CA1062103A - Internal combustion engine with exhaust cleaning means - Google Patents
Internal combustion engine with exhaust cleaning meansInfo
- Publication number
- CA1062103A CA1062103A CA254,622A CA254622A CA1062103A CA 1062103 A CA1062103 A CA 1062103A CA 254622 A CA254622 A CA 254622A CA 1062103 A CA1062103 A CA 1062103A
- Authority
- CA
- Canada
- Prior art keywords
- air
- mixture
- exhaust gases
- exhaust
- passageway
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M31/00—Apparatus for thermally treating combustion-air, fuel, or fuel-air mixture
- F02M31/02—Apparatus for thermally treating combustion-air, fuel, or fuel-air mixture for heating
- F02M31/04—Apparatus for thermally treating combustion-air, fuel, or fuel-air mixture for heating combustion-air or fuel-air mixture
- F02M31/06—Apparatus for thermally treating combustion-air, fuel, or fuel-air mixture for heating combustion-air or fuel-air mixture by hot gases, e.g. by mixing cold and hot air
- F02M31/08—Apparatus for thermally treating combustion-air, fuel, or fuel-air mixture for heating combustion-air or fuel-air mixture by hot gases, e.g. by mixing cold and hot air the gases being exhaust gases
- F02M31/087—Heat-exchange arrangements between the air intake and exhaust gas passages, e.g. by means of contact between the passages
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
- F02D41/1446—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being exhaust temperatures
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
- Control Of The Air-Fuel Ratio Of Carburetors (AREA)
Abstract
Abstract of the Disclosure In an internal combustion engine including an exhaust cleaning catalytic converter and a mixture control system for controlling the air-to-fuel ratio of the combustible mixture toward a certain value enabling the catalytic con-verter to produce its maximum exhaust cleaning perform-ance, a device is provided for forcibly evaporating the mixture in the intake manifold of the engine so as to reduce the difference between the time at which a mixture is produced in the mixture supply system of the engine and the time at which the air-to-fuel ratio of the mix-ture is monitored in the exhaust system.
Description
The present invention relates in general to internal combustion engines of automotive vehicles and, particularly, to a method of and a system for controlling the air-to-fuel ratio in an automotive internal combustion engine of the type using a catalytic converter provided in the exhaust system for exhaust cleaning purposes.
Some modernized automotive vehicles are now equipped with catalytic converters in the exhaust systems of the engines for the purpose of converting toxic air contaminative contents of the engine exhaust gases into harmless composition before the exhaust gases are discharged into the open air. A typical example of such catalytic converters is the one that uses an oxidative catalyst effective to re-oxidize unburned combustible residues of, for example, hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gases emitted from the engine cylinders into harmless compounds such as carbon dioxide and water. Experiments conducted with an oxidative catalyst of this nature have revealed that the catalyst is not only reactive to these combustible compounds but is operable j to reduce nitric oxides (NOX) in the exhaust gases provided the exhaust gases to be processed by the catalyst are conditioned to contain exhaust compounds in proportions within a certain range which is dictated by the air-to-fuel ratio of the mixture combusted in the engine cylinders. The catalytic converter using an oxidative catalyst thus exhibits triple effects to the exhaust gases of an internal combustion engine and is capable of reducing the different types of air contaminative compounds in a single unit when the combustible mixture supplied to the engine cylinders is proportioned to an air-to-fuel ratio within a certain range. The experiments have further revealed that it is the stoichiometric ratio of about 14.8:1 that enables the triple-effect or "three-way" catalytic con-verter to produce its maximum conversion efficiency against the three kinds of air contaminative compounds in the exhaust gases.
Some modernized automotive vehicles are now equipped with catalytic converters in the exhaust systems of the engines for the purpose of converting toxic air contaminative contents of the engine exhaust gases into harmless composition before the exhaust gases are discharged into the open air. A typical example of such catalytic converters is the one that uses an oxidative catalyst effective to re-oxidize unburned combustible residues of, for example, hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gases emitted from the engine cylinders into harmless compounds such as carbon dioxide and water. Experiments conducted with an oxidative catalyst of this nature have revealed that the catalyst is not only reactive to these combustible compounds but is operable j to reduce nitric oxides (NOX) in the exhaust gases provided the exhaust gases to be processed by the catalyst are conditioned to contain exhaust compounds in proportions within a certain range which is dictated by the air-to-fuel ratio of the mixture combusted in the engine cylinders. The catalytic converter using an oxidative catalyst thus exhibits triple effects to the exhaust gases of an internal combustion engine and is capable of reducing the different types of air contaminative compounds in a single unit when the combustible mixture supplied to the engine cylinders is proportioned to an air-to-fuel ratio within a certain range. The experiments have further revealed that it is the stoichiometric ratio of about 14.8:1 that enables the triple-effect or "three-way" catalytic con-verter to produce its maximum conversion efficiency against the three kinds of air contaminative compounds in the exhaust gases.
- 2 -- i It is, for this reason, desirable to have an internal combustion engine of the type using a triple-effect catalytic converter pro-vided with a mixture ratio control system adapted to regulate the air-to-fuel ratio of the mixture to be produced in the mixture supply system of the engine toward the stoichiometric level.
The mixture ratio control system used in combination with a triple-effect catalytic converter comprises an exhaust sensor operative to detect the concentration of a prescribed type of che-mical component contained in the exhaust gases and to produce an analog signal indicative of the detected concentration of the par-ticular component of the exhaust gases. The chemical composition of the exhaust gases is a fairly faithful representation of the air-to-fuel ratio of the mixture produced in the mixture supply system of an engine and, therefore, the mixture ratio control system operating on the basis of the signal thus delivered from the exhaust sensor is capable of accurately and reliably controlling the air-to-fuel ratio of the mixture to be produced in the mixture supply system toward a predetermined value such as the stoichiome-tric ratio.
The chemical component to be detected by the exhaust sen-sor may be oxygen, carbon monoxide or dioxide, hydrocarbons or ni-tric oxides although oxygen in particular is preferred for ease of detection.
The analog signal produced by the exhaust sensor is fed to an electric control circuit connected to a solenoid-operated valve unit which is arranged to vary the flow of air or fuel to be delivered into the mixture supply system of the engine in accordance -with the output signal produced by the control circuit on the basis of the analog signal supplied from the exhaust sensor. The output signal from the control circuit is usually in the form of a train of pulses which are varied in pulsewidth and frequency in such a manner as to eliminate or reduce a difference, if any, between the ~ .
