WO2020127379A1

WO2020127379A1 - Electric motor

Info

Publication number: WO2020127379A1
Application number: PCT/EP2019/085793
Authority: WO
Inventors: Hermann Bäumel; Christian Böhm; Steffen Hahn
Original assignee: Vitesco Technologies Germany Gmbh
Priority date: 2018-12-21
Filing date: 2019-12-17
Publication date: 2020-06-25
Also published as: DE102018222734A1

Abstract

The invention relates to an electric motor, in particular for driving an oil pump. The electric motor according to the invention comprises an external stator (3) which is arranged about an internal rotor (4), wherein the stator (3) and the rotor (4) extend in an axial direction along an axis of rotation (A) about which the rotor (4) rotates during operation of the electric motor (1), and wherein the stator (3) and the rotor (4) are located in a motor housing (2) in which there is a coolant circuit (7, 8, 9, 10, 17) for guiding cooling medium. The electric motor according to the invention is characterised in that the coolant circuit (7, 8, 9, 10, 17) comprises a cooling path (10) which, in order to cool the stator (3), extends adjacent to its outside side (6) which delimits the stator (3) in the radial direction with respect to the axis of rotation (A), wherein the cooling path (10) is designed such that the cooling medium is transported around the outer side (5a) of the stator (3) in the peripheral direction with respect to the axis of rotation (A).

Description

description

Electric motor

The invention relates to an electric motor, in particular for driving an oil pump.

It is known from the prior art to actively cool electric motors with an internal rotor and an external stator (so-called internal rotor) with a liquid cooling medium. This is a cooling circuit with a variety of

Cooling channels in the axial direction along the entire length of the

Motor outer jacket including a deflection in the end shields of the motor. The large number of cooling channels increases the installation space of the engine and there is pressure loss in the cooling circuit.

The object of the invention is to provide an electric motor designed as an internal rotor with efficient cooling.

This object is achieved by the electric motor according to claim 1.

Further developments of the invention are defined in the dependent claims.

The electric motor according to the invention can be used for any purpose. In a preferred variant, the electric motor is used to drive an oil pump, in particular an oil pump for circulating oil in a motor vehicle.

The electric motor is designed as an internal rotor, i.e. it includes one

external stator, which is arranged around an internal rotor. The stator and the rotor extend in an axial direction along an axis of rotation about which the rotor rotates when the electric motor is in operation. The stator and the rotor are arranged in a motor housing in which a cooling circuit for guiding cooling medium is formed. The stator or rotor can be a stator or rotor known per se. The stator is preferably designed as a laminated core with electrical windings.

The electric motor according to the invention is characterized in that the

Cooling circuit includes a cooling path which runs adjacent to and in particular on the outside for cooling the stator, which limits the stator in the radial direction with respect to the axis of rotation. This cooling path is like this formed that the cooling medium is transported in the circumferential direction with respect to the axis of rotation around the outside of the stator. The cooling medium is preferably transported in a spiral around the outside of the stator, ie the transport direction of the cooling medium has a component in addition to

Circumferential direction also a component in the axial direction.

The invention has the advantage that efficient cooling is effected locally in the area of the stator by a flow of the cooling medium in the circumferential direction around the stator. In particular, this allows the length of the cooling circuit to be shortened and pressure losses in the cooling circuit to be avoided.

In a preferred variant of the electric motor according to the invention, the cooling path is limited in the axial direction by two opposite ends of the stator. In other words, the cooling path extends along the entire axial length of the stator, so that very good cooling of the entire stator is ensured.

In a further preferred embodiment, the motor housing of the electric motor according to the invention comprises one or more spirally on the

Ribs running outside the stator, which are part of the cooling path and transport the cooling medium around the outside of the stator. With this variant, a volume flow around the stator can be easily achieved for the removal of heat.

Alternatively or additionally, a turbulator can be provided in the cooling path, which is designed in such a way that it swirls the flow of the cooling medium in the cooling path in such a way that the cooling medium is transported around the outside of the stator. Turbulators are known per se from the prior art. It is within the scope of professional action, the turbulator like that

to design that it causes the transport of the cooling medium around the outside of the stator. By using the turbulator, turbulent flow is generated in the cooling path, which increases the removal of heat via the cooling path, since the cooling medium is forced to flow around the area of the stator to be cooled for a longer time. In a preferred embodiment, the turbulator is implemented as an insert that is positioned in the cooling path. This

Insert can be made of plastic, for example. The embodiment just described, which uses a turbulator, can be designed such that no spiral ribs are formed in the cooling path. Nevertheless, the turbulator can also be combined with the variant described above, which uses spiral ribs.

