Fluid handling – Self-proportioning or correlating systems – Self-controlled branched flow systems
Reexamination Certificate
2003-05-20
2004-01-13
Hepperle, Stephen M. (Department: 3753)
Fluid handling
Self-proportioning or correlating systems
Self-controlled branched flow systems
C137S514500, C137S539500
Reexamination Certificate
active
06675823
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a relief valve.
BACKGROUND OF THE INVENTION
JP-A-H8-42513 published in 1996 by the Japanese Patent Office discloses a relief valve included in the flow control valve of a power steering device.
FIG. 10
shows this flow control valve
200
. A relief valve
250
is incorporated in a spool
201
of the flow control valve
200
, as shown in the diagram.
Oil supplied to a supply chamber
202
at the tip of the spool
201
from the pump port P is supplied to the power steering device via an orifice
203
and an oil supply port
204
.
The oil pressure on the side of the oil supply port
204
(oil pressure downstream of the orifice
203
) is introduced to a flowrate control spring chamber
205
at the base end of the spool
201
. The spool
201
displaces under a balance between a thrust force due to the oil pressure of the supply chamber
202
and the supply port
204
(oil pressure both upstream and downstream of the orifice
203
), and a reaction due to the spring force of a spring
206
provided in the flow rate control spring chamber
205
and the oil pressure of the flowrate control spring chamber
205
. When the differential pressure upstream and downstream of the orifice
203
increases due to an increase of the pump rotation speed, the thrust force due to the oil pressure of the supply chamber
202
exceeds the reaction force, the spool
201
displaces in the base direction (left-hand direction of FIG.
10
), and the supply chamber
202
communicates with a tank port T. Therefore, part of the flowrate from the pump port P is returned to the tank, and the flowrate is controlled.
When the load on the power steering device increases and the oil pressure of the oil supply port
204
sharply increases, if the oil pressure of the pressure control spring chamber
205
exceeds the set pressure of the relief valve
250
, the relief valve
250
is pushed open, and oil in the pressure control spring chamber
205
escapes to the tank port T. As a result, the spool
201
displaces in the base end direction, oil pressure in the supply chamber
202
escapes to the tank port T, and the supply pressure is prevented from increasing beyond the permitted pressure.
SUMMARY OF THE INVENTION
However, in the aforesaid relief valve
250
, there is a large gap between a ball support member
252
which supports a ball
251
, and the inner circumference of a valve hole
253
, so movable members (the ball
251
and ball support member
252
) easily vibrate in a side direction (radial direction) due to the effect of the inclination of a return spring
254
and the side force of the flow when the relief valve
250
opens.
Further, in this relief valve
250
, in a transient state when the movable members are pushed open, noise is produced by chattering which makes the operation of the movable members unstable. If the diameter of a seat orifice
255
is reduced, this chattering can be suppressed, but in this case pressure losses increase, and override characteristics of the relief valve
250
(characteristics of the difference between a set pressure and a cracking pressure) are impaired.
It is therefore an object of this invention to stabilize the operation of movable members, prevent chattering and improve override characteristics in a relief valve.
In order to achieve the above object, this invention provides a relief valve, comprising a valve seat comprising a seat hole, a ball which opens and closes the seat hole from the downstream side, a movable member which supports the ball from the downstream side, a housing part which houses the movable member, and an orifice formed downstream of the seat hole which damps the vibration of the movable member and suppresses chattering by restricting an oil flow.
According to an aspect of this invention, this invention provides a flowrate control valve which controls the flowrate supplied from a pump to a load circuit comprising a relief valve, the relief valve comprising a valve seat having a seat hole, a ball which opens and closes the seat hole from the downstream side, a movable member which supports the ball from the downstream side, a housing part which houses the movable member, and an orifice formed downstream of the seat hole which damps the vibration of the movable member
4
and suppresses chattering by restricting an oil flow. The relief valve opens when the pressure on the load circuit side rises, and part of the fluid from the pump is discharged to a tank port.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.
REFERENCES:
patent: 1104201 (1914-07-01), Lenzi
patent: 3003423 (1961-10-01), Drutchas
patent: 3217732 (1965-11-01), Haugeland
patent: 5183075 (1993-02-01), Stein
patent: 5251664 (1993-10-01), Arvidsson et al.
patent: 5595213 (1997-01-01), Brown
patent: 5685332 (1997-11-01), Overdiek et al.
patent: 5775360 (1998-07-01), Hayashi et al.
patent: 08-42513 (1996-02-01), None
Guo Maoying
Nagata Kiyokazu
Tsuchiya Hideki
Hepperle Stephen M.
Kayaba Industry Co. Ltd.
Rabin & Berdo P.C.
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