DIAGNOSTIC METHOD AND DIAGNOSTIC SYSTEM FOR MULTICYLINDER INTERNAL COMBUSTION ENGINE
First Claim
1. A diagnostic method for a multicylinder internal combustion engine for detecting a rotational fluctuation between cylinders during lean-burn operation of the engine and determining occurrence of malfunction pertaining to air-fuel ratio in a given cylinder based on the detected rotational fluctuation, the method comprising:
- determining that malfunction pertaining to the air-fuel ratio has occurred when degree of the rotational fluctuation is equal to or more than a first determination value;
determining that malfunction pertaining to the air-fuel ratio has not occurred when the degree of the rotational fluctuation is equal to or less than a second determination value that is smaller than the first determination value; and
changing mode of engine control when the degree of the rotational fluctuation is smaller than the first determination value and greater than the second determination value, so that;
the difference between torque generated in the given cylinder and torque generated in another cylinder becomes greater,the control for the given cylinder and that for the another cylinder are different, andthe torques are increased,wherein, after the changing, repeating the determining that malfunction pertaining to the air-fuel ratio has occurred.
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Accused Products
Abstract
A diagnostic method for a multicylinder internal combustion engine is provided. The method comprises determining that malfunction pertaining to the air-fuel ratio has occurred when degree of the rotational fluctuation is equal to or more than a first determination value; determining that malfunction pertaining to the air-fuel ratio has not occurred when the degree of the rotational fluctuation is equal to or less than a second determination value that is smaller than the first determination value; and changing mode of engine control when the degree of the rotational fluctuation is smaller than the first determination value and greater than the second determination value. After the changing, the determining that malfunction pertaining to the air-fuel ratio has occurred is repeated.
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Citations
9 Claims
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1. A diagnostic method for a multicylinder internal combustion engine for detecting a rotational fluctuation between cylinders during lean-burn operation of the engine and determining occurrence of malfunction pertaining to air-fuel ratio in a given cylinder based on the detected rotational fluctuation, the method comprising:
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determining that malfunction pertaining to the air-fuel ratio has occurred when degree of the rotational fluctuation is equal to or more than a first determination value; determining that malfunction pertaining to the air-fuel ratio has not occurred when the degree of the rotational fluctuation is equal to or less than a second determination value that is smaller than the first determination value; and changing mode of engine control when the degree of the rotational fluctuation is smaller than the first determination value and greater than the second determination value, so that; the difference between torque generated in the given cylinder and torque generated in another cylinder becomes greater, the control for the given cylinder and that for the another cylinder are different, and the torques are increased, wherein, after the changing, repeating the determining that malfunction pertaining to the air-fuel ratio has occurred. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A diagnostic system for a multicylinder internal combustion engine for detecting a rotational fluctuation between cylinders during lean-burn operation of the engine and determining occurrence of malfunction pertaining to an air-fuel ratio in a given cylinder based on the detected rotational fluctuation, the diagnostic system comprising:
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an electronic control unit including a CPU and memory having stored therein procedure steps executed by the CPU, the steps comprising; when degree of the rotational fluctuation is equal to or more than a first determination value, determining that malfunction pertaining to the air-fuel ratio has occurred; when the degree of the rotational fluctuation is equal to or less than a second determination value that is smaller than the first determination value, determining that malfunction pertaining to the air-fuel ratio has not occurred; and when the degree of the rotational fluctuation is smaller than the first determination value and greater than the second determination value, changing mode of engine control so that; the difference between torque generated in the given cylinder and torque generated in another cylinder becomes greater, the control for the given cylinder and that for the another cylinder are different, and the torques are increased, wherein the determining that malfunction pertaining to the air-fuel ratio has occurred is repeated.
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Specification