COMBUSTION PRESSURE CONTROL DEVICE

A combustion pressure control system of an internal combustion engine which has sub chambers 61a to 61d which are communicated with combustion chambers 5a to 5d, provided with spring devices each of which has elasticity and which has one side connected to a sub chamber which is communicated with one combustion chamber and has the other side connected to a sub chamber which is communicated with the other combustion chamber. The spring device includes a fluid sealing member 63. When at least one of the one combustion chamber and the other combustion chamber reaches a control pressure in the time period from a compression stroke to expansion stroke of the combustion cycle, the spring device contracts, whereby the volumes of the sub chambers increase and the pressure rise of the combustion chambers is suppressed.