JP2010285901A - Cetane number calculator - Google Patents

Abstract

A cetane number of a fuel is calculated in a form that does not cause misfire during operation, or at least has a low possibility of being accompanied by misfire.
A reference fuel injection amount in which a fuel injection amount to be injected from a fuel injection valve is determined in accordance with an operating state together with a reference fuel injection timing in which the fuel injection timing to be injected from the fuel injection valve is determined in accordance with the operating state. To be controlled. When it is determined that the cetane number of fuel should be calculated, the fuel injection timing is retarded from the reference fuel injection timing and the fuel injection amount is set so that the engine speed becomes a predetermined engine speed. Cetane number calculation preparation control for increasing the injection amount is executed. The difference between the retarded fuel injection timing and the reference fuel injection timing is calculated as the fuel injection timing retard amount, and the difference between the increased fuel injection amount and the reference fuel injection amount is calculated as the fuel injection amount increment. Is done. Cetane number calculation control is performed in which the cetane number of the fuel is calculated based on the fuel injection timing retardation amount and the fuel injection amount increment.
[Selection] Figure 1

Description

  The present invention relates to a cetane number calculating apparatus.

  For example, the cetane number of a fuel used for an internal combustion engine is known as one index relating to the combustibility of the fuel. That is, the greater the cetane number of the fuel, the higher the combustibility of the fuel. Conversely, the smaller the cetane number of the fuel, the lower the combustibility of the fuel. Therefore, if the cetane number of the fuel actually consumed in the internal combustion engine can be known during the operation of the internal combustion engine, the control related to the combustion of the fuel is performed so that the fuel is burned as desired based on the cetane number. Can be controlled.

  Patent Document 1 discloses a technique for calculating the cetane number of this fuel. According to this technique, the timing at which fuel is injected from a fuel injection valve in a compression self-ignition internal combustion engine (hereinafter referred to as “fuel injection timing”) is retarded until misfiring of fuel combustion occurs. Then, the difference between the fuel injection timing when the misfire of the fuel combustion occurs and the reference fuel injection timing is taken, and the cetane number of the fuel is calculated based on this difference. At this time, the larger the difference, the larger the calculated cetane number, and the smaller the difference, the smaller the calculated cetane number. That is, the technique disclosed in Patent Document 1 calculates the cetane number of fuel by using the characteristic that the misfiring of fuel combustion does not occur even if the fuel injection timing is greatly retarded as the cetane number of fuel increases. Is.

JP 2007-154699 A JP 2008-082245 A Japanese Patent Application Laid-Open No. 07-259629 JP 2004-324491 A

  By the way, the technique disclosed in Patent Document 1 uses the characteristic that, as the cetane number of the fuel is larger, the misfiring of fuel combustion does not occur even if the fuel injection timing is largely retarded, in calculating the cetane number of the fuel. Therefore, in order to calculate the cetane number of the fuel, it is necessary to cause a misfire of the fuel combustion in the internal combustion engine. However, this is not preferable from the viewpoint of maintaining high operating characteristics of the internal combustion engine.

  Accordingly, an object of the present invention is to calculate the cetane number of the fuel in a form that does not accompany the misfiring of fuel combustion during operation of the internal combustion engine, or at least a form that is unlikely to accompany the misfiring of fuel combustion. is there.

  In the first aspect of the invention, the fuel injection timing for injecting fuel from the fuel injection valve is controlled to a reference fuel injection timing determined in accordance with the operating state of the internal combustion engine and the fuel. Calculates the cetane number of fuel consumed during operation of a compression ignition type internal combustion engine in which the fuel injection amount injected from the injection valve is controlled to a reference fuel injection amount determined according to the operating state of the internal combustion engine In the cetane number calculating device, when it is determined that the cetane number of the fuel should be calculated, the fuel injection timing is retarded from the reference fuel injection timing, and the engine speed is set to a predetermined engine speed. The cetane number calculation preparation control for increasing the fuel injection amount to be greater than the reference fuel injection amount is executed, and the difference between the retarded fuel injection timing and the reference fuel injection timing is the fuel injection timing delay. And the difference between the increased fuel injection amount and the reference fuel injection amount is calculated as a fuel injection amount increment, and based on the fuel injection timing retard amount and the fuel injection amount increment, the difference between the fuel injection amount and the reference fuel injection amount is calculated. Cetane number calculation control for calculating the cetane number is executed.

  In the second invention, in the first invention, when the fuel injection timing is retarded from the reference fuel injection timing in the cetane number calculation preparation control, the fuel injection timing is determined in advance according to the operating state of the internal combustion engine. The fuel injection timing is retarded.

  In the third invention, in the first or second invention, in the cetane number calculation control, when the fuel injection timing retard amount is the same, the larger the fuel injection amount increment is, the larger the cetane number calculated is. When the fuel injection amount increment is the same and the fuel injection timing retardation amount is larger, the calculated cetane number is larger.

  According to a fourth aspect, in the first aspect, when the fuel injection timing is retarded from the reference fuel injection timing in the cetane number calculation preparation control, the fuel injection timing is determined according to the operating state of the internal combustion engine. The fuel injection timing retard amount is calculated and retarded based on each of the fuel injection timings retarded in three different predetermined fuel injection timings and in the cetane number calculation control. The fuel injection amount increment is calculated based on each fuel injection timing, and the fuel injection amount increment per unit fuel injection timing retardation amount is calculated based on the fuel injection timing retardation amount and the fuel injection amount increment. An incremental change rate is calculated, and a cetane number of the fuel is calculated based on the fuel injection amount incremental change rate.

  According to a fifth aspect, in the fourth aspect, when one of the fuel injection timing retardation amounts is the same and the other of the fuel injection timing retardation amounts is the same in the cetane number calculation control, the fuel The smaller the injection rate incremental change rate, the larger the calculated cetane number.

