Method for manufacturing rotors of electric motors

Abstract

The present invention relates to a method for manufacturing a rotor (4) for an electric motor (2), the method comprising: - a step (E1) of manufacturing a subassembly including a central shaft (8) and a set of coils (7), the central shaft being provided with at least one ring (10A, 10B), the at least one ring being made of copper in particular, each coil being wound with wire, each coil being intended to allow current to pass through the coil in order to form a magnetic pole of the rotor, the at least one ring (10A, 10B) being intended to cooperate with at least one brush (11A, 11B) in order to supply power to these coils; then - a step (E2) of impregnating the coils with resin, particularly a thermosetting polymer resin; then - a step (E3) of exposing the subassembly to a heat source (15) in order to cure the resin; then - a step (E4) of laser cleaning the at least one ring.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a rotor for an electric motor. It also relates to a method for manufacturing an electric motor for vehicles, particularly motor vehicles. Background Technology

[0002] Motor vehicles referred to as "electric" or "hybrid" vehicles include electric motors that drive the vehicle's drive wheels. Various types of electric motors exist, including so-called "wound rotor" electric motors. Such electric motors include a rotor with multiple poles, each pole comprising a coil formed by winding electrical wire. The rotor is supplied with electrical energy via rings that cooperate with brushes, causing current to circulate in each coil. This circulation of current induces a magnetic field, which interacts with the stator of the electric motor to rotate the rotor. The advantage of wound rotor electric motors is that they do not require any permanent magnets. These electric motors are simpler to manufacture and, in particular, do not require rare earth elements that are difficult to supply.

[0003] The rotor is exposed to very high temperature variations, vibrations, and centrifugal forces. These stresses can cause the wires of coil 7 to move within the rotor, which in turn leads to motor malfunction. To ensure the cohesion of coil 7 within the rotor, it is known to impregnate the coil with resin, particularly thermosetting polymer resin. The impregnation process thus involves depositing liquid resin onto the coil of the rotor, filling the empty space around the wires, and then curing the resin by exposing the rotor to a heat source (such as a heating resistor).

[0004] The resin also allows for sealing of the rotor, which in turn allows for the channeling of cooling and lubricating fluids, particularly oil, within the rotor for cooling and lubrication. The resin also allows for improved electrical insulation of each coil.

[0005] However, it has been found that electric motors obtained in this way still exhibit residual friction and malfunctions. Therefore, the efficiency of these electric motors is not optimal. Invention Overview

[0006] The purpose of this invention is to provide a method for manufacturing a rotor and a method for manufacturing an electric motor, which overcome the aforementioned disadvantages and improve upon manufacturing methods known from the prior art.

[0007] More precisely, the first object of the present invention is to provide a method for manufacturing a rotor and a method for manufacturing an electric motor, which enable the obtaining of an electric motor with optimal efficiency. Summary of the Invention

[0008] This invention relates to a method for manufacturing a rotor for an electric motor, the method comprising:

[0009] - The steps of manufacturing a subassembly, the subassembly comprising: a central shaft having at least one ring, specifically made of copper; and a set of coils, each coil wound with wire, each coil designed to allow current to flow through it to form a magnetic pole of a rotor, the at least one ring being designed to cooperate with at least one brush to supply electrical energy to the coils, and then...

[0010] - The step of impregnating the coil with resin, especially thermosetting polymer resin, followed by

[0011] - The step of exposing the sub-component to a heat source to cure the resin, followed by

[0012] - The step of laser ablation of the at least one ring.

[0013] The laser stripping step can be performed using a device for generating a laser beam with a wavelength of approximately 532 nm.

[0014] The at least one ring may include a tubular shape centered on the axis of rotation of the rotor, and the laser stripping step may be performed by rotating the at least one ring around the axis of rotation.

[0015] The at least one ring may include a tubular shape centered on the axis of rotation of the rotor, and the laser stripping step may be performed by means of a device for generating a laser beam that extends along the axis of rotation over the entire height of the ring.

[0016] The laser ablation step may include a step of evaluating the oxidation state of the at least one ring, the evaluation step being performed after the step of exposing the rotor to a heat source, and the manufacturing method may include a step of parameterizing the laser ablation step according to the oxidation state of the at least one ring.

[0017] The step of assessing the oxidation state may include acquiring at least one image of the at least one ring using an optical sensor, followed by analyzing the color of the at least one ring.

[0018] The manufacturing method may include steps such as picking up debris and laser ablation.

[0019] The stripping step can be performed using a device for generating a laser beam, positioned at a distance between 20 cm and 80 cm (including the endpoints) from at least one ring.

[0020] The at least one ring may include at least two coaxial rings assembled side by side on the same central shaft of the rotor.

