Field of the Invention:
The invention generally relates to method and apparatus of controlling ignition in an internal
combustion engine.
Background of the Invention:
Controlling ignition in an internal combustion engine and more particularly, controlling the
ignition timing of the internal combustion engine is an important aspect. By controlling the
ignition timing of the internal combustion engine, it is possible to govern many aspects of
driving of a vehicle (incorporating the internal combustion engine) including but not limited
to fuel economy, emission performance, etc.
In many instances, for the purposes of attaining controlling of the ignition of the internal
combustion engine, different types of information are needed. For example, information
pertaining to amount of throttle provided by the user, amount of air intake, air fuel ratio,
sensor for detecting operating state of the engine (such as current engine stroke, current
engine RPM etc.) are taken into consideration. While considering different types of
information makes the controlling more accurate, the problem arises in terms of costing and
complexity when each piece of information is to be obtained from a corresponding sensor
disposed on the vehicle.
Thus, the attempt has been to perform the controlling action on basis of minimum number of
sensor-based inputs. In other words, if input from a single sensor can be used for deriving two
or more different types of information (that are relevant for the controlling process), it is
possible to derive advantages in terms of reduction in the manufacturing cost, reduction in
complexity of manufacturing etc. without compromising on accuracy of controlling the
ignition of the internal combustion engine.
In case the engine is a four-stroke engine i.e. if the internal combustion engine goes through
an intake stroke, a compression stroke, a combustion stroke and an exhaust stroke it has been
observed that large combustion energy is produced during the combustion stroke while
energy is consumed during the remaining three strokes. In particular, energy is consumed due
to work done during the exhaust stroke; energy is consumed due to work done during the
intake stroke; and energy is consumed due to work done during the compression stroke. It has
been furthermore observed that the amount of work done in the exhaust stroke, the intake
stroke and the compression stroke are not equal and hence, the energy consumed during these
3
three strokes different. It has been furthermore observed that the energy produced during the
combustion stroke as well as the energy consumed in each of the exhaust stroke, intake stroke
and combustion stroke depend upon the load on the vehicle. In particular, the amount of
energy produced during the combustion stroke in a low-load condition is substantially lesser
than the amount of energy produced during the combustion stroke in a high-load condition.
Likewise, the amount of energy consumed during each of the exhaust stroke, intake stroke
and combustion stroke in a low-load condition is lesser than the amount of energy consumed
during the exhaust stroke, intake stroke and combustion stroke (respectively) in a high-load
condition.
Because of the above, if a plot is drawn between instantaneous angular velocity and the
corresponding stroke, a curve 101 as shown in figure 1 is obtained. In particular, the
instantaneous angular velocity increases during the combustion stroke and reaches its
maximum just prior to completion of the combustion stroke as represented by portion 102.
During the exhaust stroke, the instantaneous angular velocity decreases as represented by
portion 103. Compared to the exhaust stroke, the instantaneous velocity further decreases
during the intake stroke as represented by portion 104. Also compared to the intake stroke,
the instantaneous velocity further decreases during the compression stroke as represented by
portion 105. At the end of the compression stroke, ignition is provided and as a result, the
instantaneous angular velocity increases and the curve progresses in a similar manner as
described above.
It has been further observed and reported that based on the load condition (or alternatively
throttle opening level), the curve 101 shifts in the vertical direction. In particular, if the load
condition increases, the curve 101 moves upwards and forms curve 106 while if the load
condition decreases, the curve 101 moves downwards and forms curve 107. Compared to
curve 101, rate of change of instantaneous angular velocity in curve 106 is higher and the rate
of change of instantaneous angular velocity in curve 107 is lower.
It has been observed that if the engine revolution per minute (RPM) is maintained constant,
there is a strong correlation between the variation amount of the angular velocity and required
ignition timing. Therefore, if the engine RPM (which should be a constant value) and the
amount of variation in the angular velocity are determined, it is possible to select appropriate
ignition timing (or ignition period).
