JP7013691B2 - Engine control - Google Patents

Description

The present invention relates to an engine control device provided with an exhaust gas recirculation device, and more particularly to an engine control device corresponding to a delay in introducing exhaust gas to the intake air.

In general, an exhaust gas recirculation device that introduces a part of the exhaust gas into the intake air as an exhaust return gas is often provided between the exhaust passage and the intake passage of the engine. The exhaust gas recirculation device includes an exhaust gas recirculation passage that communicates between the exhaust passage and the intake passage, an exhaust recirculation valve provided in the exhaust recirculation passage, and the like. An appropriate amount of exhaust / recirculation gas is introduced into the intake air according to the pressure state in the intake passage due to the opening / closing of the exhaust / recirculation valve and the opening / closing of the throttle valve.

Since the combustion temperature in the combustion chamber is lowered by introducing the exhaust gas to the intake air, the temperature reduction can suppress nitrogen oxides, improve fuel efficiency, and suppress knocking. In particular, in a gasoline engine, it is expected that the throttle loss can be reduced because the negative pressure in the intake passage can be reduced by introducing the exhaust recirculation gas in the operating state of the partial load where the load is not the full load. ..

The exhaust gas recirculation device includes a low pressure exhaust gas recirculation device that handles a relatively low pressure exhaust recirculation gas and a high pressure exhaust gas recirculation device that handles a relatively high pressure exhaust gas recirculation device.

Compared to the high-pressure exhaust gas recirculation device, the low-pressure exhaust gas recirculation device tends to have a longer path from the branch portion of the exhaust passage to the exhaust / return passage to the combustion chamber via the junction to the intake passage. .. Therefore, the low-pressure exhaust gas recirculation device is compared with the high-pressure exhaust gas recirculation device, and the target introduction rate of the exhaust recirculation gas to the intake air (the target ratio of the exhaust gas recirculation gas to be introduced into the combustion chamber. The difference between the exhaust gas return gas rate) and the actual exhaust gas return gas introduction rate (hereinafter referred to as the actual exhaust gas return gas rate) tends to be large.

For example, during the transient operation of deceleration, the intake air amount decreases with the closing operation of the throttle valve. At this time, the target exhaust gas return gas rate is lowered according to the deceleration. However, even if the amount of intake air decreases, the pressure on the exhaust side does not decrease immediately, and the pressure on the exhaust side tends to be accompanied by a phenomenon that the pressure gradually decreases with the passage of time, that is, a so-called delay in the decrease of the exhaust pressure.

The delay in the drop of the exhaust pressure induces a state in which the actual exhaust gas return gas rate is large with respect to the target exhaust gas return gas rate, that is, a state in which the exhaust gas return gas is excessive. Excessive exhaust gas is not preferable because it causes misfire and causes deterioration of exhaust gas components such as an increase in hydrocarbons in the exhaust gas. Such a problem may occur not only in the low-pressure exhaust gas recirculation device but also in the high-pressure exhaust gas recirculation device depending on the operating conditions.

Therefore, in order to avoid misfire and deterioration of the exhaust gas component, for example, a method of suppressing the exhaust gas return gas rate to the extent that misfire and deterioration of the exhaust gas component do not occur can be considered. However, if the exhaust gas return gas rate is suppressed, there is a problem that the effect of introducing the exhaust gas return gas is also reduced accordingly.

In addition, Patent Document 1 discloses a technique for stabilizing a combustion state by performing multiple ignition in which a spark plug is ignited a plurality of times in one combustion cycle.

Japanese Unexamined Patent Publication No. 2001-159367 (see paragraph 0009 on page 3 of the specification).

However, the technique of Patent Document 1 has a problem that the implementation of multiple ignition accelerates the progress of wear and burning of the spark plug, resulting in an early deterioration of ignition performance. Shortening the life of the spark plug is not preferable because of maintenance labor and cost.

Therefore, an object of the present invention is to prevent misfire and deterioration of the exhaust gas component even under an operating condition in which an engine provided with an exhaust gas recirculation device maintains the life of the ignition device and causes a delay in the decrease of the exhaust pressure. , To stabilize the combustion state.