In a further preferred embodiment, the electric motor according to the invention comprises an electronic device for controlling it, the cooling circuit including a cooling section which is guided past the electronic device in order to effect cooling thereof. The cooling circuit can thus be used both for cooling the stator and for cooling the electronic ones

Device are used, whereby a compact and inexpensive construction of the electric motor can be achieved.

In a preferred variant of the embodiment just described, the cooling section is provided adjacent to an inlet opening for supplying the cooling medium to the cooling circuit in the motor housing. In this way, a structure of the electric motor can be achieved in which the electronic device is easily accessible.

In a further embodiment, the stator is delimited by an outer housing impermeable to the cooling medium, the outer surface of which forms the outside of the stator. This protects the inner area of the stator against the ingress of cooling medium.

In an alternative variant, the stator has one for the cooling medium

impermeable outer coating, which forms its outside. This outer coating, which can be made very thin in the range from 100 to 200 μm, ensures good heat transfer between the cooling medium and the stator. In a preferred variant, the outer coating is a ceramic and / or metallic coating which efficiently protects the stator from the ingress of cooling medium.

Exemplary embodiments of the invention are described in detail below with reference to the attached figures.

Show it: Fig. 1 is a cross-sectional view of an embodiment of a

electric motor according to the invention;

FIG. 2 shows a section through the electric motor of FIG. 1 along the line I-1;

and

Fig. 3 is a cross-sectional view analogous to Fig. 1, which is an alternative

Embodiment of the electric motor according to the invention shows.

A variant of the invention is described below with reference to an electric motor for an oil pump in a motor vehicle. However, the electric motor can also be designed for other purposes.

In the cross-sectional view of FIG. 1, the electric motor is designated by reference number 1. The electric motor comprises one in a manner known per se

external stator 3, which is only indicated schematically as a dotted ring and is positioned around a rotor 4. The rotor 4 is off

For reasons of clarity, only indicated by a white circle. From Fig.

1 also shows the rotor axis A, which in this figure extends perpendicular to the plane of the blade and corresponds to the axial direction of the electric motor.

The stator and the rotor are cylindrical and extend in the axial direction along the axis A. This can be seen from the sectional view of FIG. 2. As can be seen there, the stator 3 extends between a left and a right axial end along the axis A. The same applies to the rotor, which cannot be seen from FIG. 2 due to the selected cutting line l-l.

The stator 3 and the rotor 4 are in a lower portion of a motor housing

2 arranged. The lower section is connected to an upper section of the

Coupled motor housing, so that an inlet 9 of cooling medium is formed from the upper section to the lower section, as will be described in more detail below. To seal the two housing sections, a seal in the form of an O-ring 14 is provided in the inlet 9.

The stator 3 is in a known manner as a laminated core with electrical

Designed windings. By energizing the stator, the rotation of the inner rotor 4 about the axis A is effected. In order to achieve sufficient cooling of the stator during operation of the electric motor, a is in the motor housing 2 Cooling circuit formed, which comprises sections 7, 8, 9, 10 and 17. A liquid cooling medium, preferably water or a mixture of water and glycol, for example in equal proportions of water and glycol, flows in the cooling circuit. The direction of flow of the cooling medium is indicated by arrows P in FIG. 1 and also in FIGS. 2 and 3. Heat generated by the electric motor and possibly also heat which additionally acts on the motor from the outside via the motor housing 2 can be dissipated via the cooling circuit.

In the embodiment of FIGS. 1 and 2, the stator 3 is pressed into a metallic cylindrical housing 5, which is produced by deep drawing. The housing 5 is part of the stator 3. The outside of the housing 5 is designated by reference numeral 6 in FIG. 1 and also forms the outside of the stator 3. The housing 5 is usually also referred to as a cartridge.

