WO2020025358A1

WO2020025358A1 - Cooling of an electrical machine

Info

Publication number: WO2020025358A1
Application number: PCT/EP2019/069516
Authority: WO
Inventors: Jürgen Bäuerle; Khalid Jafoui
Original assignee: Zf Friedrichshafen Ag
Priority date: 2018-07-30
Filing date: 2019-07-19
Publication date: 2020-02-06
Also published as: DE102018212654A1

Abstract

A cylindrical electrical machine (105) comprises an axis of rotation (120) and is designed to be accommodated in a cylindrical recess in a housing (115). A cooling casing (110) for the electrical machine (105) is designed to be arranged in an annular gap between the machine (105) and the housing (115). The cooling casing (110) comprises: an inlet region (130) for a fluid (137); an outlet region (135) for a fluid (137); a plurality of ridges (145), which are designed such that a channel (150) for guiding fluid (137) from the inlet region (130) to the outlet region (135) is formed between adjacent ridges (145); wherein the channels (150), in a first section (155), run towards the outlet region (135) axially offset in the circumferential direction about the axis of rotation (120); and, in a second section (160), run from the inlet region (130) to the first section (155) in the form of a fan.

Description

Cooling an electrical machine

The present invention relates to the cooling of an electrical machine. In particular special, the invention relates to a fluid cooling for a machine that can be used as a traction drive for a motor vehicle.

A motor vehicle comprises an electrical machine as a drive motor. In under different embodiments, the electrical machine can represent the sole drive or form one of several drive machines. Another drive engine can be designed in particular as an internal combustion engine. The electrical machine can heat up considerably during operation, so that active cooling is advantageous. For this purpose, in particular, a cooling fluid can be passed to heated positions on the machine in order to absorb and remove excess heat. It has been shown that uniform cooling of the electrical machine is preferable to cooling thermally stressed points.

DE 10 2014 204 816 A1 relates to an electrical machine with a cooling element.

A cooling fluid is guided in a cooling jacket in channels around the electrical machine.

An object of the present invention is to provide an improved technique for uniformly cooling an electrical machine. The invention solves this problem by means of the subjects of the independent claims. Sub-claims reflect particularly preferred embodiments.

A cylindrical electrical machine comprises an axis of rotation and is designed to be received in a cylindrical recess in a housing. A cooling jacket for the electrical machine is set up to lie in an annular gap between the machine and the housing. The cooling jacket comprises an inlet area for a fluid; an outlet area for a fluid; a plurality of webs which are designed such that a channel for guiding fluid from the inlet area to the outlet area is located between adjacent webs. forms is; wherein the channels in a first section extend axially offset in the circumferential direction about the axis of rotation in the direction of the outlet region; and run in a fan-shaped or star-shaped manner from the inlet area to the first section in a second section.

By guiding the channels, a largely identical flow rate can be achieved in the channels. The electrical machine can be cooled evenly improved by means of the fluid. Areas well below average (“hot spots”) can be avoided. The electrical machine can thus be loaded up to its performance limit in an improved manner, without the occurrence of selective thermal damage. The electrical machine can be part of a drive train of a motor vehicle. The motor vehicle can in particular be designed as a sports vehicle for racing.

The channels can be delimited radially on the inside by the cooling jacket and radially on the outside by the housing. Coolant can thus be kept away from the electrical machine, at the same time heat transfer of the fluid from or to the housing can be improved. By using the housing as a boundary of the channels, a mass of the cooling jacket can be reduced.

In the second section, a gap can be formed between ends of the webs, the gaps preferably being dimensioned such that flow velocities in the channels are essentially the same. The gaps can act in the manner of a nozzle or orifice and oppose the fluid to a predetermined flow resistance. The flow rate of the fluid can be adjusted well over the gap width.

In a further embodiment, a guide web is provided in the second section in a channel, which divides the channel into two subchannels. The subchannels extend side by side and are essentially offset from one another about the axis of rotation on a lateral surface. The subchannels run parallel to one another and are brought together again in the channel at the end of such a guide bridge. Through the walkway a flow of fluid in the channel can be improved. The fluid can be calmed better and directed in a desired direction.

It is particularly preferred that the guide web forms two gaps in the inlet area with the webs that delimit the channel, which are dimensioned such that flow speeds in the subchannels are essentially the same. If several guide ribs are provided in different channels, the fluid from the inlet region can first pass the first gap described above between two ribs, and then two second gaps, which are each formed between a rib and the guide rib. The first distances of the first column from the inlet area can be the same. Second distances of the second column from the inlet area can also be the same, the second distances usually being greater than the first distances.

