Variable length connecting rod and variable compression ratio internal combustion engine

A variable length connecting rod comprising:

• a connecting rod body provided with a crank receiving opening for receiving a crank pin;
• an eccentric member provided with a piston pin receiving opening for receiving a piston pin and attached to the connecting rod body to be able to turn so as to make a length between a center of the piston pin receiving opening and a center of the crank receiving opening change;
• a hydraulic cylinder formed at the connecting rod body and supplied with hydraulic oil;
• a hydraulic piston sliding inside the hydraulic cylinder and moving in linkage with the eccentric member;
• a flow direction switching mechanism provided at the connecting rod body;
• and
• a hydraulic mechanism handling the hydraulic oil separate from the hydraulic cylinder, the hydraulic piston, and the flow direction switching mechanism, wherein
• the flow direction switching mechanism comprises a single check valve and a single switching mechanism,
• the check valve is configured to permit a flow of hydraulic oil from a primary side of the check valve to a secondary side of the check valve and prohibit the flow of hydraulic oil from the secondary side to the primary side,
• the switching mechanism comprises a single switching pin, the switching pin is held in a pin holding space formed in the connecting rod body,
• the connecting rod body is formed with a first oil path making the hydraulic cylinder and the pin holding space communicate, a second oil path making the hydraulic mechanism or the hydraulic mechanism and an outside space of the variable length connecting rod, and the pin holding space communicate, a third oil path making the primary side of the check valve and the pin holding space communicate, and a fourth oil path making the secondary side of the check valve and the pin holding space communicate, and
• the switching pin is configured to be switched between a first position making the first oil path communicate with the fourth oil path and making the second oil path communicate with the third oil path, and a second position making the first oil path communicate with the third oil path and making the second oil path communicate with the fourth oil path.