Control device for pole-number switching electric motor

The present application is based on and claims the benefit of priority from Japanese Patent Application No. 2018-027297 filed on Feb. 19, 2018, the contents of which are hereby incorporated by reference.

The present disclosure relates to a control device of a pole-number switching electric motor.

A control device of a pole-number switching electric motor is known. This kind of control devices includes a control device capable of suppressing torque shock of an electric motor at the time of switching the number of poles.

The present disclosure provides a control device for a pole-number switching electric motor that is able to suppress an increase in the peak value of the current flowing in the stator windings.

As a first disclosure, a control device for a pole-number switching electric motor applied to a system including an electric motor capable of switching a number of poles, and an inverter electrically connected to stator windings of the electric motor; includes: a basic operation unit configured to operate the inverter to control a current amplitude which is magnitude of a current vector flowing in the stator winding, and a switching operation unit configured to operate the inverter to reduce the current amplitude before switching and increase the current amplitude after switching.

The objects described above and other objects, features and advantages of the present disclosure will become more apparent by the following detailed description with reference to the accompanying drawings.

In the accompanying drawings:

FIG. 1 is an overall configuration diagram of an in-vehicle motor control system according to a first embodiment;

FIG. 2 is a diagram illustrating stator windings;

FIG. 3 is a block diagram illustrating vector control performed by a control device;

FIG. 4 is a diagram illustrating a pole number switching point;

FIGS. 5A to 5E are timing diagrams illustrating a pole number switching mode;

FIGS. 6A to 6E are timing diagrams illustrating transition in current amplitude and the like when switching the number of poles;

FIG. 7 is a diagram illustrating an operating point where convergence occurs after switching the number of poles;

FIG. 8 is a flowchart illustrating a procedure of a pole number switching process;

FIGS. 9A to 9F are timing diagrams illustrating a pole number switching mode;

FIGS. 10A to 10E are timing diagrams illustrating a pole number switching mode according to a Comparative Example 1;

FIGS. 11A to 11E are timing diagrams illustrating a pole number switching mode according to a Comparative Example 2;

FIGS. 12A to 12E are timing diagrams illustrating a pole number switching mode according to a second embodiment;

FIG. 13 is a diagram for explaining a minimum torque;

FIG. 14 is a flowchart illustrating a procedure of a pole number switching process;

FIGS. 15A to 15F are timing diagrams illustrating a pole number switching mode;

FIG. 16 is a time chart illustrating a pole number switching mode according to a modified example of a second embodiment;

FIG. 17 is a flowchart illustrating a procedure of a pole number switching process;

FIG. 18 is a diagram illustrating pole number switching points A 1 to A 4 according to a third embodiment;

FIG. 19 is a time chart illustrating a pole number switching mode at point A 2 ;

FIG. 20 is a time chart illustrating a pole number switching mode at point A 3 ;

FIG. 21 is a time chart illustrating a pole number switching mode at point A 4 ;

FIG. 22 is a flowchart illustrating a procedure of a pole number switching process;

FIG. 23 is a time chart illustrating a pole number switching mode according to another embodiment;

FIG. 24 is a time chart illustrating a pole number switching mode according to another embodiment;

FIG. 25 is a time chart illustrating a pole number switching mode according to another embodiment;

FIG. 26 is a time chart illustrating a pole number switching mode according to another embodiment; and

FIG. 27 is a time chart illustrating a pole number switching mode according to another embodiment.

As a conventional control device, for example, JP H08-223999 discloses a control device capable of suppressing torque shock of an electric motor at the time of switching the number of poles. More specifically, for example, at the time of switching from 8 poles to 4 poles, this control device keeps the total torque of the torque corresponding to 8 poles and the torque corresponding to 4 poles constant, and together with gradually decreasing the torque corresponding to 8 poles, gradually increases the torque corresponding to 4 poles.

Even in a case of using the control method described in the above-mentioned patent literature, there is a problem in that the peak value of the voltage generated by the electric motor at the time of switching the number of poles may become large, and the peak value of the current flowing through the stator windings of the electric motor may become large.

First Embodiment

Hereinafter, a first embodiment in which a control device according to the present disclosure is applied to a vehicle such as an electric vehicle, a hybrid vehicle or the like including an electric motor as the main in-vehicle engine will be described with reference to the drawings.

As illustrated in FIG. 1 , the in-vehicle control system includes a motor 10 , an inverter 20 , and a control device 30 .

The motor 10 is a main in-vehicle engine and is capable of transmitting power to the drive wheels 40 . In the present embodiment, the motor 10 is a squirrel-cage induction motor having a switchable number of poles, and more specifically, the number of poles is switchable between 4 poles and 8 poles. Note that an induction electric motor having a switchable number of poles is also called pole changing motor.

In a case where A is an even number of 2 or more and n is an integer of 2 or more, one of A poles and n×A poles is defined as the number of poles before switching, and the other is defined as the number of poles after switching. In a case where m is an integer of 3 or more, the motor 10 has n sets of m-phase stator windings 12 A to 12 F. In this case, the inverter 20 is an n×m phase inverter. In this embodiment, A=2, m=3, and n=2.

As illustrated in FIG. 2 , the stator of the motor 10 includes 6-phase stator windings 12 A to 12 F. These stator windings 12 A to 12 F are provided on the stator so as to be shifted from each other by an electrical angle of 60 degrees.

Returning to the description of FIG. 1 above, the motor 10 is connected to a battery 21 as a DC power source via a six-phase inverter 20 . The inverter 20 includes a serial connection body of upper and lower arm switches. Each switch of the inverter 20 is, for example, a voltage-controlled semiconductor switching element such as an IGBT, an N-channel MOSFET, or the like.

The control system includes a current sensor 22 and a speed sensor 23 . The current sensor 22 detects each phase current flowing in the motor 10 . In FIG. 1 , detected values of currents flowing in the A, B, C, D, E, and F phase stator windings 12 A, 12 B, 12 C, 12 D, 12 E, and 12 F are indicated as Iar, Ibr, Icr, Idr, Ier, and Ifr. The speed sensor 23 detects the mechanical angular frequency ωr of the rotor of the motor 10 . The detected values of the current sensor 22 and the speed sensor 23 are inputted to the control device 30 .

The control device 30 includes a microcomputer and a main component, and operates the inverter 20 in order to perform feedback control of the torque of the motor 10 to the total command torque Tr*. The total command torque Tr* is outputted to the control device 30 from a higher order control device than the control device 30 , such as a control device or the like that oversees traveling control of the vehicle.

The torque control of the motor 10 performed by the control device 30 will be described with reference to FIG. 3 .

The control device 30 includes a command value calculating unit 31 , a 4-pole control unit 32 , an 8-pole control unit 33 , and a coordinate conversion unit 34 .

The command value calculating unit 31 , based on the acquired total command torque Tr* and the mechanical angular frequency ωr, calculates a first d-axis command current Id 4 *, a first q-axis command current Iq 4 *, a second d-axis command current Id 8 *, a second q-axis command current Iq 8 *, a first slip angular frequency ωs 4 as a slip angular frequency corresponding to 4 poles, and a second slip angular frequency ωs 8 as a slip angular frequency corresponding to 8 poles. The command value calculating unit 31 calculates the first d-axis command current Id 4 *, the first q-axis command current Iq 4 *, the second d-axis command current Id 8 *, and the second q-axis command current Iq 8 * so that the added value of the torque of the motor 10 corresponding to 4 poles determined from the first d-axis command current Id 4 * and the first q-axis command current Iq 4 * and the torque of the motor 10 corresponding to 8 poles determined from the second d-axis command current Id 8 * and the second q-axis command current Iq 8 * becomes the total command torque Tr*.

The 4-pole control unit 32 is a current control system of the motor 10 when 4 poles is selected as the number of poles of the motor 10 . The 8-pole control unit 33 is a current control system of the motor 10 when 8 poles is selected as the number of poles of the motor 10 .

First, the 4-pole control unit 32 will be described. A first frequency calculating unit 32 a , based on the mechanical angular frequency ωr and the number of poles P 4 in a case of 4 poles, calculates a first electrical angular frequency ω 4 r as the electrical angular frequency of the motor 10 corresponding to 4 poles.

