Guiding method for winding an electric machine rotor

Abstract

The invention relates to a guide device (4) for winding a plurality of poles of an electric machine rotor (1) with an electrically conductive wire (3), the poles being distributed around a shaft (2) of the rotor (1), the guide device (4) comprising a guide head (5) capable of being mounted on the shaft (2), the guide head (5) extending axially between an outer face (6) and an inner face (7), the inner face (7) of the guide head (4) facing the poles, the guide head (4) comprising a central base (8) from which radial arms (9) extend. The device (4) comprises a ring (15) mounted on the shaft (2), the ring (15) extending axially between an outer face (16) and an inner face (17), the inner face (17) of the ring (15) facing the poles, the ring (15) and the guide head (5) being positioned at the same end of the poles, the ring (15) comprising a body (18) to which a finger (19) is attached, the finger (19) projecting from the side of the inner face (17) in an axial direction of the ring (15).

Description

[0001] DESCRIPTION

[0002] TITLE: Guiding device for winding an electric machine rotor.

[0003] Technical field

[0004] The invention relates to the field of electrical machines comprising a wound rotor, such as synchronous motors, and more particularly relates to a guide device for winding the rotor. The invention is used, among other things, in electric or hybrid motor vehicles.

[0005] Previous techniques

[0006] There are different types of wound rotor electrical machines, including synchronous motors. Generally, in these machines the rotor comprises a shaft intended to be mounted rotatably about its axis. A stack of laminations is placed on the rotor shaft coaxially with the axis, the stack of laminations forming a plurality of radially protruding poles, a winding of electrically conductive wire being provided to be wound around each pole. A device for guiding the electrically conductive wire is arranged axially at each end of the stack of laminations. Each guide device has a central hole for the shaft to pass through.

[0007] An example of a wound rotor synchronous electrical machine is given by the invention patent FR 3 084 220 B l. The machine according to this document can be a motor. One use of this motor is cooperation with the drive wheels of a vehicle, such as an automobile, a motorcycle, or other. For this application the motor is subject to various constraints, particularly mechanical, which can be significant. Indeed, the rotor is required to rotate at very high speeds, up to 12000 rpm, or even more. The rotor must therefore withstand the constraints linked to these speeds. To do this, the document FR 3 084 220 B l proposes a rotor adapted to high centrifugal forces, in particular by simplifying its structure, facilitating the assembly of its components, and allowing its balancing. This approach applies to the rotor as a whole, including the wire of the windings.

[0008] For optimal operation and a sufficient lifespan, the electrical wire used to make the winding must, on the one hand, be preserved during its installation and, on the other hand, retain its properties over time. This means in particular that the insulating layer surrounding the conductive core of the wire must remain intact.

[0009] The procedures used for making the windings, as well as the shapes and materials of the components used, aim to preserve the wire during its installation. The wire must not show any damage such as the beginning of a break or an alteration of the insulating layer, and it must not come into electrical contact with components that should not be. In addition, the geometry of the rotor components is designed to hold the wire in place, particularly at the poles and guide devices. This prevents unwanted movement or friction of the wire and, consequently, its structure and properties are preserved.

[0010] However, malfunctions have occasionally been observed. Despite all precautions taken, short circuits have occurred or service lives have been shortened.

[0011] In fact, from an electrical point of view, the rotor winding is connected to a power supply system by a connecting element. The winding carries a direct current whose intensity can reach high values. The rotor acts as a magnet whose strength can be adjusted. It is important that the connecting element ensures a good connection between the winding and the power supply system. To do this, the connecting element receives two strands of the winding wire and allows the passage of current between the power supply system and the winding, by friction means such as brushes, pads, or any equivalent.

[0012] The malfunctions mentioned above were caused by damage to one or both wire strands between the winding and the connecting element. Sometimes, the beginnings of breakage were observed in one or both wire strands. Damage caused by short circuits resulting from the deterioration of the insulating layer of the wire strands was also observed. As a result, the service life of the rotor, and therefore that of the motor, was reduced. Or, unscheduled maintenance had to be carried out, which is synonymous with additional costs and wasted time. Dismantling, rewinding and reassembling a motor is a long, tedious and expensive operation.

