JP5910522B2 - Fuel injection control device - Google Patents

Description

  The present invention relates to a fuel injection control device that is applied to a fuel injection system that includes a fuel injection valve provided in each cylinder of a multi-cylinder internal combustion engine and that performs fuel injection using high-pressure fuel stored in a stock pressure vessel. .

  In a fuel injection system that distributes and supplies fuel from a common rail (stock pressure vessel) to a plurality of fuel injection valves, when fuel is injected from the fuel injection valve, the fuel pressure inside the fuel injection valve changes in accordance with the change in the injection rate. . Therefore, a fuel pressure sensor mounted on each fuel injection valve detects a fluctuation waveform of fuel pressure at the time of injection, and estimates a waveform indicating a change in injection rate based on the detected fluctuation waveform. Further, the actual injection state such as the injection start timing, the injection end timing, and the injection amount is detected from the waveform indicating the estimated injection rate change, and the operation of the fuel injection valve is controlled based on the detected injection state. ing.

  However, the fluctuation in pressure detected by the fuel pump from the fuel pump is superimposed as a disturbance on the fluctuation waveform detected by the fuel pressure sensor. Therefore, in order to detect the actual injection state with high accuracy, it is necessary to extract the fluctuation waveform of the fuel pressure caused by the injection from the fluctuation waveform detected by the fuel pressure sensor, excluding the fluctuation component caused by the fuel pumping. is there.

  Therefore, Patent Document 1 detects a fluctuation waveform in a non-injection cylinder in which only a pressure fluctuation component due to fuel pumping is generated, and subtracts the fluctuation waveform detected in the non-injection cylinder from the fluctuation waveform detected in the injection cylinder. The fluctuation waveform of the resulting fuel pressure is extracted.

Japanese Patent No. 4678397

  In Patent Document 1, the fluctuation waveform of fuel pressure caused by injection is extracted by subtracting the average of disturbance components detected for a plurality of non-injection cylinders from the fluctuation waveform detected for the injection cylinder. . However, in consideration of changes in characteristics due to variations in hardware and aging, etc., non-injection cylinders whose hardware characteristics are closer to the injection cylinder than the average of disturbance components detected for a plurality of non-injection cylinders. If the disturbance component detected in this way is used, the extraction accuracy of the fluctuation waveform of the fuel pressure resulting from the injection may be higher.

  In view of the above circumstances, the present invention can optimally combine an injection cylinder that detects a fluctuation waveform and a non-injection cylinder that detects a disturbance component, and extract a fluctuation waveform of fuel pressure resulting from injection with high accuracy. The main object is to provide a simple fuel injection control device.

  In order to solve the above-mentioned problems, a first aspect of the present invention is directed to a livestock pressure container that retains high pressure fuel under pressure, a fuel pump that pumps fuel to the livestock pressure container, and a cylinder of a multi-cylinder internal combustion engine. A fuel injection valve that injects high-pressure fuel that is provided every time and is stored in the animal pressure vessel, and detects a fuel pressure in each fuel passage from the animal pressure vessel to the injection port of each fuel injector. A fuel injection control device applied to a fuel injection system including a fuel pressure sensor, wherein an injection sensor waveform is detected based on an output of the fuel pressure sensor corresponding to an injection cylinder of the cylinders A detection means, a non-injection sensor waveform detection means for detecting a non-injection sensor waveform based on an output of the fuel pressure sensor corresponding to a non-injection cylinder of the cylinders, and a combination of the non-injection cylinder and the injection cylinder. Together Non-injection cylinder selection means for selecting a non-injection cylinder to be applied, and the non-injection cylinder combined with the injection cylinder from the injection-time sensor waveform detected by the injection-time sensor waveform detection means for the injection cylinder. On the other hand, the non-injection sensor waveform detection means subtracts the non-injection sensor waveform detected at the same time as the injection sensor waveform to extract an injection waveform that represents pressure fluctuation caused by injection in the injection cylinder. A non-injection cylinder selection unit, wherein the non-injection cylinder selection unit is detected for each of the non-injection cylinders by the non-injection sensor waveform detection unit during steady operation of the engine. A non-injection sensor wave detected by the non-injection sensor waveform detection means for the injection cylinder from the sensor waveform when the injection cylinder is in a non-injection state. , The closest to select the non-ejection time sensor waveform, non-ejection time sensor waveform selected to select the non-injection cylinder that is detected.

