JP5278398B2 - Fuel injection state detection device - Google Patents

Description

  The present invention relates to a fuel injection state detection device that detects a sensor waveform representing a change in fuel pressure caused by fuel injection with a fuel pressure sensor and estimates a fuel injection state based on the detected sensor waveform.

  In order to accurately control the output torque and emission state of an internal combustion engine, it is important to accurately control the injection state, such as the injection start timing and injection end timing of fuel injected from the injection hole of the fuel injection valve. . Therefore, conventionally, a fuel pressure sensor is mounted on a fuel pipe connecting the common rail (pressure accumulating vessel) and the fuel injection valve or the fuel injection valve, and a change in fuel pressure (sensor waveform) caused by fuel injection is detected. Based on the detected sensor waveform, the actual injection state (injection start timing, injection end timing, etc.) is estimated (see Patent Documents 1 and 2). For example, change points P1, P2, P3 (see FIG. 2C) appearing in the sensor waveform detected by the fuel pressure sensor are calculated, and based on the appearance times and pressure values of these change points P1, P2, P3, the actual values are calculated. The injection state (injection start timing R1, injection end timing R4, injection amount Q, etc.) is calculated.

JP 2010-3004 A JP 2009-57924 A

  However, the sensor waveform detected by the fuel pressure sensor does not reflect the injection state as it is, and the waveform of the supply pulsation described below is superimposed on the sensor waveform. Trials revealed.

  That is, as illustrated in FIG. 3, when the fuel pressure drop pulsation (injection pulsation Ma) that occurs in the vicinity of the nozzle hole at the start of injection propagates through the internal passage of the fuel injection valve 10 and reaches the fuel pressure sensor 20. The sensor waveform starts to fall (see FIGS. 3A to 3C). Thereafter, when the injection pulsation Ma further propagates and reaches the common rail 42 through the fuel pipe 42b, fuel supply from the common rail 42 to the fuel pipe 42b is started (see FIGS. 3D and 3E). When the pulsation of the fuel pressure rise (supply pulsation Mb) generated near the inlet of the fuel pipe along with the start of fuel supply propagates through the fuel pipe 42b and the internal passage of the fuel injection valve 10 and reaches the fuel pressure sensor 20, The waveform component of the supply pulsation Mb that increases in pressure is superimposed on the sensor waveform. Therefore, if it is attempted to estimate the injection state from the sensor waveform on which such supply pulsation Mb is superimposed, an estimation error occurs due to the influence of the supply pulsation Mb.

  In particular, in the case of micro-injection that starts the valve closing operation after the start of injection and before the maximum injection rate is reached, the above-described supply pulsation waveform is present in the portion of the sensor waveform that rises as the injection rate decreases. It will be superimposed. Therefore, when estimating the injection state such as the injection end timing or the gradient of the decrease in the injection rate based on the rising waveform portion of the sensor waveform, the estimation accuracy is significantly deteriorated.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel injection state detection device capable of detecting an actual injection state with high accuracy.

  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, the pressure accumulating container for accumulating the fuel supplied from the fuel pump, the fuel pipe connected to the discharge port of the pressure accumulating container, and the fuel supplied from the pressure accumulating container through the fuel pipe are injected. And a fuel injection valve having a valve body that opens and closes the nozzle hole, and a fuel that is provided in a fuel supply path from the discharge port to the nozzle hole, detects fuel pressure, and generates fuel accompanying fuel injection It is assumed that the present invention is applied to a fuel injection system including a fuel pressure sensor that outputs a sensor waveform representing a change in pressure.

Then, with the current fuel injection, the supply pulsation generated during the injection period by the flow of fuel flowing into the fuel injection valve through the fuel pipe from the discharge port, it is estimated from the sensor waveform in the current fuel injection The pulsation estimating means, the pulsation removing means for correcting the sensor waveform so as to remove the waveform of the supply pulsation estimated by the pulsation estimating means from the sensor waveform in the current fuel injection, and the correction corrected by the pulsation removing means Injection state estimating means for estimating a fuel injection state from the nozzle hole based on a sensor waveform.

According to this, the waveform of the supply pulsation generated during the injection period due to the flow of fuel flowing from the discharge port to the fuel injection valve through the fuel pipe with the current fuel injection is estimated from the sensor waveform in the current fuel injection. Since the fuel injection state is estimated after removing the estimated supply pulsation waveform from the sensor waveform in the current fuel injection, it is possible to avoid the occurrence of an injection state estimation error due to the influence of the supply pulsation. Therefore, the injection state can be detected with high accuracy.

  In particular, even in the case of micro-injection that starts the valve closing operation after the start of injection and before reaching the maximum injection rate, the waveform of the supply pulsation is superimposed on the portion of the sensor waveform that rises as the injection rate decreases. Therefore, when estimating the injection state such as the injection end timing or the gradient of the decrease in the injection rate based on the rising waveform part of the sensor waveform, avoid the deterioration of the estimation accuracy due to the influence of the supply pulsation. it can.

  The invention according to claim 2 is characterized in that the pulsation estimating means estimates a waveform of the supply pulsation based on a descending waveform of a portion of the sensor waveform where the fuel pressure is lowered with the start of injection.

  According to various tests conducted by the present inventor, it has been found that there is a correlation between the waveform of the sensor pulsation where the fuel pressure drops as the injection starts and the waveform of the supply pulsation. This is considered for the following reason.

