Internal combustion engine and method of operation

Claims

We claim:

1. A method of operating an internal combustion engine having a plurality of sequentially operative combustion chambers, comprising the steps of:

supplying to said combustion chambers a lean air-fuel charge having an air-fuel ratio larger than 16;

supplying additional fuel to at least one of said combustion chambers relative to the quantity of air sucked-in said at least one of said combustion chambers as the engine power demand increases, said additional fuel rendering the air-fuel charge in said at least one combustion chamber richer than approximately stoichiometric, selecting in a sequential firing of all of said combustion chambers the number of combustion operations at which the combustion of said richer air-fuel charge is made to meet said engine power demand; and

converging exhaust gases of said combustion chambers.

2. A method according to claim 1 wherein said supplying additional fuel step is made only when said engine power demand is higher than a first predetermined engine power demand value; and

wherein said selecting step further comprises the step of increasing the ratio of said number of combustion operations at which the combustion of said richer air-fuel charge is made to the sequentially operative combustion operations of all of said combustion chambers as said engine power demand increases.

3. A method according to claim 1 wherein said supplying additional fuel is made only when said engine power demand is higher than a first predetermined engine power demand value; and

wherein said selecting step further comprises the step of maintaining constant the ratio of said number of combustion operations at which the combustion of said richer air-fuel charge is made to the number of sequentially operative combustion operations of all of said combustion chambers when said engine power demand exceeds said first predetermined power demand value.

4. A method according to claim 1 wherein said supplying of additional fuel is made only when said engine power demand becomes the same as or higher than said predetermined engine power demand value, and further comprising a step of:

retarding said retarded ignition pulse when sid engine power demand rises to said predetermined engine power demand value to the extent that the resulting torque generated by the combustion of said richer air-fuel charge ignited by said retarded ignition pulse as further retarded becomes equal to the torque generated by the combustion of said lean air-fuel charge ignited by said advanced ignition pulse, wherein the extent of said retarding of said ignition pulse being reduced to zero in a short period of time since said engine power demand rises to said predetermined engine power demand value.

5. A method of operating an internal combustion engine having a plurality of sequentially operative combustion chambers, comprising the steps of:

supplying a lean air-fuel charge to all of said combustion chambers when the engine power demand of said engine is lower than a first predetermined engine power demand level, the air-fuel ratio of said lean air-fuel charge being greater than 16;

supplying a rich air-fuel charge to at least some of said combustion chambers substantially immediately after said engine power demand exceeds said first predetermined engine power demand level, the air-fuel ratio of said rich air-fuel charge being smaller than the stoichiometric air-fuel ratio, and supplying said lean air-fuel charge to the remaining combustion chambers; and

converging exhaust gases of said combustion chambers.

6. A method according to claim 1, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

7. A method according to claim 2 wherein said additional fuel is supplied to all of said combustion chambers when said engine power demand exceeds a second predetermined engine power demand value.

8. A method according to claim 2, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

9. A method according to claim 7, further comprising steps of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied when said engine power demand is between said first and second predetermined engine power demand values.

10. A method according to claim 2, wherein said supplying additional fuel is made to all of said combustion chambers when said engine power demand exceeds a second predetermined engine power demand value.

11. A method according to claim 3, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

12. A method according to claim 10, further comprising steps of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied when said engine power demand is between said first and second predetermined engine power demand values.

13. A method according to claim 3 wherein said ratio of said number of combustion operations to said given number of sequentially operative combustion operations is about 0.5.

14. A method according to claim 10 wherein said ratio of said number of combustion operations to said given number of sequentially operative combustion operations is about 0.5.

15. A method according to claim 11 wherein said ratio of said number of combustion operations to said given number of sequentially operative combustion operations is about 0.5.

16. A method according to claim 12 wherein said ratio of said number of combustion operations to said given number of sequentially operative combustion operations is about 0.5.

17. A method according to claim 1 wherein the combustion chamber to which said additional fuel is supplied is changeable when the combustion chamber to which said additional fuel is supplied and the combustion chamber to which said additonal fuel is not supplied exist in said number of sequentially operative combustion operations.

