Compact generator and hub dynamo

Abstract

The present invention is a compact generator 1 that converts a rotational force rotating about a base axis J1 into electric power. The present invention comprises: a power generation member 80 that is positioned in the surroundings of the base axis J1, and generates power by rotating about a rotation axis J2 which is eccentric from the base axis J1; and a speed change member 50 that is positioned in the surroundings of the base axis J1, in a condition of being concentrically linked to the power generation member 80. The speed change member 50 increases the speed of the rotation of the rotational force and transmits the result to the power generation member 80.

Description

Small generator and hub dynamo

[0001] The disclosed technology relates to a small generator and a hub dynamo.

[0002] Generally, a bicycle may be equipped with a small generator that uses the rotational force of the wheel to supply power to the headlight. As this type of generator, a rim drive type dynamo that presses against the rotating rim of the front wheel from the side during power generation is widely known. However, this rim drive type has the drawback that the load on the wheel is large and the pedals become heavy.

[0003] Therefore, in recent years, a hub dynamo in which a generator is incorporated in a hub that rotates at the center of the wheel has been widely used.

[0004] For example, the hub dynamo of Patent Document 1 has a rotatable hub case and a non-rotatable hub shaft extending through its center. A cylindrical permanent magnet is fitted inside the inner peripheral surface of the hub case. A core (iron core) having four-pole teeth is fixed to the hub shaft. Electric wires are wound around each tooth to form a coil. When the hub case rotates, an electric current flows through the coil and that current is output.

[0005] However, conventional hub dynamos are heavy because they have a core. This is disadvantageous for a bicycle. Moreover, a cogging torque is generated by the attractive force acting between the core and the permanent magnet. The cogging torque becomes an extra load and makes the pedals heavy.

[0006] In order to suppress the cogging torque, a hub dynamo using a coreless motor has been proposed (Patent Document 2).

[0007] Japanese Patent Application Laid-Open No. 06-048341, Japanese Patent Application Laid-Open No. 2016-171723

[0008] The hub dynamo described in Patent Document 2 rotates a coreless cylindrical coil section. Therefore, the generation of cogging torque can be suppressed. However, this coreless motor is configured coaxially with the wheel. As a result, the motor surrounds the wheel axle, making it unavoidably large and prone to becoming heavy. Furthermore, increasing the power generation capacity requires an even larger motor, resulting in a larger hub dynamo.

[0009] Furthermore, to increase power generation, a gear unit composed of multiple spur gears is interposed between the hub and the coil section to increase the rotational speed of the hub. However, if the number of gear stages in the spur gears is large, the transmission efficiency tends to deteriorate. Also, the structure of the gear unit is complex. Therefore, high precision is required for the parts and assembly. Tooth damage can occur due to the meshing of the gears, making it prone to failure.

[0010] Therefore, this specification discloses a technology that enables the realization of a high-performance, lightweight, and relatively simple structure for a compact generator.

[0011] The technology being disclosed relates to a small generator that converts rotational force, which rotates around a base axis, into electricity.

[0012] The small generator comprises a power generation member arranged around the base axis and generating electricity by rotating around a rotation axis eccentric to the base axis, and a speed change member arranged around the base axis and coaxially connected to the power generation member. The speed change member increases the rotational speed of the rotational force and transmits it to the power generation member.

[0013] In other words, when converting rotational force around a base axis into electricity, it is common to arrange the power generation element and the speed change element coaxially with the base axis. As a result, the power generation element and the speed change element become large in shape, surrounding the shaft of the rotating body. In contrast, this small generator comprises a power generation element that generates electricity by rotating around a rotation axis eccentric to its base axis, and a speed change element that is arranged around the base axis while being coaxially connected to the power generation element.

[0014] Therefore, the power generation component and the speed change component can be made smaller and lighter.

[0015] The speed-shifting component then increases the rotational speed of that rotational force and transmits it to the power-generating component. Therefore, the amount of power generated can be increased.

[0016] It is also possible that a coreless motor is used in the aforementioned power generation component. That is, the coreless motor is used as a dynamo (generator).

[0017] For example, the power generation member may include a coreless rotor that is rotatably supported about the axis of rotation and includes a plurality of cylindrically formed coils, a stator that is non-rotatably supported inside the coreless rotor via an air gap and includes magnets that are arranged on the surface opposite to the coreless rotor and constitute a plurality of magnetic poles, and an electrical output assembly configured to be electrically connectable to the plurality of coils, wherein the coreless rotor rotates with the increased rotational force transmitted from the speed-shifting member, and the power generated in the coils as a result is output through the electrical output assembly. Furthermore, an assembly means a component (unit) made up of a plurality of parts.

