Engine fault integrated discrimination method based on multi-level progressive detection principle

Abstract

The application discloses an engine fault diagnosis method based on a multilevel progressive detection principle, and has the characteristics that the method comprises the following steps: engine timing geometric deviation angle measurement, to complete mechanical layer detection; engine crankshaft and camshaft Hall pulse signal measurement and correction, to complete electrical signal angle layer detection; engine cold test speed-up working condition crankshaft angle domain / frequency domain comprehensive analysis, namely vibration acceleration layer detection; and artificial intelligence fault identification based on big data. The method provided by the application can progressively judge and identify faults through the mechanical layer, the electrical signal angle layer, timing belt tension or vibration frequency and vibration acceleration layer, so that common engine faults in the engine cold test and bench test process can be quickly identified. In the judgment of the vibration acceleration layer, the engine fault is quickly identified and pre-judged by combining the mechanical layer and the electrical signal angle layer and through an artificial intelligence fault judgment algorithm based on big data.

Description

Technical Field

[0001] This invention relates to an integrated engine fault diagnosis method, and relates to automotive engine timing measurement technology, engine cold test technology, NVH analysis (vibration acceleration-crankshaft angular domain relationship and vibration acceleration-crankshaft speed), artificial intelligence integrated diagnosis method, engine bench test technology, etc. Background Technology

[0002] Currently, there are two main methods for common engine fault diagnosis, especially NVH (Noise, Vibration, and Harshness) fault diagnosis: the steady-state vibration acceleration-crankshaft speed method and the steady-state vibration acceleration-crankshaft angle method. Typically, these two methods can respectively indicate the order of the engine fault and the corresponding components with fault characteristics. However, currently, these two analysis methods are usually used independently to determine engine faults. Furthermore, fault mode determination generally relies on subjective human judgment, and there is a layered superposition phenomenon in cross-checking between different levels (e.g., mechanical installation deviations can cause deviations in electrical testing).

[0003] In addition, at present, when performing steady-state vibration acceleration-crankshaft angle method fault diagnosis of engines, there are generally two methods to collect angular domain data: the direct installation of a corner gauge or the crankshaft Hall sensor data collection method.

[0004] The direct mounting method for the corner marker involves installing the corner marker on the crankshaft pulley at the front of the engine before testing. Because the corner marker has high measurement accuracy, this method can directly obtain a good crankshaft angle signal. However, since the corner marker needs to be installed separately at the front of the engine using tooling, the installation and alignment process requires very high positioning accuracy, which can easily introduce various installation errors. Furthermore, during engine operation, the corner marker bracket has low rigidity and inevitably experiences torsion and other issues, thus affecting its dynamic acquisition characteristics.

[0005] The crankshaft Hall sensor acquisition method refers to obtaining angular domain signals by subdividing the signals from the engine crankshaft position Hall sensor. This method does not require additional sensors and is economical. However, due to certain component installation errors and machining tolerances during the press-fitting process of the crankshaft position sensor mounting plate, these deviations are easily introduced into the angular domain acquisition and are difficult to eliminate, requiring dedicated calibration methods. This is especially problematic during NVH fault diagnosis, where the angular domain signal and spectrum analysis corresponding to the vibration moment often do not reflect the actual area where the vibration occurred. Summary of the Invention

[0006] The purpose of this invention is to quickly identify common engine faults during engine cold testing and bench testing.

[0007] To achieve the above objectives, the technical solution of the present invention provides an engine fault diagnosis method based on a multi-level progressive detection principle, characterized by comprising the following steps:

[0008] Step 1: Measure the engine timing geometry deviation angle to complete the mechanical level inspection.

[0009] The timing geometry angles of the crankshaft and intake and exhaust camshafts of the engine under test are measured using an engine timing angle measuring instrument, and the timing geometry deviation angle value is calculated based on the machining tolerance information of timing-related parts.

[0010] Step 2: If the timing geometric deviation angle value obtained in Step 1 exceeds the allowable range of timing deviation, it indicates that the timing angle is out of tolerance and manual intervention is required for repair. The timing needs to be reassembled and adjusted. After repair, return to Step 1. If the timing geometric deviation angle value obtained in Step 1 does not exceed the allowable range of timing deviation, proceed to the next step. Thus, while measuring the timing geometric angle of the engine timing mechanical system, the calibration of the actual measured top dead center and the theoretical top dead center is completed.

[0011] Step 3: Measure and correct the Hall pulse signals of the engine crankshaft and camshaft to complete the electrical signal angle layer detection.

