JP5273314B2 - Cetane number estimation device - Google Patents

Abstract

In a diesel engine, the engine is controlled with a different execution mode for each of multiple, i.e. three or more regions, which are delimited with respect to one another in terms of the cetane number of the fuel. A cetane number estimation device estimates which of the multiple regions corresponds to the cetane number of the fuel. Fuel is injected by means of an auxiliary injection control corresponding to each of the multiple boundaries which delimit the multiple regions (S205, S213), and an estimation is made with respect to whether the cetane number of the fuel is at or greater than a boundary or is less than this boundary, on the basis of the amount of rotational deviation S?NE when the fuel is injected (S207, S214). The injection period for the auxiliary injection control corresponding to each boundary is set (S203, S211) such that the torque sensitivity at the time of the execution of the fuel injection in the injection period corresponding to the boundary for which the estimation is being performed is greater than the torque sensitivity when the execution of the fuel injection in the injection periods corresponding to the other boundaries is assumed.

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, Patent Document 1 discloses a device that injects a small amount of fuel from a fuel injection valve, detects an index value of engine torque generated by the fuel injection, and estimates the cetane number of the fuel based on the index value. 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

  In Patent Document 1, when estimating the cetane number of fuel, the fuel injection is repeatedly performed several tens of times while changing the injection timing, and the index value of the engine torque generated by the execution of the fuel injection is separately set. An apparatus for detection has also been proposed. This device specifies the injection timing at which misfiring starts based on the detected change tendency of the index value of the engine torque, and estimates the cetane number of the fuel based on the same period. In this apparatus, the estimation of the cetane number of the fuel is executed by utilizing the tendency that the injection timing at which misfiring starts becomes the advanced timing as the cetane number of the fuel is lower.

JP 2009-121322 A

  By the way, in order to increase the estimation accuracy in the apparatus for estimating the cetane number of the fuel based on the engine torque generated by the predetermined amount of fuel injection, the fuel injection is performed with the above-mentioned engine torque when the cetane number of the fuel changes. It is desirable to execute in a situation where the degree of change (hereinafter, torque sensitivity) becomes large.

  In the above device, the torque sensitivity is not constant, it varies depending on the timing of fuel injection and the cetane number of the fuel at that time, and the engine torque hardly changes even when the cetane number of the fuel changes. There is also.

  Therefore, if fuel injection for simply estimating the cetane number is executed, the estimation accuracy of the cetane number is lowered when the fuel injection is executed in a situation where the torque sensitivity is low. The above apparatus has room for improvement in this respect.

  Further, as in the device described in Patent Document 1, by repeatedly performing fuel injection while changing the injection timing, fuel injection is performed so as to include a situation where torque sensitivity is large (specifically, a situation where misfire occurs). Therefore, the cetane number of the fuel can be detected with high accuracy. However, in order to specify the injection timing at which misfiring starts in such a device, it is necessary to perform many fuel injections at different injection timings, which not only causes a decrease in fuel efficiency and emission performance of the diesel engine, but also fuel consumption. Therefore, the time required for determining the cetane number may become long, and it may not be possible to appropriately cope with the change in the cetane number.

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

  In order to achieve the above object, in the cetane number estimation device according to the present invention, in a diesel engine to which the device is applied, basic injection control for controlling the fuel injection mode based on the engine operating state, and estimation of the cetane number of the fuel And auxiliary injection control for controlling the fuel injection mode. Further, in this diesel engine, three or more regions that are separated from each other with respect to the cetane number of the fuel are set, and engine control is executed in a different execution manner for each region.

  In order to appropriately execute engine control in each region in such a diesel engine, it is only necessary to accurately estimate which region of the plurality of regions the cetane number of the fuel is. In order to estimate the cetane number of the fuel with high accuracy, the fuel injection by the auxiliary injection control in a situation where the degree of change in the index value of the engine torque (hereinafter referred to as torque sensitivity) increases when the cetane number of the fuel changes. It is desirable to perform.

  In the above-described configuration, fuel injection at a predetermined injection amount and injection timing is executed as auxiliary injection control corresponding to each of a plurality of boundaries that divide a plurality of regions, and the engine torque generated by the execution is controlled. An index value is detected, and based on the detected index value, it is estimated whether the cetane number of the fuel is greater than a specific boundary or less than the same boundary. Then, assuming that the injection timing corresponding to the boundary to be estimated at that time is the target injection timing and the injection timing corresponding to the other boundary is the non-target injection timing, the torque at the time of execution of fuel injection at the target injection timing The target injection timing is set such that the sensitivity is greater than the torque sensitivity when it is assumed that fuel injection is executed at the non-target injection timing. Therefore, it is possible to set the timing when the torque sensitivity increases as the injection timing corresponding to each of the plurality of boundaries, and it is possible to execute the fuel injection corresponding to these boundaries in a situation where the torque sensitivity increases. Therefore, the above estimation based on the index value of the engine torque generated with the execution of the fuel injection can be performed with high accuracy.

  Therefore, according to the above configuration, it is possible to estimate which of the plurality of regions the fuel cetane number is by executing fuel injection corresponding to each of the plurality of boundaries dividing the plurality of regions. As described above, it is possible to accurately estimate the cetane number of the fuel while suppressing the number of executions of the fuel injection, as compared with the apparatus that repeatedly executes the fuel injection while changing the injection timing.

  In a preferred aspect, as the predetermined injection timing of the auxiliary injection control, the timing on the retarded side is set such that the boundary to be estimated is a value on the high cetane number side.

  In the same aspect, in the device in which the injection timing at which the torque sensitivity becomes the highest as the cetane number of the fuel becomes the retarded timing, it is accurately estimated which region of the plurality of regions the cetane number of the fuel is. can do.

  In a preferred aspect, the estimation for the lowest cetane number boundary among the plurality of boundaries is performed prior to the estimation for the other boundaries.

  If engine control suitable for a high cetane number is being performed and fuel with a low cetane number is supplied to the diesel engine, misfire may occur due to deterioration of the combustion state of the fuel.

  According to the above aspect, at the start of execution of estimation of the cetane number of fuel, the estimation for the boundary on the lowest cetane number side can be executed first. Therefore, when the cetane number of the fuel supplied to the diesel engine changes from the high cetane number side region to the lowest cetane number side region, this can be grasped at an early stage. The occurrence of misfire can be suitably suppressed.

  In a preferred embodiment, the injection timing calculated based on the engine rotation speed based on the relationship between the predetermined engine rotation speed and the injection timing is used as the predetermined injection timing.

