Pumps – Expansible chamber type – Biasing means effects induction stroke of abutment driven,...
Reexamination Certificate
1997-08-14
2001-01-09
Freay, Charles G. (Department: 3746)
Pumps
Expansible chamber type
Biasing means effects induction stroke of abutment driven,...
C417S437000
Reexamination Certificate
active
06171081
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel pump assembly sucking a fuel in a fuel tank and pressurizing the sucked fuel for supplying to a fuel supply system associated with an internal combustion engine. More particularly, the invention relates to a fuel pump assembly performing pumping operation by reciprocally driving a push rod or a diaphragm by means of an eccentric cam fixedly mounted on a camshaft of an internal combustion engine and increasing and decreasing a volume of a pumping chamber through a pump diaphragm by reciprocal motion of the push rod or the diaphragm.
2. Description of the Related Art
The conventional fuel pump assembly is illustrated in FIG.
2
. In
FIG. 2
, the reference numeral
1
denotes a lower pump body, an upper end
1
A of which forms a flat surface. A recessed portion
1
B defining an operation chamber and opening to the upper end
1
A is defined in the lower pump body
1
. Also, a downwardly opened push rod guide bore
1
E with an upper bottom portion
1
D located at higher position than a lower end
1
C, is formed in the lower pump body
1
. The reference numeral
2
denotes an upper pump body arranged on the upper end
1
A of the lower pump body
1
. A recessed portion
2
B for defining a pump chamber is defined in the upper pump body
2
and is located in opposition to the recessed portion
1
B when the upper pump body
2
is assembled with the lower pump body. Also, a recessed portion
2
D for defining an inflow chamber and a recessed portion
2
E for defining a discharge chamber, both opening to an upper end
2
C of the upper pump body
2
, are formed. The recessed portion
2
D for defining the inflow chamber and the recessed portion
2
E for defining the discharge chamber are separated by a partitioning wall
2
F. The recessed portion
2
D for defining the inflow chamber and the recessed portion
2
E for defining the discharge chamber are communicated through an inflow hole
2
G. The recessed portion
2
B for defining the pump chamber and the recessed portion
2
E for defining the discharge chamber are communicated through a discharge hole
2
H. The reference numeral
3
denotes a suction side check valve for opening and closing the inflow hole
2
G. The reference numeral
4
denotes a discharge side check valve for opening and closing the discharge hole
2
H. The reference numeral
5
denotes a pump cover arranged on an upper end
2
C of the upper pump body
2
. The lower end
5
A of the pump cover
5
defines a recessed portion
5
B defining a first regulator chamber opposing the recessed portion
2
D for defining the inflow chamber and a recessed portion
5
C defining a second regulator chamber opposing the recessed portion
2
E for defining the discharge chamber, are formed in the pump cover
5
. The reference numeral
5
D denotes a partitioning wall separating the recessed portion
5
B defining the first regulator chamber and the recessed portion
5
C defining the second regulator chamber.
Then, on the upper end
1
A of the lower pump body
1
, the upper pump body
2
is arranged, Also, on the upper end
2
C of the upper pump body
2
, the pump cover is arranged. The lower pump body
1
, the upper pump body
2
and the pump cover
5
are fixedly assembled by means of bolts
6
. At this time, between the upper end
1
A of the lower pump body
1
and the lower end
2
A of the upper pump body
2
, a pump diaphragm
7
is clamped. Similarly, between the upper end
2
C of the upper pump body
2
and the lower end
5
A of the pump cover
5
, a regulator diaphragm
8
is arranged. By the pump diaphragm
7
and the recessed portion
1
B defining the operation chamber of the lower pump body
1
, an operation chamber A is defined. Also, by the pump diaphragm
7
and the recessed portion
2
B for defining the pump chamber of the upper pump body
2
, a pump chamber P is defined. On the other hand, by the regulator diaphragm
8
and the recessed portion
2
D for defining the inflow chamber of the upper pump body
2
, an inflow chamber B is defined, and by the regulator diaphragm
8
and the recessed portion
2
E for defining the discharge chamber, the discharge chamber C is defined. The inflow chamber B and the discharge chamber C are separated by the partitioning wall
2
F. Also, by the regulator diaphragm
8
and the recessed portion
5
B for defining the first regulator chamber of the pump cover
5
, a first regulator chamber D is defined and by the regulator diaphragm
8
and the recessed portion
5
B for defining the second regulator chamber of the pump cover
5
, a second regulator chamber E is defined. The first regulator chamber D and the second regulator chamber E are separated by the partitioning wall
5
D. Also, the first regulator chamber D is in opposition to the inflow chamber B via the regulator diaphragm
8
, and the second regulator chamber E is in opposition to the discharge chamber C via the regulator diaphragm
8
.
On the pump diaphragm
7
, a diaphragm rod
9
is integrally mounted via upper and lower retainers. The diaphragm rod
9
is arranged within the rod guide hole
1
G extending from the operation chamber A to the push rod guide hole
1
E in movable fashion. The lower end is located in the vicinity of the lower end of the push rod guide hole
1
E.
The reference numeral
10
denotes a cylindrical push rod slidably supported in the, push rod guide hole
1
E at an outer diametrical portion
10
A and is slidably supported on the diaphragm rod
9
at the inner diametrical portion
10
B. On the push rod
10
, an upwardly opened recessed portion
10
D opened upwardly and having a bottom portion
10
C and an elongated groove
10
E cut out from the inner diametrical portion
10
B to the outer diametrical portion
10
A. Within the elongated groove
10
E, a pin
11
is mounted in the vicinity of the lower end of the diaphragm rod
9
.
The reference numeral
12
denotes a push rod spring disposed within the push rod guide hole
1
E in compressed position. The upper end of the push rod spring
12
is engaged with an upper bottom portion
1
D of the push rod guide hole
1
E. The lower end is engaged with the bottom portion
10
C of the upwardly opened recessed portion
10
D of the push rod
10
. The push rod spring
12
downwardly depresses the push rod
10
to engage the push rod
10
with the pin
11
. On the other hand, within the operation chamber A, a diaphragm spring
13
is disposed within compressed position. The upper end of the diaphragm spring
13
is engaged via the retainer, and the lower end of the diaphragm spring
13
is engaged with the recessed portion
1
B of the operation chamber. The diaphragm spring
13
depresses the pump diaphragm
9
toward the pump chamber P.
Then, a relationship of spring forces between the push rod spring
12
and the diaphragm spring
13
is set, in the condition illustrated in
FIG. 2
, such that a spring force of the push rod spring
12
is set greater than a spring force of the diaphragm spring
13
. Then, when the fuel pump arrangement is installed on a not shown internal combustion engine, the lower end of the push rod
10
projecting downwardly from the lower end
1
C of the lower pump body
1
is arranged in contact with the eccentric cam mounted on the camshaft (camshaft and eccentric cam are not shown).
In the construction set forth above, when the engine is driven and a high profile portion of the eccentric cam comes into contact with the push rod
10
, the push rod
10
is moved upwardly against a spring force of the push rod spring
12
to reduce a volume of the pump chamber P of the pump diaphragm
7
. By this, the suction side check valve
3
closes the inflow hole
2
G and the discharge side check valve
4
opens the discharge hole
2
H. By this, the fuel stored in the pump chamber P is pressurized and discharged to the discharge chamber C and then supplied to the fuel supply system via a not shown duel discharge passage. Next, when the low profile portion of the eccentric cam comes into contact with the push rod
10
,
Nakajima Youichi
Oouchi Takuya
Freay Charles G.
Gray Michael K.
Keihin Corporation
Pillsbury Madison & Sutro Intellectual Property Gro
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