JPH0217391B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bicycle derailleur, and more particularly, to a chain guide having a fixed member, a deformable link mechanism consisting of a base member, two link members, and a movable member, a guide pulley, and a tension pulley. A bicycle derailleur, wherein the link mechanism is deformed by wire operation to reciprocate the chain guide, and the chain guided by the chain guide is replaced with one sprocket in a multi-stage sprocket device to change speed. Regarding.

Generally, this type of derailleur is provided with a first spring that biases the chain guide clockwise between the chain guide and the movable member, and the base member is connected to the base member through one horizontal shaft. A link mechanism is interposed between the base member and the fixed member so as to be freely swingable on the fixed member, and a second spring is interposed between the base member and the fixed member, and the second spring urges the guide pulley in a direction away from the axis of the multi-stage sprocket device. These first and second springs apply a predetermined tension to the chain, and the balance between the first and second springs determines the position of the chain guide, more specifically, the position of the guide pulley in the chain guide, and each sprocket in a multi-stage sprocket device. It is configured to set the position relative to.

However, in the case of this conventional structure, when changing the chain, the distance between the guide pulley and the small diameter sprocket of the multi-stage sprocket device tends to be larger than the distance between the guide pulley and the large diameter sprocket. Therefore, in the case of a sprocket structure in which the difference in diameter between the small diameter sprocket and the large diameter sprocket is particularly large, there is a problem that the distance between the guide pulley and the small diameter sprocket becomes too large, resulting in poor gear shifting performance. Further, as the diameter of the large-diameter sprocket increases, the force of the first spring is increased, and the force of the second spring is increased correspondingly to the force of the first spring, so that the size of the chain is increased. When changing to a diameter sprocket, it is necessary to prevent the guide pulley from coming into contact with the large diameter sprocket, so for example, the distance between the guide pulley and the large diameter sprocket is set to be a predetermined distance. In this case, when changing the chain to the small diameter sprocket, the force of the second spring with increased spring force will cause the gap between the guide pulley and the small diameter sprocket to become too large. If the distance between the guide pulley and the sprocket was set to be a predetermined distance, there was a problem that the distance between the guide pulley and the large diameter sprocket would become too small when replacing the chain with the large diameter sprocket. .

Furthermore, as disclosed in Japanese Patent Publication No. 42-23485, the connecting pin of the link member to the base member and the connecting pin of the movable member to the link member are each perpendicular to the axis of the sprocket device. A derailleur is known in which the chain guide is inclined with respect to a plane so that the chain guide is forcibly moved in the radial direction of the multi-stage sprocket device within a plane parallel to the axis of the multi-stage sprocket device.

However, in the case of this conventional structure, the moving direction of the chain guide is specified and cannot be changed, so if the sprocket configuration of the multi-stage sprocket device is changed, the guide pulley and each There was a problem with the gap between the sprocket and the sprocket being wide and narrow, resulting in poor gear shifting.

The present invention was invented in view of the above points, and an object thereof is to forcibly move the chain guide in the radial direction of a multi-stage sprocket device by tilting the connecting pin of the link member and the structure using the first and second springs. By correcting the position of the chain guide forcibly sent by the inclined structure of the connecting pin with the balance of the first and second springs, the teeth of the sprocket of the multi-stage sprocket device can be moved. Even if the set configuration has changed, even if the sprocket tooth set has a particularly large difference in diameter between the small diameter sprocket and the large diameter sprocket, or even if the diameter of the large diameter sprocket is larger than a predetermined value, the above The purpose of this invention is to maintain the distance between the guide pulley of the chain guide and each sprocket within a predetermined range.

