A method for detecting and diagnosing the oil level of a dual-clutch transmission

Abstract

The present invention relates to the field of vehicle-mounted diagnostic technology, and in particular to a dual-clutch transmission oil level detection and diagnosis method. avg 、T avg 、N avg and P avg ; Calculate the expected CCP motor speed Nt, Nt = Nt nom +Nt fac , according to N avg Calculate the failure rate i of the current driving cycle with the size of Nt j Repeat multiple driving cycles to obtain the failure rate i, which is the number of driving cycles i j If i is greater than the gearbox oil level too low judgment threshold i max If the denominator is greater than n0, the gearbox oil level is judged to be a low oil level fault; if i is less than the gearbox oil fault relief judgment threshold i min If the denominator is greater than n0, the gearbox is judged to have cleared the low oil level fault; the fault rate of the current driving cycle is i j =k j / n j , when N avg When k is greater than Nt, j Plus one, n j Add one; when N avg When k is less than or equal to Nt, j unchanged, n j plus one; each time a driving cycle is performed, n j Plus 1. The diagnostic logic of this method is simple, no additional hardware and sensors are required, the development cost is low, and the environmental adaptability is strong.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle diagnosis, and particularly relates to a method for detecting and diagnosing the oil level of a dual-clutch transmission. Background Art

[0002] With the development of automotive technology, people's requirements for automotive driving performance are constantly increasing, and the technical level of automotive transmissions is also constantly improving. The dual-clutch transmission technology has greatly improved the fuel economy and shifting smoothness of automobiles, so the assembly rate on automobiles is constantly rising. The technologies of the dual-clutch module, the torsional vibration damper module, and the control module are the core technologies of the dual-clutch automatic transmission. The working states and control precisions of these modules and key components have a great impact on the operation of the dual-clutch automatic transmission. The performance of the oil system has a quite large impact on the lubrication, cooling, and pressure transmission of the dual-clutch transmission. The dual-clutch automatic transmission has a common circulating oil path for all transmission functions. The components that need to be lubricated with the lubricating oil of the dual-clutch automatic transmission mainly include: the dual-clutch, gears, shafts, bearings, synchronizers, oil pumps, etc. For the dual-clutch transmission, a dual-clutch transmission lubricating oil with good performance is crucial.

[0003] At present, there is no relevant transmission oil level detection software. The existing oil level detection technologies for mechanical equipment are: the method of detecting with an oil level gauge, the accuracy is not particularly high and the structural design is relatively complex; the image oil level detection method based on computer vision technology, with high cost and poor environmental adaptability, etc. Summary of the Invention

[0004] The purpose of the present invention is to aim at the defects of the existing technology and provide a method for detecting and diagnosing the oil level of a dual-clutch transmission, which can realize the oil level detection function without adding additional detection mechanisms, and has a simple diagnostic logic and strong environmental adaptability.

[0005] A method for detecting and diagnosing the oil level of a dual-clutch transmission provided by the present invention includes

[0006] Start the engine and run for a period of time until the engine is stable, which is a driving cycle;

[0007] Judge whether the vehicle meets the oil level detection and diagnosis conditions. If it meets, enter the oil level detection and diagnosis process;

[0008] Start the oil level detection and diagnosis process. In a driving cycle, collect n groups of battery voltage data U1~Un, n groups of transmission oil temperature data T1~Tn, n groups of CCP motor speed data N1~Nn, and n groups of CCP motor control duty ratio data P1~Pn at a set sampling interval;

[0009] Calculate the average value of the n groups of battery voltage data U1~Un to obtain the average battery voltage Uavg ; Calculate the average value of n groups of transmission oil temperature data T1 to Tn to obtain the average transmission oil temperature T avg ; Calculate the average value of n groups of CCP motor speed data N1 to Nn to obtain the average CCP motor speed N avg ; Calculate the average value of n groups of CCP motor control duty cycle data P1 to Pn to obtain the average CCP control duty cycle P avg ;

[0010] Calculate the expected CCP motor speed Nt, Nt = Nt nom + Nt fac , Nt nom is the expected speed of the CCP motor at the current oil temperature, and Nt fac is the speed offset of the CCP motor at the current oil temperature;

