JP2008196409A - Combustion control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more accurately define fuel properties in a combustion control device for an internal combustion engine. <P>SOLUTION: This device is provided with a combustion condition change means changing parameters relating to a combustion condition of the internal combustion engine to a direction causing misfire of the internal combustion engine, a rotation speed fluctuation detection means detecting rotation speed fluctuation of the internal combustion engine, and a fuel property estimation means estimating fuel properties of the internal combustion engine based on rotation speed fluctuation of the internal combustion engine and values of the parameters when the combustion condition of the internal combustion engine is changed by the combustion condition change means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  The cetane number is used as a measure representing the ignitability of fuel in a diesel engine. This cetane number may change with each refueling.

Here, a technique for controlling the fuel injection pressure, the fuel injection amount, the fuel injection timing, or the like according to the fuel properties such as the cetane number of the fuel is known (for example, see Patent Document 1).
JP 2005-48703 A Japanese Patent Laying-Open No. 2005-320872 JP 2004-239230 A JP 2006-16994 A JP 2004-340026 A

  Thus, in order to control an internal combustion engine according to fuel properties, such as a cetane number, it is necessary to obtain | require a fuel property more correctly.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a technique capable of more accurately obtaining fuel properties in a combustion control device for an internal combustion engine.

In order to achieve the above object, a combustion control apparatus for an internal combustion engine according to the present invention provides:
Combustion state changing means for changing a parameter related to the combustion state of the internal combustion engine in a direction in which the internal combustion engine misfires;
Rotation fluctuation detecting means for detecting rotation fluctuation of the internal combustion engine;
Fuel property estimating means for estimating the fuel property of the internal combustion engine based on the value of the parameter when the combustion state of the internal combustion engine changes by the combustion state changing means and the rotational fluctuation of the internal combustion engine;
It is characterized by comprising.

  Here, the combustion state changing means changes the parameter in the direction in which the internal combustion engine misfires, that is, the direction in which the combustion state deteriorates. Here, misfire refers to a flame that does not ignite the mixture, extinguishes without igniting the flame after igniting the mixture, or when flame propagation is performed but a large amount of mixture remains. Can be included when the disappears. Further, misfiring may be caused when an air-fuel mixture exceeding an allowable ratio in the air-fuel mixture supplied into the cylinder remains without being burned. Furthermore, it may be misfired when the combustion state is deteriorated.

  The parameter related to the combustion state of the internal combustion engine is a value that changes the combustion state of the internal combustion engine by changing the parameter or changing the parameter. For example, the amount of gas in the cylinder, the amount of fuel injection , The fuel injection timing, or the cylinder internal temperature during the compression stroke. Further, for example, throttle opening, intake valve or exhaust valve opening / closing timing correlated with these values may be used as parameters.

  And the misfire of an internal combustion engine can be induced by changing the said parameter in the direction where it is easy to misfire. If the combustion state deteriorates even without misfiring, the torque generated from the internal combustion engine decreases, so that the rotational fluctuation of the internal combustion engine increases. Here, since the combustion state of the internal combustion engine varies depending on the fuel properties, the magnitude of the rotational fluctuation varies depending on the fuel properties. That is, since there is a correlation between the rotational fluctuation of the internal combustion engine and the fuel property, if the relationship between the parameter value, the magnitude of the rotational fluctuation, and the fuel property is obtained in advance, the parameter and the rotational fluctuation are obtained. Thus, the fuel property can be obtained. It should be noted that the fuel property may be estimated based on the rotational fluctuation when the internal combustion engine actually misfires, or the fuel property may be estimated based on the rotational fluctuation before the misfire.

  The present invention further includes a variable valve timing mechanism capable of changing a valve opening timing or a valve closing timing of the intake valve or the exhaust valve of the internal combustion engine, and the combustion state changing means is a valve opening timing of the intake valve or the exhaust valve. Alternatively, the valve closing timing is gradually changed to a misfire direction, and the fuel property estimating means estimates the fuel property based on the rotation fluctuation of the internal combustion engine and the opening timing or closing timing of the intake valve or exhaust valve. Can do.

