JP2019065807A - Fuel injection control device - Google Patents

Abstract

To appropriately eliminate effects of front-stage injection in rear-stage injection in multi-stage injection.SOLUTION: A fuel injection system includes: a common rail 11; a fuel pump 12 for pressure-feeding fuel to the common rail 11; a fuel injection valve 30 for injecting high-pressure fuel in the common rail 11; and a fuel pressure sensor 40 for detecting fuel pressure in a fuel passage from the common rail 11 to a nozzle hole 35 of the fuel injection valve 30. An orifice is formed in an outlet passage section of the common rail 11. An ECU 50 includes: a fuel pressure acquisition section for acquiring the fuel pressure detected by the fuel pressure sensor 40; a waveform processing section for deducting a model waveform calculated from a pressure pulsation model from a detection waveform that is a waveform of the fuel pressure acquired by the fuel pressure acquisition section after completion of front-stage injection in multi-stage injection; and an injection control section that performs rear-stage injection on the basis of the deduction result obtained by the waveform processing section. Based on orifice flow rate characteristics, the waveform processing section calculates the model waveform from the pressure pulsation model.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel injection control device applied to a fuel injection system that performs fuel injection using high pressure fuel stored in a pressure accumulation container.

  In a fuel injection system in which fuel is supplied from a common rail (accumulation container) to a fuel injection valve, when fuel is injected from the fuel injection valve, the fuel pressure (fuel pressure) inside the fuel injection valve changes according to the change in injection rate Do. Therefore, the fuel pressure sensor mounted on each fuel injection valve detects the fluctuation waveform of the fuel pressure at the time of fuel injection, and estimates the waveform showing the injection rate change based on the detected fluctuation waveform.

  In addition, when performing multistage injection by the fuel injection valve in an internal combustion engine, pressure pulsation due to the prestage injection occurs after the prestage fuel injection (prestage injection) is performed, which affects the poststage injection It is conceivable. This is because the fuel pressure is erroneously recognized by the pressure pulsation after the pre-injection when the post-injection is performed. Therefore, it has been studied to remove the influence of the pre-injection by subtracting the pressure pulsation calculated by the model from the actual pressure pulsation due to the pre-injection (see, for example, Patent Document 1).

JP, 2010-3004, A

  By the way, although the common rail is provided with an orifice in the outlet passage portion leading to the fuel injection valve, it is conceivable that the flow characteristic of the fuel flowing through the orifice changes due to the manufacturing tolerance of the orifice. Specifically, it is conceivable that the flow characteristic of the orifice changes depending on the orifice diameter, orifice inlet R, orifice smoothness and the like. And there is concern that the influence of the pre-injection can not be properly removed due to the unintentional variation in the flow rate characteristics of the orifice.

  The present invention has been made in view of the above problems, and a main object thereof is to provide a fuel injection control device capable of appropriately removing the influence of pre-stage injection at the time of post-stage injection in multi-stage injection.

  Hereinafter, a means for solving the above-mentioned subject, and its operation effect are explained.

The fuel injection control device of this means
A pressure accumulation container for accumulating and holding high pressure fuel, a fuel pump for pressure-feeding the fuel to the accumulation container, a fuel injection valve for injecting the high pressure fuel accumulated and held in the accumulation container, and the fuel injection from the pressure accumulation container And a fuel pressure sensor for detecting the fuel pressure in the fuel passage to the injection port of the valve, wherein the pressure storage container is applied to a fuel injection system in which an orifice is formed in an outlet passage connected to the fuel injection valve. A fuel injection control device that implements multiple fuel injections as multistage injection in one combustion cycle of an internal combustion engine, comprising:
A fuel pressure acquisition unit that acquires the fuel pressure detected by the fuel pressure sensor;
A waveform processing unit that subtracts a model waveform calculated by a pressure pulsation model from a detection waveform that is a waveform of fuel pressure acquired by the fuel pressure acquisition unit after completion of pre-stage injection in the multistage injection;
An injection control unit that implements post-stage injection based on the result of subtraction by the waveform processing unit;
Equipped with
The waveform processing unit calculates a model waveform based on the pressure pulsation model based on flow rate characteristics of the orifice.

  When performing multi-stage injection in an internal combustion engine, the pressure due to pre-stage injection is subtracted by subtracting the model waveform calculated by the pressure pulsation model from the detected waveform which is the waveform of fuel pressure detected by the fuel pressure sensor after completion of pre-stage injection. It becomes possible to properly implement the latter stage injection without being affected by the fluctuation. However, if there is a variation in the orifice diameter and the like due to manufacturing tolerances in the orifice provided in the outlet passage portion of the pressure accumulation container, the control accuracy of the post-stage injection is lowered.

  In this respect, according to the above configuration, a model waveform according to the pressure pulsation model is calculated based on the flow rate characteristic of the orifice, and the model waveform is subtracted (subtracted) from the detected waveform using the model waveform. The post-injection is performed based on the result of the subtraction. In this case, even if the orifice diameter or the like varies, the influence of pressure pulsation due to the pre-injection can be properly removed. Therefore, desired injection amount accuracy can be obtained.