4
On the basis of the above, Indian Patent Application No. 211/CHE/2009 describes an
operation controlling system for an internal combustion engine, comprising: a flywheel
coupled to a crankshaft; a reluctor coupled to the flywheel for measuring a revolution number
of the crankshaft; rotation-detecting means detecting passage of the reluctor; and a control
section calculating, from detection results by the rotation detecting means, an average
revolution number in a predetermined period and a partial crank angular velocity () of the
crankshaft that corresponds to a reluctor width, and determining an ignition period on the
basis of these calculation results, wherein: the control section simultaneously performs the
calculation of the crank angular velocity in a period in which the average revolution number
(Ne) is calculated in a stroke immediately prior to a compression stroke in which ignition is
to be performed, the crankshaft angular velocity (o) is calculated by dividing the angle
between a forward end of and a rearward end of the reluctor by the time () elapsed between
the detection of the forward end of the reluctor and the detection of the rearward end of the
reluctor (25a), the variation amount () of the crankshaft angular velocity () in the
compression stroke is calculated by subtracting the crankshaft angular velocity () from the
average revolution number (Ne), and the air intake amount is calculated by substituting the
variation amount () to a relation between the variation amount () of the crankshaft
angular velocity () per average engine revolution number (Ne) and the air intake amount,
and the ignition period is set by the air intake amount.
While the above patent application is able to control ignition of the internal combustion
engine merely on basis of input from a reluctor coupled to flywheel, the process adopted for
controlling the ignition merely takes into consideration difference in angular velocity as a
single parameter and hence, the accuracy of the calculations is restricted.
Thus, there is need to provide an alternative method and an apparatus for controlling ignition
in an internal combustion engine that is easy to implement and wherein the above mentioned
difficulties / deficiencies are reduced.
Summary of the Invention:
In accordance with these and other objects of the invention, a brief summary of the invention
is presented. Some simplifications and omissions may be made in the summary, which is
intended to highlight and introduce some aspects of the present invention, but not limit its
scope.
5
Accordingly, the present invention provides a method for controlling ignition in an internal
combustion engine, the internal combustion engine going through an intake stroke, a
compression stroke, a combustion stroke and an exhaust stroke. The method comprises
receiving a plurality of pulses from a reluctor operably coupled to the crank shaft and
determining a value of engine rotation per minute (RPM). The method further comprises
determining a first angular velocity of the crank shaft during a first exhaust stroke based on a
first sub-set of pulses and a second angular velocity of the crank shaft during a first
compression stroke based on a second sub-set of pulses. The method further comprises
determining at least one of a third angular velocity of the crank shaft during a second
compression stroke based on a third sub-set of pulses and a fourth angular velocity of the
crank shaft during a second exhaust stroke based on a fourth sub-set of pulses. The method
further comprises determining a de-acceleration amount between the first and the second
angular velocities of the crank shaft. The method further comprises determining an
acceleration amount, the acceleration amount being between the third angular velocity and
the first angular velocity or alternatively between the second angular velocity and the fourth
angular velocity. The method furthermore comprises selecting an ignition period based on (a)
the value of engine RPM thus determined, (b) the de-acceleration amount thus determined
and (c) the acceleration amount thus determined.
The present invention further provides an apparatus for controlling ignition in an internal
combustion engine, the internal combustion engine going through an intake stroke, a
compression stroke, a combustion stroke and an exhaust stroke. The apparatus comprises a
first unit for receiving plurality of pulses from a reluctor operably coupled to a crank shaft
and determining a value of engine rotation per minute (RPM); a second unit for determining a
de-acceleration amount, said de-acceleration amount being between a first angular velocity of
the crank shaft and a second angular velocity of the crank shaft, the first angular velocity of
the crank shaft being determined during a first exhaust stroke based on a first sub-set of
pulses and the second angular velocity of the crank shaft being determined during a first
compression stroke based on a second sub-set of pulses; a third unit for determining an
acceleration amount, said acceleration amount being between a third angular velocity of the
crankshaft and the first angular velocity of the crankshaft or alternatively between the second
angular velocity of the crankshaft and a fourth angular velocity of the crankshaft, the third
angular velocity of the crank shaft being determined during a second compression stroke
based on a third sub-set of pulses and the fourth angular velocity of the crank shaft being
6
determined during a second exhaust stroke based on a fourth sub-set of pulses; and a fourth
unit for selecting an ignition period based on (a) the value of engine RPM thus determined
and (b) the de-acceleration amount thus determined and (c) the acceleration amount thus
determined.
To further clarify advantages and features of the present invention, a more particular
description of the invention will be rendered by reference to specific embodiments thereof,
which is illustrated in the appended drawings. It is to be appreciated that these drawings
depict only typical embodiments of the invention and are therefore not to be considered
limiting of its scope. The invention will be described and explained with additional
specificity and detail with the accompanying drawings.
Brief Description of Figures:
These and other features, aspects, and advantages of the present invention will become better
understood when the following detailed description is read with reference to the
accompanying drawings in which like characters represent like parts throughout the
drawings, wherein:
Figure 1 shows the curves obtained by plotting instantaneous angular velocity and their
corresponding engine stroke;
Figure 2 shows a detailed view of a flywheel mounted with at least one reluctor and pickup
unit adapted to sense passing of the reluctor in accordance with an embodiment of the
invention;
Figure 3 shows flow chart of a method corresponding to a first embodiment of the invention;
Figure 4 shows flow chart of a method corresponding to a second embodiment of the
invention;
Figure 5 shows flow chart of a method corresponding to a third embodiment of the
invention;
Figure 7 shows a graph between the first load ratio, and de-acceleration amount for two
different engine RPM values; and
7
Figure 7 shows block diagram of an apparatus in accordance with the teachings of the
invention.
Further, skilled artisans will appreciate that elements in the drawings are illustrated for
simplicity and may not have been necessarily been drawn to scale. For example, the flow
charts illustrate the method in terms of the most prominent steps involved to help to improve
understanding of aspects of the present invention. Furthermore, in terms of the construction
of the device, one or more components of the device may have been represented in the
drawings by conventional symbols, and the drawings may show only those specific details
that are pertinent to understanding the embodiments of the present invention so as not to
obscure the drawings with details that will be readily apparent to those of ordinary skill in the
art having benefit of the description herein.
Detailed Description:
For the purpose of promoting an understanding of the principles of the invention, reference
will now be made to the embodiment illustrated in the drawings and specific language will be
used to describe the same. It will nevertheless be understood that no limitation of the scope of
the invention is thereby intended, such alterations and further modifications in the illustrated
system, and such further applications of the principles of the invention as illustrated therein
being contemplated as would normally occur to one skilled in the art to which the invention
relates.
It will be understood by those skilled in the art that the foregoing general description and the
following detailed description are exemplary and explanatory of the invention and are not
intended to be restrictive thereof.
Reference throughout this specification to “an aspect”, “another aspect” or similar language
means that a particular feature, structure, or characteristic described in connection with the
embodiment is included in at least one embodiment of the present invention. Thus,
appearances of the phrase “in an embodiment”, “in another embodiment” and similar
language throughout this specification may, but do not necessarily, all refer to the same
embodiment.
The terms "comprises", "comprising", or any other variations thereof, are intended to cover a
non-exclusive inclusion, such that a process or method that comprises a list of steps does not
8
include only those steps but may include other steps not expressly listed or inherent to such
process or method. Similarly, one or more devices or sub-systems or elements or structures or
components proceeded by "comprises a" does not, without more constraints, preclude the
existence of other devices or other sub-systems or other elements or other structures or other
components or additional devices or additional sub-systems or additional elements or
additional structures or additional components.
Unless otherwise defined, all technical and scientific terms used herein have the same
meaning as commonly understood by one of ordinary skill in the art to which this invention
belongs. The system, methods, and examples provided herein are illustrative only and not
intended to be limiting.
Embodiments of the present invention will be described below in detail with reference to the
accompanying drawings.
Now referring to figure 2, there is shown a more detailed view showing a flywheel 200 which
is connected to the crankshaft 201. The flywheel 200 is generally provided with a first
reluctor 202 and a second reluctor 203. The first reluctor 202 has smaller dimension as
compared to the second reluctor 203. Location of the second reluctor 203 on the flywheel 200
is such that it is positioned within a predetermined angle determined on basis of a crank
position before a top dead centre of a piston of the engine. Location of the first reluctor 202
on the flywheel 200 is such that it is positioned ahead of the second reluctor 203 by a fixed
angle (for example, 22.5 degrees). There is also provided a pickup 204 that detects passing of
the first reluctor 202 and the second reluctor 203.
In particular, when the pickup 204 detects:
• a forward end of the first reluctor 202 in a crankshaft rotational direction as depicted
by arrow 205, it outputs a first rise pulse 206;
• a rearward end of the first reluctor 202 in a crankshaft rotational direction as depicted
by arrow 205, it outputs a first fall pulse 207;
• a forward end of the second reluctor 203 in a crankshaft rotational direction as
depicted by arrow 205, it outputs a second rise pulse 208; and
• a rearward end of the second reluctor 203 in a crankshaft rotational direction as
depicted by arrow 205, it outputs a second fall pulse 209.
