High-pressure fuel pump

Details High-pressure fuel pump High-pressure fuel pump

2002-10-16

2004-09-14

Look, Edward K. (Department: 3745)

Expansible chamber devices

With guide or seal on cylinder end portion for piston or...

Non-metallic seal means between piston or member and end...

Reexamination Certificate

active

06789459

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention is related to a high pressure pump for pressurizing and supplying fluid, and more particularly, to a high pressure pump that is optimal for pressurizing and supplying fuel to a fuel injection valve of a vehicle engine.
Japanese Laid-Open Publication No. 8-68370 discloses a high pressure fuel pump used for a vehicle engine. The high pressure fuel pump has a cylinder, a plunger that is inserted into the cylinder, and a lifter that moves the plunger axially direction with respect to the cylinder. As the plunger reciprocates, the plunger pressurizes fuel in a pressurizing chamber, which is defined in the cylinder, and discharges the fuel from the pressurizing chamber.
The lifter contacts one end of the plunger that is projected from the cylinder. The lifter is slidably supported by a pump housing. A generally cylindrical seal member is attached to the cylinder so as to surround the portion of the plunger that is projected from the cylinder. The seal member has an annular lip portion defined at its distal end. The annular lip portion contacts an outer peripheral surface of the plunger. The seal member prevents fuel, which leaks from the pressurizing chamber through a clearance between the cylinder and the plunger from mixing with lubricating oil that lubricates the lifter.
FIGS.
4
(
a
) and
4
(
b
) are cross sectional views of a plunger
43
and a seal member
41
. Although not shown, a cylinder is positioned upward of FIGS.
4
(
a
) and
4
(
b
), and a lifter is positioned downward of FIGS.
4
(
a
) and
4
(
b
). The seal member
41
disconnects a cylinder side space (the space surrounded by the seal member
41
) from a lifter side space (the space outside the seal member
41
). The lip portion
42
of the seal member
41
has an upper lip
42
a
and a lower lip
42
b
that are spaced from each other in the axial direction of the plunger
43
. The upper lip
42
a
prevents fuel L
1
collected on the peripheral surface of the plunger
43
from entering the lifter side space. The lower lip
42
b
prevents that lubricating oil L
2
invades into the cylinder side space. Therefore, fuel and lubricating oil are prevented from mixing.
When the plunger
43
moves in a direction projecting out of the cylinder, that is, when the plunger
43
moves downward in FIG.
4
(
a
), the fuel L
1
collected on the peripheral surface of the plunger
43
is removed by the upper lip
42
a
. The removed fuel L
1
is stored in the cylinder side space and prevented from entering the lifter side space. On the other hand, when the plunger
43
moves in a direction entering the cylinder, that is, when the plunger
43
moves upward in FIG.
4
(
a
), the lubricating oil L
2
collected on the peripheral surface of the plunger
43
is removed by the lower lip
42
b
and prevented from entering the cylinder side space.
However, it is difficult to completely remove the fuel L
1
and the lubricating oil L
2
collected on the plunger
43
by the lip portion
42
. Therefore, in the high pressure fuel pump of the above publication, the mixing of the fuel and the lubricating oil is not sufficiently prevented. When the fuel leaks into the lifter side space and mixes with the lubricating oil, the lubricating oil is diluted and the lifter cannot be lubricated sufficiently.
When the plunger
43
moves from the highest position shown in FIG.
4
(
a
) to the lowest position shown in FIG.
4
(
b
), the fuel L
1
′ that is not removed by the upper lip
42
a
temporarily enters the space between the upper lip
42
a
and the lower lip
42
b
and then passes by the lower lip
42
b
to leak into the lifter side space.
When the plunger
43
moves from the lowest position shown in FIG.
4
(
b
) to the highest position shown in FIG.
4
(
a
), the lubricating oil that is not removed by the lower lip
42
b
temporarily enters the space between the upper lip
42
a
and the lower lip
42
b
and passes by the upper lip
42
a
to leak into the cylinder side space.
As the stroke of the plunger
43
lengthens to increase the discharged amount of the fuel, the leakage amount of the fuel and the lubricating oil increases.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a high pressure pump for that guarantees prevention of fluid leakage from one of two spaces, which are disconnected by a seal member, into the other one of the two spaces.
To achieve the above object, a high pressure pump includes a cylinder having a pressurizing chamber. A plunger is inserted in the cylinder. The plunger is axially reciprocated with a predetermined stroke to pressurize fluid in the pressurizing chamber. The plunger has a projected portion projected from the cylinder. A drive member drives the projected portion to reciprocate the plunger. A seal member encompasses the projected portion. The seal member has an annular lip portion that contacts a peripheral surface of the projected portion. The annular lip portion has a pair of lips separated from each other in an axial direction of the plunger. An axial distance between the lips is greater than the stroke of the plunger.


REFERENCES:
patent: 5567134 (1996-10-01), Inoue
patent: 5752430 (1998-05-01), Kawajiri et al.
patent: 04-353262 (1992-12-01), None
patent: 11-082238 (1999-03-01), None
patent: 11-153069 (1999-06-01), None
patent: 2001-050174 (2001-02-01), None
patent: 2001-055963 (2001-02-01), None
patent: WO00/47888 (2000-08-01), None

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