U.S. patent application number 14/237578 was filed with the patent office on 2014-06-19 for fuel pump.
This patent application is currently assigned to DELPHI TECHNOLOGIES HOLDING S.A.R.L.. The applicant listed for this patent is Borja Navas Sanchez. Invention is credited to Borja Navas Sanchez.
Application Number | 20140170002 14/237578 |
Document ID | / |
Family ID | 46514411 |
Filed Date | 2014-06-19 |
United States Patent
Application |
20140170002 |
Kind Code |
A1 |
Navas Sanchez; Borja |
June 19, 2014 |
FUEL PUMP
Abstract
A fuel pump is provided for pressurising fuel in a high-pressure
fuel injection system. The fuel pump comprises a pump head, a
pumping element, a frame and a casing. The pump head has a pumping
chamber that is arranged to receive fuel to be pressurised. The
pumping element is arranged to reciprocate responsive to movement
of a driving element, the pumping element defining, in part, the
pumping chamber so that, in use, as the pumping element
reciprocates, a force, transferred from the driving element, is
applied to the fuel within the pumping chamber to pressurise the
fuel. The frame is arranged to support the driving element and the
pump head. The casing defines an internal volume for containing
fluid, wherein at least a part of the frame, at least a part of the
drive element, and at least a part of the pumping element are
received in the casing.
Inventors: |
Navas Sanchez; Borja;
(Chatham, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Navas Sanchez; Borja |
Chatham |
|
GB |
|
|
Assignee: |
DELPHI TECHNOLOGIES HOLDING
S.A.R.L.
Bascharage
LU
|
Family ID: |
46514411 |
Appl. No.: |
14/237578 |
Filed: |
July 19, 2012 |
PCT Filed: |
July 19, 2012 |
PCT NO: |
PCT/EP2012/064209 |
371 Date: |
February 7, 2014 |
Current U.S.
Class: |
417/437 |
Current CPC
Class: |
F04B 53/16 20130101;
F02M 59/02 20130101; F04B 1/0404 20130101; F02M 59/44 20130101;
F04B 1/0426 20130101; F04B 35/002 20130101 |
Class at
Publication: |
417/437 |
International
Class: |
F04B 35/00 20060101
F04B035/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2011 |
EP |
11176843.8 |
Claims
1. A fuel pump for pressurising fuel in a high-pressure fuel
injection system, the fuel pump comprising: a pump head having a
pumping chamber that is arranged to receive fuel to be pressurised;
a pumping element arranged to reciprocate responsive to movement of
a driving element, the pumping element defining, in part, the
pumping chamber so that, in use, as the pumping element
reciprocates, a force, transferred from the driving element, is
applied to the fuel within the pumping chamber to pressurise the
fuel; a frame arranged to support the driving element and the pump
head; and a casing defining an internal volume for containing
fluid; wherein at least a part of the frame, at least a part of the
driving element, and at least a part of the pumping element are
received in the casing.
2. The fuel pump according to claim 1, wherein the frame is
arranged to hold the pump head and driving element in fixed
positions relative to one another to support the transfer of force
from the driving element to the pump head.
3. The fuel pump according to claim 1, wherein the frame is
constructed from a material having higher strength than a material
from which the casing is constructed.
4. The fuel pump according to claim 1, wherein the frame is formed
of a single piece.
5. The fuel pump according to claim 4, wherein the frame is formed
of a single piece by means of an extrusion process.
6. The fuel pump according to claim 1, wherein the casing is formed
of a plastics-based material.
7. The fuel pump according to claim 1, wherein the frame is
arranged for mounting the fuel pump to an engine component.
8. The fuel pump (1) according to claim 7, further comprising: a
mounting arrangement for connecting the frame of the fuel pump to
the engine component.
9. The fuel pump according to claim 8, wherein the casing and the
mounting arrangement each comprise a complementary interference
feature arranged for preventing rotation of the mounting
arrangement with respect to the casing.
10. The fuel pump according to claim 9, wherein one of the
complementary interference features comprises a protrusion and the
other complementary interference feature comprises a recess.
11. The fuel pump according to claim 1, wherein the casing
comprises one or more integrated components including one or more
of a back-leak device to aid recirculation of fluid, and a fuel
inlet to deliver fuel to the fuel pump.
12. The fuel pump according to claim 1, wherein the driving element
is formed from a plurality of parts including a shaft portion and a
cam portion.
13. The fuel pump according to claim 12, wherein the cam portion is
constructed from a higher strength material than the shaft
portion.
14. The fuel pump according to claim 1, wherein the pump head is
received within the casing.
15. The fuel pump according to claim 1, wherein the frame comprises
at least one bearing arranged to support the drive element for
rotational movement with respect to the bearing.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a national stage application under 35
U.S.C. 371 of PCT Application No. PCT/EP2012/064209 having an
international filing date of 19 Jul. 2012, which designated the
United States, which PCT application claimed the benefit of
European Patent Application No. 11176843.8 filed 8 Aug. 2011, the
entire disclosure of each of which are hereby incorporated herein
by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of fuel pumps. In
particular, the invention relates to a high-pressure fuel pump for
supply of high-pressure fuel to a fuel injector. More specifically,
but not exclusively, the present invention relates to a housing for
such a pump.
