Fuel cap

A fuel cap where a valve body held to a valve support plate for performing pressure adjustment is arranged in a cap body installed to a filler neck of a fuel tank, and the part number can be decreased. The valve body has an outer circumferential lip element which is projected from an outer circumferential edge and pressed against an annular projection projecting inward in a fluid flow path of the cap body, and an inner circumferential lip element which is projected from an inner circumferential edge in reverse direction to the outer circumferential lip element. The valve support plate supports the valve body from rear side of the outer circumferential lip element, and has a seal member against which the inner circumferential lip element is pressed from the support position to inner circumferential side. Biasing means for pressing the outer circumferential lip element of the valve body is connected to the valve support plate. At the outside of the seal member in the valve body or the valve support plate, a communication hole which performs communication of the atmosphere side with the fluid flow path of the cap body is formed when the inner lip element is separated from the seal member.

BACKGROUND OF THE INVENTION 
The present invention relates to a fuel cap which is installed to a filler 
neck of a fuel tank for automobiles and adjusts pressure in the fuel tank 
by flowing fluid such as air out of the fuel tank or into the fuel tank 
from outside when the pressure in the fuel tank is positive or negative. 
In the prior art, such fuel cap (hereinafter referred to simply as "cap") 
is disclosed in an example as shown in FIG. 1 (refer to Japanese Utility 
Model Laid-open Publication No. Sho 60-179654). 
In the cap 11, at normal state, an outer circumferential lip element 13b is 
biased downward through an annular support plate 14 by a first coil spring 
(first biasing means) 16 and pressed against an annular projection 12b of 
a cap body 12, and an inner circumferential lip element 13a is biased 
upward by a second coil spring (second biasing means) 17 and pressed 
against a disk-shaped valve plate 18 and closes a fluid flow path 12a of 
the cap body 12. When pressure in the fuel tank becomes positive pressure 
of a prescribed valve or more, the outer circumferential lip element 13b 
is elevated together with the support plate 14 against biasing force of 
the first coil spring 16 and separated from the annular projection 12b of 
the cap body 12 so that the positive pressure state within the fuel tank 
is eliminated through the gap. Also when pressure in the fuel tank becomes 
negative pressure of a prescribed valve or more, the valve plate 18 is 
moved downward against the biasing force of the second coil spring 17 and 
separated from the inner circumferential lip element 13a so that the 
negative pressure state within the fuel tank is eliminated through the 
gap. Numeral 10 designates a filler neck. 
In the cap 11, however, at normal state, since the fluid flow path 12a of 
the cap body 12 is closed by the first coil spring 16 biasing the outer 
circumferential lip element 13b downward and the second coil spring 17 
biasing the inner circumferential lip element 13a upward, the two coil 
springs 16, 17 and the valve plate 18 are indispensable. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a fuel cap wherein even if means 
for biasing an inner circumferential lip element and a valve plate are not 
installed, a fluid flow path can be closed at normal state and pressure 
can be adjusted at pressure varying state, and the part number and the 
assembling process number are small, and further the manufacture is 
possible at low cost. 
The foregoing object can be attained by a fuel cap which is installed to a 
filler neck of a fuel tank, comprising: a cap body provided with a fluid 
flow path, and an annular projection projecting inward at an inner 
circunference of the fluid flow path; an annular valve body of a rubber 
state elastic material provided with an outer circumferential lip element 
projected from an outer circumferential edge and pressed against the 
annular projection, and an inner circumferential lip element projected 
from an inner circumferential edge in reverse direction to the outer 
circumferential lip element; a disk-shaped valve support plate provided 
with a support portion disposed at rear side of the outer circumferential 
lip element for supporting the valve body, and a seal member for pressing 
the inner circumferential lip element at the inside from the support 
portion when the valve body is supported; a communication hole provided at 
the outside of the seal member in the valve body or the valve support 
plate for performing communication of the atmosphere side with the fluid 
flow path when the inner circumferential lip element is separated from the 
seal member; and means for biasing the valve support plate in such 
direction that the outer circumferential lip element of the valve body is 
pressed against the annular projection. 
In the fuel cap according to the invention, after it is installed to the 
filler neck, at normal state, the outer circumferential lip element of the 
valve body is pressed against the annular projection of the cap body by 
the spring biasing means and the inner circumferential lip element of the 
valve body is pressed against the seal member of the valve support plate 
by elasticity of the valve body, and the fluid flow path within the cap 
body is closed by the valve body and the valve support plate. 
