Method for improving the shifting quality of an automatic or automated transmission of a motor vehicle in workshop / customer service situations or at the end of the assembly line before delivery

Abstract

A method for improving the shifting quality of an automatic or automated transmission of a motor vehicle during workshop / customer service or at the end of the production line before delivery, characterized in that the filling pressure of a friction shift element of the transmission during the closing process, consisting of a rapid filling phase, a filling compensation phase and a load transfer phase, when engaging a gear with the vehicle at least approximately stationary, is determined by the fact that the piston of the friction shift element is constantly subjected to a filling pressure start value (p_start) over a predefined filling compensation time (F) during the filling compensation phase, wherein, if a drop in rotational speed at the input element of the friction shift element is detected before the end of the predefined filling compensation time (F),The actual filling pressure of the friction switching element is inferred from the difference (Dt_2) between the time (t_actual_2) of the drop in rotational speed at the input element of the friction switching element and a reference time (t_target), whereby the filling pressure start value (p_start) is reduced to the actual filling pressure and stored as the new filling pressure start value for the next closing operation of the friction switching element, and wherein, if no drop in rotational speed at the input element of the friction switching element is detected until the predefined filling compensation time (F) has elapsed, the load transfer phase is started, whereby the piston of the friction switching element is subjected to a modulated switching pressure, and the time interval starting from the switching command or from the end of the rapid filling phase until the time (t_actual_1) of the detection of a drop in rotational speed at the input element of the friction switching element is determined and compared with a predefined reference value.wherein the actual filling pressure of the friction switching element is inferred from the difference (Dt_1) between the time (t_actual_1) of the drop in rotational speed at the input element of the friction switching element and the reference time (t_target), wherein the filling pressure start value (p_start) is increased to the actual filling pressure and stored as the new filling pressure start value for the next closing operation of the friction switching element.

Description

[0001] The invention relates to a method for improving the shifting quality of an automatic transmission or automated transmission of a motor vehicle in the workshop / customer service case or at the end of the assembly line before delivery according to the preamble of claim 1.

[0002] Typically, in automatic transmissions of motor vehicles, especially stepped automatic transmissions, the filling pressure of an engaging shift element is adapted based on the evaluation of speed signals during gear activation, i.e., during gear engagement, in order to improve shifting comfort and quality over the transmission's service life. This filling pressure adaptation takes into account and compensates for undesirable deviations in the shifting process, which can occur, for example, due to component tolerances for cost and manufacturing reasons, changes in the friction coefficient of the clutch plates, and mechanical wear within the transmission.

[0003] Typically, in the event of customer complaints or after a transmission repair, the previously stored adaptation data of the shift elements of an automatic transmission are deleted in order to subsequently determine and save initial adaptation cycles for the faulty shift elements or shifts, or for any replaced shift elements, using a defined driving scenario. This can be done via pulse adaptation, in which a shift element is subjected to a pressure pulse value for a specified pulse duration, or via shift adaptation.

[0004] US Patent 5,456,647 A1 describes an adaptation procedure for friction shift elements of an automatic transmission, in which the filling pressure of the shift elements is adapted at the end of the assembly line before delivery of a vehicle comprising an automatic transmission, whereby the turbine speed of the torque converter, the engine speed and the filling pressure of the shift elements are evaluated for this purpose.

[0005] From DE 102 38 474 A1 of the applicant, a method for adapting the shift sequences of an automatic transmission during vehicle commissioning is known, in which the adaptation values ​​are determined as a function of events determining shift quality during the operation of an automatic transmission, stored in adaptation maps in a control unit, and used to adapt the control of the shift sequences. The known method is carried out on a test bench with predefined entry conditions for the adaptation curves, wherein the entry conditions are set in the control unit by means of control flags or start codes, and the control flags or start codes are specified via workshop testers or diagnostic devices.

[0006] Furthermore, DE 102 48 179 A1 of the applicant discloses a method for the filling pressure adaptation of a switching element of an automatic transmission, in which the closed switching element is opened in a defined manner when the vehicle is stationary until a predetermined differential speed threshold is exceeded, wherein the filling pressure of the switching element is then determined over the time required to reach the predetermined differential speed threshold, and wherein the switching element is closed in a defined manner after reaching the predetermined differential speed threshold.

[0007] US Patent 7 069 767 B2 discloses a method for adapting clutch parameters of an automatic transmission in the installed state at the end of the assembly line, in which the driving stage P must be engaged in the transmission to start the method.

[0008] Furthermore, DE 10 2009 051 720 A1 discloses a method for determining the value of an adaptive parameter upon recommissioning of an adaptable system, wherein the system is a drive for an actuator of an automated transmission or an automated clutch, and wherein the recommissioning of the system is carried out with the value of the adaptive parameter as it was for the initial commissioning of the system. It is provided that, after the ignition is first activated in the vehicle, predetermined operating elements, such as the gear selector or the brake pedal, must be actuated in a predetermined sequence to start the procedure.

[0009] The present invention aims to provide a method for improving the shifting quality of an automatic or automated transmission of a motor vehicle during workshop / customer service or at the end of the production line before delivery, whereby adaptation can be achieved without driving. This is intended to generate improved shifting quality from the very first drive and increase customer satisfaction.

[0010] This problem is solved by the features of claim 1. Further embodiments and advantages are set out in the dependent claims.

[0011] Accordingly, a method for improving the shifting quality of an automatic or automated transmission of a motor vehicle is proposed for use in workshop / customer service or at the end of the production line before delivery. This method determines the filling pressure of a friction shift element during the closing process when engaging a gear with the vehicle at least nearly stationary. The closing process consists of a rapid filling phase, a filling equalization phase, and a load transfer phase, which occur sequentially. The pressure provided by a control unit during the filling equalization phase is referred to as the filling pressure, and it represents the pressure level required to ensure that the pressurized piston bearing against the friction element of the friction shift element is in force equilibrium with the piston return force of the friction shift element and remains in this bearing position.

[0012] In this process, the piston of the friction switching element is constantly subjected to a starting filling pressure value during the filling compensation phase for a predefined filling compensation time. During this time, the system monitors whether a drop in rotational speed occurs at the input element of the friction switching element. If a drop in rotational speed is detected at the input element of the friction switching element before the predefined filling compensation time expires, the time interval from the switching command or the end of the rapid filling phase until the detection of the drop in rotational speed at the input element of the friction switching element is determined and compared with a predefined reference value. Any deviation of this time interval from the reference value, i.e.,The actual filling pressure of the friction switching element is inferred from the difference between the time of the drop in rotational speed at the input element of the friction switching element and a reference time, and the filling pressure start value is reduced to the actual filling pressure and stored as the new filling pressure start value for the next closing process of the friction switching element.

[0013] If no drop in rotational speed is detected at the input element of the friction switching element until the predefined filling compensation time has elapsed, the load transfer phase is started and the piston of the friction switching element is subjected to a modulated switching pressure. The time interval from the switching command or from the end of the rapid filling phase until a drop in rotational speed at the input element of the friction switching element is detected is determined and compared with the predefined reference value. The actual filling pressure of the friction switching element is inferred from any deviation of the time interval from the reference value, i.e., from the difference between the time of the drop in rotational speed at the input element of the friction switching element and a reference time. The initial filling pressure value is then increased to the actual filling pressure and stored as the new initial filling pressure value for the next closing operation of the friction switching element.The modulated switching pressure can, for example, take the form of a pressure ramp when viewed over time.

[0014] In one embodiment of the invention, the method is only carried out when the motor vehicle's drive engine is at least approximately idling.

[0015] In the event that the inventive method is controlled via a tester (i.e., the method is not carried out during normal driving operation), the closing process of the switching element is immediately aborted if a drop in rotational speed is detected at the input element of the friction switching element.

[0016] In the event that the inventive method is automatically triggered by the transmission control during normal driving operation with unchanged driver input of “position N” or “position P”, the closing process is immediately aborted as soon as a drop in speed is detected at the input element of the friction switching element.

[0017] According to the invention, the method can be applied to a friction shift element that does not transmit torque in the target gear, but is temporarily actuated during gear engagement to synchronize a positive-locking shift element that does transmit torque in the target gear. In a further development of the invention, a temperature equivalent to the transmission oil temperature is taken into account as a parameter when carrying out the method.

[0018] The invention is explained in more detail below with reference to the accompanying figure. The figure shows the curves of the clutch pressure and the rotational speed at the input element of the friction switching element during the execution of the method as a function of time.

[0019] In the upper part of the accompanying figure, curve A shows the pressure curve at the friction switching element as a function of time, assuming no drop in rotational speed is detected at the input element of the friction switching element until the predefined filling equalization time has elapsed. Curve B shows the rotational speed curve at the input element of the friction switching element as a function of time, assuming no drop in rotational speed is detected at the input element of the friction switching element until the predefined filling equalization time has elapsed.

[0020] Furthermore, curve C shows the pressure curve at the friction switching element as a function of time for the case where a drop in rotational speed at the input element of the friction switching element is detected before the predefined filling equalization time has elapsed, with the corresponding rotational speed curve at the input element of the friction switching element as a function of time being represented by curve D. The rapid filling phase is denoted in the figure as time interval E and the filling equalization phase, i.e., the filling equalization time, as time interval F; the load transfer phase begins at time t_L.

[0021] According to the invention and with reference to curves A and B in the accompanying figure, the filling pressure of a friction switching element during the closing process when engaging a gear with the vehicle at least approximately stationary is determined by the fact that the piston of the friction switching element is constantly subjected to a filling pressure start value p_start during the filling equalization phase over a predefined filling equalization time.

[0022] If, as illustrated by curve B, no drop in rotational speed is detected at the input element of the friction switching element until the predefined filling compensation time F has elapsed, the load transfer phase is started at time t_L, whereby the piston of the friction switching element is subjected to a ramp-like switching pressure.

[0023] According to the invention, the time interval from the switching command or from the end of the rapid filling phase until a drop in rotational speed at the input element of the friction switching element is determined and compared with a predefined reference value. The actual filling pressure of the friction switching element is then inferred from the deviation Dt_1 of this time interval from the reference value. In the example shown, a drop in rotational speed at the input element of the friction switching element occurs at time t_actual_1, where the reference value is time t_target.

[0024] The fill pressure start value p_start is then increased to the determined actual fill pressure and stored as the new fill pressure start value for the next closing process of the friction switching element.

[0025] The case in which a drop in rotational speed at the input element of the friction switching element is detected before the predefined filling equalization time F elapses is illustrated by curves C and D. In this case, a drop in rotational speed at the input element of the friction switching element occurs within the rapid filling phase at time t_actual_2. The actual filling pressure of the friction switching element is inferred from the difference Dt_2 between time t_actual_2 and the reference time t_target. The initial filling pressure value p_start is then reduced to the actual filling pressure and stored as the new initial filling pressure value for the next closing operation of the friction switching element.

[0026] The inventive concept allows adaptation cycles to be performed in the workshop or at the end of the production line without driving, thereby generating improved shifting quality from the very first drive and increasing customer satisfaction. Additionally, time is saved because the inventive method determines a reliable adaptation value more quickly than the known pulse-based standstill adaptation, in which an adaptation value for a specific clutch is determined using several rapid filling and filling pressure pulses. Reference sign A. Clutch pressure curve as a function of time in the case that no drop in speed is detected at the input element of the friction switching element until the predefined filling compensation time has elapsed. B. Course of the rotational speed at the input element of the friction switching element as a function of time in the case that no drop in rotational speed at the input element of the friction switching element is detected until the predefined filling compensation time has elapsed. C. Pressure curve at the friction switching element as a function of time in the case that a drop in rotational speed at the input element of the friction switching element is detected before the predefined filling compensation time has elapsed. D. Course of the rotational speed at the input element of the friction switching element as a function of time in the case that a drop in the rotational speed at the input element of the friction switching element is detected until the predefined filling compensation time has elapsed. E Rapid filling phase F Filling equalization time Dt_1 Difference between the time t_is_1 and the reference time t_should be Dt_2 Difference between the time t_is_2 and the reference time t_should be t_L Time of the start of the load transfer phase t_ist_1 Time of the drop in rotational speed at the input element of the friction switching element in the case that no drop in rotational speed is detected at the input element of the friction switching element until the predefined filling compensation time has elapsed t_ist_2 Time of the drop in rotational speed at the input element of the friction switching element in the event that a drop in rotational speed at the input element of the friction switching element is detected before the predefined filling compensation time has elapsed. t_should reference time p_start Fill pressure start value