  That is, the above-described supply pulsation (the pulsation of the fuel pressure increase generated near the inlet of the fuel pipe as the fuel supply starts) is caused by the occurrence of the injection pulsation (the pulsation of the fuel pressure decrease generated near the nozzle hole as the injection starts). Therefore, the state of the injection pulsation changes depending on the state of the supply pulsation. That is, the supply pulsation state and the injection pulsation state are highly correlated. Further, after the injection pulsation propagates and reaches the fuel pressure sensor, the supply pulsation is propagated with a delay to the fuel pressure sensor. For this reason, the descent start timing and waveform shape of the descending waveform are affected by the injection pulsation, but are hardly affected by the supply pulsation. In summary, the supply pulsation state has a high correlation with the injection pulsation state, and the injection pulsation has a high correlation with the descending waveform. Therefore, it can be said that the supply pulsation waveform has a high correlation with the descending waveform.

  In the above-mentioned invention in view of this point, since the supply pulsation waveform is estimated based on the descending waveform of the portion of the sensor waveform where the fuel pressure is lowered as the injection starts, the estimation accuracy can be improved.

  The invention according to claim 3 is characterized in that the pulsation estimating means estimates the rising slope of the supply pulsation waveform based on the falling slope of the falling waveform.

  According to various tests conducted by the present inventors, it has been found that the descending speed (slope) of the descending waveform and the ascending speed (slope) of the waveform of the supply pulsation are highly correlated. FIG. 6A shows the test results conducted by the present inventor, in which the measured value of the descending slope Pα of the descending waveform is represented on the horizontal axis, and the measured value of the ascent slope Pγ of the supply pulsating waveform is represented on the vertical axis. It is the represented graph. This test result shows that both slopes Pα and Pγ are in a proportional relationship, and that the rising speed of the supply pulsation waveform increases as the descending speed of the descending waveform increases.

  In the above-mentioned invention in view of this point, since the slope Pγ of the supply pulsation waveform is estimated based on the slope Pα of the descending waveform, for example, the slope Pα of the descending waveform is detected, and the slope Pα is represented by the correlation equation shown in FIG. By substituting into, the slope Pγ of the supply pulsation waveform can be calculated with high accuracy. Alternatively, a plurality of models of the supply pulsation waveform slope Pγ corresponding to the drop waveform slope Pα can be stored, and the optimum model of the supply pulsation waveform slope Pγ can be selected based on the detected drop waveform slope Pα. . As described above, according to the present invention, the slope Pγ of the supply pulsation waveform can be estimated with high accuracy.

  According to a fourth aspect of the present invention, the pulsation estimating means starts superimposing the supply pulsation waveform on the sensor waveform based on a descent start timing of the descent waveform or a timing when the fuel injection valve is instructed to start injection. It is characterized by estimating the time.

  By the way, when removing the supply pulsation waveform from the sensor waveform by the pulsation removing means, it is not possible to specify in which position of the sensor waveform the estimated waveform should be removed only by estimating the shape of the supply pulsation waveform. Therefore, if it is possible to estimate when the supply pulsation waveform starts to be superimposed on the sensor waveform, the supply pulsation waveform can be removed from the sensor waveform with high accuracy.

  The superimposition start timing of the supply pulsation waveform has a high correlation with the timing when the fuel injection valve is instructed to start injection or the descent start timing of the descending waveform. For example, the earlier the injection start command timing and the descent start timing, the earlier the supply pulsation waveform superposition start timing.

  In the above invention in view of this point, since the superposition start time of the supply pulsation waveform is estimated based on the descent start time of the descent waveform or the injection start command time, for example, the descent start time of the descent waveform is detected, and the detected descent start time Is substituted into the calculation formula (see (Formula 1) in FIG. 7), the superposition start time of the supply pulsation waveform can be accurately calculated. Alternatively, if the injection start command time or the descent start time estimated from the command time is substituted into the calculation formula, the superposition start time of the supply pulsation waveform can be accurately calculated. Therefore, the supply pulsation waveform can be removed from the sensor waveform with high accuracy by the pulsation removal means.

  The invention according to claim 5 is characterized in that the pulsation estimating means estimates a timing at which the waveform of the supply pulsation starts to be superimposed on the sensor waveform in accordance with a fuel pressure at a timing at which the descending waveform starts to descend. .

  Even if the injection start command timing and the descent start timing are the same, if the fuel pressure at that time is high, the supply pulsation waveform superposition start timing is advanced due to an increase in the supply pulsation propagation speed. In the above-mentioned invention in view of this point, since the superposition start time of the supply pulsation waveform is estimated according to the fuel pressure at the start time of the descent waveform, the superposition start time estimated as described above based on the descent start time of the down waveform, etc. Can be corrected based on the fuel pressure. Therefore, the estimation accuracy of the superposition start time can be improved.

  The invention according to claim 6 is characterized in that the pulsation estimating means estimates the amount of pressure increase due to the supply pulsation based on the pressure at the start of descent and the pressure at the end of descent in the descent waveform. .

