U.S. patent application number 16/390093 was filed with the patent office on 2020-06-11 for integrated outlet check valve and pressure relief valve.
The applicant listed for this patent is Stanadyne LLC. Invention is credited to Kenneth R. Morel, Dominic M. Myren, Yevgeniy Norkin, David G. Palermo, Richard P. Pellini, Michael Wegrzyniak.
Application Number | 20200182365 16/390093 |
Document ID | / |
Family ID | 66641466 |
Filed Date | 2020-06-11 |
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United States Patent
Application |
20200182365 |
Kind Code |
A1 |
Pellini; Richard P. ; et
al. |
June 11, 2020 |
Integrated Outlet Check Valve and Pressure Relief Valve
Abstract
The disclosed integrated outlet check valve and pressure relief
valve are used in a high pressure fuel pump including a pumping
chamber and an outlet fitting defining an outlet passage to a
common rail. The pressure relief valve comprises a movable pressure
relief valve shuttle including a pressure relief valve surface
configured to mate with a pressure relief valve seat in a closed
position. The pressure relief valve shuttle moves from the closed
position to an open position when pressure in the common rail
exerts a force greater than the bias of a pressure relief valve
spring. The pressure relief valve shuttle also includes an outlet
check valve seat configured to mate with an outlet check valve ball
in a closed position. The outlet valve ball moves from the closed
position to an open position when pressure in the outlet passage is
less than pressure in the pumping chamber.
Inventors: |
Pellini; Richard P.; (South
Windsor, CT) ; Morel; Kenneth R.; (Bloomfield,
CT) ; Palermo; David G.; (West Springfield, MA)
; Myren; Dominic M.; (Chicopee, MA) ; Norkin;
Yevgeniy; (Longmeadow, MA) ; Wegrzyniak; Michael;
(East Granby, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Stanadyne LLC |
Windsor |
CT |
US |
|
|
Family ID: |
66641466 |
Appl. No.: |
16/390093 |
Filed: |
April 22, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62776670 |
Dec 7, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04B 15/00 20130101;
F02M 59/442 20130101; F02M 63/005 20130101; F16K 15/044 20130101;
F02M 59/368 20130101; F04B 49/22 20130101; F02M 63/0054 20130101;
F02M 2200/26 20130101; F02M 59/466 20130101; F04B 53/102 20130101;
F02M 59/366 20130101; F04B 53/1002 20130101; F16K 17/044 20130101;
F02M 59/462 20130101; F16K 17/048 20130101; F02M 63/0245 20130101;
F16K 17/0406 20130101; F04B 53/1087 20130101; F02M 63/0075
20130101 |
International
Class: |
F16K 17/04 20060101
F16K017/04; F16K 15/04 20060101 F16K015/04; F04B 53/10 20060101
F04B053/10; F02M 63/00 20060101 F02M063/00 |
Claims
1. An integrated outlet check valve and pressure relief valve for a
high pressure fuel pump, said high pressure fuel pump having a
pumping chamber where a pumping plunger reciprocates between a
pumping phase and a charging phase and an outlet fitting defining
an outlet passage to a common rail, said integrated outlet check
valve and pressure relief valve comprising: a pressure relief valve
shuttle movable between a closed position and an open position,
said pressure relief valve shuttle having a pressure relief valve
surface configured to mate with a pressure relief valve seat and an
outlet check valve seat configured to mate with an outlet check
valve ball; a pressure relief valve cup arranged concentrically
about at least a portion of said pressure relief valve shuttle; a
pressure relief valve spring comprising a conical disc spring
arranged between said pressure relief valve shuttle and said
pressure relief valve cup, said pressure relief valve spring
biasing said pressure relief valve shuttle toward said closed
position; a pressure relief valve support defining an outlet flow
path and including said pressure relief valve seat; said outlet
check valve ball movable between a closed position and an open
position, said outlet check valve ball biased toward said closed
position by an outlet check valve spring; a pressure relief passage
defined between said pressure relief valve seat and said
complimentary pressure relief valve surface of said pressure relief
valve shuttle; and wherein, said outlet check valve ball mates with
said outlet check valve seat in said closed position preventing
fluid communication through said outlet flow path, said outlet
check valve ball moves from said closed position to said open
position permitting fluid communication through said outlet flow
path when pressure in said outlet passage is less than pressure in
said pumping chamber, said pressure relief valve surface mates with
said pressure relief valve seat in said closed position preventing
fluid communication through said pressure relief passage, and said
pressure relief valve shuttle moves from said closed position to
said open position permitting fluid communication through said
pressure relief passage when pressure in said common rail exerts a
force greater than the bias of said pressure relief valve
spring.
