Electric valve control device, electric valve control program, and electric valve

Abstract

To simplify the configuration for detecting the rotor's non-tracking state in a stepping motor for an electric valve. [Solution] The electric valve control device 100 controls an electric valve having a rotatable rotor, a stator which together with the rotor constitutes a stepping motor, and a mechanism which changes the valve opening degree by the rotational motion of the rotor. It includes a rotation control unit 120 which controls the rotation of the rotor by inputting pulses for each of the consecutive steps to the coil of the stator and according to the excitation pattern of the pulses, a flyback time measurement unit 122 which measures the flyback time until the flyback voltage generated in the coil at the zero-cross step of the pulse drops to a predetermined standard, and a state determination unit 124 which determines whether or not the rotor is in a non-following state in the rotation of the rotor and is not following the excitation pattern, based on the flyback time.

Description

Technical Field

[0001] The present invention relates to an electric valve control device for controlling an electric valve.

Background Art

[0002] An automotive air conditioner is generally configured by arranging a compressor, an external heat exchanger, an expansion device, an evaporator, etc. in a refrigeration cycle. Various control valves are provided in the refrigeration cycle to control the flow of refrigerant, such as an expansion valve as the expansion device. With the recent spread of electric vehicles and the like, an electric valve equipped with a motor as a drive unit has been widely adopted.

[0003] As such an electric valve, one equipped with a magnetic sensor for detecting the valve opening degree is known (see, for example, Patent Document 1). A valve body is provided at one end of an operating rod that rotates with a rotor, and a magnet (sensor magnet) is provided at the other end. The magnetic sensor is provided so as to face the sensor magnet in the axial direction. By capturing the change in magnetic flux accompanying the rotation of the rotor with the magnetic sensor, the rotation angle of the sensor magnet can be detected.

[0004] By comparing the rotation angle instructed to the electric valve with the rotation angle detected by the magnetic sensor, it is possible to determine whether the rotor follows the instructed rotation angle.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] Patent Document 2 discloses a technique for determining whether or not a rotation restriction state is in place based on the degree of difference between the waveform of the voltage generated in the stator by the rotation of the rotor and a reference waveform.

[0008] The technology described in Patent Document 2 has a problem in that when the rotor rotation is slow, the voltage generated by electromagnetic induction becomes small, making it difficult to make a determination. For example, in a low-temperature environment, if the viscosity of the lubricating oil applied to the motor sliding part increases and the sliding resistance increases, the rotation speed decreases, making the above determination difficult. In particular, when performing fine control with a microstepping type stepping motor, it is difficult to detect changes in voltage.

[0009] One of the objectives of the present invention is to simplify the configuration for detecting the non-tracking state of the rotor in a stepping motor of an electric valve.

[0010] In comparison with Patent Document 2, the present invention has the advantage of making it easier to determine the condition of the rotor even when the rotor is rotating slowly or has stopped. [Means for solving the problem]

[0011] An electric valve control device in one aspect of the present invention controls an electric valve having a rotatable rotor, a stator which together with the rotor constitutes a stepping motor, and a mechanism which changes the valve opening degree by the rotational motion of the rotor. The control device includes a rotation control unit which inputs pulses for each of the consecutive steps to the coil of the stator and controls the rotation of the rotor by the excitation pattern of the pulses, a flyback time measurement unit which measures the flyback time until the flyback voltage generated in the coil at the zero-cross step of the pulse drops to a predetermined standard, and a state determination unit which determines, based on the flyback time, whether or not the rotor is in a non-following state in which it is not following the excitation pattern during the rotation of the rotor.

[0012] An electric valve control program in one aspect of the present invention causes a computer that controls an electric valve having a rotatable rotor, a stator that together with the rotor constitutes a stepping motor, and a mechanism that changes the valve opening degree by the rotational motion of the rotor, to perform a rotation control function that inputs pulses for each of the consecutive steps to the coil of the stator and controls the rotation of the rotor by the excitation pattern of the pulses; a flyback time measurement function that measures the flyback time until the flyback voltage generated in the coil at the zero-cross step of the pulse drops to a predetermined standard; and a state determination function that determines whether or not the rotor is in a non-following state in the rotation of the rotor and is not following the excitation pattern, based on the flyback time.

[0013] An electric valve in one aspect of the present invention includes a rotatable rotor, a stator which together with the rotor constitutes a stepping motor, a mechanism which changes the valve opening degree by the rotational motion of the rotor, a rotation control unit which inputs pulses for each of the consecutive steps to the coil of the stator and controls the rotation of the rotor by the excitation pattern of the pulses, a flyback time measuring unit which measures the flyback time until the flyback voltage generated in the coil at the zero-cross step of the pulses decreases to a predetermined standard, and a state determination unit which determines whether or not the rotor is in a non-following state in the rotation of the rotor and is not following the excitation pattern, based on the flyback time, and an electric valve control unit which has [Effects of the Invention]

[0014] According to the present invention, a configuration for detecting the non-tracking state of the rotor in a stepping motor of an electric valve can be easily implemented. [Brief explanation of the drawing]

[0015] [Figure 1] This is a cross-sectional view showing an electric valve according to an embodiment. [Figure 2]Fig. 2(A) is a cross-sectional perspective view of the stator. Fig. 2(B) is a cross-sectional view of the stator and the rotor. Fig. 2(C) is an assembly view of the stator and the rotor. [Figure 3] Fig. 3(A) is a schematic diagram showing the positional relationship of the pole teeth. Fig. 3(B) is a schematic diagram showing the positional relationship of the rotor magnet in step s1. Fig. 3(C) is a schematic diagram showing the positional relationship of the rotor magnet in step s17. [Figure 4] It is a graph showing the excitation pattern. [Figure 5] Fig. 5(A) is a schematic diagram showing the electrical angle and the position of the rotor magnet in step s1. Fig. 5(B) is a schematic diagram showing the electrical angle and the position of the rotor magnet in step s2. Fig. 5(C) is a schematic diagram showing the electrical angle and the position of the rotor magnet in step s3. Fig. 5(D) is a schematic diagram showing the electrical angle and the position of the rotor magnet in step s4. Fig. 5(E) is a schematic diagram showing the electrical angle and the position of the rotor magnet in step s5. [Figure 6] Fig. 6(A) is a schematic diagram showing the electrical angle and the position of the rotor magnet in step s9. Fig. 6(B) is a schematic diagram showing the electrical angle and the position of the rotor magnet in step s13. [Figure 7] It is a schematic diagram of the movement range of the rotor. [Figure 8] Fig. 8(A) is a diagram showing the positive application state in the H-bridge circuit. Fig. 8(B) is a diagram showing the negative application state in the H-bridge circuit. [Figure 9] Fig. 9(A) is a diagram showing the behavior of the coil through which current flows. Fig. 9(B) is a diagram showing the behavior of the coil when the current is cut off. [Figure 10] Fig. 10(A) is a diagram showing the positive cut-off state in the H-bridge circuit. Fig. 10(B) is a diagram showing the negative cut-off state in the H-bridge circuit. [Figure 11] Fig. 11(A) is a diagram showing the change in voltage due to flyback. Fig. 11(B) is a diagram showing the change in current due to flyback. [Figure 12] It is a diagram showing voltage changes when the flyback scale is large. [Figure 13] It is a graph showing the criteria for determining the flyback time Tf at each zero-cross step. [Figure 14] Figure 14(A) is a graph showing the measurement pulse for detecting the flyback time Tf. Figure 1(B) is a graph showing the measurement pulse for detecting the flyback time Tf. [Figure 15] It is a functional block diagram of an electric valve control device. [Figure 16] It is a flowchart showing the processing process of the electric valve control device. [Figure 17] It is a flowchart showing the processing process of the electric valve control device. [Figure 18] It is a graph showing the current control in Modification 1. [Figure 19] It is a graph showing the criteria for determining the flyback time Tf in Modification 2.

Embodiments for Carrying Out the Invention

[0016] [Embodiment] Hereinafter, embodiments 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. Also, for the following embodiments and their modifications, the same reference numerals are given to substantially the same components, and the description thereof will be omitted as appropriate.

[0017] Figure 1 is a cross-sectional view showing the electric valve 1 according to the embodiment. The electric valve 1 is applied to the refrigeration cycle of an automotive air conditioning system (not shown). The refrigeration cycle includes a compressor, an external heat exchanger, an expansion valve, an evaporator, etc., and the refrigerant circulation passage is switched according to the operating state of the air conditioning system. The high-temperature, high-pressure refrigerant compressed by the compressor is cooled by passing through the external heat exchanger. As the refrigerant passes through the expansion valve, it undergoes adiabatic expansion to become low-temperature, low-pressure, and is guided to the evaporator where it evaporates. The latent heat of evaporation cools the air inside the vehicle. The electric valve 1 functions as this expansion valve.

[0018] In this embodiment, a condenser is provided as an external heat exchanger because a condensable refrigerant such as HFO-1234yf is used. However, if carbon dioxide, which has a high operating pressure, is used as the refrigerant, a gas cooler is provided instead of a condenser.

[0019] The electric valve 1 is constructed by assembling a rotor unit 2 and a stator unit 4. The rotor unit 2 has a valve body 5 that encloses the valve section. The valve body 5 includes a valve housing 6 and a valve seat member 8. The valve housing 6 has a large diameter section 7 and a small diameter section 9 integrally, and has a stepped cylindrical shape in which the outer diameter decreases towards the bottom. The valve housing 6 is obtained by machining a material made of stainless steel (hereinafter referred to as "SUS").

[0020] A valve seat member 8 is coaxially assembled to the lower end opening of the valve housing 6. The valve seat member 8 is cylindrical, and its upper part is inserted into and fixed to the small diameter portion 9. An inlet port 10 is provided on the side surface of the axial center of the valve seat member 8.

[0021] The lower inner diameter of the valve seat member 8 is reduced to form a valve hole 14, and a valve seat 16 is formed at the upper end opening of the valve hole 14. In this embodiment, the valve seat member 8 is made of SUS, but a material with excellent wear resistance such as brass may be selected. A material with better weldability than the valve seat member 8 is used for the valve housing 6, and a material with better machinability than the valve body 5 is used for the valve seat member 8.

[0022] An outlet port 12 is provided at the lower part of the valve seat member 8. The valve body 5 has an internal passage that connects the inlet port 10 and the outlet port 12. A valve chamber 18 is formed inside the valve seat member 8. The inlet port 10 and the outlet port 12 are in communication via the valve chamber 18. Refrigerant from the upstream side is introduced into the valve body 5 from the inlet port 10, passes through the valve section, and is then led downstream from the outlet port 12.

[0023] An operating rod 15 extending from the rotor 30 of the rotor unit 2 is inserted inside the valve body 5. The operating rod 15 penetrates the valve chamber 18. The operating rod 15 is obtained by machining a rod made of a non-magnetic metal, and a needle-shaped valve body 20 is integrally attached to its lower part. The valve body 20 attaches to and detaches from the valve seat 16 from the valve chamber 18 side to open and close the valve.

[0024] A guide member 22 is coaxially mounted on the large-diameter portion 7 of the valve housing 6. That is, the guide member 22 is integrally provided with the valve body 5. The guide member 22 is obtained by machining a tubular material made of a non-magnetic metal (brass in this embodiment) into a stepped cylindrical shape. An internal thread 24 is provided on the upper inner circumferential surface of the guide member 22 for supporting the operating rod 15 so that it can rotate and slide. A spring 26 is interposed between the operating rod 15 and the guide member 22 to bias the valve body 20 in the closing direction.

