JP5949075B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly, to a control device for a spark ignition type internal combustion engine equipped with an in-cylinder pressure sensor.

  Conventionally, for example, Japanese Unexamined Patent Application Publication No. 2009-74515 discloses a control device for an internal combustion engine that can determine the fuel property when the engine is started. In this control device, when the engine is cranked, a small amount of air-fuel mixture is formed so that the engine does not rotate by itself, and the air-fuel mixture is spark-ignited and combusted at the ignition timing after compression top dead center. . In this combustion, the calorific value per unit mass of the fuel is calculated, and the property of the fuel is determined based on the calorific value.

JP 2009-74515 A JP 2010-180725 A JP-A-9-158819 JP-A-60-162035

  However, in order to ensure the fuel property determination accuracy in the conventional control device, it is required to accurately calculate the heat generation amount per unit mass of the fuel. However, the conventional control device is configured to calculate the amount of heat generated when a small amount of air-fuel mixture is combusted so that the engine does not rotate by itself. For this reason, when the influence of the temperature / pressure increase due to compression is relatively large, it is assumed that the calorific value due to combustion cannot be accurately calculated, and the accuracy of determining the fuel property is lowered.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a control device for an internal combustion engine that can accurately determine the properties of fuel used in a spark ignition type internal combustion engine. And

In order to achieve the above object, a first invention is a control device for a spark ignition type internal combustion engine,
In-cylinder pressure detecting means for detecting in-cylinder pressure of one or more cylinders of the internal combustion engine;
In an initial explosion cycle in which spark ignition is performed for the first time after cranking of the internal combustion engine is started, a change in in-cylinder pressure due to self-ignition after the start of the compression stroke and before execution of spark ignition is detected by the in-cylinder pressure detecting means, Fuel property determination means for determining the fuel property of the fuel of the internal combustion engine based on a change;
It is characterized by having.

According to a second invention, in the first invention,
The fuel property determination means includes means for acquiring a maximum value of the in-cylinder pressure change, and determines the fuel property of the fuel of the internal combustion engine based on the maximum value.

According to a third invention, in the first invention,
The fuel property determination means includes means for acquiring a change rate of the in-cylinder pressure change, and determines the fuel property of the fuel of the internal combustion engine based on the change rate.

A fourth invention is any one of the first to third inventions,
The in-cylinder pressure detecting means is an in-cylinder pressure sensor mounted on a specific cylinder that is one of the one or more cylinders.
The apparatus further comprises cylinder selection means for performing the initial explosion cycle in the specific cylinder.

According to a fifth invention, in any one of the first to fourth inventions,
Control means for performing control for increasing the compression ratio of the initial explosion cycle is further provided.

A sixth invention is any one of the first to fifth inventions,
The apparatus further comprises correction means for correcting the change in the in-cylinder pressure using either the water temperature of the internal combustion engine or the in-cylinder air amount.

A seventh invention is the invention according to any one of the first to sixth inventions,
The fuel property determining means determines the octane number of the fuel of the internal combustion engine.

In an eighth aspect based on the seventh aspect,
The apparatus further includes knock suppression means for performing control for suppressing occurrence of knocking when the octane number determined by the fuel property determination means is lower than a predetermined reference value.

In a ninth aspect based on the eighth aspect,
The knock suppression means includes means for limiting the output of the internal combustion engine.

In a tenth aspect based on the eighth or ninth aspect,
The knock suppression means includes warning means for issuing a warning to the user.

  According to the first invention, in the initial explosion cycle in which spark ignition is executed for the first time after cranking, a change in in-cylinder pressure due to self-ignition after the start of the compression stroke and before execution of spark ignition is detected. This in-cylinder pressure change due to self-ignition correlates with fuel properties. Therefore, according to the present invention, it is possible to determine the fuel property before starting the internal combustion engine based on the detected in-cylinder pressure change.

  According to the second invention, in the initial explosion cycle after cranking, the in-cylinder pressure change is detected by the in-cylinder pressure detecting means, and the maximum value (maximum in-cylinder pressure) is acquired. The maximum in-cylinder pressure has a correlation with the fuel property. For this reason, according to the present invention, it is possible to determine the fuel property before starting the internal combustion engine based on the acquired maximum in-cylinder pressure.