2. The integrated outlet check valve and pressure relief valve of
claim 1, wherein said pressure relief valve cup has an interference
fit within said pump outlet fitting and traps said pressure relief
valve shuttle, said pressure relief valve spring, said check valve
ball, said check valve spring, and said pressure relief valve seat
within the pump outlet fitting.
3. The integrated outlet check valve and pressure relief valve of
claim 1, wherein said pressure relief valve seat includes an
annular, conical surface configured to mate with said pressure
relief valve surface.
4. The integrated outlet check valve and pressure relief valve of
claim 1, wherein said pressure relief valve surface and said
pressure relief valve seat form a conical surface together in said
closed position of said pressure relief valve shuttle.
5. The integrated outlet check valve and pressure relief valve of
claim 1, wherein said pressure relief valve seat is arranged
radially inward of said pressure relive valve surface.
6. The integrated outlet check valve and pressure relief valve of
claim 1, wherein said outlet check valve support defines sides of
said outlet check valve.
7. The integrated outlet check valve and pressure relief valve of
claim 1, wherein said pressure relief valve seat contacts said
pressure relief valve shuttle radially outward of said outlet check
valve ball.
8. A method of controlling pressure and discharge of fuel through
an outlet passage of a high pressure fuel pump, said high pressure
fuel pump having a pumping chamber where a pumping plunger
reciprocates between a pumping phase and a charging phase, said
method comprising: providing an outlet check valve ball; providing
a pressure relief valve support defining an outlet flow path and
having a pressure relief valve seat, said pressure relief valve
seat having an annular surface; providing a pressure relief valve
shuttle having a pressure relief valve surface configured to mate
with said annular surface of said pressure relief valve seat and an
outlet check valve seat configured to mate with said outlet check
valve ball, said pressure relief valve surface arranged radially
outward of said pressure relief valve seat, said outlet check valve
seat arranged radially outward of said outlet check valve ball,
said outlet check valve shuttle and said outlet check valve ball
exposed to pressure in said outlet passage; biasing said pressure
relief valve shuttle toward said pressure relief valve seat with a
pressure relief valve spring comprising a conical disc spring, said
pressure relief valve spring compressing in response to pressure in
said outlet passage; biasing said outlet check valve ball toward
said outlet check valve seat; defining a pressure relief passage
between said pressure relief valve seat and said pressure relief
valve surface; moving said pressure relief valve shuttle between a
closed position mated with said pressure relief valve surface and
preventing fluid communication through said pressure relief passage
and an open position permitting fluid communication through said
pressure relief passage, said pressure relief valve shuttle moving
from said closed position to said open position when pressure in
said outlet passage exerts a force greater than the bias of said
pressure relief valve spring; and moving said outlet check valve
ball between a closed position mated with said outlet check valve
seat and preventing fluid communication through said outlet flow
path and an open position permitting fluid communication through
said outlet flow path, said outlet check valve ball moving from
said closed position to said open opposition when pressure in said
outlet passage is less than pressure in said pumping chamber.
9. The method of claim 8, wherein said step of providing a pressure
relief valve cup includes said pressure relief valve cup trapping
said pressure relief valve shuttle, said pressure relief valve
spring, said check valve ball, said check valve spring, and said
pressure relief valve seat within said high pressure fuel pump.
10. The method of claim 8, wherein said step of providing a
pressure relief valve seat includes said pressure relief valve seat
having an annular, conical surface configured to mate with said
pressure relief valve surface.
11. The method of claim 8, wherein said step of providing a
pressure relief valve shuttle includes said pressure relief valve
surface and said pressure relief valve seat forming a conical
surface together in said closed position of said pressure relief
valve shuttle.
12. The method of claim 8, further comprising a step of providing
an outlet check valve support, said pressure relief valve seat
being arranged on said outlet check valve support.
13. The method of claim 8, wherein said step of providing a
pressure relief valve shuttle includes said pressure relief valve
shuttle contacting said pressure relief valve seat in said closed
position radially outward of said check valve ball.
14. The method of claim 8, further comprising a step of calibrating
an opening pressure of the pressure relief valve by setting a
position of a pressure relief valve cup concentrically about at
least a portion of said pressure relief valve shuttle.
Description
BACKGROUND
[0001] The present disclosure relates to high pressure fuel supply
pumps for gasoline common rail injection systems. More
particularly, the present disclosure relates an integrated outlet
check valve and a pressure relief valve for use in a high pressure
fuel supply pump.
