A mid-shaft transmission and a mid-mounted motor

Abstract

This utility model belongs to the field of transmission technology, and specifically relates to a mid-shaft transmission and a mid-mounted motor. The mid-shaft transmission and mid-mounted motor of this application detect the rotation angle of the crankshaft using a rotation angle sensor, and perform gear shifting between a first preset angle and a second preset angle. When the crankshaft rotates to the first preset angle and the second preset angle, the corresponding torque will be less than the maximum torque. Shifting within this range helps improve the success rate and smoothness of gear shifting.

Description

Technical Field

[0001] This utility model belongs to the field of transmission technology, and specifically relates to a central shaft transmission and a centrally mounted motor. Background Technology

[0002] Chinese patent document CN119617107A discloses a gear shifting device and a transmission, including a bushing with several mounting holes, one end of which has a mounting groove; several shift gears rotatably mounted on the bushing and corresponding to the positions of ratchet pawls; the inner rings of the shift gears are all provided with circumferential internal tooth grooves, which are arc-shaped tooth grooves; the number of ratchet pawls is equal to the total number of shift gears, one end of which has a protrusion and the other end has a sliding part, and the middle part of the ratchet rotatably mounts in the mounting groove; the shift gears include a shift gear M for meshing with the input gear. The total number of shift gears N and M that mesh with the output gear is equal to the number of available gears plus one. The tip circle diameter of each shift gear M increases in the direction of power input, while the tip circle diameter of each shift gear N decreases in the direction of power input. On the bushing, the pawls corresponding to shift gear M and shift gear N are arranged with opposite head and tail directions. The spindle has a gear drive section on its outer wall along the axial direction. The gear drive section includes several first drive sections and second and third drive sections located at both ends of the first drive sections. Adjacent first drive sections are evenly distributed at an angle along the circumference of the spindle. The total number of first, second, and third drive sections matches the number of shift gears. An elastic element is provided between the bottom of the pawl protrusion and the mounting groove to spring up the end and slide the pawl into the rotation path of the gear drive section.

[0003] When the spindle rotates, the pawl slides into the corresponding gear drive unit, and the protrusion of the pawl pops up and engages with the corresponding internal tooth groove; when the pawl slides into the outer wall of the spindle, the protrusion disengages from the internal tooth groove.

[0004] During the upshifting process, starting from first gear, as the pawl corresponding to the third drive unit slides within the third drive unit, the shift gear M engages with its corresponding pawl one by one in the direction away from the power input; as the pawl corresponding to the second drive unit slides within the second drive unit, the shift gear N engages with its corresponding pawl one by one in the direction away from the power input, thereby achieving a gradual increase in the gear ratio of each gear during upshifting.

[0005] Although shifting can be made smoother and riding more comfortable by engaging the next gear and disengaging the previous gear, as well as by improving the ratchet mechanism, situations where shifting is impossible can still occur during uphill riding or high-speed riding.

[0006] Therefore, existing technologies need to be improved and developed. Utility Model Content

[0007] The purpose of this application is to provide a central shaft transmission and a centrally mounted motor to improve shift success rate and smoothness.

[0008] This application provides a mid-shaft transmission, comprising:

[0009] The bottom bracket, rotatably supported on the frame, is connected to a crank, and torque is input from the bottom bracket;

[0010] The secondary shaft is hollow and parallel to the central shaft;

[0011] The transmission mechanism is connected to the central shaft and the secondary shaft respectively, and has at least two transmission ratios;

[0012] The drive unit, connected to the shifting mechanism, is located on the outside of the countershaft;

[0013] A shifting mechanism, linked to the transmission mechanism, is used to change the transmission ratio of the transmission mechanism;

[0014] The output component, fixed to the transmission mechanism, outputs torque;

[0015] A rotation angle sensor detects the rotation angle of the crank, and the central shaft rotates in the positive direction and performs gear shifting between a first preset angle and a second preset angle.

[0016] Furthermore, the first preset angle is 15 degrees higher than the vertical plane, and the second preset angle is 15 degrees lower than the vertical plane.

[0017] Furthermore, gear shifting is performed when the crank is in a vertical plane.

[0018] Furthermore, the gear shift is immediately performed when the central axis rotates in the opposite direction.