In order to solve the above problems, the present invention ignites an intake passage that introduces intake air into the combustion chamber, an exhaust passage that sends out exhaust gas from the combustion chamber, a throttle valve that adjusts the amount of intake air, and the combustion chamber. An ignition device that generates sparks, an ignition control means that controls the ignition device, an exhaust gas recirculation device that connects the intake passage and the exhaust passage and introduces a part of the exhaust gas into the intake as exhaust recirculation gas, and the above. The target exhaust gas return gas rate, which is the target exhaust gas return gas rate when controlling the exhaust gas return gas control means that controls the exhaust gas recirculation device and the exhaust gas return gas rate, which is the ratio of the exhaust gas return gas to the intake air. The ignition control means is provided with an exhaust gas excess detection means for detecting or predicting the occurrence of an exhaust gas excess state in which the actual exhaust gas return gas rate, which is the actual exhaust gas return gas rate, is larger than the actual exhaust gas return gas rate. When the occurrence of an exhaust gas excess state is detected or predicted, multiple ignition is performed in which the generation of ignition sparks by the ignition device is performed multiple times per combustion cycle, and the occurrence of the exhaust gas excess state is detected. Alternatively, the prediction is based on a first index indicating the degree of decrease in the intake air amount and a second index indicating the degree of decrease in the exhaust gas on the exhaust passage side of the exhaust gas recirculation device. Based on this, the exhaust gas excess detecting means detects or predicts the occurrence of the exhaust gas excess state when the ratio of the first index to the second index is larger than a predetermined ratio . A control device was adopted.

Here, the exhaust gas recirculation gas excess state is the actual exhaust gas recirculation gas after starting the control to lower the exhaust recirculation gas rate more than the actual exhaust recirculation gas rate before the control to reduce the exhaust recirculation gas rate. It is possible to adopt a configuration in which the exhaust gas recirculation gas spike with a larger rate is generated.

It is possible to adopt a configuration in which the exhaust gas excess state occurs after the throttle valve is closed during deceleration.

In each of these embodiments, a rotation sensor for detecting the engine rotation speed is provided, and the exhaust gas excess detecting means detects or predicts that the lower the rotation speed, the more likely the exhaust gas excess state is to occur. It is possible to adopt a configuration in which it is detected or predicted that the larger the difference between the actual exhaust gas return gas rate and the target exhaust gas return gas rate is, the more likely the exhaust gas return gas excess state is to occur.

The first index is the intake air amount reduction rate which is the decrease amount of the intake air amount per unit time, and the second index is the exhaust pressure decrease which is the decrease amount of the exhaust pressure per unit time. A configuration that is a rate can be adopted.

Here, the ignition control means can adopt a configuration in which the multiple ignition is terminated when the intake air amount reduction rate and the exhaust pressure reduction rate become equal.

Alternatively, the ignition control means can adopt a configuration in which the multiple ignition is terminated when the actual exhaust gas return gas rate becomes equal to the target exhaust gas return gas rate.

In each of these embodiments, a rotation sensor for detecting the rotation speed of the engine is provided, and the ignition control means advances the ignition interval of the multiple ignitions in one combustion cycle as the ignition timing advances . The smaller the rotation speed, or the larger the difference between the actual exhaust gas return gas rate and the target exhaust gas return gas rate, the longer the configuration can be adopted.

Equipped with an exhaust gas excess detection means for detecting or predicting the occurrence of an exhaust gas excess state in which the actual exhaust gas return gas rate is larger than the target exhaust gas return gas rate when controlling to lower the exhaust gas return gas rate of the intake air. Since the ignition control means for controlling the ignition device performs multiple ignition when the occurrence of an exhaust gas excess state is detected or predicted, the ignition device is used even under an operating condition in which a decrease in exhaust pressure is delayed. It is possible to prevent misfires and deterioration of exhaust gas components while maintaining the life of the exhaust gas, and to stabilize the combustion state.

Further, in the present invention, when a misfire occurs due to the above-mentioned delay in the decrease in exhaust pressure, the pressure on the intake side drops sharply, so that the actual exhaust gas return gas rate does not decrease toward the target exhaust gas return gas rate. On the contrary, the inventors of the present application have paid attention to the fact that the phenomenon may be accompanied by a temporary large increase. Such a temporary increase in the actual exhaust gas recirculation gas rate is hereinafter referred to as an exhaust gas recirculation gas spike (EGR spike). It is considered that the occurrence of the exhaust gas return gas spike has a greater effect on misfire than in the case of a mere delay in the decrease in the exhaust gas pressure, and also has a greater effect on the deterioration of the exhaust gas component. Therefore, multiple ignition is performed when the exhaust gas spike is detected or predicted, and the opportunity of multiple ignition, which places a heavy burden on the ignition device, is minimized.

