U.S. patent application number 10/614206 was filed with the patent office on 2004-05-20 for high pressure fuel pump for internal combustion engine.
Invention is credited to Abe, Masami, Kotaki, Masayoshi, Odakura, Hiroshi, Onose, Toru, Saito, Atsuji, Usui, Satoshi, Yamada, Hiroyuki.
Application Number | 20040096346 10/614206 |
Document ID | / |
Family ID | 19054225 |
Filed Date | 2004-05-20 |
United States Patent
Application |
20040096346 |
Kind Code |
A1 |
Usui, Satoshi ; et
al. |
May 20, 2004 |
High pressure fuel pump for internal combustion engine
Abstract
A high pressure fuel pump for an internal combustion engine
having a cylinder, a plunger slidably fitted in the cylinder and a
seal mechanism for blocking fuel leakage from an end of a sliding
portion between the cylinder and the plunger and also for
preventing an lubricant for a driving mechanism of the plunger from
entering into the cylinder from the end of the sliding portion of
the cylinder and the plunger. A holder surrounding the end of the
sliding portion of the cylinder and the plunger is provided. The
seal mechanism comprises two mutually independent seal devices
mounted with a specific spacing in a longitudinal direction from
the end of the sliding portion of the cylinder and the plunger
along a circumference of the plunger. The two seal devices are held
on the circumference of the plunger by the holder surrounding the
end of the sliding portion of the cylinder and the plunger while
keeping the specific spacing.
Inventors: |
Usui, Satoshi; (Hitachinaka,
JP) ; Yamada, Hiroyuki; (Hitachinaka, JP) ;
Onose, Toru; (Ibaraki, JP) ; Saito, Atsuji;
(Hitachinaka, JP) ; Abe, Masami; (Hitachi, JP)
; Kotaki, Masayoshi; (Hitachinaka, JP) ; Odakura,
Hiroshi; (Hitachiota, JP) |
Correspondence
Address: |
CROWELL & MORING LLP
INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Family ID: |
19054225 |
Appl. No.: |
10/614206 |
Filed: |
July 8, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10614206 |
Jul 8, 2003 |
|
|
|
10084386 |
Feb 28, 2002 |
|
|
|
Current U.S.
Class: |
417/470 |
Current CPC
Class: |
F02M 59/442 20130101;
F02M 59/102 20130101; F04B 53/04 20130101; F02M 2200/16
20130101 |
Class at
Publication: |
417/470 |
International
Class: |
F04B 019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 19, 2001 |
JP |
2001-220405 |
Claims
What is claimed is:
1. A high pressure fuel pump for an internal combustion engine
having a cylinder, a plunger slidably fitted in the cylinder and a
seal mechanism for blocking fuel leakage from an end of a sliding
portion between said cylinder and said plunger and also for
preventing an lubricant for a driving mechanism of said plunger
from entering into said cylinder from said end of the sliding
portion of said cylinder and said plunger, wherein: a holder
surrounding said end of the sliding portion of said cylinder and
said plunger is provided; said seal mechanism comprises two
mutually independent seal devices mounted with a specific spacing
in a longitudinal direction from said end of the sliding portion of
said cylinder and said plunger along a circumference of said
plunger; and the two seal devices are held on the circumference of
said plunger by said holder surrounding said end of the sliding
portion of said cylinder and said plunger while keeping said
specific spacing.
2. A high pressure fuel pump according to claim 1, further
comprising a spacer for regulating said specific spacing mounted
between said two seal devices.
3. A high pressure fuel pump according to claim 1, wherein the seal
device on said cylinder side, of said two seal devices, has a fuel
seal function, and the remaining seal device has a lubricant seal
function.
4. A high pressure fuel pump for an internal combustion engine
having a cylinder, a plunger slidably fitted in the cylinder, a
seal mechanism for blocking fuel leakage from an end of the sliding
portion of said cylinder and plunger and also preventing a
lubricant for a driving mechanism of said plunger from entering
into said cylinder from said end of the sliding portion of said
cylinder and said plunger, and a holder having a screw portion for
threadedly engaging with a pump body, said cylinder being mounted
in said holder and being fixed to the pump body by threadely
engaging the holder with the pump body, wherein: said holder has a
cover portion for surrounding said sliding portion of the cylinder
and plunger; said seal mechanism comprises two mutually independent
seal devices mounted with a specific spacing in a longitudinal
direction from said end of the sliding portion of said cylinder and
said plunger along a circumference of said plunger; and the two
seal devices are held on the circumference of said plunger by the
cover portion of said holder while keeping the specific
spacing.
5. A high pressure fuel pump according to claim 4, further
comprising a spacer for regulating said specific spacing mounted
between said two seal devices.
6. A high pressure fuel pump according to claim 4, wherein the seal
device on said cylinder side, of said two seal devices, has a fuel
seal function, and the remaining seal device has a lubricant seal
function.
7. A high pressure fuel pump for an internal combustion engine
comprising a plunger for force-feeding fuel in a pressurization
chamber, a suction valve provided at an inlet of the pressurization
chamber, a discharge valve provided at an exit of the
pressurization chamber, a low pressure chamber provided on an
upstream side of the suction valve, a cylinder for slidably holding
said plunger, and a seal structures for rendering an outer
circumference of said plunger sealed fluid-tight located at two
locations at an outside of said cylinder and in an axial direction
of said plunger, wherein an annular member made of a resin is used
in the seal structure located on said pressurization chamber side,
of said seal structures at two locations.
8. A high pressure fuel pump according to claim 7, wherein the seal
structure on the opposite side to the pressurization chamber, of
said seal structures at two locations, is a rubber annular
structure.
9. A high pressure fuel pump for an internal combustion engine
comprising a plunger for force-feeding the fuel in a pressurization
chamber, a suction valve provided at an inlet of the pressurization
chamber, a discharge valve provided at an exit of the
pressurization chamber, a low pressure chamber provided on an
upstream side of the suction valve, a cylinder for slidably holding
said plunger, and seal structures for rendering an outer
circumference of said plunger sealed fluid-tight located at two
locations at an outside of said cylinder and in an axial direction
of the plunger, wherein there is provided in the cylinder a
transverse hole by which the fuel leaked from the pressurization
chamber to a fuel reservoir formed on a pressurization chamber side
of the seal structures through a clearance between said cylinder
and said plunger is returned to an inlet port.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a high pressure fuel pump
for force-feeding high pressure fuel to a fuel injection valve of
an internal combustion engine.
[0002] An apparatus in the past had a rubber seal structure as
structure for sealing an outer wall of a plunger to be fluid-tight
as disclosed in JP-A-8-68370 specification. In addition, a fuel
reservoir formed on a pressurization chamber side of the seal
structure was communicated with a passage having pressure equal to
atmospheric pressure so as to be opened to the atmospheric
pressure.
[0003] However, such a high pressure fuel pump in the past requires
a clearance of several .mu.m to several tens of .mu.m between a
cylinder inner wall and a plunger outer wall for the sake of
plunger sliding. Upon fuel injection, if fuel in a fuel
pressurization chamber is pressurized, the fuel leaks from the
clearance, so that the same pressure as a suction pressure is also
applied to the fuel reservoir. In the case of using a rubber lip
seal as the seal structure, there was a problem that a limit value
of resistance to pressure is too low to withstand the suction
pressure, so that seal performance is deteriorated.
