Trailer transmission

Abstract

This invention relates to the field of power transmission between a motor and a trailer, and particularly to a trailer transmission. It includes a housing; a gear transmission mechanism including a ratchet gear; a feeder mechanism including a ratchet feeder, a push-pull cylinder, and a spring for automatically resetting the ratchet feeder, the push-pull cylinder being located inside the ratchet feeder, the ratchet feeder and the push-pull cylinder being fixedly connected by a cross pin, and the ratchet feeder and the ratchet gear having interlocking ratchet teeth on their opposing surfaces; and a push-pull shaft, one end of which is slidably disposed within the push-pull cylinder and contacts the cross pin during sliding. It features smooth gear shifting, a low failure rate, provides anti-drag protection between the motor and the trailer, and reduces the overall size of the transmission.

Description

Technical Field

[0001] This invention relates to the field of power transmission between a power unit and a trailer, and in particular to a transmission for a trailer. Background Technology

[0002] A trailer is a vehicle towed by a car but without its own power drive. Trailers are generally towed and driven by a power unit such as a tractor. When a power unit towing a heavily loaded trailer encounters steep slopes, soft roads, or enters fields, the drive wheels often slip, causing the vehicle to become stuck. To address this, some power units are equipped with drive axles, using the power take-off shaft of the power unit to drive a gearbox to power the trailer's drive axle; alternatively, a hydraulic pump mounted on the power unit drives a hydraulic motor, which in turn drives a reduction gearbox to power the trailer's drive axle, using the drive axle as auxiliary power to help the vehicle get out of trouble. The gearbox's function is to reduce speed and increase torque, and also to disengage the power after the vehicle is out of trouble (i.e., neutral).

[0003] Existing transmissions typically use shift forks to move gears along a sliding wheel. As gears increase in size, the length of the shift fork must increase to prevent interference with the gears from the shift fork bushing or sliding sleeve. This increase in length leads to a significant increase in the bending moment of the shift fork and guide rod. Furthermore, the length of the sliding contact with the shift fork also increases, necessitating a larger overall size for the transmission. However, in practical use, space constraints prevent a substantial increase in transmission size. Therefore, when the gears within the transmission are large, problems such as difficulty shifting, bending of the push-pull shaft, jamming or sticking, shift fork and sliding wheel groove wear, and rapid shift fork wear become prominent.

[0004] When the speed of the motor exceeds that of the trailer, the speed mismatch creates a significant back-dragging torque on the trailer's transmission. Furthermore, the driven components of a larger transmission often have substantial inertia or rotational moment of inertia. When the motor suddenly loses power due to manual emergency stopping or a malfunction (such as a sudden power failure in the motor or its control system, a hydraulic motor failure, a hydraulic control failure, or an oil circuit failure), it experiences an abrupt stop. When the motor stops, but the trailer connected to the transmission cannot stop immediately due to inertia, a significant back-dragging impact torque is generated on the transmission system. The peak value of this torque often far exceeds the driving torque, causing damage or destruction to the transmission system. Currently, this problem is generally solved by using friction or hydraulic couplings, but due to the large torque, the diameter of the coupling itself may be larger than the transmission. Due to space and cost constraints, couplings cannot be used to limit the back-dragging torque in many practical applications. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned defects in the prior art and to propose a trailer gearbox that shifts smoothly, has a low failure rate, achieves anti-drag protection between the engine and the trailer, and reduces the overall size of the gearbox.

[0006] The technical solution of the present invention is: a trailer transmission, including a housing, wherein the transmission mechanism includes a gear transmission mechanism, including a ratchet gear;

[0007] The cruise ship mechanism includes a ratchet cruise wheel, a push-pull cylinder, and a spring for automatically resetting the ratchet cruise wheel. The push-pull cylinder is located inside the ratchet cruise wheel. The ratchet cruise wheel and the push-pull cylinder are fixedly connected by a cross pin. The ratchet cruise wheel and the ratchet gear are respectively provided with interlocking ratchet teeth on their opposite surfaces.

[0008] The push-pull shaft has one end slidably disposed inside the push-pull cylinder, and contacts the cross pin during the sliding process.

[0009] In this invention, the ratchet gear can be rotatably sleeved on the outside of the main shaft;

[0010] The ratchet wheel is mounted on the main shaft. The ratchet wheel rotates with the main shaft and moves along the main shaft axis. The push-pull cylinder is slidably mounted in the cavity inside the main shaft. The main shaft is provided with a vertical slide groove for the horizontal pin to move up and down.

[0011] The ratchet gear includes a forward ratchet gear and a reverse ratchet gear. The reverse ratchet gear meshes with the large gear on the idler shaft for transmission, and the forward ratchet gear meshes with the countershaft gear for transmission.

[0012] The ratchet wheel includes a forward ratchet wheel and a reverse ratchet wheel. The forward ratchet wheel and the forward ratchet gear have interlocking ratchet teeth on their opposite surfaces. The reverse ratchet wheel and the reverse ratchet wheel have interlocking ratchet teeth on their opposite surfaces. The forward ratchet wheel and the reverse ratchet wheel are connected by a spring.

[0013] Both the large gear and the small gear of the idler shaft are mounted on the idler shaft, and the small gear of the idler shaft meshes with the countershaft gear for transmission.

[0014] The forward and reverse ratchet wheels are connected to the push-pull cylinders via cross pins.

[0015] The spring is located on the outside of the cross pin.

[0016] The end of the main shaft is rotatably connected to the housing via a bearing, and a spring connects the ratchet wheel and the bearing.

[0017] The ratchet gear meshes with the counterspindle gear for transmission.

[0018] The ratchet gear is rotatably mounted on the secondary shaft;

[0019] The ratchet wheel is mounted on the secondary shaft. The ratchet wheel rotates with the secondary shaft and moves along the axial direction of the secondary shaft. The push-pull cylinder is slidably mounted in the cavity inside the secondary shaft. The secondary shaft is provided with a vertical slide groove for the horizontal pin to move up and down. The ratchet gear meshes with the main shaft gear for transmission.

[0020] The end of the secondary shaft is rotatably connected to the housing via a bearing, and a spring connects the ratchet wheel to the bearing.

[0021] One end of the push-pull shaft is slidably disposed inside the push-pull cylinder, and this end of the push-pull shaft is provided with a push-pull head and an inner cross pin.

[0022] A baffle is provided on the outer side of the cross pin, and the baffle is fixedly connected to the bottom of the ratchet wheel.

[0023] The beneficial effects of this invention are:

[0024] (1) Smooth gear shifting, low failure rate, and high reliability;

[0025] (2) Anti-towing protection between the engine and the trailer is achieved through ratchet gears, ratchet wheels and springs;

[0026] (3) The ratchet wheel of this application is not limited in its setting position. In actual use, it can be set on the main shaft, the secondary shaft or the intermediate shaft as needed.

[0027] (4) Since there is no need to install shift forks in the gearbox, the overall volume of the gearbox is reduced. Attached Figure Description

[0028] Figure 1 This is a bottom view of the gear transmission mechanism inside the gearbox in Embodiment 1;

[0029] Figure 2 This is a top view of the gear transmission mechanism inside the gearbox in Embodiment 1;

[0030] Figure 3 yes Figure 2 AA-direction cross-sectional structure diagram;

[0031] Figure 4 yes Figure 1 A partial structural schematic diagram of the BB-direction cross-section;

[0032] Figure 5 A cross-sectional view of the gearbox in Example 2;

[0033] Figure 6 This is a schematic diagram of the cross-sectional structure at the secondary shaft in Example 3.