A first adding unit 32 b adds the first slip angular frequency ωs 4 calculated by the command value calculating unit 31 to the first electrical angular frequency ω 4 r calculated by the first frequency calculating unit 32 a , and outputs the result.

A first angle calculating unit 32 c calculates a first electrical angle θ 4 by integrating the output value of the first adding unit 32 b.

A first dq converting unit 32 d , based on the first electrical angle θ 4 calculated by the first angle calculating unit 32 c , converts the phase currents Iar to Ifr detected by the current sensor 22 into a first d-axis current Id 4 r and a first q-axis current Iq 4 r on the dq axes corresponding to the 4 poles. Here, the d-axis current is an excitation current for generating a secondary magnetic flux, and the q-axis current is a torque current. Moreover, the dq coordinate system corresponding to the 4 poles is an orthogonal two-dimensional rotational coordinate system that rotates at a primary angular frequency that is the rotational angular frequency of the output voltage vector of the inverter 20 .

A first current control unit 32 e , using the first d-axis current Id 4 r converted by the first dq converting unit 32 d as an operation amount for performing feedback control of the first d-axis command current Id 4 * calculated by the command value calculating unit 31 , calculates a first d-axis command voltage Vd 4 * on the d-axis. Moreover, the first current control unit 32 e , using the first q-axis current Iq 4 r converted by the first dq converting unit 32 d as an operation amount for performing feedback control of the first q-axis command current Iq 4 * calculated by the command value calculating unit 31 , calculates a first q-axis command voltage Vq 4 * on the q-axis. Note that the feedback control used by the first current control unit 32 e may be, for example, proportional-plus-integral control.

Next, the 8-pole control unit 33 will be described. A second frequency calculating unit 33 a , based on the mechanical angular frequency ωr and the number of poles P 8 in a case of 8 poles, calculates a second electrical angular frequency ω 8 r as the electrical angular frequency of the motor 10 corresponding to 8 poles.

A second adding unit 33 b adds the second slip angular frequency ωs 8 calculated by the command value calculating unit 31 to the second electrical angular frequency ω 8 r calculated by the second frequency calculating unit 33 a , and outputs the result.

A second angle calculating unit 33 c calculates a second electrical angle θ 8 by integrating the output value of the second adding unit 33 b.

A second dq converting unit 33 d , based on the second electrical angle θ 8 calculated by the second angle calculating unit 33 c , converts the phase currents Iar to Ifr detected by the current sensor 22 into a second d-axis current Id 8 r and a second q-axis current Iq 8 r on the dq axes corresponding to the 8 poles. The dq coordinate system corresponding to 8 poles is an orthogonal two-dimensional rotating coordinate system that rotates at a primary angular frequency corresponding to 8 poles.

A second current control unit 33 e , using the second d-axis current Id 8 r converted by the second dq converting unit 33 d as an operation amount for performing feedback control of the second d-axis command current Id 8 * calculated by the command value calculating unit 31 , calculates a second d-axis command voltage Vd 8 * on the d-axis. Moreover, the second current control unit 33 e , using the second q-axis current Iq 8 r converted by the second dq converting unit 33 d as an operation amount for performing feedback control of the second q-axis command current Iq 8 * calculated by the command value calculating unit 31 , calculates a second q-axis command voltage Vq 8 * on the q-axis. Note that the feedback control used by the second current control unit 33 e may be, for example, proportional-plus-integral control.

The coordinate conversion unit 34 , based on the first d and q command voltages Vd 4 *, Vq 4 * and the first electrical angle θ 4 calculated by the first current control unit 32 e , and the second d and q command voltages Vd 8 *, Vq 8 * and the second electrical angle θ 8 calculated by the second current control unit 33 e , calculates A, B, C, D, E, and F phase command voltages Va*, Vb*, Vc*, Vd*, Ve*, and Vf* in a 6-phase fixed coordinate system.

Incidentally, in a case where 4 poles are selected as the number of poles of the motor 10 , the phase command voltages Va* to VP calculated by the coordinate conversion unit 34 have waveforms that are shifted by 60 degrees each in the order of the A, B, C, D, E and F phases, as in the equation below (Eq1). In the following equation (Eq1), Vm 4 represents the amplitude of the command voltage, t represents time, ω 4 c represents the primary angular frequency, and σ 4 represents the phase of the command voltage.

On the other hand, in a case where 8 poles are selected as the number of poles of the motor 10 , the phase command voltages Va* to Vf* calculated by the coordinate conversion unit 34 have waveforms that are shifted by 120 degrees each in the order of the A, B, C, D. E and F phases, as in the equation below (Eq2). In the following equation (Eq2), Vm 8 represents the amplitude of the command voltage, ω 8 c represents the primary angular frequency, and σ 8 represents the phase of the command voltage.

In a case where it is determined that the mechanical angular frequency cur of the motor 10 is equal to or less than a threshold speed ωth, the command value calculating unit 31 selects 8 poles as the number of poles of the motor 10 , and in a case where the mechanical angular frequency cur exceeds the threshold speed ωth, the command value calculating unit 31 selects 4 poles as the number of poles of the motor 10 . In the present embodiment, as illustrated in FIG. 4 , the threshold speed ωth is set within a range of the mechanical angular frequency ωr that can be obtained when the torque of the motor 10 corresponding to 4 poles is a maximum value.

An operation signal generating unit 35 generates operation signals for setting the voltages to be applied from the inverter 20 to the stator windings 12 A, 12 B, 12 C, 12 D, 12 E, 12 F as the respective phase command voltages Va*, Vb*, Vc*, Vd*, Ve*, Vf*, and outputs the generated operation signals to each of the switches of the inverter 20 . The operation signal generating unit 35 may, for example, generate the operation signals by PWM control based on the magnitude comparison of each phase command voltage and a carrier signal such as a triangular wave signal or the like. In the present embodiment, the 4-pole control unit 32 , the 8-pole control unit 33 , the coordinate conversion unit 34 , and the operation signal generating unit 35 correspond to a basic operation unit and a switching operation unit.

Incidentally, in a case where 4 poles are selected as the number of poles of the motor 10 by the control described above, the phase currents Ia 4 , Ib 4 , Ic 4 , Id 4 , Ie 4 , If 4 given in the following equation (Eq3) flow in the respective the stator windings 12 A, 12 B, 12 C, 12 D, 12 E, 12 F of each phase. In the following equation (Eq3), Im 4 represents the amplitude of the phase current, and α 4 represents the phase of the phase current.

On the other hand, in a case where 8 poles are selected as the number of poles of the motor 10 , the phase currents Ia 8 , Ib 8 , Ic 8 , Id 8 , Ie 8 , If 8 given in the following equation (Eq4) flow in the respective the stator windings 12 A, 12 B, 12 C, 12 D, 12 E, 12 F of each phase. In the following equation (Eq4), Im 8 represents the amplitude of the phase current, and α 8 represents the phase of the phase current.

The command value calculating unit 31 performs a pole number switching process for switching the pole number of the motor 10 from one of 4 poles and 8 poles to the other during the pole number switching period. Hereinafter, the pole number switching process in a case of switching from 8 poles to 4 poles will be described with reference to FIGS. 5A to 5E . In the example illustrated in FIGS. 5A to 5E , 8 poles correspond to the number of poles before switching, and 4 poles correspond to the number of poles after switching.

FIG. 5A illustrates the transition in the 8-pole command amplitude I 8 * and the 4-pole command amplitude I 4 *. The 4-pole command amplitude I 4 * is a square root of a value obtained by adding the squared value of the first d-axis command current Id 4 * and the squared value of the first q-axis command current Iq 4 *. The 8-pole command amplitude I 8 * is a square root of a value obtained by adding the squared value of the second d-axis command current Id 8 * and the squared value of the second q-axis command current Iq 8 *. In FIGS. 5A to 5E , the 8-pole command amplitude I 8 * corresponds to the command amplitude before switching, and the 4-pole command amplitude I 4 * corresponds to the command amplitude after switching. In addition, hereinafter, the square root of the value obtained by adding the squared value of the first d-axis current Id 4 r and the squared value of the first q-axis current Iq 4 r is referred to as the 4-pole current amplitude, and the square root of the value obtained by adding the squared value of the second d-axis current Id 8 r and the squared value of the second q-axis current Iq 8 r is referred to as the 8-pole current amplitude.

