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Patent Searching and Data


Title:
ELECTRIC MOTOR
Document Type and Number:
WIPO Patent Application WO/2019/210955
Kind Code:
A1
Abstract:
Electric motor (10) with a rotatable and axially shiftable motor rotor (12), a static motor stator (14), an electromagnetic motor component (18) and a permanent-magnetic motor component (22) being magnetically coupled with the electromagnetic motor component (18), wherein the permanent-magnetic motor component (22) and the electromagnetic motor component (18) are provided axially shiftable and rotatable with respect to each other, wherein the permanent-magnetic motor component (22) and the electromagnetic motor component (18) are axially arranged with respect to each other so that the motor rotor (12) is axially pulled into an active rotor position if the electromagnetic motor component (18) is energized, and wherein the permanent-magnetic motor component (22) comprises a first axial section (30) with a lower magnetic permeability and a second axial section (32) with a higher magnetic permeability so that the motor rotor (12) is axially pulled into an inactive rotor position if the electromagnetic motor component (18) is not energized.

Inventors:
HENKE, Toni (Oberhofweg 2, Drebach, 09430, DE)
REICHEL, Clemens (Zum Zschopautal 11, Rossau, 09661, DE)
MAETER, Hemke (Reichenberger Strasse 11, Dresden, 01129, DE)
WERNER, Kornelius (Am Sonnenhof 21, Rossau OT Seifersbach, 09661, DE)
Application Number:
EP2018/061292
Publication Date:
November 07, 2019
Filing Date:
May 03, 2018
Export Citation:
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Assignee:
PIERBURG PUMP TECHNOLOGY GMBH (Alfred-Pierburg-Straße 1, Neuss, 41460, DE)
International Classes:
H02K21/02; F04D13/06; H02K1/02; H02K1/27; H02K7/12
Domestic Patent References:
WO2011069109A22011-06-09
Foreign References:
DE4302143A11994-07-28
EP3076020A12016-10-05
JPS608530A1985-01-17
EP3076020A12016-10-05
Attorney, Agent or Firm:
PATENTANWÄLTE TER SMITTEN EBERLEIN-VAN HOOF RÜTTEN PARTNERSCHAFTSGESELLSCHAFT MBB (Burgunderstr. 29, Düsseldorf, 40549, DE)
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Claims:
C L A I M S

1. Electric motor (10) with

a rotatable and axially shiftable motor rotor (12),

a static motor stator (14),

an electromagnetic motor component (18) and

a permanent-magnetic motor component (22) being magnetically coupled with the electromagnetic motor component (18),

wherein the permanent-magnetic motor component (22) and the electromagnetic motor component (18) are provided axially shiftable and rotatable with respect to each other,

wherein the permanent-magnetic motor component (22) and the electromagnetic motor component (18) are axially arranged with respect to each other so that the motor rotor (12) is axially pulled into an active rotor position if the electromagnetic motor component (18) is energized, and

wherein the permanent-magnetic motor component (22) comprises a first axial section (30) with a lower magnetic permeability and a second axial section (32) with a higher magnetic permeability so that the motor rotor (12) is axially pulled into an inactive rotor position if the electromagnetic motor component (18) is not energized.

2. Electric motor (10) according to claim 1, wherein the second axial section (32) is located at an active-rotor-position-remote axial side of the permanent-magnetic motor component (22).

3. Electric motor (10) according to any preceding claim, wherein the permanent-magnetic motor component (22) radially surrounds the electromagnetic motor component (18).

4. Electric motor (10) according to any preceding claim, wherein the permanent-magnetic motor component (22) is provided with a permanent magnet (23) and a magnetic back iron (24) radially surrounding the permanent magnet (23).

5. Electric motor (10) according to claim 4, wherein the magnetic back iron (24) is provided with a ferritic element (26) defining the second axial section (32) of the permanent-magnetic motor component (22), and with a non-ferritic element (28) defining the first axial section (30) of the permanent-magnetic motor component (22).

6. Electric motor (10) according to any preceding claim, wherein the electromagnetic motor component (18) is provided with a laminated core.

7. Electric motor (10) according to any preceding claim, wherein the motor rotor (12) comprises the permanent-magnetic motor component (22) and the motor stator (14) comprises the electromagnetic motor component (18).

8. Electric motor (10) according to claim 7, wherein a motor electronics (16) is provided for energizing the electromagnetic motor component (18).

