JPH0840342A - Externally mounted speed changer for bicycle - Google Patents

Abstract

PURPOSE:To perform a natural speed change in acceleration and during ascent running by providing a low normal type rear derailer pressing a chain to a low gear side in a pantograph link mechanism by restoring force of a return spring. CONSTITUTION:By restoring force of a return spring 25 of a low normal type rear derailer 20, a speed change cable 30 is returned to deform a pantograph link mechanisim 21, and a guide pulley 22 is displaced together with both a movable member 21B and swivel arm 24A, to press a chain to a side of low gear 11, so as to advance into a shift down condition. Here by pressing the chain to the side of low gear 11 with only restoring force of the return spring 25, in the case that large tension acts in the chain in acceleration and during ascent running, a forcing shift down to the side of low gear 11 is not performed, so as to perform a natural speed change under suitable chain tension.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bicycle having a rear wheel equipped with a transmission composed of multi-stage sprockets which is operated by operating a shift wire, and more particularly to a bicycle transmission having a multi-stage external transmission.

[0002]

2. Description of the Related Art Conventionally, there is an external transmission device which shifts gears by changing over a drive chain between multi-stage sprockets arranged on the rear wheel side in order of different diameters. In such a conventional external transmission, the ratio of the sprocket revolution length to the chain revolution length increases during a gear shift in a direction in which the sprocket diameter increases in sequence, that is, a gear shift to the low side. The tension spring of the derailleur that presses in the axial direction of the multi-stage sprocket is compressed against the spring force. (In addition, the operating force at the time of gear shifting includes the click force of the gear shift lever, the U-turn wire resistance force, etc.) Therefore, at the time of gear shifting to the low side due to such compression of the tension spring, the derailleur is connected to the multistage sprocket. It has been attempted to reduce the operating force at the time of shifting by using a so-called low normal type rear derailleur, which presses in the axial direction of the large diameter side by the restoring force of the return spring (for example, Japanese Patent Publication 4).
See JP-A-2-23485. ). However, although the operating force when shifting to the low side, which is the large diameter side, is reduced, it is only the restoring force of the return spring that obtains the axial pressing force against the spring force of the derailleur tension spring. In general, it was difficult to shift the chain in the axial direction from the small diameter sprocket, which is hard to come off, to the large diameter sprocket, which is hard to come off, and the shifting performance was insufficient.
In order to improve this, it is necessary to strengthen the spring force of the return spring, and there is a concern that the device will become large.

For this reason, when the gear is shifted to the low side due to the compression of the tension spring, the operating force is somewhat increased, but the lever is manually operated to push the derailleur in the axial direction on the large diameter side of the multi-stage sprocket. When shifting to the top side by pulling the cable and pressing the derailleur in the axial direction of the small diameter side of the multi-stage sprocket, the so-called top normal type rear derailleur that causes the restoring force of the return spring of the derailleur to perform The low normal type rear derailleur has disappeared completely. On the other hand, in recent years, a multi-stage sprocket equipped with “shift points” as shown in FIG. 8 has appeared, and a top normal that makes it easier and more secure to change the chain from a sprocket with a smaller diameter to a sprocket with a larger diameter. The type rear derailleur is extremely popular.

A multi-stage sprocket having the above "shift point" will be briefly described with reference to FIG. 8. A multi-stage sprocket device comprising at least one large-diameter sprocket 41 and at least one small-diameter sprocket 42, The respective sprockets 41, 42 are combined so that one interdental center O2 of the large diameter sprocket 41 is located on the tangent line drawn from one interdental center O1 of the small diameter sprocket 42, and the interdental centers O1, O2 are arranged. Is set to be an integer multiple of the chain pitch, and the first side of the large-diameter sprocket 41 faces the rear side in the drive rotation direction (arrow A in the figure) of the center O2 of teeth.
A tooth 51, a second tooth 52 adjacent to the rear side of the first tooth 51 in the drive rotation direction, and a third tooth 53 adjacent to the rear side of the second tooth 52 in the drive rotation direction are respectively referred to as the teeth 51 to 53. Except for the other teeth 54, other than the small sprocket 42, the small sprocket 42 is displaced to the side of the small sprocket 42 to form an easily meshing tooth. A guide surface that guides the second tooth 52 to the first tooth 51.
On the other hand, the third tooth 53 is displaced with respect to the second tooth 52 on the side opposite to the small diameter sprocket 42.

