A real-time transfer system with mechanical locking

Abstract

This invention provides an on-demand transfer case system with mechanical locking, comprising: a transfer case transmission system and a shifting system. The transfer case transmission system includes an input shaft, a planetary reduction mechanism, a 4L engagement sleeve, a rear output shaft, and a rear output flange arranged horizontally in sequence. Below the rear output shaft are a front output shaft and a shift shaft. The rear output shaft is sequentially equipped with a shift cam, a shift gear, a cam structure, a clutch, a drive sprocket, and a mechanical locking engagement sleeve. The front output shaft has a driven sprocket connected to the drive sprocket via chain drive. The shifting system drives the shift gear to rotate clockwise and counterclockwise. The drive cam mechanism presses the clutch, transmitting torque to the front output shaft, and simultaneously drives the shift shaft to move axially. Combined with the mechanical locking sleeve, the system transmits strong torque to the front output shaft, meeting the needs of customers requiring strong off-road capabilities and protecting the clutch. This system also meets the requirement of compatibility between the mechanical locking mode and the on-demand four-wheel drive mode.

Description

Technical Field

[0001] This invention relates to the field of vehicle transmission and transfer technology, and in particular to a real-time transfer system with mechanical locking. Background Technology

[0002] A vehicle power transfer system is a device that distributes engine power, allowing power to be output to the rear axle, or simultaneously to both the front and rear axles. An on-demand four-wheel drive vehicle is one that operates as a two-wheel drive vehicle under normal conditions but switches to four-wheel drive for off-road driving. Currently, on-demand transfer cases rely on a clutch to transmit front-end torque. Under heavy off-road conditions, this can easily lead to clutch slippage, overheating, or burning, affecting the off-road experience for customers and the vehicle's reliability. Summary of the Invention

[0003] This invention provides an on-demand transfer case system with mechanical locking, which can transmit strong torque to the front output shaft through a mechanical locking engagement sleeve, meeting customers' strong off-road needs and protecting the clutch.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a real-time transfer case system with mechanical locking, including a transfer case transmission system and a shifting system, wherein the transfer case transmission system includes an input shaft, a planetary reduction mechanism, a 4L coupling sleeve, a rear output shaft and a rear output flange arranged horizontally in sequence;

[0005] Below the rear output shaft are a front output shaft and a shift shaft, respectively. The rear output shaft is provided with a shift cam, a shift gear, a cam structure, a clutch, a drive sprocket and a mechanical locking sleeve in sequence. The front output shaft is provided with a passive sprocket that is connected to the drive sprocket for transmission.

[0006] The shifting system drives the shifting gear to rotate clockwise and counterclockwise; the shifting cam drives the 4L shift fork within it to move the reduction gear sleeve forward and backward when the shifting gear rotates, thus achieving 4L shifting; the shifting shaft drives the mechanical locking sleeve to approach the drive sprocket when the shifting gear rotates counterclockwise, further transmitting the torque from the rear output shaft to the mechanical locking sleeve to the drive sprocket; the cam structure moves closer to the clutch and presses the clutch when the shifting gear rotates clockwise, further transmitting the torque from the rear output shaft to the clutch to the drive sprocket.

[0007] Preferably, the shifting system includes a shifting motor, and the output end of the shifting motor and the shifting gear are connected to the shifting gear via a three-stage gear transmission.

[0008] Preferably, the shift cam is connected to the shift gear for transmission, and the inner and outer walls of the shift cam are respectively provided with rails, the rails including inclined slide rails and flat slide rails; the inner wall rail is used to cooperate with the pin of the 4L shift fork, and the outer wall rail is used to cooperate with the shift finger of the shift shaft.

[0009] Preferably, a mechanical locking fork is provided between the shift shaft and the mechanical locking engagement sleeve.

[0010] Preferably, a shift support shell is provided between the shift cam, shift gear, cam structure and the rear output shaft, the shift support shell is fixedly connected to the outer shell, and the drive sprocket is loosely fitted on the rear output shaft.

[0011] Preferably, the cam structure includes a passive cam and an active cam. The passive cam is fixed on the shift support housing. The passive cam and the active cam have a ramp groove on opposite sides, and a steel ball is placed in the ramp groove. The shift gear has a shift finger on the side near the cam structure. The shift finger is used to move the active cam to rotate counterclockwise along with the shift gear. The steel ball is used to climb up the ramp groove when the active cam rotates counterclockwise, thereby driving the active cam away from the passive cam.

