JP2024115427A - Reluctance Motor - Google Patents

Abstract

[Problem] To provide a technology for realizing a low-cost reluctance motor. [Solution] A reluctance motor includes multiple stators divided in the direction of the rotor's rotation axis, multiple rotors arranged facing each stator, and an output shaft fixed to all of the rotors. In this reluctance motor, the stator coils of each stator are connected in series. [Selected Figure] Figure 1

Description

This specification discloses technology related to reluctance motors.

Patent document 1 discloses a reluctance motor. In the reluctance motor of Patent document 1, the stator coils of each phase (first, second, and third phases) are divided into multiple systems, and each system can be energized independently. In addition, in Patent document 1, the stator coils of the multiple systems of phases (first, second, and third phases) are arranged together, and all of the stator coils are arranged in a row in the circumferential direction of the reluctance motor.

JP 2019-176562 A

The reluctance motor of Patent Document 1 has multiple systems of stator coils that can be energized independently, so it can essentially be considered as multiple reluctance motors connected in series. By having a structure in which multiple reluctance motors are essentially connected in series, Patent Document 1 overcomes the drawback of reluctance motors, which is that "the output torque is smaller than that of a permanent magnet motor of the same size." However, Patent Document 1 requires an inverter for each system, which increases the cost of the reluctance motor. The purpose of this specification is to provide technology that realizes a low-cost reluctance motor.

The first technology disclosed in this specification may be a reluctance motor that includes multiple stators that are divided in the direction of the rotor's rotation axis, multiple rotors that are arranged opposite each of the stators, and an output shaft that is fixed to all of the rotors. In this reluctance motor, the stator coils of each stator may be connected in series.

The second technology disclosed in this specification is a reluctance motor according to the first technology, which may include a switching means capable of switching the number of stator coils to which current is applied when driving the reluctance motor.

The third technology disclosed in this specification is a reluctance motor according to the second technology, and the switching means may reduce the number of energized stator coils as the rotation speed of the reluctance motor increases.

According to the first technology, it is possible to energize multiple stator coils using one inverter. As a result, it is possible to reduce the cost of the reluctance motor compared to the conventional reluctance motor described above, which uses multiple inverters to energize multiple stator coils. In other words, the first technology is capable of driving multiple reluctance motors that are essentially connected in series with one inverter. Furthermore, according to the first technology, it is also possible to reduce the size of the reluctance motor, including the inverter, compared to the conventional reluctance motor.

According to the second technology, the output torque of the reluctance motor can be changed. In other words, the number of reluctance motors to be driven can be changed in a plurality of reluctance motors that are substantially connected in series. In addition, since a conventional reluctance motor has a plurality of stator coils (multiple systems of stator coils) arranged in a group, when one stator coil (one system of stator coils) is energized, an induced current is generated in the stator coils of the other systems that are not energized. Therefore, in a conventional reluctance motor, it is necessary to apply a reverse voltage to the stator coils of the other systems that are not energized in order to cancel the induced current. However, in the reluctance motor disclosed in this specification, multiple stators (stator coils) are arranged in the direction of the rotation axis of the rotor. Therefore, even if the number of stator coils to be energized is switched in the second technology (even if the energization of one or more stator coils is stopped), the generation of induced current in the stator coils that are not energized is suppressed. As a result, it is not necessary to apply a reverse voltage to the stator coils that are not energized in order to cancel the induced current, and power consumption can be reduced.

According to the third technology, a high output torque can be obtained regardless of the rotation speed of the reluctance motor (from low rotation speed to high rotation speed). In a reluctance motor, typically, as the rotation speed increases, induced current is more likely to occur. In other words, as the motor rotation speed increases, the output torque decreases. However, if the number of stator coils that are energized as the motor rotation speed increases, as in the third technology, the total amount of induced current decreases, and the rate at which the output torque decreases decreases. As a result, a high output torque can be obtained even if the motor rotation speed is increased.