BACKGROUND TO THE INVENTION
[0003] Fuel injection systems for modern internal combustion
engines, particularly engines that utilise compression ignition,
comprise a plurality of fuel injectors arranged to deliver an
atomised spray of fuel to a respective combustion chamber for
combustion.
[0004] In order to improve atomisation of fuel within engines
utilising compression ignition it is preferable to atomise the fuel
as much as possible. Greater atomisation of fuel improves the
efficiency of the combustion process, which in turn improves the
fuel efficiency and reduces harmful emissions such as carbon
monoxide produced by the combustion process. The most common way to
improve atomisation is to increase the pressure of the fuel to be
injected. As such, there has been a continual desire to manufacture
pumps capable of pressurising fuel to higher pressures.
[0005] Known high-pressure pumps utilise a pumping element such as
a steel plunger that reciprocates inside a close-fitting
guide-bore, the plunger being driven by a driveshaft. Hence, as the
driveshaft rotates, its rotational force is transferred to the
plunger so that the plunger reciprocates within the guide bore.
Fuel enters a pumping chamber at an end of the guide bore and is
then pressurised as the reciprocating plunger applies a
pressurising force to the pumping chamber. The fuel is then forced
through a delivery valve into a high-pressure rail ready for
injection by the fuel injectors. The components of the pump are
supported by the housing. DE 10 2008 007028 discloses a fuel pump
including a plate arrangement that compensates for forces between a
pumping element and a drive element.
[0006] In order to increase the pressure of fuel that a
high-pressure fuel pump is capable of providing, a greater energy
has to be put into the system through the rotating driveshaft so
that the plunger applies a greater force to the fuel. Hence, as the
pressures that pumps are capable of providing has increased, so has
the relative strength of the pump housing due to the increase in
physical energy used within the pump.
[0007] It is common to manufacture high-pressure fuel pump housings
from cast steel to provide the strength required to withstand the
stresses to which high-pressure fuel pumps are subjected. As pumps
capable of producing higher pressure fuel have been developed, the
thickness of the steel housing has also increased to withstand the
relative increases in stress.
[0008] Increasing the thickness of a cast steel pump housing
results in the pump being heavier. As such, the fuel efficiency of
the vehicle in which the pump is used is reduced due to the heavier
components it is having to carry. Furthermore, as the thickness of
the cast steel pump housing increases, so does the overall size of
the pump.
[0009] It would be desirable to provide a high pressure fuel pump
that is of reduced weight and size. This is particularly of
relevance to "ecoefficiency" concept vehicles, where overall weight
reduction of a vehicle is a key component in improving the
efficiency to thereby reduce the environmental impact of the
vehicle. Furthermore, minimising the size of a pump is desirable
because such a pump takes up less space within a vehicle.
[0010] Embodiments of the present invention therefore aim to at
least partially mitigate one or more of the above-mentioned
problems.
SUMMARY OF THE INVENTION
[0011] According to a first aspect of the present invention, there
is provided a fuel pump for pressurising fuel in a high-pressure
fuel injection system. The fuel pump comprises a pump head having a
pumping chamber that is arranged to receive fuel to be pressurised.
The fuel pump also includes a pumping element arranged to
reciprocate responsive to movement of a driving element. The
pumping element defines, in part, the pumping chamber so that, in
use, as the pumping element reciprocates, a force, transferred from
the driving element, is applied to the fuel within the pumping
chamber to pressurise the fuel. The fuel pump also comprises a
frame arranged to support the driving element and a casing which
defines an internal volume for containing fluid. At least a part of
the frame, at least a part of the driving element, and at least a
part of the pumping element are received in the casing. This
arrangement therefore provides a lighter, smaller pump.
[0012] The frame and the casing together provide a housing for the
pump.
[0013] The frame may be arranged to hold the pump head and driving
element in fixed positions relative to one another. Such an
arrangement allows for correct operation of the fuel pump. In
particular, a large force is transferred from the driving element
to the pump head in order to pressurise fuel within the pump head
to a very high pressure. The frame therefore needs to withstand
such forces and keep the pump head and driving element in fixed
positions relative to one another so that the pump continues to
operate correctly.
[0014] The frame may be constructed from a material having higher
strength than a material from which the casing is constructed. The
frame is provided to support the pump head and driving element,
while the casing is provided for containing fluid. Hence, only the
frame has to withstand the high forces transferred from the driving
element to the pump head. The casing can therefore be made from a
material of lower strength than the frame because it only has to
contain fluid. Alternatively, the frame and casing can be made from
the same material and the frame can be made thicker than the casing
to provide the higher strength. Preferably the frame is made from
aluminium because aluminium is relatively strong compared to other
materials while being relatively low density compared to other
materials.
[0015] The materials for the frame and casing may be selected so
that they are optimised for their specific function. The material
for the frame may be selected so that it is of a sufficiently high
strength for supporting the forces transferred from the driving
element to the pump head. The material for the casing may be
selected for containing fluid.
