JP2011256840A - Cetane number estimating device - Google Patents

Abstract

A cetane number estimation device capable of accurately estimating the cetane number of a fuel is provided.
The apparatus performs fuel injection with a predetermined amount in order to estimate the cetane number of the fuel (S103). An index value (rotational fluctuation amount ΣΔNE) of the output torque of the diesel engine generated with the execution of fuel injection is calculated (S104), the rotational fluctuation amount ΣΔNE, the execution timing of the fuel injection, and the engine rotation at the time of execution of the fuel injection. An estimated cetane number is calculated based on the relationship with the speed (running speed) (S106).
[Selection] Figure 7

Description

  The present invention relates to a cetane number estimation device for estimating the cetane number of fuel of a diesel engine.

  In the diesel engine, the fuel injected into the combustion chamber by the fuel injection valve is compressed and ignited after a predetermined time (so-called ignition delay) has elapsed since the injection. In order to improve the output performance and emission performance of diesel engines, a control device that controls the execution mode of engine control such as injection timing and injection amount for fuel injection is widely adopted in consideration of such ignition delay. Yes.

  In diesel engines, the lower the cetane number of the fuel used, the longer the ignition delay. Therefore, for example, even if the engine control execution mode is set assuming that a standard cetane number fuel is used at the time of shipment of a diesel engine, a fuel with a relatively low cetane number, such as winter fuel, is a fuel tank. When the fuel is replenished, the ignition timing of the fuel is delayed and the combustion state is deteriorated. In some cases, misfire occurs.

  In order to suppress the occurrence of such inconvenience, it is desirable to correct the engine control execution mode based on the actual cetane number of the fuel injected into the combustion chamber. In order to suitably perform such correction, it is necessary to accurately estimate the cetane number of the fuel.

  Thus, conventionally, there has been proposed a device for injecting a small amount of fuel from a fuel injection valve and estimating the cetane number of the fuel based on the output torque of the diesel engine generated by the fuel injection (see, for example, Patent Document 1). . In such an apparatus, the cetane number of the fuel is estimated by utilizing the fact that the output torque of the diesel engine generated when a certain amount of fuel is injected differs according to the cetane number of the injected fuel.

  In addition, if the execution timing of the fuel injection for the cetane number estimation is different, the output torque of the diesel engine will also be different, which will be an error factor in the cetane number estimation. . Therefore, in the apparatus described in Patent Document 1, the cetane number of the fuel is estimated based on the relationship between the fuel injection execution timing and the output torque of the diesel engine.

JP 2009-180174 A

  Incidentally, the output torque of the diesel engine generated with the fuel injection for estimating the cetane number described above varies depending on the cetane number of the fuel and the execution timing of the fuel injection. It also changes depending on engine parameters such as the rotational speed of the engine (engine speed). Therefore, if a difference in the engine parameters occurs when estimating the cetane number, this will be a cause of lowering the estimation accuracy. It can be said that the apparatus described in Patent Document 1 described above has room for improvement in this respect.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a cetane number estimation device capable of accurately estimating the cetane number of fuel.

In the following, means for achieving the above object and its operational effects will be described.
The invention according to claim 1 is a cetane number estimation device that performs fuel injection in a predetermined amount to estimate the cetane number of fuel to be used for combustion of a diesel engine, and for performing the fuel injection. An index value of the output torque of the diesel engine generated along with the calculated value is calculated, and the cetane number is calculated based on a relationship between the calculated index value, an execution timing of the fuel injection, and an engine speed at the time of execution of the fuel injection. The gist of the present invention is to include estimation means for estimation.

  According to the above configuration, as an estimation parameter used for estimating the cetane number of the fuel, in addition to the index value of the output torque of the diesel engine generated along with the execution of the fuel injection and the execution timing of the fuel injection, The engine speed at the time of execution (running speed) is adopted. Therefore, the estimation of the cetane number of the fuel can be executed in view of the difference in the output torque due to the difference in the rotational speed at the time of execution, and the cetane number can be estimated with high accuracy.

  According to a second aspect of the present invention, in the cetane number estimating device according to the first aspect of the present invention, the fuel pressure that changes as the actual fuel pressure inside the fuel injection valve changes when the fuel injection valve of the diesel engine opens. The gist of the present invention is to further include a fuel pressure detecting means for detecting the above.

  According to a third aspect of the present invention, in the cetane number estimating device according to the second aspect, the error in the execution time is calculated based on the variation of the fuel pressure detected by the fuel pressure detecting means, The gist of the present invention is to further include first correction means for correcting the index value based on the calculated error.

  According to a fourth aspect of the present invention, in the cetane number estimating device according to the second or third aspect of the present invention, an injection amount error in the fuel injection is calculated based on a fuel pressure fluctuation mode detected by the fuel pressure detecting means. In addition, the gist of the present invention is to further include second correction means for correcting the index value based on the calculated error.

  When fuel injection from the fuel injection valve is executed, an error may occur in the execution timing and the fuel injection amount. Such an error causes a decrease in the estimation accuracy of the cetane number of the fuel in order to change the output torque of the diesel engine generated in the fuel injection described above. When fuel injection from the fuel injection valve is executed, the fuel pressure inside the fuel injection valve temporarily decreases. According to the configuration of the second aspect, since the fluctuation mode of the fuel pressure can be monitored, the timing at which the fuel injection is actually executed and the amount of injected fuel are accurately determined based on the fluctuation mode. It becomes possible to grasp well. Therefore, the cetane number of the fuel can be accurately estimated based on the actual execution timing and the fuel injection amount.

  Further, by comparing the actual execution timing and the fuel injection amount thus grasped with the required values, it is possible to calculate an error in the execution timing and the fuel injection amount. According to the third aspect of the present invention, since the index value of the output torque of the diesel engine is corrected based on the error in the execution time, the index value considering the influence due to the error in the execution time is also included. In addition, the cetane number of the fuel can be accurately estimated.

  According to the configuration of claim 4, since the index value of the output torque of the diesel engine is corrected based on the error of the fuel injection amount, the index value in consideration of the influence due to the error of the fuel injection amount Based on the above, the cetane number of the fuel can be accurately estimated.

  According to a fifth aspect of the present invention, in the cetane number estimating device according to any one of the first to fourth aspects, the estimating means sets the execution timing of the fuel injection based on the engine rotational speed and executes the same. The gist is to calculate the index value by executing the fuel injection at a time.

  When fuel injection is executed, the amount of unburned fuel decreases as the execution timing is advanced, the lower the rotation speed during execution, and the higher the cetane number of the fuel. Therefore, the output torque of the diesel engine generated with the fuel injection increases. The output torque has an upper limit (specifically, output torque when the unburned fuel is “0”). In the region where the output torque is at the upper limit, the output torque is at the upper limit without depending on the cetane number of the fuel. Therefore, the cetane number of the fuel cannot be determined based on the output torque. The output torque has a lower limit (output torque = “0”). In the execution region where the output torque becomes the lower limit, the output torque becomes the lower limit without depending on the cetane number of the fuel, so the cetane number of the fuel cannot be determined based on the output torque.

  According to the above configuration, the fuel injection is executed in the execution region where the output torque of the diesel engine is less likely to become the upper limit or the lower limit, such as the fuel injection being executed at the advance timing as the engine rotational speed is higher. As described above, the execution timing of the fuel injection can be set in accordance with the engine speed. Therefore, the cetane number of the fuel can be appropriately estimated based on the output torque (specifically, the index value) of the diesel engine generated with the execution of fuel injection.

  The gist of the invention described in claim 6 is that, in the cetane number estimating device according to claim 5, the estimation means sets the advance side timing as the engine speed is high as the execution timing. And

  According to the above configuration, when the rotational speed at the time of execution is high, that is, when the pressure in the combustion chamber and the temperature decrease rate are high, the fuel injection is performed early. And it can suppress that the temperature becomes too low. For this reason, it is possible to suppress the situation where the remaining amount of unburned fuel increases without depending on the cetane number of the fuel, and it is possible to suppress the index value of the output torque of the diesel engine from becoming excessively small. it can. In addition, when the rotational speed at the time of execution is low, that is, when the rate of decrease in pressure or temperature in the combustion chamber is low, the fuel injection is executed at a later time, so that the injection is performed with the pressure or temperature in the combustion chamber being higher than necessary. It can suppress that it will be in the situation where fuel burns. Therefore, it is possible to suppress a situation in which all of the injected fuel is burned without depending on the cetane number of the fuel, and it is possible to suppress an excessive increase in the index value of the output torque of the diesel engine.

  Thus, according to the above configuration, fuel injection can be executed such that the index value changes with a relatively wide range in accordance with the cetane number of the fuel, and the cetane of the fuel is based on the index value. The price can be estimated accurately.

  The invention according to claim 7 is the cetane number estimation device according to any one of claims 1 to 4, wherein the estimation means has a plurality of situations in which the execution time is the same and the engine speed is different. Each of the fuel injection is performed, and an index value of the output torque of the diesel engine generated along with the execution of the fuel injection is calculated, and the calculated index value and the engine speed at the time of the fuel injection are calculated. The gist is to estimate the cetane number based on the relationship.

According to the above configuration, the cetane number of the fuel can be accurately estimated based on the relationship between the runtime rotational speed and the index value of the output torque of the diesel engine.
According to an eighth aspect of the present invention, in the cetane number estimating device according to the seventh aspect, the estimating means determines the engine rotational speed in relation to the calculated index value and the engine rotational speed when the fuel injection is performed. The gist of the present invention is to identify a boundary between two regions having different tendency of change in the index value with respect to the change of the index value and estimate the cetane number based on the boundary.

  According to the above configuration, the index value of the output torque varies depending on the region where the index value of the output torque of the diesel engine is constant at the upper limit (or lower limit) and the runtime rotation speed without depending on the runtime rotation speed. It is possible to specify the boundary between the two regions and the region, and appropriately estimate the cetane number of the fuel based on the boundary.

  According to a ninth aspect of the present invention, in the cetane number estimating device according to the seventh or eighth aspect, the estimating means executes the fuel injection on the condition that the engine speed is decreasing. The gist.

According to the above configuration, the fuel injection can be sequentially executed in accordance with the decrease in the engine rotation speed, and each fuel injection in a situation where the engine rotation speed is different can be executed efficiently.
A tenth aspect of the present invention is the cetane number estimating device according to any one of the fifth to ninth aspects, wherein the estimating means is configured such that the peak temperature in the combustion chamber of the diesel engine is lower as the execution time. The main point is to set the time on the advance side.

  In addition, the invention according to claim 11 is the cetane number estimation device according to any one of claims 5 to 10, wherein the estimation means has a low peak pressure in the combustion chamber of the diesel engine as the execution time. The gist is to set the time on the advance side.

  Even when fuel injection is executed at the same execution time, execution time, and injection amount, the lower the peak temperature or peak pressure in the combustion chamber, the smaller the output torque of the diesel engine generated with the fuel injection. . Such a difference in output torque is undesirable because it causes a decrease in the accuracy of estimation in a device that estimates the cetane number of fuel based on the output torque of a diesel engine.

  In this regard, according to the configuration of the tenth aspect, the lower the peak temperature in the combustion chamber, that is, the smaller the output torque of the diesel engine that is generated when fuel injection is executed at the same execution timing and injection amount. As time goes on, fuel injection can be performed early in order to increase the output torque. Therefore, even when the peak temperature in the combustion chamber at the time of execution of the fuel injection is different, the change in the output torque of the diesel engine due to the difference can be suppressed, and the fuel based on the index value of the output torque can be suppressed. Cetane number estimation can be performed with high accuracy.

  Further, according to the configuration of the eleventh aspect, the lower the peak pressure in the combustion chamber, that is, the smaller the output torque of the diesel engine generated when the fuel injection is performed with the same injection amount, the same. Fuel injection can be executed early to increase the output torque. Therefore, even when the peak pressure in the combustion chamber at the time of execution of the fuel injection is different, the change in the output torque of the diesel engine due to the difference can be suppressed, and the fuel based on the index value of the output torque can be suppressed. Cetane number estimation can be performed with high accuracy.

  According to a twelfth aspect of the present invention, in the cetane number estimating device according to any one of the first to eleventh aspects, the actual fuel pressure inside the fuel injection valve when the fuel injection valve of the diesel engine is opened. Fuel pressure detecting means for detecting a fuel pressure that changes with change, determination means for determining that fuel has been supplied into a fuel tank stocked with fuel to be supplied to the diesel engine, and fuel supply is made. When it is determined that the fuel is detected, the fuel pressure detecting means detects that the fuel in the fuel path has been replaced by the fuel newly supplied in the fuel path connecting the fuel tank and the fuel injection valve. The gist of the present invention is to further include an execution permission means for detecting the fuel pressure based on the variation of the fuel pressure and permitting the execution of the fuel injection based on the detection.

  The cetane number of the fuel supplied to the diesel engine may change greatly when the fuel tank is refueled. Therefore, in order to efficiently estimate the cetane number of the fuel at an appropriate timing, it can be said that it is effective to execute the estimation when the fuel tank is refueled. However, immediately after the fuel is supplied to the fuel tank, the fuel before refueling remains in the fuel path connecting the fuel tank and the fuel injection valve. Even if the cetane number is estimated, a value corresponding to the fuel after refueling cannot be calculated as the cetane number.

  According to the above configuration, when fuel is supplied to the fuel tank, after waiting for the fuel in the fuel path to be replaced with the fuel after fuel supply, fuel injection for estimating the cetane number is executed. can do. Therefore, fuel injection for estimating the cetane number of the fuel can be executed at an appropriate timing, and the cetane number of the fuel can be accurately estimated through the fuel injection.

  A thirteenth aspect of the present invention is the cetane number estimating device according to any one of the first to twelfth aspects, wherein the device is provided inside the fuel injection valve when the fuel injection valve of the diesel engine is opened. The gist is that a pressure sensor functioning as a fuel pressure detecting means for detecting a fuel pressure that changes with a change in the actual fuel pressure is attached to the fuel injection valve.

  According to the above configuration, it is possible to detect the fuel pressure at a position close to the injection hole of the fuel injection valve as compared with a device that detects the fuel pressure at a position away from the fuel injection valve. A decrease in fuel pressure inside the fuel injection valve accompanying the valve can be detected with high accuracy. Therefore, it is possible to accurately detect the actual execution time and the fuel injection amount based on the fluctuation mode of the fuel pressure, and accurately estimate the cetane number of the fuel based on the actual execution time and the fuel injection amount. Will be able to.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows schematic structure of the cetane number estimation apparatus concerning 1st Embodiment which actualized this invention. Sectional drawing which shows the cross-section of a fuel injection valve. The time chart which shows an example of a detection time waveform. The time chart which shows an example of the relationship between the temperature in a combustion chamber, and engine speed. The graph which shows the relationship between a rotation fluctuation amount, a rotational speed at the time of execution, and the cetane number of a fuel. The graph which shows the relationship between a rotation fluctuation amount, a rotational speed at the time of execution, and the execution time of fuel injection. The flowchart which shows the execution procedure of the estimation control process concerning 1st Embodiment. Explanatory drawing explaining the calculation method of rotation fluctuation amount. The graph which shows the relationship between a rotation fluctuation amount, a rotational speed at the time of execution, and the cetane number of a fuel. The flowchart which shows the execution procedure of the estimation control process concerning 2nd Embodiment which actualized this invention.

(First embodiment)
A cetane number estimation apparatus according to a first embodiment that embodies the present invention will be described below.

FIG. 1 shows a schematic configuration of a cetane number estimation apparatus according to the present embodiment.
As shown in FIG. 1, an intake passage 12 is connected to the cylinder 11 of the diesel engine 10. Air is sucked into the cylinder 11 of the diesel engine 10 through the intake passage 12. The diesel engine 10 is mounted on a vehicle as a drive source. Further, as the diesel engine 10, an engine having a plurality of (four [# 1 to # 4] in the present embodiment) cylinders 11 is employed. A direct injection type fuel injection valve 20 that directly injects fuel into the cylinder 11 is attached to the diesel engine 10 for each cylinder 11. The fuel injected by opening the fuel injection valve 20 is ignited and burned in contact with the intake air compressed and heated in the cylinder 11 of the diesel engine 10. In the diesel engine 10, the piston 13 is pushed down by the energy generated by the combustion of the fuel in the cylinder 11, and the crankshaft 14 is forcibly rotated. The combustion gas combusted in the cylinder 11 of the diesel engine 10 is discharged as exhaust gas into the exhaust passage 15 of the diesel engine 10.

  The diesel engine 10 is provided with an exhaust-driven supercharger 16. The supercharger 16 includes a compressor 17 attached to the intake passage 12 of the diesel engine 10 and a turbine 18 attached to the exhaust passage 15. The supercharger 16 pumps intake air that passes through the intake passage 12 by using the energy of the exhaust that passes through the exhaust passage 15 of the diesel engine 10.

  Each fuel injection valve 20 is individually connected to a common rail 34 via a branch passage 31a, and the common rail 34 is connected to a fuel tank 32 via a supply passage 31b. A fuel pump 33 that pumps fuel is provided in the supply passage 31b. In the present embodiment, the fuel boosted by the pumping by the fuel pump 33 is stored in the common rail 34 and supplied to each fuel injection valve 20. A return passage 35 is connected to each fuel injection valve 20, and each return passage 35 is connected to a fuel tank 32. Part of the fuel inside the fuel injection valve 20 is returned to the fuel tank 32 through the return passage 35.

