a noise reducing groove formed at {HEAD ~ an upper surface} of {TAIL ~ the pump cover} and having a predetermined length; and 
of
a noise reducing groove formed at { HEAD ~ an upper surface } of { TAIL ~ the pump cover } and having a predetermined length ; and
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH