Electric motor having a housing-fixed switching unit, electric bicycle, and installation method for an electric motor

Abstract

The invention relates to an electric motor having a housing in which there is arranged a stator having a stator body comprising at least two coils, a housing-fixed switching unit by way of which the at least two coils are interconnected to form a stator winding, and at least one decoupling element by way of which the stator body is spring-mounted in relation to the housing. The invention also relates to an electric bicycle and to an installation method.

Description

[0001] Electric motor with a housing-fixed switching unit, electric bicycle and assembly method for an electric motor

[0002] Description

[0003] The present invention relates to an electric motor according to claim 1, an electric bicycle according to claim 10 and an assembly method according to claim 11.

[0004] An electric motor comprises a housing in which a stator is arranged. The stator comprises a stator body with a plurality of coils, which generate a rotating magnetic field to drive a rotor arranged in the stator.

[0005] During operation of the electric motor, the electromagnetic forces required to achieve the desired rotor speed can excite the stator's natural frequencies. When a natural frequency is excited, the stator generates elevated structure-borne noise levels, which can ultimately lead to undesirable airborne noise emissions. To reduce the generation of elevated structure-borne noise levels, the stator is typically decoupled from the housing by spring-mounting it on the housing via a spring element.

[0006] Typically, a first housing component is used to preload the stator against a second housing component via the spring element. For example, DE 20 2020 102 442 U1 discloses using a housing end shield to preload the stator against a housing base. For assembly, the stator is positioned on the housing base and clamped to it with the end shield under tension.

[0007] Based on this, the object is to provide an electric motor that enables a reduction in the structure-borne noise generated by the stator while allowing easier and more flexible assembly. According to a first aspect of the proposed solution, this object is achieved with an electric motor according to claim 1. The electric motor has a housing in which a stator is arranged. The stator has a stator body with at least two coils, a switching unit fixed to the housing, via which the at least two coils are connected to form a stator winding, and at least one decoupling element via which the stator body is resiliently mounted relative to the housing.

[0008] The proposed solution is based on the idea of ​​using the stator's switching unit to mount the stator securely to the housing. The switching unit can be kinematically decoupled from the stator body, allowing the stator body to move relative to the switching unit. This makes it possible to mount the stator body spring-loaded relative to the housing.

[0009] The stator body can have two coils arranged opposite one another (along a rotor's rotational axis). Each coil can be formed by a winding of winding wire. In principle, the stator body can have any number of coils arranged in a star configuration around a center, which can be defined by the rotor's rotational axis. For example, the stator body can have six pairs of coils arranged in this manner.

[0010] The at least two coils can be connected via the switching unit in such a way that a rotating magnetic field can be generated via the at least two coils, which the stator can use to drive the rotor. This can be achieved, for example, with a star or delta connection of the coils. The at least two coils can, for example, have windings formed from a common winding wire, with the winding wire being routed between the coils via the switching unit.

[0011] The stator body, with the at least two coils, can form a cylinder that surrounds the rotor in a jacket-like manner. The switching unit can be arranged on one end face of the stator body. The switching unit is preferably ring-shaped.

[0012] The interconnection of the at least two coils to form a stator winding via the switching unit can enable operation of the at least two coils in such a way that they can be switched to generate the rotating magnetic field required for rotation of the rotor. The at least one decoupling element can support the stator body axially and / or radially in a resilient manner relative to the housing. For axial support, the at least one decoupling element can have at least one spring element that projects in the direction of the housing on a side of the stator body facing away from the switching unit. For radial support, the at least one decoupling element can have at least four spring elements that project radially from the stator body in the direction of the housing, pointing away from the axis of rotation of the rotor.

[0013] In one embodiment, the housing is formed in one piece. Alternatively, at least one housing section surrounding the stator can be formed in one piece. This means that (in both variants) there is no need for an additional housing component, such as a bearing plate with which the stator body is preloaded against another housing component, which makes assembly more flexible and easier overall. For assembly, only the switching unit needs to be attached to the housing, which can create sufficient preload on the stator body to resiliently mount it relative to the housing via the at least one decoupling element.

[0014] In one embodiment, the switching unit is attached to the housing via at least one fastening element. The at least one fastening element can comprise a screw, for example. The fastening element can engage a fastening section (e.g., a projection) of the switching unit and connect it positively and / or non-positively to a counter-element (e.g., a threaded opening) on ​​the housing. The switching unit can thus exert a contact force, which can be specified during assembly, on the stator body in order to preload the at least one decoupling element.