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- 1()6~103 ~alogsignal produced by the exhaust sensor and a reference signal representative of a predetermined air-to-~uel ratio such as the stoichiometric ratio. The valve unit is thus operated to alterna-tely open and close at a frequency and for durations dictated by the frequency and pulsewidths of the pulses supplied to the unit and controls the flow of air or fuel to be delivered into the m~x-ture supply system in such a manner that the air-to-fuel ratio of the mixture approaches the value represented by the reference slgnal impressed on the control circuit.
By virtue of the signal delivered from the exhaust sènsor, the control circuit is capable of accurately monitoring the air-to-fuel ratio of the mixture combusted in the engine cylinders so that the air-to-fuel ratio of the mixture produced in the mixture supply system of the engine is constantly regulated toward a predetermined value such as the stoichiometric ratio enabling the catalytic con-verter to exhibit its maximum conversion efficiency against the dif-ferent types of air contaminative compounds. As will be readily understood by those skilled in the art, however, it is extremely difficult and practically even impossible to have the air-to-fuel ratio of the mixture regulated strictly and maintained at a prede-termined value throughout the varying operating conditions of the engine especially when the engine is of the type using a carburetor as the mixture supply system. This is because of the changes and fluctuations in the operating and ambient conditions of the engine, external disturbances such as the shocks and vibrations transferred to the mechanical components of the mixture control system and, particularly, the delay involved in feeding back the information from the exhaust system to the mixture control system and in moni-toring the air-to-fuel ratio of the mixture from the exhaust gases resulting from the mixture produced in the mixture supply system.
One of the most important considerations to be paid for exploiting the potential advantages of a mixture control system of - ~ . : : : . :
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the described character is, therefore, to reduce the delay in the response of the control system to the air-fuel mixture produced in the mixture supply s~stem. A most expedient approa~h to realizing such a scheme is to reduce the period of time from which the air-fuel mixture produced in the mixture supply system is admitted into the engine cylinders and the period of time for which the exhaust gases produced in the cylinders are passed to the exhaust sensor located in the exhaust system. The velocities of the streams of the air-fuel mixture flowing toward and into the engine cylinders and the velocities of the streams of the exhaust gases discharged from the cylinders are basically dictated by the output speed of the engine and, thus, reducing such velocities is subject to limi-tation because of the limitations imposed on the performance of the engine.
In an internal combustion engine using a carburetor as the mixture supply system, the air-fuel mixture produced in the carburetor is passed through the intake manifold partly in a vapo-rized gaseous state and partly in a liquid state flowing or creeping on the inner peripheral surface of the intake manifold, as is well known in the art. Experiments have revealed that the mixture in the gaseous state accounts for approximately 40 per cent of the total flow of the mixture at high engine speeds and approximately 60 per cent at low engine speeds. Further analyses have shown that the velocity of the stream of the mixture in a perfectly atomized state substantially equals the velocity of a stream of air through the intake manifold and reaches-to approximately a hundred times the velocity of the mixture in a liquid state flowing on the inner sur-face of the intake manifold. The air-fuel mixture produced in the carburetor will thus be enabled to reach the engine cylinders in a shortened period of time if the mixture is perfectlyatomized in its entirety when being passed through the intake manifold.
The existence of the air-fuel mixture of liquid state in . . , ~O~'~lV;3, the intake manifold is objectionable not only from the above-des-cribed point of view but because such a mixture tends to be irre-gularly distributed to the runners leading to the different engine cylinders or may be sucked in bulk into the engine cylinders and produce undue enrichment of the mixture in the cylinders during deceleration of the engine, causing deterioration of the performance efficiency of the engine and resulting in emission of increased quantities of air contaminative compounds.
The present invention aims at resolution of these problems by preheating the air-fuel mixture in the intake manifold of the engine to a temperature within a prescribed range for forcibly causing the mixture to be substantially perfectly evaporated when being passed through the intake manifold, so as to minimize the delay in the response of the mixture control system of the described nature to the variation in the air-to-fuel ratio of the air-fuel ; mixture produced in the carburetor and to assure the engine to operate at all times in proper condition.
In accordance with one important aspect of the present invention, there is provided in an internal combustion engine including a carburetor connected to the cylinders of the engine through an intake manifold including a riser portion, and an exhaust system having incorporated therein a catalytic converter which is reactive to at least one type of air contaminative com-; pound contained in the exhaust gases discharged from the engine cylinders and passed through the converter and which is operative to produce a maximum conversion efficiency when the air-fuel mix-ture produced in the carburetor is proportioned to a predetermined air-to-fuel ratio, the air-to-fuel ratio of the mixture produced in the carburetor from the exhaust gases passed through the exhaust system, regulating the air-to-fuel ratio of the mixture to be pro-duced in the carburetor toward the above-mentioned predetermined ratio, a method of controlling the air-to-fuel ratio to be produced :, .
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.: : , ~0~ 33 in the carburetor, comprising monitoring the air-to-fuel ratio of the mixture produced in the carburetor from the exhaust gases flowing in the exhaust system, regulating the air-to-fuel ratio of the mix-ture to be produced in the carburetor toward the above-mentioned predetermined ratio, directing the hot exhaust gases through a passageway in heat conductive contact with the riser portion of the intake manifold for transferring heat from the exhaust gases to the air-fuel mixture in the intake manifold, detecting the temperature ` of the exhaust gases passed through the passageway and regulating theflow of the exhaust gases through the passageway for maintaining substantially constant the quantity of heat in the exhaust gases passed through the above-mentioned passageway.
In accordance with another important aspect of the present invention, there is provided an internal combustion which comprises -~ a carburetor connected to the cylinders of-the engine through an intake manifold including a riser portion; an exhaust system having incorporated therein a catalytic converter which is reactive to at : least one type of air contaminative compound contained in the exhaust system discharged from the engine cylinders and passed through the converter and which is operative to produce a maximum : conversion efficiency when the air-fuel mixture produced in the carburetor is proportioned to a predetermined air-to-fuel ratio, - the exhaust system having a wall portion constituted by the riser : portion of the intake manifold; a mixture control system adapted to . monitor the air-to-fuel ratio of the mixture produced in the carbu-retor from the exhaust gases flowing through the exhaust system and to control the air-to-fuel ratio of the mixture to be produced in the carburetor toward the above-mentioned predetermined ratio; and a device for forcibly evaporating the air-fuel mixture in the intake manifold, the device comprising a flow control valve located within -:~
the exhaust system in the neighbourho~d of the aforesaid wall portion of the exhaust system for providing a passageway of exhaust gases ~' ', ' ,~. '. , : . -in heat conductive contact with the riser portion of the intake~
manifold, and heat-sensitive valve control means including a ~
helical bimetallic spring which is anchored at one end to the fl-ow control valve and at the other end to a wall portion of the exhaust system for varying the flow rate of the exhaust gases through the passageway substantially in inverse proportion to the temperature of the exhaust gases passed through the passageway.
