Ignition System For An Automotive Engine Having Exhaust Recirculation Arrangement

Abstract

An improved ignition system is herein proposed for use specifically in combination with an automotive engine having an exhaust recirculation system which is adapted to have the exhaust gases recirculated from the engine exhaust system to the engine during predetermined conditions in which toxic nitrogen oxides are produced in the engine in relatively great quantities. the ignition system uses an additional high-tension current generator connected between an ignition power source and an ignition distributor in parallel with a usual high-tension current generator. An electrical circuit arrangement including these two high-tension generators is adapted to fire the air-fuel mixture in the engine with usual energy when the exhaust recirculation system is inoperative and with intensified energy in response to a condition in which the recirculation system is operative.

Description

The present invention is concerned with ignition systems of motor vehicles and, more particularly, the invention relates to an automotive ignition system to be used in combination with an engine having air-pollution reducing means which is adapted to reduce the emission of toxic nitrogen oxides from the motor vehicle engine.

A variety of devices have thus far been proposed to provide a solution to the vehicular air pollution problems of late. One of such air-pollution reducing devices is the means which is adapted to recirculate the engine exhaust gases to the upstream side of the engine intake for the purpose of reducing the nitrogen oxides contained in the exhaust gases. In the nitrogen oxide reducing means of this character, the exhaust gases discharged from the engine are recirculated in a controlled proportion into an engine air-cleaner or an engine intake manifold or any other part upstream of the engine intake for lowering the temperature in the engine combustion chambers to such an extent as to prevent reaction between nitrogen and oxygen in the air-fuel mixture in the combustion chambers.

As a result of the exhaust gases thus recirculated to the engine, it is inevitable that the performance quality of the engine is degraded considerably due to undue reduction in the air-to-fuel ratio of the combustible mixture supplied to the engine and to the unwanted and uneven dilution of the mixture with the recirculated exhaust gases. Control means have therefore been used in order to regulate the flow of the recirculated exhaust gases in accordance with signals which are representative of some predetermined operating conditions of the engine such as for example the working area of the carburetor throttle valve and the vacuum level in the engine intake. By the use of such control means, the engine exhaust gases are recirculated only when the engine is operating under these conditions in which the nitrogen oxides are contained in the exhaust gases in such a proportion as to cause serious pollution of air.

The use of the control means of this nature has still failed to provide a satisfactory solution to the impairment to the performance efficiency of the engine resulting from the recirculation of the exhaust gases. Where, for instance, the engine exhaust gases are recirculated to the air-cleaner, the concentration of oxygen in the air-fuel mixture passed through the carburetor decreases with the result that an excessively rich air-fuel mixture is produced in the carburetor. If, on the other hand, the exhaust gases are recirculated to the engine intake manifold, then the air-fuel mixture is diluted with the exhaust gases and tends to be drawn into the engine combustion chambers before the recirculated exhaust gases are uniformly dispersed in the air-fuel mixture. Thus, whichsoever method of the prior art may be adopted, it is practically impossible to have the air-fuel mixture fired and combusted at a proper efficiency, resulting in a significant decrease in the power output of the engine and in a fluctuation in the engine torque characteristics.

The present invention thus contemplates the provision of a useful solution to these problems which are presently encountered in the automotive engines using exhaust recirculation arrangements.

It is, therefore, an object of the present invention to provide an improved automotive ignition system which is capable of firing the air-fuel mixture appropriately even when the engine exhaust gases are being recirculated from the exhaust system for the purpose to reduce the formation of nitrogen oxides during combustion.

It is another object of the present invention to provide an improved automotive ignition system which is adapted to have the firing performance in the engine combustion chambers increased during a condition in which a proportion of the exhaust gases is being recirculated to the engine.

It is still another object of the present invention to provide an improved automotive ignition system by which the energy to fire the air-fuel mixture in the combustion chambers is augmented in response to an engine operating condition in which a portion of the engine exhaust gases is recirculated to the engine through any part of the fuel mixture supply system which is located upstream of the engine.

It is still another object of the present invention to provide an improved automotive ignition system which is adapted to fire the air-fuel mixture with an increased energy when a portion of the engine exhaust gases is being recirculated to the engine and to restore a normal operating condition when recirculation of a portion of the exhaust gases to the engine is terminated or interrupted.

