JP2012002174A - Apparatus for obtaining fuel-pressure waveform - Google Patents

Abstract

The present invention provides a fuel pressure waveform acquisition apparatus that aims to extract a pressure waveform resulting from n-th stage injection from a detection waveform during multi-stage injection with high accuracy.
SOLUTION: A detection waveform acquisition means for acquiring a pressure waveform detected by a fuel pressure sensor when performing multi-stage injection as a detection waveform W during multi-stage injection, and a pressure waveform when performing single-stage injection Corresponds to the model waveform storage means in which the model waveform (swell waveform U) serving as a reference is stored, the phase of the waveform in the interval period in which the injection is stopped in the detected waveform W, and the interval period in the waveform waveform U The phase correlating means S35 for associating the undulation waveform U with the detection waveform W and the associated undulation waveform U are subtracted from the detection waveform W so as to minimize the deviation from the phase of the waveform of the corresponding portion, and n stages Waveform extracting means S41 for extracting the pressure waveform Wn resulting from the eye injection.
[Selection] Figure 8

Description

  The present invention relates to a fuel pressure waveform acquisition device that acquires, as a pressure waveform, 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 injection hole of the fuel injection valve and the injection start timing. Therefore, Patent Documents 1 and 2 disclose a technique for detecting an actual injection state 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. Yes.

  For example, it is possible to detect the actual injection start time by detecting the time when the fuel pressure starts to decrease along with the injection, or to detect the actual injection amount by detecting the decrease amount of the fuel pressure caused by the injection. I am trying. 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

  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, FIG. 5B shows a detection waveform W (detection waveform at the time of multi-stage injection) detected by the fuel pressure sensor when multi-stage injection is being performed. In the waveform corresponding to (see the one-dot chain line in FIG. 5B), the waveform component caused by the m-th stage injection before the n-th stage (m = n−1 in the example of FIG. 5). Are superimposed on each other (a swell waveform shown by a one-dot chain line in FIG. 5D).

  Therefore, in Patent Document 1, a model waveform CALn-1 (see FIG. 5 (d)) that expresses a waveform when the m-th stage injection is performed in a single stage is stored in advance, and FIG. By subtracting the model waveform CALn−1 from the detected waveform W as described above, a pressure waveform Wn (see FIG. 5F) resulting from the n-th stage injection is extracted, and the actual injection state is based on the extracted pressure waveform Wn. Is detected.

  However, when the model waveform CALn-1 (dotted line in FIG. 5 (e)) is overlapped with and associated with the detected waveform W (solid line in FIG. 5 (e)), it is in the time axis direction (left and right direction in FIG. 5). There may be a phase shift in which the model waveform CALn-1 is adjusted in a shifted state. When this phase shift occurs, the calculation accuracy for extracting the pressure waveform Wn resulting from the n-th stage injection deteriorates.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a fuel pressure waveform acquisition device that extracts a pressure waveform caused by the n-th stage injection from a detection waveform during multi-stage injection with high accuracy. Is to provide.

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

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

  And a detection waveform acquisition means for acquiring a pressure waveform detected by the fuel pressure sensor when performing multi-stage injection in which fuel is injected a plurality of times during one combustion cycle of the internal combustion engine, as a detection waveform during multi-stage injection; Model waveform storage means for storing a model waveform that serves as a reference for the pressure waveform when the injection prior to the n-th stage injection is performed without performing the n-th stage injection after the second stage among the multi-stage injections And the phase of the interval detection waveform corresponding to the interval period from the end of the (n-1) th stage injection to the start of the nth stage injection in the multistage injection detection waveform, A phase association for associating the model waveform with the detection waveform at the time of multi-stage injection so that the deviation from the phase of the interval model waveform in the portion corresponding to the interval period is minimized. And means, the model waveform of the association state by subtracting from the multiple injection upon detection waveform, characterized in that it comprises, a waveform extracting means for extracting a pressure wave caused by the n-th stage injection.

  In the present invention, the interval period from the end of the (n−1) -th stage injection to the start of the n-th stage injection in the detected waveform during multi-stage injection is the actual aftermath of the waveform component caused by the injection up to the previous stage (actual It is recalled by paying attention to the fact that it represents a wavy waveform.

  And since it can be said that the interval detection waveform according to the present invention represents the actual undulation waveform, the multi-stage injection detection waveform is minimized so that the deviation between the phase of the interval model waveform and the phase of the interval detection waveform is minimized. According to the present invention for associating (matching) a model waveform, the phase shift between the model waveform and the detected waveform in the injection period can be reduced. Therefore, according to the present invention for extracting the pressure waveform caused by the n-th stage injection by subtracting the model waveform in a state where the phase shift is reduced in this way from the detection waveform during the multi-stage injection, the extraction accuracy is improved. Can be accurate.

  According to a second aspect of the present invention, the phase correlating means includes a waveform of a portion where the pressure rises first in the interval detection waveform and a waveform of a portion where the pressure rises first in the interval model waveform. The correlation is performed based on the phase shift.

  The waveform of the portion where the pressure rises first in the interval detection waveform is the portion immediately after the end of the injection, and is a swell waveform with a large amplitude. Therefore, it can be said that the waveform is a portion that is not easily affected by various noises such as detection noise of the fuel pressure sensor. In the above-described invention, which focuses on this point, the portion where the pressure rises first (the portion where the swell amplitude is large) is associated so as to reduce the phase shift between the interval detection waveform and the interval model waveform. The accuracy of associating the model waveform with the waveform can be improved.

