An analysis and optimization method for gear knocking in engine balance shaft system

Abstract

The present invention discloses a method for analyzing and optimizing the gear knocking of an engine balance shaft system, comprising the following steps: studying the gear knocking vibration noise of the engine balance shaft system through a bench test; establishing a dynamic model of the engine balance shaft system; analyzing the dynamic characteristics of the gear knocking of the system; proposing a gear knocking evaluation index based on the moment of inertia in order to quantitatively evaluate the gear knocking intensity; using an orthogonal test method to study the factors affecting the gear knocking of the engine balance shaft system, and obtaining important parameters that have a significant impact on the gear knocking through range analysis; based on the selected important parameters, using a response surface method to optimize the gear knocking noise of the system. The method described in the present invention can analyze and optimize the gear knocking of an engine balance shaft system with scissor teeth, and provide a clear direction for reducing the gear knocking noise of the engine balance shaft system.

Description

Technical Field

[0001] The invention belongs to the field of automobile engine NVH, and in particular relates to an analysis and optimization method for gear knocking of an engine balance shaft system. Background Art

[0002] The quality of automobile NVH can be intuitively felt by passengers, so NVH performance has become one of the key indicators for people to evaluate automobiles. Because the vibration of the engine can easily cause various noise problems in the car, reducing the vibration of the engine is one of the key measures to improve the NVH performance of the car. For an inline four-cylinder engine, the first-order reciprocating inertia force can be balanced by its own structure, but the second-order reciprocating inertia force cannot be balanced by itself. Therefore, in order to eliminate the second-order reciprocating inertia force of the inline four-cylinder engine, a balance shaft module can be added to the engine design, which can effectively reduce the vibration of the engine, but this will additionally generate noise problems such as gear whine and gear knocking. At present, most of the research on the abnormal noise of the balance shaft scissor teeth focuses on gear whine, and there is still a lack of effective analysis and optimization methods for the gear knocking problem of the balance shaft.

[0003] At present, the research on gear knock is mainly concentrated in the fields of transmission and gearbox, and there is less research on gear knock of engine balance shaft. In addition, there is relatively little research on the evaluation index of gear knock of scissor teeth. Common gear knock evaluation indexes include gear knock evaluation index based on speed difference standard deviation, gear knock evaluation index based on impact pulse, gear knock evaluation index based on vibration angular velocity, gear knock evaluation index based on root mean square value of passive gear angular acceleration, etc. Among them, the gear knock evaluation index based on the standard deviation of the speed difference is only applicable to the case where the gear knock changes significantly. For the steady-state working condition where the gear knock does not change significantly, only qualitative analysis can be performed; for the gear knock evaluation index based on the impact pulse, due to the existence of the scissor tooth torsion spring, the gear knock force will reach the peak value quickly, which may cause errors in the gear knock evaluation; for the gear knock evaluation index based on the vibration angular velocity, since the deformation of the scissor tooth is larger than that of other gears, the accuracy of this evaluation index may be low; for the gear knock evaluation index based on the root mean square value of the angular acceleration of the passive gear, when the research parameters involve the gear moment of inertia, this evaluation index may draw an erroneous conclusion. In 2007, Barthod et al. proposed a gear knock evaluation index based on the root mean square value of the angular acceleration of the passive gear in the SCI journal Applied Acoustics. Through experiments, it was found that there is a linear relationship between the root mean square value of the angular acceleration of the non-load-bearing gear and the sound pressure that produces the knock noise. However, this evaluation index still has the following shortcomings: when the research parameters involve the gear moment of inertia, the change of the root mean square value of the gear angular acceleration is not obvious, and there is even a negative correlation, which may lead to erroneous conclusions. Summary of the invention

[0004] The purpose of the present invention is to provide a method for analyzing and optimizing the gear knocking of an engine balance shaft system. The method analyzes the gear knocking problem of the engine balance shaft system by means of experiments and simulation calculations, and on this basis, the orthogonal test method and response surface method are used to optimize the gear knocking noise, providing a basis for the analysis and optimization of the gear knocking problem of the engine balance shaft system.