  According to the third aspect of the present invention, in the initial explosion cycle in which spark ignition is executed for the first time after cranking, the in-cylinder pressure change due to self-ignition is detected by the in-cylinder pressure detecting means, and the change speed (in-cylinder pressure change speed) is acquired. The The in-cylinder pressure change speed has a correlation with the fuel property. Therefore, according to the present invention, it is possible to determine the fuel property before starting the internal combustion engine based on the acquired in-cylinder pressure change speed.

  According to the fourth invention, the cylinder pressure sensor is mounted on the specific cylinder, and the cylinder selection is performed so that the initial explosion cycle is performed in the specific cylinder. For this reason, according to the present invention, the maximum in-cylinder pressure in the initial explosion cycle can be acquired without providing a plurality of in-cylinder pressure sensors.

  According to the fifth aspect of the invention, control for increasing the compression ratio of the initial explosion cycle is executed. For this reason, according to the present invention, it is possible to create a condition in which self-ignition is likely to occur in the initial explosion cycle, so that it is possible to effectively increase the accuracy of determination of fuel properties.

  According to the sixth aspect of the invention, the detected in-cylinder pressure change is corrected using either the water temperature or the in-cylinder air amount. The in-cylinder pressure during self-ignition varies depending on the water temperature and the in-cylinder air amount. For this reason, according to the present invention, it is possible to effectively improve the determination accuracy of the fuel property by correcting the obtained in-cylinder pressure change according to these operating conditions.

  According to the seventh aspect, the octane number of the fuel is determined based on the obtained in-cylinder pressure change. For this reason, according to the present invention, the octane number can be effectively determined before the internal combustion engine is started.

  According to the eighth aspect, when the determined octane number is lower than the predetermined determination value, the control for suppressing the occurrence of knocking is performed. For this reason, according to the present invention, the occurrence of knocking can be effectively suppressed.

  According to the ninth aspect, when the determined octane number is lower than the predetermined determination value, the output of the internal combustion engine is limited. For this reason, according to the present invention, occurrence of knocking can be effectively avoided.

  According to the tenth invention, when the determined octane number is lower than the predetermined determination value, a warning to the user is issued. For this reason, according to the present invention, it is possible to effectively notify the user of a problem due to a low octane number and to avoid the occurrence of knocking.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. 4 is a timing chart showing changes in in-cylinder pressure and engine speed of a cylinder equipped with an in-cylinder pressure sensor at start-up. It is a figure which shows the relationship between the maximum value Pmax of the in-cylinder pressure change in a predetermined driving | running condition, and an octane number (RON). It is a figure which shows the tendency of the change of Pmax with respect to in-cylinder air amount and water temperature. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this 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. In addition, since the structure of a supercharger is well-known in many literatures, illustration is abbreviate | omitted. 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, an in-cylinder pressure sensor (hereinafter also referred to as “CPS”) 22 for detecting the in-cylinder pressure of the cylinder is mounted in one of the plurality of cylinders. Hereinafter, the cylinder in which the CPS 22 is mounted is referred to as “CPS mounted cylinder”.

  The system of the present embodiment includes an ECU (Electronic Control Unit) 20 as shown in FIG. In addition to the CPS 22 described above, the ECU 20 includes various sensors such as a crank angle sensor for detecting the rotational position of the crankshaft, a water temperature sensor for detecting the water temperature, and a knock sensor for detecting the occurrence of knocking. It is connected. Various actuators such as a throttle valve, a spark plug, and a fuel injection valve are connected to the output portion of the ECU 20. The ECU 20 controls the operating state of the internal combustion engine 10 based on various types of input information.

[Operation of Embodiment 1]
(Self-ignition phenomenon at start-up)
Next, the operation of the present embodiment will be described with reference to FIGS. In the spark ignition type internal combustion engine 10, self-ignition may occur in which the air-fuel mixture in the cylinder spontaneously ignites during the initial explosion cycle during cranking for starting. This self-ignition phenomenon will be described more specifically. Since cranking by the starter motor is at a low rotation (for example, 260 rpm), the air-fuel mixture in the cylinder in the initial explosion cycle is compressed very slowly. Then, in the cylinder, the oxidation reaction proceeds during the extended compression stroke period, spontaneously ignites near the compression top dead center (TDC), and the fuel in the cylinder burns at once.

