DE102011080889A1 - Electric machine and method for assembling an electric machine - Google Patents

Abstract

The invention relates to an electric machine (1) having a drive shaft (2) on which a rotor (3) and a connection element (4) are arranged and in which an at least partially non-positive torque transmission connection between the rotor (3) and the connection element (4 ) is formed by the connecting element (4) by means of a locking element (18) in the direction of the rotor (3) is urged. In this case, the locking element (18) is designed as a screw and has an external screw thread (25) which is screwed into a shaft internal thread (26) of the drive shaft (2). The invention further relates to a method for assembling an electrical machine (1).

Description

The invention relates to an electric machine having a drive shaft on which a rotor and a connecting element are arranged and in which an at least partially non-positive torque transmission connection between the rotor and the connecting element is formed by the connecting element is urged by a locking element in the direction of the rotor. The invention further relates to a method for assembling an electrical machine.

State of the art

Electric machines of the type mentioned are known from the prior art. The electrical machine can be configured as desired and, in particular, can be present as a motor, generator or motor generator of a motor vehicle. The electric machine has the drive shaft, via which it outputs a torque or alternatively absorbs the torque. On the drive shaft, the rotor and the connecting element are at least partially arranged.

The rotor is mounted in the electric machine by means of the drive shaft. In addition to the rotor, the connecting element is provided on the drive shaft, via which the torque of the drive shaft or of the rotor of a further device is provided or a torque is transmitted from the further device to the rotor. The connection element is present, for example, as a pulley, which is operatively connected via a slippery circulating means, in particular a belt, to the further device in a torque-transmitting manner. Between the rotor and the connection element is the torque transmission connection. This means that the rotor and the connecting element are connected to one another in such a way that a torque, preferably slip-free, can be transmitted between them. The torque transmission connection is at least partially non-positive, in particular completely non-positive.

This means that the torque between the rotor and the connection element is not transmitted or at least only subordinate via a form-fitting or cohesive torque transmission connection. For example, it can be provided that the rotor and the connecting element are rotatably arranged on the drive shaft and a torque transmission between the two elements is made possible only by adhesion between them. This means, in particular, that the connection element is urged in the direction of the rotor such that torque can be transmitted by frictional connection or frictional connection and the torque transmission connection is present. For this purpose, the locking element is provided, which urges the firing element in the axial direction, ie in the direction of the longitudinal axis of the drive shaft, in the direction of the rotor.

The locking element is preferably attached to the drive shaft. By this fixing, an axial force is exerted on the connecting element and a possibly present torque-transmitting element, which urges it in the direction of the rotor. The maximum torque that can be transmitted between the rotor and the connection element in such an embodiment depends on the (maximum) axial force. However, this can not be increased arbitrarily, because it is introduced into the drive shaft and it can come in too much stress to damage the drive shaft. In conventional embodiments of the electric machine, the maximum transmittable torque is about 50 to 60 Nm. If the axial force further increased, it can lead to cracking and failure of the drive shaft, in particular during assembly of the electric machine.

From the prior art, for example, the DE 10 2007 036 313 A1 which discloses a method of manufacturing a winding for the stator of an electrical machine. There, a nut is screwed onto the drive shaft to urge the connecting element in the direction of the rotor and in this way to produce a non-positive torque transmission connection.

Disclosure of the invention

The electrical machine with the features mentioned in claim 1 has the advantage that the maximum transmissible between the rotor and connecting element torque is increased, in particular by a greater axial force is exerted on the connecting element in the direction of the rotor. This is inventively achieved by the locking element is designed as a screw and has a screw outer thread which is screwed into a shaft internal thread of the drive shaft. The locking element urges the connecting element directly or indirectly in the direction of the rotor. In the former case, the locking element is directly in direct contact with the connection element. For this purpose, the locking element and the connecting element have dimensions which allow cooperation for applying an axial force to the connecting element by the locking element. If only the indirect urging to be provided, it may be provided between the connection element and the locking element, a further element which the axial force of Arresting element at least partially transmits to the connection element. This further element is for example a fastening element for the connection element.

