A preparation process and processing device of a layered squirrel cage rotor

Abstract

The present application discloses a preparation process and processing device of a layered squirrel cage rotor, which belongs to the technical field of production of motor rotors for new energy vehicles. The preparation process includes the following steps: placing an end ring in a base, connecting a protrusion at the upper end, inserting the protrusion at one end of a rotor core slot, inserting a plurality of guide bars at the other end of the rotor core slot, heating the connection between the protrusion and the guide bar by a heating ring on the base until they are melted and combined, stopping heating and removing the force module, cooling to below 250°C, and then all the guide bars away from one end of the protrusion are immersed in the rotor core slot; placing an end ring in a base, inserting the protrusion at the other end of the rotor core slot, heating the connection between the guide bar and the end ring until they are melted and combined, stopping heating and removing the force module, and cooling to below 250°C to obtain a layered squirrel cage rotor; the rotor has high precision and good quality, and has excellent electrical conductivity and mechanical strength.

Description

Technical Field

[0001] The present application relates to a preparation process and a processing device for a layered squirrel cage rotor, and belongs to the technical field of new energy vehicle motor rotor production. Background Art

[0002] With the advent of the era of electrification, new energy vehicles and high-speed trains have put forward high requirements for the performance of asynchronous motors in power traction systems, such as large drive and high power. The squirrel cage motor rotor is an important component of the asynchronous motor and has a wide range of applications in the industrial field. With the vigorous development of the new energy vehicle industry, the squirrel cage motor rotor asynchronous motor has gradually become an important choice for the main drive motor or auxiliary drive motor.

[0003] Unlike industrial asynchronous motors, new energy vehicle asynchronous motors have higher speed requirements, with the maximum speed required to reach 16,000 rpm or even exceed 18,000 rpm. In addition, the working conditions of new energy vehicle motors are complex, often in variable speed and variable load, and the motor rotor must withstand high-speed centrifugal force impact. Under the action of high-speed centrifugal force, the guide bars of the motor rotor will deform, especially the stress concentration phenomenon at the connection between the end ring and the guide bar, which poses a risk of fracture failure.

[0004] Furthermore, in the field of new energy vehicles, the strength and conductivity of the motor rotor are required to be high; however, the existing motor rotors have low conductivity, insufficient strength, or too complicated processes and are difficult to prepare, and it is difficult to meet the corresponding performance requirements. Generally speaking, the strength and conductivity of aluminum alloys are inversely proportional, high strength means low conductivity, high conductivity means low strength, and the addition of other elements will affect the conductivity of the alloy to varying degrees; therefore, in order to achieve a better matching relationship between the strength and conductivity of the alloy, it is necessary to improve the preparation process of the motor rotor. Summary of the invention

[0005] In order to solve the above problems, a preparation process and a processing device of a layered squirrel cage rotor are provided, which improve the processing accuracy and ensure the quality of the rotor. The prepared layered squirrel cage rotor has both excellent electrical conductivity and mechanical strength.

[0006] The technical solution provided by the present invention is:

[0007] A preparation process of a layered squirrel cage rotor comprises the following steps:

[0008] (1) Take an end ring and place it in the base, the upper end of which is connected to a plurality of protrusions, the protrusions are inserted into one end of the rotor core slot, and the other end of the rotor core slot is inserted into a plurality of conductor bars;

[0009] (2) Apply a force of 50-200N to the end of the conductor bar away from the protrusion, and then heat the connection between the protrusion and the conductor bar through the heating ring on the base, and at the same time apply a force of 0-10N to the end of the conductor bar away from the protrusion until the connection between the protrusion and the conductor bar melts and combines, then stop heating, remove the force module, and cool to below 250°C until the conductor bar away from the protrusion is completely immersed in the rotor core slot;

[0010] (3) Take another end ring and place it in the base, insert the protrusion into the other end of the rotor core slot, and heat the connection between the guide bar and the end ring through the heating ring on the base until the connection between the guide bar and the end ring is melted and combined. Then stop heating, remove the force module, and cool to below 250°C to obtain a layered squirrel cage rotor.

