JP6087726B2 - Fuel injection characteristic detection device - Google Patents

Description

  The present invention relates to a fuel injection characteristic detection device that detects an operation characteristic of a fuel injection valve based on a detection result of a fuel pressure in a fuel supply system.

  The internal combustion engine is attached with a fuel supply system constituted by a pressure accumulating container to which fuel in a pressurized state is supplied, a fuel injection valve, a connection passage connecting the pressure accumulating container and the fuel injection valve, and the like.

  In recent years, a device has been proposed in which a pressure sensor for detecting the fuel pressure inside the fuel supply system is provided, and the operating characteristic of the fuel injection valve is detected based on the fuel pressure detected by the pressure sensor (Patent Document 1). reference). The fuel pressure in the fuel supply system temporarily decreases with the opening and closing of the fuel injection valve so that the fuel pressure decreases with the opening of the fuel injection valve and recovers with the subsequent valve closing drive. To drop. In the above apparatus, such fuel pressure is detected, and the operating characteristic of the fuel injection valve is detected based on the detection result.

JP 2009-57925 A

  In the apparatus of the above-mentioned patent document 1, as a calculation process for detecting the operation characteristic of the fuel injection valve, a process for detecting the fuel pressure by the pressure sensor in a short cycle and a result of detecting the fuel pressure are analyzed and the operation is performed. Processing for specifying the characteristics is executed. Since these processes have a large calculation load, it takes some time to execute the processes. For this reason, for example, when the time required for executing the calculation process is short, such as when the engine rotation speed is high and the time per combustion cycle is short, it is not possible to sufficiently secure the execution time of the calculation process and fuel injection. There is a risk that the operating characteristics of the valve cannot be properly detected.

  In order to secure the execution time of the arithmetic processing, it is conceivable that the execution of the arithmetic processing is thinned out at predetermined intervals. In this case, the calculation load can be reduced, but the detection frequency of the operating characteristic of the fuel injection valve is lowered.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel that can achieve both reduction in calculation load and suppression in reduction in execution frequency for processing for detecting the operating characteristics of a fuel injection valve. An object of the present invention is to provide an ejection characteristic detection device.

A fuel injection characteristic detection device for solving the above-mentioned problem is an internal combustion engine that includes a fuel supply system that supplies fuel in a pressurized state to a fuel injection valve, and a pressure sensor that detects fuel pressure inside the fuel supply system. The detection time waveform of the fuel injection rate in the fuel injection valve is detected as the operating characteristic of the fuel injection valve based on the detection result of the fuel pressure detected by the pressure sensor applied to the engine. The apparatus detects the fuel pressure detected by the pressure sensor during a period from when the valve opening signal is output to the fuel injector to when the end of fuel injection by the fuel injector is determined based on the detection result. On the other hand, the fuel pressure at the time other than the period is not used for detection of the operation characteristic while the operation characteristic is used for detection.

In addition, a fuel injection characteristic detection device for solving the above-described problem includes a fuel supply system that supplies fuel in a pressurized state to a fuel injection valve, and a pressure sensor that detects fuel pressure inside the fuel supply system. A detection time waveform of the fuel injection rate in the fuel injection valve is detected as an operating characteristic of the fuel injection valve based on the detection result of the fuel pressure detected by the pressure sensor applied to the internal combustion engine. In the period from when a predetermined time elapses after the valve opening signal is output to the fuel injector to when the end of fuel injection by the fuel injector is determined based on the detection result. While the fuel pressure detected by the pressure sensor is used for detecting the operating characteristic, the fuel pressure at a time other than the period is not used for detecting the operating characteristic.

A fuel injection characteristic detection device for solving the above-mentioned problem is an internal combustion engine that includes a fuel supply system that supplies fuel in a pressurized state to a fuel injection valve, and a pressure sensor that detects fuel pressure inside the fuel supply system. The detection time waveform of the fuel injection rate in the fuel injection valve is detected as the operating characteristic of the fuel injection valve based on the detection result of the fuel pressure detected by the pressure sensor applied to the engine. The apparatus detects the fuel detected by the pressure sensor during a period from when a valve opening signal is output to the fuel injection valve to when a predetermined time elapses after the valve closing signal is output to the fuel injection valve. While the pressure is used for detecting the operating characteristic, the fuel pressure at a time other than the period is not used for detecting the operating characteristic.

In addition, a fuel injection characteristic detection device for solving the above-described problem includes a fuel supply system that supplies fuel in a pressurized state to a fuel injection valve, and a pressure sensor that detects fuel pressure inside the fuel supply system. A detection time waveform of the fuel injection rate in the fuel injection valve is detected as an operating characteristic of the fuel injection valve based on the detection result of the fuel pressure detected by the pressure sensor applied to the internal combustion engine. The apparatus includes a period from when a predetermined time elapses after the valve opening signal is output to the fuel injection valve to when a predetermined time elapses after the valve closing signal is output to the fuel injection valve. On the other hand, the fuel pressure detected by the pressure sensor is used for the detection of the operating characteristic, while the fuel pressure at a time other than the period is not used for the detection of the operating characteristic.

  In the above apparatus, in order to detect the operating characteristics of the fuel injection valve, it is important to grasp the fluctuation waveform of the fuel pressure during a period in which the fuel pressure temporarily decreases as the fuel injection valve opens and closes. The necessity of grasping the fluctuation waveform of the fuel pressure before the opening of the fuel injection valve or after the temporary drop of the fuel pressure due to the opening and closing of the fuel injection valve is eliminated is very low.

  According to the above apparatus, the fuel pressure detected during a period in which the fuel pressure in the fuel supply system may be temporarily reduced due to opening and closing of the fuel injection valve is used for detecting the operating characteristics of the fuel injection valve. Thus, the fuel pressure before the fuel injection valve is opened and the fuel pressure after the temporary drop in the fuel pressure associated with the opening and closing of the fuel injection valve is not used for the detection of the operating characteristics. As a result, since the fuel pressure when the necessity of grasping the fluctuation waveform of the fuel pressure is extremely low is not used for the detection of the operation characteristic, the calculation load of the process for detecting the operation characteristic of the fuel injection valve accordingly. Can be reduced. Moreover, the fluctuation waveform of the fuel pressure in the fuel supply system when the fuel injection valve is opened can be grasped based on the fuel pressure detected when the fuel pressure in the fuel supply system is temporarily reduced. . Therefore, although there is a period during which the fluctuation waveform of the fuel pressure is not grasped, the detection of the operating characteristic of the fuel injection valve based on the fluctuation waveform of the fuel pressure can be executed, so that a decrease in the detection frequency can be suppressed. .

Further, each fuel injection characteristic detection device for solving the above-described problems performs fuel injection from the fuel injection valve in one combustion cycle by multi-stage injection in which fuel injection is performed in a plurality of times, and the multi-stage The operation characteristic can be detected separately for each injection. In such an apparatus, when the number of stages of the multi-stage injection is a predetermined determination number and the engine rotational speed is equal to or higher than a predetermined determination speed, the operation characteristic for a specific fuel injection other than the first stage injection in the multi-stage injection. detecting a thinned out and do not want to run.

  As the engine speed increases, the time per combustion cycle is shortened, so that the time during which arithmetic processing for detecting the operating characteristics of the fuel injection valve can be performed is also shortened. In addition, as the number of injection stages in multi-stage injection increases, the total period during which the fuel pressure temporarily decreases as the fuel injection valve opens and closes increases, so it is necessary to grasp the fluctuation waveform of the fuel pressure accordingly. The period will be longer. Therefore, when the number of injection stages is large and the engine rotational speed is high, the calculation load of processing for detecting the operating characteristics of the fuel injection valve increases.

  The second and subsequent injections in the multi-stage injection are easily affected by the pulsation of the fuel pressure in the fuel supply system accompanying the immediately preceding fuel injection because the interval between the immediately preceding fuel injections is short. On the other hand, since the first stage injection in the multistage injection has a long interval with the immediately preceding injection, the influence of the pulsation of the fuel pressure accompanying the immediately preceding injection is small. Therefore, when the first stage injection is executed, it is possible to accurately detect the operating characteristics of the fuel injection valve in a state where the influence of the fuel pressure pulsation accompanying the immediately preceding injection is suppressed.

