EP0618648A1 - Process for manufacturing a rotor of a rotating electrical collector - Google Patents

Abstract

In order to manufacture the rotor of a rotating electrical commutator, a blank (preform) (10) of the slip rings is produced, made of an electrically conducting material, by stacking pieces (16), which have an L-shaped cross-section, so as to form an outer tubular part (14) and parts (12) forming rings, projecting radially on the inside of the tubular part. The blank (10) is held between two plates (22) and partially filled with liquid resin (28). The resin is then centrifuged and cured by application of a heat cycle. Finally, the outer tubular part (14) is removed by machining. <IMAGE>

Description

The invention relates to a method for manufacturing the rotor of a rotating electrical collector.

Rotating electrical collectors are devices which allow several electrical signals to be transmitted simultaneously between a fixed part, or stator, and a mobile part or rotor. Such devices are used in many industrial sectors, among which, by way of example only, are machine tools, air, naval and land transport, etc.

The rotor of a rotating electrical collector comprises a number of electrically conductive rings equal to the number of electrical signals which the device must transmit. These electrically conductive rings are arranged coaxially on an electrically insulating axis and separated from each other by an electrically insulating material.

The stator of the rotating electrical collectors generally comprises, opposite each of the electrically conductive rings, at least two brushes such as electrically conductive wires permanently rubbing against the rings. V-shaped grooves can be machined on the electrically conductive rings to guide the brushes.

The traditional manufacturing technique of the rotor of a rotating electrical collector consists in mounting, on a hollow or solid axis made of an electrically insulating material, a stack formed alternately of electrically conductive rings and electrically insulating rings. This stack is blocked by means of a stop ring fixed on the axis, for example by gluing. The electrical connections are provided by electrical conductors which run inside the axis and are welded to each of the electrically conductive rings at their ends.

This traditional manufacturing technique is satisfactory for many applications. However, it is relatively expensive and can practically not be used for the manufacture of small rotors.

It is also known to manufacture the rotors of rotary electrical collectors using a gravity molding technique making it possible to manufacture the electrically insulating part of the rotor from a resin initially in the liquid state. The electrically conductive rings are positioned in a mold, then the resin is introduced by gravity, without pressure. The application of a thermal cycle ensures the hardening of the resin, for example by polymerization.

Compared with traditional manufacturing techniques, this technique of manufacturing by pressure molding has the advantages of being less expensive and allowing the manufacture of rotors of any size. In addition, inserts can be introduced during molding, in particular to facilitate the mechanical connection of the rotor to the adjacent parts.

The disadvantage of the technique for manufacturing rotors by molding without pressure is that it requires the use of a mold of different size for each type of rotor to be manufactured, which makes this process expensive. In addition, compliance with very precise sizing, in particular with regard to the spacing between the different rings electrically conductive rotor is very difficult to insure.

The subject of the invention is precisely a new method for manufacturing the rotor of a rotating electrical collector using a resin initially in the liquid state but without requiring the presence of a mold, so as to take advantage of the advantages provided by the known manufacturing technique using pressure molding, while being less expensive and allowing more precise sizing.

• formation d'une ébauche de bagues collectrices, en un matériau électriquement conducteur, comportant une partie tubulaire extérieure et des parties formant bagues espacées les unes des autres et faisant saillie radialement vers l'intérieur à partir de ladite partie tubulaire ;
• fermeture partielle d'un espace intérieur à ladite ébauche, au moins dans une région périphérique de cet espace ;
• introduction d'une résine liquide dans ledit espace ;
• centrifugation de la résine par rotation de l'ébauche et application simultanée d'un cycle thermique de durcissement de la résine, de façon à former un bloc annulaire rigide ; et
• élimination de ladite partie tubulaire extérieure.

According to the invention, this result is obtained by means of a process for manufacturing a rotating electrical collector rotor, characterized in that it comprises the following steps:

• forming a blank for slip rings, made of an electrically conductive material, having an outer tubular part and ring-shaped parts spaced from each other and projecting radially inwards from said tubular part;
• partial closure of an interior space to said blank, at least in a peripheral region of this space;
• introduction of a liquid resin into said space;
• centrifugation of the resin by rotation of the blank and simultaneous application of a thermal curing cycle of the resin, so as to form a rigid annular block; and
• elimination of said outer tubular part.