When the pressure within the fuel tank becomes negative pressure or 
positive pressure of a prescribed valve or more, the inner circumferential 
lip element of the valve body is bent against the elasticity of the vlave 
body in direction separating from the seal member of the valve support 
plate thereby a gap is produced between the inner circumferential lip 
element and the valve support plate. Consequently, the closing of the 
fluid flow path of the cap body is released by the gap, and the negative 
pressure state or the positive pressure state within the fuel tank is 
eliminated. 
In other words, even if means for pressing the inner circumferential lip 
element against the seal member and the valve plate as in the prior art 
are not installed, when the pressure within the tank is varied, the inner 
circumferential lip element is bent against the elasticity of the valve 
body in direction separating from the valve support plate, thereby the 
pressure variation within the fuel tank can be eliminated. 
Consequently, the biasing means to the inner circumferential lip element 
and the valve plate become unnecessary, and corresponding to this the part 
number and the assembling process number are reduced in comparison to the 
prior art, thereby the manufacturing cost can be reduced and the fuel cap 
can be manufactured at low charge.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Embodiments of the invention will now be described referring to the 
accompanying drawings. 
A fuel cap 21 of a first embodiment shown in FIGS. 2.about.10 is composed 
of a cylindrical cap body 22 of plastics such as polyacetal, and a 
disk-shaped upper cover 42 of plastics such as nylon to be fitted to a 
flange portion 41 partially provided on upper end of the cap body 22. In 
order to prevent over-tightening of the cap 21 of the filler neck 10, as 
known in the prior art, a ratchet projection 42a is formed at lower 
surface of the upper cover 42, and an elastic finger 46 provided at its 
top end with a locking powl 45 engageable with the ratchet projection on 
42a is formed on the flange portion 41 of the cap body 22 and projected in 
the circmferential direction. A gap 47 formed in the circumferential 
direction to each flange portion 41 constructs a part of a fluid flow path 
22a of the cap body 22 which communicates with air as hereinafter 
described. 
A thread 43 for installing to the filler neck 10 is provided on the outer 
circumference of the cap body 22, and a seal ring 44 is installed outward 
to the lower surface of the flange portion 41. 
The flow path 22a for fluid such as air in the tank is formed within the 
cap body 22, and an annular projection 22b projecting inward in radial 
direction is formed on the inner circumference of the fluid flow path 22a. 
Numeral 22c designates a plurality of ribs installed on the inner 
circumference of the fluid flow path 22a in order to guide movement in a 
valve support plate 24 at positive pressure operation state, and numeral 
22d designates a fluid flowing hole. 
Also in the fluid flow path 22a a valve body 23, a valve support plate 24, 
a coil spring 26 and a spring shoe plate 28 are arranged. 
The valve body 23 is an annular body made of rubber or rubber-like elastic 
material such as thermoplastic elastomer, and composed of a base portion 
23a, an inside arm member 23b extending inward from an upper edge of the 
base member 23a, and an outside arm portion 23d extending outward from a 
lower edge of the base member 23a. An inner circunferential lip element 
23c projecting upward is formed at the top end of the inside arm member 
23b, i.e., at the inner circumferential edge of the valve body 23, and an 
outer circumferential lip element 23e projecting downward is formed at the 
top end of the outside arm member 23d, i.e., at the outer circmferential 
edge of the valve body 23. A thin portion 23i is formed at a joint portion 
of the inside arm member 23b with the base member 23a. On upper side of 
the outer circumference of the base member 23a, an annular projection 23f 
and an annular recess 23g continuing to lower side of the annular 
projection 23f are formed and engageable with a valve support plate 24 as 
hereinafter described. 
Outer diameter of the outer circumferential lip element 23e is specified so 
that the outer circumferential lip element 23e can be pressed against 
upper surface of the annular projection 22b of the cap body 22. Also inner 
diameter of the inner circumferential lip element 23c has dimension so 
that when the outer circumferential lip element 23e is pressed against the 
upper surface of the annular projection 22b, the inner circumferential lip 
element 23c is positioned inside the annular projection 22b. 
An annular thickness reducing portion 23h is formed at the lower side of 
the inner circumferential lip element 23c so that the filling pressure at 
the position of the inner circumferential lip element 23c is not rapidly 
varied during the injection molding. 
The valve support plate 24 is a disk-shaped body made of plastics such as 
polyacetal, and a disk-shaped inside plate 24a and an annular outside 
plate 24d are partially connected by a connecting element 24h having 
L-like cross-section so that a prescribed gap between upper and lower 
sides is formed. The gap between the inside plate 24a and the outside 
plate 24d becomes a communiccation hole 25. 
