Built-in variable-speed middle motor system, working method and vehicle

Abstract

The invention provides a built-in variable-speed middle motor system, a working method and a vehicle. A BB shaft is in transmission connection with a main output shaft through a first transmission device; the detection device detects rotation of the BB shaft, generates an electric signal and transmits the electric signal to the controller, and the controller controls the motor to start or stop; the motor is in transmission connection with the main output shaft through the first reduction gear, the second reduction gear is in transmission connection with the main output shaft, and the reduction ratio of the first reduction gear is different from that of the second reduction gear; under the action of the controller, the motor is started, the motor is in transmission connection with the main output shaft through the first speed reduction device, and the motor is switched to the second speed reduction device to be in transmission connection with the main output shaft according to any one or more parameters of the rotating speed of the motor, the rotating speed of the BB shaft and the vehicle speed. The pedal frequency can be stabilized in a certain interval, frequent manual gear shifting is not needed, the riding safety is improved, and the riding comfort is improved.

Description

Technical Field

[0001] The present invention relates to the field of vehicle power-assist technology, and in particular to a mid-mounted motor system with built-in speed change, a working method and a vehicle. Background Art

[0002] Power-assisted bicycle is a new type of two-wheeled vehicle, a type of bicycle. It uses batteries as an auxiliary power source, is equipped with a motor, and has a power assist system. It is a new type of transportation tool that can integrate human riding and motor assistance.

[0003] In the field of power-assisted bicycles, there are two main types of motor installation positions. One is the mid-mounted motor, which is installed in the middle of the vehicle body, that is, the motor at the bottom bracket position. The mid-mounted motor is connected to the frame and connected to the rear wheel through a chain to transmit power. At the same time, pedals are installed on both sides of the motor. When the motor has no power supply, the rider can use the pedals to achieve human riding, and the resistance is no different from that of a normal bicycle.

[0004] The other is installed in the wheel hub of the bicycle, which is called a hub motor. Compared with the hub motor, the mid-mounted motor has greater advantages in technology and performance.

[0005] At present, most bicycles have stepped speed shifting, and the gears need to be switched frequently during the speed shifting process. In addition, the speed difference between each gear is large. The excessive speed difference during speed shifting will also bring a poor riding feel, so there is room for improvement. Summary of the invention

[0006] In view of the defects in the prior art, an object of the present invention is to provide a mid-mounted motor system with built-in speed change and a vehicle.

[0007] According to the present invention, a mid-mounted motor system and vehicle with built-in speed change include: a BB shaft, a main output shaft, a first transmission device, a detection device, a controller, a motor, a first reduction device and a second reduction device; the BB shaft is connected to the main output shaft through the first transmission device; the detection device detects the rotation of the BB shaft and generates an electrical signal to transmit to the controller, and the controller controls the motor to start or shut down; the motor is connected to the main output shaft through the first reduction device and the main output shaft through the second reduction device, and the reduction ratio of the first reduction device is different from that of the second reduction device; under the action of the controller: the motor is started, the motor is connected to the main output shaft through the first reduction device, and according to any one or more parameters among the motor speed, the BB shaft speed and the vehicle speed, the motor is switched to the second reduction device and connected to the main output shaft.

[0008] Preferably, the first transmission device comprises a ratchet pawl, a planetary bracket and a first clutch, the BB shaft is transmission-connected to the planetary bracket via the ratchet pawl, and the planetary bracket is transmission-connected to the main output shaft via the first clutch.

[0009] Preferably, the first reduction device includes a triple gear and a single planetary gear, the output shaft of the motor is transmission connected to the first gear of the triple gear through a gear structure, the single planetary gear is transmission connected to the second gear of the triple gear, the single planetary gear is transmission connected to the main output shaft, and the single planetary gear is connected to the housing through a second clutch.

[0010] Preferably, the second reduction device includes a triple gear and a double planetary gear, the output shaft of the motor is transmission connected to the first gear of the triple gear through a gear structure, the first gear of the double planetary gear is transmission connected to the third gear of the triple gear, the second gear of the double planetary gear is transmission connected to the main output shaft, and the double planetary gear is connected to the planetary carrier.