[0015] In one embodiment, the at least one fastening element connects the switching unit and the housing parallel to a connecting axis that extends between the switching unit and the stator body. The connecting axis can be parallel to a rotation axis that the stator body defines for a rotor arranged therein. It can correspond to a connecting direction of the at least one fastening element and the counter element on the housing. The preload for the at least one decoupling element can be generated along the connecting axis. Thus, the switching unit can preload the at least one spring element that protrudes in the direction of the housing on the side of the stator body facing away from the switching unit. In a plane transverse to the connecting axis, the housing can have a bearing section on which the switching unit is mounted on the housing.If the bearing section is arranged in the plane transverse to the connection axis, an axial position of the switching unit can be precisely specified and thus the preload can be better defined.

[0016] In one embodiment, the stator has at least one spacer element, via which the switching unit is attached to the housing with the at least one fastening element. The spacer element can, for example, comprise a bushing. The spacer element can be used to stabilize the switching unit on the at least one fastening element. Furthermore, the spacer element can be used to specify a distance between the switching unit and the stator body and thus (possibly in addition to the bearing section) to specify a preload.

[0017] In one embodiment, at least one electrical line extends between the stator body and the switching unit. The at least one electrical line can, for example, be a section of a winding wire with which at least one of the at least two coils is formed. The stator can further be designed to compensate for a relative movement of the stator body with respect to the switching unit on the at least one electrical line. If the stator body is moved during operation due to the resilient mounting on the housing, a displacement of the stator body relative to the switching unit can occur. During this movement, the at least one electrical line is moved relative to the switching unit in order to avoid damage to the at least one electrical line, the stator body or the switching unit.

[0018] The design of the stator for compensating for the relative movement of the at least one electrical line is explained below by way of example. The at least one electrical line can extend from a fixing point on the stator body to a fixing point on the switching unit. In this case, the at least one electrical line can be longer than a distance between the two fixing points. The longer distance can result in play for the at least one electrical line, via which the at least one electrical line can compensate for the relative movement. Alternatively or additionally, the at least one electrical line can be displaceably mounted on the switching unit and / or the stator body, such that it can compensate for the relative movement via the displacement.Because the relative movement of the stator body relative to the switching unit can be compensated via the at least one electrical line, the transmission of structure-borne sound from the stator body via the switching unit into the housing can be reduced.

[0019] In one embodiment, the electric motor has a control unit with which a current flow through the at least two coils can be controlled and which has an electrical circuit board (PCB) that is permanently connected to the switching unit. The current flow through the at least two coils can be controllable such that a rotating magnetic field for driving a rotor is generated via the at least two coils. Preferably, no further elements are arranged between the control unit and the switching unit. In particular, the control unit can be adjacent to the switching unit. For assembly, it may be necessary to mount the control unit after the stator body and the switching unit. Such subsequent assembly is facilitated due to the housing-fixed design of the switching unit. In particular, no additional component such as a bearing plate is required to secure the stator to the housing.

[0020] At least one contact element can be provided between the switching unit and the control unit to establish electrical contact. The at least one contact element can be rigid. In particular, it is not necessary to compensate for relative movement between the switching unit and the control unit via the at least one contact element because both are fixedly mounted on the housing.

[0021] In one embodiment, a filler element is provided between at least one of the at least two coils and the housing and / or the switching unit, with which heat generated during operation of the at least one coil can be dissipated. The heat can be dissipated from at least one of the at least two coils into the housing. The filler element can be designed to compensate for a relative movement of the stator body with respect to the housing, so that heat can be efficiently dissipated in any position the stator body can assume under the preload exerted by the switching unit.

[0022] In a further embodiment, the electric motor has at least one metallic heat-conducting element. The heat-conducting element can be arranged between the filler element and the housing. Additionally or alternatively, at least one metallic heat-conducting element can be arranged between the filler element and the switching unit. Additionally or alternatively, the at least one metallic heat-conducting element can form a core section of the switching unit against which the filler element rests. The at least one metallic heat-conducting element can, for example, have a stamped grid that can efficiently distribute the dissipated heat to the housing.

[0023] The switching unit can, for example, comprise a switching unit body having a core section and a sheathing section that at least partially encloses the core section. For example, the switching unit body can comprise an overmolded lead frame, wherein the overmold is formed from a non-metallic material. The filler element for dissipating heat can be positioned against the core section via a recess in the sheathing section, allowing dissipated heat to spread across the core section throughout the switching unit body and thus be efficiently dissipated.

[0024] According to a second aspect of the proposed solution, the problem is solved by an electric bicycle with an electric motor according to the first aspect.