[0012] Preferably, the rear output shaft is provided with a shoulder that prevents the passive cam from moving toward the shift cam and allows the active cam to move toward the clutch.

[0013] Preferably, the passive cam and the active cam are respectively provided with a shim and a thrust bearing on both sides.

[0014] Preferably, the clutch includes a clutch hub, friction plates, steel plates, and a clutch housing, which are sequentially fitted onto the rear output shaft from the inside out. The clutch hub is splined to the rear output shaft, the steel plates are splined to the clutch housing, and the clutch housing is fixed to the drive sprocket. A pressure plate is provided between the clutch hub and the clutch housing near the cam structure. The pressure plate is used to press the friction plates, so that the torque of the rear output shaft is transmitted to the drive sprocket sequentially through the clutch hub, friction plates, steel plates, and clutch housing.

[0015] Preferably, the shift cam is provided with a shift cam disc, and the shift cam disc and the shift cam are coupled by a mounting structure and rotate together; the shift cam disc and the shift gear are respectively provided with steps of different radii, and the outer shell is provided with a position sensor for identifying the position of the steps.

[0016] The beneficial effects of this invention are:

[0017] This solution transmits strong torque to the front output shaft by setting a mechanical locking coupling sleeve, meeting customers' demanding off-road needs while protecting the clutch. Utilizing the existing shift gears in the transfer case drive system, the shift shaft drives the mechanical locking coupling sleeve close to the drive sprocket, further transferring the torque from the rear output shaft to the mechanical locking coupling sleeve to the drive sprocket. This achieves the desired off-road performance without adding numerous components, protecting the clutch. The clutch is retained for light off-road use in the on-demand four-wheel drive mode. The mechanical locking operation is compatible with the on-demand four-wheel drive mode.

[0018] This solution utilizes tracks on the inner and outer walls of the shift cam, including ramp tracks and flat tracks. With simple modifications, the maximum torque output in 4H and 4L gears can be achieved, thus meeting the reliability and off-road performance requirements of customers with strong off-road capabilities. When engaged in mechanical locking mode, the counter-clockwise rotation of the shift gears will not cause the cam structure to rotate. Furthermore, when engaged in on-demand four-wheel drive mode, the pin of the 4L shift fork and the shift finger are located on the flat track, preventing gear shifting and engagement of the mechanical locking mode. These two operating modes are independent of each other.

[0019] This solution features a shift cam disc mounted on the shift cam, which rotates together with the shift cam via a mounting structure. The shift cam disc and the three-stage shift gear each have steps of different radii, and the housing is equipped with position sensors to identify the positions of these steps. By identifying the positions of the steps, the positions of the shift cam disc and the three-stage shift gear are determined, which in turn determines the positions of the shift cam, the shift motor, and the drive cam. Furthermore, the positions of the 4L engagement sleeve and the mechanical locking engagement sleeve are identified, thus allowing the identification of the actual gear position and status of the transfer case. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a cross-sectional view of the transfer case transmission system of the present invention.

[0022] Figure 2 This is a partial structural schematic diagram of the transfer case transmission system of the present invention.

[0023] Figure 3 This is an exploded view of some components of the transfer case transmission system of the present invention.

[0024] Figure 4This is a schematic diagram showing the positional relationship between the clutch, drive sprocket, and mechanical locking sleeve in the transfer case transmission system of the present invention.

[0025] Figure 5 This is a cross-sectional view of the clutch of the present invention.

[0026] Figure 1-5 In the middle, 1. Input shaft, 2. Planetary reduction mechanism, 3. 4L engagement sleeve, 4. Front housing, 5. Shift cam, 6. Shift gear, 61. First-stage shift gear, 62. Second-stage shift gear, 63. Third-stage shift gear, 7. Cam structure, 71. Driving cam, 72. Driven cam, 73. Steel ball, 8. Clutch, 81. Clutch hub, 82. Pressure plate, 83. Clutch housing, 84. Steel plate, 85. Friction plate, 9. Rear output shaft, 10. Driving sprocket, 11. Rear output flange, 12. Mechanical locking engagement sleeve, 13. Mechanical locking shift fork, 14. Shift shaft, 15. Driven sprocket, 16. Chain, 17. Rear housing, 18. Front output shaft, 19. Shift motor, 20. Position sensor, 21. Shift support housing, 22. Shift cam disc, 23. 4L shift fork. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0029] It should also be noted that, unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The term "plural" as used in the patent application specification and claims means two or more; the terms "upper," "lower," "left," "right," "front end," "rear end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Changes or adjustments to these relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0030] The present invention will now be described in further detail with reference to the embodiments and the accompanying drawings.

