DE102017008493A1 - Hollow shaft for a rotor of an electric motor and method for producing a hollow shaft for a rotor of an electric motor - Google Patents

Abstract

The invention relates to a hollow shaft (1) for a rotor of an electric motor, comprising at least a first component (3) and a second component (5), wherein the first component (3) and the second component (5) are firmly connected to each other. It is provided that the first component (3) and the second component (5) are welded together by means of a beam welding process.

Description

The invention relates to a hollow shaft for a rotor of an electric motor and a method for producing a hollow shaft for a rotor of an electric motor.

Typically, high-load and high-speed shafts are designed as hollow shafts to reduce their weight and thus the accelerated mass. In units, in particular in electric motors and transmissions, a hollow shaft may also be provided for passing a fluid, for example for cooling thereof. In this case, a sufficient rigidity of the hollow shaft is required to prevent in particular deflections and widening. This is usually ensured by elaborately designed hollow shafts and / or complex process chains for their production. For example, hollow shafts are then made of high-quality and therefore very expensive materials, for example 42CrMo4, in one piece with a large waste and elaborately hollow drilled. Such materials are usually no longer conventionally melt-weldable and are in particular friction-welded. For this purpose, expensive devices are required. However, the quality of such a welded joint is often insufficient. In addition, a complex post-processing of a joining region of the hollow shaft, in particular a removal of a Reibschweißwulst required. Overall, there are high costs for producing known hollow shafts of the type mentioned.

The invention has for its object to provide a hollow shaft for a rotor of a high-speed electric motor and a method for their preparation, said disadvantages do not occur.

The object is achieved by providing the subject matters of the independent claims. Advantageous embodiments emerge from the subclaims.

The object is achieved in particular by providing a hollow shaft for a rotor of a high-speed electric motor, which has at least a first component and a second component, wherein the first component and the second component are firmly connected to one another to the hollow shaft. By high-revving rotational speeds are meant to exceed 5000 revolutions per minute. It is provided that at least one of the components consists of a steel with a higher carbon content and contains at least 0.35 percent by weight carbon. According to the invention, the two components are welded together by means of a beam welding process. In addition, the hollow shaft is completely or partially cured and additionally heat-treated, at least in the joining region, in particular along the weld seam.

The hollow shaft has advantages over the prior art. The fact that the first component and the second component are welded together by means of a beam welding process, the hollow shaft is inexpensive and modular ausgestaltbar. In addition, by means of the beam welding method, a locally narrow heat input can be realized, resulting in a particularly narrow joining region, in which the first and the second component are in particular welded together. Furthermore, preferably, a delay of the two components can be prevented or at least significantly reduced. The lower the distortion of the components, the less must be corrected by machining or even straightening operations a concentricity, an imbalance, and so on. Especially with electric motors, this is particularly important because of the high speeds. The hollow shaft according to the invention is cheaper and easier to manufacture than known hollow shafts in this way. There are also no beads to the outside and inward with respect to the friction welding, which must be removed consuming or inside can not be removed. The latter shortcoming carries the risk of a residual dirt carryover and also hinders the functional use of the interior of the hollow shaft. In contrast to friction welding, component-centered welds are also reliably possible.

Due to the high demands on the basic strength of the hollow shaft, according to the invention, at least one of the components consists of a steel with a higher carbon content and a carbon weight fraction of at least 0.35%, particularly preferably at least 0.45%, or has this steel. Preferably, a steel called C50E or C50R is used.

At the same time, this material use of the higher carbon steel for an at least local hardening of the shaft is advantageous if certain areas are subjected to particularly high mechanical stress, such as bearings. The first component and / or the second component preferably have at least one martensitic and / or bainitic hardened region outside the joining region.

Furthermore, the invention is characterized in that the hollow shaft is heat-treated at least in the joining region, in particular along the weld. As a result, the susceptibility to cracking and the notch sensitivity are significantly reduced, so that a particularly durable hollow shaft is realized.

