JP5126296B2 - 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 estimates a fuel injection state 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 from the discharge port of the common rail (distribution container) 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 estimating 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

  The inventor has studied a specific method for estimating the injection rate waveform as follows. First, the pressure waveform detected by the fuel pressure sensor is acquired. Next, various change points appearing in the acquired pressure waveform (for example, P1, P2, P3, P5, etc. in FIG. 2C) are detected. Specifically, each time the pressure value in the pressure waveform is differentiated, and the change point is detected based on whether the differentiated value is equal to or greater than a predetermined value. Next, the waveform of the portion where the pressure decreases as the valve opening operation starts (portion P1 to P2) and the waveform of the portion where the pressure increases as the valve closing operation starts (portion P3 to P5) are approximated to a straight line. Thus, 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.

  Further, the present inventor noticed that the correlation between the pressure waveform and the injection rate waveform differs if the fuel distribution supply pressure from the common rail to the fuel injection valve is different, and responded to the distribution supply pressure at the start of injection. Thus, the variable value for converting the pressure waveform into the injection rate waveform was variably set. According to this, the estimation accuracy of the injection rate waveform can be improved. However, the present inventors have found that there is still room for improvement in the following points.

  That is, the distribution supply pressure often changes during fuel injection. For example, in a case where a fuel pump that pumps fuel in a fuel tank to a common rail is a pump that intermittently pumps fuel, such as a plunger pump, if the pump pumping is performed during fuel injection, the distribution supply pressure is reduced during fuel injection. To rise. Even if the pumping is not performed during fuel injection, immediately after the fuel is injected, the distribution supply pressure is reduced by the amount distributed and supplied from the common rail to the fuel injection valve. Therefore, if the conversion value to the injection rate waveform is fixed and set uniformly in the pressure waveform for one injection, the pressure waveform is changed when the distribution supply pressure changes during the fuel injection as described above. The accuracy of conversion to the injection rate waveform is deteriorated.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to improve the conversion accuracy when converting the injection pressure waveform detected by the fuel pressure sensor into the injection rate waveform. It is to provide a state detection device.

  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 provided in each cylinder of a multi-cylinder internal combustion engine, a distribution container that accumulates fuel supplied from a fuel pump and distributes and supplies the fuel to a plurality of the fuel injection valves, A change in fuel pressure that is provided for each fuel injection valve and that occurs in the fuel path from the outlet of the distribution container to the injection hole as fuel is injected from the injection hole of the fuel injection valve. It is assumed that the present invention is applied to a fuel injection system including a fuel pressure sensor to be detected.

  An injection waveform acquisition means for acquiring an injection pressure waveform detected by a fuel pressure sensor corresponding to a fuel injection valve during fuel injection among the plurality of fuel pressure sensors, and the injection pressure waveform are expressed as a fuel injection rate. Conversion means for converting into an injection rate waveform representing a change in the pressure, and the conversion means sets a conversion function for converting the pressure waveform during injection into the injection rate waveform based on the distribution supply pressure in the distribution container In addition, the conversion function is changed in the pressure waveform during injection for one injection according to the change in the distribution supply pressure generated during fuel injection.

  The above invention was conceived based on the aforementioned findings such as “if the distribution supply pressure is different, the correlation between the pressure waveform and the injection rate waveform is different” and “the distribution supply pressure also changes during fuel injection”. Since the conversion function is changed in the pressure waveform during injection for one injection according to the change in the distribution supply pressure generated during fuel injection, the conversion is performed when converting the pressure waveform during injection into the injection rate waveform. Accuracy can be improved.

In the second invention, of the pressure waveform during the injection, a falling waveform (P1 to P2 in FIG. 2C) is a waveform of the portion where the pressure decreases as the fuel injection valve starts opening. 2) in the rising waveform (FIG. 2 (c)) which is a waveform of a portion where the pressure rises with the start of the closing operation of the fuel injection valve in the injection pressure waveform. Rising waveform acquisition means for acquiring the waveform (refer to the waveform of the portion of P3 to P5), setting the conversion function for the falling waveform based on the distributed supply pressure during the period in which the falling waveform appears, and The conversion function for the rising waveform is set based on the distributed supply pressure during a period in which the waveform appears.

