U.S. patent application number 09/932751 was filed with the patent office on 2002-01-24 for engine torque-detecting method and an apparatus therefore.
Invention is credited to Sano, Taketoshi.
Application Number | 20020007670 09/932751 |
Document ID | / |
Family ID | 13439548 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020007670 |
Kind Code |
A1 |
Sano, Taketoshi |
January 24, 2002 |
Engine torque-detecting method and an apparatus therefore
Abstract
A method and apparatus for measuring the instantaneous torque of
an engine by measuring the change in pressure in the combustion
chamber at two crank angles. The crank angles are chosen to
approximate the time when the change in pressure is the greatest
and when the pressure is the greatest and the change in pressure is
zero. These crank angles may be either determined by measuring the
values or by approximating the crank angles at which the values
will exist. In some instances, the torque is measured by summing
the change in pressures during the time interval and in other
methods the torque is measured by determining the pressure
differences at the two crank angles.
Inventors: |
Sano, Taketoshi;
(Shizuoka-ken, JP) |
Correspondence
Address: |
ERNEST A. BEUTLER
ATTORNEY AT LAW
500 NEWPORT CENTER DRIVE
SUITE 945
NEWPORT BEACH
CA
92660
US
|
Family ID: |
13439548 |
Appl. No.: |
09/932751 |
Filed: |
August 17, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09932751 |
Aug 17, 2001 |
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|
08833767 |
Apr 9, 1997 |
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08833767 |
Apr 9, 1997 |
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08207273 |
Mar 7, 1994 |
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Current U.S.
Class: |
73/114.04 ;
73/114.16; 73/114.25 |
Current CPC
Class: |
G01L 3/00 20130101; G01L
3/245 20130101; G01M 15/08 20130101 |
Class at
Publication: |
73/117.3 |
International
Class: |
G01L 003/26 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 8, 1993 |
JP |
5-70715 |
Claims
What is claimed is:
1. The method of measuring instantaneous engine speed for a portion
of rotation of an output shaft of an engine comprising a shaft
driven by the engine and an associated fixed component of the
engine juxtaposed to a portion of the shaft, a permanent magnet
fixed to one of the shaft and the component and an electrical coil
fixed to the other of the shaft and the component and adapted to
output a pulse upon passage of the coil and the permanent magnet
upon rotation of the shaft for indicating the angular position of
the shaft, said method comprising the steps of determining the
shaft angle when the maximum positive pulse is generated by the
coil, determining the shaft angle when the maximum negative pulse
is generated by the coil, and measuring the time interval between
the maximum positive and negative pulses to determine instantaneous
shaft rotational speed.
2. A method of measuring instantaneous engine speed as in claim 1,
wherein the engine is a four-cycle engine.
3. A method of measuring instantaneous engine speed as in claim 2,
wherein the shaft comprises a cam shaft driven by the engine
crankshaft and rotating at one-half crankshaft speed.
4. A method of measuring instantaneous engine speed as in claim 3,
wherein the coil and permanent magnet are disposed to provide an
indication of top dead center.
5. A method of measuring instantaneous engine speed as in claim 4,
further comprising determining the actual shaft angle from the
output pulse and summing the output pulses for a given time period
to determine average shaft rotational speed.
6. A method of sensing both absolute pressure in an engine
combustion chamber and its instantaneous change of pressure
comprising a piezoelectric device adapted to be exposed to
combustion chamber pressure and outputting a first electrical
signal indicative of the change in pressure in the combustion
chamber, and an amplifier circuit receiving the first electrical
signal and transforming the first electrical signal into a second
electrical signal indicative of the pressure in the combustion
chamber, said method comprising the step of selecting which of said
electrical signals is read to provide either a change in pressure
signal or an absolute pressure signal.
7. A method of sensing both absolute pressure in an engine
combustion chamber and its instantaneous change of pressure as in
claim 6, wherein the method further comprises summing the first
electrical signals for a given time period to determine engine
torque.
8. A method of sensing both absolute pressure in an engine
combustion chamber and its instantaneous change of pressure as in
claim 7, wherein the time period is selected to begin at the time
when the change in pressure is at a maximum and end the summing
when the change in pressure is zero.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of application No.
