Motor with heat dissipation for motor shaft bearing

Abstract

The invention relates to an electric motor having a motor housing (2) with a shaft section for accommodating a motor shaft (4) and a motor section for accommodating motor electronics (5) and motor windings (6), wherein the shaft section and the motor section are separated from one another in a sealed manner by a separation pot (7) arranged in the motor housing (2), wherein a metal ball bearing pot (8) is arranged in the separation pot (7), in which a ball bearing (9) is fixed, and wherein the ball bearing pot (8) is connected to a motor housing section which is in indirect abutment with the external environment via the separation pot (7), such that the motor housing serves as a cooling body and the heat generated by the ball bearing (9) during operation is dissipated onto the motor housing and the external environment via the ball bearing pot (8) and the separation pot (7).

Description

[0001] manual:

[0002] The present invention relates to an electric motor having a compact design for heat dissipation in the motor shaft bearing.

[0003] In electric motors that generate high rotational speeds on the motor shaft, the power dissipation of the ball bearings housing the motor shaft increases significantly due to intense heat generation. This is especially true in compact motor designs where the ball bearings are arranged in direct proximity to multiple other components, where the generated heat cannot be adequately dissipated.

[0004] Therefore, the basic objective of this invention is to provide improved heat dissipation in electric motors for ball bearings in which a motor shaft is mounted.

[0005] This objective is achieved by a combination of the features described in claim 1.

[0006] According to the present invention, an electric motor having a motor housing is provided, comprising a shaft section for accommodating a motor shaft and a motor section for accommodating motor electronics and motor windings. The shaft section and the motor section are sealed apart from each other by a separation tank arranged in the motor housing, wherein a ball bearing housing is arranged in the separation tank, and ball bearings are fixed in the ball bearing housing. The ball bearing housing is indirectly connected to the motor housing section of the external environment via the separation tank, such that the motor housing acts as a cooling body and the heat generated by the ball bearings during operation is dissipated to the motor housing and the external environment through the ball bearing housing and the separation tank.

[0007] The separation tank is used to separate the shaft section and the motor section, and to prevent gas exchange between the crankcase and the electronic components or motor windings.

[0008] However, the arrangement of the separator tank containing the ball bearing housing results in a design where the ball bearing must be positioned highly centered and capable of dissipating the small amount of heat generated during operation. According to the invention, heat dissipation to the motor housing occurs due to the connection between the separator tank and the ball bearing housing and the ball bearing housed therein.

[0009] In one embodiment of the electric motor, the separator is provided as a single piece, with its rotational axis about the motor shaft passing through the motor housing. Specifically, the motor housing forms a circumferential outer wall that abuts on the axial side against an axial wall into which the separator is recessed. The separator is preferably designed as a hollow cylindrical shape with sections of varying diameters, wherein a ball bearing housing is arranged in the section of the ball bearing housing that extends axially into the furthest part of the motor housing.

[0010] Here, an advantageous embodiment is the following: wherein the separating tank and the ball bearing tank are designed to have the same shape in the section of the separating tank where the ball bearing tank is arranged. In other words, the ball bearing tank and the separating tank define the same outer contour.

[0011] An advantageous embodiment of the electric motor is yet another embodiment, wherein a thermal grease is provided between the separator tank and the section of the motor housing indirectly connected to the bearing tank via the separator tank. The thermal grease preferably forms an intermediate layer and provides thermal connection between the motor housing and the separator tank without component contact. Therefore, the vibrations of the individual components remain decoupled from each other.

[0012] An improvement to the electric motor features a removable cover on the motor housing, which can be positioned on the axial side of the rest of the motor housing and forms a section of the motor housing indirectly connected to the ball bearing housing and thus to the ball bearing via the separator can. With the separator can and motor housing forming a single piece, the motor components can be mounted via the side axially facing the separator can, on which the cover is removably positioned. Simultaneously, using the cover as a cooling element provides a larger surface area for heat dissipation.

[0013] The heat dissipation performance in the electric motor is further improved in the following variant: wherein the housing cover has a cooling element that extends axially in the direction of the ball bearing can, which locally increases the surface area for indirect connection to the ball bearing can via the separator can.

