CA1116486A

CA1116486A - Internal combustion engine

Info

Publication number: CA1116486A
Application number: CA000316208A
Authority: CA
Inventors: Keiichi Sugiyama; Hiromitsu Matsumoto
Original assignee: Yamaha Motor Co Ltd
Current assignee: Yamaha Motor Co Ltd
Priority date: 1977-11-14
Filing date: 1978-11-14
Publication date: 1982-01-19
Also published as: SE7811698L; JPS5469619A; GB2008672A; DE2849213A1; AU526395B2; GB2008672B; DE2849213C2; ES475034A1; AU4152578A; FR2408723B1; IT7822559A0; SE441768B; FR2408723A1; BR7807458A; IT1094466B

Abstract

ABSTRACT OF THE DISCLOSURE
Internal combustion engine comprising a combustion chamber, a main intake passage communicating with the combus-tion chamber through an intake port, an intake valve provided in the intake port, an auxiliary passage having one end open-ing to the main intake passage at an area adjacent to the in-take port, a control valve provided in the main intake passage and adapted to be closed under a light load operation so that intake flow of fluid is introduced at a high speed through the auxiliary passage into the combustion chamber, characterized by control means for changing the timing at which peak pres-sure is produced in the combustion chamber, means for inter-connecting the control valve and the control means so that the control means is actuated when the control valve is closed so as to retard the timing at which the peak pressure is produced.

Description

~.16~-~86 The present invention relates to i~ternal combustion engines and more particularly to means for providing an improved combustion in internal combustion engines.
In recent years, extensive efforts have been made in the field of internal combustion engines in order to meet strict regulations for decreasing pollutant emissions such as hydrocarbon~ carbon monoxide and nitrogen oxides. For example, it has been proposed to operate the engines with ignition timing~ substantially retarded as compared with those which have previously been believed as being recom-mendable. ~urther, it has also be0n proposed to supply the engine with leaner air-fuel mixtures. Such conventional solutions have been efYective in certain extent to decrease pollutant emissions, however, they have been recognized as being defective in that it is difficult to attain a stabilized combustion which is essential in establishing a smooth engine operation and that the thermal efficiency of the engine is decreased resulting in a poor fuel economy.
It has also been proposed to provide a squishing configuration in the combustion chamber and/or to provide ~piral ~uide means in the intake passage so that the intake mixture iB given with an intense swirl or turbulence for providing an improved combustion. However, the~e proposals could not provide perfectl~ satisfactory solutions in respect of pollutant emissions and of fuel economy.
~ he inve~tors have formed that it is effective in producing an intense swirl or turbulence o~ mixture in the - combustion cha~ber to provide an auxiliary intake passage