[0016] The frame may be formed of a single piece. Forming the frame
from a single piece allows for the frame to be stronger because it
does not have any joins, which can lead to structural weaknesses.
Furthermore, the frame may be formed of a single piece by means of
an extrusion process. Such an extrusion process provides an easy
means for manufacturing a frame in a single piece. Furthermore,
such an extrusion process allows for additional features, such as
screw holes, to be easily formed within the frame.
[0017] The casing may be formed of a plastics-based material. Such
an arrangement results in a light-weight and easy to manufacture
casing.
[0018] The frame may be arranged for mounting the fuel pump to an
engine component. The frame supports the high-stress components of
the fuel pump. It is therefore desirable to mount the fuel pump via
the high-strength fuel pump frame.
[0019] The fuel pump may further comprise a mounting arrangement
for connecting the frame of the fuel pump to the engine component.
The mounting arrangement provides a means for providing a strong
connection between the frame and the engine component.
[0020] The housing and the mounting arrangement may each comprise a
complementary interference feature arranged for preventing rotation
of the mounting arrangement with respect to the housing. For
example, the casing and the mounting arrangement may each comprise
a complementary interference feature arranged for preventing
rotation of the mounting arrangement with respect to the casing.
When the fuel pump is in operation large forces are transferred
between the driving arrangement and the pump head. The forces
applied by these components result in the frame of the fuel pump
attempting to move in response to these forces. It is therefore
advantageous to include complementary interference features which
will prevent rotation between the frame and the mounting
arrangement, thereby helping to hold the fuel pump securely in
position.
[0021] One of the complementary interference features may comprise
a protrusion and the other complementary interference feature may
comprise a recess. Such interlocking interference features provide
a strong connection between the frame and the mounting
arrangement.
[0022] The casing may comprise one or more integrated components.
The one or more integrated components may include a back-leak
device to aid recirculation of fluid. The one or more integrated
components may include a fuel inlet to deliver fuel to the fuel
pump. The one or more integrated components may include both the
back-leak device and the fuel inlet. Providing these components
integrated within the housing provides a smaller and easier to
manufacture fuel pump.
[0023] The driving element may be formed from a plurality of parts
including a shaft portion and a cam portion. Such an arrangement is
advantageous when using a frame formed of a single piece. The cam
portion may be constructed from a higher strength material than the
shaft portion. This is because the cam portion bears the majority
of the load which is transferred to the pump head for pressurising
the fuel. Such an arrangement provides a cheaper to manufacture
driving element because only the expensive strong material is
utilised for the part requiring a strong material.
[0024] The pump head may be received within the casing. Including
the pump head within the casing improves cooling of the pump
head.
[0025] Embodiments of the invention provide a high pressure fuel
pump which is of lighter weight than currently known pumps. A high
strength frame is provided to bear the pumping loads by supporting
the high stress portions of the pump, such as the cam arrangement
and the pump head, and a lightweight casing is then provided to
seal the pump to prevent leakage of fuel from the pump.
[0026] Embodiments of the invention provide a high pressure fuel
pump that is smaller than known fuel pumps. Such embodiments
utilise a support frame and lightweight casing. The casing can be
relatively thin, and as such, the overall thickness of the housing
is reduced because only a strong frame support is provided, rather
than a strong housing that encases the whole pump.
[0027] Embodiments of the invention reduce the cost and time for
prototyping new pumps. In particular, the frame can be extruded
from metal and a plastic moulded shell can be utilised to construct
the casing. Such techniques do not require the slow and expensive
provisions required to construct a cast steel housing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Embodiments of the present invention will now be described,
by way of example only, with reference to the accompanying
drawings, in which like reference numerals are used for like parts,
and in which:
[0029] FIG. 1 illustrates a cross-sectional view of a pump
according to a first embodiment of the present invention;
[0030] FIG. 2 provides an exploded view of the pump of FIG. 1;
[0031] FIG. 3 illustrates a frame of a pump housing of the pump of
FIG. 1;
[0032] FIG. 4 illustrates a casing of the pump of FIG. 1;
[0033] FIG. 5 provides an exploded view of a fixing arrangement of
the pump in FIG. 1;
[0034] FIG. 6 provides an exploded view of the fixing arrangement
of FIG. 5 from an alternative angle;
[0035] FIG. 7 provides an exploded view of the cam arrangement
illustrated in FIGS. 1 and 2; and
[0036] FIG. 8 provides an exploded view of an alternative cam
arrangement.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0037] Reference shall firstly be made to FIGS. 1 and 2, which
provide two alternative views of a pump 1 provided in accordance
with a first embodiment of the present invention. The pump 1 shall
initially be described primarily in respect of its operation.
