Winding switching device

Abstract

A winding switching device (10) is used in an electric motor (100) having coils (32A, 32B, 32C) of multiple phases, and each coil (32A, 32B, 32C) includes a coil portion (1U, 2U, 1V, 2V, 1W, 2W). A winding switching device (10) is provided with: a switching unit (11) for switching the connection state of coil units (1U, 2U, 1V, 2V, 1W, 2W); and a control unit (13). The switching unit (11) is configured to switch between a permitted state in which the supply of power is permitted and a cut-off state in which the supply of power is cut off. The control unit (13) switches the switching unit (11) from the allowed state to the cut-off state when the rotational speed of the electric motor (100) is greater than the maximum rotational speed (Rm1) of the high-torque characteristic or greater than the maximum rotational speed (Rm2) of the high-torque characteristic, or when the output voltage of the battery (91) is equal to or less than a first voltage threshold value (Thf) of the high-torque characteristic or a second voltage threshold value (Ths) of the high-torque characteristic.

Description

Technical Field

[0001] The present disclosure relates to a winding switching device. Background Art

[0002] In Patent Document 1, an inverter control device for controlling a rotating electric machine via an inverter is disclosed. It has a structure in which power is supplied from a high-voltage storage battery to the inverter via a contactor. When the contactor is switched to the off state and power supply from the high-voltage storage battery is no longer supplied, as a fault protection control, an active short-circuit control is performed in which some of the switching elements of the inverter are set to the on state and the other switching elements are set to the off state. Hereinafter, the active short-circuit control will also be simply referred to as ASC control.

[0003] Prior Art Documents Patent Documents Patent Document 1: International Publication No. 2016 / 076429 Summary of the Invention

[0004] Problems to be Solved by the Invention

[0005] If ASC control is performed when the rotor is rotating at high speed, current flows between the rotating electric machine and the inverter, and there is a possibility of generating a regenerative torque caused by the rotation of the rotor or sintering of the coil ends of the electric motor.

[0006] An object of the present disclosure is to provide a technique capable of performing good fault protection of a multiphase motor when the rotor of the multiphase motor is rotating at high speed.

[0007] Technical Means for Solving the Problems

[0008] The winding switching device of the present disclosure is used in a multiphase motor, the multiphase motor having multiphase coils and each of the coils including a plurality of coil portions, wherein, The winding switching device includes: a switching unit that switches the connection state of the plurality of coil portions in each of the coils; and a control unit that controls the switching unit, The switching unit is configured to switch between a permitted state and a cut-off state, the permitted state permitting the supply of power from a power supply unit to the multiphase motor, and the cut-off state cutting off the supply of power from the power supply unit to the multiphase motor, When the rotational speed of the multiphase motor is greater than a rotation threshold or when the output voltage of the power supply unit is equal to or less than a voltage threshold, the control unit switches the switching unit from the permitted state to the cut-off state.

[0009] Advantages of the Invention

[0010] According to the present disclosure, even when the rotor of the polyphase motor rotates at high speed, the fault protection of the polyphase motor can be performed well. Description of the Drawings

[0011] Figure 1 is a circuit diagram schematically showing a vehicle-mounted system including a switching control device according to Embodiment 1. Figure 2 is a circuit diagram showing the structure of the motor, showing a state where the first relay switch of the switching unit is in the on state and the second relay switch is maintained in the off state. Figure 3 is a circuit diagram showing the structure of the motor, showing a state where the first relay switch of the switching unit is in the off state and the second relay switch is maintained in the on state. Figure 4 is a circuit diagram showing the structure of the motor, showing a state where the first relay switch and the second relay switch of the switching unit are maintained in the off state. Figure 5 is a graph schematically showing the relationship between the torques of high rotation characteristics and high torque characteristics and the rotational speed. Figure 6 is a flowchart in which the control unit controls the switching unit and the conversion unit based on the voltage of the battery. Figure 7 is a flowchart in which the control unit controls the switching unit and the conversion unit based on the rotational speed of the rotor. Detailed Embodiments

[0012] [Description of Embodiments of the Present Disclosure]

[0013] Hereinafter, embodiments of the present disclosure will be listed and exemplified.

[0014] The winding switching device of the present disclosure is

[0015] 〔1〕used in a polyphase motor, the polyphase motor having polyphase coils and each coil including a plurality of coil portions. The winding switching device of the present disclosure includes: a switching unit that switches the connection state of the plurality of coil portions in each coil; and a control unit that controls the switching unit. The switching unit is configured to switch between a permitted state and a cut-off state, the permitted state permitting the supply of power from the power supply unit to the polyphase motor, and the cut-off state cutting off the supply of power from the power supply unit to the polyphase motor. When the rotational speed of the polyphase motor is greater than the rotation threshold or when the output voltage of the power supply unit is below the voltage threshold, the control unit switches the switching unit from the permitted state to the cut-off state.

[0016] According to the above [1], it is possible to prevent sintering of the coil ends of the motor caused by the generation of the back electromotive force in the motor that may occur when the rotational speed of the motor exceeds the conceivable range or when the output voltage of the power supply unit is lower than the conceivable range.

[0017] 〔2〕In the above [1], it may also be that a conversion unit is further provided, the conversion unit includes a plurality of switching elements, and converts the power from the power supply unit and supplies it to the polyphase motor. It may also be that the conversion unit has a plurality of switch pairs, the switch pair is formed by connecting a high-potential-side switching element and a low-potential-side switching element, the high-potential-side switching element is connected to the high-potential-side power path to which the positive voltage of the power supply unit is applied, and the low-potential-side switching element is connected to the low-potential-side power path to which the negative voltage of the power supply unit is applied. It may also be that each switch pair corresponds to each coil, and power is supplied to each coil from the connection point of the high-potential-side switching element and the low-potential-side switching element. It may also be that the control unit switches the switching unit to the cut-off state, and sets either the high-potential-side switching element or the low-potential-side switching element to the on state, and sets the other to the off state.

[0018] According to the above [2], it is possible to form a closed loop by the polyphase motor and the conversion unit without short-circuiting the high-potential-side power path and the low-potential-side power path, keep the current generated in the polyphase motor within the closed loop, and cut off the switching unit, thereby cutting off the flow of current in the closed loop.

[0019] 〔3〕In the above [2], it may also be that before the switching unit is switched to the cut-off state, either the high-potential-side switching element or the low-potential-side switching element becomes the on state, and the other becomes the off state.

[0020] According to the above [3], by forming a closed loop in advance by the polyphase motor and the conversion unit, it is possible to prevent the back electromotive force generated in the polyphase motor from affecting the power supply unit side. And by switching the switching unit to the cut-off state, it is possible to prevent the back electromotive force generated in the polyphase motor from affecting each switching element of the conversion unit.

