Electric Motor System

Abstract

To provide an electric motor system that can reduce torque shock during switching and suppress backlash while efficiently obtaining high torque performance and output performance over a wide range from a low speed range to a high speed range by switching between series winding and parallel winding.SOLUTION: An electric motor system includes: first to fourth arms connected in parallel to a power supply B and having upper and lower arms; and a bidirectional switch SWα arranged between the second and third arms and switching a bidirectional current flowing through first and second winding parts α1, α2 of a winding α to an on state or an off state. A connection mode is set to a series or parallel winding mode according to on / off states of the bidirectional switch SWα and the upper and lower arms of the first to fourth arms, and a winding switching mode that short-circuits lower arms of the first and second arms and lower arms of the third and fourth arms, respectively, is inserted when switching the connection mode.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an electric motor system configured to switch the connection state of the windings of an electric motor between series windings and parallel windings, and in particular to a method for controlling the switching. [Background technology]

[0002] In recent years, efforts to realize a low-carbon or carbon-free society have been gaining momentum as a measure against global climate change. There is also a strong demand for reducing CO2 emissions from vehicles, and the electrification of power sources is progressing rapidly. It is desirable for electric motors used as power sources to be driven with high efficiency over a wide range of speeds, from low to high. For example, a conventional electric motor system that meets this demand is disclosed in Patent Document 1.

[0003] This electric motor system includes a motor having three-phase windings, and the motor is driven by converting DC power from a power source into three-phase AC power using an inverter and outputting the power to windings of each phase of the motor via a winding switch. The windings are composed of a pair of windings for each phase, and the winding switch is composed of a changeover switch provided for each pair of windings. By connecting the changeover switch to the ON side, the pair of windings for that phase are connected in series, and by connecting the changeover switch to the OFF side, the pair of windings for that phase are connected in parallel. For example, during low-speed operation, the windings are connected in series and the number of turns is increased, while during high-speed operation, the windings are connected in parallel and the number of turns is reduced, thereby improving the efficiency of the motor over a wide operating range. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-205707 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned conventional electric motor system, for example, when switching from series winding to parallel winding, it is possible to perform control (zero current control) to temporarily set the current supplied to the winding to 0 (zero) for a predetermined period in order to avoid the generation of surge voltage due to the sudden opening and closing of the changeover switch, as shown in Fig. 10. However, in that case, since the torque changes across 0, there is a risk of occurrence of teeth rattle noise and vibration due to large torque shock and backlash.

[0006] The present invention has been made to solve these problems, and aims to provide an electric motor system that can efficiently obtain high torque performance and output performance over a wide range from low to high speeds by switching between series windings and parallel windings, while reducing torque shock at the time of switching and suppressing backlash. [Means for solving the problem]

[0007] In order to achieve this object, the invention according to claim 1 provides an electric motor system including an electric motor M having a winding α, a power supply circuit 2 that supplies electric power from a power source B to the electric motor M, and a control device 3 that controls the power supply circuit 2, in which the winding α has a first winding portion α1 and a second winding portion α2, the power supply circuit 2 has first to fourth arms A1 to A4 connected in parallel to the power source M, and a bidirectional switch (first bidirectional switch SWα in the embodiment (hereinafter the same in this section)) that is disposed between the second arm A2 and the third arm A3 and switches a bidirectional current flow passing through the first and second winding portions α1, α2 of the winding α between an ON state and an OFF state, the first to fourth arms A1 to A4 each have upper arms AH1 to AH4 and lower arms AL1 to AL4 that have switching elements and are connected in series to each other, One end and the other end of α1 are connected between the upper arms AH1, AH2 and the lower arms AL1, AL2 of the first and second arms A1, A2, respectively, and one end and the other end of the second winding portion α2 are connected between the upper arms AH3, AH4 and the lower arms AL3, AL4 of the third and fourth arms A3, A4, respectively. The control device 3 sets the connection mode of the winding α to a series winding mode or a parallel winding mode depending on the on / off state of the bidirectional switch and the on / off states of the upper and lower arms of the first to fourth arms, and controls the power supply circuit 2 to insert a winding switching mode in which the lower arms AL1, AL2 of the first and second arms A1, A2 and the lower arms AL3, AL4 of the third and fourth arms A3, A4 are short-circuited when the bidirectional switch is off (FIGS. 4 and 5).