The figure which shows the outline of a fuel-injection system. Sectional drawing which shows the internal structure of a common rail. The functional block diagram regarding the process which subtracts a model waveform from a detection waveform. The figure which shows the relationship between an orifice flow value and an amplitude correction coefficient. The figure which shows the relationship between an orifice flow value and a frequency correction coefficient. The flowchart which shows the process sequence which subtracts a model waveform from a detection waveform. The figure which shows the comparison with this embodiment which correct | amended a model waveform based on an orifice flow value, and the conventional thing which is not correct | amending. The figure which shows the comparison with this embodiment which correct | amended a model waveform based on an orifice flow value, and the conventional thing which is not correct | amending. The time chart which shows the fuel pressure behavior etc. to the injection command signal. The flowchart which shows the process sequence which calculates a pressure peak value. 12 is a flowchart showing a processing procedure of subtracting a model waveform from a detected waveform in the second embodiment. The figure which shows the relationship between a pressure peak value and an orifice flow equivalent. The time chart which shows the fuel pressure behavior to the injection command signal. The flowchart which shows the process sequence which calculates a phase difference. 12 is a flowchart showing a processing procedure of subtracting a model waveform from a detected waveform in the third embodiment. The figure which shows the relationship between a phase difference and an orifice flow volume equivalent value. The time chart which shows a fuel pressure waveform. The figure which shows the relationship between various parameters and orifice flow equivalent value.

First Embodiment
Hereinafter, an embodiment in which a fuel injection control device is mounted on a vehicle will be described with reference to the drawings. FIG. 1 shows the configuration of a fuel injection system to which the fuel injection control device according to the present embodiment is applied. The fuel injection system is assumed to be applied to a four-cylinder diesel engine (multi-cylinder internal combustion engine). This fuel injection system includes a common rail 11 (pressure accumulation container) for accumulating and holding high pressure fuel, a fuel pump 12 for pressure-feeding the fuel to the common rail 11, and fuel injection valves provided in each cylinder # 1 to # 4 of the engine And 30, a fuel pressure sensor 40 for sequentially detecting the fuel pressure in each fuel passage from the common rail 11 to the injection port of each fuel injection valve 30.

  The fuel tank 13 is a fuel container for storing fuel (diesel oil) supplied to each cylinder # 1 to # 4 of the engine. The fuel in the fuel tank 13 is pressure-fed to the common rail 11 by the fuel pump 12 driven in conjunction with the crank shaft of the engine and accumulated and held. The pressure in the common rail 11 is the supply pressure of the fuel supplied to the fuel injection valve 30 of each cylinder. The fuel accumulated in the common rail 11 is distributed and supplied to the fuel injection valve 30 of each cylinder through the high pressure pipe 14 (fuel passage). The fuel injection valve 30 of each cylinder injects fuel in a predetermined combustion order of the engine.

  The internal structure of the common rail 11 is shown in FIG. The common rail 11 has a cylindrical main body portion 21 and a plurality of pipe connection portions 22 provided so as to project from the main body portion 21. A pressure accumulation chamber 23 is formed in the main body portion 21. A communication hole 24 communicating with the pressure accumulation chamber 23 is formed in the connection portion 22. Further, an orifice 25 is provided at an outlet passage of the common rail 11, that is, between the pressure accumulation chamber 23 and the communication hole 24. High-pressure piping 14 for each cylinder is connected to each piping connection 22. The high pressure fuel in the pressure accumulation chamber 23 flows into each high pressure pipe 14 through the orifice 25 and the communication hole 24 and is further supplied to the fuel injection valve 30.

  Next, the configuration of the fuel injection valve 30 will be described. The fuel injection valve 30 has the same configuration in any of the cylinders, and in the present embodiment, in particular, it has a pressure sensor integrated configuration.

  The fuel injection valve 30 is configured to include a body 31, a needle valve 32, and an actuator 33 formed of an electromagnetic coil, a piezo element, and the like. The body 31 has a first portion 31a and a second portion 31b connected to each other. The body 31 is formed with a high pressure passage 34 into which high pressure fuel is introduced, an injection hole 35 which is an injection port for injecting the high pressure fuel, and a low pressure passage 36 through which the high pressure fuel flows out to the low pressure side. The fuel supplied from the common rail 11 is injected from the injection hole 35 through the high pressure passage 34. The needle valve 32 slides inside the body to open and close the injection hole 35.

  Further, a back pressure chamber 37 is formed in the body 31 so as to be branched from the high pressure passage 34. High pressure fuel is introduced into the back pressure chamber 37, and a back pressure is applied to the needle valve 32 in the back pressure chamber 37. A control valve 38 is provided between the high pressure portion including the high pressure passage 34 and the back pressure chamber 37 and the low pressure passage 36, and the communication state between the high pressure side and the low pressure side is switched by the control valve 38. There is.

  Specifically, when the actuator 33 is not energized, the control valve 38 holds the high-pressure side and the low-pressure side in a state where they are disconnected from each other. In this state, the needle valve 32 is held at the valve closing position (that is, the position where the tip of the needle valve 32 is seated on the seat portion), and the fuel injection from the injection hole 35 is stopped. Then, when the actuator 33 is energized, the control valve 38 is pushed to the front end side of the fuel injection valve 30, and the high pressure side and the low pressure side are communicated with each other. As a result, the fuel pressure in the back pressure chamber 37 drops, the needle valve 32 moves to the open position (that is, the position where the tip of the needle valve 32 separates from the seat portion), and fuel is injected from the injection hole 35 . Thereafter, when energization of the actuator 33 is stopped, the high pressure side and the low pressure side are blocked again by the control valve 38, and the needle valve 32 returns to the valve closing position with the pressure increase in the back pressure chamber 37.