It is preferably provided that the hollow shaft has at least one further component beyond the first component and the second component, which is welded in particular to the first and / or the second component by means of the beam welding method. The first component and the second component are in particular permanently and / or rigidly connected to each other. In particular, the first component and the second component are integrally connected to one another. In particular, the beam welding method is a welding method in which an energy required for welding is transported via a jet.

An embodiment of the hollow shaft is preferred, which is characterized in that the beam welding method is a laser beam welding method. Alternatively, it is preferably provided that the beam welding method is an electron beam welding method. By means of such technologically mature welding methods, a particularly efficient and process-reliable connection of the two components can be produced with one another.

An embodiment of the hollow shaft is preferred, which is characterized in that the first component has a first cavity, wherein the second component has a second cavity, and wherein the first cavity and the second cavity in the hollow shaft form a coherent cavity. Preferably, the continuous cavity, in particular in the region in which the first cavity and the second cavity meet, is formed fluid-tight with respect to an environment of the hollow shaft. By means of the continuous cavity and the obstacle-free geometric design, it is easily possible to arrange a cooling channel, a cooling device or the like in the hollow shaft.

The object is also achieved in particular by providing a method for producing a hollow shaft for a rotor of an electric motor. Within the scope of the method, a hollow shaft according to the invention is particularly preferably produced according to one of the previously described exemplary embodiments. As part of the process, first of all two components are provided, at least one of which consists of or comprises a steel with a content of at least 0.35% by weight of carbon. Then, at least a first component of the hollow shaft and a second component of the hollow shaft are arranged against each other, wherein the first component and the second component in a joining region of the hollow shaft adjacent to each other. Subsequently, the first component is welded to the second component in the joining region by means of a beam welding method, wherein in the course of the welding process, the hollow shaft is heat treated at least in the joining region, in particular along the weld seam. In addition, before or during the welding process, complete or partial hardening of the hollow shaft takes place. In the context of the method, in particular, the advantages that have already been explained in connection with the hollow shaft arise.

The joining region is in particular a region of the hollow shaft in which the first component and / or the second component are changed, in particular melted, by a heat introduced during the welding. The joining region, in particular the weld seam, on the one hand comprises a zone which is locally melted in the course of the welding, that is to say a so-called melting zone. Adjacent to this melting zone, high temperatures which occur in the first and / or second component during the welding process lead to a structural change of zones of the first or second component which are adjacent to the melting zone. These adjacent zones are called heat affected zones. The joining region thus comprises the melting zone and the respective heat-affected zones of the first or second component.

In particular, the joining region is a region of the hollow shaft in which the first component and the second component are connected to one another in a material-locking manner. Preferably, the first component and the second component in the joining region are connected in alignment, wherein preferably the first and the second component are fluid-tightly interconnected.

When using steels with a carbon weight fraction of more than 0.35%, as is preferably provided according to the invention, usually occur by the welding process high levels of hardening. Expressed in terms of Vickers hardness HV1, these are cures with typically more than 600 HV1. As a result of the process control in the course of the welding process on the hollow shaft according to the invention, the welded hollow shaft in the joining region, that is to say in the earlier melting zone and in the at least one heat-affected zone, in each case has on average essentially a hardness of less than 500 HV1, preferably of less than 450 HV1, more preferably less than 400 HV1.

According to the invention, then hardening of the hollow shaft and - before and / or after - a heat treatment of the hollow shaft at least in the joining region, in particular along the weld seam.

An embodiment of the method is preferred, which is characterized in that the first component and / or the second component in each case at least in the subsequent joining region, in particular along the weld seam before Welding of the first component with the second component is at least partially preheated, or be. The preheating is preferably carried out in an arrangement in which the first and the second component are already substantially positioned in a later joining arrangement to each other. A preheating temperature is particularly dependent on the steel used, but preferably chosen so that the preheating temperature is substantially at least 450 ° C, in particular at least 500 ° C, but is less than an austenitizing temperature of the respective steels of the components to be joined. In this context, the term austenitizing temperature means a minimum temperature at which a significant proportion of the respective steel transforms into the austenite phase.

