Stator for an electrical machine

A stator for an electrical machine includes a plurality of coils arranged on a stator yoke, each coil having a pair of ends; a plurality of linking conductors which are electrically insulated from each other, each conductor having a terminal element electrically connected to two ends of two adjacent coils; and a support structure mounted on the stator yoke, the support structure having a receiving channel which holds the linking conductors and a wiring channel into which the terminal elements and the ends of the coils project. The terminal elements and the ends of the coils are electrically connected by conductor bridge elements arranged serially in the wiring channel.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention pertains to a stator for an electrical machine having a stator yoke, coils arranged on the stator yoke, and linking conductors have terminal elements which are each electrically connected to two ends of two respective coils.

2. Description of the Related Art

Known stators for electrical machines have a stator yoke with a number of stator teeth, which carry the electrical winding in the form of, for example, individually wound stator coils of insulated wire. The two ends of each coil are assigned to individual strands and are connected to each other in a predetermined manner by common linking conductors. In the case of a three-phase machine, the stator has three strands and thus at least three linking conductors, each of which is supplied with current with a phase offset of 120°. The linking conductors are wired to a switch box so that the electrical machine can be connected to a power source.

U.S. Pat. No. 6,369,473 discloses a stator for an electrical machine in which the wiring arrangement has electrically insulated linking conductors which are concentric with respect to each other. The terminals which accept the ends of the stator coils are in the form of projections extending from the linking conductors. For each coil end, a separate terminal projection is provided, and as a result of the radial staggering of the linking conductors thus realized here, the connecting points are also in different radial positions. The electrical connections can be realized here by a joining technique such as welding or soldering and/or by simply winding the wire around the terminal projection. The linking conductors are supported against each other and against the stator by interposed strips of insulating material.

Producing welded or soldered connections is highly labor-intensive and therefore expensive. There is also the disadvantage that the process heat introduced during the production of the connections can lead to damage to the insulation between the linking conductors and to the insulation on the winding wires in the area of the coils. As a result, undesirable electrical short-circuits can develop very quickly; these negatively affect the operation of the electrical machine and can even lead to its failure. Damage to the insulation provided between the linking conductors can also interfere with the stability with which the linking conductors are held in position. If they are no longer held in position reliably, they can no longer operate reliably either. Vibrations which can occur during the operation of the electrical machine or which are imposed on it from the outside lead to alternating mechanical loads on the electrical connections of the machine, which can come loose within a very short time. The wrapping of the terminal extensions represents a typical manual process, furthermore, which stands in the way of increasing the efficiency with which stators of this type can be manufactured. Because of the relatively large number of coil ends, there is also considerable danger that they will be connected incorrectly when the stator coils are being connected, that is, that they will be assigned incorrectly to their intended linking conductors. Even if great care is taken, it is still impossible to be 100% certain that all of the connections are made properly during the production of these stators.

U.S. Pat. No. 6,707,186 describes a stator of the general type in question with a wiring arrangement in which the linking conductors are arranged radially with respect to each other and have axially projecting terminals at predetermined positions for establishing connections with the ends of the stator coils. Receiving elements are formed on the winding bodies of the stator coils. The number of receiving elements present at each end of the coil is equal to the number of linking conductors. To establish the desired electrical contact, a coil end is first passed through all of the receiving elements, and then, by introducing one of the terminals between the associated coil end and the linking conductor, an electrical clamping-type of connection is formed. As an alternative to the forming of projecting terminals on the linking conductors, separate plug contacts can also be provided on them, each of which is then inserted into a receiving element to form a clamping-type of connection with an end of a coil.

In the case of a wiring arrangement with three linking conductors, this means that, although the coil ends must first be cut to length for all of the receiving elements, two of the three receiving elements per coil end are not used and remain unoccupied. When the linking conductors are arranged radially as described here, furthermore, the width of the unit is increased in the axial direction, because only the axially projecting terminals fit into the receiving elements, not the linking conductors themselves. This also results in the disadvantage that the linking conductors are mounted on the stator in such a way that they are not protected against vibrations or environmental influences.

