Motors with non-rectangular rotor magnets

Abstract

The present invention discloses an electric motor with a non-rectangular rotor magnet. A hybrid powertrain system uses an electric motor with a permanent magnet rotor. The rotor is formed by inserting parallelepiped magnets into slots. In order to reduce the possibility of demagnetization, the net magnetization of each magnet is oriented parallel to the lateral surface of the magnet and not perpendicular to the outward surface of the magnet. The magnets can be arranged in multiple rows. The magnets in each row can be perpendicular to the rotor radial direction or oblique to the rotor radial direction.

Description

Technical Field

[0001] The present disclosure relates to the field of hybrid electric vehicles and more particularly to the structure of a permanent magnet rotor. Background Art

[0002] Many vehicles are used over a wide range of vehicle speeds, including both forward and reverse motion. However, certain types of engines can only operate efficiently over a narrow speed range. Therefore, a transmission that can efficiently transfer power at a variety of gear ratios is often used. When vehicle speeds are low, the transmission is typically operated at a high gear ratio, multiplying the engine torque to improve acceleration. When vehicle speeds are high, operating the transmission at a low gear ratio allows the engine speed to be associated with a quiet, fuel-efficient cruise.

[0003] To reduce fuel consumption, some vehicles include hybrid powertrains that use stored energy to supplement the power produced by the internal combustion engine. These powertrains allow the vehicle to operate part of the time with the engine off and the rest of the time at the engine's more efficient torque level. Hybrid powertrains are also able to capture energy that would otherwise be dissipated by the braking system for subsequent use. Summary of the invention

[0004] In some embodiments, the motor includes a stator, a rotor and a plurality of permanent magnets. The rotor is supported to rotate relative to the stator and is defined with a plurality of magnet cavities. Each of the plurality of permanent magnets has a parallelepiped form of a non-rectangular body and its net magnetization direction is not perpendicular to any surface of the magnet. The magnets can be arranged in inner and outer rows. The outer surface of each magnet can be oblique to or perpendicular to the radial orientation of the rotor.

[0005] In some embodiments, the motor includes a stator, a rotor and a plurality of permanent magnets. The rotor is supported to rotate relative to the stator and is defined with a plurality of magnet cavities. Each of the plurality of permanent magnets has a non-rectangular form and its net magnetization direction is parallel to the lateral surface of the magnet and not perpendicular to the outward surface of the magnet. The magnets may be arranged in inner and outer rows. The outer surface of each magnet may be oblique to or perpendicular to the radial orientation of the rotor.

[0006] A vehicle includes a rotor and a plurality of permanent magnets. The rotor defines a plurality of magnet cavities into which the permanent magnets are inserted. The magnets have a parallelepiped form that is not a rectangular body and whose net magnetization direction is not perpendicular to any surface of the magnet. The net magnetization direction may be parallel to the lateral surface of the magnet. The vehicle may also include an inverter configured to generate alternating current in the windings of the stator to establish a magnetic field that causes the rotor to rotate relative to the stator. The vehicle may also include an internal combustion engine selectively connected to the rotor via a clutch. The vehicle may also include a multi-speed transmission configured to driveably connect the rotor to the wheels of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a schematic diagram showing a hybrid vehicle powertrain.

[0008] Figure 2 This is a cross section of a permanent magnet motor.

[0009] Figure 3 for Figure 2 A detailed view of a portion of the rotor of an electric motor.

[0010] Figure 4 for Figure 2 Detailed view of the permanent magnets and magnet cavities of the rotor.

[0011] Figure 5 for Figure 2 Detailed view of a portion of a rotor of an alternative embodiment of a rotor. DETAILED DESCRIPTION

[0012] As required, specific embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely examples of the present invention and may be implemented in a variety of alternative forms. The drawings are not necessarily drawn to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to utilize the present invention in a variety of forms.

[0013] Figure 1 A hybrid vehicle powertrain is schematically shown. Connections that provide mechanical power transmission are shown in solid lines. Connections that provide power flow are shown in dotted lines. Dashed lines indicate control signal flow. The traction motor 10 uses the electrical energy stored in the battery 12 to generate torque. In certain operating modes, the traction motor 10 can be operated to generate electricity, which is then stored in the battery 12 for subsequent use. Electric power is transmitted between the battery 12 and the inverter 14 via a direct current (DC) bus 16. The inverter 14 regulates the amplitude and phase of the alternating current (AC) voltage applied to the connector 18, wherein the connector 18 connects the inverter 14 to the windings of the motor 10. The rotor of the traction motor 10 is fixed to the transmission input shaft 20. The power from the transmission input shaft 20 is transmitted to the wheels of the vehicle through the torque converter 22, the gearbox 24 and the differential 26.

