JP5168325B2 - Fuel injection state detection device - Google Patents

Description

  The present invention relates to a fuel injection state detection device that detects a change in fuel pressure caused by injecting fuel from a fuel injection valve of an internal combustion engine with a fuel pressure sensor and calculates an injection rate waveform based on the detected pressure waveform.

  In order to accurately control the output torque and the emission state of the internal combustion engine, it is important to accurately control the injection state such as the injection amount of fuel injected from the fuel injection valve and the injection start timing. Therefore, in Patent Documents 1 and 2, etc., a fuel pressure sensor detects a change in fuel pressure caused by injection in the fuel supply path up to the injection hole of the fuel injection valve. Since the pressure waveform detected by the fuel pressure sensor has a high correlation with the injection rate waveform representing the change in the injection rate, by calculating the injection rate waveform based on the detected pressure waveform, the injection state such as the injection start timing and the injection amount We are trying to detect this. If the actual injection state can be detected in this way, the injection state can be accurately controlled based on the detected value.

JP 2010-3004 A JP 2009-57924 A

  Next, an example of a method for calculating the injection rate waveform from the pressure waveform will be described below. First, various change points appearing in the pressure waveform (for example, P1, P2, P3, P5, etc. in FIG. 2C) are detected. Next, the waveform of the portion where the pressure decreases (P1 to P2 portion) with the start of the valve opening operation of the fuel injection valve and the waveform of the portion (P3 to P5 portion) where the pressure increases with the start of the valve closing operation are shown. Approximating straight lines, the inclinations Pα and Pβ of these approximate straight lines are calculated. Further, the pressure drop amount P1-P2 from the change point P1 to P2 is calculated. The timing at which the pressure waveform change point P1 appears, the pressure drop amount P1-P2, and the slopes Pα and Pβ are respectively set to the injection start timing t (R1), the maximum injection rate Rh, And the slopes Rα and Rβ. Thereby, an injection rate waveform can be generated and an actual injection state can be estimated.

  Here, if the pressure (reference pressure Pbase) before starting the pressure drop is different, the correlation between the pressure waveform and the injection rate waveform is different. That is, even if the pressure waveforms have the same slopes Pα and Pβ, the slopes Rα and Rβ of the injection rate waveform differ if the reference pressure Pbase is different. Even if the various change points P1, P2, P3, and P5 appear at the same time, the injection start time t (R1) and the like differ if the reference pressure Pbase is different. Therefore, the present inventor has studied to variably set the conversion value for converting the pressure waveform into the injection rate waveform according to the reference pressure Pbase.

  However, when setting the reference pressure Pbase based on the waveform before the start of descent before the time point P1 in the pressure waveform, the waveform Wa before descent (see the one-dot chain line in FIG. 3B) pulsates due to the reasons exemplified below. In this case, the reference pressure Pbase becomes unstable, and the conversion accuracy from the pressure waveform to the injection rate waveform deteriorates. The cause of the pulsation is that a pressure change caused by post-injection of other cylinders propagates through the common rail and is superimposed on the waveform Wa before starting descent, or a pressure rise caused in synchronization with the fuel pumping timing by the plunger pump. For example, it may be superimposed on the waveform Wa before starting descent.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel injection state detection device that improves the calculation accuracy of the injection rate waveform by improving the calculation accuracy of the reference pressure. .

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

In the first invention, a fuel injection valve that injects fuel to be combusted in an internal combustion engine from an injection hole, and a fuel pressure generated in a fuel supply path up to the injection hole as fuel is injected from the injection hole. It is assumed that the present invention is applied to a fuel injection system including a fuel pressure sensor that detects a change.

  And a pressure waveform acquisition means for acquiring a pressure waveform representing a change in a detection value of the fuel pressure sensor, and a reference pressure based on a waveform before the start of lowering before the pressure starts to decrease with the start of injection among the pressure waveforms. A reference pressure calculating means for calculating, and an injection rate waveform calculating means for calculating an injection rate waveform representing a change in fuel injection rate based on the pressure waveform and the reference pressure, wherein the reference pressure calculating means includes the Searching means for searching for a stable portion where the pressure fluctuation is within a predetermined range in the waveform before starting descent, and calculating means for calculating the reference pressure based on the pressure of the stable portion.

