Single phase motor and method for controlling single phase motor
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- MINEBEAMITSUMI INC
- Filing Date
- 2026-01-26
- Publication Date
- 2026-08-06
Smart Images
Figure JP2026002480_06082026_PF_FP_ABST
Abstract
Description
Single-phase motor and control method for single-phase motor
[0001] The present invention relates to a single-phase motor and a control method for the single-phase motor.
[0002] For example, Patent Document 1 discloses a single-phase brushless motor having an electromagnetic coil and a permanent magnet. In avoiding the deadlock of the motor, after the start of rotation of the rotor, the rotation of the rotor reverses in response to the detection of an intermediate phase at an electrical angle of 90 degrees (π / 2).
[0003] Japanese Patent No. 4720856
[0004] In this motor, AD conversion and phase calculation are required for detecting the intermediate phase. In realizing such processing, the circuit configuration of the drive circuit for controlling the drive of the motor becomes complicated, so the cost of the motor increases.
[0005] The present invention has been made in view of the above problems, and one of the problems is to provide a single-phase motor and a control method for the single-phase motor that can improve the starting failure of rotation at a low cost.
[0006] The single-phase motor according to one aspect of the present invention includes a stator, a rotor that rotates relative to the stator around a rotation axis, a rotation position detector that detects the relative position of the rotor with respect to the stator and switches and outputs a first signal and a second signal according to the relative position, and a control circuit that controls the rotational drive of the rotor with respect to the stator. At the starting position of the rotation of the rotor, the rotor is more likely to rotate in a first direction opposite to the second direction around the rotation axis. The rotation position detector is arranged such that the switching of the first signal and the second signal occurs when the rotor rotates in the first direction from the starting position. When the control circuit rotates the rotor in the second direction, it rotates the rotor in the first direction at the start of rotation and rotates the rotor in the second direction after the switching of the first signal and the second signal.
[0007] A control method for a single-phase motor according to one aspect of the present invention comprises a stator, a rotor that rotates relative to the stator about a rotation axis, and a rotation position detector that detects the relative position of the rotor with respect to the stator and outputs a first signal and a second signal by switching them according to the relative position, wherein at the starting position of the rotation of the rotor, the rotor is more likely to rotate in a first direction opposite to the second direction about the rotation axis than in a second direction, and the rotation position detector is arranged such that the switching of the first signal and the second signal occurs when the rotor rotates in the first direction from the starting position, and the control method for a single-phase motor includes the steps of: rotating the rotor in the first direction at the start of rotation in response to a command to rotate the rotor in the second direction; detecting the switching of the first signal and the second signal output from the rotation position detector; and rotating the rotor in the second direction after the detection of the switching.
[0008] This is a schematic plan view showing the configuration of a single-phase motor 1 according to one embodiment of the present invention. This is a block diagram showing the circuit configuration of a single-phase motor 1 according to one embodiment of the present invention. This is a schematic graph showing the changes in torque and Hall signal in the single-phase motor 1. This graph corresponds to the graph in Figure 3 and is for explaining an example of rotor 3 rotation control. This is a flowchart for explaining the processing flow of the control circuit 6 that rotates the rotor 3 in the reverse direction OD. This is a timing chart for explaining the energizing pattern supplied to the coil. This is a flowchart for explaining the processing flow of the control circuit 6 that rotates the rotor 3 in the forward direction PD. This is a timing chart for explaining the switching of the energizing pattern supplied to the coil. This graph corresponds to the graph in Figure 4 and is for explaining another example of rotor 3 rotation control. This is a timing chart for explaining the switching of the energizing pattern supplied to the coil. This is a schematic diagram showing the structure of a fan motor 10, which is one usage mode of the single-phase motor 1.
[0009] Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. Figure 1 is a schematic plan view showing the configuration of a single-phase motor 1 according to an embodiment of the present invention. In one example, this single-phase motor 1 is a 4-pole, 4-slot inner rotor type motor. The single-phase motor 1 comprises a shaft 2, a rotor 3, a stator 4, and a circuit board 5. In one example, the single-phase motor 1 has a housing (not shown) that accommodates these shaft 2, rotor 3, stator 4, and circuit board 5. The shaft 2 is supported in the housing so as to be rotatable around the rotation axis x. The stator 4 and circuit board 5 are fixed to the housing, for example. The single-phase motor 1 may have, for example, 12 slots, 16 slots, or 24 slots.