  Among the correlations between the pressure waveform during injection and the injection rate waveform, the correlation regarding the descending waveform and the ascending waveform is greatly affected by the change in the distribution supply pressure. In view of this point, in the above invention, a conversion function for the falling waveform is set based on the distributed supply pressure during the period when the falling waveform appears, and the conversion for the rising waveform is performed based on the distributed supply pressure during the period when the rising waveform appears. Set the function. Therefore, since the conversion function suitable for each waveform is separately set for the descending waveform and the ascending waveform, it is possible to promote the improvement of the accuracy of converting the injection pressure waveform into the injection rate waveform.

In the third invention, the conversion function for the falling waveform includes a coefficient (see symbol Kα in FIG. 5A) for converting the slope of the falling waveform, and the conversion function for the rising waveform. Includes a coefficient for converting the slope of the rising waveform (see symbol Kβ in FIG. 5B). According to a fourth aspect of the present invention, the conversion function for the falling waveform includes a delay time (in FIG. 5C) of the pressure drop start in the injection pressure waveform with respect to the injection rate rise start in the injection rate waveform. The conversion function for the rising waveform includes a delay time (FIG. 5D) of the pressure increase start in the injection pressure waveform with respect to the injection rate decrease start in the injection rate waveform. (See the reference C3 in the figure).

  When converting the descending waveform and ascending waveform into the injection rate waveform, specifically, the slopes of the descending waveform and the ascending waveform (see symbols Pα and Pβ in FIG. 2 (c) (refer to symbols Rα and Rβ) and the pressure drop start or rise start timing (see symbols P1 and P3 in FIG. 2 (c)) injection rate increase start or injection rate decrease It is necessary to convert to the start timing (see symbols R1 and R3 in FIG. 2B). These various conversion parameters Kα, Kβ, C1, and C3 are greatly affected by changes in the distribution supply pressure.

According to the third invention in view of this point, the coefficient Kα for converting the slope of the descending waveform is set based on the distribution supply pressure during the period in which the descending waveform appears, and the coefficient Kβ for converting the slope of the ascending waveform Is set based on the distribution supply pressure during the period in which the rising waveform appears. Therefore, the coefficients Kα and Kβ for converting the descending waveform and the ascending waveform can be set to optimum values according to the change in the distribution supply pressure. Therefore, the improvement of the precision which converts the pressure waveform at the time of injection into an injection rate waveform can be promoted.

According to the fourth aspect of the invention, the delay time C1 for converting the pressure decrease start timing applied to the decrease waveform to the injection rate increase start timing is set based on the distributed supply pressure during the period in which the decrease waveform appears. The delay time C3 for converting the pressure rise start timing applied to the rise waveform to the injection rate fall start timing is set based on the distributed supply pressure during the period in which the rise waveform appears. Therefore, each of the delay times C1 and C3β for converting the descending waveform and the ascending waveform can be set to an optimum value corresponding to the change in the distribution supply pressure. Therefore, the improvement of the precision which converts the pressure waveform at the time of injection into an injection rate waveform can be promoted.

According to a fifth aspect of the invention, the converter includes a non-injection waveform acquisition unit that acquires a non-injection pressure waveform detected by a fuel pressure sensor corresponding to a fuel injection valve that is not injecting among the plurality of fuel pressure sensors, The non-injection waveform is regarded as a change in the distributed supply pressure, and the conversion function is changed.

  Since it can be said that the non-injection pressure waveform represents a change in the distribution supply pressure, according to the above invention that changes the conversion function based on the non-injection pressure waveform, a dedicated fuel pressure sensor for detecting the distribution supply pressure is provided in the distribution container. It is possible to eliminate the need to provide it.

In a sixth aspect of the invention, the conversion means corrects the injection pressure waveform by subtracting a waveform representing a change in the distributed supply pressure from the injection pressure waveform, and converts the corrected injection pressure waveform to the injection rate. It is characterized by being converted into a waveform.

