Central fixed shaft gear transmission column type speed changer of bicycle

Abstract

The utility model relates to a bicycle centrally-mounted fixed shaft gear transmission column type transmission, which optimizes and combines the structural advantages of a parallel shaft gear transmission and the structural advantages of a planetary gear transmission, and on the basis of the parallel shaft gear transmission, a crank main shaft is used as a central shaft, and the number of transition gear shaft assemblies is increased from one to several. The crank main shaft is arranged on the base and arranged along the concentric circle of the periphery of the crank main shaft to form a planetary structure, a control cam shaft assembly is arranged on the peripheral axis parallel to the crank main shaft, the crank main shaft is also an assembly, the left end of the crank main shaft is an input side, the right end of the crank main shaft is an output side, and the periphery of one section of the output side is concentrically sleeved with an output sleeve assembly.

Description

Technical Field

[0001] The technology of the present invention belongs to the field of bicycle bottom-shaft transmissions, and is further subdivided into the field of internal transmissions of bicycle transmissions. Background Art

[0002] There are relatively few mature products in the current bicycle bottom-shaft transmission technology on the market. There are already parallel-axis gear transmissions in bicycles abroad, and domestic companies are also developing them. In technical literature, the relevant patents for bicycle bottom-shaft transmissions focus on both parallel-axis gear transmissions and planetary gear transmissions. However, at the bicycle bottom-shaft position, the structures of parallel-axis gear transmissions and planetary gear transmissions have their own advantages and disadvantages.

[0003] The ideal transmission required for the bicycle's middle axis position should be a column-type shape, relatively simple structure, light weight, small size, high efficiency, safe and reliable gear control system, and low production cost. Summary of the Invention

[0004] The present invention is a bicycle center-mounted fixed-axis gear transmission column transmission, which optimizes and combines the structural advantages of a parallel-axis gear transmission and a planetary gear transmission.

[0005] The specific technical solution is: on the basis of the parallel axis gear transmission, with the crank main shaft as the central axis, the transition gear shaft assembly is increased from one to several, and arranged along the concentric circles of the outer circumference of the crank main shaft to form a planetary structure, and a control camshaft assembly is set on the outer peripheral axis parallel to the crank main shaft. The crank main shaft is also an assembly. The left end of the crank main shaft is the power input side, and the right end is the power output side. An output set assembly is concentrically mounted on the outer periphery of a section of the power output side.

[0006] The described bicycle mid-mounted fixed-axis gear transmission column transmission has a columnar outer shell, a hollow inner structure and a group of bosses and holes connected to countersunk pin bolts. A left end cover is provided on the left side of the outer shell, and a right end cover is provided on the right side of the outer shell. The left end cover and the right end cover are each connected to the columnar outer shell by a group of countersunk pin bolts to form an integral structure. The columnar outer shell is fixedly connected to the position of the five-way bracket of the bicycle bottom bracket. Bearing seats are provided at the axial positions corresponding to the left and right end covers and the crank spindle assembly, transition gear shaft assembly, output set assembly and control camshaft assembly. The left end cover and the right end cover are each connected to the crank spindle assembly, output set assembly, transition gear shaft assembly and control camshaft assembly through multiple bearing supports.

[0007] The bicycle central fixed-axis gear transmission column transmission has a control camshaft, a cable pulley, a connecting plate and a buffer torsion spring extending from a position where the left end cover is coaxial with the control camshaft assembly.

[0008] The bicycle central fixed-axis gear transmission column transmission comprises a crank spindle assembly, a transition gear shaft assembly, an output sleeve assembly, and a control camshaft assembly.

[0009] The bicycle mid-mounted fixed-axis gear transmission column transmission is provided with a column housing, a left end cover, a right end cover, a countersunk pin bolt, a left crankshaft bearing, a right crankshaft bearing, an output sleeve outer bearing, a left transition gear shaft bearing, a right transition gear shaft bearing, a left control camshaft bearing, a right control camshaft bearing, a cable ring, a connecting plate, and a buffer torsion spring.

[0010] The described bicycle mid-mounted fixed-axis gear transmission column transmission has a crank spindle assembly comprising a crank spindle, a left crank spindle bearing, an input-stage one-way overrunning clutch, an input-stage first center gear 0102, an input-stage second center gear 0103, an input-stage third center gear 0104, an input-stage shift fork clutch, and an output set assembly.

[0011] The output sleeve assembly of the bicycle central fixed-axis gear transmission column transmission includes an output stage first central gear 1401, an output stage shift fork clutch, an output stage second central gear 1402, an output stage third central gear 1403, an output stage one-way overrunning clutch, an output sleeve outer bearing, and an output sleeve.

[0012] The described bicycle mid-mounted fixed-axis gear transmission column transmission has a transition gear shaft assembly including a transition gear shaft, an input-stage first transition gear 0702, an input-stage second transition gear 0703, an input-stage third transition gear 0704, an output-stage first transition gear 0705, an output-stage second transition gear 0706, and an output-stage third transition gear 0707.

[0013] The control camshaft assembly of the bicycle central fixed-axis gear transmission column transmission includes a control camshaft, a return torsion spring, an input-stage cam groove sleeve, an input-stage clutch fork, an output-stage cam groove sleeve, an output-stage clutch fork, and a clutch fork pin shaft.

[0014] Furthermore, the crankshaft assembly of the bicycle's mid-mounted fixed-axis gear-driven column transmission has a left end that is the power input side, and a group of input-stage center gears and a group of input-stage shift fork clutches are sleeved on the outer periphery of the left section of the crankshaft. The input-stage center gears are all driving gears, and the input-stage center gear with the smallest input speed ratio in a group of input-stage center gears is connected to the crankshaft through an input-stage one-way overrunning clutch. The remaining input-stage center gears are hollowly sleeved on the crankshaft and can be selectively connected to the crankshaft through an input-stage shift fork clutch. The input-stage shift fork clutch is anti-rotationally connected to the crankshaft through a spline and can slide axially relative to the crankshaft. The right end of the crankshaft is the power output side after speed change, and an output assembly is sleeved on the outer periphery of its right section through the crankshaft bearing support.

[0015] Furthermore, the output sleeve assembly of the bicycle's mid-mounted fixed-axis gear transmission column transmission is equipped with a group of output-stage center gears and a group of output-stage shift fork clutches on the outer periphery of the left section. The output-stage center gears are all passive gears, and the output-stage center gear with the smallest output speed ratio is connected to the output sleeve through an output-stage one-way overrunning clutch. The remaining output-stage center gears are loosely mounted on the output sleeve and are selectively connected to the output sleeve through an output-stage shift fork clutch. The output-stage shift fork clutch is anti-rotationally connected to the output sleeve through a spline and can slide axially relative to the output sleeve.

[0016] Furthermore, the left end of the transition gear shaft assembly of the bicycle's mid-mounted fixed-axis gear transmission column transmission is the power input side, and a group of input-stage transition gears are provided on its left section and are meshed with a group of input-stage center gears on the crank spindle assembly. The input-stage transition gears and the transition gear shaft are both anti-rotationally connected, and a group of output-stage transition gears are provided on the right section of the transition gear shaft. The group of output-stage transition gears are meshed with a group of output-stage center gears on the output set assembly. The output-stage transition gears and the transition gear shaft are both anti-rotationally connected, and the transition gear shaft assembly rotates synchronously as a whole during operation.

[0017] Furthermore, the control camshaft assembly of the bicycle mid-mounted fixed-axis gear transmission column transmission is provided with a return torsion spring, an input-stage cam groove sleeve, and an output-stage cam groove sleeve on the control camshaft inside the transmission housing in sequence from the left side, an input-stage clutch fork is provided on the periphery of the input-stage cam groove sleeve, and an output-stage clutch fork is provided on the periphery of the output-stage cam groove sleeve. The left end of the return torsion spring is connected to the left end cover for anti-rotation, and the right end of the return torsion spring is connected to the input-stage cam groove sleeve for anti-rotation. The input-stage cam groove sleeve and the output-stage cam groove sleeve are fixedly connected to the control camshaft, and the outer peripheral surfaces of the input-stage cam groove sleeve and the output-stage cam groove sleeve are provided with corresponding axial cam grooves. The input-stage cam sleeve and the input-stage clutch fork are connected through the clutch fork pin shaft, and the clutch fork pin shaft is fixed to the input-stage clutch fork and inserted into the cam groove of the input-stage cam sleeve. The connection mode of the output-stage cam sleeve and the output-stage clutch fork is the same as that of the input stage. The rotation of the control camshaft can push the respective clutch fork pin shafts through the respective axial cam grooves of the input-stage cam sleeve and the output-stage cam sleeve to drive the input-stage clutch fork and the output-stage clutch fork to slide axially relative to the control camshaft to realize the shifting function. On the left side of the control camshaft, there is a connecting plate connected to the anti-rotation connection of the shaft section extending out of the left end cover, which is equipped with a cable ring and a buffer torsion spring.

[0018] Furthermore, the power transmission route of the bicycle's mid-mounted fixed-axis gear-driven column transmission is, in sequence, the crank mainshaft, the input-stage center gear, the input-stage transition gear, the transition gear shaft, the output-stage transition gear, the output-stage center gear, and the output sleeve, and is selectively connected by the input-stage shift fork clutch and the output-stage shift fork clutch to form a multi-gear transmission.

[0019] Furthermore, the power for upshifting control of the bicycle's mid-mounted fixed-axis gear-driven column transmission is provided by the clockwise rotation of the cable ring, and its power transmission route is, in sequence, the cable ring, the buffer torsion spring, the connecting plate, the control camshaft, the input-stage cam groove sleeve and the output-stage cam groove sleeve, the clutch fork pin shaft, the input-stage clutch fork and the output-stage clutch fork, the input-stage fork clutch and the output-stage fork clutch, and the rotation of the control camshaft is used to reserve torque energy for the return torsion spring, and when downshifting, the torque energy is released by the return torsion spring, causing the control camshaft to rotate counterclockwise to achieve downshifting. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is an isometric view of the outer shape of a bicycle's mid-mounted fixed-axis gear transmission column transmission.

[0021] Figure 2 It is an overall cross-sectional view of a bicycle's mid-mounted fixed-shaft gear transmission column transmission.

[0022] Figure 3 This is the front view of the interior of a bicycle's mid-mounted fixed-axis gear transmission column transmission.

[0023] Figure 4 This is the front view of the crank spindle assembly of a bicycle mid-mounted fixed-axis gear transmission column transmission.

[0024] Figure 5 The present invention is a front view of an output assembly assembly of a bicycle mid-mounted fixed-axis gear transmission column transmission.

[0025] Figure 6 This is the front view of the transition gear shaft assembly of a bicycle's mid-mounted fixed-axis gear transmission column transmission.

[0026] Figure 7 This is an isometric view of the camshaft assembly of a bicycle's mid-mounted fixed-axis gear-driven column transmission.

[0027] Figure 8 This is a partial isometric view of the camshaft assembly of a bicycle's mid-mounted fixed-axis gear-driven column transmission.

[0028] Attachment Figure 2 The serial numbers and names of the parts and components are as follows: 01 crankshaft assembly, 02 crankshaft left bearing, 03 input stage one-way overrunning clutch, 04 transition gear shaft left bearing, 05 left end cover, 06 column housing, 07 transition gear shaft assembly, 08 right end cover, 09 transition gear shaft right bearing, 10 output stage one-way overrunning clutch, 11 output sleeve outer bearing, 12 crankshaft right bearing, 13 crankshaft right bearing locking cover, 14 output sleeve assembly, 15 control camshaft right bearing, 16 control camshaft assembly, 17 control camshaft right bearing, 18 connecting plate, 19 buffer torsion spring, 20 cable ring.

[0029] Attachment Figure 3 , Attachment Figure 4 Parts and components serial numbers and names: 21 countersunk pin bolt, 0101 crank spindle, 0102 input stage first sun gear, 0103 input stage second sun gear, 0104 input stage third sun gear, 0105 input stage shift fork clutch, 14 output set assembly.

[0030] Attachment Figure 5 The serial numbers and names of the parts and components are: 1401 output stage first sun gear, 1402 output stage second sun gear, 1403 output stage third sun gear, 1405 output stage shift fork clutch, 1206 output sleeve.

[0031] Attachment Figure 6 The serial numbers and names of the parts and components are: 0701 transition gear shaft, 0702 input stage first transition gear, 0703 input stage second transition gear, 0704 input stage third transition gear, 0705 output stage first transition gear, 0706 output stage second transition gear, 0707 output stage third transition gear.

[0032] Attachment Figure 7 , Attachment Figure 8 Parts and components serial numbers and names: 1601 control camshaft, 1602 return torsion spring, 1603 input stage cam sleeve, 1604 input stage clutch fork, 1605 output stage cam sleeve, 1606 output stage clutch fork, 1607 fork pin shaft. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below with reference to the accompanying drawings.

[0034] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

[0035] Example:

[0036] A bicycle central fixed-axis gear transmission column transmission, whose transmission system and control system include a crank spindle assembly 01, a transition gear shaft assembly 07, an output sleeve assembly 14, and a control camshaft assembly 16.

[0037] The bicycle mid-mounted fixed-axis gear transmission column transmission is provided with three-stage input transmission, three-stage output transmission, an input-stage one-way overrunning clutch, and an output-stage one-way overrunning clutch, forming a transmission with a total of 9 gears. The input-stage transmission is an acceleration transmission, and the output-stage transmission is a reduction transmission.

[0038] Reference Figure 2 、 Figure 4The crank main shaft assembly 01 includes a crank main shaft 0101, an input stage first sun gear 0102, an input stage second sun gear 0103, an input stage third sun gear 0104, and an output set assembly 14; wherein the crank main shaft 0101 is supported and connected to the left end cover and the output sleeve through its left bearing and right bearing, and the crank main shaft is sequentially provided with an input stage one-way overrunning clutch 03, an input stage first sun gear 0102, an input stage second sun gear 0103, an input stage shift fork clutch 0105, an input stage third sun gear 0104, and an output set assembly 14 from the left side, the input stage first sun gear 0102 is fitted on the outer periphery of the input stage one-way overrunning clutch and is connected to the crank main shaft through its input stage one-way overrunning clutch, the input stage second sun gear 010 3 is hollowed out on the crank main shaft and can be selectively connected to the crank main shaft through the input stage fork clutch. The input stage third sun gear 0104 is hollowed out on the crank main shaft and can be selectively connected to the crank main shaft through the input stage fork clutch. The input stage fork clutch 0105 is splined to the crank main shaft and rotates synchronously with the crank main shaft and can slide axially relative to the crank main shaft. The input stage first sun gear 0102 is responsible for the power input of 1st gear, 4th gear and 7th gear. The input stage second sun gear 0103 is responsible for the power input of 2nd gear, 5th gear and 8th gear. The input stage third sun gear 0104 is responsible for the power input of It takes on the power input of 3rd, 6th and 9th gears; when the transmission works in 1st, 4th and 7th gears, the power of the crankshaft is transmitted to the input stage first sun gear 0102 through the input stage one-way overrunning clutch and meshes with the corresponding input stage transition gear, the input stage shift fork clutch is in the middle neutral position, and the other input stage sun gears are in an idling state; when the transmission works in 2nd, 5th and 8th gears, the input stage shift fork clutch slides to the left and combines with the input stage second sun gear 0103, and the power of the crankshaft is transmitted to the input stage second sun gear 0103 through the input stage shift fork clutch. 03 and meshes with the corresponding input-stage transition gear, the input-stage first-stage center gear 0102 is in an overrunning state, and the input-stage third center gear 0104 is in an idling state; when the transmission works in 3rd gear, 6th gear, and 9th gear, the input-stage shift fork clutch slides to the right and combines with the input-stage third center gear 0104, and the power of the crankshaft is transmitted to the input-stage third center gear 0104 through the input-stage shift fork clutch and meshes with the corresponding input-stage transition gear, the input-stage first center gear 0102 is in an overrunning state, and the input-stage second center gear 0103 is in an idling state.

[0039] Reference Figure 2 、 Figure 5The output set assembly includes 1401 output stage first center gear, 1404 output stage fork clutch, 1402 output stage second center gear, 1403 output stage third center gear, 1405 output sleeve; the output set assembly is supported on the right end cover by the output sleeve outer bearing, and supports the crank main shaft by the right bearing of the crank main shaft, and the right end of the output sleeve extends out of the right end cover and outputs power; the output stage center gears on the output sleeve are all passive gears, which receive the power of the output stage transition gear on the transition gear shaft, and the output stage transmission is set as a reduction transmission; the output stage first center gear 1401 is loosely sleeved on the outer periphery of the left side of the output sleeve and can be selectively connected to the output sleeve through the output stage fork clutch, and the output stage fork clutch is connected to the output sleeve through a spline and can be The second central gear 1402 of the output stage slides axially relative to the output sleeve, and is loosely sleeved on the outer periphery of the output sleeve and selectively connected to the output sleeve through the output stage shift fork clutch. The third central gear 1403 of the output stage is installed on the outer periphery of the output sleeve through the output stage one-way overrunning clutch. The third central gear 1403 of the output stage is responsible for the power output of the 1st, 2nd and 3rd gears, the second central gear 1402 of the output stage is responsible for the power output of the 4th, 5th and 6th gears, and the first central gear 1401 of the output stage is responsible for the power output of the 7th, 8th and 9th gears. When the transmission is working in 1st gear, the third central gear 1403 of the output stage is responsible for the power output of the 1st gear, the 2nd central gear 1402 of the output stage is responsible for the power output of the 4th gear, the 5th gear and the 6th gear. When the transmission is in the 4th, 5th and 6th gears, the output stage third sun gear 1403 receives the power of the corresponding meshed output stage transition gear and transmits it to the output sleeve through the output stage one-way overrunning clutch, the output stage shift fork clutch is in the middle neutral position, and the other output stage sun gears are in an idling state; when the transmission is working in the 4th, 5th and 6th gears, the output stage shift fork clutch slides to the right and combines with the output stage second sun gear 1402, the output stage second sun gear 1402 receives the power of the corresponding meshed output stage transition gear and transmits it through the output stage shift fork clutch The output stage third center gear 1403 is in an overrunning state, and the output stage first center gear 1401 is in an idling state; when the transmission operates in 7th, 8th, and 9th gears, the output stage shift fork clutch slides to the left and engages with the output stage first center gear 1401, and the output stage first center gear 1401 receives the power of the corresponding meshed output stage transition gear and transmits it to the output sleeve through the output stage shift fork clutch, the output stage second center gear 1402 is in an idling state, and the output stage third center gear 1403 is in an overrunning state.

[0040] Reference Figure 2 、 Figure 6The transition gear shaft assembly includes 0701 transition gear shaft, 0702 input stage first transition gear, 0703 input stage second transition gear, 0704 input stage third transition gear, 0705 output stage first transition gear, 0706 output stage second transition gear, 0707 output stage third transition gear; all input stage transition gears and output stage transition gears are fixedly connected to the transition gear shaft, and the transition gear assembly rotates synchronously as a whole during operation, and the transition gear shaft is supported on the left end cover and the right end cover through its left bearing and right bearing; the input stage transition gear is set to three levels, and the output stage transition gear is set to three levels.

[0041] Reference Figure 2 、 Figure 7 、 Figure 8 The control camshaft assembly includes 1601 control camshaft, 1602 reset torsion spring, 1603 input stage cam groove sleeve, 1604 input stage clutch fork, 1605 output stage cam groove sleeve, 1406 output stage cam groove sleeve, 1607 pin shaft, 19 connecting plate, 18 buffer torsion spring, 20 cable ring; the control camshaft is supported on the left end cover and the right end cover through its left bearing and right bearing, and the control camshaft assembly is sequentially mounted with a reset torsion spring, an input stage cam groove sleeve, and an output stage cam groove sleeve on the control camshaft inside the transmission housing from the left side, an input stage clutch fork is mounted on the periphery of the input stage cam groove sleeve, and an output stage clutch fork is mounted on the periphery of the output stage cam groove sleeve, the left end of the reset torsion spring is anti-rotationally connected to the left end cover, and the right end thereof is anti-rotationally connected to the input stage cam groove sleeve. The input-stage cam sleeve and the output-stage cam sleeve are fixedly connected to the control camshaft, and the outer circumferential surfaces of the input-stage cam sleeve and the output-stage cam sleeve are provided with corresponding axial cam grooves. The input-stage cam sleeve and the input-stage clutch fork are connected through a fork pin shaft, and the fork pin shaft is fixed to the input-stage clutch fork and inserted into the cam groove of the input-stage cam sleeve. The connection method of the output-stage cam sleeve and the output-stage clutch fork is the same as that of the input stage. The rotation of the control camshaft can push the fork pin shaft through the axial cam grooves of the input-stage cam sleeve and the output-stage cam sleeve to drive the input-stage fork clutch fork and the output-stage fork clutch fork to slide axially relative to the control camshaft to realize the shifting function. The shaft section of the left end of the control camshaft extending out of the left end cover is anti-rotationally connected with a connecting plate, and is equipped with a cable ring and a buffer torsion spring.

[0042] The embodiment described is a gear ratio table of a bicycle central fixed-axis gear transmission column transmission:

[0043] The input speed ratio is 3 levels: Level 1: 1:3.692, Level 2: 1:3.00, Level 3: 1:2.471.

[0044] The output level speed ratio is 3 levels: level 1: 1:0.818, level 2: 1:0.452, level 3: 1:0.255.

[0045] Total speed ratio: 1st gear; 1:0.630, 2nd gear; 1:0.765, 3rd gear; 1:0.941, 4th gear; 1:1.117,

[0046] 5th gear; 1:1.356, 6th gear; 1:1.669, 7th gear; 1:2.021, 8th gear; 1:2.454, 9th gear; 1:3.020.

Claims

1. A bicycle central fixed-axis gear transmission column transmission, characterized by: The structural advantages of the parallel axis gear transmission and the planetary gear transmission are optimized and combined. Based on the parallel axis gear transmission, the crankshaft is used as the central axis, and the number of transition gear shaft assemblies is increased from one to several. These are arranged concentrically along the outer circumference of the crankshaft to form a planetary structure. A control camshaft assembly is set on the outer axis parallel to the crankshaft. The crankshaft is also an assembly. The left end of the crankshaft is the power input side, and the right end is the power output side. An output assembly is concentrically mounted on the outer circumference of a section of the output side. The described bicycle mid-mounted fixed-axis gear transmission column transmission has a columnar outer shell with a hollow inner periphery and a group of bosses and holes connected to countersunk pin bolts. A left end cover is provided on the left side of the outer shell, and a right end cover is provided on the right side of the outer shell. The left end cover and the right end cover are each connected to the columnar outer shell by a group of countersunk pin bolts to form an integral structure. The columnar outer shell is fixedly connected to the position of the bicycle's bottom bracket. Bearing seats are provided at the axial positions of the left and right end covers corresponding to the crank spindle assembly, the transition gear shaft assembly, the output set assembly, and the control camshaft assembly. The left end cover and the right end cover are each supported and connected to the crank spindle assembly, the output set assembly, the transition gear shaft assembly, and the control camshaft assembly via multiple bearings. The bicycle mid-mounted fixed-axis gear transmission column transmission has a control camshaft, a cable pulley, a connecting plate and a buffer torsion spring extending from a position where the left end cover is coaxial with the control camshaft assembly; The bicycle mid-mounted fixed-axis gear transmission column transmission comprises a crank spindle assembly, a transition gear shaft assembly, an output sleeve assembly, and a control camshaft assembly; The bicycle mid-mounted fixed-axis gear transmission column transmission is provided with a column housing, a left end cover, a right end cover, a countersunk pin bolt, a left crankshaft bearing, a right crankshaft bearing, an output sleeve outer bearing, a left transition gear shaft bearing, a right transition gear shaft bearing, a left control camshaft bearing, a right control camshaft bearing, a cable ring, a connecting plate, and a buffer torsion spring. The bicycle mid-mounted fixed-axis gear transmission column transmission has a crank spindle assembly comprising a crank spindle, a left crank spindle bearing, an input-stage one-way overrunning clutch, an input-stage first sun gear, an input-stage second sun gear, an input-stage third sun gear, an input-stage shift fork clutch, and an output set assembly; The bicycle central fixed-axis gear transmission column transmission, wherein the output sleeve assembly comprises an output stage first sun gear, an output stage shift fork clutch, an output stage second sun gear, an output stage third sun gear, an output stage one-way overrunning clutch, an output sleeve outer bearing, and an output sleeve; The intermediate fixed-axis gear transmission column transmission of the bicycle, wherein the intermediate gear shaft assembly comprises an intermediate gear shaft, an input-stage first intermediate gear, an input-stage second intermediate gear, an input-stage third intermediate gear, an output-stage first intermediate gear, an output-stage second intermediate gear, and an output-stage third intermediate gear; The control camshaft assembly of the bicycle central fixed-axis gear transmission column transmission includes a control camshaft, a return torsion spring, an input-stage cam groove sleeve, an input-stage clutch fork, an output-stage cam groove sleeve, an output-stage clutch fork, and a fork pin.

2. The bicycle center-mounted fixed-axis gear transmission column transmission according to claim 1, characterized in that: The crankshaft assembly has a power input side at its left end, and a group of input-stage center gears and a group of input-stage clutches are sleeved on the outer periphery of the left section of the crankshaft. The input-stage center gears are all driving gears. The input-stage center gear with the smallest input speed ratio in a group of input-stage center gears is connected to the crankshaft through an input-stage one-way overrunning clutch. The remaining input-stage center gears are hollowly sleeved on the crankshaft and can be selectively connected to the crankshaft through an input-stage shift fork clutch. The input-stage shift fork clutch is anti-rotationally connected to the crankshaft through a spline and can slide axially relative to the crankshaft. The right end of the crankshaft is the power output side after speed change, and an output assembly is sleeved on the outer periphery of its right section through the crankshaft bearing support.

