Continuously variable transmission, control method for continuously variable transmission, and tractor

Abstract

This invention discloses a continuously variable transmission (CVT), a control method for the CVT, and a tractor. The CVT includes a CVT assembly, a stepped shifting assembly, a TCU controller, and first to third clutches. The CVT assembly includes a speed control pump motor assembly, a shift input shaft, and three shift output shafts. The stepped shifting assembly includes three shift input shafts, first to second synchronizers, and shift output shafts. Shift output shaft I is connected to shift input shaft I via a first clutch, shift output shaft II is connected to shift input shaft II via a second clutch, and shift output shaft III is connected to shift input shaft III via a third clutch. This CVT uses a combined synchronizer and clutch shifting mechanism, simplifying the transmission system and reducing its cost. The alternating switching of the synchronizer and clutch, based on the synchronizer speed difference, ensures the reliability of the synchronizer operation. Clutch shifting without speed difference can be achieved at the clutch synchronous shifting points in different segments.

Description

Technical Field

[0001] This invention relates to the field of continuously variable transmission (CVT) technology for tractors, specifically a CVT, a CVT control method, and a tractor. Background Technology

[0002] Currently, there are several main types of continuously variable transmissions (CVTs) for tractors: 1. Using a hydrostatic speed control circuit consisting of a pump and a motor to change the output speed of the transmission. However, this method has the drawback of a small speed range covered by the high-efficiency zone. 2. Relying on the friction generated between a metal belt, rubber belt, and a rotating disc to transmit power, and changing the diameter of the disc's contact surface to change the output speed of the transmission. However, this method is limited by the performance of the friction materials on the contact surface, resulting in a small torque that can be transmitted. In addition, the range of speed changes that can be achieved is limited by the disc diameter. 3. Using electric drive, the continuously variable transmission performance of the motor is used to change the output speed of the transmission. However, limited by the torque characteristics of the motor, the operating temperature environment, and the battery range, this technology cannot yet meet the requirements of long-term continuous heavy-load operation of tractors.

[0003] While simple gear transmission can achieve heavy-duty continuous operation, it only provides stepped transmission and cannot achieve continuously variable transmission (CVT). Therefore, the power-split CVT is widely used in tractors. Its technology mainly utilizes the aforementioned continuously variable speed control technology combined with stepped gear transmission to achieve both continuously variable speed and high torque transmission. Power-split CVTs mostly use hydraulic pumps and motors for speed regulation, transmitting power through a closed differential gear train with a single degree of freedom, composed of a differential gear train and a fixed-axis gear transmission (or differential gear train). They often employ multiple gear pairs and wet clutches to achieve segment switching, covering a wider speed range, but suffer from high cost and large size. If synchronizers are used for segment switching, the speed difference during shifting is too large, easily damaging the synchronizers; if meshing sleeves or sliding gears are used, segment switching can only be done by stopping the vehicle. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a continuously variable transmission (CVT), a control method for the CVT, and a tractor. The CVT employs a combined synchronizer and clutch for shifting, simplifying the transmission system and reducing its cost. The alternating switching of the synchronizer and clutch, achieved based on the synchronizer speed difference, ensures the reliability of the synchronizer's operation. Clutch shifting without speed difference can be achieved at different clutch synchronous shifting points.

[0005] To achieve the above objectives, the specific solution adopted by the present invention is as follows:

[0006] A continuously variable transmission (CVT) includes a CVT assembly, a stepped shift assembly, a TCU controller, a first clutch, a second clutch, and a third clutch.

[0007] The continuously variable transmission (CVT) assembly includes a transmission input shaft, a first gear pair, a second gear pair, a double planetary gear set, a third gear pair, a fourth gear pair, and three transmission output shafts. The transmission input shaft is fixedly connected to the first gear pair and the double planetary gear set, respectively. A speed control pump motor assembly is connected between the first gear pair and the second gear pair, which is loosely fitted on the transmission input shaft. The third and fourth gear pairs include a common gear fixedly connected to the planet carrier of the double planetary gear set. The fourth gear pair is fixedly connected to transmission output shaft I, the double planetary gear set is fixedly connected to transmission output shaft II, and the third gear pair is fixedly connected to transmission output shaft III.

[0008] The stepped shift assembly includes three shift input shafts, a fifth gear pair, a sixth gear pair, a seventh gear pair, an eighth gear pair, a ninth gear pair, and a shift output shaft. A first synchronizer is provided between the sixth and seventh gear pairs, and a second synchronizer is provided between the eighth and ninth gear pairs. Shift input shaft I is sequentially fixed to the fifth, eighth, and ninth gear pairs, shift input shaft II is sequentially fixed to the sixth and seventh gear pairs, and shift input shaft III is connected to the fifth gear pair. The first and second synchronizers are both fixed to the shift output shaft, and the sixth to ninth gear pairs are loosely fitted on the shift output shaft.

[0009] The transmission output shaft I is connected to the shift input shaft I via the first clutch, the transmission output shaft II is connected to the shift input shaft II via the second clutch, and the transmission output shaft III is connected to the shift input shaft III via the third clutch.

[0010] The TCU controller is electrically connected to the first clutch, the second clutch, the third clutch, the first synchronizer, and the second synchronizer.

[0011] Furthermore, the continuously variable transmission (CVT) also includes a first speed sensor for monitoring the speed of the first gear pair, a second speed sensor for monitoring the speed of the second gear pair, a third speed sensor for monitoring the speed of the fifth gear pair, a fourth speed sensor for monitoring the speed of the sixth gear pair, and a fifth speed sensor for monitoring the speed of the shift output shaft. All of the first to fifth speed sensors are electrically connected to the TCU controller.

[0012] Furthermore, the engine speed is split via the transmission input shaft and the first gear pair. One power is directly transmitted to the first gear 1-6a of the first planetary gear set of the double planetary gear set, while the other power is transmitted via the speed regulating pump motor assembly, the second gear pair 1-5, and the third gear 1-6c of the second planetary gear set of the double planetary gear set 1-6. After the two power paths merge through the double planetary gear set, they reach at least one of the three transmission output shafts via the third or fourth gear pair.

[0013] A continuously variable transmission (CVT) control method is proposed, which realizes the alternating switching of synchronizer and clutch through TCU controller based on synchronizer speed difference; realizes the alternating switching of different clutches based on clutch speed difference; and realizes stepless adjustment of tractor speed throughout the entire process by means of changing the displacement of speed regulating pump motor assembly.

[0014] Furthermore, it includes a forward movement mode, which sequentially includes forward movement stage I, forward movement stage II, forward movement stage III, and forward movement stage IV, with gradually increasing speed;

[0015] During the forward phase I: the TCU controller enables the engagement of the first clutch, the sy1 side of the second synchronizer, and the sy2 side of the first synchronizer, as well as the change in the displacement of the speed regulating pump motor assembly; after the power is transmitted through the transmission output shaft I, it passes through the first clutch, the shift input shaft I, the fifth gear pair, the eighth gear pair, and the sy1 side of the second synchronizer to reach the shift output shaft, and the tractor moves forward, gradually and continuously increasing speed by means of the vector increase in the displacement of the speed regulating pump motor assembly;

[0016] During the forward phase II: The TCU controller controls the engagement of the second clutch and the sy2 side of the first synchronizer, as well as the change in the displacement of the speed regulating pump motor assembly; after the power is transmitted through the transmission output shaft II, it reaches the shift output shaft through the second clutch, the shift input shaft II, the seventh gear pair, and the sy2 side of the first synchronizer, and the tractor moves forward, gradually and continuously increasing speed by means of the vector decrease in the displacement of the speed regulating pump motor assembly.

