Squid cage rotor and method for manufacturing the same

Abstract

The invention relates to a conductor bar (9) of a squirrel-cage rotor (8) of an asynchronous machine (5), which has a lower hardness in a predetermined section (11) in the longitudinal extension of the conductor bar, in particular is soft-annealed.

Description

Technical Field

[0001] The invention relates to a conductor rod, a squirrel-cage rotor of an asynchronous machine, a method for producing such a squirrel-cage rotor of an asynchronous machine, and the use of such an asynchronous machine. Background Art

[0002] The squirrel-cage rotor of an asynchronous motor is equipped with a shield made of aluminum and / or copper. Copper is particularly used to increase the efficiency of the asynchronous motor. Here, a copper rod is axially inserted into a slot in a magnet conductor, which is provided with short-circuit rings at both ends. To prevent vibrations of the conductor rod in the slot, the rod is currently inserted or driven into the squirrel-cage rotor slot with very narrow dimensional tolerances and a high level of force. This also results in long manufacturing times for such squirrel-cage rotors.

[0003] The narrow dimensional tolerances of the conductor bars relative to the slots necessitate a high level of force for inserting the conductor bars. The conductor bars are usually hammered in axially, which results in relatively long machining times for the squirrel-cage rotor. Each individual conductor bar must be hammered into its corresponding slot. Furthermore, there is the risk that the conductor bars will scrape against the slot walls of the individual laminations, thereby forming metal chips that can then prevent or at least impair operation.

[0004] Alternatively, the conductor bars are designed with a slight clearance fit, making them easy to use without expending too much effort. To secure the bars in the slots, the laminated core is now dipped in a thin potting resin. The gaps between the conductor bars and the inner walls of the rotor slots are thus filled with resin. A disadvantage is that the resin adheres to the slot side walls and can, under certain circumstances, become loose, potentially impairing the operation of the asynchronous machine.

[0005] Therefore, the conductor bars have been fixed in the rotor slots more or less reliably with relatively high effort up to now. Therefore, vibrations of the conductor bars and thus impairment of the operation of the asynchronous machine have not yet been ruled out.

[0006] It is also known that slight deformation of the laminated core in the slot region by axial rolling at the outer diameter of the laminated core leads to the fixing of the conductor bars in the slots. However, this is also very complex. Furthermore, the laminated core in the outer region is plastically deformed during this process. This negatively impacts the strength of the rotor laminate and its performance at relatively high rotational speeds.

[0007] In hybrid technologies, such as those using aluminum die casting combined with copper rods, the copper rods only partially fill the rotor slots. The remaining slots are then sprayed with aluminum by die casting, securing the conductor rods in the slots. A disadvantage is that the slots are not completely filled with copper, which has a very high conductivity. Consequently, the desired efficiency levels for asynchronous motors cannot be achieved. Summary of the Invention

[0008] Based on this, the object of the present invention is to provide a squirrel-cage rotor for an asynchronous motor that simply prevents vibrations of the conductor bars when the asynchronous motor is operated in the high speed range of the asynchronous motor and, at the same time, has a relatively high copper filling factor. The squirrel-cage rotor should be simple to manufacture and suitable for automated processing. Furthermore, the asynchronous motor should be suitable for a variety of applications requiring high speeds and / or high torques and / or varying loads.

[0009] The solution to the proposed object is achieved by a conductor bar of a squirrel-cage rotor of an asynchronous machine which has a lower hardness in provided sections in the longitudinal extension of the conductor bar, in particular is soft-annealed.

[0010] The solution of the proposed object is also achieved by a method for producing a cage rotor of an asynchronous machine by the following steps:

[0011] - providing a magnetic conductor, in particular a lamination stack having substantially axially extending slots arranged at the radially outer edge,

[0012] the conductor rod according to the invention is inserted axially into the slot with a clearance fit relative to the cross section of the respective slot and has an axial projection of the conductor rod from the end face of the magnetic conductor,

[0013] - axially upsetting the conductor bars in the respective slots, so that a defined abutment point between the conductor bars and the inner side of the slots is produced in the axial extension of the slots,

[0014] - Simultaneously or subsequently, the short-circuiting ring is brought into contact with the axial projection of the conductor rod.

