Drive unit for electric bicycle equipped with sensor device

Abstract

The present invention relates in particular to a drive unit for an electric bicycle, comprising a shaft rotatable about a rotation axis and transmitting torque, and a sensor device. The sensor device has an electronic component extending at least partially in a circumferential direction about the rotation axis. The drive unit further comprises a counter member fixed to the shaft along the axial direction and against which the electronic component abuts, and a holding member arranged on the shaft so as to press the electronic component against the counter member in the axial direction. The present invention also relates to an assembly method.

Description

[Technical Field]

[0001] The proposed solution relates to a drive unit for an electric bicycle. [Background technology]

[0002] Electric bicycles, commonly referred to as e-bikes or pedelecs, are known to use at least one electric motor in combination with a transmission, for example with a planetary gear stage, to provide motor assistance when riding the electric bicycle via an output shaft connected to the wheels of the electric bicycle.

[0003] The electric motor amplifies the torque generated by human power and provides motor torque to replace it as needed. The electric motor and the output shaft are connected to each other via the transmission of the drive unit, so the motor torque is combined with the self-torque and transmitted as a total torque to the wheels through the output shaft.

[0004] During operation of the drive unit, operating parameters such as total torque are typically measured by a sensor device and these parameters are provided to, for example, a control device of the drive unit, which can control the electric motor depending on the operating parameters.

[0005] The sensor device may include an electronic component such as a circuit board, which may in particular be formed in the shape of a ring-shaped disk surrounding the axis of rotation.

[0006] To secure the electronic components, a plastic mounting element is typically used, and the electronic components are then integrally encapsulated, for example with a liquid resin. Resin encapsulation can be complex and costly. This may be because the encapsulation resin used must be precisely metered and / or must be allowed to cure for a specified period of time. Under certain circumstances, electronic assemblies that protrude from the electronic components (e.g., wiring for on-axis strain gauges) may be exposed and unprotected depending on how the electronic components are mounted. Furthermore, manufacturing the electronic components integrally with the mounting element also complicates recycling the drive unit, as disassembly is difficult if necessary. Summary of the Invention [Problem to be solved by the invention]

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide a drive unit which overcomes the above drawbacks.

[0008] According to a first aspect of the invention, this object is achieved by a drive unit for an electric bicycle, comprising at least the following components: A shaft that can rotate around an axis of rotation and transmits torque. A sensor device having electronic components that extend at least partially circumferentially around the axis of rotation. An opposing member that is fixed to the shaft in the axial direction and against which the electronic component abuts. A retaining member disposed on the shaft configured to press the electronic component axially against an opposing member.

[0009] Furthermore, the drive unit may include an electric motor. For example, the shaft may be an output shaft through which the motor torque of the electric motor (optionally supplemented by the self-torque generated by the user of the electric bicycle through muscle power) is transmitted to an output member connected to the wheel of the electric bicycle. The sensor device may be used to measure the torque transmitted by the shaft. This makes it possible to determine the motor torque, the self-torque, and / or the total torque of the motor torque and the self-torque.

[0010] The electronic component may have, for example, a circuit board and may include at least one electronic element, such as a transistor, on one functional surface. To measure torque, the sensor device may be operatively connected to a shaft. This operative connection to the shaft may be made on the functional surface of the electronic component.

[0011] The electronic component abuts against a counter member on a support surface opposite to the functional surface of the electronic component. The counter member can support the electronic component along one of two axial directions. For this purpose, the counter member is fixed to the shaft along the axial direction. Therefore, the counter member is prevented from moving along the axial direction.

[0012] The electronic component can be fixed along the other axial direction by a holding member. For this purpose, the holding member may be configured to press the electronic component against the opposing member. The holding member may be arranged on the axis so as to be biased against the electronic component. The electronic component is thus fixed in the axial direction relative to the opposing member by a spring force applied by the holding member. The drive unit is preferably configured so that, upon disassembly, the holding member is removed and then the electronic component can be easily removed by displacing it in the axial direction.

[0013] In one embodiment, the shaft has a step extending circumferentially around the rotation axis, and the holding member presses against the step to support the electronic component. The holding member is supported on the step on the shaft, and can apply a spring force to the electronic component. For assembly purposes, it is advantageous to provide a recess in the shaft that at least partially surrounds the circumference of the rotation axis and defines two opposing steps, so that the holding member is supported on one step and the opposing component is supported on the other step.

