JP2012062805A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine control device capable of correctly detecting misfire recovery even if ignition timing is corrected to delay.SOLUTION: The engine control device having an ignition plug 11 for igniting a fuel-air mixture formed in a combustion chamber 6 at set ignition timing includes: a pressure detecting means 30 for detecting a pressure in the combustion chamber; an exhaust temperature detecting means 14; flameout detecting means 16 and 17 for detecting a misfire based on the pressure in the combustion chamber; an ignition timing adjusting means 18 for first delay conrol to low pressure ignition timing when the pressure in the combustion chamber is a pressure at the set ignition timing or lower if the misfire is detected; and misfire recovery detecting means 14, 16 and 17 for detecting misfire recovery after first delay control taking place by the ignition timing adjusting means based on an exhaust temperature detected by the exhaust temperature detecting means 14 after the low pressure ignition timing or the pressure in the combustion chamber detected by the pressure detecting means 30 after the low pressure ignition timing.

Description

  The present invention relates to an engine control apparatus for an engine including an ignition plug that ignites an air-fuel mixture formed in a combustion chamber at a set ignition timing.

  Engines such as those described above have a spark ignition type in which the air-fuel mixture in the combustion chamber is spark-ignited with an ignition plug, but for some reason, the air-fuel mixture in the combustion chamber cannot be ignited and a misfire occurs. There is a case. Therefore, the conventional engine control device is provided with misfire detection means for detecting misfire in the combustion chamber, and when the misfire detection means detects the misfire, the ignition timing for igniting the air-fuel mixture with the spark plug is set in advance from the set ignition timing. The occurrence of misfire is prevented by delaying by a predetermined correction period (for example, 1 ° in crank angle) (see, for example, Patent Document 1). In the apparatus described in Patent Document 1, even if the ignition timing is delayed from the set ignition timing by the correction period, if misfire is detected by the misfire detection means, the ignition timing is further delayed by the correction period and the misfire detection means is used. Each time a misfire is detected, the ignition timing is delayed by a correction period.

JP 2002-39007 A

  The device described in Patent Document 1 describes that when misfire is detected by the misfire detection means, the occurrence of misfire can be prevented by delaying the ignition timing by a correction period. However, depending on the cause of misfire, it may not be possible to prevent misfire by simply delaying the ignition timing by the correction period.

  One possible cause of misfire in a spark ignition engine is an increase in the required ignition voltage at the spark plug. When the spark plug is used for a long period of time, the electrode gap between the ground electrode and the center electrode is expanded, and the ignition required voltage is increased. If the required ignition voltage becomes excessively high, it becomes difficult to properly perform a spark discharge between the ground electrode and the center electrode due to dielectric breakdown between the electrodes, and the mixture cannot be ignited even if the spark plug is operated. A misfire will occur.

The required ignition voltage of the spark plug tends to increase as the atmospheric pressure increases. Therefore, if the combustion chamber pressure in the combustion chamber, which is the pressure of the ignition plug atmosphere, increases, the ignition request voltage of the ignition plug also increases. If the combustion chamber pressure decreases, the ignition request voltage also decreases. In order to prevent the occurrence of misfire due to, it is required to reduce the pressure in the combustion chamber. However, as shown in FIG. 8, in a general engine, in order to maximize efficiency or output, the set ignition timing T is set to a time before the piston reaches Top Dead Center (TDC). Therefore, every time the misfire detection means detects misfire as in the apparatus described in Patent Document 1, if the ignition timing is delayed from the set ignition timing T by the correction period S, the ignition timing is As T → Ta → Tb → Tc, the ignition timing approaches the top dead center. As a result, the combustion chamber pressure in the combustion chamber also increases. FIG. 8 shows combustion chamber combustion before and after top dead center, with the combustion chamber pressure in the combustion chamber on the vertical axis, the crank angle on the horizontal axis, and the top dead center crank angle at 0 ° (zero degrees). It shows the change of the indoor pressure.
Therefore, in the apparatus described in the above-mentioned Patent Document 1, by delaying the ignition timing by each correction period, the pressure in the combustion chamber of the combustion chamber increases, and accordingly, the required ignition voltage also increases. For example, if the spark plug has been used for a long period of time, it becomes a state where misfire is likely to occur, and in the state where misfire has occurred, there is a problem that it is difficult to recover from misfire. .

Further, in the engine control device, misfire is detected by the misfire detection means, and control is performed to prevent misfire by delaying the ignition timing by the correction period. Therefore, in order to appropriately prevent misfire, The misfire detection means is required to detect misfire promptly from the occurrence of this.
On the other hand, even after performing control to prevent misfire, if misfire continues, it is necessary to continue control to prevent misfire, so control to prevent misfire It is also required to accurately detect whether misfire has been recovered after performing the above.

  The present invention has been made in view of such circumstances, and its purpose is to appropriately detect misfires quickly from the occurrence of misfires and appropriately perform control for preventing misfires, and appropriately prevent misfires. Another object of the present invention is to provide an engine control apparatus that can appropriately detect whether or not misfire has been recovered after performing control for preventing misfire.

In order to achieve the above object, an engine control apparatus according to the present invention comprises an ignition plug for igniting an air-fuel mixture formed in a combustion chamber at a set ignition timing. A pressure detection means for detecting the pressure in the combustion chamber of the chamber, an exhaust temperature detection means for detecting the temperature of the exhaust gas from the combustion chamber, and a misfire in the combustion chamber based on the pressure in the combustion chamber detected by the pressure detection means When the misfire detection means detects misfire, the ignition timing at which the air-fuel mixture is ignited by the spark plug is set to the ignition chamber pressure at the set ignition timing. Ignition timing adjusting means for performing a first delay control for delaying to a low pressure ignition timing that is a low pressure equal to or lower than a pressure;
Based on the exhaust temperature detected by the exhaust temperature detecting means after the low pressure ignition timing or the pressure in the combustion chamber detected by the pressure detecting means after the low pressure ignition timing, the ignition timing adjusting means makes the first A misfire recovery detecting means for detecting misfire recovery after the one-delay control is performed is provided.