  According to a sixth aspect, in the first aspect, when the fuel injection timing is retarded from the reference fuel injection timing in the cetane number calculation preparation control, the fuel injection timing is determined according to the operating state of the internal combustion engine. The fuel injection timing retard amount is calculated and retarded based on each of the fuel injection timings retarded in three different predetermined fuel injection timings and in the cetane number calculation control. The fuel injection amount increment is calculated based on each fuel injection timing, and the fuel injection timing retardation amount and the fuel injection amount are coordinated with the horizontal axis as the fuel injection timing retardation amount and the vertical axis as the fuel injection amount increment. When the points determined by the combination with the increment are plotted as the first point and the second point, respectively, a straight line connecting the first point and the second point, and a horizontal line from the second point and the second point The area surrounded by the straight line extending in parallel to the vertical axis, the horizontal axis, and the straight line extending in parallel to the vertical axis from the first point to the horizontal axis is calculated as the retard amount vs. incremental area. The cetane number of the fuel is calculated based on the angular amount versus the incremental area.

  According to a seventh aspect, in the sixth aspect, when one of the fuel injection timing retardation amounts is the same and the other of the fuel injection timing retardation amounts is the same in the cetane number calculation control, The smaller the retarded amount versus the incremental area, the greater the calculated cetane number.

  In the eighth invention, in the first to seventh inventions, in the cetane number calculation preparation control, the fuel injection timing is retarded within a range in which no misfiring of fuel combustion occurs.

  According to the first aspect, the cetane number of the fuel is calculated based on the fuel injection timing retardation amount and the fuel injection amount increment. Thus, if the cetane number of the fuel is calculated based on the fuel injection timing retard amount and the fuel injection amount increment, the cetane of the fuel is not required even if the fuel injection timing is not retarded until the misfiring of fuel combustion occurs. The price can be calculated. Therefore, according to the first aspect of the invention, the cetane number of the fuel is calculated in a form that does not involve misfiring of fuel combustion or in a form that is unlikely to involve misfiring of fuel combustion.

  According to the second aspect of the invention, the fuel injection timing is retarded to a predetermined fuel injection timing that is determined according to the operating state of the internal combustion engine. Thus, if the fuel injection timing after retarding is determined according to the operating state of the internal combustion engine, it is possible to set the fuel injection timing after retarding so that misfiring of fuel combustion does not occur. Therefore, according to the second aspect of the invention, the cetane number of the fuel is calculated more reliably in a form that does not accompany the misfiring of fuel combustion or in a form that is less likely to accompany the misfiring of fuel combustion.

  According to the third aspect, the cetane number of the fuel is calculated for each combination of the fuel injection timing retardation amount and the fuel injection amount increment. For this reason, a cetane number closer to the actual cetane number is calculated.

  According to the fourth aspect of the invention, the cetane number of the fuel is calculated based on the fuel injection amount incremental change rate that is the fuel injection amount increment per unit fuel injection timing retardation amount. If the cetane number of the fuel is calculated based on the fuel injection amount incremental change rate in this way, even if the fuel injection timing retardation amount deviates from the actual fuel injection timing retardation amount, Even if the quantity increment is deviated from the actual fuel injection quantity increment, such deviation is offset when the rate of change of the fuel injection quantity increment is calculated. Therefore, according to the fourth aspect of the invention, even if the fuel injection timing retardation amount is deviated from the actual fuel injection timing retardation amount, or the fuel injection amount increment is deviated from the actual fuel injection amount increment. The exact cetane number of the fuel is calculated.

  According to the fifth aspect, the cetane number of the fuel is calculated for each fuel injection amount incremental change rate. For this reason, a cetane number closer to the actual cetane number is calculated.

  According to the sixth aspect, the cetane number of the fuel is calculated based on the retardation amount versus the incremental area. In this way, if the cetane number of the fuel is calculated based on the retard amount vs. the incremental area, even if the fuel injection timing retard amount deviates from the actual fuel injection timing retard amount, Even if the quantity increment deviates from the actual fuel injection quantity increment, this deviation is offset when the retard amount vs. incremental area is calculated. Therefore, according to the sixth aspect of the invention, even if the fuel injection timing retardation amount deviates from the actual fuel injection timing retardation amount, or the fuel injection amount increment deviates from the actual fuel injection timing retardation amount. If so, an accurate cetane number of the fuel is calculated.

  According to the seventh aspect, the cetane number of the fuel is calculated for each retarded amount vs. incremental area. For this reason, a cetane number closer to the actual cetane number is calculated.

  According to the eighth aspect of the invention, the fuel injection timing is retarded within a range where no misfiring of fuel combustion occurs. For this reason, the cetane number of the fuel is calculated in a form that does not reliably cause misfiring of fuel combustion, or in a form that is unlikely to accompany misfiring of fuel combustion.

1 is an overall view showing a compression self-ignition internal combustion engine of a first embodiment of the present invention. It is the figure which showed the map utilized when determining fuel-injection time based on engine speed and engine load in 1st Embodiment. It is the figure which showed the map utilized when determining fuel injection quantity based on engine speed and engine load in 1st Embodiment. It is the figure which showed the relationship between fuel injection timing retardation amount, fuel injection amount increment, and the cetane number of fuel. It is the figure which showed the map utilized when calculating the cetane number of fuel based on fuel injection timing retard amount and fuel injection amount increment in 1st Embodiment. It is the figure which showed an example of the flowchart which calculates the cetane number of a fuel according to 1st Embodiment. It is the figure which showed an example of the flow shaft which calculates the cetane number of a fuel according to 1st Embodiment. It is a figure for demonstrating calculation of the cetane number of the fuel according to 2nd Embodiment. It is the figure which showed the relationship between fuel injection amount increment change rate and the cetane number of a fuel. It is the figure which showed an example of the flowchart which calculates the cetane number of a fuel according to 2nd Embodiment. It is the figure which showed an example of the flowchart which calculates the cetane number of a fuel according to 2nd Embodiment. It is a figure for demonstrating calculation of the cetane number of the fuel according to 3rd Embodiment, (A) has shown the case where a cetane number is comparatively small, (B) shows the case where a cetane number is comparatively large. Show. It is the figure which showed the relationship between retard amount vs. incremental area and the cetane number of fuel. It is the figure which showed an example of the flowchart which calculates the cetane number of a fuel according to 3rd Embodiment. It is the figure which showed an example of the flowchart which calculates the cetane number of a fuel according to 3rd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 10 denotes a compression self-ignition internal combustion engine (hereinafter simply referred to as “internal combustion engine”). The internal combustion engine 10 supplies air to the cylinder block portion 20 including a cylinder block, a cylinder block lower case, and an oil pan, a cylinder head portion 30 fixed on the cylinder block portion 20, and the cylinder block portion 20. And an exhaust passage 50 for releasing the exhaust gas from the cylinder block 20 to the outside.

