Patent Publication Number: US-2022221053-A1

Title: Gear shifting mechanism, two-speed gearbox, and vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Chinese Patent Application No. 202110350869.9, filed on Mar. 31, 2021, which is hereby incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     This application relates to the field of power transmission technologies, and in particular, to a gear shifting mechanism, a two-speed gearbox, and a vehicle. 
     BACKGROUND 
     A gear shifting mechanism of an automobile gearbox is one of the most important components in an automobile transmission system. A main function of the gear shifting mechanism is to change a transmission ratio and output an appropriate traction force to wheels through a transmission shaft, to meet requirements of a vehicle in different cases. The gear shifting mechanism is an operating mechanism of the gearbox, and is usually fixed on a housing. The gear shifting mechanism drives a motor according to an indication of a driver or based on a driving status, to control the gear shifting mechanism to implement forward or backward movement of a shifting fork, so as to control opening and closing of a synchronizer, a dog clutch, or a dry clutch. Closing of the dog clutch means that two tooth surfaces of the dog clutch are meshed. When the current gear shifting mechanism controls the shifting fork to move forward, the two tooth surfaces of the dog clutch are attached tooth to tooth. In this case, the two tooth surfaces are not meshed, a drive motor continues operating, and the shifting fork cannot move forward. As a result, a motor stalling phenomenon occurs, and the motor is burnt out. 
     SUMMARY 
     This application provides a gear shifting mechanism that is capable of preventing a drive motor from being burnt out due to stalling of the drive motor when a shifting fork pushes a dog clutch to be in a tooth-to-tooth state. 
     According to a first aspect, this application provides a gear shifting mechanism. The gear shifting mechanism includes a drive motor, a shifting drum, and a first shifting mechanism. 
     The shifting drum includes a gear shifting shaft and a first guiding contour disposed in a circumferential direction of the gear shifting shaft. The first guiding contour has a path in an axial direction of the gear shifting shaft. The drive motor is capable of driving the gear shifting shaft to rotate around the axial direction of the gear shifting shaft. 
     The first shifting mechanism includes an inner shaft, an outer hub, a first coupling pin, a first shifting fork, and an elastic component. The outer hub is sleeved on the inner shaft and is capable of moving relative to an axial direction of the inner shaft. The outer hub and the gear shifting shaft are movably connected in the axial direction of the gear shifting shaft. The outer hub and the gear shifting shaft are fixedly connected in the circumferential direction of the gear shifting shaft. One end of the first coupling pin is fixed on an outer side of the outer hub, and the other end of the first coupling pin is inserted into the first guiding contour and is capable of sliding in the first guiding contour. The first shifting fork is fixed on the inner shaft and is located on the outer side of the outer hub. 
     The elastic component is sleeved on the inner shaft and is located between the inner shaft and the outer hub. There are a first limiting portion and a second limiting portion between the outer hub and the inner shaft. The second limiting portion is located on a side, of the first limiting portion, that is away from the first shifting fork. The elastic component is located between the first limiting portion and the second limiting portion in the axial direction of the inner shaft. The first limiting portion is connected to one of the outer hub and the inner shaft, and the second limiting portion is connected to the other of the outer hub and the inner shaft. 
     In this application, a benefit of disposing the elastic component between the outer hub and the inner shaft lies in that, the elastic component can continue absorbing an acting force when a first gear shifting tooth portion and a second gear shifting tooth portion are attached to each other, to absorb an axial acting force that occurs when a dog clutch is in a tooth-to-tooth state, thereby preventing the drive motor from being burnt out due to stalling of the drive motor. 
     In a possible implementation, an orthographic projection of the first guiding contour in the axial direction of the gear shifting shaft is a straight line with a specific length. 
     In a possible implementation, the first guiding contour is a groove type guiding contour or an opening type guiding contour. 
     In a possible implementation, the first coupling pin is connected and fixed to the outer hub through soldering or integral molding or by using a screw. 
     In an implementation, the first limiting portion may be connected and fixed to one of the outer hub and the inner shaft through soldering or integral molding, and the second limiting portion may be connected and fixed to the other of the outer hub and the inner shaft through soldering or integral molding. 
     In a possible implementation, two ends of the elastic component are fixedly connected to the first limiting portion and the second limiting portion respectively. 
     In a possible implementation, a first end of the elastic component may be fixedly connected to the first limiting portion through soldering or by using a hook, or the like, and a second end of the elastic component may be fixedly connected to the second limiting portion through soldering or by using a hook, or the like. Shapes of structures of the first limiting portion and the second limiting portion are not limited. The first limiting portion and the second limiting portion may be bosses, snap rings, or the like. The elastic component may be a spring, a clip, or the like. 
     In a possible implementation, two ends of the elastic component abut against the first limiting portion and the second limiting portion respectively. 
     In an implementation, a blocking portion is further disposed on a side, of the first limiting portion, that is away from the second limiting portion, and the blocking portion is fixedly connected to the inner shaft. 
     In some implementations, a first end of the elastic component is fixedly connected to the first limiting portion, and a second end of the elastic component abuts against the second limiting portion. In some implementations, a first end of the elastic component abuts against the first limiting portion, and a second end of the elastic component is fixedly connected to the second limiting portion. 
     In some implementations, the first shifting fork is adjacent to the first limiting portion, and orthographic projections of the first limiting portion and the first shifting fork on a radial profile of the inner shaft at least partially overlap. 
     In a possible implementation, the first shifting mechanism further includes a hub-rotation limiting component. One end of the hub-rotation limiting component is disposed with a first limiting portion sleeved on the outer hub. A first limiting plane is disposed on an inner surface of the first limiting portion. A second limiting plane matching the first limiting plane is disposed on the outer hub. The first limiting plane is attached to the second limiting plane. The other end of the hub-rotation limiting component is disposed with a second limiting portion. The second limiting portion includes a limiting curved surface that is concave toward the first limiting portion. The limiting curved surface surrounds a part of a surface of the gear shifting shaft and is spaced from the gear shifting shaft. 
