A method, device and storage medium for optimizing piston pin knock

Abstract

The application discloses a piston pin knocking sound optimization method and device and a storage medium, and comprises the following steps: S1, after identifying the piston pin knocking sound, it is judged whether optimization is carried out, if yes, S2 is executed, if not, the process is ended; S2, it is judged whether the piston connecting rod assembly size meets the design requirement, if yes, S3 is executed, if not, the structure of the piston connecting rod assembly is optimized until the piston connecting rod assembly size meets the design requirement; S3, a plurality of to-be-optimized parameters and to-be-optimized parameter adjustment ranges are determined based on the collision theory and actual performance requirements, the plurality of to-be-optimized parameters are taken as variables, the minimum piston pin knocking power is taken as an optimization target, and the corresponding optimal parameter combination is obtained through optimization. The application can apply the collision theory to quickly analyze the piston pin knocking sound reason, and accurately and quickly complete the noise reduction optimization of the piston pin knocking sound.

Description

TECHNICAL FIELD

[0001] The present application relates to automobile NVH, in particular to a piston pin knock sound optimization method, device and storage medium. BACKGROUND

[0002] According to the connection mode of the piston pin, the piston pin seat hole and the connecting rod small head bushing hole, the piston pin is divided into two kinds of full-floating type and semi-floating type. The full-floating connection refers to that during the normal operation of the engine, there is a proper fit clearance between the piston pin, the piston pin seat hole and the connecting rod small head bushing, and the piston pin can freely rotate in the hole. By using the full-floating connection, the wear of the piston pin is more uniform, and the service life is longer.

[0003] The kinematic pair of the full-floating piston pin knock is the piston pin and the connecting rod small head hole bushing. The gas force at the top of the piston is transmitted to the piston pin through the pin hole, and then to the connecting rod. The piston pin knock often occurs at the reversing moment of the piston pin in the connecting rod bushing, and the knock frequency is generally 1.5-5KHz, which is a high-frequency metal knock sound, giving the customer a sense of failure and affecting the sound quality of the whole machine.

[0004] Now the evaluation of the piston pin knock sound is generally based on subjective evaluation, objective measurement of vibration and noise. However, the piston pin knock always occurs in the cylinder, and its vibration is not easy to measure directly. The sound is transmitted through a series of vibration paths, and the measurement is always a manifestation. The transfer functions of different engine cylinder designs are different, so it is not easy to apply the cylinder surface vibration and noise to the most direct quantitative analysis.

[0005] The current method to solve the piston pin knock is to reduce the fit clearance between the piston pin and the connecting rod bushing, thereby reducing the knock sound. However, the sizes of parts of different engines, working environments, etc. are inconsistent, and it is impossible to have a common fit clearance value. Too small fit clearance can easily lead to blue reliability problems. Therefore, it is a major engineering problem to develop a reasonable fit clearance standard suitable for an engine. The conventional optimization design generally only considers reliability, so a scientific and feasible method is needed to ensure the sound quality of the gasoline engine.

[0006] CN114818290A discloses a car noise reduction method and system, which comprises the following steps: determining the target frequency generated by the current vehicle accelerating roar according to the road test data and modal test data of the current vehicle; formulating a target optimization scheme of the local structure of the front beam of the vehicle body based on the overall structure of the front beam of the vehicle body and the target frequency, the target optimization scheme comprising optimization parameters and optimization positions; and performing CAE simulation analysis according to the target optimization scheme to perform test verification. In the above manner, the inherent frequency of the front beam of the vehicle body and the excitation frequency of the engine can be effectively eliminated to eliminate the roar noise caused by the coupling resonance, and the user experience is greatly improved, so the method is suitable for wide application and use. CN115391918A discloses a car whistle optimization method, device, equipment and storage medium. The embodiment obtains a driver noise waterfall diagram corresponding to the vehicle to be optimized in the driving process, determines the whistle noise order according to the driver noise waterfall diagram, determines the corresponding whistle optimization strategy according to the whistle noise order, and optimizes the car whistle according to the whistle optimization strategy. By determining the whistle noise order according to the driver noise waterfall diagram, the order of the whistle generated by the vehicle to be optimized can be accurately obtained, and then the corresponding whistle optimization strategy is determined according to the whistle noise order, and the car whistle is optimized according to the whistle optimization strategy, so that the corresponding whistle optimization strategy can be clearly found according to the whistle noise order, and the car whistle can be effectively optimized according to the whistle optimization strategy, greatly improving the work efficiency. It is a beneficial attempt in the field. SUMMARY

[0007] The purpose of the present application is to provide a piston pin knock sound optimization method, device and storage medium, which can quickly analyze the cause of piston pin knock sound by applying collision theory, and accurately and quickly complete the noise reduction optimization of piston pin knock sound.