The guide web can extend in a circumferential direction on a predetermined part of the first section. This allows further guidance and calming of the fluid in the channel. In addition, the subchannels can act as a flow obstacle, so that the flow velocity in the channel can be delicately influenced over the length of the subchannels.

The outlet area can be close to an axial end of the cooling jacket, the ends of adjacent webs in the second section being offset axially in the same direction and in the circumferential direction. In other words, the webs running in the circumferential direction can end in a step-like manner. An area in which there is little or circular flow can be avoided. Such an area is also called dead water area.

The channels can be brought together in a third section between the second section and the outlet area, the third section extending obliquely to the axis of rotation. As a result, the channels can be brought together in the direction of the outlet region with a substantially uniform flow velocity of the fluid. The cooling jacket can also comprise a radial end at an axial end, with further webs preferably being formed on the radial end, between which an end-side cooling channel is formed in each case, which extends around the axis of rotation. As a result, cooling of the electrical machine at one axial end can be improved. In this area, for example, there can be a winding head of the machine that is usually subjected to high thermal loads. Widths of the end channels can be chosen depending on their lengths so that the flow velocities of the fluid are as uniform as possible. The radial termination can have a concentric recess for the passage of a shaft of the electrical machine.

The cooling jacket can be designed to be integrally connected to the housing at at least one axial end. The connection can be made in particular by welding. This can ensure that the fluid is sealed in the space between the cooling jacket and the housing. In addition, the cooling jacket can be connected to the housing precisely and with a high load capacity. In one embodiment, the cooling jacket is designed as a load-bearing element and in particular is dimensioned such that it can transmit bearing forces of the electrical machine to the housing or can stiffen the housing. A housing for an electrical machine has a cooling jacket described herein.

A method of assembling a housing described herein with a cooling jacket includes steps of axially inserting the cooling jacket into a cylindrical recess in the housing so that fluid channels are formed between the cooling jacket and the housing; and the cohesive connection of the cooling jacket to the housing at at least one axial end of the cooling jacket. The invention will now be described in more detail with reference to the accompanying figures, in which:

1 shows a drive unit with an electrical machine, a cooling jacket and a housing in one embodiment;

Figure 2 shows two views of a cooling jacket;

Figure 3 is a view of an axial end of a cooling jacket in a further embodiment; and

FIG. 4 shows a longitudinal section through a drive unit in a further embodiment.

FIG. 1 shows a drive unit 100 with an electrical machine 105, a cooling jacket 110 and a housing 115 in one embodiment. The Antriebsein unit 100 is preferably used as part of a drive train, especially on board a motor vehicle. The drive unit 100 can in particular be designed as a traction drive of the motor vehicle. The housing 115 can be designed to connect a further component of a drive train, for example a transmission or a further drive motor.

The electrical machine 105 has a substantially cylindrical shape and has an axis of rotation 120. The cooling jacket 1 10 is set up to be arranged coaxially between the electrical machine 105 and a recess 125 of the housing 1 15 provided therefor.

The cooling jacket 110 comprises an inlet area 130 and an outlet area 135 for fluid 137, with fluid 137 preferably being supplied or removed in a radial direction. The cooling jacket 110 comprises a substantially hollow cylindrical body 140, from which webs 145 extend radially in the direction of the housing 115. The webs 145 are preferably made in one piece with the base body 140. A channel 150 is formed between webs 145, which id 137 leads from inlet area 130 to outlet area 140. A plurality of channels 150 run in a first section 155 in a fan shape from the inlet area 130, in a subsequent second section 160 axially offset from one another in the circumferential direction and are then guided together in a third section 165 and to the outlet area 135. Sections 155, 160 and 165 can have different limitations at different axial locations of the cooling jacket 1 10. In particular, sections 160 and 165 can overlap one another in an axial view. In the first section 155 in particular, a channel 150 can be divided into two adjacent subchannels 175 by means of a guide bar 170.

The channels 150 preferably run at a predetermined distance around the axis of rotation 120, revolving the axis of rotation 120 between the inlet region 130 and the outlet region 135 as soon as possible. In the illustrated embodiment, a complete circulation is not quite achieved because the inlet area 130 is axially not exactly aligned with the outlet area 135 and the sense of circulation is selected as shown. It should be noted that the functions of the inlet area 130 and the outlet area 135 can also be interchanged, so that the fluid 137 flows in the opposite direction to that shown.

