Electricity: measuring and testing – Internal-combustion engine ignition system or device – In situ testing of spark plug
Patent
1991-06-26
1993-08-17
Strecker, Gerard R.
Electricity: measuring and testing
Internal-combustion engine ignition system or device
In situ testing of spark plug
324397, 324402, 313128, 123169R, F02P 1700, H01T 1322
Patent
active
052372804
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a sensor for measurement of ignition current in an internal combustion engine to monitor combustion, especially in the engine of a motor vehicle. Combustion sensors for monitoring combustion in a cylinder of an internal combustion engine are known, which, in part, also function as a spark plug and have a pin-shaped central electrode and a ground electrode.
Spark plugs are known in which knocking in an internal combustion engine is detected by knock sensors and an appropriate evaluation circuit. These knock sensors can, for example, be located in the housing of the spark plug or can be fitted as pressure pick-up rings in the clamping region of the spark plugs. In all these designs, however, the earth electrode of the spark plug is designed as an extension of the housing. These solutions are very complex and expensive. Furthermore, extraneous signals, such as the rattling of valves, are recorded along with the pressure waves and body-borne waves caused by combustion. Evaluation of the ignition current in these solutions is made more difficult by the fact that with threaded spark plugs, the thermal value of the engine block has a negative and not accurately controllable influence on the shape of the measurement curve.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a combustion sensor for an internal combustion engine which has none of the above-mentioned disadvantages.
This object, and others which will be made more apparent hereinafter, is attained in an apparatus for measuring spark plug ignition current to monitor combustion in an internal combustion engine, comprising a spark plug having a spark plug housing holding two electrodes, the electrodes consisting of a pin-shaped central electrode located in the spark plug housing and a ground electrode held in the spark plug housing insulated from the central electrode so as to be arranged to cooperate with the central electrode.
According to the invention, the apparatus further comprises at least one current measuring means for measuring an ignition current of the spark plug, the ground electrode being connected electrically to the at least one current measuring means, the at least one current measuring means being grounded so that the ground electrode is grounded via the at least one current measuring means and the ignition current flows through the at least one current measuring means.
In contrast, the sensor according to the invention has the advantage that conclusions about the combustion, about misfires during the combustion and damage of various types, e.g. defective spark plug sockets, are possible by measuring the ignition current. It is possible to monitor the ignition and also to assess the quality of the ignition of the mixture and the course of combustion. Because of a grid-type structure of the sleeve which comprises the ground electrode, the sintered insulating body can continue to be manufactured in one operation. The thermal contact between the ground electrode in the screwed-in position can be controlled in a simple manner and determined in accordance with the conditions of the application. Extension of the sleeve into the dead space of the spark plug permits electrical contact underneath the leakage current barrier.
The ground electrode can also include a sleeve portion and at its end closest to a combustion space in the engine block it can have a hook shape and can be bent toward and over the central electrode. The sleeve can also be formed like a grid. The measuring resistor can be connected to either the engine block or the spark plug housing to ground it and the ground electrode connected to it. The measuring resistor can be located in the spark plug socket and its electrical connecting lines can be fed from the housing through the spark plug socket.
BRIEF DESCRIPTION OF THE DRAWING
The objects, features and advantages of the present invention will now be illustrated in more detail by the following detailed description, reference being made t
REFERENCES:
patent: 2963620 (1960-12-01), Knudson
patent: 2969500 (1961-01-01), Andert
patent: 3235763 (1966-02-01), Candelise et al.
patent: 3238447 (1966-03-01), Bychinsky
patent: 3343366 (1967-09-01), Siegler
Arnold Herbert
Horbelt Michael
Do Diep
Robert & Bosch GmbH
Strecker Gerard R.
Striker Michael J.
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