[0011] According to the magnitude of N avg and Nt, calculate the failure rate i of the current driving cycle j ;

[0012] Repeat multiple driving cycles, and execute the oil level detection and diagnosis process once in each driving cycle to obtain the failure rate i. The failure rate i is the sum of the i values of multiple driving cycles. If i is greater than the low oil level judgment threshold i j of the transmission oil level and the denominator of the failure rate ratio is greater than n0, it is determined that the transmission oil level has a low oil level fault; if i is less than the transmission oil fault removal judgment threshold i max and the denominator of the failure rate ratio is greater than n0, it is determined that the low oil level fault of the transmission is removed, and in other cases, it is determined that the particulate trap is in a normal state; min The failure rate i of the current driving cycle

[0013] = k j / n j , n j takes values from 1 to n0, where n0 is the number of driving cycles executed repeatedly. Among them, when N j is greater than Nt, k avg is incremented by one, and n j is incremented by one; when N j is less than or equal to Nt, k avg remains unchanged, and n j is incremented by one; each time a driving cycle is executed, n j is incremented by one. j Preferably, the Nt

[0014] is obtained by querying the pre-calibrated Map_N_tar_nom table according to the power factor Pf of the CCP motor and the average transmission oil temperature T at the current moment nom ; avg ​

[0015] The Nt fac is obtained by querying the pre-calibrated Map_N_tar_fac table according to the CCP motor power factor Pf and the current gearbox oil temperature T avg ;

[0016] The CCP motor power factor Pf is calculated according to the formula Pf = U avg *P avg .

[0017] Preferably, the oil level detection and diagnosis conditions include all of the following being satisfied simultaneously:

[0018] The battery voltage reaches the diagnostic enable threshold range;

[0019] Whether the gearbox oil temperature reaches the diagnostic enable threshold;

[0020] The battery voltage signal diag_U is valid;

[0021] The oil temperature sensor signal diag_T is valid;

[0022] The motor speed signal is valid.

[0023] Preferably, when collecting n groups of CCP motor control duty ratio data P1 to Pn, the collected data is considered valid only when the CCP motor control duty ratio is within the range of 10% - 60%, otherwise the group of data is discarded and re-collected.

[0024] Preferably, the calibration method of the gearbox oil level too low judgment threshold i max includes:

[0025] Install the low oil level gearbox on the vehicle and drive the vehicle on different roads. After the oil level detection and diagnosis conditions are met, repeat multiple driving cycles, and execute the oil level detection and diagnosis process once in each driving cycle to obtain multiple groups of i j data;

[0026] Perform normal distribution processing on the multiple groups of i j data to obtain the expectation μ and standard deviation σ of this normal distribution;

[0027] Calculate the gearbox oil level too low judgment threshold i max = μ - 3σ.

[0028] Preferably, the calibration method of the gearbox oil fault removal judgment threshold i min includes:

[0029] Install a gearbox with normal oil level on a vehicle and drive the vehicle on different road surfaces. After the oil level detection and diagnosis conditions are met, repeat multiple driving cycles and perform the oil level detection and diagnosis process once in each driving cycle to obtain multiple groups of i j data;

[0030] Perform a normal distribution process on multiple groups of ij data to obtain the expectation μ and standard deviation σ of this normal distribution;

[0031] Calculate the fault judgment threshold i for the gearbox oil release min = μ + 3σ.

[0032] Preferably, the calibration method of the Map_N_tar_nom table includes:

[0033] Install a sample part of the gearbox assembly with normal oil level on a test bench for experiments, and measure the CCP motor speed under different oil temperatures, different CCP motor control duty cycles, and different battery supply voltages;

[0034] After the CCP speed stabilizes, continuously collect the CCP speed to obtain multiple groups of CCP speed data, and take the average value of all data to obtain the CCP speed at this operating point;

[0035] Repeat the above steps to obtain the CCP speed at all operating points and fill it into the table Map_N_tar_nom.

[0036] Preferably, the calibration method of the Map_N_tar_fac table includes:

[0037] Install a sample part of the gearbox assembly with low oil level on a test bench for experiments, and measure the CCP motor speed under different oil temperatures, different CCP motor control duty cycles, and different battery supply voltages;

[0038] Repeat the above test steps to obtain the test data at all operating points;

[0039] Subtract the test data at each operating point obtained during the calibration process of the Map_N_tar_nom table from the test data at each operating point to obtain Nt at all operating points fac , and fill it into the table Map_N_tar_fac.

[0040] Preferably, the n0 is the minimum value determined according to the dual-clutch hardware protection and customer perception time requirements.

[0041] The beneficial effects of the present invention are as follows: This method collects multiple groups of battery voltage data, gearbox oil temperature data, CCP motor speed data, and CCP motor control duty cycle data, and calculates the average battery voltage U avg , average gearbox oil temperature T avg, the average CCP motor speed N avg and the average CCP control duty cycle P avg . Then, based on the above data, the expected CCP motor speed Nt is calculated. The failure rate i is calculated by comparing N avg with Nt. If i is greater than the low transmission oil level judgment threshold i max and the denominator is greater than n0, it is determined that the transmission oil level is a low oil level fault; if i is less than the transmission oil fault release judgment threshold i min and the denominator is greater than n0, it is determined that the low oil level fault of the transmission is released, and in other cases, it is determined that the particulate trap is in a normal state. The diagnostic logic of this method is simple, without the need to add additional hardware and sensors, and the development cost is low. Moreover, the failure rate is calculated through data detection and calculation, so the diagnostic method has strong environmental adaptability. In addition, the overall diagnostic process of this method uses probability statistics methods, increasing stability and accuracy, and eliminating the possibility of missed reports and false reports to the greatest extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a schematic diagram of the arrangement of each sensor of the present invention;

[0043] Figure 2 is a schematic diagram of the diagnostic flow of the present invention;

[0044] Figure 3 is a schematic diagram of the operation logic of the diagnostic flow of the present invention;

[0045] Figure 4 is a schematic diagram of the failure rate alarm logic of the present invention.

[0046] In the figure: 1 - lubricating oil, 2 - lubricating oil suction port, 3 - CCP motor, 4 - temperature sensor DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0048] In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present application. However, those skilled in the art should clearly understand that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits and methods are omitted to avoid unnecessary details from interfering with the description of the present application.

[0049] It should be understood that, as used in the specification of this application and the appended claims, the term "comprising" indicates the presence of the described features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or their groups.

[0050] It should also be understood that the term "and / or" used in the specification of this application and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0051] As used in the specification of this application and the appended claims, the term "if" may be interpreted, depending on the context, as "when" or "once" or "in response to determining" or "in response to detecting". Similarly, the phrase "if determined" or "if [the described condition or event] is detected" may be interpreted, depending on the context, as meaning "once determined" or "in response to determining" or "once [the described condition or event] is detected" or "in response to detecting [the described condition or event]".

[0052] In addition, in the description of the specification of this application and the appended claims, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0053] Reference to "one embodiment" or "some embodiments" or the like described in the specification of this application means that a specific feature, structure, or characteristic described in connection with that embodiment is included in one or more embodiments of this application. Thus, statements such as "in one embodiment", "in some embodiments", "in other some embodiments", "in still other embodiments", etc. that appear in different places in this specification do not necessarily all refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "comprising", "including", "having", and their variants all mean "including but not limited to", unless otherwise specifically emphasized in other ways. "Plurality" means "two or more".

[0054] As Figure 1 shown, the various sensors in the present invention are arranged as follows:

[0055] A lubricating oil suction port 2 is provided in the gearbox oil pan. Under normal circumstances, the lubricating oil liquid 1 must be above the suction port 2. The CCP motor 3 drives the oil pump to pump the gearbox lubricating oil from the oil pan into the lubricating and cooling oil passage. The lubricating oil temperature sensor 4 is arranged at a position below the oil pan. The speed, duty cycle, and battery voltage of the CCP motor are calculated internally by the DCT controller software.

[0056] When the gearbox lubricating oil level is normal, no air enters the oil suction port 2. When the gearbox lubricating oil level is too low, some air will enter the CCP pump through the oil suction port 2. Since the viscosity of air is much smaller than that of the lubricating oil, the speed of the pump mixed with air will increase during operation, and the motor speed will also increase accordingly.

[0057] Embodiment 1

[0058] Figure 2 shows a schematic flow chart of a dual-clutch gearbox oil level detection and diagnosis method provided by a preferred embodiment ( Figure 2 shows the first embodiment of the present application). For the sake of convenience of description, only the parts related to this embodiment are shown and are described in detail as follows:

[0059] A dual-clutch gearbox oil level detection and diagnosis method provided by the present invention includes

[0060] Step 1: Start the engine and run it for a period of time, such as 300 s, until the engine is stable, which is a driving cycle. After the engine runs for a period of time, collect the battery voltage, gearbox oil temperature, and CCP motor speed signals to ensure signal stability and reduce diagnostic errors.

[0061] Step 2: Determine whether the vehicle meets the oil level detection and diagnosis conditions. If it meets, enter the oil level detection and diagnosis process; among them, the oil level detection and diagnosis conditions include all of the following being met simultaneously:

[0062] The battery voltage reaches the diagnostic enable threshold range, such as 11 V - 15 V;

[0063] Whether the gearbox oil temperature reaches the diagnostic enable threshold, such as 70 °C - 110 °C;

[0064] The battery voltage signal diag_U is valid;

[0065] The oil temperature sensor signal diag_T is valid;

[0066] The motor speed signal is valid (i.e., the gearbox is not in the shifting process).

[0067] If all the above conditions are met or valid, then execute Step 3; otherwise, return to execute Step 1. The purpose of setting the above judgment conditions is as follows: when the battery voltage is normal, there is a good linear relationship between the motor speed and the duty ratio; when the gearbox oil temperature is within the range, the viscosity change of the lubricating oil is small, and the influence on the motor load is small; when all the input signals are valid, it can avoid interference from invalid signals. Adding the above condition judgment is conducive to improving the reliability of the diagnosis.

[0068] Step 3, start the oil level detection and diagnosis process. After the gearbox oil temperature and battery voltage reach the enabling range and the signals are valid, and the CCP motor speed signal is valid, in a driving cycle, at a set sampling interval, such as 4 s, collect n groups of battery voltage data U1~Un, n groups of gearbox oil temperature data T1~Tn, n groups of CCP motor speed data N1~Nn, and n groups of CCP motor control duty cycle data P1~Pn. In this embodiment, there are three groups of data, namely [U1 U2 U3], [T1 T2 T3], [N1 N2 N3], [P1 P2 P3];

[0069] Step 4, as Figure 3 shown, calculate the average value of n groups of battery voltage data U1~Un to obtain the average battery voltage U avg ; calculate the average value of n groups of gearbox oil temperature data T1~Tn to obtain the average gearbox oil temperature T avg ; calculate the average value of n groups of CCP motor speed data N1~Nn to obtain the average CCP motor speed N avg ; calculate the average value of n groups of CCP motor control duty cycle data P1~Pn to obtain the average CCP control duty cycle P avg ;

[0070] Step 5, calculate the power factor Pf of the CCP motor, Pf = U avg *P avg . Calculate the expected CCP motor speed Nt, Nt = Nt nom +Nt fac , Nt nom is the expected speed of the CCP motor at the current oil temperature, and Nt fac is the speed offset of the CCP motor at the current oil temperature. Nt nom is obtained by querying the pre-calibrated Map_N_tar_nom table according to the power factor Pf of the CCP motor and the average gearbox oil temperature T avg at the current moment; Nt fac is obtained by querying the pre-calibrated Map_N_tar_fac table according to the power factor Pf of the CCP motor and the gearbox oil temperature T avg at the current moment.

