Low-temperature gear shifting control method for electro-hydraulic automatic transmission

Abstract

The present invention discloses a low-temperature gear shift control method for an electro-hydraulic automatic transmission. The main design concept of the present invention is that, considering that the control time of the low-temperature gear shift process is longer than that of normal-temperature operating conditions, it is proposed to promptly and effectively identify the timing of low-temperature gear shift triggering based on experimental setting of limit conditions. Then, through low-temperature gear shift strategies such as clutch engagement coordination matching control and engine speed request intervention control, gear shift resistance is reduced, making gear shift control easier to achieve at low temperatures. The present invention can identify whether the transmission system needs to activate the low-temperature gear shift execution strategy based on information such as the surrounding environment, vehicle condition, and gear position. Once activated, the low-temperature gear shift strategy related to intermediate shaft speed optimization is executed to ensure successful low-temperature gear shifting and ensure normal and safe vehicle driving, thereby effectively solving the problem of power interruption or vehicle inability to drive caused by failure of automatic transmission low-temperature gear shifting.

Description

Technical Field

[0001] The present invention relates to the technical field of automatic transmissions, and in particular to a low-temperature gear shifting control method for an electro-hydraulic automatic transmission. Background Art

[0002] At present, automatic transmission commercial vehicles have gradually attracted market attention and popularity. This is mainly because commercial vehicles are mainly used in long-distance transportation, urban cargo transportation, etc. Automatic transmission can relieve driving fatigue and improve driving experience.

[0003] Currently, domestic OEMs have independently developed AMTs for commercial vehicles, using a wet clutch and electric cylinder-controlled shift actuator. Their operating principle is as follows: The transmission control unit (TCU) calculates the vehicle's status in real time. When it detects a requested gear, the TCU first disengages the clutch, proceeds with the gear selection, selects, and engages. Once the gear is engaged, the clutch is reengaged. However, the AMT's shift actuator system is significantly affected by low temperatures. In severe cases, this can cause the low-temperature shifting function to fail, resulting in vehicle drivability or power interruption, posing a safety hazard.

[0004] Specifically, the existing system's gear selection and shift control system uses a conventional control strategy at room temperature. If a gear selection fails the first time, it will directly engage the gear using maximum engagement force, but this still may fail. Feedback from a current product model during low-temperature environmental validation indicates a high probability of gear selection failure at low temperatures (below 0°C), primarily during second gear (accounting for 95%). The failure rate increases with lower temperatures, reaching nearly 100% below -20°C.

[0005] Therefore, not only for AMT electro-hydraulic automatic transmissions, but also for other automatic transmission systems with clutches (dry or wet) and shift actuators, their low-temperature gear shifting control urgently needs corresponding response strategies. Summary of the Invention

[0006] In view of the above, the present invention aims to provide a low-temperature gear shift control method for an electro-hydraulic automatic transmission to solve the above-mentioned technical problems.

[0007] The technical solution adopted in the present invention is as follows:

[0008] The present invention provides a low-temperature gear shift control method for an electro-hydraulic automatic transmission, comprising:

[0009] Real-time detection of vehicle operating conditions and transmission working status;

[0010] Determine whether the vehicle operating condition and transmission operating status meet the preset conditions;

[0011] When the preset conditions are met, the low-temperature gear shift execution flag is activated;

[0012] According to the preset clutch engagement and matching control mode, low-temperature gear shifting is executed, including: during the process of synchronization between the transmission intermediate shaft speed and the engine speed, the intermediate shaft speed is driven to be higher than the target gear synchronization speed.

[0013] In at least one possible implementation, performing low-temperature gear shifting includes:

[0014] When the target gear is received, the clutch is disengaged with the engine intervention control in the off state;

[0015] Shift the gear to neutral. During this process, the engine intervention control is turned on, and the engine request speed = target gear synchronous speed + first speed difference;

[0016] The synchronizer fork is controlled to the gear selection layer where the target gear is located. During this process, the engine request speed = the target gear synchronization speed + the first speed difference;

[0017] After the gear is selected, the clutch oil circuit is controlled to fill with oil and torque transmission is started to be combined to increase the speed of the gearbox intermediate shaft until it is synchronized with the engine speed. During this process, the engine request speed = the target gear synchronization speed + the second speed difference;

[0018] When the actual engine speed reaches the requested speed and the intermediate shaft speed is synchronized with the engine speed, the clutch pressure is released to the semi-engaged point;

[0019] After reaching the semi-engagement point, the gear shift control is executed. During this process, the engine request speed = the target gear synchronous speed.

[0020] In at least one possible implementation, performing low-temperature gear shifting further includes:

[0021] Before disengaging the clutch, check the actual gear status:

[0022] If the actual gear status is neutral before receiving the target gear, the gear selection control link will be entered directly.

[0023] In at least one possible implementation manner, the preset condition includes:

[0024] The atmospheric ambient temperature is ≤ the first low temperature limit; and

[0025] Transmission oil temperature ≤ the second low temperature limit; and

[0026] The transmission target gear is an allowable low-temperature gear; and

[0027] Vehicle speed > preset speed limit suitable for low temperature gear shifting.

