JP2005306267A - Gearshift device for bicycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gearshift device for a bicycle capable of being easily mounted to an existing bicycle and operation with a simple structure. <P>SOLUTION: This is the gearshift device for the bicycle in which a chain is crossed over between a crank side sprocket and a rear wheel side sprocket. The crank side sprocket is constituted of a large-diameter sprocket and a small diameter sprocket, and the rear wheel side sprocket is constituted of a high-speed side sprocket and a lower speed side sprocket. The chain is constituted of a first chain crossed over between the large-diameter side sprocket and the high-speed side sprocket, and a second chain crossed over between the small-diameter side sprocket and the low-speed side sprocket. A first one-way clutch which can be switched on and off by a clutch switching mechanism is intervened between the large-diameter side sprocket and the crank side sprocket, and a second one-way clutch is intervened between the small-diameter side sprocket and the crank side sprocket. The high-speed side sprocket and the low-speed side sprocket are fixed on a rear wheel side to be constantly rotated with the rear wheel. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a transmission mounted on a bicycle.

  In general, bicycle transmissions include a so-called exterior type in which a chain is switched to one of a multi-stage sprocket and a so-called interior type in which a planetary gear mechanism is used.

The exterior type transmission is a chain change frame that supports a guide wheel for guiding the chain and a tension ring for giving tension to the chain, and the chain change frame in a multistage manner. A parallel link mechanism for translating in the axial direction of the sprocket is attached to the bicycle frame, and by operating the operation lever, the chain changing frame is operated via the operation wire and the parallel link mechanism, and the chain is Shifting to a sprocket is performed. (See Patent Document 1)
Japanese Utility Model Publication No. 07-8187

  However, in the above-described exterior-type transmission, not only a chain link frame but also a parallel link mechanism is required, and the timing of the speed change operation is difficult at the time of the speed change operation. It is difficult to handle.

On the other hand, as an example of an interior-type transmission, for example, a driven rotating body is rotatably assembled to a crankshaft, a sprocket is fixed to one side thereof, and a plurality of carriers are rotated integrally with the crankshaft. A planetary gear of a stage is pivotally supported, and a rotatable sun gear is meshed inside each stage of the planetary gear, and an internal gear provided on a driven rotating body on the outside of any stage of the planetary gear is meshed. A ratchet mechanism for absorbing the difference in rotational speed between the carrier and the driven rotor, and switching the one-way clutch for allowing or preventing the rotation of the sun gear at each stage to the crankshaft. There has been proposed a gear that is changed by switching the internal gear to be accelerated. (See Patent Document 2)
JP-A-6-263081

  However, in the above-described internal transmission, a large number of various components such as a ratchet mechanism, sun gears at each stage, and a one-way clutch corresponding to an internal gear are required, and the overall structure is complicated. There's a problem.

  The present invention has been developed in view of the above circumstances, and an object of the present invention is to provide a bicycle transmission that has a simple structure, can be easily mounted on an existing bicycle, and can be easily operated. It is to provide.

In order to achieve the above-mentioned object, according to the first aspect of the present invention, a chain is bridged between a crank side sprocket provided on the crank side that is rotated by a pedaling force and a rear wheel side sprocket provided on the rear wheel side. A transmission for a bicycle, the crank side sprocket is composed of a large diameter sprocket and a small diameter sprocket, the rear wheel side sprocket is composed of a high speed side sprocket and a low speed side sprocket, and the chain is composed of a large diameter side sprocket and a high speed side sprocket. The first one-way clutch, which is composed of a first chain spanned between the sprocket and a second chain spanned between the small-diameter sprocket and the low-speed sprocket, is turned on and off by a clutch switching mechanism. The second one-way clutch is inserted between the small-diameter sprocket and the crank. Is interposed between the high speed sprocket and the low speed sprocket is characterized in that it is configured to constant rotation between the rear wheel is fixed to the rear wheel side.
The invention according to claim 2 is characterized in that, in the bicycle transmission device according to claim 1, a speed increasing mechanism is provided for increasing the speed of rotation of the small-diameter sprocket.
The invention according to claim 3 is a bicycle transmission in which a chain is bridged between a crank side sprocket provided on the crank side that is rotated by a pedaling force of a pedal and a rear wheel side sprocket provided on the rear wheel side. The crank-side sprocket is composed of a large-diameter sprocket and a small-diameter sprocket, the rear-wheel-side sprocket is composed of a high-speed sprocket and a low-speed sprocket, and the chain is installed between the large-diameter sprocket and the high-speed sprocket. Consists of a second chain spanned between one chain, a small-diameter side sprocket, and a low-speed side sprocket,
A first one-way clutch that can be turned on and off by a clutch switching mechanism is interposed between the high-speed side sprocket and the rear wheel side, and a second one-way clutch is interposed between the low-speed side sprocket and the rear wheel side. The small-diameter sprocket is fixed to the crank side and is configured to rotate with the crank at a constant speed.

