Guide device for windings on an electrical machine rotor

Abstract

A guide device (4) for winding a conductive wire (3) around a plurality of magnetic poles of an electric machine rotor (1), the magnetic poles being arranged around a shaft (2) of the rotor (1), the guide device (4) including a guide head (5) adapted to be mounted on the shaft (2), the guide head (5) extending axially between an outer surface (6) and an inner surface (7), the inner surface (7) of the guide head (5) facing the magnetic poles, the guide head (5) including a central base (8) from which radial arms (9) extend. The device (4) includes a ring (15) mounted on the shaft (2), the ring (15) extending axially between an outer surface (16) and an inner surface (17), the inner surface (17) of the ring (15) facing the magnetic pole, the ring (15) and the guide head (5) being positioned at the same end of the magnetic pole, the ring (15) including a body (18) having fingers (19) attached thereto, the fingers (19) projecting axially from the side of the ring (15) corresponding to the inner surface (17).

Description

[Technical Field]

[0001] The present invention relates to the field of electric machines including wound rotors, such as synchronous motors, and more particularly to a guide device for windings on the rotor, which is used, inter alia, in electric and hybrid automotive vehicles. [Background technology]

[0002] There are a wide variety of electric machines with wound rotors, including synchronous motors. The rotors of these machines typically include a shaft designed to rotate about its axis. A stack of laminations is disposed on the rotor shaft coaxially with the axis, the stack of laminations forming a plurality of radially projecting magnetic poles, with a conductive wire winding wound around each pole. A device for guiding the conductive wire is disposed axially at each end of the stack of laminations. Each guide device has a central orifice through which the shaft passes.

[0003] An example of a synchronous electric machine with a wound rotor is given in patent FR3084220B1. The machine described in that document can be a motor. One application of the motor is to cooperate with the drive wheels of a vehicle, such as an automobile or motorcycle. In this application, the motor is subjected to various stresses, particularly mechanical stresses that can be high. In fact, the rotor rotates at very high speeds, up to 12,000 rpm or even higher. Therefore, the rotor must withstand the stresses associated with these speeds. To this end, document FR3084220B1 proposes a rotor adapted to withstand high centrifugal forces, in particular by simplifying its structure, facilitating the assembly of its components, and allowing the rotor to be balanced. This approach applies to the entire rotor, including the winding wires.

[0004] For optimal functionality and a sufficient service life, the wires used to construct the windings must be protected during installation and must also preserve their properties over time. This means, in particular, that the insulating layer surrounding the conductive core of the wire must remain intact.

[0005] The procedures for constructing the windings, as well as the geometry and materials of the components used, are intended to protect the wires during installation. They must not be damaged by premature breakage or deterioration of the insulation layer, and they must not come into electrical contact with components with which they should not be in electrical contact. Furthermore, the geometry of the rotor components, particularly at the height of the poles and guide devices, is designed for stable retention of the wires. This prevents untimely rubbing or movement of the wires, thus ensuring their structure and properties.

[0006] Nevertheless, malfunctions can be observed: despite all the precautions taken, short circuits occur or the service life is shortened.

[0007] Indeed, from an electrical perspective, the rotor windings are connected to the power supply system by means of connection elements. A direct current is passed through the windings, the intensity of which can reach high values. The rotor acts as a magnet, the strength of which can be adjusted. It is important that the connection elements provide a good connection between the windings and the power supply system. For this purpose, the connection elements receive two strands of the winding wire and allow the passage of current between the power supply system and the windings via friction means such as brushes, shoes or any equivalent thereof.

[0008] The malfunctions mentioned above are caused by the deterioration of one or both strands of wire between the winding and the connecting element. Premature breaks can be observed in one or both strands of wire. Damage caused by short circuits due to the deterioration of the insulation layer of the wire strands has also been observed. As a result, the service life of the rotor and therefore the motor is reduced. Alternatively, unscheduled maintenance must be performed, which means time wasted and additional costs. Disassembling the motor, rewinding it, and reassembling it is a time-consuming, laborious, and costly process. Summary of the Invention

[0009] The present invention aims to alleviate the above-mentioned drawbacks by providing a motor whose wound rotor is more reliable and has a longer service life. In particular, it is important to ensure the structure of the wires at the level of their core and at the level of their insulation layer. The present invention aims to reduce maintenance costs and motor downtime.

