Catalyst deterioration detecting system and catalyst deterioration detecting method
A system ( 9 ) of the invention is a system for detecting deterioration of a catalyst ( 8 ) provided in an exhaust passage ( 12 ) of an internal combustion engine ( 11 ), the system including: means ( 5 ) that detects a temperature of an exhaust on an upstream side of the catalyst ( 8 ); means ( 6 ) that detects a temperature of the exhaust on a downstream side of the catalyst ( 8 ); a recognition unit ( 10 ) that recognizes, both upstream and downstream of the catalyst ( 8 ), a change point at which the temperature changes from temperature fall or constant temperature to temperature rise during acceleration operation, or a change point at which the temperature changes from temperature rise or constant temperature to temperature fall during deceleration operation; and a determination unit ( 10 ) that determines that the catalyst ( 8 ) has deteriorated when a difference (ΔT or ΔT′) between the upstream and downstream change points becomes equal to or longer than a predetermined time.
1. A catalyst deterioration detecting system for detecting deterioration of a catalyst provided in an exhaust passage of an internal combustion engine, the system comprising:
an upstream-side temperature detection means that detects a temperature of an exhaust on an upstream side of the catalyst;
a downstream-side temperature detection means that detects a temperature of the exhaust on a downstream side of the catalyst; and either
(A) a recognition unit that, during acceleration operation, recognizes a change point (T 1 ) which is a time point at which the temperature detected by the upstream-side temperature detection means changes from temperature fall or constant temperature to temperature rise and a change point (T 2 ) which is a time point at which the temperature detected by the downstream-side temperature detection means changes from temperature fall or constant temperature to temperature rise, and a determination unit that determines that the catalyst has deteriorated when a difference between the change points (ΔT=T 2 −T 1 ) becomes equal to or longer than a predetermined time, or
(B) a recognition unit that, during deceleration operation, recognizes a change point (T 1 ′) which is a time point at which the temperature detected by the upstream-side temperature detection means changes from temperature rise or constant temperature to temperature fall and a change point (T 2 ′) which is a time point at which the temperature detected by the downstream-side temperature detection means changes from temperature rise or constant temperature to temperature fall, and a determination unit that determines that the catalyst has deteriorated when a difference between the change points (ΔT′=T 2 ′−T 1 ′) becomes equal to or longer than a predetermined time.
2. The catalyst deterioration detecting system according to claim 1 , comprising:
a recognition unit that, during acceleration operation, recognizes a change point (T 1 ) which is a time point at which the temperature detected by the upstream-side temperature detection means changes from temperature fall to temperature rise, and a change point (T 2 ) which is a time point at which the temperature detected by the downstream-side temperature detection means changes from temperature fall to temperature rise; and
a determination unit that determines that the catalyst has deteriorated when a difference between the change points (ΔT=T 2 −T 1 ) becomes equal to or longer than a predetermined time.
3. The catalyst deterioration detecting system according to claim 1 , wherein the upstream-side temperature detection means and the downstream-side temperature detection means respectively have different time constants.
4. The catalyst deterioration detecting system according to claim 1 , wherein:
the upstream-side temperature detection means and the downstream-side temperature detection means are each constituted by a sheathed thermocouple; and
a sheath diameter of the sheathed thermocouple used as the upstream-side temperature detection means is different from a sheath diameter of the sheathed thermocouple used as the downstream-side temperature detection means.
5. The catalyst deterioration detecting system according to claim 1 , wherein a ratio (L 2 /L 1 ) between a distance L 1 from an inlet-side end portion of the catalyst to a temperature detection position of the upstream-side temperature detection means and a distance L 2 from an outlet-side end portion of the catalyst to a temperature detection position of the downstream-side temperature detection means is from 0.18 to 5.00.
6. The catalyst deterioration detecting system according to claim 1 , wherein the internal combustion engine is a gasoline engine.
7. A catalyst deterioration detecting method for detecting deterioration of a catalyst provided in an exhaust passage of an internal combustion engine, the method comprising:
employing
an upstream-side temperature detection means that detects a temperature of an exhaust on an upstream side of the catalyst, and
a downstream-side temperature detection means that detects a temperature of the exhaust on a downstream side of the catalyst; and either
(a) recognizing, during acceleration operation, a change point (T 1 ) which is a time point at which the temperature detected by the upstream-side temperature detection means changes from temperature fall or constant temperature to temperature rise and a change point (T 2 ) which is a time point at which the temperature detected by the downstream-side temperature detection means changes from temperature fall or constant temperature to temperature rise, and determining that the catalyst has deteriorated when a difference between the change points (ΔT=T 2 −T 1 ) becomes equal to or longer than a predetermined time, or
(b) recognizing, during deceleration operation, a change point (T 1 ′) which is a time point at which the temperature detected by the upstream-side temperature detection means changes from temperature rise or constant temperature to temperature fall and a change point (T 2 ′) which is a time point at which the temperature detected by the downstream-side temperature detection means changes from temperature rise or constant temperature to temperature fall, and determining that the catalyst has deteriorated when a difference between the change points (ΔT′=T 2 ′−T 1 ′) becomes equal to or longer than a predetermined time.