JP2009030531A - Device of detecting cetane number of fuel for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device of detecting the cetane number of fuel for an internal combustion engine, properly detecting the cetane number of fuel based on the number of times performing pilot injection. <P>SOLUTION: The device of detecting the cetane number of fuel for an internal combustion engine is suitably used for detecting the cetane number of fuel. Concretely, in fuel cut, the cetane number of fuel is detected based on the number of times of pilot injection set in generation of ignition, by injecting fuel with changed number of times of pilot injection. Since fuel mixture is susceptible to diffusion and a fuel temperature is easily increased when the pilot injection is performed in a plurality of times in this way, the fuel is easy to ignition in detection of the cetane number. Compared with single injection, the ignition is stabilized to surely detect the cetane number of fuel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cetane number detection device for an internal combustion engine that detects a cetane number of a fuel.

  The fuel used for the operation of the internal combustion engine has different ignitability depending on its cetane number. Therefore, conventionally, techniques relating to a cetane number measurement method, a fuel injection amount corresponding to the cetane number, and a control method of fuel injection timing have been proposed.

  For example, Patent Document 1 describes a technique for detecting a cetane number from a correlation between a heat generation rate (dQ / dθ) during pilot injection and a cetane number. Patent Document 2 describes a technique for calculating a heat generation amount parameter from the pressure P and volume V in the combustion chamber and measuring the cetane number based on the parameter change. Further, Patent Document 3 describes a technique for controlling the injection amount and injection timing of pilot injection according to the cetane number (fuel property) detected by the specific gravity of the fuel. In addition, Patent Documents 4 and 5 describe techniques related to the present invention.

JP 2006-226188 A JP 2005-344550 A JP 2005-48703 A JP 2004-308440 A JP 2000-257467 A

  However, the techniques described in Patent Documents 1 to 5 described above do not perform stable combustion / ignition when the cetane number of the fuel is originally low, such as when the cetane number is detected using a small amount of fuel. In addition, the cetane number may not be detected properly. In addition, these documents do not describe detection of the cetane number of fuel based on the number of times pilot injection is performed.

  The present invention has been made to solve the above-described problems, and detects the fuel cetane number of an internal combustion engine that can appropriately detect the cetane number of the fuel based on the number of times pilot injection is performed. An object is to provide an apparatus.

  In one aspect of the present invention, a fuel cetane number detection device for an internal combustion engine that detects a cetane number of fuel performs fuel injection by changing the number of times of pilot injection at the time of fuel cut of the internal combustion engine. And a cetane number for detecting the cetane number of the fuel based on the number of pilot injections set by the fuel injection control means when the fuel injected by the fuel injection control means is ignited Detecting means.

  The fuel cetane number detection device for an internal combustion engine is suitably used for detecting the cetane number of fuel. Specifically, the fuel cetane number detection device for an internal combustion engine is set when ignition occurs when fuel injection is performed by changing the number of times of pilot injection during fuel cut (fuel cut). The cetane number of the fuel is detected based on the number of pilot injections. When pilot injection is performed a plurality of times in this manner, the fuel mixture is difficult to diffuse and the temperature is likely to rise, so that the ignitability of the fuel can be improved when detecting the cetane number. That is, the fuel can be easily ignited when the cetane number is detected. Therefore, according to the fuel cetane number detection device for an internal combustion engine described above, stable ignition can be performed as compared with the case where only single injection (only main injection) is performed, and the detection of the cetane number of fuel can be performed. This can be performed more reliably.

  In one aspect of the fuel cetane number detection device for an internal combustion engine, the fuel injection control means performs the first fuel injection by the pilot injection that is approximately half the maximum number of pilot injections. The fuel injection is executed by the pilot injection of the number of times in which the range of the number of pilot injections that should be determined for ignition in order to detect the cetane number based on the presence or absence of ignition by the previous fuel injection is reduced to almost half. To do. This makes it possible to determine the cetane number with a relatively small number of determinations for a wide range of cetane number fuels.

  In another aspect of the fuel cetane number detection device for an internal combustion engine, when the fuel injection control means detects the cetane number after refueling, the first fuel injection is performed on the fuel before refueling. The pilot injection is executed according to the number of pilot injections set when the cetane number is determined, and the second and subsequent fuel injections are performed based on the presence or absence of ignition by the previous fuel injection. The pilot injection is executed by the number of times of increasing or decreasing the number of times of the pilot injection set in step. As a result, when detecting the cetane number after refueling, it is possible to determine the cetane number with a relatively small number of determinations for a wide range of cetane number fuels.

  In another aspect of the fuel cetane number detection device for an internal combustion engine, the fuel injection control means performs control to change an injection timing for performing the fuel injection, and the cetane number detection means detects the ignition of the fuel. When it occurs, the cetane number is detected based on the injection timing set by the fuel injection control means. According to this aspect, it is possible to appropriately detect the cetane number of the fuel and accurately detect the cetane number as compared with the case where the injection timing is fixed.

  In another aspect of the fuel cetane number detection device for an internal combustion engine, the fuel injection control means performs control to change a total injection amount when performing the fuel injection, and the cetane number detection means includes the When fuel ignition occurs, the cetane number is detected based on the total injection amount set by the fuel injection control means. According to this aspect, it is possible to appropriately detect the cetane number of the fuel and accurately detect the cetane number as compared with the case where the injection amount is fixed.

  In another aspect of the fuel cetane number detection device for an internal combustion engine, the fuel injection control means performs control to change a fuel injection interval in the pilot injection, and the cetane number detection means When ignition occurs, the cetane number is detected based on the interval set by the fuel injection control means. According to this aspect, it is possible to appropriately detect the cetane number of the fuel and to accurately detect the cetane number as compared with the case where the interval in the pilot injection is fixed.

  In another aspect of the fuel cetane number detection device for an internal combustion engine, the fuel cetane number detection unit further includes fuel injection pressure control means for changing a fuel injection pressure when the cetane number is detected. When fuel ignition occurs, the cetane number is detected based on the fuel injection pressure set by the fuel injection pressure control means. According to this aspect, it is possible to appropriately detect the cetane number of the fuel and to accurately detect the cetane number as compared with the case where the fuel injection pressure is fixed.

  In another aspect of the fuel cetane number detection device for an internal combustion engine described above, a glow plug control means for performing control for operating a glow plug provided in a cylinder of the internal combustion engine when the cetane number is detected is further provided. Prepare. Preferably, the glow plug control means performs control to change the temperature of the glow plug, and the cetane number detection means, when the ignition of the fuel occurs, the control after the control by the glow plug control means. The cetane number is detected based on the temperature of the glow plug. Also according to this aspect, it is possible to appropriately detect the cetane number of the fuel and to accurately detect the cetane number.

  In another aspect of the fuel cetane number detection device for an internal combustion engine described above, the rotation of the turbocharger can be assisted so that the supercharging pressure by the turbocharger changes when the cetane number is detected. Motor control means for controlling the motor to operate, and the cetane number detection means, when ignition of the fuel occurs, based on a boost pressure after control by the motor control means, Is detected. Also according to this aspect, it is possible to appropriately detect the cetane number of the fuel and to accurately detect the cetane number.

  In another aspect of the fuel cetane number detection device for an internal combustion engine, the apparatus further comprises throttle control means for controlling the throttle valve so that the pressure of the intake manifold changes when the cetane number is detected, The cetane number detection means detects the cetane number based on the pressure of the intake manifold after the control by the throttle control means when the fuel is ignited. Also according to this aspect, it is possible to appropriately detect the cetane number of the fuel and to accurately detect the cetane number.

  In another aspect of the fuel cetane number detection device for an internal combustion engine, the first control is performed to change the valve timing in the internal combustion engine so that the intake air amount changes when the cetane number is detected. Valve timing control means is further provided, and the cetane number detection means detects the cetane number based on the valve timing set by the first valve timing control means when ignition of the fuel occurs. . Also according to this aspect, it is possible to appropriately detect the cetane number of the fuel and to accurately detect the cetane number.

  In another aspect of the fuel cetane number detection device for an internal combustion engine, the second control is performed to change the valve timing in the internal combustion engine so that the actual compression ratio changes when the cetane number is detected. Valve timing control means is further provided, and the cetane number detection means detects the cetane number based on the valve timing set by the second valve timing control means when the ignition of the fuel occurs. . Also according to this aspect, it is possible to appropriately detect the cetane number of the fuel and to accurately detect the cetane number.

  In another aspect of the fuel cetane number detection device for an internal combustion engine described above, an intake manifold temperature control means for performing control so that the temperature of the intake manifold in the internal combustion engine changes when the cetane number is detected. The cetane number detection means detects the cetane number based on the temperature of the intake manifold after the control by the intake manifold temperature control means when the fuel is ignited. Also according to this aspect, it is possible to appropriately detect the cetane number of the fuel and to accurately detect the cetane number.

  In another aspect of the fuel cetane number detection device for an internal combustion engine, when the cetane number is detected, swirl control means for controlling the swirl strength in a cylinder of the internal combustion engine to change. Further, the cetane number detection means detects the cetane number based on the strength of the swirl after the control by the swirl control means when the fuel is ignited. Also according to this aspect, it is possible to appropriately detect the cetane number of the fuel and to accurately detect the cetane number.

  In another aspect of the fuel cetane number detection device for an internal combustion engine, the cetane number detection means detects the cetane number based on a water temperature of the internal combustion engine when the fuel is ignited. According to this aspect, since the cetane number is detected in consideration of the water temperature, the cetane number of the fuel can be detected with high accuracy.

  In another aspect of the fuel cetane number detection device for an internal combustion engine, the cetane number detection means is configured to determine the cetane number based on an EGR rate when ignition of the fuel occurs during deceleration from the EGR region. Is detected. According to this aspect, it is possible to appropriately detect the cetane number based on the change in the EGR rate during deceleration from the EGR region. Further, by detecting the cetane number based on the EGR rate in this way, it is possible to detect the cetane number with high accuracy while reducing the number of times of determination execution.

  In another aspect of the fuel cetane number detection device for an internal combustion engine, the cetane number detection means rotates the internal combustion engine when the fuel ignition occurs when the internal combustion engine decelerates from a high speed. The cetane number is detected based on the number. According to this aspect, it is possible to appropriately detect the cetane number based on the change in the rotational speed during deceleration from high rotation. In addition, by detecting the cetane number based on the rotation speed in this way, it is possible to detect the cetane number with high accuracy while reducing the number of times of determination execution.

  Preferably, in the fuel cetane number detection device of the internal combustion engine, the cetane number detection means acquires the temperature of the exhaust gas in the internal combustion engine and determines whether or not the fuel is ignited based on the temperature of the exhaust gas. To do.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[Device configuration]
FIG. 1 is a block diagram showing a schematic configuration of a vehicle 100 to which a fuel cetane number detection device for an internal combustion engine according to this embodiment is applied. In FIG. 1, solid arrows indicate an example of gas flow, and broken arrows indicate signal input / output.

  The vehicle 100 mainly includes an intake passage 3, a throttle valve 4, an intercooler 5, a bypass passage 6, a bypass passage valve 7, an engine (internal combustion engine) 8, a fuel injection valve 9, and a glow plug 10. A variable valve timing mechanism 11a, a variable fuel injection pressure mechanism 11b, a swirl variable mechanism 11c, an exhaust passage 12, a catalyst 13, a turbocharger 14, an EGR passage 15a, and an ECU (Engine Control Unit) 20. .

  The intake air introduced from outside passes through the intake passage 3, and the throttle valve 4 adjusts the flow rate of the intake air passing through the intake passage 3. The throttle valve 4 has its opening degree controlled by a control signal S4 supplied from the ECU 20. The intake passage 3 is provided with a compressor 14a of a turbocharger 14 that supercharges intake air. The intake passage 3 is provided with an intercooler 5 for cooling the intake air and a bypass passage 6 for bypassing the intercooler 5. The bypass passage 6 is provided with a bypass passage valve 7 that controls supply / blocking of intake air to the bypass passage 6. The bypass passage valve 7 is controlled to be opened and closed by a control signal S7 supplied from the ECU 20.

  The engine 8 is supplied with intake air from the intake passage 3 and is supplied with fuel from the fuel injection valve 9. The engine 8 generates traveling power in the vehicle 100 by burning the supplied air-fuel mixture of fuel and fuel in the combustion chamber. The engine 8 corresponds to, for example, a diesel engine (compression self-ignition engine). The fuel injection valve 9 controls the number of times of fuel injection, the fuel injection amount, the injection timing, and the like by a control signal S9 supplied from the ECU 20.

  Each cylinder in the engine 8 is provided with a glow plug (hereinafter simply referred to as “glow”) 10 capable of increasing the in-cylinder temperature. The glow plug 10 is controlled on / off, its temperature, and the like by a control signal S10 supplied from the ECU 20. Further, the engine 8 is provided with a variable valve timing mechanism 11a that can change the valve timing of an intake valve (not shown) in the engine 8. The variable valve timing mechanism 11a is controlled by a control signal S11a supplied from the ECU 20. Further, the engine 8 is provided with a fuel injection pressure variable mechanism 11b capable of changing the pressure of the fuel injected from the fuel injection valve 9. For example, the variable fuel injection pressure mechanism 11b is configured by a pump or the like, and supplies fuel to the fuel injection valve 9 via a common rail (not shown). The fuel injection pressure variable mechanism 11b is controlled by a control signal S11b supplied from the ECU 20. In addition, the engine 8 is provided with a swirl variable mechanism 11c capable of changing the strength of the swirl in the cylinder. The swirl variable mechanism 11c is configured by, for example, a swirl control valve. The swirl variable mechanism 11c is controlled by a control signal S11c supplied from the ECU 20.

  The exhaust gas generated by the combustion in the engine 8 is exhausted from the exhaust passage 12. The exhaust passage 12 is provided with a turbine 14b of a turbocharger 14 that is rotated by the energy of the exhaust gas, and a catalyst 13 that can purify the exhaust gas.

  The turbocharger 14 is configured as a so-called MAT (Motor Assist Turbo), and a motor 14c is directly connected to a rotating shaft thereof. The motor 14 c functions as an electric motor that assists the rotation in the turbocharger 14. That is, the motor 14c functions to increase the supercharging pressure in the turbocharger 14. In this case, the motor 14c is controlled by a control signal S14c supplied from the ECU 20.

  The vehicle 100 is configured to recirculate exhaust gas from the upstream side of the turbine 14b to the downstream side of the compressor 14a. Specifically, the exhaust gas is recirculated by the EGR passage 15 a that connects the upstream position of the turbine 14 b in the exhaust passage 12 and the downstream position of the intercooler 5 in the intake passage 3. An EGR valve 15b capable of controlling the amount of EGR gas is provided on the EGR passage 15a.

  The vehicle 100 is provided with various sensors. Specifically, vehicle 100 includes a crank angle sensor 21, a water temperature sensor 22, an exhaust temperature sensor 23, and a rotation speed sensor 24. The crank angle sensor 21 detects a rotation angle (crank angle) of a crankshaft (not shown) and outputs a detection signal S21 corresponding to the detected crank angle to the ECU 20. The water temperature sensor 22 detects the temperature of cooling water for cooling the engine 8 and the like (hereinafter simply referred to as “water temperature”), and supplies a detection signal S22 corresponding to the detected water temperature to the ECU 20. The exhaust temperature sensor 23 is provided on the exhaust passage 12, detects the temperature of exhaust gas (exhaust temperature), and supplies a detection signal S23 corresponding to the detected exhaust temperature to the ECU 20. The rotation speed sensor 24 detects the rotation speed of the engine 8 and supplies a detection signal S24 corresponding to the detected rotation speed to the ECU 20. Note that the vehicle 100 is provided with various sensors other than the above-described sensors, but description of portions not particularly related to the present embodiment will be omitted.

  The ECU 20 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown). In the present embodiment, the ECU 20 mainly executes a process for detecting the cetane number of the fuel. More specifically, the ECU 20 executes fuel injection or the like that changes the number of times of pilot injection when the fuel of the engine 8 is cut. Based on the number of pilot injections when fuel ignition occurs, the ECU 20 The cetane number of is detected. Thus, ECU20 is corresponded to the fuel cetane number detection apparatus of the internal combustion engine in this invention. Specifically, the ECU 20 includes fuel injection control means, cetane number detection means, fuel injection pressure control means, glow plug control means, motor control means, throttle control means, first valve timing control means, and second valve timing. It operates as a control means, an intake manifold temperature control means, and a swirl control means. The ECU 20 also controls other components in the vehicle 100, but a description of portions that are not particularly related to the present embodiment is omitted.

[Cetane number detection method]
Hereinafter, examples of the cetane number detection method will be specifically described.

(First embodiment)
First, the cetane number detection method according to the first embodiment will be described. In the first embodiment, at the time of fuel cut of the engine 8 (at the time of fuel cut), the number of pilot injections is changed to execute fuel injection, and the number of pilot injections set when ignition occurs is set. Based on this, the cetane number of the fuel is detected. When pilot injection is performed a plurality of times in this manner, the fuel mixture is difficult to diffuse and the temperature is likely to rise, so that the ignitability of the fuel can be improved when detecting the cetane number. That is, the fuel can be easily ignited when the cetane number is detected. Therefore, according to the first embodiment, it is possible to perform stable ignition and more reliably detect the cetane number of the fuel as compared with the case where only single injection (only main injection) is performed. It becomes possible.

  FIG. 2 is a diagram for specifically explaining the cetane number detection method according to the first embodiment. 2A to 2C, the horizontal axis indicates the crank angle, and the vertical axis indicates the time. FIG. 2 (a) shows a graph when a high cetane number fuel is used, and FIGS. 2 (b) and 2 (c) show a graph when a low cetane number fuel is used. Yes.

  When high cetane number fuel is used, it can be seen that the fuel is ignited by performing single injection without pilot injection (that is, only main injection) (see FIG. 2A). On the other hand, when the low cetane number fuel is used, it can be seen that the fuel is not ignited in the single injection without the pilot injection (see FIG. 2B). This is because low cetane number fuels tend to be less ignitable than high cetane number fuels. Here, as shown in FIG. 2C, it is understood that the fuel is ignited when a plurality of pilot injections are performed on the same fuel as the fuel shown in FIG. 2B. This is because by performing the pilot injection a plurality of times, the fuel mixture is difficult to diffuse and the temperature is likely to rise, so that the fuel is easily ignited.

  FIG. 3 is a schematic diagram showing the relationship between the number of pilot injections when ignition is performed (hereinafter, the number of pilot injections is also simply referred to as “the number of pilots”) and the cetane number. As shown in the figure, it can be seen that the smaller the number of pilots, the narrower the range of cetane number values that cause ignition, and the larger the number of pilots, the wider the range of cetane number values that cause ignition. This is because it is easy to ignite when the cetane number is high, so it tends to ignite even with a small number of pilots, but it is difficult to ignite when the cetane number is low, so it does not ignite unless the number of pilots is increased. Because it is. In the first embodiment, the cetane number of the fuel is detected based on the relationship between the number of pilots and the cetane number.

  Next, the cetane number detection process according to the first embodiment will be specifically described with reference to FIG. FIG. 4 is a flowchart showing the cetane number detection process according to the first embodiment. The cetane number detection process is executed by the ECU 20 described above. Moreover, the said process is performed at the predetermined timing, for example after fuel supply.

