JPH0420835B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a bicycle rear derailleur for changing the chain to a selected sprocket of a multi-stage freewheel attached to the rear wheel of the bicycle.

[Prior art and its problems]

Some bicycles have a derailleur,
A rear derailleur (hereinafter referred to as a rear derailleur) is configured to select one of the different diameter sprockets of a multi-stage freewheel and change the chain to it, and a rear derailleur that is configured to change gears by selecting one of the different diameter sprockets of a multi-stage freewheel, and a multiple different diameter sprocket as a chain wheel. There is one that uses a combination of sprockets and is equipped with both a front transmission (hereinafter referred to as a front derailleur) configured to select one of these and replace the chain.
In such a bicycle, it is possible to perform fine-grained gear shifting operations by multiplying the number of sprockets of the multi-stage freewheel by the number of sprockets of the multi-stage chain wheel. As mentioned above, on bicycles equipped with a derailleur that changes gears by replacing the chain with a sprocket of a different diameter, the chain slackens when the chain is attached to a large diameter sprocket and when it is attached to a small diameter sprocket. However, this slack can be reduced by applying elastic rotational force to the tensioner, which is equipped with a guide pulley and a tension pulley, in the rear derailleur so that the tension pulley always moves rearward. Absorbed. The gear capacity of a rear derailleur refers to the number of sprocket teeth that indicates how many links the rear derailleur can absorb the slack of the chain as described above, and is usually measured by the teeth of the largest diameter sprocket and the smallest diameter sprocket in a multi-stage freewheel. The number of teeth is calculated by adding the number difference and the difference in the number of teeth between the largest diameter sprocket and the smallest diameter sprocket in the multi-stage chain wheel. Therefore, a rear derailleur for a bicycle that includes both a rear derailleur and a front derailleur is required to have a larger gear capacity than a rear derailleur for a bicycle that includes only a rear derailleur. By the way, so-called mountain bikes, as shown in Figure 1 of this application, which have recently become popular, are equipped with a multi-stage freewheel in order to be able to climb steep slopes with relatively little pedal effort. There is a trend of increasing the diameter of the maximum diameter sprocket and decreasing the diameter of the maximum diameter sprocket of multi-stage chain wheels. Therefore, a rear derailleur to be attached to such a bicycle is required to have a gear capacity far greater than that of a conventional rear derailleur. The easiest way to increase the gear capacity of the rear derailleur is, for example, by extending the length of the tensioner guard and lowering the position of the tension pulley, which takes up slack in the chain, to extend the radius of its rotational trajectory. However, on mountain bikes like the ones mentioned above that were designed primarily for off-road riding, extending the guard too much can cause the guard or tension pulley to collide with rocks or protrusions on the road surface, causing damage to the rear derailleur. In addition to the possibility of
Various problems arise, such as the need to consider the support rigidity of the rear derailleur to the frame.

[Purpose of the invention]

This invention was devised under the above circumstances, and its purpose is to provide a bicycle rear derailleur that can significantly increase gear capacity without significantly increasing the overall appearance. .

[Means to achieve the purpose]

In order to achieve the above object, the present invention takes the following technical measures. That is, in a bicycle rear derailleur equipped with a tensioner in which an outer guard plate and an inner guard plate are opposed to each other at a predetermined interval, and a guide pulley and a tension pulley are rotatably supported between them, the lower portion of the tensioner is An arm that rotatably supports the auxiliary tension pulley is rotatably supported while being elastically biased rearward in the section, and the arm is rotatably supported relative to the tensioner by more than a predetermined angle. A stopper means is provided to prevent this. The control mechanism is for moving the tensioner, around which the chain is attached, in the axial direction of the rear wheel, and usually employs a parallelogram pantograph link mechanism.