  Fuel pressure sensors 40 are mounted on the fuel injection valves 30, respectively. The fuel pressure sensor 40 includes a stem 41 as a strain generating body, a pressure sensor element 42, and a communication circuit 43. The stem 41 is attached to the body 31 and has a diaphragm portion 41a. The diaphragm portion 41 a elastically deforms under the pressure of the high pressure fuel flowing through the high pressure passage 34. The pressure sensor element 42 is attached to the diaphragm 41a, and outputs a pressure signal according to the amount of elastic deformation of the diaphragm 41a. The pressure signal output from the pressure sensor element 42 is transmitted to the ECU 50 by the communication circuit 43.

  The ECU 50 is configured by a microcomputer (an electronic control unit) including a CPU, a ROM, a RAM, an I / O, and a bus line connecting these. The RAM is a data memory, and the ROM is a program memory. The ECU 50 includes, as a storage unit, a memory 51 which is a non-volatile memory such as an EEPROM. The ECU 50 calculates a target injection state (injection stage number, injection start timing, injection end timing, injection amount, etc.) based on the accelerator operation amount of the vehicle, engine load, engine rotation speed, etc., and based on the target injection state. Fuel injection control.

  Specifically, the ECU 50 calculates a target injection state based on the engine load and the engine rotational speed each time using the injection state map in which the optimal injection state corresponding to the engine load and the engine rotational speed is defined. Further, the ECU 50 calculates an actual injection state based on time series data of the fuel pressure detected by the fuel pressure sensor 40. Then, the injection command signal is set based on the target injection state and the actual injection state. The fuel injection valve 30 is driven to open by the injection command signal.

  In the present embodiment, as fuel injection by the fuel injection valve 30, multistage injection in which fuel injection is performed a plurality of times in one combustion cycle of the engine is performed. In the case of performing the multistage injection, the following points are noted There is a need to. That is, when performing multi-stage injection, it is conceivable that pressure pulsation due to pre-stage injection occurs after post-stage fuel injection (pre-stage injection) is performed, which affects post-stage injection. Therefore, by subtracting the model waveform calculated by the pressure pulsation model determined in advance from the detected waveform which is the waveform of the fuel pressure detected by the fuel pressure sensor 40 after the end of the pre-injection, the influence of the pressure fluctuation due to the pre-injection The removal is done. In the present embodiment, as a pressure pulsation model, a model waveform is calculated using the following equation (1) which is a damped vibration equation.

式（１）中のＡ，ｋ，ω，θは、減衰振動における振幅、減衰係数、周波数、位相をそれぞれ示す。この場合、式（１）において、振幅Ａ、減衰係数ｋ、周波数ω、位相θの各値を代入することで、モデル波形の値ｐの算出が可能となっている。

In the equation (1), A, k, ω and θ respectively indicate the amplitude, damping coefficient, frequency and phase in the damped vibration. In this case, the value p of the model waveform can be calculated by substituting each value of the amplitude A, the attenuation coefficient k, the frequency ω, and the phase θ in the equation (1).

  In addition to the pressure pulsation component generated in the high pressure passage 34 of the fuel injection valve 30 and propagated to the fuel pressure sensor 40 as the fuel injection in the injection hole 35 occurs, the pressure pulsation model also includes the high pressure passage 34 and high pressure piping of the fuel injection valve 30. The pressure pulsation component which reaches the orifice 25 via the point 14 and is reflected by the orifice 25 and the pressure pulsation component generated by the other fuel injection valve 30 are included. Therefore, the model equation of equation (1) is configured by combining the damped oscillation equations of a plurality of waveform components.

  By the way, in the common rail system, it is considered that the flow characteristic of the fuel flowing through the orifice 25 changes due to the manufacturing tolerance of the orifice 25. Specifically, it is conceivable that the amplitude and frequency of pressure pulsation after the end of fuel injection change depending on the orifice diameter, orifice inlet R, orifice smoothness and the like. Therefore, in the present embodiment, a model waveform based on the pressure pulsation model is calculated based on the orifice flow rate characteristic, and the model waveform is subtracted (subtracted) from the detected waveform using the model waveform, and the result of the subtraction is further calculated. It is decided to carry out the post-stage injection on the basis of this. In the present embodiment, the ECU 50 corresponds to a fuel pressure acquisition unit, a waveform processing unit, and an injection control unit.

  In the present embodiment, as the orifice flow rate characteristic, an orifice flow rate value indicating the fuel flow rate passing through the orifice 25 is used, and the orifice flow rate value for each orifice 25 is stored in the memory 51 in advance. The orifice flow rate value may be measured before shipment of the product common rail 11 or vehicle from the factory, and the measured value may be stored in the memory 51. For example, before shipment of the common rail 11, the orifice flow value is coded, and a seal on which the code information is printed is attached to the common rail 11, or information of the orifice flow value is stored in the IC memory, and the IC memory is common rail It is also possible to adopt a method of attaching to 11 and a method of attaching an orifice flow rate value to the electrical resistance value and attaching a variable resistance adjusted to the electrical resistance value to the common rail 11.

