Air-pollution Preventive System For Motor Vehicles

Abstract

An air-pollution preventive system for use with motor vehicle internal combustion engines for effectively reducing the concentration of nitrogen oxides in the exhaust gases emitted from the engines during the city-road driving of the motor vehicle comprises means for recirculating the exhaust gases from the exhaust manifold into the intake manifold only when the vacuum in the intake manifold is lower than a predetermined lever concurrently with the throttle valve of the carburetor being within a predetermined range of open positions. The means for recirculating the exhaust gases comprises a recirculating passage, a valve for opening and closing the passage, and a double-action cam which is both axially movable in response to intake manifold vacuum conditions and angularly displaced in response to movement of the throttle valve to open the valve.

Description

This invention relates to an air-pollution preventive system for a motor vehicle and, more particularly, to a system for reducing the concentration of nitrogen oxides contained in the exhaust gases emitted from the internal combustion engine of the motor vehicle. The system proposed by this invention is characterized in that the exhaust gases are recirculated into the intake manifold only when the engine is driven under predetermined conditions represented by the level of the vacuum in the intake manifold and the angular position of the throttle valve of the carburetor.

It is well known that toxic nitrogen oxides are produced in large quantities when the vacuum in the intake manifold of the engine is decreased and the combustion temperature in the engine increased. To prevent the thus produced nitrogen oxides from being admitted to the open air, it has heretofore been proposed and put into practice to have the once emitted exhaust gases recirculated into the intake manifold and mixed with an inert gas to lower the combustion temperature so that the objectionable reaction which would otherwise take place between nitrogen and oxygen is precluded.

Continuous recirculation of the exhaust gases without regard to the operating conditions of the engine, as has thus far been the practice, results in unstable engine operation, decreased engine output and contamination within the engine and, as such, is considered unsuitable for practical purposes.

The problem of air-pollution resulting from the emission of toxic nitrogen oxides from automotive engines is a matter of great concern today, especially in urban areas and it is desired to reduce to a minimum the amount of nitrogen oxides emitted when the motor vehicle is running on city-roads. The extensive investigations conducted by the inventors have revealed that the nitrogen oxides emitted in such quantities as to cause a serious air-pollution problem in urban areas are produced mostly when the motor vehicle is accelerating or climbing a hill, as will be discussed in more detail.

The invention was thus completed under the recognition that the drawbacks which result from the continuous recirculation of the exhaust gases can be effectively eliminated by selectively recirculating the exhaust gases only when the engine is driven under predetermined conditions in which the motor vehicle accelerates or climbs up a hill in urban areas.

Such conditions of the engine providing the acceleration or hill-climbing of the motor vehicle are represented, as preferable according to the invention, by two particular factors-- the angular position of the throttle valve in the carburetor and the vacuum in the intake manifold of the engine.

A primary object of the invention is therefore to provide a system for reducing the concentration of toxic pollutants emitted from the engine when the motor vehicle is running in urban areas.

Another primary object of the invention is to provide a system which is adapted to reduce the concentration of nitrogen oxides to be admitted to the open air without detriment to the operation stability and power output of the engine and without contamination of the components and parts of the engine.

Still another primary object of the invention is to provide a system which is constructed and arranged to have the exhaust gases recirculated into the intake manifold only when the engine is driven under predetermined conditions in which the motor vehicle accelerates or climbs up a hill.

Still another primary object of the invention is to provide a system whereby the engine exhaust gases containing nitrogen oxides are recirculated into the intake manifold only when the throttle valve in the carburetor is held in predetermined angular positions and concurrently the vacuum in the intake manifold of the engine is maintained at predetermined levels.

In the drawings:

FIG. 1 is a graphical representation of a typical example of the relationships between the vehicle speed of a motor vehicle running on city-roads and the concentration of nitrogen oxides in the then emitted exhaust gases when the system according to the invention is used and not used;

FIG. 2 is a sectional view showing a preferred embodiment of the air-pollution preventive system of the invention as combined with a usual automotive carburetor;

FIG. 3 is a section on line I--I of FIG. 2;

FIG. 4 is a section on line II--II of FIG. 2; and

FIG. 5 is a graphical representation of a region of the conditions in which the engine exhaust gases are to be recirculated by means of the system illustrated in FIGS. 2 to 4.