18. A method according to claim 6 wherein the combustion chamber to which said additional fuel is supplied is changeable when the combustion chamber to which said additional fuel is supplied and the combustion chamber to which said additional fuel is not supplied exist in said number of sequentially operative combustion operations.

19. A method according to claim 2 wherein the combustion chamber to which said additional fuel is supplied is changeable when the combustion chamber to which said additional fuel is supplied and the combustion chamber to which said additional fuel is not supplied exist in said number of sequentially operative combustion operations.

20. A method according to claim 10 wherein the combustion chamber to which said additional fuel is supplied is changeable when the combustion chamber to which said additional fuel is supplied and the combustion chamber to which said additonal fuel is not supplied exist in said given number of sequentially operative combustion operations.

21. A method according to claim 8 wherein the combustion chamber to which said additional fuel is supplied is changeable when the combustion chamber to which said additional fuel is supplied and the combustion chamber to which said additional fuel is not supplied exist in said given number of sequentially operative combustion operations.

22. A method according to claim 12 wherein the combustion chamber to which said additional fuel is supplied is changeable when the combustion chamber to which said additional fuel is supplied and the combustion chamber to which said additional fuel is not supplied exist in said given number of sequentially operative combustion operations.

23. A method according to claim 1 wherein said additional fuel is supplied to a predetermined combustion chamber.

24. A method according to claim 6 wherein said additional fuel is supplied to a predetermined combustion chamber.

25. A method according to claim 3 wherein said additional fuel is supplied to a predetermined combustion chamber.

26. A method according to claim 10 wherein said additional fuel is supplied to a predetermined combustion chamber.

27. A method according to claim 11 wherein said additional fuel is supplied to a predetermined combustion chamber.

28. A method according to claim 12 wherein said additional fuel is supplied to a predetermined combustion chamber.

29. A method according to claim 1 wherein said additional fuel is supplied when an intake manifold pressure of said engine exceeds 660 mmHg.

30. A method according to claim 6 wherein said additional fuel is supplied when an intake manifold pressure of said engine exeeds 660 mmHg.

31. A method according to claim 1 wherein said additional fuel is supplied when an intake manifold pressure of said engine exceeds 680 mmHg.

32. A method according to claim 6 wherein said additional fuel is supplied when an intake manifold pressure of said engine exceeds 680 mmHg.

33. A method according to claim 1 wherein said supplying of additional fuel is made to less than all of said combustion chambers when an intake manifold pressure is between 680 mmHg and 720 mmHg, and

wherein said supplying of additional fuel is made to all of said combustion chambers when said intake manifold pressure exceeds 720 mmHg.

34. A method according to claim 6 wherein said supplying of additional fuel is made to less than all of said combustion chambers when an intake manifold pressure is between 680 mmHg and 720 mmHg, and

wherein said supplying of additional fuel is made to all of said combustion chambers when said intake manifold pressure exceeds 720 mmHg.

35. A method according to claim 7 wherein said engine power demand is represented by an intake manifold pressure, and

wherein said first and second predetermined engine power demand values correspond to 680 mmHg and 720 mmHg of intake manifold pressure, respectively.

36. A method according to claim 9 wherein said engine power demand is represented by an intake manifold pressure, and

wherein said first and second predetermined engine power demand values correspond to 680 mmHg and 720 mmHg of intake manifold pressure, respectively.

37. A method according to claim 1 wherein said supplying of additional fuel is made when all of the following three conditions are fulfilled:

(1) the cooling water temperature of said engine is above a predetermined water temperature value,

(2) the engine speed of said engine is above a first predetermined engine speed value, and p1 (3) the intake manifold pressure is above a predetermined intake manifold pressure value.

38. A method according to claim 37 wherein said predetermined water temperature value, said first predetermined engine speed value and said predetermined intake manifold pressure value are 20.degree. C, 1,000 rpm and 680 mmHg, respectively.