  Further, if an operation for associating the interval detection waveform and the interval model waveform so as to reduce the phase shift is performed on the whole of these waveforms (entire interval period), the calculation processing load becomes enormous. On the other hand, according to the above-described invention, the calculation processing is performed so that the waveform of the portion where the swell amplitude becomes the largest is related to reduce the phase shift, so that the calculation processing load can be reduced.

  According to a third aspect of the present invention, the phase correlating means includes detection waveform approximating means for approximating a waveform of a portion of the interval detection waveform where the pressure first rises to a straight line, and first pressure of the interval model waveform. Model waveform approximation means for approximating the rising waveform to a straight line, and based on a phase shift between the straight line approximated by the detection waveform approximation means and the straight line approximated by the model waveform approximation means The correlation of phases is performed.

  Of the interval detection waveform and the interval model waveform, the portion where the pressure rises first has a shape close to a straight line. In the above-described invention focusing on this point, the waveform of the portion is approximated to a straight line by the detection waveform approximating means and the model waveform approximating means, and the correlation of the phases is performed based on the phase shift between the approximated straight lines. The calculation processing load can be greatly reduced without significantly reducing the accuracy of calculating the phase shift compared to the case of calculating the phase shift amount while maintaining the curved shape without linearly approximating the waveform.

  According to a fourth aspect of the invention, there is provided amplitude correction means for correcting an amplitude gain of the model waveform so as to minimize a deviation between the amplitude of the interval model waveform in the associated state and the amplitude of the interval detection waveform. It is characterized by that.

  In the present invention, the interval period from the end of the (n−1) -th stage injection to the start of the n-th stage injection in the detected waveform during multi-stage injection is the actual aftermath of the waveform component caused by the injection up to the previous stage (actual It is recalled by paying attention to the fact that it represents a wavy waveform.

  Since the interval detection waveform according to the present invention can be said to represent the actual waviness waveform, the deviation between the amplitude of the interval model waveform and the amplitude of the interval detection waveform in a state where the phase deviation is related to be minimized. According to the present invention in which the amplitude gain of the model waveform is corrected so as to be minimized, it is possible to reduce the amplitude deviation between the multistage injection detection waveform and the model waveform. Therefore, according to the present invention for extracting the pressure waveform resulting from the n-th stage injection by subtracting the model waveform with the amplitude gain corrected in this way from the detection waveform during multi-stage injection, the extraction accuracy can be made high.

The block diagram which shows the outline of the fuel-injection system to which the fuel-pressure waveform acquisition apparatus concerning one Embodiment of this invention was applied. The flowchart which shows the basic procedure of the fuel-injection control process which concerns on the system of FIG. The flowchart which shows the process sequence of a fuel-injection state detection based on the detection pressure of the fuel pressure sensor of FIG. The timing chart at the time of single stage injection execution which shows the relationship between the waveform of the detection pressure by the fuel pressure sensor of FIG. 1, and an injection rate transition waveform. FIG. 4 is a diagram for explaining the undulation process S <b> 23 of FIG. 3. FIG. 4 is a diagram for explaining the undulation process S <b> 23 of FIG. 3. FIG. 4 is a diagram for describing phase correction and attenuation coefficient correction that are performed in the undulation processing S <b> 23 of FIG. 3. The flowchart which shows the detailed procedure of the undulation process S23 of FIG.

  Hereinafter, an embodiment in which a fuel pressure waveform acquisition apparatus according to the present invention is embodied will be described with reference to the drawings. The fuel pressure waveform acquisition device of the present embodiment is mounted on a vehicle engine (internal combustion engine), in which 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 the fuel injection valve 10, an ECU 30 that is an electronic control device mounted on a vehicle, and the like. In the engine fuel injection system including the fuel injection valve 10, the fuel in the fuel tank 40 is pumped to the common rail 42 (accumulation container) by the high-pressure pump 41 and accumulated, and is supplied to the fuel injection valve 10 of each cylinder through the high-pressure pipe 43. Distributed supply.

  The fuel injection valve 10 includes a body 11, a needle 12 (valve element), an electromagnetic solenoid 13 (actuator), and the like described below. A high pressure passage 11a is formed inside the body 11, and fuel supplied from the common rail 42 to the fuel injection valve 10 is injected from the injection hole 11b through the high pressure passage 11a. A part of the fuel in the high-pressure passage 11a flows to the back pressure chamber 11c formed in the body 11. The leak hole 11 d of the back pressure chamber 11 c is opened and closed by a control valve 14, and the control valve 14 is opened and closed by an electromagnetic solenoid 13. The needle 12 is given the elastic force of the spring 15 and the fuel pressure of the back pressure chamber 11c to the valve closing side, and the fuel pressure of the fuel reservoir 11f formed in the high pressure passage 11a is given to the valve opening side. .

  A fuel pressure sensor 20 for detecting fuel pressure is attached to a fuel supply path (for example, the high-pressure pipe 43 or the high-pressure passage 11a) from the common rail 42 to the nozzle hole 11b. In the example of FIG. 1, it is attached to a connection portion between the high-pressure pipe 43 and the body 11. Or you may attach to the body 11 as shown by the dashed-dotted line in FIG. The fuel pressure sensor 20 is provided for each of the plurality of fuel injection valves 10 (# 1) to (# 4).

  Next, the operation of the fuel injection valve 10 configured as described above will be described. When the electromagnetic solenoid 13 is not energized, the control valve 14 is closed by the elastic force of the spring 16. Then, the fuel pressure in the back pressure chamber 11c rises, the needle 12 is closed, and fuel injection from the injection hole 11b is stopped. On the other hand, when the electromagnetic solenoid 13 is energized, the control valve 14 is opened against the elastic force of the spring 16. Then, the fuel pressure in the back pressure chamber 11c is lowered, the needle 12 is opened, and fuel is injected from the injection hole 11b.

