Power generation device

Abstract

A power generation device (7) comprises: a crankshaft (3); a shaft (11) that is connected to the crankshaft (3) via transmission members (8, 9); a cylindrical frame (1b) that surrounds the shaft (11); a rotor (12) that is fixed to the shaft (11); a stator (13) that surrounds the rotor (12); and a circuit board (26) that is electrically connected to the stator (13). A conductor (33) is fixed to the inner peripheral surface of the frame (1b), and the circuit board (26) and the conductor (33) are electrically connected.

Description

power generation equipment

[0001] The present invention relates to a power generation device.

[0002] For example, Patent Document 1 discloses a drive system that is incorporated into the frame of an electrically assisted bicycle. This drive system is disposed within the bicycle frame and assists the driving force of the bicycle.

[0003] Patent No. 7121095

[0004] In such bicycles, the battery that supplies current to the motor of the drive system is located inside the frame, and the limited space inside the frame makes it difficult to establish an electrical connection between the motor and the battery.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a power generating device that can easily establish electrical connections within a frame.

[0006] A power generating device according to one aspect of the present invention comprises a crankshaft, a shaft connected to the crankshaft via a transmission member, a cylindrical frame surrounding the shaft, a rotor fixed to the shaft, a stator surrounding the rotor, and a circuit board electrically connected to the stator, wherein a conductor is fixed to the inner surface of the frame, and the circuit board and the conductor are electrically connected.

[0007] FIG. 1 is a perspective view schematically showing the appearance of a portion of a bicycle frame 1 incorporating a power generating device according to one embodiment of the present invention. FIG. 1 is a cross-sectional view taken along line 2-2 of FIG. 1. FIG. 2 is a cross-sectional view taken along line 3-3 of FIG. 2. FIG. 3 is a partially enlarged cross-sectional view corresponding to FIG. 3 and schematically showing the structure of a power generating device 7 according to one embodiment of the present invention. FIG. 4 is a perspective cross-sectional view taken along line 5-5 of FIG. 4. FIG. 4 is a cross-sectional view corresponding to FIG. 3 and schematically showing the structure of a power generating device 7 according to another specific example.

[0008] An embodiment of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a perspective view schematically illustrating the exterior of a portion of a bicycle frame 1 incorporating a power generating device according to an embodiment of the present invention. Fig. 1 illustrates some of the components that make up the bicycle frame 1, namely, a portion of a down tube 1a, a portion of a seat tube 1b, a portion of two chainstays 1c, and a bottom bracket shell 1d to which the three components, the down tube 1a, the seat tube 1b, and one end of each of the chainstays 1c, 1c, are connected. In this example, the inner circumferential surfaces of the seat tube 1b and the down tube 1a are cylindrical. The frame 1 is formed from a lightweight resin material, such as carbon fiber resin.

[0009] The frame 1 also has a head tube connected to the other end of the down tube 1a, a top tube connected to the head tube and seat tube 1b, and seat stays connected to the seat tube 1b and chain stays 1c (none of which are shown). A seat is attached to the upper end of the seat tube 1b. Handlebars are attached to the upper end of the head tube. A fork is attached to the lower end of the head tube, and a front wheel is rotatably supported by the fork. A rear wheel is rotatably supported by the rear ends of the chain stays 1c and the seat stays.

[0010] The bottom bracket shell 1d is formed, for example, in a generally cylindrical shape with the axis x1 as its central axis. To this bottom bracket shell 1d, cylindrical bottom brackets 2, 2, for example, also having the axis x1 as their central axis, are attached. In this example, the bottom brackets 2, 2 are composed of two parts. One bottom bracket 2 is disposed at one end of the bottom bracket shell 1d, and the other bottom bracket 2 is disposed at the other end of the bottom bracket shell 1d. A crankshaft 3 is supported by the bottom brackets 2, 2 so as to be rotatable about the axis x1. The crankshaft 3 is formed, for example, in a cylindrical shape with the axis x1 as its central axis.