[0018] This design eliminates the core (iron core), allowing for even greater weight reduction. It enables responsive power generation with low torque. It allows for smooth rotation at high speeds. Since cogging torque is eliminated, pedal operation is also lighter.

[0019] A cycloidal type transmission may be used for the aforementioned transmission member.

[0020] This allows cycloidal gearboxes to achieve higher gear ratios per stage than spur gear or planetary gear gear systems, enabling miniaturization, weight reduction, and increased efficiency of the gearbox mechanism.

[0021] For example, the speed change member may include a first rotating body that rotates about the axis of rotation by the rotational force, a second rotating body that is coaxially connected to the input shaft of the power generation member and rotates about the axis of rotation, a cycloidal disc disposed between the first and second rotating bodies, and a fixed ring disposed on the outer circumference of the cycloidal disc in a non-rotatable state, wherein the second rotating body has an eccentric boss portion that rotatably supports the cycloidal disc about an eccentric axis that is eccentric with respect to the axis of rotation, the cycloidal disc has a plurality of engaging teeth formed at equal intervals along its outer edge and a plurality of engaging holes that open on its surface and are formed at equal intervals along a circumference centered on the eccentric axis, the first rotating body has a plurality of engaging portions formed at equal intervals along a circumference centered on the axis of rotation and partially in contact with the inner surfaces of the plurality of engaging holes, and the fixed ring has a plurality of internal teeth that partially mesh with the plurality of engaging teeth, and the internal teeth are made of bearings.

[0022] This significantly reduces frictional resistance at the parts that partially contact each other during rotation and transmit rotational force, thanks to the smooth rotation of the bearings. This is particularly effective at high rotational speeds. Consequently, it can improve power generation efficiency.

[0023] The aforementioned speed-shifting member may also have a thrust bearing.

[0024] This will allow for stable rotation and improve power generation efficiency.

[0025] The power generation member and the speed change member may be arranged in multiple locations around the base axis.

[0026] This allows the amount of power generated to be increased by the number of components placed. Furthermore, even if multiple power generation components and speed-shifting components are placed around the base axis, the trajectory remains the same, so the outer diameter of the small generator does not change. Therefore, the amount of power generated can be increased without changing the size of the generator. Moreover, if a constant amount of power generation is to be obtained, the size of each individual power generation component and speed-shifting component can be reduced.

[0027] The small generator described above would be suitable for use in a hub dynamo, which is mounted on a bicycle wheel to generate electricity.

[0028] Specifically, the hub dynamo comprises a hub shaft supported by the fork of the bicycle and centered on the base axis, and a hub body rotatably supported on the hub shaft and connected to the rim via a plurality of spokes, wherein the hub body extends from the hub shaft and has a hollow cylinder portion housing the small generator, and a pair of disc portions integrated at both ends of the cylinder portion, each having flanges on its outer periphery to which the spokes are attached, and a rotational force transmission mechanism is provided inside the cylinder portion, and the rotational force of the hub body is transmitted to the gear shifting member through the rotational force transmission mechanism.

[0029] This would allow for the creation of a lightweight, low-load, and high-performance hub dynamo with excellent power generation capabilities. As a result, cyclists would be able to ride their bikes smoothly even at night.

[0030] For example, the rotational force transmission mechanism may include an internal gear assembled to the inner circumference of the cylinder portion and a pinion assembled to the input shaft of the speed change member and meshing with the internal gear. Alternatively, it may include a ring member assembled to the inner circumference of the cylinder portion and a pressing member assembled to the input shaft of the speed change member and pressing against the ring member, wherein at least one of the pressing portions of the ring member and the pressing member is made of an elastic material.

[0031] In either case, the rotational force of the hub can be smoothly transmitted to the gear shifting component with a relatively simple structure.

[0032] The disclosed technology enables the realization of a high-performance, lightweight, and relatively simple structure for compact generators. The disclosed technology is particularly suitable for bicycle hub dynamos.

[0033] This is a schematic diagram illustrating a preferred application example (hub dynamo) of the disclosed technology. This is a schematic cross-sectional view showing the inside of the hub dynamo. This is a schematic cross-sectional view taken from the direction of arrow Y1 in Figure 2A. This is a schematic cross-sectional view of a cycloidal speed increaser. This is a schematic cross-sectional view of a cycloidal speed increaser. This is a schematic cross-sectional view taken from the direction of arrow Y2 in Figure 3A. This is an explanatory diagram of a thrust bearing. This is a schematic diagram for illustrating the detailed structure of a cycloidal speed increaser. This is a schematic diagram for illustrating the detailed structure of a cycloidal speed increaser. This is a schematic diagram for illustrating the structure of a coreless dynamo. This is a schematic diagram showing another form of the rotational force transmission mechanism.

[0034] The following describes the technologies being disclosed. However, the following description is essentially illustrative.

[0035] <Hub Dynamo> As a preferred application example of the disclosed technology, Figure 1 illustrates a hub dynamo 1 that is assembled to a bicycle wheel 100. Figure 2A shows a schematic cross-sectional view of the inside of the hub dynamo 1. Figure 2B shows a schematic cross-sectional view from the direction of arrow Y1 in Figure 2A.

[0036] Typically, a bicycle wheel 100 consists of a tire 101, a rim 102, spokes 103, a hub 1, etc. The rim 102 is an annular part that supports the tire 101. The tire 101 is press-fitted onto the outer circumference of the rim 102.

[0037] The hub 1 is a part located at the center of the rim 102 and the tire 101, and rotatably supports them. The hub 1 comprises a hub shaft 2 supported in a non-rotatable state by the bicycle fork 104, and a hub body 3 rotatably supported on the hub shaft 2. The hub body 3 rotates around a base axis J1 that passes through the center of the hub shaft 2.

[0038] The hub body 3 has a cylindrical (hollow) cylinder portion 31 extending from the hub shaft 2, and a pair of disc portions 32, 32 integrated at both ends of the cylinder portion 31. A dynamo unit 6 (corresponding to a small generator) is housed within the cylinder portion 31 (the dynamo unit 6 will be described later). Thus, the hub dynamo 1 is formed. In other words, in this embodiment, the hub 1 described above corresponds to the hub dynamo (hereinafter referred to as hub dynamo 1).

[0039] Each disc portion 32 is provided with an annular flange portion 32a on its outer edge. Multiple spoke holes 32b are formed in each of these flange portions 32a. The hub body 3 is connected to the rim 102 via multiple spokes 103 attached to these spoke holes 32b.

[0040] Both ends of the hub shaft 2 protrude from the hub body 3. These ends are fixed to the bicycle fork 104. As shown in Figure 2A, the hub dynamo 1 also has a hub pipe 4 and a pair of hub bearings 5, 5. The hub shaft 2 is press-fitted into the hub pipe 4 and integrated with it.

[0041] A hub boss portion 32c is provided in the center of each disc portion 32. Each hub bearing 5 is fitted into these hub boss portions 32c. The hub body 3 is rotatably supported on the hub pipe 4 and hub shaft 2 via these hub bearings 5.

[0042] A rotational force transmission mechanism 20 is provided inside the cylinder portion 31. The rotational force of the hub body 3 is transmitted to the dynamo unit 6 through this rotational force transmission mechanism 20. Figures 2A and 2B show an example of a rotational force transmission mechanism 20 having an internal gear 21 and a pinion 22.

[0043] An annular internal gear 21 is assembled to the inner circumference of the cylinder portion 31. Meanwhile, a pinion 22 is assembled to the input shaft 66 of the cycloidal speed increaser 50, which will be described later and is included in the dynamo unit 6. The pinion 22 is configured to mesh with a group of teeth formed along the inner circumference of the internal gear 21.

[0044] (Dynamo Unit) The dynamo unit 6 provided in this hub dynamo 1 converts the rotational force of the wheel 100 rotating about the axis line J1 into DC power and outputs it. The dynamo unit 6 is configured using a predetermined speed-changing member and a predetermined coreless motor.

[0045] That is, a coreless motor is used as the power generation member. In the dynamo unit 6, the coreless motor is used as a dynamo (hereinafter, also referred to as a coreless dynamo 80). In the case of the coreless dynamo 80, no cogging torque is generated. Moreover, it can rotate with good response at a small torque. Also, the coreless motor can use either a brushed motor that rectifies current by a brush and rotates or a brushless motor that electronically controls a mechanical rectification function.

[0046] A cycloid type speed-changing machine is used as the speed-changing member. In the dynamo unit 6, the cycloid type speed-changing machine is used as a speed increasing machine (hereinafter, also referred to as a cycloid speed increasing machine 50). In the case of the cycloid speed increasing machine 50, the speed ratio per stage can be made large, so the rotational force can be smoothly transmitted. High-speed rotation can be realized with low energy loss. Incidentally, the speed-changing member may be configured using a planetary gear mechanism, a spur gear mechanism, or the like.

[0047] Moreover, existing products can be used for these coreless dynamo 80 and cycloid speed increasing machine 50. Therefore, a dynamo unit 6 with high mass productivity and excellent quality can be realized. The details of these coreless dynamo 80 and cycloid speed increasing machine 50 will be described later. [[ID=I1]]

[0048] The coreless dynamo 80 and the cycloid speed increasing machine 50 are coaxially connected. That is, the output side of the cycloid speed increasing machine 50 is coaxially connected to the input shaft 81 of the coreless dynamo 80 via the joint 7.

[0049] These coreless dynamo 80 and cycloidal speed increaser 50 are arranged around the base axis J1 and are configured to rotate around a rotation axis J2 that is eccentric to the base axis J1. In other words, a motor bracket 8 is attached to the hub pipe 4. The motor bracket 8 protrudes radially from the hub pipe 4 and is attached to the side of the coreless dynamo 80.

[0050] As a result, the coreless dynamo 80 is supported by the hub shaft 2, and the cycloidal speed increaser 50 is supported by the coreless dynamo 80. Since the rotational force is increased by the cycloidal speed increaser 50 which is coaxially connected to the coreless dynamo 80, it can be realized with a relatively simple structure.

[0051] However, the motor bracket 8 is not mandatory. For example, the coreless dynamo 80 may be directly fixed to the cycloidal speed increaser 50.

[0052] Since the dynamo unit 6 is arranged around the base axis J1 and rotates around a rotation axis J2 that is eccentric to the base axis J1, the size of the dynamo unit 6 can be reduced. Therefore, it can be made lighter.

[0053] As shown in Figure 2B, the dynamo unit 6 of this embodiment is equipped with multiple (three) coreless dynamos 80 and cycloidal speed increasers 50. While one coreless dynamo 80 and one cycloidal speed increaser 50 may suffice, increasing their number doubles the power generation capacity, resulting in higher power output.

[0054] Furthermore, since multiple coreless dynamos 80 and cycloidal speed increasers 50 move along the same trajectory, the amount of power generated can be increased without changing the size of the hub body 3. On the other hand, to obtain a constant amount of power, the individual coreless dynamos 80 and cycloidal speed increasers 50 can be made smaller, thereby reducing the size of the hub body 3. In this way, the number of units arranged can be changed to adjust the amount of power generated and the size of the hub body 3 according to the purpose.

[0055] In the dynamo unit 6 configured in this way, the cycloidal speed increaser 50 increases the rotational speed of the wheel 100 and transmits it to the coreless dynamo 80. The coreless dynamo 80 then generates electricity by rotating around the rotation axis J2 with the increased rotational speed. Therefore, it can generate electricity efficiently in a lightweight and compact size. No cogging torque is generated. A high-performance hub dynamo 1 can be realized.

[0056] (Cycloid Speed ​​Increaser) Figures 3A and 3B show cross-sectional views of the cycloid speed increaser 50. Figure 4 shows a schematic cross-sectional view from the direction of arrow Y2 in Figure 3A.

[0057] Figures 3A and 3B show the input and output directions for the cycloidal speed increaser 50. For convenience, the input and output directions used in the explanation will follow these figures.

[0058] The cycloidal speed increaser 50 consists of a cylindrical member whose diameter is greater than its length. The cycloidal speed increaser 50 is composed of a support base 51, a second rotating body 52, a second spacer ring 53, a cycloidal disc 54, a fixing ring 55, a first spacer ring 56, a first rotating body 57, a cover 58, and the like.

[0059] The cover 58, the first spacer ring 56, the fixing ring 55, and the second spacer ring 53 are assembled to the support base 51 with multiple fixing bolts 59, with their outer circumferences overlapping in this order from the input side. The support base 51 is fixed to the housing 82 of the coreless dynamo 80, which will be described later. Therefore, these components are not rotatable.

[0060] In contrast, the first rotating body 57, the cycloidal disk 54, and the second rotating body 52 are rotatable. That is, the first rotating body 57 and the second rotating body 52 rotate around the axis of rotation J2. On the other hand, the cycloidal disk 54 is positioned between the first rotating body 57 and the second rotating body 52 and rotates around an eccentric axis J3 that is eccentric with respect to the axis of rotation J2.

[0061] The support base 51 is a thick, disc-shaped member centered on the rotation axis J2. A large-diameter recess 51a is coaxially formed on the output end face of the support base 51. The input shaft 81 of the coreless dynamo 80 is housed in the recess 51a. A small-diameter output-side shaft insertion hole 51b is formed in the central part of the support base 51. An output-side ball bearing 60 for shaft support is fitted into the output-side shaft insertion hole 51b.

[0062] The second rotating body 52 is pivotally supported on the support base 51 via the output side ball bearing 60. The second rotating body 52 is a disc-shaped member that rotates around the rotation axis J2.

[0063] The central portion of the second rotating body 52 is provided with a coaxial boss portion 52a and an eccentric boss portion 52b. The coaxial boss portion 52a is located on the output side. The coaxial boss portion 52a is centered on the rotation axis J2. A connecting hole 52c is formed in the coaxial boss portion 52a. The joint 7 is inserted into this connecting hole 52c in a way that prevents rotation. As a result, the second rotating body 52 is coaxially connected to the input shaft 81 of the coreless dynamo 80.

