Pressure-responsive fuel delivery system

A fuel delivery system for an internal combustion engine that includes a fuel supply with a pump responsive to application of electrical power for supplying fuel under pressure. A fuel injector is coupled to the supply for controlled delivery of fuel from the supply to the engine. A check valve is positioned in the fuel line that connects the pump outlet to the injector to prevent reverse flow of fuel from the injector to the pump when the pump is shut down. A sensor is coupled to the fuel line between the check valve and the pump outlet for providing an electrical signal as a function of fuel pressure at the pump outlet, and electronic control circuitry applies electrical power to the pump as a function of such pressure signal. A fuel bypass is connected to the fuel line between the pump outlet and the check valve for providing an open but restricted fuel flow path from the pump outlet parallel to the fuel line, such that fuel continues to flow through the bypass and the pump continues operation even in the absence of fuel demand at the engine. In this way, the pump maintains a minimum level of operation so as to be able rapidly to accommodate increasing demand for fuel at the engine.

The present invention is directed to fuel delivery systems for internal 
combustion engines and like applications, and more particularly to a 
system for controlling fuel delivery as a function of fuel requirements. 
BACKGROUND AND OBJECTS OF THE INVENTION 
It has heretofore been proposed to supply fuel to an internal combustion 
engine by means of a pressure-controlled electric-motor fuel pump and a 
one-way or non-return fuel line that connects the pump to the fuel 
injectors at the engine. For example, U.S. Pat. No. 5,044,344 discloses a 
fuel delivery system in which a fuel pump is responsive to application of 
electrical power for supplying fuel under pressure from a supply or tank 
to the fuel injectors at the engine. A check valve is positioned in the 
fuel line between the pump outlet and the injectors for preventing reverse 
flow of fuel from the engine injectors to the pump. A pressure sensor is 
operatively coupled to the fuel line between the pump outlet and the check 
valve, and is coupled to electronic circuitry for applying electrical 
energy to the pump motor as a function of pressure in the fuel line. A 
pressure relief valve is connected to the fuel line between the check 
valve and the engine for returning fuel from the line to the supply in the 
event of over-pressure in the fuel line. 
Although the fuel delivery system so disclosed addresses and overcomes a 
number of problems theretofore extant in the art, further improvements 
remain desirable. For example, a problem is encountered in 
pressure-controlled pump systems of the described character in situations 
where fuel demand at the engine decreases such as during a period of 
engine deceleration, and thereafter rapidly increases such as when rapid 
acceleration is demanded by the operator. During the period of low fuel 
demand at the engine, a low level of pump operation is all that is 
necessary to maintain desired fuel pressure in the fuel line. However, 
when demand is rapidly increased, the fuel pump often cannot accelerate 
operation sufficiently quickly to satisfy the demand. 
Another problem extant in the art involves fuel vaporization in the fuel 
line at very high temperatures. For example, fuel rail temperature tends 
to increase significantly after the engine is turned off and coolant 
system operation terminates. The fuel may vaporize in the rail and 
injector area, particularly when ambient temperature is relatively high. 
This may cause difficulty in restarting the engine and/or unstable idling 
performance. 
It is therefore a general object of the present invention to provide a fuel 
delivery system for internal combustion engines in which the fuel pump 
motor is operated as a function of fuel line pressure while at the same 
time maintaining a minimum level of pump operation in low fuel demand 
situations so as to increase the ability of the pump to respond to a 
subsequent high fuel demand. Another object of the present invention is to 
provide an engine fuel delivery system of the described character that 
substantially reduces or prevents vaporization of fuel in the fuel line 
even under high operating temperature conditions. 
SUMMARY OF THE INVENTION 
A fuel delivery system for an internal combustion engine in accordance with 
the present invention includes a fuel supply with a pump responsive to 
application of electrical power for supplying fuel under pressure. A fuel 
delivery mechanism, such as a fuel injector, is coupled to the supply for 
controlled delivery of fuel from the supply to the engine. A check valve 
is positioned in the fuel line that connects the pump outlet to the 
injector to prevent reverse flow of fuel from the injector to the pump 
when the pump is shut down. A sensor is coupled to the fuel line between 
the check valve and the pump outlet for providing an electrical signal as 
a function of fuel pressure at the pump outlet, and electronic control 
circuitry applies electrical power to the pump as a function of such 
pressure signal. A fuel bypass is connected to the fuel line between the 
pump outlet and the check valve for providing a continuous open fuel flow 
path from the pump outlet parallel to the fuel line, such that fuel 
continues to flow through the bypass and the pump continues operation even 
in the absence of fuel demand at the engine. In this way, the pump 
maintains a minimum level of operation so as to be able rapidly to 
accommodate increasing demand for fuel at the engine. In a presently 
preferred embodiment of the invention in which the fuel pump takes the 
form of a self-contained electric-motor fuel pump mounted as a module 
within a vehicle fuel supply tank, the fuel bypass comprises an orifice 
formed in the fuel line adjacent to the pump outlet for bypassing fuel 
directly to the surrounding tank when the fuel line check valve is closed. 