[0011] A right crank arm 4 is attached to one end of the crankshaft 3 in the direction along the axis x1 (hereinafter referred to as the "axial direction"). A left crank arm 5 is attached to the other axial end of the crankshaft 3. The right crank arm 4 extends in a direction perpendicular to the axis x1. On the other hand, the left crank arm 5 extends in a direction perpendicular to the axis x1, in the opposite direction to the right crank arm 4. Pedals (not shown) are attached to the ends of the right crank arm 4 and the left crank arm 5, respectively. When a bicycle user steps on the pedals, the right crank arm 4 and the left crank arm 5 swing about the axis x1, causing the crankshaft 3 to rotate.

[0012] This bicycle employs, for example, a chainless drive system. Specifically, a drive motor (not shown) is attached to, for example, the rear wheel. When a user rotates the crankshaft 3 around axis x1 via the pedals, electricity is generated by a generator, described below. This electricity is transmitted to the drive motor. The driving force generated by the rotation of the drive motor is transmitted to the rear wheel. This configuration differs from mechanical systems in which driving force is mechanically transmitted to the rear wheel through a chain ring by rotating the crankshaft via the pedals. In other words, there is no need to attach a chain ring to the crankshaft 3, and no mechanical driving force transmission member such as a chain or belt is required.

[0013] FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1. FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2. The cross-section in FIG. 2 is a vertical cross-sectional view including the axis x1. The cross-section in FIG. 3 is a vertical cross-sectional view taken along an imaginary plane perpendicular to the axis x1. FIGS. 2 and 3 are cross-sectional views schematically illustrating the structure of a power generation device 7 according to one embodiment of the present invention. Referring to FIGS. 2 and 3 together, in this example, bottom brackets 2, 2 composed of two parts are fitted into respective openings 1e, 1e of a bottom bracket shell 1d. A portion of the bottom bracket 2 protrudes axially outward from the bottom bracket shell 1d. A bearing 6 is disposed between the inner peripheral surface of each bottom bracket 2 and the outer peripheral surface of the crankshaft 3. The bearing 6 is, for example, a ball bearing. The bottom brackets 2, 2 support the crankshaft 3 via the bearings 6, 6 so that the crankshaft 3 can rotate about the axis x1.

[0014] The bicycle has a generator 7 for generating electrical energy for a drive motor attached to the rear wheel. The generator 7 has a frame 1, a crankshaft 3, and a motor 10. In this example, the frame 1 is the seat tube 1b. The motor 10 is disposed adjacent to the crankshaft 3 within the seat tube 1b, which has a cylindrical inner circumferential surface with an axis x2 as its central axis. In this example, the axis x2 is perpendicular to the axis x1. The motor 10 has, for example, a cylindrical shaft 11 that is rotatable about the axis x2. The shaft 11 is surrounded by the seat tube 1b. The shaft 11 extends in a direction perpendicular to the crankshaft 3.

[0015] A first gear (transmission member) 8 is attached to the lower end of the shaft 11. This first gear 8 meshes with a second gear (transmission member) 9 that is attached to the outer peripheral surface of the crankshaft 3 between the two bottom brackets 2, 2 in the axial direction. In this example, the first gear 8 and the second gear 9 are, for example, bevel gears. The shaft angle between the first gear 8 and the second gear 9 is 90°. Furthermore, the first gear 8 is a small gear, and the second gear 9 is a large gear. As the first gear 8 and the second gear 9 mesh in this way, the rotation of the crankshaft 3 about the axis x1 is transmitted to the shaft 11, and the shaft 11 rotates about the axis x2.

[0016] FIG. 4 corresponds to FIG. 3 and is a partially enlarged cross-sectional view schematically illustrating the structure of a power generating device 7 according to one embodiment of the present invention. Referring to FIGS. 2 to 4 together, the motor 10 includes a rotor 12 fixed to a shaft 11 and a stator 13 surrounding the rotor 12. The rotor 12 can rotate relative to the stator 13 about an axis x2. The rotor 12 includes a magnet 14 fixed to the outer peripheral surface of the shaft 11. The magnet 14 is, for example, a permanent magnet. The magnet 14 is, for example, formed in a cylindrical shape with the axis x2 as its central axis. The magnet 14, i.e., the rotor 12, rotates together with the shaft 11 about the axis x2. In other words, the motor 10 is a so-called inner rotor type motor.

