Motor valve control device and valve device

Abstract

[Problem] To provide a motor valve control device and a valve device capable of normally operating a motor valve, and suppressing shortening of the service life of the motor valve by reducing deformation and wear of a member of the motor valve when a valve body contacts a valve seat. [Solution] When a motor valve control device 70 inputs a pulse to a stepping motor 66 of a motor valve 5 to rotate a rotor 28 in either a closing direction or an opening direction, the motor valve control device causes the stepping motor 66 to generate a large amount of torque corresponding to initial K pulses from the start of input of the pulses to the stepping motor 66, and causes the stepping motor 66 to generate a small amount of torque corresponding to the pulses following the initial K pulses. Then, after processing for rotating the rotor 28 in the closing direction to position the rotor 28 at the reference position, the motor valve control device 70 rotates the rotor 28 in the opening direction by inputting S pulses to the stepping motor 66.

Description

Electric valve control device and valve device

[0001] The present invention relates to an electric valve control device and a valve device having the electric valve control device and an electric valve.

[0002] Patent Document 1 discloses an example of a conventional electric valve. The electric valve of Patent Document 1 has a valve body, a valve element, a guide member, a drive shaft, a gear mechanism, and a stepping motor. The valve element faces the valve seat of the valve body. The guide member has a female screw and is attached to the valve body. The drive shaft has a male screw that is screwed into the female screw. The gear mechanism decelerates the rotation of the rotor of the stepping motor. The output shaft of the gear mechanism is connected to the drive shaft. When the drive shaft is rotated, the drive shaft moves in the axial direction.

[0003] The electric valve is connected to an electric valve control device. When the electric valve control device inputs a pulse to the stepping motor, the rotor rotates. When the rotor rotates in the closing direction, the drive shaft pushes the valve element. The valve element approaches the valve seat and contacts the valve seat. The position of the rotor at this time is the valve closing position. When the rotor rotates further in the closing direction, the valve element is pressed against the valve seat, and the rotation of the rotor in the closing direction is restricted. The position of the rotor at this time is the reference position. When the rotor rotates in the opening direction, the drive shaft moves away from the valve seat, and the valve element moves away from the valve seat. The position of the rotor when the valve element is farthest from the valve seat is the fully open position. The number of pulses required to rotate the rotor from the fully open position to the reference position is called the full stroke number.

[0004] The electric valve control device initializes the electric valve (initialization process), for example, when an unexpected power loss occurs. In the initialization process, the electric valve control device inputs a pulse of an initialization number larger than the full stroke number to the stepping motor and rotates the rotor in the closing direction. Thereby, when the input of the pulse to the stepping motor ends, the rotor is positioned at the reference position.

[0005] Furthermore, when the electric valve control device receives a valve-closing command from an external control device, it positions the rotor at the reference position (valve-closing process). In the valve-closing process, the electric valve control device inputs the necessary number of pulses to the stepping motor to rotate the rotor from its current position to the reference position, thereby rotating the rotor in the closing direction. As a result, once the input of pulses to the stepping motor is complete, the rotor is positioned at the reference position.

[0006] Japanese Patent Publication No. 2015-14306

[0007] In a stepping motor, the torque required when the rotor starts rotating (startup state) is greater than the torque required when the rotor is already rotating (rotating state). Therefore, the electric valve control device generates a large torque in the stepping motor during the startup state and a small torque in the rotating state. This ensures that the rotor rotates reliably during the startup state and that the electric valve operates normally.

[0008] When the electric valve control device starts the initialization process, it generates a large torque in the stepping motor in the startup state to rotate the rotor. Then, if the rotor is in the reference position just before the start of the initialization process, the valve body contacts the valve seat in the startup state and is strongly pressed against the valve seat. At this time, a force corresponding to the torque generated by the stepping motor is applied to components such as the valve body, valve seat, gears, and screws, and the amount of deformation and wear of each component will be proportional to this force. Therefore, a large torque accelerates the deformation and wear of the components. Furthermore, if pulse input to the stepping motor continues after the rotor has reached the reference position, the stepping motor will lose step, and a force corresponding to the torque will be intermittently applied to the components, and a large torque will further accelerate the deformation and wear of the components.

[0009] When components deform or wear, the play between components increases, which can lead to increased backlash in the electric valve. Backlash causes a period where, even if a pulse is input to the stepping motor when the rotor's rotation direction changes, the rotor's rotation is not transmitted to the drive shaft. As backlash increases, this period also increases. Changes in backlash alter the valve opening degree of the electric valve relative to the number of pulses input to the stepping motor. Furthermore, deformation or wear of the valve body or valve seat can alter the flow characteristics of the electric valve. Therefore, deformation and wear of components reduce the accuracy of flow control in the electric valve. Thus, high torque accelerates deformation and wear of components, shortening the lifespan of the electric valve.

[0010] Therefore, the present invention aims to provide an electric valve control device and a valve device that can operate an electric valve normally and reduce deformation and wear of the electric valve components when the valve body contacts the valve seat, thereby suppressing a shortened lifespan of the electric valve.

[0011] To achieve the above objective, an electric valve control device according to one aspect of the present invention controls an electric valve having a valve body having a valve seat, a valve element facing the valve seat, a stepping motor having a rotor and a stator, and a drive mechanism for moving the valve element in accordance with the rotation of the rotor, wherein when the rotor is in a reference position, the valve element is in contact with the valve seat and the rotation of the rotor in the closing direction is restricted, and when the electric valve control device inputs pulses to the stepping motor to rotate the rotor in either the closing or opening direction, it generates a large torque in the stepping motor in response to the first K pulses from the start of pulse input to the stepping motor, generates a small torque in response to pulses following the first K pulses, rotates the rotor in the closing direction and positions it in the reference position, and then inputs S pulses to the stepping motor to rotate the rotor in the opening direction, wherein K and S are natural numbers.

