Electric hydraulic gear shifting device for tractor shuttle gear box and control method thereof

Abstract

An electro-hydraulic shifting device for a tractor shuttle gearbox includes a gear shift lever cylinder, a high / low gear cylinder, a shift block cylinder, and a forward / reverse gear cylinder located under the gearbox cover. The combined movement of these cylinders controls the gearbox to any gear, forward, neutral, or reverse position. An electric clutch pushrod controls the engagement or disengagement of the clutch friction plates. Each cylinder is directly controlled by a bidirectional electric gear pump, and the TCU controls the forward / reverse rotation of the bidirectional electric gear pump and the cylinder's extension / retraction speed. The TCU monitors the gearbox's first and second shaft speeds, button signals, and displacement sensor signals. It receives shift, stop, forward / reverse, and high / low gear commands via a CAN interface, controlling the gearbox's shifting, stopping, and braking actions. This device combines manual shifting with computer-programmed shifting. The hydraulic cylinders are directly driven by the electric pump, preventing jamming and allowing for precise control of cylinder extension / retraction.

Description

Technical Field

[0001] This invention belongs to the field of tractor gearboxes, specifically relating to an automatic shifting device and its control for a tractor shuttle gearbox. Background Technology

[0002] In my country, over 95% of tractor shuttle gearboxes use mechanical shifting, which has advantages such as simple structure, reliable operation, easy maintenance, and low cost. However, with the increasing scale of agricultural production, the workload of drivers is also increasing. To reduce the workload of drivers, some new technologies for tractor shuttle gearboxes have been developed both domestically and internationally. For example, shuttle gearboxes are equipped with separate forward and reverse operating levers, simplifying the operation of switching conventional gears. Patent "An Electronically Controlled Hydraulic Speed-Regulating Tractor Gear Shifting System" (CN204267711U) proposes to control tractor gear shifting by controlling the hydraulic device through an electronic system. Patent "An Electro-hydraulic Control System for Tractor Shuttle Gearbox Clutch and Tractor" (CN216951376U) proposes an electronically controlled hydraulic speed regulation scheme. However, when the hydraulic oil is contaminated, the valve core of the solenoid valve is easily jammed, which can cause the gearbox to become uncontrollable and lead to the danger of the tractor going out of control. The patent "An Electro-hydraulic Control System for Power Shift of a Tractor" (CN112065985A) discloses an electro-hydraulic control system for power shift of a tractor. Its advantage is that the power is not interrupted during the shifting process, which can significantly improve the efficiency of labor operations. However, its cost is particularly high, making it difficult to popularize in small and medium horsepower tractors.

[0003] To overcome the shortcomings of existing automatic shifting technology for tractor shuttle gearboxes, this invention provides an electro-hydraulic shifting device for tractor shuttle gearboxes. It not only avoids loss of control caused by jamming of the electromagnetic hydraulic valve core, but also has a lower cost and is suitable for small and medium horsepower tractors.

[0004] The technical solution adopted by this invention to solve its technical problem is as follows: The structure and transmission relationship of the shuttle-type gearbox remain unchanged. In the longitudinal direction under the cover, a gear shift cylinder and a high / low gear cylinder are added side-by-side. The gear shift cylinder pushes and pulls the gear shift lever to switch the shuttle-type gearbox between first and second gear or between third and fourth gear. The high / low gear cylinder pushes and pulls the high / low gear lever to switch the high / low gear shift fork between high and low gear positions. In the transverse direction under the cover, a shift block cylinder is added. It pushes and pulls the shift block so that the gear shift lever is either in the groove of the first / second gear shift fork or in the groove of the third / fourth gear shift fork. These three cylinders are spatially offset from the manual shifting mechanism.