[0013] Statement of the invention

[0014] The invention seeks to overcome the aforementioned drawbacks, with a motor whose wound rotor has better reliability and a longer service life. This involves in particular preserving the structure of the wires, both at the level of their core and at the level of their insulating layer. The invention seeks to reduce maintenance costs as well as the time when the motor is not in use.

[0015] To do this, the invention proposes a guide device for winding with an electrically conductive wire a plurality of poles of an electric machine rotor, the poles being distributed around a shaft of the rotor, the guide device comprising a guide head capable of being mounted on the shaft, the guide head extending axially between an external face and an internal face, the internal face of the guide head being turned towards the poles, the guide head comprising a central base from which radial branches extend.The guide device comprises a ring mounted on the shaft, the ring extending axially between an external face and an internal face, the internal face of the ring being turned towards the poles, the ring and the guide head being positioned at the same end of the poles, the ring comprising a body to which a finger is secured, the finger projecting from the side of the internal face in an axial direction of the ring.

[0016] This structure allows the relative position of the guide head and the ring to be changed between a step preceding winding and a step following it. Before winding, the ring is placed on the shaft so as to leave a space between the body and the poles, and so that the finger extends along this space. Then winding is carried out while the space between the body of the ring and the poles is maintained. Finally, after the winding operation, the ring is brought closer to the poles, the space being reduced or eliminated. The space maintained during winding allows the passage of needles for placing the wire around the poles, and the finger keeps the wire away from this space.The finger is a radial obstacle for the wire, in the sense that it prevents the latter from coming into contact with the shaft, or from later being stuck between the poles and other components such as a bearing, a balancing disc, a connecting element to a power supply system, or other. By preventing the wire from getting stuck during winding, the guiding device preserves its structure. The wire is kept away from any aggression or handling that could reduce the mechanical strength of the core or alter the insulating layer. For example, the wire is protected from the use of a tool that could be used to free it after a jam. This results in greater reliability and a longer service life for the wire. As a result, the rotor and the motor as a whole are more reliable and more durable. Maintenance is simplified, and operating costs are lower.

[0017] In one embodiment, the body of the ring has a radial boss at the finger. The boss moves a strand of wire away from the body of the ring in a radial direction. This reduces, or even completely avoids, friction between the wire and the body of the ring. In a non-limiting manner, the boss also opposes a movement of the wire in a direction which goes from the internal face to the external face of the guide head, that is to say in a direction away from the poles. It will be seen better later that, in combination with other bosses, the wire is put under slight tension in the mechanical sense of the term. As a result, the position of the strand of wire outside the poles is more stable.

[0018] The body of the ring has a radial boss away from the finger. The boss prevents the wire from moving in a direction towards the poles. Thus, the boss prevents the wire from coming into contact with the poles. The boss also contributes to a slight tensioning of the wire in the mechanical sense of the term, for greater stability.

[0019] The body of the ring, the finger, the radial boss at the finger and the radial boss away from the finger form a single piece. In a non-limiting manner, this piece is made of synthetic material such as polyamide, polyethylene or any equivalent. The piece is obtained by injection or any appropriate technique, which is quite simple. The synthetic material constituting the piece is an electrical insulator, which has the advantage of placing a strand of wire from the winding away from electrically conductive surfaces. The risks of short circuits are greatly reduced, or even completely eliminated.

[0020] At the base, the external face of the guide head has an axial boss. This deflects the strand of wire emerging from the winding in a direction away from the poles. The axial boss opposes a movement of the strand of wire towards the poles. This reduces, or even completely avoids, friction between the wire and the base or between the wire and the poles. We will see more clearly later that the axial boss of the base contributes to the slight mechanical tensioning of the strand of wire, and that in fact it contributes to a better stability of the latter's position.

[0021] The base and the axial boss form a single piece. Here again, without limitation, this piece is for example made of synthetic material such as polyamide, polyethylene or any equivalent. The piece is obtained by injection or any appropriate technique. The synthetic material constituting the piece is an electrical insulator, which has the advantage of placing a strand of wire from the winding away from electrically conductive surfaces. The risks of short circuits are greatly reduced, or even completely eliminated.

[0022] The guide head rests on the poles, and the ring rests on a shoulder of the shaft. The shoulder is provided at the pole boundary. Thus the guide head and the ring are located in the same area of ​​the rotor, i.e. towards the same pole boundary. The support of the two elements, the guide head and the ring, guarantees a constant position of one in relation to the other, and therefore a constant length of the path traveled by a strand of wire from the winding.