[0021] The present invention also relates to a method for manufacturing an electric motor for a motor vehicle, the method comprising:

[0022] - Implement the method for manufacturing the rotor as defined above, and then...

[0023] - Assemble the stator around the rotor, and

[0024] - At least one brush that cooperates with at least one ring of the rotor. Attached Figure Description

[0025] These objects, features, and advantages of the present invention will be set forth in detail in the following description of a particular embodiment, given by way of non-limiting example, with reference to the accompanying drawings, in which:

[0026] Figure 1 This is a schematic diagram of a motor vehicle that includes an electric motor.

[0027] Figure 2 yes Figure 1 A 3D diagram of an electric motor.

[0028] Figure 3 This is a block diagram of a method for manufacturing an electric motor according to an embodiment of the present invention.

[0029] Figure 4 yes Figure 1 A side view of a portion of an electric motor during the process of impregnating the motor coils with resin.

[0030] Figure 5 This is after the step of exposing the rotor to a heat source to allow the resin to cure. Figure 1 Microscopic photograph of the surface of the rotor ring of a motor.

[0031] Figure 6 Yes Figure 5 A schematic cross-sectional view of the laser ablation process of the ring.

[0032] Figure 7 Yes Figure 5 A side view of the laser ablation process of the ring. Detailed Implementation

[0033] Figure 1 A motor vehicle 1, including an electric traction and / or propulsion motor 2, is schematically shown. The electric motor 2 is capable of driving the vehicle's drive wheels 3. The electric motor 2 is a wound rotor motor. It includes a rotor 4 and a stator 5. The stator 5 is arranged around the rotor 4. A radial air gap e is defined between the rotor 4 and the stator 5.

[0034] refer to Figure 2The rotor 4 includes multiple poles 6. Each pole 6 includes a coil 7, formed by winding wire (e.g., copper wire). Current circulating through the wire induces a magnetic field. Therefore, each pole 6 can be referred to as a magnetic pole. The direction of current circulation can be defined such that the direction of the magnetic field is reversed between each adjacent pole. The rotor 4 can therefore include alternating north and south poles. According to the presented embodiment, the rotor 4 includes eight poles. As a variant, the number of poles can be equal to any other number.

[0035] The rotor 4 also includes a central shaft 8, which is designed to be connected to a transmission system for driving the drive wheel 3. For this purpose, the central shaft 8 is equipped with a spline 9.

[0036] The central shaft 8 is also equipped with two conductive rings 10A and 10B. The two rings 10A and 10B are preferably made of copper. The two rings 10A and 10B are designed to contact brushes 11A and 11B to supply electrical energy to the coil 7. The two rings 10A and 10B are thus electrically connected via brushes 11A and 11B to the vehicle's electrical power source 12, such as a battery.

[0037] Each of the two rings 10A comprises a tubular shape centered on the rotation axis X of the rotor. The two rings 10A and 10B are therefore coaxial. The two rings may have the same outer diameter. Furthermore, the two rings 10A and 10B are assembled side-by-side on a central shaft 8. According to a variant embodiment of the invention, the central shaft 8 may be equipped with a different number of conductive rings.

[0038] Coil 7 (particularly via the core) is mechanically fixed to the central shaft 8. The core may include a set of radial protrusions. Each coil is then formed by winding wire around the radial protrusions.

[0039] Rotor 4 is designed to rotate on its own about the axis of rotation X. The central shaft 12 extends parallel to the axis of rotation X of rotor 4 and is centered on the axis of rotation X. When vehicle 1 is running, the rotor's rotational speed can reach, for example, 15,000 revolutions per minute.

[0040] The rotor 4 also includes an electrically insulating resin that fills the empty spaces around the coil 7. The resin can be, in particular, a thermosetting polymer resin. As will be seen in more detail below, the resin can be applied by immersing the rotor 4 in a bath of liquid resin and by rotating the rotor about its axis of rotation. The resin can thus penetrate all the empty spaces of the rotor 4 until the rotor is submerged to its full height. The resin is then cured by exposing the rotor to a heat source.

[0041] refer to Figure 3 The block diagram is now described, and a method for manufacturing an electric motor 2 according to an embodiment of the present invention will be described.

[0042] In the first step E1, a subassembly is manufactured, which specifically includes a central shaft 8 provided with rings 10A and 10B and coils 7 fixed to the central shaft 8. For example, each coil 7 may be formed around a radial protrusion of the core of the rotor 4, and the central shaft 8 may then be inserted into a central opening in the core itself equipped with the coils. The rings 10A and 10B can then be assembled to the central shaft 8. The rings 10A and 10B may, for example, be press-fitted to a portion of the central shaft 8 provided for this purpose. Alternatively, the rings 10A and 10B may be assembled to the central shaft even before the central shaft 8 is assembled to the core of the rotor. The rings 10A and 10B can then be electrically connected to the coils 7.