[0004] In order to solve such a problem, an apparatus according to
JP-A-8-68370 specification has the fuel reservoir in communication
with to the passage having the pressure equal to atmospheric
pressure, but to that end, leaked fuel must be returned to a fuel
tank and so piping for tank return must be provided. For that
reason, there were problems such as increase in working man-hours
and increased costs.
[0005] In addition, there was a problem that usable materials are
limited due to formability of the lip seal, and seal performance
deteriorates since its rigidity is extremely reduced by the fuel
including alcohol and so on resulting in little allowance.
[0006] An object of the present invention is to provide a high
pressure fuel pump for an internal combustion engine of low costs
and high reliability implemented to solve the above problems.
BRIEF SUMMARY OF THE INVENTION
[0007] According to a first aspect of the present invention, there
is provided a high pressure fuel pump for an internal combustion
engine having a cylinder, a plunger slidably fitted in the cylinder
and a seal mechanism for blocking fuel leakage from an end of a
sliding portion between said cylinder and said plunger and also for
preventing an lubricant for a driving mechanism of said plunger
from entering into said cylinder from said end of the sliding
portion of said cylinder and said plunger, wherein: a holder
surrounding said end of the sliding portion of said cylinder and
said plunger is provided; said seal mechanism comprises two
mutually independent seal devices mounted with a specific spacing
in a longitudinal direction from said end of the sliding portion of
said cylinder and said plunger along a circumference of said
plunger; and the two seal devices are held on the circumference of
said plunger by said holder surrounding said end of the sliding
portion of said cylinder and said plunger while keeping said
specific spacing.
[0008] This embodiment may further comprise a spacer for regulating
said specific spacing mounted between said two seal devices.
[0009] In this embodiment, it is preferable that the seal device on
said cylinder side, of said two seal devices, has a fuel seal
function, and the remaining seal device has a lubricant seal
function.
[0010] According to a second aspect of the present invention, there
is provided a high pressure fuel pump for an internal combustion
engine having a cylinder, a plunger slidably fitted in the
cylinder, a seal mechanism for blocking fuel leakage from an end of
the sliding portion of said cylinder and plunger and also
preventing a lubricant for a driving mechanism of said plunger from
entering into said cylinder from said end of the sliding portion of
said cylinder and said plunger, and a holder having a screw portion
for threadedly engaging with a pump body, said cylinder being
mounted in said holder and being fixed to the pump body by
threadely engaging the holder with the pump body, wherein: said
holder has a cover portion for surrounding said sliding portion of
the cylinder and plunger; said seal mechanism comprises two
mutually independent seal devices mounted with a specific spacing
in a longitudinal direction from said end of the sliding portion of
said cylinder and said plunger along a circumference of said
plunger; and the two seal devices are held on the circumference of
said plunger by the cover portion of said holder while keeping the
specific spacing.
[0011] This embodiment may further comprise a spacer for regulating
said specific spacing mounted between said two seal devices.
[0012] In this embodiment, it is preferable that the seal device on
said cylinder side, of said two seal devices, has a fuel seal
function, and the remaining seal device has a lubricant seal
function.
[0013] According to a third aspect of the present invention, there
is provided a high pressure fuel pump for an internal combustion
engine comprising a plunger for force-feeding fuel in a
pressurization chamber, a suction valve provided at an inlet of the
pressurization chamber, a discharge valve provided at an exit of
the pressurization chamber, a low pressure chamber provided on an
upstream side of the suction valve, a cylinder for slidably holding
said plunger, and a seal structures for rendering an outer
circumference of said plunger sealed fluid-tight located at two
locations at an outside of said cylinder and in an axial direction
of said plunger, wherein an annular member made of a resin is used
in the seal structure located on said pressurization chamber side,
of said seal structures at two locations.
[0014] It is preferable that the seal structure on the opposite
side to the pressurization chamber, of said seal structures at two
locations, is a rubber annular structure.
[0015] According to a fourth aspect of the present invention, there
is provided a high pressure fuel pump for an internal combustion
engine comprising a plunger for force-feeding the fuel in a
pressurization chamber, a suction valve provided at an inlet of the
pressurization chamber, a discharge valve provided at an exit of
the pressurization chamber, a low pressure chamber provided on an
upstream side of the suction valve, a cylinder for slidably holding
said plunger, and seal structures for rendering an outer
circumference of said plunger sealed fluid-tight located at two
locations at an outside of said cylinder and in an axial direction
of the plunger, wherein there is provided in the cylinder a
transverse hole by which the fuel leaked from the pressurization
chamber to a fuel reservoir formed on a pressurization chamber side
of the seal structures through a clearance between said cylinder
and said plunger is returned to an inlet port.
[0016] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0017] FIG. 1 is a vertical sectional view of a first embodiment of
a high pressure fuel pump for an internal combustion engine
according to the present invention;
[0018] FIG. 2 is a partial enlarged sectional view of the first
embodiment shown in FIG. 1;
[0019] FIG. 3 is an exploded perspective view of a main part of the
first embodiment shown in FIGS. 1 and 2;
[0020] FIG. 4 is a diagram showing a structure of a fuel injection
system using the first embodiment;
[0021] FIG. 5a is an enlarged sectional view of a discharge valve
unit of the first embodiment;
[0022] FIG. 5b is a sectional view taken along line Vb-Vb in FIG.
5a;
[0023] FIG. 6 is a sectional view of another example of the
discharge valve unit;
[0024] FIG. 7a is a sectional view of a further example of the
discharge valve unit;
[0025] FIG. 7b is an enlarged view of a part Q in FIG. 7a;
[0026] FIG. 8a is an enlarged sectional view showing an example of
a suction valve unit;
[0027] FIG. 8b is a sectional view taken along line VIIIb-VIIIb in
FIG. 8a;
[0028] FIG. 9 is a sectional view showing another example of a
plunger seal section;
[0029] FIG. 10 is a sectional view showing a further example of the
plunger seal section;
[0030] FIG. 11 is a sectional view showing a still further example
of the plunger seal section;
[0031] FIG. 12 is a vertical sectional view of a second embodiment
of the high pressure fuel pump for an internal combustion engine
according to the present invention;
[0032] FIG. 13 is a vertical sectional view of a third embodiment
of the high pressure fuel pump for an internal combustion engine
according to the present invention;
[0033] FIG. 14 is a partial enlarged sectional view of the third
embodiment; and
[0034] FIG. 15 is a partial enlarged sectional view of a fourth
embodiment of the high pressure fuel pump for an internal
combustion engine according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0035] Hereinafter, embodiments of the present invention will be
described by referring to the accompanied drawings.
[0036] Basic structure and operation of a high pressure fuel pump
for an internal combustion engine according to the present
invention will be described by referring to FIGS. 1-4. FIG. 1 is a
vertical sectional view of the whole of pump, FIG. 2 is an enlarged
view of a main part of the pump, and FIG. 3 is an exploded view of
a fuel injection system.
