Injection molding machine and injection molding method

An injection molding machine, comprising:

• a gas feeding mechanism configured to feed gas to a cavity formed between a first mold plate and a second mold plate in a clamped state;
• an injection apparatus configured to inject a foamable resin into the cavity having an inside pressure thereof increased to be higher than an atmospheric pressure by the gas feeding mechanism;
• and
• a gas releasing mechanism configured to release the gas inside the cavity to an atmosphere through a gap formed between an inner wall surface of a through hole formed through one of the first mold plate and the second mold plate and an outer circumferential surface of a mold member inserted into the through hole, during or after the injection of the foamable resin by the injection apparatus, the gas releasing mechanism including an opening and closing mechanism configured to open and close the gap,
• wherein the opening and closing mechanism includes:
• a hydro pneumatic cylinder configured to extend and retract relative to the one of the first mold plate and the second mold plate;
• a seal plate connected to the hydro pneumatic cylinder;
• and
• a sealing member provided between the seal plate and the one of the first mold plate and the second mold plate,
• wherein the sealing member moves toward the one of the first mold plate and the second mold plate to close the gap when the retracted hydro pneumatic cylinder extends to move the seal plate toward the one of the first mold plate and the second mold plate, and the sealing member moves away from the one of the first mold plate and the second mold plate to open the gap when the extended hydro pneumatic cylinder retracts to move the seal plate away from the one of the first mold plate and the second mold plate.