[0023] In fact, at the entrance or exit of the winding, the electrically conductive wire follows a path around the ring along which it is first stressed by the axial boss of the base in a direction away from the poles, then stressed by the radial boss at the finger of the ring in a direction towards the poles and in a direction away from the body, and then again stressed by the radial boss away from the finger of the ring in a direction away from the poles. The three bosses mentioned above follow one another in the order of enumeration following the contour of the ring. The bosses act on the wire alternately: that of the base in a direction away from the poles, then that at the finger of the ring in a direction towards, and finally that away from the finger again in a direction away. This alternation of contacts maintains the shape of the wire strand, possibly with slight mechanical tension.Small random movements of the wire are therefore avoided, particularly those linked to variations in the rotor rotation speed. The effects of centrifugal force on the wire strand are reduced, or even completely eliminated. As a result, the risks of wire wear, such as damage to the insulation layer, are particularly low.

[0024] The invention also relates to an electrical machine comprising a wound rotor, in particular a motor, comprising a guide device as presented above.

[0025] The invention also relates to a method for winding with an electrically conductive wire a plurality of poles of an electric machine rotor, the poles being distributed around a shaft of the rotor, the method comprising a step of placing a guide head on the shaft on the side of the poles where a connection element to a power supply system is located, the method comprising a step of placing another guide head on the shaft on the other side of the poles.The method comprises a step of placing a ring on the shaft on the pole side where the connecting element is located, the ring comprising a body to which a finger is attached, the finger projecting in an axial direction from the ring towards the poles, the ring being placed so as to leave a space between the body and the poles and so that the finger extends along this space, the method comprising a step of winding the poles while the space between the body of the ring and the poles is maintained, the method comprising a step of bringing the ring towards the poles after the winding operation, the bringing together reducing or eliminating the space.

[0026] The ring can be mounted on the shaft with a sliding fit or a slight snug fit. In all cases the finger preserves the thread.

[0027] Brief description of the drawings

[0028] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0029] - [Fig. 1] is a perspective view of a guide device for winding a rotor according to one embodiment of the invention,

[0030] - [Fig. 2] is a partial enlargement of Figure 1.

[0031] Detailed description

[0032] In Figure 1, an electrical machine, in this case a synchronous motor, is partially represented. More precisely, only a part of a wound rotor 1 of the motor is visible, its stator is not. The latter, for example, operates with a three-phase alternating current produced by a variator. Thus, the magnetic field of the stator can vary, in particular in power, speed and direction of rotation.

[0033] The rotor 1 comprises a shaft 2 intended to be rotatably mounted about its axis L2 in the stator. A stack, not shown, of laminations is placed on the shaft 2 of the rotor 1 coaxially with the axis L2, the stack of laminations forming a plurality of radially protruding poles. A winding, not shown, is carried out with an electrically conductive wire 3 wound around each pole. The only portion of the wire 3 shown in Figure 1 is a strand which connects the winding to a connecting element with an electrical power supply system, the latter not being shown.

[0034] It can be seen in Figure 1 that only one connecting strand of wire 3 is visible. However, it should be noted that two strands of wire 3 join the connecting element. In practice, these two strands are arranged, for example, symmetrically with respect to shaft 2. As a result, balancing of rotor 1 is facilitated.

[0035] The rotor 1 is provided with two guide devices, only one of which is shown, referenced 4, for winding the wire 3 around the poles. The visible guide device 4, which will be described in detail, is placed on the shaft 2 on the side of the poles where the element for connecting to the power supply system is located. The other guide device, the one which is not visible, is placed on the shaft 2 on the other side of the poles. The two guide devices are therefore each arranged at one end of the poles.

[0036] The guide device 4 comprises a guide head 5 capable of being mounted on the shaft 2, the guide head 5 extending axially between an external face 6 and an internal face 7, the internal face 7 of the guide head 5 being turned towards the poles. The guide head 5 comprises a central base 8 from which radial branches 9 extend. In a non-limiting manner, the guide head 5 comprises eight branches 9 for eight poles. As a corollary, the non-visible guide device also comprises a guide head with a central base and eight branches. This amounts to saying that the rotor 1 comprises eight poles, a number large enough to obtain a high intensity magnetic effect. It follows that the motor is able to deliver a high torque, in particular at low speed.

