Shift control method of commercial vehicle AMT under extreme working condition

Abstract

The present application belongs to the technical field of automobile gearbox control, and discloses a shift control method for a commercial vehicle AMT under extreme working conditions, which comprises the following steps: step 1, presetting a threshold value; step 2, judging whether the target gear is sent out, the clutch is opened, and the gear is disengaged; if yes, entering step 3, otherwise, executing step 2; step 3, judging whether the slope threshold value is met; if yes, entering step 4, otherwise, entering step 6; step 4, judging whether the pedal opening threshold value is greater than the pedal opening threshold value; if yes, entering step 5, otherwise, entering step 6; step 5, judging whether the deceleration threshold value is met; if yes, entering step 6, otherwise, not executing the gear engagement until the condition is met; step 6, judging whether the speed difference threshold value is met; if yes, entering step 7, otherwise, not executing the gear engagement until the condition is met; and step 7, allowing the gear engagement, and the TCU sends out an instruction to control the electromagnetic valve to complete the gear engagement action. The present application can greatly reduce the gear tooth engagement probability and reduce the risk of gearbox jam.

Description

Technical Field

[0001] This invention belongs to the field of automotive transmission control technology, specifically relating to a shift control method for commercial vehicle AMT under extreme operating conditions. Background Technology

[0002] In the current commercial vehicle sector, AMT (Automatic Mechanical Transmission) gearboxes have developed rapidly in recent years. As AMT products penetrate the domestic commercial vehicle market, more and more users and OEMs are favoring AMT products. At the same time, the application areas of AMT products in China have further expanded, including the Northwest Plateau and the Southwest Mountainous Area, where more and more AMT models can be seen.

[0003] When driving uphill on mountainous national highways or some urban slopes, you will inevitably encounter scenarios of low-speed following and repeated starts and stops. In such situations, during the gear shifting process (target gear selection - clutch disengagement - disengagement - synchronization - engagement - clutch engagement), sudden braking can easily cause gear shifting jamming, grinding, and other phenomena. At the same time, it will also be accompanied by relatively strong shifting noise and jerking, which will affect the driving experience and the service life of the transmission.

[0004] The main gearbox structure of most mainstream commercial vehicle AMT transmissions is a sliding sleeve type. Gear grinding occurs because the speed difference between the target meshing gear in the main gearbox and the sliding sleeve is too large during gear shifting. The expression is:

[0005] n d = n L i main - n o i aux (1) in, The speed difference between the target meshing gear and the sliding sleeve in the main gearbox. The intermediate shaft speed. The output shaft speed. The main gearbox transmission ratio. This is the transmission ratio of the auxiliary gearbox.

[0006] The speed difference between the target meshing gear and the sliding sleeve needs to be adjusted during the synchronization phase of gear shifting, mainly by reducing the speed of the intermediate shaft using the brake. The expression for this is: n target = n o imain i aux (2) in, The adjusted target gear speed difference between the meshing gear and the sliding sleeve in the main gearbox.

[0007] During gear shifting, the rotating part of the input shaft momentarily disengages from the output shaft power chain when disengaging, which causes a disturbance to the output shaft power chain. Under normal circumstances, the equivalent inertia of the input shaft is small, and the impact is negligible. However, in the working condition described above, the greater the deceleration, the greater the disturbance will be, which will cause the output shaft speed to jitter. As can be seen from equations (1) and (2), the jitter of the output shaft speed will not only affect the control strategy of the brake in the synchronization stage, but may also cause the jitter of the speed difference between the meshing gear and the sliding sleeve. In this case, the existing AMT control strategy generally enables the gear engagement solenoid valve when the speed difference meets the preset threshold, and the actuator will start to move immediately. At this time, the speed difference may still be oscillating. When the sliding sleeve and the target meshing gear actually start to mesh, the speed difference may be much greater than the preset threshold, which will lead to the risk of gear grinding.

[0008] Therefore, for AMT, it is essential to study control strategies under special operating conditions, especially extreme operating conditions. Continuously optimizing AMT shift control strategies can further improve the driving experience, enhance driving reliability, and extend mechanical life. Summary of the Invention

[0009] The purpose of this invention is to provide a shift control method for commercial vehicle AMT under extreme operating conditions, so as to solve the problem that the existing AMT shift control technology is prone to jamming and gear grinding under extreme operating conditions of rapid deceleration.