  According to the above apparatus, when the engine rotational speed becomes high in a situation where the number of injection stages is large, it is possible to reliably execute the detection of the operation characteristic for the first stage injection and detect the operation characteristic with high accuracy. In addition, the calculation load can be reduced by thinning out the detection of the operation characteristics for the fuel injection other than the first stage injection.

In the above apparatus, the last stage injection in the multi-stage injection can be adopted as the specific fuel injection that thins out the detection of the operation characteristic.
The above-described device can be applied to an internal combustion engine having a plurality of cylinders and detecting the operation characteristics for each cylinder of the internal combustion engine.

  In an internal combustion engine having a plurality of cylinders, a device for detecting the operation characteristics of the fuel injection valve for each cylinder is a device applied to a single-cylinder internal combustion engine or a specific cylinder among a plurality of cylinders. Compared with the apparatus to perform, the time which can perform the process which detects the operating characteristic of a fuel injection valve tends to become short.

  According to the above apparatus, in an apparatus applied to such an internal combustion engine having a plurality of cylinders, it is possible to reduce a calculation load of a process for detecting the operation characteristic while suppressing a decrease in the detection frequency of the operation characteristic of the fuel injection valve. Can do.

1 is a schematic diagram showing a schematic configuration of an embodiment of a fuel injection characteristic detection device. Sectional drawing which shows the cross-section of a fuel injection valve. (A) And (b) The timing chart which shows the relationship between a drive pulse and a fuel injection rate with each characteristic parameter of a fuel injection valve. (A)-(c) The timing chart which shows the relationship between the time waveform of fuel pressure, and the detection time waveform of a fuel injection rate. (A) And (b) The timing chart which shows the relationship between the detection time waveform of a fuel injection rate, and a basic time waveform. The conceptual diagram which shows the map structure of the first stage learning map which memorize | stored the relationship between the target injection quantity at the time of execution of pilot injection, target injection pressure, and each learning term. The conceptual diagram which shows the map structure of the main learning map which memorize | stored the relationship between the target injection quantity at the time of execution of main injection, target injection pressure, and each learning term. The table | surface which shows the relationship between the injection stage of multistage injection, and each difference correction term. The conceptual diagram of an example of the reflection aspect of a difference correction term and a learning term. (A) And (b) The timing chart which shows an example of the relationship between the output mode of a drive pulse, and the detection time waveform of a fuel injection rate. (A)-(f) The timing chart which shows the example of the relationship between the engine rotational speed, the injection stage number of multistage injection, and the detection time waveform of a fuel injection rate. The graph which shows the relationship between the injection stage number of multistage injection, an engine speed, and a calculation load factor. The flowchart which shows the execution procedure of a time waveform formation process. The flowchart which shows the execution procedure of the time waveform formation process of a modification. The flowchart which shows the execution procedure of the time waveform formation process of another modification. The flowchart which shows the execution procedure of the time waveform formation process of the other modification.

Hereinafter, an embodiment of the fuel injection characteristic detection device will be described.
As shown in FIG. 1, an intake passage 12 is connected to the cylinder 11 of the internal combustion engine 10. Air is sucked into the cylinder 11 of the internal combustion engine 10 through the intake passage 12. As the internal combustion engine 10, a diesel engine having a plurality of (four [# 1, # 2, # 3, # 4] in this embodiment) cylinders 11 is employed. The internal combustion engine 10 is provided with a direct injection type fuel injection valve 20 that directly injects fuel into the cylinder 11 for each cylinder 11 (# 1 to # 4). The fuel injected by opening the fuel injection valve 20 is ignited and burned in contact with the intake air compressed and heated in the cylinder 11 of the internal combustion engine 10. In the internal combustion engine 10, the piston 13 is pushed down by the energy generated with the combustion of fuel in the cylinder 11, and the crankshaft 14 rotates. The combustion gas combusted in the cylinder 11 of the internal combustion engine 10 is discharged as exhaust gas into the exhaust passage 15 of the internal combustion engine 10.

  Each fuel injection valve 20 is individually connected to a common rail 34 via a branch passage 31a. The common rail 34 is connected to the fuel tank 32 through a supply passage 31b. A fuel pump 33 that pumps fuel is provided in the supply passage 31b. In the present embodiment, the fuel whose pressure has been increased by pumping by the fuel pump 33 is stored in the common rail 34 as a pressure accumulating container and is supplied to the inside of each fuel injection valve 20. In the present embodiment, each fuel injection valve 20, the branch passage 31a, the supply passage 31b, the fuel pump 33, and the common rail 34 constitute a fuel supply system.

  A return passage 35 is connected to each fuel injection valve 20. The return passages 35 are each connected to the fuel tank 32. A 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). In addition, 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 at a position 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 through the introduction passage 27. The pressure chamber 26 is connected to the nozzle chamber 25 and the branch passage 31 a through 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. Specifically, a piezoelectric actuator 29 in which a piezoelectric element (for example, a piezoelectric element) that expands and contracts by input of a drive pulse (a valve opening signal or a valve closing signal) is provided inside the housing 21 of the fuel injection valve 20. A valve body 29 a is attached to the piezoelectric actuator 29. The valve body 29 a is provided inside the pressure chamber 26. Then, one of the communication passage 28 (nozzle chamber 25) and the discharge passage 30 (return passage 35) is selectively communicated with the pressure chamber 26 through the movement of the valve element 29a by the operation of the piezoelectric actuator 29. .

  In the 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, so that the communication path 28 and the pressure chamber 26 communicate with each other. At the same time, the communication between the return passage 35 and the pressure chamber 26 is blocked. 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. As a result, 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 it closes the injection hole 23 by the urging force of the spring 24. Is not injected (valve closed state).

  On the other hand, when a valve opening signal is input to the piezoelectric actuator 29, the piezoelectric actuator 29 extends and the valve body 29a moves, whereby the communication between the communication passage 28 and the pressure chamber 26 is blocked. 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 in which the outflow of fuel 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 needle valve 22 moves against the biasing force of the spring 24 due to the pressure difference. Therefore, the fuel injection valve 20 is in a state in which fuel is injected (opened state) at this time.

  A pressure sensor 51 for detecting 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 51 is provided for each fuel injection valve 20, that is, for each cylinder 11 (# 1 to # 4) of the internal combustion engine 10.

  As shown in FIG. 1, the internal combustion engine 10 is provided with various sensors as peripheral devices for detecting an operation state. As these sensors, in addition to the pressure sensor 51, for example, an intake air amount sensor 52 for detecting the amount of air passing through the intake passage 12 (passage air amount GA), the rotational speed of the crankshaft 14 (engine rotational speed NE). ) Is provided. In addition, an accelerator sensor 54 for detecting an operation amount (accelerator operation amount ACC) of an accelerator operation member (for example, an accelerator pedal) is also provided.

  Moreover, as a peripheral device of the internal combustion engine 10, an electronic control unit 40 configured with an arithmetic processing unit 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 controls the operation of the fuel injection valve 20 (injection amount control) and the operation of the fuel pump 33 based on the calculation results. Various controls related to the operation of the internal combustion engine 10 such as control (injection pressure control) are executed. In the present embodiment, the detection of the fuel pressure PQ by the pressure sensor 51 is detected at a very short cycle (10 microseconds in the present embodiment), and the fuel pressure PQ is electronically controlled in association with the detection timing. It is stored in the unit 40.

  In the present embodiment, the injection pressure control is executed as follows. That is, first, a control target value (target injection pressure) for the fuel pressure in the common rail 34 is calculated based on the passage air amount GA and the engine rotational speed NE, and the fuel is set so that the actual fuel pressure becomes the target injection pressure. The operation amount (fuel pressure feed amount or fuel return amount) of the pump 33 is adjusted. Through the adjustment of the operation amount of the fuel pump 33, the fuel pressure in the common rail 34, and thus the fuel injection pressure of the fuel injection valve 20, is adjusted to a pressure corresponding to the engine operating state.

