JP2014098341A - Fuel injection characteristic learning device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection characteristic learning device for an internal combustion engine in which a learning about an operation characteristic of a fuel injection valve can be performed precisely on the basis of a fuel pressure within a fuel supply system.SOLUTION: This device has a pressure sensor for detecting a fuel pressure PQ within a fuel supply system so as to perform a learning processing to study a plurality of characteristic parameters of a fuel injection valve on the basis of the fuel pressure PQ. During the learning processing, weighted average values of differences of a plurality of characteristic parameters Δτd, ΔQup, ΔQmax, ΔQdn, Δτe are computed and at the same time, these weighted average values are separately stored as studied values Gτd, GQup, GQmax, GQdn, and Gτe(S14). Then, as the weighted coefficients K1 to K5 of the weighted average, different values among the plurality of characteristic parameters are set (S13).

Description

  The present invention relates to a fuel injection characteristic learning device for an internal combustion engine that learns an operation characteristic of a fuel injection valve based on a fuel pressure detected by a pressure sensor.

  The internal combustion engine is provided with a fuel supply system including a supply passage for supplying fuel in a pressurized state and a fuel injection valve connected to the supply passage. 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 characteristics of the fuel injection valve are learned based on the fuel pressure detected by the pressure sensor ( Patent Document 1).

  When the fuel injection is performed, the fuel pressure in the fuel supply system temporarily decreases as the fuel injection valve starts to open and then increases as the fuel injection valve closes thereafter. In the apparatus described in Patent Document 1, the operating characteristics of the fuel injection valve are estimated and learned based on the variation of the fuel pressure inside the fuel supply system. Specifically, the time from when the valve opening signal is output to the fuel injection valve until the fuel injection from the fuel injection valve is actually started (open valve delay time), the rate of increase in the fuel injection rate, fuel injection A plurality of characteristic parameters are learned, such as the maximum value of the rate, the time from when the closing signal is input to the fuel injection valve until the actual closing of the valve (the valve closing time), and the rate of decrease in the fuel injection rate The

JP 2011-190725 A

  In the above apparatus, the variation of the detected value of the pressure sensor accompanying the opening and closing of the fuel injection valve is gradually increased over a long period of time as the components of the fuel supply system change over time (for example, deposits adhere to the injection holes of the fuel injection valve). In addition to the change to, it also changes in the short term under the influence of various factors such as noise superimposed on the detection signal and the properties (temperature, properties) of the fuel.

  In order to suppress an unnecessary change in the learned value due to such a short-term change in the detected value fluctuation mode, the past value and the latest value of the above characteristic parameter are weighted and averaged, so-called weighted average processing. It is conceivable that the learning value of each characteristic parameter is calculated by executing.

  However, since the influence of the above factors on the plurality of characteristic parameters is not necessarily the same, even if the weighted average value in the same mode is calculated as the learning value when learning each characteristic parameter, all the characteristic parameters There is a possibility that a value corresponding to the actual operating characteristic of the fuel injection valve cannot be properly learned as a learning value.

  The present invention has been made in view of such a situation, and an object of the present invention is to learn the fuel injection characteristics of an internal combustion engine that can accurately learn the operating characteristics of the fuel injection valve based on the fuel pressure in the fuel supply system. To provide an apparatus.

  A cooling device for an on-vehicle internal combustion engine for solving the above-described problem has a pressure sensor for detecting a fuel pressure inside a fuel supply system having a fuel injection valve, and is based on the fuel pressure detected by the pressure sensor. In a fuel injection characteristic learning device for an internal combustion engine that executes a learning process for learning a plurality of characteristic parameters as operating characteristics of a fuel injection valve, the apparatus calculates a weighted average value for each of the plurality of characteristic parameters in the learning process. The weighted average values are calculated and stored separately as learning values, and different values are set among the plurality of characteristic parameters as the weighted average weighting coefficients.