[0010] To achieve the above objectives, the present invention employs the following technical solution: A method for shift control of an automated manual transmission (AMT) in a commercial vehicle under extreme operating conditions includes the following steps: Step 1: Preset the slope threshold, brake pedal opening threshold, deceleration threshold, and speed difference threshold; Step 2: Determine whether the target gear has been engaged, the clutch has been disengaged, and the gear has been shifted out. If yes, proceed to Step 3; otherwise, repeat Step 2. Step 3: Determine whether the slope value emitted by the TCU slope sensor meets the preset slope threshold. If yes, the current working condition is considered to be an uphill working condition, and proceed to step 4; otherwise, proceed to step 6. Step 4: Determine whether the bus brake pedal opening signal is greater than the preset brake pedal opening threshold. If yes, it is considered that the driver's subjective intention is an emergency braking condition, and proceed to step 5; otherwise, proceed to step 6. Step 5: Determine whether the current deceleration meets the preset deceleration threshold according to the TCU preset threshold. If yes, proceed to step 6. Otherwise, do not engage gears, keep the main box displacement in the current state, and do not activate the gear engagement solenoid valve until the current deceleration meets the deceleration threshold. Step 6: Determine whether the speed difference between the current meshing gear and the sliding sleeve meets the preset speed difference threshold. If yes, proceed to step 7; otherwise, do not engage the gear until the speed difference meets the preset speed difference threshold. Step 7: Allow gear engagement. The TCU issues a command to control the solenoid valve to complete the gear engagement action; at this point, the gear shift control ends.

[0011] Furthermore, the slope threshold is 10%, the brake pedal opening threshold is 20%, and the deceleration threshold is 3 m / s². 2 The speed difference threshold is 100 rpm.

[0012] Compared to existing methods, although the method of the present invention delays the timing of gear engagement during the gear shifting phase in the above-mentioned extreme deceleration conditions, it can significantly reduce the probability of gear grinding by avoiding the speed difference jitter range in this condition, eliminate the jamming during the gear engagement process, effectively reduce the shifting time in this extreme condition, and also improve the shifting quality and subjective driving experience. Attached Figure Description

[0013] Figure 1 This is a logic block diagram of the method of the present invention; Figure 2 This is a schematic diagram of the gear shifting sticking of the existing shift control strategy under extreme conditions; where curve 1 is the target gear of the transmission, curve 2 is the actual gear of the transmission, curve 3 is the real-time deceleration, curve 4 is the transmission gear displacement schematic curve, curve 5 is the throttle opening signal, curve 6 is the brake signal, and curve 7 is the brake pedal opening signal. Figure 3 This is a schematic diagram of gear shifting under extreme conditions using the method of the present invention; wherein, curve 1 is the target gear of the transmission, curve 2 is the actual gear of the transmission, curve 3 is the real-time deceleration, curve 4 is a schematic curve of transmission gear displacement, curve 5 is the throttle opening signal, curve 6 is the brake signal, and curve 7 is the brake pedal opening signal.

[0014] The present invention will be further explained and described below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0015] like Figure 1 As shown, this invention provides a shift control method for commercial vehicle AMT under extreme operating conditions, applicable to scenarios such as sudden braking during uphill shifting on mountainous national highways or some urban slopes, specifically including the following steps: Step 1: Preset the slope threshold, brake pedal opening threshold, deceleration threshold, and speed difference threshold; Specifically, the slope threshold, brake pedal opening threshold, deceleration threshold, and speed difference threshold are pre-stored and configured by the TCU. Each threshold can be adaptively adjusted according to the commercial vehicle model, load, and usage scenario to ensure the adaptability and accuracy of shift control.

[0016] Step 2: Determine whether the target gear has been engaged, the clutch has been disengaged, and the gear has been shifted out. If yes, proceed to Step 3; otherwise, repeat Step 2. Step 3: Determine whether the slope value emitted by the TCU slope sensor meets the preset slope threshold. If yes, the current working condition is considered to be an uphill working condition, and proceed to step 4; otherwise, proceed to step 6. Step 4: Determine whether the bus brake pedal opening signal is greater than the preset brake pedal opening threshold. If yes, it is considered that the driver's subjective intention is an emergency braking condition, and proceed to step 5; otherwise, proceed to step 6. Step 5: Determine whether the current deceleration meets the preset deceleration threshold according to the TCU preset threshold. If yes, proceed to step 6. Otherwise, do not engage gears, keep the main box displacement in the current state, and do not activate the gear engagement solenoid valve until the current deceleration meets the deceleration threshold. Step 6: Determine whether the speed difference between the current meshing gear and the sliding sleeve meets the preset speed difference threshold. If yes, proceed to step 7; otherwise, do not engage the gear until the speed difference meets the preset speed difference threshold. Step 7: Allow gear engagement. The TCU issues a command to control the solenoid valve to complete the gear engagement action; at this point, the gear shift control ends.