A projection 24c is partially provided on circumferential edge at the lower 
surface of the inside plate 24a. The projection 24c prevents deterioration 
of seal property caused by that the inside arm portion 23b of the valve 
body 23 is moved upward beyond a prescribed range and abutting state of 
the inner circumferential lip element 23c on the seal portion 24b is 
deteriorated. Center portion of the inside plate 24a is projected downward 
in cylindrical form. 
An annular projection 24f is projected on the lower surface at the inner 
circumferential edge of the outside plate 24d, and an annular rib 24e is 
projected upward on the upper surface at the outer circumferential edge 
thereof so as to guide a coil spring 26 as hereinafter described. 
An inner circumferential edge 24g of the outside plate is engaged with the 
annular recess 23g of the valve body 23 so that the valve body 23 is 
supported. In other words, the inner circumferential edge 24g of the 
outside plate becomes the support position of the valve body 23. When the 
valve body 23 is assembled with the valve support plate 24, the inner 
circumferential lip element 23c of the valve body 23 is bent a little 
(about 0.5 mm) downward and pressed against the seal portion 24b. 
The spring shoe plate 28 is provided at the center with a fluid flowing 
hole 28a and made of plastics such as polyacetal, and is arrange in the 
fluid flow path 22a of the cap body 22 on the upper side of the valve 
support plate 24 and holds the upper end of the coil spring (biasing 
means) 26 for biasing the valve support plate 24 downward. 
The coil spring 26 biases the valve support plate 24 downward, and presses 
the outer circumferential lip element 23e of the valve body 23 against the 
annular projection 22b of the cap body 22. Assembling of each of these 
members to the top cap body 22 will be described. 
First, the annular recess 23g of the valve body 23 is engaged with the 
inner circumferential edge 24g of the valve support plate 24, thereby the 
valve body 23 is held to the valve support plate 24. The valve body 23 and 
the valve support plate 24 are arranged within the cap body fluid flow 
path 22a so that the outer circumferential lip element 23e is arranged on 
the upper surface of the annular projection 22b. And then the coil spring 
26 is arranged on the upper surface of the valve support plate 24, and the 
spring shoe plate 28 is arranged from upper side of the coil spring 26 
into the cap body fluid flow path 22a. 
Further the seal ring 44, the upper cover 42 and the like are assembled 
thereby the cap 21 of the embodiment can be constructed. 
After the cap 21 is installed to the filler neck 10, at normal state, the 
outer circumferential lip element 23e of the valve body 23 is pressed 
against the upper surface of the annular projection 22b of the cap body 22 
by the coil spring 26 through the valve support plate 24. Also the inner 
circumferential lip element 23c of the valve body 23 is pressed against 
the seal member 24b of the valve support plate 24 by elasticity of the 
valve body 23 itself. Consequently, the fluid flow path 22a on the lower 
side of the annular projection 22b is closed by the valve body 23 and the 
valve support plate 24. 
When pressure within the tank becomes negative pressure of prescribed valve 
or more, as shown in FIG. 8, the inside arm position 23b of the valve body 
23 is bent downward about the base portion and the inner circumferential 
lip element 23c is separated from the seal member 24b, thereby a gap is 
produced between the inner circumferential lip element 23c and the seal 
surface 24b. Consequently, air flows from outside of the cap 21 through 
the fluid flowing hole 28a of the spring shoe plate 28 and the 
communication hole 25 of the valve support plate 24 into the tank, thereby 
the negative pressure state within the tank is eliminated. 
Also when the pressure within the tank becomes positive pressure of 
prescribed valve or more, as shown in FIG. 9, the outer circumferential 
lip element 23e is elevated together with the valave support plate 24 
against the biasing force of the coil spring 26, and separated from the 
upper surface of the annular projection 22b of the cap body 22. 
Consequently, the closed state of the fluid flow path 22a of the cap body 
22 is released by a gap formed between the outer circumferential lip 
element 23e and the annular projection 22b and fluid such as air flows out 
of the tank, thereby the positive pressure state within the tank is 
eliminated. 
In the cap body 21, even if the coil spring or the valve plate as biasing 
means to the inner circumferential lip element 23c as in the prior art is 
not installed, at normal state, the inner circumferential lip element 23c 
is pressed against the seal member 24b of the valve support plate 24 by 
elasticity of the valve body 23 and closes the fluid flow path 22a. When 
pressure within the tank becomes negative pressure of prescribed valve or 
more, the inner circumferential lip element 23c is bent and the gap is 
produced between the inside lip element 23c and the seal member 24b, 
thereby air flows into the tank and the negative pressure state within the 
tank is eliminated. 