  In addition to changing according to the cetane number of the fuel, the engine torque generated by fuel injection at a predetermined amount also changes depending on the engine rotational speed at the time of execution of fuel injection. Such a difference in engine torque due to a difference in engine rotational speed is a cause of a decrease in estimation accuracy when the cetane number is estimated based on the index value of the engine torque.

  Here, the engine torque generated by fuel injection at a predetermined amount also changes depending on the execution timing of fuel injection. Therefore, by setting the injection timing according to the engine rotation speed, it becomes possible to execute the fuel injection by the auxiliary injection control so that the variation in the index value of the engine torque due to the difference in the engine rotation speed can be suppressed. I can say.

  According to the above aspect, since it becomes possible to set the injection timing so that the variation in the index value of the engine torque due to the difference in the engine speed is suppressed, the cetane number is estimated based on the index value. It becomes possible to execute with high accuracy.

In one aspect of the present invention, corresponding to each of the previous SL more boundary, whereas the cetane number of the fuel is determined to be below the border when the index value is less than the predetermined reference value, the index value is When it is equal to or greater than the determination value, it is determined that the cetane number of the fuel is equal to or greater than the boundary.

  In a diesel engine mounted on a vehicle as a drive source, fuel injection by basic injection control is stopped when fuel cut is executed during deceleration operation of the vehicle.

  In one aspect of the present invention, fuel injection is performed at a predetermined injection amount and injection timing by auxiliary injection control on the condition that fuel cut is performed during deceleration operation of a vehicle equipped with a diesel engine. Is done. According to such a configuration, when the fuel injection by the basic injection control is stopped, the fuel injection at the predetermined injection timing by the auxiliary injection control can be executed.

  In one aspect of the present invention, basic injection control is executed as the engine control.

  In one embodiment of the present invention, the plurality of regions include a low cetane number region, a medium cetane number region, and a high cetane number region.

  The fuel injection by the auxiliary injection control for estimating whether the cetane number of the fuel is greater than or equal to the boundary between the low cetane number region and the medium cetane number region (hereinafter referred to as the boundary BL) and less than the boundary BL is performed in advance. It is executed at a predetermined first injection timing, that is, an advanced timing suitable for a situation where the cetane number is low. Therefore, it is possible to set the injection timing at which the torque sensitivity becomes high in the vicinity of the boundary BL as the first injection timing, and based on the index value of the engine torque generated with the execution of fuel injection at the first injection timing. Thus, the above estimation can be performed with high accuracy.

  In addition, fuel injection by auxiliary injection control for estimating whether the cetane number of the fuel is greater than or equal to the boundary between the medium cetane number region and the high cetane number region (hereinafter referred to as boundary BH) and less than the boundary BH is performed in advance. It is executed at a predetermined second injection timing, that is, a relatively retarded timing suitable for a situation where the cetane number is high. Therefore, it is possible to set the injection timing at which the torque sensitivity is high near the boundary BH as the second injection timing, and based on the index value of the engine torque generated when the fuel injection is performed at the second injection timing. Thus, the above estimation can be performed with high accuracy.

  Therefore, the cetane number of the fuel is based on the result estimated together with the execution of the fuel injection at the first injection timing and the result estimated with the execution of the fuel injection at the second injection timing retarded from the first injection timing. It is possible to accurately estimate which of the above three regions is. Therefore, according to the above aspect, it is possible to accurately estimate the cetane number of the fuel while suppressing the number of executions of the fuel injection, as compared with the apparatus that repeatedly executes the fuel injection while changing the injection timing as described above. become.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows schematic structure of the cetane number estimation apparatus concerning one 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 graph which shows an example of the relationship between the amount of rotation fluctuations, the cetane number of fuel, and the injection timing. The graph which shows an example of the relationship between the detection frequency of the rotation fluctuation amount at the time of execution of fuel injection, and the cetane number of fuel. The graph which shows the other example of the relationship between the detection frequency of the rotation fluctuation amount at the time of execution of fuel injection, and the cetane number of fuel. The flowchart which shows the specific execution procedure of the estimation control process of 1st Embodiment. Explanatory drawing explaining the calculation method of rotation fluctuation amount. The flowchart which shows the specific execution procedure of the estimation control process of 2nd Embodiment.

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

  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. As the diesel engine 11, one having a plurality (four [# 1 to # 4] in this 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. In the present embodiment, the electronic control unit 40 functions as an estimation unit, a first estimation unit, and a second estimation unit.

  The fuel injection control of this 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 speed while the traveling speed of the vehicle 10 and the engine rotational speed NE are decelerated by releasing the operation of the accelerator operation member (accelerator operation amount ACC = “0”). When it falls within the range, control (so-called fuel cut control) for temporarily stopping fuel injection for operation of the diesel engine 11 is executed.

  Further, in the fuel injection control of the present embodiment, three regions of a low cetane number region, a medium cetane number region, and a high cetane number region are set in order from the lowest cetane number of the fuel, and the fuel is executed in different execution modes for each region. Injection control is executed. Specifically, for example, in the region where the cetane number is lower, the advance timing is set as the required injection timing Tst.

  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 this embodiment, in order to properly execute the fuel injection from each fuel injection valve 20 according to the operating state of the diesel engine 11, the fuel injection is performed based on the fuel pressure PQ detected by the pressure sensor 41. A correction process for forming the 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, a procedure for forming a fuel pressure fluctuation mode (in this embodiment, a detection time waveform of the fuel injection rate) at the time of execution of fuel injection will be described first.

  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, a timing at which the valve opening operation of the fuel injection valve 20 (specifically, movement of the needle valve 22 toward the valve opening side) is started (valve opening operation start timing Tos), fuel When the injection rate becomes maximum (maximum injection rate arrival time Toe), when the fuel injection rate starts to decrease (injection rate decrease start time Tcs), and when the fuel injection valve 20 is closed (specifically, the needle valve 22 The timing at which the movement toward the valve closing side is completed (valve closing operation completion timing Tce) is detected.

  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 (= Pbs− 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 the fuel injection control is executed, 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. The 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 Tst 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 required injection time Ttm is corrected, the deviation between the actual operating characteristics of the fuel injection valve 20 and the basic operating characteristics (the operating characteristics of the fuel injection valve 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, the drive control of the fuel injection valve 20 based on the required injection timing Tst and the required injection time Ttm functions as basic injection control for controlling the fuel injection mode based on the engine operating state.

  In the cetane number estimation device 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 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 this rotational fluctuation amount ΣΔNE. As the rotational fluctuation amount ΣΔNE, a larger value is detected when a large output torque is generated in the diesel engine 11.

  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 this 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. In the present embodiment, the control related to the fuel injection for estimating the cetane number of the fuel (drive control of the fuel injection valve 20) controls the injection mode of the fuel in relation to the estimation of the cetane number. Acts as a control.

