阅读说明：本技术 用于制造异步电机的鼠笼式转子的方法 (Method for producing a squirrel-cage rotor for an asynchronous machine ) 是由 克劳斯·比特纳 克劳斯·基希纳 马蒂亚斯·瓦尔穆特 于 2018-04-16 设计创作，主要内容包括：本发明涉及一种用于制造异步电机(1)的鼠笼式转子(4)的方法,包括以下步骤：-提供具有基本轴向延伸的凹槽(14)的转子叠片组(5),-将由第一传导材料制成的导体棒(6)置入凹槽(14)中,使得导体棒(6)从转子叠片组(5)的端面(15)伸出,-提供由被加热超过再结晶温度的第二传导材料制成的短路环盘(7),-在考虑形变的温度范围和形变速度的情况下,将至少一个短路环盘(7)在轴向上挤压到从转子叠片组(5)的端面(15)伸出的导体棒(6)上,其中,局部地超出该材料的允许的剪切应力,并且其中,通过在导体棒与短路环之间的边界面上的扩散而形成材料过渡区,-紧接着或者同时对轴向推置的短路环盘(7)进行热成形。(The invention relates to a method for producing a squirrel-cage rotor (4) of an asynchronous machine (1), comprising the following steps: -providing a rotor lamination stack (5) having substantially axially extending grooves (14), -placing conductor bars (6) made of a first conductive material in the grooves (14), so that the conductor bars (6) protrude from the end face (15) of the rotor lamination stack (5), -providing a short-circuiting ring disc (7) made of a second conductive material heated above the recrystallization temperature, -taking into account the temperature range of the deformation and the speed of the deformation, at least one short-circuiting ring disk (7) is pressed in the axial direction onto conductor bars (6) protruding from the end face (15) of the rotor lamination stack (5), wherein the permissible shear stress of the material is locally exceeded, and wherein a material transition is formed by diffusion at the boundary surface between the conductor bar and the short-circuit ring, and subsequently or simultaneously the axially pushed short-circuit ring disk (7) is thermoformed.)

1. Method for manufacturing a squirrel cage rotor (4) of an asynchronous machine (1), comprising the steps of:

-providing a rotor lamination stack (5) having substantially axially extending grooves (14),

-placing conductor bars (6) made of a first conductive material into the grooves (14) such that the conductor bars (6) protrude from an end face (15) of the rotor lamination stack (5),

-providing a short circuit ring disc (7) made of a second conductive material heated above a recrystallization temperature,

-pressing at least one short circuit ring disc (7) axially onto the conductor bars (6) protruding from the end face (15) of the rotor lamination stack (5) taking into account the temperature range, the deformation and the deformation speed, wherein the permissible shear stresses of these materials are locally exceeded and wherein material transitions are formed by diffusion at the boundary surfaces between the conductor bars and short circuit rings,

-subsequent or simultaneous thermoforming of the axially pushed short circuit ring disc (7).

2. Method according to claim 1, characterized in that the short circuit ring disc (7) has a temperature in the range of 400 ℃ to 500 ℃, a deformation in the range of 0.5 and a deformation speed in the range of 1 to 4 (1/s).

3. Method according to any of the preceding claims, characterized in that the second material is preferably aluminium, copper or an aluminium or copper alloy.

4. Method according to any of the preceding claims, characterized in that the conductor bars (6) are chamfered (10).

5. Method according to any one of the preceding claims, characterized in that the short-circuiting ring disc (7) has a recess (16) in the region of the conductor bar (6), the cross section of which corresponds to the cross section of the conductor bar (6) and is implemented smaller than the cross section of the conductor bar at least in sections, in order to ensure a micro-welding between the conductor bar (6) and the short-circuiting ring disc (7).

6. Method according to any of the preceding claims, characterized in that at least one of the conductor bars (6) is provided, which is made of drawn electrical copper having an electrical conductance of at least 58 MS/m.

7. The method according to any of the preceding claims, wherein the compressive strength of the first material is greater than the rheological stress of the second material occurring during the joining process.

