JP5772266B2 - Cetane number estimation device - Google Patents

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 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, in Patent Document 1, when a predetermined execution condition is satisfied, a small amount of fuel is injected from the fuel injection valve, and an index value of engine torque generated by the fuel injection is detected, and based on the index value. An apparatus for estimating the cetane number of fuel has been proposed. In this apparatus, focusing on the fact that the engine torque generated by a predetermined amount of fuel injection changes according to the cetane number of the fuel, the cetane number of the fuel is estimated based on the index value of the engine torque generated by the fuel injection. The

Patent Document 2 proposes an apparatus that calculates an average value for such an index value of engine torque and estimates the cetane number of the fuel based on the average value. In this apparatus, the index value of the engine torque itself is not used to estimate the cetane number of the fuel, but an average value of the index value of the engine torque, in other words, a value indicating a change tendency of the index value is used. Therefore, it is possible to perform estimation of the cetane number of the fuel based on the index value while suppressing the influence of the detection error of the index value of the engine torque.

JP 2010-24870 A JP 2009-74499 A

  By the way, in the apparatus described in each document, since fuel injection for estimating the cetane number of the fuel is executed only when the execution condition is satisfied, the fuel is replenished and the cetane number of the fuel in the fuel tank is reduced. Even if it becomes low, cetane number estimation is not executed unless the execution condition is satisfied. Therefore, at this time, an error occurs between the cetane number of the fuel actually supplied to the diesel engine and the estimated cetane number.

  In addition, in an apparatus that calculates an average value for an index value of engine torque, such as the apparatus described in Patent Document 2, an execution condition is established after replenishment of low cetane number fuel, and the cetane number of fuel is estimated. Even when fuel injection is performed, the average value gradually changes to a value commensurate with the actual cetane number. Therefore, also in this case, an error occurs between the cetane number of the fuel actually supplied to the diesel engine and the estimated cetane number.

  When such an error occurs, even though the fuel actually supplied to the diesel engine is a low cetane number fuel, the operation mode of the diesel engine corresponds to the estimated cetane number, that is, a value indicating a relatively high cetane number. It will be the situation that is executed in. In this case, there is a possibility that the combustion state of the fuel in the cylinder of the diesel engine may be deteriorated, and a misfire may be caused.

  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 detecting replenishment of a low cetane number fuel at an early stage while maintaining high estimation accuracy of the cetane number of the fuel. Is to provide.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
In the apparatus according to the first aspect, fuel injection to the diesel engine in a predetermined amount is executed on condition that the execution condition is satisfied. Then, an index value of the output torque of the diesel engine generated by the execution of the fuel injection is detected, and a plurality of cetane number quantities in which the cetane number of the fuel is divided by the cetane number based on the average value of the index values Which area of the areas belongs is specified . This makes it possible to estimate the cetane number of the fuel using the average value of the engine torque index value, in other words, the value indicating the change tendency of the index value, thereby suppressing the influence of the detection error of the engine torque index value. However, it is possible to accurately estimate the cetane number of the fuel based on the index value.

In addition, when the cetane number of the fuel supplied to the diesel engine does not change, the index value is assumed under the assumption that the distribution of the index value detected with fuel injection at a predetermined amount is a normal distribution. (In detail, almost all of the latest values R) are equal to or larger than the value obtained by subtracting three times the standard deviation σ from the average value AVE [(AVE−3 × σ) ≦ R]. On the other hand, when the fuel having a very low cetane number is replenished and the cetane number of the fuel supplied to the diesel engine becomes extremely low, the latest value R satisfies the relational expression [(AVE-3 × σ)> R]. The possibility increases.
According to the apparatus of claim 1, the latest value R of the index value satisfies the relational expression [(AVE-3 × σ)> R], that is, the fuel having the same cetane number is supplied to the diesel engine. As the latest value R is detected as a value indicating a cetane number that is as low as possible, the cetane number of the fuel supplied to the diesel engine is replenished with a very low cetane number fuel. It can be judged that it has become low.
Its to an average value without waiting for the change to the actual values commensurate with cetane, the cetane number of the fuel is more cetane number region by the detection of the index value of the engine torque are repeated in this case Can be identified as belonging to the region of the lowest cetane number side . In this way, the supply of the low cetane number fuel can be detected at an early stage, and the supply can be reflected in the estimation result of the cetane number.