9
It may however be noted that providing the first reluctor 202 in itself is not a compulsion, in
which case the pickup 205 may not output the first rise pulse and the first fall pulse and may
merely output the rise pulse in response to detecting the forward end of the second reluctor
203 the fall pulse in response to detecting the rearward end of the second reluctor 203.
On the basis of the rise and fall pulses that are output by the pickup 204, which correspond to
the second reluctor 203, an ignition controlling method is implemented. In case pickup 204
outputs the first rise pulse and the first fall pulse corresponding to the first reluctor 202 and
the second rise pulse and the second fall pulse corresponding to the second reluctor 203, the
ignition controlling method can either take into consideration only the second rise and the
second fall pulses or all of the four pulses.
Since the second reluctor 203 is located on the flywheel so as to be within a predetermined
angle determined on basis of a crank position before a top dead centre of a piston of the
engine, for every 360 degree rotation of the crankshaft, the pickup 204 outputs one rise pulse
and one fall pulse corresponding to the second reluctor 203. Likewise, for every 360 degree
rotation of the crankshaft, the pickup 204 outputs one rise pulse and one fall pulse
corresponding to the first reluctor 202 (if the first reluctor 202 is provided).
When the engine is continuously rotating, the pickup 204 thus provides a set of pulses. Since
the top dead centre of the piston corresponds to either an exhaust stroke or a compression
stroke, the pulses are generated during a exhaust stroke and the compression stoke and hence,
for the purposes of ease of identification and nomenclature, the pulses received during a first
exhaust stroke are being referred to as first sub-set of pulses, the pulses received during a first
compression stroke are referred to as second sub-set of pulses, the pulses received during a
second compression stroke are referred to as third sub-set of pulses and the pulses received
during a second exhaust stroke are referred to as fourth sub-set of pulses. It may be thus noted
that each of the first, the second, the third and the fourth sub-set of pulses may comprise of
rise and fall pulses that correspond to the second reluctor 203 or alternatively the first rise
pulse, the first fall pulse (that correspond to the first reluctor 202) and the second rise pulse
and the second fall pulse (that correspond to the second reluctor 203).
Each of the first reluctor 202 and the second reluctor 203 has a predetermined angular width.
Therefore, based on a time of receipt of the second rise pulse 208 and a time of receipt of the
second fall pulse 209 it is possible to calculate the angular velocity corresponding to the
10
passing of the second reluctor 203. Likewise, based on a time of receipt of the first rise pulse
206 and a time of receipt of the first fall pulse 207 it is possible to calculate the angular
velocity corresponding to the passing of the first reluctor 202.
Now referring to figure 3, there is illustrated a flow chart of a method 300 for controlling
ignition in an internal combustion engine in accordance with an embodiment of the invention
wherein the internal combustion engine goes through an intake stroke, a compression stroke,
a combustion stroke and an exhaust stroke. The method 300 comprises receiving 301 a
plurality of pulses from a pickup 204 corresponding to at least one reluctor 203 and/or 202
operably coupled to the crank shaft 201. Based on the received pulses, the method proceeds
to determining 302 a value of engine rotation per minute (RPM). The method further
comprises determining 303 a first angular velocity of the crank shaft during a first exhaust
stroke based on a first sub-set of pulses. The method further comprises determining 304 a
second angular velocity of the crank shaft during a first compression stroke based on a
second sub-set of pulses. The method 300 further comprises determining 305 a third angular
velocity of the crank shaft during a second compression stroke based on a third sub-set of
pulses. The method further comprises determining 306 a de-acceleration amount between the
first and the second angular velocities of the crank shaft, determining 307 an acceleration
amount between the third angular velocity and the first angular velocity and selecting 308 an
ignition period based on (a) the value of engine RPM thus determined and (b) the deacceleration
amount thus determined and (c) the acceleration amount thus determined.
Referring to figure 4, there is illustrated a flow chart of a method 400 for controlling ignition
in an internal combustion engine in accordance with another embodiment of the invention.
The method 400 comprises receiving 301 a plurality of pulses from a pickup 204
corresponding to at least one reluctor 203 and/or 202 operably coupled to the crank shaft 201.