[0025] The operating rod 15 is a stepped cylindrical member, with a male thread 28 formed on the outer circumference of its upper half, which meshes with the female thread 24 of the guide member 22. In this embodiment, the female thread 24 functions as the "first thread," and the male thread 28 functions as the "second thread." Through the screw feeding mechanism 25 using these threads, the rotational motion of the rotor 30 is converted into translational motion (axial motion) of the operating rod 15. As a result, the valve body 20 moves (up and down) in the axial direction, that is, in the opening and closing direction of the valve.

[0026] On the other hand, the rotor 30 of rotor unit 2 and the stator 32 of stator unit 4 constitute a two-phase stepping motor. Rotor unit 2 has a bottomed cylindrical can 34, and the rotor 30 is positioned inside the can 34. The stator 32 is positioned outside the can 34. The can 34 is a bottomed cylindrical member that covers the space in which the valve body 20 and its drive mechanism are positioned and encloses the rotor 30, defining an inner pressure space (internal space) where the refrigerant pressure acts and an outer non-pressure space (external space) where it does not act.

[0027] The can 34 is made of a non-magnetic metal (e.g., SUS), and its lower end is fitted onto the upper end of the valve housing 6. The valve body 5 and the can 34 are fixed together by welding (circumferential welding) along the boundary between the can 34 and the valve housing 6 (not shown), ensuring airtightness (seal) between them.

[0028] The stator 32 is constructed by coaxially assembling an A-phase coil unit 36a and a B-phase coil unit 36b (collectively referred to as "coil unit 36" when not specifically distinguished). The A-phase coil unit 36a is constructed by assembling a bobbin 39, on which an A-phase coil 38a is provided, onto an annular yoke 40. The yoke 40 has multiple pole teeth arranged along its inner circumference. Similarly, the B-phase coil unit 36b is constructed by assembling a bobbin 39, on which a B-phase coil 38b is provided, onto an annular yoke 40. When not specifically distinguishing between the A-phase coil 38a and the B-phase coil 38b, they are collectively referred to as "coil 38".

[0029] The stator 32 is enclosed within the case 42. The case 42 is obtained by injection molding (also called "insert molding" or "mold molding") of a corrosion-resistant resin material. The stator 32 is covered with the molded resin produced by injection molding. The stator unit 4 is an integrated part (molded product) of the stator 32 and the case 42.

[0030] The stator unit 4 has a hollow structure, and the stator 32 is assembled to the rotor unit 2 with the can 34 inserted coaxially. The welded joint between the can 34 and the valve body 5 is located inside the case 42. A seal ring 44 (O-ring) is interposed between the valve body 5 and the case 42 to prevent the intrusion of external elements (such as water) into the gap between the can 34 and the stator 32.

[0031] The rotor 30 comprises a cylindrical rotor core 50 and a rotor magnet 52 provided on the outer circumferential surface of the rotor core 50. The rotor magnet 52 is cylindrical in shape, and its upper end is fitted and fixed to the outer circumferential surface of the rotor core 50. The rotor magnet 52 is magnetized in multiple poles in its circumferential direction. Multiple pole teeth of the stator 32 face the magnetic poles of the rotor magnet 52 across the can 34.

[0032] The upper part of the actuating rod 15 is press-fitted along the axis of the rotor core 50. This fixes the actuating rod 15 and the rotor 30 coaxially. The actuating rod 15 functions as the rotation axis of the rotor 30.

[0033] The stator unit 4 has a circuit board 54 on the outside of the can 34. The circuit board 54 is fixed inside the case 42. Various circuits that function as an electric valve control device 100 are mounted on the lower surface of the circuit board 54. Specifically, a drive circuit for driving the motor, a control circuit (microcomputer) that outputs control signals to the drive circuit, a communication circuit for the control circuit to communicate with an external device (for example, an air conditioning controller), and a power supply circuit for supplying power to each circuit and the motor (coil) are mounted. The upper end of the case 42 is closed by a resin cover 56. The circuit board 54 is arranged in the space below the cover 56 in the case 42.

[0034] A terminal 60 extends from the bobbin 39 and connects to the coil 38, and is connected to the circuit board 54. Power terminals, ground terminals, and communication terminals (collectively referred to as "connection terminals 62") extend from the circuit board 54 and are each pulled out to the outside through the side wall of the case 42. A connector section 64 is integrally provided on the side of the case 42, and the connection terminals 62 are arranged inside the connector section 64.

[0035] The electric valve 1 configured as described above functions as an electric expansion valve whose valve opening degree can be adjusted by drive control of the rotor unit 2. That is, based on a command from an external device (not shown), the electric valve control device 100 sets a control amount (number of motor drive steps) to achieve the target opening degree and outputs a drive signal to the drive circuit to achieve this. The drive circuit supplies two-phase drive current (drive pulse) to each coil 38 at the set timing. As a result, the rotor 30 rotates with high resolution. At this time, the operating rod 15 and thus the valve body 20 operate together with the rotor 30.

[0036] The rotor 30 moves vertically by a screw feed mechanism 25 between the operating rod 15 and the guide member 22. The valve body 20 translates in the opening and closing direction of the valve, and the opening degree of the valve is adjusted to a set opening degree. The screw feed mechanism 25 converts the rotational motion of the rotor 30 around its axis into axial motion (linear motion) of the operating rod 15, driving the valve body 20 in the opening and closing direction of the valve. When the electric valve 1 functions as an expansion valve, the valve is controlled to a small opening degree. In this way, the electric valve 1 has a mechanism that changes the valve opening degree by the rotational motion of the rotor 30.

[0037] Figure 2(A) is a cross-sectional perspective view of the stator 32. In this example, a permanent magnet type two-phase stepping motor is used as the actuator for the electric valve 1. First, the stator 32, a component of this stepping motor, will be described. The stator 32 includes an A-phase coil unit 36a and a B-phase coil unit 36b arranged around the rotor 30.

[0038] The A-phase coil unit 36a includes a bobbin 39a around which the conductor of the A-phase coil 38a is wound, a first yoke 40m, and a second yoke 40n. The B-phase coil unit 36b includes a bobbin 39b around which the conductor of the B-phase coil 38b is wound, a first yoke 40m, and a second yoke 40n. When the A-phase coil 38a and the B-phase coil 38b are not specifically distinguished, they are collectively referred to as "coil 38". When the bobbin 39a and the bobbin 39b are not specifically distinguished, they are collectively referred to as "bobbin 39". The conductor of coil 38 is wound in a ring shape around bobbin 39. The first yoke 40m and the second yoke 40n are shaped to cover coil 38.

[0039] The first yoke 40m of the A-phase coil unit 36a is provided with 12 pole teeth 46s. The second yoke 40n of the A-phase coil unit 36a is provided with 12 pole teeth 46t. The first yoke 40m of the B-phase coil unit 36b is provided with 12 pole teeth 46u. The second yoke 40n of the B-phase coil unit 36b is provided with 12 pole teeth 46v. When no particular distinction is made between pole teeth 46s to v, they are collectively referred to as "pole teeth 46".

[0040] Figure 2(B) is a cross-sectional view of the stator 32 and rotor 30. When current is passed through the A-phase coil 38a, a magnetic field is generated, and the upper pole teeth 46s and lower pole teeth 46t are magnetized. In this diagram, the pole teeth 46s of the first yoke 40m become the south pole, and the pole teeth 46t of the second yoke 40n become the north pole. If the direction of the current is reversed, the south and north poles are swapped. The same thing happens when current is passed through the B-phase coil 38b. In this diagram, no current is passed through the B-phase coil 38b, and the pole teeth 46u and v are not magnetized.

[0041] Figure 2(C) is an assembly diagram of the stator 32 and rotor 30. The rotor 30 is installed inside the stator 32. The outer circumference of the rotor 30 is magnetized alternately with north and south poles along the circumferential direction. There are 12 north and 12 south poles on the rotor 30, spaced evenly apart. This number is the same as the number of pole teeth 46 on one yoke 40.

[0042] The magnetic poles of the rotor 30 are pulled by the magnetic fields generated by the A-phase coil unit 36a and the B-phase coil unit 36b. As a result, the rotor 30 rotates and stops at a stable position. In Figure 2(B), the north pole of the rotor magnet 52 is attracted to the south pole of the pole tooth 46s, and the south pole of the rotor magnet 52 is attracted to the north pole of the pole tooth 46t.

[0043] The electric valve control device 100 can rotate the rotor 30 arbitrarily by changing the magnitude of the current flowing through the A-phase coil 38a and the B-phase coil 38b, or by changing the direction of the current.

[0044] Figure 3(A) is a schematic diagram showing the positional relationship of the pole teeth. Figure 3(A) shows a planar representation of the arrangement of the pole teeth 46s~v as seen from inside the stator 32, as shown in Figure 2(A). This planar image is obtained by rotating the viewpoint from the central axis of the stator 32. The rightward direction in Figure 3(A) corresponds to the clockwise direction when viewing the central axis from above in Figure 2(A).

[0045] The A-phase coil unit 36a and the B-phase coil unit 36b each include a first yoke 40m and a second yoke 40n, respectively. The first yoke 40m and the second yoke 40n each have 12 pole teeth 46. In the A-phase coil unit 36a, the pole teeth 46s of the first yoke 40m and the pole teeth 46t of the second yoke 40n mesh with each other. Similarly, in the B-phase coil unit 36b, the pole teeth 46u of the first yoke 40m and the pole teeth 46v of the second yoke 40n mesh with each other.

[0046] The distance between the meshing pole teeth 46s and 46t is defined as 1 pitch. Similarly, the distance between pole teeth 46u and 46v is also defined as 1 pitch.

[0047] As shown in the diagram, the B-phase coil unit 36b is offset by half a pitch overall from the A-phase coil unit 36a. In other words, the pole teeth 46u of the B-phase coil unit 36b are offset by half a pitch from the pole teeth 46s of the A-phase coil unit 36a, and the pole teeth 46v are also offset by half a pitch from the pole teeth 46t. These positional relationships do not change.

[0048] The A-phase coil unit 36a and the B-phase coil unit 36b are stacked on top of each other to form a two-layer stator 32.

[0049] Figure 3(B) is a schematic diagram showing the positional relationship of the rotor magnet 52 in step s1. The rotor magnet 52 is located on the near side of the plane of the A-phase coil unit 36a and the B-phase coil unit 36b in Figure 3(A), facing them (Figure 2(C)). In the following schematic diagrams, for convenience, the rotor magnet 52 is drawn between the A-phase coil unit 36a and the B-phase coil unit 36b to represent the positional relationship of the rotor magnet 52 facing the A-phase coil unit 36a and the B-phase coil unit 36b. Note that the A-phase coil unit 36a and the B-phase coil unit 36b do not move, only the rotor magnet 52 moves.

[0050] Step s1 corresponds to the state shown in Figure 2(B). The mechanical angle and electrical angle will be explained based on Step s1. The mechanical angle and electrical angle at this time will be set to 0 degrees.

[0051] The mechanical angle represents the actual angle of the rotor 30. The electrical angle is a logical angle that two-dimensionally represents the current that excites the two coils 38 of the stator 32. The electrical angle is used by the electric valve control device 100 to control the excitation of the coils 38. The mechanical angle is directly related to the function of the electric valve 1, such as opening and closing the valve.