[0012] In the present invention, it is preferable that the following formula (1) is satisfied: (1) S ≥ K

[0013] In the present invention, when the number of pulses corresponding to the backlash of the drive mechanism is J, it is preferable that the following equation (2) is satisfied: (2) J ≥ S

[0014] In the present invention, it is preferable that when the rotor is rotated in the closing direction, the valve body reaches a closed position where it contacts the valve seat, and when it is rotated further in the closing direction, it reaches a reference position, and when the electric valve control device minimizes the valve opening of the electric valve, it positions the valve body at a position corresponding to the closed position or at a position further from the valve seat than the position corresponding to the closed position, and when the number of pulses required to rotate the rotor from the closed position to the reference position is C, the following equations (1) and (3) are satisfied: (1) S ≥ K (3) C ≥ S

[0015] In the present invention, it is preferable that the number of pulses corresponding to the backlash of the drive mechanism is J, and when the electric valve control device rotates the rotor in the opening direction and then inputs pulses to the stepping motor to rotate the rotor in the closing direction, it generates a large torque in the stepping motor in response to the first (J+K) pulses from the start of pulse input to the stepping motor to rotate the rotor in the closing direction, and generates a small torque in the stepping motor in response to pulses following the first (J+K) pulses. When the rotor rotates in the closing direction and then inputs pulses to the stepping motor to rotate the rotor in the opening direction, it generates a large torque in the stepping motor in response to the first (J+K) pulses from the start of pulse input to the stepping motor to rotate the rotor in the opening direction, and generates a small torque in the stepping motor in response to pulses following the first (J+K) pulses.

[0016] In the present invention, when the rotor is rotated from the reference position in the opening direction, the valve body reaches an open valve position where it separates from the valve seat, and when the electric valve control device inputs a pulse to the stepping motor to rotate the rotor in the opening direction, it is preferable that the stepping motor generates a large torque in response to the pulse input to the stepping motor when the rotor is in the section from the reference position to the open valve position.

[0017] In the present invention, it is preferable that when the rotor is rotated in the closing direction, the valve body reaches a closed valve position in contact with the valve seat, and when it is rotated further in the closing direction, it reaches the reference position, and the electric valve control device selectively performs a valve closing process to position the rotor at the reference position and an alternative valve closing process to position the rotor at an alternative reference position between the closed valve position and the reference position.

[0018] In the present invention, it is preferable that the electric valve control device counts the number of times the process of rotating the rotor in the closing direction to position it at the reference position is performed, and when the electric valve control device receives a valve closing command from an external control device, it performs the valve closing process if the number of executions is less than or equal to the switching determination number, and performs the alternative valve closing process if the number of executions is greater than the switching determination number.

[0019] In the present invention, it is preferable that the number of executions is the number of times the process is performed in which a number of pulses greater than the number of pulses required to position the rotor at the reference position is input to the stepping motor.

[0020] To achieve the above objective, another aspect of the present invention provides a valve device comprising the electric valve control device and the electric valve.

[0021] According to the present invention, when the electric valve control device inputs pulses to a stepping motor to rotate the rotor, it generates a large torque in the stepping motor in response to the first K pulses, and a small torque in response to pulses following the first K pulses. Then, following a process of rotating the rotor in the closing direction to position it in the reference position, the electric valve control device inputs S pulses to the stepping motor to rotate the rotor in the opening direction. In this way, after the rotor is positioned in the reference position, it rotates in the opening direction and moves to a retracted position that is a distance corresponding to S pulses from the reference position. For example, when the initialization process is performed with the rotor in the reference position, the valve body is strongly pressed against the valve seat in response to K pulses. When the initialization process is performed with the rotor in the retracted position, (i) when S < K, the valve body is strongly pressed against the valve seat in response to (K - S) pulses (less than K), or (ii) when S ≥ K, the stepping motor generates a small torque when the rotor reaches the reference position, and the valve body is not strongly pressed against the valve seat. Therefore, it is possible to suppress the valve body from being pressed too hard against the valve seat. Consequently, the electric valve can operate normally, and deformation and wear of the electric valve components when the valve body contacts the valve seat can be reduced, thereby preventing a shortened lifespan of the electric valve.

[0022] This is a cross-sectional view of a valve device according to one embodiment of the present invention. This is an enlarged cross-sectional view of a part of the valve device. This is a schematic diagram showing the rotor and stator of the valve device. This is a diagram showing the connection relationships between the rotor, stator, motor driver, and computer of the valve device. This is a diagram showing an example of the relationship between pulses and signals input to the motor driver. This is a diagram showing an example of the waveform of the current flowing through the stator. This is a diagram showing an example of the relationship between the rotor position and the valve opening of the valve device. This is a diagram showing another example of the relationship between the rotor position and the valve opening of the valve device. This is a diagram showing an example of the relationship between pulses and torque. This is a diagram showing another example of the relationship between pulses and torque.

[0023] Hereinafter, a valve device according to one embodiment of the present invention will be described with reference to Figures 1 to 10.

[0024] The valve device 1 according to this embodiment is incorporated into a refrigeration cycle system, for example, and used as a flow control valve to control the flow rate of refrigerant.

[0025] As shown in Figure 1, the valve device 1 includes an electric valve 5 and an electric valve control device 70.

[0026] The electric valve 5 comprises a valve body 10, a valve element 20, a rotor 28, a drive mechanism 30, and a stator 60.

[0027] The valve body 10 includes a housing 11, a sleeve 15, a connecting plate 16, and a can 17.

[0028] The housing 11 has a valve chamber 12, a valve port 13, and a valve seat 14. The valve port 13 is connected to the valve chamber 12. The valve seat 14 surrounds the valve port 13 in the valve chamber 12. The housing 11 integrally has a cylindrical peripheral wall portion 11a and a bottom wall portion 11b connected to the lower end of the peripheral wall portion 11a. A first conduit 18 connected to the valve chamber 12 is joined to the peripheral wall portion 11a. The valve port 13 is provided in the bottom wall portion 11b, and a second conduit 19 connected to the valve port 13 is joined to it. The inner circumferential surface of the peripheral wall portion 11a is provided with a retaining surface 11c which is an annular plane facing upward.

[0029] The sleeve 15 integrally comprises a cylindrical portion 15a and a flange portion 15b. The inner diameter of the upper part of the cylindrical portion 15a is larger than the inner diameter of the lower part of the cylindrical portion 15a. The inner circumferential surface of the cylindrical portion 15a is provided with a stepped portion 15c, which is an annular plane facing upward. The flange portion 15b has an annular shape. The inner circumferential edge of the flange portion 15b is connected to the upper end of the cylindrical portion 15a. The sleeve 15 is positioned inside the housing 11. The flange portion 15b is in contact with the retaining surface 11c of the housing 11.