With the above structure, in the chain reshuffling portion which constitutes the "shift point", the distance L between the tooth centers O1 and O2 of each sprocket is formed to be an integer multiple of the chain pitch. When the chain is changed from the sprocket on the side to the sprocket on the larger diameter side, the front roller 63 in the chain 32 meshing with the small sprocket 42, the intermediate roller 64 not meshing with any sprocket, and the large sprocket 41.
The rear roller 65 meshing with the front roller 63 and the rear roller 65 in the chain 32 is not disengaged from the front and rear rollers 63 and 65 on the sprockets 42 and 41, respectively. In addition, the first tooth 51, the second tooth 52 and the third tooth
Since the teeth 53 and the other teeth 54 other than these teeth are displaced toward the small diameter sprocket side, when the chain is changed from the small diameter sprocket 42 to the large diameter sprocket 41, the teeth 53 are pressed to the large diameter sprocket 41 side. Chain 32
The first tooth 51 or the second tooth 52, and the first tooth 5
The chain meshed with 1 can be housed in the second tooth 52, and the chain meshed with the second tooth 52 can be housed in the third tooth 53, and can be smoothly replaced in relation to the chain pitch. Since the third tooth 53 is displaced on the side opposite to the small diameter sprocket with respect to the second tooth 52, when the chain is changed from the small diameter sprocket 42 to the large diameter sprocket 41, the third tooth 53 meshes with the first and second teeth 51, 52. It is possible to prevent the outer plate of the chain, which was not used, from being caught by the third tooth 53 and being replaced, and the noise at the time of engagement can be reduced.

[0006]

However, when shifting the multi-stage sprocket having the above-mentioned "shift point" by the top normal type rear derailleur,
While the derailleur can be reliably and easily shifted to the low side by manually pulling the cable with the shift operation lever, when the pedal is stepped on during acceleration or climbing a large amount of tension on the chain. Also in the case of manual, pulling the cable by hand can easily shift down to the low side, and as a result, excessive force in the lateral direction (axial direction) is applied to the chain, causing the chain plate to deform or the worst case. In the case of, the connecting pin may come off and the chain may break. From the above, the present invention solves the problems in the conventional gear shift operating device described above,
Provide a bicycle external gearbox that enables natural gear shifting during acceleration and climbing to eliminate chain troubles, as well as gear shifting to the low side as well as gear shifting to the top side with a light operating force. To do.

[0007]

Therefore, in the present invention, the distance between the centers of the teeth of each step sprocket is set to be an integral multiple of the chain pitch, and some meshing teeth are axially displaced and a guide surface is provided. In a bicycle external transmission equipped with a multi-stage sprocket in which the chain is changed at the shift point, the shift to the low gear side by changing the chain at the shift point causes the pantograph link mechanism to move to the low gear side by the restoring force of the return spring. A low normal type rear derailleur that presses the chain is used as a feature, which is a means for solving the problem. Further, according to the present invention, the operation cable of the pantograph link mechanism, which is deformed for shifting, is directly pulled from the front by supporting the low normal type rear derailleur on the chain stay in front of the multi-stage sprocket. The operation cable of the pantograph link mechanism, which is deformed for shifting, when the low normal type rear derailleur is attached to a rear fork end that supports a hub shaft of the multi-stage sprocket. May be pulled from the rear by the U-turn outer cable.