  FIG. 2 is a timing chart showing changes in the in-cylinder pressure and the engine speed of the cylinder equipped with the in-cylinder pressure sensor at the start. In the example shown in this figure, it is shown that self-ignition occurs in the first explosion cycle during cranking. As described above, in the self-ignition, the fuel in the cylinder burns at a time unlike the combustion by the normal flame propagation. For this reason, as shown in FIG. 2, when self-ignition occurs, the in-cylinder pressure rapidly increases. After the engine speed increases due to the first explosion, the compression stroke time is shortened, and thereafter normal combustion is performed without self-ignition.

  Combustion due to self-ignition and combustion due to ignition can be determined based on the above-described degree of increase in the in-cylinder pressure, but can also be determined using, for example, a crank angle at which combustion occurs. That is, the ignition timing in the initial explosion cycle is normally set to ATDC, whereas self-ignition occurs in the vicinity of TDC. For this reason, these determinations can be easily made by detecting the crank angle at which combustion has occurred.

(About the relationship between self-ignition and octane number)
As described above, in the first explosion cycle of the internal combustion engine 10 using the low octane fuel, the in-cylinder pressure changes due to self-ignition. Here, the inventor of the present application has made extensive studies on the relationship between the change in in-cylinder pressure due to this self-ignition and the octane number (RON) of the fuel. As a result, the inventors of the present application have found that there is a predetermined correlation between the maximum value Pmax of in-cylinder pressure change due to self-ignition and the octane number (RON) of the fuel used. FIG. 3 is a diagram showing the relationship between the maximum value Pmax of in-cylinder pressure change and the octane number (RON) under a predetermined operating condition. As shown in this figure, Pmax increases as the octane number of the fuel used decreases.

  Therefore, in the system according to the present embodiment, the octane number (RON) of the fuel used is determined using the relationship shown in FIG. Specifically, the relationship between Pmax and octane number (RON) shown in FIG. 3 is stored in the ECU 20 as a map, and the octane number (RON) corresponding to the acquired Pmax is specified from the map. However, Pmax varies depending not only on the octane number (RON) but also on operating conditions such as the in-cylinder air amount (compression ratio) and the water temperature. FIG. 4 is a diagram showing a tendency of changes in Pmax with respect to the in-cylinder air amount and the water temperature. As shown in this figure, Pmax tends to become higher as the in-cylinder air amount is larger (that is, as the compression ratio is higher) and as the water temperature is higher. Therefore, in the system according to the present embodiment, correction is performed to reflect the influence of the in-cylinder air amount and the water temperature on the acquired Pmax. Then, the octane number (RON) corresponding to the corrected Pmax is specified from the map. Hereinafter, specific processing for determining the octane number (RON) of the fuel used will be described in detail with reference to the flowchart.

[Specific Processing in Embodiment 1]
FIG. 5 is a flowchart of a routine in which the ECU 20 executes processing for determining the octane number (RON) of the fuel used. As shown in this figure, first, after starting cranking, the ECU 20 performs control so that the first explosion cycle is executed in the CPS-equipped cylinder (step 100). As this method, for example, fuel may be injected first into the CPS-equipped cylinder after cylinder determination by cranking. After that, when self-ignition occurs in the first explosion cycle, the in-cylinder pressure changes. The ECU 20 detects the in-cylinder pressure change using the in-cylinder pressure sensor 22, and acquires the maximum value as Pmax (step 102). Next, the acquired Pmax is corrected based on the water temperature and the in-cylinder air amount (step 104). The ECU 20 stores the relationship between Pmax and octane number (RON) as a map. The ECU 20 specifies an octane number (RON) corresponding to Pmax from the map (step 106).

  As described above, according to the system of the present embodiment, it is possible to determine the octane number (RON) of the fuel used using the change in the in-cylinder pressure due to self-ignition in the initial explosion cycle at the start. Accordingly, it is possible to determine the octane number (RON) of the fuel used by the existing system configuration without separately mounting a sensor or the like for detecting the fuel property. In addition, since the octane number (RON) of the fuel used can be ascertained before the complete explosion, various controls according to the octane number (RON) can be performed immediately after the engine is started.

