Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Patent
1988-11-29
1990-12-04
Hart, Douglas
Power plants
Internal combustion engine with treatment or handling of...
By means producing a chemical reaction of a component of the...
60288, F01N 302
Patent
active
049744143
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to an exhaust particulate purging apparatus, which ignites particulates contained in exhaust gas of a Diesel engine by the use of an electrical heater to burn off the particulates.
BACKGROUND OF THE INVENTION
Exhaust gas discharged from a Diesel engine is passed through a trap disposed in an exhaust passage of the engine. Soot and other particulates contained in the exhaust gas are collected by a collecting material in the form of a porous ceramic substance packed in the trap. The particulates accumulate in the trap resulting in an increased impedance in the trap, and a drop in the engine output. Therefore, at the time when the particulates have accumulated in a certain quantity, it is necessary to burn off the particulates thereby regenerating the trap. For the purpose of regeneration of the trap, an electric heater is located adjacent to the upstream end of the collecting material. The heater raises the temperature of the exhaust gas to a temperature sufficient to, so ignite the particulates, which are then burnt off by the high temperature exhaust gas.
In the prior art manner of trap regeneration described above, the electric heater requires an extremely large capacity if the temperature of the entire volume of the exhaust gas is to be raised. Therefore, it has been a common practice to bypass part of the exhaust gas during the process of regeneration so as to reduce the quantity of the exhaust gas flowing into the trap.
However, when the temperature of the exhaust gas flowing into the trap is low ( for example, about 150.degree. C.), ignition and burning of the particulates is not immediately started due to the relatively large thermal capacity of the trap. The time for supply of current to the electric heater is thus correspondingly extended, with the result that the battery may be completely exhausted. Further, because the trap itself is exposed to exhaust gas whose temperature has been raised by the electric heater, a large thermal stress occurs in the trap leading to damage.
As described above, various drawbacks are involved, and improvements for obviating those drawbacks have been demanded.
SUMMARY OF THE INVENTION
The present invention provides an apparatus for purging particulates contained in exhaust gas of a Diesel engine, including a trap disposed in an exhaust passage of the Diesel engine and equipped with an electric heater, a bypass passage branched from the exhaust passage to bypass the trap, and a control valve disposed in the bypass passage to control the quantity of exhaust gas flowing into the bypass passage.
Particulates in the trap are ignited and burnt off by exhaust gas whose temperature has been raised by the electric heater.
The apparatus further comprises means for detecting the quantity of particulates accumulated in the trap, a temperature sensor disposed on the upstream side of the trap for measuring the temperature of the exhaust gas flowing into the trap, and, a control device for controlling the current supply to the electric heater and to open or close the bypass control valve on the basis of output signals from the detecting means and the temperature sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic view showing the general structure of a embodiment of the present invention;
FIG. 2 is a flow chart showing the sequence of control after regeneration of the particulate collecting trap is started; and,
FIG. 3 is a flow chart showing the sequence of control during the regeneration and until the regeneration of the trap is completed.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in FIG. 1, a trap 2 for collecting particulates is provided in an exhaust passage of a Diesel engine (not shown). A bypass passage 3 bypassing the trap 2 is provided. A throttle valve 4 is disposed in the bypass passage 3. This throttle valve 4 is opened and closed by an electromagnetic valve 5 and a air cylinder 6. Particulate collecting material 7 is contained within the trap 2. An electric heater 8 is disposed on the ups
REFERENCES:
patent: 4538412 (1985-09-01), Oishi
patent: 4558565 (1985-12-01), Kojima
patent: 4562695 (1986-01-01), Rao
Kono Yoichiro
Kumagai Yasuaki
Ogita Hiroshi
Takeda Nobuaki
Hart Douglas
Mitsubishi Jidosha Kogyo Kabushiki Kaisha
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