JP2012163071A - Cetane number estimating device - Google Patents

Abstract

A cetane number estimation device capable of appropriately performing estimation of a cetane number of a fuel while suppressing a decrease in fuel efficiency of a diesel engine.
The apparatus performs fuel injection to a diesel engine in a predetermined amount on condition that the execution condition is satisfied, and also outputs an index value (rotational fluctuation amount) of the output torque of the diesel engine generated by the execution. (ΣΔNE) is detected, and an estimated cetane number is calculated based on the average value AVE of the rotational fluctuation amount ΣΔNE (S209). The standard deviation σ of the rotational fluctuation amount ΣΔNE in the most recent predetermined period is calculated, and when the standard deviation σ is small, the frequency of fuel injection for estimating the cetane number is made lower than when the standard deviation is large ( S210 to S214).
[Selection] Figure 8

Description

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

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

  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 cylinder. In order to suitably perform such correction, it is necessary to accurately estimate the cetane number of the fuel.

  Conventionally, Patent Document 1 proposes an apparatus that injects a small amount of fuel from a fuel injection valve and estimates the cetane number of the fuel based on the engine torque generated by the fuel injection. In the device described in Patent Document 1, paying attention to the fact that the relationship between the fuel injection amount and the output torque of the diesel engine changes according to the cetane number of the fuel, the relationship between the fuel injection amount and the output torque is based on the relationship. The cetane number of the fuel is estimated.

JP 2009-121322 A

  Here, in the apparatus described in Patent Document 1, since fuel injection is executed when estimating the cetane number of the fuel, the fuel efficiency performance of the diesel engine is reduced accordingly. In order to suppress such a decrease in fuel consumption performance, it is desirable that there are few opportunities for fuel injection to estimate the cetane number of fuel.

  However, if the fuel injection execution opportunity is simply reduced, when the cetane number of the fuel changes, the timing for specifying the change is delayed. In this case, the period during which the engine control is executed in an execution mode commensurate with the cetane number before the change becomes longer, and this becomes a factor that hinders improvement in output performance and emission performance.

  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 appropriately estimating the cetane number of a fuel while suppressing a decrease in fuel efficiency of a diesel engine. There is.

In the following, means for achieving the above object and its operational effects will be described.
According to the first aspect of the present invention, an index value of the output torque of the diesel engine generated when the fuel injection to the diesel engine is performed in a predetermined amount on condition that the execution condition is satisfied and the fuel injection is performed. Is a cetane number estimation device that estimates the cetane number of the fuel based on a value obtained by gradually changing the detected index value, and calculates a standard deviation of the index value detected in the most recent predetermined period, The gist of the invention is that when the calculated standard deviation is small, the frequency of execution of the fuel injection is made lower than when the standard deviation is large.

  In a situation where the cetane number of the fuel supplied to the diesel engine hardly changes, the variation in the output torque of the diesel engine that occurs when the fuel injection is performed in a predetermined amount is small. Even if the gradually changed value (gradually changed value) is not updated frequently, the cetane number of the fuel can be estimated with high accuracy based on the gradually changed value. Therefore, in order to ensure the estimation accuracy of the cetane number of the fuel in such a situation, it can be said that the frequency of fuel injection for detecting the index value of the output torque of the diesel engine may be low.

  In the above configuration, when the standard deviation of the index value of the output torque detected in the most recent predetermined period is small, there is a high possibility that the cetane number of the fuel hardly changes because the variation of the index value is small. It is judged. At this time, the fuel injection performance of the diesel engine can be improved by setting the frequency of fuel injection for estimating the cetane number of the fuel to be low.

  On the other hand, when the cetane number of the fuel supplied to the diesel engine greatly changes due to fuel replenishment or the like, the diesel engine generated by the execution of fuel injection with a predetermined amount is accompanied by the change. The output torque also changes. In the above configuration, since the gradual change value is updated each time the index value of the output torque is detected, when the cetane number of the fuel changes greatly, until the gradual change value becomes a value commensurate with the changed cetane number. Takes time. Therefore, in order to quickly grasp the cetane number after the change based on the gradual change value, fuel injection for detecting the index value of the output torque of the diesel engine is executed at a high frequency, and the gradual change value is It is desirable to quickly change the value to a value commensurate with the changed cetane number.

  In the above configuration, when the standard deviation of the index value of the output torque detected in the most recent predetermined period is large, it is determined that there is a high possibility that the cetane number of the fuel has changed significantly. At this time, by setting a high frequency of fuel injection for estimating the cetane number of the fuel, the gradual change value is quickly changed to a value corresponding to the changed cetane number, and the cetane number after the change is changed. Can be grasped early.

Thus, according to the said structure, estimation of the cetane number of a fuel can be performed appropriately, suppressing the fall of the fuel consumption performance of a diesel engine.
The invention according to claim 2 is the cetane number estimation device according to claim 1, wherein the execution condition includes a condition that execution of fuel injection for operation of the diesel engine is stopped. Is the gist.

  When the fuel injection for the operation of the diesel engine is stopped, if the execution condition is satisfied and the fuel injection for estimating the cetane number is executed, the background noise is low, resulting in the fuel injection. Since noise (operating noise of the fuel injection valve and fuel combustion noise) is generated, the generated noise is easily noticeable and drivability is liable to be lowered.

  According to the above configuration, although the fuel injection for estimating the cetane number is executed when the fuel injection for the operation of the diesel engine is stopped, the execution frequency can be lowered. , Drivability reduction can be suppressed.

  According to a third aspect of the present invention, in the cetane number estimating device according to the first or second aspect, the device sets the lowest value as the execution frequency when the standard deviation is equal to or less than a first determination value. When the standard deviation is less than the second determination value greater than the first determination value and greater than the first determination value, a value that increases in the order in which the standard deviation is greater than the second determination value is set. This is the gist.

  When the cetane number of the fuel supplied to the diesel engine is low, compared to when the cetane number of the fuel is high, the combustion state of the fuel is likely to be unstable, so that the engine operation state is likely to be unstable. Therefore, in order to suppress deterioration of the engine operating state, it is desirable to increase the frequency of fuel injection for estimating the cetane number in order to grasp the change in the cetane number of the fuel at an early stage.

  When the cetane number of the fuel supplied to the diesel engine is low, the variation in the output torque of the diesel engine generated by the execution of fuel injection at a predetermined amount is larger than when the cetane number of the fuel is high . Further, when the cetane number of the fuel supplied to the diesel engine is low, if the cetane number hardly changes, the output torque of the diesel engine does not change as much as the cetane number of the fuel changes greatly.

  According to the above configuration, when the standard deviation is equal to or smaller than the first determination value, the variation in output torque of the diesel engine is small, and therefore, it is highly possible that the cetane number of the fuel is high. Can be executed less frequently.

  On the other hand, when the standard deviation is greater than the first determination value and less than or equal to the second determination value, the variation in output torque is larger than when the cetane number of the fuel is high, so the possibility that the cetane number of the fuel is low is high. The execution frequency can be set slightly higher. Therefore, even when the cetane number of the fuel has changed, the cetane number can be grasped relatively early and the execution mode of the engine operation can be changed, and deterioration of the engine operation state can be suppressed.

  On the other hand, when the standard deviation is larger than the second determination value, it is highly possible that the cetane number of the fuel has greatly changed because the output torque of the diesel engine has changed greatly, and the execution frequency can be set very high. it can.