[0008] According to this configuration, by turning on the bidirectional switch and controlling the upper arm of the first arm and the lower arm of the fourth arm to the on state, or by controlling the lower arm of the first arm and the upper arm of the fourth arm to the on state, a current flows through the first winding portion and the second winding portion in series with each other, thereby realizing a series winding mode. In this series winding mode, a current flows through the series winding with a larger number of turns, so that torque can be generated efficiently with a smaller current, and high torque performance can be obtained in the low rotation range.

[0009] On the other hand, by controlling the bidirectional switch to the off state and the upper arm of the first arm, the lower arm of the second arm, the upper arm of the third arm, and the lower arm of the fourth arm to the on state, current flows through each of the first winding section and the second winding section, which are in a parallel state with each other, and a parallel winding mode is realized. In this parallel winding mode, current flows through each of the pair of parallel windings, so that a larger output can be generated with a larger overall current, and high output performance can be obtained in the high rotation range.

[0010] According to the present invention, when switching the winding connection mode, a winding switching mode is inserted in which the lower arms of the first and second arms and the lower arms of the third and fourth arms are short-circuited while the bidirectional switch is in the OFF state. As a result, the first and second lower arms are short-circuited to form a closed circuit including the first winding section, and the third and fourth lower arms are short-circuited to form a closed circuit including the second winding section. As a result, during the winding switching mode, the current that had been supplied flows in the same direction through each closed circuit, so that no counter electromotive force is generated and the torque of the motor is controlled not to cross 0. As a result, it is possible to reduce torque shock and suppress backlash when switching the connection mode.

[0011] The invention of claim 2 is characterized in that, in the motor system described in claim 1, the operating region of the motor M is divided into a predetermined first operating region (orthogonal region) in which the current command value iαβ_ref, which commands the current to be supplied to the winding α, is set to an equal value between the series winding mode and the parallel winding mode, and a predetermined second operating region (field-weakening region) in which the current command value iαβ_ref is set to different values ​​between the series winding mode and the parallel winding mode, and the control device 3 switches the connection mode of the winding α (Figure 8) on the condition that the motor M is in the first operating region.

[0012] According to this configuration, the current command value is kept unchanged and the same before and after switching the winding connection mode, and accordingly the actual current value of the winding is also kept approximately the same, thereby reliably avoiding torque shock.

[0013] The invention of claim 3 is characterized in that, in the motor system described in claim 2, the threshold values ​​(first threshold value Nth1, second threshold value Nth2) for determining whether or not to switch the connection mode of the winding α are set to have hysteresis characteristics in the first operating region (Figures 4 and 8).

[0014] According to this configuration, it is possible to reduce the frequency of switching of the connection mode while maintaining the effect of reliably avoiding torque shock when switching the connection mode. [Brief description of the drawings]

