DHT hybrid transmission

Abstract

The utility model discloses a DHT hybrid transmission, including ICE engine, ICE engine is connected with the main shaft front section through the clutch, and the main shaft rear section is connected power coupling gear group and main shaft rear gear group in proper order, and the main shaft end connects the transmission power output flange of vehicle.

Description

Technical Field

[0001] This utility model belongs to the technical field of power transmission system for mining vehicles, and relates to a DHT hybrid transmission. Background Technology

[0002] Currently, the technical routes and markets for power transmission systems in wide-body mining trucks include the following: 1. Traditional internal combustion engine paired with a transmission: the technology is mature, but the maintenance and operating costs are too high and do not meet market demands; 2. Mid-mounted pure electric: the technology is mature and the maintenance and operating costs are low, but the purchase cost is high, suitable for specific markets such as heavy-load downhill driving; 3. Wheel-end pure electric solution: the structure is simple and the maintenance and operating costs are low, but the purchase cost is high, suitable for specific markets such as heavy-load downhill driving. There is an urgent need for a low-cost power transmission system for mining trucks that can be adapted to most markets. Utility Model Content

[0003] In order to overcome the shortcomings of the existing technology, the purpose of this utility model is to provide a DHT hybrid transmission that combines an internal combustion engine and an electric motor in HEV hybrid mode, with low operating and maintenance costs and the ability to adapt to most markets.

[0004] The technical solution adopted by this utility model is: a DHT hybrid transmission, including an ICE engine, the ICE engine is connected to the front section of the main shaft through a clutch, the rear section of the main shaft is connected to a power coupling gear set and a rear gear set of the main shaft in sequence, and the end of the main shaft is connected to the transmission power output flange.

[0005] Furthermore, it also includes an ISG motor, which is positioned between the clutch and the power coupling gear set. The ISG motor is connected to the front section of the main shaft via the ISG power transmission gear pair.

[0006] Furthermore, the ISG power transmission gear pair includes an ISG driving gear and an ISG driven gear that mesh with each other; the ISG motor output shaft is connected to the ISG driving gear, and the ISG driven gear is installed at the front of the main shaft.

[0007] Furthermore, it also includes a TM motor, which is connected to a TM drive gear via a TM power output gear shaft; the TM drive gear meshes with a power coupling gear set.

[0008] Furthermore, the power coupling gear set includes a power coupling output gear, and on the other side of the power coupling output gear is a TM driven gear, which meshes with the TM driving gear; the power coupling engagement teeth of the power coupling output gear can selectively mesh with the splined hub of the first shift group; the power coupling engagement teeth and the splined hub of the first shift group form the first shift assembly.

[0009] Furthermore, the rear gear set of the main shaft includes rear main shaft gear one, rear main shaft gear two, rear main shaft gear three, rear main shaft gear four, rear main shaft gear five, rear main shaft gear six, and rear main shaft gear seven arranged sequentially along the main shaft;

[0010] A second shifting assembly is arranged between rear main shaft gear 1, rear main shaft gear 2, rear main shaft gear 3, and rear main shaft gear 4; a third shifting assembly is arranged between rear main shaft gear 5, rear main shaft gear 6, and rear main shaft gear 7.

[0011] Furthermore, the second shift assembly includes a left second shift assembly located between the first rear main shaft gear and the second rear main shaft gear, and a right second shift assembly located between the third rear main shaft gear and the fourth rear main shaft gear;

[0012] The second shift assembly consists of the first left engagement gear of the second shift group, the left splined hub of the second shift group, and the second left engagement gear of the second shift group; the first left engagement gear of the second shift group is connected to the first rear main shaft gear, and the second left engagement gear of the second shift group is connected to the second rear main shaft gear.

[0013] The second shift assembly consists of the first right engagement gear of the second shift group, the right splined hub of the second shift group, and the second right engagement gear of the second shift group; the first right engagement gear of the second shift group is connected to the third rear main shaft gear, and the second right engagement gear of the second shift group is connected to the fourth rear main shaft gear.

[0014] Furthermore, the third shift assembly includes a third shift assembly left located between rear main shaft gear five and rear main shaft gear six, and a third shift assembly right located between rear main shaft gear six and rear main shaft gear seven;

[0015] The third shift assembly consists of the third shift group left engagement gear one, the third shift group left spline hub, and the third shift group left engagement gear two; the third shift group left engagement gear one is connected to the rear main shaft gear five, and the third shift group left engagement gear two is connected to one side of the rear main shaft gear six.