[0030] The connecting plate 16 has an annular shape. The peripheral wall portion 11a of the housing 11 is positioned inside the connecting plate 16. The inner peripheral edge of the connecting plate 16 is joined to the peripheral wall portion 11a.

[0031] The can 17 has a cylindrical shape. The can 17 is open at the lower end and closed at the upper end. The lower end of the can 17 is joined to the outer edge of the connecting plate 16.

[0032] The valve body 20 has a body portion 21, a valve portion 22, a spring receiving portion 23, and a ball receiving portion 24. The body portion 21 has a cylindrical shape. The valve portion 22 has a conical shape with its tip pointing downward. The valve portion 22 is coaxially connected to the lower end of the body portion 21. The valve portion 22 faces the valve seat 14 in the vertical direction (axis L direction). The spring receiving portion 23 has an annular shape. The outer diameter of the spring receiving portion 23 is larger than the outer diameter of the body portion 21. The inner periphery of the spring receiving portion 23 is connected to the upper end of the body portion 21. The body portion 21, the valve portion 22, and the spring receiving portion 23 are integrally formed. The ball receiving portion 24 is attached to the upper end surface of the body portion 21.

[0033] The body portion 21 is positioned inside the cylindrical portion 15a of the sleeve 15 and is supported by the lower part of the cylindrical portion 15a so as to be movable in the vertical direction. The valve opening spring 25 is positioned between the spring receiving portion 23 and the stepped portion 15c of the sleeve 15. The valve opening spring 25 is a compression coil spring and pushes the valve body 20 upward.

[0034] The rotor 28 is a magnetic rotor. The rotor 28 has a cylindrical shape. As shown in Figure 2, the rotor 28 is located inside the can 17. Also, as shown in Figure 3, the rotor 28 has multiple magnetic poles (multiple north poles and multiple south poles). The multiple north poles and multiple south poles are located on the outer circumferential surface of the rotor 28. The multiple north poles and multiple south poles extend in the vertical direction. The multiple north poles and multiple south poles are arranged alternately at equal angular intervals in the circumferential direction.

[0035] The drive mechanism 30 is located inside the can 17. The drive mechanism 30 includes a drive shaft 31, a guide member 35, a connecting member 42, a rotor shaft 43, a bearing member 44, and a gear mechanism 50. The drive mechanism 30 moves the valve body 20 in the vertical direction. In Figure 2, the components of the valve device 1 located outside the can 17 are omitted.

[0036] The drive shaft 31 comprises a shaft body 32, a connecting portion 33, and a ball 34. The shaft body 32 has a cylindrical shape. The shaft body 32 has a male thread 32t. The male thread 32t is located on the outer circumferential surface of the shaft body 32. The connecting portion 33 has a rectangular flat plate shape. The lower end of the connecting portion 33 is connected to the upper end surface of the shaft body 32. The shaft body 32 and the connecting portion 33 are integrally formed. The ball 34 is joined to the lower end surface of the shaft body 32. The ball 34 is in slidable contact with the ball bearing portion 24 of the valve body 20.

[0037] The guide member 35 has a cylindrical shape. The guide member 35 is positioned inside the upper part of the peripheral wall portion 11a of the housing 11. The guide member 35 is fixed to the peripheral wall portion 11a. The flange portion 15b of the sleeve 15 is held between the lower end surface of the guide member 35 and the holding surface 11c of the peripheral wall portion 11a. The guide member 35 has a female thread 35t. The female thread 35t is positioned at the lower part of the inner circumferential surface of the guide member 35. The male thread 32t of the drive shaft 31 is screwed into the female thread 35t.

[0038] The connecting member 42 has a disc shape. The connecting member 42 connects the upper end of the rotor 28 to the rotor shaft 43. The connecting member 42 rotates together with the rotor 28. The bearing member 44 is positioned above the rotor 28. The bearing member 44 rotatably supports the upper end of the rotor shaft 43.

[0039] The gear mechanism 50 is a planetary gear mechanism. The gear mechanism 50 reduces the rotation of the rotor 28 and transmits it to the drive shaft 31. The gear mechanism 50 is located inside the rotor 28. The gear mechanism 50 includes a gear case 51, a fixed ring gear 52, a sun gear 53, a plurality of planetary gears 54, a carrier 55, an output gear 56, and an output shaft 57.

[0040] The gear case 51 has a cylindrical shape. The gear case 51 is fixed to the upper part of the peripheral wall portion 11a of the housing 11. The fixed ring gear 52 is an internal gear. The fixed ring gear 52 is fixed to the upper part of the gear case 51. The sun gear 53 is connected to the lower surface of the connecting member 42. The sun gear 53 and the connecting member 42 are integrally formed. The rotor shaft 43 is inserted inside the sun gear 53. Multiple planetary gears 54 surround the sun gear 53. Multiple planetary gears 54 mesh with the fixed ring gear 52 and the sun gear 53. The carrier 55 has a plate shape. The carrier 55 has a shaft 55a that rotatably supports multiple planetary gears 54. The output gear 56 is an internal gear with a bottomed cylindrical shape. The output gear 56 meshes with multiple planetary gears 54.

[0041] The output shaft 57 has a cylindrical shape. The upper part of the output shaft 57 is fitted into a hole provided in the bottom wall of the output gear 56. The lower part of the output shaft 57 is positioned inside the guide member 35. The output shaft 57 is rotatably supported by the guide member 35. The output shaft 57 rotates together with the output gear 56. The output shaft 57 has a bearing hole in which the lower end of the rotor shaft 43 is positioned. The output shaft 57 rotatably supports the lower end of the rotor shaft 43.

[0042] The output shaft 57 has a slit 58. The slit 58 is provided on the lower end surface of the output shaft 57 and extends in the vertical direction. The width of the slit 58 is the same as (or substantially the same as) the thickness of the connecting portion 33 of the drive shaft 31. The output shaft 57 is connected to the drive shaft 31. Specifically, the connecting portion 33 is positioned in the slit 58. The connecting portion 33 is allowed to move in the direction of axis L relative to the output shaft 57, but rotation around axis L is restricted. When the output shaft 57 rotates, the connecting portion 33 (drive shaft 31) rotates together with the output shaft 57, and the connecting portion 33 moves vertically within the slit 58.

[0043] The stator 60 has a cylindrical shape. The stator 60 has an A-phase stack 61 and a B-phase stack 62.

[0044] The A-phase stack 61 has a plurality of claw-pole type pole teeth 61a and 61b, and an A-phase coil 61c. The pole teeth 61a and 61b are alternately arranged at equal angular intervals in the circumferential direction. When a current is supplied to the A-phase coil 61c, the pole teeth 61a and 61b become magnetic poles with different polarities from each other.

[0045] The B-phase stack 62 has a plurality of claw-pole type pole teeth 62a and 62b, and a B-phase coil 62c. The pole teeth 62a and 62b are alternately arranged at equal angular intervals in the circumferential direction. When a current is supplied to the B-phase coil 62c, the pole teeth 62a and 62b become magnetic poles with different polarities from each other. The B-phase stack 62 has the same configuration as the A-phase stack 61. The A-phase stack 61 is arranged above the B-phase stack 62.

[0046] Inside the stator 60, a can 17 is arranged. Inside the can 17, a rotor 28 is arranged. The magnetic poles of the rotor 28 and the pole teeth 61a, 61b, 62a, 62b of the stator 60 face each other in the radial direction with the can 17 interposed therebetween. The rotor 28 and the stator 60 constitute a stepping motor 66.

[0047] The central axes of the housing 11, the valve port 13, the valve seat 14, the sleeve 15, the can 17, the valve body 20, the rotor 28, the drive shaft 31, the guide member 35, the output shaft 57, and the stator 60 coincide with the axis L.

[0048] The electric valve control device 70 is connected to an external control device that controls the refrigeration cycle system. The electric valve control device 70 controls the electric valve 5 based on an instruction received from the external control device.

[0049] As shown in FIG. 4, the electric valve control device 70 has a motor driver 77 and a computer 80.

[0050] The motor driver 77 is connected to the terminals A1, A2 of the A-phase coil 61c and the terminals B1, B2 of the B-phase coil 62c. The motor driver 77 supplies an A-phase current to the A-phase coil 61c and a B-phase current to the B-phase coil 62c.

[0051] The computer 80 is a microcontroller that integrates a CPU, memory, input / output interface, and analog-to-digital converter into a single package. The computer 80 may also include a motor driver 77.

[0052] The electric valve control device 70 controls the stepping motor 66 using a two-phase excitation method. When the electric valve control device 70 inputs pulses P (P[1] to P[4]) to the stepping motor 66, the rotor 28 rotates. Specifically, the computer 80 inputs pulses P (pulse signals) to the motor driver 77, and the motor driver 77 supplies a current corresponding to the pulses P to the stator 60, causing the rotor 28 to rotate. In this specification, "inputting pulses P to the stepping motor 66" is synonymous with "supplying a current corresponding to the pulses P to the stator 60". The stepping motor 66 may also be controlled using a one-phase excitation method, a one-to-two-phase excitation method, a W1-to-two-phase excitation method, a 2W1-to-two-phase excitation method, or a 4W1-to-two-phase excitation method.

[0053] The computer 80 inputs a step signal (STEP) and a direction signal (DIR) to the motor driver 77. The step signal is a pulse signal. When the motor driver 77 is receiving a direction signal corresponding to the closing direction (e.g., an H-level signal), inputting the step signal corresponds to inputting pulses P to the stepping motor 66 in ascending order (P[1] to P[4]). When the motor driver 77 is receiving a direction signal corresponding to the opening direction (e.g., an L-level signal), inputting the step signal corresponds to inputting pulses P to the stepping motor 66 in descending order (P[4] to P[1]). Figure 5 schematically shows an example of the relationship between the pulses P input to the stepping motor 66 and the step signal and direction signal input to the motor driver 77.

[0054] Furthermore, the computer 80 inputs a current control signal (CTRL) to the motor driver 77. The current control signal is a signal used to set the magnitude of the current supplied to the stator 60 for the motor driver 77.

[0055] Figure 6 shows examples of waveforms for the A-phase current and B-phase current flowing through the A-phase coil 61c and B-phase coil 62c of the stator 60. In Figure 6, +I represents the A-phase current flowing from terminal A1 to terminal A2, or the B-phase current flowing from terminal B1 to terminal B2, and -I represents the A-phase current flowing from terminal A2 to terminal A1, or the B-phase current flowing from terminal B2 to terminal B1. The A-phase current and B-phase current are rectangular waves that alternate between "-I" and "+I".

[0056] When the electric valve control device 70 inputs pulses P to the stepping motor 66 in ascending order and cyclically, the rotor 28 rotates in the closing direction (clockwise in Figure 3). The rotation of the rotor 28 is transmitted to the drive shaft 31 by the gear mechanism 50. When the drive shaft 31 rotates, the drive shaft 31 moves downward due to the lead screw action. The drive shaft 31 pushes the valve body 20 downward. As the valve body 20 moves downward, the valve portion 22 approaches the valve seat 14. When the valve portion 22 contacts the valve seat 14, the valve opening 13 closes. The position of the rotor 28 when the valve portion 22 contacts the valve seat 14 is defined as the closed valve position Rc. If the rotor 28 rotates further in the closing direction, the rotation of the rotor 28 in the closing direction is restricted. The position of the rotor 28 when the valve portion 22 contacts the valve seat 14 and the rotation of the rotor 28 in the closing direction is restricted is defined as the reference position Rx. Let C be the number of pulses P required to rotate the rotor 28 from the closed position Rc to the reference position Rx.

