TWI647383B - Internal combustion engine control device - Google Patents

Abstract

When the control of repeatedly applying a high voltage to the spark plug during the period of fuel injection by the injector is applied to the activation of the exhaust purification catalyst, the combustion fluctuation during the cycle can be suppressed.

In the catalyst warm-up control, the first injection by the injector (30) is performed during the intake stroke, and the expansion stroke after compression top dead center is performed compared with the first injection A small amount of the second shot. In the catalyst warm-up control, in order to make the initial flame contact between the fuel spray generated by the second injection and the fuel spray-containing mixture generated by the first injection, the spark plug (32) The interval from the start of the generated ignition period to the end of the second injection is controlled by the ECU (40).

Description

Control device of internal combustion engine

The present invention relates to a control device for an internal combustion engine. More specifically, the present invention relates to a control device for a spark ignition type internal combustion engine provided with a barrel injector.

Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-106377) discloses an internal combustion engine including an injector having a plurality of injection holes and a spark plug in an upper portion of a combustion chamber. In this internal combustion engine, the distance from the center position of the discharge interval of the spark plug to the center position of the nozzle hole closest to the spark plug among the nozzle holes is set to a specific range. Further, in this internal combustion engine, after a predetermined time has elapsed after the fuel injection is started, and across the end of the fuel injection, high voltage control is applied to the spark plug.

When the above-mentioned control is performed, the period during which the high voltage is applied to the spark plug overlaps with the period of fuel injection by the injector. Here, fuel is supplied to the injector in a pressurized state. When the fuel injected by the injector is injected, the air around the fuel spray from each injection hole is taken away to form a low-pressure portion (spiral). Therefore, when the above-mentioned control is performed, a discharge spark generated at a discharge interval is induced in a low-pressure portion formed around the nozzle hole closest to the aforementioned spark plug. Therefore, according to this internal combustion engine, the ignitability of the mixed gas formed around the spark plug can be improved.

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2011-106377

[Patent Document 2] Japanese Patent Laid-Open No. 2008-190511

[Patent Document 3] Japanese Patent Laid-Open No. 2015-094339

[Patent Document 4] Japanese Patent Laid-Open No. 2007-263065

[Patent Document 5] Japanese Patent Laid-Open No. 2008-069713

Patent Document 1 further describes the activation of the exhaust gas purification catalyst for the application example of the above-mentioned attracting action. Although not mentioned in Patent Document 1, the activation of the exhaust gas purification catalyst is usually performed by setting an ignition period near the top dead center of compression (that is, a high-voltage period applied to the spark plug) toward the compression. The top dead center is performed by changing the retardation side.

When the above-mentioned control of Patent Document 1 is applied to the activation of a general exhaust gas purification catalyst, it is set to the side of the compression top dead center on the retarder side By repeating the ignition period and the fuel injection period, the ignitability of the gas mixture formed around the spark plug can be improved. However, in any case where the ignition environment is changed from the preferable range, even if the above-mentioned attracting action is performed, the combustion state may become unstable. In addition, if there are many such cycles in the combustion cycle during activation control of the exhaust purification catalyst, the combustion fluctuation during the cycle will increase, which will affect the driving performance.

The present invention has been made in view of the above-mentioned subject, and an object thereof is to apply control for repeating a period in which a high voltage is applied to a spark plug and a period in which fuel is generated by an injector is suitable for activating an exhaust purification catalyst. In this case, fluctuations in combustion during the cycle can be suppressed.

The control device of the internal combustion engine of the present invention is an internal combustion engine controller that will include an injector, a spark plug, and an exhaust purification catalyst. The injector is provided in the upper part of the combustion chamber and injects fuel into the cylinder from a plurality of injection holes. The spark plug is ignited to the mixture in the cylinder using a discharge spark, and is provided downstream of the fuel injected from the plurality of injection holes, and is closer to the spark than the fuel spray injected from the plurality of injection holes. The outer surface of the fuel spray of the plug is further above. The exhaust gas purification catalyst purifies exhaust gas from the combustion chamber.

The control device is a control for activating the exhaust purification catalyst, and controls the spark plug to cause a discharge spark to occur during the ignition at the retarded side of the compression top dead center, and performs: during the compression on The injector is controlled such that the first injection on the dead-end-side advancing angle side and the compression upper dead-end side on the retarding-angle side and the injection period are second injections that overlap at least a part of the ignition period.

The control device of the internal combustion engine of the present invention is further that when a parameter related to combustion fluctuations during a cycle is judged to exceed a threshold value, compared with a case where the aforementioned parameter is judged to be below the threshold value, The spark plug and the injector are controlled so as to widen a section from a start period of the ignition period to an end period of the injection period of the second injection.

The mixture including the fuel spray in the first injection generates initial flame during ignition. When the injection period is a second injection that is repeated with at least a part of the ignition period, at least the initial flame is attracted toward the low-pressure portion formed around the fuel spray from the nozzle hole closest to the spark plug. Therefore, when the second injection is performed, the fuel spray generated by the second injection is brought into contact with the induced initial flame, and the combustion that makes the initial flame grow is promoted.

However, when this contact is not sufficient, the combustion that makes the initial flame grow may become unstable. The combustion that makes the initial flame grow is an unstable cycle. If there are many combustion cycles, the combustion fluctuations during the cycle will increase.

At this point, when the parameter related to the combustion fluctuation during the cycle is judged to exceed the threshold value, compared with the case where the parameter is judged to be lower than the threshold value, from the start of the ignition period to the If the interval between the end of the injection period of 2 injections is expanded, the interval from the start of the ignition period to the end of the second injection will be longer until the initial flame. The start of the second injection is waited until the degree increases. Therefore, it can be avoided that the contact between the fuel spray generated by the second injection and the induced initial flame and discharge spark becomes insufficient.

When the control device is a case where the parameter exceeds the threshold value, the amount of expansion of the interval may be changed in accordance with the separation amount of the parameter and the threshold value.

