HMCVT tractor reversing control method

Abstract

The invention relates to an HMCVT tractor reversing control method. The method comprises the steps that current operation parameters are read through a TCU; judging a commutation signal type according to the current operation parameter; and performing multi-control-stage control on clutch control pressure and electromagnetic valve current corresponding to the reversing signal type to complete reversing control. The precision and stability of reversing control can be improved, and the stability and reliability of a transmission system are enhanced.

Description

Technical Field

[0001] The invention belongs to the field of power reversing control, and in particular relates to a reversing control method for a HMCVT tractor. Background Art

[0002] Power reversing is a common working mode of HMCVT tractors when working in the field. The typical working condition is: keep the throttle opening and the speed control handle opening unchanged, and the driver operates the shift lever to switch from forward gear to reverse gear when the vehicle is moving forward.

[0003] When a high-horsepower tractor is in field working mode, its engine has high output power and high load rate, which makes switching control difficult. Especially at full throttle and high speed, there is often a large gear shift shock, long shifting time, and even direct burning of the clutch plate, affecting vehicle safety. Summary of the invention

[0004] In view of the above deficiencies in the prior art, an object of the invention is to provide a HMCVT tractor reversing control method.

[0005] The present invention provides a HMCVT tractor reversing control method, comprising:

[0006] S1: Read the current operating parameters through TCU;

[0007] S2: Determine the type of commutation signal according to the current operating parameters;

[0008] S3: completing the reversing control by performing multi-control stage control on the clutch control pressure and the solenoid valve current corresponding to the reversing signal type.

[0009] According to a HMCVT tractor reversing control method provided by the present invention, the current operating parameters in step S1 include a shift handle signal and a vehicle speed direction signal.

[0010] According to a HMCVT tractor reversing control method provided by the present invention, the reversing signal type specifically includes:

[0011] First reversing type: the vehicle speed direction signal is forward, and the shift handle signal is switched from forward to reverse;

[0012] Second reversing type: the vehicle speed direction signal is reverse, and the shift handle signal is switched from reverse to forward.

[0013] According to a HMCVT tractor reversing control method provided by the present invention, the control stage in step S3 specifically includes:

[0014] Reversing speed reduction stage, reversing torque exchange stage, reversing speed increase stage.

[0015] According to a HMCVT tractor reversing control method provided by the present invention, the control steps in the reversing speed reduction stage further include:

[0016] S311: pre-filling the second clutch corresponding to the rear gear position with oil to the oil pressure at the KP point;

[0017] S312: reducing the oil pressure of the first clutch corresponding to the forward gear position, and maintaining the torque capacity of the first clutch greater than the input torque;

[0018] S313: Control the first solenoid valve corresponding to the first clutch to reduce current according to a preset first rate.

[0019] According to a HMCVT tractor reversing control method provided by the present invention, the control step of the reversing torque exchange stage further includes:

[0020] S321: increasing pressure on the second clutch according to a preset second speed;

[0021] S322: reducing the pressure of the first clutch according to a preset third rate, and compensating the oil pressure of the first clutch according to the speed change rate of the output shaft, so as to maintain the speed of the output shaft less than an upper limit and greater than a lower limit;

[0022] S323: Control the first solenoid valve to reduce current according to a preset fourth rate.

[0023] According to a HMCVT tractor reversing control method provided by the present invention, the control steps in the reversing speed-up stage further include:

[0024] S331: reducing the pressure of the first clutch to 0 according to a preset fifth speed;

[0025] S332: taking the difference between the actual slip and the target slip of the second clutch as input, and correcting the pressure value of the second clutch by a PID control method;

[0026] S333: Control the first solenoid valve to reduce the current to 0;

[0027] S334: When the current of the first solenoid valve is 0, control the second solenoid valve corresponding to the second clutch to increase the current to a preset displacement.

[0028] According to a HMCVT tractor reversing control method provided by the present invention, when the reversing signal type is a first reversing type, the first clutch is an HMT clutch, and the second clutch is an HST clutch;

[0029] When the reversing signal type is the second reversing type, the first clutch is an HST clutch, and the second clutch is an HMT clutch.

[0030] According to a HMCVT tractor reversing control method provided by the present invention, the fourth rate in step S323 is greater than the first rate in step S313; the third rate in step S322 is greater than the fifth rate in step S331.

[0031] According to a HMCVT tractor reversing control method provided by the present invention, after step S334, the method further includes:

[0032] S351: Operate in the shifted rear gear and monitor the ring gear speed;

[0033] S352: when it is monitored that the ring gear speed is reduced to 0, the displacement corresponding to the second solenoid valve is reduced to 0;

[0034] S353: monitoring the slip value of the second clutch, and when the monitored slip value is lower than a preset slip value, tightening the second clutch;

[0035] S354: Increase the displacement corresponding to the second solenoid valve to the displacement corresponding to the opening value of the control handle.

[0036] The present invention provides a HMCVT tractor reversing control method, which finely adjusts the control pressure of the clutch and the current of the solenoid valve through multiple control stages (reversing speed reduction stage, reversing torque exchange stage, and reversing speed increase stage), thereby ensuring a smooth transition of the tractor during the reversing process, reducing power interruption and impact, and improving driving comfort and safety; in addition, the present invention determines the reversing signal type according to the current shift handle signal and vehicle speed direction signal, and adopts corresponding control strategies for different reversing types (forward to reverse or reverse to forward), so that the method can be applicable to reversing requirements under different working conditions, thereby improving the adaptability and flexibility of the tractor; secondly, in the reversing torque exchange stage, the present invention accurately controls ... the reversing requirements under different working conditions, thereby improving the adaptability and flexibility of the tractor; secondly, in the reversing torque exchange stage, the present invention accurately controls the reversing signal type according to the current shift handle signal and vehicle speed direction signal, and adopts corresponding control strategies for different reversing types (forward to reverse or reverse to forward), The oil pressure and solenoid valve current of the clutch are controlled to maintain the output shaft speed within a reasonable range, thus avoiding gear shifting shock and power loss caused by excessive speed fluctuation, and optimizing the gear shifting process; secondly, the present invention corrects the pressure value of the clutch through the PID control method to ensure that the clutch can efficiently transmit torque during the switching process, thereby reducing energy loss and improving the fuel economy and work efficiency of the tractor; the present invention also combines sensor monitoring and intelligent control algorithms to achieve real-time monitoring and precise control of the tractor's switching process, thereby improving the intelligence level and automation degree of the tractor, and the overall fine switching control reduces the wear and impact of the clutch and the solenoid valve, prolongs the service life of these key components, and reduces maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are only used to illustrate specific embodiments and are not considered to limit the present invention. In the entire drawings, the same reference symbols represent the same components. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0038] Figure 1 A schematic flow chart of a HMCVT tractor reversing control method provided by an embodiment of the present invention;

[0039] Figure 2 A schematic diagram of a control curve of a forward-to-reverse direction switching control method provided in an embodiment of the present invention;

[0040] Figure 3 A schematic diagram of a control curve of a reverse switching control method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work should fall within the scope of protection of the present invention.

[0042] Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts disclosed in the present invention.

[0043] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. The terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of methods and systems consistent with some aspects of the present invention as detailed in the appended claims.

[0045] In order to better understand the present invention, the terms appearing in the embodiments of the present invention are first explained below.

[0046] HMCVT gearbox: Hydraulic Mechanical Continuously Variable Transmission (HMCVT) is a new technology that combines hydraulic transmission and mechanical transmission to meet the variable operating conditions of high-power agricultural machinery, and can achieve stepless speed change within the gear.

[0047] TCU (Transmission control Unit): Automatic transmission control unit.

[0048] HMT clutch: The clutch used for the power split gear.

[0049] HST clutch: A clutch driven by pure hydraulic flow.

[0050] Alpha and beta solenoid valves: The present invention uses a two-way variable pump plus a quantitative motor to perform stepless speed regulation. The pump displacement is controlled by beta and alpha solenoid valves. The displacement range is 0 to 1. When the displacement is 0, the motor speed is 0. When the displacement is 1, the motor speed is the same as the pump speed. The direction depends on the controlled valve. Since the pump is directly connected to the engine, the pump speed is always equal to the engine speed. For example, the displacement of the beta and alpha valves is 1. At this time, the pump speed is 1000rpm. If the Alpha displacement is 1, the motor speed is also 1000rpm. If the beta displacement is 1, the motor speed is -1000rpm.

[0051] HST: Hydrostatic unit, consisting of a bidirectional variable displacement pump and a fixed displacement motor. The displacement of the pump is controlled by adjusting beta and alpha, and the two solenoid valves control the forward and reverse rotation of the motor respectively.

[0052] In order to better understand the present invention, the research background of the present invention is first explained below.

