Abstract: The amount of accumulated particulate matter, which is accumulated in a particulate filter, is computed based on the amount of exhausted particulate matter, which is exhausted from an engine, and the amount of reduced particulate matter, which is reduced in the filter. The amount of reduced particulate matter includes the amount of reduced particulate matter, which is reduced through oxidizing reaction of the accumulated particulate matter with NO2. At the time of computing this amount, reduction of the particulate matter through oxidizing reaction with adsorbed NO2, which is adsorbed by the accumulated particulate matter, is concerned in addition to reduction of the particulate matter through oxidizing reaction with NO2, which is present in the surrounding atmosphere around the accumulated particulate matter.

Abstract: A flow rate of gas supplied to a diesel particulate filter is increased when it is determined that rapid combustion of collected particulates, which are collected by the particulate filter, is likely to occur based on an operating state of an internal combustion engine. Alternatively, the flow rate of gas supplied to the filter is increased when it is determined that rapid combustion of the collected particulates is initiated based on a state of the particulate filter.

Abstract: An electronic control unit (ECU) of an exhaust gas cleaning system for an internal combustion engine having a diesel particulate filter (DPF) determines whether collection quantity of exhaust particulate matters collected by the DPF is greater than a regeneration start value or not. The collection quantity is calculated from a pressure difference at the DPF and a flow rate of exhaust gas. If the collection quantity is determined to be greater than the regeneration start value, the ECU increases the temperature of the DPF to regenerate the DPF. The regeneration start value is set smaller as the detection accuracy of the collection quantity decreases. The regeneration start value is set smaller as the exhaust gas flow rate decreases and a rate of change in an accelerator position increases.

Abstract: An exhaust emission control system for an internal combustion engine is located on a vehicle and provided with a particulate filter to accumulate particulate matters in an exhaust gas of the engine. The system has a pressure difference detector, an exhaust flow rate detector, a regeneration controller and a detection accuracy increaser. The pressure difference detector detects a differential pressure in the particulate filter. The exhaust flow rate detector detects an exhaust flow rate of the engine. The regeneration controller determines to regenerate the particulate filter based on the differential pressure and the exhaust flow rate. The detection accuracy increaser increases a detection accuracy of the differential pressure.

Abstract: An electronic control unit (an ECU) detects an operating condition of an engine and quantity of particulate matters accumulated in a diesel particulate filter (a DPF) having an oxidation catalyst from a pressure difference across the DPF. The ECU operates temperature increasing means for regenerating the DPF based on the above detection results. During a low speed and light load operation, the ECU does not perform temperature increasing operation similar to an operation performed during a middle load operation. Instead, the ECU performs operation such as reduction of recirculated exhaust gas quantity in order to inhibit an increase in the quantity of the accumulated particulate matters. When the operating condition is changed afterward, the temperature increasing means is operated, so safe regeneration of the DPF is achieved.

Abstract: Unless an abnormality exists in piping introducing a pressure from front and rear of DPF 22 into a differential pressure sensor 45, pulsations of pressure propagation through an exhaust passage 21 is offset in a detection value of a pressure difference of the differential pressure sensor 45, and an amplitude of the detection value of the DPF pressure difference resulting from pulsation of the pressure becomes small. If a crack exists in one of the piping 3a and 3b, the influence of a pulsation of the pressure appears in the DPF pressure difference and the amplitude of the detection value of the DPF pressure difference becomes large. The amplitude of the detection value of the DPF pressure difference is compared with the reference value and is detected as being abnormal when it is large, utilizing the phenomenon described above.

Abstract: In an exhaust cleaning system including a DPF in exhaust passages, a pair of temperature sensors is disposed upstream and downstream the filter to detect upstream and downstream exhaust temperatures. An electronic control unit estimates a downstream exhaust temperature from the actual upstream exhaust temperature when an engine is in a predetermined condition such as a cold-start condition or a high speed and high load condition, in which no catalytic reaction heat is generated in the DPF. The control unit then compares the estimated downstream temperature with the actually detected downstream temperature, and determines an exhaust temperature senor malfunction if the difference between the compared temperatures are large.

Abstract: A compression ignition engine injects fuel through injection holes of an injector at a substantially constant injection rate to atomize the fuel so that the fuel can be easily vaporized and to make the fuel penetrate an atmosphere inside a cylinder. A spatial distribution of the injected fuel in which mixing of the fuel and air is promoted as the fuel recedes from the injection hole and the fuel reaches a premixing space where the fuel is premixed with the air is provided. The engine controls oxygen concentration inside the cylinder and an ignition delay so that a ratio of a quantity of the fuel injected before a start of ignition to a total fuel injection quantity falls within a range from 25% to 50% and so that the premixed gas formed in the premixing space is combusted serially.

Abstract: The recycling timing schedule for a diesel particulate filter (DPF) can be easily and accurately determined. There is a differential pressure sensor that detects differential pressure &Dgr;P in the DPF, and an airflow meter that detects the flow velocity v in an exhaust path. An ECU calculates the quantity of deposited fine exhaust particles ML according to: ML=[&Dgr;P−(A&mgr;v+C&rgr;v2)]/(B&mgr;v+D&rgr;v2) Recycling of the filter is determined according to a determination formula used to compare the calculated deposited quantity ML to a reference quantity. In this way, the deposited quantity can be accurately obtained without using a map.

Abstract: An exhaust gas recirculation (EGR) system of an internal combustion engine has an EGR cooler in an EGR passage connecting an exhaust manifold with an intake manifold. The EGR cooler cools EGR gas recirculated through the EGR passage. Cooling performance detecting means included in an electronic control unit (ECU) determines that cooling performance of the EGR cooler is degraded when intake pressure measured by an intake pressure sensor is lower than a normal intake pressure by at least a predetermined value. When the degradation of the cooling performance is detected, cooling performance regeneration controlling means included in the ECU increases the temperature inside the EGR cooler by heating the exhaust gas to eliminate soot or unburned hydrocarbon by oxidization. Thus, the cooling performance of the EGR cooler is regenerated.

Abstract: A diesel oxidation catalyst is disposed upstream of a diesel particulate filter (a DPF) disposed in an exhaust passage of a diesel engine. An electronic control unit (an ECU) operates temperature increasing means, which performs post-injection, to eliminate particulate matters accumulated in the DPF. The ECU includes first correcting means and second correcting means. The first correcting means corrects a manipulated variable of the temperature increasing means based on a result of comparison between target temperature and temperature of the DPF estimated based on information related to an area upstream of the DPF. The second correcting means corrects the manipulated variable of the temperature increasing means based on a result of comparison between the target temperature and the temperature of the DPF estimated based on information related to an area downstream of the DPF.

Abstract: An exhaust gas cleaning system of a diesel engine includes a diesel particulate filter (a DPF) disposed in an exhaust passage, and a diesel oxidation catalyst (a DOC) disposed upstream of the DPF. When an electronic control unit (an ECU) performs a temperature increasing operation such as post-injection to eliminate particulate matters accumulated in the DPF, a ratio (a duty ratio) between a performing period and an interrupting period of the temperature increasing operation is changed in accordance with temperature of the DPF. Thus, a quantity of hydrocarbon supplied to the DOC is controlled stepwise or continuously. Thus, the temperature of the DPF can be increased to target temperature quickly and can be maintained near the target temperature when the regeneration of the DPF is performed.

Abstract: An engine exhaust emission control device determines a differential pressure across a diesel particulate filter (DPF) to enable regeneration of the DPF at optimal timing. An ECU estimates the temperature of a differential pressure sensor provided for the DPF from the output of an intake air temperature sensor when the engine is not running, and determines an offset correction factor for correcting the sensor's offset error. The factor is set using the sensor output at this time as sensor's offset error, and stored in a memory. When detecting the differential pressure across the DPF, the temperature of the sensor at this time is estimated, and an offset correction factor that corresponds to this estimated temperature is selected. The sensor outputs are adjusted with this offset correction factor.