[0034] In the diagram: 1. Main shaft; 2. Spring retaining ring for the hole; 3. Bearing; 4. Reverse ratchet gear; 5. Spring retaining ring for the shaft; 6. Reverse ratchet wheel; 7. Push-pull cylinder; 8. Spring; 9. First cross pin; 10. Forward ratchet wheel; 11. Inner cross pin; 12. Washer; 13. Forward ratchet gear; 14. Push-pull shaft; 15. Auxiliary support ring; 18. First oil seal; 19. Bearing end cover; 20. Sealing cover; 21. Idler shaft; 22. Idler shaft pinion; 23. Idler shaft gear; 24. Second oil seal; 25. Countershaft gear; 26. Countershaft; 27. Housing; 28. Gear shift rocker arm; 29. ​​Second cross pin; 30. Third cross pin; 31. Baffle; 32. Main shaft gear. Detailed Implementation

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0036] Specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many ways other than those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0037] Example 1

[0038] like Figures 1 to 4 As shown, the trailer gearbox of the present invention includes a housing 27, a gear transmission mechanism, a cruise wheel mechanism, and a push-pull shaft 14. Both the gear transmission mechanism and the cruise wheel mechanism are housed within the housing 27. One end of the push-pull shaft 14 is located inside the housing 27 and connected to the cruise wheel mechanism, while the other end of the push-pull shaft 14 is located outside the housing 27. In this embodiment, the end of the push-pull shaft 14 located outside the housing is connected to a shift rocker arm 28, enabling the push-pull shaft 14 to reciprocate within the housing 27 via the shift rocker arm 28.

[0039] In this application, power is transmitted between the main shaft 1, the idler shaft 21, and the secondary shaft 26 via a gear transmission mechanism. The main shaft 1 is connected to the power output shaft of the power unit or a hydraulic motor. Both the main shaft 1 and the idler shaft 21 are housed within the housing 27. One end of the secondary shaft 26 is housed within the housing 27, and the other end of the secondary shaft 26 is connected to the trailer drive.

[0040] The gear transmission mechanism includes a forward ratchet 13, a reverse ratchet 4, a large idler gear 23, a small idler gear 22, and a counterspindle gear 25. The forward ratchet 13 and reverse ratchet 4 are respectively located at both ends of the main shaft 1, and are rotatably connected to the main shaft 1. Specifically, the inner annular surfaces of the forward and reverse ratchet 13 and reverse ratchet 4 are clearance-fitted with the main shaft 1, and are axially limited by a shaft spring retainer 5. The outer annular surfaces of the forward and reverse ratchet 13 and reverse ratchet 4 are respectively provided with external teeth. The forward ratchet 13 meshes with the counterspindle gear 25 through its external teeth, and the reverse ratchet 4 meshes with the large idler gear 23 through its external teeth. Additionally, the end faces of the forward and reverse ratchet 13 and reverse ratchet 4 facing the cruise ship mechanism are respectively provided with ratchet teeth.

[0041] Both the large idler gear 23 and the small idler gear 22 are mounted on the idler shaft 21. They are connected to the idler shaft 21 via splines, allowing both gears to rotate simultaneously. The large idler gear 23 meshes with the reverse ratchet gear 4, while the small idler gear 22 meshes with the counterspindle gear 25.

[0042] The counterspindle gear 25 is mounted on the counterspindle 26, and the counterspindle gear 25 and the counterspindle 26 are connected by a spline, so the counterspindle gear 25 and the counterspindle 26 rotate simultaneously. The counterspindle gear 25 meshes with the idler pinion 22 and the forward ratchet gear 13 for transmission.

[0043] The cruise ship mechanism includes a push-pull cylinder 7 and a ratchet cruise wheel. The main shaft 1 has a cavity along its axial direction. The push-pull cylinder 7 is slidably disposed in the cavity inside the main shaft 1. The ratchet cruise wheel is located on the outside of the main shaft 1 and is connected to the main shaft 1 by a key. This enables the ratchet cruise wheel and the main shaft 1 to rotate simultaneously and also enables relative axial movement between the ratchet cruise wheel and the main shaft 1.

