JP5482397B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine.

  Conventionally, preignition (pre-ignition) is known as an aspect of abnormal combustion of an internal combustion engine. Preignition is a phenomenon in which, during the piston compression process, the air-fuel mixture self-ignites from an overheated portion in the combustion chamber before the normal ignition timing of the spark plug. When pre-ignition occurs, the air-fuel mixture is burned while being compressed, so the pressure and temperature in the combustion chamber may become abnormally high.

  Therefore, conventionally, for example, Japanese Unexamined Patent Application Publication No. 2004-52624 discloses a system for suppressing the occurrence of pre-ignition regardless of the octane number of gasoline fuel. In this system, regular gasoline with a low octane number is used for an internal combustion engine with high-octane gasoline specifications, and when it is determined that the load on the internal combustion engine is increasing, fuel injection is divided into an intake stroke and a compression stroke. Executed. Thereby, since the air-fuel ratio around the spark plug can be temporarily made rich, an increase in the temperature around the spark plug can be suppressed using the increase in latent heat of vaporization.

Japanese Patent Laid-Open No. 2004-52624 Japanese Patent Laid-Open No. 5-223026 JP 2008-95525 A JP 2005-172466 A

  By the way, recent high-octane gasoline fuels contain many olefin components. This olefin component has a property that a combustion reaction is likely to occur as compared with a substance such as toluene, and is also easily adsorbed to a spark plug or the like. For this reason, the higher the concentration of the olefin component, the more deposits are accumulated around the spark plug, and as a result, preignition is likely to occur. That is, even if the gasoline fuel has a high octane number, if the concentration of the olefin component is high, it is sufficiently assumed that pre-ignition tends to occur. For this reason, in the above-mentioned conventional system that controls the pre-ignition when low-octane gasoline fuel is used, it is not possible to effectively suppress the occurrence of pre-ignition when high-octane gasoline fuel is used. Improvement was desired.

  The present invention has been made to solve the above-described problems, and provides an exhaust gas purification apparatus for an internal combustion engine that can suppress the occurrence of pre-ignition by using the concentration of an olefin component in gasoline fuel. The purpose is to do.

In order to achieve the above object, the first invention provides
A spark ignition type internal combustion engine control device including a spark plug,
Fuel property detection means for detecting the concentration of an olefin component in gasoline fuel supplied to the internal combustion engine;
Control means for controlling the temperature in the combustion chamber during the compression process of the internal combustion engine to a range in which preignition does not occur when the olefin component concentration is higher than a predetermined value .

According to a second invention, in the first invention,
A compression ratio variable means for variably setting the compression ratio of the internal combustion engine;
The control means is characterized in that the compression ratio is set lower than normal when the olefin component concentration is higher than a predetermined value.

According to a third invention, in the second invention,
The compression ratio variable means includes means for variably setting the closing timing of the intake valve,
The control means delays the closing timing of the intake valve from the normal time when the concentration of the olefin component is higher than a predetermined value.

A fourth invention is any one of the first to third inventions,
In an internal combustion engine with a supercharger,
Means for variably setting the upper limit value of the supercharging pressure;
The control means sets the limit value lower than normal when the olefin component concentration is higher than a predetermined value.

According to a fifth invention, in any one of the first to fourth inventions,
Further comprising ignition timing control means for controlling the ignition timing of the internal combustion engine;
The control means retards the ignition timing from the normal time when the olefin component concentration is higher than a predetermined value.

A sixth invention is any one of the first to fifth inventions,
In the hybrid vehicle having the internal combustion engine and the electric motor, and driving the vehicle by the driving force of the internal combustion engine and / or the electric motor,
Means for variably setting output distribution between the internal combustion engine and the electric motor;
The control means is characterized in that when the olefin component concentration is higher than a predetermined value, the output distribution of the electric motor to the internal combustion engine is increased more than usual.

A seventh invention is the invention according to any one of the first to sixth inventions,
A determination means for determining that fuel has been supplied to the fuel tank of the internal combustion engine;
The fuel property detecting means detects an olefin component concentration in the fuel supplied to the internal combustion engine when it is determined that the fuel is supplied to the fuel tank.

According to an eighth invention, in any one of the first to seventh inventions,
The fuel property detecting means is provided in a fuel tank connecting the fuel tank of the internal combustion engine or the fuel tank and the fuel system of the internal combustion engine.