[0005] In order to achieve the purpose of the present invention, the present invention provides a method for analyzing and optimizing gear knocking of an engine balance shaft system, comprising the following steps:

[0006] (1) Analyze the gear knocking problem of the engine balance shaft system through bench testing and analyze the gear knocking characteristics of the engine balance shaft system;

[0007] (2) Establish a multi-flexible body dynamics model of the engine balance shaft system;

[0008] (3) Based on the multi-flexible body dynamics model of the engine balance shaft system, the dynamic characteristics of the gear knocking of the system are analyzed;

[0009] (4) Determine the moment of inertia of the passive gear As the gear knock evaluation index of each gear pair, J is the moment of inertia of the passive gear, is the RMS value of the angular acceleration of the driven gear;

[0010] (5) The orthogonal test method was used to study the factors affecting the gear knock of the engine balance shaft system, and the important parameters that have a significant impact on the gear knock were obtained through range analysis;

[0011] (6) Based on the screened important parameters, the response surface methodology is used to optimize the gear knocking noise of the system.

[0012] Furthermore, the established engine balance shaft system dynamics model includes an engine and a balance shaft module. The balance shaft module includes a balance shaft tray, a balance shaft, a scissor gear, a driven gear, and a bearing. The scissor gear includes a scissor main tooth, a scissor auxiliary tooth, a torsion spring, a retaining spring, and a pin.

[0013] Furthermore, in step (1), by collecting the engine's far-field noise and housing surface vibration acceleration data, and drawing the sound pressure waterfall diagram and spectrum diagram, the vibration acceleration waterfall diagram and spectrum diagram, on this basis, the gear knocking characteristics of the engine balance shaft system are analyzed.

[0014] Furthermore, in step (2), a multi-flexible body dynamics model of the engine balance shaft system is established in MASTA, and boundary conditions and input operating conditions are set according to the actual conditions of the engine.

[0015] Furthermore, after the multi-flexible body dynamics model of the engine balance shaft system is established, the method includes the following steps: verifying the multi-flexible body dynamics model of the engine balance shaft system.

[0016] Furthermore, the frequency spectrum of the vibration acceleration sensor at each rotation speed is calculated in MASTA and compared with the test results in step (1).

[0017] Furthermore, in step (3), based on the dynamic model, the gear knocking dynamic characteristics of the system are studied from three aspects: the contact state of the gear, the angular acceleration of the passive gear, and the gear tooth surface meshing force.

[0018] Furthermore, in step (4), the inertia moment of the passive gear is As the gear knock evaluation index of each gear pair, where: J is the moment of inertia of the passive gear, is the root mean square value of the angular acceleration of the passive gear. The specific steps are as follows:

[0019] (a) The angular acceleration of each passive gear is calculated by the dynamic model, and then the corresponding angular acceleration root mean square value is obtained;

[0020] (b) Since there are three pairs of meshing gears in the system, the knock evaluation results RI1, RI2, and RI3 of each gear pair are calculated using the knock evaluation index of the moment of inertia.

[0021] (c) The gear knock evaluation index of the three gear pairs is:

[0022] Furthermore, in step (5), multiple influencing parameters of the gear knocking of the system are first determined, and the orthogonal test design is performed using Minitab software. The factors and levels of the orthogonal test are defined in the software, and the corresponding simulation calculation results are input. The main parameters with significant influence are further screened out through range analysis.

[0023] Furthermore, in step (6), the response surface test scheme is determined using the software Design-Expert 13, and then a response surface model is established according to the calculation results, and the gear knocking optimization is performed based on the response surface model.

[0024] Compared with the prior art, the beneficial effects of the present invention are at least:

[0025] (1) The present invention studies the gear knocking dynamic characteristics of the system from three aspects: the contact state of the gear, the angular acceleration of the passive gear, and the meshing force of the gear tooth surface, and can intuitively analyze the knocking times and knocking intensity of each gear pair;

[0026] (2) The present invention proposes a gear knocking evaluation index suitable for scissor gears, which can reduce the influence of the scissor gear's own structure and improve the accuracy of the gear knocking evaluation result;

[0027] (3) The present invention adopts orthogonal test method and response surface method to optimize gear knocking, which can optimize the main influencing parameters, and the optimization process is simple, which can provide a basis for the gear knocking optimization of the engine balance shaft system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of a method for analyzing and optimizing gear knocking of an engine balance shaft system provided by an embodiment of the present invention;

[0029] Figure 2 is a schematic diagram of a stand according to an embodiment of the present invention;