  According to the first aspect of the present invention, fuel is pumped from the fuel pump to the animal pressure vessel. The high-pressure fuel held in the animal pressure vessel is injected by a fuel injection valve provided in each cylinder. The fuel pressure in each fuel passage from the stock pressure vessel to the injection port of the fuel injection valve of each cylinder is detected by a fuel pressure sensor.

  Further, the injection sensor waveform detection means detects an injection sensor waveform in which the pressure fluctuation caused by the fuel pump is superimposed on the pressure fluctuation caused by the injection based on the output of the fuel pressure sensor corresponding to the injection cylinder. . On the other hand, the non-injection sensor waveform detection means detects a non-injection sensor waveform that represents a pressure fluctuation accompanying pumping by the fuel pump, based on the output of the fuel pressure sensor corresponding to the non-injection cylinder.

  Here, if the non-injection sensor waveform can be detected simultaneously with the injection sensor waveform for the same cylinder, the non-injection sensor waveform is the optimum non-injection representing the pressure fluctuation component accompanying the pressure feed superimposed on the injection sensor waveform. It becomes a sensor waveform at the time of injection. However, the sensor waveform during injection and the sensor waveform during non-injection cannot be detected simultaneously for the same cylinder. Therefore, by using the non-injection sensor waveform detected at the same time as the injection sensor waveform for the non-injection cylinder combined with the injection cylinder, the pressure fluctuation component accompanying the pressure feed is removed from the injection sensor waveform, and the injection is performed. A waveform at the time of injection representing the resulting pressure fluctuation is extracted.

  However, non-injection sensor waveforms also vary due to changes in characteristics due to variations in hardware and aging. Therefore, during steady operation of the internal combustion engine with a constant fuel supply pressure and supply amount, the non-injection sensor waveform detected for each non-injection cylinder is detected when the injection cylinder enters a non-injection state. The non-injection sensor waveform that is closest to the non-injection sensor waveform is selected. The selected non-injection cylinder with the detected non-injection sensor waveform is selected as a non-injection cylinder to be combined with the injection cylinder. That is, the fuel injection valve installed in the injection cylinder for detecting the sensor waveform during injection and the non-injection cylinder installed with the fuel injection valve having the closest hardware characteristics are selected as the non-injection cylinders to be combined with the injection cylinder. .

  Therefore, an injection cylinder that detects a sensor waveform during injection in which a pressure variation due to pressure feeding is superimposed on a pressure variation caused by injection, and a non-injection cylinder that detects a sensor waveform during non-injection that represents a pressure variation component due to pressure feeding. Can be combined optimally. As a result, the fluctuation of the fuel pressure caused by the injection can be extracted with high accuracy from the sensor waveform during the injection.

The figure which shows the outline of a fuel-injection system. The figure which shows the change of the injection rate and fuel pressure corresponding to an injection command signal. The time chart which shows the sensor waveform at the time of injection, and the sensor waveform at the time of non-injection. The figure which shows the difference of the sensor waveform at the time of injection, and the sensor waveform at the time of non-injection. The flowchart which shows the process sequence which determines the combination of an injection cylinder and a non-injection cylinder.

  Hereinafter, an embodiment in which a fuel injection control device is mounted on a vehicle will be described with reference to the drawings. FIG. 1 shows a configuration of a fuel injection system to which the fuel injection control device according to the present embodiment is applied. This fuel injection system is assumed to be mounted on a three-cylinder diesel engine (multi-cylinder internal combustion engine). This fuel injection system includes a common rail 42 (stock pressure vessel) that holds high-pressure fuel under pressure, a fuel pump 41 that pumps fuel to the common rail 42, and fuel provided in each cylinder # 1 to # 3 of the engine. An injection valve 10 and a fuel pressure sensor 20 that sequentially detects the fuel pressure in each fuel passage from the common rail 42 to the injection port of each fuel injection valve 10 are provided.

