Exhaust gas heating system for in-cylinder injection internal combustion engine

Claim 2

The system of claim 1, wherein said injection timing setting unit (110) includes an injection quantity computing unit (112) for determining said injection quantity of said additional fuel on a basis of a directly- or indirectly-detected quantity of oxygen still remaining after said primary combustion, an injecting duration setting unit (114) for setting an injecting duration, which corresponds to said injection quantity of said additional fuel determined by said injection quantity computing unit (112), and an injection start time setting unit (116) for setting an injection start time (T INJ ) of said additional fuel on the basis of said parameter which affects said flame lasting duration.

Claim 3

The system of claim 2, wherein said injection start time setting unit (116) includes: a basic injection start time setting unit (116A) for determining a basic injection start time (Tb inj ) on a basis of an engine speed (Ne) and an engine load of said internal combustion engine, and a flame dying time computing unit (116B) for determining an injection start time correction factor (K, K E , K F or K I ) on the basis of said parameter, which affects said flame lasting duration, while taking into consideration a flame dying time as an ending time of said flame lasting duration; and said injection start time setting unit (116) sets said injection start time (T INJ ) of said additional fuel on a basis of said basic injection start time (Tb inj ) determined by said basic injection start time setting unit (116A) and said injection start time correction factor (K, K E , K F or K I ) determined by said flame dying time computing unit (116B), so that said injection of said additional fuel is started at a timing where said additional fuel can be ignited by said flame of said primary combustion.

Claim 4

The system of claim 3, wherein said flame dying time computing unit (116B) determines said injection start time correction factor (K, K E , K F or K I ) on a basis of at least one of an engine temperature (w) of said internal combustion engine, an exhaust gas recirculation rate at a time of said primary combustion, an air/fuel ratio (A/F) at the time of said primary combustion and an ignition timing (T IG ) at the time of said primary combustion as said parameter which affects said flame lasting duration.

Claim 5

The system of claim 4, wherein said internal combustion engine includes an engine temperature detection unit (19) for detecting said engine temperature (w), and said flame dying time computing unit (116B) includes a first injection start time correction map (6A) indicating a first injection start time correction factor (K) which has been set while taking into consideration said flame dying time which advances as said engine temperature (w) becomes lower; whereby said injection start time setting unit (116) sets said injection start time (T INJ ) of said additional fuel on a basis of said first injection start time correction factor (K) which has been determined from said first injection start time correction map (6A) on the basis of said engine temperature (w) detected by said engine temperature detection unit (19).

Claim 6

The system of claim 4, wherein said internal combustion engine is provided with an exhaust gas recirculation rate control unit (104) for controlling an exhaust gas recirculation rate by opening or closing an on/off valve (10a) in an exhaust gas recirculation passage (10b) which communicates said exhaust passage (3) and said intake passage (2) with each other, and said flame dying time computing unit (116B) includes a second injection start time correction map (6B) indicating a second injection start time correction factor (K E ) which has been set while taking into consideration said flame dying time which varies in accordance with said exhaust gas recirculation rate; whereby said injection start time setting unit (116) sets said injection start time (T INJ ) of said additional fuel on a basis of said second injection start time correction factor (K E ) which has been determined from said second injection start time correction map (6B) on the basis of said exhaust gas recirculation rate controlled by said exhaust gas recirculation rate control unit (104).

Claim 7

The system of claim 4, wherein said internal combustion engine is provided with a conventional fuel injection control unit (103) for controlling an injection of fuel at the time of said primary combustion in accordance with operation conditions of said internal combustion engine, and said flame dying time computing unit (116B) includes a third injection start time correction map (6C) indicating a third injection start time correction factor (K F ) which has been set while taking into consideration said flame dying time which delays as an air/fuel ratio (A/F) at the time of said primary combustion becomes leaner; whereby said injection start time setting unit (116) sets said injection start time (T INJ ) of said additional fuel on a basis of said third injection start time correction factor (K F ) which has been determined from said third injection start time correction map (6C) on the basis of said air/fuel ratio (A/F) at the time of said primary combustion set by said conventional combustion injection control unit (103).