According to the above characteristic configuration, misfire in the combustion chamber can be detected based on the pressure in the combustion chamber detected by the pressure detection means. Therefore, for example, misfire can be detected more quickly than when the exhaust gas temperature is used for misfire detection. If exhaust temperature is used to detect misfire, the exhaust temperature does not decrease immediately after a misfire occurs due to the influence of heat received from a hot engine or the heat capacity of the temperature sensor itself. When misfire is detected, it takes time from the occurrence of misfire to the detection of misfire. On the other hand, if misfire occurs, the pressure rise due to combustion disappears, so the pressure in the combustion chamber will drop in the cycle where the misfire occurred, and by catching the drop in pressure in the combustion chamber, Misfire can be detected quickly.
And the first delay control for preventing a misfire can be started rapidly by detecting misfire rapidly based on the pressure in a combustion chamber. In the first delay control, the ignition timing is delayed from the set ignition timing to the low pressure ignition timing. At the low pressure ignition timing, since the pressure in the combustion chamber is equal to or lower than the pressure of the set ignition timing, the pressure in the combustion chamber does not rise above the pressure that appears at the preset ignition timing. Therefore, when the air-fuel mixture is ignited by the spark plug at the low pressure ignition timing, it is possible to prevent the ignition request voltage from rising, and therefore it is possible to appropriately prevent the occurrence of misfire due to the increase in the ignition request voltage.
By performing the first delay control, when the misfire is recovered, the combustion state returns to normal, and thus the exhaust temperature rises after the low pressure ignition timing. Further, the pressure in the combustion chamber also increases due to combustion, so that the pressure in the combustion chamber increases after the low pressure ignition timing. Therefore, according to the above characteristic configuration, the misfire recovery is detected based on the exhaust temperature detected by the exhaust temperature detecting means after the low pressure ignition timing or the pressure in the combustion chamber detected by the pressure detecting means after the low pressure ignition timing. it can. In detecting the misfire recovery in this way, the exhaust temperature or the pressure in the combustion chamber is detected after the low pressure ignition timing, which is the delayed ignition timing, so the misfire is recovered by the delay of the ignition timing, and the combustion state is brought about. In some cases, the recovered combustion can appropriately capture an increase in exhaust gas temperature or an increase in pressure in the combustion chamber, and can appropriately detect misfire recovery.

  According to a further characteristic configuration of the engine control device according to the present invention, the misfire recovery detection means detects misfire recovery when the exhaust temperature detected by the exhaust temperature detection means exceeds a reference misfire recovery detection exhaust temperature. It is in.

  According to the above-described feature configuration, for example, the exhaust gas temperature when the misfire is recovered by an experiment or the like is measured in advance and is known, and based on the exhaust gas temperature or the like, the reference misfire recovery detection exhaust gas temperature for detecting misfire recovery Can be set. The misfire recovery detection means can detect the misfire recovery appropriately only by determining whether or not the exhaust gas temperature detected by the exhaust gas temperature detection means exceeds the reference misfire recovery detection exhaust gas temperature.

  The engine control device according to the present invention is further characterized in that the misfire recovery detection means is a pressure in the combustion chamber detected by the pressure detection means at a pressure detection timing determined after the low pressure ignition timing within one cycle. The point is that misfire recovery is detected when the pressure exceeds the reference misfire recovery detection pressure.

  According to the above characteristic configuration, when detecting the recovery of misfire, by setting the pressure detection timing to a predetermined timing after the low pressure ignition timing, it is possible to accurately grasp the increase in the pressure in the combustion chamber due to the misfire recovery. . Accordingly, the misfire recovery detection means determines whether or not the combustion chamber pressure detected by the pressure detection means exceeds the reference misfire recovery detection pressure at the pressure detection timing determined after the low pressure ignition timing, thereby recovering the misfire. Can be accurately detected.

  The engine control device according to the present invention is further characterized in that the misfire recovery detection means is a pressure in the combustion chamber detected by the pressure detection means at a pressure detection timing determined after the low pressure ignition timing within one cycle. , The misfire recovery is detected based on the difference between the pressure in the combustion chamber in the current cycle and the pressure in the combustion chamber in the immediately preceding cycle.

  According to the above characteristic configuration, when detecting the recovery of misfire, by setting the pressure detection timing to a predetermined timing after the low pressure ignition timing, it is possible to accurately grasp the increase in the pressure in the combustion chamber due to the misfire recovery. . Moreover, the misfire recovery detection means detects the misfire recovery based on the difference between the pressure in the combustion chamber in the current cycle and the pressure in the combustion chamber in the previous cycle. By comparing, it is possible to accurately detect how much the pressure in the combustion chamber has risen and to detect misfire recovery, and to accurately detect misfire recovery.

  The engine control device according to the present invention is further characterized in that the misfire recovery detection means is a pressure in the combustion chamber detected by the pressure detection means at a pressure detection timing determined after the low pressure ignition timing within one cycle. For the above, based on the pressure difference between the pressure in the combustion chamber in the cycle in which the first delay control is performed by the ignition timing adjusting means and the pressure in the combustion chamber in the cycle in which misfire is detected by the misfire detection means, The point is to detect misfire recovery.

