TWI808807B - Crank device of bicycle - Google Patents

Abstract

A crank device of bicycle, which is mounted on a frame of a bicycle, includes a sun gear, a plurality of planetary gears, a crank assembly and a passive element. The sun gear has a predetermined number of sun teeth. The planetary gears move around the sun gear. each of the planetary gear has a first gear and a second gear, and the first gear rotates synchronously with the second gear. The first gear has a predetermined number of first teeth. The second gear has a predetermined number of second teeth. The first gears of the planetary gears engage the sun gear. The crank assembly is connected with the planetary gears, and can rotate by an external force. The passive element has a predetermined number of passive teeth. The passive element engages the second gears, so that when the crank assembly rotates, the planetary gears and the sun gear can drive the passive element to rotate.

Description

Bicycle crank gear

The present invention relates to bicycles, and more particularly to a bicycle crank mechanism that can vary transmission efficiency and optimize chain/belt tension.

Press, the general method of bicycle speed adjustment is usually by adjusting the size of the front and rear chainrings to match different gear ratios, and then produce different transmission ratios. The so-called gear ratio is the ratio of the number of teeth on the front chainring to the number of teeth on the rear chainring. For example, the number of teeth of the front chainring is 44, and the number of teeth of the rear chainring is 22, so the gear ratio is 44/22=2. A gear ratio of 2 means that the front chainring rotates 1 revolution, which will drive the rear chainring to rotate 2 revolutions. Since the front chainring is driven by the crank, the rear chainring will drive the rear wheels to rotate. Generally, the gear ratio is equal to the transmission ratio without a transmission. Therefore, in the above example, it can be known that the crank rotates 1 revolution, that is, it drives the rear wheel to rotate 2 revolutions.

The disadvantage of the conventional crank device is that a high gear ratio is required in order to pursue a high transmission ratio. However, a high gear ratio is accompanied by a large gap between the two chainrings, which easily deforms the chain/belt due to excessive tension. If you step hard while maintaining a high gear ratio, both the chain/belt and the front and rear chainrings will form serious deformation and wear over a long period of time.

Taiwan's No. M343637 new patent discloses a bicycle central shaft speed-increasing transmission device, which is a planetary gear system installed in the axial direction of a central shaft of a bicycle, wherein the central shaft is connected to two cranks and a chainring. The planetary gear system consists of an internal gear, an external gear and a plurality of internal gears The planetary gear between the wheel and the external gear, through the planetary gear system, achieves the non-uniform motion of the crank and the chainring, so that the chainring can also achieve the speed-up effect of the large chainring without increasing the size of the chainring.

However, the aforementioned conventional transmission device has a problem: since the axial space of the central shaft is limited, the number of teeth of the internal gear, the planetary gear and the external gear must not differ too much due to space constraints, resulting in limited speed-up efficiency. Therefore, how to overcome the insufficient speed-up efficiency of the crank transmission and optimize the tension of the chain/belt is one of the problems to be solved urgently by the practitioners in related fields.

The main purpose of the present invention is to provide a crank device for a bicycle, which can improve the transmission efficiency and optimize the tension of the chain/belt.

In order to achieve the above-mentioned purpose of the invention, the crank device of a bicycle provided by the present invention is installed on a frame of a bicycle, comprising: a sun gear with a predetermined number of plural sun teeth; A predetermined number of plural second teeth; the first gears of the planetary gears mesh with the sun gear; a crank member connected to the planetary gears and driven to rotate by external force, so as to drive the planetary gears to move around the sun gear; and a passive member with a predetermined number of passive teeth; the passive member meshes with the second gears of the planetary gears;

In one embodiment, there is a first transmission ratio between the driven member and the crank member, which is defined as the ratio of the rotational speed of the driven member to the rotational speed of the crank; when the number of teeth of the sun gear is a, the number of teeth of the first tooth is b, the number of teeth of the second tooth is c, and the number of teeth of the driven gear is d, then the first transmission ratio is (a*c)/(b*d)+1.

In one embodiment, the range of the first transmission ratio is 2-4.

In one embodiment, the first gear of the planetary gear only meshes with the sun gear and does not mesh with the driven member; the second gear only meshes with the driven member and does not mesh with the sun gear.

