Abstract: Timing cover plate is an important structural component of high efficiency hybrid gasoline engine, and its acoustic performance directly determines the radiated noise of the whole engine. In the noise, vibration, harshness (NVH) test of a newly developed hybrid special high efficiency gasoline engine, it is found that the radiated noise in front of the engine is at the maximum value in the four sides of the engine (front, intake side, exhaust side, above). A large number of local modes exist in the engine timing cover plate, and resonant radiation noise is generated under engine combustion excitation. The modal density and vibration amplitude of the timing cover plate can be effectively reduced by reducing the maximum pressure rise rate during engine combustion and adding bolt constraints at the dense location of the timing cover plate modes. The acceptance test results show that the radiation noise of the whole machine is reduced by 1～2.5 dB (A), which plays a key role in reducing the noise of the whole machine.

Key words: Gasoline engine; Timing plate; Acoustic response; Acoustic power

摘要： 正时盖板作为混动专用高效汽油机的重要结构组成部分，其声学性能直接决定着整机 辐射噪声的大小。在对一款新开发的混动专用高效汽油机做噪声、振动与声振粗糙度（NVH） 测试时，发现该发动机前方辐射噪声在发动机四方（前方、进气侧、排气侧、上方）中处于 最大值。对前方结构件进行调查，确认发动机正时盖板中存在大量局部模态，并在发动机燃 烧激励下产生共振辐射噪声。通过降低发动机燃烧时最大压力升高率，并在正时盖板模态密 集处增加螺栓约束，能有效降低正时盖板模态密度和振动幅值，验收测试结果表明，降低了 整机辐射噪声 1～2.5 dB(A)，对整机噪声的降低起到了关键的作用。

关键词: 汽油机；正时盖板；局部模态；辐射噪声