  According to the above characteristic configuration, when detecting the recovery of misfire, by setting the pressure detection timing to a predetermined timing after the low pressure ignition timing, it is possible to accurately grasp the increase in the pressure in the combustion chamber due to the misfire recovery. . Moreover, the misfire recovery detection means is based on the difference between the pressure in the combustion chamber in the cycle in which the first delay control is performed by the ignition timing adjustment means and the pressure in the combustion chamber in the cycle in which misfire is detected by the misfire detection means. Since misfire recovery is detected, it is possible to accurately detect how much the pressure in the combustion chamber has risen in the cycle in which misfire is detected, to detect misfire recovery, and to accurately detect misfire recovery.

  The engine control apparatus according to the present invention is further characterized in that the set ignition timing is set to a timing earlier than a top dead center by a set period for ignition, and the low pressure ignition timing is set to be higher than the top dead center. Only the ignition set period is set to a later time and a later time.

  According to the above characteristic configuration, when setting the low pressure ignition timing, using the ignition setting period used to set the set ignition timing, the top dead center is used as a reference and the ignition setting period is set from the top dead center. The low-pressure ignition timing can be set based on the ignition setting period depending on whether the timing is later or later than that timing. Therefore, it is possible to accurately detect misfire recovery while easily setting the low pressure ignition timing. In addition, since the set ignition timing is set to a timing earlier than the top dead center by the ignition set period, adjusting the ignition set period can improve the engine efficiency or increase the engine output. can do.

  According to a further characteristic configuration of the engine control device according to the present invention, the ignition timing adjusting means performs a predetermined setting until the misfire recovery is detected by the misfire recovery detecting means after performing the first delay control. The second delay control for delaying the ignition timing by a delay period is configured to be repeatedly performed.

  As described above, by performing the first delay control by the ignition timing adjusting means, it is possible to prevent the occurrence of misfire due to an increase in the ignition request voltage, but there are cases where the misfire cannot be recovered by performing only the first delay control. Conceivable. Therefore, according to the above characteristic configuration, the ignition timing adjusting means repeatedly performs the second delay control until the misfire recovery is detected by the misfire recovery detecting means. In the low pressure ignition timing, the pressure in the combustion chamber is equal to or lower than the pressure of the set ignition timing. Therefore, if the ignition timing is further delayed by the set delay period from the low pressure ignition timing, the pressure in the combustion chamber will further decrease. Further, the required ignition voltage can be further reduced. Therefore, the air-fuel mixture can be ignited by the spark plug with the ignition request voltage kept as low as possible, so that the misfire recovery can be accurately detected after ensuring the recovery of misfire due to a decrease in the ignition request voltage. Can do.

Overall schematic diagram of the engine Graph showing change in combustion chamber pressure when misfire is detected The graph which shows the change of the pressure of a combustion chamber and the change of the ignition request voltage which adapted the delay of the ignition timing in the engine control apparatus which concerns on this invention Graph showing changes in combustion chamber pressure when misfire recovery is detected The flowchart which shows operation | movement of the control part in 1st Embodiment. The flowchart which shows operation | movement of the control part in 2nd Embodiment. Graph showing changes in exhaust temperature when misfire recovery is detected Graph showing change in combustion chamber pressure adapting to ignition timing delay in conventional engine control system

An embodiment of an engine control device according to the present invention will be described with reference to the drawings.
[First Embodiment]
As shown in FIG. 1, an engine 100 controlled by the engine control apparatus according to the present invention includes a cylinder 1 and a cylinder head 2 connected to an upper portion of the cylinder 1. The piston 5 connected to the crankshaft 4 through 3 is accommodated so as to be reciprocally movable in the vertical direction.
The combustion chamber 6 is formed by the top surface of the piston 5, the inner surface of the cylinder 1, and the lower surface of the cylinder head 2. An intake passage 7 and an exhaust passage 8 are opened in the combustion chamber 6, an intake valve 9 is provided on the intake passage 7 side of the combustion chamber 6, and an exhaust valve 10 is provided on the exhaust passage 8 side of the combustion chamber 6. ing. The cylinder head 2 is provided with a spark plug 11 at the approximate center of its lower surface.

  The engine 100 reciprocates the piston 5 in the cylinder 1 and opens and closes the intake valve 9 and the exhaust valve 10 to operate the ignition plug 11 at a desired time. The compression stroke, the combustion / expansion stroke, and the exhaust stroke are sequentially performed. Thereby, the reciprocating motion of the piston 5 is output as a rotational motion of the crankshaft 4 by the connecting rod 3. Such a configuration is the same as that of a normal four-stroke internal combustion engine.

  The engine 100 uses gas fuel such as city gas (13A) as fuel. The intake passage 7 is provided with a mixer 12 that supplies fuel G to air A flowing through the intake passage 7 to form an air-fuel mixture M, and a throttle valve 13 that can adjust the passage cross-sectional area of the intake passage 7. ing. The cylinder head 2 is provided with a pressure sensor 30 (corresponding to pressure detection means) for detecting the pressure in the combustion chamber 6, and the exhaust path 8 detects the temperature of the exhaust gas flowing through the exhaust path 8. An exhaust gas temperature sensor 14 (corresponding to exhaust gas temperature detection means) is provided.

  Although not shown, the spark plug 11 is provided with a center electrode and a ground electrode facing each other at a tip portion (lower end portion in FIG. 1) with a gap between the center electrode and the ground electrode. By performing spark discharge, the air-fuel mixture M is configured to spark-ignite. The center electrode and the ground electrode are disposed at positions facing each other in the vertical direction, and the interval between them is adjusted to an interval suitable for spark ignition of the air-fuel mixture M.