  In the present embodiment, the injection amount control is basically executed as follows. That is, first, based on the operating state of the internal combustion engine 10 (specifically, the accelerator operation amount ACC and the engine speed NE), the fuel injection amount control target value (target fuel injection amount TQ) is calculated and the injection pattern. Is selected. Thereafter, based on the target fuel injection amount TQ and the engine rotational speed NE, various control target values for each injection of the injection pattern selected at this time are calculated. Then, each fuel injection valve 20 is driven to open individually according to these control target values.

  In the present embodiment, a plurality of injection patterns obtained by combining pilot injection and after injection with main injection are set in advance, and these injection patterns are stored in the electronic control unit 40. When executing the injection amount control, one of these injection patterns is selected. Various control target values include the control target value (target injection amount) of the fuel injection amount of each injection such as main injection, pilot injection, and after injection, the start timing of main injection, the interval between pilot injections, pilot injection and main injection Control target values are calculated for the execution timing of each injection such as the interval between injections and the interval between main injection and after injection.

  Then, for each injection, the control target value (target injection period TAU) for the valve opening period of the fuel injection valve 20 is set from the model formula based on the target injection amount and the fuel pressure PQ. In this embodiment, a physical model that models a fuel supply system including the common rail 34, each branch passage 31a, each fuel injection valve 20, and the like is constructed, and the target injection period TAU is calculated through the physical model. More specifically, a model expression having a target injection amount and a fuel pressure PQ, both of which will be described later, a learning term, a difference correction term, and the like as variables is determined and stored in advance in the electronic control unit 40. TAU is calculated.

  For each injection, a drive pulse is output from the electronic control unit 40 in accordance with the control target value of the execution timing and the target injection period TAU, and each fuel injection valve 20 is opened individually based on the input of the drive pulse. Valve driven. As a result, an amount of fuel commensurate with the engine operating state at that time is injected from each fuel injection valve 20 in an injection pattern suitable for the engine operating state and supplied into each cylinder 11 of the internal combustion engine 10. The rotational torque commensurate with the engine operating state is applied to the crankshaft 14. Thus, in this embodiment, fuel injection from the fuel injection valve 20 in one combustion cycle is executed by multistage injection in which fuel injection is executed in a plurality of times.

  In the present embodiment, a learning process for learning a plurality of characteristic parameters as operating characteristics of the fuel injection valve 20 based on the fuel pressure PQ detected by the pressure sensor 51 is executed. The learning process is executed on condition that an execution condition for determining that the operating state of the internal combustion engine 10 is a stable state with little change is satisfied. Satisfying the execution condition means that the change amount of the target fuel injection amount per unit period (for example, the period in which the crankshaft 14 rotates several times) is small, the change amount of the target injection pressure per unit period is small, etc. Is judged by.

FIG. 3 shows an example of characteristic parameters learned by the learning process.
As shown in FIG. 3, in the present embodiment, the valve opening delay time τd, the injection rate increasing speed Qup, the maximum injection rate Qmax, the valve closing delay time τe, and the injection rate decreasing rate Qdn are adopted as the characteristic parameters. Specifically, the valve opening delay time τd is from when the valve opening signal (FIG. 3A) is output from the electronic control unit 40 to the fuel injection valve 20 until the fuel injection by the fuel injection valve 20 actually starts. The injection rate increasing speed Qup is the increasing speed of the fuel injection rate (FIG. 3B) after the valve opening operation of the fuel injection valve 20 is started. Further, the maximum injection rate Qmax is the maximum value of the fuel injection rate, and the valve closing delay time τe is the closing operation of the fuel injection valve 20 after the valve closing signal is output from the electronic control unit 40 to the fuel injection valve 20 ( Specifically, this is the time until the needle valve 22 starts to move toward the valve closing side. Further, the injection rate decrease rate Qdn is a rate at which the fuel injection rate decreases after the valve closing operation of the fuel injection valve 20 is started.

In the learning process, first, a time waveform (detection time waveform) of the actual fuel injection rate is formed based on the fuel pressure PQ detected by the pressure sensor 51.
The fuel pressure inside the fuel injection valve 20 (specifically, the nozzle chamber 25) decreases as the lift amount of the needle valve 22 increases when the fuel injection valve 20 is driven to open, and then closes. It rises with a decrease in the lift amount of the needle valve 22 when driven. In the present embodiment, the valve opening delay time τd, the injection rate increasing speed Qup, the maximum injection rate Qmax, and the valve closing delay are based on the transition of the fuel pressure inside the fuel injection valve 20 (specifically, the fuel pressure PQ). The time τe and the injection rate decrease speed Qdn are specified. And the time waveform (detection time waveform) of an actual fuel injection rate is formed by those specified values. The time waveform of the fuel pressure PQ is a waveform formed on the basis of values smoothed by using a low-pass filter or corrected by the fuel pressure PQ detected by the pressure sensor 51 corresponding to the non-injection cylinder. Is used.

FIG. 4 shows the relationship between the time waveform of the fuel pressure PQ and the detection time waveform of the fuel injection rate.
As shown in FIG. 4, in detail, first, an average value of the fuel pressure PQ (FIG. 4 (c)) in a predetermined period T1 immediately before the opening operation of the fuel injection valve 20 is started is calculated, and the same average is calculated. The value is stored as the reference pressure Pbs. The reference pressure Pbs is used as a pressure corresponding to the fuel pressure inside the fuel injection valve 20 when the valve is closed.

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

  Thereafter, in a period in which the fuel pressure PQ drops immediately after the start of fuel injection execution, a straight line L1 in which the difference from the fuel pressure PQ becomes the smallest (in FIG. 4, the vertical axis of orthogonal coordinates is the fuel injection rate and the horizontal axis is time Is obtained using the least square method, and an intersection A between the straight 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 the timing when the fuel injection by the fuel injection valve 20 is started (injection start timing Tos, FIG. )). 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 51. This is a delay caused by the above. In the present embodiment, the time from the timing when the valve opening signal (FIG. 4A) is output from the electronic control unit 40 to the fuel injection valve 20 to the injection start timing Tos is specified as the valve opening delay time τd.

  Further, in the rising period in which the fuel pressure PQ once rises after the fuel injection is started, the straight line L2 in which the difference from the fuel pressure PQ becomes the smallest (in FIG. 4, the vertical axis of the orthogonal coordinates is the fuel injection rate. (A linear function with time on the horizontal axis) (FIG. 4B) is obtained using the least square method, and an intersection B between the straight line L2 and the operating pressure Pac is calculated. Then, 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 timing when the fuel injection by the fuel injection valve 20 is stopped (injection stop timing Tce).

  Furthermore, an intersection C between the straight line L1 and the straight line L2 is calculated, and a difference between the fuel pressure PQ and the operating pressure Pac at the intersection 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 target injection amount and the target injection pressure 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 target injection amount and the target injection pressure is calculated as a maximum injection rate Qmax (= VRt × G2). In the present embodiment, values set at the time of detection by the pressure sensor 51 of the fuel pressure PQ used for forming the detection time waveform are adopted as the target injection amount and the target injection pressure used for setting the gains G1 and G2. The

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.
And the time corresponding to this point D is specified as the time (valve closing start time Tcs) when the valve closing operation of the fuel injection valve 20 is started. In the present embodiment, the time from the timing when the valve closing signal is output from the electronic control unit 40 to the fuel injection valve 20 to the valve closing start timing Tcs is specified as the valve closing delay time τe.

  Further, a straight line L3 connecting the point D and the injection start timing Tos (specifically, the point at which the fuel injection rate becomes “0” at the same time Tos) is obtained, and the slope (specifically, the unit L3) The amount of increase in fuel injection rate per hour) is specified as the injection rate increase speed Qup.

  Further, a straight line L4 connecting the point D and the injection stop timing Tce (specifically, the point at which the fuel injection rate becomes “0” at the same time Tce) is obtained, and the slope of the straight line L4 (specifically, unit time) The amount of decrease in the fuel injection rate per hit) is specified as the injection rate decrease rate Qdn.

  In the present embodiment, a trapezoidal time waveform formed by the valve opening delay time τd, the injection rate increasing speed Qup, the maximum injection rate Qmax, the injection rate decreasing speed Qdn, and the valve closing delay time τe thus specified. Is used as a detection time waveform for the fuel injection rate.