A second important aspect of the present invention contemplates a method 
for preventing vaporization of fuel in the fuel line under hot operating 
conditions at the engine by locating a pressure relief valve in the fuel 
line between the check valve and the engine, and adjusting the pressure 
relief valve to a setting greater than vaporization pressure of the fuel 
in the line at the predetermined maximum operating temperature of the 
engine. Preferably, the pressure relief setting of the valve is adjusted 
at the time of vehicle manufacture to a setting empirically predetermined 
substantially to prevent vaporization at maximum operating temperature for 
the particular type of fuel in connection with which the engine will be 
used. A setting of 64 psi would be typical for gasoline engines, for 
example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates a fuel delivery system 10 in accordance with one 
presently preferred embodiment of the invention as comprising a 
self-contained fuel pump module 12 mounted within and surrounded by a fuel 
tank 14. Fuel pump module 12 delivers fuel under pressure through a fuel 
line 16 to a fuel rail 18 carried by an engine 20. A plurality of fuel 
injectors 22 are mounted between rail 18 and engine 20, with nozzles of 
the individual fuel injectors being adjacent to the fuel/air intake ports 
24 of associated cylinders of the engine. Combustion air may be supplied 
to an air intake manifold 26 through an air filter or the like at 
atmospheric pressure, or by a turbocharger or the like driven by the 
engine and supplying air at a pressure that varies with engine operation 
and/or throttle demand, etc. Injectors 22 may be solenoid-activated, for 
example, responsive to an on-board engine control computer (not shown). 
Fuel pump module 12 includes an electric-motor pump 28 having an inlet that 
receives fuel from surrounding tank 14 through a filter sock 30, and an 
outlet that supplies fuel under pressure through a connecting line 32 to a 
cap/manifold 34. Within manifold 34, as illustrated in FIG. 2, an internal 
fuel passage 36 is connected at one end to fuel line 32 by a fitting 38, 
and is connected at the other end to fuel line 16 by a fitting 40. A check 
valve 42 is positioned in passage 36 for preventing reverse flow of fuel 
from rail 18 to tank 14 when pump 28 is shut down. A pressure relief valve 
44 is mounted within manifold 34 and connected to passage 36 downstream of 
check valve 42 for returning fuel to tank 14 in the event of an 
over-pressure condition within fuel line 16 and/or rail 18. A pressure 
sensor 46 is mounted on a circuitboard assembly 48 carried by manifold 34, 
and is operatively coupled to fuel passage 36 extending therethrough for 
suppling an electrical signal as a function of fuel pressure within 
passage 36 upstream of check valve 42. Manifold 34 is mounted by a gland 
50 to close the opening in fuel tank 14 through which fuel pump module 12 
is inserted during vehicle assembly. 
As illustrated in FIG. 3, circuitboard 48 includes a power amplifier 52 for 
supplying a pulse width modulated signal to the motor of pump 28 as a 
function of the output signal of pressure sensor 46. Circuitboard 48 
receives electrical power from a battery 54 and is connected to electrical 
ground by means of conductors 56, 58 respectively. Likewise, amplifier 52 
is connected to pump 28 by means of conductors 60, 62. To the extent thus 
far described, fuel delivery system 10 is generally similar to that 
disclosed in U.S. Pat. No. 5,044,344, the disclosure of which is 
incorporated herein by reference. 
In accordance with a first aspect of the present invention, an orifice 64 
is drilled or otherwise formed in fitting 38 between line 32 and manifold 
34 to provide a continuously open but restricted path for fuel to bypass 
manifold 34 and return to tank 14. Thus, even when engine fuel demand is 
at a minimum level and little fuel flows through check valve 42 and fuel 
line 16, orifice 64 provides a fuel flow path so that pressure sensor 46 
will not reduce operation of pump 28 below some minimum level. In this 
way, if engine fuel demand rapidly increases, such as when the operator 
desires rapidly to accelerate the vehicle after a period of deceleration, 
velocity of the fuel pump motor can rapidly increase to the desired level 
without having to overcome high inertia at low operating speed. During 
normal operation, the small size of orifice 64 (e.g., 0.030 inches) 
presents sufficient restriction as not to offset normal fuel flow to the 
engine. 
In accordance with a second aspect of the present invention, pressure 
relief valve 44 is adjusted to a setting greater than vaporization 
pressure of fuel in fuel line 16 and fuel rail 18 at the predetermined 
maximum operating temperature of engine 20. As shown in FIG. 2, check 
valve 44 includes a valve element 66 urged by a spring 68 against a valve 
seat 70. A nut 72 provides for adjusting the force of compression of 
spring 68, and thus the force in the fuel line and fuel rail necessary to 
overcome spring 68 and return fuel to tank 14. Preferably, such spring 
force is adjusted to a setting slightly greater than vaporization pressure 
of specific type of fuel in connection with which the engine is intended 
to be used at the maximum fuel rail design temperature of the engine. For 
example, for an engine intended to run on pure gasoline at a maximum 
design temperature of less than 200.degree. F., the force of spring 68 may 
be adjusted so that bypass valve 44 will open only when pressure within 
line 16 and rail 18 exceeds 64 psi. This feature of the invention 
substantially reduces or eliminates formation of vapor in the fuel line 
and rail by allowing the fuel pressure to rise to a level that is high 
enough to keep vapor from forming at the maximum design or worst-case 
engine temperature. On the other hand, if fuel system pressure becomes 
excessive due to heat expansion, valve 44 opens to bleed off excess 
pressure. Thus, by maintaining a high fuel pressure, formation of vapor in 
the fuel rail and fuel line is reduced or eliminated. Upon restarting of 
the engine, operation of the injectors rapidly returns rail 18 and line 16 
to normal system operating pressures.