[0015] [Figure 1] It is a block diagram showing a schematic configuration of an electric motor system according to an embodiment of the present invention.It is a circuit diagram of a power supply circuit. [Diagram 2] FIG. 2 is a diagram showing a configuration of an electric motor. [Diagram 3] FIG. 2 is a circuit diagram showing a configuration of a power supply circuit. [Figure 4] 4 is a flowchart showing a winding switching control process executed by the control device. [Diagram 5] 1A and 1B are diagrams illustrating the operation of a power supply circuit in (a) a series winding mode, (b) a winding switching mode, and (c) a parallel winding mode. [Figure 6] 5 is a timing chart showing an example of an operation obtained by the winding switching control process of FIG. 4. [Figure 7] FIG. 2 is a control block diagram showing a current control executed by a control device. [Figure 8] 11 is a map showing a current command value difference between the series winding mode and the parallel winding mode, together with a region division between an orthogonal region and a field weakening region, and a threshold value used for determining switching of the connection mode. [Figure 9]1A is a diagram showing an example of operation before and after switching of a winding connection mode obtained by an embodiment, and FIG. 1B is a diagram showing a comparative example. [Figure 10] FIG. 1 is a diagram illustrating an example of control of a power supply circuit according to a conventional technique. [Figure 11] 3 is a diagram showing a configuration of an electric motor different from that in FIG. 2, and a connection relationship between windings of the electric motor and a power supply circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] A preferred embodiment of the present invention will be described in detail below with reference to the drawings. As shown in Figures 1 and 2, an electric motor system 1 to which the present invention is applied includes an electric motor M (hereinafter referred to as "motor M"), a power supply circuit 2 that supplies power from a power source B to the motor M to drive it, and a control device 3 that controls the power supply circuit 2.

[0017] As shown in FIG. 2, motor M is a two-phase synchronous motor including rotor 10, stator 11, and an α-phase winding α and a β-phase winding β wound around stator 11. The α-phase winding α and the β-phase winding β (hereinafter simply referred to as "winding α" and "winding β", respectively) are arranged with an electrical angle difference of 90° from each other. The winding α has a first winding portion α1 and a second winding portion α2, and the winding β has a third winding portion β1 and a fourth winding portion β2. The first to fourth winding portions α1, α2, β1, and β2 have the same number of turns.

[0018] 3, the power supply circuit 2 is configured with an inverter circuit that converts power input from a DC power source B into AC power and outputs it to the motor M. The power supply circuit 2 includes a first circuit 3 for an α phase that is connected to the power source B and connected to the winding α (first and second winding portions α1, α2) of the motor M, and a second circuit 4 for a β phase that is connected to the power source B in parallel with the first circuit 3 and connected to the winding β (third and fourth winding portions β1, β2) of the motor M.

[0019] The first circuit 3 has first to fourth arms A1 to A4 connected in parallel to a power source B, and a first bidirectional switch SWα disposed between the second arm A2 and the third arm A3.

[0020] The first to fourth arms A1 to A4 have the same configuration. Specifically, the first arm A1 is composed of an upper arm AH1 and a lower arm AL1. Both arms AH1 and AL1 are composed of, for example, a switching element and a free wheel diode in parallel with each other, and are connected in series with each other via a midpoint P1. Similarly, the second arm A2 has the same configuration as the upper and lower arms AH1 and AL1, and is composed of an upper arm AH2 and a lower arm AL2 connected in series with each other via a midpoint P2, the third arm A3 is composed of an upper arm AH3 and a lower arm AL3 connected in series with each other via a midpoint P3, and the fourth arm A4 is composed of an upper arm AH4 and a lower arm AL4 connected in series with each other via a midpoint P4.

[0021] As shown in FIG. 3, one end of the first winding section α1 of the motor M is connected to a midpoint P1 of the first arm A1, the other end of the first winding section α1 is connected to a midpoint P2 of the second arm A2, one end of the second winding section α2 is connected to a midpoint P3 of the third arm A3, and the other end of the second winding section α2 is connected to a midpoint P4 of the fourth arm A4.

[0022] As is clear from the above configuration, the upper and lower arms AH1, AL1 of the first arm A1 and the upper and lower arms AH2, AL2 of the second arm A2 constitute a first H-bridge circuit HC1, and the direction of the current flowing through the first winding portion α1 is switched by appropriately switching the on / off state of the switching elements of the first H-bridge circuit HC1. Similarly, the upper and lower arms AH3, AL3 of the third arm A3 and the upper and lower arms AH4, AL4 of the fourth arm A4 constitute a second H-bridge circuit HC2, and the direction of the current flowing through the second winding portion α2 is switched by appropriately switching the on / off state of the switching elements of the second H-bridge circuit HC2.

