RU2656071C1 - Control device for internal combustion engine - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention can be used in control systems of internal combustion engines. When controlling the catalyst preheating, the primary injection is performed by the injector in the intake stroke. Secondary injection is performed with a value smaller than the primary injection in the firing stroke after the compression top dead center. When adjusting the catalyst preheating, interval from the beginning of the spark plug ignition period to the completion of secondary injection is regulated by the electronic control unit in such a way, that the primary flame created from the fuel-air mixture containing the atomized fuel jet injected by the primary injection, comes into contact with the atomized fuel jet injected by secondary injection.

EFFECT: optimization of the combustion process in the engine during catalyst preheating.

4 cl, 18 dwg

Description

The invention relates to a control device for an internal combustion engine and, in particular, to a control device that is used with an internal combustion engine equipped with a spark plug and an in-cylinder injector.

An internal combustion engine disclosed in JP 2011-106377 A comprises: an injector that has a plurality of injection holes; and a spark plug, with the injector and spark plug provided at the top of the combustion chamber. In an internal combustion engine, the distance from the central position of the discharge gap of the spark plug to the central position of the injection hole, which is among the plurality of injection holes closest to the spark plug, is set within a special range. In the internal combustion engine, for a period from the time after the predetermined time elapses from the start of the fuel injection to the time when the fuel injection is completed, regulation is performed to supply a high voltage to the spark plug.

With the regulation described above, the period of fuel injection of the injector overlaps the period of supply of high voltage to the spark plug. When the fuel is injected with an injector into which the fuel is supplied in a state of increased pressure, due to the entrainment of air around the atomized jet of fuel injected from each injection (capture) opening, a low pressure region is formed. As a result of this, when performing the regulation described above, the discharge spark arising in the discharge gap is attracted from the injection hole closest to the spark plug to the low pressure region formed by the atomized fuel stream. By this, in the internal combustion engine, the flammability of the air-fuel mixture formed around the spark plug can be improved.

According to JP 2011-106377, A further introduces activation of an exhaust gas purification catalyst as methods of applying the attractive action described above. Although this is not mentioned in JP 2011-106377 A, the exhaust gas purification catalyst is usually activated by changing the ignition period, which is usually set near the top dead center of compression (i.e. the period of applying high voltage to the spark plug), lag period from top dead center compression.

When the regulation of JP 2011-106377 A described above is applied to the overall activation of an exhaust gas purification catalyst, to improve the flammability of the air-fuel mixture formed around the spark plug, the ignition period set on the delay side of the compression top dead center overlaps the fuel injection period. However, if, due to some factors, the surrounding ignition conditions change and, therefore, go beyond the required range, despite the attractive action described above, the combustion state may become unstable. In combustion cycles, in the control process to activate the exhaust gas purification catalyst, when the number of combustion cycles in which a similar situation arises increases, the fluctuation of combustion between cycles becomes large, and controllability deteriorates.

The present invention solves the above problems, and the aim of the invention is to suppress combustion fluctuations between cycles when a regulation is applied to activate the exhaust gas purification catalyst so that the injection period of the injector fuel overlaps the period of the high voltage supply to the spark plug.

The control device for an internal combustion engine according to the present application is a device for regulating an internal combustion engine, comprising: an injector, a spark plug and an exhaust gas purification catalyst. The injector is configured to provide a combustion chamber at the top and is configured to inject fuel from a plurality of injection holes into the cylinder. The spark plug is configured to ignite the air-fuel mixture in the cylinder using a discharge spark and is provided on the exhaust side of the fuel injected from the plurality of injection holes and above the contour surface of the fuel spray form, which is closest to the spark plug among the spray patterns of fuel injected from many injection holes. The exhaust gas purification catalyst is configured to purify exhaust gases from a combustion chamber. In order to activate the exhaust gas purification catalyst, the control device is configured to control the spark plug so as to create a spark during ignition delayed from the top dead center of compression, and to control the injector so as to perform the first injection at the moment time ahead of the top dead center of compression and the second injection at a time with a delay from the top dead center of compression, while the second injection is performed in such a way that The injection code covers at least part of the ignition period. When it is determined that the parameter associated with the fluctuation of the combustion between cycles exceeds a threshold value, the control device for the internal combustion engine according to the present application is further configured to adjust the spark plug and injector in such a way that the interval from the start of the ignition period to the end of the injection period the second injection is increased compared with the case when it is determined that the parameter is lower than the threshold value.

The air-fuel mixture, which contains a sprayed stream of fuel during the first injection, creates the primary flame during the ignition period. When performing the second injection in such a way that the injection period covers at least part of the ignition period, at least the primary flame is attracted to the low-pressure region formed around the atomized jet of fuel injected from the injection hole, which is closest to the spark plug. When performing the second injection, the drawn primary flame comes into contact with the atomized jet of fuel injected during the second injection, and fluctuation must be stimulated to enhance the primary flame. However, if this contact is insufficient, combustion to enhance the primary flame becomes unstable. When the number of cycles in which combustion to enhance the primary flame becomes unstable increases, the fluctuation of combustion between cycles becomes large. In this regard, when it is determined that the parameter associated with the fluctuation of combustion between cycles exceeds a threshold value, the interval from the start of the ignition period to the end of the second injection becomes longer by adjusting so that the interval from the start of the ignition period to the end of time the injection of the second injection increases compared to the case when it is determined that the parameter is lower than the threshold value, and the start of the second injection is expected until the primary flame amplifies to a certain Torah degree. Accordingly, it is possible to avoid a situation where the attracted primary flame and the discharge spark and the atomized jet of fuel injected during the second injection do not contact sufficiently.

When the parameter exceeds the threshold value, the control device can change the increasing value of the interval in accordance with the magnitude of the discrepancy between the parameter and the threshold value.

When it is determined that the parameter associated with the fluctuation of combustion between the cycles exceeds a threshold value, the increase in the interval value changes in accordance with the magnitude of the discrepancy between the parameter and the threshold value, thereby ensuring reliable and sufficient contact between the drawn primary flame and the atomized jet of fuel injected at the second injection.

