Differential output driving structure

Abstract

The utility model relates to a vehicle door system of a vehicle, in particular to a differential output driving structure which is applied to an automobile swing door, the automobile is provided with the swing door which can be connected to an automobile body in a pivoting and swinging mode, and the swing door can move along a swing path between an opening position and a closing position. The differential output driving structure comprises a power operation driver connected with the swing door, the differential output driving structure is constructed to respond to the power operation instruction, the composite rotation motion of revolution and rotation of the vehicle door is achieved through a guide rail, and the differential output driving structure can complete reliable transmission and can also drive the swing door to rotate. And the risk of clamping stagnation of a transmission system caused by complex motion postures of the vehicle door can be eliminated.

Description

Technical Field

[0001] The utility model relates to the technical field of automobiles, in particular to an automatic swing door of an automobile and a driving structure of a differential output for driving the automatic swing door. Background Art

[0002] With the continuous development and progress of the automobile industry, the utilization rate and demand of automobiles are increasing. Therefore, the convenience of automobile use is becoming more and more concerned by everyone. There are many ways to open the side doors of automobiles, such as the straight-opening door, which is the most common way to open the door. The door opens outward in the same direction as the direction of the car's movement. This design is simple and convenient, and the air flow pressure can be used to help close the door when the car is driving; side sliding door: the door of this opening method will slide along the side of the car body when it is opened, instead of folding outward. Side sliding doors are often used in MPV models because they take up little space when opened, which is convenient for passengers to get on and off the car and load and unload items; double-opening doors: usually equipped on luxury cars, the rear door opens in the same way as the front door, but in the opposite direction. This design can provide a more elegant experience of getting on and off the vehicle, and gives people a sense of nobility visually; swing door: usually refers to the way in which the door swings outward to open through specific hinges and drive mechanisms. This design is used in many car models, especially in some luxury models or vehicles with special designs. At present, electric swing doors have appeared on new energy vehicles. They can be controlled by buttons, automatically swing outward to open, and automatically close when closed. They take up little space, but the cost is relatively high, and due to the complexity of the drive system, the reliability is low. Utility Model Content

[0003] In view of the above situation, in order to overcome the defects of the prior art, the utility model provides a drive structure with differential output, which can not only achieve reliable transmission, but also eliminate the risk of jamming of the transmission system due to the complex movement posture of the door.

[0004] The drive structure of the differential output includes: a driver, the driver including a motor and a driver output shaft driven by the motor;

[0005] A differential housing assembly, comprising an upper differential housing and a lower differential housing and a mounting cavity formed therebetween, wherein the lower differential housing has a lower shaft sleeve;

[0006] The differential assembly includes an upper half-shaft gear, a planetary gear, a lower half-shaft gear and a differential output shaft in sequence; the driver output shaft is drivingly connected with the upper half-shaft gear; the planetary gear is installed in the differential housing assembly through the planetary gear shaft and meshes with the upper half-shaft gear and the lower half-shaft gear; the differential output shaft is located in the lower sleeve of the differential lower housing;

[0007] When the differential output shaft forms a differential with the driver output shaft, the differential assembly can be driven through the lower sleeve, thereby realizing the composite motion of the planetary gear's rotation and revolution.

[0008] It also includes: a mounting frame, which is provided with a guide track; a lower swing arm assembly, which includes a lower swing arm sleeve and a rack fixedly arranged in the lower swing arm sleeve; and a bushing, the insertion end of the bushing is slidably located in the lower swing arm sleeve, and the rotating end is rotatably mounted on the mounting frame.

[0009] Among them, the differential output shaft extends into the bushing and meshes with the rack transmission, and the lower shaft sleeve of the differential lower shell meshes with the bushing transmission; the position relationship between the lower swing arm sleeve and the bushing and the overall length of the lower swing arm assembly are adjusted by changing the position relationship between the differential output shaft and the rack. During the adjustment process, the lower swing arm sleeve moves relative to the mounting frame and is constrained by the guide track limit, and the bushing rotates relative to the mounting frame.

[0010] The mounting frame also includes a body, which includes an upper mounting plate, a side plate and a lower mounting plate, and the guide rails are an upper guide rail on the upper mounting plate and a lower guide rail on the lower mounting plate;

[0011] The bushing is a sleeve structure, and a convex edge is provided above the rotating end of the sleeve structure. The convex edge can be rotatably positioned in the mounting hole of the upper mounting plate, and a transmission tooth or transmission key is provided on the inner side of the convex edge to cooperate with the lower shaft sleeve of the lower housing of the differential; the rack enters from the insertion end of the sleeve structure and is connected to the differential output shaft at the rotating end.