[0030] Figure 3is a schematic diagram of the gear contact state at 2000 rpm according to an embodiment of the present invention;

[0031] Figure 4 is a schematic diagram of the angular acceleration of a gear at 2000 rpm according to an embodiment of the present invention;

[0032] Figure 5 Schematic diagram of the tooth surface meshing force of a 2000 rpm gear according to an embodiment of the present invention;

[0033] Figure 6 is a schematic diagram of the gear knocking evaluation results at various speeds according to an embodiment of the present invention;

[0034] Figure 7 It is a comparison chart of the gear knocking evaluation results before and after optimization of the embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention clearer and more specific, the present invention is further described in detail below with reference to the accompanying drawings and examples. The following implementation cases are only used to illustrate and explain the present invention, and are not intended to limit the present invention. Any modifications and / or changes made to the present invention will fall within the scope of protection of the present invention.

[0036] like Figure 1 As shown, the present invention provides a method for analyzing and optimizing gear knocking of an engine balance shaft system, comprising the following steps:

[0037] Step 1: Study the gear knocking problem of the engine balance shaft system through bench tests and provide experimental basis for subsequent dynamic models.

[0038] In some embodiments of the present invention, the schematic diagram of the stand is as follows Figure 2 As shown in the figure, the test bench mainly includes a dynamometer, a dynamometer shaft, an intermediate shaft, an elastic coupling, a connecting shaft, and a balance shaft system of the engine to be tested. The dynamometer shaft, the intermediate shaft, the elastic coupling, and the connecting shaft are connected in sequence. First, the engine is installed on the bench, and the crankshaft flywheel is connected to the connecting shaft by bolts; secondly, the connecting shaft is connected to the intermediate shaft by an elastic coupling; finally, the intermediate shaft is connected to the dynamometer shaft by bolts. Under full load conditions, the engine speed accelerates from 1000rpm to 5000rpm within 90s.

[0039] In some embodiments of the present invention, two three-axis vibration acceleration sensors and four sound pressure sensors are arranged in total. The two three-axis acceleration sensors are arranged on the housing surface of the exhaust side and the intake side of the engine, and are located above the bolts between the balance shaft tray and the cylinder block (such as Figure 2The four sound pressure sensors are arranged at the intake side, exhaust side, front end and top of the engine, and are 1 meter away from the outer envelope of the engine (such as Figure 2 The far-field noise of the engine and the vibration acceleration data of the shell surface are collected, and the sound pressure waterfall diagram and spectrum diagram, vibration acceleration waterfall diagram and spectrum diagram are drawn. On this basis, the gear knocking characteristics of the engine balance shaft system are analyzed.

[0040] Step 2: Establish a multi-flexible body dynamics model of the engine balance shaft system.

[0041] In some embodiments of the present invention, first, a multi-body dynamics model of an engine balance shaft system is established in MASTA, and the established dynamics model of the engine balance shaft system includes an engine and a balance shaft module. Among them, the balance shaft module includes a balance shaft tray, a balance shaft, a scissors gear, a driven gear, and a bearing. The scissors gear includes a scissors main tooth, a scissors auxiliary tooth, a torsion spring, a retaining spring, and a pin. Secondly, the model is flexibly processed, and the finite element models of the shaft, gear, housing, tray, etc. are imported and condensed, and coupled based on the condensed nodes. Finally, the boundary conditions and input conditions of the multi-flexible dynamics model of the engine balance shaft system are defined.

[0042] Step 3: Verify the multi-flexible body dynamics model of the engine balance shaft system.

[0043] In some embodiments of the present invention, the frequency spectrum of the vibration acceleration sensor at each speed is calculated in MASTA and compared with the test results in step 1 to verify the correctness of the dynamic model. The severity of gear knocking at each speed and the frequency range corresponding to the occurrence of gear knocking are mainly compared.

[0044] Step 4: Based on the multi-flexible body dynamics model of the engine balance shaft system, analyze the dynamic characteristics of the system's gear knocking.