[0005] A forward / reverse cylinder is added to the direction of movement of the shift fork. This cylinder pushes and pulls the shift fork to switch the shuttle gearbox between forward, neutral, and reverse. It is also spatially offset from the manually operated forward / reverse rocker arm, so manual forward, stop, and reverse movements are still possible. The clutch control lever is replaced by an electric clutch push rod. Its extended end is hinged to the clutch rocker arm, which engages or disengages the clutch friction plates via a friction plate actuation shaft. When it returns to its initial extended state, the self-locking mechanism inside the electric clutch push rod makes it a straight rod, allowing manual pedal operation to control clutch engagement or disengagement. A speed sensor for one shaft is installed on the bracket next to the gear at the input end of the first shaft. The pulse signal generated by the rotation of the first shaft is captured by the counter port of the TCU, thus calculating the speed of the first shaft. A speed sensor for the second shaft is installed on the bracket next to the gear at the extended end of the second shaft. The pulse signal generated by the rotation of the second shaft is captured by the counter port of the TCU, thus calculating the speed of the second shaft.

[0006] The bidirectional electric gear pump consists of a miniature DC motor, a synchronous belt drive, and a bidirectional gear pump. The miniature DC motor drives the input shaft of the bidirectional gear pump to rotate via the synchronous belt drive. The bidirectional gear pump comprises a pump body, end cover, a pair of gear sets, two check valves, two pressure regulating valves, an oil inlet, an oil return port, and ports A and B. The pump body, end cover, and gear sets form two oil chambers, which are connected to ports A and B respectively. The heads of the two check valves are connected to the oil inlet passage, and the tails are connected to the oil passages of the oil chambers. The driving gear and the driven synchronous belt pulley of the gear set are coaxial, and the number of teeth on the driven gear is equal to that of the driving gear. The heads of the two pressure regulating valves are connected to the oil passages of the oil chambers, and the tails are connected to the oil return passages.

[0007] Each hydraulic cylinder is directly controlled by a bidirectional electric gear pump for its extension and retraction. The A and B ports of the bidirectional gear pump are connected to the A and B ports of the hydraulic cylinder via oil pipes. When the micro DC motor of the bidirectional electric gear pump rotates forward under the control of the TCU, the bidirectional gear pump directly drives the cylinder's push rod to extend; when the micro DC motor rotates in reverse under the control of the TCU, the bidirectional gear pump directly drives the cylinder's push rod to retract. The PWM signal output by the TCU controls the speed of the micro DC motor, thereby controlling the flow rate of the hydraulic oil and the movement speed of the cylinder's push rod. When the duty cycle of the PWM signal rapidly drops to zero, the cylinder's push rod immediately stops moving, achieving precise displacement control.

[0008] The speed pulse signals from the first and second shafts are connected to the TCU's counter port. The signals from the upshift button, downshift button, stop button, and the left and right limit switches of the shift paddles are connected to the digital signal port. The displacement sensor signals from the shift paddle cylinder, high / low gear cylinder, forward / reverse gear cylinder, clutch electric push rod, and accelerator pedal angular displacement sensor are connected to the analog signal port. The TCU control output port connects to the clutch electric push rod, brake electric push rod, forward / reverse gear electro-hydraulic system, shift paddle electro-hydraulic system, shift paddle electro-hydraulic system, and high / low gear electro-hydraulic system. The TCU's CAN port can receive commands from the host computer to control gear shifting, acquire digital signals, acquire analog signals, and also request engine speed data from the engine ECU or adjust the throttle opening.