08/833,767, filed Apr. 9, 1997, which application is a file wrapper
of application No. 08/207,273, filed Mar. 7, 1994, all entitled
"ENGINE TORQUE-DETECTING METHOD AND AN APPARATUS THEREFOR", and
assigned to the assignee hereof.
BACKGROUND OF THE INVENTION
[0002] This invention relates to an engine torque-detecting method
and apparatus therefor, and more particularly to an improved method
and apparatus for measuring engine torque during running.
[0003] It is well known to attempt to improve the efficiency and
exhaust emission control of an internal combustion engine to
operate it in such a manner as to accurately control the amount of
fuel supplied to the engine. Also, other engine parameters are
controlled in order to maintain good combustion with the minimum
amount of fuel for environmental and efficiency reasons. In order
to ensure stable running, however, it is necessary to ensure that
adequate amounts of fuel are provided to the engine and that other
running conditions are accurately controlled. Therefore, there is a
need to measure the actual engine output so as to ensure stability
in its operation.
[0004] For example, it is known that fuel economy and exhaust
emission control may be achieved by operating the engine on a
so-called "lean burn" system at least at low and partial lows. With
lean burn running the fuel-air mixture supplied to the combustion
chamber is less than stoichiometric. However, it is also known that
the limits of lean burn may be readily determined by measuring the
output torque of the engine. When the output torque falls below a
predetermined value it is known that the stability and engine
running speed will deteriorate significantly. Therefore, it is
desirable to be able to measure the output torque of the engine
during its running so as to permit optimization of the lean burn
running.
[0005] Obviously, it is not possible to measure the engine output
in the form of torque through the use of normal measuring apparatus
employed for engine testing. That is, the torque-measuring devices
used to determine the performance of the engine cannot be
incorporated feasibly in a motor vehicle.
[0006] There have, therefore, been proposed methods for attempting
to measure the engine output torque during its running by measuring
some other parameter of the engine. It has been found that pressure
in the combustion chamber can be utilized to project engine output
torque and ensure stability in running. One method for measuring
the engine output torque has been to sample the pressure readings
at a number of output shaft angles during a single cycle of
operation beginning near the end of the compression stroke and
ending during the power or expansion stroke and then predict the
engine torque from these readings. However, the necessity of taking
multiple readings at varying crank angles provides a very
complicated system, and normal computers cannot make the necessary
calculations in the time period to adjust the engine to maintain
stability without time lags. These problems are particularly acute
when the engine is running at a high speed.
[0007] It is has also been proposed to measure or estimate the
output torque of the engine by measuring the peak combustion
chamber pressure. Such a system obviously only requires one
pressure reading. However, it has been found that this value is not
as closely related to engine output torque as was thought,
particularly when cycle-to-cycle measurements are being made and
compared with each other.
[0008] It is, therefore, a principal object of this invention to
provide an improved method and apparatus for measuring the torque
output of an engine during its running and per cycle.
[0009] It is a further object of this invention to provide an
improved method and apparatus for measuring engine torque per cycle
that can be utilized with a minimum number of readings.
[0010] In conjunction with measuring the torque of the engine and
other engine measurements, it is desirable to be able to determine
accurately the engine speed. It is commonly the practice to employ
with engines a crankshaft or other shaft position detector that
outputs a pulse when the shaft rotates to a particular angle. These
sensors normally employ a permanent magnet and a related coil, in
which the pulse is generated as the magnet and coil are brought
into registry with each other. These sensors are normally employed
not only to determine a reference angle position for the shaft,
such as top dead center, but also to measure engine speed by
counting the number of pulses generated in a time period. Although
these devices are particularly useful, they provide indications of
average engine speed, and not engine speed during a single
revolution or a portion of a revolution. With some measurements,
such as the measurement of engine torque, it is desirable to
measure the instantaneous angular rotational speed of the engine
shaft during a single cycle of engine operation.
[0011] It is, therefore, a further object of this invention to
provide an improved measuring device that can provide not only a
reference signal indicative of engine shaft position but also
includes means for determining instantaneous engine shaft angular
velocity in less than a complete revolution.
[0012] As has been previously noted, methods for determining or
predicting engine torque have employed sensors for sensing the
pressure in the combustion chamber. Such pressure sensors are well
known and normally employ piezoelectric devices, which are exposed
to the combustion chamber pressure. These devices actually output a
first signal that is indicative of the change in pressure exerted
on the piezoelectric device. An amplifier circuit is incorporated
in conjunction with the piezoelectric device to receive the first
signal and convert it into a second signal that will provide an
actual pressure reading.