  The fuel tank 40 is a tank for storing fuel (light oil) supplied to the cylinders # 1 to # 3 of the engine. The fuel in the fuel tank 40 is pumped to the common rail 42 and accumulated and held by a fuel pump 41 driven in conjunction with the crankshaft of the engine. The pressure in the common rail 42 becomes the fuel supply pressure Pc supplied to the fuel injection valve 10 of each cylinder. The fuel accumulated in the common rail 42 is distributed and supplied to the fuel injection valve 10 of each cylinder. The fuel injection valve 10 of each cylinder sequentially injects fuel in a preset order.

  The fuel injection valve 10 includes a body 11, a needle valve 12, and an actuator 13 such as an electromagnetic coil or a piezo element. The body 11 is formed with a high-pressure passage 11a, a low-pressure passage 11d, and an injection hole 11b (injection port) connected to the high-pressure passage 11a. The fuel supplied from the common rail 42 is injected from the injection hole 11b through the high-pressure passage 11a. The needle valve 12 is accommodated inside the body and opens and closes the nozzle hole 11b.

  Further, the body 11 is formed with a back pressure chamber 11 c for applying a back pressure to the needle valve 12. 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 11 a and the low pressure passage 11 d and the back pressure chamber 11 c is switched by the control valve 14.

  Specifically, when the actuator 13 is energized, the control valve 14 is pushed down to the nozzle hole 11b side. As a result, the back pressure chamber 11c communicates with the low pressure passage 11d, so that the fuel pressure in the back pressure chamber 11c decreases and the back pressure that presses the needle valve 12 toward the nozzle hole 11b decreases. As a result, the seat surface 12a of the needle valve 12 is separated from the seat surface 11e of the body 11 formed so as to be connected to the injection hole 11b, so that fuel is injected from the injection hole 11b.

  On the other hand, when the power supply to the actuator 13 is turned off, the control valve 14 is pushed up to the actuator 13 side. As a result, the back pressure chamber 11c communicates with the high pressure passage 11a, so that the fuel pressure in the back pressure chamber 11c increases, and the back pressure that presses the needle valve 12 toward the nozzle hole 11b increases. As a result, the seat surface 12a of the needle valve 12 is seated on the seat surface 11e of the body 11, so that fuel injection from the injection hole 11b is stopped.

  Therefore, when the drive period of the actuator 13 is controlled by the command signal, the injection amount of the fuel injected from the nozzle hole 11b is controlled.

  The fuel pressure sensor 20 is mounted on each fuel injection valve 10 and includes a stem 21 (a strain generating body), a pressure sensor element 22, and a communication circuit 22a. The stem 21 is attached to the body 11 and has a diaphragm portion 21a. The diaphragm portion 21a 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 transmits a pressure signal corresponding to the elastic deformation amount of the diaphragm portion 21a from the communication circuit 22a to the ECU 30.

  The ECU 30 (fuel injection control device) is configured as a microcomputer including a CPU, a ROM, a RAM, an I / O, a bus line connecting these, and the like. The ECU 30 calculates the target injection state based on the accelerator pedal operation amount, the engine load, the engine speed, and the like. For example, the optimal injection state corresponding to the engine load and the engine speed is stored as an injection state map. Based on the current engine load and engine speed, the target injection state is calculated with reference to the injection state map. Further, command signals Tq, t1 (see FIG. 2A) corresponding to the calculated target injection state are set based on injection rate parameters td, te, Rα, Rβ, Rmax, which will be described later, and output to the fuel injection valve 10. Thus, the operation of the fuel injection valve 10 is controlled.

  The ECU 30 also functions as an in-injection sensor waveform detection means, a non-injection sensor waveform detection means, a non-injection cylinder selection means, and an in-injection waveform extraction means, which will be described later, by the CPU executing a program stored in the ROM. Is realized.

  Further, the ECU 30 is based on an injection waveform W (refer to FIG. 2C) representing a pressure variation caused by injection, and an injection rate waveform representing a variation of the fuel injection rate with respect to time (refer to FIG. 2B). Is calculated to detect the injection state. This injection waveform W is detected by an injection waveform extraction means, which will be described later, based on a value detected by the fuel pressure sensor 20. The ECU 30 learns injection rate parameters Rα, Rβ, Rmax that specify the detected injection rate waveform (injection state), and specifies the correlation between the injection command signal (drive period Tq and drive start timing t1) and the injection state. The injection rate parameters td and te are learned.