According to the invention, it is also provided that the locking element or the screw has a screw outer thread which is screwed into a shaft internal thread of the drive shaft. The drive shaft is thus at least partially formed as a hollow shaft, wherein the screw with at least its external screw thread in the drive shaft, up to the shaft inner thread extends. In this way, the weight of the electric machine can be reduced because the hollow shaft is significantly lighter than the known from the prior art massive drive shaft. The rotor is fixed to the drive shaft so that it counteracts this axial force, so it can not dodge in the axial direction. The rotor is so far established in the axial direction on the drive shaft at least in the direction away from the connecting element direction. This can for example be done analogously to the connection element by a locking element is provided, with which the rotor is urged in the direction of the connecting element. Alternatively or additionally, it may also be provided that the rotor is non-rotatably connected to the drive shaft, for example via a crimp connection.

The rotor may have at least one permanent magnet element or be present as an electromagnetically excited rotor. In the latter case, the rotor is designed, for example, as a claw-pole rotor, and to that extent consists in particular of two claw-pole plates, on the outer circumference of which claw-pole fingers extending in the axial direction are respectively arranged. Finally, the rotor is any element which is arranged on the drive shaft and can be set in rotation. It is therefore not necessary that the rotor actually has all the elements of a rotor, armature, inductor or rotor of the electric machine. Rather, the term "rotor" can also be understood to mean only one region of such an element, in particular a rotor core. The claw pole boards are arranged, for example, to one another such that their claw pole fingers extending in the axial direction of the electric machine alternate at the periphery of the rotor as north and south poles. For this reason, claw pole spaces are usually present between the oppositely magnetized claw pole fingers. The claw-pole fingers preferably taper in the direction of their free ends and thus extend slightly obliquely with respect to a longitudinal axis of the electrical machine.

A further development of the invention provides an additional fastening element that urges the connecting element in the direction of the rotor and in particular - as seen in the axial direction - is arranged between the connecting element and the locking element. Thus, on the one hand, the locking element is provided, which urges the connecting element in the direction of the rotor. In addition, the fastening element is present, which also imparts an axial force in the direction of the rotor on the connecting element. In this way, on the one hand an additional axial force is provided for the torque transmission connection, thus increasing the maximum transmissible torque. On the other hand, the drive shaft, in particular a possibly under this circumstances provided on this freewheel notch further. In such an embodiment, the locking element is preferably only indirectly connected to the connection element in connection. It may be provided insofar as the locking element acts on the fastening element and urges it in the direction of the rotor. Alone the fastener thus urges the connection element directly in the direction of the rotor. In particular, the fastening element is present in the axial direction between the connection element and the locking element, so that the locking element with the fastening element and the fastening element are in operative connection with the connection element.

As already stated above, the rotor is fixed in the axial direction at least in the direction of the connecting element fort pointing direction on the drive shaft. In particular, it may also be rotationally fixed on the drive shaft, so that there is an operative connection between the rotor and the drive shaft. For example, there are also on the rotor side both a fastening element and a locking element, wherein the fastening element urging the rotor and the locking element, the fastening element in the direction of the connecting element. In addition, it may also be provided that the fastening element and / or the locking element of the connecting element and / or the rotor are connected to the drive shaft or to each other with a material connection, in particular a welded connection. In this way, in addition to the increase of the axial force, the elements are set in the circumferential direction against each other, so that a torque between them can be transmitted not only on the frictional connection, but also on the material connection. Thus, the maximum transmissible torque between the rotor and connecting element is increased.

