Fuel injection system

A fuel injection system has an electronic module mounted directly on a fuel body portion of the fuel injection system for cooling by fuel flow through the fuel body. The electronic module energizes a fuel pump to circulate fuel through the fuel body, even when the engine is not operating, if the temperature within the module exceeds a selected level.

TECHNICAL FIELD 
This invention relates to apparatus having an electronically operated 
injector for delivering fuel to an engine induction passage. 
BACKGROUND 
In a fuel injection system having an electronic module which operates an 
injector to deliver fuel to an engine induction passage, provision must be 
made for cooling at least some of the electronic components within the 
module to prevent excessive temperatures within the module. As proposed in 
U.S. patent application Ser. No. 256,563 filed Apr. 22, 1981 in the names 
of D. R. Kessler, D. W. Beiswenger and A. J. Makusij and now Pat. No. 
4,503,826, the electronic module may be mounted in maximum heat transfer 
relation to the fuel injection assembly adjacent a fuel passage in the 
assembly. Fuel circulating through the passage absorbs and carries away 
heat conducted from the module to prevent excessive temperatures within 
the module. 
While that proposal is effective for preventing excessive temperatures 
within the electronic module during operation of the engine, it has not 
been effective for preventing excessive temperatures within the module 
during the hot soak period which occurs immediately after the engine has 
been shut off. 
SUMMARY OF THE INVENTION 
This invention provides an improved fuel injection system in which an 
electronic module is mounted directly on a fuel body portion of the fuel 
injection system for cooling by fuel flow through the fuel body both when 
the engine is operating and when the engine is shut off. 
In a fuel injection system according to this invention, means are provided 
for energizing a fuel pump to circulate fuel through the fuel body 
whenever the temperature within the electronic module increases above a 
selected level, even though the engine may not be operating. The fuel 
absorbs and carries away heat conducted from the module and is circulated 
through the fuel body to the extent necessary to prevent excessive 
temperatures within the module. 
The details as well as other features and advantages of a preferred 
embodiment of this invention are set forth in the remainder of the 
specification and are shown in the accompanying drawing.

THE PREFERRED EMBODIMENT 
Referring to the drawing, a throttle body fuel injection assembly 10 
includes a heat conductive aluminum fuel body 12 mounted on a throttle 
body 14 and separated therefrom by a gasket 16. Throttle body 14 defines a 
portion of an engine induction passage 18 having an air inlet (not shown) 
around the sides of fuel body 12 and having a throttle 20 for controlling 
flow through induction passage 18 in the usual manner. 
Fuel body 12 includes an injector cavity 22 which receives fuel from an 
inlet passage 23 formed by bores 24, 26 and 28 and which discharges excess 
fuel through an outlet passage 30 formed by bores 32, 34, 36, 38 and 40. A 
plug 42 at the end of bore 26 directs fuel from bore 26 through bore 28 
into the lower portion of injector cavity 22, and a plug 44 closes the 
outer end of bore 28. A plug 45 between bores 32 and 38 directs fuel from 
bore 32 through bore 34 to an accumulator chamber 46 closed at one side by 
a spring biased diaphragm 47. From accumulator chamber 46, fuel flows 
through bore 36 to bores 38 and 40. 
An electromagnetic fuel injector 48 is disposed in injector cavity 22 and 
has flanges 50 supported in a recess 52 at the top of fuel body 12. An 
O-ring 54 provides a seal between injector 48 and fuel body 12 below 
injector cavity 22, and an O-ring 56 provides a seal between injector 48 
and fuel body 12 above injector cavity 22. Injector 48 receives fuel from 
injector cavity 22 through screened openings 58 and, when operated by an 
electronic module 60, delivers a timed pulse of fuel in a hollow conical 
spray pattern for mixture with the air which flows through induction 
passage 18. 
Electronic module 60 operates injector 48 at regular intervals and controls 
fuel flow by varying the duration of the fuel delivery pulses: when 
increased fuel delivery is required, module 60 increases the duration of 
the fuel delivery pulses, and when decreased fuel delivery is required, 
module 60 decreases the duration of the fuel delivery pulses. 
It is recognized, of course, that variations in the pressure of the fuel in 
injector cavity 22 also affect fuel delivery by the injectors, and a 
pressure regulator is often provided to maintain a constant fuel pressure 
in cavity 22. In the embodiment of this invention illustrated here, 
however, electronic module 60 has a sensor 62 connected through a bore 64 
to measure the fuel pressure in bore 28 and thus in cavity 22. Module 60 
adjusts the duration of the fuel delivery pulses in response to variations 
in the fuel pressure measured by sensor 62 so that the required fuel is 
delivered irrespective of variations in the fuel pressure. 
In the embodiment of this invention illustrated here, moreover, module 60 
also controls a fuel pump 66 which circulates fuel from a fuel tank 68 
through inlet passage 23, injector cavity 22, and outlet passage 30 and 
back to tank 68. Module 60 may control fuel pump 66 to maintain a constant 
fuel pressure in bore 28 and cavity 22. Preferably, however, module 60 
controls fuel pump 66 to increase the fuel pressure in bore 28 and cavity 
22 when increased fuel delivery is required and to decrease the fuel 
pressure in bore 28 and cavity 22 when decreased fuel delivery is 
required. When the fuel pressure is increased, the duration of the fuel 
delivery pulse required to deliver a particular amount of fuel is reduced, 
and when the fuel pressure is decreased, the duration of the fuel delivery 
pulse required to deliver a particular amount of fuel is decreased. Thus 
by varying the fuel pressure in injector cavity 22, module 60 maintains 
the duration of the fuel delivery pulses within a narrower range than is 
possible when the fuel pressure is held constant. 
Electronic module 60 is mounted in maximum heat transfer relation to fuel 
body 12 adjacent inlet and outlet passages 23 and 30. During engine 
operation, fuel body 12 conducts heat from module 60 and fuel circulating 
through the passages absorbs and carries the heat away from module 60 to 
prevent excessive temperatures within the module. 
Module 60 also includes a temperature sensor 70 which measures the 
temperature within module 60. Even when the engine is not operating, 
module 60 energizes fuel pump 66 to circulate fuel through fuel body 12 in 
response to an increase in the temperature measured by sensor 70 above a 
selected level. The circulating fuel absorbs and carries away heat 
conducted through fuel body 12 from module 60. Module 60 energizes pump 66 
to circulate fuel through fuel body 12 to the extent necessary to prevent 
excessive temperatures within the module. 
It will be appreciated, therefore, that this invention provides an improved 
fuel injection system in which an electronic module mounted directly on a 
fuel body portion of the fuel injection system is cooled by fuel flow 
through the fuel body both when the engine is operating and when the 
engine is shut off.