[0011] Optionally, cooling is performed by air cooling, with the air volume controlled at 190-210m 3 , the air cooling time is 0.1-1h, which improves the production efficiency.

[0012] Optionally, the specific steps for melting and combining the connection between the protrusion and the guide bar in step (2) are as follows: when the first heating temperature reaches 600-640°C, stop heating and maintain for 5-30s, then heat again to 650-730°C, the connection between the protrusion and the guide bar begins to melt and combine, and at the same time, apply a force of 0-10N to the end of the guide bar away from the protrusion. When the displacement of the force module is 3-6% of the length of the guide bar, stop heating and remove the force module.

[0013] Optionally, the specific steps for melting and bonding the connection between the conductor bar and the end ring in step (3) are as follows: when the first heating temperature reaches 600-640°C, stop heating and maintain for 5-30s, then heat up again to 650-730°C, the connection between the conductor bar and the end ring begins to melt and bond, and when the outer end of the end ring is melted and connected to the outer end of the rotor core slot, stop heating and remove the force module.

[0014] Optionally, the heating rate of the first heating is 15-20°C, and the heating rate of the second heating is 20-30°C.

[0015] Optionally, the method further includes the steps of preparing the end ring: first, the raw material of the end ring is melted, and then the end ring mold is preheated at 580-620°C, and then the melted material is injected into the end ring mold for gravity casting, and then cold water is injected into the periphery of the end ring mold, and after cooling, the mold is opened to obtain the end ring.

[0016] Optionally, the flow rate of cold water is 225-230m 3 / h, the temperature is 10-15℃, which not only does not affect the shrinkage compensation, but also speeds up the cooling rate.

[0017] Optionally, the conductive bar is composed of the following components in percentage by mass: Si 0.2-0.4%, Fe 0.1-0.3%, Cu 0.2-1% and the balance Al.

[0018] Optionally, the end ring is composed of the following components in mass percentage: Sb 0.5-1.5wt%, Mg 0.3-0.7wt%, Si 0.3-0.7wt% and the balance Al.

[0019] According to another aspect of the present application, a processing device for a layered squirrel cage rotor is provided, comprising a base and a force applying module, wherein the force applying module is arranged above the base, and an end ring, a rotor core and a guide bar are arranged between the base and the force applying module, wherein the guide bar is inserted into a rotor core slot and at least partially exposed outside the rotor core slot;

[0020] An annular groove is provided in the base for accommodating the end ring, and a heating ring is mounted on the upper end of the base;

[0021] The force-applying module is annular, and one end of the module is evenly provided with a plurality of convex ribs, and an elastic gasket is provided at one end of the convex rib away from the force-applying module.

[0022] Optionally, the end ring is ring-shaped, and one end of the end ring is connected to a plurality of protrusions, and the number of protrusions, ribs, elastic gaskets, guide bars and rotor core slots is the same.

[0023] Optionally, it further comprises an end ring mold and a die head, wherein the die head is arranged above the end ring mold;

[0024] The machine head is annular, and a first water inlet and a first water outlet are provided on the outer side thereof;

[0025] The end ring mold has an annular groove in it and a plurality of cavities at its bottom. The annular groove is connected with the cavities, and the cavities are matched with the protrusions. A second water inlet and a second water outlet are formed on the outer side of the end ring mold.

[0026] Optionally, the ratio of the protrusion cross-sectional area to the conductor bar cross-sectional area is (0.8-0.9):1, which facilitates the molten liquid to fill various gaps during hot melt welding, so that the end ring, conductor bar and rotor core are tightly combined to ensure uniform stress distribution at each position.

[0027] The beneficial effects of this application include but are not limited to:

[0028] 1. In the preparation process of the layered squirrel cage rotor of the present application, a force of 50-200N is applied to the end of the guide bar away from the protrusion to ensure that each guide bar is in full contact with the protrusion; a force of 0-10N is applied to the end of the guide bar away from the protrusion, so that the bubbles inside the guide bar can be extruded after the guide bar is melted, and the connection between the end ring and the guide bar is stronger and tighter due to the pre-pressure; the end ring is manufactured and hot-melt welded by this method, which improves the processing accuracy, ensures the quality of the rotor, and makes the prepared layered squirrel cage rotor have both excellent electrical conductivity and mechanical strength.