[0010] The shaft 2 extends along the axis of rotation x. A rotor 3 is fixed to the outer circumferential surface of the shaft 2. The rotor 3 has a rotor body 31 and a magnet 32. The rotor body 31 is a cylindrical member attached to the outer circumferential surface of the shaft 2. The magnet 32 is a permanent magnet. In this example, the magnet 32 is formed in a cylindrical shape, for example. The magnet 32 has alternating north and south magnetic poles in the circumferential direction around the axis of rotation x. That is, the magnet 32 has four magnetic poles around the axis of rotation x.
[0011] The stator 4 includes a stator core 41 and coils 42a to 42d. The stator core 41 is formed from a laminate of multiple thin plates stacked in the axial direction. The laminate is made of a magnetic material. The stator core 41 includes an annular portion 43, teeth 44, and magnetic pole portions 45. The annular portion 43 is formed in an annular shape around the axis of rotation x. In this example, four teeth 44 extend inward from the inner surface of the annular portion 43. The four teeth 44 are arranged at equal intervals in the circumferential direction around the axis of rotation x. Each magnetic pole portion 45 extends in the circumferential direction from the inner end of each tooth 44.
[0012] Coils 42a to 42d are wound around each tooth. Coils 42a to 42d are windings formed from, for example, a conductor (for example, copper wire). An insulator (not shown) is sandwiched between the coils 42a to 42d and each tooth 44. The inner circumferential surface of the magnetic pole portion 45 faces the outer circumferential surface of the magnet 32 via a predetermined magnetic gap in the radial direction perpendicular to the rotation axis x. When current is supplied to the coils 42a to 42d, the magnetic interaction that occurs between the magnet 32 and the coils 42a to 42d causes the rotor 3 to rotate relative to the stator 4 around the rotation axis x.
[0013] Specifically, of the four coils 42a to 42d, coils 42a and 42c are supplied with current at the same phase, while coils 42b and 42d are supplied with current at the same phase but shifted from the phase of the current supplied to coils 42a and 42c. In this way, the single-phase motor 1 can use the phase difference of the currents supplied to coils 42a to 42d to rotate the rotor 3 relative to the stator 4 around the rotation axis x.
[0014] In this example, the circuit board 5 is positioned to face the rotor 3 and stator 4 in the axial direction along the rotation axis x. In this example, the circuit board 5 includes a substrate body 51, a rotation position detector 52, and electronic components (not shown). In one example, the substrate body 51 is formed from a flat, annular plate. In this example, the rotation position detector 52 is mounted on the surface of the substrate body 51. The electronic components are semiconductor elements, etc., that constitute the control circuit and drive circuit, which will be described later. The electronic components are mounted on the front and back surfaces of the substrate body 51.
[0015] In one example, the rotational position detector 52 is a Hall element. In this example, one Hall element is mounted on the substrate body 51 at a position facing the magnet 32 in the axial direction. The Hall element detects the change in the magnetic poles of the magnet 32 (mutual change between the N and S poles) when the rotor 3 rotates around the rotation axis x. That is, the Hall element detects the position of the boundary of the magnetic poles of the magnet 32. The Hall element switches and outputs the first signal and the second signal, described later, according to this change in magnetic poles. In this way, the rotational position detector 52 can detect the relative position of the rotor 3 with respect to the stator 4 based on the detection of the change in magnetic poles.
[0016] Figure 2 is a block diagram showing the circuit configuration of a single-phase motor 1 according to one embodiment of the present invention. The single-phase motor 1 includes the aforementioned rotational position detector 52, a control circuit 6, an inverter circuit 7, a pre-drive circuit 8, and coils La and Lb. In this block diagram, the aforementioned coils 42a to 42d are conveniently represented as coils La and Lb. The control circuit 6 is connected to an external device (not shown) located outside the single-phase motor 1. The control circuit 6 outputs a control signal to the pre-drive circuit 8 based on a command signal (command) received from this external device.
[0017] The control circuit 6 is a program processing unit having a configuration in which a processor such as a CPU (Central Processing Unit), various storage devices such as RAM, ROM, and flash memory, and peripheral circuits such as counters (timers), A / D conversion circuits, D / A conversion circuits, clock generation circuits, and input / output interface circuits are all connected to each other via a bus or dedicated line. For example, the control circuit 6 is a microcontroller unit (MCU) in which the above-mentioned processor, storage devices, and various circuits are integrated onto a single chip.
