STRADDLED VEHICLE

Abstract

A straddled vehicle, including: an engine, which includes a combustion chamber; a three-way catalyst, which is configured to purify exhaust gas exhausted from the combustion chamber; an upstream oxygen sensor, which is provided upstream of the three-way catalyst in a flow direction of the exhaust gas, and is configured to detect an oxygen concentration in the exhaust gas; a downstream oxygen sensor, which is provided downstream of the three-way catalyst in the flow direction of the exhaust gas, and is configured to detect the oxygen concentration in the exhaust gas; and a controller, which includes a processor, and a non-transitory storage medium containing program instructions, execution of which by the processor causes the controller to execute a detachment determination process of determining whether the three-way catalyst is detached at least based on a signal input as a signal of the downstream oxygen sensor.

Claims

1. A straddled vehicle comprising: an engine, which includes a combustion chamber; a three-way catalyst, which is configured to purify exhaust gas exhausted from the combustion chamber; an upstream oxygen sensor, which is provided upstream of the three-way catalyst in a flow direction of the exhaust gas, and is configured to detect an oxygen concentration in the exhaust gas; a downstream oxygen sensor, which is provided downstream of the three-way catalyst in the flow direction of the exhaust gas, and is configured to detect the oxygen concentration in the exhaust gas; and a controller, which includes: a processor, and a non-transitory storage medium containing program instructions, execution of which by the processor causes the controller to execute a detachment determination process of determining whether the three-way catalyst is detached at least based on a signal input as a signal of the downstream oxygen sensor.

2. The straddled vehicle according to claim 1, wherein, in the detachment determination process, the controller is configured to determine whether the three-way catalyst is detached based on both a signal input as a signal of the upstream oxygen sensor and the signal input as the signal of the downstream oxygen sensor.

3. The straddled vehicle according to claim 2, wherein the controller is configured to perform feedback control of controlling a fuel amount supplied to the combustion chamber based on the signal input as the signal of the upstream oxygen sensor, the fuel amount increasing and decreasing with a cycle and an amplitude, the feedback control includes a first feedback control and a second feedback control, the cycle of the fuel amount in the second feedback control being longer than the cycle in the first feedback control, and/or the amplitude of the fuel amount in the second feedback control being larger than the amplitude in the first feedback control, and in the detachment determination process, the controller is configured to determine whether the three-way catalyst is detached based on both the signal input as the signal of the upstream oxygen sensor and the signal input as the signal of the downstream oxygen sensor, while the second feedback control is in execution.

4. The straddled vehicle according to claim 3, wherein, in the detachment determination process, the controller is configured to determine whether the three-way catalyst is detached based on an oxygen sensor delay time while the second feedback control is in execution, the oxygen sensor delay time being a time difference between a change of the signal input as the signal of the downstream oxygen sensor and a change of the signal input as the signal of the upstream oxygen sensor.

5. The straddled vehicle according to claim 4, wherein, in the detachment determination process, the controller is configured to determine whether the three-way catalyst is detached by comparing the oxygen sensor delay time while the second feedback control is in execution with a threshold.

6. The straddled vehicle according to claim 4, wherein the feedback control further includes another second feedback control that is prior to the second feedback control, and in the detachment determination process, the controller is configured to determine whether the three-way catalyst is detached by comparing the oxygen sensor delay time while the second feedback control is in execution with the oxygen sensor delay time while said another second feedback control is in execution.

7. The straddled vehicle according to claim 3, wherein, the controller is configured to execute a deterioration determination process of determining whether the three-way catalyst is deteriorated based on both the signal input as the signal of the upstream oxygen sensor and the signal input as the signal of the downstream oxygen sensor, while the second feedback control is in execution.

8. The straddled vehicle according to claim 3, wherein, the feedback control further includes a third feedback control, which is different from both the first feedback control and the second feedback control, and which controls the fuel amount in such a way that the cycle of the fuel amount in the third feedback control is longer than the cycle in the first feedback control, and/or the amplitude of the fuel amount in the third feedback control is larger than the amplitude in the first feedback control, and the controller is configured to execute a deterioration determination process of determining whether the three-way catalyst is deteriorated based on both the signal input as the signal of the upstream oxygen sensor and the signal input as the signal of the downstream oxygen sensor, while the third feedback control is in execution.

