Four-wheel drive transmission structure suitable for small off-road vehicle

Abstract

The invention relates to the technical field of vehicle driving, in particular to a four-wheel-drive transmission structure suitable for a small off-road vehicle, and mainly solves the technical problems that the four-wheel-drive transmission structure of the small off-road vehicle cannot give consideration to operation convenience and manufacturing cost and is low in transmission power. The structure comprises an engine, a front wheel transmission assembly, a rear wheel transmission assembly, a first clutch and a second clutch, the front wheel transmission assembly comprises a driving bevel gear, a driven bevel gear, a transmission shaft and a front wheel gearbox, the rear wheel transmission assembly comprises a CVT transmission and a rear wheel gearbox, and the first clutch and the second clutch are used for achieving automatic clutch through centrifugal force. The CVT transmission of the structure only provides power for the rear axle, the problem that the transmission power of the CVT transmission is small can be solved, manual operation is not needed, operation convenience is higher, the CVT transmission is of a pure mechanical structure, manufacturing cost and design difficulty are low, and meanwhile the CVT transmission has the double advantages of vehicle full-time four-wheel drive and power decoupling of the front axle and the rear axle under part of working conditions.

Description

Technical Field

[0001] The present invention relates to the field of vehicle drive technology, and in particular to a four-wheel drive transmission structure suitable for a small off-road vehicle. Background Art

[0002] Small off-road vehicles feature smaller engines, relatively compact dimensions, short wheelbases, and lightweight construction. They often utilize a truss-style frame constructed from welded steel tubes. Typical examples include university Baja racers and small beach buggies. These vehicles often navigate extreme conditions, such as rugged mountain roads, muddy tracks, and soft sand. These vehicles place stringent demands on the four-wheel drive's power response, torque distribution accuracy, and structural durability.

[0003] At present, there are mainly the following types of four-wheel drive transmission structures used in small off-road vehicles: the first is a mechanical part-time four-wheel drive structure, which relies on manual operation to switch the drive mode. During high-intensity competitions or outdoor driving, drivers often find it difficult to accurately judge and switch modes in a short period of time, and easily miss the best power output opportunity, resulting in insufficient power for the vehicle in key links such as climbing and cornering, seriously affecting the competition results and driving experience. In addition, frequent switching of the mechanical structure can easily cause component wear and reduce the reliability and service life of the transmission system; the second is an electronic timely four-wheel drive structure. Although this structure can achieve automatic mode switching, the system has extremely high requirements on sensor accuracy and algorithms, and the manufacturing difficulty and cost are too high. In addition, in harsh environments full of sand, dust, mud and water, the sensors are easily interfered with, resulting in inaccurate signal transmission, and then power distribution errors, causing the vehicle to lose power.

[0004] In addition, the existing four-wheel drive transmission structure generally adopts a rubber belt CVT transmission, and the transmission and transfer case are integrated and arranged at the output end of the rubber belt CVT transmission. This arrangement makes the system transmission power and torque limited by the rubber belt CVT transmission. When the power demand is large, the rubber belt CVT transmission slips severely, and the engine's power performance cannot be fully utilized, affecting the vehicle's acceleration and climbing ability in complex terrain.

[0005] Therefore, there is an urgent need to develop a four-wheel drive transmission structure that can balance operational convenience and manufacturing cost and has higher transmission power to improve the overall performance of the vehicle. Summary of the Invention

[0006] In order to overcome the technical defects of the existing four-wheel drive transmission structure of small off-road vehicles, such as the inability to balance operational convenience and manufacturing cost and low transmission power, the present invention provides a four-wheel drive transmission structure suitable for small off-road vehicles.

[0007] The four-wheel drive transmission structure provided by the present invention is suitable for a small off-road vehicle, comprising:

[0008] engine;

[0009] A front wheel transmission assembly, comprising a driving bevel gear, a driven bevel gear, a transmission shaft and a front wheel gearbox, wherein the driving bevel gear is rotatably sleeved on the output shaft of the engine, the driven bevel gear is fixedly sleeved on the input end of the transmission shaft and meshes with the driving bevel gear, and the output end of the transmission shaft is drivingly connected to the input shaft of the front wheel gearbox;

[0010] A rear wheel transmission assembly, comprising a CVT transmission and a rear wheel gearbox, wherein the input end of the CVT transmission is connected to the output shaft of the engine, the input shaft of the rear wheel gearbox is rotatably sleeved with a rotating drum, and the output end of the CVT transmission is connected to the rotating drum;

[0011] A first clutch is installed between the input end of the CVT transmission and the driving bevel gear and is used to realize automatic clutching by utilizing centrifugal force;

[0012] The second clutch is installed between the rotating drum and the input shaft of the rear wheel gearbox and is used for realizing automatic clutching by utilizing centrifugal force.