[0037] A pump body 1 is formed with a fuel suction passage 10, a
discharge passage 11 and a pressurization chamber 12. The fuel
suction passage 10 and the discharge passage 11 are respectively
provided with a suction valve 5 and a discharge valve 6, which are
held in one direction by springs 5a and 6a to be check valves for
limiting a fuel flow direction. The pressurization chamber 12 is
formed by a pump chamber 12 to which a plunger 2 as a
pressurization member slides, a suction port 15b in communication
with the suction valve 5 and a discharge port 6b in communication
with the discharge valve 6.
[0038] In addition, in a suction chamber 10a, a solenoid 200 is
held on the pump body 1 and an engagement member 201 and a spring
202 are arranged on the solenoid 200. The engagement member 201 is
biased by the spring 202 in a direction to open the suction valve 5
when the solenoid 200 is off. As the biasing force of the spring
202 is larger than that of a spring 5a of the suction valve 5, the
suction valve 5 is in an opened state when the solenoid 200 is off
as shown in FIGS. 1 and 2. Fuel is led by a low pressure pump 51
from a tank 50 to a fuel inlet of the pump body 1, while it is
regulated to be a certain pressure by a pressure regulator 52.
Thereafter, it is pressurized at the pump body 1, and is force-fed
from a fuel outlet to a common rail 53. The common rail 53 has
injectors 54, a relief valve 55 and a pressure sensor 56 mounted
thereon. The injectors 54 are mounted according to the number of
engine cylinders and inject the fuel in accordance with signals
from an engine control unit (ECU) 40. In addition, the relief valve
55 is opened when the pressure inside the common rail 53 exceeds a
predetermined value, and prevents damage of a piping system.
[0039] The operation will be described below.
[0040] A lifter 3 provided at a lower end of the plunger 2 is
pressed into contact with a cam 100 by a spring 4. The plunger 2 is
slidably held by a cylinder 20, and is reciprocated by the cam 100
rotated by an engine cam shaft and the like so as to change
capacity in the pressurization chamber 12.
[0041] In addition, a plunger seal 30 is provided beneath the
cylinder 20 in order to prevent the fuel from leaking to a cam
side.
[0042] When the suction valve 5 is closed during a compression
process of the plunger 2, the pressure in the pressurization
chamber 12 rises and the discharge valve 6 is thereby automatically
opened to force-feed the fuel to the common rail 53.
[0043] While the suction valve 5 is automatically opened when the
pressure in the pressurization chamber 12 becomes lower than that
at the fuel inlet, its closing is determined by the operation of
the solenoid 200.
[0044] When the solenoid 200 maintains an on (current-carrying)
state, it generates more electromagnetic force than the biasing
force of the spring 202 and draws the engagement member 201 to the
solenoid 200 side so that the engagement member 201 and the suction
valve 5 are separated. In this state, the suction valve 5 becomes
an automatic valve which is opened and closed in synchronization
with reciprocation of the plunger 2. Accordingly, during the
compression process, the suction valve 5 is closed, and the fuel
equivalent to decreased capacity of the pressurization chamber 12
is force-fed to the common rail 53 by pushing the discharge valve 6
open.
[0045] In comparison with this, when the solenoid 200 maintains an
off (no current-carrying) state, the engagement member 201 is
engaged with the suction valve 5 by the biasing force of the spring
202, so that the suction valve 5 is kept in the opened state.
Accordingly, even in the compression process, the pressure in the
pressurization chamber 12 remains almost as low as that at the fuel
inlet, and so the discharge valve 6 cannot be opened, so that the
fuel equivalent to decreased capacity of the pressurization chamber
12 is returned to the fuel inlet side through the suction valve
5.
[0046] In addition, if the solenoid 200 is turned on in the middle
of the compression process, the fuel is force-fed to the common
rail 53 from that time. Moreover, once the force-feeding is
started, the pressure in the pressurization chamber 12 rises, so
that, even if the solenoid 200 is turned off thereafter, the
suction valve 5 remains closed and is automatically opened in
synchronization with the start of the suction process.
[0047] In this pump, the pressurization chamber 12 is formed by
pressing a suction valve holder 5b, a discharge valve seat 60 and
the cylinder 20 into contact with to the pump body 1. While a
protector 70 is used in a pressed contact portion between the
cylinder 20 and the pump body 1, it is also possible to directly
press the cylinder 20 into contact with the pump body 1. Whether or
not to use the protector 70 can be selected in accordance with use
conditions described later. In addition, it is also possible, for
the purpose of obtaining the same effect, to use it for the pressed
contact portion between the pump body 1 and the other members than
the cylinder 20. Moreover, a suction chamber 10a which is a fuel
chamber, an annular chamber 10b and a fuel chamber 11b are provided
outside 12 the pressed contact portion of the pressurization
chamber.
[0048] In general, to seal the pressurization chamber, a seal more
expensive than an ordinary constant-pressure seal must be used for
the purpose of withstanding pressure fluctuation in the
pressurization chamber, whereas by adopting the above structure, a
seal may not be used in the pressed contact portion and it is
possible to prevent slight fuel leakage from the pressed contact
portion leading to fuel leakage outside the pump.
[0049] Furthermore, it is possible to improve the seal performance
by rendering a member to be pressed into contact with the pump body
1 harder than the pump body 1 to make the member dig into the pump
body 1.
[0050] In addition, it is possible to improve the seal performance
by using a soft material for the pump body 1.
[0051] On the other hand, there are the cases where the soft
material is eroded (cavitated) and a seal surface gets damaged due
to fuel cavitation when higher fuel pressure and higher-speed
operation are implemented.
[0052] This embodiment uses the protector 70, and has seal surfaces
provided at two locations, that is, a seal surface 70a (plane)
between the cylinder 20 and the pump body 1 and a seal surface 70b
(cylindrical surface) inside a pump chamber 12a. The seal surface
70a is pressed into contact with the pump body 1 by screwing a
cylinder holder 21. In addition, the seal surface 70b is pressed
into contact with the pump body 1 by press-fitting the protector
70.
[0053] Thereby, it is possible to extend the pressed contact seal
surfaces with the pump body 1 of the soft material, so that the
period until the seal surfaces are completely penetrated can be
prolonged.
[0054] In addition, as the seal surface is divided into two as 70a
and 70b, pressure propagation from the pressurization chamber is
mitigated in a dividing section so as to prevent erosion of the
seal surface 70a.
[0055] While the protector 70 is placed in the pressed contact
portion of the cylinder 20 in this embodiment, it may be placed in
any other pressed contact portion.
[0056] In addition, a low pressure chamber 10b in communication
with the inlet chamber 10a is provided above the pump chamber 12a,
which is a part of the pressurization chamber 12, and a wall
portion 1a between them is the weakest portion of the entire walls
of the pressurization chamber 12.
[0057] Thereby, in the case where the pressure in the
pressurization chamber abnormally rises due to some trouble, this
weakest portion gets damaged and high pressure fuel is released to
the low pressure chamber, allowing leakage thereof to the outside
to be prevented.
[0058] In addition, the cylinder 20 is fixed to the pump body 1 by
threadably attaching a cylinder holder 21, which is provided
outside the cylinder 20, to the pump body 1.