39. A method according to claim 6 wherein said supplying of additional fuel is made when all of the following three conditions are fulfilled:

(1) the cooling water temperature of said engine is above a predetermined water temperature value,

(2) the engine speed of said engine is above a first predetermined engine speed value, and

(3) the intake manifold pressure of said engine is above a predetermined intake manifold value;

and wherein said recirculating step is effected only when all of the following conditions are fulfilled:

(1) said cooling water temperature is above said predetermined water temperature value,

(2) said engine speed is between said first predetermined engine speed value and a second predetermined engine speed value, and

(3) said intake manifold pressure is above said predetermined intake manifold pressure value.

40. A method according to claim 39 wherein said predetermined water temperature value, said first predetermined engine speed value, said second predetermined engine speed value and said predetermined intake manifold pressure value are 20.degree. C, 1,000 rpm, 3,000 rpm and 680 mmHg, respectively.

41. A method according to claim 6 wherein said supplying of additional fuel is made to less than all of said combustion chambers and at the same time said recirculating is effected when all of the following three conditions are fulfilled:

(1) the cooling water temperature of said engine is above a predetermined water temperature value,

(2) the engine speed of said engine is between first and scond predetermined engine speed values, and

(3) the intake manifold pressure of said engine is above pressure value;

and wherein said supplying additional fuel is made to all of said combustion chambers without said recirculating when all of the following conditions are fulfilled:

(1) said cooling water temperature is above said predetermined water temperature value,

(2) said engine speed is above said second predetermined engine speed value, and

(3) said intake manifold pressure is above said predetermined intake manifold pressure value.

42. A method according to claim 41 wherein said predetermined water temperature value, said first and second predetermined engine speed values and said predetermined intake manifold pressure value are 20.degree. C, 1,000 rpm, 3,000 rpm and 680 mmHg, respectively.

43. A method according to claim 1 wherein said air-fuel ratio of said lean air-fuel charge is maintained between 17 and 22, and wherein the air-fuel ratio of said richer air-fuel charge is maintained between 11 and 14.7 (stoichiometric).

44. A method according to claim 43 wherein in said number of sequentially operative combustion operations of said combustion chambers, the number of the combustion operations at which the combustion of said richer air-fuel charge is made is less than the number of the combustion operations at which the combustion of said lean air-fuel charge is made, when said combustion operations at which the combustion of said richer air-fuel charge is made and said combustion operations at which the combustion of said lean air-fuel charge is made exist in said given number of sequentially operative combustion operations of said combustion chambers.

45. A method according to claim 1 wherein in said given number of sequentially operative combustion operations of said combustion chambers the number of the combustion operations at which the combustion of said richer air-fuel charge is made is the same as the number of the combustion operations at which the combustion of said lean air-fuel charge is made when said combustion operation at which the combustion of said richer air-fuel charge is made and said combustion operation at which said lean air-fuel charge is made exist in said given number of sequentially operative combustion operations of said combustion chambers.

46. A method according to claim 43, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

47. A method according to claim 44, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

48. A method according to claim 45, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

49. A method according to claim 1 wherein said air-fuel ratio of said lean air-fuel charge is substantially maintained at 18,

and wherein the air-fuel ratio of said richer air-fuel charge is substantially maintained at 13.

50. A method according to claim 49 wherein in said given number of sequentially operative combustion operations of said combustion chambers the number of the combustion operations at which the combustion of said richer air-fuel charge is made is less than the number of the combustion operations at which the combustion of said lean air-fuel charge is made, when said combustion operation at which the combustion of said richer air-fuel charge is made and said combustion operations at which the combustion of said lean air-fuel charge is made exist in said given number of sequentially operative combustion operations of said combustion chambers.

51. A method according to claim 49 wherein in said given number of sequentially operative combustion operations of said combustion chambers the numbers of the combustion operations at which the combustion of said richer air-fuel charge is made in the same as the number of the combustion operations at which the combustion of said lean air-fuel charge is made when said combustion operation at which the combustion of said richer air-fuel charge is made whn said combustion operation at which said lean air-fuel charge is made exist in said given number of sequentially operative combustion operations of said combustion chambers.