  The crankshaft 4 is provided with a rotation speed sensor 15 that detects the rotation speed of the crankshaft 4 and a crank angle sensor 31 that detects the crank angle, and is provided with a control unit 16 that controls the operation of the engine 100. Information detected by the speed sensor 15 and the crank angle sensor 31 is input to the control unit 16. The relationship between the engine output and the engine speed is set in advance, and the control unit 16 obtains the target output as the engine output from the magnitude of the load and the like, and the relationship between the preset engine output and the engine speed. The target rotational speed for outputting the target output from is obtained. And the control part 16 is comprised so that the opening degree etc. of the throttle valve 12 may be controlled so that the rotational speed detected by the rotational speed sensor 15 becomes the target rotational speed obtained.

In the engine 100, the intake stroke in which the air-fuel mixture M is taken into the combustion chamber 6 is performed when the piston 5 descends from the top dead center with the intake valve 9 opened. Next, when the piston 5 moves up with the intake valve 9 closed, a compression stroke for compressing the air-fuel mixture M in the combustion chamber 6 is performed.
The control unit 16 operates the spark plug 11 at the set ignition timing, sparks the spark plug 11 to ignite the mixture M in the combustion chamber 6. The set ignition timing is set, for example, to a timing that is earlier than the top dead center by an ignition setting period (for example, 14 ° in crank angle). Thereby, the air-fuel mixture M in the combustion chamber 6 is combusted and the combustion / expansion stroke is performed. Next, the engine 100 performs an exhaust stroke in which the exhaust gas E in the combustion chamber 6 is exhausted to the exhaust passage 8 by raising the piston 5 with the exhaust valve 10 being opened.
Thus, the engine 100 is configured to repeatedly perform a series of operations for performing each stroke in the order of the intake stroke, the compression stroke, the combustion / expansion stroke, and the exhaust stroke.

  When the ignition request voltage in the spark plug 11 becomes excessively high, it becomes difficult to appropriately perform a spark discharge between the ground electrode and the center electrode due to dielectric breakdown between the center electrode and the ground electrode. Even if it is operated, the air-fuel mixture cannot be ignited and a misfire may occur. Such a phenomenon occurs with respect to the spark plug 11 when the electrode gap between the ground electrode and the center electrode is widened for a long time since the start of use, and the replacement timing of the spark plug 11 is approaching. easy. Therefore, in the engine control apparatus according to the present invention, in order to prevent the occurrence of misfire due to an increase in the ignition request voltage in the spark plug 11, as shown in FIG. 1, misfire detection means 17 for detecting misfire in the combustion chamber 6, The ignition timing adjusting means 18 for adjusting the ignition timing at which the air-fuel mixture M is ignited by the spark plug 11 and the misfire recovery detecting means 19 for detecting misfire recovery are provided.

  The misfire detection means 17 includes a pressure sensor 30 and a control unit 16 to which the pressure in the combustion chamber detected by the pressure sensor 30 can be freely input. Based on the pressure in the combustion chamber in the combustion chamber 6, the misfire detection means 17 detects misfire. It is configured so that it can be detected.

Hereinafter, a specific method for detecting misfire will be described. In FIG. 2, the horizontal axis represents the crank angle measured by the crank angle sensor 31, and the vertical axis represents the combustion chamber pressure P in the combustion chamber 6 measured by the pressure sensor 30. As indicated by the solid line in the figure, the combustion chamber pressure P1 during normal combustion rises in the compression process, and the air-fuel mixture burns and expands by ignition near the compression top dead center. The indoor pressure P increases rapidly. Then, the maximum pressure P1m is reached after compression top dead center, and then the pressure P1 in the combustion chamber decreases in the expansion stroke. On the other hand, as shown by the broken line in the figure, the change in the combustion chamber pressure P2 at the time of misfiring simply indicates the pressure change of the compression / expansion due to the vertical movement of the piston 5, so There is no increase, and the maximum pressure P2m is reached at the compression top dead center, which is much lower than the maximum pressure P1m during normal combustion. And it becomes a combustion chamber pressure waveform of a right-and-left object centering around a compression top dead center.
Therefore, it is easy to detect misfire by comparing the combustion chamber pressure P1 at the time of normal combustion and the combustion chamber pressure P2 at the time of misfiring with the pressure P in the combustion chamber in the cycle in which the pressure is currently detected by the pressure sensor 30. It becomes possible. In particular, the maximum pressure P1m (for example, 9.0 MPa) at the time of normal combustion and the maximum pressure P2m (for example, 4.0 MPa) at the time of misfire are compared with the maximum pressure Pm in the combustion chamber in the cycle in which the pressure is currently detected by the pressure sensor 30. Thus, since the pressure difference can be easily detected, misfire can be detected accurately and accurately. For example, in the misfire detection means 17, a reference misfire detection pressure Ps (for example, 5.0 MPa) for detecting misfire in the range of P1m>Ps> P2m is set in advance, and the current in-combustion chamber 6 detected by the pressure sensor 30 is set. When the maximum pressure Pm becomes equal to or lower than the reference misfire detection pressure Ps, misfire is detected.

  The ignition timing adjusting means 18 is provided in the control unit 16. When the misfire detection means 17 detects misfire, the ignition timing adjusting means 18 sets the ignition timing at which the air-fuel mixture M is ignited by the spark plug 11, and the combustion in the combustion chamber 6 at the set ignition timing. The first delay control is performed to delay the low pressure ignition timing at which the pressure is lower than the indoor pressure. Therefore, at the low pressure ignition timing, the combustion chamber pressure in the combustion chamber 6 is equal to or lower than the pressure at the set ignition timing, the combustion chamber pressure in the combustion chamber 6 does not increase, and an increase in ignition request voltage can be prevented. . Therefore, when misfire is detected, the ignition timing can be adjusted to a low pressure ignition timing that can prevent an increase in the required ignition voltage, and the operation of igniting the air-fuel mixture M can be performed by the spark plug 11 to recover the misfire. Can be made.

