JP2013245633A - Fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device which can accurately calculate the maximum injection rate in a target injection by making any injection on a second and following stages among multistage injection be a target injection.SOLUTION: An ECU 30 obtains a detection waveform at multistage injection detected with a fuel pressure sensor 20 when performing multistage injection, and stores a model waveform as a reference of a pressure waveform when performing injection at a stage earlier than the target injection without performing the target injection to extract the target waveform caused by the target injection by deducting the model waveform from the detection waveform at multistage injection. The ECU 30 calculates a reference pressure based on a fuel pressure when the injection is not performed in the target waveform, and calculates the maximum injection rate at the target injection based on a first parameter indicating a degree of the fuel pressure lowered from the reference pressure associated with the performance of the target injection in the target waveform and on a second parameter reflecting the fuel pressure of the model waveform when the target injection is performed.

Description

  The present invention relates to a fuel injection control device for controlling the operation of a fuel injection valve by grasping an injection state in target injection based on a change in fuel pressure caused by injecting fuel from a fuel injection valve of an internal combustion engine. .

  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 Document 1, an injection rate waveform (injection state) in actual injection is detected by detecting a change in fuel pressure caused by injection in the fuel supply path up to the nozzle hole with a fuel pressure sensor. ing. Then, by setting an injection command signal from the next time based on this injection rate waveform, the injection state is controlled to a desired state with high accuracy.

JP 2010-3004 A

  By the way, it is necessary to pay attention to the following points when performing multistage injection in which fuel injection is performed a plurality of times per one combustion cycle. That is, the aftermath of the waveform component resulting from the injection preceding the target injection is superimposed on the pressure waveform (detection waveform at the time of multistage injection) detected by the fuel pressure sensor when performing the multistage injection.

  Therefore, in Patent Document 1, by storing in advance a model waveform that represents the pressure waveform when the pre-injection is performed in a single stage as a mathematical formula, and subtracting the model waveform from the detection waveform during multi-stage injection, The pressure waveform (target waveform) resulting from the target injection is extracted. Then, the actual injection state is detected based on the extracted target waveform.

  However, when the inventor conducted various tests, it was found that there was a difference between the maximum injection rate calculated based on the target waveform and the actual maximum injection rate. That is, since the target waveform indicates a relative pressure change with the model waveform as a reference, the influence of the model waveform on the maximum injection rate is canceled separately from the target waveform.

  The present invention has been made in order to solve the above-described problems, and the object thereof is to set any one of the second and subsequent stages of the multistage injection as the target injection, and the maximum injection rate in the target injection is highly accurate. It is providing the fuel-injection control apparatus which can be calculated by.

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

  The invention according to claim 1 is a fuel injection valve (10) for injecting fuel to be burned in an internal combustion engine from an injection hole (11b), and fuel in a fuel supply path (42b, 11a) to the injection hole. A fuel injection control device applied to a fuel injection system including a fuel pressure sensor (20) for detecting pressure, and performing multi-stage injection for injecting fuel multiple times during one combustion cycle of the internal combustion engine A detection waveform acquisition means for acquiring a pressure waveform indicating a change in the fuel pressure detected by the fuel pressure sensor as a detection waveform during multi-stage injection, and any one of the second and subsequent stages of the multi-stage injection. A model waveform memory that stores a model waveform (Wm) that serves as a reference for the pressure waveform when the injection is performed before the target injection without performing the target injection. Subtracting the model waveform from the detection waveform at the time of multistage injection and extracting the pressure waveform resulting from the target injection as a target waveform (Wt); and injection by the fuel injection valve in the target waveform Reference pressure calculating means for calculating a reference pressure (Pbase) based on the fuel pressure when not being implemented, and a first level indicating the degree to which the fuel pressure has decreased from the reference pressure in the target waveform as the target injection is performed. Based on one parameter (ΔPγ, ΔP) and a second parameter (ΔPdif) reflecting the fuel pressure of the model waveform when the target injection is being performed, the maximum injection rate (Rmax) in the target injection And a maximum injection rate calculating means for calculating.

  According to the above configuration, when fuel is injected by the fuel injection valve, the fuel pressure in the fuel supply path up to the injection hole is detected by the fuel pressure sensor. And the pressure waveform which shows the change of the fuel pressure detected by a fuel pressure sensor when performing multistage injection is acquired as a detection waveform at the time of multistage injection.

  In the model waveform storage means, when any one of the second and subsequent stages of the multistage injection is set as the target injection, the pressure waveform when the injection before the target injection is performed without performing the target injection. The model waveform that is the norm of the is stored. And a pressure waveform resulting from object injection is extracted as an object waveform by subtracting a model waveform from a detection waveform at the time of multi-stage injection. Further, the reference pressure is calculated based on the fuel pressure when the injection by the fuel injection valve is not performed in the target waveform.

  And based on the 1st parameter which shows the degree to which fuel pressure fell from the standard pressure with implementation of object injection in an object waveform, and the 2nd parameter which reflects fuel pressure of a model waveform at the time of performing object injection. Thus, the maximum injection rate in the target injection is calculated. Here, in the target waveform, the first parameter indicating the degree to which the fuel pressure has decreased from the reference pressure with the execution of the target injection has a strong correlation with the maximum injection rate in the target injection. In addition, the second parameter reflecting the fuel pressure of the model waveform when the target injection is performed reflects the influence of the model waveform on the maximum injection rate separately from the target waveform. For this reason, in addition to the first parameter having a strong correlation with the maximum injection rate in the target injection, the maximum injection rate is calculated based on the second parameter that reflects the influence of the model waveform on the maximum injection rate. As a result, when the maximum injection rate in the target injection is calculated based on the target waveform, the maximum injection rate can be calculated with high accuracy.