  First, in step S101, the ECU 20 determines whether a cetane number determination execution condition is satisfied. For example, the ECU 20 determines whether or not the engine 8 is in a fuel cut state. That is, when in the fuel cut state, the ECU 20 determines that the cetane number determination execution condition is satisfied. If the determination execution condition is satisfied (step S101; Yes), the process proceeds to step S102. If the determination execution condition is not satisfied (step S101; No), the process exits the flow.

  In step S102, the ECU 20 determines the number of pilot injections (number of pilots) that is set to determine the cetane number. Then, the process proceeds to step S103.

  In step S103, the ECU 20 executes fuel injection for determining the cetane number. Specifically, the ECU 20 performs fuel injection with the number of pilots set in step S102. More specifically, the ECU 20 performs fuel injection with an injection amount that has little influence on the deceleration state of the vehicle 100. Then, the process proceeds to step S104.

  In step S104, the ECU 20 determines whether or not the fuel is ignited by the fuel injection in step S103. Specifically, the ECU 20 obtains the crank angular velocity from the detection signal S15 supplied from the crank angle sensor 15, and determines whether or not the fuel has been ignited based on the change in the crank angular velocity. For example, the ECU 20 can determine that the fuel has been ignited when the change in the crank angular velocity (corresponding to the crank angular acceleration) exceeds a predetermined value. Note that the present invention is not limited to determining the presence or absence of ignition based on the change in crank angular velocity. In another example, the presence or absence of ignition can be determined based on a change in in-cylinder pressure (output from an in-cylinder pressure sensor or the like) instead of a change in crank angular velocity.

  If the fuel is ignited (step S104; Yes), the process proceeds to step S106. In step S106, the ECU 20 detects the cetane number based on the currently set number of pilots. For example, the ECU 20 refers to a map in which the cetane number of fuel is associated with the number of pilots, and obtains a cetane number corresponding to the currently set number of pilots. When the above process ends, the process exits the flow.

  On the other hand, when the fuel is not ignited (step S104; No), the process proceeds to step S105. In step S105, the ECU 20 executes a process for changing the number of pilots. For example, the ECU 20 executes a process for increasing the currently set number of pilots. And a process returns to step S103 and performs fuel injection again. That is, the number of pilots is changed until fuel ignition occurs by repeating the processing of steps S103 to S105. It should be noted that fuel injection is executed so that the total injection amount in one cycle does not change even if the number of pilots is changed.

  As described above, according to the cetane number detection process according to the first embodiment, the fuel can be easily ignited when the cetane number is detected by performing the pilot injection a plurality of times. Therefore, stable ignition can be performed when the cetane number is detected, and the cetane number of the fuel can be efficiently detected. In this case, since the cetane number is detected only by determining whether or not ignition has occurred, it is difficult to ignite (such as when the compression ratio of the engine is low, when the intake valve is closed late, or when the water temperature is low). However, since the ignition can be appropriately performed at the time of detecting the cetane number, the cetane number can be detected appropriately.

  In the above description, the embodiment has been described in which the number of pilots to be set for detecting the cetane number is determined by gradually increasing the number of pilots based on the presence or absence of fuel ignition. However, the present invention is not limited to this. . In another example, fuel injection is started with the number of pilots approximately half the maximum number of pilot injections (hereinafter referred to as “maximum number of pilots”), and the cetane number is determined based on the presence or absence of ignition by fuel injection. The range of the number of pilots to be determined for ignition for detection can be gradually reduced to half. Specifically, the first fuel injection is performed by pilot injection with the pilot number approximately half of the maximum number of pilots, and the second and subsequent fuel injections are based on the presence or absence of ignition by the previous fuel injection. In order to detect this, it can be executed by pilot injection of the number of pilots that narrows the range of the number of pilots to be determined for ignition to approximately half.

  FIG. 5 is a diagram for specifically explaining a pilot number determination procedure (hereinafter referred to as “first pilot number determination procedure”) according to another example. As shown in the figure, first, the ECU 20 starts pilot injection with the number of pilots approximately half the maximum number of pilots. When the maximum number of pilots is “8 times”, the first pilot injection is performed with the number of pilots of “4 times”, and when the maximum number of pilots is “7 times”, “4 times” or “3 times” The first pilot injection is performed according to the number of pilots. Next, when the ECU 20 ignites at approximately half of the maximum number of pilots, the number of pilots in the lower half region of the maximum number of pilots is used for the second pilot injection. Specifically, a substantially intermediate number of pilots in the lower half region of the maximum number of pilots is used. For example, when the maximum number of pilots is “8”, the second pilot injection is performed with the number of pilots “2”. On the other hand, if the ECU 20 does not ignite approximately half of the maximum number of pilots, the number of pilots in the upper half of the maximum number of pilots is used for the second pilot injection. Specifically, a substantially intermediate number of pilots in the upper half region of the maximum number of pilots is used. For example, when the maximum number of pilots is “8”, the second pilot injection is performed with the number of pilots of “6”. Then, the ECU 20 performs the third and subsequent pilot injections in the same manner by the number of pilots that is gradually reduced to half by the range of the number of pilots according to the presence or absence of ignition.

  In this way, in the first pilot number determination procedure, the range of the number of pilots that should be determined for ignition is gradually narrowed to half in order to detect the cetane number in accordance with the presence or absence of fuel ignition. Specifically, when ignition is performed by fuel injection with the current number of pilots, the ECU 20 uses the number of pilots in the lower half region determined by the current number of pilots and the previous number of pilots, and uses the fuel with the current number of pilots. When ignition is not caused by injection, the number of pilots for which ignition is determined is narrowed down to half by using the number of pilots in the upper half region determined by the current number of pilots and the previous number of pilots. More specifically, when ignition is performed by fuel injection with the current number of pilots, the ECU 20 subtracts approximately half of the absolute value of the difference between the current number of pilots and the previous number of pilots from the current number of pilots. The number of pilots obtained by the above (hereinafter referred to as “the intermediate pilot number on the smaller side”) is used as the next pilot number. On the other hand, if the ignition is not performed by fuel injection with the current number of pilots, the ECU 20 sets the current pilot number to approximately half the absolute value of the difference between the current pilot number and the previous pilot number. The number of pilots obtained by the addition (hereinafter referred to as “the higher number of intermediate pilots”) is used as the next pilot number.

  FIG. 6 is a flowchart showing a process for determining the number of pilots to be set in order to determine the cetane number as described above (hereinafter also referred to as “first cetane number determination pilot number determination process”). . The first cetane number determination pilot number determination process is repeatedly executed in the cetane number detection process (see FIG. 4) according to the first embodiment described above. That is, it is repeatedly executed in the process of determining the cetane number. The process is executed by the ECU 20.

  First, in step S201, the ECU 20 determines whether it is the first determination. That is, the ECU 20 determines whether or not the first pilot injection is performed to determine the cetane number. If it is the first determination (step S201; Yes), the process proceeds to step S202. In this case, in the subsequent processing, the number of pilots to be set when executing the first pilot injection is determined when the cetane number is determined. On the other hand, when it is not the first determination (step S201; No), the process proceeds to step S203. In this case, in the subsequent processing, the number of pilots to be set when executing the second and subsequent pilot injections is determined when determining the cetane number.

  In step S202, the ECU 20 determines the number of pilots to be set in the first pilot injection, which is approximately half the maximum number of pilots. That is, pilot injection for determining the cetane number is started with the number of pilots that is approximately half the maximum number of pilots. Then, the process exits the flow.

  On the other hand, in step S203, the ECU 20 determines whether ignition has occurred due to the previous pilot injection. For example, the ECU 20 determines whether or not fuel has been ignited based on a change in crank angular velocity.

  If ignition has occurred due to the previous pilot injection (step S203; Yes), the process proceeds to step S204. In this case, the ECU 20 determines the intermediate pilot number on the smaller side as the pilot number to be set in the next pilot injection (step S204). Then, the process exits the flow.

  On the other hand, when ignition did not occur due to the previous pilot injection (step S203; No), the process proceeds to step S205. In this case, the ECU 20 determines the intermediate pilot number on the larger side as the pilot number to be set in the next pilot injection (step S205). Then, the process exits the flow.

  By performing the above first cetane number determination pilot number determination process, the number of pilots to be set for detecting the cetane number can be determined efficiently, that is, the number of pilots can be determined with a relatively small number of determinations. Can be identified. Therefore, it is possible to determine the cetane number with a relatively small number of determinations for a wide range of cetane number fuels.

  In yet another example, when detecting the cetane number after refueling, instead of starting fuel injection with the number of pilots approximately half the maximum number of pilots as described above, the fuel before refueling is used. Fuel injection can be started from the number of pilots used in determining the cetane number, and the number of pilots to be set for detecting the cetane number can be narrowed down from the number of pilots. Specifically, when the amount of fuel supply is considerably smaller than the remaining amount in the fuel tank, the first fuel injection is performed by the number of pilots set when determining the cetane number in the fuel before fueling. The second and subsequent fuel injections can be executed by pilot injection of the number of pilots that is obtained by increasing or decreasing the number of pilots set in the previous fuel injection based on the presence or absence of ignition by the previous fuel injection. . This is because, when the remaining amount in the fuel tank is large and the amount of fuel supply is small, the cetane number in the fuel mixed by fueling largely reflects the influence of the fuel before fueling. That is, the cetane number in the fuel after being mixed by refueling is considered to be close to the cetane number in the fuel before refueling.