[0009] After the TCU is powered on, it initializes the internal microcontroller's I / O ports, A / D converter, CAN communication, UART communication, counter, and timer. The program runs in a cyclic scanning manner: it checks the CAN interrupt flag; when the TCU experiences a CAN interrupt, it parses the received data string: if it is a command to set displacement sensor parameters, it updates the corresponding displacement sensor parameters and saves them to the EEPROM; if it is a gear control command, the TCU immediately checks the current gear. When acceleration and upshifting are required, the TCU sends an accelerator command to the engine ECU. Simultaneously, the TCU monitors the speed of the primary shaft of the shuttle gearbox. When the speed reaches 2500 rpm, the TCU controls the clutch electric push rod to extend its full stroke, the clutch friction plates are disengaged, and the primary shaft loses power but continues to rotate due to inertia. If shifting from first to second gear, or from third to fourth gear, the electro-hydraulic system controls the retraction of the shifter cylinder. When the shifter cylinder retracts 50% of its travel, the electro-hydraulic system pauses. When the speed of the first shaft matches the speed of the second shaft, the electro-hydraulic system controls the retraction of the shifter cylinder again. When the shifter cylinder retracts 100% of its travel, the clutch electric push rod retracts 25% of its travel, monitoring the speed of the first shaft. If it does not continue to decrease, the clutch electric push rod retracts fully; otherwise, it waits for the speed of the first shaft to stabilize before retracting fully. If shifting from second to third gear, the electro-hydraulic system controls... When the shift lever cylinder extends, and the extension stroke reaches 50%, the shift lever electro-hydraulic system is paused. The shift block electro-hydraulic system controls the shift block cylinder to retract until fully retracted. The shift lever electro-hydraulic system then controls the shift lever cylinder to extend again. When the shift lever cylinder reaches 100% of its extension stroke, the clutch electric push rod continues to retract following the same shifting procedure from first to second gear. When downshifting is required, the TCU controls the clutch electric push rod to extend its full stroke, disengaging the clutch friction plates. The primary shaft loses power, and its speed continuously decreases. The shift lever electro-hydraulic system then controls the shift lever cylinder to extend again. When the shift lever cylinder reaches 50% of its extension stroke, the shift lever electro-hydraulic system is paused. In the electro-hydraulic system, when the speed of the second shaft is detected to be consistent with the set gear speed, the shift lever electro-hydraulic system controls the shift lever cylinder to extend again. When the shift lever cylinder reaches 100% of its extension stroke, the clutch electric push rod retracts 25% of its stroke. The speed of the first shaft is monitored. If it does not continue to decrease, the clutch electric push rod extends fully. Otherwise, it waits for the speed of the first shaft to stabilize before fully extending the clutch electric push rod. If it is a high / low gear switching command, the clutch electric push rod extends to disengage the clutch friction plates. The high / low gear electro-hydraulic system controls the high / low gear cylinder to extend or retract to the end, and the clutch electric push rod retracts to re-engage the clutch friction plates.If the command is to shift gears, the clutch electric push rod extends, disengaging the clutch friction plates. The forward / reverse electro-hydraulic system controls the forward / reverse cylinders to extend or retract fully. If the speed of the two shafts is zero, the clutch electric push rod retracts, engaging the clutch friction plates. If the speed of the two shafts is greater than zero, the clutch electric push rod retracts following the same steps as shifting from 1st to 2nd gear. If the command is to stop, the clutch electric push rod extends, disengaging the clutch friction plates. The forward / reverse electro-hydraulic system controls the forward / reverse cylinders to extend or retract 50% of their stroke. Then, the brake electric push rod retracts, braking the tractor. When the speed of the two shafts drops to zero, the brake electric push rod extends and returns to its original length. Inspect the digital signal ports to collect signals from the left and right limits of the shift paddles, the upshift / downshift buttons, the downshift / reverseshift buttons, and the stop button. Inspect the analog signal ports, activate the A / D converter, and collect signals from the accelerator pedal angular displacement, clutch electric push rod displacement, shift paddle cylinder displacement, high / low gear cylinder displacement, and forward / reverse gear cylinder displacement. When the upshift button is detected being pressed, the clutch electric push rod, gear shift cylinder, and shift lever cylinder operate according to the upshift control method and steps under the shift command. When the downshift button is detected being pressed, the clutch electric push rod, gear shift cylinder, and shift lever cylinder operate according to the downshift control method and steps under the shift command. When the stop button is detected being pressed, the clutch electric push rod, gear shift cylinder, and brake electric push rod operate according to the stop control method and steps under the stop command. When a change in accelerator pedal displacement is detected, the corresponding gear is calculated according to the travel ratio. When the accelerator pedal displacement increases, the clutch electric push rod, gear shift cylinder, and shift lever cylinder operate according to the upshift control method and steps under the upshift command; when the accelerator pedal displacement decreases, the clutch electric push rod, gear shift cylinder, and shift lever cylinder operate according to the downshift control method and steps under the downshift command. Any changes in other displacement values ​​are transmitted via the UART port.