[0002] Gasoline Direct Injection (GDI) fuel systems must regulate
the fuel volume delivered to the common rail as part of an overall
pressure management strategy. Two strategies are currently employed
for controlling the quantity of fuel delivered to the pumping
chamber and thus the degree to which the common rail is
pressurized. One strategy uses a digital on/off solenoid such as
disclosed in U.S. Pat. No. 7,707,996 and another uses a
proportional valve such as disclosed in U.S. Pat. No. 6,792,916.
The solenoid valves used for inlet metering are required to open
and close very fast, so the valve actuation is coordinated with the
pumping cycles of the high pressure pump. Fast acting solenoid
driven valves are known to generate noise from contact between
parts such as a valve member and a valve seat, or between a valve
member and a valve stop. It is common for inlet metering valves to
be arranged at or near the low pressure inlet of a high pressure
pump (near the outside of the pump), where the noise generated by
valve parts is easily transmitted. It is desirable to reduce the
noise associated with inlet metering valves.
[0003] Single piston, cam driven high pressure fuel pumps have
become a common solution for generating high pressure fuel in
common rail direct injection gasoline (GDI) engines. It is known in
the industry that the pump must incorporate an outlet check valve
to prevent pressure bleed back from the rail while the pump is in
the intake stroke cycle. It has become an industry requirement to
incorporate a pressure relief valve within the pump to protect the
entire high pressure system from an unexpected excess pressure
caused by a system malfunction. In order to protect the rail and
injectors, the pressure relief valve must be in hydraulic
communication with the rail, i.e., in parallel with the pump flow.
In order to make the parallel hydraulic communication, typical
executions have located the outlet check valve and pressure relief
valve as separate devices within the pump housing. It is desirable
to incorporate the outlet check valve and pressure relief valves
into an outlet connector that can be assembled and tested before
attachment to the high pressure pump, as disclosed in U.S. Pat. No.
8,132,558.
[0004] The maximum amount of fuel that can be transferred by a fuel
pump is a function of the pressure at the end of the pumping cycle,
the bulk modulus of the fuel (under that pressure and temperature),
the trapped volume of the pump, and leakage losses in the pump. The
trapped volume of a high pressure fuel pump is the volume fluidly
connected with the pumping chamber, measured when the pumping
plunger is at the end of a pumping stroke (TDC). The trapped volume
of a high pressure pump commonly includes portions of the inlet
check valve, the pump outlet check valve and pressure relief valve
exposed to the pumping chamber. The trapped volume of a pump plays
a significant role in the overall volumetric efficiency of the
pump, especially when the volume displaced by the pumping plunger
is small compared to the trapped volume. Keeping the trapped volume
as small as possible improves the volumetric efficiency of the high
pressure fuel pump. It is common for outlet check valves and
pressure relief valves employed in high pressure fuel pumps to
include coil springs to bias valve members (such as a valve ball)
toward a closed position. It is also common that one or more coil
springs employed for this purpose are in a volume exposed to the
pumping chamber, which increase the trapped volume of the pump.
[0005] Because pressure relief valve flow returns to the pumping
chamber, the springs associated with the pressure relief valve, and
the chamber containing the springs are in direct communication with
the pumping chamber. The volume of fluid in the spring chamber not
occupied by the springs contributes to the trapped volume of the
pump. The size of the springs necessary to hold the pressure relief
valve closed increase along with the operating pressure of the
direct injection system. Current and pending emissions regulations
require direct injection operating pressures of 350 bar (35 MPa) or
above, requiring increased spring dimensions to generate increased
spring loads, and can result in increased trapped volume associated
with the pressure relief valve.
SUMMARY
[0006] The disclosed integrated outlet check valve and pressure
relief valve are configured to control pressure and discharge of
fuel through a high pressure fuel pump. In the disclosed
embodiment, the high pressure fuel pump includes a pumping chamber
where a pumping plunger reciprocates between a pumping phase and a
charging phase and an outlet fitting defining an outlet passage to
a common rail. A benefit of the disclosed integrated outlet check
valve and pressure relief valve is the reduction of trapped volume
within the high pressure fuel pump.
[0007] The pressure relief valve comprises a movable pressure
relief valve shuttle which includes a pressure relief valve surface
configured to mate with a pressure relief valve seat. In the
disclosed embodiment, the pressure relief valve seat is included on
a pressure relief valve support and is arranged radially inward of
the pressure relief valve surface. The pressure relief valve
support defines an outlet flow path where fuel travels to the
common rail and also defines sides of the outlet check valve. A
pressure relief passage is defined between the pressure relief
valve seat and the pressure relief valve surface to allow excess
pressure to pass from the common rail. A pressure relief valve cup
is arranged concentrically about at least a portion of the pressure
relief valve shuttle.
