EGR/ignition timing control system for an internal combustion engine

Claim 1

In an internal combustion engine having an intake system which has an intake passage, a throttle valve incorporated in said intake passage, and a vacuum port which opens to said intake passage at a position which is upstream of said throttle valve when it is fully closed and which is downstream of said throttle valve when it is opened beyond a predetermined opening, an EGR system having an EGR passage and an EGR valve which has a first diaphragm means and opens said EGR passage when said first diaphragm means is supplied with a vacuum greater than a predetermined level, and a vacuum advancer which has a second diaphragm means and advances ignition timing in accordance with the vacuum supplied to said second diaphragm means, an EGR/ignition timing control system comprising a vacuum valve which has a third diaphragm means, a valve element operated by said diaphragm means and a valve port which is closed by said valve element when said third diaphragm means is supplied with a vacuum greater than a predetermined level, a check valve, first, second and third passage means which individually connect said first, second and third diaphragm means to said vacuum port, said second passage means incorporating therein a parallel connection of said valve port of said vacuum valve and said check valve, and said check valve being so directed as to allow fluid to flow only from said second diaphragm means toward said vacuum port.