The features and advantages of the improvements according to the present invention will be more clearly understood from the following description taken in conjunction with the accompanying ; drawings, in which: -Fig. 1 is a schematic partially cut-away view showing part of an internal combustion engine embodying the present inven-tion;
Fig. 2 is a block diagram showing a preferred example of an electric control circuit forming part of a mixture control system incorporated into the internal combustion engine illustrated in Fig. l;
Fig. 3 is a graph which shows a representative example of ; 20 the relationship between the percentage of evaporation of the air-; fuel mixture in the intake manifold of an engine and the velocity of the stream of the mixture through the intake manifold in texms ; of an index number which is assumed to be 100 when the velocity-~of the mixture stream is equal to the velocity of the stream of air through the intake manifold; and Fig. 4 is a graph in which curve a (in broken lines) and ; curve b ~in dot-and-dash lines) demonstrate the concentrations of , carbon monoxide (CO) in the exhaust gases discharged into the at-mosphere when a vehicle is driven at a speed varying as shown by curve c (in full lines), wherein the characteristics indicated'by the curve a are observed in an internal combustion engine provided with mixture preheating means in accordance with the present inven-., ~' -.
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tion and the characteristics indicated by the curve b are observed in an ordinary internal combustion engine which is void of such means.
Referring to the drawings, first to Fig. 1, an internal combustion engine includes a carburetor 10 which is assumed, by way of example, to be of a down-draft type having a mixture delivery pipe 12 connected at its upper end to an air cleaner 14 through an air horn 16 and at its lower end to an intake manifold 18 leading to the engine cylinders in a cylinder block 20. The mixture delive-10 ry pipe 12 has provided therein a venturi 22 located below the air . h~rn 16 and a throttle valve 24 located below the venturi 22.
Though not shown, the venturi 22 is in communication with a main fuel delivery circuit of the engine through a main fuel discharge - nozzle projecting into the venturi 22 for being supplied with fuel in an emulsified state when the throttle valve 24 is open, while the throttle valve 24 is mechanically connected to an accelerator pedal .~ for being moved between fully open and fully closed positions through a part throttle position depending upon the depth to which the ac-celerator pedal is depressed, as is well known. The intake mani-i :: 20 fold 18 has a riser portion 26 which is located below the mixture delivery pipe 12 and which merges into a plurality of runner por-- tions (not shown) respectively leading to the intake ports of the ~ individual engine cylinders in the cylinder block 20.
The internal combustion engine further comprises an :~
exhaust system which.includes an exhaust manifold 28 and an exhaust pipe 30 leading downstream from the exhaust manifold 28. Though not shown, the exhaust manifold 28 consists of a plurality of branch tube portions respectively leading from the exhaust ports of the individual engine cylinders in the cylinder block 20 and a single . 30 "plenum" tube portion merging downstream out of the branch tube portions and connected at its leading end to the exhaust pipe 30, as is well known. The exhaust pipe 30 is connected through a muffler _ g _ -~. d '. .~
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or mufflers to a tail pipe which is open to the atmosphere at its terminal end, though not shown.
The exhaust system is arranged with a catalytic converter 32. The catalytic converter 32 is shown to be mounted in the ex-haust pipe 30 but, if desired, the same may be mounted on the above-mentioned plenum tube portion of the exhaust manifold 28. The cata-lytic converter 32 is herein assumed, by way of example, to be of the previously described triple-effect type which is effective to process the three different kinds of air contaminative compounds of hydrocarbons, carbon monoxide and nitrogen oxides contained in the exhaust gases discharged from the engine cylinders. The cata-lytic converter 32 is, thus,permitted to produce its maximum con-version efficiency when supplied with exhaust gases which have resulted from an air-fuel mixture proportioned to the stoichiometric ratio of approximately 14.8:1 when the engine is of the type which is gasoline powered. To produce an air-fuel ratio proportioned to such a ratio in the mixture delivery pipe 12, the carburetor 10 is provided with a mixture control system which is adapted to regulate the air-to-fuel ratio of the mixture to be produced in the mixture delivery pipe 12 toward the stoichiometric ratio throughout the va-rious modes of operation or during predetermined modes of operation - of the engine. The mixture ratio control system comprises an exhaust sensor 34 provided in the exhaust system to detect the con-centration of a prescribed type of chemical component of the exhaust -gases discharged from the engine cylinders. For the purpose of des-cription, the exhaust sensor 34 is herein assumed, by way of ; example, to be of the type which is sensitive to oxygen contained in the exhaust gases passed therethrough. If desired, however! the exhaust sensor 34 of this nature may be replaced with an exhaust sensor of the type which is sensitive to, for example, hydrocarbons, carbon monoxide or dioxide or nitric oxides in the exhaust gases.
The exhaust sensor 34 is, furthermore, shown to be located in the ., -- 10 --. .
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exhaust manifold 28 with the catalytic converter 32 mounted in the exhaust pipe 30 but, if desired, the same may be located in the exhaust pipe 30 preferably upstream of the catalytic converter 32.
If the catalytic converter 32 is mounted in the plenum tube portion of the exhaust manifold 28 as previously mentioned, then it is pre-ferable to have the exhaust sensor 34 mounted on the particular por-tion of the exhaust manifold 28 upstream of the catalytic converter 32 thus arranged.