  Here, the pressure waveform at the time of injection detected by the fuel pressure sensor includes not only the pressure change caused by the injection but also the pressure change caused by the change of the distribution supply pressure. According to the above invention in view of this point, the waveform representing the change in the distribution supply pressure is corrected by subtracting from the pressure waveform at the time of injection, so that the influence due to the change in the distribution supply pressure is removed from the pressure waveform at the time of injection. Therefore, the correlation between the injection pressure waveform and the injection rate waveform can be increased. And since it converts into an injection rate waveform using the pressure waveform at the time of injection after a correlation by which the correlation was raised in this way, an injection rate waveform can be acquired with high precision.

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. (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 detected by a fuel pressure sensor shown in FIG. The time chart which shows the pressure waveform showing the change of the detected pressure made. The figure which shows the waveform W-PC correct | amended by subtracting the non-injection pressure waveform PC from the injection pressure waveform W. The flowchart which shows the procedure of the process which converts the pressure waveform at the time of injection into an injection rate waveform. The map used in the conversion process of FIG. The figure which shows the pressure waveform and injection rate waveform at the time of injection when pumping is made during fuel injection.

  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 shows a fuel injection valve 10 mounted on each cylinder of the engine, a fuel pressure sensor 20 mounted on each fuel injection valve 10, and an ECU 30 (corresponding to a control device) that is an electronic control device mounted on a vehicle. It is a schematic diagram which shows etc.

  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 high pressure pump 41, 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 12 (valve element), 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 needle 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 needle 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 needle 12 is lowered and the needle 12 is opened. 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 needle 12 rises, and the needle 12 is closed.

  Therefore, the ECU 30 controls the energization of the actuator 13 so that the opening / closing operation of the needle 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 needle 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 an electronic component such as an amplifier circuit that amplifies the pressure detection signal output from the pressure sensor element 22, and is mounted on the fuel injection valve 10 together with the stem 21. 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.

  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, an injection pressure waveform representing a change in fuel pressure detected by a 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 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 (pressure waveform at the time of injection) which arises with the change of the injection rate detected by the fuel pressure sensor 20 is shown. Since the injection pressure waveform and the injection rate waveform have the correlation described below, the injection rate waveform can be estimated (detected) from the detected injection 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, as 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.

  Incidentally, the pulsation of the portion indicated by the alternate long and short dash line A in the pressure waveform at the time of injection compensates for the fuel decrease in the high pressure passage 11a caused by the fuel injection, and immediately after reaching the maximum injection rate, from the common rail 42 to the high pressure passage 11a. This is caused by the fuel being supplied.

  Moreover, the pulsation of the part shown with the dashed-dotted line B among the pressure waveforms at the time of injection arises from the phenomenon demonstrated below.

  That is, a seat surface 12a is formed on the needle 12, and when the seat surface 12a is seated on the body 11, the high-pressure passage 11a is closed and the injection hole 11b is closed. On the other hand, when the seat surface 12a is separated from the body 11, the high-pressure passage 11a is opened and the nozzle hole 11b is opened. In the state where the needle 12 is opened to the full lift position, the flow passage area of the high pressure passage 11a is minimized at the injection hole 11b, and the flow rate of the injected fuel is in the injection hole throttled state at the injection hole 11b. . After the start of the valve closing operation, the nozzle hole throttle state continues until the stroke amount (lift up amount) of the needle 12 reaches a predetermined amount.

  On the other hand, when the stroke amount of the needle 12 becomes less than a predetermined amount, the flow passage area of the high-pressure passage 11a is minimized at the seat surface 12a, and a sheet throttle state in which the flow rate is reduced at the seat surface 12a is achieved. That is, when the needle 12 in the full lift position starts moving toward the valve closing position, the nozzle hole state is shifted to the seat throttle state, and the actual injection rate at this transition time point R3 (see FIG. 2B). Begins to decline. The injection rate becomes zero at the time R4 when the needle 12 reaches the valve closing position (that is, the time when the needle 12 is seated on the seat surface 12a).

  In view of this point, it was initially assumed that the pressure waveform starts to rise when the transition is made from the nozzle hole throttle state to the sheet throttle state. However, it has been found that a pulsation B in which the pressure slightly increases immediately before the transition to the sheet squeezed state occurs in the pressure waveform actually tested by the present inventors. The present inventor considered the mechanism of the occurrence of pulsation B as follows.

  That is, when the needle 12 moves from the full lift position toward the valve closing position, the volume of the needle storage chamber 11f (see FIG. 1) that stores the needle 12 in the high-pressure passage 11a decreases. Then, the fuel pressure in the high pressure passage 11a slightly increases by the volume reduction, and this increase becomes the pulsation B and appears in the pressure waveform. In short, when the needle 12 starts to move toward the valve closing position, a pulsation B in which the pressure slightly increases at the point P3a despite the nozzle hole throttle state due to the volume reduction of the needle housing chamber 11f. Arise. Thereafter, the pressure starts to increase at time P3 due to the shift to the sheet squeezed state.

  As explained above, the pressure waveform during injection and the injection rate waveform are highly correlated. 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 converting the injection pressure waveform into the injection rate waveform.

  By the way, the pressure of the fuel distributed and supplied from the common rail 42 to the fuel injection valve 10 changes every moment. For example, the solid line in FIG. 3A shows the pressure waveform W during injection, while the dotted line in FIG. 3A shows the change in the distribution supply pressure PC detected at the same time as the pressure waveform during injection. Show. The change in the distribution supply pressure PC is detected by using the fuel pressure sensor 20 corresponding to the fuel injection valve 10 that is not injecting. Therefore, for example, when the fuel is injected from the fuel injection valve 10 (# 1) of the # 1 cylinder and the injection is stopped from the fuel injection valve 10 (# 2) of the # 2 cylinder, the fuel pressure sensor of the # 1 cylinder The pressure detected by 20 corresponds to the pressure waveform W during injection, and the pressure detected by the fuel pressure sensor 20 of the # 2 cylinder (back cylinder) corresponds to the pressure waveform during non-injection indicating the change in the distribution supply pressure PC.

  The reason why the non-injection pressure waveform illustrated in FIG. 3A is a waveform that gradually decreases with the start of injection is that the distribution is performed by the amount distributed from the common rail 42 to the fuel injection valve 10 of the injection cylinder. This is because the supply pressure PC decreases. Incidentally, when pumping by the high-pressure pump 41 is performed during fuel injection, the distribution supply pressure PC increases even during fuel injection (see FIG. 6C).

  In short, since the injection pressure waveform W is affected by the change of the distribution supply pressure PC (non-injection pressure waveform), if the non-injection pressure waveform is subtracted from the injection pressure waveform W, the injection pressure waveform W Thus, the influence of the change in the distribution supply pressure PC is removed. The solid line in FIG. 3B shows the pressure waveform W-PC at the time of injection after performing the correction for subtraction in this way. In addition, the pressure waveform W at the time of injection illustrated in FIG. 2C is a waveform when it is assumed that the distribution supply pressure PC has not changed. The subtracted waveform W-PC and the pressure waveform W at the time of injection W Are assumed to have the same waveform.

  Next, the procedure for converting the corrected injection pressure waveform W-PC shown in FIG. 3B or FIG. 2C into the injection rate waveform shown in FIG. 2B will be described.

  FIG. 4 is a flowchart showing a processing procedure of the conversion by the microcomputer of the ECU 30. The processing is repeatedly executed at a predetermined cycle after being started with the ignition switch being turned on as a trigger.

  First, in step S10 (injection waveform acquisition means) shown in FIG. 4, the aforementioned injection pressure waveform W (FIG. 3) detected by the fuel pressure sensor 20 corresponding to the fuel injection valve 10 of the cylinder # 1 during fuel injection. (Refer to the solid line in (a)). In the subsequent step S20 (non-injection waveform acquisition means), the above-described non-injection pressure waveform PC detected by the fuel pressure sensor 20 corresponding to the fuel injection valve 10 of the cylinder # 2 that is not injecting is acquired (FIG. 3). (See broken line in (a)). In subsequent step S30, the non-injection pressure waveform PC acquired in step S20 is subtracted from the injection pressure waveform W acquired in step S10 to correct the injection pressure waveform W (see the solid line in FIG. 3B). ). Thereby, the waveform component (change in supply pressure PC) of the non-injection cylinder (back cylinder) included in the injection pressure waveform W is removed from the injection pressure waveform.