When the parameter related to the combustion fluctuation during the cycle is determined to exceed the threshold value, the fuel spray generated by the second injection can be reliably determined if the interval expansion amount is changed corresponding to the parameter and the separation amount of the threshold value And fully in contact with the initial flame induced.

The second injection may be such that the end period is located on the side of the advanced angle of the end period of the ignition period.

The end period of the second injection is a case on the retarder side of the end period of the ignition period, and only the initial flame is induced toward the low-pressure portion. In this regard, the end period of the second injection is a case where it is located on the side of the approach angle at the end period of the ignition period, and both the initial flame and the spark are attracted toward the low-pressure portion. In this way, the fuel spray generated by the second injection will come into contact with both the induced initial flame and the discharge spark. Therefore, the end period of the second injection seen from the end period of the ignition period is in the case of the advanced angle side, and the combustion that allows the initial flame to grow can be promoted more than the case of the late angle side.

The aforementioned parameter is the deviation of the time required until the crank shaft rotates to a predetermined angle, or the deviation of the crank angle period from the start of the ignition period to the time when the combustion mass ratio reaches the predetermined ratio. Yes.

The parameter related to the combustion fluctuations during the cycle is the deviation of the time required until the crank shaft rotates to a predetermined angle, or the deviation of the crank angle period from the start of the ignition period to the time when the combustion mass ratio reaches the predetermined ratio. In this case, combustion fluctuations during the cycle can be detected with high accuracy.

According to the control device of the internal combustion engine of the present invention, when the control of repeating the period of applying a high voltage to the spark plug and the period of fuel injection by the injector is applied to the activation of the exhaust purification catalyst, the cycle period can be suppressed. Burning changes.

10‧‧‧ Internal combustion engine

12‧‧‧ Inflator

14‧‧‧ cylinder block

16‧‧‧ cylinder head

18‧‧‧ Pistons

20‧‧‧Combustion chamber

22‧‧‧ Suction port

24‧‧‧Exhaust port

30‧‧‧ Ejector

32‧‧‧ Mars Plug

34‧‧‧electrode section

36‧‧‧ throat

40‧‧‧ECU

42‧‧‧Crank angle sensor

44‧‧‧Accelerator opening sensor

46‧‧‧Temperature Sensor

[FIG. 1] A diagram illustrating a system configuration of an embodiment of the present invention.

[Fig. 2] A diagram explaining the outline of the catalyst warm-up control.

[Fig. 3] A diagram illustrating an expansion stroke injection.

[Fig. 4] A diagram for explaining the spark sparks generated by the expansion stroke injection and the initial flame induction effect.

[FIG. 5] A diagram showing the relationship between the interval from the start of the ignition period to the end of the expansion stroke injection (ignition start-end injection interval) and the combustion fluctuation rate.

[Fig. 6] A diagram showing an example of a reference fit value relationship diagram.

[Fig. 7] A diagram showing the ignition timing (or more accurately, the start timing of the ignition period) generated by the spark plug 32 and the transition of the engine cooling water temperature during the cold start of the internal combustion engine.

[Fig. 8] A diagram illustrating a state in a tube when the growth rate of the initial flame is slow.

[FIG. 9] A diagram illustrating a state inside the tube when the distance between the spray outer surface and the electrode portion 34 is enlarged.

[Fig. 10] A diagram explaining a problem in a case where the ignition timing is advanced.

[FIG. 11] A diagram illustrating a correction method for a section from the start of the ignition period to the end of the expansion stroke injection.

[Fig. 12] A diagram illustrating a state in a cylinder in a case where a reference suitable value is corrected in a direction in which a section is widened from the start of an ignition period to the end of an expansion stroke injection.

13 is a diagram explaining the effect of a case where the reference suitability value is corrected in a direction in which the interval from the start of the ignition period to the end of the expansion stroke injection is extended.

14 is a flowchart showing an example of processing executed by the ECU 40 in the embodiment of the present invention.

[Fig. 15] A diagram showing an example of Gat30 at the cold start of the internal combustion engine and the transition of the deviation σ of the Gat30.

[FIG. 16] A diagram showing the relationship between the deviation σ of Gat30, the standard deviation, and the correction value for interval expansion.

[Fig. 17] A diagram showing the relationship between the combustion fluctuation rate and the deviation σ of SA-CA10 during a cold start of the internal combustion engine.

[FIG. 18] A diagram showing an example of the transition of the deviation σ of SA-CA10.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same reference numerals are attached to the elements that are common to the drawings, and redundant explanations are omitted. The present invention is not limited by the following examples.

[Explanation of the system configuration]

FIG. 1 is a diagram illustrating a system configuration of an embodiment of the present invention. As shown in FIG. 1, the system of this embodiment includes an internal combustion engine 10 mounted on a vehicle. The internal combustion engine 10 is a 4-stroke, 1-cycle engine and has a plurality of cylinders. However, in the first figure, only one of the gas cylinders 12 is drawn. The internal combustion engine 10 includes a cylinder block 14 formed with a cylinder 12 and a cylinder head 16 disposed on the cylinder block 14. A piston 18 is arranged in the gas cylinder 12 to reciprocate in the axial direction (vertical direction in this embodiment). The combustion chamber 20 of the internal combustion engine 10 is delimited by at least the wall surface of the cylinder block 14, the lower surface of the cylinder head 16, and the upper surface of the piston 18.

In the cylinder head 16, two intake ports 22 and two exhaust ports 24 communicating with the combustion chamber 20 are formed. An intake valve 26 is provided in an opening portion of the intake port 22 communicating with the combustion chamber 20, and an exhaust valve 28 is provided in an opening portion of the exhaust port 24 communicating with the combustion chamber 20. In addition, in the cylinder head 16, an injector 30 is provided so that the tip end faces the combustion chamber 20 from substantially the center of the upper portion of the combustion chamber 20. The injector 30 is connected to a fuel supply system including a fuel tank, a common rail, a supply pump, and the like. And, in the tip of the ejector 30 The plural injection holes are formed radially, and when the injector 30 is opened, fuel is injected from these injection holes under high pressure.