52. A method according to claim 49, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

53. A method according to claim 50, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

54. A method according to claim 51, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

55. A method according to claim 43 wherein

(1) said lean air-fuel charge consists of leaner and richer portions of said lean air-fuel charge,

(2) the air-fuel ratio of said leaner portion of said lean air-fuel charge is maintained larger than 17, and

(3) the air-fuel ratio of said richer portion of said lean air-fuel charge is maintained between 1.5 and 9;

and wherein

(1) said richer air-fuel charge consists of leaner and richer portions of said richer air-fuel charge,

(2) the air-fuel ratio of said leaner portion of said richer air-fuel charge is maintained larger than 17, and

(3) the air-fuel ratio of said richer portion of said richer air-fuel charge is maintained between 1 and 6.

56. A method according to claim 55 wherein in said given number of sequentially operative combustion operations of said combustion chambers, the number of the combustion operations at which the combustion of said richer air-fuel charge is made is the same as the number of the combustion operations at which the combustion of said lean air-fuel charge is made when said combustion operation at which the combustion of said richer air-fuel charge is made and said combustion operation at which said lean air-fuel charge is made exist in said given number of sequentially operative combustion operations of said combustion chambers.

57. A method according to claim 55, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

58. A method according to claim 56, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

59. A method according to claim 55 wherein the sum of a weight of air contained in said richer portion of said lean air-fuel charge sucked in by all of said combustion chambers and a weight of air contained in said richer portion of said richer air-fuel charge sucked in by all of said combustion chambers is between 1 and 10% of the total weight of air contained in said richer and lean air-fuel charges sucked in by all of said combustion chambers.

60. A method according to claim 59 wherein when in said given number of sequentially operative combustion operations of said combustion chambers the combustion operation at which the combustion of said richer air-fuel charge is made and the combustion operation at which the combustion of said lead air-fuel charge is made exist, said weight of air contained in said richer portion of said lean air-fuel charge is the same as said weight of air contained in said richer portion of said richer air-fuel charge.

61. A method according to claim 60 wherein in said given number of sequentially operative combustion operations of said combustion chambers the number of the combustion operations at which the combustion of said richer air-fuel charge is made is the same as the number of the combustion operations at which the combustion of said lean air-fuel charge is made when said combustion operation at which the combustion of said richer air-fuel charge is made and said combustion operation at which said lean air-fuel charge is made exist in said given number of sequentially operative combustion operations of said combustion chambers.

62. A method according to claim 60, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

63. A method according to claim 61, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

64. A method according to claim 49 wherein

(1) said lean air-fuel charge consists of leaner and richer portions of said lean air-fuel charge,

(2) the air-fuel ratio of said leaner portion of said lean air-fuel charge is maintained at substantially 20, and

(3) the air-fuel ratio of said richer portion of said lean air-fuel charge is maintained at substantially 5.3;

and wherein

(1) said richer air-fuel charge consists of leaner and richer portions of said richer air-fuel charge,

(2) the air-fuel ratio of said leaner portion of said richer air-fuel charge is maintained at substantially 20, and

(3) the air-fuel ratio of said richer portion of said richer air-fuel charge is maintained at substantially 1.4.

65. A method according to claim 64 wherein in said given number of sequentially operative combustion operations of said combustion chambers the number of the combustion operations at which the combustion of said richer air-fuel charge is made is the same as the number of the combustion operations at which the combustion of said lean air-fuel charge is made when said combustion operation at which the combustion of said richer air-fuel charge is made and said combustion operation at which said lean air-fuel charge is made exist in said given number of sequentially operative combustion operations of said combustion chambers.

66. A method according to claim 64, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

67. A method according to claim 65, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

68. A method according to claim 55 wherein the sum of a weight of air contained in said richer portion of said lean air-fuel charge sucked in by all of said combustion chambers and a weight of air contained in said richer portion of said richer air-fuel charge sucked in by all of said combustion chambers is substantially 4% of the total weight of air contained in said richer and lean air-fuel charges sucked in by all of said combustion chambers.