  The cylinder block unit 20 includes a cylinder head 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 through the connecting rod 23, whereby the crankshaft 24 is rotated. A combustion chamber 25 is formed by the inner wall surface of the cylinder 21, the upper wall surface of the piston 22, and the lower wall surface of the cylinder head portion 30.

  The cylinder head portion 30 communicates with the combustion chamber 25, an intake port 31 that communicates with the combustion chamber 25, an intake valve 32 that opens and closes the intake port 31, a nine-machine valve drive mechanism 32 a that drives the intake valve 32, and the combustion chamber 25. An exhaust port 33, an exhaust valve 34 for opening and closing the exhaust port 33, an exhaust valve drive mechanism 34a for driving the exhaust valve 34, a fuel injection valve 37 for injecting fuel into the combustion chamber 25, and the fuel injection valve 37 has a pressure accumulation chamber 37a for supplying fuel at a high pressure, and a fuel pump 37b for pumping fuel to the pressure accumulation chamber 37a. The intake valve drive mechanism 32a and the exhaust valve drive mechanism 34a are connected to a drive circuit 38.

  The intake passage 40 includes an intake branch pipe 41 connected to the intake port 31, a surge tank 42 connected to the intake branch pipe 41, and an intake duct 43 connected to the surge tank 42. An air filter 44 and a throttle valve 48 are arranged in the intake duct 43 in order from the upstream end. The throttle valve 48 is rotatably attached to the intake duct 43 and is driven by a throttle valve driving actuator 48a.

  The exhaust passage 50 includes an exhaust branch pipe 49 connected to the exhaust port 33 and an exhaust pipe 51 connected to the exhaust branch pipe 49. An exhaust purification catalyst 52 that purifies components in the exhaust gas is disposed in the exhaust pipe 51.

  Further, the internal combustion engine 10 detects an air flow meter 61 that detects the flow rate of air flowing through the intake duct 43, a rotational phase of the crankshaft 24, that is, a crank position sensor 62 that detects a crank angle, and a pressure in the combustion chamber 25. An in-cylinder pressure sensor 63 for detecting, an accelerator opening degree sensor 64 for detecting the depression amount of the accelerator pedal 65, and an electric control unit (ECU) 70 are provided. The crank position sensor 62 outputs a narrow pulse every time the crankshaft 24 rotates 1 °, and outputs a wide pulse every time the crankshaft 24 rotates 360 °. The rotational speed of the internal combustion engine (hereinafter referred to as “engine speed”) can be calculated based on the pulse output from the crank position sensor 62.

  The electric control unit (ECU) 70 is composed of a microcomputer, and a CPU (microprocessor) 71, a ROM (read only memory) 72, a RAM (random access memory) 73, and a backup RAM 74 connected to each other via a bidirectional bus. And an interface 75 including an AD converter. The air flow meter 61, the crank position sensor 62, the in-cylinder pressure sensor 63, and the accelerator opening sensor 64 are connected to the interface 75.

  By the way, in the present embodiment (hereinafter also referred to as “first embodiment”), the timing for injecting fuel from the fuel injection valve (hereinafter referred to as “fuel injection timing”) is determined as follows. That is, the optimum time for the fuel injection time varies depending on the operating state of the internal combustion engine. Therefore, in the first embodiment, the optimum fuel injection timing Ti is obtained by experiments or the like according to the operating state of the internal combustion engine, and this is calculated as shown in FIG. 2, that is, the engine speed. It is stored in the ECU 70 in the form of a function map of N and engine load L. During operation of the internal combustion engine, the optimum fuel injection timing Tf is read from the map of FIG. 2 according to the engine speed N and the engine load L, and fuel is injected from the fuel injection valve at this fuel injection timing Ti. The

  On the other hand, in the first embodiment, the amount of fuel injected from the fuel injection valve (hereinafter referred to as “fuel injection amount”) is determined as follows. That is, the optimum fuel injection amount varies depending on the operating state of the internal combustion engine. Therefore, in the first embodiment, the optimum fuel injection amount Af is obtained by experiments or the like according to the operating state of the internal combustion engine, and this is calculated as shown in FIG. 3, that is, the engine speed. It is stored in the ECU 70 in the form of a function map of N and engine load L. During operation of the internal combustion engine, the optimum fuel injection amount Af is read from the map of FIG. 3 according to the engine speed N and the engine load L, and fuel is injected from the fuel injection valve by this fuel injection amount Af. .

  Incidentally, as described above, in the first embodiment, the fuel injection timing and the fuel injection amount are determined according to the engine speed N and the engine load L. Here, the combustibility of the fuel varies depending on its cetane number. That is, if the cetane number is large, the combustibility of the fuel is high. Conversely, if the cetane number is small, the combustibility of the fuel is low. Therefore, when the cetane number of the fuel actually used in the internal combustion engine is the same as the cetane number of the fuel used when the optimum fuel injection timing and the fuel injection amount are obtained by experiments or the like, the fuel cell shown in FIGS. It can be said that the fuel injection timing and the fuel injection amount read from the map are the optimal timing and optimal amount. On the other hand, when the cetane number of the fuel actually used in the internal combustion engine is different from the cetane number of the fuel injection valve amount used when the optimum fuel injection timing and fuel injection amount are obtained by experiments or the like, FIG. 2 and FIG. It can not be said that the fuel injection timing and the fuel injection amount read from the map of FIG.

  Therefore, if the cetane number of the fuel actually used in the internal combustion engine can be known during operation of the internal combustion engine, the fuel injection timing and the fuel injection read from the maps of FIGS. 2 and 3 according to the cetane number. The amount can be corrected to the optimal time and optimal amount. Of course, the cetane number of the fuel can be used not only for the purpose of correcting the fuel injection timing and the fuel injection amount but also for other purposes.

