KNOCKING DETECTING DEVICE FOR ENGINE

PURPOSE:To eliminate the effect of vibration noises, by computing the vibration noises generated by a cylinder head based on the amount of deviation in outputs of knock sensors arranged on the cylinder head and a cylinder block. CONSTITUTION:A cylinder head 4 is mounted on and fixed to a cylinder block 2 of an engine body 1 through a gasket 3. Knock sensors 22 and 23 are attached to the cylinder head 4 and the cylinder block 2, respectively, and pick up the synthesized vibration of the knocking and valve noises and the synthesized vibration of the knocking and attenuating valve noises. Based on the difference between the outputs of both knock sensors, i.e., the amount of attenuation in the mechanical noise, the mechanical noise generated in the cylinder head is computed. Then, the mechanical noise is subtracted from the output of the knocking sensor 22, and a true knocking level is obtained. Whether the knocking state is present or not is judged by a judging means (i), and an ignition-time control circuit (j) and the like are controlled.