[0013] In some instances it is desirable to measure engine torque
by actually measuring absolute pressure at certain time intervals.
On the other hand, some torque measuring methods may be utilized to
measure the accumulated pressure over a time period by integrating
a differential pressure signal.
[0014] It is, therefore, a still further object of this invention
to provide a method for utilizing a pressure sensor to derive
either instantaneous change in pressure signals or absolute
pressure signals.
SUMMARY OF THE INVENTION
[0015] This invention is adapted to be embodied in a method and
apparatus for measuring the torque of an engine during its running
and for a selected cycle. The engine has a combustion chamber and
an output shaft that is driven by combustion in the combustion
chamber. Means are provided for measuring the pressure in the
combustion chamber and also for measuring the output shaft
angle.
[0016] In accordance with a method for practicing the invention,
the combustion chamber pressure is measured between no more than
two different crank angles, and the engine output torque is
determined from these two measurements.
[0017] In accordance with an apparatus for performing this
invention, means are provided for reading the combustion chamber
pressure at two distinct crank angles and calculating the engine
torque from these two readings.
[0018] In accordance with a method embodying another feature of the
invention, instantaneous engine speed for a portion of the rotation
of the output shaft of an engine is measured. The engine comprises
a shaft driven by the engine and an associated fixed component of
the engine that is juxtaposed to a portion of the shaft. A
permanent magnet is fixed to one of the shaft portion and the
component and a coil is fixed to the other of the shaft portion and
the component and is adapted to output a pulse upon the passage of
the coil and the permanent magnet upon rotation of the shaft for
indicating the angular position of the shaft. The method comprises
the steps of determining the shaft angle when the maximum positive
pulse is generated by the coil, determining the shaft angle when
the maximum negative pulse is generated by the coil, and measuring
the time interval between the maximum positive and negative pulses
to determine instantaneous shaft rotational speed.
[0019] Another feature of the invention is adapted to be embodied
in a method of sensing both absolute pressure in an engine
combustion chamber and the instantaneous change in pressure. This
method comprises a piezoelectric device that is adapted to be
exposed to combustion chamber pressure and output a first
electrical signal indicative of the change in pressure in the
combustion chamber. An amplifier circuit receives the first
electrical signal and transforms the first electrical signal into a
second electrical signal indicative of the pressure in the
combustion chamber. The method comprises the selection of one of
the first or second electrical signals to determine either the
change in pressure in the combustion chamber or the absolute
pressure in the combustion chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a block diagram and partial schematic of an
embodiment of the invention.
[0021] FIG. 2 shows the time histories demonstrating operation of
the embodiment of FIG. 1.
[0022] FIG. 3 shows crank angle histories of the combustion
pressure P.sub.2 and dP/d2 and the two detecting crank angles
.theta..sub.1, .theta..sub.2 for the output torque [T].
[0023] FIG. 4 is a block diagram of a second embodiment of the
invention, whereby pressure and rate of pressure signals are used
to determine the output torque [T].
[0024] FIG. 5 is a third embodiment of the invention where one
sensor value of either pressure P or dP/d.theta. is predetermined
and corresponds to a function represented in either Table 1, shown
in FIG. 12, or Table 3, shown in FIG. 14.
[0025] FIG. 6 is a fourth embodiment of the invention corresponding
to functions represented in Table 2 shown in FIG. 13 and Formula 1
shown in FIG. 11.
[0026] FIG. 7 is a fifth embodiment of the invention incorporating
the functions in Table 4 shown in FIG. 15.
[0027] FIG. 8 shows an alternate time T' of positive-to-negative
pulses instead of the time between positive top dead center pulses
T; this correspondence is represented in Table 4 shown in FIG.
15.
[0028] FIG. 9 shows alternate crank angles 2.sub.i wherein the
second angle is biased and the first angle is compensated as shown
in Table 5 shown in FIG. 16.
[0029] FIG. 10 shows alternate times T.sub.i wherein the second
time may be predetermined as shown in Table 6 shown in FIG. 17.
[0030] FIG. 11 shows Formula 1 which can be used to generate
reference time T.
[0031] FIG. 12 shows Table 1, which shows sample functions to
calculate detecting crank angles .theta..sub.i based on the engine
speed R.
[0032] FIG. 13 shows Table 2, which shows sample functions to
calculate detecting times T.sub.i based on Formula 1, also a
function of engine speed R.
[0033] FIG. 14 shows Table 3, which shows alternate functions for
crank angles .theta..sub.i without the engine speed R.
[0034] FIG. 15 shows Table 4, which shows the derivation of
alternate interval T' for positive-to-negative pluses using a
predetermined angle .theta..sub.T'.
[0035] FIG. 16 shows Table 5, which shows the derivation of the
first angle if the second angle is biased and refers to the
embodiment of FIG. 9.
[0036] FIG. 17 shows Table 6, which shows the derivation of the
first time if the second time is predetermined, as shown in the
embodiment of FIG. 10.
DETAILED DESCRIPTION OF THE INVENTION
[0037] The measurement of the torque of an internal combustion
engine for a motor vehicle is desirable for control of the fuel
injection and ignition timing, control of the EGR flow rate,
control of the secondary airflow rate to add to the exhaust gas,
and, for an engine with variable valve timing, control of the
opening and closing times of the intake and exhaust valves.
Referring now in detail to FIG. 1, a four-cycle engine is indicated
generally by reference numeral 11 and is shown as a cross-section
through a single cylinder. Since the internal details of the engine
11 are not necessary to understand the construction and operation
of the invention, they will be described only summarily and by
reference to a schematic drawing. Where a detailed description is
omitted, it may be considered to be conventional.
[0038] The engine 11 includes a cylinder block 12 having one or
more cylinder bores in which pistons 14 are supported for
reciprocation. The pistons 14 and cylinder bores, as well as an
attached cylinder head, define a combustion chamber 16. The pistons
14 are connected by means of connecting rods 18 to the throws of a
crankshaft, indicated generally by the reference numeral 20, and
supported within a crankcase in a known manner.
[0039] A fuel-air charge is delivered to the combustion chambers 16
through an induction system that includes an air cleaner (not
shown), which draws atmospheric air and delivers it to an induction
manifold 22. A flow-controlling throttle valve 24 is provided in
the induction manifold 22. This charge-forming system thus supplies
an air charge to the intake manifold 22 and includes an
electronically-operated fuel injector 26 having a discharge nozzle
(not shown) that sprays fuel into the intake manifold 22 downstream
of the throttle valves 24. Although manifold injection is
disclosed, it is to be understood that the invention may also be
employed in conjunction with direct cylinder injection or other
types of charge-forming systems, such as carburetors or the
like.
[0040] The charge formed in the induction system is then delivered
to the combustion chamber through the intake manifold 22 and past
an intake valve 28 operated by an overhead mounted camshaft (not
shown). The charge is compressed in the combustion chambers 16.
This charge is then fired by a spark plug 30 mounted in the
cylinder head of the engine and having its spark gap extending into
the combustion chamber 16. An ignition coil (not shown) is
connected to the spark plug 30 for it's firing, and the ignition
coil is controlled by an ignition circuit 32. The burnt charge is
discharged past exhaust valves 34 operated by an overhead exhaust
camshaft 36 to an exhaust system (not shown). The fuel injector 26
and ignition system are controlled by an air-fuel ratio control
unit, the construction of which may be considered to be
conventional, and therefore details of its construction will not be
discussed further except insofar as how the invention can be
practiced with such conventional control systems.
[0041] The engine torque-detecting system employs a pair of sensors
one of which is a combustion chamber pressure sensor 38 which may
be of the piezoelectric type and which produces a first electrical
signal indicative of change in pressure, which is normally
interconnected with a charge amplifier so as to produce, as an
output, second electrical signal indicative of pressure. This
pressure signal may be employed for certain types of controls but
in accordance with a feature of the invention, the direct output of
the piezoelectric device of the sensor 38 is employed for measuring
the torque of the engine. By using the direct output of the
piezoelectric device 38, the output signal is indicative of a
change or differential in pressure rather than absolute pressure
and this is important in being able to practice the invention and
measure output torque, as will be described.