Therefore, according to the first aspect of the present invention, the replenishment of the low cetane number fuel can be detected at an early stage while maintaining high estimation accuracy of the cetane number of the fuel .

Usually, the temporary stop of the fuel injection for the operation of the diesel engine is executed in a limited situation, for example, when the rotational speed of the engine output shaft is decreasing. According to the apparatus of claim 2 , the execution condition includes a condition that the execution of fuel injection for operation of the diesel engine is temporarily stopped, so that the cetane number is estimated in advance. In an apparatus in which the opportunity for performing fuel injection with a limited amount is limited, replenishment of low cetane number fuel can be detected early while maintaining high estimation accuracy of the cetane number of the fuel.

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 transition of the average value of rotation fluctuation amount. The flowchart which shows the 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 a plurality of injection holes 23 that communicate 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.

  The fuel injection valve 20 employs an electrically driven type, and a piezoelectric actuator 29 in which a plurality of piezoelectric elements (for example, piezo elements) that expand and contract by input of a drive signal is provided in the housing 21. It has been. 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 drive 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 operation of the diesel engine 11 is calculated based on the accelerator operation amount ACC, the engine speed NE, and the like. 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.

  In addition, in the fuel injection control of the present embodiment, two regions, a region where the cetane number of the fuel is low (low cetane number region) and a region where the fuel is high (high cetane number region) are set, and execution is different for each region. The fuel injection control is executed in a manner. For example, the required injection timing Tst in the low cetane number region is set to a timing on the advance side as compared with the required injection timing Tst in the high cetane number region. Specifically, in the present embodiment, the relationship between the engine operating state determined by the required injection amount TAU and the engine rotational speed NE and the required injection timing Tst corresponding to the low cetane number region is determined in advance based on the results of various experiments and simulations. The obtained relationship is stored in the electronic control unit 40 as the operation map ML. When in the low cetane number region, the required injection timing Tst is calculated from the calculation map ML based on the required injection amount TAU and the engine rotational speed NE. Also, the relationship between the engine operating state determined by the required injection amount TAU and the engine speed NE and the required injection timing Tst corresponding to the high cetane number region is obtained in advance based on the results of various experiments and simulations, and the relationship is calculated. The map MH is stored in the electronic control unit 40. When it is in the high cetane number region, the required injection timing Tst is calculated from the calculation map MH based on the required injection amount TAU and the engine speed NE.

  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 undesirable because it changes the output torque of the diesel engine 11. 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, by monitoring the fluctuation waveform of the fuel pressure inside the fuel injection valve 20 at the time of fuel injection execution, the actual operation characteristics of the fuel injection valve 20 (for example, the actual fuel injection amount and the valve opening operation are started). And when the valve closing operation is started). 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 d (PQ) / dt is calculated according to the time of the fuel pressure PQ in a period in which the fuel pressure PQ drops immediately after the start of fuel injection. Then, the tangent L1 of the time waveform of the fuel pressure PQ at the point where the first-order differential value becomes the minimum, that is, the point where the downward slope of the fuel pressure PQ becomes the largest is obtained, and the intersection of the tangent L1 and the operating pressure Pac is obtained. A is calculated. The timing corresponding to the point AA where the intersection A is returned to the past timing by the following 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 the maximum, that is, the point where the upward slope of the fuel pressure PQ becomes the largest, is obtained, and the intersection of the tangent L2 and the operating pressure Pac B 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. The series of processes shown in this flowchart conceptually shows the execution procedure of the correction process, and the actual process is executed by the electronic control unit 40 as an interrupt process at predetermined intervals. FIG. 5 shows an example of the relationship between the detection time waveform and the following basic time waveform.

  As shown in FIG. 4, in this correction 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 way, the deviation 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 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 apparatus of 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 above-described 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 small predetermined amount FQ (for example, several cubic millimeters) is executed, and diesel generated along with the execution of the fuel injection An index value of the output torque of the engine 11 (rotational fluctuation amount ΣΔNE described later) is detected. As the rotational fluctuation amount ΣΔNE, a larger value is detected as a large output torque is generated in the diesel engine 11.