[0018] The inverter circuit 7 is supplied with current from a power source (not shown) located outside the single-phase motor 1. The pre-drive circuit 8 controls the on / off state of switching elements Q1 to Q4 of the inverter circuit 7 based on control signals received from the control circuit 6. By controlling the on / off state of these switching elements Q1 to Q4, the direction of the current supplied to coils La and Lb is switched. Furthermore, various current supply patterns for coils La and Lb are set by controlling the on / off state. The inverter circuit 7 and the pre-drive circuit 8 constitute the drive circuit for the single-phase motor 1.
[0019] The rotational position detector 52 switches between outputting a first signal or a second signal (Hall signal) to the control circuit 6 based on the magnetic field acting on the rotational position detector 52 from the north and south poles of the magnet 32. The first signal and the second signal are, for example, either H+ (positive analog voltage signal) or H- (negative analog voltage signal). The control circuit 6 outputs a control signal to the pre-drive circuit 8 based on the command signal output to the control circuit 6 from an external device and the first signal and the second signal (Hall signal) output from the rotational position detector 52. In this way, the control circuit 6 controls the rotational drive of the rotor 3 relative to the stator 4.
[0020] The pre-drive circuit 8 controls the direction of the current supplied to coils La and Lb by controlling the on / off state of switching elements Q1 to Q4 of the inverter circuit 7. In this way, the rotor 3 rotates around the rotation axis x based on the magnetic interaction between the magnet 32 and coils 42a to 42d. The current supply patterns to coils La and Lb include a pattern that rotates the rotor 3 in the positive direction (clockwise, in one example, CW) around the rotation axis x (forward rotation current supply pattern) and a pattern that rotates the rotor 3 in the opposite direction to the positive direction (counterclockwise, in one example, CCW) (reverse rotation current supply pattern).
[0021] Figure 3 is a schematic graph showing the changes in torque and Hall signal in a single-phase motor 1. This graph shows the changes in torque generated in the single-phase motor 1 and the Hall signal HS output from the rotational position detector 52 as a function of the mechanical angle when the rotor 3 rotates 360 degrees relative to the stator 4 around the rotational axis x. In this graph, the horizontal axis represents the mechanical angle [degrees] of 360 degrees, which corresponds to one rotation of the rotor 3 around the rotational axis x. The left vertical axis is defined as the torque value [mN・m]. The right vertical axis is defined as the voltage value [V] of the Hall signal HS.
[0022] As mentioned above, the Hall signal HS includes a positive voltage signal (e.g., the first signal) H+ and a negative voltage signal (e.g., the second signal) H-. In other words, a binary voltage signal corresponding to either the north or south pole of the magnet 32 is switched and output. In this example, the switching occurs at approximately 65 degrees, 155 degrees, 245 degrees, and 335 degrees. Specifically, the rotation position detector 52 outputs the first signal H+ between approximately 335 degrees and 65 degrees, and between approximately 155 degrees and 245 degrees, and outputs the second signal H- between approximately 65 degrees and 155 degrees, and between approximately 245 degrees and 335 degrees.
[0023] The torque shown in the graph of Figure 3 includes the cogging torque CT. The cogging torque CT is a torque that is periodically generated by the magnetic attractive force produced by the magnetic interaction between the magnetic pole portion 45 of the stator core 41 and the magnet 32, regardless of the energization of the coils La and Lb. Since the magnet 32 has four magnetic poles, in this example, the cogging torque CT takes a maximum value (approximately 1 mN·m) at mechanical angles approximately 65, 155, 245, and 335 degrees, and a minimum value (approximately -1 mN·m) at mechanical angles approximately 15, 105, 195, and 285 degrees. The cogging torque CT is also 0 (zero) at mechanical angles approximately 55, 75, 145, 170, 235, 255, 325, and 345 degrees.
[0024] Furthermore, the torque shown in the graph of Figure 3 includes the torque PT that attempts to rotate the rotor 3 in the forward direction (positive torque) and the torque NT that attempts to rotate the rotor 3 in the reverse direction (negative torque). Both the positive torque PT and the negative torque NT are composite torques obtained by adding the energizing torque generated when coils La and Lb are energized and the cogging torque CT mentioned above. The energizing torque is the torque generated by the magnetic attraction force produced by the magnetic interaction between the magnetic pole portion 45 of the stator core 41 and the magnet 32 when coils La and Lb are energized. This magnetic attraction force is generated periodically as the rotor 3 rotates around the rotation axis x.