     In a possible implementation, the gear shifting mechanism further includes a worm and a worm gear that are meshed with each other. The worm is connected to the drive motor. The worm gear is sleeved on the gear shifting shaft and is fixedly connected to the gear shifting shaft. When the drive motor operates, the worm is driven to rotate, and the worm drives the worm gear to rotate, so as to drive the gear shifting shaft to rotate. 
     In a possible implementation, the second guiding contour and the worm gear are fixedly connected, and may be integrally formed. 
     In a possible implementation, the shifting drum further includes a second guiding contour disposed in the circumferential direction of the gear shifting shaft. The second guiding contour has a path in the axial direction of the gear shifting shaft. 
     The gear shifting mechanism further includes a second shifting mechanism. The second shifting mechanism includes a second coupling pin, a second shifting fork, and a supporting shaft. The second coupling pin is connected to a first end of the second shifting fork and is located in the second guiding contour. A via is disposed in the middle of the second shifting fork. The supporting shaft is inserted into the via. The second shifting fork is capable of rotating relative to the supporting shaft. When the gear shifting shaft rotates, the second coupling pin and the first end of the first shifting fork are pushed to slide in the axial direction of the gear shifting shaft, and a second end of the second shifting fork moves in a direction opposite to that of the first end of the first shifting fork through the supporting shaft. 
     In a possible implementation, a distance between the first end of the second shifting fork and the supporting shaft is greater than a distance between the second end of the second shifting fork and the supporting shaft. 
     In a possible implementation, an end face of the second end of the second shifting fork is an arc surface. 
     In a possible implementation, the second end of the second shifting fork includes at least two supporting points. 
     In a possible implementation, the second shifting mechanism further includes a push pin, and the second end of the second shifting fork abuts against one end of the push pin. 
     In a possible implementation, the second end of the second shifting fork is configured to be disconnected from and connected to a second gear shifting connection mechanism. The second gear shifting connection mechanism is a friction clutch. A path, in the second guiding contour, that is used to control connection and disconnection of the friction clutch is a curved path. 
     According to a second aspect, this application provides a two-speed gearbox. The two-speed gearbox includes a first gear shifting connection mechanism and the gear shifting mechanism according to any one of the foregoing implementations. The first gear shifting connection mechanism is connected to the first shifting fork. The first shifting fork controls connection and disconnection of the first gear shifting connection mechanism through axial movement. 
     In a possible implementation, the two-speed gear shifting mechanism further includes a second gear shifting connection mechanism. The second shifting fork controls connection and disconnection of the second gear shifting connection mechanism through axial movement. 
     In a possible implementation, the two-speed gearbox further includes a first gear apparatus and a second gear apparatus. The first gear apparatus includes a first gear and a first rotary shaft. When the first gear shifting connection mechanism is in a connected state, the first gear is connected to the first rotary shaft. In this case, the two-speed gearbox may transmit a first shifting power through the first gear and the first rotary shaft. The first shifting power is at a low gear. When the first gear shifting connection mechanism is in a disconnected state, the first gear is disconnected from the first rotary shaft. In this case, no first shifting power can be transmitted between the first gear and the first rotary shaft. The second gear apparatus includes a second gear and a second rotary shaft. When the second gear shifting connection mechanism is in a connected state, the second gear is connected to the second rotary shaft. In this case, the two-speed gearbox may transmit a second shifting power through the second gear and the second rotary shaft. The second shifting power is at a high gear. When the second gear shifting connection mechanism is in a disconnected state, the second gear is disconnected from the second rotary shaft. In this case, no second shifting power can be transmitted between the second gear and the second rotary shaft. 
     According to a third aspect, this application provides a vehicle. The vehicle includes front wheels, rear wheels, a vehicle body connected between the front wheels and the rear wheels, and the foregoing two-speed gearbox. The two-speed gearbox is mounted on the vehicle body. The vehicle further includes a reduction gear and a differential. An intermediate shaft in the two-speed gearbox is connected to the final gear. The differential is connected between two front wheels or between the front wheels and the rear wheels. The final gear can reduce a rotational speed of the intermediate shaft. The differential is configured to adjust a difference between rotational speeds of gears. The vehicle includes an automobile, an electric vehicle, or a special operation vehicle. The electric vehicle includes a two-wheeled, three-wheeled, or four-wheeled electric vehicle. The special operation vehicle includes a variety of vehicles with specific functions, for example, an engineering rescue vehicle, a sprinkler vehicle, a sewage suction vehicle, a cement mixer truck, a lifting vehicle, and a medical vehicle. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       To describe technical solutions in embodiments of this application more clearly, the following briefly describes the accompanying drawings used in the embodiments of this application. 