Hereinafter, a specific method of adjusting the ignition timing by the ignition timing adjusting means 18 will be described based on the graph of FIG.
FIG. 3A shows the combustion chamber 6 in the combustion chamber 6 before and after the top dead center with the combustion chamber pressure in the combustion chamber 6 on the vertical axis, the crank angle on the horizontal axis, and the crank angle at the top dead center at 0 °. This shows the change in the pressure in the combustion chamber. FIG. 3B shows the ignition timing delay due to the execution of the first delay control and the second delay control by the ignition timing adjusting means 18 with the ignition request voltage in the spark plug 11 taken on the vertical axis and the crank angle taken on the horizontal axis. The change of the ignition request voltage accompanying with is shown.

  In the first delay control, the ignition timing at which the air-fuel mixture M is ignited by the spark plug 11 is delayed from the set ignition timing T to the low pressure ignition timing T1. As shown in FIG. 3A, the set ignition timing T is set to a timing earlier than the top dead center by a set angle for ignition H that is a set angle (for example, 14 °) at a crank angle. The low pressure ignition timing T1 is set, for example, at a timing after the ignition set period H that is a set angle (for example, 14 °) with respect to the crank angle from the top dead center. In this way, the ignition timing adjusting means 18 performs the first delay control that delays the ignition timing from the set ignition timing T to the low pressure ignition timing T1, thereby increasing the ignition request voltage as shown in FIG. Thus, it is possible to prevent the occurrence of misfire due to an increase in the required ignition voltage.

A description will be given of the setting of the low pressure ignition timing. As shown in FIG. 3A, the low pressure ignition timing is set to a certain timing (timing) within the low pressure period W in which the pressure in the combustion chamber 6 is equal to or lower than the pressure at the set ignition timing T. . In the above-described case, the set ignition timing T and the low pressure ignition timing T1 are symmetric with respect to the top dead center depending on whether the ignition timing is set before or after the ignition dead time H. The low pressure ignition timing T1 is set. Thus, when setting the low pressure ignition timing, the ignition set period H used for setting the set ignition timing T can be used as it is with reference to the top dead center, and the low pressure ignition timing can be set. While being easy, the low pressure ignition timing can be set at an appropriate time when the pressure in the combustion chamber 6 is equal to or lower than the pressure at the set ignition timing T.
Instead of such a setting, for example, from the timing after the top dead center for the ignition set period (for example, 14 ° in crank angle) H, and for the timing after the set correction period (for the crank angle of 2 °) (see FIG. 3 (a) T21) may be the low pressure ignition timing.
In this way, for the low pressure ignition timing, only the ignition set period H is higher than the top dead center in the low pressure period W in which the pressure in the combustion chamber 6 is equal to or lower than the pressure at the set ignition timing T in one cycle. It can be set to a subsequent time (timing) or a time (timing) later than that time (timing).

  Further, the combustion chamber pressure in the combustion chamber 6 is measured in advance by an experiment or the like, and the timing at which the combustion chamber pressure in the combustion chamber 6 is lower than the pressure at the set ignition timing T is determined in advance. The obtained timing can also be set as the low pressure ignition timing.

  Further, when the misfire detection means 17 detects misfire, the ignition timing adjusting means 18 performs the first delay control. However, even if this first delay control is performed, the misfire may not be recovered. Therefore, as described above, the ignition timing adjustment means 18 delays the ignition timing by a predetermined set delay period until the misfire recovery detection means 19 detects the misfire recovery after performing the first delay control. The second delay control is repeatedly performed.

  The misfire recovery detection means 19 includes an exhaust gas temperature sensor 14 and a pressure sensor 30 and a control unit 16 to which detection information of the exhaust gas temperature sensor 14 and the pressure sensor 30 can be input. Alternatively, misfire recovery is detected based on the exhaust temperature Et in the exhaust path 8 through which exhaust gas combusted in the combustion chamber 6 is exhausted.

Next, a specific method for detecting misfire recovery will be described. In FIG. 4, the horizontal axis represents the crank angle measured by the crank angle sensor 31, and the vertical axis represents the pressure in the combustion chamber measured by the pressure sensor 30. The solid line in the figure shows the pressure waveform of the pressure P3 in the combustion chamber of the cycle in which the misfire is recovered and is in the combustion state as a result of performing the control to delay the ignition timing for misfire recovery, and the broken line in the figure is in the misfire state The pressure waveform of a certain combustion chamber pressure P2 is shown. In the solid line pressure waveform in the figure, the ignition timing delay control is performed in which the ignition timing is delayed by 20 ° ATDC (After Top Dead Center) in the crank angle by the first delay control and the second delay control. Misfire has recovered due to the timing delay, and it is in a burning state. The rise in pressure due to the combustion is detected at a timing later than the low-pressure ignition timing, which is the ignition timing subjected to delay control, and this crank angle is a combustion that shows a peak P3m of the combustion chamber pressure P3 due to combustion in the vicinity of 35 ° ATDC. The indoor pressure waveform is obtained.
Thus, the peak P3m of the combustion chamber pressure P3 obtained by the combustion when the misfire is recovered is a very high pressure compared with the combustion chamber pressure P2l when the crank angle at the time of misfire is around 35 ° ATDC. The time when the crank angle is 35 ° ATDC is set as the pressure detection timing I, and the current combustion chamber pressure obtained by the pressure detection means is obtained from the peak P3m of the combustion chamber pressure when the misfire is recovered and the combustion chamber pressure P21 when the misfire is recovered. It becomes possible to detect misfire recovery. Therefore, for example, in the misfire recovery detection means 19, a reference misfire recovery detection pressure Pbs for detecting misfire recovery in the range of P3m>Pbs> P2l is set in advance, and the crank angle in the current cycle detected by the pressure sensor 30 is 35. It can be configured that misfire recovery is detected when the pressure P in the combustion chamber at the time of ATDC becomes equal to or higher than the reference misfire recovery detection pressure Pbs.
Further, the pressure detection timing may be any timing in the misfire recovery detectable period. For example, the timing at which the crank angle is 60 ° ATDC can be set as the pressure detection timing. In this case, for example, the reference misfire recovery detection pressure Pbs can be set to 1.0 MPa. Thus, misfire recovery is detected when the detected pressure P when the crank angle in the current cycle is 60 ° ATDC becomes 1.0 MPa or more.
The pressure detection timing is set to a timing after a set period from the top dead center or the ignition timing delayed by the first delay control or the second delay control. From the delayed ignition timing, it can be set to a timing after the set period.