8. Method according to any of the preceding claims, characterized in that the yield strength of the short circuit ring disc (7) of the squirrel cage rotor (4) is increased by simultaneous and/or subsequent heat treatment.

9. Method according to any of the preceding claims, characterized in that the short circuit ring disc (7) is a disc separated from the extrusion (13).

10. An asynchronous machine (1) having a squirrel cage rotor (4) according to any of the preceding claims.

11. A drive system, in particular a compressor, a transmission drive or a vehicle drive, having at least one asynchronous machine as claimed in claim 10.

Technical Field

The invention relates to a method for manufacturing a squirrel cage rotor for an asynchronous machine, and also to the asynchronous machine itself and its use in different applications, preferably industrial applications.

Background

The squirrel-cage rotor of an electromechanical rotating machine is produced in a single process step in the lower power range by means of die-casting technology. This method of material mating is costly because die cast molds are expensive and wear relatively quickly. In addition, the squirrel-cage rotor produced in this way also has a comparatively high leakage flux in terms of quality during the production process. This is manifested, for example, in changes in the quality of the melt in the crucible as a result of impurities in the melt during the casting process, mold release agents or wear on the tools, and also, for example, as a result of shrinkage cavities or stress cracks forming on cooling of the die casting.

In the higher power range or in special applications of electromechanical rotating machines, the individual conductor bars are electrically and mechanically connected to the short-circuit ring. This is done, for example, by soldering or welding, as is known from DE 3413519C 2.

However, the disadvantage here is that in these larger motors there is a short-circuit ring with a surrounding solder pot, which is completely filled with solder during the soldering process. In this case, only the volume of the rotor rod protruding into the solder pot is not filled with solder. In this case, because of the high proportion of silver in the solder, the production of a soldered connection between the rotor bar and the short-circuit ring is not economically significant.

In order to eliminate the quality degradation that occurs even in the low-power range, a die-casting process is carried out, for example, with the introduction of a protective gas. Likewise, various venting options are provided for the tool, or even re-alloying of the melt (nachlegieren) is performed. Such interventions increase the efficiency of the asynchronous cage rotor, but additional measures, such as the provision of support rings or the use of alloys, are required to obtain higher strength values in order to obtain strength, including particularly high rotational speed suitability.

Disclosure of Invention

Starting from this, the basic object of the invention is to provide a method for producing a squirrel-cage rotor of an asynchronous machine, wherein both the electrical properties and the economic implementation of the production method are emphasized. Furthermore, a better connection between the rotor bars and the short-circuit ring should be produced simply and efficiently.

The proposed object is achieved by a method for manufacturing a squirrel-cage rotor for an asynchronous machine, comprising the steps of:

-providing a rotor lamination stack having substantially axially extending grooves,

-placing conductor bars made of a first conductive material in the grooves so that the conductor bars protrude from the end faces of the rotor lamination stack,

-providing a shorting ring disc made of a second conductive material heated above a recrystallization temperature,

-pressing at least one short-circuiting ring disk in axial direction onto conductor bars protruding from the end face of the rotor lamination stack, taking into account the temperature range of the deformation and the speed of deformation,

-subsequent or simultaneous thermoforming of the axially pushed short-circuiting ring disc.

The object set is likewise achieved by an asynchronous machine having a squirrel-cage rotor produced according to any of the methods of the invention.

The proposed object is likewise achieved by an asynchronous motor arranged in a compressor, a transmission drive or a vehicle drive having at least one asynchronous motor equipped with a squirrel cage produced according to the method of the invention.

According to the invention, instead of the known die casting method, the squirrel cage is now manufactured by a combination of micro-welding and hot deformation, i.e. the connection of the conductor bars to the short-circuit ring disc.

In this case, the individual rotor sheets are first stacked or pressed together to form the finished rotor lamination stack. In this case, the first conductive material, for example a drawn copper rod, is inserted into the existing grooves of the rotor, regardless of the groove pitch. The conductor bars project from the end face of the rotor lamination stack. In order to fix the conductor bars in position exactly in the rotor lamination stack and in order to fix them exactly together with the short-circuiting plate during the subsequent joining process without generating an imbalance in the rotor, the conductor bars are held in their position by corresponding holding devices, which may be substrates (Matrix) or the like. The ends of the bars, from which the conductor bars project, are electrically connected to a short-circuiting plate, preferably made of aluminium or an aluminium alloy, and the short-circuiting ring of the squirrel-cage rotor is thus obtained.

