Motor

Abstract

The motor includes: a stator; a rotor rotatable about an axis relative to the stator, the rotor having a permanent magnet; at least one shorting ring axially displaceable by a distance D between a first position and a second position, where the shorting ring is farther from the rotor in the first position than in the second position, and where the induced magnetic flux of the permanent magnets decreases when the at least one shorting ring is displaced towards the second position; and at least one actuator assembly actuating the at least one shorting ring to move from the first position to the second position.

Description

[0001] The present application relates to an electric motor, which comprises: a stator; a rotor rotatable relative to the stator about an axis, the rotor having a permanent magnet; at least one short-circuit ring, which can be axially displaced a distance D between a first position and a second position, wherein the short-circuit ring is farther away from the rotor in the first position than in the second position, and wherein when the at least one short-circuit ring is displaced to the second position, the induced magnetic flux of the permanent magnet is reduced; and at least one actuator assembly, which actuates the at least one short-circuit ring to shift from the first position to the second position.

[0002] Permanent magnet motors are known to provide high torque density and efficiency. The induced back EMF of a permanent magnet motor increases with speed, typically reaching the voltage limit of the inverter at base speed. In order to maintain a constant back EMF, it is known to weaken the flux linkage from the permanent magnets, which can be achieved by, for example, adjusting the relative position of the active and / or passive parts of the motor.

[0003] In US 8390232 B2, a permanent magnet motor is disclosed, wherein the rotor or stator has at least one movable iron segment. When the movable iron segment moves away from the rotor or stator, respectively, the magnetic field of the motor is weakened. When the movable iron segment is in a first position (such as in contact with the rotor or stator), the magnetic field strength is high. When the movable iron segment is in a second position (wherein the movable iron segment moves away from the rotor or stator), the magnetic field strength is low. The ability to weaken the magnetic field strength results in an increase in the constant power speed ratio, and therefore increases the practicality of the motor in applications requiring a wide speed range. The motor can be used as a permanent magnet motor and a generator.

[0004] In CN 102170211 B, a variable excitation permanent magnet synchronous motor is disclosed. The variable excitation permanent magnet synchronous motor comprises a stator and a rotor mounted on the motor shaft, wherein each side of the rotor has a set of weak magnetic adjustment mechanisms; the weak magnetic adjustment mechanism comprises soft iron plates arranged on both sides of the rotor and coaxial with the rotor; a spring is arranged between the rotor and the soft iron plate; and a connecting rod counterweight mechanism is arranged corresponding to each soft iron plate. The advantage of the variable excitation permanent magnet synchronous motor is that as the speed changes, the distance between the rotor and the soft iron plate is automatically and correspondingly adjusted, thereby changing the magnetic flux path, achieving the purpose of controlling the motor excitation intensity to decrease as the speed increases, and thereby increasing the maximum operating speed of the motor.

[0005] JPH11275787A discloses a motor with high torque and large constant output operating range. The rotor has a rotor body, a flux barrier, a permanent magnet embedded in the flux barrier, a slit portion extending from an area between the ends of adjacent flux barriers to an area near the rotor end surface, a flux channel member arranged in the slit portion, and a spring for moving the flux channel member arranged at the slit portion. The flux channel member can move in the slit portion, and when the rotor rotates at a low speed, it is in a gap position where no magnetic flux flows to the flux channel member. When the rotor rotates at a high speed, the flux channel member protrudes from the gap portion, and a flux short-circuit portion is formed at the slit portion, so that a weak magnetic field effect and high torque can be obtained regardless of whether the rotor rotates at a high speed.

[0006] An object may be to provide an electric motor with a less complex adjustment mechanism which is at least as reliable and durable as the prior art.

[0007] The object is achieved by an electric motor, which comprises: a stator; a rotor rotatable relative to the stator about an axis, the rotor having a permanent magnet; at least one short-circuit ring, the short-circuit ring being axially displaceable by a distance D between a first position and a second position, wherein the short-circuit ring is farther from the rotor in the first position than in the second position. When the at least one short-circuit ring is displaced to the second position, the induced magnetic flux of the permanent magnet is reduced. At least one actuator assembly hydraulically actuates the at least one short-circuit ring to shift from the first position to the second position according to the rotation speed of the rotor.

[0008] As an advantage, the motor allows field weakening, thereby increasing the motor speed for a given voltage after the motor's maximum power is reached. Field weakening allows the motor to reach higher speeds and lower torques at the motor's maximum power.