[0037] According to the invention, the guide device 4 comprises a ring 15 mounted on the shaft 2, the ring 15 extending axially between an external face 16 and an internal face 17, the internal face 17 of the ring 15 being turned towards the poles. The ring 15 and the guide head 5 are positioned at the same end of the poles. The ring 15 comprises a body 18 to which two fingers are secured, only one of which, reference 19, is visible, the fingers projecting from the side of the internal face 17 in an axial direction of the ring.

[0038] In fact, a particularity of the invention is that the guide device 4 comprises several elements, the guide head 5 and the ring 15. It follows that the method of winding the rotor is specific, in particular for the positioning of the wire 3 around the poles and for maintaining the strands of wire at the entry and exit of the winding.

[0039] Conventionally, the method comprises a step of placing the visible guide head 5 on the shaft 2, on the side of the poles where the element for connecting to the power supply system is located. The method also comprises a step of placing the other guide head on the shaft 2, on the other side of the poles. In practice, each guide head 5 rests on the poles.

[0040] The method comprises a step of placing the ring 15 on the shaft 2 on the pole side where the connecting element is located. The guide head 5 and the ring 15 are therefore located in the same zone of the rotor 1. In the step of its placement, the ring 15 leaves a space between its body 18 and the poles, and the fingers 19 extend along this space. This situation is not that of Figure 1.

[0041] Then, according to the method, a step consists of winding the poles while the space between the body 18 of the ring 15 and the poles is maintained. The winding is carried out by passing the wire 17 around each pole and the radial branches 9 of the guide heads 5, by means of needles. The path of the needles for the winding is possible because the space mentioned before is sufficiently wide. This space is for example between 1 and 15 mm, knowing that tests have shown that values ​​between 5 and 10 mm give good results.

[0042] Because they extend along the entire gap, the fingers 19 of the ring 15 each hold a strand of the wire 3 away from the shaft 2 of the rotor 1. More precisely, the fingers 19 hold the strands of wire 3 at a distance from the shaft 2 greater than the thickness of the body 18 of the ring 15. This function is important for the next step of the method, which consists of bringing the ring 15 towards the poles after the winding operation, the bringing together reducing or eliminating the gap. The bringing together is possible because the strands of the wire 3 are kept away from the path of the ring 15. In a non-limiting manner, the ring 15 rests on a shoulder 20 of the shaft 2, and the fingers 19 each take place in a longitudinal groove 21 of the shaft 2.Each groove 21 is a cavity which fulfills several functions, that of receiving a finger 19 after positioning the ring 15 on the shoulder 20, and that of wedging the rotation of the ring 15 relative to the shaft 2. It is in fact important that a finger 19 is at a controlled distance from an entry or exit point of the wire 3 in the winding.

[0043] An advantage of using a ring with fingers is the preservation of the wire strands, which enter or exit the winding, during rotor manufacturing. The strands remain away from parts that may be mechanically aggressive, particularly if they have sharp edges or burrs. This prevents the incipient breakage of the core or damage to the insulation layer of the wire 3.

[0044] In addition, as described below, the guide device 4 is structured for preservation of the wire strands after manufacture, that is to say during use of the motor, knowing that the latter can rotate at very high speeds, and that consequently the strands are subjected to stresses such as those resulting from centrifugal force.

[0045] As can be understood from Figures 1 and 2, at the base 8 the external face 6 of the guide head 5 has a visible axial boss 25 and another invisible axial boss. Each axial boss 25 deflects a strand of wire which emerges from the winding in a direction away from the poles. Each axial boss 25 opposes a movement of the strand of wire towards the poles, and keeps the strand of wire away from the shoulder 20 of the shaft 2.

[0046] Referring again to Figure 1, it is understood that the body 18 of the ring has a radial boss 26 at each finger 19. Each boss 26 moves a strand of wire away from the body 18 of the ring 15 in a radial direction. This reduces, or even completely avoids, friction between the wire 3 and the body 18 of the ring 15. Each boss 26 also opposes a movement of the wire 3 in a direction which goes from the internal face 7 towards the external face 6 of the guide head 5, that is to say in a direction of moving away from the poles.

