Fiber optic combustion pressure sensors for engine knock and misfire detection
OwnerMarek T. Wlodarczyk, Jerzy A Kabala +1inventors
InventorsMarek T. Wlodarczyk, Jerzy A Kabala, Andrzej Mendak
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Abstract
Spark plug (20) integrated fiber optic combustion pressure sensors (30, 36) are configured to decrease heat and fatigue damage to the critical diaphragm (40) and fiber tip (37). A cup-shaped diaphragm (40) having non-uniform thickness reduces stress on the diaphragm and increases the reliability of the sensor. The effects of overpressure on the sensor are reduced by providing an angled portion (42) on the ferrule.
Claims26
In a fiber optic diaphragm sensor in combination with a spark plug, the spark plug having at least two electrodes, the sensor comprising a body, a diaphragm attached to the body and the body enclosing a cavity, the diaphragm being moveable in response to changes in fluid pressure exerted upon the diaphragm, and
- an optical fiber inserted in the body having a tip end of the optical fiber in communication with the cavity, the tip end being disposed to inject a light beam toward the diaphragm and to receive a light beam reflected from the diaphragm;
- the sensor being positioned at the tip of one of the electrodes with the diaphragm directly exposable to the combustion gases within an engine cylinder.
A method for affixing a fiber optic diaphragm pressure sensor to a spark plug electrode,
- the fiber optic diaphragm pressure sensor comprising a ferrule and having a cavity therein, a diaphragm attached to the ferrule and partially enclosing the cavity, the diaphragm being movable in response to changes in fluid pressure exerted upon the diaphragm,
- the diaphragm comprising a top, an underside, a periphery, and a skirt depending from the top and terminating at the periphery, the skirt being thicker nearer the top than at the periphery,
- an optical fiber inserted in the ferrule having a tip end of the optical fiber in communication with the cavity, the tip end being disposed to inject a light beam toward the diaphragm and to receive a light beam reflected from the diaphragm underside,
- the center of the diaphragm being thicker than an annular portion about the center,
- the method comprising affixing the sensor into a cylindrical hole formed in the top of the electrode.
A method for mounting an optical fiber diaphragm pressure sensor to a spark plug electrode comprising the steps of:
- brazing the optical fiber to the electrode,
- capping the electrode with the sensing diaphragm of the sensor, and
- welding the diaphragm to the electrode.
In combination a unified part forming an optical fiber in-line connector and a high voltage spark plug electrode connector, the unified part comprising,
- an optical connector having a metal electrical inner shell and housing an aligning split sleeve, the inner shell permanently attachable to the spark plug electrode, and
- a mating connector permanently attached to a spark plug cable, the mating connector having an optical ferrule and an interlocking metal outer shell adapted to engage the inner shell, whereby engagement of the optical connector with the mating connector provides optical and electrical communication therebetween.
In a combination of a spark plug having an external boss and at least two electrodes, an inside volume extending about one of the electrodes adjacent the electrode tip and a combustion pressure sensor,
- the improvement comprising a passage formed in the spark plug communicating with the inside volume, the passage extending into the boss and means in the boss to attach the combustion pressure sensor.
Dependencies are inferred from the claim text.