         FIG. 1  is a schematic diagram of a structure of a gear shifting mechanism according to an implementation of this application; 
         FIG. 2  is a schematic diagram of a structure of a shifting drum according to an implementation of this application; 
         FIG. 3  is a schematic diagram of locations of a shifting drum and a first shifting structure in a gear shifting mechanism according to an implementation of this application; 
         FIG. 4  is a schematic diagram of a structure of a first shifting structure according to an implementation of this application; 
         FIG. 5  is a cross-sectional view of a first shifting structure according to an implementation of this application; 
         FIG. 6  is a cross-sectional view of a first shifting structure according to an implementation of this application; 
         FIG. 7  is a cross-sectional view of a first shifting structure according to an implementation of this application; 
         FIG. 8  is a cross-sectional view of a first shifting structure according to an implementation of this application; 
         FIG. 9  is a cross-sectional view of a first shifting structure according to an implementation of this application; 
         FIG. 10  is a schematic diagram of locations of a hub-rotation limiting component, a gear shifting shaft, and an outer hub according to an implementation of this application; 
         FIG. 11  is a schematic diagram of locations of a hub-rotation limiting component, a gear shifting shaft, and an outer hub according to an implementation of this application; 
         FIG. 12  is a schematic diagram of a structure of a second shifting structure according to an implementation of this application; 
         FIG. 13  is a schematic diagram of locations of a second shifting fork and a push pin in a second shifting structure according to an implementation of this application; 
         FIG. 14  is a schematic diagram of locations of a push pin and a friction clutch according to an implementation of this application; 
         FIG. 15  is a diagram of a relationship between a value of a friction force between a plurality of friction plates, and an axial distance of a push pin according to an implementation of this application; 
         FIG. 16  is a schematic expanded view of paths of a first guiding contour and a second guiding contour according to an implementation of this application; 
         FIG. 17  is a schematic diagram of a structure of a two-speed gearbox according to an implementation of this application; and 
         FIG. 18  is a schematic diagram of a structure of a vehicle according to an implementation of this application. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The following describes the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. It is clear that the described embodiments are merely a part but not all of the embodiments of this application. 
     The terms such as “first” and “second” in this specification are merely intended for a purpose of description, and shall not be understood as an indication or implication of relative importance or implicit indication of a quantity of indicated technical features. Therefore, a feature limited by “first” or “second” may explicitly or implicitly include one or more features. In the descriptions of this application, unless otherwise stated, “a plurality of” means two or more than two. 
     In addition, in this specification, orientation terms such as “top” and “bottom” are defined relative to orientations of structures in the accompanying drawings. It should be understood that these orientation terms are relative concepts used for relative description and clarification, and may correspondingly change according to changes in the orientations of the structures in the accompanying drawings. 
     Refer to  FIG. 1 ,  FIG. 2 , and  FIG. 3 . An implementation of this application provides a gear shifting mechanism  10 . The gear shifting mechanism  10  includes a drive motor  100 , a shifting drum  200 , and a first shifting mechanism  300 . 
     The shifting drum  200  includes a gear shifting shaft  210  and a first guiding contour  220  disposed in a circumferential direction of the gear shifting shaft  210 . The first guiding contour  220  has a path in an axial direction of the gear shifting shaft  210 . The drive motor  100  is capable of driving the gear shifting shaft  210  to rotate around the axial direction of the gear shifting shaft  210 . The path of the first guiding contour  220  encircles the gear shifting shaft  210  once in the circumferential direction of the gear shifting shaft  210 , and has a specific path in the axial direction of the gear shifting shaft  210 . In other words, an orthographic projection of the first guiding contour  220  in the axial direction of the gear shifting shaft  210  is a straight line with a specific length. Therefore, a component located in the first guiding contour  220  can be guided to move in the axial direction of the gear shifting shaft  210 . A specific path of the first guiding contour  220  may be arranged according to an actual requirement. The first guiding contour  220  is but is not limited to a groove type guiding contour or an opening type guiding contour, and is a groove type guiding contour in this implementation. The groove type guiding contour is a groove structure that has an opening only on one side and has a groove bottom on the other side. The opening type guiding contour is a guiding contour having only one sliding surface, and a component slides on the sliding surface. For example,  230  in  FIG. 2  indicates an opening type guiding contour. 
     Refer to  FIG. 3  and  FIG. 4 . The first shifting mechanism  300  includes a first shifting fork  310 , an inner shaft  320 , an outer hub  330 , a first coupling pin  340 , and an elastic component  350  (as shown in  FIG. 5 ). The outer hub  330  is sleeved on the inner shaft  320  and is capable of moving relative to an axial direction of the inner shaft  320 . The outer hub  330  and the gear shifting shaft  210  are movably connected in the axial direction of the gear shifting shaft  210  (refer to  FIG. 4 ). The outer hub  330  and the gear shifting shaft  210  are fixedly connected in the circumferential direction of the gear shifting shaft  210 . To be specific, the outer hub  330  can move only relative to the gear shifting shaft  210  in the axial direction of the gear shifting shaft  210 , but cannot rotate relative to the gear shifting shaft  210  in the circumferential direction of the gear shifting shaft  210 , and the outer hub  33  sleeved on the inner shaft  320  cannot rotate relative to the gear shifting shaft  210  around the axial direction of the gear shifting shaft  210 , either. In this implementation, the outer hub  330  is further prevented, by using a hub-rotation limiting component  360 , from rotating on its own axis around the inner shaft  320  (as shown in  FIG. 3 ). Usually, a housing is disposed outside the gear shifting mechanism  10 . The inner shaft  320  and the gear shifting shaft  210  are limited on the housing, so that the inner shaft  320  can move relative to the gear shifting shaft  210  in the axial direction of the gear shifting shaft  210 , and the gear shifting shaft  210  can only rotate on its own axis, but cannot move in its own axial direction. A manner of limiting the inner shaft  320  and the gear shifting shaft  210  on the housing is not limited in this application, provided that the inner shaft  320  can move relative to the gear shifting shaft  210  in the axial direction of the gear shifting shaft  210  rather than being fixedly locked. 
     One end of the first coupling pin  340  is fixed to an outer side of the outer hub  330  (as shown in  FIG. 3 ), and the other end of the first coupling pin  340  is inserted into the first guiding contour  220  and is capable of sliding in the first guiding contour  220 . The first coupling pin  340  may be connected and fixed to the outer hub  330  through soldering or integral molding or by using a screw. Because the outer hub  330  can move only relative to the gear shifting shaft  210  in the axial direction of the gear shifting shaft  210 , but cannot rotate around the axial direction of the gear shifting shaft  210 , the first coupling pin  340  connected to the outer hub  330  can also move only relative to the gear shifting shaft  210  in the axial direction of the gear shifting shaft  210 , but cannot rotate around the axial direction of the gear shifting shaft  210 . 
