U.S. patent application number 10/015676 was filed with the patent office on 2002-04-18 for high pressure fuel pump.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Hashida, Minoru, Kotaki, Masayoshi, Machimura, Hideki, Ono, Yoshinobu, Takahashi, Yukio, Yamamura, Takefumi.
Application Number | 20020044873 10/015676 |
Document ID | / |
Family ID | 17708646 |
Filed Date | 2002-04-18 |
United States Patent
Application |
20020044873 |
Kind Code |
A1 |
Hashida, Minoru ; et
al. |
April 18, 2002 |
High pressure fuel pump
Abstract
An axial plunger pump according to the present invention is
constructed so as to comprise a shaft having a swash plate
effecting swing motion and transmitting driving force from the
outside, plungers each reciprocating by the swing motion of the
swash plate, a cylinder block having cylinders formed so as to open
on the side of the swash plate and inserting therein the plungers
and having passages for supplying fuel to the cylinders, a body
combined with the cylinder block to enclose the swash plate, and
sealing members arranged between the plungers and the cylinders on
the swash plate side of the passages formed in the cylinder block
for sealing gaps between the plungers and the cylinders,
respectively.
Inventors: |
Hashida, Minoru;
(Hitachinaka-shi, JP) ; Takahashi, Yukio;
(Hitachinaka-shi, JP) ; Ono, Yoshinobu;
(Hitachinaka-shi, JP) ; Machimura, Hideki;
(Hitachinaka-shi, JP) ; Yamamura, Takefumi;
(Hitachinaka-shi, JP) ; Kotaki, Masayoshi;
(Hitachinaka-shi, JP) |
Correspondence
Address: |
CROWELL & MORING, L.L.P
P.O Box 14300
Washington
DC
20044-4300
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
17708646 |
Appl. No.: |
10/015676 |
Filed: |
December 17, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10015676 |
Dec 17, 2001 |
|
|
|
09414648 |
Oct 8, 1999 |
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Current U.S.
Class: |
417/269 ;
417/549 |
Current CPC
Class: |
F04B 1/124 20130101;
F04B 1/143 20130101 |
Class at
Publication: |
417/269 ;
417/549 |
International
Class: |
F04B 001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 8, 1998 |
JP |
10-286756 |
Claims
What is claimed is:
1. A high pressure fuel pump comprising: a shaft having an swash
plate effecting swing motion, and transmitting driving force from
the outside; plungers each reciprocating by the swing motion of
said swash plate; a cylinder block having cylinders formed therein
so as to open on the side of said swash plate and inserting therein
said plungers, said cylinder block having passages for supplying
fuel to said cylinders; a body combined with said cylinder block to
enclose said swash plate; and sealing members arranged between said
plungers and said cylinders for sealing gaps between said plungers
and said cylinders, respectively, said sealing members being
axially separated from said passages toward said swash plate.
2. A high pressure fuel pump according to claim 1, wherein fuel is
supplied to pump chambers formed by said plungers and said
cylinders, respectively.
3. A high pressure fuel pump according to claim 1, wherein said
pump comprises: pump chambers formed by said plungers and said
cylinders; passages arranged inside said plungers for communicating
between said passages for supplying fuel to said cylinders and said
pump chambers; grooves arranged inside said plungers so that said
passages arranged inside said plungers are always communicating
with said passage for supplying fuel to said said cylinders; and
valves for partitioning said pump chambers and said passages
arranged inside said plungers, said valves allowing communication
between said pump chambers and said passages arranged inside said
plungers when fuel is a first pressure or higher; and wherein fuel
is supplied to said pump chambers through said plungers.
4. A high pressure fuel pump according to claim 1, wherein said
pump comprises: an oil chamber enclosed by said body for
lubricating the swash plate side of said sealing members; and a
hole provided in said body for introducing oil on the engine side
into said oil chamber.