FIG. 5B illustrates the transition of the peak value of the phase current flowing in the stator windings of each phase, and FIG. 5C illustrates the transition of the 4-pole secondary magnetic flux φ 4 r and the 8-pole secondary magnetic flux φ 8 r . The 4-pole secondary magnetic flux φ 4 r is a d-axis component of the secondary magnetic flux vector of the motor 10 corresponding to the 4 poles. The 8-pole secondary magnetic flux φ 8 r is a d-axis component of the secondary magnetic flux vector of the motor 10 corresponding to the 8 poles.

FIG. 5D shows the transition in the 4-pole torque Tr 4 , 8-pole torque Tr 8 , and total torque Trt. The 4-pole torque Tr 4 is the torque of the motor 10 corresponding to 4 poles, and the 8-pole torque Tr 8 is the torque of the motor 10 corresponding to 8 poles. The total torque Trt is the total value of the 4-pole torque Tr 4 and the 8-pole torque Tr 8 .

FIG. 5E illustrates the transition in the 4-pole torque change rate dT 4 and the 8-pole torque change rate dT 8 . The 4-pole torque change rate dT 4 is the absolute value of the time derivative of the 4-pole torque Tr 4 , and the 8-pole torque change rate dT 8 is the absolute value of the time derivative of the 8-pole torque Tr 8 .

In FIGS. 5A to 5E , the times t 1 to t 3 indicate the pole number switching period TC. The command amplitude before switching determined from the d and q axis command currents at the start timing t 1 of the pole number switching period TC is referred to as the initial value before switching, and the command amplitude after switching determined from the d and q axis command currents at the end timing of the pole number switching period TC is referred to as the initial value after switching. In a case of switching from 8 poles to 4 poles, the initial value before switching is the 8-pole initial value before switching I 8 f , and the initial value after switching is the 4-pole initial value after switching I 4 f . On the other hand, in a case of switching from 4 poles to 8 poles, the initial value before switching is the 4-pole initial value before switching I 4 f , and the initial value after switching is the 8-pole initial value after switching I 8 f.

In the example illustrated in FIGS. 5A to 5E , the command value calculating unit 31 maintains the 8-pole command amplitude I 8 * at a certain value and sets the 4-pole command amplitude I 4 * to 0 before time t 1 .

The command value calculating unit 31 calculates the 8-pole command amplitude I 8 * and the 4-pole command amplitude I 4 * so that during the pole number switching period TC from time t 1 to time t 3 , the total command amplitude that is the total value of 8-pole command amplitude I 8 * and 4-pole command amplitude I 4 * becomes equal to or less than the limiting current value Imax. This makes it possible to prevent the peak value of the phase current flowing through the stator windings 12 A to 12 F of each phase from becoming excessively large during the pole number switching period TC.

The limiting current value Imax is, for example, a value set to protect the motor 10 from overcurrent. The limiting current value Imax is the larger of the limiting current value corresponding to the number of poles before switching and the limiting current value corresponding to the number of poles after switching. In the present embodiment, the limiting current value corresponding to the number of poles before switching and the limiting current value corresponding to the number of poles after switching have the same value.

At the start timing t 1 of the pole number switching period TC, the command value calculating unit 31 starts decreasing the 8-pole command amplitude I 8 * from the 8-pole initial value before switching I 8 f and increases the 4-pole command amplitude I 4 * from 0 toward the rising current value a in a stepwise manner. In the present embodiment, the rising current value a is the same value as the current margin value that is a value obtained by subtracting the 8-pole initial value before switching I 8 f from the limiting current value Imax. The command value calculating unit 31 increases the 4-pole command amplitude I 4 * in a stepwise manner, and then linearly increases the 4-pole command amplitude I 4 * toward the 4-pole initial value after switching I 4 f , and at the end timing t 3 of the pole number switching period TC, sets the 4-pole command amplitude I 4 * to the 4-pole initial value after switching I 4 f . By increasing the rising current value a in a stepwise manner at the start timing of the pole number switching period TC, the 4-pole secondary magnetic flux φ 4 r is rapidly increased while keeping the total command amplitude equal to or less than the limiting current value Imax. As a result, the 4-pole torque Tr 4 may be rapidly increased, and a decrease in the total torque Trt with respect to the total command torque Tr* may be suppressed during the pole number switching period TC.

Moreover, the command value calculating unit 31 linearly decreases the 8-pole command amplitude I 8 * toward 0, and sets the 8-pole command amplitude I 8 * to 0 at the end timing t 3 of the pole number switching period TC. Note that time t 4 is the timing at which the 4-pole torque Tr 4 becomes a torque corresponding to the 4-pole initial value after switching I 4 f , and the 8-pole torque Tr 8 becomes 0. In FIGS. 5A to 5E , the times t 1 to t 4 are represented as the torque change period Tt.

Each phase command voltage Va* to VP in the pole number switching period TC is an added value of the phase voltages given in the above equations (Eq1) and (Eq2). Moreover, the phase currents flowing in the stator windings 12 A, 12 B, 12 C, 12 D, 12 E, 12 F of the respective phases in the pole number switching period TC are the added values of the phase currents given in the above equations (Eq3) and (Eq4).

Next, the operating point where convergence occurs after switching the number of poles will be described with reference to FIGS. 6A to 6E , and FIG. 7 . 6 A illustrates the transition of the current amplitude; FIG. 6B illustrates the transition of the d-axis current Id; FIG. 6C illustrates the transition of the secondary magnetic flux φd, and FIG. 6D illustrates the transition of the shaft current Iq; and FIG. 6E illustrates the transition of the torque of the motor 10 .

The slip frequency fs of the motor 10 is expressed by the following equation (Eq5). In the following equation (Eq5), M represents a mutual inductance between the rotor winding and the stator windings, Rr represents a secondary resistance that is the resistance of the rotor winding, and Lr represents a secondary inductance that is the self-inductance of the rotor winding.

By modifying the above equation (Eq5), the following equation (Eq6) is derived.

At time t 1 in FIG. 6 , the secondary magnetic flux φd on the d-axis is 0. In a case where the current amplitude is changed in a stepwise manner from 0 to Ia at time t 1 while keeping the slip frequency fs constant, the relationship given in the following equation (Eq7) is derived based on the above equation (Eq6).

According to the equation above (Eq7), when the current amplitude increases in a stepwise manner, the d-axis current Id increases in a stepwise manner. In a case where fs≠0, after the d-axis current Id changes in a stepwise manner, the q-axis current Iq increases according to the equation above (Eq6). When the q-axis current Iq increases, the d-axis current Id decreases due to the relationship of Id=√(Ia{circumflex over ( )}2−Id{circumflex over ( )}2). Therefore, as illustrated in FIGS. 6B, 6D , and FIG. 7 , the operating point determined by the d, q-axis currents Id, Iq converges to the operating point determined by the slip frequency fs and the current amplitude Ia. By changing the current amplitude in a stepwise manner, the speed of increase of the secondary magnetic flux φd may be increased, and the torque response of the motor 10 at the time of switching the number of poles may be improved.

FIG. 8 illustrates the procedure of the pole number switching process according to the present embodiment. This process is repeatedly executed by the command value calculating unit 31 , for example, before a predetermined control cycle.

In step S 10 , it is determined whether a first flag F 1 is 0. The first flag F 1 , when set to a value of 1, indicates that switching from 8 poles to 4 poles has been instructed, and when set to a value of 0, indicates that switching from 8 poles to 4 poles has not been instructed. In this embodiment, the initial value of the first flag F 1 is 0.

