Wife's Tamkin and Marital Rape

It is not my question, But some one asked me about this issue.What are the differences of wife's submission/deference (Tamkin Khas) in Islamic law and marital rape in western law? In western law there is an idea which the husband can not force his wife to have sex (sexual intercourse), but in Islam we see some orders which show that Tamkin is the only duty of wife in her marriage.