Technical Field
[0001] The present invention relates to an ignition control device, an internal combustion
engine and a motorcycle including the same.
Background Art
[0002] In some occasions (e.g., starting of an engine), a crank shaft of a motorcycle engine
revolves in a reverse direction (note a reverse revolution of the engine crank shaft
will be hereinafter simply referred to as "a reverse revolution of the engine"). Because
of this, a variety of components of the motorcycle receive considerable shock. Specifically,
the reverse revolution of the engine occurs by the following mechanism. In some occasions
(e.g., starting of an engine), when an ignition is executed by an ignition plug immediately
before a piston reaches a top dead center within a cylinder of the engine while a
revolution speed of the engine is low, the piston is pushed back by an explosion of
the ignition before reaching the top dead center. Accordingly, the engine is about
to revolve in the reverse direction and suddenly stops revolving.
[0003] A variety of engine start devices have been conventionally produced for preventing
the aforementioned phenomenon. The engine start devices are mainly configured to prevent
an operation of an ignition device until a revolution speed of the engine reaches
a predetermined speed. Additionally, the engine start devices are configured to control
whether or not an ignition should be executed simply using a revolution speed of the
engine as a threshold. In this case, an ignition is always prevented when the revolution
speed of the engine is equal to or less than the threshold regardless of the amount
of speed reduction of engine revolution. Accordingly, an ignition may be prevented
even in a normal driving operation that the engine does not revolve in the reverse
direction. In this case, a continuous normal driving operation will be blocked. On
the other hand, when the threshold is set for preventing the useless blockage of the
continuous normal driving operation, the reverse revolution of the engine may not
be effectively prevented.
[0004] Moreover, it is widely known that the reverse revolution of the engine occurs in
some occasions other than starting of the engine. Therefore, it is desirable to take
actions for reliably inhibiting the aforementioned phenomenon in the occasions other
than starting of the engine.
[0005] In response to this, Patent Document 1 (
JP-A-2006-274998) proposes an internal combustion engine for inhibiting shock caused by the reverse
revolution of the engine not only at the starting of the engine but also at all speed
levels of the engine. According to the Patent Document 1, it is determined whether
or not the aforementioned phenomenon occurs based on a computation of the amount of
speed reduction of engine revolution. Depending on the determination, either a so-called
hard ignition (i.e., a type of ignition not controlled by a program) or a retard ignition
whose ignition timing is set to be later than the hard ignition is configured to be
executed.
Patent Document 1
Disclosure of the Invention
Technical Problem
[0007] As described above, the internal combustion engine disclosed in the Patent Document
1 is configured to compute the amount of speed reduction of engine revolution, determine
whether or not the engine revolve in the reverse direction, and execute an ignition
control. In this case, a pulser is configured to generate a plurality of pulse signals
in an engine revolution for computing the amount of speed reduction of engine revolution.
Specifically, 12 protrusions are provided on the outer periphery of a rotor of an
outer-rotor magneto-generator. The pulser is configured to detect passage of the protrusions
and generate a plurality of pulse signals immediately before the ignition is executed.
Based on the pulse signals, the amount of speed reduction of engine revolution is
computed.
[0008] The protrusions are required to be accurately disposed on the rotor. This will be
a cause of cost increase in manufacturing. On the other hand, a plurality of pulse
signals are obtained in a revolution of the engine. It is therefore possible to highly-accurately
detect the amount of speed reduction of engine revolution immediately before the ignition.
However, high-speed control processing will be required because a period of a signal
is short. As a result, expensive components will be required for the control processing.
[0009] It is an object of the present invention to determine whether or not the amount of
speed reduction of engine revolution is equal to or greater than a predetermined amount
with a simple structure, and inhibit shock on a variety of components due to a reverse
revolution of an engine with a cheap structure.
[Solution to Problem]
[0010] An ignition control device according to the present invention includes revolution
speed detection means, revolution speed reduction detection means and ignition prevention
means. The revolution speed detection means is configured to detect a revolution speed
at a given timing in an engine revolution. The revolution speed reduction detection
means is configured to detect the amount of speed reduction from a previous engine
revolution to a present engine revolution based on the detection by the revolution
speed detection means. The present engine revolution is defined as an engine revolution
in which an ignition is executed (i.e., an engine revolution performed in a present
engine stroke-cycle). On the other hand, the previous engine revolution is defined
as an immediately previous engine revolution from the present engine revolution (i.e.,
an engine revolution performed in an engine stroke-cycle immediately before the present
engine stroke-cycle). The ignition prevention means is configured to prevent the ignition
in the present engine revolution when the amount of speed reduction detected by the
revolution speed reduction detection means is greater than a predetermined amount.
[0011] According to the ignition control device of the present invention, a revolution speed
of the engine is detected at a given timing in a revolution of the engine. Based on
the detection, the amount of speed reduction of engine revolution is detected for
both of the present engine revolution in which the ignition is executed and the immediately
previous engine revolution from the present engine revolution. When the amount of
speed reduction is greater than a predetermined amount, the ignition in the present
engine revolution is prevented. With the prevention of the ignition, it is possible
to inhibit shock on a variety of components due to the reverse revolution of the engine.
[0012] In this case, the revolution speed of the engine at a giving timing in a revolution
is just detected, and the amount of speed reduction from the previous engine revolution
to the present engine revolution. Therefore, the ignition control device is not required
to generate a plurality of pulse signals in a revolution of the engine and detect
the amount of speed reduction of engine revolution immediately before an ignition
timing. In this regard, the present invention is different from the conventional arts.
Therefore, a rotation member, provided in the ignition control device, is not required
to have a plurality of protrusions. For example, it is possible to detect the amount
of speed reduction of engine revolution using a rotor member including only one protrusion.
Moreover, high-speed control processing is not required for the present invention.
Accordingly, the control processing will be simple.
Advantageous Effects of the Invention
[0013] According to the present invention, it is possible to determine whether or not the
amount of speed reduction of engine revolution is equal to or greater than a predetermined
amount with a simple structure. Additionally, it is possible to inhibit shock on a
variety of members due to the reverse revolution of the engine with a cheap structure.
Brief Explanation of the Drawings
[0014]
Figure 1 is composed of schematic diagrams (1(a) and 1(b)) for explaining two patterns
of reverse revolution of an engine.
Figure 2 is composed of a chart (2(a)) and a schematic diagram (2(b)) for indicating
a relation between the amount of speed reduction of engine revolution and whether
or not the engine revolves in the reverse direction.
Figure 3 is composed of diagrams (3(a) to 3(d)) for indicating a relation among a
protrusion provided in a rotor, an output signal generated by a pulser, and a signal
obtained by shaping a waveform of the output signal.
Figure 4 is a chart for indicating a relation among the amount of speed reduction
of engine revolution, whether or not the engine revolves in the reverse direction,
and a time when the protrusion passes through the pulser in a previous engine revolution.
Figure 5 is a chart for indicating a relation between a continuous reverse revolution
angle and whether or not an ignition is executed.
Figure 6 is a chart for indicating the amount of speed reduction of engine revolution
measured when an ignition control is executed under a condition that occurrence of
a reverse revolution of the engine is predicted.
Figure 7 is composed of a side view of a motorcycle that an ignition control device
of an embodiment of the present invention is adopted and a schematic diagram of an
ignition system.
Figure 8 is a block diagram of the ignition system.
Figure 9 is composed of flowcharts for explaining an ignition control.
[Embodiments for Carrying Out the Invention]
[0015] Following are examination and analysis results regarding occurrence and inhibition
of a reverse revolution of the engine by inventors of the present application.
[0016] First, the present invention is based on the following technical idea: whether or
not an engine revolves in the reverse direction is predictable based on the amount
of speed reduction of engine revolution. The technical idea will be hereinafter explained
in detail.
[0017] The inventors compared and examined the speed reduction of engine revolution in a
normal driving operation and that in the reverse revolution of the engine. As a result,
they found that the latter speed reduction was greater than the former speed reduction.
The difference is based on whether or not a cylinder piston of the engine in a combustion
stroke of the previous stroke-cycle has a crank revolution force enough to allow the
piston to reach the top dead center (TDC) in a compression stroke of the next stroke-cycle.
[0018] The engine easily revolves in the reverse direction in the following driving condition:
a throttle is roughly half opened rapidly in an idling state. The inventors examined
whether or not the engine revolves in the reverse direction in this driving condition.
As a result, they confirmed that the cylinder piston could not reach the top dead
center (TDC) in the compression stroke mainly in the following two cases.
[0019] Figure 1(a) illustrates one of the cases. In this case, the force of the cylinder
piston (i.e., the revolution force of the crank shaft) is less than the pressure generated
in the combustion stroke. Accordingly, the cylinder piston is pushed back before reaching
an ignition position (IT). In this case, an onset of the reverse revolution of the
engine comes before the cylinder piston reaches the ignition position (IT), and only
the pressure, generated in the compression stroke, pushes down the piston. Therefore,
the crank shaft revolves slightly less than once in the reverse direction, and stops
revolving.
[0020] On the other hand, Fig. 1(b) illustrates the other case. Similarly to the case of
Fig. 1(a), the piston is pushed back before reaching the ignition position (IT) because
the force of the piston is less than the pressure generated in the combustion stroke.