[0014] The torque converter 22 includes a pump impeller fixedly connected to the transmission input shaft 20 and a turbine fixedly connected to the input of the gearbox 24. Whenever the pump impeller rotates faster than the turbine, the torque converter 22 transfers power from the pump impeller to the turbine. The torque converter 22 may also include a stator that multiplies the torque so that the torque on the turbine is greater than the torque on the pump impeller. The torque converter 22 may also include a locking clutch that selectively connects the pump impeller and the turbine to achieve more efficient power transfer when slip associated with the hydrodynamic power transfer between the pump impeller and the turbine is not required.

[0015] The gearbox 24 includes a number of clutches and brakes that establish multiple power flow paths from the gearbox input shaft to the transmission output shaft. These power flow paths have different gear ratios. The transmission switches from one power flow path to another power flow path by disengaging one or more clutches or brakes and engaging other clutches or brakes. A neutral mode is established in which there is no power flow path between the gearbox input and the transmission output. The gearbox 24 may also include a parking pawl that can be engaged when the vehicle is idle to keep the transmission output stationary.

[0016] The transmission output shaft is connected to a differential 26 which distributes power between left drive wheel 28 and right drive wheel 30. The differential allows for slight speed differences between the wheels, such as when the vehicle is turning.

[0017] The internal combustion engine 36 is selectively connected to the transmission input shaft 20 via the clutch 32. Note that the transmission input shaft 20 extends through the traction motor 10. When the clutch 32 is engaged, the engine 36 and the traction motor 10 rotate at the same speed, and the torque on the transmission shaft 20 is equal to the sum of the torque generated by the engine 36 and the torque generated by the traction motor 10. In certain operating modes, the engine 36 can provide all the propulsion power by setting the torque of the traction motor to zero. In other operating modes, the motor can draw power from the battery 12 to assist in propelling the vehicle. In other operating modes, the engine can generate more power than is required for propulsion, wherein the motor diverts a portion of the power to charge the battery 12. When the clutch 32 is disengaged, all the propulsion force is provided by the traction motor 10.

[0018] The powertrain is controlled by a controller 34. The controller 34 can be a single microprocessor or multiple communicating microprocessors. The controller 34 receives commands from the driver through the accelerator pedal position, brake pedal position, gear selector position (PRNDL), etc. The controller also uses signals from various sensors. The controller controls the engagement and disengagement of the clutch 32, the lockup clutch of the torque converter, and the clutches and brakes in the gearbox 24. The controller also sends commands to the engine 36 and sends commands to the inverter 14 to control the torque of the motor 10.

[0019] Figure 2 A cross section of the electric machine 10 is shown. The electric machine 10 includes a fixed stator 38 having a set of stator poles 40 each associated with a winding 42. Each winding is connected to one of the three AC phases. The stator poles surround a rotor 44 fixed to the transmission input shaft 20. Permanent magnets are strategically placed within cavities in the rotor 44 to magnetize the rotor. These magnets and cavities are described below with reference to Figure 3 and Figure 4 Discuss in more detail.

[0020] The current in the windings 42 generates a magnetic field in the stator poles 40. The magnetic forces between the stator poles and the rotor exert a torque on the rotor. The magnitude of the torque depends on the current in the windings and the position of the stator magnetic field relative to the rotational position of the rotor. The inverter 14 adjusts the voltage applied to the stator windings to obtain the desired current magnitude and adjusts the current phase angle to position the stator magnetic field relative to the rotor position. During power generation, the inverter 14 converts the AC power from the motor into DC power for storage in the battery 12.

[0021] In some cases, the magnetic field generated by the stator may act to demagnetize the permanent magnets. Any demagnetization of the permanent magnets degrades future motor performance.

[0022] Figure 3 Detailed view of one rotor pole of the rotor 44. For each rotor pole, the rotor has two inner concave cavities 46 and two outer concave cavities 48. These concave cavities are generally oblique to the radial direction of the rotor (the radial direction is the line from the rotor axis to the rotor periphery). A magnet 50 is accommodated in each concave cavity. Each magnet has a non-rectangular parallelogram cross-section. The magnet has a constant thickness in the axial direction of the rotor, so that in three dimensions, the magnet is a parallelepiped of a non-rectangular body. Figure 4 A single cavity and permanent magnet are shown. Each magnet has an outward surface 52 and an inward surface 54 and two lateral surfaces 56 and 58. The outward surface 52 is parallel to the inward surface 54. The lateral surfaces 56 and 58 are parallel to each other but not perpendicular to the outward surface 52. The net magnetization direction of the magnet is indicated by 60. The net magnetization direction is not perpendicular to any magnet surface. The net magnetization direction may be parallel to the lateral surface 56.