The second injection can be completed at a point in time ahead of the time the ignition period ends.

When the second injection is completed at a time with a delay from the end of the ignition period, only the primary flame is attracted to the low-pressure region. On the other hand, when the second injection is completed at a point in time, the leading time of the end of the ignition period, both the primary flame and the discharge spark are attracted to the low-pressure region. Both the primary flame and the discharge spark so attracted come into contact with the atomized jet of fuel injected during the second injection. As a result, when the second injection is completed at a point ahead of the end of the ignition period, combustion to enhance the primary flame is further stimulated compared to the case when the second injection is completed at the time delayed from the end of the ignition period.

The parameter can be a fluctuation of the time required before the crankshaft rotates by a predetermined angle, or a fluctuation of the period of the crankshaft rotation angle from the moment the ignition period begins to the moment when the burnt mass fraction reaches the preset ratio.

When the parameter related to the fluctuation of combustion between cycles is the fluctuation of the time required before the crankshaft rotates by a predetermined angle, or the fluctuation of the period of the angle of rotation of the crankshaft from the beginning of the ignition period to the moment when the burnt mass fraction reaches a predetermined ratio, the fluctuation of combustion between cycles determined with higher accuracy.

The control device for an internal combustion engine according to the present application can suppress combustion fluctuation between cycles when a regulation is applied to activate the exhaust gas purification catalyst, such that the injection period of the fuel of the injector overlaps the period of the high voltage supply to the spark plug.

The invention will now be described in more detail with reference to the accompanying drawings, in which:

FIG. 1 is a diagram illustrating a configuration of a system according to an embodiment of the present application;

FIG. 2 is a diagram illustrating a control plan for heating a catalyst;

FIG. 3 is a diagram illustrating injection in an expansion stroke;

FIG. 4 is a diagram illustrating the attractive effect of a discharge spark and a primary flame during injection during an expansion stroke;

FIG. 5 is a graph showing the relationship between the interval from the start of the ignition period to the end of the injection in the expansion stroke (the interval between the start of ignition and the end of the injection) and the frequency of the combustion fluctuation;

FIG. 6 is a diagram illustrating an example of a map of basic adaptive values;

FIG. 7 is a graph showing the transition of the ignition moment of the spark plug 32 (more precisely, the moment the ignition period begins) and the temperature of the engine coolant when starting the cold state of the internal combustion engine;

FIG. 8 is a diagram illustrating a state in a cylinder when the rate of increase of the primary flame is slow;

FIG. 9 is a diagram for illustrating a state in the cylinder when the distance between the outer spray pattern and the electrode portion 34 increases;

FIG. 10 is a graph showing problems when the ignition timing is advanced;

FIG. 11 is a graph showing a method of changing an interval from the start of the ignition period to completion of injection in an expansion stroke;

FIG. 12 is a diagram illustrating a state in a cylinder when the base adaptive value changes with increasing interval from the start of the ignition period to the end of the injection in the expansion stroke;

FIG. 13 is a graph explaining the results when the base adaptive value changes with increasing interval from the start of the ignition period to the end of injection in the expansion stroke;

FIG. 14 is a flowchart illustrating an example of a process performed by the ECU 40 in an embodiment of the present application;

FIG. 15 is a graph showing an example of a Gat 30 when an internal combustion engine is started from a cold state and a transition of an oscillation σ Gat 30;

FIG. 16 is a graph showing the relationship between the difference between the σ Gat 30 fluctuation and the criterion and the correction value for increasing the interval;

FIG. 17 is a graph showing the relationship between the frequency of the fluctuation of the combustion and the oscillation σ SA-CA10 when the internal combustion engine is started from a cold state; but

FIG. 18 is a graph showing an example of a transition of an oscillation σ SA-CA10.

Further, embodiments of the submitted application are described based on the drawings. It should be noted that the common elements in the respective drawings are indicated by the same icons, and duplicate descriptions are omitted. The submitted application is not limited to the following embodiments.

System Configuration Description

FIG. 1 is a diagram illustrating a configuration of a system according to an embodiment of the present application. As illustrated in FIG. 1, the system according to the embodiment shown comprises an internal combustion engine 10 mounted on a vehicle. The internal combustion engine 10 is a four stroke single cycle engine. The internal combustion engine 10 has a plurality of cylinders, and one cylinder 12 is illustrated in FIG. 1. The internal combustion engine 10 comprises a cylinder block 14 in which a cylinder 12 is formed and a cylinder head 16 located on the cylinder block 14. The piston 18 is located in the cylinder 12, while the piston 18 is reciprocating in the axial direction of the piston 18 (in the present embodiment, in the vertical direction). The combustion chamber 20 of the internal combustion engine 10 is formed 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 head 16 of the cylinder block two inlet channels 22 and two exhaust channels 24 are formed, which are in communication with the combustion chamber 20. At the inlet of the inlet channel 22, an inlet valve 26 is provided which communicates with the combustion chamber 20. An exhaust valve 28 is provided in the opening of the exhaust channel 24, which communicates with the combustion chamber 20. In the cylinder head 16, the injector 30 is provided so that the tip of the injector 30 faces the combustion chamber 20 substantially from the center of the upper part of the combustion chamber 20. The injector 30 is connected to a fuel supply system comprising a fuel tank, a common pressure fuel system, a charge pump, and the like. The tip of the injector 30 has a plurality of injection holes arranged radially. When the injector valve 30 is open, fuel is injected from these injection holes in a high pressure state.

