Measuring and testing – Fluid pressure gauge – Photoelectric
Patent
1999-06-17
2000-09-26
Patel, Harshad
Measuring and testing
Fluid pressure gauge
Photoelectric
25023119, 313119, G01L 900, G01J 156, H01T 1300
Patent
active
061229717
DESCRIPTION:
BRIEF SUMMARY
My prior patent applications dealing with fiber optic pressure sensors integrated with spark plugs are Ser. No. 08/086,245, now U.S. Pat. No. 5,390,546 for Fiber Optic Diaphragm Sensors for Engine Knock and Misfire Detection; Ser. No. 08/390,970 for a Fiber Optic Combustion Pressure Sensor with Improved Long-Term Reliability; Ser. No. 08/392,315 for a Spark Plug Integrated Fiber Optic Combustion Pressure Sensor with an Integrated High Voltage Fiber Optic Connector; and PCT/US96/04637 for Fiber Optic Combustion Pressure Sensors for Engine Knock and Misfire Detection and are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The field of the invention pertains to fiber optic sensors that are sensitive to pressure or stress in a manner that causes a beam of light to be reflectively modulated in response to changes in pressure or stress on the sensor. Determination of cylinder pressure and the sensors that report the pressure are currently sought by automotive manufacturers for engine control and monitoring applications. The desired product must be inexpensive and meet stringent quality, durability and reliability requirements. Additionally, the sensor package must be robust and easily routed for placement into an engine or engine head.
Ideally, the most desirable manner in which to introduce a pressure sensor into an engine is through an existing cylinder opening. By integrating a sensor with an existing device mounted into a cylinder hole, sensors can be introduced inexpensively into new engines as well as being provided for retrofit to engines already in use.
A spark plug represents a desirable device for integration with a pressure sensor as the spark plug partially enters the engine and thusly provides a preexisting opening into the engine. While special pressure measurement spark plugs have been used in engine research with expensive sensors, such research devices are not suitable for use in production engines. Fiber optic sensors are the best candidates for integration with a spark plug. non-metallic construction and immunity to electromagnetic interference are the main advantages of fiber optic sensors over more conventional devices such as piezoelectric or piezoresistive devices.
SUMMARY OF THE INVENTION
The invention disclosed herein is an optical fiber diaphragm sensor that measures cylinder pressure before, at and after ignition of the combustion charge in combination with the spark plug and boot. Integration of the sensor to a boot surrounding the conductor of the spark plug and routing the optical fiber through the boot and cylinder pressure through a channel in the spark plug offers benefits. Effectively, the spark plug conductor is protected by the boot and the boot provides routing for the optical fiber.
The invention discloses a combustion pressure sensor integrated with a spark plug connector for applications in passenger car and industrial engines. In a preferred version, the sensor is non-electrical, such as a fiber optic. Spark plug modification and a novel sensor mounting technique are also described. This novel approach can be used with current ignition systems based upon a single coil or with multiple on-spark plug mounted coils.
The pertinent aspect of this novel technique is the installation of a pressure sensor into the spark plug. Rather than mounting the sensor into a spark plug first and then threading the spark plug into an engine head, the spark plug is threaded into the engine first (without the sensor), as is conventionally done. The sensor connector assembly is then pushed on in the same way as a conventional spark plug connector or an ignition coil connector combination is installed. The above-described technique provides a significant improvement over prior known techniques that require mounting a sensor into a spark plug first, then threading the spark plug into an engine head and finally installing separate electric high tension and sensor connectors onto the spark plug.
In the prior approach, a special installation tool is needed to achieve placement of
REFERENCES:
patent: 4711246 (1987-12-01), Alderson
patent: 5200610 (1993-04-01), Zuckerwar et al.
patent: 5600070 (1997-02-01), Wlodarczyk
Aw-Musse Abdullahi
Deimen James M.
Patel Harshad
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