Rotary expansible chamber devices – Moving cylinder – Rotating
Reexamination Certificate
2002-10-21
2004-05-25
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
Moving cylinder
Rotating
C418S166000, C418S180000, C418S189000
Reexamination Certificate
active
06739850
ABSTRACT:
The disclosure of Japanese Patent Application Nos. 2001-328425 filed on Oct. 25, and 2002-232195 filed on Aug. 9, 2002 including the specification, drawings and abstract are incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a motor-driven type fuel pump for a vehicle to be accommodated in a fuel tank for a vehicle, and more particularly to a motor-type fuel pump for a vehicle to reliably prevent entry of a fuel compressed by a compression stroke of a pump into an intake side as vapor, and further to allow a single hole to serve both as positioning pin for executing positioning when assembling a housing and a cover and as a pressure relief hole for releasing pressure in a pump chamber.
2. Description of Related Art
Recently, as a fuel pump for supplying fuel to a vehicle engine, an in-tank type motor-driven fuel pump which is installed in a fuel tank is used. Among them, a fuel pump suspending from a flange member secured to an opening of an upper wall of the fuel tank is widely used. Further, a unit-type fuel pump incorporating a filter or the like thereinto has also been used.
In such fuel pumps, a pump body portion is structured by combining a housing
42
formed with a pump chamber
41
therein and a cover
43
abutting against a lower surface of the housing
42
so as to cover the pump chamber
41
, as shown for example in a sectional view of the pump portion in FIG.
9
. The pump chamber
41
is provided, as a pump member, with an inner rotor
44
of a trochoid-gear type or the like. The inner rotor
44
is rotated by a rotation axis
46
of a motor
45
, and a fuel in the fuel tank is sucked through an intake port
47
formed on the cover
43
and discharged through a discharge hole
48
into a motor chamber
50
. Next, the fuel passing through the motor chamber
50
is pressurized, and supplied through an exhaust hole, not shown, on the upper portion of the pump body to a fuel injection system and the like.
In a fuel pump like this, particularly when the fuel temperature is increased, there are some cases where the fuel pressurized inside the pump generates vapor from the inside of the pump and deteriorates pump performance. Therefore, as shown in
FIG. 9B
, a pressure relief hole
54
communicated with the outside of the pump is formed piercing the cover
43
at a position between the intake port
47
and the discharge hole
48
at an end portion of a place at which a high-pressure area of the pump is formed.
FIGS. 10A and 10B
show this state in more detail. Particularly, as shown in
FIG. 10B
, which is a sectional view taken along line XB—XB portion in
FIG. 10A
, an internal tooth gear-like pump chamber outer peripheral surface is formed on an inner peripheral surface
56
of the pump chamber portion in an outer rotor
60
rotatably disposed in the housing
42
. Inside the internal tooth gear-like pump chamber outer peripheral surface, rotatably provided is an external tooth gear-like inner rotor
44
, capable of meshing with the pump chamber outer peripheral surface in a manner of the trochoid-gear type, and having a small diameter and a smaller number of teeth than the aforementioned internal teeth. Then, the inner rotor
44
is rotated by the rotation axis
46
driven by the motor
45
as above, and pump action is carried out.
At this time, in accordance with rotation of the inner rotor
44
in a direction shown in arrow R in the figure, the fuel sucked through the intake port
47
is sucked via an intake groove
57
formed on the upper surface of the cover
43
into a chamber portion at an intake stroke side in the pump chamber. After that, the chamber at the intake stroke side is closed and the fuel is compressed, the chamber is communicated with a discharge groove
58
formed at a discharge port
48
side, and the fuel is discharged through the discharge port
48
to the inside of the motor body.
When the inner rotor
44
is further rotated, the external teeth of the inner rotor
44
mesh with the internal teeth formed on the inner surface of the outer rotor
60
, thereby forming a high-pressure closed chamber portion P in the figure. After that, when the high-pressure closed chamber is communicated with the intake groove
57
caused by the rotation of the inner rotor
44
, a high-pressure fuel enters a low-pressure fuel through the intake hole
47
. Since the pressure is released, liquid inside carries out vacuum boiling and vaporizes. Therefore, vapor contaminates the fuel at the intake side in the pump chamber, causing a vapor lock state in which the fuel is unable to be compressed sufficiently. This may sometimes deteriorate pump performance remarkably.
As a countermeasure, for example, as shown in
FIGS. 9A
,
9
B,
10
A and
10
B, the pressure relief hole
54
is formed at a position where a high-pressure area of the pump is formed. The pressure relief hole
54
, for example, as shown in
FIG. 10B
, is provided on the cover
43
between a front edge portion of the intake groove
57
and a rear edge portion of the discharge groove so as to pierce the cover toward below the pump. Owing to this, the high-pressure fuel is introduced from a portion of the highest pressure shown as point P in the figure to the pressure relief hole
54
, through a narrow gap between opposite wall surfaces of the cover
43
and the housing
42
. Then, the fuel is released from the pressure relief hole
54
into the fuel tank.
A problem of generation of vapor lock due to entry of the high-pressure fuel at the discharge side into the intake side in the fuel pump as above occurs not only in a trochoid-gear type positive-displacement fuel pump as shown in the figure but also in other positive-displacement fuel pumps. Further, as well as in positive-displacement fuel pumps, similar problems occur in various non-positive-displacement fuel pumps of wesco type or the like.
In the meantime, when assembling the housing
42
and the cover
43
as above, in order to easily perform a precise relative positioning between the intake port
47
portion formed on the cover
43
and the discharge hole
48
portion formed on the housing
42
or the like, a positioning pin
52
is inserted into a positioning pin insertion hole
59
at the housing
42
side and fixed in advance so as to protrude toward the cover
43
side, which is then inserted into the positioning pin insertion hole
59
formed in the cover
43
. Alternatively, the positioning pin
52
is inserted into the positioning pin insertion hole
59
of the cover
43
and fixed so as to protrude toward the housing
42
side, which is then inserted into the positioning pin insertion hole
59
formed on the housing
42
.
Accordingly, when assembling this fuel pump, for example, in a case where the positioning pin
52
is fixed at the housing
42
side in advance, a tip of the positioning pin
52
is fitted into the pin insertion hole
53
of the cover
43
so as to combine the both in a state where a pump member
44
is disposed in the pump chamber
41
of the housing
42
. The combined one is incorporated into a tip of the rotation axis
46
of the motor
45
, and the tip and the rotation axis are bonded by an external casing
55
, so as to provide an integrated fuel pump unit as a whole. Note that, an example of the positioning pin
52
to be used includes a C-type pin in cross section or the like.
In a fuel pump like this, in order to prevent generation of vapor lock caused by entry of the fuel across the boundary area from the high-pressure discharge side to the low-pressure intake side in the pump, the pressure relief hole
54
for communicating the boundary area with the outside of the pump was provided. However, as the pressure relief hole is provided at one point of the area, namely in a point-like manner, pressure relief was not always carried out sufficiently. Thus, effects of preventing generation of vapor lock is not sufficient.
Further, in a fuel pump as above, it was necessary to form the positioning pin insertion hole
53
in the cover
43
throu
Ebihara Yoshio
Kawasaki Hiroaki
Kimura Akihiro
Denion Thomas
Kyosan Denki Co. Ltd.
Oliff & Berridg,e PLC
Trieu Theresa
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