A further development of the invention provides that the fastening element is in the form of a nut, in particular a flanged nut, which is screwed onto a shaft outer thread of the drive shaft, and in that the locking element is a screw, whose head is positively connected with the nut. The mother has so far on a female thread, which is in operative connection with the shaft outer thread of the drive shaft. The fastening element in the form of the nut is screwed onto the drive shaft to such an extent that it interacts with a clamping surface of the connection element in a torque-transmitting manner at least with a clamping surface. Between clamping surface and clamping counter surface is so far a clamping connection, which transmits torque substantially purely non-positively. The locking element, however, is designed as a screw, which has a head and a shaft, wherein the head rests against the fastening element or the nut in such a way that there is also a non-positive connection. The fastening element or the nut in this respect has a further clamping surface, which cooperates with a clamping counter-surface of the screw head by clamping. The screw is fastened on the side of the fastening element facing away from the rotor or the connecting element, in particular on the drive shaft.

A further development of the invention provides that the internal shaft thread and the external screw thread are present at the same axial position as the rotor. The same axial position means a position in which the internal shaft thread, the external screw thread and the rotor have at least one common axial position in the sense of a section perpendicular to the longitudinal axis of the electric machine. Preferably, the internal shaft thread and / or the external screw thread, in particular only the internal shaft thread or only the external screw thread, but completely within an axial extent of the rotor, so that the rotor prevents any widening of the drive shaft caused by the interaction of internal shaft thread and external screw thread.

A development of the invention provides that the internal shaft thread and the shaft outer thread are formed in opposite directions. The locking element forms so far a counter element for the fastener and prevents simultaneous release of fastener and locking element. Rather, it is necessary that the fastener is unscrewed with a different direction of rotation of the drive shaft than the locking element. In this way, an unintentional release of the fastener is prevented in a simple and effective manner, without, for example, that a material connection between the fastener and the drive shaft must be provided.

A development of the invention provides that the drive shaft adjacent to the fastening element has a freewheel notch. The freewheel notch is present on the drive shaft as an undercut and serves in particular as an outlet zone for the shaft outer thread, to which the fastening element or the nut is screwed. The freewheel notch is usually arranged directly adjacent to the fastening element or to the shaft outer thread. It can also be provided that it is overlapped by the connecting element and / or the fastening element at least partially. The freewheel notch is usually present in an extremely highly stressed area of the drive shaft. It is relieved by the provision of the locking element, so that an increase in the transmittable torque is possible.

A development of the invention provides that on the drive shaft between the rotor and the connecting element - viewed in the axial direction - at least one torque transmission element is arranged, which is provided for non-positive torque transmission between the rotor and the connecting element. Accordingly, the rotor and the connecting element need not be immediately adjacent to one another in order to form the torque transmission connection. Rather, it may be provided that the at least one torque transmission element is present in the axial direction between them, that is, the rotor and the connection element are so far apart in the axial direction from each other. Specifically, therefore, there are a torque transmitting connection between the rotor and the torque transmitting member and the torque transmitting member and the terminal member. Accordingly, there is a torque transmission chain between the rotor and the connection element via the at least one torque transmission element. By means of the torque transmission element, the distance in the axial direction between the rotor and the connection element can be increased.

A development of the invention provides that the connection element and / or the torque transmission element are rotatably mounted on the drive shaft. This means that the two elements have no torque transmission connection to the drive shaft, so are rotatable in the circumferential direction. In particular, no toothing between the connection element and drive shaft or torque transmission element and drive shaft is provided.

A development of the invention provides that the torque transmission element is a spacer ring, a ball bearing or a fan. Instead of the spacer ring and a spacer sleeve can be provided with a larger axial extent. The ball bearing serves to support the drive shaft and thus also the elements arranged thereon, such as the rotor and the connection element. Of course, instead of the ball bearing any bearing, in particular any roller bearing may be provided. The fan is part of a fan, which serves to cool the electric machine. The fan wheel usually has a plurality of blades, which cause a rotation of the drive shaft, an air flow in the direction of the rotor or in the opposite direction, ie in particular over or through the rotor.

