EP2151562A2

EP2151562A2 - Ignition control device of engine, internal combustion engine and motorcycle including the same

Info

Publication number: EP2151562A2
Application number: EP20090009292
Authority: EP
Inventors: Shigeo Morisugi; Hiroyuki Kidera
Original assignee: Yamaha Motor Co Ltd
Current assignee: Yamaha Motor Co Ltd
Priority date: 2008-08-08
Filing date: 2009-07-16
Publication date: 2010-02-10
Also published as: TW201016957A; CN101644221A; CN101644221B; JP2010059959A; BRPI0902795A2; TWI468585B

Abstract

An ignition control device 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 a revolution of the engine. The revolution speed reduction detection means is configured to detect the amount of speed reduction form a previous engine revolution to a present engine revolution based on the detection of the revolution speed detection means. The present engine revolution is defined as an engine revolution in which an ignition is executed. On the other hand, the previous engine revolution is defined as an immediately previous engine revolution from the present engine revolution. 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.

Description

Technical Field

The present invention relates to an ignition control device, an internal combustion engine and a motorcycle including the same.

Background Art

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.
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.
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.
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

Japan Laid-open Patent Publication No. JP-A-2006-274998

Disclosure of the Invention

Technical Problem

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.
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.
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]

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.
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.
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

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

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]

Following are examination and analysis results regarding occurrence and inhibition of a reverse revolution of the engine by inventors of the present application.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.

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.
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).
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).
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.
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.
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.
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

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.
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.
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.
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

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.
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.
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.
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

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

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.
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).
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.
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.
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).
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

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.
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: $Te \leq C_{rn} - C_{rn - 1}$
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.
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.
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: $D_{N} \leq (C_{sn} - C_{rn}) - (C_{sn - 1} - C_{rn - 1})$
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.
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.
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.
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).
In other words, it is determined whether or not the following relation is satisfied: $Tr \leq C_{rn} - C_{rn - 1}$
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

(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.
(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.
(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.
(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

(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.
(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.
(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]

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

Claims

An ignition control device (28) of an engine for controlling an ignition of the engine, comprising:
revolution speed detection means (25, 26, 27, 43, 44) for detecting a revolution speed of the engine at a given timing in a revolution of the engine;

revolution speed reduction detection means (44) for detecting the amount of speed reduction from a previous engine revolution to a present engine revolution based on the detection of the revolution speed detection means, the present engine revolution defined as an engine revolution in which an ignition is executed, the previous engine revolution defined as an immediately previous engine revolution from the present engine revolution; and

ignition prevention means for preventing 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.
The ignition control device (28) of an engine according to claim 1, wherein the predetermined amount of speed reduction, used by the ignition prevention means, corresponds to the amount of speed reduction in which a continuous crank revolution angle is predicted to be equal to or greater than 600 degrees when the engine reverses in a reverse rotation in executing the ignition.
The ignition control device (28) of an engine according to claim 1 or 2, wherein the revolution speed detection means includes:
a rotation member (25) configured to rotate in conjunction with the engine;

a speed detection component (26) provided in the rotation member (26), the speed detection component (26) having a predetermined length along a rotation direction of the rotation member (25); and

detection means (27) for detecting a time period when the speed detection component (26) passes therethrough.
The ignition control device (28) of an engine according to claim 3, wherein the speed detection component (26) is a protrusion provided on an outer periphery of the rotation member (25).
The ignition control device of an engine according to one of claims 1 to 4, further comprising ignition prevention restriction means for restricting the control of the ignition prevention means when the revolution speed of the engine detected by the revolution speed detection means is equal to or greater than a predetermined revolution speed.
An internal combustion engine, comprising:
a single-cylinder 4-stroke gasoline engine including an ignition plug (32);

an ignition coil (31) connected to the ignition plug (32); and

an ignition control device (28) according to one of claims 1 to 5, which is connected to the ignition coil (31) and which is configured to control an ignition of the ignition plug (32).
A motorcycle (1), comprising:
a vehicle body frame (2);

a driving unit (16) including:
a single-cylinder 4-stroke gasoline engine (15) supported by the vehicle body frame (2); and

an ignition control device (28) according to one claim 1 to 5;

a seat (5) disposed above the driving unit (16);

a pair of front and rear wheels (3, 4) supported by the vehicle body frame (2); and

a driving force transmission unit (17) configured to transmit a driving force of the driving unit to the front wheel (3) or the rear wheel (4).