[0010] The beneficial effects of this invention are that it not only takes into account both the manual operation and computer program control of the shuttle gearbox, but also the hydraulic cylinder is directly driven by an electric pump, which will not cause it to jam, and the extension and retraction displacement of the cylinder can be accurately controlled. Attached Figure Description

[0011] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0012] Figure 1 This is an embodiment of an electro-hydraulic shifting device in the middle structure of a gearbox.

[0013] Figure 2 This is an embodiment of an electro-hydraulic shifting device in the gearbox bridge structure.

[0014] Figure 3This is one embodiment of a bidirectional electric gear pump.

[0015] Figure 4 This is an example of an electro-hydraulic system oil circuit.

[0016] Figure 5 This is an example of TCU circuit wiring.

[0017] Figure 6 This is an example of the TCU software process.

[0018] In the diagram, 1. Shift lever, 2. Shift lever cylinder, 3. Gear shift knob cylinder, 4. First and second gear shift fork, 5. Gear shift knob, 6. Third and fourth gear shift fork, 7. High and low gear cylinder, 8. High and low gear shift knob, 9. High and low gear shift fork, 10. Shuttle gearbox, 11. First shaft speed sensor, 12. Bracket, 13. First shaft input gear, 14. Friction plate actuating shaft, 15. Clutch rocker arm, 16. Clutch, 17. Clutch electric push rod, 18. 19. Forward / reverse rocker arm; 20. Forward / reverse shift fork; 21. Forward / reverse gear cylinder; 22. Primary shaft; 23. Bracket; 24. Secondary shaft speed sensor; 25. Secondary shaft extension end gear; 26. Secondary shaft; 27. Miniature DC motor; 28. Main synchronous pulley; 29. ​​Synchronous belt drive; 30. Pressure regulating valve; 31. Driven synchronous pulley; 32. Pump body; 33. End cover; 34. Check valve; 35. Port B; 36. Main gear; 37. Driven gear; 38. Port A

[0019] Figure 1 This is an embodiment of an electro-hydraulic shifting device in the middle structure of a gearbox. The structure and transmission relationship of the shuttle shift gearbox (10) remain unchanged. In the longitudinal direction under the cover, a gear shift cylinder (3) and a high / low gear cylinder (7) are added side-by-side. The gear shift cylinder (3) can push and pull the gear shift lever (5) to switch the shuttle shift gearbox (10) between first and second gear or between third and fourth gear. The high / low gear cylinder (7) can push and pull the high / low gear lever (8) to switch the high / low gear shift fork (9) between high and low gear positions. A shift block cylinder (2) is placed in the transverse direction under the cover. It pushes and pulls the shift block (1) so that the gear shift lever (5) is either in the groove of the first / second gear shift fork (4) or in the groove of the third / fourth gear shift fork (6). These three cylinders are spatially offset from the manual shifting mechanism.

[0020] Figure 2This is an embodiment of an electro-hydraulic shifting device in the gearbox bridge structure. An advance / reverse cylinder (20) is added in the direction of movement of the advance / reverse shift fork (19). It can push and pull the advance / reverse shift fork (19) to switch the shuttle gearbox (10) between forward, neutral, and reverse. It is also spatially offset from the manually operated advance / reverse rocker arm (18), so manual forward, stop, and reverse actions can still be performed. The connecting rod controlling the clutch (16) is replaced by a clutch electric push rod (17), whose extended end is hinged to the clutch rocker arm (15). The clutch rocker arm (15) engages or disengages the friction plates of the clutch (16) via the friction plate actuation shaft (14). When it returns to its initial extended state, due to the self-locking mechanism inside the clutch electric push rod (17), it becomes a straight rod, and manual pedal operation can still be used to control the engagement or disengagement of the clutch. A single-axis speed sensor (11) is installed on a bracket (12) on the side of the gear (13) at the input end of the single-axis. The pulse signal generated by the rotation of the single-axis (21) is captured by the counter port of the TCU, thereby calculating the rotation speed of the single-axis (21). A double-axis speed sensor (23) is installed on a bracket (22) on the side of the gear (24) at the extension end of the double-axis. The pulse signal generated by the rotation of the double-axis (25) is captured by the counter port of the TCU, thereby calculating the rotation speed of the double-axis (25).