[0059] An attaching portion C of the pump body 1 and the cylinder
holder 21 is provided between a cylinder-fixing portion A on the
pump body side and a cylinder-fixing portion B on the cylinder
holder side.
[0060] It is thereby possible, even in case of combining the
materials of different coefficients of linear expansion, that is,
an aluminum material for the pump body 1 and steel for the cylinder
20 (aluminum>steel), to reduce a difference in expansion lengths
(expansion length=expanded portion length.times.coefficient of
linear expansion.times.changed temperature) on the pump body side
and the cylinder side generated on a change of temperature because
the expanded portion length on the pump body side (portion A to
portion C) is shorter than that on the cylinder side (portion A to
portion B). Accordingly, there will be neither clearance on a
contact surface of the cylinder 20 and the pump body 1 nor
deterioration of the seal performance due to reduction in pressed
contact force.
[0061] In addition, a fitting portion D into which the cylinder 20
is fitted is provided in the cylinder holder 21, and the fitting
portion D and an engagement portion C between the cylinder holder
21 and the pump body 1 have different positions on an axis of the
cylinder. The engagement portion C is provided closer to an upper
opening of the cylinder holder 21 than the fitting portion D.
Moreover, the fitting portion D has a slight clearance.
[0062] With this, even if the engagement portion C is deformed
radially inwardly of the pump body due to thermal expansion of the
pump body 1 while keeping the cylinder holder 21 and the cylinder
20 coaxial, rigidity of the engagement portion C on the cylinder
holder side is lower than that of the fitting portion D and so the
deformation radially and inwardly of the pump body hardly reaches
the fitting portion D, so that it prevents tightening of the
cylinder 20. Accordingly, it is possible to keep a sliding
clearance between the plunger and the cylinder correct so as to
prevent galling of the plunger 2 and so on.
[0063] In addition, it is possible, by using the material of lower
thermal conductivity than the pump body 1 for the cylinder holder
21, to prevent galling of the plunger 2 since heat of the pump body
1 is thereby hardly transferred to the cylinder 20.
[0064] Furthermore, it is possible to reduce heat transfer from the
pump body 1 by performing resin coating on a threaded portion of
the cylinder holder 21.
[0065] In addition, an annular chamber 10c in communication with
the suction chamber 10a is provided on a circumference of the
cylinder 20.
[0066] It is thereby possible to reduce the heat transfer from the
pump body 1 to the cylinder 20 and also cool the cylinder 20 with
the fuel.
[0067] In addition, the plunger seal 30 for sealing the fuel
leakage from the plunger 2 sliding portion to the cam side and also
sealing entry of oil from the cam side to the plunger sliding
portion is held inside the cylinder holder 21.
[0068] It is thereby possible, as both of the cylinder 20 and the
plunger seal 30 are engaged with the common cylinder holder 21, to
keep the plunger seal 30 and the plunger 2 as a sliding material
coaxial so as to maintain good seal performance of the plunger
sliding portion.
[0069] In addition, a plunger seal chamber 30a on the inner side of
the plunger seal 30 is in communication with the annular chamber
10c through a clearance X between the cylinder 20 and the plunger
2, a fuel reservoir 20a provided inside the cylinder, and a passage
20b. Moreover, the circumference of the cylinder 20 is divided into
the annular chamber 10c in communication with the suction chamber
10a and the plunger seal chamber 30a by the fitting portion B.
[0070] Moreover, the plunger seal chamber 30a is in communication
with a return pipe 40 through a communicating hole 21a provided in
the cylinder holder 21. The return pipe 40 is in communication with
the fuel tank 50 in which pressure is approximately atmospheric
pressure through return piping (not shown). Accordingly, the
plunger seal chamber 30a has atmospheric pressure almost equal to
the fuel tank pressure since it is in communication with the fuel
tank 50 through the return pipe 40.
[0071] According to the above-described structure, the fuel leaked
from the pressurization chamber 12 through the clearance between
the cylinder 20 and the plunger 2 flows into the suction chamber
10a from the fuel reservoir 20a through the passage 20b. On the
other hand, low pressure is supplied from the suction chamber 10a
to the fuel reservoir 20a, and so the fuel flows to the plunger
seal chamber 30a through the clearance X. This fuel flows to the
fuel tank 50 through the return pipe 40. At high temperature,
however, the fuel is apt to be gasified since the plunger seal
chamber 30a is almost at the atmospheric pressure.
[0072] In this embodiment, a length of the clearance X from the
fuel reservoir 20a to an opening of the cylinder 20 to the plunger
seal 30 is shorter than a reciprocating sliding length of the
plunger.
[0073] It is thereby possible to secure a fuel oil film at the
opening of the cylinder and improve lubricity so as to reduce
abrasion, since a portion that is fuel-wetted in the fuel reservoir
20a when the plunger 2 is at a top dead center passes through the
opening when it is at a bottom dead center.
[0074] In addition, a throttle portion 21b is provided between the
plunger seal chamber 30a and the return pipe 40.
[0075] It is thereby possible to regulate a fuel amount flowing
from the plunger seal chamber 30a to the fuel tank 50, so that the
fuel more easily remain in the plunger seal chamber 30a so as to
improve abrasion resistance of the plunger seal 30 and the cylinder
opening by fuel lubrication. Especially, it is effective when the
plunger seal 30 is higher than the return pipe 40 (upside down in
the indicated direction in FIG. 2) when the pump is mounted.
[0076] Further, in this embodiment, the solenoid 200 for
controlling opening and closing time of the suction valve 5 is held
inside the suction chamber 10a by a solenoid holder 210, and an
annular fuel chamber is formed between the solenoid 200 and the
solenoid holder 210.
[0077] It is thereby possible to cool the solenoid 200 by the fuel.
Alternatively, the annular fuel chamber may be formed on the
solenoid circumference without using the solenoid holder.
[0078] In addition, it is possible to reduce the transfer from the
pump body 1 to the solenoid 200 by providing a screw portion on the
circumference of the solenoid holder 210 and engaging it with a
housing.
[0079] Furthermore, it is possible, by using the material of lower
thermal conductivity than that of the pump body 1 for the solenoid
holder 210, to prevent burnout of the solenoid 200 since heat of
the pump body 1 is thereby hardly transferred to the solenoid
200.
[0080] Furthermore, it is possible to reduce the heat transfer from
the pump body 1 by performing resin coating on the screw portion of
the solenoid holder 210.
[0081] Moreover, it is possible, by gradually reducing driving
currents for the solenoid 200 when it is off as shown in FIG. 4, to
reduce collision force when it is off and prevent abrasion and
damage of a portion to be collided.
[0082] Furthermore, an operating distance of an actuator of the
solenoid 200 is rendered shorter according to that of the suction
valve 5.
[0083] It is thereby possible, even in the case where operating
time (response when it is off) of the solenoid 200 is slow, to
promptly open the suction valve 5 on a change of pressure in the
pressurization chamber (on a shift from the discharge process to
the suction process) so as to sufficiently secure opening area of
the suction valve 5 and also reduce the collision force by
shortening the operating distance of the solenoid 200.
