CN111997758B

CN111997758B - Abnormal sound diagnosis method for engine valve mechanism

Info

Publication number: CN111997758B
Application number: CN202010923710.7A
Authority: CN
Inventors: 范富贵; 杨国芳; 曹玉煌; 宋正华; 王毅
Original assignee: Dongfeng Motor Corp
Current assignee: Dongfeng Motor Corp
Priority date: 2020-09-04
Filing date: 2020-09-04
Publication date: 2021-09-14
Anticipated expiration: 2040-09-04
Also published as: CN111997758A

Abstract

The invention discloses an abnormal sound diagnosis method for an engine valve actuating mechanism, wherein the engine valve actuating mechanism comprises an engine camshaft, a valve group, a tappet and a VVT; the abnormal sound diagnosis method for the valve actuating mechanism of the engine comprises the following steps of arranging a plurality of vibration sensors and a plurality of microphones on the engine, and acquiring rotating speed signals and noise signals of a crankshaft and a camshaft; performing wavelet analysis on the noise signal to determine abnormal sound frequency; performing band-pass filtering of the abnormal sound frequency range on the vibration and noise signals, extracting the abnormal sound frequency components, performing time domain analysis, obtaining a time domain signal, converting the time value of the time domain signal into a crank angle according to the phase relation between a crank shaft and a cam shaft, determining the abnormal sound moment, and judging whether the abnormal sound is related to a valve actuating mechanism; if the abnormal sound is judged to be related to the valve actuating mechanism, the VVT angle is adjusted, and the reason of the abnormal sound is judged. Compared with the traditional method, the method is more targeted, greatly shortens the analysis time, and is beneficial to optimizing, improving and solving the abnormal sound problem.

Description

Abnormal sound diagnosis method for engine valve mechanism

Technical Field

The invention relates to the field of NVH (noise, vibration and harshness) of an engine, in particular to an abnormal sound diagnosis method of a valve mechanism of the engine.

Background

With advances in technology and increased customer requirements for automobiles, engine NVH performance is becoming increasingly important. The valve train is an important component of the engine and an important source of mechanical noise of the engine. Valve train noise is usually significant mechanical knock, affecting engine acoustic quality. In the development of NVH performance of the engine, the noise of the valve train needs to be reduced as much as possible. However, the engine mechanism is complex, the number of sound sources is large, the valve actuating mechanism is a part in the engine, and direct measurement cannot be carried out on an internal moving part, so that abnormal sound generated by the valve actuating mechanism is difficult to diagnose.

At present, the abnormal sound diagnosis aspect of the engine is mainly to carry out comparison analysis on a fault diagnosis system of a finished product engine by taking the normal level of the engine as a reference, but the abnormal sound diagnosis aspect has a small effect on the analysis of the reason of the abnormal sound. And for the abnormal sound of the engine in the development process, the problem cannot be diagnosed without comparison reference. Particularly for abnormal sound generated by complex motion mechanisms such as a valve mechanism, no corresponding diagnosis method exists at present. If the reason for generating abnormal noise of the valve train is not clear, design optimization and improvement cannot be carried out, and NVH performance of the engine is affected.

Disclosure of Invention

The invention aims to provide a diagnosis method for accurately judging the abnormal sound reason of a valve train.

In order to solve the technical problems, the technical scheme of the invention is as follows: 1. a method for diagnosing abnormal sound of an engine valve mechanism comprises the steps that the engine valve mechanism comprises an engine crankshaft, an air inlet and outlet camshaft, an air inlet valve, an exhaust valve and a VVT; the method for diagnosing the abnormal sound of the valve actuating mechanism of the engine comprises the following steps:

s1, arranging a plurality of vibration sensors and a plurality of microphones on the engine, and collecting vibration signals and noise signals;

s2, performing wavelet analysis on the noise signal to determine the abnormal sound frequency;

s3, performing band-pass filtering of the abnormal sound frequency range on the vibration signal and the noise signal, extracting the abnormal sound frequency component, performing time domain analysis, obtaining a time domain signal, converting the time of time domain data into a crank angle according to the phase relation between a crank shaft and a cam shaft, determining the abnormal sound moment, and judging whether the abnormal sound is related to the valve actuating mechanism;

and S4, if the abnormal sound is judged to be related to the valve train, adjusting the VVT angle and judging the reason of the abnormal sound.