69. A method according to claim 68 wherein when in said given number of sequentially operative combustion operations of said combustion chambers the combustion operation at which the combustion of said richer air-fuel charge is made and the combustion operation at which the combustion of said lean air-fuel charge is made exist, said weight of air contained in said richer portion of said lean air-fuel charge is the same as said weight of air contained in said richer portion of said richer air-fuel charge.

70. A method according to claim 1 wherein said supplying a lean air-fuel charge comprises:

supplying to said combustion chambers a rich air-fuel charge whose air-fuel ratio is smaller than substantially 14.7 (stoichiometric), and

supplying enough air to said combustion chambers that said lean air-fuel charge is formed in said combustion chambers; and

wherein said supplying additional fuel comprises:

stopping said supplying of air to said at least one of said combustion chambers.

71. A method according to claim 70 wherein said stopping of said supply of air is made when said engine power demand is higher than a first predetermined engine power demand value;

and wherein said selecting step comprises the step of maintaining constants the ratio of said number of the combustion operations at which the combustion of said richer air-fuel charge is made to the number of sequentially operative combustion operations of all of said combustion chambers when said engine power demand exceeds said first predetermined engine power demand value.

72. A method according to claim 71 wherein said stopping is made to all of said combustion chambers when said engine power demand exceeds a second predetermined engine power demand value.

73. A method according to claim 70 wherein said rich air-fuel charge consists of richer and leaner portions of said rich air-fuel charge.

74. A method according to claim 70 wherein

(1) said air-fuel ratio of said rich air-fuel charge is maintained between 11 and 14.7 (stoichiometric), and

(2) said air-fuel ratio of said lean air-fuel charge is maintained between 17 and 22.

75. A method according to claim 70 wherein

(1) said air-fuel ratio of said rich air-fuel charge is maintained at substantially 13, and

(2) said air-fuel ratio of said lean air-fuel charge is maintained at substantially 18.

76. A method according to claim 1 further comprising steps of:

generating an advanced ignition pulse optimum for the ignition of said lean air-fuel charge and a retarded ignition pulse optimum for the ignition of said richer air-fuel charge for every one ignition operation of each of said combustion chambers;

selecting said advanced ignition pulse for the combustion chamber to which said lean air-fuel is supplied;

selecting said retarded ignition pulse for the combustion chamber to which said richer air-fuel charge is supplied;

amplifying the voltage of the selected ignition pulse; and

igniting by the amplified selected ignition pulse the air-fuel charge of the combustion chamber for which said amplified selected ignition pulse is selected.

77. A method according to claim 76, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additions fuel is supplied.

78. A method according to claim 77, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

79. A method according to claim 5, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said to rush air-fuel charge is supplied.

80. A method according to claim 5, further comprising a step of:

supplying said rich air-fuel charge to all of said combustion chambers substantially immediately after said engine power demand exceeds a second predetermined engine power demand level.

81. A method according to claim 80, further comprising a step of:

recirculating a portion of said exhaust gases to the combustion chamber to which said rich air-fuel charge is supplied, when said engine power demand is between said first and second predetermined engine power demand levels.

82. A method according to claim 81 wherein said engine power demand is represented by an intake manifold pressure.

83. A method according to claim 82 wherein said first and second predetermined engine power demand levels correspond to intake manifold pressure levels of 680 mmHg and 720 mmHg, respectively.

84. A method according to claim 81 wherein said engine power demand is represented by a combination of an intake manifold pressure and an engine speed.

85. A method according to claim 84 wherein said first and second predetermined engine power demand levels correspond, respectively to a first combination of 680 mmHg and 1,000 rpm; and a second combination of 680 mmHg and 3,000 rpm.

86. A method according to claim 84 wherein said recirculation is made only when (1) said engine power demand is between said first and second predetermined engine power demand levels and (2) a cooling water temperature of said engine is above a predetermined water temperature value.

87. A method according to claim 86 wherein said first and second predetermined engine power demand levels correspond, respectively to a first combination of 680 mmHg and 1,000 rpm, and a second combination of 680 mmHg and 3,000 rpm;

and wherein said predetermined water temperature value is 20.degree. C.

