Electric valve control device

Abstract

To search a reference position inherent to a motor-driven valve.SOLUTION: A motor-driven valve control device is connected with a motor-driven valve which adjusts a valve opening by rotation of a rotor. The motor-driven valve control device includes: a rotation indicating section for indicating a rotation amount of the rotor; a rotation detection section for detecting the rotation amount of the rotor; and a reference specifying section for specifying a position at which a ratio of the rotation amount (sensing angle) detected for the rotor with respect to the rotation amount (indication angle) indicated by the rotor is equal to or lower than a first threshold, in other words, a position at which followability with respect to the indication angle of the rotor is degraded, as a reference position of the rotor.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a motor-operated valve, and more particularly to a method for controlling a rotor. [Background technology]

[0002] Automotive air conditioners are generally configured with a compressor, a condenser, an expansion device, an evaporator, and other components arranged in a refrigeration cycle. The refrigeration cycle is provided with various control valves, such as an expansion valve as an expansion device, to control the flow of the refrigerant. With the recent spread of electric vehicles, motor-operated valves equipped with a motor as a drive unit are becoming more widely used.

[0003] Known examples of such motorized valves include one equipped with a magnetic sensor for detecting the valve opening degree (see, for example, Patent Document 1). A valve disc is provided at one end of an actuating rod that rotates with the rotor, and a magnet (sensor magnet) is provided at the other end. A magnetic sensor is provided so as to face the sensor magnet in the axial direction. The rotational motion of the rotor is converted into axial motion of the valve disc by a screw feed mechanism. By detecting changes in magnetic flux accompanying the rotation of the rotor with the magnetic sensor, the rotational angle of the sensor magnet and therefore the axial position of the valve disc can be detected, and the valve opening degree can be calculated.

[0004] A reference position is set for the actuating rod that moves up and down inside the motor-operated valve. When the rotor continues to rotate in the valve closing direction and reaches the reference position, also called the "origin," the rotor's rotation is restricted by a stopper (see, for example, Patent Document 2).

[0005] Even for motor-operated valves of the same type, there will be individual differences in the reference position. It is not appropriate to set a uniform reference position for each motor-operated valve. For this reason, when manufacturing motor-operated valves, it is necessary to detect and record the unique reference position for each motor-operated valve. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-135908 A [Patent Document 2] JP 2020-204344 A Summary of the Invention [Problem to be solved by the invention]

[0007] When the rotor is restricted from rotating by the stopper, the back electromotive force of the stepping motor that drives the rotor decreases. Therefore, a method can be considered in which the reference position is identified by searching for a point where the back electromotive force of the stepping motor changes significantly while rotating the rotor in the valve closing direction. In this case, if the rotor is rotated at high speed, it is not preferable because a strong impact is applied to the stopper at the reference position. On the other hand, if the rotor is rotated at low speed, it becomes difficult to detect the change in the back electromotive force. In addition, if the rotor movement is restricted by impurities such as metal chips instead of the stopper, the reference position may be erroneously recognized.

[0008] A primary object of the present invention is to provide a technique for appropriately searching for a reference position specific to a motor-operated valve. [Means for solving the problem]

[0009] An electric valve control device according to one aspect of the present invention is connected to an electric valve that adjusts the valve opening degree by rotation of a rotor. This electric valve control device includes a rotation instruction unit that instructs the amount of rotation of the rotor, a rotation detection unit that detects the amount of rotation of the rotor, and a reference identification unit that identifies the position when the ratio of the amount of rotation detected for the rotor to the amount of rotation instructed to the rotor is equal to or less than a first threshold value as a reference position of the rotor.

[0010] An electric valve control device according to another aspect of the present invention is connected to an electric valve that adjusts the valve opening degree by rotation of a rotor. This electric valve control device includes a rotation instruction unit that indicates the amount of rotation of the rotor, a rotation detection unit that detects the amount of rotation of the rotor, and a reference identification unit that identifies a reference position of the rotor based on the ratio of the amount of rotation detected for the rotor to the amount of rotation instructed to the rotor. The reference identification unit identifies a position when a ratio of the amount of rotation detected for the rotor to the amount of rotation instructed to the rotor is equal to or less than a third threshold as a first candidate position, and identifies a position when a ratio of the amount of rotation detected for the rotor to the amount of rotation instructed to the rotor after identifying the first candidate position is equal to or less than a fourth threshold as a second candidate position, and identifies a reference position of the rotor based on both or one of the first candidate position and the second candidate position when a predetermined proximity condition is satisfied between the rotation angle of the rotor detected at the first candidate position and the rotation angle of the rotor detected at the second candidate position.

[0011] In one embodiment of the present invention, an electric valve control program causes a computer to perform the functions of instructing the amount of rotation of a rotor of an electric valve, detecting the amount of rotation of the rotor, and identifying the position at which the ratio of the amount of rotation detected for the rotor to the amount of rotation instructed to the rotor is equal to or less than a first threshold value as a reference position of the rotor. Effect of the Invention

[0012] According to the present invention, it is easy to appropriately search for a reference position specific to a motor-operated valve. [Brief description of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view illustrating a motor-operated valve according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a configuration of a stator and its surroundings. [Diagram 3] FIG. 2 is a diagram illustrating a configuration of a rotor. [Figure 4] 3 is a schematic diagram showing the relationship between a magnetic sensor, a sensor magnet, and magnetic lines of force generated from the sensor magnet; FIG. [Diagram 5] FIG. [Figure 6] 4 is a graph showing the relationship between the sensing angle of a sensor magnet and a sensor output value. [Figure 7] 1 is a graph showing the relationship between angle value and step. [Figure 8] FIG. 2 is a functional block diagram of the motor-operated valve control device. [Figure 9] 11 is a first flowchart showing the process of an origin inspection process. [Figure 10] 13 is a second flowchart showing the process of the origin inspection process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, for convenience, the positional relationship of each structure may be expressed based on the illustrated state. In addition, in the following embodiment and its modified examples, substantially the same components are given the same reference numerals, and the description thereof will be omitted as appropriate.

[0015] FIG. 1 is a cross-sectional view illustrating a motor-operated valve according to an embodiment. The motor-operated valve 1 is applied to a refrigeration cycle of an automobile air conditioner (not shown). This refrigeration cycle includes a compressor that compresses the circulating refrigerant, a condenser that condenses the compressed refrigerant, an expansion valve that throttles and expands the condensed refrigerant and sends it out in the form of mist, and an evaporator that evaporates the mist of refrigerant and cools the air inside the vehicle cabin with the latent heat of evaporation. The motor-operated valve 1 functions as an expansion valve for the refrigeration cycle.

[0016] The motor-operated valve 1 is constructed by assembling a valve body 2 and a motor unit 3. The valve body 2 has a body 5 that houses a valve portion. The body 5 functions as a "valve body." The body 5 is constructed by assembling a first body 6 and a second body 8 coaxially. Both the first body 6 and the second body 8 are made of stainless steel (hereinafter referred to as "SUS"). Since the second body 8 is provided with a valve seat 24, a material with excellent wear resistance is selected. The first body 6 has better weldability than the second body 8, and the second body 8 has better workability than the first body 6.

[0017] The first body 6 is a stepped cylinder whose outer diameter tapers stepwise downward. The outer diameter of the upper end of the first body 6 is slightly tapered, forming a locking portion 52 with a step. A male thread 10 is formed on the outer peripheral surface of the lower part of the first body 6 for assembling the motor-operated valve 1 to a piping body (not shown). The piping body is connected to piping extending from the condenser side and piping connected to the evaporator, but the details thereof will not be described. A seal receiving portion 12 consisting of an annular groove is formed on the outer peripheral surface of the first body 6 slightly above the male thread 10, and a seal ring 14 (O-ring) is fitted into it.

[0018] The first body 6 has a circular hole-shaped recessed fitting portion 16 at its lower portion. The second body 8 has a bottomed cylindrical shape, and its upper portion is press-fitted into the recessed fitting portion 16. A seal accommodating portion 18 consisting of an annular groove is formed on the outer peripheral surface of the lower portion of the second body 8, and a seal ring 20 is fitted into the seal accommodating portion 18. A valve hole 22 is provided so as to penetrate the bottom portion of the second body 8 in the axial direction, and a valve seat 24 is formed at the upper end opening of the valve hole 22. An inlet port 26 is provided at the side of the second body 8, and an outlet port 28 is provided at the lower portion. A valve chamber 30 is formed inside the first body 6 and the second body 8. The inlet port 26 and the outlet port 28 are in communication with each other via the valve chamber 30.

[0019] An actuating rod 32 extending from the rotor 60 of the motor unit 3 is inserted into the inside of the body 5. The actuating rod 32 passes through the valve chamber 30. The actuating rod 32 is obtained by cutting a bar made of a non-magnetic metal, and a needle-shaped valve element 34 is provided integrally at its lower part. The valve element 34 is attached to and detached from the valve seat 24 from the valve chamber 30 side to open and close the valve portion.

[0020] A guide member 36 is erected at the center of the upper part of the first body 6. The guide member 36 is obtained by cutting a tube material made of a non-magnetic metal into a stepped cylindrical shape, and a male thread 38 is formed on the outer circumferential surface of the axial center part. The lower end part of the guide member 36 has a large diameter, and the large diameter part 40 is press-fitted into the upper center of the first body 6 and fixed coaxially. The guide member 36 supports the operating rod 32 axially slidably with its inner circumferential surface, and supports the rotating shaft 62 of the rotor 60 rotatably and slidably with its outer circumferential surface.

[0021] A spring receiver 42 is provided on the operating rod 32 slightly above the valve body 34, and a spring receiver 44 is also provided on the bottom of the guide member 36. A spring 46 (functioning as a "biasing member") is interposed between the spring receivers 42, 44 to bias the valve body 34 in the valve closing direction.

[0022] On the other hand, the motor unit 3 is configured as a three-phase stepping motor including a rotor 60 and a stator 64. The motor unit 3 has a cylindrical can 66 with a bottom, with the rotor 60 disposed inside the can 66 and the stator 64 disposed outside the can 66. The can 66 is a cylindrical member with a bottom that covers the space in which the valve body 34 and its drive mechanism are disposed and contains the rotor 60, and defines an inner pressure space (internal space) where the pressure of the refrigerant acts and an outer non-pressurized space (external space) where the pressure of the refrigerant does not act.

[0023] The can 66 is made of a non-magnetic metal (SUS in this embodiment), and is assembled coaxially with its lower portion being fitted onto the upper end of the first body 6. The amount of insertion of the can 66 is regulated by engaging the lower end with the engaging portion 52. The body 5 and the can 66 are fixed and sealed by applying a full circumference weld (not shown) along the boundary between the lower end of the can 66 and the first body 6. The space surrounded by the body 5 and the can 66 forms the above-mentioned pressure space.

[0024] The stator 64 is configured by arranging a plurality of salient poles at equal intervals on the inner periphery of the laminated core 70. The laminated core 70 is configured by laminating annular cores in the axial direction. A bobbin 74 with a coil 73 (electromagnetic coil) attached thereto is attached to each salient pole. The coil 73 and the bobbin 74 form a "coil unit 75." In this embodiment, the motor unit has three coil units 75 for supplying three-phase current, which are provided at intervals of 120 degrees with respect to the central axis of the laminated core 70 (described in detail later).

[0025] The stator 64 is provided integrally with a case 76 of the motor unit 3. That is, the case 76 is obtained by injection molding (also called "insert molding" or "mold molding") of a corrosion-resistant resin material. The stator 64 is covered with the molded resin formed by the injection molding. The case 76 is made of the molded resin. Hereinafter, the molded product of the stator 64 and the case 76 is also called a "stator unit 78."

[0026] The stator unit 78 has a hollow structure, and is assembled to the body 5 while the can 66 is coaxially inserted therethrough. A seal receiving portion 80 consisting of an annular groove is formed on the outer peripheral surface of the first body 6 slightly below the locking portion 52, and a seal ring 82 (O-ring) is fitted into the seal receiving portion 80. The seal ring 82 is interposed between the upper outer peripheral surface of the first body 6 and the lower inner peripheral surface of the case 76, thereby preventing the outside atmosphere (water, etc.) from entering the gap between the can 66 and the stator 64.

[0027] The rotor 60 includes a cylindrical rotor core 102 attached to the rotating shaft 62, a rotor magnet 104 provided on the outer circumferential surface of the rotor core 102, and a sensor magnet 106 provided on the upper end surface of the rotor core 102. The rotor core 102 is attached to the rotating shaft 62. The rotor magnet 104 is magnetized (magnetized) into multiple poles in its circumferential direction. The sensor magnet 106 is also magnetized (magnetized) into multiple poles. The rotor magnet 104 and the sensor magnet 106 are obtained by magnetizing a magnet portion integrally molded with the rotor core 102 in a post-process, the details of which will be described later.

