CA1075988A - Internal combustion engine having two spark plugs for each combustion chamber and exhaust gas recirculation circuit - Google Patents
Internal combustion engine having two spark plugs for each combustion chamber and exhaust gas recirculation circuitInfo
- Publication number
- CA1075988A CA1075988A CA271,081A CA271081A CA1075988A CA 1075988 A CA1075988 A CA 1075988A CA 271081 A CA271081 A CA 271081A CA 1075988 A CA1075988 A CA 1075988A
- Authority
- CA
- Canada
- Prior art keywords
- engine
- combustion chamber
- axis
- piston
- recess
- 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
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
- F02B23/08—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- F02F1/00—Cylinders; Cylinder heads
- F02F1/24—Cylinder heads
- F02F1/242—Arrangement of spark plugs or injectors
-
- 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
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
-
- 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
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
- F02M26/41—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories characterised by the arrangement of the recirculation passage in relation to the engine, e.g. to cylinder heads, liners, spark plugs or manifolds; characterised by the arrangement of the recirculation passage in relation to specially adapted combustion chambers
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
- F02B23/08—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition
- F02B2023/085—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition using several spark plugs per cylinder
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B2275/00—Other engines, components or details, not provided for in other groups of this subclass
- F02B2275/20—SOHC [Single overhead camshaft]
-
- 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
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M2026/001—Arrangements; Control features; Details
- F02M2026/007—EGR specially adapted for engines having two or more spark plugs per cylinder
-
- 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)
- Combustion Methods Of Internal-Combustion Engines (AREA)
- Ignition Installations For Internal Combustion Engines (AREA)
- Spark Plugs (AREA)
Abstract
Abstract In an internal combustion engine of the recipro-cating piston type which is provided with an exhaust gas recirculation circuit to suppress the formation of NOx, each combustion chamber includes a recess formed on the bottom face of the cylinder head to have n simple shape such as hemisphere and is equipped with two spark plugs which work simultaneously. The spark gaps of the two spark plugs are positioned in the recess such that the ratio of the distance between them to the diameter of the cylinder bore is 0.45-0.67 and that the distance of each spark gap from the piston top at a crank angle of about 40° after the top dead center is approximately half of the distance between the two spark gaps.
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Description
~075988 Background of the Invention This invention relates to an internal combustion engine which has two spark plugs for each combustion chamber and is provided with an exhaust gas recirculation circuit.
In regard to the suppression of the formation of nitrogen oxides (NOx) in the operation of internal com-bustion engines, a recently proposed method is characterized in that the exhaust gas is recirculated to the combustion chambers in a large amount and that each combustion chamber is equipped with two spark plugs which are positioned at some distance from each other and produce sparks simultaneously. Accordinq to this method, the maximum amount of the reci~culated exhaust gas reaches about 25-45% by volume of air admitted into the combustion chambers as a component of a fresh air-fuel mixture.
The recirculation of exhaust gas in such a large amount is quite effective in loweri~g the maximum combustion temperature and hence suppressing the formation of NOx but is liable to cause an unstable combustion. The simul-taneously working tow spark plugs for each combustion ~, , chamber are provided with the purpose of not only ensuring the ignition of the diluted air-fuel mixture but also rapidly completing the combustion. Since each of the two distant spark gaps serves as a starting point of . ~ , . . .
_ ~ _ ~b : ~.
'' `~:
flame propagation in the combustion chamber, the pro-pagation of flame or combustion can be completed with a greatly shortened propagation distance. In an ideal case, flames developed at the two starting points can spread over the entire region of the combustion chamber in nearly a half of the time needed for the completion - of the flame propagation in the same combustion chamber by the use of a single spark plug. - I
. The greatest importance to this method is the arrangement of the two spark plugs. Shortening the flame - propagation time, ensuring a stable combustion and avoiding a significant increase in the fuel consumption can satis-~- factorily be achieved only when the two spark plugs are optimumly positioned in the combustion chamber.
; 15 Summary of the Invention It is an object of the present invention to provide an engine system which includes an internal combustion engine of the reciprocating piston type having two spark plugs for each combustion chamber thereof and an exhaust gas recirculation circuit, wherein the two spark plugs are positioned in a manner best suited for accomplishing the principal object of the engine system, that is, realizing a stable combustion of an air-fuel mixture diluted with a large amount of exhaust gas thereby to suppress the - 25 formation of NOx with only minimized sacrifice of the 107598~
engine performance.
It is another object of the invention to provide an engine system of the described type, which engine system features a good fuel economy despite the recir-culation of a large amount of exhaust gas.
It is still another object of the invention to provide an engine system of the described type, wherein intake and exhaust valves for each combustion chamber are arranged in a manner best suited for practicing an optimum arrangement of the two spark plugs.
An engine system according to the invention includes an internal combustion engine of the reciprocating piston type and an exhaust gas xecirculation circuit which is arr2nged to recirc~late a portlon of the exhaust gas from the exhaust line to each combustion chamber at a controlled flow rate in relation to the flow rate of air taken into each combustion chamber. Each combustion - chamber of the engine consistC of a variable volume cylindrical space defined in a cylinder bore between the top face of the pistpn and a bottom face of a cylinder head and a recess formed on this bottom face to have a larger volume than the cylindrical space at the top dead center of the piston. Each combustion chamber is provided with an intake valve, an exhaust valve and two spark plugs which produce sparks substantially simultaneously.
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1~75988 `
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As an essential feature of the engine system according to the lnvention, the spark gaps of the two spark plugs are positioned in the recess so as to meet the following conditions: (a) the two spark gaps are located respec-, 5 tively on different sides of a first plane containing , the longitudinal axis of the cylinder bore; (b) the two . spark plugs are gene~ally symmetrically arranged with :
. respect to the bore axis in a plan view taken trans-'.:~ versal to the bore axis; (c) the ratio of the distance 10 between the two gaps to the diameter of the cylinder bore is in the range from 0.45 to 0.67; and (d) the ratio of - the distance from each spark plug to the top face of the piston to the distance between the two spark gaps is in the ran~1e from 0.45 to 0.55 when the piston at each power stroke reaches a position e~pressed by a crank angle of about 40 degrees after the top dead center.
The recess portion of the combustion chamber is preferably included entirely in an imaginary and axial ~.` extension of the cylinder bore and has a simple and : 20 generally symmetrical shape with respect to the bore axis. More particularly, it is preferable that the .` periphery of the recess is given generally by a surface of . .
revolution on the axis of the cylinder bore and that the .
. cross-sectional area of the recess exhibits fundamentally :: 25 no increase as the distance from the top face of the piston ', : '. _ ,~_ : ' . ' .... . .
;` 1~75981~
increases.
Preferably, the intake and exhaust valves are located respectively on different sides of a second plane which is parallel to the bore axis and contains a line segment connecting the two spark gaps.
Br_ef Descriytion of the Drawings Fig. 1 is a schematic plan view of an engine system according to the invention;
Fig. 2 is a cross-sectional view of a combustion chamber as an embodiment of the invention;
Fig. 3 is a sectional view taken along the line 3-3 of Fig. 2 and partly rotated through an angle indicated in Fig. 2;
Fig. 4 is a s_ctional view taken along the line 4-4 of Fig. 2;
Fig. 5 is a graph showing the dependency of the fuel economy of the engine system of Fig. 1 on the distance between the two spark gaps in each combustion chamber;
Fig. 6 is a cross-sectional view of two adjacent combustion chambers as another embodiment of the invention;
Fig. 7 is a sectional view taken along the line 7-7 of Fig. 6;
Figs. 8 and 9 are cross-sectional views of two different combustion chambers, respectively, as still S
-- ~6 -- ' 1(~75988 `' different embodiments of the invention.
Description of Preferred Embo iments In Fig. 1, a four-cylinder internal combustion engine 10 is equipped with a carburetor 12 to supply S an air-fuel mixture to the respective engine cylinders through an induction passage 14, an intake manifold 16 and intake ports 18. An intake valve 20, an exhaust valve 22 and two spark plugs 24A and 24B are provided for each combustion chamber defined in each engine cylinder. The exhaust line of this engine 10 includes exhaust ports 26, an exhaust manifold 28 and an exhaust pipe 30. An exhaust gas recirculation passage 32 interconnects the exhaust manifold 28 to either the induction passage 14 at a secticn downstream from the carburetor 12 or the intake manifold 16. A flow control valve 34 is arranged to control the volumetrlc flow rate of the exhaust gas through the recirculation passage 32 in dependence on the operational condition of the engine 10. A considerably high exhaust recirculation rate is employed in this engine system. Numerically, the re-circulated exhaust gas amounts to about 25-45% by volume . .....
of air taken into the combustion chambers when the flow rate of the exhaust gas through the control valve is maximized during a steady state operation of the engine 10 in a medium speed range. Accordingly, no extra means . ~ .
~075988 is needed for preventing the emission of NOx into the atmosphere. The exhaust line may optionally include ; either a thermal reactor or a catalytic converter (not shown) for the removal of carbon monoxide and hydrocarbons.