  According to a fourth aspect of the present invention, there is provided a fuel injection valve (10) for injecting fuel combusted in an internal combustion engine from an injection hole (11b), and fuel in a fuel supply path (42b, 11a) to the injection hole. A fuel injection control device applied to a fuel injection system including a fuel pressure sensor (20) for detecting pressure, and performing multi-stage injection for injecting fuel multiple times during one combustion cycle of the internal combustion engine A detection waveform acquisition means for acquiring a pressure waveform indicating a change in the fuel pressure detected by the fuel pressure sensor as a detection waveform during multi-stage injection, and any one of the second and subsequent stages of the multi-stage injection. A model waveform memory that stores a model waveform (Wm) that serves as a reference for the pressure waveform when the injection is performed before the target injection without performing the target injection. Subtracting the model waveform from the detection waveform at the time of multistage injection to extract a pressure waveform resulting from the target injection as a target waveform (Wt), and the fuel injection valve in the detection waveform at the time of multistage injection The first parameter (Pi, Pc) that is the fuel pressure when the injection by the engine is not performed, and the second parameter (ΔPdif) that reflects the fuel pressure of the model waveform when the target injection is performed And a maximum injection rate calculating means for calculating a maximum injection rate (Rmax) in the target injection.

  According to the above configuration, the first parameter that is the fuel pressure when the injection by the fuel injection valve is not performed in the detection waveform at the time of multistage injection, and the fuel pressure of the model waveform when the target injection is performed are reflected. Based on the second parameter, the maximum injection rate in the target injection is calculated. Here, the first parameter, which is the fuel pressure when the injection by the fuel injection valve is not performed in the detection waveform at the time of multistage injection, has a strong correlation with the maximum injection rate in the target injection. In addition, the second parameter reflecting the fuel pressure of the model waveform when the target injection is performed reflects the influence of the model waveform on the maximum injection rate separately from the target waveform. For this reason, in addition to the first parameter having a strong correlation with the maximum injection rate in the target injection, the maximum injection rate is calculated based on the second parameter that reflects the influence of the model waveform on the maximum injection rate. As a result, the maximum injection rate in the target injection can be calculated with high accuracy.

The schematic diagram which shows the outline of the fuel-injection system to which the fuel-injection control apparatus was applied. The time chart which shows the change of the injection rate and fuel pressure corresponding to an injection command signal. The block diagram explaining functions, such as the setting of the injection command signal with respect to a fuel injection valve, among the functions of ECU of FIG. The flowchart which shows the procedure which calculates an injection rate parameter. The time chart which shows the fuel pressure waveform at the time of injection, the fuel pressure waveform at the time of non-injection, and the injection waveform. The graph which shows the relationship between the injection space | interval from a front | former stage injection to object injection, and an actual injection quantity. The time chart which shows an actual injection rate, the detection waveform at the time of multistage injection, and an object waveform. The time chart which shows an injection command signal, the detection waveform at the time of multistage injection, and a target waveform. The time chart which shows the modification of a model pressure difference.

  Hereinafter, an embodiment embodying a fuel injection control device will be described with reference to the drawings. The fuel injection control device of the present embodiment is mounted on a vehicle engine (internal combustion engine), and in this engine, high pressure fuel is injected into a plurality of cylinders # 1 to # 4 to perform compression auto-ignition combustion. A diesel engine is assumed.

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

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

  In addition, since the plunger pump is used for the fuel pump 41, fuel is pumped in synchronism with the reciprocating motion of the plunger. Since the fuel pump 41 is driven by the crankshaft using the engine output as a drive source, the fuel is pumped from the fuel pump 41 a predetermined number of times during one combustion cycle.

  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. When the actuator 13 such as an electromagnetic coil or a piezoelectric element is energized and the control valve 14 is pushed down in FIG. 1, the back pressure chamber 11c communicates with the low pressure passage 11d and the fuel pressure in the back pressure chamber 11c decreases. . As a result, the back pressure applied to the valve body 12 is lowered, and the valve body 12 is lifted up (opening operation). Thereby, the seat surface 12a of the valve body 12 is separated from the seat surface 11e of the body 11, and fuel is injected from the injection hole 11b.

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

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

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

  The ECU 30 calculates a target injection state (for example, the number of injection stages, the injection start timing, the injection end timing, the injection amount, etc.) based on the operation amount of the accelerator pedal, the engine load, the engine rotational speed NE, and the like. For example, the optimal injection state corresponding to the engine load and the engine speed is stored as an injection state map. Based on the current engine load and engine speed, the target injection state is calculated with reference to the injection state map. Then, the injection command signals t1, t2, and Tq (see FIG. 2A) corresponding to the calculated target injection state are set based on the injection rate parameters td, te, Rα, Rβ, and Rmax described in detail later, and the fuel By outputting to the injection valve 10, the operation of the fuel injection valve 10 is controlled. The ECU 30 (model waveform storage means), when any one of the second and subsequent stages of the multi-stage injection is set as the target injection, the injection before the target injection is performed without performing the target injection. A model waveform that serves as a reference for the pressure waveform is stored. This model waveform is expressed and stored as a mathematical expression.

  Next, an injection control method for controlling fuel injection from the fuel injection valve 10 will be described below with reference to FIGS.

  Based on the detection value of the fuel pressure sensor 20, a pressure waveform (see FIG. 2C) showing a change with time of the fuel pressure caused by the injection is detected. Based on the detected pressure waveform, an injection rate waveform (see FIG. 2B) indicating a change in the injection rate with respect to time is calculated. Then, the injection rate parameters Rα, Rβ, and Rmax that specify the calculated injection rate waveform (injection state) are learned, and the injection that specifies the correlation between the injection command signal (pulse-on timing t1 and pulse-on period Tq) and the injection state The rate parameters td and te are learned.

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

  Also, a rising approximate line Lβ is calculated by approximating the rising waveform from the inflection point P3 at which the fuel pressure rises at the end of injection to the inflection point P5 at which the rise ends from the pressure waveform by a least square method or the like. To do. Then, a time at which the fuel pressure becomes the reference value Bβ (intersection time LBβ where Lβ and Bβ intersect) is calculated from the rising approximate straight line Lβ. Focusing on the strong correlation between the intersection time LBβ and the injection end time R4, the injection end time R4 is calculated based on the intersection time LBβ. For example, a timing that is a predetermined delay time Cβ before the intersection timing LBβ may be calculated as the injection end timing R4.

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

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

  Further, the pressure corresponding to the intersection of the descending approximate straight line Lα and the ascending approximate straight line Lβ is calculated as the intersection pressure Pαβ, and the pressure difference ΔPγ between the reference pressure Pbase and the intersection pressure Pαβ, which will be described in detail later, is calculated. The pressure difference ΔPγ (first parameter) indicates the degree to which the fuel pressure has dropped from the reference pressure Pbase with the execution of target injection in the pressure waveform (target waveform). Focusing on the strong correlation between the pressure difference ΔPγ and the maximum injection rate Rmax, the maximum injection rate Rmax is calculated based on the pressure difference ΔPγ. Specifically, the maximum injection rate Rmax is calculated by multiplying the pressure difference ΔPγ by the correlation coefficient Cγ. The larger the pressure difference ΔPγ is, the larger the maximum injection rate Rmax is calculated. However, in the case of small injection where the pressure difference ΔPγ is less than the predetermined value ΔPγth, Rmax = ΔPγ × Cγ is set as described above, whereas in the case of large injection where ΔPγ ≧ ΔPγth, the pressure is set in advance according to the fuel pressure. The set value (set value Rγ) is calculated as the maximum injection rate Rmax.

  The “small injection” is assumed to be an injection in which the valve body 12 starts to be lifted down before the injection rate reaches Rγ. At this time, the maximum injection rate Rmax is determined by the fuel flowing through the high-pressure passage 11a of the fuel injection valve 10 being throttled by the seat surfaces 11e and 12a. On the other hand, the “large injection” is assumed to be an injection in which the valve body 12 starts to be lifted down after the injection rate reaches Rγ. At this time, the maximum injection rate Rmax (set value Rγ) is determined by the fuel flowing through the high-pressure passage 11a being throttled by the injection hole 11b. In short, in the case of large injection in which the injection command period Tq is sufficiently long and the valve opening state is continued even after reaching the set value Rγ, the injection rate waveform becomes a trapezoid (see the solid line in FIG. 2B). On the other hand, in the case of small injection that starts the valve closing operation before reaching the set value Rγ, the injection rate waveform is a triangle (see the dotted line in FIG. 2B).

  As described above, the injection rate parameters td, te, Rα, Rβ, and Rmax can be calculated from the pressure waveform. An injection rate waveform (FIG. 2 (b)) corresponding to the injection command signal (see FIG. 2 (a)) is based on a learned value that takes into account changes over time in these injection rate parameters td, te, Rα, Rβ, and Rmax. Reference) can be calculated. Since the area of the injection rate waveform calculated in this way (see halftone dot hatching in FIG. 2B) corresponds to the injection amount, the injection amount can also be calculated based on the injection rate parameter. For example, the relationship between the calculated injection amount and the injection command period Tq may be calculated (learned) as an injection rate parameter.

  FIG. 3 is a block diagram showing an outline of learning of these injection rate parameters, setting of an injection command signal to be output to the fuel injection valve 10, and the like. Based on the same figure, each part 31,32,33,34 which functions by ECU30 is demonstrated below. The injection rate parameter calculation unit 31 calculates the injection rate parameters td, te, Rα, Rβ, and Rmax as described above based on the pressure waveform detected by the fuel pressure sensor 20.

  The learning unit 32 learns by storing and updating the calculated injection rate parameter in the memory of the ECU 30. The injection rate parameter has a different value depending on the supply fuel pressure (pressure in the common rail 42) and the injection amount at that time. Therefore, the injection pressure is related to the fuel pressure such as a reference pressure Pbase (see FIG. 2C) and supply fuel pressure, which will be described later, and the injection amount Q calculated from the area of the injection rate waveform and the injection amount such as the injection command period Tq. The rate parameter is learned. In the example of FIG. 3, the injection rate parameter value for the injection amount Q is stored in the injection rate parameter maps M1 to M5. These maps M1 to M5 are set as different maps for each representative value of fuel pressure (for example, 30 MPa, 50 MPa, 100 MPa, etc.).

  The interpolation unit 33 calculates an injection rate parameter corresponding to the current required injection amount and fuel pressure by interpolating the learned values of the injection rate parameters stored in the injection rate parameter maps M1 to M5.

  The setting unit 34 sets an injection command signal (injection start command timing t1, injection command period Tq) corresponding to a target injection state (requested injection amount and required injection start timing) based on the injection rate parameter calculated by the interpolation unit 33. To do. Then, the fuel pressure sensor 20 detects a pressure waveform when the fuel injection valve 10 is operated according to the injection command signal set in this way. Based on the detected pressure waveform, the injection rate parameter calculation unit 31 calculates injection rate parameters td, te, Rα, Rβ, and Rmax.

  In short, an actual injection state (that is, injection rate parameters td, te, Rα, Rβ, Rmax) with respect to the injection command signal is detected and learned, and an injection command signal corresponding to the target injection state is set based on the learned value. . Therefore, the injection command signal is feedback-controlled based on the actual injection state, and the fuel injection state can be controlled with high accuracy so that the actual injection state matches the target injection state. In particular, the actual injection amount can be made to coincide with the target injection amount by performing feedback control so that the injection command period Tq is set based on the injection rate parameter so that the actual injection amount becomes the target injection amount.

  Next, the procedure for analyzing the injection state by calculating the injection rate parameters td, te, Rα, Rβ, Rmax (see FIG. 2B) from the detected pressure waveform (see FIG. 2C) is shown in FIG. This will be described with reference to the flowchart of FIG. Note that the process shown in FIG. 4 is repeatedly executed by a microcomputer included in the ECU 30.

  First, in step S10, an injection waveform Wb described below is calculated based on the detection value of the fuel pressure sensor 20. In the following description, a cylinder during fuel injection is referred to as an injection cylinder, and a cylinder that stops injection when fuel is injected in the injection cylinder is referred to as a non-injection cylinder. The fuel pressure sensor 20 mounted on the fuel injection valve 10 of the injection cylinder is referred to as an injection time sensor, and the fuel pressure sensor 20 mounted on the fuel injection valve 10 of the non-injection cylinder is referred to as a non-injection sensor.

  In step S10, a plurality of detection values detected at a predetermined sampling cycle by the injection time sensor are acquired, and based on these detection values, a fuel pressure waveform Wa (FIG. 5) that represents a change in fuel pressure at the injection time sensor that occurs with the injection. (See (a)). Next, a plurality of detection values detected at a predetermined sampling cycle by the non-injection sensor are acquired, and based on these detection values, a fuel pressure waveform Wu representing a change in fuel pressure at the non-injection sensor caused by the injection (FIG. 5 (b)).

  Incidentally, when the fuel pump 41 pressure-feeds fuel to the common rail 42 and the injection timing overlap, the fuel pressure waveform Wu is a waveform in which the pressure is generally increased as shown by the solid line in FIG. 5B. It becomes. On the other hand, when such pump pumping is not performed during fuel injection, immediately after the fuel is injected, the fuel pressure in the entire injection system is reduced by that amount. Therefore, the fuel pressure waveform Wu ′ is a waveform in which the pressure is lowered as a whole as shown by the dotted line in FIG.

  Such components of the fuel pressure waveforms Wu and Wu ′ are also included in the fuel pressure waveform Wa. In other words, the fuel pressure waveform Wa includes an injection waveform Wb (see FIG. 5C) representing a change in fuel pressure due to injection, and components of the fuel pressure waveforms Wu and Wu ′. Therefore, in step S10, the process of extracting the injection waveform Wb is performed by subtracting the fuel pressure waveforms Wu and Wu ′ in the non-injection cylinders from the fuel pressure waveform Wa in the injection cylinders (Wb = Wa−Wu).

  Next, in step S11 of FIG. 4, the swell removal process described below is performed. That is, when multistage injection is performed, the pre-stage swell component Wc (see FIG. 2C), which is the pulsation of the pressure waveform remaining after the end of the pre-stage injection, is superimposed on the fuel pressure waveform Wa. In particular, when the interval between the upstream injection and the target injection is short, the fuel pressure waveform Wa of the target injection is greatly affected by the upstream swell component Wc. Therefore, in step S11, the swell removal process for subtracting the preceding swell component Wc from the injection waveform Wb is performed. It should be noted that the upstream swell component Wc (model waveform) can be estimated from the upstream injection state.

  In the subsequent step S12, based on the reference waveform which is the waveform of the portion corresponding to the period until the fuel pressure starts to decrease with the start of injection, the reference waveform is determined based on the reference waveform. The average fuel pressure of the waveform is calculated as the reference pressure Pbase. For example, a portion corresponding to a period TA until a predetermined time elapses from the injection start command timing t1 may be set as the reference waveform. Alternatively, the inflection point P1 may be calculated based on the differential value of the descending waveform, and a portion corresponding to a period from the injection start command timing t1 to a predetermined time before the inflection point P1 may be set as the reference waveform. That is, the reference waveform is a pressure waveform when the injection by the fuel injection valve 10 is not performed in the injection waveform Wb subjected to the swell removal process, specifically, a pressure waveform immediately before the pre-stage injection is performed.

  In the subsequent step S13, an approximate straight line Lα of the descending waveform is calculated based on the descending waveform that is the waveform corresponding to the period in which the fuel pressure decreases as the injection rate increases in the injection waveform Wb. For example, what is necessary is just to set the part corresponding to predetermined period TB from the time of predetermined time having passed from injection start command timing t1 as a fall waveform. Alternatively, the inflection points P1 and P2 may be calculated based on the differential value of the descending waveform, and the portion corresponding to the inflection points P1 and P2 may be set as the descending waveform. Then, an approximate straight line Lα may be calculated by a least square method from a plurality of detected fuel pressure values (sampling values) constituting the descending waveform. Alternatively, the tangent at the time when the differential value becomes the minimum in the descending waveform may be calculated as the approximate straight line Lα.

