JP6278779B2 - engine - Google Patents

Description

In the present invention, a spark plug having an ignition chamber inside the plug cover that covers the ignition point is attached to a cylinder head, and a communication hole that connects the ignition chamber and a combustion chamber facing the piston is provided in the plug cover. Air-fuel ratio adjusting means for adjusting the excess air ratio of the air-fuel mixture sucked into the combustion chamber;
The present invention relates to an engine including control means for controlling the air-fuel ratio adjusting means so as to adjust the excess air ratio of the air-fuel mixture to a stoichiometric range or a stoichiometric range close to the stoichiometric range and a lean range larger than the stoichiometric range.

In such an engine, an ignition plug (hereinafter referred to as a pre-chamber ignition plug) having a communication hole that communicates between the ignition chamber and the combustion chamber facing the piston is formed in the plug cover that covers the ignition point. Is mounted on the cylinder head.
Then, the air-fuel ratio adjusting means is controlled by the control means so as to adjust the excess air ratio of the air-fuel mixture within the stoichiometric range or the lean range.
Incidentally, such an engine is used, for example, for driving a heat pump in a heat pump type air conditioning system, and used for driving a generator in a cogeneration system.

That is, in an engine equipped with such a pre-chamber ignition plug, the air-fuel mixture sucked into the combustion chamber in the intake step flows into the ignition chamber in the compression step, and the air-fuel mixture in the ignition chamber is pre-chamber ignited in the combustion expansion stroke. Sparks are ignited by a plug, and a combustion flame formed by the ignition is ejected to the combustion chamber through the communication hole, thereby igniting the air-fuel mixture in the combustion chamber (see, for example, Patent Document 1).
In this way, the air-fuel mixture flowing into the ignition chamber is spark-ignited, burned once in the ignition chamber, and the combustion flame is ejected from the communication hole into the combustion chamber, so that the combustion flame is rapidly brought into the combustion chamber. Since it can be expanded, even when a lean air-fuel mixture having a large excess air ratio is used as the air-fuel mixture, stable combustion can be achieved.

JP 2011-99403 A

By the way, in an engine that adjusts the excess air ratio of the air-fuel mixture within the stoichiometric range or the lean range, particularly when the excess air ratio is gradually increased (that is, adjusted to the lean side), It is easy for misfire to occur.
And when an engine with a pre-chamber spark plug has a misfire abnormality compared to an engine with a normal spark plug (a spark plug without a cover and without an ignition chamber), the misfire abnormality There was a problem that it was slow to resolve.
In other words, in an engine equipped with a pre-chamber spark plug, the burned gas remains in the ignition chamber, so that the fuel concentration around the ignition point is lighter and the ignitability is lower than in an engine equipped with a normal spark plug. Since it is easy to do, it is thought that it will be late to eliminate the misfire abnormality.
In particular, as the air excess ratio of the air-fuel mixture increases, the problem that it becomes slower to eliminate such misfire abnormality becomes more prominent.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an engine that has a pre-chamber ignition plug and can quickly eliminate the misfire abnormality when the misfire abnormality occurs. It is in.

In the engine according to the present invention, an ignition plug having an ignition chamber inside the plug cover that covers the ignition point is mounted on the cylinder head, and a communication hole that connects the ignition chamber and the combustion chamber facing the piston is provided in the plug cover. And
Air-fuel ratio adjusting means for adjusting the excess air ratio of the air-fuel mixture sucked into the combustion chamber;
Control means for controlling the air-fuel ratio adjusting means to adjust the excess air ratio of the air-fuel mixture to the stoichiometric range or the stoichiometric range close thereto and the lean range larger than the stoichiometric range,
The first characteristic configuration is misfire detection means for detecting misfire in the combustion chamber;
When the control means is controlling the air-fuel ratio adjustment means to gradually increase the excess air ratio, a predetermined cycle after the misfire start time when the misfire has occurred for the first time based on the detection information of the misfire detection means. A misfire abnormality determining means for determining a misfire abnormality in which a misfire occurrence rate that is a ratio of the number of cycles in which the misfire has occurred to a predetermined value during a period of time reaches a predetermined value;
When the misfire abnormality is determined by the misfire abnormality determining means, after the misfire abnormality is determined, the same number of cycles as the number of cycles from the misfire start time to the misfire abnormality determination time elapses. The excess air ratio at the target misfire elimination time set before or at the time when the misfire has decreased is more than twice the increase in the excess air ratio from the misfire start time to the misfire abnormality determination time The air / fuel ratio adjusting means is configured to control the air excess ratio so as to gradually lower the air excess ratio so that the target air excess ratio is obtained.

The inventors of the present invention have intensively studied to accelerate the resolution of a misfire abnormality in an engine equipped with a pre-chamber spark plug, as shown in FIG. 3 and FIG. We found that there is a significant difference in the form of eliminating misfire abnormalities between an engine with a pre-chamber spark plug and an engine with a normal spark plug (a spark plug without a plug cover and without an ignition chamber). It was.
Incidentally, FIG. 3 shows a form of eliminating misfire abnormalities in an engine equipped with a conventional pre-chamber spark plug, and FIG. 4 shows a form of solving misfire abnormalities in an engine equipped with a normal spark plug.

  That is, the misfire detection means detects the presence or absence of misfire in the combustion chamber. Further, when the air-fuel ratio adjusting means is controlled by the control means so as to gradually increase the excess air ratio, the misfire abnormality determining means determines the misfire start time at which misfire has occurred for the first time based on the detection information of the misfire detecting means. Later, when the misfire occurrence rate, which is a ratio of the number of cycles in which misfire occurred during the elapse of the predetermined cycle number, to the predetermined cycle number reaches a predetermined value, it is determined that the misfire is abnormal.

  In the example shown in FIGS. 3 and 4, when the average effective pressure in the cylinder becomes equal to or less than a predetermined value (for example, approximately 0), it is assumed that misfire has occurred, and the misfire detection means adjusts the pressure in the cylinder. An in-cylinder pressure sensor for detection is provided. For example, the predetermined number of cycles is set to 100 cycles, the predetermined value that is the misfire occurrence rate to be determined as misfiring abnormality is set to 3%, and when misfiring occurs three times or more by the end of 100 cycles, it is determined that misfiring abnormality occurs. It is configured.

  3 and 4 both show the transition of the misfire occurrence state when the fuel flow rate is decreased at a predetermined reduction rate and the excess air ratio is gradually increased with the engine speed kept constant, and From the time when the misfire occurrence rate reaches a predetermined value and it is determined that the misfire is abnormal, the fuel flow rate is increased at the same rate as the decrease rate of the fuel flow rate before the misfire abnormality is determined, and the excess air ratio is gradually lowered. The transition of the occurrence state of the misfire abnormality is shown with the passage of the number of cycles of the engine. 3 and 4, the misfire start time is indicated by Ps, and the misfire abnormality determination time is indicated by Pr. However, in FIG. 3, the transition of the fuel flow rate is indicated by a solid line.

As shown in FIG. 4, in an engine equipped with a normal spark plug, when an increase in fuel flow rate is started at the same rate as the decrease rate of the fuel flow rate before the determination from the misfire abnormality determination time Pr, After the start, the number of cycles approximately the same as the number of cycles from the misfire start time Ps to the misfire abnormality determination time Pr elapses, and the misfire does not occur.
On the other hand, as shown in FIG. 3, in the engine equipped with the pre-chamber spark plug, the increase in the fuel flow rate is started at the same rate as the decrease rate of the fuel flow rate before the determination from the misfire abnormality determination time Pr. Then, after the start, the misfire does not occur at a time point Pa at which approximately twice the number of cycles from the misfire start time point Ps to the misfire abnormality determination time point Pr has elapsed.
In other words, in an engine equipped with a normal spark plug, when a misfire abnormality is determined, the fuel flow rate is increased by approximately the same width as the decrease in the fuel flow rate from the misfire start time Ps to the misfire abnormality determination time Pr. When the excess air ratio is reduced by the same amount as the increase in the excess air ratio from the misfire start time Ps to the misfire abnormality determination time Pr, the misfire abnormality is eliminated.
On the other hand, in an engine equipped with a pre-chamber spark plug, when a misfire abnormality is determined, the fuel flow rate is at least twice as wide as the decrease in the fuel flow rate from the misfire start time Ps to the misfire abnormality determination time Pr. It is understood that the misfire abnormality cannot be resolved unless the excess air ratio is increased, that is, the excess air ratio is not reduced by more than twice the increase in the excess air ratio from the misfire start time Ps to the misfire abnormality determination time Pr.

Therefore, in the present application, after the misfire abnormality is determined, the time when the same number of cycles as the number of cycles from the misfire start time Ps to the misfire abnormality determination time Pr has passed or before, that is, the misfire abnormality determination When the excess air ratio is lowered at the same rate as the decrease rate of the excess air ratio of the fuel flow before the misfire abnormality is determined from the time point Pr, when the misfire is eliminated in an engine equipped with a normal spark plug, or The target misfire elimination time point Pt is set at a time point before that time point.
Further, the target excess air ratio is set lower than the excess air ratio at the misfire start time Ps.
When a misfire abnormality is determined by the misfire abnormality determining means, the control means causes the excess air ratio at the target misfire cancellation time point Pt to be 2 of the increase in the excess air ratio from the misfire start time to the misfire abnormality determination time. The air-fuel ratio adjusting means is controlled so as to gradually lower the excess air ratio so that the target excess air ratio decreases with a width more than doubled .
Therefore, even if a pre-chamber spark plug is provided, when a misfire abnormality occurs, the time point at which it can be resolved is equivalent to the time point at which the misfire abnormality can be resolved in an engine equipped with a normal spark plug, or at that time point It was possible to get closer and quicken the resolution of misfire abnormalities.

In addition to the first feature configuration, the second feature configuration is
When the excess air ratio is lowered from the time of determination of the misfire abnormality at a rate of decrease equal to the increase rate of the excess air ratio before the misfire abnormality is determined, from the misfire start time to the determination time of the misfire abnormality The target air excess ratio is set to an air excess ratio that is substantially the same as the air excess ratio that is reached when a cycle number approximately twice that of the above-mentioned number of cycles elapses after the misfire abnormality determination time.

As can be seen from FIG. 3, in an engine equipped with a pre-chamber spark plug, the fuel flow rate is increased from the misfire abnormality determination time Pr at an increase rate of the same rate as the fuel flow rate decrease rate before the misfire abnormality is determined. The misfire abnormality is resolved at a point Pa when approximately twice the number of cycles from the misfire start time Ps to the misfire abnormality determination time Pr has elapsed.
That is, in an engine equipped with a pre-chamber spark plug, when a misfire abnormality is determined, the fuel flow rate is decreased from the misfire start time Ps to the misfire abnormality determination time Pr rather than the misfire abnormality determination time Pr. When the width is increased by more than twice the width, that is, the excess air ratio of the air-fuel mixture is increased from the misfire start determination time Pr to the misfire start determination time Pr to the misfire start determination time Pr. If the width decreases more than twice, the misfire abnormality is eliminated.
According to the above characteristic configuration, at the target misfire elimination time point Pt, the air excess ratio of the air-fuel mixture becomes lower by about twice the increase in the air excess ratio from the misfire start time point Ps to the misfire abnormality determination time point Pr. Therefore, the misfire abnormality can be surely eliminated at the target misfire elimination time point Pt.
Therefore, in the engine equipped with the pre-chamber spark plug, when the misfire abnormality occurs, it is possible to further speed up the elimination of the misfire abnormality.

In addition to the first or second feature configuration, the third feature configuration is
After the misfire abnormality is determined, the target misfire elimination time is set at the time when approximately 1/3 of the number of cycles from the misfire start time to the misfire abnormality determination time has elapsed. .

According to the above characteristic configuration, the air excess ratio of the air-fuel mixture is the target at the time when approximately one third of the number of cycles from the misfire start time to the misfire abnormality determination time has elapsed after the misfire abnormality is determined. The excess air ratio is low.
For example, when the target excess air ratio is set to a value lower than twice the increase in the excess air ratio from the misfire start time to the misfire abnormality determination time than the misfire abnormality determination time, the misfire abnormality is After the determination, the misfire abnormality is surely resolved at the time when approximately one third of the number of cycles from the misfire start time to the misfire abnormality determination time has elapsed.
Therefore, in the engine equipped with the pre-chamber spark plug, when the misfire abnormality occurs, it is possible to further accelerate the elimination of the misfire abnormality.

The block diagram which shows the whole structure of the engine which concerns on embodiment Ignition circuit schematic The figure which shows the transition of the occurrence state of misfire accompanying the increase and decrease of the fuel flow rate in the engine equipped with the pre-chamber spark plug A diagram showing the transition of the misfire occurrence state associated with the increase or decrease of the fuel flow rate in an engine equipped with a normal spark plug

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the engine includes a cylinder 1, a piston 2 fitted in the cylinder 1 so as to be slidable in a reciprocating manner, and a pre-chamber spark plug (that is, a spark plug) mounted on a cylinder head 1h of the cylinder 1. 30 and a control unit (an example of a control means, so-called engine control unit (ECU)) 3 that controls the operation of the engine.
A combustion chamber 4 is formed in the cylinder 1 between the top of the piston 2 and the cylinder head 1h. The cylinder head 1h has an intake port 5 and an exhaust port (not shown) in communication with the combustion chamber 4, respectively. Further, an intake valve 6 for opening and closing the intake port 5 and an exhaust valve (not shown) for opening and closing the exhaust port are also provided.