[0023] The inventors have discovered that demagnetization is less likely to occur when the net magnetization direction is not perpendicular to the outward facing magnet surface. Utilizing this magnetization direction allows thinner magnets to be used in a given application without experiencing demagnetization. Having the magnetization direction parallel to the lateral surface allows the magnet to be cut from a bar magnet, thereby simplifying manufacturing.

[0024] Figure 5 An alternative arrangement of magnets in the rotor is shown. Figure 2 and Figure 3Unlike the two oblique outer concave cavities in the embodiment of the present invention, the single magnet outer concave cavity 48' is oriented perpendicularly to the radial direction of the rotor. The net magnetization direction of the magnet in the outer concave cavity is oblique to the radial direction of the rotor. In other alternative embodiments, the inner row of magnet concave cavities may be perpendicular to the radial direction of the rotor. Other alternative embodiments may have only one row of magnet concave cavities, which may be oriented obliquely or perpendicularly to the radial direction of the rotor.

[0025] Although exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the present invention. Rather, the words used in the specification are descriptive rather than restrictive, and it should be understood that various changes may be made without departing from the spirit and scope of the present invention. In addition, the features of various implemented embodiments may be combined to form further embodiments of the present invention.

Claims

1. A motor, comprising: stator; a rotor supported for rotation relative to the stator, the rotor defining a plurality of magnet cavities; a plurality of permanent magnets, inserted into respective magnet cavities, each magnet having a non-rectangular parallelepiped form and having a net magnetization direction that is not perpendicular to any surface of the magnet, In which, the multiple permanent magnets are divided into multiple magnet groups arranged along the circumference of the rotor, each magnet group includes a first magnet, a second magnet and a third magnet, the first magnet is arranged between the second magnet and the third magnet, the outer surface of the first magnet of each magnet group is oriented perpendicular to the radial direction of the rotor, and the outer surfaces of the second magnet and the third magnet of each magnet group are oriented oblique to the radial direction of the rotor.

2. The motor according to claim 1, wherein: The second magnet and the third magnet are arranged as an inner row of magnets, and the first magnet is arranged as an outer row of magnets.

3. The motor according to claim 1, wherein: The second magnet and the third magnet of each magnet group are symmetrically arranged along the radial direction of the rotor.

4. A motor, comprising: stator; a rotor supported for rotation relative to the stator, the rotor defining a plurality of magnet cavities; A plurality of permanent magnets are inserted into respective magnet cavities, each magnet having a non-rectangular body form and having a magnetization direction parallel to the lateral surface of the magnet and not perpendicular to the outward surface of the magnet, In which, the multiple permanent magnets are divided into multiple magnet groups arranged along the circumference of the rotor, each magnet group includes a first magnet, a second magnet and a third magnet, the first magnet is arranged between the second magnet and the third magnet, the outer surface of the first magnet of each magnet group is oriented perpendicular to the radial direction of the rotor, and the outer surfaces of the second magnet and the third magnet of each magnet group are oriented oblique to the radial direction of the rotor.

5. The motor according to claim 4, wherein: The second magnet and the third magnet are arranged as an inner row of magnets, and the first magnet is arranged as an outer row of magnets.

6. The electric machine according to claim 4, wherein: The second magnet and the third magnet of each magnet group are symmetrically arranged along the radial direction of the rotor.

7. A vehicle comprising: a rotor defining a plurality of magnet cavities; a plurality of permanent magnets, inserted into respective magnet cavities, each magnet having a non-rectangular parallelepiped form and having a net magnetization direction that is not perpendicular to any surface of the magnet, In which, the multiple permanent magnets are divided into multiple magnet groups arranged along the circumference of the rotor, each magnet group includes a first magnet, a second magnet and a third magnet, the first magnet is arranged between the second magnet and the third magnet, the outer surface of the first magnet of each magnet group is oriented perpendicular to the radial direction of the rotor, and the outer surfaces of the second magnet and the third magnet of each magnet group are oriented oblique to the radial direction of the rotor.

8. The vehicle of claim 7, wherein: The net magnetization direction of each permanent magnet is parallel to the lateral surface of the magnet.

9. The vehicle of claim 8, further comprising: An inverter is configured to generate alternating current in the windings of the stator to create a magnetic field that causes the rotor to rotate relative to the stator.

10. The vehicle of claim 9, further comprising: An internal combustion engine is selectively connected to a rotor via a clutch.

11. The vehicle of claim 9, further comprising: A multi-speed transmission is configured to driveably connect the rotor to wheels of the vehicle.

12. The vehicle of claim 9, wherein: The second magnet and the third magnet of each magnet group are symmetrically arranged along the radial direction of the rotor.

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