  Here, in the diesel engine 11, three regions of a low cetane number region, a medium cetane number region, and a high cetane number region are set, and the basic injection control is executed in a different execution mode for each of these regions. In order to properly execute basic injection control in each region in the diesel engine 11 according to the engine operating state, it is desirable to accurately estimate which region of the fuel cetane number is in each region. . In order to estimate the cetane number of the fuel with high accuracy, fuel injection by auxiliary injection control is executed in a situation where the degree of change in the rotational fluctuation amount ΣΔNE (hereinafter referred to as torque sensitivity) increases when the cetane number changes. It is desirable.

  FIG. 6 shows the relationship between the rotational fluctuation amount ΣΔNE, the cetane number of the fuel, and the injection timing obtained based on the results of various experiments and simulations by the inventors.

  As shown in FIG. 6, it has been confirmed by the inventors that the injection timing at which the torque sensitivity is maximized becomes a retarded timing as the cetane number of the fuel increases. In FIG. 6, the slopes of the lines L1 to L6 are values corresponding to torque sensitivity. For example, at the boundary BL between the low cetane number region and the medium cetane number region, the torque sensitivity is greatest when fuel injection is performed at the injection timing corresponding to the line L3 among the lines L1 to L6. On the other hand, at the boundary BH between the medium cetane number region and the high cetane number region, the fuel was injected at the injection timing corresponding to the line L5, that is, the injection timing that is retarded from the injection timing corresponding to the line L3. In this case, the torque sensitivity is the highest.

In this embodiment based on such a situation, when estimating the cetane number at the boundary BL between the low cetane number region and the medium cetane number region, the control target value of the injection timing in the auxiliary injection control (target injection timing TQstA), A relatively advanced injection timing at which the torque sensitivity increases at the boundary BL is set. Further, when estimating the cetane number at the boundary BH between the medium cetane number region and the high cetane number region, the control target value (target injection timing TQstB) of the injection timing in the auxiliary injection control is retarded from the target injection timing TQstA. The injection timing at which the torque sensitivity increases at the boundary BH is set. In the present embodiment, when estimating the cetane number at the boundary BL, the target injection timing TQstA is a target injection timing corresponding to the boundary BL, and the target injection timing TQstB is a non- target injection timing corresponding to another boundary BH. is there. Then, in estimating the cetane number at the boundary BL, each target is set such that the torque sensitivity at the time of executing fuel injection at the target injection timing TQstA is larger than the torque sensitivity when it is assumed that fuel injection is executed at the target injection timing TQstB. Injection timings TQstA and TQstB are set. In estimating the cetane number at the boundary BH, the target injection timing TQstB is a target injection timing corresponding to the boundary BH, and the target injection timing TQstA is a non- target injection timing corresponding to another boundary BL. Then, in estimating the cetane number at the boundary BH, each target is set such that the torque sensitivity at the time of executing the fuel injection at the target injection timing TQstB is larger than the torque sensitivity when it is assumed that the fuel injection is executed at the target injection timing TQstA. Injection timings TQstA and TQstB are set.

  Further, even when fuel injection is executed under the same situation of the cetane number of fuel and the injection amount, the output torque of the diesel engine 11 generated with fuel injection increases as the engine speed NE increases. (Specifically, the rotational fluctuation amount ΣΔNE, which is the index value) becomes smaller. This is because the higher the engine speed NE, the earlier the temperature and pressure in the cylinder 16 decrease, so that part of the fuel burns in a low-temperature and low-pressure state, and the fuel remains unburned. It is thought that this is because of the increase. For this reason, the rotational fluctuation amount ΣΔNE detected at the time of execution of fuel injection at a predetermined amount changes in accordance with the engine rotational speed NE at the time of execution of fuel injection in addition to changing according to the cetane number of fuel. It can be said. Such a difference in the rotational fluctuation amount ΣΔNE due to the difference in the engine rotational speed NE causes a decrease in estimation accuracy when the cetane number is estimated based on the rotational fluctuation amount ΣΔNE.

  Here, even when the fuel injection is performed under the condition where the cetane number of the fuel and the injection amount are the same, the rotation fluctuation amount ΣΔNE becomes smaller as the fuel injection timing is the retarded timing. Get smaller. This is considered to be because the fuel burns when the temperature and pressure in the cylinder 16 are low as the injection timing is retarded, and the amount of unburned fuel increases. Therefore, by setting the injection timing according to the engine speed NE, it is possible to execute fuel injection by auxiliary injection control so that the variation in the rotational fluctuation amount ΣΔNE due to the difference in the engine speed NE can be suppressed. It can be said.

  In view of this point, in this embodiment, the injection timing in the auxiliary injection control is set based on the engine rotational speed NE. Specifically, the target injection timing TQstA at the time of execution of estimation of the cetane number at the boundary BL on the low cetane number side is an injection timing as close as possible to the injection timing at which the torque sensitivity is highest at the boundary BL, and the engine speed An injection timing is set at which variation in the rotational fluctuation amount ΣΔNE due to the difference in speed NE is suppressed. Further, the target injection timing TQstB at the time of execution of estimation of the cetane number at the boundary BH on the high cetane number side is an injection timing as close as possible to the injection timing at which the torque sensitivity is highest at the boundary BH, and the engine speed. An injection timing is set at which variation in the rotational fluctuation amount ΣΔNE due to the difference in NE is suppressed. In the present embodiment, the relationship between the target injection timing TQstA and the engine speed NE described above is obtained in advance based on the results of various experiments and simulations, and the relationship is stored in the electronic control unit 40 as the operation map L. Yes. The target injection timing TQstA is set based on the engine rotation speed NE based on the calculation map L. Similarly, the relationship between the target injection timing TQstB and the engine speed NE described above is obtained in advance based on the results of various experiments and simulations, and the relationship is stored in the electronic control unit 40 as the operation map H. The target injection timing TQstB is set based on the engine speed NE based on the calculation map H.

  In the estimation control of this embodiment, the estimation of the cetane number at the boundary BL is executed as follows. That is, first, fuel injection at a predetermined target injection timing TQstA is executed as auxiliary injection control, and a rotational fluctuation amount ΣΔNE at the time of execution is detected. Based on the rotational fluctuation amount ΣΔNE, it is estimated whether the cetane number of the fuel is greater than or less than the boundary BL between the low cetane number region and the medium cetane number region and less than the boundary BL. In this estimation, it is determined that the cetane number of the fuel is less than the boundary BL when the rotational fluctuation amount ΣΔNE is smaller than a predetermined low cetane number determination value JL, and the rotational fluctuation amount ΣΔNE is greater than or equal to the low cetane number determination value JL. At some point, it is determined that the cetane number of the fuel is not less than the boundary BL. In the present embodiment, a determination value that can accurately determine whether the cetane number of the fuel is less than the boundary BL or greater than or equal to the boundary BL based on the results of various experiments and simulations. The same value is obtained and stored in the electronic control unit 40 as the low cetane number determination value JL.