Preferably, the preheating of the first and the second component and the welding of the first and the second component are carried out together in the same clamping of the hollow shaft. By the preheating, the properties of the two components, in particular in connection with the welding can be significantly improved. The preheating takes place here by means of at least one heat source, for example by means of an inductive heat source, by means of at least one heating lamp or by means of at least one flame, by means of at least one laser beam source, by means of at least one electron beam source, a plasma jet or a combination of said heat sources.

An embodiment of the method is preferred, which is characterized in that the hollow shaft, at least in the joining region, in particular along the weld seam immediately after welding of the first component to the second component at least partially particularly preferably for a short time over a period of at least 1 second, preferably at a temperature of at least 400 ° Celsius to at most 720 ° Celsius, preferably at a temperature of at least 450 ° Celsius to at most 720 ° Celsius, preferably at a temperature of at least 500 ° Celsius to at most 700 ° Celsius is reheated. In other words, that means that the hollow shaft is selectively kept warm for a certain time, at least in the joint area after welding. Active reheating takes place here by means of at least one heat source, for example by means of an inductive heat source, by means of at least one heating lamp, by means of at least one flame, by means of at least one laser beam source, by means of at least one electron beam source or a combination of said heat sources.

The reheating heat source (s) may be the same or the same heat source (s) as preheating.

Particularly preferably, the reheating of the hollow shaft and the welding of the first and the second component are carried out together in the same clamping of the hollow shaft. Particularly preferably, the preheating, the welding and the reheating of the first and the second component are carried out in the same clamping of the hollow shaft. By pre-heating and / or reheating the hollow shaft, the properties of the hollow shaft can be significantly improved, in particular with regard to a structural formation, hardening, a residual stress situation and a reduction or prevention of cracking in the joining area. If the pre-heating and reheating and the welding process are performed with laser beam sources, preferably one or more optics, beam sources or laser types, in particular with respect to a wavelength and / or a focus different laser beam properties, preferably for preheating, welding and reheating within a clamping of the hollow shaft intended.

An embodiment of the method is preferred, which is characterized in that a plurality of lamellar plates are arranged on the first component or the second component, preferably on the first component and the second component, before the first component is welded to the second component. Preferably, the plurality of lamellar sheets are placed on each other on the first and / or the second component immediately before the preheating and / or the welding of the first and the second component. The plurality of lamellar sheets are preferably formed as a plate pack. Preferably, the plurality of lamellar sheets are part of an armature and / or a commutator of the electric motor. Preferably, the plurality of lamellar sheets are pressed onto the first and / or the second component, wherein the plurality of sheets preferably surround the first and / or the second component in a circumferential direction of the hollow shaft, at least in sections. In this way, an assembly of the plurality of lamellar sheets on the first and / or the second component and a welding of the two components can be integrated with one another in a mounting process of the hollow shaft. Furthermore, it is possible by an arrangement of the plurality of laminar plates downstream welding of the two components with each other to provide oil guide elements on or in the hollow shaft. Furthermore, residual dirt requirements with respect to the hollow shaft can be safely met. Furthermore, one of the components to be welded can so be formed so that the lamellar sheets are held or pressed in position via a circumferentially mounted web, survey or the like. By welding the components, this holder or compression is then permanently fixed.

An embodiment of the method is preferred, which is characterized in that the first component or the second component, preferably the first component and the second component outside the joint area, at least partially or even in the entire volume are hardened preferably martensitic and / or bainitic. This is particularly advantageous for bearings. This hardening process is carried out with the help of an energy source. This energy source may be, for example, an inductive energy source and / or at least one laser beam source and / or at least one electron beam source and / or an oven. Particularly preferably, the first component or the second component, preferably the first component and the second component, hardened by means of a laser beam. Preferably, the first and / or the second component in each case hardened in mechanically and / or tribologically highly stressed areas. It is preferably provided that the first and / or the second component is at least partially hardened in an edge layer of the same or is hardened / is based on a volume of the first and / or the second component. The attainable hardness at the at least locally to be cured zone tends to be higher, the higher the carbon content of the first and / or second component used.