The use of centrifugal force makes it possible to distribute the resin uniformly inside the blank of slip rings. In addition, employment a blank with an outer tubular portion without perforation prevents the escape of the resin during centrifugation. The subsequent elimination of this external tubular part, after hardening of the resin, makes it possible to obtain the rotor directly.

It is thus possible to manufacture a rotor whose precise dimensioning is very easy to control, without the need to use a mold. Significant savings can therefore be made when rotors of different types have to be manufactured. Furthermore, the distribution of the resin by centrifugation makes it possible to remove any residual stress in the rotor thus obtained, which in particular guarantees a precise dimensioning of the spacing between the various electrically conductive rings.

In a preferred embodiment, the blank is obtained by stacking several pieces each comprising a section of the outer tubular part and one of the parts forming a ring. Advantageously, each of these parts has substantially in section the shape of an L, the two branches of which respectively constitute said section and said ring-forming part.

Then preferably used parts with complementary end faces which ensure their self-centering when stacked to form the blank.

To partially close the interior space to the blank, the latter is placed between two plates, at least one of which has an orifice for introducing the liquid resin.

Preferably, the faces of these plates facing towards the blank are then complementary to the faces ends of the latter, so as to ensure self-centering of the blank between the plates.

To ensure centrifugation, the plates are fixed on a shaft which is rotated at substantially constant speed using a motor.

Furthermore, the thermal curing cycle of the resin is applied by placing the assembly comprising the blank, the plates and the shaft in an enclosure with controlled atmosphere.

The elimination of the external tubular part of the rigid annular block obtained after centrifugation of the blank is advantageously carried out by machining.

In addition, before partially closing the interior space to the blank, an electrical conductor is welded inside each of the ring-forming parts.

• la figure 1 représente l'ébauche de bagues collectrices remplie de résine liquide et placée dans l'outillage permettant d'en assurer la centrifugation ainsi que le durcissement de la résine ;
• la figure 2 est une vue en coupe longitudinale illustrant schématiquement le bloc annulaire rigide obtenu après durcissement de la résine ; et
• la figure 3 est une vue en coupe longitudinale comparable à la figure 2 représentant le rotor terminé, obtenu après usinage du bloc rigide illustré sur la figure 2.

A preferred implementation of the method according to the invention will now be described, by way of nonlimiting example, with reference to the appended drawings, in which:

• FIG. 1 represents the blank of slip rings filled with liquid resin and placed in the tool making it possible to ensure centrifugation as well as hardening of the resin;
• Figure 2 is a longitudinal sectional view schematically illustrating the rigid annular block obtained after hardening of the resin; and
• FIG. 3 is a view in longitudinal section comparable to FIG. 2 showing the finished rotor, obtained after machining the rigid block illustrated in FIG. 2.

We will first describe, with reference to Figure 1, the first steps of the manufacturing process of a rotating electrical collector rotor, according to the invention.

Firstly, a blank 10 of slip rings is produced, made of an electrically conductive material, such as copper, etc. The blank 10 comprises an external tubular part 14 without perforation and parts 12 forming rings, which project radially inwards from the external tubular part 14.

The parts 12 forming rings are spaced from each other. They are intended to constitute the electrically conductive rings of the rotor.

The outer tubular part 14 serves both to maintain the desired spacing between the parts 12 forming the rings and to prevent the resin from escaping to the outside during centrifugation. It will be removed at a later stage of manufacturing, so it will not be part of the rotor.

It should be noted that if FIG. 1 represents a blank 10 the parts of which form the rings 12 all have the same thickness and are separated from each other by identical distances, the thicknesses of the parts 12 forming the rings as well as their spacing can take any values and in particular different over the length of the blank 10, without departing from the scope of the invention.

In the preferred embodiment illustrated in FIG. 1, the blank 10 for slip rings is formed by a stack of pieces 16 which all have a substantially L-shaped cross section. Each of these pieces 16 includes one of the parts 12 forming rings, as well as a section of the outer tubular part 14. More precisely, each of the parts forming rings 12 projects radially towards the inside of the blank 10 from one end of the corresponding section of the part tubular 14.

It should be noted that the sections of the tubular part 14 of the blank 10, formed in each of the parts 16, all have the same thickness and the same internal and external diameters. Likewise, the different parts forming rings 12 all have the same internal diameter. Thus, the blank 10 has a symmetry of revolution about its longitudinal axis when the parts 16 are stacked in a coaxial manner as illustrated in FIG. 1.

In order to ensure this coaxial or self-centering stacking of the parts 16, the end face of each of these parts 16 formed on the part 12 forming the ring of this part comprises on its outer periphery a recessed part 18. The end of the section of the outer tubular part 14 which is in contact with this end face is complementary to the recessed part 18, so that it fits there, as illustrated in FIG. 1, so as to achieve self-centering longed for.

It should be noted that, as a variant, the blank 10 for slip rings can be produced in a manner different from that which has just been described. Thus, this blank can in particular be produced in one piece by machining or by stacking pieces having in section substantially the shape of a T.

At a time which may be, as the case may be, before or after the stack of parts 16 is produced, the end of an electrical conductor 20 is welded to the inner peripheral surface of each of the parts 12 forming rings. The electrical conductors 20 are intended to ensure the transmission of electrical signals between the electrically conductive rings of the rotor and external electrical circuits or systems rotating with this rotor.

As illustrated in FIG. 1, the blank 10 of slip rings is mounted in a tool making it possible to partially fill it with resin, to rotate it around its axis to centrifuge the resin and to subject the latter to an appropriate thermal cycle. .

The part of the tool making it possible to fill the blank 10 partially with resin and to ensure its centrifugation comprises first of all two plates 22 in the form of circular disks, which are placed on the ends of the 'blank 10. These plates 22 make it possible to keep the various parts 16 of the blank in contact and to partially close the space 24 delimited inside the latter, at least in the peripheral zone adjacent to the blank 10.

As also illustrated in FIG. 1, the faces of the plates 22 turned towards the end faces of the blank 10 have shapes complementary to those of these end faces, so that the plates 22 are automatically centered on the draft.

One of the plates 22 has, near its axis, an orifice 26 for introducing liquid resin. When the plates 22 are blocked on the blank 10 so as to partially close the interior space 24, liquid resin 28 is introduced through this orifice 26.

To block the plates 22 against the ends of the blank 10 and, consequently, immobilize the parts 16 between these plates, a shaft 30 is introduced into a circular passage formed in the center of each of the plates 22. A shoulder 32 formed on the shaft 30 abuts against the outer face of one of the plates 22. A screwed nut 34 on a thread 36 formed at the opposite end of the shaft 30 is supported on the outer face of the other plate 22 to ensure the desired blocking. Optionally, keys 35 can be interposed between the shaft 30 and each of the plates 22 to secure these rotating members.

When this assembly is carried out, the resin 28 is introduced in the liquid state into the interior space 24 through the introduction orifice 26. This introduction can be done manually or in an automated manner. It is important to observe that the volume of liquid resin 28 introduced into the interior space 24 is precisely determined so that the finished rotor has the desired interior diameter.

As schematically illustrated in FIG. 1, the shaft 30 is fixed coaxially to the output shaft of a motor 38 such as an electric motor of any kind, capable of driving the shaft 30 in rotation, the plates 22 , the blank 10 as well as the liquid resin 28. The shaft 30 can be made in one piece as shown schematically in Figure 1 or, preferably, in two removable sections respectively forming the shaft motor outlet 38 and the blocking shaft of the blank 10 between the plates 22.

The assembly thus formed is mounted on a support illustrated diagrammatically at 40 in FIG. 1, for example in order to give the axis of the shaft 30 a substantially horizontal orientation. This support 40 is itself placed inside an enclosure 42 with a controlled atmosphere, such as an autoclave, making it possible to apply the resin 28 the thermal curing cycle recommended by its manufacturer.

The resin 28 may be a thermosetting resin such as an epoxy resin or a resin of any other type whose hardening can be obtained by applying a predetermined temperature cycle to it.

When the assembly illustrated diagrammatically in FIG. 1 has been carried out, the resin 28 contained in the blank 16 is centrifuged and the thermal curing cycle of this resin is applied simultaneously. To this end, the motor 38 is activated to rotate the shaft 30, the plates 22, the blank 10 and the resin 28 at substantially constant speed, as illustrated by arrow F. The speed of rotation is determined as a function of the diameter of the blank 10, so that a sufficient centrifugal force is applied to the resin 28 so that this resin is distributed homogeneously over the entire inner circumference of the blank 10.