  On the other hand, in the learning process of the present embodiment, a basic time waveform for the fuel injection rate is calculated based on various calculation parameters such as a target injection amount, a control target value for execution timing, a target injection pressure, and the like. In the present embodiment, the relationship between the engine operation region determined by these calculation parameters and the basic time waveform suitable for the operation region is obtained in advance based on the results of various experiments and simulations and stored in the electronic control unit 40. Then, the electronic control unit 40 calculates a basic time waveform from the above relationship based on various calculation parameters.

  FIG. 5 shows an example of the basic time waveform. As shown in FIGS. 5A and 5B, the basic time waveforms include valve opening delay time τdb, injection rate increasing speed Qupb, maximum injection rate Qmaxb, valve closing delay time τeb, and injection rate decreasing speed Qdnb. A trapezoidal waveform defined by is set.

  In the learning process of the present embodiment, learning terms for a plurality of characteristic parameters of the fuel injection valve 20 are learned based on the relationship between the detected time waveform and the basic time waveform. That is, first, during the operation of the internal combustion engine 10, the detected time waveform and the basic time waveform are compared, and the difference between the characteristic parameters of those waveforms is sequentially calculated. Specifically, the difference between the characteristic parameters includes a difference Δτd (= τdb−τd) in the valve opening delay time, a difference ΔQup (= Qupb−Qup) in the injection rate increase speed, and a difference ΔQmax (= Qmaxb in the maximum injection rate). -Qmax), a difference ΔQdn (= Qdnb−Qdn) in the injection rate reduction speed, and a difference Δτe (= τeb−τe) in the valve closing delay time. Then, the weighted average values of these differences Δτd, ΔQup, ΔQmax, ΔQdn, Δτe are calculated, and the weighted average values compensate the learning terms Gτd, GQup, GQmax, It is stored in the electronic control unit 40 as GQdn and Gτe.

  In the apparatus according to the present embodiment, a plurality of learning areas defined by the fuel injection pressure (specifically, target injection pressure) and the fuel injection amount (specifically, target injection quantity) are defined. Learning terms are learned and stored.

  As shown in FIG. 6, the electronic control unit 40 stores the relationship between the target injection amount, the target injection pressure, and the learning term in a learning region used in pilot injection and after injection, that is, a learning region where the target injection amount is small. A map (first learning map) is stored. When the target injection period TAU for pilot injection or after injection is calculated, the learning term is calculated from the first stage learning map shown in FIG. 6 based on the target injection amount and target injection pressure of the fuel injection to be calculated. To be used.

  Further, as shown in FIG. 7, the electronic control unit 40 has a target injection amount and a target injection in a learning region used in the main injection, that is, a learning region including a region where the target injection amount is small to a region where the target injection amount is large. A map (main learning map) storing the relationship between the pressure and the learning term is stored. In calculating the target injection period TAU of the main injection, a learning term is calculated from the main learning map shown in FIG. 7 based on the target injection amount and the target injection pressure of the main injection.

  The pressure fluctuation in the fuel supply system at the time of executing the second and subsequent fuel injections in the multi-stage injection includes the pulsation of the fuel pressure generated with the immediately preceding fuel injection. Therefore, if the learning term at the time of execution of the main injection is learned simply based on the fuel pressure PQ detected by the pressure sensor 51, the learning accuracy of the learning term may be reduced due to the influence of the pulsation of the fuel pressure.

  Therefore, in the present embodiment, in the main learning map (see FIG. 7), in the region where the fuel injection amount is small (specifically, the region where pilot injection is executed [region shown by hatching in FIG. 7)] Learning of the learning term is executed based on the fuel pressure PQ detected by the pressure sensor 51 when the stage is executed. The learning term stored in the leading stage learning map (see FIG. 6) is also learned based on the fuel pressure PQ detected by the pressure sensor 51 when the pilot injection leading stage is executed. As a result, the learning term is learned with high accuracy while the influence of the fuel pressure pulsation accompanying the other injections is suppressed to a very small level. Further, in the main learning map, in a region where the fuel injection amount is large (specifically, a region where pilot injection is not executed), learning of the learning term is executed based on the fuel pressure PQ detected by the pressure sensor 51 when the main injection is executed. .

  Further, if the learning term learned in this way is reflected in the calculation of the target injection period TAU as it is, there is a possibility that an error may occur in the fuel injection amount due to the fuel pressure pulsation generated with the immediately preceding injection. In the present embodiment, difference correction terms Kτd, KQup, KQmax, KQdn, and Kτe for correcting such an error are calculated. That is, first, the differences Δτd, ΔQup, ΔQmax, ΔQdn, Δτe of the above-described parameters for the fuel injection subject to calculation of the difference correction term are detected, and the learning term reflected in calculating the target injection period TAU of the fuel injection. Gτd, GQup, GQmax, GQdn, and Gτe are read. Then, the difference between the above parameters and the difference between the learning terms (= Δτd−Gτd, ΔQup−GQup, ΔQmax−GQmax, ΔQdn−GQdn, Δτe−Gτe) are calculated, and these differences are calculated as the difference correction terms Kτd, KQup. , KQmax, KQdn, Kτe are temporarily stored. Note that the process of calculating the difference correction term in this way is executed separately for the second and subsequent fuel injections in the multi-stage injection.

  Further, the pulsation of the fuel pressure generated with the immediately preceding injection is not constant, and varies depending on the interval between injections, the fuel injection pressure, the fuel injection amount of the immediately preceding injection, and the like. Therefore, when learning of the learning term or calculation of the difference correction term is performed without considering the fuel pressure pulsation associated with the immediately preceding injection, an unnecessary change in the time waveform of the fuel pressure PQ or the detection time waveform is caused. This contributes to lowering the learning accuracy of the learning term and the calculation accuracy of the difference correction term.

  In the present embodiment, in order to suppress such a decrease in accuracy, when the detection time waveform for the second and subsequent injections is formed, the pressure waveform generated with the immediately preceding injection is added to the time waveform of the underlying fuel pressure PQ. A process of superimposing a pressure time waveform (correction waveform) that can cancel pulsation is executed. Through this process, the influence of the fuel pressure pulsation associated with the immediately preceding injection is removed from the detection time waveform, an appropriate value is detected as the difference between the parameters, and an appropriate value is learned as a learning term. Become.

  The correction waveform is based on the injection pattern of the combustion cycle including the fuel injection to be corrected, the target injection amount of each injection, the interval between the injections, and the target injection pressure. Each is calculated. In this embodiment, based on the results of various experiments and simulations, the correction suitable for each injection after the second stage of the injection pattern, the target injection amount of each injection, the interval between each injection, the target injection pressure, and the multistage injection The relationship with the waveform is obtained in advance and stored in the electronic control unit 40. Based on this relationship, a correction waveform for the second and subsequent injections of the multi-stage injection is calculated and used.

FIG. 8 shows the relationship between the injection stage of multi-stage injection and the difference correction term.
As shown in FIG. 8, when “N” is a natural number through execution of the process of calculating the difference correction term, the value calculated based on the (N + 1) th stage fuel injection is the same as the (N + 1) th stage. Is stored as a difference correction term K (N + 1) corresponding to the fuel injection. For example, a value calculated based on the second-stage injection is stored as a difference correction term K2 corresponding to the second-stage injection, and a value calculated based on the third-stage injection corresponds to the third-stage injection. Is stored as a difference correction term K3. Note that an initial value (“0” in the present embodiment) is set as a difference correction term corresponding to an injection stage that has not been executed in multistage injection.

  Thus, in the present embodiment, the difference correction term is calculated in association with the injection position, such as a correction term corresponding to the main injection, a correction term corresponding to the pilot injection executed immediately before the main injection, and the like. Instead, the difference correction term K2 corresponding to the second-stage injection and the difference correction term K3 corresponding to the third-stage injection are calculated in association with the injection order.