[0014] In one embodiment, the retaining element has at least one recess, which increases the axial flexibility of the retaining element. The at least one recess may have a circumferentially continuous edge that closes around the rotation axis. In principle, the retaining element can be provided with multiple recesses, so that the retaining element forms at least a part of a (regular) lattice structure. Furthermore, if cost-effective manufacturing is desired, the retaining element can be formed, for example, as an injection-molded part. The retaining element has a predetermined strength due to the material (e.g., plastic), which can be adjusted as needed by the multiple recesses.

[0015] Basically, at least one recess can be arranged in a first part of the holding element extending parallel to the rotation axis. At least one recess can also be arranged in a second part of the holding element extending radially relative to the rotation axis. By providing at least one recess in the second part, the axial flexibility of the holding element can be particularly easily increased. It is also conceivable and possible to provide at least one recess in the holding element extending in the first and second parts. If multiple recesses are provided, it is also conceivable and possible to provide recesses in the first and / or second part, for example to form a lattice structure.

[0016] In one embodiment, the holding member and the counter member are fixed by at least one form-locking member to prevent relative displacement about the rotation axis. At least one form-locking member (e.g., a protruding, radially elongated rib) can be arranged on the counter member. The holding member may have a receiving portion into which the at least one form-locking member engages in the axial direction. In addition to rotational fixation, such a form-locking member has the advantage that the circumferential assembly position of the holding member relative to the counter member can be predetermined based on the principle of error-proofing with respect to the rotation axis of the shaft. This makes it possible to prevent, for example, the holding member from accidentally damaging electronic components due to an assembly error.

[0017] In one embodiment, the retaining member includes a pressing portion having at least one radially protruding portion, through which the retaining member presses the electronic component. Because the retaining member presses the electronic component only through the at least one radial protrusion, more space can be secured on the electronic component for electronic components to be placed as needed. Apart from the at least one radial protrusion and, if necessary, the at least one receiving portion for the form-fitting member, the pressing portion on the electronic component can form a closed annular portion or a ring-like shape with a closed cross section. This configuration simplifies assembly and facilitates the implementation of error-proofing principles.

[0018] In one embodiment, the holding member includes a support portion having at least one support piece and a corresponding base portion, and the holding member is supported on the shaft in the axial direction via the support portion. The at least one support piece is biased against the base. For this purpose, the at least one support piece can be formed so as to be spring-biased against the base. When assembled to the shaft, the at least one support piece is axially pressed against a step portion on the shaft, thereby biasing the support piece against the base. In this way, the at least one support piece can generate at least a portion of the pressing force that the holding member applies to the electronic component. The at least one recess can be deformed to form an additional portion. It is advantageous to provide a plurality of such support pieces (e.g., two, three, or four), and they are preferably arranged on the holding member at equal intervals around the rotation axis. This is because arranging them at equal intervals allows symmetrical pressing forces to be generated on the electronic component.

[0019] In another embodiment, the support portion has a first portion extending parallel to the rotation axis and a second portion extending obliquely, particularly in a radial direction, with the rotation axis, and at least one support piece extends along the first and second portions. By configuring the at least one support piece in this manner, the axial flexibility of the holding member in the second portion can be increased, thereby generating a pressing force against the electronic component. By extending the second portion in the radial direction, the axial flexibility can be maximized.

[0020] In one embodiment, the retaining member includes a sealing portion, and the retaining member at least partially abuts against the surface of the shaft via the sealing portion. The retaining member may be fixed to the shaft in a radial direction via the sealing portion. In this regard, the axial position of the retaining member is determined by supporting the retaining member via at least one support piece, and the radial position is determined by supporting the retaining member via the sealing portion. The sealing portion may form a (closed) ring-shaped cross section on the surface of the shaft. In general, it is desirable for the sealing portion to have as few independent ring-shaped cross sections as possible (e.g., two, four, or six) on the surface of the shaft, which may be arranged, for example, at equal intervals around the rotation shaft. In this way, the retaining member can more effectively protect the electronic components from contaminants such as grease that enter the axial direction from the side surface of the retaining member during operation of the drive unit.

[0021] In one embodiment, the seal member is provided in the seal portion. The seal member can be added to the seal portion, if necessary, to prevent or at least reduce unwanted contamination of the electronic component. The seal member can be formed as a separate member from the retaining member, for example, the seal portion can be specially configured to accommodate the seal member. Similarly, the seal member can be formed as an additional part on the retaining member. The seal member can form a closed ring-like shape on the surface of the shaft.

[0022] In one embodiment, the holding member and / or the electronic component extend annularly around the rotation shaft. The holding member may be formed in a sleeve shape and may have one or more radial steps as needed. The electronic component may be formed as a ring-shaped disk. The ring-shaped disk may have a through opening through which the shaft passes.

