JP2542203B2 - Bicycle belt drive - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a belt-driven bicycle, and more particularly to a bicycle belt driving device having an automatic tension adjusting function.

(Technical Background of the Invention and Problems Thereof) FIG. 5 shows a conventional belt drive device for a bicycle. That is, this belt drive device includes a large-diameter drive pulley 2 mounted on the crankshaft 1 and a small-diameter drive pulley 3 mounted on a shaft (not shown) on the rear wheel side. The drive pulley 2 and the driven pulley 3 A toothed belt 4 is wound around the belt. In the belt drive device having such a structure, in order to prevent the toothed belt 4 from slipping off or slipping during traveling of the bicycle, the idlers 5a, 5a approaching each other are prevented.
The toothed belt 4 is pressed by a to apply a constant tension to the toothed belt 4. But like this the idler 5a, 5
When the toothed belt 4 is pressed by a, the toothed belt 4 is rotationally driven while being bent at the idler 5a position, so that the toothed belt 4 is seriously damaged. Therefore, it is necessary to replace the toothed belt 4 in a short period of time.

In a conventional belt drive device as shown in FIG. 6,
Between the drive gear 6 that is rotated integrally with the crankshaft 1 and the toothed belt 4, a floating gear 7 that is eccentrically moved around the drive gear 6 is provided. According to this belt drive device, the drive gear 6 is passed through the floating gear 7 that meshes with the internal teeth 7a,
When tension is applied to the toothed belt 4, if the toothed belt 4 is loose, the floating gear 7 eccentrically moves around the drive gear 6, so that an idler for pressing the toothed belt 4 is not used. Therefore, it is possible to prevent the toothed belt 4 from being loosened without impairing the durability of the toothed belt 4.

However, in the belt drive device provided with the floating gear 7 and having the automatic tension adjusting function, the rotation of the crankshaft 1 is reduced by the meshing with the floating gear 7 that meshes with the drive gear 6, so this decelerated rotation is compensated. Therefore, it is necessary to set the outer diameter of the floating gear 7 to a large value, which causes an increase in the size of the belt drive device.

Further, when a strong force acts on the floating gear 7 from the drive gear 6 due to a sudden strong depression of the pedal, the floating gear 7, which is not particularly restrained from the eccentric movement, disengages from the drive gear 6 in an attempt to make a large eccentric movement. There was a risk that the meshing would be incorrect and the teeth of the floating gear would be damaged.

(Object of the Invention) An object of the present invention is to reduce the size of a belt driving device having an automatic tension adjusting function and prevent the teeth of a floating gear from being damaged.

(Summary of the Invention) The invention of the present application is directed to an outer gear part around which a toothed belt for transmitting a rotational force to the rear wheel is wound, and an inner gear part provided on an inner part of the outer gear part and having outer teeth on an outer peripheral surface. Of the outer gear part and the inner gear part fixed to the crankshaft and allowing the eccentric movement of the floating gear to automatically absorb the slack when the belt is loosened. A crank gear disposed between and having internal teeth provided on the inner peripheral surface for engaging with the inner gear portion; and means for allowing eccentric movement of the floating gear and restraining the eccentric movement, the restraining means comprising: An inner ring coaxially arranged with the crank gear inside the crank gear, an outer ring coaxially arranged with the inner gear part in the inner gear part, and rotatable between the outer ring and the inner ring. Eccentric to the inner ring And an eccentricity regulation plate for receiving the eccentricity regulation plate.

In the bicycle belt drive device according to the present invention, the rotation of the crankshaft is transmitted to the toothed belt via the floating gear that meshes with the crank gear. The crank gear and the floating gear are meshed with each other by meshing the outer teeth of the inner gear portion provided in the eccentrically movable floating gear with the inner teeth of the crank gear.

Therefore, when the rotation of the crank gear is accelerated and transmitted to the floating gear, the rotational driving force is transmitted to the toothed belt wound around the outer gear portion. At this time, if the toothed belt is loose, the floating gear eccentrically moves around the inner teeth of the crank gear with which the outer teeth of the inner gear portion mesh. That is, the floating gear rotates so that its center position is displaced by rotation. The eccentric movement of the floating gear absorbs the looseness of the toothed belt and maintains a constant tension on the toothed belt.

Since the eccentric movement of the floating gear is surely restricted by the eccentricity restricting plate of the restraining means, even if a sudden and large driving force acts on the outer teeth of the floating gear from the crank gear, The meshing with is surely maintained. Therefore, the gears are not disengaged from each other, and damage due to the disengagement of the gears is reliably prevented.