[0052] Figure 3(C) is a schematic diagram showing the positional relationship of the rotor magnet 52 in step s17. Let's assume that the rotor 30 shown in Figure 2(C) has rotated 30 degrees clockwise when viewed from above. The mechanical angle at this time is 30 degrees. As shown in Figure 3(C), the rotor magnet 52 has shifted 2 pitches to the right and is in the same magnetic state as in Figure 3(B). The electrical angle completes one full rotation (360 degrees) to reach the same magnetic state. In this example, when the mechanical angle increases by 30 degrees, the electrical angle advances by 360 degrees. The electric valve control device 100 controls this process in 16 steps. That is, 16 steps proceed from step s1 in Figure 3(B), and the state in Figure 3(C) is reached at step s17.

[0053] Over the entire rotation of the electrical angle (0 to 360 degrees) as described above, the mechanical angle and the electrical angle are proportional, and the following equation 1 holds true.

number

[0054] The mechanical angle and the electrical angle are mutually convertible according to Equation 1. The coefficient "12" is derived from the number of N and S pole pairs of the rotor magnet 52, which is "12". The relationship in Equation 1 also holds true in Figures 5 and 6, which will be discussed later.

[0055] Figure 4 is a graph showing the excitation pattern. The operation from steps s1 to s17 will be explained. The upper graph shows the level of current applied to the A-phase coil 38a (hereinafter referred to as "A-phase current") at each step. The lower graph shows the level of current applied to the B-phase coil 38b (hereinafter referred to as "B-phase current") at each step. A common reference current for the A-phase and B-phase currents is set as the maximum (100%), and the current at each step is expressed as a percentage. This percentage is used as the duty cycle in the PWM (Pulse Width Modulation) control described later.

[0056] For example, in step s1, 100% of the A-phase current is applied to the A-phase coil 38a, and no current flows through the B-phase coil 38b. In step s2, 92% of the A-phase current is applied to the A-phase coil 38a, and 38% of the B-phase current is applied to the B-phase coil 38b. If the current is expressed as a negative percentage, the current flows in the reverse direction. In this way, for each step from s1 to s16, a combination of two-phase (or multiple-phase) currents (hereinafter referred to as the "excitation pattern") is defined to achieve a predetermined excitation in the stator 32. The current parameters include the direction of the current (positive or negative) and the magnitude of the current (such as a percentage of the current level or a current value). The current parameters may also represent no current (0%). From s17 onward, the excitation patterns from s1 to s16 are repeated.

[0057] The step at which the current switches from positive to negative or from negative to positive, resulting in zero current (0%), is called a "zero-crossing step." As illustrated, there are four types of zero-crossing steps.

[0058] Step s5, where the A-phase current switches from positive to negative and there is no current (0%), is denoted as "zero-crossing A-". Step s9, where the B-phase current switches from positive to negative and there is no current (0%), is denoted as "zero-crossing B-". Step s13, where the A-phase current switches from negative to positive and there is no current (0%), is denoted as "zero-crossing A+". Step s17 (same as s1), where the B-phase current switches from negative to positive and there is no current (0%), is denoted as "zero-crossing B+".

[0059] Steps s1 to s5 will be described in detail below in relation to Figure 5. Steps s9 and s13 will also be described in detail in relation to Figure 6.

[0060] Figures 5(A) to (E) are schematic diagrams showing the electrical angles and the position of the rotor magnet 52 in steps s1 to s5. The upper circular graph represents the A-phase current of the excitation pattern as the A-phase vector 70 in the X-axis direction, and the B-phase current as the B-phase vector 72 in the Y-axis direction. The combined vector 74 is the vector obtained by combining the A-phase vector 70 and the B-phase vector 72. The combined vector 74 is a clockwise angle with the positive X-axis direction being 0 degrees, and represents the electrical angle at which the rotor 30 is stable. When the rotor 30 is following the excitation pattern of the step, the rotor 30 stops at the mechanical angle corresponding to this electrical angle. The lower schematic diagram shows the position of the rotor magnet 52 at that mechanical angle. Hereafter, the position at which the rotor 30 is stable in each step will be referred to as the "stable position" of that step.

[0061] Figure 5(A) relates to step s1. The pie chart represents the A-phase current of 100% as the A-phase vector 70 in the positive X-axis direction. Since there is no B-phase current (0%), the B-phase vector 72 is not shown. The composite vector 74 coincides with the A-phase vector 70 and points in the positive X-axis direction. Therefore, the electrical angle in step s1 is 0 degrees.

[0062] Based on Equation 1, an electrical angle of 0 degrees can be converted to a mechanical angle of 0 degrees. The schematic diagram below shows the position of the rotor magnet 52 at a mechanical angle of 0 degrees in step s1. If no external force acts on the rotor 30, the rotor magnet 52 will stop at this position. Note that this diagram is the same as Figure 3(B).

[0063] Figure 5(B) relates to step s2. The pie chart shows the A-phase current (92%) represented by the A-phase vector 70 in the positive X-axis direction, and the B-phase current (38%) represented by the B-phase vector 72 in the positive Y-axis direction. The combined vector 74 represents the electrical angle of 22.5 degrees in step s2.

[0064] Based on Equation 1, an electrical angle of 22.5 degrees can be converted to a mechanical angle of 1.875 degrees. The schematic diagram below shows the position of the rotor magnet 52 at a mechanical angle of 1.875 degrees in step s2.

[0065] Figure 5(C) relates to step s3. The pie chart shows the A-phase current of 71% as the A-phase vector 70 in the positive X-axis direction, and the B-phase current of 71% as the B-phase vector 72 in the positive Y-axis direction. The combined vector 74 represents the electrical angle of 45 degrees in step s3. The schematic diagram at the bottom shows the position of the rotor magnet 52 at a mechanical angle of 3.75 degrees in step s3.

[0066] Figure 5(D) relates to step s4. The pie chart shows the A-phase current of 38% as the A-phase vector 70 in the positive X-axis direction, and the B-phase current of 92% as the B-phase vector 72 in the positive Y-axis direction. The combined vector 74 represents the electrical angle of 67.5 degrees in step s4. The schematic diagram at the bottom shows the position of the rotor magnet 52 at the mechanical angle of 5.625 degrees in step s4.

[0067] Figure 5(E) relates to step s5. The pie chart represents the B-phase current at 100% as the B-phase vector 72 in the positive Y-axis direction. Since there is no A-phase current (0%), the A-phase vector 70 is not shown. The combined vector 74 coincides with the B-phase vector 72 and points in the positive Y-axis direction. Therefore, the electrical angle at step s5 is 90 degrees. The schematic diagram below shows the position of the rotor magnet 52 at a mechanical angle of 7.5 degrees at step s5.

[0068] Thus, when transitioning from step s1 to s5, the rotor magnet 52 slides slightly to the right in the schematic diagram below. In other words, the rotor magnet 52 rotates slightly clockwise when viewed from above in Figure 2(C).

[0069] From step s5 onward, the electrical angle increases by 22.5 degrees per step. Additionally, the mechanical angle increases by 1.875 degrees per step. Steps s6 to s8 are not illustrated.

[0070] Figure 6(A) is a schematic diagram showing the electrical angle and the position of the rotor magnet in step s9. The upper circular graph represents the A-phase current of -100% with the A-phase vector 70 pointing in the negative X-axis direction. Since there is no B-phase current (0%), the B-phase vector 72 is not shown. The combined vector 74 coincides with the A-phase vector 70 and points in the negative X-axis direction. Therefore, the electrical angle at step s9 is 180 degrees.

[0071] Based on Equation 1, an electrical angle of 180 degrees can be converted to a mechanical angle of 15 degrees. The schematic diagram below shows the position of the rotor magnet 52 at a mechanical angle of 15 degrees in step s9. Steps s10 to s12 are omitted from the illustration.

[0072] Figure 6(B) is a schematic diagram showing the electrical angle and the position of the rotor magnet in step s13. The upper circular graph represents the B-phase current of -100% as the B-phase vector 72 in the negative Y-axis direction. Since there is no A-phase current (0%), the A-phase vector 70 is not shown. The combined vector 74 coincides with the B-phase vector 72 and points in the negative Y-axis direction. Therefore, the electrical angle at step s13 is 270 degrees. The lower schematic diagram shows the position of the rotor magnet 52 at the mechanical angle of 22.5 degrees at step s13. Steps s14 to s16 are omitted from the illustration.

[0073] Figure 7 is a schematic diagram of the range of motion of the rotor 30. In Figure 7, the rightward direction indicates the opening direction (upward direction) of the rotor 30, and the leftward direction indicates the closing direction (downward direction). The origin O is the limit position where the rotor 30 can no longer rotate downward as the valve body 20 reaches the valve seat 16. In the electric valve 1 of Figure 1, the rotor 30 and the valve body 20 are integrated, so once the valve body 20 seats on the valve seat 16, the valve body 20 can no longer descend. Thus, when the rotor 30 is at the origin O, the valve is closed. In this electric valve 1, the valve opening point M, which is the position where the valve body 20 begins to rise (the position where the valve opening operation begins), is at the same position as the origin O. Strictly speaking, there is a slight difference between the origin O and the valve opening point M, corresponding to the length of backlash in the screw feed mechanism 25. The step number of the valve opening point M may be stored in the non-volatile memory of the circuit board 54. When the rotor 30 rotates upward from the valve opening point M, the valve body 20 separates from the valve seat 16, and the valve opens. As the rotor 30 continues to rotate upward, the valve opening gradually widens, and the flow rate from the inlet port 10 to the outlet port 12 increases. The rotor 30 can move up to its highest point Tp. The rotor 30 can also move in the reverse direction.

[0074] Figure 8(A) shows the positive applied state in the H-bridge circuit 84. The H-bridge circuit 84 controls the application and interruption of current to the coil 38. An H-bridge circuit 84 is provided on the circuit board 54 for both the A-phase coil 38a and the B-phase coil 38b.

[0075] Vbat represents the potential of the power supply (hereinafter referred to as "power supply potential"). GND (ground) represents the potential of 0V. An FET (field-effect transistor) 80a is provided between the left end of the coil 38 and the power supply potential Vbat, and an FET 80b is provided between the right end of the coil 38 and the power supply potential Vbat. An FET 80c is provided between the left end of the coil 38 and GND, and an FET 80d is provided between the right end of the coil 38 and GND.

[0076] FET80a to FET80d are common components that function as electrical switches. When FET80a to FET80d are not specifically distinguished, they are collectively referred to as "FET80". When an ON signal is input to the gate of an FET80, the FET80 allows current to flow, and when an OFF signal is input to the gate of an FET80, the FET80 blocks the current. In the following, inputting an ON signal to the gate will be referred to as "turning the FET80 ON," and inputting an OFF signal to the gate will be referred to as "turning the FET80 OFF."

[0077] Diodes 82a to 82d are arranged in parallel with FETs 80a to 80d, respectively. When diodes 82a to 82d are not specifically distinguished, they are collectively referred to as "diode 82". The role of diode 82 will be described later in relation to Figure 10.

[0078] Figure 8(A) shows the state in which a current is applied to the coil 38 in the rightward direction. This state is called the "positive applied state." In the positive applied state, FETs 80a and FET 80d are turned ON, and FETs 80b and FET 80c are turned OFF. In this state, a voltage is applied to coil 38 with the left end at the power supply potential Vbat, and a current flows to the right. At this time, the magnetic effect of the current generates a magnetic field inside and around coil 38. This magnetic field magnetizes the yoke 40, which is a magnetic material, and the pole teeth 46 become magnetic poles (S pole or N pole). Hereafter, the magnetic field in the positive applied state will be referred to as the "positive magnetic field."