5. A high pressure fuel pump comprising: a shaft having an swash
plate effecting swing motion, and transmitting driving force from
the outside; plungers each reciprocating by the swing motion of
said swash plate; a cylinder block having cylinders formed so as to
open on the side of said swash plate and inserting therein said
plungers, said cylinder block having passages for supplying fuel to
said cylinders; a body combined with said cylinder block to enclose
said swash plate; a radial bearing supporting said shaft mounted on
said body and a bearing arranged on the back of said swash plate
for supporting an axial load applied on said swash plate, said
bearing being a thrust roll bearing having rolls or balls larger in
rolling pitch diameter than said radial bearing.
6. A high pressure fuel pump according to claim 5, wherein a gap
for inflow and/or outflow of oil is provided between said shaft and
said radial bearing.
7. A plunger for a high pressure fuel pump, having: a radial hole
traversing the central axis of said plunger; a groove formed on the
periphery so as to overlap with said radial hole and having a
prescribed axial length; an end portion to which an axial hole
communicating with said radial hole is opened; and the other end
portion formed spherical.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a fuel pump for fuel supply
of an internal combustion engine and, more particularly, to a high
pressure fuel pump used for a fuel injection system of a so-called
direct fuel injection type internal combustion engine, which system
injects directly fuel from a fuel injection valve mounted on a
combustion chamber into the combustion chamber.
[0002] For an internal engine in which fuel is directly injected
into the combustion chamber, it is necessary to have a high
pressure pump for raising the pressure of fuel to be supplied to an
fuel injection valve to a pressure of 2 MPa or more.
[0003] As such a high pressure pump, there has been known a
conventional axial plunger pump which is disclosed in JP A
9-236080. Such a conventional axial plunger pump is constructed so
as to partition a driving mechanism part lubricated with oil and a
pump chamber compressing and discharging fuel by a metal
bellows.
[0004] Further, a conventional high pressure fuel pump disclosed in
JP A 9-250447 is constructed so as to circulate fuel also to a
sliding portion of a driving mechanism part, and the driving
mechanism part, that is, the sliding portion is lubricated with
fuel.
SUMMARY OF THE INVENTION
[0005] The above-mentioned conventional high pressure fuel pumps
have the following problems or disadvantages.
[0006] 1. The former conventional pump has a problem that the pump
is large-sized because of use of the metal bellows and it is
difficult to make the pump size small because it is necessary to
provide a seal portion on a bellows mounting portion.
[0007] 2. In the latter conventional pump, it is not necessary to
provide any bellows, however, lubrication is insufficient because
the sliding portion of the driving mechanism part is lubricated
with fuel of low viscosity.
[0008] An object of the present invention is to provide an axial
plunger pump in which any bellows is unnecessary and lubrication of
a sliding portion of a driving mechanism part is sufficient.
[0009] Another object of the present invention is to enable a roll
bearing to be used in the driving mechanism part.
[0010] In order to solve the above problems, an axial plunger pump
according to the present invention is constructed so as to comprise
a shaft having a swash plate effecting swing motion and
transmitting driving force from the outside, plungers each
reciprocating by the swing motion of the swash plate, a cylinder
block having cylinders formed so as to open on the side of the
swash plate and inserting therein the plungers and having passages
for supplying fuel to the cylinders, a body combined with the
cylinder block to enclose the swash plate, and sealing members
arranged between the plungers and the cylinders on the swash plate
side of the passages formed in the cylinder block for sealing gaps
between the plungers and the cylinders, respectively.
[0011] Another invention is a high pressure fuel pump which
comprises a shaft having an swash plate effecting swing motion, and
transmitting driving force from the outside, a plurality of
plungers each reciprocating by the swing motion of the swash plate
a cylinder block having cylinders formed so as to open on the side
of the swash plate and inserting therein the plungers, the cylinder
block having passages for supplying fuel to the cylinders, a body
combined with the cylinder block to enclose the swash plate, a
radial bearing supporting the shaft mounted on the body and a
bearing arranged on the back of the swash plate for supporting an
axial load applied on the swash plate, which bearing is a thrust
roll bearing having rolls or balls larger in rolling pitch diameter
than the radial bearing.
