Abstract: A knock sensor has a substrate having a projection at the center of one surface thereof and a bore at the center thereof, a vibrating plate having a bore at the center thereof and having a plate rigidifying projection means at the center portion of one surface thereof, the central portion being welded to the projection on the substrate, a piezoelectric ceramic element having a bore in the center thereof and electrodes on opposite faces thereof and secured to the other surface of the vibrating plate, and a terminal having a lead projection extending through the bore in the substrate, the bore in the vibrating plate and the bore in the piezoelectric ceramic element and connected to the electrode on the face of the piezoelectric ceramic element which faces away from the vibrating plate.

Abstract: A knocking sensor comprises a casing for receiving a pickup assembly including a transducer, which produces an electrical signal in accordance with engine vibrations, and a connector having at least a single pin electrically connected to the transducer. The casing comprises a threaded projection to be screwed in a screw hole of an engine, and a nut-like periphery to be rotated by a tool. The knocking sensor can be attached to the engine by means of an impact wrench, by rotating the nut-like portion. A plug connected to one end of a shielding code can be plugged in the connector to make an electrical connection between the transducer and a signal processing circuit after the knocking sensor has been attached to the engine, and therefore, the shielding code is prevented from being damaged during installation of the knocking sensor. The use of an impact wrench ensures secure attachment of the sensor, and reduces the installation time.