U.S. patent application number 11/098099 was filed with the patent office on 2006-10-05 for method for evaluating engine idle roughness.
This patent application is currently assigned to Deere & Company, a Delaware corporation. Invention is credited to Dennis Frederick Kabele.
Application Number | 20060224297 11/098099 |
Document ID | / |
Family ID | 36974604 |
Filed Date | 2006-10-05 |
United States Patent
Application |
20060224297 |
Kind Code |
A1 |
Kabele; Dennis Frederick |
October 5, 2006 |
METHOD FOR EVALUATING ENGINE IDLE ROUGHNESS
Abstract
A method is provided for evaluating the acceptability of idle
roughness levels in a newly manufactured multi-cylinder internal
combustion engine. The method involves calculating a plurality of
metrics based upon the relative firing energies of individual
cylinders in the engine and setting threshold values for each of
the metrics, below which the engine is to be accepted. Similarly,
threshold values are set for each of the metrics, above which the
engine is to be rejected. The engine is then evaluated to determine
if the engine is to be accepted or rejected based upon the
calculated metrics and the threshold values for acceptance or
rejection set for that metric. If the engine has not been
previously accepted or rejected based on a particular metric the
engine is evaluated using each of the remaining metrics. If the
engine has not been rejected after all metrics have been evaluated
the engine is finally accepted.
Inventors: |
Kabele; Dennis Frederick;
(Cedar Falls, IA) |
Correspondence
Address: |
DEERE & COMPANY
ONE JOHN DEERE PLACE
MOLINE
IL
61265
US
|
Assignee: |
Deere & Company, a Delaware
corporation
|
Family ID: |
36974604 |
Appl. No.: |
11/098099 |
Filed: |
April 4, 2005 |
Current U.S.
Class: |
701/111 |
Current CPC
Class: |
F02D 41/1498 20130101;
F02D 41/22 20130101; F02D 2041/288 20130101; F02D 41/16 20130101;
G01M 15/11 20130101 |
Class at
Publication: |
701/111 |
International
Class: |
G01M 15/04 20060101
G01M015/04 |
Claims
1. A method for evaluating the acceptability of idle roughness
levels in a newly manufactured multi-cylinder internal combustion
engine comprising the steps of: calculating two or more metrics
based upon relative firing energies of individual cylinders in the
engine; setting a first threshold value for each of the two or more
metrics, below which the engine is to be accepted; setting a second
threshold value for each of the two or more metrics, above which
the engine is to be rejected; evaluating the engine to determine if
the engine is to be accepted or rejected based upon a first
calculated metric and the threshold values for acceptance or
rejection set for that metric; and, if the engine has not been
previously accepted or rejected, evaluating the engine in the same
way using the other of the two or more calculated metrics and the
threshold values set for each of those metrics.
2. A method as described in claim 1 wherein the relative firing
energy of each cylinder is an Energy/Cycle parameter, and is
determined by: sampling raw voltage signals from a speed sensor
that is aligned with a camshaft drive gear; detecting data zero
crossings of the voltage signal; calculating the instantaneous
camshaft rpm for each gear tooth passage; locating and storing
consecutive minimum rpm values; and, subtracting the square of the
minimum rpm value of the cylinder from the square of the minimum
rpm value of a next consecutive cylinder and dividing by the
average of minimum rpm values for all cylinders.
3. A method as described in claim 2 wherein one of the two or more
metrics is a difference between a maximum Energy/Cycle parameter of
all cylinders and a minimum Energy/Cycle parameter of all
cylinders.
4. A method as described in claim 2 wherein one of the two or more
metrics is an average of a maximum Energy/Cycle parameter from all
cylinders and a second highest Energy/Cycle parameter.
5. A method as described in claim 2 wherein one of the two or more
metrics is a highest sum of Energy/Cycle parameters for two
consecutive cylinders.
6. A method as described in claim 5 wherein the highest sum of
Energy/Cycle parameters for two consecutive cylinders metric has
threshold values for acceptance and rejection such that the metric
can be used only to accept the engine and not to reject the
engine.
7. A method as described in claim 2 wherein one of the two or more
metrics is a ratio of a highest sum of Energy/Cycle parameters for
two consecutive cylinders to a highest sum of Energy/Cycle
parameters of two equi-spaced cylinders.
8. A method as described in claim 7 wherein the ratio of a highest
sum of Energy/Cycle parameters for two consecutive cylinders to a
highest sum of Energy/Cycle parameters of two equi-spaced cylinders
metric has threshold values for acceptance and rejection such that
the metric can be used only to reject the engine and not to accept
the engine.
9. A method as described in claim 2 wherein one of the two or more
metrics is an average of Energy/Cycle parameters of a three highest
cylinders.
10. A method as described in claim 9 wherein the average of
Energy/Cycle parameters of a three highest cylinders metric has
threshold values for acceptance and rejection such that the metric
can be used only to reject the engine and not to accept the
engine.
11. A method as described in claim 2 wherein one of the two or more
metrics is a maximum firing acceleration among all the
cylinders.
12. A method as described in claim 11 wherein the firing
acceleration for each cylinder is an average angular acceleration
for a period between the local minimum rpm point and a next
adjacent rpm data point, where the period is the number of crank
degrees between cam gear teeth.
13. A method for evaluating the acceptability of idle roughness
levels in a newly manufactured multi-cylinder internal combustion
engine comprising the steps of: finding a relative firing energy of
each cylinder (Energy/Cycle); calculating the following metrics
based upon the relative firing energy of each cylinder
(Energy/Cycle): a difference between a maximum Energy/Cycle
parameter of all cylinders and a minimum Energy/Cycle parameter of
all cylinders; an average of a maximum Energy/Cycle parameter from
all cylinders and a second highest Energy/Cycle parameter; a
highest sum of Energy/Cycle parameters for two consecutive
cylinders; a ratio of a highest sum of Energy/Cycle parameters for
two consecutive cylinders to a highest sum of Energy/Cycle
parameters of 2 equi-spaced cylinders; an average of Energy/Cycle
parameters of a 3 highest cylinders; a maximum firing acceleration
among all the cylinders; setting threshold values for acceptance
and rejection of the engine for each of the metrics; and,
evaluating the engine to determine whether the engine should be
accepted or rejected based upon the calculated metrics and the
threshold values for each of the metrics.
14. A method as set forth in claim 13 wherein the relative firing
energy of each cylinder (Energy/Cycle) is found by: sampling raw
voltage signals from a speed sensor that is aligned with a camshaft
drive gear of the engine; detecting data zero crossings of the
voltage signal; calculating an instantaneous camshaft rpm for each
gear tooth passage; locating and storing consecutive minimum rpm
values; and, subtracting a square of the minimum rpm value of the
cylinder from the square of the minimum rpm value of a next
consecutive cylinder and dividing by an average of minimum rpm
values for all cylinders.
15. A method as described in claim 14 wherein the highest sum of
Energy/Cycle parameters for two consecutive cylinders metric has
threshold values for acceptance and rejection such that the metric
can be used only to accept the engine and not to reject the
engine.
16. A method as described in claim 14 wherein the ratio of a
highest sum of Energy/Cycle parameters for two consecutive
cylinders to a highest sum of Energy/Cycle parameters of two
equi-spaced cylinders metric has threshold values for acceptance
and rejection such that the metric can be used only to reject the
engine and not to accept the engine.
17. A method as described in claim 14 wherein the average of
Energy/Cycle parameters of a three highest cylinders metric has
threshold values for acceptance and rejection such that the metric
can be used only to reject the engine and not to accept the
engine.
18. A method as described in claim 14 wherein the firing
acceleration for each cylinder is an average angular acceleration
for the period between a local minimum rpm point and a next
adjacent rpm data point, where the period is the number of crank
degrees between cam gear teeth.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to internal
combustion engines. More particularly, the present invention
relates to quality control measures in the manufacture of internal
combustion engines. Specifically, the present invention relates to
a method for evaluating the idle roughness of a newly manufactured
engine.
BACKGROUND OF THE INVENTION
[0002] Perceived roughness is a common problem for some diesel
engines when operating at idle conditions and light loads.
Variation of fuel delivery to the different cylinders is one of the
major sources of idle roughness. At the engine manufacturing
facility it is desirable to conduct diagnostic tests to determine
if the idle roughness is acceptable before the engine is
shipped.