  In this embodiment, the learning terms Gτd, GQup, GQmax, GQdn, Gτe, and the difference correction terms Kτd, KQup, KQmax, KQdn, Kτe are used to calculate the target injection period TAU based on the above-described model formula. Is used as a calculation parameter. By calculating the target injection period TAU for each stage of fuel injection in the multi-stage injection in this way, the influence of the variation in operating characteristics due to the temporal change of the fuel injection valve 20 and the fuel pressure pulsation accompanying the immediately preceding injection Will be compensated for each. The difference correction terms Kτd, KQup, KQmax, KQdn, and Kτe are the target injection period TAU of fuel injection in the combustion cycle (reflecting combustion cycle) following the combustion cycle (calculated combustion cycle) including the fuel injection to be calculated. This is reflected in the above model formula when calculating. In the present embodiment, the process for calculating the learning term and the process for calculating the difference correction term based on the fuel pressure PQ are performed by the pressure sensor 51 corresponding to each cylinder 11 (# 1 to # 4) of the internal combustion engine 10. It is executed based on the output signal.

FIG. 9 shows an example of how the learning term and the difference correction term are reflected in the reflected combustion cycle.
In the example shown in FIG. 9, in the calculated combustion cycle and the reflected combustion cycle, the three-stage fuel injection including the two-stage pilot injection and the main injection is executed. Therefore, the difference correction term K2 corresponding to the second-stage injection is calculated based on the second-stage pilot injection in the calculated combustion cycle, and the difference correction term K3 corresponding to the third-stage injection is calculated based on the main injection. .

  As shown in FIG. 9, the difference correction term K2 is reflected when calculating the target injection period TAU for the second pilot injection in the reflected combustion cycle, and the target injection period TAU is calculated for the main injection in the reflected combustion cycle. At this time, the difference correction term K3 is reflected. The learning term reflected when calculating the target injection period TAU for each pilot injection is calculated based on the leading stage learning map (FIG. 6), and the learning term reflected when calculating the target injection period TAU for the main injection is Calculated from the main learning map (FIG. 7).

  Here, in the apparatus of the present embodiment, as a calculation process for detecting the characteristic parameter of the fuel injection valve 20, a process of executing the detection of the fuel pressure PQ by the pressure sensor 51 in a short cycle, or a process of detecting the detected fuel pressure PQ. Processing for analyzing the time waveform and specifying the characteristic parameter is executed. Since these processes require a large calculation load on the electronic control unit 40, it takes some time to execute the processes. Therefore, when the engine processing speed NE is high and the time per combustion cycle is short, for example, when the time for which the arithmetic processing can be performed is short, the execution time of the arithmetic processing cannot be sufficiently secured and learning is performed. There is a possibility that the term learning and the difference correction term calculation cannot be executed properly.

  Further, in the apparatus of the present embodiment, the process for detecting the characteristic parameter of the fuel injection valve 20 is executed for each cylinder 11 of the internal combustion engine 10, so that the process is executed only for a specific cylinder, The time during which arithmetic processing for detecting the characteristic parameter can be executed tends to be shortened.

  In the apparatus according to the present embodiment, the start of the output of a valve opening signal (driving pulse) to the fuel injection valve 20 is the starting point, and the end of fuel injection by the fuel injection valve 20 based on the detection time waveform of the fuel injection rate (the injection stop) A period (detection period TA) that ends when the time (Tce) is determined is determined. The fuel pressure PQ detected by the pressure sensor 51 in the detection period TA is used for the process for forming the detection time waveform of the fuel injection rate (time waveform formation process), while the fuel pressure at a time other than the detection period TA is used. PQ is not used.

Hereinafter, an operation by executing the time waveform forming process in this manner will be described.
FIG. 10 shows an example of the relationship between the drive pulse output mode and the fuel injection rate detection time waveform.
As shown in FIG. 10, when forming the detection time waveform of the fuel injection rate, first, to the fuel injection valve 20 of the fuel pressure PQ stored in the electronic control unit 40 in a form associated with the detection timing. Reading of the fuel pressure PQ detected by the pressure sensor 51 after the output of the valve opening signal ((a) in FIG. 5) is started (time t11, t13, t15). At this time, the fuel pressure PQ is read in the order of detection, and the reading of the fuel pressure PQ is repeated until the timing at which the injection stop timing Tce (see FIG. 4) is specified based on the fuel pressure PQ (time t11 to t12, t13 to t14, t15 to t16). When the injection stop timing Tce (see FIG. 4) is specified based on the fuel pressure PQ (time t12, t14, t16), reading of the fuel pressure PQ is stopped and based on the read fuel pressure PQ. Thus, a detection time waveform of the fuel injection rate is formed.

  In order to detect each characteristic parameter of the fuel injection valve 20, it is important to grasp the fluctuation waveform of the fuel pressure PQ during a period in which the fuel pressure temporarily decreases as the fuel injection valve 20 opens and closes. On the other hand, the necessity of grasping the fluctuation waveform of the fuel pressure PQ before the fuel injection valve 20 is opened or after the temporary drop in the fuel pressure due to the opening and closing of the fuel injection valve 20 is eliminated is very low. .

  According to the apparatus of this embodiment, the detection period TA (time t11 to t12, t13 to t14, t15 to t16) that may cause a temporary decrease in the fuel pressure in the fuel supply system due to the opening and closing of the fuel injection valve 20 is achieved. ) Is used for the time waveform forming process. On the other hand, before the fuel injection valve 20 is opened or after the temporary drop in fuel pressure due to the opening and closing of the fuel injection valve 20 is resolved (before time t11, t12 to t13, t14 to t15, and after t16). The detected fuel pressure PQ is not used for the detection time waveform forming process. As a result, the fuel pressure PQ when the necessity of grasping the fluctuation waveform of the fuel pressure PQ is extremely low is not used for the detection time waveform forming process. It is possible to reduce the calculation load of the process for forming the detection time waveform. In addition, a fuel injection rate detection time waveform is formed based on the fuel pressure PQ detected in the detection period TA that causes a temporary decrease in the fuel pressure in the fuel supply system, and the fuel is generated based on the detection time waveform. A plurality of characteristic parameters of the injection valve 20 can be detected. Therefore, although there is a period during which the fluctuation waveform of the fuel pressure PQ is not grasped, the fluctuation waveform of the fuel pressure PQ is grasped during the period necessary for the detection of the characteristic parameter. The decrease can be suppressed.

  Further, in the apparatus of the present embodiment, the number of injection stages of the multistage injection including the fuel injection subject to execution of the time waveform forming process is a predetermined number of stages, and the engine speed NE at the time of executing the multistage injection is predetermined. When the speed is equal to or higher than the determination speed, the detection of each characteristic parameter for the last stage injection in the multistage injection is thinned out so as not to be executed. In the apparatus of the present embodiment, when the engine rotational speed NE is equal to or higher than the determination speed J1 (for example, 2200 revolutions / minute) during the execution of the four-stage injection, the above-described characteristic parameters for the fourth-stage injection are detected. Thinned out and not executed. Further, when the engine speed NE is equal to or higher than the determination speed J12 (for example, 1200 rpm) during execution of the fifth stage injection, detection of each characteristic parameter for the fifth stage injection is skipped and not executed. .

FIGS. 11A to 11F show examples of the relationship between the engine rotational speed NE, the number of injection stages in multi-stage injection, and the number of injection stages for executing detection time waveform formation.
FIG. 11A shows the above relationship when five-stage injection is performed in a situation where the engine speed NE is lower than the determination speed J2. At this time, as shown in FIG. 11A, the detection time waveform is formed for all the injection stages in the five-stage injection.

  FIG. 11B shows the above relationship when five-stage injection is executed in a situation where the engine speed NE is equal to or higher than the determination speed J2. At this time, as shown in FIG. 11B, detection time waveforms are formed for the four injection stages excluding the last stage injection (indicated by a broken line in the figure).

  FIG. 11C shows the above relationship when the four-stage injection is executed in a situation where the engine speed NE is lower than the determination speed J1. At this time, as shown in FIG. 11C, detection time waveforms are formed for all the injection stages in the four-stage injection.

  FIG. 11D shows the above relationship when the four-stage injection is executed in a situation where the engine speed NE is equal to or higher than the determination speed J1. At this time, as shown in FIG. 11 (d), detection time waveforms are formed for the three injection stages excluding the last stage injection (indicated by a broken line in the figure).

FIG. 11E shows the above relationship when the three-stage injection is executed. At this time, as shown in FIG. 11E, detection time waveforms are formed for all injection stages.
FIG. 11 (f) shows the above relationship when the two-stage injection is executed. At this time, as shown in FIG. 11 (f), detection time waveforms are formed for all injection stages.

