Fluid handling – Diverse fluid containing pressure systems – Fluid separating traps or vents
Reexamination Certificate
2001-06-08
2003-07-15
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Diverse fluid containing pressure systems
Fluid separating traps or vents
C137S043000
Reexamination Certificate
active
06591855
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of and priority from Japanese Applications No. 2000-171579 filed Jun. 8, 2000 and No. 2001-11652 filed Jan. 19, 2001, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel cutoff valve mounted on a fuel tank. More particularly, the invention relates to fuel cutoff valves for use in automobiles.
2.Description of Related Art
A conventional fuel cutoff valve is described in JPA 6-297968. In
FIG. 14
, which shows a conventional fuel valve, a fuel cutoff valve
200
comprises a full fuel control valve that shuts off when the full fuel level is exceeded, and an overfill prevention valve that shuts off when the fuel is fed past the full fuel level, and the overfill level is exceeded. Specifically, the fuel cutoff valve
200
comprises a casing
202
mounted on a fuel tank (not shown), a first float valve
210
housed in the casing
202
, a spring
219
for urging the first float valve
210
, and a second float valve
220
housed in the first float valve
210
. The upper end of the casing
202
is provided with a wall
204
. A connection hole
204
a
connected to a fuel vapor exhaust pipe
206
is formed in the center of the wall
204
. A retainer
208
is mounted on the lower end of the casing
202
.
The first float valve
210
comprises a thick-walled cylindrical lower portion
212
, an upper portion
214
configured as an upwardly extending thick-walled cylinder whose lower end is mounted around the upper end portion of the lower portion
212
, a cover plate
216
for covering the upper opening of the upper portion
214
, and a valve box
218
interposed in an airtight manner between the outer circumference of the lower end of the cover plate
216
and the upper end of the upper portion
214
. The first float valve
210
is supported by the spring
219
on the lower portion
212
. The center of the cover plate
216
is provided with a projection
216
a
. The projection
216
a
is disposed facing the connection hole
204
a
and can be attached to the connection hole
204
a
or detached therefrom. The projection
216
a
is provided with a connection hole
216
b
, which is coaxially aligned with the connection hole
204
a
. A vent
214
a
is provided above the wall surrounding the upper portion
214
, and the interior of the upper portion
214
is normally connected to the vapor phase of the fuel tank through the vent
214
a
and a vent
202
a
provided to the casing
202
. The bottom of the valve box
218
is provided with a connection hole
218
a.
The second float valve
220
is disposed inside the upper portion
214
. The second float valve
220
is supported by a spring
222
on the upper end face of the lower portion
212
of the first float valve
210
, and the upper end thereof is provided with a projection
220
a
in a facing arrangement with the connection hole
218
a
. The valve box
218
also houses a relief valve
230
. The relief valve
230
is designed to open and close the connection hole
218
a
by the urging of a valve body
232
with a spring
234
.
The operation of the fuel cutoff valve
200
will now be described. The first float valve
210
alone experiences buoyancy when the liquid level inside the tank is in the vicinity of the full fuel liquid level. The first float valve
210
moves up and blocks the connection hole
204
a
with the projection
216
a
on the upper end thereof. In the process, the second float valve
220
moves together with the first float valve
210
, but the projection
220
a
leaves the connection hole
218
a
open because of the absence of mutual displacement between the second float valve
220
and the first float valve
210
.
In this state, the relief valve
230
closes the connection hole
218
a
, so the fuel vapor exhaust pipe
206
is blocked by the mutual engagement of the connection hole
204
a
and the projection
216
a
. The relief valve
230
opens when the pressure inside the tank exceeds a predetermined level. The gas inside the tank thus escapes from the fuel vapor exhaust pipe
206
via the vent
202
a
, vent
214
a
, connection hole
218
a
, connection hole
216
b
, and connection hole
204
a
, and the inside pressure is kept below a predetermined level.
If the liquid level inside the tank rises in an abnormal manner and the second float valve
220
is also buoyed, the second float valve
220
rises relative to the first float valve
210
, blocking the connection hole
218
a
. The fuel cutoff valve
200
thus operates such that the interior of the fuel tank is separated from the outside by the second float valve
220
when the liquid level exceeds the full fuel liquid level, which is a level at which the first float valve
210
operates as a closing device.
In the fuel cutoff valve
200
, the connection hole
204
a
is a narrow conduit incapable of rapidly removing fuel vapors into the canister from the fuel tank when a large amount of fuel is supplied. However, increasing the surface area of the conduit formed by the connection hole
204
a
increases the seal diameter and presses the first float valve
210
with greater force against the sealing surface facing the connection hole
204
a
. A resulting shortcoming is that the first float valve
210
does not open as readily, that is, valve reopening characteristics are adversely affected, when the liquid level of the fuel tank drops below a prescribed value. Techniques in which the floats are provided in two stages have been proposed as a means to overcome this shortcoming, as have been structures in which the full fuel control valve and the overfill prevention valve are provided at separate locations, but these structures are too complicated and make vehicles harder to assemble.
SUMMARY OF THE INVENTION
An aspect of the present invention is to provide a fuel cutoff valve that is capable of preventing overfilling, possesses improved valve reopening characteristics, and has a simple structure.
The present invention provides a fuel cutoff valve mounted on a fuel tank and is designed to connect the interior of the fuel tank with the outside or to separate the tank from the outside. The fuel cutoff valve is characterized by a casing including a casing main body partially extending into the upper portion of the fuel tank and having a first valve chamber, an outer conduit disposed outside the fuel tank, a first connection conduit designed to connect the outer conduit and the first valve chamber and configured such that the conduit surface area thereof is at least ⅓ that of the outer conduit, and a first seat disposed on the side of the first valve chamber facing the first connection conduit. A first float including a first float main body is disposed inside the first valve chamber and is capable of moving up and down. A first valve element opens and closes the first connection conduit by attaching itself to and detaching itself from the first seat provided to the upper portion of the first float main body. A storage chamber is formed in the axial center of the first float main body and is designed to form a connection with the first valve chamber. A second connection conduit is disposed in the upper portion of the first float main body and is designed to connect together the first connection conduit and the storage chamber and provided with a smaller conduit surface area than the first connection conduit. A second float including a second float main body is disposed in the storage chamber and is capable of moving up and down. A second valve element is disposed in the upper portion of the second float main body and is designed to open and close the second connection conduit. The first float is configured such that the first connection conduit is closed by the first valve element as a result of a rising movement when the fuel level in the fuel tank exceeds a first liquid level. The second float is configured such that the second connection conduit is closed by the second valve element as a result of a
Aoki Tomohide
Nishi Hiroshi
Sugizaki Tomohiro
Michalsky Gerald A.
Posz & Bethards, PLC
Toyoda Gosei Co,., Ltd.
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