Piezoelectric engine-knock sensor
AssigneeRobert Bosch GmbH
InventorsHans J. Hamisch, Manfred Boruschweitz, Theodor Gast
Life of this patent
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Abstract
A metallic reed clamped against a piezoelectric element, and free to oscillate at its other end, generates electrical signals in a piezoelectric element which is held between clamp surfaces in fixed relation to an engine part which transmits engine knock vibrations to the sensor assembly. The reed is oriented perpendicular to the vibratory motions of the engine part on which it is mounted, so that vibrations of the reed will be excited thereby, and these will deform the piezoelectric element to generate signals. The entire assembly can be enclosed in a transverse bore in the head of a cylinder head screw.
Claims8
A sensor for detecting oscillations in an internal combustion engine resulting from engine knocks, comprising:
- a tubular body (16) of piezoelectric material having a pair of electrodes (23,24) on diammetrically opposite longitudinal patches of a first cylindrical surface of said tubular body and a counter-electrode on a second cylindrical surface of said tubular body;
- a casing having an internal cylindrical opening for receiving said piezoelectric body, said casing having an internal stop portion (13,14) for holding said tubular body against axial movement;
- means (15) for insulatingly and supportingly spacing said tubular body from said stop portion (13,14) of said casing;
- a flexure vibration member (18) having a free end extending from a base portion, said base portion having oppositely directed lateral extensions for dynamically connecting vibratory motion of said free end differentially as pressure variations to two diametrically opposite portions of the end of said tubular body (16) opposite from the end thereof supported by said spacing means (15);
- a compression spring (17) for pressing said lateral extensions of said vibration member (18) against said end portions of said tubular body (16), and
- means (19) held on said casing (25) for compressing said spring (17) against said lateral extensions of said vibration member.
Dependencies are inferred from the claim text.