  FIG. 7 is a diagram for specifically explaining a procedure for determining the number of pilots according to still another example (hereinafter referred to as a “second pilot number determining procedure”). That is, it is a figure for demonstrating the determination procedure of the number of pilots performed when detecting a cetane number after refueling. As shown in the figure, first, the ECU 20 starts pilot injection with the number of pilots corresponding to the cetane number detected last time. That is, the ECU 20 performs the first pilot injection according to the number of pilots set when determining the cetane number in the fuel before refueling. Next, when the ignition is performed by the first pilot injection, the ECU 20 uses the number of pilots reduced by one from the number of pilots set for the first time for the second pilot injection. On the other hand, if the ignition is not ignited by the first pilot injection, the ECU 20 uses the number of pilots obtained by increasing the number of pilots set by the first time by one for the second pilot injection. The ECU 20 also performs the third and subsequent pilot injections in the same manner, and the number of pilots increased by one or decreased by one according to the presence or absence of ignition. Run by.

  FIG. 8 is a flowchart showing a process for determining the number of pilots to be set in order to determine the cetane number as described above (hereinafter also referred to as “second cetane number determination pilot number determination process”). . This second cetane number determination pilot number determination process is repeatedly executed in the cetane number detection process (see FIG. 4) according to the first embodiment described above. That is, it is repeatedly executed in the process of determining the cetane number. The process is executed by the ECU 20.

  First, in step S301, the ECU 20 determines whether or not the determination is after fuel supply. Specifically, the ECU 20 determines whether the amount of fuel supply is less than the remaining amount in the fuel tank. When it is the determination after refueling (step S301; Yes), a process progresses to step S302. On the other hand, when it is not the determination after refueling (step S301; No), a process progresses to step S307. In this case, the ECU 20 executes the first cetane number determination pilot number determination process shown in FIG. 6 (step S307). That is, the ECU 20 starts fuel injection with the number of pilots that is approximately half the maximum number of pilots, and determines the number of pilots to be determined for ignition in order to detect the cetane number based on the presence or absence of ignition by fuel injection. A process of gradually narrowing the range to half is executed.

  In step S302, the ECU 20 determines whether it is the first determination. That is, the ECU 20 determines whether or not the first pilot injection is performed to determine the cetane number. If it is the first determination (step S302; Yes), the process proceeds to step S303. In this case, in the subsequent processing, the number of pilots to be set when executing the first pilot injection is determined when the cetane number is determined. On the other hand, when it is not the first determination (step S302; No), the process proceeds to step S304. In this case, in the subsequent processing, the number of pilots to be set when executing the second and subsequent pilot injections is determined when determining the cetane number.

  In step S303, the ECU 20 determines the number of pilots corresponding to the previous cetane number as the number of pilots to be set in the first pilot injection. That is, the ECU 20 determines the number of pilots set when determining the cetane number in the fuel before refueling as the number of pilots to be set in the first pilot injection. Then, the process exits the flow.

  On the other hand, in step S304, the ECU 20 determines whether ignition has occurred due to the previous pilot injection. For example, the ECU 20 determines whether or not fuel has been ignited based on a change in crank angular velocity.

  If ignition has occurred due to the previous pilot injection (step S304; Yes), the process proceeds to step S305. In this case, the ECU 20 determines the number of pilots reduced by one from the number of pilots set in the previous fuel injection as the number of pilots to be set in the next pilot injection (step S305). Then, the process exits the flow.

  On the other hand, when ignition did not occur by the previous pilot injection (step S304; No), the process proceeds to step S306. In this case, the ECU 20 determines the number of pilots obtained by increasing the number of pilots set in the previous fuel injection by 1 as the number of pilots to be set in the next pilot injection (step S306). Then, the process exits the flow.

  By performing the second cetane number determination pilot number determination process described above, when detecting the cetane number after refueling, it is possible to efficiently determine the number of pilots to be set for detecting the cetane number. That is, the number of pilots can be specified with a relatively small number of determinations. This also makes it possible to determine the cetane number with a relatively small number of determinations for a wide range of cetane number fuels.

(Second embodiment)
Next, a cetane number detection method according to the second embodiment will be described. In the second embodiment, instead of performing fuel injection by changing the number of pilots, control is performed to change the timing for performing pilot injection (injection timing), and based on the injection timing set when ignition occurs. This is different from the first embodiment described above in that the cetane number of the fuel is detected. That is, in the second embodiment, control is performed to delay or speed up the injection timing for executing pilot injection. As described above, when the pilot injection is performed a plurality of times, the fuel mixture is difficult to diffuse and the temperature is likely to rise, so that the fuel is easily ignited. It can be said that the fuel becomes easier to ignite by making it faster (that is, by making it advance). Therefore, according to the second embodiment, stable ignition can be performed as compared with the case where the injection timing is fixed, and the cetane number of the fuel can be detected more reliably. Moreover, it becomes possible to detect the cetane number with high accuracy.

  FIG. 9 is a diagram for specifically explaining the cetane number detection method according to the second embodiment. In each of FIGS. 9A to 9C, the horizontal axis indicates the crank angle and the vertical axis indicates time. FIG. 9 (a) shows a graph when a high cetane number fuel is used, and FIGS. 9 (b) and 9 (c) show a graph when a low cetane number fuel is used. Yes.

  When high cetane number fuel is used, it can be seen that the fuel is ignited by a plurality of pilot injections (see FIG. 9A). Next, when fuel injection is performed under the same conditions as shown in FIG. 9 (a), that is, when fuel injection is performed under the same conditions of the number of pilot injections and the injection timing, the low cetane number fuel When is used, it can be seen that the fuel is not ignited (see FIG. 9B). This is because when a low cetane number fuel is used, ignition tends to be difficult when the injection timing is relatively later than when a high cetane number fuel is used. Next, when the pilot timing shown in FIG. 9B is advanced (that is, the injection timing is advanced) and a plurality of pilot injections are performed, as shown in FIG. 9C, the fuel is ignited. You can see that This is because the fuel is easily ignited by making the injection timing for executing the pilot injection earlier.

  FIG. 10 is a schematic diagram showing the relationship between the number of pilots, the injection timing when ignited, and the cetane number. As shown in the figure, it can be seen that the slower the injection timing, the narrower the range of cetane number values at which ignition occurs, and the earlier the injection timing, the wider the range of cetane number values at which ignition occurs. This tends to ignite when the cetane number is high, so it tends to ignite even at a relatively slow injection timing, but it is difficult to ignite when the cetane number is low. This is because they tend not to. In the second embodiment, the ECU 20 detects the cetane number of the fuel based on the relationship between the injection timing and the cetane number.

  FIG. 11 is a flowchart showing cetane number detection processing according to the second embodiment. The cetane number detection process is executed by the ECU 20 described above.

  The processes in steps S401 and S402 are the same as the processes in steps S101 and S102 in the cetane number detection process according to the first embodiment described above (see FIG. 4). Therefore, the description is omitted. Next, in step S403, the ECU 20 determines the injection timing that is set to determine the cetane number. Then, the process proceeds to step S404.

  In step S404, the ECU 20 executes fuel injection for determining the cetane number. Specifically, the ECU 20 performs fuel injection at the injection timing set in step S403. Then, the process proceeds to step S405.

  In step S405, the ECU 20 determines whether the fuel is ignited by the fuel injection in step S404. Specifically, the ECU 20 determines the presence or absence of fuel ignition based on the change in the crank angular velocity. If the fuel is ignited (step S405; Yes), the process proceeds to step S407. In step S407, the ECU 20 detects the cetane number based on the currently set injection timing. For example, the ECU 20 refers to a map in which the fuel cetane number is associated with the injection timing, and obtains a cetane number corresponding to the currently set injection timing. When the above process ends, the process exits the flow.

  On the other hand, when the fuel is not ignited (step S405; No), the process proceeds to step S406. In step S406, the ECU 20 executes a process for changing the injection timing. For example, the ECU 20 advances (that is, advances) the currently set injection timing. And a process returns to step S404 and performs fuel injection again. That is, by repeating the processing of steps S404 to S406, the injection timing is changed until fuel ignition occurs.

  Also by the cetane number detection process according to the second embodiment, the fuel can be easily ignited when the cetane number is detected by changing the injection timing of the pilot injection. Therefore, stable ignition can be performed when the cetane number is detected, and the cetane number of the fuel can be efficiently detected.

  Note that the cetane number detection method according to the second embodiment may be combined with the cetane number detection method according to the first embodiment described above. Specifically, the cetane number of the fuel can be detected by performing the control for changing the injection timing for performing the pilot injection and the control for changing the number of times of performing the pilot injection. For example, if the fuel does not ignite even when the injection timing is changed, the number of pilot injections can be increased to detect the cetane number.

(Third embodiment)
Next, a cetane number detection method according to the third embodiment will be described. In the third embodiment, instead of executing fuel injection by changing the number of pilots, injection timing, etc., control is performed to change the total injection amount when performing fuel injection, and is set when ignition occurs. This is different from the first and second embodiments described above in that the cetane number of the fuel is detected based on the total injection amount. That is, in the third embodiment, control is performed to change the total injection amount injected in a plurality of pilot injections. It can be said that when the total injection amount is increased, the temperature of the fuel is likely to rise, so that the fuel is easily ignited. Therefore, according to the third embodiment, stable ignition can be performed as compared with the case where the total injection amount is fixed, and the cetane number of the fuel can be detected more reliably. . Moreover, it becomes possible to detect the cetane number with high accuracy.

  FIG. 12 is a schematic diagram showing the relationship between the number of pilots, the total injection amount upon ignition, and the cetane number. As shown in the figure, it can be seen that the smaller the injection amount, the narrower the cetane number range in which ignition occurs, and the larger the injection amount, the wider the cetane number range in which ignition occurs. This is because it is easy to ignite when the cetane number is high, so it tends to ignite even with a relatively small injection amount, but it is difficult to ignite when the cetane number is low. This is because they tend not to. In the third embodiment, the ECU 20 detects the cetane number of the fuel based on the relationship between the total injection amount and the cetane number.