[0012] Under constant speed churning conditions, the output signals of the crankshaft position sensor and the intake and exhaust camshaft position sensors are collected respectively, thereby measuring the Hall pulse signals of the engine crankshaft and camshaft, and determining whether the effective timing angle output by the Hall sensor meets the requirements. The effective timing angle includes the timing geometric deviation angle and the Hall sensor system error, thus completing the correction of the engine timing angle deviation from the mechanical layer to the electrical signal angle layer.

[0013] Step 4: Comprehensive analysis of crankshaft angle domain / frequency domain under engine cold test and acceleration conditions, i.e., vibration acceleration layer detection:

[0014] Under the predetermined acceleration condition, the signals output by the vibration acceleration sensor and crankshaft position sensor arranged on the cylinder block are collected by the vibration analyzer. Then, the speed-acceleration frequency domain relationship under the engine acceleration condition is obtained by combining the crankshaft speed and the acceleration values ​​of each order are calculated to identify the frequency domain contribution of each order acceleration. At the same time, the characteristic acceleration contribution of each cylinder is identified by combining the crankshaft angular domain and acceleration time domain relationship according to the order analysis to determine whether the engine vibration acceleration meets the design requirements. If the measured engine vibration acceleration characteristics exceed the requirements, proceed to step 5.

[0015] Step 5: Fault identification based on big data and artificial intelligence:

[0016] The vibration acceleration data collected in step 4 is filtered to remove background noise signals introduced by the outside world; then the characteristics of the fault acceleration signal are captured; then, an artificial intelligence fault identification algorithm based on big data is used to identify and classify the fault mode, thereby determining the fault type and completing the preliminary location of the faulty component.

[0017] Preferably, in step 1, the timing-related part machining tolerances are obtained by scanning the QR code on the engine under test.

[0018] Preferably, step 1 further includes the following steps:

[0019] Step 101: Install the engine timing angle measuring instrument to the rear end of the engine under test, and connect it to the positioning slots at the tail ends of the crankshaft and intake and exhaust camshafts respectively;

[0020] Step 102: Use a dedicated cold-test motor to slowly rotate the crankshaft of the engine under test, allowing it to complete at least two working cycles. Utilize the capacitive accelerometer of the engine timing angle measuring instrument to detect the direction of gravity and measure the timing geometry of the engine under test.

[0021] Step 103: Use a barcode scanner to scan the machining tolerance information of timing-related components on the component's QR code. After obtaining the information, the software automatically calculates and generates the timing geometric deviation angle value.

[0022] Preferably, step 3 further includes the following steps:

[0023] Step 301: Use a laser frequency meter to detect the vibration frequency of the timing belt at the tension pulley end and the idler pulley end, obtain the vibration frequency T1 at the tension pulley end and the vibration frequency T2 at the idler pulley end, and determine whether the vibration frequencies T1 at the tension pulley end and T2 at the idler pulley end satisfy the value range shown in the following formula:

[0024] f zd1 ≤T1≤f zd2 f dd1 ≤T2≤f dd2

[0025] In the formula, f zd1 f dd1 f is a pre-set lower limit value. zd2 f dd2 The upper limit value is preset.

[0026] If the value range is met, the timing belt tension or vibration frequency T is assigned a qualified value, and the process proceeds to step 302.

[0027] If the value range is met, the timing belt tension or vibration frequency T is assigned as unqualified, and the effective timing angle H is determined to be unqualified, indicating that the timing system is faulty and requires manual intervention for inspection and repair. After inspection and repair, return to step 1.

[0028] Step 302: If the timing geometry deviation angle G is qualified, i.e., the timing geometry angle F is qualified, proceed to the Hall sensor system error C evaluation process. Here, the timing geometry deviation angle G is measured and obtained. The timing geometry deviation angle G consists of three reference values ​​and three tolerances: intake camshaft geometry deviation angle G~intake, exhaust camshaft geometry deviation angle G~exhaust, and crankshaft geometry deviation angle G~crankshaft. initial Exhaust initial These are the initial values ​​of the intake and exhaust camshaft timing angles, respectively. The judgment criteria are as follows:

[0029] G~Intake=Intake initial ℃a

[0030] g Intake low ℃a≤G~intake≤g Intake up ℃a

[0031] G ~ Exhaust = Exhaust initial ℃a

[0032] g exhaust low ℃a≤G~exhaust≤ge xhaust up ℃a

[0033] G ~ crankshaft = 0℃ r

[0034] g crankshaft low ℃r≤G~crankshaft≤g Crankshaft up ℃r

[0035] g Intake low g Intake up The upper and lower limits of the tolerance for the intake camshaft geometric deviation angle G ~ intake reference value; g exhaust low ge xhaust up The upper and lower limits of the tolerance for the geometric deviation angle G of the camshaft to the exhaust reference value; g crankshaft low g Crankshaft upThe crankshaft geometric deviation angle G~ C The upper and lower limits of the tolerance values ​​of rankshaft; ℃r represents the angle of rotation of the crankshaft about the center of rotation; ℃a represents the angle of rotation of the camshaft about the center of rotation;

[0036] If the time deviation angle G exceeds the range indicated by the judgment criteria, it is determined that the timing geometric deviation angle G is unqualified, indicating that the timing angle is out of tolerance and manual intervention is required for rework, reassembly and timing adjustment. After rework, return to step 1; if the time deviation angle G does not exceed the range indicated by the judgment criteria, it is determined that the timing geometric deviation angle G is qualified.

[0037] Step 303: Proceed to the evaluation process of the Hall sensor system error C. The Hall sensor system error C includes three values: effective intake camshaft deviation angle E (intake), effective exhaust camshaft deviation angle E (exhaust), and effective crankshaft deviation angle E (crankshaft). The judgment criteria are as follows:

[0038] C = E ~ intake

[0039] E~intake=H-(G~intake)-(M~Intake)

[0040] d intake low ≤E~intake≤d intake up

[0041] In the formula, d intake low With d intake up These represent the upper and lower limits of the maximum permissible relative deviation angle of the intake camshaft, respectively; M~Intake represents the machining tolerance of the intake camshaft.

[0042] C = E ~ exhaust

[0043] E~exhaust=H-(G~exhaust)-(M~Exhaust)

[0044] d exhaust low ≤E~Exhaust≤d exhaust up

[0045] In the formula, d exhaust up With d exhaust low These represent the upper and lower limits of the maximum permissible relative deviation angle of the exhaust camshaft, respectively; M~Exhaust represents the machining tolerance of the exhaust camshaft;

[0046] C = E ~ crankshaft

[0047] E~crankshaft=H-(G~crankshaft)-(M~Crankshaft)

[0048] d crankshaft low ≤E~Exhaust≤d crankshaft up

[0049] In the formula, d crankshaft up With d crankshaft low These represent the upper and lower limits of the maximum allowable relative deviation angle of the crankshaft, respectively; M~Crankshaft represents the crankshaft machining tolerance;

[0050] If, according to the above judgment criteria, the Hall sensor system error C exceeds the range, the effective timing angle H is deemed unqualified, indicating a timing system fault requiring manual intervention for repair. After repair, return to step 1. If the Hall sensor system error C does not exceed the range, the effective timing angle H is deemed qualified.

[0051] Preferably, in step 4, the crankshaft angular domain relationship is the vibration acceleration-crankshaft angular domain relationship; the acceleration time domain relationship is the vibration acceleration-crankshaft rotation speed.

[0052] Preferably, by analyzing the vibration acceleration-crankshaft angular domain, the contribution of vibration of reciprocating linear motion parts of each cylinder to vibration acceleration can be quickly identified.

[0053] The method provided by this invention can progressively judge and identify faults through mechanical layers (part machining tolerances, part assembly errors), electrical signal angle layers (sensor system errors), timing belt tension or vibration frequency and vibration acceleration layers, thereby enabling rapid identification of common engine faults during engine cold testing and bench testing. In the vibration acceleration layer determination, the mechanical and electrical signal angle layers are combined with a big data-based artificial intelligence fault judgment algorithm to quickly identify and predict engine faults. Attached Figure Description

[0054] Figure 1 This illustrates that engine timing deviation includes multiple aspects, such as the mechanical layer and the electrical signal angle layer.

[0055] Figure 2 The diagram illustrates the typical cold test stages of an engine.

[0056] Figure 3 A typical engine crankshaft angle domain diagram is shown.

[0057] Figure 4 This illustrates artificial intelligence algorithms such as neural networks;

[0058] Figure 5 The confusion matrix of the support vector machine fault diagnosis model on the test set at different speeds is shown.

[0059] Figure 6 A flowchart illustrating the integrated workflow for engine fault detection based on a multi-level, progressive detection principle. Detailed Implementation

[0060] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0061] This invention discloses an engine fault diagnosis method based on a multi-level progressive detection principle, comprising the following:

[0062] Step 1: Measurement of engine timing geometric deviation angle

[0063] The determination of engine timing geometry deviation angle is used for engine mechanical state identification, and its basic process further includes the following steps:

[0064] Step 101: Install the engine timing angle measuring instrument T220 (instrument resolution 0.01°r, hereinafter referred to as "T220") to the rear end of the engine under test, and connect it to the positioning slots at the end of the crankshaft and intake and exhaust camshafts respectively.

