Other

Gm Global Technolgoy Operations, Inc.

Fiberoptic Sensor Technologies, Inc.

Marek T Wlodarczyk

Thomas J Poorman

Daniel L Vokovich

Mark K Krage

Dah-Lain Tang

Luciano Coletta

David O Danielson

James A Campbell

Michael J O'Rourke

Deborah J Vickers

Gang He

Jerzy A Kabala

Doug Tomasko

Mitch Van Ochten

Douglas G Tomasko

Juan Velazquez

Andrzej Mendak

Charles D Anderson

Fuel injectors () for internal combustion engines are modified and equipped with fiber optic fuel pressure sensors () and fiber optic combustion pressure sensors (). The combustion pressure sensors () are located in separate channels () formed in the fuel injectors with the lower portion () of the channels leading to the combustion chambers. Above the combustion pressure sensors () are fiber optic leads (). In the preferred embodiments the sensors () are equipped with diaphragms () of novel shape () and employ multiple pairs of fibers (), temperature sensitive components () and novel compensation and status monitoring circuits (FIGS.).

Fuel injectors with integral fiber optic pressure sensors and associated compensation and status monitoring devices

In an integrated glow plug and pressure sensor having a passage leading to the pressure sensor, a porous filter is inserted in the passage. The porous filter provides a four-fold improvement in pressure measurement by (1) acting as a trap for combustion deposits, (2) burning combustion deposits when the glow plug heater is on, (3) acting as a heat shield for reducing thermal shock error of the pressure sensor, and (4) damping acoustic high frequency ringing associated with the pressure passage.

Glow plug integrated pressure sensor with filter trap

A pressure-sensing element for an internal combustion engine is located in the sleeve of a ceramic glow plug heater having axial and radial pressure channels connecting the sensor diaphragm to the combustion chamber. The sensor signal conditioner is encapsulated in an automotive-type connector either directly attached to the glow plug body or located at the end of a cable pigtail containing the sensor fibers and the heater positive potential wire. A high temperature rated fiber optic pressure sensor capable of measuring either dynamic or absolute pressure is used. The absolute pressure sensor relies on three optical fibers combined in a common ferrule in the sensor head area and connected to one light source (LED) and two detectors (photodiodes) in the signal conditioner area. The fibers can either be identical by being spaced unequally in the ferrule or can have different diameters, numerical aperatures, or both, and be spaced equally or unequally. The fiber parameters or their spacing are selected to maximize the difference in the response of the 'measurement' and 'reference' detectors to changing pressure.

Glow plug integrated pressure sensor

Several associated techniques and fiber optic constructions are disclosed to protect a diaphragm type fiber optic cylinder pressure sensor from the effects of maximum under hood temperatures and to minimize errors associated with rapidly changing under hood and engine temperatures. The techniques include electronic compensation in response to temperature change, fuel system cooling of the optoelectronic interface, construction of the interface and construction of the sensor tip.

Automotive cylinder pressure sensors

Compensation techniques for high temperature fiber-optic pressure sensors are aimed at correcting for the sensor sensitivity and offset dependence on temperature. By using materials of different thermal expansion coefficients for the sensor diaphragm, housing, ferrule and fiber-bonding compound and by optimizing the length of such parts, the relative distance of the fiber tip with respect to the sensing diaphragm changes in a manner that reduces sensor sensitivity and/or offset dependence on temperature. In the first embodiment, the distance change results from controlled fiber movement within the ferrule and is used to reduce the temperature sensitivity of dynamic sensors. In the second embodiment, an optimum selection of the diaphragm, housing, ferrule and bonding compound materials yields a stable fiber position within the ferrule but, instead, a well defined ferrule movement with respect to the diaphragm in response to temperature changes. The latter technique is used to reduce the offset error of static sensors or the sensitivity error of dynamic sensors.

Temperature compensated fiber-optic pressure sensor

Fuel injectors ( ) for internal combustion engines are modified and equipped with fiber optic fuel pressure sensors ( ) and fiber optic combustion pressure sensors ( ). The combustion pressure sensors ( ) are located in separate channels ( ) formed in the fuel injectors with the lower portion ( ) of the channels leading to the combustion chambers. Above the combustion pressure sensors ( ) are fiber optic leads ( ). In the preferred embodiments the sensors ( ) are equipped with diaphragms ( ) of novel shape ( ) and employ multiple pairs of fibers ( ), temperature sensitive components ( ) and novel compensation and status monitoring circuits (FIGS. ).