[0011] Preferably, a triple gear, a single planetary gear, a double planetary gear and a second clutch are arranged between the output shaft of the motor and the main output shaft;

[0012] The output shaft of the motor is transmission-connected to the first gear of the triple gear through a gear structure, the single-link planetary gear transmission-connects the second gear of the triple gear to the main output shaft, and the single-link planetary gear is connected to the housing through a second clutch;

[0013] The first gear of the double planetary gear is transmission-connected to the third gear of the triple gear, the second gear of the double planetary gear is transmission-connected to the main output shaft, and the double planetary gear is connected to the planetary support;

[0014] The reduction ratio between the single planetary gear and the second gear of the triple gear is a fixed reduction ratio; the reduction ratio between the double planetary gear and the third gear of the triple gear is a variable reduction ratio.

[0015] Preferably, the detection device is arranged on the BB shaft, the crank or the housing.

[0016] According to a working method of a mid-mounted motor system with built-in speed change provided by the present invention, the working method comprises the following steps:

[0017] The BB shaft rotates and drives the main output shaft to rotate through the first transmission device;

[0018] The detection device detects the rotation of the BB shaft, generates an electrical signal and transmits it to the controller, the controller controls the motor to start, and the motor drives the main output shaft to rotate through the first reduction device;

[0019] The BB axis stops rotating, the detection device does not generate an electrical signal, the controller controls the motor to turn off, and the system returns to its initial state.

[0020] According to a working method of a mid-mounted motor system with built-in speed change provided by the present invention, the working method comprises the following steps:

[0021] The BB shaft rotates and drives the main output shaft to rotate through the first transmission device;

[0022] The detection device detects the rotation of the BB shaft, generates an electrical signal and transmits it to the controller, the controller controls the motor to start, and the motor drives the main output shaft to rotate through the first reduction device;

[0023] When any one or more parameters of the motor speed, the BB shaft speed and the vehicle speed reach a first threshold, the motor drives the main output shaft to rotate through the second reduction device;

[0024] The BB axis stops rotating, the detection device does not generate an electrical signal, the controller controls the motor to turn off, and the system returns to its initial state.

[0025] According to a working method of a mid-mounted motor system with built-in speed change provided by the present invention, the working method comprises the following steps:

[0026] The BB shaft rotates and drives the main output shaft to rotate through the first transmission device;

[0027] The detection device detects the rotation of the BB shaft, generates an electrical signal and transmits it to the controller, the controller controls the motor to start, and the motor drives the main output shaft to rotate through the first reduction device;

[0028] When any one or more parameters of the motor speed, the BB shaft speed and the vehicle speed reach a threshold value, the motor drives the main output shaft to rotate through the second reduction device;

[0029] When any one or more parameters of the rotation speed of the motor, the rotation speed of the BB shaft and the vehicle speed reach a second threshold, the first transmission device is disconnected from the main output shaft;

[0030] The BB shaft stops rotating, the detection device does not generate an electrical signal, the controller controls the motor to turn off, the first transmission device is connected to the main output shaft, the first reduction device connects the motor to the main output shaft, and the system returns to its initial state.

[0031] A vehicle provided according to the present invention also includes a frame, a front wheel and a rear wheel, the mid-mounted motor system is installed on the frame, both ends of the BB shaft are provided with pedals, a chainring is coaxially fixedly installed on the main output shaft, a flywheel is coaxially fixedly installed on the rear wheel, and the chainring and the flywheel are connected by a chain or belt drive.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention realizes different speed outputs by changing the meshing state of the planetary gears, and can stabilize the pedaling frequency in a certain range without frequent manual gear shifting, thereby improving driving safety; and whether it is a high-speed state when riding on a flat road or a low-speed state when climbing a slope, a certain pedaling frequency can be maintained, which helps to improve riding comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0035] Figure 1 It is a schematic diagram mainly showing the overall structure of the mid-mounted motor system of the present invention;

[0036] Figure 2 This is a schematic diagram of the present invention mainly showing that the torque sensor is integrated on the BB axis;

[0037] Figure 3 This is a schematic diagram of the present invention mainly showing that the strain gauge is attached to the BB axis;

[0038] Figure 4 This is a schematic diagram of the present invention mainly showing that a strain gauge is attached to a crank;

[0039] Figure 5 The present invention mainly embodies the installation schematic diagram of the mid-mounted motor system on a vehicle.

