CN107769417B

CN107769417B - Electric motor

Info

Publication number: CN107769417B
Application number: CN201610681474.6A
Authority: CN
Inventors: 朱涛; 邓实; 刘新华
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2016-08-17
Filing date: 2016-08-17
Publication date: 2021-03-05
Anticipated expiration: 2036-08-17
Also published as: CN107769417A

Abstract

The present invention relates to an electric motor comprising: a housing; a first end cap and a second end cap mounted to both ends of the housing to form a substantially enclosed interior space; a shaft rotatably supported by the first and second end caps; a rotor located in the inner space and mounted to the rotating shaft; and a stator disposed about the rotor in the interior space and proximate the housing; characterized in that the shaft is a hollow shaft, a condensation radiator is mounted at one end of the shaft and outside the inner space, the pressure of the closed hollow space of the shaft is kept below atmospheric pressure and the hollow space is partly filled with liquid. According to the present invention, it is possible to radiate heat generated by the components sealed in the substantially closed internal space of the motor to the ambient environment, thereby improving the cooling effect of the motor.

Description

Electric motor

Technical Field

The present invention relates to electric motors, and more particularly to cooling of electric motors.

Background

As the power of the electric motor used in electric vehicles such as electric motorcycles, electric bicycles, and electric automobiles increases, it becomes more and more important to efficiently cool the electric motor. The maximum allowable operating temperature of the motor components, such as bearings, rotating seals, magnets and copper windings, etc., determines the maximum continuous power of the motor. During operation of the electric motor, heat losses occur in the stator and in the rotor. Since the stator is usually arranged directly adjacent to the motor housing, the heat generated in the stator can be dissipated to the surroundings via the motor housing, whereas the heat generated in the rotor has to travel a long thermal path before being dissipated to the surroundings, so that the heat generated in the stator can generally be dissipated more easily than the heat generated in the rotor. Cooling the rotor is more challenging than cooling the stator. Especially for permanent magnet motors, effective cooling of the rotor is critical for permanent magnet motors, since the magnets in the rotor can demagnetize when subjected to excessive temperatures and thus cause damage to the motor.

To improve the efficiency of cooling the internal components of the motor, some designs employ end caps with openings so that the internal components of the motor, including the rotor, can be exposed to the ambient environment through the openings. However, this cooling method is not suitable for a motor having a high level of foreign matter protection against foreign matter such as moisture or dust. In such a motor having a high level of protection against foreign matter, in order to prevent foreign matter such as moisture or dust from entering the interior of the motor, the stator and rotor of the motor are generally sealed in a substantially closed space. This substantially closed space makes it less likely that heat generated by the motor components located therein, particularly the motor rotor, will dissipate.

Therefore, there is a need for improved cooling of existing motors.

Disclosure of Invention

The object of the present invention is to overcome at least one of the drawbacks of the prior art described above by proposing an electric motor which is capable of dissipating heat from the internal components of the motor, in particular the motor rotor, to the surrounding environment, even in the case where the stator and the rotor of the motor are sealed in a substantially closed space, thereby improving the cooling efficiency of the motor.

To this end, according to an aspect of the present invention, there is provided an electric motor including:

a housing;

a first end cap and a second end cap mounted to both ends of the housing to form a substantially enclosed interior space;

a shaft rotatably supported by the first and second end caps;

a rotor located in the inner space and mounted to the rotating shaft; and

a stator disposed about the rotor in the interior space and proximate the housing;

characterized in that the shaft is a hollow shaft, a condensation radiator is mounted at one end of the shaft and outside the inner space, the pressure of the closed hollow space inside the shaft is kept below atmospheric pressure and the hollow space is partly filled with liquid.

According to the present invention, it is possible to radiate heat generated by the components sealed in the substantially closed internal space of the motor to the ambient environment, thereby improving the cooling effect of the motor.