[0023] Although not shown, the first bidirectional switch SWα is, for example, two sets of circuits each composed of a parallel switching element and a diode connected in series in the opposite directions, and the bidirectional flow of current passing through the first bidirectional switch SWα can be switched between an ON state and an OFF state by controlling the switching of the two sets of switching elements. The first bidirectional switch SWα is disposed between the above-mentioned first H-bridge circuit HC1 and second H-bridge circuit HC2, more specifically, between the midpoint P2 of the second arm A2 and the midpoint P3 of the third arm A3.

[0024] The second circuit 4 is configured similarly to the above-mentioned first circuit 3, and will be described briefly below. The second circuit 4 has fifth to eighth arms A5 to A8 connected in parallel to a power source B, and a second bidirectional switch SWβ disposed between a sixth arm A6 and a seventh arm A7.

[0025] The fifth to eighth arms A5 to A8 have the same configuration as each other, and are composed of, for example, upper arms AH5 to AH8 constituted by switching elements and free wheel diodes connected in parallel to each other, and lower arms AL5 to AL8 having a configuration similar to that of the upper arms AH5 to AH8 and connected in series to the upper arms AH5 to AH8 via midpoints P5 to P8, respectively.

[0026] As shown in FIG. 2, one end of the third winding portion β1 of the motor M is connected to a midpoint P5 of the fifth arm A5, the other end of the third winding portion β1 is connected to a midpoint P6 of the sixth arm A6, one end of the fourth winding portion β2 is connected to a midpoint P7 of the seventh arm A7, and the other end of the fourth winding portion β2 is connected to a midpoint P8 of the eighth arm A8.

[0027] The upper and lower arms AH5 and AL5 of the fifth arm A5 and the upper and lower arms AH6 and AL6 of the sixth arm A6 constitute a third H-bridge circuit HC3, and the direction of the current flowing through the third winding portion β1 is switched by appropriately switching the on / off state of the switching elements of the third H-bridge circuit HC3. Similarly, the upper and lower arms AH7 and AL7 of the seventh arm A7 and the upper and lower arms AH8 and AL8 of the eighth arm A8 constitute a fourth H-bridge circuit HC4, and the direction of the current flowing through the fourth winding portion β2 is switched by appropriately switching the on / off state of the switching elements of the fourth H-bridge circuit HC4.

[0028] The second bidirectional switch SWβ is, for example, similar to the first bidirectional switch SWα, configured by connecting two sets of circuits, each of which is made up of a parallel switching element and a diode, in series in the opposite directions. By controlling the switching of the two sets of switching elements, it is possible to switch the bidirectional flow of current passing through the second bidirectional switch SWβ between an ON state and an OFF state. The second bidirectional switch SWβ is disposed between the third H-bridge circuit HC3 and the fourth H-bridge circuit HC4, more specifically, between the midpoint P6 of the sixth arm A6 and the midpoint P7 of the seventh arm A7.

[0029] The control device 3 is composed of a microcomputer (ECU) having a CPU, RAM, ROM, and an input / output interface (none of which are shown). Signals representing the torque (motor torque) Tq of the motor M, the rotation speed (motor rotation speed) Nm, the angular velocity ω, and the winding current values ​​Iα1, Iα2, Iβ1, and Iβ2 flowing through each winding portion of the windings α and β are input to the control device 3 from various sensors (not shown) and the like. In response to these signals, the control device 3 determines the connection mode of the windings α and β of the motor M according to a control program stored in the ROM, controls the switching of the windings according to the connection mode, and controls the motor M by executing PWM control on the power supply circuit 2.

