US6345496B1 — Method and device for purifying exhaust gas of an…

Claim 1

Independent Claim 166 words

The method for purifying an exhaust gas of an engine, the method comprising the steps of: alternately and repeatedly controlling an exhaust gas air-fuel ratio between a lean exhaust gas air-fuel ratio and a rich exhaust gas air-fuel ratio; and introducing the exhaust gas to an NH 3 synthesizing catalyst, the NH 3 synthesizing catalyst being arranged in series with a NO x occluding and reducing (NO x -OR) catalyst in a common exhaust passage, the NH 3 synthesizing catalyst synthesizing NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is rich, and synthesizing almost no NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is lean and wherein, when the exhaust gas air-fuel ratio is lean, the NO x -OR catalyst occludes NO x therein, and when the exhaust gas air-fuel ratio is rich, the NOR-OR catalyst releases the occluded NO x therefrom and reduces the NO x .

Claim 2

Independent Claim 166 words

The method for purifying an exhaust gas of an engine, the method comprising the steps of: alternately and repeatedly controlling an exhaust gas air-fuel ratio between a lean exhaust gas air-fuel ratio and a rich exhaust gas air-fuel ratio; and introducing the exhaust gas to an NH 3 synthesizing catalyst, the NH 3 synthesizing catalyst being arranged in series with a NO x occluding and reducing (NO x -OR) catalyst in a common exhaust passage, the NH 3 synthesizing catalyst synthesizing NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is rich, and synthesizing almost no NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is lean and wherein, when the exhaust gas air-fuel ratio is lean, the NO x -OR catalyst occludes NO x therein, and when the exhaust gas air-fuel ratio is rich, the NOR-OR catalyst releases the occluded NO x therefrom and reduces the NO x .

Claim 3

Dependent Claim 47 words

The method according to claim 1 , further comprising the step of controlling an engine air-fuel ratio between a lean engine air-fuel ratio to thereby form the lean exhaust gas air-fuel ratio and a rich engine air-fuel ratio to thereby form the rich exhaust gas air-fuel ratio.

Claim 4

Dependent Claim 49 words

The method according to claim 2 , wherein the engine air-fuel ratio is made lean for a lean period, and the engine air-fuel ratio is made rich for a rich period, and wherein the lean and the rich periods are set in accordance with the engine operating condition, respectively.

Claim 5

Dependent Claim 84 words

The method according to claim 3 , wherein the engine is provided with a plurality of cylinders or cylinder groups of which the exhaust stroke periods are different to each other, and wherein the lean period is set as the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made lean, and the rich period is set as the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made rich.

Claim 6

Dependent Claim 85 words

The method according to claim 4 , wherein the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made lean and the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made rich is set to vary the cylinders or cylinder groups of which the engine air-fuel ratio is to be made rich in every cycle, the cycle being formed by one lean period and one rich period which are successive.

Claim 7

Dependent Claim 78 words

The method according to claim 4 , wherein the lean and the rich period are controlled in accordance with a number ratio which is a ratio of the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made lean to the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made rich, the number ratio being set in accordance with the engine operating condition.

Claim 8

Dependent Claim 43 words

A method according to claim 2 , the engine being an internal combustion engine of spark ignition type, and the method further comprising the step of controlling the ignition timing of the engine in accordance with the engine air-fuel ratio of the engine.

Claim 9

Dependent Claim 90 words

The method according to claim 1 , wherein a making-rich device, different from the engine, is arranged in an exhaust passage of the engine upstream of the NH 3 synthesizing catalyst for making the exhaust gas air-fuel ratio rich, and wherein the method further comprises the steps of keeping an engine air-fuel ratio lean, and stopping a making-rich operation of the making-rich device to thereby form the lean exhaust gas air-fuel ratio, and performing the making-rich operation of the making-rich device to thereby form the rich exhaust gas air-fuel ratio.

Claim 10

Dependent Claim 81 words

The method according to claim 8 , wherein the making-rich device is provided with: a combustor of which an air-fuel ratio is controllable; and an introducing passage for introducing the exhaust gas of the combustor into the exhaust passage upstream of the NH 3 synthesizing catalyst, and wherein the making-rich operation of the making-rich device is performed by making an air-fuel ratio of the combustor rich and adding the exhaust gas of the combustor to the exhaust gas of the engine.

Claim 11

Dependent Claim 26 words

The method according to claim 9 , wherein the combustor is an auxiliary internal combustion engine having a crank shaft different from that of the engine.

Claim 12

Dependent Claim 13 words

The method according to claim 9 , wherein the combustor is a burner.

Claim 13

Dependent Claim 56 words

The method according to claim 8 , wherein the making-rich device is provided with a reducing agent injector for feeding a reducing agent into the exhaust passage upstream of the NH 3 synthesizing catalyst, the making-rich operation of the reducing agent injector being performed by adding the reducing agent to the exhaust gas of the engine.

Claim 14

Dependent Claim 50 words

The method according to claim 1 , the step of estimating an amount of NO x occluded in the NO x -OR catalyst, and wherein the exhaust gas air-fuel ratio is changed from lean to rich or from rich to lean in accordance with the estimated occluded NO x amount.

Claim 15

Dependent Claim 78 words

The method according to claim 13 , wherein the occluded NO x amount is estimated on the basis of a NO x amount flowing into the NO x -OR catalyst when the exhaust gas air-fuel ratio of the exhaust gas flowing into the NO x -OR catalyst is lean, and on the basis of the released NO x amount when the exhaust gas air-fuel ratio of the exhaust gas flowing into the NO x -OR catalyst is rich.