Yet, it is another object of the present invention to provide an improved vehicular air-pollution reducing arrangement which is adapted to reduce the concentration of the toxic nitrogen oxides in engine exhaust gases without imparing the performance efficiency of the engine throughout the varying operating conditions.

These and other objects of the present invention are advantageously accomplished by an automotive ignition system having first and second high-tension current generating means which are connected in parallel between a source of power and an ignition distributor, and switch means which is responsive to a condition in which a portion of the engine exhaust gases is recirculated. The first high-tension current generating means is adapted to supply the ignition distributor for firing the air-fuel mixture charges with a usual energy in the absence of the exhaust gases recirculated to the engine, while the second high-tension generating means is adapted to supply the distributor for firing the air-fuel mixture charges with an intensified energy when a portion of the exhaust gases is being recirculated from the engine exhaust system to the engine. The switch means may be of the normally-open type which is connected serially between the power source and the second high-tension current generating means so that the first high-tension current generating means is kept actuated irrespective of the operating position of the switch means. The normally-open switch means is adapted to be closed in response to a condition in which a portion of the engine exhaust gases is recirculated, whereby high-tension currents are supplied to the ignition distributor from both the first and the second high-tension current generating means. Or otherwise, the switch means may be of the two-position selector type having an input contact connected to the power source and two output contacts connected respectively to the first and second high-tension generating means. In this instance, it is important that the second high-tension current generating means have a greater capacity than the first means so as to be capable of firing the air-fuel mixture charges with an energy which is higher than the energy that is supplied to the spark plugs from the first high-tension current generator. The two-position selector switch means is biased to a position to provide electrical connection between the power source and the first high-tension current generating means and to keep the second high-tension current generating means disconnected from the power source. Thus, the connection between the second high-tension current generating means and the power source is established and concurrently the connection between the first high-tension current generating means and the power source interrupted with the two-position selector switch means actuated in response to the exhaust recirculated condition.

Features and advantages of the ignition system according to the present invention will become more apparent from the following description taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a schematic circuit diagram illustrating partly in a block form a preferred circuit arrangement of the ignition system according to the present invention; and

FIG. 2 is also a schematic circuit arrangement showing another preferred circuit arrangement of the ignition system herein proposed.

Reference is now made to the drawing, first to FIG. 1. As previously discussed, the ignition system according to the present invention is used in combination with an engine of the particular character in which a portion of the exhaust gases is recirculated to the engine in a controlled fashion. The exhaust recirculation system per se is well known in the art and is herein generally indicated by reference numeral 10 in a block form. Suffice, however, it to say that this exhaust recirculation system 10 is generally made up of a valve interposed between the exhaust system and intake manifold of the engine and a suitable actuator to open and close the valve in a controlled fashion. The exhaust recirculation system 10 is herein assumed to be controlled by a signal A which is delivered from control means 12. This control means 12 is adapted to be responsive to suitable input signals X and Y representing predetermined engine operating conditions in which toxic nitrogen oxides are produced in an excessive concentration in the combustion chambers of the engine. These operating conditions are usually monitored through detection of the working area of the throttle valve of the carburetor and/or the vacuum level in the intake manifold of the engine. The constructions and operations of the exhaust recirculation system 10 and the control means 12 for such system are rather immaterial for understanding the essential nature of the ignition system according to the present invention and, as such, no detailed description thereof will be herein incorporated.

The ignition system includes, as customary, an ignition switch 14 which is connected at one contact to a power source 16 and at the other to a high-tension current generator 18 through a line 20. This high-tension current generator 18 is shown as including primary and secondary windings 18a and 18b, respectively, and supplies high-tension surges determined by contact points 24 to an ignition distributor 20a. The ignition distributor 20a is connected to spark plugs which are commonly designated by reference numeral 22. The primary circuit of the ignition distributor is closed and opened by contact points 24, which may be substituted by an arrangement including a magnetic pick-up and a transistorized control unit where desired. The construction and operation of the ignition system of the above described general nature are well known in the art, so that no detailed description will be herein incorporated. It is, however, to be noted that the high-tension current generator 18 is of the usual capacity which is adapted to actuate the spark plugs 22 to fire the air-fuel mixture charges in the engine cylinders (not shown) with usual energy, viz. the the energy which is appropriate to fire a combustible mixture of a normal air-to-fuel ratio.