  Here, by changing the opening timing or closing timing of the intake valve or the exhaust valve, the amount of air in the cylinder and the actual compression ratio change. The internal combustion engine can be misfired by changing the opening / closing timing of the intake valve or the exhaust valve in such a direction that the amount of air in the cylinder decreases or the actual compression ratio decreases. If the valve opening timing or valve closing timing of the intake valve or exhaust valve is used as a parameter, and the relationship between the parameter, rotation fluctuation, and fuel property is obtained in advance, the fuel property is obtained based on the parameter and rotation fluctuation. be able to.

  The present invention further includes a throttle capable of changing the cross-sectional area of the intake passage of the internal combustion engine, the combustion state changing means gradually reduces the opening of the throttle, and the fuel property estimating means is the internal combustion engine of the internal combustion engine. The fuel property can be estimated based on the rotation fluctuation and the throttle opening.

  Here, if the opening of the throttle is reduced, the amount of intake air decreases and the pump loss increases, so that the internal combustion engine can be misfired. If the opening of the throttle is used as a parameter and the relationship between the parameter, rotation fluctuation, and fuel property is obtained in advance, the fuel property can be obtained based on the parameter and rotation fluctuation. Note that the intake negative pressure increases by reducing the throttle opening, but this intake negative pressure may be used as a parameter.

  In the present invention, a fuel injection valve for injecting fuel into a cylinder of the internal combustion engine is further provided, and the combustion state changing means gradually retards the fuel injection timing from the fuel injection valve, and the fuel property estimation means The fuel property can be estimated based on the rotational fluctuation of the internal combustion engine and the fuel injection timing.

  If fuel is not injected even if the piston passes the compression top dead center, the piston descends thereafter, so that the gas temperature in the cylinder decreases. And the later the fuel injection timing, the easier it is to misfire because the gas temperature in the cylinder is lower. Then, if the retard amount of the fuel injection timing is used as a parameter, and the relationship between the parameter, the rotation fluctuation, and the fuel property is obtained in advance, the fuel property can be obtained based on the parameter and the rotation fluctuation.

  In the present invention, the combustion state changing means can change a parameter related to the combustion state of the internal combustion engine in a direction of misfire during the idling operation of the internal combustion engine.

That is, during idling of the internal combustion engine, the engine speed is low and the engine speed is substantially constant, so that it is easy to detect rotational fluctuations. Therefore, the fuel property can be obtained more accurately by detecting the rotational fluctuation during the idling operation.

  The present invention further includes a fuel tank for storing fuel of the internal combustion engine, and the combustion state changing means misfires a parameter related to the combustion state of the internal combustion engine when the fuel tank is refueled. Can be changed.

  That is, when a fuel having a different property is added to the fuel tank, the property of the fuel in the tank changes. By obtaining the fuel properties at this time, it is possible to optimize the subsequent combustion control of the internal combustion engine. Here, the time when the fuel is supplied may be a time when the fuel in the fuel tank increases or a time when the fuel supply port provided in the fuel tank is opened.

  According to the combustion control apparatus for an internal combustion engine according to the present invention, the fuel property can be obtained more accurately.

  Hereinafter, specific embodiments of a combustion control apparatus for an internal combustion engine according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine 1 to which a combustion control device for an internal combustion engine according to the present embodiment is applied and an intake system thereof. The internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine.

  An intake passage 2 is connected to the internal combustion engine 1. A throttle 3 is provided in the middle of the intake passage 2. The throttle 3 is opened and closed by an electric actuator.

  The internal combustion engine 1 is provided with a fuel injection valve 4 that supplies fuel into the cylinder of the internal combustion engine 1.

