Grounding of motor rotor

Abstract

The invention relates to an electric machine (120) comprising a housing (225) and a rotor (205) which is rotatably mounted in the housing (225) about an axis of rotation (215). In the housing (225), a recess (230) is provided at one axial end of the rotor (205), in which recess a closure element (235) is removably mounted. A ground contact (280) is disposed axially between the closure element (235) and the rotor (205).

Description

Technical Field

[0001] The present invention relates to grounding of a rotor of an electric machine, and in particular to grounding of a rotor of an electric drive machine for a motor vehicle. Background Art

[0002] A motor vehicle comprises an electric machine which can be operated with the aid of energy from an electrical energy storage device in order to drive the motor vehicle. The electric machine comprises a housing having a stator and a rotor. The rotor is supported rotatably about an axis of rotation relative to the stator or the housing. In order to prevent a potential difference from arising between the rotor and the housing, a grounding contact can be provided. The grounding contact comprises a first and a second side which are electrically connected to each other but decoupled from each other in terms of torque. The bearing is mounted on the motor in such a way that one side is connected to the rotor and the other side is connected to the housing.

[0003] In order to install the grounding contact on the motor, various proposals have been made. CN 214 506 818U proposes a grounding contact which is installed on an axial end of the motor rotor. The grounding contact comprises a rolling bearing between the rotor and the housing, which is axially preloaded by means of an elastic element.

[0004] However, it has been shown that rolling bearings are susceptible to corrosion under the influence of currents flowing through them. Therefore, it has been proposed to use grounding contacts which have two elements pressed axially together and arranged along the axis of rotation. However, such bearings are subject to a certain amount of wear due to friction and it may be necessary to check and, if necessary, replace one of the contact partners at predetermined intervals. Until now, it has been necessary to open the motor housing in order to access the grounding contacts. In particular, if the motor is accommodated in a common housing with other components, maintenance of the grounding contacts is very complicated. Summary of the invention

[0005] The object of the present invention is to provide an improved technique for grounding the rotor of an electric machine. The present invention achieves this object by means of the technical solution of the independent claim. The dependent claims provide preferred embodiments.

[0006] According to a first aspect of the present invention, an electric machine comprises a housing and a rotor, wherein the rotor is rotatably supported in the housing about a rotation axis. In the housing, a recess is provided at one axial end of the rotor, and a closure element is removably mounted in the recess. A ground contact is axially provided between the closure element and the rotor.

[0007] By removing the closing element from the housing, the ground contact can be more easily accessed. It may not be necessary to open the housing to take maintenance measures on the ground contact. In many applications, it may not be necessary to remove the housing with the motor from the surrounding structure. The available construction space can advantageously be fully utilized for mounting the ground contact. The closing element may protrude only slightly or not at all beyond the boundaries of the housing.

[0008] The grounding contact may comprise a first and a second side portion, which are electrically connected to one another but are torque-decoupled from one another. Preferably, the first side portion and the second side portion form an electrical contact contact which does not comprise rolling elements. In particular, the first and second side portions may be pressed axially against one another in order to establish electrical contact with as little friction as possible. One side portion may comprise a wear-resistant end plate and the other side portion may comprise an electrical conductor configured as a wear part. For example, a carbon pin may be used for this purpose. In order to compensate for axial mechanical wear, one of the side portions may be pressed against the other side portion by means of an axially acting elastic element.

[0009] Such a grounding contact can improve the potential balance between the rotor and the housing without the risk of galvanic corrosion of the rolling bearing. Due to the improved maintainability of the grounding contact, the grounding contact can also be used advantageously on highly loaded or continuously loaded electrical machines.

[0010] It is further preferred that the grounding contact can be axially separated between the first side and the second side. One of the two sides can be connected to the closing element without loss. The separation can be carried out in particular without tools. The first side and the second side can be held together by abutment, and one of the sides can be removed after the closing element is removed from the housing. This side can be designed as a wear element, so that it can be easily checked or replaced. The other side of the grounding contact can remain in the housing.

[0011] It is further preferred that the closing element is held in the recess by means of a thread. The thread further preferably extends coaxially with the axis of rotation. Preferably, an internal thread is provided in the recess and an external thread is provided on the closing element. Thus, the closing element can be reliably held on the housing and easily removed when necessary. The thread allows an axial surface pressure between the outer part of the closing element and the housing. In this area, for example, a flat seal can be used to prevent the fluid contained in the housing from flowing out. In another embodiment, an axial or radial annular groove can be provided on the closing element, in which an O-ring can be inserted, which seals the closing element relative to the housing.

