Title of Invention	COMMUTATOR FOR AN ELECTRIC MACHINE
Abstract	The invention related to a commutator for an electric machine, comprising a support member (1, 1") made from insulating molding compound, a plurality of metal conductor segments (3, 3"), disposed thereon in evenly spaced manner around the commutator axis (2), with terminal elements disposed thereon for a rotor winding, and an interference-suppression device (9, 9', 9"), to which the conductor segments (3, 3") are connected in electrically conductive manner, wherein the interference-suppression device (9, 9', 9") comprises a number, corresponding to the number of conductor segments (3, 3"), of individual interference- suppression elements (10, 10', 10") disposed around the commutator axis (2), and an equally large number of contact bridges (11, 11', 11"), each of which is connected to an associated conductor segment in electrically conductive manner and connects two mutually adjacent interference- suppression elements (10, 10', 10") to one another and to the associated conductor segment in electrically conductive manner. Each contact bridge (11, 11', 11") is provided with two inwardly directed legs (20, 20'), which are flexible relative to one another in circumferential direction and are connected to the two associated interference- suppression elements in electrically conductive manner, and with one outwardly directed foot portion (21, 21'), which is connected to the associated conductor segment in electrically conductive manner, the contact bridges (11, 11', 11") being soldered or adhesively bonded in the region of their leg (20, 20') to the associated interference-suppression elements (10, 10', 10") and in the region of their foot portions (21,21', 21") to the associated conductor segments (3, 3").

Title of Invention

COMMUTATOR FOR AN ELECTRIC MACHINE

Abstract

The invention related to a commutator for an electric machine, comprising a support member (1, 1") made from insulating molding compound, a plurality of metal conductor segments (3, 3"), disposed thereon in evenly spaced manner around the commutator axis (2), with terminal elements disposed thereon for a rotor winding, and an interference-suppression device (9, 9', 9"), to which the conductor segments (3, 3") are connected in electrically conductive manner, wherein the interference-suppression device (9, 9', 9") comprises a number, corresponding to the number of conductor segments (3, 3"), of individual interference- suppression elements (10, 10', 10") disposed around the commutator axis (2), and an equally large number of contact bridges (11, 11', 11"), each of which is connected to an associated conductor segment in electrically conductive manner and connects two mutually adjacent interference- suppression elements (10, 10', 10") to one another and to the associated conductor segment in electrically conductive manner. Each contact bridge (11, 11', 11") is provided with two inwardly directed legs (20, 20'), which are flexible relative to one another in circumferential direction and are connected to the two associated interference- suppression elements in electrically conductive manner, and with one outwardly directed foot portion (21, 21'), which is connected to the associated conductor segment in electrically conductive manner, the contact bridges (11, 11', 11") being soldered or adhesively bonded in the region of their leg (20, 20') to the associated interference-suppression elements (10, 10', 10") and in the region of their foot portions (21,21', 21") to the associated conductor segments (3, 3").