In the cylinder head 16, a spark plug 32 is provided so as to be located on the side of the exhaust valve 28 of the injector 30 and in the upper part of the combustion chamber 20. The spark plug 32 has an electrode portion 34 at its tip, while the electrode portion 34 comprises a central electrode and a ground electrode. The electrode portion 34 is positioned so as to protrude into the region above the contour surface of the fuel atomization form (hereinafter also referred to as the "external atomization form") injected from the injector 30 (i.e., the region from the external atomization form to the lower surface of the cylinder head 16) . More specifically, the electrode portion 34 is positioned so as to protrude into the region above the contour surface of the fuel atomization shape, which is closest to the spark plug 32 among the fuel atomization forms injected radially from the injection hole of the injector 30. It should be noted that the contour line drawn in FIG. 1 represents the contour surface of a fuel atomization form that is closest to the spark plug 32 among the atomization forms of fuel injected from the injector 30.

The inlet channel 22 extends substantially directly from the inlet from the inlet channel towards the combustion chamber 20. The cross-sectional area of the flow channel of the intake channel 22 is reduced in the neck 36, which is a connecting part with the combustion chamber 20. A similar shape of the inlet channel 22 creates a vortex flow in the intake air, which flows from the inlet channel 22 into the combustion chamber 20. The vortex flow swirls in the combustion chamber 20. More specifically, the vortex flow passes from the inlet channel 22 to the exhaust channel 24 side in the upper part of the combustion chamber 20, and then flows from the upper part of the combustion chamber 20 downward on the exhaust channel 24. The vortex flows from the exhaust channel 24 to the inlet side channel 22 in the lower part of the combustion chamber 20, and then moves upward from the lower part of the combustion chamber 20 on the side of the intake channel 22, a recess is formed on the upper surface of the piston 18 forming the lower part of the combustion chamber 20 so that s to maintain the vortex flow.

As illustrated in FIG. 1, the system according to the illustrated embodiment comprises an ECU (electronic control unit) 40 as a control means. ECU 40 includes RAM (random access memory), ROM (read-only memory), CPU (central processing unit) and the like. The ECU 40 receives signals from various sensors mounted on the vehicle and processes the received signals. The various sensors include at least a crankshaft angle sensor 42, which detects a rotation angle of the crankshaft connected to the piston 18, an accelerator opening sensor 44, which determines a pressure value of the accelerator pedal controlled by the driver, and a temperature sensor 46, which detects the temperature of the coolant in an internal combustion engine 10 (hereinafter referred to as “engine coolant temperature”). The ECU 40 processes the signals received from the individual sensors to drive various actuators according to a predetermined control program. The actuator driven by the ECU 40 includes at least an injector 30 and a spark plug 32 described above.

ECU 40 Startup Management

In the present embodiment, regulation to facilitate activation of the exhaust gas purification catalyst (hereinafter also referred to as “catalyst heating control”) is performed by the ECU 40, illustrated in FIG. 1, as a regulation immediately after the cold start of the internal combustion engine 10. The exhaust gas purification catalyst is a catalyst that is provided in the exhaust pipe of an internal combustion engine 10. An example of an exhaust gas purification catalyst contains a three-component catalyst that purifies nitrogen oxides (NOx), hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gases when the catalyst atmosphere in the activated state is near stoichiometry.

The catalyst preheating control performed by the ECU 40 is described with reference to FIG. 2-7. FIG. 2 illustrates the moment of injection by the injector 30 and the initial moment of the ignition period of the spark plug 32 (the initial moment of the discharge period of the electrode portion 34) in the process of controlling the heating of the catalyst. As illustrated in FIG. 2, in the process of adjusting the catalyst heating, the injector 30 performs a primary injection (first injection) in an intake stroke, and then performs a secondary injection (second injection) with a value (as an example, approximately 5 mm ³ / st) less than the primary injection in a cycle expansion after top dead center compression. It should be noted that in the following description, the primary injection (first injection) is called “injection in the intake stroke”, and the secondary injection (second injection) is called “injection in the expansion stroke”. As illustrated in FIG. 2, in the process of adjusting the heating of the catalyst, the initial moment of the ignition period of the spark plug 32 is set at the time of delay from the compression top dead center. In FIG. 2, the injection in the expansion stroke is performed at the time delayed from the start of the ignition period, but the injection in the expansion stroke can begin at a time ahead of the start of the ignition period. In this regard, a description is provided with reference to FIG. 3.

FIG. 3 is a diagram illustrating a time relationship between the injection period and the ignition period during injection during an expansion stroke. FIG. 3 illustrates four injections A, B, C and D that start at different points in time, respectively. Injections A, B, C and D start at different points in time, respectively, but all of their injection periods have the same length when injected in the expansion stroke. The ignition period illustrated in FIG. 3, is equal to the ignition period in the process of regulating the heating of the catalyst (installation period). In the illustrated embodiment, the performed injection B, during which the ignition period begins, the performed injection C during the ignition period, and the performed injection D, during which the ignition period ends, as illustrated in FIG. 3, correspond to the injection in the expansion stroke. Injection A, performed at a point in time ahead of the start time of the ignition period, does not correspond to the injection in the expansion stroke in the present embodiment. That is why it is necessary that at least part of the injection period overlap the ignition period during injection in the expansion stroke in order to achieve the attractive action described later.

Injection attraction during expansion stroke

FIG. 4 is a diagram illustrating the attractive effect of a discharge spark and a primary flame during injection during an expansion stroke. The upper part and the middle part (or lower part) of FIG. 4 illustrates two different states of a discharge spark created by the electrode portion 34 during the ignition period of the spark plug 32, and a primary flame generated by a discharge spark from a fuel-air mixture containing a sprayed jet of fuel injected during injection at an intake stroke, respectively. The upper part of FIG. 4 illustrates a state where injection is not performed in an expansion stroke. The middle part (or lower part) of FIG. 4 illustrates a state when injection is performed in an expansion stroke. It should be noted that for the convenience of describing FIG. 4 illustrates only the form of fuel atomization that is closest to the spark plug 32 among the forms of atomization of fuel injected during injection in an expansion stroke.

