Methods and systems are provided for reducing blackening of an oxygen sensor due to voltage excursions into an over-potential region. Before transitioning the sensor from a lower voltage to an upper voltage during variable voltage operation, an operating temperature of the sensor is reduced via adjustments to a sensor heater setting. The reduction in temperature increases the range of temperatures available to the sensor before the over-potential region is entered.

An engine ignition timing control method includes: acquiring, by an engine control unit (ECU), intake air humidity of an engine using a humidity sensor; calculating, by the ECU, an amount of first ignition timing correction based on the intake air humidity and an EGR rate; calculating, by the ECU, an amount of second ignition timing correction based on an engine operation region; and correcting, by the ECU, ignition timing of the engine using the amount of first ignition timing correction and the amount of second ignition timing correction.

An internal combustion engine control device includes an engine state estimation unit, a wall surface temperature estimation unit, and an operation amount calculation unit. The engine state estimation unit calculates the energy transfer amount from the gas to the wall surface based on the parameter related to the operating condition, the parameter related to the chemical condition of combustion, and the parameter related to an operation status. The wall surface temperature estimation unit estimates the wall surface temperature on the basis of the energy transfer amount from the gas to the wall surface. The operation amount calculation unit calculates an operation amount of an actuator provided in the internal combustion engine on the basis of the wall surface temperature estimated by the wall surface temperature estimation unit.

An engine ignition timing control method includes: acquiring, by an engine control unit (ECU), intake air humidity of an engine using a humidity sensor; calculating, by the ECU, an amount of first ignition timing correction based on the intake air humidity and an EGR rate; calculating, by the ECU, an amount of second ignition timing correction based on an engine operation region; and correcting, by the ECU, ignition timing of the engine using the amount of first ignition timing correction and the amount of second ignition timing correction.

A diagnostic function of a humidity sensor is exposed to the outside and the humidity sensor is likely to deteriorate.

An aspect of the present invention includes: a capacitance-voltage conversion circuit which includes a plurality of reference capacitors having different pieces of capacitance and a switch which switches the reference capacitors and outputs a voltage according to the capacitance of a humidity sensor; and a diagnosis unit which compares an output voltage of the capacitance-voltage conversion circuit with a reference voltage obtained from a reference characteristic of the humidity sensor and diagnoses the humidity sensor based on a comparison result. Also, the diagnosis unit changes the output voltage by changing the capacitance of the capacitance-voltage conversion circuit using the switch in a state in which the output voltage of the capacitance-voltage conversion circuit is within a certain range and compares the changed output voltage with the reference voltage.

Methods and systems are provided for an engine. In one example, a method comprises stopping an engine via a soft-stop method in response to a likelihood of condensate forming being less than or equal to a threshold likelihood. The method further comprises stopping the engine via an exhaust gas evacuation method in response to the likelihood of condensate forming being greater than the threshold likelihood.

Various methods and systems are provided for controlling emissions and a likelihood of engine knock during combustion in a multi-fuel engine. A method for an engine includes mixing an amount of a first fuel and an amount of a second fuel to combust a fuel mixture having a fuel ratio of the first fuel relative to the second fuel, the first fuel having a faster combustion flame speed relative to the second fuel, the fuel mixture having an air-to-fuel ratio with an amount of air delivered to the engine. The method further includes controlling either or both of a speed of combustion and a stability of combustion of the fuel mixture with the amount of air delivered to the engine by changing at least one of the fuel ratio, the air-to-fuel ratio, or both of the fuel ratio and the air-to-fuel ratio.

The invention relates to a method for operating an internal combustion engine comprising: determining a first set point value of a volume of air to be taken into the combustion chamber of the internal combustion engine within one working cycle thereof by retrieving the first set point value from a first characteristic map stored in a memory device of an electronic computing device as a function of a current engine speed of the internal combustion engine and as a function of a torque to be provided by the internal combustion engine; and determining a second set point value by retrieving the second set point value from a second characteristic map stored in the memory device of the electronic computing device as a function of a current engine speed of the internal combustion engine and as a function of a current volume of air supplied to the combustion chamber.

The present invention obtains a humidity measuring device capable of performing self-diagnosis with high reliability. This humidity measuring device 20 has a diagnosis processing unit 25 for performing self-diagnosis by using gas temperatures and gas humidities before and after a gas in an ambient atmosphere to be measured is heat-controlled. The diagnosis processing unit has a diagnosis start determining unit 26 for determining whether the self-diagnosis can be started on the basis of an exchange state in the ambient atmosphere to be measured and the gas temperature and the gas humidity before the gas in the ambient atmosphere to be measured is heat-controlled, and a diagnosis continuation determining unit 28 for determining whether the self-diagnosis can be continued on the basis of the gas temperature and the gas humidity that are heat-controlled during the self-diagnosis.

An internal combustion engine has a humidity sensor that is disposed in an intake passage of the internal combustion engine, a temperature sensor configured to detect an intake air temperature in a position of the humidity sensor, and a controller configured to correct an offset error of the sensor value by adding a correction value to the sensor value. The controller is configured to acquire the intake air temperatures respectively at a plurality of timings in a process of the intake air temperature changing, acquire the sensor values at the respective plurality of timings, calculate values excluding influences of temperature differences of the intake air temperatures from the respective sensor values as humidity index values respectively, and determine a correction value so that a variation degree of the humidity index values becomes small.