Hereinafter, the internal structure of the fuel injection valve 20 will be described.
FIG. 2 shows a cross-sectional structure of the fuel injection valve 20.
As shown in FIG. 2, a needle valve 22 is provided inside the housing 21 of the fuel injection valve 20. The needle valve 22 is provided in a state capable of reciprocating in the housing 21 (moving up and down in the figure). Inside the housing 21 is provided a spring 24 that constantly urges the needle valve 22 toward the injection hole 23 (the lower side in the figure). A nozzle chamber 25 is formed in the housing 21 at a position on one side (lower side in the figure) with the needle valve 22 interposed therebetween, and on the other side (upper side in the figure). A pressure chamber 26 is formed.

  The nozzle chamber 25 is formed with an injection hole 23 that communicates the inside with the outside of the housing 21, and fuel is supplied from the branch passage 31 a (common rail 34) through the introduction passage 27. The pressure chamber 26 is connected to the nozzle chamber 25 and the branch passage 31a (common rail 34) via a communication passage 28. The pressure chamber 26 is connected to a return passage 35 (fuel tank 32) via a discharge passage 30.

  As the fuel injection valve 20, an electrically driven type is adopted, and a piezoelectric actuator 29 in which a piezoelectric element (for example, a piezo element) that expands and contracts by input of a drive signal is provided in the housing 21. Yes. A valve body 29 a is attached to the piezoelectric actuator 29, and the valve body 29 a is provided inside the pressure chamber 26. Then, through the movement of the valve element 29 a by the operation of the piezoelectric actuator 29, one of the communication path 28 (nozzle chamber 25) and the discharge path 30 (return path 35) is selectively communicated with the pressure chamber 26. It has become.

  In this fuel injection valve 20, when a valve closing signal is input to the piezoelectric actuator 29, the piezoelectric actuator 29 contracts and the valve body 29 a moves, and the communication path 28 and the pressure chamber 26 are in communication with each other. The communication between the return passage 35 and the pressure chamber 26 is cut off. Thereby, the nozzle chamber 25 and the pressure chamber 26 are communicated with each other in a state where the discharge of the fuel in the pressure chamber 26 to the return passage 35 (fuel tank 32) is prohibited. Therefore, the pressure difference between the nozzle chamber 25 and the pressure chamber 26 becomes very small, and the needle valve 22 moves to a position where the injection hole 23 is closed by the urging force of the spring 24. At this time, the fuel injection valve 20 does not inject fuel. State (valve closed).

  On the other hand, when a valve opening signal is input to the piezoelectric actuator 29, the piezoelectric actuator 29 expands to move the valve element 29a, the communication between the communication passage 28 and the pressure chamber 26 is cut off, and the return passage. 35 and the pressure chamber 26 are in communication with each other. As a result, part of the fuel in the pressure chamber 26 is returned to the fuel tank 32 via the return passage 35 in a state where fuel outflow from the nozzle chamber 25 to the pressure chamber 26 is prohibited. As a result, the pressure of the fuel in the pressure chamber 26 decreases and the pressure difference between the pressure chamber 26 and the nozzle chamber 25 increases, and the pressure difference causes the needle valve 22 to move against the biasing force of the spring 24 and inject. Apart from the hole 23, the fuel injection valve 20 is in a state in which fuel is injected (opened state) at this time.

A pressure sensor 41 that outputs a signal corresponding to the fuel pressure PQ inside the introduction passage 27 is integrally attached to the fuel injection valve 20. For this reason, for example, the fuel in a portion near the injection hole 23 of the fuel injection valve 20 as compared with a device that detects the fuel pressure at a position away from the fuel injection valve 20 such as the fuel pressure in the common rail 34 (see FIG. 1). The pressure can be detected, and the change in the fuel pressure inside the fuel injection valve 20 accompanying the opening of the fuel injection valve 20 can be detected with high accuracy. One pressure sensor 41 is provided for each fuel injection valve 20, that is, for each cylinder 11 of the diesel engine 10.

  As shown in FIG. 1, the diesel engine 10 is provided with various sensors as peripheral devices for detecting an operation state. As these sensors, in addition to the pressure sensor 41, for example, a supercharging pressure sensor 42 for detecting the pressure (supercharging pressure PA) in the intake passage 12 downstream of the compressor 17 in the intake flow direction, A crank sensor 43 for detecting the rotational phase (crank angle CA) and rotational speed (engine rotational speed NE) of the shaft 14 is provided. In addition, a temperature sensor 44 for detecting the temperature (THW) of the cooling water of the diesel engine 10, a storage amount sensor 45 for detecting the amount of fuel stored in the fuel tank 32, and an accelerator operating member (for example, an accelerator pedal) An accelerator sensor 46 for detecting the operation amount (accelerator operation amount ACC), a vehicle speed sensor 47 for detecting the traveling speed of the vehicle, and the like are also provided.

  As a peripheral device of the diesel engine 10, for example, an electronic control unit 40 configured with a microcomputer is also provided. The electronic control unit 40 takes in the output signals of various sensors and performs various calculations based on the output signals, and the diesel engine 10 such as operation control (fuel injection control) of the fuel injection valve 20 according to the calculation results. Various controls related to the operation are executed.

The fuel injection control of the present embodiment is basically executed as follows.
First, a control target value (target fuel injection amount TQ) for the fuel injection amount is calculated based on the accelerator operation amount ACC, the engine speed NE, the cetane number of the fuel (specifically, an estimated cetane number to be described later), and the like. . Thereafter, control target values for the fuel injection timing and the fuel injection time are calculated based on the target fuel injection amount TQ and the engine speed NE. Then, each fuel injection valve 20 is driven to open individually according to these control target values. Thus, an amount of fuel commensurate with the operation state of the diesel engine 10 at that time is injected from each fuel injection valve 20 and supplied into each cylinder 11 of the diesel engine 10.

  In the apparatus of the present embodiment, the time waveform of the fuel injection rate in the fuel injection from the fuel injection valve 20 based on the fuel pressure PQ detected by the pressure sensor 41 in accordance with the execution of such fuel injection control (detection time waveform) ) Is executed (injection rate formation control).

  Specifically, the timing at which the valve opening operation of the fuel injection valve 20 (specifically, the movement of the needle valve 22 toward the valve opening side) is started based on the transition of the fuel pressure PQ (valve opening operation start timing Tos), the fuel When the injection rate becomes maximum (maximum injection rate arrival time Toe), when the fuel injection rate starts to decrease (injection rate decrease start time Tcs), and when the fuel injection valve 20 is closed (specifically, the needle valve 22 The time when the movement toward the valve closing side is completed (minimum lift amount arrival time Tce) is specified. Then, as shown in FIG. 3, an actual fuel injection rate time waveform (detection time waveform) is formed by the identified times Tos, Toe, Tcs, and Tce.

  The fuel pressure inside the fuel injection valve 20 (specifically, the nozzle chamber 25) decreases as the lift amount increases when the fuel injection valve 20 is driven to open, and then lifts when the valve is driven to close. As the amount decreases, it increases. In the present embodiment, based on the transition of the fuel pressure inside the fuel injection valve 20 (specifically, the fuel pressure PQ), the valve opening operation start timing Tos, the maximum lift amount reaching timing Toe, and the valve closing operation start timing are described. Tcs and the minimum lift amount arrival time Tce are accurately identified.

  In the present embodiment, the change speed of the fuel pressure PQ (specifically, the first-order differential value of the fuel pressure PQ) is calculated, and the change speed is calculated based on the valve opening operation start timing Tos and the maximum lift amount arrival timing Toe. The valve closing operation start timing Tcs and the minimum lift amount reaching timing Tce are used. As a result, the timing at which the fuel pressure PQ starts to suddenly decrease with the start of the valve opening operation of the fuel injection valve 20, the timing at which the change rate of the fuel pressure PQ starts to decrease during the valve opening operation, and the valve closing operation. It is possible to easily specify the time when the fuel pressure PQ starts to rise suddenly with the start of the time, or the time when the change speed of the fuel pressure PQ changes from rising to falling during the valve closing operation. Therefore, the operation mode of the fuel injection valve 20 is properly grasped based on the fuel pressure PQ, and the valve opening operation start timing Tos, the maximum lift amount arrival timing Toe, the valve closing operation start timing Tcs, and the minimum lift amount reached. The time Tce is specified with high accuracy.

Hereinafter, control (estimation control) for estimating the cetane number of fuel will be described.
This estimation control is basically executed as follows. That is, first, when the execution condition is satisfied, fuel injection is performed in a predetermined amount (for example, several cubic millimeters), and an index of the output torque of the diesel engine 10 generated in accordance with the execution of the fuel injection. A value (rotational fluctuation amount ΣΔNE described later) is calculated. Then, the cetane number of the fuel is estimated based on this rotational fluctuation amount ΣΔNE. The higher the cetane number of the fuel supplied to the diesel engine 10, the easier the fuel is ignited, and the less unburned fuel of the fuel decreases, so the engine torque generated with the combustion of the fuel increases. In the estimation control of the present embodiment, the cetane number of the fuel is estimated based on the relationship between the cetane number of the fuel and the output torque of the diesel engine 10.