[0029] 2. In the preparation process of the layered squirrel cage rotor of the present application, the first heating is maintained for 5-30 seconds before reaching the melting point so that all the workpieces are in a hot-fitting state, and at the same time, preparation time is provided for applying pre-pressure. After the second heating reaches the melting point, the end rings are hot-melt welded. During this period, the heating rate needs to be increased to ensure welding accuracy. By controlling the heating rates twice, the rotor can achieve the desired performance.

[0030] 3. In the preparation process of the layered squirrel cage rotor of the present application, by adding appropriate amounts of Sb, Si and Mg elements, nano-scale β' (Mg2Si) phase and micron-scale AlSb phase are formed in the end ring, which significantly improves the mechanical properties of the end ring without damaging its conductive properties; 0.2-1% Cu is added to the conductor bar, and mainly θ'-Al2Cu phase and β-Al5FeSi phase are formed in the aluminum matrix. The presence of θ'-Al2Cu phase and β-Al5FeSi phase can improve the strength and conductivity of the alloy and significantly improve the high-temperature creep resistance of the conductor bar.

[0031] 4. The processing device of the layered squirrel cage rotor of the present application ensures that each guide bar is subjected to the same force by arranging an elastic gasket at the end of the rib away from the force-applying module; by arranging a machine head above the end ring mold, the cooling effect is increased while applying pressure to the molten liquid in the solidification process, which helps to compensate for shrinkage, so as to obtain end rings with smaller grain size, higher strength and toughness, and at the same time improve production efficiency; the processing device is simple and convenient to operate, ensures processing accuracy, and ensures good rotor molding quality and high production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0033] Figure 1 It is a structural explosion diagram of the layered squirrel cage rotor preparation process involved in the embodiment of the present application.

[0034] Figure 2 It is a structural explosion diagram of the end ring preparation process involved in the embodiment of the present application.

[0035] List of parts and reference numerals:

[0036] 1. Base, 2. Force module, 3. Rotor core, 4. Guide bar, 5. Annular groove, 6. Heating ring, 7. Rib, 8. Elastic gasket, 9. End ring, 10. Protrusion, 11. End ring mold, 12. Machine head, 13. First water inlet, 14. First water outlet, 15. Annular groove, 16. Cavity, 17. Second water inlet, 18. Second water outlet. DETAILED DESCRIPTION

[0037] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0038] If no specific conditions are specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The raw materials or instruments used, if no manufacturer is specified, are all conventional products that can be purchased commercially.

[0039] See also Figure 1 and 2 A processing device for a layered squirrel cage rotor comprises a base 1 and a force applying module 2, wherein the force applying module 2 is arranged above the base 1, and an end ring 9, a rotor core 3 and a guide bar 4 are arranged between the base 1 and the force applying module 2, wherein the guide bar 4 is inserted into a slot of the rotor core 3 and at least partially exposed outside the slot of the rotor core 3, so that the force applying module 2 can apply pressure to the guide bar 4;

[0040] An annular groove 5 is provided in the base 1 for accommodating the end ring 9. A heating ring 6 is provided on the upper end of the base 1 to facilitate hot-melt welding of the end ring 9, the guide bar 4 and the rotor core 3.

[0041] The force-applying module 2 is annular, and one end of the force-applying module is evenly provided with a plurality of convex ribs 7 . An elastic gasket 8 is provided at one end of the convex rib 7 away from the force-applying module 2 to ensure that each guide bar 4 is subjected to the same force.

[0042] Furthermore, the end ring 9 is ring-shaped, and one end of the end ring 9 is connected to a plurality of protrusions 10, which is convenient for insertion into the slot of the rotor core 3 and hot-melt welding with the guide bar 4 and the rotor core 3; the number of protrusions 10, ribs 7, elastic gaskets 8, guide bars 4 and slots of the rotor core 3 is the same.