[0003] It has previously been known to provide diagnosis of idle
roughness and quality at the engine manufacturing location. One
common method, listening to the engine idle in a test cell, is not
conclusive as to the level of idle quality. If the idle quality is
checked after it is installed in the end vehicle application and
found unacceptable, it can be very expensive to make the necessary
changes to the fuel system. Some fuel systems do not have the
capability to adjust the balance of fuel to the various cylinders
at both no load and full load. Fuel injectors are typically
calibrated at idle fuel on a test bench before installation in the
engine. However, there is variability in the calibration. In
addition, the injectors need to be indexed uniformly when installed
in the engine and there is further variability in this
procedure.
[0004] Generally, if the injectors are calibrated properly and if
the indexing of the injectors in the engine is accurate, there is
no problem with idle roughness. However, if these processes are not
controlled, an unsatisfactory level of idle roughness can be
present. Thus a method is needed to diagnose the idle roughness
quality while the engine is still in the engine manufacturing
facility so that problems can be addressed before the engine leaves
the facility. A previous method used was a Fourier transform of the
engine speed signal. This method worked for cases where the idle
roughness was far out of specification. However, it was not
sensitive enough to detect the vast majority of idle roughness
problems.
SUMMARY OF THE INVENTION
[0005] In view of the foregoing, it is an object of the invention
to provide a method for evaluating the idle roughness of a newly
manufactured internal combustion engine.
[0006] Another object of the invention is the provision of a method
for evaluating engine idle roughness that calculates unique metrics
based upon the relative firing energy of the engine and applies
successive accept/reject criteria to determine acceptability.
[0007] A further object of the invention is to provide such a
method that is inexpensive to implement and is compatible with
known manufacturing and testing techniques.
[0008] An additional object of the invention is the provision of a
method for evaluating idle roughness that does not significantly
increase the cycle time for engine testing.
[0009] The foregoing and other objects of the invention together
with the advantages thereof over the known art which will become
apparent from the detailed specification which follows are attained
by a method for evaluating the acceptability of idle roughness
levels in a newly manufactured multi-cylinder internal combustion
engine comprising the steps of: calculating two or more metrics
based upon relative firing energies of individual cylinders in the
engine; setting a first threshold value for each of the two or more
metrics, below which the engine is to be accepted; setting a second
threshold value for each of the two or more metrics, above which
the engine is to be rejected; evaluating the engine to determine if
the engine is to be accepted or rejected based upon a first
calculated metric and the threshold values for acceptance or
rejection set for that metric; and, if the engine has not been
previously accepted or rejected, evaluating the engine in the same
way using the other of the two or more calculated metrics and the
threshold values set for each of those metrics.
[0010] Other objects of the invention are attained by a method for
evaluating the acceptability of idle roughness levels in a newly
manufactured multi-cylinder internal combustion engine comprising
the steps of: finding the relative firing energy of each cylinder
(Energy/Cycle); calculating the following metrics based upon the
relative firing energy of each cylinder (Energy/Cycle): --a
difference between a maximum Energy/Cycle parameter of all
cylinders and a minimum Energy/Cycle parameter of all cylinders;
--an average of a maximum Energy/Cycle parameter from all cylinders
and a second highest Energy/Cycle parameter; --a highest sum of
Energy/Cycle parameters for two consecutive cylinders; --a ratio of
a highest sum of Energy/Cycle parameters for two consecutive
cylinders to a highest sum of Energy/Cycle parameters of 2
equi-spaced cylinders; --an average of Energy/Cycle parameters of a
3 highest cylinders; --a maximum firing acceleration among all the
cylinders; setting threshold values for acceptance and rejection of
the engine for each of the metrics; and, evaluating the engine to
determine whether the engine should be accepted or rejected based
upon the calculated metrics and the threshold values for each of
the metrics.
[0011] In general, a method is provided for evaluating the
acceptability of idle roughness levels in a newly manufactured
multi-cylinder internal combustion engine. The method involves
calculating a plurality of metrics based upon the relative firing
energies of individual cylinders in the engine and setting
threshold values for each of the metrics, below which the engine is
to be accepted. Similarly, threshold values are set for each of the
metrics, above which the engine is to be rejected. The engine is
then evaluated to determine if the engine is to be accepted or
rejected based upon the calculated metrics and the threshold values
for acceptance or rejection set for that metric. If the engine has
not been previously accepted or rejected based on a particular
metric the engine is evaluated using each of the remaining metrics.