[0008] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0009] In the first aspect, the present application discloses a piston pin knock sound optimization method, which comprises the following steps:

[0010] S1, after identifying the piston pin knock sound, it is judged whether to optimize, if yes, S2 is executed, if not, the process is ended;

[0011] S2, detecting whether the size of the piston connecting rod assembly meets the design requirements, if yes, S3 is executed, if not, the structure of the piston connecting rod assembly is optimized until the size of the piston connecting rod assembly meets the design requirements;

[0012] S3, determining a plurality of to-be-optimized parameters and to-be-optimized parameter adjustment ranges based on the collision theory and actual performance requirements, taking the plurality of to-be-optimized parameters as variables, and taking the minimum piston pin knock power as the optimization target, to obtain the corresponding optimal parameter combination through optimization. The definition of the collision theory is that when an object is suddenly impacted (including being suddenly constrained or suddenly contacting a constraint), the velocity of the object changes in a limited manner in a very short time, and this phenomenon is called collision.

[0013] Further, in S1, whether to perform optimization is determined by subjective judgment and / or objective judgment.

[0014] Further, in S1, whether to perform optimization is determined by objective judgment, that is, after the piston pin knock sound is identified, the sound pressure level data of the piston pin knock sound is obtained, if the sound pressure level data > preset sound pressure level threshold, S2 is executed; if the sound pressure level data ≤ preset sound pressure level threshold, the process is ended.

[0015] Further, the obtaining of the preset sound pressure level threshold is specifically as follows: a plurality of piston pin knock sound samples are prepared, subjective evaluation and objective evaluation are performed on each piston pin knock sound sample, the objective evaluation is the sound pressure level data of the piston pin knock sound, and the subjective evaluation result and the objective evaluation result of each piston pin knock sound sample are obtained; a correlation mathematical model between the subjective evaluation result and the objective evaluation result is established, a subjective evaluation set threshold of the piston pin knock sound is input into the correlation mathematical model, and the corresponding objective evaluation result output as the preset sound pressure level threshold.

[0016] Further, the identification of the piston pin knock sound in S1 specifically includes the following steps:

[0017] S11, arranging noise sensors, vibration sensors, crankshaft sensors, camshaft sensors and cylinder pressure sensors on the engine to be tested and performing NVH testing;

[0018] S12, based on the test results, applying wavelet and angle domain analysis method to obtain the knock sound frequency, knock sound periodicity and the phase moment of the engine operation, i.e. knock moment;

[0019] S13, performing dynamic analysis to obtain the motion of the internal components of the engine;

[0020] S14, analyzing the motion of the piston, piston pin and connecting rod at the knock moment in S12, if the piston pin is in the reversing state in the connecting rod small end hole at the knock moment, it is determined that the knock sound is the piston pin knock sound, otherwise it is determined that the knock sound is not the piston pin knock sound.

[0021] Further, the parameters to be optimized in S3 are the fitting clearance between the small end of the connecting rod and the piston pin and the oil film thickness between the small end of the connecting rod and the piston pin, and the fitting clearance between the small end of the connecting rod and the piston pin is the inner diameter of the small end of the connecting rod minus the outer diameter of the piston pin.

[0022] Further, the fitting clearance between the small end of the connecting rod and the piston pin and the oil film thickness between the small end of the connecting rod and the piston pin are analyzed by DOE experimental design analysis, and the influence level of the fitting clearance between the small end of the connecting rod and the piston pin and the oil film thickness between the small end of the connecting rod and the piston pin on the knocking power is determined.

[0023] Further, simulation analysis is applied to determine the upper and lower limit values of the fitting clearance between the small end of the connecting rod and the piston pin based on the threshold value of the piston pin knocking power, and the lower limit value of the oil film thickness between the small end of the connecting rod and the piston pin is obtained based on the design requirements.

[0024] Further, the piston connecting rod assembly in S2 includes a small end of a connecting rod and a piston pin, and the small end of the connecting rod is provided with a piston pin hole corresponding to the fitting of the piston pin; the size of the piston connecting rod assembly includes the surface roughness of the small end of the connecting rod, the inner diameter of the small end of the connecting rod, the cylindricity of the small end of the connecting rod, the outer diameter of the piston pin, the inner diameter of the piston pin hole, the perpendicularity of the piston pin hole, and the cylindricity of the piston pin hole.

[0025] Further, if the size of the piston connecting rod assembly does not meet the design requirements in S2, the production process or tooling of the piston connecting rod assembly is optimized, or the piston connecting rod assembly meeting the design is directly replaced.

[0026] In a second aspect, the application further discloses a piston pin knocking sound optimization device which can realize the steps of the piston pin knocking sound optimization method based on the collision theory, and the device comprises: an identification module for identifying and determining whether the knocking sound is a piston pin knocking sound; a judgment module for judging whether to optimize the piston pin knocking sound; a size detection module for detecting the size of the piston connecting rod assembly and judging whether the size of the piston connecting rod assembly meets the design requirements; and an optimization module for obtaining the optimal parameter combination of a plurality of parameters to be optimized.

[0027] In a third aspect, the application discloses a storage medium having a computer readable program stored therein, and the computer readable program can execute the steps of the piston pin knocking sound optimization method when called.