  Here, the output torque of the diesel engine 10 generated when a predetermined amount of fuel is injected changes in accordance with the engine rotational speed NE in addition to changing in accordance with the cetane number of the fuel. This is due to the following reasons.

  FIG. 4 shows an example of the relationship between the temperature (or pressure) in the combustion chamber 11a of the diesel engine 10 and the engine rotational speed NE. As shown in FIG. 4, when the engine speed NE is increased, the time during which the combustion chamber 11a is in a high temperature and high pressure state is shortened. Therefore, when fuel injection with a predetermined amount is executed in the above estimation control, the higher the engine speed NE, the lower the temperature and pressure in the combustion chamber 11a, and the more likely it is that fuel remains unburned. Therefore, the output torque of the diesel engine 10 generated with the fuel injection tends to be small.

  FIG. 5 shows the relationship between the rotational fluctuation amount ΣΔNE, the engine rotational speed NE, and the cetane number of the fuel when fuel injection is executed under the same injection timing and injection amount. As is clear from FIG. 5, when fuel injection is executed under the same injection timing and injection amount, the output torque of the diesel engine 10 (more specifically, The index value, that is, the rotational fluctuation amount ΣΔNE) becomes smaller.

  Further, the output torque of the diesel engine 10 generated when a predetermined amount of fuel is injected changes in accordance with the cetane number of the fuel and the engine rotational speed NE, and also changes depending on the execution timing of the fuel injection. .

  FIG. 6 shows the relationship between the rotational fluctuation amount ΣΔNE, the rotational speed at the time of execution, and the execution timing of the fuel injection when the fuel injection is executed under the same situation of the cetane number of the fuel and the fuel injection amount. Indicates. As shown in FIG. 6, the output torque of the diesel engine 10 generated with fuel injection (specifically, the rotational fluctuation amount ΣΔNE, which is an index value), as the execution timing of fuel injection is retarded. Becomes smaller. This is because as the fuel injection execution timing is delayed, the fuel burns in a state where the temperature and pressure in the combustion chamber 11a are low, and the amount of unburned fuel increases. Conceivable.

  As described above, in the apparatus of the present embodiment, when fuel injection is performed with a predetermined amount, as the execution timing is the advance timing, and as the engine speed NE during execution is lower, Furthermore, the higher the cetane number of the fuel, the greater the output torque of the diesel engine 10 generated with the fuel injection.

  In view of this point, in this embodiment, the cetane number of the fuel is estimated based on the relationship between the rotational fluctuation amount ΣΔNE and the execution timing of fuel injection by the estimation control and the rotational speed at the time of execution. As a result, since the estimation of the cetane number of the fuel can be executed in consideration of the difference in the output torque of the diesel engine 10 due to the difference in the rotational speed at the time of execution and the difference in the timing of the fuel injection, The price can be estimated accurately.

Hereinafter, the execution mode of the estimation control will be specifically described.
Further, there is an upper limit (specifically, output torque when the unburned fuel amount is “0”) in the output torque of the diesel engine 10 that is generated when the fuel injection is performed at a predetermined amount. The region where the output torque is at the upper limit includes a region where the fuel injection is performed in a state where the engine speed NE is low (see FIG. 5), and a region where the fuel injection is performed at the advance timing (FIG. 6). Reference). In such a region, the output torque of the diesel engine 10 becomes the upper limit without depending on the cetane number of the fuel. Therefore, the cetane number of the fuel is determined based on the output torque (specifically, the rotational fluctuation amount ΣΔNE). I can't.

  Further, the output torque of the diesel engine 10 generated by the execution of fuel injection with a predetermined amount has a lower limit (output torque = “0”) in addition to such an upper limit. The region where the output torque becomes the lower limit is a region where the fuel injection is executed in a situation where the engine rotational speed NE is high (see FIG. 5), or a region where the fuel injection is executed at the retarded timing (FIG. 6). Reference). In this region, the output torque becomes the lower limit regardless of the cetane number of the fuel, and therefore, the cetane number of the fuel cannot be determined based on the output torque (specifically, the rotational fluctuation amount ΣΔNE).

  For this reason, in order to accurately estimate the cetane number of the fuel, it is desirable to execute the fuel injection in the estimation control so that the region where the output torque of the diesel engine 10 becomes the upper limit or the lower limit is reduced. .

  As is apparent from FIG. 6, the region where the output torque of the diesel engine 10 becomes the upper limit or the lower limit changes by changing the execution timing of the fuel injection. In the estimation control according to the present embodiment based on such characteristics, a control target value (target injection timing) for the execution timing of the fuel injection is set based on the engine speed NE, and the fuel injection is performed at the target injection timing. To do. Specifically, as the target injection timing, the advance timing is set as the engine speed NE is higher.

By setting the target injection timing in this way, the following operation can be obtained.
When the above-mentioned rotational speed at the time of execution is high, that is, when the pressure or temperature decrease rate in the combustion chamber 11a is high, the fuel injection is performed early, so the pressure in the combustion chamber 11a It becomes possible to suppress the temperature from becoming too low. Therefore, it is possible to suppress the situation in which the amount of unburned fuel remaining increases without depending on the cetane number of the fuel, and the output torque of the diesel engine 10 (specifically, the rotational fluctuation amount ΣΔNE) is excessive. Can be suppressed.

  Moreover, when the rotational speed at the time of execution is low, that is, when the rate of decrease in pressure or temperature in the combustion chamber 11a is low, the fuel injection is executed at a later time, so the pressure or temperature in the combustion chamber 11a is more than necessary. Therefore, it becomes possible to suppress the situation where the injected fuel burns in a high state. Therefore, it is possible to suppress a situation in which all of the injected fuel burns without depending on the cetane number of the fuel, and the output torque of the diesel engine 10 (specifically, the rotational fluctuation amount ΣΔNE) is excessively large. Can be suppressed.

  As described above, in the estimation control according to the present embodiment, the same fuel is produced in accordance with the engine rotational speed NE so that the fuel injection is executed in the execution region in which the output torque of the diesel engine 10 is less likely to be the upper limit or the lower limit. The injection execution time (target injection time) can be set. Accordingly, since the rotational fluctuation amount ΣΔNE changes with a relatively wide range in accordance with the cetane number of the fuel, the cetane number of the fuel is accurately estimated based on the rotational fluctuation amount ΣΔNE. Will be able to.

  Even when fuel injection is executed at the same execution timing and injection amount, the lower the maximum value (peak temperature) or the maximum value (peak pressure) of the temperature in the combustion chamber 11a of the diesel engine 10 is lower. Since the time during which the inside of the combustion chamber 11a is in a high-temperature and high-pressure state is shortened, the output torque of the diesel engine 10 generated with fuel injection is reduced. In the estimation control of the present embodiment, the fuel cetane number is estimated based on the index value of the output torque of the diesel engine 10 (specifically, the rotational fluctuation amount ΣΔNE). This is a cause of lowering the estimation accuracy of the price.

  In view of this point, in this embodiment, in addition to the engine rotational speed NE, the coolant temperature THW and the supercharging pressure PA are used as setting parameters used for setting the target injection timing. Specifically, the coolant temperature THW is used as a value that serves as an index of the peak value of the temperature in the combustion chamber 11a of the diesel engine 10, and the supercharging pressure PA is an index of the peak value of the pressure in the combustion chamber 11a. Is used as a value. Then, the lower the coolant temperature THW, the lower the peak temperature in the combustion chamber 11a, and the lower the supercharging pressure PA, the lower the peak pressure in the combustion chamber 11a. Is set.

  Thus, by setting the target injection timing according to the coolant temperature THW and the supercharging pressure PA, when the peak temperature and the peak pressure in the combustion chamber 11a of the diesel engine 10 are low, that is, the same injection timing and injection amount. As the output torque of the diesel engine 10 generated when the fuel injection is executed becomes smaller, the fuel injection is executed earlier in order to increase the output torque. As a result, even if the peak temperature and the peak pressure in the combustion chamber 11a in the execution of the fuel injection are different, the change in the output torque of the diesel engine 10 due to the difference can be suppressed. The estimation of the cetane number of the fuel based on the torque index value (rotational fluctuation amount ΣΔNE) can be executed with high accuracy.

Hereinafter, the execution procedure of the process related to the estimation control (estimation control process) will be described in detail.
FIG. 7 is a flowchart showing a specific execution procedure of the estimation control process. Note that the series of processes shown in this flowchart conceptually shows the execution procedure of the estimation control process, and the actual process is executed by the electronic control unit 40 as an interrupt process at predetermined intervals. In the present embodiment, this estimation control process functions as an estimation means.

As shown in FIG. 7, in this process, it is first determined whether or not an execution condition is satisfied (step S101). Here, it is determined that the execution condition is satisfied when all of the following [Condition A] to [Condition C] are satisfied.
[Condition A] Control (so-called fuel cut control) for temporarily stopping fuel injection for operation of the diesel engine 10 during deceleration of the vehicle traveling speed and the engine rotational speed NE by releasing the operation of the accelerator operating member is executed. Being.
[Condition b] There is no history of calculating an estimated value of cetane number of fuel (estimated cetane number, which will be described later) after it is determined that the fuel tank 32 has been refueled. The fuel supply to the fuel tank 32 is determined when the amount of fuel stock detected by the stock amount sensor 45 has increased by a predetermined judgment amount or more.
[Condition C] After determining that the fuel tank 32 has been refueled, the fuel path (more specifically, the branch) connecting the fuel tank 32 and the fuel injection valve 20 with the fuel newly supplied from the fuel tank 32 The fuel in the passage 31a, the supply passage 31b, the common rail 34, and the return passage 35) has been replaced.

  Specifically, it is determined as follows that this [Condition C] is satisfied. That is, first, every time fuel injection from each fuel injection valve 20 is executed after it is determined that fuel supply to the fuel tank 32 has been performed, the detection time waveform (see FIG. 3) and the fuel injection valve 20 Based on the characteristics, an amount of fuel leaking from the inside of the fuel injection valve 20 to the return passage 35 is estimated, and an integrated value of the estimated amount is calculated. When this integrated value is equal to or greater than a predetermined determination amount, it is determined that [Condition C] is satisfied. In the present embodiment, the fuel in the return passage 35 is replaced with the fuel newly supplied from the fuel tank 32 after refueling based on the amount of fuel leaking from the inside of the fuel injection valve 20 into the return passage 35. Is detected, and with this detection, it is detected that the fuel in the fuel path has been replaced.

  [Condition B] and [Condition C] are set for the following reason. The cetane number of the fuel supplied to the diesel engine 10 may greatly change when the fuel tank 32 is refueled. Therefore, in order to efficiently estimate the cetane number of the fuel at an appropriate timing, it can be said that it is effective to execute the estimation when the fuel tank 32 is refueled. However, immediately after the fuel tank 32 is refueled, the fuel before refueling remains in the fuel path. At this time, the fuel injection described above is executed to estimate the cetane number of the fuel. However, a value corresponding to the fuel after refueling cannot be calculated as the cetane number. In this respect, since [Condition B] and [Condition C] are set in the present embodiment, when the fuel tank 32 is refueled, the fuel in the fuel path becomes the fuel after refueling. After waiting for the replacement, the fuel injection for estimating the cetane number is executed. Therefore, fuel injection for estimating the cetane number of fuel can be executed at an appropriate timing, and the cetane number can be accurately estimated through the fuel injection. In the present embodiment, the process of step S101 functions as a determination unit and an execution permission unit.

If the execution condition is not satisfied (step S101: NO), this process is temporarily terminated without executing the following process, that is, a process for estimating the cetane number of the fuel.
Thereafter, when this process is repeatedly executed and the above execution condition is satisfied (step S101: YES), the target injection timing is set based on the engine speed NE, the coolant temperature THW, and the supercharging pressure PA at this time. At the same time (step S102), the predetermined amount of fuel is injected from the fuel injection valve 20 at the target injection timing (step S103). This fuel injection is performed using a predetermined one of the plurality of fuel injection valves 20 (in this embodiment, the fuel injection valve 20 attached to the cylinder 11 [# 1]).

  Thereafter, an index value (the rotational fluctuation amount ΣΔNE) of the output torque of the diesel engine 10 generated with the fuel injection is calculated (step S104). Specifically, the rotational fluctuation amount ΣΔNE is calculated as follows. As shown in FIG. 8, in the apparatus according to the present embodiment, the engine rotational speed NE is detected every predetermined time, and at each detection, the engine rotational speed NE and the previous engine rotational speed NE are detected several times (in the present embodiment). The difference ΔNE (= NE−NEi) from the engine speed NEi detected three times before) is calculated. Then, an integrated value (a value corresponding to the area of the hatched portion in FIG. 8) for the change in the difference ΔNE accompanying the execution of the fuel injection is calculated, and this integrated value is calculated as the rotational fluctuation amount. Stored as ΣΔNE. Note that the transitions of the engine speed NE and the difference ΔNE shown in FIG. 8 are slightly different from the actual transitions because they are simplified for easy understanding of the calculation method of the rotational fluctuation amount ΣΔNE.

  Thereafter, the difference (injection timing error) between the target injection timing and the timing when fuel injection from the fuel injection valve 20 is actually executed, the target value (the predetermined amount) for the fuel injection amount, and the actual fuel injection amount (Injection amount error) is calculated. Then, the rotational fluctuation amount ΣΔNE is corrected based on the injection timing error and the injection amount error, and the corrected value is stored as a new rotational fluctuation amount ΣΔNE (step S105). In the present embodiment, the process of step S105 functions as a first correction unit and a second correction unit.

  Here, when the fuel injection from the fuel injection valve 20 is executed, an error may occur in the execution timing and the fuel injection amount. Such an error changes the output torque of the diesel engine 10 generated by the fuel injection, which causes a decrease in the estimation accuracy of the cetane number of the fuel.

  In the apparatus according to the present embodiment, the time waveform (the detected time waveform [see FIG. 3]) for the fuel injection rate is formed based on the variation mode of the fuel pressure PQ detected through the pressure sensor 41. Based on this detection time waveform, it is possible to accurately grasp the actual fuel injection timing and the actual fuel injection amount. Specifically, the actual execution timing of the fuel injection can be detected based on the valve opening operation start timing Tos and the minimum lift amount arrival timing Tce in the detection time waveform, and the actual fuel injection amount is detected by the detection time waveform. Can be detected based on the area of the trapezoidal portion connecting the respective times Tos, Toe, Tcs, and Tce. Moreover, the actual fuel injection amount and its required value can be calculated by comparing the actual fuel injection timing and its required value (target injection time) by comparing the actual fuel injection amount and the required value. The fuel injection amount error (injection amount error) can be calculated by comparing (predetermined amount).

  In this process, since the rotational fluctuation amount ΣΔNE is corrected based on the injection timing error and the injection amount error, a value that takes into account the influence due to the fuel injection execution time error and the fuel injection amount error. Can be calculated as the rotational fluctuation amount ΣΔNE, and the cetane number of the fuel can be accurately estimated based on the rotational fluctuation amount ΣΔNE.

  Specifically, the rotational fluctuation amount ΣΔNE becomes unnecessarily large when the actual execution time shifts to the advance side, while the rotational fluctuation amount ΣΔNE becomes unnecessarily small when the actual execution time shifts to the retard side. Therefore, in this process, when the target injection timing is an advance timing side from the actual injection timing, the rotational fluctuation amount ΣΔNE is corrected to decrease, while the target injection timing is set to a timing retarded from the actual injection timing. When the rotational speed is changed, the rotational fluctuation amount ΣΔNE is corrected to increase. Further, as the difference between the target injection timing and the actual injection timing is larger, the correction amount of the rotational fluctuation amount ΣΔNE is larger.

  Further, when the actual fuel injection amount exceeds the predetermined amount, the rotational fluctuation amount ΣΔNE becomes unnecessarily large. On the other hand, when the actual fuel injection amount becomes smaller than the predetermined amount, the rotational fluctuation amount ΣΔNE becomes unnecessarily small. Therefore, in this process, when the actual fuel injection amount is larger than the target value, the rotational fluctuation amount ΣΔNE is corrected to decrease, while when the actual fuel injection amount is smaller than the target value, the rotational fluctuation amount ΣΔNE is corrected to increase. Further, as the difference between the actual fuel injection amount and its target value is larger, the correction amount of the rotational fluctuation amount ΣΔNE is larger.

  After the rotational fluctuation amount ΣΔNE is corrected in this way, an estimated value (estimated cetane number) of the fuel cetane number is calculated based on the rotational fluctuation amount ΣΔNE and the rotational speed at the time of execution (step S106). In the present embodiment, the cetane number (specifically, the estimated cetane number described above), the rotational fluctuation amount ΣΔNE, and the execution time can be accurately estimated based on the results of experiments and simulations. The relationship with the rotation speed (the relationship as shown in FIG. 5) is obtained in advance and stored in the electronic control unit 40. In the process of step S106, the estimated cetane number is calculated from the relationship based on the rotation fluctuation amount ΣΔNE and the execution speed.

Then, after the estimated cetane number is calculated in this way, the present process is temporarily terminated.
As described above, according to the present embodiment, the effects described below can be obtained.

  (1) The cetane number of the fuel is estimated based on the relationship between the rotational fluctuation amount ΣΔNE and the execution timing of fuel injection by the estimation control and the rotational speed at the time of execution. Therefore, the estimation of the cetane number of the fuel can be performed in consideration of the difference in the output torque of the diesel engine 10 due to the difference in the rotational speed at the time of execution and the difference in the timing of the fuel injection. Can be estimated well.

  (2) The target injection timing is set based on the engine speed NE and the fuel injection is executed at the target injection timing. Therefore, the execution timing of the fuel injection can be set in accordance with the engine rotational speed NE so that the fuel injection is executed in the execution region where the output torque of the diesel engine 10 is less likely to reach the upper limit or the lower limit. Accordingly, since the rotational fluctuation amount ΣΔNE changes with a relatively wide range in accordance with the cetane number of the fuel, the cetane number of the fuel is accurately estimated based on the rotational fluctuation amount ΣΔNE. Will be able to.

  (3) The target injection timing is set based on the coolant temperature THW. Therefore, even if the peak temperature in the combustion chamber 11a in the execution of fuel injection for estimating the cetane number of fuel is different, the change in the output torque of the diesel engine 10 due to the difference can be suppressed, It is possible to accurately estimate the cetane number of the fuel based on the rotational fluctuation amount ΣΔNE that is an index value of the output torque.

  (4) The target injection timing is set based on the supercharging pressure PA. Therefore, even if the peak pressure in the combustion chamber 11a in the execution of the fuel injection for estimating the cetane number of the fuel is different, the change in the output torque of the diesel engine 10 due to the difference can be suppressed, It is possible to accurately estimate the cetane number of the fuel based on the rotational fluctuation amount ΣΔNE that is an index value of the output torque.

  (5) The injection timing error is calculated, and the rotational fluctuation amount ΣΔNE is corrected based on the injection timing error. Therefore, a value that takes into account the influence due to the error in the fuel injection execution timing can be calculated as the rotational fluctuation amount ΣΔNE, and the cetane number of the fuel can be accurately estimated based on the rotational fluctuation amount ΣΔNE.

  (6) The injection amount error is calculated, and the rotational fluctuation amount ΣΔNE is corrected based on the injection amount error. Therefore, a value that takes into account the influence of the fuel injection amount error can be calculated as the rotational fluctuation amount ΣΔNE, and the cetane number of the fuel can be accurately estimated based on the rotational fluctuation amount ΣΔNE.

  (7) When it is determined that the fuel tank 32 has been refueled, the fuel in the fuel path connecting the fuel tank 32 and the fuel injection valve 20 with the fuel newly supplied from the fuel tank 32 thereafter Is detected, and the detection permits the execution of fuel injection for estimating the cetane number. Therefore, the fuel injection can be performed after waiting for the fuel in the fuel path to be replaced with the fuel after the fuel supply when the fuel tank 32 is refueled. Therefore, fuel injection for estimating the cetane number of fuel can be executed at an appropriate timing, and the cetane number can be accurately estimated through the fuel injection.

  (8) The fuel pressure PQ is detected by the pressure sensor 41 integrally attached to the fuel injection valve 20. Therefore, as compared with a device that detects the fuel pressure at a position away from the fuel injection valve 20, the fuel pressure at a portion near the injection hole 23 of the fuel injection valve 20 can be detected, and the fuel injection valve 20 is opened. A change in the fuel pressure inside the fuel injection valve 20 accompanying the valve can be detected with high accuracy. Therefore, the actual execution timing and actual fuel injection amount of the fuel injection can be accurately detected based on the fluctuation mode of the fuel pressure PQ, and the fuel is calculated based on the actual execution timing and actual fuel injection amount. The cetane number of can be accurately estimated.

(Second Embodiment)
Hereinafter, a cetane number estimation apparatus according to a second embodiment that embodies the present invention will be described focusing on differences from the first embodiment. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

The cetane number estimation apparatus according to this embodiment differs from the cetane number estimation apparatus according to the first embodiment in the execution mode of estimation control for estimating the cetane number of fuel.
Hereinafter, the estimation control according to the present embodiment will be specifically described.

  As described above, when fuel injection is executed under the same injection timing and injection amount, the engine rotational speed NE (running rotational speed), the rotational fluctuation amount ΣΔNE, and the fuel cetane at the time of execution are determined. The relationship with the price shows the following tendency. That is, as apparent from the relationship shown in FIG. 9, the rotational fluctuation amount ΣΔNE decreases as the execution speed increases. Further, the upper limit of the output torque of the diesel engine 10 generated when fuel injection is executed under the same injection timing and injection amount (specifically, the output torque when the unburned fuel remains “0”). Therefore, if fuel injection is executed in the execution region where the output torque is the upper limit, the output torque will be the upper limit regardless of the cetane number of the fuel. Furthermore, since such force torque also has a lower limit (output torque = “0”), when fuel injection is executed in the execution region where the output torque is lower, the output torque becomes lower limit regardless of the cetane number of the fuel. End up.

  When fuel injection is performed at the same execution timing in a plurality of situations with different engine rotation speeds NE and the relationship between the rotation speed at the time of execution and the amount of rotation fluctuation ΣΔNE is obtained, the relationship becomes the cetane number of the fuel. The following tendencies are shown in response. That is, the boundary between the region where the rotational fluctuation amount ΣΔNE is substantially constant at the upper limit without depending on the rotational speed at execution and the region where the rotational fluctuation amount ΣΔNE changes according to the rotational speed at execution (specifically, The value corresponding to the rotational speed at the time of execution indicated by the line L1 in FIG. Further, a boundary between the region where the rotational fluctuation amount ΣΔNE changes according to the rotational speed at the time of execution and the region where the rotational fluctuation amount ΣΔNE becomes constant at the lower limit without depending on the rotational speed at the time of execution (shown by a line L2 in FIG. 9). Similarly, the value corresponding to the rotational speed at the time of execution differs depending on the cetane number of the fuel.

  Focusing on such a tendency, in the present embodiment, the boundary between two regions in which the change tendency of the rotational fluctuation amount ΣΔNE with respect to the change of the rotational speed at the time of execution is different in the relationship between the rotational speed of the execution time and the rotational fluctuation amount ΣΔNE (Specifically, the lines L1 and L2 are specified) and the cetane number of the fuel is estimated based on the boundary. Thus, the cetane number of the fuel can be accurately estimated based on the relationship (specifically, the above boundary) between the rotational speed at the time of execution and the rotational fluctuation amount ΣΔNE that differs depending on the cetane number of the fuel. Become.

  In this embodiment, the control target value (target injection timing) for the execution timing of the fuel injection is set based on the coolant temperature THW and the supercharging pressure PA. Specifically, the lower the coolant temperature THW, the lower the peak temperature in the combustion chamber 11a, and the lower the supercharging pressure PA, the lower the peak pressure in the combustion chamber 11a. It is set at the time of.

  Thus, by setting the target injection timing according to the coolant temperature THW and the supercharging pressure PA, the fuel injection is performed when the peak temperature or the peak pressure in the combustion chamber 11a of the diesel engine 10 is low, that is, at the same injection amount. As the output torque of the diesel engine 10 generated in the case where is executed, the fuel injection is executed earlier in order to increase the output torque. As a result, even if the peak temperature and the peak pressure in the combustion chamber 11a in the execution of the fuel injection are different, the change in the output torque of the diesel engine 10 due to the difference can be suppressed. The estimation of the cetane number of the fuel based on the torque index value (rotational fluctuation amount ΣΔNE) can be executed with high accuracy.

Hereinafter, the execution procedure of the estimation control process according to the present embodiment will be described in detail.
FIG. 10 is a flowchart showing a specific execution procedure of the estimation control process. Note that the series of processes shown in this flowchart conceptually shows the execution procedure of the estimation control process, and the actual process is executed by the electronic control unit 40 as an interrupt process at predetermined intervals. In the present embodiment, this estimation control process functions as an estimation means.

  As shown in FIG. 10, in this process, it is first determined whether or not an execution condition is satisfied (step S201). Here, it is determined that the execution condition is satisfied when all of [Condition A] to [Condition C] are satisfied. In the present embodiment, the process in step S201 functions as a determination unit and an execution permission unit.

  In the present embodiment, since [Condition A] is set, fuel injection for estimating the cetane number of the fuel is executed on the condition that the engine speed NE is reduced. Become. Therefore, the fuel injection is sequentially executed in accordance with the decrease in the engine speed NE, and the boundary can be specified based on the rotation fluctuation amount ΣΔNE obtained as a result. Therefore, for example, a plurality of fuel injections for estimating the cetane number are executed in a period from when the engine rotational speed NE starts to decelerate until the deceleration ends, such as when multiple engine rotational speeds NE are different. Fuel injection can be performed efficiently.