[0008] The pressure relief valve is biased toward a closed position
by a pressure relief valve spring which comprises a conical disc
spring arranged between the pressure relief valve shuttle and the
pressure relief valve cup. In the closed position of the pressure
relief valve, the pressure relief valve surface mates with the
pressure relief valve seat and forms a conical surface together.
Mating of the pressure relief valve surface and the pressure relief
valve seat prevents fluid communication through the pressure relief
passage. The pressure relief valve shuttle moves from the closed
position to an open position, wherein the pressure relief valve
surface and the pressure relief valve seat are no longer mated,
when pressure in the common rail exerts a force greater than the
bias of the pressure relief valve spring.
[0009] The pressure relief valve shuttle also includes an outlet
check valve seat that is configured to mate with an outlet check
valve ball. In the disclosed embodiment, the pressure relief valve
seat contacts the pressure relief valve shuttle radially outward of
the outlet check valve ball.
[0010] The outlet check valve ball is biased toward a closed
position by an outlet check valve spring. In the closed position,
the outlet check valve ball mates with the outlet check valve seat
and prevents fluid communication through the outlet flow path. The
outlet valve ball moves from the closed position to an open
position, permitting fluid communication through the outlet flow
path, when pressure in the outlet passage is less than pressure in
the pumping chamber.
[0011] In this manner, the pressure and discharge of fuel through a
high pressure fuel pump is controlled by the integrated outlet
check valve and pressure relief valve.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Aspects of a disclosed embodiment will be described in
reference to the drawings, where like numerals reflect like
elements:
[0013] FIG. 1 is a sectional view of a high pressure fuel pump
incorporating valves according to aspects of the disclosure;
[0014] FIGS. 2-8 are schematic diagrams of a fuel injection system
incorporating the disclosed high pressure fuel pump showing valve
position and fuel flow in different operating states of the fuel
injection system;
[0015] FIGS. 9-16 are enlarged sectional views of a portion of the
high pressure fuel pump of FIG. 1, showing the structure and
operation of valves in different operating states of the high
pressure fuel pump.
DETAILED DESCRIPTION
[0016] FIG. 1 is a sectional view of a high pressure fuel pump
(HPP) 10 incorporating illustrative examples of an inlet control
valve (ICV) 12, pressure relief valve (PRV) 14, and discharge check
valve (DCV) 16 according to aspects of the disclosure. As will be
discussed in greater detail below, the PRV 14 and DCV 16 are
integrated with each other and situated in a pump outlet fitting 18
according to aspects of the disclosure. FIG. 2 is a schematic
diagram showing the functional elements and relationships in a fuel
injection system incorporating the disclosed HPP 10. With reference
to FIG. 2, a low pressure pump (LPP) 20 supplies fuel to the HPP
10, via an inlet fitting 22. High pressure fuel leaves the HPP 10
through a discharge fitting 18 that communicates with a rail feed
passage 24 and the common rail 26. In the fuel injection system of
FIG. 2, engine control unit (ECU) 28 uses information from a
crankshaft position sensor 30 and other inputs to operate fuel
injectors 32 connected to the common rail 26. A pressure sensor 34
detects the pressure in the common rail 26 and provides this
information to the ECU 28. The ECU 28 operates the fuel injectors
32 so that fuel is injected into each combustion chamber at the
time and in the quantity demanded by the engine (not shown)
according to the engine's operational condition, i.e., accelerating
under load, idling, descending a long grade, etc. The ECU 28 and
fuel injectors 32 are configured for substantially constant
pressure in the common rail 26, which is maintained by the HPP 10
under control of the ECU 28.
[0017] The HPP 10 is illustrated in the form of a single plunger
pump driven by a cam 36. A pumping plunger 38 reciprocates in a
pump bore 40 to alternately expand the pumping chamber 42 to draw
fuel into the pumping chamber and then pressurize the pumping
chamber 42 to pump fuel to the common rail 26 via the outlet
fitting 18 and rail feed passage 24. A cam follower 44 is biased
toward the profile 46 of the cam 36 and is connected to the pumping
plunger 38 to translate the shape of the cam profile 46 into
reciprocal movement of the pumping plunger 38. The cam 36 has a
four-sided profile 46 that will generate four charge/pump cycles of
the pumping plunger 38 for each 360.degree. rotation of the cam 36.