[0008]

According to the present invention, the distance between the centers of the teeth of each step sprocket is set to be an integral multiple of the chain pitch, and some of the meshing teeth are axially displaced, and the chains are replaced at the speed change point provided with the guide surface. In the bicycle external transmission equipped with the multi-stage sprocket, gear shifting to the low gear 11 side by chain changing at the shift point pushes the pantograph link mechanism 21 to the low gear 11 side by the restoring force of the return spring 25. Since the low normal type rear derailleur 20 is used, the cable 30 is returned by the restoring force of the return spring 25 by returning the gear shift operation lever (not shown), the pantograph link mechanism 21 is deformed, and the guide pulley 22 causes the low gear to move. Push the chain to the 11 side. Since the pressing of the chain to the low gear 11 side at that time is only due to the restoring force of the return spring 25, if a large tension is applied to the chain during acceleration or climbing, the shift down to the low gear 11 side is forced. However, it was possible to eliminate chain troubles by enabling natural shifting under moderate chain tension, which reduces the lateral load that acts on the chain. This is based on the knowledge that even if a small operating force due to only the restoring force of the return spring 25 is applied, the "shift point" can be applied to perform a surprisingly smooth and light operation. Also,
Not only for downshifting to the low gear 11 side but also for upshifting to the top gear 15 side, while pulling the cable 30 manually against the spring force of the return spring 25 of the low normal type rear derailleur 20, The operation is performed in the direction to weaken the restoring force of the tension spring in the derailleur, which is extremely light. As described above, by combining the low normal type rear derailleur with the multi-stage sprocket having the "shift points", smooth and remarkably light shifting can be achieved in both downshifting and upshifting. Further, when the low normal type rear derailleur is supported on the chain stay in front of the multi-stage sprocket and the operation cable of the pantograph link mechanism deformed for shifting is directly pulled from the front, U As compared with the turn outer cable type, the operating force corresponding to the wire resistance at the U-turn portion is further reduced.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a first embodiment of the present invention,
1 is a front view, FIG. 2 is a bottom view, and FIG. 3 is a “shift point”.
It is a thing showing a multistage sprocket provided with. In FIG. 1, a rear hub shaft 36 supported by a rear fork end 35 connecting a lower end of a rear frame 34 and a rear end of a chain stay 33 supports a multi-stage sprocket 10 having a “shift point” shown in FIG. Supported. The multi-stage sprocket 10 includes a first-stage sprocket (low gear) 11, a second-stage gear 12, a third-stage gear 13, a fourth-stage gear 14, and a fifth-stage gear (top gear) in order from a large-diameter sprocket.
15 and each sprocket has the "shift points (11P, 12P, 13P as described in FIG.
P, 14P) ". In one of the multi-stage sprockets, a chain 32 is suspended between a drive sprocket fixed to a pedal (not shown), and the chain 32 is moved in a direction perpendicular to the plane of FIG. 1 to form a multi-stage sprocket. Gear shifting is performed by switching to.
In the present invention, the low normal type rear derailleur 20 is adopted as a derailleur therefor. The low normal type rear derailleur 20 is deformed for a speed change by being supported by a chain stay 33 by a link base 21A in front of the multi-stage sprocket 10 so that the operation cable 30 of the pantograph link mechanism 21 is deformed.
Is configured to be directly towed from the front. By pulling the cable 30, the pantograph link mechanism 21 is displaced from the large diameter sprocket side to the small diameter sprocket side to be deformed against the restoring force of the return spring 25. The low normal type rear derailleur 20
Is a connecting pin 21 that is displaced and deformed in the axial direction of the multi-stage sprocket 10 with respect to the link base 21A.
An outer link 21C, an inner link 21D, which form a parallelogram link pivotally supported by E, 21F, 21G, and 21H.
A pantograph link mechanism 21 including a movable member 21B and a chain guide 24B pivotally supported by the movable member 21B and supporting a pair of guide pulleys 22 and tension pulleys 23 by a tension spring 26 in a chain winding direction (see FIG. 1). And an oscillating arm 24A that urges it in the vertical direction). In addition, in order to remove the slack of the chain 32, the chain guide 24 is usually provided inside the guide pulley 22.
A tension spring for urging B in the clockwise direction in FIG. 1 is provided. The cable 30 for gear shifting is connected to a gear shift operating lever (not shown), guided by a guide roller 28 axially supported at the lower part of the link base 21A, and its end portion is connected to a cable coupling mechanism 27 provided on the movable member 21B. It has been concluded.

