Electric motor with a switching unit fixed to a housing, electric bicycle, and method for assembling an electric motor.

Abstract

The present invention relates to an electric motor having a housing on which a stator is arranged, the stator comprising a stator body having at least two coils, a switching unit fixed to the housing that interconnects at least two coils to form a stator winding, and at least one decoupling element that elastically attaches the stator body to the housing. The present invention also relates to an electric bicycle and a method of installation.

Description

Technical Field

[0001] 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.

Background Art

[0002] An electric motor includes a housing in which a stator is disposed. The stator includes a stator body having a plurality of coils, through which a rotating magnetic field for driving a rotor disposed within the stator is generated.

[0003] During operation of the electric motor, the electromagnetic force required for the desired rotational speed of the rotor may excite the natural frequency of the stator. When the natural frequency is excited, the stator generates an increased level of structure - borne sound, which may ultimately lead to undesirable airborne sound radiation. Therefore, in order to reduce the generation of the increased level of structure - borne sound, the stator is generally made such that vibration is not transmitted from the housing by elastically supporting the stator to the housing via spring elements.

[0004] Typically, a first housing component is used to bias the stator relative to a second housing component via spring elements. From Patent Document 1, for example, it is known to use the bearing shield of the housing to bias the stator against the bottom of the housing. For assembly, the stator is placed on the bottom of the housing and in that state is surrounded by the bearing shield under stress.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Means for Solving the Problems

[0006] Starting from this point, the objective is to provide an electric motor that enables a reduction in solid-borne noise generated by the stator through a simplified and more flexible assembly.

[0007] This objective is achieved by the electric motor described in claim 1, according to a first aspect of the proposed solution. The electric motor has a housing on which a stator is located. The stator has a stator body having at least two coils, a switching unit fixed to the housing that interconnects at least two coils to form a stator winding, and at least one decoupling element that elastically supports the stator body relative to the housing.

[0008] The proposed solution is based on the idea of ​​using a stator switching unit to support the stator while it is fixed to the housing. In this case, the switching unit can be kinematically independent from the stator body, allowing the stator body to move relative to the switching unit. This makes it possible to elastically support the stator body relative to the housing.

[0009] The stator body may have two coils arranged opposite each other (with the rotor's axis of rotation in between). Each coil may be formed by windings of a winding wire. In principle, the stator body can have any desired number of coils arranged in a star shape around a center predetermined by the rotor's axis of rotation. For example, the stator body may have six pairs of coils arranged in this manner.

[0010] At least two coils may be interconnected via a switching unit so that a stator can generate a rotating magnetic field through the at least two coils that can drive a rotor. This can be implemented, for example, by a star or delta connection of the coils. The at least two coils may include, for example, a winding formed from a common winding wire, which passes between the coils via the switching unit.

[0011] The stator body can be formed by a cylinder that encloses the rotor in a shell-like manner, along with at least two coils. The switching unit can be positioned on the end face of the stator body. The switching unit is preferably formed in an annular shape.

[0012] Connecting at least two coils via a switching unit to form a stator winding allows for the operation of at least two coils so that they can be switched to generate the rotating magnetic field necessary to rotate the rotor.

[0013] At least one decoupling element can elastically support the stator body axially and / or radially relative to the housing. For axial support, at least one decoupling element may have at least one spring element projecting toward the housing on the side of the stator body opposite to the switching unit. For radial support, at least one decoupling element may have at least four spring elements projecting toward the housing from the stator body so as to point radially away from the rotor's axis of rotation.

[0014] In one embodiment, the housing is integrally formed. Alternatively, at least one housing section surrounding the stator can be integrally formed. Therefore, additional housing components such as bearing shields can be omitted (in either modification). Such components are used to bias the stator body against other housing components, and eliminating them makes assembly more flexible and easier overall. During assembly, the switching unit only needs to be fixed to the housing, thereby generating sufficient preload on the stator body to elastically support the stator body against the housing via at least one decoupling element.

[0015] In one configuration, the switching unit is secured to the housing via at least one fixing element. The at least one fixing element may include, for example, a screw. The fixing element engages with a fixing section (e.g., a projection) of the switching unit, and the switching unit can be connected to a corresponding element (e.g., a screw hole) of the housing by shape fitting and / or force fitting. This allows the switching unit to exert a pressing force on the stator body that can be determined in advance at the time of assembly in order to preload at least one decoupling element.

