JP5333464B2 - Fuel injection control device - Google Patents

Abstract

The fuel injection control device has an asymptote-calculator, which calculates a decreasing asymptote by approximation of a decreasing curve course of a pressure curve course, and calculates an increasing curve course of the pressure curve course during pressure curve course. The decreasing curve course drops-out in a degradation period, in which the detected pressure is reduced corresponding to an increase of injection rate and the increasing curve course increases during an increasing period, in which the detected pressure is increased corresponding to a decline of injection rate.

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, which is applied to a fuel injection system including a fuel pressure sensor that detects the pressure of fuel supplied to a fuel injection valve.

  Patent Documents 1 and 2 and the like include a fuel pressure sensor that detects a pressure change (pressure waveform) of a supplied fuel caused by fuel injection, and a technique for analyzing a change in injection rate (injection rate waveform) from the detected pressure waveform Is disclosed. Specifically, the pressure drop amount ΔP (see FIG. 2) generated with the increase in the injection rate and the maximum injection rate Rmax (the height of the injection rate waveform) are focused on and detected from the pressure waveform. Rmax is calculated by multiplying ΔP by the correlation coefficient G. Then, based on the calculated Rmax, an injection command signal for instructing an injection start timing, an injection end timing, or the like is set. That is, the operation of the fuel injection valve is feedback controlled based on Rmax calculated based on the detected ΔP.

  However, in this method, ΔP is sequentially different for each injection depending on the environmental conditions at that time, such as the interval between injections in multistage injection and the in-cylinder pressure at the time of injection. For this reason, since the calculated value of Rmax used for feedback control varies sequentially according to the environmental conditions, the actual injection state greatly hunts with respect to the target injection state (for example, target injection start timing, target injection amount). Stability is impaired.

  The invention described in Patent Document 3 has solved this problem, and the outline thereof will be described below with reference to FIG.

  Of the detected pressure waveforms, when the waveform during the period when the pressure drops as the injection rate rises is the falling waveform and the waveform during the period when the pressure rises as the injection rate falls is the rising waveform, first, the descending waveform is approximated to a straight line And the rising approximate straight line Lβ obtained by approximating the rising waveform to a straight line. Next, the reference pressure Pbase is calculated based on the waveform in the specific period immediately before the drop waveform appears in the pressure waveform. Next, a pressure difference ΔPγ between the intersection pressure Pαβ, which is a pressure corresponding to the intersection of the descending approximate line Lα and the ascending approximate line Lβ, and the reference pressure Pbase is calculated. Next, the maximum injection rate Rmax is calculated by multiplying the calculated pressure difference ΔPγ by the correlation coefficient Ga.

  The pressure difference ΔPγ is highly correlated with the maximum injection rate Rmax. Moreover, although the drop waveform and the rise waveform used for calculating the pressure difference ΔPγ are slightly affected by the environmental conditions such as the interval and the in-cylinder pressure, changes in these waveforms are caused by the sequential fluctuation of the pressure drop amount ΔP. Compared to the impact, it is negligible. This is because the decrease in the fuel pressure accompanying the fuel injection from the start of injection until the maximum injection rate is reached and the increase in the fuel pressure from the maximum injection rate to the end of the injection are performed in a very short time. Therefore, the maximum injection rate Rmax can be calculated without being greatly affected by the sequential fluctuation of the pressure drop amount ΔP, so that the above-described problem that the stability of the feedback control is impaired can be solved.

JP 2009-103063 A JP 2010-3004 A JP 2010-223184 A

  Here, the correlation coefficient Ga described above changes as the fuel injection valve deteriorates over time. For example, when aged deterioration in which the nozzle hole of the fuel injection valve wears out proceeds, the maximum injection rate Rmax increases and the correlation coefficient Ga increases even at the same pressure difference ΔPγ. Further, as the aging deterioration in which foreign matter accumulates in the nozzle hole proceeds, the maximum injection rate Rmax decreases and the correlation coefficient Ga decreases even if the pressure difference ΔPγ is the same.

  However, the descending waveform and the ascending waveform used for calculation of the pressure difference ΔPγ are small compared to the change in ΔP even if the nozzle hole is worn and deteriorates over time. As described above, the decrease in fuel pressure accompanying combustion injection from the start of injection until the maximum injection rate is reached and the increase in fuel pressure from the maximum injection rate to the end of injection are performed in a very short time. is there. Therefore, the descending waveform and the ascending waveform used for calculating the pressure difference ΔPγ are hardly affected by the aging deterioration of the fuel injection valve. Therefore, in the invention described in Patent Document 3, the maximum injection rate Rmax in consideration of the aging deterioration is used. Cannot be calculated. Therefore, it becomes impossible to control with high accuracy so that the actual injection state matches the target injection state.

  Incidentally, the method according to Patent Document 3 described above is a case of small injection in which the valve closing operation is started before the opening degree of the fuel injection valve is fully opened, and the pressure difference ΔPγ is large enough to be a predetermined value or more. At the time of injection, a preset value is regarded as Rmax. Therefore, in this case as well, the maximum injection rate Rmax can be calculated without being affected by the sequential fluctuation of the pressure drop amount ΔP, but the maximum injection rate Rmax taking into account aging deterioration cannot be calculated.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel injection control device that achieves injection control that takes into account the stability improvement of injection control and aging degradation. is there.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  The invention described in claim 1 is premised on being applied to a fuel injection system provided with a fuel pressure sensor for detecting the pressure of fuel supplied to the fuel injection valve.

  Of the pressure waveforms detected by the fuel pressure sensor, the waveform during the period when the pressure drops as the fuel injection rate rises is the falling waveform, and the waveform during the period when the pressure rises as the fuel injection rate falls is the rising waveform In addition, a descending approximate line that approximates the descending waveform to a straight line, a linear approximation means that calculates an ascending approximate line that approximates the ascending waveform to a straight line, and the descending waveform among the pressure waveforms detected by the fuel pressure sensor appear. Based on the waveform in the immediately preceding specific period, a reference pressure calculating means for calculating a reference pressure, and calculating an intersection pressure that is a pressure corresponding to an intersection of the descending approximate straight line and the ascending approximate straight line, the intersection pressure and the reference pressure A maximum injection rate calculating means for calculating a maximum injection rate based on a pressure difference between the pressure difference, a pressure drop amount detecting means for detecting a pressure drop amount caused by an increase in the injection rate, and the pressure A secular change index calculating means for calculating a secular change index that represents the degree of change in the pressure drop detected by the lower amount detecting means with the secular change of the fuel injection valve, and based on the secular change index, the maximum Correction means for correcting the maximum injection rate calculated by the injection rate calculation means.

  Here, the pressure difference between the intersection pressure calculated based on the descending approximate line and the ascending approximate line and the reference pressure has a high correlation with the maximum injection rate. Moreover, these descending waveform and ascending waveform are hardly affected by the sequential variation of the pressure drop amount ΔP generated according to the environmental conditions such as the interval and the in-cylinder pressure. In the present invention focusing on this point, the maximum injection rate is calculated based on the pressure difference. Therefore, even if the operation of the fuel injection valve is feedback controlled based on the maximum injection rate calculated by the present invention, Large hunting of the actual injection state is suppressed, and the stability of injection control can be improved.