[0012] It is further preferred that an axial connection element is provided between the closing element and the grounding contact. The grounding bearing can thus be arranged at a greater axial distance from the housing. This can be more advantageous in electrical or mechanical terms and the connection element can be used for other purposes, in particular for guiding the fluid in the axial direction, as will be described in more detail herein.

[0013] Preferably, the connecting element is mounted on the closing element with a clearance fit. In a preferred embodiment, the connecting element is removably mounted on the closing element. It is further preferred that the connecting element is held on the closing element so as to be non-rotatable relative to one another. The rotational position can be fixed by a form fit. Despite the torque transmitted by the grounding contact due to the decoupling, this torque can still be supported in this way relative to the closing element or the housing. For example, a radial projection can be constructed on the connecting element and a radial receptacle for the projection can be constructed on the closing element. The connection can allow an axial play between the connecting element and the end element.

[0014] It is further preferred that the connecting element has an axial hole and the closing element has a fluid channel through which a fluid can enter in a radial direction and flow out in an axial direction toward the hole. A fluid line can be arranged on the housing through which the fluid can flow in the direction of the radial end of the fluid channel. The fluid line can be mounted on the housing or constructed in a housing component. An annular channel can be arranged between the fluid line and the fluid channel in order to compensate for the rotational orientation of the closing element relative to the housing. The fluid can be arranged for cooling and / or lubricating the motor. Preferably, the fluid comprises a liquid, in particular oil.

[0015] The rotor of the electric machine preferably has a coaxial bore into which the connecting element extends. The connecting element can have at least one radial recess in order to discharge fluid radially from the bore onto the rotor. The rotor can thus be supplied with fluid at any axial position in order to lubricate or cool the rotor. The fluid flowing out of the radial recess can flow out in the axial direction in the region between the connecting element and the rotor.

[0016] The delivery of the fluid after it flows out of the connecting element can increase with the rotation speed of the rotor. A fluid blocking member can be arranged between the connecting element and the rotor to reduce the flow of the fluid in the direction of the closing element. The fluid blocking member is preferably located between the closing element and the radial recess. This can facilitate the flow of the fluid in the direction of the grounding contact.

[0017] In another embodiment, an elastic element is provided in order to induce an axial force between the closing element and the connecting element. The elastic element can, for example, comprise a wave spring. The connecting element can be accommodated in a rolling bearing in the region of the grounding contact in order to support the connecting element in the radial direction. The rolling bearing can be axially preloaded by means of the elastic element in order to ensure favorable support.

[0018] According to another aspect of the present invention, a grounding device for an electric motor is provided. The electric motor comprises a housing and a rotor, wherein the rotor is supported in the housing so as to be rotatable about a rotation axis. The housing has a recess at one axial end of the rotor. The grounding device comprises: a closing element, wherein the closing element is configured to be removably mounted in the recess; and a grounding contact, wherein the grounding contact is axially mounted between the closing element and the rotor.

[0019] The electric drive axle comprises the motor described in the present application. In addition, the electric drive axle may include a transmission. In one embodiment, the drive axle is arranged to be connected to another drive machine, in particular an internal combustion engine. The torque of the motor or the other drive machine can be provided on the driven shaft.

[0020] According to another aspect of the invention, a motor vehicle comprises an electric drive axle as described in this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will now be described in more detail with reference to the accompanying drawings, which are as follows:

[0022] Figure 1 An electrically drivable motor vehicle is shown;

[0023] Figure 2 Shows the grounding arrangement on the motor; and

[0024] Figure 3 The grounding device is shown in another perspective view. DETAILED DESCRIPTION

[0025] Figure 1 The motor vehicle 100 is shown with an electric drive 105. The electric drive 105 comprises an electric drive axle 110, which acts on drive wheels 115 of the motor vehicle 100. The drive axle 110 comprises an electric machine 120, which can be operated with the aid of electrical energy from an energy storage device 125. A converter 130 is provided to convert the DC voltage, which is usually provided by the energy storage device 125, into one or more AC voltages.

[0026] Figure 2 The grounding device 200 is shown on the electric machine 120. The electric machine 120 comprises a rotor 205 and a stator 210, which are mounted so as to be rotatable relative to one another about an axis of rotation 215. Figure 2 Only the rotor shaft 220 of the rotor 205 is shown. The stator 210 is mounted 225 in a non-rotatable manner relative to the housing and is Figure 2 Not visible in.