1 is a cross-sectional view of a reluctance motor according to a first embodiment. A cross-sectional view taken along line II-II in FIG. 1 shows a circuit diagram of a reluctance motor according to a first embodiment. FIG. 13 is a cross-sectional view of a reluctance motor according to a second embodiment. FIG. 13 shows a circuit diagram of a reluctance motor according to a second embodiment. 4 shows simulation results of the motor rotation speed and output torque in the reluctance motor of the first embodiment. 11 shows simulation results of the motor rotation speed and output torque in the reluctance motor of the second embodiment.

(First embodiment)
A reluctance motor 10 will be described with reference to Figures 1 to 3. As shown in Figure 1, the reluctance motor 10 includes a first stator 22, a first rotor 6, a second stator 28, a second rotor 8, and an output shaft 2. The first stator 22 is cylindrical (see Figure 2), and the first rotor 6 is disposed facing the inside of the first stator 22. Although not shown, the second stator 28 is also cylindrical. The second rotor 8 is disposed facing the inside of the second stator 28. The output shaft 2 is fixed to both the first rotor 6 and the second rotor 8.

The stators 22, 28 and the rotors 6, 8 are arranged in a cylindrical case 4. The first stator 22 and the second stator 28 are fixed to the case 4. The first stator 22 and the second stator 28 are arranged in a divided state in the direction of the rotation axis of the rotors 6, 8 (the rotation axis of the output shaft 2). The reluctance motor 10 can be considered as having two layers of stators (stators 22, 28) and two layers of rotors (rotors 6, 8) arranged in the direction of the rotation axis. The output shaft 2 is rotatably supported by the case 4, and one end of the output shaft 2 protrudes outside the case. A rotated part (a part that transmits the rotation torque of the reluctance motor 10) is attached to the protruding part of the output shaft 2. The thickness (length in the rotation axis direction) of the first stator 22 and the second stator 28 is the same, and the thickness of the first rotor 6 and the second rotor 8 is also the same.

As shown in FIG. 2, the first stator 22 has a plurality of teeth 22u, 22v, and 22w. The teeth 22u, 22v, and 22w are repeatedly arranged in the circumferential direction of the first stator 22 in the order of "teeth 22u, 22v, 22w, 22u, 22v...". The U-phase stator coil 23u is wound around the teeth 22u, the V-phase stator coil 23v is wound around the teeth 22v, and the W-phase stator coil 23w is wound around the teeth 22w (see also FIG. 3). Similarly to the first stator 22, the second stator 28 also has a plurality of teeth 28u, 28v, and 28w, and the U-phase, V-phase, and W-phase stator coils 29u, 29v, and 29w are wound around the teeth 28u, 28v, and 28w (see also FIG. 3). In addition, the stator coils 29u, 29v, and 29w wound around the second stator 28 are separate from the stator coils 23u, 23v, and 23w wound around the first stator 22.

Figure 3 shows a motor system 90 in which a reluctance motor 10 is connected to an inverter 50. As shown in Figure 3, first terminals 20u, 20v, and 20w are connected to one end of stator coils 23u, 23v, and 23w wound around a first stator 22. One of the three first terminals 20u, 20v, and 20w is shown in Figure 1. Second terminals 24u, 24v, and 24w are connected to the other ends of stator coils 23u, 23v, and 23w, respectively. One of the three second terminals 24u, 24v, and 24w is shown in Figure 1. Third terminals 26u, 26v, and 26w are connected to one ends of stator coils 29u, 29v, and 29w, respectively, and the other ends are wired together. One of the three third terminals 26u, 26v, and 26w is shown in Figure 1.

The first terminal 20 is connected to the inverter 50. The inverter 50 includes transistors 54a and 54b connected in series, transistors 56a and 56b connected in series, transistors 58a and 58b connected in series, and a power supply 52. The transistors 54a and 54b, the transistors 56a and 56b, and the transistors 58a and 58b are each connected in parallel to the power supply 52. The first terminal 20u is connected to a midpoint 54m of the transistors 54a and 54b.
The first terminal 20v is connected to a midpoint 56m between the transistors 56a and 56b, and the first terminal 20w is connected to a midpoint 58m between the transistors 58a and 58b.

The second terminal 24u and the third terminal 26u are connected by a wire 40, the second terminal 24v and the third terminal 26v are connected by a wire 42, and the second terminal 24w and the third terminal 26w are connected by a wire 44. That is, the stator coils 23u and 29u, the stator coils 23v and 29v, and the stator coils 23w and 29w are each connected in series.