  Incidentally, when the electromagnetic solenoid 13 is energized to inject fuel, the fuel that has flowed into the back pressure chamber 11c from the high pressure passage 11a is discharged (leaked) from the leak holes 11d to 11e. That is, during the fuel injection period, the fuel in the high pressure passage 11a always leaks to the low pressure passage 11e through the back pressure chamber 11c.

  The ECU 30 controls the injection state by controlling the opening / closing operation of the needle 12 by controlling the driving of the electromagnetic solenoid 13. For example, based on the rotational speed of the engine output shaft, the engine load, and the like, target injection modes such as the injection start timing, injection end timing, and injection amount are calculated, and the drive of the electromagnetic solenoid 13 is controlled so as to achieve the target injection mode. .

  Next, the procedure in which the ECU 30 controls the fuel injection state by controlling the driving of the electromagnetic solenoid 13 will be described with reference to the flowchart of FIG.

  In the process of FIG. 2, first, in step S <b> 11, predetermined parameters representing the engine operating state, for example, the engine speed at that time, the engine load, the pressure of the fuel supplied to the fuel injection valve 10, etc. are read.

  In subsequent step S12, an injection pattern is set based on the various parameters read in step S11. For example, an optimal injection pattern corresponding to various parameters is stored in advance in an injection control map or the like, and an optimal target injection pattern is set with reference to the map based on the parameters read in step S11. The target injection pattern is determined by parameters such as the number of injection stages (the number of injections in one combustion cycle), the injection start timing, the injection time (corresponding to the injection amount), and the like. Thus, the injection control map shows the relationship between these parameters and the optimal injection pattern.

  In the subsequent step S13, an injection command signal is output to the electromagnetic solenoid 13 of the fuel injection valve 10 based on the target injection pattern set in step S12. As a result, fuel injection control is performed so as to obtain an optimal injection pattern according to the various parameters (engine operating conditions) acquired in step S11.

  However, there is a concern that the actual injection pattern injected from the injection holes 11b may deviate from the target injection pattern due to deterioration over time of the fuel injection valve 10, variation in machine differences among the fuel injection valves 10, or the like. In response to this concern, an actual injection pattern (actual injection state) can be detected by a method to be described later based on the detection value of the fuel pressure sensor 20, so that the injection command is set so that the detected actual injection pattern matches the target injection pattern. Correct the signal. Moreover, the correction content is learned, and the learned value is used for calculation of the next injection command signal.

  Next, processing for detecting (calculating) the actual injection state based on the detection value of the fuel pressure sensor 20 will be described with reference to FIG.

  A series of processes shown in FIG. 3 is executed by the microcomputer of the ECU 30 at a predetermined cycle (for example, the calculation cycle performed by the CPU described above) or at a predetermined crank angle. First, in step S21 (detected waveform acquisition means), the output value (detected pressure) of the fuel pressure sensor 20 is captured. This intake process is executed for each of the plurality of fuel pressure sensors 20. In addition, it is desirable to perform a filtering process for removing high-frequency noise and the like on the taken-in detected pressure.

  Hereinafter, the capturing process in step S21 will be described in detail with reference to FIG.

  FIG. 4A shows an injection command signal output to the fuel injection valve 10 in step S13 of FIG. 3, and the electromagnetic solenoid 13 is actuated by opening the command signal to open the nozzle hole 11b. . That is, the injection start is commanded by the pulse-on timing Is of the injection command signal, and the injection end is commanded by the pulse-off timing Ie. Therefore, the injection amount Q is controlled by controlling the valve opening time Tq of the nozzle hole 11b by the pulse-on period (injection command period) of the command signal. FIG. 4B shows the change (transition) of the fuel injection rate from the nozzle hole 11b that occurs in accordance with the injection command, and FIG. 4C shows the output value of the fuel pressure sensor 20 that occurs with the change of the injection rate ( The change (pressure waveform) of detected pressure is shown. FIG. 4 is an example of various changes when the nozzle hole 11b is opened and closed once.

  The ECU 30 detects the output value of the fuel pressure sensor 20 by a subroutine process different from the process of FIG. 3. In the subroutine process, the ECU 30 detects the output value of the fuel pressure sensor 20 using the sensor output as a locus of the pressure transition waveform ( The trajectory illustrated in FIG. 4C is sequentially acquired at intervals as short as possible (interval shorter than the processing cycle in FIG. 3). Specifically, sensor outputs are sequentially acquired at intervals shorter than 50 μsec (more desirably 20 μsec), and the values acquired in this way are taken in step S21.

  Since the pressure waveform detected by the fuel pressure sensor 20 and the change in the injection rate have a correlation described below, the transition waveform of the injection rate can be estimated from the detection waveform.

  The change in the injection rate shown in FIG. 4 (b) will be described. First, after energization of the electromagnetic solenoid 13 is started at the time of reference Is, fuel injection starts from the injection hole 11b. The rising starts at the change point R3. That is, actual injection is started. Thereafter, the maximum injection rate is reached at the change point R4, and the increase in the injection rate is stopped. This is because the needle valve 20c starts to lift up at the time point R3, and the lift-up amount becomes maximum at the time point R4.

  The “change point” in this specification is defined as follows. That is, the second-order differential value of the injection rate (or the detected pressure of the fuel pressure sensor 20) is calculated, and the extreme value of the waveform indicating the change of the second-order differential value (the point at which the change is maximum), that is, the second-order differential value waveform Is an inflection point of the waveform of the injection rate or detected pressure.