[0030] 4 shows a winding switching control process executed by the control device 3. This process is executed at every PWM period (for example, 100 μs). In this process, first, in step 1 (shown as "S1"; the same applies below), it is determined whether or not the series winding mode flag F_S is "1". As will be described later, the series winding mode flag F_S is set to "1" when the motor rotation speed Nm is lower than a threshold value and the connection mode of the windings α and β is the series winding mode.

[0031] When the determination result in step 1 is YES, in step 2, it is determined whether or not the motor rotation speed Nm is greater than a first threshold value Nth1 that is set as described below. When the determination result is NO, in step 3, the connection mode of the windings α and β is set to the series winding mode, and this process is terminated.

[0032] As shown in Fig. 5(a) for an example of the α-phase, in the series winding mode, the first bidirectional switch SWα is turned on, the first upper arm AH1 and the fourth lower arm AL4 are turned on, and the other upper and lower arms are turned off. This causes power to be supplied to the first winding section α1 and the second winding section α2, which are connected in series with each other. In this way, in the series winding mode, current flows through the series winding with a larger number of turns, so that torque can be generated efficiently with a smaller current, and high torque performance can be obtained in the low rotation range.

[0033] Returning to FIG. 4, when the judgment result in step 2 is YES, that is, when the motor rotation speed Nm exceeds the first threshold value Nth1 during the series winding mode, it is determined that the mode should be switched to the parallel winding mode, so in step 4, the series winding mode flag F_S is set to "0", and in step 5, the winding switching mode is selected as the temporary connection mode for the windings α and β only at the time of switching, and this process is terminated.

[0034] As shown in FIG. 5(b) for an example of the α-phase, in this winding switching mode, the first bidirectional switch SWα is turned off, the first to fourth upper arms AH1 to AH4 are all turned off, and the first to fourth lower arms AL1 to AL4 are all turned on. As a result, the first and second lower arms AL1 and AL2 are short-circuited to form a first closed circuit C1 including the first winding portion α1, and the third and fourth lower arms AL3 and AL4 are short-circuited to form a second closed circuit C2 including the second winding portion α2. As a result, during the winding switching mode, the currents that have been supplied until then flow in the same direction through the first and second closed circuits C1 and C2, respectively, so that no counter electromotive force is generated and the motor torque Tq is controlled not to cross 0 (see FIG. 6). As a result, it is possible to reduce torque shock and suppress backlash when switching the connection mode.

[0035] Returning to Fig. 4, after steps 3 and 4 are executed, if the result of the determination in step 1 is NO, then in step 6 it is determined whether or not the motor speed Nm is smaller than a second threshold value Nth2, which is set as described below. The second threshold value Nth2 is smaller than the first threshold value Nth1, and constitutes a hysteresis region together with the first threshold value Nth1. If the result of the determination in step 6 is NO, then in step 7 the connection mode of the windings α and β is set to the parallel winding mode, and this process is terminated.

[0036] As shown in Fig. 5(c) for an example of the α-phase, in this parallel winding mode, the first bidirectional switch SWα is turned off, the first upper arm AH1, the second lower arm AL2, the third upper arm AH3, and the fourth lower arm AL4 are turned on, and the other upper and lower arms are turned off. This causes power to be supplied to the first winding section α1 and the second winding section α2, which are in parallel with each other. In this way, in the parallel winding mode, currents flow through each of the pair of parallel windings, so that a larger output can be generated with a larger overall current, and high output performance can be obtained in the high rotation range.

[0037] 4, when the determination result in step 6 is YES, that is, when the motor rotation speed Nm falls below the second threshold value Nth2 during the parallel winding mode, it is determined that the mode should be switched to the series winding mode, and in step 8, the series winding mode flag F_S is set to "1", and in step 9, the winding switching mode is selected as a temporary connection mode for the windings α and β only during switching, and this process ends. The control content in this winding switching mode is the same as that in the winding switching mode in step 5 described above.

