Control system for flex-fuel engines

Abstract

In flex-fuel engines, this enables precise control of fuel injection volume that reflects the effect of fuel adhesion to the fuel wall. [Solution] In a control device applied to a flex fuel engine that can use alcohol-containing fuel, the following are performed: calculate the amount of fuel vaporized based on the amount of fuel deposited in the cylinder, the cylinder wall temperature, the negative pressure in the cylinder, and the alcohol concentration of the fuel (S100); calculate the amount obtained by subtracting the amount of fuel vaporized from the requested injection amount as the instructed injection amount (S120); instruct the flex fuel engine to inject the instructed injection amount (S170); calculate the amount of new deposits based on the instructed injection amount, the wall temperature, the negative pressure in the cylinder, and the alcohol concentration (S180); and update the value of the amount of fuel deposited in the cylinder by subtracting the amount of fuel vaporized from the value before the update and adding the amount of new deposits to the subtracted value to get the updated value (S190).

Claims

1. A control device applicable to a flex-fuel engine that can use alcohol-containing fuels, Based on the amount of fuel adhering to the cylinder wall, the cylinder wall temperature, the negative pressure inside the cylinder, and the alcohol concentration of the fuel, the amount of fuel vaporized from the cylinder wall is calculated. To instruct the flex-fuel engine to inject a fuel amount that is the amount obtained by subtracting the fuel volatilization amount from the required injection amount, which is the required amount of fuel to be burned inside the cylinder, Based on the indicative injection amount, the wall surface temperature, the in-cylinder negative pressure, and the alcohol concentration, the amount of newly deposited fuel, which is the amount of fuel newly adhering to the wall surface of the cylinder, is calculated. The value of the fuel deposit amount in the cylinder is updated by subtracting the fuel volatilization amount from the value before the update, and adding the newly deposited amount to the subtracted value to obtain the updated value. A control device for a flex-fuel engine that performs this function.

2. A control device for a flex fuel engine according to claim 1, which calculates the amount of new deposits based on the indicative injection amount, the wall temperature, the in-cylinder negative pressure, and the alcohol concentration, as well as the flow velocity of the intake air flowing into the cylinder and the fuel injection pressure.

3. The control device for a flex fuel engine according to claim 1, which performs a combustion stabilization treatment to reduce the in-cylinder negative pressure when the minimum injection amount of the injector that performs fuel injection in the flex fuel engine falls below the instructed injection amount.

4. A control device for a flex-fuel engine according to claim 1, wherein if the predicted value of the air-fuel ratio when the instructed injection amount of fuel is injected falls outside the combustion stability range, a combustion stabilization process is performed to reduce the in-cylinder negative pressure.

5. The control device for a flex fuel engine according to claim 3 or 4, wherein the reduction in the in-cylinder negative pressure in the combustion stabilization treatment is achieved by increasing the valve overlap amount of the intake valve and exhaust valve using a variable valve timing mechanism.

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