9. Electric pump with an electric motor (10) according to any preceding claim, wherein a pump wheel (8) is provided co-movably with the motor rotor (12) so that the pump wheel (8) is positioned within a pumping chamber (34) in the active rotor position and that the pump wheel (8) is retracted at least partially out of the pumping chamber (34) in the inactive rotor position.

Description:
Electric motor

The invention is directed to an electric motor, preferably to an electric motor of an electric coolant pump.

Such electric motors are provided with a rotatable motor rotor and with a static motor stator. Either the motor rotor or the motor stator comprises an electromagnetic motor component and the other is typically provided with a permanent-magnetic motor component. The electromagnetic motor component and the permanent-magnetic motor component are magnetically coupled for driving the motor rotor by energizing the electromagnetic motor component.

Electric coolant pumps, for example for a motor vehicle, are provided with a pump wheel being fixed to the motor rotor so that the pump wheel is driven by the electric motor. Electric coolant pumps are often used as an auxiliary pump for a coolant circuit being provided with a mechanically driven primary coolant pump, for example for a coolant circuit of a motor vehicle. The auxiliary electric coolant pump allows a coolant circulation if the primary mechanical coolant pump is not active, for example if the engine of the motor vehicle is not running. The auxiliary coolant pump can be provided with a retractable pump wheel to reduce the flow resistance caused by the auxiliary coolant pump if the primary coolant pump is circulating the coolant.

EP 3 076 020 A1 discloses an electric coolant pump provided with a rotatable and axially shiftable motor rotor and a static motor stator. The motor rotor comprises a permanent-magnetic motor component and the motor stator comprises an electromagnetic motor component. The permanent-magnetic motor component and the electromagnetic motor component are magnetically coupled for driving the motor rotor by energizing the electromagnetic motor component of the motor stator. The permanent-magnetic motor component and the electromagnetic motor component are axially arranged with respect to each other so that the motor rotor is axially pulled into an active rotor position if the electromagnetic motor component is energized. In the active rotor position, a pump wheel being co-moveably attached to the motor rotor via a rotor shaft is positioned in a pumping cavity so that the coolant pump can provide a coolant circulation. If the electromagnetic motor component is not energized, i.e. the auxiliary coolant pump is not active, the motor rotor is axially pushed into an inactive rotor position by a spring causing the pump wheel to be partially retracted out of the pumping cavity to reduce the flow resistance of the inactive coolant pump. However, the spring mechanically stresses the motor rotor so that additional friction is generated which reduces the motor efficiency and, as a result, the pump efficiency. In addition, the mechanical stress can cause a deformation of the motor rotor, in particular if the motor rotor is provided with a laminated rotor body. Furthermore, the spring can wear out because of the alternating deformation so that the pump wheel cannot be reliably retracted anymore.

It is an object of the invention to provide an electric motor which allows a reliable operation mode dependent axial positioning of the motor rotor and a high motor efficiency for a long motor lifetime.

This object is achieved with an electric motor with the features of claim 1.

The electric motor according to the invention is provided with a rotatable and axially shiftable motor rotor and with a static motor stator. The electric motor can be, for example, provided to drive a pump wheel being fixed to the motor rotor. The electric motor according to the invention is provided with an electromagnetic motor component and a permanent-magnetic motor component being magnetically coupled with the electromagnetic motor component. The electromagnetic motor component and the permanent- magnetic motor component are provided axially shiftable and rotatable with respect to each other. Typically, one motor component is provided static and the other is provided axially shiftable and rotatable. The two motor components are provided by the motor stator and the motor rotor, wherein one comprises the electromagnetic motor component and the other comprises the permanent-magnetic motor component.

The electromagnetic motor component and the permanent-magnetic motor component are axially arranged with respect to each other so that the motor rotor is axially pulled into an active rotor position if the electromagnetic motor component is active, i.e. the electromagnetic component is energized. The electromagnetic motor component and the permanent-magnetic motor component are configured and axially positioned with respect to each other so that the total magnetic reluctance of the magnetic system is not minimal at the moment of activating the electromagnetic motor component. As a result, a reluctance force is generated which strives to minimize the total magnetic reluctance of the magnetic system by axially aligning the magnetic motor components causing the motor rotor to be axially moved into the active rotor position.

The permanent-magnetic motor component according to the invention comprises a first axial section and a second axial section, wherein the first axial section is provided with a lower magnetic permeability compared to the magnetic permeability of the second axial section so that the motor rotor is axially pulled into an inactive rotor position if the electromagnetic motor component is not energized. For example, the first axial section and the second axial section can be provided with different materials having different magnetic permeabilities. Alternatively, the two axial sections can be provided with different shapes, in particular with different cross sections for the magnetic flux, to define different magnetic permeabilities for both axial sections. The magnetic permeability affects the local magnetic reluctance, wherein a higher magnetic permeability provides a lower local magnetic reluctance.