[0038] Figure 6 shows the simulation results when the connection mode of the windings α and β is switched from the series winding mode to the parallel winding mode in the winding switching control of Figure 4. The main simulation conditions are motor speed Nm = 3150 rpm, motor torque Tq = 57 Nm, and switching frequency = 10 kHz (PWM period = 100 μs).

[0039] As shown in the figure, according to the simulation results, in the series winding mode, the actual d-axis current value id_act and the q-axis current value iq_act change near their current command values ​​(target values) id_ref and iq_ref, and the motor torque Td changes at a relatively stable positive value. When it is determined that the mode should be switched from this state to the parallel winding mode, the above-mentioned control in the winding switching mode is executed for a short period of one PWM cycle (=100 μs). Accordingly, in the winding switching mode, the actual d-axis current value id_act increases with respect to the current command value id_ref, and the actual q-axis current value iq_act changes slightly with respect to the current command value iq_ref. It was also confirmed that the motor torque Td only decreases slightly and does not reach 0. After that, when the mode is switched to the parallel winding mode, it was confirmed that the actual d-axis current value id_act, the actual q-axis current value iq_act, and the motor torque Tq return to the levels of the series winding mode in a short time (about 1 ms after the transition).

[0040] Next, the control of the motor M in the series winding mode and the parallel winding mode executed by the control device 3 will be described with reference to the control block diagram of Fig. 7. Starting from the left side of the figure, the control device 3 searches for a current map 31 stored in a ROM according to the input motor torque Tq and motor rotation speed Nm.

[0041] The current map 31 is composed of a map for the series winding mode and a map for the parallel winding mode (neither is shown). Each map divides the region defined by the motor torque Tq and the motor speed Nm into a field-weakening region on the high rotation side where the field-weakening control of the motor M should be performed and an orthogonal region on the low rotation side where normal control, not field-weakening control, should be performed (see FIG. 8), and for many combinations of the motor torque Tq and the motor speed Nm, average values ​​of currents to be supplied to the windings α and β when the corresponding motor control (normal control or field-weakening control) is performed in the corresponding connection mode (series winding mode or parallel winding mode) are obtained in advance, and are mapped as winding current command values ​​iαβ_refs and iαβ_refp for the series winding mode and the parallel winding mode.

[0042] In the series winding mode, the back electromotive force is larger than in the parallel winding mode, so the orthogonal region is narrower. In addition, when in the orthogonal region, the winding current command values ​​iαβ_refs and iαβ_refp in the series winding mode and the parallel winding mode are constant and set to the same value regardless of the motor rotation speed Nm under the condition that the motor torque Tq is constant.

[0043] Based on the current map 31 set as above, a winding current command value iαβ_ref is calculated according to the motor torque Tq and the motor rotation speed Nm, and a d-axis current command value id_ref and a q-axis current command value iq_ref are calculated based on the winding current command value iαβ_ref. The current controller 32 calculates a d-axis voltage Vd and a q-axis voltage Vq by feedback control using PI control based on the d-axis and q-axis current command values ​​id_ref, iq_ref and the actual d-axis current value id and q-axis current value iq calculated as described below.

[0044] Next, the d-axis voltage Vd and the q-axis voltage Vq are subjected to a rotational coordinate transformation to calculate the winding voltages Vα and Vβ. The PWM controller 33 performs PWM control in response to the winding voltages Vα and Vβ, and outputs a drive signal to the power supply circuit 2, thereby controlling the operation of the motor M.

[0045] The d-axis current value id and q-axis current value iq used in the above-mentioned PI control are calculated as follows. First, the rotation angle θ is calculated by integrating the detected angular velocity ω of the motor M. Then, the detected current values ​​Iα1, Iα2 of the first and second winding sections α1, α2 and the detected current values ​​Iβ1, Iβ2 of the third and fourth winding sections β1, β2 are averaged to calculate current average values ​​Iα_ave, Iβ_ave. Then, the calculated rotation angle θ and current average values ​​Iα_ave, Iβ_ave are used to perform a rotational coordinate transformation to calculate the d-axis current value id and the q-axis current value iq.