  As described above, according to the above configuration, in addition to setting the frequency of fuel injection for estimating the cetane number in accordance with the change in the cetane number of the fuel supplied to the diesel engine, The execution frequency can be set according to the price. Therefore, it is possible to finely set the frequency of fuel injection for estimating the cetane number in accordance with the state of the fuel supplied to the diesel engine, and to appropriately suppress the decrease in fuel efficiency of the diesel engine Can do.

  According to a fourth aspect of the present invention, in the cetane number estimating device according to any one of the first to third aspects, an average value of the index values detected during the predetermined period is AVE, and the standard deviation is σ. When the latest value in the detected index value is R, when the respective values AVE, σ, R do not satisfy the relational expression “AVE-3 × σ ≦ R ≦ AVE + 3 × σ”, the detection is performed in the predetermined period. The gist is to calculate the gradually changed value without using at least a part of the index value.

  Normally, when fuel injection is performed in a predetermined amount under conditions where the cetane number of the fuel is constant, and when the index value of the output torque of the diesel engine generated by the execution is detected, almost all of the detected index values Is equal to or greater than a value obtained by subtracting three times the standard deviation (σ) from the average value (A) (AVE-3 × σ), and a value obtained by adding three times the standard deviation to the average value (A) (AVE + 3 × σ) falls within the following range. Therefore, when the latest value (R) of the detected index value does not satisfy the above range (specifically, the relational expression “AVE-3 × σ ≦ R ≦ AVE + 3 × σ”), the change in the cetane number of the fuel It can be determined that there is a high possibility that the amount is extremely large. When the amount of change in the cetane number of the fuel is very large, there is a high possibility that the index value detected in the predetermined period is far from the value corresponding to the actual cetane number of the fuel.

  According to the above configuration, when the latest value (R) of the index value does not satisfy the relational expression, it can be determined that the amount of change in the cetane number of the fuel has become extremely large, and at this time, it is detected in a predetermined period. At least a part of the measured index values, in other words, a value that is highly likely to be far from the value corresponding to the actual cetane number of the fuel can be prevented from being used for the calculation of the gradual change value. Thereby, it is possible to suppress the use of a value commensurate with the cetane number before the change for estimation of the cetane number, and it is possible to accurately estimate the cetane number of the fuel.

  According to a fifth aspect of the present invention, in the cetane number estimating device according to the fourth aspect, when the respective values AVE, σ, R do not satisfy the relational expression, the index values detected in the predetermined period The gist of the recently detected value is to use for the calculation of the gradually changed value.

  In a diesel engine, due to its structure, when fuel is replenished, the cetane number of fuel used for combustion in the diesel engine does not change instantaneously but gradually changes. For this reason, when the index value of the output torque of the diesel engine changes with the change in the cetane number of the fuel and the index value does not satisfy the above relational expression, the index value detected in the predetermined period is set to the index value of the fuel. It can be said that there is a high possibility that a part of the change in the output torque accompanying the change is reflected. The degree of reflection of the change in output torque in the index value is larger as the index value is detected more recently.

  According to the above configuration, a value having a large reflection degree of the change in the output torque in the index value detected during the predetermined period can be used for calculating the gradual change value. Therefore, compared to the case where not all of the index values detected in the predetermined period are used for calculation of the gradual change value, it is possible to secure the number of index values reflecting the influence of the change of the cetane number. Based on the above, it is possible to calculate a highly reliable value as a gradually changing value at an early stage.

  According to a sixth aspect of the present invention, in the cetane number estimating device according to any one of the first to fifth aspects, an actual fuel pressure inside the fuel injection valve when the fuel injection valve of the diesel engine is opened. The gist of the invention is that a pressure sensor for detecting the fuel pressure that changes with the change is provided.

  According to a seventh aspect of the present invention, in the cetane number estimating device according to the sixth aspect, the device corrects the fuel injection amount of the fuel injection based on a variation mode of the fuel pressure detected by the pressure sensor. This is the gist.

  According to an eighth aspect of the present invention, in the cetane number estimating device according to the sixth or seventh aspect, the device corrects the execution timing of the fuel injection based on a variation mode of the fuel pressure detected by the pressure sensor. The gist is to do.

  When fuel injection from the fuel injection valve is executed, an error may occur in the execution timing and the 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 sixth 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, it becomes possible to accurately set the injection timing and the injection amount in the fuel injection for estimating the cetane number of the fuel based on the actual execution timing and the injection amount, and the cetane number is accurately estimated. Will be able to. According to the configuration of the seventh aspect, the fuel injection amount in the fuel injection for estimating the cetane number can be corrected based on such a variation mode of the fuel pressure. According to the configuration described in claim 8, the execution timing in the fuel injection for estimating the cetane number can be corrected based on the fuel pressure fluctuation mode.

The gist of the ninth aspect of the invention is the cetane number estimating device according to any one of the sixth to eighth aspects, wherein the pressure sensor 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 timing and the fuel injection amount based on the fluctuation mode of the fuel pressure, and the fuel injection for estimating the cetane number based on the actual execution timing and the fuel injection amount. It is possible to set the injection timing and the injection amount at more accurately.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows schematic structure of the cetane number estimation apparatus concerning embodiment which actualized this invention. Sectional drawing which shows the cross-section of a fuel injection valve. The time chart which shows the relationship between transition of fuel pressure and the detection time waveform of a fuel injection rate. The flowchart which shows the execution procedure of a correction process. The time chart which shows an example of the relationship between a detection time waveform and a basic time waveform. The time chart which shows an example of the relationship between the rotation fluctuation amount, the average value of the rotation fluctuation amount, and the standard deviation. The flowchart which shows the specific execution procedure of an estimation control process. The flowchart which shows the specific execution procedure of an estimation control process. Explanatory drawing explaining the calculation method of rotation fluctuation amount.

Hereinafter, a cetane number estimating device according to an embodiment embodying the present invention will be described.
As shown in FIG. 1, a vehicle 10 is equipped with a diesel engine 11 as a drive source. The crankshaft 12 of the diesel engine 11 is connected to wheels 15 via a clutch mechanism 13 and a manual transmission 14. In the vehicle 10, when a clutch operating member (for example, a clutch pedal) is operated by an occupant, the clutch mechanism 13 is in an operating state in which the connection between the crankshaft 12 and the manual transmission 14 is released.

  An intake passage 17 is connected to the cylinder 16 of the diesel engine 11. Air is sucked into the cylinder 16 of the diesel engine 11 through the intake passage 17. Further, as the diesel engine 11, one having a plurality (four [# 1 to # 4] in the present embodiment) of cylinders 16 is employed. A direct injection type fuel injection valve 20 that directly injects fuel into the cylinder 16 is attached to the diesel engine 11 for each cylinder 16. 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 16 of the diesel engine 11. In the diesel engine 11, the piston 18 is pushed down by the energy generated by the combustion of the fuel in the cylinder 16, and the crankshaft 12 is forcibly rotated. The combustion gas combusted in the cylinder 16 of the diesel engine 11 is discharged as an exhaust gas into the exhaust passage 19 of the diesel engine 11.

  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.
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 16 of the diesel engine 11.