Full Text	Commutator for an electric machine The present invention relates to a commutator for an electric machine, comprising a support member made from an insulating molding compound, a plurality of metal conductor segments disposed thereon in evenly spaced manner around the commutator axis, with terminal elements disposed thereon for a rotor winding, and an interference-suppression device, to which the conductor segments are connected in electrically conductive manner. Commutators of various designs (drum commutators, flat commutators) are known in diverse configurations. To an increasing extent, commutators are being equipped with spark-suppression devices (interference-suppression devices), especially if they are designed as drum commutators, in order to prevent sparking at the commutator from impairing electronic assemblies disposed in physical proximity to the electric machine in question that is equipped with the commutator. Heretofore such interference-suppression devices have often been designed as annular interference-suppression disks, which are made of a material having voltage-dependent resistance and which are connected in electrically conductive manner to the conductor segments. In such cases the corresponding interference-suppression disk can be mounted on the one hand radially outward of the brush running surface (for example, see US 5895990 A, US 5717270 A,' GB 2183933 A and US 5796203 A), or on the other hand radially inward of the brush running surface (for example, see US 6285106 B1 and DE 19953231 A1). Also known are special forms of interference-suppressed drum commutators, in which the conductor segments are disposed on the outside of cylindrical interference-suppression sleeves (see DE 2055648 and DE 3614869 C2). Finally, EP 364292 B1 describes a drum commutator with a support member made of thermoplastic material, in which a heat-resistant reinforcing ring is provided radially underneath the terminal lug, which ring is provided with an interference-suppressing coating or can be disposed adjacent to a separate interference-suppression ring; in common with the separate interference-suppression ring that may be provided in addition, this reinforcing ring is mounted on a seat of the support member, where it is retained by straps protruding from the conductor segments. Regardless of the respective specific arrangement of interference-suppression disks, the considerable costs for the interference-suppression device constitute a disadvantage in all commutators whose interference-suppression device comprises an annular interference- suppression disk, since the ceramic material from which such interference-suppression disks are usually made is very expensive; moreover, large quantities of waste are produced in the manufacture of annular interference-suppression disks, since they are cut out of a multi-layer metal-ceramic plate. Incidentally, among the known drum commutators that are interference-suppressed by using an interference-suppression disk, only compact drum commutators with interference-suppression disks disposed radially inward of the brush running surface are feasible for many practical applications, because the space available for the respective commutator is limited. A further problem of such drum commutators with interference-suppression rings disposed radially inward of the brush running surface results from the different thermal expansion behavior of the interference-suppression disk, which is usually made of ceramic material, compared with the other components of the commutators in question. Specifically, if the thermal stresses are large enough, they can cause premature failure of commutators due to broken interference-suppression disks and/or destroyed connections between the conductor segments and the interference- suppression disks, unless special precautions are taken. As a solution to this problem, it is proposed in DE 19953231 A1 that the interference-suppression disk be joined to the support member by means of an elastic adhesive and that the conductor segments be connected to the interference-suppression disk via thin wires, which are soldered on the one hand to the terminal lug of the associated conductor segment and on the other hand to an associated metallization zone of the interference-suppression disk. In contrast, according to US 6285106 B1, which discloses a drum commutator of the class in question, there are provided, for electrical contact between the conductor segments and the interference-suppression disks, leaf springs that are disposed inside an annular cavity, which is bounded by the support member, the conductor segments and an annular cover, and in which the interference-suppression disk is also housed. The leaf springs, which permit different radial thermal insulation of the interference-suppression disk on the one hand and of the other commutator components on the other hand, can be fixed in particular to the annular cover. A particular disadvantage of the two known drum commutators, evaluated in the foregoing, each with an interference-suppression disk disposed radially inward of the conductor segments is in particular the high expense of manufacture, which is substantially due to the high manufacturing costs of the interference-suppression disk (see hereinabove) and hampers the competitiveness of the drum commutators in question. Accordingly, the problem underlying the present invention is to provide a long-lived, reliable, interference-suppressed commutator of the class in question, which commutator, in view of its suitability for mass production, can be made at low costs with little manufacturing expense. A particularly preferable object is to manufacture an interference-suppressed commutator with substantially the same dimensions as a non-interference-suppressed commutator of the same design. This object is achieved according to the present invention by the fact that the interference- suppression device comprises a number of individual interference-suppression elements corresponding to the number of conductor segments and an equally large number of contact bridges, each of which connects two mutually adjacent interference-suppression elements to one another in electrically conductive manner, each contact bridge being provided with two inwardly directed legs, which are flexible relative to one another in circumferential direction and are connected to the two associated interference-suppression elements in electrically conductive manner, and with one outwardly directed foot portion, which is connected to the associated conductor segment in electrically conductive manner. A first characteristic feature of the commutator according to the present invention is therefore that the interference-suppression device comprises not an annular interference-suppression disk but instead a number of individual interference-suppression elements corresponding to the number of conductor segments; such individual interference-suppression elements, which as multi-layer capacitors can have in particular a parallelepiped shape, can be made from a multi- layer metal-ceramic plate without any kind of cutting and thus in particularly inexpensive manner. Furthermore, it is characteristic for the inventive commutator that two mutually adjacent interference-suppression elements are respectively connected to one another in electrical manner via one contact bridge each, the two legs at which the contact bridge in question is connected to the two interference-suppression elements in electrically conductive manner being designed to be flexible relative to one another in circumferential direction. In this sense, "flexible" means that the force necessary for deformation of the contact bridges in circumferential direction is smaller than the strength of the joints of the contact bridges with the interference-suppression elements. 'The interference-suppression device characterizing the inventive commutator is composed in this way of individual interference-suppression elements and contact bridges, which are joined together in alternating sequence to form a ring structure. The flexibility of the contact bridges then has the effect that the ring structure in question is not rigid; to the contrary, the ring structure is flexible as a whole in circumferential direction, and so it can compensate for changes of the dimensions of the commutator caused by thermal expansion. Such manufacture of the contact bridges as separate components ensures that they can be selectively matched - largely without restriction - to the described function, by the fact that the material choice and dimensions are optimized in terms of flexibility and strength of the ring structure of the interference-suppression device as well as the joint of the contact bridges with the interference-suppression elements. The deformability of the contact bridges in their installation situation is based on the one hand on their flexible construction and on the other hand on the fact that the legs of the contact bridges are free, meaning that that they can be deformed without hindrance by adjoining components of the commutator during the normal thermal-expansion behavior of the commutator. As "electrically conductive connections" of the contact bridges with the contact poles or contact faces of the respective two adjacent interference-suppression elements, there can be considered, in the scope of the present invention, several electrically conductive contacting arrangements, provided they are also suitable for transmission of mechanical forces; in particular, a special joining material such as solder is preferably used (see hereinafter), but in any case it is not necessarily provided for all embodiments of the invention. Direct and indirect contacting of the contact bridges with the interference-suppression elements without having disadvantageous effects on the useful life of the commutator is achieved by the fact that the contact bridges can deform to compensate for different thermal-expansion behavior of the individual commutator components. By application of the present invention, therefore, it is obviously possible, by virtue of the combinations of the features characteristic of inventive commutators, to manufacture extremely inexpensive, long-lived and compact interference-suppressed commutators with minimal production expense. In this regard, the present invention is applicable for various commutator designs, specifically regardless of the construction of the brush running surface. Commutators with carbon running surfaces, such as are used for operating fuel pumps for motor vehicles, can be constructed particularly advantageously according to the present invention. Particularly preferably, the contact bridges are permanently connected to the interference- suppression elements by means of simple soldered joints or even joints formed with electrically conductive adhesive in the region of the contact points. The situation is analogous for the connection of the contact bridges to the respective conductor segments in the region of the foot portion in question that contacts the conductor segments. In this regard, suitable metallization (such as a coating of silver or tin) of the interference-suppression elements in the region of their contact poles and/or of the contact bridges in the region of the legs may prove favorable; and in this regard it is also favorable for the contact bridges to be manufactured from copper, brass or an alloy containing these metals. Such permanent connections of the contact bridges to the interference-suppression elements and/or to the conductor segments, which are subject to only small mechanical loads due to the flexible construction of the contact bridges in the circumferential direction, as is the case for the interference-suppression elements themselves, prove to be particularly advantageous when the inventive commutator is used in a corrosive environment. According to another preferred improvement of the inventive commutator, the interference- suppression elements are designed as parallelepiped multi-layer capacitors and are disposed around the commutator axis along the edges of a regular polygon, specifically in a manner in which each is expediently located at breaks between two mutually adjacent conductor segments. This in particular favors manufacture of the inventive commutator by a method