  Then, an average value AVE of the rotation fluctuation amount ΣΔNE detected in the most recent predetermined period (a period in which the rotation fluctuation amount ΣΔNE is detected only ten times in the present embodiment) is calculated, and the average value AVE is calculated. Based on the above, it is specified which of the low cetane number region and the high cetane number region described above. Specifically, when the average value AVE is less than the predetermined value P, the low cetane number region is selected, while when the average value AVE is equal to or greater than the predetermined value P, the high cetane number region is selected.

  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 according to the present embodiment, the cetane number region is specified based on the relationship between the cetane number of the fuel and the output torque of the diesel engine 11. In the present embodiment, since the cetane number region is specified using a value (average value AVE) obtained by gradually changing the rotational fluctuation amount ΣΔNE, in other words, a value indicating a change tendency of the rotational fluctuation amount ΣΔNE, the rotational fluctuation amount The cetane number region can be accurately identified based on the rotation fluctuation amount ΣΔNE while suppressing the influence of the detection error of ΣΔNE.

  FIG. 6 shows an example of the transition of the average value AVE of the rotational fluctuation amount ΣΔNE when the low cetane number fuel is replenished in a situation where the high cetane number fuel is stored in the fuel tank 32. In the example shown in FIG. 6, the execution condition is not satisfied at times t11 to t12, and the fuel supply is performed at any timing of times t11 to t12.

  In the present embodiment, since fuel injection for detecting the rotational fluctuation amount ΣΔNE is executed only when the execution condition is satisfied, fuel supply is performed and the cetane number of the fuel in the fuel tank 32 is lowered. Even in this case, as long as the execution condition is not satisfied (time t11 to t12 in FIG. 6), the average value AVE of the rotational fluctuation amount ΣΔNE is not updated and the cetane number region is not updated. Therefore, at this time, the cetane number region (high cetane number region in the example shown in FIG. 6) corresponding to the cetane number of the fuel actually supplied to the diesel engine 11 and the average value AVE of the rotational fluctuation amount ΣΔNE are specified and stored. The cetane number region (the same low cetane number region) is shifted. In the present embodiment, since the execution condition includes [Condition A] that the fuel cut control is being executed, opportunities for execution of fuel injection for specifying the cetane number region are limited.

  Further, even when the fuel injection for detecting the rotational fluctuation amount ΣΔNE is executed after the execution condition is satisfied after the low cetane number fuel is supplied to the fuel tank 32, the average value of the rotational fluctuation amount ΣΔNE AVE gradually changes to a value commensurate with the actual cetane number (after time t12). In the present embodiment, since the cetane number region is specified based on the average value AVE of the rotational fluctuation amount ΣΔNE, the cetane number region corresponding to the cetane number of the fuel actually supplied to the diesel engine 11 even in such a situation The cetane number area specified and stored based on the average value AVE is shifted.

  When such a cetane number region shift occurs, the fuel injection control for operation of the diesel engine 11 is performed even if the fuel actually supplied to the diesel engine 11 is a low cetane number fuel. It will be in the situation where it is executed in the execution mode suitable for. In this case, the combustion state of the fuel in the cylinder 16 of the diesel engine 11 may be deteriorated, and a misfire may be caused.

  Here, when the cetane number of the fuel injected and supplied to the diesel engine 11 does not change, the rotation fluctuation amount ΣΔNE detected when the execution condition is satisfied is assumed to be a normal distribution. When the standard deviation of the fluctuation amount ΣΔNE is “σ”, almost all of the rotation fluctuation amounts ΣΔNE (specifically, the latest value R) satisfy the following relational expression (1).

(AVE− “3.0” × σ) ≦ R ≦ (AVE + “3.0” × σ)] (1)

That is, almost all the latest values R of the rotational fluctuation amount ΣΔNE are equal to or greater than a value obtained by subtracting three times the standard deviation σ from the average value AVE and less than a value obtained by adding three times the standard deviation σ to the average value AVE. Value. In the example shown in FIG. 6, almost all the rotational fluctuation amounts ΣΔNE detected before refueling (before time t11) become values in the area AR1 indicated by hatching in FIG.