Fiber optic combustion pressure sensors for engine knock and misfire

Integrated fiber optic combustion pressure sensor

Compensation and health monitoring techniques and devices for fiber optic intensity modulated sensors provide automatic adjustment of light intensity in order to maintain continuous calibration of the fiber optic sensors in the presence of undesirable environmental or handling conditions. These undesirable conditions may arise from such factors as fiber bending, optical connector mechanical and thermal instabilities, extreme temperatures at sensors, and changes in optical coupling between optical sources (e.g., light emitting diodes) and detectors (e.g., PIN photodiodes) and the optical fibers. Through light intensity normalization, the new techniques enable a continuous calibrated sensor output and sensor health monitoring by continuous or intermittent observation of the light emitting diode current.

Compensation and status monitoring devices for fiber optic

A cup shaped diaphragm having varying thicknesses reduces stress on the diaphragm and increases reliability of a fiber optic diaphragm sensor. The hermetic seal between the optical fiber and the ferrule body is removed from proximity of the diaphragm and is located near the opposite end of the ferrule. The effects on the ferrule of overpressure on the diaphragm are controlled by angling a portion of the ferrule tip adjacent the diaphragm. A method of sealing and locating the optical fiber to the ferrule of the sensor is described.

Fiber optic combustion pressure sensor with improved long-term

An improved fiberoptic pressure sensing system is disclosed by tapering the tip end of an optical fiber, or alternatively, by tapering or bundling a fiber or group of fibers within a connector. By selectively joining together fibers with a taper while tailoring numerical apertures of the connected fibers, a fiberoptic pressure sensing system is provided with an enhanced ability to increase sensitivity and signal-to-noise performance.

Fiberoptic sensor using tapered and bundled fibers

A washer configuration fiber optic sensor comprising radial ridges in the cavity between the washer halves and an optical fiber spiralled to a terminating end within the cavity. The terminating end is mirrored and an optical filter is inserted in the fiber path adjacent the fiber entrance to the washer. Changing compression loads on the washer microbend the fiber and modulate the measuring light beam admired to the fiber and reflected back through the fiber. The optical filter is located in a connection between the washer and a transmitting fiber. The transmitting fiber both delivers light to the washer and collects light back from the washer. The connector is configured to deliver the measuring light beam to both the core and cladding of the fiber in the washer. However, the connector is configured to strip away the portion of the reflected light beam otherwise delivered to the cladding of the transmitting fiber. A reference light beam of differing wavelength is reflected by the filter. The overall result is enhanced discrimination over noise in the sensor.

Fiber optic microbend sensor for engine knock and misfire detection

An improved intensity-encoded fiber optic sensor incorporating novel drift correction and filtering means is disclosed. The first embodiments of the invention relate to means for removing unwanted higher-order core and cladding modes from an intensity-encoded signal in an optical fiber using mode strippers and mode filters located strategically at various points in the sensing system. The second set of improvements in the invention relate to an improved technique for long-term temporal drift cancellation in a fiber optic pressure sensor by periodically applying pressure to the sensor tip in order to ascertain the measured voltage at which the sensor diaphragm contacts other elements of the sensor. This measured voltage is subtracted from an initial calibration voltage, and the result is applied to the measured signal as a constant correction term.

Fiberoptic pressure sensor having drift correction means for insitu

The modulation depth of a fiber optic diaphragm sensor is increased by tapering the tip end of the optical fiber or fiber bundle. In a second embodiment, the modulation depth is increased by mechanically leveraging the diaphragm movement relative to the tip end of the optical fiber or fiber bundle. In either embodiment, the operating temperature of the tip end of the optical fiber or fiber bundle can be reduced relative to the operating temperature of the diaphragm. Thus, the diaphragm sensor can be directly exposed to combustion temperatures in an internal combustion engine and advantageously the sensor can be embodied in a spark plug adjacent the electrodes.

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Bloomfield Hills, MI, United States of America

Marek T Wlodarczyk