[0028] In at least one possible implementation manner, the preset condition includes:

[0029] The atmospheric ambient temperature is ≤ the first low temperature limit; and

[0030] The target gear shifting failed for the first time.

[0031] In at least one possible implementation, the control method further includes: during the low-temperature gear shifting process, if the gear shifting fails, the gear shifting is continued for several times until the number reaches a preset upper limit. If the gear shifting still fails, a gear shifting failure fault message is output.

[0032] Compared to the prior art, the main design concept of the present invention lies in that, considering that the control time of the low-temperature gear shifting process is longer than that under normal temperature conditions, it proposes to timely and effectively identify the triggering time of low-temperature gear shifting based on experimental setting limit conditions. Then, through low-temperature gear shifting strategies such as clutch engagement coordination matching control and engine speed request intervention control, gear shifting resistance is reduced, making gear shifting control easier to achieve at low temperatures. The present invention can identify whether the transmission system needs to activate the low-temperature gear shifting execution strategy based on information such as the surrounding environment, vehicle condition, and gear status. Once activated, the low-temperature gear shifting strategy related to intermediate shaft speed optimization is executed to ensure successful low-temperature gear shifting and ensure normal and safe vehicle operation. This effectively solves the problem of power interruption or vehicle inability to drive caused by automatic transmission low-temperature gear shifting failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described below with reference to the accompanying drawings, in which:

[0034] Figure 1 A schematic flow chart of a low-temperature gear shift control method for an electro-hydraulic automatic transmission provided by an embodiment of the present invention;

[0035] Figure 2 A flow chart of the low-temperature gear shifting execution strategy control provided by an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of the low-temperature gear shifting strategy control process provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0038] The present invention proposes an embodiment of a low-temperature gear shift control method for an electro-hydraulic automatic transmission. Specifically, Figure 1 shown, including:

[0039] Step S1: Real-time detection of vehicle operating conditions and gearbox operating conditions;

[0040] Step S2: determining whether the vehicle operating condition and the gearbox operating state meet the preset conditions;

[0041] Step S3: When the preset conditions are met, the low-temperature gear shift execution flag is triggered to activate;

[0042] Specifically, the following two types of preset conditions can be considered for setting the preset conditions:

[0043] The first precondition:

[0044] The atmospheric ambient temperature is ≤ the first low temperature limit; and

[0045] Transmission oil temperature ≤ the second low temperature limit; and

[0046] The transmission target gear is an allowable low-temperature gear; and

[0047] Vehicle speed > preset speed limit suitable for low temperature gear shifting.

[0048] Or, in other embodiments,

[0049] The second precondition:

[0050] The atmospheric ambient temperature is ≤ the first low temperature limit; and

[0051] The target gear shifting failed for the first time.

[0052] It should be noted that the limit values ​​in the above conditions are obtained based on test data statistics.

[0053] Continuing from the above, step S4, according to the preset clutch engagement and matching control mode, performs low-temperature gear shifting, including: when the intermediate shaft speed is synchronized with the engine speed, driving the intermediate shaft speed to be higher than the target gear synchronization speed.

[0054] Specifically, once the low-temperature gear shift execution flag is activated (set to 1), the TCU will execute the corresponding low-temperature gear shift strategy to ensure successful low-temperature gear shifting and normal and safe vehicle operation. It should be noted that if the execution process fails, the TCU will continue to attempt to shift gears a second time until the number of attempts reaches a preset upper limit. If it still fails, it will output a gear shift failure fault message. If the gear shift execution is successful, the control mode is exited and the subsequent vehicle driving control mode is entered.

[0055] Specifically, the complete strategy for executing low-temperature gear shifting can be found in Figure 2 As shown:

[0056] (1) Target gear position is issued. During vehicle driving, if the target gear position is received and the low-temperature gear shift trigger flag is activated, the clutch disengagement action is first performed. The clutch pressure is released to the target value according to a certain slope, and the clutch is disengaged. During this process, the engine intervention control is in the off state.

[0057] (2) Shift-off control. Shift-off control is performed by controlling the shift cylinder. The specific cylinder control is not the focus of this invention and will not be described here. During this process, engine intervention control is enabled, and the engine speed request = target gear synchronous speed + first speed difference (greater than 0). The goal is to quickly increase the engine speed to the target synchronous speed, preparing for the subsequent gear-engaging synchronous control phase.

[0058] (3) Gear selection control. After the gear is shifted to neutral, the selector cylinder is controlled to move the synchronizer fork to the target gear level. During this process, engine intervention control is enabled, and the engine request speed = target gear synchronization speed + first speed difference (greater than 0), which is consistent with the gear shift control.

[0059] (4) Clutch engagement and matching control for assisting gear shifting. When the gear is selected, the pre-control before gear shifting is started: by controlling the clutch pressure to drive the solenoid valve, the solenoid valve drive current is increased at a preset rate, so that the clutch oil circuit is filled with oil and torque transmission begins. According to the system characteristics, the clutch torque transmission will cause the speed of the gearbox intermediate shaft to increase until it is synchronized with the engine speed. In this process, the engine request speed = the target gear synchronization speed + the second speed difference (greater than 0). The purpose is to make the intermediate shaft speed higher than the target gear synchronization speed when the intermediate shaft speed is synchronized with the engine speed, so that the resistance is small when shifting, making it easy to shift gears. When the actual engine speed reaches the requested speed and the intermediate shaft speed is synchronized with the engine speed, the clutch begins to perform pressure relief control. When the actual clutch pressure is relieved to the half-engagement point, this control stage ends.