[0025] The positive torque PT reaches maximum values (approximately 4.5 mN / m) at machine angles around 30, 120, 210, and 300 degrees, and minimum values (approximately 0.5 to -1.8 mN / m) at machine angles at 90-degree intervals of 60, 150, 240, and 330 degrees. On the other hand, the negative torque NT reaches maximum values (approximately 3.0 to 5.0 mN / m) at machine angles around 60, 155, 240, and 330 degrees, and minimum values (approximately -11 mN / m) at machine angles around 30, 120, 210, and 300 degrees. The positions where the maximum and minimum values occur are reversed between the positive torque PT and the negative torque NT.
[0026] Next, we will explain the scenario in which the rotor 3 is rotated relative to the stator 4 around the rotation axis x. Figure 4 corresponds to the graph in Figure 3 and is a graph to explain an example of the control method for the single-phase motor 1, i.e., the rotation control of the rotor 3. In this example of the single-phase motor 1, we assume that the rotor 3 starts rotating in the positive direction PD from the first stop point P1. The first stop point P1 corresponds to the starting position of the rotor 3's rotation. The positive direction PD is the clockwise direction around the rotation axis x (to the right in the graph, i.e., the first direction), and the opposite direction OD to the positive direction PD is the counterclockwise direction around the rotation axis x (to the left in the graph, i.e., the second direction). In this example, the first stop point P1 is defined as a mechanical angle position of approximately 170 degrees. That is, the first stop point P1 is the mechanical angle position where the cogging torque CT is 0 (zero).
[0027] The switching of the first signal H+ and the second signal H- of the rotational position detector 52 occurs at a position approximately 75 degrees in the positive direction PD from the first stop point P1, i.e., at a mechanical angle of approximately 245 degrees. In other words, in this single-phase motor 1, the rotational position detector 52 is positioned such that the switching of the first signal H+ and the second signal H- occurs when the rotor 3 has rotated approximately 75 degrees in the positive direction PD from the first stop point P1. To put it another way, the position in which the rotor 3 is stationary relative to the stator 4 is adjusted so that the interface between the N pole and S pole is positioned on the rotational position detector 52 when the rotor 3 has rotated approximately 75 degrees in the positive direction PD.
[0028] At the first stopping point P1, the positive torque PT exceeds the cogging torque CT. Also, the positive torque PT increases in the positive direction PD from the first stopping point P1. Therefore, when the rotor 3 starts rotating in the positive direction PD from the first stopping point P1, the positive torque PT is continuously obtained. On the other hand, when the rotor 3 starts rotating in the reverse direction OD from the first stopping point P1, the positive torque PT decreases. Therefore, at the first stopping point P1, the rotor 3 is more likely to rotate in the positive direction PD than in the reverse direction OD. In other words, at the first stopping point P1, the rotor 3 is less likely to rotate in the reverse direction OD than in the positive direction PD.
[0029] Figure 5 is a flowchart illustrating the processing flow of the control circuit 6 that rotates the rotor 3 in the reverse direction OD. Referring to Figures 2, 4, and 5 together, the control circuit 6 receives a command signal from an external device to rotate the rotor 3 in the reverse direction OD (step S1). The control circuit 6 outputs a control signal to the inverter circuit 7 and the pre-drive circuit 8, i.e., the drive circuit, to start the rotation of the rotor 3 in the forward direction PD (step S2). Upon receiving the control signal from the control circuit 6, the pre-drive circuit 8 controls the on / off state of the switching elements Q1 to Q4 of the inverter circuit 7, thereby supplying current to coils La and Lb based on the forward rotation energization pattern.
[0030] Figure 6 is a timing chart illustrating the current supply pattern to the coils. Referring further to Figure 6, when the rotor 3 starts rotating from the first stop point P1, current is supplied to coils La and Lb based on the forward rotation current supply pattern a. Specifically, the switching elements Q1, Q2, Q3, and Q4 of the inverter circuit 7 are set to PWM (pulse modulation width), OFF, OFF, and ON, respectively. As a result, the rotor 3 starts rotating in the forward direction PD from the first stop point P1 (forward rotation). The rotation position detector 52 outputs a Hall signal HS, i.e., the first signal H+, to the control circuit 6. The control circuit 6 monitors whether the Hall signal HS has switched (Figure 5, step S3).
