Engine

An engine comprising:

• an EGR device that recirculates part of an exhaust gas discharged from a cylinder head as EGR gas to an intake pipe that supplies gas to the cylinder head, the EGR device including an EGR valve that adjusts a recirculation amount of the EGR gas;
• and
• a control unit that controls the EGR valve and is configured to select a predetermined control mode from at least a first mode, a second mode, and a third mode according to at least an engine speed and a fuel injection amount, wherein a first threshold and a second threshold are set in ascending order for the fuel injection amount according to the engine speed, wherein the control unit selects:
• the first mode when the fuel injection amount is equal to or less than the first threshold,
• the second mode when the fuel injection amount is greater than the second threshold, and
• the third mode when the fuel injection amount is greater than the first threshold and equal to or less than the second threshold,
• wherein when the control unit selects the first mode, the control unit is configured to increase the first threshold and control the EGR valve in the selected control mode,
• wherein the first mode is a control mode in which the EGR valve is fully closed,
• wherein the second mode is a control mode in which an opening degree of the EGR valve is adjusted according to an operation state of the engine, and
• wherein the third mode is a control mode in which an ON period in which the opening degree of the EGR valve is adjusted according to the operation state of the engine and an OFF period in which the EGR valve is fully closed are repeated.

An engine comprising:

• an EGR device that recirculates part of an exhaust gas discharged from a cylinder head as EGR gas to an intake pipe that supplies gas to the cylinder head, the EGR device including an EGR valve that adjusts a recirculation amount of the EGR gas;
• and
• a control unit that controls the EGR valve and is configured to select a predetermined control mode from at least a first mode, a second mode, and a third mode according to at least an engine speed and a fuel injection amount, wherein a first threshold and a second threshold are set in ascending order for the fuel injection amount according to the engine speed, wherein the control unit selects:
• the first mode when the fuel injection amount is equal to or less than the first threshold,
• the second mode when the fuel injection amount is greater than the second threshold, and
• the third mode when the fuel injection amount is greater than the first threshold and equal to or less than the second threshold,
• wherein when the control unit selects the third mode, the control unit is configured to decrease the first threshold and control the EGR valve in the selected control mode,
• wherein the first mode is a control mode in which the EGR valve is fully closed,
• wherein the second mode is a control mode in which an opening degree of the EGR valve is adjusted according to an operation state of the engine, and
• wherein the third mode is a control mode in which an ON period in which the opening degree of the EGR valve is adjusted according to the operation state of the engine and an OFF period in which the EGR valve is fully closed are repeated.