Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1992-01-21
1993-11-30
Dolinar, Andrew M.
Internal-combustion engines
Charge forming device
Fuel injection system
123424, 123149C, F02P 108
Patent
active
052655733
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an inductive discharge ignition system for internal combustion engines.
Inductive discharge systems for internal combustion engines are known. Essentially, they use a permanent magnet connected to the crankshaft so that it rotates synchronously with it. The rotating magnet is faced by an ignition coil wound on a magnetic core and comprising a primary winding and a secondary winding. The secondary winding is connected to the electrodes of a spark plug, and the primary winding is connected to an electronic circuit which interrupts it. This interruption is controlled by a small control coil generally located in proximity to the ignition coil. In practice the engine rotation, and thus the relative movement between the permanent magnet and the ignition coil, induces an electromotive force in the primary winding of this latter, to cause circulation of a current which is suddenly interrupted by the electronic circuit when the permanent magnet passes in front of the control coil. The sudden and considerable flux variation which occurs on interruption of the primary current in the ignition coil induces a high secondary voltage which triggers the spark between the spark plug electrodes.
The shape of the various parts and their locations are determined such that the primary current interruption takes place when this current is at its maximum value, and in synchronism with the operating cycle of the internal combustion engine.
However, in practice the petrol-air mixture requires a certain time to ignite, and it is therefore necessary for the ignition command, i.e. the interruption in the primary circuit of the ignition coil, to take place with a certain advance relative to the predetermined moment of explosion. This is generally obtained by positioning the control coil in angular advance of that position of the permanent magnet shaft which corresponds to the top dead center of the relative cylinder.
Again, as the time required for the petrol-air mixture to burn completely is substantially constant whereas the advance time, i.e. the time interval between the moment in which the permanent magnet passes in front of the control coil and the moment corresponding to said top dead center, is related to the engine rotational speed, this adjustment system cannot be effective both at high and low engine speed.
Two methods are currently used to obviate this drawback. One of this consists of inducing the interruption in the primary current by means of a microprocessor or in any event by a sophisticated electronic circuit which takes account of the engine rotational speed and adjusts the ignition advance on this basis. This methods is without doubt valid, but involves a high constructional cost and the need for a central electronic control unit, and for these reasons cannot be advantageously used in small internal combustion enginees, in which its cost and overall size impose very restrictive limits.
Another known methods currently used for small internal combustion engines is to set the ignition advance to correspond to maximum rotational speed, i.e. to normal operating conditions, and to use a controlled discharge transistor in the electronic primary current interruption circuit to ensure operation in proper time.
The main drawback of this method is that at speeds other than the maximum speed, and in particular on starting, ignition takes place too soon before the piston has reached its top dead center, resulting in kick-back which is highly undesirable not only because of the stress to which the engine is subjected but also of its effect on the operator, who generally starts the engine manually.
DE-A-2 638 616 discloses an inductive discharge ignition system for internal combustion engines comprising a permanent magnet, an ignition coil, a control coil and a controlled discharge electronic circuit connected in series with the primary winding of the ignition coil. The core of the control coil consist of a portion of the core of the ignition coil extending tangentially to the movement of the permanent ma
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Dolinar Andrew M.
I D M S.R.L.
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