[0019] Furthermore, the rotation angle sensor includes a magnetic sensor and a radial magnetic ring. The radial magnetic ring is fixed on the central shaft, and the magnetic sensor is disposed opposite to the radial magnetic ring. The magnetic sensor senses the change in the magnetic field strength of the radial magnetic ring to detect the rotation angle of the crank.

[0020] Furthermore, the shifting mechanism includes at least two pawls, a reset member, and a rotation control member. A groove is provided on the secondary shaft, and the pawl is rotatably installed in the groove. One end of the reset member abuts against the secondary shaft, and the other end of the reset member abuts against the pawl. A control groove is provided on the outer peripheral surface of the rotation control member, and the pawl is located on the outside of the rotation control member.

[0021] When the rotation angle between the rotary control component and the countershaft deflects, one end of the pawl falls into the control groove, fixing the gear of the shifting mechanism to the countershaft to change the transmission ratio.

[0022] Furthermore, the rotation control component is disposed on the inner side of the sub-shaft, and the drive device is disposed on the outer side of the rotation control component.

[0023] Furthermore, the control groove is at least two spirally arranged through grooves, which are opened along the circumference of the rotation control member, and adjacent through grooves are not connected.

[0024] This application also provides a mid-drive motor, including the aforementioned mid-shaft gearbox, and further including an assist motor and an assist motor reduction mechanism, wherein the assist motor is connected to the transmission mechanism through the assist motor reduction mechanism.

[0025] As can be seen from the above, the central shaft gearbox and centrally mounted motor of this application detect the rotation angle of the crank through a rotation angle sensor and perform gear shifting between a first preset angle and a second preset angle. When the crank rotates to the first preset angle and the second preset angle respectively, the corresponding torque will be less than the maximum torque. Shifting gears in this range is beneficial to improving the success rate and smoothness of gear shifting.

[0026] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0027] Figure 1 is a perspective view of the shaft transmission in this application.

[0028] Figure 2 is a perspective view of the shaft transmission (without housing, output components, and crank) of this application.

[0029] Figure 3 is a top view of Figure 2.

[0030] Figure 4 is a cross-sectional view of Figure 3.

[0031] Figure 5 is a schematic diagram of the assembly of the countershaft and the shifting mechanism.

[0032] Figure 6 is a schematic diagram of the gear shifting process of the gear shifting mechanism.

[0033] Figure 7 is a cross-sectional view of the gear shifting process of the gear shifting mechanism.

[0034] Figure 8 is a perspective view of the rotation control component.

[0035] Figure 9 is a schematic diagram of the speed mixing mechanism.

[0036] Figure 10 is a schematic diagram of the crank angle.

[0037] Figure 11 is a graph of the angles collected by the rotation angle sensor.

[0038] Figure 12 is a schematic diagram of the structure of the motor in this application.

[0039] Label Explanation:

[0040] 1-Outer shell,

[0041] 2-Central axis,

[0042] 3-Secondary shaft, 31-Groove,

[0043] 4-Transmission mechanism, 41-First gear set, 411-First driving gear, 412-First driven gear,

[0044] 42-Second gear set, 421-Second driving gear, 4211-Locking groove, 422-Second driven gear,

[0045] 5-Shifting mechanism, 51-Pawl, 52-Reset component, 53-Rotation control component, 531-Control slot,

[0046] 6-Drive unit,

[0047] 7-Speed ​​mixing mechanism, 71-First ring gear, 72-First sun gear, 73-Planet carrier, 74-

[0048] Multi-planetary gear, 741-double planetary gear, 7411-first planetary gear, 7412-second planetary gear

[0049] Gears, 75 - Second sun gear, 76 - Second ring gear

[0050] 8-Input component, 81-Left crank, 82-Right crank

[0051] 9-Output assembly, 91-Transmission sleeve, 92-Output component, 93-One-way clutch,

[0052] 10-Assist motor,

[0053] 11-Assisted motor reduction mechanism,

[0054] 12-Rotation angle sensor, 121-Magnetic sensor, 122-Radial magnetic ring. Detailed Implementation

