EP0503882A1
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EP
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Exhaust gas purification system for an internal combustion engine
Assignee: Toyota Motor Corp
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Filing: 1992-03-10
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Granted: —
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Expires: 2012-03-10
Abstract
Abstract An exhaust gas purification system includes a lean burn engine (2) having an exhaust conduit (4), a lean NOx catalyst (6) installed in the exhaust conduit (4), an HC amount increasing device (26, 32) capable of increasing an amount of HC included in exhaust gas flowing to the lean NOx catalyst (6), a catalyst temperature determining device (18, 102) for determining a catalyst temperature and determining whether the catalyst temperature is below a predetermined value, and an HC amount increasing device operating device (104-126) capable of intermittently operating the HC amount increasing device (26, 32) when the catalyst temperature is below the predetermined value. The HC increased at low catalyst temperatures is partially oxidized to generate a large amount of radicals which are held within small cells of the lean NOx catalyst (6). When the catalyst temperature rises, the radicals held in the cells are effectively used to reduce NOx until the radicals are compensated.
Inventors
- 👤 Shinichi C/O Toyota Jidosha K.K. Takeshima
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 11:21
CPC Classifications
F; F01; F01N; F01N3/00; F01N3/08; F01N3/10; F01N3/24; F01N3/36; B; B01; B01D; B01D53/00; B01D53/34; B01D53/92; B01D53/94; B01D53/9445; B01D53/9454; B01D53/9495; F01N3/18; F01N3/20; F01N3/2006; F01N3/2033; F01N3/206; F01N3/208; F01N2610/00; F01N2610/03; F01N2900/00; F01N2900/04; F01N2900/0422; F02; F02M; F02M26/00; F02M26/13; F02M26/14; F02M26/15; Y; Y02; Y02T; Y02T10/00; Y02T10/10; Y02T10/12
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
145 words
An exhaust gas purification system for an internal combustion engine comprising: an internal combustion engine (2) capable of fuel combustion at lean air-fuel ratios and having an exhaust conduit (4); an NOx catalyst (6) installed in the exhaust conduit (4) of the engine (2), the NOx catalyst (6) being constructed of zeolite and carrying a metal selected from the group consisting of transition metals and noble metals; HC amount increasing means capable of increasing an amount of HC included in exhaust gas flowing to the NOx catalyst (6); catalyst temperature determining means for determining a temperature representing an NOx catalyst temperature and determining whether the NOx catalyst temperature is below a predetermined temperature; and HC amount increasing means operating means for operating the HC amount increasing means intermittently when the catalyst temperature determining means determines that the NOx catalyst temperature is below said predetermined temperature.
Claim 2
Dependent Claim
45 words
An exhaust gas purification system for an internal combustion engine according to claim 1, wherein the HC amount increasing means includes an HC source (26) and an HC control valve (32) for switching supply of HC from the HC source (26) between ON and OFF.
Claim 3
Dependent Claim
64 words
An exhaust gas purification system for an internal combustion engine according to claim 1, wherein the HC amount increasing means includes an ignition plug (8) of the engine; ignition timing control means; and means for advancing a timing of the ignition timing means in response to a determination by the catalyst temperature determining means that the NOx catalyst temperature is below said predetermined value.
Claim 4
Dependent Claim
69 words
An exhaust gas purification system for an internal combustion engine according to claim 1, wherein the HC amount increasing means includes a fuel injection valve (12) for the engine; fuel injection timing control means; and means for offsetting a fuel injection timing from an optimum fuel injection timing in response to a determination by the catalyst temperature determining means that the NOx catalyst temperature is below said predetermined value.
Claim 5
Dependent Claim
74 words
An exhaust gas purification system for an internal combustion engine according to claim 1, wherein the HC amount increasing means includes an EGR valve (28) of an EGR system for the engine; EGR valve operation control means; and means for actuating the EGR valve operation control means to open the EGR valve (28) in response to a determination by the catalyst temperature determining means that the NOx catalyst temperature is below said predetermined value.
Claim 6
Dependent Claim
20 words
An exhaust gas purification system for an internal combustion engine according to claim 1, wherein the predetermined temperature is 400°C.
Claim 7
Dependent Claim
28 words
An exhaust gas purification system for an internal combustion engine according to claim 1, wherein the catalyst temperature determining means includes an exhaust gas temperature detecting sensor (18).
Claim 8
Dependent Claim
62 words
An exhaust gas purification system for an internal combustion engine according to claim 1, wherein the catalyst temperature determining means includes an intake air amount detecting sensor (16), an engine rotational speed sensor (22), and a predetermined map for determining an NOx catalyst temperature based on outputs from the intake air amount detecting sensor (16) and the engine rotational speed sensor (22).
Claim 9
Dependent Claim
67 words
An exhaust gas purification system for an internal combustion engine according to claim 1, wherein the catalyst temperature determining sensor includes means for calculating a fuel injection timing for the engine (2) and means for determing that the catalyst temperature is below said predetermined value upon a signal of "zero" for a fuel injection period of time calculated by said means for calculating the fuel injection timing.
Claim 10
Dependent Claim
59 words
An exhaust gas purification system for an internal combustion engine according to claim 1, wherein the catalyst temperature determining means includes means for determining whether or not the engine (2) is idling, based on an opening degree of a throttle valve (30) and determining that the catalyst temperature is below said predetermined value when the engine (2) is idling.
Claim 11
Dependent Claim
82 words
An exhaust gas purification system for an internal combustion engine according to claim 1, wherein the HC amount increasing means operating means (104-126) includes a first means (104-114) for holding the HC amount increasing means in an ON state for a first predetermined time period and a second means (116-126) for holding the HC amount increasing means in an OFF state for a second predetermined time period, the first means and the second means being set to be actuated one after another.
Claim 12
Dependent Claim
34 words
An exhaust gas purification system for an internal combustion engine according to claim 11, wherein the first predetermined time period (TON) is three minutes and the second predetermined time period (TOFF) is one minute.
References Cited (Backward Citations)
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