In a case where it is determined in step S 10 that the first flag F 1 is 0, the process proceeds to step S 11 , and it is determined whether a second flag F 2 is 0. The second flag F 2 , when set to a value of 1, indicates that switching from 4 poles to 8 poles has been instructed, and when set to a value of 0, indicates that switching from 4 poles to 8 poles has not been instructed. In this embodiment, the initial value of the second flag F 2 is 0.

In a case where it is determined in step S 11 that the second flag F 2 is 0, the process proceeds to step S 12 , and it is determined whether switching from 8 poles to 4 poles is instructed. In a case where an affirmative decision is made in step S 12 , the process proceeds to step S 13 , and the first flag F 1 is set to 1. Moreover, counting of the elapsed time after the instruction to switch from 8 poles to 4 poles starts.

In step S 14 , the 4-pole command amplitude I 4 * is increased in a stepwise manner from 0 to the rising current value a. In this case, the rising current value a is the same as the current margin value that is a value obtained by subtracting the 8-pole initial value before switching I 8 f from the limiting current value Imax. Moreover, the 8-pole command amplitude I 8 * starts to be reduced from the 8-pole initial value before switching I 8 f.

In a case where the process of step S 14 is completed or in a case where it is determined that the first flag F 1 is 1 in step S 10 , the process proceeds to step S 15 . In step S 15 , it is determined whether the elapsed time from the start of counting in step S 13 has passed the pole number switching period TC.

In a case where it is determined in step S 15 that the time has not passed the switching period TC, the process proceeds to step S 16 , and the 4-pole command amplitude I 4 * is gradually increased toward the 4-pole initial value after switching I 4 f . Moreover, the 8-pole command amplitude I 8 * is gradually decreased toward 0. In the present embodiment, in the pole number switching period TC, the 4-pole command amplitude I 4 * is increased with the responsiveness of a time constant τa that is equal to or less than a secondary time constant τ 4 of the motor 10 corresponding to the 4 poles. The secondary time constant is a time constant on the rotor side of the motor 10 and is a time constant of the primary delay element. The secondary time constant depends on the inductance and resistance of the rotor. The secondary time constant τ 4 depends on the rotor temperature, and the pole number switching period TC may be variably set based on the detected value of the rotor temperature.

On the other hand, in a case where it is determined in step S 15 that the pole number switching period TC has elapsed, the process proceeds to step S 17 , the first flag F 1 is set to 0, and the counted elapsed time is reset to 0.

In a case where a negative determination is made in step S 12 , the process proceeds to step S 18 , and it is determined whether switching from 4 poles to 8 poles is instructed. In a case where an affirmative decision is made in step S 18 , the process proceeds to step S 19 , and the second flag F 2 is set to 1. Moreover, counting of the elapsed time after the instruction to switch from 4 poles to 8 poles starts.

In step S 20 , the 8-pole command amplitude I 8 * is increased in a stepwise manner from 0 to the rising current value a. In this case, the rising current value a is a value obtained by subtracting the 4-pole initial value before switching I 4 f from the limiting current value Imax. Moreover, the 4-pole command amplitude I 4 * starts to be reduced from the 4-pole initial value before switching I 4 f.

In a case where the process of step S 20 is completed or in a case where it is determined that the second flag F 2 is 1 in step S 11 , the process proceeds to step S 21 . In step S 21 , it is determined whether the elapsed time from the start of counting in step S 19 has passed the pole number switching period TC.

In a case where it is determined in step S 21 that the time has not passed the pole number switching period TC, the process proceeds to step S 22 , and the 8-pole command amplitude I 8 * is gradually increased toward the 8-pole initial value after switching I 8 f . Moreover, the 4-pole command amplitude I 4 * is gradually decreased toward 0. In the present embodiment, in the pole number switching period TC, the 8-pole command amplitude I 8 * is increased with the responsiveness of a time constant that is equal to or less than a secondary time constant τ 8 of the motor 10 corresponding to the 8 poles.

On the other hand, in a case where it is determined in step S 21 that the pole number switching period TC has elapsed, the process proceeds to step S 23 , the second flag F 2 is set to 0, and the counted elapsed time is reset to 0.

FIGS. 9A to 9F illustrate the transition of each parameter in a case of switching from 8 poles to 4 poles. FIG. 9A illustrates the transition of the total command amplitude that is the total value of the 4-pole command amplitude I 4 * and the 8-pole command amplitude I 8 *, and FIG. 9B illustrates the transition of the 4-pole command amplitude I 4 * and the 8-pole command amplitude I 8 *. FIG. 9C illustrates the transition of the first d-axis current Id 4 r and the first q-axis current Iq 4 r corresponding to 4 poles, and FIG. 9D illustrates the transition of the second d-axis current Id 8 r and the second q-axis current Iq 8 r corresponding to 8 poles. FIG. 9E illustrates the transition in the 4-pole torque Tr 4 , 8-pole torque Tr 8 , and total torque Trt of the motor 10 , and FIG. 9F illustrates the transition in the 4-pole torque change rate dT 4 and the 8-pole torque change rate dT 8 .

According to the present embodiment, the total command amplitude may be suppressed to be equal to or less than the limiting current value Imax in the pole number switching period TC. Therefore, it is possible to prevent the peak value of the phase current flowing in the stator windings from increasing during the pole number switching period TC.

In addition, for example, in the pole number switching period TC, in a case of switching from 8 poles to 4 poles, the 4-pole command amplitude I 4 * is increased with a responsiveness of a value equal to or less than a secondary time constant of the motor 10 corresponding to the pole number after switching. As a result, the 4-pole secondary magnetic flux may be rapidly increased, and the effect of suppressing a decrease in torque of the motor 10 during the pole number switching period TC may be improved.

Moreover, for example, at the start timing of the pole number switching period TC in a case of switching from 8 poles to 4 poles, the 4-pole command amplitude I 4 * is increased in a stepwise manner from 0 to just the rising current value a. As a result, the 4-pole secondary magnetic flux may be increased more quickly, and the effect of suppressing a decrease in the torque of the motor 10 during the pole number switching period TC may be further improved.

On the other hand, in Comparative Example 1 illustrated in FIGS. 10A to 10E and Comparative Example 2 illustrated in FIGS. 11A to 11E , it is not possible to achieve the effect of the present embodiment. Comparative Example 1 has a configuration in which, for example, at the start timing of the pole number switching period TC in a case of switching from 8 poles to 4 poles, the 4-pole command amplitude I 4 * is increased in a stepwise manner beyond Imax-I 8 r . FIGS. 10A to 10E correspond to FIGS. 9A to 9E . In Comparative Example 1, the total command amplitude exceeds the limiting current value Imax in the pole number switching period TC.

Comparative Example 2 Illustrated in FIGS. 11A to 11E has a configuration in which, for example, in a case of switching from 8 poles to 4 poles, the timing at which the 4-pole command amplitude I 4 * is changed in a stepwise manner is delayed compared to the present embodiment. FIGS. 11A to 11E correspond to FIGS. 9A to 9E . In Comparative Example 2, although the total command amplitude may be made to be equal to or less than the limiting current value Imax in the pole number switching period TC, the total torque of the motor 10 is significantly reduced with respect to the total command torque Tr*.

Second Embodiment

Hereinafter, a second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In the present embodiment, the command amplitude after switching is increased in a stepwise manner at the end timing of the pole number switching period TC in addition to the start timing of the pole number switching period TC. Hereinafter, the pole number switching process in a case of switching from 8 poles to 4 poles will be described with reference to FIGS. 12A to 12E . FIGS. 12A to 12E correspond to the previous FIGS. 5A to 5E .

The command value calculating unit 31 calculates the 8-pole command amplitude I 8 * and the 4-pole command amplitude I 4 * so that during the pole number switching period TC from time t 1 to time t 2 , the total command amplitude that is the total value of 8-pole command amplitude I 8 * and 4-pole command amplitude I 4 * becomes equal to or less than the limiting current value Imax.