It is a block diagram of the engine control device which shows one Embodiment of this invention. It is a graph which shows the control of this invention. (A) and (b) are graphs showing multiple ignition of an ignition device. (A) to (c) are graphs showing the control of the present invention.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall view showing the configuration of the engine 1 of the present invention and the control device of the engine 1. The engine 1 is a gasoline engine which is a spark ignition type engine.

The configuration of the engine 1 includes an intake passage 4 for introducing intake air through the combustion chamber 2 of a cylinder accommodating a piston, and an exhaust passage 14 for drawing out exhaust gas from the combustion chamber 2. The intake port, which is an opening to the combustion chamber 2 of the intake passage 4, and the exhaust port, which is an opening to the combustion chamber 2 of the exhaust passage 14, are opened and closed by valves, respectively. Further, the combustion chamber 2 and the intake port are provided with a fuel injection valve for injecting fuel into the intake air.

The intake passage 4 includes a throttle valve 5 that adjusts the flow path area of the intake passage 4 toward the upstream side from the intake port, an intake cooling device (intercooler) 6 that cools the intake air flowing through the intake passage 4, and a turbocharger 10. The compressor 12, the air cleaner 7, and the like are provided. The intake passage 4 is provided with an air flow sensor 31 for detecting the amount of intake air and an intake pressure sensor 32 for detecting the intake air temperature and the intake pressure.

In the exhaust passage 14, a catalyst for removing hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOX), etc. in the exhaust gas from the turbine 11 of the turbocharger 10 toward the downstream side from the exhaust port. An exhaust purification unit 15 and a silencer (muffler) 16 provided with the above are provided. The exhaust passage 14 is provided with an exhaust pressure sensor 35, an air-fuel ratio sensor 36, and the like for detecting the exhaust temperature and the exhaust pressure on the downstream side of the exhaust purification unit 15.

Between the intake passage 4 and the exhaust passage 14, there is provided an exhaust gas recirculation device 20 that connects the intake passage 4 and the exhaust passage 14 and introduces a part of the exhaust gas into the intake air as an exhaust return gas.

The exhaust gas recirculation device 20 of this embodiment is a low-pressure exhaust gas recirculation device that handles exhaust gas having a relatively low pressure, and is between the exhaust purification unit 15 of the exhaust passage 14 and the silencer 16 and the intake passage 4. An exhaust gas recirculation passage connecting to the upstream portion of the compressor 12 and an exhaust gas recirculation gas cooler 22 provided in the middle of the exhaust recirculation passage for cooling the exhaust recirculation gas are provided. The exhaust / return gas joins the intake air in the intake passage 4 according to the opening / closing of the exhaust / return valve 21 provided in the exhaust / return passage and the pressure state in the intake passage 4. As a result, a part of the exhaust gas discharged from the combustion chamber 2 is returned to the upstream side of the intercooler 6 of the intake passage 4 as the exhaust return gas.

An exhaust gas upstream pressure sensor 33 is provided on the upstream side of the exhaust recirculation valve 21 of the exhaust recirculation passage. The exhaust gas upstream pressure sensor 33 detects the upstream pressure of the exhaust gas.

As the exhaust gas recirculation device, a configuration that employs a high-pressure exhaust gas recirculation device that handles exhaust gas with relatively high pressure, or a configuration that employs both a low-pressure exhaust gas recirculation device and a high-pressure exhaust gas recirculation device. Is also possible. The high-pressure exhaust gas recirculation device is provided in an exhaust recirculation passage that communicates between the turbine 11 and the exhaust port of the exhaust passage 14, and between the intake port of the intake passage 4 and the throttle valve 5, and the exhaust recirculation passage thereof. It is equipped with an exhaust recirculation valve and the like. The exhaust return gas joins the intake air in the intake passage 4 according to the opening and closing of the exhaust return valve and the pressure state in the intake passage 4. An exhaust return gas cooler is also provided as needed.

The electronic control unit (Electronic Control Unit) 30 included in the vehicle equipped with the engine 1 performs the supply of fuel and air to the engine 1, the opening and closing of valves, and other controls.

In the electronic control unit 30, in addition to the information on the engine rotation speed by the rotation sensor 34 included in the engine 1, the information on the intake air amount by the air flow sensor 31, the information on the intake air temperature, the intake pressure, etc. by the intake pressure sensor 32, and the exhaust return gas. Information on the upstream pressure of the exhaust recirculation gas by the upstream pressure sensor 33, information on the exhaust temperature, exhaust pressure, etc. by the exhaust pressure sensor 35, information on the air-fuel ratio by the air-fuel ratio sensor 36, and information from various other devices are acquired. Use that information for control.

The cylinder head of the engine 1 is provided with a spark plug 3 facing the combustion chamber for each cylinder. The spark plug 3 ignites the fuel in the combustion chamber 2 by generating an ignition spark, and burns the fuel.

A high voltage generated by the secondary coil of the ignition coil 8a is applied to the center electrode of the spark plug 3. The primary coil of the ignition coil 8a is connected to the igniter 8b. The ignition device is composed of the spark plug 3, the ignition coil 8a, the igniter 8b, and the like. In the ignition device, the ignition timing, the number of ignitions in one combustion cycle, the ignition interval, and the like are controlled by the ignition control means 8 included in the electronic control unit 30. It should be noted that the intermittent generation of ignition sparks a plurality of times during one combustion cycle is hereinafter referred to as multiple ignition.

During the operation of the engine 1, the igniter 8b is turned on / off by the ignition signal transmitted from the ignition control means 8 of the electronic control unit 30 to the igniter 8b. When the igniter 8b is turned on, a primary current flows through the primary coil of the ignition coil 8a to increase the stored energy of the ignition coil 8a. A high voltage is induced, and the high voltage causes ignition sparks due to discharge between the electrodes of the spark plug 3.

When performing multiple ignition, after the normal primary current is cut off, the igniter 8b is periodically turned on and off by the ignition signal, and the spark plug 3 is continuously discharged (ignited) a plurality of times. FIG. 3A is an example of the secondary current when two discharges are performed during one combustion cycle, and FIG. 3B is an example when three discharges are performed during one combustion cycle. This is an example of secondary current.

Further, the electronic control unit 30 includes an exhaust gas recirculation gas control means 23 for controlling the exhaust gas recirculation device 20. The exhaust gas recirculation gas control means 23 controls the opening / closing of the exhaust recirculation valve 21 and the pressure state in the intake passage 4 according to the operating condition, and adjusts the amount of the exhaust recirculation gas introduced into the intake air.

Further, the electronic control unit 30 includes an exhaust gas excess detecting means 24. The exhaust gas excess detection means 24 is actually exhausted with respect to the target exhaust gas return gas ratio, which is the target exhaust gas return gas ratio, when controlling to lower the exhaust gas return gas ratio, which is the ratio of the exhaust gas return gas to the intake air. Detects or predicts the occurrence of an exhaust gas excess state in which the actual exhaust gas return gas rate, which is the return gas rate, is larger.

The target exhaust return gas rate is determined by the exhaust return gas control means 23 based on the engine speed, the load of the engine, the opening degree of the throttle valve, and the like, according to the operating state. The actual exhaust gas return gas rate is estimated by the exhaust gas return gas control means 23 based on the intake air amount, the intake pressure, the opening degree of the exhaust return valve 21, and the like. Alternatively, a means for directly measuring the actual exhaust gas return gas rate may be provided in the intake port.

For example, it is assumed that control is performed to reduce the exhaust gas return gas rate of the intake air when the vehicle is decelerating or when the vehicle is approaching an uphill. At this time, a state in which the actual exhaust gas return gas rate is larger than the target exhaust gas return gas rate set to a value lower than the current actual exhaust gas return gas rate, that is, a state in which the exhaust gas return gas is excessive may occur. be. In particular, after the throttle valve is closed, the exhaust pressure does not decrease immediately even though the intake air amount decreases and the intake pressure decreases, but gradually decreases over time, so-called exhaust pressure. Since there is a tendency for the descent to be delayed, an excessive exhaust return gas state is likely to occur. If an excessive amount of exhaust gas is generated, it will lead to misfire and deterioration of the exhaust gas component, so countermeasures are required.

Therefore, the ignition control means 8 performs multiple ignition by the ignition device when the exhaust gas excess detection means 24 detects or predicts the occurrence of the exhaust gas excess state.

Only when the occurrence of an excess exhaust gas is detected or predicted, multiple ignition is performed to prevent misfire, and multiple ignition is not performed in other operating conditions. Therefore, misfire or exhaust gas due to a delay in the decrease in exhaust pressure. The life of the igniter can be maintained by preventing the deterioration of the components and implementing the minimum necessary multiple ignition.

Further, for example, as shown in FIG. 2, when the target exhaust return gas rate is set to be lowered and the intake pressure drops sharply due to the closing operation of the throttle valve 5, the actual exhaust return gas rate becomes the target exhaust return gas rate. On the contrary, a phenomenon may occur in which the gas rate does not decrease toward the gas ratio but increases temporarily. The portion indicated by reference numeral A in the figure corresponds to the temporary increase in the actual exhaust gas return gas rate. Such a temporary increase in the actual exhaust gas return gas rate is hereinafter referred to as an exhaust gas return gas spike A. The exhaust gas excess detection means 24 can detect or predict the occurrence of an exhaust gas excess state, and can also detect or predict the occurrence of an exhaust gas spike A.

Here, in the exhaust gas return gas spike A, the actual exhaust gas return gas rate after the control to lower the exhaust gas return gas rate is temporarily higher than the actual exhaust gas return gas rate before the control to lower the exhaust gas return gas rate. It is in an enlarged state. It is considered that the exhaust gas spike A has a great influence on misfire and deterioration of the exhaust gas component even in the state of excess exhaust gas. Therefore, performing multiple ignition at the time of detecting or predicting the occurrence of the exhaust gas recirculation gas spike A is particularly effective in preventing misfire and in particular, preventing deterioration of the exhaust gas component. Further, the execution of multiple ignition may be limited to the time of detecting or predicting the occurrence of the exhaust gas spike A among various exhaust gas excess states.

Here, a method for detecting the occurrence of an excess exhaust gas recirculation gas, a prediction method, a method for detecting the occurrence of the exhaust gas recirculation gas spike A, and a prediction method will be described.

The exhaust gas excess state often occurs after the throttle valve 5 is closed during deceleration. Further, the exhaust gas excess state often occurs at a low rotation speed of the engine 1 at a predetermined rotation speed (for example, 1500 rotations / minute) or less. Therefore, the detection or prediction of the occurrence of the exhaust gas excess state is the engine speed at the time immediately before the start of deceleration, the actual exhaust gas rate at that time, and the target exhaust gas newly set at the start of deceleration. It can be done based on the gas rate.

For example, for each engine speed, the exhaust gas excess state is based on the actual exhaust gas return gas rate at that time and the value of the target exhaust gas return gas rate newly set according to the closing operation of the throttle valve 5. A map showing the presence / absence of the occurrence or the presence / absence of the exhaust gas spike A may be used. In the map, the lower the engine speed, the more likely it is that the exhaust gas excess state and the exhaust gas spike A will occur, and the larger the difference between the actual exhaust gas rate and the target exhaust gas rate, the more each phenomenon will occur. It indicates that it is likely to occur.

In addition, as another method, the first index showing the degree of decrease in the amount of intake air is focused on the "delayed decrease in exhaust pressure", which is one of the causes of the excessive exhaust gas return state and the exhaust gas return gas spike A. It can be performed based on the index of the above and the second index which is an index indicating the degree of decrease of the exhaust pressure (the pressure on the upstream side of the exhaust gas recirculation gas) on the exhaust passage side of the exhaust gas recirculation device.

For example, as an index showing the degree of decrease in the intake air amount, the intake air amount decrease rate (minus value), which is the change amount (decrease amount) in the intake air amount per unit time from the start of deceleration, is set upstream of the exhaust return gas. As an index showing the degree of decrease in the side pressure, the exhaust pressure reduction rate (minus value), which is the amount of change (decrease) in the upstream side pressure of the exhaust return gas per unit time from the start of deceleration, is used to determine the exhaust pressure. The descent delay can be determined.

If the exhaust pressure is high even though the intake air amount is low, for example, if the exhaust pressure reduction rate does not match the intake air amount reduction rate, the exhaust return gas is excessively taken into the intake air. Since the pushing phenomenon occurs, an excess exhaust return gas state occurs, and when the difference is particularly large, the exhaust return gas spike A occurs.

