JP2018141404A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of suppressing misfire caused by increase of an EGR rate with a simple configuration.SOLUTION: An internal combustion engine comprises: an intake passage 3 connecting to a combustion chamber 10; a throttle valve 4 provided in the intake passage 3 for regulating an air mount sucked into the combustion chamber 10; an EGR passage 6 put in communication with a downstream side space 30 in the intake passage 3, which is closer to the combustion chamber 10 side than the throttle valve 4, for allowing exhaust gas to be sucked into the combustion chamber 10; an EGR valve 7 provided in the EGR passage 6 for regulating a recirculation amount of the exhaust gas; and an ignition control part 100i carrying out ignition several times from a compression stroke to an expansion stroke at the time of detecting that, provided that a ratio of an exhaust gas amount to the air amount is set as an EGR rate, an increase rate of the EGR rate from when the opening degree of the EGR valve 7 is equal to or more than a predetermined value is equal to or more than a predetermined value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an internal combustion engine having an EGR passage that allows exhaust gas to be taken into a combustion chamber.

In an automobile, an exhaust gas recirculation device (Exhaust gas recirculation) that takes exhaust gas exhausted from the combustion chamber into the combustion chamber again in order to reduce nitrogen oxides (NO _x ) in the exhaust gas and reduce fuel consumption. : EGR) (for example, Patent Document 1). The EGR includes an EGR passage that communicates the exhaust passage and the intake passage, and an EGR valve that is provided in the middle of the EGR passage and adjusts the recirculation amount of the exhaust gas. The EGR passes through the EGR passage to the combustion chamber. Inhale.

  The intake passage is provided with a throttle valve that opens and closes in response to the operation of an accelerator pedal disposed in the driver's seat and adjusts the amount of air taken into the combustion chamber by the degree of opening and closing (opening degree). The ratio of the amount of exhaust gas to the amount of air taken into the combustion chamber (hereinafter referred to as the EGR rate) varies depending on the opening of the throttle valve and the opening of the EGR valve. If this EGR rate rises excessively, problems such as a decrease in oxygen concentration in the intake air and misfire in the combustion chamber occur. For example, when the driver operates the accelerator pedal with a sudden throttle valve closing drive, the amount of air in the intake air decreases rapidly, while the decrease in the exhaust gas amount due to the driving of the EGR valve decreases the air amount. The EGR rate may increase with a delay with respect to the decrease. This is because the EGR valve generally has low responsiveness to the throttle valve, so that the opening and closing of the EGR valve is difficult to synchronize with the opening and closing of the throttle valve, and even if the EGR valve is closed, Among them, the exhaust gas remaining on the intake passage side from the EGR valve is taken into the combustion chamber after the throttle valve is closed.

  Therefore, Patent Document 1 discloses an EGR including an intake air flow control valve on the combustion chamber side of the intake passage in the intake passage and a control device that controls the intake air flow control valve. The intake flow control valve is located at a position closest to the opening of the EGR passage in the intake passage, thereby forming an intake upstream side and an intake downstream side in the intake passage. When there is a request to reduce the exhaust gas amount, the control device drives the intake flow control valve in a direction in which the valve tip of the intake flow control valve is separated from the opening of the EGR passage. When the valve tip of the intake flow control valve is close to the opening of the EGR passage, the passage area of the intake passage is reduced, and the pressure near the opening is compared with the pressure on the intake upstream side and the intake downstream side. Therefore, when a large amount of exhaust gas can be introduced and the valve tip of the intake flow control valve is separated from the opening of the EGR passage, the passage area of the intake passage is maximized and the pressure near the opening is increased. Since it becomes equal to the pressure on the upstream side and the downstream side of the intake air, the introduction of exhaust gas can be suppressed. That is, a suitable EGR rate is maintained by controlling the opening of the intake flow control valve by the control device in accordance with the opening of the throttle valve.