[0021] Figure 3 This is an embodiment of a bidirectional electric gear pump, which consists of a miniature DC motor (26), a synchronous belt drive, and a bidirectional gear pump. The miniature DC motor (26) drives the input shaft of the bidirectional gear pump to rotate through the main synchronous pulley (27), the synchronous belt drive (28), and the driven synchronous pulley (30). The bidirectional gear pump consists of a pump body (31), an end cover (32), a main gear (35), a driven gear (36), two check valves (33), two pressure regulating valves (29), an oil inlet, an oil return port, an A port (37), and a B port (34). The pump body (31), the end cover (32), the main gear (35), and the driven gear (36) form two oil chambers, which are connected to the A port (37) and the B port (34), respectively. The heads of the two check valves (33) are connected to the oil inlet passage, and the tails of the check valves (33) are connected to the oil chamber passage. The main gear (35) is coaxial with the driven synchronous pulley (30), and the number of teeth of the driven gear (36) is equal to that of the main gear (35). The heads of the two pressure regulating valves (29) are connected to the oil chamber passage, and the tails are connected to the return oil passage.

[0022] Figure 4This is an example of an electro-hydraulic system oil circuit. Each cylinder is directly controlled by a bidirectional electric gear pump for extension and retraction. The A port (37) and B port (34) of the bidirectional gear pump are connected to the A port and B port of the cylinder respectively via oil pipes. When the micro DC motor (26) controlled by the TCU rotates forward, the bidirectional gear pump directly drives the cylinder push rod to extend; when the micro DC motor (26) controlled by the TCU rotates in reverse, the bidirectional gear pump directly drives the cylinder push rod to retract. The PWM signal output by the TCU can control the speed of the micro DC motor (26), thereby controlling the flow rate of the hydraulic oil and the movement speed of the cylinder push rod; when the duty cycle of the PWM signal drops rapidly to zero, the cylinder push rod immediately stops moving, achieving precise displacement control.

[0023] Figure 5 This is an example of TCU circuit wiring. The speed pulse signals of the first shaft (21) and the second shaft (25) are connected to the counter port of the TCU. The left and right limit signals of the upshift button, downshift button, stop button and shift lever (1) are connected to the digital signal port of the TCU. The displacement sensor signals of the shift lever cylinder (3), high and low gear cylinder (7), forward and reverse gear cylinder (20), clutch electric push rod (17) and accelerator pedal angular displacement sensor signals are connected to the analog signal port of the TCU. The TCU control output port is connected to the clutch electric push rod (17), brake electric push rod, forward and reverse gear electro-hydraulic system, shift lever electro-hydraulic system, shift lever electro-hydraulic system and high and low gear electro-hydraulic system. The TCU CAN port can receive instructions from the host computer to control gear shifting, collect digital signal ports and analog signal ports, and can also request the engine ECU to return engine speed data or adjust the throttle opening.

