JP3743221B2 - Two-cycle internal combustion engine detonation suppression control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a detonation suppression control method for suppressing detonation of a two-cycle internal combustion engine.
[0002]
[Prior art]
In an internal combustion engine (gasoline engine), when a spark occurs in the spark plug at the ignition position, the air-fuel mixture in the vicinity of the spark plug first starts to burn, and the combustion flame propagates through the combustion chamber to advance the combustion. The explosion process takes place. However, if the temperature in the combustion chamber becomes locally high during the explosion stroke, a phenomenon occurs in which the air-fuel mixture spontaneously ignites before combustion by the propagation of flame occurs. This phenomenon is called detonation, and causes the temperature in the combustion chamber to rise abnormally locally or reduce the output torque of the engine.
[0003]
In particular, in a two-cycle gasoline engine in which an explosion stroke is performed each time the crankshaft makes one revolution, the heat load on the piston and cylinder is large, and the temperature of the ground electrode portion at the tip of the spark plug tends to increase locally. It is known that detonation is likely to occur. Once detonation occurs, it tends to occur continuously, and if left untreated, the temperature of a part of the piston or cylinder may rise abnormally and melt. Therefore, when detonation occurs, it is necessary to immediately detect it and take measures to suppress the occurrence.
[0004]
In a conventional two-cycle internal combustion engine, variations in the ignition position (rotational angle position of the crankshaft when ignition is performed) caused by an error in ignition position control, or air-fuel ratio control, when in an operating situation where detonation is likely to occur In consideration of variations in air-fuel ratio due to errors in the above, or variations in ignition position and fuel injection amount due to changes over time in the ignition device and fuel injection device, etc. By designing the ignition device so that it is later than (Minimum advance for Best Torque), or by setting the air / fuel ratio to be richer than the ideal air / fuel ratio and making the mixture rich, or both The maximum temperature in the combustion chamber during combustion was lowered to prevent the occurrence of detonation.
[0005]
However, if the ignition position is retarded or the air-fuel mixture is excessively rich, fuel consumption will increase and the amount of harmful components (carbon monoxide and hydrocarbons) contained in the exhaust gas will increase. Problem arises.
[0006]
In recent years, from the viewpoint of environmental protection and resource saving, it has been strictly demanded to improve the fuel consumption and purify exhaust gas of a two-cycle internal combustion engine. It is necessary to avoid producing an internal combustion engine that emits large amounts of carbon monoxide and hydrocarbons.
[0007]
In order to prevent engine damage due to detonation without deteriorating the fuel economy of a two-cycle internal combustion engine or increasing the emission of carbon monoxide or hydrocarbons, the occurrence of detonation can be detected immediately. In a normal state where no detonation has occurred, the internal combustion engine was operated with the control values for the ignition position and fuel supply amount set to optimum values for improving the fuel consumption rate, and the occurrence of detonation was detected. Sometimes, it is preferable to operate the internal combustion engine by setting the control value to a value that can prevent the occurrence of detonation within a range that does not extremely deteriorate the fuel consumption rate.
[0008]
As a method for detecting the occurrence of detonation, a method for detecting the in-cylinder pressure of an internal combustion engine is known. FIG. 2 shows a change in the in-cylinder pressure P when the combustion state of the engine is different in a state in which the rotational speed of the two-cycle engine is fixed to a constant value in the medium speed region, and the crankshaft rotational angle (crank angle) θ It is shown for this. FIG. 4A shows the change in in-cylinder pressure during normal combustion, and FIG. 4B shows the change in in-cylinder pressure when detonation occurs. FIG. 2C shows a change in the in-cylinder pressure when the internal combustion engine misfires. 2A to 2C, TDC indicates the rotation angle position of the crankshaft (referred to as the top dead center position) when the piston reaches the top dead center.
[0009]
From FIG. 2A, it can be seen that when the combustion is normally performed in the combustion chamber, the in-cylinder pressure becomes maximum at a position delayed by an angle θn from the top dead center position TDC. Generally, the angle θn takes a value of 13 ° or more, and the mechanical efficiency of the internal combustion engine is maximized when θn is approximately equal to 13 °. On the other hand, when detonation occurs, as shown in FIG. 2 (B), the in-cylinder pressure is increased at a position θd (<θn) advanced from a position of 13 ° after the top dead center where the mechanical efficiency becomes maximum. Become the maximum. Further, when the internal combustion engine misfires (misfire), as shown in FIG. 2C, the position where the in-cylinder pressure becomes maximum coincides with the top dead center position TDC.
[0010]
From FIG. 2, by detecting the crank angle θd when the in-cylinder pressure becomes maximum, and determining the magnitude of this crank angle θd and the crank angle θn that gives the maximum value of the in-cylinder pressure during normal combustion, It can be seen that it is possible to detect whether or not detonation has occurred.
