AT automatic transmission downshift drivability optimization method

Abstract

The invention discloses an AT automatic transmission downshift drivability optimization method, and belongs to the technical field of automatic transmissions. The method comprises the following steps: adding a transmission testing process, and collecting core parameters of a combination side clutch corresponding to each gear in a transmission; comparing the actual parameter with the basic parameter, calculating a deviation value of the two parameters, and writing the deviation value into a TCU storage system; after the vehicle leaves a factory, parameters are automatically called to control oil charging and discharging actions of the clutch in the TCU downshift process; and meanwhile, continuous self-learning optimization is carried out on control parameters of all downshift actions in the daily driving process of the whole vehicle. And multi-dimensional working condition parameters in the vehicle running process are collected in real time, downshift scenes are classified, and the oil charging pressure of the clutch on the combination side under the different downshift scenes is dynamically corrected. According to the method, the problem of initial downshift pause is solved, it is guaranteed that the vehicle can meet the basic drivability requirement when going off the line, the oil charge pressure of the clutch is dynamically corrected, the problem of accidental downshift pause after long-mileage use is solved, and downshift smoothness in the whole scene is achieved.

Description

Technical Field

[0001] This invention relates to a method for optimizing the drivability of downshifting in an automatic transmission (AT), belonging to the field of automatic transmission technology. Background Technology

[0002] The drivability of automatic transmissions is one of the core evaluation criteria in the mass production process of vehicles. Among them, AT automatic transmissions (automatic transmissions with manual mode) are significantly more difficult to optimize in terms of drivability than other types of transmissions due to their complex structure and large gear ratio span. Among the common shift jerking issues in AT transmissions, the jerking during downshifting while braking is the most noticeable, and the probability of this problem gradually increases with the transmission's service life. The essence of downshift jerking is the lurching of the vehicle caused by the shifting action during coasting or braking deceleration. Its main causes include improper clutch pressure control and fluctuations in vehicle torque and load.

[0003] Existing optimization solutions for downshift jerking do not adequately consider hardware variations at the factory, resulting in the TCU (Transmission Control Unit) preset parameters not being accurately matched with the actual clutch performance. Furthermore, they are insufficient to fully cover complex operating conditions such as different braking intensities and decelerations, and conventional calibration methods cannot effectively address occasional downshift jerking. Summary of the Invention

[0004] To address the problems existing in the background art, the present invention provides a method for optimizing the drivability of downshifting in an automatic transmission (AT).

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for optimizing the drivability of downshifting in an automatic transmission (AT), the method comprising the following steps:

[0006] S1: Implementation of offline optimization module;

[0007] S101: In the final process before the AT transmission rolls off the production line, a special test process for a single transmission is added, and core parameters of the clutch on the engagement side corresponding to each gear in the transmission are collected through professional testing equipment.

[0008] The core parameters include clutch hydraulic response time, hydraulic response speed, and accurate value of the Kiss point.

[0009] S102: Compare the actual parameters of each clutch collected with the preset basic parameters in the TCU software one by one, calculate the deviation value between the two through the preset algorithm, and write the calculated deviation value into the TCU's storage system to complete the initial correction of the control parameters.

[0010] S103: After the vehicle leaves the factory, the TCU automatically calls the corrected parameters in the storage system to control the clutch filling and releasing actions during each downshift. At the same time, during the daily driving of the vehicle, the TCU continuously learns and optimizes the control parameters of each downshift action based on the actual feedback of each downshift.

[0011] S2: Implementation of the working condition subdivision calibration optimization module.

[0012] S201: Through the TCU's operating condition recognition function, multi-dimensional operating condition parameters are collected in real time during the vehicle's driving process;

[0013] The operating parameters include braking intensity, vehicle deceleration, engine speed, turbine speed, speed difference between engine speed and turbine speed, output shaft speed change rate, and whether the engine speed and turbine speed cross over each other.

[0014] S202: Based on the collected operating parameters, downshifting scenarios are divided into three categories:

[0015] Coasting downshift: Downshifting during the natural coasting process of a vehicle, i.e., without braking operation;

[0016] Light braking downshift: Downshifting during the process of slow vehicle deceleration, i.e., braking intensity ≤30%;

[0017] Heavy braking downshift: Downshifting during rapid deceleration of the vehicle, i.e., braking intensity > 30%.