[0012] The lower swing arm sleeve is provided with rollers at the upper and lower parts, and the upper and lower rollers are respectively located in the upper guide rail and the lower guide rail.

[0013] The differential housing assembly also includes an upper cover and a lower cover; the upper differential housing is installed in the upper cover through an upper bearing, and the lower shaft sleeve of the lower differential housing is installed in the lower cover through a lower shaft sleeve.

[0014] The upper half shaft gear and the lower half shaft gear of the differential assembly are bevel gears, and the planetary gears are bevel gears and there are at least two of them. They are installed between the upper half shaft gear and the lower half shaft gear through the planetary gear shaft. When the upper half shaft gear and the lower half shaft gear rotate at the same speed, the planetary gear rotates on its own; when the upper half shaft gear and the lower half shaft gear rotate differentially, the planetary gear performs a compound motion of revolution and rotation.

[0015] The above technical solution has the following beneficial effects:

[0016] In the utility model, the running track of the electric swing door is defined by the upper swing arm assembly and the lower swing arm assembly. Since the extension length of the lower swing arm assembly is variable under the constraint of the guide track of the mounting frame, the electric swing door thus presents a complex rotation posture during the movement. The application proposes a differential drive assembly for eliminating the influence of the differential between the output shaft of the driver and the output shaft of the differential on the movement of the door, wherein the planetary gear rotates around the axis of the output shaft of the driver while performing the above-mentioned self-rotation movement - revolution, and the upper and lower half-shaft gears rotate at different speeds. That is, the risk of motion stagnation of the rack is eliminated.

[0017] Other beneficial effects of the present invention will be described one by one in the following specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of the automatic swing door for a car according to an embodiment of the utility model;

[0019] Figure 2 This is a working state diagram of the differential drive assembly of the automatic swing door of the vehicle according to the embodiment of the utility model during the opening process;

[0020] Figure 3 This is a schematic diagram of the structure of the vehicle body and the swing door when the automatic swing door of the vehicle is opened as viewed from above according to an embodiment of the utility model;

[0021] Figure 4 It is a three-dimensional general assembly schematic diagram of the differential drive assembly according to an embodiment of the utility model;

[0022] Figure 5 It is a partial cross-sectional schematic diagram of the differential drive assembly according to an embodiment of the utility model;

[0023] Figure 6 This is a first exploded view of the differential drive assembly according to an embodiment of the utility model;

[0024] Figure 7 This is a second exploded view of the differential drive assembly described in an embodiment of the utility model.

[0025] In the figure: 10 driver; 11 motor; 12 driver output shaft; 20 differential assembly; 21 upper half shaft gear; 22 lower half shaft gear; 23 planetary gear; 24 planetary gear shaft; 25 upper gear segment; 26 output shaft; 27 drive wheel mounting position; 28 drive wheel; 30 differential housing assembly; 31 upper bearing; 32 differential upper housing; 33 differential lower housing; 34 upper cover; 35 lower cover; 36 lower bearing; 37 lower bushing; 40 mounting frame; 41 body; 42 mounting hole; 43 upper guide rail; 44 lower guide rail; 50 lower swing arm assembly; 51 bushing; 52 rack; 53 fixing block; 54 lower swing arm sleeve; 55 roller; 56 lower shaft; 60 upper swing arm assembly; 61 upper swing arm body; 62 first mounting block; 63 second mounting block. DETAILED DESCRIPTION

[0026] The above and other technical features and functions of the present invention are described in detail below with reference to the attached Figures 1 to 7 The embodiments are described in detail.

[0027] Vehicles and electric swing doors

[0028] like Figure 1 As shown, an exemplary embodiment of the vehicle body part involving the door is given, including a front rear passenger door which is installed on the vehicle body through an upper swing arm assembly 60 and a lower swing arm assembly 50 to form a swing arm hinge structure, and the drive device of the electric swing door is integrated on the rear passenger door.

