A type of gearbox

Abstract

This invention relates to a gearbox, comprising a drive shaft mechanism, which includes a central shaft, a main transmission gear sleeved on the central shaft, and multiple power output gears. The main transmission gear is rotatably connected to the central shaft, and the power output gears are radially fixedly connected to the central shaft. The main transmission gear includes at least one transmission tooth. A shift shaft mechanism includes a shift shaft, on which multiple power receiving gears and at least one power return gear are sleeved. The power receiving gears mesh with the power output gears in a one-to-one correspondence, and the power return gear meshes with the transmission tooth in a one-to-one correspondence. A shift mechanism includes a camshaft, a shift power component, and a planetary gear set. The camshaft is coaxially disposed within the inner cavity of the shift shaft and is rotatably connected to the shift shaft. One end of the camshaft is fixedly connected to a shift shaft. The planetary gear set is mounted on the shift shaft. Multiple drive grooves are axially arranged on the camshaft, and multiple sets of ratchet meshing units are axially arranged on the shift shaft.

Description

Technical Field

[0001] This invention relates to the field of gearbox technology, and in particular to a gearbox. Background Technology

[0002] Currently, outdoor transportation is becoming increasingly diverse and intelligent, evolving from a single power source to two, providing a better driving experience, such as new energy hybrid vehicles and electric-assisted bicycles. However, in actual operation, how well the auxiliary power source provides appropriate power is particularly important, directly affecting the driving experience.

[0003] Chinese invention patent application publication number CN116857362B discloses an electronic gearbox system, which includes a gearbox-type transmission device and an electronic gear shifting control system. The gearbox-type transmission device includes a housing, a main shaft and a countershaft, a main shaft gear, a countershaft gear, and a ratchet. Disadvantages of this electronic gearbox system include: structural limitations making it difficult to increase the number of gears; the ratchet structure resulting in poor gear shifting timeliness, sometimes requiring the central shaft to rotate before engaging a gear; and the cam mechanism, which relies on the shift fork protrusion on the shift fork seat moving up and down on the shift drum, is flimsy, prone to wear and damage, and the elastic components are prone to failure and difficult to replace.

[0004] To solve the above-mentioned technical problems, the present invention provides a gearbox that can be used in rotating machinery that outputs two types of power simultaneously, and is not limited to hybrid vehicles and electric bicycles. Summary of the Invention

[0005] This invention addresses the technical problems existing in the prior art by providing a gearbox.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A gearbox, comprising:

[0007] A drive shaft mechanism, comprising a central shaft, a main transmission gear sleeved on the central shaft, and a plurality of power output gears, wherein the main transmission gear is rotatably connected to the central shaft, and the power output gears are radially fixedly connected to the central shaft, and the main transmission gear includes at least one transmission tooth;

[0008] A gear shifting shaft mechanism, comprising a gear shifting shaft, on which a plurality of power receiving gears and at least one power return gear are fitted, wherein the power receiving gears mesh with the power output gears in a one-to-one correspondence, and the power return gear meshes with the transmission gears in a one-to-one correspondence.

[0009] The gear shifting mechanism includes a camshaft, a gear shifting power component, and a planetary gear set. The camshaft is coaxially disposed within the inner cavity of the gear shift shaft and is rotatably connected to the gear shift shaft. One end of the camshaft is fixedly connected to a shift shaft. The planetary gear set is mounted on the shift shaft. The camshaft has multiple axially arranged drive grooves, and the gear shift shaft has multiple sets of ratchet meshing units. Each drive groove corresponds one-to-one with a ratchet meshing unit. Each power receiving gear and power return gear has internal teeth, and each power receiving gear and power return gear is correspondingly engaged with a set of ratchet meshing units. The gear shifting power component transmits power to the camshaft through the planetary gear set and the shift shaft. The rotation of the camshaft changes the state of the ratchet meshing units to achieve a radially fixed connection between one power receiving gear and one power return gear and the gear shift shaft.