Drawings

FIG. 1 is a schematic cross-sectional perspective view of an electric motor according to a preferred embodiment of the present invention;

FIG. 2 is a schematic perspective view of a condensing heat sink according to a preferred embodiment of the present invention;

FIG. 3 is a schematic perspective view of a heat collector according to a preferred embodiment of the present invention; and

fig. 4 is a schematic sectional view of a motor according to a preferred embodiment of the present invention, in which a heat transfer path and an air flow path are shown by arrows.

Detailed Description

Preferred embodiments of the present invention are described in detail below with reference to examples. It will be understood by those skilled in the art that these exemplary embodiments are not meant to limit the invention in any way.

Fig. 1 is a schematic sectional perspective view of a motor according to a preferred embodiment of the present invention. As shown in fig. 1, the motor 1 according to the preferred embodiment of the present invention includes a housing 3, first and

second end caps

7 and 9 mounted to both ends of the housing 3 to form a substantially closed internal space 5, a rotating shaft 15 rotatably supported by a first bearing 11 provided on the first end cap 7 and a second bearing 13 provided on the second end cap 9, a rotor 17 in the internal space 5 and mounted to the rotating shaft 15 to rotate with the rotating shaft 15, and a stator 19 surrounding the rotor 17 in the internal space 5 and disposed adjacent to the housing 3.

According to the invention, the shaft 15 is a hollow shaft open at one end, for example the right end of the shaft 15 is open in fig. 1. A condensation radiator 21 is installed at the open end of the rotation shaft 15 outside the inner space 5. The open end of the spindle 15 can be plugged by a removable plug to close the hollow space 15a within the spindle 15. The condensation heat sink 21 is made of a heat conductive material and may be mounted to the rotation shaft 15 by a known means such as a screw connection or an interference fit. The gas in the closed hollow space 15a of the rotating shaft 15 is at least partially evacuated to make the pressure in the hollow space 15a lower than the atmospheric pressure, and the hollow space 15a is partially filled with a liquid such as water, ethanol, ethylene glycol or a mixture thereof. The boiling point of the liquid evaporation can be adjusted by changing the pressure in the hollow space 15 a. The hollow space 15a enclosed by the shaft 15 can be evacuated as required by the particular application. When the motor operates, the liquid in the hollow space 15a of the rotating shaft 15 is tightly attached to the inner wall of the hollow space 15a of the rotating shaft 15 under the action of centrifugal force, the heat generated by the rotor 17 is transferred through the rotating shaft 15 to evaporate the liquid tightly attached to the inner wall of the hollow space 15a of the rotating shaft 15, and the hot steam generated by evaporation moves towards the part with lower pressure where the condensation radiator 21 is located, so that the heat is transferred to the condensation radiator 21, and further the heat is radiated to the surrounding environment through the condensation radiator 21. While transferring heat to the condensing radiator 21, the vapor is condensed again into liquid. Since the liquid in the rotating shaft 15 at the position of the rotor 17 is continuously evaporated, the condensed liquid moves along the left direction in the figure against the inner wall of the hollow space 15a of the rotating shaft 15, so that the processes of evaporation, condensation and re-evaporation are continuously performed, so that the heat generated by the rotor is continuously dissipated to the surrounding environment, and the rotor is effectively cooled.

