Automotive electric auxiliary unit

Abstract

An electric motor assisted unit for a motor vehicle having an electric motor (12), comprising: - a rotatable motor rotor (16) which rotates about a rotor axis (20), - a multi-piece motor stator (14) comprising a plurality of stator coils (23, 25, 27, 29, 31, 33), a plurality of stator teeth (22, 24, 26, 28, 30, 32) and a separate annular magnetic back yoke (34), wherein the separate annular magnetic back yoke (34) radially surrounds the stator teeth (22, 24, 26, 28, 30, 32) and is attached to the stator teeth (22, 24, 26, 28, 30, 32), and - a plastic motor housing (40), wherein the separate annular magnetic back yoke (34) is overmoulded by the plastic motor housing (40).

Description

Technical Field

[0001] This invention relates to an electric auxiliary unit for automobiles. Background Technology

[0002] Automotive electric auxiliary units are not provided as traction engines, but rather as auxiliary devices such as vacuum pumps, liquid pumps, or gas pumps. Typically, automotive electric auxiliary units include an electric motor. Such an electric motor for an automotive electric auxiliary unit is disclosed, for example, in patent document EP 1 306 960 A2. This electric motor includes a rotatable motor rotor and a stationary motor stator. The motor stator includes a main stator body having several stator teeth, on which several stator coils are wound. To facilitate the production of the motor stator, it is known to separately configure the stator teeth, wind them individually, and then assemble them to form a closed stator. Alternatively, the stator may include a main stator body having several stator teeth, wherein the motor stator teeth are radially internally connected to respectively adjacent stator teeth. The stator teeth can be wound radially externally. After the stator coils are wound, individual annular magnetic backing rings are provided thereon so that the stator teeth include magnetic connections radially externally.

[0003] Typically, the complete motor stator is secured to the motor housing by screws or adhesive. However, these methods require additional securing components and / or a complex installation process to attach the motor stator to the motor housing. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an electric auxiliary unit for automobiles that can be fastened in a reliable and simple manner.

[0005] This technical problem is solved by an automotive electric auxiliary unit with an electric motor, comprising: a rotatable motor rotor that rotates about a rotor shaft; a multi-piece motor stator including multiple stator coils, multiple stator teeth, and a separate annular magnetic back iron ring, wherein the separate annular magnetic back iron ring radially surrounds and is attached to the stator teeth; and a plastic motor housing, wherein the plastic motor housing is produced by injection molding, and the separate annular magnetic back iron ring is encapsulated by the plastic motor housing during the injection molding process, such that the annular magnetic back iron ring conforms to the shape of the plastic motor housing radially, tangentially, and axially, wherein after the annular magnetic back iron ring is encapsulated by the plastic motor housing, the stator teeth are inserted into and attached to the annular magnetic back iron ring.

[0006] The auxiliary unit according to the invention includes an electric motor having a motor stator and a motor rotor. The motor stator includes a stator lamination assembly consisting of pressed stator laminations and one or more motor stator coils that generate an electromagnetic field that interacts with the rotatable motor rotor. The rotor assembly includes a rotatable rotor body and permanent magnets attached to the rotor body. The motor rotor directly or indirectly drives a mechanical element. This mechanical element is, for example, a pump rotor, which is fixed to the rotor body in a manner that allows it to rotate together. The rotor assembly rotates about an axial rotor shaft.

[0007] The stator comprises multiple stator teeth, which are radially internally connected to adjacent stator teeth. Radially externally, the stator teeth are interconnected by individual annular magnetic backing rings. When the annular magnetic backing rings are removed, the stator teeth are accessible so that all stator teeth can be wound around.

[0008] The automotive electric assist unit also includes a motor housing made of plastic. The motor rotor and motor stator are arranged inside the plastic motor housing. The motor rotor is rotatably attached to the motor housing via bearing elements. The motor stator is attached to the housing.

[0009] To simplify the production of the auxiliary unit, the individual annular magnetic back iron ring is molded by covering the plastic motor housing.