[0028] The application has the following beneficial effects:

[0029] 1. The application identifies the piston pin knocking sound and judges the need to optimize the piston pin knocking sound, first detects whether the piston connecting rod assembly size meets the design requirements, i.e. first excludes the piston pin knocking sound caused by the defects of the piston connecting rod assembly itself, avoids blindness. Then, based on the collision theory and actual performance requirements, a plurality of to-be-optimized parameters and to-be-optimized parameter adjustment ranges are determined, a plurality of to-be-optimized parameters are used as variables, the minimum piston pin knocking power is used as the optimization target, and the corresponding optimal parameter combination is obtained through optimization, starting from theory and practice, comprehensively analyzing the influence factors of the piston pin knocking sound, i.e. the to-be-optimized parameters, and pertinently optimizing the related to-be-optimized parameters to obtain the corresponding optimal parameter combination, so that the noise reduction optimization of the piston pin knocking sound is accurately and quickly completed.

[0030] 2. The application adopts wavelet analysis method to quickly lock the knocking moment, applies dynamic analysis to lock the motion of the internal components of the engine at the knocking moment, so as to lock the knocking source and determine whether the knocking sound is the piston pin knocking sound.

[0031] 3. The application compares the sound pressure level data of the piston pin knocking sound with the preset sound pressure level threshold value, so as to determine whether the noise reduction optimization of the piston pin knocking sound is needed. The obtaining of the preset sound pressure level threshold value is specifically: a correlation mathematical model between subjective evaluation results and objective evaluation results is established, a subjective evaluation set threshold value of the piston pin knocking sound is input into the correlation mathematical model, and the corresponding objective evaluation result is output as the preset sound pressure level threshold value. Through subjective evaluation and objective evaluation fitting, a reasonable preset sound pressure level threshold value is prepared, and blindness is avoided.

[0032] 4. The application takes the fitting gap between the small end of the connecting rod and the piston pin and the oil film thickness between the small end of the connecting rod and the piston pin as the to-be-optimized parameters, and applies simulation analysis, based on the piston pin knocking power set threshold value, to determine the upper and lower limit values of the fitting gap between the small end of the connecting rod and the piston pin; based on the design requirements, the simulation analysis is applied to obtain the lower limit value of the oil film thickness between the small end of the connecting rod and the piston pin, so as to guide the analysis of the problem and the development of effective schemes. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is the flow chart of the piston pin knocking sound optimization method based on the collision theory according to the application.

[0034] Figure 2 It is the schematic diagram of the arrangement of various sensors during NVH objective test provided by the embodiment of the application; in the figure, 1 is a cylinder body, 2 is a cylinder cover, 3 is a cylinder cover cover, 4 is a first vibration sensor, 5 is a second vibration sensor, 6 is a cylinder pressure sensor, 7 is a camshaft position sensor, and 8 is a crankshaft position sensor.

[0035] Figure 3 It is the wavelet analysis result schematic diagram of the vibration and noise signal provided by the embodiment of the application.

[0036] Figure 4 is a schematic diagram of the motion analysis of the crank connecting rod mechanism in each working state.

[0037] Figure 5 is a schematic diagram of the force analysis of the piston pin in the intake stroke, F N is the lateral force of the piston, F S is the connecting rod force, F T is the tangential force of the crankshaft, F R is the radial force of the crankshaft.

[0038] Figure 6 is a schematic diagram of the response of the piston pin at different matching clearances of the connecting rod small head and the piston pin.

[0039] Figure 7 is a schematic diagram of the contact pressure of the piston pin in the piston pin hole of the connecting rod small head under the influence of roughness.

[0040] Figure 8 is a schematic diagram of the influence of the oil film thickness on the impact force of the full-floating piston pin.

[0041] Figure 9 is a schematic diagram of the DOE analysis results of the to-be-optimized parameters, E is the matching clearance of the connecting rod small head and the piston pin, and F is the oil film thickness between the connecting rod small head and the piston pin.

[0042] Figure 10 is a schematic diagram of the response of the reference point of the full-floating piston pin under the influence of different oil viscosities. DETAILED DESCRIPTION

[0043] Other advantages and effects of the present application can be easily understood by those skilled in the art from the disclosure herein. The present application can also be implemented or applied in other different specific embodiments, and various modifications or changes can be made to the details herein based on different views and applications without departing from the spirit of the present application. It should be understood that the preferred embodiments are only for the purpose of illustrating the present application, and are not intended to limit the protection scope of the present application.

[0044] It should be noted that the diagrams provided in the following embodiments only schematically illustrate the basic concept of the present application, and only the components related to the present application are shown in the diagrams, rather than being drawn according to the number, shape and size of the components in actual implementation. The shapes, numbers and proportions of the components in actual implementation can be arbitrarily changed, and the layout pattern of the components can also be more complex.

[0045] Embodiment one, referring to Figure 1 , the piston pin knocking sound optimization method shown therein includes the following steps:

[0046] S1, after identifying the piston pin knock, judging whether to optimize, if yes, executing S2; if no, ending the process.

