Conveying rollers pair and image forming apparatus

Abstract

A conveyance rollers pair includes a first roller and a second roller. The first roller has a uniform outer diameter and rotates around an axis. The second roller conveys a medium held between the first roller and the second roller while rotating around an axis. The second roller includes a shaft part, a plurality of columnar elastic members and a plurality of tube members. The shaft part extends in an axial direction and is supported rotatably around the axis. The elastic members are fixed to an outer circumferential surface of the shaft part at intervals in the axial direction. Each of the tube member has heat-shrinking property and water-repellency, adheres closely to an outer circumferential surface of the elastic member, and has both end portions which are protruded outward from both axial ends of the elastic member and have a diameter smaller than an outer diameter of the elastic member.

1 . A conveyance rollers pair comprising:
 a first roller extending in an axial direction, having a uniform outer diameter and rotating around an axis; and   a second roller conveying a medium held between the first roller and the second roller while rotating around an axis, wherein   the second roller includes:   a shaft part extending in an axial direction and supported rotatably around the axis; and   a plurality of columnar elastic members fixed to an outer circumferential surface of the shaft part at intervals in the axial direction; and   a plurality of tube members each having heat-shrinking property and water-repellency, adhering closely to an outer circumferential surface of the elastic member, and having both end portions which are protruded outward from both axial ends of the elastic member and have a diameter smaller than an outer diameter of the elastic member.   
     
     
         2 . The conveyance rollers pair according to  claim 1 , wherein
 the elastic members are arranged in positions that avoid both ends of the medium in a width direction parallel to the axial direction.   
     
     
         3 . The conveyance rollers pair according to  claim 1 , wherein
 the shaft part includes:   rotating shaft parts provided at both ends in the axial direction and supported rotatably; and   a fixed shaft part formed between the rotating shaft parts, having a larger diameter than the rotating shaft parts and to which the elastic members are fixed.   
     
     
         4 . The conveyance rollers pair according to  claim 1 , wherein
 an amount of protrusion of the end portions of the tube member is 1 to 2 mm, and   a thickness of the tube member is 1 to 2% of the outer diameter of the elastic member.   
     
     
         5 . The conveyance rollers pair according to  claim 1 , wherein
 the end portions are heat-shrunk to have an outer diameter smaller than an outer diameter of the elastic member.   
     
     
         6 . An image forming apparatus comprising the conveyance rollers pair according to  claim 1 . 
     
     
         7 . The image forming apparatus according to  claim 5 , wherein
 the first roller is made of metal, and   the conveyance rollers pair is a registration rollers pair that blocks the medium temporarily and then feeds the medium toward an image forming part that forms an image on the medium.   
     
     
         8 . The image forming apparatus according to  claim 7 , wherein
 the medium comes into contact with the first roller and then is temporarily blocked.