[0045] Based on the verified multi-flexible body dynamics model of the engine balance shaft system, the gear knocking dynamic characteristics of the system are studied from three aspects: the contact state of the gear, the angular acceleration of the passive gear, and the gear tooth surface meshing force. In some embodiments of the present invention, Figure 3 It is the gear contact state at 2000 rpm of the embodiment of the present invention, wherein a contact state of 1 indicates contact with the left tooth surface of the driving gear, a contact state of 0 indicates gear disengagement, and a contact state of -1 indicates contact with the right tooth surface of the driving gear. Figure 4 is the gear angular acceleration of 2000 rpm in the embodiment of the present invention; Figure 5 is the tooth surface meshing force of the 2000rpm gear in the embodiment of the present invention. Figures 3 to 5 The number of gear knocking and the gear knocking intensity of each gear pair can be seen.

[0046] Step 5: Determine the gear knocking evaluation index.

[0047] In some embodiments of the present invention, the moment of inertia of the passive gear is As the gear knock evaluation index of each gear pair, where: J is the moment of inertia of the passive gear, is the root mean square value of the angular acceleration of the passive gear. The specific steps are as follows:

[0048] (a) The angular acceleration of each passive gear is calculated by the multi-flexible body dynamics model of the engine balance shaft system, and then the corresponding angular acceleration root mean square value is obtained;

[0049] (b) Since there are three pairs of meshing gears in the system, the knock evaluation results RI1, RI2, and RI3 of each gear pair are calculated using the knock evaluation index of the moment of inertia.

[0050] (c) The gear knock evaluation index of the three gear pairs is: In some embodiments of the present invention, the gear knock evaluation results of the engine balance shaft system multi-flexible body dynamics model at each speed are as follows: Figure 6 As shown. RI stands for Rattle Index, and J stands for moment of inertia. It represents the root mean square of angular acceleration. The subscripts 1, 2, and 3 represent the first pair of gear pairs, the second pair of gear pairs, and the third pair of gear pairs, because there are three pairs of gear pairs in the system.

[0051] Step 6: Use the orthogonal test method to study the factors affecting the gear knock of the engine balance shaft system. Through the range analysis, the important parameters that significantly affect the gear knock can be obtained.

[0052] In some embodiments of the present invention, multiple influencing parameters of the gear knocking of the system (such as torsion spring stiffness, torsion spring pre-twist angle, tooth side clearance, moment of inertia) are first determined, and the orthogonal test is designed using Minitab software. The factors and levels of the orthogonal test are defined in the software, and the corresponding simulation calculation results are input. The main parameters with significant influence are further screened out through range analysis, wherein the range R represents the difference between the maximum and minimum values ​​of the gear knocking evaluation results of this column factor within its value range. The larger R is, the greater the influence of the level change of the factor on the gear knocking evaluation result, that is, the more important the factor is in this orthogonal test.

[0053] In some embodiments of the present invention, six influencing parameters are selected for research, namely, torsion spring stiffness, torsion spring pre-twist angle, crankshaft gear-scissor main tooth side clearance, scissor main tooth-driven tooth side clearance, scissor main tooth moment of inertia, and driven tooth moment of inertia. The main influencing parameters selected are torsion spring stiffness, crankshaft gear-scissor tooth side clearance, scissor main tooth moment of inertia, and driven tooth moment of inertia.

[0054] Step 7: Based on the selected important parameters, the response surface method is used to optimize the gear knocking noise of the system.

[0055] In some embodiments of the present invention, the response surface test scheme is determined by using the software Design-Expert 13, and then the response surface model is established according to the calculation results. The main influencing parameters screened out by the range analysis are used as optimization variables, the minimum gear knocking noise of the system is used as the optimization objective function, and the value range of each parameter is used as a constraint condition to optimize the gear knocking noise.

[0056] In some embodiments of the present invention, the comparison results are as follows Figure 7 As shown, by comparing the results before and after optimization, it can be seen that the gear knock optimization method of the engine balance shaft system provided by the present invention can effectively optimize the gear knock.

[0057] The method of the present invention establishes a multi-flexible body dynamic model of the engine balance shaft system, and compares the calculation results with the test results to verify the correctness of the dynamic model. The gear knocking dynamic characteristics of the system are studied from three aspects: the contact state of the gear, the angular acceleration of the passive gear, and the gear tooth surface meshing force. The knocking times and knocking intensity of each gear pair can be analyzed intuitively. A gear knocking evaluation index suitable for scissor gears is proposed (based on the inertia moment of the passive gear). As the gear knock evaluation index of each gear pair, the gear knock force is evaluated from the perspective of the root mean square of angular acceleration, and the moment of inertia is considered on the basis of the root mean square of angular acceleration, which can reduce the influence of the scissor gear's own structure and improve the accuracy of the gear knock evaluation results. The orthogonal test method and response surface method are used for gear knock optimization, which can optimize the main influencing parameters, and the optimization process is simple, which can provide a basis for the gear knock optimization of the engine balance shaft system.