  In the present embodiment, the fuel injection for estimating whether the cetane number of the fuel is greater than or less than the boundary BL between the low cetane number region and the medium cetane number region and less than the boundary BL is the target injection timing TQstA, that is, cetane. It is executed at a relatively advanced time suitable for a low-value situation. Therefore, fuel injection by the auxiliary injection control can be executed at the injection timing when the torque sensitivity becomes high in the vicinity of the boundary BL, and the above estimation is accurately performed based on the index value of the engine torque generated along with the execution of the fuel injection. Will be able to.

  FIG. 7 shows the result of detecting the rotational fluctuation amount ΣΔNE while performing fuel injection at the target injection timing TQstA using three types of fuel, low cetane number fuel, medium cetane number fuel, and high cetane number fuel. An example is shown.

As shown in FIG. 7, in this example, since fuel injection is executed at the target injection timing TQstA at which the torque sensitivity becomes high at the boundary BL, the rotational fluctuation amount ΣΔNE detected when the low cetane number fuel is used and the medium cetane The interval between the rotational fluctuation amount ΣΔNE detected when the valence fuel is used is longer. Therefore, the low cetane number judgment value JL is easily set between the range in which the rotational fluctuation amount ΣΔNE is detected when the low cetane number fuel is used and the range in which the rotational fluctuation amount ΣΔNE is detected when the medium cetane number fuel is used. Therefore, it is possible to accurately determine the fuel cetane number based on the determination value JL. Incidentally, in the example shown in FIG. 7, the interval between the rotational fluctuation amount ΣΔNE detected when the medium cetane number fuel is used and the rotational fluctuation amount ΣΔNE detected when the high cetane number fuel is used is short.
In the present embodiment, the target injection timing TQstA is set based on the engine speed NE. Therefore, the target injection timing TQstA can be set so that the variation in the rotational fluctuation amount ΣΔNE caused by the difference in the engine rotational speed NE can be suppressed. Therefore, the estimation of the cetane number based on the rotational fluctuation amount ΣΔNE can be accurately performed. Be able to run.

  Further, in the estimation control of the present embodiment, estimation of the cetane number at the boundary BH is executed as follows. That is, first, fuel injection at a predetermined target injection timing TQstB is executed as auxiliary injection control, and a rotational fluctuation amount ΣΔNE at the time of execution is detected. Based on the rotational fluctuation amount ΣΔNE, it is estimated whether the cetane number of the fuel is greater than or less than the boundary BH between the medium cetane number region and the high cetane number region and less than the boundary BH. In this estimation, it is determined that the cetane number of the fuel is less than the boundary BH when the rotational fluctuation amount ΣΔNE is smaller than a predetermined high cetane number determination value JH, and the rotational fluctuation amount ΣΔNE is greater than or equal to the high cetane number determination value JH. At some point, it is determined that the cetane number of the fuel is greater than or equal to the boundary BH. In the present embodiment, a determination value that can accurately determine whether the cetane number of the fuel is less than the boundary BH or more than the boundary BH is obtained in advance based on the results of various experiments and simulations. The same value is stored in the electronic control unit 40 as the high cetane number determination value JH.

  In the present embodiment, the fuel injection for estimating whether the cetane number of the fuel is greater than or equal to the boundary BH between the medium cetane number region and the high cetane number region and less than the boundary BH is the target injection timing TQstB, that is, cetane. It is executed at a relatively retarded angle suitable for high-value situations. Therefore, fuel injection by the auxiliary injection control can be executed at the injection timing when the torque sensitivity becomes high in the vicinity of the boundary BH, and the above estimation is accurately performed based on the index value of the engine torque generated along with the execution of the fuel injection. Will be able to.

  FIG. 8 shows the result of detecting the rotational fluctuation amount ΣΔNE while performing fuel injection at the target injection timing TQstB separately using three types of fuel, low cetane number fuel, medium cetane number fuel, and high cetane number fuel. An example is shown.

  As shown in FIG. 8, in this example, since fuel injection is executed at the target injection timing TQstB where the torque sensitivity becomes high at the boundary BH, the rotational fluctuation amount ΣΔNE detected when the medium cetane number fuel is used and the high cetane number The interval between the rotational fluctuation amount ΣΔNE detected when the fuel is used is longer. Therefore, the high cetane number judgment value JH is easily set between the range in which the rotational fluctuation amount ΣΔNE is detected when the medium cetane number fuel is used and the range in which the rotational fluctuation amount ΣΔNE is detected when the high cetane number fuel is used. Therefore, it is possible to accurately determine the cetane number of the fuel based on the determination value JH. Incidentally, in the example shown in FIG. 8, the interval between the rotational fluctuation amount ΣΔNE detected when the low cetane number fuel is used and the rotational fluctuation amount ΣΔNE detected when the medium cetane number fuel is used is short.

  In the present embodiment, the target injection timing TQstB is set based on the engine speed NE. Therefore, the target injection timing TQstB can be set so that the variation in the rotational fluctuation amount ΣΔNE caused by the difference in the engine rotational speed NE can be suppressed, so that the estimation of the cetane number based on the rotational fluctuation amount ΣΔNE can be accurately performed. Be able to run.

  In the estimation control of this embodiment, when the rotational fluctuation amount ΣΔNE at the time of execution of fuel injection at the target injection timing TQstA is less than the low cetane number determination value JL, it is determined that the cetane number of the fuel is in the low cetane number region. . On the other hand, the rotational fluctuation amount ΣΔNE at the time of execution of fuel injection at the target injection timing TQstA is equal to or higher than the low cetane number determination value JL, and the rotational fluctuation amount ΣΔNE at the time of execution of fuel injection at the target injection timing TQstB is high. When it is less than the determination value JH, it is determined that the cetane number of the fuel is in the medium cetane number region. On the other hand, if the rotational fluctuation amount ΣΔNE during execution of fuel injection at the target injection timing TQstB is equal to or higher than the high cetane number determination value JH, it is determined that the cetane number of the fuel is in the high cetane number region.