  Next, after the energization of the electromagnetic solenoid 13 is cut off at the time of the symbol Ie, the injection rate starts to decrease at the change point R7. Thereafter, at the change point R8, the injection rate becomes zero, and the actual injection ends. This is because the needle valve 20c starts to be lifted down at the time point R7, is completely lifted down at the time point R8, and the nozzle hole 11b is closed.

  The change in the detected pressure of the fuel pressure sensor 20 shown in FIG. 4C will be described. The pressure P0 before the change point P1 is the fuel supply pressure at the injection command start time Is. First, the drive current flows to the electromagnetic solenoid 13. Then, before the injection rate starts increasing at the time point R3, the detected pressure decreases at the change point P1. This is because the control valve 14 opens the leak hole 11d at the time point P1, and the back pressure chamber 11c is decompressed. Thereafter, when the back pressure chamber 11c is sufficiently depressurized, the descent from P1 is temporarily stopped at the change point P2. This is because the leak amount becomes constant depending on the diameter of the leak hole 11d because the leak hole 11d is completely opened.

  Next, as the injection rate starts increasing at the time point R3, the detected pressure starts decreasing at the change point P3. Thereafter, as the injection rate reaches the maximum injection rate at the time point R4, the decrease in the detected pressure stops at the change point P4. Note that the amount of drop from the change points P3 to P4 is larger than the amount of drop from P1 to P2.

  Next, the detected pressure rises at the change point P5. This is due to the fact that the control valve 14 closes the leak hole 11d at the time point P5, and the back pressure chamber 11c is subjected to a pressure increasing process. Thereafter, when the back pressure chamber 11c is sufficiently increased, the rise from P5 is temporarily stopped at the change point P6.

  Next, as the injection rate starts decreasing at the time point R7, the detected pressure starts increasing at the change point P7. Thereafter, as the injection rate becomes zero at the time point R8 and the actual injection ends, the increase in the detected pressure stops at the change point P8. The amount of increase from the change point P7 to the change point P8 is larger than the amount of increase from P5 to P6. The detected pressure after P8 is attenuated while repeatedly decreasing and increasing at a constant period T10.

  As described above, by detecting the change points P3, P4, P7 and P8 among the fluctuations in the detected pressure by the fuel pressure sensor 20, the injection rate rise start time R3 (actual injection start timing), the maximum injection rate arrival time R4, the injection The rate lowering start time R7 and the lowering end time R8 (actual injection end time) can be estimated. Further, based on the correlation between the change in the detected pressure and the change in the injection rate described below, the change in the injection rate can be estimated from the change in the detected pressure.

  That is, there is a correlation between the pressure decrease rate Pα from the detected pressure change points P3 to P4 and the injection rate increase rate Rα from the injection rate change points R3 to R4. There is a correlation between the pressure increase rate Pγ from the change points P7 to P8 and the injection rate decrease rate Rγ from the change points R7 to R8. There is a correlation between the pressure drop amount Pβ (maximum pressure drop amount) from the change points P3 to P4 and the injection rate increase amount Rβ (maximum injection rate) from the change points R3 to R4. Therefore, the injection rate increase rate Rα, the injection rate decrease rate Rγ, and the maximum injection rate Rβ are estimated by detecting the pressure decrease rate Pα, the pressure increase rate Pγ, and the maximum pressure decrease amount Pβ from the fluctuation of the detected pressure by the fuel pressure sensor 20. can do. As described above, various states R3, R4, R7, R8, Rα, Rβ, and Rγ of the injection rate can be estimated, and therefore the change (transition waveform) of the fuel injection rate shown in FIG. 4B is estimated. Can do.

  Further, the integral value of the injection rate from the start to the end of the actual injection (the area of the portion indicated by the hatched symbol S) corresponds to the injection amount Q. Then, the integral value of the pressure and the integral value S of the injection rate in the portion corresponding to the change in the injection rate from the start to the end of the actual injection (the change points P3 to P8) in the fluctuation waveform of the detected pressure have a correlation. Therefore, by calculating the pressure integral value from the fluctuation of the detected pressure by the fuel pressure sensor 20, the injection rate integral value S corresponding to the injection amount Q can be estimated. From the above, it can be said that the fuel pressure sensor 20 functions as an injection state sensor that detects the pressure of the fuel supplied to the fuel injection valve 10 as a physical quantity related to the injection state.

  Returning to the description of FIG. 3, in step S <b> 22 following step S <b> 21 described above, it is determined whether or not the injection to be detected is the second and subsequent injections of the multi-stage injection. When it is determined that the injection is in the second or subsequent stage (S22: YES), in the subsequent step S23, the undulation process described below with respect to the detected pressure value waveform (pressure waveform) acquired in step S21. I do.

  In FIG. 5, (a) is a time chart showing the drive current that flows through the electromagnetic solenoid 13 when an injection command signal is output so as to perform multi-stage (two-stage) injection, and (b) shows the command signal of (a). The waveform of the fuel pressure detected at the time of output (detection waveform W at the time of multistage injection) is shown. (C) is a time chart showing the drive current that flows through the electromagnetic solenoid 13 when an injection command signal is output so that single-stage injection is performed. (D) is detected when the command signal of (c) is output. The pressure waveform is shown.

  In the waveform corresponding to the n-th stage injection in the detected waveform W shown in (b) (see the alternate long and short dash line in (b)), the injection before the n-th stage (n-1 stage injection, n− Aftermath resulting from second-stage injection, n-3th-stage injection, ...) is superimposed. The aftermath of the (n-1) th stage injection shown in FIG. 5 (d) will be described as an example. Even after the completion of the (n-1) th stage injection, as the aftermath of the (n-1) th stage injection, a predetermined period (in the case of FIG. 4) In the period of T10, a undulating waveform (see the alternate long and short dash line in (d)) appears that attenuates while repeating descending and rising. This after-wave (swell waveform) is superimposed on the waveform corresponding to the n-th stage injection (see the alternate long and short dash line in (b)) of the detected waveform W of the n-th stage injection. Therefore, if an attempt is made to estimate the injection rate change (injection rate transition waveform illustrated in FIG. 4B) applied to the n-th stage injection using the detected waveform W as it is, the estimation error becomes extremely large.

  Therefore, in the swell canceling process of step S23, a process of extracting the pressure waveform Wn (see FIG. 5 (f)) resulting from the nth stage injection by subtracting the aftermath (swelling waveform) of the previous stage injection from the detected waveform W is performed. is doing. Specifically, various types of single-stage injection are tested in advance, and a swell waveform for each of these modes is acquired. As specific examples of the various aspects, the injection conditions such as the fuel pressure at the start of injection (supply fuel pressure) corresponding to P0 (or P2) in FIG. 4 and the injection amount corresponding to the valve opening time Tq are varied. Is mentioned. The waveform obtained by the above test or the waveform obtained by mathematical expression of the obtained waveform corresponds to a “model waveform”, and the model waveform for each aspect is stored in the memory (model waveform storage means) of the ECU 30 in advance. Let me.

  In the present embodiment, the swell waveform exemplified by the following Equation 1 is stored as the model waveform. P in Equation 1 represents the value of the model waveform (the normative value of the pressure detected by the fuel pressure sensor 20). A, k, ω, θ in Expression 1 indicate parameters indicating the amplitude, the damping coefficient, the frequency, and the phase in the damped vibration, respectively. T in Formula 1 shows elapsed time. Then, the reference value p of the detected pressure is specified by Equation 1 with the elapsed time t as a variable, and the parameters A, k, ω, θ are different values depending on the injection mode (for example, the fuel pressure and the injection amount at the start of injection). Is set to

p = Aexp (−kt) sin (ωt + θ) (Equation 1)
For example, when it is desired to obtain a model waveform that serves as a reference for the after-wave (swell waveform) of the n-1th stage injection, the memory is based on the injection mode such as the fuel pressure at the start of the n-1st stage injection and the injection amount. The model waveform of the closest injection mode is selected from the model waveforms for each of the various modes stored in the model waveform, and the selected model waveform is used as a model waveform CALn that serves as a reference for the after-wave (swell waveform) of the (n-1) th stage injection. Obtained as -1. For example, the dotted line in FIG. 5 (e) represents the model waveform CALn-1, and the solid line in FIG. 5 (e) represents the detected waveform W in (b). And the calculation which subtracts the model waveform CALn-1 from the detection waveform W is implemented, and the pressure waveform Wn shown in FIG.5 (f) is extracted. The pressure waveform Wn extracted in this way should be a pressure waveform that has a high correlation with the change in the injection rate due to the n-th stage injection because the undulation waveform component of the previous stage injection is removed.

  In the example of FIGS. 5E and 5F, only the model waveform CALn−1 representing the undulation waveform of the (n−1) th stage injection is subtracted from the detected waveform W. Similarly, a model waveform may be acquired for the waveform, and a plurality of acquired model waveforms may be subtracted from the detected waveform W. Incidentally, in the example of FIG. 6, the undulation waveforms (model waveforms CALn−1 and CALn−2) of the (n−1) th stage injection and the (n−2) th stage injection are subtracted from the detected waveform W.

  Returning to the description of FIG. 3, in step S24 following the undulation process S23, when it is determined that the injection to be detected is the first stage injection (S22: NO), in step S21. By differentiating the acquired detected pressure value (pressure waveform), the waveform of the pressure differential value is acquired. In the case of the second and subsequent injections (S22: YES), a differential operation is performed on the detected pressure value (pressure waveform) after the undulation process is performed in step S23.

  In subsequent steps S25 to S28, various injection states shown in FIG. 4B are calculated using the pressure differential value acquired in step S24. That is, the fuel injection start timing R3 is calculated in step S25, the injection end timing R8 is calculated in step S26, the maximum injection rate arrival timing R4 and the injection rate decrease start timing R7 are calculated in step S27, and the maximum injection rate Rβ is calculated in step S28. To do. When the injection amount is small, the maximum injection rate arrival timing R4 and the injection rate decrease start timing R7 coincide.

  Then, in the following step S29, based on the injection states R3, R8, Rβ, R4, R7 calculated in steps S25 to S28, the integrated value of the injection rate from the start to the end of the actual injection (shown by the hatched symbol S). The area of the portion is calculated, and the calculation result is set as the actual injection amount Q. The area S has a shape close to a trapezoid when the injection amount is large, and a shape close to a triangle when the injection amount is small. In addition to the injection states R3, R8, Rβ, R4, and R7, the injection rate increase rate Rα and the injection rate decrease rate Rγ are calculated from the pressure waveform, and these increase rate Rα and decrease rate Rγ are taken into account. Thus, the integral value S (injection amount Q) of the injection rate may be calculated. Thus, the process of detecting (calculating) the actual injection states R3, R8, Rβ, R4, R7, Q based on the detection value of the fuel pressure sensor 20 is completed.

  By the way, when the model waveform CAL is subtracted from the detected waveform W, it is necessary to superimpose and associate the model waveform CAL with the detected waveform W as shown in FIG. 5E, but there is a shift (phase shift) in the time axis direction. Unless the association is made so as not to occur, the accuracy of the subtraction operation is deteriorated. Therefore, in the present embodiment, association is performed by the following method.

  That is, the portion of the interval period from the end of the (n−1) th stage injection to the start of the nth stage injection (interval detection waveform WI) in the detected waveform W is the actual aftermath of the waveform component caused by the injection up to the previous stage. Focusing on the fact that it represents (actual undulation waveform), the detection waveform W is set such that the deviation between the phase of the interval period (interval model waveform) and the interval detection waveform WI of the model waveform is minimized. Link the model waveform.

  For example, when three-stage injection is performed as shown in FIG. 6, the waveform of the interval period TIn-2 from the detection waveform W after the end of the (n-2) th stage injection to the start of the (n-1) th stage injection is It should be the same as the undulation waveform (model waveform CALn-2 shown in FIG. 6C) resulting from the (n-2) th stage injection. Further, in the detected waveform W, the waveform in the interval period TIn-1 from the end of the (n-1) th stage injection to the start of the nth stage injection is a wavy waveform (model waveform CALn-2) applied to the (n-2) th stage. ) And the wave waveform U (see FIG. 7C) obtained by combining (adding) the wave waveform (model waveform CALn-1 shown in FIG. 6D) applied to the n-1 stage. is there.

  A one-dot chain line in FIG. 7C indicates the swell waveform U synthesized in this way, and a method of associating the swell waveform U with the detection waveform W indicated by the solid line in FIGS. 7B and 7C. Is described below.

  First, a point B1 (see FIG. 7A) corresponding to the injection end point in the detection waveform W is calculated. Specifically, first, the pressure P3 or P0 at the injection start time is acquired. When P0 is acquired, a reduced pressure ΔP2 corresponding to the leak amount from the leak hole 11d is set in advance, and the pressure corresponding to P3 is calculated by subtracting ΔP2 from P0. Also good. Next, a portion from the change points P4 to P8 in the detected waveform W is approximated to a straight line L2. For example, the tangent at the inflection point (the point at which the second-order differential value becomes zero) from the change points P4 to P8 may be the approximate straight line L2. Then, the point where the approximate straight line L2 and the straight line P3 intersect is calculated as the injection end point B1.

  The undulation waveform U is set assuming a waveform starting from a portion corresponding to the injection end point B1, and the start point of the undulation waveform U is matched with the injection end point B1. As a result, the undulation waveform U is associated with the detection waveform W.

  However, the injection end point B1 may be erroneously calculated at a position deviated from the actual injection end point B1 due to noise included in the detection waveform W, a calculation error, or the like. For example, as shown in FIG. 7B, when the approximate straight line L2 is erroneously calculated as the straight line indicated by L3, the point indicated by the symbol B2 is calculated as the injection end point. Then, as shown in FIG. 7C, when the start point of the undulation waveform U is made to coincide with the injection end point B2, the phase of the undulation waveform U is shifted from the phase of the detection waveform W by Δt. If the undulation elimination process for subtracting the undulation waveform U from the detection waveform W is performed in such a shifted state, the pressure waveform Wn resulting from the n-th stage injection cannot be accurately extracted.

  Therefore, in the present embodiment, the phase of the undulation waveform U is corrected and associated as follows. In the following description, the portion of the detected waveform W from the injection end point B1 to the point B3 corresponding to the start of the n-th stage injection (for example, the point corresponding to the change point P1 of the n-th stage injection or the start time Is). The waveform during the injection stop period is referred to as an interval detection waveform WI.

  First, in the interval detection waveform WI, the waveform of the portion where the pressure rises first, for example, the portion of the waveform corresponding to the predetermined period ta from the start point of the undulation waveform U is obtained using means such as the least square method. Approximate to a straight line L3 (see FIG. 7C). Note that the waveform of the portion corresponding to the predetermined period ta from the injection end point B1 may be approximated to the straight line L3.

  Next, the waveform of the portion of the undulation waveform U where the pressure rises first, for example, the waveform of the portion corresponding to the predetermined period ta from the start point is expressed by the straight line L4 (see FIG. 7 (c)). Note that the waveform from the start point to the change point UP8 may be approximated to the straight line L4.

  Next, the distance between the approximate line L3 and the approximate line L4 is calculated. In the present embodiment, the approximate straight lines L3 and L4 are considered to be substantially parallel, and the time difference between the time when the injection start pressure P3 appears in the approximate line L3 and the time when the injection start pressure P3 appears in the approximate line L4. Δt is calculated as a phase difference Δt between the undulation waveform U and the detection waveform W. The average distance between the approximate line L3 and the approximate line L4 may be calculated as the phase difference Δt.

  Next, the phase of the undulation waveform U is corrected so that the start point of the undulation waveform U is shifted from the injection end point B2 by the time difference Δt. Specifically, “Aexp (−kt) sin (ωt + θ)” in the above-described equation 1 is corrected to become “Aexp (−k (t−Δt)) sin (ω (t−Δt) + θ)”. To do. As described above, the undulation waveform U is associated with the detection waveform W so that the start point of the undulation waveform U coincides with the actual injection end point B1.

  By the way, various tests conducted by the present inventors have revealed that “the longer the injection period Tqn of the n-th injection, the smaller the amplitude of the actual undulation waveform is (the degree of attenuation is greater)”. . For example, the symbol k1 in FIG. 7B represents an asymptote along the peak value of the undulation waveform U. However, as the injection period Tqn of the n-th stage injection becomes longer, the asymptotic line indicated by the symbol k2 is obtained. The degree of attenuation increases.

