Engine of a spark ignition type

Claim 2

An internal combustion engine of a spark ignition type, having a detector means for detecting a load of the engine, said internal combustion engine comprising: a control means for controlling an amount of fuel so as to make an air-fuel ratio of a mixed fuel to be charged into the engine substantially stoichiometric in a high load region in which the load of the engine detected by the detector means is equal to or larger than a predetermined value, in response to a signal from the detector means; and a recirculation means for recirculating exhaust gases from the engine into an intake system in the high load region, in response to the signal from the detector means.

Claim 3

An internal combustion engine of a spark ignition type as claimed in claim 1, wherein the air-fuel ratio of the mixed fuel at the time of running in the high load region is leaner than A/F=13.

Claim 4

An internal combustion engine of a spark ignition type as claimed in claim 2, wherein the air-fuel ratio of the mixed fuel at the time of running in the high load is richer than A/F=16.

Claim 5

An internal combustion engine of a spark ignition type as claimed in claim 1, wherein the exhaust gases are recirculated into the intake system of the engine by the recirculation means at the time of a full load.

Claim 6

An internal combustion engine of a spark ignition type as claimed in claim 1, wherein; the recirculation means has a first cooler means disposed in an EGR gas passage connecting an exhaust system with the intake system of the engine; and wherein the exhaust gases to be recirculated into the intake system of the engine at the time of running in the high load region are cooled by the first cooler means.

Claim 7

An internal combustion engine of a spark ignition type as claimed in claim 5, further comprising a supercharger for charging the engine with intake air; wherein a second cooler means is provided in the intake system on the downstream side of the supercharger; wherein a downstream end of the EGR gas passage has an opening so as to be communicated with the intake system on the upstream side of the second cooler means; and wherein the exhaust gases to be recirculated into the intake system are cooled by the first cooler means and the second cooler means.

Claim 8

An internal combustion engine of a spark ignition type as claimed in claim 5, wherein the exhaust gases having a high temperature are recirculated into the intake system by bypassing the cooler means at the time of running in a low load region wherein the load of the engine is lower than the predetermined value.

Claim 9

An internal combustion engine of a spark ignition type as claimed in claim 7, wherein the recirculation of the exhaust gases into the intake system is inhibited at the time of running in a low load and low rotational region wherein the engine is running at least in an idling state.

Claim 10

An internal combustion engine of a spark ignition type as claimed in claim 1, wherein the compression ratio of the engine is increased.

Claim 11

An internal combustion engine of a spark ignition type as claimed in claim 9, wherein: the engine is an internal combustion engine of a natural intake system having no supercharger; and the compression ratio is set to 11 or higher.

Claim 12

An internal combustion engine of a spark ignition type as claimed in claim 9, wherein: the engine is an internal combustion engine of a supercharging type, with a supercharger equipped for charging the engine with intake air; and the compression ratio is set to 9 or higher.

Claim 13

An internal combustion engine of a spark ignition type as claimed in claim 11, wherein the supercharger is of a type driven mechanically by the engine.

Claim 14

An internal combustion engine of a spark ignition type as claimed in claim 1, wherein a rate at which the exhaust gases are to be recirculated is set to at least one of becoming constant and being increased as a load increases, at the time of running in the high load region.

Claim 15

An internal combustion engine of a spark ignition type as claimed in claim 1, further comprising a variable valve timing mechanism for changing a timing for opening and closing an intake valve and an exhaust valve in accordance with a running state of the engine.