     The first shifting fork  310  is fixed on the inner shaft  320  and is located on the outer side of the outer hub  330  (as shown in  FIG. 4 ). When the inner shaft  320  moves in an axial direction, the first shifting fork  310  may be driven to move in the axial direction of the inner shaft  320 . 
     Refer to  FIG. 5 . The elastic component  350  is sleeved on the inner shaft  320  and is located between the inner shaft  320  and the outer hub  330 . There are a first limiting portion  331  and a second limiting portion  332  between the outer hub  330  and the inner shaft  320 . The second limiting portion  332  is located on a side, of the first limiting portion  331 , that is away from the first shifting fork  310 . The elastic component  350  is located between the first limiting portion  331  and the second limiting portion  332  in an axial direction of the inner shaft  320 . The first limiting portion  331  is connected to one of the outer hub  330  and the inner shaft  320 , and the second limiting portion  332  is connected to the other of the outer hub  330  and the inner shaft  320 . 
     In this implementation, the first limiting portion  331  is connected to the outer hub  330 , and the second limiting portion  332  is connected to the inner shaft  320 . The first limiting portion  331  may be connected and fixed to the outer hub  330  through soldering or integral molding. The second limiting portion  332  may be connected and fixed to the inner shaft  320  through soldering or integral molding. 
     In this implementation, a first end  351  of the elastic component  350  is fixedly connected to the first limiting portion  331 , and a second end  352  of the elastic component  350  is fixedly connected to the second limiting portion  332 , to fixedly connect the first end  351  of the elastic component  350  to the outer hub  330 , and fixedly connect the second end  352  of the elastic component  350  to the inner shaft  320 . The first end  351  of the elastic component  350  may be fixedly connected to the first limiting portion  331  through soldering or by using a hook, or the like. The second end  352  of the elastic component  350  may be fixedly connected to the second limiting portion  332  through soldering or by using a hook, or the like. Shapes of structures of the first limiting portion  331  and the second limiting portion  332  are not limited. The first limiting portion  331  and the second limiting portion  332  may be bosses, snap rings, or the like. The elastic component  350  may be a spring, a clip, or the like. 
     The following describes an operating process of the first gear shifting mechanism  300  with reference to  FIG. 1 ,  FIG. 3 , and  FIG. 5 . When the drive motor  100  operates, the gear shifting shaft  210  is driven to rotate around the axial direction of the gear shifting shaft  210 . The first coupling pin  340  and the outer hub  330  can move only relative to the gear shifting shaft  210  in the axial direction of the gear shifting shaft  210 , but cannot rotate around the axial direction of the gear shifting shaft  210 , and the first guiding contour  220  has a path in the axial direction of the gear shifting shaft  210 . Therefore, when the gear shifting shaft  210  rotates, the first coupling pin  340  slides in the axial direction of the gear shifting shaft  210  within a specific stroke range along with rotation of the shifting drum  200 , the outer hub  330  follows the first coupling pin  340  to move in the axial direction of the gear shifting shaft  210  toward a direction A (as shown in  FIG. 5 ), the outer hub  330  drives, by using the first limiting portion  331 , the first end  351  of the elastic component  350  to move in the axial direction toward the direction A, and the second end  352  of the elastic component  350  is driven by a force of the first end  351  to push, by using the second limiting portion  332 , the inner shaft  320  to move in the axial direction toward the direction A, and drive the first shifting fork  310  fixedly connected to the inner shaft  320  to move in the axial direction toward the direction A. 
     The first shifting fork  310  controls connection and disconnection of a first gear shifting connection mechanism  20  through axial movement. The first gear shifting connection mechanism  20  is capable of switching between a connected state and a disconnected state (as shown in  FIG. 17 ). The first shift coupling mechanism  20  is a component in a first gear apparatus of a two-speed gearbox  40 . The first gear shifting connection mechanism  20  is not limited to a clutch or synchronizer. The axial movement of the first shifting fork  310  can control axial movement of the clutch or the synchronizer. The first gear shifting connection mechanism  20  is configured to connect a first gear  41  and a first rotary shaft  42  in the first gear apparatus. When the first gear shifting connection mechanism  20  is in the connected state, the first gear  41  is connected to the first rotary shaft  42 . In this case, the two-speed gearbox  40  may transmit a first shifting power through the first gear  41  and the first rotary shaft  42 . The first shifting power is at a low gear. When the first gear shifting connection mechanism  20  is in the disconnected state, the first gear  41  is disconnected from the first rotary shaft  42 . In this case, no first shifting power can be transmitted between the first gear  41  and the first rotary shaft  42 . 
     Continue to refer to  FIG. 5 . In this implementation, the first gear shifting connection mechanism  20  is a dog clutch, and the first gear shifting connection mechanism  20  includes a first gear shifting tooth portion  21  and a second gear shifting tooth portion  22 . An end, of the first shifting fork  310 , that is away from the inner shaft  320  is connected to the first gear shifting tooth portion  21 . As shown in  FIG. 5 , when the first shifting fork  310  moves in the axial direction toward the direction A and drives the first gear shifting tooth portion  21  and the second gear shifting tooth portion  22  to be attached tooth to tooth, the first gear shifting tooth portion  21  and the second gear shifting tooth portion  22  have not been meshed. The first coupling pin  340  continues moving in the axial direction toward the direction A to a target location, the outer hub  330  is driven to continue compressing the elastic component  350 , and the elastic component  350  absorbs an acting force that drives movement to the target location. As shown in  FIG. 6 , when a rotational speed of a wheel fluctuates during driving, the fluctuation is transmitted to the first gear shifting connection mechanism  20 , so that the first gear shifting tooth portion  21  and the second gear shifting tooth portion  22  are staggered at a moment when the rotational speed fluctuates. The acting force absorbed by the elastic component  350  is released, so that the first gear shifting tooth portion  21  and the second gear shifting tooth portion  22  are meshed. 
