JP2009174322A - Cetane number detection device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the detection accuracy of cetane number of fuel, in a compression self-igniting internal combustion engine. <P>SOLUTION: When an amount of injected fuel by a pilot injection is very small amount, within a predetermined range of operating condition and environmental condition (S110, S120: YES), pressure (in-cylinder pressure) P and volume V inside the pilot injected combustion chamber are sampled for a predetermined period of time until a main injection of fuel is performed (S130). Then, rate of heat release is calculated from the sampled in-cylinder pressure P and the volume V, to determine amount of heat release Q by integrating the rate of heat release (S140). Furthermore, combustion rate of fuel is calculated (S160) by converting the amount of heat release Q into the amount of fuel, and determining the ratio of the amount of fuel to the amount of injected fuel, and the cetane number of the fuel is identified from the combustion rate (S170). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cetane number detection device for detecting a cetane number of fuel in a compression self-ignition internal combustion engine having a fuel injection means for directly injecting fuel into a combustion chamber.

  In a compression ignition type internal combustion engine, the operating performance (engine output, emission, drivability, etc.) varies depending on the cetane number of the fuel used for operation. ) And the like, and the fuel injection amount and fuel injection timing are controlled according to the detected cetane number.

And as a cetane number detection apparatus used for this control, the following 1) -3) are known, for example.
1) An apparatus configured to identify the cetane number of fuel by detecting the ignition delay of fuel injected into the combustion chamber by pilot injection (see, for example, Patent Documents 1 and 2).

  2) Designed to specify the cetane number of fuel by injecting a small amount of fuel into the combustion chamber during cranking, idling, or when fuel is cut off due to deceleration, and detecting the ignition delay of the injected fuel Device (for example, see Patent Document 3).

3) At the time of combustion of the fuel injected by the pilot, the product PV ^κ of the pressure V in the combustion chamber (cylinder pressure) P and the value V ^{κ obtained} by multiplying the volume V of the combustion chamber by κ (κ is a constant representing the specific heat ratio of the mixture) An apparatus configured to specify the cetane number of the fuel by calculating as a heat generation amount parameter and detecting the amount of change (= maximum value−minimum value) (see, for example, Patent Document 4).
JP 2006-16994 A JP 2006-226188 A JP 2005-344557 A JP 2005-344550 A

  However, as in the above 1) and 2), in the apparatus for detecting the cetane number from the fuel ignition delay in the combustion chamber, the detection accuracy of the ignition delay is reduced due to the injection timing control error and the ignition timing detection error, There was a problem that the cetane number could not be detected accurately.

On the other hand, as in the above 3), in the apparatus for detecting the cetane number from the variation of the heat quantity parameter (PV ^kappa) is as long as it can determine the amount of change by calculating the heat generation amount parameter (PV ^kappa) Even if the calculation time is shifted, the cetane number can be identified without any problem.

However, although the amount of change in the heat generation amount parameter (PV ^κ ) is correlated with the heat generation amount after fuel injection, it does not coincide with (proportional to) the heat generation amount. In addition, when the fuel injection exceeds a predetermined amount, the amount of change in the heat generation amount parameter due to the cetane number is very small, and if there is a measurement error of the in-cylinder pressure, the ignitability of the fuel may not be accurately determined. As a result, there is a problem that the detection accuracy of the cetane number is lowered.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a cetane number detection device capable of detecting a cetane number of fuel with higher accuracy in a compression self-ignition internal combustion engine.

  In the cetane number detection device according to claim 1, which is made to achieve this object, the amount of fuel combusted in the combustion chamber varies greatly according to the cetane number when fuel injection is performed below a predetermined value. In particular, when a predetermined fuel injection is performed from the fuel injection unit, the combustion rate calculation unit calculates a combustion rate that represents a ratio of the fuel actually burned in the combustion chamber out of the fuel injected from the fuel injection unit. The cetane number specifying means calculates and determines the cetane number of the fuel based on the calculated combustion rate.

  That is, the combustion rate calculated by the combustion rate calculation means is a value that represents the ratio of the combustion fuel to the injected fuel. Therefore, the larger the value, the easier the fuel is ignited and the higher the cetane number. Therefore, in the present invention, the combustion rate is calculated as a parameter for specifying the ignitability (in other words, cetane number) of the fuel, and the cetane number is specified from the calculation result.

  Further, since the combustion rate can be calculated by detecting the amount of fuel burned by fuel injection from the fuel injection means and obtaining the ratio with the fuel injection amount from the fuel injection means, the conventional 1) and 2) above Like the apparatus, the detection accuracy of the cetane number does not decrease even if the calculation time is shifted.

  Therefore, according to the cetane number detection device of the present invention, it is possible to accurately detect the cetane number without restricting the cetane number detection execution condition to the operating condition where the fuel injection amount is constant.

  By the way, in the present invention, in order to calculate the combustion rate by the combustion rate calculation means, it is necessary to detect the amount of combustion fuel actually burned in the combustion chamber. Thus, a pressure detecting means for detecting the pressure in the combustion chamber (in-cylinder pressure) and a volume detecting means for detecting the volume of the combustion chamber are provided, and the in-cylinder pressure detected by each of the detecting means in the combustion rate calculating means is provided. It is preferable that the heat generation rate is calculated by sequentially calculating the heat generation rate based on the volume and the volume, and integrating the calculated heat generation rates.

  In other words, in this way, the combustion rate calculation means can calculate the amount of combustion fuel actually burned in the combustion chamber by converting the heat generation amount into the fuel amount, and the value from the fuel injection means By calculating the ratio with the amount of injected fuel, the combustion rate can be easily calculated.

  In this case, it is necessary to detect the pressure in the combustion chamber (in-cylinder pressure) and the volume of the combustion chamber, but the in-cylinder pressure can be detected using an in-cylinder pressure sensor generally used in an internal combustion engine. The volume of the combustion chamber changes with the rotation of the internal combustion engine, but the value changes according to the rotational position (crank angle) of the internal combustion engine. Therefore, the volume data describing the volume of the combustion chamber for each crank angle. Can be easily detected from the crank angle of the internal combustion engine. Therefore, the cetane number detection device according to claim 2 can be easily realized.

  Next, in the present invention (Claims 1 and 2), since the cetane number is specified based on the combustion rate of the injected fuel from the fuel injection unit, the operating condition (predetermined) when the combustion rate calculation unit calculates the combustion rate. As the fuel injection), it is necessary to set an operating condition in which the combustion rate varies depending on the cetane number of the fuel.

  When the fuel injection amount from the fuel injection means is large, the combustion rate does not change greatly even if the cetane number changes, and it is difficult to detect the cetane number from the combustion rate. Is configured to calculate the combustion rate when the fuel injection amount from the fuel injection means is a minute amount in which the combustion rate of the fuel in the combustion chamber varies depending on the cetane number. Good.

According to the experiments by the inventors of the present application, in the automobile internal combustion engine, the fuel injection amount (small amount) suitable for calculating the combustion rate by the combustion rate calculating means is as described in claim 5. It was found to be in the range of 0.3 [mm ³ / st] to 1.5 [mm ³ / st].

That is, in an internal combustion engine for automobiles, if the fuel injection amount from the fuel injection means is within this range (0.3 [mm ³ / st] or more and 1.5 [mm ³ / st] or less), the fuel injection amount is Even if they are the same, the amount of heat generation (and hence the amount of combustion fuel) changes according to the cetane number of the fuel, and the cetane number can be detected based on the combustion rate of the injected fuel obtained from the amount of heat generation. It becomes.

Then, in the internal combustion engine for an automobile, a fuel injection of such minute amount (0.3 [mm ³ / st] or 1.5 [mm ³ / st] or less) is realized by the pilot injection performed prior to main injection Therefore, when actually configuring the cetane number detection device of the present invention, when the pilot injection is made from the fuel injection means, the combustion rate calculation means calculates the combustion rate of the injected fuel by the pilot injection. The cetane number specifying means may specify the cetane number of the fuel based on the calculated combustion rate.

In addition, for example, when the fuel cut due to the deceleration of the internal combustion engine is performed, a small amount (0.3 [mm ³ / st] or more and 1.5 [mm ³ / st] or less) of fuel is injected, and the combustion rate calculating means The combustion rate of the injected fuel by the minute injection may be calculated, and the cetane number specifying means may specify the cetane number of the fuel based on the calculated combustion rate.