The inventors of the present application have found that when the concentration of olefin components in gasoline fuel is high, the pre-ignition generation temperature is significantly reduced. According to the first invention, when the concentration of the olefin component in the fuel is higher than a predetermined value , the temperature in the combustion chamber during the compression stroke is controlled to be in a temperature range where pre-ignition does not occur. For this reason, according to this invention, generation | occurrence | production of preignition can be suppressed effectively by utilizing the olefin component density | concentration in the supplied gasoline fuel.

  According to the second invention, when the concentration of the olefin component in the gasoline fuel is higher than a predetermined value, the compression ratio is set lower than that in the normal time. For this reason, according to the present invention, when the pre-ignition generation temperature is lowered, the temperature increase in the combustion chamber can be suppressed, so that the generation of the pre-ignition can be effectively suppressed.

  According to the third invention, when the concentration of the olefin component in the gasoline fuel is higher than a predetermined value, the closing timing of the intake valve is retarded from the normal time. For this reason, according to the present invention, when the pre-ignition occurrence temperature is lowered, the actual compression ratio can be lowered, so that the occurrence of pre-ignition can be effectively suppressed.

  According to the fourth invention, when the concentration of the olefin component in the gasoline fuel is higher than a predetermined value, the upper limit value of the supercharging pressure is set to a value lower than normal. For this reason, according to the present invention, when the pre-ignition occurrence temperature is lowered, the supercharging pressure can be lowered, so that the occurrence of pre-ignition can be effectively suppressed.

  According to the fifth invention, when the olefin component concentration in the gasoline fuel is higher than a predetermined value, the ignition timing is retarded from the normal time. For this reason, according to the present invention, when the pre-ignition generation temperature is lowered, the temperature increase in the combustion chamber can be suppressed, so that the generation of the pre-ignition can be effectively suppressed.

  According to the sixth invention, in a hybrid vehicle including an internal combustion engine and an electric motor, when the concentration of the olefin component in the gasoline fuel is higher than a predetermined value, the output distribution of the electric motor to the internal combustion engine is increased more than usual. . For this reason, according to the present invention, when the pre-ignition generation temperature is lowered, the temperature increase in the combustion chamber can be suppressed, so that the generation of the pre-ignition can be effectively suppressed.

  According to the seventh aspect, when it is determined that fuel has been supplied, the olefin component concentration of the gasoline fuel is detected. For this reason, according to the present invention, since the concentration detection is performed at the timing when the property of the gasoline fuel supplied to the internal combustion engine changes, the olefin component concentration of the fuel supplied to the internal combustion engine can always be accurately grasped. it can.

  According to the eighth invention, the fuel detecting means is provided in the fuel tank or the fuel pipe. For this reason, according to the present invention, the concentration of the olefin component in the gasoline fuel before being supplied to the internal combustion engine can be detected.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure for demonstrating the relationship between the olefin component density | concentration in gasoline fuel, and preignition generation | occurrence | production temperature. It is a flowchart of the routine performed in Embodiment 1 of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine (engine) 10. The internal combustion engine 10 is configured as a spark ignition internal combustion engine with a supercharger. An exhaust passage 16 communicates with the exhaust side of the internal combustion engine 10. An exhaust purification catalyst 18 for purifying harmful components in the exhaust gas is disposed in the exhaust passage 16. As the exhaust purification catalyst 18, for example, a known catalyst such as a three-way catalyst can be used.

  In addition, the system according to the present embodiment includes a fuel tank 12 for storing refueled gasoline fuel. One end of a fuel pipe 14 is connected to the fuel tank 12. The other end of the fuel pipe 14 is connected to the fuel system of the internal combustion engine 10.

  Further, the system according to the present embodiment is provided with a fuel property detection device 22 for detecting the concentration of the olefin component contained in the gasoline fuel stored in the fuel tank 12. As the fuel property detection device 22, for example, a device that detects using infrared spectroscopy (FT-IR), a device that detects using gas chromatography, or the like can be used. The arrangement and structure of the fuel property detection device 22 are not particularly limited as long as the olefin component concentration of gasoline fuel stored in the fuel tank 12 can be detected.

  The system of the present embodiment includes an ECU (Electronic Control Unit) 20 as shown in FIG. In addition to the fuel property detection device 22 described above, various sensors for detecting the operating condition and operating state of the internal combustion engine 10 are connected to the input unit of the ECU 20. In addition, various actuators for driving the internal combustion engine 10 are connected to the output portion of the ECU 20. The ECU 20 can control the state of the system shown in FIG. 1 based on various types of input information.

