JP2504839Y2 - Multi-stage sprocket device for bicycle - Google Patents

Description

[Detailed description of the device] [Industrial applications]

This invention relates to a multi-stage sprocket device for a bicycle,
More specifically, the present invention relates to a structure in which a chain can be smoothly switched from a large diameter sprocket to a small diameter sprocket.

[Prior art and problems to be solved]

A recent bicycle is a multi-stage sprocket device in which a chain wheel (front gear) attached to a crank and a free wheel (rear gear) attached to a rear hub are arranged in parallel with a plurality of sprockets having different numbers of teeth. Many of them are configured and the number of gears is increased. In the chain wheel, a large-diameter sprocket 1 having a plurality of decorative holes 1b arranged at regular intervals in the circumferential direction is attached as shown in FIG. 3 in view of design and weight reduction. There are many things. Moreover, the decorative hole 1b is usually provided with a large size as illustrated in order to reduce the weight as much as possible. However, in the chain wheel in which the large diameter sprocket 1 having such a decorative hole 1b is mounted, the difference in the number of teeth is relatively large, in other words, when the large diameter sprocket and the small diameter sprocket are combined, , There was a problem that the chain cannot be smoothly switched from the large diameter sprocket to the small diameter sprocket. In other words, when changing the chain, the chain that enters the sprocket device is forcibly pressed laterally by the derailleur during the rotation of the sprocket device so that the chain is slanted, and the chain is disengaged from the sprocket that is currently meshed. It is performed by engaging with a sprocket.
At this time, as shown in FIG. 4, the chain C, after overcoming the teeth of the large diameter sprocket 1, draws a tangent line on the small diameter sprocket 2 with the roller pin R immediately after the link plate overcoming the teeth as a fulcrum. The sprocket 2 is moved onto the small diameter sprocket 2 with its large side sprocket side surface being pushed by the large diameter sprocket. However, in a chain wheel with a large diameter difference between the large diameter sprocket and the small diameter sprocket, the height difference H (see FIG. 3) between the sprocket outer peripheral side edge portion of the decorative hole and the tooth tip of the small diameter sprocket becomes large. Therefore, if the chain in the transition path from the large diameter sprocket to the small diameter sprocket and the chain in the circumferential position of the decorative hole are matched, the chain in the transition path will be The outer peripheral edge of the sprocket is likely to fall between the large-diameter sprocket and the small-diameter sprocket through the gap between the tooth tip of the small-diameter sprocket and the chain often slips between the sprockets. When the decorative hole is located on the side of the chain in the transition path, it cannot be pushed to the backup or small sprocket side by the large sprocket, so the chain enters the decorative hole so that the large sprocket and the small sprocket It falls into the gap with the sprocket. Furthermore, when a strong pedal depression force from the crank arm acts on the chain wheel in this state, a chain biting phenomenon occurs that causes the chain to lock between the large diameter sprocket and the small diameter sprocket. When the spin rotates, the chain hits the derailleur and damages it. Therefore, in order to solve such a problem, it is possible to reduce the size of the decorative hole, but this reduces the significance of providing the decorative hole. It is also conceivable to reduce the distance between the tooth tips by reducing the distance between the large diameter sprocket and the small diameter sprocket. However, in such a case, when the chain is changed from the large-diameter sprocket to the small-diameter sprocket, it is feared that the chain will drop out further inward of the small-diameter sprocket. Further, it is necessary to change the design of the sprocket mounting portion of the sprocket support. Further, for example, as in the means disclosed in Japanese Utility Model Laid-Open No. 59-104890, a small-diameter sprocket is formed on the side of the large-diameter sprocket that faces the small-diameter sprocket over the entire or substantially the entire circumference of the sprocket. It is also conceivable to provide a bulged portion that is bulged on the side. In this method, the bulging portion can push the chain on the transition path toward the small-diameter sprocket side, and prevent the chain from falling. However, when the bulging portion is provided, there is a problem that the chain cannot be smoothly switched from the small diameter sprocket to the large diameter sprocket because the bulging portion interferes. Further, there is a problem that the weight of the large diameter sprocket increases. The present invention has been devised under the circumstances as described above, and in a sprocket device including a large-diameter sprocket having a decorative hole, a large-diameter sprocket does not cause the above problems. An object of the present invention is to make it possible to prevent the occurrence of the above idling phenomenon when changing the chain from the sprocket to the small-diameter sprocket and to dramatically improve the changing performance of the chain.