[0017] Further control over the timing of first clutch disengagement, pre-engagement, and disengagement;

[0018] Further control the timing of engagement and disengagement of the second synchronizer sy1 and sy3 sides.

[0019] When the vehicle speed increases to the synchronization point between Forward Stage II and Forward Stage I, the first clutch is disengaged via the TCU controller, while the sy1 side of the second synchronizer remains engaged. When the vehicle speed increases and is slightly higher than the synchronization point between Forward Stage II and Forward Stage I, the first clutch engages, and the sy1 side of the second synchronizer disengages. Power is transmitted through the first clutch, the shift input shaft I, the fifth gear pair, the ninth gear pair, and the sy3 side of the second synchronizer. When the vehicle speed increases to slightly lower than the synchronization point between Forward Stage II and Forward Stage III, the first clutch is disengaged via the TCU controller, and the sy3 side of the second synchronizer engages. Power is transmitted through the shift output shaft, the sy3 side of the second synchronizer, the ninth gear pair, and to the driven side of the first clutch.

[0020] When the vehicle speed decreases to the synchronization point between Forward Stage III and Forward Stage II, the first clutch disengages via the TCU controller, while the sy3 side of the second synchronizer remains engaged. When the vehicle speed decreases and is slightly below the synchronization point between Forward Stage III and Forward Stage II, the first clutch engages, and the sy3 side of the second synchronizer disengages. Power is transmitted through the first clutch, shift input shaft I, fifth gear pair, eighth gear pair, and the sy1 side of the second synchronizer. When the vehicle speed decreases and is slightly above the synchronization point between Forward Stage II and Forward Stage I, the first clutch disengages via the TCU controller, and the sy1 side of the second synchronizer engages. Power is transmitted through the shift output shaft, the sy1 side of the second synchronizer, the eighth gear pair, and to the driven side of the first clutch.

[0021] When the vehicle speed decreases to the synchronization point between Forward Stage II and Forward Stage I and further decreases, control is performed according to the control method of Forward Stage I;

[0022] When moving forward in stage III: the TCU controller enables the engagement of the first clutch and the sy3 side of the second synchronizer, as well as the change of the displacement of the speed control pump motor assembly; after the power is transmitted from the transmission output shaft I, it passes through the first clutch, the shift input shaft I, the fifth gear pair, the ninth gear pair, and the sy3 side of the second synchronizer to reach the shift output shaft, and the tractor moves forward, gradually and continuously increasing speed by means of the vector increase of the displacement of the speed control pump motor assembly;

[0023] Further control over the timing of second clutch disengagement, pre-engagement, and disengagement;

[0024] Further control the timing of engagement and disengagement of the first synchronizer sy2 and sy4 sides;

[0025] When the vehicle speed increases to the synchronization point between Forward Stage II and Forward Stage III, the second clutch is disengaged via the TCU controller, while the sy2 side of the first synchronizer remains engaged. When the vehicle speed increases and is slightly higher than the synchronization point between Forward Stage III and Forward Stage II, the second clutch engages, and the sy2 side of the first synchronizer disengages. Power is transmitted through the second clutch, the shift input shaft II, the sixth gear pair, and the sy4 side of the first synchronizer. When the vehicle speed increases and is slightly lower than the synchronization point between Forward Stage III and Forward Stage IV, the second clutch is disengaged via the TCU controller, and the sy4 side of the first synchronizer engages. Power is transmitted through the shift output shaft, the sy4 side of the first synchronizer, the sixth gear pair, and to the driven side of the second clutch.

[0026] When the vehicle speed decreases to the synchronization point between forward stage IV and forward stage III, the second clutch disengages via the TCU controller, while the sy4 side of the first synchronizer remains engaged. When the vehicle speed decreases and is slightly below the synchronization point between forward stage IV and forward stage III, the second clutch engages, and the sy4 side of the first synchronizer disengages. Power is transmitted through the second clutch, shift input shaft II, the seventh gear pair, and the sy2 side of the first synchronizer. When the vehicle speed decreases and is slightly above the synchronization point between forward stage III and forward stage II, the second clutch disengages via the TCU controller, and the sy2 side of the first synchronizer engages. Power is transmitted through the shift output shaft, the sy2 side of the second synchronizer, the seventh gear pair, and to the driven side of the second clutch.

[0027] When the vehicle speed decreases to the synchronization point between Forward Stage III and Forward Stage II and further decreases, control is performed according to the control method of Forward Stage II;

[0028] During the forward IV stage: the TCU controller enables the engagement of the second clutch, the sy3 side of the second synchronizer, and the sy4 side of the first synchronizer, as well as the change in the displacement of the speed regulating pump motor assembly; after the power is transmitted through the transmission output shaft II, it reaches the shift output shaft via the second clutch, the shift input shaft II, the sixth gear pair, and the sy4 side of the first synchronizer, and the tractor moves forward, gradually and continuously increasing speed by means of the vector decrease in the displacement of the speed regulating pump motor assembly.

[0029] Furthermore, it includes a reversing mode, which sequentially includes a reversing segment I and a reversing segment II with gradually increasing speed;

[0030] During reverse section I: The TCU controller controls the engagement of the third clutch and the second synchronizer sy1 side, as well as the change in the displacement of the speed control pump motor assembly. Power is transmitted through the transmission output shaft III, and after passing through the third clutch, shift input shaft III, fifth gear pair, shift input shaft I, eighth gear pair, and the second synchronizer Sy1 side, it is output from the shift output shaft. The vehicle reverses, and gradually and continuously increases speed by means of the vector increase in the displacement of the speed control pump motor assembly.

[0031] During the reverse phase II: The TCU controller controls the engagement of the third clutch and the second synchronizer sy3 side, as well as the change in the displacement of the speed control pump motor assembly. After passing through the third clutch, shift input shaft III, fifth gear pair, shift input shaft I, ninth gear pair, and the second synchronizer Sy3 side, the output is sent to the shift output shaft, causing the vehicle to reverse. The speed is gradually and continuously increased by means of the vector increase in the displacement of the speed control pump motor assembly.

[0032] A tractor equipped with the aforementioned continuously variable transmission (CVT).