[0044] The ratchet wheel in this embodiment includes a reverse ratchet wheel 6 and a forward ratchet wheel 10. The reverse ratchet wheel 6 is located on the side facing the reverse ratchet gear 4, and ratchet teeth are respectively provided on the opposite surfaces of the reverse ratchet wheel 6 and the reverse ratchet gear 4. The forward ratchet wheel 10 is located on the side facing the forward ratchet gear 13, and ratchet teeth are respectively provided on the opposite surfaces of the forward ratchet wheel 10 and the forward ratchet gear 13. The reverse ratchet wheel 6 and the forward ratchet wheel 10 are connected by a spring 8. The ratchet teeth in this embodiment can be pointed ratchet teeth, flat ratchet teeth, or irregularly shaped teeth.

[0045] The push-pull cylinder 7 is fixed inside the cavity of the main shaft 1. In this embodiment, the outer surface of the push-pull cylinder 7 and the inner surface of the cavity of the main shaft 1 are in clearance fit. The push-pull cylinder 7 is connected to the ratchet wheel via a cross pin. In this embodiment, the push-pull cylinder 7 and the forward ratchet wheel 10 are connected via a first cross pin 9. The first cross pin 9 passes through the forward ratchet wheel 10, the main shaft 1, and the push-pull cylinder 7 in sequence. The side wall of the main shaft 1 is provided with a sliding groove, and the corresponding forward ratchet wheel 10 and the push-pull cylinder 7 are provided with mounting holes. The first cross pin 9 can slide up and down in the vertical sliding groove of the main shaft 1. The first cross pin 10 realizes the fixed connection between the forward ratchet wheel 10 and the push-pull cylinder 7, and at the same time, the first cross pin 9 can drive the forward ratchet wheel to move along the axial direction of the main shaft 1.

[0046] The push-pull cylinder 7 is connected to the reverse ratchet wheel 6 via a second horizontal pin 29. The second horizontal pin 29 passes sequentially through the mounting hole of the reverse ratchet wheel 6, the vertical groove of the main shaft 1, and the mounting hole of the push-pull cylinder, thus achieving a fixed connection between the reverse ratchet wheel 6 and the main shaft 1. The second horizontal pin 29 slides along the vertical groove of the main shaft 1, therefore it can drive the reverse ratchet wheel to move axially along the main shaft 1.

[0047] In this embodiment, the spring 8 is located on the outer side of both ends of the first horizontal pin 9 and the second horizontal pin 29, and the spring 8 plays a role in axially limiting the two horizontal pins.

[0048] One end of the push-pull shaft 14 is located inside the push-pull cylinder 7. This end of the push-pull shaft 14 is equipped with a push-pull head, on which an inner horizontal pin 11 is fixed. Both the push-pull head and the inner horizontal pin 11 can reciprocate along the axial direction of the push-pull cylinder 7. In this embodiment, the other end of the push-pull shaft 14 is located on the outer wall of the housing 27 and is rotatably connected to the gear shift rocker arm 28. During the swinging process of the gear shift rocker arm 28, it drives the push-pull shaft 14 connected to it to reciprocate axially within the push-pull cylinder 7. In this application, any device capable of axial movement of the push-pull shaft 14 is acceptable, and it is not limited to the gear shift rocker arm 28 described in this embodiment. An anti-wear washer 12 is provided between the push-pull head and the push-pull cylinder 7. The anti-wear washer 12 serves to adjust the clearance and reduce friction.