[0047] S2, detecting whether the size of the piston connecting rod assembly meets the design requirements, if yes, executing S3; if no, optimizing the structure of the piston connecting rod assembly, optimizing the production process or tooling of the piston connecting rod assembly, or directly replacing the piston connecting rod assembly that meets the design, until the size of the piston connecting rod assembly meets the design requirements, re-collecting the knock and judging whether to optimize.

[0048] S3, determining a plurality of to-be-optimized parameters and to-be-optimized parameter adjustment ranges based on the collision theory and actual performance requirements, taking the plurality of to-be-optimized parameters as variables, and taking the minimum piston pin knock power as the optimization target, to obtain the corresponding optimal parameter combination through optimization. The definition of the collision theory is that when an object is suddenly impacted (including suddenly being constrained or suddenly being in contact with a constraint), the velocity of the object changes in a limited way in a very short time, and this phenomenon is called collision.

[0049] In this embodiment, the identification of the piston pin knock specifically includes the following steps:

[0050] S11, arranging noise sensors, vibration sensors, crankshaft sensors, camshaft sensors and cylinder pressure sensors on the engine to be tested and performing NVH testing. Referring to Figure 1 Four first vibration sensors 4 corresponding to the positions of the cylinders are arranged on the cylinder block 1 of the engine, four second vibration sensors 5 corresponding to the positions of the cylinders are arranged on the cylinder head 2, a cylinder pressure sensor 6 corresponding to the position of one cylinder is arranged on the cylinder cover 3, a camshaft position sensor 7 for detecting the position of the camshaft is arranged on the cylinder head 2, and a crankshaft position sensor 8 for detecting the position of the crankshaft is arranged on the cylinder block 1. A microphone for collecting sound signals is arranged at a position 1 meter above, in front of, to the left of and to the right of the engine. The most obvious steady-state working condition of the engine knock is subjected to NVH testing, and sound data is collected through the microphone.

[0051] S12, based on the test results, wavelet and angle domain analysis methods are applied to obtain the frequency of the knock, the periodicity of the knock and the phase moment of the engine operation, i.e. the knock moment. That is, the NVH test results of S11 are subjected to wavelet analysis, the wavelet features and the frequency, period, etc. of the knock are identified first, then the knock is associated to the vibration signal to determine which cylinder produces the knock, and then the crankshaft phase moment corresponding to the vibration feature, i.e. the knock moment, is determined.

[0052] The period of the crank connecting rod mechanism knock is generally 1 revolution, i.e. the engine operates for one-half of a cycle to produce one knock; the period of the valve train knock is 2 revolutions, i.e. the engine operates for one cycle to produce one knock.

[0053] Let ψ(x) be a square integrable function, ψ(x) ∈ L 2 (R), if the Fourier transform satisfies the admissible condition:

[0054]

[0055] Then the function ψ(t) is called a wavelet. But the wavelet is often understood as a family of functions {ψ a,b (t)} generated by the above function through scaling and translation:

[0056]

[0057] The family of functions is a continuous wavelet generated by the mother wavelet ψ(t) with the parameters a and b, a is a scale factor, and b is a position factor. Then the continuous wavelet transform (CWT) of a signal f(t) ∈ L 2 (R) can be defined as:

[0058]

[0059] The wavelet transform coefficient of a signal at a scale factor a and a translation point τ actually represents a frequency component contained in a frequency window with a center frequency and a bandwidth in the time period aΔt at the position τ.

[0060] Since the wavelet transform has the multi-resolution, i.e. multi-scale, characteristic, the signal can be observed step by step from coarse to fine, and therefore, by appropriately selecting the mother wavelet, the wavelet transform can have the ability to observe the local characteristics of the signal in the time and frequency domains, which is beneficial to detecting the transient or abnormal points of the signal.

[0061] Referring to Figure 3 , the wavelet analysis result of the vibration and noise signal provided by the example of the present application is shown, wherein 3A is a crankshaft and camshaft signal, Figure 3 B is a 1-meter noise signal, Figure 3 C is a cylinder body vibration signal, Figure 3 D is the wavelet analysis result of the 1-meter noise signal. Figure 3 The 58-tooth crankshaft signal and the 4-tooth camshaft position signal of A can identify the working stroke, top dead center and bottom dead center of the engine at each time; the analysis Figure 3 of the time domain signal of B noise can know that the tick noise occurs near 1.0554s, Figure 3The D wavelet analysis indicates that the frequency of the knock sound is mainly a wideband noise within 1500-4000 Hz, and has obvious periodic characteristics. The analysis shows that the knock sound occurs at 390-399°CA after the exhaust top dead center, at which time the two-cylinder body vibration shows a significant impact feature, and in the intake stroke.

[0062] S13, a dynamic analysis is performed to obtain the motion of the internal components of the engine, i.e., the piston, the piston pin and the connecting rod, at this time, the dynamic analysis model is input with the design parameters of the engine.

[0063] S14, the motion of the piston, the piston pin and the connecting rod at the knock time is obtained by intercepting and analyzing the knock time in S12, if the piston pin is in the reversing state in the small head hole of the connecting rod at the knock time, it is determined that the knock sound is the piston pin knock sound, otherwise it is determined that the knock sound is not the piston pin knock sound.

