Failure determination device for humidity sensor and control system for exhaust passage changeover valve
First Claim
1. A failure determination device for a humidity sensor that detects humidity of exhaust gases from an internal combustion engine,the failure determination device comprising:
- operating condition-detecting means for detecting an operating condition of the engine;
failure determination execution-judging means for judging whether or not the engine is in a predetermined operating condition in which failure determination of the humidity sensor can be executed, based on a result of detection by said operating condition-detecting means; and
humidity sensor failure-determining means for determining whether or not the humidity sensor has failed, based on a result of detection by the humidity sensor, when said failure determination execution-judging means judged that the failure determination of the humidity sensor can be executed engine is in said predetermined operating condition.
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Accused Products
Abstract
A failure determination device that detects the humidity of exhaust gases from an internal combustion engine and a control system for an exhaust passage changeover valve, which can switch the changeover valve with appropriate timing, thereby enabling sufficient purification of exhaust gases. An operating condition of the engine is detected. Based on the detected operating condition of the engine, it is determined whether the engine is in an operating condition in which failure determination of the humidity sensor can be executed. It is determined whether the humidity sensor has failed, based on a result of detection by the humidity sensor, when it has been judged that the failure determination of the humidity sensor can be executed.
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Citations
15 Claims
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1. A failure determination device for a humidity sensor that detects humidity of exhaust gases from an internal combustion engine,
the failure determination device comprising: -
operating condition-detecting means for detecting an operating condition of the engine;
failure determination execution-judging means for judging whether or not the engine is in a predetermined operating condition in which failure determination of the humidity sensor can be executed, based on a result of detection by said operating condition-detecting means; and
humidity sensor failure-determining means for determining whether or not the humidity sensor has failed, based on a result of detection by the humidity sensor, when said failure determination execution-judging means judged that the failure determination of the humidity sensor can be executed engine is in said predetermined operating condition. - View Dependent Claims (2, 3, 4, 5, 6)
the humidity sensor being arranged at a location downstream of the adsorber in the bypass exhaust passage, and wherein said failure determination execution-judging means judges that the failure determination of the humidity sensor can be executed engine is in said predetermined operating condition when the exhaust passage has been switched to the bypass exhaust passage, and at the same time the adsorber is adsorbing hydrocarbons in the exhaust gases guided into the bypass exhaust passage. -
3. A failure determination device according to claim 2, wherein the hydrocarbons are desorbed from the adsorber by switching the exhaust passage to the main exhaust passage,
the failure determination device further comprising desorption state-detecting means for detecting a state of desorption of the hydrocarbons from the adsorber, wherein said failure determination execution-judging means judges whether or not the failure determination of the humidity sensor can be executed engine is in said predetermined operation condition, based on the state of the desorption of the hydrocarbons from the adsorber at a time of termination of a preceding operation of the engine, detected by the desorption state-detecting means. -
4. A failure determination device according to claim 2, wherein said failure determination execution-judging means further includes timer means for measuring a time period after a start of the engine, and determines whether or not failure determination of the humidity sensor can be executed the engine is in said predetermined operating condition further based on the time period measured by said timer means.
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5. A failure determination device according to claim 3, wherein said failure determination execution-judging means further includes fuel injection time-integrating means for calculating a cumulative value of fuel injection time periods after a start of the engine, and determines whether or not failure determination of the humidity sensor can be executed the engine is in said predetermined operating condition further based on the cumulative value calculated by said fuel injection time-integrating means.
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6. A failure determination device according to claim 1, wherein said humidity sensor failure-determining means determines that the humidity sensor has failed when the value of humidity detected by the humidity sensor is lower than a predetermined value.
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7. A control system for controlling an exhaust passage changeover valve of an internal combustion engine, the changeover valve switching an exhaust passage having a catalytic device arranged therein for purifying exhaust gases from the engine between a main exhaust passage and a bypass exhaust passage bypassing the main exhaust passage and having an adsorber arranged therein which is capable of adsorbing hydrocarbons and water in the exhaust gases,
the control system comprising: -
a humidity sensor arranged at a location downstream of the adsorber in the bypass exhaust passage, for detecting humidity of the exhaust gases guided into the bypass exhaust passage; and
changeover valve drive means for driving the changeover valve based on a result of detection by said humidity sensor. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
the control system further comprising: a heater for heating said sensor element;
operating condition-detecting means for detecting an operating condition of the engine; and
heater control means for controlling an operation of said heater depending on the operating condition detected by said operating condition-detecting means.
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10. A control system according to claim 7, further comprising upstream-side humidity-estimating means for estimating humidity at a location upstream of the adsorber, based on a value of the humidity detected by said humidity sensor.
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11. A control system according to claim 10, wherein said changeover valve drive means drives the changeover valve based on a difference between the value of the humidity detected by said humidity sensor and a value of the humidity estimated by said upstream-side humidity-estimating means.
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12. A control system according to claim 11, wherein said changeover valve drive means drives the changeover valve further based on a cumulative value of the difference between the value of the humidity detected by said humidity sensor and the value of the humidity estimated by said upstream-side humidity-estimating means.
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13. A control system according to claim 7, further comprising an upstream-side humidity sensor for detecting humidity at a location upstream of the adsorber.
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14. A control system according to claim 10, wherein said changeover valve drive means drives the changeover valve based on a difference between a value of the humidity detected by said humidity sensor and a value of the humidity detected by said upstream-side humidity sensor.
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15. A control system according to claim 11, wherein said changeover valve drive means drives the changeover valve further based on a cumulative value of the difference between the value of the humidity detected by said humidity sensor and the value of the humidity detected by said upstream-side humidity sensor.
Specification