JP5024429B2 - Fuel injection state detection device - Google Patents

Description

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

  In order to accurately control the output torque and the emission state of the internal combustion engine, it is important to accurately control the injection state such as the injection amount of fuel injected from the fuel injection valve and the injection start timing. Therefore, in Patent Documents 1 to 3 and the like, a fuel pressure sensor detects a change in fuel pressure caused by injection in the fuel supply path from the discharge port of the common rail (distribution container) to the injection hole of the fuel injection valve. . Since the pressure waveform detected by the fuel pressure sensor has a high correlation with the injection rate waveform representing the change in the injection rate, the injection rate waveform is estimated based on the detected pressure waveform (detection waveform at the time of injection). The detection of the injection state such as the injection amount is intended. If the actual injection state can be detected in this way, the injection state can be accurately controlled based on the detected value.

  However, the detection waveform at the time of injection does not represent only the influence due to the injection, but also includes a waveform component caused by an influence other than the injection exemplified below. That is, when the fuel pump that pumps fuel in the fuel tank to the common rail is a pump that intermittently pumps fuel, such as a plunger pump, if pump pumping is performed during fuel injection, injection during the pump pumping period is performed. The time detection waveform is a waveform in which the pressure is increased as a whole. That is, the injection detection waveform W (see FIG. 3A) includes an injection pressure waveform component Wc that represents a change in fuel pressure due to injection (see FIG. 3D) and a waveform component that represents an increase in fuel pressure due to pumping. It can be said that Wb (see the solid line in FIG. 3C) is included.

  Even if such pump pumping is not performed during fuel injection, immediately after the fuel is injected, the fuel pressure in the entire injection system is reduced by that amount. Therefore, the injection detection waveform is a waveform in which the pressure is lowered as a whole. That is, the injection detection waveform W includes an injection pressure waveform component Wc that represents a change in fuel pressure due to injection, and a waveform component Wb ′ that represents a decrease in the fuel pressure in the entire injection system (see the dotted line in FIG. 3C). Can be said to be included.

  Therefore, in the invention described in Patent Document 3, the waveform detected by the fuel pressure sensor (non-injection cylinder sensor) corresponding to the fuel injection valve of the cylinder that is not injecting represents the change in the fuel pressure in the common rail (the fuel pressure in the entire injection system). Focusing on the expression, the injection pressure waveform component is obtained by subtracting the detection waveform from the non-injection cylinder sensor from the detection waveform detected by the fuel pressure sensor (injection cylinder sensor) corresponding to the fuel injection valve of the cylinder under injection. Is calculated. If the injection rate waveform is estimated based on the injection pressure waveform component thus obtained, the actual injection state can be detected with high accuracy.

JP 2010-3004 A JP 2009-57924 A Japanese Patent No. 4424395

  However, in the technique described in Patent Document 3 described above, it is necessary to generate a detection waveform from the detection value by the injection cylinder sensor and at the same time to generate a detection waveform from the detection value by the non-injection cylinder sensor. The processing load for generating is increased.

  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 that is capable of detecting the injection state with high accuracy and reducing the processing load. There is.

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

  In the first aspect of the invention, a fuel injection valve provided in each cylinder of the multi-cylinder internal combustion engine, a distribution container that accumulates fuel supplied from a fuel pump and distributes and distributes the fuel to the plurality of fuel injection valves, A fuel pressure that is provided for each of the fuel injection valves and that is generated in the fuel supply path from the discharge port of the distribution container to the injection hole as fuel is injected from the injection hole of the fuel injection valve It is assumed that the present invention is applied to a fuel injection system including a fuel pressure sensor that detects a change in the fuel pressure.

  And from the plurality of fuel pressure sensors, detection waveform acquisition means for acquiring a detection waveform at the time of injection, which is a waveform of a pressure detected by a fuel pressure sensor corresponding to a fuel injection valve during fuel injection, and the detection waveform at the time of injection Filter means for removing a high frequency component above a predetermined frequency and extracting a supply pressure waveform component representing a change in the distribution supply pressure in the distribution container; and subtracting the supply pressure waveform component from the detection waveform during injection Injection pressure waveform calculating means for calculating an injection pressure waveform component representing a change in fuel pressure due to injection, and injection state estimating means for estimating a fuel injection state from the injection hole based on the injection pressure waveform component. It is characterized by.

