Stator in an electric motor

A stator in an electric motor and to a method for producing the stator in which a plurality of individual coils are wound on laminated stator poles and are provided with an insulation, wherein the insulation bears connection contacts for bringing the individual coils into contact with a printed circuit board, wherein the connection contacts are press-fitted into the printed circuit board. The present stator provides for a compact size and for simple and economical joining processes. In a preferred embodiment, the electric motor is a dosing pump motor for drug delivery systems.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is based on, and claims priority from, German Application No. 10 2017 109 662.0, filed May 5, 2017, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The invention relates to a stator in an electric motor and to a method for producing the stator. In particular, the stator is used in a dosing pump motor for drug delivery systems.

A prior art stator has a plurality of individual coils wound on laminated stator poles and is provided with an insulation, wherein the insulation bears connection contacts for bringing the individual coils into contact with a printed circuit board, wherein the connection contacts are in the printed circuit board. A board, a printed circuit board (PCB), or a baffle can serve as a circuit board.

During the production of wound stators consisting of individual metal sheets, a large number of inaccuracies arise, which accumulate from manufacturing tolerances during rolling of the metal sheets, during packaging, and during joining. Sheet metal stacks, in particular, have very large tolerances, which cause the terminal contacts to have a different axial extension for each stator pole core. In order to compensate for these unequal positions, a correspondingly thicker circuit board must be used, in particular, when press-fitting the terminal contacts, or a soldering process must be provided when using a thinner circuit board. Both options increase the cost and cycle times in the manufacture of the stator. In addition, more space is needed.

The aim of the invention is therefore, in the case of a generic stator, to provide for a compact size and for simple and economical joining processes.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a stator in an electric motor, where the stator consists of a plurality of laminated stator pole cores each having a first end and a second end. The stator also has a printed circuit board with contact recesses. An individual coil is wound on one of the laminated stator pole cores. First and second insulation caps are provided respectively at the first and second end of each stator pole core. Terminal connection contacts are provided on the first insulation caps for bringing the individual coils into contact with the printed circuit board wherein connection contacts are press-fitted into the contact recesses of the printed circuit board. A length tolerance between a first axial end of a stator pole core (base) and one end of the associated terminal contact at the second axial end of the stator pole core (3) is substantially less than the length tolerance of the stator pole core.

The present invention is based upon the fact that the length tolerance between a first axial end of a stator pole core (base) and one end of the associated terminal contact at the second axial end of the stator pole core is substantially less than the length tolerance of the stator pole core. The length tolerance of a laminated core can be up to a thickness of one metal sheet, with a conventional number of stacked metal sheets. However, the tolerance at the contact point between the terminal contacts and the printed circuit board may be only a fraction of this tolerance, for reasons of contact reliability. The advantages of the present invention also apply if a reference plane defines from which all stator pole cores extend axially.

The present invention also relates to a method for producing a stator in an electric motor with a plurality of individual coils wound on laminated stator pole cores provided at each end of the stator pole cores with an insulation in the form of a cap, wherein the insulation bears terminal contacts for bringing the individual coils into contact with a printed circuit board, wherein the terminal contacts are press-fitted into recesses defined in the printed circuit board. The method comprises the steps of: a) providing a plurality of stator pole cores having first and second ends; b) providing first insulating caps at the first end positively connected by a baffle; c) providing second insulating caps at the second end interconnected by a retaining element; d) joining the first and second insulating caps with the stator pole cores to a mounting assembly; e) winding the insulated stator pole cores with single pole windings and bringing the wire ends into contact with the baffle; f) separating retaining regions of the baffle and shearing press-fit regions; g) separating the retaining element from the mounting assembly; h) rounding the wound stator by positioning the stator pole cores about an elongated stator axis; i) press-fitting the stator into a housing; and k) joining the printed circuit board in the housing and pressing the circuit board via the terminal contacts.

DETAILED DESCRIPTION OF THE INVENTION

In describing preferred embodiments of the present invention illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose.

FIG. 1shows a first partial sectional view A-A of a stator1with mounted printed circuit board6. The stator1has a housing16with a flange17integral therewith, from which project receptacle pins19for the reception and radial alignment of the printed circuit board6, as well as a plain bearing sleeve8for accepting a shaft (not shown). The stator1further includes a plurality of stator pole cores3, a plurality of first insulating caps9, and a plurality of second insulating caps10. A portion of the first insulating caps9is provided with terminal contacts5, a further portion is provided with a star-point baffle12, and, by this, connected to one another electrically and mechanically. The stator pole cores3are press-fitted into the housing16. In addition, they can also be welded to the housing16via the insulating caps9,10. The housing16, on its inner circumference, has no stop contours for the stator1. The axial position of the stator1is set, over the depth of insertion relative to a reference plane that is measured.