     In this application, a benefit of disposing the elastic component  350  between the outer hub  330  and the inner shaft  320  lies in that, the elastic component  350  can continue absorbing an acting force when the first gear shifting tooth portion  21  and the second gear shifting tooth portion  22  are attached to each other, to absorb an axial acting force that occurs when the dog clutch is in a tooth-to-tooth state, thereby preventing the drive motor  100  from being burnt out due to stalling of the drive motor  100 . 
     When the first gear shifting connection mechanism  20  needs to be disconnected, the first shifting fork  310  moves in an opposite direction, that is, moves in the axial direction toward a direction B, to detach the first gear shifting tooth portion  21  from the second gear shifting tooth portion  22 . 
     Refer to  FIG. 7 . A difference from the implementation shown in  FIG. 5  lies in that, in a possible implementation, the first limiting portion  331  is fixedly connected to the inner shaft  320 , and the second limiting portion  332  is fixedly connected to the outer hub  330 . When the first coupling pin  340  moves in the axial direction toward the direction A, the outer hub  330  drives, by using the second limiting portion  332 , the second end  352  of the elastic component  350  to move in the axial direction toward the direction A, and the first end  351  of the elastic component  350  is driven by a pulling force of the second end  352  to pull the inner shaft  320  to move in the axial direction toward the direction A, and drive the first shifting fork  310  fixedly connected to the inner shaft  320  to move in the axial direction toward the direction A. 
     Refer to  FIG. 8 . A difference from the implementation shown in  FIG. 5  lies in that, in a possible implementation, the two ends of the elastic component  350  abut against the first limiting portion  331  and the second limiting portion  332  respectively. Abutting means that two parts are not fixedly connected, but are adjacent in locations. In this implementation, a blocking portion  333  is further disposed on a side, of the first limiting portion  331 , that is away from the second limiting portion  332 , and the blocking portion  333  is fixedly connected to the inner shaft  320 . When the outer hub  330  is pushed in the axial direction toward the direction B, the outer hub  330  abuts against the blocking portion  333 , and drives the inner shaft  320  to move in the axial direction toward the direction B. In this implementation, the two ends of the elastic component  350  are not fixedly connected to the first limiting portion  331  or the second limiting portion  332 . Therefore, when there is no blocking portion  333 , when the outer hub  330  moves in the axial direction toward the direction B, the first limiting portion  331  detaches from the elastic component  350 , and the inner shaft  320  cannot be driven to move in the axial direction toward the direction B. In this case, the blocking portion  333  needs to be added, so that the first limiting portion  331  pushes the blocking portion  333 , to drive the inner shaft  320  to move. 
     In some implementations, the first end  351  of the elastic component  350  may be fixedly connected to the first limiting portion  331 , and the second end  352  of the elastic component  350  may abut against the second limiting portion  332 . Alternatively, in some implementations, the first end  351  of the elastic component  350  abuts against the first limiting portion  331 , and the second end  352  of the elastic component  350  is fixedly connected to the second limiting portion  332 . 
     Refer to  FIG. 9 . A difference from the implementation shown in  FIG. 8  lies in that, there is no blocking portion  333  on the inner shaft  320 , but the first shifting fork  310  is adjacent to the first limiting portion  331 . Orthographic projections of the first limiting portion  331  and the first shifting fork  310  on a radial profile of the inner shaft  320  at least partially overlap. Therefore, when the outer hub  330  moves in the axial direction toward the direction B, the first limiting portion  331  pushes the first shifting fork  310  and the inner shaft  320  to move. It should be noted that, that “the first shifting fork  310  is adjacent to the first limiting portion  331 ” means that the first shifting fork  310  is adjacent to the first limiting portion  331  before the outer hub  330  moves relative to the inner shaft  320  in the axial direction toward the direction A. When the outer hub  330  is pushed back in the axial direction toward the direction B after the inner shaft  320  moves in the axial direction toward the direction A and reaches the target location, the outer hub  300  returns to an original location, and continues to push the first shifting fork  310  to move in the axial direction toward the direction B. 
     Refer to  FIG. 3  and  FIG. 10 . In a possible implementation, the first shifting mechanism  300  further includes the hub-rotation limiting component  360 . One end of the hub-rotation limiting component  360  is disposed with a first limiting portion  361  sleeved on the outer hub  330 . A first limiting plane  362  is disposed on an inner surface of the first limiting portion  361 . A second limiting plane  363  matching the first limiting plane  362  is disposed on the outer hub  330 . The first limiting plane  362  is attached to the second limiting plane  363 . The other end of the hub-rotation limiting component  360  is disposed with a second limiting portion  364 . The second limiting portion  364  includes a limiting curved surface  365  that is concave toward the first limiting portion  361 . The limiting curved surface  365  surrounds a part of a surface of the gear shifting shaft  210  and is spaced from the gear shifting shaft  210 . The outer hub  330  cannot rotate on its own axis under actions of the first limiting plane  362 , the second limiting plane  363 , and the limiting curved surface  365 . 