Further, in S1, the specific locations of the vibration sensor are the engine head, the cylinder block and the VVT; the specific arrangement positions of the microphones are the top end of the engine, the air inlet side, the air outlet side and the front end of the engine.

Further, the step S3 includes determining a top dead center of a cylinder of the engine block according to a phase relationship between the crankshaft and the camshaft.

Further, in S3, at a time value of the predetermined time domain signal, the engine valve train starts to perform a specific motion, the specific motion includes an intake opening impact, an intake reversal impact, an intake seating impact, an exhaust opening impact, an exhaust reversal impact, an exhaust seating impact, and an oil pump reversal impact in one cylinder; the time value of the time domain signal corresponding to each specific action corresponds to the crank angle, the angle interval of execution of the same specific action is 240 degrees, and the working schedule of the engine valve mechanism is obtained according to the corresponding relation between the time value of the time domain signal corresponding to the specific action and the crank angle.

Further, the step S3 includes determining whether the abnormal sound is related to the valve train according to the valve train operation schedule of the engine, where the determining method includes: recording the corresponding crank angle of the abnormal sound moment, comparing the recorded abnormal sound moment with the working schedule of the engine valve actuating mechanism, and if the recorded abnormal sound moment corresponds to any crank angle in the schedule, correlating the abnormal sound with the valve actuating mechanism; if there is no correspondence with all crank angles in the table, the abnormal sound is irrelevant to the valve actuating mechanism.

Further, the S4 is specifically:

s4.1, judging specific actions;

s4.2, advancing or delaying the VVT angle at the corresponding position of executing the specific action;

s4.3, if the angle corresponding to the abnormal sound moment is not changed synchronously, eliminating the reason of the abnormal sound; if the angle corresponding to the abnormal sound time changes synchronously, the abnormal sound can be determined as the reason of the abnormal sound.

Compared with the prior art, the invention has the beneficial effects that:

according to the method, the top dead center of a cylinder is determined according to the phase relation between the crankshaft and the camshaft, the angle is accurate, and misjudgment caused by large angle errors is avoided; the noise is subjected to time domain analysis after the characteristic frequency is filtered, so that the interference of other frequency components is avoided; by means of adjusting the VVT angle, abnormal sound generated by the valve actuating mechanism can be judged quickly and accurately, the method is more targeted than the traditional method, analysis time is greatly shortened, and optimization, improvement and solution of the abnormal sound problem are facilitated.

Drawings

Fig. 1 is a flowchart of abnormal sound diagnosis work according to an embodiment of the present invention;

FIG. 2 is a diagram illustrating wavelet analysis of an abnormal noise signal according to an embodiment of the present invention;

FIG. 3 is a schematic illustration of a method of determining top dead center based on crankshaft and camshaft signals in an embodiment of the present invention;

FIG. 4 is a schematic diagram of a crank angle corresponding to an abnormal sound moment in the embodiment of the present invention;

fig. 5 is a schematic diagram of adjusting variation of VVT angle abnormal sound time in the embodiment of the present invention;

FIG. 6 is a timing chart of engine valve train operation according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1, the diagnostic protocol of the present invention is:

signal acquisition: the vibration sensor is arranged on each cylinder cover, each cylinder body, each VVT, each front suspension bracket and the like of the engine, and the vibration sensor is arranged on the main side surface of the engine: microphones are arranged at the positions of 1m of the top end, the air inlet side, the air outlet side and the front end, and vibration signals are collected.

Determining abnormal sound frequency: wavelet analysis is carried out on the abnormal sound noise and the vibration signal, obvious regular mechanical knocking characteristics exist in the frequency range of 650-1100Hz, and the characteristic is shown in figure 2, and the filtering playback is consistent with the subjective abnormal sound perception. The abnormal sound frequency is determined to be 650-1100 Hz. And filtering extraction in the range of 650-1100Hz is carried out on the vibration and noise signals for analysis.