A hardening of the first and / or the second component is preferably carried out before, during or after the welding of these two components together. By hardening, by means of at least one energy source, a structural and / or modal increase in strength of the hollow shaft can be realized at least in regions, in particular compressive stresses in the hollow shaft can be selectively changed. In addition, can be realized by curing an effective wear protection. Furthermore, a dimensioning of a hardened area is realized in an advantageous manner, in particular as a function of strength requirements or wear requirements.

A region of the first and / or the second component hardened by means of the method according to the invention preferably has characteristics of through hardening and / or surface hardening, for example produced by inductive hardening, laser beam hardening, electron beam hardening or oven hardening or a combination of said methods. In principle, it is also conceivable that component regions of the first and / or second component additionally or alternatively have features of a thermochemical heat treatment, for example nitriding, plasma nitriding or nitrocarburizing and / or a continuous heat treatment, for example soft annealing, quenching or normalizing.

Preferably, by the use of energy sources such as inductive energy sources, laser beam sources and electron beam sources short process times during curing, in particular during surface hardening, can be realized. Thus, in particular compared to case hardening, a process chain can be made simpler and less expensive. In particular, compared to case hardening, it is not necessary to remove the hollow shaft from an assembly process, in particular a production line, to carburize at high temperature and a long holding time, then to remove a carburizing zone in a welding area and then return the hollow shaft to the assembly process, in particular into the assembly process To introduce the production line. Rather, it is advantageously possible to carry out the curing in the production line. Furthermore, by means of laser hardening compared to case hardening, warpage of the hollow shaft can be significantly reduced or even prevented.

An embodiment of the method is preferred, which is characterized in that the welding is carried out by means of a laser beam or an electron beam, wherein the preheating and / or reheating is carried out by means of a laser beam, or the welding, pre-heating and post-heating by means of an electron beam is performed, which is technically advantageous because only a laser cabin or vacuum chamber is required.

Preferably, one of the two components is produced by means of a massive forming process, in particular forging, and the other component by means of a sheet metal forming process. It is also conceivable that both components are produced by one of the two methods. The components can also be produced by means of cutting processes of rod or tube material. For reasons of strength and weldability of the component produced, massive forming processes such as forging are particularly advantageous in use.

The description of the method on the one hand and the hollow shaft on the other hand are to be understood complementary to each other. In particular, method steps that have been explicitly or implicitly described in connection with the hollow shaft, preferably individually or combined together steps of a preferred embodiment of the method. Features of the hollow shaft, which explains explicitly or implicitly in connection with the method are preferably singly or combined with each other features of a preferred embodiment of the hollow shaft. The method is preferably characterized by at least one method step, which is caused by at least one feature of an inventive or preferred embodiment of the hollow shaft. The hollow shaft is preferably characterized by at least one feature, which is due to at least one step of a preferred embodiment of the method according to the invention or preferred embodiment.

The invention will be explained in more detail below with reference to the drawing.

Showing:

1 a first embodiment of a hollow shaft in an oblique view, and

2 a first component of a second embodiment of the hollow shaft in a longitudinal section.

1 shows a first embodiment of a hollow shaft 1 for a rotor of an electric motor in an oblique view. The hollow shaft 1 has at least a first component 3 and a second component 5 on. The first component 3 and the second component 5 are here respectively - with respect to a longitudinal axis 7 the hollow shaft 1 - formed rotationally symmetrical and coaxial with each other.

The first component 3 and the second component 5 are firmly connected. The first component 3 and the second component 5 are welded together by means of a beam welding process. The first component 3 the hollow shaft 1 and the second component 5 the hollow shaft 1 are arranged adjacent to each other and / or overlapping each other, wherein the first component 3 and the second component 5 in a joining area 9 adjoin one another. The first component 3 and the second component 5 are in the joining area 9 welded together by means of the beam welding process.

The joining area 9 is in 1 schematically shown as a dashed line. Preferably, the joining area 9 but an extension both in the axial direction, as well as - with respect to the longitudinal axis 7 - in the radial direction. At the joining area 9 it is in particular the area in which the first component 3 and the second component 5 welded together, preferably cohesively connected to each other. Preferably, the joining area comprises 9 also a heat affected zone of the hollow shaft 1 in which, in particular in the welding, in each case a material structure of the first component 3 and / or the second component 5 is or will be changed.