Both the first insulating caps9and the second insulating caps10are not shaped identically to each other; in particular, they have different wire guide geometries and, in at least one case, a coding pin35(SeeFIG. 5).

FIG. 2shows a side view of the stator1, with the flange17, as part of the housing16and the circuit board6. The printed circuit board6is provided with recesses which are received on the plain bearing sleeve8or the receptacle pin19. The circuit board6is centered by means of the plain bearing sleeve8. One of the receptacle pins19defines the angular position, and a second receptacle pin19is received in an oblong hole2, which compensates for inaccuracies. The terminal contacts5are press-fitted into contact recesses of the printed circuit board6.

FIG. 3shows a partial sectional view B-B of the housing16, in the region of the flange17, with the receptacle pins19and the printed circuit board6.

FIG. 4shows a second sectional view similar toFIG. 1of the stator1without circuit board6, with the housing16, the flange17, the receptacle pin19, the plain bearing sleeve8, a plurality of stator pole cores3, a plurality of first insulating caps9, a plurality of second insulating caps10, a plurality of individual coils4, and the terminal contacts5.

FIG. 5shows a first view of a mounting assembly20of the stator1, with a plurality of layered stator pole cores3arranged in a plane and made of magnetically conductive metal sheets, a plurality of first insulating caps9, a plurality of second insulating caps10, a baffle25, and a retaining element26. The baffle25has balancing bridges21, as part of a later star-point baffle12, a plurality of retaining sections22with perforated receptacles24, auxiliary balancing bridges23, connecting webs31, blanks30in the form of enlarged surfaces from which later press-fit regions are punched free, and positive-fit sections buried in the first insulating caps9(see punch hole7inFIG. 9).

The retaining element26is received radially into the second insulating caps10in non-recognizable retaining recesses. This connection is produced by extrusion coating with a non-positive fit or with a slight undercut (for example, by notching), wherein the retaining elements26, however, are removable in any case. The arrangement shown in a plane is suitable for a punching process in which the connecting webs31are severed. A second insulating cap10is integral with a coding pin35, which serves for the positionally correct mounting in the housing16.

FIG. 6shows a second view of the mounting assembly after a separation step. Shown are the stator pole cores3, the first insulating caps9, the second insulating caps10, a star-point baffle12with balancing bridges21, terminal contacts5, with press-fit regions15and wire connection regions14, and a plurality of single-pole coils4whose wire ends13are welded to the wire connection regions14. Further, the coding pin35and the retaining element26are shown in the retaining recesses of the second insulating caps10.

It is provided that the terminal contacts5with the insulation9,10, in particular, with first insulating caps9, be force- or positive-fittingly connected, wherein the terminal contacts5in the joint area are perforated, toothed, or provided with at least one notch. The perforation, the teeth, or the notch allows insulating material of the insulating caps9,10to fill the free space and causes a positive connection in the axial direction, whereby a release of the terminal contacts5is prevented from the insulating caps9. This results in a very strong connection, which allows the terminal contacts in a raw form to also be used as a retention means in the manufacturing process. Alternatively, the terminal contacts5can also be mounted in a non-positive manner. In particular, terminal contacts with toothing contours (arrow-shaped, sawtooth-like) are suitable for this purpose.

This design is supplemented by the fact that the second insulating caps10have retaining recesses, in particular, retaining slots, for accepting a retaining means. This measure also serves to facilitate or at least simplify the production process, in particular, the handling and mounting of a stator assembly. In said retaining recesses, retaining means can be releasably received. The retaining recesses are radially aligned here, so that they form a positive connection in the axial direction.

FIG. 7shows a rear view of the mounting assembly20according toFIG. 5, with the stator pole cores3, the first insulating caps9, the second insulating caps10, and the baffle25. The baffle25has balancing bridges21as part of a later star-point baffle12, blanks30with wire connection regions14, connecting webs31, retaining sections22with receptacles24, and auxiliary balancing bridges23. The blanks30form an enlarged punching area for the press-fit regions15still free to be punched (which are here indicated by dashed lines). The second insulating caps10have wire guide channels28through which the connecting wires are led from one coil to the next. In addition, the coding pin35can be seen.