  In the above estimation control, based on the result estimated together with the execution of fuel injection at the target injection timing TQstA and the result estimated with the execution of fuel injection at the target injection timing TQstB that is retarded from the target injection timing TQstA, Which of the three regions is the cetane number of is estimated with high accuracy. In other words, it is possible to accurately determine which of the three regions the cetane number of the fuel is by executing only the fuel injection at the target injection timing TQstA and the fuel injection at the target injection timing TQstB. . Therefore, the cetane number of the fuel can be accurately estimated while suppressing the number of executions of the fuel injection by the auxiliary injection control, as compared with the device that performs many fuel injections at different injection timings as described above.

Further, in the estimation control of the present embodiment, of the cetane number estimation performed separately at each boundary BL, BH, the cetane number estimation at the low cetane number side boundary BL is performed as the cetane number at the high cetane number side boundary BH . This is executed prior to estimation.

  If fuel having a low cetane number is supplied to the diesel engine 11 in a state where basic injection control suitable for a high cetane number is being performed, the combustion state of the fuel may deteriorate and cause misfire. According to this embodiment, at the start of execution of estimation of the cetane number of fuel by estimation control, first, estimation of the cetane number for the boundary BL on the low cetane number side can be performed, so that fuel is replenished. For example, when the low cetane number fuel is supplied to the diesel engine 11, this can be grasped early. Therefore, the execution of engine control suitable for a low cetane number can be started early, and the cetane number of the fuel supplied to the diesel engine 11 has changed from a high cetane number region or a medium cetane number region to a low cetane number region. The occurrence of misfire caused by this can be suitably suppressed.

  Hereinafter, the execution procedure of the process related to the estimation control (estimation control process) will be described in detail.

  FIG. 9 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. 9, 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] The execution completion flag is turned off.

  If the execution condition is not satisfied (step S201: NO), the process is temporarily terminated without executing the processes of the following steps S202 to S217, that is, the process of estimating the cetane number of the fuel.

  Thereafter, when this process is repeatedly executed and the above execution condition is satisfied (step S201: YES), it is determined whether or not the low cetane completion flag is turned off (step S202). The low cetane completion flag is turned off when the operation switch is turned on to start the operation of the diesel engine 11, while the cetane number is estimated at the low cetane number side boundary BL (steps S203 to S203). This flag is turned on when the execution of S207) is completed. Since the low cetane completion flag is turned off, it is determined that the estimation of the cetane number at the boundary BL on the low cetane number side is not yet completed after the operation of the diesel engine 11 is started.

  When the low cetane completion flag is turned off (step S202: YES), execution of processing for estimating the cetane number at the boundary BL is started.

  That is, first, the target injection timing TQstA is set from the calculation map L based on the engine speed NE (step S203). Thereafter, the target injection timing TQstA and the control target value (target injection time TQtm) of the predetermined fuel injection time are corrected by the correction terms K1 and K2 calculated by the correction processing described above (step S204). Specifically, a value obtained by adding the correction term K1 to the target injection time TQstA is set as a new target injection time TQstA, and a value obtained by adding the correction term K2 to the target injection time TQtm is set as a new target injection time TQtm. The

  Then, drive control of the fuel injection valve 20 based on the target injection timing TQstA and the target injection time TQtm is executed, and fuel injection from the fuel injection valve 20 is executed (step S205). In the present embodiment, fuel injection in the auxiliary injection control 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]). Executed. Similarly, the correction terms K1 and K2 used in the present processing are also set to predetermined ones of the fuel injection valves 20 (in this embodiment, the fuel injection valves 20 attached to the cylinder 16 [# 1]). Correspondingly calculated values are used.

  Thereafter, the rotational fluctuation amount ΣΔNE is detected and stored as an index value of the output torque of the diesel engine 11 generated by the fuel injection (step S206). Specifically, the rotation fluctuation amount ΣΔNE is detected as follows. As shown in FIG. 10, 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 (in this embodiment, three times). A difference ΔNE (= NE−NEi) from the engine rotational speed NEi detected before the rotation) is calculated. Then, an integrated value (a value corresponding to the area of the hatched portion in FIG. 10) 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 transition of the engine speed NE and the difference ΔNE shown in FIG. 10 is slightly different from the actual transition because it is shown in a simplified manner for easy understanding of the calculation method of the rotational fluctuation amount ΣΔNE.

  After the rotational fluctuation amount ΣΔNE is detected in this way, it is determined whether the rotational fluctuation amount ΣΔNE is less than the low cetane number determination value JL (step S207 in FIG. 9). If the rotational fluctuation amount ΣΔNE is less than the low cetane number determination value JL (step S207: YES), it is determined that the cetane number of the fuel at this time is in the low cetane number region (see FIG. 6) (step S207). (S208) After that, the basic injection control is executed in a manner commensurate with a low cetane number fuel. In this case, after the execution completion flag is turned on (step S209), this process is temporarily terminated. The execution completion flag is a flag that is turned off when the operation switch is turned on to start the operation of the diesel engine 11. When the execution completion flag is turned on, it is determined that the estimation of the cetane number is completed after the diesel engine 11 is started. In this process, when the execution completion flag is turned on, the [condition C] is not satisfied (step S201: NO), and the subsequent processes (steps S202 to S217) are not executed. Therefore, in the present embodiment, when it is determined that the cetane number region at the boundary BL is a low cetane number region, a process of estimating the cetane number at the boundary BH between the medium cetane number region and the high cetane number region is executed. The cetane number region is determined.

  On the other hand, when the rotational fluctuation amount ΣΔNE is greater than or equal to the low cetane number determination value JL (step S207: NO), the cetane number of the fuel at this time is either the medium cetane number region or the high cetane number region (see FIG. 6). If the low cetane determination flag is turned on (step S210), the process is temporarily terminated. In this case, since the determination completion flag is not turned on (the process of step S209 is jumped), [Condition C] remains established.

  Therefore, in this case, if the condition other than the execution condition [condition c] is satisfied (step S201: YES), the low cetane completion flag is turned on (step S202: NO), execution of the process for estimating the cetane number at the boundary BH on the high cetane number side (the process of steps S211 to S217) is started.

  That is, first, the target injection timing TQstB is set from the calculation map H based on the engine speed NE (step S211). Thereafter, the target injection timing TQstB and the predetermined target injection time TQtm are corrected by the correction terms K1 and K2 calculated by the correction process described above (step S212). Specifically, a value obtained by adding the correction term K1 to the target injection time TQstB is set as a new target injection time TQstB, and a value obtained by adding the correction term K2 to the target injection time TQtm is set as a new target injection time TQtm. The

  Then, drive control of the fuel injection valve 20 based on the target injection timing TQstB and the target injection time TQtm is executed, and fuel injection from the fuel injection valve 20 is executed (step S213).