[0013] Optional:

[0014] The CVT transmission includes an input pulley set, an output pulley set and a transmission belt;

[0015] The input pulley assembly includes an input end fixed cone disc and an input end movable cone disc, both of which are mounted on the output shaft of the engine, wherein the input end fixed cone disc is located axially outside the input end movable cone disc, and the input end movable cone disc is located axially outside the driving bevel gear;

[0016] The output pulley assembly includes an output end fixed cone disc and an output end movable cone disc, both of which are mounted on the rotating drum. The output end fixed cone disc is located axially inward of the output end movable cone disc, and the output end movable cone disc is provided with a first elastic reset member for driving it close to the output end fixed cone disc.

[0017] The transmission belt is wound between the input pulley assembly and the output pulley assembly.

[0018] Optional:

[0019] The first clutch includes a movable top cover, a puli bead, an active friction member and a driven friction member;

[0020] The movable top cover is sleeved on the output shaft of the engine and is located between the input end movable cone disk and the active bevel gear. The movable top cover is provided with a second elastic reset member for driving it away from the active bevel gear.

[0021] The Pulley bead is installed between the input end movable cone and the movable top cover;

[0022] The active friction member is installed on the side of the movable top cover facing the active bevel gear;

[0023] The driven friction member is mounted on the side of the driving bevel gear facing the movable top cover;

[0024] The puli beads are used to drive the movable top cover to move axially under the action of centrifugal force so that the active friction part and the driven friction part can contact and realize linkage, and are also used to drive the input end movable cone disk to move axially to realize the stepless speed change of the CVT transmission.

[0025] Optionally, the second elastic reset member is a compression spring, and the two opposite end faces of the movable top cover and the active bevel gear are both fixed with mounting pins, and the second elastic reset member is sleeved on the mounting pins.

[0026] Optionally, the movable top cover includes a puli pressure plate and a mounting plate, the puli pressure plate and the mounting plate are both conical and fixedly connected in a back-to-back posture, the puli pressure plate is docked with the input end movable cone plate to form a radial slide for installing the puli bead, and the active friction part is fixed to the end face of the mounting plate away from the puli pressure plate.

[0027] Optionally, the active friction member is a plurality of friction blocks evenly spaced along the circumferential direction, and the driven friction member is a friction ring.

[0028] Optional:

[0029] The second clutch comprises a fixed bottom shell and a flyweight clutch member;

[0030] The fixed bottom shell is sleeved on the input shaft of the rear wheel gearbox;

[0031] The flyweight clutch is mounted on the rotating drum and is located axially outside the output end movable cone, and the flyweight clutch is located inside the fixed bottom shell;

[0032] The flying weight clutch member is used to contact the inner wall of the fixed bottom shell under the action of centrifugal force to achieve linkage.

[0033] Optionally, the rotating cylinder and the fixed cone disk at the output end are integrally formed, and the movable cone disk at the output end is also integrally formed with an extension cylinder, the extension cylinder is gap-mounted on the outside of the rotating cylinder, and the extension cylinder and the rotating cylinder are circumferentially limited by a limit pin.

[0034] Optionally, the first elastic reset member is a compression spring sleeved on the outside of the extension tube, and two ends of the first elastic reset member respectively abut against the output end moving cone disk and the flyweight clutch member.

[0035] Optionally, a side of the input-end fixed cone disk away from the input-end movable cone disk is provided with a heat dissipation fin, and the fixed bottom shell is provided with a heat dissipation hole.

[0036] The technical solution provided by the present invention has the following advantages compared with the prior art:

[0037] 1) The four-wheel drive transmission structure provided by the present invention, suitable for small off-road vehicles, arranges the first clutch and front wheel drive assembly corresponding to the front axle between the engine and the input end of the CVT transmission. The front axle power is directly derived from the engine without passing through the CVT transmission, while the CVT transmission only provides power to the rear axle, which can overcome the problem of low transmission power of the CVT transmission.

[0038] 2) The four-wheel drive transmission structure provided by the present invention, suitable for small off-road vehicles, comprises a first clutch provided between the input end of the CVT transmission and the front wheel gearbox, and a second clutch provided between the output end of the CVT transmission and the rear wheel gearbox. Both the first clutch and the second clutch are centrifugal structures, enabling automatic engagement and disengagement without the need for a clutch operating mechanism. This structure is simple and requires no additional driver operation steps, making operation more convenient. Furthermore, this structure is purely mechanical, without the use of complex electrical and electronic components, resulting in high reliability, low manufacturing cost, and low design difficulty.

[0039] 3) The four-wheel drive transmission structure for small off-road vehicles provided by the present invention has the dual advantages of full-time four-wheel drive of the vehicle and power decoupling of the front and rear axles under certain working conditions through the reasonable design of the transmission ratio: when driving on a road with a high adhesion coefficient, there is almost no speed difference between the front and rear axles of the vehicle, the front axle obtains engine power through the first clutch, and the rear axle obtains torque through the second clutch; when the front wheel adhesion coefficient is high and the rear wheel adhesion coefficient is low, there is a speed difference between the front and rear axles, the front axle obtains engine power through the first clutch, and the higher the engine speed, the greater the output power and torque of the front axle, the rear axle slips due to the low road adhesion coefficient, and the speed is almost the same as the output end of the CVT transmission. Therefore, under this working condition, the front axle can drag the rear axle forward; when the front wheel adhesion coefficient is low and the rear wheel adhesion coefficient is high, there is a speed difference between the front and rear axles, the front axle slips due to the low road adhesion coefficient, and the rear axle obtains torque through the second clutch, and the higher the engine speed, the greater the output power and torque of the rear axle. Under this working condition, the rear axle can push the front axle forward; when the front and rear wheel adhesion coefficients are both low, there is a speed difference between the front and rear axles, and the front and rear axles each obtain power through different paths, the front and rear axles are decoupled, and the vehicle's escape performance is improved; when the vehicle is in a climbing condition, the front and rear axles travel different distances, and the front and rear axles can use the speed difference to enable the rear axle to obtain speed and torque, thereby improving the vehicle's climbing ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0042] Figure 1 A schematic diagram showing the overall structure of the four-wheel drive transmission structure according to an embodiment of the present invention;