SUMMARY OF THE INVENTION

An object of the present invention is to improve the design of a stator of the type described above in such a way that the individual processes involved in producing the wiring arrangement can be accomplished reliably and also so that the linking conductors and the contact points of the coil ends are mounted on the stator in such a way that they are protected.

According to the invention, a support structure mounted on the stator yoke is provided with a receiving area for the linking conductors and a wiring area into which the ends of the coils and the terminal elements project.

Designing a support structure with a receiving area to hold the linking conductors makes it possible, first, to hold the linking conductors reliably in place on the stator under operating conditions. Second, by providing a wiring area insulated from the linking conductors, which is also formed on the support structure, the elements to be wired together are clearly and logically arranged. Thus, as a result of this design, a space-saving structure is provided, which also creates the prerequisite for defect-free wiring work.

It is especially advantageous for the ends of the coils and the terminal elements to project into the wiring area only at spatially predetermined positions, where they are then available for further connecting operations.

A sturdy wiring arrangement almost completely sealed off from the outside can be achieved by designing the receiving area and the wiring area as grooves which are open on one side. Even better protection against external influences such as dust and moisture is obtained by sealing off the receiving area and/or the wiring area with a sealant, which fills up the open ring-shaped space and thus embeds the contact areas present in it.

To achieve the shortest possible conductive connections between the ends of the coils and the linking conductors, it is advantageous to arrange the support structure directly on the coil winding bodies. As a result, the vibrations to which the electrical machine is subjected during operation can be reduced significantly, especially at the electrical contact areas of the wiring arrangement. The support structure can be formed out of individual segments, each of which is formed as an integral part of a winding body. Alternatively, the segments can be separate from the winding bodies, or the structure can be designed as a ring-shaped element.

In an especially advantageous variant, the wiring of the coil ends is carried out with the use of conductor bridge elements, which are preferably designed as thin-walled sheet metal strips, which can fit into the wiring area in only one predetermined way, where advisably the coil ends and the terminal elements are connected to the conductor bridge elements by a clamping-type connection. For various reasons this makes it possible for the electrical machine to be wired both quickly and correctly.

With respect to the automated realization of the wiring process, it is especially advantageous for the electrical contact areas between the coil ends and the linking conductors to be located in a common axial and radial position, where the end of one coil and the circumferentially adjacent end of a second coil are assigned to one and the same linking conductor by a common terminal element.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The figures show part of a stator10for an electrical machine (not shown). The stator has a ring-shaped stator yoke4consisting of laminations of electric steel. This is the stator of a synchronous electrical machine of the external rotor type excited by permanent magnets, although the special design of the electrical machine is irrelevant to the following explanation. The stator yoke4has a number of radially outward-oriented teeth6arranged around the circumference. Each tooth6carries an individual coil8. The coils8consist of windings9of a single or multi-strand conductor. The individual conductors can be twisted around each other.

Each individual coil8is first wound separately in a preceding production step on two winding bodies12, consisting of insulating material, and then pushed onto a tooth6of the stator yoke4, where it is secured against slipping by a latching connection. Each, coil8has two ends18,20, which extend out from the coil8in the radially inward direction and are available at a common end surface of the stator10for connection. The coils8are assigned to individual strands and, as will be explained in greater detail below, are wired together in a predetermined manner by the use of common linking conductors24,26,28, which are components of a wiring arrangement14. For this purpose, the linking conductors24,26,28are arranged coaxially with respect to each other and are staggered axially on the stator10. They are mounted radially inside the coils8. Insulating disks38are provided between the linking conductors24,26,28to insulate them from each other.

According to the diagram ofFIG. 2, the linking conductors24,26,28are designed as strip conductors of copper, for example, which have been formed into a ring shape by edge-rolling in a plane. Several radially outward-projecting, tab-like terminal elements32, only one of which is shown inFIG. 2, are positioned at specific points on the circumference within the plane of the ring and used to connect the conductor to the ends18,20of the coils.

On the stator, the linking conductors24,26,28are inserted into a receiving area44, designed as a groove open on one side, in a support structure36. The support structure36, as can be seen inFIG. 1, is made up of individual segments. The individual segments are designed as integral parts of the winding bodies12, which cooperate with the stator to form a closed ring structure.