The exhaust sensor 34 produces an analog output signal S_ closely related to the detected concentration of the oxygen in the exhaust gases passed therethrough and supplies the signal S_ to an electric control circuit 36. The control circuit 36 is arranged to produce an output signal S_ that varies with the analog input signal S_ impressed thereon. The output signal S_ is fed to a suitable solenoid-operated valve unit 38 associated with the air delivery means and/or fuel delivery means (not shown) of the carburetor 10 and controis the rate of flow of air or fuel or the rates of flows of both air and fuel to be delivered into the mixture delivery pipe 12 in such a manner that the air-to-fuel ratio of the mixture pro-20 duced in the mixture supply system is regulated toward a stoichio-metric value. The solenoid-operated valve unit 38 may be of a two-position type having open and closed conditions or of the type which is continuously operable between open and closed conditions. If the valve unit 38 is of the two-position type, the control circuit 36 should be arranged to deliver, as the above-mentioned output si-gnal Sc, a train of pulses having a frequency and pulsewidths that vary with the analog input signal S_ impressed on the circuit 36.
Fig. 2 shows a preferred example of the control circuit 36 arranged to achieve such a function.
Referring to Fig. 2, the control circuit 36 is shown to comprise a comparator 40, a proportional amplifying integrator 42, a saw-tooth or triangular pulse generator 44 and a pulsewidth modu-. ~
.3 lator 46. The comparator 40 has a first input terminal connected to the output terminal of the above-mentioned exhaust sensor 34 and a second input terminal on which a reference signal Sr is constantly impressed. The reference signal S_ is representative of the con-centration of oxygen in the exhaust gases resulting from a stoichio-metric air-fuel mixture.
The comparator 40 is operative to compare the output~' signal So with the reference signal S_ and produces a binary output signal Sl which assumes a logic "0" value when the voltage of the signal S_ is greater in magnitude than the reference signal Sr (viz., when the air-fuel mixture supplied to the engine cylinders is richer than a stoichiometric mixture) and a logic "1" value when the former is smaller in magnitude than the latter (viz., when the mixture supplied to the cylinders is leaner than a stoichiometric mixture).
The binary signal Sl produced by the comparator 40 is fed to the proportional amplifying integrator 42 which is arranged to produce a linear ramp signal S2 which increases or decreases in response to the input signal Sl of the logic "0" or "1" value, respectively.
On the other hand, the saw-tooth or triangular pulse generator 44 is operative to produce a train of saw-tooth or triangular pulses S3 having equal pulsewidths and a predetermined constant frequency.
The ramp signal S2 from the proportional amplifying integrator 42 and the train of saw-tooth or triangular pulses S3 from the pulse generator 44 are fed to the pulsewidth modulator 46. The pulsewidth modulator 46 is, in effect, a comparator and is thus operative to compare the ramp signal S2 with the saw-tooth or triangular pulses S3, thereby producing a train of square-shaped pulses having posi-tive durations when the signal S2 is lower in magnitude than the saw-tooth or triangular pulses S3. The train of square-shaped pul-ses produced in this fashion by the pulsewidth modulator 46 provides ~ -the previously mentioned control signal Sc and is delivered from the -control circuit 36 to the soneoid-operated valve unit 38. The .. , . ~
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valve unit 38 is consequently controlled to open and close at in-tervals dictated by the pulses Sc which are fed in succession to the valve unit. --The mixture control system thus arranged depends for~its performance upon the reliability of the signal delivered by the(~
exhaust sensor 34. Because, however, there is an appreciable diffe-rence between the time at which an air-fuel mixture is produced in the mixture delivery pipe 12 of the carburetor 10 and the time ~t which the exhaust gases resulting from the mixture reaches the e~haust 10 sensor 34 and because of the fact that the air-to-fuel ratio of~the mixture produced in the carburetor 10 is subject to fluctuation which is practically beyond the control of the mixture control and the carburetor per se, the signal produced by the exhaust sensor 34 is not faithfully representative of the air-to-fuel ratio of the mix-ture produced at the very instant at which the signal is delivered t~ ~ from the sensor 34. The intent of the present invention is to`re-duce such a time difference to a minimum by promoting the evapora-; tion of the air-fuel mixture being passed through the intake mani-fold. The degree of evaporation of the air-fuel mixture in the;
intake manifold is closely related to the velocity of the stream of the mixture through the intake manifold and the mixture flow~
~ ` through the intake manifold at a velocity which is approximately Z equal to the velocity of the stream of air t~rethrough when the-mixture is evaporated substantially perfectly, as will be seen ;:
from the curve of Fig. 3. ~-To achieve such an intent of the present invention, the exhaust manifold 28 of the engine illustrated in Fig. 1 has a wall portion constituted by the riser portion 26 of the intake manifold ' ~ 18 and a flow control valve 48 is provided within the exhaust mani-30 fold 28 in the neigh~ourhood of the particular wall portion. The flow control valve 48 is rotatable with a shaft 50 journalled to the exhaust manifold and provides a passageway 52 through which the ,'~
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exhaust gases entering the exhaust manifold 28 are brought into heat conductive contact with the riser portion 26 of the intake manifold 28. The valve 48 is rotatable about the axis of the shaft 50 bet-ween an angular position indicated by full lines for providing a maximum flow rate through the passageway 52 and an angular position indicated by phantom lines for providing a minimum flow rate through the passageway 52. The valve 48 is moved between these two angular positibns by means of a helical bimetallic spring 54 which is ;- anchored at one end to the shaft 52 and at the other end to an internal wall portion of the exhaust manifold 28 as indicated at 56.
The bimetallic spring 54 is arranged to move the valve 48 between the above-mentioned two positions in such a manner as to vary the flow rate of the exhaust gases through the passageway 52 substantial-ly in inverse proportion to the temperature of the hot exhaust gases as detected by the bimetallic spring 54 so that the quantity of heat in the exhaust gases passed through the passageway 52 and according-ly the quantity of heat transferred through the riser portion 26 of the intake manifold 18 to the air-fuel mixture flowing through the intake manifold 18 are maintained substantially constant. The bi-metallic spring 54 is preferably selected and arranged to maintainthe temperature of the riser portion 26 of the intake manifold 18 within the range of between about 100 C and about 250 C.
To provide an increased heat exchange efficiency through the riser portion 26 of the intake manifold 18, the riser portion `
26 may be corrugated or ridged as shown.