  FIG. 3 is a functional block diagram relating to processing of subtracting a model waveform from a detected waveform. This function is realized by the ECU 50.

  In FIG. 3, the detected waveform calculation unit 61 calculates a detected waveform of the fuel pressure based on the fuel pressure (time-series data of the fuel pressure) detected by the fuel pressure sensor 40.

  Further, the amplitude calculation unit 62, the frequency calculation unit 63, the phase calculation unit 64, and the attenuation coefficient calculation unit 65 respectively calculate an amplitude A, a frequency ω, a phase θ, and an attenuation coefficient k as parameters of the pressure pulsation model.

  Specifically, the amplitude calculation unit 62 calculates an amplitude base value based on the fuel pressure and the fuel injection amount, calculates an amplitude correction coefficient based on the orifice flow rate value, and multiplies the amplitude base value by the amplitude correction coefficient. Calculate the amplitude A. Here, the amplitude base value is calculated using, for example, a predetermined map or table. The orifice flow rate value and the amplitude correction coefficient have the relationship shown in FIG. 4, and when the orifice flow rate value is larger than the orifice flow rate central value which is the reference value, a value larger than 1 is set as the amplitude correction factor. When the orifice flow rate value is smaller than the orifice flow rate median value, a value smaller than 1 is set as the amplitude correction coefficient. In this case, if the orifice flow rate characteristic is such that the orifice flow rate becomes larger than the reference value (if the orifice flow rate is the upper limit product), the amplitude A is corrected to a larger value than in the case of the reference value. When the flow rate characteristic is such that the orifice flow rate is smaller than the reference value (in the case of the orifice flow rate lower limit product), the amplitude A is corrected to a smaller value than in the case of the reference value.

  The frequency calculation unit 63 calculates the frequency base value based on the fuel pressure, calculates the frequency correction coefficient based on the orifice flow rate value, and calculates the frequency ω by multiplying the frequency base value by the frequency correction coefficient. Here, the frequency base value is calculated using, for example, a predetermined map or table. The orifice flow rate value and the frequency correction factor have the relationship shown in FIG. 5, and when the orifice flow rate value is larger than the orifice flow rate median value, a value larger than 1 is set as the frequency correction factor, and the orifice flow rate value is If it is smaller than the orifice flow rate median value, a value smaller than 1 is set as the frequency correction factor. In this case, if the orifice flow rate characteristic is such that the orifice flow rate becomes larger than the reference value (if the orifice flow rate is the upper limit product), the frequency ω is corrected to a larger value than in the case of the reference value. If the flow rate characteristic is such that the orifice flow rate is smaller than the reference value (if it is the orifice flow rate lower limit product), the frequency ω is corrected to a smaller value than in the case of the reference value.

  The phase calculation unit 64 calculates the phase θ based on the fuel pressure and the fuel injection amount using a predetermined map or table. Further, the attenuation coefficient calculation unit 65 calculates the attenuation coefficient k based on the fuel pressure and the fuel injection amount using a predetermined map or table.

  The model unit 66 calculates a model waveform based on the amplitude A, the frequency ω, the phase θ, and the attenuation coefficient k calculated by each of the calculation units 62 to 65 using the equation (1) described above. The subtracting unit 67 subtracts the model waveform calculated by the model unit 66 from the detected waveform calculated by the detected waveform calculating unit 61. Then, based on the fuel pressure obtained as a result of the subtraction, analysis processing in the post-stage injection is performed. In the post-stage injection, the injection state such as the injection amount and the injection timing is controlled based on the fuel pressure value from which the influence of the pre-stage injection has been eliminated.

  FIG. 6 is a flowchart showing a processing procedure of subtracting a model waveform from a detected waveform, and the processing is repeatedly performed by the ECU 50 at a predetermined cycle.

  In FIG. 6, in step S10, a detected fuel pressure waveform is calculated based on the fuel pressure detected by the fuel pressure sensor 40. In step S11, the orifice flow rate value stored in the memory 51 is read out, and in the subsequent step S12, it is determined whether the orifice flow rate value is correctly read out. At this time, under the condition that the orifice flow value is within a predetermined range (within the standard range) and the difference between the orifice flow values for each cylinder is within the predetermined range, the orifice flow is satisfied if these conditions are satisfied. Determine that the value has been read correctly. If the orifice flow value is correctly read, the process proceeds to step S13. If the orifice flow value is not correctly read, the process proceeds to step S19.

  In step S19, a predetermined abnormal process is performed. As the process at the time of abnormality, diagnosis information indicating the occurrence of abnormality is stored in the memory 51, or the execution of multistage injection is restricted. More specifically, in multistage injection, feedback control of the injection state in fuel injection of the second and subsequent stages is prohibited. It is also possible to prohibit the implementation of multistage injection.