  Then, when the intake valve 6 and the exhaust valve are opened / closed, the intake stroke, the compression stroke, the combustion expansion stroke, and the exhaust stroke are sequentially performed in the combustion chamber 4, and the reciprocating motion of the piston 2 is connected to the connecting rod. Is output as a rotational motion of the crankshaft 7. Such a configuration is the same as that of a normal four-stroke engine. The crankshaft 7 is provided with a cell motor 8 for ensuring the rotation of the crankshaft 7 without causing combustion in the combustion chamber 4 in the initial stage of startup.

  This engine uses, for example, city gas (13A), which is a gaseous fuel, as the fuel G. In the intake stroke, the intake valve 6 is opened and the combustion air A and the combustion chamber 4 are transferred from the intake port 5 to the combustion chamber 4. The air-fuel mixture with the fuel G is sucked in. In the compression stroke and the combustion expansion stroke, the air-fuel mixture taken into the combustion chamber 4 is compressed and combusted. In the exhaust stroke, the exhaust valve is opened, and the combustion exhaust gas is discharged from the combustion chamber 4 to the exhaust port.

  Further, in this engine, an injector 9 that injects fuel G into the intake port 5, a throttle valve 10 that can adjust the intake amount of the air-fuel mixture that is sucked into the combustion chamber 4 through the intake port 5, and the combustion chamber 4 is sucked into the engine. An air-fuel ratio adjusting means 11 for adjusting the excess air ratio of the air-fuel mixture and an ignition circuit 14 for supplying discharge energy to the pre-chamber spark plug 30 are provided.

In this embodiment, a fuel adjustment valve 12 that can adjust the ejection amount of the fuel G ejected from the injector 9 is provided in the fuel supply path 13 that supplies the fuel G to the injector 9.
That is, by adjusting the injection amount of the fuel G injected from the injector 9 by the fuel adjustment valve 12, the air excess ratio of the air-fuel mixture sucked into the combustion chamber 4 through the intake port 5 can be adjusted, and the air-fuel ratio adjusting means 11 However, this fuel adjustment valve 12 is provided.

As shown in FIG. 2, the ignition circuit 14 includes an ignition coil 15 that applies a discharge voltage to the pre-chamber ignition plug 30, and an igniter 16 that includes a semiconductor switching element and turns on and off the primary coil 15 f of the ignition coil 15. It is prepared for.
An ignition signal S for turning on / off the igniter 16 is supplied from the control unit 3 to the igniter 16. When the igniter 16 is turned on, a primary current flows from the battery 17 to the primary coil 15f of the ignition coil 15, and when the igniter 16 is turned off, the primary current of the primary coil 15f is cut off and the secondary coil of the ignition coil 15 is turned off. A high induced voltage is generated in 15 s, and the induced voltage is applied to the center electrode 31 of the spark plug 30 to cause a spark discharge between the center electrode 31 and the ground electrode 32.
The discharge energy applied to the prechamber spark plug 30 is adjusted by adjusting the ON time of the ignition signal S applied to the igniter 16 and adjusting the primary current flowing through the primary coil 15f of the ignition coil 15. become.

As shown in FIG. 1, the pre-chamber spark plug 30 ignites by covering a plug main body 33 and an ignition point (not shown) provided at the tip of the plug main body 33 (the lower end in FIG. 1). A plug cover 35 that forms the chamber 34 is provided, and the plug cover 35 and the plug body 33 are integrated.
The plug cover 35 is configured in a bottomed cylindrical shape including a cylindrical plug cover base end portion 35b and a dome-shaped plug cover head portion 35a that closes one end of the plug cover base end portion 35b. This plug cover 35 has a dome-shaped plug cover head portion 35a positioned on the axial center of the plug body 33 and a plug cover base end portion 35b externally fitted to the plug body 33. 33 is integrally assembled.

  The pre-chamber spark plug 30 has the plug body 33 aligned with the center axis of the combustion chamber 4 (axis along the straight line W in FIG. The cylinder head 1h is mounted in a protruding state.

  The plug cover 35 (specifically, the plug cover head portion 35a) is formed with a plurality of communication holes 36 that allow the combustion chamber 4 and the ignition chamber 34 to communicate with each other. The pre-chamber spark plug 30 sparks and burns the air-fuel mixture flowing into the ignition chamber 34 from the combustion chamber 4 through the communication hole 36, and jets the combustion flame formed by the combustion into the combustion chamber 4 through the communication hole 36. It is configured to let you. Thus, the inflow of the air-fuel mixture from the combustion chamber 4 to the ignition chamber 34 and the ejection of the combustion flame from the ignition chamber 34 to the combustion chamber 4 are performed by the plurality of communication holes 36, thereby The intake air-fuel mixture is combusted. Here, the air-fuel mixture flowing into the ignition chamber 34 is all the air-fuel mixture flowing from the combustion chamber 4 through the communication hole 36, and the fuel G and the air-fuel mixture are supplied to the ignition chamber 34 from other than the combustion chamber 4. Never happen.

