attached and fixed to the hinge axis 2 of the opening closing device h and rotates along with the rotation of the hinge axis 2 on the sector gear 12 along the rotation angle thereof that is almost equal to the rotation angle of the opening closing device h teeth 12 a are formed the small gear 13 is attached to freely rotate around the support axis 14 and is engaged with the sector gear 12 a flange portion 13 a is provided to the small gear 13 in an integrated manner the flange portion 13 a has a plain part 13 a u2032 on the tip of the support axis 14 a square headed bolt 14 a is provided and is fitted into a square hole 11 a of the attachment frame 11 to prevent it from rotating as apparent from fig5 the flange portion 13 a of the small gear 13 is fitted into a hole 15 a formed on the first internal tooth gear 15 and a plain part 15 a u2032 thereof is attached to the plain part 13 a u2032 of the flange portion 13 so that they are rotated in an integrated manner as shown in fig6 teeth 16 a of the first gear planet 16 is engaged with teeth 15 a of the first internal tooth gear 15 and can roll the first gear.