[0028] The rotating shaft 62 is a cylindrical shaft with a bottom, and is fitted onto the guide member 36 with its open end facing downward. A female thread 108 is formed on the inner peripheral surface of the lower part of the rotating shaft 62, and meshes with the male thread 38 of the guide member 36. A screw feed mechanism 109 formed by these threads converts the rotational motion of the rotor 60 into axial motion of the operating rod 32. This causes the valve element 34 to move (rise and fall) in the axial direction, that is, in the opening and closing direction of the valve portion.

[0029] The upper part of the actuation rod 32 is reduced in diameter, and the reduced diameter part 110 penetrates the bottom part 112 of the rotary shaft 62. An annular stopper 114 is fixed to the tip part of the reduced diameter part 110. Meanwhile, a spring 116 that urges the actuation rod 32 downward (i.e., in the valve closing direction) is interposed between the base end of the reduced diameter part 110 and the bottom part 112. With this configuration, when the valve is opened, the actuation rod 32 is displaced integrally with the rotor 60 in such a manner that the stopper 114 is engaged with the bottom part 112. Meanwhile, when the valve is closed, the spring 116 is compressed by the reaction force that the valve body 34 receives from the valve seat 24. The elastic reaction force of the spring 116 at this time can press the valve body 34 against the valve seat 24, improving the seating performance (valve closing performance) of the valve body 34.

[0030] The motor unit 3 has a circuit board 118 on the outside of the can 66. The circuit board 118 is fixed inside the case 76. In this embodiment, various circuits functioning as a control unit and a communication unit are mounted on the lower surface of the circuit board 118. Specifically, a drive circuit for driving the motor, a control circuit (microcomputer) for outputting a control signal to the drive circuit, a communication circuit for the control circuit to communicate with an external device, a power supply circuit for supplying power to each circuit and the motor (coil), etc. are mounted. The upper end of the case 76 is closed by a lid 77. The circuit board 118 is disposed in the space below the lid 77 of the case 76.

[0031] A magnetic sensor 119 is provided on the surface of the circuit board 118 facing the sensor magnet 106. The magnetic sensor 119 faces the sensor magnet 106 in the axial direction via the bottom end wall of the can 66. The magnetic flux generated by the sensor magnet 106 changes as the rotor 60 rotates. The magnetic sensor 119 detects the amount of displacement of the rotor 60 (the rotation angle of the rotor 60 in this embodiment) by detecting this change in magnetic flux. The control unit calculates the axial position of the valve body 34 and therefore the valve opening degree based on the amount of displacement of the rotor 60.

[0032] A pair of terminals 117 connected to the coil 73 extend from each bobbin 74 and are connected to a circuit board 118. A power supply terminal, a ground terminal, and a communication terminal (collectively referred to as "connection terminals 81") extend from the circuit board 118 and are each drawn out to the outside through a side wall of the case 76. A connector portion 79 is integrally provided on the side of the case 76, and the connection terminals 81 are arranged inside the connector portion 79.

[0033] A stopper 90 is formed below the rotor 60. As shown in Patent Document 2, the configuration of the stopper 90 is known. Ultimately, the stopper 90 comes into contact with a protrusion (locking portion) (not shown) formed as part of the guide member 36, completely restricting the rotation of the rotor 60 in the valve closing direction. Hereinafter, the position of the rotor 60 at this time, in other words, the point where the stopper 90 comes into contact with the protrusion, is referred to as the "origin." In addition, in this embodiment, the origin is referred to as the "reference position."

[0034] Fig. 2 is a diagram showing the configuration of the stator 64 and its surroundings. Fig. 2(A) corresponds to the cross section seen from the arrow AA in Fig. 1, and is a cross section of the stator unit 78. Fig. 2(B) shows only the stator 64 (before resin molding). For reference, Fig. 2(A) also shows the can 66 and the rotor 60 (see the two-dot chain line).

[0035] Since the motor unit 3 is a three-phase motor, as shown in FIG. 2A, coil units 75 are provided at equal intervals around the axis L of the rotor 60. As also shown in FIG. 2B, slots 120a to 120c (collectively referred to as "slots 120" when no particular distinction is made) are provided at intervals of 120 degrees around the axis L on the inner periphery of the laminated core 70. In each slot 120, salient poles 122a to 122c (collectively referred to as "salient poles 122") protruding radially inward from the center are formed, and a U-phase coil 73a, a V-phase coil 73b, and a W-phase coil 73c (collectively referred to as "coils 73") are respectively assembled therein. Slits 124 having a U-shaped cross section are also formed between adjacent slots 120 to optimize the magnetic path.

[0036] The rotor magnet 104 faces the salient poles 122a to 122c via the can 66. In this embodiment, the rotor magnet 104 is magnetized with 10 poles as shown in Fig. 2(A), but the number of poles can be set appropriately.

[0037] Next, the configuration of the magnets in the rotor 60 will be described in detail. Fig. 3 is a diagram showing the configuration of the rotor 60. Fig. 3(A) is a perspective view, Fig. 3(B) is a front view, Fig. 3(C) is a plan view, and Fig. 3(D) is a cross-sectional view taken along the line BB in Fig. 3(C). In the diagram, "N" indicates the north pole and "S" indicates the south pole. For ease of explanation, the rotating shaft 62 (see Fig. 1) is omitted in the diagram.

[0038] The rotor 60 has a rotor magnet 104 along the outer circumferential surface of the rotor core 102, and a sensor magnet 106 at the axial end of the rotor core 102 (FIGS. 3(A) and 3(D)). The rotor magnet 104 is cylindrical, and its outer circumferential surface is magnetized with 10 poles (FIGS. 3(B) and 3(C)). On the other hand, the sensor magnet 106 is annular, and its plane is magnetized with 2 poles.

[0039] 3(D), the inner circumferential surface of rotor magnet 104 fits into annular groove 140, and the bottom surface of sensor magnet 106 fits into annular groove 144. That is, annular groove 140 functions as a fall-off prevention structure that prevents rotor magnet 104 from falling off from rotor core 102. Similarly, annular groove 144 functions as a fall-off prevention structure that prevents sensor magnet 106 from falling off from rotor core 102.