Fig. 4 illustrates by curve _ the concentration of an air contaminative compound (exemplified by carbon monoxide) contained in the exhaust gases discharged into the atmosphere when the flow control valve 48 of the arrangement shown in Fig. 1 is operated by the bimetallic spring 54 in such a manner as to maintain the tempe-rature of the riser portion 26 of the intake manifold 18 at appro-ximately 180C. From comparison between this curve _ and the ~ `
106'~103 curve b which is indicative of the concentration of carbon monoxide in the exhaust gases dischar~ed from an ordinary internal combus-tion engine provided with a catalytic converter and a mixture con-trol system of the described nature but void of the mixture eva~o-rative means, the advantages achieved by the present invention will be self-explanatory. -~
The lower and upper limits 100C and 250C of the above-mentioned temperature range have been specified with a view to enabling the air-fuel mixture to be sufficiently atomized and pro-l.0 vlding acceptable mixture induction efficiency. ~
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The mixture ratio control system used in combination with a triple-effect catalytic converter comprises an exhaust sensor operative to detect the concentration of a prescribed type of che-mical component contained in the exhaust gases and to produce an analog signal indicative of the detected concentration of the par-ticular component of the exhaust gases. The chemical composition of the exhaust gases is a fairly faithful representation of the air-to-fuel ratio of the mixture produced in the mixture supply system of an engine and, therefore, the mixture ratio control system operating on the basis of the signal thus delivered from the exhaust sensor is capable of accurately and reliably controlling the air-to-fuel ratio of the mixture to be produced in the mixture supply system toward a predetermined value such as the stoichiome-tric ratio.
The chemical component to be detected by the exhaust sen-sor may be oxygen, carbon monoxide or dioxide, hydrocarbons or ni-tric oxides although oxygen in particular is preferred for ease of detection.
The analog signal produced by the exhaust sensor is fed to an electric control circuit connected to a solenoid-operated valve unit which is arranged to vary the flow of air or fuel to be delivered into the mixture supply system of the engine in accordance -with the output signal produced by the control circuit on the basis of the analog signal supplied from the exhaust sensor. The output signal from the control circuit is usually in the form of a train of pulses which are varied in pulsewidth and frequency in such a manner as to eliminate or reduce a difference, if any, between the ~ .
.. . . . .
- - ` ' : ' : ' :~ :
- 1()6~103 ~alogsignal produced by the exhaust sensor and a reference signal representative of a predetermined air-to-~uel ratio such as the stoichiometric ratio. The valve unit is thus operated to alterna-tely open and close at a frequency and for durations dictated by the frequency and pulsewidths of the pulses supplied to the unit and controls the flow of air or fuel to be delivered into the m~x-ture supply system in such a manner that the air-to-fuel ratio of the mixture approaches the value represented by the reference slgnal impressed on the control circuit.
By virtue of the signal delivered from the exhaust sènsor, the control circuit is capable of accurately monitoring the air-to-fuel ratio of the mixture combusted in the engine cylinders so that the air-to-fuel ratio of the mixture produced in the mixture supply system of the engine is constantly regulated toward a predetermined value such as the stoichiometric ratio enabling the catalytic con-verter to exhibit its maximum conversion efficiency against the dif-ferent types of air contaminative compounds. As will be readily understood by those skilled in the art, however, it is extremely difficult and practically even impossible to have the air-to-fuel ratio of the mixture regulated strictly and maintained at a prede-termined value throughout the varying operating conditions of the engine especially when the engine is of the type using a carburetor as the mixture supply system. This is because of the changes and fluctuations in the operating and ambient conditions of the engine, external disturbances such as the shocks and vibrations transferred to the mechanical components of the mixture control system and, particularly, the delay involved in feeding back the information from the exhaust system to the mixture control system and in moni-toring the air-to-fuel ratio of the mixture from the exhaust gases resulting from the mixture produced in the mixture supply system.
One of the most important considerations to be paid for exploiting the potential advantages of a mixture control system of - ~ . : : : . :
-~06'Z~
the described character is, therefore, to reduce the delay in the response of the control system to the air-fuel mixture produced in the mixture supply s~stem. A most expedient approa~h to realizing such a scheme is to reduce the period of time from which the air-fuel mixture produced in the mixture supply system is admitted into the engine cylinders and the period of time for which the exhaust gases produced in the cylinders are passed to the exhaust sensor located in the exhaust system. The velocities of the streams of the air-fuel mixture flowing toward and into the engine cylinders and the velocities of the streams of the exhaust gases discharged from the cylinders are basically dictated by the output speed of the engine and, thus, reducing such velocities is subject to limi-tation because of the limitations imposed on the performance of the engine.
In an internal combustion engine using a carburetor as the mixture supply system, the air-fuel mixture produced in the carburetor is passed through the intake manifold partly in a vapo-rized gaseous state and partly in a liquid state flowing or creeping on the inner peripheral surface of the intake manifold, as is well known in the art. Experiments have revealed that the mixture in the gaseous state accounts for approximately 40 per cent of the total flow of the mixture at high engine speeds and approximately 60 per cent at low engine speeds. Further analyses have shown that the velocity of the stream of the mixture in a perfectly atomized state substantially equals the velocity of a stream of air through the intake manifold and reaches-to approximately a hundred times the velocity of the mixture in a liquid state flowing on the inner sur-face of the intake manifold. The air-fuel mixture produced in the carburetor will thus be enabled to reach the engine cylinders in a shortened period of time if the mixture is perfectlyatomized in its entirety when being passed through the intake manifold.
The existence of the air-fuel mixture of liquid state in . . , ~O~'~lV;3, the intake manifold is objectionable not only from the above-des-cribed point of view but because such a mixture tends to be irre-gularly distributed to the runners leading to the different engine cylinders or may be sucked in bulk into the engine cylinders and produce undue enrichment of the mixture in the cylinders during deceleration of the engine, causing deterioration of the performance efficiency of the engine and resulting in emission of increased quantities of air contaminative compounds.
The present invention aims at resolution of these problems by preheating the air-fuel mixture in the intake manifold of the engine to a temperature within a prescribed range for forcibly causing the mixture to be substantially perfectly evaporated when being passed through the intake manifold, so as to minimize the delay in the response of the mixture control system of the described nature to the variation in the air-to-fuel ratio of the air-fuel ; mixture produced in the carburetor and to assure the engine to operate at all times in proper condition.