[0021] 〔4〕In the above [2] or [3], it may also be that when the output voltage of the power supply unit is below the voltage threshold, and the rotational speed of the polyphase motor is less than the rotation threshold and below the determination speed in the weak magnetic field region, the control unit controls all the switching elements to the off state. It may also be that when the output voltage of the power supply unit is below the voltage threshold, and the rotational speed of the polyphase motor is greater than the determination speed, the control unit sets either the high-potential-side switching element or the low-potential-side switching element to the on state, and sets the other to the off state, and switches the switching unit to the cut-off state.

[0022] According to the above [4], by controlling the switching elements differently according to the rotational speed of the polyphase motor, it is possible to perform detailed fault protection for the polyphase motor and the conversion unit.

[0023] 〔5〕In the above [4], it may also be that, regardless of whether the rotational speed is below the determination rotational speed, when the output voltage of the power supply unit is below the voltage threshold and in a voltage cut-off state where the output voltage of the power supply unit is cut off, either the high-potential side switching element or the low-potential side switching element is set to the on state, and the other is set to the off state, and the switching unit is switched to the cut-off state.

[0024] According to the above [5], even if there is a concern that the output voltage of the power supply unit becomes a voltage cut-off state, sufficient power cannot be supplied from the power supply unit to the polyphase motor, and a situation where it is impossible to counter the back electromotive force generated in the polyphase motor occurs, it is possible to reliably perform fault protection for the polyphase motor and the conversion unit.

[0025] 〔6〕In any one of the above [1] to [3], it may also be that the rotation threshold is the maximum rotational speed of the polyphase motor in the weak magnetic field region.

[0026] According to the above [6], when an excessive back electromotive force is generated in the polyphase motor, it is possible to suppress the influence of the back electromotive force from spreading to the polyphase motor, the conversion unit, etc.

[0027] 〔7〕In any one of the above [1] to [3], it may also be that the control unit sets the rotation threshold and the voltage threshold according to the connection state of the plurality of coil units.

[0028] According to the above [7], when the connection state of the coil unit changes, the characteristics of the polyphase motor change. Therefore, by setting the rotation threshold and the voltage threshold according to the connection state of the coil unit, it is possible to switch the switching unit to the cut-off state to correspond in detail to the characteristics of the polyphase motor.

[0029] <Embodiment 1>

[0030] As Figure 1 shown, the winding switching device 10 of Embodiment 1 is used in a polyphase motor, i.e., the motor 100, that utilizes a polyphase AC power supply provided in the vehicle-mounted system 1. The vehicle-mounted system 1 is a system that supplies power from a storage battery 91 as a power supply unit to the motor 100 via a conversion unit 12. The motor 100, for example, imparts a rotational force to wheels (not shown) of a vehicle. The winding switching device 10 includes a switching unit 11, a conversion unit 12, and a control unit 13.

[0031] [Structure of the motor]

[0032] The electric motor 100 has polyphase coils 32A, 32B, and 32C wound around a stator (not shown). The coils 32A, 32B, and 32C are configured as three-phase sectional coils. Coil 32A corresponds to the first phase (U phase), coil 32B corresponds to the second phase (V phase), and coil 32C corresponds to the third phase (W phase). The coil 32A of the first phase (U phase) includes coil portions 1U and 2U. The coil 32B of the second phase (V phase) includes coil portions 1V and 2V. The coil 32C of the third phase (W phase) includes coil portions 1W and 2W.

[0033] The coils 32A, 32B, and 32C are electrically connected at a short-circuit portion 90 that can be a neutral point. The coils 32A, 32B, and 32C are so-called Y-connected three-phase coils. Current detection portions 32D, 32E, and 32F are interposed between coil 32A and the short-circuit portion 90, between coil 32B and the short-circuit portion 90, and between coil 32C and the short-circuit portion 90. In each of the coils 32A, 32B, and 32C, the coil portions 1U, 2U, the coil portions 1V, 2V, and the coil portions 1W, 2W are connected in series electrically. In the electric motor 100, a rotor (not shown) is provided in a form housed in the stator. The rotor rotates by supplying three-phase AC power to the electric motor 100. A part of the rotor protrudes from the electric motor 100 and is connected to a wheel in a structure capable of imparting a rotational force to the wheel of a vehicle.

[0034] In the present disclosure, "electrically connected" preferably refers to a structure in which both connection objects are connected in a conductive state (a state in which current flows) with equal potentials. However, it is not limited to this structure. For example, "electrically connected" may also be a structure in which an electrical component is interposed between two connection objects and the two connection objects are connected in a conductive state.

[0035] [Structure of switching portion]

[0036] The switching portion 11 has a first switching portion 11A, a second switching portion 11B, and a third switching portion 11C. The first switching portion 11A has a function of switching the number of series connections (connection state) in the coil portions 1U, 2U of the coil 32A constituting the first phase (U phase). The second switching portion 11B has a function of switching the number of series connections (connection state) in the coil portions 1V, 2V of the coil 32B constituting the second phase (V phase). The third switching portion 11C has a function of switching the number of series connections (connection state) in the coil portions 1W, 2W of the coil 32C constituting the third phase (W phase). Here, the number of series connections refers to the number of coil portions that are connected in series and can be energized.

[0037] The first switching unit 11A includes a first relay switch 11D and a second relay switch 11E. The first relay switch 11D and the second relay switch 11E are configured as semiconductor relays. The semiconductor relay can be constituted by, for example, MOSFET, GaNFET, IGBT, bipolar transistors, etc. The first relay switch 11D and the second relay switch 11E are switched between the on state and the off state based on the on / off signal C1 from the control unit 13 described later for on indication or off indication. The first relay switch 11D and the second relay switch 11E become the on state allowing energization via themselves by the on indication from the control unit 13, and become the off state cutting off the energization via themselves by the off indication from the control unit 13.

[0038] The second switching unit 11B includes a first relay switch 11F and a second relay switch 11G. The first relay switch 11F and the second relay switch 11G have the same structure as the first relay switch 11D and the second relay switch 11E.

[0039] The third switching unit 11C includes a first relay switch 11H and a second relay switch 11J. The first relay switch 11H and the second relay switch 11J have the same structure as the first relay switch 11D and the second relay switch 11E.

[0040] [Structure of the conversion unit]

[0041] The conversion unit 12 is configured as a so-called inverter circuit that outputs three-phase AC power of U-phase, V-phase, and W-phase. The three-phase AC power output from the conversion unit 12 is supplied to the motor 100 via three conduction paths (the U-phase conduction path 61, the V-phase conduction path 62, and the W-phase conduction path 63) and is used for the rotational drive of the motor 100. The conversion unit 12 includes switching elements 6A, 6C, 6E as high-potential side switching elements, and switching elements 6B, 6D, 6F as low-potential side switching elements. The switching elements 6A, 6C, 6E function as upper arm elements. The switching elements 6B, 6D, 6F function as lower arm elements. The switching elements 6A, 6B, 6C, 6D, 6E, 6F are respectively constituted by, for example, insulated gate bipolar transistors (IGBTs) and freewheeling diodes D1, D2, D3, D4, D5, D6.