  In step S13, the amplitude A of pressure pulsation after completion of the pre-injection is calculated. At this time, as described above, the amplitude base value and the amplitude correction coefficient are calculated, and the amplitude A is calculated by their multiplication. In step S14, the frequency ω of pressure pulsation after completion of the pre-injection is calculated. At this time, as described above, the frequency base value and the frequency correction coefficient are calculated, and the frequency ω is calculated by their multiplication.

  Further, in step S15, the phase θ of pressure pulsation after the end of the pre-stage injection is calculated, and in step S16, the damping coefficient k of the pressure pulsation after the end of the pre-stage injection is calculated.

  Thereafter, in step S17, a model waveform is calculated based on the amplitude A, the frequency ω, the phase θ, and the attenuation coefficient k calculated in steps S13 to S16 using the above-described equation (1). In step S18, subtraction processing is performed to subtract the model waveform calculated in step S17 from the detected waveform calculated in step S10. After the subtraction process is performed, analysis processing in the post-stage injection is performed based on the fuel pressure obtained as a result of subtracting the model waveform from the detected waveform.

  7 and 8 show the comparison results of the present embodiment in which the model waveform is corrected based on the orifice flow rate value, and the conventional one not corrected.

  FIG. 7 shows the fuel pressure waveform starting from the end of injection (time axis 0), with and without orifice correction, respectively, by correcting the model waveform based on the orifice flow rate value, It can be confirmed that the influence of pressure pulsation due to the pre-injection is properly removed.

  Also, FIG. 8 is a diagram showing the difference in the injection amount difference with respect to the orifice flow rate central part for a plurality of samples having different orifice flow rates, where (a) shows no orifice correction and (b) shows orifice correction The cases are shown respectively. In FIG. 8, the axis of ordinates above zero indicates a sample having a large orifice flow rate with respect to the orifice flow rate central part, and the sample on the upper side has a larger orifice flow rate. Also, less than zero on the vertical axis indicates a sample having a smaller orifice flow rate with respect to the orifice flow rate central part, and the lower the sample, the smaller the orifice flow rate. The horizontal axis is an interval time between the pre-injection and the post-injection. Comparing (a) and (b) in FIG. 8, it is possible to confirm that the injection amount difference is reduced and the injection amount accuracy is improved by correcting the model waveform based on the orifice flow rate value.

  According to the embodiment described above, the following excellent effects can be obtained.

  In the above configuration, a model waveform based on the pressure pulsation model is calculated based on the orifice flow rate characteristic, and the model waveform is subtracted (subtracted) from the detected waveform using the model waveform, and the subsequent stage based on the result of the subtraction Carry out the injection. In this case, even if the orifice diameter or the like varies, the influence of pressure pulsation due to the pre-injection can be properly removed. Therefore, desired injection amount accuracy can be obtained.

  The orifice flow rate characteristic is stored in advance in the memory 51 for each orifice 25. When fuel is injected from the fuel injection valve 30, the orifice flow rate characteristic corresponding to the fuel injection valve 30 is read out from the memory 51 to calculate a model waveform. did. As a result, even if the flow characteristics are different at each orifice 25 for each cylinder, the influence of pressure pulsation due to the pre-injection can be properly removed.

  The memory 51 is configured to store an orifice flow value indicating the fuel flow rate passing through the orifice 25 as the orifice flow rate characteristic. According to this configuration, when the orifice diameter and the like vary due to manufacturing tolerances and the orifice flow rate varies, the influence of the pre-injection can be properly removed while reflecting the variation of the orifice flow rate. it can.

  Since the amplitude A and the frequency ω, which are parameters of the pressure pulsation model (model formula), are calculated based on the orifice flow rate characteristic, an appropriate model waveform can be obtained regardless of the orifice variation.

  When the orifice flow rate characteristic is such that the orifice flow rate becomes larger than the reference value, the amplitude A and the frequency ω are larger than in the reference value, and the orifice flow rate characteristic is such that the orifice flow rate is relative to the reference value When the value is smaller, the amplitude A and the frequency ω are smaller than in the case of the reference value. This makes it possible to obtain an appropriate model waveform even when the orifice flow rate is unintentionally large or small.

  If the orifice flow value is not within the predetermined range, or if the difference between the orifice flow values for each cylinder is not within the predetermined range, it is considered that the orifice flow value is not correctly read out, and multistage injection is performed as an abnormal process. It was set as the composition which gives restriction. As a result, it is possible to suppress the control (analysis) of the post-stage injection from being performed using an incorrect orifice flow rate value.

  Hereinafter, other embodiments will be described focusing on differences from the first embodiment.

Second Embodiment
In the second embodiment, the ECU 50 is configured to calculate an orifice flow rate characteristic. In the present embodiment, as the orifice flow rate characteristic, correlation information correlating to the orifice flow rate value is stored in the memory 51. More specifically, the pressure peak value generated after the end of the fuel injection is used as the correlation information.

  The pressure peak value Pk is a pressure value at which the fuel pressure reaches the maximum value after the injection command signal is turned off (after the fuel injection valve 30 is closed), as shown in FIG. The pressure peak value Pk differs depending on the flow rate of fuel passing through the orifice 25. If the orifice flow rate is large, the pressure peak value becomes large (Pk1) as shown by the one-dot chain line, and if the orifice flow rate is small, the solid line As shown by, the pressure peak value decreases (Pk2). In the present embodiment, a model waveform based on a pressure pulsation model is calculated using a pressure peak value Pk correlated with the orifice flow rate.