[0043] Furthermore, the processing device also includes an end ring mold 11 and a die 12, wherein the die 12 is disposed above the end ring mold 11, so as to apply pressure to the molten liquid in the solidification process, thereby facilitating shrinkage compensation, so as to obtain an end ring 9 with a smaller grain size, higher strength and toughness;

[0044] The head 12 is annular, and a first water inlet 13 and a first water outlet 14 are provided on the outer side thereof to increase the cooling effect and improve the production efficiency;

[0045] An annular groove 15 is provided in the end ring mold 11, and a plurality of cavities 16 are provided at the bottom thereof, the annular groove 15 is connected to the cavities 16, the cavities 16 are matched with the protrusions 10, and a second water inlet 17 and a second water outlet 18 are provided on the outer side of the end ring mold 11 to facilitate the circulation of the coolant around it, take away the heat, and quickly produce the end ring 9.

[0046] It can be understood that the ratio of the cross-sectional area of ​​the protrusion 10 to the cross-sectional area of ​​the conductor bar 4 is 0.85:1, which facilitates the molten liquid to fill the gaps during the hot melt welding process, so that the end ring 9, the conductor bar 4 and the rotor core 3 are tightly combined to ensure uniform stress distribution at each position.

[0047] The above processing device is used to prepare the layered squirrel cage rotor below.

[0048] Example 1

[0049] See also Figure 1 and 2 , a preparation process of a layered squirrel cage rotor, comprising the following steps:

[0050] (1) First, the raw material of the end ring is melted, and then the end ring mold is preheated at 600°C. Subsequently, the melted material is injected into the end ring mold, the die head is covered, and the die head pressure is controlled to 10N for gravity casting. Then, cold water is injected into the die head and the periphery of the end ring mold respectively, with a flow rate of 227m3 / h and a temperature of 13°C. After cooling, the mold is opened to obtain the end ring;

[0051] (2) Take an end ring and place it in the base, the upper end of which is connected to a plurality of protrusions, the protrusions are inserted into one end of the rotor core slot, and the other end of the rotor core slot is inserted into a plurality of conductor bars;

[0052] (3) A force of 120 N is applied to the end of the guide bar away from the protrusion, and then the connection between the protrusion and the guide bar is heated by the heating ring on the base. When the first heating temperature reaches 620 ° C, the heating is stopped, the heating rate is 18 ° C, and it is maintained for 16 seconds. Then the temperature is raised to 700 ° C again, and the heating rate is 25 ° C. The connection between the protrusion and the guide bar begins to melt and combine. At the same time, a force of 5 N is applied to the end of the guide bar away from the protrusion. When the displacement of the force module is 4.5% of the length of the guide bar, the heating is stopped, the force module is removed, and the temperature is cooled by air cooling. The air volume is controlled to be 200m 3 The air cooling time is 0.5h. After cooling to below 250℃, the conductor bars at the end away from the protrusion are all immersed in the rotor core slots.

[0053] (4) Take another end ring and place it in the base. Insert the protrusion into the other end of the rotor core slot. Heat the connection between the guide bar and the end ring through the heating ring on the base. Stop heating when the first heating temperature reaches 620℃. The heating rate is 18℃ and maintained for 16s. Then heat it again to 700℃ at a heating rate of 25℃. The connection between the guide bar and the end ring begins to melt and combine. When the outer end of the end ring is melted and connected with the outer end of the rotor core slot, stop heating, remove the force module, and cool it down by air cooling. The air volume is controlled to be 200m 3 , the air cooling time is 0.5h, and after cooling to below 250℃, a layered squirrel cage rotor is obtained;

[0054] The conductive bar is composed of the following components in mass percentage: Si 0.3%, Fe 0.2%, Cu 0.6% and the balance Al;

[0055] The end ring is composed of the following components in mass percentage: Sb 1.0wt%, Mg 0.5wt%, Si 0.5wt% and the balance Al.