[0011]
Effective means for suppressing detonation are the retard of the ignition position and the over-concentration of the air-fuel mixture. When the ignition position is retarded, the temperature in the exhaust pipe increases and the temperature in the combustion chamber decreases, so detonation stops immediately. If the ignition position is retarded, the output of the internal combustion engine will decrease, but the output of the internal combustion engine will increase immediately after detonation has occurred, so even if the ignition position is retarded, the driver There is little to feel the decline. However, when a certain amount of time elapses after retarding the ignition position, the output is greatly reduced, and the driver may feel that there is no power. This is because the two-cycle internal combustion engine uses the pulsation of exhaust to improve the charging efficiency.
[0012]
That is, in order to improve the output of the two-cycle internal combustion engine, it is effective to increase the charging efficiency and suppress the air-blow of the air-fuel mixture. Therefore, as shown in FIG. 3A, the scavenging port Sc The exhaust pipe of the internal combustion engine is designed so that the pressure Pex at the outlet of the exhaust port becomes a positive pressure during the interval θo from when the exhaust port is closed until the exhaust port Ex is closed.
[0013]
In a general two-cycle engine, a portion near the exhaust port of the exhaust pipe is tapered, and the diameter of the exhaust pipe is gradually increased toward the end thereof, as shown in FIG. The exhaust efficiency is increased by setting the outlet pressure of the section exhaust port (pressure at the point Q in FIG. 1) immediately after the scavenging port Sc is opened until the scavenging port Sc is closed as a negative pressure. The length of the exhaust pipe is adjusted so that the pressure wave propagating from the exhaust port side is reflected near the end of the exhaust pipe so that the reflected wave reaches the exhaust port after the scavenging port is closed. Is set so that the outlet pressure of the section exhaust port of θo from when the scavenging port Sc is closed to when the exhaust port Ex is closed is set to a positive pressure, thereby preventing the air-fuel mixture from being blown out.
[0014]
However, if the ignition position θig of the engine is retarded, as shown in FIG. 4, the temperature of the exhaust gas rises (the temperature in the combustion chamber decreases), so that the temperature of the exhaust gas and the propagation speed of the pressure wave As is clear from FIG. 5 showing the relationship, the propagation speed of the pressure wave in the exhaust pipe increases, and as shown in FIG. 3B, the pressure at the outlet of the exhaust port is negative while the exhaust port is open. It becomes pressure. For this reason, the charging efficiency is deteriorated and the amount of air-fuel mixture blown through increases, so that the output of the engine is greatly reduced. This phenomenon (decrease in output) occurs after a lapse of time after the ignition position is retarded because it takes time until the pressure wave propagation speed changes due to the heat capacity of the exhaust pipe. is there.
[0015]
When detonation occurs, if the air-fuel mixture is in a rich state, the temperature in the combustion chamber decreases as in the case where the ignition position is retarded, so detonation is suppressed, but the air-fuel mixture is excessively rich. If it will be in a state, fuel consumption will increase and the harmful substance in exhaust gas will increase. Therefore, it is necessary to minimize the enrichment of the air-fuel mixture.
[0016]
[Problems to be solved by the invention]
As described above, in a two-cycle internal combustion engine, it is possible to detect the occurrence of detonation by detecting the in-cylinder pressure, but a pressure sensor for detecting the in-cylinder pressure in a high temperature state is very expensive. Therefore, a method for detecting the occurrence of detonation by detecting in-cylinder pressure is applied to a two-cycle internal combustion engine in which low cost is emphasized and cost reduction is strictly required during design. Is difficult.
[0017]
In addition, when it is detected that detonation has occurred, it is necessary to immediately take measures to prevent it from protecting the engine and to prevent the output of the engine from decreasing.
[0018]
An object of the present invention is to make it possible to reliably detect the occurrence of detonation without using an expensive in-cylinder pressure detection sensor, and to take measures to immediately suppress the occurrence of detonation. It is an object of the present invention to provide a detonation suppression control method for a two-cycle internal combustion engine that is capable of performing the above.
[0019]
[Means for Solving the Problems]
The present invention relates to a detonation suppression control method for a two-cycle internal combustion engine that controls the ignition position of the internal combustion engine and the amount of fuel supplied to the internal combustion engine so as to suppress the detonation of the two-cycle internal combustion engine.