A diameter of the first component 3 expands here from one, the joining area 9 opposite first axial end 10 of the first component 3 in the direction of one in the joint area 9 lying second axial end 10 ' of the first component 3 on. In particular, the diameter widens in the first component 3 in a first diameter jump range 10 '' jump up. A diameter of the second component 5 expands here from a joining area 9 opposite first axial end 11 of the second component 5 in the direction of one in the joint area 9 lying second axial end 11 ' of the second component 5 on. In particular, the diameter widens in the second component 5 in a second diameter jump range 11 '' jump up.

In the embodiment according to 1 is an axial distance between the first diameter jump area 10 '' and the joining area 9 longer than an axial distance between the second diameter jump area 11 '' and the joining area 9 ,

Alternatively, the joining area 9 but also in a different way between the first end 10 and the first end 11 , preferably between the first diameter jump area 10 '' and the second diameter jump area 11 '' be arranged. Optionally, the hollow shaft 1 even without the first diameter jump range 10 '' and / or without the second diameter jump range 11 '' be educated. Optionally, the hollow shaft 1 even without the mentioned, changing diameter of the first component 3 and / or the second component 5 be educated.

The diameter of the first component 3 at the second end 10 ' and the diameter of the second component 5 at the second end 11 ' are the same size here. In particular, the two components are aligned here 3 . 5 at least in the joining area 9 together. It is equally conceivable that the diameter of the first component 3 at the second end 10 ' and the diameter of the second component 5 at the second end 11 ' are formed unequal size.

Preferably, the joining area is located 9 essentially in a plane which is perpendicular to the longitudinal axis 7 is arranged. The joining area 9 extends in particular along a circumferential direction of the hollow shaft 1 , preferably around the entire circumference of the hollow shaft 1 ,

Preferably, the beam welding process is a laser beam or electron beam welding process.

The first component 3 has a first cavity 12 on which in 1 however not visible. The first cavity 12 extends in an interior of the first component 3 in the axial direction between the first end 10 and the second end 10 ' , The second component 5 has a second cavity 13 on, which is in the axial direction between the first end 11 and the second end 11 ' extends. The first cavity 12 and the second cavity 13 form in the hollow shaft 1 a coherent cavity. In particular, the first cavity adjoin 12 and the second cavity 13 in the plane in which the joining area 9 essentially lies against each other. The coherent cavity therefore extends in particular between the first end 10 of the first component 3 and the first end 11 of the second component 5 ,

Preferably, the first component 3 and / or the second component 5 a steel on or consist of a steel. Preferably, the steel has a carbon weight fraction of at least 0.35%, more preferably at least 0.45%. For example, a steel called C50E or C50R is used.

The following is an embodiment of a method for producing the hollow shaft 1 for a rotor of an electric motor described. As part of the process, at least the first component 3 the hollow shaft 1 and the second component 5 the hollow shaft 1 arranged one another or partially overlapping, wherein the first component 3 and the second component 5 in the joining area 9 the hollow shaft 1 adjoin one another. Subsequently, the first component 3 with the second component 5 in the joining area 9 welded by means of the beam welding process.

Preferably, the hollow shaft 1 , in particular the first component 3 and the second component 5 during welding around the longitudinal axis 7 turned. Such a turn is in 1 schematically by the arrow 15 shown. The hollow shaft 1 So is according to 1 turned counterclockwise. A welding beam generated by means of the beam welding process is known in 1 shown schematically and with the reference numeral 17 designated. The welding beam 17 is in the direction of an arrow 19 on a welding beam focus area 20 in the area of the joining area 9 or the joining area 9 directed, there in particular a melting of the first component 3 and the second component 5 is effected. In particular, it is the welding beam 17 around a laser beam.

Alternatively, the hollow shaft 1 also contrary to the direction of the arrow 15 , so be turned clockwise.

Alternatively, it is possible that during the welding process, the welding beam 17 relative to the components to be joined 3 . 5 is moved.

Furthermore, it is conceivable that both the first component 3 , the second component 5 and the welding beam 17 move. It is important that a relative movement between the beam 17 on the one hand and the components to be joined 3 . 5 takes place.

