Electric valve control device, electric valve device, and method for controlling electric valve

Abstract

This electric valve control device controls an electric valve (20) having: a valve body (30) having a valve port (34a); a stepping motor having a rotor (55) and a stator (22) connected to a motor driver; and a valve body (40) that moves in relation to the valve port (34a) when the rotor (55) rotates. The electric valve control device supplies a drive current to the stator (22) to cause the rotor (55) to rotate, and after completion of the supply of the drive current, supplies the stator (22) with a post-excitation current that is greater than the amplitude of the drive current.

Description

Motor-operated valve control device, motor-operated valve device, and motor-operated valve control method

[0001] The present disclosure relates to an electric valve control device, an electric valve device, and a method for controlling an electric valve.

[0002] For example, in the motor-operated valve disclosed in Patent Document 1, a pulse is input to a motor driver, and a drive current corresponding to the pulse is supplied to a stator, causing the rotor to rotate. The rotation of the rotor is transmitted to a drive shaft by a reduction mechanism, and the drive shaft moves axially while rotating, thereby moving the valve element axially.

[0003] Japanese Patent Application Publication No. 2012-197849

[0004] In the above-mentioned motor-operated valve, when the input of pulses to the stepping motor is stopped, the rotor does not immediately stop, but rather rotates too much, which can cause the stepping motor to lose synchronization. Therefore, it is conceivable to constantly supply a relatively large drive current corresponding to the pulses to the stator to prevent the rotor from rotating too much. However, this approach has the problem of causing wear on parts such as the gears and drive shaft of the reduction mechanism, reducing the durability of the motor-operated valve.

[0005] An object of the present disclosure is to provide an electric valve control device, an electric valve device, and a control method for an electric valve that can suppress step-out of a stepping motor and a decrease in durability of an electric valve.

[0006] An electric valve control device according to one aspect of the present invention is an electric valve control device that controls an electric valve having a valve body with a valve port, a stepping motor having a rotor and a stator connected to a motor driver, and a valve body that moves relative to the valve port when the rotor rotates, wherein the electric valve control device supplies a drive current to the stator to rotate the rotor, and after the supply of the drive current is completed, supplies a post-excitation current to the stator having an amplitude greater than that of the drive current.

[0007] According to the present disclosure, it is possible to provide an electric valve control device, an electric valve device, and a control method for an electric valve that can suppress step-out of a stepping motor and a decrease in durability of an electric valve.

[0008] 1 is a block diagram of a motor-operated valve device according to an embodiment of the present disclosure; FIG. 2 is a longitudinal sectional view of a motor-operated valve according to an embodiment of the present disclosure; FIG. 3 is a schematic diagram of a rotor and a stator of a stepping motor included in a motor-operated valve according to an embodiment of the present disclosure; FIG. 4 is a graph of A-phase current and B-phase current according to a reference example; FIG. 5 is a graph of A-phase current and B-phase current according to a first embodiment of the present disclosure; FIG. 6 is a graph of A-phase current and B-phase current according to a second embodiment of the present disclosure; and FIG. 7 is a graph of A-phase current and B-phase current according to a third embodiment of the present disclosure.

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For the sake of convenience, the description of components having the same reference numerals as components already described in the description of the embodiments will be omitted. In the following description of the embodiments, the up and down directions refer to directions within the plane of the paper in FIG. 2 , and are not intended to narrow the technical scope of the present disclosure.

[0010] <Structure of Motor-Operated Valve Device> Figure 1 is a block diagram of a motor-operated valve device 100 according to an embodiment of the present disclosure. The motor-operated valve device 100 includes a motor-operated valve control device 10 and a motor-operated valve 20, and controls the flow rate of a refrigerant, for example. The motor-operated valve control device 10 includes a motor driver 11, a processor 12 such as a CPU, and a memory 13. The motor-operated valve 20 includes a stepping motor 21.

[0011] The motor driver 11 is driven by the processor 12 to supply a drive current to the stepping motor 21. The processor 12 drives the motor driver 11 by referring to drive parameters for the stepping motor 21 stored in the memory 13.

[0012] Fig. 2 is a longitudinal cross-sectional view of the motor-operated valve 20 according to the embodiment of the present disclosure. The motor-operated valve 20 has a stator 22, a valve body 30, a valve element 40, and a drive unit 50. The stepping motor 21 shown in Fig. 1 is composed of the stator 22 and a rotor 55 of the drive unit 50 shown in Fig. 2, and is, for example, a PM-type stepping motor.