[0042] When the switching elements 6A, 6B, 6C, 6D, 6E, and 6F switch from the on state to the off state, the time required is shorter than the time required for each relay switch (11D, 11E, 11F, 11G, 11H, 11J) of the switching unit 11 to switch from the on state to the off state. Therefore, when the switching elements 6A, 6B, 6C, 6D, 6E, 6F and each relay switch (11D, 11E, 11F, 11G, 11H, 11J) are switched from the on state to the off state at the same timing, the switching elements 6A, 6B, 6C, 6D, 6E, 6F become the off state earlier.

[0043] In the conversion unit 12, for example, the switching elements 6A, 6B, 6C, 6D, 6E, 6F repeat the on operation and the off operation based on the on / off signal C2 (for example, PWM signal) from the control unit 13, and generate three-phase AC power based on the output voltage from the battery 91. In other words, the conversion unit 12 converts the power from the battery 91. The control unit 13 controls the conversion unit 12 in a three-phase modulation method using a PWM signal, for example. In addition, as long as the control unit 13 controls the conversion unit 12 in a manner that can drive the motor 100, various methods such as known V / f control and known vector control can be adopted, for example.

[0044] The switching element 6A, which is an upper arm element and a high-potential side switching element, and the switching element 6B, which is a lower arm element and a low-potential side switching element, are connected to form a switching pair 6G for the U phase. The switching element 6C, which is an upper arm element and a high-potential side switching element, and the switching element 6D, which is a lower arm element and a low-potential side switching element, are connected to form a switching pair 6H for the V phase. The switching element 6E, which is an upper arm element and a high-potential side switching element, and the switching element 6F, which is a lower arm element and a low-potential side switching element, are connected to form a switching pair 6J for the W phase.

[0045] These switching elements 6A, 6B, 6C, 6D, 6E, 6F are provided between the high-potential side power path 81 electrically connected to the high-potential side terminal of the battery 91 and the low-potential side power path 82 electrically connected to the negative electrode of the battery 91. The battery 91 uses a lead-acid battery, a lithium-ion battery, etc., for example. The positive voltage of the battery 91 is applied to the high-potential side power path 81. The negative voltage of the battery 91 is applied to the low-potential side power path 82. The switching elements 6A and 6B are electrically connected in series. One end of the switching element 6A is electrically connected to the high-potential side power path 81, and the other end of the switching element 6B is electrically connected to the low-potential side power path 82.

[0046] The switching elements 6C and 6D are electrically connected in series. One end of the switching element 6C is electrically connected to the high-potential-side power path 81, and the other end of the switching element 6D is electrically connected to the low-potential-side power path 82. The switching elements 6E and 6F are electrically connected in series. One end of the switching element 6E is electrically connected to the high-potential-side power path 81, and the other end of the switching element 6F is electrically connected to the low-potential-side power path 82.

[0047] The conduction path 61 of the U phase is the conduction path between the switching elements 6A and 6B and the coil part 1U of the U phase. One end of the conduction path 61 is electrically connected to the connection point L between the two switching elements 6A and 6B. The other end of the conduction path 61 is electrically connected to one end of the coil part 1U of the U phase.

[0048] The conduction path 62 of the V phase is the conduction path between the switching elements 6C and 6D and the coil part 1V of the V phase. One end of the conduction path 62 is electrically connected to the connection point L between the two switching elements 6C and 6D. The other end of the conduction path 62 is electrically connected to one end of the coil part 1V of the V phase.

[0049] The conduction path 63 of the W phase is the conduction path between the switching elements 6E and 6F and the coil part 1W of the W phase. One end of the conduction path 63 is electrically connected to the connection point L between the two switching elements 6E and 6F. The other end of the conduction path 63 is electrically connected to one end of the coil part 1W of the W phase. Each switch pair 6G, 6H, 6J supplies power to each coil 32A, 32B, 32C via the connection point L and the conduction paths 61, 62, 63. That is, each switch pair 6G, 6H, 6J included in the conversion unit 12 corresponds to each coil 32A, 32B, 32C.

[0050] [Structure of the control unit]

[0051] The control unit 13 is a device that controls the switching unit 11 and the conversion unit 12. The control unit 13 can be, for example, an electronic control device such as an in-vehicle ECU, or an information processing device having an MPU (Micro-Processing Unit). The control unit 13 controls the on / off states of each relay switch (11D, 11E, 11F, 11G, 11H, 11J) that constitutes the switching unit 11 and each switching element 6A, 6B, 6C, 6D, 6E, 6F that constitutes the conversion unit 12. Specifically, the control unit 13 can output an on / off signal C1 to each relay switch (11D, 11E, 11F, 11G, 11H, 11J) and output an on / off signal C2 to each switching element 6A, 6B, 6C, 6D, 6E, 6F. It is configured to be able to input a signal V corresponding to the output voltage of the battery 91 from the battery 91 to the control unit 13. It is configured to be able to input a signal R corresponding to the rotational speed of the rotor from the motor 100 to the control unit 13.

[0052] [Regarding the operation of the switching unit]

[0053] As Figure 2 shown, the first relay switches 11D, 11F, 11H in the switching unit 11 are set to the on state, and the second relay switches 11E, 11G, 11J are set to the off state. Thus, a structure is formed in which the conductive paths 61, 62, 63 and the short - circuit portion 90 are electrically connected via the coil portions 1U, 1V, 1W. In this case, current flows through the coil portions 1U, 1V, 1W, and current does not flow through the coil portions 2U, 2V, 2W. The number of series connections in each of the coils 32A, 32B, 32C at this time is 1. The relationship between torque and speed in the motor 100 in this case changes according to the Figure 5 characteristic shown by the solid line.

[0054] As Figure 3 shown, the first relay switches 11D, 11F, 11H in the switching unit 11 are set to the off state, and the second relay switches 11E, 11G, 11J are set to the on state. Thus, a structure is formed in which the conductive paths 61, 62, 63 and the short - circuit portion 90 are electrically connected via the coil portions 1U, 2U, the coil portions 1V, 2V, and the coil portions 1W, 2W connected in series. In this case, current flows through all the coil portions 1U, 2U, 1V, 2V, 1W, 2W. The number of series connections in each of the coils 32A, 32B, 32C at this time is 2. The relationship between torque and speed in the motor 100 in this case changes according to the Figure 5 characteristic shown by the dotted line. When the number of series connections is 1 or 2, the switching unit 11 becomes an allowable state that allows the supply of power from the battery 91 to the motor 100.