[0079] As shown in the excitation patterns of steps s1-s4 and s14-s17 in Figure 4, when a positive current is applied to the A-phase coil 38a, the A-phase H-bridge circuit 84 is set to a positive applied state. Similarly, as shown in steps s2-s8, when a positive current is applied to the B-phase coil 38b, the B-phase H-bridge circuit 84 is set to a positive applied state.

[0080] The magnitude of the current is adjusted by PWM control. PWM control is a method of controlling the average power by generating pulse waveforms through high-speed switching.

[0081] Figure 8(B) shows the negative application state in the H-bridge circuit 84. Figure 8(B) shows the state in which a leftward current is applied to coil 38. This state is called the "negative application state". In the negative application state, the electric valve control device 100 turns FET80b and FET80c ON and turns FET80a and FET80d OFF. In this state, a voltage with the power supply potential Vbat at the right end is applied to coil 38, and a leftward current flows. At this time, a magnetic field is generated inside and around coil 38 in which the direction of the magnetic field lines is opposite to that in the case of a positive magnetic field. Due to this magnetic field, the magnetic poles (S pole or N pole) of the pole teeth 46 are opposite to those in the case of a positive magnetic field. Hereafter, the magnetic field in the negative application state will be referred to as the "negative magnetic field".

[0082] As shown in the excitation pattern of steps s6 to s12 in Figure 4, when a negative current is applied to the A-phase coil 38a, the electric valve control device 100 puts the A-phase H-bridge circuit 84 into a negative applied state. Similarly, as shown in steps s10 to s16, when a negative current is applied to the B-phase coil 38b, the electric valve control device 100 puts the B-phase H-bridge circuit 84 into a negative applied state.

[0083] Figure 9(A) shows the behavior of the coil 38 through which current flows. As explained in relation to Figures 8(A) and 8(B), when the FET 80 is turned ON and current flows through the coil 38, a magnetic field is generated inside and around the coil 38 due to the magnetic effect of the current. This magnetic field is maintained as long as the current is flowing.

[0084] Figure 9(B) shows the behavior of coil 38 when the current is interrupted. The behavior of coil 38 when FET 80 is switched OFF from the state shown in Figure 9(A) will be explained. When the electric valve control device 100 turns FET 80 OFF, no current flows through coil 38, and the magnetic field disappears. At this time, coil 38 generates a current in the same direction as the original current due to electromagnetic induction in an attempt to maintain the magnetic field. This phenomenon is called flyback, and the instantaneous high voltage generated at this time is called the flyback voltage. The flyback voltage is a type of surge. A surge is a high voltage or large current that is instantaneously applied as noise due to external factors.

[0085] Figure 10(A) shows the positive cutoff state in the H-bridge circuit 84. When interrupting the current flowing to the right in a positively applied state (Figure 8(A)), the electric valve control device 100 switches FET80a and FET80d from ON to OFF, as shown in Figure 10(A). In this figure, the electric valve control device 100 switches FET80c from OFF to ON, but it may remain OFF. Current can be interrupted whether FET80c is ON or OFF. FET80b remains OFF. This state is called the "positive interruption state".

[0086] In the positive cutoff state, both FETs 80a and 80b on the power supply potential Vbat side are OFF, so no current flows from the power supply to the coil. At this point, the question becomes where to divert the rightward current generated by the flyback. If current flows through FET 80b, there is a risk that FET 80b will be damaged by the high voltage. Therefore, the current is diverted through diode 82b. In this way, diode 82, which is connected in parallel with FET 80, plays a role in protecting FET 80.

[0087] At the timing of transitioning from the excitation pattern of step s4 to the excitation pattern of step s5 (zero-crossing A-) shown in Figure 4, the electric valve control device 100 switches the H-bridge circuit 84 of the A-phase from a positive applied state (Figure 8(A)) to a positive interrupted state (Figure 10(A)) in order to interrupt the positive current flowing through the A-phase coil 38a. The positive interrupted state is maintained until the end of step s5. Then, at the timing of transitioning to the excitation pattern of step s6, the electric valve control device 100 switches the H-bridge circuit 84 of the A-phase to a negative applied state (Figure 8(B)) so that a negative current flows through the A-phase coil 38a.

[0088] Similarly, at the timing of moving from step s8 to s9 (zero-crossing B-) in Figure 4, the electric valve control device 100 switches the B-phase H-bridge circuit 84 from a positive applied state (Figure 8(A)) to a positive interrupted state (Figure 10(A)). Then, at the timing of moving to step s10, the electric valve control device 100 switches the B-phase H-bridge circuit 84 to a negative applied state (Figure 8(B)) so that a negative current flows through the B-phase coil 38b.

[0089] The flyback voltage when transitioning to the positive cutoff state (Figure 10(A)) is measured by a voltmeter (not shown) that measures the potential difference between measurement point 86 and measurement point 88. Alternatively, the flyback voltage may be obtained by a voltmeter (not shown) that measures the potential difference between GND and measurement point 88. The current generated by the flyback is measured by an ammeter (not shown) that measures the current at measurement point 88. Alternatively, the same current may be measured by an ammeter (not shown) that measures the current at measurement point 86. The motorized valve control device 100 is capable of obtaining the voltage measured by the voltmeter and the current measured by the ammeter.

[0090] Figure 10(B) shows the negative cutoff state in the H-bridge circuit 84. When interrupting the leftward current flowing under a negative applied state (Figure 8(B)), the electric valve control device 100 switches FET80b and FET80c from ON to OFF, as shown in Figure 10(B). FET80d may be either OFF or ON. The leftward current generated by flyback flows through diode 82a to the power supply side.

[0091] At the timing of moving from step s12 to s13 (zero-crossing A+) in Figure 4, the electric valve control device 100 switches the A-phase H-bridge circuit 84 from a negative applied state (Figure 8(B)) to a negative interrupted state (Figure 10(B)). Then, at the timing of moving to step s14, the electric valve control device 100 switches the A-phase H-bridge circuit 84 to a positive applied state (Figure 8(A)) so that a positive current flows through the A-phase coil 38a.

[0092] Similarly, at the timing of moving from step s16 to s17 (same as s1, zero-crossing B+) in Figure 4, the electric valve control device 100 switches the B-phase H-bridge circuit 84 from a negative applied state (Figure 8(B)) to a negative interrupted state (Figure 10(B)). Then, at the timing of moving from step s1 (same as s17) to s2, the electric valve control device 100 switches the B-phase H-bridge circuit 84 to a positive applied state (Figure 8(A)) so that a positive current flows through the B-phase coil 38b.

[0093] The flyback voltage when transitioning to the negative cutoff state (Figure 10(B)) is measured by a voltmeter (not shown) that measures the potential difference between measurement point 88 and measurement point 86. Alternatively, the flyback voltage may be obtained by a voltmeter (not shown) that measures the potential difference between GND and measurement point 86. The current generated by the flyback is measured by an ammeter (not shown) that measures the current at measurement point 86. Alternatively, the same current may be measured by an ammeter (not shown) that measures the current at measurement point 88.

[0094] Figure 11(A) shows the change in voltage due to flyback. The vertical axis shows the voltage measured between measurement points 86 and 88 in Figure 10 (hereinafter referred to as "measured voltage"). The horizontal axis shows the elapsed time. Up to the FET switching time 90, the H-bridge circuit 84 is in a positive applied state (Figure 8(A)), and the measured voltage is equal to the power supply potential Vbat. This figure also shows the voltage change of pulses due to PWM control.

[0095] At the FET switching point 90, the H-bridge circuit 84 switches to a positive cutoff state (Figure 10(A)). At that moment, flyback occurs, and the voltage rises. If diode 82 is not provided, a high voltage will be generated as shown by the dashed line. However, in the case of the H-bridge circuit 84 with diode 82, when the voltage reaches the forward voltage of diode 82, current flows through diode 82. Therefore, a measured voltage higher than the forward voltage does not occur. In other words, the flyback voltage Vf fluctuates with the forward voltage as its upper limit. The forward voltage is the characteristic value of diode 82.

[0096] Subsequently, as the magnetic field weakens, the measured voltage decreases, and when the measured voltage drops to the power supply potential Vbat, the effect of the flyback voltage Vf is eliminated. This point where the measured voltage reaches the power supply potential Vbat is defined as the flyback end time 92. In this example, the time interval from the FET switching time 90, when the flyback occurs, to the flyback end time 92 is defined as the "flyback time Tf". After the flyback end time 92, the measured voltage drops to 0V. The flyback time Tf represents the duration of the flyback effect, and not the timing of when the flyback occurs.

[0097] Figure 11(B) shows the change in current due to flyback. The vertical axis represents the current measured at, for example, measurement point 86 or measurement point 88 in Figure 10 (hereinafter referred to as "measured current"). The horizontal axis represents the elapsed time. Up to the FET switching time 90, the H-bridge circuit 84 is in a positive applied state (Figure 8(A)), and the measured current is the current applied by the excitation pattern. For example, at the A-phase coil 38a in step s4 of Figure 4, 38% of the current is measured.

[0098] After the FET switching point at 90, the power supplied from the power source is cut off, so the measured current decreases, reaching almost 0% at the end of the flyback at 92.

[0099] Figure 12 shows the voltage change when the flyback is large in scale. As the scale of the flyback increases, the flyback time Tf becomes longer, as shown in the diagram. This is because the time it takes for the measured voltage to decrease increases.

[0100] The flyback voltage Vb is calculated using Equation 2 below. In Equation 2, the flyback voltage Vb is the voltage that rises due to flyback when diode 82 is not provided. The flyback voltage Vb represents the magnitude of the flyback.

number

[0101] Thus, the flyback voltage Vb is proportional to the inductance L of coil 38. Furthermore, the inductance L of coil 38 can be calculated using the following equation 3.

number

[0102] The number of turns N, length l, and cross-sectional area S are constant values ​​determined by the shape of the coil 38. Therefore, the inductance L changes only with respect to the permeability μ. Furthermore, the permeability μ changes with the magnetic flux density of the coil 38. If the orientation of the rotor magnet 52 changes, the magnetic flux density that the rotor magnet 52 imparts to the coil 38 changes. In other words, if the position of the rotor magnet 52 in Figure 5 changes, the magnetic flux density in the coil 38 changes, and the permeability μ changes. Then, the change in permeability μ changes the flyback voltage Vb, and ultimately the flyback time Tf changes.

[0103] In summary, the position of the rotor magnet 52 changes the magnetic flux density of the coil 38, which in turn changes the permeability μ of the coil 38. As a result, the inductance L changes, and the flyback voltage Vb and flyback time Tf also change. Specifically, a correlation exists where a larger permeability μ results in a longer flyback time Tf, and a smaller permeability μ results in a shorter flyback time Tf.

[0104] Figure 13 is a graph showing the criteria for determining the flyback time Tf at each zero-cross step. In this diagram, the criteria for each zero-crossing step are represented by multiple points corresponding to the flyback time Tf and the step number. Different point marks (◆, ●, ◇, or ○) are used depending on the type of zero-crossing step.

[0105] Points 130-134 (◆) represent the criteria for determining the flyback time Tf measured at the zero-crossing A- in step s5. These are used for determining the zero-crossing A- in step s5.

[0106] Point 130 (◆) corresponds step s5 with the flyback time Tf:ta. This means that when the flyback time Tf measured at zero-crossing A- is ta, it can be inferred that the rotor magnet 52 is at the stable position of step s5. In other words, it can be determined that the rotor magnet 52 is rotating normally and following the excitation pattern of step s5.

[0107] Thus, in the plot (◆) relating to zero-crossing A-, the points on the vertical line of the zero-crossing step (s5) represent the state in which the rotor magnet 52 is tracking normally. In this case, the flyback time Tf is called the "normal flyback time".