Fig. 2 is a schematic perspective view of a condensing radiator according to a preferred embodiment of the present invention. Although the condensation heat sink 21 may have any suitable shape, such as a circular disk, in the preferred embodiment shown in fig. 1 and 2, the condensation heat sink 21 includes a hollow central shaft 23 and a heat-dissipating disk 25 extending circumferentially from the hollow central shaft 23. The hollow central shaft 23 and the heat dissipation disc 25 are preferably integrally formed. One end of the hollow central shaft 23 communicates with the open end of the shaft 15 and the other end of the hollow central shaft 23 may be plugged by a removable plug 27 to facilitate filling and evacuation of the hollow shaft 15. The hollow central shaft 23 communicates at one end with the open end of the shaft 15 to facilitate adequate heat exchange between the steam and the condensate heat sink for improved heat dissipation efficiency, but it should be understood that the hollow central shaft 23 may be tightly nested on the shaft 15. The condensation heat sink 21 may further include a plurality of ribs 29 connected between the hollow center shaft 23 and the heat dissipation plate 25, the ribs 29 not only increasing the heat dissipation area of the condensation heat sink 21, but also increasing the strength of the condensation heat sink 21 and enhancing the air flow around the condensation heat sink 21. The hollow center shaft 23 and the heat dissipation plate 25 of the condensation radiator 21 are generally integrally formed of a heat conductive metal material. In order to further increase the air flow around the condensation heat sink 21 to improve the heat dissipation efficiency, the condensation heat sink 21 further includes fan blades 31 formed around the heat dissipation plate 25. The fan 31 may be formed of the same metal material as the heat dissipation plate 25, but it is preferable to form a plurality of fan blades made of plastic around the heat dissipation plate 25 by, for example, an over-molding process, in order to reduce the cost of the condensation heat sink, to reduce the weight, and to reduce noise generated when the condensation heat sink rotates. In order to prevent the condensate radiator from causing accidental injury during rotation, the condensate radiator may be provided with a cover 35 with an opening 33 mounted to the housing 3.

According to a preferred embodiment of the present invention, as shown in fig. 1, the hollow center shaft 23 of the condensation radiator 21 may be formed as a conical hollow space 37 gradually increasing toward the hollow space 15a of the rotation shaft 15 of the motor. Such a conical hollow space 37 gradually increasing toward the hollow space 15a of the rotating shaft 15 of the motor helps the condensed liquid to move from the hollow space 37 toward the evaporation space inside the rotating shaft 15 corresponding to the rotor 17 by centrifugal force when the motor rotates, thereby increasing the amount of evaporation of the liquid and improving heat dissipation efficiency.

According to a preferred embodiment of the present invention, as shown in fig. 1, a heat collector 39 may be further installed on the rotary shaft 15 in the inner space 5 between the rotor 17 and the first and/or

second end caps

7 and 9 to transfer heat from the inner space 5 to the rotary shaft 15. Heat collector 39 includes a heat collection disk 41 made of a thermally conductive material. More preferably, heat collector 39 further includes a plurality of protrusions 43 formed on heat collecting plate 41. The protrusions 43 not only increase the heat exchange area of the heat collector 39 but also enable the air flow in the inner space between the rotor 17 and the first end cap 7 and/or the second end cap 9 to flow. In addition, the heat collector 39 is preferably installed at a portion of the rotation shaft 15 where the hollow space 15a is formed, to improve efficiency of collecting and transferring heat. The heat generated by the stator and the rotor (especially the heat generated by the rotor) maintains a high temperature in the inner space 5 between the rotor 17 and the first end cap 7 and/or the second end cap 9, and the heat can be transferred from the inner space between the rotor 17 and the first end cap 7 and/or the second end cap 9 to the rotary shaft 15 through the heat collector 39, and then the heat can be dissipated by means of the evaporation of the liquid in the rotary shaft 15 and the condensation of the steam in the condensation radiator 21.

