Electric bicycle drive unit having sealing member

Abstract

A drive unit for an electric bicycle having a sealing member is provided. The drive unit of an electric bicycle comprises a housing (1) having an electric motor (2) disposed inside (I) that generates motor torque using external electric power, and an output member (3) disposed outside the housing (1) and functionally connected to the electric motor (2) via an output shaft (4) for transmitting the motor torque, the output member (3) providing drive torque for driving the electric bicycle, the output shaft (4) being disposed inside (I) of the housing (1) and having an inner portion (401) that receives motor torque from the electric motor (2), and an outer portion (402) that is disposed outside the housing (1) and on which the output member (3) that receives motor torque from the output shaft (4) is disposed. The housing (1) has a housing opening (11) through which an outer portion (402) of the output shaft (4) protrudes from the housing (1), and the housing (1) is provided with: an output member (3); a seal member (6) disposed in the housing opening (11) and sealing the inside (I) of the housing (1) at the output shaft (4); and an opposing member (5) disposed on the output shaft (4) and having a support surface (500) located radially outward of a rotation axis (D) of the output shaft (4), the seal member (6) being radially supported by the opposing member (5) on the support surface (500), and the output member (3) abutting against the opposing member (5).

Description

[Technical Field]

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

[0002] In electric bicycles, commonly referred to as e-bikes or pedelecs, it is known to use at least one electric motor in combination with a gearing arrangement, for example with a planetary gear stage, to provide motor assistance via an output shaft connected to the wheel during riding.

[0003] The electric motor provides a motor torque that amplifies or, if necessary, replaces the self-torque generated by muscle force. The electric motor and the output shaft are connected to each other via a gear device in the drive unit, so that the motor torque is combined with the self-torque and transmitted as a total torque to the wheels via the output shaft.

[0004] Typically, the output shaft is equipped with an output member such as a chain sprocket, through which the total torque is transmitted to the wheels via a power transmission means such as a chain. The output member requires a stopper to fix it axially on the output shaft in the direction of the electric motor. The stopper is usually a step on the output shaft or a separately provided snap ring.

[0005] However, for assembly reasons, providing a step in the output shaft requires that the diameter of all parts of the output shaft following the step be increased. Therefore, the step may affect the overall radial installation space required to install the drive unit on the electric bicycle. However, if the drive unit is installed on the electric bicycle instead of the pedal crank, an excessively large radial installation space should be avoided. This is because it is desirable to have the fulcrum of the rear wheel swing arm, which is equipped with a spring, as close as possible to the axis of rotation of the output shaft.

[0006] The separate provision of a retaining ring may increase the axial installation space (Q factor) required for the drive unit. Typically, the drive unit is located between two pedal cranks, and the self-torque generated by the leg muscles of the e-bike rider is transmitted to the drive unit via these pedal cranks. Therefore, the axial installation space required may directly affect the posture of the e-bike rider. Depending on the rider's height, this may result in an uncomfortable posture for the rider.

[0007] Therefore, a large drive unit can create undesirable design constraints. Summary of the Invention [Problem to be solved by the invention]

[0008] The challenge is therefore to create a drive unit for an electric bicycle that requires little radial installation space. [Means for solving the problem]

[0009] Against this background, the drive unit of claim 1 is proposed.

[0010] The proposed drive unit for an electric bicycle includes at least: A housing in which an electric motor is disposed to generate motor torque using external power; an output member for providing a driving torque for driving an electric bicycle, the output member being arranged outside the housing and operatively connected to the electric motor via an output shaft for transmitting the motor torque, the output shaft having an inner portion arranged inside the housing and receiving the motor torque from the electric motor, and an outer portion arranged outside the housing and on which the output member for receiving the motor torque from the output shaft is arranged, the housing having a housing opening through which the outer portion of the output shaft protrudes from the housing; a sealing member disposed in the housing opening and sealing the inside of the housing at the output shaft; A facing member disposed on the output shaft and having a support surface located radially outward of the rotation axis of the output shaft, the seal member being supported radially by the facing member on the support surface, and the output member being in contact with the facing member.

