Magnetostrictive engine-knock sensor

US4383434A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Hans-Joachim Hamisch · Berlin, DE
• Manfred Boruschewitz · Berlin, DE
• Theodor Gast · Berlin, DE

Key dates

• Filing date: Mar 9, 1981
• Grant date: May 17, 1983
• Expiry date: Mar 9, 2001

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F02B1/04
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A flexure vibrator clamped at one end and oriented in a direction perpendicular to the direction of oscillations produced at its clamped end mounting by knocks in an engine to which the sensor is affixed, is provided with a magnetostrictive body which generates electrical signals in response to vibrations of the vibrator. The vibrator may be made of magnetostrictive material and its upper and lower halves may be of opposite polarity, a result that may be obtained by folding over a strip of magnetic material on itself at one end or the other. A vibrating body of material that is not magnetostrictive may have a magnetostrictive body associated with it. If the magnetostrictive material has no remanence, a magnetic bias may be applied by an additional coil or by a permanent magnet. Sensitivity is improved if damping signals in phase opposition to the vibration-produced signals are applied from the time that the knock signals die away until the next engine spark, with damping applied to one diagonal of a bridge of which the detector coil is one arm and the detected signal being taken off from the other diagonal of the bridge.