Unit

Abstract

[Problem] To miniaturize a unit which has a fixed shaft at the center and outputs motive power from a hub on the outermost circumference. [Solution] This unit comprises: a fixed shaft; a speed reduction mechanism having a part positioned on the outer circumference of the fixed shaft; a speed change mechanism having a part positioned on the outer circumference of the fixed shaft; a motor having a part positioned on the outer circumference of the fixed shaft; and a hub having a part positioned on the outer circumference of the motor. The motor is connected to the hub through the speed reduction mechanism. The speed change mechanism is connected to the hub not through the speed reduction mechanism. The speed change mechanism has a part overlapping the motor when seen in the radial direction.

Description

unit

[0001] The present invention relates to a unit.

[0002] Patent Documents 1 to 3 disclose drive units for electrically assisted bicycles that have a motor and a planetary gear reduction mechanism. These drive units have a fixed shaft at the center and output power from a hub at the outermost periphery.

[0003] JP 2005-335535 A JP 2012-121337 A International Publication No. 2018 / 001021

[0004] The present invention aims to miniaturize a unit that has a fixed shaft at the center and outputs power from a hub at the outermost periphery.

[0005] In one aspect of the present invention, the unit comprises a fixed shaft, a reduction mechanism having a portion located on the outer periphery of the fixed shaft, a speed change mechanism having a portion located on the outer periphery of the fixed shaft, a motor having a portion located on the outer periphery of the fixed shaft, and a hub having a portion located on the outer periphery of the motor, wherein the motor is connected to the hub via the reduction mechanism, and the speed change mechanism is connected to the hub without via the reduction mechanism, and when viewed radially, the speed change mechanism has a portion that overlaps with the motor.

[0006] According to one aspect of the present invention, by radially overlapping the motor with a power transmission-independent speed change mechanism that does not directly transmit the motor's power, it is possible to reduce the axial size of a unit that has a fixed shaft at the center and outputs power from the outermost hub.

[0007] FIG. 1 is a structural diagram illustrating an overview of an electrically assisted bicycle to which a unit according to an embodiment of the present invention is applied. FIG. 2 is a cross-sectional view of the unit. FIG. 3 is a nomographic diagram of the reduction gear mechanism. FIG. 4 is a cross-sectional view of a unit according to a first comparative example. FIG. 5 is a cross-sectional view of a unit according to a second comparative example. FIG. 6A is a skeleton diagram of the transmission mechanism in the unit, illustrating a state in which the transmission is switched to the first speed. FIG. 6B is a nomographic diagram of the transmission mechanism in the unit, illustrating a state in which the transmission is switched to the first speed. FIG. 7 is a skeleton diagram of the transmission mechanism in the unit, illustrating a state in which the transmission is switched to the second speed. FIG. 8A is a skeleton diagram of the transmission mechanism in the unit, illustrating a state in which the transmission is switched to the third speed. FIG. 8B is a nomographic diagram of the transmission mechanism in the unit, illustrating a state in which the transmission is switched to the third speed. FIG. 9 is a conceptual diagram illustrating a cam.

[0008] First, the definitions of terms used in this specification will be explained as follows.

[0009] The "unit" is also called a motor unit (a unit having at least a motor), a power transmission device (a device having at least a power transmission mechanism (e.g., a gear mechanism and / or a differential gear mechanism)), etc. A device (unit) having a motor and a power transmission mechanism belongs to the concepts of both a motor unit and a power transmission device.

[0010] The "motor" is a rotating electric machine having a motor function and / or a generator function.

[0011] "Element B (component, part, etc.) connected to element A (component, part, etc.)," ​​"element B (component, part, etc.) connected downstream of element A (component, part, etc.)," ​​and "element B (component, part, etc.) connected upstream of element A (component, part, etc.)" mean that element A and element B are connected so that power can be transmitted, with the power input side being upstream and the power output side being downstream. Element A and element B may be connected via another component, part, etc. (for example, another clutch, another gear mechanism, etc.).

[0012] "Overlapping when viewed in a predetermined direction" means that multiple elements are lined up in a predetermined direction (for example, axial direction, radial direction, gravity direction, vehicle running direction (vehicle forward direction, vehicle backward direction), etc.), and is synonymous with the expression "overlapping in a predetermined direction." When a drawing shows that multiple elements (components, parts, etc.) are lined up in a predetermined direction, it may be considered that the description in the specification contains a sentence explaining that they overlap when viewed in the predetermined direction.

[0013] "Not overlapping when viewed in a predetermined direction" and "offset when viewed in a predetermined direction" mean that multiple elements are not lined up in a predetermined direction (for example, axial direction, radial direction, gravity direction, vehicle running direction (vehicle forward direction, vehicle backward direction), etc.), and are synonymous with "not overlapping in a predetermined direction" and "offset in a predetermined direction." When a drawing shows that multiple elements (components, parts, etc.) are not lined up in a predetermined direction, it may be considered that the description in the specification includes a sentence explaining that they are not overlapping when viewed in a predetermined direction.

