a spool feeding back excess discharged oil to a bypass passage of said pump in {HEAD ~ accordance} with {TAIL ~ differential pressure} between upstream and downstream sides of said variable throttle mechanism when said excess fluid exceeds a predetermined value; and 
with
a spool feeding back excess discharged oil to a bypass passage of said pump in { HEAD ~ accordance } with { TAIL ~ differential pressure } between upstream and downstream sides of said variable throttle mechanism when said excess fluid exceeds a predetermined value ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH