fuel injection control system

Abstract

To provide a fuel injection control system which properly sets a limit value of an air-fuel ratio feedback correction value, thereby making a good air-fuel ratio feedback control possible. While a variation rate of an output value of an oxygen sensor (32) is changed from the positive to the negative or from the negative to the positive predetermined times after a power source of a vehicle is turned on, a control unit (C) sets a first limit range (L1) for an air-fuel ratio feedback correction factor (K02) as an upper / lower limit value which have a predetermined upper / lower width, in which the output value of the oxygen sensor (32) detected in a stoicshiometric air-fuel ratio state is a reference value (B1), and which is allowed to be used for calculating a correction injection quantity (T1). After a variation rate of the output value of the oxygen sensor (32) is changed from the positive to the negative or from the negative to the positive predetermined times, the air-fuel ratio feedback correction factor (K02) that is calculated when the variation rate is changed the predetermined times is regarded as a reference value (B2), and a second limit range (L2) which has a predetermined upper / lower width from the reference value (B2) and is narrower than the first limit range (L1) is set.

Description

technical field [0001] The present invention relates to a fuel injection control system, and more particularly, to a fuel injection control system adapted to perform air-fuel ratio feedback control based on an output of an air-fuel ratio sensor. Background technique [0002] In the past, there has been known a fuel injection system in which feedback control of the fuel injection amount based on the air-fuel ratio is adapted for combustion in an internal combustion engine in a region close to the theoretical (theoretical) air-fuel ratio, so that The air-fuel ratio is detected by an air-fuel ratio sensor (oxygen sensor) provided at the exhaust pipe. When such air-fuel ratio feedback control is applied, if the feedback correction coefficient, that is, the feedback correction amount becomes too large or too small for any reason, there is a possibility of excessive enrichment or leaning. Therefore, in order to prevent this situation, it is considered to set a limit value for the...

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Problems solved by technology

[0005] However, in the technique described in Patent Document 1, the limit value of the air-fuel ratio feedback correction coefficient increases every time of warm-up operation, so there is a possibility that if the feedback correction amount becomes too large or hours, the warm-up operation will be performed in the state of over-rich or under-lean

Also, when the increment of the limit value is determined, any influence exerted on the air-fuel ratio by the height of the vehicle's use position, the accuracy of parts of the vehicle, changes at the time of installation, etc. is no longer considered.

In addition, the technique described in Patent Document 1 can only periodically perform failure checking, and cannot always monitor the state of the oxygen sensor because the failure checking is performed by monitoring the current generated by applying a reverse voltage to the oxygen sensor

In addition, if the learning of the air-fuel ratio feedback correction coefficient is adapted to be prohibited when the fault inspection is performed, it may happen that the output value of the oxygen sensor just before the fault inspection is started is used for the air-fuel ratio feedback control during the fault inspection, thereby causing the In the event that a sensor fails just before the fault check is started, there is a possibility that the combustion state during the fault check will become too rich or too lean

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