[0108] Point 131 (◆) corresponds to step s4 and the flyback time Tf:tb. This means that when the flyback time Tf measured at zero-crossing A- is tb, it can be inferred that the rotor magnet 52 remains in the stable position of the preceding step s4. In this case, the electric valve control device 100 can determine that the rotor magnet 52 has only rotated partway and is not following the excitation pattern of step s5. Thus, in the plot (◆) related to zero-crossing A-, points to the left of the zero-crossing step (S5) represent a state in which the rotor magnet 52 is not following. The flyback time Tf in this case is called the "abnormal flyback time".

[0109] Similarly, point 132(◆) represents the state in which the rotor magnet 52 remains in the stable position of step s3, two steps prior. If the flyback time Tf of zero-crossing A- is tc, the motor valve control device 100 can determine that the rotor magnet 52 is in the stable position of step s3.

[0110] Furthermore, point 133(◆) indicates that if the flyback time Tf for zero-crossing A- is td, the rotor magnet 52 is in the stable position of step s2, three steps prior. Point 134(◆) indicates that if the flyback time Tf for zero-crossing A- is te, the rotor magnet 52 is in the stable position of step s1, four steps prior. Points 132-134 also represent abnormal flyback times.

[0111] Just as points 130-134 (◆) represent the criteria for determining the flyback time Tf measured at zero-crossing A-, points 140-144 (●) represent the criteria for determining the flyback time Tf measured at zero-crossing B- in step s9. Points 150-154 (◇) represent the criteria for determining the flyback time Tf measured at zero-crossing A+ in step s13. Points 160-164 (〇) represent the criteria for determining the flyback time Tf measured at zero-crossing B+ in step s17.

[0112] In summary, in steps s1 to s5 shown in Figures 5(A) to (E), the position of the rotor magnet 52 differs slightly. This difference in the position of the rotor magnet 52 is reflected in the difference in the flyback time Tf at points 130 to 134(◆). Therefore, steps s1 to s5 can be distinguished by the flyback time Tf.

[0113] As explained above in relation to Figure 12, the reason why the flyback time Tf differs depending on the position of the rotor magnet 52 is that, simply put, the inductance L of the coil 38 is not constant. When the rotor magnet 52 is in a certain position, the scale of the flyback becomes smaller with a certain inductance L, and when the rotor magnet 52 is in a different position, the scale of the flyback becomes larger with a different inductance L.

[0114] Information regarding points other than points 130-134 (◆), points other than points 140-144 (●), points other than points 150-154 (◇), and points other than points 160-164 (〇) shown in Figure 13 does not necessarily need to be used.

[0115] The data shown in Figure 13 represents values ​​obtained through an experiment in which the rotor magnet 52 was locked in a predetermined position, and the flyback time Tf was measured at a zero-crossing step that progressed beyond that point. The fact that the heights are not the same, but shifted vertically depending on the type of zero-crossing, is due to the structure of the rotor 30 and stator 32 used in the experiment. In principle, there should be no difference depending on the type of zero-crossing. If the rotor 30 and stator 32 are perfectly vertically symmetrical with respect to the two-phase interface, the kind of shift seen in this experimental result is unlikely to occur.

[0116] Figure 14(A) is a graph showing the measurement pulses used to detect the flyback time Tf. Figures 14(A) and (B) are based on a portion of Figure 4. The step transition time 170, which is the boundary between steps s4 and s5, corresponds to the FET switching time 90 in Figure 11, when the H-bridge circuit 84 is in the interrupted state. Therefore, flyback occurs at the step transition time 170. However, the rotor magnet 52 may be rotating at this time. As a result, electromagnetic induction may occur in the A-phase coil 38a due to the magnetic field changed by the rotating rotor magnet 52, and this effect may appear in the measured voltage.

[0117] In particular, the magnitude of electromagnetic induction changes depending on the rotational speed of the rotor magnet 52. Therefore, it is difficult to isolate the flyback behavior by eliminating the effect of electromagnetic induction caused by the rotation of the rotor magnet 52 while taking the rotational speed into consideration.

[0118] Therefore, in this embodiment, once the rotor magnet 52 has finished rotating and stopped, a flyback is generated again to detect and analyze a measurement voltage consisting only of the flyback voltage Vf, excluding the effect of electromagnetic induction due to the rotation of the rotor magnet 52. Specifically, after the step transition time 170, the rotor magnet 52 rotates according to the excitation pattern. Then, after the step transition time 170, a measurement pulse is generated after a waiting time has elapsed. The measurement pulse is a measurement current applied for a short time. The measurement current is a current that generates a magnetic field in the coil 38 as a prerequisite for flyback to occur in order to measure the flyback time Tf. In this way, the rotor magnet 52 is stopped before the start time of the measurement pulse 172. Note that at the start time of the measurement pulse 172, the rotor magnet 52 may not be completely stopped, but may be rotating (moving) slightly. If the rotation of the rotor magnet 52 is slight, the electromagnetic induction generated by that rotation will be extremely small. Therefore, it is possible to extract the flyback behavior by substantially eliminating the effect of electromagnetic induction.

[0119] A measurement pulse is applied for a short period starting at the start time 172, and then cut off again at the end time 174. The end time 174 corresponds to the FET switching time 90 in Figure 11. In other words, flyback occurs again at the end time 174. If the rotor magnet 52 is not rotating at this time, no electromagnetic induction due to the rotation of the rotor magnet 52 occurs in the A-phase coil 38a. Furthermore, if the rotor magnet 52 is rotating only slightly, the electromagnetic induction caused by the rotation of the rotor magnet 52 becomes extremely small, to the point where it has virtually no effect. The measured voltage represents only the behavior of the flyback voltage Vf. Therefore, noise related to the judgment based on the flyback time shown in Figure 13 is eliminated, and the judgment accuracy is improved.

[0120] Furthermore, the rotor magnet 52 may rotate slightly in the reverse direction due to the magnetic field generated by the measurement pulse. This phenomenon is equivalent to the rotation of the rotor 30 by the drive current. Even if this occurs, the rotor magnet 52 can be pulled back to its original stable position and returned to normal during the interval from the end of the measurement pulse 174 to the transition to the next step 176.

[0121] When the reference current (100%) of the A-phase current and B-phase current, as explained in relation to Figure 4, is a small ampere value, the force attracting the rotor magnet 52 is weak, and the overshoot relative to the stopping position (the "stable position" of the rotor 30) is small. When the overshoot is small, the oscillation associated with the overshoot is small, and the time it takes for the rotor 30 to stop is shortened. In that case, as shown in Figure 14(A), it is possible to generate measurement pulses within a constant step time length (a time length common to each step) and complete the measurement of the flyback time. Also, when the rotational speed of the rotor 30 is low, it is easier to complete the measurement within the step time length. Note that the oscillation referred to here is the movement of the rotor 30 back and forth from the stable position, and can also be called vibration. The amplitude of the oscillation gradually decreases, and when the amplitude finally becomes 0, the rotor 30 stops at the stable position.

[0122] Figure 14(B) is a graph showing the measurement pulses used to detect the flyback time Tf. On the other hand, if the reference current (100%) of the A-phase current and B-phase current has a large ampere value, the force attracting the rotor magnet 52 is strong, and the overshoot relative to the stopping position (the "stable position" of the rotor 30) is large. When the overshoot is large, the oscillation associated with the overshoot is large, so the time it takes for the rotor 30 to stop is longer. In that case, as shown in Figure 14(B), the step time length is extended, and the measurement pulse is generated after exceeding a certain step time length. Also, when the rotational speed of the rotor 30 is high, it is difficult to complete the measurement within the step time length.

[0123] In the example shown in Figure 14(B), the rotor magnet 52, which began rotating at step transition time 180, stops after exceeding the normal step time length. Therefore, the start time of the measurement pulse 182 and the end time of the measurement pulse 184 fall within the extended period as shown. In this case as well, between the end time of the measurement pulse 184 and the next step transition time 186, the rotor magnet 52 can be pulled back to its original stable position.

[0124] As shown in the example in Figure 14(A), completing the measurement of the flyback time within the normal step time length results in more stable movement of the rotor 30 compared to the example in Figure 14(B). This is considered to be a better approach because it reduces the likelihood of disturbances in the fluid flow rate changes associated with the opening and closing of the valve.

[0125] Figure 15 is a functional block diagram of the electric valve control device 100. The electric valve control device 100 is a type of computer. Each component of the electric valve control device 100 is realized by hardware, including an arithmetic unit (microcomputer) on a circuit board 54, memory and storage devices, wired or wireless communication lines connecting them, and an H-bridge circuit 84, and software stored in the storage devices that supplies processing instructions to the arithmetic unit. The computer program may consist of a device driver and an application program, as well as a library that provides common functions to these programs. The blocks described below represent functional units, not hardware units.

[0126] The electric valve control device 100 includes a data processing unit 102, a communication unit 104, and a reference information storage unit 106. The communication unit 104 communicates with external devices connected via the connection terminal 62. The reference information storage unit 106 stores origin information and judgment criteria (Figure 13), etc. Specifically, the reference information storage unit 106 stores, for each zero-crossing step, a judgment criterion that associates the zero-crossing step with the flyback time Tf when the rotor 30 is at the stable position of that zero-crossing step, and for each of the one or more steps preceding the zero-crossing step, a judgment criterion that associates the step with the flyback time Tf when the rotor 30 is at the stable position of that step.

[0127] The reference information storage unit 106 is a storage area configured as non-volatile memory. The data processing unit 102 performs various processes based on the information stored in the reference information storage unit 106 and various data obtained from the communication unit 104. The data processing unit 102 also functions as an interface between the communication unit 104 and the reference information storage unit 106.

[0128] The communication unit 104 includes a receiving unit 110 that receives data and commands from an external device, and a transmitting unit 112 that transmits data to an external device.

[0129] The data processing unit 102 is implemented by the arithmetic unit executing a program stored in the memory device. The data processing unit 102 includes a rotation control unit 120, a flyback time measurement unit 122, and a state determination unit 124. The rotation control unit 120 controls the rotation of the rotor 30 based on information stored in the reference information storage unit 106 and commands received from an external device. Specifically, the rotation control unit 120 switches the state of the H-bridge circuit 84 according to the step excitation pattern and applies a drive current (drive pulse) to the coil 38. The flyback time measurement unit 122 switches the state of the H-bridge circuit 84 to generate flyback in the coil 38 and measures the flyback time Tf. The state determination unit 124 determines whether the rotor 30 is in a non-following state, not following the excitation pattern. The state determination unit 124 further identifies the position of the rotor 30. Specifically, the state determination unit 124 determines the non-following state and identifies the position of the rotor 30 based on the length of the flyback time Tf.

[0130] For example, if the rotor 30 is moved in the closing direction (downward direction) and the step is advanced after the rotor 30 reaches the origin O, it will enter a non-following state. Also, if an attempt is made to move the rotor 30 in the opening direction (upward direction) beyond the highest point Tp, it will enter a non-following state. In addition, the rotor 30 may enter a non-following state if it is rotating too fast or if foreign matter is mixed in and hinders the rotation of the rotor 30.

[0131] Figures 16 and 17 are flowcharts showing the processing steps of the electric valve control device 100. When the receiving unit 110 receives a movement command from an external device (S10), the rotation control unit 120 determines the rotation direction, step time length, and end step number according to the movement command. The step time length is determined by the rotation speed.