Therefore, the structure of the present invention includes a deformable link mechanism consisting of a fixed member, a base member, two link members, and a movable member, a chain guide having a guide pulley and a tension pulley, and one sprocket in a multi-stage sprocket device. A bicycle derailleur for changing a chain to a bicycle, wherein the link mechanism is pivotally connected to the fixed member via a first horizontal shaft, and a connecting pin of the link member to the base member and the movable member. The connecting pins are each inclined with respect to a plane perpendicular to the axis of the multi-stage sprocket device, and the chain guide is moved in the axial direction and radial direction of the multi-stage sprocket device when the link mechanism is deformed. , and the inclination angle of the pin is such that when the guide pulley corresponds to the largest diameter sprocket in the multistage sprocket device, and when the distance l ₂ between the guide pulley and the largest diameter sprocket corresponds to the smallest diameter sprocket, The distance between the guide pulley and the minimum diameter sprocket is set to be larger than l ₁ , and the chain guide is pivotally connected to the movable member via a second horizontal axis parallel to the first horizontal axis. A guide pulley is rotatably supported on a second horizontal axis, a first spring is provided between the chain guide and the movable member, and the guide pulley is provided with the sprocket device between the fixed member and the link mechanism. A second spring is provided which biases the guide pulley in a direction away from the axis of the sprocket, and when the guide pulley is moved toward the larger diameter sprocket, the link mechanism is controlled by the balance between the first and second springs so that the guide pulley moves away from the By making it swing in a direction approaching the axial center of the multi-stage sprocket device, when changing the chain, the chain guide is moved parallel to the axial center of the multi-stage sprocket device, and at the same time, the chain guide is moved in a plane perpendicular to the axial center. The chain guide is forcibly moved in the radial direction of the sprocket device, and the forcibly fed chain guide is further actuated by the balance of the first and second springs to change the position of the guide pulley to the position of the connecting pin. Even if the sprocket configuration of a multi-stage sprocket device is changed by modifying the position of the guide pulley determined by the inclination angle, or if the sprocket configuration has a particularly large diameter difference between the small diameter sprocket and the large diameter sprocket, Even if the diameter of the sprocket is larger than a predetermined value, the distance between the guide pulley and each sprocket can be maintained within a predetermined range,
However, even if the front side is equipped with a transmission mechanism, even if the front side is changed,
This makes it possible to reduce changes in the distance between the guide pulley and each sprocket.
The gist of the present invention is to set the distance between the guide pulley and the sprocket to l ₂ > l ₁ , and to correct it on the large diameter sprocket side by the balance of the two springs. Since the above distance can be corrected by hanging the chain, l ₂ > l ₁
It goes without saying that the settings are made on the premise that the chain is hung.

Embodiments of the derailleur of the present invention will be described below with reference to the drawings.

What is shown in the drawing is a rear derailleur, and its basic structure consists of a fixing member 1, a base member 2, two link members 3, as shown in FIGS. 1 and 2.
4 and a deformable link mechanism A consisting of a movable member 5, and a chain guide 6 having a guide pulley 61 and a tension pulley 62. The fixed member 1 is fixed to the hawk end H of the bicycle. Furthermore, the base member 2 of the link mechanism A is supported by the fixed member 1 via the first horizontal shaft 7.

Further, the base member 2 has a pair of mounting pieces facing each other on one side, and the link members 3 and 4 are pivotally connected to these mounting pieces via a pair of connecting pins 8 and 9. The movable member 5 is pivotally attached to the free ends of the link members 3 and 4 via a pair of connecting pins 10 and 11.

This movable member 5 has a similar shape to the base member 2, and has mounting pieces facing each other on one side thereof, and the two pins 10, 11 described above on this mounting piece.
The second horizontal shaft 12 extending in the same direction as the first horizontal shaft 7 is supported on the other side.

Further, in the link mechanism A configured as described above, a return spring (not shown) is provided between, for example, one of the link members 3 and 4 and the movable member 5 or the base member 2, so that the chain Guide 6
is biased in the axial direction of the multi-stage sprocket device S, that is, toward the small diameter sprocket side or the large diameter sprocket side, usually the small diameter sprocket _S1 side.

In the derailleur configured as described above, the present invention further provides the pins 8 and 9 that connect the link members 3 and 4 to the base member 2, the pin 10 that connects the movable member 5 to the link members 3 and 4,
11 with respect to a plane perpendicular to the axial center of the sprocket device S, and when the link mechanism A is deformed, the chain guide 6 is moved parallel to the axial center of the multi-stage sprocket device S, and at the same time the axial center The guide pulley is configured to move in the axial direction and radial direction of the sprocket device S in a plane perpendicular to the sprocket device S, and the inclination angle of the pin corresponds to the maximum diameter sprocket in the multi-stage sprocket device. In this case, the distance _l2 between the guide pulley and the largest diameter sprocket is set to be larger than the distance _l1 between the guide pulley and the smallest diameter sprocket corresponding to the smallest diameter sprocket, and the link mechanism The base member 2 of A is attached to the fixed member 1, and the guide pulley 61 swings through the horizontal shaft 7 so as to reciprocate in the far and near directions (direction of arrow Z in FIG. 1) with respect to the axis of the sprocket device S. While supporting possible
The guide plate 63 of the chain guide 6 is swingably supported by the movable member 5 via the second horizontal shaft 12, and the guide pulley 61 of the chain guide 6 is mounted on the second horizontal shaft 12. The chain guide 6 is rotatably supported between the guide plate 63 and the movable member 5.
A first spring 13 is provided which biases clockwise in FIG. A second spring 14 is provided that biases the guide pulley in the direction of moving away (clockwise in FIG. 1), and when the guide pulley moves toward the larger diameter sprocket, the link mechanism is activated by the balance between the first and second springs. The pulley is designed to swing in a direction toward the axis of the multi-stage sprocket device.