[0009] The electric machine may also be referred to as a permanent magnet machine or a permanent magnet motor, which may also be used as a generator. According to one embodiment, two axially displaceable short-circuit rings are provided, one at each axial end of the rotor, wherein the axial distance D between the corresponding first position and the corresponding second position is. Both short-circuit rings can be hydraulically actuated by a common actuator assembly. According to another embodiment, each of the two short-circuit rings is assigned an actuator assembly for hydraulic actuation. The distance D from the first position to the second position may be between one percent and ten percent of the axial length or diameter of the rotor, and shifting the at least one short-circuit ring from the first position to the second position will reduce the induced magnetic flux of the permanent magnet by at least 5%. According to another embodiment, the at least one short-circuit ring extends to cover the magnet section of the rotor, where the permanent magnet is located. The at least one short-circuit ring may be made of a magnetizable material.

[0010] According to another embodiment, the at least one actuator assembly rotates with the rotor about the axis. The actuator assembly may be firmly coupled to the rotor. Thus, the at least one actuator assembly may advantageously be passively controlled by centrifugal forces acting on the rotating actuator assembly.

[0011] According to another embodiment, the at least one actuator assembly has at least one cavity and a fluid in the cavity, the cavity being arranged so that the fluid is centrifuged radially outward from the axis by the centrifugal force of rotating the actuator assembly. At least one piston may be hydraulically connected to the radially outward end of the cavity. The hydraulic force generated by the centrifugal force acting on the fluid is transmitted to the short-circuit ring through the piston. The piston and the short-circuit ring may be integrally formed as a single-piece component.

[0012] According to another embodiment, the at least one cavity forms a closed hydraulic system, the volume of which is changed by the movement of a piston, wherein the piston can move in the axial direction. The at least one cavity may have a reservoir, which is arranged at the radially inward end of the at least one cavity. The actuator assembly may have only one cavity, which is provided as an annular cavity, wherein the piston is an annular piston, and the annular cavity and the annular piston are arranged around the axis. The annular cavity and the piston advantageously evenly distribute the centrifugal force acting on the fluid over the circumference of the short-circuit ring.

[0013] According to another embodiment, at least one elastic member is arranged between the rotor and the at least one short-circuit ring. The elastic member applies an axial biasing force to the short-circuit ring towards the first position, thereby providing a restoring force to shift the short-circuit ring back to its first position as the rotational speed of the rotor decreases. Each short-circuit ring may provide the at least one elastic member as an annular spring or a stack of annular springs. The elastic member may also be formed by a plurality of helical springs arranged circumferentially around the axis. The helical spring may advantageously be arranged in a groove of the rotor or in a groove of the short-circuit ring to allow the short-circuit ring to abut against the rotor in the second position.

[0014] According to another embodiment, the summarised force acting on the short-circuit ring towards the second position is composed of the hydraulic force of the fluid and the magnetic force applied by the rotor. The summarised force exceeds the axial biasing force of the elastic member acting on the short-circuit ring towards the first position at a predetermined rotational speed of the rotor. The predetermined rotational speed may be in the range of 10,000 to 30,000 revolutions per minute.

[0015] Exemplary embodiments and further advantages of the electric machine will be described below with reference to the accompanying drawings, in which

[0016] Figure 1 shows a perspective view of a first exemplary embodiment of an electric machine;

[0017] Figure 2 Shows Figure 1 A longitudinal sectional view of an embodiment of the present invention;

[0018] Figure 3 Shows Figure 2 Details in the first position;

[0019] Figure 4 Shows Figure 3 Details in the second position;

[0020] Figure 5 A second exemplary embodiment of an electric machine is shown;

[0021] Figure 6 Shows Figure 5 A longitudinal sectional view of an embodiment of the present invention;

[0022] Figure 7 Shows Figure 6 Details in the first position;

[0023] Figure 8 Shows Figure 7 Details in the second location

[0024] Fig. 9 A schematic cross-sectional view of a universal electric machine is shown.

[0025] exist Fig. 9 A schematic cross-sectional view of a universal electric machine is depicted for illustrative purposes in FIG. The electric machine comprises a stator 10 and a rotor 1 rotatable relative to the stator 10 about an axis L, the rotor 1 having permanent magnets 11. In this case, eight pairs of permanent magnets 11 arranged in pairs in a V-shape are integrated into the rotor 1. Slots 19 are provided in the stator 10 for accommodating windings (not depicted). Figures 1 to 8 In the embodiment, the stator 10 is omitted. Fig. 9 ).

[0026] exist Figure 1 A perspective, partially exploded view of an embodiment of an electric machine is shown in FIG. The electric machine comprises a stator 10 (not depicted, see Fig. 9 ), the rotor 1 can be rotated relative to the stator 10 about the axis L. The permanent magnets 11 are arranged in the V-shaped grooves of the rotor 1. Two short-circuit rings 2 are arranged at two axially spaced ends of the rotor 1, and two actuator assemblies 3 hydraulically actuate the short-circuit rings 2 to axially displace along the axis L. Figure 2 A longitudinal cross-sectional view of this embodiment is shown. Figure 3 and Figure 4 Details at different locations are depicted in A. Figures 1 to 4 are described together.