  According to the above apparatus, when the influence of the factors that change the variation of the detected value of the pressure sensor in the short term differs among a plurality of characteristic parameters, the weighting coefficient in calculating the weighted average value for the characteristic parameters As described above, a value suitable for each characteristic parameter can be set individually. Therefore, it is possible to calculate a value in which unnecessary change due to the influence of the above factors is suppressed as a weighted average value for each characteristic parameter, and to learn the same value as a learning value. Therefore, it is possible to accurately learn the operating characteristics of the fuel injection valve based on the fuel pressure in the fuel supply system.

  In the above apparatus, the plurality of characteristic parameters are learned based on a valve opening delay time of the fuel injection valve and a fuel pressure detected by the pressure sensor during a fuel pressure fluctuation period associated with the opening of the fuel injection valve. The apparatus may set a weighting coefficient in calculating the weighted average value for the valve opening delay time to a value larger than the weighting coefficient in calculating the weighted average value for the predetermined parameter. it can.

  When the fuel properties (temperature and properties) are different, the viscosity of the fuel is different. Therefore, even when the fuel injection valve is driven to open in the same mode, the fuel pressure fluctuation mode at the time of opening and closing is different. It will be a thing.

  In the above apparatus, the time from when the valve opening signal is output to the fuel injection valve to when the fuel injection from the fuel injection valve is actually started (the valve opening delay time) is a pressure drop accompanying the start of fuel injection. Since this is the time before the start of, the fuel pressure is not easily affected by variations in fuel pressure variation caused by differences in fuel properties. On the other hand, the predetermined parameter which is a characteristic parameter other than the valve opening delay time and which is learned based on the fuel pressure detected by the pressure sensor in the fuel pressure fluctuation period accompanying the opening of the fuel injection valve is the fuel pressure. Since the calculation is based on the same fuel pressure during the fluctuation period, the fuel pressure is easily affected by variations in the fluctuation mode of the fuel pressure due to the difference in fuel properties. Therefore, when paying attention to the influence of variations in the variation of fuel pressure caused by differences in fuel properties, the valve opening delay time is a characteristic parameter that is less likely to cause a short-term change compared to the predetermined parameter. It can be said that.

  According to the above apparatus, since a large value is set as the weighting coefficient when calculating the weighted average value for the valve opening delay time that is unlikely to cause a short-term change, the learning value of the valve opening delay time is relatively long. Values that change gradually over time can be learned. In addition, when a weighted average value is calculated for a predetermined parameter that is likely to cause a short-term change, a small value is set as the weighting coefficient. Therefore, the learning value of the predetermined parameter changes in a relatively short period. It is possible to learn a value, that is, a value that can follow a change in fuel properties at an early stage.

  In the above apparatus, as the predetermined parameter, a fuel injection rate increasing speed, a fuel injection rate decreasing speed, a maximum value of the fuel injection rate, and a valve closing delay time of the fuel injection valve can be adopted.

  In the above apparatus, it is preferable that the weighting coefficient is variably set according to the amount of fuel injected from the fuel injection valve when the fuel pressure used for the learning process is detected by the pressure sensor.

  The influence of factors that change the variation of the detected value of the pressure sensor in the short term also depends on the amount of fuel injected from the fuel injection valve. According to the apparatus, an appropriate value corresponding to the difference in the influence of the factor can be calculated as a weighted average value for each characteristic parameter.

In the above device, the pressure sensor may be provided integrally with the fuel injection valve.
According to the above-described device, the fuel pressure at a location near the injection hole of the fuel injection valve can be detected as compared with a device in which the fuel pressure is detected at a position away from the fuel injection valve. A decrease in fuel pressure inside the fuel injection valve accompanying the valve can be detected with high accuracy. Therefore, it is possible to accurately calculate and learn a plurality of characteristic parameters as operating characteristics of the fuel injection valve based on the variation of the fuel pressure.

  In the above apparatus, the internal combustion engine includes a plurality of cylinders, the fuel supply system includes a pressure accumulating container that stores fuel in a pressurized state, and the fuel injection valve is provided for each cylinder of the internal combustion engine. The pressure accumulating container and the fuel in a fuel supply passage for supplying the fuel to the fuel injection valve are provided for each cylinder of the internal combustion engine. It is good also as what detects the fuel pressure of the site | part between the injection holes of an injection valve.