[0065] Step 102: Use a cold-test dedicated motor to slowly rotate the crankshaft of the engine under test, allowing it to complete at least two working cycles. Utilize the T220 accelerometer's ability to sense the direction of gravity to measure the timing geometry of the engine under test.

[0066] Step 103: Use a barcode scanner to scan the machining tolerance information of timing-related components on the QR code of the component. After obtaining the information, the software (C#) automatically calculates and generates the timing geometric deviation angle value to complete the calibration of the theoretical top dead center and the geometric top dead center of the mechanical layer.

[0067] Step 2: If the timing geometric deviation angle value exceeds the allowable range of timing deviation, it indicates that the timing angle is out of tolerance and manual intervention is required for repair (reassembly and timing adjustment). After repair, return to step 1 to continue measurement.

[0068] If the timing geometry deviation angle value does not exceed the allowable range of timing deviation, then the T220 will be removed from the engine under test and ready to proceed to the next step.

[0069] Step 3: Measurement and correction of Hall pulse signals of engine crankshaft and camshaft, i.e., measurement and correction of effective timing angle. The measurement and correction of effective timing angle is an electrical signal angle layer detection, and its process includes the following steps:

[0070] After the test accessories are pre-installed on the engine under test, the engine under test is automatically sent into the cold test station using a slide rail. The cold test bench is started and the engine under test is towed at a constant speed according to the predetermined speed spectrum. The output signals of the crankshaft position sensor and the intake and exhaust camshaft position sensors are collected respectively. The Hall pulse signals of the crankshaft and camshaft are measured, which is the effective timing angle. The effective timing angle includes the sensor system error (mainly including sensor installation deviation).

[0071] Considering that the Hall signal hardware of the engine camshaft and crankshaft consists of components such as signal wheels, sensors, and flanges, and is tightened by bolts, various deviations inevitably occur during engine parts processing and assembly, including interference from equipment and human factors such as parts processing tolerances, parts assembly errors, and Hall sensor installation deviations. To effectively separate the deviations generated at each level, this invention defines the engine timing-related parameters as follows:

[0072] (1)℃r represents the angle of crankshaft rotation around the center of rotation, abbreviated as crankshaft angle. In one working cycle of the engine, the crankshaft angle is 720℃r. The relationship between the crankshaft angle and the camshaft angle is 2:1.

[0073] (2)℃a represents the angle of rotation of the camshaft around the center of rotation, abbreviated as camshaft angle. In one working cycle of the engine, the camshaft angle is 360℃a. The relationship between the camshaft angle and the crankshaft angle is 1:2.

[0074] (3) Part machining tolerance A: This refers to the machining tolerance of parts related to timing, including dimensional tolerance and geometric tolerance.

[0075] (4) QR code information: This parameter pertains to timing-related components, including the machining tolerances of the intake and exhaust camshafts and crankshaft. The machining tolerances for the intake camshaft are represented as M~Intake, the exhaust camshaft as M~Exhaust, and the crankshaft as M~Crankshaft. The machining tolerance information is displayed as a QR code on the engine.

[0076] (5) Part assembly error B: refers to the difference between the installation position of the parts and the ideal position required by the assembly specifications and process. It mainly includes part error, tooling equipment error, operation error, environmental error and awareness error.

[0077] (6) Sensor system error C: The error of sensor system error C is the difference between the measured value and the true value. Sensor system error C includes application error (installation error), insertion error, characteristic error, dynamic error and environmental error. This invention mainly refers to the installation error of Hall sensor.

[0078] (7) Theoretically, the top dead center (TDC) is the extreme position where the piston crown is furthest from the crankshaft rotation center. This parameter is a theoretical value, while actual production, processing, and measurement involve various deviations and errors. Theoretically, the top dead center (TDC) is 0°C.

[0079] (8) Geometric Top Dead Center (D): This parameter falls under the mechanical category and is the actual top dead center measured by a mechanical measuring instrument T220 after engine assembly. This parameter includes part machining deviation A and part assembly error B. The formula for calculating the geometric top dead center (D) is:

[0080] D = TDC + (A + B) or D = A + B

[0081] The acquisition of the angle between TDC and the corresponding position is performed using a T220 device (refer to T220 device patent numbers: CN201811141194.1, CN201811142869.4, CN201821592505.1, CN201821592508.5). The measurement principle is based on measuring and calculating the displacement, i.e., the angle rotated by the crankshaft, using a capacitive accelerometer. TDC is defined as 0°C r.