[0011] Because the output member abuts against the opposing member, the installation space in the axial and radial directions of the drive unit can be reduced compared to drive units in which the output member abuts against a step or a snap ring on the output shaft, as described above. This makes it possible to provide a drive unit that has a low Q factor and can be used on electric bicycles that can accommodate a wide range of rider heights.

[0012] In particular, there is no need to provide a step on the output shaft that may increase the radial installation space of the drive unit due to mounting constraints, which may arise from the additional radial space required for the step being extended along the output shaft to the outer shape of the housing.

[0013] When an opposing member is used as the seal member, the output shaft can be made of a light metal. This is because the material of the opposing member only needs to have the surface hardness required for the seal member to slide. Therefore, the opposing member can be made of a material harder than light metal, such as steel. The opposing member can be made of, for example, a sliding ring. The seal member can be a rotary shaft seal.

[0014] The output member may include, for example, a chain sprocket, a belt pulley, or a carrier for a chain sprocket or a belt pulley. A power transmission means such as a chain or a belt may be guided on the output member to transmit torque from the output shaft to the wheel of the electric bicycle. The output shaft may be, for example, a hollow shaft.

[0015] In one embodiment, the output shaft has a plurality of axially extending fitting portions at a connecting portion of the output shaft, through which the output shaft is connected to the output member in a rotationally fixed manner, and the opposing member axially overlaps the connecting portion. The plurality of fitting portions can form a toothed portion arranged in a sheath shape on the output shaft. The teeth of the toothed portion can extend along the rotation axis of the output shaft. The output member can be arranged on a portion of the connecting portion and connected in a rotationally fixed manner.

[0016] One reason why the entire connecting portion is longer than the portion required for positioning the output member is that the output member is inserted into the output shaft and guided far enough along the output shaft to allow a fastening member to be positioned on the portion of the output shaft through which the output member passes during installation. Another reason is that it may be economically advantageous to manufacture multiple fittings such that the connecting portion includes a portion that cannot be used for connecting to the output member.

[0017] Since the opposing member and the connecting portion overlap, the connecting portion can be used more efficiently and installation space in the axial direction can be secured. The opposing member may overlap the connecting portion completely or partially.

[0018] In a further embodiment, the engagements are formed by grooves extending axially on the outer surface of the output shaft, the depth of the grooves decreasing in the direction of the inner portion of the output shaft at the recessed portion of the connection portion, and the counter member axially overlapping the recessed portion. The grooves forming the engagements can essentially have any shape. The axial extension of the grooves along the outer surface of the output shaft can be splined, which serves to transmit torque particularly efficiently. In this case, wedges for engaging with the output member can be formed between the grooves. Other engagement connections between the output shaft and the output member are also envisioned and can be implemented.

[0019] The reduced depth of the grooves towards the inner portion of the output shaft may be due to the grooves being formed by an economical hobbing process, which may result in misalignment of the tooth profile during toothing production. Because the counter member axially overlaps the relief, the axial installation space required for the relief can be used to support the sealing member and is not left unused during operation according to this embodiment.

[0020] In one embodiment, the counter member has a sealing portion arranged adjacent to the connection portion of the output shaft and a retaining portion arranged at the connection portion. Basically, the counter member can be arranged over the entire axial length of the connection portion. However, to obtain a better seal between the relief portion and the inside of the housing, it may be advantageous to arrange the counter member together with the sealing portion at the portion adjacent to the connection portion of the output shaft. The retaining portion serves to hold the counter member to the output shaft, for example, by a screw connection or by being pressed into a sealing lip arranged inside the counter member.

[0021] In one embodiment, at least a portion of the opposing member on the side facing the output shaft is made of a non-metallic material, and / or at least a portion of the side facing the sealing member is made of a metal. The side of the opposing member facing the output shaft can form the inner side of the opposing member (preferably ring-shaped). In particular, the opposing member can be partially, preferably internally, made of rubber. At least a portion of the opposing member can be made of a non-metallic material to seal the relief portion via the sealing portion. For example, the opposing member on the side facing the output shaft can be made non-metallic by including a layer member disposed on the inner side and coating the metal body of the opposing member. The layer member can include one or more sealing lips for sealing the relief portion on the sealing portion. The opposing member can be constructed particularly simply and inexpensively as a pressed part. Providing a layer member to improve sealing performance eliminates the need to add a thread to the opposing member, simplifying manufacturing.