  Further, the internal combustion engine 1 is provided with an intake valve 5, and the intake valve 5 is opened and closed by an intake side camshaft 6. An intake pulley 7 is attached to the intake camshaft 6. Further, a variable valve timing mechanism (hereinafter referred to as “VVT”) 8 that can change the relative rotational phase between the intake camshaft 6 and the intake pulley 7 is provided. The VVT 8 controls the relative rotational phase between the intake side camshaft 6 and the intake side pulley 7 in accordance with a command from the ECU 10 described later.

  The rotational drive of the intake pulley 7 is performed by the driving force of the crankshaft 9. As a result, the intake side camshaft 6 is rotationally driven to open and close the intake valve 5.

  The internal combustion engine 1 configured as described above is provided with an ECU 10 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 10 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

In addition to the above sensors, the ECU 10 includes an accelerator opening sensor 12 that outputs an electrical signal corresponding to the amount of depression of the accelerator pedal 11 by the driver, and a crank position sensor 13 that detects the rotational speed of the crankshaft 9. Connected via electrical wiring, the output signals of these various sensors are input to the ECU 10. Then, the engine load is detected by the accelerator opening sensor 12, and the engine speed and the angular speed of the crankshaft 9 are detected by the crank position sensor 13.

  On the other hand, the throttle 10, the fuel injection valve 4, and the VVT 8 are connected to the ECU 10 through electric wiring, and these devices are controlled by the ECU 10.

  Here, when the combustion state of the internal combustion engine 1 deteriorates, the engine generated torque decreases, so that the rotational fluctuation of the internal combustion engine 1 increases. And when rotation fluctuation of internal-combustion engine 1 becomes larger than a threshold, it can be judged that it has misfired. Here, for example, the rotational fluctuation of the internal combustion engine 1 may be larger as the square of the difference between the maximum value and the minimum value of the angular velocity of the crankshaft 9 is smaller.

  In this embodiment, the actual compression ratio is lowered by retarding the opening / closing timing of the intake valve 5 with the VVT 8 during the idling operation of the internal combustion engine 1. Here, a value obtained by multiplying the distance that the piston 15 moves from the closing position of the intake valve to the top dead center by the cross-sectional area of the cylinder is hereinafter referred to as “execution stroke volume” or “actual displacement”. Further, a value obtained by dividing the sum of the gap volume and the execution stroke volume by the gap volume is hereinafter referred to as “actual compression ratio”. When the actual compression ratio is reduced, the temperature rise in the compression stroke is reduced, and therefore misfire is likely to occur in the internal combustion engine 1.

  Therefore, in this embodiment, the fuel property (for example, cetane number) is estimated based on the rotational fluctuation of the internal combustion engine 1 when the actual compression ratio is gradually decreased during the idling operation of the internal combustion engine 1. That is, since there is a correlation between the cetane number of the fuel and the rotational fluctuation of the internal combustion engine 1, the cetane number of the fuel is estimated based on the magnitude of the rotational fluctuation of the internal combustion engine 1. For example, the opening timing of the intake valve 5 is set after the top dead center.

  The idling operation is performed because the rotational speed of the internal combustion engine 1 is low and the rotational speed is substantially constant, so that the rotational fluctuation of the internal combustion engine 1 is easily detected. Also, the cetane number changes suddenly after refueling, for example, when the lid of the fuel filler provided in the fuel tank is opened or the amount of fuel obtained by the sensor for detecting the remaining amount of fuel increases In this case, the cetane number is estimated on the assumption that refueling has been performed.

  Here, FIG. 2 is a graph showing the relationship among the retard amount of VVT 8, the rotational fluctuation of internal combustion engine 1, and the cetane number. The retard amount of the VVT 8 is a value indicating how much the engine is delayed from the opening / closing timing of the intake valve 8 set based on the rotational speed and load of the internal combustion engine, and is represented by a crank angle. Since the actual compression ratio decreases as the retard amount of VVT 8 increases, the combustion state of the internal combustion engine 1 deteriorates and the rotational fluctuation increases. That is, when the rotational fluctuation is small despite the large amount of retardation of the VVT 8, it can be determined that fuel with a high cetane number (for example, a cetane number of 50 or more) is being used. On the other hand, when the rotational fluctuation is large despite the small amount of retardation of the VVT 8, it can be determined that a fuel having a low cetane number (for example, a cetane number of less than 40) is being used.