If the execution condition is not satisfied (step S201: NO), this process is temporarily terminated without executing the following process, that is, a process for estimating the cetane number of the fuel.
Thereafter, when this process is repeatedly executed and the above execution condition is satisfied (step S201: YES), the target injection timing is set based on the cooling water temperature THW and the supercharging pressure PA at this time (step S202).

  Then, each time the engine speed NE reaches a predetermined speed (NE1, NE2, NE3,... NEn), the predetermined amount of fuel is injected from the fuel injection valve 20 at the target injection timing. Then, an index value (the rotational fluctuation amount ΣΔNE) of the output torque of the diesel engine 10 generated with the fuel injection is calculated and stored (step S203).

  Each fuel injection in this process is executed using a predetermined one of the plurality of fuel injection valves 20 (in this embodiment, the fuel injection valve 20 attached to the cylinder 11 [# 1]). . In this process, every time fuel injection is executed, the rotational fluctuation amount ΣΔNE is calculated and stored as follows. That is, first, the rotational fluctuation amount ΣΔNE is calculated based on the fluctuation mode of the engine rotational speed NE. Further, the difference between the target injection timing and the timing when the fuel injection from the fuel injection valve 20 is actually executed (injection timing error), the target value (the predetermined amount) for the fuel injection amount, and the actual fuel injection amount (Injection amount error) is calculated. The rotational fluctuation amount ΣΔNE is corrected based on the injection timing error and the injection amount error, and the corrected value is stored as the final rotational fluctuation amount ΣΔNE. In the present embodiment, the processing in step S203 functions as a first correction unit and a second correction unit.

  Thereafter, based on each rotational fluctuation amount ΣΔNE, the boundary between two regions where the tendency of the change of the rotational fluctuation amount ΣΔNE with respect to the change in the rotational speed at the time of execution is different (specifically Specifically, values corresponding to the lines L1 and L2 in FIG. 9 are specified and stored, and the rotational fluctuation amount ΣΔNE at the same boundary is stored (step S204).

  Then, an estimated value (estimated cetane number) of the cetane number of the fuel is calculated based on the boundary and the rotational fluctuation amount ΣΔNE at the boundary (step S205). The estimated cetane number is calculated based on the following idea in detail. When the rotational fluctuation amount ΣΔNE at the boundary is a value corresponding to the upper limit, it is estimated that the cetane number of the fuel is higher than the reference value. Further, in this case, it is estimated that the cetane number of the fuel is higher as the boundary is a value on the higher rotation side. On the other hand, if there is no boundary, that is, if there is no region where the rotational fluctuation amount ΣΔNE has a value corresponding to the upper limit or a value corresponding to the lower limit, the cetane number of the fuel is estimated to be a reference value. Is done. On the other hand, when the rotational fluctuation amount ΣΔNE at the boundary is a value corresponding to the lower limit, it is estimated that the cetane number of the fuel is lower than the reference value. Further, in this case, it is estimated that the cetane number of the fuel is lower as the boundary is at the lower rotation position.

  In the present embodiment, the cetane number (more specifically, the estimated cetane number described above) that can accurately estimate the cetane number of fuel based on the results of experiments and simulations, and rotational fluctuations at the same boundary. The relationship with the quantity ΣΔNE is obtained in advance and stored in the electronic control unit 40. In the process of step S205, the estimated cetane number is calculated from the relationship based on the boundary and the rotational fluctuation amount ΣΔNE at the boundary.

Then, after the estimated cetane number is calculated in this way, the present process is temporarily terminated.
As described above, according to the present embodiment, in addition to the effects according to the effects described in (1) and (3) to (8) above, the following (9) and (10) are described. The effect to do.

  (9) The boundary between the two regions in which the change tendency of the rotational fluctuation amount ΣΔNE with respect to the change in the rotational speed at the time of execution is specified in the relationship between the rotational speed at the time of execution and the rotational fluctuation amount ΣΔNE is specified, and fuel is generated based on the boundary. The cetane number of was estimated. Therefore, the cetane number of the fuel can be accurately estimated based on the relationship between the rotational speed at the time of execution and the rotational fluctuation amount ΣΔNE that differs depending on the cetane number of the fuel.

  (10) Fuel injection for estimating the cetane number of fuel is executed on the condition that the engine speed NE is decreasing. Therefore, fuel injection can be executed sequentially in accordance with the decrease in the engine rotational speed NE, and a plurality of fuel injections can be efficiently executed in different situations of the engine rotational speed NE.

(Other embodiments)
Each of the above embodiments may be modified as follows.
In the first embodiment, one or both of the configuration for setting the target injection timing based on the coolant temperature THW and the configuration for setting the target injection timing based on the supercharging pressure PA may be omitted. In this case, the rotational fluctuation amount ΣΔNE is corrected based on the cooling water temperature THW, the rotational fluctuation amount ΣΔNE is corrected based on the supercharging pressure PA, or the cooling water is used as a calculation parameter used for calculating the estimated cetane number. The temperature THW and the supercharging pressure PA may be applied. Even with such a configuration, the estimated cetane number can be calculated in accordance with the peak temperature and the peak pressure in the combustion chamber 11a in the execution of the fuel injection, and the cetane number of the fuel can be accurately estimated.

  In the first embodiment, in order to estimate the cetane number of the fuel if there is no region where the output torque of the diesel engine 10 becomes the upper limit or the lower limit region (or is narrow) without depending on the cetane number of the fuel. The fuel injection may be executed at a predetermined time.

  In the second embodiment, one or both of the configuration for setting the target injection timing based on the coolant temperature THW and the configuration for setting the target injection timing based on the supercharging pressure PA may be omitted. If both of these configurations are omitted, fuel injection for estimating the cetane number of the fuel may be executed at a predetermined time. In the above configuration, the rotational fluctuation amount ΣΔNE is corrected based on the cooling water temperature THW, the rotational fluctuation amount ΣΔNE is corrected based on the supercharging pressure PA, and the calculation parameter used for calculating the estimated cetane number is cooled. Water temperature THW or supercharging pressure PA may be added. Even with such a configuration, the estimated cetane number can be calculated in accordance with the peak temperature and the peak pressure in the combustion chamber 11a in the execution of the fuel injection, and the cetane number of the fuel can be accurately estimated.

  In the second embodiment, instead of estimating the cetane number based on the rotational fluctuation amount ΣΔNE when the boundary is the same as the boundary, the cetane number may be estimated based only on the boundary. . If the device is such that the run-time rotational speed when the rotational fluctuation amount ΣΔNE becomes the upper limit and the run-time rotational speed when the rotational fluctuation amount ΣΔNE becomes the lower limit do not have the same value, only based on the boundary An estimated cetane number can be calculated.

  In the second embodiment, the method for calculating the boundary can be arbitrarily changed. As such a calculation method, for example, the rotational fluctuation amount ΣΔNE in a region where the rotational fluctuation amount ΣΔNE does not change according to the execution rotational speed and the rotational fluctuation amount ΣΔNE in a region where the rotational fluctuation amount ΣΔNE changes according to the execution rotational speed are calculated. In addition, it is possible to adopt a method for specifying the boundary based on the rotational fluctuation amount ΣΔNE. In addition, in a region where the rotational fluctuation amount ΣΔNE changes according to the rotational speed at the time of execution, a relational expression using the rotational fluctuation amount ΣΔNE and the rotational speed at the time of execution as variables is obtained, and the rotational fluctuation amount ΣΔNE is It is also possible to employ a method of calculating the rotation speed at the time of execution as the boundary.

  In the second embodiment, instead of executing fuel injection for estimating the cetane number of fuel every time the engine speed NE reaches a predetermined speed, every time a predetermined time elapses It may be executed every time the crankshaft 14 rotates by a predetermined crank angle.

  In each embodiment, a value other than the rotational fluctuation amount ΣΔNE may be calculated as an index value for the output torque of the diesel engine 10. For example, an engine rotational speed NE (running rotational speed) at the time of execution of fuel injection for estimating the cetane number of fuel and an engine rotational speed NE at the time when the fuel injection is not performed are detected and the difference between these speeds is detected. The difference can be calculated and used as the index value.

  In each embodiment, instead of using the cooling water temperature THW as the setting parameter for the target injection timing, for example, combustion such as the temperature of the diesel engine 10 (specifically, its cylinder head or cylinder block), the temperature of intake air, etc. A value other than the cooling water temperature THW, which is an index of the peak temperature in the chamber 11a, can also be used. It is also possible to directly detect the temperature in the combustion chamber 11a and use it as the setting parameter.