  Here, the change in fuel pressure at the position (sensor position) where the fuel pressure sensor is provided in the fuel supply path corresponds to the sensor waveform, but the flow rate of fuel supplied from the pressure accumulator to the sensor position (supply flow rate) When the flow rate of fuel flowing out from the sensor position toward the nozzle hole (injection flow rate) balances, the sensor waveform becomes a constant value (equilibrium pressure). The inventor found that the time when the equilibrium pressure was reached substantially coincided with the time when the pressure increase due to the supply pulsation was completed. The amount of pressure increase due to supply pulsation is correlated with the pressure Pa at the start of the drop and the pressure Pb at the end of the drop in the drop waveform. For example, the pressure increase amount ΔP can be calculated by substituting the pressures Pa and Pb into the calculation formula exemplified in Formula 4 in FIG.

  According to the above-mentioned invention in view of these points, the pressure increase amount ΔP is calculated based on the both pressures Pa and Pb, so that it is possible to specify the point in time when the pressure increase is reached after reaching the equilibrium pressure. Therefore, since the end point of the pressure increase can be accurately estimated based on the pressure increase amount ΔP of the supply pulsation waveform, the supply pulsation waveform can be removed from the sensor waveform with high accuracy by the pulsation removal unit.

  In the seventh aspect of the present invention, in the case of performing small injection in which the injection rate is reduced before reaching the maximum injection rate, the injection state estimating means includes the sensor waveform that is removed and corrected by the pulsation removing means. The injection end timing is calculated based on the rising waveform of the portion where the fuel pressure increases as the injection ends.

  For example, the inventor has revealed that the rising waveform is modeled as a straight line, and the time when the straight line model reaches the reference pressure and the injection end time are highly correlated. However, in the case of small injection in which the injection rate is decreased before reaching the maximum injection rate, the supply pulsation waveform is superimposed on the rising waveform of the sensor waveform. In the linear model affected by the superimposed supply pulsation waveform, the correlation with the injection end time becomes low, and the injection end time cannot be estimated with high accuracy. In other words, in the case of estimating the injection end timing in this way, the injection end timing (fuel injection state) cannot be estimated with high accuracy unless the supply pulsation waveform is removed by the pulsation removing means described above. Is particularly noticeable.

  In the above-mentioned invention in view of this point, when the injection end timing is calculated based on the rising waveform included in the sensor waveform in the case of small injection, the removal of the supply pulsation waveform by the pulsation removing means is applied. The problem that the timing (fuel injection state) cannot be estimated with high accuracy can be effectively solved.

  A configuration example for calculating the injection end timing based on the rising waveform is shown below. That is, the injection state estimating means includes an ascending waveform modeling means for modeling an ascending waveform included in the sensor waveform, and a reference pressure calculating means for calculating the fuel pressure at the injection start timing as a reference pressure, and The time when the rising waveform modeled by the rising waveform modeling means becomes the reference pressure is calculated as the injection end time.

The figure which shows the outline of the fuel-injection system with which the fuel-injection state detection apparatus concerning one Embodiment of this invention is applied. (A) is an injection command signal to the fuel injection valve shown in FIG. 1, (b) is an injection rate waveform representing a change in fuel injection rate caused by the injection command signal, and (c) is detected by a fuel pressure sensor shown in FIG. The time chart which shows the sensor waveform showing the change of the detected detection pressure. The figure explaining the generation | occurrence | production mechanism of an injection pulsation and a supply pulsation. The flowchart which shows the correction | amendment procedure of a sensor waveform, and the estimation procedure of an injection rate waveform. (A) shows sensor waveform W and supply pulsation waveform Wa, (b) shows model Wm of supply pulsation waveform, and (c) shows sensor waveform W ′ after correction obtained by subtracting model Wm from sensor waveform W. Figure. The figure which shows the test result which this inventor implemented. The figure which shows the calculation formulas 1-4 used for estimation of the model Wm. The flowchart which shows the procedure which estimates model Wm.

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

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

  First, an engine fuel injection system including the fuel injection valve 10 will be described. The fuel in the fuel tank 40 is pumped and stored in the common rail 42 (pressure accumulator) by a high pressure pump 41 (fuel pump), and is distributed and supplied to the fuel injection valves 10 (# 1 to # 4) of each cylinder. The plurality of fuel injection valves 10 (# 1 to # 4) sequentially inject fuel in a preset order. Since the plunger pump is used as the high-pressure pump 41, the fuel is intermittently pumped in synchronism with the reciprocating movement of the plunger.

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

  A back pressure chamber 11c for applying a back pressure to the valve body 12 is formed in the body 11, and the high pressure passage 11a and the low pressure passage 11d are connected to the back pressure chamber 11c. The communication state between the high pressure passage 11a and the low pressure passage 11d and the back pressure chamber 11c is switched by the control valve 14, and the actuator 13 such as an electromagnetic coil or a piezoelectric element is energized to push the control valve 14 downward in FIG. As a result, the back pressure chamber 11c communicates with the low pressure passage 11d and the fuel pressure in the back pressure chamber 11c decreases. As a result, the back pressure applied to the valve body 12 decreases and the valve body 12 opens. On the other hand, when the power supply to the actuator 13 is turned off and the control valve 14 is operated upward in FIG. 1, the back pressure chamber 11c communicates with the high pressure passage 11a and the fuel pressure in the back pressure chamber 11c increases. As a result, the back pressure applied to the valve body 12 rises and the valve body 12 is closed.