JP 2010-90752 A

  However, in the technique described in Patent Document 1, it is necessary to provide an intake flow control valve in order to adjust the pressure in the vicinity of the opening of the EGR passage, which is large and increases the cost.

  Accordingly, one object of the present invention is to provide an internal combustion engine that can suppress misfire due to an increase in the EGR rate with a simple configuration.

An internal combustion engine according to an aspect of the present invention includes:
An intake passage leading to the combustion chamber;
A throttle valve provided in the intake passage for adjusting the amount of air taken into the combustion chamber;
An EGR passage communicating with the downstream space closer to the combustion chamber than the throttle valve in the intake passage, and for sucking exhaust gas into the combustion chamber;
An EGR valve provided in the EGR passage for adjusting a recirculation amount of the exhaust gas;
When the ratio of the exhaust gas amount to the air amount is defined as an EGR rate, when it is detected that the rate of increase in the EGR rate from when the opening degree of the EGR valve is equal to or greater than a predetermined value is greater than or equal to a predetermined value. An ignition control unit that performs ignition a plurality of times from the compression stroke to the expansion stroke.

  The internal combustion engine can suppress misfire due to an increase in the EGR rate by igniting a plurality of times from the compression stroke to the expansion stroke when detecting that the increase rate of the EGR rate is equal to or greater than a predetermined value. This is because the combustion pressure in the combustion chamber can be increased by the initial ignition among a plurality of times of ignition, and ignition can be performed reliably by performing ignition again in a state where the combustion pressure is high. Since misfire can be suppressed even when the rate of increase in the EGR rate is equal to or greater than a predetermined value, the opening degree of the EGR valve can be increased to a predetermined value or more during normal operation, and fuel efficiency can be improved. Since the internal combustion engine controls the ignition several times based on the increase rate of the EGR rate, the existing internal combustion engine can be used and can be constructed with a simple configuration. Further, since the internal combustion engine controls a plurality of ignitions based on an increase rate of the EGR rate, the ignition plug is not unnecessarily performed a plurality of times, and the consumption of the spark plug can be minimized. .

1 is a schematic configuration diagram of an internal combustion engine according to an embodiment.

  An embodiment of an internal combustion engine of the present invention will be described below with reference to FIG. In the figure, white arrows indicate the flow of air, and black arrows indicate the flow of exhaust gas.

〔overall structure〕
The internal combustion engine 1 includes a combustion chamber 10 for burning an air-fuel mixture of intake air and fuel, an intake passage 3 for introducing the air-fuel mixture into the combustion chamber 10, an ignition plug 2 for igniting the air-fuel mixture in the combustion chamber 10, and a combustion And an exhaust passage 5 for exhausting exhaust gas from the chamber 10. The internal combustion engine 1 includes a plurality of cylinders 8 forming a combustion chamber 10 (one of them is shown in FIG. 1). The internal combustion engine 1 performs a four-cycle operation of intake, compression, expansion, and exhaust, thereby causing the piston 9 to reciprocate within the cylinder 8, and the reciprocating motion of the piston 9 to be rotated by a crankshaft (not shown). Convert. In the intake stroke, the intake valve 32 is opened near the top dead center of the piston 9, and air and fuel injected from an injector (not shown) are sucked into the combustion chamber 10 at the same time as the piston 9. 9 goes down. In the compression stroke, the intake valve 32 is closed at the bottom dead center of the piston 9, and the air-fuel mixture is compressed in the combustion chamber 10 by the rise of the piston 9. In the expansion stroke, the ignition plug 2 is ignited near the top dead center of the piston 9 to explode and burn, and the piston 9 descends. In the exhaust stroke, the exhaust valve 52 is opened in the vicinity of the bottom dead center of the piston 9, and the exhaust gas generated in the combustion chamber 10 due to the upward movement of the piston 9 is discharged to the exhaust passage 5. A crank angle sensor 110 that detects the rotation angle (crank angle) of the crankshaft with respect to the top dead center of the piston 9 is provided on the rotation shaft of the crankshaft.

  The intake passage 3 is provided with a throttle valve 4 that is opened and closed in accordance with the operation of an accelerator pedal disposed in the driver's seat and adjusts the amount of air taken into each combustion chamber 10 according to the degree of opening and closing (opening degree). In this example, the throttle valve 4 is a butterfly valve having a valve body that is pivotally supported in the intake passage 3 by a rotating shaft. A throttle position sensor 120 for detecting the opening degree of the throttle valve 4 is provided on the rotation shaft of the throttle valve 4.

  The internal combustion engine 1 includes an exhaust gas recirculation device (EGR) that recirculates a part of the exhaust gas discharged from the combustion chamber 10 to the exhaust passage 5 to the combustion chamber 10. The EGR includes an EGR passage 6 that connects the exhaust passage 5 and the intake passage 3, and an EGR valve 7 that is provided in the middle of the EGR passage and adjusts the recirculation amount of the exhaust gas. The EGR passage 6 communicates with the downstream space 30 on the combustion chamber 10 side than the throttle valve 4 in the intake passage 3. The EGR valve 7 is controlled according to the opening degree of the throttle valve 4. Specifically, the opening degree of the EGR valve 7 is controlled according to the opening degree of the throttle valve 4 so that the ratio (EGR rate) of the exhaust gas amount to the air amount sucked into the combustion chamber 10 becomes a suitable value. Is done. The EGR valve 7 is provided with an EGR opening degree sensor 130 that detects the opening degree of the EGR valve 7.

  The detection results of the above-described various sensors (the crank angle sensor 110, the throttle position sensor 120, and the EGR opening degree sensor 130) are sent to an ECU (Engine Control Unit) 100 as appropriate.

  The internal combustion engine 1 of the present embodiment detects a plurality of times from the compression stroke to the expansion stroke when it detects that the increase rate of the EGR rate from when the opening degree of the EGR valve 7 is equal to or greater than a predetermined value. One of the features is that it includes an ignition control unit 100i that performs ignition. The opening degree of the EGR valve 7 can be detected by the EGR opening degree sensor 130. An intake pressure sensor 140 is provided in the downstream space 30 in the intake passage 3, and the increase rate of the EGR rate can be determined by the intake pressure detected by the intake pressure sensor 140. Hereinafter, the flow of intake air in the internal combustion engine 1 will be described first, and then the details of the ignition control unit 100i will be described.

[Intake flow]
When the throttle valve 4 is in the open state, the air flowing through the intake passage 3 is directly taken into the combustion chamber 10. At this time, the pressure in the space 30 downstream of the throttle valve 4 in the intake passage 3 is atmospheric pressure. When the throttle valve 4 is open, the EGR valve 7 is also driven open. The exhaust gas recirculated to the intake passage 3 through the EGR passage 6 is taken into the combustion chamber 10 together with the air flowing through the intake passage 3. The opening degree of the EGR valve 7 is controlled so that the EGR rate becomes a suitable value.

  When the throttle valve 4 is suddenly closed from the open state, the amount of air taken into the combustion chamber 10 is drastically reduced. Even when the throttle valve 4 is closed, a minimum amount of air is sucked into the combustion chamber 10 so that the internal combustion engine 1 does not stop completely. At this time, the pressure in the downstream space 30 in the intake passage 3 is a negative pressure. When the throttle valve 4 is closed, the EGR valve 7 is also driven to the closed state. However, since the EGR valve 7 is generally less responsive to the throttle valve 4, the amount of air in the intake air rapidly decreases, while the decrease in the exhaust gas amount due to the drive of the EGR valve 7 decreases the air amount. There may be a delay. Further, after the throttle valve 4 is closed, exhaust gas may remain on the intake passage 3 side of the EGR passage 6 with respect to the EGR valve 7. Therefore, the EGR rate may increase rapidly. If the EGR rate rises rapidly, there is a risk of misfire in the combustion chamber 10.