The invention further relates to a method for assembling an electrical machine, in particular according to the preceding embodiments, wherein the electric machine has a drive shaft on which a rotor and a connection element are arranged and in which an at least partially non-positive torque transmission connection is formed between the rotor and the connection element is by the connecting element is urged by means of a locking element in the direction of the rotor. It is provided that the locking element is designed as a screw and is attached to the drive shaft by a screw outer thread of the locking element is screwed into a shaft internal thread of the drive shaft. The electrical machine can be developed according to the above statements.

When mounting the electric machine, the drive shaft is provided and then arranged the rotor, the connecting element and possibly at least one torque transmitting element on the drive shaft. It may be provided to connect the rotor, for example by crimping with the drive shaft. The connection element and the torque transmission element are usually arranged rotatably on the drive shaft. Subsequently, the present in the form of a screw locking element is attached to the drive shaft.

In addition, a fastening element may be provided in the form of a nut, which is screwed onto a shaft outer thread of the drive shaft. Only subsequently, the locking element is attached in this case, which causes an axial force on the fastening element in the direction of the rotor. For example, the drive shaft is designed as a hollow shaft and has a shaft internal thread at the height of the rotor, ie at an at least partially coincident axial position on. The locking element may in this case be in the form of a screw with a screw external thread which is screwed into the drive shaft in such a way that the screw outer thread engages with the shaft internal thread. In this way, the locking element or a head of the locking element is displaced in the direction of the rotor and thus urges the fastener also in this direction.

The invention will be explained in more detail with reference to the embodiments illustrated in the drawings, without any limitation of the invention. Showing:

1 a section of an electric machine with a drive shaft on which a connecting element is fixed in a conventional manner by means of a fastener, and

2 a longitudinal section through a portion of an electric machine according to the invention.

The 1 shows a section of an electric machine known from the prior art 1 , The electric machine 1 can be present for example as a motor, generator or as a motor generator. It has a drive shaft 2 through which they can deliver or absorb torque. On the drive shaft 2 is a rotor, not shown here 3 and, preferably in the axial direction to the rotor 3 spaced, a connecting element 4 arranged. The connection element 4 is for example as a pulley, so has a tread 5 for a slippery belt, for example for a belt. The connection element 4 is by means of a fastener 6 on the drive shaft 2 attached and becomes from this in the direction of the rotor 3 in the direction of the arrow 7 , urged. The arrow 7 lies parallel to a longitudinal axis 8th the drive shaft 2 and also the electric machine 1 ,

The fastener 6 is designed as a nut, which on a here only partially illustrated shaft outer thread 9 the drive shaft 2 is screwed on. To enable screwing, the drive shaft 2 an internal toothing 10 on which extends from the front of the drive shaft 2 in the interior of the drive shaft 2 in the direction of the rotor 3 extends. The inner toothing ends here 10 seen in the axial direction, however, at the latest with the connection element 4 , The internal toothing 10 thus extends in the direction of the rotor 3 not beyond this. Thus, a weakening of the drive shaft 2 by the formation of the internal toothing 10 avoided.

The fastener 6 urges the connection element 4 in the direction of the arrow 7 So in the direction of the rotor 3 , In this way, what is not recognizable here becomes one Torque transmission connection between the connection element 4 and the rotor 3 produced. This torque transmission connection is at least partially non-positive, preferably completely non-positive. That means the torque between the rotor 3 and the connection element 4 preferably completely transferred by adhesion.

The 2 shows a portion of an electric machine according to the invention 1 , Here again are the drive shaft 2 , the rotor 3 and the connection element 4 illustrated at least by way of example. Because the electric machine according to the invention 1 can build on a prior art, is supplementary to the above statements 1 directed. In the axial direction, ie along the longitudinal axis 8th , lie between the rotor 3 and the connection element 4 several torque transmission elements 11 in front. One of the torque transmission elements 11 is as a bearing shell 12 ' a warehouse 12 educated. The bearing is preferably a ball bearing, as in the 2 can be seen. In principle, however, any type of bearing can be provided.

