JP4356079B2 - Fuel property determination device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel property determination device for an internal combustion engine that determines the fuel property of the fuel used based on combustion parameters that are information on the combustion state of the internal combustion engine.

  Conventionally, as a fuel property determination device for an internal combustion engine, for example, heavy fuel (has a heavy fuel property) is used when the rotational speed of the internal combustion engine is lower than a target rotational speed by a predetermined value or more during a predetermined period after starting. There is something that is determined to be. In some cases, the fuel is determined to be heavy fuel when the integrated value of the rotational speed of the internal combustion engine in a predetermined cycle period after the start is equal to or less than a predetermined value.

  However, as described above, in the method for determining the fuel property based on the rotation speed of the internal combustion engine, the fluctuation in the rotation speed of the internal combustion engine due to the difference in the fuel property is caused by the friction of the internal combustion engine. The property cannot be determined accurately. Moreover, since it is difficult to accurately detect the heavy degree of fuel, it is difficult to determine an intermediate fuel (a fuel having an intermediate fuel property between a light fuel and a heavy fuel).

Therefore, for example, as described in Patent Document 1 (Japanese Patent Publication No. 7-50098), the combustion speed is calculated from the combustion pressure of the internal combustion engine, and this combustion speed is used as a judgment value (combustion speed of the reference fuel). There is a fuel property that is determined by comparison.
Japanese Patent Publication No. 7-50098 (first page, etc.)

  In general, the ignition timing of an internal combustion engine has a large contribution to the combustion state (combustion speed, combustion period, etc.), and when the ignition timing varies, the combustion state varies accordingly and the combustion speed varies. For this reason, in the case where the fuel property is determined by using the combustion speed as in Patent Document 1, the fuel property may be erroneously determined by the variation in the combustion speed caused by the variation in the ignition timing.

  The present invention has been made in view of such circumstances, and therefore the object of the present invention is to prevent misjudgment of fuel properties caused by variations in the combustion state due to variations in ignition timing during the fuel property determination process. An object of the present invention is to provide a fuel property determination device for an internal combustion engine that can improve the determination accuracy of the fuel property.

To achieve the above object, the invention according to claim 1 calculates a combustion parameter serving as information on the combustion state based on the in-cylinder pressure of the internal combustion engine by the combustion parameter calculating means, and uses the calculated combustion parameter based on the calculated combustion parameter. In the fuel property determination device for an internal combustion engine that determines the fuel property by the fuel property determination unit, the ignition timing of the internal combustion engine is fixed or the fluctuation thereof is suppressed (limited) until the fuel property is determined by the fuel property determination unit. The first feature is that the timing fixing control is executed by the ignition timing fixing control means . Further, the ignition timing fixing control is executed after a predetermined number of explosions have ended after the cranking of the internal combustion engine is started. It is the feature of.

  In this configuration, until the determination of the fuel property based on the combustion parameter is completed, the ignition timing is fixed or the variation of the ignition timing is controlled to reduce the fluctuation range, thereby causing the erroneous determination of the fuel property. The fuel properties can be accurately determined based on the combustion parameters in a state where there is almost no fluctuation in the combustion state due to the fluctuation in the ignition timing. This makes it possible to prevent erroneous determination of the fuel property caused by the variation in the combustion state due to the variation in the ignition timing during the fuel property determination processing period by the ignition timing fixing control, thereby improving the accuracy of determining the fuel property.

In this case, as in claim 1, if to perform the ignition timing fixed control from the end of the explosion of a predetermined number of times after the cranking start of the internal combustion engine, most of the variation of the combustion state due to variations in the point fire timing the fuel property may be determined accurately by eliminating the state.

Further, as in claim 2 , the ignition timing during the ignition timing fixing control may be set according to the temperature of the internal combustion engine. In this way, the ignition timing during the ignition timing fixing control can be changed and set to an appropriate value in response to the change of the appropriate ignition timing according to the temperature of the internal combustion engine.

Further, as in claim 3, the combustion period may be calculated as the combustion parameter. Since the combustion period changes according to the fuel property, the combustion period is a parameter that accurately reflects the fuel property.

Further, as in claim 4 , the fuel property may be determined based on the integrated value of the combustion parameter in a predetermined period. Since the integrated value of the combustion parameter in the predetermined period is a parameter for comprehensively evaluating the combustion state in the predetermined period, it is possible to further improve the accuracy of determining the fuel property.

