Plastic chain case

The utility model discloses a plastic chain box for the motorcycle, comprising an upside chain box and a downside chain box, and their joint face is connected via tenons. These tenons are: an integrative intercalated plate groove arranged on the interface in the middle part of the upside chain box and both sides of the plate groove are respectively provided with raised head; the interface in the middle part of the downside chain box is relative to the plate trough, and concave pits are arranged in both sides of the plate groove trough wall. When the tenons are connected, the raised heads are respectively wedged into the concave pits. The plate matches the plate trough excessively or with little surplus, and distances between the interface and concave pit are respectively longer or equal to the distances between the interface and raised head. The utility model is characterized in that, it eliminates or reduces the abnormal noise coming from the friction between the chain and the chain box, the upside chain box and the downside chain box are conveniently integrated into one part. Further, the utility model has the advantage of, such as attractive appearance, high anti-deformation capability, low cost, and is simply to manufacture, convenient to assemble and disaccemble, easy to install, and the like.