  On the other hand, when the heat generation amount is obtained by calculating and integrating the heat generation rate in the combustion chamber as described above, if the fuel injection amount from the fuel injection means is substantially constant, the heat generation amount Will change according to the cetane number.

Therefore, the cetane number detection device may be configured as described in claim 5.
That is, the cetane number detection device according to claim 5 is provided with pressure detection means, volume detection means, and heat generation amount calculation means, and the heat generation amount calculation means is described in claim 2. Similar to the combustion rate calculation means, when a predetermined fuel injection is made from the fuel injection means, the heat release rate is calculated sequentially based on the in-cylinder pressure and volume detected by the pressure detection means and the volume detection means, and the calculation is performed. The amount of heat generation is calculated by integrating the heat generation rate. Then, when the heat generation amount is calculated by the heat generation amount calculation means, the cetane number specifying means specifies the cetane number of the fuel based on the calculated heat generation amount.

  Therefore, according to the cetane number detection device of the fifth aspect, as the operating condition (predetermined fuel injection) when the heat generation amount calculating means calculates the heat generation amount, the operating condition in which the fuel injection amount becomes substantially constant. However, the heat generation amount calculation means can accurately calculate the heat generation amount corresponding to the amount of fuel actually burned by integrating the heat generation rate. Thus, the cetane number of the fuel can be detected from the heat generation amount with high accuracy, and the detection accuracy of the cetane number can be improved as compared with the conventional device 3).

  In the cetane number detection device according to claim 5, as the operating condition (predetermined fuel injection) when the heat generation amount calculation means calculates the heat generation amount, the fuel injection is performed as described in claim 6. The fuel injection amount from the means may be a substantially constant amount, and the heat generation amount in the combustion chamber may be a minute amount that varies depending on the cetane number.

As described above, in the automobile internal combustion engine, when the fuel injection amount from the fuel injection means is made substantially constant, the heat generation amount changes according to the cetane number of the fuel. 0.3 since it is time [mm ³ / st] 1.5 in [mm ³ / st] in the range, as the heat generation amount calculation means, as claimed in claim 7, the fuel injection when the fuel injection amount from the means is substantially constant amount in the range of 0.3 [mm ³ / st] or 1.5 [mm ³ / st] hereinafter, it may be configured to calculate a heat generation amount.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram showing the configuration of the entire control system of an internal combustion engine to which the present invention is applied.
The internal combustion engine of this embodiment is a diesel engine 1 for an automobile that employs an accumulator fuel injection system.

  In this diesel engine 1, a piston 4 is accommodated in a cylinder 3 formed in a cylinder block 2, and the movement of the piston 4 reciprocating in the cylinder 3 is caused by a crankshaft (not shown) of the diesel engine 1 through a connecting rod 5. To be transmitted as a rotational motion.

  A cylinder head 7 that forms a combustion chamber 6 in the upper part of the piston 4 is fixed to the upper end surface of the cylinder block 2. The cylinder head 7 is formed with an intake port 8 and an exhaust port 9 that open to the combustion chamber 6.

The intake port 8 and the exhaust port 9 are opened and closed by an intake valve 10 and an exhaust valve 11 driven by cams (not shown), respectively.
An intake pipe 12 for sucking outside air is connected to the intake port 8, and during the intake stroke in which the intake valve 10 opens the intake port 8, the piston 4 descends in the cylinder 3 to generate an in-cylinder negative pressure. Then, the outside air sucked from the intake pipe 12 flows into the cylinder through the intake port 8.

  Further, an exhaust pipe 13 for discharging combustion gas is connected to the exhaust port 9, and the exhaust valve 11 rises from the combustion chamber 6 (inside the cylinder) due to the piston 4 rising during the exhaust stroke in which the exhaust valve 11 opens the exhaust port 9. The extruded combustion gas is discharged to the exhaust pipe 13 through the exhaust port 9.

  The accumulator fuel injection system includes a common rail 14 that accumulates high-pressure fuel, a fuel supply pump (not shown) that pumps high-pressure fuel to the common rail 14, and each cylinder of the diesel engine 1 that stores the high-pressure fuel accumulated in the common rail 14. The combustion chamber 6 has a plurality of injectors 15 each of which is injected and controlled by an electronic control unit (referred to as ECU 16).

  The common rail 14 accumulates the high-pressure fuel supplied from the fuel supply pump up to the target rail pressure, and the accumulated high-pressure fuel is supplied to the injector 15 via the fuel pipe 17. The target rail pressure of the common rail 14 is set by the ECU 16. Specifically, the operating state of the diesel engine 1 is detected from the accelerator opening and the rotational speed, and a target rail pressure suitable for the operating state is set.

  The injector 15 has an electromagnetic valve electronically controlled by the ECU 16 and a nozzle that injects fuel by the opening operation of the electromagnetic valve. With the tip of the nozzle protruding into the combustion chamber 6 of each cylinder, It is attached to the cylinder head 7.

  The ECU 16 is a sensor detected by various sensors shown in FIG. 3 (NE sensor 18, accelerator opening sensor 19, fuel pressure sensor 20, in-cylinder pressure sensor 21, intake pressure sensor 22, intake air temperature sensor 23, water temperature sensor 24, etc.). Information is input and the operation state of the diesel engine 1 is controlled based on the sensor information.

  The NE sensor 18 is disposed in the vicinity of the pulsar 28 that rotates in synchronization with the crankshaft of the diesel engine 1 and corresponds to the number of teeth provided on the outer peripheral portion of the pulsar 28 while the pulsar 28 rotates once. A plurality of pulse signals (rotation angle signals) are output. The ECU 16 detects the rotational speed NE and the rotational position (crank angle θ) of the diesel engine 1 based on the rotational angle signal output from the NE sensor 18.

The accelerator opening sensor 19 detects the accelerator opening from an operation amount (depression amount) of an accelerator pedal (not shown) operated by the driver, and outputs the detected accelerator opening to the ECU 16.
The fuel pressure sensor 20 is attached to the common rail 14, detects the fuel pressure (actual rail pressure) accumulated in the common rail 14, and outputs it to the ECU 16.

  The in-cylinder pressure sensor 21 is attached to the cylinder head 7 for each cylinder of the diesel engine 1, detects the in-cylinder pressure of each cylinder (hereinafter referred to as “in-cylinder pressure”), and outputs it to the ECU 16.

The intake pressure sensor 22 is attached to the intake pipe 12, detects the intake pressure Pm in the intake pipe 12, and outputs it to the ECU 16.
The intake air temperature sensor 23 is attached to the intake pipe 12, detects the temperature of intake air (intake air temperature) Ta passing through the intake pipe 12, and outputs it to the ECU 16.

The water temperature sensor 24 is attached to the cylinder block 2, detects the temperature (water temperature) Tw of the cooling water in the cylinder block 2, and outputs it to the ECU 16.
The ECU 16 is configured around a microcomputer, and performs injection pressure control and fuel injection control based on the sensor information.

  The injection pressure control is to control the fuel pressure accumulated in the common rail 14, and the discharge amount (pump discharge amount) of the fuel supply pump so that the actual rail pressure detected by the fuel pressure sensor 20 matches the target rail pressure. Feedback control.

  The fuel injection control is to control the fuel injection amount and injection timing from the injector 15, calculate the optimal injection amount and injection timing according to the operating state of the diesel engine 1, and according to the calculation result, the solenoid valve of the injector 15 Drive. In this fuel injection control, the fuel is efficiently burned by executing the pilot injection prior to the main injection.

  Further, when the ignitability (cetane number) of the fuel used changes, the optimal injection amount and injection timing also change. Therefore, the ECU 16 detects the cetane number of the fuel under predetermined operating conditions of the diesel engine 1. When the fuel amount detection process is executed and the injection amount and the injection timing are controlled by the fuel injection control, the injection amount and the injection timing are corrected based on the cetane number of the fuel detected by the cetane number detection process.

Hereinafter, the cetane number detection process executed by the ECU 16 will be described with reference to the flowchart shown in FIG.
As shown in FIG. 2, when this process is started, first, in S110 (S represents a step), the rotational speed and accelerator of the diesel engine 1 detected via the NE sensor 18 and the accelerator opening sensor 19 are detected. It is determined whether or not the diesel engine 1 is operating under a predetermined operating condition (in other words, a predetermined load state) by determining whether or not the opening is within a preset range. .