[0033] Beneficial effects:

[0034] This invention employs a combined synchronizer and clutch for gear shifting, simplifying the transmission system and reducing its cost. The alternating switching of the synchronizer and clutch, achieved based on the synchronizer's speed difference, ensures the synchronizer's reliability. Clutch shifting can be performed without speed difference at different gear shifting points. By changing the displacement of the speed-regulating pump motor assembly, continuous speed variations across the entire tractor speed range and smooth gear shifting are achieved, significantly improving the reliability of the switching elements. During clutch shifting, the pump motor operates without drastic speed jumps, greatly protecting its stability and reliability. Through TCU control, the continuously variable transmission (CVT) can operate at any point, achieving optimal matching with the engine and ensuring the tractor's best economic performance. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the transmission route of a continuously variable transmission (CVT).

[0036] Figure 2 This is a diagram showing the speed output characteristics of a continuously variable transmission (CVT).

[0037] Figure 3 This is a schematic diagram of the shifting strategy for a continuously variable transmission (CVT).

[0038] Marked in the image:

[0039] 1. Continuously variable transmission (CVT) assembly; 1-1. First gear pair; 1-1a. First gear; 1-1b. Second gear; 1-2. First shaft; 1-3. Speed ​​control pump motor assembly; 1-4. Second shaft; 1-5. Second gear pair; 1-5a. Fourth gear; 1-5b. Third gear; 1-6. Double planetary gear set; 1-6a. First planetary gear set first gear; 1-6b. First planetary gear set second gear; 1-6e. Second planetary gear set first gear; 1-6d. Second planetary gear set second gear; 1-6c. Second planetary gear set third gear; 1-7. Third shaft; 1-8. Fourth gear pair; 1-8a. Fifth gear; 1-8b. Sixth gear; 1-9. Third gear pair; 1-9b. Seventh gear; 1-10. Second speed sensor; 1-11. First speed sensor; 2. Variable speed output shaft III; 3. Variable speed output shaft I; 4. Third clutch; 5. Shifting gear. Input shaft III, 6, stepped shift assembly, 6-1, fifth gear pair, 6-1a, eighth gear, 6-1b, ninth gear, 6-2, sixth gear pair, 6-2a, tenth gear, 6-2b, eleventh gear, 6-3, first synchronizer, 6-4, ninth gear pair, 6-4a, sixteenth gear, 6-4b, seventeenth gear, 6-5, shift output shaft, 6-6, fifth speed sensor, 6-7, second synchronizer, 6-8, eighth gear pair, 6-8a, fourteenth gear, 6-8b, fifteenth gear, 6-9, seventh gear pair, 6-9a, twelfth gear, 6-9b, thirteenth gear, 6-10, fourth speed sensor, 6-11, third speed sensor, 7, shift input shaft I, 8, shift input shaft II, 9, first clutch, 10, second clutch, 11, shift output shaft II, 12, TCU controller.

[0040] Figure 1 In the diagram: Z represents a gear, and the subscript number indicates which gear it is; Zp represents a planetary gear set, and the subscript number indicates which gear it is in which planetary set; Sn represents a speed sensor, and the subscript number indicates which speed sensor it is.

[0041] Figure 2 In the text: L represents the speed output curve, and the subscript number indicates which section of the transmission's speed output curve it is.

[0042] Figure 3 In Chinese: + indicates that the switching element is engaged, and - indicates that the switching element is disengaged. Detailed Implementation

[0043] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0044] A continuously variable transmission (CVT) for tractors mainly includes: a continuously variable transmission assembly 1, a stepped shift assembly 6, a transmission output shaft I 3, a transmission output shaft II 11, a transmission output shaft III 2, a shift input shaft I 7, a shift input shaft II 8, a shift input shaft III 5, a first clutch 9, a second clutch 10, a third clutch 4, and a TCU controller 12.

[0045] A second clutch 10, a first clutch 9, and a third clutch 4 are installed between the continuously variable transmission assembly 1 and the stepped shift assembly 6. The clutches are fixed to the three output ends of the continuously variable transmission assembly 1 via the transmission output shaft II 11, transmission output shaft I 3, and transmission output shaft III 2, respectively, and are fixed to the three input ends of the stepped shift assembly 6 via the shift input shaft II 8, shift input shaft I 7, and shift input shaft III 5, respectively.

[0046] The continuously variable transmission assembly 1 mainly includes: first gear pair 1-1, second gear pair 1-5, third gear pair 1-9, fourth gear pair 1-8, speed control pump motor assembly 1-3, speed input shaft 1-12, first shaft 1-2, second shaft 1-4, third shaft 1-7, double planetary gear set 1-6, first speed sensor 1-11, and second speed sensor 1-10.

[0047] The first gear pair 1-1 is composed of the meshing of the first gear 1-1a and the second gear 1-1b;

[0048] The second gear pair 1-5 is composed of the meshing of the fourth gear 1-5a and the third gear 1-5b;

[0049] The third gear pair 1-9 is composed of the meshing of the fifth gear 1-8a and the seventh gear 1-9b;

[0050] The fourth gear pair 1-8 is composed of the meshing of the fifth gear 1-8a and the sixth gear 1-8b.

[0051] The double planetary gear set 1-6 mainly includes: the first planetary gear set first gear 1-6a, the first planetary gear set second gear 1-6b, the second planetary gear set first gear 1-6e, the second planetary gear set second gear 1-6d, and the second planetary gear set third gear 1-6c. The second planetary gear set second gear 1-6d, which meshes with the third gear 1-6c, is fixedly connected to the first planetary gear set second gear 1-6b and loosely fitted onto the third shaft 1-7. The first planetary gear set second gear 1-6b meshes with the first planetary gear set first gear 1-6a to form the first planetary gear set. The second planetary gear set second gear 1-6d, which meshes with the third gear 1-6c, meshes with the second planetary gear set first gear 1-6e, which is fixedly connected to the transmission output shaft II 11, to form the second planetary gear set.

[0052] It should be noted that the third shaft 1-7 is also the planet carrier of the double planetary gear set 1-6. The output end of the third shaft 1-7 is fixedly connected to the fifth gear 1-8a shared by the third gear pair 1-9 and the fourth gear pair 1-8.

[0053] The first gear 1-6e, the fourth gear pair 1-8, and the third gear pair 1-9 of the second planetary gear set 1-6 are connected to the second clutch 10, the first clutch 9, and the third clutch 4 respectively, forming the three output ends of the continuously variable transmission assembly 1.

[0054] The first gear pair 1-1 located at the input end of the continuously variable transmission assembly 1 and the second gear pair 1-5 located at the input end of the double planetary gear set 1-6 are connected to the speed control pump motor assembly 1-3 through the first shaft 1-2 and the second shaft 1-4.

[0055] The transmission input shaft 1-12 is fixedly connected to the first gear 1-1a and the first gear 1-6a of the first planetary gear set, and is loosely fitted with the third gear 1-5b, which is fixedly connected to the third gear 1-6c of the second planetary gear set.

[0056] The speed-regulating pump motor assembly can be a separate pump and motor, or an integrated unit, or it can be completely replaced with other forms of stepless speed regulating components, such as motors, metal belts, rubber belts, etc.

[0057] The aforementioned technology forms a continuously variable transmission assembly 1 with one input and three outputs adjusted by a continuously variable speed control element.