For example, in the example shown in FIG. 4B, the intake air amount reduction rate is (−s / r), and the exhaust pressure reduction rate is (−p / q). Here, since {(−s / r) / (−p / q)} = 1, the exhaust gas excess state and the exhaust gas spike A do not occur. Further, even in the case of {(−s / r) / (−p / q)} <1, each phenomenon does not occur.

Next, for example, in the example shown in FIG. 4 (c), 1 <{(-s / r) / ( Since it is −p / q)}, the exhaust pressure reduction rate corresponding to the intake air amount reduction rate does not occur. Therefore, the exhaust gas recirculation gas excess state and the exhaust gas recirculation gas spike A are generated.

Here, the ratio of the intake air amount reduction rate (-s / r) to the exhaust pressure reduction rate (-p / q), that is, {(-s / r) / (-p / q)} is predetermined. It is assumed that the exhaust gas spike A is generated when the predetermined ratio (however, the predetermined ratio> 1) or more, and {(-s / r) / (-p / q)} is larger than 1 and the predetermined ratio ( However, when the predetermined ratio is less than 1), it can be estimated that the exhaust gas recirculation gas spike A does not occur, but the exhaust gas recirculation gas excess state occurs.

In summary, when {(−s / r) / (−p / q)} ≦ 1, the exhaust gas spike A and the exhaust gas excess state do not occur. When 1 <{(-s / r) / (-p / q)} <predetermined ratio (however, predetermined ratio> 1), the exhaust gas spike A does not occur, but the exhaust gas excess state occurs. .. When the predetermined ratio (however, the predetermined ratio> 1) <{(−s / r) / (−p / q)}, the exhaust gas spike A is generated. It can be estimated as described above.

The end of the multiple ignition controlled by the ignition control means 8 is when the intake air amount reduction rate (-s / r) and the exhaust pressure reduction rate (-p / q) become equal, that is, {(-s / r). ) / (−P / q)} = 1, or {(−s / r) / (−p / q)} ≦ 1.

Alternatively, the end of the multiple ignition controlled by the ignition control means 8 may be when the actual exhaust gas return gas rate becomes equal to the target exhaust gas return gas rate. With the end of multiple ignition, it shifts to normal ignition.

The symbol x shown in FIG. 4A indicates the time when the upstream pressure of the exhaust recirculated gas becomes equal to the target exhaust pressure corresponding to the intake air amount after the start of deceleration and becomes a stable exhaust pressure with little fluctuation. Shows. Reference numeral y indicates a time point when the opening degree of the exhaust recirculation valve 21 is fully closed. In many cases, the reference numerals x and the reference numerals y generally coincide with each other. The symbol z indicates a time point at which the actual exhaust gas return gas rate becomes equal to the target exhaust gas return gas rate. The timings of the reference numerals x, the reference numerals y, and the reference numerals z can be set as the end points of the multiple ignition.

In an actual engine, each numerical value in these graphs repeats minute fluctuations and converges to the target value, but these minute fluctuations are excluded for easy understanding in these graphs. The fluctuation of the numerical value is simplified and described.

Further, when performing multiple ignition, the ignition interval controlled by the ignition control means 8 (ignition interval of multiple ignition in one combustion cycle) is set to the advance state of the ignition timing, the engine speed, and the target exhaust gas. It can be decided based on the rate. As the ignition interval of multiple ignition, for example, the time between the first spark and the second spark shown in FIGS. 3 (a) and 3 (b), or the second spark and the third spark shown in FIG. 3 (b). The time between the eyes may be calculated in advance based on the advance state of the ignition timing, the engine speed, and the target exhaust gas return gas rate at that time. Further, a map for determining the ignition interval based on these factors may be used.

For example, the ignition timing can be advanced, the ignition interval of multiple ignitions can be lengthened, and the smaller the engine speed, the longer the combustion period. Therefore, the number of ignitions of multiple ignitions can be increased to lengthen the ignition interval. Further, the larger the difference from the target exhaust gas return gas rate set relatively low with respect to the actual exhaust gas return gas rate, the longer the ignition interval of multiple ignition. This is because it is generally difficult to energize the ignition current when the exhaust recirculation gas is excessive, so it is effective to use a coil that increases the peak current of the ignition discharge. Therefore, the discharge time is guaranteed by multiple ignition.