[0020]
In the present invention, the interval during which the crankshaft of the internal combustion engine rotates by a certain angle from the position corresponding to the top dead center of the piston in the cylinder of the engine is determined as the determination interval, and is normal in the cylinder of the internal combustion engine. A peak position that occurs at a position closest to the final position in the determination section among at least one peak position of the angular acceleration of the crankshaft that occurs in the determination section when a proper combustion is performed is determined as a determination reference position for detonation. . Then, a peak position that occurs at a position closest to the final position of the determination section among at least one peak position of the crankshaft angular acceleration that occurs while the crankshaft rotates in the determination section is detected as a detonation determination peak position. When the determination peak position occurs at a position advanced from the determination reference position, it is determined that detonation has occurred in the internal combustion engine. When it is determined that detonation has occurred, first, an ignition position retarding process for retarding the ignition position of the internal combustion engine is performed, and then a fuel increasing process for increasing the fuel supply amount to the internal combustion engine is performed to suppress detonation. The output torque of the internal combustion engine is recovered.
[0021]
In a two-cycle internal combustion engine, as shown in FIG. 2, when detonation occurs, the rotation angle position of the crankshaft that gives the maximum value of the in-cylinder pressure is greater than the rotation angle position that gives the maximum value of the in-cylinder pressure during normal combustion. Accordingly, at the time of detonation, the rotational angle position that gives the maximum value of the angular acceleration of the crankshaft advances more than that during normal combustion.
[0022]
FIG. 6A shows the change of the angular acceleration dω / dt of the crankshaft with respect to the crank angle θ in the medium speed region of the two-cycle internal combustion engine. Curves a and b in FIG. 6 represent normal combustion and detonation, respectively. The time of occurrence is shown, and a curve c shows a change in angular acceleration when the engine is misfired. Curves a to c in FIG. 6B show changes in the in-cylinder pressure P of the same two-cycle internal combustion engine with respect to the crank angle θ when normal combustion occurs, when detonation occurs, and when misfire occurs.
[0023]
As is apparent from these curves, when detonation occurs, the crank angle (peak position) θpn (angle measured with reference to the top dead center TDC) that gives the peak value of the angular acceleration of the crankshaft is equal to that during normal combustion. It becomes smaller than the crank angle (peak position) θpn that gives the peak value of the angular acceleration. (It can be seen that the peak position of the angular acceleration advances more than in normal combustion).
[0024]
In a two-cycle internal combustion engine, in order to prevent a decrease in output in the high speed region of the engine, control is often performed to retard the ignition position in the high speed region. In such a case, FIG. (B) As shown, after the engine is ignited in the high speed region, two peak positions occur in the angular acceleration of the crankshaft. On the other hand, when detonation occurs in the high speed region of the engine, as shown in FIG. 8D, one peak position occurs in the angular acceleration of the crankshaft near the top dead center TDC.
[0025]
Thus, in order to be able to detect detonation even under conditions where two peak positions may occur in the angular acceleration of the crankshaft, the crankshaft generated in a certain rotation section after the engine is ignited Of the peak positions of the angular acceleration, it is necessary to use the peak position that occurs later for detection.
[0026]
Therefore, in the present invention, as described above, a section during which the crankshaft of the internal combustion engine rotates by a certain angle from a position corresponding to the top dead center of the piston in the cylinder of the engine is determined as a determination section. A peak position that occurs at a position closest to the final position of the determination section among at least one peak position of the angular acceleration of the crankshaft generated in the determination section when normal combustion is performed in the cylinder of the internal combustion engine is determined. It is obtained as a judgment reference position. Then, a peak position that occurs at a position closest to the final position of the determination section among at least one peak position of the angular acceleration of the crankshaft that occurs while the crankshaft rotates in the determination section is detected as a detonation determination peak position. Thus, when the determination peak position is a position advanced from the determination reference position, it is determined that detonation has occurred in the internal combustion engine.
[0027]
According to the present invention, it is not necessary to use an expensive sensor for detecting the in-cylinder pressure, the angular acceleration is calculated by calculating the time differential value of the rotational speed of the crankshaft, and the calculated maximum value of the angular acceleration is obtained. Since the presence or absence of detonation can be detected simply by comparing the given rotation angle position with the determination reference position, measures against detonation can be taken without causing a significant increase in the cost of the two-cycle internal combustion engine.
[0028]
The angular acceleration of the crankshaft is calculated by calculating the angular velocity during the minute rotation of the crankshaft from the output pulse generation interval of the crank angle sensor (encoder) that generates a pulse every time the crankshaft rotates by a minute angle. Can be obtained by calculating the difference between the angular velocity calculated this time and the angular velocity calculated last time.
[0029]
It is sufficient that the determination section is a section between the top dead center of the engine and a position 45 ° after the top dead center.
[0030]
When it is determined that detonation has occurred as in the present invention, if the ignition position retarding process for retarding the ignition position of the internal combustion engine is performed, the temperature in the combustion chamber decreases, so detonation is immediately stopped. Can do. When the ignition position is retarded, a phenomenon occurs in which the output torque of the engine decreases with a predetermined delay time. Therefore, in the present invention, first, the ignition position is retarded to stop detonation, and then the fuel increase process for increasing the fuel supply amount to the internal combustion engine is performed to recover the output torque of the internal combustion engine.