  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 S214), and the rotational fluctuation amount ΣΔNE is less than the high cetane number determination value JH. Is determined (step S215).

  If the rotational fluctuation amount ΣΔNE is less than the high cetane number determination value JH (step S215: YES), it is determined that the cetane number of the fuel at this time is in the medium cetane number region (see FIG. 6) (step S215). S216), and thereafter, the basic injection control is executed in a mode commensurate with the medium cetane number fuel. On the other hand, if the rotational fluctuation amount ΣΔNE is greater than or equal to the high cetane number determination value JH (step S215: NO), it is determined that the cetane number of the fuel at this time is in the high cetane number region (see FIG. 6) (step S215). S217) After that, the basic injection control is executed in a manner commensurate with the high cetane number fuel. Then, after estimating whether the cetane number of the fuel is in the medium cetane number region or the high cetane number region based on the rotational fluctuation amount ΣΔNE, the execution completion flag is turned on (step S209), and this process is temporarily performed. Is terminated.

  As described above, according to the present embodiment, the following effects can be obtained.

  (1) The cetane number of the fuel is a boundary based on the rotational fluctuation amount ΣΔNE detected by executing fuel injection at a predetermined injection amount and injection timing as auxiliary injection control corresponding to each boundary BL, BH. (BL or BH) is estimated to be greater than or less than the boundary. Further, as the target injection timing (TQstA or TQstB) in the auxiliary injection control, the timing on the retard side is set as the cetane number estimation target is a higher cetane number side value. Therefore, it becomes possible to execute the fuel injection corresponding to each of the boundaries BL and BH in a situation where the torque sensitivity becomes large, and the above estimation based on the rotational fluctuation amount ΣΔNE detected when the fuel injection is executed is high. Can be done with precision. Therefore, by executing fuel injection corresponding to each boundary BL, BH, it is possible to estimate which of the three regions the cetane number of the fuel is, while changing the injection timing as described above. Compared to a device that repeatedly executes fuel injection, the cetane number of fuel can be accurately estimated while suppressing the number of times fuel injection is performed.

(2) Of the cetane number estimations performed separately for the boundaries BL and BH, the cetane number estimation at the low cetane number side boundary BL is executed prior to the cetane number estimation at the high cetane number side boundary BH. I did it. Therefore, at the start of execution of estimation of the cetane number of the fuel, first, the cetane number can be estimated for the boundary BL on the low cetane number side. Can be grasped at an early stage when the engine is supplied to the diesel engine 11. Therefore, the execution of engine control suitable for a low cetane number can be started early, and the cetane number of the fuel supplied to the diesel engine 11 has changed from a high cetane number region or a medium cetane number region to a low cetane number region . The occurrence of misfire caused by this can be suitably suppressed.

  (3) The target injection timing TQstA is set based on the engine rotation speed NE based on the calculation map L, and the target injection timing TQstB is set based on the engine rotation speed NE based on the calculation map H. Therefore, since it is possible to set the injection timing so that the variation in the rotational fluctuation amount ΣΔNE caused by the difference in the engine rotational speed NE can be suppressed, the estimation of the cetane number based on the rotational fluctuation amount ΣΔNE is accurately executed. Will be able to.

  (4) Based on the result estimated together with the execution of fuel injection at the target injection timing TQstA and the result estimated with the execution of fuel injection at the target injection timing TQstB retarded from the target injection timing TQstA, It is possible to accurately estimate which of the three regions the valence is. Therefore, the cetane number of the fuel can be accurately estimated while suppressing the number of executions of the fuel injection by the auxiliary injection control, as compared with the device that performs many fuel injections at different injection timings as described above.

(Second Embodiment)
Hereinafter, the cetane number estimation apparatus according to the second embodiment embodying the present invention will be described focusing on differences from the first embodiment.

  The cetane number estimation apparatus of this embodiment differs from the cetane number estimation apparatus of the first embodiment in the execution mode of estimation control.

  Hereinafter, the execution mode of the estimation control of this embodiment will be described. In addition, since the structure of the cetane number estimation apparatus of this embodiment is the same as the cetane number estimation apparatus of 1st Embodiment, detailed description is abbreviate | omitted.

  In the estimation control of the present embodiment, first, fuel injection is performed at a predetermined injection timing (target injection timing TQstC). The target injection timing TQstC is an injection timing (for example, an injection timing corresponding to the line L3 in FIG. 6) with a certain degree of torque sensitivity regardless of the cetane number fuel used, and the engine speed. The injection timing at which the variation in the rotational fluctuation amount ΣΔNE due to the difference in NE is suppressed is set. In the present embodiment, the relationship between the target injection timing TQstC and the engine speed NE is obtained in advance based on the results of various experiments and simulations, and the relationship is stored in the electronic control unit 40 as the operation map V. The target injection timing TQstC is set based on the engine speed NE based on this calculation map V.

  Then, the rotational fluctuation amount ΣΔNE is detected as an index value of the engine torque generated when the fuel injection is executed at the target injection timing TQstC, and the cetane number is calculated from the calculation map VS based on the rotational fluctuation amount ΣΔNE. A provisional value (provisional cetane number) is obtained. In the present embodiment, the relationship between the rotational fluctuation amount ΣΔNE and the temporary cetane number is obtained in advance based on the results of experiments and simulations, and the relationship is stored in the electronic control unit 40 as the operation map VS.

  In the estimation control of the present embodiment, by executing fuel injection at the injection timing (the target injection timing TQstC) at which torque sensitivity is increased to some extent regardless of the cetane number, the rotational fluctuation amount ΣΔNE at that time is executed. Therefore, the cetane number of the fuel at this time can be detected with a certain degree of high detection accuracy.

  Thereafter, the target injection timing TQstD is set based on the temporary cetane number and the engine speed NE, and fuel injection at the target injection timing TQstD is executed. More specifically, the target injection timing TQstD is an injection timing that is as close as possible to the injection timing at which the torque sensitivity is highest when the cetane number of the fuel is the temporary cetane number, and the amount of rotational fluctuation due to the difference in the engine rotational speed NE. The injection timing at which the variation in ΣΔNE is suppressed is set. In the present embodiment, the relationship among the target injection timing TQstD, the temporary cetane number, and the engine speed NE is obtained in advance based on the results of various experiments and simulations, and the relationship is stored in the electronic control unit 40 as the operation map R. Has been. The target injection timing TQstD is set based on the engine speed NE based on this calculation map R.