At the start timing t 1 of the pole number switching period TC, the command value calculating unit 31 starts decreasing the 8-pole command amplitude I 8 * from the 8-pole initial value before switching I 8 f and increases the 4-pole command amplitude I 4 * from 0 toward the rising current value a in a stepwise manner. The rising current value a is a value obtained by subtracting the 8-pole initial value before switching I 8 f from the limiting current value Imax. The command value calculating unit 31 increases the 4-pole command amplitude I 4 * in a stepwise manner and then linearly increases the 4-pole command amplitude I 4 *. The command value calculating unit 31 , at the end timing t 2 of the pole number switching period TC, increases the 4-pole command amplitude I 4 * in a stepwise manner toward the 4-pole initial value after switching I 4 f . In addition, the command value calculating unit 31 , at the end timing t 2 of the pole number switching period TC, decreases the 8-pole command amplitude I 8 * in a stepwise manner toward 0. The 4-pole torque Tr 4 may be quickly increased by the stepwise increase of the 4-pole command amplitude I 4 *, and the 8-pole torque Tr 8 may be quickly reduced by the stepwise decrease of the 8-pole command amplitude I 8 *. As a result, it is possible to quickly switch from 8-pole torque Tr 8 to 4-pole torque Tr 4 while suppressing a decrease in the total torque Trt in the pole number switching period TC. Note that the times t 1 to t 3 indicate the torque change period Tt.

Here, the end timing t 2 of the pole number switching period TC, or in other words, the timing at which the 4-pole command amplitude I 4 * is increased in a stepwise manner is the timing at which the torque of the motor 10 becomes the minimum torque Tmin. In this embodiment, as illustrated in FIG. 13 , the minimum torque Tmin is the minimum value that the total torque Trt (=Tr 4 +Tr 8 ) can take in a case where a condition is imposed that the total command amplitude that is the total value of the 8-pole command amplitude I 8 * and the 4-pole command amplitude I 4 * is set to the limiting current value Imax and the possible combinations of the 8-pole command amplitude I 8 * and the 4-pole command amplitude I 4 * are changed. At the timing when the torque of the motor 10 reaches the minimum torque Tmin, the 4-pole torque change rate dT 4 and the 8-pole torque change rate dT 8 become equal as illustrated in FIG. 12E .

The relationship between the current amplitude and the torque illustrated in FIG. 13 is a relationship in a state in which the 8-pole current amplitude converges to the 8-pole command amplitude I 8 * and the 4-pole current amplitude converges to the 4-pole command amplitude I 4 *, and the total torque Trt converges to the total command torque Tr*.

The change in the 4-pole command amplitude I 4 * in a case of switching from 8 poles to 4 poles will be described using FIG. 13 . In a case where the 8-pole command amplitude I 8 * is the 8-pole initial value before switching I 8 f , the value obtained by subtracting the 8-pole initial value before switching I 8 f from the limiting current value Imax is the rising current value a at the start timing of the pole number switching period TC. In FIG. 13 , the 4-pole command amplitude I 4 * in a case where the total torque Trt is the minimum torque Tmin is indicated by b, and the 8-pole command amplitude I 8 * in a case where the total torque Trt is the minimum torque Tmin is indicated by c.

FIG. 13 illustrates a case where the 4-pole initial value after switching I 4 f becomes the limiting current value Imax. In this case, when the 4-pole command amplitude I 4 * becomes the 4-pole initial value after switching I 4 f , the 8-pole command amplitude I 8 * becomes 0.

FIG. 14 illustrates the procedure of the pole number switching process according to the present embodiment. This process is repeatedly executed by the command value calculating unit 31 , for example, before a predetermined control cycle. Note that, in FIG. 14 , the same processes as the processes illustrated in FIG. 8 above are denoted by the same reference numerals for convenience.

In a case where the process of step S 14 is completed or in a case where it is determined that the first flag F 1 is 1 in step S 10 , the process proceeds to step S 30 . In step S 30 , it is determined whether it is the end timing of the pole number switching period TC. This end timing, as described above, is the timing at which the total torque Trt becomes the minimum torque Tmin. In the present embodiment, in a case where it is determined in step S 13 that the elapsed time from the start of counting has reached the determination time, it is determined to be the end timing of the pole number switching period TC. Here, the determination time is a period from the start timing of the pole number switching period TC to the timing when the total torque Trt is assumed to be the minimum torque Tmin, and may be calculated based on map information in which this period is correlated with the 8-pole initial value before switching I 8 f and the 4-pole initial value after switching I 4 f.

Note that the process of step S 30 may be changed to a process of determining that it is the end timing of the pole number switching period TC in a case where it is determined that the 4-pole command amplitude I 4 * has reached b illustrated in FIG. 13 .

In a case where it is determined in step S 30 that it is not the end timing of the pole number switching period TC, the process proceeds to step S 16 . On the other hand, in a case where it is determined in step S 30 that it is the end timing of the pole number switching period TC, the process proceeds to step S 31 and the 4-pole command amplitude I 4 * is changed in a stepwise manner from b toward the 4-pole initial value after switching I 4 f , and the 8-pole command amplitude I 8 * is decreased in a stepwise manner from c illustrated in FIG. 13 toward 0. In addition, the first flag F 1 is set to 0, and the counted elapsed time is reset to 0.

In a case where the process of step S 20 is completed or in a case where it is determined that the second flag F 2 is 1 in step S 11 , the process proceeds to step S 32 . In step S 32 , it is determined whether it is the end timing of the pole number switching period TC. This end timing, as described above, is the timing at which the total torque Trt becomes the minimum torque Tmin. In the present embodiment, in a case where it is determined in step S 19 that the elapsed time from the start of counting has reached the determination time, it is determined to be the end timing of the pole number switching period TC. Here, the determination time is a period from the start timing of the pole number switching period TC to the timing when the total torque Trt is assumed to be the minimum torque Tmin, and may be calculated based on map information in which this period is correlated with the 4-pole initial value before switching I 4 f and the 8-pole initial value after switching I 8 f.

Note that the process of step S 32 may be changed to a process of determining that it is the end timing of the pole number switching period TC in a case where it is determined that the 8-pole command amplitude I 8 * has reached c illustrated in FIG. 13 .

In a case where it is determined in step S 32 that it is not the end timing of the pole number switching period TC, the process proceeds to step S 22 . On the other hand, in a case where it is determined in step S 32 that it is the end timing of the pole number switching period TC, the process proceeds to step S 33 and the 8-pole command amplitude I 8 * is changed in a stepwise manner from c toward the 8-pole initial value after switching I 8 f , and the 4-pole command amplitude I 4 * is decreased in a stepwise manner from b toward 0. In addition, the second flag F 2 is set to 0, and the counted elapsed time is reset to 0.

FIGS. 15A to 15F illustrate the transition of each parameter in a case of switching from 8 poles to 4 poles. FIGS. 15A to 15F correspond to FIGS. 9A to 9F described above.

According to the present embodiment, the command amplitude after switching is increased in a stepwise manner at the end timing of the pole number switching period TC. Therefore, the effect of suppressing a decrease in torque of the motor 10 in the pole number switching period TC may be further enhanced.

Moreover, the command amplitude after switching is increased in a stepwise manner and the command amplitude before switching is reduced in a stepwise manner at the timing when it is determined that the total torque Trt of the motor 10 has become the minimum torque Tmin. Before the total torque Trt becomes the minimum torque Tmin, the secondary magnetic flux corresponding to the number of poles after switching does not sufficiently increase, and the secondary magnetic flux corresponding to the number of poles before switching does not sufficiently decrease. When the command amplitude after switching is increased in a stepwise manner and the command amplitude before switching is reduced in a stepwise manner in such a state, the increase in torque corresponding to the number of poles after switching is small, and the decrease in torque corresponding to the number of poles before switching is large, so the decrease in torque becomes large. On the other hand, when the command amplitude after switching is increased in a stepwise manner and the command amplitude before switching is reduced in a stepwise manner after the total torque Trt becomes the minimum torque Tmin, the rise of the torque corresponding to the number of poles after switching will be delayed. However, in the present embodiment, the command amplitude after switching is increased in a stepwise manner and the command amplitude before switching is reduced in a stepwise manner at the timing when it is determined that the total torque Trt becomes the minimum torque Tmin. This makes it possible to increase the command amplitude after switching to the initial value after switching corresponding to the number of poles after switching as early as possible while suppressing a decrease in torque during the pole number switching period TC.