[0049] Figure 3 and Figure 4This is a cross-sectional view of the gearbox in neutral, with the spring 8 between the forward ratchet wheel 10 and the reverse ratchet wheel 6 at its original length. Swinging the shift rocker arm 28 pushes the push-pull shaft 14 towards the housing 27. The push-pull head at the other end of the push-pull shaft 14 lifts the inner transverse pin 11 upwards, which in turn lifts the first transverse pin 9 upwards. As the first transverse pin moves upwards along the vertical groove of the push-pull cylinder, it drives the forward ratchet wheel 10 upwards, simultaneously guiding its axial movement. The spring 8 between the forward and reverse ratchet wheels 10 is compressed. Under the elastic force of the spring 8, the reverse ratchet wheel 6 moves towards the reverse ratchet gear 4. At this time, the second transverse pin 29 connected to the reverse ratchet wheel 6 moves along the vertical groove of the push-pull cylinder, guiding its axial movement.

[0050] The push-pull shaft 14 continues to rise until the reverse gear ratchet wheel 6 moves to contact the reverse gear ratchet 4. At the same time, the ratchet teeth on the end face of the reverse gear ratchet wheel 6 and the ratchet teeth on the end face of the reverse gear ratchet 4 mesh with each other, and the gearbox is in reverse gear. The power of the engine is transmitted to the main shaft 1 and drives the main shaft to rotate. At this time, the reverse gear ratchet wheel 6, which is splined to the main shaft, rotates with the main shaft 1. Through the ratchet meshing between the reverse gear ratchet wheel 6 and the reverse gear ratchet 4, the reverse gear ratchet wheel 6 drives the reverse gear ratchet 4 to rotate.

[0051] Through the meshing of the reverse ratchet 4 and the large idler gear 23, the rotation of the large idler gear 23 drives the idler shaft 21 connected to it, which in turn drives the small idler gear 22 on the idler shaft 21 to rotate. Finally, through the meshing of the small idler gear 22 and the countershaft gear 25, power is transmitted to the countershaft 26, causing it to rotate. The rotation of the countershaft 26 enables the trailer to operate in reverse. When the transmission is in reverse, the forward ratchet 13 is in an idling state.

[0052] When reverse towing occurs, the trailer's speed is now significantly greater than the speed of the engine in front. The inertial rotational power within the sub-shaft 26 is transmitted sequentially through the idler shaft pinion 22, idler shaft 21, and idler shaft gear 23 to the reverse ratchet 4. At this point, the speed of the reverse ratchet 4 differs from the speed of the reverse ratchet wheel 6 connected to the main shaft 1. The reverse ratchet 4 is speeding relative to the reverse ratchet wheel 6, causing the ratches on their opposing surfaces to misalign. Under the action of the ratchet's inclined surface, the reverse ratchet wheel 6 is pushed away from the reverse ratchet 4, compressing the spring 8 between the reverse ratchet wheel 6 and the forward ratchet wheel 10. The reverse ratchet wheel 6 then retracts, and there is no power transmission between it and the reverse ratchet 4, thus achieving reverse towing and slippage. As the speed of the countershaft 26 gradually decreases, when the reverse drag torque disappears or decreases to a certain extent, under the action of the elastic force in the spring 8, the spring 8 pushes the reverse ratchet wheel 6 to reset, so that the reverse ratchet wheel 6 and the reverse ratchet gear 4 can re-engage.

[0053] The push-pull shaft 14 is pulled back using the shift rocker arm 28. Figure 2 When in neutral, the entire transmission is in neutral.

[0054] When the push-pull shaft 14 is pulled outward by the shift rocker arm 28, the push-pull shaft 14 drives the forward gear ratchet wheel 10 to move towards the forward gear ratchet gear 13. When the ratchet wheel 10 moves to the point where the ratchet teeth on its end face mesh with the ratchet teeth on the end face of the forward gear ratchet gear 13, the transmission is in forward gear. The power from the power unit is transmitted to the main shaft 1 and drives the main shaft to rotate. At this time, the forward gear ratchet wheel 10 connected to the main shaft rotates with the main shaft 1. Through the ratchet meshing between the forward gear ratchet wheel 10 and the forward gear ratchet gear 13, the forward gear ratchet wheel 10 drives the forward gear ratchet gear 13 to rotate. Through the meshing between the forward gear ratchet gear 13 and the countershaft gear 25, the countershaft gear 25 drives the countershaft 26 to rotate. The rotation of the countershaft 26 realizes the forward gear movement of the trailer. When the transmission is in forward gear, the reverse gear ratchet gear 4 is in an idle state.

