DE102013223673A1 - Motor vehicle drive train - Google Patents

Abstract

Motor vehicle drive train (10) comprising an electric machine (12) with a stator (16) and a rotatable rotor (14), characterized in that the rotor (14) to the stator (16) via a contact element (60) permanently electrically connected is.

Description

The invention relates to a drive train for a motor vehicle according to the preamble of patent claim 1.

In the DE 196 18 865 C2 a generic powertrain is shown, including an internal combustion engine, an electric machine, a clutch and a transmission.

In the electric machine of such a motor vehicle drive train, shaft voltages occur between the rotor and the stator. Such shaft voltages are caused on the one hand by induction of a voltage in a conductor loop (rotor shaft, bearings, end shield and stator housing) by magnetic asymmetries of the electrical machine, on the other hand generated by steep voltage edges of an inverter. If the shaft voltages occurring between the rotor and the stator exceed a certain value, they discharge, for example as a result of arc flashovers. Such flashovers occur particularly frequently at the bearing points of the motor vehicle drive train, which generate a tribological electrical insulation between the rotor and stator due to the lubrication. In this case, bearings within the electrical machine are just as affected as bearings outside the electrical machine, such as bearings within a transmission. The discharges occur mainly at the bearings, damage their surface and change their microstructure, whereby the microstructural changes affect the material properties. This additional load on the bearings leads to increased wear and premature failure.

It is therefore an object of the shaft voltages harmless and degrade in a defined manner within a motor vehicle drive train.

This above object is achieved by means of the motor vehicle drive train according to the independent claim. In the dependent claims advantageous refinements and developments of the invention are given.

According to the invention, a generic drive train is proposed in which the rotor is permanently electrically conductively connected to the stator via a contact element.

The electrical potential differences, which justify the shaft voltages build up during operation of the electric machine between the rotor and stator and discharge as soon as the shaft voltage is sufficiently large for a sparkover. Such a spark usually occurs at the bearings between the stator and rotor. The bearing of the rotor on the stator within an electrical machine can be carried out by various types of bearings, all types of bearings having a lubricant, which isolate the intermeshing components of the bearing tribologically against each other. A permanently conductive contact between the rotor and the stator by an additional contact element, enables a permanent equipotential bonding and therefore ensures an immediate and harmless degradation occurring shaft voltages. A potential difference threshold, which triggers a sparkover, is not exceeded.

In order to reliably prevent tribological electrical insulation of the contact element, the contact element is preferably lubricant-free, in particular free of viscous or liquid lubricant. As a possible alternative, as long as the conductive contact is maintained, among other things, solid lubricants can be used. The contact element is therefore preferably formed fluid-free and / or viscosschmiermittelfrei. Furthermore, it is advantageous to form the contact element with low friction in order to keep the wear low.

It is also proposed to arrange the contact element within a lubricant-free space. A contact element, which is arranged for example in an oil-lubricated transmission of a motor vehicle drive train, would be wetted by an oil film, wherein the conductive contact between the rotor and stator is interrupted.

In a drive train, it is usually the case that housing of the individual modules are conductively connected to each other, wherein the housing of the electric machine is normally electrically connected to the stator. In addition, one of the housing, usually that of a drive motor is grounded or earthed. Furthermore, the rotating elements of the motor vehicle drive train are also conductively connected to each other, for example, the rotor shaft and a transmission input shaft and a clutch disc. The other remarks on waves or other rotating components of the motor vehicle drive train are also applicable to other elements that are electrically connected to the rotor, for example, a clutch disc transferable, the selbiges also applies vice versa. Since a conductive connection between the rotor and stator is sufficient to reduce the shaft voltages, it is proposed to arrange the contact element functionally between an element electrically connected to the stator and an element electrically connected to the rotor. These Elements may include a housing of the motor vehicle train and a shaft of the motor vehicle drive train or a clutch disc, but in particular the rotor shaft of the electric machine. The contact element can therefore be arranged at any point within the motor vehicle drive train.

