Supercharger and internal combustion engine

A supercharger comprising:

• a first introduction part having a first flow channel that is configured to direct exhaust gas away from a first exhaust gas introduction passage that leads to a turbine driven by the exhaust gas;
• a second introduction part having a second flow channel that is configured to direct the exhaust gas away from a second exhaust gas introduction passage that leads to the turbine;
• a chamber into which the exhaust gas is introduced through the first flow channel and the second flow channel;
• an outlet part having one or a plurality of outlet flow channels that is configured to direct the exhaust gas within the chamber to a system exterior;
• and
• a valve member housed in the chamber,
• wherein the chamber has a first introduction port that leads to the first flow channel, a second introduction port that leads to the second flow channel, and one or a plurality of outlet ports that lead to the outlet flow channel,
• wherein a main circulation space that allows gas to circulate thereinto is secured on a main surface side of the valve member within the chamber,
• wherein the valve member is rotatable about an axis, is capable of opening or closing the first introduction port, the second introduction port, and the outlet port in accordance with a rotational position around the axis, and allows two or more opened ports among the first introduction port, the second introduction port, and the outlet port to communicate with each other through the main circulation space,
• wherein a cutout, which forms a subsidiary circulation space that allows gas to circulate thereinto, is formed in a back surface of the valve member opposite to the main surface, and
• wherein the valve member allows any one of the first and second introduction ports and the outlet port to communicate with each other through the main circulation space, and allows the other of the first and second introduction ports and the outlet port to communicate with each other through the subsidiary circulation space.