This connection is achieved by axially pressing the shorting ring disc onto the conductor bars, or axially pressing the conductor bars onto the shorting ring disc, or by axially pressing the conductor bars and shorting ring disc towards each other, or by relatively axially pressing them (wherein the conductor bars and shorting ring disc move towards each other). The conductor bars project here at the respective end face of the rotor lamination stack.

Such axial extrusion is performed in consideration of an ideal temperature range of deformation and an optimum deformation speed. Here, plastic deformation occurs by dislocation migration of the atomic layers in the crystal lattice. The temperature increase facilitates such migration and, in turn, overcomes obstacles in the atomic lattice (e.g., dislocations, foreign atoms, etc.). Thus, starting from a specific material-dependent temperature limit, the deformability decreases. The deformation speed, temperature and rheological stress of the respective materials are thus mutually coordinated.

Here, a micro-weld is formed between the material of the short-circuit ring disc and the conductor bar. Such micro-welding is achieved in that the conductor bars and the short circuit rings are tightly rubbed against each other, thereby generating surface pressure and additional frictional heat. The shear stresses allowed by these materials are locally exceeded, and material transitions are produced by diffusion at the boundary surface between the conductor bars and the short-circuit ring. Thus, soldering in a micro area as well as micro soldering is obtained.

The short-circuit ring disk is not necessarily embodied as a hollow cylinder, as viewed geometrically. Only in the region of the conductor bars is a quantity of material provided which achieves sufficient contact and fixing of the conductor bars in the short-circuit ring, so that an efficient rotor cage is formed.

The short-circuit ring disk/short-circuit ring is heated above the recrystallization temperature of its material, whereby thermal deformation can be achieved with relatively little force.

Such deformation causes the lattice to be pre-tensioned. The material is reinforced. At high temperatures, regeneration and recrystallization processes occur in the material. However, the time required for this process decreases as the deformation speed increases.

This means that as the deformation speed increases, the time available for the regeneration and recrystallization processes decreases. Thus, during thermal deformation, velocity-dependent rheological stresses occur in the material.

Thus, in the deformation process according to the invention, the degree of deformation, the speed of deformation, the temperature and the rheological stress are coordinated according to the material used. However, the rheological stress is not allowed to be too high.

The temperatures sought for pure aluminum 99.7 are in the temperature range from 350 ℃ to 400 ℃. For so-called aluminum wrought alloys, the temperature is in the range of 400 ℃ to 500 ℃ due to the presence of the alloy composition. The conductor bars sink into the "doughnut-like" body of the short-circuiting ring disc by the axial compressive force exerted on the conductor bars by the short-circuiting ring disc. During this joining process, the above-mentioned micro-welding takes place on the contact surfaces between the conductor bars and the short-circuit ring discs. At the same time, the short-circuit ring is shaped by thermal deformation according to a preset tool profile that holds the short-circuit ring. In this case, the tool contour can be heated beyond a predetermined temperature range.

By applying an axial joining force, the stacked lamination stack is compressed in the axial direction and reinforced. After the joining process described above is completed, the rotor lamination stack is held in a tensioned state, since the conductor bars are connected in a material-locking manner to the short-circuit ring disks on the end faces of the rotor lamination stack. Thus, no additional form-fitting connection is required.

In general, wrought alloys refer to combinations of materials that have high ductility (plastic deformability) and are ideally suited to thermal deformation, i.e., high degrees of deformation can be achieved with little effort.

Preferably, a copper rod made of oxygen-free drawn electrical copper with an electrical conductance of about 58Ms/m is used as conductor rod. Preferably, these conductor bars are in a medium to hard state (60HB to 85HB, where HB stands for brinell hardness), so as to avoid deformation or even breakage of the conductor bars under the action of the axial engagement force of the shorting ring disk. It follows that the compressive strength of the conductor bar must be greater than the rheological stress during the joining process. The hardness range corresponds to about 300N/mm²To 400N/mm²The tensile strength of (2).