  Further, in the present invention, paying attention to the fact that the correlation between the pressure drop caused by the increase in the injection rate and the maximum injection rate is high, the degree of change in the pressure drop caused by the aging of the fuel injection valve (the change over time) An index) is calculated, and the maximum injection rate calculated by the maximum injection rate calculating means is corrected based on the secular change index. Therefore, it can correct | amend to the maximum injection rate which considered aging degradation.

  In short, the present invention seeks to improve the stability of injection control by calculating the maximum injection rate using a descending approximation line and an ascending approximation line that are hardly affected by the pressure drop amount ΔP that varies sequentially according to environmental conditions. On the other hand, by correcting the maximum injection rate using the pressure drop amount ΔP in which the influence of the secular change appears remarkably, it is possible to realize the control in consideration of the secular change.

  Incidentally, the correcting means according to the present invention may directly correct the maximum injection rate calculated by the maximum injection rate calculating means, or the maximum injection rate by multiplying the pressure difference between the intersection pressure and the reference pressure by a correlation coefficient. In the case of calculating the maximum injection rate, the correlation coefficient may be corrected.

  The invention according to claim 2 and claim 3 is characterized in that when the pressure difference is a predetermined value or more, a preset value is calculated as a maximum injection rate.

  Here, in the case of small injection in which the valve closing operation is started before the opening degree of the fuel injection valve is fully opened, the maximum injection rate may be calculated based on the pressure difference between the intersection pressure and the reference pressure. However, at the time of large injection in which the pressure difference is greater than or equal to a predetermined value, the maximum injection rate can be accurately calculated by calculating a preset value as the maximum injection rate as in the above invention. Further, the maximum injection rate at the time of large injection calculated in this way is not affected by the sequential fluctuation of the pressure drop amount ΔP that occurs according to the environmental conditions, so that the stability of the injection control can be improved. Further, since the maximum injection rate at the time of large injection (that is, a preset value) is corrected based on the secular change index, it can be corrected to the maximum injection rate that takes into account deterioration over time even at the time of large injection. .

In the invention according to claim 4, the aging index calculating means calculates an average value of a plurality of maximum injection rates calculated based on the plurality of pressure drop amounts detected in a predetermined period, and a degree to which the average value changes Is calculated as the aging index.

Here, contrary to the above-mentioned invention, when calculating the secular change index without averaging every time the pressure drop amount is detected and the maximum injection rate is calculated , the calculated secular change index depends on the environmental conditions. As a result, there is a concern that the corrected maximum injection rate frequently fluctuates despite the fact that the secular change does not occur and hinders improvement in the stability of the injection control. On the other hand, according to the above invention, since the change amount of the average value of the plurality of maximum injection rates calculated based on the pressure drop detected during the predetermined period is calculated as the secular change index, the corrected maximum injection rate is the environmental condition. The above-mentioned concern that it fluctuates frequently according to the situation is resolved.

  Specific examples of the “predetermined period” include a period from when the driver starts the internal combustion engine to a stop operation (one trip period), a period during which the vehicle travels a predetermined distance, and the operation of the internal combustion engine. For example, a period in which a predetermined time elapses.

  According to a fifth aspect of the present invention, the pressure drop amount detecting means detects the pressure drop amount in association with the reference pressure, the reference pressure is set by being divided into a plurality of regions, and the secular change index The calculating means calculates the average value by weighting the value of the pressure drop amount according to the number of detected pressure drop amounts for each region.

  Here, even if the injection command signal is the same, if the reference pressure is different, the detected pressure drop amount has a different value. In addition, depending on the user of the internal combustion engine, the use area of the reference pressure may be uneven. For example, in the case of a user who has many opportunities for high-load operation, there are many opportunities for fuel injection in a region where the reference pressure is high. Therefore, it is desirable to calculate the secular change index based on the pressure drop amount corresponding to the reference pressure that is frequently used by the user in order to accurately correct the maximum injection rate. In the above invention in view of this point, the aging index can be calculated by increasing the weighting of the pressure drop amount as the number of detections is larger, so that the maximum injection rate can be accurately corrected.

  The invention according to claim 6 is characterized in that the aging index calculating means calculates the aging index based on the pressure drop detected when the environmental condition during fuel injection is within a predetermined range. .

  As described above, if the environmental conditions such as the interval, the in-cylinder pressure, and the reference pressure are different, the detected pressure drop amount becomes a different value. Therefore, when calculating the secular change index by comparing the pressure drop amount detected in the past with the current pressure drop amount, if the environmental conditions at the time of detecting the pressure drop amount to be compared are greatly different, It cannot be calculated with high accuracy. In the above invention in view of this point, since the aging index is calculated based on the pressure drop detected when the environmental condition is within the predetermined range, the aging index is calculated based on the pressure drop detected under substantially the same environmental conditions. It can be calculated and the calculation accuracy of the secular change index can be improved.

  The invention according to claim 7 is characterized in that the aging index calculating means calculates the aging index based on the pressure drop amount detected when the reference pressure is higher than a predetermined pressure.

  Here, as the reference pressure is higher, the absolute value of the pressure drop becomes larger. Therefore, if the secular change index is calculated based on the pressure drop at high pressure, the absolute value of the pressure drop is higher than that calculated based on the pressure drop at low pressure. The aging index can be calculated with high accuracy. Therefore, according to the above invention, the secular change index can be calculated with high accuracy, and the maximum injection rate can be corrected with high accuracy.

It is a figure showing the outline of the fuel injection system to which the internal-combustion-engine control device concerning a 1st embodiment of the present invention is applied. It is a figure which shows the change of the injection rate and fuel pressure corresponding to an injection command signal. It is a block diagram which shows the outline | summary of the learning of an injection rate parameter, the setting of an injection command signal, etc. It is a flowchart which shows the calculation procedure of an injection rate parameter. It is a figure which shows the fuel pressure waveform Wa at the time of injection, the fuel pressure waveform Wu at the time of non-injection, and the injection waveform Wb. It is a figure which shows the aspect that pressure drop amount (DELTA) P and the maximum injection rate Rmax fall with progress of aged deterioration. It is a figure which shows the change of pressure drop amount (DELTA) P and the maximum injection rate Rmax with respect to the change of instruction | command injection amount and the reference pressure Pbase. It is a figure which shows the value of several maximum injection rate Rmax ((DELTA) P) used for calculation of average value Rmax ((DELTA) P) ave. It is a flowchart which shows the calculation procedure of correction | amendment ratio Ka used by the process of FIG. It is a figure which shows the value of several maximum injection rate Rmax ((DELTA) P) used for calculation of average value Rmax ((DELTA) P) ave in 2nd Embodiment of this invention. It is a figure which shows the value of several maximum injection rate Rmax ((DELTA) P) used for calculation of average value Rmax ((DELTA) P) ave in 3rd Embodiment of this invention.