[0024] Figure 6This is an example of the TCU software flow. After the TCU is powered on, it initializes the internal microcontroller's I / O ports, A / D conversion, CAN communication, UART communication, counter, and timer. The program runs in a cyclic scanning manner: it checks the CAN interrupt flag bit. When the TCU has a CAN interrupt, it parses the received data string: if it is an instruction to set the displacement sensor parameters, it updates the corresponding displacement sensor parameters and saves them to the EEPROM; if it is an instruction to control the gear, the TCU immediately checks the current gear. When it needs to accelerate and shift up, the TCU sends an accelerator command to the engine ECU. At the same time, the TCU monitors the speed of the first shaft of the shuttle gearbox. When the speed reaches 2500 rpm, the TCU controls the clutch electric push rod (17) to extend its full stroke, the friction plate of the clutch (16) is separated, the first shaft loses power, but continues to rotate by inertia. If shifting from first gear to second gear, or from third gear to fourth gear, the shifter electro-hydraulic system controls the retraction of the shifter cylinder (3). When the retraction stroke of the shifter cylinder (3) is 50%, the shifter electro-hydraulic system is paused. When the speed of the first shaft (21) is detected to match the speed of the second shaft (25), the shifter electro-hydraulic system controls the retraction of the shifter cylinder (3) again. When the retraction stroke of the shifter cylinder (3) reaches 100%, the clutch electric push rod (17) retracts 25% of its stroke. The speed of the first shaft (21) is monitored. If it does not continue to decrease, the clutch electric push rod (17) retracts completely. Otherwise, after the speed of the first shaft (21) stabilizes, the clutch electric push rod (17) retracts 25% of its stroke. 7) Then retract completely; if shifting from second to third gear, the shifter electro-hydraulic system controls the shifter cylinder (3) to extend. When the shifter cylinder (3) extends 50% of its stroke, the shifter electro-hydraulic system is paused, and the shift block electro-hydraulic system controls the shift block cylinder (2) to retract until fully retracted. The shifter electro-hydraulic system then controls the shifter cylinder (3) to extend. When the shifter cylinder (3) extends 100% of its stroke, the clutch electric push rod (17) continues to retract following the same method and steps as shifting from first to second gear. When it is necessary to reduce speed and downshift, the TCU controls the clutch electric push rod (17) to extend its full stroke, the friction plates of the clutch (16) are separated, and the shaft (21) loses power. The rotational speed of shaft 1 (21) continues to decrease. The shifter electro-hydraulic system controls the shifter cylinder (3) to extend. When the shifter cylinder (3) extends to 50% of its stroke, the shifter electro-hydraulic system is paused. When the rotational speed of shaft 2 (25) is found to be consistent with the set gear speed, the shifter electro-hydraulic system controls the shifter cylinder (3) to extend again. When the shifter cylinder (3) extends to 100% of its stroke, the clutch electric push rod (17) retracts to 25% of its stroke. The rotational speed of shaft 1 (21) is monitored. If it does not continue to decrease, the clutch electric push rod (17) extends fully. Otherwise, the clutch electric push rod (17) extends fully after the rotational speed of shaft 1 (21) stabilizes.If it is a high / low gear shift command, the clutch electric push rod (17) extends to disengage the friction plates of the clutch (16), and the high / low gear electro-hydraulic system controls the high / low gear cylinder (7) to extend or retract to the bottom. The clutch electric push rod (17) retracts to re-engage the friction plates of the clutch (16). If it is a forward / reverse shift command, the clutch electric push rod (17) extends to disengage the friction plates of the clutch (16), and the forward / reverse gear electro-hydraulic system controls the forward / reverse gear cylinder (20) to extend or retract to the bottom. If the rotational speed of the second shaft (25) is zero, the clutch... The clutch electric push rod (17) retracts to engage the friction plates of the clutch (16). If the rotational speed of the second shaft (25) is greater than zero, the clutch electric push rod (17) retracts according to the method and steps of shifting from first gear to second gear. If it is a stop command, the clutch electric push rod (17) extends to disengage the friction plates of the clutch (16). The forward and reverse gear electric hydraulic system controls the forward and reverse gear cylinder (20) to extend or retract by 50% of its stroke. Then the brake electric push rod retracts to brake the tractor. When the rotational speed of the second shaft (25) drops to zero, the brake electric push rod extends to return to its original length. Inspect the digital signal port and collect the signals of the left and right limit switches of the shift lever (1), the speed-up and upshift buttons, the speed-down and downshift buttons, and the stop button; inspect the analog signal port, start the A / D conversion, and collect the angular displacement signal of the accelerator pedal, the displacement signal of the clutch electric push rod (17), the displacement signal of the shift lever cylinder (3), the displacement signal of the high and low gear cylinder (7), and the displacement signal of the forward and reverse gear cylinder (20). When the upshift button is detected being pressed, the clutch electric push rod (17), gear shift cylinder (3), and shift lever cylinder (2) operate according to the upshift control method and steps under the shift command; when the downshift button is detected being pressed, the clutch electric push rod (17), gear shift cylinder (3), and shift lever cylinder (2) operate according to the downshift control method and steps under the shift command; when the stop button is detected being pressed, the clutch electric push rod (17), gear shift cylinder (3), and brake electric push rod operate according to the control method and steps under the stop command. When a change in the accelerator pedal displacement is detected, the corresponding gear is calculated according to the stroke ratio. When the accelerator pedal displacement increases, the clutch electric push rod (17), gear shift cylinder (3), and shift lever cylinder (2) operate according to the control method and steps under the acceleration / upshift command; when the accelerator pedal displacement decreases, the clutch electric push rod (17), gear shift cylinder (3), and shift lever cylinder (2) operate according to the control method and steps under the deceleration / downshift command. Any other displacement changes are transmitted via the UART port.