- 2 -1~ 16~ ~ ~
which has previously been adopted for the purpose of providing a str~tified mixture charge or preventing film flow of liquid fuel along the wall of the intake pa3sage.
Thus, the inventors have conceived to provide an auxiliar~
intake pas6age of a relatively small cross-~ectional area in such a manner that it opens to the main intake passage in an area ad~acent to the intake port whereby intake mixture i8 introduced at a relatively high speed into the combustion chamber through the auxiliary intake passage under a light load operation of the engine. As the engine load increa~es, the amount of intake mixture through the main intake passage is increased so that the relative amount of the mixture through the auxiliary intake pas~age is decreased. It will thus be noted that there will be a substantial difference in the rate of combustion or the rate of propagation of combustion flame between the part load co~dition under which substantial part of the intake mixture i8 passed through the auxiliary passage and the heavy load conditions under which relatively small amount of intake mixture is passed throngh the auxiliary passage.
It is therefore necessary to compen~ate for æuch difference in the rate of propagation of combustion flame in order to operate the engine with a high efficiency.
Specifically speaking, the ignition timing of an engine is generally determined in such a manner that the maximum or peak pressure is produced 5 to 10 after top dead center. ~owever, in an engine formed wit~ the afore~
- mentioned auxiliary int~e passage, since the rate of 11~6486 prop~6ation of combustion flame significantly changes in accordance with the load condition of the engine as previousl~ described, the peak pressure will be produced at an impermissibly advanced timing under the part load condition if the ignition timing is determined in accordance with a conventional manner. In other words, conventional ways for determining the ignition timing are no longer applicable to those engines having the aforementioned auxiliary intake passage.
It i8 therefore an object of the present invention to provide internal combustion engines which are satisfac-tory in respect of pollutant emissions and can provide ~mooth operations throughout a wide load range with an improved fuel economy.
Another object of the present invention is to provide internal combustions engines having an auxiliary intake passage in addition to a main intake passage, in which means is provided to compensate for the aforementioned difference in the rate of propagation of combustion flame.
According to the present invention, the above and other objects can be accomplished by an internal combustion engine comprising a combustion chamber, a main intake passage communicating with the combustion chamber through an intake port, an intake valve provided in said intake port, an auxiliary passage having one end opening to the main intake passage at an area adjacent to the intake port, a control valve provided in said main intake passage and adapted to - be closed under a light load operation so that intake flow fl~i of fluid is introduced at a high speed through the auxiliar~ passage into the combu~tion chamber, characterized by control means for changing the timing at which peak pressure is produced in the combustion chamber, means for interconnQcting the control valve and the control means so that the control means is actuated when the control valve is closed so as to retard the timing at which the peak pressure is produced.
According to one aspeGt of the present invention, the control means is embodied in the form of means for recirculating a part of exhaust combustion gas into the intake flow. In another aspect, the control means may be an ignition timing control device for retarding the ignition timing under the light load operation.
The above and other objects and featureR of the present invention will become apparent from the following descriptions of preferred embodiments taking reference to the accompanying drawings, in which;
Figure 1 is a sectional view of an internal combustion engine in accordance with o~e embodiment of the present invention;
Figure 2 i5 a sectional view taken substantiall~ along the line II - II in ~igure l;
~ igure ~ is an elevational view showing the exterior of the engine shown in ~igure 1;
Figure 4 is a sectional view similar to Figure 1 but showing another embodiment;
~ igure 5 i8 a sectional view similar to Figures 1 and ~.16~6 4 but showing a further embodiment;
~ igure 6(a) i 8 a diagram showing pressure changes in a conventional engine;
Fi~ure 6(b) is a diagram showing pressure changes in an engine in accordance with the present invention;
Figure 6(c) shows pressure changes in combustion stroke;
~ igure 7 shows the intake flow speed in the auxiliary intake passage and the amount of recirculated exhaust gas in the engine shown in ~igure 1;
Figure 8 is a sectional view showing an engine in accordance with a further embodiment of the present inven-tion; and~
~ igure 9 shows the relationship between the intake flow speed through the auxiliary intake passage and the ignition timing in the engine shown in ~igure 8.
Referring to the drawings, particularly to ~igure 1, the engine ~hown therein includes an engine body 1 which has a carburetor 3 mounted thereon through an intake manifold 2. ~he engine body 1 comprises a cylinder 4, a cylinder head 5 and a piston 6 which are assembled in a conventional manner to define a combustion chamber 7.
~he cylinder head 5 is formed with an exhaust passage 8 which communicates with the combustion chamber 7 through an exhaust valve 9. The cylinder head 5 is further formed with an intake passage 11 which communicates on one hand with the combustion chamber 7 through an intake valve 12 - and extends on the other hand through the intake manifold 2.

8~i The ca~buretor ~ is of a conventional compound tgpe including an u~per barrel 3a a~d a lower barrel 3b.
The carburetor 3 has a primary passage 3c and a secondary passage 3d which are communicated with the intake passage 11. ~he primar~ passage 3c is provided with a main fuel nozzle 35 and a primary throttle valve 14 and the secondary passage 3d with a fuel nozzle 3~ and a secondary throttle valve 3h.
~he primary throttle valve 14 is of a manually operated type and the primar~ passage 3c is pxov.ided with a control valve 15 downstream of the primary throttle ~alve 14. An auxiliary passage 16 is formed in the intake m~nifold 2 ~nd has one end openi.ng to the primary passage 3c between the primary throttle valve 14 a~d the control val~e 15.
The other end of the auxiliary passage 16 is opened to the ~ intake passage ].1 in the vicinity of the intake valve 12.
The control valve 15 is connected through a link 17 with a ~uction pressure responsive device 18 so that it is closed by the device under a light load operation including idling but opened under a heavy load operation~ ~'he control valve 15 ma~ not necessary be perfectl~ closedO
As shown in ~igure 3, the suction pressure responsive device 18 comprises a casing 18a and a diaphragm 18b which divides the inside of the casing 18a into a ~IICtiOn pressure chamber 18c and an atmospheric pressure chamber 18d. As ~hot~n in Figure 1, the suction pressure chamber 18c is connected through a conduit 19 with the primary passage 3c at a position adjacent to the primary throttle valve 140 ~1.16~86 ~he diaphragm 18b is connected with the link 17 and bia~ed toward right by means of a sprin~ 18e disposed in the chamber 18c so that the control valve 15 is normally forced by the spring to the open position.
An exhaust gas recirculating conduit 21 extends between the exhaust passage 8 and the auxiliary passage 16 60 tha~ a portion of the exhaust gas is recirculated from the exhaust passage 8 to the auxiliary passage 16~
In the conduit 21, there i5 provided a flow control valve 2~ for controlling the flow of the combustion gas into the intake system.
~he flow control valve 23 comprises a valve member 23a and a valve housing 23b and a diaphragm device 24 i~
provided for controlling the valve member 23a. ~he dia-1~ phragm device 24 includes a chamber 24a defined by a diaphragm 24c which is connected with the valve member 23a and forced by means of a spring 24b in the chamber 24b so as to bias the valve member 23a toward the closed position.
~he chamber 24a is connected through a conduit 22 and a kno~m type of pressure amplifier 25 with a pressure reservoir 26 which is in turn connected through a one-way valve 20 with a conduit 19 so that the suction pressure in the primary passage 3c i9 accumulated in the reservoir 26.
The amplifier 25 i8 connected with a first pressure signal line 27 leading from the venturi throat in the primary passage 3c and with a second pressure signal line 28 leading from a position adjacent to the primary throttle valve 14.
- ~hus, the amplifier 25 is opened by the first pressure signal from the line 27 and functions to control the opening of the valve 23 in accordance with the flow in the primary passage 11. Therefore, the amount of recirculated com-bustion gas is controlled in accordance with the engine operating condition as shown in ~igure 7(b).
The conduit 22 is provided with a pressure relief valve 22a which has a solenoid 22b ~o that it is opened when the solenoid 22b is energized. The solenoid 22b is connected with a power source B through a switch S which is adapted to be closed when the engine speed is increased beyond a predetermined valve. As soon as the valve 2~a is opened, the atmospheric pressure is introduced into the conduit 22 whereby the opening of the valve 23 is decreased so as to reduce the amount of recirculated combustion gas.
In operation of the engine, there prevails a very low pressure in the downstream side of the throttle valve 14 as long 8.S the throttle valve 14 is at a low opening position or the engine is under an idling operation.
~uch low pressure is applied thxough the conduit 19 to the suction pxessure responsive device 18 so that the diaphragm 18b is moved against the action of the spring 18e to close the control valve 15. Thus, substantial portion of the intake mixture which has passed through the throttle valve 14 is directed thxough the auxiliary pas~age 16 to the inlet port area of the intake passage 12 and introduced at a hi~h speed into the combustion chamber 7 during the intake stxoke wherein the intake 1~.1648~i`