[0016] The third shift assembly consists of the right engagement gear 1 of the third shift group, the right splined hub of the third shift group, and the right engagement gear 2 of the third shift group; the right engagement gear 1 of the third shift group is connected to the other side of the rear main shaft gear 6; the right engagement gear 2 of the third shift group is connected to the rear main shaft gear 7.

[0017] Furthermore, it also includes a first sub-shaft assembly and a third sub-shaft assembly located on both sides of the rear main shaft gear 1, rear main shaft gear 2, rear main shaft gear 3, and rear main shaft gear 4;

[0018] The first secondary shaft assembly consists of a first secondary shaft and first secondary shaft gear 1, first secondary shaft gear 2, first secondary shaft gear 3, and first secondary shaft gear 4 arranged thereon in sequence; first secondary shaft gear 1, first secondary shaft gear 2, first secondary shaft gear 3, and first secondary shaft gear 4 respectively mesh with rear main shaft gear 1, rear main shaft gear 2, rear main shaft gear 3, and rear main shaft gear 4;

[0019] The third auxiliary shaft assembly consists of a third auxiliary shaft and three gears arranged sequentially on it: third auxiliary shaft gear 1, third auxiliary shaft gear 2, third auxiliary shaft gear 3, and third auxiliary shaft gear 4. The third auxiliary shaft gear 1, third auxiliary shaft gear 2, third auxiliary shaft gear 3, and third auxiliary shaft gear 4 respectively mesh with the rear main shaft gear 1, rear main shaft gear 2, rear main shaft gear 3, and rear main shaft gear 4.

[0020] Furthermore, it also includes a second and a fourth sub-shaft assembly located on both sides of the rear main shaft gear five, rear main shaft gear six, and rear main shaft gear seven;

[0021] The second auxiliary shaft assembly consists of a second auxiliary shaft and two gears arranged sequentially thereon: second auxiliary shaft gear 1, second auxiliary shaft gear 2, second auxiliary shaft gear 3, and second auxiliary shaft gear 4. Second auxiliary shaft gear 1 meshes with the power coupling gear set, and second auxiliary shaft gears 2, 3, and 4 mesh with rear main shaft gear 5, 6, and 7, respectively.

[0022] The fourth countershaft assembly consists of a fourth countershaft and four fourth countershaft gears arranged sequentially thereon: fourth countershaft gear one, fourth countershaft gear two, fourth countershaft gear three, and fourth countershaft gear four. Fourth countershaft gear one meshes with the power coupling gear set, while fourth countershaft gear two, fourth countershaft gear three, and fourth countershaft gear four mesh with rear main shaft gear five, rear main shaft gear six, and rear main shaft gear seven, respectively.

[0023] The beneficial effects of this utility model are:

[0024] 1. Dual transmissions: the front section is powered by coupling, allowing for mutual gear sharing; the rear section of the dual transmissions is powered by coupling, enabling seamless gear shifting without power interruption.

[0025] 2. The coordinated operation of multiple power sources improves safety and reliability and efficiency; smooth mode switching: pure electric, hybrid, and regenerative braking effectively avoid power interruption and shock.

[0026] 3. Through the efficient coordination between multiple sets of shifting actuators, efficient collaboration between gear sets is achieved, resulting in lower energy consumption and making it more suitable for the matching needs of heavy-duty vehicles with large tonnage. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of the DHT hybrid transmission of this utility model;

[0028] Figure 2 This is a schematic diagram of the intermediate shaft structure of the DHT hybrid transmission of this utility model;

[0029] Figure 3 This is a schematic diagram of the front box structure of the DHT hybrid transmission of this utility model;

[0030] Figure 4 This is a schematic diagram of the rear compartment structure of the DHT hybrid transmission of this utility model.

[0031] In the diagram, 1. ICE engine, 2. clutch, 3. main shaft, 4. ISG motor, 5. ISG power transmission gear pair, 6. power coupling gear set, 7. first countershaft assembly, 8. second countershaft assembly, 9. main shaft rear gear set, 10. gearbox power output flange, 11. third shift assembly, 12. second shift assembly, 13. fourth countershaft assembly, 14. third countershaft assembly, 15. first shift assembly, 16. TM power output gear shaft, 17. TM motor;

[0032] 5-1. ISG drive gear; 5-2. ISG driven gear;

[0033] 6-1. TM driven gear, 6-2. power coupling output gear, 6-3. power coupling engagement gear, 6-4. first shift group splined hub;