[0132] The rotation control unit 120 sets the initial step number as an internal parameter. The initial step number indicates the step to which the rotor 30 is synchronized at the start of rotation. Normally, the rotation control unit 120 stores the step number corresponding to the position of the rotor 30 at that time. During startup or when the unit loses step, the rotation control unit 120 may perform a synchronization operation between the stator 32 and the rotor 30 and determine the step number by that operation.

[0133] The rotation control unit 120 performs the initial setup of the FET 80 based on the first step number (S14). The following processing is performed for phase A and phase B. Here, an example for phase A is shown. If the phase A current is at a positive current level in the excitation pattern of the first step number, the rotation control unit 120 sets the phase A H-bridge circuit 84 to a positive applied state (Figure 8(A)).

[0134] If the A-phase current of the excitation pattern is zero-crossing A-, the rotation control unit 120 sets the A-phase H-bridge circuit 84 to a positive interruption state (Figure 10(A)). If the A-phase current of the excitation pattern is at a negative current level, the rotation control unit 120 sets the A-phase H-bridge circuit 84 to a negative application state (Figure 8(B)). If the A-phase current of the excitation pattern is zero-crossing A+, the rotation control unit 120 sets the A-phase H-bridge circuit 84 to a negative interruption state (Figure 10(B)).

[0135] The rotation control unit 120 processes the B phase in the same manner. Based on the B phase current in the excitation pattern of the first step number, the rotation control unit 120 sets the state of the B phase H bridge circuit 84.

[0136] Control for each step begins from this point. Step transitions are managed by an internal parameter called the step number. The rotation control unit 120 starts measuring the elapsed time in the relevant step in order to determine the timing for switching to the next step (S16).

[0137] The data processing unit 102 executes the processes from S18 to S24 for both phase A and phase B. For example, the processing for phase A is executed first, followed by the processing for phase B. The processing for phase A will be explained below, but the same applies to the processing for phase B.

[0138] The rotation control unit 120 determines, based on the step number, whether the A-phase current in the A-phase excitation pattern is a zero-cross step (S18). If the A-phase current is a zero-cross step, the process shown in Figure 17 is performed via terminal A. The process shown in Figure 17 will be described later.

[0139] If the A-phase current is not in the zero-crossing step, the rotation control unit 120 determines whether the A-phase current is in the next step after the zero-crossing step (S20). If the A-phase current is not in the next step after the zero-crossing step, the process proceeds to S24.

[0140] On the other hand, if the A-phase current is in the next step after the zero-crossing step, the rotation control unit 120 switches the H-bridge circuit 84 to a current-open state (S22). If the A-phase current is in the next step after zero-crossing A- (step s6 in Figure 4), the rotation control unit 120 sets the A-phase H-bridge circuit 84 to a negative applied state (Figure 8(B)). If the A-phase current is in the next step after zero-crossing A+ (step s14 in Figure 4), the rotation control unit 120 sets the A-phase H-bridge circuit 84 to a positive applied state (Figure 8(A)). After that, the process proceeds to S24.

[0141] The rotation control unit 120 applies the A-phase current in the excitation pattern of the step number as a drive current (drive pulse) to the A-phase H-bridge circuit 84 (S24).

[0142] Once the above processing is completed for phases A and B, the rotation control unit 120 waits for the timing of the step's end (S26). Specifically, when the elapsed time reaches the step time length, the rotation control unit 120 determines that it is time to end the step.

[0143] The rotation control unit 120 determines whether the step number is a final step (S28). If the step number is a final step, the rotation control unit 120 determines that the process has completed successfully. At this time, the transmission unit 112 notifies the external device of the status of successful completion.

[0144] If the step number is not the end step, the rotation control unit 120 continues processing. The rotation control unit 120 advances the step number to the next step (S30). In this example, 1 is added to the step number. If the rotor 30 is to be moved in the reverse direction, 1 is subtracted from the step number. The rotation control unit 120 temporarily stops measuring the elapsed time in order to remeasure the elapsed time in the next step (S32). Then, it returns to the process in S16 and repeats the process described above.

[0145] If the process in S18 described above determines that the A-phase current (or B-phase current) of the excitation pattern is a zero-cross step, the process proceeds to S40 in Figure 17 via terminal A.

[0146] The rotation control unit 120 switches the H-bridge circuit 84 to the interrupted state according to the type of zero-crossing (S40). If the A-phase current of the excitation pattern for step number is zero-crossing A-, the rotation control unit 120 sets the A-phase H-bridge circuit 84 to the positive interrupted state (Figure 10(A)).

[0147] If the A-phase current of the excitation pattern is zero-crossing A+, the rotation control unit 120 sets the A-phase H-bridge circuit 84 to a negative interruption state (Figure 10(B)). If the B-phase current of the excitation pattern is zero-crossing B-, the rotation control unit 120 sets the B-phase H-bridge circuit 84 to a positive interruption state (Figure 10(A)). If the B-phase current of the excitation pattern is zero-crossing B+, the rotation control unit 120 sets the B-phase H-bridge circuit 84 to a negative interruption state (Figure 10(B)).

[0148] After that, the flyback time measurement unit 122 waits until the waiting time has elapsed (S42). As mentioned above, the oscillation is the movement of the rotor 30 back and forth around the zero-cross step position ("stable position"), and can also be called vibration. The amplitude of the oscillation gradually decreases, and when the amplitude finally becomes 0, the rotor 30 stops at the zero-cross step position ("stable position"). Three examples of waiting times are shown below.

[0149] The first example of the waiting time is the time required from the step transition time 170 in Figure 14(A) or the step transition time 180 in Figure 14(B) (the time when the excitation pattern is switched) until the rotating rotor 30 stops at the zero-crossing step position ("stable position") (hereinafter referred to as "stopping time"). The stopping time may be a predetermined time set in advance, or it may be the time until the rotor 30 stops, detected by a rotation sensor (not shown), etc.

[0150] A second example of the waiting time is the time required from the step transition time 170, 180 until the rotor 30 first reaches (crosses) the zero-crossing step position ("stable position") (hereinafter referred to as the "first arrival time"). In this example, the measuring current is applied at the timing when the rotor 30 first reaches the zero-crossing step position ("stable position"). As mentioned above, when the reference current (100%) of the A-phase current and B-phase current explained in relation to Figure 4 is a small ampere value, the force attracting the rotor magnet 52 is weak, and the overshoot with respect to the zero-crossing step position ("stable position") is small. If the overshoot is small, the effect of electromagnetic induction due to oscillation after the overshoot can be substantially eliminated. The first arrival time may be a predetermined time set in advance, or it may be the time until the first arrival of the rotor 30 to the stable position is detected by a rotation sensor (not shown), etc.

[0151] Furthermore, if the modified example 1 described later is adopted, the effect of eliminating the influence of electromagnetic induction in the second example of the standby time is further enhanced. In modified example 1, by reducing the excitation current in the phase that does not generate measurement pulses, the attractive force of the rotor 30 just before the stable position is weakened, and the overshoot can be reduced. This suppresses oscillation after the overshoot, and the effect of suppressing oscillation contributes to eliminating the influence of electromagnetic induction.

[0152] A third example of waiting time is the time required from step transition time 170, 180 until the amplitude of the oscillation of the rotor 30 attenuates to a level where the effects of electromagnetic induction can be substantially eliminated (hereinafter referred to as "attenuation time"). Even if the overshoot is large, the effects of electromagnetic induction due to the oscillation can be substantially eliminated by waiting until the oscillation settles within a predetermined range. The attenuation time may be a predetermined time set in advance, or it may be the time until the attenuation of the oscillation to a predetermined range is detected by a rotation sensor (not shown), etc.

[0153] In the case of the initial arrival time in the second example and the decay time in the third example, it is desirable that the rotor 30 does not come to a complete stop when the waiting time has elapsed, but that the rotation of the rotor 30 has slowed down to a point where the effect of electromagnetic induction due to the rotation of the rotor 30 can be substantially eliminated. The waiting time may be other than those in the above examples, and may be a predetermined time set in advance, or it may be determined by actually detecting the oscillation of the rotor 30 using an angle sensor or the like.

[0154] Once the standby period is over, the flyback time measurement unit 122 applies a measurement pulse (measurement current) (S44). For example, the flyback time measurement unit 122 applies a current of the same value as the drive current (drive pulse) in the step immediately preceding the zero-cross step for a short period of time.

[0155] Therefore, when the A-phase current of the excitation pattern for a given step number is zero-crossing A-, the flyback time measurement unit 122 switches the A-phase H-bridge circuit 84 to a positive applied state (Figure 8(A)). The flyback time measurement unit 122 then applies 38% of the A-phase current to the A-phase coil 38a. Immediately after the current stabilizes, the flyback time measurement unit 122 switches the A-phase H-bridge circuit 84 to a positive disconnected state (Figure 10(A)). This causes a flyback in the A-phase coil 38a, where current flows in the positive direction (to the right in Figure 10(A)).

[0156] Similarly, when the A-phase current of the excitation pattern for a step number is zero-crossing A+, the A-phase H-bridge circuit 84 enters a negative applied state (Figure 8(B)), applying the A-phase current -38% to the A-phase coil 38a, and immediately returning to a negative interrupted state (Figure 10(B)). Then, a negative flyback occurs in the A-phase coil 38a.

[0157] When the B-phase current of the same excitation pattern is zero-crossing B-, the B-phase H-bridge circuit 84 enters a positive applied state (Figure 8(A)), 38% of the B-phase current is applied to the B-phase coil 38b, and it immediately returns to a positive interrupted state (Figure 10(A)). Then, a positive flyback occurs in the B-phase coil 38b.

[0158] When the B-phase current of the same excitation pattern crosses zero-cross B+, the B-phase H-bridge circuit 84 enters a negative applied state (Figure 8(B)), applying a B-phase current of -38% to the B-phase coil 38b, and immediately returning to a negative interrupted state (Figure 10(B)). Then, a negative flyback occurs in the B-phase coil 38b.

[0159] The flyback time measurement unit 122 measures the flyback time Tf at this time (S46). Specifically, the flyback time measurement unit 122 measures the time from when it switches to the cutoff state until the increased measured voltage returns to the power supply voltage Vbat (see Figure 11(A)). The flyback time measurement unit 122 may also measure the time until the measured current decreases to approximately 0% and define this as the flyback time Tf (see Figure 11(B)).

[0160] The state determination unit 124 determines whether the rotor 30 is operating normally (S48). As explained in relation to Figure 13, the flyback time Tf varies depending on the position of the rotor magnet 52. If the flyback time Tf is the normal flyback time, the state determination unit 124 determines that the rotor 30 is operating normally. Here, "normal flyback time" means that the flyback time Tf matches or approximates the normal flyback time.

[0161] For example, when making a determination at zero-crossing A-(step s5) in Figure 13, if the flyback time Tf matches or approximates ta at point 130, the rotor 30 is operating normally. In this case, the process proceeds to S26 in Figure 16 via terminal B and continues.

[0162] If the flyback time Tf is not the normal flyback time, the state determination unit 124 identifies the position where the rotor 30 is stationary (S50).

[0163] According to the criteria shown in Figure 13, the state determination unit 124 identifies the step corresponding to the flyback time Tf. In the determination at zero-crossing A-(step s5), if the flyback time Tf matches or approximates the flyback time tb at point 131, it can be estimated that the rotor 30 is remaining at or near the stable position of step s4. The same applies to points 132-134. If the flyback time is midway between two steps, it may be represented by a decimal step number such as "s3.5".

[0164] The step numbers specified here are examples of parameters that represent the position of rotor 30. Instead of step numbers, the position of rotor 30 may be represented using electrical or mechanical angles.