Claim 16

Dependent Claim 29 words

The method according to claim 1 , wherein the exhaust gas air-fuel ratio is changed from lean to rich or from rich to lean gradually with a changing rate.

Claim 17

Dependent Claim 39 words

The method according to claim 15 , wherein the changing rate when the exhaust gas air-fuel ratio is changed from lean to rich is larger than that when the exhaust gas air-fuel ratio is changed from rich to lean.

Claim 18

Dependent Claim 20 words

The method according to claim 15 , wherein the changing rate is set in accordance with the engine operating condition.

Claim 19

Dependent Claim 19 words

The method according to claim 17 , wherein the changing rate becomes smaller as the engine load becomes higher.

Claim 20

Dependent Claim 22 words

The method according to claim 1 , wherein the exhaust gas air-fuel ratio is set in accordance with the engine operating condition.

Claim 21

Dependent Claim 34 words

The method according to claim 1 , wherein a period during which the exhaust gas air-fuel ratio is lean is longer than that during which the exhaust gas air-fuel ratio is rich is formed.

Claim 22

Dependent Claim 50 words

The method according to claim 1 , wherein the exhaust gas air-fuel ratio is made equal to a target air-fuel ratio on the basis of output signals of an air-fuel ratio sensor arranged in an exhaust passage of the engine adjacent to an inlet of the NH 3 synthesizing catalyst.

Claim 23

Dependent Claim 42 words

The method according to claim 1 , wherein the exhaust gas purifying catalyst is comprised of at least the NO x -OR catalyst, and wherein the NH 3 synthesizing catalyst and the NO x -OR catalyst are carried on a common substrate.

Claim 24

Dependent Claim 114 words

The method according to claim 1 further comprising the step of introducing the exhaust gas to both of the NO x -OR catalyst and an NH 3 adsorbing and oxidizing (NH 3 -AO) catalyst, after introducing the exhaust gas to the NH 3 synthesizing catalyst, the NH 3 -AO catalyst adsorbing NH 3 in the exhaust gas therein, and causing a reaction of NH 3 and NO x in the NH 3 -AO catalyst to purify the NH 3 and the NO x and to decrease an amount of NH 3 adsorbed in the NH 3 -AO catalyst when the exhaust gas includes NO x therein and the exhaust gas air-fuel ratio is lean.

Claim 25

Dependent Claim 26 words

The method according to claim 23 , wherein the NH 3 -AO catalyst is arranged in the exhaust passage downstream of the NO x -OR catalyst.

Claim 26

Dependent Claim 29 words

The method according to claim 24 , the engine further having a muffler arranged in the exhaust passage, wherein the NH 3 -AO catalyst is housed in the muffler.

Claim 27

Dependent Claim 51 words

The method according to claim 23 , further comprising the step of estimating an amount of NH 3 adsorbed in the NH 3 -AO catalyst, wherein the exhaust gas air-fuel ratio is changed from lean to rich or from rich to lean in accordance with the estimated adsorbed NH 3 amount.

Claim 28

Dependent Claim 78 words

The method according to claim 26 , wherein the adsorbed NH 3 amount is estimated on the basis of an NH 3 amount flowing into the NH 3 -AO catalyst when the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH 3 synthesizing catalyst is rich, and on the basis of the decreased NH 3 amount when the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH 3 synthesizing catalyst is lean.

Claim 29

Dependent Claim 27 words

The method according to claim 23 , wherein the NH 3 -AO catalyst comprises a solid acid carrying one of a transition metal and a precious metal.

Claim 30

Dependent Claim 137 words

The method according to claim 1 , further comprising the step of introducing the exhaust gas to both of the NO x -OR catalyst and an NH 3 adsorbing and oxidizing (NH 3 -AO) catalyst, after introducing the exhaust gas to the NH 3 synthesizing catalyst, the NH 3 -AO catalyst adsorbing NH 3 in the exhaust gas therein and causing a reaction of NH 3 and NO x in the NH 3 -AO catalyst to purify the NH 3 and the NO x and to decrease an amount of NH 3 adsorbed in the NH 3 -AO catalyst when the exhaust gas includes NO x therein and the exhaust gas air-fuel ratio is lean, and wherein the NH 3 -AO catalyst and the NO x -OR catalyst are laminated to each other on a common substrate.

Claim 31

Dependent Claim 23 words

The method according to claim 1 , wherein the NH 3 synthesizing catalyst is a three-way catalyst including at least one precious metal.

Claim 32

Dependent Claim 39 words

The method according to claim 1 , wherein the NO x -OR catalyst includes: at least one substance selected from alkali metals, alkali earth metals, rare earth metals such as lanthanum and yttrium, and transition metals and precious metals.

Claim 33

Dependent Claim 41 words

The method according to claim 1 , further comprising the step of introducing the exhaust gas to an NH 3 purifying catalyst for purifying NH 3 in the exhaust gas, after introducing the exhaust gas to the NO x -OR catalyst.

Claim 34

Dependent Claim 25 words

The method according to claim 32 , wherein the NH 3 purifying catalyst includes at least one substance selected from precious metals, and transition metals.

Claim 35

Dependent Claim 45 words

The method according to claim 32 , the NH 3 purifying catalyst purifying NH 3 under the oxidizing atmosphere, wherein the method further the step of comprises keeping the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH 3 purifying catalyst lean.

Claim 36

Dependent Claim 93 words

The method according to claim 1 , wherein the NH 3 synthesizing catalyst is a NO x occluding and NH 3 synthesizing (NO x -NH 3 ) catalyst, the NO x -NH 3 catalyst occluding NO x in the exhaust gas therein when the exhaust gas air-fuel ratio is lean, the NO x -NH 3 catalyst releasing occluded NO x therefrom, reducing NO x in the NO x -NH 3 catalyst, and synthesizing NH 3 from NO x in the NO x -NH 3 catalyst when the exhaust gas air-fuel ratio is rich.

Claim 37

Dependent Claim 62 words

The method according to claim 35 , further comprising the step of estimating an amount of NO x occluded in the NO x -NH 3 catalyst, and wherein the exhaust gas air-fuel ratio of the exhaust gas flowing into the NO x -NH 3 catalyst is made lean and rich alternately and repeatedly in accordance with the estimated occluded NO x amount.

Claim 38

Dependent Claim 61 words

The method according to claim 35 , further comprising the step of estimating an amount of NO x occluded in the NO x -OR catalyst, and wherein the exhaust gas air-fuel ratio of the exhaust gas flowing into the NO x -NH 3 catalyst is made lean and rich alternately and repeatedly in accordance with the estimated occluded NO x amount.

Claim 39

Dependent Claim 35 words

The method according to claim 35 , wherein the NO x -NH 3 catalyst includes: at least one substance selected from alkali metals, alkali earth metals, rare earth metals, and transition metals; and precious metals.

Claim 40

Dependent Claim 34 words

The method according to claim 35 , wherein the NO x -OR catalyst includes: at least one substance selected from alkali metals, alkali earth metals, rare earth metals, and transition metals; and precious metals.

Claim 41

Independent Claim 186 words

The device for purifying an exhaust gas of an engine having an exhaust passage, comprising: exhaust gas air-fuel ratio controlling means arranged in one of the engine and the exhaust passage for alternately and repeatedly controlling an exhaust gas air-fuel ratio between a lean exhaust gas air-fuel ratio and a rich exhaust gas air-fuel ratio; an NH 3 synthesizing catalyst arranged in the exhaust passage downstream of the exhaust gas air-fuel ratio controlling means, the NH 3 synthesizing catalyst synthesizing NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is rich, and synthesizing almost no NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is lean; and a NO x occluding and reducing (NO x -OR) catalyst arranged in the exhaust passage downstream of the NH 3 synthesizing catalyst, the NO x -OR catalyst occluding NO x in the exhaust gas therein when the exhaust gas air-fuel ratio is lean, and releasing the occluded NO x therefrom and reducing the NO x when the exhaust gas air-fuel ratio is rich.

Claim 42

Independent Claim 186 words

The device for purifying an exhaust gas of an engine having an exhaust passage, comprising: exhaust gas air-fuel ratio controlling means arranged in one of the engine and the exhaust passage for alternately and repeatedly controlling an exhaust gas air-fuel ratio between a lean exhaust gas air-fuel ratio and a rich exhaust gas air-fuel ratio; an NH 3 synthesizing catalyst arranged in the exhaust passage downstream of the exhaust gas air-fuel ratio controlling means, the NH 3 synthesizing catalyst synthesizing NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is rich, and synthesizing almost no NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is lean; and a NO x occluding and reducing (NO x -OR) catalyst arranged in the exhaust passage downstream of the NH 3 synthesizing catalyst, the NO x -OR catalyst occluding NO x in the exhaust gas therein when the exhaust gas air-fuel ratio is lean, and releasing the occluded NO x therefrom and reducing the NO x when the exhaust gas air-fuel ratio is rich.

Claim 43

Dependent Claim 58 words

The device according to claim 40 , wherein the exhaust gas air-fuel ratio controlling means comprises an engine air-fuel ratio control means for controlling an engine air-fuel ratio between a lean engine air-fuel ratio to thereby form the lean exhaust gas air-fuel ratio and a rich engine air-fuel ratio to thereby form the rich exhaust gas air-fuel ratio.

Claim 44

Dependent Claim 53 words

The device according to claim 41 , wherein the engine air-fuel ratio control means makes the engine air-fuel ratio lean for a lean period, and makes the engine air-fuel ratio rich for a rich period, and wherein the lean and the rich periods are set in accordance with the engine operating condition, respectively.

Claim 45

Dependent Claim 84 words

The device according to claim 42 , wherein the engine is provided with a plurality of cylinders or cylinder groups of which the exhaust stroke periods are different to each other, and wherein the lean period is set as the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made lean, and the rich period is set as the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made rich.

Claim 46

Dependent Claim 85 words

The device according to claim 43 , wherein the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made lean and the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made rich are set to vary the cylinders or cylinder groups of which the engine air-fuel ratio is to be made rich in every cycle, the cycle being formed by one lean period and one rich period which are successive.

Claim 47

Dependent Claim 78 words

The device according to claim 43 , wherein the lean and the rich period are controlled in accordance with a number ratio which is a ratio of the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made lean to the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made rich, the number ratio being set in accordance with the engine operating condition.

Claim 48

Dependent Claim 42 words

The device according to claim 41 , the engine being an internal combustion engine of spark ignition type, and the device further comprising ignition timing control means for controlling the ignition timing of the engine in accordance with the engine air-fuel ratio.

Claim 49

Dependent Claim 86 words

The device according to claim 40 , wherein the exhaust gas air-fuel ratio controlling means comprises making-rich means, different from the engine, arranged in the exhaust passage upstream of the NH 3 synthesizing catalyst for making the exhaust gas air-fuel ratio rich, and keeping means for keeping the engine air-fuel ratio lean, and wherein the making-rich means stops a making-rich operation thereof to thereby form the lean exhaust gas air-fuel ratio, and performs the making-rich operation thereof to thereby form the rich exhaust gas air-fuel ratio.

Claim 50

Dependent Claim 78 words

The device according to claim 47 , wherein the making-rich means comprises: a combustor of which an air-fuel ratio is controllable; and an introducing passage for introducing the exhaust gas of the combustor into the exhaust passage upstream of the NH 3 synthesizing catalyst, and wherein the making-rich means performs the making-rich operation thereof by making an air-fuel ratio of the combustor rich and adding the exhaust gas of the combustor to the exhaust gas of the engine.

Claim 51

Dependent Claim 26 words

The device according to claim 48 , wherein the combustor is an auxiliary internal combustion engine having a crank shaft different from that of the engine.

Claim 52

Dependent Claim 12 words

The device according to claim 48 wherein the combustor is a burner.

Claim 53

Dependent Claim 53 words

The device according to claim 47 , wherein the making-rich means comprises a reducing agent injector for feeding a reducing agent into the exhaust passage upstream of the NH 3 synthesizing catalyst, the reducing agent injector performing the making-rich operation thereof by adding the reducing agent to the exhaust gas of the engine.

Claim 54

Dependent Claim 66 words

The device according to claim 40 , wherein the device further comprises occluded NO x amount estimating means for estimating an amount of NO x occluded in the NO x -OR catalyst, and wherein the exhaust gas air fuel ratio controlling means changes the exhaust gas air-fuel ratio from lean to rich or from rich to lean in accordance with the estimated occluded NO x amount.

Claim 55

Dependent Claim 84 words

The device according to claim 52 , wherein the occluded NO x amount estimating means estimates the occluded NO x amount on the basis of a NO x amount flowing into the NO x -OR catalyst when the exhaust gas air-fuel ratio of the exhaust gas flowing into the NO x -OR catalyst is lean, and on the basis of the released NO x amount when the exhaust gas air-fuel ratio of the exhaust gas flowing into the NO x -OR catalyst is rich.

Claim 56

Dependent Claim 36 words

The device according to claim 40 , wherein the exhaust gas air fuel ratio controlling means changes the exhaust gas air-fuel ratio from lean to rich or from rich to lean gradually with a changing rate.

Claim 57

Dependent Claim 51 words

The device according to claim 54 , wherein the changing rate when the exhaust gas air-fuel ratio controlling means changes the exhaust gas air-fuel ratio from lean to rich is larger than that when the exhaust gas air-fuel ratio controlling means changes the exhaust gas air-fuel ratio from rich to lean.

Claim 58

Dependent Claim 20 words

The device according to claim 54 , wherein the changing rate is set in accordance with the engine operating condition.

Claim 59

Dependent Claim 19 words

The device according to claim 56 , wherein the changing rate becomes smaller as the engine load becomes higher.

Claim 60

Dependent Claim 22 words

The device according to claim 40 , wherein the exhaust gas air-fuel ratio is set in accordance with the engine operating condition.

Claim 61

Dependent Claim 46 words

The device according to claim 40 , wherein a period during which the exhaust gas air-fuel ratio controlling means forms the lean exhaust gas air-fuel ratio is longer than that during which the exhaust gas air-fuel ratio controlling means forms the rich exhaust gas air-fuel ratio.

Claim 62

Dependent Claim 65 words

The device according to claim 40 , further comprising an air-fuel ratio sensor arranged in the exhaust passage between the exhaust gas air-fuel ratio controlling means and the NH 3 synthesizing catalyst, and wherein the exhaust gas air-fuel ratio controlling means makes the exhaust gas air-fuel ratio equal to a target air-fuel ratio on the basis of the output signals of the air-fuel ratio sensor.

Claim 63

Dependent Claim 25 words

The device according to claim 40 , wherein the NH 3 synthesizing catalyst and the NO x -OR catalyst are carried on a common substrate.

Claim 64

Dependent Claim 100 words

The device according to claim 40 , further comprising an NH 3 adsorbing and oxidizing (NH 3 -AO) catalyst arranged in the exhaust passage downstream of the NH 3 synthesizing catalyst, the NH 3 -AO catalyst adsorbing NH 3 in the exhaust gas therein, and causing a reaction of NH 3 and NO x in the NH 3 -AO catalyst to purify the NH 3 and the NO x and to decrease an amount of NH 3 adsorbed in the NH 3 -AO catalyst when the exhaust gas includes NO x therein and the exhaust gas air-fuel ratio is lean.

Claim 65

Dependent Claim 26 words

The device according to claim 62 , wherein the NH 3 -AO catalyst is arranged in the exhaust passage downstream of the NO x -OR catalyst.

Claim 66

Dependent Claim 29 words

The device according to claim 63 , the engine further having a muffler arranged in the exhaust passage, wherein the NH 3 -AO catalyst is housed in the muffler.

Claim 67

Dependent Claim 62 words

The device according to claim 62 , further comprising adsorbed NH 3 amount estimating means for estimating an amount of NH 3 adsorbed in the NH 3 -AO catalyst, and wherein the exhaust gas air-fuel ratio controlling means changes the exhaust gas air-fuel ratio from lean to rich or from rich to lean in accordance with the estimated adsorbed NH 3 amount.

Claim 68

Dependent Claim 78 words

The device according to claim 65 , wherein the adsorbed NH 3 amount is estimated on the basis of an NH 3 amount flowing into the NH 3 -AO catalyst when the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH 3 synthesizing catalyst is rich, and on the basis of the decreased NH 3 amount when the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH 3 synthesizing catalyst is lean.

Claim 69

Dependent Claim 27 words

The device according to claim 62 , wherein the NH 3 -AO catalyst comprises a solid acid carrying one of a transition metal and a precious metal.

Claim 70

Dependent Claim 122 words

The device according to claim 40 , further comprising an NH 3 adsorbing and oxidizing (NH 3 -AO) catalyst arranged in the exhaust passage downstream of the NH 3 synthesizing catalyst, the NH 3 -AO catalyst adsorbing NH 3 in the exhaust gas therein, and causing a reaction of NH 3 and NO x in the NH 3 -AO catalyst to purify the NH 3 and the NO x and to decrease an amount of NH 3 adsorbed in the NH 3 -AO catalyst when the exhaust gas includes NO x therein and the exhaust gas air-fuel ratio is lean, and wherein the NH 3 -AO catalyst and the NO x -OR catalyst are laminated to each other on a common substrate.

Claim 71

Dependent Claim 23 words

The device according to claim 40 , wherein the NH 3 synthesizing catalyst is a three-way catalyst including at least one precious metal.

Claim 72

Dependent Claim 34 words

The device according to claim 40 , wherein the NO x OR catalyst includes: at least one substance selected from alkali metals, alkali earth metals, rare earth metals, and transition metals; and precious metals.

Claim 73

Dependent Claim 31 words

The device according to claim 40 , further comprising an NH 3 purifying catalyst arranged downstream of the exhaust gas purifying catalyst for purifying NH 3 in the inflowing exhaust gas.

Claim 74

Dependent Claim 25 words

The device according to claim 71 , wherein the NH 3 purifying catalyst includes at least one substance selected from precious metals and transition metals.

Claim 75

Dependent Claim 62 words

The device according to claim 71 , the NH 3 purifying catalyst purifying NH 3 under the oxidizing atmosphere, wherein the device further comprises keeping-lean means arranged in the exhaust passage between the exhaust gas purifying catalyst and the NH 3 purifying catalyst for keeping the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH 3 purifying catalyst lean.

Claim 76

Dependent Claim 95 words

The device according to claim 40 , wherein the NH 3 synthesizing catalyst is a NO x occluding and NH 3 synthesizing (NO x -NH 3 ) catalyst, the NO x -NH 3 catalyst occluding NO x in the exhaust gas therein when the exhaust gas air-fuel ratio is lean, the NO x -NH 3 catalyst releasing the occluded NO x therefrom, reducing the NO x in the NO x -NH 3 catalyst and synthesizing NH 3 from NO x in the NO x -NH 3 catalyst when the exhaust gas air-fuel ratio is rich.

Claim 77

Dependent Claim 66 words

The device according to claim 74 , further comprising occluded NO x amount estimating means for estimating an amount of NO x occluded in the NO x -NH 3 catalyst, and wherein the exhaust gas air-fuel ratio of the exhaust gas flowing into the NO x -NH 3 catalyst is made lean and rich alternately and repeatedly in accordance with the estimated occluded NO x amount.

Claim 78

Dependent Claim 65 words

The device according to claim 74 , further comprising occluded NO x amount estimating means for estimating an amount of NO x occluded in the NO x -OR catalyst, and wherein the exhaust gas air-fuel ratio of the exhaust gas flowing into the NO x -NH 3 catalyst is made lean and rich alternately and repeatedly in accordance with the estimated occluded NO x amount.

Claim 79

Dependent Claim 35 words

The device according to claim 74 , wherein the NO x -NH 3 catalyst includes: at least one substance selected from alkali metals, alkali earth metals, rare earth metals, and transition metals; and precious metals.

Claim 80

Dependent Claim 34 words

The device according to claim 74 , wherein the NO x -OR catalyst includes: at least one substance selected from alkali metals, alkali earth metals, rare earth metals, and transition metals; and precious metals.

Claim 81

Independent Claim 194 words

The method for purifying an exhaust gas of an engine, the method comprising the steps of: alternately and repeatedly controlling an exhaust gas air-fuel ratio between a lean exhaust gas air-fuel ratio and a rich exhaust gas air-fuel ratio; and introducing the exhaust gas to a NH 3 synthesizing catalyst, the NH 3 synthesizing catalyst synthesizing NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is rich and synthesizing almost no NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is lean and wherein a NH 3 adsorbing and oxidizing (NH 3 -AO) catalyst is arranged downstream of the NH 3 synthesizing catalyst in a common exhaust passage therewith, and wherein, when the exhaust gas air-fuel ratio is lean, the NH 3 -AO catalyst adsorbs NH 3 in the exhaust gas therein, causes a reaction of NH 3 and NO x in the NH 3 -AO catalyst to purify the NH 3 and the NO x and decreases an amount of NH 3 adsorbed in the NH 3 -AO catalyst when the exhaust gas includes NO x therein.

Claim 82

Independent Claim 194 words

The method for purifying an exhaust gas of an engine, the method comprising the steps of: alternately and repeatedly controlling an exhaust gas air-fuel ratio between a lean exhaust gas air-fuel ratio and a rich exhaust gas air-fuel ratio; and introducing the exhaust gas to a NH 3 synthesizing catalyst, the NH 3 synthesizing catalyst synthesizing NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is rich and synthesizing almost no NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is lean and wherein a NH 3 adsorbing and oxidizing (NH 3 -AO) catalyst is arranged downstream of the NH 3 synthesizing catalyst in a common exhaust passage therewith, and wherein, when the exhaust gas air-fuel ratio is lean, the NH 3 -AO catalyst adsorbs NH 3 in the exhaust gas therein, causes a reaction of NH 3 and NO x in the NH 3 -AO catalyst to purify the NH 3 and the NO x and decreases an amount of NH 3 adsorbed in the NH 3 -AO catalyst when the exhaust gas includes NO x therein.

Claim 83

Dependent Claim 47 words

The method according to claim 79 , further comprising the step of controlling an engine air-fuel ratio between a lean engine air-fuel ratio to thereby form the lean exhaust gas air-fuel ratio and a rich engine air-fuel ratio to thereby form the rich exhaust gas air-fuel ratio.

Claim 84

Dependent Claim 48 words

The method according to claim 80 , wherein the engine air-fuel ratio is made lean for a lean period, and the engine air-fuel ratio is made rich for a rich period, and wherein the lean and the rich periods are set in accordance with the engine operating condition.

Claim 85

Dependent Claim 84 words

The method according to claim 81 , wherein the engine is provided with a plurality of cylinders or cylinder groups of which the exhaust stroke periods are different to each other, and wherein the lean period is set as the number of the cylinders or cylinder groups of which the engine air-fuel ratio is made to be lean, and the rich period is set as the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made rich.

Claim 86

Dependent Claim 40 words

The method according to claim 80 , the engine being an internal combustion engine of spark ignition type, and the method further comprising the step of controlling the ignition timing of the engine in accordance with the engine air-fuel ratio.

Claim 87

Dependent Claim 90 words

The method according to claim 79 , wherein a making-rich device, different from the engine, is arranged in the exhaust passage of an engine upstream of the NH 3 synthesizing catalyst for making the exhaust gas air-fuel ratio rich, and wherein the method further comprises the steps of keeping an engine air-fuel ratio lean, and stopping a making-rich operation of the making-rich device to thereby form the lean exhaust gas air-fuel ratio, and performing the making-rich operation of the making-rich device to thereby form the rich exhaust gas air-fuel ratio.

Claim 88

Dependent Claim 82 words

The method according to claim 84 , wherein the making rich device is provided with: a combustor of which an air-fuel ratio is controllable; and an introducing passage for introducing the exhaust gas of the combustor into the exhaust passage upstream of the NH 3 synthesizing catalyst, and wherein the making-rich operation of the making-rich device is performed by making an air-fuel ratio of the combustor rich and adding the exhaust gas of the combustor to the exhaust gas of the engine.

Claim 89

Dependent Claim 56 words

The method according to claim 84 , wherein the making-rich device is provided with a reducing agent injector for feeding a reducing agent into the exhaust passage upstream of the NH 3 synthesizing catalyst, the making-rich operation of the reducing agent injector being performed by adding the reducing agent to the exhaust gas of the engine.

Claim 90

Dependent Claim 51 words

The method according to claim 79 , further comprising the step of estimating an amount of NH 3 adsorbed in the NH 3 -AO catalyst, wherein the exhaust gas air-fuel ratio is changed from lean to rich or from rich to lean in accordance with the estimated adsorbed NH 3 amount.

Claim 91

Dependent Claim 78 words

The method according to claim 87 , wherein the adsorbed NH 3 amount is estimated on the basis of an NH 3 amount flowing into the NH 3 -AO catalyst when the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH 3 synthesizing catalyst is rich, and on the basis of the decreased NH 3 amount when the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH 3 synthesizing catalyst is lean.

Claim 92

Dependent Claim 29 words

The method according to claim 79 , wherein the exhaust gas air-fuel ratio is changed from lean to rich or from rich to lean gradually with a changing rate.

Claim 93

Dependent Claim 22 words

The method according to claim 79 , wherein the exhaust gas air-fuel ratio is set in accordance with the engine operating condition.

Claim 94

Dependent Claim 50 words

The method according to claim 79 , wherein the exhaust gas air-fuel ratio is made equal to a target air-fuel ratio on the basis on output signals of an air-fuel ratio sensor arranged in an exhaust passage of the engine adjacent to an inlet of the NH 3 synthesizing catalyst.

Claim 95

Dependent Claim 30 words

The method according to claim 79 , the engine further having a muffler arranged in an exhaust passage thereof, wherein the NH 3 -AO catalyst is housed in the muffler.

Claim 96

Dependent Claim 23 words

The method according to claim 79 , wherein the NH 3 synthesizing catalyst is a three-way catalyst including at least one precious metal.

Claim 97

Dependent Claim 41 words

The method according to claim 79 , further comprising the step of introducing the exhaust gas to a NH 3 purifying catalyst for purifying NH 3 in the exhaust gas, after introducing the exhaust gas to the NH 3 -AO catalyst.

Claim 98

Dependent Claim 25 words

The method according to claim 94 , wherein the NH 3 purifying catalyst includes at least one substance selected from precious metals and transition metals.

Claim 99

Dependent Claim 27 words

The method according to claim 79 , wherein the NH 3 -AO catalyst comprises a solid acid carrying one of a transition metal and a precious metal.

