Multi-cylinder internal combustion engine

Claim 2

A multi-cylinder internal combustion engine having a first group of cylinders and a second group of cylinders, the engine being followed by an after-burner to purifying exhaust gases discharged from the first and second groups of cylinders, said engine comprising: a carburetor for supplying into the first and second groups of cylinders a first air-fuel mixture whoch is leaner than the stoichiometric air fuel mixture; a mixture enriching device arranged to supply supplemental fuel from the fuel chamber of said carburetor into portions upstream of the intake ports of said second group of cylinders to enrich the first air-fuel mixture into a second air-fuel mixture which is richer than the stoichiometric air-fuel mixture; and control means to cause said mixture enriching device to stop supply of the supplemental fuel during at least one of high engine speed, high engine load, and excessively high afterburner temperature.

Claim 3

A multi-cylinder internal combustion engine as claimed in claim 1, in which said mixture enriching device includes: a supplemental fuel jet communicating with the fuel chamber of said carburetor; fuel passage means communicating said supplemental fuel jet with the portions upstream of the intake ports of said second group of cylinders to admit fuel from the fuel chamber of said carburetor into the portions upstream of the intake ports of said second group of cylinders; a supplemental air bleed orifice communicating with said fuel passage means.

Claim 4

A multi-cylinder internal combustion engine as claimed in claim 2, in which said control means includes: a normally open solenoid valve arranged to close and block said fuel passage means in response to an electric signal transmitted thereto; at least one sensor which senses engine speed, engine load or afterburner temperature, respectively; a control circuit electrically connected between said normally open solenoid valve and said at least one sensor, said control circuit being arranged to generate the electric signal and transmit it to said normally open solenoid valve when at least one of engine speed, engine load and afterburner temperature exceeds a predetermined level.

Claim 5

A multi-cylinder internal combustion engine as claimed in claim 3, in which said at least one sensor includes an engine speed sensor, a vehicle speed sensor, an engine load sensor, an engine temperature sensor or an afterburner temperature sensor.

Claim 6

A multi-cylinder internal combustion engine as claimed in c;laim 4, in which said engine temperature sensor senses engine coolant temperature.

Claim 7

An internal combustion engine as claimed in claim 4, in which said engine load sensor senses intake vacuum.

Claim 8

A multi-cylinder internal combustion engine as claimed in claim 2, in which said fuel passage means includes a first portion which is a feed passage formed within the body casting portion of said carburetor, and a second portion which is a feed tube connecting said feed passage to the portions upstream of the intake ports of said second group of cylinders.

Claim 9

A multi-cylinder internal combustion engine as claimed in claim 2, in which said fuel passage means includes a feed conduit connecting said supplemental fuel jet and the portions upstream of the intake ports of said second group of cylinders through the outside of the air-fuel mixture induction passage of the carburetor and the outside of intake manifold

Claim 10

A multi-cylinder internal combustion engine as claimed in claim 8, in which a portion of said feed conduit is surrounded with heating means for promoting vaporization of the fuel flowing through said feed conduit.

Claim 11

A multi-cylinder internal combustion engine as claimed in claim 9, in which said heating means is a chamber through which hot fluid flows.

Claim 12

A multi-cylinder internal combustion engine as claimed in claim 9, in which said heating means is a chamber through which exhaust gases flow.

Claim 13

A multi-cylinder internal combustion engine as claimed in claim 1, in which said first air-fuel mixture has an air-fuel ratio ranging from 17:1 to 20:1.

Claim 14

A multi-cylinder internal combustion engine as claimed in claim 12, in which said second air-fuel mixture has an air-fuel ratio ranging from 10:1 to 14:1.

Claim 15

A multi-cylinder internal combustion engine having a first group of cylinders and a second group of cylinders, the engine being followed by an afterburner to purify exhaust gases discharged from the first and second groups of cylinders, said engine comprising: a carburetor for supplying into the first and second groups of cylinders a first air-fuel mixture having an air-fuel ratio ranging from 17:1 to 20:1, said carburetor including a supplemental fuel jet communicating with the fuel chamber of the carburetor, a feed passage communicating the fuel jet with the air-fuel mixture induction passage of said carburetor, a supplemental air bleed orifice communicating with the feed passage, and a chamber disposed in the feed passage and having a first opening which communicates with the supplemental fuel jet, and a second opening which communicates with the air-fuel mixture induction passage of said carburetor; a feed tube communicating the feed passage of said carburetor downstream of said chamber with portions upstream of the intake ports of the second group of cylinders, the supplemental fuel jet and the supplemental air bleed orifice being selected to supply supplemental fuel from the fuel chamber of said carburetor through the feed passage and said feed tube in a manner to enrich the first air-fuel mixture into a second air-fuel mixture having an air-fuel ratio ranging from 10:1 to 14:1; a normally open solenoid valve disposed with said carburetor, the valve member of said solenoid valve being arranged to close the second opening of the feed chamber of said carburetor in response to an electric signal transmitted thereto; at least one sensor which senses at least one parameter of engine speed, engine load and afterburner temperature; a control circuit electrically connected between said normally open solenoid valve and said at least one sensor, said control circuit being arranged to generate an electric signal and transmit it to said normally open solenoid valve when the at least one parameter of engine speed, engine load and afterburner temperature exceeds its predetermined level.

Claim 16

A multi-cylinder internal combustion engine having a first group of cylinders and a second group of cylinders, the engine being followed by an afterburner to purify exhaust gases discharged from the first and second groups of cylinders, said engine comprising: a carburetor for supplying into the first and second groups of cylinders a first air-fuel mixture having an air-fuel ratio ranging from 17:1 to 20:1, said carburetor including a supplemental fuel jet communicating with the fuel chamber of the carburetor, a feed passage communicating the fuel jet with the air-fuel mixture induction passage of said carburetor, a supplemental air bleed orifice communicating with the feed passage, and a chamber disposed in the feed passage and having a first opening which communicates with the supplemental fuel jet, and a second opening which communicates with the air-fuel mixture induction passage of said carburetor; a feed tube communicating the feed passage of said carburetor downstream of said chamber with portions upstream of the intake ports of the second group of cylinders, the supplemental fuel jet and the supplemental air bleed orifice being selected to supply supplemental fuel from the fuel chamber of said carburetor through the feed passage and said feed tube in a manner to enrich the first air-fuel mixture into a second air-fuel mixture having an air-fuel ratio ranging from 10:1 to 14:1; a normally open solenoid valve disposed with said carburetor, the valve member of said solenoid valve being arranged to close the second opening of the feed chamber of said carburetor in response to an electric signal transmitted thereto; at least one sensor which senses at least one parameter of engine speed, engine load and afterburner temperature; a control circuit electrically connected between said normally open solenoid valve and said at least one sensor, said control circuit being arranged to generate an electric signal and transmit it to said normally open solenoid valve when the at least one parameter of engine speed, engine load and afterburner temperature exceeds its predetermined level.