  Here, the correlation (the aforementioned conversion value) between the pressure waveform and the injection rate waveform changes in accordance with the pressure before the pressure drop starts with the start of injection. Therefore, according to the said invention which calculates an injection rate waveform based on the reference pressure and pressure waveform calculated based on the waveform before a fall start, an injection rate waveform can be calculated with high precision.

  Further, in the above invention, the reference pressure used for the calculation of the injection rate waveform is the pressure Wb of the stable portion where the pressure fluctuation is within the predetermined range of the waveform Wa before starting to descend (see the one-dot chain line in FIG. 3B). Calculate based on (see dotted line in FIG. 3B). For this reason, for example, the waveform before the start of pulsation became unstable due to the influence of the pressure change caused by the post injection of the other cylinders or the influence of the pressure change caused by the fuel pumping by the plunger pump. However, since the reference pressure is calculated without being affected by such an unstable portion, the reference pressure can be calculated stably. Therefore, the calculation accuracy of the injection rate waveform can be improved.

According to a second aspect of the present invention, the search means is the stable portion that includes a portion corresponding to a predetermined time before the start of pressure drop with the start of injection in the waveform before starting to descend. It is characterized by searching as a condition.

  By the way, since the waveform before descent begins to fluctuate due to, for example, electrical noise or the pressure controllability of the plunger pump, it is desirable to average the long-term waveform as much as possible in order to stably calculate the reference pressure. On the other hand, if fuel is injected (for example, post-injection), for example, in another cylinder during calculation of the reference pressure, the average pressure of the common rail fluctuates, so that the reference pressure cannot be accurately calculated. Therefore, it is desirable to calculate the reference pressure from the information immediately before the start of injection so as not to be affected by the change in the rail pressure average value due to the injection of the other cylinders. In the above invention in view of this point, since it is a condition that the stable portion includes at least a portion corresponding to the predetermined time before, the reference pressure can be calculated in the stable portion immediately before the start of injection. Therefore, the calculation accuracy of the injection rate waveform can be improved.

In a third aspect of the invention, the searching means searches that the pressure does not exceed the upper limit value and the lower limit value as a condition for the stable portion.

  Contrary to the above-mentioned invention, for example, if an attempt is made to search for the fact that the differential value of the waveform before the descent start does not exceed the upper limit value as a “stable portion where the pressure fluctuation is within a predetermined range”, Since it is necessary to perform a differential operation for each pressure value, the processing load is heavy. On the other hand, in the above invention, since the pressure is stable in a range that does not exceed the upper limit value and the lower limit value, it is searched as “a stable portion in which the pressure fluctuation is within a predetermined range”, so the calculation processing load is reduced. Can be reduced.

In a fourth aspect of the invention, the searching means searches that the pressure differential value does not exceed the upper limit value and the lower limit value as a condition for the stable portion.

  Contrary to the above-mentioned invention, for example, if an attempt is made to search that the pressure waveform before starting descent does not exceed the upper limit value as a “stable portion where the pressure fluctuation is within a predetermined range”, the upper limit is set for a certain central pressure The value and lower limit must be set, and the central pressure must be specified. On the other hand, in the said invention, since zero can be made into a reference | standard by using a differential value, it can make unnecessary to prescribe | regulate a center pressure.

In the fifth invention, the calculating means calculates an average value of the pressure in the stable portion as the reference pressure. For example, when the pressure value at one point in the stable portion is used as the reference pressure As compared with the above, it is possible to calculate a stable reference pressure in which the influence of noise or the like superimposed on the pressure waveform is reduced. Therefore, the calculation accuracy of the injection rate waveform can be improved.

In a sixth aspect of the present invention, the search means determines that the pressure fluctuation is within a predetermined range for a predetermined period set to be equal to or longer than one cycle length of the pulsation included in the waveform before starting descent. It is characterized by searching as a condition of being.

  For example, when the pressure pulsation caused by post-injection of other cylinders or the pressure pulsation caused by the fuel pumping by the plunger pump is superimposed on the waveform before descent start, the pulsation is superimposed on the waveform before descent start. In order to calculate a stable reference pressure, it is desirable to calculate the reference pressure based on the pressure of the portion that is not. However, there is a concern that, in the portion where the pulsation is superimposed, a portion in a range not including the peak value of the pulsation (for example, a portion indicated by a symbol Mb ′ in FIG. 3D) is regarded as a stable portion. Is done. In the above-mentioned invention in view of this point, the condition that the pressure change is stable in a predetermined period set longer than the length of one cycle Mc (see FIG. 3D) of the pulsation is a stable part. Therefore, it is possible to avoid calculating the reference pressure based on the pressure of the portion where the pulsation is superimposed in the waveform before starting to descend. Therefore, it is possible to promote the calculation of a stable reference pressure.