that is simple and therefore inexpensive. Within the scope of the present invention, considerable margin for variation, which can be exploited in particular as a function of the commutator design, the dimensions and the specific requirements, is available for the structural design of the contact bridges. In this regard, a first preferred embodiment of the invention is characterized by the fact that the contact bridges are each disposed spatially between two mutually adjacent interference-suppression elements and are connected to the associated interference-suppression elements in the region of contact faces at the ends thereof. Each of these contact bridges can be made in particular of a bent metal strip, in which case the basic form of the contact bridges can then be described as substantially V-shaped. According to another preferred improvement of the invention, it is provided that the contact bridges are disposed in a plane axially offset relative to the interference-suppression elements and are connected to the associated interference-suppression elements in the region of laterally disposed contact faces. In this case, the contact bridges, whose shape may resemble in particular a horseshoe with a foot portion attached thereto, may be made of plane metal flat stock (such as sheet), which proves to be particularly favorable in terms of costs. Such a construction of the contact bridges also has advantageous effects on the way in which commutators are manufactured according to the present invention. Whereas the concept underlying the present invention can be advantageously adopted for commutators with different designs (drum commutators, flat commutators) and brush running surfaces of different constructions (such as those directly on metal conductor segments or those having carbon running surfaces), the advantages achievable with the present invention are particularly marked in the case that the commutator is designed as a drum commutator with a cylindrical brush running surface, since the invention permits a particularly compact design, now that the brush running surface can be extended in axial direction beyond the interference- suppression device. As regards the construction of the terminal elements, yet another preferred improvement of the invention is characterized in that the terminal elements are designed as terminal lugs, which in the case of design of the commutator as a drum commutator are disposed in the region of the end face of the commutator opposite the interference-suppression device. In this case, the risk of damage to the connections of the contact bridges to the conductor segments as well as to the interference-suppression elements during welding of the rotor winding onto the terminal lugs is minimal. To ensure that they will be secured in position - even during assembly - it is particularly preferable that each interference-suppression element be inserted into a support-member seat countersunk axially into the support member. To brace the interference-suppression element in question in radial direction, in circumferential direction and in axial direction, the bounding walls of such a seat are disposed opposite the radial inner and outer faces, the two end faces and one side face of the interference-suppression element. It is particularly preferable for each of these seats to be bounded in radially inward and circumferential direction by a ribbed ring and in radially outward direction by molding-compound projections of the support member. It is to be pointed out in this regard that, at least in the case in which the contact bridges are each spatially disposed between two mutually adjacent interference-suppression elements in the manner explained hereinabove, the individual seats for the interference-suppression elements are connected to one another by installation spaces for the contact bridges, the configuration of the installation spaces being matched to the shape of the contact bridges. Although this is advantageous, it is not absolutely necessary, if the contact bridges, as also explained hereinabove, are disposed in a plane axially offset relative to the interference-suppression elements and are connected to the associated interference-suppression elements in the region of lateral, or in other words axially disposed contact faces. As regards the manufacture of commutators according to the present invention, it is based on the method known as such and used in the relevant industry for the manufacture of a support member and of conductor segments provided with commutator blanks and embedded therein. To this extent the invention corresponds to the sufficiently known prior art, and so no further explanations are needed. In a departure from the previously employed method used for manufacture of known commutators, however, there are molded, during manufacture of the support member, seats disposed in the end faces thereof to accommodate the interference- suppression elements and if necessary installation spaces to accommodate the contact bridges connecting these seats to one another. As a rule, subsequent assembly of the individual interference-suppression elements and of the same number of contact bridges takes place in two separate, successive steps. In this sense, the prefabricated interference-suppression elements are first inserted into the said seats in the course of the further manufacturing process; thereafter the prefabricated contact bridges are attached in such a way that they each connect two mutually adjacent interference-suppression elements and one conductor segment in electrically conductive manner. For this purpose, the contact bridges can be soldered or adhesively bonded in the region of their leg to the two respective associated interference-suppression elements and in the region of the foot portion to the respective associated conductor segment. In this regard it is favorable to apply solder or adhesive onto the contact bridges, in the region of their subsequent electrically conductive connections to the interference-suppression elements and to the conductor segments, before they are attached. If the contact bridges are manufactured by being punched out of a plane sheet strip, as was explained hereinabove, their configuration during punching preferably corresponds to their configuration in the commutator to be manufactured. After these contact bridges have been punched out of the sheet strip, they are pressed back into it again, so that the sheet strip constitutes an assembly aid for the contact bridges. After the interference-suppression elements have been inserted into the seats, all contact bridges are transferred together onto the commutator blank, by being pressed out of the sheet strip into the installation spaces, if such are provided. In this technique, any solder or adhesive to be used is preferably applied onto the contact bridges after they have been pressed back into the sheet strips. The present invention will be explained in more detail hereinafter with reference to three preferred practical examples illustrated in the accompanying drawing, wherein Fig. 1 shows an axial section through a first embodiment of a drum commutator constructed according to the present invention, Fig. 2 shows a view from above of the end of the drum commutator according to Fig. 1, Fig. 3 shows a detail, in an enlarged perspective view, of the end face shown in Fig. 1 of the drum commutator according to Figs. 1 and 2, Fig. 4 shows an axial section through a second embodiment of a drum commutator constructed according to the present invention, Fig. 5 shows a view from above of the end of the drum commutator according to Fig. 4, Fig. 6 shows a detail, in an enlarged perspective view of the end face shown in Fig. 4 of the drum commutator according to Figs. 4 and 5, and Fig. 7 shows a perspective view of a flat commutator constructed according to the present invention, with carbon running surface. The drum commutator illustrated in Figs. 1 to 3 contains as essential components a support member 1 made of insulating molding compound and ten conductor segments 3, which are disposed evenly around commutator axis 2 and whose cylindrical circumferential faces define brush running surface 4. Support member 1 is provided with a bore 5 concentric with axis 2 in order to mount the commutator on a rotor shaft (not illustrated). Armature parts 6 of conductor segments 3 are embedded in the molding compound of support member 1 in order to anchor the conductor segments securely even at high speeds, despite the centripetal forces then occurring. At the ends of conductor segments 3 there are provided terminal lugs 7, which function in a manner known as such as the terminals of the winding wires on the commutator. In the scope explained in the foregoing, the commutator according to Figs. 1 to 3 corresponds to the long-known prior art, and so no further explanations are needed for understanding in this' regard. In the region of end face 8 opposite terminal lugs 7, the commutator is provided with an interference-suppression device 9. This comprises ten individual, parallelepiped interference- suppression elements 10 of ceramic material disposed evenly around commutator axis 2, as well as ten contact bridges 11. These interference-suppression elements 10 are disposed at breaks' relative to conductor segments 3. Each has a capacitor function and is provided on two mutually opposite - in the circumferential direction with respect to the installation position in the commutator - end faces with metallized films 12, which represent contact poles 13 of the interference-suppression element in question. Each interference-suppression element 10 is housed in a pocket-like seat 14 of support member 1. Each seat 14 is bounded in radially inward and circumferential direction by a circumferential face 15 and two ribs 16 of a ribbed ring 17, which is part of support member 1; in radially outward direction, molding-compound projections 18 of support member 1 bound the respective seats 14 for interference-suppression elements 10. Two conductor segments 3 bear against the outside of each molding-compound projection 18; air gaps 19, which respectively insulate two adjacent conductor segments 3 from one another, extend into molding-compound projections 18. Contact bridges 11 are each disposed spatially between two mutually adjacent interference- suppression elements 10 and are connected to the associated interference-suppression elements in the region of end-face contact poles 13. They each comprise a metal strip, which is multiply bent to form two legs 20 and a foot portion 21 (Fig. 3). In this sense the basic form of the contact bridges can be described as substantially V-shaped. The multiple bends of contact bridges 11 means that, on the one hand, legs 21 can bear against contact poles 13 of parallelepiped interference-suppression elements 10, and that, on the other hand, elastic flexibility of the contact bridges is achieved both in circumferential direction and in radial direction. Contact bridges 11 are firmly connected to interference-suppression elements 10 via one soldered joint 22 each in the region of legs 20 and to the respective associated conductor segment 3, at the radial inner side thereof, via a soldered joint 23 in the region of foot portion 21. Seats 14 for interference- suppression elements 10 are connected to one another by installation spaces 24 for contact bridges 11, which spaces are configured such that they do not hinder free deformation of contact bridges 11. As regards its essential geometric features, the second embodiment of the inventive commutator illustrated in Figs. 4 to 6 corresponds to the embodiment according to Figs. 1 to 3. In order to avoid repetitions, reference is made to the foregoing explanations. Nevertheless, interference-suppression device 9' in the commutator according to Figs. 4 to 6 has geometry substantially different from that in the case of the commutator according to Figs. 1 to 3. In this case contact bridges 11' are made of plane metal flat stock; the form of contact bridges 11' corresponds approximately to that of a horseshoe forming the two legs 20', with a foot portion 21' attached thereto in the apex. Contact bridges 11' are disposed in a plane offset axially relative to parallelepiped interference-suppression elements 10', and their legs 20' bear on interference-suppression