[0027] A recess 230 is provided on the housing 225 coaxially with the rotation axis 215. A closing element 235 is provided in the recess 230. Preferably, the recess 230 is round and has an internal thread; the closing element 235 has an external thread corresponding thereto. A seal 240 can be provided between the closing element 235 and the housing 225. In the embodiment shown, a contact surface perpendicular to the rotation axis 215 is formed on the outer side of the housing 225, and the closing element 235 has a flange that protrudes from the contact surface. An axial groove is machined in the flange, which is circumferential around the rotation axis 215, into which an O-ring can be inserted as a seal 240.

[0028] An axial end of a connecting element 245 is accommodated in the closing element 235. The connecting element 245 is preferably hollow and comprises an axial hole 250. It is further preferred that the connecting element 245 is constructed in the form of a tube. The closing element 235 comprises a fluid channel 255, which preferably enters the closing element 235 radially and extends axially in the direction of the connecting element 245. A fluid line 260 can be provided in or on the housing 225, through which, for example, oil can flow in the direction of the closing element 235 during operation of the motor 120. The oil can flow from the fluid line 260 through the fluid channel 255 into the hole 250 of the connecting element 245. The fluid can leave at the end of the connecting element 245 that is away from the closing element 235.

[0029] A radial recess 265 can be provided on the connecting element 245, through which the fluid can enter radially into the space between the connecting element 245 and the rotor shaft 220. In order to control the outflow of the fluid from the space and in particular to promote the outflow of the fluid in the axial direction toward the ground contact 280, a fluid barrier 270 can be provided in the axial region between the recess 265 and the closing element 235. The fluid can cool the rotor shaft 220 radially from the inside.

[0030] In order to connect the connecting element 245 to the closing element 235 in a torque-locking manner, the connecting element 245 can have radial projections 275, which engage in corresponding recesses on the closing element 235. In addition, a spring element 278 can be provided, which acts axially between the connecting element 245 and the closing element 235. In the embodiment shown, the spring element 278 is axially supported on the projection 275 on the connecting element 245. In the present case, the spring element 278 is formed by one or more wave springs surrounding the connecting element 245.

[0031] The connecting element 245 supports a grounding contact 280 on the axial end away from the closing element 235, and the grounding contact has a first side 285 and a second side 290. The second side 290 is electrically and mechanically constructed on the rotor 205 or connected thereto. In this case, the second side 290 is preferably made of a wear-resistant material such as steel. The first side 285 is further preferably constructed as a wear part, especially in the form of a brush with a carbon pin, which is electrically connected to the connecting element 245 by means of a flexible stranded wire. The carbon pin can be pressed against the first side 285 by means of a coaxial elastic element (here exemplarily in the form of a column spring). The fluid contained in the space between the hollow rotor shaft and the connecting element 245 can flow through the grounding contact 280 in a predetermined portion and thus reduce wear. A generally significantly larger portion of the fluid volume flow can flow out in the axial direction and be centrifugally thrown out on the rotor 215. Alternatively, the fluid may be received into a fluid passage that may direct the fluid to a cooling location or a lubrication location, such as a bearing of the rotor shaft 220 relative to the stator 210 or the housing 225 .

[0032] It is further preferred that a rolling bearing 295 is provided in this region in order to radially support the first side 285 of the grounding contact 280 or the end of the connecting element 245 remote from the closing element 235. The rolling bearing 295 can be axially preloaded by means of the elastic element 278 in the region of the closing element 235. As a result, the rolling bearing 295 can be operated in an O-type arrangement, which facilitates the position control of the connecting element 245. Thermally induced changes in the length of the connecting element 245 can be compensated by the elasticity of the element 278.

[0033] If the closing element 235 is removed from the recess 230 of the housing 225, the connecting element 245 together with the first side 285 of the grounding contact 280 can be removed. In this way, the grounding contact 280 can be easily inspected or replaced. For this purpose, in particular, worn parts of the first side 285 can be replaced. Subsequently, the first side 285 together with the connecting element 245 can be inserted through the recess 230 into the housing 225 and fixed to the housing by means of the closing element 235.

[0034] The grounding device 200 shown can better meet mechanical, electrical and / or hydraulic requirements. Advantageously, the grounding device 200 can simplify control or maintenance and, in particular, can achieve replacement of the grounding contact without disassembling the housing 225 .