[0010] The overmolding of the magnetic backing ring results in a form-fit connection between the magnetic backing ring and the housing. During the production of the motor housing and the overmolding of the magnetic backing ring, a circumferential groove is formed on the inner surface of the motor housing. The outer peripheral surface of the magnetic backing ring contacts the bottom of the groove, so that the magnetic backing ring is radially fixed to the motor housing. Furthermore, each axial end of the magnetic backing ring contacts a side of the groove, thus the magnetic backing ring also axially fits the housing shape. Additionally, the motor stator mates with the housing shape and / or is bonded with material along the direction of rotation.

[0011] The first step in electric motor manufacturing is to wind the coil onto the stator teeth and produce the housing. In the plastic housing production step, the magnetic backing ring is encased in the plastic material of the housing and thus fixed to it. The stator teeth with the wound coil are then inserted into and secured to the magnetic backing ring. Finally, the motor rotor is inserted into the stator.

[0012] This manufacturing method for electric motors reduces production workload, as it eliminates the need for the additional step of attaching the electric motor to the housing. Furthermore, this manufacturing method provides a reliable attachment of the motor stator to the housing.

[0013] In a preferred embodiment of the invention, the plastic motor housing is produced by injection molding. Injection molding is a well-known process for manufacturing plastic parts, in which a thermoplastic material is liquefied and injected into an injection mold under pressure. Within the mold, the material recovers to a solid state through cooling or a cross-linking reaction, and is removed as a finished part after the mold is opened. Overmolding of the element is achieved by inserting the element into the injection mold, whereby the liquefied plastic flows around the element and forms a shape-fitting connection with the element in a cooled state.

[0014] Preferably, the stator teeth are attached to a separate annular magnetic backing ring via a form-fit connection and / or a force-fit connection. Both of these connection methods allow for a simple and economical way to reliably connect the stator teeth to the annular magnetic backing ring.

[0015] In a preferred embodiment of the invention, the form-fit connection is a dovetail connection, wherein a plurality of dovetail protrusions are press-fitted into corresponding grooves so that the stator teeth are form-fitted radially and tangentially with the magnetic back iron ring and force-fitted or friction-fitted axially with the magnetic back iron ring. The dovetail protrusions and corresponding grooves ensure that the stator teeth are reliably secured radially to the magnetic back iron ring.

[0016] In the manufacturing process of an electric motor, a ring is formed by overmolding the motor housing, and then the stator teeth are axially inserted into the magnetic back iron ring, thereby pushing the dovetail-shaped protrusions axially into the grooves. Therefore, the motor stator is fixed to the housing solely through the injection molding of the ring and the axial insertion of the stator teeth into the ring. This reduces the amount of work required to install the stator onto the motor housing.

[0017] In a preferred embodiment of the invention, a plurality of stator teeth are attached to each other by a plastic member. The plastic member is annular and connects the plurality of stator teeth radially inward, thus causing these stator teeth to project radially outward. The plastic member electrically isolates these stator teeth from each other. The annular plastic member can be constructed as a separate component, wherein an individual stator tooth mates with the shape of the annular plastic member. Alternatively, the stator teeth can be overmolded with a plastic member.

[0018] The fact that the stator teeth are attached together by plastic parts simplifies the installation of the stator teeth at the annular magnetic back iron ring, wherein all stator teeth can be attached to the magnetic back iron ring in just one step.

[0019] In a preferred embodiment of the invention, the auxiliary unit includes a centrifugal pump rotor that is rotatably fixed to the motor rotor. Preferably, the auxiliary unit is an electric coolant pump for supplying coolant to cool engine or vehicle components. Preferably, the auxiliary unit includes a separator arranged radially between the motor stator and the motor rotor. The separator is substantially cylindrical and radially surrounds the motor rotor. The separator separates gases or fluids, such as coolant, from the motor's core, including the motor stator.

[0020] In a preferred embodiment of the invention, the motor housing includes a first housing element defining a pump chamber, a second housing element defining a motor chamber, and a third housing element defining an electronics chamber, wherein a separate annular magnetic back ring is overmolded by the second housing element of the plastic motor housing. In the assembled state, the first housing element is attached to a first front end of the second housing element, and the third housing element is attached to a second front end. The fastening between the housing elements is, for example, made by screws. By separating the motor housing, the manufacturing of the motor housing can be simplified because the overmolding of the magnetic back ring is completed only by the second housing element.

