Patent ID: 12221912

DESCRIPTION OF EMBODIMENTS

The following will describe a straddled vehicle1of First Embodiment of the present teaching with reference toFIG.1andFIG.8. InFIG.1, the straddled vehicle1is a motorcycle. It is noted that the straddled vehicle of the present teaching is not limited to the motorcycle. The straddled vehicle1includes an engine2including a combustion chamber3, an exhaust unit4connected to the engine2, and a controller8. The exhaust unit4includes a three-way catalyst5configured to purify exhaust gas exhausted from the combustion chamber3, an upstream oxygen sensor6provided upstream of the three-way catalyst5in a flow direction of the exhaust gas, and a downstream oxygen sensor7provided downstream of the three-way catalyst5in the flow direction of the exhaust gas. The upstream oxygen sensor6and the downstream oxygen sensor7are configured to detect the oxygen concentration in the exhaust gas. The controller8is configured to execute a detachment determination process of determining whether the three-way catalyst5has been detached from the straddled vehicle1at least based on a signal input as a signal of the downstream oxygen sensor7. The positions of the three-way catalyst5, the upstream oxygen sensor6, and the downstream oxygen sensor7are not limited to those shown inFIG.1. As shown inFIG.8, the controller8includes a processor81, a non-transitory recording medium82, an upstream oxygen sensor interface83, and a downstream oxygen sensor interface84. The upstream oxygen sensor interface83is electrically connected to the upstream oxygen sensor6. The downstream oxygen sensor interface84is electrically connected to the downstream oxygen sensor7.

The following will describe Second to Ninth Embodiments of the present teaching with reference to graphs shown inFIG.2toFIG.6. Straddled vehicles1of Second to Ninth Embodiments encompass all features of First Embodiment.FIG.2toFIG.4show graphs for describing Second to Seventh Embodiments, whereasFIG.5andFIG.6show graphs for describing Eighth and Ninth Embodiments. In the graphs shown inFIG.2toFIG.6, UpO2 indicates the upstream oxygen sensor6and DnO2 indicates the downstream oxygen sensor7.FIG.2toFIG.6include a graph showing changes over time of a signal of the upstream oxygen sensor6and a signal of the downstream oxygen sensor7when the upstream oxygen sensor6and the downstream oxygen sensor7are not detached. The detachment determination processes described in Second to Ninth Embodiments are all detachment determination processes that are effective when the three-way catalyst5is detached but the upstream oxygen sensor6and the downstream oxygen sensor7are not detached. In Second to Ninth Embodiments, a signal input to the controller8as a signal of the downstream oxygen sensor7is simply termed a signal of the downstream oxygen sensor7, and a signal input to the controller8as a signal of the upstream oxygen sensor6is simply termed a signal of the upstream oxygen sensor6. In Second to Ninth Embodiments, the upstream oxygen sensor6and the downstream oxygen sensor7are O2 sensors. The controller8of each of Second to Eighth Embodiments determines, in the detachment determination process, whether the three-way catalyst5has been detached based on both a signal of the upstream oxygen sensor6and a signal of the downstream oxygen sensor7. The controller8of Ninth Embodiment determines, in the detachment determination process, whether the three-way catalyst5has been detached not based on a signal of the upstream oxygen sensor6but based on a signal of the downstream oxygen sensor7. In each of Second to Ninth Embodiments, the controller8is configured to perform feedback control of controlling a fuel amount supplied to the combustion chamber3based on a signal of the upstream oxygen sensor6. The feedback control includes at least feedback control FBα which is normal feedback control. The feedback control FBα is equivalent to first feedback control of the present teaching.

To begin with, Second and Third Embodiments will be described with reference to the graphs shown inFIG.2toFIG.4. In Second and Third Embodiments, the feedback control includes feedback control FBβ of controlling the fuel amount in such a way that the cycle of increase and decrease of the fuel amount is longer than the cycle in the feedback control FBα and/or the amplitude of increase and decrease of the fuel amount is larger than the amplitude in the feedback control FBα. Furthermore, in Second and Third Embodiments, the feedback control includes feedback control FBγ of controlling the fuel amount in such a way that the cycle of increase and decrease of the fuel amount is longer than the cycle in the feedback control FBβ and/or the amplitude of increase and decrease of the fuel amount is larger than the amplitude in the feedback control FBβ. The controller8of Second Embodiment determines, in the detachment determination process, whether the three-way catalyst5has been detached based on both a signal of the upstream oxygen sensor6and a signal of the downstream oxygen sensor7while the feedback control FBγ is in execution. The controller8of Second Embodiment is configured to execute a deterioration determination process of determining whether the three-way catalyst5has been deteriorated, based on both a signal of the upstream oxygen sensor6and a signal of the downstream oxygen sensor7while the feedback control FBβ is in execution. On the other hand, the controller8of Third Embodiment determines, in the detachment determination process, whether the three-way catalyst5has been detached based on both a signal of the upstream oxygen sensor6and a signal of the downstream oxygen sensor7while the feedback control FBβ is in execution. The controller8of Third Embodiment is configured to execute a deterioration determination process of determining whether the three-way catalyst5has been deteriorated, based on both a signal of the upstream oxygen sensor6and a signal of the downstream oxygen sensor7while the feedback control FBγ is in execution. In other words, in Second and Third Embodiments, the feedback control for executing the detachment determination process is different from the feedback control for executing the deterioration determination process and the normal feedback control. In Second Embodiment, the feedback control FBβ is equivalent to third feedback control of the present teaching, and the feedback control FBγ is equivalent to second feedback control of the present teaching. In Third Embodiment, the feedback control FBβ is equivalent to the second feedback control of the present teaching, and the feedback control FBγ is equivalent to the third feedback control of the present teaching. The cycle and amplitude of increase and decrease of the fuel amount in the feedback control FBβ in Second Embodiment may be identical with the cycle and amplitude of increase and decrease of the fuel amount in the feedback control FBγ in Third Embodiment. Each of the graphs inFIG.2toFIG.4shows changes over time of the fuel amount, a signal of the upstream oxygen sensor6, and a signal of the downstream oxygen sensor7when three feedback controls FBα, FBβ, and FBγ are executed.FIG.2shows changes over time of the fuel amount, a signal of the upstream oxygen sensor6, and a signal of the downstream oxygen sensor7, when the three-way catalyst5is not detached and not deteriorated.FIG.3shows changes over time of the fuel amount, a signal of the upstream oxygen sensor6, and a signal of the downstream oxygen sensor7, when the three-way catalyst5is not detached but is deteriorated.FIG.4shows changes over time of the fuel amount, a signal of the upstream oxygen sensor6, and a signal of the downstream oxygen sensor7, when the three-way catalyst5is detached.

The controller8of Second Embodiment determines, in the detachment determination process, whether the three-way catalyst5has been detached based on an oxygen sensor delay time Tγ that is a delay time of a change of a signal of the downstream oxygen sensor7from a change of a signal of the upstream oxygen sensor6while the feedback control FBγ is in execution in the detachment determination process. The controller8of Second Embodiment determines in the detachment determination process that the three-way catalyst5has been detached, when the oxygen sensor delay time Tγ while the feedback control FBγ is in execution is shorter than a threshold X1. InFIG.2toFIG.4, the oxygen sensor delay time Tγ is a time from a point at which the signal of the upstream oxygen sensor6becomes equal to a value A1equidistant from a first voltage V1and a second voltage V2to a point at which the signal of the downstream oxygen sensor7becomes equal to the value A1. The controller8of Second Embodiment determines in the deterioration determination process that the three-way catalyst5has been deteriorated, when an oxygen sensor delay time Tβ while the feedback control FBβ is in execution is shorter than a threshold X2. InFIG.2toFIG.4, the oxygen sensor delay time Tβ is a time from a point at which the signal of the upstream oxygen sensor6becomes equal to a value A1equidistant from a first voltage V1and a second voltage V2to a point at which the signal of the downstream oxygen sensor7becomes equal to the value A1. The threshold X2may be larger than or smaller than the threshold X1, or may be equal to the threshold X1. As shown inFIG.3andFIG.4, a difference between the oxygen sensor delay time Tγ when the three-way catalyst5is detached and the feedback control FBγ is in execution and the oxygen sensor delay time Tγ when the three-way catalyst5is deteriorated and the feedback control FBγ is in execution is larger than a difference between the oxygen sensor delay time Tβ when the three-way catalyst5is detached and the feedback control FBβ is in execution and the oxygen sensor delay time Tβ when the three-way catalyst5is deteriorated and the feedback control FBβ is in execution. On this account, by executing the detachment determination process in the feedback control FBγ in which the cycle and amplitude of increase and decrease of the fuel amount are longer (larger) than those of the feedback control FBβ for executing the deterioration determination process, it is possible to improve the determination precision of the detachment determination process. As a modification of Second Embodiment, in the detachment determination process, the controller8may determine whether the three-way catalyst5has been detached by comparing the delay time Tγ while the feedback control FBγ is in execution with the delay time Tγ while the feedback control FBγ prior to the current detachment determination process is in execution.