[0029] according to Figure 1 and Figure 2 The swing door includes inner and outer metal plates and a defined inner cavity, and the electric swing door drive device can be installed in the inner cavity. When the electric swing door is running between the open position and the closed position, it swings out to the outside of the vehicle body in the air. The running track of the electric swing door is defined by the upper swing arm assembly 60 and the lower swing arm assembly 50. Since the lower swing arm assembly 50 is constrained by the guide track of the mounting frame 40, its extended length is variable. The electric swing door thus presents a complex rotation posture during the movement process, such as the forward movement of the composite door body itself to achieve forward feeding and rotation to insert into the gap between the front door and the vehicle body, and complete the closing action of the rear passenger door. In other words, when opening and closing the door, the seals, structural parts, etc. on the vehicle body can be avoided.

[0030] At the near end of the vehicle body, the upper swing arm assembly 60 and the lower swing arm assembly 50 are pivotally mounted on the vehicle body, for example, connected to the A-pillar and / or the B-pillar through a mounting bracket. At this time, the upper swing arm assembly 60 and the lower swing arm assembly 50 extend horizontally or substantially horizontally in a cantilevered manner (meaning extending transversely or substantially transversely relative to the vertical axis, and substantially transverse means that the bracket is slightly inclined relative to the vertical axis, for example, 5 degrees or an angle considered to be within the expected range). Away from the vehicle body, the unsupported free second end, also referred to as the distal end, the upper swing arm assembly 60 and the lower swing arm assembly 50 are exemplarily extended through a port set on the closing surface of the door body, connecting the inner and outer metal plates.

[0031] The driver 10 is a power source for the electric swing door, and is connected to the vehicle control unit for communication. The driver 10 is not the creative contribution of the present utility model. For example, the applicant's prior application 2024202178686 is optional but not limited to a door driver and a vehicle, which responds to the selective actuation of the control unit and the direction of rotation of the motor. The structure of the automatic swing door driver 10 does not need to be modified, because the purpose of the utility model of the present application is to use a differential structure to solve the problem of rack jamming of the door in complex movements, rather than to make the driver 10 variable frequency output. Conventional drivers can be directly incorporated into existing swing door structures without requiring great effort and cost in changing the design, especially door structures, which were originally designed for doors with purely mechanical rack and gear systems that can be directly called or used.

[0032] The driver 10 controls the reciprocating linear motion of the rack 52, rotates the upper swing arm assembly 60 and the lower swing arm assembly 50, and opens the vehicle door in a first direction, that is, moves in an opening direction from a closed position to an open position, and conversely, moves the vehicle door in a second direction from an open position to a closed position in a closing direction.

[0033] Differential drive components

[0034] As mentioned above, the running trajectory of the electric swing door is defined by the upper swing arm assembly and the lower swing arm assembly. Since the extension length of the lower swing arm assembly is variable under the constraint of the guide track of the mounting frame, the electric swing door presents a complex rotation posture during movement.

[0035] Explained from another perspective, during the movement of the electric swing door, there is not only circumferential rotation, but also radial movement or self-rotation, which is achieved by the roller 55 of the lower swing arm assembly 50 moving in the guide rail of the complex curve. If a differential drive assembly is not provided, the continuous constant speed rotation output by the driver 10 causes the roller 55 to be stuck when running in the guide rail of the complex curve, or the roller 55 cannot move normally in the guide rail of the complex curve.

[0036] In this regard, the present application proposes a differential drive assembly for eliminating the influence of the differential between the drive output shaft 12 and the differential output shaft 26 on the movement of the vehicle door. Figure 5-7 , which is a specific application of the differential structure in the prior art in the door drive. Specifically, the differential drive assembly includes a driver 10, which includes a motor and a driver output shaft 12 driven by the motor; a differential housing assembly 30, which includes a differential upper housing 32 and a differential lower housing 33 and a mounting cavity formed therebetween, and the differential lower housing 33 has a lower shaft sleeve; a differential assembly 20, which includes an upper half shaft gear 21, a planetary gear 23, a lower half shaft gear 22 and a differential output shaft 26 in sequence; the driver output shaft 12 is transmission-connected with the upper half shaft gear 21; the planetary gear 23 is installed in the differential housing assembly 30 through the planetary gear shaft 24 and meshes with the upper half shaft gear 21 and the lower half shaft gear 22; the differential output shaft 26 is located in the lower shaft sleeve of the differential lower housing 33; The mounting frame 40 is provided with a guide track; the lower swing arm assembly 50 includes a lower swing arm sleeve 54 and a rack 52 fixedly arranged in the lower swing arm sleeve 54; it also includes a bushing 51, the insertion end of the bushing 51 is slidably located in the lower swing arm sleeve 54, and the rotating end is rotatably mounted on the mounting frame 40, wherein the differential output shaft 26 extends into the bushing 51 and is transmission-engaged with the rack 52, and the lower shaft sleeve of the differential lower shell 33 is transmission-engaged with the bushing 51; the positional relationship between the lower swing arm sleeve 54 and the bushing 51 is adjusted by changing the positional relationship between the differential output shaft 26 and the rack 52. During the adjustment process, the lower swing arm sleeve 54 moves relative to the mounting frame 40 and is limited by the guide track, and the bushing 51 rotates relative to the mounting frame 40.

