Electricity: measuring and testing – Internal-combustion engine ignition system or device – Apparatus for coupling a measuring instrument to an ignition...
Patent
1993-05-20
1995-08-22
O'Shea, Sandra L.
Electricity: measuring and testing
Internal-combustion engine ignition system or device
Apparatus for coupling a measuring instrument to an ignition...
324388, F02P 1700
Patent
active
054443768
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on a device for detecting signals in an ignition system. The ignition system contains two ignition coils, and a capacitive signal coupling provided on the coils.
U.S. Pat. No. 4,795,979 discloses a device for determining the ignition pulse provided for a specific cylinder of an internal combustion engine. The ignition system contains a plurality of ignition coils, in each case two spark plugs being connected to the secondary windings of the ignition coils. This distributorless ignition system produces an ignition spark at each spark plug at each rotation of the internal combustion engine. In four-stroke internal combustion engines, the ignition sparks are accordingly produced both in the working stroke and in the discharge stroke. For diagnosing this ignition system, three capacitive signal output couplings are provided which are arranged on the ignition cables leading from the ignition coils to the spark plugs. The known device requires the ignition cables to be accessible so that the sensors can be attached. The extracted signals are fed into different signal evaluation circuits.
U.S. Pat No. 3,959,725 discloses the arrangement of a capacitive ignition voltage sensor on a distributor housing which, in addition to the distributor, also contains the ignition coil. The capacitive signal extraction is effected with an electrically conductive surface which is attached to the distributor in a suitable manner. This known device is designed for the diagnosis of a single-coil ignition system.
SUMMARY OF THE INVENTION
The invention is based on the object of disclosing a simple device with a low cabling outlay for the diagnosis of multi-coil ignition systems.
This object is achieved by a circuit arrangement connected to the capacitive signal coupling means. The circuit includes an output and means for combining the signals extracted from the ignition coils. The combined signals are sent to the output. Further, a plurality of second capacitive signal coupling means for potential isolation are provided between the means for combining and a respective ignition coil.
The device according to the invention for detecting signals in an ignition coil system which contains more than one ignition coil has the advantage of simple adaptation. It is particularly advantageous that conventional ignition cables no longer have to be present between the ignition coils and the spark plugs. The means for the capacitive signal extraction are suitably arranged directly on the ignition coils or on the housings which contain the ignition coils. The arrangement for combining the extracted signals, which arrangement is also provided according to the invention, reduces the outlay on cabling. It is only necessary to have connections between the capacitive signal output couplings and the circuit arrangement, from where merely a single ongoing line can be provided. The circuit arrangement is to be arranged in the direct vicinity of the ignition system so that a short line routing, in particular of the single lines leading to the capacitive signal output couplings is possible.
The means for capacitive signal extraction provide signals which correspond in each case to the high voltage at the ignition coils. These signals are combined in the circuit arrangement and can be analysed in a further diagnostic device. The device according to the invention is suitable for diagnosis in multi-coil ignition systems, the secondary windings of the ignition coils being wired as desired. For example secondary windings which are earthed on one side and have a high-voltage terminal can be provided and also arrangements with spark plug terminals at both ends of the secondary windings.
A particularly advantageous further development provides for further capacitive couplings to be provided in each case between the means for capacitive signal extraction and the circuit arrangement for combining the extracted signals. The essential advantage of these further capacitive couplings resides in the potential isolation b
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Bumen Werner
Dittmann Karl-Heinz
O'Shea Sandra L.
Phillips Roger
Robert & Bosch GmbH
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