TW201706174A - Bicycle mechanism featuring rear speed change through reverse idle rotation comprising two rear derailleurs that allow an user to conduct rear speed change operations respectively in a forward pedaling condition and a reverse pedaling condition - Google Patents

Abstract

The present invention relates to a bicycle mechanism featuring rear speed change through reverse idle rotation, comprising a frame and a large chain wheel, a plurality of free wheel s, a first rear derailleur, a second rear derailleur. The first rear derailleur is mounted at a location close to the free wheels, so that when an user treads the pedals of the bicycle in a forward direction, the large chain wheel may drive, through a chain, the free wheels. Also, the user is allowed to have an operation roller of the first rear derailleur switched and displaced to a location of another one of the free wheels for carrying out a speed change operation. The second rear derailleur is mounted at a location close to the free wheels and opposite to the first rear derailleur , so that when the user treads the pedals in a reversed direction and sets the bicycle in an idling condition, the user is allowed to have an operation roller of the second rear derailleur switched and displaced to a location of another one of the free wheels for carrying out a speed change operation.

Description

Bicycle mechanism capable of reverse idling for rear shifting

The invention relates to a bicycle mechanism capable of reverse idling and rear shifting, in particular, on a bicycle frame, two rear rear derailleurs are respectively arranged adjacent to the flywheel, so that when the pedal of the bicycle is stepped forward or idling backward, the The rear derailleur can correctly and accurately drive the chain to complete the mechanism of shifting adjustment.

In recent years, the fitness and leisure of Chinese people have become more and more popular. Bicycles attract more and more people to participate because of the advantages of sports, transportation and walking. In order to obtain the favor of consumers, manufacturers also aim at the various accessories on bicycles. Continuous research and development to improve ride performance and convenience. Among them, the transmission (derailleur) is one of the most important and commonly used accessories on bicycles. It can adjust the position of the chain on the bicycle to change the transmission of the user's pedaling force. The path allows the user to select the corresponding riding mode according to different road conditions. Although the transmission has been developed for decades, there are many improvements in many seemingly necessary modes of operation that can make the performance of the bicycle more in line with the needs of the user.

The bicycle shifting principle is as follows. Please refer to Figure 1 for a bicycle structure diagram. The bicycle 1 frame (including the stand tube A1 (seat tube), the down tube A2 (down tube), the upper tube The tube A3 (chain stay) and the rear fork A5 (seat stay) are respectively provided with a large chain wheel 11 and a plurality of free wheels of different sizes. The two ends of the spindle of the large toothed disc 11 are respectively transmitted through a crank 111, and the pedals 112 are pivotally connected. The flywheels 12 are pivotally connected to the rear wheel of the bicycle, when the user steps on the pedal 112 forward. The large sprocket 11 can pass through a chain 13 to drive the engaged flywheel 12 to rotate the rear wheel of the bicycle forward; and when the user steps on the pedal 112 backward, the large sprocket 11 can The flywheel 12 that drives the phase is engaged, but at this time, the mandrel of the flywheel 12 cannot drive the latter, but will exhibit an idling state.

As shown in Figure 1, the "rear shifting" mechanism of the bicycle (there is also a "pre-shifting" mechanism, the principle is the same as the "rear shifting", so it will not be described here), the rear derailleur 14 is installed in the The bicycle is adjacent to the position of the flywheel 12, and the rear shift control is performed after the user rotates or dials one of the grips 15 and the shift lever 16 (shifter is disposed at a position adjacent to the grip) One of the shifting lines 160 in the lever will be tensioned or relaxed to adjust the position of the rear derailleur 14, for example, when the user adjusts the rear shifting lever 16 to the "low gear", the rear derailleur 14 and its upper phase The meshed chain 13 is displaced to a position corresponding to the minimum flywheel 12, so that the user can step on it more labor-savingly, but the forward speed of the bicycle is slower; otherwise, when the user adjusts the rear shift control lever 16 to the "high-end position", The rear derailleur 14 and the chain 13 meshed thereon are displaced to a position corresponding to the maximum flywheel 12. At this time, although the user's pedaling is more laborious, the bicycle advances faster, so that the user can follow different Terrain and riding needs, will Article adjust to fit on the flywheel.

Since the principle of the rear derailleur 14 is switched to the different flywheels 12 by changing the position of the chain 13, the user must rotate or toggle the rear shift control lever 16 during riding to ensure that the chain 13 is switched. Correct and accurate; if the user moves the rear shift lever 16 while the bicycle is "stationary" or "idle", the chain 13 will be detached from the flywheel 12, forming a "dropping" state in which the normal operation cannot be performed. This causes the user to spend extra time reassembling the chain 13 onto the flywheel 12.

The above-mentioned "control mode in which the shifting can be performed only when the bicycle is moving forward" has become an absolute criterion for the use of the transmission. However, this control method still causes some inconveniences for the user to ride, for example, when the user Control the bicycle in the "high-end position", and because the road conditions (such as traffic lights or pedestrians) stop, at this time, if the user wants to re-advance, it will have to take a lot of effort to overcome the "high-end position" status. The lower meshing force pushes the large chainring 11 and must be adjusted again after the bicycle has resumed moving forward. In view of the above problems, the inventor thought about whether it is possible to adjust the shifting mechanism of the bicycle to break through the stereotypes and rules that "can only be switched when the bicycle is moving forward". Therefore, how to design a new bicycle mechanism to change the control mode of the shifting speed is an important subject to be explored and solved by the present invention.

In view of the fact that the bicycle can only be switched when the bicycle is forwarded, so that the user can not switch the speed limitation at any time according to the current road condition, the inventor manually tests the various structures of the bicycle by virtue of the experience of studying the bicycle structure for many years. Improvement and dismantling, after repeated experiments, finally designed a bicycle mechanism capable of reverse idling and rear shifting, which can provide a more convenient and humanized bicycle technology.

It is an object of the present invention to provide a bicycle mechanism capable of reverse idling for rear shifting, including a frame, at least one large toothed disk, a plurality of flywheels, a first rear derailleur, a second rear derailleur, and a chain. The frame is provided with a rear shift control lever, and a shift line is extended on the rear shift control lever; the spindle of the large toothed disc is pivotally connected to one of the riser, the lower tube and the lower fork of the frame. a connecting portion, and a crank is fixed at each end thereof, and each of the cranks is pivotally connected with a pedal, wherein the large toothed disc can rotate forward when the pedals are stepped forward; the spindles of the flywheels are two The end system is fixed at the junction of the rear lower fork and the rear upper fork of the frame, and the mandrel of the flywheel can only synchronously drive a rear wheel to rotate forward when the front wheel rotates, and the center of the flywheel is axially rearward When the rotation is idling, the rear wheel is not driven; one end of the first rear derailleur is fixed at the junction of the rear lower fork and the rear upper fork, and can be connected with the shift line, the first rear The other end of the transmission is pivotally provided with a first wheel plate, the first wheel plate Connecting a first steering wheel and a first idler wheel, the first steering wheel and the first idler wheel maintain a spacing; one end of the second rear derailleur is fixed to the rear lower fork, and can be connected to the shifting line Connected to the other end of the second rear derailleur, a second wheel plate is pivotally connected to the second wheel plate, and the second wheel plate is pivotally connected with a second steering wheel; the chain is sequentially engaged on the large gear wheel and the second steering wheel. One of the flywheels, the first steering wheel, the first idler gear and the large toothed disc to be stepped forward on the pedals, and the first rear derailleur and the second rear derailleur are controlled by the rear shifting When the shifting line of the lever is driven, and the shifting to the other flywheel, the first steering wheel shifts a predetermined chain portion of the chain that is to be engaged to the current flywheel to a vertical position of the other flywheel, so that the predetermined The chain portion cannot be engaged with a predetermined tooth on the current flywheel, and the predetermined tooth will pull the chain away from the current flywheel with the current forward rotation of the flywheel, so that the chain can Fully engaged to the other flywheel; otherwise, the pedals are stepped backwards The rear wheel is idling, and the first rear derailleur and the second rear derailleur are driven by the shift line of the rear shift control lever, and when shifting to another flywheel, the second steering wheel causes the chain to be engaged Disposing a predetermined chain portion of the flywheel to a vertical position of the other flywheel to the predetermined position The chain portion cannot be engaged with a predetermined gear tooth on the current flywheel, and the predetermined gear tooth will rotate the chain from the current flywheel with the current backward rotation of the flywheel, so that the chain can be completely Engage to the other flywheel.

For the sake of review, the reviewer can have a further understanding and understanding of the technical, structural features and purposes of the present invention. The embodiments are described in conjunction with the drawings, which are described in detail as follows:

1‧‧‧Bicycle

11‧‧‧Spindle

111‧‧‧ crank

112‧‧‧ pedal

12‧‧‧Flywheel

120‧‧‧Predetermined gear teeth

13‧‧‧Chain

130‧‧‧Predetermined chain

14‧‧‧ Rear derailleur

15‧‧‧ grip

16‧‧‧ Rear shift lever

160‧‧‧Transmission line

161‧‧‧ mode switch button

21‧‧‧First rear derailleur

210‧‧‧First round board

211‧‧‧First control wheel

212‧‧‧First idler

22‧‧‧Second rear derailleur

220‧‧‧second round board

221‧‧‧Second control wheel

222‧‧‧Second idler

223‧‧‧track slot

224‧‧‧Roller

51‧‧‧Front shift arm

52‧‧‧ rear shift arm

A1‧‧‧ riser

A2‧‧‧Under the tube

A3‧‧‧Upper tube

A4‧‧‧ rear fork

A5‧‧‧After fork

P1, P2‧‧‧ departure points

1 is a schematic view of a conventional bicycle mechanism; FIG. 2 is a schematic view of a bicycle mechanism of the present invention; FIG. 3 is a schematic view of a chain operation of the bicycle mechanism of the present invention; and FIG. 4 is a schematic view showing a idling state of the bicycle mechanism of the present invention; Figure 5 is a structural view of a transmission of the bicycle mechanism of the present invention; and Figure 6 is a schematic view of another embodiment of the present invention.

The present invention is a bicycle mechanism capable of reverse idling for rear shifting. Referring to Figures 1 and 2, which is a first preferred embodiment of the present invention, the bicycle mechanism includes a frame, at least one large sprocket 11 A plurality of flywheels 12, a first rear derailleur 21, a second rear derailleur 22, and a chain 13. A rear shift control lever 16 is disposed on the frame adjacent to the grip 15, and the rear shift control lever 16 is extended with a shift line 160. When the user rotates or toggles the rear shift control lever 16, the rear The shifting lever 16 can pull or loosen the shifting line 160. Since the internal structure of the rear shifting lever 16 is well known in the art, it will not be described herein.

The spindle of the large toothed disc 11 is pivotally connected to a joint of one of the riser A1, the lower tube A2 and the rear lower fork A4 of the frame, and a crank 111 is fixed to each end of the spindle of the large toothed disc 11 respectively. Each of the cranks 111 is pivotally connected with a pedal 112 for driving the large-sized sprocket 11 to rotate forward (hereinafter referred to as "forward rotation") through the cranks 111 when the pedals 112 are stepped forward; The diameter of the flywheel 12 is different, and the ends of the mandrel are fixed at the junction of the rear lower fork A4 and the rear upper fork A5 of the frame, and the spindle of the flywheel 12 can only be rotated forward. Synchronously driving a rear wheel to rotate forward, and the heart of the flywheel 12 is idling when rotated axially backward (hereinafter simple Called "reverse rotation"), it does not drive the rear wheel.

Referring to FIGS. 1~3, one end of the first rear derailleur 21 is fixed at the junction of the rear lower fork A4 and the rear upper fork A5, and the other end is pivotally provided with a first wheel plate 210 (cage plate) The first wheel plate 210 is pivotally connected with a first steering wheel 211 and a first idler pulley 212. The first steering wheel 211 and the first idler 212 are spaced apart from each other. One end of the first rear derailleur 21 can be connected to the shift line 160 of the rear shift control lever 16, and when the rear shift control lever 16 tightens or loosens the shift line 160, the position of the first steering wheel 211 The movement is synchronously along the direction of the mandrel of the flywheels 12 to correspond to one of the flywheels 12.

One end of the second rear derailleur 22 is fixed to a position adjacent to the rear lower fork A4 (also directly locked to the rear lower fork A4), and the other end is pivotally provided with a second wheel plate 220, the second wheel A second steering wheel 221 is pivotally connected to the plate 220. One end of the second rear derailleur 22 can also be connected to the shift line 160 of the rear shift control lever 16, and when the rear shift control lever 16 tightens or loosens the shift line 160, the position of the second steering wheel 22 will follow The directions of the mandrels of the flywheels 12 are synchronously moved to correspond to one of the flywheels 12. The chain 13 is sequentially engaged on the large chainring 11, the second steering wheel 221, the flywheel 12, the first steering wheel 211, the first idler gear 212 and the large toothed disc 11 to enable the components to rotate synchronously. .

The shifting technology realized by the present invention is a second shifting mechanism when the "reverse idling" is added to the conventional shifting mechanism, that is, when the pedal is "sliding in the forward direction" to advance the bicycle, the present invention mainly transmits The first rear derailleur 21 performs shifting switching, and the principle thereof is substantially the same as that of the prior art shown in FIG. 1. When the pedal is "reversely rotated" and the bicycle is in the idling state, it is mainly transmitted through the second rear derailleur 22. Variable speed switching. In order to make the review committee easier to understand, it is explained in the prior art that if the user switches the shift when the pedal 112 is "reversely rotated", the reason for the "falling" is as follows.

Please refer to Figures 1~3 for a simplified schematic diagram of the bicycle structure. (In order to clearly demonstrate the principle of shifting, only the large chain gear 11, the flywheel 12 and the first rear derailleur 21 and the second are retained in FIG. For example, the control wheel and the idler on the transmission 22 are switched to the "low gear" as an example. When the user steps on the pedal 112 and simultaneously switches the rear shift lever 16, the shift line 160 will Pulling the rear derailleurs 21, 22 to make the rear derailleurs 21, 22 Shifting to another flywheel 12 (ie, shifting to the vertical position of the other flywheel 12), at this time, as shown in Figures 3 and 4A, the "first steering wheel 211" will cause the chain 13 to be engaged to A predetermined chain portion 130 of the flywheel 12 is currently displaced to the vertical position of the other flywheel 12 such that the predetermined chain portion 130 is unable to engage a predetermined tooth 120 on the flywheel 12.

嗣, during the subsequent forward rotation, the predetermined gear teeth 120 will be separated from the current flywheel 12 by the forward rotation of the flywheel 12, so that the chain portion of the chain 13 is detached from the current flywheel 12 The chain 13 can be completely engaged to the other flywheel 12, thereby smoothly completing the shifting. On the other hand, if it is in the "reverse rotation" and the second rear derailleur 22 is not provided, since the predetermined tooth 120 on the flywheel 12 is now "to the current flywheel 12 has been engaged with the chain 13 The chain portion is displaced in the opposite direction, so that the chain 13 cannot be aligned with the rotation, so that the chain 13 will be "chained" due to the simultaneous engagement with the flywheels 12 of different sizes.

Referring to Figures 1 to 3 and 4A, in another case, in the case where only the first rear deraleur 21 is provided on the bicycle, the chain 13 is disengaged from the current flywheel 12 when the shift is switched. The point P1" is located below the current flywheel 12. (As shown in Fig. A4, the actual break point P1 varies depending on the position and size of the flywheel 12, and the structural change is highlighted, 4A In the figure, the position of the flywheel 12 is about the lower left corner. Therefore, when "turning in the forward direction" (such as the solid arrow shown in Fig. 3), the first rear derailleur 21 will have the chain 13 The chain portion of the switching position (i.e., the lower portion of the chain 13) is fed into the other flywheel 12 in the correct direction to complete the shifting smoothly; and when "reverse rotation" (such as the hollow arrow shown in Fig. 3) Since the first rear derailleur 21 pulls the "current chain portion of the flywheel 12" toward the "other flywheel 12", it cannot prevent the "spindle 11 from being sent to the current one." The direction of the chain portion of the flywheel 12, so that different parts of the chain 13 correspond to different flywheels 12 respectively. Under natural causes "off the chain" situation, but can not shift smoothly.

Since the bicycle mechanism of the present invention incorporates the second rear derailleur 22, another "disengagement point" P2 is created in the "reverse rotation" to avoid the aforementioned "dropping" situation, see the first item. As shown in FIGS. 3 and 4B, when the pedals 112 are stepped backward, the rear wheels are idling, and the first rear derailleur 21 and the second rear derailleur 22 are driven by the shift line 160 of the rear shift control lever 16, When shifting to another flywheel 12, the "second steering wheel 22" will displace a predetermined chain portion 130 of the chain 13 that is about to be engaged to the current flywheel 12 to the The vertical position of the other flywheel 12 prevents the predetermined chain portion 130 from engaging with a predetermined tooth 120 on the flywheel 12, and the predetermined tooth 120 will rotate backward with the current flywheel 12 The chain 13 is disengaged from the current flywheel 12 so that the chain 13 can be completely engaged to the other flywheel 12 and smoothly shifted. In this way, the user can shift the chain 13 from the small flywheel 12 to the large flywheel 12 when the bicycle is parked in a red light, so that the bicycle can greatly increase the torque of the rear wheel when the green light starts, so that the starting is more labor-saving and Smooth.

As is clear from the second to third figures, with the design of the second rear derailleur 22, in the "reverse rotation", in addition to a disengagement point P1 generated by the first rear derailleur 21, the current flywheel Another detachment point P2 is generated in the upper half of the 12, whereby the second rear derailleur 22 can feed the chain 13 after the adjustment direction to the other flywheel 12, so that the problem of the chain drop can be avoided.

In the first preferred embodiment of the present invention, the second rear derailleur 22 is modified from a transmission model of RD-A070 manufactured by Sansida Co., Ltd., as shown in Figures 2 and 5, Figure 5 A top plan view of the second rear derailleur 22 includes a front shifting arm 51 and a rear shifting arm 52. One end of the front shifting arm 51 is coupled to the shifting line 160. The rear shifting arm 52 is connected to the other end of the front shifting arm 51, and the second steering wheel 221 is pivotally mounted thereon. The inventor removes the original second idler on the RD-A070 rear derailleur, and the second control The second wheel plate 220 on the wheel 221 is cut in half to serve as one of the track grooves 223 (in the present embodiment, there are two second wheel plates 220, so that a track groove 223 can be formed), and the track A roller 224 is disposed between the slots 223 (the two ends of the roller 224 are pivotally connected to the second wheel plates 220), and the roller 224 can support the chain 13 to ensure stability when the chain 13 is displaced. When the shifting line 160 is relaxed or pulled, the front shifting arm 51 will be able to rotate with it, thereby making the rear shifting arm 52 The second on the control wheel 221 to drive the chain 13.

Referring to FIG. 1 to FIG. 6 , in the foregoing embodiment, the second rear derailleur 22 is only provided with a second steering wheel 221 . In order to avoid excessive space occupied by the second rear derailleur 22 , In actual practice, the operator can also directly use the conventional rear derailleur as the second rear derailleur 22, that is, in other embodiments, the second wheel plate is pivotally connected with a second idler 222 ( Referring to the schematic diagram shown in FIG. 6 , the second control wheel 221 and the second idler 222 are also spaced apart to allow the chain 13 to pass between the two. The second steering wheel 221 and the second idler wheel 222, and the chain 13 can be sequentially engaged on the large chainring 11, the second steering wheel 221, the second idler wheel 222, the flywheel 12, and the first steering wheel. 211, the first idler gear 212 and the large toothed disc 11; thus, when the pedals 112 are stepped forward, the large chain gear 11 can pass through the chain 13, sequentially driving the second steering wheel 221, the second The idler wheel 222, the flywheel 12, the first steering wheel 211, and the first idler gear 212 are synchronously rotated forward; otherwise, when the pedals 112 are stepped backward, the large chainring 11 passes through the chain 13 and sequentially drives the first A steering wheel 211, the first idler gear 212, the flywheel 12, the second idler gear 222, and the second steering wheel 221 are synchronously rotated backward.

In addition, in order to improve the control performance of the second rear derailleur 22, the inventor has made many adjustments to the structure of the bicycle, and the features of each detail are explained one by one:

(1) The second wheel plate 220 is driven by a spring: in the transmission after the model RD-A070 manufactured by the company, the rear shift arm 52 is provided with a spring to drive the second wheel plate 220 upward. The inventor retains the spring so that the second wheel plate 220 can push the chain 13 slightly upward when shifting, so as to improve the smoothness of the displacement, but the spring force of the spring must be slightly adjusted (ie, less than the The existing spring on the first rear derailleur 51) prevents excessive elastic force from damaging the accuracy of the displacement.

(2) Synchronization of the rear derailleur: In the foregoing embodiment, the rear shift control lever 16 transmits the first rear derailleur 21 and the second rear derailleur 22 through the shift line 160, but the operator also The shifting line "non-synchronous" of the rear shifting lever 16 can be designed to control the first rear derailleur 21 and the second rear derailleur 22, for example, a mode switching button 161 is provided on the bicycle mechanism (eg, locked in the vehicle) The mode switching button 161 is disposed between the rear shifting lever 160 and the rear derailleurs 21 and 22 to adjust the rear shifting lever 160 to drive the first rear derailleur 21 and the second rear derailleur. The order of 22. As such, the mode shift knob 161 enables the first rear derailleur 21 to be first moved by the rear shift control lever 16 than the second rear derailleur 22 in a mode in which the bicycle travels forward and the pedals 112 are stepped forward. Controlling, shifting to another flywheel 12; conversely, when the bicycle is at rest and the pedals 112 are stepped back, the mode switching knob 161 enables the second rear derailleur 22 to be compared to the first rear derailleur 21 The rear shift control lever 16 controls and shifts to the other flywheel 12, whereby the shift stability in different modes can be further ensured without causing a problem of a chain or a chain.

(3) Installation position of the mode switching button 161: The mode switching button 161 can be fixed on the upper tube A3 or a grip 15 of the frame to facilitate the user to separately control the rear shifting speed in different modes. The lever 16 or the mode switching button 161. Of course, the mode switching button 161 can also be integrated with the rear shifting lever 16 (samely, the rear shifting lever 16 can also be disposed at the grip 15, the upper tube A3, and the like).

The mode switching button 161 has a plurality of design modes. For example, the rear shifting control lever 16 has two shifting lines respectively driving the two rear derailleurs 21 and 22. In general, the two shifting lines are synchronously linked. The mode switching button 161 can release the synchronous connection relationship, so that the user can manually activate the switching action of each of the rear derailleurs 21, 22 (eg, the rear shift control lever 16 or the mode switching button 161 is provided with two corresponding control buttons). Or; the shifting line 160 can be further divided into two sub-lines, and one of the toggle switches on the mode switching button 161 can change the direction or angle of force of the different sub-lines, thereby changing the respective rear derailleurs 21, 22 The timing of the drive.

The above description is only a preferred embodiment of the present invention, but the technical features of the present invention are not limited thereto, and those skilled in the relevant art can easily think of it after considering the technical content of the present invention. Equivalent changes should not depart from the scope of protection of the present invention.