[0037] Preferably, the mounting frame 40 further comprises a body 41, the body 41 comprises an upper mounting plate, a side plate and a lower mounting plate, the guide rails are an upper guide rail 43 on the upper mounting plate and a lower guide rail 44 on the lower mounting plate, the bushing 51 is a sleeve structure, the sleeve structure has a convex edge above the rotating end, the convex edge can be rotatably positioned in the mounting hole 42 of the upper mounting plate, the inner side of the convex edge has a transmission tooth or a transmission key to drive with the lower sleeve of the differential lower shell 33; the rack 52 enters from the insertion end of the sleeve structure and is in driving connection with the differential output shaft 26 at the rotating end. The lower swing arm sleeve 54 is provided with rollers 55 at the upper and lower ends, and the upper and lower rollers 55 are respectively located in the upper guide rail 43 and the lower guide rail 44, so as to assist the movement between the lower swing arm sleeve and the mounting frame 40.

[0038] Differential drive execution

[0039] In the prior art, both half-axle gears are outputted by the drive shaft, such as eliminating the speed difference of the wheels between the drive axles of the vehicle. However, unlike the prior art, in this embodiment, a symmetrical bevel gear differential in mechanical design is adopted, but in this embodiment, the drive output shaft 12 is the power input element of the differential drive assembly, and the differential output shaft 26 is the power output element. The speed difference between the drive output shaft 12 and the differential output shaft 26 is finally inputted upward to the planetary gear shaft 24 by the lower shaft sleeve 37, thereby eliminating the planetary gear 23 from rotating and revolving.

[0040] The upper half shaft gear 21 and the lower half shaft gear 22 of the differential assembly 20 are bevel gears, and the planetary gears 23 are bevel gears and there are at least two of them. They are installed between the upper half shaft gear 21 and the lower half shaft gear 22 through the planetary gear shaft 24. When the upper half shaft gear 21 and the lower half shaft gear 22 rotate at the same speed, the planetary gear 23 rotates on its own; when the upper half shaft gear 21 and the lower half shaft gear 22 rotate at a differential speed, the planetary gear 23 performs a compound motion of revolution and rotation.

[0041] In this embodiment, the differential case is composed of a differential upper case 32 and a differential lower case 33 fastened by bolts. When assembled, a spur bevel planetary gear 23 is respectively sleeved on the two journals of the planetary gear shaft 24, and they are both meshed with the upper and lower spur bevel half-shaft gears. The upper half-shaft gear 21 is connected to the driver output shaft 12 through a spline, and the lower half-shaft gear 22 is connected to the differential output shaft 26 through a spline. The driver output shaft 12 and the differential output shaft 26 are respectively supported in the corresponding upper and lower seat holes of the differential case.

[0042] After passing through the speed reducer, the power is output from the driver output shaft 12 to the rack 52 via the upper half shaft gear 21 , the planetary gear 23 , the lower half shaft gear 22 , the differential output shaft 26 , and the drive wheel 28 in sequence.

[0043] Differential drive transmission line

[0044] When the drive output shaft 12 and the differential output shaft 26 rotate at the same speed, the planetary gear rotates around its own axis - rotation. That is, the drive output shaft 12, the planetary gear 23 and the differential output shaft 26 form a balanced state.