  As described above, the relationship shown in FIG. 2 is obtained by experiments and mapped in advance, and the cetane number can be obtained by substituting the retardation amount and the rotational fluctuation of the VVT 8 into the map.

  In this embodiment, the actual compression ratio is lowered by changing the opening / closing timing of the intake valve 5. However, if the opening timing and closing timing of the intake valve 5 can be changed separately, either The actual compression ratio may be lowered by changing only one of them. If at least one of the valve opening timing and the valve closing timing of the exhaust valve 16 can be changed, the actual compression ratio is reduced by changing at least one of the valve opening timing and the valve closing timing of the exhaust valve 16. Also good.

Furthermore, in this embodiment, the cetane number is estimated based on the rotational fluctuation, but instead, the combustion state is detected by measuring the pressure in the cylinder of the internal combustion engine 1, and based on the combustion state The cetane number may be estimated. Further, the relationship between the retard amount of VVT 8 at which the internal combustion engine 1 misfires and the cetane number of the fuel is obtained in advance by experiments or the like, and the fuel amount is determined based on the retard amount of VVT 8 when the internal combustion engine 1 actually misfires. You may ask for cetane number.

  If the estimated cetane number is less than the allowable value, for example, a lamp may be lit to warn the driver. In this case, measures for improving the combustion state may be taken at the same time. For example, the glow plug is energized to increase the gas temperature in the cylinder. Further, when an intercooler is provided, a passage that bypasses the intercooler is also provided, and the temperature of the intake air is increased so that the intake air bypasses the intercooler. Further, when an exhaust throttle valve is provided, the temperature in the cylinder is raised by increasing the load of the internal combustion engine 1 or increasing the internal EGR gas by moving the exhaust throttle valve to the closing side. . Further, by delaying the opening timing of the intake valve 5 by the VVT 8, the momentum of the intake air is increased or the pressure of the intake air is increased. Further, the compression end temperature is raised by advancing the closing timing of the intake valve 5 by the VVT 8. Further, if the temperature at which the thermostat opens is adjusted to open at a higher temperature, the temperature in the cylinder can be raised. Furthermore, when the load of the internal combustion engine 1 is increased by increasing the power generation amount of the generator provided in the internal combustion engine 1, the temperature in the cylinder rises. By performing at least one of these, the combustion state can be improved.

  Further, the estimated cetane number is stored in the ECU 10 even after the internal combustion engine 1 is stopped, and the fuel injection timing is corrected, for example, to improve the combustion state when the internal combustion engine 1 is operated next time.

  As described above, according to the present embodiment, the fuel property can be estimated based on the magnitude of the rotational fluctuation of the internal combustion engine 1 when the opening / closing timing of the intake valve 5 is delayed by the VVT 8. Therefore, the internal combustion engine 1 can be controlled according to the estimated fuel property.

  In this embodiment, the ECU 10 that retards the opening / closing timing of the intake valve 5 by the VVT 8 corresponds to the combustion state changing means in the present invention. In the present embodiment, the ECU 10 that detects the rotational fluctuation of the internal combustion engine 1 based on the change in the angular velocity of the crankshaft 9 corresponds to the rotational fluctuation detecting means in the present invention. Furthermore, in this embodiment, the ECU 10 that estimates the cetane number of the fuel based on the retard amount of the VVT 8 and the rotational fluctuation of the internal combustion engine 1 corresponds to the fuel property estimation means in the present invention.