Based on the received pulses, the method proceeds to determining 302 a value of engine
rotation per minute (RPM). The method 400 further comprises determining 303 a first
angular velocity of the crank shaft during a first exhaust stroke based on a first sub-set of
pulses. The method 400 further comprises determining 304 a second angular velocity of the
crank shaft during a first compression stroke based on a second sub-set of pulses. The method
400 further comprises determining 401 a fourth angular velocity of the crank shaft during a
second exhaust stroke based on a fourth sub-set of pulses.
11
The method 400 further comprises determining 306 a de-acceleration amount between the
first and the second angular velocities of the crank shaft, determining 402 an acceleration
amount between the second angular velocity and the fourth angular velocity and selecting
403 an ignition period based on (a) the value of engine RPM thus determined and (b) the deacceleration
amount thus determined and (c) the acceleration amount thus determined.
It may be noted that whenever the specification refers to receiving pulses (such as first subset
of pulses, second sub-set of pulses, third sub-set of pulses and fourth sub-set of pulses),
the time of receiving the pulses is recorded so as to determine the value of engine RPM, the
first angular velocity, the second angular velocity, the third angular velocity, the fourth
angular velocity, the de-acceleration amount and the acceleration amount.
By way of example, if the first angular velocity corresponds to time t1 and the second angular
velocity corresponds to time t2, then the de-acceleration amount is calculated as:
De-acceleration amount =

By way of another example, if the third angular velocity corresponds to time t3, then in one
embodiment the acceleration amount is calculated as:
Acceleration amount =

By way of example, if the fourth angular velocity corresponds to time t4, then in one
embodiment the acceleration amount is calculated as:
Acceleration amount =

Now referring to figure 5, there is illustrated a flow chart of a method 500 for controlling
ignition in an internal combustion engine in accordance with an embodiment of the invention
wherein the internal combustion engine goes through an intake stroke, a compression stroke,
a combustion stroke and an exhaust stroke. The method 500 comprises receiving 301 a
plurality of pulses from a pickup 204 corresponding to at least one reluctor 203 and/or 202
operably coupled to the crank shaft 201. Based on the received pulses, the method proceeds
to determining 302 a value of engine rotation per minute (RPM). The method further
comprises determining 303 a first angular velocity of the crank shaft during a first exhaust
stroke based on a first sub-set of pulses. The method further comprises determining 304 a
second angular velocity of the crank shaft during a first compression stroke based on a
12
second sub-set of pulses. The method 500 further comprises determining 305 a third angular
velocity of the crank shaft during a second compression stroke based on a third sub-set of
pulses. The method further comprises determining 306 a de-acceleration amount between the
first and the second angular velocities of the crank shaft and determining 307 an acceleration
amount between the third angular velocity and the first angular velocity. The method 500
further comprises estimating 501 a first throttle opening extent (first load ratio) on basis of
the value of engine RPM thus determined and the de-acceleration amount thus determined.
The method 500 further comprises estimating 502 a second throttle opening extent (second
load ratio) on basis of the value of engine RPM thus determined and the acceleration amount
thus determined. The method 500 further comprises calculating 503 an average throttle
opening extent on basis of the first throttle opening extent and the second throttle opening
extent and selecting 504 an ignition period based on (a) the value of engine RPM thus
determined; (b) the de-acceleration amount thus determined; (c) the acceleration amount thus
determined and (d) the average throttle opening extent thus determined.
It may be noted that in figure 5, the step of “determining 305 a third angular velocity of the
crank shaft during a second compression stroke based on a third sub-set of pulses” can be
replaced by the step of “determining 401 a fourth angular velocity of the crank shaft during a
second exhaust stroke based on a fourth sub-set of pulses” and the step of “determining 307
an acceleration amount between the third angular velocity and the first angular velocity” can
be replaced by the step of “determining 402 an acceleration amount between the second
angular velocity and the fourth angular velocity”.
It may be noted that in an alternative embodiment (not specifically illustrated), the step of
selecting 504 need not receive absolute value of the average throttle opening extent. Instead,
the average throttle opening extent can be categorized as being greater than 50% or as being
less than or equal than 50%. It is also feasible that more than two categories can be formed.