  In the subsequent step S40 (decrease waveform acquisition means, increase waveform acquisition means), a portion (P1 ′ to P3) in which the pressure decreases as the fuel injection valve 10 starts to open in the corrected injection pressure waveform W-PC. And a rising waveform that is a waveform of a portion where the pressure rises (a portion corresponding to P3 ′ to P5 ′) with the start of the valve closing operation of the fuel injection valve 10 is acquired. . Specifically, the slope Pα ′ of the descending waveform and the descending start timing t (P1 ′) of the descending waveform, and the slope Pβ ′ of the ascent waveform and the ascent start timing t (P3 ′) of the ascending waveform are corrected. Calculated from the hourly pressure waveform W-PC.

  Here, a descending waveform and an ascending waveform of the pressure waveform W-PC at the time of injection, and a portion of the injection rate waveform shown in FIG. There is a high correlation with the portion (the portion corresponding to R3 to R4) where the injection rate decreases as the injection ends. Therefore, the correlation is acquired and stored by a test performed in advance, and using the stored correlation, the falling waveform and the rising waveform of the injection pressure waveform W-PC are expressed as R1 in the injection rate waveform. It converts into the straight line of the part corresponded to -R2 and R3-R4. However, since the correlation changes according to the distribution supply pressure PC at that time, the conversion is performed using the correlation according to the change of the distribution supply pressure PC (that is, the waveform component of the non-injection cylinder).

  More specifically, the slopes Pα ′ and Pβ ′ applied to the pressure waveform W-PC during injection correlate with the injection rate increase gradient Rα and the injection rate decrease gradient Rβ of the injection rate waveform (see FIG. 2B). Is expensive. Therefore, in the next step S50 (conversion means), Rα and Rβ are calculated by multiplying Pα ′ and Pβ ′ by conversion coefficients Kα and Kβ (see the following equations 1 and 2).

Rα = −Kα × Pα ′ (Formula 1)
Rβ = −Kβ × Pβ ′ (Formula 2)
Note that these arithmetic expressions correspond to “conversion functions” representing Rα or Rβ with Pα ′ or Pβ ′ as a variable.

  FIGS. 5A and 5B show maps M1 and M2 showing the relationship between the conversion coefficients Kα and Kβ obtained in advance and the distribution supply pressure PC. As shown in these maps M1 and M2, the conversion coefficients Kα and Kβ are set to different values according to the distribution supply pressure PC. Specifically, the conversion gains Kα and Kβ are increased by increasing the distribution supply pressure PC to increase the conversion gain. Therefore, even if the values of Pα ′ and Pβ ′ are the same, the gradients Rα and Rβ of the injection rate waveform are converted to increase as the distribution supply pressure PC at that time increases.

  In short, the distribution supply pressure PC is used as an argument for selecting the conversion coefficients Kα and Kβ in the maps M1 and M2. The distribution supply pressure PC used as an argument of the conversion coefficient Kα is a pressure (distribution supply pressure PC) detected at the same time as the time t (P1 ′) in the injection pressure waveform W among the non-injection pressure waveforms. It may be a pressure detected at the same time as the time point t (P2 ′), or may be an average pressure from the time point t (P1 ′) to the time point t (P2 ′). Alternatively, the distribution supply pressure PC detected at the same time as a predetermined time from the time t1 when the injection start command signal is output may be used as an argument.

  The distribution supply pressure PC used as an argument of the conversion coefficient Kβ is a pressure (distribution supply pressure PC) detected at the same time as the time t (P3 ′) in the injection pressure waveform W among the non-injection pressure waveforms. It may be a pressure detected at the same time as the time point t (P4 ′) or an average pressure from the time point t (P3 ′) to the time point t (P4 ′). Alternatively, the distribution supply pressure PC detected at the same time when a predetermined time has elapsed from the time t2 when the injection end command signal is output may be used as an argument.

  Decreasing start timing t (P1 ′) and rising start timing t (P3 ′) applied to the injection pressure waveform W-PC, and an injection rate increase starting timing t (R1) of the injection rate waveform (see FIG. 2B) and The correlation with the injection rate lowering start timing t (R3) is high. Therefore, in the next step S60 (conversion means), t (R1) and t (R3) are calculated by subtracting the delay times C1 and C3 from t (P1 ′) and t (P3 ′) (described below). (See Equation 3 and Equation 4).

t (R1) = t (P1 ′) − C1 (Formula 3)
t (R3) = t (P3 ′) − C3 (Formula 4)
These arithmetic expressions correspond to “conversion functions” representing t (R1) or t (R3) with t (P1 ′) or t (P3 ′) as variables.