  Therefore, the ECU 30 controls the energization of the actuator 13 so that the opening / closing operation of the valve body 12 is controlled. Thereby, the high-pressure fuel supplied from the common rail 42 to the high-pressure passage 11 a is injected from the injection hole 11 b according to the opening / closing operation of the valve body 12. For example, the ECU 30 calculates a target injection state such as an injection start timing, an injection end timing, and an injection amount based on the rotation speed of the engine output shaft, the engine load, and the like, and sends an injection command signal to the actuator 13 so that the calculated target injection state is obtained. Is output to control the operation of the fuel injection valve 10.

  The ECU 30 calculates the target injection state based on the engine load and engine speed calculated from the accelerator operation amount and the like. For example, the optimal injection state (the number of injection stages, the injection start time, the injection end time, the injection amount, etc.) corresponding to the engine load and the engine speed is stored as an injection state map. Based on the current engine load and engine speed, the target injection state is calculated with reference to the injection state map. Then, the injection command signals t1, t2, and Tq (see FIG. 2A) are set based on the calculated target injection state. For example, an injection command signal corresponding to the target injection state is stored as a command map, and the injection command signal is set with reference to the command map based on the calculated target injection state. Thus, the injection command signal corresponding to the engine load and the engine rotation speed is set and output from the ECU 30 to the fuel injection valve 10.

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

  Next, the hardware configuration of the fuel pressure sensor 20 will be described. The fuel pressure sensor 20 includes a stem 21 (distortion body), a pressure sensor element 22, a mold IC 23, and the like described below. The stem 21 is attached to the body 11, and the diaphragm portion 21a formed on the stem 21 is elastically deformed by receiving the pressure of the high-pressure fuel flowing through the high-pressure passage 11a. The pressure sensor element 22 is attached to the diaphragm portion 21a, and outputs a pressure detection signal in accordance with the amount of elastic deformation generated in the diaphragm portion 21a.

  The mold IC 23 is formed by resin molding an electronic component such as an amplifier circuit that amplifies the pressure detection signal output from the pressure sensor element 22, and is mounted on the fuel injection valve 10 together with the stem 21. A connector 15 is provided on the upper portion of the body 11, and the mold IC 23, the actuator 13, and the ECU 30 are electrically connected by a harness 16 connected to the connector 15.

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

  Next, a sensor waveform (see FIG. 2C) detected by the fuel pressure sensor 20 mounted on the fuel injection valve 10 during fuel injection, and an injection representing a change in the fuel injection rate applied to the fuel injection valve 10 The correlation with the rate waveform (see FIG. 2B) will be described.

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

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

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

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

  However, the sensor waveform detected by the fuel pressure sensor 20 does not reflect the injection state as it is, and the waveform of the supply pulsation described below is superimposed on the sensor waveform. It is required to perform correction to be removed from the waveform and to estimate the injection state based on the corrected sensor waveform.

  FIG. 3 is a schematic view of a fuel supply path from the discharge port 42a of the common rail 42 to the injection hole 11b of the fuel injection valve 10 through the high-pressure pipe 42b (fuel pipe). The generation mechanism of “supply pulsation” and the like will be described with reference to FIG.

  First, when the fuel starts to be injected from the injection hole 11b, a pulsation (injection pulsation Ma) in which the fuel pressure decreases is generated in the vicinity of the injection hole 11b in the high-pressure passage 11a (see FIG. 3A). Thereafter, the generated injection pulsation Ma propagates in the high-pressure passage 11a toward the common rail 42 (see FIG. 3B). Then, when the injection pulsation Ma reaches the diaphragm portion 21a of the fuel pressure sensor 20, the sensor waveform starts a pressure drop (that is, the change point P1 appears).

  Thereafter, when the injection pulsation Ma reaches the discharge port 42a of the common rail 42, the high-pressure fuel in the common rail 42 is supplied from the discharge port 42a to the high-pressure pipe 42b. When fuel supply is started in this manner, fuel pressure rise pulsation (supply pulsation Mb) occurs in the vicinity of the discharge port 42a in the high-pressure pipe 42b (see FIG. 3E). Thereafter, the generated supply pulsation Mb propagates in the high-pressure passage 11a toward the injection hole 11b (see FIG. 3 (f)). Then, when the supply pulsation Mb reaches the diaphragm portion 21a of the fuel pressure sensor 20, the sensor waveform starts to increase in pressure (that is, the change point P2 appears).

  After that, in the vicinity of the fuel pressure sensor 20 in the high pressure passage 11a, the flow rate of the fuel supplied from the common rail 42 and the flow rate of the fuel injected from the injection hole 11b are balanced (P2a shown in FIG. 2 (c)). At the time), the pressure increase of the sensor waveform stops and becomes a constant value (equilibrium pressure).

  In short, it can be said that the waveform component due to the supply pulsation Mb (the portion of P2 to P2a in FIG. 2C) is superimposed on the waveform component due to the injection pulsation Ma in the sensor waveform. However, since the supply pulsation Mb has not yet propagated to the fuel pressure sensor 20 in the portion of the sensor waveform up to the point P2, it can be said that the waveform represents the injection pulsation Ma and the supply pulsation Mb is not superimposed.

