Time delay exists widely in information transduction between neurons due to synaptic connection. The effects of time delay on the synchronization behaviour of four chaotic HR (Hindmarsh-Rose) neurons with ring coupling scheme were studied.By computing the synchronization errors, it is found that complete synchronization among neurons can be induced or enhanced by appropriate time delays, namely, a stable synchronous state exists at lower coupling strengths under the action of time delay. It is further observed that time delay can also induce phase synchronization and enlarge the in-phase synchronization window. Moreover, complex phenomena induced by time delay, such as the transition between nearly complete synchronization and phase synchronization, can be observed before the occurrence of complete synchronization.