Referring to Figs. 2-4, each engine cylinder of this engine 10 receives therein a reciprocating piston 36 to leave a thin cylindrical space as part of a combustion chamber 40 between the piston top 36a and the bottom face of the cylinder head 38 at the top dead center of the piston 36. A recess 42 is formed on the bottom face of the cylinder head 38 to serve as a major portion of the combustion chamber 40: the recess 42 has a larger volume than the cylindrical space at the top dead center. The recess 42 has a roughly hemispherical shape in this example but may alternatively have a ~ifferent but yet simple shape such as a pentroof shape or a pancake shape. Preferably, the bottom face of the cylinder head 38 is recessed to generally give a surface of revolution on the longitudinal axis 44 of the cylinder bore. Accordingly the recess 42 is circular in any cross section. It is preferable that the , cross-sectional area of the recess 42 exhibits no increase as the distance from the piston top 36a increases. (Of course the recess 42 may exhibit some deformation needed . to the installation of the spark plugs 24A, 24B and/or the valves 20, 22.) Furthermore, the recess 42 is preferably included entirely in an imaginary and axial extension of -- ,8 --.
the cylinder bore.
The two spark plugs 24A and 24B are screwed into the cylinder head 38 in such an arrangement that their spark gaps 25A and 25B are positioned in the recess 42 with a distance L therebetween. This distance L is determined in correlation to the diameter D of the cylinder bore such that the ratio L/D is in the range from 0.45 to 0.67. In addition, the position of the spark gaps 25A, 25B has a specific relationship to the top face 36a of the piston 36. When the piston 36 at each power stroke is in a position expressed by a crank angle of about 40 after the top dead center, each of the spark gaps 25A, 25B lS at a dis~ance H from the top face .~a of the piston 36 (the distance H is measured normal to the top face of the piston 36). The spark gaps 25A, 25B are positioned such that the ratio H/L is in the range from 0. 45 to 0.55. As another requisite to . . .
the arrangement of the two spa~k gaps 2 5A and 25B, a - spark gap should be located on either side of a plane containing the longitudinal axis 44 of the cylinder bore to give a symmetrical arrangement to the axis 44.
The intake valve 20 and the exhaust valve 22 need to be positioned so as not to interfere with the two spark plugs 24A, 24B. To provide sufficient space for the installation of the valves 20, 22 and the distantly arranged spark plugs 24A, 24B, it is preferable that the intake valve 20 is located on one side of a plane (indicated at 46 in Fig. 2) which is parallel to the axis 44 and contains the line segment connecting the two spark gaps 25A, 25B while the exhaust valve 22 on 5 the other side of this plane 46. When the thus arranged intake and exhaust valves 20 and 22 are operated by a single cam shaft 50 as shown in Fig. 4, the intake and ; exhaust valves 20 and 22 are positioned such that a plane which is parallel to the axis 44 and contains the centers of the valves 20 and 22 (on the periphery of the - recess 42) is normal to none of the cam shaft 50, the plane 46 and the firstly mentioned plane between the spark gaps 25A, 25B. By the employment of this valve arrange-ment; no interferer.-e occurs b~tween two rocker arms 52 and 54 for the intake and exh~u~t valves 20 and 22 or . between two cams 56 and 58 for the two valves 20 and 22.
: In operation, the two spark plugs 24A, 24B- produce .
; sparks substantially simultaneously a short time before the end of each compression stroke. Ideally, combustion - 20 initiated at the two spark gaps 25A, 25B should be - completed in the entire volume of the combustion chamber 40 upon meeting of two flame fronts propagated respec-tively from the two spark gaps 25A, 25B. Actually, such a manner of flame propagation cannot be realized whatever 25 arrangement of the sparl- gaps 25A, 25B may ke employed since the flame fronts are generally spherical surfaces.
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However, it was experimentally confirmed that the engine 10 runs with good stability, even though a large amount of exhaust gas is recirculated, if combustion is completed in about 80% or more of the total volume of ; 5 the combustion chamber 40 when the piston 36 at each power stroke reaches a position expressed by a crank angle of about 40 after the top dead center. The above described arrangement of the two spark gaps 25A, 25B has been devised on the basis of this experimentally confirmed fact. When the distance ratios L/D and H/L are respec-tively within the above specified ranges, two flame fronts propagated from the two spark gaps 25A, 25B meet each other upon arrival of the flam~ fronts on the top ` facé ~6a of the piston 36 at the latest even if the ~ombustion proceeds so slowly that the piston 36 is below the top dead center by a crank angle ~f about 40 when the flame fronts arrive on its top-face 36_. (Note that the distance H is specified so as to be approximately half of the distance L.) Then the propagation of flames is accomplished in about 80% of the entire volume of the combustion chamber 40 with a piston 36 in this position.
Accordingly the combustion is stable to a practical satisfaction and the engine 10 exhibits a satisfactorily high output efficiency.
We have experimentally confirmed also that the above [o :, .
. .
, specified range of the distance L between the two spark gaps 25A, 25B relative to the diameter D of the cylinder bore is quite favorable to the fuel economy of the engine 10. As shown in a qualitative graph of Fig.
S, the fuel economy becomes best when each of the spark gaps 25A, 25B is at a distance of 0.225D - 0.335D from , . , the axis 44 of the cylinder bore.
Thus, the spark plug arrangement according to the invention allows the combustion chambers of the two-point ignition type to exhibit their maximum advantage ~' and fully accomplishes the primary object, suppression -~; of the formation of NOx without substantially sacrificing ', the engine'performance.
Figs. 6 and 7 show a different arrangement of the intake valve 20 and the exhaust valve 22 in the above described combustion chamber 40. The two spark gaps 25A, 25B are arranged as specified with reference to ~' Figs. 2-4. The intake valve 20 and the exhaust valve 22 are respectively located on different sides of the plane 46 also in this case as,shown in Fig. 5. However, a plane , ' which is parallel to the axis 44 and contains the centers of the two valves 20 and 22 is normal to the plane 46.
When the engine 10 is a multi-cylinder engine as is usual, the plane 46 coincides with a plane (indicated at 47) containing the axes 44 of the engine cylinders .''~' , , .
l I
_ ~ _ arranged in a rank, and the intake valve 20 and the exhaust valve 22 are arranged generally symmetrical with respect to this plane 46 (47) in each engine cylinder.
In this case, the engine 10 has two separate and parallel S cam shafts 50A and SOB respectively in association with ; the intake valve 20 and the exhaust valve 22 via usual valve lifter mechanisms 60A and 60B. This type of cam shaft arrangement , which is called a double overhead cam shaft type, is quite convenient to realize the specified arrangement of the two spark plugs 24A, 24B
, without any interference with the intake and exhaust valves 20 and 22. The spark plugs 24A, 24B can be screwed into the cylinder head 38 generally vertically to t~e top face 36a of the piston 36 without interfering with the valves 20, 22 so that the positioning of the spark gaps 25A, 25B can be settled with great ,reedom (of course within the above specified L/D and H/L values).
If desired, each combusti~n chamber 40 may be equipped with the intake valve 20 and/or the exhaust valve 22 in plural number. Fig. 8 shows a case when a combustion chamber 40A is equipped with two intake valves 20A, 20B and a single exhaust valve 22. The two intake valves 20A, 20B are located on the same side of the plane 46 and the exhaust valve 22 on the other side. In Fig. 9, a combustion chamber 40B is equipped , 1~75988 with the two intake valves 20A, 20B both located on the same side of the plane 46 and two exhaust valves 22A, 22B both located on the other side. The two spark gaps 25A, 25B are arranged as specified hereinbefore also in Figs. 8 and 9.
.' , ..
. . .
.
In regard to the suppression of the formation of nitrogen oxides (NOx) in the operation of internal com-bustion engines, a recently proposed method is characterized in that the exhaust gas is recirculated to the combustion chambers in a large amount and that each combustion chamber is equipped with two spark plugs which are positioned at some distance from each other and produce sparks simultaneously. Accordinq to this method, the maximum amount of the reci~culated exhaust gas reaches about 25-45% by volume of air admitted into the combustion chambers as a component of a fresh air-fuel mixture.
The recirculation of exhaust gas in such a large amount is quite effective in loweri~g the maximum combustion temperature and hence suppressing the formation of NOx but is liable to cause an unstable combustion. The simul-taneously working tow spark plugs for each combustion ~, , chamber are provided with the purpose of not only ensuring the ignition of the diluted air-fuel mixture but also rapidly completing the combustion. Since each of the two distant spark gaps serves as a starting point of . ~ , . . .
_ ~ _ ~b : ~.
'' `~:
flame propagation in the combustion chamber, the pro-pagation of flame or combustion can be completed with a greatly shortened propagation distance. In an ideal case, flames developed at the two starting points can spread over the entire region of the combustion chamber in nearly a half of the time needed for the completion - of the flame propagation in the same combustion chamber by the use of a single spark plug. - I
. The greatest importance to this method is the arrangement of the two spark plugs. Shortening the flame - propagation time, ensuring a stable combustion and avoiding a significant increase in the fuel consumption can satis-~- factorily be achieved only when the two spark plugs are optimumly positioned in the combustion chamber.
; 15 Summary of the Invention It is an object of the present invention to provide an engine system which includes an internal combustion engine of the reciprocating piston type having two spark plugs for each combustion chamber thereof and an exhaust gas recirculation circuit, wherein the two spark plugs are positioned in a manner best suited for accomplishing the principal object of the engine system, that is, realizing a stable combustion of an air-fuel mixture diluted with a large amount of exhaust gas thereby to suppress the - 25 formation of NOx with only minimized sacrifice of the 107598~
engine performance.
It is another object of the invention to provide an engine system of the described type, which engine system features a good fuel economy despite the recir-culation of a large amount of exhaust gas.
It is still another object of the invention to provide an engine system of the described type, wherein intake and exhaust valves for each combustion chamber are arranged in a manner best suited for practicing an optimum arrangement of the two spark plugs.