[0064] In order to produce the knock, there must be relative motion and impact force, i.e., the piston pin knock is produced by the piston pin hitting the connecting rod. In other working conditions, the piston pin pushes the connecting rod or the connecting rod pushes the piston pin, at this time, there is no relative radial displacement, and no impact will be produced. Only when the piston pin is reversing in the small head of the connecting rod, the radial impact force will be produced.

[0065] Referring to Figure 4 , the motion analysis schematic diagram of each working state of the crank connecting rod mechanism is shown, from the test results in S12, it is known that the knock sound occurs after the intake top dead center, i.e., the intake stroke in the figure, at this time, the force of the piston pin is just reversed, i.e., the knock sound is the piston pin knock sound.

[0066] In this embodiment, whether to optimize is judged objectively, i.e., after the piston pin knock sound is identified, the sound pressure level data of the piston pin knock sound is obtained, if the sound pressure level data > preset sound pressure level threshold, S2 is executed; if the sound pressure level data ≤ preset sound pressure level threshold, the process is ended. It should be noted that whether to optimize can also be judged subjectively, or whether to optimize can be judged subjectively and objectively, and reasonable selection can be made according to actual needs.

[0067] The preset sound pressure level threshold is obtained by preparing a plurality of piston pin knocking sound samples, performing subjective evaluation and objective evaluation on each piston pin knocking sound sample, the objective evaluation being sound pressure level data of the piston pin knocking sound, that is, wavelet analysis is performed on the sound signal collected by the microphone, the main energy frequency band of the knocking sound is determined, and the time domain data is sliced in the main energy frequency band to obtain the sound pressure level data after band-passing. The subjective evaluation result and the objective evaluation result of each piston pin knocking sound sample are obtained. A correlation mathematical model between the subjective evaluation result and the objective evaluation result is established, a subjective evaluation set threshold of the piston pin knocking sound is input into the correlation mathematical model, and a corresponding objective evaluation result is output as the preset sound pressure level threshold.

[0068] In the embodiment, the piston connecting rod assembly includes a connecting rod small head and a piston pin, the connecting rod small head is provided with a piston pin hole corresponding to the piston pin; and the piston connecting rod assembly size includes surface roughness of the connecting rod small head, inner diameter of the connecting rod small head, cylindricity of the connecting rod small head, outer diameter of the piston pin, inner diameter of the piston pin hole, perpendicularity of the piston pin hole, and cylindricity of the piston pin hole.

[0069] In the embodiment, the determination of the piston pin knocking power threshold is specifically: based on the engine structure characteristics, a transfer function of the piston pin to the microphone arranged around the engine is obtained, the system is regarded as a linear system, and the transfer function refers to the ratio of the Laplace transform of the linear system response quantity to the Laplace transform of the excitation quantity under zero initial condition. The Z-direction impact excitation at the piston pin is transmitted through the connecting rod-main bearing seat-cylinder block. Based on the preset sound pressure level threshold of the piston pin knocking sound, the knocking power threshold of the piston pin and the connecting rod is calculated.

[0070] Knocking is a kind of collision, characterized by a change in motion speed in a very short time, and the intensity thereof can be represented by the change in kinetic energy per unit time or the change in impulse per unit time. The subjective evaluation of external knocking is positively correlated with the unit time energy radiated by the cylinder, and the energy of the cylinder comes from the knocking of the piston pin and the transmission energy + other energy. When the other energy remains unchanged, the greater the energy transmitted by the piston pin per unit time, the more intense the subjective feeling of knocking.

[0071] Assuming that the connecting rod is a completely elastic body, the size of the change in unit time kinetic energy determines the efficiency of the transmission energy, that is, the knocking power, and the greater the value, the greater the collision intensity, so that the knocking power is used to evaluate the piston pin knocking, which is more intuitive and more appropriate.

[0072] The change in kinetic energy is the derivative of kinetic energy: W = ma'v.

[0073] In the formula, m is the mass, and the design change involves many influences, so it is generally not changed.

[0074] v is the relative motion speed, which is related to the acceleration and the distance of acceleration, wherein the distance is the fitting gap between the small end of the connecting rod and the piston pin.

[0075] a' is the acceleration, which is related to the force, see Figure 5 , the force analysis diagram of the piston pin in the intake stroke, the generation of the piston pin knocking phenomenon is essentially caused by the impact of force. For the force at the piston pin, the switching time is the balance point of the cylinder pressure and the inertial force. The resultant force:

[0076] F z = F j +F g =-m j ·r·ω 2 ·(cosωt+λcos2ωt)+(p gas -p0)·A·10 6 ;

[0077] Wherein, F z is the resultant force, F j is the reciprocating inertia force, F g is the gas pressure, F N is the lateral force of the piston, F S is the connecting rod force, F T is the tangential force of the crankshaft, F R is the radial force of the crankshaft, m j is the reciprocating mass, r is the radius of rotation, ω is the angular velocity of rotation, t is the time, λ is the connecting rod ratio, p gas is the gas pressure.