[0031]
Thus, if the fuel increase process is performed after the ignition position retarding process is performed, the fuel consumption can be reduced compared to the case where both processes are performed simultaneously, and harmful substances contained in the exhaust gas. Can be reduced.
[0032]
The present invention is generally applicable to a two-cycle internal combustion engine having n cylinders (n is an integer of 1 or more). When applied to a two-cycle internal combustion engine having n cylinders, the interval between the crankshaft of the internal combustion engine rotating at a certain angle from the position corresponding to the top dead center of the piston in each cylinder corresponds to each cylinder. The determination interval is determined from among at least one peak position of the angular acceleration of the crankshaft generated in the determination interval corresponding to each cylinder when normal combustion is performed in each cylinder of the internal combustion engine. The peak position that occurs at the position closest to the final position is determined as a detonation determination reference position for each cylinder. The peak position generated at the position closest to the final position of the determination section among at least one peak position of the crankshaft angular acceleration generated while the crankshaft rotates in the determination section corresponding to each cylinder is determined as a detonation. Any of the internal combustion engines when the peak position for determination detected in the determination section corresponding to any cylinder occurs at a position advanced from the determination reference position corresponding to that cylinder. It is determined that detonation has occurred in the cylinder.
[0033]
When it is determined that detonation has occurred, first, an ignition position retarding process for retarding the ignition position of the internal combustion engine is performed, and then a fuel increasing process for increasing the fuel supply amount to the internal combustion engine is performed to suppress detonation. The output torque of the internal combustion engine is recovered.
[0034]
The fuel increasing process may be performed immediately after the ignition position retarding process, but a predetermined delay time is required after the ignition position is retarded until the engine output actually decreases. Yes, if the fuel is increased without delay time after performing the ignition position retarding process, the exhaust pipe temperature will decrease and the charging efficiency will decrease, so the fuel increasing process immediately after performing the ignition position retarding process It is preferable to wait for the crankshaft to rotate the set number of times before starting the fuel increase process.
[0035]
In the fuel increase process, the fuel supply amount may be gradually increased, or the fuel supply amount may be increased stepwise to the target value.
[0036]
In a two-cycle engine, the exhaust temperature that gives the maximum value of the shaft torque is substantially constant regardless of the ignition position. The exhaust gas temperature tends to decrease as the fuel supply amount is increased to increase the concentration of the air-fuel mixture. Therefore, in the fuel increase process, it is preferable to determine the increase amount of the fuel supply amount according to the exhaust temperature so that the fuel supply amount is increased as the exhaust temperature is higher.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 schematically shows a two-cycle internal combustion engine 1 to which the present invention is applied and the configuration of a control device thereof. An internal combustion engine 1 shown in FIG. 1 includes a crankcase 1a, a cylinder 1b connected to the crankcase, a cylinder head 1c that closes the head of the cylinder 1b, a piston 1d fitted in the cylinder 1b, It has a crankshaft 1e connected to 1d via a crank mechanism and a throttle body 1f connected to an intake port provided in the crankcase 1a. The cylinder 1b includes a scavenging port Sc and an exhaust port Ex. And are provided. A throttle valve 1g and a reed valve 1h are provided in the throttle body 1f, and a throttle opening degree sensor 2 for detecting the opening degree is attached to the operation shaft of the throttle valve 1g. An exhaust pipe 1i is connected to the exhaust port Ex, and a spark plug 3 and an injector (electromagnetic fuel injection valve) 4 are attached to the cylinder head 1c. The spark plug 3 is connected to the non-grounded output terminal of the ignition device 5, and the non-grounded drive signal input terminal of the injector 4 is connected to the non-grounded output terminal of the injector drive circuit 6.
[0038]
A flywheel 6 is attached to the crankshaft 1e of the engine, and a retractor 6a made of an arc-shaped protrusion extending in the circumferential direction is provided on the outer periphery of the flywheel. A ring gear 7 having a fixed number of teeth is also attached to the crankshaft 1e. By engaging a pinion gear driven by a starter motor (not shown) with the ring gear 7, the crankshaft 1e is rotated to start the engine. It is supposed to let you.
[0039]
A pulsar 8 is disposed on the outer peripheral side of the flywheel 6, and a crank angle sensor 9 is disposed on the outer peripheral side of the ring gear 7. The pulsar 8 is a well-known one provided with an iron core having a magnetic pole portion facing the reluctator 6a on the outer periphery of the flywheel 6, a pulsar coil wound around the iron core, and a permanent magnet magnetically coupled to the iron core. Thus, it is fixed to a mounting portion provided in the crankcase 1a of the engine.