[0082] (9) Effective Top Dead Center E: This parameter belongs to the category of electrical signal angle. It is obtained by acquiring the Hall pulse signals of the crankshaft / intake / exhaust camshaft sensors and calculating the phase relationship of the crankshaft / intake / exhaust camshafts. This parameter includes the Hall sensor system error C (mainly including sensor installation deviation). The formula for calculating the effective top dead center E is: E = F + C or E = (A + B + C).

[0083] (10) Timing belt tension or vibration frequency T: The vibration frequency T1 at the tensioner end and the vibration frequency T2 at the idler end are measured using a laser frequency meter to obtain the vibration frequency of the engine front crankshaft and camshaft connection, including the tensioner, idler, and timing belt assembly. The evaluation criterion is that the vibration frequency range at the tensioner end is f. zd1 ~f zd2 Hz, the vibration frequency range of the idler wheel end is f dd1 ~f dd2 Hz, i.e. f zd1 ≤T1≤f zd2 f dd1 ≤T2≤f dd2The T value is a logical judgment value. If the vibration frequency T1 at the tensioner end and the vibration frequency T2 at the idler end meet the value range, the timing belt tension or vibration frequency T is assigned a qualified value. If they do not meet the value range, they are assigned an unqualified value.

[0084] (11) Timing geometry angle F: This parameter belongs to the mechanical layer and is the timing angle actually measured after engine assembly using a mechanical measuring instrument. Generally, there are inevitably machining tolerances and assembly errors of the parts. The deviation between the actual measured geometric top dead center and the theoretical top dead center is the timing geometry deviation angle G, which is: F = TDC + (A + B) or F = A + B.

[0085] (12) Timing geometric deviation angle G:

[0086] G=∣TDC-F∣

[0087] Therefore, F = TDC + (A + B);

[0088] Since G = A + B;

[0089] This parameter was actually measured. The timing geometry deviation angle G represents three reference values ​​and three tolerances: intake camshaft geometry deviation angle G~intake, exhaust camshaft geometry deviation angle G~exhaust, and crankshaft geometry deviation angle G~Crankshaft. initial Exhaust initial These are the initial values ​​of the intake and exhaust camshaft timing angles, respectively. The judgment criteria are as follows:

[0090] G~Intake=Intake initial ℃a

[0091] g Intake low ℃a≤G~Intake≤g Intake up ℃a

[0092] G ~ Exhaust = Exhaust initial ℃a

[0093] g exhaust low ℃a≤G~Exhaust≤ge xhaust up ℃a

[0094] G ~ Crankshaft = 0℃ r

[0095] g crankshaft low ℃r≤G~Crankshaft≤g Crankshaft up ℃r

[0096] If the above range is exceeded, the timing geometric deviation angle G is unqualified, indicating that the timing angle is out of tolerance and manual intervention is required for repair (reassembly and timing adjustment).

[0097] Because there will always be some degree of error between the various components of the engine after assembly (introducing new errors). Also, the G-Crankshaft of an engine assembled online is usually not guaranteed to be at its theoretical zero point. Therefore, an out-of-tolerance detection process is needed.

[0098] (13) Effective timing angle H: This parameter belongs to the category of electrical signal angle. It is obtained and measured by a special instrument using Hall pulse signals of the engine crankshaft and camshaft. The effective timing angle includes the above-mentioned deviations and errors.

[0099] (14) The formula for the effective time angle H is shown below:

[0100] (F+C)and T→H

[0101] F = A + B

[0102] (A+B+C)and T→H

[0103] (A+B+C)==X

[0104] X and T→H

[0105] Includes the following steps:

[0106] Step 301: Determine whether the vibration frequency T1 at the tensioner end and the vibration frequency T2 at the idler end satisfy the value range shown in the following formula:

[0107] f zd1 ≤T1≤f zd2 f dd1 ≤T2≤f dd2

[0108] In the formula, f zd1 f dd1 f is a pre-set lower limit value. zd2 f dd2 This is a pre-set upper limit value.

[0109] If the value range is met, the timing belt tension or vibration frequency T is assigned a qualified value, and the process proceeds to the F+C evaluation process, where F is the timing geometry angle and C is the Hall sensor system error.