[0084] It is thereby possible, as passage resistance on the suction
valve 5 is reduced, to prevent reduction in the pressure in the
pressurization chamber in the suction process and restrain
occurrence of cavitation.
[0085] It is also feasible to render the operating distance of the
discharge valve 6 shorter than that of the suction valve 5.
[0086] It is thereby possible to hold down backflow of the high
pressure fuel into the pressurization chamber due to delay in
closing the discharge valve 6 (on the shift from the discharge
process to the inlet process) to the minimum so as to restrain the
occurrence of the cavitation in the pressurization chamber.
[0087] Next, other press contacting manners of forming the
pressurization chamber will be described by referring to FIGS. 5a,
5b, 6, 7a and 7b.
[0088] The discharge valve 6 is a ball valve, and comprises a ball
holder 63. The ball holder 63 is a cylindrical shape and is
slidably fitted in a discharge valve holder 62.
[0089] A ball is held by the ball holder 63 upon opening the ball
valve 6, and therefore, it is possible to restrain fluctuation of
the ball so as to stabilize the fuel flow. Accordingly, it is
possible to prevent the cavitation caused by disorder of the
flow.
[0090] In addition, an outer diameter of the ball holder 63 is
rendered larger than the ball and cut-out portions are formed on
the cylindrical portion as shown in FIG. 5b. In this embodiment,
three cut-out portions are formed, but the number thereof is not
limited to three.
[0091] With this structure, it is possible to form an appropriate
fuel passage in the ball valve, and therefore, it is possible to
prevent the cavitation caused by reduction in the fuel pressure due
to pressure loss.
[0092] While this structure is not limited to the discharge valve,
it is possible to secure oil tightness of high pressure piping with
an inexpensive manner by adopting it to the discharge valve as
opposed to the case of using a conical valve.
[0093] As for the discharge valve shown in FIGS. 5a and 5b, a
discharge valve seat 60 is pressed into contact with the pump body
1 to form the pressurization chamber, and a gasket 61 is placed on
the circumference side of the discharge valve seat 60 so as to form
the fuel chamber 11b. The discharge valve seat 60 and the gasket 61
are pressed into contact with the pump body 1 by screwing the
discharge valve holder 62. Accordingly, the pressed contact
portions to the pump body 1 to form the pressurization chamber 12
are two locations.
[0094] With this structure, it is possible, even if there is slight
fuel leakage from a first pressed contact portion located on the
pressurization chamber side, to prevent the fuel leakage outside
the pump.
[0095] Furthermore, it is possible to securely prevent the fuel
leakage outside the pump by rendering the gasket 61 less hard than
the discharge valve seat 60 and the pump body 1.
[0096] In addition, as a second press contact portion is not
directly influenced by the pressure fluctuation in the
pressurization chamber and the fuel flow, it can have secure seal
performance without being involved in the fuel cavitation occurring
in the pressurization chamber even if a soft material is used for
the gasket 61.
[0097] As for the discharge valve shown in FIG. 6, the fuel chamber
11b is formed by placing a protector 61a between the discharge
valve seat 60 and the pump body 1 and, outside thereof, by pressing
the gasket 61 of the soft material against both the discharge valve
seat 60 and the discharge valve holder 62.
[0098] It is thereby possible to securely seal the fuel entering
from a discharge chamber 11a downstream of the discharge valve 6 to
the fuel chamber 11b, and therefore, it is possible to improve
discharge efficiency of the pump even if there is slight fuel
leakage from the first press contact portion on the pressurization
chamber side by preventing the backflow of the discharged fuel into
the pressurization chamber.
[0099] The discharge valve shown in FIGS. 7a and 7b is an example
of the case where no excessive fuel cavitation occurs, wherein one
sheet of gasket 61 is pressed against the discharge valve seat 60,
the discharge valve holder 62 and the pump body 1. There is a
groove 11c on a surface of the gasket 61, thereby dividing the
press contact surface into two, so that the groove becomes the fuel
chamber (or a space chamber).
[0100] It is thereby possible, as the pressure propagation from the
pressurization chamber is mitigated by the groove 11c, to prevent
erosion of an outer seal surface of the gasket 61.
[0101] While the groove portion is placed on the surface of the
gasket in this example, it is also feasible to place it on an
opposite surface (a surface of the pump body and so on).
[0102] While this example shows the example on a discharge valve
seat portion, it is also feasible to apply it to another press
contact portion.
[0103] Next, the structure of the suction valve 5 will be described
by referring to FIGS. 8a and 8b.
[0104] As for the suction valve in FIG. 8, the suction valve 5 is a
flat valve having a cup-like cylindrical portion and the
cylindrical portion is slidably received in the suction valve
holder 5b.
[0105] With this structure, the cylindrical portion is held upon
opening the flat valve, and therefore, it is possible to restrain
fluctuation of a valve body and stabilize the fuel flow.
Accordingly, it is possible to prevent the cavitation caused by a
disorder of the flow. In addition, it is possible to arrange the
spring 5a for closing the valve in the cup-like cylindrical
portion, so that space can be saved.
[0106] In addition, cut-out portions forming a fuel passage are
provided in an inner circumference of the suction valve holder 50
as shown in FIG. 8b. Moreover, while it is placed at five locations
in this embodiment, the number of the cut-out portions is not
limited to five.
[0107] With this structure, it is possible to form an appropriate
fuel passage the valve mechanism without rendering the cylindrical
portion of the valve thicker. Therefore, it is possible to prevent
the cavitation caused by the reduction in the fuel pressure due to
the pressure loss and render the valve lightweight so as to improve
an opening and closing response of the valve.
[0108] While this structure is not limited to the suction valve, it
is possible to prevent the cavitation caused by the reduction in
the fuel pressure because adoption thereof in the suction valve
allows higher response on opening the valve and thereby restrain
the reduction in the fuel pressure in the pressurization chamber
due to delay in valve opening at a start of the suction
process.
[0109] In addition, in the case of adoption thereof in the
discharge valve, it allows the higher response on opening the
valve, and it is thereby possible to restrain increase in peak
pressure in the pressurization chamber due to the delay in the
valve opening at the start of the discharge process.
[0110] Next, a second embodiment of the high pressure fuel pump for
an internal combustion engine according to the present invention
will be described by referring to FIGS. 9, 10, 11 and 12.
[0111] FIG. 12 is a view showing the same section as FIG. 1, and
the symbols therein are also the same as those in FIG. 1. FIGS. 9
to 11 are the enlarged views of the plunger seal section in FIG. 12
and showing other examples of plunger seal shapes.
[0112] In the second embodiment shown in FIG. 12, the return pipe
40 in communication with the fuel tank 50 and the communicating
hole 21a are not provided as opposed to the first embodiment shown
in FIGS. 1 and 2. In addition, a plurality of seals is provided by
adding a ring seal 31 above the plunger seal 30.
[0113] With this structure, an inner side of the plunger seal 31
becomes a blind alley only in communication with the opening of the
cylinder.