[0022] The metal portion facing the seal member can be configured as a support surface for the seal member, allowing the seal member to easily slide on the support surface when the output shaft or the opposing member rotates. Furthermore, the metal portion can be configured to optimize the sliding characteristics and wear resistance of the seal member.

[0023] By constructing the counter member from two different material components (such as metal and rubber), the counter member can, in addition to abutting against the output member, provide a support surface suitable for the sealing member on the one hand and a sealing function for the output shaft on the other. As a result, additional elements such as a retaining ring or a step on the output shaft are not required, allowing for a more compact installation space for the drive unit.

[0024] In one embodiment, the output member is axially secured on the output shaft between a counter member and a fastening member. The counter member provides a stop for the output member on the housing side, while the fastening member provides a stop for the output member on the opposite side of the housing. The fastening member may include, for example, a nut. The output shaft may also be provided with threads for disposing the fastening member on the output shaft.

[0025] In one embodiment, the output shaft has a radial step, and the opposing member is at least indirectly supported on the step in the axial direction. The radial step can be a stopper that indirectly supports the axial force generated by fixing the output member to the output shaft. "Indirectly" means that an additional member may be disposed between the opposing member and the radial step, and support can be provided via that additional member. Basically, it is also conceivable and possible to directly support the opposing member on the radial step.

[0026] In one embodiment, the opposing member is supported on the radial step by at least one of a first ball bearing assembly, a ring member, and / or a second ball bearing assembly, the output shaft is rotatably supported on the housing via the first ball bearing assembly, and a drive wheel that receives motor torque from the electric motor is attached to the output shaft via the second ball bearing assembly. The above list of members is a selection of members that can be positioned between the opposing member and the radial step. Thus, fastening members can be used to secure the opposing member, the output member, and one or more additional members to the radial step. The ring member may include a spacer ring, which spaces the two ball bearing assemblies apart.

[0027] In one embodiment, the output shaft is rotatably supported on the housing via a first ball bearing assembly (e.g., the first ball bearing assembly described above). The first ball bearing assembly includes a first inner ring that receives a plurality of first bearing members, and the first inner ring has a recess in which a seal is disposed on a side of the first bearing member that faces the output shaft in a cross section along the rotation axis of the output shaft. The recess can be formed by rounding the edge of the axial peripheral portion of the inner ring. For example, the seal can include rubber and / or grease, particularly a bead-like grease. Essentially, the seal can be an O-ring.

[0028] The layer member located on the output shaft side of the counter member may have a chamfered surface on the side of the first ball bearing assembly, or may at least be recessed from the abutment surface of the counter member on the first ball bearing assembly. This facilitates mounting the counter member on the output shaft. Furthermore, the use of such a layer member may achieve sufficient sealing under certain circumstances. Adding a seal between the counter member and the first ball bearing assembly can further improve sealing.

[0029] In one embodiment, the seal is integrally formed with a layer member located on the output shaft side of the counter member. In particular, the seal may be part of a non-metallic portion of the counter member located on the output shaft side of the counter member. When such a counter member is installed, the seal may be pressed into a recess. For example, the seal may form a bead- or wedge-shaped member on the counter member or layer member, which may protrude from the counter member toward the first ball bearing assembly on the side facing the output shaft. Using such a seal can provide good sealing even when the drive unit components have a wide tolerance range.

[0030] The proposed solution also relates to an electric bicycle equipped with an embodiment of the proposed drive unit. [Brief explanation of the drawings]

[0031] The accompanying drawings show examples of possible implementations of the proposed solution.

[0032] [Figure 1] FIG. 2 is a schematic cross-sectional view of a drive unit. [Figure 2A] FIG. 1 is a cross-sectional view of a drive unit with a pedal crank. [Figure 2B] FIG. 2B is a partially enlarged view of FIG. 2A. [Figure 3A] FIG. 2 is a first perspective view of an opposing member. [Figure 3B] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0033] FIG. 1 is a cross-sectional view of an electric bicycle drive unit. The drive unit has a housing 1, in whose interior I an electric motor 2 is arranged. The housing 1 protects the electric motor 2 from dust, moisture, etc. that may occur in an external area A. The external area A is separated from the interior I by the housing 1 during normal use of the electric bicycle drive unit. The electric motor 2 is used to generate motor torque using external power.