[0031] Example 1:

[0032] This invention discloses a real-time transfer system with mechanical locking. For example... Figure 1-3 As shown, the embodiment includes a transfer case transmission system and a shifting system. The transfer case transmission system includes an input shaft 1, a planetary reduction mechanism 2, a 4L coupling sleeve 3, a rear output shaft 9, and a rear output flange 11 arranged horizontally in sequence.

[0033] Normally, the torque of the gearbox is input through the input shaft 1 and reduced by the planetary reduction mechanism 2. The reduction gear sleeve of the 4L coupling sleeve 3 can move left and right under the drive of the 4L shift fork 23 to control the torque transmission path from the input shaft 1 to the rear output shaft 9 or whether to transmit the torque.

[0034] Below the rear output shaft 9, there are a front output shaft 18 and a shift shaft 14. The rear output shaft 9 is sequentially provided with a shift cam 5, a shift gear 6, a cam structure 7, a clutch 8, a drive sprocket 10, and a mechanical locking sleeve 12. The front output shaft 18 is provided with a driven sprocket 15 that is connected to the drive sprocket 10. The drive sprocket 10 and the driven sprocket 15 are specifically driven by a chain 16.

[0035] In two-wheel drive mode, the transmission torque is transmitted to the 4L coupling sleeve 3 via the input shaft 1, then to the rear output shaft 9, and finally to the rear drive shaft via the rear output shaft 9 and the rear output flange 11 to drive the rear wheels of the vehicle. The drive sprocket 10 is loosely fitted on the rear output shaft 9, at which time there is no torque input, the driven sprocket 15 has no torque transmission, and the front output shaft 18 has no torque output.

[0036] The shifting system is used to drive the shift gear 6 to rotate clockwise and counterclockwise. The shift cam 5 is used to drive the reduction gear sleeve forward and backward when the shift gear 6 rotates, thereby realizing 4L shifting.

[0037] In the on-demand four-wheel drive mode, the cam structure 7 moves closer to the clutch 8 and presses it down when the shift gear 6 rotates clockwise, further transmitting the torque from the rear output shaft 9 to the clutch 8 to the drive sprocket 10. The torque on the rear output shaft 9 is transmitted to the front output shaft 18 via the clutch 8, drive sprocket 10, and driven sprocket 15. The front output shaft 18 then transmits the torque to the vehicle's front drive shaft, driving the front wheels to rotate. By controlling the rotation of the shift gear 6 through the shift system, the degree of clutch engagement can be controlled, thus controlling the magnitude of the torque transmitted from the rear output shaft 9 to the front output shaft 18. This achieves intelligent dynamic control of the torque output to the front wheels, thereby improving vehicle safety, comfort, and off-road performance.

[0038] When the vehicle requires strong off-road capabilities, including situations like getting out of trouble and climbing steep slopes, and when the maximum torque output of the front output shaft 18 is needed, it enters a mechanical lock-up mode. The shift shaft 14, when the shift gear 6 rotates counterclockwise, drives the mechanical lock-up sleeve 12 to approach the drive sprocket 10, further transmitting the torque from the rear output shaft 9 to the mechanical lock-up sleeve 12 to the drive sprocket 10. By controlling the rotation of the shift gear 6 through the shift system, the mechanical lock-up sleeve 12 can be brought closer to the drive sprocket 10, controlling a portion of the torque on the rear output shaft 9 to be transmitted to the drive sprocket 10 through the mechanical lock-up sleeve, and then to the front output shaft 18 through the driven sprocket 15, achieving the maximum torque output of the front output shaft 18. This meets the reliability and off-road performance requirements of customers with strong off-road needs without damaging the clutch 8.