An engine system according to the invention includes an internal combustion engine of the reciprocating piston type and an exhaust gas xecirculation circuit which is arr2nged to recirc~late a portlon of the exhaust gas from the exhaust line to each combustion chamber at a controlled flow rate in relation to the flow rate of air taken into each combustion chamber. Each combustion - chamber of the engine consistC of a variable volume cylindrical space defined in a cylinder bore between the top face of the pistpn and a bottom face of a cylinder head and a recess formed on this bottom face to have a larger volume than the cylindrical space at the top dead center of the piston. Each combustion chamber is provided with an intake valve, an exhaust valve and two spark plugs which produce sparks substantially simultaneously.
:.'' - :
: 3 ~' ' , .
. . .
1~75988 `
:.
As an essential feature of the engine system according to the lnvention, the spark gaps of the two spark plugs are positioned in the recess so as to meet the following conditions: (a) the two spark gaps are located respec-, 5 tively on different sides of a first plane containing , the longitudinal axis of the cylinder bore; (b) the two . spark plugs are gene~ally symmetrically arranged with :
. respect to the bore axis in a plan view taken trans-'.:~ versal to the bore axis; (c) the ratio of the distance 10 between the two gaps to the diameter of the cylinder bore is in the range from 0.45 to 0.67; and (d) the ratio of - the distance from each spark plug to the top face of the piston to the distance between the two spark gaps is in the ran~1e from 0.45 to 0.55 when the piston at each power stroke reaches a position e~pressed by a crank angle of about 40 degrees after the top dead center.
The recess portion of the combustion chamber is preferably included entirely in an imaginary and axial ~.` extension of the cylinder bore and has a simple and : 20 generally symmetrical shape with respect to the bore axis. More particularly, it is preferable that the .` periphery of the recess is given generally by a surface of . .
revolution on the axis of the cylinder bore and that the .
. cross-sectional area of the recess exhibits fundamentally :: 25 no increase as the distance from the top face of the piston ', : '. _ ,~_ : ' . ' .... . .
;` 1~75981~
increases.
Preferably, the intake and exhaust valves are located respectively on different sides of a second plane which is parallel to the bore axis and contains a line segment connecting the two spark gaps.
Br_ef Descriytion of the Drawings Fig. 1 is a schematic plan view of an engine system according to the invention;
Fig. 2 is a cross-sectional view of a combustion chamber as an embodiment of the invention;
Fig. 3 is a sectional view taken along the line 3-3 of Fig. 2 and partly rotated through an angle indicated in Fig. 2;
Fig. 4 is a s_ctional view taken along the line 4-4 of Fig. 2;
Fig. 5 is a graph showing the dependency of the fuel economy of the engine system of Fig. 1 on the distance between the two spark gaps in each combustion chamber;
Fig. 6 is a cross-sectional view of two adjacent combustion chambers as another embodiment of the invention;
Fig. 7 is a sectional view taken along the line 7-7 of Fig. 6;
Figs. 8 and 9 are cross-sectional views of two different combustion chambers, respectively, as still S
-- ~6 -- ' 1(~75988 `' different embodiments of the invention.
Description of Preferred Embo iments In Fig. 1, a four-cylinder internal combustion engine 10 is equipped with a carburetor 12 to supply S an air-fuel mixture to the respective engine cylinders through an induction passage 14, an intake manifold 16 and intake ports 18. An intake valve 20, an exhaust valve 22 and two spark plugs 24A and 24B are provided for each combustion chamber defined in each engine cylinder. The exhaust line of this engine 10 includes exhaust ports 26, an exhaust manifold 28 and an exhaust pipe 30. An exhaust gas recirculation passage 32 interconnects the exhaust manifold 28 to either the induction passage 14 at a secticn downstream from the carburetor 12 or the intake manifold 16. A flow control valve 34 is arranged to control the volumetrlc flow rate of the exhaust gas through the recirculation passage 32 in dependence on the operational condition of the engine 10. A considerably high exhaust recirculation rate is employed in this engine system. Numerically, the re-circulated exhaust gas amounts to about 25-45% by volume . .....
of air taken into the combustion chambers when the flow rate of the exhaust gas through the control valve is maximized during a steady state operation of the engine 10 in a medium speed range. Accordingly, no extra means . ~ .
~075988 is needed for preventing the emission of NOx into the atmosphere. The exhaust line may optionally include ; either a thermal reactor or a catalytic converter (not shown) for the removal of carbon monoxide and hydrocarbons.
Referring to Figs. 2-4, each engine cylinder of this engine 10 receives therein a reciprocating piston 36 to leave a thin cylindrical space as part of a combustion chamber 40 between the piston top 36a and the bottom face of the cylinder head 38 at the top dead center of the piston 36. A recess 42 is formed on the bottom face of the cylinder head 38 to serve as a major portion of the combustion chamber 40: the recess 42 has a larger volume than the cylindrical space at the top dead center. The recess 42 has a roughly hemispherical shape in this example but may alternatively have a ~ifferent but yet simple shape such as a pentroof shape or a pancake shape. Preferably, the bottom face of the cylinder head 38 is recessed to generally give a surface of revolution on the longitudinal axis 44 of the cylinder bore. Accordingly the recess 42 is circular in any cross section. It is preferable that the , cross-sectional area of the recess 42 exhibits no increase as the distance from the piston top 36a increases. (Of course the recess 42 may exhibit some deformation needed . to the installation of the spark plugs 24A, 24B and/or the valves 20, 22.) Furthermore, the recess 42 is preferably included entirely in an imaginary and axial extension of -- ,8 --.
the cylinder bore.
The two spark plugs 24A and 24B are screwed into the cylinder head 38 in such an arrangement that their spark gaps 25A and 25B are positioned in the recess 42 with a distance L therebetween. This distance L is determined in correlation to the diameter D of the cylinder bore such that the ratio L/D is in the range from 0.45 to 0.67. In addition, the position of the spark gaps 25A, 25B has a specific relationship to the top face 36a of the piston 36. When the piston 36 at each power stroke is in a position expressed by a crank angle of about 40 after the top dead center, each of the spark gaps 25A, 25B lS at a dis~ance H from the top face .~a of the piston 36 (the distance H is measured normal to the top face of the piston 36). The spark gaps 25A, 25B are positioned such that the ratio H/L is in the range from 0. 45 to 0.55. As another requisite to . . .
the arrangement of the two spa~k gaps 2 5A and 25B, a - spark gap should be located on either side of a plane containing the longitudinal axis 44 of the cylinder bore to give a symmetrical arrangement to the axis 44.
The intake valve 20 and the exhaust valve 22 need to be positioned so as not to interfere with the two spark plugs 24A, 24B. To provide sufficient space for the installation of the valves 20, 22 and the distantly arranged spark plugs 24A, 24B, it is preferable that the intake valve 20 is located on one side of a plane (indicated at 46 in Fig. 2) which is parallel to the axis 44 and contains the line segment connecting the two spark gaps 25A, 25B while the exhaust valve 22 on 5 the other side of this plane 46. When the thus arranged intake and exhaust valves 20 and 22 are operated by a single cam shaft 50 as shown in Fig. 4, the intake and ; exhaust valves 20 and 22 are positioned such that a plane which is parallel to the axis 44 and contains the centers of the valves 20 and 22 (on the periphery of the - recess 42) is normal to none of the cam shaft 50, the plane 46 and the firstly mentioned plane between the spark gaps 25A, 25B. By the employment of this valve arrange-ment; no interferer.-e occurs b~tween two rocker arms 52 and 54 for the intake and exh~u~t valves 20 and 22 or . between two cams 56 and 58 for the two valves 20 and 22.
: In operation, the two spark plugs 24A, 24B- produce .
; sparks substantially simultaneously a short time before the end of each compression stroke. Ideally, combustion - 20 initiated at the two spark gaps 25A, 25B should be - completed in the entire volume of the combustion chamber 40 upon meeting of two flame fronts propagated respec-tively from the two spark gaps 25A, 25B. Actually, such a manner of flame propagation cannot be realized whatever 25 arrangement of the sparl- gaps 25A, 25B may ke employed since the flame fronts are generally spherical surfaces.
:' ~~~ , .
i , .
However, it was experimentally confirmed that the engine 10 runs with good stability, even though a large amount of exhaust gas is recirculated, if combustion is completed in about 80% or more of the total volume of ; 5 the combustion chamber 40 when the piston 36 at each power stroke reaches a position expressed by a crank angle of about 40 after the top dead center. The above described arrangement of the two spark gaps 25A, 25B has been devised on the basis of this experimentally confirmed fact. When the distance ratios L/D and H/L are respec-tively within the above specified ranges, two flame fronts propagated from the two spark gaps 25A, 25B meet each other upon arrival of the flam~ fronts on the top ` facé ~6a of the piston 36 at the latest even if the ~ombustion proceeds so slowly that the piston 36 is below the top dead center by a crank angle ~f about 40 when the flame fronts arrive on its top-face 36_. (Note that the distance H is specified so as to be approximately half of the distance L.) Then the propagation of flames is accomplished in about 80% of the entire volume of the combustion chamber 40 with a piston 36 in this position.
Accordingly the combustion is stable to a practical satisfaction and the engine 10 exhibits a satisfactorily high output efficiency.
We have experimentally confirmed also that the above [o :, .
. .
, specified range of the distance L between the two spark gaps 25A, 25B relative to the diameter D of the cylinder bore is quite favorable to the fuel economy of the engine 10. As shown in a qualitative graph of Fig.
S, the fuel economy becomes best when each of the spark gaps 25A, 25B is at a distance of 0.225D - 0.335D from , . , the axis 44 of the cylinder bore.
Thus, the spark plug arrangement according to the invention allows the combustion chambers of the two-point ignition type to exhibit their maximum advantage ~' and fully accomplishes the primary object, suppression -~; of the formation of NOx without substantially sacrificing ', the engine'performance.
Figs. 6 and 7 show a different arrangement of the intake valve 20 and the exhaust valve 22 in the above described combustion chamber 40. The two spark gaps 25A, 25B are arranged as specified with reference to ~' Figs. 2-4. The intake valve 20 and the exhaust valve 22 are respectively located on different sides of the plane 46 also in this case as,shown in Fig. 5. However, a plane , ' which is parallel to the axis 44 and contains the centers of the two valves 20 and 22 is normal to the plane 46.
When the engine 10 is a multi-cylinder engine as is usual, the plane 46 coincides with a plane (indicated at 47) containing the axes 44 of the engine cylinders .''~' , , .
l I
_ ~ _ arranged in a rank, and the intake valve 20 and the exhaust valve 22 are arranged generally symmetrical with respect to this plane 46 (47) in each engine cylinder.
In this case, the engine 10 has two separate and parallel S cam shafts 50A and SOB respectively in association with ; the intake valve 20 and the exhaust valve 22 via usual valve lifter mechanisms 60A and 60B. This type of cam shaft arrangement , which is called a double overhead cam shaft type, is quite convenient to realize the specified arrangement of the two spark plugs 24A, 24B
, without any interference with the intake and exhaust valves 20 and 22. The spark plugs 24A, 24B can be screwed into the cylinder head 38 generally vertically to t~e top face 36a of the piston 36 without interfering with the valves 20, 22 so that the positioning of the spark gaps 25A, 25B can be settled with great ,reedom (of course within the above specified L/D and H/L values).
If desired, each combusti~n chamber 40 may be equipped with the intake valve 20 and/or the exhaust valve 22 in plural number. Fig. 8 shows a case when a combustion chamber 40A is equipped with two intake valves 20A, 20B and a single exhaust valve 22. The two intake valves 20A, 20B are located on the same side of the plane 46 and the exhaust valve 22 on the other side. In Fig. 9, a combustion chamber 40B is equipped , 1~75988 with the two intake valves 20A, 20B both located on the same side of the plane 46 and two exhaust valves 22A, 22B both located on the other side. The two spark gaps 25A, 25B are arranged as specified hereinbefore also in Figs. 8 and 9.
.' , ..
. . .
.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An engine system comprising:
an internal combustion engine of the recipro-cating piston type, each combustion chamber of the engine consisting of a variable volume cylindrical space defined in a cylinder bore between the top face of the piston and a bottom face of a cylinder head and a recess formed on said bottom face to have a larger volume than said cylindrical space at the top dead center of the piston, each combustion chamber being provided with an intake valve and an exhaust valve, an exhaust gas recirculation circuit arranged to recirculate a portion of the exhaust gas from the exhaust line of the engine to each combustion chamber at a controlled flow rate in relation to the flow rate of air taken into each combustion chamber; and two spark plugs which produce sparks substantially simultaneously for each combustion chamber, the spark gaps of said two spark plugs being positioned in said recess in such an arrangement that the following con-ditions are met:
(a) the two spark gaps are located respectively on different sides of a first plane containing the longi-tudinal axis of the cylinder bore;
(b) said two spark gaps are generally symme-trically arranged with respect to said axis in a plan view taken transversal to said axis;
(c) the ratio of the distance between said two spark gaps to the diameter of the cylinder bore is in the range from 0.45 to 0.67; and (d) the ratio of the distance from each of said two spark gaps to the top face of the piston to said distance between said two spark gaps is in the range from 0.45 to 0.55 when the piston at each power stroke is in a position expressed by a crank angle of about 40 degrees after the top dead center.
an internal combustion engine of the recipro-cating piston type, each combustion chamber of the engine consisting of a variable volume cylindrical space defined in a cylinder bore between the top face of the piston and a bottom face of a cylinder head and a recess formed on said bottom face to have a larger volume than said cylindrical space at the top dead center of the piston, each combustion chamber being provided with an intake valve and an exhaust valve, an exhaust gas recirculation circuit arranged to recirculate a portion of the exhaust gas from the exhaust line of the engine to each combustion chamber at a controlled flow rate in relation to the flow rate of air taken into each combustion chamber; and two spark plugs which produce sparks substantially simultaneously for each combustion chamber, the spark gaps of said two spark plugs being positioned in said recess in such an arrangement that the following con-ditions are met:
(a) the two spark gaps are located respectively on different sides of a first plane containing the longi-tudinal axis of the cylinder bore;
(b) said two spark gaps are generally symme-trically arranged with respect to said axis in a plan view taken transversal to said axis;
(c) the ratio of the distance between said two spark gaps to the diameter of the cylinder bore is in the range from 0.45 to 0.67; and (d) the ratio of the distance from each of said two spark gaps to the top face of the piston to said distance between said two spark gaps is in the range from 0.45 to 0.55 when the piston at each power stroke is in a position expressed by a crank angle of about 40 degrees after the top dead center.