Next, the operation of this embodiment will be described. By returning a gear shift operating lever (not shown), the cable 3
0 is returned by the restoring force of the return spring 25 arranged between the link base 21A and the inner link 21D,
The pantograph link mechanism 21 is deformed to move the movable member 21B.
The guide pulley 22 and the swing arm 24A are displaced as shown by an arrow D in FIG.
Press 2 to enter the downshift state. Since the pressing of the chain to the low gear 11 side at that time depends only on the restoring force of the return spring 25, when the chain is subjected to a large tension during acceleration or climbing uphill, the low gear 11 is forced to pull.
The shift down is not performed, and the "shift point"
Natural shift is performed under moderate chain tension with less lateral load acting on the chain at the section. As a result, the chain trouble can be resolved. Also,
Not only when downshifting to the low gear 11 side but also when upshifting to the top gear 15 side, the cable 30 is towed manually against the spring force of the return spring 25 of the low normal type rear derailleur 20. The up operation is an operation to reduce the ratio of the sprocket circumference to the chain circumference to weaken the restoring force of the tension spring in the derailleur, so that the manual operation can be performed extremely easily. As described above, by combining the low normal type rear derailleur with the multi-stage sprocket having the "shift points", smooth and remarkably light shifting can be achieved in both downshifting and upshifting. Further, in this embodiment, the low normal type rear derailleur 20 is supported on the chain stay 33 in front of the multi-stage sprocket 10, and the operation cable 30 of the pantograph link mechanism 21 which is deformed for shifting is pulled directly from the front. Since it is configured as described above (direct pull system), the operating force corresponding to the wire resistance at the U-turn portion is further reduced as compared with the U-turn outer cable type of the second embodiment (FIG. 4) described later. And even lighter operation is possible.

4 and 5 show a second embodiment of the present invention, in which the low normal type rear derailleur of the first embodiment is supported by a chain stay 33 in front of the multi-stage sprocket. On the other hand, in the second embodiment,
When the low normal type rear derailleur 20 is attached to the lower end of the rear fork end 35 that supports the hub axle 36 of the multi-stage sprocket 10, the operation cable 30 of the pantograph link mechanism 21 that is deformed for shifting is made into a U-turn outer. The cable 31 is configured to be pulled from the rear. In the present embodiment, a cable (inner) connected to a gear shift operation lever (not shown) is inserted through an outer cable 31 arranged in a U-shaped rearward direction between the chain stay 30 and the low normal type rear derailleur 20. As shown in FIG. 5, the terminal end thereof is fastened to the cable connecting mechanism 27 provided on the inner link 21D of the pantograph link mechanism 21. Since this embodiment is a U-turn outer cable type, the operating force corresponding to the wire resistance at the U-turn portion is slightly increased compared to that of the first embodiment, but it is a sports type. Adopted, rear hub axle 38,
The change in the tension of the cable caused by the rocking of the derailleur when the rear wheel is attached / detached together with the multi-stage sprocket 10 can be effectively absorbed in the U-turn portion. The other functions and effects are the same as those of the first embodiment, so the description thereof will be omitted.

6 and 7 show the results of a comparative test conducted between the present invention and the conventional gear shift lever operating force. FIG. 6 shows the lever operating force from the top to the low. Conventional operation force (top normal)
Regarding, the gear shift lever click force (the force that causes the gear shift lever to escape from the moderation mechanism that holds the gear in a predetermined position) + return spring force + tension spring force + U-turn wire resistance, and the more the derailleur is displaced toward the large diameter sprocket side, the more the operation is performed. Power increases. With the direct pull system, the operation force of the top normal type is gear shift lever click force + return spring force + tension spring force, which is reduced by the U-turn wire resistance compared to the above, but a derailleur is installed on the large diameter sprocket side. The operating force increases as it is displaced. In the direct pull method according to the present invention, in the low normal type, the gear shifting to the large diameter sprocket side can be left to the restoring force of the return spring, so that only the click force of the gear shifting lever should be considered as the operating force of the gear shifting lever. Good.