According to the investigations conducted by the inventors on an automotive engine of usual construction, it has been discovered that the concentration of nitrogen oxides in the engine exhaust gases increases abruptly during acceleration and hill-climbing of the motor vehicle as indicated by the dotted curves a'-b' and c'-d' which correspond to the vehicle speed indicated by the lines a-b and c-d, respectively, in FIG. 1. In view of the fact that frequent decelerations, stops and accelerations occur and that steep hills are encountered in city driving, it will be conducive to the reduction of air pollutants to lower the concentration of nitrogen oxides during the acceleration and hill-climbing of the vehicle, viz, when the vehicle is driven under the conditions represented by the lines a-b and c-d in FIG. 1.

In order to accomplish this purpose, the invention proposes to have the ranges a-b and c-d of the driving conditions of the motor vehicle represented by the angular position of the throttle valve in the carburetor and the vacuum level in the intake manifold of the engine. In other words, the air-pollution preventive system of this invention is constructed in such a manner that the engine exhaust gases are recirculated into the intake manifold of the engine only when the throttle valve of the carburetor assumes predetermined angular positions and simultaneously the intake manifold vacuum is lower than a predetermined level.

A preferred embodiment of such a system is illustrated in FIGS. 2, 3, and 4.

As best seen in FIG. 2, the system according to the invention is used in combination with a usual carburetor which is generally indicated by numeral 1. The carburetor 1 has, as customary, a throttle valve 2 mounted on a rotary shaft 3, and communicates with the engine (not shown) through an intake manifold 4.

The air-pollution preventive system of the invention essentially comprises an exhaust recirculation control valve assembly 10. The valve assembly 10 has a casing 11 which communicates on one side with the exhaust manifold (not shown) through an exhaust recirculation conduit 12 and on the other with the carburetor 1 downstream of the throttle valve 2 through an exhaust recirculation nozzle 13. If preferred, the nozzle 13 may be opened into the intake manifold 4, though not so illustrated.

The valve assembly 10 has provided in its casing 11 a valve head 14 which is positioned relative to a valve seat 15 formed integrally with the casing 11 in such a manner that the nozzle 13 is isolated from the conduit 12 when the valve head 14 is seated on the valve seat 15. The valve head 14 is integrally connected with a valve stem 16 which slidably extends through a valve guide 17 formed integrally with the casing 11. The valve stem 16 is normally held in its retracted position by the action of a positioning means comprising a spring 18 which is fast at one end on the casing 11 and at the other on an end plate 19 which is fixed relative to the valve stem 16. The valve stem 16 thus being normally kept retracted, the valve head 14 is normally held in a position to isolate the nozzle 13 from the conduit 12 and accordingly the intake manifold 4 from the exhaust manifold (not shown). The valve stem 16 protrudes through the end plate 19 and abuts at its leading end against a double-action cam 20.

The double-action cam 20 and its associated components comprise another positioning means and the cam is mounted fixedly on a cam shaft 21 which is not only pivotal but axially movable for a limited distance. The cam 20 has formed partially on its periphery a protruded abutment 20a and when the cam 20 is rotated sufficiently angularly displaced or pivoted, the abutment 20a abuts against the leading end of the valve stem 16 which consequently is moved in a direction opposite to the cam 20 to unseat the valve head 14 from the valve seat 15.

The cam 20 is connected through a connecting rod 22 with an arm 23 which, in turn, is connected with the rotary shaft 3 of the throttle valve 2 in a manner to pivot as the throttle valve 2 is angularly displaced, as seen in FIGS. 2 and 3. Thus, the cam 20 is angularly displaced about the axis of the cam shaft 21 as the throttle valve 2 is pivoted and, when the abutment 20a abuts against the valve stem 16, then the valve head 14 leaves the valve seat 15 thereby to permit the nozzle 13 to communicate with the conduit 12, as previously mentioned. The displacement of the valve head 14 from the valve seat 15 is determined by varying the length of the valve stem 16 and/or the relative position and/or size of the abutment 20a and/or cam 20 per se, so that the valve assembly 10 can be opened only when the throttle valve 2 is held in predetermined range of angular positions, for example, between 15.degree. and 45.degree..