88. A method according to claim 5 wherein said supplying of a rich air-fuel charge step includes the step of increasing the ratio of the number of the combustion operations at which the combustion of said rich air-fuel charge is made to a selected number of sequentially operative combustion operations of said combustion chambers as said engine power demand increases.

89. A method according to claim 88 wherein the lowest value of said ratio is smaller than one divided by the number of all of said combustion chambers.

90. A method according to claim 5 wherein said supplying of a rich air-fuel charge step includes the step of maintaining constant the ratio of the number of the combustion operations at which the combustion of said rich air-fuel charge is made to a selected number of sequentially operative combustion operations of said combustion chambers.

91. An internal combustion engine, comprising:

a plurality of sequentially operative combustion chambers;

means connected to said combustion chambers for supplying thereto a lean air-fuel charge having an air-fuel ratio larger than 16; said supplying means supplying additional fuel to at least one of said combustion chambers relative to the quantity of sucked-in air by said one of said combustion chambers, as the engine power demand increases, in such a manner that an air-fuel charge richer than approximately stoichiometric is substantially immediately therein formed and that in a selected number of sequentially operative combustion operations of said combustion chambers the number of the combustion operations at which the combustion of said richer air-fuel charge is made is suitably selected to meet said engine power demand, said supplying additional fuel being made in the wide range of the engine speed of said engine including medium and high engine speeds; and

means connected to said combustion chambers for converging the exhaust gases of said combustion chambers.

92. An internal combustion engine according to claim 91, further comprising means connected to said combustion chambers for recirculating a portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied.

93. An internal combustion engine according to claim 91 wherein said supplying means comprises:

as many fuel injection nozzles as said combustion chambers, each of said fuel injection nozzles being operatively connected to corresponding one of said combustion chambers; and

means connected to said fuel injection nozzles for controlling a quantity of fuel to be injected to each one of said combustion chambers.

94. An internal combustion engine according to claim 93 wherein (1) each of said combustion chambers has an intake port, and (2) each of said fuel injection nozzles being disposed in said intake port.

95. An internal combustion engine according to claim 93 wherein said controlling means controls said quantity, when said lean air-fuel charge and said richer air-fuel charge are to be formed in said combustion chambers, in such a manner that each of said combustion chambers receives said lean air-fuel charge on one occasion and said richer charge on another occasion.

96. An internal combustion engine according to claim 93 wherein said controlling means controls said quantity, when said richer and lean air-fuel charges are to be formed in said combustion chambers, in such a manner that a first set of said combustion chambers receive said richer air-fuel charge and that a second set of the remaining combustion chambers receive said lean air-fuel charge.

97. An internal combustion engine according to claim 92 wherein said supply means comprises: as many fuel injection nozzles as said combustion chambers, each of said fuel injection nozzles being operatively connected to corresponding one of said combustion chambers and to a fuel source; and means connected to said fuel injection nozzles for controlling a quantity of fuel to be injected to each one of said combustion chambers;

and wherein said recirculating means comprises: an exhaust suction passage connection to said converging means to suck in said portion of said exhaust gases therefrom; as many delivery passages as said combustion chambers, each of said delivery passages being (1) operatively connected to each corresponding one of said combustion chambers, (2) connected to said exhaust suction passage and (3) having an exhaust gas delivery valve; and recirculation control means connected to said controlling means and to all of said exhaust gas delivery valve, said recirculation control means opening said exhaust gas delivery valve so that the combustion chamber to which said richer air-fuel charge is supplied receives said portion of said exhaust gases when said lean and richer air-fuel charges are to be formed in said combustion chambers, said controlling means working when said lean and richer air-fuel charges are to be formed in said combustion chambers receives said lean air-fuel charge on one occassion and said richer air-fuel charge on another occasion.

98. An internal combustion engine according to claim 97 wherein (1) each of said combustion chambers has an intake port, and (2) each of said fuel injection nozzles being disposed in said intake port.