[0056] Example 2

[0057] See also Figure 1 and 2 , a preparation process of a layered squirrel cage rotor, comprising the following steps:

[0058] (1) First, the raw material of the end ring is melted, and then the end ring mold is preheated at 580°C. Subsequently, the melted material is injected into the end ring mold, the die head is covered, and the die head pressure is controlled to 10N for gravity casting. Then, cold water is injected into the die head and the periphery of the end ring mold respectively, with a flow rate of 225m3 / h and a temperature of 15°C. After cooling, the mold is opened to obtain the end ring;

[0059] (2) Take an end ring and place it in the base, the upper end of which is connected to a plurality of protrusions, the protrusions are inserted into one end of the rotor core slot, and the other end of the rotor core slot is inserted into a plurality of conductor bars;

[0060] (3) A force of 50 N is applied to the end of the guide bar away from the protrusion, and then the connection between the protrusion and the guide bar is heated by the heating ring on the base. When the first heating temperature reaches 600 ° C, the heating is stopped, the heating rate is 15 ° C, and it is maintained for 30 seconds. Then the temperature is raised to 650 ° C again, and the heating rate is 20 ° C. The connection between the protrusion and the guide bar begins to melt and combine. At the same time, a force of 1 N is applied to the end of the guide bar away from the protrusion. When the displacement of the force module is 3% of the length of the guide bar, the heating is stopped, the force module is removed, and the temperature is cooled by air cooling. The air volume is controlled to be 190m 3 The air cooling time is 1 hour. After cooling to below 250℃, the conductor bars at the end away from the protrusion are all immersed in the rotor core slots.

[0061] (4) Take another end ring and place it in the base. Insert the protrusion into the other end of the rotor core slot. Heat the connection between the guide bar and the end ring through the heating ring on the base. Stop heating when the first heating temperature reaches 600°C. The heating rate is 15°C and maintained for 30s. Then heat it again to 650°C at a heating rate of 20°C. The connection between the guide bar and the end ring begins to melt and combine. When the outer end of the end ring is melted and connected with the outer end of the rotor core slot, stop heating, remove the force module, and cool it down by air cooling. The air volume is controlled to be 190m 3 , the air cooling time is 1h, and after cooling to below 250℃, a layered squirrel cage rotor is obtained;

[0062] The conductive bar is composed of the following components in mass percentage: Si 0.2%, Fe 0.1%, Cu 1% and the balance Al;

[0063] The end ring is composed of the following components in mass percentage: Sb 0.5wt%, Mg 0.7wt%, Si 0.3wt% and the balance Al.

[0064] Example 3

[0065] See also Figure 1 and 2 , a preparation process of a layered squirrel cage rotor, comprising the following steps:

[0066] (1) First, the raw material of the end ring is melted, and then the end ring mold is preheated at 620°C. Subsequently, the melted material is injected into the end ring mold, the die head is covered, and the die head pressure is controlled to 10N for gravity casting. Then, cold water is injected into the die head and the periphery of the end ring mold respectively, with a flow rate of 230m3 / h and a temperature of 10°C. After cooling, the mold is opened to obtain the end ring;

[0067] (2) Take an end ring and place it in the base, the upper end of which is connected to a plurality of protrusions, the protrusions are inserted into one end of the rotor core slot, and the other end of the rotor core slot is inserted into a plurality of conductor bars;

[0068] (3) A force of 200 N is applied to the end of the guide bar away from the protrusion, and then the connection between the protrusion and the guide bar is heated by the heating ring on the base. When the first heating temperature reaches 640°C, the heating is stopped, the heating rate is 20°C, and it is maintained for 5 seconds. Then the temperature is raised to 730°C again, and the heating rate is 30°C. The connection between the protrusion and the guide bar begins to melt and combine. At the same time, a force of 10 N is applied to the end of the guide bar away from the protrusion. When the displacement of the force module is 6% of the length of the guide bar, the heating is stopped, the force module is removed, and the temperature is cooled by air cooling. The air volume is controlled to be 210m 3 The air cooling time is 0.1h. After cooling to below 250℃, the conductor bars at the end away from the protrusion are all immersed in the rotor core slots.