[0040]
The pulsar 8 is used when the reluctator 6a starts to face the magnetic pole part of the iron core (when the edge on the front end side in the rotation direction of the reluctator 6a is detected) and when the reluctator 6a finishes facing the magnetic pole part (reluctator 6). When a rear end edge in the rotational direction 6a is detected), a pair of pulse signals having different polarities are generated. Of the pair of pulse signals generated by the pulsar 8, the pulse signal generated when the front edge in the rotational direction of the reluctator 6 a is detected is a reference crank set at a position sufficiently advanced from the top dead center of the engine. It is generated at an angular position. The pulse signal generated by the pulser 8 at the reference crank angle position is converted into a signal that can be recognized by the microcomputer by the waveform shaping circuit 10, and then supplied to the CPU 11 of the microcomputer as a reference signal for providing information on the reference crank angle. ing.
[0041]
The crank angle sensor 9 has a structure similar to that of a pulsar, and generates a pair of pulses having different polarities when the front edge and the rear edge in the rotation direction of each tooth of the ring gear 7 are detected. . Of the pair of pulses generated when the crank angle sensor 9 detects each tooth of the ring gear, a pulse having one polarity is converted by the waveform shaping circuit 12 into a signal having a waveform that can be recognized by the microcomputer. Is provided to the CPU 11 as a crank angle signal for providing the above information.
[0042]
The CPU 11 also receives the output of the throttle opening sensor 2 and simultaneously receives the output of a sensor for detecting atmospheric pressure, the output of a temperature sensor for detecting the coolant temperature of the engine, and the like. This information is used as a control condition for controlling the fuel injection amount from the injector 4 and the ignition position of the internal combustion engine.
[0043]
The CPU 11 calculates the average rotation speed per rotation of the internal combustion engine by executing a program stored in a ROM (not shown), calculates the ignition position at the calculated rotation speed, and detects the calculated ignition position. The ignition signal Vi is given to the ignition circuit 5 at the time.
[0044]
The ignition circuit 5 includes an ignition coil in which the non-ground side terminal of the secondary coil is connected to the ignition plug 3, and a primary current control circuit that controls the primary current of the ignition coil in response to the ignition signal. A high voltage for ignition is induced in the secondary coil of the ignition coil by causing a sudden change in the primary current of the ignition coil when a signal is given. The engine is ignited by the spark discharge generated in the spark plug 3 by the high voltage for ignition.
[0045]
The CPU 11 also calculates a time (fuel injection time) for injecting fuel from the injector with respect to control conditions such as atmospheric pressure, engine coolant temperature, throttle valve opening, engine speed, and the like. A rectangular wave injection signal Vj having a pulse width corresponding to time is supplied to the injector drive circuit 6. The injector drive circuit 6 sends a drive current to the solenoid of the injector 4 in response to the injection signal Vj, and opens the valve of the injector 4 during the calculated fuel injection time. The fuel is supplied to the injector 4 from a fuel pump (not shown), and the pressure of the fuel supplied to the injector is kept constant by the pressure regulator. Therefore, the amount of fuel injected from the injector depends on the fuel injection time. Determined.
[0046]
When the temperature in the combustion chamber locally increases in the explosion stroke of the two-cycle engine shown in FIG. 1, before the combustion by the propagation of the flame generated by the ignition by the spark plug 3 is performed, the mixture is ignited and detonation is generated. appear. When detonation occurs, the temperature in the combustion chamber rises abnormally. Therefore, when detonation continues, problems such as melting of the piston and cylinder and opening of holes occur.
[0047]
As described above, detonation can be detected by detecting a change in the pressure in the combustion chamber. However, since a sensor for detecting the pressure in the combustion chamber is expensive, the two-cycle engine that places importance on low cost is used. Cannot be adopted.
[0048]
Therefore, in the present invention, detonation is detected by paying attention to the fact that the position at which the angular acceleration of the crankshaft reaches a peak value (peak position) differs between normal combustion and detonation.
[0049]
FIG. 7 shows the change of the in-cylinder pressure P with respect to the crank angle θ and the change of the crankshaft angular acceleration dω / dt with respect to the crank angle θ in the medium-speed rotation region of the engine, during normal combustion and when detonation occurs. In the figure, (A) and (B) show the in-cylinder pressure P and angular acceleration dω / dt during normal combustion, respectively. (C) and (D) show the in-cylinder pressure P and detonation at the time of occurrence of detonation, respectively. Angular acceleration dω / dt is shown.
[0050]
FIG. 8 also shows the change of the in-cylinder pressure P with respect to the crank angle θ and the change of the crankshaft angular acceleration dω / dt with respect to the crank angle θ in the high-speed rotation region of the engine, during normal combustion and when detonation occurs. In the figure, (A) and (B) show the in-cylinder pressure P and angular acceleration dω / dt during normal combustion, respectively. (C) and (D) show the in-cylinder pressure P and detonation at the time of occurrence of detonation, respectively. Angular acceleration dω / dt is shown.