[0064] On the other hand, the eccentric boss portion 52b is located on the input side. The eccentric boss portion 52b is centered on an eccentric axis J3 that is eccentric with respect to the rotation axis J2. An intermediate ball bearing 61 for supporting the disc is fitted onto the eccentric boss portion 52b. The intermediate ball bearing 61 is secured to the eccentric boss portion 52b by fastening a screw 62 via a washer. A balance adjustment hole 52d is formed on the outer circumference of the second rotating body 52 to compensate for the imbalance caused by the eccentricity.

[0065] The cycloidal disc 54 is a thin, disc-shaped component. The cycloidal disc 54 is rotatably supported on the second rotating body 52 via an intermediate ball bearing 61. Therefore, the cycloidal disc 54 rotates around the eccentric axis J3. As a result, when the second rotating body 52 rotates, the cycloidal disc 54 rotates while sliding radially according to the amount of eccentricity (eccentric rotation).

[0066] As shown in Figure 4, the cycloidal disc 54 has a plurality of engagement teeth 54a (23 in this embodiment) formed at equal intervals along its outer edge, and a plurality of engagement holes 54b (8 in this embodiment) opening into its surface. Each of the engagement teeth 54a is formed in a cycloidal tooth shape at equal intervals in the circumferential direction. The center of these engagement teeth 54a is the eccentric axis J3, and the engagement teeth 54a are eccentric with respect to the rotation axis J2.

[0067] On the other hand, each of the engagement holes 54b is formed as a circular hole of a predetermined diameter. These engagement holes 54b are formed at equal intervals along the circumference centered on the eccentric axis J3. In other words, the engagement holes 54b are also eccentric with respect to the rotation axis J2.

[0068] The second spacer ring 53 is a thin, annular member. With the second rotating body 52 supported by the output-side ball bearing 60, the outer circumference of the second spacer ring 53 is assembled to the input-side end face of the support base 51.

[0069] To increase the power generation efficiency of the cycloidal speed increaser 50, the outer circumference of the second rotating body 52 can be clamped between the support base 51 and the second spacer ring 53 via a pair of thrust bearings 63, 63. However, if sufficient power generation efficiency can be obtained for the intended use, the thrust bearings 63 may not be used. Furthermore, the size of the thrust bearings 63 can be appropriately selected according to the size of the cycloidal speed increaser 50.

[0070] Figure 5 shows a thrust bearing 63. The thrust bearing 63 consists of a ring-shaped retainer 63a and a plurality of hard balls 63b. The retainer 63a has a plurality of ball holes 63c formed at equal intervals in the circumferential direction.

[0071] A thrust bearing 63 is formed by inserting a hard ball 63b into each of these ball holes 63c. A pair of thrust bearings 63, 63 of this structure are interposed between the support base 51 and the second spacer ring 53.

[0072] As a result, the outer circumference of the second rotating body 52 is supported so as to be able to rotate freely. The second rotating body 52 can rotate stably without tilting, thereby increasing power generation efficiency. Furthermore, as will be described later, by providing multiple pairs of thrust bearings, the first rotating body 57, the second rotating body 52, and the cycloidal disc 54 can rotate stably without tilting, thereby increasing power generation efficiency.

[0073] The fixing ring 55 is an annular member. The fixing ring 55 is assembled to the input side of the second spacer ring 53. As a result, the fixing ring 55 is positioned non-rotatably on the outer circumference of the cycloidal disc 54. The fixing ring 55 has an annular outer edge portion 55a, a tooth support portion 55b that protrudes inward in an annular manner from the outer edge portion 55a, and a plurality (24 in this embodiment) of internal teeth 55c.

[0074] As shown in Figure 4, these internal teeth 55c are configured to partially mesh with the engaging teeth 54a of the cycloidal disc 54 to transmit rotational force.

[0075] In this embodiment, these internal teeth 55c are made up of ball bearings. Specifically, as shown in an enlarged view in Figure 6, each internal tooth 55c is made up of a shaft member 551 and an outer ball bearing 552. The shaft member 551 has a large-diameter base portion 551a and a small-diameter shaft portion 551b. The outer ball bearing 552 is fitted onto the shaft portion 551b. The internal teeth 55c may also be made up of pins.

[0076] The tooth support portion 55b has 24 embedded holes 55d formed at equal intervals in the circumferential direction. The outer peripheral edge portion 55a has arc-shaped recesses 55e formed to receive a portion of the internal teeth 55c, corresponding to these embedded holes 55d. By press-fitting the base portion 551a into the embedded holes 55d, each internal tooth 55c is supported by the fixing ring 55 in a rotatable manner.

[0077] By using ball bearings for the internal teeth 55c, frictional resistance during partial contact with the engaging teeth 54a can be significantly reduced. This is particularly effective for the high-speed rotating cycloidal speed increaser 50. It can also improve power generation efficiency.