1, the cooling medium enters the cooling circuit via an inlet opening 7 and is first passed through a cooling section 8. In the area of this cooling section there is a heat sink 11, which has pins 12 projecting downwards, which for reasons of clarity are only partially designated with this reference symbol. In one variant, the pins have a diamond-shaped shape in cross section in the horizontal direction in FIG. 1.

The cooling medium is guided in the cooling section 8 around the pins 12, so that good heat transfer takes place between the cooling medium and the cooling body 11. An electronic device is located above the heat sink, which is only indicated schematically by a circuit carrier 13 on which the corresponding electronic circuit is located. The electronic

Device is used to control the electric motor. By arranging the electronic device above the heat sink 11, an efficient cooling of this device is achieved by the cooling section 8.

After passing through the cooling section 8, the cooling medium is deflected downward. In the area of the deflection, a deflection plug 15 is provided for sealing the cooling circuit. The cooling medium then flows down via the inlet 9 into a cooling path 10 which extends around the outer circumference of the outside 6 of the stator 3. This cooling path ensures that the cooling medium for cooling the stator flows in the circumferential direction around the outside 6 thereof. In order to bring about such a flow of the cooling medium in the cooling path 10, spirally extending ribs are used in the electric motor of FIGS. 1 and 2. This can be seen from the sectional view of FIG. 2. The section of this figure (line II of FIG. 1) is selected in the region of the inlet 9 and thus does not run through the axis of rotation A. As can be seen in FIG. 2, there is a spiral rib 16

2, an upper section and a lower section can be seen from FIG. The front edge of the spiral rib rests on the outside 6 of the stator in order to thereby cause the cooling medium to spiral around the stator. In order to prevent the cooling medium from escaping from the motor housing 2, a seal in the form of an O-ring 18 is provided at each axial end of the stator 3, which seals against the

Outside 6 of the cartridge 5 rests.

In FIG. 2, the symbols SY1 and SY2 are used in addition to the arrow P to indicate the direction of flow of the cooling medium. The symbol SY1 indicates a flow direction perpendicular to the leaf plane of FIG. 2 from this, whereas the symbol SY2 indicates a flow direction in the opposite direction into the leaf plane.

As can be seen from FIG. 2, the spiral rib guides the cooling medium in the cooling path 10 from the left to the right axial end of the stator 3. After the stator rotates, the cooling medium finally emerges from the motor housing 2 via an outlet 17. The cooling medium then flows to a heat exchanger for removing heat and then re-enters the motor housing 2 via the inlet 7. A feed pump is provided to convey the cooling medium, which is not shown in the figures.

According to the embodiment in FIGS. 1 and 2, a space-saving geometry of the cooling path 10 between the motor housing 2 and the outside 6 of the stator 3 can be achieved by the spiral rib 16. The cooling path 10 is limited to the stator 3, so that long cooling channels can be dispensed with and the pressure loss in the cooling circuit can be minimized. The cooling therefore only takes place where it is necessary. By also passing the cooling medium past the heat sink 11 for the electronic device 13, a coherent cooling circuit is created both for the electric motor and for its electronics, as a result of which the electric motor can be realized in a space-saving and cost-saving manner. In the embodiment of FIGS. 1 and 2, the rib 16 causes forced convection in the form of a laminar flow and thereby improves the removal of heat from the electric motor. This leads to an increase in efficiency, since the laminar volume flow means that more heat can be removed.

In a modified variant of the invention, the transport of the

Cooling medium caused around the stator by means of a turbulator, which is arranged as an insert in the cooling path. Such a variant is shown in FIG. 3. This figure corresponds to the sectional view from FIG. 1, the electric motor of FIG. 3 only differing from the embodiment of FIG. 1 in that a turbulator 19 in the form of an insert is used in the cooling path 10 instead of a spiral rib. The turbulator is only indicated schematically as a jagged component. Turbulators are known per se from the prior art and enable the generation of turbulent flow. The turbulator 19 of FIG. 3 is shaped such that the turbulent flow is distributed in such a way that the cooling medium in the cooling path 10 is guided around the outside 6 of the stator 3.

Turbulators are inexpensive to produce and thus enable a cooling path to be implemented simply and inexpensively, in which the cooling medium is transported around the outside of the stator. Due to the turbulent

The course of the flow makes it possible to increase the removal of heat, since the cooling medium is forced to flow around the area of the stator to be cooled for a longer time. The embodiment of FIG. 3 can optionally also be combined with the embodiment of FIG. 1. That is, both the spiral rib 16 and the turbulator 17 can be provided in the cooling path 10.