  According to the above apparatus, in a multi-cylinder internal combustion engine in which the operating characteristics of the fuel injection valve are different for each cylinder, the operating characteristics of each fuel injection valve are based on the fuel pressure detected by the dedicated pressure sensor provided for each cylinder. Can be learned with high accuracy.

1 is a schematic diagram showing a schematic configuration of an embodiment of a fuel injection characteristic learning device for an internal combustion engine. 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 timing chart which shows an example of the fluctuation | variation aspect of the fuel pressure at the time of opening and closing of a fuel injection valve. The timing chart which expands and shows the intersection of the straight line and operating pressure which are shown in FIG. The flowchart which shows the execution procedure of a learning process.

Hereinafter, an embodiment of a fuel injection characteristic learning device for an internal combustion engine 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 by the combustion of fuel in the cylinder 11, and the crankshaft 14 is forcibly rotated. 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 this embodiment, each fuel injection valve 20, the branch passage 31a, the supply passage 31b, the fuel pump 33, and the common rail 34 function as 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 (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. 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, 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 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. In order to leave the injection hole 23, the fuel injection valve 20 is in a state where the 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. The pressure sensor 51 includes a sensor main body 51A that outputs a signal corresponding to the fuel pressure and a memory 51B that stores a detection value of the sensor main body 51A. It is provided for every 10 cylinders 11 (# 1 to # 4).

  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 injection pressure control is executed as follows. That is, first, a control target value (target fuel pressure) for the fuel pressure in the common rail 34 is calculated based on the passage air amount GA and the engine speed NE, and the fuel is set so that the actual fuel pressure becomes the target fuel 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, in other words, 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 executed as follows. That is, first, based on values (so-called engine parameters) correlated with the operating state of the internal combustion engine 10 such as the passage air amount GA, the engine rotational speed NE, and the accelerator operation amount ACC, the control target value (target injection amount) of the fuel injection amount. ) And a control target value (target injection timing) of the fuel injection timing is calculated. In the present embodiment, the relationship between the engine operating state determined by the engine parameters and each control target value suitable for the operating state is obtained in advance based on the results of experiments and simulations and stored in the electronic control unit 40, respectively. Then, the electronic control unit 40 sets various control target values separately from the above relationship based on the engine parameters at that time.

  And the control target value (target injection period TAU) about the valve opening period of the fuel injection valve 20 is set from a model formula based on the said 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. Specifically, a model equation having variables such as a target injection amount, fuel pressure PQ, and a learning value to be described later is determined and stored in advance in the electronic control unit 40, and the target injection period TAU is calculated through the model equation.

  Then, a drive pulse is output from the electronic control unit 40 in a manner corresponding to the target injection timing and the target injection period TAU, and each fuel injection valve 20 is driven to open individually based on the input of this drive pulse. As a result, an amount of fuel suitable for the engine operating state at that time is injected from each fuel injection valve 20 and supplied into each cylinder 11 of the internal combustion engine 10. It is applied to the shaft 14.

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.
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 speed Qdn are adopted as the characteristic parameters. Specifically, the valve opening delay time τd is from the time when the electronic control unit 40 outputs the valve opening signal (FIG. 3A) to the fuel injector 20 until the fuel injection from the fuel injector 20 is actually started. The injection rate increasing speed Qup is the increasing speed of the fuel injection rate (FIG. 3B) after the 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 increases when the fuel injection valve 20 is driven to open, and then lifts when the valve is driven to close. As the amount decreases, it increases. In the present embodiment, 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 average 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 the orthogonal coordinates is the fuel injection rate and the horizontal axis is the 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 fuel 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 fuel 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 fuel 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 the target injection amount, target injection timing, target fuel 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 values for a plurality of characteristic parameters of the fuel injection valve 20 are learned based on the relationship between the detection 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, a weighted average value of these differences Δτd, ΔQup, ΔQmax, ΔQdn, Δτe is calculated, and the weighted average value is used as a learning value Gτd, GQup, GQmax, It is stored in the electronic control unit 40 as GQdn and Gτe.

