IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0902162
(2004-07-30)
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우선권정보 |
JP-2003-282360(2003-07-30) |
발명자
/ 주소 |
- Todoroki,Hikari
- Miura,Manabu
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출원인 / 주소 |
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
26 인용 특허 :
3 |
초록
▼
In a combustion control system of an engine employing an exhaust purifying device, a control unit determines, based on an operating condition of the exhaust purifying device, whether a request for an exhaust temperature rise is present. The control unit executes, by way of fuel injection control in
In a combustion control system of an engine employing an exhaust purifying device, a control unit determines, based on an operating condition of the exhaust purifying device, whether a request for an exhaust temperature rise is present. The control unit executes, by way of fuel injection control in presence of the request of the exhaust temperature rise, a split retard combustion mode in which a main combustion needed to produce a main engine torque and at least one preliminary combustion occurring prior to the main combustion are both achieved, and the preliminary combustion occurs near top dead center on a compression stroke, and the main combustion initiates after completion of the preliminary combustion. The control unit executes a fail-safe process that an injection timing of main fuel injection is phase-advanced, when a predicted temperature value of the exhaust purifying device exceeds a predetermined threshold value.
대표청구항
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What is claimed is: 1. A combustion control system of an internal combustion engine employing an exhaust purifying device in an exhaust passage, comprising: sensors that detect operating conditions of the engine; a control unit being configured to be electronically connected to the sensors, for co
What is claimed is: 1. A combustion control system of an internal combustion engine employing an exhaust purifying device in an exhaust passage, comprising: sensors that detect operating conditions of the engine; a control unit being configured to be electronically connected to the sensors, for combustion control and fail-safe purposes; the control unit comprising a processor programmed to perform the following, (a) estimating an operating condition of the exhaust purifying device; (b) determining, based on the operating condition of the exhaust purifying device, whether a request for a rise in an exhaust temperature is present; (c) executing, by way of fuel injection control in presence of the request for the exhaust temperature rise, a split retard combustion mode in which a main combustion needed to produce a main engine torque and at least one preliminary combustion occurring prior to the main combustion are both achieved and additionally the preliminary combustion takes place near top dead center on a compression stroke and additionally the main combustion initiates after the preliminary combustion has been completed; (d) predicting a temperature of the exhaust purifying device to determine a predicted temperature value; and (e) executing a fail-safe process according to which an injection timing of main fuel injection for the main combustion is compensated for in a timing-advance direction, when the predicted temperature value exceeds a predetermined temperature threshold value. 2. The combustion control system as claimed in claim 1, wherein the processor is further programmed for: (f) calculating a feedback compensation amount for compensation for the injection timing of main fuel injection in the timing-advance direction, based on a temperature deviation between the predicted temperature value and the predetermined temperature threshold value; and (g) variably adjusting a feedback gain for calculation of the feedback compensation amount, depending on the temperature deviation. 3. The combustion control system as claimed in claim 1, wherein the processor is further programmed for: (h) retrieving the temperature of the exhaust purifying device based on an exhaust temperature detected downstream of the exhaust purifying device from a predetermined characteristic model defining a correlation between the temperature of the exhaust purifying device and the exhaust temperature detected downstream of the exhaust purifying device, based on at least one of a heat capacity and a heat conductivity of the exhaust purifying device, to determine the predicted temperature value. 4. The combustion control system as claimed in claim 3, wherein the processor is further programmed for: (i) determining the temperature of the exhaust purifying device, retrieved based on the exhaust temperature detected downstream of the exhaust purifying device from the predetermined characteristic model, as a basic predicted value of the temperature of the exhaust purifying device; (j) calculating a final exhaust-purifying-device-temperature predicted value by making a first-order lag process to the basic predicted value, based on a first-order lag gain; and (k) variably adjusting the first-order lag gain based on an exhaust gas flow rate. 5. The combustion control system as claimed in claim 1, wherein the processor is further programmed for: (l) predicting the temperature of the exhaust purifying device based on exhaust temperatures detected upstream and downstream of the exhaust purifying device, by way of a weighted-mean process for both of the exhaust temperatures. 6. The combustion control system as claimed in claim 1, wherein: an injection quantity of preliminary fuel injection for the preliminary combustion is set to a fuel injection quantity needed in order for an in-cylinder temperature obtained during a main fuel injection period for the main combustion to exceed a self-ignitable temperature value. 