[0010] To this end, the present invention proposes a guide device for winding a conductive wire onto a plurality of magnetic poles of an electric machine rotor, the magnetic poles being arranged around a shaft of the rotor, the guide device comprising a guide head adapted to be mounted on the shaft, the guide head extending axially between an outer surface and an inner surface, the inner surface of the guide head facing the magnetic poles, the guide head comprising a central base from which radial arms extend, the guide device comprising a ring mounted on the shaft, the ring extending axially between the outer surface and the inner surface, the inner surface of the ring facing the magnetic poles, the ring and the guide head being positioned at the same end of the magnetic poles, the ring comprising a body with fingers attached to it, the fingers protruding in the axial direction of the ring from the side corresponding to the inner surface.

[0011] This structure allows the relative positions of the guide head and ring to be changed between steps preceding and following the winding process. Before the winding process, the ring is positioned on the shaft to leave a space between the body and the pole, and the fingers extend along this space. The winding process is then performed while maintaining the space between the body of the ring and the pole. Finally, after the winding operation, the ring is moved toward the pole, reducing or eliminating the space. The space created during the winding process allows the needle to pass through to place the wire around the pole, and the fingers hold the wire away from this space. The fingers provide a radial obstacle to the wire in the sense that they prevent it from contacting the shaft or getting stuck between the pole and other components, such as bearings, balance disks, or connecting elements for connecting to a power system. By preventing the wire from getting stuck during the winding process, the guide device secures the structure. The wire is isolated from corrosion or manipulation that could reduce the mechanical strength of the core or degrade the insulation layer. For example, the wires are protected from tools that may be used to free them after jamming. This results in greater reliability and a longer service life for the wires. As a result, the rotor and the entire motor are more reliable and durable. Maintenance is simplified and the costs associated with use are lower.

[0012] In one embodiment, the ring body includes a radial boss at the height of the finger. The boss moves the wire strands radially away from the ring body. This reduces or even completely prevents friction between the wire and the ring body. While not limiting the invention, the boss also prevents the wire from moving from the inner surface of the guide head toward the outer surface, i.e., away from the magnetic pole. It will become clearer below that, in combination with other bosses, the wire is slightly tensioned in the mechanical sense of the word. As a result, the position of the wire strands outside the magnetic pole is more stable.

[0013] The body of the ring includes radial bosses at a certain distance from the fingers. The bosses prevent the movement of the wires towards the poles. Therefore, the bosses prevent the wires from contacting the poles. The bosses also serve to slightly tension the wires in the mechanical sense of the word for greater stability.

[0014] The ring body, the fingers, the radial bosses at the level of the fingers and the radial bosses at a distance from the fingers form a monoblock part. Without limiting the invention, this part is made from a synthetic material such as polyamide, polyethylene or any equivalent thereof. The part is obtained by injection molding, which is relatively simple, or by any other suitable technique. The synthetic material from which the part is made is an electrical insulator, which has the advantage of positioning the wire strands emerging from the winding away from conductive surfaces. The risk of short circuits is significantly reduced or even completely eliminated.

[0015] At the height of the base, the outer surface of the guide head includes an axial boss. The axial boss deflects the wire strands emerging from the winding away from the magnetic poles. The axial boss prevents the movement of the wire strands towards the magnetic poles. This reduces, or even completely eliminates, friction between the wire and the base or between the wire and the magnetic poles. It will become more apparent below that the axial boss of the base is responsible for applying a slight mechanical tension to the wire strands and that the axial boss of the base actually contributes to improved stability of the position of the wire strands.

[0016] The base and the axial boss form a monoblock part. Again, without limiting the invention, this part is made from a synthetic material, for example, polyamide, polyethylene, or any equivalent thereof. The part is obtained by injection molding or any suitable technique. The synthetic material of which the part is made is an electrical insulator, which has the advantage of positioning the wire strands emerging from the winding away from conductive surfaces. The risk of short circuits is greatly reduced or even completely eliminated.

[0017] The guide head rests against the pole piece, and the ring rests against a shoulder on the shaft, which is formed at the height of the pole piece's edge. The guide head and ring are therefore located in the same zone of the rotor, i.e., towards the same pole piece's edge. The pressure of the two elements, the guide head and the ring, ensures a constant position relative to each other and therefore a constant length of the path travelled by the wire strands emerging from the winding.