On the side of the stator with the wiring arrangement14, the winding bodies12shown inFIG. 4have a conventional winding area16to hold the winding9. This area is formed by a base area46resting against the stator yoke4and two laterally projecting sidepieces48,50. To form a segment of the support structure36, the base area46is extended radially inward with respect to the structure of the electrical machine. Two webs39,40, furthermore, which extend from the extended base in the axial direction, are also provided. As a result, a groove-shaped wiring area42, open on one side, directly adjacent to the winding area16, and a receiving area44, also open on one side, to hold the linking conductors24,26,28are formed.

The sidepiece50and the web40each include two radially oriented recesses52,54, through which the coil ends18,20pass and in which they are held. The coil ends can thus be supported on the contact areas56, which are molded here in the wiring area42. Another recess58is provided, through which a terminal element32can be introduced from the receiving area44into the wiring area42, the end of the terminal element32being held positively there in a recess60formed inside the sidepiece50. Thus it is ensured that the coil ends and the terminal elements can project into the wiring area only at spatially predetermined positions, where they are then available for further connection.

Alternatively to the support structure36assembled from individual segments shown here, the structure could also be produced as a separate plastic ring and mounted on the winding bodies12, where the wiring area42could then belong either to a winding body12or to the support structure36or to both, as desired.

In the exemplary embodiment, each of the radially oriented terminal elements32is arranged in the circumferential direction of the stator4so that it lies between the two ends18,20of one coil8. The terminal elements32, however, could also be arranged so that they lie between the end18of one coil8and the end20of an adjacent coil.

To wire the coil ends18,20, they are first bent over from the winding body12in the radially inward direction and laid in the recesses52,54provided for them in the wiring area42. Simultaneously, the ends of the coils make contact with the contact areas56. A terminal element32of a linking conductor24,26,28is contacted electrically with the ends18,20of two adjacent coils8by the use of a conductor bridge element62, consisting of a thin-walled sheet metal strip as shown inFIG. 5a,which is inserted into the wiring area42between two coils. Two slots64, proceeding from the same side, are provided in this bridge element to hold the two adjacent coil ends18,20of two adjacent coils8, and an additional slot66, proceeding from the opposite side, is provided to hold a terminal element32. To give the wiring arrangement14a certain elasticity to compensate for thermal expansion and to minimize the influence of operationally caused vibrations at the coil ends18,20, the conductor bridge element62is also provided with an additional expansion structure68in the form of openings.

When the conductor bridge element62is inserted, the coil ends18,20are pressed into the slots64and clamped between the edges of these slots, which act as blade clamps.

Then the linking conductors24,26,28and the insulating disks38are introduced into the conductor receiving area44. The terminal elements32of the various conductors are offset from each other in the circumferential direction, so that only a single terminal32of one of the linking conductors24,26,28can be introduced through a recess58and into the wiring area42, where it is held with a clamping action in the slot66of the conductor bridge element62situated there.

The distances between the slots64,66of the conductor bridge elements62can be selected in such a way that the bridge elements will fit into the wiring area42in only one predetermined position or with only one orientation. This guarantees that the end18of a coil8and the circumferentially adjacent end20of a second coil can be assigned to one and the same linking conductor24,26,28by a common terminal element32. This also guarantees that short-circuits between the two ends18,20of one and the same coil8are avoided. Overall, therefore, all of the contact areas of the coil ends18,20with the conductor bridge elements62and of the terminal elements32with the conductor bridge elements are arranged in a common radial position and also in an essentially common axial position. This offers the advantage that, when a conductor bridge element62is inserted, two coil ends18,20, are connected simultaneously to one of the linking conductors.

If, alternatively to the example explained above, the terminal elements32lie between the end18of one coil8and the end20of the adjacent coil, then the corresponding conductor bridge element62′, as shown inFIG. 5b,can have a much more compact design, and in addition a high degree of mechanical flexibility is provided without need for an additional expansion structure.

To protect the linking conductors24,26,28and the contact areas56from corrosion and to increase the sturdiness of the wiring arrangement16, the wiring area42and/or the receiving area44can be cast in a sealant. The linking conductors24,26,28and the contact areas of the conductor bridge elements62will then be completely encapsulated against the environment.