The bearing shell 12 is called by distance rings 13 trained torque transmission elements 11 - Seen in the axial direction - bordered on both sides. A last torque transmitting element 11 is as a fan 14 or as an intermediate disc.

The torque transmission elements 11 as well as the connection element 4 are basically on the drive shaft 2 rotatably arranged. This means that no positive or cohesive connection directly between these elements and the drive shaft 2 is present. The torque transmission between the rotor 3 and the connection element 4 takes place solely by the non-positive torque transmission connection, which via the torque transmission elements 11 is made. For this purpose, the fastener urges 6 not just the connection element 4 , but also the torque transmission elements 11 in the direction of the rotor 3 , The drive shaft 2 counteracts the resulting force.

By urging the connection element 4 in the direction of the rotor 3 arise between the connection element 4 and the nearest torque transmitting elements 11 , between the respective adjacent torque transmission elements 11 , as well as the rotor 3 and this adjacent torque transmitting element 11 non-positive torque transmission connections, so that a total of a frictional torque transmission chain between the rotor 3 and the connection element 4 is present. The drive shaft 2 Accordingly, transmits no or only a small proportion of the torque between the rotor 3 and the connection element 4 , Rather, it essentially serves the axial clamping of connecting element 4 , Torque transmitting elements 11 and rotor 3 ,

The connection element 4 is by means of the fastener 6 in the direction of the rotor 2 crowded. For this purpose, during assembly of the electric machine 1 the fastener 6 so far on the shaft outer thread 9 screwed on, until between connection element 4 , Torque transmitting elements 11 and rotor 3 a sufficiently large adhesion is present to the desired maximum torque between the rotor 3 and connecting element 4 to be able to transfer. In this case, the fastening element 6 a clamping surface 15 on, which with a clamping counter surface 16 of the connection element 4 cooperates to also between the fastener 6 and the connection element 4 to realize a positive connection. The of clamping surface 15 and clamp counterpart trained clamp connection 17 provides a non-positive torque transmission connection between the connection element 4 and the fastener 6 and consequently also the drive shaft 2 ago.

To the maximum between rotor 3 and connecting element 4 transferable torque to further increase, is also a locking element 18 provided, which is in the form of a screw. Of course, an embodiment can be realized in which only the locking element 18 but not the fastener 6 is provided. Even with such an embodiment, the advantages of the invention can be realized. The trained as a screw locking element 18 has a head 19 and a shaft 20 , The head 19 engages in the radial direction of the drive shaft 2 and at least partially the fastener 6 so that between the fastener 6 and the locking element 18 another clamp connection 21 is present. This consists of a clamping surface 22 on the fastener 6 and a clamping counter surface 23 on the locking element 18 ,

The shaft 20 of the locking element 18 engages at least partially in a central recess 24 the present as a hollow shaft drive shaft 2 one. On the connection element 4 facing the end of the drive shaft 2 is the internal teeth already described 10 but which only partially in the recess 24 hineinerstreckt. In particular, the axial extent of the internal toothing 10 less than that of the fastener 6 , The internal toothing 10 serves to set the drive shaft 2 in Circumferential direction during assembly of the fastener 6 on the drive shaft 2 So while screwing. For this purpose, a matched to the internal toothing rotationally fixed counter element (not shown) is introduced into this, the fastener 6 mounted and removed the counter element again. The internal toothing 10 is designed such that it can transmit a maximum occurring during assembly assembly torque, for example, 100 Nm.