elements 10' in the respective region of metallized contact faces 25 disposed laterally thereon, or in other words in an axial plane of the commutator. There, contact bridges 11' are firmly connected to interference-suppression elements 10' via soldered joints 26. Conductor segments 3 are each provided on their inside with a slot-like recess 27, in which the associated contact bridge 11' engages with its foot portion 21'. At the inner end of recess 27 there is formed a bearing surface 27a for the associated contact bridge 11'. Contact bridges 11' and conductor segments 3 are each connected firmly to one another by means of a soldered joint 28. {-' In this embodiment also, seats 14' for interference-suppression elements 10' are connected to one another via installation spaces 24' for contact bridges 11', installation spaces 24' for the contact bridges having, by virtue of the axial offset of interference-suppression elements 10' and contact bridges 11', a smaller depth than seats 14' for interference-suppression elements 10'. Expedient geometries of flat commutators designed according to the invention can also be derived directly from the practical examples illustrated in drawings and explained in the foregoing, in each case for a drum commutator. A practical example for such a flat commutator is illustrated in Fig. 7. In a manner known in itself, this flat commutator comprises a support member 1" made of molding compound and eight conductor segments 3" embedded therein. A carbon segment 29 is connected to each conductor segment 3" in electrically conductive manner, the end faces of the carbon segments defining brush running surface 4". Terminal lugs 7" are disposed on conductor segments 3" on the side of the commutator opposite brush running surface 4". The commutator is also provided on its side opposite brush running surface 4" with an interference-suppression device 9". This comprises eight substantially parallelepiped interference-suppression elements 10" and eight contact bridges 11", each of which is connected in electrically conductive manner to the two adjacent interference-suppression elements 10" as" well as to the associated conductor segment 3". Interference-suppression elements 10" are inserted into corresponding seats 14", which are molded into support member 1". Contact bridges 11" are inserted into installation spaces 24", each of which connects two adjacent seats 14" to one another, but whose depth compared with seats 14" is smaller by the thickness of interference-suppression elements 10". Incidentally, interference-suppression device 9" implemented in the flat commutator illustrated in Fig. 7 has a structure corresponding to that of the interference-suppression device of the drum commutator according to Figs. 4 to 6. In order to avoid repetitions, reference is made to the explanations concerning that commutator. The same applies with regard to manufacture of the commutator. We Claim: 1. A commutator for an electric machine, comprising a support member (1, 1") made from insulating molding compound, a plurality of metal conductor segments (3, 3"), disposed thereon in evenly spaced manner around the commutator axis (2), with terminal elements disposed thereon for a rotor winding, and an interference-suppression device (9, 9', 9"), to which the conductor segments (3, 3") are connected in electrically conductive manner, wherein the interference-suppression device (9, 9', 9") comprises a number, corresponding to the number of conductor segments (3, 3"), of individual interference- suppression elements (10, 10', 10") disposed around the commutator axis (2), and an equally large number of contact bridges (11, 11', 11"), each of which is connected to an associated conductor segment in electrically conductive manner and connects two mutually adjacent interference-suppression elements (10, 10', 10") to one another and to the associated conductor segment in electrically conductive manner, characterized in that each contact bridge (11, 11', 11") is provided with two inwardly directed legs (20, 20'), which are flexible relative to one another in circumferential direction and are connected to the two associated interference- suppression elements in electrically conductive manner, and with one outwardly directed foot portion (21, 21'), which is connected to the associated conductor segment in. electrically conductive manner, the contact bridges (11, 11', 11") being soldered or adhesively bonded in the region of their leg (20, 20') to the associated interference-suppression elements (10, 10', 10") and in the region of their foot portions (21,21', 21") to the associated conductor segments (3, 3"). 2. A commutator as claimed in claim 1, wherein the interference- suppression elements (10, 10', 10") are constructed as parallelepiped multi-layer capacitors. 3. A commutator as claimed in claim 1, wherein the interference-suppression elements (10, 10', 10") are disposed around the commutator axis (2) in a manner equally spaced along the edges of a regular polygon. 4. A commutator as claimed in claim 1, wherein each interference- suppression element (10, 10', 10") is inserted into a seat (14, 14', 14") of the support member (1, 1") that defines the location of the interference- suppression element in question in radial direction and in circumferential direction. 5. A commutator as claimed in claim 4, wherein each seat (14, 14', 14") is bounded in radially inward and circumferential direction by a ribbed ring (17, 17") and in radially outward direction by molding-compound projections (18, 18") of the support member (1, 1"). 6. A commutator as claimed in claim 4, wherein the seats (14, 14', 14") for the interference-suppression elements (10, 10', 10") are connected to one another by installation spaces (24, 24', 24") for the contact bridges (11, 11', 11"). 7. A commutator as claimed in claim 1, wherein the contact bridges (11) are each disposed spatially between two mutually adjacent interference-suppression elements (10) and are connected to the associated interference- suppression elements in the region of contact poles (13) at the ends thereof. 8. A commutator as claimed in claim 7, wherein the contact bridges (11) are made of a bent metal strip. 9. A commutator as claimed in claim 1, wherein the contact bridges (11', 11") are disposed in a plane axially offset relative to the interference-suppression elements (10', 10") and are connected to the associated interference- suppression elements in the region of laterally disposed contact faces (25). 10. A commutator as claimed in claim 9, wherein the contact bridges (11', 11") are substantially horseshoe-shaped and are made of plane metal flat stock, in particular by being punched out of a sheet. 11. A commutator as claimed in claim 1, wherein the contact bridges (11, 11', 11") are made of copper, brass or an alloy containing these metals. 12. A commutator as claimed in claim 1, wherein the conductor segments (3, 3") are provided on their radial insides with recesses (27), in which the foot portions (21') of the contact bridges (11', 11") engage. 13. A commutator as claimed in claim 1, wherein the contact bridges (11, 11', 11") are soldered or adhesively bonded in the region of their foot portions (21, 21', 21") to the associated conductor segments (3, 3"). 14. A commutator as claimed in claim 1, wherein it is constructed as a drum commutator with a cylindrical brush running surface (4). 15. A commutator as claimed in claim 14, wherein the brush running surface (4) is extended in axial direction beyond the interference-suppression device (9, 9'), the radial thickness of the conductor segments (3) under the brush running surface (4) being greater than 0.5 mm even in the region of the interference- suppression device (9, 9'). 16. A commutator as claimed in claim 14, wherein the interference-suppression device (9, 9') is disposed at the end face of the commutator opposite the terminal elements (7) for the rotor winding. 17. A commutator as claimed in claim 1, wherein it is constructed as a flat commutator with a plane brush running surface (4"), wherein the interference- suppression device (9") is disposed at the end face of the commutator remote from the brush running surface. 18. A method for manufacturing a commutator as claimed in claim 1, comprising the steps of: manufacturing a commutator blank, provided with the support member (1, 1") and the conductor segments (3, 3"), and having seats (14, 14', 14") disposed in the end faces of the support member to accommodate the interference-suppression elements (10, 10', 10"); manufacturing a plurality of interference-suppression elements (10, 10', 10"); manufacturing a number, corresponding to the number of interference-suppression elements, of contact bridges (11, 11', 11"), each of which is provided with two legs (20, 20') that are flexible relative to one another and with a foot portion (21, 21'); inserting the interference-suppression elements (10, 10', 10") into the seats (14, 14', 14") of the support member (1, 1"); attaching the contact bridges (11, 11', 11") in such a way that they each connect two mutually adjacent interference-suppression elements (10, 10', 10") and one conductor segment (3, 3") in electrically conductive manner, by virtue of being soldered or adhesively bonded in the region of their leg (20, 20') to the two associated interference-suppression elements (10, 10', 10") and in the region of their foot portion (21, 21') to the associated conductor segment (3, 3"). 19. A method as claimed in claim 18, wherein solder or adhesive is applied onto the contact bridges (11, 11', 11"), in the region of their subsequent electrically conductive connections to the interference- suppression elements (10, 10', 10") and to the conductor segments (3, 3"), before they are attached. 20. A method as claimed in claim 18, wherein the contact bridges (11', 11") are manufactured by being punched out of a plane sheet strip. 21. A method as claimed in claim 20, wherein the configuration of the contact bridges (11', 11") during punching corresponds to their configuration in the commutator to be manufactured, the contact bridges (11", 11") being pressed back into the sheet strip after they have been punched out of it, and are mounted together by being pressed out of the sheet strip onto the commutator blank, after the interference-suppression elements (10', 10") have been inserted into the seats (14', 14"). 22. A method as claimed in claim 21, wherein the solder or adhesive is applied onto the contact bridges (11, 11', 11") after they have been pressed back into the sheet strips. ABSTRACT TITLE: COMMUTATOR FOR AN ELECTRIC MACHINE The invention related to a commutator for an electric machine, comprising a support member (1, 1") made from insulating molding compound, a plurality of metal conductor segments (3, 3"), disposed thereon in evenly spaced manner around the commutator axis (2), with terminal elements disposed thereon for a rotor winding, and an interference-suppression device (9, 9', 9"), to which the conductor segments (3, 3") are connected in electrically conductive manner, wherein the interference-suppression device (9, 9', 9") comprises a number, corresponding to the number of conductor segments (3, 3"), of individual interference- suppression elements (10, 10', 10") disposed around the commutator axis (2), and an equally large number of contact bridges (11, 11', 11"), each of which is connected to an associated conductor segment in electrically conductive manner and connects two mutually adjacent interference- suppression elements (10, 10', 10") to one another and to the associated conductor segment in electrically conductive manner. Each contact bridge (11, 11', 11") is provided with two inwardly directed legs (20, 20'), which are flexible relative to one another in circumferential direction and are connected to the two associated interference- suppression elements in electrically conductive manner, and with one outwardly directed foot portion (21, 21'), which is connected to the associated conductor segment in electrically conductive manner, the contact bridges (11, 11', 11") being soldered or adhesively bonded in the region of their leg (20, 20') to the associated interference-suppression elements (10, 10', 10") and in the region of their foot portions (21,21', 21") to the associated conductor segments (3, 3").