The permanent-magnetic motor component provides a permanent magnetic field, whereas the electromagnetic motor component provides a temporary magnetic field only when being energized. If the electromagnetic motor component is not energized, a permanent reluctance force is generated which strives to minimize the total magnetic reluctance. As a result, the permanent reluctance force strives to position the magnetic center of the permanent-magnetic motor component, the magnetic center typically being located approximately on an axial centerline of the permanent-magnetic motor component, as close as possible to the electromagnetic motor component, in particular to a ferromagnetic core of the electromagnetic motor component. As a result, the permanent-magnetic motor component and the electromagnetic motor component are axially moved with respect to each other so that the axially shiftable motor rotor is positioned in the inactive rotor position if the electromagnetic motor component is not energized.

If the electromagnetic motor component is energized, the temporary magnetic field generated by the electromagnetic motor component preferably propagates within the second axial section of the permanent- magnetic motor component which is provided with the higher magnetic permeability. As a result, a temporary reluctance force is generated which strives to position the magnetic center of the electromagnetic motor component, the magnetic center being approximately defined by the position of the ferromagnetic core, as close as possible to the second axial section of the permanent-magnetic motor component. The permanent- magnetic component and the electromagnetic component are provided so that the axially shiftable motor rotor is moved into the active rotor position if the electromagnetic motor component is energized. As a result, the motor rotor is reliably axially positioned in dependence on the energization status of the electromagnetic motor component and, as a result, in dependence on the present operation mode of the electric motor. No mechanical actuation means are required, which are liable to wear and can cause a mechanical deformation of the motor rotor. This allows a reliable operation mode dependent axial positioning of the motor rotor for a long motor lifetime.

Preferably, the second axial section is located at an active-rotor-position- remote axial side of the permanent-magnetic motor component, i.e. the first axial section with the lower magnetic permeability is facing towards the active rotor position and the second axial section with the higher magnetic permeability is facing away from the active rotor position. As a result, the permanent-magnetic motor component is axially moved towards the active rotor position if the electromagnetic motor component is energized. This allows to simply co-movably connect the permanent- magnetic motor component with the axially shiftable motor rotor.

In a preferred embodiment of the invention, the permanent-magnetic motor component radially surrounds the electromagnetic motor component. More preferably, the permanent-magnetic motor component is provided with a magnetic back iron affecting the local magnetic permeability of the permanent-magnetic motor component. This allows simply defining the two axial sections with different magnetic permeabilities by different magnetic back iron sections, for example, made of different materials and/or provided with different shapes. The magnetic back iron can be provided at the radial outside of the permanent-magnetic motor component so that the permanent-magnetic motor component can be arranged very close to the radially inner electromagnetic motor component. This allows a high efficiency of the electric motor.

Preferably, the back iron is provided with a ferritic element and a non- ferritic element, wherein the ferritic element has a significantly higher magnetic permeability than the non-ferritic element. The ferritic element defines the second axial section of the permanent-magnetic motor component and the non-ferritic element defines the first axial section of the permanent-magnetic so that the first axial section is provided with a lower magnetic permeability compared to the second axial section. This allows a cost-efficient and reliable realization of the two axial sections with different magnetic permeabilities.

In a preferred embodiment of the invention, the electromagnetic motor component is provided with a laminated core, i.e. the core is composed of stacked metal lamination sheets. The laminated core reduces eddy currents within the electromagnetic motor component and, as a result, allows a high efficiency of the electric motor. Preferably, the motor rotor comprises the permanent-magnetic motor component and the motor stator comprises the electromagnetic motor component so that the electromagnetic motor component is provided static. This allows a simple and reliable electric connection of the electromagnetic component, not requiring any sliding contacts being liable to wear.

In a preferred embodiment of the invention, a motor electronics is provided for energizing the electromagnetic motor stator. The motor electronics allows a simple control of the electric motor. In particular, the motor electronics allows a simple electrical commutation of the drive energy of the electromagnetic motor component so that no mechanical commutation means are required. The electric motor according to the invention can be provided to drive an electric pump, wherein a pump wheel is provided co-movably with the motor rotor so that the pump wheel is positioned within a pumping chamber in the active rotor position and that the pump wheel is retracted at least partially out of the pumping chamber in the inactive rotor position. As a result, the pump wheel is positioned in the pumping chamber if the pump is active and the pump wheel is retracted out of the pumping chamber if the pump is not active. This allows to significantly reduce the flow resistance of the pump if the pump is not active.