[Means for Solving the Problems]

In order to solve the above problems, the present invention takes the following technical means. That is, the bicycle multi-stage sprocket device of the present invention includes at least one large diameter sprocket having a plurality of decorative holes formed at predetermined intervals in the circumferential direction, and at least one small diameter sprocket, and a crank arm. A multi-stage sprocket device for a bicycle, which is rotated by the pedaling force applied to the sprocket. At the selected circumferential position within the angular range of degrees, this chain is used when changing the chain between the large sprocket and the small sprocket at the sprocket outer edge of the decorative hole. Chain extended radially inward to prevent it from entering the decorative hole of the radial sprocket Is characterized in that pressure section is provided.

[Action and effect]

Chain wheel (front gear) Free wheel (rear gear)
Are placed almost horizontally apart in the front and back,
The chain from the freewheel to the chainwheel enters and meshes with the chainwheel from near the top of the rotating chainwheel. The rotational torque transmitted from the crank arm to the chain wheel is minimum when the crank arm is near its top-bottom dead center, and when it is in the middle of the top-bottom dead center, that is, when the crank arm faces a substantially horizontal direction. It will be the maximum. This is because the pedaling force of the occupant who rides the bicycle acts almost downward along the standpipe of the frame. When the rotation torque transmitted to the chain wheel is large, the tension of the chain trying to enter the chain wheel is large, so it is difficult to displace this sideways by the derailleur and it is difficult to remove the chain from the sprocket. When the rotational torque transmitted to the chain wheel is small, the tension of the chain trying to enter the chain wheel is smaller than that in the above case, so that the chain is easily displaced laterally by the derailleur and is easily disengaged from the sprocket. Therefore, the separation of the chain from the large diameter sprocket to the small diameter sprocket actually occurs when the tension of the chain is small, that is, when the crank arm is near the top and bottom dead center. Also, the chain separated from the large diameter sprocket has a roller pin immediately after the link plate that has passed over the teeth of the large diameter sprocket as a fulcrum, and is positioned on the small diameter sprocket with a tangential line toward the rear in the rotation direction. Transition. By the way, conventionally, in a chain wheel to which a large-diameter sprocket with a decorative hole is attached, when the large-diameter sprocket and the small-diameter sprocket have a large diameter difference,
When changing the chain from a large diameter sprocket to a small diameter sprocket, the chain easily falls between the large diameter sprocket and the small diameter sprocket from the gap between the sprocket outer peripheral edge of the decorative hole and the tooth tip of the small diameter sprocket. was there. However, in the multi-stage sprocket device of the present invention used as a chain wheel, a chain pressing portion extending inward in the radial direction is provided at the sprocket outer peripheral side edge portion of the decorative hole, and the chain pressing portion is further provided. Is the circumferential position selected within an angle range of 90 degrees rearward in the rotational direction from the position intersecting with the crank arm and the position facing the sprocket shaft center with respect to this, in other words, the crank arm is located at the upper and lower dead points. It is behind the place where the chain is likely to come off the sprocket,
It is provided until the crank arm is oriented substantially horizontally and the torque transmitted to the chain is maximized. That is, as is apparent from the above, the chain pressing portion is provided at the edge of the decorative hole located rearward in the rotational direction from the part where the chain is actually most likely to be separated, while the chain separated from the large diameter sprocket is provided. Moves to the small diameter sprocket as it goes backward in the direction of rotation. Therefore, when changing the chain from the large diameter sprocket to the small diameter sprocket, the chain enters the decorative hole of the large diameter sprocket in order to conveniently push the chain in the transition path to the backup or the small diameter sprocket side by the chain pressing portion. Is prevented. As a result, the chain can be effectively prevented from falling between the large diameter sprocket and the small diameter sprocket. In addition, since the chain pressing portion basically needs to be provided only in a part of the decorative hole, the weight and material cost of the sprocket can be slightly increased by providing the decorative hole, while the chain pressing portion between the sprockets as described above. Since it is possible to prevent the slump from falling, it is possible to make the size of the decorative hole larger than ever, and it is possible to combine a large diameter sprocket and a small diameter sprocket with a larger diameter difference. Furthermore, it is not intended to narrow the gap between the tooth tips of the large diameter sprocket and the small diameter sprocket, or to provide a bulging part that bulges toward the small diameter sprocket on the side surface of the large diameter sprocket on the small sprocket side. Also, there is no problem that the chain may drop inside the small diameter sprocket when the chains are changed, or that the smoothness of the chain change from the small diameter sprocket to the large diameter sprocket may be impaired. As described above, in the multi-stage sprocket device of the present invention, the phenomenon of a chain dropping between sprockets, which is a problem in a chain wheel equipped with a large-diameter sprocket with a decorative hole, deteriorates the switching performance of other chains. Can be prevented without causing damage, and therefore the chain changing performance can be greatly improved as a whole.