FIG. 8shows a second rear view after the separation step, corresponding toFIG. 6, with the stator pole cores3, the first insulating caps9, the second insulating caps10, with the coding pin35, the star-point baffle12with the balancing bridges21and the terminal contacts5with the wire connection regions14, and the press-fit regions15.

FIG. 9shows a partial view of a terminal contact5, with a wire connection region14, a press-fit region15, a punch hole7(dashed line), and a wire end13, which is welded to the wire connection region14. The press-fit region15has V-shaped side edges, which run towards a blunt end. Between the V-shaped side edges, a core punch hole32is provided, which allows a slight bending of the press-fit contour.

FIG. 10shows a first side or bottom view of the mounting assembly20with the retaining element26, the first insulating caps9, and the baffle25. The retaining element26is formed as a continuous metal strip with a plurality of openings33. In the form shown, the sheet metal strip cannot bend in the plane of the sheet metal. The openings33serve as receiving means for a retaining tool (not shown). The retaining element26serves as a reference surface for the free-punching operation of the terminal contacts5.

FIG. 11shows a second bottom view of a part of the mounting assembly after the separation step of the retaining section from the baffle, whereby the terminal contacts5and the star-point baffle12are punched free. Further free-punches separate the retaining element26into a plurality of retaining element sections27. In this form, they can serve as retaining means during rounding whereby the stator pole cores are arranged about the stator longitudinal axis. The retaining element sections27ensure that, after the rounding, the axial arrangement of the stator pole cores3, and thus the axial position of the terminal contacts5, in particular, the press-fit regions, corresponds to the position of the layer before the rounding operation.

FIG. 12shows an assembled stator after rounding (without housing and without printed circuit board), with a plurality of stator pole cores3, a plurality of first insulating caps9, a plurality of second insulating caps10, with the coding pin35, the terminal contacts5, with their press-fit regions15, the star-point baffle12, with a balance bridge21. The stator pole cores3are not rigidly connected to each other; rather, only a portion of the stator pole cores3are resiliently connected to each other via the balancing bridges21.

FIG. 13shows a side or bottom view of the rounded stator (without housing and without printed circuit board), with a plurality of stator pole cores3, a plurality of first insulating caps9, the single-pole coils4, the terminal contacts5, and the star-point baffle12, with the balancing bridges21.

FIG. 14shows a second side or top view of the rounded stator (without housing and without printed circuit board), with a plurality of second insulating caps10, the coding pin35, the wire guide channels28, and the single-pole coils4.

FIG. 15shows an exploded view of the mounting assembly20, with the stator pole cores3, the single-pole coils4, the first insulating caps9with the baffle25, the second insulating caps10, with the coding pin35, and the retaining element26. The baffle has blanks30, connecting webs31, balancing bridges21, retaining sections22, auxiliary compensating bridges23, and receptacles24.

The two insulating caps9,10are shaped so as to cover end portions of the stator pole cores3in an accommodating region for the individual coils. When assembled, the stator pole cores form slots, and the insulating caps9,10form partial slot liners. It has been found that a complete slot liner is not required over the entire length of the stator pole cores. The insulating caps9,10form, with the stator pole cores3, positive connections in the radial direction.

FIG. 16shows a three-dimensional view of the mounting assembly before the rounding and after the separating step, with a plurality of stator pole cores3, a plurality of first insulating caps9, a plurality of second insulating caps10, terminal contacts5, the star-point baffle12, the coding pin35, and the retaining element26.

With reference toFIGS. 5-11, according to one embodiment of the invention, a star-point baffle12is provided, which is positively connected to several first insulating caps9, wherein the star-point baffle in the joint area7is perforated, serrated, or provided with at least one notch. Again, the positive connection is created by filling the perforation, the teeth, or the notch with the plastic material of the insulating caps9. Alternatively, the star-point baffle can be mounted non-positively; for this purpose, star-point baffles with toothing contours (arrow-shaped, sawtooth) are, in particular, suitable. The star-point baffle also serves, in a raw form, as a retaining means. Electrically, the star-point baffle forms a contact point for several individual coils4. Contacting the printed circuit board6is possible in principle, but not provided. As a result, the number of printed circuit board contacts is minimized, and a simpler circuit board may be used. Further, this makes the mounting of the circuit board6easier.