It is extremely expedient according to an advantageous embodiment, when the contact element is arranged on a contact element receiving area. A contact element receiving region may be formed, for example, on an element that is conductively in contact with the stator, or on an element that is conductively in contact with the rotor, in particular on a housing of the motor vehicle drive train or on a shaft, in particular the rotor shaft. This contact element receiving area can be designed as a separate component or integrated within an existing component, in particular on a housing. A contact element receiving region is characterized inter alia in that the contact element is arranged captively within the contact element receiving region. The contact element is therefore limited in its mobility so that it can move freely only within a predetermined range. This free movable area may be selected to be relatively large or relatively small relative to the size of the contact element, depending on the embodiment.

It is also favorable if a clearance is formed between the contact element and the element in electrical contact with the stator, as well as between the contact element and the element in electrical contact with the rotor. Such a clearance, for example between the shaft and the contact element and between the contact element receiving area and the contact element, is preferably to be formed in such a way that there is a permanent contact between rotor and stator. If the contact element is annular, for example, then the radial clearance between the contact element and the shaft should be smaller than the radial clearance between the contact element and the contact element receiving area. Due to vibration and gravity, the contact element can not remain within a non-contact position. Furthermore, due to the force of gravity, the contact element subject to play experiences a preferred contact position, with the contact element conforming to the shaft. A contact element subject to play can therefore also be adapted to the movements of the shaft, e.g. Tumbling, follow. Electrical and physical contact between shaft and contact element is always present.

With particular advantage, the contact element is substantially non-rotating, but with little clearance, formed with respect to the contact element receiving area. In one embodiment, the contact element has at least one tooth and the contact element receiving region has at least one recess. In the following, advantages and possible embodiments of a tooth and a recess are explained, which, however, are transferable to other teeth. A tooth is associated with a recess and engages in this. In one possible variant, the tooth is arranged radially on the outside of the contact element and engages with clearance in the circumferential direction in the recess. The play in the circumferential direction allows a low rotatability of the contact element relative to the contact element receiving area, wherein a rotation may optionally cause a lifting movement in the radial direction to the rotational axis of the shaft. Such play allows the contact element to follow the movements of the shaft with permanent electrical contact. The rotation of the shaft entrains the contact element and causes at least one tooth of the contact element to produce an electrically conductive contact on at least one receptacle of the contact element receiving region. The contact element thus produces a continuous contact between the rotor and the stator. Since the contact element only rests freely, the wear is low. The arrangement of the teeth on the contact element and the receptacle on the contact element receiving area can also be reversed. Other versions that use a similar or the same functionality, are also conceivable. The operation of the contact element is independent in this case of the direction of rotation of the shaft.

It has already been mentioned above that it is extremely favorable if the radial clearance between the shaft and the contact element is smaller than the radial clearance between the contact element receiving region and the contact element. In the event that the radial clearance between the contact element receiving area and contact element is greater than the radial play between the shaft and contact element, the contact element is located on the contact element receiving area, between the shaft and contact element in this case, however, still a game available. This results in that no electrical contact between the shaft and contact element is made. In other words, the contact element must rest on the shaft, wherein the outer diameter of the contact element is free and the teeth make a conductive contact with the housing. Preferably, the game is designed such that a failure of the contact element is excluded by wear over the entire at least over a specified part of the life.

In a further development, the teeth of the contact element are distributed uniformly around the circumference.

A contact element without play wears much faster in comparison with the contact element subject to play, since it can not follow the movements of the shaft and therefore not only rests, but force is applied. Furthermore, a contact element without play has a higher drag torque and is from a certain degree of wear due to wear no longer able to make electrical contact between the rotor and stator. Such wear is compensated by a game-afflicted contact element, at least in the previously explained embodiment by the predetermined game. The predetermined game is designed so that the contact element retains its functionality even when worn and worn on the contact surface facing the shaft. The main wear surface is therefore the contact surface between the contact element and the shaft.

Preferably, the contact element is formed of a hard and resistant material with a small coefficient of friction coefficient. This allows a long service life with low wear and low drag torque. The contact element may be formed, for example, as a steel component, in particular from ZF7B, or as a plastic component.

