U.S. patent application number 10/344588 was filed with the patent office on 2005-01-13 for magnetically coupled fuel injector pump.
Invention is credited to Djordjevic, Ilija.
Application Number | 20050005911 10/344588 |
Document ID | / |
Family ID | 33554781 |
Filed Date | 2005-01-13 |
United States Patent
Application |
20050005911 |
Kind Code |
A1 |
Djordjevic, Ilija |
January 13, 2005 |
MAGNETICALLY COUPLED FUEL INJECTOR PUMP
Abstract
A pump (10) of high pressure direct injection fuel supply system
is connected to the engine through a magnetic clutch which includes
a motorizing function. The magnetic clutch comprises rotating
electromagnetic cogs (20) attached to and driven by the engine and
rotating permanent magnets (34) attached to and driving the pump.
The slippage of the clutch is controlled by the on-off cycle of
electrical power which is simultaneously supplied to all of the
electromagnetic coils and may be responsive to the pressure in the
fuel injections rail. The clutch may be op as an electrical motor
by sequentially activating the electromagnetic coils for the
purpose of providing fuel pressure even prior to rotation or
cranking of the engine. An isolation barrier hermetically seals the
fuel injection pump from the engine.
Inventors: |
Djordjevic, Ilija; (East
Granby, CT) |
Correspondence
Address: |
L. James Ristas
Alix Yale & Ristas
Suite 1400
750 Main Street
Hartford
CT
06103
US
|
Family ID: |
33554781 |
Appl. No.: |
10/344588 |
Filed: |
February 13, 2003 |
PCT Filed: |
August 13, 2001 |
PCT NO: |
PCT/US01/25213 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60225159 |
Aug 14, 2000 |
|
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|
Current U.S.
Class: |
123/458 ;
417/223 |
Current CPC
Class: |
F02M 39/02 20130101;
F16D 27/004 20130101 |
Class at
Publication: |
123/458 ;
417/223 |
International
Class: |
F02M 051/00 |
Claims
1. In the combination of a fuel injection pump having a rotatable
pump shaft and a fuel outlet into a common fuel injection rail and
an engine having a rotatable engine member for driving said
rotatable pump shaft, a magnetic clutch between said rotatable
engine member and said rotatable pump shaft for transferring torque
from said rotatable engine member to said rotatable pump shaft
wherein said magnetic clutch comprises means for controlling
slippage of said magnetic clutch.
2. In the combination recited in claim 1 wherein said magnetic
clutch g comprises electromagnetic coils attached for rotation with
said rotatable engine member and permanent magnets juxtaposed to
said electromagnetic coils and attached for rotating said rotatable
pump shaft.
3. In a combination as recited in claim 2 and including an
isolation barrier located between said permanent magnets and said
electromagnetic coils thereby sealing said fuel injection pump from
said engine.
4. In a combination as recited in claim 2 wherein said means for
controlling slippage comprises means for modulating the on-off
cycle of electrical power simultaneously applied to said
electromagnetic coils to maintain a desired fuel pressure in said
common rail.
5. In a combination as recited in claim 1 and further including
means for rotating said permanent magnets and said rotatable pump
shaft prior to rotation of said rotatable engine member and said
electromagnetic coils comprising means for producing a rotating
magnetic field from said electromagnetic coils.
6. In a combination as recited in claim 5 wherein said means for
producing a rotating magnetic field comprises means for
sequentially applying electrical power to said electromagnetic
coils.
7. In a combination as recited in claim 2 wherein said magnetic
clutch is controlled by varying the pulse width of power applied to
said electromagnetic coils to maintain a desired fuel pressure in
said common rail.
Description
BACKGROUND OF THE INVENTION
[0001] A number of potential advantages have led the automotive
industry to look with increasing interest toward utilizing common
rail (manifold) high pressure direct injection for gasoline
engines. A number of design constraints or difficulties seem to
stand in the way of fully achieving the advantages.
[0002] The pressurization of fuel to high levels (e.g., above 100
bar) requires considerable pumping power, which generates
considerable heat. Moreover, the industry is looking for even
higher rail pressures, above 200 bar. This heat could be dissipated
to a large extent, if all the fuel that is pressurized, can be
quickly injected into the engine cylinders. This is not possible,
however, because the fuel pump flow rate is typically sized for
engine cranking, which may be at 20-30 bar pressure at a high
quantity discharge flow rate, whereas typical steady state cruising
conditions require much lower quantity flow rates at 100 bar.
Therefore, in a conventional pumping scheme, the volume of fuel
raised to injection pressure during the course of an hour of
typical vehicle use, is much greater than the volume of fuel
actually injected during that same hour of use. Although
pre-metering and various spill control techniques can be used to
some advantage in this regard, none of these techniques
satisfactorily regulates the power output of the high pressure pump
itself.
[0003] Another difficulty is encountered with high pressure pumps
that are driven directly by the engine (e.g., crank shaft, cam
shaft, accessory belt). During transients when fuel demand is low
(e.g., downhill or during gear shifting), the engine continues to
turn and the pump continues to deliver high pressure fuel to the
common rail that may already be at maximum pressure.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to provide a high
pressure gasoline common rail direct injection fuel supply system,
in which the high pressure discharge of the pump for raising and
maintaining the rail pressure above 100 bar, is responsive to
engine demand. The energy imparted to the discharged fuel (e.g.,
pressure increase) is over time, significantly reduced relative to
conventional systems.