valve 12 is opened. It should therefore be noted that an intense swirl or turbulence is produced in the combustion chamber and combustion will take place rapidly as soon as ignition flame is produced since the rate of propagation of combustion flame is increased due to the swirl or turbulence.
In other words, due to the auxiliary passage 16, it is possible to produce even under idling or other light load operation a swirl or turbulence which is as strong as that produced under a high fipeed operation of a conventional engine. Thus, it is possible to accomplish a ~tabilized combustionO
At this instance, the first pressure signal line 27 i8 opened slightly upstream side of the throttle valve 14 and a high or substantially atmospheric pressure is transmitted to the amplifier 25 to close the same. Thus, the supply of suction pressure to the chamber 24a is interrupted and the valve member 23a iB forced under the action of the sprin~ 24b to close the valve 23 to block the flow of combustion gas into the intake system.
Under a part load operation wherein the throttle valve 14 is opened to a certain amount, the intake flow is appreciably increased and a suction pressure is still produced at the downstream side of the throttle valve 14 so that the device 18 functions to maintain the control valve in the closed position. The intake flow through the auxiliar~ passage 16 is therefore increased to produce - an extreme]y strong swirl or turbulence so that it becomes i ~l 6~ ~ 6 nece~sary to retard the ti~ning at which the peak p~s~ure is produced.
SinGe the throttle valve 14 is partially opened at this instance, the line ~7 is opened to the primary passage 3c at the downstream side of the throttle valve 14 whereb~ the suction pressure is applied to the amplifier ~5 to open the same. ~he venturi pressure through the line 28 is applied to the amplifier 25 and functions to control the ,suction pressure applied to the diaphragm device 24. It should therefore be noted that the valve 23 is controlled in such a manner that the amount of recirculated combustion gas is increased in accordance with an increa6e in the flow thrQugh the auxiliary passage 16.
More specifically, the suction pressure in the reservoir 26 is applied to the diaphragm device 24 under the control of the venturi pressure which represents the amount of intake f'ow and the diaphragm 24c in the device 24 i8 moved to a position where the pressure in the chamber 24a is balanced with the spring 24bo ~hus, the val~e member 2~a is maintained at a position corresponding to the amount of intake flow to allow a corresponding amount of combustion gas to pass into the intake ~ystem. It is preferable to control the recirculation of combustion gas in such a manner that such recirculation is started with a relatively small amount of combustion gas and gradually increased in accordance with an increase in the intake mixture flow in order to avoid rough engine operation.