  As described above, when the engine rotational speed NE is increased, the time per combustion cycle is shortened, and the time during which arithmetic processing for controlling the operation of the fuel injection valve 20 can be performed is shortened. Further, when the number of injection stages in the multi-stage injection increases, the total period during which the fuel pressure temporarily decreases as the fuel injection valve 20 opens and closes increases. become longer. Therefore, when the number of injection stages of multi-stage injection is large and the engine speed NE is high, it can be said that the calculation load of the calculation process for detecting the characteristic parameter of the fuel injection valve 20 tends to increase.

  The second and subsequent injections in the multi-stage injection are easily affected by the pulsation of the fuel pressure in the fuel supply system accompanying the immediately preceding injection because the interval between the immediately preceding injections is short. On the other hand, since the first stage injection in the multistage injection has a long interval with the immediately preceding injection, the influence of the fuel pressure pulsation due to the immediately preceding injection is small. Therefore, when the first stage injection is performed, each characteristic parameter of the fuel injection valve 20 can be accurately detected in a state where the influence of the fuel pressure pulsation accompanying the immediately preceding injection is suppressed.

  According to the apparatus of the present embodiment, even when the engine rotational speed NE is high in a situation where the number of injection stages of the multistage injection is large, the detection time waveform for the first stage injection is reliably formed, The detection of each characteristic parameter based on the detection time waveform can be performed with high accuracy. In addition, by decimating the detection time waveform for the last stage injection, which has a relatively large influence of the fuel pressure pulsation due to the immediately preceding injection, the characteristic parameter is detected while suppressing a decrease in the detection accuracy of the characteristic parameter of the fuel injection valve 20. It is possible to reduce the calculation load of the calculation processing for the purpose.

  FIG. 12 shows the relationship between the number of injection stages of multi-stage injection, the engine speed NE, and the calculation load factor of the electronic control unit 40 (the ratio of the actual calculation load to the maximum value of the calculation capability). In FIG. 12, the alternate long and short dash line indicates the above-described relationship in the apparatus of the comparative example that forms the detection time waveform of the fuel injection rate in all periods, and the solid line indicates that the detection time waveform is formed only in the predetermined period TA. The above relationship in the apparatus is shown. Further, the broken line in FIG. 12 indicates the execution limit of the multistage injection determined by the performance of the drive circuit of the fuel injection valve 20.

  In the apparatus of this embodiment, the fuel pressure PQ used for forming the detection time waveform of the fuel injection rate is limited to the value detected in the detection period TA (see FIG. 10). Therefore, as shown by a white arrow in FIG. 12, compared with the device of the comparative example (shown by a one-dot chain line in the drawing), the device of this embodiment (shown by a solid line in the drawing) has a calculation load factor. Becomes lower. Thereby, it is possible to expand an operation region (in this embodiment, a region where the calculation load factor is a predetermined ratio [for example, 80%] or less) in which the learning processing and the processing for calculating the difference correction term can be performed. In the apparatus of the present embodiment, even if the two-stage injection is executed at the execution limit (C2 in FIG. 12) of the two-stage injection determined by the performance of the drive circuit of the fuel injection valve 20, the detection time described above. Formation of detection time waveforms for all injection stages is executed without thinning out the processing for forming the waveforms. Even when the three-stage injection is executed at the execution limit (C3 in FIG. 12) determined by the performance of the drive circuit of the fuel injection valve 20, the process for forming the detection time waveform is not thinned out. The formation of detection time waveforms for all injection stages is executed.

  When the engine speed NE is equal to or higher than the determination speed J1 when executing the four-stage injection, the process for reading the fuel pressure PQ and the process for forming the detection time waveform for the fourth-stage injection that is the last-stage injection are not executed. This also reduces the calculation load, so that the area where the four-stage injection can be performed is expanded by the amount indicated by the black arrow in the figure. That is, it is suppressed that the four-stage injection cannot be performed in the operation control of the fuel injection valve 20 because the detection time waveforms cannot be formed for all the four injection stages. In the apparatus of the present embodiment, when it is assumed that detection time waveforms are formed for all four injection stages, the determination speed J1 (two-dot chain line in FIG. 12) becomes the execution limit of the four-stage injection. In the apparatus of this embodiment, when the engine speed NE is equal to or higher than the determination speed J1, detection time waveforms are formed only for the three injection stages other than the fourth injection, and as a result, the drive circuit for the fuel injection valve 20 The four-stage injection can be executed up to the execution limit (C4 in FIG. 12) determined by the performance.

  Further, when the engine speed NE is equal to or higher than the determination speed J2 when the five-stage injection is performed, the process for reading the fuel pressure PQ and the process for forming the detection time waveform for the fifth-stage injection that is the last-stage injection are not performed. . This also reduces the calculation load, so that the area where five-stage injection can be performed is expanded. Thereby, in the apparatus of the present embodiment, the five-stage injection can be executed up to the execution limit of the five-stage injection (C5 in FIG. 12) determined by the performance of the drive circuit of the fuel injection valve 20.

  FIG. 13 shows an execution procedure of the time waveform forming process. The series of processes shown in the flowchart of FIG. 6 conceptually shows the execution procedure of the time waveform forming process, and is performed by the electronic control unit 40 each time fuel injection of each stage of multistage injection is executed. Executed.

  As shown in FIG. 13, in this process, first, it is determined whether or not the fuel injection for which the detection time waveform is to be formed is any one of the first stage injection, the second stage injection, and the third stage injection in the multi-stage injection. (Step S11).

  In the case of any of the first stage injection, the second stage injection, and the third stage injection (step S11: YES), it is detected after the valve opening signal for the fuel injection to be formed is output to the fuel injection valve 20. The fuel pressure PQ thus read is read in the order of detection (step S12). Thereafter, until the injection stop timing Tce (see FIG. 4) is specified based on the read fuel pressure PQ (step S13: NO), the fuel pressure PQ is repeatedly read (step S12). . When the injection stop timing Tce is specified based on the read fuel pressure PQ (step S13: YES), the injection stop timing Tce is determined based on the detection result of the fuel pressure PQ from when the valve opening signal is output. After the detection time waveform is formed based on the fuel pressure PQ detected in the detection period TA up to the time (step S14), the present process is terminated.

  On the other hand, when none of the first-stage injection, the second-stage injection, and the third-stage injection (step S11: NO), the engine speed NE is the determination speed J1, which is the fourth-stage injection and is executed. It is determined whether or not it is less than (step S15).

  When the fifth stage injection is performed or when the engine rotational speed NE at the time of executing the fourth stage injection is equal to or higher than the determination speed J1 (step S15: NO), the fifth stage injection is performed and the injection is performed. It is determined whether the engine speed NE at that time is less than the determination speed J2 (step S16).

  Here, when it is not the fifth stage injection or when the engine speed NE at the time of executing the fifth stage injection is equal to or higher than the determination speed J2 (step S16: NO), a process for forming a detection time waveform (NO) This process is terminated without executing steps S12 to S14).

  On the other hand, when the engine speed NE is the fourth stage injection and the injection speed is less than the determination speed J1 (step S15: YES), the engine speed is the fifth stage injection and the execution of the injection. When the speed NE is less than the determination speed J2 (step S16: YES), the process is terminated after the process for forming the detection time waveform (steps S12 to S14) is executed.

In the apparatus of the present embodiment, learning of a learning term and calculation of a difference correction term are executed based on this detection time waveform.
As described above, according to the present embodiment, the following effects can be obtained.

  (1) The fuel pressure detected by the pressure sensor 51 during the detection period TA from when the valve opening signal is output to the fuel injection valve 20 to when the injection stop timing Tce is determined based on the detection result of the fuel pressure PQ. While PQ is used for the time waveform forming process, the fuel pressure PQ at a time other than the detection period TA is not used for the time waveform forming process. As a result, the fuel pressure PQ detected before the fuel injection valve 20 is opened and the fuel pressure PQ detected after the temporary drop in the fuel pressure due to opening and closing of the fuel injection valve 20 is eliminated form a detection time waveform. Since it is no longer used for processing, it is possible to reduce the processing load for reading the fuel pressure PQ and the processing load for forming the detection time waveform accordingly. In addition, although there is a period in which the fluctuation waveform of the fuel pressure PQ is not grasped, the fluctuation waveform of the fuel pressure PQ can be grasped in the period necessary for detecting the characteristic parameter. The decrease can be suppressed.