[0016] In one configuration, at least one fixed element connects the switching unit to the housing parallel to a connecting axis extending between the switching unit and the stator body. The connecting axis may be parallel to the axis of rotation defined by the stator body with respect to a rotor located inside the stator body. It may correspond to the connection direction between at least one fixed element and a corresponding element of the housing. Along the connecting axis, a preload can be generated for at least one decoupling element. As a result, at least one spring element protruding toward the housing on the side of the stator body opposite to the switching unit can be biased by the switching unit.

[0017] In a plane lateral to the connection axis, the housing may have a support section on which the switching unit is supported. When the support section is positioned in a plane lateral to the connection axis, this allows for precise definition of the axial position of the switching unit and, therefore, better definition of the preload.

[0018] In one configuration, the stator has at least one spacer element through which the switching unit is fixed to the housing by at least one fixing element. The spacer element may include, for example, a bushing. The switching unit can be stabilized by the spacer element by at least one fixing element. Furthermore, the spacer element can be used to define the distance of the switching unit from the stator body, and therefore to define preload (optionally in addition to the support section).

[0019] In one configuration, at least one electrical line extends between the stator body and the switching unit. The at least one electrical line may be, for example, a section of winding wire on which at least one of at least two coils is formed. The stator may further be formed to compensate for the relative movement of the stator body with respect to the switching unit in at least one electrical line. If the stator body moves during operation due to elastic support to the housing, displacement of the stator body with respect to the switching unit may occur. During this movement, at least one electrical line moves to follow the switching unit in order to avoid damage to at least one electrical line, the stator body, or the switching unit.

[0020] A stator configuration for compensating relative movement in at least one electrical line is described below illustratively. At least one electrical line can extend from a fixed point on the stator body to a fixed point on the switching unit. In this case, the at least one electrical line can be longer than the distance between the two fixed points. The longer distance can provide clearance for the at least one electrical line, through which the at least one electrical line can compensate for relative movement. Alternatively, or in addition to this, at least one electrical line can be assembled to be displaceable to the switching unit and / or stator body so that relative movement can be compensated through displacement. Since the relative movement of the stator body with respect to the switching unit can be compensated through at least one electrical line, the transmission of solid-borne sound from the stator body to the housing through the switching unit can be reduced.

[0021] In one configuration, the electric motor includes a control unit having an electrical printed circuit board (PCB) that is fixedly connected to a switching unit and capable of controlling the flow of current through at least two coils. The flow of current through at least two coils may be controllable such that a rotating magnetic field for driving a rotor is generated through at least two coils. Preferably, no further elements are placed between the control unit and the switching unit. In particular, the control unit can be adjacent to the switching unit. For assembly purposes, it may be necessary to assemble the control unit after the stator body and the switching unit in terms of time. Such later assembly is facilitated by the housing-fixed configuration of the switching unit. In particular, assembly of additional components such as bearing shields is not required to fix the stator to the housing.

[0022] To generate electrical contact, at least one contact element can be provided between the switching unit and the control unit. This at least one contact element may be rigid. In particular, relative movement between the switching unit and the control unit does not need to be compensated through the at least one contact element, since both are fixedly positioned within the housing.

[0023] In one configuration, a packing element is provided between at least one of the at least two coils and the housing and / or switching unit, and this packing element can be used to dissipate heat generated during the operation of at least one of the coils. The heat can be dissipated from at least one of the at least two coils into the housing. The packing element can be configured to compensate for the relative movement of the stator body with respect to the housing, and as a result, heat can be efficiently dissipated at each position of the stator body that can be taken under the preload exerted by the switching unit.

[0024] In further embodiments, the electric motor has at least one metallic heat conduction element. The heat conduction element may be positioned between the filling element and the housing. Furthermore, or otherwise, at least one metallic heat conduction element may be positioned between the filling element and the switching unit. Furthermore, or otherwise, at least one metallic heat conduction element may form the core section of the switching unit with which the filling element abuts. The at least one metallic heat conduction element may have, for example, a punched grid that can efficiently distribute the released heat to the housing.

[0025] The switching unit can have a switching unit body having, for example, a core section and a covering section at least partially covering the core section. For example, the switching unit body can have an injection-molded punched grid, where the injection-molded part is formed from a non-metallic material. Through a notch in the covering section, the filling element can abut against the core section to dissipate heat, and as a result, the released heat spreads across the core section throughout the switching unit body and is thus dissipated efficiently.