[0043] Figure 2 A schematic structural diagram of a front wheel transmission assembly according to an embodiment of the present invention is shown;

[0044] Figure 3 A schematic diagram showing the structure of a rear wheel transmission assembly and a clutch in an embodiment of the present invention;

[0045] Figure 4 A cross-sectional view showing the output shaft and accessory structures of an engine according to an embodiment of the present invention;

[0046] Figure 5 An exploded view of the output shaft and accessory structures of an engine according to an embodiment of the present invention is shown;

[0047] Figure 6 A cross-sectional view showing the input shaft and accessory structures of a rear wheel reduction gearbox according to an embodiment of the present invention;

[0048] Figure 7 An exploded view of the input shaft and accessory structures of a rear wheel reduction gearbox according to an embodiment of the present invention is shown;

[0049] Figure 8 A schematic structural diagram showing a movable top plate according to an embodiment of the present invention;

[0050] Figure 9 A schematic diagram showing the assembly of the input end movable cone and the Pulley bead according to an embodiment of the present invention;

[0051] Figure 10 A schematic diagram showing the structure of a fixed cone disc at the output end according to an embodiment of the present invention;

[0052] Figure 11 A schematic diagram showing the structure of a movable cone at the output end according to an embodiment of the present invention;

[0053] Figure 12 A schematic diagram showing the structure of a fixed bottom shell according to an embodiment of the present invention;

[0054] Figure 13A schematic structural diagram showing a flying weight clutch member according to an embodiment of the present invention;

[0055] In the picture:

[0056] 1. Engine; 2. Front wheel transmission assembly; 21. Driving bevel gear; 22. Driven bevel gear; 23. Drive shaft; 231. Shaft body; 232. Shaft end; 233. First universal joint; 24. Front wheel gearbox; 241. Second universal joint; 3. Rear wheel transmission assembly; 31. CVT transmission; 311. Fixed cone disc at input end; 3111. Cooling fins; 312. Moving cone disc at input end; 313. Fixed cone disc at output end; 3131. Rotating drum; 314. Moving cone disc at output end; 3141. Extension Extension cylinder; 315, first elastic return member; 316, transmission belt; 32, rear wheel gearbox; 321, third universal joint; 4, first clutch; 41, movable top cover; 411, Puli pressure plate; 412, mounting plate; 42, Puli bead; 43, active friction member; 44, driven friction member; 45, second elastic return member; 46, mounting pin; 5, second clutch; 51, fixed bottom shell; 511, heat dissipation hole; 52, flyweight clutch; 521, connecting plate; 522, flyweight; 523, connecting spring. DETAILED DESCRIPTION

[0057] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0058] In the description, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance. It should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood broadly. For example, they can refer to fixed connections, removable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms based on specific circumstances.

[0059] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all the embodiments.

[0060] The following combination Figures 1 to 13 Specific embodiments of the present invention are described in detail.

[0061] This embodiment provides a four-wheel drive transmission structure suitable for a small off-road vehicle, including an engine 1, a front wheel transmission assembly 2, a rear wheel transmission assembly 3, a first clutch 4 and a second clutch 5.

[0062] Among them, the engine 1 is the power source of the entire device, which is a mature structure in this field and will not be described here.

[0063] Among them, the front wheel transmission assembly 2 includes a driving bevel gear 21, a driven bevel gear 22, a transmission shaft 23 and a front wheel gearbox 24. The driving bevel gear 21 is rotatably sleeved on the output shaft of the engine 1, and the driven bevel gear 22 is fixedly sleeved on the input end of the transmission shaft 23 and meshes with the driving bevel gear 21. The output end of the transmission shaft 23 is transmission-connected to the input shaft of the front wheel gearbox 24.

[0064] During operation, the active bevel gear 21 drives the driven bevel gear 22 to rotate, thereby driving the transmission shaft 23 to rotate, and then driving the front wheel gearbox 24 to operate, ultimately realizing the rotation of the front wheels.

[0065] Specifically, the rotating sleeve connection structure of the driving bevel gear 21 and the output shaft of the engine 1 is not limited. For example, in this embodiment, a rotating bearing is installed between the driving bevel gear 21 and the output shaft of the engine 1, and the rotation performance of the driving bevel gear 21 is ensured by the rotating bearing. In other embodiments, the driving bevel gear 21 can also be loosely sleeved on the output shaft of the engine 1 to achieve rotating sleeve connection.