  Here, FIG. 3D illustrates an injection pressure waveform component Wc that represents a change in fuel pressure due to injection, and a solid line in FIG. 3C illustrates a waveform component Wb that represents an increase in fuel pressure due to pumping. The dotted line in FIG.3 (c) illustrates waveform component Wb 'showing the fuel pressure fall of the whole injection system. Thus, the injection pressure waveform component Wc is a waveform that changes abruptly in a short time compared to the waveform components Wb and Wb ′ due to the effects other than the injection due to pumping and the like, and has a higher frequency than Wb and Wb ′. It can be said that it is a waveform. Therefore, if high frequency components are removed from the injection detection waveform W (see FIG. 3A), the waveform components Wb, Wb ′ such as pump pressure can be extracted. The present inventor recalled the above-mentioned invention by paying attention to this point.

  In short, the invention described above essentially removes high-frequency components of a predetermined frequency or more from the detection waveform W during injection to extract supply pressure waveform components Wb, Wb ′ such as pump pumping (filter means) and supplies the supply pressure from the detection waveform W during injection. The injection pressure waveform component Wc is calculated by subtracting the waveform components Wb and Wb ′ (injection pressure waveform calculation means). Therefore, the injection pressure waveform component in which the waveform components Wb and Wb ′ such as pump pressure are removed from the detected waveform W during the injection without requiring the waveform of the fuel pressure detected by the non-injection cylinder sensor as described in Patent Document 3. Wc can be acquired.

  And according to the said invention which estimates a fuel-injection state based on the injection pressure waveform component Wc acquired in this way, an actual injection state can be detected accurately. Therefore, according to the above-described invention, it is possible to achieve both the detection of the injection state with high accuracy and the reduction in the load of the arithmetic processing for generating the detection waveform from the detection value of the fuel pressure sensor.

  In the invention of claim 2, the high frequency component removed by the filter means includes a waveform component from the start of fuel pressure decrease at the start of injection to the end of fuel pressure increase at the end of injection. A predetermined frequency is set.

  According to the invention, since the filter component removes the waveform component from the start of the fuel pressure decrease at the start of the injection to the end of the increase in the fuel pressure at the end of the injection, the supply pressure waveform components Wb and Wb ′ are accurately obtained. As a result, the estimation accuracy of the fuel injection state by the injection state estimating means can be improved.

  According to a third aspect of the present invention, the high frequency component removed by the filter means does not include a waveform component that increases in fuel pressure as fuel is pumped from the fuel pump to the distribution container. A predetermined frequency is set.

  As illustrated in FIG. 3C, among the waveform components Wb and Wb ′ due to influences other than injection, the fuel pressure increase waveform component Wb due to pumping represents a decrease in the fuel pressure in the entire injection system caused by the injection. The fuel pressure change is larger than the reduced fuel pressure waveform component Wb ′. Therefore, removing the fuel pressure increase waveform component Wb from the injection detection waveform W greatly contributes to improving the calculation accuracy of the injection pressure waveform component Wc compared to removing the fuel pressure decrease waveform component Wb ′. According to the above-described invention in view of this point, since the predetermined frequency is set so that at least the fuel pressure increasing waveform component Wb due to pumping is removed by the filter means, it is possible to promote improvement in calculation accuracy of the injection pressure waveform component Wc.

  The invention according to claim 4 is characterized by comprising noise filter means for removing a noise component higher than the predetermined frequency from the injection detection waveform.

  Here, as illustrated in FIG. 3A, the injection detection waveform W includes noise N due to various factors. On the other hand, according to the above invention, the injection detection waveform used for the calculation of the injection pressure waveform calculating means can be made the waveform from which the noise N is removed by the noise filter means. Therefore, the calculation accuracy of the injection pressure waveform component by the injection pressure waveform calculation means can be improved.

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 the fuel injection rate caused by the injection command signal, and (c) is detected by the fuel pressure sensor shown in FIG. The figure which shows the injection pressure waveform component Wc based on a waveform. (A) is an injection detection waveform W, (b) is an injection detection waveform W after noise removal, (c) is a supply pressure waveform component Wb, and (d) is an injection pressure waveform component Wc. The functional block diagram which shows the various means for calculating the injection pressure waveform component Wc. The flowchart which shows the process sequence which calculates the injection pressure waveform component Wc.