[0014] The phrase "element A (component, part, etc.) is located between element B (component, part, etc.) and element C (component, part, etc.) when viewed in a predetermined direction" means that element A can be observed to be located between element B and element C when viewed from a predetermined direction (e.g., axial direction, radial direction, gravity direction, etc.). For example, if element B, element A, and element C are lined up in this order along the axial direction, it can be said that element A is located between element B and element C when viewed in the radial direction. If a drawing shows that element A is located between element B and element C when viewed in a predetermined direction, it can be considered that the description in the specification contains a sentence explaining that element A is located between element B and element C when viewed in the predetermined direction.

[0015] The "axial direction" refers to the axial direction of the rotation shaft of a component that constitutes the unit. The component is, for example, a motor, a reduction mechanism, a transmission mechanism, etc.

[0016] Hereinafter, with reference to the drawings, an electric assist unit 100 as a unit according to an embodiment of the present invention and an electric assist bicycle (hereinafter simply referred to as "bicycle") 1 as a vehicle to which the electric assist unit 100 is applied will be described.

[0017] First, the overall configuration of a bicycle 1 will be described with reference to FIG.

[0018] FIG. 1 is a structural diagram illustrating an outline of a bicycle 1 to which an electric assist unit 100 is applied.

[0019] As shown in Figure 1, the bicycle 1 comprises a frame 2, a front wheel 3a, a rear wheel 3b as a drive wheel, a handlebar 4, a saddle 5, a drive sprocket 6a, a driven sprocket 6b, a chain 6c, a pair of pedals 7, a pair of crank arms 7b as a crank section, a crankshaft 7c, a support shaft 8 as a fixed shaft, a controller 9a, a power storage section 9b, and an electric assist unit 100.

[0020] The bicycle 1 is driven by a rider sitting astride the saddle 5 and pedaling the crank arms 7b via pedals 7. The bicycle 1 drives the rear wheel 3b with a pedaling force (driving torque) transmitted from the crank arms 7b to the crankshaft 7c, and a driving force (assist torque) from the electric assist unit 100, the magnitude of which corresponds to the pedaling force.

[0021] The frame 2 is a so-called diamond frame that is generally parallelogram-shaped in side view. A front wheel 3a and a rear wheel 3b are rotatably mounted on the frame 2. The frame 2 has a front fork 2a that supports the front wheel 3a.

[0022] The front wheel 3a is steered left and right by rotating the front fork 2a through the operation of the handlebars 4 by the rider.

[0023] The rear wheel 3b rotates around a support shaft 8. A driven sprocket 6b and an electric assist unit 100 are attached to the rear wheel 3b.

[0024] The driving torque is transmitted to the driven sprocket 6b via a chain 6c that is wound around the driving sprocket 6a, to which the driving force from the crank arm 7b is input.

[0025] The electric assist unit 100 generates an assist torque that assists the pedal force applied by the driver. The electric assist unit 100 will be described in detail later with reference to FIGS.

[0026] The pedal 7 is used by the driver to input driving torque, and is connected to a crankshaft 7c via a crank arm 7b.

[0027] The support shaft 8 is attached to the frame 2. The support shaft 8 is provided so as to be unable to rotate relative to the frame 2.

[0028] The controller 9a is composed of a microcomputer equipped with a CPU, RAM, ROM, input / output interface, etc. The controller 9a can also be composed of multiple microcomputers. The controller 9a performs various processes by having the CPU read and execute programs stored in the ROM. Specifically, the controller 9a calculates an assist torque based on an electrical signal corresponding to the magnitude of the pedal force input from a torque sensor (not shown), which will be described later, and outputs a command signal so that the motor 30 generates the assist torque.

[0029] The power storage unit 9b is a rechargeable secondary battery such as a nickel-metal hydride battery or a lithium-ion battery, etc. The power storage unit 9b is provided so as to be detachable from the frame 2.

[0030] Next, the configuration of the electric assist unit 100 will be described with reference to FIGS.

[0031] Fig. 2 is a cross-sectional view of the electric assist unit 100. Fig. 3 is a nomographic diagram of the reduction gear mechanism 40. Fig. 4 is a cross-sectional view of the electric assist unit 100 according to a first comparative example. Fig. 5 is a cross-sectional view of the electric assist unit 100 according to a second comparative example. Figs. 2, 4, and 5 show only the portion above the central axis of the electric assist unit 100, which is a rotating body that rotates around the central axis (support shaft 8).

[0032] 2, the electric assist unit 100 includes a support shaft 8, a case 20 as a hub, a motor 30, a torque sensor (not shown), a reduction mechanism 40, a speed change mechanism 50, a bearing 61 as a first bearing, and a bearing 62 as a second bearing. The electric assist unit 100 can be switched between three gears, namely, a first gear (lowest gear), a second gear, and a third gear (highest gear), by the speed change mechanism 50.