[0031] If the control circuit 6 has not yet switched the Hall signal HS (step S3, NO), it returns to step S2 and outputs a control signal to the pre-drive circuit 8 so that current continues to be supplied based on the forward rotation energizing pattern a. When the rotor 3 rotates further in the forward direction PD and reaches the switching point P2 where the Hall signal HS switches, the Hall signal HS switches from the first signal H+ to the second signal H-. In this example, the switching point P2 is approximately at a mechanical angle of around 245 degrees (see Figure 4). When the second signal H- is output from the rotation position detector 52 to the control circuit 6, the control circuit 6 detects that the Hall signal HS has switched (step S3, YES).
[0032] When the control circuit 6 detects the switching of the Hall signal HS, it outputs a control signal to the drive circuit so that current is supplied to coils La and Lb based on the reverse rotation energizing pattern A (Figure 5, step S4). In the reverse rotation energizing pattern A, each switching element Q1, Q2, Q3, and Q4 is set to PWM, OFF, OFF, and ON, respectively. That is, the on / off control of each switching element Q1 to Q4 is the same as the control of the forward rotation energizing pattern a. However, as an exception, the direction of the current supplied to coils La and Lb is not changed. On the other hand, the direction of the magnetic force generated between the magnet 32 and coils 42a to 42d is reversed. In this way, a negative torque NT acts on the rotor 3, which tries to rotate the rotor 3 in the reverse direction OD around the rotation axis x (reverse rotation).
[0033] Specifically, as the rotor 3 rotates in the positive direction PD from the first stopping point P1 to the switching point P2, an inertial force is generated on the rotor 3 in the positive direction PD. Due to this inertial force, a positive torque PT1 acts on the rotor 3, causing it to rotate in the positive direction PD over a predetermined mechanical angle beyond the switching point P2. This positive torque PT1 is different from the positive torque PT generated when the rotor is energized. As mentioned above, once the rotor 3 is beyond the switching point P2, a negative torque NT acts on the rotor 3, causing it to rotate in the reverse direction OD. Therefore, the rotor 3 beyond the switching point P2 comes to a stop when the positive torque PT1 generated by the inertial force and the negative torque NT balance each other.
[0034] While stationary, a negative torque NT exceeding the cogging torque CT acts on the rotor 3, causing it to rotate in the reverse direction OD. Subsequently, the control circuit 6 monitors whether the Hall signal HS has switched (Figure 5, step S5). If a switch in the Hall signal HS is detected (step S5, YES), the process returns to step S4. The control circuit 6 outputs a control signal to the drive circuit so that current is supplied to coils La and Lb based on the reverse rotation energizing pattern B (step S4). In the reverse rotation energizing pattern B, each switching element Q1, Q2, Q3, and Q4 is set to OFF, ON, PWM, and OFF, respectively. Thus, current is supplied to coils La and Lb in the opposite direction to when energized based on the forward rotation energizing pattern a and the reverse rotation energizing pattern A.
[0035] Subsequently, the control circuit 6 repeats steps S5 and S4 until it receives a command signal to stop the rotation of the rotor 3. As shown in Figure 6, each time the control circuit 6 detects a change in the Hall signal HS, it alternately switches between reverse rotation energization pattern B and reverse rotation energization pattern A. Specifically, when the second signal H- is output, reverse rotation energization pattern A is applied, and when the first signal H+ is output, reverse rotation energization pattern B is applied. This switching between reverse rotation energization pattern A and reverse rotation energization pattern B sets the direction of the current supplied to coils La and Lb to opposite directions. In this way, the single-phase motor 1 continues to rotate the rotor 3 in the reverse direction OD (reverse rotation).
[0036] Figure 7 is a flowchart illustrating the processing flow of the control circuit 6 that rotates the rotor 3 in the forward direction PD. The control circuit 6 receives a command signal from an external device to rotate the rotor 3 in the forward direction PD (step S11). The control circuit 6 outputs a control signal to the inverter circuit 7 and the pre-drive circuit 8, i.e., the drive circuit, to start the rotation of the rotor 3 in the forward direction PD (step S12). In the drive circuit that receives the control signal from the control circuit 6, the pre-drive circuit 8 controls the on / off state of the switching elements Q1 to Q4 of the inverter circuit 7, thereby supplying current to coils La and Lb based on the forward rotation energization pattern.