[0021] The aforementioned technical problem is also solved by a method for manufacturing an electric motor, the electric motor comprising a motor housing, a stator having multiple stator teeth, and a separate annular magnetic back iron ring. The method includes the following steps:

[0022] - A ring-shaped magnetic back iron ring is formed by covering the motor housing; and

[0023] - Attach the stator teeth to the annular magnetic back iron ring.

[0024] The advantages of this method are explained in the previous section. Attached Figure Description

[0025] Embodiments of the present invention are described with reference to the accompanying drawings, wherein...

[0026] Figure 1 A schematic longitudinal sectional view of an automotive electric auxiliary unit with an electric motor is shown.

[0027] Figure 2 Showing has Figure 1 A cross-sectional view of the electric motor in an automotive electric auxiliary unit, and

[0028] Figure 3 Show Figure 1 A perspective view of the motor housing and motor stator of an electric motor. Detailed Implementation

[0029] Figure 1 and Figure 2The diagram shows an automotive auxiliary unit 10, which is designed as a coolant pump. The automotive auxiliary unit 10 is provided with an electric motor 12, which includes a stationary motor stator 14, a rotatable motor rotor 16 having a rotor body 18, and a permanent magnet attached to the rotor body 18.

[0030] The motor rotor 16 rotates about the rotor shaft 20, and is supported by bearings that position the motor rotor 16 axially and radially. The pump rotor 54 is attached to the motor rotor 16.

[0031] Motor stator 14 is composed of Figure 3 The six stator teeth 22, 24, 26, 28, 30, and 32 shown are formed with a separate magnetic back iron ring 34. Each stator tooth 22, 24, 26, 28, 30, and 32 comprises a stack of multiple identical stator laminations, wherein these laminations are stacked together by a die-cutting lamination method. The stator teeth 22, 24, 26, 28, 30, and 32 are non-removably fastened to a plastic part 36 so that the six stator teeth 22, 24, 26, 28, 30, and 32 and the plastic part 36 are assembled into a mounting unit 38. The plastic part 36 is annular and connects the stator teeth 22, 24, 26, 28, 30, and 32 radially inward. The plastic part 36 magnetically separates the stator teeth 22, 24, 26, 28, 30, and 32 from each other. Each stator tooth 22, 24, 26, 28, 30, 32 includes a winding that forms electromagnetic coils 23, 25, 27, 29, 31, 33.

[0032] The magnetic back iron ring 34 radially surrounds the stator teeth 22, 24, 26, 28, 30, and 32. The magnetic back iron ring 34, the stator teeth 22, 24, 26, 28, 30, and 32 including the plastic part 36, and the stator coils 23, 25, 27, 29, 31, and 33 constitute the motor stator 14.

[0033] Additionally, the vehicle auxiliary unit 10 includes a motor housing 40, which also serves as a pump housing. The generally cylindrical motor housing 40 includes a first housing element 42, a second housing element 44, and a third housing element 46. The first housing element 42 and the third housing element 46 are canister-shaped. The second housing element 44 is annular. The first housing element 42 is attached to the second housing element 44 by several screws. The third housing element 46 is attached to the second housing element 44. The first housing element 42 defines a pump chamber 43. The second housing element 44 defines a motor chamber 45. The third housing element 46 defines an electronics chamber 47. A separator 48 separates the fluid between the pump chamber 43 and the motor chamber 45. The first housing element 42 has an axial pump inlet 50 and a radial pump outlet 52.

[0034] According to the present invention, the magnetic back iron ring 34 is encased and formed by the motor housing 40, particularly by the second housing element 44. The magnetic back iron ring 34 is attached to the mounting unit 38 by a dovetail connection, wherein the stator teeth 22, 24, 26, 28, 30, and 32 each include a dovetail-shaped protrusion 60, and the magnetic back iron ring 34 includes a plurality of grooves 62 corresponding to the dovetail-shaped protrusions 60.