[0013] The stator 22 is composed of an A-phase stack 23 and a B-phase stack 24, and rotates the rotor 55 when a drive current is supplied from the motor driver 11 shown in Fig. 1. The A-phase stack 23 and the B-phase stack 24 face each other in the central axis direction Y, and the A-phase stack 23 is located above the B-phase stack 24.

[0014] The valve body 30 is a cylindrical member with a bottom extending in the central axis direction Y and has a main valve chamber 32 therein that houses the valve element 40. The valve body 30 has an inlet passage 33 that communicates with the main valve chamber 32 in the left-right direction and an outlet passage 34 that extends downward from the main valve chamber 32. An inlet pipe 35 is connected to the inlet passage 33, and an outlet pipe 36 is connected to the outlet passage 34. A main valve seat 37 that surrounds the outlet passage 34 is formed around the valve opening 34a of the outlet passage 34. The motor-operated valve may also be used by allowing fluid to flow in the reverse direction. In this case, the fluid flows into the main valve chamber 32 from the outlet passage 34 side and flows out of the inlet passage 33.

[0015] The valve body 40 has a body portion 41, a valve portion 42, a spring receiving portion 43, and a ball receiving portion 44. The body portion 41 has a generally cylindrical shape extending in the central axis direction Y. The valve portion 42 has a generally conical shape with its tip facing downward and is located below the body portion 41. The tip of the valve portion 42 faces the valve opening 34a of the outflow channel 34 in the central axis direction Y. The spring receiving portion 43 has a ring shape and is located above the body portion 41. The outer diameter of the spring receiving portion 43 is larger than the outer diameter of the body portion 41. The body portion 41, the valve portion 42, and the spring receiving portion 43 may be formed integrally. The ball receiving portion 44 is fixed to the upper end of the body portion 41.

[0016] The valve element 40 is provided so as to be movable in the vertical direction within the internal space of the valve body 30, and can open and close the outflow path 34 by seating on or separating from the main valve seat 37. Therefore, when the valve element 40 is in the open state, the fluid that flows in from the inflow path 33 flows out into the outflow path 34 via the main valve chamber 32, and when the valve element 40 is in the closed state, the fluid remains in the main valve chamber 32 without flowing out into the outflow path 34.

[0017] Within the internal space of the valve body 30, between the valve body 30 and the valve element 40, a substantially cylindrical sleeve 60 and a valve-opening spring 61 are provided along the central axis direction Y. The sleeve 60 is held on the inner peripheral surface of the valve body 30. The valve-opening spring 61 is disposed radially between a main body portion 60a of the sleeve 60 and a barrel portion 41 of the valve element 40. The valve-opening spring 61 is also disposed vertically between a spring support portion 60b of the sleeve 60 and a spring bearing portion 43 of the valve element 40, and biases the valve element 40 in a direction away from the valve port 34a. The valve element 40 is supported by a lower portion 60c of the sleeve 60 so as to be vertically movable.

[0018] The drive unit 50 includes a drive shaft 51 , a bearing member 52 , a connecting member 53 , a planetary gear mechanism 54 , a rotor 55 , and a rotor shaft 56 .

[0019] The drive shaft 51 has a ball 51a and a male screw 51t, and is located in the internal space of the valve body 30 and above the valve element 40. The ball 51a is joined to the ball receiver 44 and contacts the lower end surface of the drive shaft 51. The male screw 51t is provided on the outer circumferential surface of the drive shaft 51. The ball 51a prevents the rotation of the drive shaft 51 from being transmitted to the ball receiver 44, but transmits the vertical movement of the drive shaft 51 to the ball receiver 44.

[0020] The bearing member 52 has a generally cylindrical shape and has a female thread 52t on its inner circumferential surface. The bearing member 52 is disposed so as to cover the internal space of the valve body 30 and the side surface of the drive shaft 51. The female thread 52t protrudes radially inward from the inner circumferential surface of the bearing member 52 and is disposed so as to be threadedly engaged with the male thread 51t.

[0021] The connecting member 53 is a substantially disk-shaped member that is molded integrally with the rotor 55 and the sun gear of the planetary gear mechanism 54. The connecting member 53 is journaled by a rotor shaft 56 and transmits the rotation of the rotor 55 to the sun gear of the planetary gear mechanism 54.