[0071] Calculate the failure rate i of the current driving cycle according to the magnitude of N avg and Nt j ;

[0072] Step 6, repeat steps 2 to 5. By repeating multiple driving cycles and performing the oil level detection and diagnosis process once in each driving cycle, obtain the failure rate i. As Figure 4 shown, the failure rate i is the i of multiple driving cycles jIf i is greater than the gearbox oil level too low judgment threshold i max If the denominator is greater than n0, the gearbox oil level is judged to be a low oil level fault; if i is less than the gearbox oil fault relief judgment threshold i min If the denominator is greater than n0, the gearbox is judged to have cleared the low oil level fault, and in other cases the particulate filter is judged to be in normal state, completing the diagnosis. The denominator adopts a repeated confirmation strategy to take into account false alarms caused by sensor fluctuations, oil level fluctuations, etc.

[0073] Among them, the failure rate of the current driving cycle is j =k j / n j , n j The range is 1 to n0, where n0 is the number of driving cycles to be repeated and n0 is the minimum value determined based on the dual clutch hardware protection and customer perception time requirements. avg When k is greater than Nt, j Plus one, n j Add one; when N avg When k is less than or equal to Nt, j unchanged, n j plus one; each time a driving cycle is performed, n j Plus one.

[0074] In one embodiment, when collecting n groups of CCP motor control duty cycle data P1-Pn, the collected data is considered valid only when the CCP motor control duty cycle is in the range of 10%-60%, otherwise the group of data is discarded and re-collected.

[0075] In one embodiment, the transmission oil temperature sampling values T1, T2, and T3 are all measured by the temperature sensor 4 in the system of the present invention; the battery voltages U1, U2, and U3 are obtained by the DCT controller collecting the power supply pin voltage information; the CCP motor speeds N1, N2, and N3 are calculated by the DCT controller according to the motor Hall signal; the CCP motor control duty ratios P1, P2, and P3 are calculated by the DCT controller based on the internal signal. The transmission oil temperature diagnostic signal diag_T, the battery voltage signal diagnostic signal diag_U, and the clutch lubrication cooling motor speed signal diagnostic signal diag_n are monitored, and the above signals are provided by the transmission software diagnostic module.

[0076] In one embodiment, the gearbox oil level is too low judgment threshold i max The calibration methods include:

[0077] The low oil level gearbox is installed on the vehicle and the vehicle is driven on different roads. After the oil level detection and diagnosis conditions are met, multiple driving cycles are repeated, and the oil level detection and diagnosis process is executed once in each driving cycle to obtain multiple groups of i j data;

[0078] For multiple groups i j The data is processed into a normal distribution to obtain the expected μ and standard deviation σ of the normal distribution;

[0079] Calculate the gearbox oil level too low judgment threshold i max =μ-3σ.

[0080] Among them, the lubricating oil in the low oil level gearbox case is 0.5L.

[0081] In one embodiment, the gearbox oil release fault judgment threshold i min The calibration methods include:

[0082] The normal oil level gearbox is installed on the vehicle and the vehicle is driven on different roads. After the oil level detection diagnosis conditions are met, multiple driving cycles are repeated, and the oil level detection diagnosis process is executed once in each driving cycle to obtain multiple groups of i j data;

[0083] Perform normal distribution processing on multiple groups of ij data to obtain the expected μ and standard deviation σ of the normal distribution;

[0084] Calculate the gearbox oil fault relief judgment threshold i min =μ+3σ.

[0085] Among them, the normal oil level of lubricating oil in the gearbox is 3.5L.

[0086] Due to the differences in the installation position and layout angle of the gearbox, the i max 、i min There will be differences, and the diagnostic threshold can be adjusted appropriately based on customer needs.

[0087] In one embodiment, the calibration method of the Map_N_tar_nom table includes:

[0088] The normal oil level dual clutch transmission assembly sample was installed on the test bench for experiment, and the CCP motor speed was measured under different oil temperatures, different CCP motor control duty ratios, and different battery supply voltages;

[0089] After the CCP speed is stable, the CCP speed is continuously collected to obtain multiple sets of CCP speed data, and the average value of all data is taken to obtain the CCP speed at the operating point;

[0090] Repeat the above steps to obtain the CCP speeds of all operating points and fill them into the table Map_N_tar_nom. The Map_N_tar_nom table is as follows:

[0091] Table 1

[0092]

[0093]

[0094] The sizes m and k of the two-dimensional table depend on the degree of subdivision.

