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CN-116522702-B - Gear knocking calculation and evaluation method suitable for balance shaft scissor teeth

CN116522702BCN 116522702 BCN116522702 BCN 116522702BCN-116522702-B

Abstract

The invention discloses a calculation and evaluation method suitable for gear knocking of balance shaft scissors teeth, which comprises the steps of constructing a rigid model of an engine balance shaft system, conducting grid division to obtain a finite element model, arranging condensation nodes on the finite element model, coupling the condensation nodes with contact boundaries, completing condensation treatment of the finite element model, generating a condensation model, replacing the finite element model to conduct mechanical analysis, flexibly converting gears, applying rotation speed excitation on a crankshaft, starting simulation calculation, extracting tooth surface meshing force of gear pairs at each rotation speed, conducting data processing on the meshing force to obtain meshing force peaks, obtaining impact indexes based on the meshing force peaks, and obtaining knocking evaluation based on the impact indexes. The method can establish a fully-flexible balance shaft system simulation model and quantitatively evaluate the abnormal knocking sound of the balance shaft scissor teeth, and provides a basis for analyzing and optimizing the gear knocking problem of the balance shaft scissor teeth.

Inventors

  • ZHAO XUEZHI
  • GUO GENGLIANG
  • SHANGGUAN WENBIN

Assignees

  • 华南理工大学

Dates

Publication Date
20260505
Application Date
20230307

Claims (10)

  1. 1. A method of calculating and evaluating gear rattle for balance shaft scissor teeth, comprising the steps of: (1) Setting up a rigid model of an engine balance shaft system and setting boundary conditions; (2) Grid division is carried out on other parts except gears and bearings in a rigid model of the engine balance shaft system, so that a finite element model is obtained; (3) Setting a condensation node on the finite element model, and coupling the condensation node with a contact boundary; (4) Introducing the finite element model for generating the condensation node into transmission system analysis software, replacing finite elements according to the connection relation, completing polycondensation treatment of the finite element model in the software, and replacing the finite element model with the generated polycondensation model to perform mechanical analysis; (5) Carrying out gear flexibility; (6) Applying each rotation speed excitation on the crankshaft, and starting simulation calculation; (7) Extracting tooth surface meshing force of each gear pair at each rotating speed from simulation calculation results; (8) Performing data processing on the meshing force to obtain a meshing force peak value, obtaining an impact index based on the meshing force peak value, and obtaining a knocking evaluation based on the impact index, wherein: Impact index I driven is the moment of inertia of the driven gear, Is all three working cycles of the engine at a certain rotating speed Is used to determine the accumulated value of (a), Is the meshing force peak value to derive time, and the knocking evaluation is that RI n represents an evaluation of the rattle occurring between the nth pair of intermeshing gears.
  2. 2. The method of claim 1, wherein the model of the balance shaft system of the engine comprises an engine cylinder, a crankshaft, a balance shaft tray, a balance shaft, a crankshaft gear, a scissors gear, a driven gear and a bearing, and the scissors gear comprises a scissors main tooth, a scissors auxiliary tooth, a torsion spring, a clamp spring and a pin.
  3. 3. The method for calculating and evaluating the gear knocking of the scissor teeth of the balance shaft according to claim 2 is characterized in that the assembly relation of the scissor gears is that the scissor main teeth are fixed on the balance shaft through interference fit, the scissor auxiliary teeth float on the hub of the scissor main teeth and are limited axially through snap springs, and the main auxiliary gears generate preload torque through middle pins and torsion springs during relative rotation, so that the scissor main teeth and the auxiliary teeth are respectively contacted with the left tooth surface and the right tooth surface of the crank gear, and the effect of eliminating the backlash is achieved.
  4. 4. A method of calculating and evaluating a gear rattle for a balance shaft scissor tooth according to claim 1, characterized in that in software, in order to indicate the force conditions between the parts in contact with each other, axial or radial clearance bearings are provided at the corresponding contact locations for the transmission of forces.
  5. 5. A method of calculating and evaluating gear rattle for balanced shaft scissor teeth according to claim 1, wherein in step (2) the mesh type selects a second order tetrahedral unit.
  6. 6. The method of claim 1, wherein in step (3), the condensation node is disposed at a point where the middle surface of the contact surface intersects the rotation axis of the part, and the condensation node is coupled to the actual contact surface by Rbe 3.
  7. 7. The method for calculating and evaluating the gear rattle of the scissors teeth of the balance shaft according to claim 1, wherein in the step (4), the finite element model is aligned first when the finite element is replaced, and then the condensation nodes of different parts at the same position are coupled together, and then the polycondensation treatment is performed.
  8. 8. The method for calculating and evaluating the gear rattle of the scissors teeth of the balance shaft according to claim 1, wherein in the step (5), the gear is divided into a hub and a gear ring, the hub automatically creates a condensation node in software when connecting the gear ring, and the node connection mode is to create a flexible node ring, namely corresponding nodes are uniformly generated on the circumference, and the nodes are coupled with grids of all areas.
  9. 9. The method of calculating and evaluating gear rattle for balanced shaft scissors teeth according to claim 1, wherein in step (8), the data processing of the rattle force comprises the steps of: (a) Screening meshing force data, namely, when tooth surfaces are disengaged and contacted again, knocking is calculated, so that whether the meshing force starts from 0kN or not at each time is judged; (b) Identifying peak value of meshing force of each knocking and corresponding time thereof, and obtaining derivative of peak value of meshing force with respect to time (C) All three working cycles of the engine at a certain rotating speed Accumulating to obtain (D) Calculating an impact index; (e) Calculating knocking evaluation of the whole balance shaft system; (f) And (3) repeating the tooth surface meshing force data processing processes (a) to (e) at other rotating speeds, and obtaining knocking evaluation results at other rotating speeds.
  10. 10. The method according to any one of claims 1 to 9, wherein the step (8) is performed to obtain a gear rattle evaluation value at each rotational speed, and the subjective evaluation of the test is combined to identify from which rotational speed an apparent gear rattle occurs, and the evaluation value corresponding to the rotational speed is used as a rattle threshold of the model, so that in the subsequent simulation calculation, as long as the rattle rating value is higher than the threshold, the gear rattle is considered to occur.