Further, in the cylinder head 16, a spark plug 32 is provided on an upper portion of the combustion chamber 20 on the exhaust valve 28 side than where the injector 30 is provided. The spark plug 32 includes an electrode portion 34 including a center electrode and a ground electrode at the tip. The electrode portion 34 protrudes toward a range (ie, a range from the spray outer surface to the lower surface of the cylinder head 16) that is higher than the outer surface of the fuel spray from the injector 30 (hereinafter also referred to as "spray outer surface").地 Configuration. To describe in detail, the electrode portion 34 is arranged to protrude from a fuel spray injected radially from the nozzle hole of the injector 30 to a range higher than the outer peripheral surface of the fuel spray closest to the spark plug 32. The outer line drawn in FIG. 1 is the outer surface showing the fuel spray closest to the spark plug 32 among the fuel sprays from the injector 30.

The intake port 22 extends almost straight from the inlet on the intake path side toward the combustion chamber 20, and the cross-sectional area of the flow path is reduced at the connection portion with the combustion chamber 20, that is, the throat 36. This shape of the intake port 22 causes a tumble flow in the intake air supplied from the intake port 22 to the combustion chamber 20. The tumble flow orbits within the combustion chamber 20. In detail, the tumble flow is from the upper part of the combustion chamber 20 to the exhaust port 24 side toward the exhaust port 24 side, and from the upper part of the combustion chamber 20 to the lower part on the exhaust port 24 side. The tumble flow is directed from the exhaust port 24 side toward the intake port 22 side in the lower portion of the combustion chamber 20 and upward from the lower portion of the combustion chamber 20 in the intake port 22 side. On the upper surface of the piston 18 forming the lower part of the combustion chamber 20, a depression for retaining a tumble flow is formed.

As shown in FIG. 1, the system of this embodiment includes an ECU (Electronic Control Unit) 40 as a control means. The ECU 40 includes a RAM (Random Random Access Memory, Random Access Memory), a ROM (Read Only Memory, Read Only Memory), a CPU (Central Processing Unit, Central Processing Unit), and the like. The ECU 40 takes in signals from various sensors mounted on the vehicle. The various sensors include at least a crank angle sensor 42 that detects a rotation angle of a crank shaft connected to the piston 18, and an accelerator opening that detects a depression amount of an accelerator pedal generated by a driver of the vehicle. A sensor 44 and a temperature sensor 46 that detects a cooling water temperature of the internal combustion engine 10 (hereinafter also referred to as "engine cooling water temperature"). The ECU 40 operates the various actuators in accordance with a predetermined control program by processing the received signals from each sensor. The actuator operated by the ECU 40 includes at least the injector 30 and the spark plug 32 described above.

[Start-up control by ECU40]

In this embodiment, as shown in FIG. 1, the control subsequent to the cold start of the internal combustion engine 10 generated by the ECU 40 is a control that promotes activation of the exhaust purification catalyst (hereinafter also referred to as "catalyst warming machine" control"). The exhaust gas purification catalyst is a catalyst provided in the exhaust passage of the internal combustion engine 10. For example, when the atmosphere of the catalyst in the activated state is located near the stoichiometry, an example is nitrogen oxides in the exhaust gas (NOx ), Hydrocarbon (HC) and carbon monoxide (CO) purification of the three-way catalyst.

The catalyst warm-up control performed by the ECU 40 will be described with reference to FIGS. 2 to 7. In FIG. 2, the injection timing by the injector 30 during the catalyst warm-up control and the start period of the ignition period by the spark plug 32 (the start period of the discharge period in the electrode portion 34) are depicted. ). As shown in Figure 2, in the catalyst warm-up control, the first injection (first injection) generated by the injector 30 is performed during the intake stroke, and during the expansion stroke after compression top dead center, it is The second shot (second shot) was performed in a smaller amount (one example was about 5 mm ³ / st) than the first shot. In the following description, the first injection (first injection) is also referred to as "intake stroke injection", and the second injection (second injection) is also referred to as "inflation stroke injection". Moreover, as shown in FIG. 2, in the catalyst warm-up control, the start period of the ignition period generated by the spark plug 32 is set to the retarded side of the compression top dead center. In addition, in FIG. 2, the expansion stroke injection is performed on the retarded side of the start period of the ignition period, but the expansion stroke injection may be started on the receded angle side of the start period of the ignition period. This will be described with reference to FIG. 3.

FIG. 3 is a diagram illustrating the relationship between the injection period of the expansion stroke injection and the timing of the ignition period. In FIG. 3, three injections A, B, C, and D having different drawing start times are shown. The injections A, B, C, and D have different start times, and the injection periods of these are equal to the injection period of the expansion stroke injection. The ignition period depicted in FIG. 3 is equal to the ignition period (setting period) in the catalyst warm-up control. As shown in FIG. 3, the injection B performed across the start period of the ignition period, the injection C performed during the ignition period, and the injection D performed across the end period of the ignition period, in this embodiment In terms of the expansion stroke injection, at the point In the present embodiment, the injection A performed on the side of the forward angle should not be an expansion stroke injection in this embodiment. This reason is that at least a part of the injection period of the expansion stroke injection needs to be repeated with the ignition period in order to obtain the attracting effect described later.

[Attractive effect by expansion stroke injection]

FIG. 4 is a diagram for explaining the spark sparks generated by the expansion stroke injection and the effect of attracting the initial flame. In the upper and middle sections (or lower sections) of FIG. 4, the discharge sparks generated by the electrode portion 34 during the ignition period generated by the spark plug 32 and the discharge sparks are injected from the intake stroke. There are two different states of the initial flame caused by the generated gas mixture including the fuel spray. The state shown in the upper part of FIG. 4 is equivalent to the case where the expansion stroke injection is not performed, and the state shown in the middle (or lower) part of FIG. 4 is equivalent to the case where the expansion stroke injection is performed. status. For convenience of explanation, only the fuel spray generated by the expansion stroke injection is shown in FIG. 4 as the fuel spray closest to the spark plug 32.

As shown in the upper stage of FIG. 4, when the expansion stroke injection is not performed, the discharge spark and the initial flame generated by the electrode portion 34 extend in the flow direction of the tumble flow. On the other hand, as shown in the middle part of FIG. 4, in the case of the expansion stroke injection, a low-pressure portion (roll-up) is formed around the fuel spray. Therefore, the discharge spark and the initial flame generated by the electrode portion 34 are directed toward The direction opposite to the flow of the tumble flow is induced. In this case, as shown in the lower part of Figure 4, the induced sparks and initial flames are caused by The fuel spray produced by the expansion stroke injection comes into contact, engulfing these and growing explosively. The growth of the initial flame caused by both the spark of the discharge and the induction of the initial flame occurs during the injection of B and C in FIG. 3. The case of the injection D in FIG. 3 is described later.

The fuel spray injected by the expansion stroke is affected by the tumble flow and the pressure in the barrel. Therefore, in the case where the expansion stroke on the side of the approach angle is injected at the beginning of the ignition period generated by the spark plug 32 (refer to injection A in FIG. 3), the fuel spray generated by the injection is following The shape of the electrode portion 34 is changed before. Therefore, the concentration of the gas mixture around the spark plug is unstable and the combustion fluctuation during the cycle becomes large. At this point, if at least a part of the injection period is an expansion stroke injection repeated with the ignition period (refer to injections B and C in FIG. 3), the attracting action shown in the middle of FIG. 4 can be utilized. Therefore, even if the shape of the fuel spray generated by the expansion stroke injection is changed, the combustion that ignites the initial flame growth (hereinafter also referred to as "initial combustion") can be stabilized, and the combustion fluctuation during the cycle can be suppressed. Furthermore, the combustion after the initial combustion, that is, the combustion at the initial stage of the growth, the combustion (hereinafter also referred to as "main combustion") in which the mixture including the fuel spray generated by the intake stroke injection is further drawn in may be stabilized. In the case of injection D in FIG. 3, although the spark of discharge disappears with the end of the ignition period, the initial flame remains. Therefore, the fuel spray and the initial flame can be brought into contact by the attraction effect of the fuel spray generated by the expansion stroke injection. Therefore, as in the case of the injections B and C in FIG. 3, the initial combustion can be stabilized, and the combustion fluctuation during the cycle can be suppressed.

[Interval Control]

In the catalyst warm-up control, a section from the start of the ignition period generated by the spark plug 32 to the end of the expansion stroke injection is controlled by the ECU 40. FIG. 5 is a graph showing the relationship between the interval from the start of the ignition period to the end of the expansion stroke injection (the ignition start-end injection interval) and the combustion fluctuation rate. The combustion fluctuation rate shown in FIG. 5 is obtained by fixing the start period and the end period of the ignition period and changing the injection period (that is, the injection amount) to a fixed expansion stroke injection start period. As shown in FIG. 5, the combustion fluctuation rate becomes downward convex for the “ignition start-end injection period”. In addition, in FIG. 5, the combustion fluctuation rate is the smallest value, and is shown when the start period of the ignition period (ignition start) and the start period of the expansion stroke injection (start of injection) are aligned (start of ignition = start of injection). By the late angle side.

In the ROM of the ECU 40, the combustion fluctuation rate shown in FIG. 5 is a value of the "ignition start-end of injection period" when the minimum value is displayed (hereinafter also referred to as "reference suitability value"), and is stored in the A relationship diagram (hereinafter also referred to as a "reference fit value relationship diagram") related to the engine operation state is read from this during the catalyst warm-up control. FIG. 6 is a diagram showing an example of a reference fit value relationship diagram. As shown in FIG. 6, the reference fit value relationship diagram is a two-dimensional relationship diagram with the engine rotation speed and the engine load k1 as two axes. By the way, since the reference fit value relationship diagram is created for each engine cooling water temperature region separated by a predetermined temperature scale, in fact, this two-dimensional relationship diagram exists in plural. And, as shown by the arrow in Fig. 6, the reference is suitable The value is set to obtain a retardation side value when the engine rotation speed becomes higher or the engine load becomes lower. This reason is because the initial flame growth is relatively slow when the engine rotation speed is high, and when the engine load is high, the initial flame growth is relatively faster by improving the environment in the cylinder.

In the catalyst warm-up control, the start period of the ignition period and the end period of the expansion stroke injection by the spark plug 32 are specifically determined as follows. First, the starting period of the ignition period generated by the spark plug 32 is determined based on the basic ignition period and the retardation correction amount. In addition, the end time of the expansion stroke injection is determined by adding the start time of the determined ignition period to the reference suitable value obtained from the reference suitable value map and the engine operating state. FIG. 7 is a diagram showing the ignition timing (or more accurately, the start timing of the ignition period) generated by the spark plug 32 and the transition of the engine cooling water temperature during the cold start of the internal combustion engine. At time t ₀ shown in FIG. 7, when the engine is started, the operation mode of the catalyst warm-up control (hereinafter also referred to as “catalyst warm-up mode”) is started from the subsequent time t _{1. The} ignition timing is Gradually set to the value on the retard side. The catalyst warm-up mode ends at time t ₂ when the engine cooling water temperature reaches a standard (50 ° C. in one example), and the ignition timing is gradually set to a value on the timing side.

The basic ignition timing is a value stored in the ROM of the ECU 40 according to the engine operating conditions (mainly the intake air amount and the engine rotation speed). In addition, the retardation correction amount is determined based on a relationship diagram (hereinafter also referred to as a "retardation correction amount relationship diagram") related to the engine cooling water temperature. Incidentally, the relationship diagram of the retardation correction amount is stored in the ROM of the ECU 40 in the same manner as the reference fit value relationship diagram, and is used from the time of the catalyst warm-up control. This is read out.