[0037] Figure 8 is a timing chart illustrating the switching of the energization pattern supplied to the coils. Referring to Figures 4, 7, and 8 together, current is supplied to coils La and Lb based on the forward rotation energization pattern a when the rotor 3 starts rotating from the first stop point P1. Specifically, the switching elements Q1, Q2, Q3, and Q4 of the inverter circuit 7 are set to PWM, OFF, OFF, and ON, respectively. As a result, the rotor 3 starts rotating in the forward direction PD from the first stop point P1. The rotation position detector 52 outputs a Hall signal HS, i.e., the first signal H+, to the control circuit 6. The control circuit 6 monitors whether the Hall signal HS has switched (Figure 7, step S13).
[0038] If no switching of the Hall signal HS occurs (step S13, NO), the control circuit 6 returns to step S12, and current continues to be supplied based on the forward rotation energizing pattern a. When the rotor 3 rotates further in the forward direction PD and reaches the switching point P2 where the switching of the Hall signal HS occurs, the Hall signal HS switches from the first signal H+ to the second signal H-. When the second signal H- is output from the rotation position detector 52 to the control circuit 6, it is detected that the Hall signal HS has switched (step S13, YES), and the control circuit 6 proceeds to step S14.
[0039] In step S14, the control circuit 6 outputs a control signal to the drive circuit so that current is supplied to coils La and Lb based on the forward rotation energizing pattern b. In the forward rotation energizing pattern b, each switching element Q1, Q2, Q3, and Q4 is set to OFF, ON, PWM, and OFF, respectively. By switching between this forward rotation energizing pattern a and the forward rotation energizing pattern b, the direction of the current supplied to coils La and Lb is set to opposite directions. From the first stopping point P1 to the switching point P2, the positive torque PT exceeds the cogging torque CT, and similarly beyond the switching point P2, the positive torque PT also exceeds the cogging torque CT, so the rotor 3 continues to rotate in the forward direction PD.
[0040] In the single-phase motor 1 described above, the physical position of the rotation position detector 52 is adjusted relative to the stationary position of the rotor 3 so that the Hall signal HS switches when the rotor 3 rotates in the first direction, i.e., the forward direction PD, from the starting position, i.e., the first stop point P1. When rotating the rotor 3 in the second direction, i.e., the reverse direction OD, the rotor 3 rotates in the forward direction PD at the start of rotation, and then rotates in the reverse direction OD after the Hall signal HS switches. As a result, even if it is difficult for the rotor 3 to rotate in the reverse direction OD at the first stop point P1, the rotor 3 can be reliably rotated in the reverse direction OD. In this way, the starting failure of the rotor 3 can be improved by adjusting the position of the rotation position detector 52 and detecting the switching of the Hall signal HS. Complex processing such as AD conversion and phase calculation is not required, so the cost of the single-phase motor 1 can also be reduced.
[0041] In a single-phase motor 1 having a magnet 32 with four magnetic poles, a mechanical angle of approximately 75 degrees (electrical angle of 150 degrees) is ensured from the first stop point P1 to the switching point P2, which is the point where the Hall signal HS first switches. In this way, a relatively large positive rotation PD is ensured from the first stop point P1 to the switching point P2, and a relatively large inertial force is generated by the rotation of the positive PD. As a result, the rotor 3 can reliably exceed the cogging torque CT, which has a maximum value near the switching point P2. The rotor 3, having exceeded the switching point P2 in the positive PD, can reliably reverse to the reverse direction OD in response to the negative torque NT and start rotating. It is preferable that a mechanical angle of approximately 60 degrees (electrical angle of 120 degrees) or more is specified from the first stop point P1 to the switching point P2.
[0042] Figure 9 corresponds to the graph in Figure 4 and is a graph illustrating another example of rotor 3 rotation control. In this example, we assume a scenario where rotor 3 starts rotating in the reverse direction OD from a second stop point P3. The second stop point P3 corresponds to the starting position of rotor 3 rotation. In one example, the second stop point P3 is defined as a position with a mechanical angle of approximately 325 degrees. That is, the second stop point P3 is the position where the cogging torque CT becomes 0 (zero). Furthermore, the switching point P4 between the first signal H+ and the second signal H- is defined as a position approximately 80 degrees in the reverse direction OD from the second stop point P3, i.e., a position with a mechanical angle of approximately 245 degrees. In other words, the rotation position detector 52 is positioned such that the switching between the first signal H+ and the second signal H- occurs when rotor 3 has rotated approximately 80 degrees in the reverse direction OD from the second stop point P3.