[0010] Preferably, in the aforementioned gearbox, a torque sensor is mounted on the main transmission gear.

[0011] Preferably, in the above-mentioned gearbox, the ratchet engagement unit includes ratchet teeth, an elastic wire ring, and a ratchet cavity. The outer side of the gearbox shaft is provided with multiple annular grooves, the elastic wire ring is embedded in the annular grooves, and the ratchet teeth are installed in the ratchet cavity.

[0012] Preferably, in the aforementioned gearbox, the ratchet includes a brake foot, a rotary table, a meshing part, and a release groove. The elastic steel wire ring passes through the release groove to bind the ratchet within the ratchet cavity. The meshing part is used to mesh with the internal teeth of the power receiving gear and the power returning gear. A through hole is provided at the bottom of the ratchet cavity. The brake foot passes through the through hole and can swing within the through hole. The drive groove is used to drive the brake foot to swing around the rotary table.

[0013] Preferably, in the aforementioned gearbox, the planetary gear set includes a planetary carrier, a fixedly mounted external gear ring, and a rotatably mounted shift gear ring. The planetary carrier is rotatably connected to the shift shaft. Two sets of planetary transmission mechanisms are mounted on the planetary carrier. Sun gear A and sun gear B are mounted on the shift shaft. Sun gear A and sun gear B mesh with the two sets of planetary transmission mechanisms in a one-to-one correspondence. The shift gear ring is provided with internal shift gear teeth. One set of planetary transmission mechanisms meshes with the external gear ring, and the other set of planetary transmission mechanisms meshes with the internal shift gear teeth.

[0014] Preferably, in the above-described gearbox, a limiting groove is provided on the camshaft, and a limiting post is installed on the gearbox shaft, the limiting post being inserted into the limiting groove.

[0015] Preferably, in the above-described gearbox, a toothed disc is fixed on the main transmission gear.

[0016] Preferably, in the above-described gearbox, the shift shaft is radially fixedly connected to the sun gear B, and the shift shaft is radially rotatably connected to the sun gear A.

[0017] Preferably, in the above-mentioned gearbox, a retaining ring is fixed on the gear shift shaft, the sun gear A is fixedly connected to the retaining ring, the retaining ring is rotatably connected to the shift shaft, and the sun gear A, the retaining ring, and the gear shift shaft are coaxially arranged.

[0018] Preferably, in the above-mentioned gearbox, the shift ring gear is provided with external shift ring gear teeth, the shift power component is a shift motor, and a drive gear is mounted on the output shaft of the shift motor, the drive gear meshing with the external shift ring gear teeth.

[0019] The beneficial effects of this invention are:

[0020] 1. The gearbox provided by the present invention has a simple structure and timely shift response. It is also easy to assemble and process the entire gearbox and reduce the difficulty of later maintenance.

[0021] 2. The gearbox provided by this invention integrates a torque sensor, which can collect the rider's cadence and pedaling torque throughout the entire process when applied to an electric-assist bicycle. The torque sensor transmits the collected cadence and pedaling torque information to the control board of the electric-assist bicycle. The control board can accurately analyze how much electric assistance the rider needs and output the corresponding power through the motor, thereby improving the riding experience. Attached Figure Description

[0022] Figure 1 This is a three-dimensional diagram of the internal structure of the present invention.

[0023] Figure 2 This is a three-dimensional diagram of the speed-changing shaft mechanism of the present invention.

[0024] Figure 3 This is an internal sectional view of the speed change shaft mechanism of the present invention.

[0025] Figure 4 This is an exploded view of some components of the speed-changing shaft mechanism of the present invention.

[0026] Figure 5 This is a three-dimensional schematic diagram of some components of the speed change shaft mechanism of the present invention.

[0027] Figure 6 This is a three-dimensional diagram of the ratchet of the present invention.

[0028] Figure 7 This is a schematic diagram of the transmission main gear of the present invention.