[0058] A first speed sensor 1-11 and a second speed sensor 1-10 are respectively installed at the positions of the first gear pair 1-1 and the second gear pair 1-5 of the continuously variable transmission assembly 1.

[0059] The speed sensor can be placed on any gear of the corresponding gear pair, or on any gear of other gear pairs that are fixedly connected to the corresponding gear pair.

[0060] The stepped shift assembly 6 mainly includes: fifth gear pair 6-1, sixth gear pair 6-2, seventh gear pair 6-9, eighth gear pair 6-8, ninth gear pair 6-4, shift output shaft 6-5, third speed sensor 6-11, fourth speed sensor 6-10, fifth speed sensor 6-6, first synchronizer 6-3, and second synchronizer 6-7.

[0061] The fifth gear pair 6-1 is composed of the meshing of the eighth gear 6-1a and the ninth gear 6-1b;

[0062] The sixth gear pair 6-2 is composed of the meshing of the tenth gear 6-2a and the eleventh gear 6-2b;

[0063] The seventh gear pair 6-9 is composed of the meshing of the twelfth gear 6-9a and the thirteenth gear 6-9b;

[0064] The eighth gear pair 6-8 is composed of the meshing of the fourteenth gear 6-8a and the fifteenth gear 6-8b;

[0065] The ninth gear pair 6-4 is composed of the meshing of the sixteenth gear 6-4a and the seventeenth gear 6-4b.

[0066] The tenth gear 6-2a and the twelfth gear 6-9a, located at the input end of the stepped shift assembly 6, are fixedly connected to the shift input shaft II 8. The ninth gear 6-1b, the fourteenth gear 6-8a, and the sixteenth gear 6-4a, located at the input end of the stepped shift assembly 6, are fixedly connected to the shift input shaft I 7. The first synchronizer 6-3 and the second synchronizer 6-7, located at the output end of the stepped shift assembly 6, are fixedly connected to the shift output shaft 6-5, and are respectively arranged between the sixth gear pair 6-2 and the seventh gear pair 6-9, and between the intermediate eighth gear pair 6-8 and the ninth gear pair 6-4. The eleventh gear 6-2b, the thirteenth gear 6-9b, the fifteenth gear 6-8b, and the seventeenth gear 6-4b are loosely fitted on both sides of the first synchronizer 6-3 and the second synchronizer 6-7 on the shift output shaft 6-5. The eighth gear 6-1a, located at the input end of the stepped shift assembly 6, is fixedly connected to the shift input shaft III 5.

[0067] The first and second synchronizers 6-3 and 6-7, which are fixed on the switching output shaft 6-5, can be equivalently replaced by meshing sleeves.

[0068] The third speed sensor 6-11, the fourth speed sensor 6-10, and the fifth speed sensor 6-6 are installed at the positions of the fifth gear pair 6-1, the sixth gear pair 6-2, and the eleventh output shaft 6-5 of the stepped gear assembly 6.

[0069] The speed sensor can be placed on any gear of the corresponding gear pair, or on any gear of other gear pairs that are fixedly connected to the corresponding gear pair.

[0070] The TCU controller 12 is connected to the first speed sensor 1-11, the second speed sensor 1-10, the third speed sensor 6-11, the fourth speed sensor 6-10, and the fifth speed sensor 6-6 via wiring harnesses. It is also connected to the solenoid valves (not shown in the figure) of the first clutch 9, the second clutch 10, the third clutch 4, the first synchronizer 6-3, and the second synchronizer 6-7, which are combined with the separation mechanism, via wiring harnesses.

[0071] The continuously variable transmission (CVT) composed of the aforementioned technologies will form the forward segment of the tractor's movement when the first clutch 9 and the second clutch 10 are engaged, and will form the reverse segment of the tractor's movement when the third clutch 4 is engaged.

[0072] When the second clutch 10 and the first synchronizer 6-3 are engaged, a curve is formed in which the transmission output speed decreases as the control current of the speed regulating pump motor assembly 1-3 or the motor speed vector increases. When the first clutch 9 and the second synchronizer 6-7 are engaged, a curve is formed in which the transmission output speed increases as the control current of the speed regulating pump motor assembly 1-3 or the motor speed vector increases. When the third clutch 4 and the second synchronizer 6-7 are engaged, a curve is formed in which the transmission output speed increases as the control current of the speed regulating pump motor assembly 1-3 or the motor speed vector increases.

[0073] At the intersection points (A, B, E) of the output speed variation curves on the output shaft S11 of the transmission, different clutch and synchronizer combinations will have the same speed at the driving and driven ends of the synchronizer and clutch.

[0074] When the first clutch 9 or the third clutch 4 engages and a synchronizer is combined, the speed output can be 0 at the intersection (D) of the speed output curve on the output shaft S11 of the transmission.

[0075] like Figure 2 A control method for a tractor continuously variable transmission (CVT) is as follows: based on the synchronizer speed difference, the synchronizer and clutch are switched alternately through the TCU controller; based on the clutch speed difference, different clutches are switched alternately; and by changing the displacement of the speed regulating pump motor assembly, the tractor speed can be continuously adjusted throughout the entire range.

[0076] It should be noted that the continuously variable transmission (CVT) control method in this invention includes a forward mode and a reverse mode. The forward mode sequentially includes forward stage I, forward stage II, forward stage III, and forward stage IV, with gradually increasing speed; the reverse mode sequentially includes reverse stage I and reverse stage II, with gradually increasing speed. The specific control method is as follows:

[0077] During the forward phase I: the TCU controller 12 enables the engagement of the first clutch 9, the sy1 side of the second synchronizer 6-7 and the sy2 side of the first synchronizer 6-3, and changes the displacement of the speed regulating pump motor assembly 1-3; after the power is transmitted through the transmission output shaft I 3, it reaches the shift output shaft 6-5 via the first clutch 9, the shift input shaft I 7, the fifth gear pair 6-1, the eighth gear pair 6-8, and the sy1 side of the second synchronizer 6-7, causing the tractor to move forward, and gradually and continuously increasing speed by means of the vector increase in the displacement of the speed regulating pump motor assembly 1-3.

[0078] During the forward movement (Section II): TCU controller 12 controls the engagement of the second clutch 10 and the sy2 side of the first synchronizer 6-3, as well as the change in displacement of the speed regulating pump motor assembly 1-3; after the power is transmitted through the transmission output shaft II 11, it reaches the shift output shaft 6-5 via the second clutch 10, the shift input shaft II 8, the seventh gear pair 6-9, and the sy2 side of the first synchronizer 6-3, causing the tractor to move forward and gradually and continuously increase speed by means of the vector decrease in displacement of the speed regulating pump motor assembly 1-3;

[0079] Further control over the timing of disengagement, pre-engagement, and disengagement of the first clutch 9;

[0080] Further control the engagement and disengagement timing of the second synchronizer 6-7 sy1 and sy3 sides;

[0081] When the vehicle speed increases to the synchronization point between Forward Stage II and Forward Stage I, the first clutch 9 is disengaged via the TCU controller 12, while the sy1 side of the second synchronizer 6-7 remains engaged. When the vehicle speed increases and is slightly higher than the synchronization point between Forward Stage II and Forward Stage I, the first clutch 9 engages, and the sy1 side of the second synchronizer 6-7 disengages. Power is transmitted through the first clutch 9, the shift input shaft I 7, the fifth gear pair 6-1, the ninth gear pair 6-4, and the sy3 side of the second synchronizer 6-7. When the vehicle speed increases to slightly lower than the synchronization point between Forward Stage II and Forward Stage III, the first clutch 9 is disengaged via the TCU controller 12, and the sy3 side of the second synchronizer 6-7 engages. Power is transmitted through the shift output shaft 6-5, the sy3 side of the second synchronizer 6-7, the ninth gear pair 6-4, and to the driven side of the first clutch 9.

