Exhaust gas purification device

Abstract: Disclosed is an exhaust emission control device in which adopted as a filter body 7 for capturing particulates is a heat-regenerative particulate filter 10 with electric heater, the captured particulates being burned by heating of the electric heater 9 to forcedly regenerate the particulate filter 10. A control unit 37 responsible for a series of control operations with respect to the forced regeneration of the particulate filter 10 is constructed such that the forced regeneration in an engine stopping status is conduced only when the voltage of the battery 34 is higher than a stipulated value, and is temporarily interrupted when engine starting operation is conducted during the forced regeneration in the engine stopping status. An exhaust emission control device is realized which causes no battery exhaustion nor deterioration in engine startability even when the forced regeneration using the electric heater is conducted in the engine stopping status. (end of abstract)

Agent: Oblon, Spivak, Mcclelland Maier & Neustadt, P.C. - Alexandria, VA, US
Inventor: Tatsuki Igarashi
USPTO Applicaton #: #20070277515 - Class: 060303000 (USPTO)
Related Patent Categories: Power Plants, Internal Combustion Engine With Treatment Or Handling Of Exhaust Gas, By Means Producing A Chemical Reaction Of A Component Of The Exhaust Gas, Having Heater, Igniter, Or Fuel Supply For Reactor

Exhaust gas purification device description/claims

The Patent Description & Claims data below is from USPTO Patent Application 20070277515, Exhaust gas purification device.

Brief Patent Description - Full Patent Description - Patent Application Claims

TECHNICAL FIELD

[0001] The present invention relates to an exhaust emission control device which removes particulates from exhaust gas in an internal combustion engine such as a diesel engine.

BACKGROUND ART

[0002] Particulate or particulate matter from a diesel engine is mainly constituted by carbonic soot and soluble organic fraction (SOF) of high-boiling hydrocarbon and contains a trace of sulfate (misty sulfuric acid fraction). In order to suppress such kind of particulates from being discharged to atmosphere, it has been envisaged as shown in FIG. 1 that a particulate filter 4 is incorporated in an exhaust pipe 3 through which exhaust gas 2 from a diesel engine 1 flows.

[0003] As shown in particular in FIG. 2, this particulate filter 4 comprises a porous honeycomb-structured filter body 7 made of ceramics such as cordierite and having lattice-like compartmentalized passages 5; alternate ones of the passages 5 have inlets plugged with plugs 8 and the remaining passages with unplugged open inlets are plugged at their outlets with the plugs 8. Thus, only the exhaust gas 2 passing through thin porous walls 6 compartmentalizing the respective passages 5 is discharged downstream, and particulates are captured on inner surfaces of the walls 6.

[0004] The particulates in the exhaust gas 2, which are captured and accumulated on the inner surfaces of the walls 6, are burned off through spontaneous combustion when operation is shifted to an area with high exhaust temperature level. However, for example in a vehicle such as a city shuttle-bus tending to travel on congested roads, an engine operation at or above a required, predetermined temperature level do not continue for a long period of time, so that a captured particle amount may exceed a treated particulate amount, resulting in clogging of the particulate filter 4.

[0005] To overcome this, it has been under review to provide an electric heater so as to satisfactorily burn off particulates even in an engine operation area with low exhaust temperature level. When heating is positively carried out by this kind of electric heater, the particulates can be burned off satisfactorily even in an engine operation area with low exhaust temperature level.

[0006] A heat-regenerative particulate filter provided with an electric heater has been proposed for example in the following Patent Reference 1 in the name of the applicant of the present invention.

[0007] However, in such conventional proposals using an electric heater, much electricity is consumed for regeneration of the particulate filter 4 so that required is a bulk power source which cannot be covered by an existing battery for vehicles; the consumed electricity must be compensated for by the corresponding electric charge, disadvantageously resulting in lowering of mileage. There is also a fear that harmful gas such as highly concentrated CO and HC may be generated and discharged to the atmosphere since the particulates are burned off at a relatively low temperature level upon regeneration of the particulate filter 4.

[0008] Then, the inventor devised and filed a prior application (Patent Reference 2 below) for an exhaust emission control device with a heat-regenerative particulate filter which is low in electric consumption and discharges no harmful gas into atmosphere.