[0045] Since the lower arm sleeve 54 is fixedly connected to the rack 52, when the lower arm sleeve 54 is stuck in the movement along the guide rail, the movement of the rack 52 is also stuck. At this time, a differential is formed between the driver output shaft 12 and the differential output shaft 26. The bushing 51 drives the lower sleeve 37 through the spline, and further drives the differential case to rotate. The differential case and the planetary gear shaft 24 are fixedly connected. Therefore, while the planetary gear performs the above-mentioned rotation movement, it also rotates around the axis of the driver output shaft 12 - revolution, and the upper and lower half-shaft gears rotate at different speeds. That is, the risk of the movement of the rack 52 being stuck is eliminated.

[0046] Fixing of differential drive components in door systems

[0047] The differential housing assembly 30 also includes an upper housing 34 and a lower housing 35; the upper differential housing 32 is mounted in the upper housing 34 via an upper bearing 31, and the lower sleeve of the lower differential housing 33 is mounted in the lower housing 35 via a lower sleeve 37. In this system, the upper housing 34 and the lower housing 35 are external housings that are stationary and can therefore be fixed between the driver 10 and the mounting frame 40.

[0048] The differential case is composed of a differential upper case 32 and a differential lower case 33 fastened with bolts. It keeps stationary and rotates accordingly according to the state of the same speed and the differential.

[0049] The swing door of the car uses a differential drive assembly for its door body. During installation, the lower swing arm assembly 50 of the differential drive assembly is hinged to the vehicle body, and the mounting frame 40 of the lower swing arm assembly 50 is fixed to the door body. The differential drive assembly drives the rack to make a linear reciprocating motion, thereby driving the lower swing arm sleeve 54 to move relative to the mounting frame 40 and be guided to the track limit constraint, so that the door body opens and closes in an outward swinging manner.

[0050] The car body includes the A-pillar, B-pillar and C-pillar, which are important components of the car body structure. They each play an important role in protecting the safety of passengers and the stability of the car body. The A-pillar refers to the pillars on both sides of the front windshield, located between the engine compartment and the passenger compartment. The main function of the A-pillar is to connect the roof and the body, and bear the brunt of the front collision of the car to prevent the wheels and suspension from invading the passenger compartment. The quality of the A-pillar is crucial to protecting the safety of the driver and the front passenger. The B-pillar is located between the front seat and the back seat of the cockpit and is a pillar connecting the front and rear doors of the car. It not only serves as a connecting part between the roof and the chassis, but also plays a connecting role in side collisions to protect the occupants in the car from injury. The quality of the B-pillar directly affects the safety performance of the vehicle in a side collision. The C-pillar is a pillar located between the rear side window glass and the rear windshield. Its main function is to support the structure of the roof and body, and it also helps to improve the overall rigidity of the vehicle. The design and inclination of the C-pillar will affect the rear view and the aerodynamic performance of the vehicle.

[0051] Preferably, the upper swing arm assembly and the lower swing arm assembly are connected between the C-pillar and the swing door of the vehicle body.

[0052] Preferably, an upper swing arm assembly 60 is further included; an upper swing arm body 61 of the upper swing arm assembly 60 is hinged to the vehicle body and the vehicle door through a first mounting block 62 and a second mounting block 63 respectively.

[0053] Automatic swing door control

[0054] The automatic swing door is controlled by an electronic control module, which may include a microprocessor and a memory having executable computer-readable instructions stored thereon. The electronic control module may communicate with a remote key fob and / or an interior / exterior handle switch for receiving a request from a user to open or close the door; in another way, the electronic control module may receive a command signal from the remote key fob and / or the interior / exterior handle switch to start the opening or closing of the door, and upon receiving the command, the electronic control module continues to provide a signal to the driver 10 to turn on the motor 11 and start the pivoting swing of the door.

[0055] Preferably, while providing the signal, the electronic control module also obtains feedback from the Hall Effect sensor of the motor to ensure that there is no contact obstacle. If there is no obstacle, a rotational force will continue to be generated to drive the rack to achieve rotation.

[0056] The electronic control module may also receive additional input from a proximity sensor, such as an ultrasonic or radar sensor positioned on the vehicle door, the ultrasonic sensor assessing whether an obstacle, such as another vehicle, a tree or a pole, is close to or very close to the vehicle door, and if such an obstacle is present, the ultrasonic sensor will send a signal to the electronic control module and the electronic control module will proceed to close the motor to block the vehicle door from moving to prevent the vehicle door from avoiding striking the obstacle. Alternatively, a contact obstacle avoidance system may be placed in the vehicle including a contact sensor mounted on the door and operable to send a signal to the electronic control module.