  Then, the rotational fluctuation amount ΣΔNE at the time of execution of fuel injection at the target injection timing TQstD is detected, and an estimated value (estimated cetane number) for the cetane number is calculated from the operation map RS based on the rotational fluctuation amount ΣΔNE. Desired. In the present embodiment, the relationship between the rotational fluctuation amount ΣΔNE and the estimated cetane number is obtained in advance based on the results of experiments and simulations, and the relationship is stored in the electronic control unit 40 as the operation map RS.

  In the estimation control of the present embodiment, the injection timing (target injection timing TQstD) at which the torque sensitivity becomes large when the temporary cetane number is a value close to the actual cetane number is set, and the fuel at the target injection timing TQstD is set. Injection can be performed. Therefore, the actual cetane number at that time can be detected with high accuracy based on the rotational fluctuation amount ΣΔNE when the fuel injection is performed.

  As described above, in the estimation control of the present embodiment, the cetane number of the fuel at this time can be roughly specified as the temporary cetane number through the fuel injection at the predetermined target injection timing TQstC. Then, by executing fuel injection at the target injection timing TQstD set based on this temporary cetane number, the cetane number of the fuel at this time can be detected with high accuracy.

  Hereinafter, the execution procedure of the process (estimation control process) concerning the estimation control of the present embodiment will be described in detail.

  FIG. 11 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. 11, in this process, it is first determined whether or not an execution condition is satisfied (step S301). Here, it is determined that the execution condition is satisfied when all of [Condition A] to [Condition C] are satisfied.

  If the execution condition is not satisfied (step S301: NO), the process is temporarily terminated without executing the processes of the following steps S302 to S314, that is, the process of estimating the cetane number of the fuel.

  Thereafter, when this process is repeatedly executed and the execution condition is satisfied (step S301: YES), it is determined whether or not the pre-determination completion flag is turned off (step S302). The pre-determination completion flag is turned off when the operation switch is turned on to start operation of the diesel engine 11, while the process for calculating the temporary cetane number (steps S303 to S307) is completed. This flag is turned on. Since the pre-determination completion flag is turned off, it is determined that the calculation of the temporary cetane number has not yet been completed after the operation of the diesel engine 11 is started.

  When the pre-determination completion flag is turned off (step S302: YES), execution of the process for calculating the temporary cetane number is started.

  That is, first, the target injection timing TQstC is set from the calculation map V based on the engine speed NE (step S303). Thereafter, the target injection timing TQstC and the control target value (target injection time TQtm) of the predetermined fuel injection time are corrected by the correction terms K1 and K2 calculated by the correction processing described above (step S304). Specifically, a value obtained by adding the correction term K1 to the target injection time TQstC is set as a new target injection time TQstC, and a value obtained by adding the correction term K2 to the target injection time TQtm is set as a new target injection time TQtm. The

  Then, drive control of the fuel injection valve 20 based on the target injection timing TQstC and the target injection time TQtm is executed, and fuel injection from the fuel injection valve 20 is executed (step S305). In the present embodiment, fuel injection in the auxiliary injection control 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]). Executed. Similarly, the correction terms K1 and K2 used in the present processing are also set to predetermined ones of the fuel injection valves 20 (in this embodiment, the fuel injection valves 20 attached to the cylinder 16 [# 1]). Correspondingly calculated values are used.

  Thereafter, the rotational fluctuation amount ΣΔNE at the time of execution of the fuel injection is calculated and stored (step S306), and a temporary cetane number is calculated from the calculation map VS based on the rotational fluctuation amount ΣΔNE. (Step S307). Then, after the pre-determination flag is turned on (step S308), this process is temporarily ended.

When the pre-judgment completion flag is turned on (step S302: NO ), execution of processing for calculating the estimated cetane number (steps S309 to S314) is started.

  That is, first, the target injection timing TQstD is set from the calculation map R based on the engine speed NE (step S309). Thereafter, the target injection timing TQstD and the predetermined target injection time TQtm are corrected by the correction terms K1 and K2 calculated by the correction processing described above (step S310). Specifically, a value obtained by adding the correction term K1 to the target injection time TQstD is set as a new target injection time TQstD, and a value obtained by adding the correction term K2 to the target injection time TQtm is set as a new target injection time TQtm. The

  Then, drive control of the fuel injection valve 20 based on the target injection timing TQstD and the target injection time TQtm is executed, and fuel injection from the fuel injection valve 20 is executed (step S311).

  Thereafter, the rotational fluctuation amount ΣΔNE is detected and stored as an index value of the output torque of the diesel engine 11 generated by the fuel injection (step S312), and based on the rotational fluctuation amount ΣΔNE, the calculation map RS is used. An estimated cetane number is calculated (step S313). Then, after the execution completion flag is turned on (step S314), this process is temporarily ended. The execution completion flag is a flag that is turned off when the operation switch is turned on to start the operation of the diesel engine 11. When the execution completion flag is turned on, it is determined that the estimation of the cetane number is completed after the diesel engine 11 is started. In this process, when the execution completion flag is turned on, [Condition C] is not satisfied (step S301: NO), and the subsequent processes (steps S302 to S314) are not executed. Therefore, in the present embodiment, the estimation of the estimated cetane number is performed only once every time the operation switch is turned on to start the operation of the diesel engine 11.

(Other embodiments)
Each of the above embodiments may be modified as follows.

  ・ EGR control, pilot injection control, etc. may be executed instead of or in addition to adopting basic injection control as engine control executed separately in each of the three regions divided by the cetane number of fuel Good. In short, any engine control that changes the combustion state of the fuel can be employed as such engine control executed separately.

  In the first embodiment, instead of setting the target injection timing TQstA (or target injection timing TQstB) based on the engine speed NE, the low cetane number determination value JL (or high cetane number determination value JH) is corrected. You may make it do. In the second embodiment, instead of setting the target injection timing TQstC based on the engine rotational speed NE, the calculation map VS used for calculating the temporary cetane number is corrected, or the target injection timing is based on the engine rotational speed NE. Instead of setting TQstD, the calculation map RS used for calculating the estimated cetane number may be corrected. Furthermore, in each embodiment, instead of setting the target injection timing (TQstA, TQstB, TQstC, TQstD) based on the engine rotational speed NE, the rotational fluctuation amount ΣΔNE may be corrected.

  The configuration for setting the target injection timing (TQstA, TQstB, TQstC, TQstD) based on the engine speed NE may be omitted. Specifically, a fixed time is set as the target injection timings TQstA and TQstB of the first embodiment and the target injection timing TQstC of the second embodiment, or the target injection timing TQstD of the second embodiment is determined by the engine speed NE. And can be set based only on the provisional cetane number.