     As shown in  FIG. 3 , when the gear shifting shaft  210  rotates in a clockwise direction α, because the first guiding contour  220  has a path in the axial direction and a path in the circumferential direction, a wall of the first guiding contour  220  also has an acting force in the axial direction and an acting force in a counterclockwise direction β on the first coupling pin  340 . The acting force in the counterclockwise direction β causes a tendency that the outer hub  330  connected to the first coupling pin  340  rotates around an axis of the outer hub  330 , and a tendency that the first coupling pin  340  detaches from the first guiding contour  220 . However, due to limiting actions of the first limiting plane  345  and the second limiting plane  363 , the first limiting portion  361  and the outer hub  330  remain fixed relative to each other, that is, the outer hub  330  cannot rotate on its own axis relative to the first limiting portion  361 . When the outer hub  330  is to rotate around an axial direction of the outer hub  330 , the limiting curved surface  365  of the second limiting portion  364  abuts against the gear shifting shaft  210 , and end points  366  of the limiting curved surface  365  press against the gear shifting shaft  210 . Therefore, the first limiting portion  361  in the hub-rotation limiting component  360  cannot rotate, the outer hub  330  cannot rotate on its own axis (as shown in  FIG. 11 ), and the first coupling pin  340  fixedly connected to the outer hub  330  cannot rotate around the axial direction of the outer hub  330 . This prevents the first coupling pin  340  from detaching from the first guiding contour  220 , so that the first coupling pin  340  can only keep moving in the axial direction. In this implementation, the gear shifting shaft  210  can overcome a friction force between the limiting curved surface  365  and the gear shifting shaft  210 , and rotate around the axial direction of the gear shifting shaft  210 . 
     It should be noted that the hub-rotation limiting component  360  may alternatively have another structure. This is not limited in this application, provided that the outer hub  330  is prevented from rotating on its own axis around the axial direction of the outer hub  330  when the gear shifting shaft  210  rotates. 
     Continue to refer to  FIG. 1 . In a possible implementation, the gear shifting mechanism  10  further includes a worm  401  and a worm gear  402  that are meshed with each other. The worm  401  is connected to the drive motor  100 . The worm gear  402  is sleeved on the gear shifting shaft  210  and is fixedly connected to the gear shifting shaft  210 . When the drive motor  100  operates, the worm  401  is driven to rotate, and the worm drives the worm gear  402  to rotate, so as to drive the gear shifting shaft  210  to rotate. In this implementation, a power of the drive motor  100  is transmitted to the gear shifting shaft  210  by using the worm  401  and the worm gear  402 . This saves space compared with power transmission by using two or more gears. 
     Continue to refer to  FIG. 2 . In a possible implementation, the shifting drum  200  further includes a second guiding contour  230  disposed in the circumferential direction of the gear shifting shaft  210 . The second guiding contour  230  has a path in the axial direction of the gear shifting shaft  210 . The path of the second guiding contour  230  encircles the gear shifting shaft  210  once in the circumferential direction of the gear shifting shaft  210 , and has a specific path in the axial direction of the gear shifting shaft  210 . In other words, an orthographic projection of the second guiding contour  230  in the axial direction of the gear shifting shaft  210  is a straight line with a specific length. Therefore, a component located in the second guiding contour  230  can be guided to move in the axial direction of the gear shifting shaft  210 . A specific path of the second guiding contour  230  may be arranged according to an actual requirement. The second guiding contour  230  is but is not limited to a groove type guiding contour or an opening type guiding contour, and is an opening type guiding contour in this implementation. 
     Continue to refer to  FIG. 1  and  FIG. 12 . The gear shifting mechanism  10  further includes a second shifting mechanism  400 . The second shifting mechanism  400  includes a second coupling pin  410 , a second shifting fork  420 , and a supporting shaft  430 . The second coupling pin  410  is connected to a first end  421  of the second shifting fork  420  and is located in the second guiding contour  230  (as shown in  FIG. 3 ). A via  403  is disposed in the middle of the second shifting fork  420 . The supporting shaft  430  is inserted into the via  403 . When the gear shifting shaft  210  rotates, the second coupling pin  410  and the first end  421  of the second shifting fork  420  are pushed to slide in the axial direction of the gear shifting shaft  210 , and a second end  422  of the second shifting fork  420  moves in a direction opposite to that of the first end  421  of the second shifting fork  420  through the supporting shaft  430 . 
     The supporting shaft  430  may be fixed to the housing of the gear shifting mechanism  10  or a housing of the two-speed gearbox. The supporting shaft  430  is fixed, and the supporting shaft  430  is inserted into the via  403  to constitute a fixed support of the second shifting fork  420 . The second shifting fork  420  is capable of rotating relative to the supporting shaft  430 . 
     In this implementation, the second guiding contour  230  and the worm gear  402  are fixedly connected, and may be integrally formed to save space. 
     When the second end  422  of the second shifting fork  420  moves, connection and disconnection of a second gear shifting connection mechanism  30  is controlled. The second gear shifting connection mechanism  30  is capable of switching between a connected state and a disconnected state (as shown in  FIG. 17 ). The second shift coupling mechanism  30  is a component in a second gear apparatus of the two-speed gearbox  40 . The second gear shifting connection mechanism  30  is configured to connect a second gear  43  and a second rotary shaft  44  in the second gear apparatus. When the second gear shifting connection mechanism  30  is in the connected state, the second gear  43  is connected to the second rotary shaft  44 . In this case, the two-speed gearbox  40  may transmit a second shifting power through the second gear  43  and the second rotary shaft  44 . The second shifting power is at a high gear. When the second gear shifting connection mechanism  30  is in the disconnected state, the second gear  43  is disconnected from the second rotary shaft  44 . In this case, no second shifting power can be transmitted between the second gear  43  and the second rotary shaft  44 . 
     In a possible implementation, the second shifting mechanism  400  further includes a push pin  440  (as shown in  FIG. 1 ), and the second end  422  of the second shifting fork  420  abuts against one end of the push pin  440 . The other end of the push pin  440  is configured to be connected to the second gear shifting connection mechanism  30 . 
     In a possible implementation, a distance between the first end  421  of the second shifting fork  420  and the supporting shaft  430  is greater than a distance between the second end  422  of the second shifting fork  420  and the supporting shaft  430  (as shown in  FIG. 12 ). The supporting shaft  430  forms a lever, so that the distance between the first end  421  of the second shifting fork  420  and the supporting shaft  430  is greater than the distance between the second end  422  of the second shifting fork  420  and the supporting shaft  430 . This can amplify an acting force of the second end  422  of the second shifting fork  420 , and therefore can effectively control connection and disconnection of the second gear shifting connection mechanism  30 . 