  Therefore, in the first embodiment, the cetane number of the fuel actually used in the internal combustion engine is calculated as follows. First, based on the engine speed and engine load at that time, the fuel injection timing and the fuel injection amount are read as the reference fuel injection timing and the reference fuel injection amount from the maps of FIGS. Then, the fuel injection timing is retarded to a predetermined fuel injection timing. Then, the fuel injection amount is increased so that the engine speed becomes the predetermined engine speed when the fuel injection time is retarded to the predetermined fuel injection time. Then, when the engine speed reaches a predetermined engine speed, the difference between the predetermined fuel injection timing and the reference fuel injection timing is calculated as the fuel injection timing retard amount and the fuel at this time The difference between the injection amount and the reference fuel injection amount is calculated as the fuel injection amount increment.

  Here, there is a relationship as shown in FIG. 4 among the fuel injection timing retardation amount, the fuel injection amount increment, and the cetane number of the fuel. That is, if the fuel injection timing retardation amount is the same, the smaller the fuel injection amount increment, the larger the cetane number of the fuel. Further, if the fuel injection amount increment is the same, the larger the fuel injection timing retardation amount, the larger the cetane number of the fuel. If the cetane number is the same, the fuel injection amount increment increases as the fuel injection timing retardation amount increases. Therefore, in the first embodiment, the relationship between the fuel injection timing retardation amount ΔTi, the fuel injection amount increment ΔAf, and the cetane number Cn of the fuel is obtained by experiments or the like, and this relationship is shown in FIG. The ECU 70 stores the map in the form of a function of the retard amount and the fuel injection amount increment. Then, the cetane number Cn of the fuel is obtained from the map of FIG. 5 based on the fuel injection timing retardation amount ΔTi and the fuel injection amount increment ΔAf calculated as described above.

  The predetermined fuel injection timing is preferably a timing according to the operating state of the internal combustion engine, for example, the engine speed and the engine load, but may be a specific timing depending on circumstances. In particular, when the cetane number of the fuel is calculated when the engine speed is a specific engine speed and the engine load is a specific engine load, the predetermined fuel injection timing is a specific one time. But you can. Further, from the viewpoint of maintaining high operating characteristics of the internal combustion engine, the predetermined fuel injection timing is preferably within a range in which misfiring of fuel combustion does not occur. Further, the predetermined engine speed is preferably an engine speed according to the operating state of the internal combustion engine, for example, the engine load or a predetermined fuel injection timing, but may be a specific engine speed. . In particular, when the cetane number of the fuel is calculated when the engine speed is a specific engine speed and the engine load is a specific engine load, the predetermined engine speed is a specific engine. The number of revolutions may be used.

  In order to calculate the cetane number of the fuel according to the first embodiment, it is necessary to retard the fuel injection timing and increase the fuel injection amount. Therefore, the calculation of the cetane number of the fuel according to the first embodiment is preferably performed when the engine speed is small and the engine load is small, that is, when the operating state of the internal combustion engine is in the idling operation state.

  Furthermore, when the cetane number of the fuel is calculated according to the first embodiment, the temperature of the cooling water for cooling the internal combustion engine is extremely low or high, or the temperature of the air sucked into the combustion chamber is extremely low. In an internal combustion engine of the type in which the exhaust gas exhausted from the combustion chamber is reintroduced into the combustion chamber when the pressure of the air sucked into the combustion chamber is extremely low or high If the ratio of exhaust gas re-introduced into the combustion chamber to the air sucked into the combustion chamber is extremely high, or if the disturbance to the cetane number calculation of the fuel is large, such as when the engine load is extremely high, There is a possibility that the cetane number of the fuel calculated according to one embodiment may deviate from the actual cetane number. Therefore, in such a case, the cetane number of the fuel calculated according to the first embodiment may not be adopted.

  Further, when the cetane number of the fuel is calculated according to the first embodiment, parameters relating to the operating state of the internal combustion engine other than the engine speed and the engine load are read, and the parameters, the engine speed and the engine load are associated with each other. When the calculated cetane number of the fuel is stored in the ECU as a learned value, and the cetane number of the fuel is calculated using the above parameters in addition to the engine speed and the engine load the next time the cetane number of the fuel is calculated It may be used as a parameter.

  Next, an example of a flowchart for calculating the cetane number of fuel according to the first embodiment will be described with reference to FIGS. 6 and 7. In the routines of FIGS. 6 and 7, first, at step 100, it is determined whether or not the current operating state of the internal combustion engine is an idling operation state, that is, whether or not the engine speed is low and the engine load is low. Is determined. Here, when it is determined that the operating state of the internal combustion engine is not in the idling operating state, the routine ends without calculating the cetane number. On the other hand, when it is determined that the operation state of the internal combustion engine is in the idling operation state, the routine proceeds to step 101.

  In step 101, whether or not the current operating state of the internal combustion engine satisfies the condition for calculating the cetane number, that is, the temperature of the cooling water for cooling the internal combustion engine is a temperature within a predetermined range, and the combustion chamber It is determined whether the temperature of the air sucked into the combustion chamber is a temperature within a predetermined range and whether the pressure of the air sucked into the combustion chamber is a pressure within a predetermined range. Here, when it is determined that the operating state of the internal combustion engine does not satisfy the condition for calculating the cetane number, the routine ends without calculating the cetane number. On the other hand, when it is determined that the operating state of the internal combustion engine satisfies the condition for calculating the cetane number, the routine proceeds to step 102.

  In step 102, the fuel injection timing at that time is read as the reference fuel injection timing Tib. Next, at step 103, the fuel injection amount at that time is read as the reference fuel injection amount Afb.

  Next, at step 104, the fuel injection timing Ti is retarded to a predetermined fuel injection timing. Next, at step 105, the fuel injection amount Af is increased by a predetermined amount. Next, at step 106, it is judged if the engine speed N is a predetermined engine speed TN (N = TN). When it is determined that T ≠ TN, the routine returns to step 105, and the fuel injection amount Af is increased again by a predetermined amount. That is, in the routine of FIG. 6, the fuel injection amount Af is continuously increased by a predetermined amount in step 105 until it is determined in step 106 that N = TN. On the other hand, when it is determined in step 106 that N = TN, the routine proceeds to step 107.