[0051]
From these figures, a section during which the crankshaft of the internal combustion engine rotates by a certain angle from a position corresponding to the top dead center TDC of the piston in the cylinder of the engine is determined as a determination section θx. The detonation criterion is the peak position θpn that occurs at a position closest to the final position θxe of the determination section among at least one peak position of the angular acceleration of the crankshaft that occurs in the determination section θx when normal combustion is performed in Determining the peak position that occurs at a position closest to the final position θxe of the determination section among at least one peak position of the crankshaft angular acceleration that occurs while the crankshaft rotates the determination section θx When the peak position for detection θpx is detected, the peak position for determination θpx is detected by the internal combustion engine when it occurs at a position advanced from the determination reference position. It is understood that it can be determined that the destination has occurred. It is sufficient that the determination section is a section from the top dead center to a position 45 ° after the top dead center.
[0052]
When the engine has a plurality of cylinders, as described above, a determination section is set for each cylinder, and a determination similar to the above is performed, so that detonation has occurred in any of the cylinders. Can be detected.
[0053]
The characteristics of the crankshaft angular acceleration with respect to the crank angle vary depending on the average engine speed per rotation of the engine and the throttle valve opening. Therefore, in order to detect detonation more accurately, it is preferable to obtain the determination reference position using the average engine speed and the throttle valve opening as parameters.
[0054]
In order to obtain the determination reference position using the average engine speed and the detected value of the throttle valve opening as parameters, for example, the determination reference position of detonation is obtained for various average engine speeds and throttle valve openings. By performing an experiment, a three-dimensional map for calculating a reference position for giving a relationship among the average rotational speed, the throttle valve opening, and the reference position is created and stored in the ROM of the microcomputer. Means for detecting the average rotational speed and the throttle valve opening, and a determination criterion for each average rotational speed and throttle valve opening based on the detected average rotational speed and throttle valve opening and a determination reference position calculation map The position may be calculated.
[0055]
The average rotational speed of the engine may be calculated from the output pulse of the crank angle sensor that generates a pulse every time the crankshaft rotates by a minute angle, or from the output of a pulser that generates a pulse at a specific rotational angle position of the engine You may make it do.
[0056]
The determination reference position may be determined with reference to the top dead center of the engine, or may be determined with reference to the position where the pulser generates a specific pulse.
[0057]
As described above, when it is determined that detonation has occurred, an ignition position retarding process for retarding the ignition position of the internal combustion engine is first performed, and then a fuel increasing process for increasing the fuel supply amount to the internal combustion engine is performed. Thus, detonation is suppressed and the output torque of the internal combustion engine is recovered.
[0058]
As described above, when it is determined that detonation has occurred, if the ignition position retarding process for retarding the ignition position of the internal combustion engine is performed, the temperature in the combustion chamber decreases, so detonation can be stopped immediately. it can. When the ignition position is retarded, a phenomenon occurs in which the output torque of the engine decreases with a predetermined delay time. Therefore, in the present invention, after the ignition position is retarded and detonation is stopped, a fuel increasing process for increasing the fuel supply amount to the internal combustion engine is performed to recover the output torque of the internal combustion engine.
[0059]
If the ignition position is retarded, the exhaust temperature rises, which increases the propagation speed of the pressure wave in the exhaust pipe, causing a situation where the exhaust port outlet pressure becomes negative in the section where the exhaust port is open. As a result, the charging efficiency decreases and the output torque of the engine decreases. However, due to the heat capacity of the exhaust pipe, even if the exhaust temperature rises due to the retard of the ignition position, the temperature of the exhaust pipe does not change immediately, but rises with a predetermined time delay from the rise of the exhaust temperature. For this reason, even if the exhaust temperature rises due to the retard of the ignition position, the propagation speed of the pressure wave in the exhaust pipe does not rise immediately, but rises with a predetermined time delay. Therefore, there is a predetermined delay time from when the ignition position is retarded until when the engine output actually decreases.
[0060]
The fuel increase process may be performed immediately after the ignition position retardation process, but as described above, a predetermined delay time is required until the engine output tends to decrease due to the ignition position retardation. Yes, if the fuel is increased without delay time after the ignition position retarding process, the exhaust pipe temperature may drop and the charging efficiency may decrease, so the ignition position retarding process is performed. Then, it is preferable not to immediately perform the fuel increase process, but to wait for the crankshaft to rotate the set number of waiting times before performing the fuel increase process.
[0061]
In the fuel increase process, the fuel supply amount may be gradually increased, or the fuel supply amount may be increased stepwise to the target value.
