ACCUMULATOR OIL PRESSURE SENSOR RATIONALITY DIAGNOSIS METHOD FOR A GEARBOX

Abstract

Accumulator-oil pressure sensor rationality diagnostic procedure (50) for a transmission with an accumulator (28) and a pressure sensor (38), comprising: charging the accumulator (28) to a maximum pressure and storing the maximum pressure value (52); performing an outlet pressure event and measuring the outlet pressure value (54); determining whether a difference between the maximum pressure value (52) and the outlet pressure value (54) is below a predetermined differential threshold value (58); and performing (64) at least one corrective action if the difference is less than the predetermined differential threshold value (58).

Description

TECHNICAL AREA The present disclosure relates to an accumulator-oil pressure sensor rationality diagnostic method for a transmission and in particular a pressure sensor rationality diagnostic method for a dual-clutch transmission. BACKGROUND The background information provided herein serves to present the general context of the disclosure. The work of the inventors currently named, to the extent described in this background section, as well as aspects of the description that were not otherwise considered prior art at the time of filing, are neither expressly nor implicitly considered prior art with respect to the present disclosure. A manual transmission powertrain consists of an internal combustion engine (ICE), a clutch, and a manual gearbox. The clutch engages with a flywheel on the ICE and transmits the engine's torque to the gearbox. Torque transmission from the ICE to the gearbox is interrupted when a driver manually shifts gears. During a gear change, the clutch is disengaged (i.e., the ICE is disconnected from the gearbox), a desired gear is manually selected, and the clutch is re-engaged. A dual-clutch transmission (DCT) powertrain includes an internal combustion engine (ICE) and a DCT (or semi-automatic transmission). The DCT incorporates two clutches, an inner and an outer transmission shaft, and two sets of gears, each with its own transmission shaft and / or a countershaft. For example, the inner transmission shaft can be assigned to a first set of gears and controlled by a first clutch. The outer transmission shaft can be assigned to a second set of gears and controlled by a second clutch. The first set of gears can include first, third, and fifth gears. The second set of gears can include second, fourth, and sixth gears. By using two transmission shafts, a DCT powertrain can ensure uninterrupted torque transfer between the ICE and a DCT output shaft during gear changes. This reduces shift times and improves fuel economy. The DCT incorporates a type of energy storage device in the form of a hydraulic fluid accumulator (oil) that keeps the fluid under pressure until it is needed to engage the internal or external clutch during a gear change. The accumulator allows the DCT's hydraulic pressure system to handle extreme demands with a less powerful pump, respond more quickly to temporary needs, and smooth out pulsations. An oil pressure sensor is connected to the hydraulic fluid reservoir to monitor the hydraulic system's oil pressure. It's important to note that the hydraulic system's fluid pressure directly influences the timing and function of the transmission's shifting into higher or lower gears. Excessively high or low hydraulic pressures can lead to transmission malfunctions during shifting, potentially damaging internal components. The transmission's oil pressure sensor detects impermissible hydraulic pressures, thus alerting the driver when maintenance is required. Therefore, it's crucial to have a reliable means of determining whether the oil pressure sensor has failed or if the sensor's data is inaccurate, necessitating replacement. The publication DE 10 2013 008 741 B3 discloses the detection of a pressure storage charging requirement without the need for pressure sensors by using a current measuring device and a speed sensor. SUMMARY One or more exemplary implementation variants address this problem by providing a pressure sensor rationality diagnostic for a dual-clutch transmission. Aspects include charging a pressure accumulator to a maximum pressure and storing the maximum pressure value before discharge; performing a discharge pressure event and measuring the discharge pressure value after discharge; determining whether the difference between the maximum pressure value and the discharge pressure value is less than a predetermined threshold; and performing at least one corrective action if the difference is less than the predetermined difference threshold. Another aspect is determining and storing an average maximum pressure value before the discharge pressure event. A further aspect involves calculating absolute extreme values ​​for the average maximum pressure and the average discharge pressure over a predefined average pressure period. Finally, at least one corrective action is implemented if the difference between the average maximum pressure and the average discharge pressure is less than a predefined threshold. Further aspects of the exemplary embodiment include switching off a battery charging motor and resetting a charging timer, switching on the battery charging motor, and starting the charging timer after switching off the battery charging motor and resetting the charging timer. Another aspect involves executing at least one corrective action if the charging timer value exceeds a predefined threshold value. Another aspect is determining and storing the battery charge pressure when the battery charging motor is switched on. Yet another aspect involves calculating the difference between the actual battery charge pressure and the stored charge pressure after a predetermined charging time. And a further aspect is implementing at least one corrective action if the difference between the actual battery charge pressure and the stored charge pressure is less than a predetermined charge pressure threshold, or if the difference between the actual battery charge pressure and the stored charge pressure is greater than the predetermined charge pressure threshold. Another aspect involves measuring absolute extreme pressure values ​​during a predetermined discharge period. And yet another aspect involves implementing at least one corrective action if the difference between the absolute extreme pressure values ​​measured during the predetermined discharge period is less than a predetermined difference in absolute extreme pressure values ​​expected during the predetermined discharge period. Further applications of the present disclosure will become apparent from the detailed description below. It should be noted that the detailed description and specific examples serve only for illustrative purposes and are not intended to limit the scope of the disclosure. It is understood that while the exemplary embodiment describes pressure sensor rationality diagnostics with regard to a DCT, it may nevertheless also be applicable to other transmissions, including, but not limited to, manual transmissions, automatic transmissions, and CVTs. BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure will be more readily understood with the aid of the detailed description and the accompanying drawings, wherein: Fig. 1 is a functional block diagram of an exemplary oil flow for a (DCT) according to an exemplary embodiment; Fig. 2a is an algorithm for a pressure sensor rationality diagnosis for a DCT according to the exemplary embodiment; Fig. 2b is a continuation of the algorithm for a pressure sensor rationality diagnosis for a DCT according to the exemplary embodiment; Fig. 2c continues the algorithm for a pressure sensor rationality diagnosis for a DCT; Fig. 2d continues the algorithm again for a pressure sensor rationality diagnosis for a DCT according to the exemplary embodiment; and Fig. 2e continues the algorithm further for a pressure sensor rationality diagnosis for a DCT according to the exemplary embodiment. DETAILED DESCRIPTION The following description is merely exemplary and is not intended to limit the present disclosure in its applications or uses. For clarity, the same reference numerals are used in the drawings to identify similar elements. As used here, the expression A, B, and C should be interpreted as signifying a logical expression (A or B or C), using a non-exclusive logical OR. It should be noted that steps within a process may be performed in a different order without altering the principles of the present disclosure. In Fig. 1, a DCT oil flow system 10 connects to the shift forks 12-1, 12-2, 12-3, and 12-4, which together are referred to as shift forks 12 and correspond to the respective synchronizers (not shown). These synchronizers translate the forks bidirectionally into at least two engaged positions and a neutral (or unengaged) position by means of an actuator or a piston (not shown). The first and second clutch elements 14 and 16 are also connected to the DCT oil flow system 10 and serve to shift the transmission when actuated. For example, the first clutch element can shift gears 1, 3, and 5, while the second element shifts gears 2, 4, and 6. An electric pump 18 is in fluid communication with the clutch control solenoids 20 and the shift rail control solenoids and valves 22. The DCT control module 24 controls the actuation of the clutch control solenoids 20 and the shift rail control solenoids and valves 22. The electric pump 18 applies fluid pressure to the first and second clutch elements 14, 16 for actuation via the clutch control solenoids 20. Conversely, the electric pump 18 actuates the pistons 26-1, 26-2, 26-3, and 26-4, collectively referred to as pistons 26, via the shift rail control solenoids and valves 22 with fluid pressure. Each piston 26 actuates one of the shift forks 12. The DCT oil flow system 10 includes an accumulator 28. For example, the accumulator 28 can be a nitrogen-filled accumulator. The accumulator 28 comprises a first chamber 30 containing a pressurized gas, such as nitrogen, and a second chamber 32 containing hydraulic fluid (e.g., transmission oil) and connected to the hydraulic line 34 (e.g., oil). The accumulator 28 includes a floating piston 36. The accumulator 28 stores the oil in the second chamber 32 under the pressure of the gas in the first chamber 30, which acts on the floating piston 36. The first chamber 30 is charged to pressurize the oil contained in the second chamber 32 to the desired pressure. The DCT control module 24 measures and / or estimates the pressure of the accumulator 28. For example, the DCT control module 24 can be connected to a pressure sensor 38. The DCT control module 24 determines a pre-charge pressure (i.e., a pressure at or before the vehicle starts moving) and dynamic pressure estimates of the accumulator during vehicle operation. The DCT control module 24 switches a pump motor 40 on and off based on the pressure estimates, previously measured pre-charge pressures, and other system measurements and / or estimates, including, but not limited to, an oil quantity estimate, system temperatures, and various vehicle operating modes. With reference to Fig. 2a, an algorithm 50 for pressure sensor rationality diagnostics for a DCT according to the exemplary embodiment is provided. It is understood that the algorithm described below serves to perform rationality checks in order to reduce the occurrence of malfunctions of the DCT oil pressure sensor. At block 52, the procedure begins with the activation of the electric pump 18 and the pump motor 40 to charge the fluid accumulator 28 to a maximum pressure and the subsequent reading and storage of the pressure value in the DCT control module 24 or another module suitable for this purpose before a discharge operation is carried out. After reading and storing the maximum pressure load of the fluid accumulator 28, the procedure continues at block 54 with the execution of a discharge operation and then measures the actual pressure of the accumulator 28 after completion of the discharge operation. Block 56 then calculates the difference between the actual pressure after the discharge process and the maximum stored pressure value in the DCT control module 24. It should be understood that all calculations, counters, timers, and the entire algorithm itself are stored and executed in the suitable DCT control module 24 or a similar module. If, at block 58, the difference between the actual post-discharge pressure and the maximum pressure is less than a predetermined threshold, the procedure proceeds to block 60, incrementing a failure counter. If, at block 62, the failure counter is not equal to a predetermined counter threshold, e.g., 2 or 3, the procedure returns to block 54 to continue the test steps. Otherwise, the procedure proceeds to block 64 to perform at least one corrective action, which may include, but is not limited to, illuminating a service indicator / alarm, setting a fault code in a controller (DCT module), resetting the failure counter, and / or activating the DCT oil flow system 10 to operate in a standard mode.In standard mode, the DCT oil flow system 10 activates the pump at a constant speed for the remainder of the driving cycle and can reset the system to the standard value in subsequent driving cycles until the vehicle is serviced. If, at block 58, it is determined that the difference between the actual pressure and the maximum pressure is not less than a predetermined threshold, the process continues to block 68. Referring to Fig. 2b, at block 68, after the accumulator 28 has been charged to maximum pressure, the process continues by calculating and storing the average pressure before each movement of the fork 12 or the clutch element (14, 16). At block 70, the process continues with the movement of the forks / clutch elements, i.e., during discharge, and then calculates the average pressure during and until the movements are completed.When the forks 12 or clutch elements are actuated, the accumulator pressure should decrease / be discharged by a reasonable amount to facilitate the shifting process. At Block 72, the procedure continues by determining whether the difference between the average pressure value before the unloading process (fork or coupling movement) and the average pressure value during the unloading process is less than a predetermined pressure threshold. If so, a failure counter is incremented at Block 74, and at Block 76, the procedure determines whether the failure counter meets a predetermined count threshold. If not, the procedure returns to Block 68 to repeat the process steps for this test. If the failure counter reaches the predetermined count threshold, the procedure continues at Block 78, performing at least one corrective action as described above.If, in block 72, the difference between the average pressure value before the discharge process and the average pressure value during the discharge process is not less than the predetermined pressure threshold, the process proceeds to block 80. Turning to Fig. 2c, the process continues at block 80 with the switching off of the electric pump 18 and the pump motor 40 and the discharging of the storage device 28. At block 82, a charging timer (not shown) is reset to zero (0). The charging timer monitors the charging time of the storage device 28. At block 84, the electric pump 18, the pump motor 40, and the charging timer are switched on to charge the storage device 28 during the overrun time. At block 86, the procedure continues to determine whether the actual charging time of memory 28 is greater than a predefined charging time threshold. At block 87, the procedure determines whether memory 28 is fully charged, and if not, it returns to block 84 to continue the charging process. If, at block 86, it is determined that the actual charging time of memory at block 86 is greater than the predefined time threshold, a failure counter at block 88 is incremented. If the failure counter at block 90 is not equal to a predefined counter threshold, the procedure returns to block 80 to repeat the test steps a second time. If the failure counter equals the predefined counter threshold, at least one corrective action as described above is performed at block 92. Starting again from block 86, if the actual memory loading time is not greater than a predetermined loading time threshold and the memory is fully loaded, the procedure continues at block 94. Turning to Fig. 2d, the procedure continues at block 94 with measuring and storing the pressure of the accumulator 28 at the beginning of a charge while the charge timer is starting. At block 96, the accumulator is charged for a specific duration. Subsequently, at block 98, the procedure continues with calculating the difference between the actual accumulator pressure after the specified charge duration has elapsed and the stored accumulator pressure at the beginning of the charge. If, at block 100, the difference between the actual storage pressure after the specified time interval and the storage pressure stored at the beginning of the charging process is less than a specified pressure difference threshold, a failure counter is incremented at block 102. If the failure counter at block 104 is not equal to (2), the procedure returns to block 94 to repeat the process steps. If the failure counter is equal to two (2), at least one corrective action as specified above is performed at block 106.If the difference in block 100 between the actual storage pressure and the storage pressure stored at the beginning of the charging process is not less than a first predefined pressure difference threshold, then the procedure proceeds to block 101 to determine whether the difference between the actual storage pressure after the predetermined time interval and the storage pressure stored at the beginning of the charging process is less than a second predefined pressure difference threshold. If so, then the procedure proceeds to block 102 to increment the failure counter. If not, the procedure proceeds to block 108. Turning to Fig. 2e, the procedure proceeds at block 108 by starting a system timer when the engine is switched on, regardless of whether the memory is charging or discharging (i.e., always during DCT vehicle operation). The procedure then proceeds at block 110 by measuring the absolute extreme pressure values ​​(absolute maximum and absolute minimum values ​​measured during a predetermined time period) and calculating the difference between them. If, at block 112, the difference between the absolute extreme values ​​measured during a predetermined time period is greater than a predetermined difference for that period, the test at block 114 is marked as passed, and the procedure proceeds at block 115 by resetting the system timer and then returns to block 108 to restart the timer.If the difference between the absolute extreme values ​​measured during the specified time period is not greater than the specified difference for the specified time period, the procedure determines the elapsed time of the specified time period at Block 116. If not, the procedure proceeds to Block 117, incrementing the system timer, and then returns to Block 110 to continue measuring the absolute extreme values. If the specified time period has elapsed, the test is marked as failed at Block 118. The procedure may then be instructed to return to Block 108 to repeat the test, or at least one corrective action as described above may be taken at Block 120.

Claims

Accumulator-oil pressure sensor rationality diagnostic procedure (50) for a transmission with an accumulator (28) and a pressure sensor (38), comprising: charging the accumulator (28) to a maximum pressure and storing the maximum pressure value (52); performing an outlet pressure event and measuring the outlet pressure value (54); determining whether a difference between the maximum pressure value (52) and the outlet pressure value (54) is below a predetermined differential threshold value (58); and performing (64) at least one corrective action if the difference is less than the predetermined differential threshold value (58). Method (50) according to claim 1, further comprising determining and storing (68) an average maximum pressure value before performing the outlet pressure event. Method (50) according to claim 2, wherein determining (68, 70) the average maximum pressure value and an average outlet pressure value further comprises calculating absolute extreme values ​​for the average maximum pressure value and the average outlet pressure value over a predetermined average pressure period (110). Method (50) according to claim 3, further comprising carrying out at least one remedial measure (78) when a difference between the average maximum pressure value and the average outlet pressure value is less than a predetermined threshold value (72). Method (50) according to claim 1, further comprising switching off (80) a battery charging motor (40) and resetting (82) a charging timer. Method (50) according to claim 5, further comprising switching on (84) the accumulator charging motor (40) and starting (84) the charging timer. Method (50) according to claim 6, further comprising carrying out (92) at least one remedy when the value of the charging timer is greater than a predetermined accumulator charging timer threshold (86). Method (50) according to claim 6, further comprising determining and storing (94) an accumulator charge pressure when switching on the accumulator charging motor (40). Method (50) according to claim 8, further comprising calculating (98) a difference between an actual accumulator charge pressure and the stored accumulator charge pressure after the expiry of a predetermined accumulator charge period (96).

Images