EP3970266A1

EP3970266A1 - Method for producing a squirrel-cage rotor of an asynchronous machine

Info

Publication number: EP3970266A1
Application number: EP20746909.9A
Authority: EP
Inventors: Klaus Büttner; Klaus Kirchner; Matthias Warmuth
Original assignee: Siemens AG
Current assignee: Innomotics GmbH
Priority date: 2019-08-16
Filing date: 2020-07-17
Publication date: 2022-03-23
Also published as: US20220320975A1; WO2021032379A1; CN114223117A

Abstract

The invention relates to a method for producing a squirrel-cage rotor (4) of an asynchronous machine (1) by way of the following steps: - providing a substantially cylindrical magnetically permeable body, in particular a laminated rotor core (5), having substantially axially running slots (14), - inserting conductor bars (6), composed of a first conductive material (13), into the slots (8) in such a way that the conductor bars (6) project out of the end sides (20) of the magnetically permeable body, in particular of the laminated rotor core (5), and thereby form at least one projection (23) on one side, in particular one projection on either side, - providing a short-circuiting disc (7), composed of a second conductive material (14), with recesses (9) which are open radially to the outside, - axially positioning at least one short-circuiting disc (7) on the projections of the respective conductor bars (6) which project out of the end side of the magnetically permeable body, in particular of the laminated rotor core (5), - subsequently heating, in particular hot-forming, the axially pushed-on short-circuiting disc (7) by way of contact being made virtually simultaneously between the conductor bars (6) and at least one short-circuiting disc (7).

Description

description

Method for manufacturing a squirrel cage rotor for an asynchronous machine

The invention relates to a method for producing a squirrel-cage rotor of an asynchronous machine, as well as the asynchronous machine itself and its use in different, preferably industrial, applications.

Squirrel cage dynamo-electric rotary machines are manufactured in the lower power range using die-casting technology in one operation. This cohesive process is costly since the die casting molds are expensive and wear out comparatively quickly. Furthermore, there is a comparatively high degree of variation in the quality of a squirrel cage manufactured in this way during manufacture. This manifests itself, for example, in the change in the quality of the melt in the crucible, through contamination of the melt during the casting process, through release agents or abrasion on the tool, as well as through the formation of cavities or stress cracks when the die casting cools down.

In the higher power range or for special applications of dynamic electrical rotary machines, individual conductor bars are electrically and mechanically connected with a short-circuit ring. This is done, for example, by soldering or welding processes, as can be seen from DE 3413 519 C2.

The disadvantage here, however, is that these larger dynamo-electric machines have short-circuit rings that have a circumferential soldering trough that has to be completely filled with solder during the soldering process. Only the volume of the runner bars protruding into the soldering tub is not filled with solder. Due to the high silver content in the solder, among other things, the manufacture of the soldered connection fertilizing between rotor bars and short-circuit ring does not make particularly economic sense.

In order to remedy the quality losses that occur even in the low power range, the pressure casting process is carried out under the influence of protective gas, for example. Tools with several ventilation options are also provided, or even re-alloying of the melt is carried out. These interventions enable the efficiency of the asynchronous squirrel cage rotor to be increased, but additional measures are necessary for strength, which include, in particular, a high speed capability, such as support rings in order to obtain higher strength values.

From US 2013/0291373 A1 a resistance welding method is known in which short-circuit rings are connected to the conductor bars by means of resistance welding. The disadvantage here is that as the number of welded conductor rods on the short-circuit ring increases, the current flows through the connections that have already been made, making resistance welding of the remaining rods to the short-circuit ring considerably more difficult. The welding of all conductor bars in one process is laborious and, among other things, also very expensive in terms of energy.

Proceeding from this, the invention is based on the object of creating a method for producing a squirrel-cage rotor of an asynchronous machine, with both the electrical properties and the economic nature of the production method being in the foreground. Furthermore, a more powerful connection of conductor bars and short-circuit rings should be easy and effective to produce.

The task at hand is achieved by a method for producing a squirrel cage rotor of an asynchronous machine through the following steps:

- Provision of an essentially cylindrically shaped magnetically conductive body, in particular a rotor core, with essentially axially extending grooves, - Inserting conductor bars made of a first conductive material into the grooves in such a way that the conductor bars protrude from the end faces of the magnetically conductive body, in particular rotor laminations, and thus form at least one protrusion on one side, in particular one on both sides,

- Providing a short-circuit disk, made of a second conductive material, with radially outwardly open recesses,

- Axial positioning of at least one short-circuit washer on the protrusions of the respective conductor bars which protrude from the end face of the magnetically conductive body, in particular the laminated rotor core,

- Subsequent heating, in particular hot forming, of the axially pushed-on short-circuit disk, in that the conductor bars are almost simultaneously contacted with at least one short-circuit disk.

The problem posed is also achieved by an asynchronous machine with a squirrel cage rotor produced by the method according to the invention.

The problem posed is also achieved by a drive system which in particular drives compressors, conveyor systems, machine tools or vehicles with at least one asynchronous machine according to the invention.

According to the invention, the magnetically conductive body is first provided, that is to say sintered material or a body that is at least partially 3D-printed or individual metal sheets are stacked, glued and / or stamped to form a finished rotor core.