  As shown in FIG. 1, the diesel engine 11 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 crank sensor 42 for detecting the rotational phase and rotational speed (engine rotational speed NE) of the crankshaft 12 is provided. Further, an accelerator sensor 43 for detecting an operation amount (accelerator operation amount ACC) of an accelerator operation member (for example, an accelerator pedal), a vehicle speed sensor 44 for detecting a traveling speed of the vehicle 10, and an operation of the clutch operation member A clutch switch 45 for detecting the presence or absence is also provided.

  In addition, as a peripheral device of the diesel engine 11, 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 11 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 (required injection amount TAU) for the fuel injection amount for engine operation based on the accelerator operation amount ACC, the engine rotational speed NE, the cetane number of the fuel (specifically, an estimated cetane number to be described later), and the like. Is calculated. Thereafter, a control target value for fuel injection timing (required injection timing Tst) and a control target value for fuel injection time (required injection time Ttm) are calculated based on the required injection amount TAU and the engine speed NE. Based on the required injection timing Tst and the required injection time Ttm, the valve opening drive of each fuel injection valve 20 is executed. Thus, an amount of fuel commensurate with the operation state of the diesel engine 11 at that time is injected from each fuel injection valve 20 and supplied into each cylinder 16 of the diesel engine 11.

  In the fuel injection control of the present embodiment, the engine rotational speed NE is set to a predetermined value during the deceleration of the traveling speed of the vehicle 10 and the engine rotational speed NE by releasing the operation of the accelerator operation member (accelerator operation amount ACC = “0”). When the speed is within the speed range, control for temporarily stopping fuel injection for operation of the diesel engine 11 (so-called fuel cut control) is executed.

  When the fuel injection from the fuel injection valve 20 is executed in this way, an error may occur in the execution timing and the injection amount due to the initial individual difference or change with time of the fuel injection valve 20. Such an error is not preferable because the output torque of the diesel engine 11 is changed. Therefore, in the present embodiment, in order to properly execute fuel injection from each fuel injection valve 20 in accordance with the operating state of the diesel engine 11, the fuel is based on the fuel pressure PQ detected by the pressure sensor 41. A correction process for forming the injection rate detection time waveform and correcting the required injection timing Tst and the required injection time Ttm based on the detection time waveform is executed. This correction process is executed for each cylinder 16 of the diesel engine 11 separately.

  The fuel pressure inside the fuel injection valve 20 is reduced when the fuel injection valve 20 is opened, and then increased when the fuel injection valve 20 is closed. It fluctuates with it. Therefore, the actual operating characteristics of the fuel injection valve 20 (for example, the timing when the valve opening operation is started or the timing when the valve closing operation is started) are monitored by monitoring the fluctuation waveform of the fuel pressure when the fuel injection is performed. It can be accurately grasped. Therefore, by correcting the required injection timing Tst and the required injection time Ttm based on the actual operating characteristics of the fuel injection valve 20, the fuel injection timing and the fuel injection amount can be accurately adjusted in accordance with the operating state of the diesel engine 11. Can be set.

Hereinafter, such correction processing will be described in detail.
Here, first, a procedure for forming a fuel pressure fluctuation mode (in this embodiment, a detection time waveform of the fuel injection rate) during execution of fuel injection will be described.

FIG. 3 shows the relationship between the transition of the fuel pressure PQ and the detection time waveform of the fuel injection rate.
As shown in FIG. 3, in the present embodiment, the timing at which the fuel injection valve 20 opens (specifically, the movement of the needle valve 22 toward the valve opening side) starts (valve opening operation start timing Tos), When the fuel 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 closes (specifically, the needle valve 22) ) (The movement to the valve closing side) is completed (valve closing operation completion timing Tce).

  First, the average value of the fuel pressure PQ in a predetermined period T1 immediately before the start of the valve opening operation of the fuel injection valve 20 is calculated, and the average value is stored as the reference pressure Pbs. The reference pressure Pbs is used as a pressure corresponding to the fuel pressure inside the fuel injection valve 20 when the valve is closed.

  Next, a value obtained by subtracting the predetermined pressure P1 from the reference pressure Pbs is calculated as the operating pressure Pac (= Pbse−P1). The predetermined pressure P1 corresponds to the change in the fuel pressure PQ, that is, the movement of the needle valve 22 even when the needle valve 22 is in the closed position when the fuel injection valve 20 is driven to open or close. This is a pressure corresponding to a change in the fuel pressure PQ that does not contribute.

  Thereafter, a first-order differential value of the fuel pressure PQ during a period in which the fuel pressure PQ decreases immediately after the start of fuel injection is calculated. Then, a tangent line L1 of the time waveform of the fuel pressure PQ at the point where the first-order differential value is minimized is obtained, and an intersection point A between the tangent line L1 and the operating pressure Pac is calculated. The timing corresponding to the point AA where the intersection A is returned to the past timing by the detection delay of the fuel pressure PQ is specified as the valve opening operation start timing Tos. The detection delay is a period corresponding to the delay of the change timing of the fuel pressure PQ with respect to the pressure change timing of the nozzle chamber 25 (see FIG. 2) of the fuel injection valve 20, and the distance between the nozzle chamber 25 and the pressure sensor 41. This is a delay caused by the above.

  Further, the first-order differential value of the fuel pressure PQ in the period in which the fuel pressure PQ rises after dropping once immediately after the start of fuel injection is calculated. Then, the tangent L2 of the time waveform of the fuel pressure PQ at the point where the first-order differential value becomes maximum is obtained, and the intersection B between the tangent L2 and the operating pressure Pac is calculated. The timing corresponding to the point BB where the intersection B is returned to the past timing by the detection delay is specified as the valve closing operation completion timing Tce.

  Further, an intersection C between the tangent line L1 and the tangent line L2 is calculated, and a difference between the fuel pressure PQ and the operating pressure Pac at the intersection point C (virtual pressure drop ΔP [= Pac−PQ]) is obtained. Further, a value obtained by multiplying the virtual pressure drop ΔP by a gain G1 set based on the required injection amount TAU is calculated as a virtual maximum fuel injection rate VRt (= ΔP × G1). Further, a value obtained by multiplying the virtual maximum fuel injection rate VRt by a gain G2 set based on the required injection amount TAU is calculated as the maximum injection rate Rt (= VRt × G2).

  Thereafter, a time CC at which the intersection C is returned to the past time by the detection delay is calculated, and a point D that becomes the virtual maximum fuel injection rate VRt in the simultaneous CC is specified. The timing corresponding to the intersection E between the straight line L3 connecting the point D and the valve opening operation start timing Tos (specifically, the point at which the fuel injection rate becomes “0” at the same time Tos) and the maximum injection rate Rt is obtained. It is specified as the maximum injection rate arrival time Toe.

  Further, the timing corresponding to the intersection F between the straight line L4 and the maximum injection rate Rt connecting the point D and the valve closing operation completion timing Tce (specifically, the point at which the fuel injection rate becomes “0” at the same time Tce) is injected. It is specified as the rate drop start time Tcs.

  Further, the trapezoidal time waveform formed by the valve opening operation start timing Tos, the maximum injection rate arrival timing Toe, the injection rate drop start timing Tcs, the valve closing operation completion timing Tce and the maximum injection rate Rt is a fuel injection rate in fuel injection. Is used as a detection time waveform.

Next, with reference to FIGS. 4 and 5, the processing procedure of the process (correction process) for correcting various control target values of the fuel injection control based on such a detection time waveform will be described in detail.
FIG. 4 is a flowchart showing a specific processing procedure of the correction processing, and a series of processing shown in the flowchart is executed by the electronic control unit 40 as interrupt processing at predetermined intervals. FIG. 5 shows an example of the relationship between the detection time waveform and the basic time waveform.