Claim 16

An internal combustion engine of a spark ignition type as claimed in claim 14, wherein: the engine is an internal combustion engine of a supercharging type, with an supercharger equipped for charging the engine with intake air; a running region in which the engine is running is divided into a first region, a second region, and a third region; wherein, in the first region which is a high rotational region in which the number of rotation of the engine is equal to or higher than a predetermined value, the variable valve timing mechanism is arranged to set an overlap of an open state of the exhaust valve in which the exhaust valve is opened with an open state of the intake valve in which the intake valve is opened so as to become larger than those in the second region and in the third region and to delay the closing of the intake valve at a timing late enough after bottom dead center; wherein, in the second region in which the number of rotation of the engine is so low and the load is so low as containing at least an idling running state of the engine, the variable valve timing mechanism is arranged to set an overlap of the open state of the exhaust valve with the open state of the intake valve so as to become smaller than those in the first region and in the third region and to delay the closing of the intake valve at a timing sufficiently later than the timing at which the intake valve is closed in the first region; and wherein, in the third region, the variable valve timing mechanism is arranged to set an overlap of the open state of the exhaust valve with the open state of the intake valve so as to become smaller than that in the first region yet larger than that in the second region and to set the timing of closing the intake valve to be substantially the same as the timing of closing the intake valve in the first region.

Claim 17

An internal combustion engine of a spark ignition type as claimed in claim 8, further comprising a variable valve timing mechanism for changing a timing for opening and closing an intake valve and an exhaust valve in accordance with a running state of the engine; wherein the engine is an internal combustion engine of a supercharging type with a supercharger equipped for charging the engine with intake air; and a running region in which the engine is running is divided into a first region, a second region, and a third region; wherein, in the first region which is a high rotational region in which the number of rotation of the engine is equal to or higher than a predetermined value, the variable valve timing mechanism is arranged to set an overlap of an open state of the exhaust valve in which the exhaust valve is opened with an open state of the intake valve in which the intake valve is opened so as to become larger than those in the second region and in the third region and to delay the closing of the intake valve at a timing late enough after bottom dead center; wherein, in the second region in which the number of rotation of the engine is so low and the load is so low as containing at least an idling running state of the engine, the variable valve timing mechanism is arranged to set an overlap of the open state of the exhaust valve with the open state of the intake valve so as to become smaller than those in the first region and in the third region and to delay the closing of the intake valve at a timing later than the timing at which the intake valve is closed in the first region; and wherein, in the third region, the variable valve timing mechanism is arranged to set an overlap of the open state of the exhaust valve with the open state of the intake valve so as to become smaller than that in the first region yet larger than that in the second region and to set the timing of closing the intake valve to be substantially the same as the timing of closing the intake valve in the first region.

Claim 18

An internal combustion engine of a spark ignition type as claimed in claim 14, wherein: the engine is an internal combustion engine of a natural intake type, without a supercharger for charging the engine with intake air; and a running region in which the engine is running is divided into a first region, a second region, and a third region; wherein, in the first region in which a load is equal to or higher than a predetermined second value, the variable valve timing mechanism is arranged so as to set a predetermined range containing top dead center, in which an open state of the exhaust valve in which the exhaust valve is opened overlaps with an open state of the intake valve in which the intake valve is opened; wherein, in the second region in which the number of rotation of the engine is so low and the load is so low as containing at least an idling running state of the engine, the variable valve timing mechanism is arranged to open the intake valve so as not to overlap with a timing for closing the exhaust valve and to delay the closing of the intake valve at a timing late enough after bottom dead center; and wherein, in the third region, the variable valve timing mechanism is arranged to set an overlap of the open state of the exhaust valve with the open state of the intake valve so as to become substantially the same as that in the first region and so as to open the intake valve after top dead center and to delay a timing for closing the intake valve at substantially the same timing as the timing for closing the intake valve in the second region.

Claim 19

An internal combustion engine of a spark ignition type as claimed in claim 17, wherein the predetermined second value is set on the side higher than said predetermined load.

Claim 20

An internal combustion engine of a spark ignition type as claimed in claim 7, further comprising a variable valve timing mechanism for changing a timing for opening and closing the intake valve and the exhaust valve in accordance with a running state of the engine; wherein the engine is an internal combustion engine of a natural intake type, without a supercharger for charging the engine with intake air; and a running region in which the engine is running is divided into a first region, a second region, and a third region; wherein, in the first region which is a high load region wherein the load of the engine is equal to or higher than the predetermined second value, the variable valve timing mechanism is arranged so as to set a predetermined range containing top dead center, in which an open state of the exhaust valve in which the exhaust valve is opened overlaps with an open state of the intake valve in which the intake valve is opened; wherein, in the second region which is a low load and low rotational region containing an idling running state of the engine, the variable valve timing mechanism is arranged to open the intake valve so as not to overlap with a timing for closing the exhaust valve and to delay the closing of the intake valve at a timing late enough after bottom dead center; and wherein, in the third region, the variable valve timing mechanism is arranged to set an overlap of the open state of the exhaust valve with the open state of the intake valve so as to become substantially the same as that in the first region and so as to open the intake valve after top dead center and to delay a timing for closing the intake valve at substantially the same timing as the timing for closing the intake valve in the second region.