[0053] Power reversing is a common working mode of HMCVT tractors when working in the field. A typical working condition is: keeping the throttle opening and the speed control handle opening unchanged, the driver operates the shift lever to switch from forward gear to reverse gear when the vehicle is moving forward. The ideal performance of the whole machine is: the forward speed drops rapidly to zero, then the vehicle reverses and the speed gradually increases until the target speed value is reached, and then the vehicle reverses at a stable speed. The whole process requires short reversing time, fast response, small gear shifting shock, and uninterrupted power.

[0054] There are two types of switching conditions: one is to shift to R gear when the vehicle is moving forward, and the other is to shift to F gear when the vehicle is moving backward.

[0055] A new type of HMCVT gearbox structure is currently used, in which the mechanical gear is divided into forward gear and reverse gear. Based on this gearbox structure, a corresponding gear control strategy is also proposed: the fixed forward gear and reverse gear are only combined with one clutch separately, the forward gear is always only combined with the HMT clutch, and the engine power is first diverted through the HST (hydrostatic unit) and then merged through the planetary gear mechanism for output; the reverse gear is always only combined with the HST clutch, and the full engine power is output through the HST. The switching process involves the condition of two clutches slipping at the same time. The power is not interrupted during the switching process, and the clutch slip and the transmitted torque need to be coordinated through the HST to adjust the speed ratio.

[0056] The technical problem solved by the present invention is how to control the hydraulic pump during the power switching process. Taking the forward gear to reverse gear as an example, the two reversing clutches HST and HMT dominate the shifting process, and the solenoid valve of the clutch is controlled. The main task is to smoothly and quickly transfer the torque of the HMT clutch to the HST clutch to complete the shifting. In this process, it involves the problem of how the hydraulic motor should adjust the speed in different shifting stages to cooperate with the clutch slip and the transmitted torque. The present invention focuses on how to control the speed of the hydraulic motor to coordinate the torque acceptance of the clutch and the speed control of the input and output shafts of the gearbox.

[0057] The embodiments of the present invention are described below with reference to the accompanying drawings.

[0058] like Figure 1 As shown, the present invention provides a HMCVT tractor reversing control method, comprising:

[0059] S1: Read the current operating parameters through TCU.

[0060] Wherein, the current operating parameters in step S1 include a shift handle signal and a vehicle speed direction signal.

[0061] Furthermore, in step S1, the vehicle status information is first obtained in real time through the TCU. In addition to the above-mentioned shift handle signal and vehicle speed direction signal, it is also necessary to receive real-time signals such as oil pump displacement, HST clutch opening, and HMT clutch opening.

[0062] S2: Determine the type of commutation signal according to the current operating parameters.

[0063] The commutation signal types specifically include:

[0064] First reversing type: the vehicle speed direction signal is forward, and the shift handle signal is switched from forward to reverse;

[0065] Second reversing type: the vehicle speed direction signal is reverse, and the shift handle signal is switched from reverse to forward.

[0066] Furthermore, the above-mentioned switching type is specifically: when the TCU internal algorithm detects that the vehicle is moving forward and the shift handle is in R gear, or the vehicle is moving backward and the shift handle is in F gear, if any of the above two situations occurs, the subsequent switching control logic is activated.

[0067] S3: completing the reversing control by performing multi-control stage control on the clutch control pressure and the solenoid valve current corresponding to the reversing signal type.

[0068] The control stage in step S3 specifically includes:

[0069] Reversing speed reduction stage, reversing torque exchange stage, reversing speed increase stage.

[0070] The control steps in the reversing and speed reduction stage further include:

[0071] S311: pre-filling the second clutch corresponding to the rear gear position with oil to the oil pressure at the KP point;

[0072] S312: reducing the oil pressure of the first clutch corresponding to the forward gear position, and maintaining the torque capacity of the first clutch greater than the input torque;

[0073] S313: Control the first solenoid valve corresponding to the first clutch to reduce current according to a preset first rate.

[0074] In a specific embodiment, the HMT / HST clutch power shift control is described by taking the judgment that the switching condition is forward switching and reverse switching as an example.

[0075] The process from step S311 to S313 is the switching preparation stage, i.e. the above-mentioned switching deceleration stage. HST first enters the pre-oil control to quickly eliminate the piston gap and keep the oil pressure near the KISSPOINT oil pressure to improve the torque response speed. At the same time, the HMT clutch quickly reduces the oil pressure and monitors the engine torque in real time to ensure that the torque capacity of the HMT clutch is always higher than the input torque. At this stage, the beta solenoid valve current decreases slowly at a fixed slope and a smaller rate of change.

[0076] Furthermore, the HST pre-fill oil control helps to improve the torque response speed, while the HMT clutch quickly reduces the oil pressure in preparation for releasing the current power transmission. Real-time monitoring of the engine torque is carried out throughout the process to ensure that the torque capacity of the HMT clutch is always higher than the input torque to prevent overload. Finally, the current of the beta solenoid valve slowly decreases at a fixed slope to control the oil pressure change of the clutch.

[0077] The control steps in the reversing torque exchange stage further include:

[0078] S321: increasing pressure on the second clutch according to a preset second speed;

[0079] S322: reducing the pressure of the first clutch according to a preset third rate, and compensating the oil pressure of the first clutch according to the speed change rate of the output shaft, so as to maintain the speed of the output shaft less than an upper limit and greater than a lower limit;

[0080] S323: Control the first solenoid valve to reduce current according to a preset fourth rate.

[0081] The process from steps S321 to S323 is the reversing torque exchange stage. In this stage, the HST pressure increases at a fixed slope, and the HMT clutch decreases at a fixed slope. The output shaft speed change rate is monitored in real time, and the HMT oil pressure is compensated in real time based on the change rate to ensure that the output shaft speed change rate is always within the upper and lower limits. In this stage, the beta solenoid valve current decreases slowly at a medium change rate according to a fixed slope.

[0082] Furthermore, first, the pressure of the HST increases at a fixed slope, while the pressure of the HMT clutch decreases at a fixed slope. The pressure change helps to achieve a smooth exchange of torque. The current of the subsequent beta solenoid valve continues to decrease at a fixed slope, but the rate of change is moderate, which can meet the needs of torque exchange.

[0083] The control steps in the reversing speed-up stage further include:

[0084] S331: reducing the pressure of the first clutch to 0 according to a preset fifth speed;

[0085] S332: taking the difference between the actual slip and the target slip of the second clutch as input, and correcting the pressure value of the second clutch by a PID control method;

[0086] S333: Control the first solenoid valve to reduce the current to 0;

[0087] S334: When the current of the first solenoid valve is 0, control the second solenoid valve corresponding to the second clutch to increase the current to a preset displacement.

[0088] Steps S331 to S334 are the reversing speed regulation stage, that is, the above-mentioned reversing speed increase stage. In this stage, the HMT clutch decreases at a relatively low slope until it is reduced to zero. The HST adopts PID control, and the difference between the HST target slip and the actual slip is input. The HST clutch pressure value is corrected in real time through PID control. At the same time, the beta solenoid valve adopts the "maximum time limit" filtering algorithm to reduce the displacement value to ensure that it is reduced to 0 within the maximum timing time. When the beta displacement is reduced to 0, the alpha solenoid valve also adopts the "maximum time limit" filtering algorithm to increase the alpha displacement to around 0.8.

[0089] Furthermore, in the switching speed regulation stage, the pressure of the HMT clutch is first controlled to continue to decrease until it drops to zero, indicating that the HMT has completely released the current power transmission. Subsequently, the PID control algorithm is used for the HST, and the difference between the target slip and the actual slip is used as input to correct the pressure value of the HST clutch in real time, which can achieve more precise speed control. Finally, the beta and alpha solenoid valve displacement control helps to achieve a smoother shifting process.

[0090] Wherein, when the reversing signal type is the first reversing type, the first clutch is the HMT clutch, and the second clutch is the HST clutch;

[0091] When the reversing signal type is the second reversing type, the first clutch is an HST clutch, and the second clutch is an HMT clutch.

[0092] Specifically, the process described above through the embodiment is a control process of the vehicle switching from forward to reverse, and switching from reverse to forward is the reverse process of the above process, that is, when switching from forward to reverse, the first clutch is the HMT clutch and the second clutch is the HST clutch, and when switching from reverse to forward, the first clutch is the HST clutch and the second clutch is the HMT clutch.

[0093] Among them, the fourth rate in step S323 is greater than the first rate in step S313; the third rate in step S322 is greater than the fifth rate in step S331.

[0094] like Figure 2 As shown, it is a schematic diagram of the control curve of forward switching and reverse switching based on the reversing control method of the present invention. Curves ① to ③ are respectively the clutch oil pressure control curve, the HST displacement control curve, and the shift lever position curve. For each curve, the curve before point a is the Beta control curve, and the curve after point a is the Alpha control curve.