[0165] The rotation control unit 120 terminates processing due to an error. At this time, the transmission unit 112 notifies the external device of the error termination status (that the rotor 30 is in a non-following state) and parameters representing the position of the rotor 30 (such as a step number). This error termination corresponds to a warning level indicating that the electric valve 1 did not complete its operation according to the movement command, and is a situation that can be expected in normal use (for example, the event of reaching the origin in origin search). An error termination also occurs if the non-following state occurs due to malfunction caused by foreign matter jamming, etc.

[0166] As described above, in this embodiment, with respect to the stepping motor of the electric valve 1, the electric valve control device 100 detects the non-following state of the rotor 30 based on the length of the flyback time Tf generated in the coil 38, thereby simplifying the configuration of the electric valve 1. For example, it is not necessary to provide the electric valve 1 with a magnetic sensor or the like to detect the non-following state.

[0167] Furthermore, the electric valve control device 100 measures the flyback time after a waiting period has elapsed since the transition to the zero-cross step (after the rotating rotor 30 has stopped, or after the rotation of the rotor 30 has been decelerated to a point where the effects of electromagnetic induction due to the rotation of the rotor 30 can be substantially eliminated). This avoids the influence of the induced electromotive force due to the rotation of the rotor magnet 52, and allows for the acquisition of an accurate flyback time.

[0168] Furthermore, even with a simple configuration electric valve 1, the electric valve control device 100 can identify the position of the rotor 30 when it is not tracking.

[0169] In particular, the electric valve control device 100 refers to a determination criterion that correlates the flyback time with the position of the rotor 30, so it can more accurately and easily determine the non-following state and identify the position of the rotor 30.

[0170] Although preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these specific embodiments, and various modifications are possible within the scope of the technical concept of the present invention.

[0171] [Example 1] Modification 1 provides a method for shortening the oscillating time after the rotor 30 has moved by reducing the drive current of the other phase in advance when generating the measurement pulse.

[0172] Figure 18 is a graph showing the current control in Modification Example 1. Here, we show an example of zero-crossing A-, but the same applies to other zero-crossing cases. At step transition time 170, the H-bridge circuit 84 of phase A becomes disconnected, and at the same time, the phase B current becomes 100% according to the excitation pattern. Phase A is an example of a phase that generates a measurement pulse, and phase B is an example of a phase that does not generate a measurement pulse.

[0173] In this state, the B-phase current is maintained at 100%, and then reduced to 38%. The length of time the B-phase current is maintained at 100% is called the "excitation duration." The timing at which the B-phase current is reduced to 38% is called the excitation de-energization point 171. By reducing the B-phase current, the force inducing the rotor 30 is weakened, and the oscillating time is shortened.

[0174] The excitation sluggishness time 171 is before the measurement pulse start time 172. The length of the period between the excitation sluggishness time 171 and the measurement pulse start time 172 is called the "excitation relaxation time". The "excitation duration" and the "excitation relaxation time" are both predetermined lengths.

[0175] At the start of the measurement pulse (172), the B-phase current is returned to 100%. After that, the procedure is the same as in Figure 14(A).

[0176] Specifically, in S44 of Figure 16, the flyback time measurement unit 122 reduces the current of the phase that does not generate a measurement pulse (measurement current) before applying the measurement pulse (measurement current). Furthermore, when the flyback time measurement unit 122 applies the measurement pulse, it restores the current of the other phase to the original magnitude of the drive current (drive pulse).

[0177] The extent to which the current of the B phase (an example of the other phase) is reduced should be determined by considering various factors such as the behavior of the B phase coil 38b and the rotational resistance force of the rotor 30.

[0178] According to Modification 1, the oscillation time of the rotor 30 is shortened, allowing the start time of the measurement pulse 172 to be set earlier. This makes it easier to complete the measurement of the flyback time within the normal step time length, as shown in Figure 14(A), and the time required for all steps can be made uniform. Therefore, the movement becomes the same as that of a normal rotor 30.

[0179] [Differentiation 2] In the above embodiment, an example was shown in which the electric valve control device 100 determines whether or not the stepping motor is in a non-following state and identifies the position of the rotor 30 that is in a non-following state, based on the length of the flyback time Tf of one of the two phases of the stepping motor. Modification 2 provides a method for determining whether or not the stepping motor is in a non-following state and identifying the position of the rotor 30 that is in a non-following state, based on the length of the flyback time Tf of both phases.

[0180] Figure 19 is a graph showing the criteria for determining the flyback time Tf in Modification Example 2. Figure 19 is based on a portion of Figure 13. In the above embodiment, the flyback time Tf corresponding to the four steps preceding the zero-crossing step was identified as the criterion for determining the flyback time Tf measured at a predetermined zero-crossing step (see Figure 13). In Modification 2, as shown in the figure, the flyback time Tf corresponding to the eight steps preceding the zero-crossing step is identified as the criterion.

[0181] Points 140-148 (●) represent the criteria for the flyback time Tf measured at the zero-crossing B- in step s9. Although not shown in this diagram, the criteria for other types of zero-crossing steps are also represented by eight points.

[0182] The steps are advanced in an ascending order from s1 to s5, and it is determined in the zero-crossing A- (step s5) that an abnormal flyback time in phase A is detected. In that case, the state determination unit 124 identifies the step number corresponding to the current position of the rotor 30, as described above. At this stage, one of steps s1 to s4 is identified.

[0183] In the above embodiment, the process terminates at this point due to an error. However, in Modification 2, the operation continues in order to verify the abnormality detection result. The rotation control unit 120 continues to advance the steps until the next zero-cross step even after an abnormal flyback time for phase A is detected. In this example, the rotation control unit 120 continues the steps until zero-cross B-(step s9).

[0184] In step s9, the flyback time measurement unit 122 applies a measurement pulse to the B-phase coil 38b and measures the flyback time Tf. The state determination unit 124 determines whether the measured B-phase flyback time Tf is a normal flyback time. Logically, if a non-following state (abnormal flyback time) is determined in zero-crossing A- (step s5), then a non-following state (abnormal flyback time) should also be determined in the subsequent zero-crossing B- (step s9). This is because it is rare for a non-following state to occur first and then return to a following state. For example, if the flyback time measurement unit 122 measures a flyback time Tf that approximates points 140 and 148 in zero-crossing B- (step s9), it is difficult for the state determination unit 124 to determine whether the rotor 30 is in step s1 or s9. In contrast, if the state determination unit 124 refers to the determination result of zero-cross A- (step s5) at zero-cross B- (step s9), it becomes easier to determine whether the rotor 30 is at step s1 or s9. Specifically, if the state determination unit 124 determines that the rotor 30 is at step s1 at zero-cross A- (step s5), then it is already in a non-following state at step s5, so it is unlikely to be following at step s9. Therefore, the state determination unit 124 can determine that this corresponds to the flyback time (point 148) of step s1. Conversely, if the state determination unit 124 determines that the rotor 30 is at step s5 at zero-cross A- (step s5), then it is in a following state at step s5, so it is unlikely to remain at the earlier step s1. Therefore, the state determination unit 124 can determine that this corresponds to the flyback time (point 140) of step s9.

[0185] If a non-following state is detected in phase A, but does not occur in phase B, the rotation control unit 120 will terminate the operation due to an unexpected error. The transmission unit 112 will notify an external device of the error termination status (unexpected error occurred). This corresponds to a severe error.

[0186] If the B phase is determined to be in a non-following state as expected, the state determination unit 124 verifies whether the step number (one of s1 to s4) identified in the A phase state determination performed in step s5 is correct. The state determination unit 124 refers to the flyback time Tf corresponding to the five to eight steps back (s1 to s4) as the criterion for determining zero-crossing B-. Points 145 to 148 (●) correspond to the criteria that are referenced.

[0187] If the flyback time Tf measured at zero-crossing B-(step s9) matches or approximates the tf at point 145, the state determination unit 124 identifies step number (s4) as the second determination result according to the determination criteria at point 145. Similarly, if the flyback time Tf matches or approximates the tg at point 146, the state determination unit 124 identifies step number (s3) as the second determination result. Alternatively, the state determination unit 124 identifies step number (s2) according to the determination criteria at point 147. When the flyback times are approximate for two step numbers, the state determination unit 124 may consider those two step numbers as candidates. For example, since the flyback times of step number (s1) and step number (s9) are close, step number (s1) identified by the determination criteria at point 148 and step number (s9) identified by the determination criteria at point 140 may be considered as candidates. The state determination unit 124 only needs to refer to the determination result of zero-crossing A- (step s5) and identify one of the multiple candidates (s1 and s9).

[0188] If the first step number identified in Zero Cross A- matches the second step number identified in Zero Cross B-, the state determination unit 124 determines that the determination result is correct. Also, if Zero Cross A- cannot determine whether the step number is in the range close to the stable position (s4) or (s5), the state determination unit 124 can refer to the step number (s4 or s5) identified in Zero Cross B- to make a decision. In this way, the determination accuracy of Zero Cross A- can be improved by referring to the determination in Zero Cross B-. As described above, if two step numbers are selected as candidates in Zero Cross B-, the state determination unit 124 can determine that the first step number is correct if either of the two step numbers matches the first step number.

[0189] Then, the rotation control unit 120 terminates processing with a warning-level error, as in the above embodiment. The transmission unit 112 notifies the external device of the error termination status (that the rotor 30 is in a non-following state) and parameters representing the position of the rotor 30 (such as a step number).

[0190] On the other hand, if the first step number identified by Zero Cross A- and the second step number identified by Zero Cross B- do not match, the status determination unit 124 determines that the determination result is incorrect. In this case, the rotation control unit 120 terminates processing with, for example, a warning-level error. The transmission unit 112 notifies an external device of the error termination status (that the rotor 30 is in a non-following state) and that the position of the rotor 30 is unknown. Alternatively, the rotation control unit 120 may treat it as a severe error.

[0191] If the first step number and the second step number do not match, the state determination unit 124 may determine an intermediate value (for example, an average value) between the first and second step numbers, and the transmission unit 112 may transmit that average value as a step number representing the position of the rotor 30.

[0192] Note that the second zero-cross step for verification may extend beyond the end step. In other words, the flyback time measurement unit 122 and the state determination unit 124 may advance the step beyond the end step to perform verification. In that case, it is desirable to reverse the step after verification and return to the end step.

[0193] In the modified example 2, the determination of whether or not the rotor is in a non-following state is made based on the length of the flyback time Tf of both phases, and the position of the rotor 30 in the non-following state is identified, thus increasing the reliability of the above determination and identification.

[0194] [Difference 3] The magnitude of the measurement current (measurement pulse) may be arbitrarily determined by considering various factors. Figures 14(A) and (B) show an example where the measurement current (measurement pulse) in step s5 is set to 38%, the same as the drive current (drive pulse) in the previous step s4. In other words, it was matched to the lowest current among the four levels of drive current (100%, 92%, 71%, and 38%).

[0195] However, if the accuracy of the flyback time measurement is high, errors in state determination are unlikely to occur even with small-scale flyback, so measurement may be performed with a current smaller than 38% of the drive current (drive pulse) in the previous step s4. Reducing the value of the measurement current (measurement pulse) makes it easier to suppress reverse rotation of the rotor 30.

[0196] Conversely, if the measuring current (measuring pulse) is large, it is easier to determine the state even if the accuracy of the flyback time measurement is not high. However, since reverse rotation is more likely to occur, it is desirable to use a measuring current (measuring pulse) that is smaller than 100%, which is the highest of the four levels of drive current.