[Actions and effects of the invention]

The bicycle rear derailleur of the present invention has the following functions and effects as a result of employing the above-mentioned means. The chain runs around the back of the auxiliary tension pulley, the back of the tension pulley, or the front of the guide pulley, and then hangs up on one sprocket of the multi-stage freewheel. The tensioner itself naturally has a tendency for its tension pulley to elastically move backwards, and the lower part of the arm supporting the auxiliary tension pulley elastically rotates backwards. As a result, the chain near the tension pulley or the auxiliary tension pulley is elastically pulled in the rearward direction, thereby removing slack in the chain. In other words,
The arm supporting the tensioner and the auxiliary tension pulley is pulled forward by the chain around the tension pulley or the auxiliary tension pulley. The above arm has
A stopper mechanism is provided to prevent the tensioner from rotating forward beyond a predetermined angle, so for example, when there is a large amount of slack in the chain that needs to be removed, the lower part of the tensioner will not move significantly backward. During rotation, the auxiliary tension pulley supported by the tensioner via the arm may be positioned downwardly and in front of the tension pulley with the stopper mechanism in effect. At this time, the guide pulley, tension pulley, and auxiliary tension pulley are arranged in a triangular shape, so the gear capacity is lower than that of a conventional derailleur tensioner, which has only two pulleys: the guide pulley and the tension pulley. Increase significantly. In other words, since the chain is wrapped around three pulleys: the auxiliary tension pulley, the tension pulley, and the guide pulley, which are arranged in a triangular shape, the length of the chain that is wrapped around these three pulleys is This is because the length of the chain is longer than the length of the chain on which the two pulleys are hung in a conventional tensioner. Also, if the amount of slack in the chain is small, the lower part of the tensioner will rotate forward and the stopper mechanism of the arm that supports the auxiliary tension pulley will become ineffective, but this arm always has a tendency to rotate backward. Therefore, the auxiliary tension pulley is elastically pressed by the chain before entering the tension pulley, and problems such as the chain falling off from the auxiliary tension pulley, for example, can be prevented. Note that at this time, it is not the auxiliary tension pulley that performs the slack removal function of the chain, but the original tension pulley at the bottom of the tensioner. As described above, the bicycle rear derailleur of the present invention can significantly increase its gear capacity, and since the guard plate of the tensioner is not extended, the appearance does not become so large.

[Explanation of Examples]