[0012] Still another invention is a plunger for a high pressure
fuel pump, which plunger has a radial hole traversing the central
axis of the plunger, a groove formed on the periphery so as to
overlap with the radial hole and having a prescribed axial length,
and an end portion to which an axial hole communicating with the
radial hole is opened and the other end portion is formed
spherical.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a sectional view of a high pressure fuel pump of a
first embodiment of the present invention:
[0014] FIG. 2 is a partially sectional view of a construction of
passage in a rear body of the first embodiment;
[0015] FIGS. 3a and 3b each are a sectional view of a plunger and a
surrounding portion thereof for explaining strokes;
[0016] FIG. 4 is a sectional view of a shaft seal of a first
embodiment;
[0017] FIG. 5 is a sectional view of a shaft seal of a second
embodiment;
[0018] FIG. 6 is a sectional view of a shaft seal of a third
embodiment; and
[0019] FIG. 7 is a sectional view of a high pressure fuel pump of a
second embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0020] A high pressure fuel pump of a first embodiment of the
present invention is shown in FIGS. 1 and 2.
[0021] In FIG. 1, a coupling 2 for transmitting drive force
transmitted from a cam shaft of an engine to the pump has a shaft 5
connected by a pin 4 fitted to the coupling 2. The shaft 5 has
thereon a swash plate 12 which radially expands and which is formed
in oblique flat plane at its end. The swash plate 12 is in contact
with slippers 13 at the oblique flat plane and the slippers 13 each
are formed substantially flat so that the slippers 13 can smoothly
slide on the swash plate 12 rotating together with the shaft 5. The
slippers 13 each are formed in spherical shape on the other side,
and swinging motion of the swash plate 12 imparts reciprocating
motion to a plurality of plungers 14 each sliding in a cylinder
bore 17 of a cylinder block 16.
[0022] With the pump of the above construction, intake and
discharge of fuel is carried out as follows.
[0023] The plurality of cylinder bores 17 and plungers 14 form a
plurality of pump chambers 42. An intake space 25 communicating
with each plunger 14 is provided at the center of the cylinder
block 16 so as to supply fuel to the pump chambers 42. In order to
introduce fuel into the intake space 25, fuel piping is provided
out of the pump, and the fuel is led to the intake space 25 through
an intake passage 35 formed in a rear body 34 and an intake chamber
26 formed at the center of the rear body 34 and connected to the
intake space 25.
[0024] In each plunger 14, an intake valve 18 (a check valve) is
disposed, and the intake valve 18 is formed of a ball 22, a spring
21 and a stopper 23 supporting the spring 21. A plunger spring 24
is inserted for the purpose of causing the plunger 14 to follow the
slipper 13 and the swash plate 12. The stopper 23 is also used for
supporting spring force of the plunger spring 24.
[0025] A communication passage A 50 to the plunger intake valve 18
is formed as an oblique passage which is inclined against an axial
direction and led from the intake space 25 to the cylinder side. An
intake groove 30 is formed in the outer periphery of the plunger 14
so that even if the plunger reciprocates, the communication passage
A 50 and the intake valve 18 are always communicated, that is, they
are communicated over the full stroke of the plunger 14.
Concretely, the groove of width larger than the stroke of the
plunger is formed. Since it is simple in construction because of
groove formation without use of any other devices, it serves for
making the construction small in size.
[0026] FIG. 3 shows an enlarged view of the plunger 14 for
explanation of strokes. When the above-mentioned intake stroke is
turned to a discharge stroke (a stroke in which the space of the
pump chamber 42 decreases) and when the pressure in a discharge
chamber 28 formed in the rear body 34 reaches to a prescribed
pressure, a discharge valve 20 constructed of a ball 22 and a
spring 21 as well as the intake valve 18 formed in the cylinder
block 16 is opened, and the fuel supplied to the pump chamber 42
formed by the cylinder and the plunger 14 during the
above-mentioned intake stroke is discharged from the pump chamber
42. Here, the intake chamber 26 and discharge chamber 28 are
separated by an O-ring 32, the intake chamber 26 is provided on the
central side more than the discharge chamber 28, whereby a passage
construction in the pump itself is made compact.