The controller8of Third Embodiment determines, in the detachment determination process, whether the three-way catalyst5has been detached based on an oxygen sensor delay time Tβ that is a delay time of a change of a signal of the downstream oxygen sensor7from a change of a signal of the upstream oxygen sensor6while the feedback control FBβ is in execution in the detachment determination process. The controller8of Third Embodiment determines in the detachment determination process that the three-way catalyst5has been detached, when the oxygen sensor delay time Tβ while the feedback control FBβ is in execution is shorter than a threshold X3. The controller8of Third Embodiment determines in the deterioration determination process that the three-way catalyst5has been deteriorated, when the oxygen sensor delay time Tγ while the feedback control FBγ is in execution is shorter than a predetermined threshold. The predetermined threshold is larger than the threshold X3. The feedback control FBγ for executing the deterioration determination process is performed in known straddled vehicles, too. Because the feedback control FBβ for executing the detachment determination process is shorter (smaller) in cycle and amplitude of increase and decrease of the fuel amount than the feedback control FBγ for executing the deterioration determination process, it is possible to suppress the deterioration of drivability as compared to the known straddled vehicles. As a modification of Third Embodiment, in the detachment determination process, the controller8may determine whether the three-way catalyst5has been detached by comparing the delay time Tβ while the feedback control FBβ is in execution with the delay time Tβ while the feedback control FBβ prior to the current detachment determination process is in execution.

Now, Fourth and Fifth Embodiments will be described with reference to the graphs shown inFIG.2toFIG.4. In Fourth and Fifth Embodiment, the feedback control includes feedback control FBβ of controlling the fuel amount in such a way that the cycle of increase and decrease of the fuel amount is longer than the cycle in the feedback control FBα and/or the amplitude of increase and decrease of the fuel amount is larger than the amplitude in the feedback control FBα. The controller8of each of Fourth and Fifth Embodiments determines, in the detachment determination process, whether the three-way catalyst5has been detached based on both a signal of the upstream oxygen sensor6and a signal of the downstream oxygen sensor7while the feedback control FBβ is in execution. In Fourth and Fifth Embodiments, the controller8is configured to execute a deterioration determination process of determining whether the three-way catalyst5has been deteriorated, based on both a signal of the upstream oxygen sensor6and a signal of the downstream oxygen sensor7while the feedback control FBβ is in execution. In other words, in Fourth and Fifth Embodiments, the feedback control for executing the detachment determination process is identical with the feedback control for executing the deterioration determination process. In Fourth and Fifth Embodiments, the feedback control FBβ is equivalent to the second feedback control. The controller8of each of Fourth and Fifth Embodiments determines, in the detachment determination process, whether the three-way catalyst5has been detached based on an oxygen sensor delay time Tβ that is a delay time of a change of a signal of the downstream oxygen sensor7from a change of a signal of the upstream oxygen sensor6while the feedback control FBβ is in execution in the detachment determination process. The controller8of Fourth Embodiment determines in the detachment determination process that the three-way catalyst5has been detached, when the oxygen sensor delay time Tβ while the feedback control FBβ is in execution is shorter than a threshold X3. The controller8of Fourth Embodiment determines in the deterioration determination process that the three-way catalyst5has been deteriorated, when the oxygen sensor delay time Tβ while the feedback control FBβ is in execution is not shorter than the threshold X3and shorter than the threshold X2. The controller8of Fifth Embodiment determines in the detachment determination process that the three-way catalyst5has been detached, when the oxygen sensor delay time Tβ while the feedback control FBβ is in execution is shorter than an average of the oxygen sensor delay times Tβ while the feedback controls FBβ prior to the current detachment determination process are in execution and a difference between the oxygen sensor delay time Tβ and the average is larger than a reference value Y1. As a modification of Fourth and Fifth Embodiments, the controller8may execute the deterioration determination process and the detachment determination process based on a signal of the upstream oxygen sensor and a signal of the downstream oxygen sensor while the feedback control FBγ is in execution. In this modification, the feedback control FBγ is equivalent to the second feedback control.