The double-action cam 20, when seen in end view as shown in FIG. 4, has formed on its periphery a radially reduced section 20b which merges with the abutment 20a through a conical section 20c. The cam shaft 21 which is integrally connected with the thus shaped cam 20 is axially slidably inserted into a hollow cylinder 24 which is fixed relative to or connected integrally with the casing 11. In a chamber 25 defined by the inside walls of the cam shaft 21 and cylinder 24 is mounted a return spring 26 whereby the cam shaft 21 is forced or biased away from the end wall 25a of the cylinder so that the cam 20 is normally held in the farthest position possible from the cylinder 24 as shown. The chamber 25 communicates with the intake manifold 4 through a vacuum conduit 27.

The double-action cam 20 is positioned in such a manner that, when it is held in the position farthest from the cylinder 24, the abutment 20a thereof is in line with the leading end of the valve stem 16 as shown and when in the position nearest the cylinder, the radially reduced section 20b is in line with the valve stem 16 as indicated by the broken line in FIG. 4.

The axial movement of the cam 20 is determined by selecting the loading of the spring 26 so that the valve stem 16 and accordingly the valve head 14 can be moved against the action of the spring 26 only when the vacuum drawn from the intake manifold 4 through the conduit 27 is lower than a predetermined level, for example, -350 mm of Hg.

An orifice 13a may preferably be provided in the nozzle 13 for obtaining a constant flow rate.

When, in operation, the engine is driven under conditions in which the amount of nitrogen oxides emitted therefrom is allowable from practical standpoint as during deceleration or normal cruising, the angular position of the throttle valve 2 and the vacuum level in the intake manifold 4 remain outside those ranges in which the abutment 20a of the double-action cam 20 is not permitted to contact the valve stem 16. In this instance, the cam 20 is held, when seen as shown in FIG. 4, in a position indicated by a broken line against the action of the return spring 26 because of a high vacuum in the intake manifold and, when seen in plan view as in FIG. 2, in the illustrated position in which the abutment 20a is not in contact with the valve stem 16. Thus, the cam 20 is held in a position where the reduced section 20b is in line with the valve stem 16 and can not act upon the valve stem 16 so that the valve head 14 is seated on the valve seat 15 to shut off the flow of exhaust gases in the exhaust recirculation conduit 12.

When, on the other hand, the engine output increases to such an extent as to produce nitrogen oxides in quantities to cause a serious pollution problem as represented by the dotted curve a'-b' or c'-d' in FIG. 1, then the intake manifold vacuum drops under the aforesaid predetermined level, for example, -350 mm of Hg and the angular position of the throttle valve 2 falls within the aforesaid predetermined range, for example, anywhere between 15.degree. and 45.degree.. In this condition, the spring 26 overpowers the vacuum drawn from the intake manifold 2 to cause the cam 20 to axially move into a position where the abutment 20a is in alignment with the valve stem 16 and at the same time the cam 20 is rotated angularly displaced into a position where the abutment 20a contacts the leading end of the valve stem 16. As a result of such double action of the cam 20, the stem 16 is depressed in a direction opposite to the cam 20 against the action of the spring 18 so that the valve head 14 is unseated from the valve seat. The engine exhaust gases are now permitted to recirculate into the intake manifold 2 through the conduit 12, valve assembly 10 and nozzle 13. The combustion temperature in the engine is lowered and the concentration of nitrogen oxides emitted to the open air is reduced from the levels represented by the dotted curves a'-b' and c'-d' to the solid curve a'-b'-c'-d' in FIG. 1.

The range in which the engine exhaust gases are recirculated into the intake manifold is illustrated in FIG. 5, wherein the valve assembly 10 is assumed to open when the throttle valve is opened at an angle from 15.degree. to 45.degree. and the intake manifold vacuum is lower than -350 mm of Hg. The recirculation range is indicated by the hatched area.

Other embodiments of the exhaust recirculation control valve assembly may be constructed to recirculate the exhaust gases only when the angular position of the throttle valve and the intake manifold vacuum are in predetermined ranges without departing from the scope and spirit of the invention as set forth in the appended claims.