In accordance with the present invention wherein the ignition system is used in combination with the air-pollution reducing arrangement of the above described character, a second high-tension current generator 26 is provided so as to actuate the spark plugs 22 when a portion of the exhaust gases is being recirculated directly or indirectly to the intake manifold of the engine. This second high-tension current generator 26 has a primary winding 26a connected through switch means 28 of te normally-open type to the ignition system via the line 20 and a secondary winding 26b connected in parallel with the secondary winding 18b of the first high-tension current generator 18 to the ignition distributor. The normally-open switch means 28 may be constructed and arranged in any desired manner insofar as it is so biased as to assume the open position and arranged to close in response to a signal A which is delivered from the control means 12 to the exhaust recirculation system 10. This switch means 28 is herein shown as having normally open contacts 28a intervening between the ignition switch 14 and the second high-tension current generator 26 and an exciting coil 28b which is connected to an output of the control means 12 through a line 30.

When, thus, the signal A from the control means 12 is absent, the first high-tension current generator 18 is energized from the power source 16 with the ignition switch 14 closed so that the individual spark plugs 22 receive usual high-tension surges from the current generator 18 to fire the air-fuel mixture charges in the engine combustion chambers (not shown) with usual energy.

Under those conditions in which toxic nitrogen oxides are produced in the engine in an excessive concentration, then the control means 12 responds to such condition through detection of the signals X and Y and delivers the signal A at its output. This signal A is supplied to the exhaust recirculation system 10 whereby a portion of the exhaust gases in the engine exhaust system (not shown) is recirculated in a controlled proportion directly or indirectly to the engine intake manifold (not shown) to aid in reducing the amount of nitrogen oxides produced in the engine. At the same time, the signal A from the control means 12 is also supplied to the exciting coil 28b of the normally-open switch means 28 so as to cause the contacts 28a to be closed. The second high-tension current generator 26 is consequently energized from the power source 16 through the ignition switch 14 and supplies through the distributor 20a high-tension surges to the spark plugs 22 in cooperation with the first high-tension current generator 18 which is constantly kept energized. The spark plugs 22 are in this manner enabled to fire the air-fuel mixture charges with increased energy. When the recirculation of a portion of the exhaust gases to the engine terminates, then the actuating signal A impressed upon the switch means 28 disappears so that the exciting coil 28b thereof is de-energized and accordingly the contacts 28a restore the initial open position, disconnecting the second high-tension current generator 26 from the power source 16. The air-fuel mixture charges in the engine combustion chambers are now ignited with the usual energy and, thus, the period of term in which the toxic compounds are produced due to high combustion temperatures can be prevented advantageously and, at the same time, undue wear of the spark plugs 22 due to oxidization by increased high-tension currents can be avoided.

The capacity of the second high-tension current generator 26 of the above described embodiment of the present invention may be selected in any desired manner. Where preferred, the second high-tension current generator 26 may be of the same capacity as that of the first high-tension current generator 18 so as to significantly reduce the production cost of the whole arrangement.

Another preferred embodiment of the air-pollution reducing arrangement according to the present invention is shown in FIG. 2. In the embodiment herein shown, the ignition system is constructed essentially similarly to that shown in FIG. 1 and, thus, like reference numerals designate corresponding parts in the two figures. Referring to FIG. 2, the first and second high-tension current generators 18 and 26 are connected in parallel to the ignition distributor 20a and to the ignition switch 14 through switch means 32 of the two-position selector type. The switch means 32 thus has two sets of contacts 32a and 32b which intervene between the ignition switch 14 and the primary and secondary windings 18a and 26a of the first and second high-tension current generators 18 and 26, respectively. The switch means 32 further has an exciting coil 32c which is connected to the output of the control means 12 (FIG. 1) through the line 30 so as to receive the signal A when the control means 12 (not shown in FIG. 2) is in an actuated condition. The switch means 32 is so arranged that one set of the contacts 32a intervening between the ignition switch 14 and the first high-tension current generator 18 is biased to a closed condition when the coil 32c remains deenergized. The spark plugs 22 thus receive the high-tension surges from the first high-tension current generator 18 under usual conditions in which the output signal A from the control means 12 is absent. Under this condition, the other set of two contacts 32b is open so that the associated second high-tension current generator 26 is kept disconnected from the power source 14.