[0058] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for analyzing and optimizing gear knocking of an engine balance shaft system, characterized in that: The following steps are involved: (1) Analyze the gear knocking problem of the engine balance shaft system through bench testing and analyze the gear knocking characteristics of the engine balance shaft system; By collecting the engine's far-field noise and shell surface vibration acceleration data, and drawing the sound pressure waterfall diagram and spectrum diagram, vibration acceleration waterfall diagram and spectrum diagram, on this basis, the gear knocking characteristics of the engine balance shaft system are analyzed; (2) Establish a multi-flexible body dynamics model of the engine balance shaft system. The multi-flexible body dynamics model of the engine balance shaft system was established in MASTA, and the engine was fixed on three suspension brackets. The instantaneous speed of the crankshaft was used as the input condition of the MASTA model for calculation; (3) Based on the multi-flexible body dynamics model of the engine balance shaft system, the gear knocking dynamic characteristics of the system are analyzed: the gear knocking dynamic characteristics of the system are analyzed from three aspects: the contact state of the gear, the angular acceleration of the passive gear, and the gear tooth surface meshing force; (4) Determine the moment of inertia of the passive gear As the gear knock evaluation index of each gear pair, J is the moment of inertia of the passive gear, is the root mean square value of the angular acceleration of the passive gear; the moment of inertia of the passive gear As the gear knock evaluation index of each gear pair, the specific steps include: The angular acceleration of each passive gear is calculated by the multi-flexible body dynamics model of the engine balance shaft system, and then the corresponding angular acceleration root mean square value is obtained; Since there are three pairs of meshing gear pairs in the engine balance shaft system, the knock evaluation results RI1, RI2, and RI3 of each gear pair are calculated using the knock evaluation index of the inertia moment. RI stands for knock index, J stands for moment of inertia, It represents the root mean square of angular acceleration, and the subscripts 1, 2, and 3 represent the first pair of gear pairs, the second pair of gear pairs, and the third pair of gear pairs; Then, the gear knock evaluation index of the three gear pairs is (5) The orthogonal test method was used to study the factors affecting the gear knock of the engine balance shaft system, and the important parameters that have a significant impact on the gear knock were obtained through range analysis; (6) Based on the important parameters screened out, the response surface methodology is used to optimize the gear knocking noise of the system. The response surface analysis software is used to determine the response surface test plan, and then a response surface model is established according to the calculation results. The gear knocking optimization is performed based on the response surface model.

2. The method for analyzing and optimizing gear knocking of an engine balance shaft system according to claim 1, characterized in that: The established multi-flexible body dynamics model of the engine balance shaft system includes an engine and a balance shaft module, wherein the balance shaft module includes a balance shaft tray, a balance shaft, a scissors gear, a driven gear, and a bearing; the scissors gear includes a scissors main tooth, a scissors auxiliary tooth, a torsion spring, a retaining spring, and a pin.

3. The method for analyzing and optimizing gear knocking of an engine balance shaft system according to claim 1, characterized in that: After the multi-flexible body dynamics model of the engine balance shaft system is established, the steps include: verifying the multi-flexible body dynamics model of the engine balance shaft system.

4. The method for analyzing and optimizing gear knocking of an engine balance shaft system according to claim 3, characterized in that: The spectrum of the vibration acceleration sensor at each rotation speed is calculated in MASTA, and the spectrum is compared with the spectrum obtained by the bench test in step (1) to verify the correctness of the dynamic model.

5. The method for analyzing and optimizing gear knocking of an engine balance shaft system according to claim 1, characterized in that: In step (5), multiple influencing parameters of the gear knocking of the engine balance shaft system are first determined, and the orthogonal experiment is designed using Minitab software. The factors and levels of the orthogonal experiment are defined in the software, and the corresponding simulation calculation results are input. The main parameters with significant influence are then further screened out through range analysis.

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