1.  Field of the Invention
The present invention involves an optical disk playing device, especially involves an optical disk transport device for optical disk playing device, which holds optical disks of big or small diameter via tapered delivery roll and optical disk guiding device, to transport them to the plummer. 
2.  Description of the Related Art
The optical disk transport device has been disclosed, via tapered delivery roll and optical disk guiding device, which holds optical disks of big or small diameter inserted from the insertion inlet, to transport them to the plummer.  For example:
The Japanese patent (below called as “patent documentation 1”) with the patent number of No.  3012832 (P3012832) disclosed the following structure: a tapered roll is located at the optical disk insertion inlet; an optical disk guiding device is located at the position opposite to the tapered roll; a pair of detection bars is provided, which contact the periphery of the optical disks inserted from the insertion inlet, have detection parts, and are able to rotate freely; a linkage plate is provided, which is capable of shaking, moving according to the rotating of the detection bars, and making the pair of detection bars to move together.  Besides, the technique of guiding optical disks of small diameter to the center of the insertion inlet via the detection bars is also disclosed. 
The Japanese patent application (below called as “patent documentation 2”) with the publication number of 2008-140524 (P2008-140524A) disclosed the following structure: a tapered roll is located at the insertion inlet; an optical disk guiding device is located at the position opposite to the tapered roll; a pair of detection bars are located behind the plummer, which contact the periphery of the optical disks and have detection parts, and are able to rotate freely.  Besides, the technique is also disclosed that when the center of the optical disks being held and transported by the tapered roll and optical disk guiding device is passing through the center of the plummer, the detection parts contact the periphery of the optical disks of small diameter to stop the transporting of the optical disks of small diameter. 
In the above mentioned patent documentation 1, the detection parts of the detection bars are located between the tapered roll and the insertion inlet.  The optical disk inserted from the insertion inlet is forcibly guided to the center of the insertion inlet by the detection parts.  For the optical disk is forcibly guided at the insertion inlet, the problem that the feeling of inserting is not good occurs.  Besides, when the optical disk of small diameter is above the plummer, the detection parts of the detection bars are far away from the periphery of the optical disk of small diameter.  So, when the optical disk playing device is laid vertically (that is, the face of the optical disk is at vertical state), the optical disk of small diameter being loaded will deviate from the transport path because of its self weight, and the optical disk of small diameter can not be guided to the plummer safely. 
In the above mentioned patent documentation 2, for the detection parts of the detection bars are located behind the plummer, the problem that the feeling of inserting is not good doesn't occur at all.  But, when the optical disk of small diameter is above the plummer, the detection parts of the detection bars are located behind the optical disk of small diameter; in this situation, when the optical disk playing device is laid vertically (that is, the face of the optical disk is at vertical state), the optical disk of small diameter being loaded will also deviate from the transport path because of its self weight, and the optical disk of small diameter can not be guided to the plummer safely.