  FIGS. 5C and 5D show maps M3 and M4 showing the relationship between the delay times C1 and C3 obtained by testing in advance and the distribution supply pressure PC. As shown in these maps M3 and M4, the delay times C1 and C3 are set to different values according to the distribution supply pressure PC. Specifically, the values of the delay times C1 and C3 are increased as the distribution supply pressure PC is lower. Therefore, even if the appearance times of t (P1 ′) and t (P3 ′) are the same, the lower the distribution supply pressure PC at that time, the lower the start timing t (R1) and the lower start timing t (R3) of the injection rate waveform. ) Is converted to be slower.

  In short, the distribution supply pressure PC is used as an argument for selecting the delay time C1 in the maps M3 and M4. The distribution supply pressure PC used as an argument of the delay time C1 is a pressure (distribution supply pressure PC) detected at the same time as the time t (P1 ′) in the injection pressure waveform W among the non-injection pressure waveforms. It may be a pressure detected at the same time as the time point t (P2 ′), or may be an average pressure from the time point t (P1 ′) to the time point t (P2 ′). Alternatively, the distribution supply pressure PC detected at the same time as a predetermined time from the time t1 when the injection start command signal is output may be used as an argument.

  The distribution supply pressure PC used as an argument of the delay time C3 is a pressure (distribution supply pressure PC) detected at the same time as the time t (P3 ′) in the injection pressure waveform W among the non-injection pressure waveforms. It may be a pressure detected at the same time as the time point t (P4 ′) or an average pressure from the time point t (P3 ′) to the time point t (P4 ′). Alternatively, the distribution supply pressure PC detected at the same time when a predetermined time has elapsed from the time t2 when the injection end command signal is output may be used as an argument.

  In subsequent step S70, a trapezoidal height Rh (see FIG. 2B) of an injection rate waveform having a trapezoidal shape is calculated based on the distribution supply pressure PC. This trapezoidal height Rh corresponds to the maximum injection rate. When the fuel is injected at the maximum injection rate, the above-described nozzle hole throttle state is set, and the injection rate in this state is determined by the distribution supply pressure PC. That is, the correlation between the distribution supply pressure PC and the injection rate is high when the nozzle hole is in the throttle state.

  Therefore, the maximum injection rate Rh can be accurately calculated based on the distribution supply pressure PC as described above. The distribution supply pressure PC used for calculating Rh is the average pressure PCave during a predetermined period of the non-injection pressure waveform. Specific examples of the predetermined period include a period corresponding to P1 to P3, a period corresponding to R1 to R4, and the like. Then, as shown in FIG. 5E, Rh is calculated based on the equation Rh = Kh × PCave, where Kh is a predetermined coefficient.

  If the various values Rα, Rβ, t (R1), t (R3), and Rh described above are specified, a trapezoidal injection rate waveform can be specified. In step S80, Rα and Rβ obtained by the conversion in step S50, t (R1) and t (R3) obtained by the conversion in step S60, and the maximum injection rate Rh calculated in step S70. Calculate the injection rate waveform.

  Incidentally, when the injection command period Tq is short and the injection amount is small, the shape of the injection rate waveform is a triangle. In this case, without calculating the value of Rh, if Rα, Rβ, t (R1), and t (R3) are specified, a triangular injection rate waveform can be specified.

  Here, when pumping is performed during fuel injection, the non-injection pressure waveform rises during the plunger discharge period as shown in FIG. Then, with this increase, the injection pressure waveform W-PC and the injection rate waveform increase as shown by the dotted lines in FIGS. On the other hand, when pumping is not performed during fuel injection, the non-injection pressure waveform (distributed supply pressure PC) gradually decreases as shown by the dotted line in FIG. Thus, the distribution supply pressure PC often changes during fuel injection.

