1. The utility model provides a multistage change gear box, includes box (1), input shaft (2), output shaft (3) and variable speed unit (4), and input shaft (2) both ends link to each other with the bicycle footboard, output shaft (3) link to each other with the wheel, link to each other its characterized in that through variable speed unit (4) between input shaft (2) and the output shaft (3): the variable speed unit (4) comprises a driving gear set (5), a driven gear set (6), a transmission gear set (7) and a variable speed gear set (8), wherein the driving gear set (5) comprises a plurality of driving gears (51), the driven gear set (6) comprises a plurality of driven gears (61), the transmission gear set (7) comprises transmission gears (71) with the number being the sum of the driving gears (51) and the driven gears (61), the variable speed gear set (8) comprises a variable speed driving gear (81), a variable speed driven gear (82), a driving variable speed shifting fork rod (83) with the number being consistent with that of the driving gears (51) and a driven variable speed shifting fork rod (84) with the number being consistent with that of the driven gears (61), the driving gear set (5) is sleeved on the input shaft (2), the driven gear set (6) is sleeved on the output shaft (3), and the transmission gear set (7) is fixed on the box body (1) through a bearing, the speed change gear set (8) is fixed on the box body (1) through a bearing, each driving gear (51) and each driven gear (61) are respectively meshed with a corresponding transmission gear (71), driving ratchet wheels (21) with the number consistent with that of the driving gears (51) are arranged on the input shaft (2), the driving ratchet wheels (21) synchronously rotate along with the input shaft (2), ratchets are arranged below the driving ratchet wheels (21), ratchets are arranged above the driving gears (51), the driving ratchet wheels (21) are downwards pushed through corresponding driving speed change fork shifting rods (83) to realize meshing with the driving gears (51), driven ratchet wheels (31) with the number consistent with that of the driven gears (61) are arranged on the output shaft (3), the driven ratchet wheels (31) synchronously rotate along with the output shaft (3), ratchets are arranged below the driven ratchet wheels (31), and ratchets are arranged above the driven gears (61), the driven ratchet wheel (31) is pushed downwards through a corresponding driven shifting fork rod (84) to realize meshing with the driven gear (61), a driving jack (811) is arranged on the shifting driving gear (81), the edge of the driving jack (811) is of an inclined plane structure, the lower end of the driving shifting fork rod (83) is of an arc end surface structure, the driving shifting fork rod (83) enables the lower end to be inserted into the driving jack (811) through the elastic downward action of a spring, and along with the rotation of the shifting driving gear (81), the arc lower end of the driving shifting fork rod (83) is ejected out of the driving jack (811) through the edge of the driving jack (811) which is of an inclined plane structure, a driven slot (821) is arranged on the shifting driven gear (82), the edge of the driven slot (821) is of an inclined plane structure, the lower end of the driven shifting fork rod (84) is of an arc end surface structure, and the driven shifting fork rod (84) enables the lower end to be inserted into the driven slot (821) through the elastic downward action of the spring, and the circular arc lower end of the driven gear shifting fork rod (84) is ejected out of the driven slot (821) by the edge of the driven slot (821) in an inclined surface structure along with the rotation of the gear shifting driven gear (82).

2. The bicycle bottom bracket inner transmission of claim 1, wherein: the two ends of the driving speed change shifting fork rod (83) and the driven speed change shifting fork rod (84) are respectively sleeved on the box body (1) in a penetrating way.

3. A bicycle bottom bracket inner gearbox according to claim 1 or 2, wherein: the gear-shifting mechanism is characterized in that the driving shifting fork rods (83) are sequentially arranged along the circumferential direction of the gear-shifting driving gear (81), driving insertion holes (811) which are uniformly distributed along the circumferential direction are formed in the gear-shifting driving gear (81), the distance between every two adjacent driving insertion holes (811) is consistent with the distance between every two driving shifting fork rods (83) at the head and the tail, the driven shifting fork rods (84) are sequentially arranged along the circumferential direction of the gear-shifting driven gear (82), driven slots (821) which are provided with arc-shaped structures along the circumferential direction are formed in the gear-shifting driven gear (82), the arc-shaped length of each driven slot (821) is consistent with the distance between every two adjacent driving insertion holes (811), and the distance between every two adjacent driven shifting fork rods (84) is consistent with the arc-shaped length of each driven slot (821).

Background

With the continuous progress of bicycle speed changing technology, the requirement on a gearbox is higher and higher, the stability and the reliability of the bicycle speed changer are greatly improved from the initial chain gear set speed changer to the middle shaft speed changer at the present stage, the speed regulation range and the stability of the existing bicycle middle shaft speed changer are in inverse proportion to the size and the reliability of the speed changer, how to realize the middle shaft speed changer with large speed regulation range, high stability and high reliability, and small size becomes the biggest obstacle of the current middle shaft speed changer technology development.

Disclosure of Invention

The invention provides a gearbox in a bicycle center shaft, which has the advantages of simple structure, large speed regulation range, high stability, high reliability and small volume.

In order to solve the technical problems, the invention adopts the following technical scheme: a speed changing box in a middle shaft of a bicycle comprises a box body, an input shaft, an output shaft and a speed changing unit, wherein two ends of the input shaft are connected with pedals of the bicycle, the output shaft is connected with wheels, the input shaft and the output shaft are connected through the speed changing unit, the speed changing unit comprises a driving gear set, a driven gear set, a transmission gear set and a speed changing gear set, the driving gear set comprises a plurality of driving gears, the driven gear set comprises a plurality of driven gears, the transmission gear set comprises transmission gears with the number equal to the sum of the driving gears and the driven gears, the speed changing gear set comprises speed changing driving gears, speed changing driven gears, driving speed changing fork rods with the number equal to that of the driving gears and driven speed changing fork rods with the number equal to that of the driven gears, the driving gear set is sleeved on the input shaft, the driven gear set is sleeved on the output shaft, and the transmission gear set is fixed on the box body through a bearing, the speed change gear set is fixed on the box body through a bearing, each driving gear and each driven gear are respectively meshed with corresponding transmission gears, driving ratchets with the same number as the driving gears are arranged on the input shaft and synchronously rotate along with the input shaft, ratchets are arranged below the driving ratchets, ratchets are arranged above the driving gears, the driving ratchets are downwards pushed through corresponding driving speed change shifting fork rods to realize the meshing with the driving gears, driven ratchets with the same number as the driven gears are arranged on the output shaft and synchronously rotate along with the output shaft, ratchets are arranged below the driven ratchets, ratchets are arranged above the driven gears, the driven ratchets are downwards pushed through corresponding driven speed change shifting fork rods to realize the meshing with the driven gears, driving jacks are arranged on the speed change driving gears, and the edges of the driving jacks are of an inclined plane structure, the lower end of the driving speed change shifting fork rod is of an arc-shaped end face structure, the driving speed change shifting fork rod enables the lower end to be inserted into the driving jack through the downward action of spring elasticity, the arc-shaped lower end of the driving speed change shifting fork rod is pushed out of the driving jack through the edge of the driving jack in an inclined plane structure along with the rotation of the speed change driving gear, a driven slot is arranged on the speed change driven gear, the edge of the driven slot is of an inclined plane structure, the lower end of the driven speed change shifting fork rod is of an arc-shaped end face structure, the lower end of the driven speed change shifting fork rod is inserted into the driven slot through the downward action of the spring elasticity, and the arc-shaped lower end of the driven speed change shifting fork rod is pushed out of the driven slot through the edge of the driven slot in an inclined plane structure along with the rotation of the speed change driven gear.

The beneficial effects provided by the invention are as follows: by rotating two speed change gears of the speed change gear set, different driving speed change fork rods are inserted into the driving insertion holes under the elastic downward action of the springs, and meanwhile, corresponding driving ratchet wheels are pushed to move downward to be meshed with corresponding driving gears, so that the driving gears are driven by the input shaft to rotate coaxially and drive transmission gears matched with the driving gears to rotate together, so that the transmission gear set rotates integrally, then driven ratchet wheels pushed downward by driven speed change fork rods falling into driven slots are meshed with the corresponding driven gears, so that the driven gears and the output shaft rotate coaxially, the transmission force of the driven gears is transmitted by the transmission gears meshed with the driven gears in the integral rotation process of the transmission gear set, and finally, the purpose of transmission from the input shaft to the output shaft is achieved, except for a driving gear rotating coaxially with the input shaft and a driven gear rotating coaxially with the output shaft, other driving gears and driven gears rotate under the driving of the integral rotation of the transmission gear set, but are in a slipping state with the input shaft and the output shaft, the transmission is not influenced, and when different transmission ratios need to be adjusted, a common adjusting knob arranged at the position of a handle can be adopted, a speed change gear set is pulled by a steel wire to rotate, so that different driving speed change fork rods are inserted into the driving insertion holes, different driven speed change fork rods are inserted into the driven insertion holes, different driving gears and the input shaft rotate coaxially, different driven gears and the output shaft rotate coaxially, in the speed change process, the circular arc end surface structures at the lower ends of the driving speed change fork rods and the driven speed change fork rods are matched with the driving insertion hole edges in an inclined surface structure and the driven insertion hole edges in an inclined surface structure, can easily realize changing, this kind of structural stability is good, and control is convenient, simultaneously just can increase the variable speed scope in a large number through the quantity that increases driving gear and driven gear, the gear number of its variable speed is by the quantity product of driving gear and driven gear, and through being regarded as transition transmission by drive gear group, can the significantly reduced intensity requirement to the gear, and service life is prolonged, when avoiding traditional big torsion when stepping on the board to move the input shaft, only through the damage of the produced big torsion of one-level transmission to the gear.

Furthermore, the two ends of the driving speed change shifting fork rod and the two ends of the driven speed change shifting fork rod are both penetrated through and sleeved on the box body, and the positioning accuracy and stability of the driving speed change shifting fork rod and the driven speed change shifting fork rod can be improved by penetrating and sleeving the two ends of the driving speed change shifting fork rod and the driven speed change shifting fork rod on the box body.

Furthermore, the plurality of driving shifting fork rods are sequentially arranged along the circumferential direction of the speed-changing driving gear, the speed-changing driving gear is provided with a plurality of driving jacks which are uniformly distributed along the circumferential direction, the distance between every two adjacent driving jacks is consistent with the distance between every two driving shifting fork rods at the head and the tail, the plurality of driven shifting fork rods are sequentially arranged along the circumferential direction of the speed-changing driven gear, the speed-changing driven gear is provided with a driven slot which is provided with an arc-shaped structure along the circumferential direction, the arc-shaped length of the driven slot is consistent with the distance between every two adjacent driving jacks, the distance between every two adjacent driven shifting fork rods is consistent with the arc-shaped length of the driven slot, and the speed-changing gear set with the structure can preferentially adjust the transmission ratio of the driving gear during speed adjustment, and after all driving gear ratios are adjusted for one wheel, the transmission ratio of the primary driven gear can be driven, then the transmission ratio of the primary driven gear is adjusted after the transmission ratio of all driving gears of one wheel is adjusted, the whole transmission ratio can be gradually increased or decreased, and the structure is very reasonable and reliable.

The invention is described in further detail below with reference to the figures and examples.

Drawings

FIG. 1 is a schematic view of a transmission case in a bottom bracket of a bicycle according to the present invention at a minimum transmission ratio.

Fig. 2 is a schematic view of the structure of fig. 1 with the case removed.

FIG. 3 is a schematic view of the present invention showing the maximum transmission ratio of the transmission case in the bottom bracket of the bicycle.

Fig. 4 is a schematic view of the structure of fig. 3 with the case removed.

Fig. 5 is a schematic orthographic view of fig. 4.

Fig. 6 is a schematic structural view of the speed change gear set of fig. 4.

Detailed Description

As shown in fig. 1, 2, 3, 4, 5 and 6, the present invention provides a bicycle bottom bracket inner transmission, which comprises a box 1, an input shaft 2, an output shaft 3 and a transmission unit 4, wherein two ends of the input shaft 2 are connected to bicycle pedals, the output shaft 3 is connected to wheels, the input shaft 2 and the output shaft 3 are connected to each other through the transmission unit 4, the transmission unit 4 comprises a driving gear set 5, a driven gear set 6, a driving gear set 7 and a transmission gear set 8, the driving gear set 5 comprises three driving gears 51, the driven gear set 6 comprises four driven gears 61, the transmission gear set 7 comprises driving gears 71 with the sum of the driving gears 51 and the driven gears 61, the transmission gear set 8 comprises a transmission driving gear 81, a transmission driven gear 82, driving shift fork rods 83 with the same number as that of the driving gears 51 and driven shift fork rods 84 with the same number as that of the driven gears 61, the driving gear set 5 is sleeved on the input shaft 2, the driven gear set 6 is sleeved on the output shaft 3, the transmission gear set 7 is fixed on the box body 1 through a bearing, the speed change gear set 8 is fixed on the box body 1 through a bearing, each driving gear 51 and each driven gear 61 are respectively meshed with the corresponding transmission gear 71, the input shaft 2 is provided with driving ratchets 21 with the number consistent with that of the driving gears 51, the driving ratchets 21 synchronously rotate along with the input shaft 2, ratchets are arranged below the driving ratchets 21, ratchets are arranged above the driving gears 51, the driving ratchets 21 are downwards pushed through corresponding driving speed change fork levers 83 to realize meshing with the driving gears 51, the output shaft 3 is provided with driven ratchets 31 with the number consistent with that of the driven gears 61, the driven ratchets 31 synchronously rotate along with, the driven gear 61 is provided with ratchets above, the driven ratchet 31 is pushed downwards by the corresponding driven shift fork lever 84 to realize meshing with the driven gear 61, the shift driving gear 81 is provided with a driving insertion hole 811, the edge of the driving insertion hole 811 is a slope structure, the lower end of the driving shift fork lever 83 is a circular arc end surface structure, the driving shift fork lever 83 is inserted into the driving insertion hole 811 by the downward action of the spring elasticity, and along with the rotation of the shift driving gear 81, the circular arc lower end of the driving shift fork lever 83 is pushed out of the driving insertion hole 811 by the slope structure of the edge of the driving insertion hole 811, the shift driven gear 82 is provided with a driven slot 821, the edge of the driven slot 821 is a slope structure, the lower end of the driven shift fork lever 84 is a circular arc end surface structure, the driven shift fork lever 84 is inserted into the driven slot 821 by the downward action of the spring elasticity, and along with the rotation of the speed change driven gear 82, the circular lower end of the driven shift fork rod 84 is ejected out of the driven slot 821 by the edge of the driven slot 821 in an inclined plane structure, the two ends of the driving shift fork rod 83 and the driven shift fork rod 84 are sleeved on the box body 1 in a penetrating way, the driving shift fork rods 83 are sequentially arranged along the circumferential direction of the speed change driving gear 81, the speed change driving gear 81 is provided with a plurality of driving insertion holes 811 uniformly distributed along the circumferential direction, the distance between two adjacent driving insertion holes 811 is consistent with the distance between two driving shift fork rods 83 at the head and the tail, the driven shift fork rods 84 are sequentially arranged along the circumferential direction of the speed change driven gear 82, the speed change driven gear 82 is provided with the driven slot 821 in an arc structure along the circumferential direction, the arc length of the driven slot 821 is consistent with the distance between two adjacent driving insertion holes 811, the spacing between two adjacent driven shift fork levers 84 corresponds to the arcuate length of the driven socket 821.

As shown in fig. 1 and 2, the driving shift fork 83 at the first position controls the uppermost driving gear 51 to engage with the driving ratchet 21, so that the highest primary transmission ratio is achieved between the driving gear 51 with the largest number of teeth and the transmission gear 71 with the smallest number of teeth, and the driven shift fork 84 at the fourth position controls the lowermost driven gear 61 to engage with the driven ratchet 31, so that the highest secondary transmission ratio is achieved between the transmission gear 71 with the largest number of teeth and the driven gear 61 with the smallest number of teeth, and the highest transmission ratio is achieved through the two-stage transmission.

As shown in fig. 3, 4, 5 and 6, the driving shift fork 83 at the third position controls the lowest driving gear 51 to mesh with the driving ratchet 21, so that the lowest primary transmission ratio is achieved between the driving gear 51 with the smallest number of teeth and the driving gear 71 with the largest number of teeth, and the driven shift fork 84 at the first position controls the highest driven gear 61 to mesh with the driven ratchet 31, so that the lowest secondary transmission ratio is achieved between the driving gear 71 with the smallest number of teeth and the driven gear 61 with the largest number of teeth, thereby achieving the effect of the smallest transmission ratio through the two-stage transmission.