[0114] It is thereby possible, as the inner side of the plunger
seal 31 is kept at the pressure on the suction side, to prevent
gasification of the fuel and keep lubricity so as to improve the
abrasion resistance. In addition, even when the pressure in the
suction chamber 10a pulsates due to the pump operation, the
pressure pulsation is attenuated by the sliding portion clearance X
between the plunger 2 and the cylinder 20, so that it is not
conveyed to the plunger seal 31. Accordingly, it is possible to
prevent the damage and abrasion of the plunger seal 31.
[0115] In addition, lubricant (oil, grease, etc.) is sealed in the
plunger seal chamber 30a.
[0116] It is thereby possible to improve the abrasion resistance of
the seal and also to reduce the fuel leakage from the plunger seal
30 since the fuel in the pump does not come into directly contact
with the plunger seal 30.
[0117] Moreover, while this second embodiment uses a plurality of
plunger seals, it is also effective in the case of using only a lip
seal 30 as the plunger seal as in the first embodiment shown in
FIG. 1. To be more specific, the inner side of the plunger seal 30
becomes the blind alley only in communication with the opening of
the cylinder.
[0118] With this structure, the inner side of the plunger seal 30
is kept at the pressure on the suction side, and therefore, it is
possible to prevent gasification of the fuel and keep lubricity so
as to improve the abrasion resistance. In addition, even when the
pressure in the suction chamber 10a pulsates due to the pump
operation, the pressure pulsation is attenuated by the sliding
portion clearance X between the plunger 2 and the cylinder 20, so
that it is not conveyed to the plunger seal 30. Accordingly, it is
possible to prevent the damage and abrasion of the plunger seal
30.
[0119] In addition, a lubricant (oil, grease, etc.) is sealed in
the plunger seal chamber 30a.
[0120] It is thereby possible to improve the abrasion resistance of
the seal and also to reduce the fuel leakage from the plunger seal
30 since the fuel in the pump does not come into directly contact
with the plunger seal 30.
[0121] In addition, as in this second embodiment, it is possible,
by adding the ring seal 31 above the plunger seal 30, to improve
pressure resistance of the seal which is direct contact with the
fuel and alleviate the pressure exerted on the seal located outside
of the pump so as to improve reliability of the seal
performance.
[0122] Alternatively, a plurality of seals of different shapes is
placed in the plunger sliding portion, and the seal located outside
of the pump is rendered lip-shaped.
[0123] The ring seal shapes are the shapes such as an O ring shown
in FIG. 12, an O ring having a resin ring 31a placed on the sliding
side shown in FIG. 9, an X ring shown in FIG. 10, or a K ring shown
in FIG. 11.
[0124] It is possible, as the ring seals such as O, X and K have
better formability than that of the lip seals, to select rubber
materials according to the fuel to be used (alcohol, etc.) because
of the degree of freedom of material selection.
[0125] Next, the structure of a third embodiment of the high
pressure fuel pump for an internal combustion engine according to
the present invention will be described by referring to FIGS. 13
and 14.
[0126] In this third embodiment, the cylinder 20 and the pump body
1 are separate, and the pressurization chamber 12 is not in contact
with the pump body 1 but is formed by the suction valve holder 5b,
the discharge valve seat 60 and cylindrical tubes 5f, 6f
press-fitted in the cylinder 20. Moreover, while the pressurization
chamber is formed by a plug 20f press-fitted in an upper part of
the cylinder 20 in order to improve workability of the cylinder 20,
the plug may be integral with the cylinder.
[0127] It is thereby possible, even when the cylinder 20 and the
suction valve 5 or the discharge valve 6 is positioned apart from
each other, to connect them by the cylindrical tubes 5f, 6f and to
deform the cylindrical tubes and to fix them upon assembling, so
that variations in dimensions are absorbed. Accordingly, it is
feasible to render the entire pump smaller, even in the case where
the pump body 1 is not used to the wall of the pressurization
chamber 12, because there is a degree of freedom in placement of
the suction valve 5 or the discharge valve 6.
[0128] In addition, it is possible to absorb the variations in
dimensions with the press contact portions of the cylindrical tubes
upon assembling.
[0129] Furthermore, it is possible to absorb the variations in
dimensions in two directions of X and Y by rendering the
cylindrical tubes into a flanged-shape and having one side of the
press contact portion in a plane surface contact and the other side
of the press contact portion in cylindrical surface contact.
[0130] The above structure can prevent cavitation damage even in
the case of using the soft material such as aluminum for the pump
body 1.
[0131] In addition, it is possible, even in the case of using the
materials of significantly different coefficients of linear
expansion for the pump body 1 and the cylinder 20, to prevent the
plunger 2 from sticking caused by deformation of a sliding hole of
the cylinder due to change of temperature.
[0132] Moreover, it is possible, even in the case of using the
material of high thermal conductivity for the pump body 1, to
prevent the burnout of the solenoid 200 and the galling of the
plunger 2.
[0133] Accordingly, it is possible, by rendering the pump body
all-aluminum, to provide the pump of high reliability that is
lower-cost and lighter-weight due to improvement in
cuttability.
[0134] A fourth embodiment of the present invention will be
described by referring to FIG. 15.
[0135] An annular seal member 301 made of resin (Teflon for
instance) is used as a gasoline seal structure in order to improve
the pressure resistance to the fuel.
[0136] An rubber annular seal member 302 is mounted outside the
resin annular seal member 301, and they are fixed by being
sandwiched by a spacer 304 and a seal holder 305. The rubber
annular seal member 302 provides an adequate clamping pressure
between the resin annular seal member 301 and the plunger 2, so
that good seal performance is obtained.
[0137] An X ring 303 made of resin is used as a seal located on the
oil side. The X ring is used not only because of the abrasion
resistance but because it also has a function of forming a gasoline
seal between it and the holder 21 and forming an oil seal between
it and the plunger. To be more specific, it has two seal functions
formed by one seal. Thus, the seal for the gasoline becomes more
effective.
[0138] The spacer 304 is made of aluminum, and the seal holder 305
uses an iron metal alloy called SUM 23 in JIS standards.
[0139] The spacer has a flange portion formed on its circumference,
and the flange portion is sandwiched and fixed by the seal holder
305 and a step portion formed on an inner circumference of the
holder 21. A seal effect can also be expected between the spacer
304 and the X ring 303. A seal effect can also be expected between
an X ring accepting surface of the holder and the X ring 303.
[0140] The seal holder 305 is press-fitted in the holder, and the
seal mechanism can thereby be unitized with a bottom portion of the
holder to be held. The cylinder 20 is fixed on the pump body 1 by
the cylinder holder 21 thus having the seal mechanism mounted, and
the plunger is lastly mounted, that is, after applying the grease
thereto so that the X ring is not damaged. Thus, assembly
workability can be improved.
[0141] The gasoline leaked and accumulated in a fuel reservoir 300a
flows back in the clearance between the cylinder and the plunger to
reach a fuel reservoir 20a, and is returned to the suction chamber
10a from the passage 20b (see the broken line in FIG. 4).
[0142] A return passage was thereby removed. It is especially
effective, from the viewpoints of reducing the man-hours and costs,
that the return passage for returning only below 1 cc per minute of
leaked gasoline to a gasoline tank is removed.
[0143] Hereinafter, the embodiments and advantages of the present
invention will be described.