FIG. 7 shows the lever operating force when shifting from low to top. Regarding the conventional operation force of (top normal), the gear shift to the top is due to the restoring force of the return spring, so only the gear shift lever click force is used. With the direct pull system, the operation force of the top normal type is only the shift lever click force.
In the direct pull method according to the present invention, in the low normal type, gear shifting to the top is manually performed against the restoring force of the return spring, so that an operating force including the return spring force and the shift lever click force is applied. Become. From the above results, in the conventional one, the operation force from the top to the low is heavy, and the operation force from the low to the top is small, so that the difference in the operation force between the two is large, whereas in the present invention, the operation force from the low to The operation force to the top is slightly heavier than the operation force from the top to the low, but the difference in the operation force between the two is extremely small and the absolute value of the operation force is also smaller than the conventional one, so downshifting There was no discomfort in the operation between the upshift and the upshift, and it became possible to shift gears with an extremely smooth feeling.

Although the embodiments of the present invention have been described above, it is a matter of course that the shape of the derailleur, the method, the mounting form, the shape of the multi-stage sprocket, the number of steps, etc. can be appropriately selected within the scope of the present invention. Not again.

[0015]

As described above in detail, according to the present invention, since the pressing of the chain toward the low gear side is due only to the restoring force of the return spring, a large tension acts on the chain during acceleration or climbing uphill. If it is, the shift down to the low gear side will not be done aggressively, and it will be possible to eliminate chain troubles by enabling natural shifting under moderate chain tension with a small lateral load acting on the chain. . In addition to downshifting to the low gear side,
Even when shifting up to the top gear side, while pulling the cable manually against the spring force of the return spring of the low normal type rear derailleur, it can be operated in a direction that weakens the restoring force of the tension spring in the derailleur. Because of this, it can be done extremely lightly. As mentioned above, "shift point"
By combining a low-normal rear derailleur with a multi-stage sprocket equipped with, it is possible to achieve smooth and remarkably light shifting in both downshifting and upshifting. Further, when the low normal type rear derailleur is supported on the chain stay in front of the multi-stage sprocket and the operation cable of the pantograph link mechanism deformed for shifting is directly pulled from the front, U As compared with the turn outer cable type, the operating force corresponding to the wire resistance at the U-turn portion is further reduced.

[Brief description of drawings]

FIG. 1 is a front view showing an exterior transmission for a bicycle according to a first embodiment of the present invention.

FIG. 2 is a bottom view of FIG.

FIG. 3 is a view showing a multistage sprocket used in the present invention.

FIG. 4 is a front view showing an exterior transmission for a bicycle according to a second embodiment of the present invention.

5 is a bottom view of the derailleur of FIG. 4. FIG.

FIG. 6 is a comparative explanatory diagram of the operating force of the shift lever during downshifting.

FIG. 7 is a comparative explanatory diagram of the operating force of the shift lever when shifting up.

FIG. 8 is an explanatory diagram of a multi-stage sprocket including shift points.

[Explanation of symbols]

 10 multi-stage sprocket 20 low normal rear derailleur 21 pantograph link mechanism 22 guide pulley 23 tension pulley 25 return spring 26 tension spring 27 cable connection mechanism 30 speed change cable 31 outer cable 32 chain 33 chain stay 34 rear frame 35 rear end plate 36 rear hub axle P speed change point

Claims (3)

[Claims] 1. The chain sprocket has a center-to-center spacing between teeth that is an integral multiple of a chain pitch, and some meshing teeth are displaced in the axial direction and chains are replaced at a shift point provided with a guide surface. In a bicycle exterior transmission equipped with a multi-stage sprocket, shifting to the low gear side by chain changing at the shift point is performed by a low normal type rear derailleur that pushes the pantograph link mechanism to the low gear side by the restoring force of the return spring. An exterior transmission device for a bicycle, which is configured to perform. 2. The low normal type rear derailleur is supported by a chain stay in front of the multi-stage sprocket, so that an operation cable of a pantograph link mechanism that is deformed for shifting can be directly pulled from the front. The exterior transmission for a bicycle according to claim 1, wherein the exterior transmission is a bicycle. 3. The operation cable of the pantograph link mechanism, which is deformed for shifting when the low normal type rear derailleur is attached to a rear fork end that supports a hub axle of the multi-stage sprocket, is rearwardly moved by the U-turn outer cable. The external gearbox for a bicycle according to claim 1, wherein the external gearbox is configured to be pulled from the bicycle.