[0066] Specifically, the fixed socket structure of the driven bevel gear 22 and the transmission shaft 23 is not limited. For example, the driven bevel gear 22 of this embodiment is interference-fitted on the transmission shaft 23 and circumferentially limited by a key. In other embodiments, the driven bevel gear 22 can also be welded or fixed to the transmission shaft 23 by fasteners such as bolts.

[0067] Specifically, the transmission shaft 23 includes a shaft body 231 and shaft ends 232 arranged at both ends of the shaft body 231. The two shaft ends 232 are connected to the shaft body 231 through a first universal joint 233, which can compensate for the relative position offset of components caused by working conditions such as road bumps and vehicle body tilt, and avoid transmission interference or structural damage caused by rigid connection.

[0068] It is easy to understand that the front wheel transmission case 24 should be provided with two output shafts to connect the two front wheels respectively.

[0069] Specifically, the output shaft of the front wheel gearbox 24 transmits power to the front wheels through the second universal joint 241 to ensure the stability of power transmission.

[0070] Among them, the rear wheel transmission assembly 3 includes a CVT transmission 31 and a rear wheel gearbox 32. The input end of the CVT transmission 31 is connected to the output shaft of the engine 1. The input shaft of the rear wheel gearbox 32 is rotatably sleeved with a rotating drum 3131, and the output end of the CVT transmission 31 is connected to the rotating drum 3131.

[0071] It is easy to understand that the CVT transmission 31 is a mature structure in the field. This embodiment provides a preferred improved structure:

[0072] The CVT transmission 31 includes an input pulley set, an output pulley set, and a transmission belt 316;

[0073] The input pulley assembly includes an input-end fixed cone disc 311 and an input-end movable cone disc 312, both of which are mounted on the output shaft of the engine 1. The input-end fixed cone disc 311 is located axially outside the input-end movable cone disc 312, and the input-end movable cone disc 312 is located axially outside the driving bevel gear 21.

[0074] The output pulley assembly includes an output end fixed cone disc 313 and an output end movable cone disc 314, both of which are mounted on a rotating drum 3131. The output end fixed cone disc 313 is located axially inward of the output end movable cone disc 314. The output end movable cone disc 314 is provided with a first elastic return member 315 for driving it toward the output end fixed cone disc 313.

[0075] The transmission belt 316 is wound between the input pulley set and the output pulley set.

[0076] During operation, the output shaft of the engine 1 rotates, driving the fixed cone disc 311 at the input end and the movable cone disc 312 at the input end to rotate, thereby driving the transmission belt 316 to operate, and further realizing the rotation of the fixed cone disc 313 at the output end and the movable cone disc 314 at the output end.

[0077] It should be noted that the so-called "fixed cone disc" and "movable cone disc" refer to the cone discs relative to the mounting shaft. For example, the fixed cone disc 311 at the input end is fixed relative to the output shaft of the engine 1, the movable cone disc 312 at the input end is axially movable relative to the output shaft of the engine 1, the fixed cone disc 313 at the output end is fixed relative to the rotating cylinder 3131, and the movable cone disc 314 at the output end is axially movable relative to the rotating cylinder 3131.

[0078] It should be noted that, for the input-end movable cone disc 312 and the output-end movable cone disc 314, the required degree of freedom is that they can move axially along the corresponding mounting axis. Although the friction of the transmission belt 316 can also drive the rotation and transmit torque, it will cause greater wear to the transmission belt 316 and is prone to slipping. Therefore, it should be limited in the circumferential direction. For example, in this embodiment, a circumferential limiting structure is adopted between the output-end movable cone disc 314 and the rotating cylinder 3131. Specifically, the output-end movable cone disc 314 is integrally formed with an extension cylinder 3141, which is loosely mounted on the outer side of the rotating cylinder 3131, and the extension cylinder 3141 and the rotating cylinder 3131 are circumferentially limited by a limiting pin. Similarly, pins or other structures should also be used to limit the circumference between the input-end movable cone disc 312 and the output shaft of the engine 1 to transmit torque.

[0079] Specifically, a heat dissipation fin 3111 is provided on a side of the input-end fixed cone disk 311 away from the input-end movable cone disk 312 to ensure the heat dissipation capability of the structure.

[0080] Specifically, the fixed connection structure between the rotating cylinder 3131 and the output-end fixed cone disk 313 is not limited. For example, in this embodiment, the rotating cylinder 3131 and the output-end fixed cone disk 313 are integrally formed. In other embodiments, the rotating cylinder 3131 can also be fixedly connected to the output-end fixed cone disk 313 by interference fitting, welding, or other methods.

[0081] Specifically, the rotational connection structure between the rotating drum 3131 and the input shaft of the rear wheel gearbox 32 is not limited. For example, in this embodiment, a rotational bearing is installed between the rotating drum 3131 and the input shaft of the rear wheel gearbox 32, and the rotation performance of the rotating drum 3131 is ensured by the rotational bearing. In other embodiments, the rotating drum 3131 can also be loosely mounted on the input shaft of the rear wheel gearbox 32 to achieve rotational connection.