Further, in consideration of the characteristic that the combustion state changes as the fuel evaporability changes according to the temperature of the internal combustion engine and the combustion parameters such as the combustion period and the combustion speed change, as in claim 5 . In addition, the determination value for determining the fuel property based on the combustion parameter may be set according to the temperature of the internal combustion engine. If it does in this way, the judgment value at the time of judging fuel property can be set as an appropriate value according to the temperature of an internal-combustion engine.

Hereinafter, an embodiment embodying the best mode for carrying out the present invention will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 that detects the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 for introducing air into each cylinder of the engine 11, and a fuel injection valve 21 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 20 of each cylinder. Yes. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each ignition plug 22.

  On the other hand, the exhaust pipe 23 of the engine 11 is provided with an exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or rich / lean of the exhaust gas. A catalyst 25 such as a three-way catalyst for purifying gas is provided.

  A cooling water temperature sensor 26 that detects the cooling water temperature and a crank angle sensor 28 that outputs a pulse signal each time the crankshaft 27 of the engine 11 rotates a predetermined crank angle are attached to the cylinder block of the engine 11. Based on the output signal of the crank angle sensor 28, the crank angle and the engine speed are detected.

  Further, the cylinder head of the engine 11 is provided with an in-cylinder pressure sensor 30 for detecting the in-cylinder pressure for each cylinder (or only a specific cylinder). The in-cylinder pressure sensor 30 may be of a type integrated with the spark plug 22, or may be of a type attached so that a sensor part separate from the spark plug 22 faces the combustion chamber. Also good.

  Outputs of these various sensors are input to a control circuit (hereinafter referred to as “ECU”) 29. The ECU 29 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 21 according to the engine operating state. The ignition timing of the spark plug 22 is controlled.

  Further, the ECU 29 executes a fuel property determination routine of FIG. 4 to be described later, thereby calculating a combustion period as a combustion parameter serving as combustion state information based on the in-cylinder pressure detected by the in-cylinder pressure sensor 30, The fuel property of the used fuel is determined by comparing the integrated value of the combustion period in the period with a predetermined determination value.

Here, the calculation method of a combustion period is demonstrated based on FIG.2 and FIG.3.
FIG. 2 is a time chart showing the relationship between the in-cylinder pressure and the heat generation amount.
FIG. 3 is a time chart showing the relationship between the total heat generation amount and the combustion period.

In general, the heat generation amount at the crank angle θ is calculated by the following equation.
Heat generation amount = {dP (θ) · V (θ) + κ · P (θ) · dV (θ)} / (κ−1)
κ: Specific heat ratio
P (θ): In-cylinder pressure at crank angle θ
dP (θ): In-cylinder pressure change amount at crank angle θ
V (θ): combustion chamber volume at crank angle θ
dV (θ): Combustion chamber volume change at crank angle θ

Further, the total heat generation amount in the combustion section from the start of combustion to the end of combustion is calculated by the following equation.
Total heat generation amount = ∫ (heat generation amount) dθ

  As shown in FIG. 3, in this embodiment, the crank angle at which the total heat generation amount reaches 10% (that is, the total heat generation amount from the start of combustion reaches 10% of the total heat generation amount from the start of combustion to the end of combustion). ) To the 90% position of the total heat generation amount (that is, the crank angle at which the total heat generation amount from the start of combustion reaches 90% of the total heat generation amount from the start of combustion to the end of combustion) is defined as the combustion period. ing. The combustion period is not limited to the period from the 10% position to the 90% position of the total heat generation amount, and may be changed as appropriate. For example, the period from the 5% position to the 95% position of the total heat generation amount Alternatively, the period from the 0% position to the 100% position of the total heat generation amount may be the combustion period, or the 15% position to 85% position of the total heat generation amount may be the combustion period.

  By the way, generally, the ignition timing of the engine 11 greatly contributes to the combustion state (combustion speed, combustion period, etc.), and when the ignition timing varies, the combustion state also varies accordingly. In consideration of such circumstances, in this embodiment, ignition timing fixing control for fixing the ignition timing is executed from the start of cranking (for example, the starter switch is turned on) until the determination of the fuel property is completed. As a result, the fuel property is determined based on the combustion period in a state where there is almost no fluctuation in the combustion period due to fluctuations in the ignition timing.