  (2) When the engine speed NE is equal to or higher than the determination speed J1 during the execution of the four-stage injection, the process for forming the detection time waveform for the fourth-stage injection is thinned out and not executed. Further, when the engine speed NE is equal to or higher than the determination speed J2 when the five-stage injection is performed, the process of forming the detection time waveform for the fifth-stage injection is thinned out and not executed. Therefore, even when the engine speed NE is high in a situation where the number of injection stages of the multistage injection is large, the detection time waveform for the first stage injection is reliably formed, and each of the above-described each based on the detection time waveform is executed. The characteristic parameter can be detected with high accuracy. In addition, the calculation load of the calculation process for detecting the characteristic parameter of the fuel injection valve 20 can be reduced by thinning out the formation of the detection time waveform for the last stage injection.

The above embodiment may be modified as follows.
Instead of the detection period TA, the starting point is when a predetermined time Tb has elapsed after the valve opening signal is output to the fuel injection valve 20, and the end point is when the injection stop timing Tce is determined based on the detection result of the fuel pressure PQ. A detection period TB may be determined. The fuel pressure PQ detected by the pressure sensor 51 in the detection period TB is used for the process for forming the detection time waveform of the fuel injection rate, while the fuel pressure PQ at a time other than the detection period TB is not used for the process. It may be.

  In the apparatus of the above-described embodiment, if the output timing of the valve opening signal to the fuel injection valve 20 is known, the opening of the fuel injection valve 20 is based on the same timing and the operating characteristics of the fuel injection valve 20 (such as the valve opening delay time). The timing at which the valve is started can be estimated. For this reason, an effect similar to that of the device of the above embodiment can be obtained by a device that determines the detection period TB instead of the detection period TA. In addition, as compared with the apparatus of the above-described embodiment, the period during which the fuel pressure PQ is read can be shortened, so that the total number of fuel pressures PQ for which the detection time waveform is to be formed can be reduced. Therefore, it is possible to further reduce the calculation load of the calculation processing related to the detection of each characteristic parameter of the fuel injection valve 20. In the above-described apparatus, a certain period of time during which the detection time waveform can be properly formed while shortening the detection period TB so that a part of the fuel pressure PQ detected during the valve opening delay time is not read is used for various experiments. Or based on the result of the simulation and stored in the electronic control unit 40 as the predetermined time Tb.

  FIG. 14 shows an execution procedure of the time waveform forming process in the apparatus. FIG. 14 mainly shows a portion different from the time waveform forming process shown in FIG. 13. In the following description, the same processing as the time waveform forming process shown in FIG. The detailed explanation is omitted. As shown in FIG. 14, in this process, when the detection time waveform is formed (step S11: YES, step S15: YES, or step S16: YES), after the valve opening signal is output to the fuel injection valve 20, The fuel pressure PQ detected after the predetermined time Tb has elapsed is read in the order of detection (step S22). Thereafter, until the injection stop timing Tce is specified based on the read fuel pressure PQ (step S13: NO), the fuel pressure PQ is repeatedly read (step S22). Then, when the injection stop timing Tce is specified based on the read fuel pressure PQ (step S13: YES), the injection stop is based on the detection result of the fuel pressure PQ from when a predetermined time Tb has elapsed after the valve opening signal is output. A detection time waveform is formed based on the fuel pressure PQ detected in the detection period TB until the time Tce is determined (step S24). Thereafter, this process is terminated.

  Instead of the detection period TA, the starting point is the time when a valve opening signal is output to the fuel injection valve 20, and the end point is when a predetermined time Tc has elapsed after the closing signal is output to the fuel injection valve 20. The detection period TC to be used may be determined. The fuel pressure PQ detected by the pressure sensor 51 in the detection period TC is used for the process for forming the detection time waveform of the fuel injection rate, while the fuel pressure PQ at a time other than the detection period TC is not used for the process. It may be.

  In the apparatus of the above-described embodiment, if the output timing of the valve closing signal to the fuel injector 20 is known, the fuel is determined based on the timing and the operating characteristics of the fuel injector 20 (valve closing delay time, injection rate reduction speed, etc.). The timing at which the injection valve 20 is closed can be estimated. For this reason, an effect similar to that of the apparatus of the above embodiment can be obtained by an apparatus that determines the detection period TC instead of the detection period TA. In the above apparatus, the detection time waveform can be properly formed while shortening the detection period TC so that the fuel pressure PQ detected after the fuel injection valve 20 is closed is not read as much as possible. May be obtained in advance based on the results of various experiments and simulations, and stored in the electronic control unit 40 as the predetermined time Tc.

  FIG. 15 shows an execution procedure of the time waveform forming process in the apparatus. FIG. 15 shows only a part different from the time waveform forming process shown in FIG. 13. In the following description, the same process as the time waveform forming process shown in FIG. I will omit the detailed explanation. As shown in FIG. 15, in this process, when the detection time waveform is formed (step S11: YES, or step S15: YES, or step S16: YES), the fuel pressure PQ detected in the detection period TB is read. (Step S32). The detected fuel pressure PQ, that is, the detection period TC from when the valve opening signal for the fuel injection to be formed is output until when a predetermined time Tc elapses after the valve closing signal for the fuel injection is output. After the detection time waveform is formed based on the detected fuel pressure PQ (step S33), this process is terminated.

  In place of the detection period TA, a predetermined time Tc after a predetermined time Tb after the valve opening signal is output to the fuel injection valve 20 and a predetermined time Tc after the valve closing signal is output to the fuel injection valve 20 A detection period TD whose end point is when the time elapses may be determined. The fuel pressure PQ detected by the pressure sensor 51 in the detection period TD is used for the process for forming the detection time waveform of the fuel injection rate, while the fuel pressure PQ at a time other than the detection period TD is not used for the process. It may be.

  FIG. 16 shows the execution procedure of the time waveform forming process in the apparatus. FIG. 16 shows only a part different from the time waveform forming process shown in FIG. 13. In the following description, the same process as the time waveform forming process shown in FIG. I will omit the detailed explanation. As shown in FIG. 16, in this process, when the detection time waveform is formed (step S11: YES, step S15: YES, or step S16: YES), the fuel pressure PQ detected in the detection period TC is read. (Step S42). Then, when the predetermined time Tb has elapsed after the output of the valve closing signal for the fuel injection PQ, that is, when the predetermined time Tb has elapsed after the output of the valve opening signal for the fuel injection to be formed, After the detection time waveform is formed based on the fuel pressure PQ detected during the detection period TD up to (step S43), the present process is terminated.

  When the engine rotational speed NE is four-stage injection and the same injection is performed, the engine rotational speed NE is equal to or higher than the determination speed J1, or when the engine rotational speed NE is five-stage injection and the same injection is performed, the engine rotational speed NE is equal to or higher than the determination speed J2. Sometimes, the injection stage to be thinned out in the process for forming the detection time waveform of the fuel injection rate is not limited to the last stage injection, but can be any injection stage other than the first stage injection.

  The formation of fuel injection rate detection time waveforms for a plurality of injection stages may be thinned out when the number of stages of multi-stage injection is a predetermined number and the engine rotational speed NE is equal to or higher than the determination speed. As such a device, for example, the following devices can be considered. That is, when the engine speed NE is less than the first determination speed when the five-stage injection is performed, the detection time waveform is formed for all the injection stages. When the engine speed NE is equal to or higher than the first determination speed and lower than the second determination speed, the detection time waveform is formed for the four-stage fuel injection except the last-stage injection, and the engine speed NE is When the speed is higher than the determination speed, the detection time waveform is formed for the three-stage fuel injection excluding the last-stage injection and the fourth-stage injection.

