Electric motor and method for installing an electric motor

Abstract

An electric motor (1), in particular suitable for use in a camshaft adjuster, has a multi-part housing (2) which comprises a housing shell (3) made of a first material, in particular steel sheet, and a housing cover (4) made of a second material, in particular light metal, wherein a stator-rotor assembly (5) and an associated electronics module (10) including a circuit board (17) are accommodated in the space formed between the housing shell (3) and the housing cover (4), wherein the circuit board (17) is in each case both mechanically fixed and electrically contacted in three ways, specifically - firstly by shaped material of the housing cover (4), - secondly by a motor contact (21) which is supported on the stator-rotor assembly (5), and - thirdly by a pin (27) which is held in a plug module (20) which is inserted between the housing shell (3) and the housing cover (4).

Description

[0001] Electric motor and method for assembling an electric motor

[0002] The invention relates to an electric motor comprising an electronic module and particularly suitable for use in an electromechanical camshaft adjuster. Furthermore, the invention relates to a method for assembling an electric motor.

[0003] The assembly of a brushless electric motor is, for example, the subject of DE 10 2017 121 218 A1. The known assembly method includes, among other things, the rotationally fixed joining of a magnetic element carrier to a rotor shaft. Furthermore, the axial joining of two bearing devices from opposite sides of the magnetic element carrier is provided. Welding is proposed as a method for securing the bearing devices in place in DE 10 2017 121 218 A1.

[0004] An electric motor with an electronics module is described, for example, in WO 2019 / 206374 A1. This motor is suitable for use in an electric camshaft adjuster or in a mechanism for adjusting the piston stroke of an internal combustion engine. The electronics module of the electric motor known from WO 2019 / 206374 A1 comprises power electronics, driver electronics, and control electronics.

[0005] Another electric motor for a motor vehicle actuator is described in DE 10 2020 131 327 A1. In this case, a plug module is screwed to a housing of the electric motor. The plug module has a groove into which a seal is inserted.

[0006] An electric motor described in US 2021 / 0288561 A1 also serves to adjust the timing of an internal combustion engine. The electric motor comprises electronic components. A sensor of the electric motor is designed as a Hall sensor. The object of the invention is to provide more advanced options for mounting an electric motor compared to the cited prior art, wherein the electric motor should be compact and suitable for various types of internal combustion engines, if possible without structural modifications.

[0007] This object is achieved according to the invention by a method for assembling an electric motor according to claim 1. The object is also achieved by an electric motor having the features of claim 4. The electric motor is particularly suitable for use in an electric camshaft adjuster according to claim 10. The embodiments and advantages of the invention explained below in connection with the devices, i.e., the electric motor and the camshaft adjuster, also apply mutatis mutandis to the assembly method, and vice versa.

[0008] The assembly procedure according to the application includes the following steps:

[0009] - Provision of a multi-part housing comprising a housing shell and a housing cover,

[0010] - Provision of an electronic module comprising a printed circuit board on which there is at least one motor contact which is connected to the printed circuit board by means of a press fit,

[0011] - Provision of a stator-rotor assembly,

[0012] - Inserting the circuit board into the housing cover, whereby a heat-conducting paste is inserted into a gap between the inner wall of the housing cover and the circuit board,

[0013] - forming a mechanical and electrically conductive connection between the housing cover and the circuit board,

[0014] - Placing a connector module on the circuit board, whereby a pin held in the connector module is inserted into the circuit board,

[0015] - Placement of the stator-rotor assembly in the housing shell,

[0016] - Assembling the housing cover including the printed circuit board and the plug module with the housing shell including the stator-rotor assembly, whereby the motor contact arranged on the printed circuit board is electrically connected to the stator-rotor assembly and is simultaneously pressed against the printed circuit board,

[0017] - Creating a positive connection between the housing cover and the housing shell.

[0018] The assembly steps that occur before the housing cover and housing shell are assembled and that exclusively concern the housing shell can be carried out independently of the steps that exclusively concern the housing cover.

[0019] "Press-fit" generally refers to connections created by pressing a contact terminal into a printed circuit board. For technical background information, please refer to documents DE 10 2005 043 033 B3 and DE 10 2008 001 787 A1.

[0020] According to a particularly efficient design of the assembly process, the mechanically and electrically conductive connection between the housing cover and the printed circuit board, as well as the connection between the housing cover and the housing shell, is created by forming the material of the housing cover. By forming the material of the housing cover, this material, particularly light metal, can be brought into contact with a metallic coating located on the inner surface of an opening in the printed circuit board.

[0021] The electric motor according to the application has a multi-part housing comprising a housing shell made of a first material and a housing cover made of a second material. A stator-rotor assembly and an associated electronics module, including a printed circuit board, are accommodated in the interior of the housing formed between the housing shell and the housing cover. The printed circuit board is both mechanically fixed and electrically contacted in three ways. Specifically, these contacts are created by formed material of the housing cover, by at least one motor contact supported on the stator-rotor assembly, and by at least one pin held in a connector module inserted between the housing shell and the housing cover. In particular, the housing cover is made of light metal, whereas the housing shell is made of sheet steel by forming.

[0022] By forming the material of the housing cover, form-fitting connections can be created between the housing shell and the housing cover in the same way as between the housing cover and the circuit board. Forming areas of the housing shell to create form-fitting connections is also possible.

[0023] Various possible embodiments provide for a circular recess that is matched to the shape of the stator-rotor assembly to be formed by the housing shell. A tab that describes a rectangle adjoins a section of the edge of the recess, wherein the width of the tab corresponds at least to the radius, in particular at least to the diameter, of the recess. In these embodiments, the housing cover covers both the area of ​​the recess and the aforementioned tab and has a V-shaped, plateau-like elevation that extends from the edge of the recess facing away from the tab into the area of ​​the at least approximately rectangular tab. The V-shaped elevation accommodates the likewise V-shaped circuit board that is to be assigned to the electronics module, which widens from the recess to the tab in accordance with the shape of the V-shaped elevation.For both the V-shaped elevation of the housing cover and the V-shaped circuit board, sections of the outer contour of the corresponding component can be cut off or rounded, for example, in order to modify the V-shape.

[0024] It has been shown that the V-shaped contour, defined by the housing cover, in particular, provides sufficient space within the housing for accommodating electrical and electronic components while maintaining compact external dimensions, thus creating good conditions for installing the electric motor in different vehicle types. The V-shape of the housing also offers good conditions for installing the electric motor at different angles in different vehicles, if necessary. The electric motor can be designed to be particularly flat on the sides next to the V-shaped protrusion. This translates into a partial reduction in axial installation space.

[0025] The positive-locking connections between the housing shell and the housing cover can be formed, in particular, by caulking. For example, positive-locking connections can be produced by clinching. The clinching connection technology is also known under the brand name Tox. In this context, reference is made to the documents DE 10 2021 120 409 A1 and DE 10 2016 115 595 A1 as examples. Clinching connections or comparable connections can also be formed between the housing cover and the printed circuit board. Components of the electric motor can also be glued together. The motor contacts pre-assembled on the printed circuit board using press-fit can, for example, be designed as insulation displacement contacts. With the help of the combined press-fit insulation displacement contacts, an electrically conductive connection to the windings of the stator assembly can be established in a simple and reliable manner during assembly of the electric motor.

[0026] The area provided by the circuit board can be divided into a first sub-area for logic components and a second sub-area for other functions. The latter sub-area, for example, provides space for components for supplying electrical power and / or for power line filtering. Interfaces, such as pulse width modulation and for connecting to a data network, particularly CAN, as well as diagnostic, regulation, and control functions, can also be implemented by the electronics module.

[0027] The circuit board can, in particular, be a single-sided circuit board, with the first partial area, i.e. the partial area on which the logic components are located, being defined in particular by the narrower section of the circuit board extending to the tip of the V. The adjoining second, wider partial area of ​​the circuit board, in contrast, can be populated with comparatively tall components, for example electrolytic capacitors, thus enabling an overall particularly space-saving design of the electric motor in the axial direction. In general, this means that components located on the circuit board that are arranged in the area covering the stator-rotor assembly can be flatter than components that are located in an area of ​​the circuit board that covers the tab of the housing shell.