2. An engine system as claimed in Claim 1, wherein said recess is entirely included in an imaginary and axial extension of the cylinder bore and has a generally symmetrical shape with respect to said axis.
3. An engine system as claimed in Claim 2, wherein said recess is shaped such that the periphery thereof is given generally by a surface of revolution on said axis and that the cross-sectional area thereof exhibits fundamentally no increase as the distance from the top face of the piston increases.
4. An engine system as claimed in Claim 2, wherein said intake valve and said exhaust valve are located respectively on different sides of a second plane which is parallel to said axis and contains a line segment connecting said two spark gaps.
5. An engine system as claimed in Claim 4, wherein said intake valve and said exhaust valve are associated with a single cam shaft, a third plane which is parallel to said axis and contains the centers of said intake valve and said exhaust valve on the periphery of said recess not being normal to said cam shaft.
6. An engine system as claimed in Claim 4, wherein said intake valve and said exhaust valve are respectively associated with two separate and parallel cam shafts, a third plane which is parallel to said axis and contains the centers of said intake valve and said exhaust valve on the periphery of said recess being substantially normal to said two cam shafts.
7. An engine system as claimed in Claim 6, wherein the engine is a multi-cylinder engine, said second plane coinciding with a plane which contains the longi-tudinal axes of a plurality of engine cylinders arranged in a rank.
8. An engine system as claimed in Claim 1, wherein said exhaust gas recirculation circuit is constructed such that the maximum amount of the recirculated exhaust gas reaches to about 25-45% by volume of air admitted into each combustion chamber.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1191476A JPS5294908A (en) | 1976-02-06 | 1976-02-06 | Two points firing engine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1075988A true CA1075988A (en) | 1980-04-22 |
Family
ID=11790964
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA271,081A Expired CA1075988A (en) | 1976-02-06 | 1977-02-04 | Internal combustion engine having two spark plugs for each combustion chamber and exhaust gas recirculation circuit |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5294908A (en) |
| CA (1) | CA1075988A (en) |
| DE (1) | DE2704721A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109578130A (en) * | 2017-09-29 | 2019-04-05 | Ifp新能源公司 | Internal combustion engine with the direct fuel injection along charge motion direction |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5851130B2 (en) * | 1978-07-20 | 1983-11-15 | トヨタ自動車株式会社 | Combustion chamber structure of internal combustion engine |
| JPS56175519U (en) * | 1980-05-29 | 1981-12-24 | ||
| JPS56175518U (en) * | 1980-05-29 | 1981-12-24 | ||
| JPS57105565A (en) * | 1980-12-22 | 1982-07-01 | Kawasaki Heavy Ind Ltd | Spark ignition type internal combustion engine |
| JPS61164436U (en) * | 1986-03-20 | 1986-10-13 | ||
| FR2650630A1 (en) * | 1989-08-02 | 1991-02-08 | Renault | MULTI-CYLINDER ENGINE WITH FUEL INJECTION, COMPRISING FOUR VALVES PER CYLINDER |
| DE4222797A1 (en) * | 1992-07-10 | 1993-08-05 | Daimler Benz Ag | Multicylinder combustion engine with exhaust gas recycling - has dual-inlet cylinders arranged in two gps. with one or more injectors downstream from flaps |
| EP2787193A1 (en) | 2010-05-21 | 2014-10-08 | Cummins Intellectual Properties, Inc. | Internal combustion engine having combustion chamber with blended hemispherical and pent-proof portions |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5844858B2 (en) * | 1971-12-22 | 1983-10-05 | 株式会社日立製作所 | Gasoline engine |
-
1976
- 1976-02-06 JP JP1191476A patent/JPS5294908A/en active Pending
-
1977
- 1977-02-04 CA CA271,081A patent/CA1075988A/en not_active Expired
- 1977-02-04 DE DE19772704721 patent/DE2704721A1/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109578130A (en) * | 2017-09-29 | 2019-04-05 | Ifp新能源公司 | Internal combustion engine with the direct fuel injection along charge motion direction |
| CN109578130B (en) * | 2017-09-29 | 2022-02-08 | Ifp新能源公司 | Internal combustion engine with direct fuel injection in the direction of intake air movement |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2704721A1 (en) | 1977-08-11 |
| JPS5294908A (en) | 1977-08-10 |
| AU2180777A (en) | 1977-06-23 |
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| MKEX | Expiry |