[0035] Figure 3 Another perspective view Figure 2 The grounding device 200 of the type shown in FIG. Here, the rotation axis 215 is inclined relative to the plane of the drawing. The rotation axis 215 extends toward the observer at its right end.

[0036] It can be seen that an annular channel 305 is formed between the fluid line 260 and the fluid channel 255. The fluid line 260 is part of the housing 225 in the present case, but can also be designed as a separate element. The fluid line 260 ends in the annular channel 305 and the inlet of the fluid channel 255 begins there. Through the annular channel 305, the closure element 225 can be oriented arbitrarily around the rotation axis 215, so as to enable a fluid passage from the fluid line 260 to the fluid channel 255.

[0037] The illustrated section of the housing 225 may include, for example, a housing cover which may be produced, for example, as a light metal casting.

[0038] In the right region of the illustration, the rotor shaft 220 has a toothing 310 for meshing with a gear wheel of a transmission. The toothing 310 is preferably designed as a helical toothing and can act on the drive wheel 115 via the transmission.

[0039] Reference numerals list

[0040] 100 Motor Vehicles

[0041] 105 Electric drive

[0042] 110 Electric drive axle

[0043] 115 driving wheel

[0044] 120 Motor

[0045] 125 Energy Storage

[0046] 130 Converter

[0047] 200 grounding device

[0048] 205 rotor

[0049] 210 stator

[0050] 215 Rotation axis

[0051] 220 rotor shaft

[0052] 225 Shell

[0053] 230 Notch

[0054] 235 Closure element

[0055] 240 seals

[0056] 245 connection element

[0057] 250 holes

[0058] 255 fluid channels

[0059] 260 fluid pipeline

[0060] 265 Notch

[0061] 270 fluid blocking parts

[0062] 275 protrusion

[0063] 278 elastic element

[0064] 280 grounding contact

[0065] 285 first side

[0066] 290 Second side

[0067] 295 rolling bearing

[0068] 305 Ring Channel

[0069] 310 teeth

Claims

1. An electric motor (120), comprising a housing (225) and a rotor (205), the rotor being rotatably supported in the housing (225) about a rotation axis (215); the housing (225) having a recess (230) at one axial end of the rotor (205); and further comprising: a closure element (235) removably mounted in the recess (230); and A grounding contact (280) is axially arranged between the closing element (235) and the rotor (205).

2. The electric machine (120) according to claim 1, wherein: The ground contact (280) includes a first side portion (285) and a second side portion (290) which are electrically connected to each other but torque-decoupled from each other.

3. The electric machine (120) according to claim 2, wherein: The ground contact (280) is axially separable between a first side (285) and a second side (290).

4. The electric machine (120) according to any one of the preceding claims, wherein The closure element (235) is held in the recess (230) by means of a thread.

5. The electric machine (120) according to any one of the preceding claims, further comprising an axial connecting element (245) between the closing element (235) and the grounding contact (280).

6. The electric machine (120) according to claim 5, wherein: The connecting element (245) is mounted on the closing element (235) in a rotationally fixed manner.

7. The electric machine (120) according to any one of claims 5 or 6, wherein: The connecting element (245) has an axial hole (250); and the closing element (235) has a fluid channel (255) through which a fluid can enter in a radial direction and flow out in an axial direction toward the hole.

8. The electric machine (120) according to claim 7, wherein: The rotor (205) has a coaxial bore into which the connecting element (245) extends; the connecting element (245) has at least one radial notch (265) for radially discharging fluid from the bore (250).

9. The electric machine (120) according to claim 8, wherein: A fluid blocking member (270) is provided between the connecting element (245) and the rotor (205) to reduce the flow of the fluid toward the closing element (235).

10. The electric machine (120) according to any one of claims 5 to 9, wherein: An elastic element (278) is provided in order to induce an axial force between the closing element (235) and the connecting element (245).

11. A grounding device (200) for an electric machine (120), the electric machine comprising a housing (225) and a rotor (205), the rotor being rotatably supported in the housing (225) about a rotation axis (215); the housing (225) having a recess (230) at one axial end of the rotor (205); the grounding device (200) comprising the following elements: a closure element (235) configured to be removably mounted in the recess (230); and A grounding contact (280) is axially mounted between the closing element (235) and the rotor (205).

12. An electric drive axle (110) comprising an electric machine (120) according to any one of claims 1 to 10.

13. A motor vehicle (100) comprising the electric drive axle (110) according to claim 12.

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