3. The bicycle center-mounted fixed-axis gear transmission column transmission according to claim 1, characterized in that: A group of output stage sun gears and a group of output stage shift fork clutches are sleeved on the outer periphery of the left section of the output set assembly. The output stage sun gears are all passive gears. The output stage sun gear with the smallest output speed ratio is connected to the output sleeve through the output stage one-way overrunning clutch. The remaining output stage sun gears are loosely sleeved in the output sleeve and are selectively connected to the output sleeve through the output stage shift fork clutch. The output stage shift fork clutch is anti-rotationally connected to the output sleeve through a spline and can slide axially relative to the output sleeve.

4. The bicycle center fixed axis gear transmission column transmission according to claim 1, characterized in that: The left end of the gear shaft assembly is the power input side. A group of input-stage transition gears are provided on its left section and are meshed with a group of input-stage central gears on the crank spindle assembly. The input-stage transition gears and the transition gear shaft are both anti-rotationally connected. A group of output-stage transition gears are provided on the right section of the transition gear shaft. A group of output-stage transition gears are meshed with a group of output-stage central gears on the output set assembly. The output-stage transition gears and the transition gear shaft are both anti-rotationally connected. During operation, the transition gear shaft assembly rotates synchronously as a whole.

5. The bicycle center-mounted fixed-axis gear transmission column transmission according to claim 1, characterized in that: The control camshaft assembly is provided with a return torsion spring, an input-stage cam sleeve, and an output-stage cam sleeve in sequence from the left side on the control camshaft inside the transmission housing. An input-stage shift fork clutch fork is provided on the periphery of the input-stage cam sleeve, and an output-stage shift fork clutch fork is provided on the periphery of the output-stage cam sleeve. The left end of the return torsion spring is anti-rotationally connected to the left end cover, and the right end of the return torsion spring is anti-rotationally connected to the input-stage cam sleeve. The input-stage cam sleeve and the output-stage cam sleeve are fixedly connected to the control camshaft. The outer peripheral surfaces of the input-stage cam sleeve and the output-stage cam sleeve are provided with corresponding axial cam grooves. The input-stage cam sleeve is anti-rotationally connected to the output-stage cam sleeve. The input-stage shift fork clutch fork is connected through a shift fork pin shaft, and its shift fork pin shaft is fixed to the shift fork of the input-stage shift fork clutch and inserted into the cam groove of the input-stage cam groove sleeve. The connection method between the output-stage cam groove sleeve and the output-stage shift fork clutch fork is the same as that of the input stage. The rotation of the control camshaft can push the respective axial cam grooves of the input-stage cam groove sleeve and the output-stage cam groove sleeve to push the respective shift fork pin shafts to drive the input-stage shift fork clutch fork and the output-stage shift fork clutch fork to slide axially relative to the control camshaft to realize the shifting function. The shaft section of the left end of the control camshaft extending out of the left end cover is anti-rotationally connected with a connecting plate, and is equipped with a cable ring and a buffer torsion spring.

6. The bicycle center-mounted fixed-axis gear transmission column transmission according to claim 1, characterized in that: The power transmission route is the crank main shaft, input stage central gear, input stage transition gear, transition gear shaft, output stage transition gear, output stage central gear, output sleeve, and is selectively connected through the input stage shift fork clutch and the output stage shift fork clutch to form a multi-gear transmission.

7. The bicycle center-mounted fixed-axis gear transmission column transmission according to claim 1, characterized in that: The power for upshift control is provided by the clockwise rotation of the cable ring, and the power transmission route is the cable ring, buffer torsion spring, connecting plate, control camshaft, input stage cam groove sleeve and output stage cam groove sleeve, shift fork pin shaft, input stage shift fork clutch fork and output stage shift fork clutch fork, input stage shift fork clutch and output stage shift fork clutch, and the rotation of the control camshaft is used to reserve torque energy for the reset torsion spring. When downshifting, the reset torsion spring releases the torque energy, causing the control camshaft to rotate counterclockwise to achieve downshift.

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