In one embodiment, the crank member has a base, a central shaft and a crank, and the base is fixed on the vehicle frame; the central shaft is rotatably installed in the axial interior of the base; one end of the crank is pivoted on the central shaft, so that the crank can be driven by an external force to rotate relative to the base.

In one embodiment, one end of the base has a first positioning portion; the sun gear has a ring gear, the sun teeth are formed on the outer peripheral surface of the ring gear, and one side of the ring gear has a second positioning portion corresponding to the first positioning portion; when the sun gear is connected to the base, the second positioning portion fits into the first positioning portion, thereby preventing the sun gear from rotating relative to the base.

In one embodiment, the crank further has a planetary carrier that can rotate synchronously with the crank; the planetary gears are connected to the planetary carrier and can be driven by the planetary carrier to move around the sun gear.

In one embodiment, the planet carrier has a plurality of pillars, one end of which extends into the passive element; the planetary gears are pivotally mounted on the pillars of the planet carrier, and can be driven by the planet carrier to rotate around the pivoted pillars.

In one embodiment, it further includes a plurality of bearing gears, connected to the crank member, capable of moving around the sun gear, and each rotating along an axial direction; wherein, the bearing gears are only engaged with the driven member but not engaged with the sun gear.

According to the purpose, function and structural configuration disclosed in the present invention, preferred embodiments are listed below and described in detail with reference to the drawings.

1: Bicycle

2: Frame

3: Wheels

4: crank device

5: The second passive element

6: Drive belt

10: crank piece

11: base

110: The first positioning department

12: Axis

13: Crank

14:Planet carrier

140: convex part

141: shaft hole

142: screw

143: column part

15: Arm

16: Pedal

20: Passive components

21: Passive teeth

22: Transmission gear

30: sun gear

31: Ring gear

310: sun tooth

311: The second positioning department

32: Second bearing

40: side cover

41: through hole

42: Screws

50: planetary gear

51: First gear

510: first tooth

52: second gear

520: second tooth

60: Bearing gear

61: Bearing teeth

Figure 1 is a schematic view of the appearance of a preferred embodiment of the present invention installed on a bicycle.

Figure 2 is an exploded view of a preferred embodiment of the present invention.

Fig. 3 is a sectional view of a preferred embodiment of the present invention.

Fig. 4 is a sectional view of another viewing angle of a preferred embodiment of the present invention.

Please refer to FIG. 1 , a preferred embodiment of the present invention provides a bicycle 1 comprising a frame 2 , two wheels 3 , a crank device 4 , a second passive member 5 and a transmission belt 6 . The two wheels 3 are pivotally arranged on the front and rear sides of the vehicle frame 2 . The crank device 4 is pivotally mounted on the frame 2 and is operable to generate a torsion force. The second driven element 5 is located at the center of the wheel 3 on the rear side of the vehicle frame 2 and can rotate together with the wheel 3 . The transmission belt 6 connects the crank device 4 and the second driven member 5 . Thereby, the torsion generated by the crank device 4 can be transmitted to the second driven member 5 through the transmission belt 6, so that it generates a corresponding driving torsion, causing the wheel 3 to rotate by the driving torsion, and to make the bicycle 1 move forward.

2 to 4, the crank device 4 provided by a preferred embodiment of the present invention mainly includes: a crank member 10, a driven member 20, a sun gear 30, a side cover 40 and a planetary gear 50. Wherein: the crank member 10 has a base 11 , a center shaft 12 and a crank 13 . The base 11 is fixed on the vehicle frame 2 and cannot move or rotate relative to the vehicle frame 2 . The base 11 is generally hollow tubular, and a first positioning portion 110 is provided at one end thereof. In this embodiment, the first positioning portion 110 is a ring-shaped tenon that surrounds the outer wall of the base 11 with alternating concave and convex. The central axis 12 is disposed axially inside the base 11 , and its two ends protrude out of the base 11 along the two ends of the base 11 . Two first bearings (not shown) are disposed between the central shaft 12 and the base 11 so that the central shaft 12 can rotate relative to the base 11 . The crank 13 is disposed on one side of the base 11 and can rotate relative to the base 11 . The crank 13 has a planet carrier 14 and an arm portion 15 . The planet carrier 14 is roughly disc-shaped, with a convex portion 140 at its center, and a shaft hole 141 is further provided at the center of the convex portion 140, so that one end of the central shaft 12 is inserted into the shaft hole 141, and a screw 142 is used to fix the central shaft 12 to the crank 13, so that the crank 13 and the central shaft 12 can rotate together. The planet carrier 14 is further provided with a plurality of columns 143 extending along the vertical direction of the planet carrier 14 and surrounding the protrusion 140 . Wherein, the column portion 143 is generally hollow, and an internal thread is provided on the inner wall thereof. The arm portion 15 extends away from the planet carrier 14 along the periphery of the planet carrier 14. A pedal 16 (as shown in FIG. 1 ) can be configured at one end of the planet carrier 14 away from the planet carrier 14, and the pedal 16 is stepped on by the operator to drive the crank 13 to rotate relative to the base 11. It should be added that the crank member 10 generally has two cranks 13 , which are respectively disposed at two ends of the base 11 . Because of the same connection relationship with the base 11 and the central shaft 12 , only one of the cranks 13 is specifically described in this embodiment, and the other crank 13 can be pushed by itself.