In the case of Fig. 1(b), however, the onset of the reverse revolution of the engine
corresponds to when the cylinder piston is positioned between the ignition position
(IT) and the top dead center (TDC) in the compression stroke. Specifically, the onset
of the reverse revolution of the engine comes after the cylinder piston reaches the
ignition position (IT) and before the cylinder piston reaches the top dead center
(TDC) in the compression stroke. Consequently, an ignition is herein executed. However,
it takes some time to expand combustion since the ignition by an ignition plug of
the engine cylinder. Therefore, combustion expands after the cylinder piston is pushed
back (i.e., after the engine starts revolting in the reverse direction). The revolution
force of the engine is thus generated in the course of combustion. In this case, the
cylinder piston is pushed by the pressure in the compression stroke and the revolution
force generated in the combustion stroke of the previous stroke-cycle. Therefore,
the cylinder piston is more strongly pushed down than the case of Fig. 1(a). As a
result, the engine revolves roughly twice in the reverse direction.
[0021] Also, the speed reduction of engine revolution in the normal driving condition is
classified as a case that the cylinder piston is capable of reaching the top dead
center (TDC). Therefore, the engine often continues revolving.
[0022] Experimental results will be hereinafter explained regarding whether or not the engine
revolves in the reverse direction and an extent (i.e., angle) of the reverse revolution
of the engine.
[0023] Based on the aforementioned examination result, the inventors reached the following
conclusion. It is possible to discriminate the following two cases using the amount
of speed reduction of engine revolution as a criterion: (1) a case that the piston
is capable of reaching the top dead center (TDC) in the compression stroke; and (2)
a case that the piston is incapable of reaching the top dead center (TDC) in the compression
stroke. Here, the case (1) means that the engine is capable of continuing revolting,
whereas the case (2) means that the engine simply stops revolving or stops revolving
after revolving in the reverse direction. As a conclusion, it is possible to inhibit
the extent (i.e., angle) of reverse revolution of the engine and further inhibit shock
on a variety of components due to the reverse revolution of the engine by preventing
an ignition when the piston is incapable of reaching the top dead center (TDC) in
the compression stroke.
[0024] The aforementioned patent document 1 also discloses a similar mechanism for predicting
the reverse revolution of the engine using the amount of speed reduction of engine
revolution. According to the patent document 1, a plurality of pulse signals are generated
while the engine (i.e., the crank shaft) revolves once. The amount of speed reduction
of engine revolution, immediately before the ignition of the engine, is then computed
based on the plurality of pulse signals. More specifically, according to the patent
document 1, the amount of speed reduction of engine revolution, in a period from the
intake stroke to the compression stroke, is computed based on the plurality of pulse
signals generated in the meantime. Based on the computation result, it is determined
whether or not the engine revolves in the reverse direction. Moreover, based on the
determination result, the ignition timing is controlled.
[0025] According to the examination and analysis results, the inventors found that the reverse
revolution of the engine is predictable without detailed detection of the revolution
speed of the engine in the present engine revolution in which an ignition is executed.
In other words, they found that the reverse revolution of the engine is predictable
with high probability by detecting the amount of speed reduction of engine revolution
from a predetermined crank timing of the previous engine revolution and that of the
present engine revolution, and by categorizing the amount of speed reduction of engine
revolution into two groups using a predetermined threshold. Note the term "the present
engine revolution" hereinafter means an engine revolution in which an ignition is
executed. On the other hand, the term "the previous engine revolution" hereinafter
means an immediately previous engine revolution from the present engine revolution.
The above fact was derived by the following conclusion that the inventors finally
reached. In short, the amount of speed reduction of engine revolution is mainly based
on:
- (a) the revolution force generated by an explosion (i.e., a pressure change within
a combustion chamber in each stroke); and
- (b) the friction force of revolution-related components.
Both of the forces (a) and (b) have unique values depending on engine types. Therefore,
the inventors found that the amount of speed reduction of engine revolution for predicting
the reverse revolution of the engine is obtained by detecting a difference between
the revolution speed of the engine in the previous engine revolution and that in the
present engine revolution without detecting the revolution speed of the engine in
a plurality of revolution angle positions immediately before the ignition. Moreover,
it is possible to compute the revolution speed in the previous engine revolution and
that in the present engine revolution, specifically, using a passage time of a protrusion
provided in a rotation member. In this case, the rotation member is configured to
rotate in conjunction with movement of a crank shaft. Additionally, the protrusion
has a predetermined length along a circumferential direction of the rotation member.
[0026] Figures 2(a) and 2(b) illustrate data for supporting the aforementioned technical
idea. Figure 2(a) illustrates the revolution speed of the engine in the present engine
revolution t
n and that in the previous engine revolution t
n-1, measured in a plurality of experiments. In Fig. 2(a), the vertical axis is the revolution
speed of the engine. Additionally, the revolution speed of the engine in the previous
engine revolution t
n-1 and that in the present engine revolution t
n in a predetermined experiment are connected with a line. Accordingly, it is possible
to clearly show a difference between the revolution speed of the engine in the previous
engine revolution t
n-1 and that in the present engine revolution t
n in a predetermined experiment. The data of Fig. 2(a) indicate changes of the revolution
speed of the engine and whether or not the engine revolves in the reverse direction.