The cam may have any number of lobes, with most having three or
four lobes. The durations of the charging and pumping cycles are a
function of the cam profile 46 and rotational speed of the cam 36.
The cam 36 in FIG. 2 is shown at a "top dead center" (TDC) of the
cam profile, which defines the end of a pumping cycle and the
beginning of a charging cycle. In the symmetrical cam profile used
to illustrate this application, the mid-point of each side of the
cam profile 46 corresponds to the "lowest point" and is the "bottom
dead center" (BDC) of the cam profile 46, which defines the end of
a charging cycle and the beginning of a pumping cycle. In a cam
profile having asymmetrical shape, the lowest point of the cam
profile corresponding to BDC may not be at the mid-point between
lobes. The total stroke of the pumping plunger is defined by the
radial distance from the cam's TDC and BDC positions. Each lobe of
the cam profile 46 may be asymmetric such that the angular
displacement from BDC to TDC may be different from TDC to BDC. The
shape of all lobes of the cam 36 is typically the same, but this is
not required.
[0018] As shown in FIG. 1 a pump body 48 is the primary structural
component of the disclosed HPP 10, and provides locations for
receiving and mounting the components of the HPP 10. In addition to
conventional fasteners, components of the HPP 10 may be secured to
the pump body 48 by threaded, interference fit, or welded
connections. Other methods of assembly and connection will occur to
those skilled in the art, and the disclosed HPP 10 is not limited
by exemplary methods discussed in this application. Stepped bores
can be employed to trap internal components within the pump body
48. The inlet fitting 22 may include an inlet filter 50 and
communicates with a volume defined by an accumulator cover 52
secured to the pump body 48. The accumulator cover 52 surrounds a
volume containing an accumulator 54 configured to damp pressure
fluctuations generated by the HPP 10 during operation. The
accumulator 54 includes gas filled metal bellows supported within
the accumulator cover 52 by an accumulator support and accumulator
spacers, so that the accumulator 54 can change shape to absorb
pressure pulses generated by the HPP 10. A control valve feed
passage 56 defined by the pump body 48 leads from the accumulator
54 to the ICV 12.
[0019] An embodiment of an ICV 12 according to aspects of the
disclosure is illustrated in FIG. 1 and FIGS. 9-16. As will be
described in greater detail below, the disclosed ICV 12 functions
as both a pump inlet check valve and an inlet metering valve to
control both the timing and quantity of fuel flow through the ICV
12 to the pumping chamber 42. Elimination of a dedicated pump inlet
check valve reduces the part count of the disclosed HPP 10, and
also reduces the trapped volume of the pump by eliminating volume
that would be associated with a dedicated pump inlet check valve.
The illustrated ICV 12 is a two port, two position, normally open,
directly solenoid actuated flow control valve. A control valve seat
58 is received in a stepped bore defined by the pump body 48 and
defines a fluid flow passage connecting the control valve feed
passage 56 with part of the pumping chamber 42 defined by a stop
pin support 60. As best seen in FIGS. 9-16, the inlet valve 62
includes a disc shaped valve member 64 integrally connected to a
valve stem 66 that passes through the inlet valve seat 58. The stop
pin support 60 supports a stop pin 68 and defines part of the
pumping chamber 42 in communication with the valve seat 58 and high
pressure discharge from the pumping chamber 42 to the outlet
fitting 18. The valve stem 66 is coupled to an inlet valve armature
70 by an armature retaining ring 71. The inlet valve armature 70
and inlet valve 64 are biased toward an open position (shown in
FIGS. 1 and 9) by an inlet valve spring 72.
[0020] A control valve solenoid 74 includes a coil that generates a
magnetic field in a control valve pole 76 aligned with and adjacent
to the inlet valve armature 70. When the control valve solenoid 74
is energized under control of the ECU 28, the magnetic field
generated by the solenoid coil attracts the inlet valve armature 70
and the inlet valve 62 is moved to a closed position (shown in FIG.
10) against the bias of the inlet valve spring 72. In a closed
position, the valve member 64 is in contact with the inlet valve
seat 58, separating the control valve feed passage 56 from the
pumping chamber 42. Closure of the inlet valve 62 during a pumping
cycle allows fuel in the pumping chamber 42 to be pressurized and
pumped through the DCV 16, outlet fitting 18 and high pressure
passage 24 to the common rail 26. The timing of closure of the ICV
12 is set by the ECU 28 in response to inputs including the
pressure of the common rail 26 detected by pressure sensor 34 and
the camshaft position reported by the camshaft position sensor 30.