  In step 107, the difference of the fuel injection timing at this time with respect to the reference fuel injection timing Tib read in step 102, that is, the difference of the predetermined fuel injection timing with respect to the reference fuel injection timing Tib read in step 102 is determined. It is calculated as the fuel injection timing retardation amount ΔTi. Next, at step 108, the difference in the fuel injection amount at this time with respect to the reference fuel injection amount Afb read at step 103 is calculated as a fuel injection amount increment ΔAf. Next, at step 109, the cetane number Cn of the fuel is calculated from the map of FIG. 5 based on the fuel injection timing retardation amount ΔTi calculated at step 107 and the fuel injection amount increment ΔAf calculated at step 108, and the routine is performed. Proceeds to step 110.

  In step 110, whether or not the current operating state of the internal combustion engine satisfies the learning condition, that is, the temperature of the cooling water for cooling the internal combustion engine is within a predetermined range, and is sucked into the combustion chamber. It is determined whether or not the temperature of the air is a temperature within a predetermined range and the pressure of the air sucked into the combustion chamber is a pressure within a predetermined range. When it is determined that the operating state of the internal combustion engine satisfies the learning condition, the routine proceeds to step 111 where the cetane number Cn of the fuel calculated at step 109 is the cetane of the fuel currently used in the internal combustion engine. The ECU 70 stores the fuel cetane number as a learning value of the fuel together with parameters other than the engine speed and the engine load. On the other hand, when it is determined that the operating state of the internal combustion engine does not satisfy the learning condition, it is determined that the cetane number Cn of the fuel calculated in step 109 may not be the actual cetane number, and is calculated in step 107. The routine ends without adopting the cetane number of the fuel as the cetane number of the fuel currently used in the internal combustion engine.

  Incidentally, in the first embodiment, the cetane number of the fuel is calculated based on the fuel injection timing retardation amount and the fuel injection amount increment. Instead, the cetane number of the fuel is calculated as follows. May be. That is, in this embodiment (hereinafter, also referred to as “second embodiment”), first, based on the engine speed and the engine load at that time, the fuel injection timing and the fuel injection amount are respectively determined from the maps of FIG. 2 and FIG. The fuel injection timing and the reference fuel injection amount are read. Then, the fuel injection timing is retarded to a predetermined fuel injection timing (hereinafter referred to as “first fuel injection timing”). Then, the fuel injection amount is increased so that the engine speed becomes a predetermined engine speed when the fuel injection time is retarded to the first fuel injection time. Then, when the engine speed reaches a predetermined engine speed, the difference between the first fuel injection timing and the reference fuel injection timing is calculated as a first fuel injection timing retard amount ΔTi1, and at this time A difference between the fuel injection amount and the reference fuel injection amount is calculated as a first fuel injection amount increment ΔAf1.

  Next, the fuel injection timing is delayed to a predetermined fuel injection timing (hereinafter referred to as “second fuel injection timing”) that is later than the first fuel injection timing. Then, the fuel injection amount is increased so that the engine speed becomes a predetermined engine speed when the fuel injection time is retarded to the second fuel injection time. Then, when the engine speed reaches a predetermined engine speed, the difference between the second fuel injection timing and the reference fuel injection timing is calculated as a second fuel injection timing retard amount ΔTi2, and at this time A difference between the fuel injection amount and the reference fuel injection amount is calculated as a second fuel injection amount increment ΔAf2.

  The first fuel injection timing retardation amount ΔTi1, the second fuel injection timing retardation amount ΔTi2, the first fuel injection amount increment ΔAf1, and the second fuel injection amount increment ΔAf2 are used to retard the fuel injection timing retardation. Change rate of the fuel injection amount increment when the amount changes from the first fuel injection timing retardation amount to the second fuel injection timing retardation amount, that is, the change rate of the fuel injection amount increment per unit fuel injection timing retardation amount Is calculated as the fuel injection amount incremental change rate G. Here, the fuel injection amount incremental change rate when the cetane numbers of the fuels are different is shown in FIG. That is, FIG. 8 shows the fuel injection amount incremental change rate Gs when the fuel cetane number is relatively small and the fuel injection amount incremental change rate Gl when the fuel cetane number is relatively large. As can be seen from FIG. 8, the fuel injection amount incremental change rate Gs when the fuel cetane number is relatively small is larger than the fuel injection amount incremental change rate when the fuel cetane number is relatively large. In other words, when the first fuel injection timing retard amount and the second fuel injection timing retard amount are the same, the fuel injection amount incremental change rate decreases as the cetane number of the fuel increases.

  Therefore, in the second embodiment, for each combination of the first fuel injection timing and the second fuel injection timing, the relationship between the fuel injection amount incremental change rate Raf and the cetane number Cn of the fuel is obtained by experiments or the like. Each combination of the first fuel injection timing and the second fuel injection timing is stored in the ECU 70 in the form of a function map of the fuel injection amount incremental change rate as shown in FIG. Then, the cetane number Cn of the fuel is obtained from the map of FIG. 9 according to the combination of the first fuel injection timing and the second fuel injection timing based on the fuel injection amount incremental change rate Raf calculated as described above.

  In the second embodiment, the first fuel injection timing and the second fuel injection timing may be determined in the same manner as in the first embodiment.

  Also in the second embodiment, the calculation of the cetane number of the fuel is performed when the engine speed is small and the engine load is small, that is, when the operating state of the internal combustion engine is in the idling operating state, as in the first embodiment. Preferably it is done.

  Further, in the second embodiment, as in the first embodiment, when the disturbance to the calculation of the cetane number of the fuel is large, the cetane number of the fuel calculated according to the second embodiment may not be adopted.

  Also in the second embodiment, as in the first embodiment, when the cetane number of the fuel is calculated, parameters relating to the operating state of the internal combustion engine other than the engine speed and the engine load are read, and this parameter and the engine speed are read. The fuel cetane number calculated this time in a form corresponding to the engine load is stored in the ECU as a learned value, and the next time the fuel cetane number is calculated, in addition to the engine speed and the engine load, The parameter may be used as a parameter for calculating the cetane number of the fuel.

  Next, an example of a flowchart for calculating the cetane number of fuel according to the second embodiment will be described with reference to FIGS. 10 and 11. In the routines of FIGS. 10 and 11, first, at step 200, whether or not the current operating state of the internal combustion engine is an idling operation state, that is, whether or not the engine speed is low and the engine load is low. Is determined. Here, when it is determined that the operating state of the internal combustion engine is not in the idling operating state, the routine ends without calculating the cetane number. On the other hand, when it is determined that the operation state of the internal combustion engine is in the idling operation state, the routine proceeds to step 201.