[0110] Step 302: According to the formula G=F=(A+B), the G value and the F value are the relationship between angular and linear quantities. If the timing geometric deviation angle G is qualified, then the timing geometric angle F is qualified, and the Hall sensor system error C evaluation process is entered.

[0111] Step 303: The Hall sensor system error C (sensor installation error) is the difference between the mechanical layer and the electrical signal angle layer. When entering the evaluation process for the Hall sensor system error C, the timing geometry deviation angle G has already been judged as a qualified value. Simultaneously, the Hall sensor system error C is also the value that needs to be corrected relative to the timing geometry deviation angle G. The Hall sensor system error C includes three values: the effective deviation angle E~intake of the intake camshaft, the effective deviation angle E~exhaust of the exhaust camshaft, and the effective deviation angle E~crankshaft. The judgment criteria are as follows:

[0112] C = E ~ intake

[0113] E~intake=H-(G~Intake)-(M~Intake)

[0114] d intake low ≤E~Intake≤d intake up

[0115] In the formula, d intake low With d intake up These represent the upper and lower limits of the maximum permissible relative deviation angle of the intake camshaft, respectively.

[0116] C = E ~ exhaust

[0117] E~exhaust=H-(G~exhaust)-(M~exhaust)

[0118] d exhaust low ≤E~Exhaust≤d exhaust up

[0119] In the formula, d exhaust up With d exhaust low These represent the upper and lower limits of the maximum permissible relative deviation angle of the exhaust camshaft.

[0120] C = E ~ crankshaft

[0121] E~crankshaft=H-(G~crankshaft)-(M~crankshaft)

[0122] d crankshaft low ≤E~Exhaust≤d crankshaft up

[0123] In the formula, d crankshaft up With d crankshaft low These represent the upper and lower limits of the maximum allowable relative deviation angle of the crankshaft, respectively.

[0124] If, according to the above judgment criteria, the Hall sensor system error C exceeds the range, then according to the formula (F+C)and T→H, the effective timing angle H→ is deemed unqualified, indicating that the timing system is faulty and requires manual intervention for repair.

[0125] If the timing belt tension or vibration frequency T is not up to standard, the effective timing angle H is also deemed unqualified, indicating a timing system malfunction that requires manual intervention for inspection and repair.

[0126] Step 4: Comprehensive analysis of crankshaft angle domain / frequency domain under engine cold test and acceleration conditions, i.e., vibration acceleration layer detection.

[0127] After completing the uniform speed towing in step 3, the cold test bench tows the engine under test according to the predetermined acceleration conditions. Simultaneously, the vibration analyzer collects data from the vibration acceleration sensors and crankshaft position sensors located on the cylinder block. Then, combining the crankshaft speed, methods such as Fast Fourier Transform are used to obtain the speed-acceleration frequency domain relationship (spectral graph) under the engine acceleration conditions, and the acceleration values ​​of each order are calculated to identify the frequency domain contribution of each order of acceleration. Simultaneously, combining the crankshaft angular domain and acceleration time domain relationship, the characteristic acceleration contribution of each cylinder is identified according to order analysis. This determines whether the engine vibration acceleration meets the design requirements.

[0128] like Figure 3 As shown in the crankshaft angle domain analysis, 0℃r is the effective top dead center of each cylinder, the angle resolution is 0.5℃r, and the adaptive dimension of the amplitude is ±5m / s2. The vibration signal is analyzed after corresponding to the crankshaft rotation angle 0°~720℃r (angle domain), which is one working cycle of the engine.

[0129] Step 5: Fault Identification Based on Big Data and Artificial Intelligence

[0130] If the vibration acceleration characteristics of the tested engine exceed the limit after completing the judgments in steps 1 to 4, then proceed to this step.

[0131] In this step, since the acceleration signal acquired by the accelerometer will most likely contain signal noise introduced by external interference or EMC interference, the vibration acceleration data acquired in step 4 needs to be filtered first to remove background noise signals introduced by the external environment. Then, the characteristics of the fault acceleration signal (such as the ranking of the contributions of each order of vibration acceleration and the corresponding angular domain) are captured. Then, methods such as... Figure 4The artificial intelligence algorithms shown are such as neural networks or... Figure 5 The fault diagnosis model of the support vector machine shown uses the confusion matrix of the test set at different speeds to identify and classify fault modes, thereby determining the fault type and completing the preliminary location of the faulty component.