Expediently as shown inFIG. 6, wire ends13of the individual coils4are electrically connected to the terminal contacts5. For this purpose, the terminal contacts have a wire connection area14. In addition, the terminal contacts each have at least one press-fit region15, which must be formed very precisely in order to always ensure a secure contact with the circuit board. For this reason, it is also not allowed to make the position of these contacts dependent upon the tolerance of the laminated core length.

In order to generate the most secure connection possible between the wire ends13and the terminal contacts5, they are welded or bonded together. For wire diameters of approx. 0.5 mm or more, welded connections as well as crimp connections can be reliably manufactured. Bonding is particularly suitable for very small wire diameters of less than 0.2 mm.

It is further provided that the star-point baffle12has balancing bridges21with tolerance compensation contours, wherein the length of the balancing bridges21along these tolerance compensation contours is greater than the bridged linear distance between adjacent contact points of the winding wire ends at the star-point baffle12. As a result, the star-point baffle can compensate for large changes in shape and/or length which occur during a bending process. In particular, the star-point baffle can contact the individual coils4while they are arranged in a plane, and maintain this contact when the stator is rounded.

The aim of the invention is also achieved by the method, in which the following method steps are carried out: a) providing a plurality of stator pole cores3; b) providing first insulating caps9positively connected by a guide plate25, providing second insulating caps10interconnected by a retention element26; c) joining the first and second insulating caps9,10with the stator pole cores3to a mounting assembly20; d) winding the insulated stator pole cores3with single pole windings and bringing the wire ends13of the windings into contact with the baffle25; e) separating retaining regions of the baffle25and shearing press-fit regions15; f) separating the retaining element26from the mounting assembly20; g) rounding the wound stator; h) press-fitting the rounded stator1into a housing16; i) joining the printed circuit board6in the housing16and pressing the circuit board6via the terminal contacts5.

With reference toFIG. 5, the baffle25has a retaining section22with several perforated receptacles24, but also the contours of the terminal contacts and the star-point baffle12. The retaining section22as well as the retaining elements26are merely aids in the assembly process, including the winding of the isolated single-pole cores3. The baffle25is dimensioned so that the later position of the terminal contacts5, in particular, the press-fit regions15on the guide plate25, is finally determined only by a separation process (FIG. 11). The separation takes place by shearing with the aid of a cutting tool, which is toleranced very accurately and thus determines the position of the press-fit contacts with corresponding accuracy. The separation process takes place in three steps: first, the press-fit contacts are perforated, then, the outer contour is cut, and, finally, the fastening area is cut off. The positive connection between the terminal contacts5and the insulating caps9remains, even after the separation of the auxiliary contours. The retaining element26consists of a sheet metal strip which cannot be bent in the sheet metal plane; therefore, it is separated from the second insulating caps10before rounding. The separation is done by pulling the retaining elements out of the retaining recesses.

According to a variant, the retaining element26remains joined in the retaining recesses during the rounding (FIG. 10). To facilitate the rounding, the retaining element26is separated into a plurality of retaining element sections27(FIG. 11). Their number corresponds to the number of stator pole cores3.

Before the actual installation, the baffle25is extrusion coated with plastic material in an injection molding process as an insert in an injection molding machine, whereby the first insulating caps9are cast, wherein they are bound with the baffle25as an assembly. In order to produce a positive connection, the areas later enclosed by the plastic material each have perforations, toothings, or at least one notch, which is/are filled by the plastic material.

The retaining element26, before installation, is extrusion coated with plastic material in an injection molding process as an insert in an injection molding machine, whereby the second insulating caps10are cast, wherein they are temporarily bound with the mounting element26to an assembly. In contrast to the baffle25, the retaining element26is not, in the areas surrounded by the plastic material, perforated, toothed, or provided with notches or other permanent, positive-fitting contours, in order to facilitate later separation from the second insulating caps27. However, it is possible to use notches or slight undercuts (e.g., dovetail), through which an increased retaining force is achieved during assembly. However, these geometries are dimensioned so that they allow disassembly.

It is particularly important that the axial position of the stator pole cores3be fixed in a shearing station and remain fixed during the rounding. As a result, no alignment process is needed, and the very precise location of the terminal contacts is maintained, even when rounding.

It is equally important that the fixed axial position of the stator pole cores3not be changed, even during the press-fitting process in the housing16. In this way, the correct position arrangement of the press-fit contacts, from the shearing process to the assembly of the circuit board and the final assembly state, is maintained.

Modifications and variations of the above-described embodiments of the present invention are possible, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described.