In addition to the electric machine, a motor vehicle drive train further comprises a transmission, a clutch device and a drive motor. If the shaft voltages that arise within the electrical machine are not degraded and the bearings of the electrical machine merely insulated, it is the case that the shaft voltages degrade within other components of the motor vehicle drive train. This may be the case, inter alia, due to flashover within the coupling device, the drive motor or within the transmission. Insulating bearings therefore only shift the shaft voltage problem to another location in another powertrain assembly.

As already mentioned above, the contact element can be integrated due to the contacting of the individual module housing within any assembly of the motor vehicle drive train. In principle, the contact element can be arranged at any point within the motor vehicle drive train, as long as the rotor and the stator are electrically conductively connected to one another via the contact element.

In a further embodiment, the contact element is arranged within the coupling device with a clutch disc, a pressure plate and a flywheel between the clutch disc and the pressure plate or the flywheel. In one embodiment, the contact element is formed on a drive plate of the clutch disc, wherein the contact element is arranged within a recess of a friction lining. With the clutch open, i. the friction lining and the pressure plate or the flywheel are at a distance from each other, the contact element is shaped so that it bridges the clearance gap between the friction lining and the flywheel or the pressure plate and creates an electrical contact between the drive plate and pressure plate or flywheel. The contact element is designed so elastic that it is compressible at least to the clearance between the clutch when closing the clutch. A contact surface of the contact element is in the closed state of the coupling device substantially in a plane with a friction surface of the friction lining. A permanent contact by the bridging of the clearance between the friction lining and the pressure plate or the flywheel can be generated inter alia by a spring element which applies the contact element on the one hand to the pressure plate or flywheel and on the other hand is compressible to bridge the clearance gap.

Another possibility is to arrange the contact element laterally on a bearing of the shaft. The contact element creates a conductive contact between an outer bearing shell of the bearing and an inner bearing shell of the bearing. This conductive contact may be produced, inter alia, by a conductive plate in physical contact with the inner bearing shell and the outer bearing shell. Furthermore, the contact element can be formed completely or only over part of the bearing. In this case, the contact element is advantageously acted upon by a force in the direction of the bearing, wherein the contact element is applied only to the inner and the outer bearing shell with continuous contact. The acting force, which applies the contact element to the bearing, can be generated inter alia by a spring element or by gravity. In an advantageous embodiment, the contact element also has a wear reservoir, which ensures a long service life and can be achieved, for example, by a thickened material region. In a further variant, the contact element can produce a contact between a contact element receiving region and a contact flange of the shaft. The contact flange may, among other things, be pressed onto the shaft or formed directly from the shaft. According to an advantageous embodiment that is Contact element mounted on the one hand on the housing, or on a component or an element which is in conductive contact with the housing, wherein at least one conductive connection to the stator is required, on the other hand, the contact element is in contact with the shaft or the contact flange. The contact element may be applied laterally, in particular via a force application, on the bearing and on the housing. In a further development, the contact element is in particular rotatably mounted on the housing, and applied in a rotary motion on the contact flange or on the shaft in conductive contact. In an advantageous embodiment, this contact element also has a wear reservoir.

The contact element is favorably designed such that irrespective of the movements of the shaft, an electrically conductive contact between the stator and rotor is ensured.

The various embodiments can be combined with each other in an advantageous manner.

The invention is explained below by way of example with reference to the accompanying figures.

Show it:

1 a schematic structure of a motor vehicle drive train;

2 an embodiment of a contact element of the motor vehicle drive train 1 ;

3 a coupling device of the motor vehicle drive train with contact element;

4a , b is the contact element of the coupling device 3 ;

5 a schematic representation of the contact element, which is arranged on a bearing;

6 a further schematic representation of the contact element, which is arranged on a contact flange;

7 an alternative embodiment of the contact element 6 ;

In 1 is a schematic construction of a motor vehicle powertrain 10 with an electric machine 12 shown. The electric machine 12 has a rotor 14 , a stator 16 and a housing, in the following EM housing 18 called, up. The permanent-magnet rotor 14 is radially inside the stator 16 arranged and with a rotor shaft 20 opposite the stator 16 and the EM package 18 freely rotatable via a bearing 22 , in this case two rolling bearings 22 , on the EM housing 18 stored. A lubricant or a smear layer within the bearing 22 provides tribologically based electrical insulation between rotor 14 and stator 16 ,