[0017] On the other hand, the stator 13 includes a coil 15, a yoke (i.e., a stator core 16), and a housing 17. The stator core 16 is formed from a laminated body in which multiple annular silicon steel plates (or electromagnetic steel plates) are stacked in a direction along the axis x2 (hereinafter referred to as the "rotational axis direction"). The stator core 16 surrounds the shaft 11. Conductive wires forming the coils 15 are wound around multiple spokes of the stator core 16 that extend radially, perpendicular to the axis x2. Note that an insulator (not shown) having electrical insulation properties is disposed between the coils 15 and the spokes of the stator core 16. The inner peripheral surface of the stator core 16 faces the outer peripheral surface of the magnet 14 of the rotor 12 with a predetermined magnetic gap therebetween.

[0018] The stator core 16 has its outer peripheral surface attached to the inner peripheral surface of the housing 17. The housing 17 has a cylindrical main body 18 and a cover (first plate) 19 covering one end (upper end) of the main body 18. The cover 19 is formed, for example, in a flat disk shape. The main body 18 has a cylindrical wall 20 around the axis x2 and a plate (second plate) 21 extending radially from the other end (lower end) of the wall 20 in the rotational axis direction in a direction perpendicular to the axis x2. The plate 21 is formed, for example, in a flat disk shape. The main body 18 and the cover 19 are integrally formed, for example, from a thermally conductive metal material or resin material. The outer peripheral surface of the stator core 16 described above is attached to the inner peripheral surface of the wall 20. For example, an adhesive is used for attachment.

[0019] The cover 19 covers the upper end of the wall 20 in the rotation axis direction. That is, the cover 19 is attached to the wall 20 so as to close an opening at the upper end of the wall 20, for example. That is, the cover 19 is a plate extending radially from the upper end of the wall 20. The cover 19 closes the upper end of the main body 18, thereby forming an accommodation space for the housing 17. The rotor 12 is accommodated in the accommodation space between the cover 19 and the plate 21. Meanwhile, the wall 20 covers the outer periphery of the stator core 16. The cover 19 is made of, for example, a thermally conductive metal material or resin material. At least a portion of the outer periphery of each of the cover 19, the wall 20, and the plate 21 contacts the inner periphery of the seat tube 1b.

[0020] Radially extending holes 19a and holes 21a are formed in the outer peripheral surfaces of the cover 19 and the plate 21, respectively. The holes 19a and 21a are, for example, blind holes. In this example, the holes 19a and 21a are positioned at the same positions around the axis x2 in a plan view in the rotation axis direction. Meanwhile, holes 22a and 22b are formed in the seat tube 1b at positions corresponding to the holes 19a and 21a, respectively. The holes 22a and 22b are through holes. Fixing members 23 are fixed to the holes 19a and 21a through the holes 22a and 22b in the seat tube 1b, respectively. The fixing members 23 are, for example, fastening members such as bolts. The housing 17 is fixed to the inner peripheral surface of the seat tube 1b by the fixing members 23. In this example, the holes 22a and 22b are positioned on the outer peripheral surface of the rear side of the seat tube 1b.

[0021] The shaft 11 is supported by two bearings 24, 25 to be rotatable about the axis x2. The bearings 24, 25 are, for example, ball bearings. The upper bearing 24 in the direction of the rotation axis is mounted, for example, in a recess 19b formed in the underside of the cover 19. Meanwhile, the lower bearing 25 in the direction of the rotation axis is mounted, for example, in a hole 21b formed in a plate 21 of the main body 18. The hole 21b penetrates the plate 21 in the direction of the rotation axis. Thus, the shaft 11 protrudes a predetermined length downward from the motor 10. A printed circuit board (circuit board or control board) 26 is disposed between the cover 19 and the rotor 12 and stator 13. The printed circuit board 26 is, for example, formed in a flat ring shape and surrounds the outer periphery of the shaft 11. The printed circuit board 26 is electrically connected to the conductors of the coil 15 of the stator 13.

