Internal-combustion engines – High tension ignition system – Power supply – ignition coil primary – and interrupter element...
Reexamination Certificate
2000-03-23
2001-07-10
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
High tension ignition system
Power supply, ignition coil primary, and interrupter element...
C315S2090SC, C123S655000, C123S650000, C327S432000, C327S564000
Reexamination Certificate
active
06257216
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates, in general, to a device for suppressing undesired ignitions in a spark ignition engine. Such a device is known from EP 0 370 301 A1.
If an ignition coil is energized by an ignition output stage when a spark ignition engine is being controlled, the switch-on signal edge induces a voltage on the secondary side of the ignition coil when the primary circuit is switched on. This voltage is capable of generating an ignition spark at the spark plug given specific operating states of the spark ignition engine. Such an ignition spark can lead to undesired ignition of the petrol/air mixture, and can damage the engine because of an excessively early ignition angle.
An ignition coil is a system that is capable of oscillating and that is made of inductors and parasitic capacitors. If the system has a switch-on signal edge applied to it, among other things, the secondary winding is excited so that it undergoes damped oscillation, which can reach a voltage amplitude that is virtually twice as high as the voltage determined by the transformer property of the ignition coil.
For this reason, efforts are made to slow down the switching-on process of the ignition coil in such a way that no oscillation is excited, and the secondary voltage thus assumes only the voltage value that is determined by the transformer property of the ignition coil.
In the circuit that is known from EP 0 370 301 A1, a passive damping network is used that is configured between the positive pole and the negative pole of the voltage source of a vehicle's electrical system. The passive damping network is made of a series circuit including two resistors and a capacitor and has an output that is connected to the connecting point between the ignition switch and primary winding of the ignition coil. The fact that the voltage at the capacitor that discharges via the ignition switch decreases when the ignition switch is switched on slows down the voltage drop at the ignition switch. For this purpose, a large capacitance value of the capacitor is already necessary for the anticipated current limiting of the primary current. The capacitor without such current limiting would have to assume unrealistically high values in order to be able to cause the switching-on signal edge of the primary current to slow down.
Further circuits of this type can be found in DE 29 27 058 A1 and DE 196 12 984 A1.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a device for suppressing undesired ignitions which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type in such a way that a significantly lower valued capacitor is required.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for suppressing undesired ignitions in a spark ignition engine. The device includes a voltage source having a positive pole and a negative pole, an ignition switch having a base and a collector, and at least one spark plug. Additionally, an ignition coil having a primary winding and a secondary winding is provided. The secondary winding is connected to the spark plug. The primary winding and the ignition switch are connected in series between the positive pole and the negative pole of the voltage source. A control circuit is provided for switching the ignition switch. A first resistor connects the control circuit to the base. A second resistor having a first terminal and a second terminal is provided. The second terminal is connected to the negative pole. A capacitor has a first terminal connected to the collector and a second terminal connected to the first terminal of the second resistor. A diode is provided for conducting a current away from the base. The diode is connected between the second terminal of the capacitor and the base.
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 device for suppressing undesired ignitions in a spark ignition 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 of the invention, however, 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.
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patent: 196 12 984 A1 (1996-09-01), None
patent: 0 323 412 (1989-07-01), None
patent: 0 370 301 (1990-05-01), None
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Japanese Patent Abstract No. 07243369 (Naoto), dated Sep. 19, 1995.
Japanese Patent Abstract No. 09209892 (Ryoichi), dated Aug. 12, 1997.
Japanese Patent Abstract No. 09177647 (Noboru), dated Jul. 11, 1997.
Fisch Alfons
Forster Ralf
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
Vo Hieu T
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