Preferably, the hollow shaft 1 , in particular the first component 3 and the second component 5 during welding in the direction of or in the opposite direction of the arrow 15 rotated, so that welding of the first component 3 with the second component 5 in the joining area 9 is realized. Preferably, the hollow shaft 1 at least 360 ° around the longitudinal axis 7 rotated, so that welding over the entire circumference of the hollow shaft 1 is effected.

In particular, when the first component 3 and / or the second component 5 made of a steel with a carbon weight fraction of more than 0.35%, is the first component 3 and / or the second component 5 preferably at least in each case in the joining region 9 before welding the first component 3 with the second component 5 at least partially preheated and / or reheated after welding.

The preheating process serves, in particular, to prepare the post-welding process which takes place after welding. The preheating takes place here by means of at least one energy source, for example by means of an inductive heat source, by means of a heating lamp, by means of a flame, by means of an at least laser beam source, by means of an at least electron beam source or a combination of said heat sources.

Preheating turns out to be very advantageous as a local preheating of the joining area 9 out. Therefore, also in 1 the energy source for preheating is schematically shown as a preheating jet and denoted by the reference numeral 21 Mistake. The preheat jet 21 is in the direction of an arrow 23 to a preheat beam focus area 24 in the area of the joining area 9 or the area of the joining area 9 directed, there being a heating of the first component 3 and the second component 5 is effected. By the hollow shaft 1 while passing through the preheat jet 21 caused energy impact around the longitudinal axis 7 is rotated, the hollow shaft 1 in the joining area 9 to be preheated along the circumferential direction. In addition to the schematic representation of the effect of energy in the form of Vorwärmstrahls 21 it is also advantageous to the hollow shaft 1 around the longitudinal axis 7 to turn while an energy exposure, for example, with a hollow shaft 1 partially or completely comprehensive heat source takes place, so that the hollow shaft 1 in the joining area 9 is preheated along its circumferential direction. One such essentially the hollow shaft 1 comprehensive heat source may be, for example, an induction coil or a hollow shaft 1 surrounding arrangement of laser beam sources.

At a correspondingly high rotational speed of the hollow shaft 1 - in or opposite to the direction of the arrow 15 - can in this case in the joining area 9 a relatively uniform preheat field are generated.

Similarly, it is also conceivable that the preheat beam 21 around the hollow shaft 1 is moved, so that thereby a relatively uniform preheating field is generated.

After preheating or partially parallel to the preheating time, the welding process takes place. This is the hollow shaft 1 preferably with a welding beam 17 acted upon while the hollow shaft 1 in the direction of or in the opposite direction of the arrow 15 preferably at least 360 ° about the longitudinal axis 7 is turned. In this way, in exactly one clamping of the hollow shaft 1 a preheating and welding of the two components 3 . 5 be implemented particularly efficiently.

Preferably, the hollow shaft 1 at least in the joining area 9 after welding the first component 3 with the second component 5 reheated at least in certain areas. The reheating takes place after the welding process or already starts parallel to the welding process. The reheating takes place here by means of at least one energy source, for example by means of an inductive heat source, by means of a heating lamp, by means of a flame, by means of at least one laser beam source, by means of at least one electron beam source or a combination of said heat sources.

As very advantageous, the reheating turns as a local reheating, so a local keeping warm the joining area 9 out. Therefore, in 1 the energy source for reheating as a Nachwärmstrahl schematically drawn and with the reference numeral 25 Mistake. The reheat jet 25 is in the direction of an arrow 27 to a - here only hinted - Nachwärmstrahlfokusbereich 28 in the area of the joining area 9 or on the area of the joining area 9 directed, there keeping warm the first component 3 and / or the second component 5 is effected.

By the hollow shaft 1 during an energy action around the longitudinal axis 7 - in or opposite to the direction of the arrow 15 - Is rotated, the hollow shaft 1 in the joining area 9 to be reheated along the circumferential direction. In addition to the schematic representation of the energy effect in the form of Nachwärmstrahls 25 it is also advantageous to the hollow shaft 1 around the longitudinal axis 7 to turn while an energy exposure, for example, using a hollow shaft 1 partially or completely comprehensive heat source takes place, so that the hollow shaft 1 in the joining area 9 is reheated along the circumferential direction. This essentially the hollow shaft 1 Partially or completely comprehensive heat source may be, for example, an induction coil or the hollow shaft 1 surrounding arrangement of laser beam sources.

