CN111404295A

CN111404295A - Stator for an electric machine, electric machine and method for producing such a stator

Info

Publication number: CN111404295A
Application number: CN202010002772.4A
Authority: CN
Inventors: C.罗伊特; J.罗伊特
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-01-03
Filing date: 2020-01-02
Publication date: 2020-07-10
Also published as: DE102019200023A1

Abstract

The invention comprises a stator (10), in particular for driving or regulating an auxiliary assembly of components in a motor vehicle, and an electric machine (14), in particular for driving or regulating an auxiliary assembly of components in a motor vehicle, having a stator base body (18), wherein the stator base body (18) has a yoke ring (20) from which stator teeth (14) project radially inward, and the stator base body (18) has an outer circumferential surface (28), wherein a metal sleeve (50) is fastened to an axial end face (19) of the stator base body (18), said sleeve extending axially beyond the outer circumferential surface (28) of the stator base body (18), and the sleeve (50) is pressed into a cylindrical housing (70) made of metal.

Description

Stator for an electric machine, electric machine and method for producing such a stator

Technical Field

The invention relates to a stator for an electric machine, to an electric machine and to a method for producing a stator of the type according to the independent claims.

Background

An electric machine is known from DE 102006036836 a1, for which a stator is arranged in a motor housing. In order to fix the stator in the motor housing, a plurality of spring elements, which are preferably designed as clamping pins, are arranged between the inner wall of the motor housing and the outer circumference of the stator, which is spaced radially apart from the latter. These clamping pins can compensate for different material expansions of different components over a large temperature range.

Different hub connections are known from various applications, which have a force-fitting connection between a preferably hollow cylindrical hub and a shaft inserted axially into the hub with an interference fit. Due to the overpressure fit, a high force closure exists between the hub and the shaft, so that the shaft is fixedly connected to the hub in the axial direction and in the rotational direction. Also known here are shaft-hub combinations with different materials for the shaft and the hub, wherein the material selection is also accompanied by different high thermal expansion coefficients for the shaft and the hub. If, for example, the hub has a high thermal expansion coefficient and the shaft has a significantly lower thermal expansion coefficient, there is the risk that, when the press fit (Pressverband) is heated up intensively, the hub experiences a greater radial widening than the shaft and the clamping force between the mating parts is reduced — if necessary until the connection is released. These disadvantages should be avoided by the following invention.

Disclosure of Invention

In contrast, the device according to the invention and the method according to the invention, which have the features of the independent claims, have the following advantages: by configuring the shaft as a stator which is pressed into a motor housing configured as a hub, a reliable hub shaft press fit is achieved which has a sufficient press fit over a large temperature range. Since the stator base body generally has a significantly smaller thermal expansion than the stator housing, the stator base body is inserted according to the invention into a bushing whose thermal expansion lies in a range similar to the thermal expansion of the stator housing. The stator housing and the shaft sleeve thus expand in the same manner both at very high temperatures and at very low temperatures, so that neither a loosening of the shaft sleeve in the stator housing nor an overpressure fitting of the shaft sleeve through the stator housing occurs. The hub connection is therefore suitable for a temperature range of-50 ℃ to +150 ℃, as occurs when it is used in motor vehicles. It is ensured here that the clamping force between the stator housing and the bushing is sufficiently high at high ambient temperatures and that the mechanical stability of the stator housing is not impaired by the overpressure fit at very low temperatures. It is important here that such a shaft-hub connection can be realized with a relatively cost-effective manner by means of shrink-compression (schrumpfressen). In this case, for example, the stator housing is heated to such an extent that it can be axially pressed onto the shaft sleeve of the stator with little effort.

Advantageous developments and improvements of the embodiments specified in the independent claims can be achieved by the measures specified in the dependent claims. For fastening to the stator base body, the sleeve therefore particularly advantageously has a flange which extends transversely to the stator axis. The flange can thereby be fixed directly on the axial end side of the stator base body, so that the cylindrical wall of the sleeve does not have to be fixed on the outer circumferential surface of the stator base body. This has the advantage that the radially outer surface of the cylinder wall of the bushing has no deformation zones, but can be optimized for a press fit with the inside of the stator housing. In order to produce the bushing, it is simple to bend a flange, which extends radially inward, onto the cylindrical tube in one piece. Thereby, the cylindrical pipe is reliably connected to the stator base via the flange.

Since the electrical steel sheets have a low coefficient of thermal expansion, it is particularly advantageous for this embodiment to sleeve (aufsetzen) onto the stator base body, which has a similar coefficient of thermal expansion to the stator housing.

In a preferred embodiment, the flange extends radially along the stator teeth. The flange here approximately has an inner contour similar to the stator base body. The flange thus forms the uppermost lamella of the stator base body, the cylindrical wall of the bushing being integrally formed on the flange. In this embodiment of the sleeve, the same process steps can therefore be used for winding the stator base body without the use of such a sleeve.

Particularly advantageously, an insulating foil (isolerlamelle) can be placed directly axially on the flange, preferably with an outer closed ring on which the cover for the stator teeth extends radially inward. Such an insulating foil can be fixed, for example, by form-locking in the region of the yoke ring (Jochring) or can be pressed onto the stator base body in another manner. An electrical coil, which is preferably designed as a single-tooth coil, can then be wound onto each stator tooth by means of the winding wire. If the flange approximately coincides with the uppermost sheet metal part of the stator base body, the same insulating sheet can be used as it would without the use of an additional bushing. If the inner contour of the flange deviates from the sheet cut (blechchnitt) of the uppermost sheet metal piece, the shaping of the insulating sheet can be adapted accordingly.

In order to reduce the assembly effort for the bushing, the bushing is axially slipped onto the stator base body in a particularly simple manner, so that the flange of the bushing bears axially against the end face of the stator base body. If the flange now extends radially along the stator teeth, the insulating foil is pressed axially against the flange when the stator teeth are wound, whereby the flange is in turn pressed axially directly against the stator body. The flange is thereby fixedly connected to the stator teeth via the entire electrical winding. Since the cylindrical tube is formed integrally with the flange, the entire bushing is fixedly secured to the stator base body. If the sleeve is now pressed into the housing, the wound stator is also connected to the housing in a non-movable manner.

In an alternative embodiment, the flange can also be adhesively or fixedly welded to the end face of the stator base body. Alternatively, the flange may be stamped or riveted with the uppermost sheet of material. In this embodiment, it is possible for the flange to extend radially only over the region of the yoke ring and not over the radial region of the stator teeth. The flange can be connected to the stator base body in the region of the yoke thereof in a particularly advantageous manner. In an alternative embodiment, it is also possible for the sleeve to be connected to the outer circumferential surface of the stator base radially in the region of the cylindrical tube in a material-locking or form-locking manner.

The bushing can be produced particularly cost-effectively by means of a deep-drawing method. The cylindrical tube is open on one side and is integrally formed with a flange on the opposite side. The inner contour of the flange can be punched out in such a way that it approximately has a contour similar to the sheet metal cut of the stator teeth. Alternatively, the inner contour of the flange can also be punched out as an outer ring, which then bears axially against the yoke ring.

The advantage of the hub connection according to the invention is that the material of the bushing and the material of the housing have approximately the same expansion coefficient, and therefore the press connection is completely independent of the material of the stator base. Since the bushing is not connected to the stator base body by means of a press fit, but rather is connected in a form-fitting or material-fitting manner, the stator base body is connected fixedly and reliably to the bushing even in the event of large temperature fluctuations. In contrast, since the same material is used, the press fit between the bushing and the housing can be reliably constructed over a large temperature range.

In a preferred embodiment, the motor housing is made of aluminum, wherein the motor housing can be made of aluminum or an aluminum alloy, for example, as a press housing or as a die-cast housing. The bushing is therefore also made of aluminum, wherein the aluminum alloy used can be adapted to the exact coefficient of thermal expansion of the housing if necessary. The main advantage of aluminum for the housing and for the bushing is that aluminum can dissipate heat very well from the motor to the environment and can absorb thermal stresses well over a large temperature range.