Next, the control operation of the control unit 3 will be described.
The control unit 3 includes a microcomputer that can execute a program for controlling the engine and the like, and applies an ignition signal S to the igniter 16 of the ignition circuit 14 so that the center electrode 31 of the pre-chamber ignition plug 30 is grounded. It is configured to control the timing of the spark discharge with the electrode 32.

In the engine, for example, in steady operation such as rated operation, the piston 2 descends from the top dead center while the intake valve 6 is opened, whereby an intake stroke for sucking the air-fuel mixture into the combustion chamber 4 is performed. Next, the piston 2 ascends in a state where the intake valve 6 is closed, whereby a compression stroke for compressing the air-fuel mixture in the combustion chamber 4 is performed. In this compression stroke, the volume of the combustion chamber 4 is reduced by raising the piston 2 from the bottom dead center, so that the air-fuel mixture sucked into the combustion chamber 4 flows into the ignition chamber 34 through the communication hole 36.
The control unit 3 operates the plug body 33 at the ignition timing (for example, immediately before the top dead center), sparks at the ignition point, and ignites the air-fuel mixture in the ignition chamber 34. Then, combustion in the ignition chamber 34 proceeds, and a combustion flame is ejected to the combustion chamber 4 through the communication hole 36. Thereby, the air-fuel mixture in the combustion chamber 4 is combusted, the combustion expansion stroke is performed, and the piston 2 descends. Next, when the piston 2 rises with the exhaust valve opened, an exhaust stroke is performed in which the combustion exhaust gas in the combustion chamber 4 is guided to the exhaust port and discharged.
In this way, the engine is configured as a four-stroke engine that repeats 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.

In addition, the control unit 3 is configured to control the fuel adjustment valve 12 so as to adjust the excess air ratio of the air-fuel mixture to a stoichiometric range or a stoichiometric range close to the stoichiometric range and a lean range larger than the stoichiometric range.
For example, when the engine is used for driving a heat pump in a heat pump type air conditioning system, the engine is loaded according to the air conditioning load, so the control unit 3 should adjust the rotational speed of the engine according to the engine load. The throttle valve 10 is configured to be controlled.
For example, when the rotational speed is in the high rotational speed range, the control unit 3 controls the fuel adjustment valve 12 to adjust the excess air ratio of the air-fuel mixture within the stoichiometric range, and the rotational speed is within the high rotational speed range. When the rotational speed range is lower than that, the fuel adjustment valve 12 is controlled so as to adjust the excess air ratio of the air-fuel mixture within the lean range.
Incidentally, the stoichiometric range is set to, for example, approximately 1.0, and the lean range is set, for example, to a range of 1.5 to 1.9.

Also, when changing the excess air ratio of the air-fuel mixture significantly, such as when increasing the excess air ratio of the air-fuel mixture from the stoichiometric range to the lean range, or when reducing the air excess ratio of the air-fuel mixture to the stoichiometric range, If the engine speed is changed rapidly, the operation of the engine may become unstable due to, for example, unstable ignition of the air-fuel mixture in the combustion chamber 4.
Therefore, when the excess air ratio of the air-fuel mixture is increased from the stoichiometric range to the lean range, the controller 3 controls the fuel adjustment valve so as to gradually decrease the fuel flow rate at a predetermined reduction rate so as to gradually increase the excess air ratio. 12, when the air excess ratio of the air-fuel mixture is lowered from the lean range to the stoichiometric range, the fuel adjustment valve 12 is set so that the fuel flow rate is gradually increased at a predetermined increase rate in order to gradually reduce the air excess ratio. Configured to control.

The above is the basic configuration of the engine and the pre-chamber spark plug 30 of the present invention.
As described above, the engine of the present invention is configured to expedite the resolution of the misfire abnormality when the misfire abnormality occurs. Hereinafter, control for speeding up the resolution of the misfire abnormality will be described.
As shown in FIG. 1, in the present invention, misfire detection means 21 for detecting misfire in the combustion chamber 4 for each cycle, and the control unit 3 controls the fuel adjustment valve 12 to gradually increase the excess air ratio. The misfire occurrence rate, which is the ratio of the number of cycles in which misfire has occurred during the elapse of the predetermined number of cycles after the misfire start time at which misfire has occurred for the first time, based on the detection information of the misfire detection means 21 And misfire abnormality determining means 24 for determining a misfire abnormality that reaches a predetermined value.
When the misfire abnormality determination means 24 determines that the misfire abnormality is determined by the control unit 3, after the misfire abnormality is determined, the same number of cycles as the number of cycles from the misfire start time to the misfire abnormality determination time has elapsed. The excess air ratio is gradually lowered so that the excess air ratio at the target misfire elimination time set at or before that time becomes the target excess air ratio set lower than the excess air ratio at the start of misfire. The fuel adjustment valve 12 is preferably controlled.

