The retarders which are broadly used in Japan at the present time are exhaust brakes of exhaust pipe open/close type. The history of employment of these retarders, which are now adopted not only in heavy trucks but also in medium and light trucks, is explained in this paper. The while, observing the process of improvement of components and of the control system as well as the braking effects of exhaust brakes, the reasons for such a growth are examined.
As a recent technical trend the purpose of use of exhaust pipe open/close valves are diversified to acceleration of engine warmup besides retarding effects to the vehicle. And it is also necessary today to correspond to engines with turbochargers.
Therefore, high temperature resistance improvement of working durability and so forth can be raised as technical subjects to be solved in the future, and these subjects are explained in this paper.