The housing can be produced particularly cost-effectively in the form of a pot, so that the housing has a base at the axial end. The base can be formed integrally with the side walls of the housing, for example, by means of extrusion or deep drawing or injection molding. Preferably, the base part assumes the function of a bearing cap, so that, for example, a bearing for the rotor is arranged on the base part.

A stator with a press fit between the bushing and the housing is particularly advantageous for an electric machine in which the rotor is supported radially inside the stator. The stator preferably has electronically commutated electrical windings, which interact with permanent magnets fixed to the rotor. In this case, a further bearing cap is preferably arranged on the open side of the housing, so that the rotor is rotatably mounted axially on both sides of the stator base body.

For actuating the electrical winding, a contact plate is arranged inside the housing on the wound stator base body, which contact plate is in electrical contact with the coils of the electrical winding. The electrical winding preferably consists of a single-tooth coil, the connecting leads of which are guided in an insulating foil. These connecting leads can be electrically connected to the connecting leads according to the desired electrical contacting. The connection is preferably produced by hot stamping or welding, but can also be produced by cutting a clamping connection.

By the manufacturing method according to the invention of the stator, a reliable connection between the stator and the housing can be established without changing the manufacturing solution. For this purpose, as an additional component, only a sleeve (which is made of the same material as the housing as far as possible) has to be produced and axially inserted onto the stator base body. In this case, the flange of the sleeve preferably bears directly against the end face of the stator base. As is usual, the insulating foil can then be placed axially onto the stator base body, wherein the insulating foil bears axially against the flange. Subsequently, the stator teeth are wound according to the usual method, wherein the sleeve with the flange does not differ here in the winding. Thereafter, the sleeve may be engaged into the housing with the outside of the sleeve forming a press fit with the inside of the housing. For the axial joining of the housing, the housing is correspondingly heated, so that the joining process requires as little or at least as little pressing force as possible. By using materials for the bushing and the housing which have as similar a coefficient of thermal expansion as possible, the two components can be joined to one another without problems, wherein the press fit which is formed does not loosen or break even under extreme external boundary conditions.

It is particularly advantageous if the sleeve is connected to the stator base body in a material-locking or form-locking manner before the insulating cover (isolimmask) is placed on the sleeve. This can preferably be achieved by means of gluing or welding (material-locking) or by means of stamping or riveting (form-locking) of the sleeve to the stator base body. The sleeve is therefore already fixed to the stator base body before the insulating jacket is placed on it and before the stator teeth are wound.

The electric machine thus produced can be used particularly advantageously for adjusting movable components or for the rotary drive of auxiliary units in motor vehicles. Such EC motors are particularly suitable as drives for, for example, servo steering motors or pumps or compressors in motor vehicles.

Drawings

Embodiments of the invention are illustrated in the drawings and are explained in detail in the following description.

In which is shown:

figure 1a shows a first embodiment of a stator according to the invention,

figure 1b shows a second embodiment of the stator according to the invention,

FIG. 2 shows a detail of another embodiment, an

Fig. 3 schematically shows an electric machine according to the invention according to fig. 2.