[0034] To provide a driving torque for driving the electric bicycle, the motor torque is transmitted to an output member 3. The driving torque can be transmitted to a wheel of the electric bicycle using, for example, a chain or a belt (not shown). The output member 3 is disposed outside the housing 1 and is operatively connected to the electric motor 2 via an output shaft 4. The output shaft 4 transmits the motor torque to the output member 3. Other gear members (not shown) may be disposed between the electric motor 2 and the output shaft 4.

[0035] The output shaft 4 has an inner portion 401 inside the housing 1 and receives motor torque from the electric motor 2. The output shaft 4 further has an outer portion 402 outside the housing 1, and the output member 3 is disposed on the outer portion 402 and receives motor torque from the output shaft 4.

[0036] Since the output member 3 is disposed outside the housing 1, a housing opening 11 is provided in the housing 1. An outer portion 402 of the output shaft 4 protrudes from the housing 1 through the housing opening 11, and the output member 3 can be disposed on the output shaft 4.

[0037] Due to the presence of the housing opening 11, a seal member 6 must be provided on the output shaft 4, which serves to seal the interior of the housing 1. The seal member 6 surrounds the output shaft 4 in an annular shape and prevents, for example, dust and moisture from entering the interior I from the external area A through the housing opening 11.

[0038] An opposing member 5 that supports a seal member 6 is disposed on the output shaft 4. The opposing member 5 has a support surface 500 located radially outward of the rotation axis of the output shaft 4, and the seal member 6 is supported radially by the opposing member 5 on the support surface. Therefore, the seal member 6 does not come into direct contact with the output shaft 4.

[0039] The output member 3 abuts against the opposing member 5. This allows the axial force acting from the output member 3 toward the electric motor 2 to be supported by the opposing member 5. In addition, the opposing member 5 separates the outer portion 402 of the output shaft 4 from the inner portion 401 of the output shaft 4.

[0040] The interior I is sealed from the outside in the counter element 5 by a seal 6 between the counter element 5 and the housing 1 on the one hand, and between the counter element 5 and the output shaft 4 on the other hand. The latter seal can be provided by the counter element 5 itself. Figure 2A shows a cross section of the drive unit of Figure 1. To illustrate the normal use of the drive unit, a pedal crank K is also shown. The pedal crank K is located on the drive unit and, in an electric bicycle, transfers torque generated by the rider's leg muscles to the drive unit.

[0041] The output shaft 4 of the drive unit is rotatably supported in the housing 1 via a first ball bearing assembly 10. A second ball bearing assembly 80 is provided to rotatably support a drive wheel 8 that receives motor torque from the electric motor 2 of the drive unit on the output shaft 4. The motor torque is transmitted, inter alia, via a freewheel assembly F. A ring member 7 is disposed between the ball bearing assemblies 10, 80 and maintains a distance between the two ball bearing assemblies 10, 80. A fastening member 32 is disposed on the outermost axial end of the output shaft 4. The output member 3 abuts against the fastening member 32 in the axial direction on the housing 1 side. The output member 3 further abuts against a counter member 5 in the axial direction on the housing side. The counter member 5 abuts against the first ball bearing assembly 10. This is followed by the ring member 7 and the second ball bearing assembly 80. The second ball bearing assembly 80 abuts against a radial step 42 on the output shaft 4. In this way, the axial force from the fastening member 32 or the output member 3 is indirectly introduced into the radial step 42 .

[0042] The output member 3 is held by a connection portion 41 of the output shaft 4. The connection portion 41 is formed by a plurality of grooves 410 extending in the axial direction of the output shaft 4 in a splined shaft shape, with wedges 411 formed between the grooves 410. The output member 3 engages with the grooves 410 by an engagement member 31, and the output member 3 is fixed to the output shaft 4 in the rotational direction. Because the grooves 410 are machined from the outer end of the output shaft 4, the outer profile of the output shaft 4 is jagged on the radial surface of the outer end (because the wedges 411 protrude above the grooves 410). The jagged outer profile is preferably formed rectangular. Therefore, the cross section of the wedges 411 can be rectangular. On the other hand, the grooves 410 may have a U-shaped cross section.