In the existing grooves of this magnetically conductive Kör pers of the rotor, regardless of whether a bevel of the groove is provided or not, conductor bars made of a first electrically conductive material, for example, drawn copper bars are used. The grooves are located on the radially outer ßeren area of the magnetically conductive body and are depending Weil, viewed in the circumferential direction, closed, semi-open or open.

These conductor bars are completely or at least in the area of their predeterminable overhang before being inserted into the magnetically conductive body after pickling, preferably immediately after pickling the conductor bars with a coating to prevent the formation of an oxidation layer on the stripped conductor bar. From the section of the conductor bar that protrudes from the face of the magnetically conductive body, it is referred to as an overhang.

The coating is preferably applied galvanically in the range between 2 and 5 μm in order to optimize the diffusion process into the first and second material described below.

The coating can alternatively also be sprayed on, but then the adjustable layer thicknesses are subject to a greater tolerance.

This third material, that is to say the coating, is preferably made of tin, since with the first and second materials in the context of this manufacturing process it produces a comparatively very good electrical connection between this first and second material.

In order to fix the conductor bars precisely in the magnetically conductive body and for the subsequent connection process with the short-circuit disks, without creating an imbalance in the rotor, they can be held in their position by a corresponding holding device, be it a matrix, etc.

The rod ends of the conductor rods protruding from the magnetically conductive body, i.e. the protrusions, are at least over- predominantly with the short-circuit disk, which is preferably made of aluminum or an aluminum alloy, electrically connected and thus created a short-circuit cage of the rotor of the asynchronous machine, that is, the squirrel-cage rotor.

These short-circuit disks are obtained from an extruded profile, in particular a cylindrical profile. These discs are adjustable in their axial height, this is achieved by separating a respective disc from the profile.

The short-circuit disk or short-circuit disk segments who are thus preferably made by extrusion of the second material with subsequent cutting to length. It is possible that the recesses on the radially outer area of the short-circuit disk, closed in the circumferential direction, are designed to be semi-open or open. In the case of closed and half-open recesses, the conductor bars must be inserted axially. In the case of open cutouts, the conductor bars could also be introduced radially into the short-circuit disk, which is an alternative in particular in the case of segmented short-circuit disks and / or open grooves in the laminated core of the rotor.

Advantageously, the short-circuit disk has prefabricated recesses for the conductor bars, which is easy to produce in extrusion technology. The geometric cross-section of the recesses provided is slightly larger than the geometric bar cross-section of a conductor bar in order to obtain a clearance fit between the conductor bar and the short-circuit disk.

The short-circuit disks can alternatively also have a segmented structure when viewed in the circumferential direction and / or axially. This ensures an economical production of a squirrel cage rotor, especially for asynchronous machines with larger shaft heights. This connection or electrical contact between the coated protrusion of the conductor bars and the short-circuit disks, in particular in the area of a contact surface, takes place according to the invention by heating, in particular hot forming, of this area, in particular inductive hot forming.

Hot forming refers to deformations that take place above the recrystallization temperature of a metal, in particular of the first and / or second material. Recrystallization describes the breakdown of lattice defects in the metal crystals through the formation of a new structure due to nucleation and grain growth.

During the hot forming process, the short-circuit disk is heated to approx. 450 ° to 500 ° C.

This hot forming is done by an inductor and a press, wherein the inductor can be adjusted in a simple manner to different diameters and / or heights of the short circuit disc. The inductor advantageously has a shield acting in the direction of the laminated core in order not to unnecessarily heat the end faces of the laminated core and thus possibly change the material properties of these laminations. This is especially important for short-circuit disks that are in direct contact with the end faces of the laminated core, that is, are not arranged at a distance. Such shielding of the inductor also has a positive effect on short-circuit disks that are arranged from the end face of the laminated core.

The heating and pressing are done in series, i.e. one after the other. The process can, however, also begin with heating, whereby the pressing process can already start in the final phase of heating.

In order to reach the required temperature for hot forming, the short-circuit disks can also be preheated differently, in particular special in an oven. The press sen then takes place after the short-circuit disks have been placed on the protrusions.

The coating made of the third material melts on the protrusion of the conductor bar, in particular on the protrusion of the copper bar. Due to the comparatively low layer thickness of this coating on the protrusion combined with the surface tension, the melted coating on the protrusion of the conductor rod initiates a process that is a reflow process of the coating on the conductor rod.

The protrusion denotes the part of the conductor bars protruding axially from the magnetically conductive body, in particular the laminated core. Contact is made with the short-circuit disk on a section of the protrusion, axially and / or circumferentially or on the entire protrusion. The protrusion thus has a section which has a contact surface with the short-circuit disk, on which the coating also dissolves. This contact surface is formed by the depth of immersion of the protrusion in the short-circuit disk and the recess of the short-circuit disk that surrounds the protrusion with little play.

Furthermore, the heated short-circuit disk is subjected to a force on its one end face facing away from the laminated core and is molded onto the conductor bars, in particular the overhangs or the sections of the overhangs provided for this purpose. This results in a very good electrical connection between the conductor bar and the short-circuit washer.