[0040] As shown in the figure:

[0041] Transmission mechanism 1 First clutch 11

[0042] Triple gear 2 Main output shaft 12

[0043] BB axis 3 Foot pedal 13

[0044] Housing 4 Crank 14

[0045] Single planetary gear 5 toothed disc 15

[0046] Second clutch 6 Chain 16

[0047] Double planetary gear 7 Flywheel 17

[0048] Detection device 8 Controller 18

[0049] Ratchet pawl 9 Motor 19

[0050] Planetary bracket 10 DETAILED DESCRIPTION

[0051] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0052] like Figure 1 As shown, a mid-mounted motor system with built-in speed change provided according to the present invention includes a housing 4, a BB shaft 3, a main output shaft 12, a first transmission device, a detection device 8, a controller 18, a motor 19, a first clutch 11, a second clutch 6, a first reduction device and a second reduction device.

[0053] The BB shaft 3, the main output shaft 12, the first transmission device, the first reduction device, the second reduction device, the first clutch 11 and the second clutch 6 are all arranged on the housing 4, the motor 19 is arranged inside or outside the housing 4, the controller 18 can be arranged inside or outside the housing 4, and the detection device 8 can be arranged inside or outside the housing 4.

[0054] The BB shaft 3 is connected to the main output shaft 12 through the first transmission device. The detection device 8 detects the rotation of the BB shaft 3 and generates an electrical signal to transmit to the controller 18, and the controller 18 controls the motor 19 to start or shut down. The motor 19 is connected to the main output shaft 12 through the first reduction gear and the second reduction gear respectively, and the reduction ratio of the first reduction gear is different from the reduction ratio of the second reduction gear. Under the action of the controller 18: the motor 19 is started, and the motor 19 is connected to the main output shaft 12 through the first reduction gear. According to the rotation speed of the motor 19, the rotation speed of the BB shaft 3 and any one or more parameters of the vehicle speed, the motor 19 switches to the second reduction gear and is connected to the main output shaft 12.

[0055] It should be noted that the switching between the first reduction gear and the second reduction gear can be determined by the rotation speed of the motor 19. For example, when the rotation speed of the motor 19 reaches the first threshold, the transmission structure between the motor 19 and the main output shaft 12 is switched from the first reduction gear to the second reduction gear. It can also be determined by the rotation speed of the BB shaft 3, or by the vehicle speed. Of course, in another feasible implementation, it can also be determined by any two parameters or three parameters. The core of the technical solution of the present application is to have two sets of reduction routes, and the switching of the two sets of reduction routes can be regulated by the controller 18.

[0056] Specifically, the first transmission device includes a ratchet pawl 9 , a planetary bracket 10 and a first clutch 11 . The BB shaft 3 is transmission-connected to the planetary bracket 10 via the ratchet pawl 9 , and the planetary bracket 10 is transmission-connected to the main output shaft 12 via the first clutch 11 .

[0057] The first reduction device includes a triple gear 2 and a single planetary gear 5. The output shaft of the motor 19 is connected to the first gear of the triple gear 2 through the gear structure 1, the single planetary gear 5 is connected to the second gear of the triple gear 2, the single planetary gear 5 is connected to the main output shaft 12, and the single planetary gear 5 is connected to the housing 4 through the second clutch 6.

[0058] The second reduction device includes a triple gear 2 and a double planetary gear 7. The output shaft of the motor 19 is connected to the first gear of the triple gear 2 through the gear structure 1. The first gear of the double planetary gear 7 is connected to the third gear of the triple gear 2. The second gear of the double planetary gear 7 is connected to the main output shaft 12, and the double planetary gear 7 is fixedly connected to the planetary bracket 10 through bearings or sleeves.