[0042] In addition, the engine is provided with a crank reference
angle sensor 40 which is employed to provide signals for other
controls for the engine indicative of position of the shaft or by
counting the pulses in a given time the average shaft speed. In
conjunction with the torque measuring aspect, the output of this
position sensor is utilized so as to measure engine speed during
single cycle of operation so as to permit the accurate
determination of the engine output torque. Again, this will be
described in more detail later but in accordance with a feature of
the invention the reference angle signal is associated with one of
the camshafts, in this case the exhaust camshaft 36 which like the
intake camshaft (not shown) is driven in a suitable manner from the
crankshaft 20 at one-half crankshaft speed. By operating this
sensor from the camshaft rather than the crankshaft it is possible
to measure the speed at top dead center at the time when combustion
is occurring without having to discriminate between the cycle when
the engine fires and the portion of the cycle when the engine does
not fire.
[0043] It has been determined that the engine output torque may be
accurately determined during each cycle of operation of the engine
by taking measurements at .theta. finite crank angle or time
positions and either integrating the output of the piezoelectric
sensor 38 during this time period or actually comparing actual
pressure measurements at the two time periods. The embodiment of
FIGS. 1 and 2 uses the former method and selects as the two time
periods the time when the change in combustion chamber pressure in
relation to time (dP/dt) is at its maximum (pressure increase rate
is the greatest) and at another time when the change in pressure in
relation to time (dP/dt) is zero (this being the point of maximum
pressure, as will be seen hereinafter). Also, rather than measuring
the initial time t.sub.1 when the change in pressure is the
greatest, it is possible to make a calculation indicative of the
crank angle position when this condition will occur, as will become
apparent by the following description.
[0044] Referring now again to FIG. 1, an engine control unit 42, or
CPU, may be of the preferred construction as shown. Other engine
control or protection systems may be incorporated in the CPU 42,
but these embodiments will not be detailed in the discussion of the
present invention which deals only with the way engine torque is
measured to permit lean burn operation with maximum stability. Of
course other applications for this principle will present
themselves to those skilled in the art.
[0045] As shown in FIG. 1, the CPU 42 may first include a means 44
to determine the reference crank angle 2.sub.0 occurring at the
time t.sub.0. Second, a means 46 to calculate the reference time L
for the engine to rotate through a known angle and hence
instantaneous speed N.sub.s. Third, a means 48 to calculate the
time D from the reference crank angle position t.sub.0 to the time
t.sub.1 where it will be known that dP/dt is maximum. From the
calculation of the time D it is possible to determine at a stage 50
of the CPU 42 the time t.sub.1 when the change in pressure is
maximum.
[0046] These relationships can be best understood by reference to
FIG. 2 which shows, among other things, the output signal from the
crank or camshaft angle sensor 40 (curve A). The camshaft angle
sensor 40 is comprised of a permanent magnet that is affixed at a
point on the camshaft 36 which is indicative of top dead center
position after the intake valve has closed and when combustion has
been initiated. This magnet cooperates with a winding that is fixed
relative to the engine in proximity to the camshaft 36 and which
will output first a positive output signal when the magnet passes
it and then a signal which diminishes to a maximum negative value
when the camshaft 36 has rotated through a predetermined crank
angle 2 from the initial crank angle 2.sub.0 at the time T.sub.0.
This rotational angle 2.sub.N is then used at the stage 46 so as to
determine the time duration L that it takes the engine shaft
(camshaft 36 in this embodiment) to rotate through this angle and
this speed N.sub.s. This time is calculated by using a timer that
outputs a number of equal time pulses and the number of pulses for
the camshaft to rotate through the angle 2.sub.N is determine by
the output of the counter. This in essence gives an instantaneous
crankshaft speed and the time period L can be employed to determine
from known parameters the time delay D after T.sub.0 when the
maximum change in pressure will occur from the following
equation:
D=L.theta.[f+r.theta.(/L-C)]
[0047] In the foregoing equation, the factors f, r, and c are all
constants which can be determined experimentally.
[0048] As has been previously noted, it would be possible to
measure the point t.sub.1 by checking the output of the
piezoelectric part of the pressure sensor 38, but it is equally as
acceptable to calculate this time from the aforenoted equation and
thus simplify the overall control circuitry.