[0047] It is further understood that the body 18 of the ring 15 has a radial boss 27 away from each finger 19. Each of the bosses 27 opposes a movement of the wire 3 in a direction of bringing the poles closer together. Each radial boss 27 opposes contact of the wire 3 with the poles.

[0048] If we follow the path of a strand of wire 3 at the exit of the winding, we see that it is first moved away from the poles by the axial boss 25 of the central base 8, that it is then prevented from moving away from the poles by the radial boss 26 at the finger 19, that it is then prevented from approaching the poles by the radial boss 27 located away from the finger 19, to finally be subjected to an electrical contact 28 of the ring 15. In practice, the ring 15 is placed in abutment on the shoulder 20 after the strand of wire has been secured to the contact 28. The movement of the ring for the abutment places each strand of wire under slight mechanical tension. As a result, its position is very stable, even under the action of centrifugal forces. Consequently, the risk of alteration of each strand of wire is reduced, or even non-existent.

[0049] The invention is not limited to the embodiment described, and includes all equivalents which may fall within the scope of the claims which follow.

[0050] In particular, various variant shapes may be provided for the components of the guide device 4. When reference is made to a finger or a boss, it is at least one finger or at least one boss.

Claims

CLAIMS 1. Guiding device (4) for winding with an electrically conductive wire (3) a plurality of poles of a rotor (1) of an electric machine, the poles being distributed around a shaft (2) of the rotor (1), the guiding device (4) comprising a guiding head (5) capable of being mounted on the shaft (2), the guiding head (5) extending axially between an external face (16) and an internal face (17), the internal face (17) of the guiding head (5) being turned towards the poles, the guiding head (5) comprising a central base (8) from which radial branches (9) extend, characterized in that it comprises a ring (15) mounted on the shaft (2), the ring (15) extending axially between an external face (16) and an internal face (17), the internal face (17) of the ring (15) being turned towards the poles, the ring (15) and the guide head (5) being positioned at the same end of the poles, the ring (15) comprising a body (18) to which a finger (19) is attached, the finger (19) projecting from the side of the internal face (17) in an axial direction of the ring (15).

2. Device (4) according to claim 1, in which the body (18) of the ring (15) has a radial boss (26) at the finger (19).

3. Device (4) according to claim 1 or 2, in which the body (18) of the ring (15) has a radial boss (27) away from the finger (19).

4. Device (4) according to claim 3, in which the body (18) of the ring (15), the finger (19), the radial boss (26) at the finger (19) and the radial boss (27) away from the finger (19) form a single piece.

5. Device (4) according to one of claims 1 to 4, in which, at the base (8), the external face (6) of the guide head (5) has an axial boss (25).

6. Device (4) according to claim 5, in which the base (8) and the axial boss (25) form a single piece.

7. Device (4) according to one of claims 1 to 6, for which the guide head (5) rests on the poles, and for which the ring (15) rests on a shoulder (20) of the shaft (2).

8. Device (4) according to claim 7, for which, at the entry or exit of the winding, the electrically conductive wire (3) follows a path around the ring (15) along which it is first stressed by the axial boss (25) of the base (8) in a direction away from the poles, then stressed by the radial boss (26) at the finger (19) of the ring (15) in a direction towards the poles and in a direction away from the body (18), and then again stressed by the radial boss (27) away from the finger (19) of the ring (15) in a direction away from the poles.

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

10. Method for winding with an electrically conductive wire (3) a plurality of poles of a rotor (1) of an electric machine, the poles being distributed around a shaft (2) of the rotor (1), the method comprising a step of placing a guide head (5) on the shaft (2) on the side of the poles where a connecting element to a power supply system is located, the method comprising a step of placing another guide head on the shaft (2) on the other side of the poles, the method being characterized in that it comprises a step of placing a ring (15) on the shaft (2) on the side of the poles where the connecting element is located, the ring (15) comprising a body (18) to which a finger (19) is secured, the finger (19) projecting in an axial direction from the ring (15) towards the poles, the ring (15) being placed so as to leave a space between the body (18) and the poles and so that the finger (19) extends along this space,the method comprising a step of winding the poles while the space between the body (18) of the ring (15) and the poles is maintained, the method comprising a step of bringing the ring (15) closer to the poles after the winding operation, the bringing closer reducing or eliminating the space.,

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