Abstract: An exhaust gas purification system of an internal combustion engine supplies hydrocarbon by performing a post injection and the like in order to combust particulate matters accumulated in a diesel particulate filter (a DPF) having an oxidation catalyst. An electronic control unit (an ECU) senses temperature of exhaust gas upstream of the DPF with an exhaust gas temperature sensor and determines an upper limit value of permissible quantity of the hydrocarbon supplied to the DPF based on the sensed temperature. The ECU controls post injection quantity so that the quantity of the actually supplied hydrocarbon does not exceed the upper limit value. Thus, hydrocarbon poisoning can be precluded, since the quantity of the actually supplied hydrocarbon does not exceed the upper limit value.

Abstract: An electronic control unit (an ECU) detects an operating condition of an engine and quantity of particulate matters accumulated in a diesel particulate filter (a DPF) having an oxidation catalyst from a pressure difference across the DPF. The ECU operates temperature increasing means for regenerating the DPF based on the above detection results. During a low speed and light load operation, the ECU does not perform temperature increasing operation similar to an operation performed during a middle load operation. Instead, the ECU performs operation such as reduction of recirculated exhaust gas quantity in order to inhibit an increase in the quantity of the accumulated particulate matters. When the operating condition is changed afterward, the temperature increasing means is operated, so safe regeneration of the DPF is achieved.

Abstract: In an exhaust gas cleaning system of an internal combustion engine having a diesel particulate filter (DPF), measuring accuracy of a collection quantity of particulate matters collected by the DPF is estimated based on an accelerator position change rate and an exhaust gas flow rate. When the measuring accuracy is high, the collection quantity is calculated based on a pressure difference and the exhaust gas flow rate at the DPF. If the measuring accuracy is low, an increment value of the collection quantity is calculated based on a quantity of the particulate matters discharged from an engine main body. Then, the collection quantity is calculated by adding the collection quantity increment value to the previous collection quantity calculated based on the pressure difference and the exhaust gas flow rate while the measuring accuracy is high.

Abstract: A diesel particulate filter (DPF) having an oxidation catalyst is disposed between exhaust pipes of an internal combustion engine. An exhaust gas temperature sensor senses outlet gas temperature of the DPF. An engine control unit (ECU) calculates estimated central temperature of the DPF from an output of the exhaust gas temperature sensor with the use of an inverse transfer function of a change in the outlet gas temperature with respect to a change in temperature of the DPF. Based on the estimated temperature, the ECU performs excessive temperature increase prevention control or regeneration control of the DPF. The transfer function is simply expressed with first-order lag and dead time. A time constant of the first-order lag and the dead time are set in accordance with an exhaust gas flow rate.

Abstract: An engine control unit of an exhaust gas purification system of an internal combustion engine measures a pressure difference between an upstream and a downstream of a diesel particulate filter (DPF) after heating the DPF at least to a predetermined temperature and maintaining the DPF at the temperature for a while. The DPF is disposed in an exhaust pipe of the engine. A soluble organic fraction included in particulate matters in exhaust gas can be eliminated at the predetermined temperature. The ECU calculates a quantity of the particulate matters trapped by the DPF from the measured pressure difference. Thus, the quantity of the trapped particulate matters is calculated precisely, independently of a composition of the particulate matters or a state of the soluble organic fraction.

Abstract: The recycling timing schedule for a diesel particulate filter (DPF) can be easily and accurately determined. There is a differential pressure sensor that detects differential pressure &Dgr;P in the DPF, and an airflow meter that detects the flow velocity v in an exhaust path.

Abstract: An exhaust gas cleaning system for a diesel engine has a diesel particulate filter (DPF) disposed in an exhaust pipe. An electronic control unit of the system controls regeneration of the DPF. The DPF is heated and regenerated only when an operating state of the engine is in an area where temperature-increasing efficiency is high, in the case where a quantity of particulate matters collected by the DPF is equal to or greater than a first threshold and is less than a second threshold. The second threshold is greater than the first threshold. If the quantity of the collected particulate matters becomes equal to or greater than the second threshold, the regeneration is performed even if the operating state is not in the area of the high temperature-increasing efficiency.