It may be noted that for a given value of engine RPM, there is a strong correlation between
the first throttle opening extent (first load ratio) and the de-acceleration amount. Figure 6
illustrates the nature of correlations between the first throttle opening extent (first load ratio)
and the de-acceleration amount for two different values of engine RPM. In particular, higher
is the de-acceleration amount at a particular value of engine RPM, higher would be the first
throttle opening extent (or higher would be the first load ratio). Between a first engine RPM
and a second engine RPM, wherein the second engine RPM is higher than the first engine
13
RPM, the de-acceleration amount is lesser as shown by graph 601 which corresponds to a
first (low) engine RPM and the graph 602 which corresponds to a second (high) engine RPM.
Thus, it is possible to store data pertaining to different de-acceleration amounts and the first
throttle opening level corresponding to such different values of de-acceleration amounts
corresponding to a particular value (or range) of engine RPM. In other words, it is possible to
store the data pertaining to graph 601. Likewise, it is possible to store the aforesaid type of
data for different values (or ranges) of engine RPM. In other words, it is possible to
additionally store data pertaining to graph 602 (and other such additional graphs, not
illustrated). Based on the data thus stored, the first throttle opening extent (first load ratio)
can be easily and effectively obtained. In other words, the step of estimating 501 may include
a step of fetching/obtaining data pertaining to the first throttle opening extent (first load
ratio), from a stored location, on basis of the value of engine RPM thus determined and the
de-acceleration amount thus determined.
Although not illustrated, for a given value of engine RPM, there is a strong correlation
between the second throttle opening extent (second load ratio) and the acceleration amount.
Hence, it is possible to store data pertaining to acceleration amounts, second throttle opening
extents and engine RPM values (in a mapped manner in relation to one another). Based on
the data thus stored, the second throttle opening extent (first load ratio) can be easily and
effectively obtained. In other words, the step of estimating 502 may include a step of
fetching/obtaining data pertaining to the second throttle opening extent (second load ratio),
from a stored location, on basis of the value of engine RPM thus determined and the
acceleration amount thus determined.
It can be seen that since the method of the present invention primarily takes into
consideration de-acceleration amount and acceleration amount, wherein each of the deacceleration
amount and the acceleration amount is determined as described in the above
portions. In this regard, in a preferred aspect of the invention, the second compression stroke
may be immediately preceding the first exhaust stroke. It may also be noted that in a
preferred aspect of the invention, the second exhaust stroke may be between the first
compression stroke and the compression stroke in respect of which the ignition period is to be
set/selected.
Thus, by adopting the method of the present invention, it is possible to attain the controlling
action on basis of minimum number of sensor-based inputs. Compared to Indian Patent
14
Application No. 211/CHE/2009, the method of the present invention is equally placed in
terms of the number of sensors used for deriving the controlling function. However,
compared to the method described in Indian Patent Application No. 211/CHE/2009, the
accuracy in selecting the ignition period is improved because of the fact that now we have
more parameters on basis of which the calculations are performed. By way of a first example,
the parameters include the first angular velocity, the second angular velocity, the time period
between the first angular velocity and the second angular velocity, the third angular velocity,
and the time period between the third angular velocity and the first angular velocity. By way
of a second example, the parameters include the first angular velocity, the second angular
velocity, the time period between the first angular velocity and the second angular velocity,
the fourth angular velocity and the time period between the second angular velocity and the
fourth angular velocity. In other words, angular velocities at three different points of time
(more particularly three different strokes) and at least two time differences between said three
angular velocities are available.
It may be noted that the first compression stroke is immediately preceding a compression
stroke in respect of which the ignition period is selected and the first exhaust stroke is
immediately preceding the first compression stroke; the second compression stroke is
immediately preceding the first exhaust stroke and the second exhaust stroke being between
the first compression stroke and the compression stroke in respect of which the ignition
period is selected.
Now referring to figure 7, there is illustrated an apparatus 700 for controlling the ignition
timing of the internal combustion engine by the implementing any of the method as described
above in accordance with the teachings of the invention.
In particular, the apparatus 700 comprises a first unit 701 (or alternatively referred to as
engine RPM calculating section) for receiving plurality of pulses from a pickup 204
corresponding to at least one reluctor 203 and/or 202 operably coupled to the crank shaft 201
and determining a value of engine rotation per minute (RPM). The apparatus 700 further
comprises a second unit 702 (or alternatively referred to as de-acceleration amount
determining section) for determining a de-acceleration amount, said de-acceleration amount
being between a first angular velocity of the crank shaft and a second angular velocity of the
crank shaft, the first angular velocity of the crank shaft being determined during a first
15
exhaust stroke based on a first sub-set of pulses and the second angular velocity of the crank
shaft being determined during a first compression stroke based on a second sub-set of pulses.
The apparatus 700 further comprise a third unit 703 (or alternatively referred to as
acceleration amount determining section) that can calculate an amount of acceleration. In one
embodiment, said acceleration amount is between a third angular velocity of the crank shaft
and the first angular velocity of the crank shaft, the third angular velocity of the crank shaft
being determined during a second compression stroke based on a third sub-set of pulses. In
another embodiment, the acceleration amount is between the second angular velocity of the
crank shaft and a fourth angular velocity of the crank shaft, the fourth angular velocity of the
crank shaft being determined during a second exhaust stroke based on a fourth sub-set of
pulses.
The apparatus 700 furthermore comprises a fourth unit 704 (or alternatively referred to
ignition period selection section) for selecting an ignition period based on (a) the value of
engine RPM thus determined, (b) the de-acceleration amount thus determined and (c) the
acceleration amount thus determined.
The apparatus 700 may contain additional elements and each of such additional elements as
may be present is described herein below. By way of a non-limiting example, the apparatus
may comprise angular velocity calculating section(s) 705. The angular velocity calculation
section(s) 705 may be configured to calculate the first angular velocity, the second angular
velocity, the third angular velocity and the fourth angular velocity.
By way of another non-limiting example, the apparatus 700 may comprise a unit 706 (or
alternatively referred to as throttle opening extent estimating section) adapted to estimate a
first throttle opening extent (first load ratio) on basis of the value of engine RPM thus
determined and the de-acceleration amount thus determined. The throttle opening extent
estimating section 706 may further be adapted to estimate a second throttle opening extent
(second load ratio) on basis of the value of the engine RPM thus determined and the
acceleration amount thus determined. The throttle opening extent estimating section 706 may
furthermore be adapted to calculate an average throttle opening extent on basis of the first
and the second throttle opening extent thus determined.
16
The throttle opening extent estimating section 706 may refer to data as may be pre-stored in a
memory unit 707 for the purpose of estimating the first throttle opening extent (first load
ratio) and the second throttle opening extent (second load ratio).
In case the apparatus 700 comprises the throttle opening extent estimating section 706, the
ignition period selection section 704 maybe adopted to receive estimate of the average
throttle opening extent as an additional input from the throttle opening extent estimating
section 705 and use the additional input while selecting the ignition period.
In an embodiment of the invention the RPM calculating section 701, the de-acceleration
amount determining section 702, the acceleration amount determining section 703, the
ignition period selection section 704, the angular velocity calculation section(s) 705 and the
throttle opening extent estimating section 706 can all be implemented within a microprocessor.
Alternatively, some, but not all of the RPM calculating section 701, the deacceleration
amount determining section 702, the acceleration amount determining section
703, the ignition period selection section 704, the angular velocity calculation section(s) 705
and the throttle opening extent estimating section 706 can be implemented within a microprocessor
and the remaining sections can be implemented as discreet components that are
operably connected to the micro-processor. In yet another alternative all of the RPM
calculating section 701, the de-acceleration amount determining section 702, the acceleration
amount determining section 703, the ignition period selection section 704, the angular
velocity calculation section(s) 705 and the throttle opening extent estimating section 706 can
be implemented as discreet components which are appropriately interconnected. Data
(including data as may be pre-stored and which may be retrieved during any processing step)
may be stored upon read only memory (ROM) or alternatively, volatile/erasable type of
memory, such as a random access memory (RAM).
The drawings the foregoing descriptions give examples of embodiments. Those skilled in the
art will appreciate that one or more of the described elements may well be combined into a
single functional element. Alternatively certain elements may be split into multiple functional
elements. Elements from one embodiment may be added to another embodiment. For
example, orders of process described herein may be changed and are not limited to the
manner described herein. Moreover the actions of any flow diagram need not be implemented
in the order shown; nor do all of the acts necessarily need to be performed. In addition, those
acts that are not dependent on other acts may be performed in parallel with the other acts. The
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scope of embodiments is by no means limited by these specific examples. The scope of
embodiments is at least as broad as the following claims.
While certain embodiments of the invention have been illustrated and described herein, it is
to be understood that the invention is not limited thereto. Clearly, the invention may be
otherwise variously embodied and practiced within the scope of the following claims.

We Claim:
1. A method for controlling ignition in an internal combustion engine, the internal
combustion engine going through an intake stroke, a compression stroke, a
combustion stroke and an exhaust stroke, said method comprising the steps of:
• receiving a plurality of pulses from a reluctor operably coupled to the crank
shaft and determining a value of engine rotation per minute (RPM);
• determining a first angular velocity of the crank shaft during a first exhaust
stroke based on a first sub-set of pulses and a second angular velocity of the
crank shaft during a first compression stroke based on a second sub-set of
pulses;
• determining at least one of a third angular velocity of the crank shaft during a
second compression stroke based on a third sub-set of pulses and determining
a fourth angular velocity of the crank shaft during a second exhaust stroke
based on a fourth sub-set of pulses;
• determining a de-acceleration amount between the first and the second angular
velocities of the crank shaft;
• determining an acceleration amount, the acceleration amount being between
the third angular velocity and the first angular velocity or alternatively
between the second angular velocity and the fourth angular velocity; and
• selecting an ignition period based on (a) the value of engine RPM thus
determined, (b) the de-acceleration amount thus determined, and (c) the
acceleration amount thus determined.
2. The method as claimed in claim 1, further comprising estimating a first throttle
opening extent (first load ratio) on basis of the value of engine RPM thus determined
and the de-acceleration amount thus determined.
3. The method as claimed in claim 1, further comprising estimating a second throttle
opening extent (second load ratio) on basis of the value of engine RPM thus
determined and the acceleration amount thus determined.
4. The method as claimed in any one of claims 2 or 3, further comprising calculating an
average throttle opening extent on basis of the first throttle opening extent and the
second throttle opening extent.
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5. The method as claimed in claim 4, wherein the average throttle opening extent is
categorized as being greater than 50% or as being less than or equal than 50%.
6. The method as claimed in claim 5, wherein selecting the ignition period is further
based on the average throttle opening extent.
7. An apparatus for controlling ignition in an internal combustion engine, the internal
combustion engine going through an intake stroke, a compression stroke, a
combustion stroke and an exhaust stroke, said apparatus comprising:
• a first unit for receiving plurality of pulses from a reluctor operably coupled to
a crank shaft and determining a value of engine rotation per minute (RPM);
• a second unit for determining a de-acceleration amount, said de-acceleration
amount being between a first angular velocity of the crank shaft and a second
angular velocity of the crank shaft, the first angular velocity of the crank shaft
being determined during a first exhaust stroke based on a first sub-set of
pulses and the second angular velocity of the crank shaft being determined
during a first compression stroke based on a second sub-set of pulses; and
• a third unit for determining an acceleration amount, said acceleration amount
being between a third angular velocity of the crankshaft and the first angular
velocity of the crankshaft or alternatively between the second angular velocity
of the crankshaft and a fourth angular velocity of the crankshaft, the third
angular velocity of the crank shaft being determined during a second
compression stroke based on a third sub-set of pulses and the fourth angular
velocity of the crank shaft being determined during a second exhaust stroke
based on a fourth sub-set of pulses; and
• a fourth unit for selecting an ignition period based on (a) the value of engine
RPM thus determined and (b) the de-acceleration amount thus determined and
(c) the acceleration amount thus determined.
8. The apparatus as claimed in claim 7, comprising a further unit adapted to: (a) estimate
a first throttle opening extent (first load ratio) on basis of the value of engine RPM
thus determined and the de-acceleration amount thus determined; (b) estimate a
second throttle opening extent (second load ratio) on basis of the value of the engine
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RPM thus determined and the acceleration amount thus determined; and (c) calculate
an average throttle opening extent on basis of the first and the second throttle opening
extent thus determined.
9. The apparatus as claimed in claim 8, wherein the further unit is operably connected to
a memory unit and is adapted to retrieve from the memory unit the first load ratio and
the second load ratio.
10. The apparatus as claimed in claim 8, wherein the further unit is operably connected to
the fourth unit such that the fourth unit selects the ignition period based on (a) the
value of engine RPM thus determined; (b) the de-acceleration amount thus
determined; (c) the acceleration amount thus determined and (d) the average throttle
opening extent thus determined.