[0059] It should be noted that the first reduction gear and the second reduction gear of the present application can be of an integral design or a split design. The integral design means that the first reduction gear and the second reduction gear are two completely independent devices. The present application preferably adopts the first reduction gear and the second reduction gear of the integral design. In the transmission route, the first reduction gear and the second reduction gear share the motor 19, the gear structure 1 and the triple gear 2, which reduces the number of parts of the motor system as a whole, reduces the volume of the motor system, and improves the integration of the motor system.

[0060] In a preferred embodiment, the first reduction gear and the second reduction gear are of integral design:

[0061] A triple gear 2, a single planetary gear 5, a double planetary gear 7 and a second clutch 6 are arranged between the output shaft of the motor 19 and the main output shaft 12. The output shaft of the motor 19 is transmission-connected to the first gear of the triple gear 2 through the gear structure 1, the single planetary gear 5 transmission-connects the second gear of the triple gear 2 to the main output shaft 12, and the single planetary gear 5 is connected to the housing 4 through the second clutch 6. The first gear of the double planetary gear 7 is transmission-connected to the third gear of the triple gear 2, the second gear of the double planetary gear 7 is transmission-connected to the main output shaft 12, and the double planetary gear 7 is fixedly connected to the planetary bracket 10 through a bearing or a sleeve. The reduction ratio between the single planetary gear 5 and the second gear of the triple gear 2 is a fixed reduction ratio, and the reduction ratio between the double planetary gear 7 and the third gear of the triple gear 2 is a variable reduction ratio.

[0062] like Figure 2 , Figure 3 as well as Figure 4As shown, further, the detection device 8 of the technical solution of the present application can be configured inside the housing 4 or outside the housing 4. Specifically, the detection device 8 is configured on the BB shaft 3 or the crank 14 or the housing 4.

[0063] In a feasible implementation, the detection device 8 can be a torque sensor, which is integrated on the BB shaft 3. The torque and the cadence signal can be detected in an integrated manner, or in a dispersed manner, or only the cadence signal can be detected. It should be noted that the technical solution of the present application can also use a cadence sensor to detect the cadence signal. The cadence sensor can also use an external split sensor.

[0064] In another feasible implementation, the detection device 8 may be a strain gauge, and the strain gauge may be attached to the BB shaft 3 or the crank 14. It should be emphasized that the detection device 8 of the technical solution of the present application may adopt any detection device 8 in the prior art that can collect any one or more of the three signals of the pedaling frequency signal, the motor 19 speed signal, and the vehicle speed signal.

[0065] It should be noted that the first clutch 11 and the second clutch 6 of the present application are both overrunning clutches. When the first reduction gear drives the motor 19 and the main output shaft 12, a fixed reduction ratio is used between the motor 19 and the main output shaft 12. When the second reduction gear drives the motor 19 and the main output shaft 12, a variable reduction ratio is used between the motor 19 and the main output shaft 12.

[0066] The present invention provides a working method of a mid-mounted motor system with built-in speed change, the working method comprising the following steps:

[0067] The BB shaft 3 rotates and drives the main output shaft 12 to rotate through the first transmission device;

[0068] The detection device 8 detects the rotation of the BB shaft 3, generates an electrical signal and transmits it to the controller 18. The controller 18 controls the motor 19 to start, and the motor 19 drives the main output shaft 12 to rotate through the first reduction device;

[0069] The BB shaft 3 stops rotating, the detection device 8 does not generate an electrical signal, the controller 18 controls the motor 19 to turn off, and the system returns to the initial state.