  In the subsequent step S14, an approximate straight line Lβ of the rising waveform is calculated based on the rising waveform that is the waveform corresponding to the period in which the fuel pressure increases as the injection rate decreases in the injection waveform Wb. For example, what is necessary is just to set the part corresponding to the predetermined period TC from the time of predetermined time having passed since the injection end instruction | command time t2 as a rising waveform. Alternatively, the inflection points P3 and P5 may be calculated based on the differential value of the rising waveform, and a portion corresponding to the inflection points P3 and P5 may be set as the rising waveform. Then, the approximate straight line Lβ may be calculated from the plurality of detected fuel pressure values (sampling values) constituting the rising waveform by the least square method. Alternatively, the tangent at the time when the differential value becomes the maximum in the rising waveform may be calculated as the approximate straight line Lβ.

  In subsequent step S15, reference values Bα and Bβ are calculated based on the reference pressure Pbase. For example, values lower than the reference pressure Pbase by a predetermined amount may be calculated as the reference values Bα and Bβ. It is not necessary to set both reference values Bα and Bβ to the same value. The predetermined amount may be variably set according to the value of the reference pressure Pbase, the fuel temperature, and the like.

  In the subsequent step S16, a time (intersection time LBα between Lα and Bα) at which the fuel pressure becomes the reference value Bα is calculated from the approximate straight line Lα. Focusing on the fact that the intersection time LBα and the injection start time R1 are strongly correlated, the injection start time R1 is calculated based on the intersection time LBα. For example, a timing that is a predetermined delay time Cα before the intersection timing LBα may be calculated as the injection start timing R1.

  In the subsequent step S17, a time at which the fuel pressure becomes the reference value Bβ (intersection time LBβ between Lβ and Bβ) is calculated from the approximate straight line Lβ. Focusing on the strong correlation between the intersection time LBβ and the injection end time R4, the injection end time R4 is calculated based on the intersection time LBβ. For example, a timing that is a predetermined delay time Cβ before the intersection timing LBβ may be calculated as the injection end timing R4. The delay times Cα and Cβ may be variably set according to the value of the reference pressure Pbase, the fuel temperature, and the like.

  In the subsequent step S18, paying attention to the fact that the slope of the approximate straight line Lα and the slope of the increase in the injection rate are strongly correlated, the slope of the straight line Rα indicating the increase in the injection rate in the injection rate waveform shown in FIG. Calculation is based on the slope of the straight line Lα. For example, the slope of Rα may be calculated by multiplying the slope of Lα by a predetermined coefficient. Note that, based on the injection start timing R1 calculated in step S16 and the slope of Rα calculated in step S18, a straight line Rα representing the rising portion of the injection rate waveform with respect to the injection command signal can be specified.

  Further, in step S18, paying attention to the fact that the slope of the approximate line Lβ and the slope of the injection rate decrease are strongly correlated, the slope of the straight line Rβ indicating the decrease in the injection rate in the injection rate waveform is calculated based on the slope of the approximate line Lβ. To do. For example, the slope of Rβ may be calculated by multiplying the slope of Lβ by a predetermined coefficient. Note that, based on the injection end timing R4 calculated in step S17 and the slope of Rβ calculated in step S18, a straight line Rβ representing the descending portion of the injection rate waveform with respect to the injection command signal can be specified. The predetermined coefficient may be variably set according to the value of the reference pressure Pbase, the fuel temperature, and the like.

  In subsequent step S19, based on the straight lines Rα and Rβ of the injection rate waveform calculated in step S18, a time (valve closing operation start time R23) at which the valve body 12 starts lift-down in response to the command to end the injection is calculated. . Specifically, the intersection of both straight lines Rα and Rβ is calculated, and the intersection timing is calculated as the valve closing operation start timing R23.

  In the subsequent step S20, a delay time (injection start delay time td) of the injection start timing R1 calculated in step S16 with respect to the injection start command timing t1 is calculated. Further, a delay time (injection end delay time te) with respect to the injection end command timing t2 of the valve closing operation start timing R23 calculated in step S19 is calculated. The injection end delay time te is a delay time from the timing t2 at which the injection end is commanded to the timing at which the operation of the control valve 14 is started. In short, these delay times td and te are parameters representing the response delay of the injection rate change with respect to the injection command signal. Besides, the delay time from the injection start command timing t1 to the maximum injection rate arrival timing R2, the injection end command Examples include a delay time from the timing t2 to the injection rate decrease start timing R3, a delay time from the injection end command timing t2 to the injection end timing R4, and the like.

  In the subsequent step S21, it is determined whether or not the pressure difference ΔPγ (first parameter) between the reference pressure Pbase and the intersection pressure Pαβ is less than a predetermined value ΔPγth. When it is determined that ΔPγ <ΔPγth (S21: YES), in the next step S22, the pressure difference ΔPγ is corrected in order to take into account the influence of the model waveform described above on the maximum injection rate Rmax. This process will be described later. In this case, it is considered that the injection is small, and in the next step S23, the maximum injection rate Rmax is calculated based on the corrected pressure difference ΔPγ (Rmax = ΔPγ × Cγ).