[0015] The solution to the stated object is also achieved by a squirrel-cage rotor for an asynchronous machine, which is produced according to the method according to the invention, wherein the conductor bars in the slots have defined abutment points in order to optimize the vibration behavior of the squirrel-cage rotor during operation.

[0016] The solution to the stated object is also achieved by an asynchronous machine having a squirrel-cage rotor according to the invention, wherein the asynchronous machine has a reduced vibration behavior.

[0017] The solution to the stated object is also achieved by at least one asynchronous machine according to the invention having a squirrel-cage rotor according to the invention, used in drive systems of machine tools, for example in the food, transportation or chemical industries.

[0018] The conductor rod, in particular a copper rod, according to the present invention therefore has one or more sections in its axial extension in which the conductor rod is relatively soft. This can be achieved, for example, by briefly heating the conductor rod at specific locations by induction or by heating with a flame or other method. Advantageously, this method can already be used during rod manufacturing or during conductor rod cutting. However, this brief heating can also be performed immediately after cutting at the predetermined sections / locations of the conductor rod.

[0019] In this case, heating to above the recrystallization temperature is only required briefly, which is 750° C., for example, in the case of conductor rods made of copper.

[0020] As a result, the conductor rod has a section with lower hardness at a predetermined position of the axial extension of the conductor rod.

[0021] In methods for producing conductor bars with soft annealed sections, it has previously been possible to upset the conductor bars in these softer sections by applying axial pressure to the ends of the conductor bars after axially joining the conductor bars into the magnet conductor. Because the softer sections are located within the slots of the cage rotor, defined contact points of the conductor bars are formed on the inside of the slots. This prevents vibrations of one or more conductor bars during operation of the asynchronous machine.

[0022] By this deformation, the previously relatively small fit play of the conductor rod in the slot is filled at least in sections. The previous vibration of the rod during operation of the asynchronous machine is avoided by the abutment of the conductor rod on the inner wall of the slot.

[0023] The conductor rod preferably abuts the inner wall of the slot by upsetting, wherein there is a clearance fit between the conductor rod and the inner wall within the slot and a softer section of the conductor rod is present.

[0024] Depending on the frequency of the vibration to be achieved, one or more such sections can be integrated in the axial extension of the conductor rod or introduced into the conductor rod.

[0025] Without this upset, the conductor rod's so-called fundamental vibration f1 results. With the upset, the first resonance is 2*f1, with two upsets per conductor rod, 3*f1, and so on. Depending on the axial length of the magnetizer, one or more upsets are provided per unit length of the conductor rod in order to prevent vibrations of the conductor rod relative to its natural frequency by one or more additionally used vibration nodes. The natural frequency of the conductor rod is twice or several times higher due to one or more additional nodes, i.e., adjacent points, at the inner wall of the slot and, therefore, lies outside the excitation frequency during operation of the asynchronous machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention and other advantageous embodiments of the present invention are explained in detail based on the exemplary embodiments shown in principle.

[0027] Figure 1 shows a cross-sectional view of a magnetic conductor,

[0028] Figure 2 Shown Figure 1 Detailed cross-sectional view of

[0029] Figure 3 A conductor rod is shown,

[0030] Figure 4 Detail view showing the conductor bars in the slots,

[0031] Figure 5 shows a conductor rod after upsetting,

[0032] Figure 6 A schematic diagram showing a conductor rod in a magnetic conductor is shown,

[0033] Figure 7 A detailed view of the trough arrangement is shown,

[0034] Figure 8 A slot arrangement with an axis is shown,

[0035] Figure 9 A detail view of the slot arrangement with the shaft is shown,

[0036] Figure 10 A longitudinal section of an asynchronous machine is shown. DETAILED DESCRIPTION

[0037] Figure 1 A cross section through a magnet conductor 1 is shown, in particular a cross section through a laminated core having slots 2 extending substantially axially at the radially outer edge, which are shown partially open in this exemplary embodiment. The partial opening involves a small slot gap 3, which leads to an air gap 4 (not shown in detail) of an asynchronous motor 5. Furthermore, a shaft hole 6 is shown, in which a shaft 7 is subsequently connected to the laminated core of a squirrel-cage rotor 8 in a rotationally fixed manner.

[0038] Here, a predeterminable number of grooves 24 and / or a predeterminable shape are arranged on the inside, i.e. on the inside of the shaft hole 6 of the magnet conductor 1, in particular on the inside of the lamination stack of the cage rotor 8. Figure 7 Begins to be described in detail.

[0039] Figure 2A detailed view of a slot 2 with a conductor rod 9 located in the slot 2 is shown, which conductor rod has a circumferential clearance fit 10 at least in sections in relation to the cross section of the slot 2 in the circumferential direction 23, so that the axial insertion of the conductor rod 9 in the slot 2 can be achieved almost forcelessly and without cutting on the inner wall of the slot 2.

[0040] The definition of the ISO fit system is used here as the basis for the clearance fit 10. The conductor rod 9 can then be slightly moved or displaced within the slot 2, even manually. The crucial point is that the upsetting of the conductor rod 9 at the predetermined section 12 results in a contact area 21 between the inner wall of the slot 2 and the conductor rod 9.

[0041] Such a conductor rod 9 is soft annealed at a predetermined section 11 of the conductor rod 9, which is located in the axial direction of the longitudinal extension, so that a relatively low hardness is set there. Figure 5 In principle, the conductor rod 9 is upset by an axially external force 18, so that a thickening 12 of the conductor rod 9 is provided in this region. The thickening 12 results in a tensioning of the conductor rod 9 in the slot 2. Figure 4 The wedging and spreading are shown in the detail view.

[0042] The thickening 12 of the conductor bar 9 can be formed over the entire axial section 11. However, it is also possible that the thickening 12 is present only in a single direction relative to the axial section 11, namely in the radial direction 22 and / or in the circumferential direction 24. What is decisive is that a defined abutment region 21 is formed between the conductor bar 9 and the inner wall of the slot 2 (see Figure 2 ).

[0043] The present invention can apply different slot shapes or conductor rod cross sections in the double cage rotor, such as round rods, wedge-shaped rods, L-shaped rods, tall rods, teardrop-shaped rods / slots, and combinations thereof.

[0044] The axial upsetting of the conductor bars 9 can also be achieved by placing the short-circuiting rings 13 on the axial projections 20 of the conductor bars 9 protruding from the laminated core 1. Thus, two steps can be achieved in one working process: upsetting the short-circuiting rings 13 and the conductor bars 9 and making electrical contact.

[0045] There are various possibilities for electrically contacting the conductor rod 9 with the short-circuiting ring 13. This can be achieved by mechanical compression, a welding process, induction heating or electrical heating or a combination thereof.

[0046] By wedging / expanding the conductor rods at predeterminable sections in the corresponding grooves 2 within the magnetic conductor according to the invention, vibrations of the conductor rods 9 during operation of the asynchronous machine 5 are avoided.

[0047] Figure 6The squirrel-cage rotor 8 is shown without short-circuiting rings 13, with an axial projection 20 of the conductor bars 9 at the end face 14 of the laminated core 1. In this case, the conductor bars 9 have, due to upsetting, thickenings 12 extending axially in the slots 2. Consequently, abutment regions 21 are located between the inner wall of the slots 2 and the conductor bars 9. The short-circuiting rings 13 are installed and electrically contacted in the following steps.

[0048] Figure 7 A detailed view of the groove arrangement 24 at the shaft bore 6 is shown. In this embodiment, the shaft bore has a thread groove 26 and two pressure relief grooves 25 on either side. The thread groove 26 thus has a substantially triangular profile, the corners of which are provided with radii 28. Therefore, it is not a semicircular groove, but rather has at least two different radii of the profile. There are two smaller radii in the corners, and a larger radius in the segment 30 connecting the two smaller radii.

[0049] The thread grooves 26 also serve to align the individual laminations during the packaging of the lamination stack of the cage rotor 8. However, in order to ensure adequate torque transmission from the lamination stack of the cage rotor 8 to the shaft 7 at the relatively high rotational speeds of the asynchronous machine, which requires a high interference fit in the lamination stack seat on the shaft 7, the thread grooves 26 are supplemented with pressure relief grooves 25. Using the thread grooves 26 alone carries the risk of mechanical overloading of the laminations in this area.

[0050] Figure 8 The shaft hole 6 is shown with a slot arrangement 24 of the shaft hole, in which slot arrangement the shaft 7 is introduced into the shaft hole 6 .

[0051] Figure 9 The groove arrangement 24 with the shaft 7 is shown in a detailed view. Figure 7 The groove arrangement 24 in the shaft 7 is shown. Here, a positive-locking area 29 and a contact area 27 are present. When the shaft 7 is axially inserted into the shaft bore 6, the tabs 31 (i.e., the intermediate pieces between the thread grooves 26 and the pressure relief grooves 25) also smooth out the waves, grooves, or furrows produced by the manufacture of the shaft 7. Consequently, a positive-locking area 29 is formed in the region of the thread grooves 26 and the pressure relief grooves 25. The positive-locking area 29 also serves as a safety feature to prevent the shaft 7 from slipping into the interior of the laminated core 1 and thus improves the torque transmission performance.

[0052] The groove arrangement 24 , ie the combination of the thread groove 26 and the pressure relief groove 25 , significantly reduces mechanical stresses in the core, in particular in the case of high interference dimensions in the core seat on the shaft 7 .

[0053] Advantageously, the groove arrangement 24 is evenly distributed on the shaft opening 6 in order to achieve a sufficient distribution of the torque to be transmitted.

[0054] The contour of the thread groove 26 and / or the pressure relief groove 25 also has an arc-shaped or elliptical arc-shaped contour at least in sections. As a result, the mechanical pressure in this area is reduced, especially when there is a strong excess dimension between the laminated core 1 and the shaft 7 in order to ensure the required centrifugal force stress and high torque transmission performance.

[0055] The slot 2 is used to accommodate the conductor rod 9. The conductor rod 9 in the slot 2 generates torque through electromagnetic interaction with the winding system 16 of the stator 19. The thread groove 26 and the pressure relief groove 25 in the slot arrangement 24 do not generate torque, but only transmit torque to the shaft 7.

[0056] Figure 10 The asynchronous machine 5 with the squirrel-cage rotor 8 according to the invention is shown in a schematic longitudinal section. The rotation of the shaft 7 about the axis 15 is achieved by the electromagnetic interaction between the winding system 16 in the stator 15 and the squirrel-cage rotor 8. The shaft 7 is supported in bearings 17 and is connected to the laminated core 1 of the squirrel-cage rotor 8 in a rotationally fixed manner.

[0057] In this embodiment, the squirrel-cage rotor 8 shows short-circuiting rings 13, which adjoin the end face 14 of the laminated core 1. It is self-evident that the concept according to the invention can also be implemented if the short-circuiting rings 13 are spaced apart from the end face 14.

[0058] The concept according to the invention can also be used for a rotor in which permanent magnets and a short-circuit cage are present.