Claim 8

The system of claim 4, wherein said internal combustion engine is provided with an ignition timing control unit (107) for controlling an ignition timing (T IG ) of said primary fuel, which has been injected from said fuel injection device (8 and 8a), by said spark plug (108), and said flame dying time computing unit (116B) includes a fourth injection start time correction map (6D) indicating a fourth injection start time correction factor (K I ) which has been set while taking into consideration said flame dying time which delays as an ignition timing (T IG ) at the time of said primary combustion is retarded; whereby said injection start time setting unit (116) sets said injection start time (T INJ ) of said additional fuel on a basis of said fourth injection start time correction factor (K I ) which has been determined from said fourth injection start time correction map (6D) on the basis of said ignition timing (T IG ) set by said ignition timing control unit (107).

Claim 9

The system of claim 3, wherein said injection start time setting unit (116) sets said injection start time (T INJ ) of said additional fuel at a timing close to said flame dying time of said flame lasting duration.

Claim 10

The system of claim 2, wherein said injection start time setting unit (116) includes a flame lasting duration adjusting unit (116C) for adjusting said flame lasting duration; said flame lasting duration adjusting unit (116C) has a control unit (116C1) for adjusting a control amount for said parameter and a storage unit (116C2) for storing flame lasting durations corresponding to predetermined control amounts for said parameter, whereby said flame lasting duration adjusting unit (116C) adjusts said flame lasting duration by obtaining from said storage unit (116C2) one of said predetermined control amounts for said parameter, said one control amount being required to make said ending time of said flame lasting duration become equal to a flame dying time corresponding to a degree of activation required for said exhaust gas purification device (9), and then adjusting said parameter through said control unit (116C1) to give said one control amount; and said injection start time setting unit (116) sets said injection start time (T INJ ) of said additional fuel within said flame lasting duration adjusted by said flame lasting duration adjusting unit (116C).

Claim 11

The system of claim 10, wherein said internal combustion engine is provided with an exhaust gas recirculation rate control unit (104) for controlling an exhaust gas recirculation rate by opening or closing an on/off valve (10a) in an exhaust gas recirculation passage (10b) which communicates said exhaust passage (3) and said intake passage (2) with each other; said storage unit (116C2) includes a first map (7A) indicating flame dying times corresponding to control amounts for said exhaust gas recirculation rate; and said flame lasting duration adjusting unit (116C) obtains from said first map (7A) one of said control amounts on a basis of a flame lasting duration corresponding to a temperature determined by said purification device temperature computing unit (26 and 23), and controls said exhaust gas recirculation rate control unit (104) through said control unit (116C1) to give said one control amount.

Claim 12

The system of claim 10, wherein said internal combustion engine is provided with an ignition timing control unit (107) for controlling an ignition timing (T IG ) of said spark plug (108), at which said primary fuel injected from said fuel injection device (8 and 8a) is subjected to spark ignition; said storage unit (116C2) includes a second map (7B) indicating flame dying times corresponding to control amounts for said ignition timing (T IG ) of said primary combustion; and said flame lasting duration adjusting unit (116C) obtains from said second map (7B) one of said control amounts on a basis of a flame lasting duration corresponding to a temperature determined by said purification device temperature computing unit (26 and 23), and controls said ignition timing control unit (107) through said control unit (116C1) to give said one control amount.

Claim 13

The system of claim 10, wherein said internal combustion engine is provided with a conventional fuel injection control unit (103) for controlling said fuel injection at the time of said primary combustion in accordance with operation conditions; said storage unit (116C2) includes a third map (7C) indicating flame dying times corresponding to control amounts for said air/fuel ratio (A/F) of said primary combustion; and said flame lasting duration adjusting unit (116C) obtains from said third map (7C) one of said control amounts on a basis of a flame lasting duration corresponding to a temperature determined by said purification device temperature computing unit (26 and 23), and controls said conventional fuel injection control unit (103) through said control unit (116C1) to give said one control amount.

Claim 14

The system of claim 2, wherein said injection timing setting unit (110) includes a first injecting duration correcting unit (118) for correcting a basic injecting duration determined by said injecting duration setting unit (114) in accordance with a temperature of said exhaust gas purification device (9) determined by said purification device temperature computing unit (26 and 23).

Claim 15

The system of claim 14, wherein said first injecting duration correcting unit (118) has a correcting factor setting unit (118A) for correcting said basic injecting duration by a first injecting duration correcting factor (K 2 ), which has been predetermined corresponding to said temperature of said exhaust gas purification device (9), so that the injection quantity of said additional fuel becomes smaller as said temperature of said exhaust gas purification device rises.

Claim 16

The system of claim 14, wherein said internal combustion engine include plural cylinders; and said first injecting duration correcting unit (118) has a cylinder designating unit (118B) which, based on a cylinder number map (17C) preset corresponding to temperatures of said exhaust gas purification device (9), decreases a number of additional-injection-performed cylinders as said temperature of said exhaust gas purification device (9) rises.

Claim 17

The system of claim 2, wherein said injecting duration setting unit (110) includes a second injecting duration correcting unit (120) which, by a second injecting duration correcting factor (K 1 ) predetermined corresponding to said injection start time (T INJ ) of said additional fuel in said expansion stroke of said primary combustion, corrects said basic injecting duration (t B ) determined by said injecting duration setting unit (114) so that an actual injection quantity conforms with said injection quantity of said additional fuel determined by said injection quantity computing unit (112).

Claim 18

The system of claim 1, wherein said additional fuel injection control unit (102) includes an injection quantity computing unit (112) for determining said injection quantity of said additional fuel on a basis of a directly- or indirectly-detected quantity of oxygen still remaining after said primary combustion; and said injection timing setting unit (110) is provided with a divided injection start time setting unit (122) which sets injection start times (T1 INJ , T2 INJ , ....) of plural divided injections so that said injection quantity of said additional fuel determined by said injection quantity computing unit (112) is divided and injected in like plural portions.

Claim 19

The system of claim 18, wherein, when said injection quantity of said additional fuel is injected by dividing the same in N portions, said divided injection start time setting unit (122) sets an injection start time (TN INJ ) of an N th divided injection at a timing immediate before said exhaust valve (5) opens.

Claim 20

The system of claim 18, wherein said injection timing setting unit (110) is provided with an injecting duration setting unit (114) which, when said injection quantity of said additional fuel is injected by dividing the same in N portions, sets an N-1 th divided injecting duration and an N th divided injecting duration so that an N-1 th divided injection quantity becomes smaller than an N th divided injection quantity.

Claim 21

The system of claim 18, wherein said injecting duration setting unit (114) includes third injecting duration correcting factors (K 3 ) predetermined corresponding to values of said engine temperature (w) and, when said injection quantity of said additional fuel is injected by dividing the same in N portions, said injecting duration setting unit (114) sets an N-1 th divided injecting duration and an N th divided injecting duration by said third injecting duration correcting factors (K 3 ) so that an N-1 th divided injection quantity becomes still smaller than an N th divided injection quantity as said engine temperature rises.

Claim 22

The system of claim 2, wherein said injection start time setting unit (116) sets said injection start time (T INJ ) so that, when said temperature of said exhaust gas purification device (9) determined by said purification device temperature computing unit (26 and 23) is lower than a preset temperature permitting combustion of an unburnt fuel portion within said exhaust purification device (9), said injection of said additional fuel is effected within said flame lasting duration in which the flame of said primary combustion based on said injection of said primary fuel remains; and, when said temperature of said exhaust purification device (9) is equal to or higher than said preset temperature, said injection start time setting unit (116) sets said injection start time (T INJ ) so that said injection of said additional fuel is performed after said flame lasting duration.

Claim 23

An exhaust gas heating system for an in-cylinder injection internal combustion engine, comprising: a fuel injection device (8 and 8a) for injecting fuel directly into a combustion chamber (1) of said internal combustion engine, a spark plug (108) for subjecting fuel, which has been injected as primary fuel from said fuel injection device, to spark ignition so that said primary fuel undergoes primary combustion, an exhaust gas purification device (9) arranged in an exhaust passage (3) of said internal combustion engine, and an additional fuel injection control unit (102) for controlling said fuel injection device (8 and 8a) so that, when said exhaust gas purification device (9) is found to require activation of a catalyst thereof, fuel is injected as additional fuel within a flame lasting duration in which a flame of said primary combustion remains; wherein said additional fuel injection control unit (102) includes: an injection quantity computing unit (112) for determining an injection quantity of said additional fuel on a basis of a directly- or indirectly-detected quantity of oxygen still remaining after said primary combustion, and an injection timing setting unit (110) including an injecting duration setting unit (114) for setting a basic injecting duration corresponding to said injection quantity of said additional fuel determined by said injection quantity computing unit (112), and an injection start time setting unit (116) for setting an injection start time (T INJ ) of said additional fuel on a basis of a parameter which affects said flame lasting duration; and said injection start time setting unit (116), upon starting up said internal combustion engine at a low temperature, sets said injection start time so that said injection of said additional fuel is effected within said flame lasting duration and, in an operation state from which said exhaust gas purification device (9) is expected to be reduced in temperature, sets said injection start time so that said injection of said additional fuel is effected after said flame lasting duration.