The stator 16 includes a stator lamination stack 24 and on the stator lamination stack 24 arranged stator coils 26 where the stator coils 26 from an inverter 28 , in particular a frequency converter 28 , are driven. The EM housing 18 is electrically connected to the stator lamination, in particular via attachment points 19 (shown schematically) of the stator 16 on the EM housing 18 For example, about screwing, riveting, pressing or other known fasteners. Among other things are also housing 9 . 18 individual assemblies 8th of the motor vehicle drive train 10 via attachment points 19 (also shown schematically) connected to each other. Basically, the type of connection or attachment of the housing to each other irrelevant, as long as equipotential bonding is ensured or an electrically conductive connection between the components is present. The conductive connections between the various components are in 1 again clarified.

As already described above, occur between rotor 14 and stator 16 Shaft voltages on. To reduce these shaft voltages, the drive train points 10 a contact element 60 which is on a contact element receiving area 58 , in particular on the EM housing 18 , is arranged. The contact element receiving area 58 is here axially laterally of the bearing 22 arranged and provides an electrically conductive connection between the housing 18 and the stator 16 ago. Radially within the contact element receiving area 58 is the contact element 60 arranged and fixed substantially in the axial direction. The contact element 60 is radially outward on the rotor shaft 20 arranged and electrically conductive with the contact element receiving area 58 connected. Furthermore, the contact element 60 an electrical contact between the rotor 14 and stator 16 come and close this short. Shaft voltages between rotor 14 and stator 16 occur, are therefore dismantled immediately. A spark in the warehouse 22 does not take place

In 2 is a variant of the contact element 60 and the contact element receiving area 58 in the axial direction B shown in more detail. The contact element 60 is circular and has teeth 62 on, which are evenly distributed radially outwardly in the circumferential direction. The teeth 62 grab with a game in the circumferential direction Su ( Circumferential play) in recordings 56 one. The contact element 60 is substantially rotationally fixed to the contact element receiving area except for the circumferential clearance Su 58 , to the EM housing 18 and the stator 16 arranged. In addition to the circumferential clearance Su, the contact element 60 inter alia a clearance S2 between the contact element receiving area 58 and the contact element 60 , as well as a game S1 between the rotor shaft 20 and the contact element 60 on. The game S1, the game S2 and the circumferential game Su allow the contact element 60 with low wear a continuous electrical contact between the stator 16 and rotor 14 manufacture. In this embodiment, the game S2 is made larger than the game S1, depending on the embodiment of the contact element 60 is and in principle can be solved differently. The contact element 60 is due to the smaller design of the game S1 against the game S2 always in contact with the rotor shaft 20 , A freewheel of the rotor shaft 20 ie a state of the rotor shaft 20 without contact with the contact element 60 , is due to the vibrations in the motor vehicle powertrain 10 and not possible due to gravity. Due to the rotation of the rotor shaft 20 becomes the contact element 60 taken rotatably, with at least one tooth 62 electrical contact with a boundary surface 54 one of the shots 56 receives. The electrically conductive contact between contact element 60 and contact element receiving area 58 or stator 16 is guaranteed. The contact element receiving area 58 may be designed, inter alia, such that the torque or the force in the circumferential direction, the on the tooth 62 acts in a radial direction to the rotor shaft 20 directed force is implemented. This is a contact between contact element 60 and rotor shaft 20 , as well as between contact element 60 and contact element receiving area 58 secured by a low application of force. Basically, the contact element is only on.

The game S1, the game S2 and the circumferential clearance Su, as well as a slight play in the axial direction are necessary so that the contact element is free to move and can form a necessary minimum of contact points depending on the operating condition.

The powertrain 10 points next to the electric machine 12 even more modules 8th on, for example, a coupling device, a drive motor or a manual transmission, which are indicated here only schematically and in the flow of action before or after the electric machine 12 can be arranged. Because the housings of different building units 8th via connector means 19 are fixed to each other, is an electrical contact between the units 8th present, for example, is grounded via a contact on the drive motor to ground. It is therefore the case that the contact element 60 in any unit 8th in the drive train 10 can be arranged. Basically, it is only necessary that the rotor 14 and the stator 16 at any arbitrary position of the motor vehicle drive train 10 electrically conductively connected to each other.