[0022] FIG. 5 is a perspective cross-sectional view taken along line 5-5 in FIG. 4. FIG. 6 is a partial cross-sectional view taken along line 6-6 in FIG. 4. The cover 19 is not shown in FIG. 5. Referring to FIGS. 4 to 6, the printed circuit board 26 includes an annular board body 27, one or more electronic components 28 mounted on the opposing upper and lower surfaces of the board body 27, and a pair of input / output terminals 29, 29 mounted on the board body 27. The board body 27 includes a conductive pattern (not shown) made of a conductive metal material such as copper, formed on a base material made of, for example, a resin material. The electronic components 28 include, for example, a rotation sensor for detecting the rotation speed of the shaft 11 and a rectifying element. The coil 15 is electrically connected to the printed circuit board 26.

[0023] As shown in FIG. 6 , terminal pads 30, 30 electrically connected to the conductive pattern formed on the substrate body 27 are exposed on the substrate body 27. Terminals 29, 29 are electrically connected to the terminal pads 30, 30, respectively. In this example, the terminals 29, 29 extend radially parallel to each other toward the shaft 11. The terminals 29, 29 also protrude radially from a recess 20a formed in the main body 18, i.e., the wall 20, of the housing 17. In this example, each terminal 29 is formed, for example, in a generally cylindrical shape with a central axis in the radial direction. As is clear from FIG. 5 , the fixing member 23 and the terminals 29, 29 face each other radially across the axis x2.

[0024] A wiring 31 is electrically connected to the terminals 29, 29. The wiring 31 is fixed in a groove 32 recessed from the inner circumferential surface of the seat tube 1b toward the outer circumferential surface. In this example, the groove 32 extends in the longitudinal direction of the seat tube 1b parallel to the axis x2. The wiring 31 includes conductors 33, 33 electrically connected to the terminals 29, 29, respectively, and an insulating layer 34 covering the conductors 33, 33. In this example, the conductors 33, 33 extend parallel to each other. The terminals 29, 29 are biased radially toward the outer circumferential surface by a biasing member (not shown), such as a leaf spring. Thus, the outer circumferential ends of the terminals 29, 29 are constantly pressed against the conductors 33, 33. In this way, the terminals 29, 29 are electrically connected to the conductors 33, 33.

[0025] Each conductor 33 is exposed from the insulating layer 34 in the connection area with the terminals 29, 29. Outside these connection areas, the conductors 33 are embedded in the insulating layer 34. The terminals 29 and conductors 33 are formed from a conductive metal material, such as copper. The insulating layer 34 is formed from an insulating resin material, for example. In this example, the insulating layer 34 has a cross-sectional shape that matches the cross-sectional shape of the groove 32 along an imaginary plane perpendicular to the axis x2. That is, the inner circumferential surface of the insulating layer 34 is continuous with the inner circumferential surface of the seat tube 1b. Such wiring 31 may be formed from, for example, a flexible printed circuit board. As is clear from FIG. 5 , the hole 22a of the seat tube 1b and the conductors 33 face each other in the radial direction across the axis x2.

[0026] When such a power generating device 7 is incorporated into a bicycle, the conductors 33, 33 of the wiring 31 pass through the frame 1 and are electrically connected to a drive motor incorporated into, for example, the rear wheel. When the crankshaft 3 rotates as a result of pedaling, the rotation of the crankshaft 3 about the axis x1 is converted, for example, at an increased speed, into rotation of the shaft 11 about the axis x2 via the bevel gears 9 and 8. As a result, magnetic interaction between the magnet 14 and the coil 15 generates electrical energy in the coil 15. The generated electrical energy is sent to the drive motor through the wiring 31 via the printed circuit board 26. The rotation of the drive motor imparts driving force to the rear wheel. In this way, the bicycle is driven.