The driven element 20 is generally ring-shaped, located between the base 11 of the crank element 10 and the crank 13 , and can rotate simultaneously with the crank 13 . In this embodiment, the driven part 20 and the second driven part 5 are a pulley, and the transmission belt 6 is a belt corresponding to the pulleys, forming a belt transmission system; The driven part 20 has a predetermined number of driven teeth 21 formed on the inner wall of the driven part 20 ; and a predetermined number of driving teeth 22 formed on the outer wall of the driven part 20 for the transmission belt 6 to mesh with.

The sun gear 30 is fixed on the base 11 so that the sun gear 30 will not move relative to the base 11 . In this embodiment, the sun gear 30 includes a ring gear 31 and a second bearing 32 . The ring gear 31 has a predetermined number of sun teeth 310 formed on the outer peripheral surface of the ring gear 31, and a second positioning portion 311 extends on one side of the ring gear 31 in the axial direction. By fitting the second positioning portion 311 of the ring gear 31 with the first positioning portion 110 of the base 11 , the sun gear 30 can be fixed on one end of the base 11 to prevent the sun gear 30 from rotating relative to the base 11 . The second bearing 32 is disposed between the inner wall of the ring gear 31 and the outer wall of the protrusion 140 , so that the sun gear 30 will not be driven by the crank 13 to rotate.

The side cover 40 is accommodated on one axial side of the driven member 20 and fixed to the planet carrier 14 of the crank 13 , so that the driven member 20 is located between the side cover 40 and the crank 13 . The side cover 40 is generally annular, and is provided with a plurality of through holes 41 along the axial direction. These through holes 41 surround the side cover 40 and correspond to the column parts 143 of the planet carrier 14. A plurality of screws 42 pass through the through holes 41 and engage with the column parts 143, so that the side cover 40 can be locked on the crank 13 so as to rotate synchronously with the crank 13 . Wherein, one end of the column parts 143 protrudes into the driven element 20 , and the axial direction of the column parts 143 is parallel to the axial direction of the sun gear 30 .

The planetary gears 50 are respectively pivoted on the column portions 143 of the planet carrier 14 , and arranged around the planet carrier 14 in a ring shape with the column portions 143 as intervals. Each of the planetary gears 50 has a first gear 51 and a second gear 52, the first gear 51 has a predetermined number of first teeth 510 formed on the outer peripheral surface of the first gear 51; Wherein, the first teeth 510 of the first gear 51 only mesh with the sun teeth 310 of the sun gear 30 and do not mesh with the driven teeth 21 of the driven member 20; In this embodiment, the first gear 51 and the second gear 52 are integrally formed coaxially and arranged side by side.

In this embodiment, a plurality of bearing gears 60 are further included. The carrying gears 60 are respectively pivoted on the column portions 143 of the planet carrier 14 , and are interlaced with the planetary gears 50 , that is, there is the planetary gear 50 between any two carrying gears 60 , or there is the carrying gear 60 between any two carrying gears 50 . Each of the bearing gears 60 has a predetermined number of bearing teeth 61 formed on the outer peripheral surface of the bearing gear 60 . The load teeth 61 of the load gears 60 are only meshed with the driven teeth 21 of the driven member 20 and are not meshed with the sun teeth 310 of the sun gear 30 . The bearing gears 60 are only used to provide a bearing capacity of the passive member 20 and do not affect the transmission relationship of the crank device 4 .