[0033] The case 20 supports the rear wheel 3b rotatably relative to the support shaft 8. The case 20 transmits at least one of a pedal force and a driving force to the rear wheel 3b. The case 20 rotates together with the rear wheel 3b around the support shaft 8. The case 20 has an outer peripheral portion 21 and a pair of side wall portions 22, 23. The case 20 is divided into two portions in the axial direction: a portion where the side wall portion 22 is provided and a portion where the side wall portion 23 is provided, and these portions are fixed together by bolting.

[0034] The outer peripheral portion 21 is provided in a substantially cylindrical shape. The outer peripheral portion 21 covers the outer peripheries of the motor 30, the reduction mechanism 40, and at least a portion of the transmission mechanism 50. The outer peripheral portion 21 has a portion located on the outer periphery of the motor 30. The rear wheel 3b is attached to the outer peripheral portion 21 via spokes (not shown).

[0035] The side wall portion 22 is provided at one axial end of the outer circumferential portion 21. The side wall portion 22 is provided in the shape of an annular plate and closes one open end of the outer circumferential portion 21. The side wall portion 22 is rotatably supported on the support shaft 8 via a bearing 63. That is, the side wall portion 22 is rotatably supported with respect to the support shaft 8.

[0036] The side wall portion 23 is provided at the other axial end of the outer circumferential portion 21. The side wall portion 23 is provided in the shape of an annular plate and closes the other open end of the outer circumferential portion 21. The side wall portion 23 is connected downstream of a power transmission member 59 (described later) of the speed change mechanism 50. The side wall portion 23 rotates around the support shaft 8 integrally with the power transmission member 59.

[0037] The motor 30 assists the driving force in response to the pedal force applied by the driver. The motor 30 is driven by a command from the controller 9 a (see FIG. 1 ). The motor 30 generates an assist torque using electric power supplied from the power storage unit 9 b (see FIG. 1 ).

[0038] The motor 30 is connected to the case 20 via a reduction mechanism 40. The motor 30 has a stator 31, a rotor 32, a support member 33, and wiring .

[0039] The stator 31 is supported by a carrier 43 of the reduction mechanism 40 so as to be non-rotatable with respect to the support shaft 8 .

[0040] The rotor 32 is provided on the inner circumferential side of the stator 31 and rotates relative to the stator 31. A sun gear 41 (described later) of the reduction mechanism 40 is attached to the rotor 32 via a support member 33. The rotor 32 rotates together with the sun gear 41.

[0041] The support member 33 has a support portion 33a and a power transmission portion 33b.

[0042] The support portion 33a is formed in a generally cylindrical shape and extends in the axial direction. The support portion 33a is rotatably supported on the outer periphery of the power transmission member 59 of the speed change mechanism 50 via a pair of bearings 62.

[0043] The power transmission portion 33b is formed in the shape of an annular plate extending radially. The power transmission portion 33b is provided integrally with the support portion 33a at one axial end of the support portion 33a. The outer peripheral surface of the power transmission portion 33b is fixed to the rotor 32 of the motor 30. The one axial end surface of the power transmission portion 33b is fixed to the sun gear 41 of the reduction mechanism 40.

[0044] The wiring 34 electrically connects the controller 9a and the stator 31, enabling the controller 9a to control the motor 30. The wiring 34 connects the power storage unit 9b and the stator 31, allowing power to be supplied from the power storage unit 9b to the stator 31. The wiring 34 is configured to pass through a carrier 43 (described later) of the reduction gear mechanism 40.

[0045] This allows the wiring 34 to be taken out to the outside by providing a hollow shaft in the carrier 43 or by forming a through hole in a part of the carrier 43. At this time, the planetary reduction mechanism 40a is fixed to the carrier 43, and the carrier 43 does not rotate, so it is possible to arrange the wiring so that the wiring 34 will not be caught in the rotation.

[0046] The motor 30 has a portion located on the outer periphery of the support shaft 8. The motor 30 is disposed radially sandwiched between a power transmission member 59 (described later) of the speed change mechanism 50 and the case 20. This configuration is advantageous in that providing a partition wall between the motor 30 and a planetary gear mechanism 50a (described later) of the speed change mechanism 50 in the axial direction would result in the electric assist unit 100 expanding in the axial direction.

[0047] The torque sensor detects the driving torque generated when the rider pedals the crank arm 7b via the pedals 7 and transmitted to the crankshaft 7c. The torque sensor is, for example, a non-contact torque sensor that detects torque based on the torsion of the crankshaft 7c measured magnetically.

[0048] The reduction mechanism 40 includes a planetary reduction mechanism 40a and a one-way clutch 45. That is, the reduction mechanism 40 includes the planetary reduction mechanism 40a. The planetary reduction mechanism 40a includes a sun gear 41, planetary gears 42, a carrier 43, and a ring gear 44.

[0049] As shown in FIG. 3, the reduction mechanism 40 has a fixed carrier 43 of a planetary reduction mechanism 40a, and reduces the assist force input from the motor 30 via a sun gear 41 and outputs it from a ring gear 44.

[0050] 2, the sun gear 41 is attached to the rotor 32 of the motor 30 via a support member 33. The sun gear 41 has a gear portion 41a and a power transmission portion 41b.