[0082] When the vehicle speed decreases to the synchronization point between Forward Stage III and Forward Stage II, the first clutch 9 is disengaged via the TCU controller 12, while the sy3 side of the second synchronizer 6-7 remains engaged. When the vehicle speed decreases and is slightly below the synchronization point between Forward Stage III and Forward Stage II, the first clutch 9 engages, and the sy3 side of the second synchronizer 6-7 disengages. Power is transmitted through the first clutch 9, the shift input shaft I 7, the fifth gear pair 6-1, the eighth gear pair 6-8, and the sy1 side of the second synchronizer 6-7. When the vehicle speed decreases to slightly above the synchronization point between Forward Stage II and Forward Stage I, the first clutch 9 is disengaged via the TCU controller 12, and the sy1 side of the second synchronizer 6-7 engages. Power is transmitted through the shift output shaft 6-5, the sy1 side of the second synchronizer 6-7, the eighth gear pair 6-8, and to the driven side of the first clutch 9.

[0083] When the vehicle speed decreases to the synchronization point between Forward Stage II and Forward Stage I and further decreases, the Forward Stage I control method shall be followed.

[0084] During the forward III stage: the TCU controller 12 enables the engagement of the first clutch 9 and the second synchronizer 6-7 on the sy3 side, as well as the change in displacement of the speed control pump motor assembly 1-3; after the power is transmitted from the transmission output shaft I 3, it passes through the first clutch 9, the shift input shaft I 7, the fifth gear pair 6-1, the ninth gear pair 6-4, and the sy3 side of the second synchronizer 6-7 to reach the shift output shaft 6-5, and the tractor moves forward, gradually and continuously increasing speed by means of the vector increase in displacement of the speed control pump motor assembly 1-3;

[0085] Further control over the timing of disengagement, pre-engagement, and disengagement of the second clutch 10;

[0086] Further control the engagement and disengagement timing of the first synchronizer 6-3 sy2 and sy4 sides;

[0087] When the vehicle speed increases to the synchronization point of forward stage II and forward stage III, the second clutch 10 is disengaged through the TCU controller 12, while the sy2 side of the first synchronizer 6-3 remains engaged. When the vehicle speed increases and is slightly higher than the synchronization point of forward stage III and forward stage II, the second clutch 10 engages, and the sy2 side of the first synchronizer 6-3 disengages. Power is transmitted through the second clutch 10, the shift input shaft II 8, the sixth gear pair 6-2, and the sy4 side of the first synchronizer 6-3. When the vehicle speed increases to slightly lower than the synchronization point of forward stage III and forward stage IV, the second clutch 10 is disengaged through the TCU controller 12, and the sy4 side of the first synchronizer 6-3 engages. Power is transmitted through the shift output shaft 6-5, the sy4 side of the first synchronizer 6-3, the sixth gear pair 6-2, and to the driven side of the second clutch 10.

[0088] When the vehicle speed decreases to the synchronization point of forward stage IV and forward stage III, the second clutch 10 is disengaged through the TCU controller 12, while the sy4 side of the first synchronizer 6-3 remains engaged. When the vehicle speed decreases and is slightly below the synchronization point of forward stage IV and forward stage III, the second clutch 10 engages, and the sy4 side of the first synchronizer 6-3 disengages. Power is transmitted through the second clutch 9, the shift input shaft II 8, the seventh gear pair 6-9, and the sy2 side of the first synchronizer 6-3. When the vehicle speed decreases to slightly above the synchronization point of forward stage III and forward stage II, the second clutch 10 is disengaged through the TCU controller 12, and the sy2 side of the first synchronizer 6-3 engages. Power is transmitted through the shift output shaft 6-5, the sy2 side of the second synchronizer 6-3, the seventh gear pair 6-9, and to the driven side of the second clutch 10.

[0089] When the vehicle speed decreases to the synchronization point between Forward Stage III and Forward Stage II and further decreases, the Forward Stage II control method shall be followed.

[0090] During the forward IV stage: the TCU controller 12 enables the engagement of the second clutch 10, the sy3 side of the second synchronizer 6-7, the sy4 side of the first synchronizer 6-3, and the displacement change of the speed regulating pump motor assembly 1-3; after the power is transmitted through the transmission output shaft II 11, it reaches the shift output shaft 6-5 through the second clutch 10, the shift input shaft II 8, the sixth gear pair 6-1, and the sy4 side of the first synchronizer 6-3, and the tractor moves forward, gradually and continuously increasing speed by means of the vector decrease in the displacement of the speed regulating pump motor assembly 1-3.

[0091] During reverse section I: The TCU controller 12 controls the engagement of the third clutch 4, the sy1 side of the second synchronizer 6-7, and the displacement change of the speed pump motor assembly 1-3. Power is transmitted through the transmission output shaft III 2, and then through the third clutch 4, the shift input shaft III 5, the fifth gear pair 6-1, the shift input shaft I 7, the eighth gear pair 6-8, and the Sy1 side of the second synchronizer 6-7 before being output by the shift output shaft 6-5. The vehicle reverses and gradually and continuously increases speed by means of the vector increase of the displacement of the speed pump motor assembly 1-3.

[0092] During the reverse phase II: The TCU controller 12 controls the engagement of the third clutch 4, the sy3 side of the second synchronizer 6-7, and the displacement change of the speed pump motor assembly 1-3. After passing through the third clutch 4, the shift input shaft III 5, the fifth gear pair 6-1, the shift input shaft I 7, the ninth gear pair 6-4, and the Sy3 side of the second synchronizer 6-7, the output is output from the shift output shaft 6-5, causing the vehicle to reverse and gradually and continuously increase speed by means of the vector increase of the displacement of the speed pump motor assembly 1-3.

[0093] For the speed output curve based on the aforementioned technical solution, please refer to... Figure 2 Including: the first curve L I The second curve L Ⅱ Third curve L III The fourth curve L Ⅳ Fifth curve L Ⅴ The sixth curve L Ⅵ .

[0094] Second curve L Ⅱ Above, near points A and B, working points A1 and B1 are set, on the third curve L. III Above, near points B and E, are operating points B2 and E1. Operating points A1, B1, B2, and E1 are set based on the rotational speeds measured by speed sensors located at the driving and driven ends of the first synchronizer 6-3 and the second synchronizer 6-7 on the pre-engagement or pre-disengagement sides, or the calculated speed difference limit. Operating points A, B, and E are set based on the rotational speeds measured by speed sensors located at the driving and driven ends of the first clutch 9 and the second clutch 10, or the calculated speed difference limit.