[0055] When reverse drag occurs, the working principle between the forward ratchet wheel 10 and the forward ratchet gear 13 is the same as the working principle between the reverse ratchet gear and the reverse ratchet wheel in reverse drag state, so it will not be described again here.

[0056] In this application, both ends of the main shaft 1 are rotatably connected to the housing 27 via bearings 3, and a bearing end cap 19 is provided on the outer side of the bearing facing the shift rocker arm. An oil seal 18 is provided between the bearing end cap 19 and the main shaft 1. An auxiliary support ring 15 is provided between the inner cavity of the main shaft 1 and the push-pull shaft 14. The auxiliary support ring 15 can effectively prevent the push-pull shaft 14 from generating excessive deviation due to large lateral forces during the assembly of the entire transmission, thereby preventing damage to the inner surface of the push-pull cylinder that slides with the push-pull shaft. Both ends of the idler shaft 21 and both ends of the secondary shaft 26 are connected to the housing 27 via bearings. The end of the idler shaft 21 is provided inside the housing 27 via a sealing cap 20.

[0057] Example 2

[0058] In some practical work situations, trailers do not require a reverse gear function. In such cases, there is no need to include a reverse ratchet wheel, reverse ratchet gear, or idler shaft in the gearbox. For example... Figure 5 As shown, the gearbox housing contains a ratchet wheel and a ratchet gear, namely the forward ratchet wheel 10 and the forward ratchet gear 13. At this time, the push-pull cylinder 7 and the forward ratchet wheel 10 are fixedly connected by a third cross pin 30, and a baffle 31 is provided on the outer side of the third cross pin, which serves to axially limit the third cross pin 30.

[0059] The positive gear ratchet 13 meshes with the negative gear 25. Figure 5 When the transmission is in forward gear, the shift rocker arm 28 drives the push-pull shaft 14 to move. The push-pull shaft 14 pushes the forward gear ratchet wheel 10 towards the forward gear ratchet gear 13, and the ratches on the opposite surfaces of the forward gear ratchet wheel 10 and the forward gear ratchet gear 13 mesh with each other. During the rotation of the main shaft 1, its power is transmitted sequentially through the forward gear ratchet wheel 10, the forward gear ratchet gear 13, and the countershaft gear 25 to the countershaft 26, thereby driving the countershaft 26 to rotate. During the rotation of the countershaft 26, the trailer is in forward gear working state. The end of the main shaft 1 is connected to the gearbox through a bearing, and a spring 8 is connected between the forward gear ratchet wheel 10 and the bearing.

[0060] Everything else is the same as in Example 1.

[0061] Example 3

[0062] In some practical working situations, such as when two hydraulic motors drive the main shaft simultaneously, there is not enough space on the main shaft to install the aforementioned transmission structure. In this case, the transmission structure can be installed on the countershaft.

[0063] like Figure 6As shown, the ratchet gear is rotatably sleeved on the outside of the countershaft 26, and meshes with the main shaft gear 32 on the main shaft 1. The main shaft 1 and the main shaft gear 32 are connected by a spline. The ratchet wheel is connected to the countershaft 26 by a spline, and the push-pull cylinder 7 is slidably disposed in the cavity inside the countershaft 26. The countershaft 26 is provided with a vertical groove that allows the cross pin to move up and down.

