Electricity: measuring and testing – Internal-combustion engine ignition system or device – Electronic ignition system
Reexamination Certificate
1998-09-11
2001-02-13
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Internal-combustion engine ignition system or device
Electronic ignition system
C073S116070, C123S630000, C123S644000
Reexamination Certificate
active
06188224
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The subject of the present invention is a process and a device for diagnosing an ignition system of an internal combustion engine, more particularly adapted to the diagnosis of ignition systems having multiple coils.
The prior art discloses numerous devices for the diagnosis of ignition systems able to diagnose a short circuit or an open circuit of a primary circuit of a coil. Those devices generally consist of an apparatus for measuring a current flowing through the primary circuit of the coil and through an associated switch, as well as a device, generally analog, for comparing the current with a reference value. However, those devices are not suitable when multiple coils have to be controlled at least partially simultaneously. It is then necessary to employ one diagnostic device per ignition coil so that the current flowing through another coil should not disturb a previous current measurement. Moreover, those diagnostic devices need to be matched accurately to the characteristics of the coil to be monitored and have to be matched as a function of the variations in those characteristics, due either to manufacturing scatter, or to variations in operating conditions.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a process for the diagnosis of an ignition device of an internal combustion engine and a device for performing the diagnosis which overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, which is easily adaptable regardless of the type of coil employed and which allows diagnosis even in the case of a system having multiple ignition coils.
With the foregoing and other objects in view there is provided, in accordance with the invention, in a process for diagnosing an ignition device of an internal combustion engine, the ignition device having at least one ignition coil, a switch connected to the at least one ignition coil, a control computer emitting at least one control signal for controlling the switch, and a current measuring means for measuring a current flowing through the switch, the improvement which includes: a) periodically extracting samples of a value of the current flowing through the switch with the current measuring means; b) determining a moment of extraction and a conducting state of a circuit formed of the at least one coil and the switch at the moment of extraction for each of the samples; c) checking if the moment of extraction for each of the samples satisfies at least one temporal condition with respect to the at least one control signal emitted by the control computer; d) comparing each of the samples with a predetermined threshold value if the at least one temporal condition was satisfied during the checking step; and e) deducing a presence and nature of an operating fault of the circuit from results of the comparing step.
The objectives of the invention are achieved, together with others that will be detailed in the description that follows, by a process for the diagnosis of an ignition system for an internal combustion engine. The system includes at least one ignition coil associated with a switch controlled by a signal emitted by a control computer, and a device for measuring the current flowing through the switch. According to the invention, samples of the value of the current are extracted periodically, with each sample are associated a moment of extraction and a coil/switch circuit conduction at the moment of extraction. A check is made as to whether the moment of extraction satisfies at least one temporal condition with respect to at least one control moment emitted by the computer. The sample is compared with a predetermined threshold on the basis of the temporal condition being satisfied, and the presence and the nature of any operating fault in the associated coil/switch circuit is deduced therefrom.
According to a mode of implementation of the process according to the invention, a check is made as to whether the moment of extraction is later than the moment at which the switch is turned on by at least a first lag. The sample is compared with an open-circuit fault threshold, and an open-circuit fault is inferred if the sample is below the open-circuit fault threshold
Advantageously, the steps for associating and checking the moment of extraction are repeated until the last sample is obtained and whose moment of extraction is earlier than the moment of the associated switch being turned off.
According to an advantageous characteristic of the process, when it is applied to a system having at least two coils and their associated switch, and a common device of measurement, a check is made as to whether the moment of extraction is moreover earlier than the moment of turning on of the switch of the next circuit.
According to another characteristic of the process, the first lag is determined as a function of the maximum current desired in the coil, the open-circuit fault threshold and the period of the sampling.
According to another mode of implementation of the process, applied to a system having at least two coil/switch circuits, and a common device for measuring the current flowing through the circuits, a check is made as to whether the moment of extraction of the sample is later on the one hand than the moment of turning on the switch associated with the sample by at least a second lag, and on the other hand than the moment of turning off the switch associated with previous circuit by at least a third lag. The sample is compared with a short-circuit fault threshold, and a short-circuit fault is inferred if the sample is above the short-circuit fault threshold.
With the foregoing and other objects in view there is also provided, in accordance with the invention, in an ignition device having a plurality of circuits each formed of a coil and a switch, a diagnosis apparatus including: current measuring means for measuring a current common to the plurality of circuits; means for determining a moment of events including a moment of extraction of current measuring samples, and a moment of turning on and off a respective switch of the plurality of circuits; storage means for recording at least one collection of values including a current sample, a moment of extraction of the current sample, a reference to a conduction state of each of the plurality of circuits, a set of pre-established threshold values and time lag values, and an instruction set forming part of a piece of software; and calculation and comparison means adapted for executing checking and comparison operations defined according to a process by running and executing the instruction set stored in the storage means.
The invention further discloses a device for implementing the process. The device includes a means of measurement common to a plurality of coil/switch circuits, means for determining the moment of events such as extraction of samples, turning on and off the switches, storage means adapted for recording on the one hand at least one collection of values which consists of a sample, of its moment of extraction and of a reference to an associated coil/switch circuit, on the other hand a set of pre-established values of thresholds and lags, and a set of instructions forming part of a piece of software, calculation and comparison means, adapted for executing the checking and comparison operations defined according to the process by running and executing the instruction set stored in the storage means.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a process for the diagnosis of an ignition device of an internal combustion engine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation o
Blanchard Philippe
Geoffroy Yves
Hannoyer Gilles
Meyer Catherine
Greenberg Laurence A.
Lerner Herbert L.
LeRoux E. P.
Metjahic Safet
Siemens Automotive S.A.
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