  Hereinafter, each embodiment which actualized the control device concerning the present invention is described based on a drawing. A control device described below is mounted on an engine (internal combustion engine) for a vehicle, and in the diesel engine, high pressure fuel is injected into a plurality of cylinders # 1 to # 4 to perform compression self-ignition combustion. An engine is assumed.

(First embodiment)
FIG. 1 is a schematic diagram showing a fuel injection valve 10 mounted on each cylinder of the engine, a fuel pressure sensor 20 mounted on each fuel injection valve 10, an ECU 30 that is an electronic control device mounted on a vehicle, and the like. is there.

  First, an engine fuel injection system including the fuel injection valve 10 will be described. The fuel in the fuel tank 40 is pumped and stored in the common rail 42 (pressure accumulating container) by the fuel pump 41, and distributed and supplied to the fuel injection valves 10 (# 1 to # 4) of each cylinder. The plurality of fuel injection valves 10 (# 1 to # 4) sequentially inject fuel in a preset order. In addition, since the plunger pump is used for the fuel pump 41, fuel is pumped in synchronism with the reciprocating motion of the plunger.

  The fuel injection valve 10 includes a body 11, a needle-shaped valve body 12, an actuator 13, and the like described below. The body 11 forms a high-pressure passage 11a inside and a nozzle hole 11b for injecting fuel. The valve body 12 is accommodated in the body 11 and opens and closes the nozzle hole 11b.

  A back pressure chamber 11c for applying a back pressure to the valve body 12 is formed in the body 11, and the high pressure passage 11a and the low pressure passage 11d are connected to the back pressure chamber 11c. The communication state between the high pressure passage 11a and the low pressure passage 11d and the back pressure chamber 11c is switched by the control valve 14, and the actuator 13 such as an electromagnetic coil or a piezoelectric element is energized to push the control valve 14 downward in FIG. As a result, the back pressure chamber 11c communicates with the low pressure passage 11d and the fuel pressure in the back pressure chamber 11c decreases. As a result, the back pressure applied to the valve body 12 is lowered and the valve body 12 is lifted up (opening operation). Thereby, the seat surface 12a of the valve body 12 is separated from the seat surface 11e of the body 11, and fuel is injected from the injection hole 11b.

  On the other hand, when the power supply to the actuator 13 is turned off and the control valve 14 is operated upward in FIG. 1, the back pressure chamber 11c communicates with the high pressure passage 11a and the fuel pressure in the back pressure chamber 11c increases. As a result, the back pressure applied to the valve body 12 increases and the valve body 12 is lifted down (closed valve operation). Thereby, the seat surface 12a of the valve body 12 is seated on the seat surface 11e of the body 11, and the fuel injection from the injection hole 11b is stopped.

  Therefore, the ECU 30 controls the energization of the actuator 13 so that the opening / closing operation of the valve body 12 is controlled. Thereby, the high-pressure fuel supplied from the common rail 42 to the high-pressure passage 11 a is injected from the injection hole 11 b according to the opening / closing operation of the valve body 12.

  The fuel pressure sensor 20 is mounted on each fuel injection valve 10 and includes a stem 21 (a strain generating body) and a pressure sensor element 22 described below. The stem 21 is attached to the body 11, and the diaphragm portion 21a formed on the stem 21 is elastically deformed by receiving the pressure of the high-pressure fuel flowing through the high-pressure passage 11a. The pressure sensor element 22 is attached to the diaphragm portion 21a, and outputs a pressure detection signal to the ECU 30 in accordance with the amount of elastic deformation generated in the diaphragm portion 21a.

  The ECU 30 calculates a target injection state (for example, the number of injection stages, the injection start timing, the injection end timing, the injection amount, etc.) based on the operation amount of the accelerator pedal, the engine load, the engine rotational speed NE, and the like. For example, the optimal injection state corresponding to the engine load and the engine speed is stored as an injection state map. Based on the current engine load and engine speed, the target injection state is calculated with reference to the injection state map. Then, the injection command signals t1, t2, and Tq (see FIG. 2A) corresponding to the calculated target injection state are set based on the injection rate parameters td, te, Rα, Rβ, and Rmax described in detail later, and the fuel By outputting to the injection valve 10, the operation of the fuel injection valve 10 is controlled.

  Further, based on the detected value of the fuel pressure sensor 20, a change in the fuel pressure caused by the injection is detected as a fuel pressure waveform (see FIG. 2C), and an injection representing a change in the fuel injection rate based on the detected fuel pressure waveform. The rate waveform (see FIG. 2B) is calculated to detect the injection state. Then, while learning the injection rate parameters Rα, Rβ, and Rmax that specify the detected injection rate waveform (injection state), the correlation between the injection command signals (pulse-on timing t1, pulse-off timing t2, and pulse-on period Tq) and the injection state. The injection rate parameters td and te for specifying

  Specifically, in the fuel pressure waveform, a descending approximation line that approximates a descending waveform from the inflection point P1 at which the fuel pressure drop starts at the start of injection to the inflection point P2 at which the descent ends by a least square method or the like. Lα is calculated. Then, a time (a crossing time LBα between Lα and Bα) that is the reference value Bα in the descending approximate straight line Lα is calculated. Focusing on the fact that the intersection time LBα and the injection start time R1 are highly correlated, the injection start time R1 is calculated based on the intersection time LBα. For example, a timing that is a predetermined delay time Cα before the intersection timing LBα may be calculated as the injection start timing R1.

  In addition, a rising approximation line Lβ is calculated by approximating the rising waveform from the inflection point P3 where the fuel pressure rises at the end of injection to the inflection point P5 where the descent ends from the fuel pressure waveform by a least square method or the like. To do. Then, a time (intersection time LBβ between Lβ and Bβ) that is the reference value Bβ in the rising approximate straight line Lβ is calculated. Focusing on the fact that the intersection timing LBβ and the injection end timing R4 are highly correlated, the injection end timing R4 is calculated based on the intersection timing LBβ. For example, a timing that is a predetermined delay time Cβ before the intersection timing LBβ may be calculated as the injection end timing R4.

  Next, paying attention to the fact that the slope of the descending approximate line Lα and the slope of the injection rate increase are highly correlated, the slope of the straight line Rα indicating the increase in the injection rate waveform shown in FIG. Calculation is based on the slope of Lα. For example, the slope of Rα may be calculated by multiplying the slope of Lα by a predetermined coefficient. Similarly, since the slope of the rising approximate line Lβ and the slope of the injection rate decrease are highly correlated, the slope of the straight line Rβ indicating the decrease in injection in the injection rate waveform is calculated based on the slope of the rising approximate line Lβ.

  Next, based on the straight lines Rα and Rβ of the injection rate waveform, a timing (valve closing operation start timing R23) at which the valve body 12 starts lift-down in response to the command to end injection is calculated. Specifically, the intersection of both straight lines Rα and Rβ is calculated, and the intersection timing is calculated as the valve closing operation start timing R23. Further, a delay time (injection start delay time td) with respect to the injection start command timing t1 of the injection start timing R1 is calculated. Further, a delay time (injection end delay time te) with respect to the injection end command timing t2 of the valve closing operation start timing R23 is calculated.