Modification of the Second Embodiment

FIG. 16 illustrates a case where the number of poles is changed from 8 poles to 4 poles. As illustrated in FIG. 16 , the period from the start timing t 1 of the pole number switching period TC to the timing t 2 at which the torque of the motor 10 is determined to be the minimum torque Tmin is defined as the specified period Tj. In the period from the end timing t 2 of the specified period Tj to the end timing t 3 of the pole number switching period TC, the command value calculating unit 31 may gradually increase the 4-pole command amplitude I 4 * instead of in a stepwise manner. In this case, in the period TH from time t 2 to time t 3 , the 4-pole command amplitude I 4 * is increased with the responsiveness of the time constant τa of the secondary time constant τ 4 or less of the motor 10 corresponding to the 4 poles.

On the other hand, in the period from the end timing t 2 of the specified period Tj to the end timing t 3 of the pole number switching period TC, the command value calculating unit 31 gradually decreases the 8-pole command amplitude I 8 * instead of in a stepwise manner. In this case, in the period TH from time t 2 to time t 3 , the 8-pole command amplitude I 8 * is decreased with the responsiveness of the time constant τb of the secondary time constant τ 8 or less of the motor 10 corresponding to the 8 poles.

FIG. 17 illustrates the procedure of the pole number switching process according to the present embodiment. This process is repeatedly executed by the command value calculating unit 31 , for example, before a predetermined control cycle. Note that, in FIG. 17 , the same processes as the processes illustrated in FIG. 8 above are denoted by the same reference numerals for convenience.

In a case where the process of step S 14 is completed or in a case where it is determined that the first flag F 1 is 1 in step S 10 , the process proceeds to step S 40 . In step S 40 , it is determined whether it is the end timing of the specified period Tj. This end timing, as illustrated in FIG. 13 , is the timing at which the total torque Trt becomes the minimum torque Tmin. In the present embodiment, it is determined whether the elapsed time from the start of counting in step S 13 has passed the specified period Tj.

In a case where it is determined in step S 40 that it is not the end timing of the specified period Tj, the process proceeds to step S 16 . On the other hand, in a case where it is determined in step S 30 that it is the end timing of the specified period Tj, the process proceeds to step S 41 , and the speed of gradual increase of the 4-pole command amplitude I 4 * changes as illustrated from time t 2 to t 3 in FIG. 16 . The speed of gradual increase of the 4-pole command amplitude I 4 * immediately after the time t 2 is higher than the speed of gradual increase of the 4-pole command amplitude I 4 * immediately before the time t 2 . Further, the speed of gradual decrease of the 8-pole command amplitude I 8 * changes as illustrated from time t 2 to t 3 in FIG. 16 . The speed of gradual decrease of the 8-pole command amplitude I 8 * immediately after the time t 2 increases more than the speed of gradual decrease of the 8-pole command amplitude I 8 * immediately before the time t 2 .

In step S 42 , it is determined whether it is the end timing of the pole number switching period TC. This process is similar to the process of step S 30 in FIG. 14 . In a case where an affirmative determination is made in step S 42 , the process proceeds to step S 17 .

In a case where the process of step S 20 is completed or in a case where it is determined that the second flag F 2 is 1 in step S 11 , the process proceeds to step S 43 . In step S 43 , it is determined whether it is the end timing of the specified period Tj. This end timing, as illustrated in FIG. 13 , is the timing at which the total torque Trt becomes the minimum torque Tmin. In the present embodiment, it is determined whether the elapsed time from the start of counting in step S 19 has passed the specified period Tj.

In a case where it is determined in step S 43 that it is not the end timing of the specified period Tj, the process proceeds to step S 22 . On the other hand, in a case where it is determined in step S 43 that it is the end timing of the specified period Tj, the process proceeds to step S 44 , and the speed of gradual increase of the 8-pole command amplitude I 8 * is changes. Moreover, the speed of gradual decrease of the 4-pole command amplitude I 4 * changes.

In step S 45 , it is determined whether it is the end timing of the pole number switching period TC. This process is similar to the process of step S 32 in FIG. 14 . In a case where an affirmative determination is made in step S 45 , the process proceeds to step S 23 .

According to the present embodiment described above, it is possible to obtain an effect similar to that of the second embodiment.

Third Embodiment

Hereinafter, a third embodiment will be described with reference to the drawings, and focusing on the differences from the first embodiment. In the first embodiment, as illustrated by the first switching point A 1 in FIG. 18 , the number of poles is switched within the range of the mechanical angular frequency (or that is obtained in a case where the torque of the motor 10 corresponding to 4 poles is the maximum value thereof. In the present embodiment, in addition to the first switching point A 1 , the number of poles may be switched at the second to fourth switching points A 2 to A 4 in the range of the mechanical angular frequency (or that is obtained in a case where the torque of the motor 10 corresponding to the 4 poles is less than the maximum value thereof.

A case of switching from 8 poles to 4 poles at the second to fourth switching points A 2 to A 4 will be described with reference to FIG. 19 to FIG. 21 .

FIG. 19 illustrates the transition of the current amplitude in a case where switching is performed at the second switching point A 2 .

The example illustrated in FIG. 19 is a case where the current margin value that is a value obtained by subtracting the 8-pole initial value before switching I 8 f from the limiting current value Imax is smaller than the 4-pole initial value after switching 14 f . At the start timing t 1 of the pole number switching period TC, the command value calculating unit 31 increases the 4-pole command amplitude I 4 * in a stepwise manner by just the rising current value a that is the same value as the current margin value, and after that, gradually increases the 4-pole command amplitude I 4 * until the end timing t 2 of the pole number switching period TC. At this end timing t 2 , the command value calculating unit 31 increases the 4-pole command amplitude I 4 * in a stepwise manner from b to the 4-pole initial value after switching I 4 f . As illustrated in FIG. 13 , b is the 4-pole command amplitude I 4 * in a case where the total torque Trt is the minimum torque Tmin, and will hereinafter be referred to as the 4-pole reference value bopt.

On the other hand, in the pole number switching period TC, the command value calculating unit 31 gradually decreases the 8-pole command amplitude I 8 * from the 8-pole initial value before switching I 8 f toward c, and at time t 2 , decreases the 8-pole command amplitude I 8 * in a stepwise manner toward 0. As illustrated in FIG. 13 , c is the 8-pole command amplitude I 8 * in a case where the total torque Trt is the minimum torque Tmin, and will hereinafter be referred to as the 8-pole reference value copt.

FIG. 20 illustrates the transition of the current amplitude in a case where switching is performed at the third switching point A 3 .

The example illustrated in FIG. 20 is a case where the current margin value that is a value obtained by subtracting the 8-pole initial value before switching I 8 f from the limiting current value Imax is the same as the 4-pole initial value after switching I 4 f . At the start timing t 1 of the pole number switching period TC, the command value calculating unit 31 increases the 4-pole command amplitude I 4 * in a stepwise manner by just the rising current value a that is the same value as the 4-pole initial value after switching I 4 f , and after that, maintains the 4-pole command amplitude I 4 * at the 4-pole initial value after switching I 4 f until the end timing t 2 of the pole number switching period TC. On the other hand, in the pole number switching period TC, the command value calculating unit 31 gradually decreases the 8-pole command amplitude I 8 * from the 8-pole initial value before switching I 8 f toward 0. In the example illustrated in FIG. 20 , b=I 4 f and c =0. By maintaining the 4-pole command amplitude I 4 * at a constant value in the pole number switching period TC, it is possible to suppress torque fluctuations of the motor 10 during the pole number switching period TC.

FIG. 21 illustrates the transition of the current amplitude in a case where switching is performed at the fourth switching point A 4 .