A switching means 70 and a switch 80 are provided on the wirings 40, 42, and 44. More specifically, the switching means 70 has a transistor 70a and a transistor 70b, with the transistor 70a being connected between the wirings 40 and 42, and the transistor 70b being connected between the wirings 42 and 44. The switch 80 is provided downstream (toward the third terminal 26) of the switching means 70, and has transistors 80u, 80v, and 80w. The transistor 80u is provided on the wiring 40, the transistor 80v is provided on the wiring 42, and the transistor 80w is provided on the wiring 44.

The motor system 90 controls the on/off of the transistors 54a, 54b, 56a, 56b, 58a, and 58b to drive the reluctance motor 10. Specifically, the inverter 50 is used to change the phase of the current flowing between the U phase and the V phase, between the V phase and the W phase, and between the W phase and the U phase to drive the reluctance motor 10.

As described above, the switching means 70 and the switch 80 are provided on the wiring 40, 42, 44. When the transistors 70a, 70b of the switching means 70 are turned on while the reluctance motor 10 is being driven, the wiring 40, 42, and 44 are shorted. At this time, when the transistors 80u, 80v, and 80w of the switch 80 are turned off, the wiring 40, 42, and 44 are connected, and current flows only through the stator coils 23u, 23v, and 23w of the first stator 22. In other words, the reluctance motor 10 is driven only by the stator coils 23u, 23v, and 23w (first stator 22).

On the other hand, when the transistors 70a and 70b of the switching means 70 are turned off while the reluctance motor 10 is being driven, the connection state of the wires 40, 42, and 44 is released. At this time, when the transistors 80u, 80v, and 80w of the switch 80 are turned on, current is supplied to the stator coils 29u, 29v, and 29w through the wires 40, 42, and 44. In other words, the reluctance motor 10 is driven by the stator coils 23u, 23v, and 23w (first stator 22) and the stator coils 29u, 29v, and 29w (second stator 28).

As described above, the reluctance motor 10 can switch between a state in which only the stator coils 23u, 23v, and 23w are energized and a state in which both the stator coils 23u, 23v, and 23w and the stator coils 29u, 29v, and 29w are energized. In other words, the reluctance motor 10 can switch the number of stator coils to be energized. Specifically, in the reluctance motor 10, when the motor rotation speed is equal to or lower than a predetermined value, both the stator coils 23u, 23v, and 23w and the stator coils 29u, 29v, and 29w are energized, and when the motor rotation speed exceeds the predetermined value, only the stator coils 23u, 23v, and 23w are energized. The reluctance motor 10 can switch the number of stator coils to be energized in two stages.

The reluctance motor 10 (motor system 90) can energize two (two types) of stator coils 23u, 23v, 23w and stator coils 29u, 29v, 29w using one inverter 50. Therefore, the reluctance motor 10 requires fewer inverters and is less expensive than a configuration in which two inverters are used to energize two (two types) of stator coils. In addition, the reluctance motor 10 can suppress the generation of induced currents and obtain a high output torque by changing the number of energized stator coils (reducing the number of energized stator coils when driving the motor at high speed).

Second Example
4 and 5, the reluctance motor 100 will be described. The reluctance motor 100 is a modified example of the reluctance motor 10, and differs from the reluctance motor 10 in the number of stators and rotors arranged in the direction of the rotation axis. For the reluctance motor 100, the configurations that are substantially the same as those of the reluctance motor 10 are given the same reference numbers as those of the reluctance motor 10, and descriptions thereof may be omitted.

As shown in FIG. 4, the reluctance motor 100 includes a first stator 22, a first rotor 6, a second stator 28, a second rotor 8, an output shaft 2, a third stator 134, and a third rotor 130. The third stator 134 is cylindrical, and the third rotor 130 is disposed facing the inside of the third stator 134. The output shaft 2 is fixed to the third rotor 130.

In the direction of the rotation axis, the third stator 134 is disposed between the first stator 22 and the second stator 28, and the third rotor 130 is disposed between the first rotor 6 and the second rotor 8. The thickness (length in the direction of the rotation axis) of the first stator 22 and the third stator 134 is equal, and the thickness of the second stator 28 is twice that of the stators 22, 134. Similarly, the first rotor 6 and the third rotor 130 are equal, and the thickness of the second rotor 8 is twice that of the rotors 6, 130.