  Further, the pressure corresponding to the intersection of the descending approximate straight line Lα and the ascending approximate straight line Lβ is calculated as the intersection pressure Pαβ, and a pressure difference ΔPγ between the reference pressure Pbase and the intersection pressure Pαβ, which will be described in detail later, is calculated. Focusing on the fact that the correlation with the maximum injection rate Rmax is high, the maximum injection rate Rmax is calculated based on the pressure difference ΔPγ. Specifically, the maximum injection rate Rmax is calculated by multiplying the pressure difference ΔPγ by the correlation coefficient Cγ. However, in the case of the small injection in which the pressure difference ΔPγ is less than the predetermined value ΔPγth, Rmax = ΔPγ × Cγ is set as described above, while in the case of the large injection in which ΔPγ ≧ ΔPγth, it is set in advance. The value (set value Rγ) is calculated as the maximum injection rate Rmax.

  Note that the “small injection” is assumed to be an injection in which the valve body 12 starts to be lifted down before the injection rate reaches Rγ, and the fuel is throttled at the seat surfaces 11e and 12a to thereby reduce the injection amount. The injection rate when it is restricted becomes the maximum injection rate Rmax. On the other hand, the “large injection” is assumed to be an injection in which the valve body 12 starts to lift down after the injection rate reaches Rγ, and the injection amount is limited by the fuel being throttled at the injection hole 11b. The injection rate when the engine is running is the maximum injection rate Rmax. In short, when the injection command period Tq is sufficiently long and the valve opening state is continued even after reaching the maximum injection rate, the injection rate waveform shown in FIG. On the other hand, in the case of small injection that starts the valve closing operation before reaching the maximum injection rate, the injection rate waveform is a triangle.

  As described above, the injection rate parameters td, te, Rα, Rβ, and Rmax can be calculated from the fuel pressure waveform. Based on the learned values of the injection rate parameters td, te, Rα, Rβ, and Rmax, an injection rate waveform (see FIG. 2B) corresponding to the injection command signal (see FIG. 2A) is calculated. be able to. Since the area of the injection rate waveform calculated in this way (see halftone dot hatching in FIG. 2B) corresponds to the injection amount, the injection amount can also be calculated based on the injection rate parameter.

  FIG. 3 is a block diagram showing an outline of learning of these injection rate parameters, setting of an injection command signal, and the like. Each means 31, 32, 33 functioning by the ECU 30 will be described below. The injection rate parameter calculation means 31 calculates injection rate parameters td, te, Rα, Rβ, Rmax based on the fuel pressure waveform detected by the fuel pressure sensor 20.

  The learning means 32 learns by updating the calculated injection rate parameter in the memory of the ECU 30. Since the injection rate parameter varies depending on the supply fuel pressure (pressure in the common rail 42) at that time, the injection rate parameter can be learned in association with the supply fuel pressure or a reference pressure Pbase (see FIG. 2C) described later. desirable. In the example of FIG. 3, the injection rate parameter value corresponding to the fuel pressure is stored in the injection rate parameter map M.

  The setting means 33 (control means) acquires the injection rate parameter (learned value) corresponding to the current fuel pressure from the injection rate parameter map M. And based on the acquired injection rate parameter, the injection command signals t1, t2, and Tq corresponding to the target injection state are set. The fuel pressure sensor 20 detects the fuel pressure waveform when the fuel injection valve 10 is operated in accordance with the injection command signal set in this way, and the injection rate parameter calculation means 31 based on the detected fuel pressure waveform, the injection rate parameter td, te, Rα, Rβ, Rmax are calculated.

  In short, an actual injection state (that is, injection rate parameters td, te, Rα, Rβ, Rmax) with respect to the injection command signal is detected and learned, and an injection command signal corresponding to the target injection state is set based on the learned value. . Therefore, the injection command signal is feedback-controlled based on the actual injection state, and the fuel injection state can be controlled with high accuracy so that the actual injection state coincides with the target injection state even when the above-described aging deterioration proceeds.

  Next, the procedure for calculating the injection rate parameters td, te, Rα, Rβ, and Rmax (see FIG. 2B) from the detected fuel pressure waveform (see FIG. 2C) will be described using the flowchart of FIG. To do. Note that the process shown in FIG. 4 is executed each time fuel is injected by the microcomputer of the ECU 30. The fuel pressure waveform is a set of a plurality of detection values obtained by the fuel pressure sensor 20 acquired at a predetermined sampling period.

  First, in step S10 shown in FIG. 4, an injection waveform Wb (corrected fuel pressure waveform) described below, which is a fuel pressure waveform used for calculating the injection rate parameter, is calculated. In the following description, a cylinder that is injecting fuel from the fuel injection valve 10 is an injection cylinder (front cylinder), and a cylinder that is not injecting fuel when the injection cylinder is injecting fuel is a non-injection cylinder ( The fuel pressure sensor 20 corresponding to the injection cylinder and the fuel pressure sensor 20 corresponding to the non-injection cylinder is referred to as the non-injection fuel pressure sensor.

  The fuel pressure waveform Wa during injection, which is the fuel pressure waveform detected by the fuel pressure sensor during injection (see FIG. 5A), does not represent only the influence due to the injection, but is caused by the influence other than the injection exemplified below. It also includes waveform components. That is, when the fuel pump 41 that pumps the fuel in the fuel tank 40 to the common rail 42 pumps the fuel intermittently like a plunger pump, if pump pumping is performed during fuel injection, the pump pumping period The fuel pressure waveform Wa during the injection is a waveform in which the pressure is increased as a whole. That is, the injection fuel pressure waveform Wa (see FIG. 5 (a)) represents the injection waveform Wb (see FIG. 5 (c)), which is a fuel pressure waveform representing the change in fuel pressure due to injection, and the increase in fuel pressure due to pumping. It can be said that the fuel pressure waveform (see the solid line Wu in FIG. 5B) is included.

  Even if such pump pumping is not performed during fuel injection, immediately after the fuel is injected, the fuel pressure in the entire injection system is reduced by that amount. Therefore, the fuel pressure waveform Wa at the time of injection becomes a waveform in which the pressure is lowered as a whole. That is, the injection fuel pressure waveform Wa includes a component of the injection waveform Wb that represents a change in fuel pressure due to injection and a fuel pressure waveform that represents a decrease in the fuel pressure in the entire injection system (see the dotted line Wu ′ in FIG. 5B). It can be said that the ingredients are included.

  Therefore, in step S10 of FIG. 4, paying attention to the non-injection fuel pressure waveform Wu (Wu ′) detected by the non-injection cylinder sensor represents a change in the fuel pressure in the common rail (the fuel pressure in the entire injection system), The injection waveform Wb is calculated by subtracting the non-injection fuel pressure waveform Wu (Wu ′) from the non-injection cylinder sensor from the injection fuel pressure waveform Wa detected by the injection cylinder sensor. The fuel pressure waveform shown in FIG. 2C is the injection waveform Wb.