  The cetane number detection method according to the third embodiment may be executed in combination with the cetane number detection method according to the first embodiment described above. Specifically, the cetane number of the fuel can be detected by performing control for changing the total injection amount when performing fuel injection and performing control for changing the number of times of pilot injection.

(Fourth embodiment)
Next, a cetane number detection method according to the fourth embodiment will be described. In the fourth embodiment, instead of performing fuel injection by changing the number of pilots, injection timing, etc., control is performed to change the fuel injection interval (hereinafter referred to as “pilot interval”) in pilot injection, This is different from the first to third embodiments described above in that the cetane number of the fuel is detected based on the pilot interval set when ignition occurs. It can be said that when the pilot interval is shortened, it becomes difficult for the fuel mixture to diffuse, so that the fuel is easily ignited. Therefore, according to the fourth embodiment, stable ignition can be performed as compared with the case where the pilot interval is fixed, and the cetane number of the fuel can be detected more reliably. Moreover, it becomes possible to detect the cetane number with high accuracy.

  FIG. 13 is a schematic diagram showing the relationship between the number of pilots, the pilot interval when ignited, and the cetane number. As shown in the figure, it can be seen that the longer the pilot interval, the narrower the cetane number value range where ignition occurs, and the shorter the pilot interval, the wider the cetane number value range where ignition occurs. This tends to ignite when the cetane number is high, so it tends to ignite even with a relatively long pilot interval. However, it is difficult to ignite when the cetane number is low. This is because they tend not to. In the fourth embodiment, the ECU 20 detects the cetane number of the fuel based on the relationship between the pilot interval and the cetane number.

  Note that the cetane number detection method according to the fourth embodiment may be combined with the cetane number detection method according to the first embodiment described above. Specifically, the cetane number of the fuel can be detected by performing the control for changing the pilot interval and the control for changing the number of pilot injections.

(5th Example)
Next, a cetane number detection method according to the fifth embodiment will be described. In the fifth embodiment, instead of executing fuel injection by changing the number of pilots, injection timing, etc., control is performed to change the fuel injection pressure, and based on the fuel injection pressure set when ignition occurs. The difference from the first to fourth embodiments described above is that the cetane number of the fuel is detected. That is, in the fifth embodiment, the ECU 20 detects the cetane number of the fuel by changing the fuel injection pressure by controlling the variable fuel injection pressure mechanism 11b. Specifically, the ECU 20 changes the fuel injection pressure from a high pressure to a lower side, or changes the fuel injection pressure from a lower pressure to a higher side, based on the fuel injection pressure when ignition occurs. Determine the cetane number. Moreover, it becomes possible to detect the cetane number with high accuracy.

  FIG. 14 is a schematic diagram showing the relationship between the number of pilots, the fuel injection pressure when ignited, and the cetane number. Specifically, FIG. 14 (a) shows the relationship between the fuel injection pressure and the cetane number on the higher fuel injection pressure side, and FIG. 14 (b) shows the fuel injection pressure on the lower fuel injection pressure side. And the cetane number.

  As shown in FIG. 14 (a), the higher the fuel injection pressure, the narrower the cetane number value range where ignition occurs, and the lower the fuel injection pressure, the wider the cetane number value range where ignition occurs. Recognize. This is because if the fuel injection pressure becomes too high, the fuel spray becomes too fine and the air-fuel mixture tends to diffuse, making it difficult to ignite. Therefore, if the cetane number is high, it is easy to ignite, so it can be said that it tends to ignite even at a relatively high fuel injection pressure. However, if the cetane number is low, it is difficult to ignite. It can be said that there is a tendency not to ignite. When changing the fuel injection pressure from a high pressure to a lowering side, the ECU 20 detects the cetane number of the fuel based on the relationship between the fuel injection pressure and the cetane number.

  On the other hand, as shown in FIG. 14B, the lower the fuel injection pressure, the narrower the range of cetane number that causes ignition, and the higher the fuel injection pressure, the range of cetane number that causes ignition. It turns out that becomes wide. This is because if the fuel injection pressure becomes too low, the atomization of the fuel spray becomes worse, the air-fuel mixture becomes difficult and ignition becomes difficult. Therefore, when the cetane number is high, it is easy to ignite, so it can be said that there is a tendency to ignite even at a relatively low fuel injection pressure. However, when the cetane number is low, it is difficult to ignite. It can be said that there is a tendency not to ignite. The ECU 20 detects the cetane number of the fuel based on the relationship between the fuel injection pressure and the cetane number when the fuel injection pressure is changed from a low pressure to a higher side.

  It is also possible to detect the cetane number by using the fuel injection pressure approximately in the middle of the range of the fuel injection pressure shown in FIGS. 14 (a) and 14 (b). As described above, it is difficult to ignite if the fuel injection pressure becomes too high or too low. However, when such an approximately intermediate fuel injection pressure is used, the fuel injection has little effect on the ignitability. Cetane number can be detected by pressure. Therefore, it is possible to stably detect the cetane number without deteriorating accuracy.

  Further, the cetane number detection method according to the fifth embodiment may be executed in combination with the cetane number detection method according to the first embodiment described above. Specifically, the cetane number of the fuel can be detected by performing the control for changing the fuel injection pressure and the control for changing the number of pilot injections.

(Sixth embodiment)
Next, a cetane number detection method according to the sixth embodiment will be described. The sixth embodiment differs from the first to fifth embodiments described above in that control is performed to operate the glow plug 10 provided in the cylinder of the engine 8 when the cetane number is detected. That is, in the sixth embodiment, the cetane number of the fuel is detected while the glow plug 10 is heated. More specifically, the ECU 20 performs control to change the temperature of the glow plug 10 (hereinafter simply referred to as “glow temperature”), and detects the cetane number of the fuel based on the glow temperature when ignition occurs. By heating the glow plug 10 in this way, the in-cylinder temperature tends to increase, so that it can be said that the fuel is more easily ignited than when the glow plug 10 is not heated. Therefore, according to the sixth embodiment, stable ignition can be performed at the time of detecting the cetane number, and the cetane number can be detected more reliably. Moreover, it becomes possible to detect the cetane number with high accuracy.

  FIG. 15 is a schematic diagram showing the relationship between the number of pilots, the glow temperature when ignited, and the cetane number. As shown in the figure, it can be seen that the lower the glow temperature, the narrower the range of cetane number values at which ignition occurs, and the higher the glow temperature, the wider the range of cetane number values at which ignition occurs. This tends to ignite when the cetane number is high, so it tends to ignite even at a relatively low glow temperature, but it is difficult to ignite when the cetane number is low. This is because they tend not to. In the sixth embodiment, the ECU 20 detects the cetane number of the fuel based on the relationship between the glow temperature and the cetane number.

  FIG. 16 is a flowchart showing cetane number detection processing according to the sixth embodiment. The cetane number detection process is executed by the ECU 20 described above.

  The processes in steps S501 and S502 are the same as the processes in steps S101 and S102 in the cetane number detection process according to the first embodiment described above (see FIG. 4). Therefore, the description is omitted. Next, in step S503, the ECU 20 determines a glow temperature that is set to determine the cetane number. Then, the process proceeds to step S504. In step S504, the ECU 20 executes fuel injection for determining the cetane number. Then, the process proceeds to step S505.

  In step S505, the ECU 20 determines whether the fuel is ignited by the fuel injection in step S504. Specifically, the ECU 20 determines the presence or absence of fuel ignition based on the change in the crank angular velocity. If the fuel is ignited (step S505; Yes), the process proceeds to step S507. In step S507, the ECU 20 detects the cetane number based on the current glow temperature. For example, the ECU 20 refers to a map in which the cetane number of fuel is associated with the glow temperature, and obtains a cetane number corresponding to the current glow temperature. When the above process ends, the process exits the flow.

  On the other hand, when the fuel is not ignited (step S505; No), the process proceeds to step S506. In step S506, the ECU 20 executes a process for changing the glow temperature. For example, the ECU 20 controls the glow plug 10 so that the glow temperature increases. And a process returns to step S504 and performs fuel injection again. That is, by repeating the processes of steps S504 to S506, the glow temperature is changed until fuel ignition occurs.

  Also in the cetane number detection process according to the sixth embodiment, by changing the glow temperature of the glow plug 10, the fuel can be easily ignited when the cetane number is detected. Therefore, stable ignition can be performed when the cetane number is detected, and the cetane number of the fuel can be efficiently detected.

  The cetane number detection method according to the sixth embodiment and the cetane number detection method according to the first embodiment described above may be executed in combination. Specifically, the cetane number of the fuel can be detected by performing control to change the glow temperature and control to change the number of pilot injections. This makes it possible to detect the cetane number with high accuracy.

(Seventh embodiment)
Next, a cetane number detection method according to the seventh embodiment will be described. In the seventh embodiment, instead of executing fuel injection by changing the number of pilots, injection timing, etc., control was performed on the motor 14c provided in the turbocharger 14 so that the supercharging pressure was changed, and ignition occurred. This differs from the first to sixth embodiments described above in that the cetane number of the fuel is detected based on the supercharging pressure at the time. When the supercharging pressure becomes high, the air in the cylinder of the engine 8 increases and the temperature is unlikely to decrease, so it can be said that the fuel is easily ignited. Therefore, according to the seventh embodiment, stable ignition can be performed as compared with the case where the supercharging pressure is not changed, and the cetane number of the fuel can be detected more reliably.