By axially placing the short-circuit disk on the conductor rods or the conductor rods on the short-circuit ring disk or by mutual axial insertion, the conductor rod / conductor rods and the short-circuit disk move towards each other with the corresponding recesses. The initially existing gaps at least between the protrusion and the recesses of the short-circuit washers (clearance fit) during cold joining (temperature range between room temperature and max. 100 ° C). There is almost no friction and / or deformation between the conductor bars and the short-circuit disks during cold joining. At least the gaps in the clearance fit are closed by hot forming. The heating, in particular the temperatures of the hot forming, also results in a reflow process from the coating to the short-circuit disk. The coating made of the third material dissolves completely. The coating material, in particular tin, diffuses into the surfaces in the area of the predeterminable section of the protrusion of the conductor bar and the surface to be contacted in the recess of the short-circuit disk. The desired contact is only established where the clearance fit between the protrusion and the recess - the desired contact area - was present.

The complete dissolution of this coating during the manufacturing process (diffusion) in the area of the contact surfaces is decisive for the quality of the contact between the conductor rod and the short-circuit disk. As a result of the complete dissolution there are no longer any accumulations of the coating material in the gap. If certain materials are used, such as tin, in a temperature range of approx. -40 ° C to 200 ° C when the asynchronous machine is operated, there would otherwise be undesirable conversions of beta tin into alpha tin or gamma tin. This would result in tin powder with a comparatively poor electrical conductivity. This would mean that the contact between the conductor bar and the short-circuit disk would be comparatively poor, which would lead to unnecessary thermal heating during operation and to a poorer efficiency of the asynchronous machine.

As a result of this diffusion and alloy formation, in particular the tin in the first and second conductive materials of the conductor bar and short-circuit disk, for example copper and Aluminum or its alloys, the phase transformation of the coating material described above is excluded.

The reflow and diffusion processes create a cohesive connection between the conductor rods and the short-circuit washer without the application of current, as is the case with the manufacture of a squirrel-cage rotor using resistance welding.

In addition to the electrical connection due to the molding, there is also an additional material connection due to diffusion.

It is crucial that the melting point of the third material, i.e. the coating, is lower than the heating temperature of the hot forming on the short-circuit disk made of the second electrically conductive material.

From a geometrical perspective, the short-circuit disk is designed as a hollow cylinder with radially outwardly open recesses.

The idea of the invention can also be implemented with radially closed recesses, but could require additional manufacturing steps.

By applying an axial joining force, the magnetically conductive body, in particular the stacked laminated core, can simultaneously be compressed and solidified in the axial direction.

After completing the joining process described above, the laminated core remains in the clamped state, since the conductor bars are firmly connected to the short-circuit disks on the end faces of the rotor. An additional form fit is therefore not required. This also prevents the conductor bars from "slagging" in the groove of the magnetically conductive body. It is advantageous for the manufacturing process, especially with axially thicker or higher short-circuit disks, if a temperature gradient in the heating process, i.e. a temperature gradient, is established axially outward from the end face of the short-circuit disk facing the laminated core.

The temperature in the area of the side of the short-circuit disk facing the laminated core is kept higher, so that the first deformation occurs in the form of a compression on the contact surface. The further upsetting generates frictional heat that is continued axially outwards. This measure makes it possible to avoid thermal overloading of the material and to guide the deformation axially outwards from the inside over a large area.

This process can also be referred to as reverse rivet closure, since the rod is not expanded (riveted), but the short-circuit disk is molded onto the conductor rod. In this way, positive connections can be integrated into the link in a comparatively simple manner, since it is easier to engrave contours in the conductor bar, especially in the overhang, than to intervene in the geometry of the recesses in the short-circuit disk.

The conductor bar or the protrusion does not take up the entire axial length or height of the short-circuit disk.

If the conductor bar does not take up the entire contour of the mainly open / half-open recess, the radially outer recess acts as a fan.

In addition to this or optionally, the protrusion of the conductor bars can of course also protrude axially over the short-circuit disk and thus take on a fan function.

In general, the wrought alloys are material compositions that have a high ductility (plastic Deformability) and are therefore ideally suited for hot forming, ie high degrees of deformation are possible with comparatively little effort.

Copper rods made from oxygen-free drawn electrical copper with a conductance of approx. 58 MS / m are preferably used as conductor rods.

Al-wrought alloys are preferably chosen as short-circuit disks, since they are ideally suited for hot forming, since with a relatively high formability the force required for forming is comparatively low. For example, the materials EN AW 6082 or EN AW 6060 are used.

If, for example, an Al alloy disc is used, i.e. a short-circuit ring disc made of an Al wrought alloy, the temperatures are in the range of 500 ° C. With a copper alloy, these temperatures are around 800 ° C. The Formänderungsge speed of the material will be different for different materials.

Guide values for Al alloys of the short circuit disks are a temperature range of approx. 400 to 500 ° C, a shape change in the range of 0.5 and a deformation rate of 1 to 41 / s.

To increase the efficiency and speed suitability of the squirrel cage rotor produced, a supplementary, downstream heat treatment can also be applied. This subsequent heat treatment, known as tempering, enables the mechanical and electrical material properties such as tensile strength and electrical conductivity to be increased further. The strength is increased by the fact that finely divided precipitates form as a result of the annealing. This aging takes place preferably at moderate temperatures of approx. 140 to 190 ° C, which is also referred to as artificial aging. In this way, for example, tensile strength and electrical conductivity of the individual components, but also of the entire cage of the squirrel cage, can be positively influenced.

