ELECTRIC MOTOR WITH AN AIR-GUIDING ELEMENT

Abstract

An electric motor is described, having a rotor, a stator, a housing surrounding the elements having a circumferential wall and an end wall, and an air-guiding element arranged axially between the end wall and an end surface of the rotor. The air-guiding element has a first section that is disk-shaped about the axis (A) and axially spaced apart from the end wall and which extends radially and a second section of tubular form about the axis (A) and which adjoins the first section radially at the inside and which extends in the direction of an end surface of the rotor. The air-guiding element forms an air channel with a heat-exchange region situated between the first section and the end wall and with an intake region running within the second section.

Claims

1-10. (canceled)

11. An electric motor, comprising: a stator with a stator winding and an end-face winding head, a rotor rotatable about an axis A; a housing, which surrounds the stator and the rotor with a circumferential wall and at least one end wall; and an air-guiding element fixed to the housing and arranged axially between the at least one end wall and an end face of the rotor, and comprising: a first portion formed in a shape of a disk around the axis A and is axially spaced from the at least one end wall and which extends in a radial direction with respect to the axis A and the at least one end wall; and a second portion formed in the shape of a tube around the axis A and adjoins the first portion on a radially inner side of the first portion and which extends in a direction of the end face of the rotor; and an air channel formed by the air-guiding element with a heat exchange region located between the first portion and the at least one end wall and an intake region extending inside the second portion.

12. The electric motor as claimed in claim 11, wherein the air-guiding element is arranged with the second portion radially inside the end-face winding head and coincides with the end-face winding head axially.

13. The electric motor as claimed in claim 11, wherein the air-guiding element further comprises: a third portion formed in a shape of a disk and which adjoins the second portion on an axially inner side of the second portion and which extends radially outwards with an axial spacing radially with respect to the end face of the rotor.

14. The electric motor as claimed in claim 11, wherein the air-guiding element is made from an insulating material.

15. The electric motor as claimed in claim 11, wherein the electric motor is a permanently excited internal rotor machine and the rotor has a plurality of circumferentially spaced and axially extending permanent magnets, which are located radially inside the stator winding and the end-face winding head.

16. The electric motor as claimed in claim 11, wherein the electric motor is an asynchronous machine and the rotor has, at the end face, a short-circuit ring located radially inside the stator winding and the end-face winding head.

17. The electric motor as claimed in claim 13, wherein the stator has an interconnection device for an interconnection of the stator winding, which is arranged radially inside a winding head and which extends axially between the first portion and the second portion and radially at least partially inside the third portion.

18. The electric motor as claimed in claim 11, wherein the at least one end wall has a bearing flange extending axially in the direction of the rotor to support a rotor shaft, wherein the intake region is formed between the second portion and the bearing flange.

19. The electric motor as claimed in claim 11, wherein the at least one end wall has radially extending cooling ribs on an inner side and/or the at least one end wall has cooling ribs on an outer side opposite the air-guiding element.

20. The electric motor as claimed in claim 11, wherein the housing has cooling channels for conducting a cooling fluid.

21. The electric motor as claimed in claim 14, wherein the insulating material is a temperature-resistant plastic.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In the drawings:

[0025] FIG. 1 is a schematic axial sectional illustration of an electric motor, designed as a permanently excited synchronous machine, with an air-guiding element;

[0026] FIG. 2 is a schematic illustration of an airflow formed in the housing of the electric motor, between the housing wall and the rotor end face, under the influence of the air-guiding element; and

[0027] FIG. 3 is a schematic partial illustration of an electric motor, designed as an asynchronous machine, with an air-guiding element.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0028] FIG. 1 shows a schematic illustration of an electric motor 100 designed as a permanently excited synchronous machine in an internal rotor design. The electric motor 100 is provided as a drive in an electric or hybrid vehicle. The electric motor 100 comprises a stator 103 fixed to a stator carrier 102, with a stator winding 105 arranged on a laminated stator core 103a. At the end face of the stator 103, winding heads 105a, b protrude axially over a laminated stator core 103a. The stator winding in the present case is designed as a hairpin winding and comprises conductor elements 105c designed as hairpins and inserted into stator grooves. At an end face of the electric motor 100, the individual conductor elements 105c are connected at contact points 105d to form a plurality of coils by welding or soldering the free ends to one another. By an interconnection device 107, the coils are in turn connected to a plurality of ring-shaped or ring-segment-shaped connection conductors in a predetermined manner according to the intended phase count and a predetermined interconnection type. The interconnection device 107 is furthermore connectable or connected to an energy source, for example a drive battery or a generator, by connection conductors, which are not illustrated in the drawing here.

[0029] The electric motor 100 furthermore comprises a rotor 104, which is rotatable about an axis A, and a housing 101, which surrounds the stator 103 and the rotor 104 with a circumferential wall 101a and with two end walls 101b; 101c. The housing 101 in the present case is at least partially formed by the stator carrier 102. The end walls 101b; 101c each have a bearing flange 122a, b extending axially in the direction of the rotor 104 to support a rotor shaft 108. A plurality of circumferentially spaced and axially extending permanent magnets 104c are furthermore inserted into slots inside the rotor 104, which permanent magnets are therefore located radially inside the stator winding 105 and the winding heads 105, 105b. In their axial end regions, the permanent magnets 104c are thermally influenced by heat radiation released by the winding heads 105a, b and can heat up compared to a region located axially between them, i.e. they can reach a higher temperature.