In addition, the meshing of the internal teeth of the crank gear with the external teeth of the floating gear causes the floating gear to rotate at an increased speed. It is possible to secure a predetermined speed increasing ratio without setting a large value, and by reducing the diameter of the floating gear, it is possible to reduce the size of the belt drive device having the automatic tension adjusting function.

Embodiments of the Invention Embodiments of the present invention will be described in detail below with reference to the drawings.

The bicycle belt drive device according to the present invention includes a crank gear 10, as shown in FIGS. 1 and 2. This crank gear 10 is provided with teeth 10a on its inner peripheral surface and side walls 10b.
Are integrally formed. A boss portion 10c projects from the center of the side wall 10b, and a square hole 10d is formed in the boss portion 10c. A square fitting portion 11a protruding from one end of the crank arm 11 is inserted into the square hole 10d. This fitting part 11a
Is fitted on a square crankshaft 12, and a cap 13 is screwed onto a threaded portion 12a at the tip of the crankshaft 12. A pedal (not shown) is attached to the other end of the crank arm 11.

The floating gear 14 driven by the crank gear 10 has an outer gear portion 14A having a large diameter. The outer gear portion 14A has teeth 14a provided on the outer peripheral surface thereof, and a toothed belt 15 is wound around the outer gear portion 14A. Inside the outer gear 14A, the inner gear 1 is coaxial
4B is arranged. This inner gear portion 14B is the crank gear 1
The diameter is slightly smaller than 0, and teeth 14b are provided on the outer peripheral surface. A cover member 16A is integrally formed at one of the other ends of the outer gear portion 14A and the inner gear portion 14B, and the crank gear 10 is provided inside the crank arm 11 on the other end surface of the outer gear portion 14A. The other cover member 16B that covers is bolted. Then, the crank gear 10 is located between the outer gear portion 14A and the inner gear portion 14B and has its teeth 10a.
Mesh with the teeth 14b of the inner gear portion 14B.

A small-diameter inner ring 18 is crimped onto the boss portion 10c of the crank gear 10. In addition, a large diameter outer ring 1 is provided on the inner peripheral surface of the inner gear 14B.
9 is inserted. An eccentricity restricting plate 21 is rotatably arranged between the inner ring 18 and the outer ring 19 via a bearing 20. The eccentricity restricting plate 21 is eccentric with respect to the inner ring 18 by a predetermined amount.

The toothed belt 15 is made of a rubber material containing Kepler fibers, and is wound around the outer gear portion 14A and the driven pulley 17.

 Next, the operation of the belt driving device of the present invention will be described.

If you give the toothed belt 15 some allowance,
As shown in Figure (A), a floating gear is attached to the non-running character of the bicycle.
The inner gear portion 14B of 14 is eccentric to the lower left with respect to the crank gear 10, and meshes the tooth 14b with the tooth 10a of the crank gear 10. On the other hand, in this state, the eccentricity restricting plate 21 is eccentric to the lower left with respect to the inner ring 18, as shown in FIG. 4 (A).

The crank gear 10
3 starts rotating, the inner gear portion 14B is eccentric to the upper left with respect to the crank gear 10 by meshing with the crank gear 10, as shown in FIG. 3 (B). On the other hand, eccentricity control plate
Since the outer ring 19 is eccentrically rotated together with the inner gear portion 14B, the outer ring 21 is similarly eccentrically moved to the upper left with respect to the inner ring 18 (crank gear 10) as shown in FIG. 4 (B).

When the pedal is fully depressed and the bicycle runs, as shown in FIG. 3 (C), the inner gear portion 14B is eccentric to the crank gear 10 near the center on the right side, and the outer gear portion 14A moves forward in the traveling direction. And the tension is applied to the toothed belt 15. Therefore, thereafter, the inner gear portion 14B is rotated by the rotation of the crank gear 10, so that the toothed belt 15 is rotationally driven by the outer gear portion 14A. On the other hand, the eccentricity regulation plate 21
As shown in FIG. 4 (C), is eccentric to the inner ring 18 near the center of the right side and is positioned at this position.

As described above, when tension is applied to the toothed belt 15 by the eccentric movement of the floating gear 14, the toothed belt 15 can be rotationally driven without being bent, so that the toothed belt 15 can be used for a long period of time. No damage.