  In step 201, whether or not the current operating state of the internal combustion engine satisfies the condition for calculating the cetane number, that is, the temperature of the cooling water for cooling the internal combustion engine is within a predetermined range, and the combustion chamber It is determined whether the temperature of the air sucked into the combustion chamber is a temperature within a predetermined range and whether the pressure of the air sucked into the combustion chamber is a pressure within a predetermined range. Here, when it is determined that the operating state of the internal combustion engine does not satisfy the condition for calculating the cetane number, the routine ends without calculating the cetane number. On the other hand, when it is determined that the operating state of the internal combustion engine satisfies the condition for calculating the cetane number, the routine proceeds to step 202.

  In step 202, the fuel injection timing at that time is read as the reference fuel injection timing Tib. Next, at step 203, the fuel injection amount at that time is read as the reference fuel injection amount Afb.

  Next, at step 204, the fuel injection timing Ti is retarded until the first fuel injection timing. Next, at step 205, the fuel injection amount Af is increased by a predetermined amount. Next, at step 206, it is judged if the engine speed N is a predetermined engine speed TN1 (N = TN1). Here, when it is determined that T ≠ TN1, the routine returns to step 205, and the fuel injection amount Af is increased again by a predetermined amount. That is, in the routine of FIG. 10 and FIG. 11, the fuel injection amount Af is continuously increased by a predetermined amount in step 205 until it is determined in step 206 that N = TN1. On the other hand, when it is determined in step 206 that N = TN1, the routine proceeds to step 207.

  In step 207, the difference in fuel injection timing at this time with respect to the reference fuel injection timing Tib read in step 202, that is, the difference in the first fuel injection timing with respect to the reference fuel injection timing Tib read in step 202 is the first. It is calculated as the fuel injection timing retardation amount ΔTi1. Next, at step 208, the difference between the fuel injection amount at this time and the reference fuel injection amount Afb read at step 203 is calculated as the first fuel injection amount increment ΔAf1.

  Next, at step 209, the fuel injection timing Ti is retarded until the second fuel injection timing. Next, at step 210, the fuel injection amount Af is increased by a predetermined amount. Next, at step 211, it is judged if the engine speed N is a predetermined engine speed TN2 (N = TN2). When it is determined that T ≠ TN2, the routine returns to step 210, and the fuel injection amount Af is increased again by a predetermined amount. That is, in the routines of FIGS. 10 and 11, the fuel injection amount Af is continuously increased by a predetermined amount in step 210 until it is determined in step 211 that N = TN2. On the other hand, when it is determined in step 211 that N = TN2, the routine proceeds to step 212.

  In step 212, the difference in fuel injection timing at this time with respect to the reference fuel injection timing Tib read in step 202, that is, the difference in second fuel injection timing with respect to the reference fuel injection timing Tib read in step 202 is the second fuel. It is calculated as the injection timing retardation amount ΔTi2. Next, at step 213, the difference of the fuel injection amount at this time with respect to the reference fuel injection amount Afb read at step 203 is calculated as a second fuel injection amount increment ΔAf2.

  Next, at step 214, the first fuel injection timing retardation amount ΔTi1 calculated at step 207, the first fuel injection amount increment ΔAf1 calculated at step 208, and the second fuel injection timing retardation amount calculated at step 212. The fuel injection amount increment change rate Raf is calculated based on ΔTi2 and the second fuel injection amount increment ΔAf2 calculated in step 213. Next, at step 215, the cetane number Cn of the fuel is calculated from the map of FIG. 9 based on the fuel injection amount incremental change rate Raf calculated at step 214, and the routine proceeds to step 216.

  In step 216, whether or not the current operating state of the internal combustion engine satisfies the learning condition, that is, the temperature of the cooling water for cooling the internal combustion engine is within a predetermined range, and is sucked into the combustion chamber. It is determined whether or not the temperature of the air is a temperature within a predetermined range and the pressure of the air sucked into the combustion chamber is a pressure within a predetermined range. When it is determined that the operating state of the internal combustion engine satisfies the learning condition, the routine proceeds to step 217, where the cetane number Cn of the fuel calculated in step 215 is the cetane of the fuel currently used in the internal combustion engine. The ECU 70 stores the fuel cetane number as a learning value of the fuel together with parameters other than the engine speed and the engine load. On the other hand, when it is determined that the operating state of the internal combustion engine does not satisfy the learning condition, it is determined that the cetane number Cn of the fuel calculated in step 215 may not be the actual cetane number, and is calculated in step 215. The routine ends without adopting the cetane number of the fuel as the cetane number of the fuel currently used in the internal combustion engine.

  In the first embodiment, the cetane number of the fuel is calculated based on the fuel injection timing retardation amount and the fuel injection amount increment. In the second embodiment, the cetane number of the fuel is calculated based on the rate of change in the fuel injection amount increment. However, instead of this, the cetane number of the fuel may be calculated as follows. That is, in this embodiment (hereinafter referred to as “third embodiment”), first, based on the engine speed and the engine load at that time, the fuel injection timing and the fuel injection amount are respectively obtained from the maps of FIG. 2 and FIG. Read as injection timing and reference fuel injection amount. Then, the fuel injection timing is retarded to a predetermined fuel injection timing (hereinafter referred to as “first fuel injection timing”). Then, the fuel injection amount is increased so that the engine speed becomes a predetermined engine speed when the fuel injection time is retarded to the first fuel injection time. Then, when the engine speed reaches a predetermined engine speed, the difference between the first fuel injection timing and the reference fuel injection timing is calculated as a first fuel injection timing retard amount ΔTi1, and at this time A difference between the fuel injection amount and the reference fuel injection amount is calculated as a first fuel injection amount increment ΔAf1.

  Next, the fuel injection timing is delayed to a predetermined fuel injection timing (hereinafter referred to as “second fuel injection timing”) that is later than the first fuel injection timing. Then, the fuel injection amount is increased so that the engine speed becomes a predetermined engine speed when the fuel injection time is retarded to the second fuel injection time. Then, when the engine speed reaches a predetermined engine speed, the difference between the second fuel injection timing and the reference fuel injection timing is calculated as a second fuel injection timing retard amount ΔTi2, and at this time A difference between the fuel injection amount and the reference fuel injection amount is calculated as a second fuel injection amount increment ΔAf2.