[0043] exist Figure 4 In the second step E2, which is schematically shown, the coil 7 is impregnated with resin. For this purpose, the sub-assembly manufactured during the first step E1 is partially immersed in a bath 13 containing liquid resin 14. Then, the rotor 4 is rotated about its axis of rotation X so that the entire outer periphery of the rotor 4 is gradually submerged.

[0044] Next, also Figure 4 In the third step E3 shown, the rotor 4 is exposed to a heat source 15 to cure the resin. The heat source 15 may be, for example, a heating resistor, which may optionally be integrated into an oven in which the rotor 4 is positioned. The third step E3 may optionally be performed in parallel with the second step E2, or may begin at least after the second step E2 has ended. By exposing the sub-assemblies to the heat source, oxidation occurs on the outer surfaces of rings 10A and 10B. Rings 10A and 10B then contain an irregular oxide layer 16 on their outer surfaces.

[0045] Figure 5 A microscopic view of the oxide layer 16 formed on rings 10A and 10B at the end of the third step E3 is shown. Therefore, rings 10A and 10B have a degraded surface state, which may result in imperfect electrical contact between brushes 11A and 11B and rings 10A and 10B, and thus cause friction during rotor 4 rotation, leading to premature brush wear.

[0046] Next, the manufacturing process advantageously includes step E4, which involves laser stripping of rings 10A and 10B. This process is performed after rings 10A and 10B have been assembled onto the central shaft 8 of rotor 4.

[0047] like Figure 6As shown, this step is performed using a stripping device 17 equipped with a means 18 for generating a laser beam. The means 18 for generating the laser beam is connected to an electrical power source 19 and a control device 20, which is adapted to control the activation state of the means 18 for generating the laser beam. The control device 20 can be specifically configured to control the frequency of the laser beam, and / or the pulse duration of the laser beam, and / or the energy distribution of the laser beam, and / or the scanning speed of the laser beam. Additionally, the stripping device 17 includes a suction device 21 for removing debris generated during the stripping process.

[0048] Laser ablation offers several advantages over other known prior art ablation processes. In particular, this process removes very little material from the rings being processed. Therefore, providing a significant excess thickness to each ring is not useful, and the amount of debris to be removed is moderate. Laser ablation does not require direct mechanical contact with the rings, as they are supported by a central shaft 8. This avoids any unnecessary handling of each ring and prevents damage or contamination. Furthermore, the ablation process is rapid. Specifically, the ablation process for each ring requires at most approximately twenty seconds. The ablation process does not require extensive maintenance of the device 18 used to generate the laser beam. The ablation process is therefore easy to implement and exhibits very good repeatability over time.

[0049] The same stripping device 17 can be used to sequentially perform the stripping steps on each ring 10A, 10B. Alternatively, for each ring 10A, 10B, the stripping steps can be performed in parallel using a separate stripping device 17 for each ring. It should be noted that... Figure 6 and Figure 7 The steps for stripping ring 10A are shown, and the stripping of ring 10B is performed in the same manner.

[0050] The device 18 for generating the laser beam can be positioned at a distance D1 between 20 cm and 80 cm (including the endpoint values) from the ring to be processed, for example, approximately 40 cm. The stripping device 17 thus occupies a relatively small volume. Therefore, this device is quite easily integrated into the rotor manufacturing workshop.

[0051] The device 18 for generating the laser beam is advantageously configured to emit so-called "green" laser light, that is, laser light with a wavelength of approximately 532 nm. It has been observed that this wavelength allows the rings 10A and 10B to be processed to reflect less of the laser beam. This allows for better management of the absorption of the laser beam by the oxide layer. Alternatively, laser light with a wavelength of 1064 nm can also be envisioned.

[0052] Figure 7A side view of ring 10A during the stripping process is shown. The device 18 for generating the laser beam is designed to produce a laser beam FL incident along the rotation axis X over the entire height of the ring. In other words, the resulting laser spot extends along the rotation axis X over the entire height of ring 10A. Therefore, the outer surface of ring 10A is completely processed by completing one full rotation around the rotation axis X. The processed ring can optionally be rotated several times around the rotation axis X to complete the stripping. One advantage of rotating the ring 10A during laser stripping is that the device 18 for generating the laser beam can remain stationary.

[0053] exist Figure 7 In this context, region Z1 corresponds to the region of ring 10A that has not been peeled off and is therefore covered with oxide layer 16. Region Z2 corresponds to the region of ring that has been peeled off. Region Z2 is free of oxide layer and has excellent surface conditions, thereby minimizing friction between brush 11A and ring 10A.