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

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

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

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

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

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

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

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

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

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

  Here, the fuel pressure (fuel pressure) in the high-pressure passage 11a decreases with the start of fuel injection from the nozzle hole 11b, and the fuel pressure increases with the end of injection. That is, it can be said that the change in the fuel pressure and the change in the injection rate (injection amount injected per unit time) have a correlation, 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 detection waveform that is a waveform of the pressure detected by the fuel pressure sensor 20 mounted on the fuel injection valve 10 during fuel injection, and an injection rate waveform that represents a change in the fuel injection rate applied to the fuel injection valve 10 The correlation will be described with reference to FIG.

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

  FIG. 2 (b) shows a change in fuel injection rate (injection rate waveform) from the nozzle hole 11b caused by the injection command, and FIG. 2 (c) is provided in the fuel injection valve 10 during fuel injection. The change of the detection pressure which arises with the change of the injection rate detected by the fuel pressure sensor 20 is shown. FIG. 2C shows an injection pressure waveform component Wc, which will be described later, but is simply referred to as “injection pressure waveform” here.

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

  As described above, the correlation between the injection 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 injection pressure waveform.

  Here, the pressure detection signal output from the fuel pressure sensor 20 corresponding to the fuel injection valve 10 during fuel injection to the ECU 30 is A / D converted by the ECU 30, and a waveform representing the change in the digital signal (detection at injection) The waveform W) is the waveform illustrated in FIG. This injection detection waveform W does not represent only the influence of the injection, but also includes a waveform component that represents a change in the pressure of the fuel distributed and supplied from the common rail 42 to the fuel injection valve 10.

  That is, if pump pumping by the high pressure pump 41 is performed during fuel injection, the detection waveform W during injection during the pump pumping period becomes a waveform in which the pressure is increased as a whole. That is, the injection detection waveform W (see FIG. 3A) includes an injection pressure waveform component Wc that represents a change in fuel pressure due to injection (see FIG. 3D) and a waveform component that represents an increase in fuel pressure due to pumping. It can be said that Wb (see the solid line in FIG. 3C) is included.

  Even if such pump pumping is not performed during fuel injection, immediately after fuel injection, the entire injection system (that is, the common rail 42, the high-pressure pipe 42b, the high-pressure passage 11a, etc.) The fuel pressure of the entire fuel supply path including the fuel pressure decreases. Therefore, the injection detection waveform W is a waveform in which the pressure is lowered as a whole. That is, the injection detection waveform W includes an injection pressure waveform component Wc that represents a change in fuel pressure due to injection, and a waveform component Wb ′ that represents a decrease in the fuel pressure in the entire injection system (see the dotted line in FIG. 3C). Can be said to be included.

  In short, since the detection waveform W at the time of injection is affected by the distribution supply pressure PC and the fuel pressure change in the entire injection system, the waveform components Wb and Wb ′ (corresponding to the supply pressure waveform components) are detected from the detection waveform W at the time of injection. If subtracted, the influence of the change in the distribution supply pressure PC and the overall fuel pressure in the system is removed from the detection waveform W during injection. The solid line in FIG. 3D shows the waveform component (injection pressure waveform component Wc) obtained by subtracting in this way.

  Therefore, in the present embodiment, as described below with reference to FIG. 4, the waveform components Wb and Wb ′ due to the influence other than the injection are calculated, and the waveform components Wb and Wb ′ are subtracted from the detection waveform W at the time of injection to thereby calculate the injection pressure waveform. The component Wc is calculated.

  As shown in FIG. 4, the ECU 30 includes an A / D converter 31, a first low-pass filter 32, a second low-pass filter 33, a subtracter 34, and an injection rate waveform calculator 35 described below. The A / D converter 31 performs A / D conversion on the pressure detection signal output from the fuel pressure sensor 20 to the ECU 30, and generates an injection detection waveform W shown in FIG.

  The first low-pass filter 32 (noise filter means) removes various noises N (FIG. 3A) such as electrical noise included in the ejection detection waveform W. Specifically, the cutoff frequency is set to 3 kHz, for example, and frequency components of 3 kHz or higher in the ejection detection waveform W are cut to extract frequency components of less than 3 kHz. Incidentally, FIG. 3B shows a detection waveform Wa at the time of injection in a state where noise is removed by the first low-pass filter 32.

  The second low-pass filter 33 (filter means) removes a high frequency component of a predetermined frequency (for example, 500 Hz) or more included in the ejection detection waveform Wa, and extracts a low frequency component less than the predetermined frequency. The predetermined frequency (cutoff frequency) is set so that the injection pressure waveform component Wc is included in the high frequency component removed by the second low-pass filter 33. Specifically, in the injection pressure waveform component Wc, a frequency lower than the frequency of the waveform component having a half-wavelength from the change point P1 generated at the start of injection to the change point P5 generated at the end of injection, The predetermined frequency is set.

