Method of operating an engine

An internal combustion engine having a luminosity probe and an arrangement for adjusting the running parameters of the engine to obtain the desired luminosity. Also disclosed is an arrangement for maintaining uniformity from cycle to cycle in a given combustion chamber and uniformity combustion in the combustion chambers of a multi-chamber engine.

BACKGROUND OF THE INVENTION 
This invention relates to a method of operating an engine and an engine 
apparatus and more particularly to an improved method and apparatus for 
operating an engine in response to actual conditions in the combustion 
chamber during each combustion cycle. 
With the modern technology and electronics many of the components and 
running conditions of an internal combustion engine can be controlled more 
accurately than with previous mechanical systems. For example, the control 
of the fuel/air ratio, spark timing and other adjustable factors of engine 
operation are greatly facilitated through the use of electronic components 
and electronic computers. However, in order to accurately sense the 
running of the engine and the combustion during each combustion cycle, it 
is necessary to provide a sensor that is directly positioned within the 
combustion chamber or in proximity to it and which senses the actual 
combustion conditions in the engine. Most engine controls employ external 
devices such as oxygen sensors or knock sensors which actually sense only 
average conditions due to their inherent nature. 
It has been understood that knocking can be determined by an optical sensor 
that operates within the combustion chamber and which senses the 
luminosity of the gases in that chamber. A wide variety of knock sensors 
have been proposed that employ such sensors. However, the inventors have 
discovered that luminosity in the combustion chamber can indicate a much 
wider range of running conditions that previously realized. 
It is, therefore, a principal object of this invention to provide an 
improved system and method for operating an engine wherein the engine 
adjustable parameters can be varied in response to actual sensed 
conditions in the combustion chamber during each combustion cycle. 
It is a further object of this invention to provide an engine control 
system wherein the engine can be controlled in response to actual 
combustion conditions occurring in the combustion chamber on individual 
cycles. 
Because of the aforenoted averaging tendency of the prior art type of 
sensors, it is also difficult to determine the existence of cylinder to 
cylinder or cycle to cycle variation. It is, therefore, a still further 
object of this invention to provide an improved system for sensing engine 
operation and sensing and determining cycle to cycle and chamber to 
chamber variations during running. 
A type of engine sensor has been proposed that senses the actual luminosity 
of the gases within the combustion chamber. A wide variety of patents 
illustrating and describing the use of such sensors have issued including 
the following: 
U.S. Pat. No. 4,358,952, 
U.S. Pat. No. 4,369,748, 
U.S. Pat. No. 4,377,086, 
U.S. Pat. No. 4,393,687, 
U.S. Pat. No. 4,409,815, 
U.S. Pat. No. 4,412,446, 
U.S. Pat. No. 4,413,509, 
U.S. Pat. No. 4,419,212, 
U.S. Pat. No. 4,422,321, 
U.S. Pat. No. 4,422,323, 
U.S. Pat. No. 4,425,788, 
U.S. Pat. No. 4,468,949, 
U.S. Pat. No. 4,444,043, 
U.S. Pat. No. 4,515,132. 
For the most part, these patents disclose arrangements wherein the sensor 
is utilized to sense only total luminosity and to equate the luminosity 
signal to a knocking signal. However and as has been noted, the inventors 
have discovered that this signal can also be employed to sense a wide 
variety of other engine running characteristics and it is a further object 
of this invention to use these signals to control the engine parameters to 
obtain better running and to obtain consistent running from cylinder to 
cylinder and cycle to cycle. 
SUMMARY OF THE INVENTION 
This invention is adapted to be embodied in a method of operating an 
internal combustion engine and an apparatus therefor that has a combustion 
chamber and means for forming a combustible fuel air mixture within the 
combustion chamber. In accordance with this feature of the invention, the 
luminosity of the gases in the combustion chamber is sensed and the fuel 
air ratio is adjusted to maintain the desired luminosity. 
In accordance with another feature of the invention, there is provided a 
method and apparatus for operating an internal combustion engine having a 
combustion chamber and means for providing a fuel air mixture within the 
combustion chamber and for igniting that fuel air mixture. In accordance 
with this feature of the invention, the luminosity of the gases in the 
combustion chamber is measured and the engine running characteristics are 
adjusted so as to maintain the desired degree of luminosity and the peak 
pressure rate at the desired crank or output shaft angle. 
Another feature of the invention is also adapted to be embodied in a method 
of operating an internal combustion engine having a combustion chamber and 
means for causing combustion to occur in the combustion chamber. In 
accordance with this feature of the invention, the luminosity of the gases 
in the combustion chamber are sensed during each combustion cycle and the 
engine is adjusted to minimize cyclic variations. 
Yet another feature of the invention is adapted to be embodied in a method 
and apparatus for operating a multi-combustion chamber internal combustion 
engine that includes mean for effecting combustion in each of the 
combustion chambers. In accordance with this feature of the invention, the 
luminosity of the gases are sensed in each of the combustion chamber and 
adjustments are made so as to maintain uniformity between the luminosity 
in the various combustion chambers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the single FIGURE of the drawings, a multiple cylinder 
internal combustion engine is identified generally by the reference 
numeral 11. It is to be understood that, although the invention has 
particular utility in multiple cylinder engines, certain facets of the 
invention may find application in single cylinder engines. Also, although 
the invention is described in conjunction with a reciprocating type 
engine, the principles of the engine may be utilized with engines of the 
non-reciprocating, such as rotary, type and with engines operating on 
either two stroke or four stroke cycles. 
Inasmuch as the invention is directed primarily with the combustion chamber 
and the conditions therein, only a cross-sectional view taken through one 
of the combustion chambers is believed to be necessary to understand the 
invention. This cross-sectional view shows a cylinder block 12 having a 
cylinder bore 13 in which a piston 14 is supported for reciprocation. The 
piston 14 is connected by means of a connecting rod (not shown) to a 
crankshaft for providing output power from the engine. 
A cylinder head 15 is affixed in a known manner to the cylinder block 12 
and has a recess 16 which cooperates with the cylinder bore 13 and head of 
the piston 14 to provide a chamber of variable volume, sometimes referred 
to hereinafter as the combustion chamber. 
An intake port 17 and an exhaust port (not shown) extend through the 
cylinder head 15 and have their communication with the combustion chamber 
15 controlled by poppet type intake and exhaust valves (not shown) for 
admitting a charge to the combustion chamber 15 and for discharging the 
burnt charge from the combustion chamber. 
The charge admitted to the combustion chamber 16 may comprise pure air or a 
fuel/air mixture that is formed by a suitable charge former such as a port 
or throttle body type fuel injector or carburetor. Alternatively, if pure 
air is injected, direct cylinder injection may be employed for injecting 
fuel into the combustion chamber 16 to form the fuel air mixture. The fuel 
air ratio may be controlled in any of a wide variety of known manners such 
as by means of throttle vales, fuel control valves, injection duration, 
injection timing, etc. Although an important feature of the invention is 
the parameters under which the fuel air ratio are controlled, the actual 
physical hardware for adjusting the fuel air ratio forms no part of the 
invention. 
The engine 11 may be of the diesel or spark ignited type but the types of 
controls exercised and the nature of luminosity sensing may vary with the 
engine type. The following discussion is concerned primarily with a spark 
ignited engine. If the engine 11 is of the diesel type, combustion is 
initiated through the timing of the direct cylinder fuel injection or in 
any of the other known manners normally employed in connection with diesel 
engines. If, on the other hand, the engine 11 is of the spark ignited 
type, a spark plug will be carried in the cylinder head 15 and have its 
gap exposed in the combustion chamber 16. The spark timing is controlled 
by a suitable mechanism which may be of any conventional type; however, 
the timing of the spark firing can be varied in accordance with 
parameters, hereinafter to be described. 
As has been previously noted, the invention is capable of embodiment in any 
of a wide variety of conventional types of internal combustion engines 
and, for that reason, the details of the engine construction are not 
necessary to understand how the invention can be practiced by those 
skilled in the art. However, in accordance with the invention there is 
provided in the combustion chamber 16, a luminosity detector, indicated 
generally by the reference numeral 18. The luminosity detector 18 includes 
a fiber optic probe 19 or other types of optical access which extends 
through the cylinder head 15 and has its end terminating at the combustion 
chamber 16. Although the fiber optic probe 19 may be of any type, a high 
temperature glass bundle consisting of boresilicate clad crown glass which 
exhibits nearly flat spectral response in the range to be sensed has been 
found to be particularly advantageous. A probe having a diameter of 0.06 
inches has been found to be practical and makes it relatively easy to 
install in the cylinder head. 