  As the engine rotational speed NE increases, the time during which the arithmetic processing for detecting each characteristic parameter of the fuel injection valve 20 can be performed becomes shorter, so it becomes difficult to secure the execution time of the arithmetic processing. In this regard, according to the above apparatus, for example, when the engine rotational speed NE is high, the calculation process for two stages of multi-stage injection is thinned out, and when the engine rotational speed is relatively low, the calculation process for one stage is thinned out. The number of injection stages for thinning out the process for forming the detection time waveform can be determined in accordance with the change in the time during which the process can be performed. Therefore, it is possible to suitably achieve both the suppression of the decrease in the detection frequency of each characteristic parameter of the fuel injection valve 20 and the reduction in the calculation load of the process for detecting the characteristic parameter.

-You may abbreviate | omit the process of step S11, step S15, and step S16 of FIGS.
In the learning process, the difference itself is stored as learning terms Gτd, GQup, GQmax, GQdn, and Gτe without calculating the weighted average values of the differences Δτd, ΔQup, ΔQmax, ΔQdn, and Δτe of the plurality of characteristic parameters. It may be.

  The learning area can be defined by only one of the target injection amount and the target injection pressure. Further, the parameters for dividing the learning region are not limited to using the target injection amount and the target injection pressure, but the engine rotational speed NE, the passage air amount GA, the accelerator operation amount ACC, the intake air amount, and the like can be used.

-Calculation and reflection of the correction waveform may be omitted.
-The apparatus of the said embodiment can be applied also to the apparatus which performs pre injection prior to main injection, after changing the structure suitably.

  The characteristic parameter as the operating characteristic of the fuel injection valve 20 can be arbitrarily changed. For example, only one of the valve opening delay time τd, the injection rate increasing speed Qup, the maximum injection rate Qmax, the injection rate decreasing speed Qdn, and the valve closing delay time τe is used as a characteristic parameter, or only two are used as characteristic parameters. Or only three as characteristic parameters, or only four as characteristic parameters. In addition, the time when the fuel injection rate reaches the maximum injection rate, the time when the fuel injection rate starts to decrease from the maximum injection rate, the time when the fuel injection rate becomes “0”, and the like can be newly adopted as characteristic parameters. .

  If the pressure that is an index of the fuel pressure inside the fuel injection valve 20 (specifically, in the nozzle chamber 25), in other words, the fuel pressure that changes with the change in the fuel pressure can be properly detected. The pressure sensor 51 is not limited to being directly attached to the fuel injection valve 20, and the manner of attaching the pressure sensor 51 can be arbitrarily changed. Specifically, the pressure sensor 51 may be attached to a portion (branch passage 31 a) between the common rail 34 and the fuel injection valve 20 in the fuel supply passage, or may be attached to 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 fuel injection characteristic detection device can be applied not only to an internal combustion engine having four cylinders but also to an internal combustion engine having one to three cylinders, or an internal combustion engine having five or more cylinders.

  The fuel injection characteristic detection device can be applied not only to a diesel engine but also to a gasoline engine using gasoline fuel and a natural gas engine using natural gas fuel.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Cylinder, 12 ... Intake passage, 13 ... Piston, 14 ... Crankshaft, 15 ... 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 element, 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, 51 ... pressure sensor, 52 ... intake air amount sensor, 53 ... crank sensor, 54 ... accelerator sensor.

Claims (6)

Fuel pressure detected by the pressure sensor applied to an internal combustion engine having a fuel supply system for supplying fuel in a pressurized state to a fuel injection valve and a pressure sensor for detecting fuel pressure inside the fuel supply system In a fuel injection characteristic detection device that detects a detection time waveform of a fuel injection rate in the fuel injection valve as an operation characteristic of the fuel injection valve based on the detection result of
The device is
The fuel injection from the fuel injection valve in one combustion cycle is performed by multi-stage injection in which fuel injection is performed in a plurality of times, and the operation characteristics are detected separately for each injection of the multi-stage injection. Yes,
The fuel pressure detected by the pressure sensor during the period from when the valve opening signal is output to the fuel injector to when the end of fuel injection by the fuel injector is determined based on the detection result is On the other hand, the fuel pressure at a time other than the period is not used for the detection of the operating characteristics ,
When the number of stages of the multi-stage injection is a predetermined determination number and the engine speed is equal to or higher than a predetermined determination speed, the detection of the operation characteristic for a specific fuel injection other than the first stage injection in the multi-stage injection is thinned out. The fuel injection characteristic detecting device is not executed . Fuel pressure detected by the pressure sensor applied to an internal combustion engine having a fuel supply system for supplying fuel in a pressurized state to a fuel injection valve and a pressure sensor for detecting fuel pressure inside the fuel supply system In a fuel injection characteristic detection device that detects a detection time waveform of a fuel injection rate in the fuel injection valve as an operation characteristic of the fuel injection valve based on the detection result of
The device is
The fuel injection from the fuel injection valve in one combustion cycle is performed by multi-stage injection in which fuel injection is performed in a plurality of times, and the operation characteristics are detected separately for each injection of the multi-stage injection. Yes,
Detected by the pressure sensor during a period from when a predetermined time elapses after the valve opening signal is output to the fuel injector to when the end of fuel injection by the fuel injector is determined based on the detection result The fuel pressure is used for detection of the operating characteristics, while the fuel pressure at a time other than the period is not used for detection of the operating characteristics .
When the number of stages of the multi-stage injection is a predetermined determination number and the engine speed is equal to or higher than a predetermined determination speed, the detection of the operation characteristic for a specific fuel injection other than the first stage injection in the multi-stage injection is thinned out. The fuel injection characteristic detecting device is not executed . Fuel pressure detected by the pressure sensor applied to an internal combustion engine having a fuel supply system for supplying fuel in a pressurized state to a fuel injection valve and a pressure sensor for detecting fuel pressure inside the fuel supply system In a fuel injection characteristic detection device that detects a detection time waveform of a fuel injection rate in the fuel injection valve as an operation characteristic of the fuel injection valve based on the detection result of
The device is
The fuel injection from the fuel injection valve in one combustion cycle is performed by multi-stage injection in which fuel injection is performed in a plurality of times, and the operation characteristics are detected separately for each injection of the multi-stage injection. Yes,
The fuel pressure detected by the pressure sensor during the period from when a valve opening signal is output to the fuel injector to when a predetermined time elapses after the valve closing signal is output to the fuel injector On the other hand, the fuel pressure at a time other than the period is not used for the detection of the operating characteristic, while the characteristic is used for detection .
When the number of stages of the multi-stage injection is a predetermined determination number and the engine speed is equal to or higher than a predetermined determination speed, the detection of the operation characteristic for a specific fuel injection other than the first stage injection in the multi-stage injection is thinned out. The fuel injection characteristic detecting device is not executed . Fuel pressure detected by the pressure sensor applied to an internal combustion engine having a fuel supply system for supplying fuel in a pressurized state to a fuel injection valve and a pressure sensor for detecting fuel pressure inside the fuel supply system In a fuel injection characteristic detection device that detects a detection time waveform of a fuel injection rate in the fuel injection valve as an operation characteristic of the fuel injection valve based on the detection result of
The device is
The fuel injection from the fuel injection valve in one combustion cycle is performed by multi-stage injection in which fuel injection is performed in a plurality of times, and the operation characteristics are detected separately for each injection of the multi-stage injection. Yes,
The pressure sensor during a period from when a predetermined time elapses after the valve opening signal is output to the fuel injection valve to when a predetermined time elapses after the valve closing signal is output to the fuel injection valve Is used to detect the operating characteristic, while the fuel pressure at a time other than the period is not used to detect the operating characteristic .
When the number of stages of the multi-stage injection is a predetermined determination number and the engine speed is equal to or higher than a predetermined determination speed, the detection of the operation characteristic for a specific fuel injection other than the first stage injection in the multi-stage injection is thinned out. The fuel injection characteristic detecting device is not executed . In the fuel-injection characteristic detection apparatus as described in any one of Claims 1-4 ,
The fuel injection characteristic detecting device according to claim 1, wherein the specific fuel injection is a last-stage injection in the multi-stage injection. In the fuel-injection characteristic detection apparatus as described in any one of Claims 1-5 ,
The internal combustion engine has a plurality of cylinders;
The said apparatus performs the detection of the said operation characteristic for every cylinder of the said internal combustion engine, The fuel-injection characteristic detection apparatus characterized by the above-mentioned.