[Problems when the ignition environment moves away from a better range]

However, in the case of the system shown in FIG. 1, when the ignition environment is changed from any suitable range, the above-mentioned expansion effect of the expansion stroke injection is not involved, and the combustion state is also changed. The possibility of instability. For example, in the case where the deposits of the nozzle holes of the injector 30 are accumulated, the injection amount in the intake stroke injection becomes small. In addition, when the amount of air when the injection amount of the intake stroke injection is calculated is misunderstood to be smaller than the original amount, the injection amount in the intake stroke injection is also reduced. In addition, if the injection amount during the intake stroke injection is reduced, the fuel concentration around the spark plug 32 will be thinner, and the initial flame growth rate (referred to as the initial flame growth rate before the fuel spray generated by the expansion stroke injection contacts). (The same below) will slow down. In addition, when learning about the valve timings of the intake valve 26 and the exhaust valve 28 is not good, the rate of exhaust gas remaining in the combustion chamber 20 increases, so that the initial flame growth rate becomes slow. If the growth rate of the initial flame is slowed, the fuel spray generated by the expansion stroke injection and the initial flame cannot be contacted, and the combustion fluctuation during the cycle will increase.

FIG. 8 is a diagram illustrating a state in the tube in a case where the growth rate of the initial flame becomes slow. The upper part of FIG. 8 depicts the state of the inside of the barrel when the ignition environment is within a preferred range, which is the same as the state of the inner case shown in the lower portion of FIG. 4. Incidentally, when this case has been described, the discharge sparks and initial flames generated by the electrode portion 34 are attracted toward and contacted with the fuel spray generated by the expansion stroke injection, so that the initial flames explode. In this case, it can be said that there is no particular problem in the growth rate of flame in the initial stage. On the other hand, in the lower part of FIG. 8, the inside state of the tube is depicted in the case where the growth rate of the initial flame is slow. In this case, the discharge spark generated by the electrode portion 34 is attracted toward the fuel spray generated by the expansion stroke injection, but the induction of the initial flame with a slow growth rate is insufficient. Therefore, the fuel spray and initial flame generated by the expansion stroke injection become inaccessible. Therefore, the initial combustion becomes unstable, and the main combustion after the initial combustion also becomes unstable.

Furthermore, for example, when the amount of protrusion of the combustion chamber 20 toward the electrode portion 34 is reduced by the exchange of the spark plug 32 and when the spray angle is changed by deposits deposited on the nozzle of the ejector 30, the outer periphery of the spray is changed. The distance between the surface and the electrode portion 34 increases. If the distance between the spray outer surface and the electrode portion 34 is increased, the fuel spray generated by the expansion stroke injection and the initial flame cannot be contacted, and there is a possibility that the combustion fluctuation during the cycle becomes large.

FIG. 9 is a diagram illustrating a state inside the tube when the distance between the spray outer surface and the electrode portion 34 is enlarged. The upper part of FIG. 9 depicts the inside state of the cylinder when the ignition environment is within a preferred range, which is the same as the inner state of the cylinder as shown in the lower part of FIG. 4 and the upper part of FIG. 8. On the other hand, in the lower stage of FIG. 9, the inside state of the tube is depicted when the distance between the spray outer surface and the electrode portion 34 is enlarged. In this case, since the distance from the low-pressure portion formed around the fuel spray generated by the expansion stroke injection to the discharge sparks and initial flames generated by the electrode portion 34 is widened, these inducements are insufficient. Therefore, the Fuel spray and initial flame became inaccessible. The peripheral line drawn in FIG. 9 is the peripheral surface showing the fuel spray closest to the spark plug 32 among the fuel sprays from the injector 30.

It is assumed that if the start of the ignition period is advanced, the environment in the cylinder is improved. Therefore, in the case where the growth rate of the initial flame is reduced (refer to the lower stage of FIG. 8), the decline can be eased and the fuel spray generated by the expansion stroke injection can be brought into contact with the initial flame. Further, when the distance between the spray outer surface and the electrode portion 34 is widened (refer to the lower stage of FIG. 9), the growth rate of the initial flame can be promoted, and the fuel spray and the initial flame produced by the expansion stroke injection can be brought into contact. However, if the starting period of the ignition period is advanced, the exhaust energy that can be injected into the exhaust purification catalyst is reduced, so this time it takes time for the activation of the exhaust purification catalyst.

This problem will be described in detail with reference to FIG. 10. In the case where the ignition environment is within a preferable range, the period from the initial flame generated by the fuel spray generated by the intake stroke injection is increased to the extent that it can come into contact with the fuel spray generated by the expansion stroke injection. As a value within the appropriate range. Therefore, as shown by the solid line (normal) in the middle of FIG. 10, even if the ignition timing (or more accurately, the start timing of the ignition timing) is set to the crank angle CA ₁ on the retard side, the initial flame can be set. The growth rate of is a value within a suitable range (v ₁ ). Therefore, as shown by the solid line (normal) in the upper stage of FIG. 10, the combustion fluctuation rate can be made smaller than the standard. However, if the ignition environment changes from a better range, the initial flame from the fuel spray produced by the intake stroke injection will grow to a level where it can come into contact with the fuel spray produced by the expansion stroke injection. The period until the size becomes longer. Therefore, as shown by the dashed line in the middle of FIG. 10 (when the combustion deteriorates), the initial flame growth rate in the state set at the crank angle CA ₁ decreases to a value (v ₂ ) outside the appropriate range. Therefore, as shown by the dotted line (at the time of deterioration of combustion) in the upper stage of FIG. 10, the combustion fluctuation rate becomes higher than the standard.