The fiber optic probe 19 is held in place by means of a compression fitting 
22 and has its outer end disposed within a light sealed housing 22 in 
proximity to a silicon photo detector 23. In one application the detector 
23 specifically had a peak response of 0.74 microns with a fifty percent 
band width of 0.08 microns, although other types of detectors can be 
utilized depending upon the type of fiber optic probe employed. The 
detector 23 is connected to a remotely positioned computer control unit by 
means of conductors 24. 
The remotely positioned control unit may be of any suitable type and is 
particularly adapted to transmit the signal from the silicon photo 
detector 23 into an output indicative of luminosity within the combustion 
chamber 16. Various luminosity spectra may be detected or merely a total 
luminosity signal may be read. It has been found that certain constituents 
of the glowing gases in the combustion chamber 16 glow at different 
spectral ranges and this may be utilized to sense the amount and condition 
of such components in the combustion chamber 16 during each cycle of 
operation. 
It has been discovered that a wide variety of combustion phenomena and 
other characteristics can be determined by the luminosity probe 18 and the 
signals employed to adjust the parameters of the engine to obtain optimum 
performance. For example, the luminosity signal is a signal which gives a 
very good indication of the start of combustion. Heat release analysis 
indicates that one percent (1%) fuel mass burn fraction coincides with the 
start of the luminosity signal and the location of ninety percent (90%) 
mass burn fraction coincides with the return of the luminosity signal to 
zero. Thus, unlike cylinder pressure or other parameters, the luminosity 
signal clearly defines the actual start of combustion and combustion 
duration. 
Therefore, the output of the luminosity probe 18 may be employed to control 
spark timing or injection timing in a diesel engine so as to control when 
combustion begins to obtain optimum performance characteristics. The 
control circuitry and mechanism for adjusting either spark timing or the 
initiation of injection in a diesel engine in response to this signal are 
believed to be well within the scope of those skilled in the art once they 
understand that the luminosity signal is indicative of the start of 
combustion and also that this signal can be used so as to control the 
beginning of combustion. Also, the duration of the signal can be utilized 
to determine the amount of fuel which has been or should be injected or 
introduced into the cylinder from a carburetor or port type injector so as 
to obtain the desired burn time. 
In addition to the beginning and ending of combustion, the luminosity 
signal also provides an indication of heat release and also be employed so 
as to control the beginning of combustion and or the amount of fuel 
introduced so as to provide the desired heat release and timing cycles. It 
has been noted that peak luminosity and maximum rate of heat release are 
substantially the same and hence the engine parameters may be controlled 
in conjunction with the luminosity signal to provide the desired rate of 
heat release. 
It has also been noted that the luminosity signal is very sensitive to 
air/fuel ratio variations when all other conditions are held constant and, 
accordingly, the luminosity probe 18 can be used as a detector of in 
cylinder air/fuel ratio for adjusting the charge former so as to provide 
the desired air/fuel ratio in response to any preset program. 
In addition to the aforenoted factors, such conditions as high pressure or 
hot cycles produce sharp luminosity signals whereas partial burn cycles 
produce weak luminosity signals. Complete misfire results in no luminosity 
signals and hence the luminosity signal may be employed so as to sense 
cylinder to cylinder or cycle to cycle variations and the engine 
parameters adjusted to minimize such variations. 
It should be readily apparent that the use of the luminosity probe is 
extremely effective in sensing a wide variety of running characteristics 
within the combustion chamber and variations from chamber to chamber and 
cycle to cycle. Those skilled in the art armed with this knowledge should 
be able to provide the various engine controls such as the timing of spark 
ignition and timing and duration of fuel injection or changing of fuel/air 
ratios through premixing devices such as carburetors or port injectors so 
as to obtain optimum performance and minimum cycle to cycle and cylinder 
to cylinder variations. As has been previously noted, the presence of 
certain combustion products may also be sensed by sensing specific light 
ranges in the cylinder to obtain optimization of these factors. 
The foregoing description is that of a preferred embodiment of the 
invention and various changes in modifications may be made without 
departing from the spirit and scope of the invention, as defined by the 
appended claims.