[0144] It is possible, by dividing the materials of the first and
second press contact portions to use a hard material for the
pressurization chamber side and the soft material for the outside,
to prevent the first press contact portion from getting damaged by
the cavitation and improve the seal performance of the second press
contact portion.
[0145] Moreover, it is possible, preferably by rendering hardness
of the second press contact material softer than that of the
housing, to reduce the deformation of the seal surface on the
housing side so as to keep good seal performance just by replacing
the press contact material upon disassembling and reassembling.
[0146] In addition, the pressurization chamber and the low pressure
chamber are formed with the same material, and an isolating wall
between them has strength that is the weakest in the pressurization
chamber.
[0147] Thus, if the pressure in the pressurization chamber rises
abnormally due to some failure, this weakest portion gets damaged
and the high pressure fuel is released to the low pressure chamber
so as to prevent the fuel leakage to the outside.
[0148] Alternatively, there is the cylinder holder, for fixing the
cylinder, of the material different from the housing, where the
engagement portion C of the cylinder holder and the housing is
provided between the cylinder-fixing portion A on the housing side
and the cylinder-fixing portion B on the cylinder holder side.
[0149] It is thereby possible, in the case of combining materials
of different coefficients of linear expansion, that is, aluminum
for the housing and steel for the cylinder, an expansion length on
the aluminum side is smaller than that on the cylinder side, so
that the expansion length on the aluminum side can be rendered
equal to the expansion length on the cylinder side when the
temperature is high. Accordingly, there is neither clearance
generated on the contact surface of the cylinder and the housing
nor deterioration of the seal performance due to reduction in the
press contact force.
[0150] In addition, it is preferable to fit the cylinder into the
cylinder holder and locate this fitting portion and the engagement
portion of the cylinder holder and the housing at different
positions on the cylinder axis.
[0151] It is thereby possible, while keeping the cylinder holder
and the cylinder coaxial, to prevent the cylinder holder from
deforming radially and inwardly due to expansion of the housing and
tightening the cylinder. Accordingly, it is possible to keep the
clearance of the sliding portion between the plunger and the
cylinder correct so as to prevent the galling of the plunger and so
on.
[0152] In addition, it is preferable to engage a seal member for
sealing the plunger sliding portion with the cylinder holder.
[0153] It is thereby possible to keep the cylinder and the seal
coaxial and keep the good seal performance of the sliding portion
of the plunger.
[0154] In addition, it is preferable to place the engagement
portion C of the cylinder holder and the housing closer to the
opening end of the cylinder holder than the fitting portion D of
the cylinder holder and the cylinder.
[0155] Thereby, the rigidity of the engagement portion C of the
cylinder holder is lower than that of the fitting portion D and so
the deformation in the inner diameter direction due to the
expansion of the housing hardly reaches the fitting portion D.
Accordingly, it is possible to keep the clearance between the
plunger and the cylinder correct so as to prevent the galling of
the plunger and so on.
[0156] In addition, it is preferable to provide the screw portion
on the circumference of the cylinder holder and engage it with the
housing.
[0157] It is thereby possible to securely fix the cylinder by an
inexpensive method. In addition, it is possible, by using the
material of lower thermal conductivity than the housing for the
cylinder holder, to prevent galling of the plunger since the heat
of the housing is hardly transferred to the cylinder.
[0158] In addition, it is preferable to perform the resin coating
on the screw portion.
[0159] It is thereby possible to further reduce the heat transfer
from the housing.
[0160] Alternatively, the annular fuel chamber is formed on the
circumference of the cylinder, which chamber is in communication
with the low pressure chamber.
[0161] It is thereby possible to reduce the heat transfer from the
housing to the cylinder and also cool the cylinder with the
fuel.
[0162] Alternatively, it is feasible to provide the seal on the
sliding portion of the plunger and provide the fuel reservoir in
communication with the low pressure fuel chamber on the part of the
sliding portion between the cylinder and the plunger in
communication with the inner side of the seal. In this case, the
inner side of the seal is the blind alley only in communication
with the cylinder opening.
[0163] It is thereby possible, as the inner side of the seal is
kept at the pressure on the suction side, to prevent gasification
of the fuel and keep lubricity so as to improve the abrasion
resistance. In addition, even when the pressure of the low pressure
fuel chamber pulsates due to the pump operation, the pressure
pulsation is attenuated by the clearance of the sliding portion
between the plunger and the cylinder, so that it is not conveyed to
the inner side portion of the seal. Accordingly, it is possible to
prevent the damage and abrasion of the seal.
[0164] In addition, the seal is placed on the sliding portion of
the plunger, and the fuel reservoir in communication with the low
pressure fuel chamber is provided on the part of the sliding
portion between the cylinder and the plunger in communication with
the inner side of the seal, wherein the distance from the fuel
reservoir to the seal side opening of the cylinder is shorter than
the sliding reciprocation length of the plunger.
[0165] It is thereby possible, as the portion of the plunger
fuel-wetted in the fuel reservoir when at the top dead center
passes through the cylinder opening when at the bottom dead center,
to secure the oil film at the opening and improve the lubricity so
as to reduce abrasion.
[0166] Alternatively, the seal is placed on the sliding portion of
the plunger, and the pump side of the seal is in communication with
the chamber of approximately the atmospheric pressure such as the
fuel tank so as to place the throttling portion on a part of the
communication passage.
[0167] It is thereby possible, by reducing the pressure exerted on
the seal and regulating a fuel amount flowing from the seal portion
to the atmospheric pressure chamber, to fill the seal portion with
the fuel so as to improve the abrasion resistance of the seal and
the cylinder opening. It is especially effective when the seal is
located higher than the communication passage.
[0168] Alternatively, the seal is placed on the sliding portion of
the plunger, and the pump side of the seal is sealed with the
lubricant (oil, grease, etc.).
[0169] It is thereby possible to improve the abrasion resistance of
the seal and also to reduce the fuel leakage from the seal portion
since the fuel in the pump does not directly come into contact with
the seal.
[0170] Alternatively, the annular fuel chamber is formed on the
circumference of a heat generation portion (solenoid coil portion,
etc.) of the actuator for controlling the opening and closing time
of the suction valve, and this chamber is in communication with the
low pressure chamber.
[0171] It is thereby possible to cool the actuator with the
fuel.
[0172] In addition, it is preferable to provide an actuator holder
for fixing the actuator and provide the screw portion on the
circumference of the actuator holder so as to engage it with the
housing.
[0173] It is thereby possible to reduce the heat transfer from the
housing to the actuator and also securely fix the cylinder by the
inexpensive method. In addition, it is possible, by using the
material of lower thermal conductivity than the housing for the
actuator holder, to prevent burnout of the actuator since the heat
of the housing is hardly transferred.
[0174] In addition, it is preferable to perform the resin coating
on the screw portion.
[0175] It is thereby possible to further reduce the heat transfer
from the housing.
[0176] Alternatively, a driving power of the actuator for
controlling the opening and closing time of the suction valve is
gradually reduced when it is off.
[0177] It is thereby possible to reduce the collision force when it
is off and prevent the abrasion and damage of the colliding
portion.
[0178] In addition, it is preferable to make a driving portion of
the actuator and the suction valve in separate bodies so as to
render the operating distance of the actuator driving portion
shorter than that of the suction valve.
[0179] It is thereby possible, even in the case where the operating
time (response when it is off) of the actuator is slow, to open the
suction valve on the change of the pressure in the pressurization
chamber (on the shift from the discharge process to the suction
process).
[0180] In addition, it is possible to reduce the collision force by
shortening the operating distance of the actuator and also
sufficiently secure the opening area of the suction valve.
[0181] It is thereby possible, as the passage resistance on the
suction valve is reduced, to prevent the reduction in the pressure
in the pressurization chamber upon the suction process and restrain
the occurrence of the cavitation.
[0182] It is also feasible to render the operating distance of the
discharge valve equal to or shorter than that of the suction
valve.
[0183] It is thereby possible to hold down the backflow of the high
pressure fuel into the pressurization chamber due to the delay in
closing the discharge valve (on the shift from the discharge
process to the suction process) to the minimum so as to restrain
the occurrence of the cavitation in the pressurization chamber.
[0184] Alternatively, at least one of the discharge valve and the
suction valve is a ball valve, and there is a cylindrical member
fitting this ball valve, and the cylindrical member is rendered
slidable in the cylindrical member holder.
[0185] It is thereby possible, as the ball is held by the
cylindrical member on opening the ball valve, to restrain the
deflections of the ball so as to stabilize the fuel flow.
Accordingly, it is possible to prevent the cavitation caused by the
disorder of the flow.
[0186] In addition, it is preferable to render the outer diameter
of the cylindrical member larger than the ball valve diameter so as
to form a notch at a part of the outer circumference of the
cylindrical member.
[0187] It is thereby possible, as the appropriate fuel passage can
be formed in the valve mechanism, to prevent the cavitation caused
by the reduction in the fuel pressure due to the pressure loss.
[0188] In addition, it is to secure the oil tightness of the high
pressure piping with the inexpensive technique by adopting the
above structure to the discharge valve.
[0189] Alternatively, at least one of the suction valve and the
discharge valve is the flat valve having the cup-like cylindrical
portion, and the cylindrical portion is slidably held in the
cylindrical portion holding member.
[0190] It is thereby possible, as the cylindrical portion is held
upon opening of the flat valve, to restrain the deflections of the
valve body and stabilize the fuel flow. Accordingly, it is possible
to prevent the cavitation caused by the disorder of the flow. In
addition, the space can be saved by placing the spring for closing
the valve in the cup portion.
[0191] In addition, it is preferable to provide the notch forming
the fuel passage in a part of the inner circumference of the
cylindrical portion holding member.
[0192] It is thereby possible, as the appropriate fuel passage can
be formed in the valve mechanism without rendering the valve body
thicker, to prevent the cavitation caused by the reduction in the
fuel pressure due to the pressure loss and render the valve body
lightweight so as to improve the response upon opening and closing
the valve.
[0193] In addition, it is preferable to prevent the cavitation
caused by the reduction in the fuel pressure because adoption of
the above structure in the suction valve allows higher response
upon opening the valve and thereby restrain the reduction in the
pressure in the pressurization chamber due to delay in the valve
opening at the start of the suction process.
[0194] Alternatively, the cylinder and the housing are separated,
and the cylindrical tubes are used for a part of the pressurization
chamber.
[0195] It is thereby possible, even when the cylinder member and
the suction valve or the discharge valve are positioned apart from
each other, to connect them by the cylindrical tubes and thereby
deform the cylindrical tubes and fix them on assembly so as to
abosorb variations in the dimensions. Accordingly, it is feasible
to render the entire pump smaller, even in the case where the
housing is not used on the wall of the pressurization chamber,
because there is a degree of freedom in the placement of the
suction valve or the discharge valve.
[0196] In addition, it is preferable to hold the cylindrical tubes
by press contact.
[0197] It is thereby possible to absorb the variations in the
dimensions in the press contact portions upon assembling.
[0198] In addition, it is preferable to absorb the variations in
the dimensions in the two directions of X and Y by having one side
of the press contact portion in the plane contact and the other
side in the cylindrical surface contact.
[0199] The above structure can prevent the cavitation damage even
in case of using the soft material such as aluminum for the
housing.
[0200] In addition, it is possible, even in case of using the
materials of significantly different coefficients of linear
expansion for the housing and the cylinder, to prevent the plunger
from sticking caused by the deformation of the sliding hole of the
cylinder due to the change of temperature.
[0201] Moreover, it is possible, even in case of using the material
of high thermal conductivity for the housing, to prevent the
burnout of the actuator and the galling of the plunger.
[0202] Accordingly, it is possible, by rendering the housing
all-aluminum, to provide the pump of high reliability that is
lower-cost and lighter-weight due to improvement in the
cuttability.
[0203] Moreover, a plurality of seals of different shapes are
placed on the plunger sliding portion.
[0204] In addition, it is preferable to render the seal in the pump
outer side direction lip-shaped.
[0205] Furthermore, the seals in the pump inner side direction have
the shapes such as the O ring (including the one having the resin
ring and so on placed on the sliding side) or the X/K rings.
[0206] It is thereby possible to improve the resistance to pressure
of the seal contacting the fuel chamber on the pump inner side and
alleviate the pressure exerted on the seal on the pump outer side
so as to improve reliability of the seal performance.
[0207] In addition, the ring seals such as O, X and K have better
formability than the lip seals and so there is a degree of freedom
of material selection. Accordingly, it is thereby possible to
select the rubber materials according to the fuel to be used.
[0208] According to the embodiments, it is possible to provide the
high pressure fuel pump which solves the problem when using the
soft material such as an aluminum alloy for a pump housing, is
highly reliable and has good cutting workability. It is thereby
feasible to implement a lower-cost and lighter-weight high pressure
fuel supply pump.
[0209] Of the seal structures for rendering the outer circumference
of the plunger fluid-tight at an outside of the cylinder and at two
locations in the axial direction of the plunger, the structure on
the pressurization chamber side is the one using an annular member
made of a highly rigid resin.
[0210] It is thereby possible to secure the resistance to pressure
against the fuel and also prevent mixing of the fuel into the
oil.
[0211] In addition, a rubber annular member is used for the seal
structure on the opposite side to the pressurization chamber.
[0212] It is thereby possible to prevent mixing of the oil into the
fuel and also prevent contamination in the oil from flowing into
the pump.
[0213] In addition, it should have a mechanism wherein the fuel
leaked to the reservoir formed on the pressurization chamber side
of the seal structure is returned to a suction port from the
pressurization chamber through the clearance between the cylinder
and the plunger.
[0214] It is thereby possible to omit the piping from the pump to
the fuel tank so as to reduce man-hours and costs.
[0215] According to the present invention, it is possible, by
adding a contrivance to the seal mechanism, to implement the high
pressure fuel pump which is low-cost and has the secure seal.
[0216] It will be further understood by those skilled in the art
that the foregoing description has been made on embodiments of the
invention and that various changes and modifications may be made in
the invention without departing from the spirit of the invention
and scope of the appended claims.
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