  On the other hand, when it is determined that ΔPγ ≧ ΔPγth (S21: NO), a value preset in accordance with the pressure of the fuel supplied to the fuel injection valve 10 (set value Rγ) in the next step S24. Is calculated as the maximum injection rate Rmax. As the pressure (first parameter) of the fuel supplied to the fuel injection valve 10, the fuel pressure Pc in the common rail 42 or the fuel pressure Pi when the fuel injection valve 10 does not perform injection in the injection waveform Wb is used. Can do. The larger the first parameter is, the larger the maximum injection rate Rmax is calculated. In this case, it is assumed that the injection is large, and in the next step S25, the maximum injection rate Rmax (set value Rγ) is corrected in order to take into account the effect of the model waveform described above on the maximum injection rate Rmax. This process will be described later.

  Then, this series of processing is temporarily ended (END). In addition, the process of step S10 corresponds to the process as a detection waveform acquisition means, the process of step S11 corresponds to the process as target waveform extraction means, the process of step S12 corresponds to the process as reference pressure calculation means, The processing of steps S22 and 23 and the processing of steps S24 and 25 correspond to processing as maximum injection rate calculation means, respectively.

  FIG. 6 is a graph showing the relationship between the injection interval from the previous stage injection to the target injection and the actual injection amount when the processes of steps S22 and S25 of FIG. 4 are not performed. Here, the target injection state (including the target value of the injection amount) is calculated based on the same engine load and engine speed (engine operating state). Then, the injection command signals t1, t2, and Tq corresponding to the calculated target injection state are set based on the injection rate parameters td, te, Rα, Rβ, and Rmax described above, and the operation of the fuel injection valve 10 is controlled. Yes. Note that feedback control of the actual injection amount with respect to the target value of the injection amount is not performed.

  As shown in the figure, the actual injection amount periodically changes according to the injection interval, and there is a difference between the target value of the injection amount and the actual injection amount. In particular, as indicated by the one-dot chain line, when the injection interval is short, the deviation between the target value and the actual injection amount is large.

  Next, the reason why such a deviation between the target value and the actual injection amount occurs will be described. FIG. 7 is a time chart showing (a) an actual injection rate, (b) a detected waveform during multi-stage injection, and (c) a target waveform. Here, the result of actually measuring the injection rate by performing small injection while changing only the injection interval from the preceding injection to the target injection is shown. The target waveform Wt is obtained by subtracting the pressure pulsation (model waveform Wm) due to the preceding stage injection from the detection waveform during multistage injection. In addition, each code | symbol in the figure respond | corresponds with each code | symbol in FIG. 2, and the injection (short dashed line) with the subscript "1" and the longest injection interval for the shortest injection interval (solid line waveform) The subscript “2” is attached to the waveform.

  As shown in (a) and (b), the change in the maximum injection rate Rmax (Rmax1 to Rmax2) and the change in the pressure difference ΔPγ (ΔPγ1 to ΔPγ2) are correlated between the actual injection rate waveform and the detection waveform during multistage injection. doing. On the other hand, as shown in (a) and (c), in the actual injection rate waveform and the target waveform Wt, the change in the maximum injection rate Rmax (Rmax1 to Rmax2) and the change in the pressure difference ΔPγ (ΔPγ1 to ΔPγ2) are correlated. Not done. For this reason, if the maximum injection rate Rmax is calculated based on the target waveform Wt, it will deviate from the actual maximum injection rate Rmax.

  The reason for this is that, as shown in (b), the fuel pressure at the start of injection (inflection point P1) differs depending on the injection interval, but as shown in (c), the target waveform Wt is injected. This is due to the cancellation of the difference in fuel pressure at the start. That is, in the target waveform Wt, since the intersection pressure Pαβ is calculated based on the fuel pressure of the model waveform Wm at the start of injection, even if the fuel pressure of the model waveform Wm at the start of injection changes according to the injection interval, the change Is not reflected in the calculation of the maximum injection rate Rmax. However, as shown in (a) and (b), the actual injection rate is affected by the fuel pressure at the start of injection and the fuel pressure during injection, so the maximum injection rate Rmax calculated based on the target waveform Wt is an actual value. It will deviate from the maximum injection rate Rmax.

  Even in the case of large injection, the actual injection rate is affected by the fuel pressure at the start of injection and the fuel pressure during injection, so these must be taken into account when calculating the maximum injection rate Rmax.

  Therefore, in the present embodiment, the following processing is performed in steps S22 and 23 and steps S24 and 25 in FIG. 4 in order to correct such a deviation in the maximum injection rate Rmax. FIG. 8 is a time chart showing (a) a drive injection command, (b) a detected waveform during multi-stage injection, and (c) a target waveform.

  In step S22, the pressure difference ΔPγ (first parameter) in the target waveform Wt is corrected based on the model pressure difference ΔPdif (second parameter) reflecting the fuel pressure of the model waveform Wm when the target injection is performed. . Specifically, the model pressure difference ΔPdif corresponds to the fuel pressure P11 at the start timing t1 of the target injection in the model waveform Wm and the time t12 (or the intersection pressure Pαβ at which the fuel pressure of the target waveform Wt becomes minimum as the target injection is performed). The difference between the model waveform Wm and the fuel pressure P12 of the model waveform Wm. Then, the model pressure difference ΔPdif multiplied by the correction coefficient Km1 is added to the pressure difference ΔPγ to obtain a corrected pressure difference ΔPγ. The correction coefficient Km1 may be a constant value, or according to the fuel pressure Pc in the common rail 42 or the fuel pressure Pi when the fuel injection valve 10 is not performing injection (immediately before the previous stage injection) in the multistage injection detection waveform. It may be variable. In step S23, as described above, the maximum injection rate Rmax is calculated based on the corrected pressure difference ΔPγ (Rmax = ΔPγ × Cγ).

