Combustion pressure control device

A combustion pressure control system of an internal combustion engine having a plurality of combustion chambers and sub chambers which are communicated with those combustion chambers, the combustion pressure control system is provided with

• spring devices each of which has elasticity and is formed to contract, which has one side in the contraction direction which is connected to a sub chamber which is communicated with one combustion chamber, and which has the other side opposite to the one side in the contraction direction which is connected to a sub chamber which is communicated with the other combustion chamber, wherein
• the spring device is formed so as to contract while using a pressure change of the combustion chambers as a drive source when the pressures of combustion chambers reach a predetermined control pressure, and
• when at least one of the one combustion chamber and the other combustion chamber reaches the control pressure in the time period from a compression stroke to a expansion stroke of combustion cycle, the spring device contracts, whereby volumes of the sub chambers increase and pressure rise of the combustion chambers is suppressed.