[0055] As Figure 5As shown, among the characteristics of the solid line and the characteristics of the dotted line, in the region where the rotational speed is below the specified rotational speeds Th1 and Th2, the torque represents a constant value. In the characteristics of the dotted line, when the rotational speed exceeds the specified rotational speed Th1, the torque gradually decreases. In the characteristics of the solid line, when the rotational speed exceeds the specified rotational speed Th2, the torque gradually decreases. The specified rotational speed Th1 in the characteristics of the dotted line is smaller than the specified rotational speed Th2 in the characteristics of the solid line. In the characteristics of the dotted line, the region above the specified rotational speed Th1 is the weak magnetic field region Wr1. The maximum rotational speed in the weak magnetic field region Wr1 is Rm1. In the characteristics of the solid line, the region above the specified rotational speed Th2 is the weak magnetic field region Wr2. The maximum rotational speed in the weak magnetic field region Wr2 is Rm2. Here, the maximum rotational speeds Rm1 and Rm2 also include the substantial maximum rotational speeds in the weak magnetic field regions Wr1 and Wr2, and also include the values within the range of ±10% of the substantial maximum rotational speed. The specified rotational speed Th2 is the determination rotational speed in the weak magnetic field region Wr2, and the specified rotational speed Th1 is the determination rotational speed in the weak magnetic field region Wr1. Here, the determination rotational speed is a value preset based on the minimum rotational speed in each of the weak magnetic field regions Wr1 and Wr2. In each of the weak magnetic field regions Wr1 and Wr2, in order to weaken the back electromotive force generated in the motor 100, control is performed to make the current that should flow through each of the coils 32A, 32B, and 32C flow through a bypass path (not shown), and the amount of current flowing through each of the coils 32A, 32B, and 32C is suppressed. That is, the weak magnetic field region is a region where the rotational speed of the motor 100 is increased by weakening the back electromotive force generated in the motor 100.

[0056] Regarding the magnitude of the torque in the region where the torque represents a constant value (the region below the specified rotational speeds Th1 and Th2), the torque of the characteristics of the dotted line is larger. Moreover, the rotational speed of the characteristics of the solid line is wider than that of the characteristics of the dotted line, and the range extends toward the high rotation side. That is, the characteristics of the dotted line are characteristics that can output a larger torque than the characteristics of the solid line. Moreover, the characteristics of the solid line are characteristics that can rotate at a higher rotational speed than the characteristics of the dotted line. Hereinafter, the characteristics of the dotted line will also be referred to as the high torque characteristics, and the characteristics of the solid line will also be referred to as the high rotation characteristics.

[0057] For example, the control unit 13 can perform control to select either the high torque characteristics or the high rotation characteristics according to an instruction signal from an external ECU or the like. In the high torque characteristics, the first relay switches 11D, 11F, and 11H of the switching unit 11 are in the off state, and the second relay switches 11E, 11G, and 11J are in the on state. In the high rotation characteristics, the first relay switches 11D, 11F, and 11H of the switching unit 11 are in the on state, and the second relay switches 11E, 11G, and 11J are in the off state.

[0058] As Figure 4As shown, when the first relay switches 11D, 11F, 11H and the second relay switches 11E, 11G, 11J of the switching unit 11 are set to the off state, the conduction paths 61, 62, 63 and the short-circuit unit 90 are electrically disconnected. In this case, current does not flow through all of the coil units 1U, 2U, 1V, 2V, 1W, 2W. In other words, by setting the first relay switches 11D, 11F, 11H and the second relay switches 11E, 11G, 11J to the off state, the switching unit 11 switches to the cut-off state where the power supply to the motor 100 is cut off. The number of series connections in each of the coils 32A, 32B, 32C at this time is 0. In this way, the switching unit 11 is configured to switch between the allowed state and the cut-off state.

[0059] [Operation of the winding switching device]

[0060] Next, the operation of the winding switching device 10 will be described. First, an ignition switch (not shown) provided in the vehicle is switched from the off state to the on state. Then, the switching unit 11 becomes the allowed state where the power supply from the battery 91 to the motor 100 is allowed. For example, the control unit 13 sets the first relay switches 11D, 11F, 11H to the off state and the second relay switches 11E, 11G, 11J to the on state according to an instruction signal from an external ECU or the like to select the high torque characteristic. Or, the control unit 13 sets the first relay switches 11D, 11F, 11H to the on state and the second relay switches 11E, 11G, 11J to the off state according to an instruction signal from an external ECU or the like to select the high rotation characteristic. And, by stepping on an accelerator (not shown), three-phase AC power is supplied from the battery 91 to the motor 100 via the conversion unit 12. Thereby, the rotor of the motor 100 starts to rotate. Hereinafter, the rotation of the rotor of the motor 100 will also be simply referred to as the rotation of the motor 100.

[0061] After the motor 100 starts to rotate, the control unit 13 executes Figure 6 、 7 the control shown. Figure 6 、 7 The control shown is sequentially executed in the control unit 13. First, in step S1 shown in Figure 6 the control unit 13 determines whether to control the motor 100 according to the high rotation characteristic. For example, the control unit 13 can determine whether it is the high rotation characteristic or the high torque characteristic based on an instruction signal from an external ECU or the like.

[0062] When the control unit 13 determines in step S1 that the motor 100 is to be controlled according to the high rotation characteristic (Yes in step S1), the process proceeds to step S2, and the output voltage of the storage battery 91 is measured. Specifically, the control unit 13 grasps the output voltage of the storage battery 91 based on the signal V. Next, when the process proceeds to step S3, the control unit 13 determines whether the output voltage of the storage battery 91 grasped based on the signal V is lower than the first voltage threshold Thf which is the voltage threshold. The first voltage threshold Thf is stored, for example, in a storage area such as the ROM possessed by the control unit 13. The first voltage threshold Thf is set, for example, to the magnitude of the minimum voltage value required for the motor 100 to rotate according to the high rotation characteristic. In step S3, when the control unit 13 determines that the output voltage of the storage battery 91 is higher than the first voltage threshold Thf (No in step S3), the process proceeds to step S2, and step S2 is executed again.

[0063] In step S3, when the control unit 13 determines that the output voltage of the storage battery 91 is lower than the first voltage threshold Thf (Yes in step S3), the process proceeds to step S4. When the process proceeds to step S4, the control unit 13 determines whether the motor 100 is rotating in the weak magnetic field region Wr2 of the high rotation characteristic. In step S4, when the control unit 13 determines that the motor 100 is rotating in the weak magnetic field region Wr2 of the high rotation characteristic (Yes in step S4), the process proceeds to step S5, and ASC control is executed.