8~.~

~he combustion gas introduced into the auxiliary passage 16 is directed into the combustion chamber 7 together with the intake mixture. Thus, the amount of flow through the auxiliary passage 16 is increased by an amou~t corresponding to the amount of the recirculated combustion gas so that the flow speed in the passage 16 is correspondingl~ increased to thereby intensif~ the swirl or turbulence in the combustion chamber. ~urthex, the recirculation of the combustion gas is also effective in suppressing nitrogen oxidesO It has been found that in an engine having an auxiliary passage 16 the amount of recirculation ga6 can be increa~ed approximately two times as much as that allowed in a conventional engine without having any adverse effect on the stability of operation due to a significant improvement in combustion through the employment of the auxiliary passage.
When the throttle valve 14 is opened to a full or wide open position for heavy load operation, the pressure at the downstream side of the throttle valve 14 is increased substantially to the atmospheric pressure. ~he pressure i~ applied to the suction pressure responsive device 18 and acts on the diaphragm 18b so that the diaphragm 18b is moved under the action of the spring 18e to open the control valve 15.
As the control valve 15 is opened, the amount of flow through the auxiliary passage 16 is correspondingly decreased.
With the control ~al~e 15 in full open position, substantial part of the intake mixture is allowed to pass through the ~116486 control valve 15. Therefore, it will be noted that as the control valve 15 i6 opened the contribution of the auxiliary pa~sage 16 to the swirl or turbulence in the combustion chamber 7 is correspondingly decreased. It will therefore become nece~sary to decrease or terminate recirculation of combustion gas since there will be a decrease in the r~te of propagation of combustion flame.
In the illustrated embodiment, the pressure in the vicinity of the throttle valve 14 is transmitted through the line 27 to the amplifier 25 so as to close the same whereb~ the diaphragm 24c of the device 24 is relieved of the suction pre~sure. ~he valve member 23a is therefore moved under the action of the sprin~ 24b to close the valve 23. ~hus, the flow of combustion gas i8 blocked by the valve 23~
It should be noted, however, that the timing at which the recirculation of combustion gas is blocked does not alway~ coincide with the timing at which the contribution of the auxiliar~ passage 16 to the swirl or turbulence in the combustion chamber 7 is weakened.
Further~ asshown in Figure 7, the flow speed in the auxiliary passage 16 is not linearly proportional to the amount of recirculation gas.
Further, ~o specific or direct relationship is provided between the amount of the recirculated combus-tion gas and the position of the control valve 15 in the hope that the control vhlve 15 may also be utilized for controlling other factors such as acceleration, deceleration 6~8~i and speed of the engine. Thus, it wil]. be noted that the present invention is based on the concept of engine control in which an increased amount of combustion gas is recirculated to the intake system to decrease the rate of propagation of combustion flame under a part load operation wherein the auxiliary passage i8 functioning to intensif~ the swirl or turbulence in the combustion chamber while the amount of the recirculati.on 6as is decreased or the recirculation is completely stopped under a heavy load operation wherein the function of the auxiliary passage is weakened so as to increase the rate of propagation o~ combustion flame. In the embodi-ment described, the carburetor i5 of a co~pound type, however, the present invention is not limited to a use of this t~pe of carburetor and it is apparently within the scope of the present inventlon to use a single barrel type carburetor. ~urther, the present invention may also be applied to rotary piston engines.
Referring now to ~igure 4, there is sho~m an embodiment in which the present invention is applied to an engine having a so-called dual induction type intake system. In ~igure 4, corresponding parts are designated by the same reference numerals and detailed descriptions are therefore omitted. In this embodiment, each intake passage 11 leading from each combustion chamber 7 is provided with a carburetor 3' having ~ throttle valve 3ho An auxiliar~ passage 16 is co~Lnected with a manifold 16a which is in turn connected with bra~ch passa~es l~b fi provided one for each cylinder. Each branch pa~sage 16b is opened to the corresponding intake passage 11 in the vicinity of the intake valve 12. '~he auxiliary passage 16 is provided with an auxiliary carburetor ~" which is common to all of the cylinders.
~ he a~xiliary carburetor 3" has an auxiliary throttle valve 14" which i~ connected with a manually operated member such as a foot pedal P. The throttle valve 3h is interconnected with the auxiliar~ throttle valve 14' so that the former starts to open when the latter is opened beyond a predetermined valve. In normal design, under the vehicle speed less thatn lOOkm/h, substantially all of the intake mixture is supplied through the auxiliary passage 16. Preferably, a slight amount of mixture should be allowed to pass through the throttle valve 3h even when it is in the closed position.
~ igure 5 shows an embodiment in which the present invention is applied to an engine having a fuel injection type intake ~ystem. In this embodiment, the intake system has an air-flowmeter 51 which produces an air-flow signal adapted to be used for metering fuel. r~he metered fuel is injected into the intake passage 11 through a fuel in~ection nozzle 52. The auxiliary passage 16 has an upstream end opening at the downstream side of the air-flowmeter 51. r~he fuel in~ection type intake system doesnot have any venturi configuration which has been utilized in the previous embodiments for deriving a first pressure signal for the amplier 25. r~herefore, in this embodiment, ~II.lfi~