[0038] Low-pressure fuel enters the pump 1 through a fuel inlet 2,
which is integrated into a casing 3 of the pump 1. The fuel then
passes through an inlet metering valve (IMV) 4a of an IMV
arrangement 4 mounted on the casing 3, which controls the rate of
flow of fuel into the pump 1. The casing 3 forms part of a pump
housing and defines an internal cavity 5 in which pumping and
driving components of the pump 1 are arranged, the internal cavity
5 being filled with fuel. The IMV arrangement 4 is partially
arranged between the fuel inlet 2 and the internal cavity 5; fuel
therefore passes from the fuel inlet 2 through the IMV 4a and into
the internal cavity 5.
[0039] The fuel within the internal cavity 5 acts as a lubricant to
the moving parts of the fuel pump 1, and it also acts to cool
components of the pump 1 by absorbing heat generated in the pumping
process so that the heat is transferred away from the pumping
components of the pump 1. In order to aid the cooling process a
back-leak device 6 such as a venturi device is provided to allow
fuel to be drawn from internal cavity 5 and returned to a low
pressure drain or engine cam box, so that the fuel is recirculated.
The back-leak device 6 therefore aids the recirculation of fuel so
that the heat generated by the pumping components is transferred
away from the fuel pump 1.
[0040] The pumping components include a pump head 7, a pumping
element in the form of a plunger 8 and a drive arrangement
comprising a follower arrangement 9 and a driveshaft or cam
arrangement 10. The pumping process takes place within the pump
head 7. The pump head is therefore made of a strong material, such
as hardened steel, in order to withstand the high-pressure fuel
which is pressurised within a pumping chamber 7a of the pump head
7, in addition to the large forces applied to the pump head 7 by
the pumping element 8 in order to pressurise the fuel.
[0041] The pumping chamber 7a of the pump head 7 is arranged at one
end of a plunger bore 7b provided in the pump head 7 and is a
cavity comprising a low-pressure fuel inlet (not shown) for
receiving fuel from the internal cavity 5 defined by the casing 3,
and a high-pressure fuel outlet (not shown) in the form of an
outlet valve. The pumping chamber 7a is defined in part by a
pumping head at a first end of the plunger 8. The plunger 8 is
arranged to reciprocate so that a pumping head of the plunger
increases and decreases the volume of the pumping chamber 7a. As
the volume of the pumping chamber decreases, the pressure of fuel
within the pumping chamber 7a increases. When the fuel within the
pumping chamber 7a reaches a predetermined pressure, the outlet
valve opens allowing the high-pressure fuel to pass through into a
high-pressure rail (not shown) where the fuel is stored ready for
injection by one or more fuel injectors (not shown).
[0042] At a second end of the plunger 8, remote from the pumping
chamber 7a, the follower arrangement 9 is arranged to cooperate
with the cam arrangement 10 to transform a rotational movement of
the cam arrangement 10 into the reciprocal movement of the plunger
8 within the plunger bore 7b.
[0043] The cam arrangement 10 is provided with a shaft portion 10a
located at least partially outside the casing 3 of the pump 1 to
engage with a drive source (not shown), such as a drive gear. The
cam arrangement 10 rotates responsive to the input force provided
by the drive gear. The shaft portion 10a of the cam arrangement 10
is also located in part within the internal cavity 5 of the casing
3, and has a cam portion 10b connected on the shaft 10a at a
portion within the internal cavity 5.
[0044] The follower arrangement 9 comprises a roller 9a which abuts
the cam 10b so that the roller 9a and cam 10b are communicatively
coupled. The roller 9a is held within a roller shoe 9b connected to
the second end of the plunger 8. As the cam 10b rotates, the roller
9a rotates within the roller shoe 9b. The arrangement of the roller
9a and roller shoe 9b limits the transfer of lateral movement from
the cam 10b to the plunger 8, while transferring reciprocal
movement of the cam 10b to the plunger 8. A spring 11 is maintained
in position between the pump head 7 and a spring seat 8a mounted on
the plunger 8, in order to urge the plunger 8, and the roller shoe
9b connected thereto, into contact with the cam 10b. Due to the
spring 11, the follower arrangement 9 continually follows the
reciprocating movement of the cam 10b.
[0045] The follower arrangement 9 also includes a shoe guide 9c,
which is provided around the peripheral surface of the roller shoe
9b in order to guide the movement of the roller shoe 9b. The guide
9c therefore allows the roller shoe 9b to move along the axis of
the plunger 8, allowing reciprocating movement, but restricting
lateral movement, of the guide shoe 9c. The rotation of the cam
arrangement 10 exerts a lateral force on the follower arrangement 9
and as such the shoe guide 9c is constructed of a strong material
in order to resist such lateral movement and to withstand the
stress associated with such resistance.
[0046] While the above-mentioned follower arrangement 9 has been
described as a roller-based arrangement it will be appreciated that
any suitable following arrangement could be used (e.g. a tappet or
other intermediate drive component).
[0047] The pump housing includes a frame 12 in addition to the
casing 3. The frame 12 is provided to support various pumping and
driving components, in particular, the pumping components 7, 9, 10
that are subjected to high levels of stress due to the pumping
process. Hence, the frame 12 is arranged to support the pump head
7, the roller shoe 9, and the shaft 10a of the cam arrangement 10.