[0095] The operating point on the operating curve can be used as a specific operating point of the control system, or it can be transformed into the ratio of the output speed to the input speed of the transmission, or into the speed ratio, transmission ratio, displacement ratio, and control current value of the speed regulating pump motor assembly (or other speed regulating elements).

[0096] like Figure 1 , Figure 2 , Figure 3 As shown, the first curve L I Above, except for the engagement of the first clutch 9 and the second synchronizer 6-7 on the Sy1 side and the engagement of the first synchronizer 6-3 on the Sy2 side through the TCU controller 12, all other shifting components are disengaged.

[0097] like Figure 1 , Figure 2 , Figure 3 As shown, the second curve L II In addition to the engagement of the second clutch 10 and the Sy2 side of the first synchronizer 6-3 via the TCU controller 12, there is an alternating switching between the Sy1 and Sy3 sides of the second synchronizer 6-7 and the first clutch 9. In segment AA1, the Sy1 side of the second synchronizer 6-7 is engaged; in segment A1B1, the first clutch 9 is engaged; and in segment B1B, the Sy3 side of the second synchronizer 6-7 is engaged. All other shifting elements are disengaged.

[0098] like Figure 1 , Figure 2 , Figure 3 As shown, the third curve L IIIIn addition to the engagement of the first clutch 9 and the Sy3 side of the second synchronizer 6-7 via the TCU controller 12, there is an alternating switching between the Sy2 and Sy4 sides of the first synchronizer 6-3 and the second clutch 10. In segment BB2, the Sy2 side of the first synchronizer 6-3 is engaged; in segment B2E1, the second clutch 10 is engaged; and in segment E1E, the Sy4 side of the first synchronizer 6-3 is engaged. All other shifting elements are disengaged.

[0099] like Figure 1 , Figure 2 , Figure 3 As shown, the fourth curve L IV In addition to the second clutch 10 and the first synchronizer 6-3 being engaged on the Sy4 side via the TCU controller 12, the second synchronizer 6-7 is engaged on the Sy3 side, and all other shifting components are disengaged.

[0100] like Figure 1 , Figure 2 , Figure 3 As shown, the fifth curve L V Apart from the engagement of the third clutch 4 and the second synchronizer 6-7 on the Sy1 side via the TCU controller 12, all other shifting components are disengaged.

[0101] like Figure 1 , Figure 2 , Figure 3 As shown, the sixth curve L VI Above, except for the engagement of the third clutch 4 and the second synchronizer 6-7 on the Sy3 side via the TCU controller 12, all other shifting components are disengaged.

[0102] like Figure 2 As shown, in the first curve L I Third curve L III Fifth curve L V The sixth curve L VI As the vehicle speed increases, the output speed vector of the speed control pump motor assembly gradually increases and adjusts; in the second curve L II The fourth curve L IV As the vehicle speed increases, the output speed vector of the speed regulating pump motor assembly gradually decreases and changes accordingly.

[0103] like Figure 1 , Figure 2 , Figure 3 As shown, based on the aforementioned transmission system technology, the control current of the speed regulating pump motor assembly 1-3 is changed by the TCU controller 12, and the synchronizer and clutch are controlled in combination, along the speed curve DA-AB-BE-L of the transmission system output. IVBy alternating the working order, the tractor can achieve a continuous change in speed from 0 to its maximum speed.

[0104] like Figure 1 , Figure 2 , Figure 3 As shown, based on the aforementioned transmission system technology, by changing the control current combination of the speed regulating pump motor assembly 1-3 through the TCU controller 12 to control the first clutch 9 and the second synchronizer 6-7, the tractor can achieve two different speeds that change continuously from a speed of 0.

[0105] like Figure 1 , Figure 2 , Figure 3 As shown, when the tractor accelerates forward, after the engine starts, the TCU controller 12 controls the engagement of the first clutch 9, the Sy1 side of the second synchronizer 6-7, and the Sy2 side of the first synchronizer 6-3, adjusting the control current of the speed regulating pump motor assembly 1-3 to a certain value. The tractor is stationary. As the control current of the speed regulating pump motor assembly 1-3 increases, the engine speed is split through the transmission input shaft 1-12 and the first gear pair 1-1. One power is directly transmitted to the first gear 1-6a of the first planetary gear set of the double planetary gear set 1-6, and the other power is transmitted through the speed regulating pump motor assembly 1-3 → the second gear pair 1-5 → the third gear 1-6c of the second planetary gear set of the double planetary gear set 1-6. After the two power paths merge through the double planetary gear set 1-6, they pass through the third shaft 1-7 → the fourth gear pair 1-8 → the transmission output shaft I 3 → the first clutch 9 → the shift input shaft I 7 → Eighth gear pair 6-8 → Sy1 side of second synchronizer 6-7 → Output from shift output shaft 6-5, the tractor moves forward and gradually and continuously increases speed along the first curve L I Work.

[0106] like Figure 1 , Figure 2 , Figure 3 As shown, when the vehicle speed (transmission output speed) reaches the first curve L I At operating point A, the TCU controller 12 controls the first clutch 9 to disengage and the second clutch 10 to engage. At this time, the combined power of the double planetary gear set 1-6 flows through the first gear 1-6e of the second planetary gear set → transmission output shaft II 11 → second clutch 10 → shift input shaft II 8 → seventh gear pair 6-9 → Sy2 side of the first synchronizer 6-3 → output through shift output shaft 6-5. As the control current of the TCU-controlled speed pump motor assembly 1-3 decreases, the tractor moves along the second curve L. II Continue accelerating forward. During this process, to ensure the alternation of the two synchronizers remains within a reasonable speed difference range, when the tractor speed (gearbox output speed) follows the second curve L... IIWhen the speed increases to the A1 operating point, the TCU controller 12 controls the first clutch 9 to engage and the Sy1 side of the second synchronizer 6-7 to disengage; when the tractor speed (transmission output speed) follows the second curve L II When the speed is increased to the B1 operating point, the TCU controller 12 controls the first clutch 9 to disengage and the Sy3 side of the second synchronizer 6-7 to engage.

[0107] like Figure 1 , Figure 2 , Figure 3 As shown, when the vehicle speed (transmission output speed) reaches the second curve L II When the tractor reaches operating point B, the TCU controller 12 controls the second clutch 10 to disengage and the first clutch 9 to engage. At this time, the power after the double planetary gear set 1-6 merges is output through the third shaft 1-7 → fourth gear pair 1-8 → transmission output shaft I 3 → first clutch 9 → shift input shaft I 7 → ninth gear pair 6-4 → Sy3 side of the second synchronizer 6-7 → shift output shaft 6-5. The tractor moves forward and gradually and continuously increases in speed along the third curve L. III Work. As the control current of the speed regulating pump motor assembly 1-3 controlled by the TCU controller 12 increases, the tractor moves along the second curve L. II Continue accelerating forward. During this process, to ensure the synchronizer's switching is within a reasonable speed difference range, when the tractor speed (gearbox output speed) follows the third curve L... III When the speed increases to the B2 operating point, the TCU controller 12 controls the second clutch 10 to engage and the Sy2 side of the first synchronizer 6-3 to disengage; when the tractor speed (transmission output speed) follows the third curve L III When the speed is increased to the E1 operating point, the TCU controller 12 controls the second clutch 10 to disengage and the Sy4 side of the first synchronizer 6-3 to engage.