  The present inventors considered the mechanism by which such a phenomenon occurs as follows. First, after the fuel pressure wave propagating in the fuel supply path propagates toward the nozzle hole 11b, a part of the fuel pressure wave is reflected by the nozzle hole part and propagates toward the fuel pressure sensor 20. Then, under the influence of the reflected fuel pressure wave, a wavy waveform (a waveform along asymptotic lines k1 and k2) appears in the fuel pressure waveform detected by the fuel pressure sensor 20. When the nozzle hole is closed to stop fuel injection, the degree of reflection of the fuel pressure wave at the nozzle hole portion increases.

  On the other hand, when the nozzle hole 11b is opened to inject fuel, a part of the fuel pressure wave escapes from the nozzle hole 11b, so that the degree of reflection is reduced. Therefore, the amplitude of the pulsation (swell waveform) included in the fuel pressure waveform is smaller during fuel injection than when injection is stopped. The longer the valve opening time Tqn is, the smaller the amount of reflection becomes, so the amplitude of pulsation becomes smaller.

  Therefore, for example, even if the phase of the undulation waveform U is corrected as described above, the amplitude of the undulation waveform U indicated by the alternate long and short dash line in FIG. 7D is indicated by a solid line when the injection period Tqn of the n-th stage injection is increased. It becomes larger than the amplitude of the actual undulation waveform.

  Therefore, in the present embodiment, the amplitude of the undulation waveform U is corrected so that such a deviation in amplitude is zero. Specifically, after the phase of the undulation waveform U is corrected as described above, the sum of the differences between the interval detection waveform WI and the undulation waveform U in the predetermined period Tb (the area with halftone dots in FIG. 7D). ) Is corrected so that the attenuation coefficient k (amplitude gain) of “Aexp (−k (t−Δt)) sin (ω (t−Δt) + θ)” in Equation 1 is corrected. The predetermined period Tb may be set to a period until a predetermined time elapses from the injection end point B1, and is preferably set to be a period of one cycle or more of the undulation waveform U. As described above, the attenuation coefficient k of the undulation waveform U is corrected so that the amplitude of the undulation waveform U approaches the amplitude of the actual interval detection waveform WI.

  Next, the procedure of the above-described undulation processing S23 will be described with reference to the flowchart of FIG. 8 focusing on the processing procedures of the phase correction and attenuation coefficient correction. This process is a subroutine process corresponding to step S23 in FIG. 4, and first, in step S31, the m-th injection start fuel pressure P0m and the injection amount Qm are acquired. As the injection amount Qm, the injection amount calculated in step S29 of FIG. 3 may be used, or an injection amount estimated from the valve opening time Tqm based on the injection command signal may be used.

  In the subsequent step S32, the model waveform CALm of the closest injection mode is selected from the model waveforms for each mode stored in the memory, based on the fuel pressure P0m at the start of injection acquired in step S31 and the injection amount Qm. In the subsequent step S33, a waveform (swell waveform U) obtained by synthesizing a plurality of model waveforms CALn-2 and CALn-1 is calculated. In subsequent step S34, the injection end point B2 in the detected waveform W acquired in step S21 of FIG. 3 is calculated. As described above with reference to FIG. 7B, the calculation method approximates the waveform of the detected waveform W that rises with the end of injection to the straight line L3, and shows the approximate straight line L3 and the injection start pressure P3. Is calculated as an injection end point B2.

  In subsequent step S35 (phase correlation means), the undulation waveform U is associated with the detected waveform W by matching the start point of the undulation waveform U calculated in step S33 with the injection end point B2 calculated in step S34. In the subsequent step S36 (detected waveform approximating means), an approximate straight line L3 is calculated based on the waveform of the portion corresponding to the predetermined period Ta from the injection end point B2 in the detected waveform W. In the subsequent step S37 (model waveform approximating means), an approximate straight line L4 is calculated based on the waveform of the portion of the undulation waveform U corresponding to the predetermined period Ta from the injection end point B2.

  In the subsequent step S38, the distance between the two approximate straight lines L3 and L4 is calculated as a phase shift Δt. In the following step S39, the undulation waveform U is corrected so that the phase shift Δt calculated in step S38 is zero.

  In the subsequent step S40 (amplitude correction means), the undulation waveform U in a state after the phase shift is corrected in the portion corresponding to the predetermined period Tb from the start point of the undulation waveform U after correction (that is, the actual injection end point B1). The attenuation coefficient k of the undulation waveform U is corrected so that the total sum of amplitude differences from the detection waveform W is minimized.

  In the subsequent step S41 (waveform extraction means), the wavy waveform U in the state where the phase correction and the attenuation coefficient correction are performed is subtracted from the detected waveform W. The waveform obtained by this subtraction corresponds to the pressure waveform Wn resulting from the n-th injection illustrated in FIG. 5 (f) or FIG. 6 (e).

  As described above, according to the present embodiment, the phase shift Δt between the waveform WI corresponding to the interval period in which the injection is stopped in the detected waveform W and the model waveform (swell waveform U) is calculated, and the phase is calculated. The undulation waveform U is corrected so that the shift Δt becomes zero. Therefore, since the phase shift between the undulation waveform U and the detection waveform W for the injection periods Tqn−1 and Tqn is also reduced, the undulation waveform U is subtracted from the detection waveform W to obtain the pressure waveform Wn resulting from the n-th injection. The extraction accuracy can be improved. Therefore, the actual injection states R3, R8, Rβ, R4, R7, Q can be detected with high accuracy, and the engine output torque and emission state can be controlled with high accuracy.

  Further, according to the present embodiment, the phase shift Δt is calculated based on the waveform of the portion where the pressure rises first (the portion where the undulation amplitude is large) out of the interval detection waveform WI and the undulation waveform U, so the calculation accuracy thereof Can be improved. In addition, by utilizing the fact that the above-described portion with a large undulation amplitude has a shape close to a straight line, the interval detection waveform WI and the undulation waveform U are approximated to a straight line, and the phase shift Δt based on both approximate lines L3 and L4. Therefore, the calculation processing load can be greatly reduced without significantly reducing the calculation accuracy of the phase shift Δt.