[0051] The gear portion 41a is formed in a generally cylindrical shape extending in the axial direction. The gear portion 41a faces the support shaft 8 at a distance so as to surround the outer periphery of the support shaft 8. A tooth surface that meshes with the planetary gear 42 is formed on the outer periphery of the gear portion 41a.

[0052] The power transmission portion 41b is formed in a ring-shaped plate shape extending in the radial direction. One end of the power transmission portion 41b is fixed to one axial end of the gear portion 41a. The other end of the power transmission portion 41b is fixed to the support member 33 of the motor 30.

[0053] The planetary gear 42 is supported by a carrier 43. The planetary gear 42 rotates about a central axis. As will be described later, the carrier 43 is fixed so that the planetary gear 42 cannot rotate, so the planetary gear 42 does not revolve around the outer periphery of the sun gear 41.

[0054] The planetary gear 42 has a large diameter portion 42 a that meshes with the sun gear 41 and a small diameter portion 42 b that meshes with the ring gear 44 .

[0055] The large diameter portion 42 a is formed in a substantially cylindrical shape, and a tooth surface that meshes with the sun gear 41 is formed on the outer periphery of the large diameter portion 42 a.

[0056] The small diameter portion 42b is provided coaxially with the large diameter portion 42a. The small diameter portion 42b is formed in a generally cylindrical shape with a smaller diameter than the large diameter portion 42a. A tooth surface that meshes with the ring gear 44 is formed on the outer periphery of the small diameter portion 42b. In other words, a plurality of tooth surfaces are provided coaxially with one another to constitute the planetary gear 42.

[0057] The carrier 43 has a fixing portion 43a, a connecting portion 43b, an extending portion 43c, and a supporting portion 43d.

[0058] The fixed portion 43a is formed in an annular plate shape extending radially. The fixed portion 43a is fixed to the outer periphery of the support shaft 8. That is, the carrier 43 is fixed to the support shaft 8 so as not to be rotatable. The fixed portion 43a is provided so as to be adjacent to the small diameter portion 42b of the planetary gear 42 in the axial direction. The fixed portion 43a supports the planetary gear 42 so as to be rotatable on its axis.

[0059] The connecting portions 43b extend in the axial direction from multiple circumferential positions on the fixed portion 43a. The connecting portions 43b are disposed between multiple planetary gears 42 in the circumferential direction, i.e., at positions where no planetary gears 42 are provided. The connecting portions 43b connect the fixed portion 43a and the extending portions 43c. The wiring 34 is configured to pass through the connecting portions 43b. Alternatively, the wiring 34 may be fixed so as to run along the outer surface of the connecting portions 43b.

[0060] The extending portion 43c is formed in an annular plate shape extending radially. The extending portion 43c is formed with a larger diameter than the fixed portion 43a. The extending portion 43c is provided adjacent to the large diameter portion 42a of the planetary gear 42 in the axial direction. The extending portion 43c supports the planetary gear 42 so that it can rotate on its axis. In other words, the extending portion 43c rotatably supports the planetary gear 42 between itself and the fixed portion 43a.

[0061] The support portion 43d is formed in a substantially cylindrical shape so as to extend in the axial direction from the radial end of the extension portion 43c. The stator 31 of the motor 30 is attached to the inner periphery of the support portion 43d. That is, the stator 31 of the motor 30 is supported by the carrier 43. As a result, the stator 31 is provided non-rotatably with respect to the support shaft 8 via the carrier 43.

[0062] As a result, by using a planetary reduction mechanism 40a fixed to the carrier 43, the carrier 43 can be given the function of fixing the stator 31, so that separate parts for fixing the stator 31 can be omitted, which contributes to the miniaturization of the electric assist unit 100.

[0063] The ring gear 44 is provided on the outer periphery of the small diameter portion 42b of the planetary gear 42. The outer periphery of the ring gear 44 is attached to a one-way clutch 45. The inner periphery of the ring gear 44 is formed with a tooth surface that meshes with the tooth surface of the small diameter portion 42b.

[0064] The one-way clutch 45 is provided between the outer periphery of the ring gear 44 and the inner surface of the side wall portion 22 of the case 20. The one-way clutch 45 switches between a state in which the assist force of the motor 30 is transmitted to the case 20 via the reduction mechanism 40 and a state in which the rotation of the case 20 is not transmitted to the motor 30.

[0065] The reduction mechanism 40 has a portion located on the outer periphery of the support shaft 8. The reduction mechanism 40 has a portion that overlaps with the speed change mechanism 50 when viewed in the axial direction. As a result, if a large reduction ratio is set in the reduction mechanism 40, the radial length becomes large, so by arranging the reduction mechanism 40 by utilizing the large radial space on the axial side of the speed change mechanism 50, it is possible to provide an electric assist unit 100 that can be made smaller in the radial direction.

[0066] The speed change mechanism 50 has a planetary gear mechanism 50a as a gear unit and a power transmission member 59 as an output wall. The planetary gear mechanism 50a will be described in detail later with reference to Figures 6A to 9.