[0095] In one embodiment, the calibration method of the Map_N_tar_fac table includes:

[0096] Install the sample of the low oil level dual clutch transmission assembly on the test bench for experiments, and measure the CCP motor speeds under different oil temperatures, different CCP motor control duty cycles, and different battery supply voltages;

[0097] Repeat the above test steps to obtain the test data of all working condition points;

[0098] Subtract the test data of each working condition point from the test data of each working condition point obtained during the calibration of the Map_N_tar_nom table to obtain Nt of all working condition points fac , and fill it into the table Map_N_tar_fac. The obtained Map_N_tar_fac table is as follows:

[0099] Table 2

[0100]

[0101] The sizes m and k of the two-dimensional table depend on the degree of subdivision.

[0102] It should be understood that the specific order or hierarchy of the steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of the steps in the process can be rearranged without departing from the scope of the present disclosure. The appended method claims present the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy.

[0103] In the above detailed description, various features are combined in a single embodiment to simplify the present disclosure. This method of disclosure should not be construed as reflecting an intention that the embodiments of the claimed subject matter require more features than are clearly recited in each claim. On the contrary, as reflected in the appended claims, the present invention lies in a state less than all the features of the disclosed single embodiment. Therefore, the appended claims are hereby expressly incorporated into the detailed description, where each claim stands alone as a separate preferred embodiment of the present invention.

[0104] The above-described disclosed embodiments are described so that any person skilled in the art can implement or use the present invention. For those skilled in the art, various modification methods of these embodiments are obvious, and the general principles defined herein can also be applied to other embodiments without departing from the spirit and protection scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0105] The above description includes examples of one or more embodiments. Of course, it is impossible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but those of ordinary skill in the art should recognize that each embodiment can be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the protection scope of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the way this term is covered is similar to the term "including", as explained when "including" is used as a connecting word in the claims. In addition, any term "or" used in the specification and claims of the patent application is to mean "non-exclusive or".

[0106] The above-described embodiments are only used to illustrate the technical solutions of this application, rather than to limit them; although this application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of each embodiment of this application, and should all be included within the protection scope of this application.

Claims

1. A method for detecting and diagnosing the oil level of a dual-clutch transmission, characterized in that: including Start the engine and run it for a period of time until the engine is stable, which is regarded as one driving cycle; Judge whether the vehicle meets the oil level detection and diagnosis conditions. If it meets, enter the oil level detection and diagnosis process; Start the oil level detection and diagnosis process. In one driving cycle, collect n groups of battery voltage data U1~Un, n groups of transmission oil temperature data T1~Tn, n groups of CCP motor speed data N1~Nn, and n groups of CCP motor control duty cycle data P1~Pn at a set sampling interval; Calculate the average value of n groups of battery voltage data U1 to Un to obtain the average battery voltage U avg ; Calculate the average value of n groups of transmission oil temperature data T1 to Tn to obtain the average transmission oil temperature T avg ; Calculate the average value of n groups of CCP motor speed data N1 to Nn to obtain the average CCP motor speed N avg ; Calculate the average value of n groups of CCP motor control duty cycle data P1 to Pn to obtain the average CCP control duty cycle P avg ; Calculate the expected CCP motor speed Nt, Nt = Nt nom + Nt fac , Nt nom is the expected speed of the CCP motor at the current oil temperature, and Nt fac is the speed offset of the CCP motor at the current oil temperature; According to N avg Calculate the failure rate i of the current driving cycle based on the magnitude of Nt j ; Repeat multiple driving cycles, and execute the oil level detection diagnostic process once in each driving cycle to obtain a failure rate i, where the failure rate i is i of multiple driving cycles. j If i is greater than the gearbox oil level too low judgment threshold i max If the denominator of the fault rate ratio is greater than n0, the gearbox oil level is judged to be a low oil level fault; if i is less than the gearbox oil fault relief judgment threshold i min If the denominator of the failure rate ratio is greater than n0, the gearbox is judged to have cleared the low oil level fault, and the particulate filter is judged to be in normal state in other cases; The failure rate i of the current driving cycle j = k j / n j , n j takes values from 1 to n0, where n0 is the number of driving cycles executed repeatedly. Among them, when N avg is greater than Nt, k j is incremented by one, and n j is incremented by one; when N avg is less than or equal to Nt, k j remains unchanged, and n j is incremented by one; each time a driving cycle is executed, n j is incremented by one; The Nt nom is obtained by querying the pre-calibrated Map_N_tar_nom table according to the CCP motor power factor Pf and the average gearbox oil temperature T at the current moment; avg ​ The Nt fac is obtained by querying the pre-calibrated Map_N_tar_fac table according to the CCP motor power factor Pf and the current gearbox oil temperature T avg ; The power factor Pf of the CCP motor is calculated according to the formula Pf = U avg *P avg and is obtained by calculation; When collecting n groups of CCP motor control duty cycle data P1~Pn, only when the CCP motor control duty cycle is within the range of 10%-60% is the collected data considered valid. Otherwise, discard this group of data and collect it again.

2. The method for detecting and diagnosing the oil level of a dual clutch transmission according to claim 1, wherein The oil level detection and diagnosis conditions include all of the following being met simultaneously: The battery voltage reaches the diagnostic enable threshold range; Whether the transmission oil temperature reaches the diagnostic enable threshold; The battery voltage signal diag_U is valid; The oil temperature sensor signal diag_T is valid; The motor speed signal is valid.

3. The dual-clutch transmission oil level detection and diagnosis method according to claim 1, wherein The calibration method of the judgment threshold i for too low gearbox oil level max includes: Install a low oil level gearbox on a vehicle, drive the vehicle on different road surfaces, repeat multiple driving cycles after the oil level detection and diagnosis conditions are met, and perform the oil level detection and diagnosis process once in each driving cycle to obtain multiple sets of i j data; For multiple groups of i j Perform normal distribution processing on the data to obtain the expected value μ and standard deviation σ of the normal distribution; Calculate the low oil level judgment threshold i of the transmission max = μ - 3σ.

4. The method for detecting and diagnosing the oil level of a dual-clutch transmission according to claim 1, characterized in that, The calibration method of the failure judgment threshold i of the transmission oil min includes: Install a normal oil level gearbox on a vehicle and drive the vehicle on different road surfaces. After the oil level detection and diagnosis conditions are met, repeat multiple driving cycles, and execute the oil level detection and diagnosis process once in each driving cycle to obtain multiple groups of i j data; Perform normal distribution processing on multiple groups of ij data to obtain the expectation μ and standard deviation σ of this normal distribution; Calculate the failure judgment threshold i for the transmission oil min = μ + 3σ.

5. The dual clutch transmission oil level detection and diagnosis method according to claim 1, characterized in that The calibration method of the Map_N_tar_nom table includes: Install the assembly sample of the normal oil level transmission on the test bench for experiments, and measure the CCP motor speed under different oil temperatures, different CCP motor control duty cycles, and different battery supply voltages; After the CCP speed is stable, continuously collect the CCP speed to obtain multiple groups of CCP speed data, and take the average value of all data to obtain the CCP speed at this operating point; Repeat the above steps to obtain the CCP speed at all operating points and fill it into the table Map_N_tar_nom.

6. The method for detecting and diagnosing the oil level of a dual-clutch transmission according to claim 5, characterized in that, The calibration method of the Map_N_tar_fac table includes: Install the assembly sample of the low oil level transmission on the test bench for experiments, and measure the CCP motor speed under different oil temperatures, different CCP motor control duty cycles, and different battery supply voltages; Repeat the above test steps to obtain the test data at all operating points; Subtract the test data of each operating condition point from the test data of each operating condition point obtained during the calibration of the Map_N_tar_nom table to obtain Nt for all operating condition points fac , and fill it into the Map_N_tar_fac table.

7. The method for detecting and diagnosing the oil level of a dual-clutch transmission according to claim 1, characterized in that: The n0 is the minimum value determined according to the dual-clutch hardware protection and customer perception time requirements.

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