Claims

1. An electro-hydraulic shifting device for a tractor shuttle gearbox, characterized in that: In the longitudinal direction beneath the gearbox cover, gear shift cylinders and high / low gear cylinders are added side-by-side; in the transverse direction beneath the cover, shift lever cylinders are added; these three cylinders are spatially offset from the manual shifting mechanism. In the direction of movement of the shift forks, forward / reverse cylinders are added, also spatially offset from the manual mechanism. The clutch control linkage is replaced by a clutch electric push rod; the two-way electric gear pump... The head of the one-way valve is connected to the inlet oil passage, and the tail is connected to the oil chamber passage; the heads of the two pressure regulating valves are connected to the oil chamber passage, and the tails are connected to the return oil passage; each cylinder is directly controlled by a bidirectional electric gear pump for extension and retraction. The A and B ports of the bidirectional gear pump are connected to the A and B ports of the cylinder via oil pipes; when the micro DC motor of the bidirectional electric gear pump controlled by the TCU rotates forward, the bidirectional gear pump directly drives the cylinder push rod to extend; when the micro DC motor controlled by the TCU rotates in reverse, the bidirectional gear pump directly drives the cylinder push rod to retract; the PWM signal output by the TCU can control the speed of the micro DC motor, thereby controlling the flow rate of the hydraulic oil and the movement speed of the cylinder push rod; when the duty cycle of the PWM signal drops rapidly to zero, the cylinder push rod immediately stops moving, achieving precise displacement control; one shaft The rotational speed pulse signals of the two shafts are connected to the counter port of the TCU. The signals of the upshift button, downshift button, stop button, and left and right limit switches of the shift paddles are connected to the digital signal port. The displacement sensor signals of the shift paddle cylinder, high and low gear cylinder, forward and reverse gear cylinder, clutch electric push rod, and accelerator pedal angular displacement sensor signals are connected to the analog signal port. The TCU control output port is connected to the clutch electric push rod, brake electric push rod, forward and reverse gear electro-hydraulic system, shift paddle electro-hydraulic system, shift paddle electro-hydraulic system, and high and low gear electro-hydraulic system. The TCU's CAN port can receive instructions from the host computer to control gear shifting, acquire digital signal data, acquire analog signal data, and also request engine speed data or adjust throttle opening from the engine ECU.