9. The straddled vehicle according to claim 2, wherein, the controller is configured to perform feedback control of controlling a fuel amount supplied to the combustion chamber based on the signal input as the signal of the upstream oxygen sensor, the fuel amount increasing and decreasing with a cycle and an amplitude, the feedback control includes a first feedback control and a second feedback control, the cycle of the fuel amount in the second feedback control being longer than the cycle in the first feedback control, and/or the amplitude of the fuel amount in the second feedback control being larger than the amplitude in the first feedback control, and in the detachment determination process, the controller is configured to determine whether the three-way catalyst is detached based on both the signal input as the signal of the upstream oxygen sensor and the signal input as the signal of the downstream oxygen sensor, while the first feedback control is in execution.

10. The straddled vehicle according to claim 9, wherein, when the signal input as the signal of the downstream oxygen sensor is changed while the first feedback control is in execution, the controller is configured to execute the detachment determination process of determining whether the three-way catalyst is detached based on an oxygen sensor delay time while the first feedback control is in execution, the oxygen sensor delay time being a time difference between the change of the signal input as the signal of the downstream oxygen sensor and a change of the signal input as the signal of the upstream oxygen sensor.

11. The straddled vehicle according to claim 10, wherein, in the detachment determination process, the controller is configured to determine whether the three-way catalyst is detached by comparing the oxygen sensor delay time while the first feedback control is in execution with a threshold.

12. The straddled vehicle according to claim 10, wherein the feedback control further includes another first feedback control that is prior to the first feedback control, and in the detachment determination process, the controller is configured to determine whether the three-way catalyst is detached by comparing the oxygen sensor delay time while the first feedback control is in execution with the oxygen sensor delay time while said another first feedback control is in execution.

13. The straddled vehicle according to claim 9, wherein, in the detachment determination process, the controller is configured to determine whether the three-way catalyst is detached based on a number of changes of the signal input as the signal of the upstream oxygen sensor during a first time period in which the first feedback control is in execution and a number of changes of the signal input as the signal of the downstream oxygen sensor during the first time period.

14. The straddled vehicle according to claim 2, wherein, the controller is configured to perform feedback control of controlling a fuel amount supplied to the combustion chamber based on the signal input as the signal of the upstream oxygen sensor, and when the feedback control shifts to a fuel cut control in which supply of fuel to the combustion chamber is paused, the controller is configured to execute the detachment determination process of determining whether the three-way catalyst is detached based on a time difference between a change of the signal input as the signal of the downstream oxygen sensor while the fuel cut control is in execution and a change of the signal input as the signal of the upstream oxygen sensor while the feedback control or the fuel cut control is in execution.

15. The straddled vehicle according to claim 1, wherein, the controller is configured to perform feedback control of controlling a fuel amount supplied to the combustion chamber based on the signal input as the signal of the upstream oxygen sensor, and when the feedback control shifts to a fuel cut control in which supply of fuel to the combustion chamber is paused, the controller is configured to execute the detachment determination process of determining whether the three-way catalyst is detached based on a time difference between a change of the signal input as the signal of the downstream oxygen sensor while the fuel cut control is in execution and a start of the fuel cut control.

16. The straddled vehicle according to claim 2, wherein, the controller is configured to determine, in the detachment determination process, that the three-way catalyst is detached, when the signal that is input as the signal of the upstream oxygen sensor is a signal that is input when the upstream oxygen sensor is detached from the straddled vehicle and the signal that is input as the signal of the downstream oxygen sensor is a signal that is input when the downstream oxygen sensor is detached from the straddled vehicle.

17. The straddled vehicle according to claim 1, wherein, in the detachment determination process, the controller is configured to determine that the three-way catalyst is detached when the signal input as the signal of the downstream oxygen sensor is a signal that is input when the downstream oxygen sensor is detached from the straddled vehicle.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0087] FIG. 1 is a side view of a straddled vehicle of First Embodiment of a first invention, a second invention, and a third invention.