[0057] When the automatic swing door is opened, the differential drive assembly as described above will be used to prevent the transmission system from getting stuck.

[0058] The above description is only for illustrating the present invention, and it should be understood that the present invention is not limited to the above embodiments, and various variations that conform to the concept of the present invention are within the protection scope of the present invention.

Claims

1. A drive structure with differential output, characterized in that: include: A driver (10), the driver (10) comprising a motor (11) and a driver output shaft (12) driven by the motor; A differential housing assembly (30) comprises a differential upper housing (32) and a differential lower housing (33) and a mounting cavity formed therebetween, wherein the differential lower housing (33) has a lower shaft sleeve; A differential assembly (20) comprises an upper half-shaft gear (21), a planetary gear (23), a lower half-shaft gear (22) and a differential output shaft (26) in sequence; the driver output shaft (12) is drivingly connected to the upper half-shaft gear (21); the planetary gear (23) is installed in the differential housing assembly (30) through the planetary gear shaft (24) and meshes with the upper half-shaft gear (21) and the lower half-shaft gear (22); the differential output shaft (26) is located in the lower sleeve of the differential lower housing (33); When the differential output shaft (26) forms a differential with the driver output shaft (12), the differential assembly (20) can be driven through the lower sleeve, thereby realizing the composite motion of the planetary gear (23) rotating automatically and revolving.

2. The driving structure of differential output according to claim 1, characterized in that: Also includes: A mounting frame (40) provided with a guide track; The lower swing arm assembly (50) comprises a lower swing arm sleeve (54) and a rack (52) fixedly arranged in the lower swing arm sleeve (54); and also comprises a bushing (51), wherein the insertion end of the bushing (51) is slidably located in the lower swing arm sleeve (54), and the rotation end is rotatably mounted on the mounting frame (40). The differential output shaft (26) extends into the bushing (51) and is in driving engagement with the rack (52), and the lower shaft sleeve of the differential lower shell (33) is in driving engagement with the bushing (51); the positional relationship between the differential output shaft (26) and the rack (52) is changed to adjust the positional relationship between the lower swing arm sleeve (54) and the bushing (51) and the overall length of the lower swing arm assembly (50); during the adjustment process, the lower swing arm sleeve (54) moves relative to the mounting frame (40) and is limited by the guide track, and the bushing (51) rotates relative to the mounting frame (40).

3. The driving structure of differential output according to claim 1, characterized in that: The mounting frame (40) further comprises a body (41), the body (41) comprising an upper mounting plate, a side plate and a lower mounting plate, the guide rails being an upper guide rail (43) on the upper mounting plate and a lower guide rail (44) on the lower mounting plate; The bushing (51) is a sleeve structure, and a convex edge is provided above the rotating end of the sleeve structure. The convex edge can be rotatably positioned in the mounting hole (42) of the upper mounting plate, and a transmission tooth or a transmission key is provided on the inner side of the convex edge to be transmission-matched with the lower shaft sleeve of the differential lower shell (33); the rack (52) enters from the insertion end of the sleeve structure and is transmission-connected with the differential output shaft (26) at the rotating end.

4. The driving structure of differential output according to claim 3, characterized in that: The lower swing arm sleeve (54) is provided with rollers (55) at the top and bottom, and the upper and lower rollers (55) are respectively located in the upper guide rail (43) and the lower guide rail (44).

5. The driving structure of differential output according to claim 4, characterized in that: The differential housing assembly (30) also includes an upper housing (34) and a lower housing (35); the differential upper housing (32) is installed in the upper housing (34) via an upper bearing (31), and the lower shaft sleeve of the differential lower housing (33) is installed in the lower housing (35) via a lower shaft sleeve (37).

6. The driving structure of differential output according to claim 5, characterized in that: The upper half shaft gear (21) and the lower half shaft gear (22) of the differential assembly (20) are bevel gears, and the planetary gears (23) are bevel gears and the number of the planetary gears (23) is at least two. The planetary gears (23) are installed between the upper half shaft gear (21) and the lower half shaft gear (22) through the planetary gear shaft (24). When the upper half shaft gear (21) and the lower half shaft gear (22) rotate at the same speed, the planetary gears (23) rotate on their own; when the upper half shaft gear (21) and the lower half shaft gear (22) rotate at a differential speed, the planetary gears (23) perform a composite motion of revolution and rotation.

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