[Operation of Embodiment 1]
Next, the operation of the present embodiment will be described with reference to FIG. In the internal combustion engine 10, pre-ignition may occur during the piston compression process, in which the air-fuel mixture self-ignites from an overheated portion in the combustion chamber before the normal ignition timing of the spark plug. When pre-ignition occurs, the air-fuel mixture is burned while being compressed, so the pressure and temperature in the combustion chamber may become abnormally high. In particular, in recent years, there has been an increasing demand for supercharged engines and high compression ratio engines in order to ensure high output with small displacement, but these high compression ratio engines have a high pres- Is more likely to occur.

  In order to suppress the occurrence of pre-ignition, the temperature in the combustion chamber during the compression process may be controlled to be lower than the temperature at which the pre-ignition occurs. However, the pre-ignition generation temperature varies in a complicated manner depending on the compression ratio of the internal combustion engine 10 and the fuel properties of the supplied gasoline fuel. Accordingly, the inventors of the present application have made extensive studies focusing on the relationship between the occurrence of pre-ignition and fuel properties. As a result, the inventors of the present application have found that there is a relationship shown in FIG. 2 between the occurrence of pre-ignition and the concentration of the olefin component contained in the gasoline fuel.

  FIG. 2 is a diagram for explaining the relationship between the olefin component concentration in gasoline fuel and the pre-ignition generation temperature. As shown in this figure, the pre-ignition generation temperature rapidly decreases in the region where the olefin component concentration in the gasoline fuel is high. The reason for this is considered that the olefin component is more likely to cause a combustion reaction than a substance such as toluene, and also has a property of being easily adsorbed to a ceramic such as an insulator of a spark plug. For this reason, the higher the concentration of the olefin component, the more deposits are deposited around the spark plug, and as a result, preignition tends to occur. As shown in FIG. 2, the higher the compression ratio of the internal combustion engine 10, the lower the pre-ignition generation temperature. In particular, the tendency is conspicuous in the region where the olefin component concentration in gasoline fuel is high.

  There are no specific restrictions on the concentration of olefin components in gasoline fuel except in some areas. For this reason, it is also assumed that gasoline fuel contains a large amount of olefin components due to the spread of unconventional oil and the use of reformed oil as an octane improver. When gasoline fuel having such a high olefin component concentration is supplied, the pre-ignition generation temperature of the internal combustion engine is remarkably lowered, and unexpected pre-ignition may occur.

  Therefore, in the system of the present embodiment, based on the olefin component concentration in the gasoline fuel, the temperature in the combustion chamber during the compression stroke is a temperature range in which pre-ignition does not occur, specifically, a pre-corresponding to the olefin component concentration. The following control is executed so that the temperature range does not reach the ignition generation temperature. In this control, when the concentration of the olefin component in the gasoline fuel is high, it is determined that the risk of occurrence of pre-ignition is high, and pre-ignition avoidance control is executed. More specifically, first, the olefin component concentration Co of the gasoline fuel in the fuel tank 12 is detected using the fuel property detection device 22. When the olefin component concentration Co is higher than a predetermined specified value x (for example, 25%), the upper limit value of the supercharging pressure is changed to a predetermined allowable value lower than the normal set value. Thereby, since the supercharging pressure at the time of high supercharging can be effectively limited, the temperature rise around the spark plug can be effectively suppressed in the operation region where pre-ignition is likely to occur. Thereby, generation | occurrence | production of preignition can be suppressed effectively.

  It should be noted that the allowable value of the supercharging pressure when the olefin component concentration is high is preferably specified in advance through experiments or the like. More specifically, when the engine combustion is performed using gasoline fuel having an olefin component concentration higher than the specified value x, an allowable value (upper limit value) of the supercharging pressure that can avoid the occurrence of pre-ignition is previously tested. For example, the ECU 20 stores the obtained information. Thereby, even when a fuel having a high olefin component concentration is used, the occurrence of pre-ignition can be effectively suppressed.

  Further, the allowable value of the supercharging pressure upper limit value may be set such that the higher the olefin component concentration in the gasoline fuel, the lower the allowable value. These settings can be realized, for example, by creating map data in which the relationship between the olefin component concentration and the allowable value is converted into data and storing the map data in the ECU 20 in advance. According to such a configuration, it is possible to optimize the upper limit value of the supercharging pressure in accordance with the olefin component concentration.

  Further, the olefin component concentration in the gasoline fuel changes mainly after the fuel is supplied. Therefore, the timing for detecting the olefin component concentration is preferably the timing at which gasoline fuel is supplied. Thereby, when the olefin component concentration changes, the olefin component concentration after the change can be detected quickly.