[0026] According to a second aspect of the proposed solution, the object is achieved by an electric bicycle equipped with an electric motor according to the first aspect.

[0027] According to a third aspect of the proposed solution, the object is achieved by a method for assembling an electric motor. The assembly method includes the following steps. Providing a housing, arranging a stator body having at least two coils in the housing by elastically supporting the stator body to the housing via at least one decoupling element, interconnecting at least two coils via a switching unit to form a stator winding, and fixing the switching unit to the housing.

[0028] The assembly method can be further configured according to the features and advantages described in relation to the first aspect of the proposed solution.

Brief Description of the Drawings

[0029] The accompanying drawings show, by way of example, possible embodiments of the proposed solution. Here, the following are shown.

[0030] [Figure 1] It is a perspective view of the stator. [Figure 2] It shows a perspective view of the decoupling element. [Figure 3] It shows a cross-sectional view of an exemplary embodiment of the electric motor. [Figure 4] A partial cross-sectional view of a further exemplary embodiment of an electric motor is shown. [Modes for carrying out the invention]

[0031] Figure 1 shows a perspective view of a stator 2 comprising a stator body 20 with 12 coils and a switching unit 23. Here, the number of coils is shown as an example. In principle, the stator body 20 can have any desired number of coils. Together, the coil group forms a covering that surrounds the space between the coils, within which the rotor can be placed. At least two coils are connected via the switching unit 23 to form a stator winding. This allows current to be supplied to the coils so 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.

[0032] The switching unit 23 is formed in an annular shape and is positioned on the end face of the stator body 20. On the side of the switching unit 23 opposite to the stator 2, the ends 212 of the winding wires protrude from the switching unit 23. Two of the ends 212 each belong to the winding wires 211 that form the windings 21 of the respective coils. The first section 211 of the winding wires is wound around the stator teeth 22 in each case, while the two second sections 212 of the winding wires protrude from the coils through the switching unit 23. The second sections 212 of the winding wires can be used for the electrical contact of the respective coils.

[0033] Furthermore, three contact elements 231 protrude from the switching unit 23 on the side opposite to the stator body 20, and the switching unit 23 can contact these contact elements to control the switching process between the electrical coils. In this case, the contact elements 231 are rigid. Each contact element 231 is positioned on a base element 232 which contributes to increasing the rigidity of the contact element 231. In principle, any number of contact elements 231 can be provided on the switching unit 23. A rigid configuration of the contact elements 231 is preferred, but not required, to establish reliable mechanical and electrical contact with the control unit 5. The ability to make the contact elements 231 rigid stems from the configuration that allows the switching unit 23 to be assembled so that it cannot move relative to the control unit 5.

[0034] The switching unit 23 can be supported independently of the stator body 20, and as a result, relative movement between the switching unit 23 and the stator body 20 is possible. The switching unit 23 can be supported in a fixed state relative to the housing 1. For fixed support to the housing, the switching unit 23 has three connecting elements 233, each of which works in cooperation with a fixing element 4 to fix the switching unit 23 to the housing 1. In this case, the connecting elements 233 have the form of through openings. They are arranged at the vertices of a (virtual) isosceles triangle of the switching unit 23. In principle, any number of connecting elements 233 can be provided on the switching unit 23, and these connecting elements can fix the switching unit 23 to the housing 1.

[0035] The connecting element 233 is positioned on a projection 34 that radially protrudes from the annularly formed switching unit body 230. In this case, the connecting element 233 is configured to allow the fixing element 4 to pass through the connecting element 233 in the axial direction. For this purpose, the connecting element 233 has through openings. These are each defined by spacer elements 235 in the form of bushings. By using bushings, each through opening can be stabilized and electrically isolated from the projection 234 on which the bushings are positioned.

[0036] To be supported by the housing 1, the stator body 20 has a plurality (12 in this case) of decoupling elements 3, which enable axial and radial elastic support of the stator body 20. For support, the spring sections 31 and 32 of the decoupling elements 3 protrude radially and axially from the stator body 20. In principle, any desired number of decoupling elements 3 can be provided. Preferably, the number of decoupling elements 3 corresponds to the number of coils in the stator body 20, thereby enabling effective decoupling as close as possible to each coil.

