CN-121973774-A - Control system and control method for small horsepower stepless speed change and power reversing tractor

CN121973774ACN 121973774 ACN121973774 ACN 121973774ACN-121973774-A

Abstract

The invention relates to a control system and a control method of a small horsepower stepless speed change and power reversing tractor, which designs a low-cost and highly integrated electric control system for the small horsepower tractor, greatly reduces the complexity and the manufacturing cost of the system on the premise of ensuring the core function by sharing a sensing network and optimizing the number of actuators, is suitable for a small horsepower tractor market ‌ sensitive to cost by ‌, can realize intelligent identification and switching of dual-mode starting, cooperatively controls the stepless speed change and power reversing function, optimizes the stepless speed change and power reversing control strategy, ensures the smoothness of torque transmission under different working conditions by using a dual-mode closed-loop control strategy, and provides a new platform for the intelligent development of the small horsepower tractor.

Inventors

ZHOU JUNWEI
WANG LISHA
WANG MENGHUA
FU TIANZHI
LIU YUKUN
WANG YONG
FU SHIYU
ZHANG CHUANCHUAN
FANG WEILI
XING XIAOXU

Assignees

洛阳拖拉机研究所有限公司

Dates

Publication Date: 20260505
Application Date: 20260116

Claims (10)

1. The control system comprises a signal source, a stepless speed change controller and a terminal execution device, and is characterized in that the signal source comprises a reversing handle, a stepless speed change push rod, a motor rotating speed sensor, a reversing input rotating speed sensor, a reversing output rotating speed sensor, a vehicle speed sensor, an oil temperature sensor and a sensitivity knob, the stepless speed change controller is integrated with a signal acquisition module, a stepless speed change module, a power reversing module, a torque current conversion module, a fault diagnosis module, a driving and information transmission module, the terminal execution device comprises 4 proportional solenoid valves and 2 wet clutches, wherein the 2 proportional solenoid valves control 2 oil ways of the stepless speed change HST to realize stepless speed change of a vehicle, the 2 proportional solenoid valves control 2 wet clutches of the power reversing to realize smooth engagement and separation between forward and backward gears, and a driver can realize automatic starting and power reversing functions of the tractor by changing the reversing handle position and can realize stable continuous speed change of the tractor under different working conditions and loads by comprehensively adjusting the rotating speed of the engine and the stepless speed change push rod.
2. The small horsepower stepless speed change and power reversing tractor control system according to claim 1 is characterized in that a stepless speed change controller determines starting and reversing types of a tractor according to a power reversing module, determines whether the tractor needs to be accelerated or decelerated according to the stepless speed change module, calculates actual displacement ratio of HST output according to an engine rotating speed value sent by an engine controller CAN bus and an acquired motor rotating speed value, calculates real-time speed difference of a forward clutch and a backward clutch according to the acquired reversing input rotating speed value and the reversing output rotating speed value, calculates torque which CAN be transmitted when each clutch is completely engaged according to a CAN bus torque signal sent by the engine controller, provides a data basis for follow-up accurate control, combines the characteristics of each proportional electromagnetic valve and the clutch, calculates corresponding required current value through a torque current conversion module, and finally is executed by a driving and information transmission module to drive the proportional electromagnetic valve to obtain accurate actual current.
3. The small horsepower infinitely variable and power reversing tractor control system of claim 1, wherein the fault diagnosis module monitors all signal states in real time, and once an abnormality is found, the infinitely variable controller immediately sends diagnosis information through the CAN bus and automatically takes corresponding processing measures according to the severity level of the fault.
4. The control method of the small horsepower stepless speed change and power reversing tractor is characterized in that the tractor adopts the control system of the small horsepower stepless speed change and power reversing tractor as set forth in any one of claims 1-3, and the control method is as follows: (1) The driver starts the engine, and the control system performs self-checking, namely if the reversing handle is not placed in the neutral position, the forward/backward proportional electromagnetic valve is locked by a hardware level, the request current cannot be obtained, and the request current must be returned to the neutral position to unlock the direction control function; (2) After the control system self-tests, if the serious faults affecting the running of the vehicle are not determined, the tractor performs cooperative control of automatic starting, power reversing and stepless speed change, a driver operates a reversing handle, and a stepless speed change controller calculates real-time speed difference according to the rotating speed of a reversing input/output rotating speed sensor to realize the functions of automatic starting and power reversing of the vehicle; (3) When the tractor starts, commutates or runs, if the clutch speed difference exceeds the set value and lasts for a certain time, the controller immediately cuts off the clutch current to prevent the clutch from wearing, and meanwhile, the instrument displays corresponding fault codes and fault warning information, and the driver is required to turn off the tractor and then turn on again to normally control the vehicle.