[0030] In FIGS. 1-3, an air-guiding element 106 can furthermore be seen, which is arranged axially between the end wall 101b and an end face 104a of the rotor 104 and which can specifically influence an airflow circulating inside the electric machine 100 to enable a cooling effect on the rotor 104 and the stator 103. The air-guiding element 106 is produced from an insulating material, preferably a plastic, for example a thermoplastic or thermosetting plastic which is thermally dimensionally stable under operating conditions, and generally has an approximately donut-shaped or toroidal structure which is open on the outer circumferential side. The air-guiding element 106 in the present case is fixed on the end wall 101b and on the bearing flange 122a by plastic elements, which are not illustrated in the drawing.

[0031] The air-guiding element 106 has a first portion 106a, which is formed in the shape of a disk around the axis A and is axially spaced from the end wall 101b, and which extends in the radial direction with respect to the end wall 101b. As can be seen in FIGS. 1, 2, the axial spacing of the first portion 106a from the end wall 101b is comparatively small compared to its axial spacing from the end face 104a of the rotor 104. The air-guiding element 106 has a second portion 106b, which is formed in the shape of a tube around the axis A and which adjoins the first portion 106a on the radially inner side and which extends in the direction of the end face 104a of the rotor 104. It can be seen that the air-guiding element 106 forms an air channel 120 with a heat exchange region 120a located between the first portion 106a and the end wall 101b and an intake region 120b extending inside the second portion 106b. The intake region 120b in the exemplary embodiment extends between the second portion 106b and the bearing flange 122a.

[0032] The air-guiding element 106 furthermore has a third portion 106c, which is formed in the shape of a disk and which adjoins the second portion 106b on the radially inner side and which extends radially outwards with an axial spacing radially with respect to the end face 104a of the rotor 104.

[0033] It can be seen that the air-guiding element 106 is arranged with the second portion 106b radially inside the winding head 105a and coincides with the winding head 105a axially. It can furthermore be seen that the interconnection device 107 is arranged radially inside a winding head 105a and that it is located axially between the first portion 106a and the second portion 106b and extends radially at least partially inside the third portion 106c.

[0034] FIG. 2 shows a detail of the electric motor in a schematic illustration with the air-guiding element 106 explained above, which is arranged between the end wall 101b, designed as an end shield and having the bearing flange 122a, on one side and the rotor end face 104a on the other side. The air-guiding element 106 has been modified slightly compared to the illustration of FIG. 1 and has a respective, somewhat conical, bridge portion 106d between the first portion 106a and the second portion 106b and between the second portion 106b and the third portion 106c. The bridge portions 106d can differ in size and be designed according to the characteristics specified in the present case. In FIG. 1, the bridge portion 106d is merely shown as rounded transitions. Fastening elements for the arrangement of the air-guiding element 106 are not illustrated in FIG. 2. The flow direction of an airflow generated under the influence of the air-guiding element 106 there is indicated by the arrows.

[0035] A laminar airflow is generated in the air channel 120 formed between the air-guiding element 106 and the end wall 101 with the bearing flange 122a. This flow is driven by a rotation of the rotor 104, wherein, by the heat exchange region 120a and by the intake region 120b, air from the area near to the end wall 101b is taken in towards the rotor 104 via the bearing flange 122a. This air has a comparatively low temperature as a result of a heat exchange with the end wall 101b and the bearing flange 122a and is accelerated radially outwards in an acceleration region 120c of the air channel 120 at the end face 104a. Along its path, the air flowing past can cool the permanent magnets 104c, which are located at the rotor 104 there and heated during operation, at the end face. The cooling in this region can have an effect on the mean value of the temperature distribution along the entire axial extent of the permanent magnet 104c. This temperature mean value can be reduced by up to 5K.

[0036] The airflow breaks away at an outer circumferential surface 104d of the rotor 104 and forms a radially outwardly dispersing eddy, which can pass radially further outwards through the winding head 105a and thereby likewise cools the winding head 105a and entrains the air heated in this region. In this case, the temperature of the winding head 105a can be reduced by ca. 1K. The airflow the experiences suction as a result of the negative pressure in the air channel 120 and can enter the radially outer region of the air-guiding element 106 again. This flow cycle is maintained so long as the rotor 104 is rotating. In the region enclosed by the air-guiding element 106 and in which the interconnection device 107 is located, a flow cycle likewise forms according to the arrow shown therein, which flow cycle, to a certain extent, moreover exchanges air with the airflow explained above. A cooling effect is therefore likewise present at the interconnection device 107.

[0037] To promote the cooling effect, radially extending cooling ribs 124 are provided on the inner side of the end wall 101b for improved heat absorption. Cooling ribs 126 can likewise be formed on the outer side of the end wall 101b, which is opposite the air-guiding element 106, for improved heat release.

[0038] Referring to FIG. 1, a closed fluid cooling circuit can moreover be provided on the electric motor 100 to increase the cooling effect, to which end cooling channels 128; 130 for conducting a cooling fluid are formed between the circumferential wall 101a and the stator carrier 102 or only on the circumferential wall 101a and/or on the end wall 101b of the housing 101.

[0039] According to a further exemplary embodiment as an alternative to FIG. 1, the electric motor 100, as is shown in part in a modified form in FIG. 3, can be designed as an asynchronous machine. The asynchronous machine in this case should be constructed identically to the machine explained by FIG. 1, wherein, instead of the permanent magnets 104c, the rotor 104 merely has a rod winding, inserted into grooves, with conductor elements 105c and with a short-circuit ring 104e arranged at the end face 104a. This short-circuit ring 104e is located radially inside the stator winding 105 and the winding heads 105a. The airflow explained with reference to FIG. 1 likewise applies, wherein the air flowing radially past the end face 104a now encompasses and cools the short-circuit ring 104e before the air passes through the winding head 105a in the manner explained above.

[0040] In the exemplary embodiments, the air-guiding element 106 is arranged merely at one end face of the electric motor. It goes without saying that such an air-guiding element 106 can also be arranged at both end faces.

[0041] Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.