  Specifically, the average fuel pressure of the portion of the waveform at the time of injection W until the fuel pressure starts decreasing with the start of injection is calculated as the reference pressure Pbase. Further, in the waveform W at the time of injection, a descending approximate line Lα that approximates a descending waveform from the inflection point P1 at which the fuel pressure drop starts at the start of the injection to the inflection point P2 at which the descent ends by a least square method or the like. Is calculated. Then, a time (a crossing time LBα between Lα and Bα) that is the reference value Bα in the descending approximate straight line Lα is calculated. Focusing on the fact that the intersection time LBα and the injection start time R1 are highly correlated, the injection start time R1 is calculated based on the intersection time LBα. For example, a timing that is a predetermined delay time Cα before the intersection timing LBα may be calculated as the injection start timing R1.

  Further, in the waveform W at the time of injection, the rising approximate line Lβ approximating the rising waveform from the inflection point P3 at which the fuel pressure rises with the end of the injection to the inflection point P5 at which the descent ends is approximated by a least square method or the like. Is calculated. Then, a time (intersection time LBβ between Lβ and Bβ) that is the reference value Bβ in the rising approximate straight line Lβ is calculated. Focusing on the fact that the intersection timing LBβ and the injection end timing R4 are highly correlated, the injection end timing R4 is calculated based on the intersection timing LBβ. For example, a timing that is a predetermined delay time Cβ before the intersection timing LBβ may be calculated as the injection end timing R4.

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

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

  Further, the pressure corresponding to the intersection of the descending approximate straight line Lα and the ascending approximate straight line Lβ is calculated as the intersection pressure Pαβ, and the pressure difference ΔPγ between the reference pressure Pbase and the intersection pressure Pαβ is calculated. Focusing on the fact that the pressure difference ΔPγ and the maximum injection rate Rmax are highly correlated, the maximum injection rate Rmax is calculated based on the pressure difference ΔPγ. Specifically, the maximum injection rate Rmax is calculated by multiplying the pressure difference ΔPγ by the correlation coefficient Cγ. However, in the case of small injection in which the pressure difference ΔPγ is less than the predetermined value ΔPγth, Rmax = ΔPγ × Cγ is set as described above, whereas in the case of large injection in which ΔPγ ≧ ΔPγth, it is set in advance The value (set value Rγ) is calculated as the maximum injection rate Rmax.

  The “small injection” is assumed to be an injection in which the needle valve 12 starts to be lifted down before the injection rate reaches Rγ. The fuel is throttled by the seat surfaces 11e and 12a, and the injection amount The injection rate when is limited is the maximum injection rate Rmax. On the other hand, the “large injection” is assumed to be an injection in which the needle valve 12 starts to be lifted down after the injection rate reaches Rγ, and the fuel is throttled at the injection hole 11b to limit the injection amount. The injection rate when the fuel injection is being performed becomes the maximum injection rate Rmax. In short, when the valve opening state is continued even after the driving period Tq is sufficiently long and the maximum injection rate is reached, the injection rate waveform becomes trapezoidal as shown in FIG. On the other hand, in the case of small injection that starts the valve closing operation before reaching the maximum injection rate, the injection rate waveform is a triangle.

  As described above, the injection rate parameters td, te, Rα, Rβ, and Rmax can be calculated from the waveform W during injection. Based on the learned values of the injection rate parameters td, te, Rα, Rβ, and Rmax, an injection rate waveform (see FIG. 2B) corresponding to the injection command signal (see FIG. 2A) is calculated. be able to. Further, an injection rate parameter Q representing the injection amount can be calculated from the calculated area of the injection rate waveform (see halftone dot hatching in FIG. 2B).

  Next, the injection sensor waveform detection means, the non-injection sensor waveform detection means, the non-injection cylinder selection means, and the injection waveform extraction means will be described. Here, cylinder # 1 is an injection cylinder (predetermined injection cylinder), and cylinders # 2 and # 3 are non-injection cylinders. The injection cylinder is a cylinder in which the fuel injection valve 10 provided in the cylinder injects fuel, and the non-injection cylinder is the fuel injection valve 10 provided in the cylinder injecting fuel. There are no cylinders.