If the engine has not been rejected after all metrics have been
evaluated the engine is finally accepted.
[0012] The examples used herein are specifically applied to a
four-stroke engine where each cylinder fires once per two
revolutions of the crankshaft. The invention can also be applied in
a similar manner to a two-stroke engine where each cylinder fires
once per revolution of the crankshaft. This invention also applies
only to engines with equally spaced firing intervals.
[0013] The present invention utilizes a speed signal from a
magnetic pickup operating on a camshaft gear to determine the
variation in rpm during the firing of the various cylinders. It
calculates unique metrics and applies successive accept/reject
criteria to determine acceptability of the engine with respect to
idle roughness. Alternative methods of measuring engine speed can
also be utilized. Examples include, but are not limited to, a) a
magnetic pickup operating on a gear which rotates at a speed
proportional to the crankshaft speed, or b) an encoder mounted on
the crankshaft or another shaft which rotates at a speed
proportional to the crankshaft speed.
[0014] To acquaint persons skilled in the art most closely related
to the present invention, one preferred embodiment of the invention
that illustrates the best mode now contemplated for putting the
invention into practice is described herein by and with reference
to, the annexed drawings that form a part of the specification. The
exemplary embodiment is described in detail without attempting to
show all of the various forms and modifications in which the
invention might be embodied. As such, the embodiment shown and
described herein is illustrative, and as will become apparent to
those skilled in the art, can be modified in numerous ways within
the spirit and scope of the invention--the invention being measured
by the appended claims and not by the details of the
specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] For a complete understanding of the objects, techniques, and
structure of the invention reference should be made to the
following detailed description and accompanying drawings,
wherein:
[0016] FIG. 1 is a graph wherein engine speed is plotted against
time for purposes of determining minimum rpm values for each
cylinder of a 4-cylinder engine;
[0017] FIG. 2 is a graph wherein engine speed is plotted against
time for purposes of determining the ZipRPM value for a particular
cylinder; and,
[0018] FIG. 3 is a flowchart illustrating the steps for evaluating
an engine for idle roughness.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0019] The developed algorithms are unique for both 4 and 5
cylinder engines models. Thus the test system needs to detect the
number of engine cylinders from e.g. the bar code information and
use the appropriate data reduction program.
[0020] Raw voltage is sampled from a speed sensor that is aligned
with a camshaft drive gear. From that data, zero crossings of the
voltage signal are detected to calculate the instantaneous camshaft
rpm for each gear tooth passage. For 4 cylinder engines, 5
consecutive minimum rpm values, or "valleys" are located and
stored. For 5 cylinder engines, 6 consecutive minimum rpm values,
or "valleys" are located and stored, etc.. The number of teeth on
the camshaft gear must be such that an integer number of teeth
corresponds to the interval between the firing of consecutive
cylinders. For example, with 60 teeth on the camshaft gear and a
4-cylinder engine with even firing intervals, there will be 60/4=15
teeth per firing interval. For a 5-cylinder engine with 60 teeth on
the camshaft, there will be 60/5=12 teeth per firing interval.
Those having skill in the art will recognize that there are various
alternate methods of measuring engine speed which can also be
utilized. Examples include, but are not limited to, a) a magnetic
pickup operating on a gear which rotates at a speed proportional to
the crankshaft speed, or b) an encoder mounted on the crankshaft or
another shaft which rotates at a speed proportional to the
crankshaft speed.
[0021] The relative Energy/Cycle parameters, average rpm, and
accelerations for use in six (6) Idle Roughness Metrics are
calculated.