[0108] like Figure 1 , Figure 2 , Figure 3 As shown, when the vehicle speed (transmission output speed) reaches the third curve L III At operating point E, the TCU controller 12 controls the first clutch 9 to disengage and the second clutch 10 to engage. At this time, the combined power of the double planetary gear set 1-6 flows through the first gear 1-6e of the second planetary gear set → transmission output shaft II 11 → second clutch 10 → shift input shaft II 8 → sixth gear pair 6-2 → Sy4 side of the first synchronizer 6-3 → output through shift output shaft 6-5. As the control current of the TCU-controlled speed pump motor assembly 1-3 decreases, the tractor moves along the second curve L. II Continue to accelerate the work forward.

[0109] like Figure 1 , Figure 2 , Figure 3 As shown, when the tractor decelerates, it is the reverse change of the tractor accelerating. At the set working point on the curve, the clutch and synchronizer switch to opposite states instantaneously to ensure that the clutch and synchronizer have the same working state regardless of acceleration or deceleration within each working range of vehicle speed (transmission output speed).

[0110] like Figure 1 , Figure 2 , Figure 3 As shown, when the tractor reverses, the TCU controller 12 controls the engagement of the Sy1 side of the third clutch 4 and the second synchronizer 6-7, adjusting the control current of the speed regulating pump motor assembly 1-3 to a certain value, keeping the tractor stationary. As the control current of the speed regulating pump motor assembly 1-3 increases, the engine speed is split through the transmission input shaft 1-12 and the first gear pair 1-1. One power path is directly transmitted to the first gear 1-6a of the first planetary gear set of the double planetary gear set 1-6, while the other power path passes through the speed regulating pump motor assembly 1-3 → the second gear pair 1-5 → the third gear 1-6c of the second planetary gear set of the double planetary gear set 1-6. After the two power paths merge through the double planetary gear set 1-6, they pass through the third shaft 1-7 → the third gear pair 1-9 → the transmission output shaft III 2 → the third clutch 4 → the shift input shaft III 5 → the fifth gear pair 6-1 → the shift input shaft I. 7 → Eighth gear pair 6-8 → Sy1 side of second synchronizer 6-7 → Output of shift output shaft 6-5, tractor reverses, and gradually and continuously increases speed along the fifth curve L V Work.

[0111] like Figure 1 , Figure 2 , Figure 3 As shown, when the tractor reverses, the TCU controller 12 controls the engagement of the Sy3 side of the third clutch 4 and the second synchronizer 6-7, adjusting the control current of the speed regulating pump motor assembly 1-3 to a certain value. The tractor is stationary. As the control current of the speed regulating pump motor assembly 1-3 increases, the engine speed is split through the transmission input shaft 1-12 and the first gear pair 1-1. One power is directly transmitted to the first gear 1-6a of the first planetary gear set of the double planetary gear set 1-6, and the other power is transmitted through the speed regulating pump motor assembly 1-3 → the second gear pair 1-5 → the third gear 1-6c of the second planetary gear set of the double planetary gear set 1-6. After the two power paths merge through the double planetary gear set 1-6, they pass through the third shaft 1-7 → the third gear pair 1-9 → the transmission output shaft III 2 → the third clutch 4 → the shift input shaft III 5 → the fifth gear pair 6-1 → the shift input shaft I 7 → Ninth gear pair 6-4 → Sy3 side of the second synchronizer 6-7 → Output of the shift output shaft 6-5, the tractor reverses, and gradually and continuously increases speed along the sixth curve L VI Work.

[0112] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention in any way. All equivalent transformations or modifications made in accordance with the essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A continuously variable transmission, characterized in that: It includes a continuously variable transmission (CVT) assembly, a stepped shift assembly, a TCU controller, a first clutch, a second clutch, and a third clutch; The continuously variable transmission (CVT) assembly includes a transmission input shaft, a first gear pair, a second gear pair, a double planetary gear set, a third gear pair, a fourth gear pair, and three transmission output shafts. The transmission input shaft is fixedly connected to the first gear pair and the double planetary gear set, respectively. A speed control pump motor assembly is connected between the first gear pair and the second gear pair, which is loosely fitted on the transmission input shaft. The third and fourth gear pairs include a common gear fixedly connected to the planet carrier of the double planetary gear set. The fourth gear pair is fixedly connected to transmission output shaft I, the double planetary gear set is fixedly connected to transmission output shaft II, and the third gear pair is fixedly connected to transmission output shaft III. The stepped shift assembly includes three shift input shafts, a fifth gear pair, a sixth gear pair, a seventh gear pair, an eighth gear pair, a ninth gear pair, and a shift output shaft. A first synchronizer is provided between the sixth and seventh gear pairs, and a second synchronizer is provided between the eighth and ninth gear pairs. Shift input shaft I is sequentially fixed to the fifth, eighth, and ninth gear pairs, shift input shaft II is sequentially fixed to the sixth and seventh gear pairs, and shift input shaft III is connected to the fifth gear pair. The first and second synchronizers are both fixed to the shift output shaft, and the sixth to ninth gear pairs are loosely fitted on the shift output shaft. The transmission output shaft I is connected to the shift input shaft I via the first clutch, the transmission output shaft II is connected to the shift input shaft II via the second clutch, and the transmission output shaft III is connected to the shift input shaft III via the third clutch. The TCU controller is electrically connected to the first clutch, the second clutch, the third clutch, the first synchronizer, and the second synchronizer. The power transmission route of the continuously variable transmission (CVT) is as follows: the engine speed is split through the transmission input shaft and the first gear pair. One power is directly transmitted to the first gear of the first planetary gear set of the double planetary gear set, and the other power is transmitted through the speed regulating pump motor assembly and the second gear pair to the third gear of the second planetary gear set of the double planetary gear set. After the two power paths are combined through the double planetary gear set, they reach at least one of the three transmission output shafts through the third or fourth gear pair.

2. A continuously variable transmission according to claim 1, characterized in that: The continuously variable transmission (CVT) also includes a first speed sensor for monitoring the speed of the first gear pair, a second speed sensor for monitoring the speed of the second gear pair, a third speed sensor for monitoring the speed of the fifth gear pair, a fourth speed sensor for monitoring the speed of the sixth gear pair, and a fifth speed sensor for monitoring the speed of the shift output shaft. All of the first to fifth speed sensors are electrically connected to the TCU controller.

3. A control method for a continuously variable transmission according to any one of claims 1-2, characterized in that, The synchronizer and clutch are switched alternately by a TCU controller based on the speed difference of the synchronizer; the different clutches are switched alternately based on the speed difference of the clutch; and the tractor speed is continuously adjustable throughout the entire range by changing the displacement of the speed regulating pump motor assembly.

