(19)
(11) EP 1 674 729 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
17.10.2012 Bulletin 2012/42

(43) Date of publication A2:
28.06.2006 Bulletin 2006/26

(21) Application number: 05027802.7

(22) Date of filing: 19.12.2005
(51) International Patent Classification (IPC): 
F04C 14/26(2006.01)
(84) Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TR
Designated Extension States:
AL BA HR MK YU

(30) Priority: 22.12.2004 JP 2004370463

(71) Applicant: KAYABA INDUSTRY CO., LTD.
Minato-ku, Tokyo 105-6190 (JP)

(72) Inventors:
  • Fujita, Tomoyuki c/o Kayaba Industry Co., Ltd.
    Minato-ku Tokyo 105-6190 (JP)
  • Sugihara, Masamichi c/o Kayaba Industry Co., Ltd.
    Minato-ku Tokyo 105-6190 (JP)
  • Yasue, Yoshinobu c/o Kayaba Industry Co., Ltd.
    Minato-ku Tokyo 105-6190 (JP)

(74) Representative: Grünecker, Kinkeldey, Stockmair & Schwanhäusser 
Leopoldstrasse 4
80802 München
80802 München (DE)

   


(54) Pump device


(57) A fixed capacity pump (P) sucks working oil from a reservoir (R) through a conduit (Rp) and a suction passage (1), and discharges the pressurized working oil into a discharge passage (2) connected to an actuator (A). A choke (21) is disposed in the discharge passage (2), and a flow control valve (F) recirculates a part of the working oil in the discharge passage (2) upstream of the choke (21) to the suction passage (1) according to a pressure loss generated by the choke (21). The characteristic of the choke (21) which significantly increases the flow resistance in a low temperature state makes the flow rate of the recirculated working oil increase, thereby preventing cavitation/noise from occurring in the pump (P) when operated at high speed and in a low temperature state.







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