[0078] The change of gas pressure and reciprocating inertia force can reduce the engine performance and the structure of parts to realize, often contrary to the design intention of the engine, generally not to change.

[0079] In summary, the parameters to be optimized in S3 are the fitting gap between the small end of the connecting rod and the piston pin, and the oil film thickness between the small end of the connecting rod and the piston pin. The fitting gap between the small end of the connecting rod and the piston pin is the inner diameter of the small end of the connecting rod minus the outer diameter of the piston pin.

[0080] By applying simulation analysis, based on the piston pin knocking power threshold, the upper and lower limit values of the fitting gap between the small end of the connecting rod and the piston pin are determined. Referring to Figure 6 , the response result diagram of the piston pin under different fitting gaps between the small end of the connecting rod and the piston pin is shown. The response size of different fitting gaps is 10μm<12μm<14μm<16μm<18μm<20μm. When the fitting gap between the small end of the connecting rod and the piston pin is ≥16μm, there is a relatively obvious knocking signal at the reference point of the piston pin, that is, the upper limit value of the fitting gap between the small end of the connecting rod and the piston pin is set to 16μm.

[0081] The lower limit of the oil film thickness between the small end of the connecting rod and the piston pin is obtained based on the simulation analysis according to the design requirements. The oil film between the small end of the connecting rod and the piston pin can play a role in buffering the collision, reducing the acceleration when the piston pin collides with the small end of the connecting rod. The thicker the oil film, the more obvious the effect, so the acceleration can be reduced by increasing the oil film thickness, thereby reducing the knocking energy. However, the oil film thickness cannot be infinitely reduced, because it is limited by the surface roughness of the shaft neck and the bearing surface, the rigidity of the shaft, and the geometric shape error of the bearing and the shaft neck. Therefore, the relevant performance requirements need to be met first.

[0082] The extended Reynolds equation is used to describe and calculate the motion state and law of the piston pin in the bushing under the influence of the oil film. The finite element model and the oil film described by the difference grid are iterated with each other to obtain the theoretical oil film thickness.

[0083]

[0084] In the formula, P is the oil film pressure, η is the dynamic viscosity of the oil, θ is the oil filling rate, u is the axial velocity of the shaft neck (pin), h is the gap height, t is the time, x is the circumferential position, z is the axial position, μ1 is the shaft neck velocity, and μ2 is the bearing velocity.

[0085] To ensure that the bearing can be in a liquid friction state, the minimum oil film thickness h min must be equal to or greater than the allowable oil film thickness [h], and at the same time, the theoretical oil film thickness h t between the small end of the connecting rod and the piston pin must be equal to or greater than the minimum oil film thickness, that is,

[0086]

[0087] [h]=S(R z1 +R z2 ),

[0088] In the formula, R z1 and R z2 are the surface roughness of the piston pin hole of the piston pin and the small end of the connecting rod respectively, S is the safety factor, r' is the radius of the piston pin, is the relative gap, and x is the eccentricity.

[0089] If the minimum oil film thickness requirement is not met, optimization is performed from the design to make the oil film thickness between the small end of the connecting rod and the piston pin meet the minimum oil film thickness requirement, thereby playing a role in buffering the impact.

[0090] Referring to Figure 7, the roughness shown in the schematic diagram of the contact pressure of the piston pin in the piston pin hole of the small head of the connecting rod, because the minimum oil film thickness is strongly related to the surface roughness of the piston pin and the small head of the connecting rod, and the piston pin generally has high precision, and the roughness is very small, and more attention should be paid to the surface roughness of the piston pin hole of the small head of the connecting rod, and it is suggested that the surface roughness of the piston pin hole of the small head of the connecting rod R z2 Control in R z2 ≤0.4.

[0091] There are many factors that affect the oil film thickness between the small head of the connecting rod and the piston pin, such as the quality and viscosity of the lubricating oil, the fit clearance, the surface roughness, the oil temperature, the pressure per unit area of the oil film, and the rotational speed vibration, etc.

[0092] Referring to Figure 8 , the first oil film thickness and the second oil film thickness are shown in the schematic diagram of the impact force of the piston pin, and with the increase of the oil film thickness, the impact force gradually decreases, and when the oil film thickness reaches a certain critical value, the impact of the oil film thickness on the impact force is no longer obvious. That is, the oil film between the piston pin and the small head of the connecting rod plays a buffering role, reduces the acceleration of relative motion, thereby reducing the impact force and the knocking power, and reducing the knocking sound.

[0093] Through DOE test design analysis, the fit clearance E of the small head of the connecting rod and the piston pin, and the oil film thickness F between the small head of the connecting rod and the piston pin are analyzed, to determine the influence level of the fit clearance of the small head of the connecting rod and the piston pin, and the oil film thickness between the small head of the connecting rod and the piston pin on the knocking power. The upper limit value of the fit clearance of the small head of the connecting rod and the piston pin is 16μm, and the lower limit value is 10μm. The upper limit value of the oil film thickness between the small head of the connecting rod and the piston pin is 7μm, and the lower limit value is 3μm. The results are shown in Figure 9 , which shows that the oil film thickness between the small head of the connecting rod and the piston pin has the most significant contribution level to the piston pin knocking power.

