Motor vehicles – Steering gear – With fluid power assist
Patent
1994-12-16
1996-11-26
Hurley, Kevin
Motor vehicles
Steering gear
With fluid power assist
180423, B62D 506
Patent
active
055775730
ABSTRACT:
A hydraulic power steering system includes a pump, a flow control valve, and a bypass control valve. The flow control valve responds to a pressure drop across a metering orifice disposed in a fluid supply passage so as to control the flow rate of operating fluid by bypassing a part of the operating fluid to a reservoir. A spring chamber of the flow control valve is connected to the supply passage through a control orifice. The bypass control valve is disposed between the spring chamber and the reservoir so as to increase the amount of bypassed fluid by controlling the pressure in the spring chamber. The bypass control valve has a control spool, a load pressure introduction port connected to the upstream side of the control orifice for leading the load pressure to a first end of the control spool and a pilot port connected to the downstream side of the control orifice for leading the pressure in the spring chamber of the flow control valve to a second end of the control spool. Moreover, a pressure receiving area of the second end of the control spool is smaller than that of the first end of the control spool. Accordingly, a spring having a small spring constant can be used in the bypass control valve, even when the control spool is controlled within a short stroke. Further, the control spool, the load pressure introduction port, and the pilot port are formed in a sleeve.
REFERENCES:
patent: 4473128 (1984-09-01), Nakayama et al.
patent: 4714413 (1987-12-01), Duffy
patent: 5439070 (1995-08-01), Haga et al.
patent: 5471838 (1995-12-01), Suzuki et al.
patent: 5474145 (1995-12-01), Haga et al.
Fukumura Kenichi
Haga Kyosuke
Inaguma Yoshiharu
Kato Hideya
Suzuki Mikio
Hurley Kevin
Toyoda Koki Kabushiki Kaisha
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