  FIG. 10 is a flowchart showing a processing procedure for calculating the pressure peak value Pk, and this processing is performed by the ECU 50 at a predetermined cycle.

  In step S21 of FIG. 10, it is determined whether the current fuel injection is the first injection or the single injection. In step S22, it is determined whether the fuel pressure is larger than a predetermined reference value after the injection command signal is turned off. The reference value is, for example, the fuel pressure before the start of fuel injection. In step S23, it is determined whether the pressure peak value Pk has been detected. Then, when the pressure peak value Pk is detected in the state where the fuel pressure is larger than the reference value after the injection command signal is turned off during the execution of the first injection or the single injection, (all steps S21 to S23 are YES In the case), the process proceeds to step S24. In step S24, the pressure peak value Pk is stored in the memory 51.

  FIG. 11 is a flow chart showing a processing procedure of subtracting a model waveform from a detected waveform, and this processing is implemented replacing the processing of FIG. 6 described above. In FIG. 11, the same processes as in FIG. 6 are assigned the same step numbers, while the processes different from FIG. 6 are assigned new step numbers (steps S31 and S32).

  In FIG. 11, after the detection waveform is calculated in step S10, it is determined whether or not the pressure peak value Pk is stored in the memory 51 in step S31. And if pressure peak value Pk is memorized, it will progress to Step S32, and if pressure peak value Pk is not memorized, it will progress to Step S19. In step S19, an abnormal process is performed.

  In step S32, the pressure peak value Pk is converted into an orifice flow rate equivalent value. At this time, an orifice flow equivalent value is calculated based on the pressure peak value Pk using, for example, the relationship shown in FIG. Here, as the pressure peak value Pk is larger, the orifice flow equivalent value is calculated to a larger value.

  Thereafter, in steps S13 and S14, the amplitude A of the pressure pulsation and the frequency ω after the end of the pre-injection are calculated based on the orifice flow flow equivalent value. At this time, if the orifice flow rate value is replaced with the orifice flow rate equivalent value in FIG. 4 described above, the relationship between the orifice flow rate equivalent value and the amplitude correction coefficient is the same as that in FIG. The amplitude A is calculated. Also in FIG. 5 described above, the relationship between the orifice flow equivalent value and the frequency correction coefficient is the same as in FIG. 5, and the frequency ω is calculated using the frequency correction coefficient calculated according to the relationship.

  Thereafter, in steps S15 and S16, the phase θ of the pressure pulsation and the damping coefficient k after the end of the pre-stage injection are calculated, and in step S17, the model waveform is calculated using the above equation (1). A subtraction process is performed to subtract the model waveform from the detected waveform.

  The orifice flow rate characteristic is calculated based on the detected waveform which is the waveform of the fuel pressure detected by the fuel pressure sensor 40 when performing the first injection or the single injection in the multistage injection. As a result, the flow rate characteristic information of each orifice 25 can be properly possessed even after the orifice 25 or the factory shipment of the vehicle.

  When the first injection in the multistage injection is performed or in the case where the single injection is performed, it is possible to obtain a pressure waveform which is not affected by the pressure fluctuation due to the pre-injection after and after the start of the fuel injection . In consideration of that point, when the first injection in the multistage injection is carried out or when the single injection is carried out, the pressure peak value Pk as the fuel pressure parameter correlated with the orifice flow rate by the detection waveform after the end of the fuel injection. Is calculated, and the pressure peak value Pk is stored in the memory 51. Thereby, the orifice flow rate characteristic can be suitably acquired during engine operation.

Third Embodiment
In the third embodiment, the phase difference ΔT between the detected waveform calculated by the detected fuel pressure of the fuel pressure sensor 40 and the model waveform calculated by the pressure pulsation model is used as the orifice flow rate characteristic (correlation information correlating with the orifice flow rate value). It is configured to calculate.

  The phase difference ΔT is calculated after fuel pressure pulsation is started after the injection command signal is turned off (after the fuel injection valve 30 is closed), as shown in FIG. Specifically, after the injection command signal is turned off, timing t1 at which the fuel pressure rises to the start fuel pressure detected when the injection command signal is turned on is the start timing, and at timing t2 a predetermined time has elapsed from that timing t1. The phase difference ΔT between the detected waveform and the model waveform is calculated. It is also possible to calculate the phase difference ΔT at a timing when a predetermined time has elapsed since the injection command signal was turned off. The phase difference ΔT differs in magnitude depending on the flow rate of fuel passing through the orifice 25. The phase difference ΔT increases as the orifice flow rate increases, and decreases as the orifice flow rate decreases. In the present embodiment, a model waveform based on a pressure pulsation model is calculated using a phase difference ΔT correlated with the orifice flow rate.

  FIG. 14 is a flowchart showing a processing procedure for calculating the phase difference ΔT. This processing is performed by the ECU 50 at a predetermined cycle.