[0028] The flatter components can be assigned to a logic module of the electric motor, whereas the comparatively tall components belong to a power module. From the point of view of electromagnetic compatibility, it is particularly advantageous if the signal lines on the one hand and the power lines on the other, to which the components of the logic module are connected in the first case and the components of the power module in the second case, do not overlap.

[0029] A plug module of the electric motor can be held, in particular, on the housing cover, whereby the contours of the plug module can engage positively with the contours of the housing cover. When the plug module is inserted into the housing cover, electrically conductive connections to the circuit board can be established in the manner described. Electrical contacts can be made by means of contact surfaces arranged side by side to complement the previously mentioned design features of the circuit board.

[0030] The total surface area of ​​the circuit board is divided into a power section and a logic section. The aforementioned motor contact, optionally with insulation displacement connectors, is located in the power section area. The second, wider part of the circuit board can be used for the power section, whereas the logic section is further away from the connector module. The various current paths, namely power paths on the one hand and signal paths on the other, can thus be designed not only without crossings but also short overall. The thermally conductive paste, which is used as a potting material and has a defined thermal resistance, is located in particular between the inner wall of the housing cover formed by the V-shaped elevation and the unpopulated back of the circuit board.The potting material can contain solids, particularly in the form of solid or hollow spheres, for example glass beads, and ensures a defined insulation distance between the electronic module and the housing cover.

[0031] The potting material, which is applied as a paste or adhesive, contributes to reliable heat dissipation within the finished electric motor during intended operation. A mounting counterpart provided by the combustion engine can be used as a heat sink. In general, heat can flow from the electronic module, particularly its power section, to the combustion engine. A heat path may exist that extends from the power section of the electronic module through the potting material and the light metal housing cover of the electric motor to a cylinder head of the combustion engine. The heat path may include screw bosses located near the power section, at which a mechanical and thermally conductive connection is established between the electric motor and the cylinder head.

[0032] The electric motor can optionally be equipped with sensors. In particular, these are sensors for detecting the angular position and / or speed of the electric motor shaft. Such sensors include, for example, a sensor ring located on the rotor of the electric motor, which can be manufactured, in particular, as a deep-drawn part. Hard ferrites are possible materials for the sensor ring. In general, any known sensor technology, including magnetic and optical sensors, can be used.

[0033] When it comes to assembling the electric motor and the associated actuator, the fact that the individual, partially pre-assembled components can be attached to an internal combustion engine in an axial direction is particularly advantageous. The axial direction refers to the alignment of the electric motor's motor shaft, which coincides with the longitudinal direction of the camshaft to be adjusted. This applies regardless of the type of actuator connected between the electric motor and the camshaft of the internal combustion engine.

[0034] The applicability of the electric motor is not limited to electromechanical camshaft adjusters. Rather, the electric motor can also be used to drive other components in an automobile, such as a water pump, or for stationary applications.

[0035] An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. The drawings show, in some simplified form:

[0036] Fig. 1 shows an electric motor for a camshaft adjuster in a sectional view,

[0037] Fig. 2 Components of the electric motor in simplified sectional view,

[0038] Fig. 3 Components of the electric motor in a roughly simplified sectional view,

[0039] Fig. 4 a detail of the electric motor, namely a section of a housing cover with a circuit board mechanically attached and electrically contacted thereto,

[0040] Fig. 5 the electric motor in perspective view,

[0041] Fig. 6 shows a housing cover of the electric motor including an electronic module inserted into the housing cover, Fig. 7 shows the electric motor including the electronic module in an exploded view,

[0042] Fig. 8 Components of the electric motor in a sectional perspective view,

[0043] Fig. 9 the electric motor including the electronic module in a partially sectioned view,

[0044] Fig. 10 an insulation displacement contact assigned to the electronic module and intended for press-fit mounting,

[0045] Fig. 11 in a representation analogous to Fig. 6 components of the electric motor including a plug module,

[0046] Fig. 12 a detail of the electric motor including a positive connection between components of the electric motor,

[0047] Fig. 13 another detail of the electric motor including a motor contact,

[0048] Fig. 14 the opened housing of the electric motor, with electronic module and marking of heat flows,

[0049] Fig. 15 the complete electric motor with heat flows marked,

[0050] Fig. 16 the electric motor in a first installation situation,

[0051] Fig. 17 shows the electric motor in a second installation situation. An electric motor, designated overall by reference numeral 1, is intended for use in an electromechanical camshaft adjuster (not shown in detail) of an internal combustion engine. Regarding the basic design and function of electromechanical camshaft adjusters, reference is made to the prior art cited above.