[0064] For example, in step S4, the control unit 13 compares the signal R corresponding to the rotational speed of the rotor with the determination rotational speed Th2 of the weak magnetic field region Wr2. Then, when the signal R is greater than the determination rotational speed Th2 and is below the maximum rotational speed Rm2 of the weak magnetic field region Wr2, the control unit 13 determines that the motor 100 is rotating in the weak magnetic field region Wr2. In the ASC control, the control unit 13 performs the following control: maintaining either one of the switching elements 6A, 6C, 6E that function as the upper arm elements and the switching elements 6B, 6D, 6F that function as the lower arm elements in the ON state, and maintaining the other in the OFF state.

[0065] In addition, in step S4, it may be configured such that, in addition to determining whether the motor 100 is rotating in the weak magnetic field region Wr2, it is also determined whether it is a voltage cut-off state in which the output voltage of the storage battery 91 is cut off due to a failure of the storage battery 91 or the like and rapidly decreases within a specified short period of time. Specifically, in step S4, the control unit 13 determines whether it is rotating in the weak magnetic field region Wr2, or whether the output voltage of the storage battery 91 is in the voltage cut-off state.

[0066] As a method for determining whether the output voltage of the storage battery 91 is in a voltage cut-off state, a configuration is considered in which the control unit 13 acquires the signal V at regular intervals and obtains the difference obtained by subtracting the previously obtained signal V from the latest signal V obtained at regular intervals. For example, when the output voltage of the storage battery 91 decreases, the difference becomes a negative value, and the greater the degree of decrease (i.e., the sharper the decrease in the output voltage), the farther it is from 0. In addition, when the output voltage of the storage battery 91 increases, the difference becomes a positive value, and the greater the degree of increase (i.e., the sharper the increase in the output voltage), the farther it is from 0. In addition, a voltage cut-off threshold is stored in the ROM or the like of the control unit 13. For example, the voltage cut-off threshold is set to a negative value. Then, this difference is compared with the voltage cut-off threshold, and when the difference is less than the voltage cut-off threshold (the difference is greater than the voltage cut-off threshold in the negative direction), it is determined that the output voltage of the storage battery 91 is in the voltage cut-off state.

[0067] Then, in step S4, when either the rotation in the weak magnetic field region Wr2 or the output voltage of the storage battery 91 being in the voltage cut-off state holds, the process proceeds to step S5. As another definition of the voltage cut-off state, it is also possible to consider that the signal V is a ground voltage or a magnitude regarded as a ground voltage. In addition, as the voltage cut-off state, it is also possible to define a state in which both the difference is less than the voltage cut-off threshold and the signal V is a ground voltage or a magnitude regarded as a ground voltage hold.

[0068] Next, when the process proceeds to step S6, the control unit 13 performs control to keep all of the first relay switches 11D, 11F, 11H and the second relay switches 11E, 11G, 11J of the switching unit 11 in the off state. As a result, the switching unit 11 is switched from the allowed state to the cut-off state, the supply of power to the motor 100 is stopped, and the process proceeds to step S7, and the rotational speed of the motor 100 becomes 0 (i.e., the rotation of the rotor stops). In this way, when the output voltage of the storage battery 91 is equal to or lower than the first voltage threshold Thf and the rotational speed of the motor 100 is greater than the determination rotational speed Th2, the control unit 13 keeps either one of the switching elements 6A, 6C, 6E and the switching elements 6B, 6D, 6F in the on state and keeps the other in the off state, and performs control to switch the switching unit 11 from the allowed state to the cut-off state. In addition, regardless of whether it is equal to or lower than the determination rotational speed Th2, when the output voltage of the storage battery 91 is equal to or lower than the first voltage threshold Thf and is in the voltage cut-off state in which the output voltage of the storage battery 91 is cut off, the control unit 13 performs ASC control and switches the switching unit 11 from the allowed state to the cut-off state.

[0069] Before the switching unit 11 switches from the allowed state to the cut-off state in step S6, the control unit 13 maintains either one of the switching elements 6A, 6C, 6E and the switching elements 6B, 6D, 6F in the on state and the other in the off state in step S5.

[0070] In step S4, when the control unit 13 determines that the motor 100 is not rotating in the weak magnetic field region Wr2 of the high rotation characteristic (No in step S4), it transfers to step S8. In the case of No in step S4, the signal R corresponding to the rotational speed of the rotor is equal to or lower than the determination rotational speed Th2. Further, in step S4, when it is also determined whether the output voltage of the storage battery 91 is in the voltage cut-off state, since the motor 100 is not rotating in the weak magnetic field region Wr2 of the high rotation characteristic and the output voltage of the storage battery 91 is not in the voltage cut-off state, it becomes No in step S4.

[0071] When transferring to step S8, a shut-off control for maintaining all the switching elements 6A, 6B, 6C, 6D, 6E, 6F of the conversion unit 12 in the off state is executed, and it transfers to step S7. Thus, when the rotational speed of the motor 100 is lower than the maximum rotational speed Rm2 and is equal to or lower than the determination rotational speed Th2 in the weak magnetic field region Wr2, the control unit 13 executes control for maintaining all the switching elements 6A, 6B, 6C, 6D, 6E, 6F in the off state.

[0072] When the control unit 13 determines in step S1 that the motor 100 is not controlled according to the high rotation characteristic (No in step S1), it transfers to step S9, and the control unit 13 grasps the output voltage of the storage battery 91 based on the signal V. No in step S1 corresponds to the control unit 13 determining that it is the high torque characteristic based on the command signal from the external ECU.

[0073] Next, when transferring to step S10, the control unit 13 determines whether the output voltage of the storage battery 91 grasped based on the signal V is lower than the second voltage threshold Ths which is the voltage threshold. The second voltage threshold Ths is stored in a storage area such as the ROM possessed by the control unit 13, for example. The second voltage threshold Ths is set to the magnitude of the minimum voltage value required for the motor 100 to rotate according to the high torque characteristic, for example. In step S10, when the control unit 13 determines that the output voltage of the storage battery 91 is higher than the second voltage threshold Ths (No in step S10), it transfers to step S9, and step S9 is executed again.

[0074] In step S10, when the control unit 13 determines that the output voltage of the storage battery 91 is lower than the second voltage threshold Ths (Yes in step S10), the process proceeds to step S11. When the process proceeds to step S11, the control unit 13 determines whether the electric motor 100 rotates in the weak magnetic field region Wr1 of the high torque characteristic. In step S11, when the control unit 13 determines that the electric motor 100 is rotating in the weak magnetic field region Wr1 of the high torque characteristic (Yes in step S11), the process proceeds to step S12.