[0040] Given the above configuration, next, a description will be given of a method in which the magnetic sensor 119 detects the rotation angle of the rotor 60. In the following, the up-down direction on the paper surface of FIG.

[0041] FIG. 4 is a schematic diagram showing the relationship between the magnetic sensor 119, the sensor magnet 106, and the magnetic lines of force generated from the sensor magnet 106. As shown in FIG. FIG. 4 is a schematic diagram of the magnetic sensor 119 and the sensor magnet 106 as viewed from the side. As shown in FIG. 4, magnetic lines of force are generated from N to S of the sensor magnet 106 (permanent magnet). The magnetic sensor 119 located directly above the sensor magnet 106 is a rotary sensor of a known configuration that detects the magnetic lines of force generated from the sensor magnet 106. The magnetic sensor 119 detects the rotation angle of the sensor magnet 106 (rotor 60) based on the direction of the magnetic lines of force (described in detail later). Note that in this embodiment, the magnetic sensor 119 can detect the rotation angle of the sensor magnet 106, but the magnetic sensor 119 cannot directly detect the distance to the sensor magnet 106, in other words, the amount of movement of the operating rod 32 in the opening and closing direction.

[0042] FIG. 5 is a plan view of the sensor magnet 106. A rotational driving force is applied to the rotor 60 by passing a driving current through the coil 73 of the stator 64 in a manner described below. When the rotor 60 is rotated in the valve closing direction (downward) (hereinafter referred to as "downward rotation"), the actuating rod 32 moves in the valve closing direction, i.e., downward in Fig. 1, in conjunction with the rotor 60. When the rotor 60 is rotated in the valve opening direction (hereinafter referred to as "upward rotation"), the actuating rod 32 moves in the valve opening direction, i.e., upward in Fig. 1, in conjunction with the rotor 60.

[0043] The sensor magnet 106 also rotates in conjunction with the rotation of the rotor 60. As the sensor magnet 106 rotates, the magnetic field direction MA of the sensor magnet 106 also changes. When an XY coordinate system (corresponding to the horizontal plane in FIG. 1) is set as shown in FIG. 5, the angle that the magnetic field direction MA makes with the X-axis is defined as θ. The magnetic sensor 119 detects the rotation angle θ of the sensor magnet 106 using a known method shown in the angle sensor of Patent Document 1.

[0044] FIG. 6 is a graph showing the relationship between the sensing angle of the sensor magnet 106 and the sensor output value. The horizontal axis indicates the actual rotation angle θ of the sensor magnet 106 detected by the magnetic sensor 119 (hereinafter referred to as the "sensor angle"). The vertical axis indicates the output value of the magnetic sensor 119 (hereinafter referred to as the "sensor value"). The sensor value is further normalized by the magnetic sensor 119 within a range of "lower limit value DA to upper limit value TA". The lower limit value DA and upper limit value TA can be set arbitrarily. As shown in FIG. 6, the magnetic sensor 119 outputs the sensor value in a sawtooth waveform corresponding to the sensor angle. Hereinafter, the value obtained by normalizing the sensor value within the above range will be referred to as the "angle value". Based on the angle value, the control circuit can detect the sensor angle, i.e., the actual rotation angle of the sensor magnet 106.

[0045] FIG. 7 is a graph showing the relationship between the angle value and the step. In this embodiment, when the valve body 34 is moved from the highest point (valve open) to the lowest point (valve closed), the rotor 60 rotates a total of four times. Although details will be described later, the control circuit rotates the rotor 60 by changing the magnetic field direction of each coil 73 by changing the drive current supplied to the three-phase coils 73. In this embodiment, the control circuit rotates the rotor 60 in units of u1 degrees (details will be described later). Hereinafter, this unit rotation amount is called a "step". Since 360 ​​degrees x 4 rotations ÷ u1 degrees = 1440 / u1 = SM4, the control circuit instructs the rotor 60 to rotate a total of SM4 steps within the operating range of the actuation rod 32. Corresponding to the four rotations of the rotor 60, the angle value changes four times between DA and TA.

[0046] The control circuit applies a drive current of a predetermined level to the U-phase coil 73a. At this time, a drive current of a predetermined level is also applied to the V-phase coil 73b and the W-phase coil 73c. ​​By applying a drive current to each coil 73, the balance of the magnetic field in the coil 73 changes, and the rotation angle to be instructed to the rotor 60 is set (hereinafter referred to as the "instructed angle"). A combination of the current values ​​of the drive current applied to each of the U-phase coil 73a, the V-phase coil 73b, and the W-phase coil 73c is called an "excitation pattern." In this embodiment, there are N types of excitation patterns. Changing a certain excitation pattern P1 to the excitation pattern P2 of the motor-operated valve next thereto corresponds to a "one step" rotation, in other words, a rotation instruction for a unit rotation amount.

[0047] The command angle α changes by changing the excitation pattern, in other words, by changing the excitation pattern one step at a time. The command angle α and the sensed angle θ usually match. After changing the excitation pattern, the control circuit can determine whether the command angle α (the rotation angle commanded to the rotor 60) and the sensed angle θ (the actual rotation angle of the rotor 60 detected by the magnetic sensor 119) match by calculating the sensed angle θ from the angle value detected by the magnetic sensor 119. Hereinafter, the state in which the sensed angle follows the direction indicated by the excitation pattern will be referred to as "synchronization," and the state in which the sensed angle cannot follow will be referred to as "loss of synchronization."

[0048] N types of pattern IDs are assigned to the excitation patterns. The drive current values ​​of the U-phase coil 73a, the V-phase coil 73b, and the W-phase coil 73c in the excitation pattern with pattern ID=N1 (hereinafter, referred to as "excitation pattern (N1)") are IU(N1), IV(N1), and IW(N1), respectively. In other words, the excitation pattern (N1) means the combination of {IU(N1), IV(N1), IW(N1)}.

[0049] When the control circuit changes the excitation pattern (N1) to the excitation pattern (N1+1), i.e., {IU(N1+1), IV(N1+1), IW(N1+1)}, the balance of the magnetic force strengths of the three coils 73 and the magnetic field direction change, causing the rotor 60 to rotate upward by a unit rotation amount. When the control circuit changes the excitation pattern (N1) to the excitation pattern (N1-1), the rotor 60 rotates downward by a unit rotation amount. N types of excitation patterns correspond to N steps.