  By the way, in Embodiment 1 mentioned above, although it does not specifically limit about the driving | running condition of the initial explosion cycle at the time of starting, the determination accuracy of a fuel property is raised more by making the driving | running condition concerned into the conditions which a self-ignition tends to occur It becomes possible. Specifically, self-ignition in the first explosion cycle is more likely to occur as the compression ratio is higher. For this reason, by increasing the in-cylinder air amount in the initial explosion cycle, it is possible to effectively increase the compression ratio and create conditions advantageous for self-ignition. As a method for increasing the in-cylinder air amount, for example, a method of expanding the opening of the throttle valve or a closing timing (IVC) of the intake valve in a system including an electric variable valve timing mechanism (electric VVT). A method of delaying the angle can be considered. Further, a variable compression ratio (VCR) engine may be used as the internal combustion engine 10 to increase the compression ratio.

  In addition, regarding the operating conditions of the first explosion cycle at the time of starting, the self-ignition in the first explosion cycle is more likely to occur as the water temperature is higher. Therefore, when the water temperature detected by the water temperature sensor is lower than a predetermined reference value, the determination of the fuel property may be limited. As a result, it is possible to effectively suppress erroneous determination when self-ignition does not occur.

  In the first embodiment described above, Pmax detected by the CPS 22 is corrected using the in-cylinder air amount and the water temperature, so that these operating conditions are reflected in the determination of the fuel property. Is not limited to this. That is, a map in which an octane number (RON) is associated with Pmax is stored for each operating condition such as in-cylinder air amount and water temperature, and the fuel reflecting the operating condition is selected by selecting a map according to the operating condition. The property may be determined. Further, regarding the operation conditions to be corrected, the operation conditions are not limited to the in-cylinder air amount and the water temperature, and other operation conditions such as the injection amount and the atmospheric pressure may be used as further correction objects.

  In the first embodiment described above, the CPS 22 is mounted on one of the cylinders. However, the CPS 22 may be mounted on the plurality of cylinders. In this case, the initial explosion cycle may be controlled so as to be performed in any CPS-equipped cylinder.

  In Embodiment 1 described above, the maximum value (Pmax) of in-cylinder pressure change due to self-ignition in the initial explosion cycle is used to determine the octane number (RON) of the fuel used. The index of the in-cylinder pressure change is not limited to the maximum value. That is, since self-ignition is a phenomenon synchronized with the crank angle, the rate of change of the in-cylinder pressure up to Pmax inevitably increases as Pmax increases. Therefore, as the rate of change of the in-cylinder pressure, for example, an in-cylinder pressure change amount (ΔP / ΔCA °) per unit crank angle is acquired, and the octane number (RON) of the fuel used is determined using the in-cylinder pressure change amount. It is good as well.

  In the first embodiment described above, the CPS 22 corresponds to the “in-cylinder pressure detecting means” in the first aspect of the invention, and the ECU 20 executes the processing of steps 102 and 106 described above, thereby The “fuel property determination means” in the first aspect of the invention is realized.

  In the first embodiment described above, the ECU 20 executes the process of step 100, so that the “cylinder selection means” in the fourth aspect of the invention executes the process of step 104. The “correction means” in the sixth invention is realized.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment can be realized by executing a routine shown in FIG. 6 to be described later using the system shown in FIG.

  The system of the present embodiment includes a knocking control system (hereinafter referred to as “KCS”). The KCS is a system that avoids knocking by retarding the ignition timing when the occurrence of knocking or its sign is detected by a knock sensor. However, there is a limit to the operating range of KCS. That is, for example, when fuel with an octane number lower than the octane number (RON) assumed by the KCS is supplied, it is assumed that the KCS cannot sufficiently cope and knocking cannot be avoided. .

  Here, as described above, the system according to the present embodiment can determine the octane number (RON) of the fuel used based on the Pmax of the self-ignition in the initial explosion cycle. Therefore, in the system according to the second embodiment, when the determined octane number (RON) is lower than the KCS operation limit, the output of the internal combustion engine 10 is limited to avoid knocking and a warning is issued to the driver. I will do it. In addition, as output restrictions, implementing limp home mode, fail safe mode, etc. can be considered, for example. Further, as the warning, for example, MIL lighting or warning sound can be considered. This makes it possible to effectively avoid the occurrence of knocking even when poor fuel having a low octane number is supplied.