  Thus, according to the system of the present embodiment, when the olefin component concentration Co of the gasoline fuel supplied to the internal combustion engine 10 is higher than the predetermined specified value x, the upper limit value of the supercharging pressure is higher than normal. Is also changed to a lower value. For this reason, it is possible to effectively suppress the occurrence of pre-ignition during high supercharging by performing engine combustion based on the post-change supercharging pressure limitation.

[Specific Processing in Embodiment 1]
Next, with reference to FIG. 3, the specific content of the process performed in this Embodiment is demonstrated. FIG. 3 is a flowchart of a routine executed by the ECU 20. In the routine shown in FIG. 3, first, the fuel property in the fuel tank 12 is determined (step 100). Specifically, the olefin component concentration Co (%) of the gasoline fuel in the fuel tank 12 is detected using the fuel property detection device 22.

  Next, it is determined whether or not the olefin component concentration Co is greater than a predetermined value x (step 102). As the predetermined value x, a preset value is read as the olefin component concentration at which pre-ignition occurs during the compression stroke of the internal combustion engine 10. As a result, when the establishment of Co> x is not recognized, it is determined that there is a low possibility that pre-ignition will occur during combustion of the internal combustion engine 10, and the routine proceeds to the next step, where the internal combustion engine 10 by normal adaptation is determined. Is executed (step 104).

  On the other hand, if it is determined in step 102 that Co> x is established, it is determined that preignition may occur when the internal combustion engine 10 is supercharged, and the process proceeds to the next step. Ignition avoidance control is executed (step 106). The ECU 20 stores in advance an upper limit allowable value of the supercharging pressure that can avoid the occurrence of pre-ignition when gasoline fuel having a higher olefin component concentration than the predetermined value x is used. Here, specifically, the upper limit value of the supercharging pressure is changed to such an allowable value, and engine combustion is performed.

  Next, it is determined whether gasoline fuel has been supplied into the fuel tank 12 (step 108). The presence / absence of fuel supply can be determined by detecting the opening / closing of the fuel cap or detecting a change in the remaining amount of fuel. As a result, when it is determined that the fuel is not supplied, it is determined that the fuel property in the fuel tank 12 has not changed, and the process of step 106 is repeatedly executed. On the other hand, if it is determined in step 106 that the fuel has been supplied, it is determined that there is a possibility that the fuel property in the fuel tank 12 has changed, and the routine returns to step 100 and this routine is executed again. The

  As described above, according to the system of the present embodiment, when the olefin component concentration Co of the supplied gasoline fuel is higher than the predetermined value x, the supercharging pressure upper limit value of the supercharging operation is lower than normal. The internal combustion engine 10 is operated after the value is changed. Thereby, even if it is a case where gasoline fuel with high olefin component concentration is used, generation | occurrence | production of pre-ignition can be suppressed effectively.

  By the way, in Embodiment 1 mentioned above, although it demonstrated reducing the upper limit of supercharging pressure in the internal combustion engine 10 with a supercharger as one aspect | mode of pre-ignition avoidance control, executable pre-ignition was carried out. The avoidance control is not limited to this. That is, in the operation region where pre-ignition occurs, other control as described below may be executed as long as the combustion chamber temperature during the compression stroke of the internal combustion engine 10 can be reduced.

  That is, as another mode of pre-ignition avoidance control, for example, in an internal combustion engine in which the compression ratio can be variably set, when the olefin component concentration in the gasoline fuel is higher than a predetermined value, the compression ratio is set to be higher than that in the normal state. It is good also as setting low. As a means for lowering the compression ratio, for example, a method of using a variable compression ratio engine as an internal combustion engine, or an internal compression engine in which the intake valve timing can be varied, the intake valve closing timing is retarded (delayed) and actual compression is performed. A method of reducing the ratio is conceivable. The compression ratio may be set to a predetermined low compression ratio when the concentration of the olefin component in the gasoline fuel is higher than a predetermined threshold, or the lower the compression ratio, the higher the olefin component concentration. You may set so that it becomes. In particular, in the case of a variable compression ratio engine, it is preferable that the compression ratio at the time of high load is set low and the high compression ratio region is not expanded to the high load region. These settings are made, for example, by creating map data in which the relationship between the olefin component concentration and the compression ratio or the retard amount of the intake valve closing timing corresponding to the compression ratio is created, and this map data is stored in the ECU 20. It can be realized by letting it go. Thereby, since the combustion chamber temperature during the compression stroke of the internal combustion engine 10 can be reduced, the occurrence of pre-ignition can be effectively suppressed.