As illustrated at the top of FIG. 4, when injection is not performed in the expansion stroke, a discharge spark was created by the electrode portion 34, and the primary flame passes in the direction of the vortex flow. On the other hand, as illustrated in the middle part of FIG. 4, when the injection is performed in the expansion stroke, a low pressure region (trapping) is formed around the sprayed fuel stream, and a discharge spark was created by the electrode section 34, and the primary flame is attracted in the opposite direction to the vortex flow. Thus, as illustrated at the bottom of FIG. 4, an attracted discharge spark and a primary flame come into contact with a sprayed jet of fuel injected during injection in an expansion stroke, are captured into a sprayed jet of fuel, and are rapidly amplified. In the injections B and C illustrated in FIG. 3, amplification of the primary flame occurs, caused by both a discharge spark and a primary flame thus drawn. Primary flame amplification by injection D in FIG. 3 is described later.

The sprayed jet of fuel injected in the expansion stroke depends on the vortex flow and pressure in the cylinder. When the injection in the expansion stroke is performed at a point in time ahead of the start time of the ignition period of the spark plug 32 (see injection A in FIG. 3), the shape of the atomized jet of fuel injected during this injection changes before reaching the electrode portion 34. As a result, the concentration of the air-fuel mixture around the spark plug is unstable, and the fluctuation of combustion between cycles becomes large. However, if the injection in the expansion stroke is performed such that at least part of the injection period overlaps the ignition period (see injection B, C in FIG. 3), the attractive action illustrated in the middle part of FIG. 4. Even if the shape of the atomized jet of fuel injected during injection during the expansion stroke changes, combustion to enhance the primary flame (hereinafter also referred to as “primary combustion”) can be stabilized, thereby suppressing fluctuation of combustion between cycles. In addition, combustion after primary combustion or an increasing primary flame can stabilize combustion, further involving a fuel-air mixture containing a sprayed stream of fuel injected by injection in the intake stroke (hereinafter also referred to as “main combustion”). With the injection D illustrated in FIG. 3, the discharge spark disappears when the ignition period ends, but the primary flame remains. The attractive effect caused by the atomized jet of fuel injected during injection during the expansion stroke allows the primary flame to be brought into contact with the atomized jet of fuel. Accordingly, the primary flame is stabilized similarly to the injection cases B, C illustrated in FIG. 3, thereby suppressing fluctuation of combustion between cycles.

Interval Adjustment

When adjusting the heating of the catalyst, the ECU 40 adjusts the interval from the start of the ignition period of the spark plug 32 to the end of the injection in the expansion stroke. FIG. 5 is a graph showing the relationship between the interval from the start of the ignition period to the end of the injection in the expansion stroke (the interval between the start of ignition and the end of the injection) and the frequency of the combustion fluctuation. The fluctuation frequency of combustion in FIG. 5 is obtained by changing the start time of the injection in the expansion stroke, the injection period of which (i.e., the injection amount) is fixed, fixing at the same time the start time and the end time of the ignition period. As shown in FIG. 5, the line that indicates the frequency of the fluctuation of the combustion with respect to the “interval between the start of ignition and the end of injection” is a convex downward line. In FIG. 5, when the start time of the ignition period (start of ignition) and the moment of start of injection in the expansion stroke (start of injection) are the same, the frequency of combustion fluctuations indicates the lowest value on the delay side from the moment of ignition start, which is the same as at the moment of start of injection.

The ROM ECU 40 stores a map of the value of the “interval between the start of ignition and the end of injection” when the frequency of the combustion fluctuation indicates the lowest value, as shown in FIG. 5 (hereinafter also referred to as the “base adaptive value”) associated with the engine operating state (hereinafter also referred to as the “base adaptive value map”), and the card is read from the ROM when the catalyst heating control is performed. FIG. 6 is a diagram illustrating an example of a map of basic adaptive values. As illustrated in FIG. 6, a map of basic adaptive values is created as a two-dimensional map by generating the engine speed and engine load k1 as both axes. Since a map of basic adaptive values is created due to each of the regions, the temperature of the engine coolant divided by the intervals of the given temperature, in fact, there are many similar two-dimensional maps. As indicated by the arrow in FIG. 6, the base adaptive value is set to have a value on the lag side when the engine speed becomes higher, or when the engine load becomes lower. This is why the increase in the primary flame is relatively late when the engine speed is high, and the increase in the primary flame is relatively fast, as the environment in the cylinder improves when the engine load is high.

When controlling the heating of the catalyst, specifically, the time of the start of the ignition period of the spark plug 32 and the moment of completion of the injection in the expansion stroke are determined as follows. First, the start time of the ignition period of the spark plug 32 is determined in accordance with the base ignition moment and the amount of delay correction. Then, the moment of completion of the injection in the expansion stroke is determined by adding the base adaptive value obtained from the map of the base adaptive values and the state of engine operation to a certain point in the beginning of the ignition period. FIG. 7 is a graph showing the transition of the ignition moment of the spark plug 32 (more precisely, the moment the ignition period begins) and the temperature of the engine coolant during cold start of the internal combustion engine. When the engine is started at time t ₀ , indicated in FIG. 7, the operation mode for performing the catalyst heating control (hereinafter also referred to as the “catalyst heating mode”) starts from a time t ₁ immediately after a time t ₀ , and the ignition moment is gradually set to a value on the delay side. The catalyst heating mode ends at t ₂ when the engine coolant temperature reaches the criterion (as an example, 50 ° C), and then the ignition moment is gradually set to the value on the delay side.

It should be noted that the ignition timing is stored in the ROM ECU 40 as a value according to the operating conditions of the engine (mainly the amount of intake air and engine speed). The amount of lag correction is determined based on a map of the amount of lag correction associated with the temperature of the engine coolant (hereinafter also referred to as the “map of lag correction value”). The lag correction value map is stored in the ROM of the ECU 40 in the same way as the adaptive value base map, and is read from the ROM when the catalyst heating control is performed.