In a condition in which the signal A issues from the control means 12 and accordingly the exhaust recirculation system 10 is actuated, the exciting coil 32c is energized so that the contacts 32b close and concurrently the other contacts 32a open, thereby establishing a circuit connection between the power source 16 and spark plugs 22 via the generator 26 and cutting off the circuit connection between the generator 18 and the spark plugs. The spark plugs 22 are now producing sparks of high tension from the second high-tension current generator 26. It is, in this instance, important that the second high-tension current generator 26 has a greater capacity than the first high-tension current generator 18 whereby the spark plugs 22 can produce sparks of higher energy when the high-tension current source is shifted from the first to second high-tension current generator. When the supply of the signal A from the control means 12 terminates, then the coil 32c of the switch means 32 is de-energized so that the contacts 32b open and the contacts 32a close. The second high-tension current generator 26 is now dis-connected from the power source 16 and, in turn, the first high-tension current generator 18 is energized so as to cause the spark plugs 22 to fire the combustible mixture with usual energy.

The second preferred embodiment of the arrangement according to the present invention thus has its first and second high-tension current generators 18 and 26, respectively, actuated selectively depending upon the absence or presence of the output signal A from the control means 12, different from the embodiment described with reference to FIG. 1. This will provide advantages in that the two high-tension current generators 18 and 26 are free from electrical interferences from each other and in that the intensity of the energy to fire the air-fuel mixture in the engine can be prescribed pertinently through proper selection of the second high-tension current generator 26 independently of the first high-current generator 18.

Although the switch means 28 and 32 in the first and second embodiments, respectively, have thus far been described as using relay type switches, such is merely by way of example and, if desired, switching means of any construction may be utilized insofar as it finds a proper application in each of the embodiments.

Firing the air-fuel mixture with intensified energy during the condition in which a portion of the engine exhaust gases is recirculated would result in an increased tendency of the reaction being brought about between nitrogen and oxygen and, as a consequence, an increased amount of nitrogen oxides would be produced in the engine when the spark plugs are energized from both of the first and second high-tension current generators as in the case of the first embodiment of the present invention or from the second high-tension current generator as in the case of the second embodiment of the present invention. Experiments conducted by us have, however, revealed that this is actually not the case. The fact is that, when the air-fuel mixture charge is fired with intensified energy, then the flow of the air-fuel mixture through the carburetor can be throttled or reduced for the required engine power output so that the resultant mixture contains nitrogen and oxygen in significantly reduced quantities with a resultant decrease in the quantity of toxic nitrogen oxides in the exhaust gases.

Where, thus, the air-pollution preventive system combined with the ignition system of the above described nature is placed in use, not only the amount of nitrogen oxides in the exhaust gases can be reduced without detriment to the performance efficiency of the engine but, since the combustion efficiency of the air-fuel mixture can be enhanced when the mixture is fired with intensified energy, production of the other toxic compounds such as carbon monoxide and hydrocarbons can be considerably reduced so as to further contribute to solving the vehicular air-pollution problems.

Claims

What is claimed is:

1. A combination with an exhaust gas recirculation system for recirculating at least a portion of exhaust gases to an engine for the reduction of the concentration of nitrogen oxides in the exhaust gases, of an ignition system which comprises first high-tension current generating means connected between an ignition power source and an ignition distributor, normally open switch means to be closed in response to a condition in which a portion of the exhaust gases is recirculated to the engine through said recirculation system, and second high-tension current generating means connected through said switch means to the ignition power source and connected in parallel with said first high-tension current generating means to the distributor, whereby the ignition distributor is energized from the first high-tension generating means in the absence of a portion of the exhaust gases being recirculated to the engine through said recirculation system and from both the first and second high-tension generating means under said recirculated condition.

2. A combination as claimed in claim 1, in which said first and second high-tension current generators have substantially the same capacity.

3. A combination with an exhaust recirculation system for recirculating at least a portion of exhaust gases to an engine for the reduction of the concentration of nitrogen oxides in the exhaust gases, of an ignition system which comprises two-position selector switch means connected to an ignition power source and responsive to a condition in which a portion of the exhaust gases is recirculated to the engine through said recirculation system, and first and second high-tension current generating means which are connected in parallel between said switch means and an ignition distributor, said second high-tension current generating means being greater in capacity than the first high-tension current generator, said switch means being biased to provide connection between said ignition power switch and said distributor and shifted in response to said recirculated condition to a position providing connection between the ignition power source and distributor through said second high-tension current generating means, whereby ignition distributor is energized with intensified energy during said condition.