The reluctance motor 100 can be considered to have three layers of stators (stators 22, 134, 28) and three layers of rotors (rotors 6, 130, 8) arranged in the direction of the rotation axis. The third stator 134, like the stators 22 and 28, has multiple teeth 134u, 134v, 134w, and U-phase, V-phase, and W-phase stator coils 135u, 135v, 135w are wound around each of the teeth 134u, 134v, 134w (see also FIG. 5).

Figure 5 shows a motor system 190 in which a reluctance motor 100 is connected to an inverter 50. Fourth terminals 132u, 132v, and 132w are connected to one end of stator coils 135u, 135v, and 135w wound around the third stator 134, respectively. One of the three fourth terminals 132u, 132v, and 132w is shown in Figure 4. Fifth terminals 136u, 136v, and 136w are connected to the other ends of stator coils 135u, 135v, and 135w, respectively. One of the three fifth terminals 136u, 136v, and 136w is shown in Figure 4.

The fourth terminal 132u is connected to the second terminal 24u by a wire 140. The fourth terminal 132v is connected to the second terminal 24v by a wire 142. The fourth terminal 132w is connected to the second terminal 24w by a wire 144. The fifth terminal 136u is connected to the third terminal 26u by a wire 40. The fifth terminal 136v is connected to the third terminal 26v by a wire 42. The fifth terminal 136w is connected to the third terminal 26w by a wire 44.

A switching means 170 and a switch 180 are provided on the wirings 140, 142, and 144. The switching means 170 has a transistor 170a and a transistor 170b, with the transistor 170a being connected between the wirings 140 and 142, and the transistor 170b being connected between the wirings 142 and 144. The switch 180 is provided downstream (toward the fifth terminal 136) of the switching means 170, and has transistors 180u, 180v, and 180w. The transistor 180u is provided on the wiring 140, the transistor 180v is provided on the wiring 142, and the transistor 180w is provided on the wiring 144.

The function of the switching means 170 is the same as that of the switching means 70, and the function of the switch 180 is the same as that of the switch 80. Therefore, when the transistors 170a and 170b of the switching means 170 are turned on while the reluctance motor 100 is being driven, the wirings 140, 142, and 144 are shorted. At this time, when the transistors 180u, 180v, and 180w of the switch 180 are turned off, the wirings 140, 142, and 144 are connected, and current flows only through the stator coils 23u, 23v, and 23w of the first stator 22. In other words, the reluctance motor 10 is driven only by the stator coils 23u, 23v, and 23w (first stator 22).

In addition, when the transistors 170a and 170b of the switching means 170 are turned off while the reluctance motor 100 is being driven, the wirings 140, 142, and 144 are disconnected. At this time, when the transistors 180u, 180v, and 180w of the switch 180 are turned on, current is supplied to the stator coils 135u, 135v, and 135w through the wirings 140, 142, and 144. When the transistors 70a and 70b of the switching means 70 are turned on and the transistors 80u, 80v, and 80w of the switch 80 are turned off while current is flowing through the stator coils 135u, 135v, and 135w, the wirings 40, 42, and 44 are connected. As a result, no current is supplied to the stator coils 29u, 29v, and 29w, and the reluctance motor 100 is driven by the stator coils 23u, 23v, and 23w (first stator 22) and the stator coils 135u, 135v, and 135w (third stator 134).

On the other hand, when the transistors 70a and 70b of the switching means 70 are turned off and the transistors 80u, 80v, and 80w of the switch 80 are turned on while current is flowing through the stator coils 135u, 135v, and 135w, the wiring 40, 42, and 44 are disconnected. Current is supplied to the stator coils 29u, 29v, and 29w through the wiring 40, 42, and 44, and the reluctance motor 100 is driven by the stator coils 23u, 23v, and 23w (first stator 22), the stator coils 135u, 135v, and 135w (third stator 134), and the stator coils 29u, 29v, and 29w (second stator 28).

The reluctance motor 100 can switch between a state in which current is passed only through stator coils 23u, 23v, and 23w, a state in which current is passed through stator coils 23u, 23v, and 23w and stator coils 135u, 135v, and 135w, and a state in which current is passed through all of stator coils 23u, 23v, and 23w, stator coils 135u, 135v, and 135w, and stator coils 29u, 29v, and 29w.

The reluctance motor 100 can switch the number of stator coils to be energized in three stages. In the reluctance motor 100, when the motor rotation speed is equal to or lower than a first predetermined value, all of the stator coils 23u, 23v, 23w, stator coils 135u, 135v, 135w, and stator coils 29u, 29v, 29w are energized. When the motor rotation speed is greater than the first predetermined value and equal to or lower than a second predetermined value, the stator coils 23u, 23v, 23w and stator coils 135u, 135v, 135w are energized. Then, when the motor rotation speed exceeds the second predetermined value, only the stator coils 23u, 23v, 23w are energized. That is, in the reluctance motor 100, the switching means 70 and 170 are controlled, and the number of stator coils to be energized is reduced as the motor rotation speed increases.

(Simulation result 1)
6 shows the relationship between motor rotation speed and output torque in the reluctance motor 10. The horizontal axis of the graph shows motor rotation speed (rpm), and the vertical axis shows output torque (Nm). The solid line in the graph shows the result of energizing both stator coils 23u, 23v, 23w and stator coils 29u, 29v, 29w, and the dashed line shows the result of energizing only stator coils 23u, 23v, 23w.

As shown in FIG. 6, when current was applied to both stator coils 23u, 23v, and 23w and stator coils 29u, 29v, and 29w (hereinafter referred to as condition A), a constant output torque was obtained up to a motor rotation speed of approximately 3000 rpm. However, when the motor rotation speed exceeded approximately 3000 rpm, a decrease in output torque was confirmed as the motor rotation speed increased. The decrease in output torque is due to the generation of a large amount of induced current as the motor rotation speed increases.

When current was applied only to stator coils 23u, 23v, and 23w (hereinafter referred to as condition B), a constant output torque was obtained up to a motor rotation speed of approximately 5000 rpm. However, the obtained output torque was smaller than that of condition A. This result is due to the fact that condition A drives the reluctance motor 10 using two stator coils (stator coils 23u, 23v, and 23w and stator coils 29u, 29v, and 29w), whereas condition B drives the reluctance motor 10 using only one stator coil (stator coils 23u and 23v).

Even under condition B, when the motor rotation speed exceeded approximately 5,000 rpm, a decrease in output torque was confirmed as the motor rotation speed increased. However, the decrease in output torque was more gradual than under condition A. This result is due to the fact that under condition B, the number of energized stator coils is smaller than under condition A, making it difficult for induced current to occur.

As is clear from FIG. 6, it was confirmed that when the motor rotation speed exceeds approximately 7000 rpm, condition B provides a higher output torque than condition A. As described above, in the reluctance motor 10, when the motor rotation speed is equal to or lower than a predetermined value, current is applied to both stator coils 23u, 23v, 23w and stator coils 29u, 29v, 29w (current is applied under condition A), and when the motor rotation speed exceeds the predetermined value, current is applied only to stator coils 23u, 23v, 23w (current is applied under condition B). Therefore, when the timing (predetermined value) for switching the number of stator coils to be energized in the reluctance motor 10 is set between 5000 and 7000 rpm, a high output torque can be obtained in the range from low rotation speed to high rotation speed.

(Simulation result 2)
7 shows the relationship between motor rotation speed and output torque in reluctance motor 100. The horizontal axis of the graph shows motor rotation speed (rpm), and the vertical axis shows output torque (Nm). The solid line in the graph shows the result of energizing all of stator coils 23u, 23v, 23w, stator coils 135u, 135v, 135w, and stator coils 29u, 29v, 29w, the dashed and dotted line shows the result of energizing stator coils 23u, 23v, 23w and stator coils 135u, 135v, 135w, and the dashed line shows the result of energizing only stator coils 23u, 23v, 23w.

When current is applied to all of stator coils 23u, 23v, 23w, stator coils 135u, 135v, 135w, and stator coils 29u, 29v, 29w (hereinafter referred to as condition C), a constant output torque is obtained up to about 3000 rpm of motor rotation speed, and when the motor rotation speed exceeds about 3000 rpm, a decrease in output torque is confirmed as the motor rotation speed increases. When current is applied to stator coils 23u, 23v, 23w and stator coils 135u, 135v, 135w (hereinafter referred to as condition D), a constant output torque is obtained up to about 5000 rpm of motor rotation speed, and when the motor rotation speed exceeds about 5000 rpm, a decrease in output torque is confirmed as the motor rotation speed increases. In addition, when electricity was applied only to the stator coils 23u, 23v, and 23w (hereinafter referred to as condition E), a constant output torque was obtained up to a motor rotation speed of approximately 10,000 rpm, and it was confirmed that when the motor rotation speed exceeded approximately 10,000 rpm, the output torque decreased as the motor rotation speed increased.

As is clear from FIG. 7, it was confirmed that condition D provides a higher output torque than condition C when the motor rotation speed exceeds approximately 7000 rpm, and condition E provides a higher output torque than condition D when the motor rotation speed exceeds approximately 12000 rpm. In the reluctance motor 100, when the motor rotation speed is equal to or less than a first predetermined value, current is applied under condition C, when the motor rotation speed is greater than the first predetermined value and equal to or less than a second predetermined value, current is applied under condition D, and when the motor rotation speed exceeds the second predetermined value, current is applied under condition D. Therefore, when the timing (first predetermined value) for switching the number of stator coils to be energized from three to two in the reluctance motor 100 is set between 5000 and 7000 rpm, and the timing (second predetermined value) for switching the number of stator coils to be energized from two to one is set between 10000 and 12000 rpm, a high output torque can be obtained in the range from low to high rotation. The reluctance motor 100 has a large number of switching stator coils that are energized, so it can obtain a higher output torque up to a higher rotational speed than the reluctance motor 10.

Other Embodiments
In the above embodiment, an example was described in which the number of energized stator coils is reduced as the motor rotation speed increases. However, the number of energized stator coils may be switched depending on the required output torque. For example, when the required output torque is small, the number of energized stator coils may be reduced even when the motor is driven at a low rotation speed. For example, in the above simulation result 1, when the required output torque is small, the motor may be driven under condition B (energized only one stator coil) when the motor rotation speed is 3000 rpm. Also, for example, in the above simulation result 2, when the required output torque is small, the motor may be driven under condition D (energized two stator coils) or condition E (energized only one stator coil) when the motor rotation speed is 3000 rpm.

In addition, the number of stators (stator coils) divided and arranged in the direction of the rotor's rotation axis is not limited to two or three, but may be four or more.

In the first embodiment, a reluctance motor is described in which the first stator and the second stator are equal in thickness, and the first rotor and the second rotor are also equal in thickness. However, the thicknesses of the first stator and the second stator, and the thicknesses of the first rotor and the second rotor may be different.

In the second embodiment, a reluctance motor in which the thicknesses of the first stator (first rotor), third stator (third rotor), and second stator (second rotor) are in a ratio of "1:1:2" has been described. However, the thicknesses of the first stator (first rotor), third stator (third rotor), and second stator (second rotor) are not limited to the above ratio, and may be, for example, all the same thickness.

Although the embodiments of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Furthermore, the technical elements described in this specification or drawings exert technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings achieves multiple objectives simultaneously, and achieving one of those objectives is itself technically useful.

2: Output shaft 6: First rotor (rotor)
8: Second rotor (rotor)
10: Reluctance motor 22: First stator (one of multiple stators)
28: Second stator (one of the multiple stators)

Claims (3)

A reluctance motor,
a plurality of stators divided in a direction of a rotation axis of the rotor;
A plurality of rotors arranged opposite to each of the stators;
an output shaft fixed to all of the rotors;
A reluctance motor in which the stator coils of each stator are connected in series. 2. A reluctance motor according to claim 1,
A reluctance motor is provided with a switching means capable of switching the number of stator coils to be energized when the reluctance motor is driven. 3. A reluctance motor according to claim 2,
The switching means reduces the number of energized stator coils as the rotation speed of the reluctance motor increases.

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