  The injection sensor waveform detection means detects the injection sensor waveform Wi based on the output of the fuel pressure sensor 20 corresponding to the injection cylinder among the cylinders # 1 to # 3. The in-injection sensor waveform Wi shown in FIG. 3A is an in-injection sensor waveform detected for the cylinder # 1 when the injection is performed in the cylinder # 1. The injection sensor waveform Wi is a fuel pressure fluctuation waveform in which a fuel pressure fluctuation caused by fuel pump 41 is superimposed on a fuel pressure fluctuation caused by injection. That is, the injection sensor waveform Wi is a fluctuation waveform of the fuel pressure in which a disturbance is superimposed on the injection waveform W.

  The non-injection sensor waveform detection means detects the non-injection sensor waveform based on the output of the fuel pressure sensor 20 corresponding to the non-injection cylinder among the cylinders # 1 to # 3. The non-injection sensor waveform is a fluctuation waveform that generally represents fluctuations in the fuel pressure associated with the fuel pump 41 being pumped. The non-injection sensor waveforms Wb and Wc shown in FIGS. 3C and 3D are detected simultaneously with the injection sensor waveform Wi for the cylinders # 2 and # 3 when the cylinder # 1 performs the injection. This is a non-injection sensor waveform. Since it is detected at the same time as the sensor waveform Wi at the time of injection, the fluctuation of the fuel pressure due to pressure feeding appears in the sensor waveforms Wb and Wc at the time of non-injection at the timing when the fuel pressure fluctuation accompanying pressure feeding appears in the sensor waveform Wi during injection. The non-injection sensor waveform Wa shown in FIG. 3B is detected for the cylinder # 1 when the cylinder # 1 is in the non-injection state, that is, when injection is performed in the cylinder # 2 or # 3. It is a sensor waveform at the time of non-injection.

  The non-injection sensor waveform for the non-injection cylinder combined with the injection cylinder # 1 is determined from the injection-time sensor waveform Wi detected by the injection-time sensor waveform detection means for the injection cylinder # 1. The non-injection sensor waveform detected at the same time as the injection sensor waveform Wi by the detection means is subtracted. That is, the disturbance waveform component accompanying pressure feeding is removed from the injection sensor waveform Wi, and the injection waveform W representing the pressure fluctuation caused by the injection in the injection cylinder # 1 is extracted. The combination of the injection cylinder and the non-injection cylinder is determined by the non-injection cylinder selection means.

  The non-injection cylinder selection means selects a non-injection cylinder to be combined with the injection cylinder # 1 from the non-injection cylinders # 2 and # 3. Non-injection sensor waveforms also vary due to changes in characteristics due to variations in hardware and aging. Accordingly, the non-injection cylinder selection means is related to the influence of the fuel pump 41 by the fuel pumping, and the non-injection cylinder selection means is provided with the fuel injection valve 10 provided in the injection cylinder # 1 and the fuel injection valve 10 with similar hardware characteristics. Select the injection cylinder.

  Specifically, the non-injection sensor waveforms Wa, Wb, and Wc are detected during steady operation of the engine with the fuel injection amount Q and supply pressure Pc constant, that is, during steady running. The non-injection sensor waveforms Wb and Wc detected for each of the non-injection cylinders # 2 and # 3 are detected for the injection cylinder # 1 when the injection cylinder # 1 is in the non-injection state. The non-injection sensor waveform that most closely approximates the injection sensor waveform Wa is selected.

  Here, a method of selecting the non-injection sensor waveform closest to the non-injection sensor waveform Wa from the non-injection sensor waveforms Wb and Wc will be described. Since the non-injection sensor waveforms Wb and Wc and the non-injection sensor waveform Wa are not detected at the same time, first, the timings of the non-injection sensor waveforms Wb and Wc and the non-injection sensor waveform Wa are matched. For example, the timing at which the fuel pressure starts to increase with the fuel pumping is matched. After matching the timing, the square value of the difference in fuel pressure at each time point is calculated using each of the non-injection sensor waveforms Wb and Wc and the non-injection sensor wave Wa. The non-injection sensor waveform that minimizes the sum of the calculated square values is selected as the non-injection sensor waveform that most closely approximates the non-injection sensor waveform Wa.

  FIG. 4 shows the sum of the square values of the difference in fuel pressure calculated at each time point for each of the non-injection sensor waveforms Wb and Wc and the non-injection sensor waveform Wa. In this case, the sum of the square values of the differences with respect to the non-injection sensor waveform Wb is smaller than the sum of the square values of the differences with respect to the non-injection sensor waveform Wc. Therefore, the non-injection sensor waveform Wb that minimizes the sum of the squares of the differences is selected as the non-injection sensor waveform that most closely approximates the non-injection sensor waveform Wa. Then, the selected non-injection cylinder # 2 in which the non-injection sensor waveform is detected is selected as a non-injection cylinder to be combined with the injection cylinder # 1.

  Of the non-injection sensor waveforms detected when cylinder # 1 enters the non-injection state, non-injection detected for cylinder # 1 when the injection is performed in the cylinder immediately before or immediately after cylinder # 1. The in-injection sensor waveform Wa is a waveform that most closely approximates the pressure fluctuation associated with the pressure feed superimposed on the in-injection sensor waveform of the cylinder # 1. In view of this, the non-injection sensor waveforms Wb and Wc detected for each of the cylinders # 2 and # 3 when the injection is performed in the cylinder # 1, and the injection is performed in the cylinder immediately before or after the cylinder # 1. The non-injection sensor waveform Wa closest to the non-injection sensor waveform Wa detected for the cylinder # 1 is selected.

  In this embodiment, since the fuel injection system is mounted on a three-cylinder engine, the cylinder immediately before or immediately after cylinder # 1 is cylinder # 2 or cylinder # 3. Therefore, the non-injection sensor waveform Wa detected for the cylinder # 1 when the injection is performed in the cylinder # 2 or the cylinder # 3 is used as a comparison target of the non-injection sensor waveforms Wb and Wc. The same applies when the fuel injection system is mounted on an engine having four or more cylinders. That is, the injection is performed immediately before or after the predetermined injection cylinder as a comparison target of the non-injection sensor waveform detected for each of the non-injection cylinders when injection is performed in the predetermined injection cylinder. A non-injection sensor waveform that is sometimes detected for a given injection cylinder is used.

  Next, a procedure for determining a non-injection cylinder to be combined with the target cylinder when the target cylinder is an injection cylinder will be described with reference to FIG. This process is executed by the ECU 30 every time the engine is operated for a predetermined period, that is, every time the vehicle travels a predetermined distance.

  First, in S11, it is determined whether or not the engine is in steady operation, that is, in steady running. As described above, when cylinder # 1 is an injection cylinder, non-injection sensor waveform Wa compared with non-injection sensor waveforms Wb and Wc cannot be detected simultaneously with non-injection sensor waveforms Wb and Wc. Therefore, it is necessary to make the engine operating state when detecting the non-injection sensor waveform Wa and the engine operating state when detecting the non-injection sensor waveforms Wb and Wc the same. Therefore, if it is not during steady running (NO), this process is terminated and the combination of the injection cylinder and the non-injection cylinder is not determined. In the case of steady running (YES), the process proceeds to S12.

  In S12, when the target cylinder is in the non-injection state, the non-injection sensor waveform detected for the target cylinder is stored in the RAM. Here, it is assumed that the target cylinder is cylinder # 1, and fuel is injected in the order of cylinders # 1, # 3, and # 2. In S12, the non-injection sensor waveform Wa detected for the cylinder # 1 when the injection is performed in the cylinder # 2 immediately before the cylinder # 1 is stored.

  Next, in S13, the non-injection sensor waveforms Wb and Wc detected for the cylinders # 2 and # 3 other than the target cylinder when the injection is performed in the cylinder # 1 as the target cylinder are stored in the RAM. To do.

  Next, in S14, a non-injection sensor waveform Wa detected for the cylinder # 1 as the target cylinder, and a non-injection sensor waveform Wb detected for the cylinders # 2 and # 3 other than the target cylinder. The sum of squares of the difference in fuel pressure at each time point is calculated for each Wc. That is, the non-injection sensor waveform Wa stored in S12 and the non-injection sensor waveforms Wb and Wc stored in S13 are read from the RAM. The square value of the difference in fuel pressure at each time point is calculated from the read non-injection sensor waveform Wa and the read non-injection sensor waveforms Wb and Wc, and the sum of the calculated square values is calculated. Is calculated.

  Next, in S15, the non-injection sensor waveform that minimizes the sum of the square values of the differences calculated in S14 is selected, and the non-injection cylinder in which the selected non-injection sensor waveform is detected is the target cylinder. Select as a non-injecting cylinder in combination with cylinder # 1.

  Next, in S16, it is determined whether or not selection of a non-injection cylinder to be combined with each of all cylinders has been completed. When the selection of the non-injection cylinders to be combined with all the cylinders is not completed (NO), the processes of S11 to S15 are repeatedly executed. For example, when only the selection of the non-injection cylinder to be combined with the cylinder # 1 has been completed, the non-injection cylinder to be combined with the cylinder # 2 is selected with the target cylinder as the cylinder # 2. Further, when the selection of the non-injection cylinder combined with each of the cylinders # 1 and # 2 is completed, the target cylinder is the cylinder # 3, and the non-injection cylinder combined with the cylinder # 3 is selected. In this way, combinations of injection cylinders and non-injection cylinders are determined by the number of cylinders. When the selection of the non-injection cylinders to be combined with all the cylinders is completed (YES), this process is terminated. After completion of this process, until the combination of the injection cylinder and the non-injection cylinder is newly determined, the injection waveform W is extracted using the combination of the injection cylinder and the non-injection cylinder determined by this process.

  According to this embodiment described above, the following effects are obtained.

  Regarding the influence of fuel pumping by the fuel pump 41, the fuel injection valve 10 of the injection cylinder that detects the sensor waveform during injection and the non-injection cylinder in which the fuel injection valve 10 with the closest hardware characteristics is installed It is selected as a non-injection cylinder combined with a cylinder. Therefore, an injection cylinder that detects a sensor waveform during injection in which a pressure variation due to pressure feeding is superimposed on a pressure variation caused by injection, and a non-injection cylinder that detects a sensor waveform during non-injection that represents a pressure variation component due to pressure feeding. Can be combined optimally. As a result, the fluctuation of the fuel pressure caused by the injection can be extracted with high accuracy from the sensor waveform during the injection.

  Non-injection time detected for a predetermined injection cylinder when injection is performed in a cylinder immediately before or immediately after a predetermined injection cylinder from a non-injection sensor waveform detected for each non-injection cylinder The non-injection sensor waveform that is closest to the sensor waveform is selected. Thereby, an injection cylinder and a non-injection cylinder can be combined optimally.

  Each time the engine is operated for a predetermined period, that is, every time the vehicle travels a predetermined distance, a non-injection cylinder to be combined with the injection cylinder is selected. Thus, even if the hardware characteristics change due to the operation of the engine, the injection cylinder and the non-injection cylinder can be optimally combined.

  The non-injection sensor waveform detected for each of the non-injection cylinders and the non-injection sensor waveform detected for the injection cylinder when the injection cylinder enters the non-injection state, The square value of the difference is calculated, and the non-injection sensor waveform that minimizes the sum of the calculated square values is selected. Thus, the non-injection sensor waveform detected for the injection cylinder when the injection cylinder enters the non-injection state from the non-injection sensor waveform detected for each of the non-injection cylinders. The hour sensor waveform can be selected.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows.

  In the above embodiment, the fuel pressure sensor 20 is provided at the fuel intake port of the fuel injection valve 10. However, the fuel path from the common rail 42 to the injection hole 11 b of the fuel injection valve 10 is more fuel than the fuel outlet of the common rail 42. It may be provided anywhere on the downstream side.

  The non-injection cylinder selection means includes a non-injection sensor waveform detected for each of the non-injection cylinders, and a non-injection sensor waveform detected for the injection cylinder when the injection cylinder enters a non-injection state. Thus, the absolute value of the difference in fuel pressure at each time point may be calculated, and the non-injection sensor waveform that minimizes the sum of the calculated absolute values may be selected.

  ・ Injection is performed in a cylinder other than immediately before or after the predetermined injection cylinder as a comparison target of the non-injection sensor waveform detected for each of the non-injection cylinders when injection is performed in the predetermined injection cylinder. During non-injection, a non-injection sensor waveform detected for a predetermined injection cylinder may be used. However, it is desirable to use a non-injection sensor waveform that is detected for a predetermined injection cylinder when injection is performed in a cylinder immediately before or after the predetermined injection cylinder.

