Electricity: measuring and testing – Internal-combustion engine ignition system or device – Coil
Patent
1997-09-23
1999-05-25
Do, Diep N.
Electricity: measuring and testing
Internal-combustion engine ignition system or device
Coil
324399, 73116, 123435, F02P 1700, G01M 1500
Patent
active
059072431
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a measuring circuit for sensing ionisation within a cylinder of a combustion engine, where the combustion is initiated with a spark plug.
STATE OF THE ART
In U.S. Pat. No. 4,648,367, a measuring circuit for sensing ionisation in a Otto-engine is shown. By the application of a substantially constant bias voltage in the grounded connection of the secondary winding of the ignition coil, the ionisation within the combustion chamber may be detected. The detection is obtained via a measuring resistance connected in series between a capacitor and ground, which measuring resistance is protected by a diode connected in parallel. The diode will by-pass the spark current and the measuring capacitance and will promote a current, i.e. the ionisation current, via the spark plug gap.
In U.S. Pat. No. 5,271,268, the same concept is patented. In a preferred embodiment, the induced voltage in the secondary winding is used as a source for charging the measuring capacitor to a substantial constant measuring voltage.
In both of these solutions, the spark current will be conducted to a ground connection also used for the measuring resistance. The spark current is in the order of some 100 m Ampere, and the ionisation current only reaches an order of some .mu.Ampere. In order to be able to detect the ionisation current in a reliable manner, the detection should be made as close to the measuring resistance as possible, and the electronic circuitry should be designed with sufficient sensitivity in order to detect the relatively low order of variations in the ionisation current. If for example the measuring signal at the output 6 in above mentioned U.S. Pat. No. 5,271,268 should be forwarded to a central processor located at a protected location in the engine compartment, possibly the firewall or inside the passenger compartment, then there is a risk that the signal is subject to interference. The signal processing is thus usually handled as close as possible to the measuring resistance. Integration of signal processing circuitry with the ignition coil has been designed in the customary fashion with protective diodes and measuring resistance integrated on the same circuit board having a common ground connection. Another disadvantage is that the primary current developed in the primary winding of the ignition coil in most cases is conducted via the engine casing and a ground strap back to battery ground, which results in an extended primary current circuit with a large physical area. The Primary circuit will then become extremely susceptible to electromagnetic interference from other units, and will itself emit interference of a high order. Emitted interference could then affect other systems and interference received could distort ion current measurements.
SUMMARY OF THE INVENTION
One object of the invention is that measuring circuits used for sensing ion currents control spark currents such that the electronic circuitry used for sensing ion currents would not be affected by the spark currents.
Another object is that the parts of the ignition system in a convenient manner could be designed such that the electromagnetic interference emitted from the ignition system could be reduced.
Yet another object with a further developed embodiment is that the spark current and the primary current are divided into two physically separated electric circuits, both designed with a limited physical size. The electric circuits could then be designed with a low susceptibility for external interference which in itself will reduce emitted interference.
The foregoing and other objects are accomplished in accordance with the present invention by a measuring circuit which includes a measuring resistance, a rectifying element in parallel with the measuring resistance and a measuring voltage source, wherein the rectifier element is connected directly to engine ground without passing through the ground plane of the measuring circuit.
By the inventive measuring circuit may the spark current be
REFERENCES:
patent: 4359893 (1982-11-01), Kizler et al.
patent: 5087882 (1992-02-01), Iwata
patent: 5207200 (1993-05-01), Iwata
patent: 5271268 (1993-12-01), Ikeuchi et al.
patent: 5396176 (1995-03-01), Ishii et al.
patent: 5444375 (1995-08-01), Ohsawa et al.
patent: 5769049 (1998-06-01), Nytomt et al.
Bjorquist Gunnar
Goras Anders
Do Diep N.
Mecel AB
LandOfFree
Measuring circuit for sensing ionisation within a cylinder of a does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Measuring circuit for sensing ionisation within a cylinder of a , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Measuring circuit for sensing ionisation within a cylinder of a will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-403078