[0070] According to a working method of a mid-mounted motor system with built-in speed change provided by the present invention, the working method comprises the following steps:

[0071] The BB shaft 3 rotates and drives the main output shaft 12 to rotate through the first transmission device;

[0072] The detection device 8 detects the rotation of the BB shaft 3, generates an electrical signal and transmits it to the controller 18. The controller 18 controls the motor 19 to start, and the motor 19 drives the main output shaft 12 to rotate through the first reduction device;

[0073] When any one or more parameters of the rotation speed of the motor 19, the rotation speed of the BB shaft 3 and the vehicle speed reach a first threshold, the motor 19 drives the main output shaft 12 to rotate through the second reduction device;

[0074] The BB shaft 3 stops rotating, the detection device 8 does not generate an electrical signal, the controller 18 controls the motor 19 to turn off, and the system returns to the initial state.

[0075] According to a working method of a mid-mounted motor system with built-in speed change provided by the present invention, the working method comprises the following steps:

[0076] The BB shaft 3 rotates and drives the main output shaft 12 to rotate through the first transmission device;

[0077] The detection device 8 detects the rotation of the BB shaft 3, generates an electrical signal and transmits it to the controller 18. The controller 18 controls the motor 19 to start, and the motor 19 drives the main output shaft 12 to rotate through the first reduction device;

[0078] When any one or more parameters of the rotation speed of the motor 19, the rotation speed of the BB shaft 3 and the vehicle speed reach a threshold value, the motor 19 drives the main output shaft 12 to rotate through the second reduction device;

[0079] When any one or more parameters of the rotation speed of the motor 19, the rotation speed of the BB shaft 3 and the vehicle speed reach a second threshold, the first transmission device is disconnected from the main output shaft 12;

[0080] The BB shaft 3 stops rotating, the detection device 8 does not generate an electrical signal, the controller 18 controls the motor 19 to turn off, the first transmission device is connected to the main output shaft 12, the first reduction device connects the motor 19 to the main output shaft 12, and the system returns to the initial state.

[0081] like Figure 5 As shown, a vehicle provided by the present invention also includes a frame, a front wheel and a rear wheel, a mid-mounted motor system is installed on the frame, both ends of the BB shaft 3 are equipped with pedals 13 through cranks 14, a chain plate 15 is coaxially fixedly installed on the main output shaft 12, and a flywheel 17 is coaxially fixedly installed on the rear wheel, and the chain plate 15 and the flywheel 17 are connected by a chain 16 or a belt drive. The flywheel 17 and the chain plate 15 have a fixed reduction ratio.

[0082] How it works

[0083] Specifically, when the motor 19 is not working, the pedal torque is transmitted through the BB shaft 3, the torque sensor, the ratchet pawl 9, the planetary bracket 10, the first clutch 11K2, and the output shaft. The toothed disc 15 is fixed on the output shaft, thereby driving the toothed disc 15 to rotate together, and the toothed disc 15 drives the flywheel 17 through the chain 16 or the belt, so that the bicycle starts to ride. This state is a pure human power state, and the reduction ratio is a fixed reduction ratio between the toothed disc 15 and the flywheel 17.

[0084] When the motor 19 is working, the pedal torque drives the torque sleeve through the BB shaft 3 to make the detection device 8, that is, the torque sensor, generate an electrical signal. The controller 18 receives the signal to start the motor 19, and the motor 19 starts to work. The power of the motor 19 is transmitted to the triple gear 2 through the transmission mechanism. Because the single planetary gear 5 is fixed to the housing 4 through the second clutch 6, there is a large fixed reduction ratio between the triple gear 2, the single planetary gear 5, and the main output shaft 12, and there is a large torque output, which is suitable for the working conditions when just starting or climbing. When the pedal torque signal continues to be generated, the motor 19 starts to accelerate. When the speed reaches a certain value, the second clutch 6 is disconnected. At this time, there is no more power transmission between the triple gear 2, the single planetary gear 5, and the main output shaft 12. The power is mainly transmitted through the triple gear 2, the double planetary gear 7 and the main output shaft 12. Therefore, the path reduction ratio is small, and then there is a large output speed. Therefore, the vehicle enters the high-speed mode, which is a variable reduction ratio. The main output shaft 12 rotates with the planetary bracket 10 through the first clutch 11. When the speed further reaches a certain value, the pedaling frequency cannot keep up with the rotation speed of the planetary bracket 10, the torque sensor cannot receive the pedaling torque, no signal is generated, the motor 19 stops working, and the high-speed state cannot be sustained. At this time, the first clutch 11 needs to be disconnected, the planetary bracket 10 stops rotating, and the pedaling torque continues to act on the torque sleeve to generate a torque signal to maintain the high-speed output of the motor 19. When the ride is completed, the pedaling torque stops, the torque sensor no longer generates an electrical signal, the controller 18 no longer starts the motor 19, the motor 19 stops working, the vehicle speed begins to decrease, the first clutch 11 is connected, and the second clutch 6 is connected after the speed is further reduced. The speed change mechanism returns to the low-speed mode until the vehicle speed drops to zero, and the entire ride ends. The advantage of this mechanism is that whether it is a high-speed state of flat road riding or a low-speed state when climbing a slope, a certain pedaling frequency can be maintained, giving the rider a comfortable and stable riding experience. The present application realizes different speed outputs by changing the meshing state of the planetary gears, and can stabilize the pedaling frequency within a certain range without frequent manual gear shifting, thereby improving driving safety.