5. The method of claim 4, wherein the continuously variable transmission control process includes detecting an engine state and a system pressure after the tractor is started, when the engine speed and the system pressure both exceed a set threshold, selecting a high section or a low section by a driver through a high-low gear switching button, then operating a forward or backward direction clutch, if the continuously variable transmission push rod is not in a zero position at this time, the system will limit the function of the continuously variable transmission push rod, the push rod is required to be manually reset to unlock the continuously variable transmission control function, when the driver pushes the continuously variable transmission push rod, the controller determines a request displacement ratio according to the real-time position of the continuously variable transmission push rod, calculates an actual displacement ratio based on the engine speed and the motor output speed, if the difference between the request value and the actual value exceeds the set threshold, adjusts currents of two continuously variable speed ratio solenoid valves through a PID algorithm, so that the actual displacement ratio tracks the request displacement ratio, thereby realizing smooth control of an expected vehicle speed, and continuously variable transmission keeps the current state until the power commutation is finished.
6. The method for controlling a small horsepower stepless speed change and power reversing tractor according to claim 4, wherein the tractor comprises two starting modes, namely a first mode of switching directions and then adjusting speeds, a second mode of presetting speeds and then switching directions, and the control system intelligently distinguishes the two starting modes according to the operation sequence of a stepless speed change push rod and a reversing handle by a driver, so that accurate and smooth power connection is realized.
7. The method for controlling a small horsepower stepless speed change and power reversing tractor according to claim 6, wherein when the driver is in a zero position of the stepless speed change push rod, ‌ firstly switches the reversing handle from a neutral gear to a forward or backward gear ‌, then pushes the stepless speed change push rod to start, the system is judged to be in a mode one, at the moment, the difference of the rotating speeds at two ends of the reversing clutch is close to zero, the clutch can rapidly complete oil filling and mechanical engagement, and meanwhile, the stepless speed change proportional electromagnetic valve starts current regulation according to a preset slope curve to realize linear speed lifting ‌; If the driver ‌ pushes the stepless speed change push rod to the target percentage position ‌, then operates the reversing handle to switch the forward or backward gear, the system enters a mode two, at this time, the stepless speed change module has established the target displacement in advance, the hydraulic motor starts accelerating, ‌ has generated a significant rotation speed difference ‌ before the reversing clutch is engaged, when the rotation speed difference exceeds the system setting threshold, the control system starts ‌ the double-closed-loop torque compensation mechanism ‌, the request current of the reversing clutch proportional solenoid valve is determined by superposition of two parts, namely, the current corresponding to the slope torque set based on acceleration, and the current corresponding to the torque obtained by PID adjustment according to the rotation speed difference, the stepless speed change controller converts the calculated total torque into the corresponding proportional solenoid valve control current, automatic starting is completed, and when the rotation speed difference in the clutch engagement process is lower than the setting threshold, or the engagement time exceeds the setting threshold, the proportional solenoid valve current is rapidly increased to the maximum value in a preset maximum step size, and the reliable completion of the engagement process is ensured.
8. The method for controlling a small horsepower stepless speed change and power reversing tractor according to claim 7, wherein the slope of the slope torque can be automatically adjusted according to the rotating speed of the reversing input shaft and continuously increased in the simulation step length, so that stable and rapid clutch engagement can be realized at different rotating speeds, the slope of the slope torque is automatically corrected in real time by introducing the rotating speed factor Map of the reversing input shaft, and a user can also customize the slope of the slope torque by a reversing sensitivity knob so as to adapt to the starting stability requirements under different working conditions.
9. The method of claim 4 wherein the reverse control flow is that the reverse handle is moved from the current direction to the opposite direction during the running of the tractor, the tractor enters the reverse power state, the controller judges the clutch to be separated and engaged according to the vehicle state and the sensor information, and obtains the speed difference, the speed and the oil charge time in real time, then the clutch to be separated enters the pre-opening stage, the transmission torque gradually decreases to the actual input torque value of the engine from the maximum value according to the set curve, meanwhile, the clutch to be engaged starts to be pre-engaged, the hydraulic pressure is only balanced to the spring force and does not transmit the actual torque until the idle stroke is completely eliminated, the torque curve transmitted by the separation clutch is regulated by closed loop control, the sum of the preset torque defined by the acceleration and the PID regulation is calculated to obtain the total torque value of the separation clutch, and finally the torque smooth transition and the speed synchronization are realized, and when the speed difference of the rotation speed of the clutch to be engaged is smaller than the set threshold, or the engagement time is larger than the maximum setting value, the clutch is rapidly engaged until the torque is completely eliminated, and the reverse torque is completely increased.
10. The method for controlling a small horsepower continuously variable transmission and power reversing tractor according to claim 4, wherein when the control system detects that the continuously variable transmission push rod is zero, the control system synchronously cuts off the control current of the currently engaged reversing clutch when a displacement ratio request corresponding to zero vehicle speed is sent, so that the vehicle is forced to be stationary at a mechanical transmission level and is not influenced by the change of volumetric efficiency, and when the driver pushes the continuously variable transmission push rod again, the system re-engages the reversing clutch according to an automatic starting curve and cooperatively controls the continuously variable transmission module to ensure the stable starting of the vehicle.

