Electricity: measuring and testing – Internal-combustion engine ignition system or device – In situ testing of spark plug
Patent
1993-05-07
1995-08-01
O'Shea, Sandra L.
Electricity: measuring and testing
Internal-combustion engine ignition system or device
In situ testing of spark plug
F02P 1712
Patent
active
054382688
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an ignition system for internal combustion engines.
More particularly, it relates to a circuit arrangement for ignition systems for detecting an arc voltage at a spark plug, which voltage is transformed onto a primary side of an ignition coil.
An ignition system is already known from U.S. Pat. No. 4,918,389 or from the corresponding EP-A-0,344,349, and in this the monitoring of the ignition system is carried out by means of a primary-side monitoring of the spark duration. The disadvantage of this method, however, is that it does not give exact information on the combustion trend, in order thereby to draw conclusions as to the functioning of the ignition system and/or injection system. Malfunctions therefore cannot be detected reliably, and because of this an increased exchange of harmful substances can occur and the catalyst be put at risk.
To satisfy the exhaust-gas value requirements of the environmental authorities, the aim is to develop ignition controls which guarantee the least possible ejection of harmful substances in four-stroke petrol engines.
One possibility of ignition and explosion detection is afforded by means of a pressure sensor or optical sensor. However, such function monitoring by the sensors additionally incorporated in the ignition system entails high cost.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an ignition system for internal combustion engines, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a circuit arrangement for ignition systems of the above-mentioned type, in which the pnp type transistor is connected on the base side to the battery voltage, in that a resistor is assigned as an emitter follower to the pnp-type transistor and in that the latter, with its collector connection, feeds to a measuring element which is designed as a resistor, a collector current which is proportional to the arc voltage.
When the circuit arrangement is designed in accordance with the present invention, the advantage of such an arrangement is that there is generated a current which is proportional to the arc voltage and is monitored via a measuring member and by means of which exact information on the combustion trend is obtained.
In accordance with a further feature of the invention, it is especially advantageous if the resistors used have the same temperature coefficient in order to prevent temperature influences.
A further advantage is the decoupling of the voltage signal and the feed of the control signal for the ignition transistor by way of a signal line. The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the basic circuit for detecting the arc voltage and FIG. 2 the basic circuit in modified form.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The basic circuit, illustrated in FIG. 1, for detecting the arc voltage shows an ignition coil 1 consisting of a primary winding 2 and of a secondary winding 3 which is connected to a spark plug 4 for the transmission of the high voltage. The primary winding 2 is connected, on the one hand, to a battery voltage U.sub.B by way of a feed line 5 and, on the other hand, to earth potential by way of a feed line 6 and by way of an ignition transistor 7. The feed line 5 is connected to the base of a pnp transistor 8, whilst the latter is connected on the emitter side to the feed line 6 by way of a resistor 9 serving as an emitter follower. On the collector side, the pnp transistor 8 is assigned a resistor 10 w
REFERENCES:
patent: 4918389 (1990-04-01), Schleupen et al.
patent: 5156127 (1992-10-01), Ghaem
patent: 5226394 (1993-07-01), Shimasaki et al.
patent: 5237279 (1993-08-01), Shimasaki et al.
Bentel Ulrich
Heyke Klaus
Nelle Ulrich
Schleupen Richard
Edmonds Warren S.
O'Shea Sandra L.
Robert & Bosch GmbH
Striker Michael J.
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