The figure which shows the outline of the fuel-injection system with which the fuel-injection state detection apparatus concerning one Embodiment of this invention is applied. In the above embodiment, (a) is an injection command signal to the fuel injection valve shown in FIG. 1, (b) is an injection rate waveform representing a change in fuel injection rate caused by the injection command signal, and (c) is shown in FIG. The figure which shows the pressure waveform component Wc based on the pressure waveform by the fuel pressure sensor which shows. In the said embodiment, the figure which shows the search range Ma (waveform before fall start Wa) in a pressure waveform, and the stable range Mb (stable part) in the search range Ma. 4 is a flowchart showing a procedure for calculating a reference pressure Pbase in the embodiment. The figure explaining the procedure which searches the stable range Mb (stable part) used for calculation of the reference pressure Pbase in the said embodiment.

  Hereinafter, an embodiment embodying a fuel injection state detection device according to the present invention will be described with reference to the drawings. The fuel injection state detection device according to the present embodiment is mounted on a vehicle engine (internal combustion engine), and compression auto-ignition is performed by injecting high-pressure fuel into a plurality of cylinders # 1 to # 4. It assumes a diesel engine that burns.

  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 accumulator) by a high pressure pump 41 (fuel pump), and is 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. Since the plunger pump is used as the high-pressure pump 41, the fuel is intermittently pumped in synchronism with the reciprocating movement 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 decreases and the valve body 12 opens. 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 rises and the valve body 12 is closed.

  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. For example, the ECU 30 calculates a target injection state such as an injection start timing, an injection end timing, and an injection amount based on the rotation speed of the engine output shaft, the engine load, and the like, and sends an injection command signal to the actuator 13 so that the calculated target injection state is obtained. Is output to control the operation of the fuel injection valve 10.

  The ECU 30 calculates the target injection state based on the engine load and engine speed calculated from the accelerator operation amount and the like. For example, the optimal injection state (the number of injection stages, the injection start time, the injection end time, the injection amount, etc.) 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, injection command signals t1, t2, and Tq are set based on the calculated target injection state. For example, an injection command signal corresponding to the target injection state is stored as a command map, and the injection command signal is set with reference to the command map based on the calculated target injection state. Thus, the injection command signal corresponding to the engine load and the engine rotation speed is set and output from the ECU 30 to the fuel injection valve 10.

  Here, the actual injection state with respect to the injection command signal changes due to deterioration of the fuel injection valve 10 such as wear of the injection hole 11b. Therefore, as described in detail later, the fuel injection rate waveform is calculated based on the pressure waveform detected by the fuel pressure sensor 20 to detect the injection state, and the detected injection state and the injection command signal (pulse on timing t1, pulse off timing t2). And the correlation with the pulse-on period Tq), and the injection command signal stored in the command map is corrected based on the learning result. Thus, the fuel injection state can be controlled with high accuracy so that the actual injection state matches the target injection state.

  Next, the hardware configuration of the fuel pressure sensor 20 will be described. The fuel pressure sensor 20 includes a stem 21 (distortion body), a pressure sensor element 22, a mold IC 23, and the like 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 in accordance with the amount of elastic deformation generated in the diaphragm portion 21a.

  The mold IC 23 is formed by resin molding electronic components such as an amplification circuit that amplifies the pressure detection signal output from the pressure sensor element 22 and a transmission circuit that transmits the pressure detection signal. 10 is installed. A connector 15 is provided on the upper portion of the body 11, and the mold IC 23, the actuator 13, and the ECU 30 are electrically connected by a harness 16 connected to the connector 15. The amplified pressure detection signal is transmitted to the ECU 30 and received by a receiving circuit included in the ECU 30. This communication process for transmission / reception is performed for each fuel pressure sensor 20 of each cylinder.

  Here, the fuel pressure (fuel pressure) in the high-pressure passage 11a decreases with the start of fuel injection from the nozzle hole 11b, and the fuel pressure increases with the end of injection. That is, it can be said that the change in the fuel pressure and the change in the injection rate (injection amount injected per unit time) are correlated, and the change in the injection rate (actual injection state) can be detected from the change in the fuel pressure. Then, the above-described injection command signal is corrected so that the detected actual injection state becomes the target injection state. Thereby, the injection state can be controlled with high accuracy.

  Next, a pressure waveform (pressure waveform) detected by the fuel pressure sensor 20 mounted on the fuel injection valve 10 during fuel injection, and an injection rate waveform representing a change in the fuel injection rate applied to the fuel injection valve 10; The correlation will be described with reference to FIG.

  FIG. 2A shows an injection command signal output from the ECU 30 to the actuator 13 of the fuel injection valve 10. When the command signal is turned on, the actuator 13 is energized to open the nozzle hole 11b. That is, the injection start is commanded by the pulse-on timing t1 of the injection command signal, and the injection end is commanded by the pulse-off timing t2. Therefore, the injection amount Q is controlled by controlling the valve opening time of the nozzle hole 11b according to the pulse-on period (injection command period Tq) of the command signal.

  FIG. 2 (b) shows a change in fuel injection rate (injection rate waveform) from the nozzle hole 11b caused by the injection command, and FIG. 2 (c) is provided in the fuel injection valve 10 during fuel injection. The change of the detection pressure which arises with the change of the injection rate detected by the fuel pressure sensor 20 is shown.

  Since the pressure waveform and the injection rate waveform have a correlation described below, the injection rate waveform can be estimated (detected) from the detected pressure waveform. That is, first, as shown in FIG. 2 (a), after the time t1 when the injection start command is given, the injection rate starts to rise and the injection is started when the injection rate is R1. On the other hand, the detected pressure starts decreasing at the change point P1 when the delay time C1 elapses after the injection rate starts increasing at the time R1. Thereafter, as the injection rate reaches the maximum injection rate at the time of R2, the decrease in the detected pressure stops at the change point P2. Next, when the delay time C3 elapses after the injection rate starts decreasing at the time point R3, the detected pressure starts increasing at the change point P3. Thereafter, as the injection rate becomes zero at the time point R4 and the actual injection ends, the increase in the detected pressure stops at the change point P5.

  As explained above, the correlation between the pressure waveform and the injection rate waveform is high. The injection rate waveform shows the injection start time (R1 appearance time), the injection end time (R4 appearance time), and the injection amount (area of the halftone dot portion in FIG. 2B). The injection state can be detected by estimating the injection rate waveform from the pressure waveform.

  Next, an example of a procedure for estimating the injection rate waveform from the pressure waveform will be described.

  First, various change points appearing in the pressure waveform (for example, P1, P2, P3, P5, etc. in FIG. 2C) are detected. Next, the waveform of the portion where the pressure decreases (P1 to P2 portion) with the start of the valve opening operation of the fuel injection valve and the waveform of the portion (P3 to P5 portion) where the pressure increases with the start of the valve closing operation are shown. Approximating straight lines, the inclinations Pα and Pβ of these approximate straight lines are calculated. Further, the pressure drop amount P1-P2 from the change point P1 to P2 is calculated. Then, the timing at which the pressure waveform change points P1, P3 appear, the pressure drop amount P1-P2, and the slopes Pα, Pβ are respectively set to the injection start timing t (R1) necessary for generating the injection rate waveform, and the injection rate decrease. Conversion is made to the start timing t (R3), the maximum injection rate Rh, and the gradients Rα and Rβ. Thereby, an injection rate waveform can be generated and an actual injection state can be estimated.

  The conversion coefficients and delay times C1 and C3 used for the conversion are different values depending on the pressure immediately before the change point P1 appears in the pressure waveform (reference pressure Pbase shown in FIG. 2C). It became clear by the test which this inventor conducted. Therefore, in the present embodiment, the conversion coefficient and the delay times C1 and C3 are variably set according to the reference pressure Pbase, and the ECU 30 (injection rate waveform calculating means) calculates the injection rate waveform.

  Of the pressure waveforms illustrated in FIG. 2C, the waveform immediately before the change point P1 appears (the waveform before the descent start) is a waveform in which the pressure is constant. In such a case, there is no problem even if the pressure at an arbitrary point before P1 in the pressure waveform is set as the reference pressure Pbase, but actually, as shown by the one-dot chain line in FIG. The waveform Wa before starting to descend in the pressure waveform may be pulsating. The cause of this pulsation is that a pressure change caused by post-injection of other cylinders propagates through the common rail 42 and is superimposed on the waveform Wa before starting descent, or pressure generated in synchronization with the timing of fuel pumping by the high-pressure pump 41. For example, the increase is superimposed on the waveform Wa before starting the decrease.

