Engine controller

1. An engine controller that performs a premixed combustion operation and a diffusion combustion operation and switches between the premixed combustion operation and the diffusion combustion operation in accordance with a traveling state of a vehicle, the engine having at least one of a fuel injection valve that injects fuel directly into a combustion chamber, a throttle valve that controls an amount of air provided to the combustion chamber, and an EGR valve that controls an amount of exhaust gas supplied from an exhaust passage to an intake passage of the engine, the engine controller comprising:

a processor and a memory that stores a program that causes the processor to:

detect, as a detector, a gear position of a transmission mounted in the vehicle;

change, as a changer, operational conditions of the premixed combustion operation on the basis of the detected gear position; and

control, as a controller, at least one of the fuel injection valve and the throttle valve and the EGR valve to perform the premixed combustion operation when the traveling state of a vehicle satisfies the operational condition,

wherein the memory stores a map that determines a region for performing the premixed combustion operation based on an engine speed and an engine load, the region for performing the premixed combustion operation on the map expands as an ordinal number of gear positions increases.

2. The engine controller according to claim 1 , wherein the changer increases an upper limit of engine speed among the operational conditions as a reduction ratio of the gear position decreases.

3. The engine controller according to claim 2 , wherein the changer increases the upper limit of the engine speed among the operational conditions if the reduction ratio is lower than a first reduction ratio, compared to the case where the reduction ratio is equal to or higher than the first reduction ratio, and increases an upper limit of the engine load among the operational conditions if the reduction ratio is lower than a second reduction ratio lower than the first reduction ratio, compared to the case where the reduction ratio is equal to or higher than the second reduction ratio.

4. The engine controller according to claim 2 , wherein the changer increases the upper limit of the engine load among the operational conditions if the reduction ratio of the gear position decreases.

5. The engine controller according to claim 1 ,

wherein the controller performs the diffusion combustion operation after the gear position is changed and at least before a predetermined time elapses.

6. The engine controller according to claim 2 ,

wherein the controller performs the diffusion combustion operation after the gear position is changed and at least before a predetermined time elapses.

7. The engine controller according to claim 3 ,

wherein the controller performs the diffusion combustion operation after the gear position is changed and at least before a predetermined time elapses.

8. The engine controller according to claim 7 , wherein the predetermined time decreases as the reduction ratio of the gear position decreases.

9. The engine controller according to claim 8 , wherein the predetermined time is a time until a difference between a target value and an actual value of each of a boost pressure and an intake-air oxygen level of the engine is equal to or smaller than a predetermined value.

10. A vehicle equipped with an engine that selectively operates in a premixed combustion operation and a diffusion combustion operation in accordance with a traveling state of the vehicle, the engine having at least one of a fuel injection valve that injects fuel directly into a combustion chamber, a throttle valve that controls an amount of air provided to the combustion chamber, and an EGR valve that controls an amount of exhaust gas supplied from an exhaust passage to an intake passage of the engine, the vehicle comprising:

a gear position sensor that detects a position of a gear selector; and

a processor and a memory that stores a program that causes the processor to:

detect, as a detector, a gear position of a transmission mounted in the vehicle based on the detected position of the gear selector;

change, as a changer, operational conditions of the premixed combustion operation on the basis of the detected gear position; and

control, as a controller, at least one of the fuel injection valve and the throttle valve and the EGR valve to perform the premixed combustion operation when the traveling state of the vehicle satisfies the operational condition,

wherein the memory stores a map that determines a region for performing the premixed combustion operation based on an engine speed and an engine load, the region for performing the premixed combustion operation on the map expands as an ordinal number of gear positions increases.