  Further, when performing multi-stage injection, the pulsation Wc (see FIG. 2C) of the fuel pressure waveform applied to the previous stage injection is superimposed on the fuel pressure waveform Wa. In particular, when the interval with the pre-stage injection is short, the fuel pressure waveform Wa is greatly affected by the pulsation Wc. Therefore, it is desirable to calculate the injection waveform Wb by performing a process of subtracting the pulsation Wc from the fuel pressure waveform Wa in addition to the non-injection fuel pressure waveform Wu (Wu ′).

  In the subsequent step S11 (reference pressure calculation means), the average fuel pressure of the reference waveform is calculated based on the reference waveform which is the waveform corresponding to the period until the fuel pressure starts to decrease with the start of injection in the injection waveform Wb. Calculated as the reference pressure Pbase. For example, a portion corresponding to a period TA until a predetermined time elapses from the injection start command timing t1 may be set as the reference waveform. Alternatively, the inflection point P1 may be calculated based on the differential value of the descending waveform, and a portion corresponding to a period from the injection start command timing t1 to a predetermined time before the inflection point P1 may be set as the reference waveform.

  In the subsequent step S12 (linear approximation means), an approximate straight line Lα of the descending waveform is calculated based on the descending waveform that is the waveform corresponding to the period in which the fuel pressure decreases as the injection rate increases in the injection waveform Wb. To do. For example, what is necessary is just to set the part corresponding to predetermined period TB from the time of predetermined time having passed since injection start instruction | command time t1 as a fall waveform. Alternatively, the inflection points P1 and P2 may be calculated based on the differential value of the descending waveform, and the portion corresponding to the inflection points P1 and P2 may be set as the descending waveform. Then, an approximate straight line Lα may be calculated by a least square method from a plurality of detected fuel pressure values (sampling values) constituting the descending waveform. Alternatively, the tangent line at the time when the differential value becomes the minimum in the descending waveform may be calculated as the approximate straight line Lα.

  In the subsequent step S13 (linear approximation means), an approximate straight line Lβ of the rising waveform is calculated based on the rising waveform that is the waveform corresponding to the period in which the fuel pressure increases as the injection rate decreases in the injection waveform Wb. To do. For example, what is necessary is just to set the part corresponding to the predetermined period TC from the time of predetermined time having passed since the injection end instruction | command time t2 as a rising waveform. Alternatively, the inflection points P3 and P5 may be calculated based on the differential value of the rising waveform, and a portion corresponding to the inflection points P3 and P5 may be set as the rising waveform. Then, the approximate straight line Lβ may be calculated from the plurality of detected fuel pressure values (sampling values) constituting the rising waveform by the least square method. Alternatively, the tangent at the time when the differential value becomes the maximum in the rising waveform may be calculated as the approximate straight line Lβ.

  In subsequent step S14, reference values Bα and Bβ are calculated based on the reference pressure Pbase. For example, values lower than the reference pressure Pbase by a predetermined amount may be calculated as the reference values Bα and Bβ. It is not necessary to set both reference values Bα and Bβ to the same value. The predetermined amount may be variably set according to the value of the reference pressure Pbase, the fuel temperature, and the like.

  In the subsequent step S15, a time (intersection time LBα between Lα and Bα) at which the approximate value Lα becomes the reference value Bα is calculated. Focusing on the fact that the intersection time LBα and the injection start time R1 are highly correlated, the injection start time R1 is calculated based on the intersection time LBα. For example, a timing that is a predetermined delay time Cα before the intersection timing LBα may be calculated as the injection start timing R1.

  In the subsequent step S16, a time (intersection time LBβ between Lβ and Bβ) that is the reference value Bβ in the approximate straight line Lβ is calculated. Focusing on the fact that the intersection timing LBβ and the injection end timing R4 are highly correlated, the injection end timing R4 is calculated based on the intersection timing LBβ. For example, a timing that is a predetermined delay time Cβ before the intersection timing LBβ may be calculated as the injection end timing R4. The delay times Cα and Cβ may be variably set according to the value of the reference pressure Pbase, the fuel temperature, and the like.

  In subsequent step S17, focusing on the fact that the slope of the approximate line Lα and the slope of the injection rate increase are highly correlated, the slope of the straight line Rα indicating the increase in injection in the injection rate waveform shown in FIG. Calculation is based on the slope of Lα. For example, the slope of Rα may be calculated by multiplying the slope of Lα by a predetermined coefficient. Note that, based on the injection start timing R1 calculated in step S15 and the slope of Rα calculated in step S17, a straight line Rα representing the rising portion of the injection rate waveform with respect to the injection command signal can be specified.

  Further, in step S17, paying attention to the fact that the slope of the approximate straight line Lβ and the slope of the injection rate decrease are highly correlated, the slope of the straight line Rβ indicating the decrease in the injection rate waveform is calculated based on the slope of the approximate straight line Lβ. . For example, the slope of Rβ may be calculated by multiplying the slope of Lβ by a predetermined coefficient. Note that, based on the injection end timing R4 calculated in step S16 and the slope of Rβ calculated in step S17, a straight line Rβ representing the descending portion of the injection rate waveform with respect to the injection command signal can be specified. The predetermined coefficient may be variably set according to the value of the reference pressure Pbase, the fuel temperature, and the like.

  In the subsequent step S18, based on the injection rate waveform straight lines Rα and Rβ calculated in step S17, a timing (valve closing operation start timing R23) at which the valve body 12 starts lift-down in response to the command to end the injection is calculated. . Specifically, the intersection of both straight lines Rα and Rβ is calculated, and the intersection timing is calculated as the valve closing operation start timing R23.

  In the subsequent step S19, a delay time (injection start delay time td) of the injection start timing R1 calculated in step S15 with respect to the injection start command timing t1 is calculated. Further, a delay time (injection end delay time te) with respect to the injection end command timing t2 of the valve closing operation start timing R23 calculated in step S18 is calculated. The injection end delay time te is a delay time from the timing t2 at which the injection end is commanded to the timing at which the operation of the control valve 14 is started. In short, these delay times td and te are parameters representing the response delay of the injection rate change with respect to the injection command signal. Besides, the delay time from the injection start command timing t1 to the maximum injection rate arrival timing R2, the injection end command Examples include a delay time from the timing t2 to the injection rate decrease start R3, a delay time from the injection end command timing t2 to the injection end timing R4, and the like.

  In the subsequent step S20, it is determined whether or not the pressure difference ΔPγ between the reference pressure Pbase and the intersection pressure Pαβ is less than a predetermined value ΔPγth. When it is determined that ΔPγ <ΔPγth (S20: YES), in the next step S21 (maximum injection rate calculation means), it is considered that the small injection is described above, and the maximum injection rate Rmax is calculated based on the pressure difference ΔPγ. (Rmax = ΔPγ × Cγ). On the other hand, when it is determined that ΔPγ ≧ ΔPγth (S20: NO), a preset value (set value Rγ) is calculated as the maximum injection rate Rmax in the next step S22 (maximum injection rate calculation means). To do. In subsequent step S23 (correction means), the maximum injection rate Rmax is corrected by multiplying the maximum injection rate Rmax calculated in step S21 or S22 by a correction ratio Ka (aging index) described later.