A coupling device 100 a motor vehicle powertrain 10 that is a contact element 600 is in 3 shown. The coupling device 10 has, among other things, a flywheel 102 , a printing plate 104 and a clutch disc 106 on. The clutch disc further comprises a lining carrier 108 and a friction lining 110 on. Other components of the coupling device 100 and the clutch disc 106 themselves are not discussed here because they are irrelevant to the function. On the one hand is the clutch disc 106 conductive with the rotor 14 (In 3 not shown), on the other hand, the flywheel 102 or the pressure plate 104 conductive with the stator 16 (in 3 not shown). An electrical contact between rotor 14 and stator 16 is through a contact element 600 produced. The contact element 600 is axially laterally on the lining carrier 108 the clutch disc 106 within a recess of the friction lining 110 established. In the closed state of the coupling device 100 is the contact element 600 with flywheel 102 and lining carrier 108 and therefore also the rotor 14 and the stator 16 conductively connected. In the open state of the coupling device 100 the contact element relaxes 600 such that the resulting air gap between friction lining 110 and flywheel 102 is bridged, wherein the electrical contact between the flywheel 102 and contact element 600 does not break off.

The resulting air gap with the coupling device open 100 , as well as the elasticity and wear resistance of the contact element 600 are to adapt to each other. To optimize the life and elasticity, the contact element should 600 have a possible advantageous form. One possible form of training is in 3 already shown and in 4a , b shown again in more detail. The circular trained contact element 600 has a pedestal 602 , as well as a pot-shaped shell 604 on, viewed in the axial direction to the flywheel 102 expands radially outward. The shell 604 is also by four grooves 606 broken up the shell 604 split. The number of grooves 606 is basically arbitrary. By breaking up and the special widening pot or shell shape, the contact element 600 a significantly improved compressibility or can relax with open clutch over a long distance difference with length expansion. Such a contact element 600 For example, to the lining carrier 108 riveted. In principle, it is also possible to integrate a spring element.

In the following, three further embodiments are shown schematically on the 5 to 7 explained, with only the operation of the contact element 60 is executed. Since only the basic operation is explained here, the structure of such contact elements 60 different from the one shown here. There are usually only explained the differences between the different versions, the different variants can also be combined with each other. The same components are given the same reference numerals.

In 5 is a wave 20 , a housing 18 and a warehouse 22 shown. The wave 20 is on the case 18 about a camp 22 freely rotatably arranged, the bearing 22 the housing opposite the shaft 20 tribologically isolated. Axial side of the bearing 22 is a contact element 60 disposed within a contact element receiving area 58 passing through the housing 18 is formed, is arranged. The contact element 60 is arranged and guided within a kind of receptacle, and with a force, in this case by a spring element 80 , in the direction of the camp 22 applied. The contact element is still located on an inner race 22a and an outer race 22b of a warehouse. The contact element creates a conductive contact between the housing 18 and the wave 20 or the rotor 14 and the stator 16 (in 5 - 7 not shown). The contact element is on the application of force to the spring element 80 only to the bearing shells 22a and 22b created.

An alternative embodiment is in 6 shown. The contact element 60 is here, compared with 5 , not at a warehouse 22 arranged but on a contact flange 20a the wave 20 as well as on the housing 18 , The contact element 60 is again in a contact element receiving area 58 arranged and guided and is subject to a force, again by a spring element 80 , The contact element, which is designed as a plate, lies at the same time at contact areas 82 of the housing 18 , as well as at a contact area 82 of the contact flange 20a at. The contact area 18a of the housing can in principle be designed as an independent component, with only a direct or indirect contact with the housing or the stator must be present. The contact flange 20a can also be arbitrary on the shaft 20 be formed, for example as a wave ring 20a the on the wave 20 pressed.