[0014] As an advantageous embodiment, the cooling element is provided to have a cylindrical or conical shape, having an axial surface for connection to the axial outer wall of the separator. Therefore, heat from the ball bearing is transferred from the ball bearing tank to the separator, then further from its axial outer wall surface to the connection surface of the cylindrical cooling element, and finally to the entire surface of the outer casing.

[0015] In a preferred embodiment, the ball bearing can is formed into a ball bearing housing in which a ball bearing is pressed in.

[0016] Furthermore, one variant of the electric motor is characterized in that the ball bearing housing has a free space between the ball bearing and the section of the motor housing that connects to the external environment. Therefore, the ball bearing can directly dissipate heat to the air entering the free space and is not directly connected to the axial surfaces of the adjacent separator and cooling body of the ball bearing housing.

[0017] Furthermore, in one improvement to the electric motor, the separating tank extends axially through the motor housing to the housing cover. Therefore, the separating tank defines a large portion of the central inner motor housing around the rotation axis in the axial direction (i.e., along the axis of rotation of the motor shaft). Preferably, the separating tank extends axially through 60-95% of the total axial length of the motor housing, more preferably through 70-95%, and even more preferably through 80-90%.

[0018] An advantageous embodiment example is yet another embodiment example, wherein the motor housing and the separation tank are made of plastic, and the metal ball bearing tank is directly overmolded with plastic in an injection molding process.

[0019] For a compact design, the motor advantageously features windings that circumferentially enclose the separator. Simultaneously, it is advantageous that the windings are axially spaced from the ball bearings. Therefore, the heat generated by the motor windings is kept separate from the heat generated by the ball bearings.

[0020] Furthermore, for a compact design of the electric motor, the motor electronics are arranged on a circuit board with a central opening, and cooling elements protruding from the housing cover extend through the central opening. Alternatively, the separator can extend through the central opening. Furthermore, alternatively, heat dissipation can also be achieved directly through the circuit board. The central opening can then be omitted.

[0021] Other advantageous improvements of the invention are characterized in the dependent claims and are shown in more detail together with the description of preferred embodiments of the invention with reference to the accompanying drawings. In the drawings:

[0022] Figure 1 A cross-sectional view of the electric motor through an example of the implementation scheme is shown;

[0023] Figure 2 Showing from Figure 1 Detailed diagram.

[0024] exist Figure 1 and Figure 2 In the present invention, embodiments of the electric motor 1 are shown in cross-sectional views and detailed views.

[0025] The electric motor 1 includes a one-piece motor housing 2 with a housing cover 3, which is axially fixed to the motor housing 2 in a detachable manner and forms part of the motor housing when fixed. On the side axially facing the housing cover 3, the motor housing 2 is formed as a single piece extending into the interior of the motor housing 2 into a separation tank 7. A motor section is positioned between the inner wall of the motor housing 2 and the outer shell of the separation tank 7, in which windings 6 and motor electronics 5 fixed to a circuit board 14 are housed. A shaft section, sealed and demarcated by the separation tank 7, is positioned within the separation tank 7, in which a motor shaft 4 extends along its axis of rotation. The separation tank 7 extends axially substantially through the entire motor housing 2 to the housing cover 3.

[0026] In the deepest section of the separator tank 7, when viewed axially, a ball bearing housing 8 made of a heat-conducting material (specifically, metal) is arranged. The motor housing 2, containing the separator tank 7, is injection molded around the ball bearing housing 8 in a plastic injection molding process, such that the separator tank 7 and the ball bearing housing 8 have the same shape or inner and outer contours and are directly adjacent to each other. The ball bearing housing 8 defines a bearing housing in which a press-fit ball bearing 9 is mounted on the motor shaft 4. A free space 13 is formed between the ball bearing 9 and the axial inner wall surface of the separator tank 7, into which the motor shaft 4 extends through its free end.

[0027] Around the rotation axis, on the outer casing 3, a cooling element 11 is designed to be a single-piece component in the form of a cylindrical form. This cooling element is formed of a solid material and protrudes axially in the direction of the ball bearing can 8. A layer of thermal paste 10 is provided axially between the cooling element 11 and the axial outer wall surface of the separation can 7.

[0028] The heat generated during the operation of the ball bearing 9 is dissipated from the ball bearing 9 to the ball bearing housing 8, further to the separator 7, and axially through the thermal paste 10 to the cooling element 11 of the housing cover 3 of the motor housing 2. The heat is further dissipated from the housing cover 3 to the external environment. Therefore, the motor housing, and specifically its housing cover 3, serves as a coolant. In an alternative embodiment not shown, the thermal paste 10 is omitted, and the cooling element 11 is in direct contact with the separator 7.

[0029] The separator 7 is a hollow cylinder, subdivided into three axial sections, each with a different inner diameter. A free space 13 is arranged in the region with the smallest diameter, a bearing housing with ball bearings 9 is arranged in the central region, and motor windings 6 are arranged radially around the separator 7 in the region with the largest inner diameter. Therefore, when viewed axially, the ball bearings 9 do not overlap with the motor windings 5.

[0030] Circuit board 14 defines a central opening 15 around the rotation axis of motor shaft 4. A cooling element 11, axially projecting from housing cover 3, extends through this central opening to the separator 7. In alternative variations not shown, instead of cooling element 11, a region of minimum diameter of separator 7 may extend through 15, such that contact between separator 7 and cooling element 11 occurs axially above circuit board 14. Alternatively, housing cover 3 may be designed without cooling element 11, allowing separator 7 to move directly against the axial inner wall of housing cover 3, either directly or via thermal paste 10.

Claims

1. An electric motor having a motor housing, comprising: The device includes a shaft section for accommodating a motor shaft and a motor housing for accommodating motor electronics and motor windings. The shaft section and the motor housing are sealed apart from each other by a separation tank integrally formed with the motor housing. A metal ball bearing tank is arranged in the closed end of the separation tank, and a ball bearing is fixed in the ball bearing tank. The ball bearing tank is indirectly attached to the portion of the motor housing connected to the external environment through the separation tank, such that the motor housing serves as a cooling body. The heat generated by the ball bearing during operation is dissipated to the motor housing and the external environment through the ball bearing housing and the separation tank; The motor housing has a removable housing cover that can be placed on the axial side of the rest of the motor housing and forms a section of the motor housing that is indirectly connected to the ball bearing housing via the separator tank; and The outer casing has a cooling element that extends axially in the direction of the ball bearing can, which locally increases the surface area for indirect connection to the ball bearing can via the separator can.

2. The electric motor according to claim 1, characterized in that... The separation tank and the ball bearing tank are designed to have the same shape in the section of the separation tank in which the ball bearing tank is arranged.

3. The electric motor according to claim 1, characterized in that... Thermal paste is applied between the separator tank and the section of the motor housing that is indirectly connected to the ball bearing tank via the separator tank.

4. The electric motor according to claim 1, characterized in that... The cooling element is designed to have a cylindrical or conical shape and has an axial surface for connection to the axial outer wall surface of the separation tank.

5. The electric motor according to claim 1, characterized in that... The ball bearing can is formed into a ball bearing housing in which the ball bearing is pressed or inserted.

6. The electric motor according to claim 1, characterized in that... The ball bearing housing has free space between the ball bearing and the section of the motor housing that connects to the external environment.

7. The electric motor according to claim 1, characterized in that... The separator extends axially through the motor housing to the housing cover.

8. The electric motor according to claim 1, characterized in that... The motor housing and the separation tank are made of plastic, and the ball bearing tank is directly encapsulated in the plastic.

9. The electric motor according to claim 1, characterized in that... The motor windings enclose the separator in the circumferential direction and are arranged axially spaced from the ball bearings.

10. The electric motor according to claim 1, characterized in that... The motor electronics are arranged on a circuit board with a central opening, and the cooling element, which protrudes from the housing cover, extends through the central opening.

11. The electric motor according to claim 1, characterized in that... The motor electronics are arranged on a circuit board with a central opening, and the separation tank extends through the central opening.

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