  If it is determined in S110 that the diesel engine 1 is not operated under the predetermined operating condition, the process is terminated as it is, and conversely, it is determined that the diesel engine 1 is operated under the predetermined operating condition. Then, the process proceeds to S120.

  In S120, the diesel engine 1 determines whether the intake air temperature, the water temperature, etc. detected by the intake air temperature sensor 23, the water temperature sensor 24, etc. are within a preset range. It is determined whether or not the vehicle is operated under a predetermined environmental condition defined by the water temperature or the like.

  If it is determined in S120 that the diesel engine 1 is not operated under the predetermined environmental condition, the process is terminated as it is, and conversely, it is determined that the diesel engine 1 is operated under the predetermined environmental condition. Then, the process proceeds to S130.

  In S130, while the diesel engine 1 rotates at a predetermined crank angle, the in-cylinder pressure P detected by the in-cylinder pressure sensor 21 is repeatedly sampled at a predetermined interval, and the volume V of the combustion chamber 6 at each sampling timing is detected.

  For detecting the volume V of the combustion chamber 6, volume data describing the relationship between the crank angle of the diesel engine 1 and the volume V of the combustion chamber 6 is used. In S120, the cylinder pressure P is determined from the volume data. By reading the volume V corresponding to the crank angle at the time of sampling, the volume V of the combustion chamber 6 at each sampling timing is detected.

  Further, in the sampling period for sampling the in-cylinder pressure in S130, as shown in FIG. 5A, after the pilot injection is performed in the specific cylinder of the diesel engine 1, the injected fuel burns (pilot combustion), Thereafter, the predetermined crank angle period θ1 to θ2 until the main injected fuel burns (main combustion) is set in advance. In S130, a plurality of in-cylinder pressures P and volumes V are sampled at predetermined intervals during the sampling period (crank angles θ1 to θ2).

  Next, when the in-cylinder pressure P and the volume V of the combustion chamber 6 are sampled in S130, the process proceeds to S140, and based on the sampled plurality of in-cylinder pressures P and the volume V of the combustion chamber 6, the following equation ( 1) is used to calculate the heat generation amount Q generated in the combustion chamber 6 of the specific cylinder by the pilot injection.

つまり、Ｓ１４０では、（１）式に従い、ディーゼル機関１がクランク角度θ１からθ２まで回転する間にサンプリングした複数の筒内圧Ｐと、各筒内圧Ｐに対応した燃焼室６の容積Ｖとから、サンプリングタイミング毎の熱発生率（図５（ａ）参照）を逐次算出し、その算出した熱発生率を積算することで、パイロット噴射された燃料によって生じた熱発生量Ｑを算出するのである。

That is, in S140, from the plurality of in-cylinder pressures P sampled while the diesel engine 1 is rotated from the crank angle θ1 to θ2 and the volume V of the combustion chamber 6 corresponding to each in-cylinder pressure P according to the equation (1), The heat generation rate Q generated by the pilot-injected fuel is calculated by sequentially calculating the heat generation rate (see FIG. 5A) at each sampling timing and integrating the calculated heat generation rates.

  In the subsequent S150, the heat generation amount Q calculated in S140 is unit-converted into a fuel amount (combustion fuel amount) corresponding to this heat amount, and in the subsequent S160, the heat generation amount Q (that is, the unit heat conversion amount after the unit conversion) The combustion rate (= combustion fuel amount / pilot injection amount) of the fuel injected by pilot is calculated by dividing the combustion fuel amount) by the fuel amount injected from the injector 15 (that is, the pilot injection amount).

  Next, when the combustion rate is calculated in S160, the process proceeds to S170, where the cetane number of the fuel is specified using a map representing the relationship between the calculated combustion rate and the cetane number of the fuel, and the processing is performed. Exit.

  As described above, in the cetane number detection process of the present embodiment, the in-cylinder pressure P and the volume V in the combustion chamber 6 pilot-injected when the diesel engine 1 is operated under predetermined operating conditions and environmental conditions. Is calculated for a predetermined period, and a heat generation amount Q in the combustion chamber 6 generated by pilot injection is calculated based on the sampled plurality of in-cylinder pressures P and volumes V. The heat generation amount Q and the fuel amount injected by pilot injection are calculated. From this, the combustion rate of the fuel is obtained, and the cetane number of the fuel is specified from this combustion rate.

  For this reason, according to the present embodiment, the control error of the fuel injection timing and the detection of the ignition timing are detected as in the conventional device that identifies the cetane number by detecting the ignition timing (call delay) after fuel injection from the in-cylinder pressure. The detection accuracy is not reduced by errors, in-cylinder pressure detection errors, etc., and the cetane number detection accuracy can be improved.

In the present embodiment, since the cetane number is specified based on the combustion rate that represents the ratio between the amount of combustion fuel burned by pilot injection and the pilot injection amount, the heat generation amount parameter (PV ^κ ) that varies with the fuel injection amount is used. Compared with the conventional apparatus that specifies the cetane number, the cetane number detection conditions (operating conditions, environmental conditions) can be broadened.

  Here, in the present embodiment, there are operating conditions defined by the rotational speed of the diesel engine 1 and the accelerator opening (in other words, the load of the diesel engine 1) and the environmental condition ring defined by the intake air temperature, the water temperature, and the like. When each is within the predetermined range, it is determined that the cetane number detection condition is satisfied, and sampling of the in-cylinder pressure P and the volume V is started.

This is because the fuel combustion rate by pilot injection (pilot combustion rate) varies depending on the load and temperature of the diesel engine 1 as shown in FIG. 5B, and in particular, the pilot combustion rate greatly varies depending on the cetane number. Is during low-load operation of the diesel engine 1 where the fuel injection amount by pilot injection is very small (more preferably 0.3 [mm ³ / st] or more and 1.5 [mm ³ / st] or less). Because.

  In other words, in the present embodiment, when the diesel engine 1 is operated at a low load and the pilot combustion rate greatly changes due to the cetane number, the in-cylinder pressure P and the volume V are sampled, and the pilot combustion rate (and thus the cetane number) In other words, the conditions for detecting the cetane number are limited by the operating conditions and the environmental conditions of the diesel engine 1 described above.

Therefore, according to the present embodiment, the cetane number of the fuel can be accurately detected by sampling the cylinder pressure P and the volume V under the limited conditions.
In the present embodiment, the injector 15 corresponds to the fuel injection means of the present invention, the ECU 16 that executes the cetane number detection process corresponds to the cetane number detection device of the present invention, and the process of S130 in the cetane number detection process Is equivalent to the pressure detecting means and the volume detecting means of the present invention, the processing of S140 to S160 is also equivalent to the combustion rate calculating means of the present invention, and the processing of S170 is also equivalent to the cetane number specifying means of the present invention. To do.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, a various aspect can be taken.
[Modification 1]
For example, in the above embodiment, in the processing of S170 as the cetane number specifying means, it has been described that the cetane number is specified using one map representing the relationship between the combustion rate and the cetane number of the fuel. Since the relationship with the cetane number changes depending on the operating conditions and environmental conditions of the diesel engine 1, it is necessary to narrow down the operating conditions and environmental conditions when detecting the cetane number if one map for specifying the cetane number is used. There is.

  For this reason, in order to broaden the execution conditions for specifying the cetane number of the fuel from the combustion rate, a plurality of maps for specifying the cetane number are prepared for each operating condition and environmental condition of the diesel engine 1, and the cetane number The detection process may be executed as shown in FIG.

  That is, in the cetane number detection process of FIG. 3, in S210, the in-cylinder pressure P and the volume V are sampled during a predetermined sampling period after the pilot injection of the diesel engine 1, and in the subsequent S220, the sampled in-cylinder pressure is sampled. Based on P and the volume V, the heat generation amount Q is calculated using the calculation formula (1).

  In the subsequent S230, the heat generation amount Q calculated in S220 is converted into a fuel amount (combustion fuel amount), and in the subsequent S240, the heat generation amount Q (that is, the combustion fuel amount) after the unit conversion and the pilot are converted. The fuel combustion rate is calculated from the injection amount.