[0043] At the second stop point P3, the negative torque NT exceeds the cogging torque CT. Also, from the second stop point P3 in the reverse direction OD, the negative torque NT increases. Therefore, when the rotor 3 starts rotating in the reverse direction OD from the second stop point P3, the negative torque NT can be continuously obtained. On the other hand, when the rotor 3 starts rotating in the forward direction PD from the second stop point P3, the negative torque NT decreases. Therefore, at the second stop point P3, the rotor 3 is more likely to rotate in the reverse direction OD than in the forward direction PD. In other words, at the second stop point P3, the rotor 3 is less likely to rotate in the forward direction PD than in the reverse direction OD. In this example, the forward direction PD corresponds to the second direction, and the reverse direction OD corresponds to the first direction.
[0044] When the control circuit 6 receives a command signal to rotate the rotor 3 in the forward direction PD from an external device, it outputs a control signal to the inverter circuit 7 and the pre-drive circuit 8 to start the rotation of the rotor 3 in the reverse direction OD. FIG. 10 is a timing chart for explaining the switching of the energization pattern supplied to the coil. Referring to FIGS. 9 and 10 together, when current is supplied to the coils La and Lb based on the reverse rotation energization pattern A, the rotor 3 starts rotating (reverse rotation) in the reverse direction OD from the second stop point P3. The hall signal HS, that is, the second signal H−, is output from the rotation position detector 52 to the control circuit 6.
[0045] When the rotor 3 reaches the switching point P4 where the switching of the hall signal HS occurs, the hall signal HS switches from the second signal H− to the first signal H+. As a result, the reverse rotation energization pattern A is switched to the forward rotation energization pattern a. Similar to the above, exceptionally, even if the energization pattern is changed, the direction of the current supplied to the coils La and Lb is not changed. On the other hand, the direction of the magnetic force generated between the magnet 32 and the coils 42a to 42d is reversed. Thus, a positive torque PT that attempts to rotate the rotor 3 in the forward direction PD about the rotation axis x acts on the rotor 3.
[0046] Specifically, when the rotor 3 rotates in the reverse direction OD from the second stop point P3 to the switching point P4, an inertial force is generated in the reverse direction OD on the rotor 3. Due to this inertial force, a negative torque NT1 that attempts to rotate in the reverse direction OD over a predetermined mechanical angle beyond the switching point P4 acts on the rotor 3. This negative torque NT1 is different from the negative torque NT generated during energization. When the switching point P4 is exceeded, a positive torque PT that attempts to rotate the rotor 3 in the positive direction PD acts on the rotor 3. Therefore, the rotor 3 beyond the switching point P4 stops when the negative torque NT1 generated by the inertial force and the positive torque PT balance each other.
[0047] When the rotor 3 is in this stationary state, a positive torque PT exceeding the cogging torque CT acts on the rotor 3, causing the rotor 3 to reverse and rotate in the positive direction PD. Thereafter, as described above, the energization pattern is switched each time the hall signal HS switches. Specifically, the forward rotation energization pattern a and the forward rotation energization pattern b are alternately switched. By switching between the forward rotation energization pattern a and the forward rotation energization pattern b, the directions of the currents supplied to the coils La and Lb are set to be opposite to each other. In this way, in the single-phase motor 1, the rotation of the rotor 3 in the positive direction PD (forward rotation) continues. Even in such a single-phase motor 1, the same operational effects as described above can be achieved.
[0048] FIG. 11 is a timing chart for explaining the switching of the energization pattern supplied to the coil. As shown in FIG. 11, when the rotor 3 is rotated in the reverse direction OD, currents are supplied to the coils La and Lb based on the reverse rotation energization pattern A. Thereafter, when the rotor 3 reaches the switching point P4, the reverse rotation energization pattern B is applied instead of the reverse rotation energization pattern A. By switching between the reverse rotation energization pattern A and the reverse rotation energization pattern B, the directions of the currents supplied to the coils La and Lb are set to be opposite to each other. From the second stop point P3 to the switching point P4, the negative torque NT exceeds the cogging torque CT, and even after the switching point P4 is exceeded, the negative torque NT similarly exceeds the cogging torque CT, so the rotor 3 continues to rotate in the reverse direction OD.