According to the embodiments in FIGS. 1 to 3, the stator 3 is delimited by a cartridge 5 which prevents the cooling medium from penetrating into the interior of the stator. Alternatively, it is also possible that the cartridge is omitted and instead a coating impermeable to the cooling medium is provided on the outside of the stator, such as a ceramic or a metallic coating. In this way, the heat transfer between the stator and the cooling medium can be increased again and an additional increase in the heat removal through the cooling medium can be achieved. The embodiments of the invention described above have a number of advantages. In particular, a cooling circuit in one

Electric motor created that includes a locally limited cooling path for the stator. In order to transport cooling medium in this cooling path around the outside of the stator, depending on the configuration, a spiral rib and / or a turbulator can be used. In addition, the cooling circuit can also be used to cool the electronics in the electric motor, which leads to a reduction in installation space and cost savings. Furthermore, the cooling of the stator can be further improved in that the stator is not arranged in a cartridge, but with one for the cooling medium

impermeable outer coating is provided.

Reference numerals

1 electric motor

2 motor housing

3 stator

4 rotor

5 cartridges

6 outside of the cartridge

7 inlet opening

8 cooling section

9 inflow

10 cooling path

1 1 heat sink

12 pins

13 electronic device

14 O-ring

15 deflection plugs

16 spiral rib

17 outlet

18 O-ring

19 turbulator

A axis of rotation

P arrow

SY1, SY2 Symbols for displaying the flow direction

Claims

1 . Electric motor, in particular for driving an oil pump, comprising an external stator (3) which is arranged around an internal rotor (4), the stator (3) and the rotor (4) being in an axial direction along an axis of rotation (A) extend around which the rotor (4) rotates during operation of the electric motor (1), and wherein the stator (3) and the rotor (4) are arranged in a motor housing (2) in which a cooling circuit (7, 8, 9 , 10, 17) for the management of

Cooling medium is formed,

d a d u r c h g e k e n n z e i c h n e t, d a s s

the cooling circuit (7, 8, 9, 10, 17) comprises a cooling path (10) which, in order to cool the stator (3), runs adjacent to its outside (6), which extends the stator (3) in the radial direction with respect to the The axis of rotation (A) is limited, the cooling path (10) being designed such that the cooling medium is transported in the circumferential direction with respect to the axis of rotation (A) around the outside (5a) of the stator (3).

2. Electric motor according to claim 1, characterized in that the cooling path (10) is limited in the axial direction by two opposite ends of the stator (3).

3. Electric motor according to claim 1 or 2, characterized in that the motor housing (2) comprises one or more ribs (16) extending spirally on the outside (6) of the stator (3), which are part of the cooling path (10) and the Transport the cooling medium around the outside (6) of the stator (3).

4. Electric motor according to one of the preceding claims, characterized

characterized in that a turbulator (19) is provided in the cooling path (10), which is designed such that it swirls the flow of the cooling medium in the cooling path (10) such that the transport of the cooling medium around the outside (6) of the stator (3 ) is caused around.

5. Electric motor according to one of the preceding claims, characterized

characterized in that the turbulator (19) is an insert which is positioned in the cooling path (10).

6. Electric motor according to one of the preceding claims, characterized

characterized in that the electric motor (1) comprises an electronic device (13) for its control, the cooling circuit having a cooling section (8) includes, which is guided past the electronic device (13) to effect its cooling.

7. Electric motor according to claim 6, characterized in that the cooling section (8) adjacent to an inlet opening (7) for supplying the cooling medium to

Cooling circuit is provided in the motor housing (2).

8. Electric motor according to one of the preceding claims, characterized

characterized in that the stator (3) is delimited by an outer housing (5) impermeable to the cooling medium, the outer surface of which forms the outside (6) of the stator (3).

9. Electric motor according to one of claims 1 to 7, characterized in that the stator (3) has an outer coating impermeable to the cooling medium, which forms its outside (6).

10. Electric motor according to claim 9, characterized in that the

External coating is a ceramic and / or metallic coating.