[0082] Specifically, the structure of the first elastic return member 315 is not limited, as long as it can make the output end moving cone disk 314 close to the output end fixed cone disk 313. For example, the first elastic return member 315 of this embodiment is a compression spring; elastic blocks can also be used in other embodiments.

[0083] Specifically, the transmission belt 316 is preferably but not limited to a rubber belt. The transmission belt 316 is placed between the input end fixed cone disc 311 and the input end movable cone disc 312 and between the output end fixed cone disc 313 and the output end movable cone disc 314 to achieve transmission by friction.

[0084] It should be noted that the input shaft of the aforementioned rear wheel gearbox 32 refers to the whole formed by the original input shaft of the rear wheel gearbox 32 and the fixed auxiliary shaft. In this embodiment, the input shaft of the rear wheel gearbox 32 is divided into two sections, one section serves as the original input shaft of the rear wheel gearbox 32, and the other section is inserted into the output end of the CVT transmission 31, and the two sections are connected by a coupling.

[0085] It is easy to understand that the rear wheel transmission case 32 should be provided with two output shafts to connect the two rear wheels respectively.

[0086] Specifically, the output shaft of the rear wheel transmission case 32 transmits power to the rear wheels via the third universal joint 321 to ensure the stability of power transmission.

[0087] The first clutch 4 is installed between the input end of the CVT transmission 31 and the driving bevel gear 21 and is used to realize automatic clutching by utilizing centrifugal force.

[0088] It should be noted that the use of centrifugal force to achieve automatic clutching is easy for those skilled in the art to design. This embodiment provides a preferred improved structure:

[0089] The first clutch 4 includes a movable top cover 41, a puli bead 42, an active friction member 43 and a driven friction member 44;

[0090] The movable top cover 41 is mounted on the output shaft of the engine 1 and is located between the input end movable cone disk 312 and the driving bevel gear 21. The movable top cover 41 is provided with a second elastic reset member 45 for driving it away from the driving bevel gear 21.

[0091] The Pulley bead 42 is installed between the input end movable cone 312 and the movable top cover 41;

[0092] The active friction member 43 is mounted on the side of the movable top cover 41 facing the active bevel gear 21;

[0093] The driven friction member 44 is mounted on the side of the driving bevel gear 21 facing the movable top cover 41;

[0094] Under the action of centrifugal force, the puli bead 42 is used to drive the movable top cover 41 to move axially so that the active friction member 43 and the driven friction member 44 come into contact and realize linkage, and is also used to drive the input end movable cone 312 to move axially to realize the stepless speed change of the CVT transmission 31.

[0095] During operation, the output shaft of the engine 1 rotates, driving the input-end movable cone 312 and the puli ball 42 therein. The greater the speed, the greater the centrifugal force on the puli ball 42. Therefore, when the speed reaches a certain value, the puli ball 42 moves radially outward under the action of centrifugal force, driving the input-end movable cone 312 toward the input-end fixed cone 311 and simultaneously driving the movable top cover 41 toward the driving bevel gear 21. When the input-end movable cone 312 approaches the input-end fixed cone 311, the compression of the drive belt 316 increases the input transmission radius. The output-end movable cone 314 is forced away from the output-end fixed cone 313, reducing the output transmission radius, thereby achieving continuously variable transmission of the CVT transmission 31. When the movable top cover 41 approaches the driving bevel gear 21, causing the driving friction member 43 to contact the driven friction member 44, the input-end movable cone 312, the movable top cover 41, and the driving bevel gear 21 rotate synchronously, thus achieving interlocking rotation. As the speed decreases, the process reverses.

[0096] Specifically, the movable top cover 41 includes a puli pressure plate 411 and a mounting plate 412. The puli pressure plate 411 and the mounting plate 412 are both conical and fixedly connected in a back-to-back posture. The puli pressure plate 411 is docked with the input end movable cone plate 312 to form a radial slide for installing the puli bead 42. The active friction part 43 is fixed on the end face of the mounting plate 412 away from the puli pressure plate 411.

[0097] More specifically, the fixed connection structure of the pressure plate 411 and the mounting plate 412 is not limited and may be formed in one piece or welded or connected by fasteners or other methods.

[0098] It is easy to understand that the puli bead 42 is a mature structure in this field. When in use, it needs to cooperate with the aforementioned radial slide, and the radial slide becomes smaller as it moves outward, so that when the puli bead 42 moves radially outward under the action of centrifugal force, it can drive the input end moving cone disk 312 and the moving top cover 41 to move axially away from the puli bead 42.

[0099] Specifically, the active friction member 43 comprises multiple friction blocks evenly spaced along the circumference, while the driven friction member 44 comprises a friction ring. The active friction member 43 is designed as multiple friction blocks primarily to meet heat dissipation and lightweight requirements; however, the active friction member 43 can also be designed as a ring structure.

[0100] More specifically, there is no limitation on the fixing method of the active friction member 43 and the driven friction member 44 . For example, in this embodiment, bolts are used to fix the active friction member 43 and the driven friction member 44 .