  Therefore, in the present embodiment, the ECU 30 (reference pressure calculation means) calculates the average value of the waveform Wb of the portion where the pressure fluctuation is small and stable in the waveform Wa before starting descent as the reference pressure Pbase, so that the stable reference pressure Pbase is obtained. Is calculated. FIG. 4 is a flowchart showing a procedure for calculating the reference pressure Pbase as described above, and a pressure waveform for one injection is acquired by the microcomputer of the ECU 30 as shown in FIGS. 2 (c) and 3 (b). This is a process that starts execution every time it is executed and is repeatedly executed at a predetermined cycle.

  First, in step S10 (pressure waveform acquisition means) shown in FIG. 4, the detection value (sample) of the fuel pressure sensor 20 in the injection period is acquired at a predetermined sampling period. The injection period is a period t1 to t3 (see FIG. 3) until a predetermined time elapses from the pulse-on timing t1 of the injection command signal, and the period t1 to t3 is sufficient for the change point P5 to appear. Length is set.

  In the subsequent step S11, the calculation end time t4 shown in FIG. 3D is calculated. FIG.3 (d) is an enlarged view which shows the part of the waveform Wa before a fall start among the pressure waveforms shown in FIG.3 (b). The calculation end time t4 may be set to the time when the change point P1 appears. Alternatively, in order to surely avoid the calculation end time t4 being later than the change point P1, the calculation end time t4 is set to be a time that is a predetermined time earlier than the time P1 appears. May be.

  In subsequent steps S20 and S21, among the plurality of detection values acquired in step S10, the detection value S1 before the calculation end time t4 calculated in step S11 and closest to the calculation end time t4 (see FIG. 5B). As a target, it is determined whether or not the detected value S1 is a stable portion where the pressure fluctuation is within a predetermined range.

  Specifically, first, in step S20 (search means), it is determined whether or not the detection value S1 is within the range between the upper limit value Pg1 and the lower limit value Pg2. The upper limit value Pg1 and the lower limit value Pg2 may be set based on a detection value S0 (see FIG. 5B) after the detection value S1. For example, the upper limit value Pg1 and the lower limit value Pg2 may be set by adding and subtracting a predetermined amount with respect to the detection value S0, or the upper limit value Pg1 and the lower limit value may be set by multiplying the detection value S0 by a predetermined coefficient. Pg2 may be set. Alternatively, instead of setting based on the detection value S0, preset fixed values may be used as the upper limit value Pg1 and the lower limit value Pg2.

  In the next step S21 (search means), it is determined whether or not the differential value (slope) of the detected value S1 is within the range between the upper limit value and the lower limit value. The differential value may be calculated based on the difference between the detected value S1 and the detected values S2 and S0 before and after that. In addition, the upper limit value and the lower limit value used in step S21 may be set based on the detection value S0 after the detection value S1 in the same manner as the upper limit value Pg1 and the lower limit value Pg2 in step S20, or may be set in advance. A fixed value may be used.

  When affirmative determination is made in both steps S20 and S21, the detection value S1 that is the determination target is regarded as a stable portion in which the pressure fluctuation is within a predetermined range, and the next step S22 (search means) ), It is determined whether or not the appearance time of the detection value S1 is before the calculation start time t1 (has reached t1). The calculation start time t1 (see FIG. 5A) is set at the same time as the pulse-on timing t1 of the injection command signal.

  When it is determined that the appearance time of the detection value S1 as the determination target is after the calculation start time t1 (not reached t1) (S22: NO), the process proceeds to step S23 (search means), The detection value S1 to be determined is changed to the detection value S2 of the previous time (see FIG. 5C), and the process returns to step S20. In the next steps S20 and S21, it is determined whether or not the changed detection value S2 is a stable portion.

  Accordingly, the detection values to be determined are returned one by one from the calculation end time t4 in accordance with the processing of step S23, and all the detection values S3 at the calculation start time t1 (see FIG. 5D) are all stable portions. If determined, an affirmative determination is made in step S22. In this case, in the next step S30 (calculation means), the reference pressure Pbase is calculated based on the detected values from the calculation start time t1 to the calculation end time t4. Specifically, the average of all detected values from the calculation start time t1 to the calculation end time t4 is calculated, and the average value is used as the reference pressure Pbase.