  Further, the predetermined frequency is set so that the high frequency component removed by the second low pass filter 33 does not include the waveform component Wb representing the increase in the supply pressure caused by the pumping. Further, the high-frequency component removed by the second low-pass filter 33 does not include a waveform component Wb ′ that represents a decrease in the fuel pressure in the entire injection system corresponding to the injection amount, and a fluctuation waveform described below. Is set to

  That is, when the pressure in the common rail 42 (rail pressure) is controlled by the high-pressure pump 41, a pressure reducing valve (not shown) or the like, a waveform component that fluctuates in a longer cycle than the detection waveform Wa at the time of injection due to a decrease in controllability. (Long-cycle waveform component) is included in the detection waveform W upon injection. For example, immediately after the target rail pressure changes, the above-described long-cycle fluctuation occurs in a transition period in which the actual rail pressure is controlled to match the target rail pressure. Note that this long-period waveform component is assumed to have the same shape as the waveform component Wb ′ described above, and is an example of the supply pressure waveform component.

  As described above, according to the second low-pass filter 33 in which the predetermined frequency is set as described above, the injection pressure waveform component Wc included in the injection detection waveform Wa is removed, and the waveform components Wb and Wb ′ are extracted. The Rukoto.

  The subtractor 34 (injection pressure waveform calculating means) calculates the waveform components Wb and Wb ′ due to the influence other than the injection extracted by the second low-pass filter 33 from the detection waveform Wa at the time of injection from which noise has been removed by the first low-pass filter 32. Perform subtraction and subtraction operations. Thereby, the injection pressure waveform component Wc shown in FIG. 3D is calculated. The injection rate waveform calculator 35 (injection state estimation means) calculates an injection rate waveform from the injection pressure waveform component Wc calculated by the subtractor 34 based on the correlation between the pressure waveform and the injection rate waveform described above with reference to FIG. Calculate.

  FIG. 5 is a flowchart showing a procedure from the injection detection waveform W to the calculation of the injection rate waveform as described above. First, in step S10 (detection waveform acquisition means), the microcomputer included in the ECU 30 performs fuel injection. An injection detection waveform W detected by the fuel pressure sensor 20 corresponding to the fuel injection valve 10 of the middle cylinder # 1 is acquired.

  In the subsequent step S20, the first low-pass filter 32 performs a process of removing the noise N included in the injection detection waveform W from which noise has been removed. In subsequent step S30, the second low-pass filter 33 removes the injection pressure waveform component Wc from the injection detection waveform Wa, and extracts the waveform components Wb, Wb 'due to effects other than the injection.

  In subsequent step S40, the subtractor 34 calculates the injection pressure waveform component Wc by subtracting the waveform components Wb and Wb 'from the injection detected waveform Wa from which noise has been removed. In subsequent step S50, the injection rate waveform calculator 35 calculates an injection rate waveform based on the injection pressure waveform component Wc.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) The injection pressure waveform component Wc is removed by the second low-pass filter 33 and the waveform components Wb and Wb ′ are extracted from the detection waveform W at the time of injection detected by the fuel pressure sensor 20 corresponding to the cylinder # 1 during fuel injection. Therefore, the waveform components Wb and Wb ′ due to the influence other than the injection can be acquired without using the fuel pressure sensor 20 corresponding to the non-injection cylinder # 2. Then, since the acquired waveform components Wb and Wb ′ are subtracted from the detection waveform W during injection to calculate the injection pressure waveform component Wc, it is necessary to generate a detection waveform by the fuel pressure sensor 20 corresponding to the non-injection cylinder # 2. The injection pressure waveform component Wc can be acquired. Therefore, it is possible to achieve both the detection of the injection pressure waveform component Wc representing the actual injection state with high accuracy and the reduction of the calculation processing load of the ECU 30 that generates the detection waveform from the detection value of the fuel pressure sensor 20.

  Further, since it is unnecessary to simultaneously acquire detection values from both the fuel pressure sensor 20 corresponding to the fuel cylinder # 1 and the fuel pressure sensor 20 corresponding to the non-injection cylinder # 2, the ECU 30 communicates with both the sensors simultaneously. Can be made unnecessary. Therefore, complication of communication processing between the ECU 30 and the fuel pressure sensor 20 can be avoided, and the communication processing load on the ECU 30 can be reduced.