[0017] This embodiment uses a standard-load 18-ton 4x2 flatbed truck to simulate a 10% gradient driving condition, with sudden braking during gear shifting. When the brake pedal opening is ≥20%, the vehicle deceleration is ≥3m / s². 2 The transmission is prone to gear grinding at high speed differences due to excessive oscillations caused by the speed difference between the sliding sleeve and the target meshing gear. In this embodiment, the slope threshold is 10%, the brake pedal opening threshold is 20%, and the vehicle deceleration threshold is 3 m / s². 2 The speed difference threshold is 100 rpm.

[0018] Verification has shown that, for extreme operating conditions, the method of the present invention can effectively reduce the risk of gear grinding and shifting jams by independently limiting conditions such as slope, brake pedal opening and deceleration through the gear shifting execution logic during TCU shifting.

[0019] like Figure 2As shown, in the first half, the driver accelerates from a standstill by pressing the accelerator. At time t1, the accelerator is released, and the target gear changes, triggering an upshift request. At time t2, the brake is applied, and the deceleration begins to increase sharply. At time t3, the transmission begins to disengage, and the master gear shift returns to neutral. According to the original control strategy, no deceleration and brake pedal opening threshold conditions are set before the gear shift is executed. When the gear shift is executed at time t4, the transmission is prone to jamming, and the master gear shift moves in a stepped manner. The first gear shift fails, and the master gear shift returns to neutral until the gear shift is executed again at time t5. Due to the jamming during the gear shift, the power interruption time during the process from disengaging at time t3 to re-engaging at time t5 is relatively long, resulting in a poor subjective driving experience.

[0020] like Figure 3 The diagram shows the shifting process of the method of the present invention under the same working conditions. By adding deceleration and brake pedal opening threshold restrictions before the gear shifting action is performed, the timing of the gear shifting action is delayed. The gear is disengaged at time t3, and the gearbox is restricted from performing gear shifting when the deceleration is large between t3 and t4. Gear shifting is not allowed until time t4. As can be seen in the figure, compared with the original control strategy, the risk of gearbox jamming can be reduced.

[0021] As can be seen from the above, compared with the existing methods, although the method of the present invention delays the timing of gear engagement during the gear shifting stage in the extreme deceleration condition described above, it can significantly reduce the probability of gear grinding by avoiding the speed difference jitter range under this condition, eliminate the jamming during the gear engagement process, effectively reduce the shifting time under this condition, and also improve the shifting quality and subjective driving experience.

Claims

1. A shift control method for an AMT (Automated Manual Transmission) in a commercial vehicle under extreme operating conditions, characterized in that, Includes the following steps: Step 1: Preset the slope threshold, brake pedal opening threshold, deceleration threshold, and speed difference threshold; Step 2: Determine whether the target gear has been engaged, the clutch has been disengaged, and the gear has been shifted out. If yes, proceed to Step 3; otherwise, repeat Step 2. Step 3: Determine whether the slope value emitted by the TCU slope sensor meets the preset slope threshold. If yes, the current working condition is considered to be an uphill working condition, and proceed to step 4; otherwise, proceed to step 6. Step 4: Determine whether the bus brake pedal opening signal is greater than the preset brake pedal opening threshold. If yes, it is considered that the driver's subjective intention is an emergency braking condition, and proceed to step 5; otherwise, proceed to step 6. Step 5: Determine whether the current deceleration meets the preset deceleration threshold according to the TCU preset threshold. If yes, proceed to step 6. Otherwise, do not engage gears, keep the main box displacement in the current state, and do not activate the gear engagement solenoid valve until the current deceleration meets the deceleration threshold. Step 6: Determine whether the speed difference between the current meshing gear and the sliding sleeve meets the preset speed difference threshold. If yes, proceed to step 7; otherwise, do not engage the gear until the speed difference meets the preset speed difference threshold. Step 7: Allow gear engagement. The TCU issues a command to control the solenoid valve to complete the gear engagement action; at this point, the gear shift control ends.

2. The shift control method for commercial vehicle AMT under extreme operating conditions as described in claim 1, characterized in that, The slope threshold is 10%, the brake pedal opening threshold is 20%, and the deceleration threshold is 3 m / s². 2 The speed difference threshold is 100 rpm.

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