[0055] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0056] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "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. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0057] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0058] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0059] The bottom bracket derailleur of this application is fixedly installed at the bottom center of the vehicle frame. The bottom bracket derailleur includes a housing 1, a bottom bracket 2, a countershaft 3, a transmission mechanism 4, a drive unit 6, a shifting mechanism 5, and an output component 92. The housing 1 is fixed to the frame, and the countershaft 3 is rotatably supported within the housing 1. Except for the output component 92, all other parts are concealed inside the housing 1. Both ends of the bottom bracket 2 extend from the housing 1 and are rotatably supported on the frame. The two ends of the bottom bracket 2 are respectively fixedly connected to an input assembly 8, which includes a left crank 81 and a right crank 82. The cranks are rotatably connected to pedals. The rider transmits the torque generated by pedaling to the bottom bracket 2, which then inputs it to the transmission mechanism 4. The shifting mechanism 5 is linked to the transmission mechanism 4, which is used to change the gear ratio and output speed. Different gears are switched by changing the meshing relationship of different gears. The output component 92 is fixed to the transmission mechanism 4 and is used to output torque. The torque is then transmitted to the flywheel via chain or belt drive, which in turn drives the vehicle's rear wheels to rotate.

[0060] This device can be used on bicycles, folding bicycles, ebikes, electric-assisted bicycles, electric vehicles, electric motorcycles, electric cargo vehicles, tricycles, scooters, electric scooters, and other vehicles.

[0061] Figure 1 is a perspective view of the central shaft transmission of this application. Figure 2 is a perspective view of the central shaft transmission of this application (with housing 1, output component 92, and crank hidden). Figure 3 is a top view of Figure 2. Figure 4 is a cross-sectional view of Figure 3. The transmission mechanism 4 includes a first gear set 41 and a second gear set 42. The first gear set 41 includes a first driving gear 411 and a first driven gear 412 that mesh with each other. The first driving gear 411 is fixed to the central shaft 2, and the first driven gear 412 is fixed to the countershaft 3. The first driving gear 411 is driven to rotate by the central shaft 2, which in turn drives the first driven gear 412 to rotate the countershaft 3. In this embodiment, the number of teeth of the first driving gear 411 is greater than the number of teeth of the first driven gear 412. Therefore, the transmission ratio of the first gear set 41 is less than 1, which is a speed-increasing transmission.

[0062] The rotation of the countershaft 3 is transmitted to the second gear set 42, which includes a second driving gear 421 and a second driven gear 422 that mesh with each other. The second driving gear 421 is movably connected to the countershaft 3, and the second driven gear 422 is fixedly connected to a transmission sleeve 91, which is movably connected to the central shaft 2. The second driving gear 421 can be fixed or movable relative to the countershaft 3 through the shifting mechanism 5 to perform gear shifting. The transmission sleeve 91 and the output component 92 are collectively referred to as the output assembly 9.

[0063] In this embodiment, the second gear set 42 is provided with seven second driving gears 421 and seven second driven gears 422. As can be seen in Figure 4, the number of teeth of the second driving gears 421 decreases progressively from left to right, and correspondingly, the number of teeth of the second driven gears 422 increases progressively from left to right. Therefore, the second gear set 42 may be either a speed-increasing transmission or a speed-reducing transmission. This central shaft transmission has seven gears.

[0064] To achieve gear shifting, a gear shifting mechanism 5 is provided, which allows one of the six second drive gears 421 to be fixed to the countershaft 3. Figure 5 is a schematic diagram of the assembly of the countershaft 3 and the gear shifting mechanism 5. Figure 6 is a schematic diagram of the gear shifting process of the gear shifting mechanism 5. The gear shifting mechanism 5 includes at least two pawls 51, a reset member 52, and a rotation control member 53. A groove 31 is provided on the countershaft 3 along its circumference, and a rotating shaft is installed in the groove 31. At least two pawls 51 are arranged in a row along the axial direction of the countershaft 3 and are rotatably installed in the groove 31 after being mounted on the rotating shaft. The outer diameter of the rotation control member 53 is smaller than the outer diameter of the countershaft 3. The rotation control member 53 is hollow, and a control groove 531 is provided on the outer circumferential surface of the rotation control member 53. The pawls 51 are located on the outside of the rotation control member 53. One end of the reset member 52 abuts against the secondary shaft 3, and the other end of the reset member 52 abuts against the pawl 51. The reset member 52 presses down one end of the pawl 51, keeping it abutting against the outer peripheral surface of the rotation control member 53. It should be noted that the rotation control member 53 is not stationary; it rotates synchronously with the secondary shaft 3.