[0037] Figure 2 shows a perspective view of the decoupling element 3. The decoupling element 3 has a base section 30 from which three spring sections 31 and 32 project radially. Another spring section projects from the base section 30 along the axial direction. The decoupling element 3 is integrally formed. In principle, the number of spring sections 31 and 32 is arbitrary. The decoupling element 3 is configured to be positioned in a groove that extends axially (relative to the rotor's axis of rotation) in the stator body 20. It is fixedly supported by the stator body 20 through the groove. Alternative supports are also conceivable and possible.

[0038] Figure 3 shows a cross-sectional view of one embodiment of an electric motor having a housing 1 in which a stator 2 is arranged. The coil of the stator body 20 is shown in cross-section. The coil has a winding 21, and a first section 211 of the winding wire is wound several times around a winding axis W provided in this case by stator teeth 22. A second section 212 of the winding wire protrudes to a switching unit 23 located in the stator body 20 laterally to the winding axis W in the installation direction E. Through the switching unit 23, the coil shown in cross-section is connected to at least one further coil to form the stator winding. The installation direction E is parallel to the connecting axis extending between the switching unit 23 and the stator body 20. This also corresponds to the rotation axis D of the rotor, and the stator 2 is configured to rotate the rotor.

[0039] The control unit 5 is positioned on the switching unit 23 along the installation direction E. The current flow through the coils of the stator body 20 is controllable by the control unit 5. The control unit 5 includes an electrical circuit board that is fixedly connected to the switching unit 23. The fixed connection of the control unit 5 to the switching unit 23 ensures reliable and uninterrupted control of the coils. The electrical printed circuit board of the control unit 5 is positioned here along a plane that crosses the installation direction E.

[0040] The stator body 20 is elastically supported by the housing 1 via a decoupling element 3. The decoupling element 3 is configured such that the stator body 20 is elastically supported by the housing 1 along and across the winding axis W. This corresponds to the elastic support of the stator body 20, which is positioned radially and axially with respect to the rotation axis D.

[0041] For the assembly of the electric motor, a housing 1 is first provided. The housing 1 has a stator support 10 in the form of a recess. The stator support 10 further has a bottom section 102 surrounded by a wall section 101, where the wall section 101 extends circumferentially around the axis of rotation D of the rotor of the electric motor. The stator body 20 is positioned in the stator support 10, and the stator body 20 is elastically supported to the bottom section 102 and the wall section 101 via a decoupling element 3. Specifically, the decoupling element 3 is positioned in the stator body 20 via its base section 30. Three first spring sections 31 project from the base section 30 toward the wall section 101 and abut against the wall section 101. Second spring sections 32 project from the base section 30 toward the bottom section 102 and abut against the bottom section 102.

[0042] The switching unit 23 interacts with the stator body 20 so that the second spring section 32 is biased. As a result, the stator body 20 can be decoupled from the housing 1.

[0043] The interaction between the switching unit 23 and the stator body 20 is defined by the fact that the switching unit 23 is fixed to the housing 1. For this purpose, a fixing element 4 (shown here as a screw, for example) is passed along the installation direction E through a connecting element 233 provided on a projection 234 of the switching unit 23 and fixed to a corresponding element 11 of the housing 1 (shown here as a screw hole, for example). Alternative connecting elements 233 and corresponding elements 11 are similarly conceivable and possible. Through the fixing element 4, the projection 234 on the switching unit body 230 is held in the support section 12 of the housing 1. The connection here is provided via a spacer element 235 that abuts against the support section 12 and to which the projection 234 is connected in a shape-fit manner. The fixing element 4 has a head 41 and a neck 42, the head 41 pressing the spacer element 235 against the support section 12 and the neck 42 being supported by a corresponding element 11 provided on the housing 1. The threads of the neck portion 42 interact with the threads of the corresponding element 11 here for fixing.

[0044] After the switching unit 23 is fixed to the housing 1, the control unit 5 can be assembled in an independent, optionally delayed assembly step. There is no need to assemble any further housing components that interact with the switching unit 23 in order to fix the stator 2 to the housing 1.

[0045] Between the coil with the windings 21 and the bottom section 102, there is a packing element 6 that can dissipate the heat generated during the operation of the coil. For this purpose, the packing element 6 is in direct contact with the winding wires 211 and the bottom section 102.