[0035] During the manufacturing process of the coolant pump, mounting units 38 with stator teeth 22, 24, 26, 28, 30, 32, plastic parts 36, and coils 23, 25, 27, 29, 31, 33 are produced. Simultaneously, the motor housing 40 is produced through an injection molding process. During the injection molding of the second housing element 44, the magnetic back iron ring 34 of the motor stator 14 is overmolded with the plastic of the second housing element 44. Therefore, the magnetic back iron ring 34 is shaped to fit the second housing element 44 radially, tangentially, and axially. In the next step, the mounting unit 38 is pushed axially into the magnetic back iron ring 34, wherein dovetail protrusions 60 are pressed into grooves 62. Therefore, the mounting unit 38 is press-fitted axially with the magnetic back iron ring 34 and shaped to fit the magnetic back iron ring 34 radially and tangentially. In the following steps, the separator tank 48 is installed, the motor rotor 16 including the pump rotor 54 is installed, and the housing elements 42, 44, 46 of the motor housing 40 are joined together.

[0036] This manufacturing of the automotive auxiliary unit 10 reduces the workload, as it eliminates the need for the additional step of attaching the motor stator 14 to the motor housing 40.

Claims

1. An electric assist unit for automobiles, comprising an electric motor (12), the electric assist unit for automobiles including - A rotatable motor rotor (16) that rotates about a rotor shaft (20); - a multi-piece motor stator (14) comprising a plurality of stator coils (23, 25, 27, 29, 31, 33), a plurality of stator teeth (22, 24, 26, 28, 30, 32) and a separate annular magnetic back-iron ring (34), wherein, The separate annular magnetic back iron ring (34) radially surrounds the stator teeth (22, 24, 26, 28, 30, 32) and is attached to the stator teeth (22, 24, 26, 28, 30, 32); and - A plastic motor housing (40), wherein the plastic motor housing (40) is produced by injection molding, and the individual annular magnetic back iron ring (34) is encapsulated by the plastic motor housing (40) during the injection molding process, such that the annular magnetic back iron ring (34) conforms to the shape of the plastic motor housing (40) in the radial, tangential and axial directions. After the annular magnetic back iron ring (34) is covered and formed by the plastic motor housing (40), the stator teeth (22, 24, 26, 28, 30, 32) are inserted into the annular magnetic back iron ring (34) and attached to the annular magnetic back iron ring (34).

2. The automotive electric assist unit of claim 1, wherein, The stator teeth (22, 24, 26, 28, 30, 32) are attached to the individual annular magnetic back iron ring (34) by form fit and / or force fit.

3. The automotive electric auxiliary unit according to claim 2, wherein, The shape-fit connection is a dovetail connection, wherein multiple dovetail protrusions (60) are press-fitted into corresponding grooves (62).

4. The automotive electric auxiliary unit according to claim 1, wherein, The stator teeth (22, 24, 26, 28, 30, 32) are attached to each other by plastic parts (36).

5. The automotive electric auxiliary unit according to claim 4, wherein, The plurality of stator teeth (22, 24, 26, 28, 30, 32) and the plastic part (36) are fastened to the mounting unit (38), wherein the stator teeth (22, 24, 26, 28, 30, 32) are shaped to fit the plastic part (36) and are non-removably fastened to the plastic part.

6. The automotive electric auxiliary unit according to claim 1, wherein, The auxiliary unit (10) is equipped with a centrifugal pump rotor (54), which is fixed to the motor rotor (16) in a way that allows it to rotate together.

7. The automotive electric auxiliary unit according to claim 6, wherein, The auxiliary unit (10) is an electric coolant pump.

8. The automotive electric auxiliary unit according to claim 6 or 7, wherein, The plastic motor housing (40) includes a first housing element (42) defining a pump chamber (43), a second housing element (44) defining a motor chamber (45) and a third housing element (46) defining an electronics chamber (47), wherein the separate annular magnetic back iron ring (34) is overmolded by the second housing element (44) of the plastic motor housing (40).

9. A method for manufacturing an electric auxiliary unit for an automobile according to any one of claims 1 to 8, comprising the following steps: - A ring-shaped magnetic back iron ring (34) is formed by covering the plastic motor housing (40); and - Attach the stator teeth (22, 24, 26, 28, 30, 32) to the annular magnetic back iron ring (34).

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