Plasticizing device, injection molding device, and screw

A screw to be mounted on a plasticizing device, the screw comprising:

• a groove forming surface at which a groove is formed, wherein
• the groove has a shape based on an involute curve from a central portion of the groove forming surface toward a peripheral edge portion of the groove forming surface,
• the groove is defined by an outer wall, an inner wall having a distance from the central portion in a radial direction shorter than a distance of the outer wall from the central portion, and a bottom surface between the outer wall and the inner wall,
• the groove includes
• a first groove portion, and
• a second groove portion located closer to the central portion than the first groove portion in a direction along the groove,
• an involute coefficient of the second groove portion is smaller than an involute coefficient of the first groove portion, and
• a groove width of the second groove portion is smaller than a groove width of the first groove portion.

A screw to be mounted on a plasticizing device, the screw comprising:

• a groove forming surface at which a spiral groove is formed, wherein
• the groove is defined by an outer wall, an inner wall having a distance from a central portion of the groove forming surface in a radial direction shorter than a distance of the outer wall from the central portion, and a bottom surface between the outer wall and the inner wall,
• the groove includes
• a first groove portion, and
• a second groove portion located closer to the central portion than the first groove portion in a direction along the groove,
• a thickness in the radial direction of the inner wall defining the first groove portion is different from a thickness in the radial direction of the inner wall defining the second groove portion, and
• a groove width of the second groove portion is smaller than a groove width of the first groove portion.