[0059] This asynchronous motor 5 can be used in both the low-voltage and high-voltage ranges. Applications include industrial drives and vehicle drives. Advantageously, even at high speeds and / or high torques of the asynchronous motor 5 , conductor rod vibrations are not noticeable in the respective applications. This makes it possible, for example, to ensure a high surface quality of workpieces produced using a machine tool equipped with an asynchronous motor according to the invention.

Claims

1. A conductor rod (9) of a squirrel-cage rotor (8) of an asynchronous motor (5), wherein the conductor rod has a lower hardness at a predetermined section in its longitudinal extension, wherein: The relatively soft section is achieved by soft annealing, brief induction heating or by flame heating, so that after the conductor rod is axially engaged in the slot of the magnet conductor (1) of the cage rotor (8) by axial pressure, the conductor rod (9) is upset at a predetermined section, wherein the predetermined section adjoins the inner wall of the slot of the cage rotor.

2. A method for producing a cage rotor (8) of an asynchronous motor (5), the method comprising the following steps: - providing a magnetic conductor (1), The conductor rod (9) has a lower hardness at a predetermined section in its longitudinal extension, wherein: The relatively soft section is achieved by soft annealing, brief induction heating or by flame heating, so that after the conductor rod is axially engaged in the slot of the magnet conductor (1) of the cage rotor (8) by axial pressure, the conductor rod (9) is upset at a predetermined section, wherein the predetermined section adjoins the inner wall of the slot of the cage rotor, wherein the conductor rod (9) is inserted axially into the slot and has a clearance fit (10) for the corresponding slot cross section, and the conductor rod has an axial projection (20) of the conductor rod (9) from the end side (14) of the magnet conductor (1), - axially upsetting the conductor rod (9) in the corresponding slot so that a defined abutment point is produced between the conductor rod (9) and the inner side of the slot in the axial extension of the slot, - Simultaneously or subsequently bringing the short-circuiting ring (13) into contact with the axial projection (20) of the conductor rod (9).

3. The method according to claim 2, characterized in that The magnetic conductor (1) is a stack of laminations having slots extending in the axial direction and arranged at the radial outer edge.

4. A cage rotor (8) of an asynchronous motor (5), the cage rotor having a magnetizer (1), the cage rotor having slots extending in the axial direction and arranged at a radial outer edge, wherein: The conductor rod (9) has an abutment point defined in the slot in order to optimize the vibration behavior of the cage rotor (8) during operation of the asynchronous machine, wherein the conductor rod (9) has a lower hardness at a predetermined section in the longitudinal extension of the conductor rod, wherein the relatively soft section is achieved by soft annealing, brief induction heating or by heating with a flame, so that after the conductor rod is axially engaged in the slot of the magnet conductor (1) of the cage rotor (8) by axial pressure, the conductor rod (9) is upset at the predetermined section, wherein the predetermined section abuts the inner wall of the slot of the cage rotor.

5. The cage rotor (8) of the asynchronous motor (5) according to claim 4, characterized in that The magnetic conductor (1) is a lamination stack.

6. The cage rotor (8) of the asynchronous motor (5) according to claim 5, characterized in that The squirrel-cage rotor (8) has short-circuit rings (13) which directly adjoin the end face (14) of the laminated core or are spaced apart from the end face of the laminated core.

7. The cage rotor (8) of the asynchronous motor (5) according to any one of claims 4 to 6, characterized in that The abutment points produced by upsetting form a thickening of the conductor rod (9), which can occur over the entire axial section or only in a single direction.

8. The cage rotor (8) of the asynchronous motor (5) according to any one of claims 4 to 6, characterized in that The cage rotor (8) has a short-circuit cage and permanent magnets.

9. An asynchronous motor (5) having a cage rotor (8) according to any one of claims 4 to 8, characterized in that: In order to achieve reduced vibration behavior, the cage rotor (8) has a slot arrangement (24) at the shaft opening (6) and / or the cage rotor has a defined abutment point of the conductor rod (9) in the slot, wherein the slot arrangement (24) has a thread groove (26) and two pressure relief grooves (25).

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