4. The control method for a continuously variable transmission according to claim 3, characterized in that: It includes a forward mode, which consists of forward stage I, forward stage II, forward stage III, and forward stage IV, with gradually increasing speed. During the forward phase I: the TCU controller enables the engagement of the first clutch, the sy1 side of the second synchronizer, and the sy2 side of the first synchronizer, as well as the change in the displacement of the speed regulating pump motor assembly; after the power is transmitted through the transmission output shaft I, it passes through the first clutch, the shift input shaft I, the fifth gear pair, the eighth gear pair, and the sy1 side of the second synchronizer to reach the shift output shaft, and the tractor moves forward, gradually and continuously increasing speed by means of the vector increase in the displacement of the speed regulating pump motor assembly; During the forward phase II: The TCU controller controls the engagement of the second clutch and the sy2 side of the first synchronizer, as well as the change in the displacement of the speed regulating pump motor assembly; after the power is transmitted through the transmission output shaft II, it reaches the shift output shaft through the second clutch, the shift input shaft II, the seventh gear pair, and the sy2 side of the first synchronizer, and the tractor moves forward, gradually and continuously increasing speed by means of the vector decrease in the displacement of the speed regulating pump motor assembly. When the vehicle speed increases to the synchronization point between Forward Stage II and Forward Stage I, the first clutch is disengaged via the TCU controller, while the sy1 side of the second synchronizer remains engaged. When the vehicle speed increases and is slightly higher than the synchronization point between Forward Stage II and Forward Stage I, the first clutch engages, and the sy1 side of the second synchronizer disengages. Power is transmitted through the first clutch, the shift input shaft I, the fifth gear pair, the ninth gear pair, and the sy3 side of the second synchronizer. When the vehicle speed increases to slightly lower than the synchronization point between Forward Stage II and Forward Stage III, the first clutch is disengaged via the TCU controller, and the sy3 side of the second synchronizer engages. Power is transmitted through the shift output shaft, the sy3 side of the second synchronizer, the ninth gear pair, and to the driven side of the first clutch. When the vehicle speed decreases to the synchronization point between Forward Stage III and Forward Stage II, the first clutch disengages via the TCU controller, while the sy3 side of the second synchronizer remains engaged. When the vehicle speed decreases and is slightly below the synchronization point between Forward Stage III and Forward Stage II, the first clutch engages, and the sy3 side of the second synchronizer disengages. Power is transmitted through the first clutch, shift input shaft I, fifth gear pair, eighth gear pair, and the sy1 side of the second synchronizer. When the vehicle speed decreases and is slightly above the synchronization point between Forward Stage II and Forward Stage I, the first clutch disengages via the TCU controller, and the sy1 side of the second synchronizer engages. Power is transmitted through the shift output shaft, the sy1 side of the second synchronizer, the eighth gear pair, and to the driven side of the first clutch. When the vehicle speed decreases to the synchronization point between Forward Stage II and Forward Stage I and further decreases, control is performed according to the control method of Forward Stage I. When moving forward in stage III: the TCU controller enables the engagement of the first clutch and the sy3 side of the second synchronizer, as well as the change of the displacement of the speed control pump motor assembly; after the power is transmitted from the transmission output shaft I, it passes through the first clutch, the shift input shaft I, the fifth gear pair, the ninth gear pair, and the sy3 side of the second synchronizer to reach the shift output shaft, and the tractor moves forward, gradually and continuously increasing speed by means of the vector increase of the displacement of the speed control pump motor assembly; When the vehicle speed increases to the synchronization point between Forward Stage II and Forward Stage III, the second clutch is disengaged via the TCU controller, while the sy2 side of the first synchronizer remains engaged. When the vehicle speed increases and is slightly higher than the synchronization point between Forward Stage III and Forward Stage II, the second clutch engages, and the sy2 side of the first synchronizer disengages. Power is transmitted through the second clutch, the shift input shaft II, the sixth gear pair, and the sy4 side of the first synchronizer. When the vehicle speed increases and is slightly lower than the synchronization point between Forward Stage III and Forward Stage IV, the second clutch is disengaged via the TCU controller, and the sy4 side of the first synchronizer engages. Power is transmitted through the shift output shaft, the sy4 side of the first synchronizer, the sixth gear pair, and to the driven side of the second clutch. When the vehicle speed decreases to the synchronization point between forward stage IV and forward stage III, the second clutch disengages via the TCU controller, while the sy4 side of the first synchronizer remains engaged. When the vehicle speed decreases and is slightly below the synchronization point between forward stage IV and forward stage III, the second clutch engages, and the sy4 side of the first synchronizer disengages. Power is transmitted through the second clutch, shift input shaft II, the seventh gear pair, and the sy2 side of the first synchronizer. When the vehicle speed decreases and is slightly above the synchronization point between forward stage III and forward stage II, the second clutch disengages via the TCU controller, and the sy2 side of the first synchronizer engages. Power is transmitted through the shift output shaft, the sy2 side of the second synchronizer, the seventh gear pair, and to the driven side of the second clutch. When the vehicle speed decreases to the synchronization point between Forward Stage III and Forward Stage II and further decreases, control is performed according to the control method of Forward Stage II; During the forward IV stage: the TCU controller enables the engagement of the second clutch, the sy3 side of the second synchronizer, and the sy4 side of the first synchronizer, as well as the change in the displacement of the speed regulating pump motor assembly; after the power is transmitted through the transmission output shaft II, it reaches the shift output shaft via the second clutch, the shift input shaft II, the sixth gear pair, and the sy4 side of the first synchronizer, and the tractor moves forward, gradually and continuously increasing speed by means of the vector decrease in the displacement of the speed regulating pump motor assembly.

5. The control method for a continuously variable transmission according to claim 3, characterized in that: This includes a reverse mode, which consists of a reverse I stage and a reverse II stage with gradually increasing speed. During reverse section I: The TCU controller controls the engagement of the third clutch and the second synchronizer sy1 side, as well as the change in the displacement of the speed control pump motor assembly. Power is transmitted through the transmission output shaft III, and after passing through the third clutch, shift input shaft III, fifth gear pair, shift input shaft I, eighth gear pair, and the second synchronizer Sy1 side, it is output from the shift output shaft. The vehicle reverses, and gradually and continuously increases speed by means of the vector increase in the displacement of the speed control pump motor assembly. During the reverse phase II: The TCU controller controls the engagement of the third clutch and the second synchronizer sy3 side, as well as the change in the displacement of the speed control pump motor assembly. After passing through the third clutch, shift input shaft III, fifth gear pair, shift input shaft I, ninth gear pair, and the second synchronizer Sy3 side, the output is sent to the shift output shaft, causing the vehicle to reverse. The speed is gradually and continuously increased by means of the vector increase in the displacement of the speed control pump motor assembly.

6. A tractor, characterized in that, The tractor is equipped with a continuously variable transmission as described in any one of claims 1-2.

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