[0009] An underlying concept in the prior application is as shown in FIG. 3. A filter body 7 made of silicon carbide and with a same structure as that shown in the above with respect to FIG. 2 is provided at its front end with an electric heater 9 such as a sheathed heater to thereby provide a heat-regenerative particulate filter 10. Arranged frontward and backward of and in proximity to the particulate filter 10 are oxidation catalysts 11 and 12, respectively, so as to obtain heat-retention effect on the filter 10.

[0010] In such exhaust emission control device, the particulates captured by the filter body 7 can be effectively burned off through heating of the electric heater 9 even in an engine operation condition with low exhaust temperature level such as light-load operation; moreover, the heat-retention property of the front- and backward oxidation catalysts 11 and 12 causes the filter body 7 to be promptly elevated in temperature into a situation for easy burn-off of the particulates. As a result, the burn-off of the particulates can be completed in a shorter energization time period than usual, thereby attaining substantial reduction in electric consumption.

[0011] Harmful gas such as highly concentrated CO and HC generated from burning-off of the particulates through heating by the electric heater 9 at a relatively low temperature level can be oxidized into and discharged as harmless CO.sub.2 and H.sub.2O through its passage through the rearward oxidation catalyst 12, whereby the harmful gas can be preliminarily prevented from remaining in the exhaust gas 2 finally discharged to the atmosphere.

[0012] Passage of the exhaust gas 2 through the frontward oxidation catalyst 11 can convent NO, which occupies majority of NO.sub.x in the exhaust gas 2, into highly reactive NO.sub.2. As a result, the oxidation reaction of the particulates can be substantially accelerated in the operational condition with relatively high exhaust temperature level, thereby facilitating spontaneous combustion of the particulates without heating by the electric heater 9, resulting in good burning-off. [0013] [Reference 1] JP 62-255512A [0014] [Reference 2] JP 2005-090450A

SUMMARY OF THE INVENTION

[0014] Problems to be Solved by the Invention

[0015] Even if the heat-regenerative exhaust emission control device using the electric heater 9 may be put to practical use through the means illustrated above, it still an important issue that the forced regeneration of the particulate filter 10 can be properly conducted or not irrespective of the fact that engine is in motion or not especially in application to a vehicle having operation style with frequent engine stops such as a commercial vehicle used for parcel-delivery service or service of delivering goods to convenience stores. The forced regeneration using the electric heater 9 during the engine stopping status will burden the battery extremely greatly and may disadvantageously cause battery exhaustion or failure of engine starting during forced regeneration in the engine stopping status.

[0016] The invention was made in view of the above and has its object to provide an exhaust emission control device which causes no battery exhaustion nor deterioration in engine startability even if the forced regeneration using the electric heater is conducted during engine stopping status.

Means or Measures for Solving the Problems

[0017] The invention is directed to an exhaust emission control device wherein employed is a heat-regenerative particulate filter comprising a filter body for capturing particulates and an electric heater, the captured particulates being burned by heating through the electric heater for forced regeneration of the particulate filter, characterized in that a control unit responsible for a series of control operations for forced regeneration of the particulate filter is constructed such that the forced regeneration in an engine stopping status is conducted only when voltage of a battery is higher than a stipulated value, and is temporarily interrupted when the engine starting operation is conducted in the engine stopping status.

[0018] Thus, when the battery voltage is lower than the stipulated value, the forced regeneration in the engine stopping status is not conduced nor continued by the control unit. As a result, there is no fear that battery exhaustion is caused due to electricity consumption by the electric heater in the engine stopping status.

[0019] When the engine starting operation is conducted during the forced regeneration in the engine stopping status, the forced regeneration is temporarily interrupted by the control unit. As a result, the forced regeneration and the engine starting operation which cause high electric burden are prevented from being conducted simultaneously in the engine stopping status, the engine starting operation being prioritized to cause the starting of the engine with no problem.

EFFECTS OF THE INVENTION

[0020] According to an exhaust emission control device of the invention mentioned above, the following excellent effect will be obtained. Forced regeneration of an particulate filter in engine stopping status is not conducted when voltage of a battery is lower than a stipulated value, and the forced regeneration is temporarily interrupted when an engine starting operation is conducted during the forced regeneration in the engine stopping status, so that battery exhaustion and deterioration in engine startability can be preliminarily prevented even when the forced regeneration of the particulate filter is conducted using the electric heater in the engine stopping status.

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Diesel gas turbine system and related methods
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Structure for filtering an internal engine exhaust gases and associated exhaust line
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