Patent Document ID: 6161511
Application ID: 09417111
Patent Flag: 1

Claim One:
1. A valve timing control system for an internal combustion engine, comprising: an intake valve and an exhaust valve driven in synchronism with rotation of said internal combustion engine for opening/closing an intake passage and an exhaust passage, respectively, which are communicated to a combustion chamber of said internal combustion engine; engine operation state detecting means for detecting operation states of said internal combustion engine; desired valve timing arithmetic means for arithmetically determining a desired valve timing for at least one of said intake valve and said exhaust valve in dependence on said engine operation state as detected; variable valve timing mechanism for changing open/close timing of at least one of said intake valve and said exhaust valve; actual valve timing detecting means for detecting an actual valve open/close timing of at least one of said intake valve and said exhaust valve; actual valve timing control means for generating a control quantity for said variable valve timing mechanism so that a timing deviation of said actual valve timing from said desired valve timing becomes zero; and learning means for learning a most retarded valve timing of said actual valve timing as a learned value, wherein said learning means is so arranged as to reflect a detected value of said actual valve timing in said learned value when said actual valve timing is detected at a timing which retards relative to said learned value in the course of operation of said internal combustion engine, and wherein said actual valve timing control means is so arranged as to determine arithmetically said control quantity in dependence on said learned value as a maximum retard reference.