[0022] The planetary gear mechanism 54 is a reduction mechanism that reduces the rotation speed of the rotor 55 and transmits the reduced rotation speed to the drive shaft 51. The planetary gear mechanism 54 is composed of, for example, a fixed ring gear, a sun gear, multiple planet gears, a carrier, an output gear, an output shaft, etc.

[0023] When a drive current is supplied to the stator 22, the rotor 55 rotates. The rotation of the rotor 55 is transmitted to the drive shaft 51 by the planetary gear mechanism 54. When the drive shaft 51 rotates, the drive shaft 51 moves downward due to the feed screw action, and the valve element 40 is pushed down. When the valve portion 42 of the valve element 40 seats on the main valve seat 37, the motor-operated valve 20 is closed.

[0024] FIG. 3 is a schematic diagram of a rotor 55 and a stator 22 of a stepping motor 21 included in the motor-operated valve 20 according to the embodiment of the present disclosure.

[0025] The A-phase stack 23 has a plurality of claw-pole-shaped pole teeth 23a, 23b. The tip of the pole tooth 23a faces downward in FIG. 2, and the tip of the pole tooth 23b faces upward in FIG. 2. The pole teeth 23a and the pole teeth 23b are arranged so as to mesh with each other and are shifted by half a pitch in the circumferential direction. The A-phase stack 23 has, for example, 12 pole teeth 23a and 12 pole teeth 23b. The A-phase stack 23 also has an A-phase coil 23c (not shown). When the A-phase coil 23c is energized, the pole teeth 23a and the pole teeth 23b become magnetic poles of mutually opposite polarities.

[0026] The B-phase stack 24 has a plurality of claw-pole-type pole teeth 24a, 24b and a B-phase coil 24c (not shown). The tip of the pole tooth 24a faces downward in FIG. 2, and the tip of the pole tooth 24b faces upward in FIG. 2. The pole teeth 24a and the pole teeth 24b are arranged to mesh with each other and are shifted by half a pitch in the circumferential direction. The B-phase stack 24 has, for example, 12 pole teeth 24a and 12 pole teeth 24b. The B-phase stack 24 also has a B-phase coil 24c (not shown). When the B-phase coil 24c is energized, the pole teeth 24a and the pole teeth 24b become magnetic poles of opposite polarities.

[0027] The pole teeth 23a, 23b of the A-phase stack 23 and the pole teeth 24a, 24b of the B-phase stack 24 are arranged with a quarter-pitch offset in the circumferential direction and form the inner circumferential surface of the stator 22. A rotor 55 having a plurality of rotor magnets 57 is arranged inside the inner circumferential surface of the stator 22. The rotor magnets 57 are permanent magnets and are substantially identical in size, material, and composition. The magnetic poles of the rotor magnets 57 and the pole teeth 24a, 24b of the stator 22 face each other in the radial direction. The number of magnetic poles of the rotor 55 and the number of pole teeth of the stator 22 can be changed depending on the application of the motor-operated valve device 100.

[0028] <Drive Control of Motor-Operated Valve Device> In this embodiment, the stepping motor 21 is controlled by a 2-2 phase excitation method. Note that the stepping motor 21 may also be controlled by a 1 phase excitation method, a 1-2 phase excitation method, a W1-2 phase excitation method, a 2W1-2 phase excitation method, or a 4W1-2 phase excitation method, or may be controlled by microsteps.

[0029] When the processor 12 inputs a pulse signal P (pulses P[1] to P[4]) to the motor driver 11, the motor driver 11 supplies a drive current corresponding to the pulses P[1] to P[4] to the stepping motor 21, causing the rotor 55 to rotate. Here, the pulse signal P represents a signal that controls the drive current supplied to the stepping motor 21. Furthermore, the pulses P[1] to P[4] each represent the signal waveform of one step of the pulse signal P. As a reference example, FIG. 4 shows an example of the waveforms of the A-phase current and the B-phase current when the processor 12 cyclically inputs the pulse signal P to the motor driver 11 in the order of pulses P[1] to P[4] and then inputs an excitation signal.

