Measuring and testing – Engine detonation – Specific type of detonation sensor
Patent
1995-04-03
1997-06-03
Chilcot, Richard
Measuring and testing
Engine detonation
Specific type of detonation sensor
73 3513, G01L 110, G01L 2322, G01H 900
Patent
active
056356293
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a knock sensor to detect abnormal vibration due to a knocking phenomenon in an engine for a vehicle or the like.
BACKGROUND ART
A knock control system intended to control a knocking phenomenon, increase engine torque, and improve fuel consumption by sensing a knocking phenomenon in an engine of a vehicle or the like, conveying the presence or absence of the knocking phenomenon to an engine control unit (ECU), and controlling the ignition timing of spark plugs within cylinders of the engine with the ECU is known conventionally. This knock sensor senses vibration characteristic to the knocking phenomenon, and the vibration detector thereof has conventionally used a piezoelectric element composed of ceramic.
Broadly speaking, there are two types of detection methods for knock vibration of this knock sensor. One is a resonance type which causes a piezoelectric element to resonate together with a knocking frequency and detects output due to the resonance thereof as a knock signal, as is described in Japanese Patent Application Laid-open No. 62-96823 Patent Gazette, Japanese Patent Application Laid-open No. 59-164921 Patent Gazette, or Japanese Utility Model Application Laid-open No. 62-128332. The other is a flat type which detects a knock signal in a flat region in which an output signal output by a piezoelectric element is not subject to the influence of resonance, as described in Japanese Utility Model Application Laid-open No. 57-99133. Because the former causes resonance with the knock vibration, output with a good signal-to-noise ratio is obtained, but conversely only a unique knock vibration can be detected, and in the case of an engine with many cylinders it is impossible to detect knock vibration of all cylinders at a single location, and the problem exists that a plurality of knock sensors are required. On the other hand, the latter can detect knock vibration of various frequencies, but the possibility exists that, aside from the influence of the resonant frequency of the element itself, the vibration of other components may exert an influence on the vibration detection region, and there exists the problem wherein the degree of freedom in design of the knock sensor itself is narrow.
As the structure of these sensors, a structure disposing a piezoelectric element composed of a vibration detector within a space formed by a housing made of metal (or a housing composed of a strong material to be substituted thereby) having a projection of screw configuration so as to be installed directly on an engine and of a connector molded of resin which allows connector connection with an external portion is common.
Accordingly, there are two types of piezoelectric element installations: a type firmly fixed to the housing side by means of a screw or the like, and a type fixed in a state fixed to a stem of metal which becomes a fixing pedestal (or a strong fixing pedestal to be substituted thereby) on the connector side. Additionally, for the latter there exist, as similar types thereof, a type fixed to the stem, and not fixed directly to the connector side but fixed by means of caulking, and a type wherein the contact point of the step and housing are connected by means of gluing or welding or the like. That is to say, the latter can be termed a type fixed to the stem and disposed within a spaced formed by the stem and housing.
In a case where the piezoelectric element is fixed to the housing side, resonant frequency is high because the housing itself is made of metal, the housing itself does not resonate due to engine vibration, and influence thereof is not exerted on the piezoelectric element. However, it is necessary to perform the electrical connection from the piezoelectric element to the connector terminal by means of for example lead wires, the connector and housing must be fixed by means of caulking or the like to fix the piezoelectric element to the housing and connect the lead wires, and there exists the problem of a difficult fabrication process.
On the
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Gotou Nobuyasu
Imai Masahito
Kamabora Koichi
Kanemaru Kenji
Kitao Norio
Chilcot Richard
Dombroske George M.
Nippondenso Co. Ltd.
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