FIG. 1 is an external view of a mountain bike to which the rear derailleur of the present invention is most suitable. As is clear from the figure, this bicycle has thick tires 3 mounted on a sturdy frame 2 with the crankshaft 1 set higher than usual so that it can ride on uneven terrain without any trouble. It is equipped with both rear derailleur 4 and front derailleur 5. Furthermore, since the outer diameter of the minimum diameter sprocket of the chain wheel 6 is quite small, it is clear that the rear derailleur is required to have a considerably large gear capacity. An example of the rear derailleur of the present invention is shown below in FIG. The basic structure of the rear derailleur 4 of the present invention may be the same as that used in conventional rear derailleurs. That is, the guide pulley 8
and a tensioner pulley 9.
0, a control mechanism 1 such as a pantograph link mechanism
1, it may be configured to be able to move in parallel in the hub axis direction or in a direction diagonal to the hub axis along a line connecting the tips of the teeth of each sprocket of the multi-stage freewheel. The pantograph link mechanism 11 is attached to the rear end plate 12 of the bicycle frame 2 with a bolt 1.
For the base member 14 attached using 3,
The base portions of a pair of link plates 15 and 16 arranged in the horizontal direction are rotatably supported, and a movable member 17 is rotatably attached to the tip portions of the pair of link plates 15 and 16. The base member 14, the pair of link plates 15, 16, and the movable member 17 cooperate to form a deformable parallelogram. Therefore, when this parallelogram is deformed, the movable member 17 moves to the base. It moves parallel to the member 14 substantially in the hub axis direction. Although not shown in the drawings, there are four holes for connecting the base member 14 and the pair of link plates 15 and 16 so as to be mutually rotatable.
A spring for elastically deforming the pantograph link mechanism 11 in one direction is inserted into one of the book pins. Further, as shown in FIG. 4, this pantograph link mechanism 11 has an operating cable W attached to it so that the diagonal length of the parallelogram is forcibly shortened against the elasticity of the spring. It is operated by towing with a gear shift control lever attached to the handlebar or appropriate part of the frame. Movable member 1 of the pantograph link mechanism 11
A tensioner 10 is attached to 7 for moving the chain C in the hub axis direction and replacing the chain C with one of the sprockets 18 of the multi-stage freewheel 7.
This tensioner 10 usually has an outer guard plate 19
and an inner guard plate 20 facing each other at a predetermined interval, and a guide pulley 8 and a tension pulley 9 are rotatably supported above and below between the inner and outer guard plates 19 and 20, respectively. . These pulleys 8 and 9 are usually attached to the inner and outer guard plates 1.
Two upper and lower bolts used to connect 9 and 20 with each other at a predetermined interval are used as shafts 21 and 22,
By rotatably fitting the center hole into this,
Supported. Tensioner 1 configured in this way
0 is a movable member 17 of the pantograph link mechanism 11 that is rotatable about an axis 23 parallel to the hub axis.
is supported so as to be swingable back and forth with respect to the hanging piece 24 of the
In addition, the tension pulley 9 is always moved rearward by the spring 26 in the spring box 25 attached to the hanging piece 24, that is,
It is elastically biased in the direction of arrow R in FIG. Above spring 2
Basically, the elasticity of chain C 6 elastically pulls the chain C around the tension pulley 9 backwards, takes up the slack of the chain C, and tightens the chain C.
A constant tension is applied to the Furthermore, in the present invention, the auxiliary tension pulley 2
An arm 28 that rotatably supports the tensioner 7 is supported at a lower proper portion of the tensioner 10 so as to be swingable in the front and rear directions. In the illustrated example, a pair of inner and outer arms 28 is rotatably supported on a shaft 22 for supporting the tension pulley 9 in the tensioner 10, and a shaft 29 is stretched around the tips of the pair of arms 28. The auxiliary tension pulley 27 is rotatably supported. This arm 28 is the third
As clearly shown in the figure, the arm 28 is always elastically rotated backward, that is, in the direction of arrow r in FIG. A tendency is given. The elasticity of the coil spring 30 that biases the arm 28 supporting the auxiliary tension pulley 9 is set to be smaller than the elasticity of the spring 26 that biases the entire tensioner 10 to rotate backward. Further, a stopper means 32 is provided in which a stopper piece 31 is provided at the base of the arm 28, and the stopper piece 31 comes into contact with the edge of the outer guard plate 19 of the tensioner 10 to restrict the forward rotation of the arm 28. Next, the operation of the rear derailleur of this embodiment will be explained. As shown in FIG. 2, when the chain C is meshing with the small diameter sprocket of the multi-stage freewheel 7 and also meshing with the small diameter sprocket of the chain wheel (not shown), there is a lot of slack in the chain C; Tensioner 1 to take up slack
0 is a position in which the tension pulley 9 has rotated significantly backward. In the case of the present invention, the chain C passes around the back side of the auxiliary tension pulley 27, the back side of the tension pulley 9, and the front side of the guide pulley 8, and then hangs up on the back side of one sprocket 18 of the freewheel 7. Since the auxiliary tension pulley 2 is