[0005] According to the invention, a high pressure rotary pump is
coupled to the engine with a magnetic clutch which may also serve
as a motorized drive. The speed of the pump can be controlled by
the degree of slippage of the clutch, which is responsive to the
rail pressure.
[0006] The clutch can quickly increase the pump drive shaft speed
by reducing slippage and thus provide high pumping volume during
cranking, while reducing speed to a low level by slippage with
associated low pumping volume when the vehicle is cruising.
Similarly, the clutch can intermittently increase speed as needed
to accommodate load demand during acceleration or, in essence, stop
the pump drive when the vehicle is coasting. In a particularly
noteworthy aspect, the clutch is arranged and controllable so that
the clutch can include a "motorizing" feature, which can be used to
increase the speed of the pump during cranking when the pump speed
would otherwise be slower than desired. The invention also provides
for the positive sealing of the pump by an isolation barrier.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a view partially in cross section of a fuel pump
drive by a magnetic clutch attached to a rotating shaft of an
engine with the fuel pump discharging into a common fuel injection
rail with the clutch controlling the rail pressure.
[0008] FIG. 2 diagrammatically illustrates a face view of the
arrangement of coils and permanent magnets for the version of the
invention shown in FIG. 1.
[0009] FIG. 3 is a view similar to FIG. 1 showing another
embodiment of the clutch arrangement.
[0010] FIG. 4 diagrammatically illustrates a face view of the
arrangement of coils and permanent magnets for the version of the
invention shown in FIG. 3.
[0011] FIG. 5 is a schematic of the controller and electrical
connections to the clutch for controlling the slippage of the
clutch.
[0012] FIGS. 6 and 7 are charts illustrating the on-off cycles for
the coils over time to control the slippage with FIG. 6 producing
more slippage and low output and FIG. 7 producing less slippage and
higher output.
[0013] FIG. 8 is a schematic of the controller and electrical
connections to the coils for the motorizing function.
[0014] FIG. 9 is a chart illustrating the on-off cycles for the
coils in the motorized operation of the clutch.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] According to the invention, as first exemplified in FIG. 1,
an engine mounted fuel injection pump generally designated 10 is
driven by any rotating shaft of the engine, for example a camshaft,
crank shaft, or engine accessory shaft. However, rather than being
transferred directly, the power is transferred from the engine to
the pump by a magnetic clutch. Magnetic clutches are used in
various industries to control slippage between the input and output
shaft at more or less constant torque. The magnetic clutch consists
of two rotating members, a drum with magnetic coils mounted on the
torque input shaft and a rotor with permanent magnets mounted on
the torque output shaft. As shown in FIG. 1, the torque input shaft
12 is an engine camshaft, whereas the torque output shaft 14 is the
pump shaft (usually an eccentric shaft) of a typical radially
reciprocating, multi-plunger gasoline direct injection pump of
known construction.
[0016] Again referring to FIG. 1, a portion 16 of an engine houses
the camshaft 12. Mounted onto the end of the camshaft 12 is a drum
18 with a series of electromagnetic coils 20 each connected to the
slip rings 22, 23 and 24. The slip rings are contacted by the
brushes 26 which are connected into the controller 28 as will be
discussed further below. During cranking, the coils 20 produce a
rotating magnetic field which is used to drive the output shaft 14
of the pump 10. Rigidly mounted on the output shaft 14 is a rotor
comprising the hub 30 and support disk 32 on which are mounted the
permanent magnets 34. Torque is transmitted from the camshaft 12 by
the magnetic coils 20 to the permanent magnets 34 and then to the
output shaft 14. FIG. 2 is a diagram illustrating the relationship
of the coils 20 and permanent magnets 34. Since the energy
transmitting components (the magnetic coils and the permanent
magnets) are substantially annular and face each other in the axial
direction with an air gap separation, some axial forces are
generated which are supported by drive shaft bearings 36 and pump
bearings 38. However, this configuration permits the use of a
relatively simple isolation barrier 40 between the input side
comprising the camshaft 12, drum 18 and magnetic coils 20 and the
output side comprising the pump and including the hub 30, support
disk 32 and permanent magnets 34. With this arrangement, the
isolation barrier 40 is a simple flat plate or diaphragm usually of
stainless steel where all radial forces are balanced and mechanical
axial forces are absent. There will, however, be an axial force
component acting on the positive pressure barrier 40 originating
from hydraulic pressure in the pump housing. This axial force needs
to be considered in the dimensioning and design of the barrier 40
and especially its minimum thickness. The thickness of the barrier
40 affects the size of the air gap between the coils and magnets,
and by that, also the efficiency of the clutch. In order to reduce
the hydraulic pressure in the pump housing, it is possible to
provide separate inlet and outlet check valves located in the
hydraulic head and allow the hydraulic pressure in the housing to
be reduced to a lower level. This would require a leak-off line
which is not shown.