Detailed Description

Fig. 1 shows a section through a stator 10, the stator base 18 of which consists of a single sheet 36 of metal. The stator 10 has an outer yoke ring 20, which is closed over the entire circumference. Extending radially inwardly from the yoke ring 20 are stator teeth 14 which in this embodiment have a tooth top (Zahnkopf) 15 on their radially inner side. Between the stator teeth 14, stator slots 16 are formed, which can accommodate electrical windings 24 of the stator. The stator slots 16 do not extend exactly in the axial direction 4 but slightly staggered in the circumferential direction 8. However, in an alternative embodiment, which is not shown, the stator slots 16 can also extend exactly in the axial direction 4. The individual sheet metal sheets 36 are punched out of, for example, electrical sheet steel, preferably made of steel. The individual sheet metal webs 36 are connected to one another axially by material forming, for example by means of caulking or stamping. Fig. 1, for example, therefore shows how the material of the second uppermost sheet metal web 36 engages in the corresponding axial recess of the uppermost sheet metal web 35 in order to form a positive connection. A sleeve 50, which is made of aluminum in this case, is placed on the stator base 18 made of steel. The sleeve 50 has a cylindrical wall 52 which extends over the entire stator base body 18 in the circumferential direction 8. The cylinder wall 52 furthermore extends in the axial direction 4 along the stator base body 18. The stator base 18 has an outer circumferential surface 28, which is preferably completely covered by a sleeve 50. A flange 54 extends radially inwardly from the cylindrical wall 52 on the end side 19 of the stator body 18. The flange 55 is configured here to approximately coincide with the plate cut of the uppermost plate material web 35, whereby the uppermost plate material web is completely covered by the flange 54. In this exemplary embodiment, the flange 54 is formed integrally with the cylinder wall 52, in particular as a deep-drawn part, at which the sheet metal cut of the flange 54 is correspondingly stamped. The sleeve 50 with the flange 54 is in this example only fitted onto the stator base 18 and is not connected to it in a material-locking or form-locking manner. In this embodiment, the connection of the sleeve 50 to the stator base 18 is effected by means of a subsequent winding process of the electrical winding 24 onto the stator 10.

Fig. 1b shows an alternative embodiment in which the sleeve 50 is connected, for example by material bonding, to the end face 19 of the stator base 18. In this case, the flange 54 of the sleeve 50 extends in the radial direction 6 only over the region of the yoke ring 20 and, for example, does not extend over the radial region of the stator teeth 14. A plurality of welding points 56 are formed on the flange 54 distributed over the circumference, on which the bush 50 made of aluminum is welded at least to the uppermost sheet metal part 35 of the stator base body 18. Preferably, the weld spots 56 are constructed by means of laser transmission welding. In this case, no material increase occurs on the axial surface 55 of the flange 54. In this embodiment, the flange 54 has a circular inner circumference 58, which is approximately aligned with a groove bottom 59 of the stator base body 18. In this embodiment, a step is produced from the flange 54 in the radial direction 6 inward to the uppermost sheet metal web 35. This has the advantage that the axial construction height of this embodiment can be reduced compared to the embodiment in fig. 1 a.

In fig. 2, a detail of a stator 10 is shown, which stator 10 has been wound with winding wires 22. In this embodiment, the sleeve 50 is bonded to the stator base 18. For this purpose, an adhesive 60 is arranged on the axial end face 19 of the stator base body 18, which adhesive forms a cohesive connection with the flange 54 of the sleeve 50. In this exemplary embodiment, the adhesive 60 is arranged in a planar manner over the entire end face 19 of the stator base body 18. The flange 54 is therefore bonded to the corresponding cut-out of sheet metal of the flange 54 not only in the region of the yoke ring 20 but also over the entire radial extent of the stator teeth 14. After the sleeve 50 is placed on the stator base 18, the insulating cover 40 is placed on the axial surface 55 of the flange 54 in the axial direction. On the axially opposite side of the flange 54, the second insulating cover 41 is also placed on the stator base body 18, as is shown, for example, in fig. 3. Preferably, a groove structure 42 is formed on the insulating covers 40, 41, into which the winding wires 22 are inserted. By winding the stator teeth 14, the flange 54 is also pressed against the stator base 18 in the axial direction 4. Thus, in the embodiment according to fig. 1, without a cohesive or form-fitting connection between the flange 54 and the stator base 18, it is also possible to fixedly connect the flange 54 to the stator base 18 merely by winding the stator teeth 14 with the winding wires 22. Preferably, a single-tooth coil 17 is wound around each stator tooth 14, which are connected to each other by a connecting line 30. In a preferred embodiment, the stator slots 16 are lined axially between the two insulating

shells

40, 41 with a further insulation 46 (auskleiden). The insulation 46 can be embodied, for example, as an insulating paper against which the winding wire 22 in the stator slot 16 rests. The insulating covers 40, 41 are, for example, designed as injection molded parts and are preferably pressed axially onto the stator base body 18.