In the above configuration, a mechanism ( When the guide pulley 61 moves between the small-diameter sprocket S ₁ and the large-diameter sprocket S ₂ in the multi-stage sprocket device S, the movement locus (hereinafter referred to as slant mechanism) is shown in FIGS. 3 and 4. As shown in the figure, the large diameter sprocket S ₂ and the guide pulley 6 in the large diameter sprocket S ₂
1 is larger than the distance l ₁ between the small diameter sprocket S ₁ and the guide pulley ₆₁ in the small diameter sprocket S ₁ , and when the guide pulley 61 corresponds to the large diameter sprocket S ₂ , this The reaction force of the second spring 14 is configured to be stronger than the reaction force when dealing with the small diameter sprocket _S1 .

Further, the first and second springs 13 and 14 control the radial position of the guide pulley 61 relative to the multi-stage sprocket device S, which is set by the slant mechanism by the inclination of the pins 8 to 11. , 14. The first spring 13 is for providing chain tension to the chain, and the second spring 13 is for providing chain tension to the chain.
4, and when the link mechanism A is deformed, the spring reaction force when the guide pulley 61 corresponds to the large diameter sprocket _S2 due to the rocking of the chain guide 6 corresponds to the small diameter sprocket _S1 . It becomes strong against the spring reaction force when the chain is turned, and provides a certain chain tension to the chain.

Further, the second spring 14 moves the chain guide 6 clockwise in FIG. 1 with respect to the movable member 5 via the link mechanism A, more specifically, the link mechanism A. Although the guide pulley 6 is biased away from the axis of the device S,
The reason why the spring reaction force when 1 corresponds to the large diameter sprocket _S2 is stronger than the spring reaction force when it corresponds to the small diameter sprocket _S1 is that when the guide pulley 61 is located at the large diameter sprocket _S2 , The slant mechanism forcibly moves the guide pulley 61 away from the large diameter sprocket _S2 , so the link mechanism A swings counterclockwise in FIG. 1 due to the balance with the first spring 13. This is because the counterclockwise swinging of the link mechanism A brings the guide pulley 61 closer to the larger diameter sprocket as shown by the dotted line in Figures 3 and 4. It is.

The first and second springs 13 and 14 are made of coil springs wound in the middle, and the middle winding portions are wound around the respective horizontal shafts 12 and 7 to form the first
One end of the spring 13 is hooked to the guide plate 63 of the chain guide 6, and the other end is hooked to the guide plate 64 fixed to the movable member 5, and one end of the second spring 14 is hooked to the fixed member 1, and the other end is hooked to the guide plate 63 of the chain guide 6. are respectively hung on the base member 2.

The chain guide 6 also includes the guide pulley 61 and tension pulley 62, and a guide plate 63 that supports these pulleys 61 and 62.
and a guide plate 64 fixed to the movable member 5, the guide pulley 61 is supported on the second horizontal shaft 12 which pivots the guide plate 63 to the movable member 5, and the guide plate 63
A tension pulley 62 is rotatably supported at the tip of the sprocket, and a drive chain C is hung on these pulleys 61 and 62 in an inverted S-shape to connect multiple sprockets (5 in the drawing) with different numbers of teeth. The chain C can be guided to one sprocket of the multi-stage sprocket device S provided.

Incidentally, in the figure, W is an operating wire fixed to the fixture 15, and O is an outer cylinder for guiding this wire W, which is supported on the base member 2 via a support 16.

Next, the operation of the derailleur constructed as above will be explained.

The state shown in FIGS. 1 and 2 is a state in which the chain guide 6 is located at a position corresponding to the small diameter sprocket _S1 of the multi-stage sprocket device S. By pulling and operating the operating wire W from this state, the link mechanism A is deformed, and the chain guide 6 of this link mechanism is rotated parallel to the axis of the multi-stage sprocket device S by the inclination of the pins 8 to 11 to the large diameter sprocket _S2. At the same time, it moves radially outward of the sprocket device S in a plane perpendicular to the axis.

Next, in this state, the first and second springs 13 and 14
With this balance, the link mechanism A operates with respect to the fixed member 1, and the chain guide 6 operates with respect to the movable member 5, so that the radial position of the guide pulley 61 in the chain guide 6 with respect to the multi-stage sprocket device S becomes As shown by the dotted line in Figures 3 and 4, the position is corrected with respect to the position using the slant mechanism. That is, when the link mechanism A is deformed,
The chain guide 6 is moved along with the movable member 5 by the slant mechanism in the axial direction of the multi-stage sprocket device S, that is, toward the large diameter sprocket _S2 , and is also moved radially outward of the large diameter sprocket _S3 . Moreover, the distance _l2 between the guide pulley 61 and the large diameter sprocket _S2 is larger than the distance _l1 between the guide pulley ₆₁ and the small diameter sprocket S1.

For this reason, the first spring 13, which acts to provide chain tension to the chain C, is bent that much, and the spring reaction force increases, and the second spring 14 is overcome and the link mechanism A is oscillated counterclockwise from the position shown in FIG. ₁ to the position shown in FIG. As shown in FIGS. 3 and 4, the position of the guide pulley 61 relative to the large diameter sprocket _S2 is corrected.

When the link mechanism A swings, the second spring 14
is deflected, and its spring reaction force increases, and the swinging of the link mechanism A is caused by the first spring 13 and the second spring 13.
It is determined by the balance with the spring 14.

Furthermore, when the operating wire W is loosened after the drive chain C has been replaced with the large-diameter sprocket _S2 as described above, and the link mechanism A is deformed by the restoring force of the return spring provided in the link mechanism A, the chain guide 6 is moved parallel to the axis of the multi-stage sprocket device S toward the small diameter sprocket _S1 due to the inclination of the pins 8 to 11, and at the same time moves inward in the radial direction of the sprocket device S in a plane orthogonal to the axis.

Also in this case, the first and second springs 13, 14
With this balance, the link mechanism A operates with respect to the fixed member 1, and the chain guide 6 operates with respect to the movable member 5.

That is, the small diameter sprocket _S1 of the link mechanism A
When deforming to the side, contrary to the case described above, the slant mechanism causes the guide pulley 61 to move closer toward the small diameter sprocket _S1 .

Therefore, the amount of deflection of the first spring 13 is reduced, and the second spring 14 overcomes the bending, so that the link mechanism A returns to the fixed member 1 and swings clockwise.

This swinging of the link mechanism A moves the guide pulley 61 away from the small diameter sprocket _S1 , but the slant mechanism allows the guide pulley 61 to be set at the minimum required distance from the small diameter sprocket _S1 .

By changing the spring forces of the first and second springs 13 and 14, the link mechanism A can be moved to the first position even when the guide pulley 61 is located corresponding to the small diameter sprocket _S1 , that is, at the top position.
The guide pulley 61 can also be brought closer to the small diameter sprocket _S1 by swinging counterclockwise from the position shown in the figure.

Also in this case, when the guide pulley 61 is located corresponding to the large diameter sprocket _S2 , that is, in the low position, the reaction force of the first spring 13 increases, so that the link mechanism A in this low position increases. Needless to say, the vibration in the counterclockwise direction becomes larger.

Therefore, in the case of the present invention, the chain guide 6 can be forcibly moved in a specific direction, and the guide pulley 61 of the chain guide 6 can be moved by the balance between the first and second springs 13 and 14. The chain guide can be operated in accordance with the sprocket configuration of the multi-stage sprocket device, so by setting the moving direction of the chain guide forced movement mechanism to a direction corresponding to the maximum practicable sprocket configuration, the chain guide can be operated in accordance with the sprocket configuration of the multi-stage sprocket device. Even if the sprocket configuration changes from the configuration shown in FIG. 3 to the configuration shown in FIG. Even if it is larger than the specified value,
The distance between the guide pulley 61 and each sprocket can be maintained within an allowable range, and any sprocket configuration can provide good speed change performance.
Note that the above-mentioned maximum practicable sprocket configuration refers to the maximum sprocket configuration among a plurality of sprocket configurations that can be changed, and does not mean the maximum sprocket configuration among all sprocket configurations that exist in the world.

Furthermore, in the shifting operation performed as described above, the chain guide 6 swings around the second horizontal shaft 12 that supports the guide pulley 61, so there is no change in the position of the guide pulley 61 due to the swing of the chain guide 6. , the guide pulley 61 due to the displacement due to the inclination of the connecting pins 8 to 11 and the correction displacement due to the balance of the first and second springs 13 and 14.
Therefore, the first and second springs 13 and 14 can be easily balanced, and deviations can be reduced, and the distance between the guide pulley 61 and the sprocket can be set more accurately. It can be maintained within a predetermined range.

Furthermore, when the present invention is applied to a device in which a multi-stage sprocket is provided on the front side and the speed is changed by a front derailleur, even if the chain is changed on the front multi-stage sprocket, the guide pulley 61 and the sprocket device Changes in the spacing between S and each sprocket can be almost eliminated.

Furthermore, since one guide plate 64 constituting the chain guide 6 can be fixed to or integrally formed with the movable member 5, the number of members can be reduced, and
The guide plate 64 has the function of pressing the chain when changing the chain to the large-diameter sprocket _S2 , but since it can be fixed or integrated with the movable member 5, rattling due to repeated use can be reduced. , durability can be improved accordingly.

Moreover, since the link mechanism A is capable of swinging around the first horizontal axis 7 with respect to the fixed member 1 and has a structure that holds the second spring 14, the link mechanism A is combined with the structure that holds the second spring 14. In addition to maintaining the distance between the sprocket and the sprocket, the speed change performance can also be improved. That is, when shifting toward the large-diameter sprocket _S2 , the second spring 14 is bent, and after the link mechanism A is swung clockwise and the chain is replaced, the first and second springs 13 and 14 are bent. Since the chain replacement is completed after the chain is returned to the predetermined position with balance, shifting can be performed smoothly and shocks during shifting can be reduced.

Furthermore, in the embodiment described above, since the second horizontal shaft 12 supporting the chain guide 6 is provided near the pivot point with the link members 3 and 4 in the movable member 5, the connecting pins 8 to When the chain guide 6 moves due to the inclination of the connecting pin 8
The influence caused by the slope of .about.11 can be minimized.

That is, when displacing the chain guide 6 from the top position corresponding to the small diameter sprocket S1 shown in FIG. ₁ to the low position corresponding to the large diameter sprocket _S2 , the chain guide 6
Due to the inclination of ~11, the deformation of the link mechanism A causes it to shift toward the rear of the bicycle (to the left in FIG. 1). By bringing them close together, the amount of deviation can be minimized.

This also allows the chain guide 6 to be pivotally attached to the second horizontal shaft 12 and the guide pulley 61
Coupled with the structure that supports the first and second springs 13 and 14, the first and second springs 13 and 14 can be easily balanced, the deviation can be further reduced, and the guide pulley 61 can be set at a desired position with respect to the sprocket. .

As described above, in the present invention, the link mechanism is pivotally connected to the fixed member via the first horizontal axis, and the chain guide is pivotally connected to the movable member via the second horizontal axis parallel to the first horizontal axis. At the same time, the connecting pin of the link member constituting the link mechanism to the base member and the connecting pin to the movable member are inclined as described above, and a first spring is provided between this inclined structure, the chain guide and the movable member. In addition, a balance structure in which a second spring is provided between the fixed member and the link mechanism to achieve balance is combined with a pendulum structure of the chain guide, and further,
The connection pin in the inclined structure is connected to the guide pulley when the guide pulley corresponds to the largest diameter sprocket in the multi-stage sprocket device, and the distance _l2 between the guide pulley and the largest diameter sprocket corresponds to the smallest diameter sprocket. Since the distance between the sprocket and the minimum diameter sprocket is set to be larger than l ₁ , the inclined structure allows the chain guide having the guide pulley and the tension pulley to move parallel to the axis of the multi-stage sprocket device. While it is possible to forcibly move the sprocket device in the radial direction within a plane perpendicular to the axis, the balance structure also allows the guide pulley that has been forcibly moved by the inclined structure to change its radial position relative to the multi-stage sprocket. This can be corrected by adjusting the balance between the first and second springs.

Therefore, even if the sprocket configuration of a multi-stage sprocket device changes, even if the sprocket configuration has a particularly large diameter difference between the small diameter sprocket and the large diameter sprocket, or if the diameter of the large diameter sprocket is larger than a predetermined value, However, the distance between the guide pulley and each sprocket can be maintained within a predetermined range, and good shifting performance can be achieved with either sprocket configuration.

Furthermore, since the guide pulley is supported on the second horizontal axis and the rotation center of the guide pulley is aligned with the swing center of the chain guide, the position of the guide pulley does not change due to the swing of the chain guide. The balance between the first and second springs can be easily achieved and deviations can be reduced, and therefore the distance between the guide pulley ( ) and the sprocket can be maintained more accurately.

Furthermore, when a speed change mechanism is provided on the front side, even if the speed is changed on the front side, the chain guide only swings, and the distance between the guide pulley and the sprocket hardly changes. still,
In the description of the purpose and effect, it is stated in Japanese Patent Publication No. 42-23485 that even if the sprocket configuration of the multi-stage sprocket device changes, the distance between the guide pulley and the largest sprocket can be maintained within a predetermined range. In response to the problem of the conventional technology using the so-called slant mechanism shown in , it is described that the problem can be solved, and in the case of a sprocket tooth set configuration in which the diameter difference between a small diameter sprocket and a large diameter sprocket is particularly large. Also, it does not attempt to solve the problem when the diameter of the large-diameter sprocket is larger than a predetermined value. Furthermore, even in the case of a sprocket tooth configuration in which the difference in diameter between the small diameter sprocket and the large diameter sprocket is particularly large, the statement that the distance between the guide pulley and each sprocket can be maintained within a predetermined range is due to two reasons. In the conventional technology of the balance structure using a spring, that is, the so-called double tension spring mechanism, this document describes that the problem of the slant mechanism and the problem of the slant mechanism can be solved in response to the problem that cannot be solved by this mechanism alone. It does not attempt to simultaneously solve the problem of the diameter of the large diameter sprocket being larger than a predetermined value, and furthermore, even if the diameter of the large diameter sprocket is larger than a predetermined value, it is not possible to maintain the distance between the guide pulley and each sprocket within a predetermined range. The reason why it is stated that it can be done is in response to the problem that cannot be solved when the diameter of the large diameter spring becomes larger than a predetermined value even if the spring force is changed in the double tension spring mechanism. It describes what can be done.

[Brief explanation of drawings]

FIG. 1 is a front view showing the derailleur of the present invention attached to a bicycle frame together with a multi-stage sprocket device, FIG. 2 is a side view of the same, and FIGS. 3 to 5 are operational illustrations. 1... Fixed member, 2... Base member, 3, 4...
... Link member, 5 ... Movable member, A ... Link mechanism, 6 ... Chain guide, 61 ... Guide pulley, 62 ... Tension pulley, 7 ... First horizontal shaft, 8, 9, 10, 11 ...Connecting pin, 12...
Second horizontal axis, 13...first spring, 14...second spring, S...multistage sprocket device.

Claims (1)

[Claims] 1. A deformable link mechanism consisting of a fixed member, a base member, two link members, and a movable member, and a chain guide having a guide pulley and a tension pulley, for changing the chain to one sprocket in a multi-stage sprocket device. A bicycle derailleur comprising: the link mechanism;
It is pivotally connected to the fixed member via a first horizontal axis, and the connecting pin of the link member to the base member and the connecting pin to the movable member are respectively connected to a plane perpendicular to the axis of the multi-stage sprocket device. the chain guide is moved in the axial direction and radial direction of the multi-stage sprocket device when the link mechanism is deformed; When corresponding to the largest diameter sprocket, the distance _l2 between the guide pulley and the largest diameter sprocket is set to be larger than the distance _l1 between the guide pulley and the smallest diameter sprocket when corresponding to the smallest diameter sprocket. On the other hand, the chain guide is pivotally connected to the movable member via a second horizontal axis parallel to the first horizontal axis, and a guide pulley is rotatably supported on the second horizontal axis, and the chain guide A first spring is provided between the fixed member and the movable member, and a second spring is provided between the fixed member and the link mechanism for biasing the guide pulley in a direction away from the axis of the sprocket device. When the pulley moves to the larger diameter sprocket, the link mechanism is configured such that the guide pulley swings in a direction toward the axis of the multi-stage sprocket device with the balance between the first and second springs. Bicycle dayrailer.