[0030] 4, when the processor 12 inputs a pulse P[1] to the motor driver 11, a +I A-phase current is supplied from the motor driver 11 to the A-phase coil 23c, and a −I B-phase current is supplied from the motor driver 11 to the B-phase coil 24c. When the processor 12 inputs a pulse P[2] to the motor driver 11, a +I A-phase current is supplied from the motor driver 11 to the A-phase coil 23c, and a +I B-phase current is supplied from the motor driver 11 to the B-phase coil 24c. When the processor 12 inputs a pulse P[3] to the motor driver 11, a −I A-phase current is supplied from the motor driver 11 to the A-phase coil 23c, and a +I B-phase current is supplied from the motor driver 11 to the B-phase coil 24c. Furthermore, when the processor 12 inputs a pulse P[4] to the motor driver 11, an A-phase current of -I is supplied from the motor driver 11 to the A-phase coil 23c, and a B-phase current of -I is supplied from the motor driver 11 to the B-phase coil 24c.

[0031] When the processor 12 periodically inputs the pulse signal P to the motor driver 11 in the order of pulses P[1] to P[4], the rotor 55 rotates in the first direction (clockwise in Figure 3) as described above, the drive shaft 51 moves downward via the planetary gear mechanism 54, the valve body 40 is pushed down, and the electric valve 20 is closed.

[0032] However, even when the processor 12 inputs the pulse signal P to the motor driver 11 and completes the supply of drive current to the stator 22, the rotor 55 does not immediately stop, but may rotate too much, causing the stepping motor 21 to lose synchronization. Therefore, as shown in Figure 4, the processor 12 inputs a post-excitation signal to the motor driver 11 in the post-excitation current section after the drive current section ends, and the motor-operated valve control device 10 supplies a +I A-phase current to the A-phase coil 23c as a post-excitation current, and a -I B-phase current to the B-phase coil 24c as a post-excitation current. This stops the rotor 55 and prevents loss of synchronization.

[0033] Here, the inventors considered supplying a post-excitation current larger than the amplitude of the drive current to the stator 22 after the supply of the drive current has been completed, in order to stop the stepping motor 21 more quickly and more effectively prevent loss of synchronization.

[0034] 5 is a graph of the A-phase current and the B-phase current according to the first embodiment of the present disclosure. As shown in FIG. 5 , after the supply of the drive current to the stator 22 is completed, i.e., after the drive current section ends, the motor-operated valve control device 10 supplies A-phase current and B-phase current of +I', which are larger than the amplitude |I| of the drive current, to the A-phase coil 23c and the B-phase coil 24c, respectively, in the post-excitation current section. This more effectively prevents stepping motor 21 from losing synchronization after the supply of the drive current is completed, without reducing the durability of the motor-operated valve 20. Note that, immediately after the supply of the drive current to the stator 22 is completed, A-phase current and B-phase current of +I', which are larger than the amplitude |I| of the drive current, may be supplied as post-excitation current to the A-phase coil 23c and the B-phase coil 24c, respectively.

[0035] 6 is a graph of the A-phase current and the B-phase current according to the second embodiment of the present disclosure. As shown in FIG. 6 , in the post-excitation current section, the motor-operated valve control device 10 may supply, as post-excitation currents, A-phase currents and B-phase currents of +I, which have the same magnitude as the amplitude |I| of the drive current, to the A-phase coil 23c and the B-phase coil 24c, respectively, from the completion of supply of the drive current to the stator 22 until a predetermined time T1. After the predetermined time T1 has elapsed, the motor-operated valve control device 10 may supply, as post-excitation currents, A-phase currents and B-phase currents of +I', which are larger than the amplitude |I| of the drive current, to the A-phase coil 23c and the B-phase coil 24c, respectively. Furthermore, the motor-operated valve control device 10 may supply the A-phase current and the B-phase current of +I' to the A-phase coil 23c and the B-phase coil 24c, respectively, for only a predetermined period Td, or may continue to supply them for a period longer than the predetermined period Td. The predetermined period Td is longer than the time it takes for the rotor 55 to come to a complete stop (when the rotation amplitude substantially disappears), and is, for example, 100 times the period of the pulse P.