[0067] The power transmission member 59 is connected downstream of the planetary gear mechanism 50 a and functions as a partition wall separating the speed change mechanism 50 chamber and the motor 30 chamber within the case 20 .

[0068] The bearing 61 is disposed between the power transmission member 59 and the support shaft 8. The bearing 62 is disposed between the power transmission member 59 and the motor 30. As a result, the motor 30 is supported on the support shaft 8 via the bearing 61, the power transmission member 59, and the bearing 62.

[0069] If the motor 30 were to be supported directly on the support shaft 8 by only the bearing 61 on the transmission mechanism 50 side, the electric assist unit 100 would expand in the axial direction or the radial direction. Specifically, if a bearing 62 is provided next to the bearing 61 in the axial direction, as in the first comparative example shown in Fig. 4, the electric assist unit 100 would expand in the axial direction by the size of the bearing 62. Furthermore, if the bearing 62 is provided to support the sun gear 41 on the support shaft 8, as in the second comparative example shown in Fig. 5, the planetary reduction mechanism 40a needs to be moved radially outward by the size of the bearing 62, and therefore the electric assist unit 100 would expand in the radial direction.

[0070] Furthermore, if the motor 30 were to be supported directly on the support shaft 8 using only the bearing 61, the support stability of the motor 30 would be lower than in one aspect of the present invention. Therefore, one aspect of the present invention can be said to be a preferable support aspect.

[0071] Furthermore, if a partition wall is separately provided to separate the entire transmission mechanism 50 from the entire motor 30 in order to improve the sealing between the transmission mechanism 50 chamber and the motor 30 chamber within the case 20, the electric assist unit 100 will become larger by the size of the partition wall. However, in this configuration, the power transmission member 59 functions as a partition wall, which contributes to miniaturization.

[0072] The speed change mechanism 50 has a portion located on the outer periphery of the support shaft 8. The speed change mechanism 50 has a portion that overlaps with the motor 30 when viewed radially. In this way, by having the speed change mechanism 50, which is independent in terms of power transmission and does not directly transmit the power of the motor 30, overlap the motor 30 in the radial direction, the electric assist unit 100, which has the support shaft 8 at its center and outputs power from the outermost case 20, can be made smaller in the axial direction.

[0073] Furthermore, the planetary gear mechanism 50a has a portion that overlaps with the motor 30 when viewed radially. This allows for downsizing when at least the power transmission member 59, which is a part of the speed change mechanism 50, overlaps with the motor 30 in the radial direction, but further downsizing in the axial direction is possible when the planetary gear mechanism 50a overlaps with the motor 30 in the radial direction.

[0074] Next, the transmission mechanism 50 will be described with reference to FIGS. 6A to 9. FIG.

[0075] Fig. 6A is a skeleton diagram of the transmission mechanism 50 in the electric assist unit 100, showing a state where it is switched to the first speed. Fig. 6B is a nomographic diagram of the transmission mechanism 50 in the electric assist unit 100, showing a state where it is switched to the first speed. Fig. 7 is a skeleton diagram of the transmission mechanism 50 in the electric assist unit 100, showing a state where it is switched to the second speed. Fig. 8A is a skeleton diagram of the transmission mechanism 50 in the electric assist unit 100, showing a state where it is switched to the third speed. Fig. 8B is a nomographic diagram of the transmission mechanism 50 in the electric assist unit 100, showing a state where it is switched to the third speed. Fig. 9 is a conceptual diagram for explaining the cam 57.

[0076] First, the configuration of the speed change mechanism 50 will be described mainly with reference to FIG. 6A.

[0077] 6A , the speed change mechanism 50 has a planetary gear mechanism 50a, a power input member 51, a speed change shaft 52, a cam 57, an engaging member 58, and a power transmission member 59. The speed change mechanism 50 is connected to the case 20 without passing through the reduction mechanism 40. The planetary gear mechanism 50a has a sun gear 53, a planetary gear 54, a carrier 55, and a ring gear 56.

[0078] A power different from the power of the motor 30 (for example, human power) is input from the power input member 51. Here, the driving torque generated when the rider pedals the crank arm 7b via the pedals 7 is transmitted and input from the power input member 51 via the driving sprocket 6a, the chain 6c, and the driven sprocket 6b. The power input member 51 is connected to the ring gear 56 via a one-way clutch 51b. The power input member 51 has a meshing portion 51a.

[0079] The meshing portion 51a is provided on the inner periphery of the power input member 51. The meshing portion 51a is formed to be long in the axial direction. The meshing portion 51a meshes with the transmission shaft 52 to transmit power.

[0080] The one-way clutch 51 b switches between a state in which the driving torque input to the power input member 51 is transmitted to the ring gear 56 and a state in which the rotation of the ring gear 56 is not transmitted to the power input member 51 .

[0081] The shift shaft 52 is movable in the axial direction around the outer periphery of the support shaft 8, and switches between three gears: first, second, and third, depending on its axial position. The axial position of the shift shaft 52 is changed based on the rider's operation. This allows the rider to change gears by operating a lever or the like at hand, similar to shifting gears on a regular bicycle. The shift shaft 52 has a first large diameter portion 52a, a second large diameter portion 52b, and a small diameter portion 52c.

[0082] The first large diameter portion 52a is provided on the outer periphery of the speed change shaft 52. The first large diameter portion 52a has a first meshing portion 52d that meshes with the meshing portion 51a of the power input member 51.

[0083] The first meshing portion 52d is provided on the outer periphery of the first large diameter portion 52a. The first meshing portion 52d is formed to be shorter in the axial direction than the meshing portion 51a of the power input member 51. The first meshing portion 52d meshes with the meshing portion 51a of the power input member 51 in all gear positions. That is, power is transmitted from the power input member 51 to the transmission shaft 52 in all gear positions.

[0084] The second large diameter portion 52b is provided on the outer periphery of the transmission shaft 52. The second large diameter portion 52b is provided axially spaced apart from the first large diameter portion 52a. The second large diameter portion 52b has a second meshing portion 52e that can mesh with a meshing portion 55a of the carrier 55, which will be described later.

[0085] The second meshing portion 52e is provided on the outer periphery of the second large diameter portion 52b. The second meshing portion 52e is formed to have the same outer diameter as the first meshing portion 52d. The second meshing portion 52e meshes with a meshing portion 55a (described later) of the carrier 55 when the gear is shifted to the third gear.

[0086] The small diameter portion 52c is provided between the first large diameter portion 52a and the second large diameter portion 52b in the axial direction and has a smaller diameter than the first large diameter portion 52a and the second large diameter portion 52b.

[0087] The planetary gear mechanism 50a is rotatably supported on the support shaft 8 via a bearing 64 (see FIG. 2). The planetary gear mechanism 50a rotatably supports a power transmission member 59 via a bearing 65 (see FIG. 2).

[0088] The sun gear 53 is fixed to the outer periphery of the support shaft 8. In other words, the sun gear 53 does not rotate.

[0089] A plurality of planetary gears 54 are provided and supported by a carrier 55. The planetary gears 54 are provided on the outer periphery of the sun gear 53 and mesh with the sun gear 53. The planetary gears 54 are provided on the inner periphery of the ring gear 56 and mesh with the ring gear 56. The planetary gears 54 rotate about their central axes and revolve around the outer periphery of the sun gear 53.

[0090] The carrier 55 rotates around the support shaft 8 as the planetary gear 54 revolves. The carrier 55 has a meshing portion 55a. The carrier 55 is connected to a power transmission member 59 via a one-way clutch 55b.

[0091] The meshing portion 55a meshes with the second meshing portion 52e when the speed-change shaft 52 moves axially and the speed change stage is switched to the third stage (the state shown in FIG. 8A).

[0092] The one-way clutch 55 b switches between a state in which the power output from the carrier 55 is transmitted to the power transmission member 59 and a state in which the rotation of the power transmission member 59 is not transmitted to the carrier 55 .

[0093] The ring gear 56 is provided on the outer periphery of the planetary gear 54 and meshes with the planetary gear 54. The ring gear 56 is connected to the power input member 51 via a one-way clutch 51b. A rotation shaft of a cam 57 is inserted into the ring gear 56.

[0094] 9, a plurality of cams 57 are provided on the outer periphery of the speed change shaft 52. The cams 57 revolve around the outer periphery of the speed change shaft 52 as the ring gear 56 rotates. The angle of the cam 57 changes depending on whether the second large diameter portion 52b is located on the inner periphery or the small diameter portion 52c is located on the inner periphery.

[0095] When the second large diameter portion 52b is located on the inner periphery of the cam 57, the cam 57 rotates freely without engaging with the outer engaging member 58 (the state shown by the solid line in FIG. 9). On the other hand, when the small diameter portion 52c is located on the inner periphery of the cam 57, the cam 57 engages with the engaging portion 58a of the outer engaging member 58 and rotates together (the state shown by the two-dot chain line in FIG. 9).

[0096] 6A, the engagement member 58 is connected to a power transmission member 59. When the engagement member 58 is engaged with the cam 57, power is transmitted from the power input member 51 to the engagement member 58 via the cam 57.

[0097] Next, the gear stages of the transmission mechanism 50 will be described with reference to Figures 6A to 8B. In Figures 6A, 7, and 8A, the power transmission paths through which power is transmitted are indicated by thick lines.

[0098] As shown in FIG. 6A, when the speed change mechanism 50 is switched to the first speed, the speed change shaft 52 is located at a first axial position.

[0099] The speed change shaft 52 meshes with the meshing portion 51 a of the power input member 51 but does not mesh with the meshing portion 55 a of the carrier 55. The second large diameter portion 52 b of the speed change shaft 52 abuts against the cam 57.

[0100] Therefore, the power input from the power input member 51 is transmitted to the ring gear 56 via the one-way clutch 51b. The power transmitted to the ring gear 56 is then transmitted to the planetary gear 54 and output as rotation of the carrier 55. The rotation of the carrier 55 is transmitted to the power transmission member 59 via the one-way clutch 55b.