In this embodiment, an in-cylinder pressure sensor 22 that detects the pressure in the cylinder 1 (pressure in the combustion chamber 4) is provided, and the average effective pressure for each cycle based on the detection information of the in-cylinder pressure sensor 22 is provided. Mean effective pressure calculation means 23 for calculating the above is configured using the control unit 3. When the average effective pressure calculated by the average effective pressure calculating means 23 becomes equal to or less than a predetermined value (for example, approximately 0), the in-cylinder pressure sensor 22 and the average effective pressure are calculated so that a misfire has occurred. The means 23 constitutes misfire detection means 21.
The misfire abnormality determination means 24 is also configured using the control unit 3.

Further, for example, when the predetermined number of cycles is 100 cycles, the predetermined value which is the misfire occurrence rate for determining the misfire abnormality is 3%, and the misfire abnormality determining means 24 causes the misfire to occur three times or more before 100 cycles elapses. The misfire is determined to be abnormal.
In other words, the misfire abnormality determination means 24 monitors the detection information of the misfire detection means 21 for each cycle, and for each cycle in which misfire is detected by the misfire detection means 21, the number of cycles starting from that cycle is integrated. In addition to obtaining the number, the number of cycles in which misfire is detected by the misfire detection means 21 is integrated to obtain the number of misfire cycles. Further, the misfire abnormality determining means 24 determines that the misfire abnormality occurs when the misfire cycle number reaches 3 cycles before the elapsed cycle number reaches 100 cycles. If the number of misfire cycles does not reach 3 even after reaching 100 cycles, it is configured not to determine that the misfire is abnormal.

Next, a setting example of the target excess air ratio and the target misfire elimination time will be described based on FIG.
FIG. 3 shows that, as described above, in an engine equipped with a pre-chamber spark plug, the fuel flow rate is gradually decreased at a predetermined reduction rate with the engine speed maintained constant (eg, 1200 rpm). From the transition of the misfire occurrence state when the excess air ratio is gradually increased and the misfire occurrence rate reaches a predetermined value and the misfire abnormality is determined, the excess air ratio is increased by gradually increasing the fuel flow rate. The transition of the state of occurrence of misfire abnormality when gradually lowered is shown along with the passage of the number of cycles of the engine.
In the example shown in FIG. 3, the rate of decrease of the fuel flow rate is about 0.115 liters (standard state) / minute at a fuel flow rate indicated by the volume of fuel in the standard state per minute every about 2.9 seconds. It is a rate that gradually decreases.

In FIG. 3, the misfire start time at which misfire occurs for the first time is indicated by Ps. After the misfire start time Ps, the misfire occurrence rate reaches a predetermined value (3% in this embodiment), and misfire is determined to be abnormal misfire. The abnormality determination time is indicated by Pr.
In the example shown in FIG. 3, when the fuel flow rate is decreased at a predetermined reduction rate while maintaining the engine speed constant, it is determined that the misfire is abnormal when about 180 cycles have elapsed from the misfire start point Ps. The point of time becomes the misfire abnormality determination point Pr.
Then, as shown by the solid line in FIG. 3, when the fuel flow rate is increased at the same rate as the fuel flow rate decrease rate before the misfire abnormality is determined from the misfire abnormality determination time Pr, the increase in the fuel flow rate is increased. After starting, the misfire does not occur at a time point Pa when approximately twice the number of cycles from the misfire start time point Ps to the misfire abnormality determination time point Pr has elapsed.

  That is, when the misfire abnormality is determined, the fuel flow rate is more than twice the decrease in the fuel flow rate from the fuel flow rate Qs at the misfire start time point Ps to the fuel flow rate Qr at the misfire abnormality determination time point Pr. When the fuel flow rate Qr at the determination time Pr is increased from Qr to Qt, that is, the excess air ratio is more than twice the increase in the excess air ratio from the misfire start time Ps to the misfire abnormality determination time Pr. If the excess air ratio at the determination time Pr is decreased, the misfire abnormality is eliminated.