  FIG. 17 is a schematic diagram showing the relationship between the number of pilots, the supercharging pressure when ignited, and the cetane number. As shown in the drawing, it can be seen that the lower the supercharging pressure, the narrower the range of cetane number values that cause ignition, and the higher the supercharging pressure, the wider the range of cetane number values that cause ignition. This is because it is easy to ignite when the cetane number is high, so it tends to ignite even at a relatively low supercharging pressure. This is because there is a tendency not to ignite. In the seventh embodiment, the ECU 20 detects the cetane number of the fuel based on the relationship between the supercharging pressure and the cetane number.

  The cetane number detection method according to the seventh embodiment may be executed in combination with the cetane number detection method according to the first embodiment described above. Specifically, the cetane number of the fuel can be detected by controlling the motor 14c so as to change the supercharging pressure and controlling the number of pilot injections.

(Eighth embodiment)
Next, a cetane number detection method according to the eighth embodiment will be described. In the eighth embodiment, instead of executing fuel injection by changing the number of pilots, injection timing, etc., control on the throttle valve 4 so that the pressure of the intake manifold (hereinafter simply referred to as “in manifold pressure”) changes. And the cetane number of the fuel is detected on the basis of the intake manifold pressure when ignition occurs, which is different from the first to seventh embodiments described above. When the intake manifold pressure increases, the air in the cylinder of the engine 8 increases and the temperature is unlikely to decrease, so it can be said that the fuel is easily ignited. Therefore, according to the eighth embodiment, stable ignition can be performed as compared with the case where the intake manifold pressure is not changed, and the cetane number of the fuel can be detected more reliably.

  FIG. 18 is a schematic diagram showing the relationship between the number of pilots, the intake manifold pressure when ignited, and the cetane number. As shown in the figure, it can be seen that the lower the intake manifold pressure, the narrower the range of cetane number at which ignition occurs, and the higher the intake manifold pressure, the wider the range of cetane number at which ignition occurs. This is because it is easy to ignite when the cetane number is high, so it tends to ignite even with a relatively low intake manifold pressure, but it is difficult to ignite when the cetane number is low. This is because they tend not to. In the eighth embodiment, the ECU 20 detects the cetane number of the fuel based on such a relationship between the intake manifold pressure and the cetane number.

  The cetane number detection method according to the eighth embodiment and the cetane number detection method according to the first embodiment described above may be executed in combination. Specifically, the cetane number of the fuel can be detected by controlling the throttle valve 4 so as to change the intake manifold pressure and performing control to change the number of times of pilot injection. This makes it possible to detect the cetane number with high accuracy.

(Ninth embodiment)
Next, a cetane number detection method according to the ninth embodiment will be described. In the ninth embodiment, instead of executing fuel injection by changing the number of pilots, injection timing, etc., control is performed to change the valve timing in the engine 8 so that the intake air amount changes, and when ignition occurs The difference from the first to eighth embodiments described above is that the cetane number of the fuel is detected based on the valve timing. For example, the ECU 20 changes the intake air amount by performing control to change the opening timing of the intake valve of the engine 8 (hereinafter referred to as “intake opening timing”). In this case, if the intake opening timing is delayed, the intake air amount increases due to the inertial effect due to the initial negative pressure. Thus, it can be said that when the intake air amount increases, the temperature in the cylinder is less likely to decrease, and the fuel is easily ignited. Therefore, according to the ninth embodiment, stable ignition can be performed as compared with the case where the intake air amount is not changed, and the cetane number of the fuel can be detected more reliably. Moreover, it becomes possible to detect the cetane number with high accuracy.

  FIG. 19 is a schematic diagram showing the relationship between the number of pilots, the intake opening timing when ignited, and the cetane number. As shown in the figure, it can be seen that the earlier the intake opening timing, the narrower the range of cetane number that causes ignition, and the slower the intake opening timing, the wider the range of cetane number that causes ignition. This is because if the cetane number is high, it tends to ignite, so it tends to ignite even if the intake opening timing is relatively early, but if the cetane number is low, it is difficult to ignite, so the intake opening timing is This is because it tends not to ignite unless it is slow. In the ninth embodiment, the ECU 20 detects the cetane number of the fuel based on the relationship between the intake opening timing and the cetane number.

  Note that the cetane number detection method according to the ninth embodiment may be executed in combination with the cetane number detection method according to the first embodiment described above. Specifically, the fuel cetane number can be detected by performing control to change the valve timing so that the amount of intake air changes and control to change the number of pilot injections. This makes it possible to detect the cetane number with high accuracy.

(Tenth embodiment)
Next, a cetane number detection method according to the tenth embodiment will be described. In the tenth embodiment, instead of executing fuel injection by changing the number of pilots, injection timing, etc., control is performed to change the valve timing in the engine 8 so that the actual compression ratio changes, and when ignition occurs The difference from the first to ninth embodiments described above is that the cetane number of the fuel is detected based on the valve timing. For example, the ECU 20 changes the actual compression ratio by performing control to change the closing timing of the intake valve of the engine 8 (hereinafter referred to as “intake closing timing”). In this case, it can be said that when the intake closing timing is brought close to the bottom dead center (BDC) (that is, when the intake closing timing is advanced), the actual compression ratio increases and the fuel is easily ignited. Therefore, according to the tenth embodiment, stable ignition can be performed as compared with the case where the actual compression ratio is not changed, and the cetane number of the fuel can be detected more reliably.

  FIG. 20 is a schematic diagram showing the relationship between the number of pilots, the intake air closing timing when ignited, and the cetane number. As shown in the figure, it can be seen that the slower the intake closing timing, the narrower the cetane number range where ignition occurs, and the earlier the intake closing timing, the wider the cetane number range where ignition occurs. This is because ignition tends to occur when the cetane number is high, so it tends to ignite even if the intake close timing is relatively slow, but it is difficult to ignite when the cetane number is low. This is because there is a tendency not to ignite unless it is made early. In the tenth embodiment, the ECU 20 detects the cetane number of the fuel based on the relationship between the intake air closing timing and the cetane number.

  The cetane number detection method according to the tenth embodiment may be combined with the cetane number detection method according to the first embodiment described above. Specifically, the fuel cetane number can be detected by performing control to change the valve timing so as to change the actual compression ratio and control to change the number of pilot injections.

(Eleventh embodiment)
Next, a cetane number detection method according to the eleventh embodiment will be described. In the eleventh embodiment, control is performed so that the temperature of the intake manifold in the engine 8 (hereinafter referred to as “intake manifold temperature”) is changed instead of performing fuel injection by changing the number of pilots, the injection timing, and the like. This is different from the first to tenth embodiments described above in that the cetane number of the fuel is detected based on the intake manifold temperature when ignition occurs. For example, the ECU 20 controls the bypass passage valve 7 so that the intake air flows into the bypass passage 6 that bypasses the intercooler 5, thereby suppressing the intake air from being cooled by the intercooler 5, thereby increasing the intake manifold temperature. . When the intake manifold temperature becomes high in this way, the air temperature in the cylinder becomes high, and it can be said that the fuel is easily ignited. Therefore, according to the eleventh embodiment, stable ignition can be performed as compared with the case where the intake manifold temperature is not changed, and the cetane number of the fuel can be detected more reliably. Moreover, it becomes possible to detect the cetane number with high accuracy. Moreover, it becomes possible to detect the cetane number with high accuracy.

  FIG. 21 is a schematic diagram showing the relationship between the number of pilots, the intake manifold temperature when ignited, and the cetane number. As shown in the figure, it can be seen that the lower the intake manifold temperature, the narrower the range of cetane number values at which ignition occurs, and the higher the intake manifold temperature, the wider the range of cetane number values at which ignition occurs. This is because it is easy to ignite when the cetane number is high, so it tends to ignite even if the intake manifold temperature is relatively low, but it is difficult to ignite when the cetane number is low, so the intake manifold temperature must be increased. This is because there is a tendency not to ignite. In the eleventh embodiment, the ECU 20 detects the cetane number of the fuel based on the relationship between the intake manifold temperature and the cetane number.

  The cetane number detection method according to the eleventh embodiment may be combined with the cetane number detection method according to the first embodiment described above. Specifically, the cetane number of the fuel can be detected by performing control so as to change the intake manifold temperature and changing the number of pilot injections.

(Twelfth embodiment)
Next, a cetane number detection method according to the twelfth embodiment will be described. In the twelfth embodiment, instead of executing fuel injection by changing the number of pilots, injection timing, etc., control is performed such that the strength of swirl in the engine 8 (hereinafter referred to as “swirl strength”) changes. This is different from the first to eleventh embodiments described above in that the cetane number of the fuel is detected based on the swirl strength when ignition occurs. For example, the ECU 20 changes the swirl strength by controlling the swirl variable mechanism 11c. When the swirl strength is strong, the air-fuel mixture is easily diffused and difficult to ignite. However, when the swirl strength is weak, the air-fuel mixture is difficult to diffuse and it can be said that the fuel is easily ignited. Therefore, according to the twelfth embodiment, as compared with the case where the swirl strength is not changed, stable ignition can be performed, and the detection of the cetane number of the fuel can be more reliably performed. Moreover, it becomes possible to detect the cetane number with high accuracy.

  FIG. 22 is a schematic diagram showing the relationship between the number of pilots, the swirl strength when ignited, and the cetane number. As shown in the figure, it can be seen that the stronger the swirl strength, the narrower the range of cetane number values that cause ignition, and the weaker the swirl strength, the wider the range of cetane number values that cause ignition. This is because it is easy to ignite when the cetane number is high, so it tends to ignite even if the swirl strength is relatively strong, but it is difficult to ignite when the cetane number is low, so the swirl strength is weakened This is because it tends not to ignite unless it is done. In the twelfth embodiment, the ECU 20 detects the cetane number of the fuel based on the relationship between the swirl strength and the cetane number.