[0025] According to a third aspect of the proposed solution, the problem is solved by an assembly method for an electric motor. The assembly method comprises the following steps: providing a housing, arranging a stator body with at least two coils on the housing by resiliently mounting the stator body on the housing via at least one decoupling element, connecting the at least two coils to form a stator winding via a switching unit, and fastening the switching unit to the housing.

[0026] The assembly method may be further developed according to the features and advantages described in connection with the first aspect of the proposed solution.

[0027] The attached figures illustrate possible embodiments of the proposed solution.

[0028] Here we show:

[0029] Figure 1 is a perspective view of a stator;

[0030] Figure 2 is a perspective view of a decoupling element;

[0031] Figure 3 is a sectional view through an embodiment of an electric motor; and Figure 4 is a sectional view through a section of another

[0032] Example of the electric motor.

[0033] Figure 1 shows a perspective view of a stator 2 with a stator body 20 with twelve coils and a switching unit 23. The number of coils is shown here as an example. In principle, the stator body 20 can have any number of coils. The coils together form a casing that encloses a space between the coils in which a rotor can be arranged. At least two coils are connected to form a stator winding via the switching unit 23. The coils can thus be supplied with electrical current in such a way that a rotating magnetic field can be generated in the space between the coils. The rotating magnetic field can be used to drive the rotor to rotate.

[0034] The switching unit 23 is ring-shaped and arranged on the end face of the stator body 20. On a side of the switching unit 23 facing away from the stator 2, ends of a winding wire 212 protrude from the switching unit 23. Two of the ends 212 each belong to a winding wire 211, which forms a winding 21 of the respective coil. A first section of the winding wire 211 is wound around a stator tooth 22, while two second sections of the winding wire 212 protrude from the coil through the switching unit 23. The second sections of the winding wire 212 can be used to electrically contact the respective coil.

[0035] From a side of the switching unit 23 facing away from the stator body 20, three contact elements 231 also protrude, via which the switching unit 23 can be contacted to control the switching processes between the electrical coils. The contact elements 231 are rigid. The contact elements 231 are each arranged on a base element 232, which contributes to the stiffening of the contact elements 231. In principle, any number of contact elements 231 can be provided on the switching unit 23. A rigid design of the contact elements 231 is preferred in order to establish reliable mechanical and electrical contact with a control unit 5, but is not absolutely necessary. The possibility of designing the contact elements 231 rigidly arises from the fact that the switching unit 23 can be mounted immovably relative to the control unit 5.

[0036] The switching unit 23 can be mounted decoupled from the stator body 20, so that a relative movement between the switching unit 23 and the stator body 20 is possible. The switching unit 23 can be mounted on a housing 1 in a housing-fixed manner. For mounting in a housing-fixed manner, the switching unit 23 has three connecting elements 233, each of which can interact with a fastening element 4 to fasten the switching unit 23 to the housing 1. In the present case, the connecting elements 233 have the form of through-openings. They are arranged at the vertices of an (imaginary) isosceles triangle on the switching unit 23. In principle, any number of connecting elements 233 can be provided on the switching unit 23, via which the switching unit 23 can be fastened to the housing 1.

[0037] The connecting elements 233 are arranged on projections 34 that protrude radially from a ring-shaped switching unit body 230. In the present case, the connecting elements 233 are designed such that an axial penetration of a fastening element 4 through the connecting elements 233 is possible. For this purpose, the connecting elements 233 have penetration openings. These are each defined by a spacer element 235 in the form of a bushing. The bushing can stabilize the respective penetration opening and electrically insulate it from the projection 234 on which the bushing is arranged.

[0038] The stator body 20 has several (in this case, twelve) decoupling elements 3 for mounting on the housing 1, which enable axial and radial resilient mounting of the stator body 20. For mounting, spring sections 31, 32 of the decoupling element 3 protrude radially and axially from the stator body 20. In principle, any desired number of decoupling elements 3 can be provided. A number of decoupling elements 3 corresponding to the number of coils of the stator body 20 is preferred, so that effective decoupling can occur as close as possible to each coil.