Fig. 4 is a schematic sectional view of a motor according to a preferred embodiment of the present invention, in which a heat transfer path and an air flow path are shown by arrows. In fig. 4, a dotted arrow a indicates a heat transfer path, and a solid arrow B indicates a heat airflow flow path. As shown in fig. 4, when the motor is operated, the liquid filled in the hollow space 15a of the hollow rotary shaft 15 of the motor forms a liquid film 45 on the inner wall of the hollow space 15a of the hollow rotary shaft 15 by the centrifugal force. The heat on the rotor 17 and the heat collected by the heat collector 39 is transferred to the liquid film 45 via the rotating shaft 15 to evaporate the liquid, and the steam flowing to the condensing heat radiator 21 transfers the heat to the condensing heat radiator 21, and further, the heat is radiated to the surrounding environment through the condensing heat radiator 21. While transferring heat to the condensation radiator 21, the steam is condensed back into liquid and flows back to the evaporation space within the hollow rotating shaft 15 along the hollow space 37 of the hollow central shaft 23 of the condensation radiator 21 and the inner wall of the hollow space 15a of the hollow idle shaft 15, so that the processes of evaporation, condensation and re-evaporation are continuously performed, so that the heat generated by the rotor is continuously radiated to the surrounding environment. Meanwhile, the fan 31 of the condensation heat sink 21 rotating with the rotation shaft 15 drives the cold air around the condensation heat sink 21 through the opening 33 of the cover 35 and drives the cold air into the atmosphere along the groove 49 formed by the heat radiating fin 47 on the housing 3 after exchanging heat with the condensation heat sink 21, thereby improving the cooling efficiency.

Thus, according to the present invention, heat can be radiated from the motor internal components, particularly the motor rotor, to the ambient environment even in the case where the stator and the rotor of the motor are sealed in a substantially closed space, preventing the motor from being damaged due to overheating.

The present invention has been described in detail with reference to the specific embodiments. It is to be understood that both the foregoing description and the embodiments shown in the drawings are to be considered exemplary and not restrictive of the invention. For example, although the present invention is preferably applicable to permanent magnet motors, the present invention is applicable to virtually any motor in which the stator and rotor are sealed within a substantially enclosed space and the rotor rotates with the shaft. It will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit of the invention, and these changes and modifications do not depart from the scope of the invention.

Claims

1. An electric motor (1) comprising:

a housing (3);

a first end cap (7) and a second end cap (9) mounted to both ends of the housing (3) to form a substantially enclosed interior space (5);

a rotating shaft (15) rotatably supported by the first end cover (7) and the second end cover (9);

a rotor (17) located in the inner space (5) and mounted to the rotating shaft (15); and

a stator (19) disposed in the inner space (5) around the rotor (17) and in close proximity to the housing (3);

characterized in that the shaft (15) is a hollow shaft, at one end of which and outside the inner space (5) a condensation radiator (21) is mounted, the pressure of the closed hollow space (15a) inside the shaft (15) being kept below atmospheric pressure and the hollow space (15a) being partly filled with liquid;

a heat collector (39) is further mounted on the rotary shaft (15) and located in an inner space between the rotor (17) and the first end cover (7) and/or the second end cover (9) to transfer heat from the inner space to the rotary shaft (15), and the heat collector (39) includes a heat collecting plate (41) made of a heat conductive material.

2. Electric motor (1) according to claim 1, characterized in that said condensation radiator (21) communicates with said hollow space (15 a).

3. The electric motor (1) according to claim 2, wherein the condensation radiator (21) comprises a hollow central shaft (23) and a radiating disc (25) extending circumferentially from the hollow central shaft (23), one end of the hollow central shaft (23) communicating with the open end of the rotating shaft (15), the other end of the hollow central shaft (23) being plugged by a removable plug (27).

4. The electric motor (1) according to claim 3, characterized in that said condensation radiator (21) further comprises a plurality of ribs (29) connected between said hollow central shaft (23) and said heat-dissipating disc (25).

5. The electric motor (1) according to claim 3, characterized in that said condensation radiator (21) further comprises fan blades (31) formed around said heat-dissipating disc (25).

6. Electric motor (1) according to claim 5, characterized in that said heat-dissipating disc (25) is made of metal material and said fan blades (31) are made of plastic.

7. The electric motor (1) according to claim 3, characterized in that the hollow central shaft (23) has a conical hollow space (37) which gradually increases towards the hollow space (15a) of the rotating shaft (15).

8. The electric motor (1) according to claim 1, characterized in that said heat collector (39) further comprises a plurality of protrusions (43) formed on said heat collecting plate (41).