[0069] (4) Take another end ring and place it in the base. Insert the protrusion into the other end of the rotor core slot. Heat the connection between the guide bar and the end ring through the heating ring on the base. Stop heating when the first heating temperature reaches 600℃. The heating rate is 20℃ and maintained for 5s. Then heat it to 730℃ again at a heating rate of 30℃. The connection between the guide bar and the end ring begins to melt and combine. When the outer end of the end ring is melted and connected with the outer end of the rotor core slot, stop heating, remove the force module, and cool it down by air cooling. The air volume is controlled to be 210m 3 , the air cooling time is 1h, and after cooling to below 250℃, a layered squirrel cage rotor is obtained;

[0070] The conductive bar is composed of the following components in mass percentage: Si 0.4%, Fe 0.3%, Cu 0.2% and the balance Al;

[0071] The end ring is composed of the following components in mass percentage: 1.5 wt% Sb, 0.3 wt% Mg, 0.7 wt% Si and the balance Al.

[0072] Example 4

[0073] A preparation process of a layered squirrel cage rotor comprises the following steps:

[0074] (1) First, the raw material of the annular end ring (the difference from the end ring is that one end of the end ring is not connected to a plurality of protrusions) is melted, and then the end ring mold (the difference from the end ring mold is that the bottom of the end ring is not provided with a plurality of cavities) is preheated at 600°C, and then the melted material is injected into the end ring mold, the die is covered, and the die pressure is controlled to be 15N for gravity casting, and then cold water is injected into the die and the periphery of the end ring mold respectively, with a flow rate of 227m3 / h and a temperature of 13°C. After cooling, the mold is opened to obtain an annular end ring;

[0075] (2) All the bars are inserted into the rotor core slots with the same length. Then the annular end ring is placed in the base. One end of the rotor core is heat-melted to the annular end ring at 700°C through a heating ring. Then the temperature is lowered by air cooling. The air volume is controlled to 200m 3 The air cooling time is 0.5h. After cooling to below 250℃, take another annular end ring and place it in the base. The other end of the rotor core is hot-melt welded to the annular end ring at 700℃ through the heating ring. Then the temperature is lowered by air cooling. The air volume is controlled to 200m 3 , the air cooling time is 0.5h, and after cooling to below 250℃, a layered squirrel cage rotor is obtained;

[0076] The conductive bar is composed of the following components in mass percentage: Si 0.3%, Fe 0.2%, Cu 0.6% and the balance Al;

[0077] The annular end ring is composed of the following components in mass percentage: Sb 1.0wt%, Mg 0.5wt%, Si 0.5wt% and the balance Al.

[0078] Test example

[0079] The performance test was performed on the layered squirrel cage rotors prepared in the above Examples 1-4. The conductivity test was performed according to the size of the conductivity sample in accordance with the requirements of GB / T12966-2008. The mechanical properties test sample size standard complies with ASTM E8 and tensile properties analysis was performed. The mechanical properties and conductivity test results are shown in Table 1:

[0080] Table 1

[0081] Test No. Tensile strength MPa Yield strength MPa Elongation % ConductivityMS / m Example 1 144 62 52.5 31.8 Example 2 109 72 46 30.5 Example 3 92 63 47 31 Example 4 70 56 44 30

[0082] It can be seen from Table 1 that the layered squirrel cage rotor prepared by the embodiment of the present application has excellent mechanical strength and electrical conductivity, with a tensile strength of not less than 92 MPa; a yield strength of not less than 62 MPa; an elongation of not less than 46%; and an electrical conductivity of not less than 30.5 MS / m; meeting the requirements for motor rotors for new energy vehicles.