[0062]
In the two-cycle engine, as shown in FIG. 9, the exhaust temperature tex that gives the maximum value of the shaft torque is substantially constant regardless of the ignition position θig. Further, the exhaust gas temperature tex tends to decrease as the fuel supply amount Lf is increased to increase the concentration of the air-fuel mixture. From these facts, it can be seen that in the fuel increase process, it is preferable to determine the increase amount of the fuel supply amount according to the exhaust temperature so that the fuel supply amount is increased as the exhaust temperature is higher.
[0063]
In this way, it is possible to compensate for a decrease in engine output accompanying an increase in exhaust temperature due to the retard of the ignition position without consuming unnecessary fuel, so the amount of increase in harmful components contained in the exhaust gas can be reduced. While suppressing to a minimum, it is possible to prevent a decrease in engine output during detonation suppression control.
[0064]
FIG. 9 shows the relationship between the fuel supply amount Lf and the exhaust temperature and the relationship between the fuel supply amount Lf and the shaft torque with the ignition position as a parameter. In FIG. 9, curves a, b and c show the relationship between the exhaust temperature and the fuel supply amount when the ignition position θig is 18 ° before top dead center, 12 ° before top dead center and 6 ° before top dead center, respectively. Curves p, q and r show the relationship between the fuel flow rate and the shaft torque τ when the ignition position θig is 18 ° before top dead center, 12 ° before top dead center and 6 ° before top dead center, respectively. ing.
[0065]
As is apparent from FIG. 9, in the two-cycle engine, the exhaust temperature tex that gives the maximum value of the shaft torque τ is substantially constant regardless of the ignition position θig. Further, the exhaust gas temperature tex tends to decrease as the fuel supply amount Lf is increased to increase the concentration of the air-fuel mixture. From these facts, it can be seen that in the fuel increase process, it is preferable to determine the increase amount of the fuel supply amount according to the exhaust temperature so that the fuel supply amount is increased as the exhaust temperature is higher.
[0066]
In this way, it is possible to compensate for a decrease in engine output accompanying an increase in exhaust temperature due to the retard of the ignition position without consuming unnecessary fuel, so the amount of increase in harmful components contained in the exhaust gas can be reduced. While minimizing. It is possible to prevent a decrease in engine output during detonation suppression control.
[0067]
FIG. 10 is a diagram for explaining the detonation suppression control according to the present invention. In FIG. 10, a curve a in FIG. 10 represents the exhaust temperature and the fuel supply amount Lf when the ignition position is 18 ° before top dead center. The curve b shows the relationship between the exhaust temperature and the fuel supply amount Lf when the ignition position is 12 ° before top dead center. Curve p shows the relationship between the engine shaft torque τ and the fuel supply amount Lf when the ignition position is 18 ° before top dead center, and curve q shows the ignition position at 12 ° before top dead center. The relationship between the shaft torque and the fuel flow rate Lf is shown. Further, in FIG. 10, point A indicates an operating point when detonation occurs, and point B indicates an operating point when the ignition position is brought close to suppress detonation. Point C indicates the final operating point when the fuel increasing process is performed to retard the ignition position and then increase the fuel supply amount to make the mixture rich. When the operating point is changed from A through B to C, the actual exhaust temperature changes as shown by the curve e, and the actual shaft torque changes as shown by the curve f shown.
[0068]
【The invention's effect】
As described above, according to the present invention, when it is detected that detonation has occurred, the ignition position is first retarded to suppress detonation, so that detonation continues and the engine is damaged. Can be prevented. Further, according to the present invention, after retarding the ignition position and suppressing detonation, the fuel supply amount is increased to recover the output torque of the engine, so that the fuel consumption rate is not deteriorated. And control which suppresses detonation can be performed, without causing the fall of the output of an engine.
[Brief description of the drawings]
FIG. 1 is a block diagram schematically showing the configuration of a two-cycle internal combustion engine and its control device according to the present invention.
FIGS. 2A to 2C are graphs showing the relationship between in-cylinder pressure and crankshaft rotation angle during normal combustion, detonation occurrence, and misfire, respectively, of a two-cycle internal combustion engine.
FIG. 3A is a graph showing the relationship between the outlet pressure of the exhaust port and the crank angle when the two-cycle internal combustion engine is normally burning in the high speed region. (B) is a diagram showing the relationship between the outlet pressure of the exhaust port and the crank angle when the ignition position of the two-cycle internal combustion engine is retarded in the high speed region.
FIG. 4 is a diagram showing the relationship between the exhaust gas temperature and the ignition position and the relationship between the shaft torque and the ignition position of the two-cycle engine.
FIG. 5 is a diagram showing the relationship between the pressure wave propagation speed in the exhaust pipe of a two-cycle engine and the exhaust gas temperature.
FIG. 6 is a graph showing the relationship between the angular acceleration and crank angle of a crankshaft of a two-cycle engine and the relationship between in-cylinder pressure and crank angle of a two-cycle engine.