In the case of the EN AW 6060 material, for example, constant tempering for 10 hours at 185 ° C increases the yield strength from 80 N / mm ² to approx. 200 N / mm ² . The electrical conductivity of the short-circuit ring can also be increased from 28 MS / m to 34 MS / m, since the tension in the grid is reduced during the heat treatment.

This heat treatment is carried out, for example, by solution annealing with subsequent quenching. This reduces the tension in the grid and "freezes" it. The less the grid is tensioned, the better the electrical conductivity.

The yield strength of the short-circuit ring thus obtained is higher by a factor of 10 than the yield strength for die-cast short-circuit rings with Al 99.6. This enables higher speeds of the rotor of an asynchronous machine, e.g. without additional bandages on the short-circuit ring.

If a ductile material is loaded below the elongation limit (also called Rp-0.2 elongation limit), it will return to its original state after the load has been removed. Plastic deformation occurs at higher loads.

When a rotor is subjected to high speed, the centrifugal force acts on the short-circuit ring. The higher the yield strength, the more security there is against plastic deformation of the short-circuit ring.

Targeted subsequent heat treatment can increase the yield strength, which is higher than that of pure aluminum, even further. For example, the yield strength of Al 99.6 is approx.

20 N / mm ² , while the yield strength of AlMgSi (EN AW 6060) after heat treatment is approx. 200 N / mm ² .

In a further refinement of the invention, for example, the short-circuit disks are provided with a closed outer radial contour made of steel or another material with high tensile strength or yield strength in order to achieve even higher speeds with an asynchronous machine.

A short-circuit disk made of aluminum has a lower moment of inertia and thus a higher speed capability due to its lower mass compared to copper short-circuit disks.

According to the invention, a material bond is now established for the contact between the conductor bar and the short-circuit disk, without the use of die casting and welding processes such as resistance welding, friction stir welding or laser welding.

Conductor bars, in particular copper bars, are provided with a coating provided at least in the protrusion. Pure aluminum or a ductile wrought alloy of aluminum is used as the short-circuit disk. The short-circuit disk is brought to temperature and then, or at least temporarily, molded in parallel and optionally kept at temperature. This creates a diffusion and material connection / contact between the protrusion of the conductor rod and the short-circuit disk.

Both the drawn copper rods and the extruded short-circuit disks are free of cavities, cracks and contamination.

The machinery required to manufacture a cage for a squirrel-cage rotor for an asynchronous machine is reduced to a press and induction system. In addition, there is an electrically safe link between the conductor rod and the short-circuit disk due to a full-area, low-resistance electrically conductive connection.

The diffusion and the cohesive connection / contact between the protrusion only occurs where the play between the coating on the conductor rod and inside the recess is comparatively small, i.e. 0.1 mm or less. The decisive factor here is that the mechanical axial joining of the short-circuit disks to the protrusions of the conductor rods also takes place more or less cold, without having to apply a lot of deformation work in the so-called cold state. The temperature must be kept below 50 ° C in any case below 100 ° C.

This can also be facilitated if the ends of the conductor bars are beveled or formed conically.

It is also important that the necessary contact areas between the protrusions of the conductor bars and the surfaces of the respective recesses are designed in a predeterminable range of 30 to 100% of the maximum possible contact areas.

The contact area results, for example, from the length of the clearance fit of the recesses viewed in the circumferential direction multiplied by the immersion depths of the conductor bars in the short-circuit disk.

This depends, among other things, on the desired efficiency class of the engine.

The coating of the third material, preferably with tin, is also made so comparatively thin that due to the internal stress of this material when heated, especially hot forming, it does not drip and thus does not detach from the surface of the protrusion to be contacted. The inventive idea can also be implemented in squirrel cage rotors with short-circuit rings / short-circuit washer spaced from the laminated core.

The projection can thus be composed axially of the distance between the end face of the laminated core and the short-circuit disk and the immersion depth and fan section.

The axial length of the conductor rod in the short-circuit disk is basically referred to as the immersion depth.

The axial length of the conductor rod is referred to as the fan section, which extends axially beyond the short-circuit disk on the side of the short-circuit disk facing away from the laminated core.

In the case of spaced-apart short-circuit rings / short-circuit disks, for example, only a reusable tool is necessary, which sets and maintains this required distance during manufacture.

Since the conductor bars can be axially pushed back and forth in the groove to a certain extent during the manufacturing process of the asynchronous rotor, an asynchronous rotor with short-circuit disks but also with spaced-apart short-circuit rings / short-circuit disks can be manufactured as follows within the scope of the invention . The conductor bars are inserted into the magnetically conductive body so that there is a protrusion only on one side. The short-circuit disk is placed on this overhang - as written above - and contacted. Before cooling begins, the conductor bars with the already molded short-circuit disk are axially displaced by a predeterminable distance within the laminated core, so that protrusions arise on the other side of the laminated core, which are then also contacted with a short-circuit disk. The melting points of the individual materials:

First material: e.g. Cu 1080 ° C,

Second material: e.g. Al 660 ° C,

Third material: e.g. tin 230 ° C.