An embodiment of the invention is described with reference to the enclosed drawings, wherein

figure 1 shows a schematic cross section of an electric coolant pump with an electric motor according to the invention, wherein the motor rotor is axially positioned in an inactive rotor position, and

figure 2 shows the electric coolant pump of figure 1, wherein the motor rotor is axially positioned in an active rotor position. The electric coolant pump is provided with a pump wheel 8 and an electronically commutated electric motor 10 comprising a rotatable and axially shiftable annular motor rotor 12, a static annular motor stator 14 and a motor electronics 16. The radially inwardly arranged motor stator 14 is provided with an electromagnetic motor component 18 being controlled and energized by the motor electronics 16 for driving the electric motor 10. The electromagnetic motor component comprises a ferromagnetic laminated core 19 with substantially axially extending pole shoes 21 and with substantially radially extending holding arms 25, wherein each holding arm 25 is wound with a coil wire 27 to provide a stator coil. The electromagnetic motor component 18 generates a temporary magnetic field M2 when being energized by the motor electronics 16.

The motor rotor 12 radially surrounds the motor stator 14 and is rotatably and axially shiftably supported by a rotor shaft 20. The motor rotor 12 is provided integrally with the pump wheel 8, wherein the pump wheel 8 is located at a motor-electronics-remote axial end of the motor rotor 12. The motor rotor 12 comprises a permanent-magnetic motor component 22 with several permanent magnets 23 and with an annular magnetic back iron 24. The permanent-magnetic motor component 22 generates a permanent magnetic field Ml which interacts with the temporary magnetic field M2 of the electromagnetic motor component 18 so that the motor rotor 12 is driven by the motor stator 14. The magnetic back iron 24 is located at the radial outside of the permanent magnets 23. The magnetic back iron 24 is provided with a ferritic element 26 and with a non-ferritic element 28 being arranged at the pump-wheel faced axial side of the ferritic element 26. The non-ferritic element 28 defines a first axial section 30 of the permanent-magnetic motor component 22 and the ferritic element 26 defines a second axial section 32 of the permanent-magnetic motor component 22. The ferritic element 26 has a significantly higher magnetic permeability compared to the non-ferritic element 28 so that the first axial section 30 is provided with a lower magnetic permeability compared to the second axial section 32.

If the electromagnetic motor component 18 is not energized, the permanent magnetic field Ml generates a permanent reluctance force FI which strives to minimize the total magnetic reluctance by axially aligning the permanent-magnetic motor component 22 and the electromagnetic motor component 18. As a result, the motor rotor 12 with the permanent- magnetic motor component 22 is axially moved so that the magnetic centers of the permanent magnets 23, the magnetic centers being axially located on a permanent magnet centerline PC, are aligned with a holding arm centerline HC of the holding arms 25. As a result, if the electromagnetic motor component 18 is not active, the motor rotor 12 is axially moved towards the motor electronics 16 into the rotor inactive position shown in figure 1, in which the pump wheel 8 is retracted out of a pumping chamber 34.

If the electromagnetic motor component 18 is active, i.e. the electromagnetic motor component 18 is energized by the motor electronics 16, the temporary magnetic field M2 is generated by the electromagnetic motor component 18. Because of the higher magnetic permeability of the second axial section 32, the temporary magnetic field M2 propagates preferably through the second axial section 32. As a result, a temporary reluctance force F2 is generated which axially moves the motor rotor 12 with the permanent-magnetic motor component 22 so that a section centerline SC extending through the axial middle of the second axial section 32 is aligned with the holding arm centerline HC. As a result, if the electromagnetic motor component 18 is active, the motor rotor 12 is axially moved away from the motor electronics 16 into the active rotor position shown in figure 2, in which the pump wheel is positioned in the pumping chamber 34.

Reference list

8 pump wheel

10 electric motor

12 motor rotor

14 motor stator

16 motor electronics

18 electromagnetic motor component

19 ferromagnetic laminated core

20 rotor shaft

21 pole shoes

22 permanent-magnetic motor component

23 permanent magnets

24 magnetic back iron

25 holding arms

26 ferritic element

27 coil wires

28 non-ferritic element

30 first axial section

32 second axial section

34 pumping chamber

HC holding arm centerline

PC permanent magnet centerline

SC section centerline

FI permanent reluctance force

F2 temporary reluctance force

Ml permanent magnetic field

M2 temporary magnetic field