  If the distribution supply pressure PC is different, the correlation between the injection pressure waveform W and the injection rate waveform is different. For example, the slope Pβ ′ of the injection pressure waveform W when the distributed supply pressure is 100 MPa (see the solid line in FIG. 6B) and the slope Pβ ′ when the distributed supply pressure is 120 MPa are the same. Since the correlation is different, the slope Rβ of the injection rate waveform is different. Specifically, even if the slope Pβ ′ is the same, the higher the distribution supply pressure PC at that time, the greater the slope Rβ of the drop in the injection rate waveform, and the injection rate falls rapidly.

  According to this embodiment in view of this point, the conversion coefficient Kα and the delay time C1 for converting the descending portion (the descending waveforms P1 ′ to P2 ′) of the injecting pressure waveform W-PC into the injecting rate waveform, and the injecting pressure Since the conversion coefficient Kβ for converting the rising portion of the waveform W (the rising waveforms P3 ′ to P5 ′) into the injection rate waveform and the delay time C3 are set to different values according to the distribution supply pressure PC at that time, the injection pressure In converting the waveform W-PC into the injection rate waveform, the conversion accuracy can be improved.

  Further, according to the present embodiment, attention is paid to the fact that the waveform (non-injection pressure waveform) detected by the fuel pressure sensor 20 of the non-injection cylinder at the same time as the injection pressure waveform represents a change in the distribution supply pressure PC. In addition, since the conversion coefficients Kα and Kβ and the delay times C1 and C3 are calculated based on the non-injection pressure waveform, it is unnecessary to provide the common rail 42 with a dedicated fuel pressure sensor for detecting the distributed supply pressure.

  Furthermore, according to the present embodiment, the waveform representing the change in the distribution supply pressure PC is corrected by subtracting it from the injection pressure waveform W, so that the influence due to the change in the distribution supply pressure PC is removed from the injection pressure waveform W. Therefore, the correlation between the injection pressure waveform W-PC and the injection rate waveform can be increased. And since it converts into an injection rate waveform using the pressure waveform W-PC after the injection in which the correlation was improved in this way, the injection rate waveform can be acquired with high accuracy.

(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 embodiment shown in FIG. 4, R3 is calculated from P3 based on the correlation (delay time C3) between P3 in the injection pressure waveform W-PC and R3 in the injection rate waveform. As this modification, for example, R4 may be calculated from P3, R3 or R4 may be calculated from P3a (see FIG. 2C), or R3 or R4 may be calculated from P5. Alternatively, P4 ′ that is the intersection of the reference pressure indicated by the dotted line in FIG. 3B and the pressure waveform W-PC during injection may be calculated, and R3 or R4 may be calculated from the P4 ′. The reference pressure is set to a pressure value in a period from the time t1 when the injection start command is issued to the time P1 is released. The shape of the trapezoidal injection rate drop part representing the injection rate waveform can also be specified by the above modification.

  In the embodiment shown in FIG. 4, R1 is calculated from P1 based on the correlation (delay time C1) between P1 in the injection pressure waveform W-PC and R1 in the injection rate waveform. As a modification, for example, R2 may be calculated from P1, or R1 or R2 may be calculated from P2. The shape of the trapezoidal injection rate increasing portion representing the injection rate waveform can also be specified by the above modification.

  In the above embodiment, the change in the distribution supply pressure PC is acquired based on the pressure waveform detected by the fuel pressure sensor 20 of the non-injection cylinder, but a fuel pressure sensor (not shown) is mounted on the common rail 42, A change in the distribution supply pressure PC may be acquired based on the pressure waveform detected by the fuel pressure sensor.

  In the above embodiment, the non-injection pressure waveform is corrected by subtracting from the injection pressure waveform W, and the injection rate waveform is calculated by converting the corrected injection pressure waveform W-PC. Alternatively, the injection pressure waveform may be calculated by converting the injection pressure waveform W. In particular, as illustrated in FIG. 6, when the pump pumping start is later than the falling waveform portion of the injection pressure waveform W, the above correction is not performed, but based on the falling waveform portion of the injection pressure waveform W that has not been corrected. Even if the injection start timing t (R1) is calculated, the calculation accuracy can be sufficiently ensured because it is not affected by pumping.