[0057] When the electric valve control device 70 inputs pulses P to the stepping motor 66 in a descending, cyclical manner, the rotor 28 rotates in the opening direction (counterclockwise in Figure 3). The rotation of the rotor 28 is transmitted to the drive shaft 31 by the gear mechanism 50. As the drive shaft 31 rotates, the drive shaft 31 moves upward due to the lead screw action. The valve body 20, pushed by the valve opening spring 25, moves upward, the valve portion 22 separates from the valve seat 14, and the valve port 13 opens. The position of the rotor 28 when the valve portion 22 separates from the valve seat 14 is defined as the valve opening position Ro. The valve opening position Ro may be the position of the rotor 28 immediately after the valve portion 22 separates from the valve seat 14, or it may be a position a distance equivalent to several pulses away from the last position of the rotor 28 when the valve portion 22 was in contact with the valve seat 14. The position of the rotor 28 when the valve portion 22 is furthest from the valve seat 14 is defined as the fully open position Rz. The number of pulses P required to rotate the rotor 28 from the fully open position Rz to the reference position Rx is called the full stroke number. Let the full stroke number be Z.

[0058] There is play (gap) between the gears of the gear mechanism 50, between the male screw 32t of the drive shaft 31 and the female screw 35t of the guide member 35, and between the connection portion 33 of the drive shaft 31 and the slit 58 of the output shaft 57. This play is called the backlash of the drive mechanism 30. Due to the backlash, when the rotor 28 rotates in the closing direction after rotating in the opening direction, and when the rotor 28 rotates in the opening direction after rotating in the closing direction, there is a section in which the rotation of the rotor 28 is not transmitted to the drive shaft 31. Let J be the number of pulses P corresponding to this section (i.e., backlash).

[0059] In other words, when the rotor 28 rotates in the opening direction and then a pulse P is input to the stepping motor 66 to rotate it in the closing direction, the rotation of the rotor 28 is not transmitted to the drive shaft 31 from the first to the Jth pulse P, and transmission to the drive shaft 31 begins from the (J+1)th pulse P. When the rotor 28 rotates in the closing direction and then a pulse P is input to the stepping motor 66 to rotate it in the opening direction, the rotation of the rotor 28 is not transmitted to the drive shaft 31 from the first to the Jth pulse P, and transmission to the drive shaft 31 begins from the (J+1)th pulse P.

[0060] Figures 7 and 8 show examples of the relationship between the position of the rotor 28 and the valve opening of the electric valve 5 (opening of the valve port 13).

[0061] Figure 7 shows the relationship when the rotor 28 is rotated in the opening direction to the fully open position Rz, and then a pulse P is input to the stepping motor 66 to rotate the rotor 28 to the reference position Rx.

[0062] When the rotor 28 is in the fully open position Rz, the valve opening is 100%. Z pulses P are input to the stepping motor 66 to rotate the rotor 28 in the closing direction. The rotation of the rotor 28 is not transmitted to the drive shaft 31 from the first to the Jth pulse P. Transmission of the rotation of the rotor 28 to the drive shaft 31 begins from the (J+1)th pulse P. In response to the input of pulses P to the stepping motor 66, the valve body 20 approaches the valve seat 14, and the valve opening gradually decreases. When the valve body 20 contacts the valve seat 14, the rotor 28 reaches the closed valve position Rc, and the valve opening becomes 0%. When the input of Z pulses P to the stepping motor 66 is complete, the rotor 28 is positioned at the reference position Rx. The number of pulses P input to the stepping motor 66 during the rotation of the rotor 28 from the closed valve position Rc to the reference position Rx is C.

[0063] Figure 8 shows the relationship when the rotor 28 is rotated in the closing direction to the reference position Rx, and then a pulse P is input to the stepping motor 66 to rotate the rotor 28 to the fully open position Rz.

[0064] When the rotor 28 is in the reference position Rx, the valve opening is 0%. Z pulses P are input to the stepping motor 66 to rotate the rotor 28 in the opening direction. The rotation of the rotor 28 is not transmitted to the drive shaft 31 from the first to the Jth pulse P. Transmission of the rotation of the rotor 28 to the drive shaft 31 begins from the (J+1)th pulse P. When the (J+C)th pulse P is input to the stepping motor 66, the valve body 20 is in contact with the valve seat 14. The position of the valve body 20 at this time is the same as the position of the valve body 20 when the rotor 28 is in the closed position Rc, and is called the position corresponding to the closed position Rc. When the (J+C+1)th pulse P is input to the stepping motor 66, the valve body 20 moves away from the valve seat 14. When the (J+C+A)th pulse P is input to the stepping motor 66, the rotor 28 reaches the open position Ro. A is a natural number, for example, between 1 and 10. The position of the valve body 20 when the rotor 28 is in the open position Ro is called the position corresponding to the open position Ro. In response to the input of pulse P to the stepping motor 66, the valve body 20 moves away from the valve seat 14, and the valve opening gradually increases. When the input of Z pulses P to the stepping motor 66 is complete, the rotor 28 is positioned in the fully open position Rz. The position of the valve body 20 when the rotor 28 is in the fully open position Rz is called the position corresponding to the fully open position Rz.

[0065] In this embodiment, the computer 80 inputs pulses P to the stepping motor 66 at a constant speed to rotate the rotor 28. The stepping motor 66 has an upper limit on the load on the rotor 28. When the load on the rotor 28 is below the upper limit, the rotor 28 can rotate in sync with the pulses P. When the load on the rotor 28 is greater than the upper limit, the rotor 28 cannot rotate in sync with the pulses P and loses steps. Furthermore, in the stepping motor 66, the upper limit when the rotor 28 starts to rotate (starting state) is smaller than the upper limit when the rotor 28 is already rotating (rotating state). The upper limit can be increased by increasing the torque generated by the stepping motor 66. Therefore, in order to ensure that the rotor 28 starts to rotate reliably, the computer 80 generates a large torque in the stepping motor 66 in the starting state to rotate the rotor 28, and then generates a small torque in the stepping motor 66 in the subsequent rotating state to rotate the rotor 28. Figures 9 and 10 show examples of the relationship between the pulse P input to the stepping motor 66 and the torque generated by the stepping motor 66.

[0066] Specifically, the computer 80 operates as follows: (a) When rotating the rotor 28 in the same direction as before, the computer 80 generates a large torque in the stepping motor 66 in response to the first K pulses P from the start of input of pulses P to rotate the rotor 28 in the same direction as before, and generates a small torque in the stepping motor 66 in response to pulses P following the first K pulses (Figure 9). (b) When rotating the rotor 28 in the opposite direction as before, the computer 80 generates a large torque in the stepping motor 66 in response to the first (J+K) pulses P from the start of input of pulses P to rotate the rotor 28 in the opposite direction as before, and generates a small torque in the stepping motor 66 in response to pulses P following the first (J+K) pulses (Figure 10).