  2A, 2B, and 2C are examples of injection (trapezoidal injection) in which the injection command period Tq is sufficiently long and the valve closing operation is started after reaching the maximum injection rate. The rate waveform is trapezoidal. In contrast, the injection command period Tq is shortened as shown by the one-dot chain line in FIGS. 2A and 2B, and minute injection (triangular injection) is performed so that the injection rate starts to decrease at the same time as the maximum injection rate is reached. The injection rate waveform is a triangle. In the case of triangular injection, the injection pulsation waveforms P2 to P2a are superimposed on the portion of the rising waveform that occurs as the injection rate decreases (portion P3 to P5 in FIG. 2C) of the sensor waveform. The waveform is as shown in FIG.

  Then, in the trapezoidal injection, the approximate straight line Lb is calculated based on the rising waveform (FIG. 2 (c) P3 to P5) where the injection pulsation waveforms P2 to P2a are not superimposed, whereas in the triangular injection, the injection pulsation waveform It is feared that the approximate straight line Lb is calculated based on the rising waveform (FIG. 2 (d) P3 to P5) where P2 to P2a overlap. Therefore, it is difficult to calculate the approximate straight line Lb having a high correlation with the injection end timing, and the approximate straight line Lb ′ deviating from the optimum approximate straight line Lb is calculated as indicated by a symbol Lb ′ in FIG. There is a concern that the injection state such as the injection end timing cannot be estimated with high accuracy.

  Therefore, in the present embodiment, the model Wm (see FIG. 5B) of the waveform component of the supply pulsation Mb is calculated, and the correction is performed by subtracting the calculated model waveform Wm from the sensor waveform W and removing it. The injection state is estimated based on the sensor waveform W ′.

  Next, an example of the above correction procedure and a procedure for estimating the injection rate waveform from the corrected sensor waveform W ′ will be described with reference to the flowchart of FIG. 4. Note that the process shown in FIG. 4 is a process that is executed each time fuel is injected by the microcomputer of the ECU 30.

  First, in step S10 shown in FIG. 4, a plurality of detection values (sensor waveform W) output at a predetermined sampling period from the fuel pressure sensor 20 of the injection cylinder during one fuel injection period are acquired. The solid line in FIG. 5A indicates the sensor waveform W, and the dotted line indicates the supply pulsation waveform Wa. In a subsequent step S20 (pulsation estimating means), a supply pulsation waveform model Wm (see FIG. 5B) is calculated. This calculation method will be described in detail later. In the subsequent step S30 (pulsation removing means), the calculated model Wm is subtracted from the sensor waveform W to calculate the sensor waveform W ′ from which the supply pulsation waveform Wa has been removed (W ′ = W−Wm). The dotted line in FIG. 5C shows the sensor waveform W before correction, and the solid line shows the sensor waveform W ′ after correction.

  In the subsequent step S40, a lowered waveform W (P1-P2) (a waveform of the portion of P1 to P2), which is a portion of the corrected sensor waveform W ′ where the pressure drops as the valve body 12 starts to open. The approximate straight line La is calculated. In the next step S50 (rising waveform modeling means), the rising waveform W (P3-P5) (the portion of the corrected sensor waveform W ′ where the pressure increases as the valve body 12 starts to close the valve) An approximate straight line Lb (modeled ascending waveform) of the portion of P3 to P5) is calculated. These approximate straight lines La and Lb may be calculated, for example, by linearly approximating a plurality of detected values constituting the descending waveform W (P1-P2) or the ascending waveform W (P3-P5) by the least square method, The tangent line at the point where the derivative is the minimum in the falling waveform W (P1-P2) may be calculated as a linear model, or the tangent line at the point where the derivative is the maximum in the rising waveform W (P3-P5). May be calculated as

  Next, in step S60 (reference pressure calculation means), the pressure (reference pressure Pbase) immediately before starting the pressure drop (immediately before the change point P1) in the corrected sensor waveform W ′ is calculated, and the reference pressure Pbase is calculated. Based on the above, reference straight lines Lc and Ld (see FIG. 2C) used in the subsequent processing are calculated. Note that an average value of pressure in a period from when the injection command signal t1 is output to when the P1 change point appears may be calculated as the reference pressure Pbase. For example, a predetermined time after the injection command signal t1 is output. What is necessary is just to calculate the pressure average value until it passes as the reference pressure Pbase. The same value as the reference pressure Pbase is adopted for the reference straight line Lc. A value obtained by lowering the pressure by a predetermined amount from the reference pressure Pbase is adopted for the reference straight line Ld. The predetermined amount is set to a larger value as the pressure drop amount ΔP (P1-P2) from the P1 pressure to the P2 pressure is larger or as the injection command period Tq is longer.

  In the subsequent step S70, the intersection of the reference straight line Lc and the approximate straight line La is calculated. The time indicated by this intersection almost coincides with the appearance time of the change point P1. Therefore, since the timing indicated by the intersection of the reference straight line Lc and the approximate straight line La has a high correlation with the injection start timing R1, the injection start timing R1 is calculated based on the intersection. In the subsequent step S80, the intersection of the reference straight line Ld and the approximate straight line Lb is calculated. Since the timing indicated by this intersection has a high correlation with the injection end timing R4, the injection end timing R4 is calculated based on the intersection.

  In the subsequent step S90, focusing on the fact that the slope Rα (see FIG. 2B) at which the injection rate increases and the slope of the approximate line La are highly correlated, the slope Rα of the increase in injection rate based on the slope of the approximate line La. Is calculated. Further, paying attention to the fact that the slope Rβ (see FIG. 2B) at which the injection rate falls and the slope of the approximate line Lb are highly correlated, the slope Rβ of the injection rate drop is calculated based on the slope of the approximate line Lb. . In the following step S100, paying attention to the fact that the pressure drop amount ΔP (P1-P2) from the P1 pressure to the P2 pressure and the maximum injection rate Rh (see FIG. 2B) are highly correlated, the pressure drop amount ΔP ( The maximum injection rate Rh is calculated based on P1-P2).