[0052] A housing 2 of the electric motor 1 comprises a housing shell 3 and a housing cover 4. The housing shell 3 is a sheet metal part made of sheet steel. In contrast, the housing cover 4 is a component of the electric motor 1 made of light metal, namely an aluminum alloy. In this case, the housing cover 4 is made of light metal sheet by deep drawing. Alternatively, the housing cover 4 could be manufactured by casting, for example.

[0053] A stator 28 of a stator-rotor assembly 5 of the electric motor 1 comprises energizable windings 6 and is inserted into a recess 11 of the housing shell 3. A stator carrier is designated by 29. The rotor of the electric motor 1 is mounted by means of a rolling bearing 30 and is designated overall by 7. The rotor 7 comprises, among other things, a motor shaft 8, which contacts a bearing shell 37, and a sensor ring 9, which is a component manufactured by deep drawing. After deep drawing, the sensor ring 9 is overmolded with plastic-bonded ferrite, thus providing a sensor surface of the sensor ring 9, which is designed as a multi-component component. An electronics module 10, which will be discussed in more detail below, is integrated into the electric motor 1.

[0054] The housing shell 3 forms a tab 12 with a rectangular basic shape that adjoins the recess 11. The width of the tab 12 corresponds at least to the radius of the recess 12. In the present case, the tab 12 is wider than the recess 11. In the present case, there are no fastening openings in the tab 12, which is referred to as rectangular for the sake of simplicity. Three fastening tabs 13 arranged at different points on the circumference of the housing shell 3 are aligned with fastening tabs 14 of the housing cover 4. The motor shaft 8 of the electric motor 1 is located inside the triangle described by the fastening tabs 13, 14. A torque transmission element 16 located outside the housing 2 is connected to the motor shaft 8.

[0055] The electronics module 10 is accommodated in the housing cover 4 and comprises a circuit board 17 with a triangular basic shape. Various components 18, 19, including several capacitors 19, are located on the circuit board 17. In the exemplary embodiment, all components 18, 19 are arranged on the side of the circuit board 17 facing the rotor 7 and the stator-rotor assembly 5. Adapted to the triangular basic shape of the circuit board 17, a V-shaped elevation 15 is visible on the outside of the housing cover 4. The tip of the V-shaped elevation is located near the fastening tabs 13, 14 which are diametrically opposite the rectangular tab 12. Starting from this, the V-shaped elevation 15 widens towards the rectangular tab 12.On the side of the widened end of the V-shaped protrusion 15, there is a connector module 20, which is held in the housing cover 4, with positive-locking contours between the connector module 20 and the housing cover 4 being designated by 23. Pins 27 for contacting the printed circuit board 17 are held in the connector module 20.

[0056] Regarding the assembly of the electric motor 1, reference is made to Figures 1 to 4. A paste 31 is applied to the inside of the housing cover 4 as a potting compound. The paste 31 serves as a heat-conducting material within the finished electric motor. The paste 31 creates a gap between the inside of the housing cover 4 and the unpopulated back of the printed circuit board 17, designated 32. The printed circuit board 17 has openings 26 into which material of the housing cover 4 protrudes in a peg-like manner. After the printed circuit board 17 has been inserted into the housing cover 4, the peg-shaped material of the housing cover 4 is deformed such that it rests against an electrically conductive coating 34, which is also present on the wall of the opening 26. This deformation both mechanically fixes the printed circuit board in place and electrically contacts it.The resulting positive connection is designated 35, a deformation area of ​​the housing cover 4 is designated 36.

[0057] In addition to the aforementioned form-fitting connections 35, there are two further types of connection between the housing cover 4 and the printed circuit board 17, which also each form both an electrical and a mechanical contact.