The example illustrated in FIG. 21 is a case where the current margin value that is a value obtained by subtracting the 8-pole initial value before switching I 8 f from the limiting current value Imax is smaller than the 4-pole initial value after switching I 4 f . At the start timing t 1 of the pole number switching period TC, the command value calculating unit 31 increases the 4-pole command amplitude I 4 * in a stepwise manner by just the rising current value a that is the same value as the 4-pole initial value after switching I 4 f , and after that, maintains the 4-pole command amplitude I 4 * at the 4-pole initial value after switching I 4 f until the end timing t 2 of the pole number switching period TC. On the other hand, in the pole number switching period TC, the command value calculating unit 31 gradually decreases the 8-pole command amplitude I 8 * from the 8-pole initial value before switching I 8 f toward 0. In the example illustrated in FIG. 21 , b=I 4 f and c =0.

FIG. 22 illustrates the procedure of the pole number switching process according to the present embodiment. This process is repeatedly executed by the command value calculating unit 31 , for example, before a predetermined control cycle. Note that, in FIG. 22 , the same processes as the processes illustrated in FIG. 14 above are denoted by the same reference numerals for convenience.

In a case where it is determined in step S 10 that the first flag F 1 is 0, the process proceeds to step S 50 , and it is determined whether a third flag F 3 is 0. The third flag F 3 , by the value being set to 1, indicates that switching from 8 poles to 4 poles has been instructed, and that a negative determination has been made in step S 52 described later, and by the value being set to 0, indicates that switching from 8 poles to 4 poles has been instructed, and that an affirmative determination has been made in step S 52 . In this embodiment, the initial value of the third flag F 3 is 0.

In a case where it is determined in step S 50 that the third flag F 3 is 0, the process proceeds to step S 11 . In a case where it is determined in step S 11 that the second flag F 2 is 0, the process proceeds to step S 51 , and it is determined whether a fourth flag F 4 is 0. The fourth flag F 4 , by the value being set to 1, indicates that switching from 4 poles to 8 poles has been instructed, and that a negative determination has been made in step S 59 described later, and by the value being set to 0, indicates that switching from 4 poles to 8 poles has been instructed, and that an affirmative determination has been made in step S 59 . In this embodiment, the initial value of the fourth flag F 4 is 0.

In a case where it is determined in step S 51 that the fourth flag F 4 is 0, the process proceeds to step S 12 . In a case where an affirmative determination is made in step S 12 , the process proceeds to step S 52 . In step S 52 , it is determined whether the current margin value that is a value obtained by subtracting the 8-pole initial value before switching I 8 f from the limiting current value Imax, is greater than or equal to the 4-pole initial value after switching I 4 f.

In a case where a negative determination is made in step S 52 , the process proceeds to step S 53 via step S 13 . In step S 53 , the rising current value a is set to the current margin value calculated in step S 52 , and b=bopt and c=copt.

In a case where the process of step S 53 is completed or in a case where it is determined that the first flag F 1 is 1 in step S 10 , the process proceeds to step S 30 .

In a case where an affirmative decision is made in step S 52 , the process proceeds to step S 54 , and the third flag F 3 is set to 1. Moreover, counting of the elapsed time after the instruction to switch from 8 poles to 4 poles starts.

In step S 55 , the rising current values a and b are set to the 4-pole initial value after switching I 4 f , and c =0.

In a case where the process of step S 55 is completed or in a case where it is determined that the third flag F 3 is 1 in step S 50 , the process proceeds to step S 56 . In step S 56 , it is determined whether it is the end timing of the pole number switching period TC. The process of step S 56 may be performed by the same method as the process of step S 30 .

In a case where a negative determination is made in step S 56 , the process proceeds to step S 57 , where the 4-pole command amplitude I 4 * is maintained at the 4-pole initial value after switching I 4 f , and the 8-pole command amplitude I 8 * is gradually reduced. On the other hand, in a case where an affirmative determination is made in step S 56 , the process proceeds to step S 58 , the third flag F 3 is set to 0, and the counted elapsed time is reset to 0.

In a case where a negative determination is made in step S 12 and an affirmative determination is made in step S 18 , the process proceeds to step S 59 , and it is determined whether the current margin value that is a value obtained by subtracting the 4-pole initial value before switching I 4 f from the limiting current value Imax is equal to or greater than the 8-pole initial value after switching I 8 f.

In a case where a negative determination is made in step S 59 , the process proceeds to step S 60 via step S 19 . In step S 60 , the rising current value a is set to the current margin value calculated in step S 59 , and b=bopt and c=copt.

In a case where the process of step S 60 is completed or in a case where it is determined that the second flag F 2 is 1 in step S 11 , the process proceeds to step S 32 .

In a case where an affirmative decision is made in step S 59 , the process proceeds to step S 61 , and the fourth flag F 4 is set to 1. Moreover, counting of the elapsed time after the instruction to switch from 4 poles to 8 poles starts.

In step S 62 , the rising current values a and b are set to the 8-pole initial value after switching I 8 f , and c =0.

In a case where the process of step S 62 is completed or in a case where it is determined that the fourth flag F 4 is 1 in step S 51 , the process proceeds to step S 63 . In step S 63 , it is determined whether it is the end timing of the pole number switching period TC. The process of step S 63 may be performed by the same method as the process of step S 32 .

In a case where a negative determination is made in step S 63 , the process proceeds to step S 64 , here the 8-pole command amplitude I 8 * is maintained at the 8-pole initial value after switching I 8 f , and the 4-pole command amplitude I 4 * is gradually reduced. On the other hand, in a case where an affirmative determination is made in step S 63 , the process proceeds to step S 65 , the fourth flag F 4 is set to 0, and the counted elapsed time is reset to 0.

According to the present embodiment described above, the command amplitude before switching and the command amplitude after switching in the pole number switching period TC may be appropriately calculated according to the operating point for switching the number of poles.

Other Embodiments

Note that the embodiments described above may be modified and implemented as described below.

The manner of increasing the command amplitude after switching is not limited to a stepwise increase of the command amplitude after switching at the start timing of the pole number switching period TC. Hereinafter, a case of switching from 8 poles to 4 poles will be described as an example with reference to FIG. 23 to FIG. 25 . In the examples illustrated in FIG. 23 to FIG. 25 , in the pole number switching period TC, the total command amplitude is equal to or less than the limiting current value Imax.

As illustrated in FIG. 23 , the command value calculating unit 31 linearly increases the 4-pole command amplitude I 4 * in the period from the start timing t 1 to the time t 2 of the pole number switching period TC. The 4-pole command amplitude I 4 * at time t 2 is a value obtained by subtracting the 8-pole initial value before switching I 8 f from the limiting current value Imax. In the period from time t 2 to the end timing t 3 of the pole number switching period TC, the command value calculating unit 31 linearly increases the 4-pole command amplitude I 4 * at a speed of increase lower than the speed of increase of the 4-pole command amplitude I 4 * in the period of t 1 to t 2 . Here, the period from t 1 to t 2 corresponding to a first period is shorter than the period from t 2 to t 3 corresponding to a second period. By making the speed of increase of the 4-pole command amplitude I 4 * in the period t 1 to t 2 higher than the speed of increase of the 4-pole command amplitude I 4 * in the period t 2 to t 3 , the 4-pole command amplitude I 4 * may be appropriately increased to □Imax−I 8 f at time t 2 . Moreover, by setting the period t 1 to t 2 to be shorter than the period t 2 to t 3 , the secondary magnetic flux φ 4 r of the 4 poles may be rapidly increased. As a result, according to the example illustrated in FIG. 23 , it is possible to suppress a decrease in torque of the motor 10 in the pole number switching period TC.

The example illustrated in FIG. 24 differs from the example illustrated in FIG. 23 in that the manner of increasing the 4-pole command amplitude I 4 * and the manner of decreasing the 8-pole command amplitude I 8 * during the period from t 2 to t 3 are different. More specifically, in the period t 2 to t 3 , the speed of increase of the 4-pole command amplitude I 4 * is gradually decreased and the speed of decrease of the 8-pole command amplitude I 8 * is gradually decreased.