[0046] Figure 4 shows a partial cross-sectional view of a further embodiment of an electric motor. The electric motor has a housing 1 in which a stator 2 is housed. The stator 2 includes a coil having a winding 21 formed by a first section 211 of winding wire wound around stator teeth 22. A second section 212 of the winding wire protrudes from the winding 21 to a switching unit 23. The second section 212 of the winding wire is formed to have a clearance, thereby compensating for the relative movement of the coil with respect to the switching unit 23. For this purpose, the second section 212 of the winding wire is bent (twice here) between the stator body 20 and the switching unit 23. The second section of the winding wire is here a form of an electrical line extending between the stator body 20 and the switching unit 23. The bent configuration of the second section of the winding wire configures the stator 2 to compensate for the relative movement of the stator body 20 with respect to the switching unit 23 via the electrical line 212.

[0047] The switching unit 23 includes a switching unit body 230 having a covering section 2301 that covers a core section 2302 of the switching unit body 230. The covering section 2301 is formed of a non-metallic material such as plastic. In contrast, the core section 2302 is made of metal and can conduct heat. The covering section 2301 has a notch that allows the core section 2302 to be freely accessed. A filling element 6 is placed in the notch, and through this filling element, the coil is thermally coupled to the core section 2302. Specifically, the core section 2302 extends to a fixing member 4 that secures the switching unit 23 to the housing 1. The fixing element 4 is made of metal in this case and therefore thermally couples the core section 2302 and the housing 1 to each other.

[0048] Thus, the core section 2302 of the switching unit 23 is used as a heat conduction element to dissipate heat from the coil into the housing 1 via the filling element 6 and the fixed element 4. Basically, a similar function can be achieved by a heat conduction element separately provided between the switching unit 23 and the stator body 20. A punched grid, for example, is suitable as a heat conduction element. [Explanation of symbols]

[0049] 1 Housing 10 Stator support 101 Wall Section 102 Bottom Section 11 Corresponding elements 12 Support Sections 2 staters 20 Stator body 21 windings 211 First Section Winding Wire 212 Second Section Winding Wire 22 stator teeth 23 Switching Units 230 Switching Unit Body 2301 Covering section 2302 Core Section 231 Contact elements 232 Base element 233 Connection Elements 234 Protrusion 235 Spacer element 3 Decoupling elements 30 Base section 31,32 Spring sections 4 Fixed elements 41 Head 42 Neck 5. Control Unit 6 Filling elements D Rotation axis E Installation direction W winding shaft

Claims

1. An electric motor having a housing (1) in which a stator (2) is arranged, the stator is A stator body (20) having at least two coils, A switching unit (23) fixed to the housing interconnects at least two of the coils to form a stator winding, The stator body (20) is elastically supported by at least one decoupling element (3) relative to the housing (1), An electric motor characterized by having the following features.

2. The electric motor according to claim 1, characterized in that the housing (1) is integrally formed.

3. The electric motor according to claim 1 or 2, characterized in that the switching unit (23) is fixed to the housing (1) via at least one fixing element (4).

4. The electric motor according to claim 3, characterized in that the at least one fixed element (4) connects the switching unit (23) and the housing (1) parallel to a connecting shaft extending between the switching unit (23) and the stator body (20).

5. The electric motor according to claim 3 or 4, characterized in that the stator (2) has at least one spacer element (235), and the switching unit (23) is fixed to the housing (1) by at least one fixing element (4) via the at least one spacer element (235).

6. An electric motor according to any 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), and the stator (2) is configured to compensate for the relative movement of the stator body (20) with respect to the switching unit (23) in the at least one electrical line (212).

7. An electric motor according to any one of the preceding claims, characterized in that it has a control unit (5) having an electrical printed circuit board that is capable of controlling the flow of current through at least two of the coils and is fixedly connected to the switching unit (23).

8. An electric motor according to any 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 at least one of the housing (1) and the switching unit (23), and the filling element can be used to dissipate heat generated during the operation of the at least one coil.

9. It is placed between the filling element (6) and the housing (1), It is placed between the filling element (6) and the switching unit (23), The filling element (6) forms the core section (2302) of the switching unit (23) that it contacts, The electric motor according to claim 8, characterized by having at least one metallic heat conductive element which is at least one of the following.

10. An electric bicycle having an electric motor according to any one of claims 1 to 9.

11. A method for assembling an electric motor, To provide a housing (1), The stator body (20) having at least two coils is positioned in the housing (1) by elastically supporting the stator body (20) in the housing (1) via at least one decoupling element (3). The switching unit (23) interconnects the at least two coils to form a stator winding, and The switching unit (23) is fixed to the housing (1). Assembly method including.

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