Recrystallization temperature occurs at over approx. 40 to 50% of the respective melting temperature. In addition, in the case of Al, for example, from 500 ° C, an undesirable giant grain formation forms, which deteriorates the desired material properties.

In principle, with the respective manufacturing methods, the conductor bars are fixed in the magnetically conductive body by the fact that the short-circuit disks cool down after hot forming and the short-circuit ring or short-circuit disks contract and thus permanently fix the conductor bars in their respective grooves. Temperatures of over 400 ° C are normally not reached when the machines are in operation, so that sufficient fixation of the conductor rods in the respective groove is given over the service life.

The invention and advantageous embodiments of the inven tion are explained in more detail with the aid of exemplary embodiments shown in principle. Show in it:

1 shows a basic longitudinal section of an asynchronous machine,

FIG. 2 shows an arrangement of conductor bars, FIG. 3 laminated core of a rotor, FIG. 4 short-circuit disk, FIG. 5 segmented short-circuit disk, FIG. 6 partial section of the rotor, FIG. 7 illustration of the basic heating, FIG. 8 basic illustration of the axial joining, FIG. 9 illustration of the layers of the conductive Materials,

FIG 10 is a perspective view of the rotor, FIG 11 Detailed representation of the finished rotor,

FIG 12 is a perspective view of the rotor with shaft,

13 detailed view of the contacting of the conductor bar and short-circuit disk,

FIG 14 squirrel cage rotor with long conductor bars

FIG 15 squirrel cage rotor with spaced short-circuit disk.

1 shows a basic longitudinal section of an asynchronous machine 1 with a stator 2, which forms a winding system 3 on its end faces, which forms winding heads of a winding system 3 there. The winding system 3 can, for example, be constructed from stringed coils, preformed coils, tooth coils of different or identical coil widths.

A rotor 4 is arranged at a distance from the stator 2 via an air gap 18 of this asynchronous machine 1. This squirrel-cage rotor 4 has a magnetically conductive body which is made from sintered material or as a laminated core 5. In the area of its end faces 20 there is at least one short-circuit ring, in particular a short-circuit disk 7. The short-circuit ring, in particular the short-circuit disk 7, connects and contacts conductor bars 6 which are arranged in grooves 8, not shown in detail, of laminated core 5.

The short-circuit ring, in particular the short-circuit disk 7, is in contact with a shaft 16, as shown in FIG. 1, which brings about a thermal connection and thus also a cooling of the short-circuit ring when the asynchronous machine 1 is in operation. The rotor core is also in rotationally fixed contact with the shaft 16, which causes a thermal connection and thus also a cooling.

According to FIG. 1, the short-circuit ring, in particular the short-circuit ring disk 7, is in contact with the end face 20 of the laminated core 5 and the shaft 16, that is to say in each case. The short-circuit disk 7 of the squirrel-cage rotor 4 can be spaced apart from the shaft 16 and / or the end face 20.

The short-circuit ring, in particular a short-circuit washer 7, can be spaced from the end face 20 of the laminated core 5 and / or the shaft 16 in order, for example, to improve cooling or to avoid scattering losses in the laminated core.

The shaft 16 rotates as a result of electromagnetic interaction between the energized stator 2 and a short-circuit cage of the rotor 4, which is formed by the conductor bars 6 and the short-circuit disks 7.

When the asynchronous machine 1 is in operation, the rotor 4 thus rotates with the shaft 16 connected in a rotationally fixed manner about an axis of rotation 17.

2 shows an arrangement of conductor bars 6, without the mag netic conductive body, so the laminated core 5. The Lei terstänke 6 are preferably made of drawn copper or a copper alloy and are teardrop-shaped in cross section. This arrangement is also implicitly to take a bevel of the grooves 8 over the axial length of the laminated core 5. The cross-sectional shape of the conductor bars 6 essentially corresponds to the cross-section of the grooves 8. Furthermore, the conductor bars 6 have a cone 28 on which facilitates axial insertion.

3 shows a magnetically conductive body which is designed as a laminated core 5 made of dynamo sheet and which has 10 elements 21 for the rotationally fixed connection with the shaft 16 in its shaft bore 10. The grooves 8 are arranged in the radially outer region of the laminated core 5 and are executed circumferentially Lich considered closed. But they can also be designed to be half-open or open. 4 shows a short-circuit disk 7 which has recesses 9 which are open radially outward and which correspond to the spacing of the grooves 8 of the laminated core 5 such that the conductor bars 6 arranged in the grooves 8 can be inserted into these recesses 9. Preferably, protrusions 23 of the luminescent rods 6 form, at least in the region of the recesses 9, a clearance fit of approximately 0.1 to 0.05 mm or even smaller.

In a further embodiment, FIG. 5 shows segments of short-circuit disks 7, such as are used, for example, for machines with larger shaft heights. Two or more segments according to FIG. 5 result in a short-circuit disk 7, the segments being mechanically connected at the joints by a kind of dovetail.

Advantageously, in the segmented structure of the short-circuit disks 7, these are also formed in the axial direction from several layers, so that the joints 24 are offset like masonry, which ultimately also creates the electrical transitions in the short-circuit ring through axial pressing processes.