  According to a fourth aspect of the invention, in the bicycle transmission of the third aspect, a speed increasing mechanism is provided for increasing the speed of rotation of the low speed side sprocket.

  According to the invention described in claim 1 or 3, there is no need to provide multi-stage planetary gears, sun gears, internal gears, and the like as in the case of a conventional internal transmission, and the structure is simplified as much as in use. It is possible to provide a transmission capable of two-speed shifting with good operability and good reliability.

  In addition, according to the invention described in claim 2, the effect of the invention described in claim 1 can be obtained only by providing a speed increasing mechanism for increasing the speed of rotation of the small diameter sprocket between the large diameter sprocket and the small diameter sprocket. In addition, a three-speed shift can be easily achieved.

  According to the invention described in claim 4, for example, the speed increasing mechanism for increasing the rotation speed of the low speed side sprocket is provided between the high speed side sprocket and the low speed side sprocket, for example. In addition to the above effect, a three-speed shift can be easily achieved.

  FIG. 1 schematically shows a bicycle equipped with a two-stage transmission which is an example of the present invention. As is known, this bicycle rotates a front wheel 11 and a rear wheel 12 on a frame 1. The chain 5 is bridged between the crank side sprocket 3 provided on the crankshaft 2 side and the rear wheel side sprocket 4 provided on the rear wheel 12, and the rear wheel 12 is inserted through the chain 5 by depressing the pedal 13. Is driven to rotate.

  Next, a description will be given of a first embodiment of a transmission mounted on the bicycle.

(First embodiment)
First, the crank side sprocket 3 includes a large-diameter sprocket 3a having a large number of teeth and a small-diameter sprocket 3b having a small number of teeth.
The rear wheel side sprocket 4 includes a high speed side sprocket 4a and a low speed side sprocket 4b. The high speed side sprocket 4a and the low speed side sprocket 4b are fixed to the rear wheel 12 so as to rotate integrally with the rear wheel 12. It is configured.

  The high speed side sprocket 4a and the low speed side sprocket 4b have the same number of teeth.

  The chain 5 includes a first chain 5a spanned between the large-diameter sprocket 3a and the high-speed side sprocket 4a, and a second chain 5b spanned between the small-diameter sprocket 3b and the low-speed side sprocket 4b.

  As shown in FIG. 2, a rotating body 22 that rotates together with the crankshaft 2 is fixed to a boss portion 21 of the crank 20 assembled to the crankshaft 2, and the large-diameter sprocket 3a and the small-diameter sprocket 3b described above are rotated. A cylindrical portion 23 provided on the outer periphery of the body 22 is rotatably assembled via a bearing 31.

  The rotating body 22 may be assembled to the crankshaft 2.

  Further, between the cylindrical portion 23 of the rotating body 22 and the large-diameter sprocket 3a, a plurality of ratchet claws 61a (four in the embodiment) and ratchet teeth 62a with which these ratchet claws 61a engage are first. A one-way clutch 6a is provided, and a plurality of ratchet claws 61b (four in the embodiment) and ratchet teeth 62b with which these ratchet claws 61b engage are also provided between the cylindrical portion 23 of the rotating body 22 and the small-diameter sprocket 3b. A second one-way clutch 6b is provided.

  The ratchet claws 61a and 61b are swingably assembled to the cylindrical portion 23 of the rotating body 22 via a pivot pin 63, and the ratchet teeth 62a and 62b are respectively connected to the boss portions 32a and 62 of the large diameter sprocket 3a and the small diameter sprocket 3b. It is engraved on the inner peripheral surface of 32b.

  Thus, when the crankshaft 2 is rotated forward (in the direction of the arrow X in FIG. 4) by depressing the pedal 13, the sprockets 3a and 3b rotate together via the first and second one-way clutches 6a and 6b. It becomes free when the crankshaft 2 rotates in reverse.

  A clutch switching mechanism 7 for turning on and off the first one-way clutch 6a provided on the large-diameter sprocket 3a side is also provided.

  As shown in FIG. 2, the clutch switching mechanism 7 includes a ratchet switching body 72 urged by a spring 71 in a direction away from the ratchet pawl 61a, and the ratchet switching body 72 against the spring 71 against the ratchet pawl 61a side. A ring member 73 for moving the ring member 73. The ring member 73 is engaged with a screw 15 having a large lead provided on the outer periphery of the support cylinder 14 of the crankshaft 2 in the frame 1 to rotate the ring member 73. Thus, the ring member 73 is moved in the axial direction of the crankshaft 2, and the ratchet switching body 62 is moved against the spring 71 at the edge of the ring member 73.

The ring member 73 is interlocked and connected to an operation lever 10 provided on a bicycle handle via an operation wire (not shown).
Next, the operation of the above transmission will be described.

  First, as shown in FIG. 2, when the first one-way clutch 6a is not disengaged, the large-diameter sprocket 3a also rotates in the forward direction as the crankshaft 2 is rotated via the crank 20 by stepping on the pedal 13. The rear wheel 12 rotates at high speed via the first chain 5a.

  At this time, the small-diameter sprocket 3b is allowed to rotate in the reverse direction of the small-diameter sprocket 3b with respect to the rotating body 22 by the action of the second one-way clutch 6b, and is faster than the large-diameter sprocket 3a regardless of power transmission. Will rotate.

  On the other hand, when the ring member 73 is rotated by the speed change operation and the ratchet switching body 72 is moved rightward in FIG. 2, the ratchet pawl 61a pushes the rear portion of the ratchet pawl 61a as shown in FIG. Thus, the ratchet pawl 61a swings, whereby the engagement between the ratchet pawl 61a and the ratchet teeth 62a is released, and the first one-way clutch 6a is disengaged.

  In this state, when the crankshaft 2 is rotated by depressing the pedal 13, the large-diameter sprocket 3a becomes free with respect to the rotating body 22, and the small-diameter sprocket 3b to which the second one-way clutch 6b is connected is rotated. As a result, the rear wheel 12 rotates at a low speed via the second chain 5b.

  When the reverse speed change operation is performed from the above state, the ring member 73 moves while being reversely rotated, and accordingly, the ratchet switching body 72 is pushed by the spring 71, as shown in FIG. The ratchet pawl 61a and the ratchet teeth 52 are engaged again, and the rear wheel 12 is switched to high speed rotation.

(Second Embodiment)
Next, as a second embodiment of the present invention, a three-speed bicycle transmission will be described with reference to FIGS.

  Note that description of parts common to the first embodiment is omitted here.

  In the transmission shown in FIGS. 5 to 7, a speed increasing mechanism 8 for increasing the rotation speed of the small diameter sprocket 3b is incorporated between the large diameter sprocket 3a and the small diameter sprocket 3b.

  The speed increasing mechanism 8 includes a ring-shaped intermediate member 81 interposed between the large-diameter sprocket 3 a and the small-diameter sprocket 3 b, and the intermediate member 81 is freely arranged with respect to the cylindrical portion 23 of the rotating body 22. Has been.

  As shown in FIG. 5, a plurality of ratchet claws 61 c (four in the embodiment) and ratchet teeth 62 c with which these ratchet claws 61 c engage are formed between the intermediate member 81 and the cylindrical portion 23. A third one-way clutch 6c is provided.

  The ratchet pawl 61 c is assembled to the cylindrical portion 23 of the rotating body 22 via a pivot pin 63 so as to be swingable, and the ratchet teeth 62 c are engraved on the inner peripheral surface of the intermediate member 81.

  Further, four bevel gears 82 are rotatably attached to the outer periphery of the intermediate member 81 at intervals in the circumferential direction. The bevel gears 82 are formed on the boss portions 32a and 32b of the large-diameter sprocket 3a and the small-diameter sprocket 3b. The ring-shaped bevel teeth 83 and 84 are engaged with each other.

  Both annular bevel teeth 83 and 84 have the same number of teeth.

  Next, the operation of the above transmission will be described.

