# US 6,058,700 A · Device for purifying exhaust gas of engine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,058,700 A - Document ID: US6058700A - Status: Granted - Kind: A - Application number: 09/083,738 - Filed: 1998-05-22 - Granted: 2000-05-09 - Earliest claimed: 1998-05-22 - Assignees: Toyota Jidosha Kabushiki Kaisha - Inventors: Tetsuya Yamashita; Toshiaki Tanaka; Shinichi Takeshima; Shinya Hirota; Eiji Iwasaki; Kouji Yoshizaki; Nobumoto Ohashi; Kazuhiro Itoh - Web page: https://patentgrep.com/patent/US6058700A ## CPC - F01N 3/0842: {Nitrogen oxides} - F02D 41/0275: {the exhaust gas treating apparatus being a NOx trap or adsorbent} - F02D 41/028: {Desulfurisation of NOx traps or adsorbent} - F01N 2570/04: Sulfur or sulfur oxides - F02D 2200/0806: NOx storage amount, i.e. amount of NOx stored on NOx trap - F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16) - F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W) ## Abstract A device for purifying the exhaust gas of an engine comprises a NO.sub.X absorbent arranged in the exhaust passage. The NO.sub.X absorbent absorbs NO.sub.X therein when the air-fuel ratio of the inflowing exhaust gas is lean, and releases the absorbed NO.sub.X therefrom when the oxygen concentration in the inflowing exhaust gas becomes lower. The NO.sub.X absorbent also absorbs SO.sub.X therein when the air-fuel ratio of the inflowing exhaust gas is lean, and releases the absorbed SO.sub.X therefrom when the oxygen concentration in the inflowing exhaust gas becomes lower, with the temperature of the NO.sub.X absorbent being higher than a SO.sub.X releasing temperature. The air-fuel ratio of the exhaust gas flowing to the NO.sub.X absorbent is made rich temporarily when the temperature of the NO.sub.X absorbent is higher than SO.sub.X releasing temperature and when the flow rate of the exhaust gas flowing through the NO.sub.X absorbent is lower than a predetermined flow rate, to release the absorbed SO.sub.X from the NO.sub.X absorbent. ## Claims ### Claim 1 A device for purifying the exhaust gas of an engine having an exhaust passage, comprising: a sulphur containing components absorbent arranged in the exhaust passage, the sulphur containing components absorbent absorbing the sulphur containing components therein when the air-fuel ratio of the inflowing exhaust gas is lean, and releasing the absorbed sulphur containing components therefrom when the oxygen concentration in the inflowing exhaust gas becomes lower with the temperature of the sulphur containing components absorbent being higher than a sulphur containing components releasing temperature of the sulphur containing components absorbent; and releasing means for making the air-fuel ratio of the exhaust gas flowing to the sulphur containing components absorbent stoichiometric or rich temporarily, when the temperature of the sulphur containing components absorbent is higher than the sulphur containing components releasing temperature and when the flow rate of the exhaust gas flowing through the sulphur containing components absorbent is lower than a predetermined flow rate, to release the absorbed sulphur containing components from the sulphur containing components absorbent. ### Claim 2 (depends on 1) A device according to claim 1, wherein the sulphur containing components is comprised of sulphur oxide SO.sub.X. ### Claim 3 (depends on 1) A device according to claim 1, wherein the air-fuel ratio of the air-fuel mixture to be burned in the combustion chamber of the engine is made stoichiometric or rich, to make the air-fuel ratio of the exhaust gas flowing to the sulphur containing components absorbent stoichiometric or rich. ### Claim 4 (depends on 1) A device according to claim 1, wherein the engine is provided with a fuel injector injecting fuel directly into the combustion chamber of the engine, and wherein the releasing means controls the fuel injector to inject fuel secondarily at the power stroke or the exhaust stroke of the engine, to make the air-fuel ratio of the exhaust gas flowing to the sulphur containing components absorbent stoichiometric or rich. ### Claim 5 (depends on 1) A device according to claim 1, further comprising judging means for judging whether the temperature of the sulphur containing components absorbent is higher than the sulphur containing components releasing temperature and whether the flow rate of the exhaust gas flowing through the sulphur containing components absorbent is lower than the predetermined flow rate, wherein the air-fuel ratio of the exhaust gas flowing to the sulphur containing components absorbent is made stoichiometric or rich temporarily when the temperature of the sulphur containing components absorbent is judged to be higher than the sulphur containing components releasing temperature and the flow rate of the exhaust gas flowing through the sulphur containing components absorbent is judged to be lower than the predetermined flow rate. ### Claim 6 (depends on 5) A device according to claim 5, wherein the judging means judges whether the temperature of the sulphur containing components absorbent is higher than the sulphur containing components releasing temperature on the basis of the engine operating condition. ### Claim 7 (depends on 5) A device according to claim 5, wherein the judging means judges whether the flow rate of the exhaust gas flowing through the sulphur containing components absorbent is lower than the predetermined flow rate on the basis of the engine operating condition. ### Claim 8 (depends on 1) A device according to claim 1, further comprising temperature control means for controlling the temperature of the sulphur containing components absorbent to make the temperature higher than the sulphur containing components releasing temperature. ### Claim 9 (depends on 8) A device according to claim 8, wherein the temperature control means comprises an electric heater to heat the sulphur containing components absorbent. ### Claim 10 (depends on 8) A device according to claim 8, wherein the engine is provided with a fuel injector injecting fuel directly into the combustion chamber of the engine, and wherein the temperature control means controls the fuel injector to inject fuel secondarily at the power stroke or the exhaust stroke of the engine, to heat the sulphur containing components absorbent. ### Claim 11 (depends on 8) A device according to claim 8, further comprising estimating means for estimating an amount of sulphur containing components absorbed in the sulphur containing components absorbent, wherein the temperature control means makes the temperature of the sulphur containing components absorbent higher than the sulphur containing components releasing temperature when the estimated sulphur containing components amount is larger than a predetermined amount. ### Claim 12 (depends on 1) A device according to claim 1, further comprising flow rate control means for controlling the flow rate of the exhaust gas flowing through the sulphur containing components absorbent to make the flow rate lower than the predetermined flow rate. ### Claim 13 (depends on 12) A device according to claim 12, wherein the flow rate control means comprises reducing means for reducing an amount of the exhaust gas flowing to the sulphur containing components absorbent to make the flow rate of the exhaust gas flowing through the sulphur containing components absorbent lower than the predetermined flow rate. ### Claim 14 (depends on 13) A device according to claim 13, wherein the reducing means comprises a release passage connected to the exhaust passage upstream of the sulphur containing components absorbent, and means for introducing the exhaust gas from the engine to the release passage, and wherein the amount of the exhaust gas introduced to the release passage is increased to make the flow rate of the exhaust gas flowing through the sulphur containing components absorbent lower than the predetermined flow rate. ### Claim 15 (depends on 12) A device according to claim 12, further comprising estimating means for estimating an amount of sulphur containing components absorbed in the sulphur containing components absorbent, wherein the flow rate control means makes the flow rate of the exhaust gas flowing through the sulphur containing components absorbent lower than the predetermined flow rate when the estimated sulphur containing components amount is larger than a predetermined amount. ### Claim 16 (depends on 1) A device according to claim 1, wherein the sulphur containing components absorbent comprises a NO.sub.X absorbent, the NO.sub.X absorbent absorbing NO.sub.X therein when the air-fuel ratio of the inflowing exhaust gas is lean, and releasing the absorbed NO.sub.X therefrom when the oxygen concentration in the inflowing exhaust gas becomes lower. ### Claim 17 (depends on 16) A device according to claim 16, wherein the NO.sub.X absorbent is comprised of at least one substance, selected from alkali metals such as potassium, sodium, lithium, and cesium, alkali earth metals such as barium and calcium, rare earth metals such as lanthanum and yttrium, and of precious metals such as platinum, carried on a carrier. ### Claim 18 (depends on 16) A device according to claim 16, further comprising means for making the air-fuel ratio of the exhaust gas flowing to the NO.sub.X absorbent temporarily stoichiometric or rich, to release the absorbed NO.sub.X from the NO.sub.X absorbent. ### Claim 19 (depends on 1) A device according to claim 1, wherein the sulphur containing components absorbent comprises a SO.sub.X absorbent, the SO.sub.X absorbent absorbing SO.sub.X therein when the air-fuel ratio of the inflowing exhaust gas is lean, and releasing the absorbed SO.sub.X therefrom when the oxygen concentration in the inflowing exhaust gas becomes lower with the temperature of the SO.sub.X absorbent being higher than a SO.sub.X releasing temperature of the SO.sub.X absorbent. ### Claim 20 (depends on 19) A device according to claim 19, wherein the SO.sub.X absorbent is comprised of at least one substance, selected from lithium and transition metals such as iron, copper, manganese, nickel, and tin, carried on a carrier. ### Claim 21 (depends on 19) A device according to claim 19, further comprising a NO.sub.X absorbent arranged in the exhaust passage downstream of the SO.sub.X absorbent, the NO.sub.X absorbent absorbing NO.sub.X therein when the air-fuel ratio of the inflowing exhaust gas is lean, and releasing the absorbed NO.sub.X therefrom when the oxygen concentration in the inflowing exhaust gas becomes lower. ### Claim 22 (depends on 21) A device according to claim 21, wherein the NO.sub.X absorbent is comprised of at least one substance, selected from alkali metals such as potassium, sodium, lithium, and cesium, alkali earth metals such as barium and calcium, rare earth metals such as lanthanum and yttrium, and of precious metals such as platinum, carried on a carrier. ### Claim 23 (depends on 21) A device according to claim 21, further comprising a bypass passage connecting the exhaust passage upstream of the SO.sub.X absorbent and the exhaust passage between the SO.sub.X absorbent and the NO.sub.X absorbent, and means for introducing the exhaust gas from the engine to the bypass passage, and wherein the amount of the exhaust gas introduced into the bypass passage is increased to make the flow rate of the exhaust gas flowing through the SO.sub.X absorbent lower than the predetermined flow rate. ### Claim 24 (depends on 21) A device according to claim 21, further comprising means for making the air-fuel ratio of the exhaust gas flowing to the NO.sub.X absorbent temporarily stoichiometric or rich, to release the absorbed NO.sub.X from the NO.sub.X absorbent. ### Claim 25 (depends on 1) A device according to claim 1, wherein the air-fuel ratio of the air-fuel mixture to be burned in the combustion chamber of the engine is usually made lean.