At a correspondingly high rotational speed of the hollow shaft 1 can in this case in the joining area 9 a relatively uniform Nachwärmfeld be generated. The reheating temperature is preferably in a temperature range of at least 400 ° C to at most 720 ° C, preferably in a temperature range of at least 450 ° C to at most 720 ° C, preferably in a temperature range of at least 500 ° C to at most 700 ° C preferably via a Duration of at least 1 second held. Depending on the steel used, holding times of several seconds or minutes may be required.

As the welding process and the Nachwärmprozess preferably with the same clamping of the hollow shaft 1 take place, a particularly efficient joining process is realized.

Similarly, it is also conceivable that the Nachwärmstrahl 25 around the hollow shaft 1 moves, so that thereby a relatively uniform Nachwärmfeld is generated.

It is preferably provided that in a single clamping of the hollow shaft 1 a preheating of the joining area 9 , a welding and a reheating of the joining area 9 the hollow shaft 1 is realized, whereby a particularly efficient and reliable welding of the two components 3 . 5 is realized. The hollow shaft 1 will be in the direction of the arrow 15 , alternatively in the opposite direction of the arrow 15 , rotated and experiencing time after another or temporally overlapping the preheating process, at least in the joint area 9 , the welding process and the reheating process at least in the joint area 9 , For the duration of the actual welding process, the hollow shaft 1 advantageously at least 360 ° about the longitudinal axis 7 turned. For the purpose of preheating and / or Nachwärmprozesses very high rotational speeds can be advantageous. In particular, it is favorable for the purpose of preheating and / or reheating that the hollow shaft 1 several revolutions around the longitudinal axis 7 experiences.

Preferably, the preheating, the welding and / or the reheating can each also be carried out by preheating the energy source (s) 1 schematically as Vorwärmstrahl 21 represented, and / or the welding beam 17 and / or the energy source (s) for reheating, in figure schematically as Nachwärmstrahl 25 represented, according to the hollow shaft 1 be led around / will.

It is also advantageous if the energy source for preheating and / or the energy source for reheating are stationary heat sources, which the hollow shaft 1 essentially partially or completely.

Optionally, before welding the first component 3 with the second component 5 several - in 1 not shown - lamellar sheets on the first component 3 and / or on the second component 5 arranged, preferably pressed. Preferably, the lamellar sheets are formed as a plate pack of the electric motor, which on the first component 3 and / or the second component 5 arranged, preferably pressed.

In an embodiment of the method, not shown here, it is provided that the first component 3 and / or the second component 5 , especially outside the joining area 9 , at least partially hardened. In this case, hardening methods include inductive hardening, laser beam hardening or electron beam hardening, or a combination of the methods mentioned. The hardening process can take place before the welding process, during the welding process or after the welding process.

Optionally, the welding is carried out by means of an electron beam, wherein the preheating and / or the reheating is carried out by means of a laser beam. Alternatively, the welding, pre-heating and post-heating is carried out by means of an electron beam. The first component is preferred 3 with a massive forming process and the second component 5 produced by a sheet metal forming process, or the first component 3 with a sheet metal forming process and the second component 5 produced by a massive forming process. The production of both components 3 and 5 By means of the same mentioned forming process or by cutting processes of rod or tube material is also conceivable.

2 shows the first component 3 a second embodiment of the hollow shaft 1 in a longitudinal section. Identical and functionally identical elements are provided with the same reference numerals, so that reference is made to the preceding description. In 2 is the first cavity 12 of the first component 3 shown, which is axially between the first end 10 and the second end 10 ' of the first component 3 extends. In particular, for welding the first component 3 with the - not shown here - second component 5 the second component 5 - seen from the perspective of the beholder - on the left side of the first component 3 arranged, the second end 11 ' of the second component 5 to the second end 10 ' of the first component 3 borders. The - here only hinted - joining area 9 is then in the area of the second end 10 ' ,

Overall, it turns out that by means of the hollow shaft 1 and the method for producing the hollow shaft 1 a particularly simple and inexpensive design and realization of the hollow shaft 1 is possible. In this case, the hollow shaft 1 process-reliable and cost-efficient with high quality. Incidentally, the components can 3 and 5 each formed from at least two shells and be prepared according to the above-described process technology, wherein the joined shells said cavity 12 . 13 form.