[0050] When the control circuit advances the excitation pattern by N steps, the rotor 60 rotates F degrees. Therefore, to rotate the rotor 60 one revolution (360 degrees), the excitation pattern must be changed by (360 / F) periods. A command angle of 360 degrees (one revolution) corresponds to N×5 steps. Calculating backwards, 360÷(N×5)=72 / N means that the rotor 60 rotates 72 / N=u1 degrees per step. As mentioned above, four revolutions results in a total of SM4=N×5×4 steps. The command angle is specified by changing the excitation pattern, and the rotor 60 rotates according to the command angle.

[0051] In this embodiment, the position of the rotor 60 when the stopper 90 abuts against the guide member 36 (more precisely, the protrusion of the guide member 36) is set as the origin (reference position), and the control circuit records the angle value and excitation pattern at this time as "origin information (reference information)." The control circuit identifies the origin based on the tracking of the sensed angle. When the motor-operated valve 1 is manufactured, the origin is searched for by a method described below. The circuit board 118 is equipped with a non-volatile memory. When the origin is detected, the control circuit records the origin information in the non-volatile memory.

[0052] As an example, the angle value in the origin information of the motor-operated valve 1a is assumed to be "15." Meanwhile, the angle value in the origin information of another motor-operated valve 1b is assumed to be "23." Since there are individual differences in the motor-operated valves 1, the origin information is also set for each motor-operated valve 1. In this embodiment, when the motor-operated valve 1 is manufactured (when shipped from the factory), an "origin inspection process" to be described later is executed only once, whereby the control circuit searches for the origin information of the motor-operated valve 1 and records it in the built-in non-volatile memory.

[0053] Assume that an initialization command is sent from the outside to the motor-operated valve 1a after shipment. The control circuit of the circuit board 118 receives various commands such as the initialization command from the master (external device). When the initialization command is received, the control circuit rotates the rotor 60 downward little by little. Also, during the downward rotation, the magnetic sensor 119 detects an angle value. The control circuit can search for the reference position by comparing the angle value of the origin information with the angle value detected by the magnetic sensor 119. For example, the control circuit of the motor-operated valve 1a can determine that the operating rod 32 may have reached the origin when the angle value detected during the downward rotation is "15". Similarly, the control circuit of the motor-operated valve 1b can determine that the operating rod 32 may have reached the origin when the angle value detected during the downward rotation is "23".

[0054] The control circuit adjusts the amount of movement of the operating rod 32, that is, the valve opening degree of the motor-operated valve 1, by specifying the number of steps based on the origin (valve closed position).

[0055] FIG. 8 is a functional block diagram of the motor-operated valve control device 200. Each component of the motor-operated valve control device 200 is realized by hardware (control circuits) including a control circuit (microcomputer) on a circuit board 118, storage devices such as memory and storage, and wired or wireless communication lines connecting them, and software stored in the storage devices and supplying processing instructions to the arithmetic unit. The computer program may be composed of device drivers and application programs, as well as libraries that provide common functions to these programs. Each block described below represents a functional block rather than a hardware-based configuration.

[0056] The motor-operated valve control device 200 includes a rotation instruction unit 202 , a rotation detection unit 204 , a reference specification unit 206 , and a reference information storage unit 208 . The reference specifying unit 206 specifies an origin (reference position) and controls the rotation instruction unit 202 and the rotation detection unit 204. The rotation instruction unit 202 outputs a drive current to each of the U-phase coil 73a, the V-phase coil 73b, and the W-phase coil 73c in accordance with the excitation pattern. The rotation detection unit 204 acquires an angle value (a normalized value of the sensor value) from the magnetic sensor 119. The reference specifying unit 206 calculates a sensed angle based on the angle value. The reference specifying unit 206 specifies an origin (reference position) based on the command angle and the tracking ability of the sensed angle. The reference information storage unit 208 is a storage area configured in a non-volatile memory. The reference specifying unit 206 records origin information (reference information) in the reference information storage unit 208.

[0057] FIG. 9 is a first flowchart showing the process of the origin inspection process. After the motor-operated valve 1 is manufactured, the following origin inspection process is executed in the factory. The purpose of the origin inspection process is to search for the origin, which is the reference position of the motor-operated valve 1, and to record the origin information, which is data specific to the origin, in the reference information storage unit 208.

[0058] First, the reference identification unit 206 resets the counter C to "0" (S10). The counter C is a variable prepared to determine the origin candidate. Next, the rotation instruction unit 202 rotates the rotor 60 upward for several steps, for example, about N steps (hereinafter referred to as "confirmation rise") (S12). After that, the rotation instruction unit 202 rotates the rotor 60 downward. At this time, the rotation instruction unit 202 sets the downward rotation speed of the rotor 60 to the rotation speed V1 (S14). By the confirmation rise, the instruction angle by the excitation pattern and the sensed angle of the rotor 60 can be synchronized. In addition, when the rotor 60 starts to rotate, there is a possibility that impurities such as metal chips are caught in the screw feed mechanism 109 between the guide member 36 and the rotor 60. By the reverse rotation of the rotor 60 accompanying the confirmation rise, the impurities caught by the rotor 60 can be released. In addition, by performing the confirmation ascent, appropriate vibrations can be applied to the screw feed mechanism 109, which can encourage impurities to fall out of the screw feed mechanism 109.

[0059] The rotation instruction unit 202 rotates the rotor 60 downward at a constant pace according to the rotation speed V1. The rotation instruction unit 202 rotates the rotor 60 downward by one step (S16). The magnetic sensor 119 detects the sensed angle, and the rotation detection unit 204 calculates an angle value from a sensor value output from the magnetic sensor 119. The rotation detection unit 204 calculates an actual rotation change amount a of the sensor magnet 106 for a one-step downward rotation instruction. Usually, a rotation change amount a of u1 degrees is assumed for a one-step rotation instruction, as described above. The reference determination unit 206 determines whether the rotation change amount a is less than a threshold value T1 (S18). In other words, the reference determination unit 206 determines whether the ratio (tracking ability) of the change amount (rotation amount) of the sensed angle to the change amount (rotation amount) of the instruction angle is less than a predetermined threshold value T1. The value of the threshold value T1 can be set arbitrarily as long as it is smaller than u1.