[0034] 7-1. First countershaft gear one; 7-2. First countershaft gear two; 7-3. First countershaft gear three; 7-4. First countershaft gear four;

[0035] 8-1. Second countershaft gear one; 8-2. Second countershaft gear two; 8-3. Second countershaft gear three; 8-4. Second countershaft gear four;

[0036] 9-1. Rear main shaft gear one, 9-2. Rear main shaft gear two, 9-3. Rear main shaft gear three, 9-4. Rear main shaft gear four, 9-5. Rear main shaft gear five, 9-6. Rear main shaft gear six, 9-7. Rear main shaft gear seven;

[0037] 11-1. Third shift assembly left, 11-1a. Third shift group left engagement tooth one, 11-1b. Third shift group left splined hub, 11-1c. Third shift group left engagement tooth two, 11-2. Third shift assembly right, 11-2a. Third shift group right engagement tooth one, 11-2b. Third shift group right splined hub, 11-2c. Third shift group right engagement tooth two;

[0038] 12-1. Second shift assembly left, 12-1a. Second shift group left engagement tooth one, 12-1b. Second shift group left splined hub, 12-1c. Second shift group left engagement tooth two, 12-2. Second shift assembly right, 12-2a. Second shift group right engagement tooth one, 12-2b. Second shift group right splined hub, 12-2c. Second shift group right engagement tooth two;

[0039] 13-1. Fourth countershaft gear one; 13-2. Fourth countershaft gear two; 13-3. Fourth countershaft gear three; 13-4. Fourth countershaft gear four;

[0040] 14-1. Third countershaft gear one, 14-2. Third countershaft gear two, 14-3. Third countershaft gear three, 14-4. Third countershaft gear four. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0042] like Figure 1-4 As shown, a DHT hybrid transmission includes an ICE engine 1, which is connected to the front section of a main shaft 3 via a clutch 2. The rear section of the main shaft 3 is sequentially connected to a power coupling gear set 6 and a rear gear set 9. The end of the main shaft 3 is connected to the transmission power output flange 10 of the vehicle.

[0043] It also includes an ISG motor 4, which is located between the clutch 2 and the power coupling gear set 6. The ISG motor 4 is connected to the front section of the main shaft 3 through the ISG power transmission gear pair 5.

[0044] The ISG power transmission gear pair 5 includes an ISG driving gear 5-1 and an ISG driven gear 5-2 that mesh with each other; the output shaft of the ISG motor 4 is connected to the ISG driving gear 5-1, and the ISG driven gear 5-2 is installed at the front of the main shaft 3.

[0045] It also includes a TM motor 17, which is connected to a TM drive gear 16-1 via a TM power output gear shaft 16; the TM drive gear 16-1 meshes with a power coupling gear set 6.

[0046] The power coupling gear set 6 includes a power coupling output gear 6-2, and on the other side of the power coupling output gear 6-2 is a TM driven gear 6-1, which meshes with the TM driving gear 16-1; the power coupling engagement teeth 6-3 of the power coupling output gear 6-2 can selectively mesh with the first shift group splined hub 6-4; the power coupling engagement teeth 6-3 and the first shift group splined hub 6-4 form the first shift assembly 15.

[0047] The rear gear set 9 of the main shaft includes the following rear main shaft gears arranged sequentially along the main shaft 3: rear main shaft gear 1 9-1, rear main shaft gear 2 9-2, rear main shaft gear 3 9-3, rear main shaft gear 4 9-4, rear main shaft gear 5 9-5, rear main shaft gear 6 9-6, and rear main shaft gear 7 9-7.

[0048] A second shifting assembly 12 is arranged between the rear main shaft gear 1 (9-1), the rear main shaft gear 2 (9-2), the rear main shaft gear 3 (9-3), and the rear main shaft gear 4 (9-4); a third shifting assembly 11 is arranged between the rear main shaft gear 5 (9-5), the rear main shaft gear 6 (9-6), and the rear main shaft gear 7 (9-7).

[0049] The second shift assembly 12 includes a second shift assembly left 12-1 located between the rear main shaft gear 1 9-1 and the rear main shaft gear 2 9-2, and a second shift assembly right 12-2 located between the rear main shaft gear 3 9-3 and the rear main shaft gear 4 9-4;

[0050] The second shift assembly left 12-1 consists of the second shift group left engagement gear one 12-1a, the second shift group left spline hub 12-1b, and the second shift group left engagement gear two 12-1c; the second shift group left engagement gear one 12-1a is connected to the rear main shaft gear one 9-1, and the second shift group left engagement gear two 12-1c is connected to the rear main shaft gear two 9-2.