  A point determined by a combination of the first fuel injection timing retardation amount and the first fuel injection amount increment is a first point on the coordinates where the horizontal axis is the fuel injection timing retardation amount and the vertical axis is the fuel injection amount increment. And a point determined by the combination of the second fuel injection timing retardation amount and the second fuel injection amount increment is plotted as the second point. And, a straight line connecting the first point and the second point, a straight line extending in parallel to the vertical axis from the second point to the horizontal axis, the horizontal axis, and the vertical from the first point to the horizontal axis An area surrounded by a straight line extending in parallel to the axis is calculated as retardation amount versus incremental area A.

  Here, the retarded amount versus the incremental area when the cetane numbers of the fuels are different is shown in FIG. That is, FIG. 12 (A) shows the retardation amount vs. incremental area As when the cetane number of the fuel is relatively small, and FIG. 12 (B) shows the case where the cetane number of the fuel is relatively large. The amount of retarded angle vs. the incremental area Al is shown. As can be seen from FIG. 12, the retardation amount vs. incremental area As when the cetane number of the fuel is relatively small is smaller than the rate of change of the fuel injection amount increment when the cetane number of the fuel is relatively large. In other words, when the first fuel injection timing retard amount and the second fuel injection timing retard amount are the same, the larger the cetane number of the fuel, the smaller the retard amount vs. the incremental area.

  Therefore, in the third embodiment, for each combination of the first fuel injection timing and the second fuel injection timing, the relationship between the retard amount vs. the incremental area A and the cetane number Cn of the fuel is obtained by experiments, and this relationship is obtained. Each combination of the first fuel injection timing and the second fuel injection timing is stored in the ECU 70 in the form of a map of a function of retard amount vs. incremental area as shown in FIG. Then, the cetane number Cn of the fuel is obtained from the map of FIG. 13 according to the combination of the first fuel injection timing and the second fuel injection timing based on the retard amount vs. the increment area A calculated as described above.

  In the third embodiment, the first fuel injection timing and the second fuel injection timing may be determined in the same manner as in the first embodiment.

  Also in the third embodiment, the calculation of the cetane number of the fuel is performed when the engine speed is small and the engine load is small, that is, when the operating state of the internal combustion engine is in the idling operating state, as in the first embodiment. Preferably it is done.

  Further, in the third embodiment, as in the first embodiment, when the disturbance to the calculation of the cetane number of the fuel is large, the cetane number of the fuel calculated according to the third embodiment may not be adopted.

  Also in the third embodiment, as in the first embodiment, when the cetane number of the fuel is calculated, parameters relating to the operating state of the internal combustion engine other than the engine speed and the engine load are read, and this parameter and the engine speed are read. The fuel cetane number calculated this time in a form corresponding to the engine load is stored in the ECU as a learned value, and the next time the fuel cetane number is calculated, in addition to the engine speed and the engine load, The parameter may be used as a parameter for calculating the cetane number of the fuel.

  Next, an example of a flowchart for calculating the cetane number of fuel according to the third embodiment will be described with reference to FIGS. 14 and 15. In the routines of FIGS. 14 and 15, first, at step 300, whether or not the current operating state of the internal combustion engine is an idling operation state, that is, whether or not the engine speed is low and the engine load is low. Is determined. Here, when it is determined that the operating state of the internal combustion engine is not in the idling operating state, the routine ends without calculating the cetane number. On the other hand, when it is determined that the operation state of the internal combustion engine is in the idling operation state, the routine proceeds to step 301.

  In step 301, whether or not the current operating state of the internal combustion engine satisfies the condition for calculating the cetane number, that is, the temperature of the cooling water for cooling the internal combustion engine is a temperature within a predetermined range, and the combustion chamber It is determined whether the temperature of the air sucked into the combustion chamber is a temperature within a predetermined range and whether the pressure of the air sucked into the combustion chamber is a pressure within a predetermined range. Here, when it is determined that the operating state of the internal combustion engine does not satisfy the condition for calculating the cetane number, the routine ends without calculating the cetane number. On the other hand, when it is determined that the operating state of the internal combustion engine satisfies the condition for calculating the cetane number, the routine proceeds to step 302.

  In step 302, the fuel injection timing at that time is read as the reference fuel injection timing Tib. Next, at step 303, the fuel injection amount at that time is read as the reference fuel injection amount Afb.

  Next, at step 304, the fuel injection timing Ti is retarded until the first fuel injection timing. Next, at step 305, the fuel injection amount Af is increased by a predetermined amount. Next, at step 306, it is judged if the engine speed N is a predetermined engine speed TN1 (N = TN1). If it is determined that T ≠ TN1, the routine returns to step 305, and the fuel injection amount Af is increased again by a predetermined amount. That is, in the routines of FIGS. 14 and 15, the fuel injection amount Af is continuously increased by a predetermined amount in step 305 until it is determined in step 306 that N = TN1. On the other hand, when it is determined in step 306 that N = TN2, the routine proceeds to step 307.

  In step 307, the difference in the fuel injection timing at this time with respect to the reference fuel injection timing Tib read in step 302, that is, the difference in the first fuel injection timing with respect to the reference fuel injection timing Tib read in step 302 is the first. It is calculated as the fuel injection timing retardation amount ΔTi1. Next, at step 308, the difference of the fuel injection amount at this time with respect to the reference fuel injection amount Afb read at step 303 is calculated as a first fuel injection amount increment ΔAf1.

  Next, at step 309, the fuel injection timing Ti is retarded until the second fuel injection timing. Next, at step 310, the fuel injection amount Af is increased by a predetermined amount. Next, at step 311, it is judged if the engine speed N is a predetermined engine speed TN2 (N = TN2). If it is determined that T ≠ TN2, the routine returns to step 310, and the fuel injection amount Af is increased again by a predetermined amount. That is, in the routine of FIG. 14 and FIG. 15, the fuel injection amount Af is continuously increased by a predetermined amount in step 310 until it is determined in step 311 that N = TN2. On the other hand, when it is determined in step 311 that N = TN2, the routine proceeds to step 312.