Claims

[1] Method for improving the shifting quality of an automatic or automated transmission of a motor vehicle in the workshop / customer service case or at the end of the assembly line before delivery, characterized by, that the filling pressure of a friction shift element of the transmission during the closing process, consisting of a rapid filling phase, a filling compensation phase and a load transfer phase, when engaging a gear with the vehicle at least nearly stationary, is determined by the fact that the piston of the friction shift element is constantly subjected to a starting filling pressure value (p_start) over a predefined filling compensation time (F) during the filling compensation phase, wherein, if a drop in rotational speed at the input element of the friction shift element is detected before the end of the predefined filling compensation time (F), the actual filling pressure of the friction shift element is deduced from the difference (Dt_2) between the time (t_actual_2) of the drop in rotational speed at the input element of the friction shift element and a reference time (t_target).wherein the fill pressure start value (p_start) is reduced to the actual fill pressure and stored as the new fill pressure start value for the next closing operation of the friction switching element, and wherein, if no drop in rotational speed is detected at the input element of the friction switching element until the predefined fill compensation time (F) has elapsed, the load transfer phase is started, wherein the piston of the friction switching element is subjected to a modulated switching pressure, wherein the time interval starting from the switching command or from the end of the rapid fill phase until the time (t_actual_1) of the detection of a drop in rotational speed at the input element of the friction switching element is determined and compared with a predefined reference value, wherein the actual fill pressure of the friction switching element is inferred from the difference (Dt_1) between the time (t_actual_1) of the drop in rotational speed at the input element of the friction switching element and the reference time (t_target).where the fill pressure start value (p_start) is increased to the actual fill pressure and stored as the new fill pressure start value for the next closing operation of the friction switching element. [2] Method for improving the shifting quality of an automatic transmission or automated transmission of a motor vehicle in the workshop / customer service case or at the end of the assembly line before delivery according to claim 1, characterized by , that during the load transfer phase the piston of the friction switching element is subjected to a ramp-like switching pressure. [3] Method for improving the shifting quality of an automatic transmission or automated transmission of a motor vehicle in the workshop / customer service case or at the end of the assembly line before delivery according to claim 1 or 2, characterized by that the procedure is only carried out if the motor vehicle's engine is at least approximately idling. [4] Method for improving the shifting quality of an automatic transmission or automated transmission of a motor vehicle in the workshop / customer service case or at the end of the assembly line before delivery according to claim 1, 2 or 3, characterized by , that if the procedure is carried out via a tester and not in normal driving operation, the closing process of the switching element is immediately aborted if a drop in speed is detected at the input element of the friction switching element. [5] Method for improving the shifting quality of an automatic transmission or automated transmission of a motor vehicle in the workshop / customer service case or at the end of the assembly line before delivery according to claim 1, 2 or 3, characterized by, that if the procedure is automatically triggered by the transmission control during normal driving operation with unchanged driver input of “Position N” or “Position P”, the closing process is immediately aborted as soon as a drop in speed is detected at the input element of the friction switching element. [6] Method for improving the shifting quality of an automatic transmission or automated transmission of a motor vehicle in the workshop / customer service case or at the end of the assembly line before delivery according to one of the preceding claims, characterized by , that it is applied to a friction switching element which is not torque-carrying in the target gear, but is temporarily actuated to synchronize a positive-locking switching element which is torque-carrying in the target gear during gear engagement.

Images