[0036] 7 is a graph of the A-phase current and the B-phase current according to a third embodiment of the present disclosure. As shown in FIG. 7 , in the post-excitation current section, the motor-operated valve control device 10 may supply, as post-excitation currents, A-phase currents and B-phase currents of +I, which are the same in magnitude as the amplitude |I| of the drive current, to the A-phase coil 23c and the B-phase coil 24c, respectively, from the completion of supply of the drive current to the stator 22 until a predetermined time T2. After the predetermined time T2 has elapsed, the magnitude of the post-excitation current may gradually increase to +I', which is greater than the amplitude |I| of the drive current. Alternatively, the motor-operated valve control device 10 may gradually decrease the magnitude of the post-excitation current from +I' to +I or to 0 after a predetermined time T3 has elapsed from the start of supply of the post-excitation current. Note that the difference between the predetermined time T2 and the predetermined time T3, T3 - T2, is longer than the time until the rotor completely stops (the rotational amplitude substantially disappears), and is, for example, 100 times the period of the pulse P.

[0037] In Fig. 5, the magnitude of the post-excitation current may be gradually increased to +I' immediately after the supply of the drive current to the stator 22 is completed. In Fig. 6, the predetermined time T1 may be set to 0. In Fig. 7, the predetermined time T2 may be set to 0. Furthermore, in Figs. 6 and 7, the magnitude of the post-excitation current may be gradually increased from +I to +I' and then quickly decreased from +I' to +I, or the magnitude of the post-excitation current may be quickly increased from +I to +I' and then gradually decreased from +I' to +I.

[0038] In this way, by supplying a post-excitation current to the stator 22 that is greater than the amplitude of the drive current after the supply of the drive current to the stator is completed, it is possible to prevent the stepping motor 21 from losing synchronization after the supply of the drive current is completed without reducing the durability of the electric valve 20.

[0039] Although the embodiments of the present disclosure have been described above, it goes without saying that the technical scope of the present disclosure should not be interpreted as being limited by the description of the present embodiments. The present embodiments are merely examples, and it will be understood by those skilled in the art that various modifications of the embodiments are possible within the scope of the invention described in the claims. The technical scope of the present disclosure should be determined based on the scope of the invention described in the claims and its equivalents.

[0040] For example, in the embodiment of the present disclosure, the motor-operated valve 20 may be a direct-acting motor-operated valve in which the rotation of the rotor 55 is directly transmitted to the drive shaft 51 .

[0041] Furthermore, in an embodiment of the present disclosure, the motor-operated valve control device 10 may calculate the angular velocity ω of the rotor 55, and if it determines that the angular velocity ω of the rotor 55 has reached a preset peak value Cp when the supply of the drive current is completed, the post-excitation current may be made larger than the amplitude of the drive current in the post-excitation current section. If the angular velocity ω has reached the peak value Cp when the supply of the drive current is completed, the stepping motor 21 is more likely to lose synchronization. Therefore, by controlling the magnitude of the post-excitation current in accordance with the angular velocity ω of the rotor 55 as described above, it is possible to more effectively prevent the stepping motor 21 from losing synchronization after the supply of the drive current is completed.

[0042] The angular velocity ω can be calculated using the back electromotive force e generated in the rotor 55 according to the following formula 1. Here, Ke represents a back electromotive force constant. The back electromotive force constant Ke is a value determined by the capacitance of the A-phase coil 23c and the B-phase coil 24c, etc. (Formula 1) e=Ke×ω

[0043] The relationship between the angular velocity ω and the back electromotive force e generated in the rotor 55 until the angular velocity ω reaches the peak value Cp, and the relationship between the number of input pulse signals P input by the processor 12 to the motor driver 11 and the back electromotive force e generated in the rotor 55 are measured in advance. Table data indicating these relationships and the peak value Cp are stored in the memory 13 as drive parameters, and the processor 12 can refer to these drive parameters from the memory 13. Note that instead of the table data indicating the relationship between the angular velocity ω and the back electromotive force e generated in the rotor 55, the back electromotive force constant Ke in the above equation 1 may be stored in the memory 13 as a drive parameter.

[0044] The processor 12 refers to table data stored in the memory 13 that shows the relationship between the number of input pulse signals P and the back electromotive force e, and calculates the back electromotive force e generated in the rotor 55 based on the number of input pulse signals P. Next, the processor 12 refers to the table data stored in the memory 13 that shows the relationship between the angular velocity ω and the back electromotive force e, or the back electromotive force constant Ke, and calculates the angular velocity ω based on the back electromotive force e. It determines whether the angular velocity ω calculated at the completion of the supply of the drive current has reached its peak value Cp. If the angular velocity ω has reached its peak value Cp at the completion of the supply of the drive current, the processor 12 makes the post-excitation current larger than the amplitude of the drive current in the post-excitation current section, and if the angular velocity ω has not reached its peak value Cp, the processor 12 does not make the post-excitation current larger than the amplitude of the drive current in the post-excitation current section.

