A hot runner-type injection structure 4 is provided with: a hot runner nozzle 5; and a valve pin 6 that is provided to be able to advance and retreat in the axial line O1 direction inside the flow passage of the hot runner nozzle 5 and that opens/closes the flow passage by coming into contact/being spaced apart from a valve opening/closing part 13 which has a tip part disposed on the tip side of the hot runner nozzle 5, wherein a heat insulating groove 16, which is recessed inward toward the axial line O1 side from an outer circumferential surface and extends in the circumferential direction, is provided on the outer periphery in a valve pin contact section M in which the valve opening/closing part 13 of the hot runner nozzle 5 is formed.

An injection molding apparatus including a fixed die including a gate via which a molding material flows in, a movable die that forms along with the fixed die a cavity and separates from the fixed die at a point of time of mold opening, an open-gate hot runner that includes a nozzle including a channel that guides the molding material to the gate and a heater that heats the channel, the hot runner being attachable to and detachable from the fixed die, and a cap member that is disposed between the fixed die and the hot runner and has a melting point higher than a melting point of the molding material.

An injection molding apparatus including a fixed die including a gate via which a molding material flows in, a movable die that forms along with the fixed die a cavity and separates from the fixed die at a point of time of mold opening, an open-gate hot runner that includes a nozzle including a channel that guides the molding material to the gate and a heater that heats the channel, the hot runner being attachable to and detachable from the fixed die, and a cap member that is disposed between the fixed die and the hot runner and has a melting point higher than a melting point of the molding material.

A sprue bush that is attached to a mold used to mold synthetic resin includes: a sprue bush main body (10) that has a flow passage, through which synthetic resin injected from an injection molding nozzle flows, and a recessed portion (13) formed in a surface of the sprue bush main body on a synthetic resin injection port side thereof; and a bush component (20) that is embedded in the recessed portion (13), the bush component (20) including: a nozzle contact surface (21) that is contacted by the injection molding nozzle; a through hole (22) that extends from an opening in the nozzle contact surface (21) and communicates with the flow passage in the sprue bush main body so as to form the flow passage for the synthetic resin; and a plurality of ribs (23) that extend radially outward from an inner peripheral surface of the through hole.