  As shown in FIG. 4, in this process, first, as described above, a detection time waveform at the time of execution of fuel injection is formed based on the fuel pressure PQ (step S101). Further, based on the operating state of the diesel engine 11 such as the accelerator operation amount ACC and the engine rotational speed NE, a basic value (basic time waveform) for the time waveform of the fuel injection rate at the time of executing fuel injection is set (step). S102). In the present embodiment, the relationship between the operation state of the diesel engine 11 and the basic time waveform suitable for the operation state is obtained in advance based on the results of experiments and simulations and stored in the electronic control unit 40. In the process of step S102, a basic time waveform is set from the above relationship based on the operation state of the diesel engine 11 at that time.

  As shown in FIG. 5, the basic time waveform (one-dot chain line) includes the valve opening operation start timing Tosb, the maximum injection rate arrival timing Toeb, the injection rate drop start timing Tcsb, the valve closing operation completion timing Tceb, and the maximum injection rate. The specified trapezoidal time waveform is set.

  Then, the basic time waveform and the detection time waveform (solid line) are compared, and a correction term for correcting the control target value (the required injection timing Tst) of the fuel injection start timing based on the comparison result. K1 and a correction term K2 for correcting the control target value (required injection time Ttm) of the execution time of the same fuel injection are respectively calculated. Specifically, a difference ΔTos (= Tosb−Tos) between the valve opening operation start timing Tosb in the basic time waveform and the valve opening operation start timing Tos in the detection time waveform is calculated, and the difference ΔTos is stored as the correction term K1. (Step S103 in FIG. 4). Further, a difference ΔTcs (= Tcsb−Tcs) between the injection rate decrease start timing Tcsb (FIG. 5) in the basic time waveform and the injection rate decrease start timing Tcs in the detection time waveform is calculated, and the difference ΔTcs is corrected by the correction term K2. (Step S104 in FIG. 4).

After the correction terms K1 and K2 are calculated in this way, the present process is temporarily terminated.
When executing the fuel injection control, a value obtained by correcting the required injection timing Tst by the correction term K1 (in this embodiment, a value obtained by adding the correction term K1 to the required injection timing Tst) is calculated as the final required injection timing Tst. Is done. By calculating the required injection timing Tst in this manner, the deviation between the valve opening operation start timing Tosb in the basic time waveform and the valve opening operation start timing Tosb in the detection time waveform can be suppressed to be small. The injection start time is accurately set in accordance with the operation state of the diesel engine 11.

  Further, a value obtained by correcting the required injection time Ttm by the correction term K2 (in this embodiment, a value obtained by adding the correction term K2 to the required injection time Ttm) is calculated as the final required injection time Ttm. By calculating the required injection time Ttm in this way, the deviation between the injection rate decrease start timing Tcsb in the basic time waveform and the injection rate decrease start timing Tcs in the detection time waveform can be suppressed to be small. The time when the fuel injection rate starts to decrease in the fuel injection is set with high accuracy in accordance with the operating state of the diesel engine 11.

  As described above, in the present embodiment, the required injection timing is based on the difference between the actual operating characteristic (specifically, the detection time waveform) of the fuel injection valve 20 and the predetermined basic operating characteristic (specifically, the basic time waveform). Since the Tst and the required injection time Ttm are corrected, the deviation between the actual operating characteristics of the fuel injector 20 and the basic operating characteristics (the operating characteristics of the fuel injector having standard characteristics) can be suppressed. Therefore, the injection timing and the injection amount in the fuel injection from each fuel injection valve 20 are set appropriately so as to match the operation state of the diesel engine 11.

In the present embodiment, control (estimation control) for estimating the cetane number of the fuel provided for combustion in the diesel engine 11 is executed. The outline of this estimation control will be described below.
In this estimation control, an execution condition including a condition that the fuel cut control is being executed ([Condition A] described later) is set. Then, when this execution condition is satisfied, fuel injection to the diesel engine 11 at a predetermined amount (for example, several cubic millimeters) is executed, and the diesel engine 11 generated with the execution of the fuel injection. The output torque index value (rotational fluctuation amount ΣΔNE described later) is detected and stored. Thereafter, the cetane number of the fuel is estimated based on a value obtained by gradually changing the rotational fluctuation amount ΣΔNE (specifically, an average value AVE of the latest ten rotational fluctuation amounts ΣΔNE).

  The higher the cetane number of the fuel supplied to the diesel engine 11, the easier it is to ignite the fuel, and the less unburned fuel of the fuel decreases. Therefore, 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 11.

  Here, in the apparatus of the present embodiment, since fuel injection is executed when estimating the cetane number of the fuel, the fuel efficiency performance of the diesel engine 11 is reduced accordingly. In order to suppress a decrease in fuel efficiency of the diesel engine 11, it is desirable that there are few opportunities for fuel injection to estimate the cetane number of the fuel.

  Further, in the apparatus of the present embodiment, since fuel injection for estimating the cetane number is executed during the execution of fuel cut control, the noise caused by the fuel injection (operation sound of the fuel injection valve 20 and fuel injection) Combustion noise) is generated in a situation where background noise is low, the generated sound is easily noticeable, and drivability is liable to deteriorate. Also in this respect, it can be said that it is desirable that there are few opportunities for performing fuel injection for estimating the cetane number of fuel.

  However, if the fuel injection execution opportunity for estimating the cetane number is simply reduced, when the cetane number of the fuel supplied to the diesel engine 11 changes, the timing for specifying the change is delayed. In this case, since the period during which the operation control of the diesel engine 11 is executed in an execution mode commensurate with the cetane number before the change becomes longer, this becomes a factor that hinders improvement in output performance and emission performance.

  Based on this point, in the present embodiment, the standard deviation σ of the rotational fluctuation amount ΣΔNE detected in the most recent predetermined period (in the present embodiment, the period in which the rotational fluctuation amount ΣΔNE is detected only 10 times in the latest) is calculated. When the standard deviation σ is small, the fuel injection execution frequency for estimating the cetane number is made lower than when the standard deviation σ is large. Specifically, as such execution frequency, the lowest value is set when the standard deviation σ is equal to or smaller than the first determination value JL, and the standard deviation σ is larger than the first determination value JL and the second determination value JH (however, JL <JH) When the value is less than or equal to, a value that increases in the order in which the standard deviation σ is greater than the second determination value JH is set. Hereinafter, the effect | action by setting the execution frequency of the fuel injection for estimation of a cetane number in this way is demonstrated.

FIG. 6 shows an example of the relationship between the rotational fluctuation amount ΣΔNE, the average value AVE of the rotational fluctuation amount ΣΔNE, and the standard deviation σ of the rotational fluctuation amount ΣΔNE.
As shown in FIG. 6, when the cetane number of the fuel supplied to the diesel engine 11 greatly changes due to fuel supply to the fuel tank 32 (see FIG. 1) (timing t <b> 1), a predetermined amount is associated with the change. The index value (rotational fluctuation amount ΣΔNE) of the output torque of the diesel engine 11 generated along with the execution of the fuel injection at this time also changes. In the apparatus according to the present embodiment, the average value AVE of the rotational fluctuation amount ΣΔNE is updated each time the rotational fluctuation amount ΣΔNE is detected. Therefore, when the cetane number of the fuel changes greatly, the average value AVE It takes time to reach a value corresponding to the cetane number (timing t1 to t2). Therefore, in order to quickly grasp the changed cetane number based on the average value AVE, the fuel injection for estimating the cetane number and the detection of the rotational fluctuation amount ΣΔNE are executed at a high frequency, and the average It is desirable to quickly change the value AVE to a value commensurate with the changed cetane number.