  According to the processing of FIG. 4 as described above, in steps S70 to S100 (injection state estimation means), the injection start timing R1, the injection end timing R4, the injection rate increase gradient Rα, the injection rate decrease gradient Rβ, and the maximum injection rate. Rh is calculated. Therefore, the injection rate waveform illustrated in FIG. 2B can be estimated.

  Next, a method of calculating the estimated supply pulsation waveform model Wm (see FIG. 5B) in step S20 will be described.

  As shown in FIG. 5A, the actual supply pulsation waveform Wa is zero pressure until the time point ta, the pressure gradually increases from the time point ta at which the superposition is started, and the pressure increase stops at the time point tb. It becomes a constant pressure. Therefore, it can be said that the model Wm (see FIG. 5B) of the supply pulsation waveform Wa can be estimated if the ta point at which superposition starts, the slope Pγ of the pressure increase from the ta point to the tb point, and the pressure increase amount ΔP can be estimated. . In the present embodiment, the model Wm is estimated by calculating the superposition start timing ta, the slope Pγ, and the increase amount ΔP by the following method.

  FIG. 6A is a test result showing that the slope Pγ (rising speed) of the supply pulsation waveform Wa has a correlation with the slope Pα (falling speed) of the descending waveform W (P1-P2). According to this test result, both slopes Pγ and Pα are in a proportional relationship, and the higher the descending speed of the descending waveform W (P1-P2), the faster the ascending speed of the supply pulsation waveform Wa. In addition, the several detected value shown in a figure shows each result of having tested by changing fuel temperature into -20 degreeC, 40 degreeC, and 80 degreeC. In the present embodiment in view of the test results, the proportional relationship formula is obtained by testing in advance, the slope Pα of the fall waveform W (P1-P2) is calculated from the detected sensor waveform W, and the calculated slope is calculated. The slope Pγ of the supply pulsation waveform Wa is calculated by substituting Pα into the proportional relationship equation. The slope Pα of the descending waveform W (P1-P2) may be the same as the slope of the approximate straight line La (see FIG. 2C).

  Next, a method for calculating the superposition start time ta will be described. First, the time (supply pulsation propagation time Ta) required from the descent start time Tsta to the superposition start time ta is calculated based on (Equation 1) in FIG. As shown in the schematic diagram of FIG. 7, L in Formula 1 is a path length from the position of the fuel pressure sensor 20 (more precisely, the position of the diaphragm portion 21a) to the discharge port 42a in the fuel supply path. In Equation 1, a is the propagation speed (sound speed) of the injection pulsation Ma and the supply pulsation Mb. Since the propagation speed a changes according to the fuel pressure at that time, the propagation speed a may be calculated based on the reference pressure Pbase described above, for example.

  L can be calculated based on the design value, a can be calculated based on the reference pressure Pbase, and Tsta can be calculated from the sensor waveform W. Therefore, if these values are substituted into Equation 1, the supply pulsation propagation time Ta can be calculated. Then, the superposition start time ta can be calculated by adding the superposition start time ta calculated in this way to the descent start time Tsta. FIG. 6B is a diagram showing a detected value obtained by testing the supply pulsation propagation time Ta that changes according to the fuel pressure (reference pressure Pbase), and a theoretical value of the supply pulsation propagation time Ta calculated by the above equation 1. Yes, it was confirmed by tests that the theoretical value almost coincided with the detected value.

  Next, a method for calculating the pressure increase amount ΔP will be described. The increase amount ΔP can be calculated based on (Expression 4) derived from (Expression 2) and (Expression 3) in FIG. The term of μ2A2V2 in (Expression 2) represents the flow rate (supply flow rate) of the fuel flowing into the high-pressure passage 11a by the supply pulsation Mb, and the term of μ0A0V0 in (Expression 2) represents the nozzle hole due to the injection pulsation Ma. This represents the flow rate of fuel flowing out from 11b (injection flow rate). In the equation, symbol a represents the speed of sound, μ represents a flow coefficient, V represents a flow velocity, and A represents a cross-sectional area. The subscripts 0, 1, and 2 of these symbols indicate values at the nozzle hole 11b, the high-pressure passage 11a, and the high-pressure pipe 42b, respectively.

  When trapezoidal injection is performed instead of the above-described micro injection (triangular injection), if the supply flow rate and the injection flow rate balance after reaching the maximum injection rate, the sensor waveform becomes a constant value (equilibrium pressure Peq). Then, it can be said that the time when the equilibrium pressure Peq is reached in the sensor waveform is the time when the superposition of the supply pulsation waveform is finished, and the value obtained by subtracting the equilibrium pressure Peq from the pressure at the time point P2 is the increase amount ΔP. I can say that. In view of this point, even in the case of triangular injection, the amount of increase ΔP can be calculated by calculating the equilibrium pressure Peq on the assumption that trapezoidal injection has been performed and subtracting the equilibrium pressure Peq from the pressure at the point of change P3.