[0027] In the generator 7 described above, the motor 10 is incorporated into the frame 1, for example, in the seat tube 1b. The shaft 11 of the motor 10 is connected to the crankshaft 3 via the bevel gears 9 and 8. This allows the size of the bottom bracket shell 1d of the frame 1 to be maintained the same as before. Furthermore, for electrical connection between the motor 10 and the drive motor, wiring 31 is fixed in a groove 32 formed on the inner circumferential surface of the frame 1. By locating the motor 10 within the seat tube 1b, electrical connection can be easily established within the seat tube 1b. Furthermore, since there is no need to route wiring on the outer circumferential surface of the frame 1, the aesthetic appearance of the bicycle can be improved. If the wiring 31 is formed from, for example, a flexible printed circuit, the weight of the wiring 31 itself can also be reduced.

[0028] Furthermore, the housing 17 of the motor 10 is in contact with the frame 1, i.e., the inner circumferential surface of the seat tube 1b. Even if the coil 15 generates heat during the generation of electrical energy, the heat can be efficiently released into the atmosphere through the stator core 16, housing 17, and seat tube 1b. This prevents excessive heat generation in the motor 10. As a result, the performance of the motor 10 can be improved. Note that a highly thermally conductive grease or the like may be placed between the outer circumferential surfaces of the cover 19, wall 20, and plate 21 of the housing 17 and the inner circumferential surface of the seat tube 1b.

[0029] When assembling the power generating device 7, the frame 1 is first manufactured. For example, a carbon fiber resin prepreg is attached to a core material made of a resin or metal material. Pressure and heat are then applied to the prepreg to harden it. The core material either remains as is or melts away. When manufacturing this frame 1, the above-mentioned wiring 31 is formed integrally with the frame 1 in advance. The wiring 31 may be fixed in a groove formed in the core material, or the wiring 31 may be placed on the core material in advance when the prepreg is attached. Note that the wiring 31 may be placed not only on the above-mentioned seat tube 1b, but also on the inner circumferential surface of the down tube 1a or the inner circumferential surface of the chainstay 1c.

[0030] Next, the bottom brackets 2 and crank axle 3 are attached to the bottom bracket shell 1d. The motor 10 is placed inside the seat tube 1b. Specifically, the motor 10 is inserted through an opening formed at the top end of the seat tube 1b. At this time, the terminals 29 of the motor 10 are maintained pressed inward against the biasing force of the biasing member. The holes 22a and 22b in the seat tube 1b are aligned with the holes 19a and 21a in the cover 19 and plate 21 of the motor 10. The holes 22a and 22b, the terminals 29, and the conductors 33 are radially opposed across the axis x2. Therefore, the holes 22a and 22b are aligned with the holes 19a and 21a, and the terminals 29 are electrically connected to the conductors 33. This facilitates electrical connection between the motor 10 and the conductors 33 inside the seat tube 1b.

[0031] In the power generating device 7, two motors 10 may be disposed within the frame 1, for example, along the axis x2. Alternatively, one motor 10 may be disposed within the seat tube 1b, while another motor 10 may be disposed within the down tube 1a. When multiple motors 10 are disposed within the frame 1 in this manner, an electromagnetic clutch or the like may be incorporated into the power generating device 7. By using the electromagnetic clutch to switch the motor 10 that outputs electric energy, the amount of electric energy supplied to the drive motor can be changed. This may achieve a change in driving force, similar to a gear shift. Alternatively, the motor 10 may be disposed within the frame 1 through a hinged lid (not shown) formed on the seat tube 1b or the down tube 1a, for example, that can be opened and closed.