[Explanation of the embodiment]

Hereinafter, an embodiment of the present invention will be specifically described with reference to FIGS. 1 and 2. FIG. 1 is a side view of a multi-stage sprocket device according to this embodiment, showing an example in which the present invention is applied to a chain wheel CW having one large diameter sprocket 1 and one small diameter sprocket 2. There is. The chain wheel CW is attached at one end of the crank shaft 3, and the crank arms 4 are provided at both ends of the crank shaft 3, respectively. The pedal effort is transmitted as a rotational force to the chain wheel CW via the crank arm 4, and the chain wheel CW is thereby rotated. As shown in FIG. 1 and FIG. 2, in the chain wheel CW of this example, the large diameter sprocket 1 and the small diameter sprocket 2 are formed in a substantially ring shape, and inside thereof, respectively, inward in the radial direction. Multiple stays 1a extending to
…, 2a… are provided at equal intervals. On the other hand, the crank arm 4 is integrally formed with a plurality of sprocket support arms 5 ... And large diameter sprocket 1 and small diameter sprocket 2
Are arranged on both sides of the sprocket support arms 5, and the stays 1a of the sprockets 1 and 2 are connected to the stay connection portions 5a of the sprocket support arms 5 ...
The sprockets 1 and 2 are connected to the crank arm 4 by being fixed by a nut 6 that is inserted into the nut insertion hole 5b of the 5a and a bolt 7 that is screwed into the nut 6. Further, the large diameter sprocket 1 is provided with a plurality of decorative holes 1b formed by being surrounded by the stays 1a and the sprocket supporting arms 5 at regular intervals in the circumferential direction. In the present invention, the chain presser 8 extending radially inward is provided in the decorative hole 1b of the large diameter sprocket 1 at the outer peripheral edge of the sprocket 1 to improve the chain changing performance. Planned. As shown in FIG. 1, the chain pressing portion 8 (the hatched portion in the drawing) rotates from a position where it crosses the crank arm 4 of the large diameter sprocket 1 and a position where it opposes the crank arm 4 with the sprocket shaft center interposed therebetween. Direction hole located backward in the direction
Provided in 1b. This is from large sprocket 1 to small sprocket 2
When changing the chain to the chain, the chain is disengaged from the large-diameter sprocket 1 in a state where the rotating torque acting on the chain wheel CW, in other words, the tension acting on the chain is small, and the rotating torque is The crank arm 4 becomes smaller when it is near the top-bottom dead center, and the chain separated from the large sprocket 1 has a shape such that a tangential line is drawn from the large sprocket 1 to the small sprocket 2 toward the rear in the rotational direction. The focus is on shifting to the small diameter sprocket 2 side. That is, the chain pressing portion 8 is provided in the decorative hole 1b located at the position where the chain is most likely to enter the transition from the large diameter sprocket 1 to the small diameter sprocket 2. In the case of the present example, the decorative hole 1b provided at the position where the chain pressing portion 8 intersects the crank arm 4,
The decorative holes 1b adjacent to the rear of the 1b in the direction of rotation and the decorative holes 1b provided immediately behind in the direction of the rotation of the crank arm 4 facing each other with the sprocket shaft interposed therebetween are provided at a total of three positions. The chain pressing portion 8 is formed by extending the lower end of the bridging portion 1c connecting the left and right stays 1a, 1a inward in the radial direction. Further, the chain pressing portion 8 is formed so that its extending amount gradually increases as it goes backward in the rotational direction so that the chain pressing portion 8 does not conspicuously destroy the shape of the decorative hole 1b. In the chain wheel of this example configured as described above, the diameter difference between the large diameter sprocket 1 and the small diameter sprocket 2 is large, and the height difference between the sprocket outer peripheral side edge of the decorative hole 1b and the tooth tip of the small diameter sprocket 2 is high. Even if the difference is large,