[0067] In (a), the stepping motor 66 is in the starting state during the period when the first K pulses P are input, and the stepping motor 66 is in the rotating state during the period when pulses P following the first K pulses P are input. In (b), the stepping motor 66 is in the starting state during the period when the first (J+K) pulses P are input, and the stepping motor 66 is in the rotating state during the period when pulses P following the first (J+K) pulses P are input.

[0068] When the computer 80 generates a small torque in the stepping motor 66, it supplies a small current to the stator 60, and when it generates a large torque in the stepping motor 66, it supplies a large current to the stator 60. For example, the magnitude of the large current is 1.1 to 1.5 times the magnitude of the small current.

[0069] Furthermore, when the computer 80 generates a small torque in the stepping motor 66, it may input a pulse P to the stepping motor 66 at a first speed, and when it generates a large torque in the stepping motor 66, it may input a pulse P to the stepping motor 66 at a second speed lower than the first speed. For example, the second speed is 0.5 to 0.8 times the first speed.

[0070] In this way, the effects of backlash in the drive mechanism 30 can be avoided, and the rotor 28 can be rotated reliably.

[0071] The memory of computer 80 stores C, Z, J, A, and K. C, Z, J, A, and K are natural numbers. Note that J may be 0. In this embodiment, C=40, Z=2500, J=20, A=1, and K=12.

[0072] Furthermore, the memory of the computer 80 stores an initialization number, X. X is a number sufficient to rotate the rotor 28 from the fully open position Rz to the reference position Rx, and is set to a number obtained by adding a predetermined number (for example, 200) to Z. In this embodiment, X = Z + 200 = 2700.

[0073] Furthermore, the memory of the computer 80 stores a retraction number S. A predetermined natural number is set for S. After the rotor 28 is rotated in the closing direction and positioned at the reference position Rx, S pulses P are input to the stepping motor 66 to rotate the rotor 28 in the opening direction, and the rotor 28 is positioned at the retraction position Rs. S satisfies the following equations (1), (2), and (3): (1) S ≥ K (2) J ≥ S (3) C ≥ S In this embodiment, S = 15.

[0074] Next, examples of initialization and retraction processes performed by the electric valve control device 70 will be described. The retraction process is performed following the initialization process.

[0075] The electric valve control device 70 performs an initialization process when it detects, for example, a stepping motor 66 losing step or an unexpected power loss. The electric valve control device 70 also performs an initialization process when it receives an initialization command from an external control device. In the initialization process, the electric valve control device 70 inputs X pulses P to the stepping motor 66 to rotate the rotor 28 in the closing direction. X is the number of pulses to be initialized. When the electric valve control device 70 has finished inputting X pulses P to the stepping motor 66, the rotor 28 is positioned at the reference position Rx. The electric valve control device 70 resets the position of the rotor 28 (i.e., sets the reference position Rx as the current position Rp of the rotor 28), and the initialization process is completed. The initialization process is the process in which a number of pulses P greater than the number of pulses P required to position the rotor 28 at the reference position Rx is input to the stepping motor 66. In the retraction process that follows the initialization process, the electric valve control device 70 inputs S pulses P to the stepping motor 66 to rotate the rotor 28 in the opening direction. S is the number of retractions. As a result, the rotor 28 is positioned at a retraction position Rs, which is a distance (angle) from the reference position Rx that corresponds to S pulses P in the opening direction.

[0076] Next, examples of valve closing and retraction processes performed by the electric valve control device 70 will be described. The retraction process is performed following the valve closing process.

[0077] When the electric valve control device 70 receives a valve closing command from an external control device, it executes a valve closing process. In the valve closing process, the electric valve control device 70 calculates T, which is the number of pulses P required to rotate the rotor 28 from its current position Rp to a reference position Rx. The electric valve control device 70 inputs T pulses P to the stepping motor 66 to rotate the rotor 28 in the closing direction. When the electric valve control device 70 has finished inputting T pulses P to the stepping motor 66, the rotor 28 is positioned at the reference position Rx, and the valve closing process is completed. In the retraction process that follows the valve closing process, the electric valve control device 70 inputs S pulses P to the stepping motor 66 to rotate the rotor 28 in the opening direction. As a result, the rotor 28 is positioned at the retracted position Rs.

[0078] In the valve closing process, the electric valve control device 70 may input U pulses P greater than T to the stepping motor 66 to rotate the rotor 28 in the closing direction. U is the number of pulses P sufficient to rotate the rotor 28 from its current position Rp to a reference position Rx. For example, U = T + 200. When the electric valve control device 70 has finished inputting U pulses P to the stepping motor 66, the rotor 28 is positioned at the reference position Rx. The electric valve control device 70 resets the position of the rotor 28, and the valve closing process is completed. This valve closing process is the process of inputting a number of pulses P greater than the number of pulses P required to position the rotor 28 at the reference position Rx to the stepping motor 66. In this way, each time the electric valve control device 70 performs the valve closing process, the position of the rotor 28 is reset, and the position of the rotor 28 can be accurately determined.

[0079] The initialization process and valve closing process involve rotating the rotor 28 in the closing direction to position it at the reference position Rx.

[0080] When the electric valve control device 70 changes the valve opening degree (Dv) of the electric valve 5 in response to a command received from an external control device, it moves the valve body 20 only within the range from the position corresponding to the open valve position Ro to the position corresponding to the fully open valve position Rz. When the valve body 20 is in the position corresponding to the open valve position Ro, the valve opening degree is at its minimum (Dv > 0%), and when the valve body 20 is in the position corresponding to the fully open valve position Rz, the valve opening degree is at its maximum (Dv = 100%). Alternatively, when the electric valve control device 70 changes the valve opening degree (Dv) of the electric valve 5 in response to a command received from an external control device, it may move the valve body 20 only within the range from the position corresponding to the closed valve position Rc to the position corresponding to the fully open valve position Rz. When the valve body 20 is in the position corresponding to the closed valve position Rc, the valve opening degree is at its minimum (Dv = 0%), and when the valve body 20 is in the position corresponding to the fully open valve position Rz, the valve opening degree is at its maximum (Dv = 100%). In this way, when the valve opening is at its minimum, the rotor 28 is positioned at the open position Ro (or closed position Rc), preventing the valve body 20 from being pressed against the valve seat 14. Furthermore, when the valve opening is at its minimum, the position of the rotor 28 is at least a distance equivalent to at least C pulses P from the reference position Rx. C is greater than or equal to S, and S is greater than or equal to K. Therefore, even if the electric valve control device 70 starts the initialization process or the closing process when the valve opening is at its minimum, the stepping motor 66 generates a small torque when the rotor 28 reaches the reference position Rx. As a result, the valve body 20 is prevented from being strongly pressed against the valve seat 14.