[0049] Thus, at the stage 50 of the CPU 42 the time t.sub.1 is
calculated as being equal to the following equation:
t.sub.1=t.sub.0+D
[0050] This time signal t.sub.1 is outputted to an integrating
circuit 54 so as to open a gate and permit this integrating circuit
54 to receive the output signal from the piezoelectric device of
the pressure sensor 38 so as to perform an integrating function as
follows:
T(torque)=.function..sub.t.sub..sub.2.sup.t.sup..sub.2dP
[0051] This integrating circuit 54 is shut off by a shut-off device
52 which shuts off the gate when the output from the piezoelectric
device of the pressure sensor 38 indicates that dP/dt=0, this being
the time t.sub.2 on the pressure curve shown in the FIG. 2C and
also the time when the change in pressure from the combustion
chamber pressure sensor 38 in relation to time reaches 0. This time
interval G is also equal to L.theta.w where w is a constant and L
is the value previously calculated by determining the speed of
rotation of the camshaft.
[0052] The integrating function occurring at the stage 54 thus
calculates output torque from an equation that can be determined
experimentally and then output signals are outputted to a fuel
control circuit, indicated at 56 and an ignition timing control
circuit 58 which controls the firing of the spark plug 30 through
the ignition circuit 32. This can be done in accordance with any
desired control strategy.
[0053] In the previously described embodiment, two specific time
intervals were chosen depending upon the rate of change of pressure
in the combustion chamber and the pressure variations during this
time period were integrated to determine torque. It has also been
determined that torque can be accurately determined by measuring
the actual difference in pressure signals from the pressure sensor
38 at two different time intervals or degrees of crankshaft
rotation during each cycle of engine operation so long as the
angular positions are accurately chosen. These two crankshaft
measurement angles .theta..sub.1 and .theta..sub.2 may be
determined to be the points in time when the change in pressure in
relation to time or crank angle is at a maximum and 0, respectively
as with the previously described embodiments. These points are not
determined by actual pressure measurements but merely by crank
angles. This may be seen by reference to FIG. 3 which shows the
combustion pressures as functions of the crank angles 2.sub.i. The
first angle 2.sub.1 may be chosen as the position near to the top
dead center (TDC) of the piston stroke; the other angle
.theta..sub.2 may be 10 to 20 degrees after the TDC. Here,
.theta..sub.1 is the crank angle corresponding to time t.sub.1 and
crank angle .theta..sub.2 corresponds to time t.sub.2. The pressure
differential dP/d2 may then be derived from the aforementioned
angle-time relationships and shown as in the lower curve of FIG. 3,
as a function of crank angle .theta..
[0054] In determining the time or crank angles .theta..sub.1 and
.theta..sub.2 when the pressure measurements are made it has to be
borne in mind that the change in pressure in the combustion chamber
is a function of when spark timing occurs. That is, the pressure
begins to rise rapidly whence the spark plug is fired after the
intake valve has been closed. Thus, in order to practice this
embodiment of the invention it is desirable to vary the angles
.theta..sub.1 and .theta..sub.2 in response to the change in spark
timing. Most engines operate with timing curves that vary in
relation to engine speed R and hence the shift in the measurement
angles .theta..sub.1 and .theta..sub.2 can be varied in response to
engine speed. Table 1 as shown in FIG. 12 and reproduced below
shows a number of variations in which this may be done in relation
to engine speed R. In this table the values of .theta..sub.x,
.alpha., .beta. and .phi. are constant and .theta..sub.0 is the
reference angle position when the camshaft position sensor 40
outputs its maximum plus signal as seen in FIG. 2A.
1 TABLE 1 1 ( 1 = 0 + x - UR 1 = 0 + R 1 = 0 + R 1 = 0 + log R ) 2
( 2 = 1 + 2 = 1 + - R 2 = 1 + + R 2 = 1 + + R 2 = 1 + + log R )
[0055] It is also possible to practice the invention by actually
measuring the points when the change in pressure in relation to
time or crank angle is the maximum and when it is 0 by actually
measuring these conditions. As has been noted, the output of the
piezoelectric sensor portion of the pressure sensor 38, shown
schematically at 139 in FIG. 4 is indicative of dP/dt while the
actual output of the sensor and its amplifier, indicated
schematically at 138 in FIG. 4 is indicative of the actual
combustion chamber pressure P. The system shown in FIG. 4 can be
employed to measure the pressure at the maximum pressure change
condition and the second maximum pressure by actually determining
when these pressure conditions occur. This is done by using the
pressure value detected by the pressure sensor 138, when the value
dP/dt detected by the dP/dt sensor 139 is maximum and a maximum
pressure when the value of the dP/dt sensor 139 is zero. The
estimated output torque [T] is then calculated by the difference
between the higher pressure and the lower pressure.