[0049] Figure 12 is a schematic diagram showing the structure of a fan motor 10, which is one application of the single-phase motor 1. This fan motor 10 comprises the aforementioned single-phase motor 1 and an impeller 11. In this example, the impeller 11 is shown attached to the shaft 2, but it may also be attached to the rotor 3. This fan motor 10 can rotate the rotor 3, i.e., the impeller 11, based on a command signal from an external device. The fan motor 10 is used, for example, to cool a power supply by supplying it with airflow generated by the rotation of the impeller 11. Note that the single-phase motor 1 may be used for applications other than the fan motor 10.
[0050] Although the present invention has been described above through the embodiments described above, the technical scope of the present invention is not limited to the scope described in the embodiments above. It will be obvious to those skilled in the art that various modifications or improvements can be made to the embodiments described above. It will be clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention.
[0051] The embodiments described above are for the purpose of facilitating understanding of the present invention and are not intended to limit its interpretation. Furthermore, the embodiments described above do not limit the scope of application of the present invention, and the present invention may encompass anything as its target application. The components of the above embodiments, as well as their arrangement, materials, conditions, shapes, sizes, etc., are not limited to those exemplified and can be modified as appropriate.
[0052] For example, the present invention includes differences that arise in the implementation of manufacturing tolerances, etc. Furthermore, components shown in different embodiments can be partially substituted or combined to the extent that they do not conflict with the technical requirements. In addition, each component can be selectively combined as appropriate to achieve at least some of the above-mentioned problems and effects.
[0053] 1 Single-phase motor, 2 Shaft, 3 Rotor, 31 Rotor body, 32 Magnet, 4 Stator, 41 Stator core, 42a-42d Coils, 43 Annular section, 44 Teeth, 45 Magnetic pole section, 5 Circuit board, 51 Board body, 52 Rotation position detector, 6 Control circuit, 7 Inverter circuit, 8 Pre-drive circuit, 10 Fan motor, 11 Impeller, La, Lb Coils, Q1-Q4 Switching elements, x Rotation axis
Claims
1. A single-phase motor comprising: a stator; a rotor that rotates relative to the stator about a rotation axis; a rotation position detector that detects the relative position of the rotor with respect to the stator and outputs a first signal and a second signal by switching them according to the relative position; and a control circuit that controls the rotational drive of the rotor relative to the stator, wherein, at the starting position of the rotor's rotation, the rotor is more likely to rotate in a first direction opposite to the second direction about the rotation axis than in a second direction; the rotation position detector is arranged such that the switching of the first signal and the second signal occurs when the rotor rotates in the first direction from the starting position; and, when the control circuit rotates the rotor in the second direction, it rotates the rotor in the first direction at the start of rotation and rotates the rotor in the second direction after the switching of the first signal and the second signal.
2. The single-phase motor according to claim 1, wherein the rotor rotates in the first direction over a predetermined angle after the switching of the first signal and the second signal, and then reverses direction and rotates in the second direction.
3. The single-phase motor according to claim 1, wherein, when the control circuit rotates the rotor in the first direction, it rotates the rotor in the first direction at the start of rotation and continues to rotate the rotor in the first direction even after the switching of the first signal and the second signal.
4. The single-phase motor according to any one of claims 1 to 3, wherein the control circuit switches the energization pattern to the stator coil when the first signal and the second signal are switched.
5. The single-phase motor according to claim 1, wherein the rotor has a magnet having four magnetic poles around the axis of rotation.
6. The single-phase motor according to claim 5, wherein a mechanical angle of 60 degrees or more around the rotation axis is defined between the starting position and the position where the switching of the first signal and the second signal occurs.
7. A fan motor comprising a single-phase motor as described in claim 1, and an impeller attached to the rotor of the single-phase motor.
8. A single-phase motor control method comprising: a stator; a rotor that rotates relative to the stator about a rotation axis; and a rotation position detector that detects the relative position of the rotor with respect to the stator and switches and outputs a first signal and a second signal according to the relative position, wherein at the starting position of the rotor's rotation, the rotor is more likely to rotate in a first direction opposite to the second direction about the rotation axis than in a second direction, and the rotation position detector is arranged such that the switching of the first signal and the second signal occurs when the rotor rotates in the first direction from the starting position, the method comprising: rotating the rotor in the first direction at the start of rotation in response to a command to rotate the rotor in the second direction; detecting the switching of the first signal and the second signal output from the rotation position detector; and rotating the rotor in the second direction after the detection of the switching.