  In the present embodiment, the opening degree of the throttle 3 is gradually reduced during the idling operation of the internal combustion engine 1, and based on the negative pressure downstream of the throttle 3 at that time (hereinafter referred to as intake negative pressure). Estimate fuel properties (eg cetane number). Here, when the intake negative pressure is increased, the temperature rise in the cylinder during the compression stroke is reduced, so that the combustion state is deteriorated and misfire is easily caused. That is, in the first embodiment, the cetane number is estimated by increasing the rotation fluctuation by the VVT 8, but in this embodiment, the cetane number is estimated by increasing the rotation fluctuation by reducing the opening of the throttle 3. . The intake negative pressure is detected by a pressure sensor 17 attached to the intake passage 2 downstream of the throttle 3.

  Here, FIG. 3 is a diagram showing the relationship among the intake negative pressure, the rotational fluctuation of the internal combustion engine 1, and the cetane number. Since the intake negative pressure increases as the throttle 3 is closed, the combustion state of the internal combustion engine 1 deteriorates and the rotational fluctuation increases. That is, when the rotational fluctuation is small even though the intake negative pressure is large, it can be determined that fuel with a high cetane number (for example, a cetane number of 50 or more) is being used. On the other hand, when the rotational fluctuation is large even though the intake negative pressure is small, it can be determined that fuel with a low cetane number (for example, less than cetane number 40) is used.

  Thus, the cetane number can be obtained by previously obtaining the relationship of FIG. 3 through experiments or the like and mapping it, and substituting the intake negative pressure and the rotational fluctuation into the map.

  Note that the opening degree of the throttle 3 may be used instead of the intake negative pressure. That is, the relationship between the throttle opening, the rotational fluctuation of the internal combustion engine 1 and the cetane number is obtained by an experiment or the like in advance and mapped, and the cetane number is obtained by substituting the opening and rotational fluctuation of the throttle 3 into the map. May be.

  As described above, according to this embodiment, the fuel property can be estimated based on the magnitude of the rotational fluctuation of the internal combustion engine 1 when the throttle 3 is closed. Therefore, the internal combustion engine 1 can be controlled according to the estimated fuel property.

  In this embodiment, the ECU 10 that reduces the opening of the throttle 3 corresponds to the combustion state changing means in the present invention. In this embodiment, the ECU 10 that estimates the cetane number of the fuel based on the opening degree of the throttle 3 and the rotational fluctuation of the internal combustion engine 1 corresponds to the fuel property estimating means in the present invention.

  In this embodiment, the cetane number of the fuel is estimated while increasing the rotational fluctuation of the internal combustion engine 1 by changing the fuel injection timing from the fuel injection valve 4. Here, since the temperature in the cylinder decreases during the expansion stroke, if the retard amount of the fuel injection timing increases, the combustion state deteriorates and misfire is likely to occur. That is, in the first embodiment, the cetane number is estimated by increasing the rotational fluctuation by the VVT 8, but in this embodiment, the rotational fluctuation is increased by delaying the fuel injection timing to estimate the cetane number.

  Here, FIG. 4 is a graph showing the relationship among the retard amount of the fuel injection timing, the rotational fluctuation of the internal combustion engine 1, and the cetane number. The retard amount of the fuel injection timing is a value indicating how much the fuel injection timing is delayed from the fuel injection timing of the fuel injection valve 4 set based on the rotation speed and load of the internal combustion engine, and is represented by a crank angle. . As the retard amount of the fuel injection timing is increased, the combustion state of the internal combustion engine 1 is deteriorated and the rotational fluctuation is increased. That is, when the rotational fluctuation is small despite the large retardation amount of the fuel injection timing, it can be determined that fuel with a high cetane number (for example, a cetane number of 50 or more) is being used. On the other hand, when the rotational fluctuation is large despite the small retardation amount of the fuel injection timing, it can be determined that the fuel having a low cetane number (for example, less than cetane number 40) is used.

  As described above, the relationship shown in FIG. 4 is obtained in advance through experiments or the like and mapped, and the cetane number can be obtained by substituting the retard amount and the rotational fluctuation of the fuel injection timing into the map.