  In this respect, in the present embodiment, when the standard deviation σ of the rotational fluctuation amount ΣΔNE is larger than the second determination value JH, the output torque of the diesel engine 11 is greatly changed, so that the cetane number of the fuel may be greatly changed. Therefore, the frequency of fuel injection for estimating the cetane number can be set high. Therefore, the detection frequency of the rotational fluctuation amount ΣΔNE can be increased, and the average value AVE can be quickly changed to a value commensurate with the changed cetane number so that the changed cetane number can be grasped at an early stage. Become.

  On the other hand, in a situation where the cetane number of the fuel supplied to the diesel engine 11 hardly changes (before timing t1 and after timing t2), there is a variation in output torque of the diesel engine 11 that occurs as a result of fuel injection at a predetermined amount. small. Therefore, the cetane number of the fuel can be estimated with high accuracy based on the average value AVE without frequently updating the average value AVE of the rotational fluctuation amount ΣΔNE. Therefore, in order to ensure the estimation accuracy of the cetane number of the fuel in such a situation, it can be said that the frequency of fuel injection for detecting the rotational fluctuation amount ΣΔNE may be low.

  In this regard, in this embodiment, when the standard deviation σ of the rotational fluctuation amount ΣΔNE is equal to or smaller than the second determination value JH, there is a possibility that the cetane number of the fuel hardly changes because the variation in the rotational fluctuation amount ΣΔNE is small. Is judged to be high. At this time, the fuel efficiency of the diesel engine can be improved by setting the execution frequency of the fuel injection for estimating the cetane number and the detection of the rotational fluctuation amount ΣΔNE low. In addition, although fuel injection for estimating the cetane number is executed during execution of fuel cut control, it is possible to reduce the frequency of execution, thereby suppressing the generation of noise associated with the execution of the fuel injection. Drivability can be reduced.

  Even when the cetane number of the fuel supplied to the diesel engine 11 hardly changes, when the cetane number of the fuel supplied to the diesel engine 11 is low, compared to when the cetane number of the fuel is high. Further, since the combustion state of the fuel is likely to be unstable, the operation state of the diesel engine 11 is likely to be unstable. Therefore, in order to suppress the deterioration of the operating state of the diesel engine 11, it is desirable to increase the frequency of fuel injection for estimating the cetane number so as to grasp the change in the cetane number of the fuel at an early stage.

  When the cetane number of the fuel supplied to the diesel engine 11 is low, the variation in the output torque of the diesel engine generated when the fuel injection is performed at a predetermined amount is larger than when the cetane number of the fuel is high. When the cetane number of the fuel supplied to the diesel engine 11 is low, if the cetane number hardly changes, the output torque of the diesel engine 11 does not change as much as the cetane number of the fuel changes greatly. Therefore, based on the standard deviation σ of the rotational fluctuation amount ΣΔNE that is an index value of the output torque of the diesel engine 11, the cetane number is high in a situation where the cetane number of the fuel supplied to the diesel engine 11 hardly changes. And the low state can be discriminated.

  In view of this point, in the present embodiment, when the standard deviation σ of the rotational fluctuation amount ΣΔNE is equal to or smaller than the first determination value JL, the variation in the output torque of the diesel engine 11 is small, and thus the cetane number of the fuel is high. As the possibility is high, the frequency of fuel injection for estimating the cetane number is set to the lowest. Thereby, the fuel consumption performance of the diesel engine 11 can be improved, and the fall of drivability can be suppressed.

  On the other hand, when the standard deviation σ of the rotational fluctuation amount ΣΔNE is greater than the first determination value JL and equal to or less than the second determination value JH, the variation in output torque is larger than when the cetane number of the fuel is high. Since the possibility that the price is low is high, the execution frequency of the fuel injection for estimating the cetane number is set slightly higher. Therefore, even if the cetane number of the fuel changes so that the standard deviation σ does not exceed the second determination value JH, the execution mode of engine operation can be changed by grasping the cetane number relatively early. , Deterioration of the engine operating state can be suppressed.

  As described above, in the apparatus according to the present embodiment, the frequency of fuel injection for estimating the cetane number can be set according to whether or not the cetane number of the fuel supplied to the diesel engine 11 has changed. The execution frequency of the fuel injection can be set according to the cetane number of the fuel. Therefore, it is possible to finely set the frequency of fuel injection for estimating the cetane number in accordance with the state of the fuel supplied to the diesel engine 11, and to reduce the fuel consumption performance and drivability of the diesel engine 11. It is possible to properly estimate the cetane number of the fuel while suppressing the decrease.

  Normally, when fuel injection is performed with a predetermined amount under the condition that the cetane number of the fuel is constant and the rotational fluctuation amount ΣΔNE is detected, almost all of the rotational fluctuation amount ΣΔNE is an average value of the rotational fluctuation amount ΣΔNE. It is within a range not less than a value obtained by subtracting three times the standard deviation σ from AVE (AVE-3 × σ) and not more than a value obtained by adding three times the standard deviation to the average value AVE (AVE + 3 × σ). Therefore, if the latest value R of the rotational fluctuation amount ΣΔNE does not satisfy the above range (specifically, the relational expression “AVE-3 × σ ≦ R ≦ AVE + 3 × σ”), the output torque of the diesel engine 11 at this time is It can be determined that there is a high possibility that the fuel has changed significantly, and that the cause of the change is highly likely that the cetane number of the fuel has changed significantly.

  When the amount of change in the cetane number of the fuel is extremely large, the rotational fluctuation amount ΣΔNE detected and stored in the predetermined period, that is, a part of the rotational fluctuation amount ΣΔNE used for calculating the average value AVE is actually There is a high possibility that the value is far from the value corresponding to the cetane number of the fuel. For this reason, if the cetane number of the fuel is simply estimated based on the average value AVE of the rotational fluctuation amount ΣΔNE detected and stored in a predetermined period, a value far from the value corresponding to the actual cetane number of the fuel is used. As a result, the cetane number of the fuel is estimated, leading to a decrease in estimation accuracy.

  In view of this point, in the present embodiment, when the latest value R of the rotational fluctuation amount ΣΔNE does not satisfy the above range (specifically, the relational expression “AVE-3 × σ ≦ R ≦ AVE + 3 × σ”), The average value AVE is calculated without using a part of the rotational fluctuation amount ΣΔNE detected and stored in the predetermined period.

  Accordingly, it can be determined that the amount of change in the cetane number of the fuel is extremely large when the latest value R of the rotational fluctuation amount ΣΔNE does not satisfy the above relational expression. At this time, at least a part of the rotational fluctuation amount ΣΔNE detected in the predetermined period, in other words, a value that is highly likely to be far from the value corresponding to the actual cetane number of the fuel is not used for the calculation of the average value AVE. Can be. Accordingly, it is possible to suppress the use of a value commensurate with the cetane number before the change for estimating the cetane number, and it is possible to accurately estimate the cetane number of the fuel.

  Here, in the diesel engine 11, the fuel is filled in the fuel path (specifically, the path constituted by the branch passage 31 a, the supply passage 31 b, the common rail 34, and the return passage 35) connecting the fuel tank 32 and the fuel injection valve 20. ing. Therefore, when fuel is supplied to the fuel tank 32, the cetane number of the fuel used for combustion in the diesel engine 11 does not change instantaneously but gradually changes.

  Therefore, when the rotational fluctuation amount ΣΔNE changes with the change in the cetane number of the fuel and the latest value R does not satisfy the above relational expression, the rotational fluctuation amount ΣΔNE detected in the predetermined period is added to the cetane number of the fuel. It can be said that there is a high possibility that a part of the change in the output torque accompanying the change is reflected. The degree of reflection of the change in the output torque to the rotational fluctuation amount ΣΔNE is larger as the recently detected rotational fluctuation amount ΣΔNE.

  In view of this point, in the present embodiment, when the latest value R of the rotational fluctuation amount ΣΔNE does not satisfy the relational expression, the recently detected value of the rotational fluctuation amount ΣΔNE detected in the predetermined period is stored. The average value AVE is used for calculation. On the other hand, values other than the recently detected values are reset to the initial values so as not to be used for calculating the average value AVE.

  As a result, a value having a large reflection degree of the change in the output torque can be used for calculating the average value AVE among the rotational fluctuation amounts ΣΔNE detected in the predetermined period. Therefore, as compared with the case where not all of the rotational fluctuation amount ΣΔNE detected in the predetermined period is used for calculation of the average value AVE, it is possible to secure the storage number of the rotational fluctuation amount ΣΔNE reflecting the influence of the change in the cetane number. Therefore, a highly reliable value can be calculated as the average value AVE based on the rotational fluctuation amount ΣΔNE. As a result, a value commensurate with the changed cetane number can be calculated early as the average value AVE, so that the changed cetane number can be grasped early.

  In the present embodiment, the “recently detected value” used for calculating the average value AVE of the rotational fluctuation amount ΣΔNE is detected during a period when the latest predetermined amount (for example, several liters) of fuel is consumed. The rotational fluctuation amount ΣΔNE is adopted. In the present embodiment, based on the results of experiments and simulations, it is possible to calculate the rotational fluctuation amount ΣΔNE that can estimate the cetane number at an early stage while suppressing a decrease in the estimation accuracy of the cetane number of the fuel. The fuel consumption amount is obtained in advance, and the fuel consumption amount is stored in the electronic control unit 40 as the fixed amount. In the present embodiment, the latest fuel consumption amount is calculated such that the injection amount in each injection is calculated based on the detection time waveform and the injection amount is added.

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.

As shown in FIG. 7, 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 the following [Condition A] to [Condition D] are satisfied.
[Condition A] The fuel cut control is executed.
[Condition B] The clutch mechanism 13 is in an operating state in which the connection between the crankshaft 12 and the manual transmission 14 is released. Specifically, the clutch operating member is operated.
[Condition C] Correction terms K1 and K2 are calculated through the correction process.
[Condition D] The execution flag is turned on.

  The execution flag is turned on when the number of times that all of [Condition A] to [Condition C] are satisfied reaches a predetermined number of times, while the execution flag is turned off when detection of the rotational fluctuation amount ΣΔNE is executed. Is done. In the present embodiment, the predetermined number of times is changed according to the standard deviation σ of the rotation fluctuation amount ΣΔNE. Specifically, when the standard deviation σ is equal to or smaller than the first determination value JL, “4” is set as the predetermined number. In this case, the number of times that all of [Condition A] to [Condition C] are satisfied is 4. Each time, the fuel injection for estimating the cetane number and the detection of the rotational fluctuation amount ΣΔNE are executed. On the other hand, when the standard deviation σ is greater than the first determination value JL and equal to or less than the second determination value JH, “2” is set as the predetermined number of times. In this case, all of [Condition A] to [Condition C] are satisfied. The fuel injection for estimating the cetane number and the detection of the rotational fluctuation amount ΣΔNE are executed every time the number of times of the change is two. On the other hand, when the standard deviation σ is larger than the second determination value JH, “1” is set as the predetermined number of times, and fuel injection for estimating the cetane number is performed every time all of [Condition A] to [Condition C] are satisfied. And the rotation fluctuation amount ΣΔNE are detected. As described above, in the present embodiment, the execution frequency of the fuel injection for estimating the cetane number and the detection of the rotational fluctuation amount ΣΔNE is adjusted through the operation of the execution flag based on the standard deviation σ of the rotational fluctuation amount ΣΔNE.

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), a predetermined control target value for the fuel injection timing (target fuel injection timing TQst) and a control target value for the target injection time (target) The fuel injection time TQtm) is corrected by the correction terms K1 and K2 calculated by the correction processing described above (step S202). Specifically, a value obtained by adding the correction term K1 to the target fuel injection timing TQst is set as a new target fuel injection timing TQst, and a value obtained by adding the correction term K2 to the target fuel injection time TQtm is a new target fuel injection time. Set as TQtm.

  Then, drive control of the fuel injection valve 20 based on the target fuel injection timing TQst and the target fuel injection time TQtm is executed, and fuel injection from the fuel injection valve 20 is executed (step S203). 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 16 [# 1]). Similarly, the correction terms K1 and K2 used in this process are also predetermined ones of the fuel injection valves 20 (in this embodiment, the fuel injection valves 20 attached to the cylinders 16 [# 1]). The value calculated corresponding to is used.

  Thereafter, the rotational fluctuation amount ΣΔNE is calculated and stored as an index value of the output torque of the diesel engine 11 generated by the fuel injection (step S204). In the present embodiment, the most recent predetermined value (specifically, 10 times) of detection values including the latest value R are stored as the rotational fluctuation amount ΣΔNE. Specifically, the rotation fluctuation amount ΣΔNE is calculated as follows. As shown in FIG. 9, 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 engine rotational speed NE are detected several times before (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. 9) 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. The changes in the engine speed NE and the difference ΔNE shown in FIG. 9 are slightly different from the actual changes because they are shown in a simplified manner to facilitate understanding of the calculation method of the rotational fluctuation amount ΣΔNE.

  Then, it is determined whether or not the number of rotation fluctuations ΣΔNE calculated and stored reaches a predetermined number N (specifically, “10”) (step S205). When the initial value is stored, the value is not counted as the number of stored rotational fluctuation amounts ΣΔNE, and when the rotational fluctuation amount ΣΔNE is calculated and stored is less than a predetermined number N (step S205: NO), assuming that the number of data that can accurately estimate the cetane number of the fuel is not secured, the present process is temporarily terminated without executing the following process.

  Thereafter, when this processing is repeatedly executed and the number of stored rotational fluctuation amounts ΣΔNE reaches a predetermined number N (step S205: YES), the stored N rotational fluctuation amounts ΣΔNE are calculated from a pre-stored arithmetic expression. The average value AVE (step S206) and the standard deviation σ (step S207) of the rotation fluctuation amount ΣΔNE are calculated. In the present embodiment, the standard deviation σ is calculated based on the following idea. That is, first, for each of the N rotational fluctuation amounts ΣΔNE, a value obtained by subtracting the average value AVE from the rotational fluctuation amount ΣΔNE (ΣΔNE−AVE) and a value obtained by squaring the same value are calculated. Thereafter, the squared values are added, and the added value is divided by the number of data (predetermined number N). Then, the square root of the divided value is calculated, and the calculated value is stored as the standard deviation σ.