Preferably, an aluminum wrought alloy is selected as the shorting ring disk because it is ideally suited for thermal deformation because the force required for deformation is small where the deformability is stronger. Thus, for example, the material EN AW 6082 or ENAW 6060 is used. These materials EN AW 6082 or EN AW6060 are in particular in the soft material state according to the standard DIN EN 515, for example T4. In this state, the highest degree of deformation can be achieved. T4 describes a relatively soft regime achieved by solution annealing in combination with natural failure treatment.

The short-circuiting ring disk is obtained here from an extrusion-drawn cylinder. Here, the axial width of the discs is adjustable, which is achieved by determining the separation position on the cylinder.

For a safe joining operation, the following parameters, such as temperature and joining speed and thus also deformation speed, can be set depending on the materials to be coupled to one another (for example copper, aluminum or other materials). This means that the above values are different depending on the selected material combination. If for example an aluminium alloy disc, i.e. a short circuit ring disc made of aluminium wrought alloy, is used, the temperature is in the range of 500 ℃. In the case of copper alloys, the temperature is approximately 800 ℃. The deformation speed and the speed of pressing the short circuit ring disc are different under the condition of different materials.

Here, the standard values for the aluminum alloy of the short circuit ring disk include a temperature range of about 400 ℃ to 500 ℃, a deformation or deformation degree in the range of 0.5 and a deformation speed of 1l/s to 4 l/s.

In order to increase the efficiency and speed applicability of the manufactured squirrel cage rotor, a heat treatment may be performed simultaneously and/or subsequently. By this subsequent heat treatment, the so-called annealing, the mechanical and electrical properties of the material, such as tensile strength and electrical conductivity, can be increased. Since finely distributed precipitates are formed by annealing, the strength is increased. Such ageing treatment is preferably carried out at moderate temperatures of about 140 to 190 ℃, which is also referred to as thermal ageing.

This can have a favorable effect on the tensile strength and the electrical conductivity of the individual components, and also of the entire cage of the squirrel cage rotor, for example.

Thus, when using a material conforming to the standard EN AW6060, the tensile strength is brought from 80N/mm by annealing at a temperature of 185 ℃ for 10 consecutive hours²Lifting to about 200N/mm². The conductivity of the shorting ring can also be raised from 28MS/m to 34MS/m because the stress in the crystal lattice is reduced during the heat treatment.

The heat treatment is accomplished, for example, by solution annealing in conjunction with subsequent quenching. Thus, the stress in the lattice is reduced and "freezes". The smaller the stress of the lattice, the better the conductivity.

The yield strength of the short-circuit ring thus obtained is 10 times higher than the yield strength of a short-circuit ring made by die casting and containing 99.6 of aluminium. This allows higher rotational speeds of the ASM rotor to be achieved without the need for additional hoops on the short-circuit ring, for example.

If the ductile material is loaded below the yield strength (also referred to as Rp-0.2-yield strength), it returns to its original state again after unloading. In the case of a larger load, plastic deformation will be caused. When a high rotational speed is applied to the rotor, centrifugal forces act on the short-circuit ring. The higher the yield strength, the higher the safety against plastic deformation of the short-circuit ring.

By targeted heat treatment, the higher yield strength values than pure aluminum can also be increased again.

Thus, for example, the yield strength of aluminum 99.6 is about 20N/mm²Whereas the yield strength of AlMgSi (EN AW6060) after heat treatment is about 200N/mm²。

In a further embodiment of the invention, the short-circuiting ring disk is provided, for example, with a closed outer radial contour, which is made of steel or another material with a high tensile strength or yield strength, so that a higher rotational speed of the ASM is achieved.

Advantageously, the short-circuit ring disk has a prefabricated recess for the conductor bar, which is easy to produce in an extrusion technique. The geometric cross section of the preset hollow part is slightly smaller than that of the rod body of the conductor rod, so that the interference fit between the conductor rod and the short circuit ring disc is realized, and the micro-welding is further realized.