11‧‧‧Spindle

111‧‧‧ crank

12‧‧‧Flywheel

13‧‧‧Chain

160‧‧‧Transmission line

161‧‧‧ mode switch button

21‧‧‧First rear derailleur

210‧‧‧First round board

212‧‧‧First idler

22‧‧‧Second rear derailleur

220‧‧‧second round board

221‧‧‧Second control wheel

A1‧‧‧ riser

A2‧‧‧Under the tube

A4‧‧‧ rear fork

A5‧‧‧After fork

Claims (9)

A bicycle mechanism capable of reverse idling for rear shifting includes: a frame on which a rear shift control lever is mounted, and a shift line extending from the rear shift control lever; at least one large toothed disc, the large chainring The heart shaft is pivotally connected to a joint of one of the riser, the lower tube and the rear lower fork of the frame, and a crank is fixed to each end of the frame, and each of the cranks is pivotally connected with a pedal to be In the case of the front stepping, the large toothed disc can rotate forward; a plurality of flywheels, the two ends of the flywheel of the flywheel are fixed at the junction of the rear lower fork and the rear upper fork of the frame, and the flywheel The mandrel can only synchronously drive a rear wheel to rotate forward when the front wheel rotates. The heart of the flywheel rotates axially and then rotates, which does not drive the rear wheel; a first rear derailleur is fixed at one end thereof. At the junction of the rear lower fork and the rear upper fork, and connected to the shifting line, the other end of the first rear derailleur is pivotally provided with a first wheel plate, and the first wheel plate is pivotally connected with a first a steering wheel and a first idler, the first steering wheel and the first idler remain a second rear transmission, one end of which is fixed to the rear lower fork and can be connected to the shift line, and the other end of the second rear derailleur is pivotally provided with a second wheel plate, the second wheel plate a second steering wheel is coupled; and a chain is sequentially engaged on the large toothed disc, the second steering wheel, one of the flywheels, the first steering wheel, the first idler gear and the large toothed disc; Accordingly, when the pedals are stepped forward, and the first rear derailleur and the second rear derailleur are driven by the shift line of the rear shift control lever, and the shift to another flywheel, the first steering wheel causes the A predetermined chain portion of the chain that is to be engaged to the current flywheel is displaced to a vertical position of the other flywheel, such that the predetermined chain portion cannot be engaged with a predetermined tooth on the current flywheel. 嗣, the predetermined tooth will rotate the current flywheel away from the current flywheel with the current forward rotation of the flywheel, so that the chain can be completely engaged to the other flywheel; otherwise, the pedals are stepped backwards The rear wheel is idling, and the first rear derailleur and the second rear derailleur are driven by the shift line of the rear shift control lever, and when shifting to another flywheel, the second steering wheel causes the chain to be engaged A predetermined chain portion connected to the current flywheel is displaced to a vertical position of the other flywheel, so that the predetermined chain portion cannot be engaged with a predetermined gear tooth on the current flywheel, and the predetermined gear tooth will follow The current backward rotation of the flywheel displaces the chain from the current flywheel, allowing the chain to fully engage the other flywheel. The bicycle mechanism of claim 1, wherein the second rear derailleur is provided with two second wheel plates, and a track groove can be formed between the second wheel plates. The bicycle mechanism of claim 2, wherein the second wheel plate is pivotally connected with a second idler wheel, and the second control wheel and the second idler wheel are also spaced apart to allow the chain to pass therethrough. And respectively engaging the second steering wheel and the second idler, and the chain can be sequentially engaged on the large chainring, the second steering wheel, the second idler, the flywheel, the first steering wheel, The first idler wheel and the large toothed disc. The bicycle mechanism of claim 1, 2 or 3, wherein the rear shift control lever synchronously controls the first rear derailleur and the second rear derailleur to shift from the current flywheel to the other flywheel. The bicycle mechanism of claim 1, 2 or 3, wherein the rear shift control lever asynchronously controls the first rear derailleur and the second rear derailleur to shift from the current flywheel to the other flywheel. The bicycle mechanism of claim 5, further comprising a mode switching button fixed to the frame between the rear shifting lever and the rear derailleur to adjust the rear shifting control The rod drives the sequence of the first rear derailleur and the second rear derailleur. The bicycle mechanism according to claim 6, wherein the rear shift lever or the mode switching button is fixed to an upper tube of the frame. The bicycle mechanism according to claim 6, wherein the rear shift lever or the mode switching button is fixed to a grip of the frame. The bicycle mechanism according to claim 6, wherein the mode switching button is integrated with the rear shifting control lever.