  In step 312, the difference in fuel injection timing at this time with respect to the reference fuel injection timing Tib read in step 302, that is, the difference in second fuel injection timing with respect to the reference fuel injection timing Tib read in step 302 is the second fuel. It is calculated as the injection timing retardation amount ΔTi2. Next, at step 313, the difference between the reference fuel injection amount Afb read at step 203 and the fuel injection amount at this time is calculated as a second fuel injection amount increment ΔAf2.

  Next, at step 314, the first fuel injection timing retardation amount ΔTi1 calculated at step 307, the first fuel injection amount increment ΔAf1 calculated at step 308, the second fuel injection timing retardation amount calculated at step 312. Based on ΔTi2 and the second fuel injection amount increment ΔAf2 calculated in step 313, the retard amount vs. incremental area A is calculated. Next, at step 315, the cetane number Cn of the fuel is calculated from the map of FIG. 13 based on the retard amount vs. the increment area A calculated at step 314, and the routine proceeds to step 316.

  In step 316, whether or not the current operating state of the internal combustion engine satisfies the learning condition, that is, the temperature of the cooling water for cooling the internal combustion engine is a temperature within a predetermined range, and is sucked into the combustion chamber. It is determined whether or not the temperature of the air is a temperature within a predetermined range and the pressure of the air sucked into the combustion chamber is a pressure within a predetermined range. When it is determined that the operating state of the internal combustion engine satisfies the learning condition, the routine proceeds to step 317, where the cetane number Cn of the fuel calculated in step 315 is the cetane of the fuel currently used in the internal combustion engine. The ECU 70 stores the fuel cetane number as a learning value of the fuel together with parameters other than the engine speed and the engine load. On the other hand, when it is determined that the operating state of the internal combustion engine does not satisfy the learning condition, it is determined that the cetane number Cn of the fuel calculated in step 315 may not be the actual cetane number, and is calculated in step 315. The routine ends without adopting the cetane number of the fuel as the cetane number of the fuel currently used in the internal combustion engine.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 25 ... Combustion chamber, 37 ... Fuel injection valve, 40 ... Intake passage, 50 ... Exhaust passage, 70 ... Electronic control unit (ECU)

Claims (8)

  A fuel that is a compression self-ignition internal combustion engine, in which fuel injection timing for injecting fuel from the fuel injection valve is controlled to a reference fuel injection timing that is determined according to the operating state of the internal combustion engine, and fuel that is injected from the fuel injection valve In a cetane number calculating device for calculating a cetane number of fuel consumed during operation of a compression auto-ignition internal combustion engine whose injection amount is controlled to a reference fuel injection amount determined according to an operating state of the internal combustion engine, When it is determined that the cetane number of the fuel should be calculated, the fuel injection amount is set so that the fuel injection timing is retarded from the reference fuel injection timing and the engine speed becomes a predetermined engine speed. A cetane number calculation preparation control for increasing the reference fuel injection amount is executed, and a difference between the retarded fuel injection timing and the reference fuel injection timing is calculated as a fuel injection timing retardation amount. At the same time, the difference between the increased fuel injection amount and the reference fuel injection amount is calculated as the fuel injection amount increment, and the cetane number of the fuel is calculated based on the fuel injection timing retardation amount and the fuel injection amount increment. The cetane number calculating device is characterized in that the cetane number calculating control is executed.   When the fuel injection timing is retarded from the reference fuel injection timing in the cetane number calculation preparation control, the fuel injection timing is retarded to a predetermined fuel injection timing that is determined according to the operating state of the internal combustion engine. The cetane number calculating device according to claim 1, wherein:   In the cetane number calculation control, when the fuel injection timing retardation amount is the same, the larger the fuel injection amount increment, the larger the cetane number calculated, and when the fuel injection amount increment is the same, the fuel The cetane number calculation device according to claim 1, wherein the cetane number calculated is larger as the injection timing retardation amount is larger.   When the fuel injection timing is retarded from the reference fuel injection timing in the cetane number calculation preparation control, the fuel injection timing is retarded to two different predetermined fuel injection timings determined according to the operating state of the internal combustion engine. The fuel injection timing retardation amount is calculated based on each of the retarded fuel injection timings in the cetane number calculation control, and the fuel injection amount increment is calculated based on each of the retarded fuel injection timings. The fuel injection amount increment per unit fuel injection timing retardation amount is calculated as the fuel injection amount increment change rate based on the fuel injection timing retardation amount and the fuel injection amount increment, and the fuel injection amount increment The cetane number calculation device according to claim 1, wherein the cetane number of the fuel is calculated based on the rate of change.   In the cetane number calculation control, when one of the fuel injection timing retardation amounts is the same and the other of the fuel injection timing retardation amounts is the same, the cetane calculated as the fuel injection amount incremental change rate decreases. The cetane number calculation apparatus according to claim 4, wherein the cetane number calculation apparatus has a large value. When the fuel injection timing is retarded from the reference fuel injection timing in the cetane number calculation preparation control, the fuel injection timing is retarded to two different predetermined fuel injection timings determined according to the operating state of the internal combustion engine. The fuel injection timing retardation amount is calculated based on each of the retarded fuel injection timings in the cetane number calculation control, and the fuel injection amount increment is calculated based on each of the retarded fuel injection timings. Are calculated by the combination of the fuel injection timing retardation amount and the fuel injection amount increment, with the horizontal axis as the fuel injection timing retardation amount and the vertical axis as the fuel injection amount increment. A straight line connecting the first point and the second point when plotted as the second point, a straight line extending parallel to the vertical axis from the second point to the horizontal axis, And an area surrounded by a straight line extending in parallel to the vertical axis from the first point to the horizontal axis is calculated as a retard amount vs. incremental area, and a cetane number of the fuel is calculated based on the retard amount vs. the increment area The cetane number calculating device according to claim 1, wherein   In the cetane number calculation control, when one of the fuel injection timing retardation amounts is the same and the other one of the fuel injection timing retardation amounts is the same, the smaller the retardation amount vs. the incremental area, the smaller the calculation. The cetane number calculation device according to claim 6, wherein the cetane number is large.   The cetane number calculation device according to any one of claims 1 to 7, wherein the fuel injection timing is retarded within a range in which misfiring of fuel combustion does not occur in the cetane number calculation preparation control.

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