[0085] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0086] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A mid-mounted motor system with built-in speed change, characterized in that: include: A BB shaft (3), a main output shaft (12), a first transmission device, a detection device (8), a controller (18), a motor (19), a first reduction device, and a second reduction device; The BB shaft (3) is transmission-connected to the main output shaft (12) via a first transmission device; The detection device (8) detects the rotation of the BB shaft (3) and generates an electrical signal which is transmitted to the controller (18), and the controller (18) controls the motor (19) to start or stop; The motor (19) is respectively connected to the main output shaft (12) through a first reduction gear and connected to the main output shaft (12) through a second reduction gear, and the reduction ratio of the first reduction gear is different from the reduction ratio of the second reduction gear; Under the action of the controller (18), the motor (19) is started, the motor (19) is connected to the main output shaft (12) through a first reduction gear, and according to the rotation speed of the motor (19), the rotation speed of the BB shaft (3) and any one or more parameters of the vehicle speed, the motor (19) is switched to the second reduction gear to be connected to the main output shaft (12).

2. The mid-mounted motor system with built-in speed change as claimed in claim 1, characterized in that: The first transmission device comprises a ratchet pawl (9), a planetary bracket (10) and a first clutch (11); the BB shaft (3) is transmission-connected to the planetary bracket (10) via the ratchet pawl (9); and the planetary bracket (10) is transmission-connected to the main output shaft (12) via the first clutch (11).

3. The mid-mounted motor system with built-in speed change as claimed in claim 1, characterized in that: The first reduction device comprises a triple gear (2) and a single planetary gear (5); the output shaft of the motor (19) is transmission-connected to the first gear of the triple gear (2) via a gear structure (1); the single planetary gear (5) is transmission-connected to the second gear of the triple gear (2); the single planetary gear (5) is transmission-connected to the main output shaft (12); and the single planetary gear (5) is connected to the housing (4) via a second clutch (6).

4. The mid-mounted motor system with built-in speed change as claimed in claim 2, characterized in that: The second reduction device comprises a triple gear (2) and a double planetary gear (7); the output shaft of the motor (19) is transmission-connected to the first gear of the triple gear (2) through a gear structure (1); the first gear of the double planetary gear (7) is transmission-connected to the third gear of the triple gear (2); the second gear of the double planetary gear (7) is transmission-connected to the main output shaft (12); and the double planetary gear (7) is connected to the planetary carrier (10).