The example illustrated in FIG. 25 differs from the example illustrated in FIG. 23 in that the manner of increasing the 4-pole command amplitude I 4 * and the manner of decreasing the 8-pole command amplitude I 8 * during the period from t 1 to t 2 are different. More specifically, in the period t 1 to t 2 , the speed of increase of the 4-pole command amplitude I 4 * is gradually decreased and the speed of decrease of the 8-pole command amplitude I 8 * is gradually decreased.

In the second embodiment, it is not essential to increase the command amplitude after switching in a stepwise manner at the start timing of the pole number switching period TC. Hereinafter, a case of switching from 8 poles to 4 poles will be described as an example with reference to FIG. 26 .

As illustrated in FIG. 26 , the command value calculating unit 31 linearly increases the 4-pole command amplitude I 4 * in the period from the start timing t 1 to the time t 2 of the pole number switching period TC. The 4-pole command amplitude I 4 * at the time t 2 is the rising current value a described in the second embodiment. In the period from time t 2 to the end timing t 3 of the pole number switching period TC, the command value calculating unit 31 linearly increases the 4-pole command amplitude I 4 * at a speed of increase lower than the speed of increase of the 4-pole command amplitude I 4 * in the period of t 1 to t 2 . Here, the period from t 1 to t 2 is shorter than the period from t 2 to t 3 .

In the second embodiment, it is not essential to increase the command amplitude after switching in a stepwise manner at the end timing of the pole number switching period TC. Hereinafter, a case of switching from 8 poles to 4 poles will be described as an example with reference to FIG. 27 .

Of the pole number switching period TC, the period from the start timing t 1 to t 2 of the period is taken to be a first period, the period from t 2 to t 3 is taken to be a second period, and the period from t 3 to t 4 is taken to be a third period. The first and third periods are shorter than the second period. The command value calculating unit 31 makes the minimum value of the speed of increase of the 4-pole command amplitude I 4 * in each of the first period and the third period higher than the maximum value of the speed of increase of the 4-pole command amplitude I 4 * in the second period. Here, the time t 3 may be the timing when it is determined that the total torque Trt becomes the minimum torque Tmin.

In FIG. 5A of the first embodiment, the amount by which the 4-pole command amplitude I 4 * is increased in a stepwise manner at time t 1 may be less than the value obtained by subtracting the 8-pole initial value before switching I 8 f from the limiting current value Imax. The start timing of increasing the command amplitude after switching may be different from the start timing of decreasing the command amplitude before switching. For example, the start timing of decreasing the command amplitude before switching may be timing after the start timing of increasing the command amplitude after switching. In the pole number switching period TC, the control amount that is controlled so that the total value of the current amplitude before switching and the current amplitude after switching does not exceed the limiting current value Imax is not limited to the current, and for example, may be the applied voltage of the stator windings or It may be the torque of the motor. As the motor, a motor having four or more phases may be used. Also, three or more sets of stator windings may be provided in the stator. When A is an even number of 2 or more, the set of the number of poles of the motor capable of being switched may be a set of A poles and “n×A” poles. Therefore, the set of the number of poles is not limited to a set of 4 poles and 8 poles; for example, when n=2, the set may be 2 poles and 4 poles or may be a set of 8 poles and 16 poles. The number of poles of the motor that may be switched is not limited to two and may be three or more. For example, in the case of a motor that may switch between 4 poles, 8 poles and 16 poles, when switching from one of 4 poles and 8 poles to the other and when switching from one of 8 poles and 16 poles to the other, the pole number switching process described above may be applied. The motor is not limited to the one used as an on-vehicle main motor, and may be, for example, a motor used as an on-vehicle auxiliary motor. Moreover, a system in which a motor and an inverter are provided is not limited to a system mounted in a vehicle.

The present disclosure has been described with reference to exemplary embodiments, however, it is understood that the present disclosure is not limited to such exemplary embodiments and structures. The present disclosure also includes various modifications and modifications within an equivalent range. In addition, various combinations and forms, and furthermore, other combinations and forms including only one element, or more or less than that are also within the scope and spirit of the present disclosure.

(Conclusion)

It is a main object of the present disclosure to provide a control device for a pole-number switching electric motor that is able to suppress an increase in the peak value of the current flowing in the stator windings.

As a first disclosure, a control device for a pole-number switching electric motor applied to a system including an electric motor capable of switching a number of poles, and an inverter electrically connected to stator windings of the electric motor; includes: a basic operation unit that, in a case where a magnitude of a current vector flowing in the stator winding is a current amplitude, and when there is a drive instruction for a number of poles before switching, operates the inverter to control the current amplitude before switching that is the current amplitude corresponding to the number of poles before switching, and when there is a drive instruction for a number of poles after switching, operates the inverter to control the current amplitude after switching that is the current amplitude corresponding to the number of poles after switching; and a switching operation unit that, in a case of an instruction to switch from the number of poles before switching to the number of poles after switching, in a pole number switching period, operates the inverter to reduce the current amplitude before switching and increase the current amplitude after switching; wherein the switching operation unit, in the pole number switching period, operates the inverter so that a total value of the current amplitude before switching and the current amplitude after switching does not exceed a limiting current value.

The basic operation unit of the first disclosure, in a case where there is a drive instruction for the number of poles before switching, operates the inverter to control the current amplitude before switching, and in a case where there is a drive instruction for the number of poles after switching, operates the inverter to control the current amplitude after switching. Moreover, the switching operation unit of the first disclosure, in a case where there is an instruction to switch from the number of poles before switching to the number of poles after switching, in the pole number switching period, operates the inverter to decrease the current amplitude before switching and increase the current amplitude after switching. As a result, the number of poles of the electric motor is switched from the number of poles before switching to the number of poles after switching.

In this case, the switching operation unit, in the pole number switching period, operates the inverter so that the total value of the current amplitude before switching and the current amplitude after switching does not exceed a limiting current value. Therefore, in the pole number switching period, it is possible to suppress an increase in the peak value of the current flowing in the stator windings.

In a second disclosure, in a case where a command value of the current amplitude before switching is taken to be a command amplitude before switching, and a command value of the current amplitude after switching is taken to be a command amplitude after switching, the basic operation unit, when there is a drive instruction for the number of poles before switching, operates the inverter to control the current amplitude before switching to the command amplitude before switching, and when there is a drive instruction for the number of poles after switching, operates the inverter to control the current amplitude after switching to the command amplitude after switching; in a case where the command amplitude after switching at end timing of the pole number switching period is taken to be an initial value after switching, the switching operation unit increases the command amplitude after switching toward the initial value after switching, and decreases the command amplitude before switching toward 0; and in a case where of the pole number switching period, a first period starting from a start timing of that period is taken to be a first period, a period that is a remaining period following the first period and that is longer than the first period is taken to be a second period, the switching operation unit sets a maximum value of a speed of increase of the command amplitude after switching in the first period to be greater than a maximum value of a speed of increase of the command amplitude after switching in a period of the second period that does not include the end timing of the pole number switching period.

The switching operation unit of the second disclosure increases the command amplitude after switching toward the initial value after switching, and decreases the command amplitude before switching toward 0. In this case, the maximum value of the speed of increase of the command amplitude after switching in the first period that is shorter than the second period becomes higher than the maximum value of the speed of increase of the command amplitude after switching in the second period. Therefore, it is possible to rapidly increase the current amplitude after switching from the start timing of the pole number switching period, and it is possible to rapidly increase a secondary magnetic flux corresponding to the number of poles after switching. Accordingly, it is possible to increase the effect of suppressing a drop in torque of the electric motor in the pole number switching period.

In a third disclosure, the switching operation unit, at the start timing of the pole number switching period, increases the command amplitude after switching in a stepwise manner, and then at the end timing of the pole number switching period, gradually increases the command amplitude after switching so that the command amplitude after switching becomes the initial value after switching.

In the third disclosure, the command amplitude after switching is increased in a stepwise manner at the start timing of the pole number switching period. Therefore, it is possible to more rapidly increase the current amplitude after switching from the start timing of the pole number switching period, and it is possible to more rapidly increase the secondary magnetic flux corresponding to the pole number after switching. Accordingly, it is possible to further increase the effect of suppressing a drop in torque of the electric motor in the pole number switching period.