Methods and systems are provided for an exhaust system. In one example, a method may include determining presence of a zone flow based on a comparison of a first exhaust sensor and a second exhaust sensor. The presence or absence of the zone flow may determine a rate at which an air-fuel ratio is adjusted.

An exhaust device in which an exhaust passage wraps around from a front side of an engine to a lower side of the engine and extends to a rear side is provided. The exhaust device includes a catalyst configured to purify exhaust gas in the exhaust passage and disposed in front of the engine, and a gas sensor disposed on a wall surface of the exhaust passage at an upstream side than the catalyst. The gas sensor is disposed in front of the engine so as to be directed toward the engine.

The probability of a heater portion of a sensor element being exposed to water is lowered. The sensor element includes a built-in heater that extends in a longitudinal direction and a surrounding housing extending in the longitudinal direction. The heater includes a heat generation portion and a lead portion. The heat generation portion has a front end and a rear end, and is positioned on the same side as a front end portion side of the sensor element. The housing includes an enlarged diameter portion having a diameter of an inner wall that increases in a direction toward the front end of the sensor. The enlarged diameter portion includes a front end portion and a rear end portion. The rear end of the heat generation portion is located closer to the front end of the sensor than the rear end portion of the enlarged diameter portion is.

An exhaust gas aftertreatment system includes: a first sensor configured to measure a parameter in the exhaust gas aftertreatment system; a second sensor configured to measure the parameter in the exhaust gas aftertreatment system, the second sensor disposed proximate the first sensor; and at least one controller configured to simultaneously receive sensor values from the first sensor and receive sensor values from the second sensor.

A method for ascertaining an exhaust gas composition of an exhaust gas of an internal combustion engine with regard to an ammonia fraction and a nitrogen oxides fraction in an exhaust gas system including an SCR catalytic converter. The method includes detecting, using a sensor, a first signal whose magnitude is a function of the nitrogen oxides fraction of the exhaust gas upstream from the SCR catalytic converter, detecting using a sensor a second signal whose magnitude is a function of the ammonia fraction and the nitrogen oxides fraction of the exhaust gas downstream from the SCR catalytic converter, storing the two signals over an observation period, and ascertaining the ammonia fraction and optionally the nitrogen oxides fraction of the exhaust gas downstream from the at least one SCR catalytic converter using a calculation rule that uses the two signals during the observation period as input variables.

A method for monitoring a gas sensor (14) which comprises two electrochemical measuring cells (20, 30) and which is arranged in an exhaust tract (10) of an internal combustion engine (11), wherein the sensor elements (20, 30) exhibit a substantially identical sensitivity towards a first gas component and a different sensitivity towards a second gas component and are insensitive towards further gas components. In an operating state in which an exhaust gas stream at the gas sensor (14) contains less of the second gas component than of the first gas component a concentration of the first gas component is calculated from each of the sensor signals from the sensor elements (20, 30) and a defect in a sensor element (20, 30) is deduced from the concentrations of the first gas component.

A tractor including: an engine mounted on a traveling body; a post-processing device configured to purify exhaust gas of the engine; and a tail pipe long in an up-down direction and configured to emit exhaust gas having passed through the post-processing device to the outside. The post-processing device is arranged in a standing posture in front of an operation unit on the traveling body so that the exhaust gas flows from the bottom to the top. An upwardly protruding outlet pipe is provided on an upper surface side of the post-processing device. The inner diameter of an exhaust gas inlet side of the tail pipe is set larger than the outer diameter of the outlet pipe which is inserted and communicated with the exhaust gas inlet side of the tail pipe.

A method for monitoring a concentration of a corrosive gas including at least observing at least one gas fuse, the gas fuse having at least one metal wire, which is configured for breaking due to corrosion if exposed to the corrosive gas in a way that a time-integrated concentration of the corrosive gas exceeds a critical value.

An exhaust gas aftertreatment system includes: a first sensor configured to measure a parameter in the exhaust gas aftertreatment system; a second sensor configured to measure the parameter in the exhaust gas aftertreatment system, the second sensor disposed proximate the first sensor; and at least one controller configured to alternately receive sensor values from the first sensor for a first target period of time, and receive sensor values from the second sensor for a second target period of time.

The control section of a control apparatus executes a first control for operating a voltage application section such as to cause a current to flow in a first direction through a gas sensor in a first period, and a second control for operating the voltage application section such as to cause a current to flow in a second direction, opposite to the first direction, through the gas sensor in a second period. The control apparatus changes the length of at least one of the first period and the second period based on a comparison between a first measurement value, which is the absolute value of a value measured by a sweep measurement section during execution of the first control, and a second measurement value, which is the absolute value of a value measured by the sweep measurement section during execution of the second control.