  Then, on condition that the latest value R of the rotational fluctuation amount ΣΔNE satisfies the relational expression “AVE-3 × σ ≦ R ≦ AVE + 3 × σ” (step S208 in FIG. 8: YES), the average rotational fluctuation amount ΣΔNE is calculated. Based on the value AVE, an estimated value (estimated cetane number) of the cetane number of the fuel is calculated (step S209). In the present embodiment, the relationship (estimated map) between the estimated cetane number that can accurately estimate the cetane number of the fuel and the average value AVE is obtained in advance based on the results of experiments and simulations, and the electronic It is stored in the control unit 40. In the process of step S209, the estimated cetane number is calculated based on the average value AVE of the rotational fluctuation amount ΣΔNE based on the estimated map.

  Thereafter, the fuel injection execution frequency for estimating the cetane number is set according to the standard deviation σ of the rotational fluctuation amount ΣΔNE. Specifically, when the standard deviation σ is equal to or smaller than the first determination value JL (step S210: YES), a predetermined value CL (“4” in the present embodiment) is set as the predetermined number of times, and the execution frequency is low. It is set (step S211). On the other hand, when the standard deviation σ is greater than the first determination value JL and equal to or less than the second determination value JH (step S210: NO and step S212: NO), the predetermined number CM (in this embodiment, “2”). ”) Is set, and the execution frequency is set to a medium level (step S213). On the other hand, when the standard deviation σ is larger than the second determination value JH (step S210: NO and step S212: YES), the predetermined value CH (“1” in the present embodiment) is set as the predetermined number of times, and the above execution is performed. The frequency is set high (step S214). Note that values satisfying the relation “CL> CM> CH” may be set as the predetermined values CL, CM, and CH. In this way, after the execution frequency of the fuel injection for estimating the cetane number is set, this process is temporarily terminated.

  Thereafter, when this process is repeatedly executed and the latest value R of the rotational fluctuation amount ΣΔNE does not satisfy the relational expression “AVE-3 × σ ≦ R ≦ AVE + 3 × σ” (step S208: NO), the value is stored. Of the N rotational fluctuation amounts ΣΔNE, values other than the most recently detected value are reset to initial values (step S215). At this time, assuming that there is a high possibility that the cetane number of the fuel supplied to the diesel engine 11 has greatly changed, “1” is set as the predetermined number of times, and the frequency of fuel injection for estimating the cetane number is set. It is set high (step S214). After such processing, this processing is temporarily terminated.

  In the apparatus according to the present embodiment, for example, based on the detection signal of the pressure sensor 41 provided in the cylinder 16 [# 1] of the diesel engine 11, various processes (fuel injection) for fuel injection to the cylinder 16 [# 1]. Various processes are executed based on the output signal of the pressure sensor 41 corresponding to each cylinder 16 (# 1 to # 4) of the diesel engine 11 such as executing a process related to control and a correction process. For this reason, in the multi-cylinder diesel engine 11 in which the operating characteristics of the fuel injection valve 20 are different for each cylinder 16 due to initial individual differences and temporal changes, the pressure is detected by a dedicated pressure sensor 41 provided for each cylinder 16. The amount of fuel injected from each fuel injection valve 20 can be accurately adjusted based on the fuel pressure PQ.

  Moreover, it is calculated in the fuel injection control of the fuel injection valve 20 by using one of the fuel injection valves 20 (in this embodiment, the fuel injection valve 20 corresponding to the cylinder 16 [# 11]). Based on the correction terms K1 and K2, fuel injection in the estimation control is executed. As a result, since the amount of fuel actually injected in the estimation control is adjusted with high accuracy, the cetane number of the fuel is accurately estimated based on the output torque of the diesel engine 11 generated by the fuel injection. Will be able to.

As described above, according to the present embodiment, the effects described below can be obtained.
(1) When the standard deviation σ of the rotational fluctuation amount ΣΔNE detected in the most recent predetermined period is small, compared to when the standard deviation σ is large, the frequency of execution of fuel injection for estimating the cetane number of fuel Was lowered. Therefore, the estimation of the cetane number of the fuel can be properly executed while suppressing the deterioration of the fuel efficiency of the diesel engine 11.

  (2) Although the fuel injection for estimating the cetane number is executed when the fuel cut control is being executed, the execution frequency can be lowered, and the drivability can be prevented from being lowered.

  (3) As the execution frequency of fuel injection for estimating the cetane number, the lowest value is set when the standard deviation σ is equal to or smaller than the first determination value JL, and the standard deviation σ is greater than the first determination value JL and When the value is equal to or less than 2 determination value JH, a value that increases in the order in which the standard deviation σ is greater than the second determination value JH is set. Therefore, it is possible to finely set the frequency of fuel injection for estimating the cetane number in accordance with the state of the fuel supplied to the diesel engine 11, and to suitably reduce the fuel efficiency of the diesel engine 11. Can be suppressed.

  (4) When the latest value R of the rotational fluctuation amount ΣΔNE does not satisfy the relational expression “AVE-3 × σ ≦ R ≦ AVE + 3 × σ”, the rotational fluctuation amount ΣΔNE detected and stored in a predetermined period The average value AVE was calculated without using a part. Therefore, when the amount of change in the cetane number of the fuel is very large, it is possible to prevent the value corresponding to the cetane number before the change from being used for the estimation of the cetane number, and to accurately estimate the cetane number of the fuel. be able to.

  (5) When the latest value R of the rotational fluctuation amount ΣΔNE does not satisfy the above relational expression, the recently detected value of the rotational fluctuation amount ΣΔNE detected in the predetermined period is used for calculating the average value AVE. . Thereby, as compared with the case where not all of the rotational fluctuation amount ΣΔNE detected in the predetermined period is used for calculating the average value AVE, the number of stored rotational fluctuation amounts ΣΔNE reflecting the influence of the change in the cetane number is secured. Therefore, a highly reliable value can be calculated at an early stage as the average value AVE based on the rotational fluctuation amount ΣΔNE.

  (6) Based on the variation of the fuel pressure PQ detected by the pressure sensor 41, the actual fuel injection timing and the amount of injected fuel can be accurately grasped. Based on the fuel injection amount, it is possible to accurately set the injection timing and the injection amount in the fuel injection for estimating the cetane number of the fuel. Therefore, the estimation of the cetane number can be performed with high accuracy.

  (7) The fuel pressure PQ is detected by the pressure sensor 41 integrally attached to the fuel injection valve 20. Therefore, compared with a device that detects the fuel pressure at a position away from the fuel injection valve 20, 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. Can do. Therefore, it is possible to accurately detect the actual execution timing and the injection amount based on the fluctuation mode of the fuel pressure PQ, and in the fuel injection for estimating the cetane number based on the actual execution timing and the injection amount. The injection timing and the injection amount can be set with higher accuracy.

The embodiment described above may be modified as follows.
The “recently detected value” is not limited to adopting the rotational fluctuation amount ΣΔNE detected in the period in which a certain amount of fuel has been consumed most recently, but the vehicle 10 has a predetermined distance (for example, several kilometers) ), The rotational fluctuation amount ΣΔNE detected during the traveling period can be employed. In addition, the rotational fluctuation amount ΣΔNE detected during the most recent period during which the vehicle 10 has traveled for a predetermined time (for example, several minutes) can be employed. The point is to set a period during which the amount of rotation fluctuation ΣΔNE can be calculated while suppressing the deterioration of the estimation accuracy of the cetane number of fuel at an early stage, and to detect the rotation fluctuation detected during the same period. The amount ΣΔNE may be adopted as the “recently detected value”.