[0132] A specific implementation method of the above-mentioned technical content includes the following steps:

[0133] 1. Engine pre-inspection and installation of T220 angle measuring instrument;

[0134] In this step, the engine under test is first mounted on a process tray, and its appearance and accessories are visually inspected to observe for any abnormalities such as missing parts or lubricating oil leaks. Then, a T220 timing angle measuring instrument is installed at the rear end of the crankshaft and the intake and exhaust camshafts, respectively.

[0135] 2. Scan the QR codes on engine parts to read the part machining tolerance information;

[0136] In this step, a barcode scanner is used to scan the dimensional tolerance information of timing-related engine parts processed during the machining stage and automatically input it into the computer.

[0137] The dedicated station on the engine cold test bench completes T220 measurements and timing geometry angle determination / calculation and correction of timing geometry deviation angle (geometric top dead center);

[0138] In this step, the engine crankshaft is driven by a T220 special motor at a low speed (<30 Rpm) to rotate the engine crankshaft and complete two or more full work cycles. Timing geometry angles (including part assembly errors) are collected and automatically input into the computer. Subsequently, the computer automatically calculates the timing geometry deviation angle (geometric top dead center) based on the part machining tolerance information obtained in the previous step, using the formula G = F - (A + B). The geometric top dead center is a correction to the theoretical top dead center; this step means that the geometric top dead center after mechanical correction is infinitely close to the theoretical top dead center. After measurement, the instrument is removed, and the pre-inspection and cold-test preparation of the engine are completed, preparing it for the next step.

[0139] 3. Uniform speed rotation and acquisition of Hall pulse signals from crankshaft and camshaft.

[0140] After preparation, the engine pallet is moved to the cold test bench. The pallet is secured and the process flywheel is connected. The test bench is then started, and the engine is towed under a predetermined constant speed condition. By collecting the engine crankshaft and Hall pulse signals (i.e., the effective timing angle) under constant speed conditions, the computer calculates and corrects the deviation from the timing geometry (geometric top dead center) according to a preset algorithm (F+C) and T→H. This deviation is the Hall sensor system error (crankshaft position sensor installation error). The computer then checks if the deviation meets the tolerance requirements. If it does, the engine timing deviation angle is corrected a second time, meaning the timing geometry, effective timing angle, or geometric top dead center and effective top dead center are infinitely close to the theoretical top dead center. This completes the calibration of the engine timing angle deviation from the mechanical level to the electrical signal angle level.

[0141] 4. Measurement and judgment of engine timing belt tension (vibration frequency)

[0142] In this step, while the engine is running in a cold test chamber, a laser frequency meter is used to detect the timing belt vibration frequency at the tensioner and idler ends. This yields the vibration frequency of the engine's front crankshaft and camshaft connection, including the tensioner, idler, and timing belt assembly. The evaluation criteria are: the timing belt tensioner end vibration frequency T1 is the tensioner end, and T2 is the idler end, where f... zd1 ≤T1≤f zd2 f dd1 ≤T2≤f dd2 If the timing exceeds this range, the engine timing angle will deviate or show a tendency to deviate, such as skipping teeth. In this case, the engine should be stopped immediately to check whether the tensioner pulley, idler pulley, and timing belt assembly at the front of the engine meet the process requirements, especially the installation process of the tension and whether the parts themselves meet the quality requirements. This inspection item can quickly determine whether the tension of the tensioner pulley at the crankshaft and camshaft connection, the concentricity of the idler pulley (circular runout), and the material properties of the timing belt meet the process requirements.

[0143] 5. Comprehensive analysis of vibration acceleration in the angular and frequency domains during engine cold test acceleration.

[0144] After the engine completes the constant-speed towing test, the cold test bench is accelerated and towed according to the predetermined operating conditions. Simultaneously, a vibration analyzer is used to collect signals from the crankshaft position sensor and the cylinder head and cylinder block acceleration sensors. Subsequently, the vibration acceleration-crankshaft angular domain relationship (time domain analysis) and the vibration acceleration-crankshaft speed relationship (frequency domain waterfall plot analysis) are identified. The frequency domain contribution of each order of engine acceleration and the acceleration contribution of each cylinder are calculated to determine whether the engine vibration acceleration meets the qualification standard. Afterwards, the engine, having completed the cold test, is disassembled and removed from the cold test bench.

[0145] 6. Engine cold test fault identification and judgment

[0146] If, during the cold test, the engine exhibits faults such as excessive vibration acceleration or abnormal vibration order, the engine cold test fault identification and judgment process will be initiated.