[0022] First the local minimums are determined from the
instantaneous engine idle rpm curve. A sample curve for a 4
cylinder engine is illustrated in FIG. 1. More particularly, 5
consecutive local minimums or "valleys" are selected. The changes
in minimum rpm from cycle to cycle represent the relative strengths
of each cylinder firing after the compression stroke. The stronger
the firing of the cylinder, the greater will be the minimum rpm
value. Ideally, for smooth idle noise, all local minimums would
have the same value. In a 4-cylinder engine, the first "valley" and
the fifth "valley" correspond to the same individual cylinder. If
the engine is running at a stable time-averaged speed, these two
"valleys" will be equal. For a 5-cylinder engine, the first
"valley" and the sixth "valley" would correspond to the same
individual cylinder. If the engine is running at a stable
time-averaged speed, these two "valleys" will be equal.
[0023] A point, herein referred to as the ZipRPM point, is next
found. This is the adjacent rpm data point just after each local
minimum, or valley as illustrated in FIG. 2. As will be described
in more detail below, the ZipRPM point is used to calculate what is
herein referred to as the "Zip Max" parameter, which is the
instantaneous acceleration. After the local minimums are
identified, then the next rpm data point for each local minimum rpm
is located.
[0024] Next the Energy/Cycle parameter is found. Specifically, the
relative firing energy of each cylinder is calculated using
following the example formulae (for a 4-cylinder engine):
Energy/Cycle.sub.1=((MinRPM.sub.2).sup.2-(MinRPM.sub.1).sup.2)/Average(Mi-
nRPM.sub.1, . . . MinRPM.sub.4)
Energy/Cycle.sub.2=((MinRPM.sub.3).sup.2-(MinRPM.sub.2).sup.2)/Average(Mi-
nRPM.sub.1, . . . MinRPM.sub.4)
Energy/Cycle.sub.3=((MinRPM.sub.4).sup.2-(MinRPM.sub.3).sup.2)/Average(Mi-
nRPM.sub.1, . . . MinRPM.sub.4)
Energy/Cycle.sub.4=((MinRPM.sub.5).sup.2-MinRPM.sub.4).sup.2)/Average(Min-
RPM.sub.1, . . . MinRPM.sub.4)
[0025] Next the second highest Energy/Cycle parameter is determined
from the Energy/Cycle calculations as follows: Second Highest=Max
(3 Lowest Energy/Cycle parameters)
[0026] Next a parameter herein referred to as the "Oneness"
parameter is found: Oneness=Max (Energy/Cycle1, . . . 4)
[0027] The highest sum of 2 equi-spaced cylinders, herein referred
to as the "Twoness Even" parameter, is found as follows: Twoness
Even=Max (Energy/Cycle1+Energy/Cycle3,
Energy/Cycle2+Energy/Cycle4)
[0028] The Twoness Even parameter is defined only for engines
having an even number of cylinders. In engines having an odd number
of cylinders e.g. 5 cylinders the Twoness Even parameter does not
exist because there are no two cylinders which fire exactly one
revolution apart.
[0029] The Zip parameters for each cylinder are calculated. The Zip
parameter is the average angular acceleration for the 12.degree.
period between the local minimum rpm point and the next rpm data
point, where 12 is the number of crank degrees between cam gear
teeth: Zip.sub.1=(ZipRPM.sub.1-MinRPM.sub.1)/12
Zip.sub.2=(ZipRPM.sub.2-MinRPM.sub.2)/12
Zip.sub.3=(ZipRPM.sub.3-MinRPM.sub.3)/12
Zip.sub.4=(ZipRPM.sub.4-MinRPM.sub.4)/12
[0030] Next a parameter herein referred to as Max Spread is
calculated, wherein: MAX SPREAD=Max(Energy/Cycle.sub.1, . . .
4)-Min(Energy/Cycle.sub.1, . . . 4)
[0031] A parameter herein referred to as the Twoness parameter is
next found as follows: TWONESS=Average(Oneness, Second Highest)
[0032] A parameter known as the Twoness Uneven Metric is next
calculated. Wherein Twoness Uneven is the highest sum of two
consecutive cylinders as follows: TWONESS
UNEVEN=Max[(Energy/Cycle.sub.1+Energy/Cycle.sub.2),
(Energy/Cycle.sub.2+Energy/Cycle.sub.3),
(Energy/Cycle.sub.3+Energy/Cycle.sub.4),
(Energy/Cycle.sub.4+Energy/Cycle.sub.1)]
[0033] Then the Twoness Uneven/Twoness Even Ratio Metric is
calculated: TWONESS UNEVEN/TWONESS EVEN=TWONESS UNEVEN
parameter/TWONESS EVEN parameter
[0034] The metric, Twoness Uneven/Twoness Even applies only to the
4-cylinder engine. Those having skill in the art will recognize
that similar algorithms can also be applied to other engine
configurations, such as engines with 3 and 6 cylinders.