Full Text

Commutator for an electric machine
The present invention relates to a commutator for an electric machine, comprising a support
member made from an insulating molding compound, a plurality of metal conductor segments
disposed thereon in evenly spaced manner around the commutator axis, with terminal elements
disposed thereon for a rotor winding, and an interference-suppression device, to which the
conductor segments are connected in electrically conductive manner.
Commutators of various designs (drum commutators, flat commutators) are known in diverse
configurations. To an increasing extent, commutators are being equipped with spark-suppression
devices (interference-suppression devices), especially if they are designed as drum commutators,
in order to prevent sparking at the commutator from impairing electronic assemblies disposed in
physical proximity to the electric machine in question that is equipped with the commutator.
Heretofore such interference-suppression devices have often been designed as annular
interference-suppression disks, which are made of a material having voltage-dependent resistance
and which are connected in electrically conductive manner to the conductor segments. In such
cases the corresponding interference-suppression disk can be mounted on the one hand radially
outward of the brush running surface (for example, see US 5895990 A, US 5717270 A,'
GB 2183933 A and US 5796203 A), or on the other hand radially inward of the brush running
surface (for example, see US 6285106 B1 and DE 19953231 A1). Also known are special forms
of interference-suppressed drum commutators, in which the conductor segments are disposed on
the outside of cylindrical interference-suppression sleeves (see DE 2055648 and DE 3614869

C2). Finally, EP 364292 B1 describes a drum commutator with a support member made of
thermoplastic material, in which a heat-resistant reinforcing ring is provided radially underneath
the terminal lug, which ring is provided with an interference-suppressing coating or can be
disposed adjacent to a separate interference-suppression ring; in common with the separate
interference-suppression ring that may be provided in addition, this reinforcing ring is mounted
on a seat of the support member, where it is retained by straps protruding from the conductor
segments.
Regardless of the respective specific arrangement of interference-suppression disks, the
considerable costs for the interference-suppression device constitute a disadvantage in all
commutators whose interference-suppression device comprises an annular interference-
suppression disk, since the ceramic material from which such interference-suppression disks are
usually made is very expensive; moreover, large quantities of waste are produced in the
manufacture of annular interference-suppression disks, since they are cut out of a multi-layer
metal-ceramic plate.
Incidentally, among the known drum commutators that are interference-suppressed by using an
interference-suppression disk, only compact drum commutators with interference-suppression
disks disposed radially inward of the brush running surface are feasible for many practical
applications, because the space available for the respective commutator is limited. A further
problem of such drum commutators with interference-suppression rings disposed radially inward
of the brush running surface results from the different thermal expansion behavior of the
interference-suppression disk, which is usually made of ceramic material, compared with the

other components of the commutators in question. Specifically, if the thermal stresses are large
enough, they can cause premature failure of commutators due to broken interference-suppression
disks and/or destroyed connections between the conductor segments and the interference-
suppression disks, unless special precautions are taken. As a solution to this problem, it is
proposed in DE 19953231 A1 that the interference-suppression disk be joined to the support
member by means of an elastic adhesive and that the conductor segments be connected to the
interference-suppression disk via thin wires, which are soldered on the one hand to the terminal
lug of the associated conductor segment and on the other hand to an associated metallization
zone of the interference-suppression disk. In contrast, according to US 6285106 B1, which
discloses a drum commutator of the class in question, there are provided, for electrical contact
between the conductor segments and the interference-suppression disks, leaf springs that are
disposed inside an annular cavity, which is bounded by the support member, the conductor
segments and an annular cover, and in which the interference-suppression disk is also housed.
The leaf springs, which permit different radial thermal insulation of the interference-suppression
disk on the one hand and of the other commutator components on the other hand, can be fixed in
particular to the annular cover.

A particular disadvantage of the two known drum commutators, evaluated in the foregoing, each
with an interference-suppression disk disposed radially inward of the conductor segments is in
particular the high expense of manufacture, which is substantially due to the high manufacturing
costs of the interference-suppression disk (see hereinabove) and hampers the competitiveness of
the drum commutators in question.

Accordingly, the problem underlying the present invention is to provide a long-lived, reliable,
interference-suppressed commutator of the class in question, which commutator, in view of its
suitability for mass production, can be made at low costs with little manufacturing expense. A
particularly preferable object is to manufacture an interference-suppressed commutator with
substantially the same dimensions as a non-interference-suppressed commutator of the same
design.
This object is achieved according to the present invention by the fact that the interference-
suppression device comprises a number of individual interference-suppression elements
corresponding to the number of conductor segments and an equally large number of contact
bridges, each of which connects two mutually adjacent interference-suppression elements to one
another in electrically conductive manner, each contact bridge being provided with two inwardly
directed legs, which are flexible relative to one another in circumferential direction and are
connected to the two associated interference-suppression elements in electrically conductive
manner, and with one outwardly directed foot portion, which is connected to the associated
conductor segment in electrically conductive manner.
A first characteristic feature of the commutator according to the present invention is therefore
that the interference-suppression device comprises not an annular interference-suppression disk
but instead a number of individual interference-suppression elements corresponding to the
number of conductor segments; such individual interference-suppression elements, which as
multi-layer capacitors can have in particular a parallelepiped shape, can be made from a multi-
layer metal-ceramic plate without any kind of cutting and thus in particularly inexpensive

manner. Furthermore, it is characteristic for the inventive commutator that two mutually adjacent
interference-suppression elements are respectively connected to one another in electrical manner
via one contact bridge each, the two legs at which the contact bridge in question is connected to
the two interference-suppression elements in electrically conductive manner being designed to be
flexible relative to one another in circumferential direction. In this sense, "flexible" means that
the force necessary for deformation of the contact bridges in circumferential direction is smaller
than the strength of the joints of the contact bridges with the interference-suppression elements.
'The interference-suppression device characterizing the inventive commutator is composed in this
way of individual interference-suppression elements and contact bridges, which are joined
together in alternating sequence to form a ring structure. The flexibility of the contact bridges
then has the effect that the ring structure in question is not rigid; to the contrary, the ring structure
is flexible as a whole in circumferential direction, and so it can compensate for changes of the
dimensions of the commutator caused by thermal expansion. Such manufacture of the contact
bridges as separate components ensures that they can be selectively matched - largely without
restriction - to the described function, by the fact that the material choice and dimensions are
optimized in terms of flexibility and strength of the ring structure of the interference-suppression
device as well as the joint of the contact bridges with the interference-suppression elements.
The deformability of the contact bridges in their installation situation is based on the one hand on
their flexible construction and on the other hand on the fact that the legs of the contact bridges
are free, meaning that that they can be deformed without hindrance by adjoining components of
the commutator during the normal thermal-expansion behavior of the commutator.