[0065] When the rotation angle between the rotation control component 53 and the secondary shaft 3 deviates, such as Figure 7 As shown, one end of the pawl 51 falls into the control groove 531, and the other end of the pawl 51 springs up and gets into the locking groove 4211 of the second drive gear 421, so that the second drive gear 421 of the shifting mechanism 5 is fixed to the countershaft 3 to change the transmission ratio.

[0066] In this embodiment, as shown in FIG8, the control groove 531 provided on the outer peripheral surface of the rotation control member 53 consists of at least two spirally arranged through grooves. The cross-section of the through groove is rectangular, and the length and width of the cross-section are adapted to the length and width of the pawl 51, respectively. The through grooves are opened along the circumference of the rotation control member 53, and adjacent through grooves are not connected. When one end of the pawl 51 falls into the control groove 531, the groove wall will restrict the axial movement of one end of the pawl 51, preventing the force of the gear of the transmission mechanism 4 on the pawl 51 from causing the other end of the pawl 51 to disengage from the locking groove 4211 of the second driving gear 421, ensuring that there is no gear skipping and guaranteeing the accuracy of gear shifting.

[0067] In this embodiment, six pawls 51 are provided. The second driving gear 421 with the fewest teeth is fixed to the countershaft 3. A one-way clutch 93 is provided between the second driven gear 422 with the largest number of teeth and the transmission sleeve 91. This design saves the need to set up a pawl 51 to control the second driving gear 421 with the fewest teeth. The principle is as follows: when none of the pawls 51 fall into the control groove 531 of the rotation control member 53, the one-way clutch 93 engages, and the second driving gear 421 with the fewest teeth meshes with the second driven gear 422 with the largest number of teeth for transmission. When one of the pawls 51 falls into the control groove 531 of the rotation control member 53, the second driving gear 421, except for the one with the fewest teeth which is fixed to the countershaft 3, rotates at a speed higher than the second driven gear 422 with the largest number of teeth, and the one-way clutch 93 disengages.

[0068] One-way clutch 93 can be roller clutch, wedge clutch, pawl clutch, friction clutch, electromagnetic clutch, etc.

[0069] The rotation control component 53 is located inside the sub-shaft 3, and the drive device 6 is located outside the rotation control component 53. This location on the outside facilitates heat dissipation for the drive device 6 and also makes its assembly easier. The rotation control component 53 can be directly controlled by the drive device 6, but the drive device 6 needs to acquire the rotational speed of the sub-shaft 3 and maintain it at the same speed as the rotation control component 53, which results in significant power consumption.

[0070] To facilitate the control of the rotation control element 53 of the shift mechanism 5, a speed mixing mechanism 7 is provided. Figure 9 shows the schematic diagram of the speed mixing mechanism 7. The speed mixing mechanism 7 is connected to the shift mechanism 5, the countershaft 3, and the drive device 6. When the drive device 6 does not perform a shift operation, that is, when the drive device 6 does not input rotation to the speed mixing mechanism 7, the speed mixing mechanism 7 causes the rotation control element 53 of the shift mechanism 5 and the countershaft 3 to rotate synchronously. When the drive device 6 performs a shift operation, the speed mixing mechanism 7 causes the rotation angle of the rotation control element 53 of the shift mechanism 5 and the countershaft 3 to deflect.

[0071] The speed mixing mechanism 7 includes a first ring gear 71, a first sun gear 72, a planet carrier 73, a multi-planet gear 74, a second ring gear 76, and a second sun gear 75. The multi-planet gear 74 is rotatably connected to the planet carrier 73 and meshes with the first ring gear 71, the first sun gear 72, the second ring gear 76, and the second sun gear 75 respectively. The first ring gear 71 is connected to the rotation control element 53 of the shifting mechanism 5, the second ring gear 76 is connected to the countershaft 3, the first sun gear 72 is connected to the drive unit 6, and the second sun gear 75 is connected to the housing 1.

[0072] The first gear ring 71 and the rotation control component 53 can be separate or integrated. Separate parts are easier to process, while integrated parts have higher structural strength. As shown in Figure 8, the first gear ring 71 and the rotation control component 53 are integrally formed.

[0073] The multi-planetary gear 74 can be a double, triple, or more planetary gear set. The more planetary gears there are, the larger the transmission ratio the speed mixing mechanism 7 can achieve. The larger the transmission ratio of the speed mixing mechanism 7, the less torque the drive unit 6 needs to provide under the same load.