  Further, in step S24, as described above, a value (set value Rγ) set in advance according to the pressure (first parameter) of the fuel supplied to the fuel injection valve 10 is calculated as the maximum injection rate Rmax. To do. In step S25, the maximum injection rate Rmax (set value Rγ) is corrected based on the model pressure difference ΔPdif (second parameter). Specifically, the model pressure difference ΔPdif multiplied by the correction coefficient Km2 is added to the maximum injection rate Rmax, which is used as the corrected maximum injection rate Rmax. Alternatively, the ratio of the pressure difference ΔPγ plus the model pressure difference ΔPdif (ΔPγR) and the pressure difference ΔPγ (or the ratio multiplied by the correction coefficient Km2) is multiplied by the maximum injection rate Rmax and corrected. The maximum injection rate Rmax. The correction coefficient Km2 may be a constant value, or according to the fuel pressure Pc in the common rail 42 or the fuel pressure Pi when the fuel injection valve 10 is not performing injection (immediately before the previous stage injection) in the multistage injection detection waveform. It may be variable.

  The embodiment described in detail above has the following advantages.

  In the small injection, the intersection pressure Pαβ (first parameter) indicating the degree to which the fuel pressure has decreased from the reference pressure Pbase with the execution of the target injection in the target waveform Wt, and the model waveform Wm when the target injection is performed Based on the model pressure difference ΔPdif (second parameter) reflecting the fuel pressure, the maximum injection rate Rmax in the target injection is calculated. Here, the intersection pressure Pαβ has a strong correlation with the maximum injection rate Rmax in the target injection. Further, the model pressure difference ΔPdif reflects the influence of the model waveform Wm on the maximum injection rate Rmax separately from the target waveform Wt. Therefore, based on the model pressure difference ΔPdif reflecting the influence of the model waveform Wm on the maximum injection rate Rmax in addition to the intersection pressure Pαβ strongly correlated with the maximum injection rate Rmax in the target injection, the maximum injection rate Rmax Is calculated. As a result, when the maximum injection rate Rmax for the target injection is calculated based on the target waveform Wt, the maximum injection rate Rmax can be calculated with high accuracy.

  In the large injection, the fuel pressure Pi (first parameter) when the injection by the fuel injection valve 10 is not performed in the detection waveform at the time of multistage injection and the fuel pressure of the model waveform Wm when the target injection is performed are reflected. Based on the model pressure difference ΔPdif (second parameter) to be calculated, the maximum injection rate Rmax (set value Rγ) in the target injection is calculated. Here, the fuel pressure Pi has a strong correlation with the maximum injection rate Rmax in the target injection. Further, the model pressure difference ΔPdif reflects the influence of the model waveform Wm on the maximum injection rate Rmax separately from the target waveform Wt. Therefore, in addition to the fuel pressure Pi that has a strong correlation with the maximum injection rate Rmax in the target injection, the maximum injection rate Rmax is also based on the model pressure difference ΔPdif that reflects the effect of the model waveform Wm on the maximum injection rate Rmax. Calculated. As a result, the maximum injection rate Rmax in the target injection can be calculated with high accuracy.

  The fuel pressure P11 at the start timing t11 of the target injection in the model waveform Wm and the model waveform Wm at the time t12 when the fuel pressure of the target waveform Wt becomes the minimum as the target injection is performed (or the time corresponding to the intersection pressure Pαβ). A model pressure difference ΔPdif, which is a difference from the fuel pressure P12, is used as the second parameter. For this reason, the maximum injection rate Rmax in the target injection can be calculated with higher accuracy.

  In addition, it is not limited to the description content of the said embodiment, You may deform | transform and implement as follows. Moreover, you may make it combine the characteristic structure of each embodiment arbitrarily, respectively.

  -You may change the process of step S22, 23 of FIG. 4 as follows. That is, in step S22, the maximum injection rate Rmax is calculated based on the pressure difference ΔPγ (first parameter) in the target waveform Wt. In step S23, the maximum injection rate Rmax is corrected based on the model pressure difference ΔPdif (second parameter). Specifically, the maximum injection rate Rmax may be corrected as in step S25 of FIG. 4 described above.

  -You may change the process of step S24, 25 of FIG. 4 as follows. That is, in step S24, the fuel pressure Pi (first parameter) supplied to the fuel injection valve 10 is changed to a model pressure difference ΔPdif (second parameter) that reflects the fuel pressure of the model waveform Wm when the target injection is performed. Correct based on. Specifically, the model pressure difference ΔPdif multiplied by the correction coefficient Km1 is added to the fuel pressure Pi, and this is used as the corrected fuel pressure Pi. The correction coefficient Km1 may be a constant value, or according to the fuel pressure Pc in the common rail 42 or the fuel pressure Pi when the fuel injection valve 10 is not performing injection (immediately before the previous stage injection) in the multistage injection detection waveform. It may be variable. In step S25, the maximum injection rate Rmax is calculated based on the corrected fuel pressure Pi.