[0081] In cases where the valve body 20 only needs to contact the valve seat 14 during the valve closing process, and it is not necessary to rotate the rotor 28 to the reference position Rx, the electric valve control device 70 may, upon receiving a valve closing command from an external control device, perform an alternative valve closing process instead of the valve closing process. In the alternative valve closing process, the electric valve control device 70 calculates T, which is the number of pulses P required to rotate the rotor 28 from the current position Rp to the alternative reference position Ry. The alternative reference position Ry lies between the closed valve position Rc and the reference position Rx. When Y is the number of pulses P required to rotate the rotor 28 from the alternative reference position Ry to the reference position Rx, Y is preferably less than or equal to C and greater than or equal to S (C ≥ Y ≥ S). The electric valve control device 70 inputs T pulses P to the stepping motor 66 to rotate the rotor 28 in the closing direction. When the electric valve control device 70 has finished inputting T pulses P to the stepping motor 66, the rotor 28 is positioned at the alternative reference position Ry, and the alternative valve closing process is completed. This reduces the force pressing the valve body 20 against the valve seat 14.

[0082] As described above, the valve device 1 includes an electric valve 5 and an electric valve control device 70. The electric valve 5 includes a valve body 10 having a valve seat 14, a valve element 20 facing the valve seat 14, a stepping motor 66 having a rotor 28 and a stator 60, and a drive mechanism 30 that moves the valve element 20 in accordance with the rotation of the rotor 28. When the rotor 28 is in the reference position Rx, the valve element 20 is in contact with the valve seat 14 and the rotation of the rotor 28 in the closing direction is restricted. When the electric valve control device 70 inputs pulses P to the stepping motor 66 to rotate the rotor 28 in either the closing or opening direction, it generates a large torque in the stepping motor 66 corresponding to the first K pulses P from the start of pulse P input to the stepping motor 66, and generates a small torque in the stepping motor 66 corresponding to pulses P following the first K. The electric valve control device 70, following initialization and valve closing processes, inputs S pulses P to the stepping motor 66 to rotate the rotor 28 in the opening direction. Then, the following equation (1) is satisfied: (1) S ≥ K

[0083] As a result of this, after the rotor 28 is positioned at the reference position Rx, it rotates in the opening direction and moves to a retracted position Rs, which is a distance corresponding to S pulses P from the reference position Rx. Therefore, when the initialization process is performed with the rotor 28 in the retracted position Rs, since S ≥ K, the stepping motor 66 generates a small torque when the rotor 28 reaches the reference position Rx, and the valve body 20 is not strongly pressed against the valve seat 14. Thus, the electric valve 5 can be operated normally. In addition, deformation and wear of the components of the electric valve 5 when the valve body 20 contacts the valve seat 14 can be reduced, thereby preventing a shortened lifespan of the electric valve 5.

[0084] In addition, in the electric valve control device 70, S < K is also acceptable. For example, when the initialization process is performed with the rotor 28 in the reference position Rx, the valve body 20 is strongly pressed against the valve seat 14 in response to K pulses P. When the initialization process is performed with the rotor 28 in the retracted position Rs, since S < K, the valve body 20 is strongly pressed against the valve seat 14 in response to fewer than K pulses P (K - S). Therefore, the number of pulses P that strongly press the valve body 20 against the valve seat 14 can be reduced. Consequently, deformation and wear of the components of the electric valve 5 can be reduced.

[0085] Furthermore, when the number of pulses P corresponding to the backlash of the drive mechanism 30 is J, the following equation (2) is satisfied: (2) J ≥ S In this way, the rotor 28 is positioned in the retracted position Rs before the rotation of the rotor 28 is transmitted to the drive shaft 31. Therefore, when the rotor 28 is positioned in the retracted position Rs, the valve body 20 can maintain contact with the valve seat 14.

[0086] Furthermore, when the rotor 28 is rotated in the closing direction, it reaches the closed valve position Rc, and when it is rotated further in the closing direction, it reaches the reference position Rx. When the electric valve control device 70 minimizes the valve opening of the electric valve 5, it positions the valve body 20 to the position corresponding to the closed valve position Rc (or the open valve position Ro). When the number of pulses P required to rotate the rotor 28 from the closed valve position Rc to the reference position Rx is C, the following equations (1) and (3) are satisfied: (1) S ≥ K (3) C ≥ S In this way, even if the electric valve control device 70 starts the initialization process or the valve closing process when the valve opening is at its minimum, the stepping motor 66 generates a small torque when the rotor 28 reaches the reference position Rx. Therefore, it is possible to avoid the valve body 20 being strongly pressed against the valve seat 14.

[0087] Furthermore, when the electric valve control device 70 rotates the rotor 28 in the opening direction and then inputs pulses P to the stepping motor 66 to rotate the rotor 28 in the closing direction, it generates a large torque in the stepping motor 66 in response to the first (J+K) pulses P from the start of the input of pulses P to rotate the rotor 28 in the closing direction, and generates a small torque in the stepping motor 66 in response to the pulses P following the first (J+K) pulses P. In this way, after the rotor 28 has passed the section where its rotation is not transmitted to the drive shaft 31 due to backlash, a large torque is generated in the stepping motor 66 in response to K pulses P, and this torque rotates the rotor 28. This avoids the effects of backlash in the drive mechanism 30, ensuring that the rotor 28 rotates reliably and the electric valve 5 operates normally.