     In a possible implementation, an end face, used to act on the second gear shifting connection mechanism  30 , of the second end  422  of the second shifting fork  420  is an arc surface (as shown in  FIG. 12 ). After an acting force of the shifting drum  200  is applied to the second shifting fork  420  by using the lever, the second end  422  of the second shifting fork  420  moves upward or downward in an arc shape. The end face of the second end  422  is set to be an arc surface. Therefore, it can be ensured that the end face of the second end  422  of the second shifting fork  420  always abuts against the push pin  440 . Further, it can be ensured that an acting force in the axial direction can still be applied to the push pin  440  when the second end  422  moves in an arc shape. As shown in  FIG. 13 , the arc end face of the second end  422  abuts against the push pin  440 . When the second shifting fork  420  rotates in the counterclockwise direction β under actions of the shifting drum  200  and the supporting shaft  430 , the arc end face of the second end  422  can continuously abut against a central axis O of the push pin  440 , thereby ensuring a smoother pushing force in an axial direction of the push pin  440  toward the direction A. 
     In a possible implementation, the second end  422  of the second shifting fork  420  includes at least two supporting points  423  (as shown in  FIG. 12 ). In other words, there may be a plurality of supporting points  423 . The plurality of supporting points  423  can increase a contact area of an acting force, so that a force applied to the second gear shifting connection mechanism  30  is more uniform. A quantity of push pins  440  is the same as that of supporting points  423 . 
     In a possible implementation, the second end  422  of the second shifting fork  420  is configured to be disconnected from and connected to the second gear shifting connection mechanism  30 . The second gear shifting connection mechanism  30  is a friction clutch. A path, in the second guiding contour  230 , that is used to control connection and disconnection of the friction clutch is a curved path (as shown in  FIG. 2 ). Refer to  FIG. 14 . The friction clutch  30  includes a plurality of friction plates  31 . When an external force acts on the plurality of friction plates  31 , the friction plates  31  are gradually combined to transmit the acting force. In this case, the friction clutch  30  is in a connected state. In this implementation, the second end  422  of the second shifting fork  420  pushes the push pin  440  to move in the axial direction, and the push pin  440  acts on the plurality of friction plates  31 . The plurality of friction plates  31  can be combined when the push pin  440  moves in the axial direction. A relationship between a value of a friction force F between the plurality of friction plates  31  and an axial distance L by which the push pin  440  pushes the friction plates  31  to move is a curve relationship (as shown in  FIG. 15 ). Therefore, the path, in the second guiding contour  230 , that is used to control connection and disconnection of the friction clutch  30  is set to be a curved path. This is more suitable for a torque curve of the friction clutch  30 , so that the friction clutch  30  is disconnected and connected more smoothly, and therefore a power is transmitted more stably. The friction clutch  30  may be a normally open clutch or a normally closed clutch. It should be noted that a structure of the friction clutch  30  is not limited to the structure shown in  FIG. 12 , and may be specifically arranged according to an actual requirement. This is not limited in this application.  FIG. 15  is merely intended to show that the value of the friction force F between the friction plates  31  and the axial distance L by which the second shifting fork  420  pushes the friction plates  31  to move are in a curve relationship, but does not indicate an actual curve relationship. A specific curve relationship needs to be set according to an actual requirement. 
     The following describes an operating process of the gear shifting mechanism  10  in this implementation with reference to  FIG. 1 ,  FIG. 16 , and  FIG. 17 .  FIG. 16  shows expanded paths of the first guiding contour  220  and the second guiding contour  230  in the shifting drum  200 . In  FIG. 16 , a first direction X indicates a distance by which the first coupling pin  340  or the second coupling pin  410  moves in the axial direction of the gear shifting shaft  210 , and a second direction Y indicates a circumferential rotation angle of the gear shifting shaft  210 . A total rotation angle in the second direction Y is 360°. 
     In a case of an N gear, the first coupling pin  340  is at a location at which the path of the first guiding contour  220  is open, and the second coupling pin  410  is at a location at which the path of the second guiding contour  230  is open. The “location at which the path of the first guiding contour  220  is open” indicates that the first gear shifting connection mechanism  20  is in the disconnected state. In this case, the first gear  41  and the first rotary shaft  42  in the first gear apparatus  45  are disconnected. The “location at which the path of the second guiding contour  230  is open” indicates that the second gear shifting connection mechanism  30  is in the disconnected state. In this case, the second gear  43  and the second rotary shaft  44  in the second gear apparatus  46  are disconnected. 
     In a case of a 1st gear, where the 1st gear is a low gear, that is, a power is transmitted at the first gear, the first coupling pin  340  is at a location at which the path of the first guiding contour  220  is closed, and the second coupling pin  410  is at a location at which the path of the second guiding contour  230  is closed. The “location at which the path of the first guiding contour  220  is closed” indicates that the first gear shifting connection mechanism  20  is in the connected state. In this case, the first gear  41  and the first rotary shaft  42  in the first gear apparatus  45  are connected, and the first rotary shaft  42  drives the first gear  41  on the first rotary shaft  42  to rotate. The “location at which the path of the second guiding contour  230  is open” indicates that the second gear shifting connection mechanism  30  is in the disconnected state. In this case, the second gear  43  and the second rotary shaft  44  in the second gear apparatus  46  are disconnected. That is, in the case of the 1st gear, the first gear  41  and the first rotary shaft  42  in the first gear apparatus  45  transmit a power, and the second gear  43  and the second rotary shaft  44  in the second gear apparatus  46  have a speed difference and do not transmit a power. 