  In step S41 of FIG. 14, it is determined whether the current fuel injection is the first injection or the single injection. In step S42, it is determined whether or not a predetermined phase difference calculation timing has come after the injection command signal is turned off. Then, when the phase difference calculation timing is reached after the injection command signal is turned off when the first injection or the single injection is performed (when both steps S41 and S42 are YES), the process proceeds to step S43. In step S43, a phase difference ΔT between the detected waveform and the model waveform is calculated. In step S44, the phase difference ΔT is stored in the memory 51.

  FIG. 15 is a flowchart showing a processing procedure of subtracting a model waveform from a detected waveform, and the present processing is implemented replacing the processing of FIG. 6 described above. In FIG. 15, the same processing as in FIG. 6 is given the same step number, while the processing different from FIG. 6 is given new step numbers (steps S51 and S52).

  In FIG. 15, after the detected waveform is calculated in step S10, it is determined whether or not the phase difference ΔT is stored in the memory 51 in step S51. If the phase difference ΔT is stored, the process proceeds to step S52. If the phase difference ΔT is not stored, the process proceeds to step S19. In step S19, an abnormal process is performed.

  In step S52, the phase difference ΔT is converted to an orifice flow rate equivalent value. At this time, an orifice flow equivalent value is calculated based on the phase difference ΔT using, for example, the relationship shown in FIG. Here, as the phase difference ΔT is larger, the orifice flow equivalent value is calculated to be larger.

  Thereafter, in steps S13 and S14, the amplitude A of the pressure pulsation and the frequency ω after the end of the pre-injection are calculated based on the orifice flow flow equivalent value. At this time, if the orifice flow rate value is replaced with the orifice flow rate equivalent value in FIG. 4 described above, the relationship between the orifice flow rate equivalent value and the amplitude correction coefficient is the same as that in FIG. The amplitude A is calculated. Also in FIG. 5 described above, the relationship between the orifice flow equivalent value and the frequency correction coefficient is the same as in FIG. 5, and the frequency ω is calculated using the frequency correction coefficient calculated according to the relationship.

  Thereafter, in steps S15 and S16, the phase θ of the pressure pulsation and the damping coefficient k after the end of the pre-stage injection are calculated, and in step S17, the model waveform is calculated using the above equation (1). A subtraction process is performed to subtract the model waveform from the detected waveform.

  Also in the present embodiment, the orifice flow rate characteristic can be suitably acquired during engine operation as described above.

(Other embodiments)
The above embodiment may be modified, for example, as follows.

  In the above embodiment, when correlation information correlating to the orifice flow rate value is used as the orifice flow rate characteristic, the pressure peak value Pk generated after the end of fuel injection and the phase difference ΔT of the detected waveform and the model waveform are detected as the correlation information. Although other fuel pressure parameters may be used. FIG. 17 shows fuel pressure parameters (indicators, physical quantities) that may differ depending on the orifice flow rate in the fuel pressure waveform after the start of fuel injection and after the end of fuel injection. In FIG. 17, each parameter of X1 to X4 shown before timing tx is a fuel pressure parameter related to the valve opening expansion wave generated with opening of the fuel injection valve 30, and each parameter of X5 to X8 shown after timing tx Is a fuel pressure parameter related to the valve closing water destruction that occurs with the closing of the fuel injection valve 30.

  More specifically, X1 is the minimum value (open valve bottom pressure) of the fuel pressure after the fuel injection valve 30 is opened. X2 is a reflection timing at which the fuel pressure becomes the minimum value after the fuel injection valve 30 is opened. X3 is the reflection speed when the fuel pressure rises from the minimum value. X4 is an equilibrium pressure of fuel pressure during fuel injection. X5 is a pressure increase rate when the fuel pressure rises and changes after the fuel injection valve 30 is closed. X6 is the maximum value of the fuel pressure (valve closing peak pressure) after the fuel injection valve 30 is closed. X7 is a phase difference when the fuel pressure pulsates after the fuel injection valve 30 is closed. X8 is a frequency at which the fuel pressure pulsates after the fuel injection valve 30 is closed. The valve-opening bottom pressure X1 and the valve-closing peak pressure X6 are amplitudes based on the fuel pressure at the start of injection.

  FIG. 18 shows the relationship between the above-mentioned parameters and the equivalent value of the orifice flow rate. Among the parameters X1 to X8, the relationship between the valve closing peak pressure (X6) and the orifice flow equivalent value, and the relationship between the phase difference (X7) and the orifice flow equivalent value have been described in FIGS. 12 and 16, respectively. Therefore, FIG. 18 shows the relationship with the orifice flow flow equivalent value for the other parameters.

In FIG.
(A) is a figure which shows the relationship between the valve-opening bottom pressure and an orifice flow volume equivalent value,
(B) is a diagram showing the relationship between the reflection timing and the orifice flow equivalent value,
(C) is a diagram showing the relationship between the reflection velocity and the equivalent orifice flow rate,
(D) is a diagram showing the relationship between the equilibrium pressure and the orifice flow equivalent value,
(E) shows the relationship between the pressure rise rate and the orifice flow equivalent value,
(F) is a figure which shows the relationship between frequency and orifice flow equivalent value.