[0018] Special operating conditions are also marked;

[0019] S203: Based on the principle that the greater the speed difference and the greater the rate of change of speed, the more negative correction is required, the oil filling pressure of the clutch on the engagement side is dynamically corrected under different downshifting scenarios and special working conditions.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention eliminates hardware discrepancies at the transmission's factory stage through an offline optimization module, ensuring precise matching between TCU control parameters and actual clutch performance. This resolves the initial downshift jerking issue and guarantees that vehicles meet basic drivability requirements immediately upon production. Furthermore, the working condition subdivision calibration optimization module covers complex and special working conditions such as coasting downshifts and downshifts under varying braking intensities, dynamically correcting clutch filling pressure to effectively address occasional downshift jerking after long-mileage use, achieving smooth downshifting across all scenarios. Moreover, the solution is highly adaptable and can be extended to various AT transmissions based on clutch-clutch control principles, providing a standardized basis for improving automatic transmission drivability and fully meeting the mass production requirements of OEMs and the driving experience needs of end users. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the clutch in its free state;

[0023] Figure 2 This is a schematic diagram of the clutch at the Kiss Point state. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] A method for optimizing downshifting performance of an automatic transmission (AT) is disclosed, primarily applicable to various transmission structures of AT transmissions based on clutch-clutch control principles. This method involves collaborative execution of an offline optimization module and a condition-specific calibration optimization module. First, offline optimization addresses initial hardware variance issues. Then, condition-specific calibration optimization covers complex usage scenarios, ultimately improving downshift smoothness across all scenarios. The method includes the following steps:

[0026] S1: Implementation of offline optimization module;

[0027] S101: In the final process before the AT transmission rolls off the production line, a special test process for a single transmission is added, and core parameters of the clutch on the engagement side corresponding to each gear in the transmission are collected through professional testing equipment.

[0028] The core parameters include clutch hydraulic response time, hydraulic response speed, and the accurate value of the Kiss point (engagement critical point); among which, the positional characteristics of the Kiss point are referenced. Figure 1 and Figure 2 To ensure accurate data collection location.

[0029] S102: Compare the actual parameters of each clutch collected with the preset basic parameters in the TCU software one by one, calculate the deviation value between the two through the preset algorithm, and write the calculated deviation value into the TCU's storage system to complete the initial correction of the control parameters.

[0030] S103: After the vehicle leaves the factory, the TCU automatically calls the corrected parameters in the storage system to control the clutch filling and releasing actions during each downshift, ensuring that the hardware characteristics and control parameters are accurately matched. At the same time, during the daily driving of the vehicle, the TCU continuously learns and optimizes the control parameters of each downshift action based on the actual feedback of each downshift, and constantly improves the drivability.

[0031] S2: Implementation of the working condition subdivision calibration optimization module.

[0032] S201: Through the TCU's operating condition recognition function, multi-dimensional operating condition parameters are collected in real time during the vehicle's driving process;

[0033] The operating parameters include braking intensity (determined by the brake pedal travel sensor signal), vehicle deceleration (calculated by the vehicle speed sensor signal), engine speed, turbine speed, speed difference between engine speed and turbine speed, output shaft speed change rate (the ratio of the change in output shaft speed to the change in time), and whether the engine speed and turbine speed cross over (i.e., whether the engine speed and turbine speed cross numerically).

[0034] S202: Based on the collected operating parameters, downshifting scenarios are divided into three categories:

[0035] Coasting downshift: Downshifting during the natural coasting process of a vehicle, i.e., without braking operation;

[0036] Light braking downshift: Downshifting during the process of slow vehicle deceleration, i.e., braking intensity ≤30%;

[0037] Heavy braking downshift: Downshifting during rapid deceleration of the vehicle, i.e., braking intensity > 30%.

[0038] At the same time, special operating conditions such as engine and turbine speed crossing and vehicle speed in the 20-40km / h range are marked as key areas of focus for calibration.

[0039] S203: Based on the principle that the greater the speed difference and the greater the rate of change of speed, the more negative correction is required, the oil filling pressure of the clutch on the engagement side is dynamically corrected under different downshifting scenarios and special working conditions to delay the engagement speed of the clutch on the engagement side.

[0040] The principle that the greater the speed difference and the greater the rate of change of rotational speed, the more negative correction is applied is as follows:

[0041] For coasting downshifts, since the speed difference and the output shaft speed change rate are small (speed difference gap≤500rpm and output shaft speed change rate dntout≤100rpm / ms), only a small negative correction of 5%-15% is made, which slightly delays the engagement speed of the clutch on the engagement side.

[0042] For light braking downshifting, when 500rpm < gap ≤ 1500rpm and 100rpm / ms < dntout ≤ 300rpm / ms, a moderate negative correction of 15%-35% is made based on the actual values ​​of the speed difference and the output shaft speed change rate, and the engagement speed of the clutch on the engagement side is moderately delayed.

[0043] For special operating conditions such as heavy braking downshifting, engine and turbo speed crossing, and specific vehicle speed ranges, due to the large speed difference and output shaft speed change rate (gap>1500rpm and dntout>300rpm / ms), a large negative correction of 35%-60% is performed to significantly delay the engagement speed of the clutch on the engagement side and avoid jerking caused by excessively fast shifting speed.

[0044] Example 1: Application of a rear-wheel drive eight-speed automatic transmission

[0045] In D mode, this rear-wheel-drive eight-speed automatic transmission utilizes three clutches working in tandem for each gear: for example, D3 engages clutches B, C, and E, while D2 engages clutches A, B, and E. When the vehicle shifts from D3 to D2, the process is as follows:

[0046] Offline optimization: The hydraulic pressure response time, hydraulic pressure response speed and Kiss point current of clutch A (engaged side clutch) are collected through special tests. The actual parameters collected are compared with the TCU preset basic parameters, the deviation value is calculated and written into the TCU, and the corrected hydraulic pressure response time and hydraulic pressure response speed are obtained.