[0075] For example, in step S11, the control unit 13 compares a signal R corresponding to the rotational speed of the rotor with a determination rotational speed Th1 of the weak magnetic field region Wr1. Then, when the signal R is greater than the determination rotational speed Th1 and is equal to or lower than the maximum rotational speed Rm1 of the weak magnetic field region Wr1, the control unit 13 determines that the rotation is in the weak magnetic field region Wr1. When the process proceeds to step S12, the control unit 13 maintains either the switching elements 6A, 6C, 6E that function as upper arm elements and the switching elements 6B, 6D, 6F that function as lower arm elements in the on state, and maintains the other in the off state.

[0076] In addition, in step S11, it may be configured such that, in addition to determining whether the rotation is in the weak magnetic field region Wr1, it is also determined whether the output voltage of the storage battery 91 is in a voltage cut-off state. In this case, in step S11, the control unit 13 determines whether the rotation is in the weak magnetic field region Wr1 or whether the output voltage of the storage battery 91 is in a voltage cut-off state. Then, in step S11, when either one of the rotation in the weak magnetic field region Wr1 and the output voltage of the storage battery 91 being in a voltage cut-off state is satisfied, the process proceeds to step S12.

[0077] Next, when transferring to step S13, the control unit 13 maintains all of the first relay switches 11D, 11F, 11H and the second relay switches 11E, 11G, 11J of the switching unit 11 in the off state. Thereby, the switching unit 11 switches from the permitted state to the cut-off state, stops the supply of power to the motor 100, transfers to step S14, and the rotational speed of the motor 100 becomes 0 (i.e., the rotation of the rotor stops). When the output voltage of the storage battery 91 is equal to or lower than the second voltage threshold Ths and the rotational speed of the motor 100 is greater than the determination rotational speed Th1, the control unit 13 performs the following control: maintains either one of the switching elements 6A, 6C, 6E and the switching elements 6B, 6D, 6F in the on state, and maintains the other in the off state, and switches the switching unit 11 from the permitted state to the cut-off state. In addition, regardless of whether it is equal to or lower than the determination rotational speed Th1, when the output voltage of the storage battery 91 is equal to or lower than the second voltage threshold Ths and is in the voltage cut-off state where the output voltage of the storage battery 91 is cut off, the control unit 13 performs ASC control and switches the switching unit 11 from the permitted state to the cut-off state.

[0078] In step S11, when the control unit 13 determines that the motor 100 is not rotating in the weak magnetic field region Wr1 of the high torque characteristic (''No'' in step S11), it transfers to step S15. In the case of ''No'' in step S11, the signal R corresponding to the rotational speed of the rotor is equal to or lower than the determination rotational speed Th1. In addition, when it is also determined in step S11 whether the output voltage of the storage battery 91 is in the voltage cut-off state, since the motor 100 is not rotating in the weak magnetic field region Wr1 of the high rotational characteristic and the output voltage of the storage battery 91 is not in the voltage cut-off state, it becomes ''No'' in step S11.

[0079] When transferring to step S15, the control unit 13 performs a closing control to maintain all of the switching elements 6A, 6B, 6C, 6D, 6E, 6F of the conversion unit 12 in the off state, and transfers to step S14. Thus, when the rotational speed of the motor 100 is less than the maximum rotational speed Rm1 and is equal to or lower than the determination rotational speed Th1 in the weak magnetic field region Wr1, the control unit 13 performs a control to maintain all of the switching elements 6A, 6B, 6C, 6D, 6E, 6F in the off state. In Figure 6 In the flowchart of, the control unit 13 sets the voltage threshold for comparison with the signal V to either the first voltage threshold Thf or the second voltage threshold Ths according to the connection state of the coil units 1U, 2U, 1V, 2V, 1W, 2W.

[0080] Next, the control performed by the control unit 13 is described. First, in Figure 7 shown is described. First, in Figure 7In step S20 shown above, the control unit 13 determines whether to control the motor 100 according to the high rotation characteristic based on an instruction signal from an external ECU or the like. In step S20, when the control unit 13 determines to control the motor 100 according to the high rotation characteristic (Yes in step S20), it transfers to step S21 to measure the rotational speed of the rotor. Specifically, the control unit 13 grasps the rotational speed of the motor 100 based on the signal R.

[0081] Next, when it transfers to step S22, the control unit 13 determines whether the rotational speed of the rotor grasped based on the signal R is greater than the maximum rotational speed Rm2 in the high rotation characteristic. The maximum rotational speed Rm2 is a rotation threshold. In step S22, when the control unit 13 determines that the rotational speed of the rotor grasped based on the signal R is equal to or less than the maximum rotational speed Rm2 in the high rotation characteristic, it transfers to step S21 and executes step S21 again.

[0082] In step S22, when the control unit 13 determines that the rotational speed of the rotor grasped based on the signal R is greater than the maximum rotational speed Rm2 in the high rotation characteristic (Yes in step S22), it transfers to step S23. When the rotational speed of the rotor is greater than the maximum rotational speed Rm2 in the high rotation characteristic, it is assumed that the rotor rotates due to an external force and a large back electromotive force is generated. When it transfers to step S23, the control unit 13 executes ASC control. The ASC control is as follows: either the switching elements 6A, 6C, 6E that act as upper arm elements and the switching elements 6B, 6D, 6F that act as lower arm elements are maintained in the on state, and the other is maintained in the off state.

[0083] Next, when it transfers to step S24, the control unit 13 maintains all of the first relay switches 11D, 11F, 11H and the second relay switches 11E, 11G, 11J of the switching unit 11 in the off state. Thereby, the switching unit 11 switches from the allowed state to the cut-off state, stops the supply of power to the motor 100, and transfers to step S25, and the rotational speed of the motor 100 becomes 0 (that is, the rotation of the rotor stops). In this way, when the rotational speed of the motor 100 is greater than the maximum rotational speed Rm2 (rotation threshold) in the weak magnetic field region Wr2, the control unit 13 executes control to maintain all of the switching elements 6A, 6B, 6C, 6D, 6E, 6F in the off state.

[0084] In step S20, when the control unit 13 determines that the motor 100 is not being controlled according to the high rotation characteristic ( "No" in step S20), the process proceeds to step S26. "No" in step S20 corresponds to the control unit 13 determining, based on an instruction signal from an external ECU or the like, that control is being performed according to the high torque characteristic. When the process proceeds to step S26, the control unit 13 grasps the rotational speed of the rotor based on signal R. Then, when the process proceeds to step S27, the control unit 13 determines whether the rotational speed of the rotor grasped based on signal R is greater than the maximum rotational speed Rm1 in the high torque characteristic (refer to Figure 5 ). In step S27, when the control unit 13 determines that the rotational speed of the rotor grasped based on signal R is less than the maximum rotational speed Rm1 in the high torque characteristic, the process proceeds to step S26, and step S26 is executed again.