  In such a configuration, it is desirable to set the injection timing at which the torque sensitivity is greatest at the boundary BL as the target injection timing TQstA. Further, as the target injection timing TQstB, it is desirable to set the injection timing at which the torque sensitivity is greatest at the boundary BH. Furthermore, as the target injection timing TQstD, it is desirable to set an injection timing at which the torque sensitivity is maximized when the cetane number of the fuel is a value corresponding to the temporary cetane number. According to such a configuration, fuel injection by auxiliary injection control can be executed in a situation where torque sensitivity is maximized, so that estimation of the cetane number based on the rotational fluctuation amount ΣΔNE can be executed more accurately. .

  -The cetane number estimation device of each embodiment is also configured in a device in which four or more regions divided by the cetane number of fuel are set and engine control is performed in different execution modes for each region. It can be applied with appropriate changes. When applied to the first embodiment, the cetane number of the fuel may be estimated as follows. That is, fuel injection at a predetermined injection amount and injection timing is executed corresponding to each boundary, and the rotational fluctuation amount ΣΔNE at the time of execution is detected, and the fuel cetane is determined based on the rotational fluctuation amount ΣΔNE. Estimate whether the valence is greater than or less than the boundary. Based on the estimation results, it is determined which of the above four regions the cetane number of the fuel is. In this case, when the boundary to be estimated has a higher cetane number side value, the retarded timing is set as the target injection timing, thereby increasing the torque sensitivity of the fuel injection corresponding to each boundary. Can be executed in Therefore, the above estimation based on the rotational fluctuation amount ΣΔNE detected when these fuel injections are performed can be performed with high accuracy.

  In the case of an internal combustion engine that does not show a tendency that the injection timing at which the torque sensitivity becomes higher as the fuel cetane number becomes higher when the auxiliary injection control is executed, the timing at which the retarded side is retarded, the higher the cetane number side boundary, the auxiliary injection control It is not necessary to adopt a configuration in which the retard side timing is set as the target injection timing. In this case, assuming that the target injection timing corresponding to the boundary to be estimated is the target injection timing and the target injection timing corresponding to the other boundaries is the non-target injection timing, the fuel injection time at the target injection timing is The target injection timing corresponding to each boundary may be set so that the torque sensitivity at is higher than the torque sensitivity when it is assumed that the fuel injection is executed at the non-target injection timing. Further, as each target injection timing in this case, it is desirable to set an injection timing at which the torque sensitivity is highest at the boundary to be estimated (or an injection timing as close as possible to the same injection timing).

  -In a device in which four or more regions divided by the cetane number of fuel are set, that is, a device in which three or more boundaries are set, the target injection timing corresponding to at least two of the boundaries However, if different timings are set in the above-described manner, the same injection timing can be set as the target injection timing corresponding to a plurality of boundaries.

  The configuration for correcting the target injection timing (TQstA, TQstB, TQstC, TQstD) and the target 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 detected, and a difference between these speeds is calculated. The difference can be used as the index value.

  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.

  Instead 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 on which the clutch mechanism 13 and the manual transmission 14 are mounted, but also to a vehicle on which a torque converter and an automatic transmission are mounted. . 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 that employs a lock converter with a built-in lock-up clutch, [Condition D] that the lock-up clutch is not engaged is newly set and the [Condition D] 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 (8)

The basic injection control for controlling the fuel injection mode based on the engine operating state and the auxiliary injection control for controlling the fuel injection mode in relation to the estimation of the fuel cetane number are executed and separated from each other with respect to the fuel cetane number. In addition, it is applied to a diesel engine in which three or more regions are set and engine control is executed in different execution modes for each region, and the fuel cetane number is any of the regions A cetane number estimation device for estimating
Corresponding to each of a plurality of boundaries that divide the plurality of regions, fuel injection at a predetermined injection amount and injection timing is executed as the auxiliary injection control, and an index value of the engine torque generated by the execution is set. An estimator that detects and estimates whether the cetane number of the fuel is greater than or less than the boundary and less than the boundary based on the detected index value;
The degree of change in the engine torque when the cetane number of the fuel is changed is defined as torque sensitivity, the injection timing corresponding to the estimation target boundary is set as the target injection timing, and the injection timing corresponding to other boundaries is not set as target. Assuming the injection time
The estimation unit is configured to cause the torque sensitivity when the fuel injection is performed at the target injection timing to be greater than the torque sensitivity when it is assumed that the fuel injection is performed at the non-target injection timing. The cetane number estimation device, wherein the target injection timing corresponding to each of the above is set. The cetane number estimation apparatus according to claim 1,
The estimator for estimating a cetane number is characterized in that the estimation unit sets the timing on the retard side as the predetermined injection timing when the boundary to be estimated is a value on the high cetane number side. In the cetane number estimation apparatus according to claim 1 or 2,
The estimator for estimating a cetane number, wherein the estimation unit executes the estimation of a boundary on the lowest cetane number side among the plurality of boundaries prior to the estimation of other boundaries. In the cetane number estimating device according to any one of claims 1 to 3,
The estimation unit uses an injection timing calculated based on the engine rotation speed based on a relationship between a predetermined engine rotation speed and an injection timing as the predetermined injection timing. Cetane number estimation device. In the cetane number estimation apparatus according to any one of claims 1 to 4,
The estimation unit determines that the cetane number of fuel is less than the boundary when the index value is smaller than a predetermined determination value corresponding to each of the plurality of boundaries, and the index value is determined by the determination A cetane number estimation device for determining that the cetane number of a fuel is greater than or equal to the boundary when the value is greater than or equal to a value. In the cetane number estimating device according to any one of claims 1 to 5,
The diesel engine is mounted on a vehicle as a drive source,
The estimation unit performs fuel injection at the predetermined injection amount and injection timing on the condition that fuel cut is performed during deceleration operation of the vehicle. Price estimation device. In the cetane number estimating device according to any one of claims 1 to 6,
The cetane number estimation device, wherein the engine control is the basic injection control. In the cetane number estimating device according to any one of claims 1 to 7,
The plurality of regions include a low cetane number region, a medium cetane number region and a high cetane number region,
The estimation unit includes
Fuel injection at a predetermined first injection timing is executed as the auxiliary injection control, an index value of engine torque generated along with the execution is detected, and the cetane number of the fuel is calculated based on the detected index value. A first estimation unit that estimates whether the boundary between the low cetane number region and the medium cetane number region is greater than or less than the boundary;
The fuel injection is executed at the second injection timing that is retarded from the first injection timing, which is predetermined as the auxiliary injection control, and the index value of the engine torque generated by the execution is detected, and the detected index value And a second estimation unit that estimates whether the cetane number of the fuel is greater than or less than the boundary between the medium cetane number region and the high cetane number region, and a cetane number, Estimating device.

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