Engine device

1. An engine device comprising:

an engine capable of coping with both a premix combustion mode in which premixed fuel obtained by mixing gaseous fuel with air in advance is supplied into a cylinder and combusted and a diffusion combustion mode in which liquid fuel is injected into the cylinder and combusted;

a gas supply device configured to supply the gaseous fuel into the cylinder in the premix combustion mode;

a pilot injection device configured to inject the liquid fuel into the cylinder in the premix combustion mode;

a main injection device configured to inject the liquid fuel into the cylinder in the diffusion combustion mode; and

wherein the engine device is configured to initiate a failure diagnosis process in the pilot injection device, the pilot injection device configured to inject a liquid fuel while the engine operates in the diffusion combustion mode during the failure diagnosis process, and the failure diagnosis process based on a pressure difference between a first maximum pressure detected in the cylinder and a second maximum pressure detected in the cylinder, the first maximum pressure based on a first amount of the liquid fuel injected from the pilot injection device and the second maximum pressure based on a second amount of the liquid fuel injected from the pilot injection device, the second amount of the liquid fuel greater than the first amount of the liquid fuel.

2. The engine device according to claim 1 , wherein:

an injection amount from the pilot injection device is increased at a time of failure diagnosis of the pilot injection device.

3. The engine device according to claim 2 , wherein:

the pilot injection device in the diffusion combustion mode is configured to inject a small amount of liquid fuel at a predetermined injection timing, and

an injection timing of the pilot injection device is advanced as compared to an injection timing during an idling state, at a time of failure diagnosis.

4. The engine device according to claim 1 , wherein:

the engine device is operated in the diffusion combustion mode without a transition to the premix combustion mode, when failure in the pilot injection device is detected.

5. The engine device according to claim 1 , wherein:

the cylinder comprises a plurality of cylinders; and

failure in the pilot injection device is diagnosed for each cylinder of the plurality of cylinders.

6. The engine device according to claim 1 , wherein:

the pilot injection device in the diffusion combustion mode is configured to inject the liquid fuel at a predetermined injection timing.

7. An apparatus comprising:

a control device configured to initiate a failure diagnosis process associated with a pilot injection valve based on a pressure difference between a first pressure detected in a cylinder of an engine and a second pressure detected in the cylinder, the first pressure based on a first amount of a liquid fuel injected from the pilot injection valve and the second pressure based on a second amount of the liquid fuel injected from the pilot injection valve, the second amount greater than the first amount; and

wherein the pilot injection valve is configured to inject the liquid fuel while the engine operates in a diffusion combustion mode based on the initiated failure diagnosis process.

8. The apparatus according to claim 7 , wherein the control device includes a central processing unit.

9. The apparatus according to claim 7 , wherein the control device includes an electronic control unit.

10. The apparatus according to claim 7 , wherein:

the control device is configured to:

determine the first pressure;

determine the second pressure; and

compare the first pressure to the second pressure.

11. The apparatus according to claim 7 , wherein the control device is configured to compare a difference between the first pressure and the second pressure to a value.

12. The apparatus according to claim 7 , wherein the control device is configured to output a signal indicating the pilot injection valve is in a failed state based on a determination that a difference between the first pressure and the second pressure is greater than or equal to a value.

13. The apparatus according to claim 7 , wherein the control device is configured to output a signal indicating the pilot injection valve is in a functional state based on a determination that a difference between the first pressure and the second pressure is less than a value.

14. The apparatus according to claim 7 , further comprising:

the pilot injection valve; and

wherein the control device is configured to send, based on the initiated failure diagnosis process, a first signal to the pilot injection valve to inject the first amount of the liquid fuel for a first time period.

15. The apparatus according to claim 14 , wherein the control device is configured to send, based on the initiated failure diagnosis process and a determination that the pilot injection valve injected the first amount of the liquid fuel for the first time period, a second signal to the pilot injection valve to inject the second amount of the liquid fuel for a second time period.

16. The apparatus according to claim 7 , wherein:

the first pressure includes a first maximum pressure detected in the cylinder between injection of the first amount of the liquid fuel and at least one full rotation of an output shaft of the engine; and

the second pressure includes a second maximum pressure detected in the cylinder between the injection of the second amount of the liquid fuel and at least one full rotation of the output shaft of the engine.

17. The apparatus according to claim 7 , further comprising:

the pilot injection valve configured to inject a first liquid fuel; and

a main injection valve configured to inject a second liquid fuel; and

wherein:

the engine is configured to operate in a pre-mixed combustion mode;

based on the engine operating in the pre-mixed combustion mode, the cylinder is configured to receive a gaseous fuel and the first liquid fuel via the pilot injection valve; and

based on the engine being configured to operate in the diffusion combustion mode, the cylinder is configured to receive the liquid fuel.

18. A method comprising:

initiating a failure diagnosis process associated with a pilot injection valve based on a pressure difference between a first pressure detected in a cylinder of an engine and a second pressure detected in the cylinder, the first pressure based on a first amount of a liquid fuel injected from the pilot injection valve and the second pressure based on a second amount of the liquid fuel injected from the pilot injection valve, the second amount greater than the first amount; and

injecting, based on initiating the failure diagnosis process, the liquid fuel via the pilot injection valve while the engine operates in a diffusion combustion mode.

19. The method according to claim 18 , further comprising:

determining the first pressure in the cylinder; and

determining the second pressure in the cylinder.

20. The method according to claim 18 , further comprising outputting a signal indicating the pilot injection valve is in a failed state based on a determination that a difference between the first pressure and the second pressure is greater than or equal to a value.