[0085] In step S27, when the control unit 13 determines that the rotational speed of the rotor grasped based on signal R is greater than the maximum rotational speed Rm1 in the high torque characteristic ( "Yes" in step S27), the process proceeds to step S28. The maximum rotational speed Rm1 is a rotation threshold. When the process proceeds to step S28, the control unit 13 executes ASC control, maintaining either one of the switching elements 6A, 6C, 6E and the switching elements 6B, 6D, 6F in the ON state and maintaining the other in the OFF state.

[0086] Then, when the process proceeds to step S29, the control unit 13 maintains all of the first relay switches 11D, 11F, 11H and the second relay switches 11E, 11G, 11J of the switching unit 11 in the OFF state. Thereby, the switching unit 11 is switched from the allowed state to the cut-off state, the supply of power to the motor 100 is stopped, and the process proceeds to step S30, and the rotational speed of the motor 100 becomes 0 (i.e., the rotation of the rotor stops). In this way, when the rotational speed of the motor 100 is greater than the maximum rotational speed Rm1 (rotation threshold) in the weak magnetic field region Wr1, the control unit 13 executes control to maintain all of the switching elements 6A, 6B, 6C, 6D, 6E, 6F in the OFF state. In Figure 7 the flowchart, the control unit 13 sets the rotation threshold for comparison with signal R to either the maximum rotational speed Rm1 or the maximum rotational speed Rm2 according to the connection state of the coil units 1U, 2U, 1V, 2V, 1W, 2W.

[0087] Next, the effects of this structure are illustrated.

[0088] The winding switching device 10 is used in the motor 100. The motor 100 includes polyphase coils 32A, 32B, and 32C. Each of the coils 32A, 32B, and 32C includes a plurality of coil portions 1U, 2U, 1V, 2V, 1W, and 2W. The winding switching device 10 includes: a switching unit 11 that switches the connection states of the plurality of coil portions 1U, 2U, 1V, 2V, 1W, and 2W in each of the coils 32A, 32B, and 32C; and a control unit 13 that controls the switching unit 11. The switching unit 11 is configured to switch between a permission state that permits the supply of power from the storage battery 91 to the motor 100 and a cut-off state that cuts off the supply of power from the storage battery 91 to the motor 100. When the rotational speed of the motor 100 is greater than the maximum rotational speed Rm1 in the high torque characteristic or the maximum rotational speed Rm2 in the high rotation characteristic, or when the output voltage of the storage battery 91 is equal to or lower than the first voltage threshold Thf in the high rotation characteristic or the second voltage threshold Ths in the high torque characteristic, the control unit 13 switches the switching unit 11 from the permission state to the cut-off state.

[0089] According to this configuration, it is possible to prevent sintering or the like of the coil ends of the motor 100 caused by the generation of the back electromotive force in the motor 100 that may occur when the rotational speed of the motor 100 exceeds the conceivable range or when the output voltage of the storage battery 91 is lower than the conceivable range.

[0090] The winding switching device 10 further includes a conversion unit 12, which includes a plurality of switching elements 6A, 6B, 6C, 6D, 6E, and 6F, converts the power from the storage battery 91, and supplies it to the motor 100. The conversion unit 12 has switch pairs 6G, 6H, and 6J. The switch pairs 6G, 6H, and 6J are formed by connecting the switching elements 6A, 6C, 6E and the switching elements 6B, 6D, 6F. The switching elements 6A, 6C, 6E are connected to the high-potential side power path 81 to which the positive electrode voltage of the storage battery 91 is applied, and the switching elements 6B, 6D, 6F are connected to the low-potential side power path 82 to which the negative electrode voltage of the storage battery 91 is applied. Each of the switch pairs 6G, 6H, and 6J corresponds to each of the coils 32A, 32B, and 32C, and power is supplied from the connection point L between the switching elements 6A, 6C, 6E and the switching elements 6B, 6D, 6F to the coils 32A, 32B, and 32C. The control unit 13 switches the switching unit 11 from the permission state to the cut-off state, and sets any one of the switching elements 6A, 6C, 6E and the switching elements 6B, 6D, 6F to the on state and the other to the off state.

[0091] According to this structure, a closed loop can be formed by the motor 100 and the conversion unit 12 without short-circuiting the high-potential side power path 81 and the low-potential side power path 82. Thus, the current generated in the motor 100 can be retained within the closed loop, and the switching unit 11 can be cut off, thereby cutting off the flow of current in the closed loop.

[0092] In the winding switching device 10, before the switching unit 11 switches from the allowed state to the cut-off state, either one of the switching elements 6A, 6C, 6E and the switching elements 6B, 6D, 6F becomes in the on state, and the other becomes in the off state. According to this structure, by forming a closed loop in advance by the motor 100 and the conversion unit 12, it is possible to prevent the back electromotive force generated in the motor 100 from affecting the battery 91 side. Also, by switching the switching unit 11 from the allowed state to the cut-off state, it is possible to prevent the back electromotive force generated in the motor 100 from affecting the respective switching elements 6A, 6B, 6C, 6D, 6E, 6F of the conversion unit 12.

[0093] When the output voltage of the battery 91 is equal to or lower than the first voltage threshold Thf and the second voltage threshold Ths, and the rotational speed of the motor 100 is less than the maximum rotational speed Rm1 or Rm2 and is equal to or lower than the determination rotational speeds Th1, Th2 in the weak magnetic field regions Wr1, Wr2, the control unit 13 controls all of the switching elements 6A, 6B, 6C, 6D, 6E, 6F to be in the off state. When the output voltage of the battery 91 is equal to or lower than the first voltage threshold Thf and the second voltage threshold Ths, and the rotational speed of the motor 100 is greater than the determination rotational speeds Th1, Th2 in the weak magnetic field regions Wr1, Wr2, the control unit 13 sets either one of the switching elements 6A, 6C, 6E and the switching elements 6B, 6D, 6F to be in the on state, sets the other to be in the off state, and switches the switching unit 11 from the allowed state to the cut-off state. According to this structure, by controlling the switching elements 6A, 6B, 6C, 6D, 6E, 6F differently according to the rotational speed of the motor 100, it is possible to perform detailed fault protection for the motor 100 and the conversion unit 12.

[0094] Regardless of whether the rotational speeds are below the determination rotational speeds Th1 and Th2, when the output voltage of the storage battery 91 is equal to or lower than the first voltage threshold Thf and the second voltage threshold Ths and is in a voltage cut-off state in which the output voltage of the storage battery 91 is cut off, the control unit 13 sets either one of the switching elements 6A, 6C, 6E and the switching elements 6B, 6D, 6F to an ON state, sets the other one to an OFF state, and switches the switching unit 11 from an allow state to a cut-off state. Therefore, even if there is a concern that the output voltage of the storage battery 91 becomes a voltage cut-off state, sufficient power cannot be supplied from the storage battery 91 to the electric motor 100, and a situation occurs in which the counter electromotive force generated in the electric motor 100 cannot be resisted, it is possible to reliably perform failure protection of the electric motor 100 and the conversion unit 12.