Claim 21

An internal combustion engine of a spark ignition type as claimed in claim 1, wherein a rate at which exhaust gases are to be recirculated is set to be increased as a load increases, at time of running in the high load region.

Claim 22

An internal combustion engine of a spark ignition type as claimed in claim 1, wherein the high load region, in which the air fuel ratio is substantially stoichiometric and the exhaust gas is recirculated into the intake system, contains a full load region.

Claim 23

An internal combustion engine of a spark ignition type as claimed in claim 1, further comprising a supercharger provided in an intake passage of the engine for charging the engine with intake air, wherein the recirculation means has an outlet port to the intake passage which is located in a position upstream of the supercharger.

Claim 24

An internal combustion engine of a spark ignition type as claimed in claim 13, wherein the high load region, in which the air-fuel ratio is substantially stoichiometric and the exhaust gas is recirculated into the intake system, contains a full load region.

Claim 25

An internal combustion engine of a spark ignition type as claimed in claim 13, further comprising a supercharger provided in an intake passage of the engine for charging the engine with intake air, wherein the recirculation means has an outlet port to the intake passage which is located in a position upstream of the supercharger.

Claim 26

An internal combustion engine of a spark ignition type as claimed in claim 13, wherein the air-fuel ratio of the mixed fuel at the time of running in the high load region is richer than A/F=16.

Claim 27

An internal combustion engine of a spark ignition type, having a detector means for detecting a load of the engine, said internal combustion engine comprising: a control means for controlling an amount of fuel so as to make an air-fuel ratio of a mixed fuel to be charged into the engine substantially stoichiometric in a high load region in which the load of the engine detected by the detector means is equal to or larger than a predetermined value, in response to a signal from the detector means; a recirculation means for recirculating exhaust gases from the engine into an intake system in the high load region, in response to the signal from the detector means; and wherein a rate at which the exhaust gases are to be recirculated is set to be at least one of constant and increased as a load increases, at the time of running in the high load region.

Claim 28

An internal combustion engine of a spark ignition type, having a detector means for detecting a load of the engine, said internal combustion engine comprising: a control means for controlling an amount of fuel so as to make an air-fuel ratio of a mixed fuel to be charged into the engine substantially stoichiometric in a high load region in which the load of the engine detected by the detector means is equal to or larger than a predetermined value, in response to a signal from the detector means; a recirculation means for recirculating exhaust gases from the engine into an intake system in the high load region, in response to the signal from the detector means; and wherein a rate at which the exhaust gases are to be recirculated is set to be at least one of constant and increased as a load increases, at the time of running in the high load region.

Claim 29

An internal combustion engine of a spark ignition type, having a detector means for detecting a load of the engine, said internal combustion engine comprising: a recirculation means for recirculating exhaust gases from the engine into an intake system in a high load region, in which the load of the engine detected by the detector means is equal to or larger than a predetermined value, in response to a signal from the detector means; wherein a rate at which the exhaust gases are to be recirculated is set to be at least one of constant and increased as a load increases, at the time of running in the high load region.

Claim 30

An internal combustion engine of a spark ignition type, having a detector means for detecting a load of the engine, said internal combustion engine comprising: a recirculation means for recirculating exhaust gases from the engine into an intake system in a high load region, in which the load of the engine detected by the detector means is equal to or larger than a predetermined value, in response to a signal from the detector means; wherein a rate at which the exhaust gases are to be recirculated is set to be at least one of constant and increased as a load increases, at the time of running in the high load region.