[0094] To increase the oil film thickness between the small head of the connecting rod and the piston pin, more lubricating oil can be provided to achieve the effect of rich lubrication, and the main ways are as follows:

[0095] 1. Review whether the crankshaft splash lubrication meets the requirements, and open an inclined oil groove on the large head of the connecting rod to provide lubricating oil in the main oil passage to the piston pin through the centrifugal force of the rotating crankshaft;

[0096] 2. Drill oil collection holes or mill oil collection grooves on the small head and the bushing to collect the splash lubricating oil to lubricate the piston pin;

[0097] 3. If it is a fully controllable PCJ, the Map can be modified to open the PCJ function in the knocking condition to provide more lubricating oil for the piston pin.

[0098] Referring to Figure 10The diagram shows the response of different oil viscosities to the reference point of a fully floating piston pin. When the oil viscosity is reduced, the impact load of the piston pin on the connecting rod remains basically unchanged without changing the clearance between the connecting rod small end and the piston pin. However, the oil film height decreases, the clearance switching during contact deteriorates, and the response of the piston pin reference point increases.

[0099] The beneficial effects of the collision theory-based analysis method for the knocking sound of a fully floating piston pin provided in this invention are as follows: Wavelet analysis is applied to quickly pinpoint the knocking moment; dynamic analysis is applied to pinpoint the movement of components at the knocking moment, thereby identifying the knocking source; subjective evaluation and mathematical fitting of frequency slices are used to establish reasonable standards, i.e., sound pressure level threshold settings, avoiding blindness; based on collision theory, key factors affecting collisions are obtained, and optimizable factors are derived from practical experience, providing a comprehensive analysis of the problem from both theoretical and practical perspectives; knocking kinetic energy is used for simulation evaluation, providing quantitative indicators for simulation analysis, and a knocking power standard is established based on the cylinder transfer function; standards for the fit clearance between the connecting rod small end and the piston pin, and the oil film thickness between the connecting rod small end and the piston pin, are established based on structural parameters to guide problem analysis and the formulation of effective solutions; the provision of multiple solutions makes engineering implementation easier.

[0100] In Embodiment 2, the present invention also discloses a piston pin knocking sound optimization device, which can implement the steps of the piston pin knocking sound optimization method based on collision theory described in Embodiment 1, including: an identification module for identifying and determining whether the knocking sound is a piston pin knocking sound; a judgment module for determining whether to optimize the piston pin knocking sound; a size detection module for detecting the size of the piston connecting rod assembly and determining whether the size of the piston connecting rod assembly meets the design requirements; and an optimization module for finding the optimal parameter combination of several parameters to be optimized.

[0101] In Embodiment 3, the present invention discloses a storage medium storing a computer-readable program, which, when invoked, can execute the steps of the piston pin knocking sound optimization method described in Embodiment 1 of the present invention.

[0102] It should be noted that the storage medium shown in the figure can be a computer readable signal medium or a computer readable storage medium or any combination of the above two. The computer readable storage medium may, for example, be an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or apparatus, or any combination of the above. More specific examples of the computer readable storage medium can include, but are not limited to, an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read only memory (ROM), an erasable programmable read only memory (EPROM), a flash memory, an optical fiber, a portable compact disk read only memory (Compact Disc Read-Only Memory, CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present embodiment, the computer readable signal medium can include a data signal propagating in the baseband or as a carrier wave part of a data signal propagating in the baseband, in which the computer readable computer program is carried. Such a propagating data signal can take various forms, including but not limited to electromagnetic signals, optical signals or any suitable combination of the above. The computer readable signal medium can also be any computer readable medium other than the computer readable storage medium, which can send, propagate or transmit programs for use by or in connection with an instruction execution system, device or apparatus. The computer program contained on the computer readable medium can be transmitted by any suitable medium, including but not limited to wireless, wired, etc., or any suitable combination of the above.

[0103] The flowcharts and block diagrams in the drawings illustrate the possible implementation architecture, function and operation of the system, method and computer program product according to various embodiments of the present application. In the flowchart or block diagram, each block can represent a module, a program segment or a part of code, which contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the block can also occur in different order from that marked in the figure. For example, two blocks represented in succession can actually be executed substantially in parallel, and sometimes they can be executed in reverse order, depending on the function involved. It should also be noted that each block in the block diagram or flowchart, and the combination of blocks in the block diagram or flowchart, can be implemented by a special hardware-based system for executing the specified function or operation, or can be implemented by a combination of special hardware and computer instructions.

[0104] The above embodiments are only the preferred embodiments of the present application for fully illustrating the present application, and the protection scope of the present application is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art based on the present application are within the protection scope of the present application.