  The ECU 50 calculates each of the above parameters by the detection waveform after the start of the fuel injection or the detection waveform after the end of the fuel injection when the first injection in the multistage injection is performed or when the single injection is performed. And the parameters are stored in the memory 51. Then, the parameter is converted to an orifice flow equivalent value, and a model waveform is calculated based on the orifice flow equivalent value. Thereby, the orifice flow rate characteristic can be suitably acquired during engine operation.

  In the above embodiment, the amplitude A and the frequency ω, which are parameters of the pressure pulsation model (model expression), are calculated based on the orifice flow rate characteristic, but this is changed to one of the amplitude A and the frequency ω One of them may be calculated based on the orifice flow rate characteristic.

  The orifice flow rate value may be divided into levels according to the flow rate, and the flow rate level may be stored in the memory 51 for each orifice 25. For example, three flow levels are defined, and it is configured to store for each orifice 25 whether the flow characteristic is a large flow level, a medium flow level or a small flow level.

  The fuel pressure sensor 40 may be any sensor that detects the fuel pressure in the fuel passage from the common rail 11 to the injection hole 35 of the fuel injection valve 30, and the fuel pressure sensor 40 may be used in the body 31 of the fuel injection valve 30. Alternatively, the fuel pressure sensor 40 may be provided in the middle of the high pressure pipe 14, or the fuel pressure sensor 40 may be provided at the pipe connection 22 of the common rail 11 (but downstream of the orifice).

  In the above embodiment, the present invention is applied to a fuel injection system of a diesel engine. However, the present invention is not limited to this, and may be applied to a fuel injection system of a direct injection gasoline engine. In this case, in the fuel injection system in which the high pressure fuel accumulated and held in the delivery pipe as the accumulator container is injected by the fuel injection valve, it is possible to properly control the injection state of the fuel injection valve at the time of multistage injection.

  11 common rail (accumulated pressure vessel) 12 fuel pump 25 orifice 30 fuel injection valve 40 fuel pressure sensor 50: ECU (fuel injection control device).

Claims (8)

An accumulator container (11) for accumulating and holding high-pressure fuel, a fuel pump (12) for pumping fuel to the accumulator container, and a fuel injection valve (30) for injecting high-pressure fuel accumulated and held in the accumulator container And a fuel pressure sensor (40) for detecting the fuel pressure in the fuel passage from the pressure accumulation container to the injection port (35) of the fuel injection valve, and an outlet passage connected to the fuel injection valve in the pressure accumulation container A fuel injection control device (50) is applied to a fuel injection system in which an orifice (25) is formed in a portion, and performs multiple fuel injections as multistage injection in one combustion cycle of an internal combustion engine,
A fuel pressure acquisition unit that acquires the fuel pressure detected by the fuel pressure sensor;
A waveform processing unit that subtracts a model waveform calculated by a pressure pulsation model from a detection waveform that is a waveform of fuel pressure acquired by the fuel pressure acquisition unit after completion of pre-stage injection in the multistage injection;
An injection control unit that implements post-stage injection based on the result of subtraction by the waveform processing unit;
Equipped with
The said waveform process part is a fuel-injection control apparatus which calculates the model waveform by the said pressure pulsation model based on the flow volume characteristic of the said orifice. The flow rate characteristic of the orifice is previously stored in the storage unit (51) for each orifice,
2. The fuel according to claim 1, wherein the waveform processing unit reads out the flow rate characteristic corresponding to the fuel injection valve from the storage unit upon fuel injection of the fuel injection valve, and calculates a model waveform based on the pressure pulsation model. Injection control device.   3. The fuel injection control device according to claim 2, wherein an orifice flow rate value indicating a fuel flow rate passing through the orifice or correlation information correlating therewith is stored as the flow rate characteristic in the storage unit.   The fuel injection according to claim 2 or 3, further comprising a characteristic calculation unit that calculates the flow rate characteristic based on the detected waveform when the first injection in the multistage injection is performed or when the single injection is performed. Control device.   When the first injection in the multistage injection is performed or the single injection is performed, the characteristic calculation unit may use the detection waveform after the start of fuel injection or the detection waveform after the end of fuel injection. 5. The fuel injection control device according to claim 4, wherein a fuel pressure parameter that may differ depending on a fuel flow rate at the orifice is calculated as the flow rate characteristic, and the fuel pressure parameter is stored in the storage unit. The pressure pulsation model includes, as model parameters, the amplitude and frequency of the pressure waveform after the end of fuel injection,
The fuel injection control device according to any one of claims 1 to 5, wherein the waveform processing unit calculates an amplitude and a frequency as the model parameter based on a flow rate characteristic of the orifice.   When the flow rate characteristic is such that the flow rate of fuel passing through the orifice becomes larger than a reference value, the waveform processing unit makes the amplitude larger than in the case of the reference value, and the flow rate characteristic is 7. The fuel injection control device according to claim 6, wherein, when the flow rate of fuel passing through the orifice is smaller than a reference value, the amplitude is smaller than in the case of the reference value.   When the flow rate characteristic is such that the flow rate of fuel passing through the orifice becomes larger than a reference value, the waveform processing unit makes the frequency larger than in the case of the reference value, and the flow rate characteristic is 8. The fuel injection control device according to claim 6, wherein when the fuel flow rate passing through the orifice is smaller than a reference value, the frequency is made smaller than when the fuel flow rate is the reference value.

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