Problems when Ambient Ignition Conditions Are Out of Required Range

In the system illustrated in FIG. 1, if the surrounding ignition conditions change due to some factors and, therefore, fall outside the required range, the state of combustion can easily become unstable, despite the attractive action described above caused by injection during the expansion stroke. For example, when deposits accumulate in the injection hole of the injector 30, the amount of injection injection in the intake stroke decreases. Even when the amount of air is read incorrectly in an amount less than the initial amount, when the amount of injection injection in the intake stroke is calculated, the amount of injection injection in the intake stroke is reduced. When the injection injection amount in the intake stroke decreases, the fuel concentration around the spark plug 32 becomes lower, and the primary flame increase rate (called the primary flame increase rate before contact with the sprayed fuel jet injected during the expansion stroke, the same will apply further) getting slower. In the case of little knowledge regarding the timing of the intake valve 26 and exhaust valve 28, the proportion of exhaust gases remaining in the combustion chamber 20 increases, and the rate of increase of the primary flame becomes slower. When the rate of increase of the primary flame becomes slower, the primary flame may not come into contact with the atomized jet of fuel injected during the expansion stroke, and the fluctuation of combustion between cycles becomes large.

FIG. 8 is a diagram illustrating a state in a cylinder when the rate of increase of the primary flame is slow. The upper part of FIG. 8 illustrates a state in a cylinder when the surrounding ignition conditions are within the desired range, the state in the cylinder being the same as the state in the cylinder illustrated at the bottom of FIG. 4. In this case, the discharge spark and the primary flame generated in the electrode portion 34 are attracted and come into contact with a sprayed jet of fuel injected during injection in the expansion stroke, and the primary flame rapidly increases, as described above. That is, in this case, there is no specific problem of increasing the speed of the primary flame. On the other hand, the lower part of FIG. 8 illustrates a state in a cylinder when the rate of increase of the primary flame is slow. In this case, the discharge spark created by the electrode portion 34 is attracted to the atomized jet of fuel injected during injection in the expansion stroke, but the expected primary flame attraction, the rate of increase of which is slow, may not be achieved. As a result of this, the primary flame may not come into contact with a sprayed jet of fuel injected during injection in an expansion stroke. Primary combustion becomes unstable, and primary combustion after primary combustion also becomes unstable.

For example, when the projection of the electrode portion 34 into the combustion chamber 20 decreases due to replacement of the spark plug 32, and when the spray angle is changed due to accumulation of deposits in the injection hole of the injector 30, the distance between the outer spray pattern and the electrode portion 34 increases. When the distance between the outer spray pattern and the electrode portion 34 increases, the primary flame may not come into contact with a sprayed jet of fuel injected during the expansion stroke, and the fluctuation of combustion between cycles may become large.

FIG. 9 is a diagram for illustrating a state in a cylinder when the distance between the outer spray pattern and the electrode portion 34 increases. The upper part of FIG. 9 illustrates a state in a cylinder when the surrounding ignition conditions are within the desired range, the state in the cylinder being the same as the state in the cylinders illustrated at the bottom of FIG. 4 and at the top of FIG. 8. On the other hand, the lower part of FIG. 9 illustrates the state in the cylinder when the distance between the outer spray pattern and the electrode portion 34 increases. In this case, since the distance between the low-pressure region and the discharge spark and the primary flame created by the electrode portion 34 increases, the low-pressure region is formed around the atomized jet of fuel injected during injection in the expansion stroke, and the expected attraction may not be achieved. As a result of this, the primary flame may not come into contact with a sprayed jet of fuel injected during injection in an expansion stroke. It should be noted that the contour line drawn in FIG. 9 represents the contour surface of the fuel atomization form, which is closest to the spark plug 32 among the atomization forms of fuel injected from the injector 30.

If the timing of the start of the ignition period moves forward, the environment in the cylinder improves. When the rate of increase of the primary flame decreases (see the bottom of FIG. 8), the primary flame may come into contact with a sprayed jet of fuel injected during injection during the expansion stroke by attenuating the decrease in growth rate. When the distance between the outer spray pattern and the electrode portion 34 increases (see the bottom of FIG. 9), the primary flame can come into contact with the atomized jet of fuel injected during injection during the expansion stroke, by facilitating the rate of increase of the primary flame. However, if the start time of the ignition period is shifted forward, the exhaust energy that can be applied to the exhaust gas purification catalyst is reduced, and time is required to activate the exhaust gas purification catalyst.

These problems are described in detail with reference to FIG. 10. When the surrounding ignition conditions are within the required range, the period before the primary flame generated from the atomized jet of fuel injected by injection in the intake stroke increases to a size sufficient to come into contact with the atomized jet of fuel injected when Injection at the expansion stroke, there may be a period within the proper range. As indicated by the solid line (in normal condition) in the middle of FIG. 10, even when the ignition timing (more precisely, the timing of the start of the ignition period) is set to the angle _of rotation CA ₁ of the crankshaft on the lag side, the rate of increase of the primary flame can be a value (v1) within an appropriate range. As indicated by the solid line (in normal condition) at the top of FIG. 10, the frequency of combustion fluctuations may be less than the criterion. However, when the surrounding ignition conditions change and, therefore, fall outside the required range, the period before the primary flame created from the atomized jet of fuel injected by injection in the intake stroke increases to a size sufficient to come into contact with sprayed fuel injected during injection in the expansion stroke increases. As indicated by a dashed line (when combustion is impaired) in the middle of FIG. 10, when the ignition timing is set at a crank angle of CA ₁ , the rate of increase of the primary flame decreases to a value (v2) that is outside the proper range. As a consequence, as indicated by the dashed line (when combustion deteriorates) at the top of FIG. 10, the frequency of combustion fluctuations exceeds the criterion.