  In the present embodiment, these learned values Gτd, GQup, GQmax, GQdn, and Gτe are used as calculation parameters for calculating the target injection period TAU based on the above-described model formula. By calculating the target injection period TAU in this way, the influence of the variation in the operating characteristics of the fuel injection valve 20 is compensated. In the present embodiment, the process of calculating the learning value based on the fuel pressure PQ is executed based on the output signal of the pressure sensor 51 corresponding to each cylinder 11 (# 1 to # 4) of the internal combustion engine 10. In the apparatus according to the present embodiment, a plurality of learning areas defined by the fuel pressure (specifically, the target fuel pressure) and the fuel injection amount (specifically, the target injection amount) are defined, and learning is performed for each of these areas. The value is learned and stored.

  Here, the variation mode of the detected value of the pressure sensor 51 accompanying the opening and closing of the fuel injection valve 20 is prolonged with a change with time in the components of the fuel supply system (such as deposit adhesion to the injection hole 23 of the fuel injection valve 20). In addition to gradually changing over a period, it also changes in the short term due to the influence of various factors such as noise superimposed on the detection signal and the properties (temperature, properties) of the fuel.

  In the present embodiment, in order to suppress unnecessary changes in the learning values Gτd, GQup, GQmax, GQdn, and Gτe due to such short-term changes in the detected value fluctuation mode, the differences Δτd, ΔQup, Weighted average values of ΔQmax, ΔQdn, and Δτe are calculated and stored as learning values.

  By the way, since the influence of the above factors on a plurality of characteristic parameters is not necessarily the same, even if a weighted average value is calculated in the same manner when learning each characteristic parameter, all the characteristic parameters are actually calculated. There is a possibility that a value corresponding to the operation characteristic of the fuel injection valve 20 cannot be properly learned as a learning value.

  For example, when the fuel properties (temperature and properties) are different, the fuel viscosity is different. Therefore, even when the fuel injection valve 20 is driven to open in the same mode, the variation mode of the fuel pressure PQ at the time of opening and closing the fuel injection valve 20 Will be different.

  Among the plurality of characteristic parameters, the valve opening delay time τd is a time before the timing when the fuel pressure PQ starts to decrease due to the start of fuel injection from the fuel injection valve 20, and therefore fuel caused by differences in fuel properties. It is difficult to be affected by variations in the variation mode of the pressure PQ. On the other hand, predetermined parameters (injection rate increasing speed Qup, maximum injection rate Qmax, injection rate decreasing speed Qdn, valve closing delay time τe) other than the valve opening delay time τd (FIG. 4) among the plurality of characteristic parameters are as follows. The fuel pressure PQ is detected based on the fuel pressure PQ detected by the pressure sensor 51 during the fuel pressure fluctuation period accompanying the opening of the fuel injection valve 20. For this reason, the fuel pressure PQ is easily affected by variations in the variation of the fuel pressure PQ due to the difference in fuel properties.

  For this reason, when focusing on the influence of the variation in the variation of the fuel pressure PQ caused by the difference in fuel properties, the valve opening delay time τd causes a short-term change compared to other characteristic parameters. It can be said that this is a difficult characteristic parameter.

  However, as a result of various experiments and simulations by the inventors, it has been found that the valve opening delay time τd is likely to change in the apparatus of this embodiment. This is thought to be caused by the following.

FIG. 6 shows an example of the variation of the fuel pressure when the fuel injection valve 20 is opened and closed.
As indicated by lines M1 to M3 in FIG. 6, when the fuel injection valve 20 is opened at time t11, the fuel pressure PQ immediately decreases at a relatively slow speed, and thereafter gradually increases and decreases. To come. As described above, in the present embodiment, when calculating the detection time waveform in the learning process, a straight line (straight line in FIG. 6) using the least square method based on the fuel pressure PQ that decreases immediately after the fuel injection valve 20 is opened. L5 to L7) are obtained, and the fuel injection start timing (the injection start timing Tos) is specified based on the intersection of this straight line and the operating pressure Pac (see FIG. 4).