2. The electro-hydraulic shifting device for a tractor shuttle gearbox according to claim 1, characterized in that: After the TCU is powered on, it initializes the internal microcontroller's I / O ports, A / D conversion, CAN communication, UART communication, counter, and timer. The program runs in a cyclic scanning manner: it checks the CAN interrupt flag bit, and when the TCU has a CAN interrupt, it parses the received data string: if it is an instruction to set the displacement sensor parameters, it updates the corresponding displacement sensor parameters and saves them to the EEPROM. If the command is to control the gear position, the TCU immediately checks the current gear. When acceleration and upshifting are needed, the TCU sends an accelerator command to the engine ECU. Simultaneously, the TCU monitors the speed of the primary shaft of the shuttle gearbox. When the speed reaches 2500 rpm, the TCU controls the clutch electric push rod to extend its full stroke, disengaging the clutch friction plates and causing the primary shaft to lose power, but continuing to rotate due to inertia. If it's a shift from first to second gear, or from third to fourth gear, the shifter electro-hydraulic system controls the retraction of the shifter cylinder. When the shifter cylinder retracts 50% of its stroke, the shifter electro-hydraulic system pauses. When the speed of the primary shaft matches the speed of the secondary shaft, the shifter electro-hydraulic system resumes gear shifting. The shift lever cylinder retracts. When the shift lever cylinder retracts to 100% of its travel, the clutch electric push rod retracts 25% of its travel, monitoring the primary shaft speed. If it doesn't continue to decrease, the clutch electric push rod retracts fully; otherwise, it waits for the primary shaft speed to stabilize before fully retracting. For shifting from second to third gear, the shift lever electro-hydraulic system controls the shift lever cylinder to extend. When the shift lever cylinder extends to 50% of its travel, the shift lever electro-hydraulic system pauses, and the shift block electro-hydraulic system controls the shift block cylinder to retract until fully retracted. Then, the shift lever electro-hydraulic system controls the shift lever cylinder to extend. When the shift lever cylinder extends to 100% of its travel, the clutch electric push rod... Continue retracting the clutch according to the method and steps for shifting from first to second gear; when downshifting is required, the TCU controls the clutch electric push rod to extend its full stroke, the clutch friction plates are disengaged, the primary shaft loses power, and its speed continues to decrease. The shifter electro-hydraulic system controls the shifter cylinder to extend. When the shifter cylinder extends to 50% of its stroke, the shifter electro-hydraulic system pauses. When the speed of the secondary shaft is detected to match the set gear speed, the shifter electro-hydraulic system controls the shifter cylinder to extend again. When the shifter cylinder extends to 100% of its stroke, the clutch electric push rod retracts to 25% of its stroke. The primary shaft speed is monitored; if it does not continue to decrease, the clutch electric push rod extends fully, reversing the shift. After the speed of the first shaft stabilizes, the clutch electric push rod extends fully. If it is a high / low gear shift command, the clutch electric push rod extends to disengage the clutch friction plates. The high / low gear electro-hydraulic system controls the high / low gear cylinder to extend or retract fully, and the clutch electric push rod retracts to re-engage the clutch friction plates. If it is a forward / reverse shift command, the clutch electric push rod extends to disengage the clutch friction plates. The forward / reverse gear electro-hydraulic system controls the forward / reverse gear cylinder to extend or retract fully. If the speed of the second shaft is zero, the clutch electric push rod retracts to engage the clutch friction plates. If the speed of the second shaft is greater than zero, the clutch electric push rod retracts according to the method and steps of shifting from 1st to 2nd gear.If a stop command is issued, the clutch electric push rod extends, disengaging the clutch friction plates. The forward / reverse electro-hydraulic system controls the forward / reverse cylinders to extend or retract 50% of their stroke. Then, the brake electric push rod retracts, braking the tractor. When the speed of the two shafts drops to zero, the brake electric push rod extends and returns to its original length. The digital signal ports are inspected to collect signals from the left and right limits of the shift levers, the upshift / downshift button, the downshift / downshift button, and the stop button. The analog signal ports are inspected, and an A / D converter is activated to collect signals from the accelerator pedal's angular displacement, the clutch electric push rod's displacement, the shift lever cylinder's displacement, the high / low gear cylinder's displacement, and the forward / reverse cylinder's displacement. When the upshift / upshift button is detected as being pressed, the clutch electric push rod, the shift lever cylinder, and the shift lever cylinder control the upshift / upshift according to the shift command. The system operates according to the following steps: When the downshift button is detected being pressed, the clutch electric push rod, gear shift cylinder, and shift lever cylinder operate according to the downshift control method and steps under the shift command; when the stop button is detected being pressed, the clutch electric push rod, gear shift cylinder, and brake electric push rod operate according to the control method and steps under the stop command; when a change in accelerator pedal displacement is detected, the corresponding gear is calculated according to the travel ratio; when the accelerator pedal displacement increases, the clutch electric push rod, gear shift cylinder, and shift lever cylinder operate according to the control method and steps under the acceleration / upshift command; when the accelerator pedal displacement decreases, the clutch electric push rod, gear shift cylinder, and shift lever cylinder operate according to the control method and steps under the downshift command; any changes in other displacement values ​​are transmitted via the UART port.

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