[0029] Figure 8 This is a schematic diagram of the external structure of the present invention.

[0030] Figure 9 This is a schematic diagram of the structure of the present invention applied to an electric-assisted bicycle.

[0031] Figure 10 This is a partial schematic diagram of the handlebar position when the present invention is applied to an electric-assisted bicycle.

[0032] The attached diagram lists the components represented by each number as follows:

[0033] 60. Electric-assisted bicycle; 61. Crank; 62. Gearbox; 63. Chainring; 64. Hub motor; 65. Speedometer; 66. Throttle; 67. Bottom bracket; 68. Drive gear A; 69. Drive gear B; 70. Drive gear C; 71. Main drive gear; 72. Torque sensor; 721. Strain gauge; 722. Torque sensor control board; 723. Plastic cover; 725. Coil sleeve; 7251. Limiting foot; 726. Shielding cover; 727. Communication cable; 73. Shift ring gear; 74. Planetary gear set; 75. Shift motor; 76. Shift gear A; 77. Shift gear B; 78. Shift gear C; 79. Shift gear D; 80. Shift gear E; 81. Spacer; 82. 821. Shift shaft, 83. Racket cavity, 84. Racket, 85. Brake foot, 86. Rotary table, 87. Shift groove, 88. Engaging part, 89. Elastic steel wire ring, 80. Limiting post, 81. Camshaft, 82. Drive groove, 83. Limiting groove, 84. Shift shaft, 85. Pin, 86. Retaining ring, 97. Planetary gear carrier, 98. External gear ring, 99. Planetary gear shaft, 90. Planetary gear, 91. Sun gear A, 92. Sun gear B, 93. Deep groove ball bearing, 94. Open retaining ring, 95. Sealing ring, 96. Left cover, 100. Middle cover, 101. Right cover, 102. Chain, 103. Freewheel, 104. Pedal, 105. Bicycle bottom bracket. Detailed Implementation

[0034] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0035] like Figures 1 to 8 As shown, a gearbox includes a drive shaft mechanism, a gear shifting shaft mechanism, and a gear shifting mechanism. The gearbox housing is composed of a left cover 99, a middle cover 100, and a right cover 101. The left cover 99, the middle cover 100, and the right cover 101 are connected by screws, surrounding the internal structure of the gearbox 62.

[0036] The drive shaft mechanism includes a central shaft 67, a main transmission gear 71 fitted on the central shaft 67, and three power output gears. The central shaft 67 passes through the interior of the main transmission gear 71, and the main transmission gear 71 is rotatably connected to the central shaft 67. The central shaft 67 supports the main transmission gear 71 via needle roller bearings. The main transmission gear 71 includes two transmission teeth. The power output gears are radially fixedly connected to the central shaft 67. The three power output gears are transmission gear A68, transmission gear B69, and transmission gear C70. The inner rings of transmission gears A68, B69, and C70 have a spline structure. A portion of the central shaft 67 is a splined shaft. Transmission gears A68, B69, and C70 are connected to the central shaft 67 via splines. A toothed disc 63 is fixed on the main transmission gear 71 for power transmission.

[0037] The transmission shaft mechanism includes a transmission shaft 82, on which three power receiving gears and two power return gears are mounted. These gears can engage and disengage via ratchet 83. When disengaged, they are rotatably connected to the transmission shaft 82; when engaged, they share the same angular velocity with the shaft. The three power receiving gears are transmission gear A 76, transmission gear B 77, and transmission gear C 78, and the two power return gears are transmission gear D 79 and transmission gear E 80. Gear A 76, gear B 77, gear C 78, gear D 79, and gear E 80 have both internal and external teeth. Gear A 76, gear B 77, gear C 78, gear D 79, and gear E 80 mesh with two transmission teeth of transmission gear A 68, transmission gear B 69, transmission gear C70, and main transmission gear 71.

[0038] The shift mechanism includes a camshaft 86, a shift motor 75, and a planetary gear set 74. The camshaft 86 is coaxially mounted within the inner cavity of the shift shaft 82, and is rotatably connected to the shift shaft 82. One end of the camshaft 86 is fixedly connected to a shift shaft 87 via a pin 88. The planetary gear set 74 is mounted on the shift shaft 87. The planetary gear set 74 includes a planet carrier 90, a fixedly mounted external gear ring 91, and a rotatably mounted shift gear ring 73. The planet carrier 90 is rotatably connected to the shift shaft 87, the external gear ring 91 is fixed to the right cover 101, and a deep groove ball bearing 96 is installed between the planet carrier 90 and the shift shaft 87. A fixed ring 89 is fixed to the shift shaft 82, and a sun gear A94 is fixedly connected to the fixed ring 89. The fixed ring 89 is rotatably connected to the shift shaft 87, and the sun gear A94, fixed ring 89, and shift shaft 82 are coaxially arranged. Two planetary transmission mechanisms are mounted on the planetary gear carrier 90, sharing a single planetary gear carrier 90. The planetary set 74 has four sets of planetary gears 93, each set sharing a planetary gear shaft 92. The planetary gears 93 are mounted on the planetary gear shaft 92 via open retaining rings 97, and the two planetary gears 93 in each set can rotate freely relative to each other. A sun gear A94 and a sun gear B95 are mounted on the shift shaft 87, meshing with the two sets of planetary transmission mechanisms respectively. The shift shaft 87 can rotate freely within the sun gear A94. A sealing ring 98 is arranged between the shift shaft 87 and the sun gear A94. The sun gear B95 has a polygonal hole in the center, and the head of the shift shaft 87 is also a polygonal shaft. The sun gear B95 is connected to the shift shaft 87 via a polygonal structure, and the sun gear B95 and the shift shaft 87 have the same angular velocity.

[0039] The gear ring 73 has external gears and internal gears. One set of planetary transmission mechanisms meshes with the external gear ring 91, and the other set meshes with the internal gear ring. A drive gear is mounted on the output shaft of the gear shift motor 75, and the drive gear meshes with the external gear ring. The gear ring 73 is fitted onto the outer cylinder of the right cover 101 and can rotate freely.

[0040] When the transmission shaft 82 rotates, the sun gear A 94 drives the lower layer of planetary gears 93 of the planetary set 74 to rotate. The rotation of the lower layer of planetary gears 93 of the planetary set 74 drives the planet carrier 90 to rotate. The rotation of the planet carrier 90 drives the upper layer of planetary gears 93 to rotate, which in turn drives the sun gear B 95 to rotate. Since the sun gear B 95 and the shift shaft 87 have the same angular velocity, the shift shaft 87 also rotates together. Therefore, when the transmission shaft 82 rotates, the shift shaft 87 also rotates together.

[0041] When the shift motor 75 drives the shift ring gear 73 to rotate, the rotation of the shift ring gear 73 can drive the upper layer of planetary gears 93 on the planetary set 74 to rotate. The rotation of the upper layer of planetary gears 93 on the planetary set 74 can drive the sun gear B 95 to rotate. The rotation of the sun gear B 95 can drive the shift shaft 87 to rotate. The rotation of the shift shaft 87 can drive the camshaft 86 to rotate. The rotation of the camshaft 86 relative to the shift shaft 82 is the action of shifting gears. Because the upper and lower layers of planetary gears 93 on the planetary set 74 can rotate freely relative to each other, shifting gears and the rotation of the shift shaft 82 do not affect each other.