[0023] In one embodiment, the sensor device has at least one electronic assembly protruding axially from the electronic component, and the holding member has an opening through which the electronic assembly protrudes. The electronic assembly may include, for example, one or more measurement wires. An operative connection between the sensor device and the shaft may be established via the electronic assembly. For example, the shaft may be provided with at least one strain gauge that measures torque acting on the shaft by strain, and the strain gauge is connected via the electronic assembly. By having the electronic assembly protruding into the opening in the holding member, the electronic assembly is protected from accidental collisions (especially radial collisions) during transportation and assembly of the drive unit.

[0024] According to a second aspect of the present invention, the object of the present invention is achieved by a method for assembling a drive unit for an electric bicycle, the method comprising the following steps: A process of arranging an opposing member on a shaft that is rotatable about a rotation axis and transmits torque so that the opposing member is fixed along the axial direction. A process of arranging the electronic components of the sensor device on the axis and abutting the electronic components against an opposing member. A process of arranging a holding member on the shaft so that the holding member presses the electronic component axially against an opposing member.

[0025] The above-mentioned arrangement may include arranging the counter member, the electronic component, and the retaining member on a shaft. Arranging the retaining member on the shaft may particularly include engaging the retaining member with a step on the shaft. In a first sub-step of the assembly process, the retaining member may be pressed against the electronic component for engagement, thereby compressing the retaining member in the axial direction. In a second sub-step, the retaining member can be engaged with the step, thereby being held on the electronic component in a biased state (due to the above-mentioned axial compression).

[0026] Configurations of the proposed assembly method may be implemented with particular configurations of the proposed drive unit, and therefore, the features and advantages described above and below in relation to configurations of the proposed drive unit may also apply to corresponding configurations of the proposed assembly method, and vice versa. [Brief explanation of the drawings]

[0027] The accompanying drawings show examples of possible implementations of the proposed solution. [Figure 1] FIG. [Figure 2] FIG. [Figure 3] FIG. 2 is a perspective view showing a cross section of a drive unit.

[0028] FIG. 1 shows a cross section of a drive unit of an electric bicycle. The drive unit comprises a shaft 1 rotatable about a rotation axis D for transmitting torque. The shaft 1 is configured as a hollow shaft. Inside it, another shaft W is arranged. On the one hand, a motor torque is applied to the shaft 1 in one rotation direction via a drive member A arranged on the shaft 1. The drive member A is attached to the shaft 1 via a first freewheel F1 so that the shaft 1 can rotate in the opposite direction. On the other hand, a self-torque, generated, for example, by human power, is applied to the shaft 1 via another shaft W. The shaft W is supported on the shaft 1 via a second freewheel F2.

[0029] The drive unit is also provided with a sensor device 2, which has an electronic component 20 extending (completely) circumferentially around the rotation axis D. The electronic component 20 abuts against a counter element 3 fixed to the shaft 1 along the axial direction. The counter element 3 abuts against the electronic component 20 in the axial direction, but can also be fixed radially.

[0030] In principle, the electronic component 20 is positioned in such a way that it can be easily separated from the opposing member 3 along the axial direction away from the opposing member 3. To fix the electronic component 20 in this axial direction, a holding member 4 is arranged on the shaft 1 and is configured to press the electronic component 20 against the opposing member 3 in the axial direction. In this way, the electronic component 20 is held in the axial direction between the holding member 4 and the opposing member 3. The holding member 4 has a pressing portion 41 for pressing the electronic component 20. The pressing portion 41 is provided with a plurality of radial protrusions 411, which protrude radially inward on the pressing portion 41 in the direction of the rotation axis D. The holding member 4 presses the electronic component 20 via these protrusions (see FIG. 2).

[0031] The shaft 1 is provided with a recess 10 extending in the circumferential direction around the rotation axis D. The recess 10 defines two steps 11, 12 that are opposed to each other in the axial direction and face towards the recess 10. The holding member 4 is arranged on the first step 11, and the opposing member 3 is arranged on the second step 12.

[0032] The top of the first step 11 is closer to the rotation axis D than the top of the second step 12. During assembly, the opposing member 3 is guided axially onto the first step 11 and placed on the second step 12. Similarly, the electronic component 20 is guided onto the first step 11 and placed on the opposing member 3 during the assembly process, and then the holding member 4 can be placed on the first step 11. The holding member 4 is configured to support the electronic component 20 by pressing it against the first step 11.

[0033] For example, the holding member 4 is provided with a plurality of recesses 44, which increase the flexibility of the holding member 4 in the axial direction. During assembly, the holding member 4 is pressed against the electronic component 20 and elastically deforms in the axial direction until the first step 11 abuts against and supports the electronic component 20. As a result, the holding member 4 engages with the first step.