  Next, the technical significance of the correction in step S23 will be described.

  FIG. 6A shows the secular change of the injection amount with respect to the vehicle travel distance when the injection command signal is the same and the environmental conditions such as the interval, the in-cylinder pressure, and the reference pressure Pbase are the same. In the example of FIG. 6 (a), aged deterioration of a mode in which foreign matter such as deposit accumulates in the nozzle hole 11b and the injection amount decreases is shown, and from the initial value (2) ( The injection amount decreases to 3).

  FIGS. 6B and 6C show changes over time in the injection rate waveform and the fuel pressure waveform with respect to the vehicle travel distance when the injection command signal is the same and the environmental conditions are the same. When the injection amount decreases as shown in FIG. 6 (a), the maximum injection rate changes from the initial state shown in (1) in FIGS. 6 (b) and 6 (c) to (2) and (3). Rmax and pressure drop amount ΔP decrease. Note that the pressure drop amount ΔP is the amount of decrease in the detected pressure caused by the increase in the injection rate. For example, the pressure drop amount from the reference pressure Pbase to the inflection point P2 or the change from the inflection point P1. It is the amount of pressure drop to the bend point P2.

  FIG. 6D shows a change in the maximum injection rate Rmax according to the reference pressure Pbase, and shows that the maximum injection rate Rmax increases as the reference pressure Pbase increases. As the aging deterioration proceeds from (1) → (2) → (3), the value of the maximum injection rate Rmax decreases in the entire region of the reference pressure Pbase.

  In short, as the nozzle hole area is reduced due to aging, the maximum injection rate Rmax is reduced as shown in FIG. 6B, and the injection amount is reduced as shown in FIG. 6A. As the maximum injection rate Rmax decreases in this way, the pressure drop amount ΔP also decreases.

  Incidentally, the upper part of FIG. 7 shows the result of testing the change in the pressure drop amount ΔP with respect to the command injection amount with the reference pressure Pbase being varied from (a) to (f). Moreover, the upper part of FIG. 7 shows the result of testing the change in the actual maximum injection rate Rmax with respect to the command injection amount with the reference pressure Pbase varied from (a) to (f). As shown in FIG. 7, when commanding small injection, the actual pressure drop amount ΔP and the maximum injection rate Rmax increase as the command injection amount increases, but when commanding large injection, the actual pressure drop The amount ΔP and the maximum injection rate Rmax are constant values (set values Rγ). And as aged deterioration advances as illustrated in FIG. 6, the characteristic line in FIG.

  Here, in the method of calculating the maximum injection rate Rmax in steps S20 to S22 of FIG. 4, a drop approximation is performed so that the pressure drop amount ΔP is not affected by the sequential fluctuation according to the environmental conditions such as the interval and the in-cylinder pressure. The maximum injection rate Rmax is calculated based on the straight line Lα and the rising approximate straight line Lβ. Then, even if the fuel pressure waveform changes over time so that the pressure drop amount ΔP becomes low as shown in FIG. 6C, the approximate lines Lα and Lβ do not change greatly. For this reason, even if the maximum injection rate Rmax changes over time, the maximum injection rate Rmax calculated in steps S21 and S22 does not take into account the change over time, and the calculation accuracy of the maximum injection rate Rmax deteriorates with the progress of change over time. Will be.

  Therefore, in the present embodiment, as shown in FIGS. 6B and 6C, focusing on the fact that the secular change of the actual maximum injection rate Rmax and the secular change of the pressure drop amount ΔP are highly correlated, the detection of the pressure drop amount ΔP is detected. A secular change index of the actual maximum injection rate Rmax is estimated from the result, and the maximum injection rate Rmax calculated in steps S21 and S22 of FIG. 4 is corrected based on the estimated secular change index.

  Specifically, the pressure drop amount ΔP is detected for each injection, and the maximum injection rate is calculated for each injection by multiplying the detected ΔP by a predetermined correlation coefficient. In the following description, the maximum injection rate calculated based on the pressure drop amount ΔP is described as Rmax (ΔP), and is distinguished from the maximum injection rate Rmax calculated in steps S21 and S22. Then, a correction ratio Ka (aging index) is calculated based on an average value Rmax (ΔP) ave of a plurality of maximum injection rates Rmax (ΔP) detected in a predetermined period (for example, one trip), and the correction ratio Ka is calculated as the maximum injection. Correction is made by multiplying the rate Rmax.

  A plurality of dots surrounded by a one-dot chain line in FIG. 8 indicates the value of the maximum injection rate Rmax calculated for each injection in a period (one trip period) from when the driver starts the engine to when it stops. Indicates. Then, an amount by which the average value Rmax (ΔP) ave of the maximum injection rate Rmax (ΔP) changes for each trip is calculated as a secular change index, and the correction in step S23 of FIG. 4 is performed based on the secular change index. The correction ratio Ka used in is calculated.

  FIG. 9 is a flowchart showing the calculation procedure of the correction ratio Ka, and is repeatedly executed by the microcomputer of the ECU 30 every time the engine is started or every time the engine is stopped.

  First, in step S30 (pressure drop amount detecting means) shown in FIG. 9, an average value Rmax (ΔP) ave for one trip of the maximum injection rate Rmax (ΔP) calculated based on the pressure drop amount ΔP is calculated. In subsequent step S31 (aging change index calculating means), an aging deterioration rate K that is an average value Rmax (ΔP) ave ratio with respect to a learning value of the maximum injection rate Rmax (ΔP) is calculated (K = Rmax (ΔP) ave / Rmax). (ΔP) learning value). That is, if the calculated aging deterioration rate K is smaller than 1, it can be said that the deterioration in which the injection hole 11b is closed and the injection amount decreases is progressing. On the other hand, if the calculated aging deterioration rate K is greater than 1, it can be said that deterioration in which the injection amount increases due to wear of the nozzle holes 11b, damage to the sheet surfaces 11e, 12a, or the like is proceeding.

  In subsequent step S32, it is determined whether or not the aging deterioration rate K calculated in step S31 has become equal to or higher than the threshold value Ku or lower than the threshold value Kd for two consecutive trips. When it is determined that the aging deterioration rate K has exceeded the threshold values Ku and Kd for two consecutive trips (S32: YES) as shown by the black circles in FIG. 6 (e), the next step S33 (aging change) The index calculation means) learns a value calculated by multiplying the previous value of the correction ratio Ka by the aging deterioration rate K as an updated value (aging index) of the correction ratio Ka. In the next step S34, the learning value of the maximum injection rate Rmax (ΔP) is updated to Rmax (ΔP) ave calculated in step S30.