  When the internal combustion engine 1 has a plurality of cylinders, the delay of the fuel injection timing may be performed by only one of the cylinders. By doing so, vibration of the internal combustion engine 1 can be suppressed.

  As described above, according to the present embodiment, the fuel property can be estimated based on the magnitude of the rotational fluctuation of the internal combustion engine 1 when the fuel injection timing from the fuel injection valve 4 is delayed. Therefore, the internal combustion engine 1 can be controlled according to the estimated fuel property.

  In this embodiment, the ECU 10 that retards the fuel injection timing corresponds to the combustion state changing means in the present invention. In this embodiment, the ECU 10 that estimates the cetane number of the fuel based on the retard amount of the fuel injection timing and the rotational fluctuation of the internal combustion engine 1 corresponds to the fuel property estimation means in the present invention.

It is a figure which shows schematic structure of the internal combustion engine which applies the combustion control apparatus of the internal combustion engine which concerns on an Example, and its intake system. It is the figure which showed the relationship between the retard amount of VVT, the rotation fluctuation | variation of an internal combustion engine, and a cetane number. It is the figure which showed the relationship between intake negative pressure, the rotation fluctuation | variation of an internal combustion engine, and a cetane number. It is the figure which showed the relationship between the retard amount of fuel-injection time, the rotation fluctuation | variation of an internal combustion engine, and a cetane number.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake passage 3 Throttle 4 Fuel injection valve 5 Intake valve 6 Intake side camshaft 7 Intake side pulley 8 Variable valve timing mechanism (VVT)
9 Crankshaft 10 ECU
11 Accelerator pedal 12 Accelerator opening sensor 13 Crank position sensor 15 Piston 16 Exhaust valve 17 Pressure sensor

Claims (6)

Combustion state changing means for changing a parameter related to the combustion state of the internal combustion engine in a direction in which the internal combustion engine misfires;
Rotation fluctuation detecting means for detecting rotation fluctuation of the internal combustion engine;
Fuel property estimating means for estimating the fuel property of the internal combustion engine based on the value of the parameter when the combustion state of the internal combustion engine changes by the combustion state changing means and the rotational fluctuation of the internal combustion engine;
A combustion control device for an internal combustion engine, comprising:   A variable valve timing mechanism capable of changing a valve opening timing or a valve closing timing of the intake valve or the exhaust valve of the internal combustion engine, and the combustion state changing means sets the valve opening timing or the valve closing timing of the intake valve or the exhaust valve. The fuel property estimating means estimates the fuel property based on the rotational fluctuation of the internal combustion engine and the opening timing or closing timing of the intake valve or the exhaust valve. Item 6. A combustion control apparatus for an internal combustion engine according to Item 1.   A throttle capable of changing a cross-sectional area of the intake passage of the internal combustion engine, the combustion state changing means gradually reduces the throttle opening, and the fuel property estimating means 2. The combustion control device for an internal combustion engine according to claim 1, wherein the fuel property is estimated based on the opening degree.   The fuel injection valve for injecting fuel into the cylinder of the internal combustion engine is further provided, the combustion state changing means gradually retards the fuel injection timing from the fuel injection valve, and the fuel property estimation means is provided for the internal combustion engine. 2. The combustion control apparatus for an internal combustion engine according to claim 1, wherein the fuel property is estimated based on the rotational fluctuation and the fuel injection timing.   The internal combustion engine according to any one of claims 1 to 4, wherein the combustion state changing means changes a parameter related to the combustion state of the internal combustion engine in a misfire direction during the idling operation of the internal combustion engine. Combustion control device.   The fuel tank further comprises a fuel tank for storing fuel of the internal combustion engine, and the combustion state changing means changes a parameter related to the combustion state of the internal combustion engine to a misfire direction when the fuel tank is refueled. 6. A combustion control device for an internal combustion engine according to claim 1, wherein the combustion control device is an internal combustion engine.

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