[0060] When the amount of change in rotation a is less than the threshold value T1, it is possible that the origin has been reached and the stopper 90 has been locked. Alternatively, it is possible that impurities such as metal chips have made it temporarily difficult for the rotor 60 to move. In any case, the ability of the rotor 60 to follow the indicated angle has decreased for some reason. In summary, when the amount of change in rotation a is less than the threshold value T1, it is possible that the rotor 60 has reached the origin, but it is also possible that the ability of the rotor 60 to follow has temporarily decreased at a position other than the origin.

[0061] When the rotation change amount a is equal to or greater than the threshold value T1 (N in S18), that is, when the rotor 60 can sufficiently follow the command angle, the reference determination unit 206 resets the counter value C to "0" (S20). In addition, the reference determination unit 206 clears the first origin candidate information HP1 (described later) when it is stored (S22). Thereafter, the process returns to S16, and the rotation detection unit 204 again commands one step of downward rotation. Therefore, as long as the rotor 60 can follow the command, the downward rotation of the rotor 60 continues at the rotation speed V1.

[0062] On the other hand, when the rotation change amount a is less than the threshold T1 (Y in S18) and the counter value C=0 (Y in S24), that is, when the rotation change amount a becomes less than the threshold T1 for the first time, the reference determination unit 206 temporarily stores the current angle value and excitation pattern as the first origin candidate information HP1 (S26). After that, the reference determination unit 206 increments the counter value C (S28). When the counter value C is not zero (N in S24), that is, when an "event in which the rotation change amount a becomes less than the threshold T1 (hereinafter referred to as "tracking performance degradation detection")" is continuously detected, the process of S26 is skipped. The first origin candidate information HP1 is maintained as it is. As long as tracking performance degradation detection continues, the first origin candidate information HP1 is maintained and the counter value C continues to increase.

[0063] When the counter value C is less than the threshold value K1 (N in S30), the first origin candidate information HP1 is stored and the process returns to S16. The threshold value K1 is an arbitrary natural number. On the other hand, when the counter value C is equal to or greater than the threshold value K1, that is, when the tracking performance degradation detection has occurred K1 or more times in succession (Y in S30), the process proceeds to the process shown in FIG.

[0064] FIG. 10 is a second flowchart showing the process of the origin inspection process. The reference identification unit 206 resets the counter value C to "0" again (S40). The rotation instruction unit 202 executes the confirmation ascent again (S42). At the stage of S42, the rotor 60 may have reached the origin. In S42, the rotor 60 is rotated upward by a predetermined amount of rotation to move the rotor 60 away from the origin. If the rotor 60 is not at the origin but has impurities stuck thereon, the confirmation ascent in S42 can encourage the impurities to fall off in the same manner as in S12. After the confirmation ascent, the rotation instruction unit 202 sets the descending rotation speed of the rotor 60 to V2, which is slower than V1 (S44). By slowing down the descending rotation speed, the rotation torque is increased. By slowing down the rotor 60 and increasing the rotation torque, the rotor 60 becomes less susceptible to the influence of impurities and more reliably reaches the origin.

[0065] The rotation instruction unit 202 rotates the rotor 60 downward by one step (S46). The rotation detection unit 204 calculates the actual rotation change amount a of the sensor magnet 106 in response to the downward rotation instruction for one step. The reference identification unit 206 determines whether the rotation change amount a is less than a threshold value T2 (S48). The value of the threshold value T2 is arbitrary. The threshold value T1 and the threshold value T2 may be the same.

[0066] When the rotation change amount a is less than the threshold value T2, the possibility that the rotor 60 is restricted from rotating due to the stopper 90 coming into contact with the protrusion (the locking portion) becomes even higher.

[0067] When the rotation change amount a is equal to or greater than the threshold value T2 (N in S48), that is, when the rotor 60 can sufficiently follow the command angle, the reference determination unit 206 resets the counter value C to "0" (S50). In addition, the reference determination unit 206 clears second origin candidate information HP2 (described later) if it is stored (S22). The first origin candidate information HP1 is not cleared. Thereafter, the process returns to S46, and the rotation detection unit 204 again commands a downward rotation of one step.

[0068] On the other hand, when the rotation change amount a is less than the threshold value T2 (Y in S18) and the counter value C=0 (Y in S54), that is, when the tracking performance degradation is detected for the first time after S46, the reference determination unit 206 temporarily stores the current angle value and excitation pattern as the second origin candidate information HP2 (S56). After that, the reference determination unit 206 increments the counter value C (S58). When the counter value C is not zero (N in S54), the process of S56 is skipped. In this case, the second origin candidate information HP2 is maintained as it is.

[0069] When the counter value C is less than the threshold value K2 (N in S60), the second origin candidate information HP2 is stored and the process returns to S46. The threshold value K2 is an arbitrary natural number and may be the same as the threshold value K1. On the other hand, when the counter value C is equal to or greater than the threshold value K2, that is, when the tracking performance degradation detection has occurred K2 or more times in succession (Y in S60), the reference identification unit 206 compares the first origin candidate information HP1 with the second origin candidate information HP2 (S62). More specifically, the reference identification unit 206 determines whether the angle difference, which is the difference between the angle value of the first origin candidate information HP1 and the angle value of the second origin candidate information, is less than the threshold value W. The threshold value W is arbitrary.

[0070] When the angle difference is less than the threshold value W (Y in S62), that is, when the position of the actuating rod 32 when the first origin candidate information HP1 is registered and the position of the actuating rod 32 when the second origin candidate information HP2 is registered are sufficiently close, the reference identification unit 206 officially registers the second origin candidate information HP2 in the reference information storage unit 208 as origin information (S64). The reference identification unit 206 calculates the angle difference, which is the difference between the angle value of the first origin candidate information HP1 and the angle value of the second origin candidate information HP2, and when the angle difference is less than the threshold value W, the "proximity condition" is established, and the origin is identified by the establishment of the proximity condition. On the other hand, when the angle difference is equal to or greater than the threshold value W (N in S62), the reference identification unit 206 transmits an error signal (S66). When the inspector receives the error signal, he or she inspects the motor-operated valve 1.

[0071] The reason why the second origin candidate information HP2 is used as the origin information instead of the first origin candidate information HP1 is that when the rotational torque is increased and the origin is detected, in other words, there is a higher possibility that the origin can be reached more accurately at the time point S56 than at the time point S26. This is because the rotor 60 is less susceptible to rotation restriction by impurities when the rotational torque is high, as described above.