By this measure, the degree of deformation and the joining force can be reduced, since material displacement is reduced.

Advantageously, the copper bars are chamfered at the ends, so as to obtain a better centering effect and reduce the joining forces.

By means of the different angles of the chamfers in the radial plane, it is achieved during the engagement of the short-circuiting disk that the bars are pressed ideally in a uniform manner onto the groove bottom of the lamination stack of the rotor. In this case, the outside angle should optionally be greater or steeper than the inside.

One or more additional balance discs may be integrated in a form-fitting manner with the process. It is also possible to mold the short-circuit ring with blades of almost any desired design, which serve for the air circulation inside the electric machine.

The advantage of this manufacturing method is that impurities in the conductor bars and in the short-circuit rings are avoided. Shrinkage cavities, which may occur during casting due to the process itself, do not occur. Furthermore, since the entire surface is micro-welded, an electrically safe connection is produced between the conductor bar and the short-circuit ring.

Short-circuit rings made of aluminum have a smaller moment of inertia due to their smaller weight compared to short-circuit rings made of copper, and thus have a higher rotational speed applicability.

Drawings

The invention and the advantageous embodiments of the invention are explained in more detail by means of embodiments which are shown in principle. In which is shown:

figure 1 is a diagrammatic longitudinal section through an asynchronous machine,

figures 2 to 7 show a principle representation of the manufacturing method,

figure 8 shows in perspective a squirrel cage rotor with a short-circuit ring arranged on one side,

figure 9 shows in perspective a longitudinal section through a squirrel cage rotor with a short-circuit ring arranged on one side,

figure 10 is another embodiment of a squirrel cage rotor,

fig. 11 is an extrusion profile.

Detailed Description

Fig. 1 shows a schematic longitudinal section through an asynchronous machine 1 having a stator 2, the stator 2 forming a winding system 3 at its end faces, which winding system forms a winding head there. The winding system 3 can be formed here, for example, by a string coil, a formed coil, a tooth coil of different or identical coil widths.

The rotor 18 is arranged at a distance from the stator 2 via the air gap 17 of the asynchronous machine 1. The rotor 18, which also has the rotor lamination stack 5, has in each case at least one short-circuit ring, in particular a short-circuit ring disk 7, in the region of the end face 15 of the rotor lamination stack 5. The short-circuit rings, in particular the short-circuit ring disks 7, are connected to and contact the conductor bars 6, which are arranged in recesses 14, not shown in detail, of the rotor lamination stack 5.

As shown in fig. 1, the short-circuit ring, in particular the short-circuit ring disk 7, is in contact with the shaft 19, so that the thermal connection of the short-circuit ring and thus the cooling of the short-circuit ring during operation of the asynchronous machine 1 is achieved.

However, it is likewise possible to space the short-circuit ring, in particular the short-circuit ring disk 7, from the shaft 19.

The short-circuit rings, in particular the short-circuit ring disks 7, can thus be spaced apart from the end face 15 of the rotor lamination stack 5 and/or the shaft 19. It is also conceivable for the short-circuit ring, in particular the short-circuit ring disk 7, to be in contact with the end face 15 of the rotor lamination stack 5 and the shaft 19, i.e. to bear against each other.

The shaft 19 is caused to rotate by an electromagnetic reaction between the energized stator 2 and the cage of the rotor 18 formed by the conductor bars 6 and the short circuit ring 7.

Fig. 2 shows a schematic detail of a rotor lamination stack 5, from which conductor bars 6 project and on which a short-circuiting ring disk 7 is pressed by an axial joining force 8. Such axial joining 8 is preferably carried out simultaneously for all conductor bars 6 projecting from the end face 15 of the rotor lamination stack 5.

Fig. 3 shows how the short-circuiting ring disk 7 is pressed onto the conductor bars 6 protruding from the rotor lamination stack 5, where electrical contact and fixing is then achieved by means of micro-soldering. The short-circuit ring disk 7 bears directly against the rotor lamination stack 5.