Hereinafter, the processing content of the fuel property determination routine of FIG. 4 executed by the ECU 29 will be described.
The fuel property determination routine shown in FIG. 4 is executed at a predetermined cycle while the ECU 29 is turned on, and serves as fuel property determination means in the claims. When this routine is started, first, in step 101, it is determined whether or not the fuel property determination execution flag is on. For example, the fuel property determination execution flag is set to ON when a predetermined fuel property determination execution condition is satisfied, and is reset to OFF when the fuel property determination is completed.

  If it is determined in step 101 that the fuel property determination execution flag is ON, the process proceeds to step 102, and ignition timing fixing control is executed to fix the ignition timing from the start of cranking (eg, starter switch ON). Thus, the fluctuation of the combustion period due to the fluctuation of the ignition timing is almost eliminated. The processing in step 102 serves as ignition timing fixing control means in the claims.

  The calculation may be simplified by setting the fixed ignition timing (ignition timing during ignition timing fixing control) as a fixed value set in advance, but it is fixed according to the cooling water temperature or oil temperature (engine temperature substitute information). The ignition timing may be calculated by a map or a mathematical formula. In this case, the fixed ignition timing map or numerical formula may be set such that the fixed ignition timing is advanced as the coolant temperature or the oil temperature decreases, for example. In this way, it is possible to set the proper ignition timing by changing the fixed ignition timing in response to the change of the appropriate ignition timing in accordance with the engine temperature.

  Thereafter, the process proceeds to step 103, where the total heat generation amount of the combustion section from the start of combustion to the end of combustion is calculated by the method described above, and the period from the 10% position to the 90% position of the total heat generation amount is burned. Calculate as period. The process of step 103 serves as a combustion parameter calculation means in the claims.

After this, the routine proceeds to step 104, where the current combustion period is added to the integrated value of the previous combustion period to obtain the integrated value of the current combustion period.
Integrated value of the current combustion period = Integrated value of the previous combustion period + Current combustion period

  Thereafter, the process proceeds to step 105, where the count value of the integration counter for setting the period for integrating the combustion period is counted up, and then the process proceeds to step 106, where it is determined whether or not the count value of the integration counter exceeds a predetermined value. To do.

  When it is determined in step 106 that the count value of the integration counter does not exceed the predetermined value, the ignition timing fixing control is executed until the count value of the integration counter exceeds the predetermined value (ignition timing fluctuation). The combustion period is calculated and accumulated in a state in which almost no fluctuations in the combustion period due to the above are eliminated.

  Thereafter, when it is determined in step 106 that the count value of the integration counter has exceeded a predetermined value, the routine proceeds to step 107, where it is determined whether or not the integration value of the combustion period is smaller than a predetermined determination value K1, If it is determined that the integrated value of the combustion period is smaller than the determination value K1, the routine proceeds to step 109, where it is determined that the fuel is light fuel (the fuel property is light) and the light fuel flag is turned on. Exit.

  On the other hand, if it is determined in step 107 that the integrated value of the combustion period is equal to or greater than the determination value K1, the process proceeds to step 108, where the integrated value of the combustion period is a predetermined determination value K2 (where K1 <K2). If it is determined that the integrated value of the combustion period is equal to or greater than the determination value K1 and smaller than the determination value K2, the process proceeds to step 110, where the intermediate fuel (the fuel property is light and heavy). This routine is terminated after the intermediate fuel flag is turned on.

  If it is determined in step 108 that the accumulated value of the combustion period is greater than or equal to the determination value K2, the process proceeds to step 111, where it is determined that the fuel is heavy (the fuel property is heavy), After the quality fuel flag is turned on, this routine is terminated.

  Although the calculation may be simplified by setting the determination values K1 and K2 when determining the fuel properties to preset fixed values, the fuel evaporability changes according to the engine temperature and the combustion period changes. Therefore, the determination values K1 and K2 may be calculated by a map or a mathematical expression according to the cooling water temperature or the oil temperature (engine temperature substitute information). In this way, the determination values K1 and K2 when determining the fuel properties can be set to appropriate values according to the engine temperature.