[0039] Example 2:

[0040] like Figure 1-3 As shown, the difference between this embodiment and Embodiment 1 is that: a shift support shell 21 is provided between the shift cam 5, the shift gear 6, the cam structure 7 and the rear output shaft 9, and the shift support shell 21 is fixedly connected to the outer shell. The drive sprocket 10 is loosely fitted on the rear output shaft 9. A mechanical locking fork 13 is provided between the shift shaft 14 and the mechanical locking coupling sleeve 12. The outer shell includes a front shell 4 and a rear shell 17.

[0041] Example 3:

[0042] like Figure 1-3 As shown, the difference between this embodiment and Embodiment 1 is that the shift cam 5 is connected to the shift gear 6 in a transmission manner, and the inner and outer walls of the shift cam 5 are respectively provided with tracks, including inclined slides and flat slides. The inner wall track is used to cooperate with the pin of the 4L shift fork 23, and the outer wall track is used to cooperate with the shift finger of the shift shaft 14.

[0043] When the shift cam 5 rotates, the 4L shift fork 23 moves on the inclined slide rail on the inner wall of the shift cam 5, driving the reduction gear sleeve to move left and right, thus achieving 4L shifting. When the shift cam 5 rotates, the shift finger of the shift shaft 14 moves on the inclined slide rail on the outer wall of the shift cam 5, driving the mechanical locking engagement sleeve 12 to move left and right, entering the mechanical locking condition. When in the mechanical locking condition, the counterclockwise rotation of the shift gear 6 will not drive the cam structure 7 to rotate. Furthermore, when entering the on-demand four-wheel drive mode, the pin of the 4L shift fork 23 and the shift finger of the shift shaft 14 are in the plane slide rail of the track, and shifting and mechanical locking will not occur. The two conditions do not interfere with each other.

[0044] 4H gear: The shift system drives the shift gear 6 to rotate counterclockwise. The 4L shift fork 23 slides on the inner wall plane of the shift cam 5, while the shift finger of the shift shaft 14 slides on the outer wall ramp of the shift cam 5. The shift shaft 14 moves to the left, causing the mechanical locking shift fork 13 to move the mechanical locking engagement sleeve 12 to the left as well. The splines on the mechanical locking engagement sleeve 12 engage with the splines on the drive sprocket 10. Simultaneously, the inner diameter of the mechanical locking engagement sleeve 12 is designed with internal splines to engage with the rear output shaft 9, and it can slide left and right on the rear output shaft 9. When the mechanical locking engagement sleeve 12 engages with the splines of the drive sprocket 10, part of the torque on the rear output shaft 9 is transmitted to the drive sprocket 10 through the mechanical locking sleeve 12, and then to the front output shaft 18 through the chain 16 and the driven sprocket 15, ultimately reaching the vehicle's front drive shaft. Simultaneously, the torque on the rear output shaft 9 is transmitted to the vehicle's rear drive shaft through the rear output flange 11, achieving four-wheel drive.

[0045] 4L Gear: With 4H gear maintained, the shift system drives the shift gear 6 to continue rotating counterclockwise. At this time, the shift finger of the 4L shift fork 22 moves on the inclined slide rail inside the shift cam 5, causing the 4L shift fork 22 to move to the right, and the reduction gear sleeve moves to the right at the same time. The external spline of the 4L engagement sleeve 3 engages with the internal spline of the planetary carrier of the planetary reduction mechanism 2, and the internal spline of the 4L engagement sleeve 3 engages with the external spline of the rear output shaft 9. The torque of the input shaft 1 needs to be reduced and amplified by the planetary reduction mechanism 2 and then transmitted to the 4L engagement sleeve 3, and then transmitted to the rear output shaft 9 through the 4L engagement sleeve 3. At this time, the mechanical locking engagement sleeve 12 remains engaged with the drive sprocket 10, so the torque on the rear output shaft 9 is simultaneously distributed by the rear output 9 to the rear flange 11 and the front output shaft 18, and the vehicle achieves low-speed four-wheel drive.

[0046] Similarly, by controlling the shifting system to drive a series of shifting actions, the 4L coupling sleeve 3 can be directly connected to the input shaft 1 and the rear output shaft 9, and the mechanical lock can be disengaged. This restores the 2WD mode.