  Furthermore, according to the present embodiment, the attenuation coefficient k of the undulation waveform U is corrected so that the deviation between the amplitude of the undulation waveform U corrected to eliminate the phase shift Δt and the amplitude of the interval detection waveform WI is minimized. Since the correction is made so as to approach the actual undulation waveform U, the extraction accuracy can be further improved in extracting the pressure waveform Wn resulting from the n-th stage injection.

(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 above embodiment, the phase shift Δt from the undulation waveform U is calculated for the waveform of the portion of the interval detection waveform WI where the pressure rises first. As a modified example, the phase shift Δt with respect to the undulation waveform U may be calculated for the waveform after the portion of the interval detection waveform WI where the pressure rises first. Alternatively, the phase shift Δt from the undulation waveform U may be calculated for the entire interval detection waveform WI.

  In the above embodiment, a part of the interval detection waveform WI is approximated to the straight line L3, and a part of the undulation waveform U is approximated to the straight line L4, and the phase shift Δt is calculated based on a comparison of these approximate straight lines L3 and L4. Although it is calculated, the phase difference between the interval detection waveform WI (or part of the waveform) and the undulation waveform U (or part of the waveform) may be calculated without approximating a straight line. . For example, the phase of the undulation waveform U is shifted by a predetermined minute phase, and the total sum (approximation degree) of the difference between the undulation waveform U and the interval detection waveform WI is calculated each time the phase is shifted by a minute phase. Then, it is only necessary to calculate which phase is shifted to the most approximate waveform and correct it to the phase when the most approximate waveform is obtained.

  In the above embodiment, the above-described phase correction and attenuation coefficient correction are performed on a waveform (swell waveform U) obtained by synthesizing a plurality of model waveforms CALn-2 and CALn-1. As a modified example, the above-described phase correction and attenuation coefficient correction are performed on each of the model waveforms CALn-2 and CALn-1, and after the correction, the model waveforms CALn-2 and CALn-1 are combined and swelled. The waveform U may be calculated.

  The model waveform CAL according to the above-described embodiment is expressed by Equation 1, and the parameters A, k, ω, θ are injected in such a manner that the reference value p of the detected pressure can be calculated from Equation 1 with the elapsed time t as a variable. For example, different values are set and stored according to the fuel pressure at the start of injection, the injection amount, and the like. In contrast, the reference value p of the detected pressure with respect to the elapsed time t may be stored as it is in a map or the like, and the map may be stored as an injection mode and used as a model waveform.

  The fuel injection valve 10 to which the above embodiment is applied is a fuel in the back pressure chamber 11c during the injection period in which the needle 12 is opened due to the adoption of a two-way valve as the control valve 14. Is configured to constantly leak. However, the present invention is also applicable to a fuel injection valve that employs a three-way valve as the control valve 14 and that does not leak the fuel in the back pressure chamber 11c even during the injection period.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 20 ... Fuel pressure sensor, S21 ... Detection waveform acquisition means, 30 ... ECU (model waveform storage means), S35 ... Phase correlation means, Detection waveform approximation means, S37 ... Model waveform approximation means, S40 ... Amplitude correction Means, S41 ... waveform extraction means, k ... attenuation coefficient (amplitude gain), Δt ... phase shift.

Claims (4)

A fuel injection valve that injects fuel to be burned in an internal combustion engine from an injection hole, and a fuel pressure sensor that detects a change in fuel pressure that occurs in the fuel supply path up to the injection hole as fuel is injected from the injection hole And applied to a fuel injection system comprising
Detection waveform acquisition means for acquiring a pressure waveform detected by the fuel pressure sensor when performing multi-stage injection in which fuel is injected a plurality of times during one combustion cycle of the internal combustion engine as a detection waveform during multi-stage injection;
Model waveform storage means for storing a model waveform that serves as a reference for the pressure waveform when the injection prior to the n-th stage injection is performed without performing the n-th stage injection after the second stage among the multi-stage injections When,
The phase of the interval detection waveform corresponding to the interval period from the end of the (n-1) th stage injection to the start of the nth stage injection in the multistage injection detection waveform, and the interval period of the model waveform Phase correlation means for associating the model waveform with the detection waveform at the time of multi-stage injection so that the shift from the phase of the interval model waveform of the portion corresponding to
Waveform extraction means for subtracting the model waveform in the associated state from the detection waveform at the time of multistage injection to extract a pressure waveform resulting from the nth stage injection;
A fuel pressure waveform acquisition device comprising: The phase correlation means includes
The correlation of the phases is performed based on a phase shift between a waveform of a portion where the pressure rises first in the interval detection waveform and a waveform of a portion where the pressure rises first in the interval model waveform. The fuel pressure waveform acquisition device according to claim 1. The phase correlation means includes
Detection waveform approximating means for approximating the waveform of the first rising pressure portion of the interval detection waveform to a straight line, and model waveform for approximating the waveform of the first rising pressure portion of the interval model waveform to a straight line And approximating means,
3. The fuel pressure waveform acquisition apparatus according to claim 2, wherein the correlation is performed based on a phase shift between a straight line approximated by the detected waveform approximating unit and a straight line approximated by the model waveform approximating unit. .   2. An amplitude correction unit that corrects an amplitude gain of the model waveform so as to minimize a deviation between the amplitude of the interval model waveform in the associated state and the amplitude of the interval detection waveform. The fuel pressure waveform acquisition device according to any one of?

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