[0034] The elastic deformation is achieved as follows: The holding member 4 is provided with four sets of three recesses 44 each, which are equally spaced around the rotation axis D of the holding member 4 (see FIG. 2, which is a separate view of the holding member). In this way, the holding member 4 has a lattice structure. In addition to the recesses 44, the holding member 4 is provided with a plurality of openings 45, which will be described later in relation to FIG. 3, which also increase the axial flexibility of the holding member 4.

[0035] To enable engagement and support in the first step portion 11, the holding member 4 has a support portion 42, and this support portion 42 is provided with a plurality of support pieces 422. Each support piece 422 has a corresponding base portion 421, and extends from each base portion 421 onto the support portion 42. The support pieces 422 are formed integrally with the support portion 42, particularly with the base portion 421. Each support piece 422 has a head portion 4221, and abuts against the first step portion 11 via this head portion.

[0036] The support pieces 422 are formed so that the heads 4221 are elastically adjustable in the radial and axial directions relative to the base 421. During assembly, the holding member 4 is pushed onto the shaft 1 to be positioned in the assembly position. This causes the heads 4221 of the support pieces 422 to be pushed radially outward. The heads 4221 hold the holding member 4 in the assembly position by forced engagement. The support pieces 422 are configured to engage with the first step 11 (after the holding member 4 is pressed against the electronic component 20 and elastically deformed by the recesses 44). This allows each head 4221 to elastically return to its initial radial position when it enters the recess. Finally, the support pieces 422 are configured to apply a biasing force to the electronic component 20. This is achieved by the support pieces 422 being elastically displaced in the assembly position and being pressed axially against the first step 11 via their heads 4221. The holding member 4 is biased against the electronic component 20 via the support pieces 422 , so that the elastic deformation of the recesses 44 is at least partially compensated for by the displacement of the support pieces 422 .

[0037] The specific configuration of the support piece 422 is as follows. The holding member 4 has, on the support part 42, a first part 4201 extending parallel to the rotation axis D and a second part 4202 extending radially relative to the rotation axis D. The support piece 422 extends along the first part 4201 and the second part 4202. As a result, each support piece 422 forms a right angle with the base part 421.

[0038] The support portion 42 has a recess 44 for each support piece 422, and each support piece 422 extends therein. The support piece 422 is substantially flush with the support portion 42. Only the head 4221 protrudes radially inward from the first portion 4201. The protruding portion allows the head 4221 to abut against the first step portion 11 when the holding member 4 is in the assembled position. The protruding portion of the head 4221 displaces the support piece 422 radially when the support member 4 is attached to the shaft 1. To facilitate radial displacement of the support piece 422 during assembly, the head 4221 is formed obliquely with respect to the rotation axis D in a cross section passing through the rotation axis D in the assembly direction (i.e., the direction toward the electronic component 20). The head 4221 has a flat end face 4221a on the first step portion 11 side, and partially abuts against the first step portion 11 via this end face.

[0039] The support pieces 422 are arranged circumferentially at 90° intervals from one another on the holding member 4. Therefore, the support pieces 422 are arranged at equal intervals around the rotation axis D. The number of support pieces 422 is basically arbitrary, but providing two or more makes assembly easier. This is because arranging the support pieces 422 at equal intervals makes it possible to easily guide the holding member 4 onto the shaft 1 symmetrically with respect to the rotation axis D.

[0040] The arrangement in which the holding member 4 engages on the shaft 1 via the support piece 422 makes it easier to disassemble the holding member 4, making it easier to process the drive unit when recycling.

[0041] As is clear from FIG. 1 , the holding member 4 has a seal 43, through which it partially abuts against the surface 13 of the shaft 1. A first freewheel F1 is arranged on the side of the seal 43 away from the electronic component 20, through which the drive member A for the shaft 1 is attached to the shaft 1. Grease is applied to the first freewheel F1 during operation to ensure smooth operation. At the point where the seal 43 contacts the surface 13 of the shaft 1, the grease does not spread toward the electronic component and does not damage it. In this way, the holding member 4 helps protect the electronic component from the grease of the first freewheel F1.

[0042] A sealing element 5 is arranged between the sealing portion 43 and the first freewheel F1, extending circumferentially around the rotation axis D. This sealing element 5 also seals the installation space around the electronic assembly from the grease of the first freewheel F1. The sealing element 5 can be formed as a separate part, such as an annular rubber seal. Alternatively, the sealing element 5 can be injection molded onto the sealing portion 43 of the holding member 4. In particular, the injection molded sealing element 5 can be provided with a sealing lip that provides a sealing function.