  FIG. 7 shows a specific example of the intersection of the straight line (straight lines L5 to L6 shown in FIG. 6) and the operating pressure Pac when the fuel pressure decrease rate is different. As shown in FIG. 7, even when the fuel injection valve 20 is opened at the same timing (time t11), the rate of decrease in the fuel pressure PQ due to differences in fuel properties, fuel injection amounts, etc. Is different, the intersections (A1, A2, A3) of the straight lines L5 to L7 and the operating pressure Pac are different, and therefore the injection start timing Tos specified based on the same period is also different.

  The apparatus according to the present embodiment is accompanied by a change in the fuel property, even though the valve opening delay time τd is a value that is hardly affected by the variation in the variation of the fuel pressure PQ caused by the difference in the fuel property. The control structure is highly likely to cause a change in the valve opening delay time τd due to the change when the rate of decrease in the fuel pressure PQ changes.

  In light of this situation, in this embodiment, when calculating a weighted average value for each of a plurality of characteristic parameters (specifically, a weighted average value of differences between the characteristic parameters), a plurality of characteristics are used as the weighting coefficients. Different values are set for each parameter. Specifically, the coefficient K1 for the difference Δτd in the valve opening delay time τd, the coefficient K2 for the difference ΔQup in the injection rate increase speed Qup, the coefficient K3 for the difference ΔQmax in the maximum injection rate Qmax, and the difference in the injection rate decrease speed Qdn A coefficient K4 for ΔQdn and a coefficient K5 for the difference Δτe of the valve closing delay time τe are set. The weighting coefficient K1 in the calculation of the weighted average value of the difference Δτd in the valve opening delay time τd is the weighting coefficient K2 to K5 in the calculation of the weighted average values of the other characteristic parameter differences ΔQup, ΔQmax, ΔQdn, Δτe. It is set to a larger value (K1> K2, K1> K3, K1> K4, and K1> K5).

The operation of setting the weighting coefficients K1 to K5 in this way will be described below.
In the apparatus according to the present embodiment, as described above, when calculating the weighted average value of the difference Δτd in the valve opening delay time τd that is unlikely to cause a short-term change, a large value is set as the weighting coefficient K1. As the learning value Gτd for the valve delay time τd, a value that gradually changes over a relatively long period can be learned.

  In addition, when calculating the weighted average values of the differences ΔQup, ΔQmax, ΔQdn, Δτe among the predetermined parameters that are likely to cause a short-term change, relatively small values are set as the weighting coefficients K2 to K5. Therefore, as the learning values GQup, GQmax, GQdn, and Gτe for the predetermined parameter, it is possible to learn values that change in a relatively short period, that is, values that can promptly follow changes in fuel properties.

  As described above, according to the present embodiment, although the influence of the factor that changes the variation of the detection value of the pressure sensor 51 described above in a short period is different among a plurality of characteristic parameters, the weighted average of the differences between the characteristic parameters is obtained. Values suitable for each characteristic parameter can be individually set as the weighting coefficients K1 to K5 in the calculation of the values. Therefore, it is possible to calculate a value in which unnecessary changes due to the influence of the above factors are suppressed as weighted average values of the differences Δτd, ΔQup, ΔQmax, ΔQdn, Δτe between the characteristic parameters, and the same values are learned values Gτd, GQup, It can be learned as GQmax, GQdn, Gτe.

Hereinafter, a specific execution procedure of the learning process described above will be described.
FIG. 8 shows an execution procedure of the learning process. The series of processes shown in the flowchart of FIG. 6 is executed by the electronic control unit 40 as an interrupt process at predetermined intervals.

  As shown in FIG. 8, in this process, first, the fuel pressure PQ stored in the memory 51B of the pressure sensor 51 is read, and a detection time waveform of the fuel injection rate is formed based on the variation mode of the fuel pressure PQ. (Step S10). Specifically, 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 speed Qdn are specified.

