on a plunger that moves to open and close the valve section based on the magnetomotive force of a coil and the elastic force of an elastic part, and the pressure acting on the valve section are set to be the same, a proportional valve control device that sets the valve opening degree of the valve section by controlling the coil, A drive unit that applies a pulse voltage to the coil to drive the plunger, The system includes a control unit that applies a pulse voltage having an amplitude corresponding to a command value for the valve opening degree from the drive unit to the coil, and controls the valve opening degree of the valve by flowing a current corresponding to the pulse voltage through the coil, The control unit is a proportional valve control device that changes the amplitude by processing such that one of the bottom and peak of the amplitude is a fixed value and the other is a variable value.

7. The proportional valve control device according to claim 1, wherein the control unit changes the amplitude by processing that makes both the bottom and peak of the amplitude variable.

8. In a balanced proportional valve in which the pressure acting on a plunger that moves to open and close the valve section based on the magnetomotive force of a coil and the elastic force of an elastic part, and the pressure acting on the valve section are set to be the same pressure, a proportional valve control method for setting the valve opening degree of the valve section by controlling the coil, A proportional valve control method is provided, wherein a drive unit that applies a voltage to the coil to drive the plunger applies a pulse voltage having an amplitude corresponding to a command value for the valve opening to the coil, thereby causing a current corresponding to the pulse voltage to flow through the coil to control the valve opening of the valve, and the method is set so that the difference between the bottom and peak of the amplitude of the pulse voltage is larger when the valve opening is near the middle of the valve opening than when the valve is near the fully closed or fully open.

Images