Further, since the crank gear 10 causes the small-diameter inner gear portion 14B to eccentrically rotate, the rotation speed of the outer gear portion 14A increases, so that the driven pulley 17 does not increase the outer diameter dimension of the outer gear portion 14A so much. Can be rotated at a predetermined speed. Therefore, by reducing the diameter of the floating gear 14, the belt drive device can be downsized, and the length of the engaging belt 15 can be reduced, and the crank gear 10 and the inner gear portion 14B can be reduced. Since the difference in the outer diameter dimension between and is small, the generation of noise can be prevented.

Further, since the eccentricity restricting plate 21 restricts the eccentricity of the inner gear portion 14B with respect to the crank gear 10 to a constant value, the inner gear portion 14B surely fixes the teeth 14b of the crank gear 10 on the teeth 14b.
The tooth is eccentric to the position shown in FIG. 3 (C). Therefore, the teeth 10a of the crank gear 10 and the teeth of the inner gear portion 14B
Since it can completely prevent disengagement with 14b,
The teeth 10a and 14b are not damaged. Further, as shown in FIG. 3 (C), the eccentric area of the inner gear portion 14B is large in the range of about 180 ° (see the angle X). Therefore, the pedal can be depressed smoothly and the teeth are provided. Since tension is gradually applied to the belt 15, its elongation and damage are significantly reduced. Further, since the maximum movement amount 1 due to the eccentricity of the inner gear portion 14B (driving gear 14) is large, the setting of the length dimension of the toothed belt 15 does not require so much precision,
Moreover, it is easy to wind around the drive gear, etc., and even if the toothed belt 15 stretches due to long-term use, it is a floating gear.
Since the toothed belt 15 moves largely, the toothed belt 15 can be rotationally driven.

In the above-mentioned embodiment, the inner ring 18 may be fixed to the crankshaft 12, and in short, it may be arranged coaxially with the crank gear.

(Effects of the Invention) According to the present invention, a crank gear having an outer gear part around which a floating gear is wound around a toothed belt and an inner gear part inside thereof is attached to a crankshaft and has teeth on its inner peripheral surface. The inner gear part meshes with the inner gear part, and an eccentricity regulation plate is arranged between the inner ring that rotates coaxially with the crank gear and the outer ring that is fitted to the inner gear part. Since it is regulated to the value of, the toothed belt can be rotationally driven without bending, the rotation speed on the rear wheel side can be secured without increasing the size of the floating gear, and noise is also prevented. You can Further, not only can the floating gear be moved while being eccentrically secured by ensuring the meshing of the crank gear and the inner gear portion, but also the eccentric area of the floating gear and the amount of movement are large, which facilitates smooth pedaling. In addition, the toothed belt is less stretched or damaged, the length of the toothed belt is not required to be set accurately, and the winding operation is easy. Furthermore, even if the toothed belt is stretched, it can be rotationally driven. it can. Therefore, it is possible to provide a belt drive device that can continuously use the toothed belt for a long period of time and that can reduce the weight of the bicycle and improve the assembling workability.

[Brief description of drawings]

1 and 2 are an exploded perspective view and a front view of a belt driving device according to the present invention, and FIGS. 3 (A) to (C) and FIGS. 4 (A) to (C) are the devices of FIG. FIGS. 5 and 6 are front views showing a conventional belt driving device, respectively, for explaining the operation of the above stepwise. 10 …… Crank gear, 10a …… Tooth, 11 …… Crank arm, 12 …… Crank shaft, 14 …… Floating gear, 14A …… Outer gear section, 14B …… Inner gear section, 15 …… Toothed belt, 18 …… Inner ring, 19 …… Outer ring, 20 …… Bearing, 21 …… Eccentricity control plate.

Claims (1)

(57) [Claims] 1. A floating gear including an outer gear portion around which a toothed belt for transmitting a rotational force to the rear wheels is wound, and an inner gear portion provided on an inner portion of the outer gear portion and having outer teeth on an outer peripheral surface. Fixed to the crankshaft and disposed between the outer gear portion and the inner gear portion to allow eccentric movement of the floating gear to automatically absorb the slack in the belt when the slack occurs. A crank gear having inner teeth provided on its inner peripheral surface for engaging with the inner gear portion, and means for allowing eccentric movement of the floating gear and restraining the eccentric movement,
The restraint means includes an inner ring coaxially arranged with the crank gear inside the crank gear, an outer ring coaxially arranged with the inner gear part in the inner gear part, the outer ring and the inner ring. A belt drive device for a bicycle, comprising: an eccentricity restricting plate rotatably disposed between the inner ring and the eccentricity restricting plate.