In accordance with one important aspect of the present invention, there is provided in an internal combustion engine including a carburetor connected to the cylinders of the engine through an intake manifold including a riser portion, and an exhaust system having incorporated therein a catalytic converter which is reactive to at least one type of air contaminative com-; pound contained in the exhaust gases discharged from the engine cylinders and passed through the converter and which is operative to produce a maximum conversion efficiency when the air-fuel mix-ture produced in the carburetor is proportioned to a predetermined air-to-fuel ratio, the air-to-fuel ratio of the mixture produced in the carburetor from the exhaust gases passed through the exhaust system, regulating the air-to-fuel ratio of the mixture to be pro-duced in the carburetor toward the above-mentioned predetermined ratio, a method of controlling the air-to-fuel ratio to be produced :, .
s~
.: : , ~0~ 33 in the carburetor, comprising monitoring the air-to-fuel ratio of the mixture produced in the carburetor from the exhaust gases flowing in the exhaust system, regulating the air-to-fuel ratio of the mix-ture to be produced in the carburetor toward the above-mentioned predetermined ratio, directing the hot exhaust gases through a passageway in heat conductive contact with the riser portion of the intake manifold for transferring heat from the exhaust gases to the air-fuel mixture in the intake manifold, detecting the temperature ` of the exhaust gases passed through the passageway and regulating theflow of the exhaust gases through the passageway for maintaining substantially constant the quantity of heat in the exhaust gases passed through the above-mentioned passageway.
In accordance with another important aspect of the present invention, there is provided an internal combustion which comprises -~ a carburetor connected to the cylinders of-the engine through an intake manifold including a riser portion; an exhaust system having incorporated therein a catalytic converter which is reactive to at : least one type of air contaminative compound contained in the exhaust system discharged from the engine cylinders and passed through the converter and which is operative to produce a maximum : conversion efficiency when the air-fuel mixture produced in the carburetor is proportioned to a predetermined air-to-fuel ratio, - the exhaust system having a wall portion constituted by the riser : portion of the intake manifold; a mixture control system adapted to . monitor the air-to-fuel ratio of the mixture produced in the carbu-retor from the exhaust gases flowing through the exhaust system and to control the air-to-fuel ratio of the mixture to be produced in the carburetor toward the above-mentioned predetermined ratio; and a device for forcibly evaporating the air-fuel mixture in the intake manifold, the device comprising a flow control valve located within -:~
the exhaust system in the neighbourho~d of the aforesaid wall portion of the exhaust system for providing a passageway of exhaust gases ~' ', ' ,~. '. , : . -in heat conductive contact with the riser portion of the intake~
manifold, and heat-sensitive valve control means including a ~
helical bimetallic spring which is anchored at one end to the fl-ow control valve and at the other end to a wall portion of the exhaust system for varying the flow rate of the exhaust gases through the passageway substantially in inverse proportion to the temperature of the exhaust gases passed through the passageway.
The features and advantages of the improvements according to the present invention will be more clearly understood from the following description taken in conjunction with the accompanying ; drawings, in which: -Fig. 1 is a schematic partially cut-away view showing part of an internal combustion engine embodying the present inven-tion;
Fig. 2 is a block diagram showing a preferred example of an electric control circuit forming part of a mixture control system incorporated into the internal combustion engine illustrated in Fig. l;
Fig. 3 is a graph which shows a representative example of ; 20 the relationship between the percentage of evaporation of the air-; fuel mixture in the intake manifold of an engine and the velocity of the stream of the mixture through the intake manifold in texms ; of an index number which is assumed to be 100 when the velocity-~of the mixture stream is equal to the velocity of the stream of air through the intake manifold; and Fig. 4 is a graph in which curve a (in broken lines) and ; curve b ~in dot-and-dash lines) demonstrate the concentrations of , carbon monoxide (CO) in the exhaust gases discharged into the at-mosphere when a vehicle is driven at a speed varying as shown by curve c (in full lines), wherein the characteristics indicated'by the curve a are observed in an internal combustion engine provided with mixture preheating means in accordance with the present inven-., ~' -.
:'' .
06;~
tion and the characteristics indicated by the curve b are observed in an ordinary internal combustion engine which is void of such means.
Referring to the drawings, first to Fig. 1, an internal combustion engine includes a carburetor 10 which is assumed, by way of example, to be of a down-draft type having a mixture delivery pipe 12 connected at its upper end to an air cleaner 14 through an air horn 16 and at its lower end to an intake manifold 18 leading to the engine cylinders in a cylinder block 20. The mixture delive-10 ry pipe 12 has provided therein a venturi 22 located below the air . h~rn 16 and a throttle valve 24 located below the venturi 22.
Though not shown, the venturi 22 is in communication with a main fuel delivery circuit of the engine through a main fuel discharge - nozzle projecting into the venturi 22 for being supplied with fuel in an emulsified state when the throttle valve 24 is open, while the throttle valve 24 is mechanically connected to an accelerator pedal .~ for being moved between fully open and fully closed positions through a part throttle position depending upon the depth to which the ac-celerator pedal is depressed, as is well known. The intake mani-i :: 20 fold 18 has a riser portion 26 which is located below the mixture delivery pipe 12 and which merges into a plurality of runner por-- tions (not shown) respectively leading to the intake ports of the ~ individual engine cylinders in the cylinder block 20.
The internal combustion engine further comprises an :~
exhaust system which.includes an exhaust manifold 28 and an exhaust pipe 30 leading downstream from the exhaust manifold 28. Though not shown, the exhaust manifold 28 consists of a plurality of branch tube portions respectively leading from the exhaust ports of the individual engine cylinders in the cylinder block 20 and a single . 30 "plenum" tube portion merging downstream out of the branch tube portions and connected at its leading end to the exhaust pipe 30, as is well known. The exhaust pipe 30 is connected through a muffler _ g _ -~. d '. .~
- - . .
': ' ' ' .; ' ; '~ ' " ' ' , ', --i It~
or mufflers to a tail pipe which is open to the atmosphere at its terminal end, though not shown.
The exhaust system is arranged with a catalytic converter 32. The catalytic converter 32 is shown to be mounted in the ex-haust pipe 30 but, if desired, the same may be mounted on the above-mentioned plenum tube portion of the exhaust manifold 28. The cata-lytic converter 32 is herein assumed, by way of example, to be of the previously described triple-effect type which is effective to process the three different kinds of air contaminative compounds of hydrocarbons, carbon monoxide and nitrogen oxides contained in the exhaust gases discharged from the engine cylinders. The cata-lytic converter 32 is, thus,permitted to produce its maximum con-version efficiency when supplied with exhaust gases which have resulted from an air-fuel mixture proportioned to the stoichiometric ratio of approximately 14.8:1 when the engine is of the type which is gasoline powered. To produce an air-fuel ratio proportioned to such a ratio in the mixture delivery pipe 12, the carburetor 10 is provided with a mixture control system which is adapted to regulate the air-to-fuel ratio of the mixture to be produced in the mixture delivery pipe 12 toward the stoichiometric ratio throughout the va-rious modes of operation or during predetermined modes of operation - of the engine. The mixture ratio control system comprises an exhaust sensor 34 provided in the exhaust system to detect the con-centration of a prescribed type of chemical component of the exhaust -gases discharged from the engine cylinders. For the purpose of des-cription, the exhaust sensor 34 is herein assumed, by way of ; example, to be of the type which is sensitive to oxygen contained in the exhaust gases passed therethrough. If desired, however! the exhaust sensor 34 of this nature may be replaced with an exhaust sensor of the type which is sensitive to, for example, hydrocarbons, carbon monoxide or dioxide or nitric oxides in the exhaust gases.