[0056] The structure for doing this is as shown in FIG. 4. An
analog-to-digital converter (A/D) 142, is used to provide digitized
input to a data converter 144, which generates the parameters as a
function of the crank angle 2. These parameters, P(.theta.) and
dP/d.theta.(.theta.), are used by a data selector means 146 to
determine the values P(.theta..sub.1) and P(.theta..sub.2). These
values at the appropriate angle times may then be incorporated in
the calculating elements 148, 150 to generate the difference
between these pressures, which is used to calculate engine torque
[T].
[0057] Of course, in the system shown in FIG. 4, the computer must
have a program and memories to determine when the value dP/dt is
maximum and also if it is 0 so as to select the two measurements at
the points .theta..sub.1 and .theta..sub.2 as shown in FIG. 4. Of
course, this is well within the scope of those skilled in the
computer art.
[0058] As has been noted in conjunction with the description of the
embodiment involving the use of Table 1 as shown above and in FIG.
12, it is possible to have the system merely preprogrammed for the
angles .theta..sub.1 and .theta..sub.2 when the pressure or change
in pressure measurements are made. These points in time can be
determined experimentally by actual engine testing and then
programmed into the computer. Such another embodiment of the
invention is depicted in FIG. 5, whereby the crank angles
.theta..sub.i for the detecting pressures, or the detecting times,
are based on the engine speed R. A TDC angle sensor 240 is utilized
in conjunction with a chamber pressure sensor 238 and a A/D element
242 to generate the digital signals. A data converter 244 next
generates the pressure as a function of crank angle .theta., while
a calculating means 243 generates the engine speed R, which may be
determined as a function of the interval of the dead center pulses.
Sample values of the functions for the crank angles .theta..sub.1
and .theta..sub.2 may be as shown in Table 1, and the values for
constants .A-inverted., and ( are kept in a memory element 245. The
functions shown in FIG. 12, Table 1 may then be combined with the
engine speed information in a calculating element 247; the
resultant angles .theta..sub.1 and .theta..sub.2 are then utilized
in a data selector unit 246, which determines the corresponding
pressures at those angles. Calculating means 248, 250 then generate
the difference between the pressures to output the estimated engine
torque [T].
[0059] In the embodiment shown in FIG. 5, the system operates by
having a series of measured crank angles at which point the
pressure or change in pressure must be measured in order to obtain
the torque reading.
[0060] The embodiment of FIG. 6 does not utilize engine speed
information. A TDC angle sensor 340 and a chamber pressure sensor
338 are processed by an A/D unit 342 to generate digitized values;
the discrete angle sensor value is then used to generate a
reference time T in a calculating element 343 based on Formula 1,
as set out below and reproduced in FIG. 11 3 T 1 = T 0 + T R = T 0
360 + T .times. .times. R 360 = 1 360 ( T .times. 0 + T .times.
.times. 60 T ) = T + FORMULA1
[0061] , wherein .mu. and .nu. are constants. As shown in Table 2,
as set out below and reproduced in FIG. 13 sample functions are
used to determine the times for the detecting crank angles
.theta..sub.1 and .theta..sub.2, which are based on predetermined
constants .mu., .nu., .gamma. and .kappa..
2 TABLE 2 4 ( T 1 = T + T 1 = T + T 2 T 1 = T + T T T 1 + T + T log
T ) 5 ( T 2 = T 1 + T T 2 = T 1 + T + K T 2 = T 1 + T + KT 2 T 2 =
T 1 + T + KT T T 2 = T 1 + T + K T log t )
[0062] These values are stored in a memory 345 and used in a
calculating means 347 to determine times T.sub..theta.1 and
T.sub..theta.2 for the corresponding angles .theta..sub.1 and
.theta..sub.2. A data selector unit 346 next determines the
pressures at the selected times of the selected crank angles, which
pressures then go into calculating means 348,350 to determine the
difference in the pressures and the estimated engine torque
[T].