(Ignition control unit)
The ignition control unit 100i has an EGR opening degree determining unit 100x that determines whether or not the opening degree of the EGR valve 7 is equal to or greater than a predetermined value, and EGR that determines whether or not the rate of increase in the EGR rate is equal to or greater than a predetermined value. And an increase rate determination unit 100y. The increase rate of the EGR rate is the increase rate of the EGR rate per unit time. The ignition control unit 100i uses the EGR opening degree determination unit 100x and the EGR increase rate determination unit 100y to quickly close the throttle valve 4 when the opening degree of the EGR valve 7 is equal to or greater than a predetermined value, and the increase rate of the EGR rate When it is detected that the value is equal to or greater than a predetermined value, ignition is performed a plurality of times from the compression stroke to the expansion stroke. As described above, when the EGR rate suddenly increases, there is a risk of misfire in the combustion chamber 10, but the misfire can be suppressed by performing ignition multiple times by the ignition control unit 100i. The ignition control unit 100i can use the ECU 100.

  The EGR opening degree determination unit 100x acquires the opening degree of the EGR valve 7 detected from the EGR opening degree sensor 130 and performs the determination. The EGR increase rate determination unit 100y performs determination by acquiring the opening of the throttle valve 4 detected from the throttle position sensor 120 and the intake pressure of the downstream space 30 detected from the intake pressure sensor 140. Specifically, the EGR increase rate determination unit 100y performs the determination as follows.

  First, a decrease in the intake pressure detected from the intake pressure sensor 140 with reference to the time when the opening of the throttle valve 4 detected from the throttle position sensor 120 is less than or equal to a predetermined value (the closing amount is greater than or equal to a predetermined value). Judge by quantity. When the throttle valve 4 is suddenly closed, the EGR valve 7 cannot follow the throttle valve 4 and the valve closing drive is delayed. Therefore, the exhaust gas recirculates even though the pressure in the downstream space 30 in the intake passage 3 rapidly decreases as the throttle valve 4 is closed. In particular, since the pressure in the downstream space 30 decreases, the exhaust gas tends to recirculate to the intake passage 3 in a short time due to the pressure difference between the exhaust passage 5 and the intake passage 3, and the EGR rate increases rapidly.

  Second, the transition of the intake pressure of the downstream space 30 in the intake passage 3 when it is assumed that the EGR valve 7 can be driven to follow the throttle valve 4 when the throttle valve 4 is suddenly closed. Is determined from the difference between the reference pressure and the actually detected intake pressure. Since the reference pressure fluctuates in each stroke of four cycles, intake pressure data corresponding to the crank angle is stored in advance. Then, the actually detected intake pressure is compared with the reference pressure corresponding to the crank angle when the intake pressure is measured. When the throttle valve 4 is in the closed state, air does not intentionally flow in the downstream space 30, and therefore the reference pressure should be almost constant unless the exhaust gas is recirculated. If the exhaust gas is recirculated despite the throttle valve 4 being closed, the intake pressure in the downstream space 30 becomes higher than the reference pressure. In particular, if the transition of the intake pressure increases rapidly compared to the reference pressure, the EGR rate will increase rapidly. In this embodiment, it is determined whether or not the difference between the reference pressure and the actually detected intake pressure is greater than or equal to a predetermined value.

  Only when the EGR opening degree determination unit 100x determines that the opening degree of the EGR valve 7 is equal to or greater than a predetermined value and the EGR increase rate determination unit 100y determines that the increase rate of the EGR rate is equal to or greater than the predetermined value. The ignition control unit 100i performs ignition multiple times. That is, when at least one of the EGR opening degree determination unit 100x and the EGR increase rate determination unit 100y does not satisfy the above determination, the ignition control unit 100i does not perform ignition a plurality of times and performs one ignition per cycle. I do.