[0045] Note that instead of the processor 12 calculating the back electromotive voltage e generated in the rotor 55 based on the number of input pulse signals P, the back electromotive voltage e may be measured in real time by a voltage acquisition unit (not shown) included in the motor-operated valve control device 10. This allows for a more accurate calculation of the angular velocity ω.

[0046] This application is based on a Japanese patent application (Patent Application No. 2024-092914) filed on June 7, 2024, the contents of which are incorporated herein by reference.

[0047] 10: Motor-operated valve control device 11: Motor driver 12: Processor 13: Memory 20: Motor-operated valve 21: Stepping motor 22: Stator 23: A-phase stack 23a, 23b: Pole teeth 24: B-phase stack 24a, 24b: Pole teeth 30: Valve body 32: Main valve chamber 33: Inlet passage 34: Outlet passage 35: Inlet pipe 36: Outlet pipe 37: Main valve seat 40: Valve element 41: Body portion 42: Valve portion 43: Spring bearing portion 44: Ball bearing portion 50: Drive portion 51: Drive shaft 51a: Ball 51t: Male thread 52: Bearing member 52t: Female thread 53: Connecting member 54: Planetary gear mechanism 55: Rotor 56: Rotor shaft 57: Rotor magnet 60: Sleeve 60a: Main body portion 60b: Spring support portion 60c: Lower portion 61: Valve opening spring

Claims

1. An electric valve control device for controlling an electric valve having a valve body having a valve port, a stepping motor having a rotor and a stator connected to a motor driver, a valve body that moves relative to the valve port when the rotor rotates, a planetary gear mechanism for reducing the rotation of the rotor, and a drive shaft that is moved by a lead screw action and pushes down the valve body when the rotation of the rotor is transmitted by the planetary gear mechanism, The electric valve controls the flow rate of the refrigerant and has a structure in which the rotor, the planetary gear mechanism, and the drive shaft are exposed to the refrigerant. The electric valve control device is characterized in that it supplies a drive current to the stator to rotate the rotor, and after the supply of the drive current is completed, it supplies a post-excitation current to the stator that is larger in amplitude than the drive current.

2. The electric valve control device according to claim 1, wherein if the electric valve control device determines that the angular velocity of the rotor has reached a peak value when the supply of the drive current is completed, it increases the post-excitation current to be greater than the amplitude of the drive current.

3. The electric valve control device according to claim 1, wherein the electric valve control device supplies the stator with a post-excitation current that is larger in amplitude than the drive current immediately after the completion of supplying the drive current.

4. The electric valve control device according to claim 1, wherein the electric valve control device supplies the stator with a post-excitation current that is larger in amplitude than the drive current after a first predetermined time has elapsed since the completion of supplying the drive current.

5. The electric valve control device according to claim 1, wherein the electric valve control device supplies the stator with a post-excitation current greater than the amplitude of the drive current for a predetermined period of time.

6. The electric valve control device according to claim 1, wherein the electric valve control device gradually increases the magnitude of the post-excitation current from the start of supplying the post-excitation current to the stator.

7. The electric valve control device according to claim 1, wherein the electric valve control device gradually reduces the magnitude of the post-excitation current after a second predetermined time has elapsed from the start of supplying the post-excitation current to the stator.

8. The electric valve control device according to claim 1, wherein, after a third predetermined time has elapsed since the start of supplying the post-excitation current to the stator, the magnitude of the post-excitation current is reduced to the amplitude of the drive current.

9. An electric valve device comprising the electric valve and an electric valve control device according to any one of claims 1 to 8.

10. A control method for an electric valve having a valve body with a valve port, a stepping motor having a rotor and a stator connected to a motor driver, a valve body that moves relative to the valve port when the rotor rotates, a planetary gear mechanism that reduces the rotation of the rotor, and a drive shaft that is moved by a lead screw action and pushes down the valve body, wherein the control method controls the flow rate of a refrigerant and the rotor, the planetary gear mechanism, and the drive shaft are exposed to the refrigerant, A drive current consisting of pulses is supplied to the stator to rotate the rotor. A method for controlling an electric valve, characterized by supplying a post-excitation current to the stator that is larger in amplitude than the drive current after the supply of the drive current has been completed.