Research on the way to solve the knock of automobile transmission gear

At present, the transmission knocking noise is mainly solved in the following ways (see Table 2): from the aspect of control source, i.e. control engine torsional vibration; from the aspect of improving transmission path, it mainly includes adjusting clutch parameters, improving transmission path damping and vibration isolation performance; from the aspect of restraining response, it can increase the drag torque of loose gear (reduce the efficiency of gear system), reduce the backlash, etc

1. Control excitation to restrain gear knocking

In the aspect of control excitation, it is mainly to control the amplitude of engine torque fluctuation. Barthod [43] established a transmission transmission test-bed, analyzed the influence of different input speed excitation order and frequency on the phenomenon of gear knocking. The results show that the higher the amplitude of engine second harmonic excitation frequency, the greater the possibility of transmission knocking; Under the excitation of the second, fourth and sixth harmonics of the engine, the amplitude of the second harmonic has the largest contribution to the generation of knocking. Through the analysis of the test, it can be seen that the reasonable control of the engine speed excitation frequency and the reduction of the amplitude of the larger contribution can effectively improve the knocking phenomenon of the transmission gear. In engineering practice, the engine calibration is often used

2. Improve the transmission path to suppress the gear knocking noise

In terms of improving the transmission path, the main measures include adjusting the clutch parameters, directly using DMF to replace the traditional clutch and optimizing the pull lock (including shift pull lock, clutch pull lock and throttle pull lock, etc.), The results show that the main transmission path of knocking vibration noise is clutch pull lock and shift pull lock. By optimizing clutch pull lock and shift pull lock, the sound pressure level of driver’s right ear is reduced by 2dB (a) and 1dB (a) respectively, DMF can change the inherent characteristics of the whole transmission system and effectively reduce the speed fluctuation of the engine to the transmission input shaft. It is a feasible solution to solve the transmission knocking phenomenon, However, compared with the traditional clutch, the cost of the whole vehicle is higher. For example, Wang et al. [14] established a five speed manual transmission gear knock model based on the torsional vibration of the main line. Using the objective evaluation index of gear knock, the knock strength of each non load-bearing gear pair when DMF and traditional clutch are used respectively is analyzed and compared. The results show that DMF can effectively inhibit the gear knock phenomenon

3. Control response to suppress knocking noise

In terms of control response sensitivity, it is mainly through reasonably setting the backlash between gears, optimizing the moment of inertia of passive gears, changing the drag torque and lubrication conditions, etc. for example, Russo et al. [45] take a pair of meshing non bearing gear pairs as an example, analyze the influence of lubrication conditions and backlash between gears on the knock strength, and find that the lubrication conditions are good, and the phenomenon of bilateral knock of gears can be effectively suppressed, The lubrication condition is an important factor in the study of the transient response of gears

The knock vibration of transmission gear is transmitted to transmission case through shaft and bearing. As a typical elastic structural system, the case can adjust the natural frequency of structural system to keep away from dynamic excitation frequency by using the theory and method of structural dynamic modification, so as to avoid common vibration and reduce radiation noise. For example, Tuma et al. [46] control the noise of transmission by improving the rigidity of transmission case, In order to reduce the impact vibration of the gear, the stiffener is used to increase the rigidity of the box. The stiffener in the box is perpendicular to the gear shaft, while the stiffener on the box surface is parallel to the shaft, so as to achieve the purpose of suppressing the vibration of the box

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