Even if the ignition environment is shifted from a preferable range, and the ignition timing is changed to the advancing side, the tendency of the initial combustion growth rate can be changed. Specifically, when the ignition timing is reset from the crank angle CA ₁ to the crank angle CA ₂ , as shown by the dashed line in the middle of FIG. 10 (when the combustion deteriorates), the initial flame growth rate can be adjusted from a range outside the appropriate range. The value (v ₂ ) returns to a value (v ₁ ) within a suitable range. In this way, since the initial flame generated by the fuel spray generated from the intake stroke injection can be brought into contact with the fuel spray generated by the expansion stroke injection and the initial flame at an appropriate time, the combustion fluctuation ratio can be compared. The standard is smaller. However, as shown in the lower part of FIG. 10, when the ignition timing is reset to the crank angle CA ₂ , the exhaust energy is lower than that when the ignition timing is set to the crank angle CA ₁ . The activation of the medium only requires a reduction in exhaust energy time.

In order to avoid such a situation, in the present embodiment, the relationship between the reference fit value and the graph is corrected when it is predicted that the fuel spray generated by the expansion stroke injection and the initial flame become inaccessible due to the change in the ignition environment. Calculated reference suitability. FIG. 11 illustrates a correction method for a section from the start of the ignition period to the end of the expansion stroke injection. Illustration. As in FIG. 5, in FIG. 11, the relationship between the “ignition start-end injection interval” and the combustion fluctuation rate is depicted. Comparing FIG. 5 and FIG. 11, it can be understood that the relationship drawn by the solid line in FIG. 5 is drawn by the dotted line in FIG. 11.

As illustrated in Figs. 8 to 10, if the fuel spray and initial flame generated by the expansion stroke injection cannot be contacted, the combustion fluctuation rate will increase. That is, as shown in FIG. 11, the relationship between the “ignition start-end injection interval” and the combustion fluctuation rate changes from a relationship drawn by a dotted line to a relationship drawn by a solid line. However, if the expansion stroke injection is performed in a state set to the reference suitable value, the combustion fluctuation rate will exceed the standard. At this point, in accordance with the relationship shown by the solid line after the change, if the reference suitable value is corrected in the direction in which the "ignition start-end injection interval" is enlarged, the combustion fluctuation rate can be made smaller than the standard.

As described above, the reference suitability value is a value indicating the "ignition start-end injection interval" when the combustion fluctuation rate is the smallest value when the ignition environment is within a preferable range. Therefore, even when the expansion stroke injection is performed based on the corrected "ignition start-injection end interval", the combustion fluctuation rate itself does not become smaller than the case where the ignition environment is in a better range. However, if the reference suitable value is corrected in the direction of the "ignition start-end injection interval" being expanded, the combustion fluctuation rate can be made smaller than the standard, and the combustion fluctuation rate can be approached when the ignition environment is in a better range.

FIG. 12 illustrates the correction of the reference suitability value in a direction in which the interval is widened from the start of the ignition period to the end of the expansion stroke injection. Diagram of the state of the tube in the case. In the upper section and the lower section of FIG. 12, each of them is a state of the inside of the barrel depicting a case where the ignition environment is separated from a preferable range. However, the difference between the upper and lower paragraphs in FIG. 12 is that the upper stage shows the ignition timing being advanced while the "ignition start-end of injection interval" is fixed at a reference value, and the lower stage shows the direction toward "start of ignition-end of injection In the case where the "interval" is extended, the reference fit value is corrected.

Comparing the upper and lower sections of Fig. 12 shows that in a state where the "ignition start-end of injection" is fixed at a reference suitable value (refer to the upper section), the fuel spray generated by the expansion stroke injection and the growth rate are slow. The initial flame was inaccessible. In this regard, if the reference suitability value is corrected in a direction in which the "ignition start-end injection interval" is enlarged (refer to the lower stage), the fuel spray generated by the expansion stroke injection can be brought into contact with the stage where the initial flame has grown to a certain degree. Therefore, in a state where the initial flame is in contact with the fuel spray generated by the expansion stroke injection, it is possible to approach the contact state between the two in a case where the ignition environment is within a preferable range. Therefore, the initial combustion can be stabilized and combustion fluctuations can be suppressed, and the main combustion can be stabilized.

Furthermore, if the reference suitability value is corrected in the direction of the "ignition start-end injection interval" being extended, a large advance angle of the ignition timing is not required, so it is possible to suppress a decrease in exhaust energy input to the exhaust purification catalyst. FIG. 13 is a diagram illustrating an effect of a case where the reference suitability value is corrected in a direction in which a section is widened from the start of the ignition period to the end of the expansion stroke injection. The "reference suitability value (positive)" shown in Fig. 13 is when the ignition environment is in a better range. Exhaust energy to be supplied to the exhaust purification catalyst when the heating medium control is executed, and the combustion fluctuation rate during the heating medium control of the catalyst are displayed. In addition, the "reference suitability value (when combustion is deteriorated)" is the case where the ignition environment is separated from a better range, which is equivalent to the same exhaust energy and the same combustion fluctuation rate when the catalyst warm-up control is performed according to the reference suitability value. . Comparing the two, it can be understood that, in the "baseline suitability value (when combustion deteriorates)", although the exhaust gas energy equivalent to the "baseline suitability value (positive time)" can be obtained, the combustion fluctuation rate is larger than the standard.

In addition, the "ignition timing (fixed interval)" shown in Fig. 13 is a case where the ignition timing (or more accurately, the start timing of the ignition period) is advanced when the ignition environment is separated from a better range, and is equivalent. The same exhaust gas energy and the same combustion fluctuation rate when the catalyst warm-up control is implemented according to the reference suitable value. Comparing "Ignition advance angle (constant interval)" and "Reference suitability value (when combustion deteriorates)", it can be understood that in "Ignition advance angle (constant interval)", although the combustion fluctuation rate can be smaller than the standard, Qi energy is reduced.