[0072] [Summary] The motor-operated valve 1, and in particular, the motor-operated valve control device 200, have been described above based on the embodiment. According to this embodiment, the origin (reference position) can be identified by detecting a decrease in the tracking ability of the rotor 60 with respect to the command angle by the magnetic sensor 119. The motor-operated valve control device 200 can inspect the tracking ability of the rotor 60 every time the rotor 60 is rotated one step at a time.

[0073] The origin information is stored in the reference information storage unit 208 of the motor-operated valve 1. Therefore, the motor-operated valve 1 can be provided to a user with the origin information added to the mechanism body according to individual differences. When the motor-operated valve 1 is in use, the operating rod 32 can be set to an appropriate reference position for each motor-operated valve 1 based on the origin information recorded in the reference information storage unit 208.

[0074] In this embodiment, the position where the rotation change amount a falls below the threshold T1 K1 or more times in succession and where the rotation change amount a falls below the threshold T2 K2 or more times in succession is specified as the origin. By setting K1 and K2 to a number of times, the risk of mistaking a point where the rod 32 becomes temporarily difficult to move due to impurities for the origin is reduced. K1 and K2 may be any integer of 1 or more.

[0075] After detecting the first origin candidate information HP1, the rotation instruction unit 202 slows down the rotation speed of the rotor 60. By slowing down the rotor 60 and increasing the rotation torque, the influence of impurities between the rotor 60 and the origin is suppressed, and the rotor 60 can more reliably reach the origin.

[0076] In the origin inspection process, a confirmation ascent is performed before the rotor 60 is rotated downward. The confirmation ascent allows the angle indicated by the excitation pattern and the sensed angle of the rotor 60 to be synchronized. The reverse rotation of the rotor 60 accompanying the confirmation ascent allows impurities trapped in the rotor 60 to be released. In addition, by performing the confirmation ascent, appropriate vibrations can be applied to the screw feed mechanism 109, so that impurities that may remain in the screw feed mechanism 109 can be effectively removed.

[0077] The present invention is not limited to the above-mentioned embodiment and modified examples, and the components can be modified without departing from the gist of the present invention. Various inventions can be formed by appropriately combining multiple components disclosed in the above-mentioned embodiment and modified examples. In addition, some components can be deleted from all the components shown in the above-mentioned embodiment and modified examples.

[0078] [Variations] In this embodiment, the valve closed position has been described as the origin (reference position). As a modified example, the valve fully open position (the upper limit position of the rotor 60) may be set as the reference position. The reference position may be any position that serves as a reference for driving the actuating rod 32 by the rotor 60. The reference position may be set arbitrarily as long as it is a position where the rotation of the rotor 60 can be restricted by the stopper 90.

[0079] In the present embodiment, the driving current supplied to the stepping motor is defined by the excitation pattern, and the rotor 60 is changed by unit rotation amount by switching the excitation pattern step by step. However, the present invention is not limited to this, and the rotor 60 may be rotated continuously at a constant speed, and the reference identification unit 206 may search for the reference position based on the tracking ability of the sensed angle to the indicated angle per unit time.

[0080] In the present embodiment, the reference position is specified on the condition that the rotation change amount a is continuously below the thresholds T1 and T2. As a modified example, the reference specifying unit 206 may specify the reference position when the total number of times that the rotation change amount a is below the thresholds T1 and T2 is equal to or greater than a predetermined number of times, regardless of whether the detection is continuous or not. When the risk of misidentification due to impurities or the like is considered to be low, the reference specifying unit 206 may register the first origin candidate information HP1 specified in S26 of FIG. 10 as reference information without performing subsequent processing.

[0081] In the present embodiment, the first origin candidate information HP1 and the second origin candidate information HP2 are detected, and when a proximity condition is satisfied between the first origin candidate information HP1 and the second origin candidate information HP2, the second origin candidate information HP2 is registered as the reference information. As a modified example, the reference identification unit 206 may register the first origin candidate information HP1 as the reference information instead of the second origin candidate information HP2, or may register the average value of the angle value of the first origin candidate information HP1 and the angle value of the second origin candidate information HP2 as the angle value of the reference information.

[0082] After the origin information is registered, the motor-operated valve 1 can determine whether or not the rotor 60 is approaching the origin by comparing the angle value registered in the origin information with the angle value actually detected by the magnetic sensor 119. As a modified example, after the origin information is registered, the motor-operated valve 1 may determine whether or not the rotor 60 is approaching the origin by comparing the excitation pattern registered in the origin information with the excitation pattern actually set in the coil 73.

[0083] In the above embodiment, a configuration in which the magnetic sensor 119 faces the sensor magnet 106 in the axial direction is exemplified (see FIG. 1). In a modified example, the magnetic sensor may be disposed to the side (radially outward) of the sensor magnet. That is, the two may face each other in the radial direction. The outer peripheral surface of the sensor magnet may be magnetized. The number of poles may be appropriately set, for example, to two poles on the valve body.

[0084] In the above embodiment, a configuration in which the rotor magnet 104 and the sensor magnet 106 are spaced apart in the axial direction has been exemplified. In a modified example, the rotor magnet and the sensor magnet may be integrally configured. The rotor magnet portion and the sensor magnet portion may be integrally molded in the magnet portion molding process. In that case, the area (outer diameter) of the sensor magnet may be increased so that the magnetic sensor can reliably detect magnetic flux. Since the sensor magnet protrudes beyond the outer periphery of the rotor core, it becomes easier to injection mold the sensor magnet and the rotor magnet.

[0085] In each embodiment, a laminated core (laminated magnetic core) is exemplified as the core of the stator. In a modified example, a dust core or other core may be adopted. A dust core is also called a "powder core" and is obtained by powdering a soft magnetic material, coating the powder with a non-conductive resin or the like, kneading the powder with a resin binder, and compression molding and heating it.

[0086] In each embodiment, a configuration in which the drive circuit, control circuit, communication circuit, and power supply circuit are mounted on the underside of the circuit board has been illustrated, but the circuits to be mounted can be changed as appropriate. For example, the drive circuit and power supply circuit may be mounted, while the control circuit may be installed outside the motor-operated valve. In addition, each circuit may be mounted on the upper surface of the circuit board.

[0087] In each embodiment, a PM type stepping motor is used as the motor unit, but a hybrid type stepping motor may also be used. In the above embodiments, the motor unit is a three-phase motor, but it may be another type such as a two-phase, four-phase, or five-phase motor. The number of electromagnetic coils in the stator is not limited to three for the motor unit or six for the first body, and may be set appropriately according to the number of phases of the motor.