[0074] In this embodiment, the multi-planetary gear 74 is a double-planetary gear 741, as shown in Figure 9. The double-planetary gear 741 includes a first planetary gear 7411 and a second planetary gear 7412 with the same number of teeth. The first planetary gear 7411 meshes with the first ring gear 71 and the first sun gear 72, respectively, and the second planetary gear 7412 meshes with the second ring gear 76 and the second sun gear 75, respectively. The double-planetary gear 741 has a simple structure and is easy to assemble. Since the transmission ratio of the speed mixing mechanism 7 is small, the drive device 6 needs to be a high-torque model.

[0075] When no gear shifting operation is performed, i.e., the drive device 6 does not rotate, the first sun gear 72 is essentially fixed due to the resistance of its output shaft. Since the first planetary gear 7411 and the second planetary gear 7412 of the double planetary gear 741 have the same number of teeth, the rotation control component 53 will be driven by the countershaft 3 and rotate in the same direction and at the same speed.

[0076] When a gear shift is required, the drive unit 6 rotates a certain number of revolutions in either the forward or reverse direction. The speed of the countershaft 3 and the speed of the first sun gear 72 are mixed and output to the rotation control unit 53. Specifically, when the speed of the first sun gear 72 and the speed of the countershaft 3 are in the same direction, the speed of the rotation control unit 53 is the sum of the speeds of the countershaft 3 and the first sun gear 72; when the speeds of the first sun gear 72 and the countershaft 3 are in opposite directions, the speed of the rotation control unit 53 is the difference between the speeds of the countershaft 3 and the first sun gear 72. After the gear shift is completed, the rotation control unit 53 resumes synchronous rotation with the countershaft 3.

[0077] The drive unit 6 is a shift motor, preferably an encoder motor. Encoder motors can acquire real-time information such as the motor's position, speed, and angle through an encoder, offering high measurement accuracy and suitability for applications requiring high precision in position, speed, and angle. The shift motor is fixedly connected to the housing 1, eliminating the need for it to rotate with the countershaft 3, thus avoiding power supply issues and reducing maintenance complexity.

[0078] Figure 10 is a schematic diagram of the crank angles. Let 0 degrees be the position of the right crank 82 directly above and the left crank 81 directly below; 90 degrees be the position of the right crank 82 directly to the right and the left crank 81 directly to the left; 180 degrees be the position of the right crank 82 directly below and the left crank 81 directly above; 270 degrees be the position of the right crank 82 directly to the left and the left crank 81 directly to the right; and 360 degrees be the position of the right crank 82 directly above and the left crank 81 directly below. This is a complete cycle.

[0079] Figure 11 is a graph of the angles collected by the rotation angle sensor 12. The process of maintaining a constant cadence by the cyclist is as follows: When the bottom bracket 2 rotates from 0 degrees clockwise (D1 direction) to 90 degrees, the cyclist's right foot gradually increases the pedaling force on the pedal and right crank 82, while the left foot does not produce any pedaling force on the pedal and left crank 81; when rotating from 90 degrees clockwise to 180 degrees, the cyclist's right foot gradually decreases the pedaling force on the pedal and right crank 82, while the left foot does not produce any pedaling force on the pedal and left crank 81; when rotating from 180 degrees clockwise to 270 degrees, the cyclist's left foot gradually increases the pedaling force on the pedal and left crank 81, while the right foot does not produce any pedaling force on the pedal and right crank 82; when rotating from 270 degrees clockwise to 360 degrees, the cyclist's left foot gradually decreases the pedaling force on the pedal and left crank 81, while the right foot does not produce any pedaling force on the pedal and right crank 82.

[0080] Ultimately, this is represented in Figure 11 as a sine wave function, with the expression: T = A |sin(θ)|, and a period of 180 degrees. The vertical axis represents the torque T (Torque) passing through the central axis 2, and the horizontal axis represents the rotation angle θ of the central axis 2. Tmin represents the minimum torque, which occurs at angles of 0 degrees, 180 degrees, 360 degrees, etc.; Tmax represents the maximum torque, which occurs at angles of 90 degrees, 270 degrees, 450 degrees, etc.