In fig. 3, a completely wound stator 10 is shown, in which the single-tooth coil 17 is wound at least partially with an uninterrupted winding wire 22 (durchwickeln). The connecting line 30 is guided between the single-tooth coils 17 on the guide element 44 of the second insulating housing 41. The winding wires 22 are guided radially outward, for example, through radial bores 43 in the second insulating cover 41 and are guided on the circumferential side of the second insulating cover 41 to the next single-tooth coil 17. In a subsequent process step, which is not shown, the connecting lines 30 can be brought into electrical contact with the contact plate in order to connect the single-tooth coils 17 to one another as required. The wound stator 10 has a cylindrical wall 52 of the sleeve 50 over its entire circumference. The cylinder wall 52 preferably extends the entire axial length of the stator base 18. In fig. 3, the stator 10 is pressed into a housing 70 of the electric machine 12, wherein the cylinder wall 52 bears directly against an inner wall 72 of the housing 70 in the radial direction 6. The housing 70 is made of the same material as the boss 50 and therefore also has approximately the same coefficient of thermal expansion. The housing 70 has, in particular at an axial end, a base 74, which is designed, for example, as a bearing cap 75. The base can be designed as a housing pot in one piece with the housing 70. The sleeve 50 forms a press fit with the housing 70, wherein at least the housing 70 is heated prior to pressing into the sleeve 50 to facilitate the bonding process. As shown in fig. 2, a radius 53 is formed in the transition from the cylinder wall 52 to the flange 54, which serves as an insertion aid for axial insertion into the housing 70. The housing 70 is designed, for example, as a press-fit housing or a die-cast housing, which in each case form a reliable connection to the bearing bush 50 made of aluminum over a large temperature range. In this case, the sleeve 50 can compensate for radial pressure exerted on the stator 10 by the housing 70, in particular at low temperatures. After the stator 10 has been inserted into the housing 70, a switch-on plate is preferably fitted to the second insulating housing 41, by means of which the electrical winding 24 can be actuated by the control unit. Likewise, a further bearing cap is preferably inserted into the housing 70 on the axially open side of the housing 70. In this case, the rotor, not shown, is supported in the radial inner space 11 of the stator 10 by means of the two bearing covers 75. In the exemplary embodiment according to fig. 3, the base 74 has a central recess 76 through which a rotor shaft 80 of the rotor protrudes from the housing 70, in order to transmit a drive torque to a control device or a pump, for example. For this purpose, a bearing 78 carrying a rotor shaft 80 is arranged, for example, in the bearing cover 50 around the central recess 76. Preferably, the bearing 78 is configured as a ball bearing 79. The electric machine 12 is designed here as an electronically commutated electric motor, which drives a servo steering system or a pump assembly in a motor vehicle, for example.

It is noted that, with regard to the embodiments shown in the figures and in the description, various combination possibilities of the individual features with one another are possible. Thus, for example, the specific configuration, arrangement and number of stator teeth 14 and electrical windings 24, as well as the configuration of shaft sleeve 50 and flange 54, may be varied accordingly. Likewise, the connection of the sleeve 50 to the stator base 18 can be adapted to the manufacturing process. Alternatively, the stator base body 18 can also be formed in one piece. The sleeve 50 and the housing 70 are each made of approximately the same material, which may also be a material other than aluminum. The invention is suitable in a particular manner for rotary drives of pumps or wheels or as a servo drive for movable components in motor vehicles, but is not limited to this application.

