Intake manifold pressure compensation for the closed-loop pressure regulation of a fuel pump

The fuel supply system of an internal combustion engine delivers liquid fuel to electrically operated fuel injectors by means of an electric pump whose output pressure is regulated by control electronics which receives as feedback from a pressure sensor connected into a fuel delivery passage serving the injectors a signal representing the pressure differential between manifold absolute pressure (MAP) and absolute pumped fuel pressure. The pressure sensor has a movable wall that divides its interior into an intake manifold pressure sensing chamber space communicated to the engine intake manifold and a fuel pressure sensing chamber space communicated to the fuel delivery line to the injectors. A magnet is mounted on a central region of the movable wall to transmit a signal to a Hall-effect sensor mounted within the intake manifold pressure sensing chamber space. The feedback pressure signal is derived from the Hall-effect sensor sensing the position of the magnet, and hence that of the movable wall.

FIELD OF THE INVENTION 
This invention relates to internal combustion engine fuel systems. 
BACKGROUND AND SUMMARY OF THE INVENTION 
U.S. Pat. No. 4,756,291 discloses a pressure control for the fuel system of 
an internal combustion engine. The known system has a pressure sensor in a 
fuel line between an electric fuel pump and a carburetor. The pressure 
sensor supplies to electrical control circuitry a signal representing the 
sensed pressure. The electrical control circuitry in turn controls the 
electrical power to the pump such that the fuel pressure delivered to the 
carburetor is closed-loop regulated to a commanded pressure. The commanded 
pressure may be established by an engine management computer, and is 
subject to being varied in accordance with engine operating conditions. 
The disclosure of U.S. Pat. No. 4,756,291 is directed toward elimination 
of a fuel return line from the engine for returning excess pumped fuel to 
the fuel tank. 
Certain U.S. patents relate to electronic multi-point fuel injection 
systems. Typically, such a system comprises a fuel rail assembly that 
contains several electrically operated fuel injectors and a mechanical 
fuel pressure regulator. Fuel is pumped into the fuel rail assembly at a 
rate exceeding the maximum engine demand. The fuel pressure regulator 
regulates the pumped fuel pressure, returning excess fuel to the tank via 
a return line. The typical pressure regulator comprises a housing divided 
by a movable wall into a fuel pressure chamber that is communicated to the 
fuel in the fuel rail assembly and a chamber that is communicated to 
intake manifold vacuum. The movable wall carries a valve element that 
co-acts with an internal seat in the fuel pressure chamber to control the 
return fuel flow such that the pressure in the fuel rail is thereby 
regulated to a pressure that is pressure-compensated with respect to 
changes in intake manifold pressure whereby the pressure across each fuel 
injector is held substantially constant despite variations in the intake 
manifold pressure. In the typical naturally aspirated engine, the intake 
manifold pressure is sub-atmospheric, ranging from relatively high vacuum 
at light loads to relatively low vacuum at high loads. With a 
substantially constant pressure drop across a fuel injector, the amount of 
fuel injected by the injector for each injection is a function of the 
electrical pulse width energization of the injector applied by an 
associated engine management computer. 
If it is attempted to embody an electronic fuel injection fuel system, such 
as one of those of the patents referred to in the immediately preceding 
paragraph, with a pump whose output pressure is electrically controlled in 
the manner of the first-mentioned patent above, the failure to take the 
intake manifold pressure into account will introduce error into the fuel 
injections whenever the intake manifold pressure varies from a particular 
set-point. The use of pressure regulators such as those just described 
will obviously be unacceptable since a return line is required, and the 
disclosure of the first-mentioned patent apparently does not appear to 
address any question of intake manifold pressure, possibly because of the 
fact that it uses a carburetor. 
The present invention relates to a new and unique internal combustion 
engine fuel system in which the electric power delivered to an 
electrically powered fuel pump is controlled by means of closed-loop 
feedback which derives a feedback signal from a pressure sensor that takes 
intake manifold pressure variations into account. As a result, the pump 
output pressure is closed-loop regulated to commanded pressure despite the 
variations in intake manifold pressure that typically occur during engine 
operation. 
The invention includes the advantages of: embodying the fuel pressure 
sensing and intake manifold pressure sensing functions in a single device; 
eliminating any need to interface with a separate MAP (manifold absolute 
pressure) sensor; and possible savings in wiring and circuitry. Further 
features, advantages, and benefits of the invention will be seen in the 
ensuing description and claims which are accompanied by drawings. The 
drawings disclose a presently preferred embodiment of the invention 
according to the best mode contemplated at the present time in carrying 
out the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a fuel supply system 8 for an internal combustion engine in 
accordance with principles of the invention. The system includes a fuel 
rail assembly 10 containing several electrically operated fuel injectors 
12 and a single pressure sensor 14 at spaced apart locations along its 
length. Fuel enters the fuel rail assembly at a port 16 at one lengthwise 
end. The opposite end is closed. The fuel injectors and pressure sensor 
are disposed in respective sockets that are provided in body 18 of the 
fuel rail assembly. These sockets transversely intercept the main fuel 
passage that extends longitudinally into the body from port 16. A tubular 
conduit 20 extends from an electric fuel pump 22 to port 16 for conveying 
liquid fuel from the pump to the fuel rail assembly. Pump 22 draws fuel 
from a fuel tank 24. 
The system further includes control electronics 26 which receives an 
electric signal from pressure sensor 14 via an electrical connection 30 
and delivers electric power to pump 22 via an electrical connection 28. 