The frame 12 is therefore made of a relatively strong material,
such as aluminium, in order to withstand the high levels of stress
within the pump 1, particularly due to the forces being transferred
from the cam arrangement 10 to the plunger 8 and then into the fuel
within the pump head 7.
[0048] In order to aid rotation of the cam arrangement 10, and
prevent excessive load and wear to the frame 12, bushes 13a, 13b
are provided at the portions of the frame 12 that support the cam
arrangement 10.
[0049] As can be seen in FIG. 2, a mounting arrangement 14 is
provided with a mounting plate 14a external to the casing 3 which
connect the pump 1 to the engine. The mounting arrangement 14
connects to the frame 12 through the casing 3 in order to provide a
solid support for the frame 12 and therefore the pump 1. Since the
frame 12 and mounting arrangement 14 are connected through the
casing 3, the mounting arrangement 14 includes a plurality of seals
14b, 14c in order to prevent leakage of fuel through the casing
3.
[0050] Each of the components of the pump 1 shall now be discussed
in more detail with reference to various figures.
[0051] The construction of the frame 12 shall be discussed with
further reference to FIG. 3, which shows the frame 12 of the pump
of the first embodiment of the present invention.
[0052] The frame 12 is provided with two cam support sections 12a,
12b, which each define a hole 12c, 12d through which the cam
arrangement 10 (shown in FIGS. 1 and 2) can be supported, wherein
the cam 10b is located between the two cam support sections 12a,
12b. The holes 12c, 12d defined by the cam support sections 12a,
12b respectively are shaped so as to complement the external
surface of the shaft 10a of the cam arrangement 10. Hence, in this
case the holes 12c, 12d are circular to complement the cylindrical
shape of the shaft 10a of the cam arrangement 10. As such, smooth
rotation of the cam arrangement 10 is possible. The dimensions of
the frame 12 are arranged so that within the holes 12c, 12d defined
by each cam support section 12a, 12b one of the bushes 13a, 13b can
be placed in order to aid rotation of the shaft 10a of the cam
arrangement 10. The fuel in the internal cavity 5 defined by the
internal walls of the casing 3 helps to lubricate the frame 12 and
bushes 13a, 13b in order to aid smooth rotation of the shaft 10a of
the cam arrangement 10 and minimise wear. The cam support sections
12a, 12b bear the majority of the weight and stress of the cam
arrangement 10. However, the mounting arrangement 14 bears a
portion of the load applied to the cam support section 12a which is
adjacent to the mounting arrangement 14.
[0053] The frame 12 is also provided with a pump head support
section 12e. This section 12e has a hole 12f for receiving the pump
head 7. In particular, a front face of the pump head 7 protrudes,
at least partially, through this hole 12f. The front face of the
pump head 7 includes a recess defining, in part, the pumping
chamber 7a into which the pumping head of the plunger 8 is inserted
to thereby define the pumping chamber 7a.
[0054] A plurality of screw holes 12g (only one shown in FIG. 3)
are provided in the pump head support section 12e of the frame 12
through which screws (not shown) can connect the pump head 7 to the
frame 12. A strong clamping of the pump head 7 to the frame 12 is
required in order to prevent the pump head 7 from being separated
from the frame 12 when the plunger 8 drives into the pump head 7,
in such a way that a force is provided that urges the pump head 7
away from the frame 12. Alternatively, the frame 12 could be
arranged to provide at least one support member (not shown) that
abuts a rear face of the pump head so that connection screws are
not relied upon for holding the pump head 7 onto the frame 12.
[0055] The frame 12 is also provided with shoe-guide support
sections 12h (only one shown), which includes a plurality of struts
(not shown) that support the shoe-guide 9c.
[0056] The cam support sections 12a, 12b, pump head support section
12e and the shoe-guide support sections 12h are joined together by
the main structure of the frame 12. Structural rigidity is required
between these sections 12a, 12b, 12e, 12h, and in particular the
cam support sections 12a, 12b and the pump head support section 12e
because the pressurisation of the fuel is achieved by the relative
movement of the plunger 8, driven by the cam arrangement 10, into
the pump head 7. Hence, the position of the pump head 7 with
respect to the cam arrangement 10 needs to remain constant in order
to allow for correct operation of the pump 1.
[0057] Holes or cut-outs 12i are provided within the main body of
the frame 12 in order to reduce the weight of the frame 12 without
reducing the relative strength of the frame 12 so that the frame 12
is able to provide strong support to the components of the pump
subjected to high levels of stress.
[0058] It will be appreciated that while the cam support sections
12a, 12b, pump head support section 12e and the shoe-guide support
sections 12h are supported by the main body of the frame 12 in this
embodiment of the invention, alternatively, strut supports could be
provided between each of the sections of the frame 12 in order to
link the sections together. Use of strut supports between the
sections of the frame 12 could help to further reduce the weight of
the frame 12, and in certain arrangements allow for a reduction in
the size of the frame 12.
