Exhaust gas cleaning apparatus for lean burn internal combustion engine
First Claim
1. An exhaust gas cleaning apparatus for cleaning exhaust gas from an internal combustion engine, the apparatus comprising:
- a Lean NOx Trap (LNT) provided in an exhaust gas passage of the engine through which the exhaust gas flows, the LNT being configured to absorb NOx contained in the exhaust gas when the exhaust gas is lean and reduce the absorbed NOx when the exhaust gas turns to rich;
a fuel adding device located upstream of the LNT to add fuel to the exhaust gas for making the exhaust gas rich;
an exhaust gas returning passage that branches off from the exhaust gas passage at a position downstream of a turbocharger of the engine to return part of the exhaust gas to an intake air passage of the engine; and
a controller configured to determine an operating condition of the engine and control the exhaust gas cleaning apparatus to selectively operate in one of first and second operation modes according to the determined operating condition of the engine, in the first operation mode the fuel adding device adding the fuel to the exhaust gas with the exhaust gas returning passage closed, in the second operation mode the part of the exhaust gas being returned to the intake air passage through the exhaust gas returning passage without the fuel being added by the fuel adding device to the exhaust gas, whereinthe controller is configured to determine whether the engine operates in a first operation region, in which both the rotational speed and load of the engine is low, or in a second operation region in which either or both of the rotational speed and load of the engine are high, andthe controller is configured to control the exhaust gas cleaning apparatus to operate in the first operation mode when the engine operates in the first operation region and in the second operation mode when the engine operates in the second operation region.
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Accused Products
Abstract
An exhaust gas cleaning apparatus includes a LNT, a fuel adding device, an exhaust gas returning passage, and a controller. The LNT is provided in an exhaust gas passage of an engine. The fuel adding device is located upstream of the LNT to add fuel to exhaust gas flowing through the exhaust pipe. The exhaust gas returning passage branches off from the exhaust gas passage at a position downstream of the fuel adding device. The controller controls the apparatus to selectively operate in one of first and second modes according to the operating condition of the engine. In the first mode, the fuel adding device adds the fuel to the exhaust gas with the exhaust gas returning passage closed; in the second mode, the exhaust gas is partially returned to an intake air passage through the exhaust gas returning passage without the fuel being added by the fuel adding device.
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Citations
6 Claims
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1. An exhaust gas cleaning apparatus for cleaning exhaust gas from an internal combustion engine, the apparatus comprising:
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a Lean NOx Trap (LNT) provided in an exhaust gas passage of the engine through which the exhaust gas flows, the LNT being configured to absorb NOx contained in the exhaust gas when the exhaust gas is lean and reduce the absorbed NOx when the exhaust gas turns to rich; a fuel adding device located upstream of the LNT to add fuel to the exhaust gas for making the exhaust gas rich; an exhaust gas returning passage that branches off from the exhaust gas passage at a position downstream of a turbocharger of the engine to return part of the exhaust gas to an intake air passage of the engine; and a controller configured to determine an operating condition of the engine and control the exhaust gas cleaning apparatus to selectively operate in one of first and second operation modes according to the determined operating condition of the engine, in the first operation mode the fuel adding device adding the fuel to the exhaust gas with the exhaust gas returning passage closed, in the second operation mode the part of the exhaust gas being returned to the intake air passage through the exhaust gas returning passage without the fuel being added by the fuel adding device to the exhaust gas, wherein the controller is configured to determine whether the engine operates in a first operation region, in which both the rotational speed and load of the engine is low, or in a second operation region in which either or both of the rotational speed and load of the engine are high, and the controller is configured to control the exhaust gas cleaning apparatus to operate in the first operation mode when the engine operates in the first operation region and in the second operation mode when the engine operates in the second operation region. - View Dependent Claims (2)
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3. An exhaust gas cleaning apparatus for cleaning exhaust gas from an internal combustion engine, the apparatus comprising:
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a Lean NOx Trap (LNT) provided in an exhaust gas passage of the engine through which the exhaust gas flows, the LNT being configured to absorb NOx contained in the exhaust gas when the exhaust gas is lean and reduce the absorbed NOx when the exhaust gas turns to rich; a fuel adding device located upstream of the LNT to add fuel to the exhaust gas for making the exhaust gas rich; an exhaust gas returning passage that branches off from the exhaust gas passage at a position downstream of the fuel adding device to return part of the exhaust gas to an intake air passage of the engine; and a controller is configured to determine an operating condition of the engine and controls the exhaust gas cleaning apparatus to selectively operate in one of first and second operation modes according to the determined operating condition of the engine, in the first operation mode the fuel adding device adding the fuel to the exhaust gas with the exhaust gas returning passage closed, in the second operation mode the part of the exhaust gas being returned to the intake air passage through the exhaust gas returning passage without the fuel being added by the fuel adding device to the exhaust gas, wherein the controller is configured to determine whether the engine operates in a first operation region, in which both the rotational speed and load of the engine is low, or in a second operation region in which either or both of the rotational speed and load of the engine are high, the controller is configured to control the exhaust gas cleaning apparatus to operate in the first operation mode when the engine operates in the first operation region and in the second operation mode when the engine operates in the second operation region, the exhaust gas cleaning apparatus further comprises a detector configured to detect the deterioration degree of a NOx catalyst of the LNT, and as the deterioration degree of the NOx catalyst detected by the detector increases, the controller reduces the first operation region of the engine while accordingly expanding the second operation region of the engine. - View Dependent Claims (4, 5, 6)
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Specification