Even when the surrounding ignition conditions are outside the required range, the trend of the rate of increase of the primary flame can be changed by changing the ignition moment in the direction of advance. Specifically, if the ignition timing is reset from the crankshaft rotation angle CA _{1 to} the crankshaft rotation angle CA ₂ , the primary flame increase rate may return from a value (v2) that is outside the proper range to a value (v1) that is within proper range. Thus, the primary flame generated from the sprayed jet of fuel injected by injection in the intake stroke can come into contact with the sprayed jet of fuel injected during injection in the expansion stroke, thereby allowing the frequency of combustion fluctuations to be less than the criterion. However, as shown at the bottom of FIG. 10, when the ignition timing is reset to the crankshaft angle CA ₂ , the exhaust energy is reduced compared to the case when the ignition timing is set to the crankshaft angle CA ₁ . As a consequence, the activation of the exhaust gas purification catalyst takes time only to reduce the exhaust energy.

In the presented embodiment, in order to avoid such situations, the base adaptive value obtained from the map of base adaptive values changes when it is expected that the primary flame may not come into contact with the sprayed jet of fuel injected during injection in the expansion stroke, because the surrounding ignition conditions. FIG. 11 is a graph showing a method of changing an interval from the start of the ignition period to completion of injection in an expansion stroke. Similarly to FIG. 5, FIG. 11 illustrates the relationship between the “interval between the start of ignition and the end of injection” and the fluctuation of combustion. As can be seen from the comparison of FIG. 5 and 11, the relationship is drawn by the solid line in FIG. 5, but drawn with a dashed line in FIG. eleven.

As explained in FIG. 8-10, when the primary flame may not come into contact with a sprayed jet of fuel injected during injection during the expansion stroke, the frequency of combustion fluctuations becomes large. That is, as shown in FIG. 11, the relationship between the “interval between the start of ignition and the end of the injection” and the fluctuation of the combustion changes from the relationship drawn by the dashed line to the relationship drawn by the solid line. However, when the injection in the expansion stroke is performed with the combustion fluctuation frequency set to the base adaptive value, the combustion fluctuation frequency exceeds the criterion. In this regard, if the base adaptive value changes with an increase in the “interval between the start of ignition and the end of injection” according to the relationship indicated by the solid line after the change, the frequency of combustion fluctuations may be less than the criterion.

It should be noted that, as described above, the base adaptive value is the value of the “interval between the start of ignition and the end of injection” when the frequency of the fluctuation of combustion indicates the lowest value when the surrounding ignition conditions are within the required range. Even when the injection in the expansion stroke is performed on the basis of the modified “interval between the start of ignition and the end of the injection”, the frequency of combustion fluctuations does not become small compared to the case when the surrounding ignition conditions are within the required range. However, if the base adaptive value changes with an increase in the “interval between the start of ignition and the end of the injection”, the frequency of the combustion fluctuation can be made close to the frequency of the combustion fluctuation in the case when the surrounding ignition conditions are within the required range, by obtaining a lower frequency of combustion fluctuation than the criterion.

FIG. 12 is a diagram illustrating a state in a cylinder when the base adaptive value changes with increasing interval from the start of the ignition period to the end of injection in the expansion stroke. Both the upper part and the lower part of FIG. 12 illustrate a state in a cylinder when the surrounding ignition conditions are outside the required range. As a difference between the upper part and the lower part of FIG. 12, the upper part illustrates the case when the ignition moment is shifted forward with the “interval between the start of ignition and the end of injection” fixed at the base adaptive value, and the lower part illustrates the case when the base adaptive value changes with increasing “interval between the start of ignition and the end of injection ".

As can be seen from a comparison of the top and bottom of FIG. 12, when the “interval between the start of ignition and the end of injection” is fixed at the base adaptive value (see the upper part), the primary flame, whose increase rate is slow, may not come into contact with the sprayed jet of fuel injected during injection during the expansion stroke. On the other hand, if the base adaptive value changes with an increase in the “interval between the start of ignition and the end of the injection” (see bottom), the primary flame may come into contact with a sprayed jet of fuel injected during injection in the expansion stroke at the stage when the primary flame amplified to some extent. The state when the primary flame comes into contact with a sprayed jet of fuel injected during injection during the expansion stroke approaches the state when both the primary flame and the sprayed fuel stream are in contact when the surrounding ignition conditions are within the required range. As a result of this, primary combustion can be stabilized while suppressing fluctuations in combustion, and primary combustion can also be stabilized.

If the base adaptive value changes with an increase in the “interval between the start of ignition and the end of injection”, there is no need for a strong forward shift of the ignition moment, thereby suppressing the decrease in exhaust energy that must be applied to the exhaust gas purification catalyst. FIG. 13 is a graph explaining the results when the base adaptive value changes with increasing interval from the start of the ignition period to the end of injection in the expansion stroke. “The base adaptive value (in the normal state) in FIG. 13 provides the exhaust energy that must be applied to the exhaust gas purification catalyst when the catalyst heating control is performed in accordance with the base adaptive value and the frequency of combustion fluctuations when controlling the catalyst heating in the case where the surrounding ignition conditions are within the required range. The “base adaptive value (when combustion deteriorates)” provides the exhaust energy and the frequency of the combustion fluctuations when the catalyst heating is controlled in accordance with the base adaptive value when the surrounding ignition conditions are outside the required range. As can be seen from a comparison of both basic adaptive values, the exhaust energy corresponding to the “base adaptive value (when the combustion deteriorates)” is equivalent to the energy corresponding to the “base adaptive value (in the normal state)”, but the frequency of combustion fluctuations corresponding to the “base adaptive value ( when combustion worsens) ”more than a criterion.

“Ignition timing (fixed interval)” in FIG. 13 represents the exhaust energy and the frequency of the combustion fluctuations when the regulation of the heating of the catalyst is carried out in accordance with the basic adaptive value, while at the same time ahead of the ignition moment (more precisely, the moment the ignition period begins) in the case when the surrounding ignition conditions are outside the required range. As can be seen from comparing the “ignition timing (fixed interval)” and the “base adaptive value (when the combustion deteriorates)”, the frequency of the combustion fluctuation corresponding to the “ignition timing (fixed interval)” is less than the criterion, but the exhaust energy corresponding to “ ignition timing (fixed interval) ”decreases.