[0047] Example 4:

[0048] like Figure 1-3 As shown, the difference between this embodiment and Embodiment 2 is that the shifting system includes a shifting motor 19. The output end of the shifting motor 19 and the shifting gear 6 are connected by a three-stage gear transmission for torque transmission. The three-stage gear transmission includes a first-stage shifting gear 61, a second-stage shifting gear 62, and a third-stage shifting gear 63. The first-stage shifting gear 61 is located on the output shaft of the shifting motor 19, and the third-stage shifting gear 63 is located on the shifting support housing 21. This three-stage gear torque transmission improves the overall rationality of the arrangement of the internal components of the shifting motor 19 and the transfer case transmission system, preventing interference with the shifting shaft 14.

[0049] Example 5:

[0050] like Figure 1-3 As shown, the difference between this embodiment and Embodiment 1 is that the cam structure 7 includes a passive cam 72 and an active cam 71. The passive cam 72 is fixed to the shift support housing 21 and secured by a keyway and retaining ring, ensuring that the passive cam 72 is limited by the shift support housing 21 and cannot rotate. A ramp groove is provided on the opposite side of the passive cam 72 and the active cam 71, and a steel ball 73 is provided within the ramp groove. A shift finger is provided on the side of the shift gear 6 near the cam structure 7. The shift finger is used to actuate the active cam 71 to rotate counterclockwise along with the shift gear 6; the steel ball 73 is used to climb the ramp groove when the active cam 71 rotates counterclockwise, thereby driving the active cam 71 away from the passive cam 72. By controlling the rotation position of the shift system, the rotation angle of the active cam 71 relative to the passive cam 72 can be adjusted, thereby controlling the axial displacement of the active cam 71, controlling the clamping degree of the clutch 8, and causing the clutch 8 to output different torques forward, achieving active and intelligent control of the forward output torque.

[0051] Example 6:

[0052] like Figure 1-3 As shown, the difference between this embodiment and embodiment 5 is that the rear output shaft 9 is provided with a shoulder that prevents the passive cam 72 from moving towards the shift cam 5 and allows the active cam 71 to move towards the clutch 8. Shims and thrust bearings are respectively provided on both sides of the passive cam 72 and the active cam 71 to transmit axial force while absorbing the differential speed between the rear output shaft 9, the passive cam plate 72, the clutch 8, and the active cam 71.

[0053] Example 7:

[0054] like Figure 1-5 As shown, the difference between this embodiment and embodiment 5 is that the clutch 8 includes a clutch hub 81, friction plate 85, steel plate 84, and clutch housing 83, which are sequentially fitted outside the rear output shaft 9 from the inside out. The clutch hub 81 is splinedly connected to the rear output shaft 9, the steel plate 84 is splinedly connected to the clutch housing 83, and the clutch housing 83 is fixed on the drive sprocket 10. A pressure plate 82 is provided between the clutch hub 81 and the clutch housing 83 near the cam structure 7. The pressure plate 82 is used to press the friction plate 85 so that the torque of the rear output shaft 9 is transmitted to the drive sprocket 10 sequentially through the clutch hub 81, friction plate 85, steel plate 84, and clutch housing 83.

[0055] By controlling the rotation of the shift gear 6 through the shift system, the rotation angle of the active cam 71 relative to the passive cam 72 can be controlled, thereby controlling the tightness of the clutch pressure plate 82 and the magnitude of the torque transmitted from the friction plate 85 to the steel plate 84. Ultimately, this achieves intelligent dynamic control of the torque output to the front wheels of the vehicle, thereby improving the vehicle's safety, comfort, and off-road performance.

[0056] Example 8:

[0057] like Figure 1-3 As shown, the difference between this embodiment and embodiment 4 is that: the shift cam 5 is provided with a shift cam disc 22, and the shift cam disc 22 and the shift cam 5 are fitted together by a mounting structure and rotate together; the shift cam disc 22 and the three-stage shift gear 63 are respectively provided with steps of different radii, and the outer casing is provided with a position sensor 20 for identifying the position of the steps. By identifying the position of the steps, the position of the shift cam disc 22 and the three-stage shift gear 63 is determined, thereby determining the position of the shift cam 5, the shift motor 19 and the drive cam 71, and further identifying the position of the 4L engagement sleeve 3 and the mechanical locking engagement sleeve 12, thus identifying the actual gear and state of the transfer case.