[Specific Processing in Second Embodiment]
FIG. 6 is a flowchart of a routine in which the ECU 20 executes a process for avoiding knocking. As shown in this figure, first, the ECU 20 performs control so that the initial explosion cycle is executed in the CPS-equipped cylinder after the start of cranking (step 200). After that, when self-ignition occurs in the first explosion cycle, the in-cylinder pressure changes. The ECU 20 detects the in-cylinder pressure change using the in-cylinder pressure sensor 22, and acquires the maximum value as Pmax (step 202). Next, the acquired Pmax is corrected based on the water temperature and the in-cylinder air amount (step 204). The ECU 20 stores the relationship between Pmax and octane number (RON) as a map. The ECU 20 specifies an octane number (RON) corresponding to Pmax from the map (step 206). In steps 200 to 206, the same processing as that in steps 100 to 106 is executed.

  Next, it is determined whether or not the octane number (RON) determined in step 206 is lower than a predetermined reference value (step 208). The predetermined reference value is a lower limit value of the KCS operating range, and a value stored in advance in the ECU 20 is read. As a result, if the establishment of the octane number (RON) <reference value is not recognized, it is determined by the KCS that knocking can be avoided, and this routine is immediately terminated. On the other hand, if it is determined in step 208 that the octane number (RON) <reference value is established, it is determined by the KCS that the occurrence of knocking cannot be avoided, the process proceeds to the next step, and the output limit of the internal combustion engine 10 is limited. And a warning is given to the driver (step 210).

  As described above, according to the system of the second embodiment, since the output of the internal combustion engine 10 is limited when the octane number (RON) is lower than the KCS operation limit, occurrence of knocking can be effectively avoided. it can.

  In the second embodiment described above, the CPS 22 corresponds to the “in-cylinder pressure detecting means” in the first aspect of the invention, and the ECU 20 executes the processing of steps 202 and 206 described above, whereby the first The “fuel property determination means” in the first aspect of the invention is realized.

  In the second embodiment described above, the ECU 20 executes the process of step 200, so that the “cylinder selection means” in the fourth aspect of the invention executes the process of step 104. The “correction means” in the sixth invention is realized.

  In the second embodiment described above, the “knock suppression means” according to the eighth to tenth aspects of the present invention is realized by the ECU 20 executing the processing of steps 208 and 210 described above.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Fuel tank 14 Fuel piping 16 Exhaust passage 18 Exhaust purification catalyst 20 ECU (Electronic Control Unit)
22 In-cylinder pressure sensor (CPS)

Claims (10)

A spark ignition internal combustion engine control device,
In-cylinder pressure detecting means for detecting in-cylinder pressure of one or more cylinders of the internal combustion engine;
In an initial explosion cycle in which spark ignition is performed for the first time after cranking of the internal combustion engine is started, a change in in-cylinder pressure due to self-ignition after the start of the compression stroke and before execution of spark ignition is detected by the in-cylinder pressure detecting means, Fuel property determination means for determining the fuel property of the fuel of the internal combustion engine based on a change;
A control device for an internal combustion engine, comprising:   2. The internal combustion engine according to claim 1, wherein the fuel property determination means includes means for acquiring a maximum value of the in-cylinder pressure change, and determines the fuel property of the fuel of the internal combustion engine based on the maximum value. Engine control device.   2. The internal combustion engine according to claim 1, wherein the fuel property determination means includes means for acquiring a change speed of the in-cylinder pressure change, and determines the fuel property of the fuel of the internal combustion engine based on the change speed. Engine control device. The in-cylinder pressure detecting means is an in-cylinder pressure sensor mounted on a specific cylinder that is one of the one or more cylinders.
4. The control device for an internal combustion engine according to claim 1, further comprising cylinder selection means for performing the initial explosion cycle in the specific cylinder.   The control device for an internal combustion engine according to any one of claims 1 to 4, further comprising control means for performing control for increasing a compression ratio of the initial explosion cycle.   The control apparatus for an internal combustion engine according to any one of claims 1 to 5, further comprising correction means for correcting the change in the in-cylinder pressure using any one of a water temperature and an in-cylinder air amount of the internal combustion engine. .   The control apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the fuel property determination means determines an octane number of fuel of the internal combustion engine.   8. The internal combustion engine according to claim 7, further comprising knock suppression means for performing control for suppressing occurrence of knocking when the octane number determined by the fuel property determination means is lower than a predetermined reference value. Control device.   9. The control apparatus for an internal combustion engine according to claim 8, wherein the knock suppression means includes means for limiting an output of the internal combustion engine.   The control device for an internal combustion engine according to claim 8 or 9, wherein the knock suppression means includes warning means for issuing a warning to a user.

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