[0043] Towards the housing, i.e. towards the inner part 401 of the output shaft 4 arranged in the housing 1, the depth of the groove 410 gradually decreases at the relief portion 4101 of the connecting part 41. This decrease is due to the manufacturing process of hobbing the groove 410. The counter element 5 is arranged to overlap the relief portion 4101 in the axial direction.

[0044] 2A shown in FIG. 2B is an enlarged partial view of the cross-sectional view of FIG. 2A. The opposing member 5 has a retaining portion 502 on the outside and a sealing portion 501 on the inside, with the retaining portion 502 overlapping the relief portion 4101 and the sealing portion 501 being disposed axially outward of the connecting portion 41. The sealing portion 501 is disposed axially inward of the connecting portion 41 so as to isolate the connecting portion 41 from the interior I of the housing 1. This prevents dust or water that may enter the groove 410 of the output shaft 4 from the outside from entering the interior I, and in particular prevents it from entering the first ball bearing assembly 10 via the relief portion 4101.

[0045] To obtain good sealing, the opposing member 5 preferably has a non-metallic side facing the output shaft 4, resulting in good adhesion to the output shaft 4. For this purpose, the opposing member 5 has a layer member 51 extending along the entire inside of the main body 50 of the opposing member 5. The layer member 51 may be chamfered or recessed or protruded on one axial side. By making the opposing member 5 partially non-metallic, particularly a rubber layer, at the sealing portion 501, adhesion at the sealing position between the opposing member 5 and the output shaft 4 is improved. Furthermore, by making the opposing member 5 partially non-metallic, the possibility of damaging the output shaft 4, particularly at the outer portion 410, during installation of the opposing member 5 is reduced.

[0046] The first and second ball bearing assemblies 10 and 80 each include a first and second inner ring 101 and 801 and a first and second outer ring 102 and 802, with a plurality of first and second bearing members 103 and 803 disposed therebetween. The first and second ball bearing assemblies 10 and 80 are attached to the output shaft 4 via their respective inner rings 101 and 801. The opposing member 5 abuts against the first inner ring 101, and the ring member 7 is located between the first inner ring 101 and the second inner ring 801. The second ball bearing assembly 80 is supported by a radial step 42 of the output shaft 4 via the second inner ring 801. The arrangement of these members allows a continuous force flow from the output member 3, via the opposing member 5, to the radial step 42. The first and second ball bearing assemblies 10 and 80, together with their respective inner rings 101 and 801, are located on this force flow.

[0047] 3A and 3B are perspective views of the opposing member 5. A main body 50 of the opposing member 5 is made of metal, for example, steel. The main body 50 has a support surface 500 for the seal member 6. The support surface 500 has a cylindrical surface for supporting the seal member 6. During operation, the seal member 6 slides on the support surface 500, or the output shaft 4 rotates together with the opposing member 5 below the seal member 6 on the support surface 500.

[0048] The counter element 5 includes a non-metallic layer 51 located radially inward. The layer 51 is made of, for example, rubber. During normal use, the layer 51 forms a chamfered portion 511 on the side of the counter element 5 that faces the drive unit housing, and this chamfered portion 511 accommodates a sealing material (e.g., an O-ring). Alternatively, the layer 51 may protrude axially beyond the main body 50, e.g., in the form of a wedge or bead. In a predetermined mounting state, the protruding portion is pressed into the recess 1011 of the inner ring 101 of the first ball bearing assembly 10, providing a good seal. On the opposite side, which is located outside the drive unit (on the retaining portion 502) during normal use, the main body 50 of the counter element 5 has an annular rounded edge on the support surface 500. This rounded edge serves to gradually expand the diameter of the seal element 6 on the counter element 5 when the seal element 6 is mounted. This facilitates installation, for example by eliminating the need for an additional mounting sleeve for the sealing member 6 and by preventing the sealing member 6 from being accidentally sheared off onto the counter member 5 . [Explanation of symbols]