  First, as shown in FIG. 5, when the first one-way clutch 6a is not disengaged, the large-diameter sprocket 3a is rotated in the forward direction as the crankshaft 2 is rotated via the crank 20 by the depression of the pedal 13. The rear wheel 12 rotates at high speed via the first chain 5a.

  At this time, the small-diameter sprocket 3b is allowed to rotate in the reverse direction of the small-diameter sprocket 3b with respect to the rotating body 22 by the action of the second one-way clutch 6b, and is faster than the large-diameter sprocket 3a regardless of power transmission. Will rotate.

  On the other hand, by the shifting operation, the ring member 73 and the ratchet switching body 72 are moved to the right in FIG. 5 by one step so that the ratchet switching body 72 releases the engagement between the ratchet pawl 61a and the ratchet teeth 62a. When the first one-way clutch 6a is disengaged, the large-diameter sprocket 3a becomes free with respect to the rotating body 22, and the small-diameter sprocket is caused by the rotational action between the annular bevel gears 83 and 84 of the bevel gear 82 constituting the speed increasing mechanism 8. The rotation of 3b is increased, and the rear wheel 12 rotates at a medium speed via the first and second chains 5a and 5b.

  Further, when the first one-way clutch 6a and the third one-way clutch 6c are disengaged as shown in FIG. 6 by moving the ring member 73 and the ratchet switching body 72 one step further in the right direction in FIG. The large-diameter sprocket 3a and the intermediate member 81 become free with respect to the rotating body 22, and the rear wheel 12 rotates at a low speed via the second chain 5b.

  Thus, in the above embodiment, basically, in the transmission of the first embodiment, the speed increasing mechanism including the bevel gear 82 is interposed between the large-diameter sprocket 3a and the small-diameter sprocket 3b. It can be a shift.

(Third embodiment)
Next, a bicycle transmission according to a third embodiment of the present invention will be described with reference to FIGS.

  First, the crank-side sprocket 3 is composed of a large-diameter sprocket 3a having a large number of teeth and a small-diameter sprocket 3b having a small number of teeth. Both the sprockets 3a and 3b are fixed to the crankshaft 2, and the crankshaft 2 And are configured to rotate together.

  The rear wheel side sprocket 4 includes a high speed side sprocket 4a and a low speed side sprocket 4b.

  The chain 5 includes a first chain 5a spanned between the large-diameter sprocket 3a and the high-speed side sprocket 4a, and a second chain 5b spanned between the small-diameter sprocket 3b and the low-speed side sprocket 4b.

  The high speed side sprocket 4 a and the low speed side sprocket 4 b are assembled to the hub 16 of the rear wheel 12 via a bearing 310 so as to freely rotate.

  The high speed side sprocket 4a and the low speed side sprocket 4b have the same number of teeth.

  Further, between the hub 16 of the rear wheel 12 and the high speed side sprocket 4a, a first one-way constituted by a plurality of ratchet claws 610a (four in the embodiment) and ratchet teeth 620a with which the ratchet claws 610a engage. A clutch 60a is provided, and a plurality of ratchet pawls 610b (four in the embodiment) and ratchet teeth 620b with which the ratchet pawls 610b engage are provided between the hub 16 of the rear wheel 12 and the low-speed sprocket 4b. A first one-way clutch 60b is provided.

  The ratchet pawls 610a and 610b are swingably assembled to the hub 16 of the rear wheel 12 via a pivot pin 630, and the ratchet teeth 620a and 620b are boss portions 41a and 41b of the high speed side sprocket 4a and the low speed side sprocket 4b. It is engraved on the inner peripheral surface of.

  Thus, when the crankshaft 2 is rotated forward (in the direction of the arrow X in FIG. 10) by depressing the pedal 13, the sprockets 4a and 4b rotate together via the first and second one-way clutches 60a and 60b. It becomes free when the shaft 2 rotates in the reverse direction.

  A clutch switching mechanism 70 for turning on and off the first one-way clutch 60a provided on the high speed side sprocket 4a is also provided.

  The clutch switching mechanism 7 is provided with a screw 18 having a large lead on the outer periphery of a shaft 17 that rotatably supports the hub 16 of the rear wheel 12, while a ratchet switching body 720 is screwed to the screw 18 so that the ratchet switching body. The ratchet switching body 720 is moved in the axial direction of the shaft 17 by the rotation operation of 720.