[0078] The first spacer ring 56 is a thin, annular member. With the outer ball bearing 552 inserted into the shaft portion 551b of each internal tooth 55c, the outer circumference of the first spacer ring 56 is assembled to the input side of the outer peripheral edge 55a of the fixing ring 55.

[0079] To increase the power generation efficiency of the cycloidal speed increaser 50, the outer circumference of the cycloidal disc 54 can be clamped between the first spacer ring 56 and the second spacer ring 53 via a pair of thrust bearings 64, 64. This ensures that the cycloidal disc 54 does not tilt and achieves stable rotation, thereby increasing power generation efficiency.

[0080] The outer circumference of the cycloidal disc 54 is supported so as to be able to rotate freely and slide radially. Furthermore, if sufficient power generation efficiency can be obtained for the intended use, a thrust bearing may not be necessary. Also, the size of the thrust bearing 64 can be appropriately selected according to the size of the cycloidal speed increaser 50.

[0081] Furthermore, the first spacer ring 56 is provided with ring-shaped projections 56a. These ring-shaped projections 56a prevent the outer ball bearing 552 from coming off.

[0082] The cover 58 is a disc-shaped member. It has a circular lid portion 58a and a ring-shaped fastening portion 58b provided on the outer circumference of the lid portion 58a. With the first rotating body 57 sandwiched between the lid portion 58a and the cycloidal disc 54, the fastening portion 58b is assembled to the input side of the outer circumference of the first spacer ring 56.

[0083] An input-side shaft insertion hole 58c is formed in the center of the lid portion 58a. An input-side ball bearing 65 for shaft support is fitted into the input-side shaft insertion hole 58c. The first rotating body 57 is rotatably supported on the cover 58 via the input-side ball bearing 65.

[0084] The first rotating body 57 is a disc-shaped member that rotates around the rotation axis J2. A first boss portion 57a ​​is formed in the central part of the first rotating body 57, centered on the rotation axis J2. An input shaft 66 is press-fitted into the first boss portion 57a. A pinion 22, which receives the rotational force of the hub body 3, is attached to the tip of this input shaft 66.

[0085] The outer circumference of the first rotating body 57 can be clamped between the cover 58 and the first spacer ring 56 via a pair of thrust bearings 63, 63, similar to the outer circumference of the second rotating body 52. ​​This ensures that the first rotating body 57 does not tilt and provides stable rotation, thereby increasing power generation efficiency. However, if sufficient power generation efficiency can be obtained for the intended use, the thrust bearings 63 may not be used. The size of the thrust bearings 64 can be appropriately selected according to the size of the cycloidal speed increaser 50.

[0086] As shown in Figure 4, by using a pair of thrust bearings 63, 63 or thrust bearings 64, 64 arranged on the outer circumference of the first rotating body 57, the second rotating body 52, and the cycloidal disk 54, respectively, stable rotation can be obtained without tilting of the first rotating body 57, the cycloidal disk 54, and the second rotating body 52, thereby increasing power generation efficiency.

[0087] On the surface of the first rotating body 57 facing the cycloidal disk 54, a plurality of engagement portions 57b (eight in this embodiment) are provided, corresponding to the engagement holes 54b of the cycloidal disk 54. Unlike the engagement holes 54b, these engagement portions 57b are arranged at equal intervals along the circumference centered on the rotation axis J2.

[0088] Furthermore, these engaging portions 57b are configured to be located within the engaging holes 54b. As a result, as shown in Figure 4, these engaging portions 57b are configured to partially contact the inner circumferential surface of the engaging holes 54b of the cycloidal disk 54 and transmit rotational force.

[0089] In this embodiment, these engaging portions 57b are constructed with ball bearings, similar to the internal teeth 55c. Specifically, as shown in Figure 7, each engaging portion 57b is composed of a second shaft member 571 and an inner ball bearing 572. The second shaft member 571 has a large-diameter second base portion 571a, a small-diameter second shaft portion 571b, and a press-fit ring 571c. The inner ball bearing 572 is fitted onto the second shaft portion 571b, and the press-fit ring 571c prevents the inner ball bearing 572 from coming off. The engaging portions 57b may also be constructed with pins.

[0090] By using ball bearings for the engaging portion 57b in addition to the internal teeth 55c, frictional resistance during partial contact with the engaging hole 54b can be significantly reduced. This is particularly effective for the high-speed rotating cycloidal speed increaser 50. It can improve power generation efficiency.

[0091] (Coreless Dynamo) Figure 8 shows the structure of the coreless dynamo 80. The coreless dynamo 80 consists of an input shaft 81, a housing 82, a coreless rotor 83, a stator 84, an electrical output assembly 85, and the like. A brushless motor with electronically controlled mechanical rectification can also be used in the coreless dynamo 80.

[0092] The housing 82 consists of a cylindrical member with one end sealed. The other open end of the housing 82 is sealed by a brush base 86. A bearing pipe 87, shorter than the housing 82, extends coaxially inside the housing 82, with one end attached to the sealed end (sealed end) of the housing 82. Oil-less metal 88 is installed at both ends of the bearing pipe 87, and the input shaft 81 is pivotally supported by the bearing pipe 87 via these oil-less metal 88.

[0093] One end of the input shaft 81 protrudes outward from the sealed end, to which the joint 7 is connected. The other end of the input shaft 81 is located inside the housing 82, protruding from the bearing pipe 87. This protruding portion is attached to the center of the disc-shaped rotor hub 81a. A coreless rotor 83, formed in a cylindrical shape from electric wires, is attached to the periphery of the rotor hub 81a and is supported so as to be rotatable around the rotation axis J2.

[0094] In this embodiment, the coreless rotor 83 has multiple coils woven together in a predetermined pattern. As a result, the coreless rotor 83 includes multiple coils with different phases.

[0095] A cylindrical stator 84 is coaxially mounted around the bearing pipe 87. As a result, the stator 84 is non-rotatably supported inside the coreless rotor 83 via an air gap. In this embodiment, the stator 84 is composed solely of magnets.

[0096] An electrical output assembly 85 is installed between the rotor hub 81a and the brush base 86. The electrical output assembly 85 includes a commutator 85a and a pair of brushes 85b, 85b, and is configured to be electrically connectable to multiple coils of the coreless rotor 83.

[0097] The commutator 85a has arc-shaped commutator segments that are divided in the circumferential direction. The tip of each brush 85b is in elastic contact with the commutator 85a, and each brush 85b is configured to be electrically connectable to a predetermined coil.

[0098] The base end of each brush 85b is connected to an output terminal provided on the brush base 86. Each output terminal is connected to positive and negative wires 85e that are drawn out to the outside of the brush base 86. These wires 85e are connected to a load such as a headlight. As a result, rotational force is transmitted to the input shaft 81, and when the coreless rotor 83 rotates, power is generated in the coil. This power is output through the electrical output assembly 85 and the two wires 85e.

[0099] The rotation of the input shaft 81 is accelerated by the cycloidal speed increaser 50, thus increasing power generation. Because it is a coreless rotor 83, cogging torque is not generated. Therefore, smooth high rotation can be achieved. It is lightweight and has excellent responsiveness. Therefore, the bicycle can be ridden comfortably even at night.

[0100] Furthermore, by arranging multiple power generation and transmission components around the base axis, it is possible to increase power generation without changing the size of the hub body, or to reduce the size of individual power generation and transmission components to achieve a constant power generation while making the hub body smaller.

[0101] Motor constant calculations have confirmed that even with just one coreless dynamo 80 and cycloidal speed increaser 50, the same amount of power generation as a conventional hub dynamo 1 (for example, about 3W at 6V) can be obtained. Therefore, when three of these are provided, as in the dynamo unit 6 of this embodiment, the amount of power generation can be increased to about three times that amount.

[0102] Furthermore, the disclosed technology is not limited to the embodiments described above, but also encompasses various other configurations.

[0103] In other words, the disclosed technology is suitable for bicycle hub dynamos, as described above, but can also be applied to other applications. For example, it can be applied to wind power generation, hydroelectric power generation, and portable small generators used in disaster relief and camping.

[0104] The structure of the hub dynamo 1 is just one example. The structure of the hub 1, which forms its base, can be modified according to the specifications. The structure of the cycloidal speed increaser 50 is also just one example. For example, the gear ratio can be modified as appropriate according to the specifications.

[0105] The rotational force transmission mechanism 20 described above is one example. For example, frictional resistance may be used instead of gear meshing. Specifically, as shown in Figure 9, a ring-shaped ring member 25 is assembled to the inner circumference of the cylinder portion 31. On the other hand, a cylindrical pressing member 26 is attached to the input shaft 66 of the cycloidal speed increaser 50. The ring member 25 and pressing member 26 in the illustrated example are made of metal.

[0106] Furthermore, the contact portion of at least one of the ring member 25 and the pressing member 26 is made of a material with excellent elasticity and frictional resistance, such as rubber (corresponding to an elastic body). In the illustrated example, a rubber tube 26a is attached to the outer circumference of the pressing member 26. Thus, the pressing member 26 is configured to press against the ring member 25.

[0107] The rotational force transmission mechanism 20 may also be composed of belts, magnetic gears, or other components.