The exhaust sensor 34 is, furthermore, shown to be located in the ., -- 10 --. .
,~ . . . : . :
- - . , . . ~
':
exhaust manifold 28 with the catalytic converter 32 mounted in the exhaust pipe 30 but, if desired, the same may be located in the exhaust pipe 30 preferably upstream of the catalytic converter 32.
If the catalytic converter 32 is mounted in the plenum tube portion of the exhaust manifold 28 as previously mentioned, then it is pre-ferable to have the exhaust sensor 34 mounted on the particular por-tion of the exhaust manifold 28 upstream of the catalytic converter 32 thus arranged.
The exhaust sensor 34 produces an analog output signal S_ closely related to the detected concentration of the oxygen in the exhaust gases passed therethrough and supplies the signal S_ to an electric control circuit 36. The control circuit 36 is arranged to produce an output signal S_ that varies with the analog input signal S_ impressed thereon. The output signal S_ is fed to a suitable solenoid-operated valve unit 38 associated with the air delivery means and/or fuel delivery means (not shown) of the carburetor 10 and controis the rate of flow of air or fuel or the rates of flows of both air and fuel to be delivered into the mixture delivery pipe 12 in such a manner that the air-to-fuel ratio of the mixture pro-20 duced in the mixture supply system is regulated toward a stoichio-metric value. The solenoid-operated valve unit 38 may be of a two-position type having open and closed conditions or of the type which is continuously operable between open and closed conditions. If the valve unit 38 is of the two-position type, the control circuit 36 should be arranged to deliver, as the above-mentioned output si-gnal Sc, a train of pulses having a frequency and pulsewidths that vary with the analog input signal S_ impressed on the circuit 36.
Fig. 2 shows a preferred example of the control circuit 36 arranged to achieve such a function.
Referring to Fig. 2, the control circuit 36 is shown to comprise a comparator 40, a proportional amplifying integrator 42, a saw-tooth or triangular pulse generator 44 and a pulsewidth modu-. ~
.3 lator 46. The comparator 40 has a first input terminal connected to the output terminal of the above-mentioned exhaust sensor 34 and a second input terminal on which a reference signal Sr is constantly impressed. The reference signal S_ is representative of the con-centration of oxygen in the exhaust gases resulting from a stoichio-metric air-fuel mixture.
The comparator 40 is operative to compare the output~' signal So with the reference signal S_ and produces a binary output signal Sl which assumes a logic "0" value when the voltage of the signal S_ is greater in magnitude than the reference signal Sr (viz., when the air-fuel mixture supplied to the engine cylinders is richer than a stoichiometric mixture) and a logic "1" value when the former is smaller in magnitude than the latter (viz., when the mixture supplied to the cylinders is leaner than a stoichiometric mixture).
The binary signal Sl produced by the comparator 40 is fed to the proportional amplifying integrator 42 which is arranged to produce a linear ramp signal S2 which increases or decreases in response to the input signal Sl of the logic "0" or "1" value, respectively.
On the other hand, the saw-tooth or triangular pulse generator 44 is operative to produce a train of saw-tooth or triangular pulses S3 having equal pulsewidths and a predetermined constant frequency.
The ramp signal S2 from the proportional amplifying integrator 42 and the train of saw-tooth or triangular pulses S3 from the pulse generator 44 are fed to the pulsewidth modulator 46. The pulsewidth modulator 46 is, in effect, a comparator and is thus operative to compare the ramp signal S2 with the saw-tooth or triangular pulses S3, thereby producing a train of square-shaped pulses having posi-tive durations when the signal S2 is lower in magnitude than the saw-tooth or triangular pulses S3. The train of square-shaped pul-ses produced in this fashion by the pulsewidth modulator 46 provides ~ -the previously mentioned control signal Sc and is delivered from the -control circuit 36 to the soneoid-operated valve unit 38. The .. , . ~
~, . . .
~O~
valve unit 38 is consequently controlled to open and close at in-tervals dictated by the pulses Sc which are fed in succession to the valve unit. --The mixture control system thus arranged depends for~its performance upon the reliability of the signal delivered by the(~
exhaust sensor 34. Because, however, there is an appreciable diffe-rence between the time at which an air-fuel mixture is produced in the mixture delivery pipe 12 of the carburetor 10 and the time ~t which the exhaust gases resulting from the mixture reaches the e~haust 10 sensor 34 and because of the fact that the air-to-fuel ratio of~the mixture produced in the carburetor 10 is subject to fluctuation which is practically beyond the control of the mixture control and the carburetor per se, the signal produced by the exhaust sensor 34 is not faithfully representative of the air-to-fuel ratio of the mix-ture produced at the very instant at which the signal is delivered t~ ~ from the sensor 34. The intent of the present invention is to`re-duce such a time difference to a minimum by promoting the evapora-; tion of the air-fuel mixture being passed through the intake mani-fold. The degree of evaporation of the air-fuel mixture in the;
intake manifold is closely related to the velocity of the stream of the mixture through the intake manifold and the mixture flow~
~ ` through the intake manifold at a velocity which is approximately Z equal to the velocity of the stream of air t~rethrough when the-mixture is evaporated substantially perfectly, as will be seen ;:
from the curve of Fig. 3. ~-To achieve such an intent of the present invention, the exhaust manifold 28 of the engine illustrated in Fig. 1 has a wall portion constituted by the riser portion 26 of the intake manifold ' ~ 18 and a flow control valve 48 is provided within the exhaust mani-30 fold 28 in the neigh~ourhood of the particular wall portion. The flow control valve 48 is rotatable with a shaft 50 journalled to the exhaust manifold and provides a passageway 52 through which the ,'~
` ~
10~
exhaust gases entering the exhaust manifold 28 are brought into heat conductive contact with the riser portion 26 of the intake manifold 28. The valve 48 is rotatable about the axis of the shaft 50 bet-ween an angular position indicated by full lines for providing a maximum flow rate through the passageway 52 and an angular position indicated by phantom lines for providing a minimum flow rate through the passageway 52. The valve 48 is moved between these two angular positibns by means of a helical bimetallic spring 54 which is ;- anchored at one end to the shaft 52 and at the other end to an internal wall portion of the exhaust manifold 28 as indicated at 56.