Claims (10)

Hollow shaft ( 1 ) for a rotor of a high-speed electric motor, in particular an electric traction motor, with - at least a first component ( 3 ) and a second component ( 5 ), wherein - the first component ( 3 ) and the second component ( 5 ) to a hollow shaft ( 1 ) are firmly connected, characterized in that - at least one of the components ( 3 . 5 ) consists of or comprises a steel containing at least 0.35% by weight of carbon, - the first component ( 3 ) and the second component ( 5 ) are welded together by means of a beam welding process, - the hollow shaft ( 1 ) completely or partially hardened and at least in the joining area ( 9 ), in particular heat-treated along the weld seam. Hollow shaft ( 1 ) according to claim 1, characterized in that the first component ( 3 ) a first cavity ( 12 ), wherein the second component ( 5 ) a second cavity ( 13 ), and wherein the first cavity ( 12 ) and the second cavity ( 13 ) in the hollow shaft ( 1 ) form a coherent cavity. Hollow shaft ( 1 ) according to claim 2, characterized in that the contiguous cavity forms a cooling channel for a cooling fluid. Hollow shaft ( 1 ) according to one of claims 1 to 3, characterized in that the first component ( 3 ) and / or the second component ( 5 ) outside the joining area ( 9 ) have at least one martensitic and / or bainitic hardened area. Method for producing a hollow shaft ( 1 ) for a rotor of a high-speed electric motor, in particular an electric traction motor, in particular a hollow shaft ( 1 ) according to one of claims 1 to 4, comprising the method steps: - first providing two components ( 3 . 5 ), at least one of which consists of or comprises a steel with a content of at least 0.35% by weight of carbon, - then arranging the first component ( 3 ) of the hollow shaft ( 1 ) and the second component ( 5 ) of the hollow shaft ( 1 ), wherein the first component ( 3 ) and the second component ( 5 ) in a joining area ( 9 ) of the hollow shaft ( 1 ) adjoin one another, - welding of the first component ( 3 ) with the second component ( 5 ) in the joining area ( 9 ) by means of a beam welding process to form the hollow shaft ( 1 ), wherein in the course of the welding process, the hollow shaft ( 1 ) at least in the joining area ( 9 ), in particular heat treatment along the weld seam, - before, during or after the welding process complete or regional hardening of the hollow shaft ( 1 ). Method according to claim 5, characterized in that the first component ( 3 ) and / or the second component ( 5 ) in each case in the joining area ( 9 ), in particular along the weld seam prior to welding of the first component ( 3 ) with the second component ( 5 ) is at least partially preheated / and / or reheated immediately after welding is / are. Method according to one of claims 5 and 6, characterized in that the hollow shaft ( 1 ) at least in the joining area ( 9 ) after welding the first component ( 3 ) with the second component ( 5 ) is at least partially reheated, preferably briefly over a period of at least 1 second in a temperature range between 450 ° C and 720 ° C, in particular in a temperature range between 500 ° C and 700 ° C. Method according to one of claims 5 to 7, characterized in that before the welding of the first component ( 3 ) with the second component ( 5 ) several lamellar sheets on the first component ( 3 ) and / or the second component ( 5 ) to be ordered. Method according to one of claims 5 to 8, characterized in that the first component ( 3 ) and / or the second component ( 5 ) outside the joining area ( 9 ) at least partially hardened / is. Method according to one of claims 5 to 9, characterized in that one of the two components ( 3 . 5 ) by means of a massive forming process and the other component ( 5 . 3 ) by means of a sheet metal forming process or both components ( 3 . 5 ) is produced by one of the two methods.

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