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Ffi.008 Quantitative Estimation of Impact Noise of Mechanical Science and Technology Gears Shao Renping, Sun Jincai, Shen Yunwen, Jia Purong (Northwestern Polytechnical University, Xi'an Shao Renping and Elastic Deformation Influence on Gear Meshing Impact, Impact Velocity and Impact Time The expression, combined with the acoustic theory, calculates the acoustic characteristics such as the noise pressure and the acoustic radiation power generated by the gear meshing impact, which can be used to estimate the gear shock acceleration noise. The gear transmission system relies on multi-tooth alternating and cyclic meshing. In the transmission of power, there will inevitably be various errors in the transmission, which will cause the actual meshing process to mutate. In fact, the slight tooth shape error and the base curve error will cause the gear to generate a large vibration in the transmission. Noise, so it is necessary to conduct in-depth research on the impact vibration and noise caused by error and elastic deformation. A lot of work has been done at home and abroad 1~31, and some satisfactory results have been obtained, but most of these studies It analyzes the vibration generated by the gear mesh excitation from the perspective of dynamics and its The small degree of influence, and by reducing the vibration to reduce the noise, and the impact noise generated by the acoustic angle of the gear meshing is very little. In the early 1980s, Richards proposed a new concept of impact noise 41, for gear noise The research has brought new hopes. He believes that the impact noise is composed of two parts: impact acceleration noise and self-sounding noise, and targets the spheres and cylinders that impact each other. After a large number of teeth on the driving wheel 1 The base of ab is TQ, the base of tooth a:b on passive wheel 2 is Tg, and T is the intersection of the extension line of the tooth profile curve and the meshing line, then TQ
2 Impact acceleration noise is estimated to radiate acceleration noise when two objects are impacted, and the impact acceleration noise is related to the impact speed, the volume of the impact object and the impact time. The calculation method of radiation efficiency, impact sound pressure and impact sound radiation power during gear transmission impact is analyzed below.
2.1 Impact radiation efficiency and radiation power The radiation efficiency of the object is different from the radiation efficiency of the structural vibration self-sounding noise, which can be expressed as the material density; Vo is the impact velocity; VoL is decelerated from Vo to 0 or accelerated by 0. The volume that changes to Vo.
When two spheres are impacted at a speed Vo, their impact energy can represent a diameter; to is the impact time; c is the speed of sound in the air.
Let ctona be the impact acceleration parameter. After the formula (10) is derived, the gear transmission is transmitted by the alternating contact between the tooth surfaces and the meshing impact. The contact shock between the tooth surfaces can be regarded as two cylinders with variable curvature. The mutual impact, if the volume of the gear is V, the impact radiation efficiency can be obtained by using 2V1/3 instead of na, that is, å©V=nr2b, rrf is the radius of the gear tip circle, and b is the tooth width na to obtain the value of the gear transmission impact radiation efficiency. .
For the logarithm of equation (10), the sound power of the gear drive impact acceleration noise radiation is obvious: obviously the impact radiation efficiency is related to the impact time to to the volume V changed during the impact, and the impact sound power is related to the impact radiation efficiency. It is related to the impact velocity Vo. After substituting the obtained impact velocity Vs and other parameters, the magnitude of the impact sound power of the gear transmission can be obtained.
2.2 Impact Radiation Sound Pressure The impact sound pressure when two objects impact can be expressed as P(r, 0, t) = P0(r, t)coS3, and Po(r, t) is the sound pressure in the impact direction. So it is a complex function of spatial distance, direction and time. l6 We are concerned with the maximum amplitude of sound pressure when the gear meshes impact, where the gear transmission is treated as an acoustic model of two cylinders with varying curvatures. After derivation, the relevant parameters are substituted into the post-simplification degree (m/s); r is the distance from the center of the curvature of the gear space (m); c is the speed of sound in the air (m/S).
Therefore, the sound pressure value at the time of the gear meshing impact can be calculated from the equation (15).
3 Simulation calculation 60, z2=40 modulus m=2.0 transmission power is 7.5kW. The driving wheel speed is 1=12(1)r/min, the gear precision grade is 9~9~8, the tooth width b=0.025m, the space distance r= Firstly, the elastic deformation on the common normal line is calculated, that is, the contact deformation, bending deformation and shear deformation are obtained according to the Weber formula. The result is 0.945 mm and then the gear impact velocity is simulated. The result is 0.054 m/s. The final simulation calculates the impact sound power Leq. With the impact time, if not. The relationship between the peak sound pressure and the impact time is as shown. It can be seen that the sound power and sound pressure of the radiation are inversely related to the impact time. The less the impact time, the greater the sound power and sound pressure. For steel gears, the minimum impact time is generally 2< 1 (T4s, then the maximum radiated sound power is 90db (actually it is impossible to reach this value by the speed limit). In addition, the impact sound pressure time relationship is converted into the frequency domain. The simulation calculation shows the relationship between the acoustic power and the red power rate. As shown in the figure, it can be seen that in the low frequency band and the high 5H6 frequency band, the power is small, while in the middle frequency band, the radiated sound power is the largest, which is followed by a large number of experiments and theoretical studies. The impact radiation characteristics obtained by 宄 are caused, and KXX)0 indirectly proves the rationality of the above analysis process and conclusions, so the radiated sound power can be used to calculate the impact noise of the gear transmission.
4 Conclusion This paper analyzes the variation of gear meshing caused by machining error and elastic deformation, and gives the expression of gear impact velocity and impact time and the calculation formula of impact radiation noise, which can quantitatively calculate gear impact acceleration noise, which gives gear Noise Research provides a new approach