Straddle-type vehicle

1. A straddle-type vehicle comprising:

a supercharger which compresses intake-air to be sent to a combustion chamber of an engine;

a catalyst provided in an exhaust passage through which an exhaust gas emitted from the engine flows;

an electronic control unit (ECU) which controls the engine; and

a transmission provided in a driving power transmission path from the engine to a drive wheel,

wherein a current transmission ratio of the transmission is among a plurality of transmission ratios,

wherein the ECU performs an increase suppressing control for suppressing an increase in an exhaust gas temperature, in a case where the ECU estimates that the exhaust gas temperature has exceeded an increase suppressing temperature set to be equal to or lower than a catalyst permissible temperature, the current transmission ratio is less than a preset reference transmission ratio, and an engine speed of the engine is lower than a predetermined upper limit engine speed.

2. The straddle-type vehicle according to claim 1 ,

wherein the ECU performs a cylinder combustion ceasing control for ceasing combustion in a cylinder of the engine in a case where a predetermined cylinder combustion ceasing condition is met, and

wherein an initiation condition of the increase suppressing control is set so that the increase suppressing control is performed before the cylinder combustion ceasing control is performed.

3. The straddle-type vehicle according to claim 2 , wherein the ECU performs the cylinder combustion ceasing control in a case where the engine speed has reached the predetermined upper limit engine speed, and wherein the ECU performs the increase suppressing control in a case where the engine speed has exceeded an increase suppressing engine speed set to be lower than the predetermined upper limit engine speed.

4. The straddle-type vehicle according to claim 1 ,

wherein the ECU estimates whether or not the exhaust gas temperature has exceeded the increase suppressing temperature set to be equal to or lower than the catalyst permissible temperature, based on a value corresponding to a throttle valve opening degree and the engine speed.

5. The straddle-type vehicle according to claim 1 ,

wherein the ECU performs the increase suppressing control in such a manner that an intake-air flow rate is suppressed to be lower than that in a case where the increase suppressing control is not performed.

6. The straddle-type vehicle according to claim 5 ,

wherein the ECU performs the increase suppressing control in such a manner that a cross-sectional area of an air-intake passage becomes smaller than that in a case where the increase suppressing control is not performed.

7. The straddle-type vehicle according to claim 5 ,

wherein the ECU performs the increase suppressing control in such a manner that an increase in a supercharging pressure applied by the supercharger is suppressed more than in a case where the increase suppressing control is not performed.

8. The straddle-type vehicle according to claim 6 ,

wherein the ECU performs the increase suppressing control in such a manner that an amount of fuel to be supplied to the engine is increased to be greater than that in a case where the increase suppressing control is not performed.

9. The straddle-type vehicle according to claim 6 ,

wherein the increase suppressing control includes a plurality of increase suppressing stages, and initiation conditions which are different and are used to initiate the plurality of increase suppressing stages, respectively, are set to correspond to the plurality of increase suppressing stages, respectively.

10. The straddle-type vehicle according to claim 5 ,

wherein the ECU performs the increase suppressing control in such a manner that an amount of fuel to be supplied to the engine is increased to be greater than that in a case where the increase suppressing control is not performed, and then the intake-air flow rate is suppressed to be lower than that in a case where the increase suppressing control is not performed.

11. The straddle-type vehicle according to claim 6 ,

wherein a condition used to initiate the increase suppressing control is set so that the increase suppressing control is performed more easily in a case where a first transmission ratio of the plurality of transmission ratios is selected by the transmission than in a case where a second transmission ratio of the plurality of transmission ratios is selected by the transmission, the first transmission ratio being lower than the second transmission ratio.

12. A straddle-type vehicle comprising:

a supercharger which compresses intake-air to be sent to a combustion chamber of an engine;

a catalyst provided in an exhaust passage through which an exhaust gas emitted from the engine flows;

an electronic control unit (ECU) which controls the engine;

a transmission provided in a driving power transmission path from the engine to a drive wheel;

an air-intake chamber disposed downstream of the supercharger and upstream of the engine;

a main fuel injector; and

a sub-fuel injector,

wherein a current transmission ratio of the transmission is selected from a plurality of transmission ratios,

wherein the ECU performs an increase suppressing control for suppressing an increase in an exhaust gas temperature, in a case where the ECU estimates that the exhaust gas temperature has exceeded an increase suppressing temperature set to be equal to or lower than a catalyst permissible temperature,

wherein a condition used to initiate the increase suppressing control is set to vary based on the current transmission ratio,

wherein the sub-fuel injector is configured to inject fuel into the air-intake chamber,

wherein the main fuel injector is disposed downstream of the air-intake chamber, and

wherein the ECU performs the increase suppressing control in such a manner that a fuel injection amount of the sub-fuel injector is increased to be greater than that in normal control.