6 shows the arrangement in the area of the end face 20 during hot forming, in particular inductive heating, when the conductor bars 6 are positioned in the laminated core 5 and have been inserted into the short-circuit disks 7 as a clearance fit with their, preferably already coated, protrusions 23.

The heating takes place, advantageously by means of a temperature gradient 11, in the heating process, that is to say before the hot forming or at least temporarily during the hot forming.

There is a temperature gradient, starting from the face 20 of the short-circuit disk 7 facing the laminated core 5 axially outward. The temperature in the area of the side of the short-circuit disk 7 facing the laminated core 5 is kept higher, so that the first deformation occurs in the form of a compression on the contact surface for the coated overhang 23 of the conductor bars 6. The further upsetting generates frictional heat that is continued axially outwards. This measure makes it possible to avoid thermal overloading of the mate rials and to guide the deformation from the inside linearly axially outwards.

7 shows an exemplary induction arrangement 12 which surrounds the short-circuit disk 7, in which the coated protrusions 23 of the conductor bars 6 are arranged and are subjected to the heating process.

FIG. 8 shows an example of the joining process in which the conductor bars 6 are located in the laminated core 5. The protrusions 23 are provided with a coating 15 which is in the range of 2-5 μm. There is an immersion depth 26 of the protrusions 23 in the short-circuit disk 7, which is less than the height 25 of the short-circuit disk 7. Depending on the required contact surface of 30 to 100%.

The axial joining is preferably carried out simultaneously with a predeterminable immersion depth 26 for all of the conductor bars 6 protruding from an end face 20 of the laminated core 5.

In order to simplify the joining process, the conductor rods 6 are formed on their conductor rod ends protruding from the laminated core 5 ko cally or pointed to facilitate the joining process.

9 shows in principle, in particular in the over stand 23 the coating 15 on the first material 13 and separated therefrom by a clearance fit 31 the second material 14. During the heating process 11, the coating 15 is melted or melted and ultimately dissolves through the Hot forming process through which this the diffusion and / or reflow process and thus the formation of the alloy completely or almost completely.

FIG. 10 shows a perspective illustration of the rotor core 4 with the conductor bars 6, which show the immersion depth 26 in the short-circuit disk 7.

FIG. 11 shows a detailed illustration of FIG. 10, the radially outwardly open recesses 9 of the short-circuit disk 7 can be seen.

FIG. 12 shows the squirrel cage rotor 4, which is connected to the shaft 16 in a rotationally fixed manner.

The shaft 16 can, however, also be connected to the laminated core 5 in a rotationally fixed manner before the axial joining process of conductor bars 6 with the short-circuit disks 7.

The reduced immersion depth 26 compared to the height 25 results in fan-like effects in the operation of the machine.

Likewise, fan-like blades can also be formed by means of an axia len penetration of the conductor bars 6 through the short-circuit disk 7. The protrusion 23 thus extends axially beyond the height 25 of the short-circuit disk 7.

A plurality of short-circuit rings or short-circuit disks 7 arranged isolated from one another can also be arranged on each end face 20 of the laminated core 5. Electrically isolated short-circuit cages in the rotor 4 reduce the harmonic waves in the air gap 18 of the asynchronous machine 1, especially if the stator 2 has a winding system 3 with toothed coils, each tooth of the stator 2 being given by a toothed coil.

FIG. 13 shows a detailed illustration of the contact surfaces 27 between the conductor bar 6 and the short-circuit disk 7. This occurs the alloy preferably only on the contact surfaces 27, which have the clearance fit 31 at the beginning of the manufacturing process. This is where the hot forming process can be implemented particularly effectively. The other openings between rule bar 6 and short-circuit disk 7 can be used for cooling, among other things.

The contact surface 27 of a conductor bar 6 in a recess 9 results, for example, from the length of the clearance fit 31 in the recess 9, viewed in the circumferential direction, multiplied by the immersion depth 26 of the conductor bar 6 in the short-circuit disk 7.

14 shows a squirrel-cage rotor 4, the conductor bars 6 of which protrude axially beyond the squirrel-cage disk 7 and thus form fan blades. Furthermore, the short-circuit disk 7 is not in direct contact with the shaft 16 (as in FIG. 1), but rests against the end face 20 of the laminated core 5.

15 shows a squirrel-cage rotor 4, the short-circuit disk 7 or short-circuit ring of which is spaced from the end face 20 of the laminated core 5. This enables cooling through axially running cooling channels 29 in the laminated core 5.

A method according to the invention for producing a squirrel-cage rotor 4 or an asynchronous rotor with a squirrel cage rotor of an asynchronous machine 1 is thus carried out, taking into account the relationships presented above, by the following steps:

An essentially cylindrically shaped magnetically conductive body, in particular a laminated rotor core 5, is provided which has essentially axially extending grooves 14. The laminated core is made up of axially historically th dynamo sheets. The grooves 14 are closed, half-open or open in the circumferential direction.

- Then the conductor bars 6 are inserted into the grooves 14 before preferably axially. The conductor bars 6 are made of a first conductive material 13, in particular drawn Copper. The conductor bars 6 are used in such a way that they protrude from the end faces 20 of the magnetically conductive body, in particular of the laminated rotor core 5, and thus form at least one protrusion 23 on one side, in particular one on both sides. The complete conductor bars 6, but at least the sections of the protrusions 23, which are later contacted with the short-circuit disks 7, are preferably coated with tin before being inserted. The coating is between 2 and 5 pm. The cross-section of the conductor bars 6 essentially corresponds to the cross-section of the grooves 14. During insertion, no significant friction occurs between the conductor bar 6 and the inside of the groove 14.