[0095] Specifically, Figure 2 In the preparation stage, the beta valve controls the displacement to decrease at a lower slope, which improves the gear shifting process. In the torque exchange stage, the HST displacement decrease speed is slightly increased, which further speeds up the gear shifting process and shortens the gear shifting time. The HST control in the speed exchange stage can be divided into four sub-stages. In the first stage, the beta valve rapidly decreases to zero at a slow speed first and then a fast speed. At this time, the vehicle speed is still positive. In the second stage, the alpha displacement increases rapidly. The vehicle speed is still positive in this stage and the vehicle speed is further reduced. After reaching point b, the vehicle speed is reduced to zero. In the third stage, the HST clutch uses PID slip control to always control the slip within the specified range. The alpha displacement is reduced to 0 within several cycles. During this process, the vehicle speed is always zero. In the fourth stage, the alpha displacement gradually increases, the whole machine enters the reverse starting condition, and the vehicle speed gradually increases.

[0096] Similarly, Figure 3 for Figure 2 The reverse process of Figure 3 Schematic diagram of the control curve of the reverse switching forward switching based on the reversing control method of the present invention, the difference is that the control processes of the two clutch curves are swapped. Figure 3 Before point a in the middle of middle curve ②, the vehicle speed is reverse, the vehicle is stationary in sections a and b, and the vehicle speed is forward after section b.

[0097] Among them, after step S334, the following steps are also included:

[0098] S351: Operate in the shifted rear gear and monitor the ring gear speed.

[0099] S352: When it is monitored that the ring gear speed is reduced to 0, the displacement corresponding to the second solenoid valve is reduced to 0.

[0100] Furthermore, in step S352, if the system detects that the ring gear speed has dropped to 0, it means that the transmission system has stabilized at the new gear and there is no additional power transmission demand. Therefore, in this case, the TCU (transmission control unit) will reduce the displacement of the alpha solenoid valve to 0 within several sampling cycles in order to reduce unnecessary energy loss and wear.

[0101] S353: monitoring the slip value of the second clutch, and when the monitored slip value is lower than a preset slip value, tightening the second clutch.

[0102] Furthermore, in step S353, while reducing the displacement of the alpha solenoid valve, the system also needs to monitor the slip value of the HST clutch. The slip value is an indicator for evaluating the degree of clutch engagement. If the system detects that the slip value is lower than the preset threshold, it means that the HST clutch is engaged tightly enough to transmit the required torque. At this time, the system will further tighten the clutch to ensure smooth power transmission.

[0103] S354: Increase the displacement corresponding to the second solenoid valve to the displacement corresponding to the opening value of the control handle.

[0104] After the gear shift is completed, it is also necessary to monitor the ring gear speed in real time. When the ring gear speed is detected to be reduced to 0, the TCU will reduce the alpha displacement to zero within several sampling cycles. During this process, the vehicle speed is kept at 0; when the monitored HST clutch slip value is lower than the preset value, the HST clutch is tightened; the alpha displacement gradually increases in a trend of first fast and then slow, until the displacement decreases to the displacement corresponding to the opening value of the test handle, and the overall reversing process is completed.

[0105] A HMCVT tractor reversing control method provided by the present invention first improves the accuracy and stability of the reversing control: the present invention subdivides the reversing speed reduction stage, the reversing torque exchange stage and the reversing speed increase stage, each stage has a specific control target and strategy, thereby achieving precise control of the reversing process. In addition, in each control stage, the clutch oil pressure and the solenoid valve current are finely adjusted according to a preset rate, ensuring the stability and controllability of the reversing process.

[0106] Secondly, the stability and reliability of the transmission system are enhanced: during the entire switching process, the system monitors key parameters such as engine torque and output shaft speed change rate in real time, and adjusts the clutch oil pressure and solenoid valve current in real time according to these parameters, ensuring the stability and reliability of the transmission system; it also effectively prevents overload of the transmission system by monitoring the engine torque in real time and ensuring that the clutch torque capacity is always higher than the input torque.

[0107] Secondly, the shifting time is shortened and the shifting efficiency is improved: the control curve of the present invention adopts optimized control strategies in the switching preparation stage and the torque exchange stage, such as the beta valve is rapidly reduced to zero at a slow speed first and then a fast speed, and the alpha displacement is rapidly increased, etc. These strategies effectively shorten the shifting time and improve the shifting efficiency; in the switching speed increase stage, the present invention adopts a PID control algorithm to correct the pressure value of the clutch in real time, thereby achieving more precise speed control and further improving the shifting efficiency.