[0197] [Differentiation Example 4] For example, as shown in Patent Document 3, there is an electric valve (for example, a ball valve) that directly transmits the rotational motion of a rotor to rotate the valve body. In this method, the flow rate of the medium flowing through the passage inside the valve body is adjusted by rotating the valve body. This type of electric valve also has a mechanism that changes the valve opening degree by the rotational motion of the rotor. In the electric valve exemplified in the embodiment, the rotational motion of the rotor is converted into the axial motion of the valve body, but in this type of electric valve, the rotational motion of the rotor is directly transmitted as the rotation of the valve body, causing the opening and closing operation of the ball valve based on the shape of the opening of the valve body. This rotary type electric valve is also a type of stepping motor driven valve, and a non-following state may occur due to foreign matter getting caught. Even with this rotary type electric valve, it is possible to determine whether or not it is in a non-following state based on the flyback time. Therefore, similar to the electric valve in the embodiment, it is possible to apply the techniques shown in the embodiment, modified examples 1 to 3, and other modified examples described later.

[0198] [Other variations] The state determination unit 124 may determine step loss based on the position of the rotor 30 in a non-following state. For example, the state determination unit 124 determines that the stepping motor has lost step if the difference between the zero-cross step in which it is determined to be in a non-following state and the step indicating the position of the lagging rotor 30 is greater than a predetermined value.

[0199] In the above embodiment, an example was described in which the endpoint of the flyback time is defined as the flyback end point 92 when the measured voltage drops to the power supply potential Vbat. The predetermined voltage reference for determining the endpoint of the flyback time may be greater than the power supply potential Vbat, as long as it is less than the forward voltage of the diode 82. Alternatively, the predetermined reference may be less than the power supply potential Vbat. It is sufficient if the scale of the flyback can be represented by the flyback time.

[0200] In Figure 14(A), the start time of the measurement pulse 172 is plotted midway between the step transition time 170 and the next step transition time 176. However, the start time of the measurement pulse 172 may be closer to the step transition time 170 or closer to the next step transition time 176.

[0201] In Figure 14(B), the step time length of step s5 is shown to be doubled, but the additional time due to the extension may be shorter or longer than the step time length.

[0202] In the above embodiments and modifications, the flyback time was measured after the rotor 30 stopped and then the flyback occurred. However, it is also possible to measure the flyback time by inducing the flyback before the rotor 30 stops. In that case, the electric valve control device 100 determines the non-following state and identifies the stopping position of the rotor, taking into account the effect of the induced electromotive force due to the rotation of the rotor magnet 52. If the rotational speed of the rotor magnet 52 when the flyback occurs is always the same, the voltage change due to the induced electromotive force is constant, so it is relatively easy to eliminate its effect.

[0203] The flyback time Tf shown in Figure 11(A) can be measured using a time measurement unit (not shown). The flyback time Tf may also be determined by other methods. For example, sampling measurements can be performed at timings repeated at predetermined sampling intervals, and the number of times the effect of the flyback voltage Vf remains can be counted. The flyback time Tf can be calculated by multiplying this count by the sampling interval. The number of times the effect of the flyback voltage Vf remains corresponds to the number of samples where the measured voltage was equal to or greater than the power supply potential Vbat. Even with the sampling method, the flyback time Tf can be determined. Therefore, the determination of the non-tracking state based on the length of the flyback time Tf is the same as in the method using the time measurement unit.

[0204] In the above embodiments and modifications, a determination method based on the flyback time Tf has been described. However, instead of the flyback time Tf, the number of counts counted at predetermined intervals (sampling intervals) within the flyback time Tf may be used. Alternatively, the number of counts at predetermined intervals may be transformed using an exponential or logarithmic function and used as the number of counts. The number of counts within the flyback time Tf has a positive correlation with the flyback time Tf. In other words, as the number of counts increases, the flyback time Tf increases, exhibiting a similar increase-decrease relationship. Because of this positive correlation, the determination result will be the same even if the flyback time Tf is replaced with the number of counts. The number of counts at predetermined intervals can be said to be substantially equivalent to the flyback time Tf, differing only in units.

[0205] The electric valve 1 may be equipped with other means for measuring the displacement of the rotor 30, such as an angle sensor (for example, a magnetic sensor and a magnet) for measuring the angle of the rotor, and the electric valve control device 100 may utilize the determination result based on the measurement result of such means in accordance with the above-described technology.

[0206] In the above embodiments and modifications, examples were shown in which the steps are advanced in ascending order of step number. However, even when the steps are advanced in descending order of step number to move the rotor in the reverse direction, it is similarly possible to determine the non-following state and identify the rotor's stopping position.

[0207] The above embodiments and modifications show examples of a stepping motor using a "microstepping method" in which one period of the electrical angle progresses in 16 steps. Other 1 / n microstepping methods may also be used (where n is, for example, 8). In addition to these, a stepping motor using a "full stepping method" in which one period of the electrical angle progresses in 4 steps, or a "half stepping method" in which one period of the electrical angle progresses in 8 steps may also be used. Even in the case of the "full stepping method" and the "half stepping method," the position of the rotor magnet 52 is different at different steps, so the flyback time will have characteristics of both long and short.

[0208] In the above embodiment, a configuration in which the operating rod 15 functions as the rotation axis of the rotor 30 is illustrated. In a modified example, a rotation axis (cylindrical shaft) made of a non-magnetic metal may be provided inside the rotor 30, and the rotation axis and the operating rod may be fixed together. A screw feed mechanism may be configured between the rotation axis and the guide member. Specifically, a male screw (first screw) is formed on the outer circumferential surface of the guide member, and a female screw (second screw) is formed on the inner circumferential surface of the rotation axis. The inner circumferential surface of the guide member does not have a female screw, and the operating rod is inserted through it so as to be slidable in the axial direction.

[0209] In this configuration, the screw feed mechanism is formed by the first screw of the guide member and the second screw of the rotating shaft. The rotating shaft and the operating rod rotate together and are displaced in the axial direction by the drive of the rotor 30. The control of the above embodiment can also be applied in this configuration.

[0210] In the above embodiment, the stator includes a yoke having pole teeth. In a modified example, a stator including a laminated core may also be used.

[0211] In the above embodiment, the stator unit 4 is a two-phase stepping motor, but it may also be configured as a three-phase or more stepping motor.

[0212] In the above embodiment, the electric valve was configured as an expansion valve, but it may also be configured as an on-off valve that does not have an expansion function.

[0213] In the above embodiment, an example was shown in which the electric valve is applied to the refrigeration cycle of an automotive air conditioning system. However, it is applicable to air conditioning systems equipped with an electric expansion valve, not limited to vehicles. It may also be configured as an electric valve to control the flow of fluids other than refrigerant, such as in a hot water supply system or a hydraulic control device.

[0214] It should be noted that the present invention is not limited to the embodiments and modifications described above, and the components can be modified and implemented without departing from the spirit of the invention. Various inventions may be formed by appropriately combining the multiple components disclosed in the embodiments and modifications described above. In addition, some components may be deleted from all the components shown in the embodiments and modifications described above. [Explanation of symbols]

[0215] 1 Electric valve, 2 Rotor unit, 4 Stator unit, 5 Valve body, 6 Valve housing, 7 Large diameter section, 8 Valve seat member, 9 Small diameter section, 10 Inlet port, 12 Outlet port, 14 Valve hole, 15 Actuating rod, 16 Valve seat, 18 Valve chamber, 20 Valve body, 22 Guide member, 24 Female thread, 25 Screw feed mechanism, 26 Spring, 30 Rotor, 32 Stator, 34 Can, 36 Coil unit, 36a Phase A coil unit, 36b Phase B coil unit, 38 Coil, 38a Phase A coil, 38b Phase B coil, 39 Bobbin, 40 Yoke, 40m First yoke, 40n Second yoke, 42 Case, 44 Seal ring, 46 Pole teeth, 50 Rotor core, 52 Rotor magnet, 54 Circuit board, 56 Cover, 60 Terminal, 62 Connection terminal, 64 Connector section, 70 A-phase vector, 72 B-phase vector, 74 composite vector, 80 FET, 82 diode, 84 H-bridge circuit, 86 measurement point, 88 measurement point, 90 FET switching point, 92 flyback end point, 100 electric valve control device, 102 data processing unit, 104 communication unit, 106 reference information storage unit, 110 receiving unit, 112 transmitting unit, 120 rotation control unit, 122 flyback time measurement unit, 124 state determination unit, 130-164 points, 170 step transition point, 172 start of measurement pulse, 174 end of measurement pulse, 176 step transition point, 180 step transition point, 182 start of measurement pulse, 184 end of measurement pulse, 186 step transition point.

Claims

1. A rotatable rotor and a stator that, together with the rotor, constitute a stepping motor, An electric valve control device for controlling an electric valve having a mechanism for changing the valve opening degree by the rotational motion of the rotor, A rotation control unit inputs pulses in succession at each step to the coil of the stator and controls the rotation of the rotor according to the excitation pattern of the pulses, A flyback time measuring unit measures the flyback time until the flyback voltage generated in the coil during the zero-cross step of the pulse decreases to a predetermined standard, An electric valve control device comprising: a state determination unit that determines, based on the flyback time, whether or not the rotor is in a non-following state in which it is not following the excitation pattern during the rotation of the rotor.

2. The electric valve control device according to claim 1, characterized in that the flyback time measuring unit applies a measuring current to the coil to cause flyback after a waiting time has elapsed since moving to the zero-cross step, and measures the flyback time.

3. The electric valve control device according to claim 2, characterized in that the waiting time is a first hour until the rotor stops, a second hour until the rotor first reaches the stable position of the zero-cross step, or a third hour until the amplitude of the rotor's oscillation is attenuated to a level that substantially eliminates the effects of electromagnetic induction.

4. The electric valve control device according to claim 1, characterized in that the state determination unit identifies the position of the rotor in the non-following state based on the length of the flyback time or the number of counts at predetermined intervals within the flyback time.

5. The electric valve control device according to claim 1, characterized in that the state determination unit refers to a determination criterion that associates the flyback time with the position of the rotor.

6. The stepping motor has two or more phase coils, The electric valve control device according to claim 2, characterized in that the flyback time measurement unit reduces the pulse current applied to the other coil before applying the measurement current to one of the coils.

7. The stepping motor has two or more phase coils, The electric valve control device according to claim 1, characterized in that the state determination unit determines the non-following state based on the flyback time in each of the two or more coils.

8. A computer controls an electric valve having a rotatable rotor, a stator that together with the rotor constitutes a stepping motor, and a mechanism that changes the valve opening degree by the rotational motion of the rotor. A rotation control function that controls the rotation of the rotor by inputting a series of step-by-step pulses to the coil of the stator, and the excitation pattern of the pulses, A flyback time measurement function that measures the flyback time until the flyback voltage generated in the coil during the zero-cross step of the pulse drops to a predetermined standard, An electric valve control program characterized by providing a state determination function that determines whether or not the rotor is in a non-following state in which it is not following the excitation pattern during the rotation of the rotor, based on the flyback time.

9. A rotatable rotor, The stator, which together with the rotor constitutes a stepper motor, A mechanism for changing the valve opening degree by the rotational motion of the rotor, An electric valve control device comprising: a rotation control unit that inputs pulses in succession at each step to the coil of the stator and controls the rotation of the rotor according to the excitation pattern of the pulses; a flyback time measurement unit that measures the flyback time until the flyback voltage generated in the coil at the zero-cross step of the pulses decreases to a predetermined standard; and a state determination unit that determines, based on the flyback time, whether or not the rotor is in a non-following state in which it is not following the excitation pattern during the rotation of the rotor.

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