  As described above, according to the present embodiment, the pressure difference ΔPγ between the intersection pressure Pαβ of the descending approximate straight line Lα and the ascending approximate straight line Lβ and the reference pressure Pbase is hardly affected by the environmental conditions such as the interval and the in-cylinder pressure. Focusing on the fact that the correlation with the actual maximum injection rate Rmax is high, the maximum injection rate Rmax is calculated based on this pressure difference ΔPγ. Therefore, the maximum injection rate Rmax can be calculated with high accuracy while avoiding the calculated maximum injection rate Rmax from fluctuating sequentially due to the influence of environmental conditions. Therefore, according to the present embodiment in which the injection command signals t1, t2, Tq are set based on the learning value (injection rate parameter) of the maximum injection rate Rmax calculated in this way, and the fuel injection valve 10 is feedback-controlled. The stability of the feedback control can be improved while suppressing the actual injection state from greatly hunting with respect to the target injection state.

  Further, in the present embodiment, paying attention to the fact that the correlation between the pressure drop amount ΔP and the maximum injection rate Rmax is high, the maximum injection rate Rmax with respect to a plurality of pressure drop amounts ΔP detected in a predetermined period (one trip period). (ΔP) is calculated, and the correction ratio Ka is calculated based on the average value Rmax (ΔP) ave of the maximum injection rate Rmax (ΔP). Since the maximum injection rate Rmax calculated from the pressure difference ΔPγ described above is corrected using the correction ratio Ka, it can be corrected to the maximum injection rate Rmax taking into account aging degradation.

(Second Embodiment)
In the first embodiment, the average value of all the maximum injection rates Rmax (ΔP) accumulated in one trip period is calculated as the average value Rmax (ΔP) ave used for calculating the aging deterioration rate K. On the other hand, in the present embodiment, the average value Rmax (ΔP) ave used for calculating the aging deterioration rate K is calculated as follows.

  First, the pressure drop amount ΔP is detected in association with the reference pressure Pbase, and the maximum injection rate Rmax (ΔP) is calculated. Next, among all the maximum injection rates Rmax (ΔP) accumulated in one trip period, the average value avehigh of the maximum injection rate Rmax (ΔP) in the high pressure region where the reference pressure Pbase is equal to or higher than a predetermined pressure, and the reference pressure Pbase are An average value avelow of the maximum injection rate Rmax (ΔP) in the low pressure region that is less than the predetermined pressure is calculated. Next, the values avehigh and avelow are weighted according to the number of data points in the high pressure region and the number of data points in the low pressure region. Next, the weighted average value of avehigh and avelow is calculated as an average value Rmax (ΔP) ave used for calculating the aging deterioration rate K.

  For example, as illustrated in FIG. 10, when the number of data points in the high pressure region is larger than that in the low pressure region, the weight of the average value avehigh in the high pressure region is set larger than the weight of the average value avelow in the low pressure region, An average value of both values avehigh and avelow is calculated as an average value Rmax (ΔP) ave.

  According to this, in the case of a user who frequently operates the engine at a high load, the data distribution is biased as illustrated in FIG. Since the correction ratio Ka is calculated by setting a large weight to the rate Rmax (ΔP), correction suitable for the actual driving state can be performed, and the correction accuracy in step S23 can be improved.

(Third embodiment)
In the second embodiment, the reference pressure Pbase is divided into a low pressure region and a high pressure region. However, in the present embodiment, as shown in FIG. 11, a plurality of regions w1 to w7 arranged discretely. Is set, and an average value Rmax (ΔP) ave used for calculating the aging deterioration rate K is calculated from the value of the maximum injection rate Rmax (ΔP) corresponding to each of the regions w1 to w7. The value of the maximum injection rate Rmax (ΔP) not included in any of them is not used for calculating the aging deterioration rate K.

  Specifically, the average values avew1 to ave7 of the maximum injection rate Rmax (ΔP) are calculated in the respective regions w1 to w7, and the average value of these values avew1 to ave7 is calculated as the average value Rmax (ΔP) ave. At this time, similarly to the second embodiment, the average value Rmax (ΔP) ave may be calculated by weighting the avew1 to ave7 according to the number of data points of the areas w1 to w7.

  Here, the value of the maximum injection rate Rmax (ΔP) varies as the reference pressure Pbase changes, but as in this embodiment, the average value Rmax (ΔP) ave for the past one trip and the current In comparing the average value Rmax (ΔP) ave for one trip, the aging deterioration rate K is calculated by comparing the maximum injection rate Rmax (ΔP) in the same reference pressure Pbase region, so the calculation accuracy of the correction ratio Ka is increased. It can be improved.

(Modification of the third embodiment)
In the third embodiment, the average value Rmax (ΔP) is calculated using the maximum injection rate Rmax (ΔP) calculated from the pressure drop amount ΔP when the reference pressure Pbase is within the predetermined range (avew1 to avew7). ) Although ave is calculated, for example, the pressure drop amount ΔP is detected in association with the interval, and the value of the maximum injection rate Rmax (ΔP) calculated from the pressure drop amount ΔP when the interval is within a predetermined range May be used to calculate the average value Rmax (ΔP) ave.

  Alternatively, the pressure drop amount ΔP is detected in association with the in-cylinder pressure, and the average value Rmax is calculated using the value of the maximum injection rate Rmax (ΔP) calculated from the pressure drop amount ΔP when the in-cylinder pressure is within the predetermined range. (ΔP) ave may be calculated.

  Also in these cases, when comparing the average value Rmax (ΔP) ave for the past one trip with the average value Rmax (ΔP) ave for the current one trip, the maximum injection under the same environmental conditions (interval or in-cylinder pressure) Since the aging deterioration rate K is calculated by comparing the rate Rmax (ΔP), the calculation accuracy of the correction ratio Ka can be improved.

(Fourth embodiment)
In the first embodiment, all the calculated pressure drop amounts ΔP (that is, the maximum injection rate Rmax (ΔP)) are used to calculate the average value Rmax (ΔP) ave, but in this embodiment, the reference pressure Pbase is The maximum injection rate Rmax (ΔP) calculated from the pressure drop amount ΔP detected at the time of high pressure that is equal to or higher than the predetermined pressure Punder (see FIG. 8) is used as the calculation target of the average value Rmax (ΔP) ave.

  Here, since the absolute value of the pressure drop amount ΔP increases as the reference pressure Pbase increases, the average value Rmax (ΔP) ave calculated based on the pressure drop amount ΔP at the time of high pressure is the past average value Rmax. When (ΔP) ave is compared with the current average value Rmax (ΔP) ave, a change amount (aging deterioration amount) of the average value Rmax (ΔP) ave due to aging appears greatly. Therefore, the aged deterioration rate K can be calculated with high accuracy.

  In this embodiment in view of this point, the average value Rmax (ΔP) ave is calculated using the maximum injection rate Rmax (ΔP) based on the pressure drop amount ΔP detected at the time of high pressure, and is detected at a low pressure less than the predetermined pressure Punder. The maximum injection rate Rmax (ΔP) resulting from the pressure drop amount ΔP is not used for calculating the average value Rmax (ΔP) ave. Therefore, the aging deterioration rate K corresponding to the aging index can be calculated with high accuracy.