Claims

1. A method for optimizing piston pin knocking sound, characterized in that, Includes the following steps: S1: After detecting the piston pin knocking sound, determine whether to optimize. If yes, execute S2; otherwise, end the process. S2, check whether the dimensions of the piston connecting rod assembly meet the design requirements. If yes, proceed to S3; otherwise, optimize the structure of the piston connecting rod assembly until the dimensions of the piston connecting rod assembly meet the design requirements. S3. Based on collision theory and actual performance requirements, several parameters to be optimized and their adjustment ranges are determined. These parameters are used as variables, with the minimum piston pin impact power as the optimization objective. The optimal parameter combination is obtained through optimization. The parameters to be optimized are the clearance between the small end of the connecting rod and the piston pin, and the oil film thickness between the small end of the connecting rod and the piston pin. The clearance between the small end of the connecting rod and the piston pin is the inner diameter of the small end of the connecting rod minus the outer diameter of the piston pin. The DOE experimental design analysis was used to conduct a full factorial analysis of the fit clearance between the connecting rod small end and the piston pin, and the oil film thickness between the connecting rod small end and the piston pin, to determine the influence of these two parameters on the knocking power.

2. The method for optimizing piston pin knocking sound according to claim 1, characterized in that, In S1, optimization is performed based on subjective and / or objective judgments.

3. The method for optimizing piston pin knocking sound according to claim 2, characterized in that, In S1, an objective judgment is made as to whether to perform optimization. That is, after the piston pin knocking sound is detected, the sound pressure level data of the piston pin knocking sound is obtained. If the sound pressure level data is greater than the preset sound pressure level threshold, then S2 is executed; if the sound pressure level data is less than or equal to the preset sound pressure level threshold, then the process ends.

4. The method for optimizing piston pin knocking sound according to claim 3, characterized in that, The specific steps for obtaining the preset sound pressure level threshold are as follows: Prepare several piston pin knocking sound samples, and perform subjective and objective evaluations on each piston pin knocking sound sample. The objective evaluation is the sound pressure level data of the piston pin knocking sound, and obtain the subjective evaluation result and objective evaluation result for each piston pin knocking sound sample; establish a correlation mathematical model between the subjective evaluation result and the objective evaluation result, input the set threshold of the piston pin knocking sound subjective evaluation into the correlation mathematical model, and output the corresponding objective evaluation result as the preset sound pressure level threshold.

5. The method for optimizing piston pin knocking sound according to claim 1 or 2, characterized in that, The identification of piston pin knocking sound in S1 specifically includes the following steps: S11, Noise sensors, vibration sensors, crankshaft sensors, camshaft sensors and cylinder pressure sensors are installed on the engine under test and NVH tests are performed; S12. Based on the test results, wavelet and angle domain analysis methods are applied to obtain the frequency of the knocking sound, the periodicity of the knocking sound, and its phase time relative to the engine operation, i.e., the knocking time. S13. Perform dynamic analysis to obtain the motion of internal engine components; S14. Analyze the moment of impact in S12 to obtain the movement of the piston, piston pin, and connecting rod inside the engine at the moment of impact. If the piston pin is in a reversing state in the small end hole of the connecting rod at the moment of impact, the impact sound is determined to be the piston pin impact sound; otherwise, the impact sound is determined not to be the piston pin impact sound.

6. The method for optimizing piston pin knocking sound according to claim 1, characterized in that: By applying simulation analysis and setting a threshold based on the piston pin impact power, the upper and lower limits of the fit clearance between the connecting rod small end and the piston pin are determined. Based on the design requirements, simulation analysis was used to obtain the lower limit of the oil film thickness between the small end of the connecting rod and the piston pin.

7. The method for optimizing piston pin knocking sound according to claim 1 or 2, characterized in that, The piston connecting rod assembly in S2 includes a connecting rod small end and a piston pin, wherein the connecting rod small end is provided with a piston pin hole that corresponds to and mates with the piston pin. The dimensions of the piston connecting rod assembly include the surface roughness of the connecting rod small end, the inner diameter of the connecting rod small end, the cylindricity of the connecting rod small end, the outer diameter of the piston pin, the inner diameter of the piston pin hole, the perpendicularity of the piston pin hole, and the cylindricity of the piston pin hole.

8. The method for optimizing piston pin knocking sound according to claim 1 or 2, characterized in that, If the dimensions of the piston connecting rod assembly in S2 do not meet the design requirements, then optimize the manufacturing process or tooling of the piston connecting rod assembly, or directly replace it with a piston connecting rod assembly that meets the design requirements.

9. A piston pin knocking sound optimization device, characterized in that, The steps for implementing the piston pin knocking sound optimization method based on collision theory as described in any one of claims 1 to 8 include: The identification module is used to identify and determine whether the knocking sound is a piston pin knocking sound; The judgment module is used to determine whether to optimize the piston pin knocking sound; The dimension inspection module is used to inspect the dimensions of the piston connecting rod assembly and determine whether the dimensions of the piston connecting rod assembly meet the design requirements. The optimization module is used to find the optimal combination of several parameters to be optimized.

10. A storage medium, characterized in that: It contains a computer-readable program that, when invoked, performs the steps of the piston pin knocking sound optimization method as described in any one of claims 1 to 8.

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