  Further, as another aspect of the pre-ignition avoidance control, for example, when the olefin component concentration in the gasoline fuel is higher than a predetermined value, the ignition timing of the internal combustion engine 10 may be retarded. The ignition timing retardation amount may be set to a predetermined retardation amount when the olefin component concentration in the gasoline fuel is higher than a predetermined threshold value. The retard amount may be set to be large. These settings can be realized, for example, by creating map data in which the relationship between the olefin component concentration and the ignition timing retard amount is converted into data, and storing this map data in the ECU 20. Thereby, since the combustion chamber temperature during the compression stroke of the internal combustion engine 10 can be reduced, the occurrence of pre-ignition can be effectively suppressed.

  Further, as another aspect of the pre-ignition avoidance control, for example, in a hybrid vehicle including an internal combustion engine and an electric motor, when the olefin component concentration in gasoline fuel is higher than a predetermined value, the output distribution of the internal combustion engine is reduced. The output distribution of the electric motor may be increased. The output distribution may be set to a predetermined output distribution when the concentration of the olefin component in the gasoline fuel is higher than a predetermined threshold, or the output distribution of the motor is increased as the olefin component concentration is higher. May be set to be larger. These settings can be realized, for example, by creating map data in which the relationship between the olefin component concentration and the output distribution is converted into data, and storing this map data in the ECU 20. Thereby, since the combustion chamber temperature during the compression stroke of the internal combustion engine 10 can be reduced, the occurrence of pre-ignition can be effectively suppressed.

  In the first embodiment described above, the ECU 20 executes the process of step 100, so that the “fuel property detecting means” in the first invention executes the processes of steps 102 and 106. The “control means” in the first to sixth aspects of the present invention is realized.

  In the first embodiment described above, the “determination means” according to the seventh aspect of the present invention is implemented when the ECU 20 executes the process of step 108.

10 Internal combustion engine (supercharged engine)
12 Fuel tank 14 Fuel pipe 16 Exhaust passage 18 Exhaust purification catalyst 20 ECU (Electronic Control Unit)
22 Fuel property detection device

Claims (8)

A spark ignition type internal combustion engine control device including a spark plug,
Fuel property detection means for detecting the concentration of an olefin component in gasoline fuel supplied to the internal combustion engine;
Control means for controlling the temperature in the combustion chamber during the compression process of the internal combustion engine to a range in which preignition does not occur when the olefin component concentration is higher than a predetermined value. . A compression ratio variable means for variably setting the compression ratio of the internal combustion engine;
2. The control device for an internal combustion engine according to claim 1, wherein the control means sets the compression ratio lower than normal when the olefin component concentration is higher than a predetermined value. The compression ratio variable means includes means for variably setting the closing timing of the intake valve,
3. The control device for an internal combustion engine according to claim 2, wherein the control means retards the closing timing of the intake valve from the normal time when the olefin component concentration is higher than a predetermined value. In an internal combustion engine with a supercharger,
Means for variably setting the upper limit value of the supercharging pressure;
4. The control of the internal combustion engine according to claim 1, wherein the control unit sets the limit value lower than normal when the olefin component concentration is higher than a predetermined value. 5. apparatus. Further comprising ignition timing control means for controlling the ignition timing of the internal combustion engine;
The internal combustion engine control according to any one of claims 1 to 4, wherein the control means retards the ignition timing from a normal time when the olefin component concentration is higher than a predetermined value. apparatus. In the hybrid vehicle having the internal combustion engine and the electric motor, and driving the vehicle by the driving force of the internal combustion engine and / or the electric motor,
Means for variably setting output distribution between the internal combustion engine and the electric motor;
The said control means increases the output distribution of the said electric motor with respect to the said internal combustion engine rather than the normal time, when the said olefin component density | concentration is higher than predetermined value, The any one of Claims 1 thru | or 5 Control device for internal combustion engine. A determination means for determining that fuel has been supplied to the fuel tank of the internal combustion engine;
7. The fuel property detecting means detects an olefin component concentration in fuel supplied to the internal combustion engine when it is determined that fuel is supplied to the fuel tank. The control device for an internal combustion engine according to any one of the preceding claims.   The fuel property detection means is provided in a fuel pipe connecting the fuel tank of the internal combustion engine or the fuel tank and the fuel system of the internal combustion engine, according to any one of claims 1 to 7. Control device for internal combustion engine.

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