Power assist drive unit for power-assisted bicycle

Abstract

To provide a power assist drive unit for power-assisted bicycle which is small-sized and provides a power-assisted bicycle with a power assist that offers a preferable speed reduction ratio.SOLUTION: A power assist drive unit for power-assisted bicycle in accordance with the present invention includes a motor 10, a planetary gear group 12, an annular support member 18, a left shaft 24, a right shaft 26, a first clutch 14, and a second clutch 16. The motor is incorporated in a bottom bracket of a bicycle and has a tubular core 22. The tubular core has a small-diameter step 23. The planetary gear group includes a small sun gear 36 disposed in the small-diameter step of the tubular core. The annular support member is connected to at least one sprocket. The left shaft is inserted into the tubular core and includes a left end 28 connected to a crank, a right end 30, and a small-diameter step 34 inserted into the small-diameter step of the tubular core.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to bicycles, and more particularly to an electric power assisted drive device for an electrically assisted bicycle. [Background technology]

[0002] A conventional power-assisted bicycle power drive unit includes a motor, a planetary gear set, two clutches, an annular support member, and a crankshaft set. The motor is disposed inside the bottom bracket of the bicycle. The motor has a tubular core. The planetary gear set has a sun gear mounted on the tubular core. The crankshaft set has a shaft and two cranks. The shaft is inserted into the tubular core but is not connected to each other, and the shaft is rotatable relative to the tubular core. A first clutch is disposed between the tubular core and the annular support member. A second clutch is disposed between the annular support member and the shaft. The annular support member is connected to at least one sprocket. The sprocket is connected to at least one flywheel via a chain. The flywheel is connected to one rear wheel of the bicycle.

[0003] A simple calculation method for calculating the reduction ratio of a planetary gear is to divide the number of teeth on one internal ring by the number of teeth on the sun gear and add a fixed coefficient of 1 to the result. The number of teeth on the internal ring is fixed, and the reduction ratio is determined by the number of teeth on the sun gear.

[0004] The above-mentioned shaft is inserted into a tubular core. A sun gear is mounted on the tubular core. The diameter of the shaft determines the two inner and outer diameters of the tubular core. The outer diameter of the tubular core determines the two inner and outer diameters of the sun gear (i.e., the number of teeth). The diameter of the shaft is fixed because it combines two cranks. Since the number of teeth on the sun gear is fixed, the reduction ratio is fixed. However, this was an undesirable structural design unless the internal tooth ring was enlarged. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a power-assisted drive device for a power-assisted bicycle that is compact and provides power assistance with a desirable reduction ratio to the power-assisted bicycle. [Means for solving the problem]

[0006] In view of the current situation, the present inventors have conducted extensive research and have completed the present invention by improving the problems of the prior art. That is, in order to solve the above-mentioned problems, according to a first aspect of the present invention, there is provided an electric power assisted drive device for an electrically assisted bicycle, comprising one motor (10), one planetary gear set (12), one annular support member (18), one left shaft (24), one right shaft (26), one first clutch (14), and one second clutch (16), wherein the motor (10) is provided in one bottom bracket of one bicycle and has one tubular core (22), the tubular core (22) having one small diameter step (23), the planetary gear set (12) having one small sun gear (36) provided in the small diameter step (23) of the tubular core (22), the annular support member (18) being connected to at least one sprocket, and the left shaft (24) having The power-assisted drive device for an electrically assisted bicycle is characterized in that the right shaft (26) has one left end (28) inserted through the tubular core (22) and connected to one crank, one right end (30), and one small-diameter step (34) inserted into the small-diameter step (23) of the tubular core (22), the right end (30) being smaller than the left end (28), the right shaft (26) has one right end (38) connected to the other crank and one left end (40) connected to the right end (30) of the left shaft (24), the left shaft (24) and the right shaft (26) rotate together, the first clutch (14) is disposed between the planetary gear group (12) and the annular support member (18), and the second clutch (16) is disposed between the right shaft (26) and the planetary gear group (12).