  (2) The cutoff frequency of the second low-pass filter 33 is such that at least a portion of the injection pressure waveform component Wc from the change point P1 generated at the start of injection to the change point P5 generated at the end of injection is removed. Is set to Therefore, the main part of the injection pressure waveform component Wc can be reliably removed, and the extraction accuracy of the waveform components Wb and Wb ′ due to the influence other than the injection can be improved. As a result, the calculation accuracy of the injection pressure waveform component Wc can be improved, and consequently the calculation accuracy of the injection pressure waveform component Wc can be improved.

  (3) The cut-off frequency of the second low-pass filter 33 is set so that the waveform component Wb representing the increase in the supply pressure PC caused by pumping is not removed. Therefore, the extraction accuracy of the supply pressure waveform component Wb can be improved.

  (4) Moreover, even if pump pumping is not performed during fuel injection, the fuel pressure in the entire injection system is reduced by the amount of fuel injection. The cut-off frequency of the second low-pass filter 33 is set so that the waveform component Wb ′ representing the decrease in the fuel pressure in the entire injection system is not removed. Therefore, it is possible to improve the extraction accuracy of the waveform component Wb ′.

  (5) Since the first low-pass filter 32 for noise removal is provided in addition to the second low-pass filter 33, the noise N due to various factors can be sufficiently removed from the detection waveform W at the time of injection used for the calculation of the subtractor 34. Therefore, the calculation accuracy of the injection pressure waveform component Wc by the subtractor 34 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 above embodiment, the digital signal after A / D conversion by the A / D converter 31 is used as a target to detect the injection pressure waveform component Wc from the detection waveform W during injection using the digital filter (second low-pass filter 33). However, the injection pressure waveform component Wc may be removed from the detection waveform W during injection using an analog filter (not shown) for the analog signal before A / D conversion. . Similarly, the first low-pass filter 32 may be changed to an analog filter instead of a digital filter.

  In the above embodiment, the first low-pass filter 32 for noise removal is provided separately from the second low-pass filter 33. However, the first low-pass filter 32 is eliminated and the second low-pass filter 33 is also used for noise removal. May be.

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

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 11b ... Injection hole, 20 ... Fuel pressure sensor, 32 ... 1st low-pass filter (noise filter means), 33 ... 2nd low-pass filter (filter means), 34 ... Subtractor (injection pressure waveform calculation means) 35 ... Injection rate waveform calculator (injection state estimation means), 42 ... Common rail (distribution container), S10 ... Detection waveform acquisition means, S40 ... Injection pressure waveform calculation means, S50 ... Injection rate waveform calculator.

Claims (4)

A fuel injection valve provided in each cylinder of the multi-cylinder internal combustion engine;
A distribution container for accumulating and supplying fuel supplied from a fuel pump to the plurality of fuel injection valves;
Fuel that is provided for each of the plurality of fuel injection valves and that is generated in the fuel supply path from the outlet of the distribution container to the injection hole as fuel is injected from the injection hole of the fuel injection valve A fuel pressure sensor for detecting a change in pressure;
Applied to the fuel injection system with
A detection waveform acquisition means for acquiring a detection waveform during injection, which is a waveform of a pressure detected by a fuel pressure sensor corresponding to a fuel injection valve during fuel injection among the plurality of fuel pressure sensors;
Filter means for removing a high frequency component of a predetermined frequency or more from the detection waveform at the time of injection and extracting a supply pressure waveform component representing a change in the distribution supply pressure in the distribution container;
An injection pressure waveform calculating means for subtracting the supply pressure waveform component from the injection detection waveform to calculate an injection pressure waveform component representing a fuel pressure change due to injection;
Injection state estimation means for estimating a fuel injection state from the nozzle hole based on the injection pressure waveform component;
A fuel injection state detection device comprising:   The predetermined frequency is set so that the high frequency component removed by the filter means includes a waveform component from when the fuel pressure decrease starts at the start of injection until the fuel pressure increase ends at the end of injection. The fuel injection state detection device according to claim 1.   The predetermined frequency is set so that a high-frequency component removed by the filter means does not include a waveform component that increases in fuel pressure as fuel is pumped from the fuel pump to the distribution container. The fuel injection state detection device according to claim 1 or 2.   The fuel injection state detection device according to any one of claims 1 to 3, further comprising noise filter means for removing a noise component having a frequency higher than the predetermined frequency from the detection waveform at the time of injection. .

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