Description

Gear knocking calculation and evaluation method suitable for balance shaft scissor teeth Technical Field The invention belongs to the NVH field of automobile engines, and particularly relates to a method for calculating and evaluating gear knocking suitable for balance shaft scissor teeth. Background With the continuous development and consumption upgrading of the automobile industry, the requirements of people on the comfort of automobiles are higher and higher, and the vibration and noise level of an engine become one of important evaluation indexes of the comprehensive performances of the engine and the automobiles. The reciprocating engine generates a rotational inertial force and a reciprocating inertial force due to the periodicity of the working process and the periodicity of the movement of the machine member, and for an in-line four-cylinder engine, the generated second-order reciprocating inertial force cannot be balanced by itself. In engineering, a balance shaft with scissor teeth is often adopted to balance the second-order reciprocating inertial force of an engine, but the second-order reciprocating inertial force can generate noise problems such as gear squeal, gear knocking and the like. Most of researches on abnormal sound of scissors teeth of a balance shaft are focused on gear squeal, and the problem of abnormal sound of gear rattle of scissors teeth is still not formed into a uniform evaluation method due to the specificity of the structure of the scissors teeth and the complexity of a gear rattle mechanism. Currently, the evaluation for gear rattle mainly includes a rotational speed fluctuation evaluation index, a rotational speed standard deviation evaluation index, an energy evaluation index, an impulse evaluation index, a Jerk evaluation index, and the like. The energy index and the impulse index are accurate and more in application to the knocking evaluation of a common idler gear, but due to the torsion spring action of the cutter teeth, the pre-torsion moment exists between the meshing gears, so that energy loss is generated not only by knocking, but also by reasons of tooth surface friction, gear howling and the like, and the energy index or the impulse index can generate great errors even completely different from test results when being applied to the cutter teeth. In 2013, yogesh Bile et al have proposed a Jerk strike evaluation index on SAE journal (american society of automotive engineers) which can evaluate gear strike noise well. However, the evaluation index still has the following defects that (1) a root mean square processing mode is adopted for knocking evaluation in a certain time, and (2) the acquired gear meshing force is calculated indiscriminately. The number of times of knocking the gears is different in the same period, and the root mean square can only reflect the average strength of each knocking and cannot reflect the total knocking strength in the same period. Disclosure of Invention The invention aims to provide a method for calculating and evaluating gear knocks of balance shaft scissor teeth, which is characterized by fully flexibly modeling a balance shaft system, and obtaining tooth surface meshing force of each gear pair according to the simulation model, and processing the tooth surface meshing force to obtain impact indexes for evaluating the knocking of the scissor teeth. The gear knocking abnormal sound of the balance shaft scissor teeth can be quantitatively evaluated by using impact indexes, and the gear knocking degree of the balance shaft system under different rotating speeds is analyzed, so that a basis is provided for analyzing and optimizing the gear knocking problem of the balance shaft scissor teeth. In order to achieve the purpose of the invention, the invention provides a method for calculating and evaluating gear knocking suitable for balance shaft scissor teeth, which comprises the following steps: (1) Setting up a rigid model of an engine balance shaft system and setting boundary conditions; (2) Grid division is carried out on other parts except gears and bearings in a rigid model of the engine balance shaft system, so that a finite element model is obtained; (3) Setting a condensation node on the finite element model, and coupling the condensation node with a contact boundary; (4) Introducing the finite element model for generating the condensation node into transmission system analysis software, replacing finite elements according to the connection relation, completing polycondensation treatment of the finite element model in the software, and replacing the finite element model with the generated polycondensation model to perform mechanical analysis; (5) Carrying out gear flexibility; (6) Applying each rotation speed excitation on the crankshaft, and starting simulation calculation; (7) Extracting tooth surface meshing force of each gear pair at each rotating speed from simulation calculation results; (8) Performing data processing