[0043] FIG. 3 is a perspective view showing a cross section of the drive unit, taken along a plane away from the rotation axis D. From this view, it can be seen that the opposing member 3 is provided with a form-locking member 31 that axially engages with a receiving portion 412 on the holding member 4. The form-locking member 31 fixes the holding member 4 circumferentially on the opposing member 3. This simplifies the work of assembling the holding member 4 to the opposing member 3, because the rotational position of the holding member 4 relative to the opposing member 3 (and thus the electronic component 20) can be predetermined in a fixed state.

[0044] The retaining member 4 also includes an opening 45 provided in the support 42. The opening 45 extends along the first portion 4201 and the second portion 4202 of the support 42. The electronic assembly 22 protrudes axially from the electronic component and extends into the opening 45. The electronic assembly 22 is at least partially protected from potential damage by the support 42, which surrounds the opening 45. [Explanation of symbols]

[0045] 1 axis 10 recess 11, 12 steps 13 Surface 2. Sensor device 20 Electronic Components 21 Electronic elements 22 Electronic Assembly 3 opposing members 31 Form-engaging member 4 Retaining member 41 Pressing section 411 Protrusion 412 Receiving part 42 Support part 4201 Part 1 4202 Part 2 421 Base 422 Support piece 4221 Head 4221a End face 43 Seal part 44 Recess 45 Opening 5 Sealing material A Driving member F1, F2 freewheel D rotation axis W Another axis

Claims

1. A shaft (1) that is rotatable around a rotation axis (D) and transmits torque; a sensor device (2) having an electronic component (20) extending at least partially in a circumferential direction around the rotation axis (D); an opposing member (3) fixed to the shaft (1) along the axial direction and against which the electronic component (20) abuts; a holding member (4) arranged on the shaft (1) so as to press the electronic component (20) against the opposing member (3) in the axial direction.

2. The shaft (1) has a step (11) extending circumferentially around the rotation axis (D), 2. The drive unit according to claim 1, wherein the holding member (4) presses the electronic component (20) against the step portion (11) to support the electronic component (20).

3. 3. A drive unit according to claim 1 or 2, characterized in that the holding member (4) has at least one recess (44) which increases the axial flexibility of the holding member (4).

4. 4. The drive unit according to claim 1, wherein the holding member (4) and the opposing member (3) are fixed by at least one form-locking member (31) so that relative displacement about the rotation axis (D) does not occur.

5. 5. A drive unit according to claim 1, wherein the holding member (4) has a pressing portion (41) provided with at least one radial protrusion (411), and presses the electronic component (20) via the protrusion (411).

6. the holding member (4) comprises a support portion (42) having at least one support piece (422) and a corresponding base portion (421), and is assembled to the shaft (1) in the axial direction via the support portion (42); 6. A drive unit according to any one of claims 1 to 5, characterized in that the at least one support piece (422) is biased against the base (421).

7. The support portion (42) has a first portion (4201) extending parallel to the rotation axis (D) and a second portion (4202) extending obliquely, particularly in a radial direction, with respect to the rotation axis (D), 7. A drive unit according to claim 6, characterized in that said at least one support piece (422) extends along said first portion (4201) and said second portion (4202).

8. 8. A drive unit according to claim 1, wherein the retaining member (4) has a sealing portion (43) and abuts at least partially against the surface (13) of the shaft (1) via the sealing portion (43).

9. 9. A drive unit according to claim 8, characterized in that a sealing element (5) is provided on the sealing portion (43).

10. 10. A drive unit according to any one of claims 1 to 9, characterized in that the holding member (4) and / or the electronic component (20) extend annularly around the rotation axis (D).

11. The sensor device (2) has at least one electronic assembly (22) protruding axially from the electronic component (20), 11. A drive unit according to any one of claims 1 to 10, characterized in that the holding member (4) is provided with an opening (45) through which the electronic assembly (22) projects.

12. An electric bicycle comprising a drive unit according to any one of claims 1 to 11.

13. A method for assembling a drive unit for an electric bicycle, A step of arranging an opposing member (3) on a shaft (1) that is rotatable around a rotation axis (D) and transmits torque so that the opposing member (3) is fixed along the axial direction; a step of placing an electronic component (20) of a sensor device (2) on the shaft (1) and abutting the electronic component (20) against the opposing member (3); and placing a holding member (4) on the shaft (1), wherein the holding member (4) presses the electronic component (20) axially against the opposing member (3).

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