[0083] The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

1. A process for preparing a layered squirrel cage rotor, characterized in that: The rotor comprises an end ring, a rotor core and a guide bar, one end of the end ring is connected to a plurality of protrusions, and the protrusions are inserted into the slots of the rotor core; The preparation process comprises the following steps: (1) Take an end ring and place it in the base, the upper end of which is connected to a plurality of protrusions, the protrusions are inserted into one end of the rotor core slot, and the other end of the rotor core slot is inserted with a plurality of conductor bars; (2) Apply a force of 50-200N to the end of the conductor bar away from the protrusion, and then heat the connection between the protrusion and the conductor bar through the heating ring on the base, and at the same time apply a force of 0-10N to the end of the conductor bar away from the protrusion until the connection between the protrusion and the conductor bar melts and combines, then stop heating, remove the force module, and cool to below 250°C until the conductor bar away from the protrusion is completely immersed in the rotor core slot; (3) Take another end ring and place it in the base, insert the protrusion into the other end of the rotor core slot, and heat the connection between the guide bar and the end ring through the heating ring on the base until the connection between the guide bar and the end ring is melted and combined, then stop heating, remove the force module, and cool to below 250°C to obtain a layered squirrel cage rotor; The specific steps of melting and bonding the connection between the protrusion and the guide bar in step (2) are as follows: when the first heating temperature reaches 600-640°C, stop heating and keep it for 5-30s, then heat it again to 650-730°C, the connection between the protrusion and the guide bar starts to melt and bond, and at the same time, apply a force of 0-10N to the end of the guide bar away from the protrusion. When the displacement of the force-applying module is 3-6% of the length of the guide bar, stop heating and remove the force-applying module. The specific steps of melting and bonding the connection between the conductor bar and the end ring in step (3) are as follows: when the first heating temperature reaches 600-640°C, the heating is stopped and maintained for 5-30s, and then the temperature is raised to 650-730°C again, and the connection between the conductor bar and the end ring begins to melt and bond. When the outer end of the end ring is melted and connected with the outer end of the rotor core slot, the heating is stopped and the force application module is removed; The heating rate for the first heating is 15-20°C, and the heating rate for the second heating is 20-30°C; The conductor bar is composed of the following components in mass percentage: Si 0.2-0.4%, Fe 0.1-0.3%, Cu 0.2-1% and the balance Al; The end ring is composed of the following components in percentage by mass: Sb 0.5-1.5wt%, Mg 0.3-0.7wt%, Si 0.3-0.7wt% and the balance Al.

2. The process for preparing a layered squirrel cage rotor according to claim 1, characterized in that: The method also includes the steps of preparing the end ring: first, the raw materials of the end ring are melted, and then the end ring mold is preheated at 580-620°C, and then the melted material is injected into the end ring mold for gravity casting, and then cold water is injected into the periphery of the end ring mold. After cooling, the mold is opened to obtain the end ring.

3. A processing device for a layered squirrel cage rotor for realizing the preparation process of the layered squirrel cage rotor according to claim 1 or 2, characterized in that: The processed rotor comprises an end ring, a rotor core and a guide bar, one end of the end ring is connected with a plurality of protrusions, and the protrusions are inserted into the grooves of the rotor core; The processing device comprises a base and a force-applying module, wherein the force-applying module is arranged above the base, and an end ring, a rotor core and a guide bar are arranged between the base and the force-applying module, wherein the guide bar is inserted into a rotor core slot and at least partially exposed outside the rotor core slot; An annular groove is provided in the base for accommodating the end ring, and a heating ring is mounted on the upper end of the base; The force-applying module is annular, and one end of the module is evenly provided with a plurality of convex ribs, and an elastic gasket is provided at one end of the convex rib away from the force-applying module.

4. The processing device for layered squirrel cage rotor according to claim 3, characterized in that: The end ring is ring-shaped, and one end of the end ring is connected with a plurality of protrusions, and the number of the protrusions, ribs, elastic gaskets, guide bars and rotor core slots is the same.

5. The processing device for layered squirrel cage rotor according to claim 4, characterized in that: It also includes an end ring mold and a die head, wherein the die head is arranged above the end ring mold; The machine head is annular, and a first water inlet and a first water outlet are provided on the outer side thereof; The end ring mold has an annular groove in it and a plurality of cavities at its bottom. The annular groove is connected with the cavities, and the cavities are matched with the protrusions. A second water inlet and a second water outlet are formed on the outer side of the end ring mold.

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