On the shaft 20 of the locking element 18 is a screw outer thread 25 provided, which with a wave internal thread 26 the drive shaft 2 for holding the locking element 18 interacts. The locking element 18 is so far in the recess 24 the drive shaft 2 screwed. The wave inside thread 26 is opposite to the shaft outer thread 9 designed so that the locking element 18 as a counter element for the fastening element 6 serves. The locking element 18 serves to apply an additional axial force in the direction of the rotor 3 , so that between the connecting element 4 and the rotor 3 there is a stronger tension in the axial direction and thus a greater maximum torque can be transmitted via the non-positive torque transmission connection. In addition, by the locking element 18 a freewheel notch 27 or an undercut for the shaft outer thread 9 in the drive shaft 2 relieved.

Overall, the inventive electric machine allows 1 the non-positive transmission of a larger maximum torque between the rotor 3 and the connection element 4 , At the same time, the load on the drive shaft 2 decreases and a release of the fastener 6 effectively prevented. This is both the case when the fastener 6 and the locking element 18 is provided, as well as, if only the locking element 18 but not the fastener 6 is present.

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 102007036313 A1 [0006]

Claims (10)

Electric machine ( 1 ) with a drive shaft ( 2 ), on which a rotor ( 3 ) and a connection element ( 4 ) are arranged and in which an at least partially non-positive torque transmission connection between the rotor ( 3 ) and the connection element ( 4 ) is formed by the connecting element ( 4 ) by means of a locking element ( 18 ) in the direction of the rotor ( 3 ), characterized in that the locking element ( 18 ) is designed as a screw and an external screw thread ( 25 ), which in a wave inside thread ( 26 ) of the drive shaft ( 2 ) is screwed. Electrical machine according to claim 1, characterized in that in addition a fastening element ( 6 ) is provided, which the connection element ( 4 ) in the direction of the rotor ( 3 ) urges and in particular - seen in the axial direction - between the connecting element ( 4 ) and the locking element ( 18 ) is arranged. Electrical machine according to one of the preceding claims, characterized in that the fastening element ( 6 ) is present as a nut, in particular flanged nut, which on a shaft outer thread ( 9 ) of the drive shaft ( 2 ) is screwed on, and that a head ( 19 ) of the locking element ( 18 ) with the mother ( 6 ) is non-positively connected. Electrical machine according to one of the preceding claims, characterized in that the internal shaft thread ( 26 ) and the external screw thread ( 25 ) are at the same axial position as the rotor ( 3 ). Electrical machine according to one of the preceding claims, characterized in that the internal shaft thread ( 26 ) and the shaft outer thread ( 9 ) are formed in opposite directions. Electrical machine according to one of the preceding claims, characterized in that the drive shaft ( 2 ) adjacent to the fastener ( 6 ) a freewheel notch ( 27 ) having. Electrical machine according to one of the preceding claims, characterized in that on the drive shaft ( 2 ) between the rotor ( 3 ) and the connection element ( 4 ) - viewed in the axial direction - at least one torque transmission element ( 11 ) is arranged, which is for non-positive torque transmission between the rotor ( 3 ) and the connection element ( 4 ) is provided. Electrical machine according to one of the preceding claims, characterized in that the connecting element ( 4 ) and / or the torque transmission element ( 11 ) on the drive shaft ( 2 ) are rotatably arranged. Electrical machine according to one of the preceding claims, characterized in that the torque transmission element ( 11 ) a spacer ring ( 13 ), a ball bearing ( 12 ) or a fan ( 14 ). Method for assembling an electric machine ( 1 ), in particular according to one or more of the preceding claims, wherein the electric machine ( 1 ) a drive shaft ( 2 ), on which a rotor ( 3 ) and a connection element ( 4 ) are arranged and in which an at least partially non-positive torque transmission connection between the rotor ( 3 ) and the connection element ( 4 ) is formed by the connecting element ( 4 ) by means of a locking element ( 18 ) in the direction of the rotor ( 3 ), characterized in that the locking element ( 18 ) is designed as a screw and on the drive shaft ( 2 ) is attached by an external screw thread ( 25 ) of the locking element ( 18 ) in a shaft internal thread ( 26 ) of the drive shaft ( 2 ) is screwed.

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