[0042] The camshaft 86 has multiple drive grooves 861 of different shapes and depths arranged axially, and the shift shaft 82 has multiple sets of ratchet meshing units arranged axially. Each drive groove 861 corresponds to one ratchet meshing unit. Each power receiving gear and power returning gear is matched with a set of ratchet meshing units. When the shift motor 75 rotates, it transmits power to the camshaft 86 through the planetary gear set 74 and the shift shaft 87. The rotation of the camshaft 86 changes the state of the ratchet meshing units to achieve a radially fixed connection between one power receiving gear and one power returning gear and the shift shaft 82. Simultaneously, only one power receiving gear and one power returning gear are radially fixedly connected to the shift shaft 82 at any given time. This gearbox can achieve a 3x2 six-speed transmission. A spacer 81 is fitted onto the outer end of the shift shaft 82 to isolate the shift shaft 82 from the gearbox housing.

[0043] The camshaft 86 is provided with a limiting groove 862, and the transmission shaft 82 is equipped with a limiting post 85, which is inserted into the limiting groove 862. The camshaft 86 can rotate inside the transmission shaft 82, but the camshaft 86 cannot rotate arbitrarily inside the transmission shaft 82; there is a rotation range. This rotation range is controlled by the limiting post 85 and the limiting groove 862 of the camshaft 86. The limiting post 85 has external threads, which can be fixed to the transmission shaft 82. The limiting post 85 has a cylindrical head, which extends into the limiting groove 862 to perform a limiting function.

[0044] The ratchet engagement unit includes ratchet 83, elastic wire ring 84, and ratchet cavity 821. The external surface of the transmission shaft 82 has multiple annular grooves, in which the elastic wire ring 84 is embedded. The ratchet 83 is installed in the ratchet cavity 821. The ratchet 83 includes a brake foot 831, a rotating platform 832, an engagement part 834, and a disengaging groove 833. The disengaging and retraction of the ratchet 83 involves the ratchet 83 rotating around the center of its rotating platform 832. The elastic wire ring 84 passes through the disengaging groove 833 and binds the ratchet 83 within the ratchet cavity 821. The ratchet 83 is pressed into the opening groove 833 by an elastic steel wire ring 84 and fitted onto the slot of the gear shift shaft 82. This not only prevents the ratchet 83 from falling out of the ratchet cavity 821 on the gear shift shaft 82, but also, due to the elasticity of the steel wire ring 84, keeps the ratchet 83 pressed down, keeping it in the open state. When the ratchet 83 is fully retracted, it is completely hidden in the ratchet cavity 821 on the gear shift shaft 82, allowing the gear paired with the ratchet 83 to rotate freely relative to the gear shift shaft 82. The meshing part 834 is used to mesh with the internal teeth of the power receiving gear and the power return gear. The bottom of the ratchet cavity 821 is provided with a through hole, through which the brake foot 831 passes and can swing within the through hole. The drive groove 861 is used to drive the brake foot 831 to swing around the rotary table 832. When the camshaft 86 rotates, the brake foot 831 of the ratchet 83 performs cam motion in the drive groove 861 opposite to the camshaft 86. This motion, in conjunction with the elastic wire ring 84, controls the opening and closing of the ratchet 83. The rotation of the camshaft 86, combined with the elasticity of the elastic wire ring 84, drives the ratchet 83 to open and close. The opening and closing of the ratchet 83 determines whether gears A76, B77, C78, ​​D79, and E80 have the same angular velocity as the gearbox shaft 82, and simultaneously determines which gear the transmission is in, ensuring timely gear shifting.

[0045] A torque sensor 72 is installed on the main transmission gear 71. Specifically, a strain gauge 721 of the torque sensor 72 is arranged on the main transmission gear 71. The strain gauge 721 can capture the minute rigid deformation of the main transmission gear 71 itself. An induction coil is arranged on the coil sleeve 725. The induction coil is surrounded by a shield 726. Different rigid deformations of the main transmission gear 71 itself can affect the generation of different electrical signals between the strain gauge 721 and the induction coil arranged on the coil sleeve 725, and transmit them to the torque sensor control board 722 of the torque sensor 72. The torque sensor control board processes the electrical signals and transmits them out via the communication line 727. The torque sensor 72 is covered by a plastic cover 723. The limiting foot 7251 on the coil sleeve is locked on the left cover 99, allowing the main transmission gear 71 to rotate freely at the center of the torque sensor 72.