[0007] Preferably, the right end (30) of the left shaft (24) is cubic in shape, and the left end (40) of the right shaft (26) has a rectangular hole (42) that receives the rectangular right end (30) of the left shaft (24). [Effects of the Invention]

[0008] The power-assisted drive device for an electrically assisted bicycle according to the present invention is compact and can provide an electrically assisted bicycle with power assistance at a desirable reduction ratio. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a power-assisted driving device for an electrically assisted bicycle according to one embodiment of the present invention. [Figure 2] FIG. 2 is an exploded perspective view showing the power assist drive device of FIG. [Figure 3] FIG. 3 is a cross-sectional view showing the power assisted drive device of FIG. [Figure 4] FIG. 4 is a front view showing the state in which the clutch of the power assisted drive device is disengaged. [Figure 5] FIG. 5 is a front view showing the state in which the clutch of the power assisted drive device is engaged. [Figure 6] FIG. 6 is a front view showing another state of the power assisted drive device with the clutch disengaged. [Figure 7] FIG. 7 is a front view showing the state in which another clutch of the power assisted drive device is engaged. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or similar structures or units used in the drawings are designated by the same reference numerals. Of course, the above-described embodiment is only one embodiment of the present invention and does not represent all embodiments. Alternative embodiments may be obtained based on the above-described embodiment, or structures may be modified or altered as necessary, which are within the scope of protection of the present invention.

[0011] In the following description, terms indicating directions such as "upper", "lower", "left", "right", "front", "rear", "inner", "outer", and "side" simply indicate directions in the drawings. Terms indicating directions are used to make the present application easier to understand by providing a clearer explanation, and do not necessarily indicate or imply that a device or component is to be configured or operated in a specific direction, nor do they limit the technical content of the present application in any way.

[0012] Unless otherwise specified or clearly defined and limited, the terms "attached," "coupled," "connected," or "mounted on" described below should be understood in a broad sense, including, for example, fixed connection, detachable connection, integral connection, mechanical connection, direct connection, indirect connection, connection between two components, etc., and a person skilled in the art should understand the specific implications of the above terms in each embodiment or the present application based on their knowledge or experience.

[0013] Unless otherwise specified, the term "multiple" used below refers to two or more than two.

[0014] Referring to Figures 1 to 3, as shown in Figures 1 to 3, an electric power-assisted drive device for an electrically assisted bicycle according to one embodiment of the present invention has one motor 10, one planetary gear set 12, two clutches 14 and 16, one annular support member 18, and a crankshaft set. The motor 10 is mounted in one bottom bracket (not shown) of one bicycle. The motor 10 has one housing 20, one tubular core 22, one set of magnets (not shown), and one set of coils. The housing 20 houses the tubular core 22, the magnets, and the coils. The magnets are attached to the tubular core 22. The tubular core 22 has one small-diameter step 23.

[0015] The planetary gear set 12 has one sun gear 36 provided on the small diameter stepped portion 23 of the tubular core 22 .

[0016] The crankshaft group includes one left shaft 24 and one right shaft 26. The left shaft 24 passes through the tubular core 22, but the two shafts are not connected to each other. The left shaft 24 is rotatable relative to the tubular core 22. The clutch 14 is disposed between the tubular core 22 and the annular support member 18. The clutch 16 is disposed between the annular support member 18 and the right shaft 26. The annular support member 18 is connected to at least one sprocket (not shown). The sprocket is connected to at least one flywheel (not shown) via a chain (not shown). The flywheel is connected to one rear wheel (not shown) of the bicycle.

[0017] The left shaft 24 has a left end 28, a right end 30, a large diameter step 32, and a small diameter step 34. The large diameter step 32 is adjacent to the left end 28. The left end 28 and the right end 30 are cubic in shape. The left end 28 can be inserted into a rectangular hole (not shown) in the left crankshaft. The small diameter step 34 is located adjacent to the right end 30. The large diameter step 32 and the small diameter step 34 are adjacent to each other. The diameter of the large diameter step 32 is equal to the diameter of a typical crankshaft. The diameter of the small diameter step 34 is smaller than the diameter of a typical crankshaft.

[0018] The small diameter step 34 of the left shaft 24 is inserted into the small diameter step 23 of the tubular core 22. The small diameter step 34 of the left shaft 24 and the small diameter step 23 of the tubular core 22 allow the diameter of the sun gear 36 to be smaller than the diameter of the sun gear of a planetary gear set of a general power-assisted drive device. Therefore, the planetary gear set 12 can achieve a more preferable reduction ratio than the planetary gear set of a general power-assisted drive device.

[0019] The right shaft 26 has a right end 38 and a left end 40. The right end 38 is inserted into a square hole (not shown) in a right crank. The left end 40 of the right shaft 26 has a square hole 42 that receives the right end 30 of the left shaft 24. Therefore, the right shaft 26 does not rotate relative to the left shaft 24; the two only rotate together.