[0088] Furthermore, when the electric valve control device 70 inputs a pulse P to the stepping motor 66 to rotate the rotor 28 in the opening direction, it may be configured to generate a large torque in the stepping motor 66 in response to the pulse P input to the stepping motor 66 when the rotor 28 is in the range from the reference position Rx to the open valve position Ro. In this way, the stepping motor 66 generates a large torque while the valve body 20 is in contact with the valve seat 14, which can more reliably rotate the rotor 28 to the open valve position Ro and separate the valve body 20 from the valve seat 14.

[0089] Furthermore, the electric valve control device 70 may selectively perform a valve closing process that positions the rotor 28 at the reference position Rx, and an alternative valve closing process that positions the rotor 28 at an alternative reference position Ry located between the valve closing position Rc and the reference position Rx. For example, the electric valve control device 70 counts the number of times the initialization process and the valve closing process are executed. The electric valve control device 70 may count only the number of times the initialization process is executed. When the electric valve control device 70 receives a valve closing command from an external control device, it executes the valve closing process if the number of executions is less than or equal to the switching determination number, and executes the alternative valve closing process if the number of executions is greater than the switching determination number. The switching determination number is set appropriately according to the durability of the components of the electric valve 5. For example, the switching determination number is 1000 to 5000. By the electric valve control device 70 executing the alternative valve closing process instead of the valve closing process, the force pressing the valve body 20 against the valve seat 14 is made relatively smaller, and deformation and wear of the components of the electric valve 5 can be reduced.

[0090] The valve device 1 described above reduces the rotation of the rotor 28 and transmits it to the drive shaft 31. The present invention may also be applied to a valve device having a direct-acting electric valve that transmits the rotation of the rotor to the drive shaft without reducing it.

[0091] In this specification, terms indicating shapes such as "cylinder" and "column" are also used to refer to members or parts of members that substantially have the shape of those terms. For example, "cylindrical member" includes both cylindrical members and substantially cylindrical members.

[0092] Although embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Additions, deletions, design modifications, and combinations of features of the embodiments, as appropriate by those skilled in the art, are also included within the scope of the present invention, as long as they do not contradict the spirit of the invention.

[0093] 1...Valve device, 5...Electric valve, 10...Valve body, 14...Valve seat, 20...Valve element, 28...Rotor, 30...Drive mechanism, 60...Stator, 66...Stepping motor, 70...Electric valve control device, 77...Motor driver, 80...Computer

Claims

1. An electric valve control device for controlling an electric valve having a valve body having a valve seat, a valve element facing the valve seat, a stepping motor having a rotor and a stator, and a drive mechanism for moving the valve element in accordance with the rotation of the rotor, wherein when the rotor is in a reference position, the valve element is in contact with the valve seat and the rotation of the rotor in the closing direction is restricted, and when the electric valve control device inputs pulses to the stepping motor to rotate the rotor in either the closing or opening direction, it generates a large torque in the stepping motor in response to the first K pulses from the start of pulse input to the stepping motor, generates a small torque in response to pulses following the first K pulses, rotates the rotor in the closing direction and positions it in the reference position, and then inputs S pulses to the stepping motor to rotate the rotor in the opening direction, wherein K and S are natural numbers.

2. An electric valve control device according to claim 1, satisfying the following formula (1): (1) S ≥ K 3. The electric valve control device according to claim 1, wherein when the number of pulses corresponding to the backlash of the drive mechanism is J, the following equation (2) is satisfied. (2) J ≥ S 4. The electric valve control device according to claim 1, wherein when the rotor is rotated in the closing direction, the valve body reaches a closed valve position in contact with the valve seat, and when it is rotated further in the closing direction, it reaches the reference position, and when the electric valve control device minimizes the valve opening of the electric valve, it positions the valve body at a position corresponding to the closed valve position or at a position further away from the valve seat than the position corresponding to the closed valve position, and when the number of pulses required to rotate the rotor from the closed valve position to the reference position is C, the following equations (1) and (3) are satisfied. (1) S ≥ K (3) C ≥ S 5. The electric valve control device according to claim 1, wherein the number of pulses corresponding to the backlash of the drive mechanism is J, and when the electric valve control device rotates the rotor in the opening direction and then inputs pulses to the stepping motor to rotate the rotor in the closing direction, it generates a large torque in the stepping motor in correspondence to the first (J+K) pulses from the start of pulse input to the stepping motor for rotating the rotor in the closing direction, and generates a small torque in the stepping motor in correspondence to pulses following the first (J+K) pulses, and when the electric valve control device rotates the rotor in the closing direction and then inputs pulses to the stepping motor to rotate the rotor in the opening direction, it generates a large torque in the stepping motor in correspondence to the first (J+K) pulses from the start of pulse input to the stepping motor for rotating the rotor in the opening direction, and generates a small torque in the stepping motor in correspondence to pulses following the first (J+K) pulses.

6. The electric valve control device according to claim 1, wherein when the rotor is rotated from the reference position in the opening direction, the valve body reaches an open valve position where it separates from the valve seat, and when the electric valve control device inputs a pulse to the stepping motor to rotate the rotor in the opening direction, it generates a large torque in the stepping motor in response to the pulse input to the stepping motor when the rotor is in the section from the reference position to the open valve position.

7. The electric valve control device according to claim 1, wherein when the rotor is rotated in the closing direction, the valve body reaches a closed valve position in contact with the valve seat, and when it is rotated further in the closing direction, it reaches the reference position, and the electric valve control device selectively performs a valve closing process to position the rotor at the reference position and an alternative valve closing process to position the rotor at an alternative reference position between the closed valve position and the reference position.

8. The electric valve control device according to claim 7, wherein the electric valve control device counts the number of times the process of rotating the rotor in the closing direction to position it in the reference position is performed, and when the electric valve control device receives a valve closing command from an external control device, it performs the valve closing process if the number of executions is less than or equal to the switching determination number, and performs the alternative valve closing process if the number of executions is greater than the switching determination number.

9. The electric valve control device according to claim 8, wherein the number of executions is the number of times the process is performed in which a number of pulses greater than the number of pulses required to position the rotor at the reference position is input to the stepping motor.

10. A valve device having the electric valve control device described in claim 1 and the electric valve.

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