There are other inputs to control electronics 26, and they are represented 
generally by reference numeral 31. A retainer 32 that is removably 
fastened to body 18 serves to keep the fuel injectors and the pressure 
sensor captured in their respective sockets in body 18. Intake manifold 
pressure 34 (MAP) is obtained from the intake manifold and supplied to 
pressure sensor 14 via a conduit 35. 
Further detail of pressure sensor 14 is presented in FIG. 2. The pressure 
sensor comprises a housing 38, generally cylindrical, that is shown 
captured in its socket in body 18 by retainer 32. Screws 36 that are 
disposed at particular locations are an illustrative means of attachment 
of the retainer to the body, and the retainer is shaped to retain the 
sensor by engaging a circular flange 39 of housing 38 that radially 
overlaps the rim of the socket and forcing the flange against an annular 
surface portion of body 18 that surrounds the socket rim. 
Housing 38 comprises an upper housing part 40 and a lower housing part 42. 
A nipple 44 extends through and is affixed to the upper end wall of part 
40. The two parts 40, 42 are united by flange 39 and capture between them 
the radially outer margin of a movable wall 46. Wall 46 divides the 
interior of housing 38 into a lower fuel pressure sensing chamber space 48 
and an upper intake manifold pressure sensing chamber space 50. A nipple 
52 that is formed integrally with the central region of the bottom end 
wall of housing part 42 places chamber space 48 in communication with the 
fuel in the fuel rail assembly. One end of conduit 35 fits over nipple 44 
for communicating chamber space 50 with intake manifold pressure. 
A permanent magnet 54 is affixed to the central region of wall 46 on the 
face thereof that is exposed to chamber space 50. A Hall-effect sensor 56 
is affixed to the central region of an electronic circuit board assembly 
58 that is mounted on housing 38 by any suitable means of attachment in 
proper position within chamber space 50 relative to permanent magnet 54. 
The circuit board assembly, including sensor 56, is disposed in spaced 
apart, generally parallel relation to wall 46, including magnet 54. There 
are through-apertures 57 in the circuit board assembly so that the 
mounting of the circuit board assembly does not create a restriction 
between the respective portions of chamber space 50 that lie on opposite 
sides of the circuit board assembly. The face of the circuit board 
assembly that is opposite the face containing sensor 56 contains certain 
electronic circuit components, reference numeral 60, associated with the 
sensor to form in conjunction therewith a sensing circuit. The sensing 
circuit has an output that is connected to an electrical connector plug 
62. Plug 62 is mounted on circuit board assembly 58 and extends through a 
hole 64 in the housing wall so that its exterior termination can mate with 
a complementary connector plug 66 at one end of the connection 30 leading 
to the control electronics. 
Wall 46 possesses a certain inherent flexibility and resiliency that enable 
it to resiliently flex in response to changing pressure differential 
between the two chamber spaces 48, 50. In particular, the wall's central 
region is able to be selectively positioned in the axial sense to 
correspondingly position magnet 54 axially relative to Hall-effect sensor 
56. Assuming that the illustrated position in FIG. 2 represents a certain 
pressure differential between the two chamber spaces, then an increasing 
intake manifold pressure relative to fuel pressure will result in magnet 
54 being positioned increasingly further away from the Hall-effect sensor 
while a decreasing intake manifold pressure relative to fuel pressure will 
result in the magnet being positioned increasingly closer toward the 
Hall-effect sensor. 
Hall-effect sensor 56 is responsive to the amount of magnetic flux that is 
incident on it. Hence, as the magnet is increasingly moved away, less flux 
is incident on the sensor while as the magnet is positioned increasingly 
toward the sensor, the amount of magnetic flux increases. The sensor 
produces an output that is indicative of the flux that is incident upon 
it. The circuitry on the circuit board assembly processes the sensor 
signal into a suitable signal that can be relayed to control electronics 
26. Accordingly, the pressure sensor 14 provides, via connector plug 62, a 
signal that is indicative of the pressure differential between manifold 
absolute pressure (MAP) and pressure of fuel pumped by pump 22. The 
control electronics 26 acts upon this signal to cause the pump output 
pressure to be closed-loop regulated to a commanded pressure that will 
cause the pressure differential across each fuel injector to be 
essentially independent of changes in the manifold absolute pressure. 
Thus, the magnet is a transmitter of the selective positioning of wall 46, 
and sensor 56 is a receiver of the position information transmitted. 
In use of the fuel rail, the variable output pressure fuel pump produces an 
output pressure that is set by the engine management computer and 
closed-loop regulated in the manner that has been herein described. Each 
fuel injector delivers injections of fuel into the air entering the 
cylinder's combustion chamber so that a combustible mixture is thereby 
created and combusted in the combustion chamber to power the engine. 
Pressure sensor 14 can be fabricated by conventional fabrication 
techniques. If calibration of the pressure sensor is necessary, it can be 
performed by conventional calibration techniques, externally, and/or 
internally. Calibration is frequently done by adjustment or trimming of 
signal conditioning circuitry associated with the sensor. External 
calibration of pressure sensor 14 can be performed by connecting the 
sensor with external signal conditioning circuitry, which may or may not 
be additional to any circuitry on circuit board assembly 58 associated 
with Hall sensor 56, and adjusting or trimming such external circuitry 
during the calibration procedure. Where the circuitry to be trimmed or 
adjusted is on circuit board assembly 58, the housing is designed to 
provide suitable access to the component(s) to be trimmed or adjusted, or 
it could even be possible to obtain access via nipple 44. 
While a presently preferred embodiment of the invention has been disclosed, 
it should be appreciated that the inventive principles can be practiced in 
embodiments that fall within the scope of the following claims.