When changing the chain from the large diameter sprocket 1 to the small diameter sprocket 2, it is possible to effectively prevent the chain from entering the decorative hole 1b and falling between the large diameter sprocket 1 and the small diameter sprocket 2. This is because the chain on the transfer path can be conveniently pushed by the chain pressing portion 8 to the backup side or the small diameter sprocket side. Therefore, it is possible to prevent the occurrence of the idling phenomenon and the chain biting phenomenon, which have been conventionally problems, in the chain wheel to which the large-diameter sprocket with the decorative hole is attached, and improve the chain changing performance. By the way, the scope of the invention of the present application is not limited to the above-described embodiment, and it goes without saying that the shape of the chain pressing portion and the like can be variously modified according to the shape of the decorative hole and the like. Further, the chain pressing portion may basically be provided in a decorative hole located at the rear in the rotation direction such as a position intersecting with the crank arm, and the position of the decorative hole is not strictly limited. However, the substantial top and bottom dead center position of the crank arm is a position where it extends along the stand pipe of the bicycle frame, and the stand pipe is normally inclined rearward. Therefore, in practice, the chains are most likely to be disengaged from the sprocket at the position intersecting with the crank arm and the position opposite to the position opposite to the crank arm with the sprocket shaft center therebetween by about 5 ° to 15 ° in the rotational direction. Become. Therefore, preferably, as shown in the above embodiment, the chain pressing portion may be provided in the decorative hole located rearward in the rotational direction with respect to the position shifted about 5 ° to 15 ° forward in the rotational direction. . In the above embodiment, the invention is applied to the chain wheel composed of two sprockets.
The present invention can be applied to a chain wheel having three or more sprockets without any problem.

[Brief description of drawings]

1 is a side view of a chain wheel according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, FIG. 3 is a side view of a conventional chain wheel, and FIG. It is a schematic diagram which shows the state at the time of replacement. 1 ... Large sprocket, 1b ... Decorative hole, 2 ... Small sprocket, 4 ... Crank arm, 8 ... Chain pressing part.

Claims (1)

(57) [Scope of utility model registration request] 1. A crankshaft comprising at least one large-diameter sprocket having a plurality of decorative holes formed at predetermined intervals in the circumferential direction and at least one small-diameter sprocket, and rotated by a pedaling force applied to a crank arm. A multi-stage sprocket device for a bicycle, which is selected within a range of 90 degrees rearward in the rotational direction from a position intersecting with the crank arm of the large diameter sprocket and a position on the opposite side of the sprocket shaft center. At the specified circumferential position, the chain enters the decorative hole of the large diameter sprocket at the edge of the decorative hole on the outer peripheral side of the sprocket when the chains are exchanged between the large diameter sprocket and the small diameter sprocket. In order to prevent this, a chain pressing portion extending inward in the radial direction is provided, Rolling car for the multi-stage sprocket assembly.