[0058] This invention adds 4H and 4L mechanical locks to the existing transfer case, achieving maximum torque output in 4H and 4L gears to meet customers' strong off-road needs for reliability and performance. Simultaneously, it retains intelligent torque output via the clutch, ensuring safety and stability for customers in light off-road and urban driving conditions.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A real-time transfer system with mechanical locking, characterized in that: It includes a transfer case transmission system and a shifting system. The transfer case transmission system includes an input shaft (1), a planetary reduction mechanism (2), a 4L coupling sleeve (3), a rear output shaft (9), and a rear output flange (11) arranged horizontally in sequence. Below the rear output shaft (9) are a front output shaft (18) and a shift shaft (14). The rear output shaft (9) is provided with a shift cam (5), a shift gear (6), a cam structure (7), a clutch (8), a drive sprocket (10), and a mechanical locking sleeve (12) in sequence. The front output shaft (18) is provided with a passive sprocket (15) that is connected to the drive sprocket (10) for transmission. The shifting system is used to drive the shifting gear (6) to rotate clockwise and counterclockwise; the shifting cam (5) is used to drive the reduction gear sleeve to move forward and backward when the shifting gear (6) rotates, thereby realizing 4L shifting; the shifting shaft (14) is used to drive the mechanical locking sleeve (12) to approach the drive sprocket (10) when the shifting gear (6) rotates counterclockwise, thereby further transmitting the torque transmitted from the rear output shaft (9) to the mechanical locking sleeve (12) to the drive sprocket (10); the cam structure (7) is used to move close to the clutch (8) and press the clutch (8) when the shifting gear (6) rotates clockwise, thereby further transmitting the torque transmitted from the rear output shaft (9) to the clutch (8) to the drive sprocket (10). The shifting system includes a shifting motor (19). The output end of the shifting motor (19) and the shifting gear (6) are connected by a three-stage gear transmission. The three-stage gear transmission includes a first-stage shifting gear (61), a second-stage shifting gear (62), and a third-stage shifting gear (63). The first-stage shifting gear (61) is located on the output shaft of the shifting motor (19), and the third-stage shifting gear (63) is located on the shifting support housing (21). The shift cam (5) is connected to the shift gear (6) for transmission. The inner wall and outer wall of the shift cam (5) are respectively provided with rails. The rails include inclined slides and flat slides. The inner wall rail is used to cooperate with the pin of the 4L shift fork (23), and the outer wall rail is used to cooperate with the shift finger of the shift shaft (14). When the shift cam (5) rotates, the 4L shift fork (23) moves on the inclined slide of the inner wall of the shift cam (5), driving the reduction gear sleeve to move left and right, realizing 4L shifting; when the shift cam (5) rotates, the shift finger of the shift shaft (14) moves on the inclined slide of the outer wall of the shift cam (5), driving the mechanical locking engagement sleeve (12) to move left and right, entering the mechanical locking condition; when entering the mechanical locking condition, the shift gear (6) rotates counterclockwise and does not drive the cam structure (7) to rotate; when entering the on-demand four-wheel drive mode, the pin of the 4L shift fork (23) and the shift finger of the shift shaft (14) are in the plane slide of the track, and will not perform shifting or enter the mechanical locking condition; the two conditions do not interfere with each other; A shift support shell (21) is provided between the shift cam (5), the shift gear (6), the cam structure (7) and the rear output shaft (9). The shift support shell (21) is fixedly connected to the outer shell. The drive sprocket (10) is loosely fitted on the rear output shaft (9). A mechanical locking fork (13) is provided between the shift shaft (14) and the mechanical locking coupling sleeve (12). The cam structure (7) includes a passive cam (72) and an active cam (71). The passive cam (72) is fixed on the shift support housing (21) by a keyway and a retaining ring, ensuring that the passive cam (72) is limited by the shift support housing (21) and cannot rotate. The passive cam (72) and the active cam (71) have a ramp groove on opposite sides, and a steel ball (73) is provided in the ramp groove. The shift gear (6) has a shift finger on the side near the cam structure (7), and the shift finger is used to shift gears. The active cam (71) rotates counterclockwise along with the shift gear (6); the steel ball (73) is used to climb in the ramp groove when the active cam (71) rotates counterclockwise, thereby driving the active cam (71) away from the passive cam (72); by