The “invention” shown in FIG. 13 is a case where the ignition environment is separated from a preferable range, which is equivalent to the same exhaust energy and the same combustion variation when the catalyst warm-up control is performed according to the revised reference suitable value. rate. Comparing "the present invention" with others, it can be understood that although "the present invention" can reduce the combustion fluctuation rate lower than the standard and lower the exhaust energy than the "baseline suitable value (positive)", it can obtain the ratio Exhaust energy with higher exhaust energy in "ignition timing (constant interval)". Therefore, even when the ignition environment is separated from a preferable range, the combustion fluctuation rate can be suppressed from increasing, and the exhaust energy necessary for the early activation of the exhaust purification catalyst can be secured.

[Specific processing in the embodiment]

FIG. 14 is a flowchart showing an example of processing executed by the ECU 40 in the embodiment of the present invention. In addition, the example stroke type shown in this figure is a person who repeatedly executes each cycle in each cylinder after the internal combustion engine 10 is started.

In the example stroke formula shown in FIG. 14, it is first determined whether the temperature of the engine cooling water has reached a standard or whether a mark regarding the end of the catalyst warm-up mode appears (step S100). Specifically in this step S100, it is determined based on the detection value of the temperature sensor 46 whether the engine cooling water temperature has reached the standard (refer to FIG. 7) or whether the end mark (refer to step S110) is erected. Furthermore, if it is judged that the engine cooling water temperature has reached the standard, or it is judged that the end mark is raised (in the case of "Yes"), the stroke formula of this example is left.

In step S100, it is determined that the temperature of the engine cooling water has not reached the standard, and it is determined that the end mark has not been raised (in the case of "No"). The start period of the ignition period and the end period of the expansion stroke injection (step S102). In this step S102, first, the retarded angle correction amount can be obtained based on the engine cooling water temperature based on the detected value of the temperature sensor 46 and the retarded angle correction amount relationship diagram. In addition, the start period of the ignition period generated by the spark plug 32 is determined based on the retardation correction amount and the basic ignition period. In addition, based on the engine rotation speed calculated based on the detection value of the crank angle sensor 42, the engine load calculated based on the detection value of the accelerator opening sensor 44, and the detection based on the temperature sensor 46 Value of the engine cooling water temperature and the reference fit value, and obtain the reference fit value. And, by adding the obtained reference fit value, The start time of the ignition period generated by the determined spark plug 32 is determined to determine the end time of the expansion stroke injection.

After step S102, a determination is made regarding a change in the ignition environment (step S104). In this step S104, for example, it is determined whether the deviation (standard deviation) σ of Gat30 after the start of the catalyst warm-up control exceeds the standard. The rotor of the crank angle sensor 42 is provided with teeth at intervals of 30 °, and the crank angle sensor 42 emits a signal every 30 ° of the crank shaft rotation. Gat30 is calculated as the time between the signal and the signal, that is, the time required for the crank shaft to rotate 30 °. FIG. 15 is a diagram showing an example of the Gat30 at the time of the cold start of the internal combustion engine and the transition of the deviation σ of the Gat30. The horizontal axis of FIG. 15 shows the elapsed time after the engine is started, and time t ₁ is the start time of the display catalyst warm-up control. As shown in FIG. 15, during the period from time t ₁ to time t ₃ , the fluctuation of Gat30 is small. Therefore, the deviation σ determined as Gat30 is smaller than the standard. It is determined that the deviation σ of Gat30 is smaller than the standard (the case of "No"), and the process proceeds to step S108.

On the other hand, as shown in FIG. 15, during the period from time t ₃ to time t ₄ , the fluctuation of Gat30 increases. Therefore, the deviation σ determined as Gat30 is larger than the standard. It is judged that the deviation σ of Gat30 is beyond the standard (the case of "Yes"), and it can be judged that: by any reason, the ignition environment is changed from a better range, and the fuel spray generated by the expansion stroke injection and the The initial flame may become inaccessible. Therefore, the start time of the ignition period generated by the spark plug 32 and the end time of the expansion stroke injection are corrected (step S106). In this step S106, first, according to the relationship between the engine cooling water temperature and the retardation correction amount, the retardation correction amount can be obtained. In addition, the start period of the ignition period generated by the spark plug 32 is determined based on the retardation correction amount and the basic ignition period. And, based on the relationship diagram of the engine rotation speed, the engine load, the engine cooling water temperature, and the reference fitness value, a reference fitness value is obtained. The processing up to this point is the same as the processing in step S102. In this step S106, the obtained reference suitability value is added to the start time of the ignition period generated by the determined spark plug 32, and a correction value (constant value) for extending the interval is further added. This determines the end time of the expansion stroke injection.

After the step S106, in step S108, it determines whether or not the exhaust gas temperature exceeds the standard T _1. In this step, it is determined whether the exhaust gas temperature exceeds the standard T ₁ based on the detection value of a temperature sensor provided downstream of, for example, the exhaust gas purification catalyst. Then, it is determined that the engine cooling water temperature has reached the standard (in the case of "Yes"), and the end mark is raised (step S110).

In the above, according to the example stroke formula shown in FIG. 14, it is possible to determine the change in the ignition environment based on the deviation σ of Gat30 after the start of the catalyst warm-up control. In addition, when the result of the determination is judged to have any possibility that the ignition environment may change from a preferable range due to a change in the ignition environment, the interval from the start of the ignition period to the end of the expansion stroke injection can be expanded. Therefore, even if the ignition environment is separated from the preferable range, the combustion fluctuation during the cycle can be suppressed.