[0101] Specifically, the structure of the second elastic return member 45 is not limited, as long as it can keep the movable top cover 41 away from the active bevel gear 21. For example, the second elastic return member 45 of the present embodiment is a compression spring, and the two opposite end surfaces of the movable top cover 41 and the active bevel gear 21 are fixed with mounting pins 46, and the second elastic return member 45 is sleeved on the mounting pins 46; elastic blocks, etc. can also be used in other embodiments.

[0102] More specifically, the method of fixing the mounting pin 46 on the movable top cover 41 and the active bevel gear 21 is not limited. For example, in this embodiment, the mounting pin 46 is interference-fitted on the movable top cover 41 and threadedly connected to the active bevel gear 21. In other embodiments, the mounting pin 46 can also be fixed by welding or other methods.

[0103] It should be noted that the distance between the two relatively arranged mounting pins 46 determines the wear limit of the first clutch 4. If the first clutch 4 is worn to the limit, the front axle will not be able to obtain power, but the rear axle can still obtain all the power independently, and the vehicle becomes a pure rear-wheel drive vehicle. At this time, although the off-road capability of the vehicle is damaged, it still has sufficient power to ensure driving safety.

[0104] The second clutch 5 is installed between the drum 3131 and the input shaft of the rear wheel gearbox 32 and is used to realize automatic clutching by utilizing centrifugal force.

[0105] It should be noted that the use of centrifugal force to achieve automatic clutching is easy for those skilled in the art to design. This embodiment provides a preferred improved structure:

[0106] The second clutch 5 includes a fixed bottom shell 51 and a flying weight clutch member 52;

[0107] The fixed bottom shell 51 is sleeved on the input shaft of the rear wheel gearbox 32;

[0108] The flyweight clutch 52 is mounted on the rotating drum 3131 and is located axially outside the output end movable cone 314. The flyweight clutch 52 is located inside the fixed bottom shell 51.

[0109] The flying weight clutch member 52 is used to contact the inner wall of the fixed bottom shell 51 under the action of centrifugal force to achieve linkage.

[0110] During operation, the drum 3131 rotates driven by the CVT transmission 31, thereby driving the flyweight clutch 52 to rotate. When the speed reaches a certain value, the flyweight clutch 52 overcomes the spring force and expands outward, contacting the inner wall of the fixed bottom housing 51, thereby driving the fixed bottom housing 51 and the input shaft of the rear wheel transmission 32 to rotate, thus achieving linkage. When the rotation slows down, the process is reversed.

[0111] Specifically, the fixed bottom shell 51 is designed as a barrel-shaped structure, the side wall of the barrel-shaped structure is used to cooperate with the flyweight clutch 52, and the barrel bottom of the barrel-shaped structure is used to connect with the input shaft of the rear wheel transmission case 32.

[0112] More specifically, the fixed bottom shell 51 is provided with a heat dissipation hole 511, which is located on the bottom of the barrel structure and is used to promptly dissipate the heat generated by the friction between the flying weight clutch 52 and the inner wall of the fixed bottom shell 51 during the driving of the vehicle into the air.

[0113] More specifically, an internal spline is provided in the center hole of the fixed bottom shell 51 for connecting with the input shaft of the rear wheel reducer to transmit torque.

[0114] It is easy to understand that the flyweight clutch 52 is a well-established structure in the art, comprising a connecting disc 521 and a plurality of flyweights 522 evenly distributed along the circumference of the connecting disc 521. The flyweights 522 are connected to the connecting disc 521 via connecting springs 523. When the centrifugal force reaches a certain value, the flyweights 522 overcome the elastic force of the connecting springs 523 and expand outward, contacting the inner wall of the fixed bottom shell 51 to achieve engagement. When the centrifugal force drops to a certain value, the flyweights 522 retract under the elastic force of the connecting springs 523, disengaging from the inner wall of the fixed bottom shell 51 to achieve separation.

[0115] Specifically, the first elastic reset member 315 is a compression spring sleeved on the outside of the extension tube 3141 , and two ends of the first elastic reset member 315 respectively abut against the output end moving cone 314 and the flyweight clutch member 52 .

[0116] The working principle of the four-wheel drive transmission structure of this embodiment applicable to small off-road vehicles is as follows:

[0117] When the engine 1 is idling, the centrifugal force of the puli beads 42 cannot overcome the force of the second return spring, so the active friction member 43 of the first clutch 4 is separated from the driven friction member 44, and the power cannot be transmitted to the front axle; the centrifugal force of the flyweight clutch 52 is also unable to overcome the spring force and retracts, and the flyweight clutch 52 is separated from the inner wall of the fixed bottom shell 51, and the power cannot be transmitted to the rear axle; at this time, the car is parked and the engine 1 is idling;

[0118] When the speed of engine 1 gradually increases:

[0119] On the one hand, under the action of centrifugal force, the puli beads 42 move outward along the radial slideway, gradually overcoming the force of the second elastic return member 45, pushing the movable top cover 41 axially close to the driving bevel gear 21 until the driving friction member 43 contacts the driven friction member 44. The power of the engine 1 is transmitted to the front axle of the vehicle through the first clutch 4, the driving bevel gear 21, the driven bevel gear 22, the transmission shaft 23 and the front wheel gearbox 24 in sequence. At the same time, the puli beads 42 also drive the input-end moving cone disc 312 to approach the input-end fixed cone disc 311, thereby increasing the input-end transmission radius, while the output-end moving cone disc 314 overcomes the force of the second elastic return member 45 and moves away from the output-end fixed cone disc 313, thereby reducing the output-end transmission radius, thereby realizing stepless adjustment of the CVT transmission 31.