[0039] Figure 2 shows a perspective view of a decoupling element 3. The decoupling element 3 has a base section 30, from which three spring sections 31, 32 protrude in the radial direction. A further spring section protrudes from the base section 30 along an axial direction. The decoupling element 3 is formed in one piece. In principle, the number of spring sections 31, 32 is arbitrary. The decoupling element 3 is designed to be arranged on grooves of the stator body 20 that extend axially (to the axis of rotation of a rotor). It is fixedly mounted on the stator body 20 via the grooves. An alternative mounting is also conceivable and possible. Figure 3 shows a sectional view through an embodiment of an electric motor with a housing 1 in which a stator 2 is arranged. A coil of the stator body 20 is shown in cross section.The coil has a winding 21, for which a first section of a winding wire 211 is wound several times around a winding axis W, which in this case is provided by a stator tooth 22. A second section of the winding wire 212 projects into a switching unit 23, which is arranged on the stator body 20 in an installation direction E transverse to the winding axis W. Via the switching unit 23, the coil shown in cross section is connected to at least one other coil to form a stator winding. The installation direction E is parallel to a connecting axis that extends between the switching unit 23 and the stator body 20. This also corresponds to a rotational axis D of a rotor, for whose rotational drive the stator 2 is designed.

[0040] A control unit 5 is arranged on the switching unit 23 along the installation direction E. The control unit 5 controls the current flow through the coils of the stator body 20. The control unit 5 has an electrical circuit board that is permanently connected to the switching unit 23. The permanent connection of the control unit 5 to the switching unit 23 ensures reliable and uninterrupted control of the coils. The electrical circuit board of the control unit 5 is arranged along a plane that is perpendicular to the installation direction E.

[0041] The stator body 20 is resiliently mounted relative to the housing 1 via a decoupling element 3. The decoupling element 3 is designed such that the stator body 20 is resiliently mounted on the housing 1 along the winding axis W and additionally transversely to the winding axis W. This corresponds to a resilient mounting of the stator body 20 arranged radially and axially relative to the rotational axis D.

[0042] To assemble the electric motor, the housing 1 is first prepared. The housing 1 has a stator bearing 10 in the form of a recess. The stator bearing 10, in turn, has a base section 102, which is enclosed by a wall section 101. The wall section 101 extends along a circumferential direction around the axis of rotation D of a rotor of the electric motor. The stator body 20 is arranged on the stator bearing 10. The stator body 20 is resiliently supported on the base section 102 and the wall section 101 via the decoupling element 3. Specifically, the decoupling element 3 is arranged on the stator body 20 via its base section 30. Three first spring sections 31 protrude from the base section 30 in the direction of the wall section 101 and rest against the wall section 101. A second spring portion 32 protrudes from the base portion 30 toward the bottom portion 102 and bears against the bottom portion 102.

[0043] The switching unit 23 interacts with the stator body 20 in such a way that the second spring section 32 is preloaded. This allows decoupling of the stator body 20 from the housing 1 to be achieved.

[0044] The interaction of the switching unit 23 with the stator body 20 is defined by the fact that the switching unit 23 is fastened to the housing 1. For this purpose, a fastening element 4 (here shown as an example as a screw) is passed along the installation direction E through the connecting element 233 on the projection 234 of the switching unit 23 and fastened to a counter-element 11 of the housing 1 (here shown as an example as a threaded opening). Alternative connecting elements 233 and counter-elements 11 are also conceivable and possible. The projection 234 on the switching unit body 230 is held to a bearing section 12 of the housing 1 via the fastening element 4. The connection is mediated by a spacer element 235, which rests against the bearing section 12 and with which the projection 234 is positively connected.The fastening element 4 has a head portion 41 and a neck portion 42, wherein the head portion 41 presses the spacer element 235 against the bearing portion 12 and the neck portion 42 is mounted on the counter element 11 on the housing 1. A thread of the neck portion 42 cooperates with a thread of the counter element 11 for fastening.

[0045] After the switching unit 23 is attached to the housing 1, the control unit 5 can be mounted in an independent, possibly delayed, assembly step. The assembly of additional housing components that interact with the switching unit 23 to attach the stator 2 to the housing 1 is not required.

[0046] A filler element 6 is provided between the coil with its winding 21 and the base section 102, with which heat generated during operation of the coil can be dissipated. For this purpose, the filler element 6 is in direct contact with the winding wire 211 and the base section 102.

[0047] Figure 4 shows a sectional view through a section of another embodiment of the electric motor. The electric motor has a housing 1 in which a stator 2 is arranged. The stator 2 has a coil with a winding 21, which is formed by a first section of a winding wire 211 wound around a stator tooth 22. A second section of the winding wire 212 projects from the winding 21 into a switching unit 23. The second section of the winding wire 212 is designed such that it has play so that it can compensate for a relative movement of the coil with respect to the switching unit 23. For this purpose, the second section of the winding wire 212 is bent (twice here) between the stator body 20 and the switching unit 23. The second section of the winding wire is in the form of an electrical line that extends between the stator body 20 and the switching unit 23.Due to the curved design of the second section of the winding wire, the stator 2 is designed to compensate for a relative movement of the stator body 20 with respect to the switching unit 23 via the electrical line 212.