[0049] 1. Housing 10 First Ball Bearing Assembly 101 Inner Ring 1011 recess 102 outer ring 103 Bearing materials 11 Housing opening 2 electric motors 3 Output member 31 Engagement member 32 Fastening members 4 output shaft 401 Inner part 402 Outer part 41 Connection 410 Groove 4101 Relief 411 Wedge 42 Radial step 5 opposing member 50 main unit 500 Support surface 501 Seal part 502 Holding part 51 Layers 511 Chamfered part 6 Sealing material 7 Ring member 8 driving wheels 80 Second Ball Bearing Assembly 801 Inner ring 802 outer ring 803 Bearing materials A external area D rotation axis F Freewheel Assembly I inside K pedal crank

Claims

1. a housing (1) having an electric motor (2) disposed therein (I) for generating motor torque using external electric power; an output member (3) that provides a driving torque for driving the electric bicycle, the output member (3) being arranged outside the housing (1) and functionally connected to the electric motor (2) via an output shaft (4) for transmitting the motor torque, the output shaft (4) having an inner portion (401) that is arranged in the interior (I) of the housing (1) and receives the motor torque from the electric motor (2), and an outer portion (402) that is arranged outside the housing (1) and on which the output member (3) is arranged and receives the motor torque from the output shaft (4), the housing (1) having a housing opening (11) through which the outer portion (402) of the output shaft (4) protrudes from the housing (1); a seal member (6) disposed in the housing opening (11) and sealing the interior (I) of the housing (1) at the output shaft (4); an opposing member (5) disposed on the output shaft (4) and having a support surface (500) located radially outward of a rotation axis (D) of the output shaft (4), wherein the seal member (6) is supported radially by the opposing member (5) on the support surface (500), and the output member (3) abuts against the opposing member (5). Electric bicycle drive unit.

2. The output shaft (4) has a plurality of fitting portions (410, 411) extending in the axial direction at a connection portion (41) of the output shaft (4), and is connected to the output member (3) via the fitting portions (410, 411) in a fixed manner in the rotational direction, and the opposing member (5) overlaps with the connection portions (41) in the axial direction. A drive unit according to claim 1.

3. the plurality of fitting portions (410, 411) are formed as grooves extending in the axial direction on the outer surface of the output shaft (4), the depth of the grooves decreases in a relief portion (4101) of the connection portion (41) toward the inner portion (401) of the output shaft (4), and the opposing member (5) overlaps the relief portion (4101) in the axial direction. A drive unit according to claim 2.

4. The opposing member (5) has a sealing portion (501) arranged in a portion adjacent to the connection portion (41) of the output shaft (4), and a retaining portion (502) arranged in the connection portion (41). A drive unit according to claim 2 or 3.

5. At least a part of the opposing member (5) on the side opposing the output shaft (4) is made of a non-metallic material, in particular, at least a part of the opposing member is made of rubber, and / or at least a part of the side opposing the sealing member (6) is made of a metal. A drive unit according to any one of claims 1 to 4.

6. the output member (3) is fixed in the axial direction on the output shaft (4) between the opposing member (5) and a fastening member (32). A drive unit according to any one of claims 1 to 5.

7. The output shaft (4) has a step in the radial direction, and the opposing member (5) is at least indirectly supported in the axial direction on the step. A drive unit according to any one of claims 1 to 6.

8. the opposing member (5) is supported on the radial step by at least one of a first ball bearing assembly (10), a ring member (7), and / or a second ball bearing assembly (80); the output shaft (4) is rotatably supported on the housing (1) via the first ball bearing assembly (10); and a drive wheel (8) that receives the motor torque from the electric motor (2) is attached to the output shaft (4) via the second ball bearing assembly (80). A drive unit according to claim 7.

9. the output shaft (4) is rotatably supported in the housing (1) via a first ball bearing assembly (10), the first ball bearing assembly (10) has a first inner ring (101) that receives a plurality of first bearing members (103), and the first inner ring (101) has a recess (1011) in which a sealing material is disposed on a side of the opposing member (5) that faces the output shaft (4) in a cross section taken along the rotation axis (D) of the output shaft (4). A drive unit according to any one of claims 1 to 8.

10. The sealing material is formed integrally with a layer member (51) disposed on the output shaft (4) side of the opposing member (5). A drive unit according to claim 9.

11. An electric bicycle comprising the drive unit according to any one of claims 1 to 10.

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