7 is pulled forward by the chain C, and the stopper piece 31 is in contact with the guard plate 19. That is, when the vertical position of the auxiliary tension pulley 27 is below the tension pulley 9, the arm 28 supporting the auxiliary tension pulley
The stopper means 32, which restricts the forward rotation of the robot, is in an effective state. In the state shown in FIG. 2, the guide pulley 8, tension pulley 9, and auxiliary tension pulley 27 are arranged in a triangular shape with the auxiliary tension pulley 27 located at the lowest position. Since the chain C will be stretched around along the two rear sides of this triangle, the length of the chain C held by the tensioner 10 will be extended by that amount, and as a result, the amount of slack in the chain that can be removed by the tensioner 10 will be increased. In other words, the gear capacity of the rear derailleur increases. This means that the conventional rear derailleur has only two pulleys corresponding to the guide pulley 8 and tension pulley 9 or the guide pulley 8 and auxiliary tension pulley 27 in FIG. This becomes clear if you imagine the route of the chain that goes around each pulley. On the other hand, as shown in FIG. 5, when the chain C meshes with the large diameter sprocket of the multistage freewheel 7 and also meshes with the large diameter sprocket of the multistage chain wheel (not shown), the amount of slack in the chain C is small. , therefore tensioner 1
0 is pulled by chain C and tension pulley 9
assumes a position where it has been rotated significantly forward. However, as is clear from a comparison between FIG. 2 and FIG. 5, in the state shown in FIG. The tension pulley 9 and the auxiliary tension pulley 27 are now aligned in the longitudinal horizontal direction by being rotated slightly backward from the state shown in the figure. This is due to the action of the coil spring 30 which urges the arm 28 to rotate backwards, and when the auxiliary tension pulley 2 is in the state shown in FIG.
7 is engaged in such a way as to press chain C downward with a small force. Thereby, the effect that the auxiliary tension pulley 27 always meshes with the chain C and that the chain C does not fall off from the auxiliary tension pulley 27 is derived. This means that
Assuming that the arm 28 supporting the auxiliary tension pulley 27 is fixed to the tensioner 10, the auxiliary tension pulley 27 will move in the process of transition from the state shown in FIG. 2 to the state shown in FIG.
This is clear from the fact that the chain C is removed from the chain C. The auxiliary tension pulley 27 and the arm 28 that supports it during the transition from a case where the chain C has a lot of slack to a case where the chain C has a small slack
To summarize the movement of the arm 28, while the auxiliary tension pulley 27 is located below the tension pulley 9 in the process of the tensioner 10 rotating forward from a large backward rotation state, the arm 28 moves forward. When the stopper means 32 is working and the relative relationship between the arm 28 or the auxiliary tension pulley 27 and the tensioner 10 is constant, the difference in the vertical position between the auxiliary tension pulley 27 and the tension pulley 9 disappears. That is, from the time when the auxiliary tension pulley 27 and the tension pulley 9 are lined up horizontally in the front and back, the stopper means 32 is released and the arm 28 is moved so that the auxiliary tension pulley 27 and the tension pulley 9 are aligned in the front and back horizontally. Due to the elasticity of the coil spring 30, the tensioner 10 is rotated backward relative to the tensioner 10. As described above, the bicycle rear derailleur of the present invention can increase gear capacity without significantly increasing its appearance, and can also minimize failures in which the chain comes off from the tensioner. Note that the scope of the present invention is of course not limited to the above-described embodiments, and, for example, the support type of the tensioner or the form of the tensioner itself does not matter. That is, although FIGS. 2 to 5 show examples of tensioners supported in a balance type on the movable member of the pantograph link mechanism, as shown in FIG. 6, tensioners supported in a pendulum type, or The present invention can also be applied to a tensioner supported in a combination of a balance type and a pendulum type, as shown in Japanese Patent Publication No. 55-10428.

[Brief explanation of drawings]

The drawings show embodiments of the present invention; FIG. 1 is an overall view of an example of a bicycle to which the rear derailleur of the present invention is preferably installed; FIG. 2 is a front view of a rear derailleur according to an embodiment of the present invention; and FIG. FIG. 4 is a view taken along the - line in FIG. 2; FIG. 5 is an explanatory diagram of the operation of the rear derailleur shown in FIG. 2;
The figure is a front view of another embodiment of the invention. 4...Rear derailleur, 8...Guide pulley,
9...Tension pulley, 10...Tensioner, 19...Outer guard plate, 20...Inner guard plate,
27... Auxiliary tension pulley, 28... Arm, 32... Stopper means.

Claims (1)

[Claims] 1. In a bicycle rear derailleur equipped with a tensioner in which an outer guard plate and an inner guard plate are opposed to each other at a predetermined interval, and a guide pulley and a tension pulley are rotatably supported between them, An arm rotatably supporting the auxiliary tension pulley is rotatably supported while being elastically biased rearward, and the arm is prevented from rotating forward beyond a predetermined angle with respect to the tensioner. A rear derailleur for a bicycle, characterized in that it is provided with a stopper means for stopping the movement.