  The ratchet switching body 720 is linked to an operation lever 10 provided on a bicycle handle via an operation wire (not shown).

  Next, the operation of the above transmission will be described.

  First, as shown in FIG. 8, when the first one-way clutch 60a is not disengaged, as the crankshaft 2 is rotated via the crank 20 by depressing the pedal 13, the speed is increased via the first chain 5a. The side sprocket 4a also rotates in the forward direction, and the rear wheel 12 rotates at high speed.

  At this time, the low-speed side sprocket 4b is allowed to rotate in the reverse direction of the low-speed side sprocket 4b with respect to the hub 16 by the action of the second one-way clutch 60b. It will rotate at low speed.

  On the other hand, when the ratchet switching body 72 is moved to the left in FIG. 8 by a speed change operation, the rear portion of the ratchet pawl 61a is pushed by the ratchet switching body 720, and the ratchet pawl 610a swings, and the ratchet pawl 610a. And the ratchet teeth 620a are disengaged, and the first one-way clutch 60a is disengaged.

  In this state, when the crankshaft 2 is rotated by depressing the pedal 13, the high speed side sprocket 4a becomes free with respect to the hub 16, and the rotation of the low speed side sprocket 4b to which the second one-way clutch 60b is connected. As a result, the rear wheel 12 rotates at a low speed.

  If the reverse speed change operation is performed from the above state, the ratchet switching body 720 moves to the right from the position shown in FIG. 9, and the ratchet pawl 610a and the ratchet teeth 620a are engaged again as shown in FIG. The rear wheel 12 is switched to high speed rotation.

(Fourth embodiment)
Next, as a fourth embodiment of the present invention, a three-speed bicycle transmission will be described with reference to FIGS.

  In addition, description about the part which is common in above-mentioned 3rd Embodiment is abbreviate | omitted here.

  In the transmission shown in FIGS. 11 to 13, a speed increasing mechanism 80 for increasing the speed of rotation of the low speed side sprocket 4b is incorporated between the high speed side sprocket 4a and the low speed side sprocket 4b.

  The speed increasing mechanism 80 includes a ring-shaped intermediate member 810 interposed between the high speed side sprocket 4 a and the low speed side sprocket 4 b, and the intermediate member 810 is disposed so as to be freely rotatable with respect to the hub 16.

  A third one-way clutch 60c is provided between the intermediate member 810 and the hub 16 and includes a plurality of ratchet claws 610c (four in the embodiment) and ratchet teeth 620c with which the ratchet claws 610c engage. It has been.

  The ratchet pawl 610c is assembled to the hub 16 via a pivot pin 630 so as to be swingable, and the ratchet teeth 620c are engraved on the inner peripheral surface of the intermediate member 810.

  Further, four bevel gears 820 are rotatably attached to the outer periphery of the intermediate member 810 at intervals in the circumferential direction. The bevel gears 82 are attached to the boss portions 41a and 41b of the high speed side sprocket 4a and the low speed side sprocket 4b. It meshes with the formed annular bevel teeth 830 and 840.

  The ratchet switching body 720 constituting the clutch switching mechanism 70 is assembled to the operation rod 721, and this operation rod 721 is incorporated into the shaft hole 18 provided in the shaft 17. doing.

  Next, the operation of the above transmission will be described.

  First, as shown in FIG. 11, in the state where the first one-way clutch 60a is not disengaged, the large-diameter sprocket 3a and the first chain are rotated as the crankshaft 2 is rotated via the crank 20 by stepping on the pedal 13. The high speed side sprocket 4a also rotates in the forward direction through 4a, and the rear wheel 12 rotates at high speed.

  At this time, the low-speed side sprocket 4b is allowed to rotate in the reverse direction of the low-speed side sprocket 4b with respect to the hub 16 by the action of the second one-way clutch 60b. It will rotate at low speed.

  On the other hand, by the shifting operation, the ratchet switching body 720 is moved to the right in FIG. 11 by one step, whereby the ratchet switching body 720 releases the engagement between the ratchet pawl 610a and the ratchet teeth 620a, and the first one-way clutch When 60a is cut off, the high speed side sprocket 4a becomes free with respect to the hub 16, and the first and second chains 5a, 5a, and 5b are rotated by the rotating action of the bevel gear 820 constituting the speed increasing mechanism 80 between the annular bevel teeth 830 and 840. The rotation of the low speed side sprocket 4b is increased through 5b, and the rear wheel 12 rotates at a medium speed.