controlling the rotation position of the shift system, the rotation angle of the active cam (71) relative to the passive cam (72) is adjusted, thereby controlling the axial displacement of the active cam (71), controlling the clamping degree of the clutch (8), and causing the clutch (8) to output different torques forward; The clutch (8) includes a clutch hub (81), friction plates (85), steel plates (84), and a clutch housing (83) sequentially fitted outside the rear output shaft (9) from the inside out. The clutch hub (81) is splinedly connected to the rear output shaft (9), and the steel plates (84) are splinedly fixedly connected to the clutch housing (83). The clutch housing (83) is fixed on the drive sprocket (10). A pressure plate (82) is provided between the clutch hub (81) and the clutch housing (83) near the cam structure (7). The pressure plate (82) is used to press the friction plates (85) so that the torque of the rear output shaft (9) is transmitted to the drive sprocket (10) sequentially through the clutch hub (81), friction plates (85), steel plates (84), and clutch housing (83). The shift cam (5) is provided with a shift cam disc (22), and the shift cam disc (22) and the shift cam (5) are connected by an installation structure and rotate together; the shift cam disc (22) and the shift gear (6) are respectively provided with steps of different radii, and the outer shell is provided with a position sensor (20) for identifying the position of the steps; by identifying the position of the steps, the position of the shift cam disc (22) and the three-stage shift gear (63) is determined, and then the position of the shift cam (5), the shift motor (19) and the active cam (71) is determined, and then the position of the 4L coupling sleeve (3) and the mechanical locking coupling sleeve (12) is identified, thereby identifying the actual gear position and status of the transfer case; 4H gear: The shift system drives the shift gear (6) to rotate counterclockwise, and the 4L shift fork (23) slides on the inner wall plane slide of the shift cam (5), but the shift finger of the shift shaft (14) slides on the outer wall ramp slide of the shift cam (5). The shift shaft (14) moves to the left, driving the mechanical locking shift fork (13) to move together with the mechanical locking engagement sleeve (12) to the left. The spline on the mechanical locking engagement sleeve (12) engages with the spline on the drive sprocket (10); at the same time, the inner diameter of the mechanical locking engagement sleeve (12) is designed with an internal spline. It cooperates with the rear output shaft (9) and slides left and right on the rear output shaft (9); when the mechanical locking sleeve (12) is engaged with the spline of the drive sprocket (10), part of the torque on the rear output shaft (9) is transmitted to the drive sprocket (10) through the mechanical locking sleeve (12), and then to the front output shaft (18) through the chain (16) and the driven sprocket (15), and finally to the front drive shaft of the vehicle; at the same time, the torque on the rear output shaft (9) is transmitted to the rear drive shaft of the vehicle through the rear output flange (11), and the vehicle achieves four-wheel drive; 4L gear: When the 4H gear is maintained, the shift system drives the shift gear (6) to continue to rotate counterclockwise. At this time, the shift finger of the 4L shift fork (22) moves on the ramp slide of the inner wall of the shift cam (5), driving the 4L shift fork (22) to move to the right. At the same time, the reduction gear sleeve moves to the right. The outer spline of the 4L coupling sleeve (3) is engaged with the inner spline of the planetary carrier of the planetary reduction mechanism (2). The inner spline of the 4L coupling sleeve (3) is engaged with the outer spline of the rear output shaft (9). The torque of the input shaft (1) needs to be reduced and amplified by the planetary reduction mechanism (2) and transmitted to the 4L coupling sleeve (3), and then transmitted to the rear output shaft (9) through the 4L coupling sleeve (3). At this time, the mechanical locking coupling sleeve (12) is engaged with the drive sprocket (10). Therefore, the torque on the rear output shaft (9) is simultaneously distributed by the rear output (9) to the rear flange (11) and the front output shaft (18), and the vehicle achieves low-speed four-wheel drive.

2. The on-demand transfer system with mechanical locking according to claim 1, characterized in that: The rear output shaft (9) is provided with a shoulder that prevents the passive cam (72) from moving toward the shift cam (5) and allows the active cam (71) to move toward the clutch (8).

3. The on-demand transfer system with mechanical locking according to claim 1, characterized in that: The passive cam (72) and the active cam (71) are respectively provided with a gasket and a thrust bearing on both sides.

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