[0046] The following examples illustrate the application of this gearbox in electric-assisted bicycles.

[0047] like Figure 9 , Figure 10 As shown, the electric-assist bicycle 60 is equipped with a rear hub motor 64, and the gearbox 62 is installed at the bottom bracket 105 of the bicycle. The gearbox 62 can collect the rider's cadence and the torque during pedaling through the torque sensor 72 arranged inside it. The torque sensor 72 converts the collected cadence and the torque during pedaling into electrical signals and transmits them to the control board of the electric-assist bicycle. The chip in the control board of the electric-assist bicycle 60 analyzes the signals transmitted by the torque sensor through software algorithms and issues instructions to the rear hub motor 64. The rear hub motor 64 of the electric-assist bicycle 60 determines how much electric assistance to provide to the bicycle based on the received instructions.

[0048] When the rider does not need assistance from the electric-assisted bicycle 60, the rider provides power to the electric-assisted bicycle 60 by pedaling the pedals 104. The pedals 104 are fixed to the crank 61, which is fixed to the bottom bracket 67 of the gearbox 62. The chainring 63 of the electric-assisted bicycle 60 is fixed to the drive gear 71 of the gearbox 62. The gearbox 62 can convert the power provided by the rider's pedaling to the drive gear 71. The drive gear 71 drives the chainring 63 to rotate, which in turn drives the chain 102 to rotate. The chain 102 drives the freewheel 103 to rotate, which in turn drives the rear wheel of the electric-assisted bicycle 60 to rotate, thus starting the electric-assisted bicycle 60.

[0049] Figure 10 This image shows a partial 3D view of the handlebars of an electric-assist bicycle (60). The shifting mechanism of the gearbox (62) is located on the throttle (66), which can have one or more buttons. The rider shifts gears by pressing these buttons, which provide a slight mechanical vibration feedback to the rider's finger and a brief beep. The speedometer (65) displays the number of gears, providing a satisfying shifting experience. The shifting mechanism is electronic, and the control system precisely controls the angular displacement of the shift motor, thereby precisely controlling the camshaft's angular displacement for accurate shifting. This design allows for a high number of gears while maintaining a compact structure, reducing the overall weight of the electric-assist bicycle and simplifying operation.

[0050] Similarly, when this transmission is used in a hybrid vehicle, the engine's output shaft is connected to the central shaft 67. The torque output through the transmission is transmitted to the chainring 63, which then transmits power to the vehicle's axles via a power transmission mechanism. The transmission 62 can collect engine speed and torque through a torque sensor 72 located inside it. The torque sensor 72 converts the collected data into electrical signals and transmits them to the control board. The chip in the control board analyzes the signals transmitted by the torque sensor through software algorithms to determine how much electric assist the vehicle needs and issues instructions to the vehicle's motor. The motor then determines how much electric assist to provide to the vehicle based on the received instructions.