  In the above embodiment, the combination of the injection cylinder and the non-injection cylinder is determined every time the vehicle travels a predetermined distance. However, the combination of the injection cylinder and the non-injection cylinder is determined every time the vehicle becomes a steady travel. Good.

  -The fuel injection system may be mounted not only on a diesel engine but also on a gasoline engine or a gas engine. The fuel injection system may be mounted on an engine other than the three cylinders. Further, the fuel injection system is not limited to a vehicle engine, and may be mounted on an engine such as a ship.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 20 ... Fuel pressure sensor, 30 ... ECU, 41 ... Fuel pump, 42 ... Common rail, W ... Waveform at injection, Wa, Wb, Wc ... Sensor waveform at non-injection, Wi ... Sensor waveform at injection.

Claims (5)

An animal pressure vessel (42) for holding high-pressure fuel under pressure, a fuel pump (41) for pumping fuel to the animal pressure vessel, and an accumulator provided in each cylinder of a multi-cylinder internal combustion engine. A fuel injection valve (10) for injecting high-pressure fuel maintained at a pressure, and a fuel pressure sensor (20) for detecting the fuel pressure in each fuel passage from the animal pressure vessel to the injection port (11b) of each fuel injection valve. A fuel injection control device (30) applied to a fuel injection system comprising:
An injection sensor waveform detection means for detecting an injection sensor waveform based on an output of the fuel pressure sensor corresponding to the injection cylinder of the cylinders;
Non-injection sensor waveform detection means for detecting a non-injection sensor waveform based on the output of the fuel pressure sensor corresponding to a non-injection cylinder of the cylinders;
Non-injection cylinder selection means for selecting a non-injection cylinder to be combined with the injection cylinder from the non-injection cylinder;
From the sensor waveform at the time of injection detected by the sensor waveform detector at the time of injection with respect to the injection cylinder, the sensor waveform detector at the time of injection is used to detect the non-injection cylinder combined with the injection cylinder. An injection waveform extraction means for subtracting the non-injection sensor waveform detected at the same time as the sensor waveform to extract an injection waveform representing pressure fluctuations caused by injection in the injection cylinder, and
The non-injection cylinder selection means is configured to detect the non-injection cylinder from the non-injection sensor waveforms detected by the non-injection sensor waveform detection means for each of the non-injection cylinders during steady operation of the engine. The non-injection sensor waveform detected by the non-injection sensor waveform detection means for the injection cylinder is selected for the injection cylinder, and the selected non-injection sensor waveform is detected. The fuel injection control device is characterized in that the selected non-injection cylinder is selected.   The non-injection cylinder selection means is configured to calculate the predetermined value from the non-injection sensor waveform detected for each of the non-injection cylinders by the non-injection sensor waveform detection means when the injection is performed in the predetermined injection cylinder. The non-injection sensor waveform closest to the non-injection sensor waveform detected by the non-injection sensor waveform detection means for the predetermined injection cylinder when the injection is performed in the cylinder immediately before the injection cylinder The fuel injection control device according to claim 1, wherein:   The non-injection cylinder selection means is configured to calculate the predetermined value from the non-injection sensor waveform detected for each of the non-injection cylinders by the non-injection sensor waveform detection means when the injection is performed in the predetermined injection cylinder. The non-injection sensor waveform closest to the non-injection sensor waveform detected by the non-injection sensor waveform detection means for the predetermined injection cylinder when injection is performed in a cylinder immediately after the injection cylinder The fuel injection control device according to claim 1, wherein:   The fuel injection control device according to any one of claims 1 to 3, wherein the non-injection cylinder selection unit selects the non-injection cylinder to be combined with the injection cylinder every time the engine is operated for a predetermined period.   The non-injection cylinder selection means detects the non-injection sensor waveform detected for each of the non-injection cylinders, and detects the non-injection sensor waveform for the injection cylinder when the injection cylinder enters a non-injection state. 2. The non-injection sensor waveform detected by the means is calculated as a square value of the difference in fuel pressure at each time point, and the non-injection sensor waveform that minimizes the sum of the calculated square values is selected. The fuel-injection control apparatus in any one of -4.

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