The data were obtained under conditions that a throttle of a single-cylinder 4-stroke
gasoline engine was roughly half opened rapidly from an idling state. In Fig. 2(b),
a time period T1 corresponds to the revolution speed of the engine in the present
engine revolution, whereas a time period T2 corresponds to the revolution speed of
the engine in the previous engine revolution. Again, with reference to Fig. 2(a),
solid lines indicate the amount of speed reduction of engine revolution when the engine
revolved in the forward direction (i.e., the engine did not revolve in the reverse
direction). On the other hand, dashed lines indicate the amount of speed reduction
of engine revolution when the engine revolved in the reverse direction. In Fig. 2(a),
the engine obviously revolved in the reverse direction when a difference between the
time period T1 and the time period T2 is equal to or greater than a predetermined
value. As illustrated in Figs. 3(a) and 3(b), a protrusion 26 is provided in a rotor
25 of an outer-rotor magneto-generator. The rotor 25 is herein configured to rotate
in conjunction with a crank shaft 23. A pulser 27 is configured to detect passage
of the protrusion 26. A passage time T of the protrusion 26 is thus detected by the
pulser 27, and the revolution speed of the engine is computed based on the detected
passage time T. The protrusion 26 has a predetermined length along a circumferential
direction of the rotor 25. The circumferential length of the protrusion 26 corresponds
to a length of an arc of the rotor 25 having a central angle of 60 degrees. Note Fig.
7 similarly illustrates the structure.
[0027] More specifically, as illustrated in Fig. 3(a) and 3(b), the crank shaft 23 is configured
to revolve in the clockwise direction (i.e., a revolution direction R). As illustrated
in Fig. 3(a), the pulser 27 is configured to output a signal "u" of Fig. 3(c) at a
timing when the protrusion 26 starts passing through the pulser 27. Additionally,
as illustrated in Fig. 3(b), the pulser 27 is configured to output a signal "d" of
Fig. 3(c) at a timing when the protrusion 26 finishes passing through the pulser 27.
The signals "u" and "d" are inputted into a CDI unit 28 illustrate in Fig. 7. The
waveforms of the signals "u" and "d" are shaped by the CDI unit 28, and a new pulse
signal is subsequently produced as illustrated in Fig. 3(d).
[0028] In this case, signals, outputted at timings T1u and T2u of Fig. 2(b), correspond
to the signal "u" of Fig. 3(c). On the other hand, signals, outputted at timings T1d
and T2d of Fig. 2(c), correspond to the signal "d" of Fig. 3(c).
[0029] Figure 4 is a chart created based on the data of Fig. 2(b). Figure 4 illustrates
a relation between the time period T2, corresponding to the revolution speed of the
engine in the previous engine revolution, and a time period T1-T2 (see square dots
of Fig. 4), corresponding to the revolution speed of the engine when the engine revolved
in the reverse direction. Simultaneously, Fig. 4 illustrates a relation between the
time period T2 and a time period T1-T2 (see circle dots of Fig. 4), corresponding
to the amount of speed reduction of engine revolution when the engine revolved in
the forward direction (i.e., the engine did not revolve in the reverse direction).
In Fig. 4, the horizontal axis is the time period T2, whereas the vertical axis is
the time period T1-T2 corresponding to the amount of speed reduction of engine revolution.
According to Fig. 4, the engine easily revolves in the reverse direction when the
value of T2 is large (i.e., when the-revolution speed of the engine in the previous
engine revolution is low). When the ignition is controlled using a predetermined rotation
speed of the engine in the previous engine revolution as a threshold, unnecessary
ignition control will be executed. Accordingly, a period of continuous engine revolution
will be shortened. Next, in focusing on the amount of speed reduction of engine revolution,
it is obviously possible to inhibit unnecessary ignition control when the ignition
is controlled using a predetermined value T1-T2 shown with a dashed-dotted line of
Fig. 4 as a threshold.
[0030] Figure 5 illustrates experimental results of execution and prevention of an ignition
under the condition of Fig. 1(b). Specifically, Fig. 5 illustrates a relation between
whether or not the ignition control was executed and a crank revolution angle Dr of
a continuous reverse revolution of the engine when the engine revolved in the reverse
direction (hereinafter referred to as "a continuous reverse revolution angle Dr").
In Fig. 5, the horizontal axis is data numbers, whereas the vertical axis is the continuous
reverse revolution angle Dr. The data of an area A corresponds to the case that the
ignition was executed, whereas the data of an area B corresponds to the case that
the ignition was not executed. As is obvious with respect to Fig. 5, the data of the
area A indicates that the engine continues revolving roughly twice (i.e., angle of
600 to 700 degrees) in the reverse direction. On the other hand, the data of the area
B indicates that the engine revolved slightly less than once in the reverse direction.
Therefore, the engine revolves slightly less than once in the reverse direction if
the ignition is prevented under the condition that occurrence of the reverse revolution
of the engine is predicted. As a result, it is possible to inhibit shock on a variety
of components due to reverse revolution of the engine and further inhibit damage of
the components.
[0031] Figure 6 comprehensively illustrates the above content. In Fig. 6, the horizontal
axis is a time, whereas the vertical axis is the revolution speed of the engine. In
Fig. 6, the throttle is roughly half opened rapidly at a time t while the engine revolves
at an idling revolution speed (IDL). In Fig. 6, a property S indicates a condition
that the engine continued revolving in the forward direction without revolving in
the reverse direction even when the throttle was rapidly opened. On the other hand,
properties P and Q indicate conditions that the engine revolved in the reverse direction.
Specifically, the property P indicates a condition that the ignition was prevented
when the throttle is rapidly opened under the condition that the amount of speed reduction
of engine revolution is large. On the other hand, the property Q indicates a condition
that the ignition was executed when throttle was rapidly opened under the condition
that the speed reduction of engine revolution was large. In this case, the reverse
revolution speed of the engine is low in the property P. Additionally, the continuous
reverse revolution angle is small in the property P. Specifically, the engine continued
revolving slightly less than once in the reverse direction as a result of an experiment.
On the other hand, the reverse revolution speed of the engine is high in the property
Q. Additionally, the continuous reverse revolution angle is large in the property
Q. Specifically, the engine continued revolving roughly twice in the reverse direction
as a result of an experiment. Based on the above, it is possible to inhibit shock
on a variety of components due to reverse revolution of the engine and further inhibit
damage of the components by detecting the amount of speed reduction of engine revolution,
predicting whether or not the engine revolves in the reverse direction based on the
amount of speed reduction of engine revolution, and preventing an ignition when occurrence
of the reverse revolution of the engine is predicted.
[0032] Figure 7 illustrates a motorcycle that an ignition control device of the engine according
to an embodiment of the present invention is adopted. Specifically, Fig. 7 is composed
of a left side view of the motorcycle and a schematic diagram of components of an
ignition system.
Entire Structure
[0033] As illustrated in Fig. 7, a motorcycle 1 according to an embodiment of the present
invention is of a so-called motorized bicycle type. The motorcycle 1 mainly includes
a man body frame 2, a pair of front and rear wheels 3 and 4, a seat 5, a power unit
6 and a cover member 7.
[0034] The main body frame 2 is mainly composed of a head pipe 10, a main frame 11, a pair
of right and left side frames (not illustrated in the figure). A steering shaft 12
is rotatably supported by the head pipe 10. A steering handle 13 is fixed to an upper
end of the steering shaft 12, whereas a front fork 14 is attached to a lower end of
the steering shaft 12. The front wheel 3 is supported by a lower end of the front
fork 14. The main body frame 2 is mostly covered with cover members.
[0035] The power unit 6 mainly includes a driving unit 16 and a transmission device 17.
The driving unit 16 includes a single-cylinder 4-stroke gasoline engine 15. The engine
15 is supported by brackets of the main frame 11 etc. The transmission device 17 is
configured to transmit a driving force of the driving unit 16 to the rear wheel 4.
The transmission device 17 is supported by the pair of right and left side frames
through a rear shock unit 18. Additionally, according to the present embodiment, the
motorcycle 1 is assumed to be a type of motorcycle that an intake system of the engine
15 is provided with a carburetor (not illustrated in ,the figure). However, the present
invention is similarly applicable to another type of motorcycle that an intake system
is provided with a fuel injection (FI) device.
[0036] The driving unit 16 includes a starter motor 20 and a speed reduction gear 21. The
starter motor 20 is configured to start the engine 15. The speed reduction gear 21
is configured to reduce a revolution speed of the starter motor 20. An output side
of the speed reduction gear 21 is coupled to a crank shaft 23 of the engine 15 through
a one-way clutch 22.