[0051] In the description of this invention, it should be understood that the terms "upper," "lower," "left," and "right," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or a specific orientational structure and operation. Therefore, they should not be construed as limitations on the invention. Furthermore, "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0052] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0053] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A gearbox, characterized in that, include: The drive shaft mechanism includes a central shaft (67), a transmission main gear (71) sleeved on the central shaft (67), and a plurality of power output gears. The transmission main gear (71) is rotatably connected to the central shaft (67), and the power output gears are radially fixedly connected to the central shaft (67). The transmission main gear (71) includes at least one transmission tooth. The gear shifting shaft mechanism includes a gear shifting shaft (82), on which a plurality of power receiving gears and at least one power return gear are sleeved. The power receiving gear meshes with the power output gear in a one-to-one correspondence, and the power return gear meshes with the transmission gear in a one-to-one correspondence. The gear shifting mechanism includes a camshaft (86), a gear shifting power component, and a planetary gear set (74). The camshaft (86) is coaxially disposed in the inner cavity of the gear shifting shaft (82) and is rotatably connected to the gear shifting shaft (82). One end of the camshaft (86) is fixedly connected to a shift shaft (87). The planetary gear set (74) is mounted on the shift shaft (87). The camshaft (86) has multiple drive grooves (861) axially disposed on it, and the gear shifting shaft (82) has multiple sets of ratchet teeth axially disposed on it. The meshing unit, the drive groove (861) corresponds one-to-one with the ratchet meshing unit, each of the power receiving gear and power return gear is provided with internal teeth, each of the power receiving gear and power return gear is correspondingly engaged with a set of ratchet meshing units, the gear shifting power component transmits power to the camshaft (86) through the planetary gear set (74) and the shift shaft (87), the camshaft (86) rotates to change the state of the ratchet meshing unit so as to realize that one power receiving gear and one power return gear are radially fixedly connected to the gear shifting shaft (82).

2. The gearbox according to claim 1, characterized in that: A torque sensor (72) is installed on the main transmission gear (71).

3. The gearbox according to claim 1, characterized in that: The ratchet engagement unit includes a ratchet (83), an elastic wire ring (84), and a ratchet cavity (821). The gearbox (82) has multiple annular grooves on its exterior. The elastic wire ring (84) is embedded in the annular grooves, and the ratchet (83) is installed in the ratchet cavity (821).

4. The gearbox according to claim 3, characterized in that: The ratchet (83) includes a brake foot (831), a rotating platform (832), a meshing part (834), and a disengaging groove (833). The elastic steel wire ring (84) passes through the disengaging groove (833) to bind the ratchet (83) in the ratchet cavity (821). The meshing part (834) is used to mesh with the internal teeth of the power receiving gear and the power return gear. The bottom of the ratchet cavity (821) is provided with a through hole. The brake foot (831) passes through the through hole and can swing in the through hole. The driving groove (861) is used to drive the brake foot (831) to swing around the rotating platform (832).

5. The gearbox according to claim 1, characterized in that: The planetary gear set (74) includes a planetary gear carrier (90), a fixed external gear ring (91), and a rotatable shift gear ring (73). The planetary gear carrier (90) is rotatably connected to the shift shaft (87). Two sets of planetary transmission mechanisms are installed on the planetary gear carrier (90). Sun gear A (94) and sun gear B (95) are installed on the shift shaft (87). Sun gear A (94) and sun gear B (95) mesh with the two sets of planetary transmission mechanisms in a one-to-one correspondence. The shift gear ring (73) is provided with internal teeth of the shift gear ring. One set of planetary transmission mechanisms meshes with the external gear ring (91), and the other set of planetary transmission mechanisms meshes with the internal teeth of the shift gear ring.

6. The gearbox according to claim 4, characterized in that: The camshaft (86) is provided with a limiting groove (862), and the transmission shaft (82) is installed with a limiting post (85), which is inserted into the limiting groove (862).

7. The gearbox according to claim 1, characterized in that: A toothed disc (63) is fixed on the main transmission tooth (71).

8. The gearbox according to claim 5, characterized in that: The shift shaft (87) is radially fixedly connected to the sun gear B (95), and the shift shaft (87) is radially rotatably connected to the sun gear A (94).

9. The gearbox according to claim 8, characterized in that: A fixing ring (89) is fixed on the gear shaft (82). The sun gear A (94) is fixedly connected to the fixing ring (89). The fixing ring (89) is rotatably connected to the shift shaft (87). The sun gear A (94), the fixing ring (89), and the gear shaft (82) are coaxially arranged.

10. The gearbox according to claim 5, characterized in that: The gear ring (73) is provided with external gear ring teeth, the gear shifting power component is a gear shifting motor (75), and a drive gear is installed on the output shaft of the gear shifting motor (75), the drive gear meshing with the external gear ring teeth.

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