[0046] Next, a method for setting the first and second thresholds Nth1 and Nth2 of the motor rotation speed Nm used in the winding switching control of FIG. 4 will be described with reference to FIG. 8. As described above, the current map 31 of FIG. 7 is composed of a map in which the winding current command value iαβ_refs for the series winding mode is set and a map in which the winding current command value iαβ_refp for the parallel winding mode is set in the region formed by the motor torque Tq and the motor rotation speed Nm. The map of FIG. 8 shows the difference Δiαβ_ref (=iαβ_refs-iαβ_refp) between the two current command values ​​in the same Tq-Nm region as these two maps. FIG. 8 also shows the division between the orthogonal region and the field weakening region in the series winding mode, the boundary between the two regions in the parallel winding mode is shown by a dashed line, and the first and second thresholds Nth1 and Nth2 are shown by a solid line and a dotted line, respectively.

[0047] As described above, the orthogonal region is narrower in the series winding mode than in the parallel winding mode. In addition, in the orthogonal region, under the same condition of the motor torque Tq, the winding current command values ​​iαβ_refs and iαβ_refp in the series winding mode and the parallel winding mode are constant regardless of the motor rotation speed Nm and are set to the same value. Therefore, in the orthogonal region, the current command value difference Δiαβ_ref becomes 0. In addition, as shown in FIG. 8, the first threshold value Nth1 is set on the high rotation side close to the boundary with the field weakening region in the orthogonal region in the series winding mode, and the second threshold value Nth2 is set on the low rotation side smaller by a predetermined value than the first threshold value Nth1 in the orthogonal region.

[0048] As described above, when the motor rotation speed Nm crosses the first or second threshold value Nth1 or Nth2 set in this manner, the connection mode is switched between the series winding mode and the parallel winding mode. Therefore, as shown in FIG. 9(a), the current command value iαβ_ref is kept unchanged and is the same before and after the switching of the connection mode, and accordingly, the actual current value iαβ_act of the winding α is also kept approximately the same, thereby making it possible to reliably avoid a torque shock. In contrast, FIG. 9(b) shows a conventional example in which the current command value iαβ_ref changes before and after the switching of the connection mode. In this case, the actual current value iαβ_act of the winding changes significantly according to the current command value iαβ_ref, and a torque shock may occur.

[0049] Furthermore, since a hysteresis region is formed by the first and second threshold values ​​Nth1, Nth2, it is possible to suppress the frequency of switching the connection mode between the series winding mode and the parallel winding mode.

[0050] The present invention is not limited to the embodiment described above, and can be embodied in various aspects. For example, instead of the motor system 1 of FIG. 2 and FIG. 3, an electric motor system 51 shown in FIG. 11 may be used. The two electric motor systems 1 and 51 have different circuit configurations of the motor M. Specifically, as shown in FIG. 2, in the motor M of the electric motor system 1, the first and second winding portions α1 and α2 are wound around a pair of teeth of the stator 11 facing each other, and the third and fourth winding portions β1 and β2 are wound around the other pair of teeth. In contrast, as shown in FIG. 11, in the motor M of the electric motor system 51, the first and second winding portions α1 and α2 are wound around only one of the pair of teeth of the stator 11, and the third and fourth winding portions β1 and β2 are wound around only one of the other pair of teeth. On the other hand, the configuration of the power supply circuit 2 in the electric motor system 51 and the connection relationship between the windings of the motor M and the power supply circuit 2 are the same as those in the electric motor system 1.