This rotation at a substantially constant speed controlled by the motor 38 continues throughout the duration of the application of the thermal cycle such as a polymerization cycle allowing the resin 28 to harden inside the blank 10.

Of course, the assembly illustrated schematically in Figure 1 is given for explanatory purposes. In fact, within the framework of an industrial implementation of the process according to the invention, a single motor is used to simultaneously drive in rotation several blanks filled with resin initially in the liquid state, by means of transmission of movements well known to specialists. In this arrangement, the motor 38 can be placed either inside the enclosure 42, or outside of the latter.

When mounting the blank 10 between the plates 22, the electrical conductors 20 are placed in the position which it is desired to obtain on the rotor in progress Manufacturing. This position can be such that the conductors are embedded in the resin 28 inside the rotor and exit from the latter by an end face as illustrated in the figures. It is also possible to arrange each of the electrical conductors 20 so that they exit radially inside the resin 28, then pass through the hollowed-out central part of the rotor. In both cases, the electrical conductors 20 pass through passages provided for this purpose in one of the plates 22.

When the simultaneous operations of centrifugation and application of a thermal curing cycle for the resin 28 are completed, the assembly constituted by the blank 10 of slip rings and by the resin 28 forms a rigid annular block 43 such that illustrated in FIG. 2. In this rigid annular block, the solidified resin 28 fills the spaces formed between the ring-forming parts 12 and forms, inside these parts 12, a hollow shaft whose internal diameter is uniform and depends, as as we have seen, of the quantity of liquid resin initially introduced into the interior space 24.

Taking into account the process used, it is important to observe that the rigid annular block 43 of FIG. 2 is devoid of residual stresses and that the thickness of the electrically insulating resin between the parts 12 forming rings corresponds precisely to the desired spacing .

To complete the manufacture of the rotor 44 illustrated in FIG. 3, the external tubular part 14 of the blank 10 is then removed, preferably by machining, in order to obtain electrically conductive rings 12a isolated from each other. others by resin 28. At the end of this operation, at least one guide groove 46 with a V-shaped section is machined on the outer surface of each of the rings 12a, in which the electrically conductive brushes of the stator will be placed.

In addition, subsequent surface treatments can be carried out, in a conventional manner, to increase the life of the rotor. Thus, a protective material can be deposited on the periphery of each of the electrically conductive rings 12a, according to a known technique.

Claims (10)

Method for manufacturing a rotor (44) of a rotating electrical collector, characterized in that it comprises the following steps: - Formation of a blank (10) of slip rings, made of an electrically conductive material, comprising an outer tubular part (14) and ring-forming parts (12) spaced apart from each other and projecting radially inwards from of said tubular part; - partial closure of a space (24) inside said blank, at least in a peripheral region of this space; - introduction of a liquid resin (28) into said space; - centrifugation of the resin by rotation of the blank and simultaneous application of a thermal cycle of hardening of the resin, so as to form a rigid annular block (43); and - elimination of said outer tubular part (14). Method according to claim 1, characterized in that said blank (10) is formed by stacking several pieces (16) each comprising a section of said outer tubular part (14) and one of the ring-forming parts (12). Method according to claim 2, characterized in that parts (16) are used having substantially in cross-section the shape of an L, the two branches of which respectively constitute said section and said ring-forming part (12). Method according to either of Claims 2 and 3, characterized in that parts (16) having faces are used complementary end ensuring their self-centering when stacked to form said blank (10). Method according to any one of the preceding claims, characterized in that the interior space is partially closed to the blank (10) by placing the latter between two plates (22), at least one of which has an orifice ( 26) for introducing the liquid resin (28). Method according to claim 5, characterized in that plates (22) are used whose faces facing the blank (10) are complementary to the end faces of this blank, so as to ensure self-centering of the blank between the plates. Method according to either of Claims 5 and 6, characterized in that the resin (28) is centrifuged by fixing the plates (22) on a shaft (30) which is rotated at substantially constant speed. Method according to claim 7, characterized in that the thermal curing cycle of the resin is applied by placing an assembly comprising the blank (10), the plates (22) and the shaft (30) in an enclosure ( 42) with a controlled atmosphere. Method according to any one of the preceding claims, characterized in that the external tubular part (14) is removed by machining. Method according to any one of the preceding claims, characterized in that before partially closing the space (24) inside the blank (10), an electrical conductor (20) is welded inside each of parts forming rings (12).

Images