Determining abnormal sound time: and finding a cylinder top dead center according to the phase relation of signals of a crankshaft and a camshaft (one of the intake camshaft and the exhaust camshaft is selected). As shown in FIG. 3, T1 through T3 are two missing tooth signals from the crankshaft, separated by 720 of one engine cycle. According to the phase relation between the crankshaft and the camshaft, the crankshaft missing tooth signal corresponding to the camshaft signal tooth corresponding to the T1 moment is separated from the 1-cylinder top dead center angle by 78 degrees, and the T1+78 degrees can obtain the top dead center moment of T2. The time domain is converted into the crank angle by taking T2 as a starting point and taking T3-T1 as 720 degrees. The filtered signal is taken as a crank angle, and as shown in fig. 4 and fig. 6, the crank angle corresponding to the abnormal sound time is about 122 °, 362 ° and 602 °. According to the peak value moments of different vibration measuring points of the three cylinders and by combining with the graph of FIG. 6, the mechanical knocking at the air inlet opening moment is preliminarily determined, wherein the unit impact moment corresponds to the crank angle unit in Degrees (DEG).

Adjusting the VVT angle: the intake VVT angle is adjusted by a calibration means, and after the offset is 20 degrees, the abnormal sound time is also offset by 20 degrees to 142 degrees, 382 degrees and 622 degrees, as shown in FIG. 5. Not only the vibration peak time is pushed back by 20 degrees, but also the noise peak time is pushed back by 20 degrees, and then the abnormal sound can be judged to be mechanical knocking at the air inlet opening time. According to the working principle, the knocking tappet of the air inlet camshaft can be judged to be generated when the air inlet valve is opened, and the optimization can be realized by optimizing a cam profile line or adjusting the valve clearance. The two schemes have obvious effect of improving abnormal sound.

The above embodiments are only used for illustrating the design idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention accordingly, and the protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes and modifications made in accordance with the principles and concepts disclosed herein are intended to be included within the scope of the present invention.

Claims

1. The abnormal sound diagnosis method of the engine valve actuating mechanism is characterized in that the engine valve actuating mechanism comprises an engine camshaft, a valve group, a tappet and a VVT; the method for diagnosing the abnormal sound of the valve actuating mechanism of the engine comprises the following steps:

s1, arranging a plurality of vibration sensors and a plurality of microphones on the engine, and collecting vibration signals and noise signals, wherein the specific arrangement positions of the vibration sensors are the cylinder cover, the cylinder body and the VVT of the engine; the specific arrangement positions of the microphones are the top end of the engine, the air inlet side, the air exhaust side and the front end of the engine;

s3, performing band-pass filtering of an abnormal sound frequency range on the vibration signal and the noise signal, extracting an abnormal sound frequency component, performing time domain analysis, obtaining a time domain signal, converting time of time domain data into a crank angle according to a phase relation between a crank shaft and a cam shaft, determining an upper dead center of a cylinder of an engine cylinder body according to the phase relation between the crank shaft and the cam shaft, and starting an engine valve actuating mechanism to execute a specific action at a time value of the preset time domain signal, wherein the movement of the specific action in the cylinder comprises an air inlet opening impact, an air inlet reversing impact, an air inlet seating impact, an exhaust opening impact, an exhaust reversing impact, an exhaust seating impact and an oil pump reversing impact; the time value of the time domain signal corresponding to each specific action corresponds to the crank angle, the angle interval of the execution of the same specific action is 240 degrees, an engine valve actuating mechanism working schedule is obtained according to the corresponding relation between the time value of the time domain signal corresponding to the specific action and the crank angle, whether abnormal sound is related to the valve actuating mechanism or not is judged according to the engine valve actuating mechanism working schedule, and the judgment method comprises the following steps: recording the corresponding crank angle of the abnormal sound moment, comparing the recorded abnormal sound moment with the working schedule of the engine valve actuating mechanism, and if the recorded abnormal sound moment corresponds to any crank angle in the schedule, correlating the abnormal sound with the valve actuating mechanism; if the crank angle does not correspond to the crank angle in the meter, the abnormal sound is irrelevant to the valve actuating mechanism;

2. The engine valve train abnormal sound diagnostic method according to claim 1, wherein the S4 is specifically:

s4.1, judging specific actions;