[0058] Firstly, there are insulation displacement contacts 21 located on the circuit board 17, which enable the supply of current to the windings 6. The insulation displacement contacts 21 are electrically connected to the circuit board 17 by press-fitting and function as motor contacts within the electronics module 10. In the assembled electric motor 1, the insulation displacement contacts 21 are supported on the stator carrier 29. Secondly, the aforementioned pins 27, in addition to their electrical function, also perform, at least to a subordinate extent, a mechanical function. Also worth mentioning is an adhesive 33, which is inserted, among other things, between the connector module 20 and the housing shell 3, as well as between the housing cover 4 and the housing shell 3.

[0059] In the exemplary embodiment, the housing shell 3 is permanently connected to the housing cover 4 by several positive-locking connections 22, which are produced by material forming. Alternatively, rivets can be attached at the corresponding locations. Screw connections, however, are not provided. It is assumed that non-destructive disassembly of the electric motor 1, which in this case is operated with electronic commutation, is not necessary.

[0060] The operation of the electric motor 1, including the electronics module 10, is associated with a significant heat development. This particularly affects the circuit board area designated L2, in which the components 19 are located, but also the comparatively narrow circuit board area L1, which is populated with the relatively small components 18. S1, S2 designate the current flow between the connector module 20 and the various circuit board areas L1, L2. A heat flow designated WF, which is visualized in Figures 14 and 15, flows, among other things, through the mounting tabs 13, 14, thus allowing the cylinder head of the combustion engine to be used as a heat sink.

[0061] Regarding the installation of the electric motor 1, reference is made to Figures 16 and 17, which show alternative installation situations. In both cases, surrounding components that allow space for the installation of the electric motor 1 are designated 38, 39. As can be seen from a comparison of Figures 16 and 17, the two installation situations differ both with regard to the position of the central axis MA of the electric motor and with regard to the angular position of the housing 2. According to Figure 16, the angle bisector of the V-shaped elevation 15 is aligned parallel to the surrounding components 38, 39, which are shown here as stripes. In contrast, Figure 17 shows a clear inclination of the housing 2. The uniform distance between the surrounding components 38, 39 is indicated in both cases by d ges designated.

[0062] In the arrangement according to Fig. 16, the distance designated d between the central axis MA and the surrounding component 39 corresponds to half the distance d gesbetween the surrounding components 38, 39, which means a central positioning of the housing 2 and thus of the entire electric motor 1. In contrast, in the arrangement according to Fig. 1, the electric motor 1 is positioned asymmetrically between the surrounding components 38, 39, which is associated with the fact that the distance of the central axis MA from the surrounding component 39, designated in this case by dR2, is less than half the distance d g it is between the surrounding components 38, 39. Figures 16 and 17 illustrate the installation situation in various vehicle types and show that no fundamental changes to the electric motor 1 are required for the various uses of the camshaft adjuster.

[0063] electric motor

[0064] Housing

[0065] Housing shell

[0066] Housing cover

[0067] Stator-rotor assembly

[0068] winding

[0069] rotor

[0070] Motor shaft

[0071] Sensor ring

[0072] Electronic module

[0073] Recess of the housing shell rectangular tab

[0074] Mounting tab of the housing shell

[0075] Mounting tab of the housing cover V-shaped elevation of the housing cover Torque transmission element, rotor-fixed Printed circuit board

[0076] Component, flat

[0077] capacitor, component

[0078] Plug module

[0079] Insulation displacement contact, motor contact

[0080] Form-fitting connection

[0081] Form-fitting contour

[0082] Adhesive surface on the connector module

[0083] Adhesive surface on the housing cover

[0084] Opening in the circuit board

[0085] Pin

[0086] stator

[0087] Stator carrier

[0088] Rolling bearings

[0089] Paste, potting compound 32 back of the circuit board

[0090] 33 Adhesive

[0091] 34 Coating of the circuit board

[0092] 35 Form-fitting connection

[0093] 36 Deformation area

[0094] 37 bearing shell

[0095] 38 Surrounding component

[0096] 39 Surrounding component dges Distance between the surrounding components d , dR2 Distance between the central axis and a surrounding component