  On the other hand, if a negative determination is made in one of steps S20 and S21, it is considered that the detection value that is the determination target has greatly fluctuated beyond a predetermined range, and the determination target detection value is a stable portion. It is determined that it is not. Then, in the next step S24, it is determined whether or not the appearance time of the determination target detection value is before the guard time tg described below. The guard time tg is set to a time before the calculation end time t4 by a predetermined time (stable range Mb shown in FIG. 3D). The length of the stable range Mb is set to be longer than one cycle length Mc of the pulsation included in the waveform Wa before starting descent. The one cycle length Mc of the pulsation may be acquired by testing in advance, and the length of the stable range Mb may be set in advance based on the acquired one cycle length Mc.

  Accordingly, the detection value to be determined is returned one by one from the calculation end time t4 in accordance with the processing of step S23, and the detection value S4 at the time exceeding the guard time tg (see FIG. 5D) is not a stable portion. If it is determined, an affirmative determination is made in step S24. In this case, in the next step S31 (calculation means), all detection values from the detection value at the time immediately after the detection value S4 determined not to be a stable portion to the calculation end time t4, that is, the stable portion. An average of all detected values within the stable range Mb determined to be present is calculated, and the average value is set as a reference pressure Pbase. Alternatively, an average of all detection values from the detection value at the guard time tg to the calculation end time t4 may be calculated, and the average value may be used as the reference pressure Pbase.

  Further, the detection value to be determined is returned one by one from the calculation end time t4 along with the processing of step S23, and the detection value S5 (see FIG. 5D) at the time when the guard time tg has not been reached is a stable portion. If it is determined that it is not, a negative determination is made in step S24. In this case, the calculation of the reference pressure Pbase is stopped in the next step S32. When the calculation of the reference pressure Pbase is stopped, the calculation of the injection rate waveform related to the injection is stopped, and the learning of the correlation between the injection state and the injection command signal is stopped for the injection.

  In short, in the process of FIG. 4, the calculation start time t1 to the calculation end time t4 are set as the search range Ma (see FIG. 3), and the pressure fluctuation is within a predetermined range for each of the detection values of the search range Ma. It is determined in order from the detection value at the calculation end time t4 whether or not it is a stable portion. Then, the detected value determined as not stable is set as the stable range Mb, and the average value of the detected values in the stable range Mb is calculated as the reference pressure Pbase. However, if the stable range Mb does not include the guard time tg, the calculation of the reference pressure Pbase is stopped.

  Note that the portion of the pressure waveform corresponding to the search range Ma corresponds to the “waveform Wa before starting descent”. Further, the waveform of the portion corresponding to the period of the stable range Mb corresponds to “a portion corresponding to a predetermined time before the start of the pressure drop with the start of injection in the waveform Wa before starting to descend”. Further, the period of the stable range Mb corresponds to “a predetermined period set to be equal to or longer than one cycle length of the pulsation included in the waveform Wa before starting descent”.

  Then, based on the calculated reference pressure Pbase, conversion coefficients used for conversion from the pressure waveform to the injection rate waveform and delay times C1 and C3 are set, and the injection rate waveform is calculated from the pressure waveform using these conversion coefficients and the like. . Then, the correlation between the injection command signal and the injection state such as the actual injection start timing R1, the actual injection end timing R4, and the injection amount, which is apparent from the calculated injection rate waveform, is learned.

  As described above, according to this embodiment, the reference pressure Pbase is calculated based on the waveform Wa before descent before the change point P1 in the pressure waveform, and the conversion coefficient and the like are variably set using the reference pressure Pbase. The rate waveform can be calculated with high accuracy.

  Furthermore, according to the present embodiment, the reference pressure Pbase used for the calculation of the injection rate waveform is calculated based on the detected pressure value of the portion Wb in which the pressure fluctuation is stable in the waveform Wa before starting descent. Even if pulsation is superimposed on the waveform Wa before starting descent due to the influence of injection or fuel pumping, the reference pressure Pbase is calculated based on the pressure detection value of the stable portion Wb where such pulsation is not superimposed. A stable reference pressure Pbase that is not influenced by the influence of pulsation can be calculated. Therefore, the conversion coefficient and the values of the delay times C1 and C3 can be set with high accuracy, and the calculation accuracy of the injection rate waveform can be improved.