[0081] During uphill climbing or high-speed riding, the rider generates a large torque, with Tmax exceeding 80 Nm. If shifting is performed at a high torque, the large meshing force between the pawl 51 and the locking groove 4211 of the second drive gear 421 will hinder the rotation of the rotary control component 53, causing the rotary control component 53 to fail to rotate normally and thus preventing normal shifting. Furthermore, the drive device 6 that drives the rotary control component 53 may stall and burn out.

[0082] To avoid the above situation, the rotation angle sensor 12 detects the rotation angle of the crank and performs gear shifting between the first preset angle and the second preset angle. When the crank rotates to the first preset angle and the second preset angle respectively, the corresponding torque will be less than the maximum torque. Shifting gears in this range helps to improve the success rate and smoothness of gear shifting.

[0083] Specifically, the first preset angle is 15 degrees higher than the vertical plane, and the second preset angle is 15 degrees lower than the vertical plane. The vertical plane refers to the plane where the crank is located when the rotation angle θ of the central shaft 2 is 0 degrees, 180 degrees, 360 degrees, etc. If the rotation angle θ of the central shaft 2 is 0 degrees, the first preset angle is 15 degrees (∠a in Figure 10), and the second preset angle is -15 degrees (∠b in Figure 10); if the rotation angle θ of the central shaft 2 is 180 degrees, the first preset angle is 195 degrees, and the second preset angle is 165 degrees; and so on. The value of sin15° is approximately 0.26. If Tmax is 80 Nm, then the torque through the central shaft 2 between the first and second preset angles is controlled to be below 20.8 Nm. After passing through the reduction mechanism, the drive unit 6 can smoothly overcome the biting force between the pawl 51 and the locking groove 4211 of the second drive gear 421 to drive the rotation control component 53 to rotate, thereby smoothly completing the gear shift and improving the success rate of gear shifting and the riding experience.

[0084] Preferably, when the crank is in a vertical plane, the value of sin0° is 0, the biting force between the pawl 51 and the locking groove 4211 of the second drive gear 421 is very small, which can further improve the shift success rate, but the shift response speed will be reduced accordingly.

[0085] The rotation angle is obtained by setting a rotation angle sensor 12. The rotation angle sensor 12 includes photoelectric, resistive, inertial, and magnetic types. In this embodiment, a magnetic angle sensor with fewer parts, simple structure, low manufacturing cost, and high precision is used. It includes a magnetic sensor 121 and a radial magnetic ring 122. The radial magnetic ring 122 is fixed on the central shaft 2. There are two types of radial magnetic rings 122: one with the inner ring being the N pole and the outer ring being the S pole, and the other with half of the magnetic ring being the N pole and the other half being the S pole. Both types of radial magnetic rings 122 can generate changes in magnetic field strength when they rotate. The magnetic sensor 121 is set opposite to the radial magnetic ring 122. Specifically, the magnetic sensor 121 can be set on the radial outer side of the radial magnetic ring 122. The magnetic sensor 121 senses the change in magnetic field strength of the radial magnetic ring 122 to detect the rotation angle of the crank.

[0086] During riding, the rider may pedal backwards. During backwards pedaling, the bottom bracket 2 rotates in the opposite direction (D2 direction). At this time, the one-way clutch 93 is disengaged, and the biting force between the pawl 51 and the locking groove 4211 of the second drive gear 421 is small. Therefore, no matter what angle the bottom bracket 2 rotates in the opposite direction, gear shifting can be performed, which can improve the shifting response speed.

[0087] This application also provides a mid-drive motor, including the aforementioned mid-shaft gearbox, enabling the mid-drive motor to have both shifting and electric assist functions. As shown in Figure 12, the difference from the mid-shaft gearbox is the addition of an assist motor 10 and an assist motor reduction mechanism 11. The assist motor 10 is connected to the transmission mechanism 4. Specifically, the axis of the output shaft of the assist motor 10 is parallel to the axis of the mid-shaft 2. The assist motor 10 is connected to the first gear set 41 of the transmission mechanism 4 through the assist motor reduction mechanism 11.

[0088] When the assist motor 10 is working, in addition to the torque generated by the rider pedaling, there is also the torque generated by the assist motor 10. The combined torque of the two is output to the output component 92, enabling the rider to achieve higher riding speed or longer riding distance in a less strenuous riding manner.

