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