7. The combustion control system as claimed in claim 1, wherein: a start of the main combustion is retarded from a start of the preliminary combustion by at least 20 degrees of crankangle, for initiating the main combustion after completion of the preliminary combustion. 8. The combustion control system as claimed in claim 1, wherein: an end of the main combustion is retarded by at least 50 degrees of crankangle from the top dead center on the compression stroke. 9. The combustion control system as claimed in claim 1, wherein: the exhaust temperature is controlled by changing the injection timing of main fuel injection during the main combustion. 10. The combustion control system as claimed in claim 1, wherein the processor is further programmed for: (m) executing a torque compensation process that keeps a torque generated by the engine constant during the main combustion for minimizing an engine torque difference before and after switching to the split retard combustion mode. 11. The combustion control system as claimed in claim 1, wherein: the exhaust purifying device comprises a particulate filter that accumulates particulate matter (PM) contained in exhaust gases, and a period that the request for the exhaust temperature rise based on the operating condition of the exhaust purifying device is present, is at least a particulate-filter regeneration period during which the PM accumulated in the particulate filter is burned and removed from the particulate filter by rising up the exhaust temperature. 12. The combustion control system as claimed in claim 1, wherein: the exhaust purifying device comprises a NOx trap catalyst that traps nitrogen oxides contained in exhaust gases when an exhaust air-fuel mixture ratio is lean, and a period that the request for the exhaust temperature rise based on the operating condition of the exhaust purifying device is present, is at least a sulfur poisoning release period during which sulfur oxides trapped by the NOx trap catalyst is desorbed from the NOx trap catalyst by rising up the exhaust temperature. 13. The combustion control system as claimed in claim 1, wherein: the exhaust purifying device comprises (i) a NOx trap catalyst that traps nitrogen oxides contained in exhaust gases when an exhaust air-fuel mixture ratio is lean, and (ii) a particulate filter that accumulates particulate matter contained in the exhaust gases and is disposed downstream of the NOx trap catalyst, and which further comprises a first exhaust temperature sensor disposed downstream of the NOx trap catalyst and upstream of the particulate filter, and a second exhaust temperature sensor disposed downstream of the particulate filter, and wherein a temperature of the NOx trap catalyst is predicted based on an exhaust temperature detected by the first exhaust temperature sensor disposed downstream of the NOx trap catalyst, and a temperature of the particulate filter is predicted based on both of the exhaust temperature detected by the first exhaust temperature sensor and an exhaust temperature detected by the second exhaust temperature sensor disposed downstream of the particulate filter. 14. The combustion control system as claimed in claim 13, wherein the processor is further programmed for: (n) calculating a temperature deviation between the NOx-trap-catalyst temperature predicted and the predetermined temperature threshold value; (o) variably adjusting a feedback gain of a feedback compensation amount for compensation for the injection timing of main fuel injection in the timing-advance direction, depending on the temperature deviation; (p) calculating the feedback compensation amount by multiplying the temperature deviation by the feedback gain; and (q) advancing the injection timing of main fuel injection by the feedback compensation amount, when the NOx-trap-catalyst temperature predicted based on the exhaust temperature detected by the first exhaust temperature sensor exceeds the predetermined temperature threshold value. 15. The combustion control system as claimed in claim 13, wherein the processor is further programmed for: (n) calculating a temperature deviation between the particulate-filter temperature predicted and the predetermined temperature threshold value; (o) variably adjusting a feedback gain of a feedback compensation amount for compensation for the injection timing of main fuel injection in the timing-advance direction, depending on the temperature deviation; (p) calculating the feedback compensation amount by multiplying the temperature deviation by the feedback gain; and (q) advancing the injection timing of main fuel injection by the feedback compensation amount, when the particulate-matter temperature predicted based on the exhaust temperatures detected by the first and second exhaust temperature sensors exceeds the predetermined temperature threshold value. 16. A combustion control system of an internal combustion engine employing an exhaust purifying device in an exhaust passage, comprising: sensor means for detecting operating conditions of the engine; a control unit being configured to be electronically connected to the sensor means, for combustion control and fail-safe purposes; the control unit comprising: (a) means for estimating an operating condition of the exhaust purifying device; (b) means for determining, based on the operating condition of the exhaust purifying device, whether a request for a rise in an exhaust temperature is present; (c) means for executing, by way of fuel injection control in presence of the request for the exhaust temperature rise, a split retard combustion mode in which a main combustion needed to produce a main engine torque and at least one preliminary combustion occurring prior to the main combustion are both achieved and additionally the preliminary combustion takes place near top dead center on a compression stroke and additionally the main combustion initiates after the preliminary combustion has been completed; (d) means for predicting a temperature of the exhaust purifying device to determine a predicted temperature value; and (e) means for executing a fail-safe process according to which an injection timing of main fuel injection for the main combustion is compensated for in a timing-advance direction, when the predicted temperature value exceeds a predetermined temperature threshold value. 17. A method of executing a fail-safe function for an exhaust purifying device disposed in an exhaust passage of an internal combustion engine capable of recovering an operating condition of the exhaust purifying device, the method comprising: estimating the operating condition of the exhaust purifying device; determining, based on the operating condition of the exhaust purifying device, whether a request for a rise in an exhaust temperature is present; executing, by way of fuel injection control in presence of the request for the exhaust temperature rise, a split retard combustion mode in which a main combustion needed to produce a main engine torque and at least one preliminary combustion occurring prior to the main combustion are both achieved and additionally the preliminary combustion takes place near top dead center on a compression stroke and additionally the main combustion initiates after the preliminary combustion has been completed; predicting a temperature of the exhaust purifying device to determine a predicted temperature value; and executing a fail-safe process according to which an injection timing of main fuel injection for the main combustion is compensated for in a timing-advance direction, when the predicted temperature value exceeds a predetermined temperature threshold value. 18. A method of executing a fail-safe function for an exhaust purifying device including (i) a NOx trap catalyst that traps nitrogen oxides contained in exhaust gases when an exhaust air-fuel mixture ratio is lean, and (ii) a particulate filter that accumulates particulate matter contained in the exhaust gases and is disposed downstream of the NOx trap catalyst, both disposed in an exhaust passage of an internal combustion engine capable of recovering an operating condition of the exhaust purifying device, the method comprising: disposing a first exhaust temperature sensor downstream of the NOx trap catalyst and upstream of the particulate filter; disposing a second exhaust temperature sensor downstream of the particulate filter, predicting a temperature of the NOx trap catalyst based on an exhaust temperature detected by the first exhaust temperature sensor; predicting a temperature of the particulate filter based on both of the exhaust temperature detected by the first exhaust temperature sensor and an exhaust temperature detected by the second exhaust temperature sensor; estimating the operating condition of the exhaust purifying device; determining, based on the operating condition of the exhaust purifying device, whether a request for a rise in an exhaust temperature is present; executing, by way of fuel injection control in presence of the request for the exhaust temperature rise, a split retard combustion mode in which a main combustion needed to produce a main engine torque and at least one preliminary combustion occurring prior to the main combustion are both achieved and additionally the preliminary combustion takes place near top dead center on a compression stroke and additionally the main combustion initiates after the preliminary combustion has been completed; and executing a fail-safe process according to which an injection timing of main fuel injection for the main combustion is phase-advanced, when the at least one of the NOx-trap-catalyst temperature predicted and the particulate-filter temperature predicted exceeds a predetermined temperature threshold value. 19. The method as claimed in claim 18, further comprising: calculating a temperature deviation between the NOx-trap-catalyst temperature predicted and the predetermined temperature threshold value; variably adjusting a feedback gain of a feedback compensation amount for phase-advance of the injection timing of main fuel injection, depending on the temperature deviation; calculating the feedback compensation amount by multiplying the temperature deviation by the feedback gain; and phase-advancing the injection timing of main fuel injection by the feedback compensation amount, when the NOx-trap-catalyst temperature predicted based on the exhaust temperature detected by the first exhaust temperature sensor exceeds the predetermined temperature threshold value. 20. The method as claimed in claim 18, further comprising: calculating a temperature deviation between the particulate-filter temperature predicted and the predetermined temperature threshold value; variably adjusting a feedback gain of a feedback compensation amount for phase-advance of the injection timing of main fuel injection, depending on the temperature deviation; calculating the feedback compensation amount by multiplying the temperature deviation by the feedback gain; and phase-advancing the injection timing of main fuel injection by the feedback compensation amount, when the particulate-matter temperature predicted based on the exhaust temperatures detected by the first and second exhaust temperature sensors exceeds the predetermined temperature threshold value.
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