[0051] The second shift assembly right 12-2 consists of the second shift group right engagement gear one 12-2a, the second shift group right splined hub 12-2b, and the second shift group right engagement gear two 12-2c; the second shift group right engagement gear one 12-2a is connected to the rear main shaft gear three 9-3, and the second shift group right engagement gear two 12-2c is connected to the rear main shaft gear four 9-4.

[0052] The third shift assembly 11 includes a third shift assembly left 11-1 located between the rear main shaft gear 5 9-5 and the rear main shaft gear 6 9-6, and a third shift assembly right 11-2 located between the rear main shaft gear 6 9-6 and the rear main shaft gear 7 9-7;

[0053] The third shift assembly left 11-1 consists of the third shift group left engagement gear one 11-1a, the third shift group left spline hub 11-1b, and the third shift group left engagement gear two 11-1c; the third shift group left engagement gear one 11-1a is connected to the rear main shaft gear five 9-5, and the third shift group left engagement gear two 11-1c is connected to one side of the rear main shaft gear six 9-6.

[0054] The third shift assembly right 11-2 consists of the third shift group right engagement gear one 11-2a, the third shift group right splined hub 11-2b, and the third shift group right engagement gear two 11-2c; the third shift group right engagement gear one 11-2a is connected to the other side of the rear main shaft gear six 9-6; the third shift group right engagement gear two 11-2c is connected to the rear main shaft gear seven 9-7.

[0055] It also includes a first sub-shaft assembly 7 and a third sub-shaft assembly 14 located on both sides of the rear main shaft gear 9-1, the rear main shaft gear 9-2, the rear main shaft gear 9-3, and the rear main shaft gear 9-4;

[0056] The first secondary shaft assembly 7 consists of a first secondary shaft and first secondary shaft gears 7-1, 7-2, 7-3, and 7-4 arranged sequentially thereon; the first secondary shaft gears 7-1, 7-2, 7-3, and 7-4 mesh with the rear main shaft gears 9-1, 9-2, 9-3, and 9-4 respectively.

[0057] The third auxiliary shaft assembly 14 consists of a third auxiliary shaft and three auxiliary shaft gears arranged sequentially thereon: a first auxiliary shaft gear 14-1, a second auxiliary shaft gear 14-2, a third auxiliary shaft gear 14-3, and a fourth auxiliary shaft gear 14-4. The first auxiliary shaft gear 14-1, the second auxiliary shaft gear 14-2, the third auxiliary shaft gear 14-3, and the fourth auxiliary shaft gear 14-4 mesh with the rear main shaft gears 19-1, 29-2, 39-3, and 49-4, respectively.

[0058] It also includes a second sub-shaft assembly 8 and a fourth sub-shaft assembly 13 located on both sides of the rear main shaft gear 9-5, the rear main shaft gear 9-6, and the rear main shaft gear 9-7;

[0059] The second auxiliary shaft assembly 8 consists of a second auxiliary shaft and, sequentially arranged thereon, second auxiliary shaft gear 1 8-1, second auxiliary shaft gear 2 8-2, second auxiliary shaft gear 3 8-3, and second auxiliary shaft gear 4 8-4; second auxiliary shaft gear 1 8-1 meshes with the power coupling output gear 6-2 of the power coupling gear set 6, and second auxiliary shaft gear 2 8-2, second auxiliary shaft gear 3 8-3, and second auxiliary shaft gear 4 8-4 mesh with the rear main shaft gear 5 9-5, rear main shaft gear 6 9-6, and rear main shaft gear 7 9-7, respectively;

[0060] The fourth secondary shaft assembly 13 consists of a fourth secondary shaft and four secondary shaft gears arranged sequentially thereon: fourth secondary shaft gear 13-1, fourth secondary shaft gear 2 13-2, fourth secondary shaft gear 3 13-3, and fourth secondary shaft gear 4 13-4. Fourth secondary shaft gear 13-1 meshes with the power coupling output gear 6-2 of the power coupling gear set 6, and fourth secondary shaft gear 2 13-2, fourth secondary shaft gear 3 13-3, and fourth secondary shaft gear 4 13-4 mesh with the rear main shaft gear 5 9-5, rear main shaft gear 6 9-6, and rear main shaft gear 7 9-7, respectively.