[0095] The maximum rotational speed Rm1 (rotation threshold) in the high torque characteristic and the maximum rotational speed Rm2 (rotation threshold) in the high rotation characteristic are the maximum rotational speeds of the electric motor 100 in the weak magnetic field regions Wr1 and Wr2. With this configuration, when an excessive counter electromotive force is generated in the electric motor 100, it is possible to suppress the influence of the counter electromotive force from spreading to the electric motor 100, the conversion unit 12, etc.

[0096] The control unit 13 sets either one of the maximum rotational speed Rm1 in the high torque characteristic and the maximum rotational speed Rm2 (rotation threshold) in the high rotation characteristic according to the connection states of the plurality of coil units 1U, 2U, 1V, 2V, 1W, 2W. Further, the control unit 13 sets either one of the first voltage threshold Thf in the high rotation characteristic and the second voltage threshold Ths (voltage threshold) in the high torque characteristic. Therefore, as the connection states of the coil units 1U, 2U, 1V, 2V, 1W, 2W change, the characteristics of the electric motor 100 change. Therefore, by setting the rotation threshold and the voltage threshold according to the connection states of the coil units 1U, 2U, 1V, 2V, 1W, 2W, it is possible to switch the switching unit 11 from an allow state to a cut-off state in a manner that corresponds in detail to the characteristics of the electric motor 100.

[0097] <Other Embodiments>

[0098] It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed this time, but is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0099] Different from the first embodiment, the number of coil units in each coil may also be three or more. Further, the number of turns of each coil may also be different from each other.

[0100] Different from Embodiment 1, the order of the ASC control and the control for switching the switching unit from the allowed state to the cut-off state may also be swapped. Additionally, it may be configured to switch the switching unit from the allowed state to the cut-off state and perform the ASC control.

[0101] If the switching speed of the relay switch of the switching unit is the same as the switching speed of the switching element of the conversion unit, the relay switch of the switching unit and the switching element of the conversion unit may be set to the off state without performing the ASC control.

[0102] Different from Embodiment 1, it may also be configured to execute only Figure 6 the flowchart of Figure 7 and any one of the flowcharts of

[0103] Different from Embodiment 1, all the relay switches of the switching unit may be set to the off state after executing the closing control.

[0104] Reference Numeral Description 1U, 1V, 1W, 2U, 2V, 2W... coil parts 6A, 6C, 6E... switching elements (high-potential side switching elements) 6B, 6D, 6F... switching elements (low-potential side switching elements) 6G, 6H, 6J... switch pairs 10... winding switching device 11... switching unit 11A... first switching unit 11B... second switching unit 11C... third switching unit 11D, 11F, 11H... first relay switches 11E, 11G, 11J... second relay switches 12... conversion unit 13... control unit 32A, 32B, 32C... coils 32D, 32E, 32F... current detection parts 61, 62, 63... conduction paths 81... high-potential side power path 82... low-potential side power path 90... short-circuit part 91... storage battery (power supply unit) 100... motor (polyphase motor) C1, C2... on-off signals D1, D2, D3, D4, D5, D6... freewheeling diodes L... connection point R... signal Rm1…Highest rotational speed (rotation threshold) in high torque characteristics Rm2…Highest rotational speed (rotation threshold) in high rotation characteristics Th1…Specified rotational speed in high torque characteristics (judgment rotational speed in weak magnetic field region) Th2…Specified rotational speed in high rotation characteristics (judgment rotational speed in weak magnetic field region) Thf…First voltage threshold in high rotation characteristics (voltage threshold) Ths…Second voltage threshold in high torque characteristics (voltage threshold) V…Signal Wr1…Weak magnetic field region in high torque characteristics Wr2…Weak magnetic field region in high rotation characteristics.

Claims

1. A winding switching device used in a polyphase motor, the polyphase motor having polyphase coils and each of the coils including a plurality of coil portions, wherein, the winding switching device includes: a switching unit that switches the connection state of the plurality of coil portions in each of the coils; and a control unit that controls the switching unit, the switching unit is configured to switch between a permitted state and a cut-off state, the permitted state permitting the supply of power from a power supply unit to the polyphase motor, and the cut-off state cutting off the supply of power from the power supply unit to the polyphase motor, when the rotational speed of the polyphase motor is greater than a rotational threshold or when the output voltage of the power supply unit is equal to or lower than a voltage threshold, the control unit switches the switching unit from the permitted state to the cut-off state.

2. The winding switching device according to claim 1, wherein, the winding switching device further includes a conversion unit that includes a plurality of switching elements and converts the power from the power supply unit and supplies it to the polyphase motor, the conversion unit has a plurality of switch pairs, each switch pair being formed by connecting a high-potential side switching element and a low-potential side switching element, the high-potential side switching element being connected to a high-potential side power path to which the positive voltage of the power supply unit is applied, and the low-potential side switching element being connected to a low-potential side power path to which the negative voltage of the power supply unit is applied, each of the switch pairs corresponds to each of the coils, and power is supplied to each of the coils from the connection point of the high-potential side switching element and the low-potential side switching element, the control unit switches the switching unit to the cut-off state, and sets either the high-potential side switching element or the low-potential side switching element to an on state and sets the other to an off state.

3. The winding switching device according to claim 2, wherein, before the switching unit is switched to the cut-off state, either the high-potential side switching element or the low-potential side switching element becomes an on state and the other becomes an off state.

4. The winding switching device according to claim 2 or claim 3, wherein, when the output voltage of the power supply unit is equal to or lower than the voltage threshold and the rotational speed of the polyphase motor is less than the rotational threshold and is equal to or lower than a determination rotational speed in a weak magnetic field region, the control unit controls all of the plurality of switching elements to an off state, when the output voltage of the power supply unit is equal to or lower than the voltage threshold and the rotational speed of the polyphase motor is greater than the determination rotational speed, the control unit sets either the high-potential side switching element or the low-potential side switching element to an on state and sets the other to an off state, and switches the switching unit to the cut-off state.

5. The winding switching device according to claim 4, wherein, Regardless of whether it is below the determination rotational speed, when the output voltage of the power supply unit is below the voltage threshold value and in a voltage cut-off state where the output voltage of the power supply unit is cut off, the control unit sets either the high-potential side switching element or the low-potential side switching element to an on state, sets the other to an off state, and switches the switching unit to the cut-off state.

6. The winding switching device according to any one of claims 1 to 3, wherein the rotation threshold is the maximum rotational speed of the polyphase motor in the weak magnetic field region.

7. The winding switching device according to any one of claims 1 to 3, wherein the control unit sets the rotation threshold and the voltage threshold according to the connection states of the plurality of coil units.

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