[0101] As a result, as shown in FIG. 6B, since the sun gear 53 is fixed, the speed change mechanism 50 reduces the speed of the power input from the power input member 51 via the ring gear 56 and outputs the reduced power from the carrier 55.

[0102] As shown in FIG. 7, when the speed change mechanism 50 is switched to the second speed, the speed change shaft 52 is located at a second axial position.

[0103] The speed change shaft 52 meshes with the meshing portion 51 a of the power input member 51, but does not mesh with the meshing portion 55 a of the carrier 55. Furthermore, the small diameter portion 52 c of the speed change shaft 52 abuts against the cam 57. Therefore, the cam 57 engages with the engaging member 58.

[0104] Therefore, the power input from the power input member 51 is transmitted to the cam 57 via the one-way clutch 51b. The power transmitted to the cam 57 is then transmitted to the power transmission member 59 via the engagement member 58.

[0105] As a result, the power input member 51 and the ring gear 56 of the transmission mechanism 50 are directly connected, and the power input from the power input member 51 is output from the ring gear 56 at a constant speed.

[0106] As shown in FIG. 8A, when the speed change mechanism 50 is switched to the third speed, the speed change shaft 52 is located at a third position in the axial direction.

[0107] The speed change shaft 52 meshes with the meshing portion 51 a of the power input member 51, and also meshes with the meshing portion 55 a of the carrier 55. The small diameter portion 52 c of the speed change shaft 52 abuts against the cam 57. Therefore, the cam 57 engages with the engaging member 58.

[0108] Therefore, the power input from the power input member 51 is transmitted to the carrier 55 via the speed change shaft 52. The power transmitted to the carrier 55 is then transmitted to the power transmission member 59 via the ring gear 56, the cam 57, and the engagement member 58.

[0109] As a result, as shown in FIG. 8B, since the sun gear 53 is fixed, the speed of the transmission mechanism 50 increases the power input from the power input member 51 via the carrier 55 and outputs it from the ring gear 56.

[0110] As described above, the transmission mechanism 50 can be switched between three gear stages: first, second, and third. However, the configuration of the transmission mechanism 50 is merely an example, and other transmission mechanisms may be provided. For example, a transmission mechanism that can switch between two or four or more gear stages instead of three may be provided.

[0111] The configuration and effects of the present embodiment will now be described.

[0112] (1) The electric assist unit 100 comprises a support shaft 8, a reduction mechanism 40 having a portion located on the outer periphery of the support shaft 8, a speed change mechanism 50 having a portion located on the outer periphery of the support shaft 8, a motor 30 having a portion located on the outer periphery of the support shaft 8, and a case 20 having a portion located on the outer periphery of the motor 30, wherein the motor 30 is connected to the case 20 via the reduction mechanism 40, and the speed change mechanism 50 is connected to the case 20 without via the reduction mechanism 40, and when viewed radially, the speed change mechanism 50 has a portion that overlaps with the motor 30.

[0113] According to this configuration, by overlapping the motor 30 radially with the power transmission-independent speed change mechanism 50, to which the power of the motor 30 is not directly transmitted, the electric assist unit 100, which has a support shaft 8 in the center and outputs power from the outermost case 20, can be made smaller in the axial direction.

[0114] (2) When viewed in the axial direction, the reduction mechanism 40 has a portion that overlaps with the speed change mechanism 50 .

[0115] With this configuration, if a large reduction ratio is set in the reduction mechanism 40, the radial length will become large. Therefore, by utilizing the large radial space on the axial side of the transmission mechanism 50, an electric assist unit 100 can be provided that can be made smaller in the radial direction.

[0116] (3) The transmission mechanism 50 has a planetary gear mechanism 50a and a power transmission member 59 connected downstream of the planetary gear mechanism 50a, and the motor 30 is arranged radially sandwiched between the power transmission member 59 and the case 20.

[0117] This configuration is preferable in that providing a partition wall between the motor 30 and the planetary gear mechanism 50a of the speed change mechanism 50 in the axial direction would result in the electric assist unit 100 becoming larger in the axial direction.

[0118] Furthermore, if a partition wall is provided to separate the entire transmission mechanism 50 from the entire motor 30 in order to improve the sealing between the transmission mechanism 50 chamber and the motor 30 chamber, the electric assist unit 100 will become larger by the size of the partition wall. However, in this configuration, the power transmission member 59 functions as a partition wall, which contributes to miniaturization.

[0119] (4) The transmission mechanism 50 has a planetary gear mechanism 50a and a power transmission member 59 connected downstream of the planetary gear mechanism 50a, and the case 20 is connected downstream of the power transmission member 59. When viewed radially, the planetary gear mechanism 50a has a portion that overlaps with the motor 30.

[0120] According to this configuration, miniaturization is possible if at least the power transmission member 59, which is part of the transmission mechanism 50, overlaps radially with the motor 30, but further axial miniaturization is possible if the planetary gear mechanism 50a overlaps radially with the motor 30.