[0120] On the other hand, the output shaft of the engine 1 transmits power to the drum 3131 through the CVT transmission 31, and the drum 3131 drives the flyweight clutch 52 to rotate. As the centrifugal force of the flyweight 522 becomes greater and greater, it gradually overcomes the elastic force of the connecting spring 523, expands outward and contacts the inner wall of the fixed bottom shell 51, and the clamping force becomes greater and greater. The friction between the flyweight clutch 52 and the fixed bottom shell 51 also becomes greater and greater, thereby providing driving force for the rear axle of the vehicle.

[0121] It should be noted that if the transmission ratio of the front wheel transmission assembly 2 is defined as , the transmission ratio range of the CVT transmission 31 is , the transmission ratio of the rear wheel gearbox 32 is , then the design of this structure needs to meet the following requirements: .

[0122] The comprehensive performance of this structure is explained through several specific working conditions:

[0123] When driving on a road with a high adhesion coefficient, there is almost no speed difference between the front and rear axles of the vehicle, and the front axle directly obtains the engine power. Assuming that the speed of engine 1 is , the front axle speed is , the rear axle speed is also , the input shaft speed of the rear wheel gearbox 32 is , that is, the rotation speed of the fixed bottom shell 51 is also , and the minimum speed of the flying weight clutch 52 is , the maximum is According to the above formula, , that is, the rotational speeds of the fixed base 51 and the flyweight clutch 52 are not synchronized. Since the rotational speed of the fixed base 51 is lower than that of the flyweight clutch 52, the rear axle can obtain torque through the friction between the flyweight clutch 52 and the fixed base 51, thus improving vehicle dynamics. If the rotational speed of the fixed base 51 were higher than that of the flyweight clutch 52, the flyweight clutch 52 would not only be unable to output power, but would also hinder the rotation of the fixed base 51, thereby creating resistance to the rotation of the rear axle and losing overall vehicle power.

[0124] Under sandy or muddy road conditions, when the front wheel adhesion coefficient is high and the rear wheel adhesion coefficient is low, there is a speed difference between the front and rear axles, and the front axle obtains power from the engine 1. The higher the speed of the engine 1, the greater the pressure of the first clutch 4, the greater the output power and torque, and can drag the rear axle forward; when the front wheel adhesion coefficient is low and the rear wheel adhesion coefficient is high, there is a speed difference between the front and rear axles, and the rear axle obtains torque through the friction between the flyweight clutch 52 and the fixed bottom shell 51. At this time, the flyweight clutch 52 and the fixed bottom shell 51 are basically synchronized, and the higher the speed of the engine 1, the greater the output power and torque of the rear axle, which can push the front axle forward; when the front and rear wheel adhesion coefficients are both low, there is a speed difference between the front and rear axles, the front axle obtains power from the engine 1, and the rear axle obtains speed and torque through the friction between the flyweight clutch 52 and the fixed bottom shell 51, the front and rear axle power are decoupled, and the vehicle's escape performance is improved.

[0125] When climbing, the front axle of a vehicle can often climb relatively easily due to driving force, but the rear axle has difficulty climbing due to the vehicle's large inclination angle and insufficient driving force. This structure allows the front and rear axles to have different rotational speeds. During climbing, on slopes generally less than 45°, the rear axle travels a longer distance than the front axle. Because the speed of the flyweight clutch 52 is higher than that of the fixed base 51, the rear axle quickly gains speed and torque through friction between the flyweight clutch 52 and the fixed base 51, thereby helping the rear axle climb.

[0126] The above is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions have been made with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents; and such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments, and they should all be covered by the scope of protection of the claims.

Claims

1. A four-wheel drive transmission structure suitable for a small off-road vehicle, characterized in that: include: Engine (1); A front wheel transmission assembly (2), comprising a driving bevel gear (21), a driven bevel gear (22), a transmission shaft (23) and a front wheel gearbox (24), wherein the driving bevel gear (21) is rotatably sleeved on the output shaft of the engine (1), the driven bevel gear (22) is fixedly sleeved on the input end of the transmission shaft (23) and meshes with the driving bevel gear (21), and the output end of the transmission shaft (23) is drivingly connected to the input shaft of the front wheel gearbox (24); A rear wheel transmission assembly (3) comprising a CVT transmission (31) and a rear wheel gearbox (32), wherein the input end of the CVT transmission (31) is connected to the output shaft of the engine (1), the input shaft of the rear wheel gearbox (32) is rotatably sleeved with a rotating drum (3131), and the output end of the CVT transmission (31) is connected to the rotating drum (3131); A first clutch (4) is installed between the input end of the CVT transmission (31) and the driving bevel gear (21) and is used to achieve automatic clutching by utilizing centrifugal force; The second clutch (5) is installed between the rotating drum (3131) and the input shaft of the rear wheel gearbox (32) and is used to realize automatic clutching by utilizing centrifugal force.