The meaning of “presented application” in FIG. 13 provides exhaust energy and a frequency of combustion fluctuations when the regulation of catalyst heating is performed in accordance with a modified base adaptive value in a case where the ambient ignition conditions are outside the required range. As can be seen from comparing the values of the “presented application” and other values, the frequency of combustion fluctuations corresponding to the value of the “presented application” may be less than the criterion. An exhaust energy corresponding to the “present application” value that is lower than the energy corresponding to the “base adaptive value (in the normal state)” but higher than the energy corresponding to the “fixed ignition timing angle” can be obtained. As a result, the exhaust energy necessary for the early activation of the exhaust gas purification catalyst can be guaranteed, while at the same time suppressing an increase in the frequency of combustion fluctuations, even when the surrounding ignition conditions are outside the required range.

Special process

FIG. 14 is a flowchart illustrating an example of a process performed by the ECU 40 in an embodiment of the present application. It should be noted that the routines illustrated in this drawing are repeatedly executed in each cylinder in a cycle after starting the internal combustion engine 10.

In the routines illustrated in FIG. 14, it is first determined whether the engine coolant temperature reaches the criterion, or if a check box is selected regarding completion of the catalyst heating mode (step S100). Specifically, in step S100, it is determined whether the engine coolant temperature reaches the criterion (see FIG. 7) according to the detected value of the temperature sensor 46, or whether the completion flag is set (see Step S110). When it is determined that the engine coolant temperature reaches the criterion, or when it is determined that the completion flag is set (in the case of “yes”), the process exits this subprogram.

When it is determined in step S100 that the engine coolant temperature does not meet the criterion and the completion flag is not set (in the case of "no"), the start time of the ignition period of the spark plug 32 and the moment of completion of the injection in the expansion stroke are determined based on the engine operation state (step S102 ) In step S102, the engine coolant temperature is first obtained in accordance with the detected value of the temperature sensor 46, and the lag correction amount is obtained based on the lag correction amount map. The start time of the ignition period of the spark plug 32 is determined in accordance with the amount of delay correction and the ignition base moment. the base adaptive value is obtained in accordance with the engine speed calculated in accordance with the detected value of the crankshaft angle sensor 42, the engine load calculated in accordance with the detected value of the accelerator opening sensor 44, and the engine coolant temperature calculated in accordance with the detected sensor value 46 temperatures, and a map of basic adaptive values. The moment of completion of the injection in the expansion stroke is determined by adding the obtained base adaptive value to a certain moment of the start of the ignition period of the spark plug 32.

After step S102, it is determined whether the surrounding ignition conditions change (step S104). At step S104, it is determined whether the fluctuation (standard deviation) σ Gat 30 exceeds the criterion, for example, after the start of the regulation of catalyst heating. The rotor of the crankshaft angle sensor 42 is provided with teeth having intervals of 30 °. The crankshaft angle sensor 42 is configured to transmit a signal each time the crankshaft rotates 30 °. Gat 30 is calculated as the time between the signals to be transmitted, that is, the time required to rotate the crankshaft by 30 °. FIG. 15 is a graph showing an example of a Gat 30 when an internal combustion engine is started from a cold state and a transition of an oscillation σ Gat 30. In FIG. 15, the abscissa represents the time elapsed after the engine was started, and the time t ₁ represents the start time of the catalyst heating control. As shown in FIG. 15, the fluctuation Gat 30 between time t1 and time t ₃ is small. As a result of this, it is determined that the variation of σ Gat 30 is less than the criterion. When it is determined that the oscillation σ Gat 30 is less than the criterion (in the case of “no”), the process proceeds to step S108.

On the other hand, as shown in FIG. 15, the fluctuation of Gat 30 becomes large between time t ₃ and time t ₄ . As a result of this, it is determined that the variation of σ Gat 30 is greater than the criterion. When it is determined that the variation of σ Gat 30 exceeds the criterion (in the case of “yes”), it can be determined that there is a possibility that the surrounding ignition conditions change due to some factors and, therefore, is outside the required range, and the primary flame may not come into contact with a sprayed jet for combustion injected during injection in the expansion stroke. As a result of this, the start time of the ignition period of the spark plug 32 and the end time of the injection in the expansion stroke are changed (step S106). In step S106, first, in accordance with the engine coolant temperature and the lag correction amount map, the lag correction amount is obtained. In accordance with the magnitude of the delay correction and the ignition timing, the timing of the start of the ignition period of the spark plug 32 is determined. In accordance with the engine speed, engine load and engine coolant temperature and a map of basic adaptive values, a basic adaptive value is obtained. So far, the process is the same as the process in step S102. In step S106, the obtained base adaptive value is added to the determined moment of the start of the ignition period of the spark plug 32. In addition, a correction value (fixed value) is added to it to increase the interval. In the expansion stroke, the moment of completion of the injection is determined.

After step S106, it is determined in step S108 whether the temperature of the exhaust gases exceeds the criterion T ₁ . At this stage, it is determined whether the exhaust gas temperature exceeds the criterion T ₁ in accordance with the detected temperature sensor value provided, for example, on the exhaust side of the exhaust gas purification catalyst. If it is determined that the engine coolant temperature reaches the criterion (in the case of “yes”), the completion flag is set (step S110).

According to the routines illustrated in FIG. 14, it can be determined whether the surrounding ignition conditions change in accordance with the variation of σ Gat 30 after the start of the regulation of the heating of the catalyst. When, as a result of the determination, it is found that there is a possibility that the surrounding ignition conditions change due to certain factors and, therefore, are outside the required range, the interval from the start of the ignition period to the end of the injection in the expansion stroke can be increased. Even when the surrounding ignition conditions are outside the required range, fluctuation in combustion between cycles can be suppressed.