  The value obtained by subtracting the outflow amount (μ0A0V0) from the inflow amount (μ2A2V2) into the diaphragm portion 21a of the fuel pressure sensor 20 represents the inflow amount (inflow balance) contributing to the fuel compression of the diaphragm portion 21a. The amount of increase ΔP can be calculated by multiplying the balance by K / aA1 (see (Equation 2) in FIG. 7).

  Further, since the supply pulsation Mb has not yet propagated during the period from the descent start timing Tsta to the superposition start timing ta in FIG. 5, the amount of fuel expansion in the high-pressure passage 11a is the same as the injection amount from the nozzle hole 11b. Match. Therefore, the equation shown in (Expression 3) in FIG. 7 is established. In the equation, aA1dt is the volume of fuel in the high-pressure passage 11a and represents the original volume before expansion, and Δv / v represents the expansion ratio. Then, if the left side of Equation 3 is substituted into Equation 2, Equation 4 is obtained. P1 in Equation 4 indicates the pressure at the descent start time Tsta (that is, the pressure in the common rail 42), and P2 indicates the pressure at the overlap start time ta.

  As described above, if the pressure P1 at the descent start timing Tsta and the pressure P2 at the overlap start timing ta are detected from the sensor waveform W and the detected pressure is substituted into the equation 4, the Δ pressure increase amount P can be calculated. FIG. 6C is a diagram showing a value obtained by testing the pressure rise amount and a theoretical value of the pressure rise amount ΔP calculated by the above equation 4. The test shows that the theoretical value substantially matches the detected value. Confirmed by

  FIG. 8 is a flowchart showing an example of a procedure for estimating the model Wm of the supply pulsation waveform Wa as described above, and is a subroutine process of step S20 in FIG.

  First, a correlation equation (correlation equation shown in FIG. 6A) showing the correlation between the slope Pα of the descending waveform W (P1-P2) and the slope Pγ of the supply pulsation waveform, the reference pressure Pbase, the supply pulsation propagation time Ta, A map showing the relationship (see FIG. 6B) and Equation 4 shown in FIG. 7 are stored in the memory in advance. In step S21 in FIG. 8, the slope Pα of the descending waveform W (P1-P2) is detected from the sensor waveform W, and the detected slope Pα is substituted into the correlation equation stored in the memory to supply the supply pulsation waveform. The slope of increase of Wa Pγ is calculated. In the correlation equation shown in FIG. 6A, y is a variable indicating the inclination Pα, and x is a variable indicating the inclination Pγ.

  In the subsequent step S22, the supply pulsation propagation time Ta is calculated based on the reference pressure Pbase with reference to a map showing the relationship with the supply pulsation propagation time Ta. In the subsequent step S23, the superposition start time ta is calculated by adding the supply pulsation propagation time Ta calculated in step S22 to the descent start time Tsta detected from the sensor waveform W.

  In the subsequent step S24, the values of the pressure P1 at the descent start timing Tsta and the pressure P2 at the overlap start timing ta detected from the sensor waveform W are substituted into the equation 4 in FIG. The pressure increase amount ΔP of the waveform is calculated. In the subsequent step S25, a model Wm of the supply pulsation waveform Wa illustrated in FIG. 5B is calculated based on the slope Pγ calculated in steps S21, S23, and S24, the superposition start timing ta, and the increase amount ΔP.

  As described above, according to the present embodiment, the model Wm of the supply pulsation waveform Wa is calculated by the process of FIG. 8, and the calculated model Wm is subtracted from the sensor waveform W to remove the supply pulsation waveform Wa. Therefore, the sensor after removing the supply pulsation waveform Wa is used to calculate the injection end timing R4 and the gradient Rβ of the injection rate drop using the straight line Lb approximating the rising waveform W (P3-P5) included in the sensor waveform. Using the approximate straight line Lb of the rising waveform calculated from the waveform W ′, the injection end timing R4 and the gradient Rβ of the injection rate drop are calculated. Therefore, the calculation accuracy of the injection end timing R4 and the gradient Rβ of the injection rate drop can be improved.

  In particular, paying attention to the fact that the slope Pα of the fall waveform W (P1-P2) and the slope Pγ of the supply pulsation waveform are correlated, the slope Pγ of the supply pulsation waveform is calculated from the slope Pα of the fall waveform W (P1-P2). Therefore, the calculation accuracy of the model Wm of the supply pulsation waveform Wa can be improved.

  Further, paying attention to the fact that the supply pulsation propagation time Ta changes according to the reference pressure Pbase, the superposition start time ta is calculated using the supply pulsation propagation time Ta calculated based on the reference pressure Pbase. The calculation accuracy of the model Wm can be improved.

  Further, based on the values of the pressure P1 at the descent start timing Tsta and the pressure P2 at the overlap start timing ta, it is noted that the pressure increase amount ΔP of the supply pulsation waveform can be calculated according to Equation 4, and the pressures P1 and P2 are Since the pressure increase amount ΔP is calculated based on this, the calculation accuracy of the model Wm of the supply pulsation waveform Wa can be improved.

(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 pulsation estimation unit according to the above embodiment, the superposition start time ta, the slope Pγ, and the increase amount ΔP of the supply pulsation waveform Wa are calculated to estimate the model Wm as the supply pulsation waveform. The calculation of ta and the amount of increase ΔP may be abolished and only the slope Pγ may be calculated, and the slope Pγ may be estimated as the supply pulsation waveform. In this case, the approximate straight line Lb calculated with respect to the sensor waveform W before correction is corrected according to the slope Pγ, and the injection end timing R4 and the injection end timing R4 in steps S80 and S90 in FIG. The injection rate lowering speed Rβ may be calculated.