  In the above-described embodiment, the reference misfire recovery detection pressure Pbs is set and compared with the combustion chamber pressure P in the current cycle detected by the pressure sensor 30, so that misfire recovery is detected. For example, the misfire recovery may be detected by a pressure difference between the combustion chamber pressure P obtained in the current cycle and the combustion chamber pressure P2 obtained in the immediately preceding cycle. In this case, a reference misfire recovery detection pressure difference Prs is set in advance as a reference for detecting misfire recovery based on the pressure difference. In the detection of misfire recovery in the present embodiment, as shown in FIG. 4, the pressure in the combustion chamber P detected at the pressure detection timing I (for example, the crank angle is 35 ° ATDC) in the current cycle subjected to delay control, and the immediately preceding The pressure difference (P−P2l) compared with the reference misfire recovery detection pressure difference Prs set in advance at the pressure detection timing I in the combustion chamber pressure P2 of the cycle in the misfire state is compared with the preset reference misfire recovery detection pressure difference Prs. -P2l) may be configured such that misfire recovery is detected when the reference misfire recovery detection pressure difference Prs is greater than or equal to.

  When misfire recovery is detected by a pressure difference, the object to be compared with the combustion chamber pressure obtained in the current cycle may be the pressure in the combustion chamber in the cycle in which misfire is detected. By doing so, even if the misfire gradually recovers and the pressure in the combustion chamber gradually recovers accordingly, the misfire recovery is detected by the pressure difference based on the pressure in the combustion chamber immediately after the misfire. It is possible to detect a misfire recovery. The history of the pressure in the combustion chamber detected by the pressure sensor 30 including the pressure in the combustion chamber detected in the cycle immediately after the misfire is detected is stored in data storage means (not shown) of the control unit 16. .

The operations of the misfire detection means 17, the ignition timing adjustment means 18 and the misfire recovery detection means 19 performed by the control unit 16 will be described based on the flowchart of FIG. When the engine is a multi-cylinder engine, this flow is executed for each cylinder. In step # 1 (referred to as # 1 in FIG. 5 and so on), the pressure P in the combustion chamber detected by the pressure sensor 30 is detected for each predetermined crank angle θ. Here, the predetermined crank angle θ may be detected at any angle as long as misfire detection can be accurately performed. However, in order to maintain high misfire detection accuracy, the crank angle is usually set to 0 at the crank angle. The pressure is detected with a detection cycle of 5 ° or less. In addition, since the maximum pressure and the maximum pressure increase rate can be obtained in the compression / expansion stroke, the pressure sampling interval may be limited to the compression / expansion stroke interval.
In step # 2, the maximum value Pm of the combustion chamber pressure P obtained in the above cycle is obtained. In step # 3, it is determined whether or not the maximum value Pm of the combustion chamber pressure P detected in step # 2 is greater than a preset reference misfire detection pressure Ps. If it is larger than the reference misfire detection pressure Ps, misfire is not detected and the flow ends. On the other hand, if it is below reference misfire detection pressure Ps, it will progress to Step # 4. That is, it is determined that the detected maximum combustion chamber pressure Pm is not sufficiently increased and misfire has occurred, and in step # 4, the first delay control for recovery from misfire is performed.

  Next, the controller 16 determines in step # 6 whether or not misfire has actually recovered after the ignition timing adjusting means 18 performs the first delay control in step # 4. Detection of misfire recovery in step # 6 is performed based on the pressure in the combustion chamber detected in step # 5. That is, when the pressure P in the combustion chamber detected at the pressure detection timing I (for example, the crank angle is 60 ° ATDC) is larger than a preset reference misfire recovery detection pressure Pbs (for example, 0.5 MPa), it is determined that the combustion state is present. Detect misfire recovery. On the other hand, when the pressure P in the combustion chamber at the pressure detection timing I is equal to or lower than the reference misfire recovery detection pressure Pbs, it is determined that the misfire state continues, and the process proceeds to step # 7 to recover misfire. Delay control is performed.

  As described above, if the misfire recovery is not detected by the first delay control by the ignition timing adjusting means 18, the second delay control is performed to delay the ignition timing by a predetermined set delay period (for example, 2 ° in crank angle). In this way, the ignition timing adjusting means 18 performs the second delay control as described above, thereby delaying the ignition timing from the low pressure ignition timing T1 to T21 as shown in FIG. . As a result, as shown in FIG. 3B, when the ignition timing is delayed from the low pressure ignition timing T1 to T21, the ignition request voltage is lowered. Therefore, it is possible to perform an operation of igniting the air-fuel mixture M with the spark plug 11 in a state where the ignition request voltage is lowered, and to recover from misfire.