[0054] Advantageously, the laser stripping step includes a first sub-step E41 for evaluating the oxidation state of ring 10A. Evaluation sub-step E41 is performed immediately after the third step E3. This sub-step E41 may include a sub-step E411 of acquiring at least one image of ring 10A by means of optical sensor 22, followed by a sub-step E412 of analyzing the color of ring 10A. Sub-step E41 can advantageously be performed automatically by a control device 20 connected to optical sensor 22.

[0055] Next, the laser stripping step includes a sub-step E42 that parameterizes the laser stripping step based on the oxidation state of the ring obtained at the end of sub-step E41. This parameterization step specifically includes adjusting the operating parameters (laser beam frequency, pulse duration, energy distribution, etc.) suitable for the device 18 that generates the laser beam. The laser beam is then collimated and irradiated onto the oxide layer 16, separating the oxide layer from the ring 10A.

[0056] Advantageously, the manufacturing process further includes a step E5 of removing debris generated from the oxide layer 16. Step E5 is performed in parallel with the laser stripping step E4. Therefore, the small amount of debris generated by the laser stripping is removed. This prevents the debris from contaminating the rotor 4.

[0057] At the end of steps E4 and E5, rotor 4 is obtained, ready to be assembled into the other components of electric motor 2. To continue manufacturing electric motor 2, stator 5 is assembled around rotor 4 during the sixth step E6, and brushes 11A and 11B are assembled such that they establish electrical contact with rings 10A and 10B to transmit the current delivered by 12 to the rotor coils 7. Steps E6 and E7 can be reversed.

[0058] Finally, an electric motor 2 is obtained, with its rotor 4 impregnated with cured resin. The coils 7 of the rotor 4 are thus well held and well electrically insulated. Furthermore, rings 10A and 10B possess excellent surface properties obtained by means of the laser stripping step E4. Brushes 11A and 11B can slide in contact with rings 10A and 10B without generating significant friction. Therefore, the efficiency of the electric motor 2 is optimal.

Claims

1. A method for manufacturing a rotor (4) for an electric motor (2), the method comprising: - Step (E1) of manufacturing a subassembly, the subassembly comprising: a central shaft (8) having at least one ring (10A, 10B) specifically made of copper; and a set of coils (7), each coil being wound with wire, each coil being designed to allow current to flow through it to form the magnetic poles of the rotor, the at least one ring (10A, 10B) being designed to cooperate with at least one brush (11A, 11B) to supply electrical energy to the coils, and then... - The step of impregnating the coil with resin, especially thermosetting polymer resin (E2), followed by - The step of exposing the sub-component to a heat source (15) to allow the resin to cure (E3), followed by - The step of laser stripping the at least one ring (E4).

2. The manufacturing method as described in the preceding claim, characterized in that, The laser stripping step (E4) is performed by a device (18) for generating a laser beam (FL) with a wavelength of about 532 nm.

3. The manufacturing method as described in any one of the preceding claims, characterized in that, The at least one ring (10A, 10B) comprises a tubular shape centered on the rotation axis (X) of the rotor (4), and the laser stripping step (E4) is performed by rotating the at least one ring around the rotation axis.

4. The manufacturing method as described in any one of the preceding claims, characterized in that, The at least one ring (10A, 10B) comprises a tubular shape centered on the rotation axis (X) of the rotor (4), and the laser stripping step (E4) is performed by means of a device (18) for generating a laser beam (FL) that extends along the rotation axis over the entire height of the ring.

5. The manufacturing method as described in any one of the preceding claims, characterized in that, The laser stripping step (E4) includes a step (E41) to evaluate the oxidation state of the at least one ring, which is performed after the step (E3) to expose the rotor to a heat source, and the laser stripping step includes a step (E42) to parameterize the laser stripping step according to the oxidation state of the at least one ring.

6. The manufacturing method as described in the preceding claim, characterized in that, The step of assessing the oxidation state (E41) includes acquiring at least one image of the at least one ring by means of an optical sensor (22) (E411), followed by analyzing the color of the at least one ring (10A, 10B) (E412).

7. The manufacturing method as described in any one of the preceding claims, characterized in that, The method includes a step (E5) that is parallel to the laser ablation step (E4).

8. The manufacturing method as described in any one of the preceding claims, characterized in that, The stripping step (E4) is performed by a device (18) for generating a laser beam, which is positioned at a distance between 20 cm and 80 cm from the at least one ring, including the endpoint value.

9. The manufacturing method as described in any one of the preceding claims, characterized in that, The at least one ring (10A, 10B) comprises at least two coaxial rings assembled side by side on the same central shaft (8) of the rotor (4).

10. A method for manufacturing an electric motor (2) for a motor vehicle (1), characterized in that... The method includes: - Implement the method for manufacturing the rotor (4) as described in any one of the preceding claims, and then... - Assemble the stator (5) around the rotor (4), and - Assemble at least one brush (11A, 11B) that cooperates with at least one ring (10A, 10B) of the rotor.

Images