Structure of Ignition System
[0037] The rotor 25, forming a part of the outer-rotor magneto-generator, is fixed to the
crank shaft 23 of the engine 15. The rotor 25 is configured to rotate in synchronization
with the crank shaft 23. A protrusion 26 is provided on the outer periphery of the
rotor 25. The protrusion 26 extends along a circumferential direction of the outer
periphery of the rotor 25. The circumferential length of the protrusion 26 corresponds
to a length of an arc of the rotor 25 having a central angle of 60 degrees. A pulser
27 is disposed in proximity to the protrusion 26. The pulser 27 is configured to detect
passage of the protrusion 26 (i.e., a rotation-directional start edge and a rotation-directional
end edge of the protrusion 26) and generate a pulse signal of Figs. 2(b) and 3. An
output signal of the pulser 27 is inputted into a CDI unit 28. The CDI unit 28 is
connected to a battery 30 through a main switch 29. Additionally, an ignition coil
31 is connected to the CDI unit 28. An ignition plug 32 is connected to the ignition
coil 31. In this case, an ignition is set to be executed at a timing when the rotation-directional
end edge of the protrusion 26 is detected.
[0038] Figure 8 illustrates a schematic block diagram of the CDI unit 28. The CDI unit 28
mainly includes a voltage increase circuit 40, a power source circuit 41, an ignition
circuit 42, a waveform shaping circuit 43 and a control unit 44. These components
are connected to the battery 30 through the main switch 29.
[0039] The voltage increase circuit 40 is configured to increase a voltage supplied by the
battery 30 up to a primary voltage suitable for executing an ignition. The power source
circuit 41 is configured to generate a power source voltage suitable for a control
circuit. The ignition circuit 42 mainly includes a condenser and a thylister. The
ignition circuit 42 is configured to output the voltage from the voltage increase
circuit 40 to the ignition coil 31 in accordance with a control by the control unit
43. The waveform shaping circuit 43 is configured to shape a waveform of a signal
from the pulser 27 illustrated in Fig. 3(c) and newly output a signal illustrated
in Fig. 3(d). The control unit 44 has a function of receiving the shaped signal from
the waveform shaping circuit 43 and detecting a passage time of the protrusion 26
(T1, T2... of Fig. 2(b)) corresponding to the revolution speed of the engine. Additionally,
the control unit 44 has a function of detecting a difference between the time period
T1 and the time period T2 as the amount of speed reduction of engine revolution. In
this case, the time period T1 corresponds to the revolution speed of the engine in
the present engine revolution, whereas the time period T2 corresponds to the revolution
speed of the engine in the previous engine revolution (i.e., an immediately previous
revolution from the present engine revolution). In other words, the control unit 44
has functions of detecting the revolution speed of the engine and detecting the amount
of speed reduction of engine revolution.
[0040] The rotor 25 provided with the protrusion 26, the pulser 27, and the control unit
of the CDI unit 28 form revolution speed detection means. The control unit 44 forms
revolution speed reduction amount detection means. The revolution speed detection
means and the revolution speed reduction amount detection means form an ignition control
device. Moreover, the engine 15 including the ignition plug 32, the ignition control
device, and the ignition coil 31 form an internal combustion.
Ignition Control Processing
[0041] Next, ignition control processing for inhibiting the reverse revolution of the engine
will be hereinafter explained in detail. Note a series of steps of the ignition control
processing are executed by the control unit 44 of the CDI unit 28.
Acquisition Processing of Pick-up Signal
[0042] First, processing of acquiring a signal (i.e., a pick-up signal) from the pulser
27 will be hereinafter explained in detail with reference to Fig. 9(a). The pick-up
signal is used for detecting the revolution speed of the engine 15.
[0043] In Step S1 of the pick-up signal acquisition processing, it is determined whether
or not rising of a signal was detected. The rising of a pick-up signal herein means
rising of a pick-up signal in the previous engine revolution. Also, the rising of
a pick-up signal herein corresponds to the timing T2u in Fig. 2(b). When the rising
of the pick-up signal was detected, the processing proceeds to Step S2. In Step S2,
a value of a free-running counter (FRC) is acquired as a counter value (C
rn-1) in an immediately previous engine revolution (more specifically, a counter value
counted when rising of a pick-up signal is detected in the previous engine revolution).
[0044] In this case, the FRC is a type of counter configured to always increment a smallest
unit and repeat counting from zero when the counted value reaches a maximum digit
value. The FRC is normally used for counting time.
[0045] When Step S2 is completed, the processing proceeds to Step S3. In Step S3, it is
determined whether or not falling of a pick-up signal was detected. The falling of
a pick-up signal herein means falling of a pick-up signal in the previous engine revolution.
Also, the falling of a pick-up signal herein corresponds to the timing T2d in Fig.
2(b). When the falling of a pick-up signal was detected, the processing proceeds to
Step S4. In Step S4, a value of the FRC is acquired as a counter value (C
sn-1) counted when the falling of a pick-up signal was detected in the previous engine
revolution.
[0046] When Step S4 is completed, the processing proceeds to Step S5. In Step S5, it is
determined whether or not the next rising of a pick-up signal was detected. The next
rising of a pick-up signal herein means rising of a pick-up signal in the present
engine revolution. Also, the next rising of a pick-up signal corresponds to the timing
T1u in Fig. 2(b). When the rising of a pick-up signal was detected, the processing
proceeds to Step S6. In Step S6, a value of the FRC is acquired as a counter value
(C
rn) in the present engine revolution (more specifically, a counter value counted when
rising of a pick-up signal was detected in the present engine revolution).
[0047] Next, in Step S7, it is determined whether or not falling of a pick-up signal was
detected. The falling of a pick-up signal herein means falling of a pick-up signal
in the present engine revolution. Also, the falling of a pick-up signal herein corresponds
to the timing T1d in Fig. 2(b). When the falling of a pick-up signal was detected,
the processing proceeds to Step S8. In Step S8, a counter value of the FRC is acquired
as a counter value (C
sn) counted when falling of a pick-up signal was detected in the present engine revolution.
Control Condition Determination Processing
[0048] Processing of an ignition control will be executed using the counter values obtained
by the aforementioned processing. Figure 9(b) illustrates a series of steps of the
ignition control processing.
[0049] First, in Step S10, the counter value (C
rn-1), counted when the rising of a pick-up signal was detected in the previous engine
revolution, is subtracted from the counter value (C
rn), counted when the rising of a pick-up signal was detected in the present engine
revolution. Subsequently, it is determined whether or not the obtained value is equal
to or greater than a control start setting value (Te). In other words, it is determined
whether or not the following relation is satisfied:
[0050] In this case, the value "C
rn - C
rn-i" corresponds to the revolution speed of the engine. When the value is large, the
revolution speed of the engine is low. When the value is small, on the other hand,
the revolution speed of the engine is high.
[0051] The control start setting value (Te) is set for restricting the ignition control
processing. In general, the engine does not revolve in the reverse direction when
the revolution speed of the engine is higher than a predetermined speed. Based on
this, in the present embodiment, useless ignition processing is prevented in the revolution
speed zone at which the engine normally does not revolve in the reverse direction.
Specifically, the control start setting value (Te), corresponding to the revolution
speed at which the ignition control is started, is thus set. The ignition control
processing is configured to be executed only when the value "C
rn - C
rn-1" is equal to or greater than the control start setting value Te. In other words,
the ignition control processing is configured to be executed only when the revolution
speed of the engine is lower than the revolution speed corresponding to the control
start setting value Te. For example, the control start setting value Te corresponds
to the revolution speed of the engine of 600 rpm.
[0052] When the revolution speed of the engine in the present engine revolution is lower
than the control start setting value Te, the processing proceeds to Step S 11. In
Step S11, it is determined whether not the amount of speed reduction of engine revolution
is equal to or greater than a predetermined value. Specifically, the counter value
(C
rn), counted when the rising of a pick-up signal was detected in the present engine
revolution, is subtracted from the counter value (C
sn), counted when the falling of a pick-up signal was detected in the present engine
revolution. The obtained result corresponds to the revolution speed of the engine
at the time period T1 of Fig. 2(b), that is, the revolution speed of the engine in
a predetermined crank timing (i.e., when the protrusion 26 passes through the pulser
27) of the present engine revolution. Moreover, the counter value (C
rn-1), counted when the rising of a pick-up signal was detected in the previous engine
revolution, is subtracted from the counter value (C
sn-1), counted when the falling of a pick-up signal was detected in the previous engine
revolution. The obtained value corresponds to the revolution speed of the engine at
the time period T2 of Fig. 2(b), that is, the revolution speed of the engine in a
predetermined crank timing (i.e., when the protrusion 26 passes through the pulser
27) of the previous engine revolution. Subsequently, the subtraction result in the
previous engine revolution (i.e., T2 = C
sn-1- C
rn-1) is subtracted from the subtraction result in the present engine revolution (i.e.,
T1 = C
sn - C
rn). Then, it is determined whether or not the subtraction result (T1 - T2) is equal
to or greater than a reverse revolution detection setting value (D
N). In other words, it is determined whether or not the following relation is satisfied:
[0053] In Step S11, the amount of speed reduction from the revolution speed of the engine
in the previous engine revolution to that in the present engine revolution is computed.
Then, it is determined whether or not the amount of speed reduction of engine revolution
is equal to or greater than a predetermined value.
[0054] In this case, as described with reference to Figs. 2 to 5, the reverse revolution
detection setting value (D
N) corresponds to a threshold of the amount of speed reduction of engine revolution
for determining whether or not the engine revolves in the reverse revolution. Especially,
the reverse revolution detection setting value (D
N) corresponds to a threshold illustrated with the dashed-dotted line of Fig. 4. As
described above, the reverse revolution detection setting value (D
N) is preliminarily set as a unique value depending on engine types.
[0055] Through the aforementioned processing, the ignition is prevented when the amount
of speed reduction of engine revolution is equal to or greater than a predetermined
value. Therefore, as illustrated in Figs. 5 and 6, the engine revolves slightly less
than once in the reverse direction (i.e., a continuous reverse revolution angle is
slightly less than 360 degrees). Accordingly, shock on a variety of components will
be inhibited in the reverse revolution of the engine.
[0056] Next, in Step S13, the counter value (C
rn-1), counted when the rising of a pick-up signal was detected in the previous engine
revolution, is subtracted from the counter value (C
rn), counted when the rising of a pick-up signal was detected in the present engine
revolution. Then, it is determined whether or not the obtained result is equal to
or greater than a control reset setting value (Tr).
[0057] In other words, it is determined whether or not the following relation is satisfied:
[0058] The determination in Step S13 is executed for restarting normal ignition processing
when the revolution speed of the engine exceeds a predetermined speed (i.e., the setting
value Tr or greater) under the condition that the engine once stops revolving in Steps
S 11 and S12 and then starts revolving again. When the determination result in Step
S13 is "Yes," the processing proceeds to Step S14. Then, the ignition is allowed to
be executed at a preliminarily-set timing.
Advantageous Effects of the Present Embodiment
[0059] (a) According to the present embodiment, the reverse revolution of the engine is
predicted based on the amount of speed reduction of engine revolution from the previous
revolution to the present engine revolution. When the reverse revolution of the engine
is predicted, the ignition is prevented in the present engine revolution. With the
configuration, it is possible to inhibit shock on a variety of components due to the
reverse revolution of the engine while the continuous reverse revolution angle of
the engine is controlled to be small. Additionally, the revolution speed of the engine
in the present engine revolution (i.e., the present stroke-cycle) and that in the
previous engine revolution (i.e., the immediately previous stroke-cycle from the present
stroke-cycle) are compared. With the configuration, the control processing will be
simple.
[0060] (b) According to the present embodiment, the revolution speed of the engine is detected
using only one protrusion for detecting the amount of speed reduction of engine revolution.
Accordingly, components, used for detecting the revolution speed of the engine, will
be simple. Simultaneously, high-speed control processing is not herein required. In
other words, it is possible to adopt simple control processing.
[0061] (c) According to the present invention, the ignition control is restricted in the
revolution speed zone at which the engine normally does not revolve in the reverse
direction. Therefore, it is possible to reliably execute a necessary ignition without
executing a useless control processing.
[0062] (d) In a cylinder of a four-stroke-cycle engine, the ignition is executed once while
the crank shaft revolves twice. In a plural-cylinder engine, on the other hand, ignition
timings of the cylinders are different from each other. In other words, a plurality
of ignitions are executed while the crank shaft revolves twice. Accordingly, the revolution
force of the crank shaft is large. In a single-cylinder 4-stroke engine, the revolution
force is generated once by an explosion while the crank shaft revolves twice. Therefore,
the revolution force of the crank shaft of the single-cylinder 4-stroke engine, immediately
before the ignition in the low revolution speed zone, is smaller than that of the
plural-cylinder engine. In other words, the single-cylinder 4-stroke engine has higher
chances that the engine revolves in the reverse direction in the low revolution speed
zone. Consequently, it is effective to apply the present invention to the single-cylinder
4-stroke engine.
Other Example Embodiments
[0063] (a) In the aforementioned embodiment, a protrusion is provided in the rotor of the
outer-rotor magneto-generator. The revolution speed of the engine is configured to
be obtained by detecting the protrusion. However, a rotor, provided with a plurality
of protrusions, may be used. In this case, it is possible to achieve similar advantageous
effects to the present invention, i.e., simplicity of the control processing, by obtaining
the revolution speed of the engine through detection of passage of any one of the
plurality of protrusions.
[0064] (b) In the aforementioned embodiment, the free-running counter is configured to detect
the revolution speed of the engine. However, any suitable components may be used as
a component for detecting the revolution speed of the engine.
[0065] (c) In the aforementioned embodiment, the ignition is set to be executed at a timing
when the revolution-directional end-edge of the protrusion of the rotor is detected.
However, the ignition timing is not limited to this. For example, the ignition may
be set to be executed when a predetermined period of time elapses after the revolution-directional
end-edge of the protrusion is detected. Alternatively, the ignition may be set to
be executed when the crank shaft revolves at a predetermined angle after the revolution-directional
end-edge of the protrusion is detected.
[Explanation of the Reference Numerals]
[0066]
- 1
- motorcycle
- 2
- vehicle body frame
- 3
- front wheel
- 4
- rear wheel
- 5
- seat
- 6
- power unit
- 15
- engine
- 16
- driving unit
- 23
- crank shaft
- 26
- protusion
- 27
- pulser
- 28
- CDI unit
- 31
- ignition coil
- 32
- ignition plug