  In some cases, misfire recovery may not be achieved if the ignition timing adjusting means 18 performs the second delay control only once. Therefore, the ignition timing adjusting means 18 repeatedly performs the second delay control until the misfire recovery is detected (steps # 5, # 6, and # 7). In this way, the ignition timing adjusting means 18 repeatedly performs the second delay control, so that the ignition timing is sequentially delayed from T21 → T22 → T23 as shown in FIG. As a result, as shown in FIG. 3B, when the ignition timing is sequentially delayed from T21 to T22 to T23, the ignition request voltage is sequentially decreased. Therefore, it is possible to perform the operation of igniting the air-fuel mixture M with the spark plug 11 with the ignition request voltage kept as low as possible, and the misfire can be recovered by increasing the ignition request voltage.

[Second Embodiment]
The overall configuration of the second embodiment is substantially the same as that of the first embodiment, and only the misfire detection control performed by the control unit 16 is different. Therefore, the description of the ignition timing adjustment and misfire recovery detection control is omitted. That is, in the first embodiment, misfire is detected based on the detected maximum combustion chamber pressure Pm. However, in this embodiment, the rate of increase in the combustion chamber pressure (dP / dθ) from the detected combustion chamber pressure P is detected. D is determined, and the misfire is detected by the maximum pressure increase rate Dm.

In FIG. 2, the maximum pressure increase rate (dP / dθ) is illustrated in the pressure waveform during normal combustion indicated by the solid line and the pressure waveform in the misfire state indicated by the broken line. As shown in the figure, in the pressure waveform during normal combustion indicated by the solid line, the pressure in the combustion chamber also suddenly increases due to the combustion of the air-fuel mixture near the compression top dead center, but combustion occurs when the pressure in the combustion chamber during normal combustion increases. The maximum value D1m of the indoor pressure increase rate is obtained. On the other hand, in the misfire state pressure increase rate indicated by the broken line, there is no sudden increase in the pressure in the combustion chamber due to the combustion of the air-fuel mixture, so the pressure rises due to compression and expansion without combustion, and before the compression top dead center The maximum value D2m of the pressure increase rate in the combustion chamber is obtained, and a large increase rate is not obtained unlike the pressure increase rate D1m in the combustion chamber obtained during normal combustion.
Therefore, the maximum value D1m of the pressure increase rate D1 in the combustion chamber during normal combustion and the maximum value D2m of the pressure increase rate D2 in the combustion chamber at the time of misfire are obtained from the pressure in the combustion chamber detected from the pressure in the combustion chamber. It becomes possible to detect misfire by comparing with the maximum combustion chamber pressure increase rate Dm. For example, in the misfire detection means 17, a reference misfire detection pressure increase rate Ds for detecting misfire in a range of D1m>Ds> D2m is set in advance, and the maximum of the current cycle obtained from the pressure in the combustion chamber detected by the pressure sensor 30 is set. When the pressure increase rate Dm in the combustion chamber becomes equal to or less than the reference misfire detection pressure increase rate Ds, misfire is detected.

  Control of misfire detection in the present embodiment will be described with reference to the flowchart of FIG. In step # 11, as in the first embodiment, the pressure in the combustion chamber detected by the pressure sensor 30 is sampled for each predetermined crank angle θ. In step # 12, the pressure increase rate D is calculated based on the pressure in the combustion chamber detected by the pressure sensor 30. In step # 13, the maximum value Dm of the pressure increase rate D obtained in step # 12 is obtained. Here, since the maximum pressure increase rate Dm is obtained in the compression / expansion stroke, the pressure sampling interval in step # 11 may be limited to the compression / expansion stroke interval. Next, in step # 14, it is determined whether or not the maximum pressure increase rate Dm obtained in step # 13 is larger than a preset reference misfire detection pressure increase rate Ds. As a result, if the maximum pressure increase rate Dm is greater than the reference misfire detection pressure increase rate Ds, it is determined that no misfire has occurred, and this flow ends. On the other hand, if the reference misfire detection pressure increase rate Ds or less, the process proceeds to step # 15. That is, it is determined that the actual combustion chamber pressure increase rate Pm is small and misfire has occurred, and the first delay control is performed in step # 15. And about the step after step # 16, the same control as the step after step # 5 of FIG. 5 in 1st Embodiment is performed.

[Third Embodiment]
The overall configuration of the third embodiment is substantially the same as that of the first embodiment, and only the misfire recovery detection control performed by the control unit 16 is different. Therefore, the description of misfire detection control and ignition timing adjustment is omitted, and misfire is performed. The recovery detection control will be described. In other words, the third embodiment differs from the first embodiment shown in the flowchart of FIG. 5 only in the determination method of misfire recovery detection in step # 5 and step # 6. In the first embodiment, the detection of misfire recovery in step # 6 is performed by the pressure in the combustion chamber, but in the present embodiment, it is performed by the exhaust gas temperature Et. Therefore, in step # 5, the combustion chamber pressure P is detected in the first embodiment, and in this embodiment, the exhaust temperature Et is detected. The detection of the exhaust temperature Et is the exhaust valve opening period during the exhaust stroke after the low pressure ignition timing in the combustion cycle, for example, at a crank angle of 40 ° BBDC (Before Bottom Dead Center) to 10 ° ATDC. It is preferable to detect misfire recovery by detecting the exhaust temperature Et.

  In step # 6, the detected exhaust temperature Et is compared with a preset reference misfire recovery detection exhaust temperature Ets, and the detected exhaust temperature Et is higher than the preset reference misfire recovery detection exhaust temperature Ets. Determines that a combustion state has occurred and detects misfire recovery. On the other hand, when the actual exhaust temperature Et has not risen to the reference misfire recovery detection exhaust temperature Ets, it is determined that the misfire state has occurred, and the second ignition timing delay for performing further misfire recovery control in step # 7 Control is performed.