[0059] In this example, the frame 12 is also provided with
attachment holes 12j, 12k, 12l, 12m for connecting the pump 1, via
the frame 12, to the mounting arrangement 14. The holes 12j, 12k,
12l, 12m and their relationship to the mounting arrangement 14
shall be discussed when the mounting arrangement 14 is described in
detail with respect to FIGS. 5 and 6.
[0060] The frame 12 is made by extruding an aluminium bar. The
extrusion process is fast and cheap to perform. By forming the
frame 12 by an extrusion process the frame 12 can be formed of one
part. That is, it is extruded from a single bar of metal and as
such no parts have to be joined. In contrast, casting processes
require two or more parts to be cast, which are then joined
together. There is a risk of structural weaknesses forming at the
joins between these parts. Hence, the extrusion process overcomes
these problems.
[0061] Furthermore, since the frame 12 is extruded, the amount of
cutting and drilling of the frame is minimised. In particular, the
extrusion process allows for certain characteristics of the frame
12, such as holes, to be formed in the frame 12 during the
extrusion process. In contrast, casting techniques require all
characteristics to be added after the casting, therefore leading to
further structural weaknesses.
[0062] It will be appreciated that while the frame 12 is described
as being made of aluminium, any suitably strong material could be
utilised. In particular, any suitable metal could be used or other
materials like a composite plastic or composite plastic
encapsulated in sintered metal. It is noted that while an extrusion
process is preferable for constructing the frame 12, other
construction processes such as casting could be utilised.
[0063] The casing 3, which defines the internal cavity 5, is
arranged to enclose the frame 12 and the pumping and driving
components that the frame 12 supports. In other words, the pumping
and driving components are at least partially arranged within the
internal cavity defined by the frame 12. The casing 3 therefore
provides a fluid tight shell around the pumping components so that
fuel does not leak from the internal cavity.
[0064] While in FIG. 1 the casing 3 is shown to enclose all pumping
and driving components of the pump 1 it will be appreciated that
the casing 3 is arranged to define an internal cavity containing
fuel for cooling and lubrication purposes. The moving driving and
pumping parts of the pump 1, such as the plunger 8, follower
arrangement 9, and cam arrangement 10 therefore require such
lubrication and cooling. As such, it will be appreciated that it is
not necessary for the whole of the pump head 7 to be enclosed
within the casing 3. The casing could be provided so that it joins
a peripheral surface of the pump head 7 or the front face of the
pump head 7. In such circumstances the front face of the pump head
7 would be in fluid communication with the fuel within the internal
cavity 5, and at least part of the side portion and the whole of
the rear portion of the pump head 7 would be external to the casing
3. It is noted that due to the constant flow of fuel through the
pump head, the heat created within the pump is, at least in part,
transferred away by the pressurised fuel, and therefore cooling of
the pump head is not as important as cooling of the moving
components of pumping process.
[0065] The casing 3 is formed of two parts 3a, 3b, as shown in FIG.
2. The parts 3a, 3b are arranged to fit around the components
attached to and within the frame 12. The two parts 3a, 3b of the
plastic casing can then be joined together so that the two-part
casing 3 seals fluid within. The two parts can be joined by any
method capable of providing a fluid tight bond.
[0066] FIG. 4 shows one half 3a of the casing 3. In FIG. 4, it can
be seen that the casing 3 has a plurality of internal supporting
struts 3s. The supporting struts 3s stiffen the casing 3 to improve
the strength of the casing 3. As such it is possible to have a
thinner casing 3, while still providing sufficient strength. The
struts 3s could also be provided to abut the outer surface of the
frame 12 so that the casing 3 is tightly formed around the frame
12.
[0067] In this embodiment of the invention the frame 12 is only
joined to the casing 3 via the mounting arrangement 14. However, it
will be appreciated that the casing 3 could be connected to the
frame 12 in various ways, such as by utilisation of one or more
connection screws having suitable sealing to prevent leakage from
the casing 3.
[0068] The two casing parts 3a, 3b are formed from plastic using an
injection moulding technique. As such, high-frequency welding would
provide a suitable bond between the two parts 3a, 3b. However,
other materials such as a metal could be used for the casing 3. For
example, an aluminium frame 12 and casing 3 could be provided.
Since the casing 3 only needs to provide fluid tightness it could
be made much thinner than the frame 12. Furthermore, due to the
relative strength of metal compared to plastic, a metal casing 3
could be made much thinner than a plastic casing 3. Due to its
conductive properties, a metal casing 3 would also assist in
transferring heat away from the fuel within the internal
cavity.
[0069] While in the embodiment of the invention discussed in
respect of FIGS. 1 and 2 the internal cavity 5 defined by the
casing 3 is filled with fuel, it will be appreciated that other
fluid could be provided within the internal cavity 5. For example,
specific cooling/lubrication fluid could be contained in the
internal cavity. In such circumstances, the IMV arrangement 4 would
connect directly, or via a contained channel, from the fuel inlet 2
to the pump head 7. In such an arrangement a cooling fluid inlet
(not shown) could be provided, and the back-leak device 6 would
help to recirculate the cooling fluid.