[0032] Furthermore, instead of the bevel gears 8 and 9, other means such as a worm gear or a magnetic coupling may be used as the transmission member connecting the crankshaft 3 and the shaft 11 of the motor 10. As shown in FIG. 7 , the wiring 31 may be electrically connected to a battery 40 installed adjacent to the motor 10 inside the seat tube 1b. The electrical energy generated by the power generator 7 may be used to charge the battery 40. The battery 40 may supply power to a drive motor that drives the rear wheel, or to other electronic components mounted on the bicycle. Furthermore, the hole 22a in the seat tube 1b and the conductor 33 do not necessarily have to be radially opposed across the axis x2. For example, the hole 22a and the conductor 33 may be spaced apart by 45 degrees, 90 degrees, or another angle around the axis x2.

[0033] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the scope of the present invention. Furthermore, the above-described embodiments do not limit the scope of the present invention, and the present invention may include any and all applications. The components of the above-described embodiments, as well as their arrangement, materials, conditions, shape, size, etc., are not limited to those illustrated and may be modified as appropriate. For example, the present invention includes differences that arise during implementation due to manufacturing tolerances, etc. Furthermore, components illustrated in different embodiments may be partially substituted or combined within the scope of technical inconsistency. Furthermore, the various configurations may be selectively combined as appropriate to achieve at least some of the above-described problems and effects.

[0034] 1 Frame, 1a Down tube, 1b Seat tube, 1c Chain stay, 1d Bottom bracket shell, 1e Opening, 2 Bottom bracket, 3 Crankshaft, 4 Right crank arm, 5 Left crank arm, 6 Bearing, 7 Generator, 8, 9 Bevel gear (transmission member), 10 Motor, 11 Shaft, 12 Rotor, 13 Stator, 14 Magnet, 15 Coil, 16 Stator core, 17 Housing, 18 Main body, 19 Cover (first plate), 19a Hole, 19b Recess, 20 Wall, 20a Recess, 21 Plate (second plate), 21a Hole, 22a Hole, 22b Hole, 23 Fixing member, 24 Bearing, 25 Bearing, 26 Printed circuit board (circuit board), 27 Board main body, 28 Electronic component, 29 Terminal, 30 Terminal pad, 31 Wiring, 32 Groove, 33 conductor, 34 insulating layer, 40 battery, x1 axis, x2 axis

Claims

1. A power generating device comprising: a crankshaft; a shaft connected to the crankshaft via a transmission member; a cylindrical frame surrounding the shaft; a rotor fixed to the shaft; a stator surrounding the rotor; and a circuit board electrically connected to the stator, wherein a conductor is fixed to the inner peripheral surface of the frame, and the circuit board and the conductor are electrically connected.

2. The power generating device according to claim 1, wherein the circuit board has a terminal extending in the direction of the shaft, and the terminal and the conductor are electrically connected.

3. The power generating device according to claim 1 or 2, wherein the conductor is covered with an insulating layer, and the insulating layer is fixed to the inner peripheral surface of the frame.

4. A power generating device according to any one of claims 1 to 3, wherein a groove extending in the direction of the rotation axis of the shaft is formed in the frame, and the conductor is fixed to the groove.

5. A power generating device according to any one of claims 1 to 4, wherein the stator comprises a housing that covers the outer periphery of the stator, and the housing is in contact with the frame.

6. The power generating device described in claim 5, wherein the housing comprises: a cylindrical wall covering the stator; a first plate extending radially from one end of the cylindrical wall in the direction of the rotational axis of the shaft; and a second plate extending radially from the other end of the cylindrical wall in the direction of the rotational axis of the shaft, and the rotor is housed between the first plate and the second plate in the direction of the rotational axis.

7. A power generating device as described in claim 6, wherein the first plate and the second plate each have a hole extending in the radial direction, the frame has holes corresponding to the holes, fixing members are fixed to the holes in the first plate and the holes in the frame, and fixing members are fixed to the holes in the second plate and the holes in the frame.

8. The power generating device according to claim 7, wherein the hole in the frame and the conductor are opposed to each other in the radial direction.

9. The power generating device according to any one of claims 1 to 8, wherein the conductor is electrically connected to a battery.

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