[Modification of Embodiment]

However, in the above-mentioned embodiment, the tumble flow formed in the combustion chamber 20 is such that the tumble flow from the upper portion of the combustion chamber 20 to the lower portion in the exhaust port 24 side, and The air intake port 22 orbits around from the lower part of the combustion chamber 20 to the upper side. However, this tumble flow flows in the opposite direction, that is, from the upper part of the combustion chamber 20 toward the lower side in the intake port 22 side, and around the lower part of the combustion chamber 20 toward the upper part in the exhaust port 24 side. Turning is also possible. However, in this case, it is necessary to change the arrangement position of the spark plug 32 from the exhaust valve 28 side to the intake valve 26 side. If the arrangement of the Mars plug 32 is changed in this way, the Mars plug 32 is positioned downstream of the ejector 30 in the flow direction of the tumble flow, so that the attracting effect by the expansion stroke injection can be obtained.

For further explanation, the tumble flow may not be formed in the combustion chamber 20. This is because the combustion fluctuations during the above-mentioned cycle occur irrespective of the formation of the tumble flow.

In the above-mentioned embodiment, the first injection (first injection) generated by the injector 30 is performed by the intake stroke, and the second injection (second injection) is performed in the expansion stroke after the compression top dead center. ). However, this first injection (first injection) may be performed by the compression stroke. In addition, the first injection (first injection) may be divided into a plurality of times, and a part of the divided injection may be performed by an intake stroke, and the remaining portion may be performed by a compression stroke. As described above, the injection timing and the number of injections of the first injection (first injection) can be variously modified.

Further, in the above-mentioned embodiment, in the process of step S106 in FIG. 14, the correction value for section expansion is set to a fixed value. However, the correction value for interval expansion may not be a fixed value. For example, the larger the deviation σ and the standard deviation of Gat30 shown in FIG. 15 may be, the larger the correction value for the interval expansion may be set. When making this setting, The ROM of the ECU 40 stores a relationship diagram showing the relationship between the deviation σ and the standard deviation of the Gat 30 and the correction value for the interval expansion (refer to FIG. 16), and it can be read from this during the processing in step S106.

Furthermore, in the above-mentioned embodiment, in the process of step S104 in FIG. 14, the determination of the change in the ignition environment is performed using the deviation σ of Gat30 after the start of the catalyst warm-up control. However, instead of this deviation σ, the deviation σ from the start of the ignition period to the crank angle period (hereinafter also referred to as “SA-CA10”) until the combustion mass ratio (MFB) reaches 10% may be used. MFB is calculated based on the analysis result of the cylinder pressure sensor (not shown) provided separately from the combustion chamber 20 and the cylinder pressure data obtained by using the crank angle sensor 42, and is calculated based on the calculated MFB. Calculate SA-CA10. The method of calculating the MFB and the method of calculating SA-CA10 from the analysis results of the cylinder pressure data are described in detail in, for example, Japanese Patent Application Laid-Open No. 2015-094339 and Japanese Patent Application Laid-Open No. 2015-098799. Explanation is omitted in the description.

FIG. 17 is a diagram showing the relationship between the combustion fluctuation rate and the deviation σ of SA-CA10. FIG. 18 is a diagram showing an example of the transition of the deviation σ of SA-CA10 during a cold start of the internal combustion engine. As shown in Fig. 17, the larger the deviation σ of SA-CA10, the larger the combustion fluctuation rate. That is, the deviation σ of SA-CA10 is related to the combustion fluctuation rate. Therefore, for example, from the time t ₅ to the time t ₆ in FIG. 18, when the deviation σ of SA-CA10 after the start of the catalyst warm-up control is judged to exceed the standard, it is judged to be caused by any factor. The ignition environment is changed and separated from a preferable range. The fuel spray and initial flame generated by the expansion stroke injection may become inaccessible. The processing after step S106 in FIG. 14 may be performed.

For further explanation, it is not limited to Gat30 and SA-CA10, even if it is used: the time required for the crank shaft to rotate 60 ° during the ignition period (Gat60), the crank angle period from the start of the ignition period to the MFB reaching 5% (SA -CA5) and a crank angle period (SA-CA15) from the start of the ignition period to 15% of the MFB. In this way, it is possible to discriminate the parameters of the contact state of the fuel spray and the initial flame generated by the expansion stroke injection (parameters related to the combustion fluctuations during the cycle), and it can be used as a parameter related to the change in the ignition environment in the above embodiment. Discrimination indicators.

Claims (4)

A control device for an internal combustion engine is a control device for an internal combustion engine, comprising: an injector provided in an upper part of a combustion chamber to inject fuel from a plurality of injection holes into a cylinder; and a spark plug that uses a spark to ignite a mixture in the cylinder, and Is provided downstream of the fuel sprayed from the plurality of injection holes, and is higher than the outer surface of the fuel spray closest to the spark plug among the fuel sprays sprayed from the plurality of injection holes; and Exhaust gas purification catalyst for purifying exhaust gas; The control device, which controls the activation of the exhaust gas purification catalyst, is performed to make the discharge spark during the ignition period on the retarder side than the compression top dead center. The mode of occurrence is to control the aforementioned Mars plug, and the first injection in the angle side more than the compression top dead center; and in the angle side more than the compression top dead center, and the injection period is the same as the ignition The method of the second injection in which at least a part of the period is repeated controls the injector, and the control device is further judged to exceed a threshold in a parameter related to the combustion fluctuation during the cycle. In the case of the case, compared with the case where the parameter is judged to be lower than the threshold value, the Mars is extended so that the interval from the start period of the ignition period to the end period of the injection period of the second injection is extended. Plug and aforementioned injector control. For example, the control device for an internal combustion engine in the first patent application range, wherein the control device, when the parameter exceeds the threshold value, changes the expansion amount of the interval corresponding to the parameter and the separation amount of the threshold value. For example, the control device for an internal combustion engine in the scope of claims 1 or 2, wherein the end period of the second injection is closer to the angle side than the end period of the ignition period. For example, the control device for an internal combustion engine in the scope of claims 1 or 2, wherein the aforementioned parameter is the deviation of the time required until the crank shaft rotates to a predetermined angle, or the combustion mass ratio is from the start of the aforementioned ignition period to Deviation during crank angle up to a predetermined ratio.