[0051] The electric motor system 51 configured as described above is electrically equivalent to the electric motor system 1, and therefore can similarly obtain the above-described operations and effects of the electric motor system 1. For example, as described above, by switching the on / off states of the first and second bidirectional switches SWα, SWβ and controlling the on / off states of the first to eighth upper arms AH1-AH8 and the first to eighth AL1-AL8 of the first to fourth H-bridge circuits HC1-HC4, the connection mode of the windings α, β can be switched between the series winding mode or the parallel winding mode.

[0052] When switching between these connection modes, the first and second bidirectional switches SWα and SWβ are turned off, the first to eighth upper arms AH1 to AH8 of the first to fourth H-bridge circuits HC1 to HC4 are all turned off, and the first to eighth lower arms AL1 to AL8 are turned on, so that the connection mode of the windings α and β is temporarily switched to a winding switching mode in which the lower arms AL1 and AL2 of the first and second arms A1 and A2, the lower arms AL3 and AL4 of the third and fourth arms A3 and A4, the lower arms AL5 and AL6 of the fifth and sixth arms A5 and A6, and the lower arms AL7 and AL8 of the seventh and eighth arms A7 and A8 are short-circuited. This similarly provides the effects of reducing torque shock and suppressing backlash when switching the connection mode.

[0053] Furthermore, although the embodiment is an example of a two-phase winding, the present invention may be applied to an electric motor system having a single-phase or three or more phase winding. In addition, although the winding method is concentrated winding for one pole pair in the embodiment, it may be distributed winding instead, and the number of pole pairs is not limited. Furthermore, the specific configurations shown in the embodiment, such as the configurations of the first and second bidirectional switches SWα and SWβ, are merely examples, and other appropriate configurations may be adopted. Other detailed configurations may be changed within the scope of the spirit of the present invention. [Explanation of symbols]

[0054] 1. Electric motor system 2 Power supply circuit 3. Control device 51 Electric Motor System M Electric motor B power supply α α-phase winding (winding) α1 First winding part of winding α α2 Second winding part of winding α β β-phase winding (winding) SWα 1st bidirectional switch (bidirectional switch) A1~A4 1st~4th Arms AH1~AH4 Upper arms of arms 1~4 AL1~AL4 Lower arms of 1st~4th arms Nth1 First threshold (threshold) Nth2 Second threshold (threshold) iαβ_ref Winding current command value

Claims

1. A motor system including a motor having a winding, a power supply circuit that supplies power from a power source to the motor, and a control device that controls the power supply circuit, the winding has a first winding portion and a second winding portion, The power supply circuit includes: first to fourth arms connected in parallel to the power source; a bidirectional switch disposed between the second arm and the third arm for switching bidirectional current flow through the first and second winding portions of the winding to an on state or an off state; each of the first to fourth arms includes an upper arm and a lower arm having a switching element and connected in series with each other; one end and the other end of the first winding portion are connected between the upper arm and the lower arm of the first and second arms, respectively, and one end and the other end of the second winding portion are connected between the upper arm and the lower arm of the third and fourth arms, respectively; the control device sets a connection mode of the windings to a series winding mode or a parallel winding mode depending on an on / off state of the bidirectional switch and an on / off state of the upper and lower arms of the first to fourth arms, and controls the power supply circuit to insert a winding switching mode in which the lower arms of the first and second arms, and the lower arms of the third and fourth arms, are short-circuited, when the winding connection mode is switched, with the bidirectional switch in an off state.

2. 2. The electric motor system according to claim 1, wherein an operating region of the electric motor is divided into a predetermined first operating region in which a current command value, which commands a current to be supplied to the windings, is set to an equal value between the series winding mode and the parallel winding mode, and a predetermined second operating region in which the current command value is set to different values ​​between the series winding mode and the parallel winding mode, and the control device switches the connection mode of the windings on condition that the electric motor is in the first operating region.

3. 3. The electric motor system according to claim 2, wherein a threshold value for determining whether or not the winding connection mode can be switched is set to have a hysteresis characteristic in the first operating region.

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