The short-circuit disk 7 is also provided, made of a second conductive material 14, in particular aluminum, with recesses 9 that are open radially outward. The recesses 9 can also be designed to be closed, semi-open or open. This short-circuit disk 7 can be constructed in several parts axially and / or in the circumferential direction. So either segmented and / or axially layered when viewed in the circumferential direction. The parts are connected to one another in advance. Preferably, however, the short-circuit disk 7 is made from a part that has been cut off from an extruded extrusion profile 19 and thus has the required height 25.

- This short-circuit washer 7 is now positioned axially on the protrusion or protrusions of the respective conductor rods 6 with a clearance fit of max. 0.1mm, which protrude from the end face 20 of the magnetically conductive body, in particular of the laminated rotor core 5. This takes place as cold joining, with no significant friction or even deformation of the conductor rod 6 and recess 9 of the short-circuit disk 7.

- The subsequent heating of the short-circuit disk 7 can be done by an inductor or in an oven. The inductor allows the short-circuit disk to be heated up to 450 to 500 ° C within approx. 30s, depending on the short-circuit disk. Any shielding of the inductor in In the direction of the laminated rotor core 5, the laminations on the end face 20 are prevented from heating up unnecessarily.

- The press takes place under pressure a hot forming of the short-circuit disk 7 on the projections 23 of about one minute, depending on process parameters, such as Ma materials used, size of the squirrel-cage rotor 4, etc. It follows an almost simultaneous contacting of the conductor rods 6 with at least Predeterminable sections of the short-circuit washer 7. The clearance fit "dissolves" and electrical contact is made in the sections where the clearance fit between recess 9 and coated protrusion 23 existed. The gaps that initially exist at least between protrusion and recesses of the short-circuit washers (clearance fit) for cold joining (temperature range between room temperature and max.

100 ° C) are no longer available after the process. During cold joining between the conductor bars 6 and the short-circuit disks 7, there is almost no friction and / or deformation. At least the gaps in the clearance fit are closed by hot forming. As a result of the heating, in particular temperatures of the hot forming, a reflow process is also established from the coating 15 to the short-circuit disk 7. The coating 15 made of the third material, that is to say in particular tin, dissolves completely. The coating material, in particular tin, diffuses into the upper surfaces in the area of the predeterminable section of the overhang 23 of the conductor bar 6 and the surface to be contacted in the recess 9 of the short-circuit disk 7. So only where the clearance fit between the overhang 23 and recess 9 - the desired contact surface - was present, the desired contact occurs.

The complete dissolution of this coating 15 during the manufacturing process (diffusion) in the area of the contact surfaces 27 is crucial for the quality of the contact between the conductor bar 6 and the short-circuit disk 7. As a result of the complete dissolution, there are no more accumulations of the coating material in the gap. When using If materials were right, such as tin in a temperature range when the asynchronous machine was operated from approx. -40 ° C to 200 ° C, undesirable conversions of beta tin into alpha tin or gamma tin would occur, as stated above. This would result in tin powder with a comparatively poor electrical conductivity. This would make the contact between the conductor bar 6 and the short-circuit disk 7 comparatively bad, which would lead to unnecessary thermal Aufhei tion during operation of the asynchronous machine 1 and a poorer efficiency.

This diffusion and alloy formation, in particular of the tin in the first and second conductive materials of conductor bar 6 and short-circuit disk 7, for example copper and aluminum or their alloys, excludes the phase transformation of the coating material described above.

The reflow and diffusion processes create a cohesive connection between the conductor bars 6 and the short-circuit washer 7 without the application of current, as is the case with the manufacture of a squirrel-cage rotor by resistance welding.

Asynchronous machines with a squirrel-cage rotor 4 produced according to the invention have a stator, in whose stator bore the squirrel-cage rotor 4 is inserted. The shaft 16 to which the squirrel-cage rotor 4 is connected in a rotationally fixed manner is mounted in a housing on one or both sides.

Machines manufactured according to the invention have a wide range of uses and are used, among other things, for both standard and high-speed applications, for example in the compressor, fan and pump sector, conveyor technology, in toolmaking. mechanical engineering, the food industry and drive in rail-bound and non-rail-bound vehicle technology. These machines are reliable, efficient and easy to manufacture. They can also be used for other drive tasks.