As "electrically conductive connections" of the contact bridges with the contact poles or contact
faces of the respective two adjacent interference-suppression elements, there can be considered,
in the scope of the present invention, several electrically conductive contacting arrangements,
provided they are also suitable for transmission of mechanical forces; in particular, a special
joining material such as solder is preferably used (see hereinafter), but in any case it is not
necessarily provided for all embodiments of the invention. Direct and indirect contacting of the
contact bridges with the interference-suppression elements without having disadvantageous
effects on the useful life of the commutator is achieved by the fact that the contact bridges can
deform to compensate for different thermal-expansion behavior of the individual commutator
components.
By application of the present invention, therefore, it is obviously possible, by virtue of the
combinations of the features characteristic of inventive commutators, to manufacture extremely
inexpensive, long-lived and compact interference-suppressed commutators with minimal
production expense. In this regard, the present invention is applicable for various commutator
designs, specifically regardless of the construction of the brush running surface. Commutators
with carbon running surfaces, such as are used for operating fuel pumps for motor vehicles, can
be constructed particularly advantageously according to the present invention.
Particularly preferably, the contact bridges are permanently connected to the interference-
suppression elements by means of simple soldered joints or even joints formed with electrically
conductive adhesive in the region of the contact points. The situation is analogous for the
connection of the contact bridges to the respective conductor segments in the region of the foot

portion in question that contacts the conductor segments. In this regard, suitable metallization
(such as a coating of silver or tin) of the interference-suppression elements in the region of their
contact poles and/or of the contact bridges in the region of the legs may prove favorable; and in
this regard it is also favorable for the contact bridges to be manufactured from copper, brass or an
alloy containing these metals. Such permanent connections of the contact bridges to the
interference-suppression elements and/or to the conductor segments, which are subject to only
small mechanical loads due to the flexible construction of the contact bridges in the
circumferential direction, as is the case for the interference-suppression elements themselves,
prove to be particularly advantageous when the inventive commutator is used in a corrosive
environment.
According to another preferred improvement of the inventive commutator, the interference-
suppression elements are designed as parallelepiped multi-layer capacitors and are disposed
around the commutator axis along the edges of a regular polygon, specifically in a manner in
which each is expediently located at breaks between two mutually adjacent conductor segments.
This in particular favors manufacture of the inventive commutator by a method that is simple and
therefore inexpensive.
Within the scope of the present invention, considerable margin for variation, which can be
exploited in particular as a function of the commutator design, the dimensions and the specific
requirements, is available for the structural design of the contact bridges. In this regard, a first
preferred embodiment of the invention is characterized by the fact that the contact bridges are
each disposed spatially between two mutually adjacent interference-suppression elements and are

connected to the associated interference-suppression elements in the region of contact faces at the
ends thereof. Each of these contact bridges can be made in particular of a bent metal strip, in
which case the basic form of the contact bridges can then be described as substantially V-shaped.
According to another preferred improvement of the invention, it is provided that the contact
bridges are disposed in a plane axially offset relative to the interference-suppression elements
and are connected to the associated interference-suppression elements in the region of laterally
disposed contact faces. In this case, the contact bridges, whose shape may resemble in particular
a horseshoe with a foot portion attached thereto, may be made of plane metal flat stock (such as
sheet), which proves to be particularly favorable in terms of costs. Such a construction of the
contact bridges also has advantageous effects on the way in which commutators are
manufactured according to the present invention.

Whereas the concept underlying the present invention can be advantageously adopted for
commutators with different designs (drum commutators, flat commutators) and brush running
surfaces of different constructions (such as those directly on metal conductor segments or those
having carbon running surfaces), the advantages achievable with the present invention are
particularly marked in the case that the commutator is designed as a drum commutator with a
cylindrical brush running surface, since the invention permits a particularly compact design, now
that the brush running surface can be extended in axial direction beyond the interference-
suppression device.
As regards the construction of the terminal elements, yet another preferred improvement of the
invention is characterized in that the terminal elements are designed as terminal lugs, which in
the case of design of the commutator as a drum commutator are disposed in the region of the end
face of the commutator opposite the interference-suppression device. In this case, the risk of
damage to the connections of the contact bridges to the conductor segments as well as to the
interference-suppression elements during welding of the rotor winding onto the terminal lugs is
minimal.
To ensure that they will be secured in position - even during assembly - it is particularly
preferable that each interference-suppression element be inserted into a support-member seat
countersunk axially into the support member. To brace the interference-suppression element in
question in radial direction, in circumferential direction and in axial direction, the bounding walls
of such a seat are disposed opposite the radial inner and outer faces, the two end faces and one
side face of the interference-suppression element. It is particularly preferable for each of these

seats to be bounded in radially inward and circumferential direction by a ribbed ring and in
radially outward direction by molding-compound projections of the support member.
It is to be pointed out in this regard that, at least in the case in which the contact bridges are each
spatially disposed between two mutually adjacent interference-suppression elements in the
manner explained hereinabove, the individual seats for the interference-suppression elements are
connected to one another by installation spaces for the contact bridges, the configuration of the
installation spaces being matched to the shape of the contact bridges. Although this is
advantageous, it is not absolutely necessary, if the contact bridges, as also explained hereinabove,
are disposed in a plane axially offset relative to the interference-suppression elements and are
connected to the associated interference-suppression elements in the region of lateral, or in other
words axially disposed contact faces.
As regards the manufacture of commutators according to the present invention, it is based on the
method known as such and used in the relevant industry for the manufacture of a support
member and of conductor segments provided with commutator blanks and embedded therein. To
this extent the invention corresponds to the sufficiently known prior art, and so no further
explanations are needed. In a departure from the previously employed method used for
manufacture of known commutators, however, there are molded, during manufacture of the
support member, seats disposed in the end faces thereof to accommodate the interference-
suppression elements and if necessary installation spaces to accommodate the contact bridges
connecting these seats to one another. As a rule, subsequent assembly of the individual
interference-suppression elements and of the same number of contact bridges takes place in two

separate, successive steps. In this sense, the prefabricated interference-suppression elements are
first inserted into the said seats in the course of the further manufacturing process; thereafter the
prefabricated contact bridges are attached in such a way that they each connect two mutually
adjacent interference-suppression elements and one conductor segment in electrically conductive
manner. For this purpose, the contact bridges can be soldered or adhesively bonded in the region
of their leg to the two respective associated interference-suppression elements and in the region
of the foot portion to the respective associated conductor segment.
In this regard it is favorable to apply solder or adhesive onto the contact bridges, in the region of
their subsequent electrically conductive connections to the interference-suppression elements and
to the conductor segments, before they are attached.
If the contact bridges are manufactured by being punched out of a plane sheet strip, as was
explained hereinabove, their configuration during punching preferably corresponds to their
configuration in the commutator to be manufactured. After these contact bridges have been
punched out of the sheet strip, they are pressed back into it again, so that the sheet strip
constitutes an assembly aid for the contact bridges. After the interference-suppression elements
have been inserted into the seats, all contact bridges are transferred together onto the commutator
blank, by being pressed out of the sheet strip into the installation spaces, if such are provided. In
this technique, any solder or adhesive to be used is preferably applied onto the contact bridges
after they have been pressed back into the sheet strips.
The present invention will be explained in more detail hereinafter with reference to three

preferred practical examples illustrated in the accompanying drawing, wherein
Fig. 1 shows an axial section through a first embodiment of a drum
commutator constructed according to the present invention,
Fig. 2 shows a view from above of the end of the drum commutator
according to Fig. 1,
Fig. 3 shows a detail, in an enlarged perspective view, of the end face
shown in Fig. 1 of the drum commutator according to Figs. 1 and 2,
Fig. 4 shows an axial section through a second embodiment of a drum
commutator constructed according to the present invention,
Fig. 5 shows a view from above of the end of the drum commutator
according to Fig. 4,
Fig. 6 shows a detail, in an enlarged perspective view of the end face
shown in Fig. 4 of the drum commutator according to Figs. 4 and 5, and
Fig. 7 shows a perspective view of a flat commutator constructed
according to the present invention, with carbon running surface.