  On the other hand, when a fuel having a very low cetane number is replenished to the fuel tank 32 and the cetane number of the fuel injected and supplied to the diesel engine 11 becomes low, the rotational fluctuation amount detected when the subsequent execution condition is satisfied. Since ΣΔNE becomes very small, the latest value R of the rotational fluctuation amount ΣΔNE does not satisfy the relational expression (1). In the example shown in FIG. 6, almost all the rotational fluctuation amounts ΣΔNE detected after the execution condition after fuel replenishment (after time t12) is the value in the area AR2 indicated by the hatching in FIG. Therefore, when the execution condition is satisfied for the first time after replenishing the low cetane fuel (time t12), the latest value R of the rotational fluctuation amount ΣΔNE satisfies the following relational expression (2).

(AVE− “3.0” × σ)> R (2)

As described above, when a fuel having a very low cetane number is replenished in a state where the high cetane number fuel is stored in the fuel tank 32, the rotational fluctuation amount ΣΔNE detected immediately after the standard deviation σ is deviated from the average value AVE. There is a high possibility that the value will be less than the value obtained by subtracting three times.

In the present embodiment, it is determined that such a standard deviation σ is used to supply the fuel tank 32 with a fuel having a very low cetane number.
That is, first, the standard deviation σ of the rotational fluctuation amount ΣΔNE detected in the most recent predetermined period (in this embodiment, the period in which the rotational fluctuation amount ΣΔNE is detected only 10 times in the latest) is calculated. When the latest value R, the average value AVE, and the standard deviation σ of the rotational fluctuation amount ΣΔNE satisfy the relational expression (2), it is almost detected as long as the fuel having the same cetane number is supplied to the diesel engine 11. It is determined that a value indicating a cetane number as low as possible is detected as the latest value R. Further, it is assumed that the rotational fluctuation amount ΣΔNE has changed to a very small value by replenishing the fuel with a very low cetane number fuel in a situation where the fuel tank 32 stores high cetane number fuel. The low cetane number region is forcibly selected without depending on the average value AVE of the rotational fluctuation amount ΣΔNE. In the present embodiment, the situation in which the above relational expression is satisfied is that the latest value R indicates a cetane number lower than the average value AVE, and the difference between the latest value R and the average value AVE is equal to or greater than the determination threshold value. Act as a situation.

  As described above, according to the present embodiment, when the relational expression (2) is satisfied, the cetane number of the fuel injected and supplied to the diesel engine 11 at the time of detecting the latest value R becomes lower than that. It can be determined that the cetane number is very low compared to the cetane number of the fuel injected and supplied to the diesel engine 11 to detect the rotational fluctuation amount ΣΔNE when the execution condition is satisfied.

  In this case, the detection of the rotational fluctuation amount ΣΔNE is repeated so that the average value AVE does not change to a value commensurate with the actual cetane number. A valence region can be selected. According to the present embodiment, it is possible to detect the replenishment of the low cetane number fuel at an early stage and reflect the replenishment in the estimation result of the cetane number.

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 C] 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.

When the execution condition is not satisfied (step S201: NO), this process is temporarily terminated without executing the following process, that is, the process for specifying the cetane number region.
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. 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.

  Then, it is determined whether or not the number of rotation fluctuations ΣΔNE calculated and stored reaches a predetermined number M (specifically, “10”) (step S205). If an initial value is stored, the value is not counted as the number of stored rotational fluctuation amounts ΣΔNE, and if the rotational fluctuation amount ΣΔNE is calculated and stored is less than a predetermined number M (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 process is repeatedly executed and the number of stored rotational fluctuation amounts ΣΔNE reaches a predetermined number M (step S205: YES), the stored M rotational fluctuation amounts ΣΔNE are calculated from the 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, for each of the M rotational fluctuation amounts ΣΔNE, a value obtained by subtracting the average value AVE from the rotational fluctuation amount ΣΔNE (ΣΔNE−AVE) is calculated, and a value obtained by squaring the same value is calculated. Thereafter, the squared values are added, and the added value is divided by the number of data (predetermined number M). Then, the square root of the divided value is calculated, and the calculated value is stored as the standard deviation σ.