[0027] The pressure in the discharge chamber 28 of the rear body 34
can be controlled to an optimum pressure by a pressure regulator 36
provided on the discharge side. The purpose of controlling the
discharge pressure is for controlling the pressure applied to an
injector (not shown) disposed downstream of the discharge side.
Excess high pressure side fuel supplied from the high pressure
chamber of the rear body 34 to the pressure regulator 36 is
returned to the intake chamber 26 through a ball valve 48 provided
in the pressure regulator 36 and a communication passage B 52
provided in the rear body 34. The intake passage 35, intake chamber
26, intake space 25 and communication passage A 50 form passages
for supplying fuel from a fuel source to each cylinder.
[0028] In this manner, the fuel pressure in the pump chamber 42
also changes from an intake pressure (in general, 0.2 MPa to 0.5
MPa) to pressure in the high pressure chamber (in general, 3 MPa to
20 MPa). A load generated by the fuel pressure in the pump chamber
42 is transmitted to the swash plate 12 of the shaft 5 through the
slippers 13. The load to the slippers 13 is transmitted from each
plunger 14 and transmitted to the swash plate 12. On the other
hand, the resultant force of forces of the plurality of plungers 14
is applied to the shaft 5. The resultant force acts as; axial force
and radial load according to the inclination angle of the swash
plate 12. In order to support those loads and achieve smooth
rotation, the radial bearing 6 and the thrust bearing 8 are fitted
to the shaft 5, and the loads are supported by the body 10.
[0029] Portions (the slippers 13/the swash plate 12 and the bearing
portions) supporting those loads are portions at which a relative
speed due to rotation exists and loads are supported. By
lubricating those portions, wear due to sliding can be decreased.
It, therefore, is necessary to provide a construction for storage
of oil in the swash plate chamber 44 formed between the body 10 and
cylinder block 16.
[0030] In this embodiment, therefore, a shaft seal 38 sealing fuel
and oil when the plungers 14 reciprocate is provided on the slipper
side of the intake groove 30 of the plunger 14. The shaft seal 38
is for sealing a gap between the plunger 14 and the cylinder bore
17 and it is a boundary between fuel and oil. By constructing in
this manner, intake pressure of low pressure on the side of the
intake groove 30 is always applied to the shaft seal 38. The intake
pressure does not largely change as the pressure in the pump
chamber 42, a constant pressure is applied on the shaft seal 38.
This construction raises the sealing performance and reliability of
the shaft seal 38.
[0031] In this embodiment, one shaft seal 38 is provided on the
plunger 14, however, the same effect can be attained even by
providing it on the cylinder side and also it can be attained by
providing a plurality of shaft seals.
[0032] On the other hand, the shaft seal 38 of the plunger 14
becomes a resistance against reciprocation of the plunger 14. In
the pump construction of the present embodiment, in order to raise
the property that the plunger 14 follows the slippers 13 and swash
plate 12, the plunger spring 24 is provided, and it is necessary to
lower the resistance at the portion of the shaft seal 38. In order
to decrease the slide friction resistance due to the seal at the
portion of the shaft seal 38, it is important to elect material of
low friction coefficient and to elect a suitable shape.
[0033] FIG. 4 shows seals of such a shape. Material of PTFE which
is small in friction coefficient is used on the sliding surface
side.
[0034] FIG. 5 shows an X-shaped rubber seal which is reduced in
sliding surface area. In view of being high in circumference
temperature in use of the pump, fluorine-contained rubber is used
for the rubber material.
[0035] FIG. 6 shows a rip seal of another embodiment of the seal
member. Further, instead of formation of the intake groove 30, a
counterbore is formed in the cylinder bore 17. The counterbore is a
bore of larger diameter than the diameter of the cylinder bore 17,
and in order that fuel can be sufficiently introduced into the
plunger 14, the counterbore is formed to the depth of such extent
as the counterbore can communicate with an introduction hole 60
even when the pump chamber 42 becomes sufficiently small. If fuel
can be sufficiently introduced into the plunger 14 in this manner
even when the displacement of the pump chamber 42 is reduced to a
sufficiently small one, the communication passage A 50 is
unnecessary to be oblique.