[0063] In the discussion previously when reference has been made to
engine speed R, the engine speed R has been generally considered
the speed that requires the engine to rotate through a complete or
series of revolutions. The normal output pulses from a crankshaft
rotational speed sensor are measured and summed in a time period to
determine engine speed as shown by the distance T in FIG. 8 which
shows successive pulses during a complete revolution either of the
crankshaft or, in the embodiments as described, of the camshaft.
However, as was noted in the earlier discussion, it is possible to
make an instantaneous time determination T' of a shorter time
interval between when the output pulse is at a maximum and minimum.
This may be utilized to shorten the sample time interval required
for the aforementioned calculations and if this data is used, then
some of the tables must be modified for this measure of
calculation. See for example Table 3, which is shown in FIG. 14 and
reproduced below, that could be utilized with the embodiment of
FIG. 5 wherein different values are given for the variable
constants dependent upon this information.
3 TABLE 3 6 ( 1 = 0 + R - 1 T 1 = 0 + 1 T 1 = 0 + 1 T 1 = 0 + 1 1
logT ) 7 ( 2 = 1 T 1 2 = 1 T - 1 T 2 = 1 + 1 T 2 = 0 + 1 T 1 = 0 +
1 - 1 1 log T )
[0064] An embodiment using this time T' as shown in FIG. 7, whereby
a crank angle sensor 440 is utilized along with a pressure rate
sensor 439. The values are processed through an A/D unit 442, and
the resulting digitized angle is processed in a detector element
for T'443.
[0065] Referring to Table 4, shown in FIG. 15 and also set out
below, a value for T is determined in a calculating means 444.
Referring again to Table 2, the constants .mu., .nu., .gamma. and
.kappa., in a memory 445, are utilized with time T in a calculating
element 447 to generate the times T.sub..theta.1 for angles
.theta..sub.1 and .theta..sub.2. An integrating element 449 is
utilized to determine the pressures at the crank angle times by
integrating the rate values from the time T.sub..theta.1 to the
T.sub..theta.2 directly to output the signal
P.sub.(T.theta.1)-P.sub.(T.theta.2) to the calculating means 450.
Calculating means 450 determines the estimated engine torque value
[T] from this data.
4TABLE 4 8 R = 60 .times. T 360 .times. T 1 = T 1 60 T 1 9 T = 360
T 1 T 1
[0066] As previously noted, because the ignition timing is
controlled relative to the engine speed R, it is shown in Table 1
that the crank angles for the detecting pressures, or the detecting
times, may be chosen by the CPU 42 based upon the engine speed R,
and at a low engine speed both of the times or angles may be
delayed, while at a high engine speed they may be advanced. As
shown in Table 1, .theta..sub.x .alpha., .beta., and .gamma. are
all constant values. The detecting crank angles may be changed as
shown in FIG. 9 and Table 5 set out below and reproduced in FIG.
16. If a second detecting crank angle .theta..sub.2 is biased by a
delta value (.DELTA..theta.), the first detecting crank angle would
then be advanced by a value equal to a constant C multiplied by
this delta value, where C is a value less than one.
5TABLE 5 10 2 - 2 1 = 1 - 1 1 = C 2 11 - 2 = 1 1 - 1 1 = C 1 1 C
< 1 C 1 < 1
[0067] Similarly, as shown in FIG. 10 and Table 6, shown below and
in FIG. 17 the detecting times may be changed. A calculating
program may choose T.sub..theta.'2 or T.sub..theta."2 (which is
predetermined) instead of T.sub..theta.2 as a second detecting
time. In this case, T.sub..theta.'1 must be used as the first
detecting time.
6TABLE 6 11 T 2 - T . 2 = T T 1 - T . 1 = C T C < 1 T 2 - T 2 =
T 1 T 1 - T . 1 = C . T 1 C . < 1
[0068] The preferred and alternate embodiments previously described
demonstrate that the use of one or two crank angle sensors yields
several possibilities for the generation of an engine torque value.
It has also been indicated that the crank angle sensor, in addition
to providing a signal indicative of crank angle, can be utilized to
provide an indication of accurate instantaneous engine shaft speed.
Although in the illustrated embodiments this has been done with one
sensor, it is to be understood that a number of such sensors may be
positioned at spaced intervals around the shaft so as to measure
instantaneous shaft speeds at desired shaft angles. Various other
changes and modifications may be made from the embodiments
presented herein without departure from the spirit and scope of the
invention, as defined by the appended claims.
* * * * *