Electric lamp and discharge devices – Spark plugs – Particular electrode structure or spacing
Reexamination Certificate
1998-06-12
2001-03-20
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Spark plugs
Particular electrode structure or spacing
C313S140000, C313S118000
Reexamination Certificate
active
06204594
ABSTRACT:
TECHNICAL FIELD
The invention relates to spark plugs, and, more particularly, to spark plugs having pressure sensors.
BACKGROUND
Pressure sensors have been placed in various locations relative to the cylinder chambers of internal combustion engines to monitor the pressures in the chambers during operation. For example, a shielded piezo-electric pressure sensor probe has been installed in a hole bored in the cylinder head for the purpose of holding the pressure sensor probe.
Sensors also have been integrated into spark plugs as an alternative to drilling holes in the cylinder head. For example, Lindner, U.S. Pat. No. 4,489,596, describes a spark plug arrangement having plates positioned within the spark plug. The plates include different types of sensors, such as a pressure sensor, a temperature sensor, and a gas composition sensor. Similarly, Steinke, U.S. Pat. No. 4,969,353, describes a spark plug having a bore extending through an outer portion of the spark plug so that a pressure sensor may be located within the bore. The central electrode is positioned nonconcentrically in the outer portion to provide space for accommodating the sensors.
Wlodarczyk, PCT Application No. PCT/US96/04637, describes a spark plug having a bore extending through an outer portion of the spark plug and containing a fiber optic diaphragm sensor. The diaphragm sensor may be exposed directly to the combustion gases within the engine cylinder.
SUMMARY
The invention provides a simple and economical way of monitoring the internal pressure of an engine cylinder.
In one general aspect, the invention features a spark plug having a sensor in an outer shell. The outer shell has a central longitudinal axis and defines a first bore extending along the central longitudinal axis and a second bore offset from the central longitudinal axis. The sensor is located in the second bore. An insulative core is positioned in the first bore and defines a third bore concentric with the first bore. A firing electrode is positioned in and has a firing end extending beyond the third bore. A ground electrode that includes a firing surface is located adjacent to the firing end of the first electrode.
Embodiments may include one or more of the following features. For example, the second bore may include a first section terminating at a first opening and a second section connected to the first section and terminating at a second opening. The first and second sections may connect at an angle less than 180°. The first opening may be located adjacent to an end of a threaded section of the outer shell and the second opening may be located adjacent to an opposite end of the threaded section of the outer shell. The second bore may have an opening adjacent to a firing end of the spark plug. The sensor may be configured to measure pressure.
Performance of a combustion engine may be monitored by installing the spark plug in a combustion cylinder of the engine. The sensor then is connected to a monitoring circuit, and the output of the monitoring circuit is monitored. For example, the output may be a display of pressure in the combustion cylinder.
Other features and advantages will be apparent from the following description, including the drawings, and from the claims.
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R.H. Kuratle, “Measuring Spark Plugs with Integrated Cylinder Pressure Sensor”, Piezo-Instrumentation Kistler IMechE 1993, C465/019/93, pp. 1-8 (no month).
Gang He, et al., “Evaluation of a Spark-Plug-Integrated Fiber-Optic Combustion Pressure Sensor”, Sae Technical Paper Series, Feb. 28-Mar. 3, 1994, 940381, pp. 207-214 (no month).
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Cooper Automotive Products, Inc.
Patel Ashok
Reising Ethington, Barnes, Kisselle, Learman & McCulloch, P.C.
Williams Joseph
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