     In a case of a 2nd gear, where the 2nd gear is a high gear, that is, a power is transmitted at the second gear, the first coupling pin  340  is at a location at which the path of the first guide groove  220  is open, and the second coupling pin  410  is at a location at which the path of the second guiding contour  230  is closed. The “location at which the path of the first guiding contour  220  is open” indicates that the first gear shifting connection mechanism  20  is in the disconnected state. In this case, the first gear  41  and the first rotary shaft  42  in the first gear apparatus  45  are disconnected, and the first rotary shaft  42  cannot drive the first gear  41  on the first rotary shaft  42  to rotate. The “location at which the path of the second guiding contour  230  is closed” indicates that the second gear shifting connection mechanism  30  is in the connected state. In this case, the second gear  43  and the second rotary shaft  44  in the second gear apparatus  46  are connected, and the second rotary shaft  44  drives the second gear  43  to rotate. That is, in the case of the 2nd gear, the first gear  41  and the first rotary shaft  42  in the first gear apparatus  45  have a speed difference and do not transmit a power, and the second gear  43  and the second rotary shaft  44  in the second gear apparatus  46  transmit a power. 
     In a case of a P position, the first coupling pin  340  is at a location at which the path of the first guiding contour  220  is closed, and the second coupling pin  410  is at a location at which the path of the second guiding contour  230  is closed, to connect the first gear  41  and the first rotary shaft  42  in the first gear apparatus  45 , and connect the second gear  43  and the second rotary shaft  44  in the second gear apparatus  46 . In this case, the first gear apparatus  45  and the second gear apparatus  46  simultaneously transmit powers, thereby causing a mutual lockup. 
     As shown in  FIG. 16 , the path of the second guiding contour  230  is a curve in a process of switching from the 2nd gear to the N gear and a process of switching from the 1st gear to the P position, so that a power is transmitted more smoothly. 
     It should be noted that the four states in  FIG. 16  may be switched according to a requirement, including but not limited to switching from the 1st gear to the 2nd gear, switching from the 1st gear to the N gear, switching from the 2nd gear to the N gear, switching from the 1st gear to the P position, and switching from the 2nd gear to the P position. 
     Refer to  FIG. 17 . An implementation of this application further provides a two-speed gearbox  40 . The two-speed gearbox  40  includes a first gear shifting connection mechanism  20  and the gear shifting mechanism  10  according to any one of the foregoing implementations. The first shifting fork  310  controls connection and disconnection of the first gear shifting connection mechanism  20  through axial movement. 
     The two-speed gear shifting mechanism  40  further includes a second gear shifting connection mechanism  30 . The second shifting fork  420  controls connection and disconnection of the second gear shifting connection mechanism  30  through axial movement. 
     The two-speed gearbox  40  further includes a first gear apparatus  45  and a second gear apparatus  46 . The first gear apparatus  45  includes a first gear  41  and a first rotary shaft  42 . When the first gear shifting connection mechanism  20  is in a connected state, the first gear  41  is connected to the first rotary shaft  42 . In this case, the two-speed gearbox  40  may transmit a first shifting power through the first gear  41  and the first rotary shaft  42 . The first shifting power is at a low gear. When the first gear shifting connection mechanism  20  is in a disconnected state, the first gear  41  is disconnected from the first rotary shaft  42 . In this case, no first shifting power can be transmitted between the first gear  41  and the first rotary shaft  42 . The second gear apparatus  46  includes a second gear  43  and a second rotary shaft  44 . When the second gear shifting connection mechanism  30  is in a connected state, the second gear  43  is connected to the second rotary shaft  44 . In this case, the two-speed gearbox  40  may transmit a second shifting power through the second gear  43  and the second rotary shaft  44 . The second shifting power is at a high gear. When the second gear shifting connection mechanism  30  is in a disconnected state, the second gear  43  is disconnected from the second rotary shaft  44 . In this case, no second shifting power can be transmitted between the second gear  43  and the second rotary shaft  44 . 
     One of the first rotary shaft  42  and the second rotary shaft  44  may be an input shaft, the other may be an intermediate shaft. In some cases, the first rotary shaft  42  and the second rotary shaft  44  may be a same rotary shaft. In some cases, the first gear  41  and the second gear  43  each may include two or more gears. It should be noted that a specific structure of the two-speed gearbox  40  in this application is not limited to the structure shown in  FIG. 17 , and a gear and a rotary shaft may be specifically disposed according to an actual requirement. 
     Refer to  FIG. 18 , an implementation of this application further provides a vehicle  1 . The vehicle  1  includes front wheels  2 , rear wheels  3 , a vehicle body  4  connected between the front wheels  2  and the rear wheels  3 , and the foregoing two-speed gearbox  40 . The two-speed gearbox  40  is mounted on the vehicle body  4 . The vehicle  1  further includes a final gear and a differential. An intermediate shaft in the two-speed gearbox  40  is connected to the final gear. The differential is connected between two front wheels  2  or between the front wheels  2  and the rear wheels  3 . The final gear can reduce a rotational speed of the intermediate shaft. The differential is configured to adjust a difference between rotational speeds of gears. The vehicle  1  includes an automobile, an electric vehicle, or a special operation vehicle. The electric vehicle includes a two-wheeled, three-wheeled, or four-wheeled electric vehicle. The special operation vehicle includes a variety of vehicles with specific functions, for example, an engineering rescue vehicle, a sprinkler vehicle, a sewage suction vehicle, a cement mixer truck, a lifting vehicle, and a medical vehicle. 
     The foregoing describes in detail the gear shifting mechanism, the two-speed gearbox, and the vehicle provided in the embodiments of this application. Specific examples are used in this specification to describe the principles and the embodiments of this application. The descriptions of the foregoing embodiments are merely intended to help understand the method of this application and the core ideas thereof. In addition, a person of ordinary skill in the art may change the specific embodiments and the application scope based on the ideas of this application. To sum up, the content of this specification shall not be construed as a limitation on this application.