  When the latest value R of the rotation fluctuation amount ΣΔNE does not satisfy the relational expression, all of the N rotation fluctuation amounts ΣΔNE stored in the electronic control unit 40 may be reset to the initial values.

-You may abbreviate | omit the process of FIG.8 S208 and the process of step S215.
-Instead of changing the execution frequency of fuel injection for estimating the cetane number of fuel to three stages, it may be changed to two stages. Even with this configuration, the frequency of fuel injection for estimating the cetane number of the fuel is switched between when the cetane number of the fuel changes and when it hardly changes, or when the cetane number of the fuel is high and low. And can be switched. Moreover, the execution frequency of fuel injection for estimating the cetane number of fuel may be changed to four or more stages. According to such a configuration, when the cetane number of the fuel changes, the change degree of the cetane number can be estimated based on the standard deviation σ of the rotational fluctuation amount ΣΔNE, and the execution frequency can be finely switched according to the change degree. . And any structure can perform appropriately estimation of the cetane number of a fuel, suppressing the fall of the fuel consumption performance of the diesel engine 11. FIG. In short, the execution frequency may be set such that the lower the standard deviation σ of the rotational fluctuation amount ΣΔNE detected in the most recent predetermined period, the lower the fuel injection execution frequency for estimating the cetane number.

  The calculation of the estimated cetane number based on the average value AVE of the rotational fluctuation amount ΣΔNE may be performed based on an arithmetic expression instead of based on the estimated map. In short, the relationship between the estimated cetane number and the rotational fluctuation amount ΣΔNE may be stored in advance in the electronic control unit 40, and the estimated cetane number may be calculated based on the relationship.

  As a calculation parameter used for calculating the estimated cetane number, a gradually changing value other than the average value AVE of the rotational fluctuation amount ΣΔNE, for example, an annealing value of the rotational fluctuation amount ΣΔNE, or the like may be adopted. As the annealing value, for example, the latest annealing value is “B”, the annealing value calculated at the time of the previous processing is “Bi”, the latest value of the rotational fluctuation amount ΣΔNE is “R”, and the annealing coefficient is When “D (where 0 <D <1)”, it can be calculated from the relational expression “B = Bi + (R−Bi) × D”. In addition, it is also possible to calculate the above-described smoothing value from the relational expression “B = (E × Bi + R) / (E + 1)”, assuming that the smoothing coefficient is “E (where E is a natural number)”.

The configuration for correcting the target fuel injection timing TQst and the target fuel injection time TQtm by the correction terms K1, K2 may be omitted.
A value other than the rotational fluctuation amount ΣΔNE may be calculated as an index value of the output torque of the diesel engine 11. For example, during execution of the estimation control, an engine rotation speed NE (running rotation speed) at the time of execution of fuel injection and an engine rotation speed NE immediately before the execution of the fuel injection are respectively detected and a difference between these speeds is calculated The difference can be used as the index value.

  The change of the fuel injection execution frequency for estimating the cetane number may be performed through a method other than the method performed through the operation of the execution flag. As such a method, for example, a prohibition period for temporarily prohibiting the execution of the fuel injection immediately after the execution of the fuel injection for estimating the cetane number is set, and the prohibition period is set according to the standard deviation σ of the rotational fluctuation amount ΣΔNE. It is possible to adopt a method of variably setting. In this case, the prohibition period may be set longer as the standard deviation σ is smaller.

  The pressure sensor 41 is mounted in an appropriate manner so that the fuel pressure indicator in 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 is appropriately set. As long as it can be detected, the present invention is not limited to the mode of being directly attached to the fuel injection valve 20, but can be arbitrarily changed. Specifically, the pressure sensor 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 cetane number estimation device according to the above embodiment can be applied not only to the vehicle 10 equipped with the clutch mechanism 13 and the manual transmission 14 but also to a vehicle equipped with a torque converter and an automatic transmission. it can. In such a vehicle, for example, when [Condition A], [Condition C], and [Condition D] are satisfied, fuel injection for estimating the cetane number of the fuel may be executed. In a vehicle that employs a lockup clutch built-in as a torque converter, a new [Condition E] that the lockup clutch is not engaged is set and the [Condition E] is satisfied. The fuel injection for estimating the cetane number of the fuel may be executed on the condition that

  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 ... Vehicle, 11 ... Diesel engine, 12 ... Crankshaft, 13 ... Clutch mechanism, 14 ... Manual transmission, 15 ... Wheel, 16 ... Cylinder, 17 ... Intake passage, 18 ... Piston, 19 ... Exhaust passage, 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, 42 ... crank sensor 43 ... Accelerator sensor, 44 ... Vehicle speed sensor, 45 ... Clutch switch.

Claims (9)

When the fuel injection to the diesel engine is performed in a predetermined amount on condition that the execution condition is satisfied, the index value of the output torque of the diesel engine generated along with the execution of the fuel injection is detected, and the detected index value A cetane number estimation device for estimating a cetane number of a fuel based on a value obtained by gradually changing
A standard deviation of the index value detected during the most recent predetermined period is calculated, and when the calculated standard deviation is small, the execution frequency of the fuel injection is made lower than when the standard deviation is large. Price estimation device. The cetane number estimation apparatus according to claim 1,
The cetane number estimating device, wherein the execution condition includes a condition that execution of fuel injection for operation of the diesel engine is stopped. In the cetane number estimation apparatus according to claim 1 or 2,
The apparatus sets the lowest value as the execution frequency when the standard deviation is less than or equal to a first determination value, and the second determination is greater than the first determination value and greater than the first determination value. A cetane number estimating device, wherein when the value is less than or equal to a value, a value that increases in the order in which the standard deviation is greater than the second determination value is set. In the cetane number estimating device according to any one of claims 1 to 3,
Assuming that the average value of the index values detected during the predetermined period is AVE, the standard deviation is σ, and the latest value of the detected index values is R, each of these values AVE, σ, R is expressed by the relational expression “AVE -3 × σ ≦ R ≦ AVE + 3 × σ ”is calculated, the gradual value is calculated without using at least a part of the index value detected during the predetermined period. Price estimation device. In the cetane number estimation apparatus according to claim 4,
When each of the values AVE, σ, R does not satisfy the relational expression, the recently detected value of the index values detected in the predetermined period is used for calculating the gradually changed value. A cetane number estimation device. The pressure sensor which detects the fuel pressure which changes with the change of the actual fuel pressure inside the fuel injection valve at the time of opening of the fuel injection valve of the diesel engine is provided. The cetane number estimation apparatus as described. The cetane number estimation apparatus according to claim 6,
The apparatus corrects the fuel injection amount of the fuel injection based on a fuel pressure fluctuation mode detected by the pressure sensor. In the cetane number estimation apparatus according to claim 6 or 7,
The apparatus corrects the execution timing of the fuel injection based on the fluctuation mode of the fuel pressure detected by the pressure sensor. In the cetane number estimating device according to any one of claims 6 to 8,
The cetane number estimating device, wherein the pressure sensor is attached to the fuel injection valve.

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