  Further, the fuel is based on the target injection amount, the target injection timing, and the target fuel pressure that are set when the fuel injection valve 20 is driven to open, which causes the fluctuation of the fuel pressure PQ that is read at the time of the current execution of this process. A basic time waveform of the injection rate is set (step S11). Specifically, the valve opening delay time τdb, the injection rate increasing speed Qupb, the maximum injection rate Qmaxb, the valve closing delay time τeb, and the injection rate decreasing speed Qdnb are calculated.

  Based on the comparison between the detected time waveform of the fuel injection rate and the basic time waveform, the differences Δτd, ΔQup, ΔQmax, ΔQdn, Δτe of the characteristic parameters (τd, Qup, Qmax, τe, Qdn) are calculated. (Step S12).

  Further, the weighted average of the differences Δτd, ΔQup, ΔQmax, ΔQdn, Δτe based on the target injection amount set when the fuel injection valve 20 is driven to open, which causes the fluctuation of the fuel pressure PQ read at this time. Weighting coefficients K1 to K5 used for calculating values are calculated (step S13). In the present embodiment, a relationship between coefficients K1 to K5 that can calculate an appropriate value as a learning value based on the results of various experiments and simulations and the target injection amount is obtained in advance, and this relationship is electronic. It is stored in the control unit 40. In the process of step S13, the coefficients K1 to K5 are calculated based on this relationship.

  The degree to which the fluctuation mode of the detected value of the pressure sensor 51 is changed in the short term when the fuel property is changed varies depending on the amount of fuel injected from the fuel injection valve 20. In view of this point, in the present embodiment, the amount of fuel injected from the fuel injection valve 20 at the time of detection by the pressure sensor 51 of the fuel pressure PQ used for forming the detection time waveform (specifically, the target injection amount at that time) ), The coefficients K1 to K5 are variably set. Therefore, an appropriate value can be calculated as a weighted average value for each characteristic parameter in a manner corresponding to the difference in influence due to the change in fuel properties caused by the difference in fuel injection amount.

  After the coefficients K1 to K5 are calculated in this way, the weighted average of the differences Δτd, ΔQup, ΔQmax, ΔQdn, and Δτe from the following relational expressions (1) to (5) using the coefficients K1 to K5. Values are calculated separately and the weighted average values are stored as learning values Gτd, GQup, GQmax, GQdn, Gτe (step S14). In the following relational expressions (1) to (5), the learning values stored in the electronic control unit 40 when calculating the learning values in the process of step S14 are Gτd [i] and GQup [i], respectively. , GQmax [i], GQdn [i], Gτe [i].

Gτd = Gτd [i] + (Δτd−Gτd [i]) / K1 (1)
GQup = GQup [i] + (ΔQup−GQup [i]) / K2 (2)
GQmax
= GQmax [i] + (ΔQmax−GQmax [i]) / K3 (3)
GQdn = GQdn [i] + (ΔQdn−GQdn [i]) / K4 (4)
Gτe = Gτe [i] + (Δτe−Gτe [i]) / K5 (5)

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

  (1) In the learning process, weighted average values of a plurality of characteristic parameter differences Δτd, ΔQup, ΔQmax, ΔQdn, Δτe are calculated, and the weighted average values are used as learning values Gτd, GQup, GQmax, GQdn, It was memorized separately as Gτe. Then, different values are set among the plurality of characteristic parameters as the weighting coefficients K1 to K5 in the calculation of the weighted average value. For this reason, it is possible to calculate values in which unnecessary changes due to the influence of the factors are suppressed as weighted average values of the differences Δτd, ΔQup, ΔQmax, ΔQdn, Δτe between the characteristic parameters, and the same values are learned values Gτd, GQup, It can be learned as GQmax, GQdn, Gτe. Therefore, it is possible to accurately learn the operating characteristics of the fuel injection valve 20 based on the fuel pressure in the fuel supply system.