Now, Sixth to Eighth Embodiments will be described with reference to the graphs shown inFIG.2toFIG.4. The controller8of each of Sixth to Eighth Embodiments determines, in the detachment determination process, whether the three-way catalyst5has been detached based on both a signal of the upstream oxygen sensor6and a signal of the downstream oxygen sensor7while the feedback control FBα is in execution. In Sixth to Eighth Embodiments, the feedback control FBα is executed irrespective of whether to execute the detachment determination process. The controller8of each of Sixth and Seventh Embodiments determines, in the detachment determination process, whether the three-way catalyst5has been detached based on an oxygen sensor delay time Ta that is a delay time of a change of a signal of the downstream oxygen sensor7from a change of a signal of the upstream oxygen sensor6while the feedback control FBα is in execution in the detachment determination process. The controller8of Sixth Embodiment determines in the detachment determination process that the three-way catalyst5has been detached, when the oxygen sensor delay time Tα while the feedback control FBα is in execution is shorter than a threshold X4. InFIG.2toFIG.4, the oxygen sensor delay time Tα is a time from a point at which the signal of the upstream oxygen sensor6becomes equal to a value A1equidistant from a first voltage V1and a second voltage V2to a point at which the signal of the downstream oxygen sensor7becomes equal to the value A1. The controller8of Seventh Embodiment determines in the detachment determination process that the three-way catalyst5has been detached, when the oxygen sensor delay time Tα while the feedback control FBα is in execution is shorter than an average of the oxygen sensor delay times Ta while the feedback controls FBα prior to the current detachment determination process are in execution and a difference between the oxygen sensor delay time Tα and the average is larger than a reference value Y2.

The controller8of Eighth Embodiment determines, in the detachment determination process, whether the three-way catalyst5has been detached based on the number of changes of the signal of the upstream oxygen sensor6during a first time period in which the feedback control FBα is in execution and the number of changes of the signal of the downstream oxygen sensor7during the first time period. The controller8of Eighth Embodiment determines, in the detachment determination process, that the three-way catalyst5has been detached when the number of changes of the signal of the upstream oxygen sensor6during the first time period is larger than a threshold Z1and the number of changes of the signal of the downstream oxygen sensor7during the first time period is larger than a threshold Z2. The first time period may be, for example, a period of several seconds. The number of changes of the signal of the upstream oxygen sensor6during the first time period may be, for example, the number of times when the signal of the upstream oxygen sensor6becomes at the second voltage V2during the first time period, or the number of times when the signal of the upstream oxygen sensor6becomes at the value A1. The number of changes of the signal of the downstream oxygen sensor7during the first time period may be, for example, the number of times when the signal of the downstream oxygen sensor7becomes at the second voltage V2during the first time period, or the number of times when the signal of the downstream oxygen sensor7becomes at the value A1. As shown inFIG.3andFIG.4, between the same periods in which the feedback control FBα is in execution, the number of changes of the signal of the downstream oxygen sensor7when the three-way catalyst5is detached tends to be larger than the number of changes of the signal of the downstream oxygen sensor7when the three-way catalyst5is deteriorated. On this account, it is less likely to mistake a case where the three-way catalyst5is deteriorated for a case where the three-way catalyst5is detached. It is possible to execute the detachment determination process without needing, for the detachment determination process, feedback control that is different from the normal feedback control.

Now, Ninth and Tenth Embodiments will be described with reference to the graphs shown inFIG.5toFIG.6. In Ninth and Tenth Embodiments, the controller8executes the detachment determination process by utilizing fuel cut control of temporarily stopping supply of fuel to the combustion chamber3. In Ninth and Tenth Embodiments, the controller8executes the detachment determination process by utilizing at least a signal of the downstream oxygen sensor7when the feedback control FBα is shifted to the fuel cut control. Each of the graphs inFIG.5andFIG.6shows changes over time of a signal of the upstream oxygen sensor6and a signal of the downstream oxygen sensor7when the feedback control FBα is shifted to the fuel cut control. The graph ofFIG.5shows changes over time of a flag of the fuel cut control, a signal of the upstream oxygen sensor6, and a signal of the downstream oxygen sensor7when the three-way catalyst5is not detached. The graph ofFIG.6shows changes over time of a flag of the fuel cut control, a signal of the upstream oxygen sensor6, and a signal of the downstream oxygen sensor7when the three-way catalyst5is detached. The controller8of Ninth Embodiment determines, in the detachment determination process, whether the three-way catalyst5has been detached based on a delay time Tψ of a change of a signal of the downstream oxygen sensor7while the fuel cut control is in execution from a change of a signal of the upstream oxygen sensor6while the feedback control FB a or the fuel cut control is in execution. The controller8of Ninth Embodiment determines in the detachment determination process that the three-way catalyst5has been detached, when the delay time Tψ is shorter than a threshold X5. InFIG.5andFIG.6, the delay time Tψ is a time from a point at which the signal of the upstream oxygen sensor6becomes equal to a value A1equidistant from a first voltage V1and a second voltage V2to a point at which the signal of the downstream oxygen sensor7becomes equal to the value A1. To be more specific, the delay time Tψ is a time from a point at which the signal of the upstream oxygen sensor6becomes equal to the value A1immediately before the signal becomes constant at the second voltage V2to a point at which the signal of the downstream oxygen sensor7becomes equal to the value A1. While inFIG.5andFIG.6the signal of the upstream oxygen sensor6becomes equal to the value A1during the fuel cut control, the signal of the upstream oxygen sensor6may become equal to the value A1during the feedback control FBα. The controller8of Tenth Embodiment determines, in the detachment determination process, whether the three-way catalyst5has been detached based on a delay time Tω of a change of a signal of the downstream oxygen sensor7while the fuel cut control is in execution from the start of the fuel cut control. The controller8of Tenth Embodiment determines in the detachment determination process that the three-way catalyst5has been detached, when the delay time Tω is shorter than a threshold X6. InFIG.5andFIG.6, the delay time Tω is a time from the start of the fuel cut control to a time point at which the signal of the downstream oxygen sensor7becomes equal to a value A1which is equidistant from the first voltage V1and the second voltage V2. As a modification of Ninth and Tenth Embodiments, the controller8may determine in the detachment determination process whether the three-way catalyst5has been detached, by comparing the delay time Ty, To with the delay time Tψ, Tω at the time of the shift from the feedback control FBα to the fuel cut control prior to the current detachment determination process.

The following will describe Eleventh Embodiment of the present teaching. A straddled vehicle1of Eleventh Embodiment encompasses all features of First Embodiment. The controller8of Eleventh Embodiment determines in the detachment determination process whether a signal that is input as a signal of the downstream oxygen sensor7is a signal that is input to the controller8not electrically connected to the downstream oxygen sensor7. When it is determined that a signal input as a signal of the downstream oxygen sensor7is a signal input to the controller8not electrically connected to the downstream oxygen sensor7, the controller8determines that the three-way catalyst5has been detached. Therefore, when a signal that is input as a signal of the downstream oxygen sensor7is a signal that is input when the downstream oxygen sensor7is detached from the straddled vehicle1, the controller8determines that the three-way catalyst5has been detached.FIG.7Ashows an example of the signal that is input to the controller8as the signal of the downstream oxygen sensor7when the downstream oxygen sensor7is detached. The signal input to the controller8as a signal of the downstream oxygen sensor7when the downstream oxygen sensor7is detached is different from a signal input to the controller8as a signal of the downstream oxygen sensor7when the downstream oxygen sensor7is not detached. The same applies to the upstream oxygen sensor6. For example, when the downstream oxygen sensor7is an O2 sensor, a signal that is at neither the first voltage V1nor the second voltage V2shown inFIG.2toFIG.6is input to the controller8. The straddled vehicle1may be arranged so that, when the three-way catalyst5is detached from the straddled vehicle1, the downstream oxygen sensor7is detached together with the three-way catalyst5. In such a case, when the downstream oxygen sensor7is detached, the three-way catalyst5is assumed to be detached, too. Even if the straddled vehicle1is not structured in this way, when the three-way catalyst5is detached from the straddled vehicle1, the downstream oxygen sensor7is likely to be detached, too. It is therefore possible to determine whether the three-way catalyst5has been detached based on a signal input as a signal of the downstream oxygen sensor7.

The following will describe Twelfth Embodiment of the present teaching. A straddled vehicle1of Twelfth Embodiment encompasses all features of First Embodiment. The controller8of Twelfth Embodiment determines in the detachment determination process whether a signal that is input as a signal of the upstream oxygen sensor6is a signal that is input to the controller8not electrically connected to the upstream oxygen sensor6and a signal that is input as a signal of the downstream oxygen sensor7is a signal that is input to the controller8not electrically connected to the downstream oxygen sensor7. When it is determined that a signal input as a signal of the upstream oxygen sensor6is a signal input to the controller8not electrically connected to the upstream oxygen sensor6and a signal input as a signal of the downstream oxygen sensor7is a signal input to the controller8not electrically connected to the downstream oxygen sensor7, the controller determines that the three-way catalyst5has been detached. Therefore, when a signal that is input as a signal of the upstream oxygen sensor6is a signal that is input when the upstream oxygen sensor6is detached from the straddled vehicle1and a signal that is input as a signal of the downstream oxygen sensor7is a signal that is input when the downstream oxygen sensor7is detached from the straddled vehicle1, the controller8determines that the three-way catalyst5has been detached.FIG.7Bshows an example of a signal that is input to the controller8as a signal of the upstream oxygen sensor6and a signal that is input to the controller8as a signal of the downstream oxygen sensor7, when the upstream oxygen sensor6and the downstream oxygen sensor7are detached. The straddled vehicle1may be arranged so that, when the three-way catalyst5is detached from the straddled vehicle1, the upstream oxygen sensor6and the downstream oxygen sensor7are detached together with the three-way catalyst5. In such a case, when the upstream oxygen sensor6and the downstream oxygen sensor7are detached, the three-way catalyst5is assumed to be detached, too. Even if the straddled vehicle1is not structured in this way, when the three-way catalyst5is detached from the straddled vehicle1, the upstream oxygen sensor6and the downstream oxygen sensor7are likely to be detached, too. It is therefore possible to determine whether the three-way catalyst5has been detached based on a signal input as a signal of the upstream oxygen sensor6and a signal input as a signal of the downstream oxygen sensor7. Because both a signal input as a signal of the upstream oxygen sensor6and a signal input as a signal of the downstream oxygen sensor7are used, the precision of determination in the detachment determination process can be improved as compared to Eleventh Embodiment.

Second to Twelfth Embodiment may be implemented in combination. In other words, the controller8may be arranged to have two or more of the detachment determination processes of Second to Twelfth Embodiments. For example, the controller8of each of Second and Third Embodiments may be arranged to perform the detachment determination process of Fourth Embodiment or Fifth Embodiment. For example, the controller8of each of Second to Fifth Embodiments may be arranged to perform the detachment determination process of any one of Sixth Embodiment to Eighth Embodiment. For example, the controller8of each of Second to Eighth Embodiments may be arranged to perform the detachment determination process of Ninth Embodiment or Tenth Embodiment. The controller8of each of Second to Tenth Embodiments may be arranged to perform the detachment determination process of Eleventh Embodiment or Twelfth Embodiment.

The controller8of each of First to Twelfth Embodiments may be configured to further execute a detachment determination process of determining whether the three-way catalyst5has been detached based not on a signal input as a signal of the downstream oxygen sensor7but on a signal input as a signal of the upstream oxygen sensor6. For example, the controller8may execute the detachment determination process of determining that the three-way catalyst5has been detached, when a signal that is input as a signal of the upstream oxygen sensor6is a signal that is input when the upstream oxygen sensor6is detached from the straddled vehicle1. A controller of a straddled vehicle may be arranged to execute only this detachment determination process, although such an arranged is not encompassed in the present teaching.

The controller8of each of First to Twelfth Embodiments may be arranged to further execute a detachment determination process of determining whether the three-way catalyst5has been detached based on a signal of a detection unit that is neither the upstream oxygen sensor6nor the downstream oxygen sensor7. A controller of a straddled vehicle may be arranged to execute only this detachment determination process, although such an arranged is not encompassed in the present teaching. The detection unit may be a sensor exclusively used for the detachment determination process. The detection unit may be a sensor that is used for a process or control different from the detachment determination process. The detection unit used for a process or control different from the detachment determination process may be an intake pressure sensor. The detection unit exclusively used for the detachment determination process may be, for example, a camera which is configured to read a two-dimensional barcode provided on an outer surface of a catalyst unit that is detached together with the three-way catalyst. When one-dimensional barcode is provided in place of the two-dimensional barcode, the detection unit exclusively used for the detachment determination process may be a line sensor. The detection unit may be an exhaust gas temperature sensor configured to detect the temperature sensor of exhaust gas. The exhaust gas temperature sensor may be provided downstream or upstream of the three-way catalyst in a flow direction of the exhaust gas. The exhaust gas temperature sensor may be used exclusively for the detachment determination process, or may be used for a process or control different from the detachment determination process. The detection unit may be an exhaust gas pressure sensor configured to detect the pressure of exhaust gas. The exhaust gas pressure sensor may be provided downstream or upstream of the three-way catalyst in a flow direction of the exhaust gas. The exhaust gas pressure sensor may be used exclusively for the detachment determination process, or may be used for a process or control different from the detachment determination process.