  In this way, after the fuel property determination is completed, when it is determined in step 101 that the fuel property determination execution flag is OFF, the process proceeds to step 112, the ignition timing fixing control is terminated, and the ignition timing is ended. The ignition timing is controlled in accordance with the engine operating state and the like.

  In the present embodiment described above, since the ignition timing fixing control for fixing the ignition timing is executed from the start of cranking until the determination of the fuel property is completed, the ignition timing that causes the erroneous determination of the fuel property is determined. The fuel property can be accurately determined based on the combustion period in a state where the fluctuation of the combustion period due to the fluctuation is almost eliminated. This makes it possible to prevent erroneous determination of the fuel property due to the variation of the combustion state caused by the variation of the ignition timing during the fuel property determination processing period by the ignition timing fixing control, thereby improving the accuracy of determining the fuel property.

  In addition, in this embodiment, since the ignition timing fixing control is executed from the start of cranking, the ignition timing fixing control is reliably executed (a state in which almost no fluctuation in the combustion state due to the fluctuation of the ignition timing is eliminated). The fuel property can be accurately determined.

In the above embodiment, although so as to perform the ignition timing fixed control from the start of cranking, executes the ignition timing fixed control explosions of a predetermined number of times after the start of cranking (e.g. 2-3 times) of from Ryoshi final It is desirable to do.

  In the above embodiment, the ignition timing is fixed during the ignition timing fixing control. However, the fluctuation of the ignition timing is suppressed (limited) within a range in which the influence on the combustion state does not become a problem, and the ignition timing is controlled. The fluctuation range may be reduced. In short, it is only necessary to suppress (limit) the fluctuation of the combustion state due to the fluctuation of the ignition timing within a range in which erroneous determination of the fuel property can be prevented.

  Moreover, in the said Example, although the fuel property was determined in three steps (light, middle, and heavy), you may make it determine a fuel property in two steps or four steps or more. Further, the fuel heavy degree using the integrated value of the combustion period as a parameter may be referred to a map, and the heavy degree of fuel may be determined steplessly according to the integrated value of the combustion period.

  In the above-described embodiment, the combustion period is used as a combustion parameter serving as information on the combustion state. However, the fuel property may be determined using another combustion parameter such as a combustion speed.

  In addition, the scope of application of the present invention is not limited to a system for determining the fuel properties of gasoline, but the fuel properties of fuels other than gasoline, such as alcohols such as methanol and ethanol, mixed fuels obtained by mixing alcohol and gasoline, and light oils. Needless to say, the present invention may be applied to such a system.

It is a schematic block diagram of the whole engine control system in one Example of this invention. It is a time chart which shows the relationship between a cylinder pressure and the amount of heat generation. It is a time chart which shows the relationship between total heat generation amount and a combustion period. It is a flowchart explaining the flow of a process of a fuel property determination routine.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve, 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe, 29 ... ECU (combustion parameter calculation means, fuel property judgment means, ignition timing) Fixed control means), 30 ... In-cylinder pressure sensor

Claims (5)

Combustion parameter calculation means for calculating a combustion parameter serving as combustion state information based on the in-cylinder pressure of the internal combustion engine, and fuel property determination for determining the fuel property of the fuel used based on the combustion parameter calculated by the combustion parameter calculation means An internal combustion engine fuel property determination apparatus comprising:
Ignition timing fixing control means for executing ignition timing fixing control for fixing or suppressing the fluctuation of the ignition timing of the internal combustion engine until the fuel property is determined by the fuel property determining means ,
The ignition timing fixing control means executes the ignition timing fixing control after a predetermined number of explosions have ended after the cranking of the internal combustion engine is started . 2. The fuel property determination apparatus for an internal combustion engine according to claim 1, wherein the ignition timing fixing control means sets the ignition timing during the ignition timing fixing control according to the temperature of the internal combustion engine. The fuel property determination device for an internal combustion engine according to claim 1 or 2 , wherein the combustion parameter calculation means calculates a combustion period as the combustion parameter. The fuel property determination means fuel property determining apparatus for an internal combustion engine according to any of claims 1 to 3, characterized in that to determine the fuel property on the basis of the integrated value of the combustion parameter during a predetermined period. The internal combustion engine according to any one of claims 1 to 4 , wherein the fuel property determination means sets a determination value for determining the fuel property based on the combustion parameter in accordance with the temperature of the internal combustion engine. Fuel property determination device.

Images