FIG. 7 is a diagram showing the relationship between in-cylinder pressure and crank angle and the relationship between crankshaft angular acceleration and crank angle in the medium speed range of a two-stroke engine when normal combustion and when detonation occurs.
FIG. 8 is a diagram showing the relationship between in-cylinder pressure and crank angle and the relationship between crankshaft angular acceleration and crank angle in a high-speed region of a two-cycle engine when normal combustion and when detonation occurs.
FIG. 9 is a diagram showing the relationship between the exhaust temperature of the two-cycle engine and the fuel supply amount and the relationship between the shaft torque and the fuel supply amount with the ignition position as a parameter.
FIG. 10 is a diagram for explaining detonation suppression control according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... 2 cycle internal combustion engine, 1a ... Crankcase, 1b ... Cylinder, 1c ... Cylinder head, 1d ... Piston, 1g ... Throttle valve, 1i ... Exhaust pipe, 2 ... Throttle opening sensor, 3 ... Spark plug, 4 ... Injector 5 ... Ignition circuit, 6 ... Injector drive circuit, 11 ... CPU.

Claims (7)

A detonation suppression control method for a two-cycle internal combustion engine, which controls the ignition position of the internal combustion engine and the amount of fuel supplied to the internal combustion engine so as to suppress the detonation of the two-cycle internal combustion engine and restore the engine output torque to a normal value Because
The interval during which the crankshaft of the internal combustion engine rotates by a certain angle from the position corresponding to the top dead center of the piston in the cylinder of the engine is determined as a determination interval,
A peak generated at a position closest to the final position of the determination section among at least one peak position of the angular acceleration of the crankshaft generated in the determination section when normal combustion is performed in the cylinder of the internal combustion engine. Find the position as the detonation criterion position,
Among the at least one peak position of the angular acceleration of the crankshaft that occurs while the crankshaft rotates in the determination section, the peak position that occurs at the position closest to the final position of the determination section is used as the detonation determination peak position. Detecting and determining that detonation has occurred in the internal combustion engine when the peak position for determination is a position advanced from the determination reference position;
When it is determined that the detonation has occurred, first, an ignition position retarding process for retarding the ignition position of the internal combustion engine is performed, and then a fuel increasing process for increasing the amount of fuel supplied to the internal combustion engine is performed, A detonation suppression control method for a two-cycle internal combustion engine, wherein the detonation is suppressed and the output torque of the internal combustion engine is recovered. The ignition position of the internal combustion engine and the fuel supply to the internal combustion engine so that the detonation of the two-cycle internal combustion engine having n cylinders (n is an integer of 1 or more) is suppressed and the output torque of the engine is restored to a normal value. A detonation suppression control method for a two-cycle internal combustion engine for controlling an amount,
The interval during which the crankshaft of the internal combustion engine rotates by a certain angle from the position corresponding to the top dead center of the piston in each cylinder is determined as a determination interval corresponding to each cylinder,
Among the at least one peak position of the angular acceleration of the crankshaft that occurs in the determination section corresponding to each cylinder when normal combustion is performed in each cylinder of the internal combustion engine, the most final position of the determination section Find the peak position that occurs at a close position as the detonation judgment reference position for each cylinder,
Detonation is a peak position generated at a position closest to the final position of the determination section among at least one peak position of the angular acceleration of the crankshaft generated while the crankshaft rotates in the determination section corresponding to each cylinder. When the peak position for detection detected in the determination section corresponding to any cylinder is a position advanced from the determination reference position corresponding to the cylinder, the peak position for determination is detected as the determination peak position. It is determined that detonation has occurred in any cylinder,
When it is determined that the detonation has occurred, first, an ignition position retarding process for retarding the ignition position of the internal combustion engine is performed, and then a fuel increasing process for increasing the amount of fuel supplied to the internal combustion engine is performed, A detonation suppression control method for a two-cycle internal combustion engine, wherein the detonation is suppressed and the output torque of the internal combustion engine is recovered. 3. The detonation suppression of the two-cycle internal combustion engine according to claim 1, wherein after the ignition position retarding process is performed, the fuel increasing process is performed after waiting for the crankshaft to rotate for a set number of waiting times. Control method. The detonation suppression control method for a two-cycle internal combustion engine according to claim 1 or 2, wherein the fuel increase process is performed immediately after performing the ignition position retarding process. The detonation suppression control method for a two-cycle internal combustion engine according to any one of claims 1 to 4, wherein, in the fuel increase process, the supply amount of the fuel is gradually increased. 5. The detonation suppression control method for a two-cycle internal combustion engine according to claim 1, wherein in the fuel increase process, the supply amount of the fuel is increased stepwise to a target value. 6. 7. The fuel increase amount is determined according to the exhaust temperature so that the fuel supply amount increases as the exhaust temperature of the internal combustion engine increases. The detonation suppression control method for a two-cycle internal combustion engine according to one of the above.

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