Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
2000-10-26
2002-05-07
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
By means producing a chemical reaction of a component of the...
C060S277000, C060S285000, C060S286000, C060S324000
Reexamination Certificate
active
06381952
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 11-304388 filed on Oct. 26, 1999 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exhaust temperature raising apparatus and method for an internal combustion engine.
2. Description of the Related Art
Diesel engines produce large amounts of unburned HCs during low-load engine operations, and particularly during a warm-up operation, since the combustion chamber temperature is low during such operations.
There is a known technology in which an exhaust control valve is disposed in an engine exhaust passage, and the combustion chamber temperature is raised by closing the exhaust control valve and increasing the amount of fuel injected, so as to curb production of unburned HCs (see, for example, Japanese Patent Application Laid-Open No. SHO 49-80414).
When the exhaust control valve is substantially completely closed after the combustion chamber temperature has been raised by increasing the amount of fuel injected as mentioned above, the pressure in the exhaust passage, that is, the back pressure, becomes considerably high. If the back pressure is high, the exhaust gas temperature is unlikely to decrease, so that exhaust gas in the exhaust passage remains in a high temperature state. Furthermore, if the back pressure rises, the exhaust gas flow rate decreases, so that high-temperature exhaust gas resides or dwells in a portion of the exhaust passage upstream of the exhaust control valve. While exhaust gas resides in this fashion, the exhaust gas is in a high-temperature state. As a result, unburned HCs among the exhaust gas components are oxidized, and the amount of unburned HCs contained in exhaust gas emitted into the atmosphere is reduced.
In another technology for lessening unburned HCs, an emission control catalyst is disposed in an engine exhaust passage. However, unless activated, the catalyst is unable to sufficiently control emission, that is, unable to lessen unburned HCs.
There is a well-known technology in which in addition to main injection, that is, fuel injection for producing the engine output, sub-injection, that is, subsidiary fuel injection after the main injection, is performed during the expansion stroke (see, for example, Japanese Patent Application Laid-Open Nos. HEI 8-303290 and HEI 10-212995).
If the sub-injection is performed in addition to the main injection, unburned HCs produced by the combustion attributed to the main injection (hereinafter, referred to as “main combustion”) are burned in the combustion attributed to the sub-injection (hereinafter, referred to as “sub-combustion”), so that the amount of unburned HCs itself decreases to a considerably low level. Furthermore, since unburned HCs produced by the main combustion burn together with the sub-injection fuel, the amount of combustion increases. As a result, the exhaust gas temperature rises so that a high catalyst temperature is achieved. Thus, the amount of unburned HCs is reduced.
Although various technologies for lessening unburned HCs have been proposed, further reduction of the amount unburned HCs is still raised as a great issue.
Therefore, the present inventors, through experiments and researches, conceived of performing the main fuel injection in an excess-air condition, and after the main fuel injection, the sub-injection is performed to increase the amount of combustion, and an exhaust control valve provided in an exhaust passage is substantially completely closed.
Due to the synergetic effect of the combustion attributed to the subsidiary injection and the exhaust throttling in this design, the oxidation of unburned HCs in the combustion chamber is accelerated and the temperature in the exhaust passage becomes high, so that the amount of unburned HCs is considerably reduced. Therefore, a considerable reduction in the proportion of unburned HCs to the total amount of exhaust gas components emitted into the atmosphere can be expected.
Based on verification of the above-described effect through experiments and researches, the present applicant has already applied for a patent regarding a technology for lessening unburned HCs by performing the main fuel injection in an excess-air condition, and performing, after the main fuel injection, the subsidiary fuel injection to increase the amount of combustion, and, in addition, by providing an exhaust control valve in an exhaust passage and operating the valve to a substantially completely closed state.
Whether unburned HCs have been normally lessened is determined based on detection values provided by various sensors, for example, an exhaust gas temperature sensor, a back pressure sensor, etc. It is conceivable that a failure in any one of the sensors can adversely affect the exhaust gas temperature. If such a sensor fails, the exhaust gas temperature cannot be monitored, so that the exhaust gas temperature control becomes impossible. As a result, the exhaust gas temperature does not remain in a temperature range of a target level (hereinafter, referred to as “target exhaust gas temperature”), so that production of unburned HCs may not be curbed.
The target exhaust gas temperature refers to an exhaust gas temperature which is sufficiently high to promote oxidation of unburned HCs, that is, generally-termed post-combustion, and which is not excessively high and therefore, if a catalyst is provided in an exhaust passage, will not cause heat deterioration of the catalyst.
Furthermore, due to a failure or defect in a fuel injection valve or a fuel injection valve control apparatus, as for example, a sufficient amount of fuel may not be injected, and therefore the exhaust gas temperature may not reach the target exhaust gas temperature, or the amount of fuel injected may be excessively large, and therefore the exhaust gas temperature may exceed the target exhaust gas temperature.
Still further, it is also conceivable that due to, for example, a sensor failure or the like, it is falsely determined that the exhaust gas temperature has not reached the target exhaust gas temperature although the exhaust gas temperature is actually higher than the target exhaust gas temperature. In such a case, an engine control unit (hereinafter, referred to as “ECU”) will determine that it is necessary to burn more fuel in order to bring the exhaust gas temperature to the target exhaust gas temperature. Therefore, the catalyst may deteriorate due to overheating, or the amount of HCs produced may increase more than necessary.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an internal combustion engine exhaust temperature raising apparatus and method capable of detecting an abnormality in sensors, fuel injection valves, or the like during an early period and therefore capable of preventing an increase in the amount of unburned HCs in exhaust gas and, if a catalyst is provided in the exhaust passage, preventing heat deterioration of the catalyst.
In accordance with a first aspect of the invention, an exhaust temperature raising apparatus for an internal combustion engine includes an exhaust throttle valve that is provided in an exhaust passage of the internal combustion engine and that adjusts an amount of an exhaust gas flowing in the exhaust passage based on an amount of throttling by the exhaust throttle valve, a fuel injection valve that performs a main injection that is a fuel injection for producing an engine output and a sub-injection that is a subsidiary fuel injection after performance of the main injection, directly into a cylinder, exhaust gas temperature increase means for, during an engine operation during which a need to lessen an unburned fuel component contained in the exhaust gas is high, performing and controlling exhaust throttling by the exhaust throttle valve and performing and controlling an exhaust gas temperature increase through combustion attributed to the main injection performed in an excess-a
Asanuma Takamitsu
Hirota Shinya
Ohashi Nobumoto
Toshioka Shunsuke
Denion Thomas
Kenyon & Kenyon
Nguyen Tu M.
Toyota Jidosha & Kabushiki Kaisha
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