[0089] A mid-drive motor with shifting function, compared to a rear-drive motor (hub motor) with shifting function, has its gear shifting structure located on the frame instead of the rear wheel. When impacted on rough roads, the impact is not directly transmitted to the hub through the rim and spokes, but is transmitted through the frame. The frame has a certain vibration absorption function, which greatly reduces the impact force. It is relatively less affected by external forces and less prone to bumps, making the mid-drive motor more durable.

[0090] Furthermore, vehicles equipped with a mid-drive motor are also equipped with a speed feedback system. For example, a GPS chip is added to obtain location information and calculate the vehicle's speed. In automatic mode, the rider does not need to operate the vehicle; the mid-drive gearbox performs gear shifting operations based on the vehicle's speed. For instance, when the vehicle speed reaches 10 kilometers per hour, it automatically shifts from first to second gear; conversely, when the vehicle speed drops below 10 kilometers per hour, it automatically shifts from second to first gear. Riders can switch to manual mode to freely change gears according to actual road conditions, increasing riding flexibility, or switch to free mode for automatic gear shifting, improving riding comfort.

[0091] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the described embodiment or example is included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0092] The above descriptions are merely some embodiments of this utility model. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of this utility model, and all such modifications and improvements fall within the protection scope of this utility model.

Claims

1. A mid-shaft transmission, characterized in that, include: The central shaft (2) is rotatably supported on the frame and connected to a crank, from which torque is input; The secondary shaft (3) is hollow and parallel to the central shaft (2); The transmission mechanism (4) is connected to the central shaft (2) and the secondary shaft (3) respectively, and has at least two transmission ratios; The drive unit (6) is connected to the shifting mechanism (5) and is located on the outside of the subshaft (3); The shifting mechanism (5) is linked with the transmission mechanism (4) and is used to change the transmission ratio of the transmission mechanism (4); The output component (92) is fixed to the transmission mechanism (4) and outputs torque; A rotation angle sensor (12) detects the rotation angle of the crank, and the central shaft (2) rotates in the forward direction and performs gear shifting between a first preset angle and a second preset angle.

2. The central shaft transmission according to claim 1, characterized in that, The first preset angle is 15 degrees higher than the vertical plane, and the second preset angle is 15 degrees lower than the vertical plane.

3. The central shaft transmission according to claim 1, characterized in that, Shifting is performed when the crank is in a vertical plane.

4. The central shaft transmission according to claim 1, characterized in that, The central shaft (2) rotates in the opposite direction and immediately performs a gear shift.

5. The central shaft transmission according to claim 1, characterized in that, The rotation angle sensor (12) includes a magnetic sensor (121) and a radial magnetic ring (122). The radial magnetic ring (122) is fixed on the central shaft (2). The magnetic sensor (121) is arranged opposite to the radial magnetic ring (122). The magnetic sensor (121) senses the change in the magnetic field strength of the radial magnetic ring (122) to detect the rotation angle of the crank.

6. The central shaft transmission according to claim 1, characterized in that, The shifting mechanism (5) includes at least two pawls (51), a reset member (52), and a rotation control member (53). The sub-shaft (3) has a groove (31). The pawl (51) is rotatably installed in the groove (31). One end of the reset member (52) abuts against the sub-shaft (3), and the other end of the reset member (52) abuts against the pawl (51). The outer circumferential surface of the rotation control member (53) is provided with a control groove (531), and the pawl (51) is located on the outside of the rotation control member (53). When the rotation angle between the rotation control component (53) and the countershaft (3) deflects, one end of the pawl (51) falls into the control groove (531), fixing the gear of the shifting mechanism (5) to the countershaft (3) to change the transmission ratio.

7. The central shaft transmission according to claim 6, characterized in that, The rotation control element (53) is located inside the sub-shaft (3), and the drive device (6) is located outside the rotation control element (53).

8. The central shaft transmission according to claim 6, characterized in that, The control slot (531) consists of at least two spirally arranged through slots (5312), which are opened along the circumference of the rotation control member (53), and adjacent through slots (5312) are not connected.

9. A mid-drive motor, comprising a mid-shaft gearbox as described in any one of claims 1-8, characterized in that, It also includes a power assist motor (10) and a power assist motor reduction mechanism (11), wherein the power assist motor (10) is connected to the transmission mechanism (4) through the power assist motor reduction mechanism (11).

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