  (2) The weighting coefficient K1 in the calculation of the weighted average value of the difference Δτd of the valve opening delay time τd is used as the weighting coefficient K2 in the calculation of the weighted average value of the differences ΔQup, ΔQmax, ΔQdn, Δτe of the other characteristic parameters. A value larger than ˜K5 was set. As a result, a large value is set as the weighting coefficient K1 when calculating the weighted average value of the difference Δτd in the valve opening delay time τd, which is unlikely to cause a short-term change, and therefore, as the learning value Gτd of the valve opening delay time τd. Values that change gradually over a relatively long period can be learned. In addition, when calculating the weighted average value of the difference ΔQup, ΔQmax, ΔQdn, Δτe among the predetermined parameters that are likely to cause a short-term change, relatively small values are set as the weighting coefficients K2 to K5. As the learning values GQup, GQmax, GQdn, and Gτe, it is possible to learn values that can quickly follow changes in fuel properties.

  (3) The coefficients K1 to K5 are variably set according to the target injection amount set when the fuel pressure PQ used for forming the detection time waveform is detected by the pressure sensor 51. Therefore, it is possible to calculate an appropriate value as a weighted average value for each characteristic parameter in a manner corresponding to a difference in influence due to a change in fuel properties caused by a difference in fuel injection amount.

  (4) As the fuel injection valve 20, one in which a pressure sensor 51 that outputs a signal corresponding to the fuel pressure PQ in the introduction passage 27 is integrally attached is adopted. For this reason, for example, the fuel pressure at a portion near the injection hole 23 of the fuel injection valve 20 is detected 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. Therefore, a 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. Therefore, a plurality of characteristic parameters as operating characteristics of the fuel injection valve 20 can be accurately calculated and learned on the basis of the fluctuation mode of the fuel pressure PQ detected by the pressure sensor 51.

  (5) The learning process is executed based on the output signal of the pressure sensor 51 corresponding to each cylinder 11 (# 1 to # 4) of the internal combustion engine 10. Therefore, in the multi-cylinder internal combustion engine 10 in which the operating characteristics of the fuel injection valve 20 are different for each cylinder 11, a plurality of characteristic parameters are set based on the fuel pressure PQ detected by the dedicated pressure sensor 51 provided for each cylinder 11. It can be calculated and learned with high accuracy.

The above embodiment may be modified as follows.
When the detection time waveform is formed, instead of obtaining the straight line L1 using the least square method, a single differential value of the fuel pressure PQ during the period in which the fuel pressure PQ drops immediately after the start of fuel injection is calculated. At the same time, the tangent of the time waveform of the fuel pressure PQ at the point where the one-time differential value is minimized may be obtained.

  In the formation of the detection time waveform, instead of obtaining the straight line L2 using the least square method, the fuel pressure PQ is once differentiated in the period in which the fuel pressure PQ rises after dropping once immediately after the start of fuel injection execution. While calculating the value, the tangent of the time waveform of the fuel pressure PQ at the point where the one-time differential value becomes maximum may be obtained.

  Instead of calculating the weighted average value of the differences Δτd, ΔQup, ΔQmax, ΔQdn, Δτe among the plurality of characteristic parameters of the fuel injection valve 20 and storing the same value as a learning value, a plurality of characteristic parameters (τd, Qup, The weighted average value of Qmax, Qdn, τe) itself may be calculated and stored as a learning value. As long as it is a device that calculates a weighted average value for a plurality of characteristic parameters and stores the same value as a learning value, the device of the above-described embodiment can be applied with its configuration changed as appropriate.

  A fuel pressure (specifically, a reference pressure Pbs, a target fuel pressure, etc.) may be used as a calculation parameter used for calculating the coefficients K1 to K5. The degree of short-term change in the fluctuation mode of the detection value of the pressure sensor 51 when the fuel property changes depends on the pressure of the fuel injected from the fuel injection valve 20. According to the above apparatus, since the coefficients K1 to K5 are variably set according to the reference pressure Pbs and the target fuel pressure when the fuel pressure PQ is detected by the pressure sensor 51, the fuel caused by such a difference in fuel pressure. An appropriate value can be calculated as a weighted average value for each characteristic parameter in accordance with the difference in influence due to changes in properties.