Consequently, the coil spring (biasing means) for the inner circumferential 
lip element 23c and the valve plate are obviated, and corresponding to 
this the part number may be decreased and the manufacturing cost may be 
reduced thereby the fuel cap can be manufactured at low charge. 
Also, in the first embodiment, a thin portion 23i is formed at the joint 
portion of the inside arm portion 23b of the valve body 23 thereby the 
inside arm section 23b is liable to be bent downward. Consequently, it can 
react sharply to the negative pressure state within the tank. 
Further in the cap 21 of the first embodiment, an annular projection 24f is 
formed at lower side of the outside plate 24d of the valve support plate 
24, and at non-pressed state of the outer circumferential lip element 23e 
to the annular projection 22b, the gap is produced between the upper 
surface of the outer circumferential lip element 23e and the valve support 
plate 24. The outer circumferential lip element 23e is liable to be bent 
upward according to this gap, and even if the surface precision 
(undulation precision) of the seal surface is not sufficient in the 
annular projection 22b to which the outer circumferential lip element 23e 
is pressed, error in the surface precision of the seal surface can be 
absorbed by the gap. Consequently, manufacture of the upper surface of the 
annular projection 22b of the cap body 22 becomes easy. 
Although in the cap 21 of the first embodiment, the inner circumferential 
lip element 23c of the valve body 23 acts at the negative pressure state 
and the outer circumferential lip element 23e acts at the positive 
pressure, state, another construction may be taken as in a cap 51 of a 
second embodiment shown in FIG. 11 where an outer circumferential lip 
element 53e acts at the negative pressure state and an inner 
circumferential lip element 53c acts at the positive pressure state. 
In the second embodiment, the inner circumferential lip element 53c 
projecting downward is formed at inner circumferential edge of an inside 
arm member 53b of a base member 53a in a valve body 53, and the other 
circumferential lip element 53e projecting upward is formed at the outer 
circumferential edge thereof. The inner circumferential lip element 53c is 
provided at the inner ciecumferential edge of the inside arm member 53b of 
the base member 53a, and the outer circumferential lip element 53e is 
provided at upper side of the base member 53a. A thin portion 53i is 
formed at joint position of the inside arm member 53b. Also a recess 53j 
partially notched is formed at lower side of the base member 53a being 
rear side of the outer circumferential lip element 53e. 
The valve body 53 is fixed to an upper surface 54j (support position) at 
circumferential edge portion of a disp-shaped valve support plate 54 by 
bonding the base member 53a being rear side of the outer circumferential 
lip element 53e, and the notched portion 53j at lower side of the base 
member 53a becomes a communication hole 55. Then the inner circumferential 
lip element 53c of the valve body 53 is pressed against the upper surface 
(seal member 54b) at inside from the communicating hole 55 of the valve 
support plate 54. 
The valve body 53 and the valve support plate 54 are biased upward by a 
coil spring 56 with lower end held to a spring shoe plate 58, and the 
outer circumferential lip element 53e of the valve body 53 is pressed 
against the lower surface of the annular projection 52b and assembled to 
the fluid flow path 52a of the cap body 52. 
In the cap 51 at normal state, the outer circumferential lip element 53e is 
pressed against the lower surface of the annular projection 52b by the 
coil spring 56 through the valve support plate 54. Also the inner 
circumferential lip element 53c is pressed against the seal member 54b of 
the valve support plate 54. Consequently the fluid flow path 52a is closed 
by the valve body 53 and the valve support plate 54. 
When the pressure within the tank becomes negative pressure of prescribed 
valve or more, the outer circumferential lip element 53e is moved downward 
together with the valve support plate 54 against the biasing force of the 
coil spring 56, and separated from the lower surface of the annular 
projection 52b of the cap body 52. Consequently, according the gap between 
the outer circumferential lip element 53e and the annular projection 52b, 
fluid such as air flow from the outside of the cap 51 into the tank 
thereby the negative pressure state within the tank is eliminated. 
Also when the pressure within the tank becomes positive pressure of 
prescribed valve or more, the inner circumferential lip element 53c is 
bent upward against the elasticity of the valve body 53, and separated 
from the seal memeber 54b of the valve support plate 54 thereby the gap is 
produced. Consequently fluid passes through the gap and flows out of the 
tank thereby the positive pressure state within the tank is eliminated. 
Consequently, in the second embodiment, even if means for biasing the inner 
circumferential lip element 53c is not installed, the pressure within the 
tank can be asjusted thereby similar effects to the first embodiment can 
be obtained.