[0018] In fact, when entering or leaving the winding, the conductive wire follows a path around the ring, along which it is first urged away from the magnetic pole by the axial boss at the base, then towards the pole and away from the body by the radial boss at the height of the ring's fingers, and then again away from the pole by the radial boss at a distance from the ring's fingers. The three bosses mentioned above run along the ring's contour in the order of their numbers. The bosses act on the wire alternately: the boss at the base urges it away from the pole, then the boss at the height of the ring's fingers urges it towards the pole, and finally the boss at a distance from the fingers urges it away from the pole again. This alternating contact maintains the shape of the wire strands, possibly with a slight mechanical tension. Small random movements of the wire, especially those linked to fluctuations in the rotor's rotational speed, are thus prevented. The effect of centrifugal forces on the wire strands is attenuated or even completely eliminated. As a result, the risk of wire wear and of degradation of the insulating layer is particularly low.

[0019] The invention also relates to an electrical machine, in particular a motor, including a wound rotor including a guide device as described above.

[0020] The present invention further relates to a method for winding a conductive wire around a plurality of magnetic poles of an electric machine rotor, the magnetic poles being arranged around a shaft of the rotor, the method comprising the steps of: arranging a guide head on the shaft on the same side of the magnetic pole as where a connection element for connection to a power supply system is arranged; and arranging another guide head on the shaft on an opposite side of the magnetic pole. The method comprises the steps of: arranging a ring on the shaft on the same side of the magnetic pole as where the connection element is arranged, the ring including a body with fingers attached thereto, the fingers protruding in an axial direction of the ring toward the magnetic pole, the ring being arranged to leave a space between the body and the magnetic pole and the fingers extending along this space; winding the magnetic pole while maintaining a space between the body of the ring and the magnetic pole; and moving the ring toward the magnetic pole after the winding operation, which movement reduces or eliminates the space.

[0021] The ring can be mounted on the shaft either as a sliding fit or as a slight interference fit. In all cases, fingers secure the wire.

[0022] Other objects, features and advantages of the present invention will become apparent on reading the following description, given by way of non-limiting example only, and on referring to the accompanying drawings, in which: [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a perspective view of a guide device for winding a rotor according to an embodiment of the present invention; [Figure 2] FIG. 2 is an enlarged view of a portion of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0024] In Figure 1, part of an electric machine, in this case a synchronous motor, is shown. More precisely, only part of the motor's wound rotor 1 is visible, not its stator. The stator operates with a three-phase alternating current, for example generated by a variable speed drive. The magnetic field of the stator can therefore vary, inter alia, in power, speed and direction of rotation.

[0025] Rotor 1 includes shaft 2 designed to rotate in the stator about its axis L2. A stack of laminations, not shown, is disposed on shaft 2 of rotor 1 coaxially with axis L2, the stack of laminations forming a plurality of radially projecting magnetic poles. Windings, not shown, are made using conductive wire 3 wound around each pole. The only portions of wire 3 shown in FIG. 1 are strands connecting the windings to connection elements for connection to an electrical power supply system, not shown.

[0026] It should be noted that only one connecting strand of the wire 3 is visible in Figure 1. However, it should be noted that two strands of the wire 3 are coupled to the connecting element. In practice, these two strands are, for example, arranged symmetrically with respect to the shaft 2. This makes it easier to balance the rotor 1.

[0027] The rotor 1 is provided with two guide devices for winding the wire 3 around the magnetic poles, of which only the one with the reference number 4 is shown. The visible guide device 4, which will be described in detail, is arranged on the shaft 2 on the same side of the magnetic poles as the connection elements to the power supply system are arranged. The other guide device, the non-visible guide device, is arranged on the shaft 2 on the opposite side of the magnetic poles. Each of the two guide devices is therefore arranged at one end of a magnetic pole.

[0028] The guide device 4 includes a guide head 5 adapted to be mounted on the shaft 2. The guide head 5 extends axially between an outer surface 6 and an inner surface 7, with the inner surface 7 of the guide head 5 facing the magnetic poles. The guide head 5 includes a central base 8 from which radial arms 9 extend. Although not limiting to the invention, the guide head 5 includes eight arms 9 for the eight magnetic poles. As a corollary of this, the guide device (not visible) also includes a guide head with a central base and eight arms. This corresponds to the rotor 1 including a relatively large number of eight magnetic poles to obtain a high-strength magnetic effect. This enables the motor to provide high torque, especially at low speeds.

[0029] According to the invention, the guide device 4 comprises a ring 15 mounted on the shaft 2, the ring 15 extending axially between an outer surface 16 and an inner surface 17, the inner surface 17 of the ring 15 facing the magnetic pole. The ring 15 and the guide head 5 are positioned at the same end of the magnetic pole. The ring 15 comprises a body 18 with two fingers attached to it, only the one of which, designated 19, is visible, protruding in the axial direction of the ring from the side corresponding to the inner surface 17.

[0030] Indeed, one particular feature of the present invention is that the guide device 4 comprises several elements, namely a guide head 5 and a ring 15, so that the present method of winding the rotor is special, in particular for arranging the wire 3 around the poles and for holding the wire strands as they enter and exit the windings.

[0031] As is conventional, the method comprises the step of placing a recognizable guide head 5 in a predetermined position on the shaft 2 on the same side of the magnetic pole where the connection element for connecting to the power supply system is located. The method also comprises the step of placing another guide head in a predetermined position on the shaft 2 on the opposite side of the magnetic pole. In practice, each guide head 5 abuts a magnetic pole.

[0032] The method includes a step of placing a ring 15 in a predetermined position on the shaft 2 on the same side of the magnetic poles as the connecting elements are located. The guide head 5 and the ring 15 are therefore located in the same area of ​​the rotor 1. In placing the ring 15 in a predetermined position, the ring 15 leaves a space between its body 18 and the magnetic poles, and the fingers 19 extend along this space. This situation is not the case in FIG. 1.

[0033] The next step of the method is to wind the poles while leaving a space between the body 18 of the ring 15 and the poles. The winding process is achieved by winding the wire 3 around each pole and the radial arm 9 of the guide head 5 using a needle. The space mentioned above is wide enough so that the needle can advance to carry out the winding process. This space may be, for example, between 1 and 15 mm in width, with tests showing that values ​​between 5 and 10 mm produce good results.

[0034] The fingers 19 of the ring 15 extend over the entire space, so that each finger 19 holds a strand of the wire 3 away from the shaft 2 of the rotor 1. More precisely, the fingers 19 hold the strands of the wire 3 at a distance from the shaft 2 that exceeds the thickness of the body 18 of the ring 15. This function is important for the next step of the method, which is to move the ring 15 towards the pole after the winding operation, which reduces or eliminates the space. This movement is possible because the strands of the wire 3 are kept away from the track of the ring 15. Without limiting the invention, the ring 15 abuts a shoulder 20 of the shaft 2, and each of the fingers 19 fits into a predetermined position in a longitudinal groove 21 of the shaft 2. Each groove 21 is a cavity that has several functions: to receive a finger 19 after placement of the ring 15 on the shoulder 20, and to lock the ring 15 against rotation relative to the shaft 2. Indeed, it is important that the fingers 19 are at a controlled distance from the point of entry or exit of the wire 3 into or from the winding.

[0035] The advantage of using a ring with fingers is the security of the stranding of the wires entering and exiting the windings during rotor manufacture. The strands remain away from areas that may be mechanically aggressive, especially if those areas have sharp edges or burrs. This prevents premature breakage of the core and deterioration of the insulation of the wires 3.

[0036] Additionally, as explained below, the guide device 4 is constructed to secure the stranding of the wires after manufacture, i.e., during use of the motor, since the motor may rotate at very high speeds and the stranding is consequently subjected to stresses, such as those resulting from centrifugal forces.

[0037] 1 and 2, at the level of the base 8, the outer surface 6 of the guide head 5 includes an axial boss 25, which is visible, and another axial boss, which is not visible. Each axial boss 25 deflects the wire strands emerging from the windings away from the magnetic poles. Each axial boss 25 prevents the movement of the wire strands towards the magnetic poles and keeps the wire strands away from the shoulder 20 of the shaft 2.

[0038] 1, it can be seen that the body 18 of the ring includes a radial boss 26 at the level of each finger 19. Each boss 26 moves the wire strands radially away from the body 18 of the ring 15. This reduces, or even completely eliminates, friction between the wire 3 and the body 18 of the ring 15. Each boss 26 also prevents movement of the wire 3 from the inner surface 7 towards the outer surface 6 of the guide head 5, i.e., away from the magnetic poles.

[0039] It can also be seen that the body 18 of the ring 15 includes a radial boss 27 at a distance from each finger 19. Each of the bosses 27 prevents movement of the wire 3 towards the magnetic pole. Each radial boss 27 prevents contact of the wire 3 with the magnetic pole.

[0040] If we trace the path of the wire 3 strands as they leave the winding, we can see that they are first moved away from the pole by the axial boss 25 of the central base 8, then prevented from moving away by the radial boss 26 at the level of the fingers 19, then prevented from moving towards the pole by the radial boss 27 located at a certain distance from the fingers 19, and finally attached to the electrical contacts 28 of the ring 15. In fact, the ring 15 abuts against the shoulder 20 after the wire strands have been attached to the contacts 28. This movement of the ring places each wire strand under slight mechanical tension. As a result, the position of the wire strands is very stable even under the action of centrifugal forces. As a result, the risk of deterioration of the wire strands is reduced or even eliminated.

[0041] The present invention is not limited to the described embodiments, but encompasses all equivalents that fall within the scope of the following claims.

[0042] In particular, the components of the guide device 4 can have a variety of different shapes. When referring to a finger or a boss, this means at least one finger or at least one boss.

Claims

1. A guide device (4) for winding conductive wires (3) around a plurality of magnetic poles of an electric machine rotor (1), the magnetic poles being arranged around a shaft (2) of the rotor (1), the guide device (4) comprising a guide head (5) adapted to be mounted on the shaft (2), the guide head (5) extending axially between an outer surface (6) and an inner surface (7), the inner surface (7) of the guide head (5) facing the magnetic poles, the guide head (5) comprising a central base (8) from which radial arms (9) extend ... a guide device (4) comprising a ring (15) mounted on the shaft (2), the ring (15) extending in the axial direction between an outer surface (16) and an inner surface (17), the inner surface (17) of the ring (15) facing the magnetic pole, the ring (15) and the guide head (5) being positioned at the same end of the magnetic pole, the ring (15) comprising a body (18) to which fingers (19) are attached, the fingers (19) protruding in the axial direction of the ring (15) from the side corresponding to the inner surface (17).

2. 2. The device (4) according to claim 1, wherein the body (18) of the ring (15) comprises a radial boss (26) at the level of the fingers (19).

3. 3. A device (4) according to claim 1 or 2, wherein the body (18) of the ring (15) comprises a radial boss (27) at a distance from the fingers (19).

4. 4. The device (4) according to claim 3, wherein the body (18) of the ring (15), the fingers (19), the radial bosses (26) at the level of the fingers (19) and the radial bosses (27) at a distance from the fingers (19) form a monoblock part.

5. 5. The device (4) according to any one of claims 1 to 4, wherein at the level of the base (8), the outer face (6) of the guide head (5) comprises an axial boss (25).

6. 6. The device (4) according to claim 5, wherein the base (8) and the axial boss (25) form a monoblock part.

7. 7. A device (4) according to any one of claims 1 to 6, wherein the guide head (5) abuts against the magnetic pole and the ring (15) abuts against a shoulder (20) on the shaft (2).

8. 8. The device (4) according to claim 7, wherein when entering or leaving a winding, the conductive wire (3) follows a path around the ring (15), along which path it is first urged away from the magnetic pole by an axial boss (25) of the base (8), then urged towards the magnetic pole and away from the body (18) by a radial boss (26) at the level of the fingers (19) of the ring (15), and then urged once again away from the magnetic pole by the radial boss (27) of the ring (15) at a distance from the fingers (19).

9. An electric machine comprising a guide device (4) according to any one of claims 1 to 8.

10. A method for winding a conductive wire (3) around a plurality of magnetic poles of an electric machine rotor (1), the magnetic poles being arranged around a shaft (2) of the rotor (1), the method comprising the steps of: arranging a guide head (5) on the shaft (2) on the same side of the magnetic poles as where a connecting element for connecting to a power supply system is arranged; arranging another guide head on the shaft (2) on the opposite side of the magnetic poles as where the connecting element is arranged; and arranging a ring (15) on the shaft (2) on the same side of the magnetic poles as where the connecting element is arranged, the ring (15) having fingers (19) attached thereto. a ring (15) having a body (18) attached thereto, the fingers (19) projecting in the axial direction of the ring (15) towards the magnetic pole, the ring (15) being arranged so as to leave a space between the body (18) and the magnetic pole and so that the fingers (19) extend along this space, the method comprising the step of winding a wire around the magnetic pole while maintaining the space between the body (18) of the ring (15) and the magnetic pole, the method comprising the step of moving the ring (15) towards the magnetic pole after the winding operation, the movement reducing or eliminating the space.

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