the first pressure ~ignal line 27 is opened at a point adjacent to the auxiliary throttle valve 14' ~nd the second pressure signal line slightl~ upstream side of the seid point. In this em~odiment, the auxiliary throttle valve 14' corresponas to the control valve 24 in the embodiment of ~igure 1.
Referring now to Figure 81 there is shown a further embodiment of the present invention. In this embodiment, the engine body 1 itself is basically identical with that in the embodiment of Figure 1 but the control valve 1 i8 located do~mstream side of the intake manifold 2.
In an engine having a plurality of cylinders, a control valve 15 is provided for each cylinder. As in the embodiment of ~'igure 1, the control valve 15 is co~trolled by the suction pressure in the intake passage 11 at downstream side of the throttle valve 14.
~ he engine includes an ignition circuit IG which is connected through a main switch SW with a power source B.
The ig~ition circuit IG is connected with a distributor 55 which is in turn connected with ignition plugs for the cylinders. ~he distributor 55 includes a conventi~nal breaker device and ignition timing can be controlled by an adjustment of the breaker device. In the embodiment shown in ~igure 8, the distributor has an adjusting lever 55a which is connected with a diaphragm device 61. ~he diaphragm device 61 includes a diaphragm 64 defining a suction pressure chamber 61a which is connected through a line 62 with the first pre~sure signal line 270 ~he diaphragm 64 is forced by a spring 6~ in the chamber 61a toward left or in the direction of advancing the ignition timing. When a suction pre~sure is applied to the chamber 61a, the diaphragm 64 is moved toward right to rotate the lever 55a in the direction of retarding the ignition timing.
Although not ~hown in the drawing, the distributor 55 further includes a centrifugPl governor which functions to control the ignition timing as shown by a line ~ in ~igure 9.
In this embodiment, under the idling operation of the engine, the chamber 61a is su~aected to a pressure substantially equal to the atmospheric pressure so that the diaphragm 64 is forced leftwards under the action of the spring 6~ to maintain the le~er 55a at the advanced position. Under a part load operation wherein the throttle valve 14 is at a partially opened position, the chamber 61a is subjected to a suction pressure 80 that the dia-phragm 64 is displaced toward right against the action of the spring 63. ~hus, the lever 55a is moved in the retarding direction and the ignition timing is retarded as shown by a line G in Figure 9.
When the throttle valve 14 is widely opened, the chamber 61a is again subaected to a pressure equal or close to the atmospheric pressure whereby the diaphragm 64 is displaced toward left to advance the ignition timing.
In ~igure 9, the line H shows the i~nition timing in a conventional engine in which the ignition timing is 11164~6 advanced under the part load operation.
In this embodiment, the ignition timing is controlled in a stepless m~nner by using the diaphragm device 61, however, it should be noted that the control may be performed stepwisely by using electric switches. Further, it may be possible to use two or more distributors having different ignition timings so that they may be selectively used in accordance with the pres~ure in the line 62.
As described above, according to the present in~rention9 stable operation of the engine can be ensured throughout the load range by providing means for controlling the timing at which the peak pressure is produced either by recirculating combustion ga5 to the intake system in an amount 10 to 30% of the intake mixture or b~ retarding the ignition timin~ under the part load operation. Referring ~ for example to ~`igure 6(a~ which shows pressure changes in the combustion chamber, it will be noted that the peak pressure changes significantly as shown by H in accordance with the load condition. However, in an engine embodying the present invention, the change in the peak pressure can be decreased as ~hown by h in ~igure 6(b).
According to the engine having the auxiliary intake pa~sage, the recirculated combustion gas can be increased as much as 10 to 30% of the intake mixture without having any adverse effect on the combustion of mixture. ~herefore, such recirculated combustion gas will also function to decrea~e nitrogen oxide~ in the exhaust gas.
In an engine in which production of nitrogen oxides _ 18 -is compaxatively small, it is preferable to embody the present invention by providing mean~ for retardlng the ig~ition timing because such arran~ement provides an ad.vantsgeous e~fect on fuel econom~. It is of course within the scope of the present invention to provide both the e~haust gas recirculating meàns and the ignition timing retarding means in embodying the present invention~
The invention. h.as thus been shown and desc.ribed with reference to specific arrangements, ho~rever, it should be noted that the invention is in no way limited to the details of the illustrated structures but changes and modification~ may be made without departing from the scope of the appended claims.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. Internal combustion engine comprising a combustion chamber, a main intake passage communicating with the combustion chamber through an intake port, an intake valve provided in said intake port, an auxiliary passage having one end opening to the main intake passage at an area adjacent to the intake port, a control valve provided in said main intake passage and adapted to be closed under a light load operation so that intake flow of fluid is introduced at a high speed through the auxiliary passage into the combustion chamber, characterized by control means for changing the timing at which peak pressure is produced in the combustion chamber, means for interconnecting the control valve and the control means so that the control means is actuated when the control valve is closed so as to retard the timing at which the peak pressure is produced.

2. Internal combustion engine in accordance with claim 1 in which said control means is means for recirculating combustion gas into the intake system.

3. Internal combustion engine in accordance with claim 1 in which said control means is ignition timing control means for retarding the ignition timing under the light load operation.

4. Internal combustion engine in accordance with anyone of claims 1 through 3 in which said control means is actuated under a part load operation excluding idling operation.

5. Internal combustion engine in accordance with claim 3 in which said ignition timing control means includes a plurality of ignition timing control devices having different timings, which are selectively used in accordance with the load conditions.