5. The mid-mounted motor system with built-in speed change as claimed in claim 2, characterized in that: A triple gear (2), a single-link planetary gear (5), a double-link planetary gear (7) and a second clutch (6) are arranged between the output shaft of the motor (19) and the main output shaft (12); The output shaft of the motor (19) is transmission-connected to the first gear of the triple gear (2) through the gear structure (1); the single-link planetary gear (5) transmission-connects the second gear of the triple gear (2) to the main output shaft (12); and the single-link planetary gear (5) is connected to the housing (4) through the second clutch (6); The first gear of the double planetary gear (7) is transmission-connected to the third gear of the triple gear (2), the second gear of the double planetary gear (7) is transmission-connected to the main output shaft (12), and the double planetary gear (7) is connected to the planetary support (10); The reduction ratio between the single-link planetary gear (5) and the second gear of the triple gear (2) is a fixed reduction ratio; the reduction ratio between the double-link planetary gear (7) and the third gear of the triple gear (2) is a variable reduction ratio.

6. The mid-mounted motor system with built-in speed change as claimed in claim 1, characterized in that: The detection device (8) is arranged on the BB shaft (3) or the crank (14) or the housing (4).

7. A method for operating a mid-mounted motor system with built-in speed change, characterized in that: The mid-mounted motor system with built-in speed change according to any one of claims 1 to 6 is adopted, and the working method comprises the following steps: The BB shaft (3) rotates and drives the main output shaft (12) to rotate through the first transmission device; The detection device (8) detects the rotation of the BB shaft (3) to generate an electrical signal and transmits it to the controller (18). The controller (18) controls the motor (19) to start, and the motor (19) drives the main output shaft (12) to rotate through the first reduction device. The BB shaft (3) stops rotating, the detection device (8) does not generate an electrical signal, the controller (18) controls the motor (19) to turn off, and the system returns to an initial state.

8. A method for operating a mid-mounted motor system with built-in speed change, characterized in that: The mid-mounted motor system with built-in speed change according to any one of claims 1 to 6 is adopted, and the working method comprises the following steps: The BB shaft (3) rotates and drives the main output shaft (12) to rotate through the first transmission device; The detection device (8) detects the rotation of the BB shaft (3) to generate an electrical signal and transmits it to the controller (18). The controller (18) controls the motor (19) to start, and the motor (19) drives the main output shaft (12) to rotate through the first reduction device. When any one or more parameters of the rotation speed of the motor (19), the rotation speed of the BB shaft (3) and the vehicle speed reach a first threshold, the motor (19) drives the main output shaft (12) to rotate through the second reduction device; The BB shaft (3) stops rotating, the detection device (8) does not generate an electrical signal, the controller (18) controls the motor (19) to turn off, and the system returns to an initial state.

9. A method for operating a mid-mounted motor system with built-in speed change, characterized in that: The mid-mounted motor system with built-in speed change according to any one of claims 1 to 6 is adopted, and the working method comprises the following steps: The BB shaft (3) rotates and drives the main output shaft (12) to rotate through the first transmission device; The detection device (8) detects the rotation of the BB shaft (3) to generate an electrical signal and transmits it to the controller (18). The controller (18) controls the motor (19) to start, and the motor (19) drives the main output shaft (12) to rotate through the first reduction device. When any one or more parameters of the rotation speed of the motor (19), the rotation speed of the BB shaft (3) and the vehicle speed reach a threshold value, the motor (19) drives the main output shaft (12) to rotate through the second reduction device; When any one or more parameters of the rotation speed of the motor (19), the rotation speed of the BB shaft (3) and the vehicle speed reach a second threshold, the first transmission device is disconnected from the main output shaft (12); The BB shaft (3) stops rotating, the detection device (8) does not generate an electrical signal, the controller (18) controls the motor (19) to turn off, the first transmission device is connected to the main output shaft (12), the first reduction device connects the motor (19) to the main output shaft (12), and the system returns to an initial state.

10. A vehicle, characterized in that: The mid-mounted motor system with built-in speed change as claimed in any one of claims 1 to 6 further comprises a frame, a front wheel and a rear wheel, wherein the mid-mounted motor (19) system is mounted on the frame, pedals (13) are arranged at both ends of the BB shaft (3), a chainring (15) is coaxially fixedly mounted on the main output shaft (12), a flywheel (17) is coaxially fixedly mounted on the rear wheel, and the chainring (15) and the flywheel (17) are connected by a chain (16) or a belt drive.

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