  Further, when the first one-way clutch 60a and the third one-way clutch 60c are disengaged as shown in FIG. 12 by moving the ratchet switching body 720 to the right in FIG. 4a and the intermediate member 810 become free with respect to the hub 16, and the rear wheel 12 rotates at a low speed.

  Thus, in the above embodiment, basically, in the transmission of the third embodiment, the speed increasing mechanism 80 including the bevel gear 820 is interposed between the high speed side sprocket 4a and the low speed side sprocket 4b. A three-speed shift can be achieved.

Explanatory drawing of the bicycle by which the transmission of this invention is mounted. Sectional drawing of the principal part of the transmission of 1st Embodiment. Sectional drawing of the principal part of the transmission of 1st Embodiment. Explanatory drawing of the principal part of the transmission of 1st Embodiment. Sectional drawing of the principal part of the transmission which concerns on 2nd Embodiment. Sectional drawing of the principal part of the transmission of 2nd Embodiment. Explanatory drawing of the principal part of the transmission of 2nd Embodiment. Sectional drawing of the principal part of the transmission which concerns on 3rd Embodiment. Sectional drawing of the principal part of the transmission of 3rd Embodiment. Explanatory drawing of the principal part of the transmission of 3rd Embodiment. Sectional drawing of the principal part of the transmission which concerns on 3rd Embodiment. Sectional drawing of the principal part of the transmission of 3rd Embodiment. Explanatory drawing of the principal part of the transmission of 3rd Embodiment.

Explanation of symbols

1 Frame 11 Front wheel 12 Rear wheel 13 Pedal 2 Crankshaft 20 Crank 22 Rotating body 3 Crank side sprocket 3a Large diameter sprocket 3b Small diameter sprocket 4 Rear wheel side sprocket 4a High speed side sprocket 4b Low speed side sprocket 5 Chain 5a First chain 5b Second Chain 6a / 60a First one-way clutch 6b / 60b Second one-way clutch 6c / 60c Third one-way clutch 7.70 Clutch switching mechanism 8.80 Speed increasing mechanism

Claims (4)

A bicycle transmission in which a chain is bridged between a crank-side sprocket provided on the crank side that is rotated by a pedal depression force and a rear-wheel side sprocket provided on the rear wheel side,
The crank-side sprocket is composed of a large-diameter sprocket and a small-diameter sprocket, the rear-wheel-side sprocket is composed of a high-speed sprocket and a low-speed sprocket, and the chain is installed between the large-diameter sprocket and the high-speed sprocket. A first one-way clutch, which is composed of a second chain spanned between one chain, a small-diameter side sprocket and a low-speed side sprocket, and which can be turned on and off by a clutch switching mechanism, is interposed between the large-diameter sprocket and the crank side. The second one-way clutch is interposed between the small-diameter sprocket and the crank side, and the high speed side sprocket and the low speed side sprocket are fixed to the rear wheel side and are configured to rotate at a constant speed with the rear wheel. A bicycle transmission.   2. The bicycle transmission according to claim 1, further comprising a speed increasing mechanism for speeding up the rotation of the small-diameter sprocket. A bicycle transmission in which a chain is bridged between a crank-side sprocket provided on the crank side that is rotated by a pedal depression force and a rear-wheel side sprocket provided on the rear wheel side,
The crank-side sprocket is composed of a large-diameter sprocket and a small-diameter sprocket, the rear-wheel-side sprocket is composed of a high-speed sprocket and a low-speed sprocket, and the chain is installed between the large-diameter sprocket and the high-speed sprocket. The first one-way clutch, which is composed of the first chain, the second chain spanned between the small-diameter side sprocket and the low-speed side sprocket and can be turned on / off by the clutch switching mechanism, is interposed between the high-speed side sprocket and the rear wheel side. The second one-way clutch is interposed between the low-speed side sprocket and the rear wheel side, and the large-diameter sprocket and the small-diameter sprocket are fixed to the crank side and configured to rotate with the crank. A bicycle transmission.   4. The bicycle transmission according to claim 3, further comprising a speed increasing mechanism for increasing the speed of rotation of the low speed side sprocket.

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