2. The four-wheel drive transmission structure suitable for a small off-road vehicle according to claim 1, characterized in that: The CVT transmission (31) includes an input pulley set, an output pulley set, and a transmission belt (316); The input pulley assembly comprises an input-end fixed cone disc (311) and an input-end movable cone disc (312), both of which are mounted on the output shaft of the engine (1); the input-end fixed cone disc (311) is located axially outside the input-end movable cone disc (312); and the input-end movable cone disc (312) is located axially outside the active bevel gear (21); The output pulley assembly comprises an output end fixed cone disc (313) and an output end movable cone disc (314), both of which are mounted on the rotating cylinder (3131); the output end fixed cone disc (313) is located axially inside the output end movable cone disc (314); and the output end movable cone disc (314) is provided with a first elastic reset member (315) for driving it close to the output end fixed cone disc (313); The transmission belt (316) is wound between the input pulley assembly and the output pulley assembly.

3. The four-wheel drive transmission structure suitable for a small off-road vehicle according to claim 2, characterized in that: The first clutch (4) comprises a movable top cover (41), a puli bead (42), an active friction member (43) and a driven friction member (44); The movable top cover (41) is mounted on the output shaft of the engine (1) and is located between the input end movable cone disk (312) and the active bevel gear (21). The movable top cover (41) is provided with a second elastic reset member (45) for driving it away from the active bevel gear (21). The Puli bead (42) is installed between the input end movable cone (312) and the movable top cover (41); The active friction member (43) is mounted on a side of the movable top cover (41) facing the active bevel gear (21); The driven friction member (44) is mounted on a side of the driving bevel gear (21) facing the movable top cover (41); The puli beads (42) are used to drive the movable top cover (41) to move axially under the action of centrifugal force so that the active friction member (43) and the driven friction member (44) contact and realize linkage, and are also used to drive the input end movable cone disc (312) to move axially to realize stepless speed change of the CVT transmission (31).

4. The four-wheel drive transmission structure suitable for a small off-road vehicle according to claim 3, characterized in that: The second elastic reset member (45) is a compression spring. Mounting pins (46) are fixed to two opposite end surfaces of the movable top cover (41) and the active bevel gear (21). The second elastic reset member (45) is sleeved on the mounting pins (46).

5. The four-wheel drive transmission structure suitable for a small off-road vehicle according to claim 3, characterized in that: The movable top cover (41) includes a puli pressure plate (411) and a mounting plate (412), wherein the puli pressure plate (411) and the mounting plate (412) are both conical and fixedly connected in a back-to-back posture, and the puli pressure plate (411) is docked with the input end movable cone plate (312) to form a radial slideway for mounting the puli bead (42), and the active friction member (43) is fixed to the end surface of the mounting plate (412) away from the puli pressure plate (411).

6. The four-wheel drive transmission structure suitable for a small off-road vehicle according to claim 5, characterized in that: The active friction member (43) is a plurality of friction blocks evenly spaced along the circumferential direction, and the driven friction member (44) is a friction ring.

7. The four-wheel drive transmission structure suitable for a small off-road vehicle according to claim 2, characterized in that: The second clutch (5) comprises a fixed bottom shell (51) and a flying weight clutch member (52); The fixed bottom shell (51) is sleeved on the input shaft of the rear wheel gearbox (32); The flyweight clutch (52) is mounted on the rotating cylinder (3131) and is located axially outside the output end movable cone (314), and the flyweight clutch (52) is located inside the fixed bottom shell (51); The flying weight clutch (52) is used to contact the inner wall of the fixed bottom shell (51) under the action of centrifugal force to achieve linkage.

8. The four-wheel drive transmission structure suitable for a small off-road vehicle according to claim 7, characterized in that: The rotating cylinder (3131) and the output-end fixed cone disk (313) are integrally formed, and the output-end movable cone disk (314) is further integrally formed with an extension cylinder (3141). The extension cylinder (3141) is loosely sleeved on the outside of the rotating cylinder (3131), and the extension cylinder (3141) and the rotating cylinder (3131) are circumferentially limited by a limiting pin.

9. The four-wheel drive transmission structure suitable for a small off-road vehicle according to claim 8, characterized in that: The first elastic reset member (315) is a compression spring sleeved on the outside of the extension tube (3141), and two ends of the first elastic reset member (315) respectively abut against the output end moving cone disc (314) and the flyweight clutch member (52).

10. The four-wheel drive transmission structure suitable for a small off-road vehicle according to claim 7, characterized in that: A heat dissipation fin (3111) is provided on a side of the input-end fixed cone disk (311) away from the input-end movable cone disk (312), and the fixed bottom shell (51) is provided with a heat dissipation hole (511).

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