[0048] The switching unit 23 has a switching unit body 230, which has a casing section 2301, with which a core section 2302 of the switching unit body 230 is covered. The casing section 2301 is made of a non-metallic material, such as plastic. The core section 2302, in contrast, is metallic, so that it can conduct heat. The casing section 2301 has a recess through which the core section 2302 is freely accessible. A filling element 6 is arranged at the recess, via which the coil is thermally coupled to the core section 2302. In particular, the core section 2302 extends to the fastening element 4, via which the switching unit 23 is fastened to the housing 1. The fastening element 4 is metallic in the present case and thus thermally couples the core section 2302 and the housing 1 to one another.

[0049] Thus, the core section 2302 of the switching unit 23 is used as a heat-conducting element for dissipating waste heat from the coil via the filler element 6 and the fastening element 4 into the housing 1. In principle, such a function can also be provided by an additional heat-conducting element provided between the switching unit 23 and the stator body 20. A lead frame, for example, is suitable as a heat-conducting element.

[0050] 1 housing

[0051] 10 stator bearings

[0052] 101 wall section

[0053] 102 floor section

[0054] 11 Counter element

[0055] 12 storage section

[0056] 2 Stator

[0057] 20 stator bodies

[0058] 21 winding

[0059] 211 first section winding wire

[0060] 212 second section winding wire

[0061] 22 stator tooth

[0062] 23 Switching unit

[0063] 230 Switch unit body

[0064] 2301 Enclosure section

[0065] 2302 core section

[0066] 231 Contact element

[0067] 232 Base element

[0068] 233 connecting element

[0069] 234 lead

[0070] 235 spacer element

[0071] 3 Decoupling element

[0072] 30 Base section

[0073] 31, 32 spring section

[0074] 4 Fastening element

[0075] 41 Head section

[0076] 42 neck section

[0077] 5 Control unit

[0078] 6 Filling element

[0079] D axis of rotation

[0080] E Installation direction

[0081] W winding axis

Claims

Claims 1 . Electric motor with a housing (1) in which a stator (2) is arranged, the - a stator body (20) with at least two coils, - a housing-fixed switching unit (23), via which the at least two coils are connected to form a stator winding, and - at least one decoupling element (3) via which the stator body (20) is resiliently mounted relative to the housing (1).

2. Electric motor according to claim 1, characterized in that the housing (1) is formed in one piece.

3. Electric motor according to one of claims 1 or 2, characterized in that the switching unit (23) is fastened to the housing (1) via at least one fastening element (4).

4. Electric motor according to claim 3, characterized in that the at least one fastening element (4) connects the switching unit (23) and the housing (1) parallel to a connecting axis which extends between the switching unit (23) and the stator body (20).

5. Electric motor according to one of claims 3 or 4, characterized in that the stator (2) has at least one spacer element (235) via which the switching unit (23) is fastened to the housing (1) with the at least one fastening element (4).

6. Electric motor according to one of the preceding claims, characterized in that at least one electrical line (212) extends between the stator body (20) and the switching unit (23), wherein the stator (2) is designed to compensate for a relative movement of the stator body (20) with respect to the switching unit (23) on the at least one electrical line (212).

7. Electric motor according to one of the preceding claims, characterized by a control unit (5) with which a current flow through the at least two coils can be controlled and which has an electrical circuit board which is fixedly connected to the switching unit (23).

8. Electric motor according to one of the preceding claims, characterized in that a filling element (6) is provided between at least one of the at least two coils and the housing (1) and / or the switching unit (23), with which heat generated during operation of the at least one coil can be dissipated.

9. Electric motor according to claim 8, characterized by at least one metallic heat-conducting element which is arranged between the filling element (6) and the housing (1), which is arranged between the filling element (6) and the switching unit (23) and / or which forms a core section (2302) of the switching unit (23) against which the filling element (6) rests.

10. Electric bicycle with an electric motor according to one of claims 1 to 9.

11. Assembly method for an electric motor, comprising the following steps: - Providing a housing (1), - Arranging a stator body (20) with at least two coils on the housing (1) by means of a resilient mounting of the stator body (20) on the housing (1) via at least one decoupling element (3), - connecting the at least two coils to a stator winding via a switching unit (23), and - Fasten the switching unit (23) to the housing (1). *********

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