[0088] The motor-operated valve of each embodiment is preferably applied to a refrigeration cycle that uses a refrigerant such as an alternative fluorocarbon (HFC-134a) as a refrigerant, but can also be applied to a refrigeration cycle that uses a refrigerant with a high operating pressure such as carbon dioxide. In that case, an external heat exchanger such as a gas cooler is disposed in the refrigeration cycle instead of a condenser.

[0089] In each embodiment, the motor-operated valve is configured as an expansion valve, but it may be configured as an opening / closing valve or a flow control valve that does not have an expansion function.

[0090] In each embodiment, the motor-operated valve is applied to the refrigeration cycle of an air conditioner for an automobile, but the motor-operated valve can be applied to any air conditioner equipped with an electric expansion valve, not limited to vehicles. Also, the motor-operated valve can be configured to control the flow of a fluid other than a refrigerant.

[0091] The sensor magnet 106 may be magnetized with four poles on both sides (one-sided valve body with two poles magnetized on both sides). The magnetic flux can be strengthened by reversing the polarity of the magnetic poles on the upper and lower sides. In this case, even if the rotor 60 is displaced in the valve closing direction and the distance between the sensor magnet 106 and the magnetic sensor 119 increases, the sensitivity of the magnetic sensor 119 can be maintained at a good level. [Explanation of symbols]

[0092] 1 motor-operated valve, 2 valve body, 3 motor unit, 5 body, 6 first body, 8 second body, 10 male thread, 12 seal housing, 14 seal ring, 16 concave fitting portion, 18 seal housing, 20 seal ring, 22 valve hole, 24 valve seat, 26 inlet port, 28 outlet port, 30 valve chamber, 32 operating rod, 34 valve body, 36 guide member, 38 male thread, 40 large diameter portion, 42 spring retainer, 44 spring retainer, 46 spring, 52 locking portion, 60 rotor, 62 rotating shaft, 64 stator, 66 can, 70 laminated core, 73 coil, 73a U-phase coil, 73b V-phase coil, 73c W-phase coil, 74 bobbin, 75 coil unit, 76 case, 77 cover, 78 stator unit, 79 Connector portion, 80 seal housing portion, 81 connection terminal, 82 seal ring, 90 stopper, 102 rotor core, 104 rotor magnet, 106 sensor magnet, 108 female screw, 109 screw feed mechanism, 110 reduced diameter portion, 112 bottom portion, 114 stopper, 116 spring, 117 terminal, 118 circuit board, 119 magnetic sensor, 120 slot, 122 salient pole, 124 slit, 140 annular groove, 142 shaft end portion, 144 annular groove, 200 motor-operated valve control device, 202 rotation instruction portion, 204 rotation detection portion, 206 reference identification portion, 208 reference information storage portion, L axis line, MA magnetic field direction

Claims

1. A stepping motor is connected to an electric valve that adjusts the valve opening by rotating a rotor, a rotation instruction unit that indicates an amount of rotation of the rotor; a rotation detection unit that detects an amount of rotation of the rotor; a reference specifying unit that specifies, as a reference position of the rotor, a position at which a ratio of an amount of rotation detected for the rotor to an amount of rotation instructed to the rotor is equal to or smaller than a first threshold value; the rotation instruction unit instructs an amount of rotation of the rotor for each unit rotation amount, which is an amount of rotation of the rotor per step of the stepping motor; the rotation detection unit detects an amount of rotation of the rotor each time the unit amount of rotation is specified; The electric valve control device is characterized in that the reference identification unit identifies a reference position of the rotor on the condition that a state in which the ratio of the rotation amount detected for the rotor to the unit rotation amount is equal to or less than the first threshold value is detected multiple times.

2. The electric valve control device according to claim 1, wherein the reference identification unit further registers reference information including both or one of an angle value indicating a rotation angle of the rotor when the reference position is identified and an excitation pattern.

3. 3. The motor-operated valve control device according to claim 1, wherein the rotation instruction unit reduces the rotation speed of the rotor when a state is detected in which a ratio of an amount of rotation detected for the rotor to an amount of rotation instructed to the rotor is equal to or smaller than a second threshold value.

4. 4. The electric valve control device according to claim 1, wherein the rotation instruction unit searches for the reference position by rotating the rotor in a first direction, rotates the rotor a predetermined amount in a second direction opposite to the first direction at the start of the search, and then rotates the rotor in the first direction.

5. It is connected to an electric valve that adjusts the valve opening by rotating the rotor. a rotation instruction unit that indicates an amount of rotation of the rotor; A rotation detection unit that detects an amount of rotation of the rotor; a reference specifying unit that specifies a reference position of the rotor based on a ratio of a rotation amount detected for the rotor to a rotation amount instructed to the rotor, the reference identification unit identifies as a first candidate position a position when a ratio of the amount of rotation detected for the rotor to the amount of rotation instructed to the rotor is equal to or less than a third threshold value, and identifies as a second candidate position a position when a ratio of the amount of rotation detected for the rotor to the amount of rotation instructed to the rotor after the identification of the first candidate position is equal to or less than a fourth threshold value, and identifies a reference position of the rotor based on both or one of the first candidate position and the second candidate position when a predetermined proximity condition is satisfied between the rotation angle of the rotor detected at the first candidate position and the rotation angle of the rotor detected at the second candidate position.

6. The electric valve control device according to claim 5, characterized in that the rotation instruction unit searches for the first candidate position by rotating the rotor in a first direction, and before starting the search for the second candidate position, rotates the rotor a predetermined amount in a second direction opposite to the first direction, and then rotates the rotor in the first direction.

7. For an electric valve that adjusts the valve opening by rotating a rotor using a stepping motor, a function of instructing the amount of rotation of the rotor; A function of detecting an amount of rotation of the rotor; and specifying, as a reference position of the rotor, a position at which a ratio of an amount of rotation detected for the rotor to an amount of rotation instructed to the rotor is equal to or smaller than a first threshold value; specifying a rotation amount of the rotor for each unit rotation amount, which is a rotation amount of the rotor per step of the stepping motor; detecting an amount of rotation of the rotor each time the unit amount of rotation is specified; An electric valve control program characterized by identifying a reference position of the rotor on the condition that a state in which the ratio of the rotation amount detected for the rotor to the unit rotation amount is equal to or less than the first threshold value is detected multiple times.

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