Claims

1. A method for producing a squirrel-cage rotor (4) of an asynchronous machine (1) by the following steps:

- Providing a substantially cylindrically shaped magnetically conductive body, in particular a rotor core (5), with substantially axially extending grooves (14),

- Inserting conductor rods (6) made of a first conductive material (13) into the grooves (8) in such a way that the conductor rods (6) protrude from the end faces (20) of the magnetically conductive body, in particular laminated rotor core (5), and so form with at least one protrusion (23) on one side, in particular one on both sides,

- Providing a short-circuit disk (7), made of a second conductive material (14), with radially outwardly open recesses (9),

- Axial positioning of at least one short-circuit washer (7) on the protrusions of the respective conductor bars (6) which protrude from the end face of the magnetically conductive body, in particular the laminated core (5),

- Subsequent heating, in particular hot forming, of the axially pushed-on short-circuit disk (7), in that the conductor bars (6) are almost simultaneously contacted with at least one short-circuit disk (7), the conductor bars (6), at least the protrusion of the conductor bars (6) is coated with a third material (15), the layer thickness of the third material (15) being selected such that this third material (15) after heating, in particular hot forming, with the first material (13) and with the second Material (14) enters into alloys, so that the third material (15) is then completely dissolved in that it has entered into a diffusion with the first material (13) and the second material (14), the short-circuit disk (7) being pressed on the ladder rods is molded.

2. A method for producing a squirrel cage rotor (4) ei ner asynchronous machine (1) according to claim 1, d a d u r c h g e k e n n z e i c h n e t that only the protrusion (23) of the conductor bars (6) ultimately located in the short-circuit disk (7) is coated.

3. A method for producing a squirrel-cage rotor (4) egg ner asynchronous machine (1) according to any one of claims 1 or 2, characterized in that the layer thickness, in particular on the protrusions (23) of the Lei terststabs (6) before heating, in particular hot forming is preferably between 2 and 5pm.

4. A method for producing a squirrel-cage rotor (4) egg ner asynchronous machine (1) according to one of the preceding claims 1 to 3, characterized in that this coating of the conductor bars (6) with the third material (15) after, in particular immediately after egg nem Stripping bath of the conductor bars (6) takes place.

5. A method for producing a squirrel cage rotor (4) egg ner asynchronous machine (1) according to one of the preceding claims, characterized in that the third material (15) has a lower melting point than the first material (13) and the second material (14) shows.

6. A method for producing a squirrel-cage rotor (4) of an asynchronous machine (1) according to one of the preceding claims, in which the first material (13) has a higher melting point than the second material (14).

7. A method for producing a squirrel-cage rotor (4) egg ner asynchronous machine (1) according to one of the preceding claims, characterized in that the protrusion (23) of the conductor bars (6) to the respective corresponding recesses (9) of the short-circuit disk (7) has a clearance fit prior to hot forming, in particular around a running clearance fit of approx. 0.1mm.

8. A method for producing a squirrel-cage rotor (4) of an asynchronous machine (1) according to one of the preceding claims, in which the heating, in particular hot forming, takes place by means of inductive heating in the area of the short-circuit disk (7).

9. A method for producing a squirrel cage rotor (4) egg ner asynchronous machine (1) according to claim 8, characterized in that the inductive heating, by means of an inductor during heating, in particular hot forming, an axially outwardly falling temperature gradient, in particular a temperature gradient on the short-circuit washer (7) generated.

10. A method for producing a squirrel-cage rotor (4) of an asynchronous machine (1) according to claim 9, d a d u r c h g e k e n n z e i c h n e t that the temperature gradient is generated by means of a different distance between the inductor and the short-circuit disk (7) and / or by the different number of turns of the inductor (12).

11. A method for producing a squirrel-cage rotor (4) of an asynchronous machine (1) according to one of the preceding claims, in that the squirrel-cage pulley (7) is constructed in a segmented manner in the circumferential direction and / or axially.

12. A method for producing a squirrel-cage rotor (4) of an asynchronous machine (1) according to one of the preceding claims, characterized in that the conductor bars (7) in the deformed state cover the entire axial height (25) of the respective recess (9) of the short-circuit washer ( 7) take 30 to 70%.

13. A method for producing a squirrel-cage rotor (4) of an asynchronous machine (1) according to one of the preceding claims, characterized in that the conductor bars (7) have additional contours at least in the axial projection (23) in order to provide a supplementary positive connection with the short-circuit disk ( 7) obtained by hot forming.

14. A method for producing a squirrel-cage rotor (4) of an asynchronous machine (1) according to one of the preceding claims, characterized in that the first material (13) is copper or a copper alloy, the second material (14) is aluminum or an aluminum alloy and the third material (15) comprises tin.

15. A method for producing a squirrel-cage rotor (4) of an asynchronous machine (1) according to one of the preceding claims, in which the conductor bars (6) are beveled at their ends (10) or have a cone (28).

16. A method for producing a squirrel-cage rotor (4) of an asynchronous machine (1) according to one of the preceding claims, in which at least one conductor bar (6) made of drawn electro-copper with a conductance of at least 58 MS / m is provided.

17. A method for producing a squirrel-cage rotor (4) of an asynchronous machine (1) according to one of the preceding claims, stating that the yield strength is increased by targeted heat treatment of the squirrel-cage washer (7).

18. A method for producing a squirrel-cage rotor (4) of an asynchronous machine (1) according to one of the preceding claims, characterized in that the short-circuit disk (7) is present as a disk separated from an extruding part (19).

19. Asynchronous machine (1) with a squirrel cage rotor (4) produced according to one of the preceding claims, characterized in that the over stands (23) of the conductor bars (7) axially only a predeterminable fraction of the axial height (25) of the recess (9) of the Fit short circuit washer (7).

20. Drive system, in particular compressor, conveyor system, machine tool or vehicle with at least one asynchronous machine (1) according to claim 19.