(Modification of the fourth embodiment)
In the fourth embodiment, the average value Rmax (ΔP) ave is calculated using the value of the maximum injection rate Rmax (ΔP) calculated from the pressure drop amount ΔP when the reference pressure Pbase is equal to or higher than the predetermined pressure Pander. However, for example, the pressure drop amount ΔP is detected in association with the interval, and the value of the maximum injection rate Rmax (ΔP) calculated from the pressure drop amount ΔP when the interval is equal to or larger than a predetermined amount (or no pre-stage injection) is obtained. The average value Rmax (ΔP) ave may be calculated by using it.

  Alternatively, the pressure drop amount ΔP is detected in association with the in-cylinder pressure, and the average value Rmax is calculated using the value of the maximum injection rate Rmax (ΔP) calculated from the pressure drop amount ΔP when the in-cylinder pressure is within the predetermined range. (ΔP) ave may be calculated.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows. Moreover, you may make it combine the characteristic structure of each embodiment arbitrarily, respectively.

  In each of the above embodiments, the average value Rmax (ΔP) ave used to calculate the correction ratio Ka is calculated using a plurality of pressure drop amounts ΔP detected in one trip period, but the vehicle is only a predetermined distance away. It may be changed to use a plurality of pressure drop amounts ΔP detected during the traveling period, or may be changed to use a plurality of pressure drop amounts ΔP detected during a period when the engine operation time has elapsed for a predetermined time. Good.

  In each of the above embodiments, the “aging index” indicating the degree of change in the pressure drop ΔP with the aging of the fuel injection valve 10 is expressed as the average value Rmax (ΔP) with respect to the learning value of the maximum injection rate Rmax (ΔP). ) Ave ratio (aging rate K or correction ratio Ka). On the other hand, the amount of secular change that is the difference between the learned value of the maximum injection rate Rmax (ΔP) and the average value Rmax (ΔP) ave may be used as the “aging change index”.

  In the above embodiment, the maximum injection rate Rmax is corrected based on the correction ratio Ka (aging index), but the maximum injection rate Rmax may be corrected based on the aging deterioration rate K. In this case, the aging deterioration rate K corresponds to the aging index. Further, the maximum injection rate Rmax may be corrected based on the secular change amount of the pressure drop amount ΔP and the secular change amount of the maximum injection rate Rmax (ΔP). In this case, these aging amounts correspond to the aging index.

  In the embodiment shown in FIG. 1, the fuel pressure sensor 20 is mounted on the fuel injection valve 10, but the fuel pressure sensor is disposed in the fuel supply path from the discharge port 42a of the common rail 42 to the injection hole 11b. Also good. Therefore, for example, a fuel pressure sensor may be mounted on the high-pressure pipe 42 b that connects the common rail 42 and the fuel injection valve 10. Further, the fuel pressure sensor 20 may be disposed on the common rail 42, or the fuel pressure sensor may be disposed in the fuel supply path from the discharge port of the fuel pump 41 to the common rail 42.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 20 ... Fuel pressure sensor, 42 ... Common rail (accumulation container), Ka ... Correction ratio (aging index), L (alpha) ... Falling approximation straight line, L (beta) ... Rising approximation straight line, Pbase ... Reference pressure, P (alpha) beta ... Intersection pressure , ΔPγ ... pressure difference, ΔP ... pressure drop amount, Rmax ... maximum injection rate, S11 ... reference pressure calculation means, S12, S13 ... linear approximation means, S21, S22 ... maximum injection rate calculation means, S23 ... correction means, S30 ... Pressure drop amount detection means, S33... Aging index calculation means.

Claims (7)

Applied to a fuel injection system having a fuel pressure sensor for detecting the pressure of fuel supplied to the fuel injection valve;
Of the pressure waveforms detected by the fuel pressure sensor, when the waveform of the period when the pressure drops as the fuel injection rate increases, the waveform of the period when the pressure increases as the fuel injection rate decreases, Linear approximation means for calculating a descending approximation line approximating the descending waveform to a straight line, and an ascending approximation line approximating the rising waveform to a straight line;
Reference pressure calculation means for calculating a reference pressure based on a waveform in a specific period immediately before the drop waveform appears among the pressure waveforms detected by the fuel pressure sensor;
A maximum injection rate calculating means for calculating an intersection pressure that is a pressure corresponding to an intersection of the descending approximate line and the rising approximate line, and calculating a maximum injection rate based on a pressure difference between the intersection pressure and the reference pressure;
A pressure drop amount detecting means for detecting a pressure drop amount caused by an increase in the injection rate;
A secular change index calculating means for calculating a secular change index representing a degree of change of the pressure drop detected by the pressure drop amount detecting means with the secular change of the fuel injection valve;
Correction means for correcting the maximum injection rate calculated by the maximum injection rate calculation means based on the secular change index;
A fuel injection control device comprising:   The maximum injection rate calculating means calculates a maximum injection rate based on the pressure difference when the pressure difference is less than a predetermined value, and is preset when the pressure difference is greater than or equal to a predetermined value. The fuel injection control device according to claim 1, wherein the value is calculated as a maximum injection rate. Applied to a fuel injection system having a fuel pressure sensor for detecting the pressure of fuel supplied to the fuel injection valve;
Of the pressure waveforms detected by the fuel pressure sensor, when the waveform of the period when the pressure drops as the fuel injection rate increases, the waveform of the period when the pressure increases as the fuel injection rate decreases, Linear approximation means for calculating a descending approximation line approximating the descending waveform to a straight line, and an ascending approximation line approximating the rising waveform to a straight line;
Reference pressure calculation means for calculating a reference pressure based on a waveform in a specific period immediately before the drop waveform appears among the pressure waveforms detected by the fuel pressure sensor;
When an intersection pressure that is a pressure corresponding to an intersection of the descending approximate straight line and the rising approximate straight line is calculated, a pressure difference between the intersection pressure and the reference pressure is calculated, and the pressure difference is equal to or greater than a predetermined value A maximum injection rate calculation means for calculating a preset value as a maximum injection rate;
A pressure drop amount detecting means for detecting a pressure drop amount caused by an increase in the injection rate;
A secular change index calculating means for calculating a secular change index representing a degree of change of the pressure drop detected by the pressure drop amount detecting means with the secular change of the fuel injection valve;
Correction means for correcting the maximum injection rate calculated by the maximum injection rate calculation means based on the secular change index;
A fuel injection control device comprising: The aging index calculating means calculates an average value of a plurality of maximum injection rates calculated based on the plurality of pressure drop amounts detected during a predetermined period, and calculates a degree of change of the average value as the aging index. The fuel injection control device according to claim 1, wherein the fuel injection control device is a fuel injection control device. The pressure drop amount detecting means detects the pressure drop amount in association with the reference pressure,
The reference pressure is set to be divided into a plurality of regions,
The said aging index calculation means weights the value of the said pressure drop amount according to the detection number of the said pressure drop amount for every said area | region, The said average value is calculated. Fuel injection control device.   6. The aging index calculating means calculates the aging index based on the pressure drop detected when an environmental condition during fuel injection is within a predetermined range. The fuel-injection control apparatus as described in one.   The aging index calculating means calculates the aging index based on the pressure drop detected at a high pressure when the reference pressure is equal to or higher than a predetermined pressure. A fuel injection control device according to claim 1.

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