  And if a combustion rate is calculated in S240, it will transfer to S250 and will detect the present driving | running conditions (rotation speed, accelerator opening degree, etc.) and environmental conditions (intake air temperature, water temperature, etc.) of the diesel engine 1, In S260, a map for specifying the cetane number corresponding to the detected operating condition and environmental condition is extracted from a plurality of maps, and based on the extracted map and the combustion rate calculated in S240, the fuel The cetane number is specified, and the cetane number detection process ends.

  Thus, in the cetane number detection process shown in FIG. 3, the map corresponding to the operating conditions and environmental conditions of the diesel engine 1 is selected from a plurality of maps and the cetane number of the fuel is specified. The operating conditions and environmental conditions that can specify the cetane number from the combustion rate can be widened, and when the cetane number of the fuel changes due to refueling or the like, the change in the cetane number can be detected earlier.

In the cetane number detection process shown in FIG. 3, the process of S210 corresponds to the pressure detection means and the volume detection means of the present invention, and the processes of S220 to S250 correspond to the combustion rate calculation means of the present invention. The process of S260 corresponds to the cetane number specifying means of the present invention.
[Modification 2]
Further, in the above embodiment, after the pilot injection during the low load operation of the diesel engine 1, the combustion rate of the injected fuel is calculated and the cetane number of the fuel is detected. If the fuel injection amount is very small (more preferably in the range of 0.3 [mm ³ / st] to 1.5 [mm ³ / st]), it will vary greatly depending on the cetane number of the fuel. The cetane number can be well identified from the combustion rate.

  For this reason, it is not always necessary to set the execution condition of the cetane number detection process after the pilot injection. For example, when the automobile enters a deceleration operation and the diesel engine 1 is in the fuel cut state, fuel is supplied to a specific cylinder. As shown in FIG. 5 (c), heat is generated from the in-cylinder pressure P and the volume V of the combustion chamber 6 of the minutely injected cylinder, as shown in FIG. 5C. By determining the quantity Q, the cetane number of the injected fuel may be specified.

In this case, as shown in FIG. 4, the cetane number detection process is performed by determining whether or not the diesel engine 1 enters the fuel cut state and a predetermined environmental condition is satisfied in S310. It is determined whether or not the injection execution condition is satisfied. If the minute injection execution condition is not satisfied, the cetane number detection process is terminated. If the minute injection execution condition is satisfied, the process proceeds to S320. Then, a small amount of fuel injection may be executed from the injector 15 of the specific cylinder at a predetermined fuel injection timing, and then a series of processes of S130 to S170 may be executed.
[Modification 3]
On the other hand, in the above-described embodiment and the modification, it has been described that the cetane number of the fuel is specified from the combustion rate of the fuel. For example, if the fuel injection amount from the injector 15 into the combustion chamber 6 is a constant amount, the fuel Since the heat generation amount Q used to calculate the combustion rate as well as the combustion rate of the fuel changes depending on the cetane number, the cetane of the fuel is calculated from the heat generation amount Q without calculating the combustion rate. The price can also be specified.

  In order to do this, for example, in the cetane number detection process shown in FIG. 2, the operating conditions and environmental conditions of the diesel engine 1 determined in S110 and S120 are the operating conditions in which the pilot injection amount is a substantially constant amount. And it may be narrowed so as to satisfy the environmental conditions.

  That is, in this way, the heat generation amount Q generated after the pilot injection in the combustion chamber 6 of the specific cylinder is calculated under the condition that the pilot injection amount becomes a substantially constant amount (S140). It becomes possible to specify the cetane number of the fuel using the map with the parameter as the parameter (S170), convert the heat generation amount Q into the fuel amount (S150), and burn from the converted fuel amount and the pilot injection amount The cetane number can be detected without calculating the rate (S160).

  Further, for example, in the cetane number detection process shown in FIG. 4, even if the amount of fuel to be finely injected is limited to a constant amount in S320, the heat generation amount Q is converted into the fuel amount (S150), or the conversion In S170, the cetane number of the fuel can be specified from the heat generation amount Q calculated in S140 without calculating the combustion rate from the calculated fuel amount and the pilot injection amount (S160).

It is a schematic block diagram showing the structure of the diesel engine of the embodiment and the whole control system. It is a flowchart showing the cetane number detection process performed by ECU. 10 is a flowchart showing a cetane number detection process of Modification 1; 10 is a flowchart showing a cetane number detection process of Modification 2. It is explanatory drawing explaining the cetane number detection operation | movement of embodiment and the modification 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Diesel engine (compression ignition internal combustion engine), 2 ... Cylinder block, 4 ... Piston, 5 ... Connecting rod, 6 ... Combustion chamber, 7 ... Cylinder head, 8 ... Intake port, 9 ... Exhaust port, 10 ... Intake valve , 11 ... Exhaust valve, 12 ... Intake pipe, 13 ... Exhaust pipe, 14 ... Common rail, 15 ... Injector, 17 ... Fuel piping, 18 ... NE sensor, 19 ... Accelerator opening sensor, 20 ... Fuel pressure sensor, 21 ... In-cylinder pressure Sensor: 22 ... Intake pressure sensor, 23 ... Intake air temperature sensor, 24 ... Water temperature sensor, 28 ... Pulser.

Claims (7)

In a compression self-ignition internal combustion engine having a fuel injection means for directly injecting fuel into a combustion chamber, a cetane number detection device for detecting the cetane number of fuel,
A combustion rate calculating means for calculating a combustion rate representing a ratio of fuel actually burned in the combustion chamber among fuels injected from the fuel injection means when predetermined fuel injection is performed from the fuel injection means; ,
Cetane number specifying means for specifying the cetane number of the fuel based on the combustion rate calculated by the combustion rate calculating means;
An apparatus for detecting a cetane number of an internal combustion engine, comprising: Pressure detecting means for detecting the pressure in the combustion chamber;
Volume detecting means for detecting the volume of the combustion chamber;
With
The combustion rate calculating means includes
The heat generation rate is sequentially calculated based on the pressure detected by the pressure detection unit and the volume detected by the volume detection unit, and the calculated heat generation rate is integrated to obtain from the fuel injection unit. Calculating the amount of heat generated by fuel injection, converting the calculated amount of heat generated into the amount of combustion fuel actually burned, and determining the ratio between the amount of combustion fuel and the amount of fuel injected from the fuel injection means The cetane number detection device for an internal combustion engine according to claim 1, wherein the combustion rate is calculated by: The combustion rate calculating means includes
3. The combustion rate is calculated when the fuel injection amount from the fuel injection means is a minute amount in which the combustion rate of fuel in the combustion chamber varies depending on the cetane number. A cetane number detection device for an internal combustion engine according to claim 1. The combustion rate calculating means includes
The combustion rate is calculated when a fuel injection amount from the fuel injection means is in a range of 0.3 [mm ³ / st] to 1.5 [mm ³ / st]. Item 4. The cetane number detection device for an internal combustion engine according to Item 3. In a compression self-ignition internal combustion engine having a fuel injection means for directly injecting fuel into a combustion chamber, a cetane number detection device for detecting the cetane number of fuel,
Pressure detecting means for detecting the pressure in the combustion chamber;
Volume detecting means for detecting the volume of the combustion chamber;
When a predetermined fuel injection is made from the fuel injection means, the heat generation rate is sequentially calculated based on the pressure detected by the pressure detection means and the volume detected by the volume detection means, and the calculation A heat generation amount calculating means for calculating a heat generation amount associated with fuel injection from the fuel injection means by integrating the heat generation rates obtained;
Cetane number specifying means for specifying the cetane number of the fuel based on the heat generation amount calculated by the heat generation amount calculating means;
An apparatus for detecting a cetane number of an internal combustion engine, comprising: The heat generation amount calculation means includes:
6. The heat generation amount is calculated when the fuel injection amount from the fuel injection means is a substantially constant amount and the heat generation amount is a very small amount that varies depending on the cetane number. A cetane number detection device for an internal combustion engine as described. The heat generation amount calculation means includes:
Calculating the heat generation amount when the fuel injection amount from the fuel injection means is substantially constant within a range of 0.3 [mm ³ / st] to 1.5 [mm ³ / st]. The cetane number detection device for an internal combustion engine according to claim 6.

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