[0121] (5) The electric assist unit 100 further includes a bearing 61 and a bearing 62, and the transmission mechanism 50 includes a planetary gear mechanism 50a and a power transmission member 59 connected downstream of the planetary gear mechanism 50a, with the bearing 61 being disposed between the power transmission member 59 and the support shaft 8 and the bearing 62 being disposed between the power transmission member 59 and the motor 30.

[0122] In this configuration, the motor 30 is supported on the support shaft 8 via the bearing 61, the power transmission member 59, and the bearing 62. If the motor 30 were to be directly supported on the support shaft 8 only by the bearing 61 on the transmission mechanism 50 side, the electric assist unit 100 would expand in the axial direction or the radial direction. Furthermore, if the motor 30 were to be directly supported on the support shaft 8 only by the bearing 61, the support stability of the motor 30 would be reduced compared to one aspect of the present invention. Therefore, one aspect of the present invention can be said to be a preferred support aspect.

[0123] (6) The reduction mechanism 40 includes a planetary reduction mechanism 40 a. The carrier 43 of the planetary reduction mechanism 40 a is fixed to the support shaft 8 , and the stator 31 of the motor 30 is supported by the carrier 43 .

[0124] According to this configuration, by using a planetary reduction mechanism 40a fixed to the carrier 43, the carrier 43 can be given the function of fixing the stator 31, so that separate parts for fixing the stator 31 can be omitted, which contributes to the miniaturization of the electric assist unit 100.

[0125] (7) The wiring 34 connected to the stator 31 is configured to pass through the carrier 43 .

[0126] In this configuration, the wiring 34 can be taken out by providing a hollow shaft in the carrier 43 or by forming a through hole in a part of the carrier 43. In this case, the planetary reduction mechanism 40a is fixed to the carrier 43, and the carrier 43 does not rotate, so it is possible to arrange the wiring so that the wiring 34 will not be caught in the rotation.

[0127] Although an embodiment of the present invention has been described above, the above embodiment merely shows one application example of the present invention, and is not intended to limit the technical scope of the present invention to the specific configuration of the above embodiment.

[0128] For example, in the above embodiment, the electric assist unit 100 is attached to the rear wheel 3b together with the driven sprocket 6b. However, the electric assist unit 100 may also be attached to the crankshaft 7c together with the driving sprocket 6a. In this case, the rider may pedal the crank arm 7b via the pedal 7, and the pedaling force (driving torque) transmitted from the crank arm 7b to the crankshaft 7c may be input to the sun gear 53. Alternatively, the output of the electric assist unit 100 may be transmitted to the driving sprocket 6a via the case 20, and then to the driven sprocket 6b via a chain 6c wound around the driving sprocket 6a, thereby rotating the rear wheel 3b.

[0129] In the above embodiment, the rotor 32 is a so-called inner rotor that is provided on the inner periphery of the stator 31. Alternatively, the stator may be provided on the inner periphery side, and the rotor may be a so-called outer rotor that rotates on the outer periphery of the stator.

[0130] 100 Electric assist unit (unit) 8 Support shaft (fixed shaft) 20 Case (hub) 30 Motor 31 Stator 32 Rotor 34 Wiring 40 Reduction mechanism 40a Planetary reduction mechanism 43 Carrier 50 Speed ​​change mechanism 50a Planetary gear mechanism (gear portion) 59 Power transmission member (output wall) 61 Bearing (first bearing) 62 Bearing (second bearing)

Claims

1. A unit comprising: a fixed shaft; a reduction mechanism having a portion located on the outer periphery of the fixed shaft; a speed change mechanism having a portion located on the outer periphery of the fixed shaft; a motor having a portion located on the outer periphery of the fixed shaft; and a hub having a portion located on the outer periphery of the motor, wherein the motor is connected to the hub via the reduction mechanism, and the speed change mechanism is connected to the hub without the reduction mechanism, and when viewed in a radial direction, the speed change mechanism has a portion that overlaps with the motor.

2. A unit according to claim 1, wherein the reduction mechanism has a portion that overlaps with the speed change mechanism when viewed in the axial direction.

3. A unit according to claim 1, wherein the speed change mechanism has a gear section and an output wall connected downstream of the gear section, and the motor is disposed between the output wall and the hub in the radial direction.

4. A unit as described in claim 1, wherein the speed change mechanism has a gear portion and an output wall connected downstream of the gear portion, the hub is connected downstream of the output wall, and when viewed in a radial direction, the gear portion has a portion that overlaps with the motor.

5. A unit as claimed in claim 1, further comprising a first bearing and a second bearing, said speed change mechanism having a gear section and an output wall connected downstream of said gear section, said first bearing being disposed between said output wall and said fixed shaft, and said second bearing being disposed between said output wall and said motor.

6. A unit according to claim 1, wherein the reduction mechanism includes a planetary reduction mechanism, a carrier of the planetary reduction mechanism is fixed to the fixed shaft, and a stator of the motor is supported by the carrier.

7. The unit according to claim 6, wherein wiring connected to the stator is configured to pass through the carrier.