Claims

What is claimed is:

1. An air pollution preventive system for a motor vehicle having an internal combustion engine with a carburetor having a throttle valve comprising: a recirculation passage communicating at one end with an exhaust manifold of said engine and at the other with an intake manifold of said engine; a recirculation control valve mounted in said recirculation passage for opening and closing same comprising a casing communicating on one side with the exhaust manifold and on the other side with the intake manifold, a valve seat integral with said casing, a valve head movably mounted in said casing to seat and unseat on said valve seat, a valve stem connected integrally with said valve head with its leading end extending outwardly through said casing, and a compression spring biasing said valve stem to a position in which said valve head is seated on said valve seat; cam means pivotal in response to angular movement of said throttle valve of said carburetor for actuating said control valve to open said recirculation passage when said throttle valveis in a predetermined range of angular positions comprising a pivotal and axially movable cam shaft, a double-action cam fixedly mounted on said cam shaft and having on its periphery a protruded abutment and a radially reduced section merging with said abutment through a conical section, said abutment being so shaped and sized as to contact and depress said valve stem into a position in which said valve head is unseated from said valve seat when said cam is both axially moved by said cam shaft to a position in which the abutment is in line with said valve stem and when said cam is angularly displaced to an angle corresponding to the angular position of the throttle valve within said predetermined range thereby to bring its abutment in abutting engagement with said leading end of said valve stem, and means including an arm fixedly connected with said throttle valve and a rod connecting said cam with said arm for effecting angular displacement of said cam in response to movement of said throttle valve; and means for putting said cam means in an operative condition when vacuum in said intake manifold is under a predetermined level comprising a hollow cylinder fixed relative to said casing and into which said cam shaft is axially slidably inserted to define therebetween a chamber, means communicating said chamber with the intake manifold to enable the vacuum therein to force said cam shaft toward a position in which said reduced section is in line with said valve stem, and a compression spring mounted in said chamber to force said cam shaft against said vacuum drawn into said chamber toward a position in which said abutment is in line with said valve stem whereby as the vacuum in the intake manifold decreases to said predetermined level the last-named compression spring overpowers the thus decreased vacuum to axially move said cam shaft to a position in which said abutment is in line with said valve stem;whereby engine exhaust gases are recirculated through the engine to reduce the concentration of nitrogen oxides in the engine exhaust gases in accordance with varying driving conditions of said motor vehicle.

2. An air pollution preventive system for a motor vehicle having an internal combustion engine with a carburetor having a throttle valve comprising: a recirculation passage communicating at one end with an exhaust manifold of said engine and at the other with an intake manifold of said engine; a recirculation control valve mounted in said recirculation passage; and double action cam means axially movable between operative and inoperative positions in response to the level of intake manifold vacuum and rotatable in response to angular movement of said throttle valve of said carburetor, said control valve being opened only when said intake manifold vacuum is below a predetermined level concurrently with said throttle valve being within a predetermined range of angular positions; whereby engine exhaust gases are recirculated through the engine to reduce the concentration of nitrogen oxides in the engine exhaust gases in accordance with varying driving conditions of said motor vehicle.

3. In a motor vehicle having an internal combustion engine provided with an intake manifold, an exhaust manifold, and a carburetor with a movable throttle valve connected to said intake manifold, an air-pollution preventive system for reducing the concentration of nitrogen oxides in the engine exhaust gases in accordance with varying driving conditions of the motor vehicle comprising: means defining a recirculation passage communicating said intake manifold with said exhaust manifold; valve means disposed within said recirculation passage alternately positionable in an open position thereby opening said recirculation passage to allow engine exhaust gases from said exhaust manifold to flow into said intake manifold and in a closed position thereby closing said recirculation passage; first positioning means for positioning said valve means in said open position; and second positioning means for positioning said valve means in said closed position whenever said throttle valve is within a predetermined range of open positions concurrently with the vacuum level within said intake manifold being below a predetermined level, said second positioning means comprising a cam, means mounting said cam both for axial movement into and out of an actuating position wherein same can open said valve means and for angular camming movement, linkage connecting said cam to said throttle valve to effect angular camming movement of said cam in response to angular movement of said throttle valve, and vacuum-operated means for effecting axial movement of said cam into said actuating position whenever the vacuum level within said intake manifold is below said predetermined level; whereby engine exhaust gases are recirculated during both acceleration and heavy loading of the motor vehicle at low speeds.