Thereafter, it is determined whether or not the average value AVE, standard deviation σ, and latest value R of the rotational fluctuation amount ΣΔNE satisfy the relational expression (2) (step S208).
When the relational expression (2) is not satisfied (step S208: NO), any one of the low cetane number region and the high cetane number region divided by the cetane number of the fuel based on the average value AVE of the rotational fluctuation amount ΣΔNE. To belong to the region. Specifically, first, it is determined whether or not the average value AVE is equal to or greater than a predetermined value P (step S209).

  If the average value AVE is equal to or greater than the predetermined value P (step S209: YES), after determining that the cetane number of the fuel at this time is in the high cetane number region (step S210), the process is temporarily performed. Is terminated. In this case, the fuel injection control for the operation of the diesel engine 11 is subsequently executed in a mode commensurate with the high cetane number fuel. That is, the required injection timing Tst is calculated from the calculation map MH based on the required injection amount TAU and the engine rotational speed NE.

  On the other hand, when the average value AVE is less than the predetermined value P (step S209: NO), after determining that the cetane number of the fuel at this time is in the low cetane number region (step S211), this process is temporarily performed. Is terminated. Thereafter, the fuel injection control for the operation of the diesel engine 11 is executed in a manner commensurate with the low cetane number fuel. That is, the required injection timing Tst is calculated from the calculation map ML based on the required injection amount TAU and the engine rotational speed NE.

  When the relational expression (2) is satisfied (step S208: YES), after it is determined that the cetane number of the fuel is in the low cetane number region (step S211), this process is temporarily terminated. That is, in this case, the detection of the rotational fluctuation amount ΣΔNE is repeated, and without waiting for the average value AVE to change to a value commensurate with the actual cetane number, a plurality of estimation results of the cetane number of the fuel are obtained. Of the cetane number regions, the region on the low cetane number side is selected.

  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) Since the cetane number region is specified by using the average value AVE of the rotation fluctuation amount ΣΔNE, in other words, the value indicating the change tendency of the rotation fluctuation amount ΣΔNE, the influence of the detection error of the rotation fluctuation amount ΣΔNE is suppressed. On the other hand, the cetane number region can be accurately identified based on the rotation fluctuation amount ΣΔNE. Moreover, the low cetane number region is forcibly selected when the latest value R of the rotational fluctuation amount ΣΔNE satisfies the relational expression [(AVE− “3.0” × σ)> R]. Therefore, the supply of the low cetane number fuel can be detected at an early stage, and the supply can be reflected in the estimation result of the cetane number. Therefore, the replenishment of the low cetane number fuel can be detected at an early stage while maintaining high estimation accuracy of the cetane number of the fuel.

  (2) Since the execution condition includes [Condition A] that the fuel cut control is being executed, the fuel cetane number of the fuel is limited in the apparatus in which the opportunity for the fuel injection for detecting the rotational fluctuation amount ΣΔNE is limited. Replenishment of low cetane fuel can be detected early while maintaining high estimation accuracy.

The embodiment described above may be modified as follows.
When the latest value R of the rotational fluctuation amount ΣΔNE does not satisfy the relational expression [(AVE− “3.0” × σ)> R], the rotational fluctuation amount ΣΔNE is used as a specific parameter used for specifying the cetane number region. In addition to using the average value AVE, a value other than the average value among values obtained by gradually changing the rotational fluctuation amount ΣΔNE, such as a weighted average value of the rotational fluctuation amount ΣΔNE, may be used. As the weighted average value, the weighted average value is (G), the previous value of the weighted average value is (G [i]), and a predetermined positive number (specifically, “0 <W <1. When a constant value satisfying “0” is defined as (W), a value satisfying the relational expression {G = G [i] + (“latest value R” −G [i]) × W} is calculated. Can do.