To mount the cooling jacket 1 10 on the housing 1 15, the cooling jacket 1 10 can be inserted into the recess 125, so that the webs 145 extending in the radial direction preferably rest against the radial inside of the housing 1 15 in a fluid-tight manner. A small leakage between a web 145 and the housing 115 is often unavoidable and can be tolerated. After insertion, the cooling jacket 1 10 can be attached to the housing 1 15. A classic O-ring seal can be used for this, but a material connection of the cooling jacket 110 to at least one axial end of the housing 110 is preferred, in particular by means of welding. The cooling jacket 110 and the Ge housing 1 15 are preferably each made of a light metal, for example based on aluminum or magnesium. The cooling jacket 1 10 and the housing 1 15 can each be produced, for example, by die casting. Different welding processes are used to connect the two elements. costume. In a first variant, a friction stir welding process is used. In a second variant, the elements are joined together using an electron beam welding process, in particular a multi-bath process. In a third variant, a laser welding process can also be used. The welding process used is preferably selected depending on the materials used and the accessibility of the weld.

FIG. 2 shows two views of a cooling jacket 110, which essentially differ in the selected rotations of the cooling jacket 110 about the axis of rotation 110. Both views are described together below.

The sections 155, 160 and 165 are essentially adjacent to one another on a circumference about the axis of rotation 120; a slight overlap between sections 160 and 165 can be neglected. In the first section 155, the channels 150 run essentially only in the circumferential direction and are axially offset from one another. In the second section 160, the channels 150 run essentially star-shaped towards the entrance area 130. In the present case, however, the channels 150 do not form a complete star, but approach the inlet area 130 in a fan shape at an angle of approximately 180 °, smaller or larger angles are also possible. At an angle of approx. 360 ° there is also talk of a star-shaped approach.

In the vicinity of the inlet region 130, adjacent webs 145, which each delimit a channel 150, form a gap 205 with a predetermined width. The gap 205 forms a flow obstacle and influences the flow velocity of the fluid 137. On one side of the inlet area 130, on which no channels 150 are connected, a tear-off edge 210 can be provided to increase the flow resistance of the fluid 137 into a channel 150, which is extends near an axial end of the cooling jacket 1 10.

A guide bar 170 in a channel 150 can form a further gap 215 with an adjacent bar 145 at an end facing the inlet area 130. Two gaps 215 of the same width are preferred between the guide web 175 and the webs 145 delimiting the channel 150. The gaps 215, like the gaps 205 or the tear-off edge 210, have the task of influencing the flow velocity of the fluid 137 between the inlet region 130 and the outlet region 135. The guide bar 170 can only extend into the first section 155. All guide webs 170 preferably end on one side at the same point in the circumferential direction about the axis of rotation 120. On their other sides facing the inlet region 130, the guide webs 170 can end essentially the same distance from the inlet region 130.

The third section 165 can be seen particularly well in the lower illustration. Here the channels 150 are brought together and to the outlet area 135. For this purpose, the webs 145, which axially delimit the channels 150, preferably end offset in the circumferential direction as shown. Approximately, the ends of the webs 145 can be connected here with a straight line 220, which includes an acute angle with the axis of rotation 120. In the embodiment shown, the outlet area 135 is not in the center but offset in the direction of one of the axial ends of the cooling jacket 110. In the third section 165, the area in which the channels 150 are brought together is preferably designed with an enlarged cross section on an axial side that is distant from the outlet area 135. As a result, fluid 137 exiting from a channel 150 axially further away from the outlet area 135 can be adapted in terms of its flow rate to fluid 137 which exits axially closer to the outlet area 135 from a channel 150. The enlarged cross section is not recommended if the straight line 220 is parallel to the axis of rotation 120.

Figure 3 shows a view of an axial end of a cooling jacket 110 in a wide ren embodiment. Here, the cooling jacket 110 comprises a radial termination 305, so that the base body 140 is cup-shaped. The radial termination 305 can have a concentric recess 310, in particular for the passage of a shaft of the electrical machine 105. In this area, the cooling jacket 110 can be reinforced in order to better support the electrical machine 105 or, for example, a shaft bearing. The housing 115 preferably likewise comprises a radial termination, so that a surface gap is formed between the radial terminations, which can be divided into channels 150 by webs 145 on the radial termination 305 of the cooling jacket 110. In the area of the radial termination 305, the channels 150 preferably run concentrically and revolve around the axis of rotation 120 as far as possible. Ends of the substantially circular end channels 150 are fluidly connected to the inlet area 130 and the outlet area 135. Fluid 137 can thus flow from the inlet area 130 to an end channel 150, through this around the axis of rotation 120 and to the outlet area 135.