[0047] Operating condition subdivision calibration: During vehicle operation, the TCU collects braking intensity, deceleration, engine and turbine speed difference and output shaft speed change rate in real time, and determines the downshift type (coasting downshift, light braking downshift or heavy braking downshift) based on the collected operating condition parameters.

[0048] Dynamic control: Based on the judgment results, and following the principle that the greater the speed difference and the greater the rate of change of speed, the more negative correction is required, the oil filling pressure of clutch A is dynamically adjusted to slow down its engagement speed and ensure that there is no jerking during the downshift from 3rd to 2nd gear.

[0049] Example 2: Application of a front-wheel drive eight-speed automatic transmission

[0050] In D mode, the front-wheel-drive eight-speed automatic transmission uses two clutches working in tandem for each gear: for example, D3 corresponds to the engagement of clutches C1 and C3, and D2 corresponds to the engagement of clutches C1 and B1. The process of downshifting from D3 to D2 is the same as that of the rear-wheel-drive eight-speed automatic transmission.

[0051] Offline optimization: The hydraulic pressure response time, hydraulic pressure response speed and accurate value of the B1 clutch (engaged side clutch) are collected through special tests, compared with the TCU preset basic parameters, the deviation value is calculated, corrected and written into the TCU;

[0052] Operating condition subdivision calibration: The TCU collects multi-dimensional operating condition parameters in real time, classifies downshifting scenarios, and focuses on special operating conditions;

[0053] Dynamic control: Based on the classification of working conditions and core principles, the oil filling pressure of clutch B1 is dynamically adjusted to slow down the engagement speed and achieve smooth downshifting.

[0054] Real-vehicle verification results:

[0055] Through real-vehicle testing of the rear-wheel drive and front-wheel drive eight-speed automatic transmissions in the two application examples above, the results before and after optimization are shown as follows:

[0056] In its initial state, the vehicle exhibits no noticeable lurching during downshifting, and its drivability meets the basic requirements of end users.

[0057] After long-distance driving, under complex operating conditions such as different braking intensities and different decelerations, the fluctuation range of engine and turbine speeds is significantly reduced, and the vehicle speed curve remains stable, fully meeting the requirements of OEMs and end users for driving smoothness.

[0058] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0059] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for optimizing the downshifting performance of an automatic transmission (AT), characterized in that: The method includes the following steps: S1: Implementation of offline optimization module; S2: Implementation of the working condition subdivision calibration optimization module.

2. The method for optimizing the drivability of downshifting in an automatic transmission according to claim 1, characterized in that: S1 includes the following steps: S101: In the final process before the AT transmission rolls off the production line, a special test process for a single transmission is added, and core parameters of the clutch on the engagement side corresponding to each gear in the transmission are collected through professional testing equipment. S102: Compare the actual parameters of each clutch collected with the preset basic parameters in the TCU software one by one, calculate the deviation value between the two through the preset algorithm, and write the calculated deviation value into the TCU's storage system to complete the initial correction of the control parameters. S103: After the vehicle leaves the factory, the TCU automatically calls the corrected parameters in the storage system to control the clutch filling and releasing actions during each downshift. At the same time, during the daily driving of the vehicle, the TCU continuously learns and optimizes the control parameters of each downshift action based on the actual feedback of each downshift.

3. The method for optimizing the drivability of downshifting in an automatic transmission according to claim 2, characterized in that: The core parameters mentioned in S101 include clutch oil pressure response time, oil pressure response speed, and accurate value of the Kiss point.

4. The method for optimizing the drivability of downshifting in an automatic transmission according to claim 3, characterized in that: S2 includes the following steps: S201: Through the TCU's operating condition recognition function, multi-dimensional operating condition parameters are collected in real time during the vehicle's driving process; S202: Based on the collected operating parameters, downshifting scenarios are divided into three categories, and special operating conditions are marked at the same time; S203: Based on the principle that the greater the speed difference and the greater the rate of change of speed, the more negative correction is required, the oil filling pressure of the clutch on the engagement side is dynamically corrected under different downshifting scenarios and special working conditions.

5. The method for optimizing the drivability of downshifting in an automatic transmission according to claim 4, characterized in that: The operating parameters mentioned in S201 include braking intensity, vehicle deceleration, engine speed, turbine speed, speed difference between engine speed and turbine speed, output shaft speed change rate, and whether the engine speed and turbine speed cross over.

6. The method for optimizing the drivability of downshifting in an automatic transmission according to claim 5, characterized in that: S202 divides downshifting scenarios into three categories: Coasting downshift: Downshifting during the natural coasting process of a vehicle, i.e., without braking operation; Light braking downshift: Downshifting during the process of slow vehicle deceleration, i.e., braking intensity ≤30%; Heavy braking downshift: Downshifting during rapid deceleration of the vehicle, i.e., braking intensity > 30%.

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