Description

Control system and control method for small horsepower stepless speed change and power reversing tractor Technical Field The invention relates to the field of tractor control, in particular to a small horsepower stepless speed change and power reversing tractor control system and a control method. Background The tractor is used as core power equipment in the agricultural and engineering fields, and the transmission system and the control performance of the tractor directly influence the operation efficiency, the fuel economy and the operation comfort. The small horsepower tractor is mainly applied to vast rural areas, the farmland area is relatively small, frequent gear shifting and reversing operations are needed in field operation, the traditional mechanical stepped transmission is needed to cut off power transmission in the gear shifting or reversing process, so that operation continuity is poor, particularly, the operation efficiency is remarkably reduced under the working conditions that frequent gear shifting is needed in cultivated lands, seeding and the like or frequent reversing is needed in narrow spaces such as orchards and greenhouses, and meanwhile, due to the fact that fixed gears are adopted, an engine cannot continuously run in a high-efficiency section and is difficult to adapt to the requirements of complicated and changeable working conditions. At present, the stepless speed change tractor and the power reversing tractor have remarkable advantages in the aspects of improving the working efficiency and the intellectualization, but are limited by high manufacturing cost and maintenance cost, and are generally only applied to high horsepower tractors insensitive to the cost, while the small horsepower tractors are still mainly mechanical tractors, the gear shifting and reversing functions can be realized only after the vehicle stops, the operation is complex, and the stepless speed regulation cannot be realized. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a small horsepower stepless speed change and power reversing tractor control system and a control method, so that the small horsepower tractor can realize stepless speed change function, power reversing function and cooperative control thereof, thereby reducing the working strength of a driver, improving the driving comfort and improving the working efficiency of the tractor. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: The control system comprises a signal source, a stepless speed change controller and a terminal execution device, wherein the signal source comprises a reversing handle, a stepless speed change push rod, a motor rotating speed sensor, a reversing input rotating speed sensor, a reversing output rotating speed sensor, a vehicle speed sensor, an oil temperature sensor and a sensitivity knob, the stepless speed change controller is integrated with a signal acquisition module, a stepless speed change module, a power reversing module, a torque current conversion module, a fault diagnosis module and a driving and information transmission module, the terminal execution device comprises 4 proportional solenoid valves and 2 wet clutches, 2 proportional solenoid valves control 2 oil ways of the stepless speed change HST to realize stepless speed change of a vehicle, and 2 proportional solenoid valves control 2 wet clutches of power reversing to realize smooth engagement and separation between forward and backward gears, and a driver can realize automatic starting and power reversing functions of the tractor by changing the reversing handle position and can realize stable continuous speed change of the tractor under different working conditions and loads by comprehensively adjusting the rotating speed of an engine and the stepless speed change push rod. Further, the stepless speed change controller determines starting and reversing types of the tractor according to the power reversing module, determines whether the tractor needs to be accelerated or decelerated according to the stepless speed change module, calculates the actual displacement ratio of HST output according to an engine rotating speed value sent by an engine controller CAN bus and an acquired motor rotating speed value, calculates the real-time speed difference of the forward clutch and the backward clutch according to the acquired reversing input rotating speed value and the reversing output rotating speed value, calculates torque which CAN be transmitted when each clutch is fully engaged according to a CAN bus torque signal sent by the engine controller, provides a data basis for follow-up accurate control, combines the characteristics of each proportional electromagnetic valve and the clutch, calculates a corresponding required current value through a torque current conversion module, and finally is executed by a driving and information transmission module to drive the prop