The bimetallic spring 54 is arranged to move the valve 48 between the above-mentioned two positions in such a manner as to vary the flow rate of the exhaust gases through the passageway 52 substantial-ly in inverse proportion to the temperature of the hot exhaust gases as detected by the bimetallic spring 54 so that the quantity of heat in the exhaust gases passed through the passageway 52 and according-ly the quantity of heat transferred through the riser portion 26 of the intake manifold 18 to the air-fuel mixture flowing through the intake manifold 18 are maintained substantially constant. The bi-metallic spring 54 is preferably selected and arranged to maintainthe temperature of the riser portion 26 of the intake manifold 18 within the range of between about 100 C and about 250 C.
To provide an increased heat exchange efficiency through the riser portion 26 of the intake manifold 18, the riser portion `
26 may be corrugated or ridged as shown.
Fig. 4 illustrates by curve _ the concentration of an air contaminative compound (exemplified by carbon monoxide) contained in the exhaust gases discharged into the atmosphere when the flow control valve 48 of the arrangement shown in Fig. 1 is operated by the bimetallic spring 54 in such a manner as to maintain the tempe-rature of the riser portion 26 of the intake manifold 18 at appro-ximately 180C. From comparison between this curve _ and the ~ `
106'~103 curve b which is indicative of the concentration of carbon monoxide in the exhaust gases dischar~ed from an ordinary internal combus-tion engine provided with a catalytic converter and a mixture con-trol system of the described nature but void of the mixture eva~o-rative means, the advantages achieved by the present invention will be self-explanatory. -~
The lower and upper limits 100C and 250C of the above-mentioned temperature range have been specified with a view to enabling the air-fuel mixture to be sufficiently atomized and pro-l.0 vlding acceptable mixture induction efficiency. ~
. . .
~ " .
~ ~;
. .
; - 15 -., ~ , .
Claims (5)
1. In an internal combustion engine including a carbure-tor connected to the cylinders of the engine through an intake mani-fold including a riser portion and an exhaust system having incor-porated therein a catalytic converter which is reactive to at least one type of air contaminative compound contained in the exhaust gases discharged from the engine cylinders and passed through the converter and which is operative to produce a maximum conversion efficiency when the air-fuel mixture produced in the carburetor is proportioned to a predetermined air-to-fuel ratio, a method of con-trolling the air-to-fuel ratio of the mixture to be produced in the carburetor, comprising monitoring the air-to-fuel ratio of the mix-ture produced in the carburetor from the exhaust gases flowing in the exhaust system, regulation the air-to-fuel ratio of the mixture to be produced in the carburetor toward said predetermined ratio, directing the hot exhaust gases through a passageway in heat con-ductive contact with the riser portion of the intake manifold for transferring heat from the exhaust gases to the air-fuel mixture in the intake manifold, detecting the temperature of the exhaust gases passed through said passageway and regulating the flow of the exhaust gases through the passageway for maintaining substan-tially constant the quantity of heat in the exhaust gases passed through the passageway.
2. A method as set forth in claim 1, in which the flow rate of the exhaust gases through said passageway is controlled to maintain the temperature of said riser portion of the intake mani-fold within the range of from about 100°C to about 250°C.
3. A method as set forth in claim 1 or 2, in which the flow rate of the exhaust gases through said passageway is varied substantially in inverse proportion to the temperature of the exhaust gases passed through said passageway.
4. An internal combustion engine which comprises a car-buretor connected to the cylinders of the engine through an intake manifold including a riser portion; an exhaust system having incor-porated therein a catalytic converter which is reactive to at least one type of air contaminative compound contained in the exhaust gases discharged from the engine cylinders and passed through the converter and which is operative to produce a maximum conversion efficiency when the air-fuel mixture produced in the carburetor is proportioned to a predetermined air-to-fuel ratio, the exhaust sys-tem having a wall portion constituted by the riser portion of the intake manifold; a mixture control system adapted to monitor the air-to-fuel ratio of the mixture produced in the carburetor from the exhaust gases flowing through the exhaust system and to control the air-to-fuel ratio of the mixture to be produced in the carbure-tor toward said predetermined ratio; and a device for forcibly eva-porating the air-fuel mixture in the intake manifold, the device comprising a flow control valve located within the exhaust system in the neighbourhood of said wall portion of the exhaust system for providing a passageway of exhaust gases in heat conductive contact with the riser portion of the intake manifold, and heat-sensitive valve control means including a helical bimetallic spring which is anchored at one end to said flow control valve and at the other end to a wall portion of the exhaust system for varying the flow rate of the exhaust gases through said passageway substantially in in-verse proportion to the temperature of the exhaust gases passed through the passageway.
5. An internal combustion engine as set forth in claim 4, in which said riser portion is corrugated.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP50081027A JPS5126096A (en) | 1974-07-05 | 1975-07-02 | Kongokichuno sansonodoteiryoyosokuteiseru |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1062103A true CA1062103A (en) | 1979-09-11 |
Family
ID=13734981
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA254,622A Expired CA1062103A (en) | 1975-07-02 | 1976-06-11 | Internal combustion engine with exhaust cleaning means |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA1062103A (en) |
| DE (1) | DE2626258A1 (en) |
| GB (1) | GB1550462A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2836927A1 (en) * | 1978-08-24 | 1980-04-10 | Volkswagenwerk Ag | IC engine intake heating system - supplies electric current and cuts off water to hot spot when warming up |
-
1976
- 1976-06-11 DE DE19762626258 patent/DE2626258A1/en not_active Withdrawn
- 1976-06-11 CA CA254,622A patent/CA1062103A/en not_active Expired
- 1976-06-14 GB GB24488/76A patent/GB1550462A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1550462A (en) | 1979-08-15 |
| DE2626258A1 (en) | 1976-12-23 |
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