  In addition, paying attention to the fact that the conversion coefficient and the values of the delay times C1 and C3 can be set with higher precision as the reference pressure Pbase calculated using the pressure immediately before the change point P1 is stabilized by steps S20 and S21. Since the determination is performed retroactively from the calculation end time t4, the portion immediately before the change point P1 is included in the stable range Mb. Therefore, the conversion coefficient and the values of the delay times C1 and C3 can be set with high accuracy, and the calculation accuracy of the injection rate waveform can be improved.

  Also, on the condition that the stable range Mb is longer than the predetermined length (has reached the guard time tg), the average of the stable range Mb is calculated as the reference pressure Pbase, so that a sufficient number of samples for calculating the average value is secured. Thus, the accuracy of the reference pressure Pbase can be secured to a certain level. In addition, since the length of the stable range Mb is set to be longer than one cycle length Mc of the pulsation included in the waveform Wa before starting descent, the portion where the pulsation is superimposed on the waveform Wa before descent starts. Can be set as the stable range Mb.

(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 the process shown in FIG. 4, when searching for a stable portion from the waveform Wa before starting descent, whether or not the detection value constituting the waveform Wa before starting descent is within the range of the upper limit value Pg1 and the lower limit value Pg2. Both the determination (S20) and the determination (S21) whether or not the differential value of the detected value is within the range of the upper limit value and the lower limit value are carried out. Of these determination processes S20 and S21, Either one may be abolished.

  In the above embodiment, by performing the stability determination in steps S20 and S21 in order from the calculation end time t4, the stable range Mb (stable portion) from the calculation end time t4 to a predetermined time (until the guard time tg). ) Is included, the reference pressure Pbase is calculated. On the other hand, when the above condition is abolished and, for example, a stable portion is searched only at the intermediate position from the calculation start time t1 to the calculation end time t4, the reference pressure Pbase is based on the stable portion at the intermediate position. May be calculated.

  The upper limit value Pg1 and the lower limit value Pg2 used in the determination in step S20 of FIG. 4 may be variably set according to the fuel temperature.

  In the above embodiment shown in FIG. 1, the fuel pressure sensor 20 is mounted on the fuel injection valve 10, but the fuel pressure sensor according to the present invention is in the fuel supply path from the discharge port 42a of the common rail 42 to the injection hole 11b. Any fuel pressure sensor may be used so long as it detects the fuel pressure. 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. That is, the high-pressure pipe 42b connecting the common rail 42 and the fuel injection valve 10 and the high-pressure passage 11a in the body 11 correspond to the “fuel supply path”.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 20 ... Fuel pressure sensor, 30 ... ECU (reference pressure calculation means, injection rate waveform calculation means), Pbase ... Reference pressure, S10 ... Pressure waveform acquisition means, S20-S23 ... Search means, S30, S31 ... Calculation means.

Claims (5)

A fuel injection valve that injects fuel to be burned in an internal combustion engine from an injection hole, and a fuel pressure sensor that detects a change in fuel pressure that occurs in the fuel supply path up to the injection hole as fuel is injected from the injection hole And applied to a fuel injection system comprising
Pressure waveform acquisition means for acquiring a pressure waveform representing a change in the detected value of the fuel pressure sensor;
Among the pressure waveforms, a reference pressure calculating means for calculating a reference pressure based on a waveform before starting a decrease before starting a pressure decrease with the start of injection;
An injection rate waveform calculating means for calculating an injection rate waveform representing a change in the fuel injection rate based on the pressure waveform and the reference pressure;
With
The reference pressure calculating means includes
Search means for searching for a stable portion in which the pressure fluctuation is within a predetermined range over a predetermined period of time set to be equal to or longer than one cycle length of the pulsation included in the waveform before the start of lowering ,
Calculating means for calculating the reference pressure based on the pressure of the stable portion searched by the searching means ;
A fuel injection state detection device comprising:   The search means searches for a portion corresponding to a predetermined time before a point in time when the pressure starts to decrease from the start of injection in the waveform before the start of lowering as a condition for the stable part. The fuel injection state detection device according to claim 1.   3. The fuel injection state detection device according to claim 1, wherein the search unit searches that the pressure does not exceed an upper limit value and a lower limit value as a condition for the stable portion. 4.   The said search means searches as a condition of the said stable part that the differential value of pressure does not exceed the upper limit value and the lower limit value, The search means as described in any one of Claims 1-3 characterized by the above-mentioned. Fuel injection state detection device.   The fuel injection state detection device according to any one of claims 1 to 4, wherein the calculation means calculates an average value of pressures in the stable portion as the reference pressure.

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