[0017] FIGS. 3 and 4 of the drawings illustrate another embodiment
of the invention. In this embodiment, the energy-transmitting
components are closely spaced apart radially rather than being
axially arranged as in FIGS. 1 and 2. Specifically, the plurality
of coils 42 are now mounted around the periphery of a rotor 44 with
the rotor 44 also incorporating the slip rings 46, 48 and 50
contacted by the bushes 51. Although the minimum of three brushes
and three slip rings are illustrated as well as three coils and
four permanent magnets, the number of coils and/or permanent
magnets can be varied to produce the desired clutch and motorizing
functions for any particular situation. The rotor 44, which is
partially enclosed in the housing segment 52, is both supported and
driven by the extension 54 of the driving (cam) shaft 12 which is
inserted into the central opening in the rotor 44. In this
embodiment of the invention, the plurality of permanent magnets 56
are mounted on the support member 58 which is attached to the hub
30 much like the support disk 32 in FIG. 1. The support member 58
has an outer peripheral edge or flange 60 shaped to surround the
coils 42. The permanent magnets 56 are mounted on this peripheral
edge 60 such that they are directly radially outward from the coils
42. Mounted between the input side of the clutch with the drive
shaft 12, rotor 44 and coils 42 and the output side with the pump
and including the hub 30, the support member 58 and the permanent
magnets 56 is the isolation barrier 62. The isolation barrier 62 is
now cup shaped such that it extends between the coils 42 and the
radially outward permanent magnets 56. Since the magnetic forces
are now radial instead of axial, the bearing 64 supporting the pump
shaft 14 does not need to accommodate axial forces. The clutch
slippage is regulated by the same controller 28 as in FIG. 1.
[0018] Because there is no physical contact between the input and
output shafts 12 and 14, the entire drive portion of the pumping
component is hermetically sealed by the isolation barrier 40 or 62
and no shaft seals are needed. The absence of a shaft seal reduces
friction losses, reduces heat rejection and drive power
requirement, and also assures higher reliability by avoiding wear
of the sealing components.
[0019] It is also very likely that the total cost of such a system
is very competitive.
[0020] As indicated earlier, the fuel injection pump 10 is
connected at 66 to the common rail or manifold 68 of the fuel
injection system as shown in FIG. 1. The fuel injectors themselves
would be connected into the rail 68. Mounted on the rail 68 is a
pressure transducer 70 which is connected by the line 72 to the
previously mentioned controller 28. In a typical industrial
application, the reference feedback for a magnetic clutch is
provided by a tachometer mounted on the output shaft. In the
present invention, the actual pressure in the rail 68 is used as
the reference feedback. The controller 28 modulates the application
of power to the coils of the clutch in response to the rail
pressure. That is, the current to the coils is turned on and off to
vary the pulse width and control the amount of slippage. FIG. 5 is
a schematic illustrating the connection of the coils 20 (or 42) to
the controller 28 for the control of slippage. For this function,
the switches 74 in the controller operate simultaneously. In FIG.
5, they are all shown as being open. The amount of slippage in the
clutch is controlled by the ratio of the amount of time the
switches are closed (power applied to coils) compared to the amount
of time the switches are open. This is illustrated in FIGS. 6 and 7
with FIG. 6 illustrating short applications of power to the coils
(short pulse width) resulting in greater slippage and lower output
and FIG. 7 illustrating longer applications of power (long pulse
width) and less slippage and greater output. This closed loop mode
of operation permits regulation accuracy within 0.5% to 1%.
Magnetic clutches commonly have a 34:1 speed range and, during a
short period of time can transmit up to 250% of the rated torque.
The torque transmission is very energy efficient and the power to
the coils is only about 10% of the total drive power
requirement.
[0021] A magnetic clutch unit can be purchased commercially, rated
for 24V and capable of transmitting 108 Ncm torque at speeds
between 50 RPM and 3300 RPM, at a global efficiency of 91%
(electric motor and clutch). This compares very favorably with the
expected losses of, for example, up to 50% with a solenoid valve
demand controlled gasoline pump. Another advantage is that because
the clutch can be deliberately overloaded up to 100% for a short
time period (for example, during transient operation), the clutch
can be relatively undersized. As a result, the heat rejection
during the normal operation can be minimized.
[0022] As the internal magnetic clutch components are very similar
to the components of a stepper motor or a brushless electric motor,
the clutch can be designed and the driving function can be expanded
in such a way as to provide a "motorizing feature" for the clutch
output shaft. This means that the clutch output shaft can be forced
to rotate by an induced rotating magnetic field even before the
engine starter begins to spin. This results in a very rapid
pressure build up during cranking, which is a very desirable
feature. Even with a modest motorizing capability of, for example,
a maximum achievable speed of 1000 RPM, it could be used to enhance
transient operation of a generally undersized pump. Referring to
FIG. 8, the switches 74 are now closed and opened sequentially to
produce the rotating magnetic field and cause the permanent magnets
to rotate even when the input shaft 12 has not yet rotated. The
time line application of power to the coils is illustrated in FIG.
9.
* * * * *