Modification of Embodiment

In an embodiment, the vortex flow generated in the combustion chamber 20 swirls from the upper part of the combustion chamber 20 downward on the side of the exhaust channel 24, and from the lower part of the combustion chamber 20 upwards on the side of the intake duct 22. However, the vortex flow can swirl in the opposite direction this direction of flow, that is, the vortex flow can swirl from the upper part of the combustion chamber 20 down on the side of the intake channel 22 and from the lower part of the combustion chamber 20 up on the side of the exhaust channel 24. In this case, it is necessary change the location of the spark plug 32 from the side of the exhaust valve 28 to the side of the inlet valve 26. By changing the location of the spark plug 32 in this way, the spark plug 32 is located on the outlet side of the injector 30 in the direction of the swirl flow, thereby achieving an attractive action during injection during the expansion stroke . In addition, the vortex flow cannot be formed in the combustion chamber 20 because the fluctuation of combustion between cycles described above occurs regardless of the presence of the formation of the vortex flow.

In an embodiment, the primary injection (first injection) by the injector 30 is performed in the intake stroke, and the secondary injection (second injection) is performed in the expansion cycle at the time of delay from the top compression dead center. However, a primary injection (first injection) may also be performed in a compression stroke. In addition, the primary injection (first injection) may be performed separately multiple times, or a separate portion of the primary injection may also be performed in the intake stroke and the remaining portion may also be performed in the compression stroke. Thus, the injection time and the number of injections in the primary injection (in the first injection) can be changed in various ways.

In the above embodiment, in the process of step S106 of FIG. 14, the correction value for increasing the interval is determined as a fixed value. However, the correction value for increasing the interval may be a non-fixed value. For example, a correction value for increasing the interval can be set with increasing when the difference between the fluctuation σ Gat 30 and the criterion shown in FIG. 15, getting big. When such a setup is performed, a map showing the relationship between the difference between the σ Gat 30 fluctuation and the criterion and the correction value for increasing the interval (see Fig. 16) is stored in the ROM ECU 40, and can be read from the ROM ECU 40 during step S106.

In the above embodiment, in the process of step S104 of FIG. 14, using the σ Gat 30 oscillation after starting to control the catalyst preheating, a determination is made whether the surrounding ignition conditions change. Instead of this variation of σ, a variation of the period of the crankshaft angle (hereinafter also referred to as “SA-CA10”) from the start of the ignition period to the achievement of the mass fraction equal to 10% (MFB) can be used to make the determination. The MFB is calculated based on an analysis of the pressure inside the cylinder obtained using the pressure sensor inside the cylinder (not illustrated) provided separately in the combustion chamber 20 and the crankshaft angle sensor 42, and SA-CA10 is calculated based on the calculated MFB. It should be noted that the method for calculating MFB from the result of the analysis of pressure data inside the cylinder and the method for calculating SA-CA10 are described in detail in JP 2015-094339 A and JP 2015-098799 A, and their descriptions are omitted.

FIG. 17 is a graph showing the relationship between the frequency of the fluctuation of combustion and the oscillation σ SA-CA10. FIG. 18 is a graph showing an example of a transition of an oscillation σ SA-CA10 when an internal combustion engine is started from a cold state. As shown in FIG. 17, the frequency of combustion fluctuations becomes large when the oscillation σ SA-CA10 becomes large. That is, the oscillation σ SA-CA10 correlates with the frequency of combustion fluctuations. For example, it is determined that the oscillation σ SA-CA10 exceeds the criterion between time t ₅ and time t ₆ , as shown in FIG. 18 after starting the adjustment of the catalyst preheater, the process after step S106 of FIG. 14 may be performed by determining that it is likely that the surrounding ignition conditions change due to certain factors and, therefore, are outside the required range, and the primary flame may not come into contact with the injected atomized spray for combustion, due to oscillation during injection into expansion stroke. In addition, not only the Gat 30 and SA-CA10, but also the time needed to rotate the crankshaft 60 ° during the ignition period (Gat60), the period of the crankshaft angle from the start of the ignition period until the MFB reaches 5% can also be used ( SA-CA5) and the period of the crank angle from the start of the ignition period until the MFB reaches 15% (SA-CA15). Thus, parameters that can determine the state when the primary flame comes into contact with a sprayed jet of fuel injected during injection in the expansion stroke (parameters related to the fluctuation of combustion between cycles) can be used as indices of determining whether the environmental conditions change ignition in the embodiment above.

Claims (9)

1. A control device for an internal combustion engine, wherein the internal combustion engine comprises: an injector located in the upper part of the combustion chamber and configured to inject fuel into the cylinder from a plurality of injection holes; a spark plug configured to ignite the air-fuel mixture in the cylinder using a discharge spark, the spark plug being located on the exhaust side of the fuel injected from the plurality of injection holes and above the contour surface of the fuel atomization pattern, which is closest to the spark plug among the spray patterns fuel injected from a plurality of injection holes; and an exhaust gas purification catalyst that is configured to purify exhaust gases from a combustion chamber, at the same time, to activate the exhaust gas purification catalyst, the control device is configured to control the spark plug in such a way as to create a spark during the ignition period delayed from the top dead center of compression, and to control the injector so as to perform the first injection at a point in time ahead of the top dead point of compression and the second injection at a time with a delay from the top dead center of compression, and the second injection is performed so that the injection period is overlapping t at least part of the period of ignition, and when it is determined that the parameter associated with the fluctuation of combustion between cycles exceeds a threshold value, the control device is further configured to control the spark plug and injector in such a way that the interval from the start of the ignition period to the end of the injection period of the second injection is increased compared to the case when it is determined that the parameter is lower than the threshold value. 2. The control device for an internal combustion engine according to claim 1, wherein, when the parameter exceeds a threshold value, the control device is configured to change an increase in an interval value that is changed in accordance with a magnitude of a discrepancy between a parameter and a threshold value. 3. The control device for an internal combustion engine according to claim 1, wherein the moment of completion of the second injection is on the leading side of the moment of completion of the ignition period. 4. The control device for an internal combustion engine according to claim 1, wherein the parameter is a fluctuation in the time required before the crankshaft rotates by a predetermined angle, or a fluctuation in the period of the crankshaft rotation angle from the moment the ignition period begins until the burnt mass fraction reaches given ratio.

Images