  As shown in FIG. 9, as the model pressure difference ΔPdif (second parameter), the fuel pressure P11 at the target injection start timing t1 in the model waveform Wm and the injection by the fuel injection valve 10 in the model waveform Wm are not performed. The difference from the fuel pressure P13 at the time (immediately before the front injection) can also be adopted. The model pressure difference ΔPdif in this case differs from the model pressure difference ΔPdif shown in FIG. 8 by the error pressure ΔPer, but the tendency is substantially the same. According to such a configuration, the maximum injection rate Rmax in the target injection can be calculated with high accuracy by a simple configuration.

  As shown in FIGS. 2 and 7, the pressure difference ΔP between the reference pressure Pbase and the fuel pressure at the inflection points P2 and P23 in the target waveform Wt can be used as the first parameter. This pressure difference ΔP also indicates the degree to which the fuel pressure has fallen from the reference pressure Pbase with the execution of the target injection in the target waveform Wt.

  In the above embodiment, the fuel pressure sensor 20 is mounted on the fuel injection valve 10, but the fuel pressure sensor is arranged to detect the fuel pressure in the fuel supply path from the discharge port 42a of the common rail 42 to the nozzle hole 11b. Any fuel pressure sensor may be used. 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, 11a ... High pressure passage, 11b ... Injection hole, 20 ... Fuel pressure sensor, 30 ... ECU, 31 ... Injection rate parameter calculation part, 32 ... Learning part, 33 ... Interpolation part, 34 ... Setting part, 42 ... Common rail, 42b ... High pressure piping.

Claims (8)

A fuel injection valve (10) for injecting fuel to be burned in the internal combustion engine from the nozzle hole (11b), and a fuel pressure sensor (20) for detecting fuel pressure in the fuel supply path (42b, 11a) to the nozzle hole And applied to a fuel injection system comprising
When multistage injection in which fuel is injected a plurality of times during one combustion cycle of the internal combustion engine is performed, a pressure waveform indicating a change in the fuel pressure detected by the fuel pressure sensor is acquired as a detection waveform during multistage injection. Detection waveform acquisition means;
When any one of the second and subsequent stages of the multi-stage injection is the target injection, the pressure waveform norm when the injection before the target injection is performed without performing the target injection, Model waveform storage means for storing the model waveform (Wm)
A target waveform extraction means for subtracting the model waveform from the detection waveform at the time of multi-stage injection and extracting a pressure waveform resulting from the target injection as a target waveform (Wt);
A reference pressure calculating means for calculating a reference pressure (Pbase) based on a fuel pressure when injection by the fuel injection valve is not performed in the target waveform;
In the target waveform, a first parameter (ΔPγ, ΔP) indicating a degree to which the fuel pressure has decreased from the reference pressure with the execution of the target injection, and a fuel pressure of the model waveform when the target injection is performed. Maximum injection rate calculating means for calculating a maximum injection rate (Rmax) in the target injection based on the second parameter (ΔPdif) to be reflected;
A fuel injection control device comprising:   The first parameter includes the reference pressure and a straight line (Lα) approximating a portion where the fuel pressure decreases in the target waveform with the execution of the target injection, and a straight line (Lβ) approximating a portion where the fuel pressure increases. 2. The fuel injection control device according to claim 1, wherein the pressure difference (ΔPγ) is a fuel pressure (Pαβ) corresponding to an intersection with the fuel pressure.   The fuel injection control device according to claim 2, wherein the maximum injection rate calculation means calculates the maximum injection rate to be larger as the pressure difference is larger. A fuel injection valve (10) for injecting fuel to be burned in the internal combustion engine from the nozzle hole (11b), and a fuel pressure sensor (20) for detecting fuel pressure in the fuel supply path (42b, 11a) to the nozzle hole And applied to a fuel injection system comprising
When multistage injection in which fuel is injected a plurality of times during one combustion cycle of the internal combustion engine is performed, a pressure waveform indicating a change in the fuel pressure detected by the fuel pressure sensor is acquired as a detection waveform during multistage injection. Detection waveform acquisition means;
When any one of the second and subsequent stages of the multi-stage injection is the target injection, the pressure waveform norm when the injection before the target injection is performed without performing the target injection, Model waveform storage means for storing the model waveform (Wm)
A target waveform extraction means for subtracting the model waveform from the detection waveform at the time of multi-stage injection and extracting a pressure waveform resulting from the target injection as a target waveform (Wt);
The first parameter (Pi, Pc), which is the fuel pressure when the fuel injection valve is not injecting in the multistage injection detection waveform, and the fuel pressure of the model waveform when the target injection is being performed A maximum injection rate calculating means for calculating a maximum injection rate (Rmax) in the target injection based on the second parameter (ΔPdif) reflecting
A fuel injection control device comprising:   The fuel injection control device according to claim 4, wherein the maximum injection rate calculation means calculates the maximum injection rate to be larger as the first parameter is larger.   The second parameter includes a fuel pressure (P11) at the start of the target injection in the model waveform, and a fuel pressure (P11) in the model waveform when the fuel pressure of the target waveform becomes the minimum as the target injection is performed. The fuel injection control device according to any one of claims 1 to 5, which is a difference from P12).   The second parameter is a difference between a fuel pressure (P11) at the start of the target injection in the model waveform and a fuel pressure (P13) when the fuel injection valve is not injected in the model waveform. The fuel injection control device according to any one of claims 1 to 5.   The fuel injection control device according to any one of claims 1 to 7, wherein the maximum injection rate calculating means increases or decreases the maximum injection rate based on the second parameter.

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