  The cetane number detection method according to the twelfth embodiment may be combined with the cetane number detection method according to the first embodiment described above. Specifically, the cetane number of the fuel can be detected by performing control so as to change the swirl strength and changing the number of pilot injections.

(Thirteenth embodiment)
Next, a cetane number detection method according to the thirteenth embodiment will be described. The thirteenth embodiment differs from the first to twelfth embodiments described above in that the cetane number is detected based on the water temperature in the engine 8 when fuel ignition occurs. This is because the ease of fuel ignition changes depending on the water temperature of the engine 8. For example, if the water temperature is high, the compression end temperature becomes high and the fuel is easily ignited.

  FIG. 23 is a schematic diagram showing the relationship between the number of pilots, the water temperature when ignited, and the cetane number. As shown in the figure, it can be seen that the lower the water temperature, the narrower the range of cetane number values at which ignition occurs, and the higher the water temperature, the wider the range of cetane number values at which ignition occurs. This is because it is easy to ignite when the cetane number is high, so it tends to ignite even when the water temperature is relatively low, but it is difficult to ignite when the cetane number is low, so it will not ignite unless the water temperature is high. This is because there is a tendency. In the thirteenth embodiment, the ECU 20 detects the cetane number of the fuel based on the relationship between the water temperature and the cetane number.

  FIG. 24 is a flowchart showing cetane number detection processing according to the thirteenth embodiment. The cetane number detection process is executed by the ECU 20 described above.

  The processes in steps S601 and S602 are the same as the processes in steps S101 and S102 in the cetane number detection process according to the first embodiment described above (see FIG. 4). Therefore, the description is omitted. Next, in step S603, the ECU 20 acquires the water temperature (corresponding to the detection signal S22) from the water temperature sensor 22. Then, the process proceeds to step S604. In step S604, the ECU 20 executes fuel injection for determining the cetane number. Then, the process proceeds to step S605.

  In step S605, the ECU 20 detects the presence or absence of ignition due to fuel injection in step S604. Specifically, the ECU 20 determines the presence or absence of fuel ignition based on the change in the crank angular velocity. Then, the process proceeds to step S606.

  In step S606, the ECU 20 determines the cetane number of the fuel based on the water temperature acquired in step S603 and the presence or absence of ignition detected in step S604. Specifically, the ECU 20 determines the cetane number of the fuel with reference to a map in which the cetane number is associated with the water temperature and the presence or absence of ignition. When the above process ends, the process exits the flow.

  According to the cetane number detection process according to the thirteenth embodiment, the cetane number is detected in consideration of the water temperature. Therefore, the cetane number of the fuel can be detected with high accuracy.

  The cetane number detection method according to the thirteenth embodiment may be executed in combination with the cetane number detection method according to the first embodiment described above. Specifically, the cetane number of the fuel can be detected in consideration of the water temperature of the engine 8 while performing control to change the number of times of performing pilot injection. This makes it possible to detect the cetane number with higher accuracy.

(14th embodiment)
Next, a cetane number detection method according to the 14th embodiment will be described. In the fourteenth embodiment, the first cetane number is detected in that the cetane number is detected based on the EGR rate (the ratio of EGR gas to the total exhaust gas) when fuel ignition occurs during deceleration from the EGR region. Or different from the thirteenth embodiment. That is, in the fourteenth embodiment, the cetane number is detected from the EGR rate at the time of ignition by utilizing the fact that the EGR gas escapes and the EGR rate changes during deceleration from the EGR region. This is because the ease of fuel ignition varies depending on the EGR rate, so that the cetane number can be determined based on the presence or absence of ignition at each EGR rate. Specifically, since the EGR rate is high at the initial stage of deceleration from the EGR region, it can be said that ignition is difficult. On the other hand, as the deceleration progresses, the EGR rate decreases, so it can be said that ignition is easier.

  FIG. 25 is a schematic diagram showing the relationship between the number of pilots, the EGR rate when ignited, and the cetane number. As shown in the figure, it can be seen that the higher the EGR rate, the narrower the range of cetane number values at which ignition occurs, and the lower the EGR rate, the wider the range of cetane number values at which ignition occurs. This is because it is easy to ignite when the cetane number is high, so it tends to ignite even if the EGR rate is relatively high. However, if the cetane number is low, it is difficult to ignite, so the EGR rate must be low. This is because there is a tendency not to ignite. In the fourteenth embodiment, the ECU 20 detects the cetane number of the fuel based on such a relationship between the EGR rate and the cetane number.

  FIG. 26 is a flowchart showing cetane number detection processing according to the fourteenth embodiment. The cetane number detection process is executed by the ECU 20 described above.

  In step S701, the ECU 20 determines whether or not a cetane number determination execution condition is satisfied. Specifically, ECU 20 determines whether vehicle 100 is in a deceleration state from the EGR region. If the determination execution condition is satisfied (step S701; Yes), the process proceeds to step S702. If the determination execution condition is not satisfied (step S701; No), the process exits the flow.

  In step S702, the ECU 20 determines the number of pilots set for determining the cetane number. Then, the process proceeds to step S703. In step S703, the ECU 20 executes fuel injection for determining the cetane number. Then, the process proceeds to step S704.

  In step S704, the ECU 20 acquires the current EGR rate. For example, the ECU 20 calculates the EGR rate using an arithmetic expression. Then, the process proceeds to step S705. In step S705, the ECU 20 determines whether or not the fuel is ignited by the fuel injection in step S703. Specifically, the ECU 20 determines the presence or absence of fuel ignition based on the change in the crank angular velocity. When the fuel is ignited (step S705; Yes), the process proceeds to step S707. In step S707, the ECU 20 detects the cetane number based on the EGR rate obtained in step S704. For example, the ECU 20 refers to a map in which the cetane number of fuel is associated with the EGR rate, and obtains a cetane number corresponding to the current EGR rate. When the above process ends, the process exits the flow.

  On the other hand, when the fuel is not ignited (step S705; No), the process returns to step S703, and the fuel injection is performed again. That is, by repeating the processes in steps S703 to S705, the EGR rate is continuously acquired until fuel ignition occurs.

  According to the cetane number detection processing according to the fourteenth embodiment, it is possible to appropriately detect the cetane number by using the change in the EGR rate during deceleration from the EGR region. By detecting the cetane number based on the EGR rate in this way, it is possible to detect the cetane number with high accuracy while reducing the number of times of determination execution.

  The cetane number detection method according to the fourteenth embodiment may be executed in combination with the cetane number detection method according to the first embodiment described above. Specifically, the cetane number can be detected in consideration of the EGR rate during deceleration from the EGR region while performing control to change the number of times of pilot injection. This makes it possible to detect the cetane number with higher accuracy.

(15th embodiment)
Next, a cetane number detection method according to the 15th embodiment will be described. In the fifteenth embodiment, when the engine 8 decelerates from a high speed, the cetane number is detected based on the number of revolutions of the engine 8 when fuel ignition occurs. And different. This is because the ease of fuel ignition varies depending on the number of revolutions of the engine 8, so that the cetane number can be determined based on the presence or absence of ignition at each number of revolutions. Specifically, at the initial stage of deceleration from high rotation, since the engine 8 has a high rotation speed, the swirl in the cylinder is strong and the reaction time is short, so it can be said that the fuel is difficult to ignite. On the other hand, it can be said that the fuel is easily ignited because the rotational speed of the engine 8 decreases as the deceleration progresses.

  FIG. 27 is a schematic diagram showing the relationship among the number of pilots, the number of revolutions when ignited, and the cetane number. As shown in the figure, it can be seen that the higher the number of rotations, the narrower the range of cetane number values at which ignition occurs, and the lower the number of rotations, the wider the range of cetane number values at which ignition occurs. This is because it is easy to ignite when the cetane number is high, so it tends to ignite even when the engine 8 has a relatively high rotational speed. This is because it tends not to ignite unless it is low. In the fifteenth embodiment, the ECU 20 detects the cetane number of the fuel based on the relationship between the rotational speed of the engine 8 and the cetane number.

  FIG. 28 is a flowchart showing cetane number detection processing according to the fifteenth embodiment. The cetane number detection process is executed by the ECU 20 described above.

  In step S801, the ECU 20 determines whether or not a cetane number determination execution condition is satisfied. Specifically, the ECU 20 determines whether or not the vehicle 100 is in a deceleration state from high rotation. If the determination execution condition is satisfied (step S801; Yes), the process proceeds to step S802. If the determination execution condition is not satisfied (step S801; No), the process exits the flow.

  In step S802, the ECU 20 determines the number of pilots set for determining the cetane number. Then, the process proceeds to step S803. In step S803, the ECU 20 executes fuel injection for determining the cetane number. Then, the process proceeds to step S804.

  In step S804, the ECU 20 acquires the current rotational speed of the engine 8. Specifically, the ECU 20 acquires the rotation speed (corresponding to the detection signal S24) from the rotation speed sensor 24. Then, the process proceeds to step S805. In step S805, the ECU 20 determines whether the fuel is ignited by the fuel injection in step S803. Specifically, the ECU 20 determines the presence or absence of fuel ignition based on the change in the crank angular velocity. If the fuel is ignited (step S805; Yes), the process proceeds to step S807. In step S807, the ECU 20 detects the cetane number based on the rotational speed obtained in step S804. For example, the ECU 20 refers to a map in which the cetane number of the fuel is associated with the rotational speed of the engine 8 to obtain a cetane number corresponding to the current rotational speed. When the above process ends, the process exits the flow.

  On the other hand, when the fuel is not ignited (step S805; No), the process returns to step S803, and the fuel injection is performed again. That is, by repeating the processes in steps S803 to S805, the rotation speed of the engine 8 is continuously acquired until fuel ignition occurs.