Fig. 4 shows a further embodiment of the invention, in which the short-circuiting ring disk 7 has a recess 11 which has a smaller dimension than the geometric cross section of the conductor bar 6, so that sufficient micro-welding can be achieved between the conductor bar 6 and the short-circuiting ring disk 7. It is also essential here that the shear stress permitted by the material of the short-circuit ring disk 7 and the conductor bar 6 is locally exceeded, and therefore a material transition region is realized by diffusion at the boundary surface between the conductor bar 6 and the short-circuit ring disk 7.

In order to simplify the joining process, the end of the conductor bars 6 projecting from the rotor lamination stack 15 is conically shaped or pointed according to fig. 5, which is advantageous in any production manner in order to make the joining process easier.

Fig. 6 shows the principle of the joining process according to fig. 2 and 3, wherein an excess of material 21 can occur on the short-circuiting ring disk 7 by the joining process, since the material is pressed into the empty space provided by the tool by the material displacement of the end of the conductor bar.

As is shown by way of example in fig. 7, it is advantageous here that, by means of this excess material 21, the balancing element 9 or the fan blades 12 can be formed or molded at the same time on the side facing away from the rotor lamination stack 5. This is achieved by pressing the material excess 21 into a corresponding predetermined matrix of the tool or device.

It is also possible to arrange additional elements made of another material (for example fan blades 12 or compensating elements 9) on the end face of the short-circuiting ring disk 7 facing away from the rotor lamination stack 6 by means of the excess material 21.

Fig. 8 shows the rotor lamination stack 5 in perspective view, on one side of which a short-circuit ring disk 7 has been molded. On the other side of the rotor lamination stack 5, the chamfered ends of the conductor bars 6 project from the rotor lamination stack 5, and a short-circuit ring disk 7 is pressed against the rotor lamination stack 5. Also visible is a shaft bore 20 into which the shaft 19 is then press-fitted or connected in a rotationally fixed manner to the rotor lamination stack 5 by means of a sliding-key connection.

However, the shaft 19 can also be connected to the rotor lamination stack 5 in a rotationally fixed manner before the axial engagement 8 of the conductor bars 6 with the short-circuit ring disk 7.

Fig. 9 shows a longitudinal section through the rotor lamination stack 5, on one side of which a short-circuiting ring disk 7 has already been pushed axially onto the ends of the conductor bars 6, wherein, in addition to the tapering of the conductor bars 6, a material displacement 21 is also produced in the short-circuiting ring disk 7, which forms fan-like blades 12 on the end face of the short-circuiting ring disk 7.

The fan-like blades 12 can also be formed as separate elements which are fixed to the end face of the short-circuiting ring disk 7 by means of a material displacement 21.

Likewise, these fan-like blades 12 can also be constructed by inserting the conductor bars 6 axially through the short-circuit ring disk 7.

Fig. 10 shows a further perspective view of a short-circuiting ring disk 7 on rotor lamination stack 5, wherein the end face of short-circuiting ring disk 7 facing away from rotor lamination stack 5 is embodied as a plane, in particular parallel to the end face of rotor lamination stack 5. The end faces of the ends of the conductor bars 6 terminate flush with the end faces of the short-circuit ring disk 7.

Fig. 11 shows an extruded profile made of the material of the short-circuit ring, preferably an aluminum forged alloy, which also has a corresponding recess 11 and, depending on the field of application and the performance of the asynchronous machine 1(ASM), can be cut off axially in addition to the short-circuit ring disk 7.

A plurality of short-circuit rings or short-circuit ring disks 7 arranged in an insulated manner from one another can also be arranged on each end face 15 of the rotor lamination stack 5. The mutually electrically insulated squirrel cages in the rotor 18 reduce harmonics in the air gap 17 of the asynchronous machine, in particular when the stator 2 has a winding system 3 with tooth coils, where each tooth of the stator 2 is surrounded by a tooth coil.

Machines of this type have a wide range of applications, not only for standard applications in the field of compressors, fans and pumps, but also for their high-speed applications and in automotive technology, and can thus be produced safely, efficiently and simply. Likewise, other drive tasks are also possible.