In 7 is an alternative variant with contact flange 20a shown. The contact element 60 Here, however, is at a contact element receiving area 58 rotatably mounted and loaded on one side with a force. The application of force by the spring element 80 sets the contact element 60 only to the contact area 82 of the contact flange 20a the wave 20 on, wherein the contact of the contact element 60 with the housing 18 via the contact element holder 58 given is. The contact element 60 can also be designed here such that the force of gravity, the contact element 60 over the dead weight to the contact flange 20a invests. Furthermore, the contact element is in one area 84 which is the contact flange 20a or facing the shaft, respectively amplified or made wider. This allows a long life, since a correspondingly large wear reservoir 84 is available.

LIST OF REFERENCE NUMBERS

8th

module

9

casing

10

Motor vehicle drive train

12

Electric machine

14

rotor

16

stator

18

EM-housing

19

connector means

20

Rotor shaft / shaft

20a

Contact flange / shaft ring

22

camp

22a

Inner race

22b

Outer shell

24

stator lamination

26

stator

28

Inverter / frequency converter

54

boundary surface

56

admission

58

Contact element receiving area

60

contact element

62

tooth

80

spring element

82

contact area

84

wear reservoir

100

coupling device

102

flywheel

104

printing plate

106

clutch disc

108

lining support

110

friction lining

600

contact element

602

base

604

Bowl

606

groove

S1

game

S2

game

Su

circumferential play

F

force

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19618865 C2 [0002]

Claims (11)

Motor vehicle drive train ( 10 ) - a brushless electric machine ( 12 ) with a stator ( 16 ) and a rotatable rotor ( 14 ), characterized in that the rotor ( 14 ) with the stator ( 16 ) via a contact element ( 60 ) is permanently electrically connected. Motor vehicle drive train ( 10 ) according to claim 1, characterized in that the contact element ( 60 ) is free of fluid lubricant. Motor vehicle drive train ( 10 ) according to claim 1 or 2, characterized in that the contact element ( 60 ) is disposed within a fluid lubricant-free space. Motor vehicle drive train ( 10 ) according to one of claims 1 to 3, characterized in that the contact element ( 60 ) functionally between one with the stator ( 16 ) electrically conductive connected element, in particular the housing ( 9 . 18 ) of an assembly ( 8th ) of the motor vehicle drive train ( 10 ), and one with the rotor ( 14 ) electrically conductively connected element, in particular a shaft ( 20 ) one of the assemblies ( 8th ) of the motor vehicle drive train ( 10 ) is arranged. Motor vehicle drive train ( 10 ) according to one of claims 1 to 4, characterized in that the contact element ( 60 ) on the element connected to the stator ( 16 ) is in conductive contact, or on the element which is in contact with the rotor ( 14 ) is conductively in contact, at a contact element receiving area ( 58 ) is arranged. Motor vehicle drive train ( 10 ) according to one of claims 1 to 5, characterized in that between the contact element ( 60 ) and with the stator ( 16 ) in electrically contacting element, as well as between the contact element ( 60 ) and with the rotor ( 14 ) is formed in electrically contacting element a game. Motor vehicle drive train ( 10 ) according to claim 5 or 6, characterized in that the contact element ( 60 ) with respect to the contact element receiving area ( 58 ) is formed substantially against rotation. Motor vehicle drive train ( 10 ) according to one of claims 1 to 7, characterized in that the contact element ( 60 ) is annular and the element which is connected to the rotor ( 14 ) is in electrically conductive contact, at least partially encloses. Motor vehicle drive train ( 10 ) according to one of claims 1 to 8, characterized in that the motor vehicle drive train ( 10 ) further comprises a coupling device ( 100 ), wherein the contact element ( 600 ) within the coupling device ( 100 ) is arranged. Motor vehicle drive train ( 10 ) according to one of claims 1 to 9, characterized in that the contact element ( 60 ) is formed elastically deformable. Motor vehicle drive train ( 10 ) according to one of claims 1 to 10, characterized in that the contact element ( 10 ) side of a bearing ( 22 ) or laterally on a contact flange ( 20a ), which at the conductive with the rotor ( 14 ), in particular on the shaft ( 20 ) of the motor vehicle drive train ( 10 ) is arranged.

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