[0064] Under the pushing action of the push-pull shaft, Figure 6 The ratchet wheel and ratchet gear in the main shaft are engaged. As the main shaft 1 rotates, the power of the main shaft is transmitted sequentially through the main shaft gear 32, the ratchet gear, and the ratchet wheel to the secondary shaft 26, thus realizing the rotation of the secondary shaft 26. Simultaneously, the rotation of the secondary shaft 26 enables the trailer to operate in either forward or reverse gear. The end of the secondary shaft 26 is connected to the chassis via a bearing, and a spring 8 connects the ratchet wheel to the bearing.

[0065] Everything else is the same as in Example 1.

[0066] The trailer transmission provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention. The above description of the disclosed embodiments enables those skilled in the art to implement or use this invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this invention. Therefore, this invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A trailer transmission, comprising a housing, characterized in that, Also includes: Gear transmission mechanisms, including ratchet gears; The cruise ship mechanism includes a ratchet cruise wheel, a push-pull cylinder, and a spring for automatically resetting the ratchet cruise wheel. The push-pull cylinder is located inside the ratchet cruise wheel. The ratchet cruise wheel and the push-pull cylinder are fixedly connected by a cross pin. The ratchet cruise wheel and the ratchet gear are respectively provided with interlocking ratchet teeth on their opposite surfaces. The push-pull shaft has one end slidably disposed inside the push-pull cylinder and contacts the cross pin during sliding. The ratchet gear is rotated and sleeved on the outside of the main shaft; The ratchet wheel is mounted on the main shaft. The ratchet wheel rotates with the main shaft and moves along the main shaft axis. The push-pull cylinder is slidably mounted in the cavity inside the main shaft. The main shaft is provided with a vertical slide groove for the horizontal pin to move up and down. The ratchet gear includes a forward ratchet gear and a reverse ratchet gear. The reverse ratchet gear meshes with the large gear on the idler shaft for transmission, and the forward ratchet gear meshes with the countershaft gear for transmission. The ratchet wheel includes a forward ratchet wheel and a reverse ratchet wheel. The forward ratchet wheel and the forward ratchet gear have interlocking ratchet teeth on their opposite surfaces. The reverse ratchet wheel and the reverse ratchet wheel have interlocking ratchet teeth on their opposite surfaces. The forward ratchet wheel and the reverse ratchet wheel are connected by a spring. Both the large gear and the small gear of the idler shaft are mounted on the idler shaft, and the small gear of the idler shaft meshes with the countershaft gear for transmission.

2. The trailer transmission according to claim 1, characterized in that, The forward and reverse ratchet wheels are connected to the push-pull cylinders via cross pins.

3. The trailer transmission according to claim 2, characterized in that, The spring is located on the outside of the cross pin.

4. The trailer transmission according to claim 1, characterized in that, One end of the push-pull shaft is slidably disposed inside the push-pull cylinder, and this end of the push-pull shaft is provided with a push-pull head and an inner cross pin.

5. A trailer transmission, comprising a housing, characterized in that, Also includes: Gear transmission mechanisms, including ratchet gears; The cruise ship mechanism includes a ratchet cruise wheel, a push-pull cylinder, and a spring for automatically resetting the ratchet cruise wheel. The push-pull cylinder is located inside the ratchet cruise wheel. The ratchet cruise wheel and the push-pull cylinder are fixedly connected by a cross pin. The ratchet cruise wheel and the ratchet gear are respectively provided with interlocking ratchet teeth on their opposite surfaces. The push-pull shaft has one end slidably disposed inside the push-pull cylinder and contacts the cross pin during sliding. The ratchet gear is rotatably mounted on the secondary shaft; The ratchet wheel is mounted on the secondary shaft. The ratchet wheel rotates with the secondary shaft and moves along the axial direction of the secondary shaft. The push-pull cylinder is slidably mounted in the cavity inside the secondary shaft. The secondary shaft is provided with a vertical slide groove for the horizontal pin to move up and down. The ratchet gear meshes with the main shaft gear for transmission. The end of the secondary shaft is rotatably connected to the housing via a bearing, and a spring connects the ratchet wheel to the bearing.

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