Therefore, the target fuel flow rate Qt corresponding to the target excess air ratio decreases from the fuel flow rate Qs at the misfire start time Ps to the fuel flow Qr at the misfire error determination time Pr with respect to the fuel flow rate Qr at the misfire abnormality determination time Pr. It is set to a value obtained by adding a width that is approximately twice the reduced width.
In other words, the target excess air ratio increases from the excess air ratio at the misfire abnormality determination time point Pr to the excess air ratio at the misfire abnormality determination time point Pr to the excess air ratio at the misfire abnormality determination time point Pr. It is set to a value that is lower by about twice the width.
That is, when the excess air ratio is lowered from the misfire abnormality determination time Pr at the same rate as the increase rate of the excess air ratio before the misfire abnormality is determined, the misfire start time is determined from the misfire abnormality determination time Pr. The target excess air ratio is set to approximately the same excess air ratio as the excess air ratio reached when the number of cycles approximately twice the number of cycles from Ps to the misfire abnormality determination time Pr has passed and no misfire occurs. Will be.

  Further, the target misfire elimination time Pt is set to the time when the number of cycles substantially equal to the number of cycles from the misfire start time Ps to the misfire abnormality determination time Pr is determined after the misfire abnormality is determined.

When the misfire is detected by the misfire detection means 21 for the first time when the fuel flow rate is decreased at a predetermined decrease rate in order to switch the excess air ratio of the air-fuel mixture from the stoichiometric range to the lean range, The fuel flow rate at the misfire start time Ps at which misfire is detected for the first time is stored.
Further, when the misfire abnormality determining means 24 determines that the misfire is abnormal, the control unit 3 obtains the number of cycles from the misfire start time Ps to the misfire abnormality determination time Pr and from the fuel flow rate Qs at the misfire start time Ps. A reduction width up to the fuel flow rate Qr at the abnormality determination time Pr is obtained.
Further, when the misfire abnormality is determined by the misfire abnormality determining means 24, the controller 3 determines that the same number of cycles as the number of cycles from the misfire start time Ps to the misfire abnormality determination time Pr has elapsed after the misfire abnormality is determined. The target misfire elimination time Pt is set, and further, with respect to the fuel flow rate Qr at the misfire abnormality determination time Pr, the fuel flow rate Qs at the misfire start time Ps to the fuel flow rate Qr at the misfire abnormality determination time Pr. The target fuel flow rate Qt is set to a value obtained by adding a width twice the decrease width.

Then, when the misfire abnormality determination unit 24 determines that the misfire abnormality is determined, the control unit 3 controls the fuel adjustment valve 12 to gradually increase the fuel flow rate so as to reach the target fuel flow rate Qt at the target misfire elimination time point Pt. To do.
Specifically, for example, by controlling the fuel adjustment valve 12 to increase the fuel flow rate by a predetermined amount every time a predetermined number of cycles elapses, the fuel flow rate becomes the target fuel flow rate Qt at the target misfire elimination time point Pt. Configure as follows.
Then, as shown by the thick dashed line in FIG. 3, the fuel flow rate is increased from the misfire abnormality determination time Pr, and reaches the target fuel flow rate Qt at the target misfire elimination time Pt.
Therefore, when the number of cycles substantially equal to the number of cycles from the misfire abnormality determination point Pr to the misfire start point Ps to the misfire abnormality determination point Pr elapses, the misfire abnormality is eliminated.

[Another embodiment]
Next, another embodiment will be described.
(A) In the above embodiment, the fuel adjustment is performed so that the target fuel flow rate Qt corresponding to the target excess air ratio is set and the fuel flow rate is gradually increased to reach the target fuel flow rate Qt at the target misfire elimination time point Pt. The valve 12 is controlled. Instead, the fuel excess adjustment ratio 12 is controlled to set the target excess air ratio so that the excess air ratio of the air-fuel mixture gradually becomes lower so as to reach the target excess air ratio at the target misfire elimination time point Pt. Also good. In this case, the control unit 3 is configured to calculate the excess air ratio based on the fuel flow rate obtained from the opening information of the fuel adjustment valve 12.

(B) The setting example of the target fuel flow rate Qt corresponding to the target excess air ratio is not limited to the setting example described in the above embodiment. For example, when the target fuel flow rate Qt is set, the fuel flow rate Qr at the misfire abnormality determination time point Pr is reduced by 2 from the fuel flow rate Qs at the misfire start time point Ps to the fuel flow rate Qr at the misfire abnormality determination time point Pr. A value larger than the value obtained by adding the double width may be set.
Further, the setting example of the target misfire elimination time point Pt is not limited to the setting example described in the above embodiment. For example, when the target misfire elimination time Pt is set, it is set before the time when the same number of cycles as the number of cycles from the misfire start time Ps to the misfire abnormality determination time Pr is determined after the misfire abnormality is determined. Also good.