[0147] In this step, since the acceleration signal acquired by the accelerometer will most likely contain signal noise introduced by external interference or EMC interference, the vibration acceleration data acquired in step three needs to be filtered first to remove background noise signals introduced by the external environment. Then, the characteristics of the fault acceleration signal (such as the ranking of the contributions of each order of vibration acceleration and their corresponding angular domains) are captured.

[0148] Subsequently, artificial intelligence algorithms (such as neural networks or support vector machines) are used to identify and classify the fault modes, thereby determining the fault type and completing the initial location of the faulty component.

Claims

1. An engine fault diagnosis method based on a multi-level progressive detection principle, characterized in that, Includes the following steps: Step 1: Measure the engine timing geometry deviation angle to complete the mechanical level inspection. The timing geometry angles of the crankshaft and intake and exhaust camshafts of the engine under test are measured using an engine timing angle measuring instrument, and the timing geometry deviation angle value is calculated based on the machining tolerance information of timing-related parts. Step 2: If the timing geometric deviation angle value obtained in Step 1 exceeds the allowable range of timing deviation, it indicates that the timing angle is out of tolerance and manual intervention is required for repair. The timing needs to be reassembled and adjusted. After repair, return to Step 1. If the timing geometric deviation angle value obtained in Step 1 does not exceed the allowable range of timing deviation, proceed to the next step. Thus, while measuring the timing geometric angle of the engine timing mechanical system, the calibration of the actual measured top dead center and the theoretical top dead center is completed. Step 3: Measure and correct the Hall pulse signals of the engine crankshaft and camshaft to complete the electrical signal angle layer detection. Under constant speed churning conditions, the output signals of the crankshaft position sensor and the intake and exhaust camshaft position sensors are collected respectively, thereby measuring the Hall pulse signals of the engine crankshaft and camshaft, and determining whether the effective timing angle output by the Hall sensor meets the requirements. The effective timing angle includes the timing geometric deviation angle and the Hall sensor system error, thus completing the correction of the engine timing angle deviation from the mechanical layer to the electrical signal angle layer. Step 4: Comprehensive analysis of crankshaft angle domain / frequency domain under engine cold test and acceleration conditions, i.e., vibration acceleration layer detection: Under the predetermined acceleration condition, the signals output by the vibration acceleration sensor and crankshaft position sensor arranged on the cylinder block are collected by the vibration analyzer. Then, the speed-acceleration frequency domain relationship under the engine acceleration condition is obtained by combining the crankshaft speed and the acceleration values ​​of each order are calculated to identify the frequency domain contribution of each order acceleration. At the same time, the characteristic acceleration contribution of each cylinder is identified by combining the crankshaft angular domain and acceleration time domain relationship according to the order analysis to determine whether the engine vibration acceleration meets the design requirements. If the vibration acceleration characteristics of the tested engine exceed the limit, proceed to step 5. Step 5: Fault identification based on big data and artificial intelligence: The vibration acceleration data collected in step 4 is filtered to remove background noise signals introduced by the outside world; then the characteristics of the fault acceleration signal are captured. Subsequently, an AI-based fault identification algorithm based on big data is used to identify and classify fault modes, thereby determining the fault type and completing the initial location of the faulty component.

2. The engine fault diagnosis method based on the multi-level progressive detection principle as described in claim 1, characterized in that, In step 1, the timing-related part machining tolerances are obtained by scanning the QR code on the engine under test.

3. The engine fault diagnosis method based on the multi-level progressive detection principle as described in claim 1, characterized in that, Step 1 further includes the following steps: Step 101: Install the engine timing angle measuring instrument to the rear end of the engine under test, and connect it to the positioning slots at the tail ends of the crankshaft and intake and exhaust camshafts respectively; Step 102: Use a cold test special motor to slowly rotate the crankshaft of the engine under test to complete two or more working cycles. Utilize the capacitive acceleration sensor of the engine timing angle measuring instrument to sense the direction of gravity and measure the timing geometry of the engine under test. Step 103: Use a barcode scanner to scan the machining tolerance information of timing-related components on the component's QR code. After obtaining the information, the software automatically calculates and generates the timing geometric deviation angle value.

4. The engine fault diagnosis method based on the multi-level progressive detection principle as described in claim 1, characterized in that, In step 4, the crankshaft angular domain relationship is the vibration acceleration-crankshaft angular domain relationship; the acceleration time domain relationship is the vibration acceleration-crankshaft speed.

5. The engine fault diagnosis method based on the multi-level progressive detection principle as described in claim 1, characterized in that, By analyzing the vibration acceleration-crankshaft angular domain, the contribution of vibration to vibration acceleration of reciprocating linear motion parts of each cylinder can be quickly identified.

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