  In the above embodiment, the sensor waveform W is corrected by estimating the model Wm when micro injection (triangular injection) is performed so that the injection rate starts to decrease at the same time as or before the maximum injection rate is reached. However, the sensor waveform W may be corrected using the model Wm even in the case of trapezoidal injection in which the reduction in the injection rate starts after the maximum injection rate is reached.

  In the above embodiment, the model Wm is estimated by calculating the superposition start timing ta, the slope Pγ, and the increase amount ΔP of the supply pulsation waveform Wa. However, a plurality of patterns of models are stored in advance, and the drop waveform W The optimum model may be selected from a plurality of patterns based on (P1-P2) (for example, descent start timing Tsta, inclination Pα, etc.).

  In the above embodiment, when calculating the ta point at which the supply pulsation waveform Wa starts to be superimposed on the sensor waveform W, the descent start time Tsta of the descent waveform W (P1-P2) and the overlap start time ta have a correlation. In view of this, the superposition start time ta is calculated based on the descent start time Tsta. In contrast, in view of the correlation between the timing at which the injection command signal shown in FIG. 2A is output (pulse-on timing t1) and the superposition start timing ta, the superposition start timing ta is based on the timing t1 at which the injection start is commanded. May be calculated.

  In the above embodiment shown in FIG. 1, the fuel pressure sensor 20 is mounted on the fuel injection valve 10, but the fuel pressure sensor according to the present invention is located in the fuel path from the discharge port 42a of the common rail 42 to the injection hole 11b. Any fuel pressure sensor arranged to detect the fuel pressure may be used. Therefore, for example, a fuel pressure sensor may be mounted on the high-pressure pipe 42b. That is, the high-pressure passage 11a of the fuel injection valve 10 and the internal passage of the high-pressure pipe 42b correspond to the “fuel supply passage”.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 11b ... Injection hole, 20 ... Fuel pressure sensor, 41 ... High pressure pump (fuel pump), 42 ... Common rail (accumulation container), 42a ... Discharge port, 42b ... High pressure piping (fuel piping), S10 ... Pressure Waveform acquisition means, S20 ... pulsation estimation means, S30 ... pulsation removal means, S70 to S100 ... injection state estimation means, P1 ... pressure at the start of descent of the descent waveform, P2 ... pressure at the end of descent of the descent waveform, Pγ ... slope of increase of supply pulsation waveform, t1 ... injection start command time, ta ... supply superposition start time of supply pulsation waveform, Tsta ... drop start time of drop waveform, W (P1-P2) ... drop waveform.

Claims (7)

A pressure accumulating container for accumulating fuel supplied from the fuel pump;
A fuel pipe connected to a discharge port of the pressure accumulating vessel;
A fuel injection valve having a nozzle hole for injecting fuel supplied from the pressure accumulating vessel through the fuel pipe;
A fuel pressure sensor that is provided in a fuel supply path from the discharge port to the nozzle hole, detects a fuel pressure, and outputs a sensor waveform representing a change in fuel pressure caused by fuel injection;
Applied to the fuel injection system with
With the current fuel injection, the supply pulsation generated during the injection period by the flow of fuel flowing into the fuel injection valve through the fuel pipe from the discharge port, pulsation estimation to estimate from the sensor waveform in the current fuel injection Means,
Pulsation removing means for correcting the sensor waveform so as to remove the waveform of the supply pulsation estimated by the pulsation estimating means from the sensor waveform in the current fuel injection ;
Injection state estimating means for estimating the fuel injection state from the nozzle hole based on the sensor waveform that has been corrected for removal by the pulsation removing means;
A fuel injection state detection device comprising:   2. The fuel injection state detection according to claim 1, wherein the pulsation estimating unit estimates the waveform of the supply pulsation based on a descending waveform of a portion of the sensor waveform in which a fuel pressure decreases as the injection starts. apparatus.   3. The fuel injection state detection device according to claim 2, wherein the pulsation estimation unit estimates an increase gradient of the supply pulsation waveform based on a decrease gradient of the decrease waveform.   The pulsation estimating means estimates a timing at which the supply pulsation waveform starts to be superimposed on the sensor waveform based on a descent start timing of the descent waveform or a timing instructed to start injection to the fuel injection valve. The fuel injection state detection device according to claim 2 or 3.   5. The fuel injection according to claim 4, wherein the pulsation estimating unit estimates a timing at which the supply pulsation waveform starts to be superimposed on the sensor waveform in accordance with a fuel pressure at a descent start timing of the descending waveform. State detection device.   The said pulsation estimation means estimates the pressure rise amount by the said supply pulsation based on the pressure at the time of descent | fall start, and the pressure at the time of descent | fall end among the said descent | fall waveforms. The fuel-injection state detection apparatus as described in one.   In the case of carrying out small injection that lowers the injection rate before reaching the maximum injection rate, the injection state estimating means increases the fuel pressure with the end of injection in the sensor waveform that has been corrected for removal by the pulsation removing means. The fuel injection state detection device according to any one of claims 1 to 6, wherein an injection end timing is calculated based on a rising waveform of a certain portion.

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