Figure 4 shows a longitudinal section through a drive unit 100 still in another embodiment. The radial termination 305 of FIG. 3 is implemented. The electrical machine 105 is also shown in section, so that a radially outer stator 405 can be seen, which can comprise a laminated core, which carries grooves 410, in which conductors can lie as a winding for generating a magnetic field. In this area, a strong heating can occur due to the current flow, which can be counteracted in an improved manner by the described cooling jacket 110.

Reference number drive unit

electrical machine

cooling jacket

casing

axis of rotation

recess

inlet area

outlet

fluid

body

web

channel

first section

second part

third section

conducting land

Subchannel gap

tear-off edge

gap

Straight radial termination

Stator recess

groove

Claims

claims

1 . Cooling jacket (1 10) for a cylindrical electrical machine (105) with an axis of rotation (120), the machine (105) being set up to be received in a cylindrical recess (125) of a housing (1 15), the Cooling jacket (1 10) is set up to lie in an annular gap between the machine (105) and the housing (1 15); the cooling jacket (110) comprising: an inlet region (130) for a fluid (137); an outlet area (135) for a fluid (137); a plurality of webs (145) which are designed such that a channel (150) for guiding fluid (137) from the inlet region (130) to the outlet region (135) is formed between adjacent webs (145); wherein the channels (150) in a first section (155) extend axially offset in the circumferential direction around the axis of rotation (120) in the direction of the outlet region (135); and in a second section (160) run in a fan shape from the inlet area (130) to the first section (155).

2. cooling jacket (1 10) according to claim 1, wherein the channels (150) radially inside through the cooling jacket (1 10) and radially outside through the housing (1 15) are limited.

3. cooling jacket (1 10) according to claim 1 or 2, wherein in the second section (160) rule between ends of the webs (145) in each case a gap (205) is formed and the column (205) are dimensioned so that flow velocities in the Channels (150) are essentially the same.

4. cooling jacket (1 10) according to claim 3, wherein in the second section (160) in a Ka channel (150) a guide bar (145) is provided which divides the channel (150) into two sub-channels (21 5).

5. cooling jacket (1 10) according to claim 4, wherein the guide web (145) in the inlet area (130) with the webs (145) which delimit the channel (150) forms two gaps (215) which are dimensioned such that Flow velocities in the subchannels (215) are essentially the same.

6. cooling jacket (1 10) according to one of claims 4 or 5, wherein the guide web (145) extends on a predetermined part of the first section (155) in the circumferential direction.

7. cooling jacket (1 10) according to any one of the preceding claims, wherein the outlet region (135) near an axial end of the cooling jacket (1 10) and ends of adjacent webs (145) in the second section (160) in the same direction axially and in circumference direction are offset.

8. cooling jacket (1 10) according to claim 7, wherein the channels (150) in a third section (165) from the second section (160) and the outlet region (135) are brought together and the third section (165) obliquely to Axis of rotation (120) extends.

9. cooling jacket (1 10) according to one of the preceding claims, further comprising a radial end (305) at an axial end, wherein at the radial end (305) further webs (145) are formed, between each of which an end-side cooling channel (150) is formed, which extends around the axis of rotation (120).

10. cooling jacket (1 10) according to claim 9, wherein the radial end (305) has a con-centric recess, in particular (310) for passage of a shaft of the electrical machine (105).

1 1. Cooling jacket (1 10) according to any one of the preceding claims, wherein the cooling jacket (1 10) is adapted to be integrally connected to the housing (1 15) at at least one axial end.

12. Housing (1 15) for an electrical machine (105), the housing (1 15) comprising a cooling jacket (1 10) according to any one of the preceding claims.

13. The method for assembling a housing (1 15) according to claim 12, the method comprising the following steps: axially inserting the cooling jacket (1 10) into a cylindrical recess of the housing (1 15) so that between the cooling jacket tel (1 10) and the housing (1 15) channels (150) for fluid (137) are formed; and integrally connecting the cooling jacket (1 10) with the housing (1 15) at least one axial end of the cooling jacket (1 10).