99. An internal combustion engine according to claim 92 wherein said supplying means comprises:

as many fuel injection nozzles as said combustion chambers, each of said fuel injection nozzles being operatively connected to corresponding one of said combustion chambers and to a fuel source; and means connected to said fuel injection nozzles for controlling a quantity of fuel to be injected to each one of said combustion chambers;

said controlling means controlling said quantity, when said richer and lean air-fuel charges are to be formed in said combustion chambers, in such a manner that a first set of said combustion chambers at turn thereof always receive said richer air-fuel charge and that said second set of the remaining combustion chambers at turn thereof always receive said lean air-fuel charge; and further wherein said recirculating means comprises: an exhaust suction passage connected to said converging means to suck in said portion of said exhaust gases therefrom; an exhaust gas recirculation control valve connected to said exhaust suction passage;

as many delivery passages as said first set of combustion chambers, each of said delivery passages being (1) operatively connected to each corresponding one of said first set of combustion chambers and (2) connected to said exhaust gas recirculation control valve; and

recirculation control means connected to said exhaust gas recirculation control valve and to said control means, said recirculation control means opening said exhaust gas recirculation control valve so that the combustion chamber to which said richer air-fuel charge is supplied receives said portion of said exhaust gases when said lean and richer air-fuel charges to be formed in said combustion chambers.

100. An internal combustion engine according to claim 99 wherein (1) each of said combustion chambers has an intake port, and (2) each of said fuel injection nozzles being disposed in said intake port.

101. An internal combustion engine according to claim 91 wherein each of said combustion chambers has a trap chamber (1) disposed therein, (2) enclosing a spark plug, (3) having at least one suction aperture and one discharge aperture and (4) further having a partition disposed within said trap chamber between said suction and discharge apertures to form within said trap chamber a uniflow path in communication with said suction and discharge apertures, said spark plug being exposed to said path; and wherein said supplying means comprises: means connected to said combustion chambers for delivering an air-fuel charge to be supplied to each of said combustion chambers in such a manner (1) that said air-fuel charge consists of a richer portion and a leaner portion, (2) that said richer and leaner portions are delivered to each of said combustion chambers in stratified charge form, (3) that said richer portion is directed to said suction aperture to be sucked therein and (4) that said richer and leaner portions form, as a whole, said lean air-fuel charge or said richer air-fuel charge depending on said engine power demand, whereby said richer portion trapped in said trap chamber, when ignited, forms a flame which spurts out of said trap chamber to burn said leaner portion remaining outside said trap chamber.

102. An internal combustion engine according to claim 92 wherein each of said combustion chambers has a trap chamber (1) disposed therein, (2) enclosing a spark plug, (3) having at least one suction aperture and one discharge aperture and (4) further having a partition disposed within said trap chamber between said suction and discharge apertures to form within said trap chamber a uniflow path in communication with said suction and discharge apertures, said spark plug being exposed to said path; and wherein said supplying means comprises: means connected to said combustion chambers for delivering an air-fuel charge to be supplied to each of said combustion chambers in such a manner (1) that said air-fuel charge consists of a richer portion and a leaner portion, (2) that said richer and leaner portions are delivered to each of said combustion chambers in stratified charge form, (3) that said richer portion is directed to said suction aperture to be sucked therein and (4) that said richer and leaner portions form, as a whole, said lean air-fuel charge or said richer air-fuel charge depending on said engine power demand; and wherein said recirculating means supplies said portion of said exhaust gases to the combustion chamber to which said additional fuel is supplied, whereby said richer portion trapped in said trap chamber, when ignited, forms a flame which spurts out of said trap chamber to burn said leaner portion remaining outside said trap chamber.

103. An internal combustion engine according to claim 102 wherein each of said combustion chamber has an intake port and an intake valve disposed therein said intake valve having a valve head having a back face facing upstream of said valve head; and

wherein said recirculating means comprises as many delivery passage as the number of the combustion chamber to which said portion of said exhaust gases is supplied, each of said delivery passage having an opening end disposed near said suction aperture of said trap chamber disposed in said combustion chamber to which said portion of said exhaust gases is supplied and in the vicini