For example, the target fuel flow rate Qt is set from the fuel flow rate Qs at the misfire start time Ps to the fuel flow rate Qr at the misfire abnormality determination time Pr with respect to the fuel flow rate Qr at the misfire abnormality determination time Pr, as in the above embodiment. The target misfire cancellation time point Pt is set to a value obtained by adding twice the width of the decrease in the range, and after the misfire abnormality is determined, approximately 1 / the number of cycles from the misfire start time Ps to the misfire abnormality determination time Pr. Set when the number of cycles of 3 has passed.
Then, as shown by a thick two-dot chain line in FIG. 3, when a misfire abnormality is determined, a cycle number of approximately 1/3 of the cycle number from the misfire start time Ps to the misfire abnormality determination time Pr has elapsed. At the target misfire elimination time point Pt, the fuel flow rate reaches the target fuel flow rate Qt, and the misfire abnormality is eliminated.

(C) The predetermined number of cycles for determining the misfire occurrence rate is not limited to 100 cycles exemplified in the above embodiment, and may be set to, for example, fewer than 100 cycles. Further, the predetermined value that is the misfire occurrence rate for determining the misfire abnormality is not limited to 3% exemplified in the above embodiment, and may be set to a value larger than 3%, for example.

(D) The specific configuration of the air-fuel ratio adjusting means 11 is not limited to the configuration including the fuel adjustment valve 12 as described in the above embodiment. For example, an air amount adjusting unit capable of adjusting the intake air amount of combustion air may be provided, and the air-fuel ratio adjusting unit 11 may be configured to include an air amount adjusting unit.

  As described above, it is possible to provide an engine that includes a pre-chamber ignition plug, and that can quickly eliminate the misfire abnormality when the misfire abnormality occurs.

1h Cylinder head 2 Piston 3 Control part (control means)
4 Combustion chamber 11 Air-fuel ratio adjustment means 21 Misfire detection means 24 Misfire abnormality determination means 30 Pre-chamber ignition plug (ignition plug)
34 Ignition chamber 35 Plug cover 36 Communication hole Pa Time when approximately twice the number of cycles from the misfire start time Ps to the misfire abnormality determination time Pr has elapsed from the misfire abnormality determination time Pr Pr Pr misfire abnormality determination time Ps Misfire start time Pt Target misfire elimination time

Claims (3)

An ignition plug having an ignition chamber inside the plug cover that covers the ignition point is mounted on the cylinder head, and a communication hole that connects the ignition chamber and the combustion chamber facing the piston is provided in the plug cover.
Air-fuel ratio adjusting means for adjusting the excess air ratio of the air-fuel mixture sucked into the combustion chamber;
An engine having control means for controlling the air-fuel ratio adjusting means in order to adjust the excess air ratio of the air-fuel mixture to a stoichiometric range or a stoichiometric range close thereto and a lean range larger than the stoichiometric range,
Misfire detection means for detecting misfire in the combustion chamber;
When the control means is controlling the air-fuel ratio adjustment means to gradually increase the excess air ratio, a predetermined cycle after the misfire start time when the misfire has occurred for the first time based on the detection information of the misfire detection means. A misfire abnormality determining means for determining a misfire abnormality in which a misfire occurrence rate that is a ratio of the number of cycles in which the misfire has occurred to a predetermined value during a period of time reaches a predetermined value;
When the misfire abnormality is determined by the misfire abnormality determining means, after the misfire abnormality is determined, the same number of cycles as the number of cycles from the misfire start time to the misfire abnormality determination time elapses. The excess air ratio at the target misfire elimination time set before or at the time when the misfire has decreased is more than twice the increase in the excess air ratio from the misfire start time to the misfire abnormality determination time An engine configured to control the air-fuel ratio adjusting means so as to gradually lower the excess air ratio so as to achieve a target excess air ratio.   When the excess air ratio is lowered from the time of determination of the misfire abnormality at a rate of decrease equal to the increase rate of the excess air ratio before the misfire abnormality is determined, from the misfire start time to the determination time of the misfire abnormality 2. The engine according to claim 1, wherein the target excess air ratio is set to an excess air ratio that is substantially the same as an excess air ratio that is reached when a number of cycles that is approximately twice the number of cycles of the misfire abnormality has elapsed from the determination point of the misfire abnormality. .   The target misfire elimination time is set at a time when approximately one third of the number of cycles from the misfire start time to the misfire abnormality determination time has elapsed after the misfire abnormality is determined. Or the engine of 2.

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