[0060] (5) Gear engagement control. Gear engagement control is performed by controlling the shift cylinder. During this process, engine intervention control is turned on and the engine request speed = target gear synchronization speed.

[0061] The above is the execution process of low temperature gear shift control. The control process diagram is as follows: Figure 3 In addition, it can be supplemented that if the actual gear state is already in neutral N when the target gear is issued, the gear removal control is directly skipped and the gear selection control step is entered.

[0062] In summary, the main design concept of the present invention lies in that, considering that the control time of the low-temperature gear shift process is longer than that of normal temperature operating conditions, it proposes to timely and effectively identify the triggering time of low-temperature gear shift based on experimental setting limit conditions. Then, through low-temperature gear shift strategies such as clutch engagement coordination matching control and engine speed request intervention control, gear shift resistance is reduced, making gear shift control easier to achieve at low temperatures. The present invention can identify whether the transmission system needs to activate the low-temperature gear shift execution strategy based on information such as the surrounding environment, vehicle condition, and gear status. Once activated, the low-temperature gear shift strategy related to intermediate shaft speed optimization is executed to ensure successful low-temperature gear shift and ensure normal and safe vehicle operation. This effectively solves the problem of power interruption or vehicle inability to drive caused by automatic transmission low-temperature gear shift failure.

[0063] In the embodiment of the present invention, "at least one" refers to one or more, and "more" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b and c can be represented by: a, b, c, a and b, a and c, b and c, or a, b and c, where a, b, c can be single or multiple.

[0064] The above describes in detail the structure, features and effects of the present invention based on the embodiments shown in the drawings, but the above is only a preferred embodiment of the present invention. It should be noted that the technical features involved in the above embodiments and their preferred modes can be reasonably combined and matched into a variety of equivalent schemes by those skilled in the art without departing from or changing the design ideas and technical effects of the present invention; therefore, the scope of implementation of the present invention is not limited to what is shown in the drawings. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which still do not exceed the spirit covered by the description and drawings, should be within the scope of protection of the present invention.

Claims

1. A low-temperature gear shift control method for an electro-hydraulic automatic transmission, characterized in that: include: Real-time detection of vehicle operating conditions and transmission working status; Determine whether the vehicle operating condition and transmission operating status meet the preset conditions; When the preset conditions are met, the low-temperature gear shift execution flag is activated; Executing low-temperature gear shifting according to a preset clutch engagement and matching control mode includes: driving the intermediate shaft speed to be higher than the target gear synchronization speed during synchronization of the transmission intermediate shaft speed with the engine speed; Wherein, executing low temperature gear shifting includes: When the target gear is received, the clutch is disengaged with the engine intervention control in the off state; Shift the gear to neutral. During this process, the engine intervention control is turned on, and the engine request speed = the target gear synchronous speed + the first speed difference; Control the synchronizer fork to the gear selection layer where the target gear is located. During this process, the engine request speed = the target gear synchronization speed + the first speed difference; After the gear is selected, the clutch oil circuit is controlled to fill with oil and torque transmission is started to be combined to increase the speed of the gearbox intermediate shaft until it is synchronized with the engine speed. During this process, the engine request speed = the target gear synchronization speed + the second speed difference; When the actual engine speed reaches the requested speed and the intermediate shaft speed is synchronized with the engine speed, the clutch pressure is released to the semi-engaged point; After reaching the semi-engagement point, the gear shift control is executed. During this process, the engine request speed = the target gear synchronous speed.

2. The low-temperature gear shift control method of an electro-hydraulic automatic transmission according to claim 1, characterized in that: The execution of low temperature gear shifting further includes: Before disengaging the clutch, check the actual gear status: If the actual gear status is neutral before receiving the target gear, the gear selection control link will be entered directly.

3. The low-temperature gear shift control method of an electro-hydraulic automatic transmission according to claim 1, characterized in that: The preset conditions include: The atmospheric ambient temperature is ≤ the first low temperature limit; and Transmission oil temperature ≤ the second low temperature limit; and The transmission target gear is an allowable low-temperature gear; and Vehicle speed > preset speed limit suitable for low temperature gear shifting.

4. The low-temperature gear shift control method of an electro-hydraulic automatic transmission according to claim 1, characterized in that: The preset conditions include: The atmospheric ambient temperature is ≤ the first low temperature limit; and The target gear shifting failed for the first time.

5. The low-temperature gear shift control method for an electro-hydraulic automatic transmission according to any one of claims 1 to 4, characterized in that: The control method further includes: during the low-temperature gear shifting process, if the gear shifting fails, continuing to shift the gear several times until the number of times reaches a preset upper limit, and if the gear shifting still fails, outputting a gear shifting failure fault message.

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