[0108] In addition, energy loss and wear are reduced: after the reversing process is completed, the system of the present invention will intelligently adjust the displacement of the solenoid valve according to parameters such as the ring gear speed and the clutch slip value, ensuring that the displacement is reduced when additional power transmission is not required, thereby reducing energy loss and wear; through precise clutch control and solenoid valve adjustment, the smoothness of the gear shifting process is achieved, reducing the wear caused by gear shifting shock.

[0109] Finally, the driver's driving experience is improved: the switching control method of the present invention makes the gear shifting process more controllable and smooth, reducing the driver's discomfort and operating difficulty during the gear shifting process; the control strategy of the present invention can be customized and optimized according to different vehicle models and usage environments, improving the vehicle's adaptability and the driver's driving experience.

[0110] In summary, the HMCVT tractor reversing control method of the present invention has brought significant beneficial effects in improving the accuracy and smoothness of reversing control, enhancing the stability and reliability of the transmission system, shortening the shifting time and improving the shifting efficiency, reducing energy loss and wear, and improving the driver's driving experience.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the above embodiments, or replace some of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. Any changes or replacements that can be easily thought of by those skilled in the art within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention.

Claims

1. A HMCVT tractor reversing control method, characterized in that: include: S1: Read the current operating parameters through TCU; S2: Determine the type of commutation signal according to the current operating parameters; S3: completing the reversing control by performing multi-control stage control on the clutch control pressure and the solenoid valve current corresponding to the reversing signal type.

2. A HMCVT tractor reversing control method according to claim 1, characterized in that: The current operating parameters in step S1 include a shift handle signal and a vehicle speed direction signal.

3. A HMCVT tractor reversing control method according to claim 2, characterized in that: The commutation signal types specifically include: First reversing type: the vehicle speed direction signal is forward, and the shift handle signal is switched from forward to reverse; Second reversing type: the vehicle speed direction signal is reverse, and the shift handle signal is switched from reverse to forward.

4. The HMCVT tractor reversing control method according to claim 1, characterized in that: The control phase in step S3 specifically includes: Reversing speed reduction stage, reversing torque exchange stage, reversing speed increase stage.

5. A HMCVT tractor reversing control method according to claim 4, characterized in that: The control steps in the reversing and speed reduction stage further include: S311: pre-filling the second clutch corresponding to the rear gear position with oil to the oil pressure at the KP point; S312: reducing the oil pressure of the first clutch corresponding to the forward gear position, and maintaining the torque capacity of the first clutch greater than the input torque; S313: Control the first solenoid valve corresponding to the first clutch to reduce current according to a preset first rate.

6. A HMCVT tractor reversing control method according to claim 5, characterized in that: The control steps in the reversing torque exchange stage further include: S321: increasing pressure on the second clutch according to a preset second speed; S322: reducing the pressure of the first clutch according to a preset third rate, and compensating the oil pressure of the first clutch according to the speed change rate of the output shaft, so as to maintain the speed of the output shaft less than an upper limit and greater than a lower limit; S323: Control the first solenoid valve to reduce current according to a preset fourth rate.

7. A HMCVT tractor reversing control method according to claim 6, characterized in that: The control steps in the reversing speed-up stage further include: S331: reducing the pressure of the first clutch to 0 according to a preset fifth speed; S332: taking the difference between the actual slip and the target slip of the second clutch as input, and correcting the pressure value of the second clutch by a PID control method; S333: Control the first solenoid valve to reduce the current to 0; S334: When the current of the first solenoid valve is 0, control the second solenoid valve corresponding to the second clutch to increase the current to a preset displacement.

8. A HMCVT tractor reversing control method according to claim 7, characterized in that: When the reversing signal type is the first reversing type, the first clutch is the HMT clutch, and the second clutch is the HST clutch; When the reversing signal type is the second reversing type, the first clutch is an HST clutch, and the second clutch is an HMT clutch.

9. The HMCVT tractor reversing control method according to claim 7, characterized in that: The fourth rate in step S323 is greater than the first rate in step S313; the third rate in step S322 is greater than the fifth rate in step S331.

10. The HMCVT tractor reversing control method according to claim 7, characterized in that: After step S334, the following steps are also included: S351: Operate in the shifted rear gear and monitor the ring gear speed; S352: when it is monitored that the ring gear speed is reduced to 0, the displacement corresponding to the second solenoid valve is reduced to 0; S353: monitoring the slip value of the second clutch, and when the monitored slip value is lower than a preset slip value, tightening the second clutch; S354: Increase the displacement corresponding to the second solenoid valve to the displacement corresponding to the opening value of the control handle.

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