Abstract: The ECU executes a program that includes the steps of: calculating the temperature Texp of the wall surface of the exhaust port and the temperature Tsen of the wall surface of the inner cover covering the zirconia element of the A/F sensor (S110); heating the zirconia element by the heater (S130) when at least one of the condition that the temperature Texp is equal to or higher than the first threshold and the condition that the temperature Tsen is equal to or higher than the second threshold is in effect (S120: YES); and prohibiting the heating of the zirconia element by the heater (S140) when the temperature Texp is lower than the first threshold and the temperature Tsen is lower than the second threshold (S120: NO).

Abstract: The ECU executes a program that includes the steps of: calculating the temperature Texp of the wall surface of the exhaust port and the temperature Tsen of the wall surface of the inner cover covering the zirconia element of the A/F sensor (S110); heating the zirconia element by the heater (S130) when at least one of the condition that the temperature Texp is equal to or higher than the first threshold and the condition that the temperature Tsen is equal to or higher than the second threshold is in effect (S120: YES); and prohibiting the heating of the zirconia element by the heater (S140) when the temperature Texp is lower than the first threshold and the temperature Tsen is lower than the second threshold (S120: NO).

Abstract: In one embodiment of an engine (1) in which air-fuel ratio feedback control is performed based on output of an exhaust gas sensor (100) disposed in an exhaust path, when the engine (1) starts in an extremely low temperature state (e.g., ?20 to ?30° C.), a heater (200) that heats a sensor element (110) of the exhaust gas sensor (100) is not powered immediately after the engine (1) starts, rather, power to the heater (200) is started when an engine coolant water temperature has reached a temperature near an air-fuel ratio feedback control starting water temperature.

Abstract: An engine ECU executes a program including the steps of: detecting an engine speed NE and an engine load (S100, S110); when determination is made of being in an idle region based on the engine speed NE and engine load (YES at S120), determining whether in a high load idle region or a low load idle region (S130); reducing the operation sound by stopping a high-pressure fuel pump in a high load idle region (S150); and aiming for combustion stabilization without stopping the high-pressure fuel pump in a low load idle region (S170).

Abstract: An engine ECU executes a program including the steps of: detecting an engine speed NE and an engine load (S100, S110); when determination is made of being in an idle region based on the engine speed NE and engine load (YES at S120), determining whether in a high load idle region or a low load idle region (S130); reducing the operation sound by stopping a high-pressure fuel pump in a high load idle region (S150); and aiming for combustion stabilization without stopping the high-pressure fuel pump in a low load idle region (S170).

Abstract: When an inner wall of a cylinder head is viewed along an axis of a cylinder, a line that passes through a center of a fuel injection port and a center of a valve opening adjacent to the injection port is defined as a first line, and a line that is perpendicular to the first line is defined as a second line. A notch is formed in a part of the inner wall that defines the injection port. Specifically, when the inner wall is divided into sections by the second line, the notch is located in the section in which the adjacent opening exists. The notch is also displaced from the first line. Therefore, a sufficient thickness of the section corresponding to the valve seats of intake and exhaust valves are easily ensured.

Abstract: When an inner wall of a cylinder head is viewed along an axis of a cylinder, a line that passes through a center of a fuel injection port and a center of a valve opening adjacent to the injection port is defined as a first line, and a line that is perpendicular to the first line is defined as a second line. A notch is formed in a part of the inner wall that defines the injection port. Specifically, when the inner wall is divided into sections by the second line, the notch is located in the section in which the adjacent opening exists. The notch is also displaced from the first line. Therefore, a sufficient thickness of the section corresponding to the valve seats of intake and exhaust valves are easily ensured.