[0061] A DHT hybrid transmission, its operating state and control process for different gears are as follows: ;

[0062] In the table: ● represents start-up, ○ represents stop-operation, "left" represents the left side of the shift assembly, "right" represents the right side of the shift assembly, ↑ represents the sliding engagement sleeve in the shift assembly being in the middle position, i.e., not engaging in transmission, and "←" and "→" respectively represent the sliding engagement sleeve in the shift assembly being in the left or right position, respectively, and engaging in shifting and transmission.

[0063] The advantages of this transmission are:

[0064] 1. Dual transmissions: the front section is powered by coupling, allowing for mutual gear sharing; the rear section of the dual transmissions is powered by coupling, enabling seamless gear shifting without power interruption.

[0065] 2. The coordinated operation of multiple power sources improves safety and reliability and efficiency; smooth mode switching: pure electric, hybrid, and regenerative braking effectively avoid power interruption and shock.

[0066] 3. Through the efficient coordination between multiple sets of shifting actuators, efficient collaboration between gear sets is achieved, resulting in lower energy consumption and making it more suitable for the matching needs of heavy-duty vehicles with large tonnage.

Claims

1. A DHT hybrid transmission, characterized in that, It includes an ICE engine (1), which is connected to the front section of the main shaft (3) via a clutch (2). The rear section of the main shaft (3) is connected to the power coupling gear set (6) and the rear gear set (9) of the main shaft in sequence. The end of the main shaft (3) is connected to the power output flange (10) of the vehicle's gearbox.

2. The DHT hybrid transmission according to claim 1, characterized in that, It also includes an ISG motor (4), which is arranged between the clutch (2) and the power coupling gear set (6). The ISG motor (4) is connected to the front section of the main shaft (3) through the ISG power transmission gear pair (5).

3. A DHT hybrid transmission according to claim 2, characterized in that, The ISG power transmission gear pair (5) includes an ISG driving gear (5-1) and an ISG driven gear (5-2) that mesh with each other; the output shaft of the ISG motor (4) is connected to the ISG driving gear (5-1), and the ISG driven gear (5-2) is installed on the front section of the main shaft (3).

4. A DHT hybrid transmission according to claim 1, characterized in that, It also includes a TM motor (17), which is connected to a TM drive gear (16-1) via a TM power output gear shaft (16); the TM drive gear (16-1) meshes with a power coupling gear set (6).

5. A DHT hybrid transmission according to claim 4, characterized in that, The power coupling gear set (6) includes a power coupling output gear (6-2), and a TM driven gear (6-1) on the other side of the power coupling output gear (6-2). The TM driven gear (6-1) meshes with the TM driving gear (16-1). The power coupling engagement teeth (6-3) of the power coupling output gear (6-2) can selectively mesh with the first shift group spline hub (6-4). The power coupling engagement teeth (6-3) and the first shift group spline hub (6-4) form the first shift assembly (15).

6. A DHT hybrid transmission according to claim 1, characterized in that, The main shaft rear gear set (9) includes rear main shaft gear one (9-1), rear main shaft gear two (9-2), rear main shaft gear three (9-3), rear main shaft gear four (9-4), rear main shaft gear five (9-5), rear main shaft gear six (9-6), and rear main shaft gear seven (9-7) arranged sequentially along the main shaft (3). A second shifting assembly (12) is arranged between the rear main shaft gear 1 (9-1), the rear main shaft gear 2 (9-2), the rear main shaft gear 3 (9-3), and the rear main shaft gear 4 (9-4); a third shifting assembly (11) is arranged between the rear main shaft gear 5 (9-5), the rear main shaft gear 6 (9-6), and the rear main shaft gear 7 (9-7).

7. A DHT hybrid transmission according to claim 6, characterized in that, The second shift assembly (12) includes a second shift assembly left (12-1) located between the first rear main shaft gear (9-1) and the second rear main shaft gear (9-2), and a second shift assembly right (12-2) located between the third rear main shaft gear (9-3) and the fourth rear main shaft gear (9-4). The left (12-1) of the second shift assembly consists of the first left engagement gear of the second shift group (12-1a), the left splined hub of the second shift group (12-1b), and the second left engagement gear of the second shift group (12-1c); the first left engagement gear of the second shift group (12-1a) is connected to the first rear main shaft gear (9-1), and the second left engagement gear of the second shift group (12-1c) is connected to the second rear main shaft gear (9-2); The right (12-2) of the second shift assembly consists of the first right engagement gear of the second shift group (12-2a), the right splined hub of the second shift group (12-2b), and the second right engagement gear of the second shift group (12-2c). The first right engagement gear of the second shift group (12-2a) is connected to the third rear main shaft gear (9-3), and the second right engagement gear of the second shift group (12-2c) is connected to the fourth rear main shaft gear (9-4).