[0097] L1, L2 circuit board areas

[0098] MA central axis

[0099] S1 , S2 current paths

[0100] WF heat flow

Claims

Patent claims 1 . Method for assembling an electric motor (1), comprising the following steps: - Providing a multi-part housing (2) comprising a housing shell (3) and a housing cover (4), - providing an electronic module (10) comprising a printed circuit board (17) on which there is at least one motor contact (21) which is connected to the printed circuit board (17) by means of a press fit, - provision of a stator-rotor assembly (5), - inserting the printed circuit board (17) into the housing cover (4), wherein a heat-conducting paste (31) is introduced into a gap between the inner wall of the housing cover (4) and the printed circuit board (17), - forming a mechanical and electrically conductive connection between the housing cover (4) and the printed circuit board (17), - placing a plug module (20) on the circuit board (17), wherein a pin (27) held in the plug module (20) is inserted into the circuit board (17), - Placement of the stator-rotor assembly (5) in the housing shell (3), - assembling the housing cover (4) including the printed circuit board (4) and the plug module (20) with the housing shell (3) including the stator-rotor assembly (5), wherein the motor contact (21) arranged on the printed circuit board (17) is electrically connected to the stator-rotor assembly (5) and is simultaneously pressed against the printed circuit board (17), - Establishing a positive connection (22) between the housing cover (4) and the housing shell (3).

2. Method according to claim 1, characterized in that the mechanically and electrically conductive connection between the housing cover (4) and the printed circuit board (17) as well as the connection between the housing cover (4) and the housing shell (3) is produced by deformation of material of the housing cover (4).

3. Method according to claim 2, characterized in that by forming material of the housing cover (4) this material is brought into contact with a metallic coating (34) which is located on an inner surface of an opening (26) of the circuit board (17).

4. Electric motor (1), with a multi-part housing (2), which comprises a housing shell (3) made of a first material and a housing cover (4) made of a second material, wherein a stator-rotor assembly (5) and an associated electronic module (10) including a printed circuit board (17) are accommodated in the space formed between the housing shell (3) and the housing cover (4), wherein the printed circuit board (17) is arranged three times, namely - firstly by deformed material of the housing cover (4), - secondly by a motor contact (21) which is supported on the stator-rotor assembly (5), and - thirdly, by a pin (27) which is held in a plug module (20) which is inserted between the housing shell (3) and the housing cover (4), and is both mechanically fixed and electrically contacted.

5. Electric motor (1) according to claim 4, characterized in that the housing cover (4) is made of light metal and the housing shell (3) is made of sheet steel.

6. Electric motor (1) according to claim 4 or 5, characterized in that form-fitting connections (22) between the housing shell (3) and the housing cover (4) are formed by deformed material of the housing cover (4) in the same way as between the housing cover (4) and the printed circuit board (17).

7. Electric motor (1) according to one of claims 4 to 6, characterized in that the housing shell (3) has a circular recess (11) adapted to the shape of the stator-rotor assembly (5) and a tab (12) adjoining a portion of the edge of the recess (11) and describing a rectangle, wherein the width of the tab corresponds to at least half the diameter of the recess (11), and wherein the housing cover (4) covers both the area of the recess (11) and said tab (12) and has a V-shaped plateau-like elevation (15) which extends from the edge of the recess (11) facing away from the tab (12) into the area of the tab (12) and accommodates the printed circuit board (17), wherein this describes a V-shape which widens from the recess (11) to the tab (12) in accordance with the shape of the V-shaped elevation (15).

8. Electric motor (1) according to claim 7, characterized in that components (18) arranged on the circuit board (17) in the area which covers the stator-rotor assembly (5) are flatter than components (19) which are located in an area of the circuit board (17) covering the tab (12).

9. Electric motor (1) according to one of claims 4 to 8, characterized in that the stator-rotor assembly (5) has a rotor (7) to which a sensor ring (9) is assigned, which is designed as a deep-drawn part and comprises hard ferrite.

10. Use of an electric motor (1) according to claim 4 in an electric camshaft adjuster of an internal combustion engine.

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