[0020] Please refer to Figures 2, 3, and 6. As shown in Figures 2, 3, and 6, the clutch 14 is composed of one frame 44 of the planetary gear set 12, a plurality of steel balls 46, a plurality of springs 48, and one ring 50. The frame 44 has one central hole 52, a plurality of grooves 54, and a plurality of peripheral holes 56. The central hole 52 communicates with each of the grooves 54. Each groove 54 communicates with an adjacent peripheral hole 56. Each groove 54 extends from the central hole 52 to the corresponding peripheral hole 56. The central hole 52 accommodates the ring 50. Each groove 54 accommodates one steel ball 46. Each peripheral hole 56 accommodates a single spring 48.

[0021] The right side of ring 50 has a non-circular portion 58. The left side of annular support member 18 has a non-circular hole 60 that accommodates non-circular portion 58. Therefore, ring 50 does not rotate relative to annular support member 18; the two only rotate together. In other embodiments, ring 50 and annular support member 18 can be molded as a single piece.

[0022] Please refer to Figures 2 and 4. As shown in Figures 2 and 4, the clutch 16 is composed of a plurality of teeth 62 and a plurality of pawls 64. The plurality of teeth 62 are formed on the inside of the annular support member 18. The plurality of pawls 64 are pivotally attached to the right shaft 26, and the plurality of pawls 64 expand outward from the right shaft 26 by elastic force. Each pawl 64 can abut against one of the teeth 62.

[0023] When not in operation, clutches 14 and 16 are in a disengaged state (see Figures 4 and 6).

[0024] When using only human power, clutch 16 is in the engaged state (see FIG. 5) and clutch 14 is in the disengaged state.

[0025] When using electrical power only, clutch 14 is in the engaged state (see FIG. 7) and clutch 16 is in the disengaged state (see FIG. 4).

[0026] When using human and electrical power, clutch 16 is in the engaged state (see FIG. 5) and clutch 14 is in the engaged state (see FIG. 7).

[0027] The clutches 14, 16 are conventional and will not be described in detail here.

[0028] The preferred embodiments of the present invention have been disclosed above so that those skilled in the art can understand, but they are not intended to limit the present invention in any way. Various changes and modifications can be made within the scope of the present invention. Therefore, the scope of the claims of the present invention should be interpreted broadly to include such changes and modifications. [Explanation of symbols]

[0029] 10 Motor 12 Planetary gear group 14 Clutch 16 Clutch 18 Annular support member 20. Housing 22 Tubular Core 23 Small diameter stepped section 24 left axis 26 Right axis 28 leftmost 30 right end 32 Large diameter step 34 Small diameter stepped section 36 Sun Gear 38 right end 40 leftmost 42 square hole 44 Frame 46 steel ball 48 Spring 50 rings 52 Center hole 54 Groove 56 Peripheral foramen 58 Non-circular part 60 Non-circular holes 62 teeth 64 Nails

Claims

1. A power-assisted drive device for an electrically assisted bicycle, comprising one motor (10), one planetary gear set (12), one annular support member (18), one left shaft (24), one right shaft (26), one first clutch (14), and one second clutch (16), The motor (10) is provided in one bottom bracket of one bicycle and has one tubular core (22), the tubular core (22) having one small diameter step (23); The planetary gear group (12) has one small sun gear (36) provided on the small diameter step portion (23) of the tubular core (22), The annular support member (18) is connected to at least one sprocket; The left shaft (24) is inserted through the tubular core (22) and has one left end (28) connected to one crank, one right end (30), and one small diameter step (34) inserted through the small diameter step (23) of the tubular core (22), the right end (30) being smaller than the left end (28); The right shaft (26) has one right end (38) connected to the other crank and one left end (40) connected to the right end (30) of the left shaft (24), causing the left shaft (24) and the right shaft (26) to rotate together; The first clutch (14) is disposed between the planetary gear set (12) and the annular support member (18); The power-assisted drive device for an electrically assisted bicycle is characterized in that the second clutch (16) is disposed between the right shaft (26) and the planetary gear set (12).

2. the right end (30) of the left shaft (24) is cubic in shape; 2. The power-assisted drive device for an electrically assisted bicycle according to claim 1, wherein the left end (40) of the right shaft (26) has a square hole (42) that accommodates the square-shaped right end (30) of the left shaft (24).

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