A linear compressor is provided. The linear compressor includes a cylinder, a piston configured to reciprocate inside the cylinder, the piston including a head portion and a sliding portion extending rearward from a radially outer edge of the head portion, a supporter including a plate disposed at a rear of the piston, an elastic body disposed in the piston, the elastic body including an outer side coupled to an inner circumferential surface of the piston, and a rod configured to extend axially, the rod including one side coupled to a radially central area of the elastic body and other side connected to a radially central area of the plate.

A positive displacement machine includes a case including a tubular guide part in which a pressure chamber is provided, a slide member including a shaft extending in a first direction and a piston provided at an end portion of the shaft and disposed in the guide part, a coupling member coupled to the slide member and extending in a second direction intersecting the first direction, a first rotating member coupled to one end of the coupling member and configured to rotate around a first rotation axis extending in the second direction, and a rocking absorbing mechanism configured to absorb a rocking motion of the piston around an axis extending in the first direction. The rocking absorbing mechanism is provided between the coupling member and the slide member, between the shaft and the piston, or between the piston and an inner wall of the guide part.

A portable blowing and suction air compressor including a motor, a piston having first and second ends opposite to each other, a sealing member, a cylinder, and first and second check valves is disclosed. The first end is connected to the motor, the sealing member is sheathed onto the second end, and the second end is movably coupled to an inner wall of the cylinder. The second end leans against the inner wall through the sealing member. A cross section of the sealing member generates multiple contact zones on the inner wall. A recess is formed between two adjacent contact zones. The cylinder has an air inlet pipe and an air outlet pipe connected to an inner space of the cylinder and to an exterior environment respectively. The first check valve is disposed in the air inlet pipe, and the second check valve is disposed in the air outlet pipe.

A portable blowing and suction air compressor including a motor, a piston having first and second ends opposite to each other, a sealing member, a cylinder, and first and second check valves is disclosed. The first end is connected to the motor, the sealing member is sheathed onto the second end, and the second end is movably coupled to an inner wall of the cylinder. The second end leans against the inner wall through the sealing member. A cross section of the sealing member generates multiple contact zones on the inner wall. A recess is formed between two adjacent contact zones. The cylinder has an air inlet pipe and an air outlet pipe connected to an inner space of the cylinder and to an exterior environment respectively. The first check valve is disposed in the air inlet pipe, and the second check valve is disposed in the air outlet pipe.