  In each embodiment, instead of using the supercharging pressure PA as the setting parameter for the target injection timing, it is a value that serves as an index of the peak pressure in the combustion chamber 11a, such as the pressure of the intake air or the pressure of the atmosphere. A value other than the supercharging pressure PA can also be used. It is also possible to directly detect the pressure in the combustion chamber 11a and use it as the setting parameter. Such a configuration can also be applied to a diesel engine in which the supercharger 16 is not provided. Even in a diesel engine that is not provided with the supercharger 16, the peak pressure in the combustion chamber 11a is slightly different depending on the operating state or operating environment of the diesel engine, and therefore is based on the peak pressure (or its index value). By correcting the target injection timing, it is possible to improve the estimation accuracy of the cetane number of the fuel.

  In each embodiment, one or both of the configuration for correcting the rotational fluctuation amount ΣΔNE based on the injection timing error and the configuration for correcting the rotational fluctuation amount ΣΔNE based on the injection amount error may be omitted. In this case, an injection timing error or an injection amount error may be added to the calculation parameter used for calculating the estimated cetane number. Also with such a configuration, the estimated cetane number can be calculated in consideration of the influence of the fuel injection execution timing error and the fuel injection amount error, and the cetane number of the fuel can be accurately estimated.

  In each embodiment, the method for determining that fuel has been supplied to the fuel tank 32 is not limited to the method for determining based on the detection signal of the stockpiling amount sensor 45, and the lid of the fuel tank 32 is opened and closed. Arbitrary methods such as a method of making a determination based on what has been done can be employed.

  In each embodiment, the method for determining that the fuel in the fuel path has been replaced is not limited to the method for determining based on the amount of fuel leaking from the inside of the fuel injection valve 20 to the return passage 35, for example, fuel injection Arbitrary methods such as a determination method based on the amount of fuel supplied to the valve 20 and a determination method based on the amount of fuel injected from the fuel injection valve 20 can be adopted.

  -In each embodiment, if the process for estimating the cetane number of the fuel can be executed in an appropriate situation, the execution condition can be arbitrarily changed. For example, any one or two of [Condition A] to [Condition C] may be set as execution conditions. Further, instead of [Condition C], it is possible to set [Condition D] that “a predetermined time has passed after it is determined that the fuel tank 32 has been refueled”. According to this [Condition D], it is possible to determine that the fuel in the fuel path has been replaced, as in [Condition C], by setting a relatively short time as the predetermined time. On the other hand, by setting a relatively long time as the predetermined time, it is possible to determine that the property of the fuel in the fuel tank 32 may have changed with the passage of time after refueling through [Condition D]. Based on the determination, a process for estimating the cetane number of the fuel can be executed. In addition, [Condition E] that “the operation for stopping the operation of the diesel engine 10 has been performed” can be set. When the operation of the diesel engine 10 is stopped, the temperature is often sufficiently high, so that the operation state is more likely to be stable than when the temperature is low. It can be said that the environment is such that the estimation of the cetane number of the fuel based on the NE (specifically, the rotational fluctuation amount ΣΔNE) can be executed with high accuracy. By setting [Condition E] above, it is possible to execute processing for estimating the cetane number of fuel in such an environment. In addition, since the cetane number of the fuel used when starting the diesel engine 10 can be accurately estimated, the starting performance of the diesel engine 10 can be improved. It can be determined that [Condition E] is satisfied, for example, when an operation switch is operated by an occupant to stop the operation of the diesel engine 10.

  If the pressure that is an index of the fuel pressure inside the fuel injection valve 20 (specifically, in the nozzle chamber 25), in other words, the fuel pressure that changes with the change in the fuel pressure can be properly detected. The pressure sensor 41 is not limited to being directly attached to the fuel injection valve 20, and the manner of attaching the pressure sensor 41 can be arbitrarily changed. Specifically, the pressure sensor 41 may be attached to the branch passage 31 a or the common rail 34.

  In place of the type of fuel injection valve 20 driven by the piezoelectric actuator 29, a type of fuel injection valve driven by an electromagnetic actuator having a solenoid coil or the like may be employed.

  The present invention is not limited to a diesel engine having four cylinders, but also to a single cylinder diesel engine, a diesel engine having two cylinders, a diesel engine having three cylinders, or a diesel engine having five or more cylinders. Can be applied.

  DESCRIPTION OF SYMBOLS 10 ... Diesel engine, 11 ... Cylinder, 11a ... Combustion chamber, 12 ... Intake passage, 13 ... Piston, 14 ... Crankshaft, 15 ... Exhaust passage, 16 ... Supercharger, 17 ... Compressor, 18 ... Turbine, 20 ... Fuel Injection valve, 21 ... housing, 22 ... needle valve, 23 ... injection hole, 24 ... spring, 25 ... nozzle chamber, 26 ... pressure chamber, 27 ... introduction passage, 28 ... communication passage, 29 ... piezoelectric actuator, 29a ... valve body , 30 ... discharge passage, 31a ... branch passage, 31b ... supply passage, 32 ... fuel tank, 33 ... fuel pump, 34 ... common rail, 35 ... return passage, 40 ... electronic control unit, 41 ... pressure sensor (fuel pressure detection means) 42 ... Supercharging pressure sensor, 43 ... Crank sensor, 44 ... Temperature sensor, 45 ... Stockpile sensor, 46 ... Accelerator sensor, 47 ... Vehicle speed sensor.

Claims (13)

A cetane number estimation device that performs fuel injection at a predetermined amount to estimate a cetane number of fuel to be used for combustion of a diesel engine,
An index value of the output torque of the diesel engine generated with the execution of the fuel injection is calculated, and the relationship between the calculated index value, the execution timing of the fuel injection, and the engine speed at the time of the fuel injection is calculated. A cetane number estimation apparatus comprising an estimation means for estimating the cetane number based on the cetane number. 2. The cetane number estimating device according to claim 1, further comprising fuel pressure detecting means for detecting a fuel pressure that changes with a change in an actual fuel pressure inside the fuel injection valve when the fuel injection valve of the diesel engine is opened. 3. A first correction unit that calculates an error in the execution timing based on a variation mode of the fuel pressure detected by the fuel pressure detection unit, and that corrects the index value based on the calculated error. The cetane number estimation apparatus described in 1. The apparatus further includes second correction means for calculating an injection amount error in the fuel injection based on the fuel pressure fluctuation mode detected by the fuel pressure detection means, and correcting the index value based on the calculated error. The cetane number estimation apparatus according to claim 2 or 3. In the cetane number estimation apparatus according to any one of claims 1 to 4,
The estimation means sets the execution time of the fuel injection based on the engine speed, and calculates the index value by executing the fuel injection at the execution time. In the cetane number estimation apparatus according to claim 5,
The estimator for estimating a cetane number is characterized in that the estimation means sets the advance timing as the engine rotation speed increases as the execution timing. In the cetane number estimation apparatus according to any one of claims 1 to 4,
The estimation means executes the fuel injection in a plurality of situations where the execution timing is the same and the engine rotation speed is different, and an index value of the output torque of the diesel engine generated by the execution of the fuel injection And estimating the cetane number based on the relationship between the calculated index value and the engine speed at the time of execution of the fuel injection. The cetane number estimation apparatus according to claim 7,
The estimation means specifies a boundary between two regions in which a tendency of a change in the index value with respect to a change in the engine rotation speed is different in a relationship between the calculated index value and the engine rotation speed at the time of execution of the fuel injection, A cetane number estimation device that estimates the cetane number based on the boundary. The cetane number estimation apparatus according to claim 7 or 8,
The estimation means performs the fuel injection on the condition that the engine rotational speed is reduced. In the cetane number estimating device according to any one of claims 5 to 9,
The estimation means sets the advance time as the peak temperature in the combustion chamber of the diesel engine is lower as the execution time. In the cetane number estimating device according to any one of claims 5 to 10,
The estimation means sets the advance time as the peak pressure in the combustion chamber of the diesel engine is lower as the execution time. A fuel pressure detecting means for detecting a fuel pressure that changes with a change in an actual fuel pressure inside the fuel injection valve when the fuel injection valve of the diesel engine is opened;
Determining means for determining that fuel has been supplied into a fuel tank in which fuel supplied to the diesel engine is stored;
When it is determined that the fuel has been replenished, it is determined that the fuel in the fuel path has been replaced by the fuel newly supplied into the fuel path connecting the fuel tank and the fuel injection valve thereafter. The cetane number according to any one of claims 1 to 11, further comprising: an execution permission unit that detects the fuel pressure based on a variation of the fuel pressure detected by the detection unit and permits the execution of the fuel injection based on the detection. Estimating device. In the cetane number estimating device according to any one of claims 1 to 12,
In this apparatus, a pressure sensor functioning as a fuel pressure detecting means for detecting a fuel pressure that changes with a change in an actual fuel pressure inside the fuel injection valve when the fuel injection valve of the diesel engine is opened is provided in the fuel injection valve. A cetane number estimation device characterized by being attached.

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