Claim 100

Dependent Claim 95 words

The method according to claim 79 , wherein the NH 3 synthesizing catalyst is a NO x occluding and NH 3 synthesizing (NO x -NH 3 ) catalyst, the NO x -NH 3 catalyst occluding NO x in the exhaust gas therein when the exhaust gas air-fuel ratio is lean, the NO x -NH 3 catalyst releasing the occluded NO x therefrom, reducing the NO x in the NO x -NH 3 catalyst and synthesizing NH 3 from NO x in the NO x -NH 3 catalyst when the exhaust gas air-fuel ratio is rich.

Claim 101

Dependent Claim 62 words

The method according to claim 97 , further comprising the step of estimating an amount of NO x occluded in the NO x -NH 3 catalyst, and wherein the exhaust gas air-fuel ratio of the exhaust gas flowing into the NO x -NH 3 catalyst is made lean and rich alternately and repeatedly in accordance with the estimated occluded NO x amount.

Claim 102

Dependent Claim 61 words

The method according to claim 97 , further comprising the step of estimating an amount of NH 3 adsorbed in the NH 3 -AO catalyst, and wherein the exhaust gas air-fuel ratio of the exhaust gas flowing into the NO x -NH 3 catalyst is made lean and rich alternately and repeatedly in accordance with the estimated adsorbed NH 3 amount.

Claim 103

Dependent Claim 35 words

The method according to claim 97 , wherein the NO x -NH 3 catalyst includes: at least one substance selected from alkali metals, alkali earth metals, rare earth metals, and transition metals; and precious metals.

Claim 104

Dependent Claim 24 words

The method according to claim 97 , wherein the NH 3 -AO catalyst comprises solid acid carrying one of transition metals and precious metals.

Claim 105

Independent Claim 214 words

The device for purifying an exhaust gas of an engine having an exhaust passage, comprising: exhaust gas air-fuel ratio controlling means arranged in one of the engine and the exhaust passage for alternately and repeatedly controlling an exhaust gas air-fuel ratio between a lean exhaust gas air-fuel ratio and a rich exhaust gas air-fuel ratio; an NH 3 synthesizing catalyst arranged in the exhaust passage downstream of the exhaust gas air-fuel ratio controlling means, the NH 3 synthesizing catalyst synthesizing NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is rich, and synthesizing almost no NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is lean; and an NH 3 adsorbing and oxidizing (NH 3 -AO) catalyst arranged in the exhaust passage downstream of the NH 3 synthesizing catalyst, the NH 3 -AO catalyst adsorbing NH 3 in the exhaust gas therein, and causing a reaction of NH 3 and NO x in the NH 3 -AO catalyst to purify the NH 3 and the NO x and to decrease an amount of NH 3 adsorbed in the NH 3 -AO catalyst when the exhaust gas includes NO x therein and the exhaust gas air-fuel ratio is lean.

Claim 106

Independent Claim 214 words

The device for purifying an exhaust gas of an engine having an exhaust passage, comprising: exhaust gas air-fuel ratio controlling means arranged in one of the engine and the exhaust passage for alternately and repeatedly controlling an exhaust gas air-fuel ratio between a lean exhaust gas air-fuel ratio and a rich exhaust gas air-fuel ratio; an NH 3 synthesizing catalyst arranged in the exhaust passage downstream of the exhaust gas air-fuel ratio controlling means, the NH 3 synthesizing catalyst synthesizing NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is rich, and synthesizing almost no NH 3 from NO x in the NH 3 synthesizing catalyst when the exhaust gas air-fuel ratio is lean; and an NH 3 adsorbing and oxidizing (NH 3 -AO) catalyst arranged in the exhaust passage downstream of the NH 3 synthesizing catalyst, the NH 3 -AO catalyst adsorbing NH 3 in the exhaust gas therein, and causing a reaction of NH 3 and NO x in the NH 3 -AO catalyst to purify the NH 3 and the NO x and to decrease an amount of NH 3 adsorbed in the NH 3 -AO catalyst when the exhaust gas includes NO x therein and the exhaust gas air-fuel ratio is lean.

Claim 107

Dependent Claim 61 words

The device according to claim 102 , wherein the exhaust gas air-fuel ratio controlling means comprises an engine air-fuel ratio control mean for controlling an engine air-fuel ratio to make the engine air-fuel ratio lean to thereby form the lean exhaust gas air-fuel ratio and to make the engine air-fuel ratio rich to thereby form the rich exhaust gas air-fuel ratio.

Claim 108

Dependent Claim 52 words

The device according to claim 103 , wherein the engine air-fuel ratio control means makes the engine air-fuel ratio lean for a lean period, and makes the engine air-fuel ratio rich for a rich period, and wherein the lean and the rich periods are set in accordance with the engine operating condition.

Claim 109

Dependent Claim 84 words

The device according to claim 104 , wherein the engine is provided with a plurality of cylinders or cylinder groups of which the exhaust stroke periods are different to each other, and wherein the lean period is set as the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made lean, and the rich period is set as the number of the cylinders or cylinder groups of which the engine air-fuel ratio is to be made rich.

Claim 110

Dependent Claim 42 words

The device according to claim 103 , the engine being an internal combustion engine of spark ignition type, and the device further comprising ignition timing control means for controlling the ignition timing of the engine in accordance with the engine air-fuel ratio.

Claim 111

Dependent Claim 86 words

The device according to claim 102 , wherein the exhaust gas air-fuel ratio controlling means comprises making-rich means, different from the engine, arranged in the exhaust passage upstream of the NH 3 synthesizing catalyst for making the exhaust gas air-fuel ratio rich, and keeping means for keeping the engine air-fuel ratio lean, and wherein the making-rich means stops a making-rich operation thereof to thereby form the lean exhaust gas air-fuel ratio, and performs the making-rich operation thereof to thereby form the rich exhaust gas air-fuel ratio.

Claim 112

Dependent Claim 78 words

The device according to claim 107 , wherein the making-rich means comprises: a combustor of which an air-fuel ratio is controllable; and an introducing passage for introducing the exhaust gas of the combustor into the exhaust passage upstream of the NH 3 synthesizing catalyst, and wherein the making-rich means performs the making-rich operation thereof by making an air-fuel ratio of the combustor rich and adding the exhaust gas of the combustor to the exhaust gas of the engine.

Claim 113

Dependent Claim 53 words

The device according to claim 107 , wherein the making-rich means comprise a reducing agent injector for feeding a reducing agent into the exhaust passage upstream of the NH 3 synthesizing catalyst, the reducing agent injector performing the making-rich operation thereof by adding the reducing agent to the exhaust gas of the engine.

Claim 114

Dependent Claim 62 words

The device according to claim 102 , further comprising adsorbed NH 3 amount estimating means for estimating an amount of NH 3 adsorbed in the NH 3 -AO catalyst, and wherein the exhaust gas air-fuel ratio controlling means changes the exhaust gas air-fuel ratio from lean to rich or from rich to lean in accordance with the estimated adsorbed NH 3 amount.

Claim 115

Dependent Claim 84 words

The device according to claim 110 , wherein the adsorbed NH 3 amount estimating means estimates the adsorbed NH 3 amount on the basis of an NH 3 amount flowing into the NH 3 -AO catalyst when the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH 3 synthesizing catalyst is rich, and on the basis of the decreased NH 3 amount when the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH 3 synthesizing catalyst is lean.

Claim 116

Dependent Claim 35 words

The device according to claim 102 , wherein the exhaust gas air-fuel ratio controlling means changes the exhaust gas air-fuel ratio from lean to rich or from rich to lean gradually with a changing rate.

Claim 117

Dependent Claim 22 words

The device according to claim 102 , wherein the exhaust gas air-fuel ratio is set in accordance with the engine operating condition.

Claim 118

Dependent Claim 65 words

The device according to claim 102 , further comprising an air-fuel ratio sensor arranged in the exhaust passage between the exhaust gas air-fuel ratio controlling means and the NH 3 synthesizing catalyst, and wherein the exhaust gas air-fuel ratio controlling means makes the exhaust gas air-fuel ratio equal to a target air-fuel ratio on the basis of the output signals of the air-fuel ratio sensor.

Claim 119

Dependent Claim 28 words

The device according to claim 102 , engine further having a muffler arranged in the exhaust passage, wherein the NH 3 -AO catalyst is housed in the muffler.

Claim 120

Dependent Claim 23 words

The device according to claim 102 , wherein the NH 3 synthesizing catalyst is a three-way catalyst including at least one precious metal.

Claim 121

Dependent Claim 30 words

The device according to claim 102 , further comprising an NH 3 purifying catalyst arranged downstream of the exhaust gas purifying catalyst for purifying NH 3 in the exhaust gas.

Claim 122

Dependent Claim 25 words

The device according to claim 117 , wherein the NH 3 purifying catalyst includes at least one substance selected from precious metals and transition metals.

Claim 123

Dependent Claim 28 words

The device according to claim 102 , wherein the NH 3 -AO catalyst comprises a solid acid carrying a one of a transition metal and a precious metal.

Claim 124

Dependent Claim 94 words

The device according to claim 102 , wherein the NH 3 synthesizing catalyst is a NO x occluding and NH 3 synthesizing (NO x -NH 3 ) catalyst, the NO x -NH 3 catalyst occluding NO x in the exhaust gas when the exhaust gas air-fuel ratio is lean, the NO x -NH 3 catalyst releasing the occluded NO x therefrom, reducing the NO x in the NO x -NH 3 catalyst and synthesizing NH 3 from NO x in the NO x -NH 3 catalyst when the exhaust gas air-fuel ratio is rich.

Claim 125

Dependent Claim 66 words

The device according to claim 120 , further comprising occluded NO x amount estimating means for estimating an amount of NO x occluded in the NO x -NH 3 catalyst, and wherein the exhaust gas air-fuel ratio of the exhaust gas flowing into the NO x -NH 3 catalyst is made lean and rich alternately and repeatedly in accordance with the estimated occluded NO x amount.

Claim 126

Dependent Claim 65 words

The device according to claim 120 , further comprising adsorbed NH 3 amount estimating means for estimating an amount of NH 3 adsorbed in the NH 3 -AO catalyst, and wherein the exhaust gas air-fuel ratio of the exhaust gas flowing into the NO x -NH 3 catalyst is made lean and rich alternately and repeatedly in accordance with the estimated adsorbed NH 3 amount.

Claim 127

Dependent Claim 35 words

The device according to claim 120 , wherein the NO x -NH 3 catalyst includes: at least one substance selected from alkali metals, alkali earth metals, rare earth metals, and transition metals; and precious metals.

Claim 128

Dependent Claim 24 words

The device according to claim 120 , wherein the NH 3 -AO catalyst comprises solid acid carrying one of transition metals and precious metals.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2005-02-11	2005-08-13	2006-02-12	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2009-02-11	2009-08-13	2010-02-12	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2013-02-11	2013-08-13	2014-02-12	$7700.00	Window Closed / Lapsed

Method and device for purifying exhaust gas of an engine

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