A predetermined constant value may be set as the coefficients K1 to K5.
Any two of the coefficients K2 to K5 may be set to the same value, any three may be set to the same value, or all may be set to the same value.

  A fuel property as a factor that changes the variation of the detected value of the pressure sensor 51 in a short period when the relationship between the target injection amount and the coefficients K1 to K5 that can calculate an appropriate value as a learning value is obtained in advance. Other factors may be considered. In such an apparatus, a value smaller than any one of the coefficients K2 to K5 may be set as the coefficient K1 depending on a factor newly adopted. In short, the weighted average value for each characteristic parameter is calculated so that unnecessary values due to the above factors can be suppressed as weighted average values for a plurality of characteristic parameters, and the same value can be learned as a learned value. It is only necessary that the weighting coefficient can be set.

  A plurality of characteristic parameters as operating characteristics of the fuel injection valve 20 can be arbitrarily changed. For example, only two 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 are used as specific parameters, or only three of them are used. Specific parameters can be set, or only four can be set as specific 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.

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

  The fuel injection characteristic learning 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 learning 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, 51A ... Sensor body, 51B ... Memory, 52 ... Intake sensor, 53 ... Crank sensor, 54 ... Accelerator Sensor.

Claims (6)

A pressure sensor for detecting the fuel pressure inside the fuel supply system having the fuel injection valve, and learning a plurality of characteristic parameters as operating characteristics of the fuel injection valve based on the fuel pressure detected by the pressure sensor In the fuel injection characteristic learning device for the internal combustion engine that executes the learning process,
The apparatus calculates a weighted average value for each of the plurality of characteristic parameters in the learning process, stores the weighted average values separately as learning values, and uses the plurality of characteristic parameters as a weighting coefficient for the weighted average. A fuel injection characteristic learning device for an internal combustion engine, wherein different values are set between the two. The fuel injection characteristic learning device for an internal combustion engine according to claim 1,
The plurality of characteristic parameters are a delay time for opening the fuel injection valve, and a predetermined parameter learned based on a fuel pressure detected by the pressure sensor in a fuel pressure fluctuation period associated with the opening of the fuel injection valve. Including
The apparatus sets the weighting coefficient in calculating the weighted average value for the valve opening delay time to a value larger than the weighting coefficient in calculating the weighted average value for the predetermined parameter. Injection characteristic learning device. 3. The fuel injection characteristic learning device for an internal combustion engine according to claim 1, wherein the predetermined parameters are a fuel injection rate increase rate, a fuel injection rate decrease rate, a maximum value of the fuel injection rate, and the fuel injection valve. A fuel injection characteristic learning device for an internal combustion engine, characterized by including a valve closing delay time. The fuel injection characteristic learning device for an internal combustion engine according to any one of claims 1 to 3,
The apparatus variably sets the weighting coefficient according to the amount of fuel injected from the fuel injection valve when the fuel pressure used for the learning process is detected by the pressure sensor. Fuel injection characteristic learning device. In the fuel injection characteristic learning device for an internal combustion engine according to any one of claims 1 to 4,
The fuel injection characteristic learning apparatus for an internal combustion engine, wherein the pressure sensor is provided integrally with the fuel injection valve. In the fuel injection characteristic learning device for an internal combustion engine according to any one of claims 1 to 5,
The internal combustion engine has a plurality of cylinders and a pressure accumulating container for storing fuel in a state where the fuel supply system is pressurized,
The fuel injection valve is provided for each cylinder of the internal combustion engine and is separately connected to the pressure accumulating vessel,
The pressure sensor is provided for each cylinder of the internal combustion engine, and measures a fuel pressure at a portion between the pressure accumulating container and an injection hole of the fuel injection valve in a fuel supply passage for supplying fuel to the fuel injection valve. An apparatus for learning fuel injection characteristics of an internal combustion engine, characterized in that it detects.