The drum commutator illustrated in Figs. 1 to 3 contains as essential components a support
member 1 made of insulating molding compound and ten conductor segments 3, which are
disposed evenly around commutator axis 2 and whose cylindrical circumferential faces define
brush running surface 4. Support member 1 is provided with a bore 5 concentric with axis 2 in
order to mount the commutator on a rotor shaft (not illustrated).
Armature parts 6 of conductor segments 3 are embedded in the molding compound of support
member 1 in order to anchor the conductor segments securely even at high speeds, despite the
centripetal forces then occurring. At the ends of conductor segments 3 there are provided
terminal lugs 7, which function in a manner known as such as the terminals of the winding wires
on the commutator.
In the scope explained in the foregoing, the commutator according to Figs. 1 to 3 corresponds to
the long-known prior art, and so no further explanations are needed for understanding in this'
regard.
In the region of end face 8 opposite terminal lugs 7, the commutator is provided with an
interference-suppression device 9. This comprises ten individual, parallelepiped interference-
suppression elements 10 of ceramic material disposed evenly around commutator axis 2, as well
as ten contact bridges 11. These interference-suppression elements 10 are disposed at breaks'
relative to conductor segments 3. Each has a capacitor function and is provided on two mutually
opposite - in the circumferential direction with respect to the installation position in the
commutator - end faces with metallized films 12, which represent contact poles 13 of the

interference-suppression element in question. Each interference-suppression element 10 is
housed in a pocket-like seat 14 of support member 1. Each seat 14 is bounded in radially inward
and circumferential direction by a circumferential face 15 and two ribs 16 of a ribbed ring 17,
which is part of support member 1; in radially outward direction, molding-compound projections
18 of support member 1 bound the respective seats 14 for interference-suppression elements 10.
Two conductor segments 3 bear against the outside of each molding-compound projection 18; air
gaps 19, which respectively insulate two adjacent conductor segments 3 from one another, extend
into molding-compound projections 18.
Contact bridges 11 are each disposed spatially between two mutually adjacent interference-
suppression elements 10 and are connected to the associated interference-suppression elements in
the region of end-face contact poles 13. They each comprise a metal strip, which is multiply bent
to form two legs 20 and a foot portion 21 (Fig. 3). In this sense the basic form of the contact
bridges can be described as substantially V-shaped. The multiple bends of contact bridges 11
means that, on the one hand, legs 21 can bear against contact poles 13 of parallelepiped
interference-suppression elements 10, and that, on the other hand, elastic flexibility of the contact
bridges is achieved both in circumferential direction and in radial direction. Contact bridges 11
are firmly connected to interference-suppression elements 10 via one soldered joint 22 each in
the region of legs 20 and to the respective associated conductor segment 3, at the radial inner side
thereof, via a soldered joint 23 in the region of foot portion 21. Seats 14 for interference-
suppression elements 10 are connected to one another by installation spaces 24 for contact
bridges 11, which spaces are configured such that they do not hinder free deformation of contact
bridges 11.

As regards its essential geometric features, the second embodiment of the inventive commutator
illustrated in Figs. 4 to 6 corresponds to the embodiment according to Figs. 1 to 3. In order to
avoid repetitions, reference is made to the foregoing explanations.
Nevertheless, interference-suppression device 9' in the commutator according to Figs. 4 to 6 has
geometry substantially different from that in the case of the commutator according to Figs. 1 to 3.
In this case contact bridges 11' are made of plane metal flat stock; the form of contact bridges
11' corresponds approximately to that of a horseshoe forming the two legs 20', with a foot
portion 21' attached thereto in the apex. Contact bridges 11' are disposed in a plane offset axially
relative to parallelepiped interference-suppression elements 10', and their legs 20' bear on
interference-suppression elements 10' in the respective region of metallized contact faces 25
disposed laterally thereon, or in other words in an axial plane of the commutator. There, contact
bridges 11' are firmly connected to interference-suppression elements 10' via soldered joints 26.
Conductor segments 3 are each provided on their inside with a slot-like recess 27, in which the
associated contact bridge 11' engages with its foot portion 21'. At the inner end of recess 27
there is formed a bearing surface 27a for the associated contact bridge 11'. Contact bridges 11'
and conductor segments 3 are each connected firmly to one another by means of a soldered joint
28.
{-'
In this embodiment also, seats 14' for interference-suppression elements 10' are connected to one
another via installation spaces 24' for contact bridges 11', installation spaces 24' for the contact
bridges having, by virtue of the axial offset of interference-suppression elements 10' and contact

bridges 11', a smaller depth than seats 14' for interference-suppression elements 10'.
Expedient geometries of flat commutators designed according to the invention can also be
derived directly from the practical examples illustrated in drawings and explained in the
foregoing, in each case for a drum commutator. A practical example for such a flat commutator
is illustrated in Fig. 7. In a manner known in itself, this flat commutator comprises a support
member 1" made of molding compound and eight conductor segments 3" embedded therein. A
carbon segment 29 is connected to each conductor segment 3" in electrically conductive manner,
the end faces of the carbon segments defining brush running surface 4". Terminal lugs 7" are
disposed on conductor segments 3" on the side of the commutator opposite brush running surface
4".
The commutator is also provided on its side opposite brush running surface 4" with an
interference-suppression device 9". This comprises eight substantially parallelepiped
interference-suppression elements 10" and eight contact bridges 11", each of which is connected
in electrically conductive manner to the two adjacent interference-suppression elements 10" as"
well as to the associated conductor segment 3". Interference-suppression elements 10" are
inserted into corresponding seats 14", which are molded into support member 1". Contact
bridges 11" are inserted into installation spaces 24", each of which connects two adjacent seats
14" to one another, but whose depth compared with seats 14" is smaller by the thickness of
interference-suppression elements 10". Incidentally, interference-suppression device 9"
implemented in the flat commutator illustrated in Fig. 7 has a structure corresponding to that of
the interference-suppression device of the drum commutator according to Figs. 4 to 6. In order to

avoid repetitions, reference is made to the explanations concerning that commutator. The same
applies with regard to manufacture of the commutator.

We Claim:
1. A commutator for an electric machine, comprising a support member (1,
1") made from insulating molding compound, a plurality of metal
conductor segments (3, 3"), disposed thereon in evenly spaced manner
around the commutator axis (2), with terminal elements disposed thereon
for a rotor winding, and an interference-suppression device (9, 9', 9"), to
which the conductor segments (3, 3") are connected in electrically
conductive manner, wherein the interference-suppression device (9, 9',
9") comprises a number, corresponding to the number of conductor
segments (3, 3"), of individual interference- suppression elements (10,
10', 10") disposed around the commutator axis (2), and an equally large
number of contact bridges (11, 11', 11"), each of which is connected to an
associated conductor segment in electrically conductive manner and
connects two mutually adjacent interference-suppression elements (10,
10', 10") to one another and to the associated conductor segment in
electrically conductive manner, characterized in that each contact bridge
(11, 11', 11") is provided with two inwardly directed legs (20, 20'), which
are flexible relative to one another in circumferential direction and are
connected to the two associated interference- suppression elements in

electrically conductive manner, and with one outwardly directed foot portion
(21, 21'), which is connected to the associated conductor segment in.
electrically conductive manner, the contact bridges (11, 11', 11") being
soldered or adhesively bonded in the region of their leg (20, 20') to the
associated interference-suppression elements (10, 10', 10") and in the region
of their foot portions (21,21', 21") to the associated conductor segments (3,
3").
2. A commutator as claimed in claim 1, wherein the interference- suppression
elements (10, 10', 10") are constructed as parallelepiped multi-layer
capacitors.
3. A commutator as claimed in claim 1, wherein the interference-suppression
elements (10, 10', 10") are disposed around the commutator axis (2) in a
manner equally spaced along the edges of a regular polygon.
4. A commutator as claimed in claim 1, wherein each interference-
suppression element (10, 10', 10") is inserted into a seat (14, 14', 14") of the
support member (1, 1") that defines the location of the interference-
suppression element in question in radial direction and in circumferential
direction.

5. A commutator as claimed in claim 4, wherein each seat (14, 14', 14") is
bounded in radially inward and circumferential direction by a ribbed ring (17,
17") and in radially outward direction by molding-compound projections (18,
18") of the support member (1, 1").
6. A commutator as claimed in claim 4, wherein the seats (14, 14', 14") for the
interference-suppression elements (10, 10', 10") are connected to one another
by installation spaces (24, 24', 24") for the contact bridges (11, 11', 11").
7. A commutator as claimed in claim 1, wherein the contact bridges (11) are
each disposed spatially between two mutually adjacent interference-suppression
elements (10) and are connected to the associated interference- suppression
elements in the region of contact poles (13) at the ends thereof.
8. A commutator as claimed in claim 7, wherein the contact bridges (11) are
made of a bent metal strip.
9. A commutator as claimed in claim 1, wherein the contact bridges (11', 11")
are disposed in a plane axially offset relative to the interference-suppression
elements (10', 10") and are connected to the associated interference-
suppression elements in the region of laterally disposed contact faces (25).

10. A commutator as claimed in claim 9, wherein the contact bridges (11', 11")
are substantially horseshoe-shaped and are made of plane metal flat stock, in
particular by being punched out of a sheet.
11. A commutator as claimed in claim 1, wherein the contact bridges (11, 11',
11") are made of copper, brass or an alloy containing these metals.
12. A commutator as claimed in claim 1, wherein the conductor segments (3,
3") are provided on their radial insides with recesses (27), in which the foot
portions (21') of the contact bridges (11', 11") engage.
13. A commutator as claimed in claim 1, wherein the contact bridges (11, 11',
11") are soldered or adhesively bonded in the region of their foot portions (21,
21', 21") to the associated conductor segments (3, 3").
14. A commutator as claimed in claim 1, wherein it is constructed as a drum
commutator with a cylindrical brush running surface (4).
15. A commutator as claimed in claim 14, wherein the brush running surface (4)
is extended in axial direction beyond the interference-suppression device (9, 9'),
the radial thickness of the conductor segments (3) under the brush running
surface (4) being greater than 0.5 mm even in the region of the interference-
suppression device (9, 9').

16. A commutator as claimed in claim 14, wherein the interference-suppression
device (9, 9') is disposed at the end face of the commutator opposite the
terminal elements (7) for the rotor winding.
17. A commutator as claimed in claim 1, wherein it is constructed as a flat
commutator with a plane brush running surface (4"), wherein the interference-
suppression device (9") is disposed at the end face of the commutator remote
from the brush running surface.
18. A method for manufacturing a commutator as claimed in claim 1, comprising
the steps of:
manufacturing a commutator blank, provided with the support member
(1, 1") and the conductor segments (3, 3"), and having seats (14, 14', 14")
disposed in the end faces of the support member to accommodate the
interference-suppression elements (10, 10', 10");
manufacturing a plurality of interference-suppression elements (10, 10',
10"); manufacturing a number, corresponding to the number of
interference-suppression elements, of contact bridges (11, 11', 11"), each
of which is provided with two legs (20, 20') that are flexible relative to one
another and with a foot portion (21, 21');

inserting the interference-suppression elements (10, 10', 10") into the
seats (14, 14', 14") of the support member (1, 1");
attaching the contact bridges (11, 11', 11") in such a way that they each
connect two mutually adjacent interference-suppression elements (10,
10', 10") and one conductor segment (3, 3") in electrically conductive
manner, by virtue of being soldered or adhesively bonded in the region of
their leg (20, 20') to the two associated interference-suppression elements
(10, 10', 10") and in the region of their foot portion (21, 21') to the
associated conductor segment (3, 3").
19. A method as claimed in claim 18, wherein solder or adhesive is
applied onto the contact bridges (11, 11', 11"), in the region of their
subsequent electrically conductive connections to the interference-
suppression elements (10, 10', 10") and to the conductor segments (3,
3"), before they are attached.
20. A method as claimed in claim 18, wherein the contact bridges (11',
11") are manufactured by being punched out of a plane sheet strip.

21. A method as claimed in claim 20, wherein the configuration of the
contact bridges (11', 11") during punching corresponds to their
configuration in the commutator to be manufactured, the contact bridges
(11", 11") being pressed back into the sheet strip after they have been
punched out of it, and are mounted together by being pressed out of the
sheet strip onto the commutator blank, after the interference-suppression
elements (10', 10") have been inserted into the seats (14', 14").
22. A method as claimed in claim 21, wherein the solder or adhesive is
applied onto the contact bridges (11, 11', 11") after they have been
pressed back into the sheet strips.

ABSTRACT

TITLE: COMMUTATOR FOR AN ELECTRIC MACHINE
The invention related to a commutator for an electric machine, comprising a
support member (1, 1") made from insulating molding compound, a plurality of
metal conductor segments (3, 3"), disposed thereon in evenly spaced manner
around the commutator axis (2), with terminal elements disposed thereon for a
rotor winding, and an interference-suppression device (9, 9', 9"), to which the
conductor segments (3, 3") are connected in electrically conductive manner,
wherein the interference-suppression device (9, 9', 9") comprises a number,
corresponding to the number of conductor segments (3, 3"), of individual
interference- suppression elements (10, 10', 10") disposed around the
commutator axis (2), and an equally large number of contact bridges (11, 11',
11"), each of which is connected to an associated conductor segment in
electrically conductive manner and connects two mutually adjacent interference-
suppression elements (10, 10', 10") to one another and to the associated
conductor segment in electrically conductive manner. Each contact bridge (11,
11', 11") is provided with two inwardly directed legs (20, 20'), which are flexible
relative to one another in circumferential direction and are connected to the two
associated interference- suppression elements in electrically conductive manner,
and with one outwardly directed foot portion (21, 21'), which is connected to the
associated conductor segment in electrically conductive manner, the contact
bridges (11, 11', 11") being soldered or adhesively bonded in the region of their
leg (20, 20') to the associated interference-suppression elements (10, 10', 10")
and in the region of their foot portions (21,21', 21") to the associated conductor
segments (3, 3").

COMMUTATOR FOR AN ELECTRIC MACHINE

Documents:

Inventors:

PCT Conventions: