Insert molding die and method for molding hollow component

An insert molding die for a hollow component, comprising:

• an upper die;
• a lower die arranged under the upper die, wherein the upper die and the lower die forms a cavity which accommodates the hollow component and is charged with molten resin;
• a plurality of upper-die pin members disposed on the upper die movably up and down, wherein the upper-die pin members hold the hollow component in the cavity;
• upper-die urging means disposed on the upper die to urge the upper-die pin members downwardly so that the upper-die pin members project from the upper die by opening the upper die and the lower die and the upper-die pin members pressed into the upper die by closing the upper die and the lower die, the upper-die urging means including a first spring for urging a selected upper-die pin member downwardly and a second spring for urging the selected upper-die pin member upwardly, an urging force of the first spring being larger than that of the second spring;
• a plurality of lower-die pin members disposed on the lower die movably up and down so as to oppose the upper-die pin members respectively, wherein the lower-die pin members hold the hollow component in the cavity in cooperation with the upper-die pin members to form a gap between the hollow component and the lower-die;
• and
• lower-die urging means disposed on the lower die to urge the lower-die pin members upwardly so that the lower-die pin members project from the lower die by opening the upper die and the lower die and the lower-die pin members pressed into the lower die by closing the upper die and the lower die, the lower-die urging means including a third spring for urging a selected lower-die pin member upwardly and a fourth spring for urging the selected lower-die pin member downwardly, an urging force of the third spring being larger than that of the fourth spring.