  According to the cetane number detection process according to the fifteenth embodiment, it is possible to appropriately detect the cetane number by utilizing the change in the rotational speed when the engine 8 is decelerated from a high speed. By detecting the cetane number based on the rotational speed of the engine 8 in this way, it is possible to detect the cetane number with high accuracy while reducing the number of determination executions.

  The cetane number detection method according to the fifteenth embodiment may be combined with the cetane number detection method according to the first embodiment described above. Specifically, the cetane number can be detected in consideration of the number of revolutions of the engine 8 when decelerating from a high revolution while performing control to change the number of times pilot injection is performed. This makes it possible to detect the cetane number with higher accuracy.

(Modification)
In the above description, the embodiment has been described in which the presence or absence of fuel ignition is determined based on the change in the crank angular velocity. However, the present invention is not limited to this. In another example, the presence or absence of fuel ignition can be determined based on the temperature of the exhaust gas (exhaust temperature). Specifically, the ECU 20 can determine the presence or absence of ignition from the difference in the exhaust temperature (the temperature acquired from the exhaust temperature sensor 23) in the presence or absence of fuel injection. In detail, ECU20 judges the presence or absence of ignition in the following procedures.

  When ignition occurs due to fuel injection, the temperature of the exhausted gas tends to increase due to heat generation as compared to the case without fuel injection. Therefore, in one example, the ECU 20 determines that fuel ignition has occurred when the exhaust temperature with fuel injection is higher than the exhaust temperature immediately before fuel injection. In another example, the ECU 20 determines that fuel ignition has occurred when the exhaust temperature with fuel injection is higher than the exhaust temperature predicted when there is no injection. In this case, the ECU 20 can predict the exhaust temperature when there is no injection, based on the water temperature of the engine 8, the in-cylinder, the exhaust system temperature, and the like that are predicted based on the operating conditions until immediately before.

It is a block diagram which shows schematic structure of the vehicle which concerns on this embodiment. It is a figure for demonstrating the cetane number detection method concerning 1st Example concretely. It is the schematic which showed the relationship between the number of pilots and a cetane number. It is a flowchart which shows the cetane number detection process based on 1st Example. It is a figure for demonstrating the determination procedure of the 1st pilot number concretely. It is a flowchart which shows the 1st cetane number determination pilot number determination process. It is a figure for demonstrating the determination procedure of the 2nd pilot number concretely. It is a flowchart which shows the 2nd cetane number determination pilot number determination process. It is a figure for demonstrating specifically the cetane number detection method which concerns on 2nd Example. It is the schematic which showed the relationship between injection timing and a cetane number. It is a flowchart which shows the cetane number detection process which concerns on 2nd Example. It is the schematic which showed the relationship between the total injection amount and a cetane number. It is the schematic which showed the relationship between a pilot interval and a cetane number. It is the schematic which showed the relationship between fuel-injection pressure and a cetane number. It is the schematic which showed the relationship between glow temperature and a cetane number. It is a flowchart which shows the cetane number detection process based on 6th Example. It is the schematic which showed the relationship between a supercharging pressure and a cetane number. It is the schematic which showed the relationship between an intake manifold pressure and a cetane number. It is the schematic which showed the relationship between intake opening timing and a cetane number. It is the schematic which showed the relationship between intake closing timing and a cetane number. It is the schematic which showed the relationship between intake manifold temperature and a cetane number. It is the schematic which showed the relationship between swirl strength and a cetane number. It is the schematic which showed the relationship between water temperature and a cetane number. It is a flowchart which shows the cetane number detection process based on 13th Example. It is the schematic which showed the relationship between an EGR rate and a cetane number. It is a flowchart which shows the cetane number detection process based on 14th Example. It is the schematic which showed the relationship between an engine speed and a cetane number. It is a flowchart which shows the cetane number detection process based on 15th Example.

Explanation of symbols

3 Intake passage 5 Intercooler 6 Bypass passage 7 Bypass passage valve 8 Engine (internal combustion engine)
DESCRIPTION OF SYMBOLS 9 Fuel injection valve 10 Glow plug 11a Valve timing variable mechanism 11b Fuel injection pressure variable mechanism 11c Swirl variable mechanism 12 Exhaust passage 14 Turbocharger 14c Motor 15a EGR passage 20 ECU
21 Crank angle sensor 22 Water temperature sensor 23 Exhaust temperature sensor 100 Vehicle

Claims (19)

A fuel cetane number detection device for an internal combustion engine for detecting a cetane number of fuel,
Fuel injection control means for executing fuel injection by changing the number of times of pilot injection at the time of fuel cut of the internal combustion engine;
A cetane number detection means for detecting the cetane number of the fuel based on the number of pilot injections set by the fuel injection control means when the fuel injected by the fuel injection control means is ignited; A fuel cetane number detection device for an internal combustion engine, comprising: The fuel injection control means includes
The first fuel injection is executed by the pilot injection which is approximately half the maximum pilot injection number,
In the second and subsequent fuel injections, the range of the number of pilot injections that should be determined for ignition in order to detect the cetane number based on the presence or absence of ignition by the previous fuel injection is reduced to approximately half 2. The fuel cetane number detection device for an internal combustion engine according to claim 1, wherein the fuel cetane number detection device is executed by pilot injection. The fuel injection control means, when detecting the cetane number after refueling,
In the first fuel injection, the pilot injection is executed according to the number of pilot injections set when the cetane number is determined in the fuel before refueling,
The second and subsequent fuel injections are executed by the number of pilot injections that are increased or decreased based on the presence or absence of ignition by the previous fuel injection. The fuel cetane number detection device for an internal combustion engine according to claim 1 or 2. The fuel injection control means performs control to change an injection timing for performing the fuel injection,
2. The cetane number detection unit detects the cetane number based on the injection timing set by the fuel injection control unit when the fuel is ignited. 3. A fuel cetane number detection device for an internal combustion engine. The fuel injection control means performs control to change the total injection amount when performing the fuel injection,
2. The cetane number detecting means detects the cetane number based on the total injection amount set by the fuel injection control means when the fuel is ignited. A fuel cetane number detection device for an internal combustion engine according to claim 1. The fuel injection control means performs control to change an interval for injecting fuel in the pilot injection,
2. The cetane number detection unit detects the cetane number based on the interval set by the fuel injection control unit when the fuel is ignited. 3. A fuel cetane number detection device for an internal combustion engine. A fuel injection pressure control means for changing the fuel injection pressure when detecting the cetane number;
The cetane number detection means detects the cetane number based on the fuel injection pressure set by the fuel injection pressure control means when the fuel is ignited. A fuel cetane number detection device for an internal combustion engine according to claim 1.   2. The fuel cetane of the internal combustion engine according to claim 1, further comprising a glow plug control unit that performs control to operate a glow plug provided in a cylinder of the internal combustion engine when the cetane number is detected. Valence detector. The glow plug control means performs control to change the temperature of the glow plug,
9. The cetane number detection means detects the cetane number based on the temperature of the glow plug after the control by the glow plug control means when the fuel is ignited. A fuel cetane number detection device for an internal combustion engine as described. Motor control means for controlling the operation of a motor configured to be capable of assisting rotation of the turbocharger so that the supercharging pressure by the turbocharger changes when the cetane number is detected;
2. The internal combustion engine according to claim 1, wherein the cetane number detection unit detects the cetane number based on a supercharging pressure after control by the motor control unit when ignition of the fuel occurs. 3. Engine fuel cetane number detection device. When detecting the cetane number, further comprising a throttle control means for controlling the throttle valve so that the pressure of the intake manifold changes,
The cetane number detection means detects the cetane number based on the pressure of the intake manifold after the control by the throttle control means when the fuel is ignited. A fuel cetane number detection device for an internal combustion engine. A first valve timing control means for performing control to change the valve timing in the internal combustion engine so that the intake air amount changes when the cetane number is detected;
2. The cetane number detecting means detects the cetane number based on a valve timing set by the first valve timing control means when the fuel is ignited. A fuel cetane number detection device for an internal combustion engine according to claim 1. A second valve timing control means for performing control to change the valve timing in the internal combustion engine so that the actual compression ratio changes when the cetane number is detected;
2. The cetane number detection means detects the cetane number based on a valve timing set by the second valve timing control means when the fuel is ignited. A fuel cetane number detection device for an internal combustion engine according to claim 1. An intake manifold temperature control means for performing control so that the temperature of the intake manifold in the internal combustion engine changes when the cetane number is detected;
The cetane number detection means detects the cetane number based on the temperature of the intake manifold after the control by the intake manifold temperature control means when the fuel is ignited. A fuel cetane number detection device for an internal combustion engine as described. Swirl control means for performing control so as to change the strength of the swirl in the cylinder of the internal combustion engine when detecting the cetane number;
The cetane number detection means detects the cetane number based on the strength of the swirl after the control by the swirl control means when the fuel is ignited. A fuel cetane number detection device for an internal combustion engine.   2. The fuel cetane number detection device for an internal combustion engine according to claim 1, wherein the cetane number detection means detects the cetane number based on a water temperature of the internal combustion engine when the fuel is ignited.   2. The internal combustion engine according to claim 1, wherein the cetane number detection unit detects the cetane number based on an EGR rate when ignition of the fuel occurs during deceleration from an EGR region. Fuel cetane number detection device.   The cetane number detection means detects the cetane number based on the number of revolutions of the internal combustion engine when the ignition of the fuel occurs when the internal combustion engine decelerates from a high speed. Item 2. The fuel cetane number detection device for an internal combustion engine according to Item 1.   19. The cetane number detection means acquires the temperature of exhaust gas in the internal combustion engine, and determines whether or not the fuel has been ignited based on the temperature of the exhaust gas. The fuel cetane number detection device for an internal combustion engine according to the item.

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