  A plurality of times of ignition by the ignition control unit 100i can be performed, for example, a plurality of times when the crank angle is 15 ° before top dead center and 15 ° after top dead center. In particular, the crank angle is performed at least once in the region of 15 ° before the top dead center from the top dead center, and the crank angle is performed at least once in the region after the top dead center of 15 ° after the top dead center. To do. The ignition performed in the region before the top dead center is mainly pre-combustion and is performed to increase the combustion pressure in the combustion chamber 10. This pre-combustion allows misfire due to an excessive increase in the EGR rate. The ignition performed in the region after the top dead center is mainly the main combustion, and is performed for sure ignition. In the main combustion, since the pressure of the combustion chamber 10 is increased by the pre-combustion, the certainty of ignition can be improved by this pressure and the ignition energy.

  When the EGR rate is higher, it is preferable to increase the interval between the ignition performed in the region before top dead center and the ignition performed in the region after top dead center. This is because if the EGR rate is too high, the combustion in the region before the top dead center is likely to be slow, and the increase in the combustion pressure resulting from the ignition is likely to be slow. For example, when igniting once in the region before top dead center and igniting once in the region after top dead center, the ignition performed in the region before top dead center is greatly advanced and the ignition performed in the region after top dead center is advanced slightly. It is possible to horn. By doing so, when the combustion pressure by the ignition performed in the region before the top dead center is optimum, the ignition in the region after the top dead center can be performed, and it becomes easy to ignite.

  The number of ignitions performed in the region before the top dead center and the number of ignitions performed in the region after the top dead center can be appropriately selected. By increasing the number of ignitions performed in the region before top dead center, the combustion pressure can be further increased, and by increasing the number of ignitions performed in the region after top dead center, the certainty of ignition can be further increased. The number of ignitions in the region before the top dead center and the number of ignitions in the region after the top dead center may be the same or different. Of course, it can be performed once for each region. In that case, it is possible to ignite once when the crank angle is around 15 ° before top dead center and ignite once around 15 ° after top dead center.

〔effect〕
Since the internal combustion engine 1 described above includes the ignition control unit 100i, misfire due to an increase in the EGR rate can be suppressed. Since the ignition control unit 100i is controlled by the rate of increase in the EGR rate, the ignition plug 2 is not unnecessarily ignited a plurality of times, and a reduction in the life of the spark plug 2 can be suppressed. Since misfire can be suppressed even when the rate of increase of the EGR rate is equal to or greater than a predetermined value, the opening degree of the EGR valve 7 can be increased to a predetermined value or more during normal operation, and fuel consumption can be improved.

  The present invention is not limited to these exemplifications, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 10 Combustion chamber 2 Spark plug 3 Intake passage 30 Downstream space 32 Intake valve 4 Throttle valve 5 Exhaust passage 52 Exhaust valve 6 EGR passage 7 EGR valve 8 Cylinder 9 Piston 100 ECU
DESCRIPTION OF SYMBOLS 100i Ignition control part 100x EGR opening degree determination part 100y EGR increase rate determination part 110 Crank angle sensor 120 Throttle position sensor 130 EGR opening degree sensor 140 Intake pressure sensor

Claims (1)

An intake passage leading to the combustion chamber;
A throttle valve provided in the intake passage for adjusting the amount of air taken into the combustion chamber;
An EGR passage communicating with the downstream space closer to the combustion chamber than the throttle valve in the intake passage, and for sucking exhaust gas into the combustion chamber;
An EGR valve provided in the EGR passage for adjusting a recirculation amount of the exhaust gas;
When the ratio of the exhaust gas amount to the air amount is defined as an EGR rate, when it is detected that the rate of increase in the EGR rate from when the opening degree of the EGR valve is equal to or greater than a predetermined value is greater than or equal to a predetermined value. An internal combustion engine comprising: an ignition control unit that performs ignition multiple times from a compression stroke to an expansion stroke.

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