  The reference misfire recovery detection exhaust temperature Ets can be set to any appropriate value. The reference misfire recovery detection exhaust temperature Ets can be obtained in advance by an experiment or the like. It can also be obtained by theoretical calculation such as the exhaust temperature Et during motoring and the state equation of gas. FIG. 7 shows an example of detection of misfire recovery when the reference misfire recovery detection exhaust temperature Ets is 350 ° C. In the figure, the horizontal axis indicates time, and the vertical axis indicates temperature. The temperature detected by the exhaust gas temperature sensor 14 is indicated. When the exhaust gas temperature Et detected by the exhaust gas temperature sensor 14 becomes higher than the reference misfire recovery detection exhaust gas temperature Ets 350 ° C., it is determined that the misfire has been recovered.

  In the present embodiment, the detection temperature of the exhaust gas temperature sensor is used for detection of misfire. However, when noise or the like becomes a problem, the detection temperature Et is set to, for example, a crank angle of 40 ° BBDC to 10 ° ATDC. It is also possible to detect misfire by detecting a plurality of times during the period and averaging. Further, the misfire is detected by providing the reference misfire recovery detection exhaust temperature Ets. For example, the misfire detection is performed based on the exhaust temperature at the time of misfire and the temperature change amount of the temperature detected in the current cycle. You can also.

  Further, in the present embodiment, the exhaust gas temperature sensor 14 is provided for each cylinder and the exhaust gas temperature Et is detected for each cylinder. However, although the accuracy is somewhat lowered, the response speed is sufficiently rapid. If the exhaust gas temperature sensor 14 that can detect the exhaust gas temperature change in the cycle with high responsiveness is used, the exhaust gas from each cylinder may be provided with a single exhaust gas temperature sensor after the exhaust gas merges in the exhaust pipe. Misfire detection and misfired cylinders can be identified based on the temperature detection result.

[Another embodiment]
In the above embodiment, after the ignition timing adjusting means 18 performs the first delay control, if the misfire recovery detecting means 19 cannot detect the misfire recovery, it immediately shifts from the first delay control to the second delay control. Thus, the second delay control is performed. Instead of this configuration, for example, after the ignition timing adjusting means 18 performs the first delay control, an ignition operation in which the air-fuel mixture M is ignited by the spark plug 11 with the ignition timing as the low pressure ignition timing T1 is performed a set number of times ( If misfire recovery cannot be detected by the misfire recovery detection means 19 even if it is performed once or more, the second delay control may be performed by shifting from the first delay control to the second delay control.

  As explained above, the control for detecting misfire quickly from the occurrence of misfire and appropriately preventing the misfire can be appropriately prevented, and the control for preventing the misfire can be performed. It is possible to provide an engine control device that can appropriately detect whether a misfire has been recovered later.

6 Combustion chamber 11 Spark plug 14 Exhaust temperature detection means 14, 16, 19 Misfire recovery detection means 16, 17 Misfire detection means 18 Ignition timing adjustment means 30 Pressure detection means 100 Engine E Exhaust I Pressure detection timing P Combustion chamber pressure Ps Reference misfire Recovery detection pressure Et Exhaust temperature Ets Standard misfire recovery detection exhaust temperature

Claims (7)

In an engine control device for an engine having an ignition plug for igniting an air-fuel mixture formed in a combustion chamber at a set ignition timing,
Pressure detecting means for detecting a pressure in the combustion chamber of the combustion chamber;
Exhaust temperature detecting means for detecting the temperature of the exhaust from the combustion chamber;
Misfire detection means for detecting misfire in the combustion chamber based on the pressure in the combustion chamber detected by the pressure detection means;
When the misfire detection means detects misfire, the ignition timing at which the air-fuel mixture is ignited by the spark plug is set to a low pressure at which the combustion chamber pressure in the combustion chamber is lower than the pressure at the set ignition timing. Ignition timing adjusting means for performing first delay control for delaying the pressure ignition timing;
Based on the exhaust temperature detected by the exhaust temperature detecting means after the low pressure ignition timing or the pressure in the combustion chamber detected by the pressure detecting means after the low pressure ignition timing, the ignition timing adjusting means makes the first An engine control device comprising misfire recovery detection means for detecting misfire recovery after one delay control is performed.   The engine control apparatus according to claim 1, wherein the misfire recovery detection means detects misfire recovery when the exhaust temperature detected by the exhaust temperature detection means exceeds a reference misfire recovery detection exhaust temperature.   The misfire recovery detection means performs misfire recovery when the pressure in the combustion chamber detected by the pressure detection means exceeds a reference misfire recovery detection pressure at a pressure detection timing determined after the low pressure ignition timing within one cycle. The engine control device according to claim 1 to detect.   The misfire recovery detection means has a pressure in the combustion chamber detected by the pressure detection means at a pressure detection timing determined after the low pressure ignition timing in one cycle, and one before the pressure in the combustion chamber in the current cycle. The engine control apparatus according to claim 1, wherein the misfire recovery is detected based on a difference from the pressure in the combustion chamber in the cycle.   The misfire recovery detection means performs the first delay control by the ignition timing adjustment means on the pressure in the combustion chamber detected by the pressure detection means at a pressure detection timing determined after the low pressure ignition timing within one cycle. 2. The engine control device according to claim 1, wherein the misfire recovery is detected based on a pressure difference between the pressure in the combustion chamber in the cycle performed and the pressure in the combustion chamber in the cycle in which misfire is detected by the misfire detection means. . The set ignition timing is set to a timing earlier than the top dead center by a set period for ignition,
The engine control device according to any one of claims 1 to 5, wherein the low pressure ignition timing is set after the ignition set period and after the ignition timing, after the top dead center.   The ignition timing adjusting means performs second delay control for delaying the ignition timing by a predetermined set delay period after performing the first delay control until the misfire recovery detecting means detects the misfire recovery. The engine control device according to any one of claims 1 to 6, wherein the engine control device is configured to be repeatedly performed.

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