8. A DHT hybrid transmission according to claim 6, characterized in that, The third shift assembly (11) includes a third shift assembly left (11-1) located between the rear main shaft gear five (9-5) and the rear main shaft gear six (9-6) and a third shift assembly right (11-2) located between the rear main shaft gear six (9-6) and the rear main shaft gear seven (9-7). The left (11-1) of the third shift assembly consists of the first left engagement gear of the third shift group (11-1a), the left splined hub of the third shift group (11-1b), and the second left engagement gear of the third shift group (11-1c); the first left engagement gear of the third shift group (11-1a) is connected to the fifth rear main shaft gear (9-5), and the second left engagement gear of the third shift group (11-1c) is connected to one side of the sixth rear main shaft gear (9-6); The right (11-2) of the third shift assembly consists of the right engagement gear 1 (11-2a), the right splined hub (11-2b), and the right engagement gear 2 (11-2c); the right engagement gear 1 (11-2a) is connected to the other side of the rear main shaft gear 6 (9-6); the right engagement gear 2 (11-2c) is connected to the rear main shaft gear 7 (9-7).

9. A DHT hybrid transmission according to claim 6, characterized in that, It also includes a first sub-shaft assembly (7) and a third sub-shaft assembly (14) located on both sides of the rear main shaft gear 1 (9-1), rear main shaft gear 2 (9-2), rear main shaft gear 3 (9-3), and rear main shaft gear 4 (9-4). The first secondary shaft assembly (7) consists of a first secondary shaft and first secondary shaft gear 1 (7-1), first secondary shaft gear 2 (7-2), first secondary shaft gear 3 (7-3), and first secondary shaft gear 4 (7-4) arranged thereon in sequence; the first secondary shaft gear 1 (7-1), first secondary shaft gear 2 (7-2), first secondary shaft gear 3 (7-3), and first secondary shaft gear 4 (7-4) mesh with the rear main shaft gear 1 (9-1), rear main shaft gear 2 (9-2), rear main shaft gear 3 (9-3), and rear main shaft gear 4 (9-4) respectively; The third auxiliary shaft assembly (14) consists of a third auxiliary shaft and three gears arranged sequentially thereon: a third auxiliary shaft gear 1 (14-1), a third auxiliary shaft gear 2 (14-2), a third auxiliary shaft gear 3 (14-3), and a third auxiliary shaft gear 4 (14-4). The third auxiliary shaft gear 1 (14-1), the third auxiliary shaft gear 2 (14-2), the third auxiliary shaft gear 3 (14-3), and the third auxiliary shaft gear 4 (14-4) mesh with the rear main shaft gear 1 (9-1), the rear main shaft gear 2 (9-2), the rear main shaft gear 3 (9-3), and the rear main shaft gear 4 (9-4), respectively.

10. A DHT hybrid transmission according to claim 6, characterized in that, It also includes a second sub-shaft assembly (8) and a fourth sub-shaft assembly (13) located on both sides of the rear main shaft gear five (9-5), the rear main shaft gear six (9-6), and the rear main shaft gear seven (9-7). The second secondary shaft assembly (8) consists of a second secondary shaft and second secondary shaft gears 1 (8-1), 2 (8-2), 3 (8-3), and 4 (8-4) arranged sequentially thereon; the second secondary shaft gear 1 (8-1) meshes with the power coupling gear set (6), and the second secondary shaft gears 2 (8-2), 3 (8-3), and 4 (8-4) mesh with the rear main shaft gear 5 (9-5), 6 (9-6), and 7 (9-7) respectively; The fourth secondary shaft assembly (13) consists of a fourth secondary shaft and four gears arranged sequentially thereon: fourth secondary shaft gear 1 (13-1), fourth secondary shaft gear 2 (13-2), fourth secondary shaft gear 3 (13-3), and fourth secondary shaft gear 4 (13-4). Fourth secondary shaft gear 1 (13-1) meshes with the power coupling gear set (6), and fourth secondary shaft gear 2 (13-2), fourth secondary shaft gear 3 (13-3), and fourth secondary shaft gear 4 (13-4) mesh with rear main shaft gear 5 (9-5), rear main shaft gear 6 (9-6), and rear main shaft gear 7 (9-7), respectively.

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