[0035] Next the average of the 3 highest cylinders is determined,
this is known as the Threeness parameter:
THREENESS=[Sum(Energy/Cycle.sub.1, . . .
Energy/Cycle.sub.4)-Min(Energy/Cycle.sub.1, . . . ,
Energy/Cycle.sub.4)]/3
[0036] Those having skill in the art will recognize that the
metrics, Twoness Uneven/Twoness Even, and Threeness would not apply
to a 3-cylinder engine.
[0037] A measure of the firing acceleration for each cylinder,
known as the Zip Max Metric is calculated as follows:
ZIPMAX=Max(Zip.sub.1, . . . , Zip.sub.4)
[0038] The various metrics were derived to determine the extent to
which all cylinders are delivering the same amount of net work. If
each cylinder delivers exactly the same work, the idle roughness
will be minimized.
[0039] Other than the Zip parameter, the metrics are derived on a
kinetic energy basis from the firing cycle of one cylinder to the
firing cycle of the next cylinder. The engine rpm will increase
during the period a given cylinder fires, then the rpm will
decrease as compression takes place on the next firing cylinder.
For a perfect engine, the instantaneous engine rpm will be the same
at TDC of each cylinder. The metrics are all related through the
energy parameter.
[0040] Once the metrics have been calculated they are applied to
either accept or reject an engine according to the flow chart of
FIG. 3. As shown, each metric has a range of limits for acceptance.
It should be noted that the limit values shown in FIG. 3 are by way
of example only. Those having skill in the art will recognize that
the values used in a particular application can vary from those
shown, based upon the particular engines being evaluated and the
level of idle quality desired. The score for each metric is
compared to the allowable limits for that metric. Acceptance is
evaluated in a sequence through each metric in a specified order.
The engine is accepted outright if the metric is below a specified
value, or rejected outright if it exceeds a specified limit. If the
metric value is between the Accept/Reject limits, then the
evaluation continues to the next metric in the specified order. If
an engine makes it through all the metrics without being rejected,
then it is accepted. The limits are set up so that the Twoness
Uneven metric can only accept, while the Twoness Uneven/Twoness
Even Ratio and Threeness metrics can only reject.
[0041] A series of tests was conducted on a large sample of
engines, some of which had been previously rejected (subjectively)
and some of which had been previously accepted (subjectively). All
these engines were rated subjectively from 1-5, with 3 being the
minimum acceptable. Then the metric values were plotted against the
subjective ratings on a scatter plot. It was found that the "Max
Spread" metric could be used to establish a high limit, above which
it could be used to reject engines. It could also be used to
establish a low limit, below which it could be used to accept
engines. The same was done with the other metrics. The order as to
which the metrics are applied has been chosen so that as many
engines as possible are either accepted or rejected before going to
the next metric.
[0042] The time taken during engine final test for this method is
quite minimal. Each engine is built with a provision for a magnetic
pickup on the camshaft gear. The magnetic pickup signal is
typically already being used for other tests so there is no
additional cost for the engine. This method prevents defective
engines from being shipped and it also alerts as to injector
calibration problems and assembly problems. The primary advantages
of this method are savings in both cost and time.
[0043] Thus it can be seen that the objects of the invention have
been satisfied by the structure presented above. While in
accordance with the patent statutes, only the best mode and
preferred embodiment of the invention has been presented and
described in detail, it is not intended to be exhaustive or to
limit the invention to the precise form disclosed. Obvious
modifications or variations are possible in light of the above
teachings. The embodiment was chosen and described to provide the
best illustration of the principles of the invention and its
practical application to thereby enable one of ordinary skill in
the art to utilize the invention in various embodiments and with
various modifications as are suited to the particular use
contemplated. All such modifications and variations are within the
scope of the invention as determined by the appended claims when
interpreted in accordance with the breadth to which they are fairly
and legally entitled.
* * * * *