  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 located in the fuel path from the discharge port 42a of the common rail 42 to the injection hole 11b. Any fuel pressure sensor arranged to detect the fuel pressure may be used. Therefore, for example, a fuel pressure sensor may be mounted on a high-pressure pipe connecting the common rail 42 and the fuel injection valve 10.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 11b ... Injection hole, 20 ... Fuel pressure sensor, 42 ... Common rail (distribution container), 42a ... Discharge port, S10 ... Waveform acquisition means at injection, S20 ... Waveform acquisition means at non-injection, S40 ... Falling waveform Acquisition means, rising waveform acquisition means, S50, S60... Conversion means, Kα... Coefficient for converting the slope of the falling waveform, Kβ... Coefficient for converting the slope of the rising waveform, C1. Start delay time.

Claims (8)

A fuel injection valve provided in each cylinder of the multi-cylinder internal combustion engine;
A distribution container for accumulating and supplying fuel supplied from a fuel pump to the plurality of fuel injection valves;
Fuel pressure that is provided for each of the plurality of fuel injection valves and is generated in the fuel path from the outlet of the distribution container to the injection hole as fuel is injected from the injection hole of the fuel injection valve A fuel pressure sensor that detects changes in
Applied to the fuel injection system with
An injection waveform acquisition means for acquiring an injection pressure waveform detected by a fuel pressure sensor corresponding to a fuel injection valve during fuel injection among the plurality of fuel pressure sensors;
Conversion means for converting the pressure waveform during injection into an injection rate waveform representing a change in fuel injection rate;
With
The converting means includes
A conversion function for converting the injection pressure waveform into the injection rate waveform is set based on the distribution supply pressure in the distribution container, and
A fuel injection state detection device that changes the conversion function within a pressure waveform during injection for one injection in accordance with a change in the distributed supply pressure generated during fuel injection. A descending waveform acquisition means for acquiring a descending waveform that is a waveform of a portion where the pressure decreases as the fuel injection valve starts opening operation of the injection pressure waveform;
An ascending waveform obtaining means for obtaining an ascending waveform that is a waveform of a portion where the pressure rises with the start of the closing operation of the fuel injection valve in the injection pressure waveform;
With
Setting the conversion function for the falling waveform based on the distributed supply pressure during the period in which the falling waveform appears;
2. The fuel injection state detection device according to claim 1, wherein the conversion function for the rising waveform is set based on the distributed supply pressure during a period in which the rising waveform appears. The converting means includes
The higher the distribution supply pressure in the period in which the descending waveform appears, the greater the conversion gain when converting the injection pressure waveform into the injection rate waveform,
3. The fuel according to claim 2, wherein a conversion gain when the pressure waveform during injection is converted into the injection rate waveform is increased as the distribution supply pressure in a period in which the rising waveform appears is increased. Injection state detection device. The conversion function for the falling waveform includes a coefficient for converting the slope of the falling waveform,
The fuel injection state detection device according to claim 2 or 3 , wherein the conversion function for the rising waveform includes a coefficient for converting a slope of the rising waveform. The conversion function for the falling waveform includes a delay time of the pressure drop start in the injection pressure waveform with respect to the injection rate increase start in the injection rate waveform,
Wherein the said conversion function for rising waveform of claims 2-4, characterized in that the contains the delay time of the pressure increase start during an injection time of the pressure waveform for injection rate decrease start in the injection rate waveform The fuel-injection state detection apparatus as described in any one . The converting means includes
The lower the distribution supply pressure in the period in which the falling waveform appears, the greater the delay time of the pressure drop start,
6. The fuel injection state detection device according to claim 5, wherein the delay time of the pressure increase start is increased as the distribution supply pressure is lower during the period in which the rising waveform appears. Non-injection waveform acquisition means for acquiring a non-injection pressure waveform detected by a fuel pressure sensor corresponding to a fuel injection valve that is not injecting among the plurality of fuel pressure sensors,
And the converting means, the fuel injection detecting device according to any one of claims 1-6, characterized in that varying the conversion function the non-ejection time waveform is regarded as a change in the distribution supply pressure. The converting means corrects the injection pressure waveform by subtracting a waveform representing a change in the distributed supply pressure from the injection pressure waveform, and converts the corrected injection pressure waveform into the injection rate waveform. fuel injection detecting device according to any one of claims 1-7, characterized.

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