  When a relational expression [(AVE− “N” × σ)> R] is set with a positive number “N”, N is “3.0” as in relational expression (2) in the above embodiment. However, the value of N in the relational expression may be a value slightly larger or slightly smaller than “3.0”. Further, as N in the relational expression, a value much larger than “3.0” such as “5.0” or “6.0” can be adopted. Even with such a device, it is possible to determine that a value indicating a cetane number that is low enough to be hardly detected as long as fuel of the same cetane number is supplied to the diesel engine 11 is detected as the latest value R. it can.

  ・ If it is possible to accurately determine that the difference between the latest value R and the average value AVE of the rotational fluctuation amount ΣΔNE is equal to or greater than the determination threshold, the standard deviation indicates that the specific condition has been reached. The determination method is not limited to the method based on σ, and the determination method can be arbitrarily changed. For example, a determination value J that can accurately determine that a specific situation has been reached is determined in advance based on the results of experiments and simulations, and the difference between the latest value R and the average value AVE is greater than or equal to the determination value J. When it becomes ([AVE-R] ≧ J), it may be determined that a specific situation has been reached.

  In the estimation control process (FIG. 7) according to the above-described embodiment, if an error in the fuel injection timing and the fuel injection amount due to the initial individual difference of the fuel injection valve 20 and a change with time can be appropriately suppressed, the target The process of correcting the fuel injection timing TQst and the target fuel injection time TQtm using the correction terms K1 and K2 (step S202) may be omitted.

  -The cetane number estimation apparatus according to the above embodiment has an actual fuel cetane number in any of the three or more regions divided by the cetane number of the fuel based on a value obtained by gradually changing the rotational fluctuation amount ΣΔNE. The present invention can also be applied to a device that determines whether or not a device belongs, after changing its configuration as appropriate.

  The cetane number estimation device according to the above embodiment is not limited to a device that determines which region of the plurality of regions divided by the cetane number of the fuel belongs to the actual fuel cetane number, but the rotational fluctuation amount ΣΔNE The present invention can also be applied to an apparatus for estimating the cetane number of a fuel itself based on a value obtained by gradually changing the above, after appropriately changing its configuration. In such an apparatus, for example, the lowest cetane number among the cetane numbers of fuel that may be replenished in the fuel tank 32 or a cetane number slightly higher than the cetane number is determined in advance as a predetermined low cetane number SL. When a specific situation is reached, the low cetane number SL may be calculated as an estimated cetane number. The predetermined low cetane number SL can be set to an arbitrary value based on the results of experiments and simulations.

  EGR control or pilot injection control instead of or in addition to adopting fuel injection control for operation of the diesel engine 11 as engine control executed according to the cetane number region specified through the estimation control process Etc. may be executed. In short, any engine control that changes the combustion state of the fuel can be adopted as engine control executed in accordance with such a cetane number region.

  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, the engine rotational speed NE at the time of fuel injection and the engine rotational speed NE immediately before the execution of the fuel injection are detected and the difference between these speeds is calculated, and the difference is calculated as the index value. Can be used as

  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] and [Condition C] are satisfied, fuel injection for estimating the cetane number of fuel may be executed. In a vehicle in which a torque converter with a built-in lock-up clutch is adopted, [Condition D] that the lock-up clutch is not engaged is newly set and the [Condition D] is also 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 (engine output shaft), 13 ... Clutch mechanism, 14 ... Manual transmission, 15 ... Wheel, 16 ... Cylinder, 17 ... Intake passage, 18 ... Piston, 19 ... Exhaust 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 (2)

Executing fuel injection to the diesel engine in a predetermined amount on condition that the execution condition is satisfied, and storing an index value of the output torque of the diesel engine generated in accordance with the execution of the fuel injection . A cetane number estimating device for identifying which of a plurality of cetane number regions divided by a cetane number belongs to a cetane number region based on an average value of the index values of
While calculating the standard deviation of the index value used to calculate the average value,
When the standard deviation is “σ”, the average value is “AVE”, and the latest value in the index value is “R”,
When the relational expression [(AVE-3 × σ)> R] is satisfied, the cetane number of the fuel is identified as belonging to the lowest cetane number region among the plurality of cetane number regions,
When the above relational expression is not satisfied, the higher the average value is, the higher the cetane number of the fuel is identified as belonging to the region on the higher cetane number side in the plurality of cetane number amount ranges. A cetane number 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.

Images