A 2-cycle internal combustion engine in which the intake cycle begins before and ends after the exhaust cycle, resulting in a longer power stroke, increased torque and greater efficiency is disclosed herein. In the preferred embodiment, the 2-cycle engine has a power stroke of about 160 degrees, an exhaust stage of about 70 degrees, and an intake cycle of about 110-115 degrees.

Provided is a compression ratio varying mechanism, including: a discharge oil passage connected to a first hydraulic chamber; a supply oil passage connected to a hydraulic pump; a pump cylinder including a first oil storage chamber connected to the discharge oil passage and the supply oil passage and a second oil storage chamber partitioned from the first oil storage chamber by a plunger; a branch oil passage connected to the second oil storage chamber; and an orifice provided in the branch oil passage.

A two-stroke engine includes: a scavenging port communicating with a crank chamber and a side portion of a cylinder, and switchably brought into communication with or shut off from the cylinder by a piston; and multiple fuel injection valves for injecting fuel into the scavenging port. Since the fuel injection valves inject fuel into the scavenging port, there is no need to apply a high pressure injection system. By causing the start of fuel injection to be delayed from a timing at which the scavenging port is opened, fresh air is sent into the cylinder at an early stage of scavenging, and air-fuel mixture is sent into the cylinder at a late stage of scavenging. Thereby, even in a long-stroke engine, stratified scavenging is performed to suppress blow-by of air-fuel mixture.

A two-stroke engine includes: a scavenging port communicating with a crank chamber and a side portion of a cylinder, and switchably brought into communication with or shut off from the cylinder by a piston; and multiple fuel injection valves for injecting fuel into the scavenging port. Since the fuel injection valves inject fuel into the scavenging port, there is no need to apply a high pressure injection system. By causing the start of fuel injection to be delayed from a timing at which the scavenging port is opened, fresh air is sent into the cylinder at an early stage of scavenging, and air-fuel mixture is sent into the cylinder at a late stage of scavenging. Thereby, even in a long-stroke engine, stratified scavenging is performed to suppress blow-by of air-fuel mixture.

Provided is a marine engine, including: a piston; and a compression ratio controller configured to execute lowering processing of moving a top dead center position of the piston toward a bottom dead center side when an engine rotation speed falls within a resonance occurrence range set in advance. A geometrical compression ratio is reduced, and a resonance stress caused by a torsional vibration in a rotary system can thus be suppressed while suppressing a decrease in thermal efficiency compared with a case in which retarding control is applied to a fuel injection timing or a closing timing of an exhaust valve.

Provided is a compression ratio varying mechanism, including a communication hole including: a first opening opened in an outer peripheral side surface of a piston rod; and a second opening, which is prevented from being opposed to the first opening in a radial direction of a piston rod, and is connected to an oil passage at a position apart from the first opening in a stroke direction.

Provided is a marine engine, including: an air controller configured to supply compressed air to a combustion chamber in an upstroke of a piston after a crash astern signal is output; a fuel controller configured to stop supply of fuel to the combustion chamber when the crash astern signal is output, and to resume the supply of the fuel after a backward rotation of a crankshaft; and a compression ratio controller configured to move a top dead center position of the piston toward an opposite side of a bottom dead center position of the piston when the crash astern signal is output, and the top dead center position of the piston is on the bottom dead center position side with respect to a predetermined position set in advance.

Provided is an engine system including: a bypass pipe (bypass flow passage) connecting an upstream side and a downstream side of the turbine on an exhaust flow passage; a bypass valve configured to open and close the bypass flow passage; and a catalytic activation controller configured to control the bypass valve and a compression ratio of a combustion chamber.

A method of raising exhaust gas temperatures of a two-cycle uniflow scavenged engine at lower loads. At lower loads, the exhaust valves are activated with a frequency that is less frequent than every engine cycle. This exhaust valve deactivation may be combined with additional engine operating strategies, such as by using fewer than all cylinders as combusting cylinders, adjusting fueling to combusting cylinders, and reducing compressor output.

This method of gas exchange for four-stroke piston internal combustion engine comprising gas exchange through an intake and an exhaust valves and includes gas exchange through a piston-controlled port in a cylinder sleeve: exhausting combustion products through the port at the end of the power stroke and at the beginning of the exhaust stroke, removal of exhaust gases from the port (from the space outside the port, outside the cylinder) and air supply to the port (supply into afore-mentioned space). As a result, the combustion products do not return to the cylinder through the port at the end of the intake stroke and at the beginning of the compression stroke. This effect is combined with air intaking into the cylinder through the port at the end of the intake stroke and at the beginning of the compression stroke.