Internal-combustion engines – High tension ignition system – Current or voltage sensing in coil primary
Patent
1990-04-19
1991-09-24
Nelli, Raymond A.
Internal-combustion engines
High tension ignition system
Current or voltage sensing in coil primary
F02P 312
Patent
active
050505734
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to ignition devices for internal combustion engines and, in particular, to ignition devices employing transistors in the output stages thereof.
BACKGROUND INFORMATION
An ignition device for an internal combustion engine is shown in German Patent No. 28 25 830. The ignition device uses a pnp-transistor in its output stage. The primary winding of an ignition transformer is coupled to the collector terminal of the transistor. The emitter terminal of the transistor is coupled to ground by a current measuring resistor. During the operation of the ignition device, there are high power losses at the output stage, which are removed from the collector terminal to a heat sink. However, the collector terminal must also be electrically insulated from the heat sink when a square-shaped voltage appears during the shut-down process. These opposing requirements have been fulfilled by using an electrically-insulating ceramic layer having good thermal conductivity located between the collector terminal and the heat sink. One problem with the ceramic layer, however, is that it makes the assembly of the ignition device considerably more expensive and often does not compensate for the alternating thermal stresses occurring particularly in high power ignition devices.
Ignition devices are also shown in French Patent Nos. 2,407,363 and 2,318,323, U.S. Pat. Nos. 3,945,362 and 4,106,462, and German Patent No. 3,231,125, wherein the emitter terminals of the transistors in the output stages are coupled to ground connections.
SUMMARY OF THE INVENTION
The present invention is directed to an ignition device for an internal combustion engine. The ignition device comprises an ignition transformer including a primary winding and a secondary winding. A direct current source is coupled to the primary winding for supplying electric current thereto. First means are coupled to the primary winding for controlling the flow of electric current therethrough. The first means includes a preselector stage and an output stage. The output stage includes a first transistor having a first conductivity. The collector terminal of the first transistor is directly coupled to a ground connection of the ignition device.
The ignition device further comprises second means coupled between the preselector stage and the output stage for decoupling the output stage from the preselector stage and preventing the uncontrolled starting of the output stage. The second means includes a second transistor. The collector terminal thereof is coupled to the base terminal to the first transistor; the emitter terminal thereof is coupled to the emitter terminal of the first transistor; and the base terminal thereof is coupled to the positive terminal of the direct current source. The second means further includes a first resistor coupled between the base terminal of the second transistor and the positive terminal of the direct current source.
In one ignition device of the present invention, the second means further includes a third transistor having a second conductivity. The collector terminal of the third transistor is coupled to the base terminal of the first transistor. The emitter terminal of the third transistor is coupled to a ground connection of the ignition device. The preselector stage is coupled to the base terminal of the third transistor to control that transistor.
In another ignition device of the present invention, the output stage further includes an electric current measuring device coupled to the primary winding and to the preselector stage. The current measuring device measures the electric current flowing through the primary winding. It in turn transmits signals indicative thereof to the preselector stage. The current measuring device includes a second resistor coupled to the primary winding and to the preselector stage. The second resistor transmits signals to the preselector stage indicative of the voltage drop across the primary winding.
One ignition device of the present invention further compris
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Meinders Horst
Nelle Ulrich
Nelli Raymond A.
Robert & Bosch GmbH
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