[0036] In order to lubricate the driving mechanism portion with
fuel as in a conventional manner, it is necessary for all the
bearings to be slide bearings. Therefore, excess drive torque due
to the slide friction resistance becomes necessary (the viscosity
coefficient of fuel is low, particularly, since oil film formation
is difficult at a low speed operation, frictional resistance
becomes extremely large).
[0037] However, as mentioned above, by a construction separating
oil and fuel within the reciprocating portion, it is possible to
lubricate the inside of the swash plate chamber 44 with oil.
Further, in the present embodiment, leakage of oil onto the fuel
side is prevented by making the pressure in the swash plate chamber
44 less than the intake fuel pressure, whereby the oil is prevented
from being decreased in amount.
[0038] By the construction in which oil is always stored in the
swash plate chamber 44 in this manner, it becomes possible to use
roll bearings for the bearings supporting the above-mentioned
loads. Particularly, it is possible to use the roll bearings for
the thrust bearings, whereby reduction of the drive torque and the
reliability of the siding portion can be improved.
[0039] However, the shaft seal 38 inside the reciprocating portion
of the plunger 14 diffuses the fuel adhered to the surface of the
plunger 14 into oil in a thin layer. Oil in the swash plate chamber
44 is inserted when the pump is assembled, and it is necessary to
introduce, into the pump, oil on the side of engine, used on the
cam shaft side during engine driving operation after it is mounted
on the engine. In order to introduce engine oil into the pump, in
the present embodiment, any shaft seal is not provided so that the
oil can be introduced from the radial bearing portion 6 of the
shaft 5. Therefore, if oil is introduced from the radial bearing
portion 6 to an upper portion, oil leaks from a gap between the
shaft 5 and the radial bearing 6 to the engine side. If an amount
of oil introduced therein is more than the leaked oil, the oil is
stored to a level higher than the radial bearing portion 6.
Further, in this embodiment, a ball bearing is used for the radial
bearing 6, however, a roll bearing also can be used therefor. Since
the radial bearing 6 is small in load and used in oil, a slide
bearing also can be used therefor.
[0040] Even if an amount of oil stored is a level lower than the
radial bearing 6, in order that rotating members are always
submerged in the oil, a pitch circle of rolls (or rolling pitch
circle of balls) of the thrust bearing 8 and the outer diameter of
the swash plate 12 are made larger than radial bearing 6. The
slippers 13 contacting with the swash plate 12 and converting
swinging motion to reciprocation also is lubricated with oil
adhered to the swash plate 12, whereby the swash plate portion is
able to be lubricated with oil.
[0041] FIG. 7 show a second embodiment in which an oil introduction
passage 46 for positively introducing oil on the engine into the
swash plate chamber 44 is provided. The oil introduction passage 46
is provided on the body 100. In this case, the pressure on the oil
introduction side is made higher than the oil pressure in the swash
plate chamber 44. Here, the pressure in the swash plate chamber 44
is made smaller than the fuel intake pressure as shown in the first
embodiment. Further, the engine oil introduce is returned to the
engine side from the radial bearing 6 portion at the center of
shaft 5. Foreign matters contained in the oil introduced from the
engine side are scattered toward the body inner side by centrifugal
force due to rotation of the shaft 5, so that portions of the
thrust bearing 8 and radial bearing fitted to the shaft 5 can be
lubricated with clean oil.
[0042] Since a member such as bellows and a seal member provided at
the mounting portion thereof in order to separate an oil
circulation portion and a fuel circulation portion become
unnecessary, the pump body can be made small in size. Further,
since the swash plate portion can be lubricated with lubrication
oil, roll bearings can be used for bearings, therefore, frictional
resistance at a low speed can be reduced, so that small driving
torque is sufficient for driving.
* * * * *