Three-speed bicycle transmission structure and transmission method thereof

The present invention discloses a three-speed bicycle transmission structure and the transmission method thereof, aiming at overcoming the drawbacks that the overall structure of the prior art cannot support three-speed transmission in a small space and requires high manufacturing costs. The present invention comprises a central shaft, a three-speed transmission structure and a gearbox housing; wherein, the three-speed transmission structure comprises a centrifugal clutch shifting mechanism, a composite planetary gear ring and a first-level transmission mechanism, a second-level transmission mechanism and a third-level transmission mechanism. The centrifugal clutch shifting mechanism is used for shifting among the above three levels of transmission mechanisms to carry out three-speed transmission, and the composite planetary gear ring is used for cooperating with the centrifugal clutch shifting mechanism to realize partial gear shifting. The present invention realizes simplified structure, compressed structure space, improved transmission efficiency and cost saving.

TECHNICAL FIELD

The present invention relates to the technical field of bicycle gear-shifting structures. More specifically, the present application relates to a three-speed bicycle transmission structure and the transmission method thereof.

BACKGROUND

In recent years, a technological revolution in bicycle electrification has emerged worldwide. The realization of electrification technology in traditional bicycles means the use of new electric parts have been added on the basis of traditional man-powered bicycles, such as motors, batteries, electronic controls, torque sensors and speed sensors. When the cyclist starts, climbs, or encounters greater resistance, the electric system feeds back data collected by the torque sensor to the motor controller, so that the motor can provide the cyclist with auxiliary power to gain better riding experience.

The new technology has greatly improved the acceleration performance of bicycles, and it also requires the transmission to respond in a smarter and faster way. However, the traditional manual control transmissions from the two global giants, Shimano of Japan and SRAM of the United States, is targeted at traditional human-powered bicycles. To gain a more comfortable pedaling frequency; the cyclists are required to judge the time for gear shifting by themselves, and constantly shift gears as the speed varies. Assisted by the electric power technology; it even increases the gear-shifting frequency to serve for comfortable pedaling. The traditional manual control transmission has become a burden instead of help to new technologies.

To overcome the drawbacks, a three-speed transmission method and structure with automatic shifting is proposed particularly to meet the needs of new bicycle technologies. This automatic gear-shifting structure overcomes the draw back of traditional manual control transmissions that require manual gear shifting, and can perfectly match electric bicycles. It is able to automatically shift gears according to the rider's speed and improve the comfort of pedaling.

Its novelty lies in the three-speed transmission that relies on only one set of planetary gear mechanism, which is extremely small in space occupation and parts size. It not only excels in automatic transmission, but also meets the needs for light-weight and low-cost bicycles with high transmission efficiency.

SUMMARY

Accordingly; the main object of the present invention is to provide a three-speed bicycle transmission structure and the transmission method thereof with automatic gear shifting.

To realize the above-mentioned object, the present invention brings forward the technical proposal comprising a central shaft (1), a three-speed transmission structure and a gearbox housing (6), wherein:

Further, the outer side of the central shaft is fixedly connected with a sun gear, and the interior of the composite planet carrier is rotatably connected with a planet gear set adapted to the sun gear;

In summary, the beneficial technical effects of the present invention are;

EMBODIMENTS

The present invention is described in further detail below in connection with the drawings.

Referring to FIG. 1 and FIG. 2, a three-speed bicycle transmission structure comprises the central shaft 1, the three-speed transmission structure and the gearbox housing 6 for power output. The three-speed gear-shifting structure includes the centrifugal clutch shifting mechanism 2 for switching output modes and the composite planetary gear ring 7 cooperating with the centrifugal clutch shifting mechanism 2 to realize partial gear shifting. The three-speed gear-shifting structure further includes the first-level transmission mechanism 3, the second-level transmission mechanism 4 and the third-level transmission mechanism 5 for realizing integral multi-speed transmission. The centrifugal clutch shifting mechanism 2 is used for shifting among the above transmission mechanisms and to carry out different modes of transmission. The first centrifugal shifting mechanism 41 cooperating with the composite planetary carrier 7 is intended for shifting the deceleration transmission into normal transmission, and the second centrifugal shifting mechanism 51 cooperating with the composite planetary carrier 32 is intended for shifting the normal transmission into acceleration transmission.

When the hub rotation reaches the design speed, the centrifugal force of the centrifugal block exceeds the spring force, and the centrifugal block opens and drives the clutch plate to rotate counterclockwise, and the pawl locking position on the clutch plate fails, the second-speed pawl springs off and engages with the inner ratchet composite planetary third gear ring 73; as a result, the second drive seat and the inner ratchet composite planetary third gear ring 73 carry out power transmission. The transmission speed at this time is faster than the output speed of the previous first-speed transmission through the planetary mechanism. As the power is transmitted through a one-way clutch between the original planetary carrier and the second drive seat, when the second drive seat moves faster than the planetary carrier end, the clutch overrunning takes place, and the first-speed transmission fails, and the transmission power is replaced by the second-speed transmission, and the output speed is consistent with the input speed, the planetary mechanism does not participate in power transmission. The first-level transmission mechanism 3 and the third-level transmission mechanism 5 include the planetary transmission mechanism 31 for realizing the variable-speed transmission of the gearbox housing 6. The planetary transmission mechanism 31 includes the composite planetary carrier 32. The planetary transmission mechanism 31 acts for deceleration transmission and acceleration transmission separately in the first-level transmission mechanism 3 and the third-level transmission mechanism 5 respectively. The three-speed transmission mechanism realizes the transmission of the planetary transmission mechanism 31 in different ways through the centrifugal clutch shifting mechanism 2 cooperating with the composite planetary gear ring 7 and the composite planetary carrier 32. The second-level transmission mechanism 4 includes the first centrifugal shifting mechanism 41 for centrifugal clutch gear-shifting. The third-level transmission mechanism 5 includes the second centrifugal shifting mechanism 51 for centrifugal clutch shifting. The first centrifugal shifting mechanism 41 cooperates with the composite planetary gear ring 7 to shift the deceleration transmission into normal transmission. The second centrifugal shifting mechanism 51 cooperates with the composite planetary carrier 32 to shift the normal transmission into acceleration transmission. When the speed of the third-speed centrifugal block reaches the design speed, the centrifugal block opens to push the clutch plate to rotate counterclockwise as shown in the figure. The third-speed pawl breaks away from the clutch plate locking, and springs off inwardly; and engages with the ratchet teeth on the internal planetary carrier. At this time, the first-level drive seat directly transmits power to the planetary carrier. The original planetary deceleration mechanism shifts to the mode that the sun gear is fixed, the planetary carrier inputs, and the third gear ring 73 outputs. The output speed becomes higher than the input speed. The specific acceleration ratio can be adjusted by different gear parameters. Power is transmitted to the hub housing through the planetary gear ring outputting power to connect with the rear-end power output route of the preceding second-speed planetary gear ring. However, the opening of the third-speed pawl results in the inwardly rotation of the pawl locking spring, and the force originally exerted to the first-speed pawl disappears, resulting in clutch overrunning; and the power transmission route of the original second-speed pawl shifts from the output of the first-speed pawl to that of the third-speed pawl, realizing the third-speed transmission.

Referring to FIG. 4, the composite planetary gear ring 7 internally includes the first gear ring 71, the second gear ring 72 and the third gear ring 73 fixed to each other. The three gear rings are concentrically arranged in the axial space of the transmission. The tooth profile functions of the first gear ring 71, the second gear ring 72 and the third gear ring 73 are different. The first gear ring 71, the second gear ring 72 and the third gear ring 73 are fixed connection structures. The tooth form of the first gear ring 71 is an involute gear. which is an outer gear ring among the three elements for the planetary transmission of the planetary transmission mechanism 31. The second gear ring 72 is in the tooth form of an inner ratchet, and the third gear ring 73 an outer ratchet. The tooth number of the composite planetary gear ring 7 can be adjusted according to the actual situation, so as to ensure that the overall rotational speed can be adjusted in manufacturing.

Referring to FIG. 3 and FIG. 5, the sun gear 11 is fixedly connected to the outer side of the central central shaft 1. The planetary gear set 33 adapted to the sun gear 11 is rotatably connected to the inner side of the composite planet carrier 32. The outer side of the planetary gear set 33 meshes with the first gear ring 71, and the inner side of the planetary gear set 33 meshes with the sun gear 11. The first gear ring 71 and the planetary gear set 33 that is fixedly connected to the composite planet carrier 32, and the sun gear 11 on the central shaft 1 form the planetary variable-speed transmission structure. One end of the composite planet carrier 32 is fixedly connected to the fourth gear ring 34 for cooperating with the second centrifugal shifting mechanism 51 to realize acceleration transmission. The fourth gear ring 34 is a ratchet ring. The first-speed transmission 3 includes inside the first drive disk 35 rotatably connected to the outer side of the central shaft 1. The outer side of the first drive disk 35 is fixedly connected with the first-speed drive block 36 that is hinged to the outer side first-speed transmission pawl 37 adapted to the second gear ring 72. A power locking mechanism 38 for reinforcement is provided on the inner side of the first-speed transmission pawl 37. The first-speed drive block 36 is located on the inner side of the second gear ring 72. The power locking mechanism 38 includes the mounting shaft 39 fixed on the upper end of the first drive disk 35, and the outer side of the mounting shaft 39 is rotatably connected with the power locking spring 310: one end of the power locking spring 310 is closely linked with the outer side first-speed transmission pawl 37. The first-speed transmission pawl 37 cooperates with the second gear ring 72 to form a one-way transmission locking structure, and the power locking spring 310 cooperates with the first-speed transmission pawl 37 to form a locking enforcement structure. The first pawl compression spring 311 for pressing and positioning the first-speed transmission pawl 37 is provided between the first-speed drive block 36 and the first-speed transmission pawl 37. The second gear ring 72 and the first-speed transmission pawl 37 on the outer side of the first drive disk 35 form the one-way transmission of the first-speed drive blocks of the first-level transmission mechanism 3 and the second-level transmission mechanism 4 toward the composite planetary gear ring 7. Preferably, the power locking mechanism 38 adopts the power locking spring 310 which is one of the varied locking structures, and the optimal structure is used in the present design; the first-speed transmission pawl 37 cooperates with the second gear ring 72 to form a locking structure of one-way transmission, and the power locking spring 310 cooperates with the first-speed transmission pawl 37 to form a locking reinforcement structure.

Referring to FIG. 6, the first centrifugal shifting mechanism 41 includes the second drive seat 42 fixed on the inside of the gearbox housing 6. The side of the second drive seat 42 close to the composite planetary gear ring 7 is fixedly connection with the second-speed drive block 43. The second-speed transmission pawl 44 for engaging the third gear ring 73 is hinged to the inside of the second drive block 43, and the side of the second drive block 43 close to the second-speed transmission pawl 44 is fixedly connected with the return spring 45. The side of the return spring 45 away from the second-speed drive block 43 is hinged to the second-speed transmission pawl 44. The third gear gear 73 is unidirectionally connected to the second-speed transmission pawl 44 on the second drive seat 42, and cooperates with the first centrifugal shifting mechanism 41 to achieve the power transmission and disconnection of one-way transmission. The composite planetary carrier 32 is fixedly connected to the input shaft with a one-way clutch on the other side of the fourth gear gear 34. Its function is to realize one-way transmission through the one-way clutch and the second drive seat 42. One-way transmission power is realized in the first-level transmission mechanism 3, while the second-level transmission mechanism 4 and the third-level transmission mechanism 5 realize clutch overrunning to disconnect the first-speed transmission power.

Referring to FIG. 5, the second-speed centrifugal control mechanism 46 for controlling the second-speed transmission pawl 44 is hinged on one side of the second drive seat 42 close to the composite planetary gear ring 7. When the second-speed centrifugal control mechanism 46 does not reach the set point and generates no centrifugal clutching, the second-speed transmission pawl 44 shrinks and does not engage with the third gear ring 73. When the second-speed centrifugal control mechanism 46 reaches the set point and generates centrifugal clutching, the second-speed transmission pawl 44 springs off to engage with the third gear ring 73. The second centrifugal shifting mechanism 51 internally includes the third-speed transmission pawl 52 that is hinged on a side of the first-speed drive block 36 away from the first-speed transmission pawl 37. There second centrifugal compression spring 53 for pressing and positioning the third-speed transmission pawl 52 is set between the third-speed transmission pawl 52 and the first-speed drive block 36. The outer side of the third-speed transmission pawl 52 is closely linked with the other end of the power locking spring 310. The third-speed centrifugal control mechanism 54 for controlling the third-speed transmission pawl 52 is provided on one side of the first drive disk 35 close to the first-speed drive block 36. The fourth gear ring 34 combines with the inner side one-speed transmission pawl 37 on the first drive disk 35 to form a one-way transmission mechanism. The composite planetary carrier 32 is fixedly connected with the input shaft with a one-way clutch on the other side of the fourth gear ring 34, and its function is to realize one-way transmission through the one-way clutch and the second drive seat 42, to transmit power in one way in the first-level transmission mechanism 3, to realize clutch overrunning and disconnection of the first-speed transmission power in the second-level transmission mechanism 4 and the third-level transmission mechanism 5. When the speed of the third-speed centrifugal control mechanism 54 does not reach the set point and generates no centrifugal clutching, the third-speed transmission pawl 52 shrinks and does not engage with the fourth gear ring 34, and the first-speed transmission pawl 37 engages with the second gear ring 72. When the speed of the third-speed centrifugal control mechanism 54 reaches the set point and centrifugal clutching occurs, the third-speed transmission pawl 52 springs off and engages with the fourth gear ring 34, and the first-speed transmission pawl 37 shrinks and breaks away from the second gear ring 72 or overruns the state. As a result, the centrifugal force of the centrifugal block is less than the force of the spring, and the centrifugal block closes inwardly, pushing the clutch plate to rotate clockwise. As it decelerates, the hub housing moves faster than the input end under the rotation inertia, that is, the ratchet ring moves faster than the pawl, and the gear ring pushes away the pawl, and the clutch plate just clutches into the pawl under the force of the centrifugal block shrinking inwardly, and the pawl enters a closed state. The transmission power is disconnected and upshifted. The area of clutch overrunning due to previous upshifting starts to mesh and transmits power, and the outer side of the third-speed transmission pawl 52 closely links with the other end of the power locking spring 310.

The working principles are as follows:

While a presently preferred embodiment of the present invention have been described herein, it should be understood by persons skilled in the art that the invention is not limited to such embodiments; but on the contrary, it is intended to cover such alternatives, modifications and equivalents of the structures, shapes and working principles contained herein, without departing from the spirit and scope thereof.