[0088] FIG. 2 shows graphs for explaining Second to Seventh Embodiments of the first invention.

[0089] FIG. 3 shows graphs for explaining Eighth and Ninth Embodiments of the first invention.

DESCRIPTION OF EMBODIMENTS

[0090] The following will describe a straddled vehicle 1 of First Embodiment of the first invention, the second invention, and the third invention with reference to FIG. 1. The straddled vehicle 1 is a motorcycle. The straddled vehicle 1 includes an engine 2 including a combustion chamber 3, an exhauster 4 connected to the engine 2, and a controller 8 performing a detachment determination process. The exhauster 4 includes a three-way catalyst 5, an upstream oxygen sensor 6 provided upstream of the three-way catalyst 5 in a flow direction of the exhaust gas, and a downstream oxygen sensor 7 provided downstream of the three-way catalyst 5 in the flow direction of the exhaust gas.

[0091] The following will describe Second Embodiment of the present invention with reference to a graph shown in FIG. 2. In the graphs shown in FIG. 2 and later-described FIG. 3, UpO2 indicates the upstream oxygen sensor and DnO2 indicates the downstream oxygen sensor. In Second Embodiment of the first invention, the upstream oxygen sensor and the downstream oxygen sensor are O2 sensors. In Second Embodiment of the first invention, 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.

[0092] The graph of FIG. 2(a) shows changes over time of the fuel supply amount, a signal of the upstream oxygen sensor, and a signal of the downstream oxygen sensor, when the three-way catalyst is not detached and not deteriorated. The graph of FIG. 2(b) shows changes over time of the fuel supply amount, a signal of the upstream oxygen sensor, and a signal of the downstream oxygen sensor, when the three-way catalyst is not detached and is deteriorated. The graph of FIG. 2(c) shows changes over time of the fuel supply amount, a signal of the upstream oxygen sensor, and a signal of the downstream oxygen sensor, when the three-way catalyst is detached. Each of the graphs in FIG. 2(a) to FIG. 2(c) shows changes over time of the fuel supply amount, a signal of the upstream oxygen sensor, and a signal of the downstream oxygen sensor when three feedback controls FB, FB, and FB are executed. The feedback control FB is normal feedback control. In Second Embodiment of the first invention, the feedback control FB is equivalent to first feedback control. In Second Embodiment of the first invention, the feedback control FB is feedback control for performing the deterioration determination process and is equivalent to the third feedback control. In Second Embodiment of the first invention, the feedback control FB is feedback control for performing the detachment determination process and is equivalent to the second feedback control.

[0093] The controller of Second Embodiment of the first invention determines that, in the detachment determination process, the three-way catalyst has been detached when an oxygen sensor delay time T that is a delay time of a change of a signal of the downstream oxygen sensor from a change of a signal of the upstream oxygen sensor while the feedback control FB is in execution is shorter than a threshold X1. In FIG. 2, the delay time T is a time from a point at which the signal of the upstream oxygen sensor becomes equal to a value Al equidistant from a first voltage V1 and a second voltage V2 to a point at which the signal of the downstream oxygen sensor becomes equal to the value A1.

[0094] The controller of Second Embodiment of the first invention determines in the deterioration determination process that the three-way catalyst has been deteriorated, when an oxygen sensor delay time T that is a delay time of a change of a signal of the downstream oxygen sensor from a change of a signal of the upstream oxygen sensor while the feedback control FB is in execution is shorter than a threshold X2. In FIG. 2, the delay time T is a time from a point at which the signal of the upstream oxygen sensor becomes equal to a value A1 equidistant from a first voltage V1 and a second voltage V2 to a point at which the signal of the downstream oxygen sensor becomes equal to the value A1. The threshold X2 may be larger than or smaller than the threshold X1, or may be equal to the threshold X1.

[0095] As shown in FIG. 2, a difference between the oxygen sensor delay time T when the three-way catalyst is detached and the feedback control FB is in execution and the oxygen sensor delay time T when the three-way catalyst is deteriorated and the feedback control FB is in execution is smaller than a difference between the oxygen sensor delay time TO when the three-way catalyst is detached and the feedback control FB is in execution and the oxygen sensor delay time T when the three-way catalyst is deteriorated and the feedback control FB is in execution. Therefore, because the feedback control for the detachment determination process is different from the feedback control for the deterioration determination process, the precision of the detachment determination process is improved as compared to a case where the feedback control for the detachment determination process is identical with the feedback control for the deterioration determination process.

[0096] The following will describe Third and Fourth Embodiments of the first invention with reference to a graph shown in FIG. 2. In Third and Fourth Embodiments of the first invention, the upstream oxygen sensor and the downstream oxygen sensor are O2 sensors. In Third and Fourth Embodiments of the first invention, the feedback control for executing the detachment determination process is identical with the feedback control for executing the deterioration determination process. A controller of Third and Fourth Embodiments of the first invention executes 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 FB is in execution. In Third and Fourth Embodiments of the first invention, the feedback control FB is equivalent to the second feedback control.

[0097] In Third Embodiment of the first invention, the controller determines in the detachment determination process that the three-way catalyst has been detached, when the delay time T while the feedback control FB is in execution is shorter than a threshold X3. The threshold X3 is smaller than the threshold X2. The threshold X3 is equal to or smaller than the threshold X1. In the case above, the controller determines in the deterioration determination process that the three-way catalyst has been deteriorated, when the delay time T while the feedback control FB is in execution is equal to or longer than the threshold X3 and shorter than the threshold X2. In Fourth Embodiment of the first invention, the controller determines in the detachment determination process that the three-way catalyst has been detached, when the delay time T while the feedback control FB is in execution is shorter than an average of the oxygen sensor delay times T while the feedback controls FB prior to the current detachment determination process are in execution and a difference between the delay time T and the average is larger than a reference value Y1.

[0098] As a modification of Third and Fourth Embodiments of the first invention, the controller may 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 FB is in execution. In this modification, the feedback control FB is equivalent to the second feedback control.

[0099] The following will describe Fifth to Seventh Embodiments of the first invention with reference to the graph shown in FIG. 2. In Fifth to Seventh Embodiments of the first invention, the upstream oxygen sensor and the downstream oxygen sensor are O2 sensors. In Fifth to Seventh Embodiments of the first invention, the controller executes a detachment determination process based on a signal of the upstream oxygen sensor and a signal of the downstream oxygen sensor while the feedback control FB that is the normal feedback control is in execution.

[0100] In Fifth Embodiment of the first invention, the controller determines in the detachment determination process that the three-way catalyst has been detached, when the delay time T while the feedback control FB is in execution is shorter than a threshold X4. The threshold X4 is smaller than the threshold X2. The threshold X4 is equal to or smaller than the threshold X1. The threshold X4 is equal to or smaller than the threshold X3. The threshold X1, the threshold X3, and the threshold X4 may be identical with one another. In FIG. 2, the delay time T is a time from a point at which the signal of the upstream oxygen sensor becomes equal to a value A1 equidistant from a first voltage V1 and a second voltage V2 to a point at which the signal of the downstream oxygen sensor becomes equal to the value A1.

[0101] In Sixth Embodiment of the first invention, the controller determines in the detachment determination process that the three-way catalyst has been detached, when the delay time T while the feedback control FB is in execution is shorter than an average of the oxygen sensor delay times Ta while the feedback controls FB prior to the current detachment determination process are in execution and a difference between the delay time T and the average is larger than a reference value Y2.

[0102] In Seventh Embodiment of the first invention, the controller determines, in the detachment determination process, that the three-way catalyst has been detached when the number of changes of the signal of the upstream oxygen sensor during the first time period while the feedback control FB is in execution is larger than a threshold Z1 and the number of changes of the signal of the downstream oxygen sensor during the first time period while the feedback control FB is in execution 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 sensor during the first time period may be, for example, the number of times when the signal of the upstream oxygen sensor becomes at the second voltage V2 during the first time period, or the number of times when the signal of the upstream oxygen sensor becomes at the value A1. The number of changes of the signal of the downstream oxygen sensor during the first time period may be, for example, the number of times when the signal of the downstream oxygen sensor becomes at the second voltage V2 during the first time period, or the number of times when the signal of the downstream oxygen sensor becomes at the value A1. As shown in FIG. 2, the number of changes of the signal of the downstream oxygen sensor while the feedback control FB is in execution when the three-way catalyst is detached tends to be larger than the number of changes of the signal of the downstream oxygen sensor while the feedback control FB is in execution when the three-way catalyst is deteriorated. On this account, it is less likely to mistake a case where the three-way catalyst is deteriorated for a case where the three-way catalyst is detached even through feedback control different from the normal feedback control is not performed for the detachment determination process.

[0103] In Fifth to Seventh Embodiments of the first invention, the controller may execute the deterioration determination process based on a signal of the upstream oxygen sensor and a signal of the downstream oxygen sensor while the feedback control FB or the feedback control FB is in execution.

[0104] The following will describe Eighth and Ninth Embodiment of the first invention with reference to a graph shown in FIG. 3. In Eighth and Ninth Embodiment of the first invention, the upstream oxygen sensor and the downstream oxygen sensor are O2 sensors. In Eighth Ninth Embodiment of the first invention, the controller executes a detachment determination process based on a signal of the downstream oxygen sensor while the feedback control FB that is the normal feedback control is in execution. In Eighth and Ninth Embodiments of the first invention, the controller executes the detachment determination process by utilizing fuel cut control.

[0105] The graph of FIG. 3(a) shows changes over time of a flag of the fuel cut control, a signal of the upstream oxygen sensor, and a signal of the downstream oxygen sensor when the three-way catalyst is not detached. The graph of FIG. 3(b) shows changes over time of a flag of the fuel cut control, a signal of the upstream oxygen sensor, and a signal of the downstream oxygen sensor when the three-way catalyst is detached. Each of the graphs in FIG. 3(a) and FIG. 3(b) shows changes over time of a signal of the upstream oxygen sensor and a signal of the downstream oxygen sensor when the feedback control FB is shifted to the fuel cut control.

[0106] In Eighth Embodiment of the first invention, the controller determines that the three-way catalyst has been detached when a delay time T that is a delay time of a change of a signal of the downstream oxygen sensor from a change of a signal of the upstream oxygen sensor when the feedback control FB shifts to the fuel cut control is shorter than a threshold X5. In FIG. 3, the delay time T is a time from a point at which the signal of the upstream oxygen sensor becomes equal to a value A1 equidistant from a first voltage V1 and a second voltage V2 to a point at which the signal of the downstream oxygen sensor becomes equal to the value A1. To be more specific, the delay time T is a time from a point at which the signal of the upstream oxygen sensor becomes equal to the value A1 immediately before the signal becomes constant at the second voltage V2 to a point at which the signal of the downstream oxygen sensor becomes equal to the value A1. While in FIG. 3(a) and FIG. 3(b) the signal of the upstream oxygen sensor becomes equal to the value A1 during the fuel cut control, the signal of the upstream oxygen sensor may become equal to the value A1 during the feedback control FB.

[0107] In Eighth Embodiment of the first invention, the controller determines that the three-way catalyst has been detached when a delay time T that is a delay time of a change of a signal of the downstream oxygen sensor from a start time of the fuel cut control is shorter than a threshold X6. In FIG. 3, the delay time T is a time from the start of the fuel cut control to a time point at which the signal of the downstream oxygen sensor becomes equal to a value A1 which is equidistant from the first voltage V1 and the second voltage V2.

[0108] In Eight and Ninth Embodiments of the first invention, the controller may execute the deterioration determination process based on a signal of the upstream oxygen sensor and a signal of the downstream oxygen sensor while the feedback control FB or the feedback control FB is in execution.