Once the inlet valve 62 is closed, the inlet valve spring 72 cannot
open the inlet valve 62 until the pressure of the pumping chamber
falls to a minimum. This allows the control valve solenoid 74 to be
de-energized before completion of a pumping cycle to reduce
electrical power consumption and reduce heat added to the
system.
[0021] The disclosed ICV configuration reduces the number of
impacts between components to two impacts per actuation cycle,
specifically impact of the inlet valve 62 and valve seat 58 and
impact of the inlet valve 62 and stop pin 68. These impacts occur
near the center of the HPP 10, and far from the extremities of the
HPP 10 where noise is more easily radiated. Further noise reduction
can be attained by selection of the material from which the stop
pin 68 is constructed, such that the impact would generate less
energetic vibrations. The surface of the valve member 64 that
contacts the stop pin may include material such as engineered
plastic, for example PEEK, to reduce noise generated by impact of
the inlet valve 62 with the stop pin. The stop pin support 60 may
be configured to reduce the transmission of impact vibrations from
the stop pin to surrounding structures. In the disclosed HPP 10,
the end of the stop pin 68 opposite the inlet valve 62 is exposed
to a fluid volume leading to the DCV 16 and outlet fitting 18,
which may reduce noise radiated from the stop pin 68.
[0022] The pumping plunger 38 reciprocates in the pumping bore 40
defined by a plunger sleeve 78. The plunger sleeve 78 is secured to
the pump body 48 by a pilot tube 80 received in a shallow bore
defined by the pump body 48. The plunger sleeve 78 is biased toward
the pump body 48 by a load ring 82 compressed between an internal
shoulder 84 of the pilot ring 80 and the lower end of the plunger
sleeve 78. A neck portion 86 of the pilot tube 80 supports a
plunger seal 88 that seals against a lower portion of the pumping
plunger 38. A plunger return spring seat 90 is secured to the lower
end of the pumping plunger 38 and a plunger return spring 92 is
biased between the plunger return spring seat 90 and an external
shoulder 94 of the pilot tube 80. A plunger retaining ring 96 is
received in a groove defined at the lower end of the pumping bore
40 to prevent the pumping plunger 38 from being pulled out of the
pumping bore 40 by the plunger return spring 92. As shown in FIG.
2, a cam follower 44 is situated between the pumping plunger 38 and
the cam 36 and is arranged to follow the cam profile 46, exerting
reciprocal motion on the pumping plunger 38.
[0023] Some leakage will occur between the pumping plunger 38 and
pumping bore 40 during pump operation. The disclosed HPP 10 defines
a pump drain 98 from the pilot tube 80 to the control valve feed 56
via passages in the control valve seat 58, allowing leakage flow
back to the low pressure inlet of the HPP 10. A pumping plunger 38
having a pumping end with a greater diameter than the driven end as
shown in FIG. 1, will tend to "pump" leakage flow during the
charging cycle, and this "pumped" leakage flow is also directed to
the pump drain 98.
[0024] With reference to FIGS. 1, 9 and 10, the ICV 12 includes the
control valve solenoid 74 with control valve pole 76, inlet valve
62, control valve seat 58, inlet valve armature 70 and inlet valve
spring 72. The inlet valve 62 includes a valve stem 66 integrally
connected to a valve member 64 configured to mate with an annular
surface on the valve seat 58 when moved to the closed position. The
valve stem 66 reciprocates in a bore defined by the valve seat 58,
guiding movement of the inlet valve 62 between the open position
(FIG. 9) and the closed position (FIG. 10). The inlet valve 62 is
biased toward an open position by the inlet valve spring 72, which
acts on the inlet valve armature 70 and inlet valve 62. The open
position of the inlet valve 62 is determined by contact between the
valve member 64 and the stop pin 68 as shown in FIG. 9. When the
inlet valve 62 is in the open position, there is an air gap between
the inlet valve armature 70 and the control valve pole 76. As shown
in FIG. 10, when the solenoid 74 is energized, the inlet valve
armature 70 and inlet valve are attracted to the control valve pole
76, compressing the inlet valve spring 72 and closing the valve
member 64 against the valve seat 58.
[0025] Movement of the inlet valve 62 between contact with the stop
pin 68 and contact with the valve seat 58 defines the ICV stroke as
shown in FIG. 10. According to aspects of the disclosure, the ICV
stroke is less than the air gap between the control valve pole 76
and the inlet valve armature 70 when the inlet valve 62 is in the
open position, leaving an armature gap between the control valve
pole 76 and the inlet valve armature 70 when the inlet valve is in
the closed position. The length of the valve stem 66 and the shape
of the inlet valve armature 70 are selected to ensure the inlet
valve armature 70 does not contact the control valve pole 76 when
the inlet valve 62 is in the closed position. As shown in FIG. 10,
an armature gap remains between the inlet valve armature 70 and the
control valve pole 76 when the inlet valve 62 is in the closed
position. The armature gap eliminates one point of contact between
moving components in the disclosed ICV 12.
[0026] FIGS. 1 and 9-16 illustrate a discharge/outlet check valve
(DCV) 16 and pressure relief valve (PRV) 14 integrated into a pump
outlet fitting 18 according to aspects of the disclosure. With
specific reference to FIGS. 1 and 9, the pump outlet fitting 18
defines a stepped bore 100 communicating at one end with the
pumping chamber 42 (or a passage fluidly connected to the pumping
chamber) and at the other end with the high pressure passage 24 to
the common rail 26. A PRV seat 102 defines an outlet flow path 103
through bores disposed around a discharge check valve spring seat
(DCV spring seat) 104 arranged on an axis A of the outlet fitting
18. The discharge check valve ball (DCV ball) 106 is biased by the
DCV spring 108 toward a discharge check valve seat (DCV seat) 110
on a pressure relief valve shuttle (PRV shuttle) 112. The PRV seat
102 includes an annular, conical surface 114 that mates with a
complementary surface 116 (surrounding the DCV seat 110) on the PRV
shuttle 112. The PRV seat 102 is in a fixed position defined by the
stepped bore 100, and the PRV shuttle 112 is biased against the PRV
seat 102 by a PRV spring 118.
[0027] According to aspects of the disclosure, the PRV spring 118
is a stack of conical disc springs compressed between a pressure
relief valve cup (PRV cup) 120 and the PRV shuttle 112 to bias the
PRV shuttle 112 toward a closed position illustrated in FIGS. 1 and
9. The stacked conical disc springs generate the high force
necessary to maintain the PRV 14 in the closed position against
operating pressures in the common rail 26 of 350 bar (35 MPa) or
more, in a very compact configuration. Little or no space is left
between the stacked conical disc springs, and the stroke of the PRV
shuttle 112 is very short, meaning very little trapped volume is
associated with the disclosed PRV 14. The PRV cup 120 has an
interference fit within the stepped bore 100 of the pump outlet
fitting 18, and traps the PRV shuttle 112, PRV spring 118, DCV ball
106, DCV spring 108, and PRV seat 102 within the pump outlet
fitting 18. The position of the PRV cup 120 in the stepped bore 100
is set during assembly to calibrate the opening pressure of the PRV
14. The opening pressure of the PRV 14 can be calibrated before
assembly of the outlet fitting 18 to the pump body 48. The PRV cup
120 and PRV shuttle 112 are configured to occupy most of the space
within the stepped bore 100 between the DCV ball 106 and the
pumping chamber 42, further reducing the trapped volume of the HPP
10 attributable to the PRV 14.
[0028] The outlet fitting 18 including an integrated PRV 14 and DCV
16 minimize the trapped volume of the HPP 10 to which the outlet
fitting 18 is attached, provide high flow capacity through the PRV
14, and the short stroke of the PRV shuttle 112 results in fast
actuation and closure of the PRV 14 while the HPP 10 is operating.
The DCV ball 106 opens only when the pressure in the high pressure
passage 24 leading to the common rail 26 is less than the pressure
in the pumping chamber 42 or passage leading from the pumping
chamber to the pump outlet fitting 18 as shown in FIGS. 10, 13, and
16. This condition occurs during a pumping cycle when the pressure
of the pump outlet passage 24 and common rail 26 are below maximum
pressure.
[0029] FIGS. 3 and 11 illustrate fuel flow in the disclosed HPP 10
during a charging cycle of the pump, i.e., during retraction of the
pumping plunger 38. Fuel pumped by the LPP 20 enters the inlet
fitting 22 and passes through the inlet filter 50 (if present). The
inlet fitting 22 is in fluid communication with the accumulator 54,
and fuel may be routed through the accumulator 54 as shown in FIG.
1. The ICV 12 is in its normally open state, and allows fuel to
flow into the pumping chamber 42 as the pumping plunger 38 is
retracted. The DCV 16 is held closed by pressure behind the DCV
ball 106, which is exposed to the pressure of the common rail 26.
In the disclosed HPP 10, the pumping chamber 42 is completely
filled with fuel by the end of the charging cycle. When the cam
follower 44 reaches the center of a side of the cam profile 46 the
plunger stops retracting, ending the charging cycle. As the cam 36
rotates further, the cam follower 44 begins pushing the pumping
plunger 38 into the pumping bore, beginning a pumping cycle.
[0030] FIGS. 4 and 12 illustrate an initial portion of a pumping
cycle, during which the ICV 12 remains open. When the pumping
plunger 38 is being driven into the pumping bore 40, the volume of
the pumping chamber 42 is reduced, pushing fuel out of the pumping
chamber 42. With the ICV 12 open, fuel is "spilled" from the
pumping chamber back toward the low pressure inlet. When the ICV 12
is closed by the ECU 28 energizing the control valve solenoid 74,
fuel in the pumping chamber 42 begins to be pressurized by the
pumping plunger 38. When the pressure in the pumping chamber 42
exceeds the pressure of the common rail 26, the DCV 16 opens and
fuel is pumped to the common rail 26. The timing of ICV 12 closure
determines the quantity of fuel pumped to the common rail 26,
because fuel pressurization cannot begin until the ICV 21 is
closed. In this manner, the ICV 12 meters the quantity of fuel
pumped to the common rail 26 under control of the ECU 28.
[0031] FIGS. 5 and 13 illustrate the position of the ICV 12 and DCV
16 during fuel delivery to the common rail 26. The control valve
solenoid 74 is energized, the ICV 12 is closed, and fuel in the
pumping chamber 42 has reached a pressure greater than the pressure
of the common rail 26, opening the DCV 16. Any fuel that leaks
between the pumping plunger 38 and the pumping bore 40 is directed
by the pump drain 98 back to the low pressure inlet of the HPP 10.
Pressure in the pumping chamber 42 acts on the valve member 64 to
hold the inlet valve 62 in the closed position. The inlet valve
spring 72 cannot open the inlet valve 62 until the pressure of the
pumping chamber 42 drops to a minimum. This permits intentionally
de-energizing the control valve solenoid 74 before the completion
of a pumping cycle to reduce electrical power consumption and
reduce heat added to the system.
[0032] FIGS. 6 and 14 illustrate actuation of the PRV 14 in
response to a heat soak condition where the pressure of the common
rail 26 is greater than maximum pressure. The PRV shuttle 112 and
closed DCV ball 106 are exposed to the pressure of the common rail
26 through the high pressure passage 24 connected to the pump
outlet fitting 18. The PRV shuttle 112 is moved away from the PRV
seat 102 against the bias of the PRV spring 118 and allows excess
pressure to pass between valve surfaces 114, 116, through the
pumping chamber 42, the open ICV 12, and control valve feed passage
56 to the low pressure inlet. In a heat soak condition, the PRV
shuttle 112 will move (open) a small amount because the volume of
fluid being relieved is small and the rate of fluid flow is
low.
[0033] FIGS. 7 and 15 illustrate actuation of the PRV 14 during
pump operation, which is exactly the same as PRV 14 actuation in
response to a heat soak, except the PRV shuttle 112 will open
further due to the larger volume of fluid to be relieved and the
high rate of fluid flow required to relieve pressure during a
charging cycle of the pump. As shown in FIG. 15, the inlet valve 62
is held closed by high pressure fuel being relieved from the common
rail through the PRV 14. Fuel being relieved from the common rail
26 fills the pumping chamber 42 as the pumping plunger 38 is
retracted during a charging cycle of the pump.
[0034] FIGS. 8 and 16 illustrate fuel flow through the ICV 12,
pumping chamber 42 and DCV 16 during a "limp home" scenario where
the HPP 10 is not operational. In this scenario, the high pressure
passage 24 and common rail 26 are no longer being supplied with
high pressure fuel. The DCV valve spring 108 is selected with a
light bias that will open when exposed to feed pressure generated
by the LPP 20 that has passed through the open ICV 12 and the
pumping chamber 42. With no pressure behind it, the DCV ball 106
opens when exposed to feed pressure and allows low pressure fuel to
fill the common rail 26. Common rail pressure corresponding to feed
pressure from the LPP 20 is sufficient to allow the fuel injectors
32 and engine to operate at reduced power. Engine operation will be
sub-optimal, but sufficient to provide minimum driving capabilities
towards a safe environment or maintenance facility.
[0035] While the embodiment of the disclosed integrated outlet
check valve 16 and pressure relief valve 14 has been set forth for
purposes of illustration, the foregoing description should not be
deemed a limitation of the invention. Accordingly, various
modifications, adaptations and alternatives may occur to one
skilled in the art without departing from the spirit of the
disclosure and the scope of the claimed coverage.
* * * * *