[0070] As well as defining the internal cavity 5, the casing 3 also
defines various features of the fuel pump 1, as discussed
below.
[0071] The casing 3 includes an IMV connection portion 3b, which is
arranged to enable the shell of the IMV arrangement 4 to be
connected to the pump 1. The IMV connection portion 3b defines a
hole 3c in which a portion of the IMV arrangement 4 can be
positioned, so that the IMV 4a can connect to the fuel inlet 2. One
or more connection holes 3d can be provided within the casing 3 to
enable the IMV arrangement 4 to be attached to the casing so that
the IMV arrangement 4 is held in place on the pump 1.
[0072] The casing 3 also provides an integrated back-leak device 6,
and an integrated fuel inlet 2. Integrating these components into
the casing 3 is advantageous when the casing 3 is constructed from
plastic using an injection moulding method because the components
are formed as part of the casing 3 in the moulding process.
Furthermore, integrating these components within the casing 3
simplifies the overall manufacturing process of the fuel pump 1 and
reduces the size of the fuel pump 1.
[0073] The housing, which includes the frame 12 and the casing 3,
is much smaller than known housings. This is because the minimum
structural support required can be provided by the frame 12, and
then a comparatively thin and light casing 3 can be provided to
provide a fluid-tight seal for the pump 1. Overall, this allows for
the overall size of the housing and therefore the pump 1 to be
reduced. In addition, the materials used for the frame 12 and
casing 3 can be selected so as to best suit their respective
functions, which allows for the weight of the housing and the
therefore pump 1 to be reduced.
[0074] A further advantage of such a housing construction is that
it is possible to place the IMV arrangement 4 much closer to the
pump head 7 than is possible in a fuel pump that utilises a cast
steel housing. This is because the frame 12 can be provided only in
those portions that require support, and the casing 3 can be
arranged to closely surround this frame 12, enabling the IMV
arrangement 4 to be positioned close to the pump head 7. As such,
the overall pump head 7 can be reduced further.
[0075] While the frame 12 has been described as being arranged
within the casing 3 above, it will be appreciated that the frame 12
could be provided so that it is only partially within the casing 3.
For example, the main structure of the frame 12 could be provided
outside the casing 3 with support arms extending through the casing
3 to support the high stress components of the pump 1. In such a
case, the mounting arrangement 14 can be easily connected to the
frame 12, or even be formed integrally with the frame 12.
[0076] The mounting arrangement 14 shown in FIG. 2 shall now be
described in further detail with reference to FIGS. 5 and 6.
[0077] The mounting arrangement 14 comprises a mounting plate 14a,
which is arranged to connect to a component of the engine to secure
and stabilise the pump 1. The mounting plate 14 is a substantially
planar structure with a plurality of holes or cutaways to reduce
the weight of the plate 14a. The mounting plate 14a is provided
with a plurality of screw holes 14d, 14e, 14f for screws (not
shown) to connect the mounting plate to the engine. Further screw
holes 14g, 14h, 14i, 14j are provided to allow the mounting plate
14 to be connected by screws through holes in the casing 3 and
connect to the frame 12. As such, one face of the mounting plate
14a is arranged to sit flush against the casing 3, connected
through the casing 3 to the frame 12, so that the casing 3 is held
between the mounting plate 14a and the frame 12.
[0078] Since the screws for connecting the mounting plate 14a to
the frame 12 pass through the casing 3 it is necessary to provide a
mounting arrangement sealing means. This is achieved by providing
first and second seals 14b, 14c, which seal the gap between the
mounting plate 14a and the casing 3, and the gap on the outer
surface of the mounting plate 14a, respectively.
[0079] The first seal 14b takes the form of a gasket positioned
between the mounting plate 14a and the casing 3. The gasket 14b is
arranged so that it surrounds all of the screw holes in the casing
3 and those 14g, 14h, 14i, 14j in the mounting plate 14 thereby
creating an internal cavity between the mounting plate 14a and the
casing 3 for fluid. The gasket 14b is clamped between the mounting
plate 14a and casing 3 due to the screws clamping the frame 12 and
the mounting plate 14a together. The gasket 14b therefore provides
a fluid-tight seal between the casing 3 and the mounting plate 14a.
Alternatively, the first seal could be provided by a plurality of
gaskets, each provided around an individual screw hole.
[0080] The second seal 14c takes the form of a rubber O-gasket and
is arranged on an outer surface of the mounting plate 14a. The
O-gasket 14c prevents fuel leaking from around the heads of the
screws that pass through the mounting plate 14a.
[0081] To prevent rotation of the housing with respect to the
mounting plate 14a, the casing 3 is provided with a plurality of
protrusions 3m, which are arranged to engage with a plurality of
complementary recesses 14k within the mounting plate 14a. In use,
this engagement of the casing 3 and mounting plate 14a helps to
prevent rotation of the mounting plate 14a with respect to the
casing 3. Hence, this feature of the mounting arrangement 14
provides an interference which is radial with respect to the shaft
10a of the cam arrangement 10, in order to help prevent rotation of
the mounting arrangement 14.