1 Engine 2 Combustion chamber 3 Spark plug 4 Intake passage 5 Throttle valve 6 Intake cooling device (intercooler)
7 Air cleaner 8 Ignition control means 8a Ignition coil 8b Igniter 10 Turbocharger 11 Turbine 12 Compressor 13 Wastegate device 13a Exhaust bypass passage 13b Exhaust bypass valve 14 Exhaust passage 15 Exhaust purification unit 16 Silent 20 Exhaust gas recirculation device (low pressure exhaust gas) Recirculation device)
21 Exhaust recirculation valve 22 Exhaust recirculation gas cooler 23 Exhaust recirculation gas control means 24 Exhaust recirculation gas excess detection means 30 Electronic control unit 31 Air flow sensor 32 Intake pressure sensor 33 Exhaust recirculation gas upstream pressure sensor 34 Rotation sensor 35 Exhaust pressure sensor 36 Air-fuel ratio sensor

Claims (8)

An intake passage that introduces intake air into the combustion chamber,
The exhaust passage that sends out the exhaust from the combustion chamber and
Throttle valve that adjusts the amount of intake air,
An ignition device that generates an ignition spark in the combustion chamber,
An ignition control means for controlling the ignition device and
An exhaust gas recirculation device that connects the intake passage and the exhaust passage and introduces a part of the exhaust gas into the intake air as an exhaust return gas.
An exhaust gas recirculation control means for controlling the exhaust gas recirculation device, and an exhaust gas recirculation control means.
When controlling to lower the exhaust recirculation gas ratio, which is the ratio of the exhaust recirculation gas to the intake air, the actual exhaust recirculation gas, which is the actual exhaust recirculation gas ratio, with respect to the target exhaust recirculation gas ratio, which is the target exhaust recirculation gas ratio. Exhaust gas excess detection means for detecting or predicting the occurrence of an exhaust gas excess state with a higher rate, and
Equipped with
When the ignition control means detects or predicts the occurrence of the exhaust gas excess state, the ignition control means performs multiple ignition in which the generation of ignition sparks by the ignition device is performed a plurality of times per combustion cycle.
The detection or prediction of the occurrence of the exhaust gas excess state is the first index which is an index showing the degree of decrease in the intake air amount, and the degree of decrease in the exhaust pressure on the exhaust passage side of the exhaust gas recirculation device. It is done based on the second indicator, which is the indicator,
The exhaust gas excess detecting means detects or predicts the occurrence of the exhaust gas excess state when the ratio of the first index to the second index is larger than a predetermined ratio.
Engine control device. The exhaust gas excess state is the actual exhaust gas return gas rate after the control to lower the exhaust gas return gas rate is started, rather than the actual exhaust gas return gas rate before the control to lower the exhaust gas return gas rate. The engine control device according to claim 1, wherein is a period in which a large exhaust gas spike is generated. The engine control device according to claim 1 or 2, wherein the exhaust gas excess state occurs after the throttle valve is closed during deceleration. Equipped with a rotation sensor that detects the number of revolutions of the engine
The exhaust gas excess detecting means detects or predicts that the exhaust gas excess state is more likely to occur as the rotation speed is lower, and the larger the difference between the actual exhaust gas rate and the target exhaust gas rate is, the greater the difference between the actual exhaust gas rate and the target exhaust gas rate. The engine control device according to any one of claims 1 to 3, wherein the exhaust gas excess state is likely to occur . The first index is the intake air amount reduction rate which is the decrease amount of the intake air amount per unit time, and the second index is the exhaust pressure decrease which is the decrease amount of the exhaust pressure per unit time. The engine control device according to any one of claims 1 to 4, which is a rate. The engine control device according to claim 5 , wherein the ignition control means terminates the multiple ignition when the intake air amount reduction rate and the exhaust pressure reduction rate become equal. The engine control device according to any one of claims 1 to 5 , wherein the ignition control means terminates the multiple ignition when the actual exhaust recirculation gas rate becomes equal to the target exhaust recirculation gas rate. Equipped with a rotation sensor that detects the number of revolutions of the engine
The ignition control means sets the ignition interval of the multiple ignitions in one combustion cycle as the ignition timing advances , the rotation speed decreases , or the actual exhaust recirculation gas rate and the target exhaust. The larger the difference from the return gas rate, the longer it will be.
The engine control device according to any one of claims 1 to 7 .

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