Claims

1. A stator (10) for an electric machine (12), in particular for a motor for driving or adjusting components in a motor vehicle, having a stator base body (18), wherein the stator base body (18) has a yoke ring (20) from which stator teeth (14) project radially inward, and the stator base body (18) has an outer circumferential surface (28), wherein a metal sleeve (50) is fastened to an axial end face (19) of the stator base body (18), said sleeve extending axially beyond the outer circumferential surface (28) of the stator base body (18), and the sleeve (50) is pressed into a cylindrical housing (70) made of metal.

2. Stator (10) according to claim 1, characterized in that the bushing (50) is designed as a cylindrical tube (52) on which a flange (54) is integrally formed radially inwardly, which flange bears axially against the end face (19) of the stator base body (18).

3. Stator (10) according to claim 1 or 2, characterized in that the stator base body (18) consists of a single axially stacked sheet metal (36) which is punched out of electrical steel sheet as a closed ring (20), and in particular is made of steel.

4. Stator (10) according to one of the preceding claims, characterized in that the flange (54) completely covers all stator teeth (14) and in particular has the same sheet material cut as the sheet material web (36) of the stator base body (18).

5. Stator (10) according to one of the preceding claims, characterized in that an insulating foil (40) made of plastic is arranged axially above the flange (54), on which insulating foil (40) an electrical winding (24) of the stator (10) preferably consisting of a plurality of single-tooth coils (17) is arranged.

6. Stator (10) according to one of the preceding claims, characterized in that the flange (54) is connected with the stator base body (18) by means of the electrical winding (24), wherein the electrical winding (24) presses an insulating foil (40) axially against the flange (54) and the flange (54) thereby presses axially against the end side (19) in the radial region of the stator teeth (14).

7. Stator (10) according to one of the preceding claims, characterized in that the flange (54) is connected to the stator base body (18) by means of gluing or stamping or riveting or welding, wherein in particular the flange (54) is fixed on the stator base body (18) in the radial region of the yoke ring (20) and/or in the radial region of the stator teeth (14).

8. Stator (10) according to any of the preceding claims, characterized in that the bushing (50) is manufactured as a deep drawn piece, on which the radially inner contour of the flange (54), preferably of the same shape as the stator teeth (14), is punched.

9. Stator (10) according to any of the preceding claims, characterized in that the metal of the housing (70) and the metal of the bushing (50) have approximately the same thermal expansion coefficient.

10. Stator (10) according to one of the preceding claims, characterized in that the housing (70) comprises at least predominantly aluminum, and is in particular configured as a die-cast housing or a die-cast housing, and the bushing (50) likewise comprises at least predominantly aluminum.

11. Stator (10) according to one of the preceding claims, characterized in that a base (74) configured as a bearing cover (75) for a rotor (80) is integrally formed on the housing (70) at an axial end.

12. An electric machine (12) with a stator (10) according to any of the preceding claims, characterized in that a rotor (80) with permanent magnets is arranged radially inside the stator teeth (14), which rotor is supported in a bearing cover (75) of the housing (70).

13. The electrical machine (12) according to claim 12, characterized in that a switch-on plate for switching on the electrical winding (24) is arranged axially above the electrical winding (24) axially opposite the bottom (74) of the housing (70), wherein the switch-on plate has an electrical conductor element which is in electrical contact with a connecting lead (30) between the single-tooth coils (17) of the electrical winding (24) by means of a welded or hot stamped or cut-clamped connection, and in particular a second bearing cap is axially plugged into the housing (12) above the switch-on plate.

14. A method for manufacturing a stator (10) according to any of claims 1 to 11, characterized by the following method steps:

-axially joining the sleeve (50) to the stator base body (18) in such a way that a flange (54) of the sleeve (50) axially bears against an end face (19) of the stator base body (18);

-axially nesting the insulating sheet (40) on the flange (54);

-winding an insulating sheet (40) with an electric winding (24);

-axially pressing the bushing (50) into the housing (70), wherein at least the housing (70) is preheated.

15. Method according to claim 14, characterized in that the flange (54) of the bushing (50) is fixed to the end face (19) of the stator base body (18) by means of gluing or caulking or welding or riveting before the insulating cover (40) is axially slipped onto the flange (54).