[0082] It will be appreciated that the radial interference features
provided between the casing 3 and the mounting plate 14a could
include further protrusions in the frame 12 which protrude into the
rear of the protrusions 3m in the casing 3. As such, the frame 12
would support the protrusions 3m and thereby provide additional
resistance to the relative rotation of the housing and mounting
plate 14.
[0083] The mounting plate 14a can be extruded from an aluminium
bar. Such a manufacturing process is cheap and quick. However, any
suitable material or manufacturing process could be used.
[0084] The construction of the cam arrangement 10 shown in FIGS. 1
and 2 shall now be considered in detail with reference to FIG.
7.
[0085] In general, known driveshafts are constructed from a single
piece of metal and supported by a two-part cast steel housing,
which is constructed around the driveshaft. However, when utilised
with an extruded aluminium frame or any fixed frame structure it is
not possible to utilise a standard driveshaft.
[0086] In the embodiment of the invention shown in FIGS. 1 and 2 a
multiple part cam arrangement 10 is provided. The cam arrangement
10 includes three portions: the shaft 10a, the cam 10b and a rear
bearing journal 10c. The shaft 10a runs along the length of the cam
arrangement 10 and the cam 10b and rear bearing journal 10c are
mounted thereon so that the cam arrangement 10 can be constructed
within the fixed frame 12.
[0087] The shaft 10a is an elongate structure with a stepped
cylindrical form, having a plurality of cylindrical parts, which
reduce in diameter towards one end of the shaft 10. The shaft has a
first reduced diameter portion 10aa onto which the cam 10b is
press-fitted, and a neighbouring second reduced diameter section
10ab at an end of the shaft 10a onto which the rear bearing journal
10c is press-fitted. The second reduced diameter section 10ab has a
smaller diameter than the first reduced diameter section 10aa.
[0088] In order to assemble the cam arrangement 10 within the frame
12 it is firstly necessary to insert the cam 10b through the gap
between the two cam support sections 12a, 12b in FIG. 3. Then, the
shaft 10a is inserted through the first cam support section 12a of
the frame 12 and through the cam 10b and into the rear bearing
journal 10c which is arranged to support the shaft 10a within the
second cam support section 12b of the frame 12.
[0089] FIG. 8 shows an alternative cam arrangement 100, which
utilises a key interference join. In this embodiment of the
invention the cam arrangement 100 includes a shaft 100a, a cam
100b, a rear bearing journal and two engagement elements (or keys)
100d, 100e. The shaft 100a and the cam 100b are provided with
recessed portions 100aa, 100ba, 100bb (or keyways) with which the
engagement elements 100d, 100e engage. The engagement elements
100d, 100e therefore act as intermediate connecting parts which
provide a join or bridge between the shaft 100a and the cam 100b in
order to help prevent the parts of the cam arrangement 100 moving
out of position with respect to one another. The arrangement 100 of
FIG. 8 therefore provides a driveshaft arrangement 100 which is
stronger than the above-mentioned arrangement 10 that relies upon
press-fitting of parts.
[0090] It will be appreciated that while press-fit and
key-interference fit arrangements have been described, the parts of
the cam arrangement could be connected by any suitable means such
as a serial interference, a thermal expansion interference, a
spline interference, or by hyrdo-forming.
[0091] Constructing the cam arrangement 10, 100 from multiple parts
allows for a cheaper cam arrangement to be constructed compared to
a driveshaft made from a single piece. In particular, the cam 10b,
100b can be made from high-tensile steel because it takes the
majority of the stress and then the shaft and rear bearing journal
can be made of cheaper grade steel.
[0092] The cam arrangement 10 of the illustrated embodiment serves
as a drive element of the pump for transferring a driving force to
the pumping element for pressurising fuel within the pump head. It
will be appreciated that other drive elements could be
contemplated.
[0093] For example, even though use of a fixed frame 12 with a cam
arrangement 10 made of multiple parts has been described herein it
will be appreciated that in certain circumstances it may be
preferable to utilise a drive element comprising a single-part
driveshaft and a frame made of multiple parts.
[0094] The invention has been described with use of a linear
pumping arrangement, wherein a cam 10b, 100b drives an elongate
plunger 8 to drive into a pumping chamber 7a. However, it will be
appreciated that alternative pumping arrangements could be used.
For example, a drive element comprising a rocker-arm type pumping
arm can be utilised. In such a case, drive members of the rocker
arrangement could be supported by the frame in a similar way to the
cam arrangement illustrated in FIG. 1.
[0095] The above-mentioned embodiments of the present invention
have been described with reference to a single pump 1 having a
single pump head 7 and single cam arrangement 10. However, it will
be appreciated that the principles of the present invention apply
equally to pumping systems including multiple pumping heads, with
one or more driveshafts.
[0096] Further variations and modifications will be apparent to a
person skilled in the art without departing from the scope of the
invention as defined in the appended claims. For example, it will
be appreciated that although the embodiments described relate to
fuel pumps which are fuel-lubricated, the invention is equally
applicable to oil-lubricated pumps.
* * * * *