[0027] The short-circuit ring 2 can be in the first position (in Figure 3 ) and a second position (depicted in Figure 4 The axial displacement distance D between the Figure 3 The short-circuit ring 2 is further away from the rotor 1 in the first position than in the second position. When the short-circuit ring 2 is displaced to the second position, the induced magnetic flux of the permanent magnet 11 is reduced. The actuator assembly 3 hydraulically actuates the short-circuit ring 2 from the first position to the second position according to the rotation speed of the rotor 1. The actuator assembly 3 is passively controlled by centrifugal force, which will now be further described.

[0028] Figure 1 1 shows one of the two actuator assemblies 3 in exploded view. The actuator assembly 3 has a first body portion 14 and a second body portion 15, both of which are annular and form an annular cavity 4 between them after assembly. A body O-ring 17 is provided to seal the cavity 4. The short-circuit ring 2 is connected to an annular piston 5, which cooperates with an annular piston chamber 18 formed between the first body portion 14 and the second body portion 15, which is Figure 4 The piston 5 has a recess with a piston O-ring 16. The piston chamber also has a recess with a piston O-ring 16 formed at the second body portion 15. The piston O-ring 16 seals the cavity 4.

[0029] The actuator assembly 3 rotates together with the rotor 1 about the axis L. In the depicted embodiment, the rotor 1 and the first body portion 14 and the second body portion 15 of the actuator assembly 3 are all connected to the drive shaft 12. Inside the cavity 4 is a fluid, such as oil. Due to the shape of the cavity 4, the fluid is centrifuged radially outward from the axis L under the centrifugal force of the rotating actuator assembly 3. Since the piston 5 is hydraulically connected to the radially outward end of the cavity 4, the hydraulic pressure of the fluid acts on the piston 5 and the short-circuit ring 2 connected to the piston 5. The cavity 4 forms a closed hydraulic system, the volume of which is changed by the movement of the axially movable piston 5. The rotational force acting on the fluid causes the fluid to be centrifuged from the reservoir chamber 6 disposed at the radially inward end of at least one cavity 4 to the radially outward piston chamber 18.

[0030] An elastic member 7 is arranged between the rotor 1 and each short-circuit ring 2, and the elastic member 7 applies an axial biasing force toward the first position to the corresponding short-circuit ring 2. In the depicted embodiment, at least one elastic member 7 is an annular spring 7a, whose outer diameter may be smaller than the inner diameter of the short-circuit ring 2, which allows the short-circuit ring 2 to abut against the rotor 1 in the second position, as shown in FIG. Figure 4 as shown in .

[0031] exist Figure 5 A perspective, partially exploded view of a second embodiment of an electric machine is shown in FIG. The electric machine comprises a stator 10 (not depicted, see Fig. 9), the rotor 1 is rotatable relative to the stator 10 about an axis L. Permanent magnets 11 are arranged in V-shaped grooves of the rotor 1. Two short-circuit rings 2 are arranged at two axially spaced ends of the rotor 1, and two actuator assemblies 3 hydraulically actuate the short-circuit rings 2 to be displaced axially along the axis L. In this respect, the second embodiment is identical to the first embodiment described and will not be described in detail. Figure 6 A longitudinal cross-sectional view of this embodiment is shown. Figure 7 and Figure 8 Details at different locations are depicted in A. Figures 5 to 8 are described together.

[0032] In the second embodiment, the elastic member 7 is formed by a plurality of helical springs 7b (instead of an annular spring 7a) distributed circumferentially around the axis L. Eight helical springs 7b are arranged in grooves 8 in the rotor 1 and in grooves 9 in the short-circuit ring 2, as shown in FIG. Figure 7 to allow the short-circuit ring 2 to abut against the rotor 1 in the second position, which is best seen in Figure 8 Shown in.

[0033] The short-circuit ring 2 extends radially to overlap with the outer radial extension of the rotor 1, preferably overlaps with the magnet section of the rotor 1, where the permanent magnet is located. The short-circuit ring 2 can be made of a magnetizable material. At a predetermined rotational speed of the rotor 1, the combined force of the hydraulic pressure of the fluid and the magnetic force applied by the rotor 1 to the short-circuit ring 2 in the axial direction exceeds the biasing force of the elastic member 7, and the predetermined rotational speed is, for example, in the range of 10,000 to 30,000 revolutions per minute. The distance D from the first position to the second position can be between one percent and ten percent of the axial length or diameter of the rotor 1. Shifting at least one short-circuit ring 2 from the first position to the second position reduces the induced magnetic flux of the permanent magnet 11 by at least 5%.

[0034] Reference numerals

[0035] 1 rotor

[0036] 2 short circuit ring

[0037] 3 Actuator assembly

[0038] 4 Cavity

[0039] 5 Piston

[0040] 6 Liquid storage chamber

[0041] 7 Elastic components

[0042] 7a Ring spring

[0043] 7b coil spring

[0044] 8 grooves

[0045] 9 grooves

[0046] 10 Stator

[0047] 11 permanent magnet

[0048] 12 Drive shaft

[0049] 14 First Subject

[0050] 15 Second Subject

[0051] 16 Piston O-ring

[0052] 17 Main body O-ring

[0053] 18 Piston chamber

[0054] 19 slots

Claims

1. Motor, including: stator (10); A rotor (1) rotatable about an axis (L) relative to a stator (10), the rotor having permanent magnets (11); at least one short-circuit ring (2) axially displaceable by a distance D between a first position and a second position, wherein the short-circuit ring (2) is further away from the rotor (1) in the first position than in the second position, and wherein when the at least one short-circuit ring (2) is displaced toward the second position, the induced magnetic flux of the permanent magnet (11) decreases; as well as At least one actuator assembly (3) hydraulically actuates the at least one short-circuit ring (2) to shift from a first position to a second position according to the rotation speed of the rotor (1).

2. The motor according to claim 1, characterized in that The at least one actuator assembly (3) is passively controlled by centrifugal force.

3. An electric machine according to any one of the preceding claims, characterized in that The at least one actuator assembly (3) rotates together with the rotor (1) about the axis (L).

4. An electric machine according to any one of the preceding claims, characterized in that The at least one actuator assembly (3) has at least one cavity (4) and a fluid in the cavity, the cavity being arranged such that the fluid is centrifuged radially outward from the axis (L) by the centrifugal force of rotating the actuator assembly (3).

5. The motor according to claim 4, characterized in that The actuator assembly (3) has at least one piston (5) which is hydraulically connected to the radially outward end of the cavity (4) to transmit the hydraulic pressure of the fluid to the short-circuit ring (2), wherein the piston (5) and the short-circuit ring (2) are integrally formed as a single-piece component.

6. An electric machine according to any one of the preceding claims 4 or 5, characterized in that The at least one chamber (4) forms a closed hydraulic system, the volume of which is varied by the movement of the piston (5), wherein the piston is axially movable.

7. An electric machine according to any one of the preceding claims 4 to 6, characterized in that The at least one cavity (4) has a liquid storage chamber (6), which is arranged at the radially inward end of the at least one cavity (4).

8. An electric machine according to any one of the preceding claims 4 to 7, characterized in that The actuator assembly has only one cavity (4), which is configured as an annular cavity, wherein the piston (5) is an annular piston, the annular cavity and the annular piston being arranged around the axis (L).

9. An electric machine according to any one of the preceding claims, characterized in that At least one elastic member (7) is arranged between the rotor (1) and the at least one short-circuit ring (2), and the at least one elastic member (7) applies an axial biasing force toward a first position to the at least one short-circuit ring (2).

10. The motor according to claim 9, characterized in that The at least one elastic member (7) is an annular wave spring (7a).

11. The motor according to claim 9, characterized in that The elastic member (7) is formed by a plurality of coil springs (7b) distributed circumferentially around the axis (L).

12. The motor according to claim 11, characterized in that The helical spring (7b) is arranged in a groove (8) in the rotor (1) and / or in a groove (9) in the short-circuit ring (2) to allow the short-circuit ring (2) to abut against the rotor (1) in the second position.

13. An electric machine according to any one of the preceding claims, characterized in that The at least one short-circuit ring (2) covers a magnet section of the rotor (1).

14. An electric machine according to any one of the preceding claims 9 to 13 and claim 5, characterized in that At a predetermined rotational speed of the rotor (1), the combined axial force of the hydraulic pressure of the fluid and the magnetic force applied by the rotor (1) to the short-circuit ring (2) exceeds the biasing force of the elastic member (7), and the predetermined rotational speed is preferably in the range of 10,000 to 30,000 revolutions per minute.

15. An electric machine according to any one of the preceding claims, characterized in that Two short-circuit rings (2) are arranged in respective first positions at two axially spaced ends of the rotor (1), and wherein two actuator assemblies (3) hydraulically actuate respective ones of the two short-circuit rings (2) to shift from the respective first position to the respective second position.

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