[0108] 1 Hub (hub dynamo) 2 Hub shaft 3 Hub body 4 Hub pipe 5 Hub bearing 6 Dynamo unit (small generator) 7 Joint 20 Rotational force transmission mechanism 21 Internal gear 22 Pinion 31 Cylinder section 32 Disc section 32a Flange section 32b Spoke hole 32c Hub boss section 50 Cycloid speed increaser (speed change component) 51 Support base 52 Second rotating body 52a Coaxial boss section 52b Eccentric boss section 52c Connecting hole 52d Balance adjustment hole 53 Second spacer ring 54 Cycloid disc 54a Engaging teeth 54b Engaging hole 55 Fixing ring 55c Internal teeth 56 First spacer ring 57 First rotating body 57b Engaging section 58 Cover 60 Output side ball bearing 61 Intermediate ball bearing 62 Screw 63 Thrust bearing 64 Thrust bearing 65 Input side ball bearing 66 Input shaft 80 Coreless dynamo (coreless motor, power generation component) 81 Input shaft 82 Housing 83 Coreless rotor 84 Stator 85 Electrical output assembly 85a Commutator 85b Brush 85e Wire 86 Brush base 87 Bearing pipe 88 Oil-less metal 100 Wheel 104 Fork 551 Shaft member 552 Outer ball bearing 571 Second shaft member 572 Inner ball bearing J1 Base axis J2 Rotation axis J3 Eccentric axis

Claims

1. A small generator that converts rotational force rotating around a base axis into electricity, comprising: a power generation member arranged around the base axis and generating electricity by rotating around a rotation axis eccentric to the base axis; and a speed change member arranged around the base axis in a state where it is coaxially connected to the power generation member, wherein the speed change member increases the rotational speed of the rotational force and transmits it to the power generation member.

2. A small generator according to claim 1, wherein a coreless motor is used as the power generation member.

3. A small generator according to claim 2, wherein the power generation member comprises: a coreless rotor that is rotatably supported about the axis of rotation and includes a plurality of cylindrically formed coils; a stator that is non-rotatably supported inside the coreless rotor via an air gap and includes magnets that are arranged on the surface opposite to the coreless rotor and constitute a plurality of magnetic poles; and an electrical output assembly configured to be electrically connectable to the plurality of coils, wherein the coreless rotor rotates with the increased rotational force transmitted from the speed-shifting member, and the power generated in the coils as a result is output through the electrical output assembly.

4. A small generator according to claim 1, wherein a cycloidal type transmission is used in the speed change member.

5. In the small generator according to claim 4, the speed change member comprises: a first rotating body that rotates about the axis of rotation by the rotational force; a second rotating body that is coaxially connected to the input shaft of the power generation member and rotates about the axis of rotation; a cycloidal disc disposed between the first rotating body and the second rotating body; and a fixed ring disposed on the outer circumference of the cycloidal disc in a non-rotatable state, wherein the second rotating body has an eccentric boss portion that rotatably supports the cycloidal disc about an eccentric axis that is eccentric with respect to the axis of rotation; the cycloidal disc has a plurality of engaging teeth formed at equal intervals along its outer edge; and a plurality of engaging holes that open on its surface and are formed at equal intervals along a circumference centered on the eccentric axis; the first rotating body has a plurality of engaging portions formed at equal intervals along a circumference centered on the axis of rotation and partially in contact with the inner surfaces of the plurality of engaging holes; and the fixed ring has a plurality of internal teeth that partially mesh with the plurality of engaging teeth. A small generator in which the internal teeth are formed by bearings.

6. A small generator according to claim 4, wherein the speed change member has a thrust bearing.

7. A small generator according to claim 1, wherein a plurality of the power generation member and the speed change member are arranged around the base axis.

8. A hub dynamo that is mounted on a bicycle wheel and generates electricity using the small generator described in any one of claims 1 to 7, comprising: a hub shaft supported by the fork of the bicycle and centered on the base axis; and a hub body rotatably supported on the hub shaft and connected to a rim via a plurality of spokes, wherein the hub body comprises: a hollow cylinder portion extending from the hub shaft and housing the small generator; and a pair of disc portions having flanges on their outer periphery to which the spokes are attached, and integrated at both ends of the cylinder portion, wherein a rotational force transmission mechanism is provided inside the cylinder portion, and the rotational force of the hub body is transmitted to the gear shifting member through the rotational force transmission mechanism.

9. A hub dynamo according to claim 8, wherein the rotational force transmission mechanism includes an internal gear assembled to the inner circumference of the cylinder portion and a pinion assembled to the input shaft of the gear shifting member and meshing with the internal gear.

10. A hub dynamo according to claim 8, wherein the rotational force transmission mechanism includes a ring member assembled to the inner circumference of the cylinder portion and a pressing member assembled to the input shaft of the gear shifting member and pressing against the ring member, and at least one of the pressing portions of the ring member and the pressing member is made of an elastic material.

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