The actual operation of the present invention formed by combining the structures of the above-mentioned elements is as follows: please refer to FIG. 4 , the crank device 4 makes the crank 13 and the passive member 20 form non-uniform motion through the sun gear 30 and the planetary gears 50 . In this embodiment, since the sun The gear 30 can not rotate relative to the base 11 (can be regarded as a fixed end); the planet carrier 14 is driven by the crank 13 to rotate (can be regarded as an input end), and then drives the planetary gears 50 and the load gears 60 to rotate; and the driven part 20 is driven by the planetary gears 50 and the load gears 60 to rotate (can be regarded as an output end); therefore the planet carrier 14 and the passive part 20 are in the same direction. Wherein, there is a first transmission ratio between the crank 13 and the passive member 20, and the first transmission ratio is defined as the ratio of the rotational speed of the passive member 20 to the rotational speed of the crank 13 with the crank 13 as the input and the passive member 20 as the output. The first gear ratio is affected by the number of teeth of the sun gear 30 , the driven member 20 and the planetary gears 50 . When the quantity of the sun teeth 310 of the sun gear 30 is a; the quantity of the first teeth 510 of the first gear 51 is b, the quantity of the second teeth 520 of the second gear 52 is c; the quantity of the driven teeth 21 of the driven member 20 is d; then the first transmission ratio is (a*c)/(b*d)+1. For example, in one embodiment, the number of the sun gears 310 is 54 teeth, the number of the first teeth 510 is 12 teeth, the number of the second teeth 520 is 20 teeth, and the number of the driven teeth 21 is 84 teeth, then the first transmission ratio is (54*20)/(12*84)+1=2.03, which means that when the crank 13 of the crank member 10 rotates once, it can drive the planet carrier 14 to rotate by one The planetary gears 50 also revolve around the sun gear 30 for one revolution, and the planetary gears 50 can rotate in the axial direction of the column part 143, so that the passive part 20 is simultaneously driven by the revolution and rotation torque of the planetary gears 50 to rotate 2.03 circles. It can be seen that the sun gear 30 and the planetary gears 50 do have the effect of increasing the first transmission ratio between the crank 13 and the driven member 20, and compared with the conventional planetary gear system, the present invention arranges the first gear 51 and the second gear 52 of the planetary gear 50 side by side and coaxially, so that it is not limited by the space between the sun gear 30 and the driven member 20, and the number of teeth can be adjusted as required to achieve a higher first transmission ratio and improve the speed-up efficiency. It should be added that the present invention is not limited to the number of teeth of each gear disclosed in this embodiment. In fact, the preferred range of the first transmission ratio is 2-4.

Referring back to FIG. 1 and FIG. 2 , this embodiment further discloses the relationship between the crank device 4 and the second passive member 5 . The second passive member 5 has a predetermined number of second transmission teeth (not shown), formed on the outer peripheral surface of the second passive member 5 , for the transmission belt 6 to engage and receive the torsion transmitted from the passive member 20 . Wherein, there is a gear ratio between the driven part 20 and the second driven part 5, and the gear ratio is defined as the ratio of the number of the driving teeth 22 of the driven part 20 and the number of the second driving teeth of the second driven part 5 with the driven part 20 as the input end and the second driven part 5 as the output end. For example, if the number of the transmission teeth 22 is 20, and the number of the second transmission teeth is 10, then the gear ratio is 20/10=2, which means that when the passive part 20 rotates one revolution, the second passive part 5 can be driven by the transmission belt 6 to rotate two revolutions. In this embodiment, the gear ratio preferably ranges from 1 to 3.

In addition, there is a second transmission ratio between the crank device 4 and the wheel 3 . The second transmission ratio is defined as the ratio of the rotation speed of the wheel 3 (or the second driven member 5 ) to the rotation speed of the crank 13 with the crank 13 as the input and the wheel 3 as the output. Wherein, the product of the first transmission ratio and the gear ratio is the second transmission ratio. For example, when the first transmission ratio is 4 and the gear ratio is 2, then the second transmission ratio is 4*2=8, which means that when the crank 13 rotates 1 turn, it will drive the wheel 3 to rotate 8 times. In this embodiment, the preferred range of the second transmission ratio is 2-8. It is worth noting that, in the case of the same second transmission ratio, by increasing the first transmission ratio, the gear ratio can be relatively reduced, that is, the size of the driven element 20 and the second driven element 5 will not differ too much. As a result, the tension of the drive belt 6 can also be maintained within an acceptable range, and tension imbalance will not be caused by the gear ratio being too large or too small. Generally speaking, the present invention can achieve the effect of optimizing the tension of the transmission belt 6 by adjusting the first transmission ratio and the gear ratio.

In summary, the bicycle crank device provided by the present invention uses the first gear 51 and the second gear 52 of the planetary gear 50 to mesh with the sun gear 30 and the driven member 20 respectively, so that the first transmission ratio between the crank 13 and the driven member 20 is effectively increased, thereby improving the overall transmission efficiency of the crank device 4 . Furthermore, the first transmission ratio generated by the crank device 4 can maintain the gear ratio between the driven member 20 and the second driven member 5 within a predetermined range, further increasing the second transmission ratio between the crank 13 and the wheel 3 . Compared with the conventional bicycle drive system, which can only control the transmission ratio by adjusting the gear ratio of the front and rear chainrings, it is easy to encounter the situation that the chain/belt tension is unbalanced due to too large or too small gear ratio; the present invention can effectively improve the tension problem, and control the gear ratio within a predetermined range while maintaining the same second transmission ratio. In this way, not only the tension of the transmission belt 6 can be optimized, but the service life of the transmission belt 6 can be relatively improved; the size of the passive part 20 and the second passive part 5 can also be kept similar to achieve an aesthetic effect.

The above-mentioned embodiments are only illustrative to illustrate the technology and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify and change the above-mentioned embodiments without violating the technical principle and spirit of the present invention. Therefore, the protection scope of the present invention should be as the scope of patent application described later.

1: Bicycle

2: Frame

3: Wheels

4: crank device

5: The second passive element

6: Drive belt

16: Pedal

Claims (7)

A crank device for a bicycle, which is installed on a frame of a bicycle, includes: a sun gear with a predetermined number of plural sun teeth; The first gears of the gear mesh with the sun gear; a crank member is connected to the planetary gears and is driven to rotate by external force so as to drive the planetary gears to move around the sun gear; a passive member has a predetermined number of driven teeth; the passive member meshes with the second gears of the planetary gears; Each rotates along an axial direction; wherein, the load gears are only meshed with the driven member but not meshed with the sun gear. The crank device of a bicycle as described in claim 1, wherein there is a first transmission ratio between the driven member and the crank member, which is defined as the ratio of the rotational speed of the driven member to the rotational speed of the crank member; when the number of the sun teeth is a, the number of the first teeth is b, the number of the second teeth is c, and the number of the driven teeth is d, then the first transmission ratio is (a*c)/(b*d)+1. The crank device of the bicycle according to claim 2, wherein the range of the first transmission ratio is 2~4. The bicycle crank device according to claim 1, wherein the first gear of the planetary gear only meshes with the sun gear and does not mesh with the driven member; the second gear only meshes with the driven member and does not mesh with the sun gear. A crank device for a bicycle, which is installed on a frame of a bicycle, includes: a sun gear with a predetermined number of plural sun teeth; The first gears of the gear mesh with the sun gear; a crank part is connected to the planetary gears and is driven to rotate by external force, so as to drive the planetary gears to move around the sun gear; and a passive part has a predetermined number of driven teeth; the passive part meshes with the second gears of the planetary gears; On the vehicle frame; the central shaft is rotatably installed axially inside the base; one end of the crank is pivotally arranged on the central shaft so that the crank can be driven by external force to rotate relative to the base; wherein one end of the base has a first positioning portion; the sun gear has a ring gear, the sun teeth are formed on the outer peripheral surface of the ring gear, and one side of the ring gear has a second positioning portion corresponding to the first positioning portion; when the sun gear is connected to the base, the second positioning portion fits in the first positioning portion, In order to prevent the sun gear from rotating relative to the base. According to the bicycle crank device described in claim 5, the crank further has a planetary carrier that can rotate synchronously with the crank; the planetary gears are connected to the planetary carrier and can be driven by the planetary carrier to move around the sun gear. The crank device for a bicycle as described in claim 6, wherein the planet carrier has a plurality of columns, one end of which extends into the driven member; the planetary gears are pivotally mounted on the columns of the planet carrier, and can be driven by the planet carrier to rotate around the pivoted column as the axis.

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