JP2014238040A - Fuel injection state analysis device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection state analysis device capable of suppressing decrease of an analysis opportunity while reducing a processing load of an analysis part.SOLUTION: A fuel injection system comprises: a fuel injection valve 10 which is provided in each of cylinders (#1-#4) of a multi-cylinder internal combustion engine and injects fuel held in a pressure storage state in a pressure storage container 42; and a fuel pressure sensor 20 for detecting fuel pressure within a fuel passage 11a from a discharge port 42a of the pressure storage container 42 to an injection hole 11b of the fuel injection valve 10. A fuel injection state analysis device 30 comprises: an analysis part 34 for analyzing an injection state of fuel by the fuel injection valve 10 on the basis of an extraction value obtained by sampling a detection value of the fuel pressure sensor 20 at a preset sampling rate; and a rate change part 34 for changing the sampling rate so as to finish analysis by the analysis part 34 while successively injecting the fuel from the fuel injection valves 10 of the cylinders.

Description

  The present invention relates to an apparatus for analyzing a fuel injection state by a fuel injection valve provided in an internal combustion engine.

  2. Description of the Related Art Conventionally, there is a fuel pressure sensor that detects a change in fuel pressure in a fuel passage caused by fuel injection by a fuel injection valve and analyzes a fuel injection state based on the pressure change (see, for example, Patent Document 1). . In the technique described in Patent Document 1, when fuel is sequentially injected by the fuel injection valve of each cylinder, the analysis of the injection state based on the detection value of the fuel pressure sensor is not continuously performed in the order of injection of each cylinder. This is intermittently performed for the injection of each cylinder. Thereby, it is possible to improve the efficiency of the arithmetic processing for analyzing the injection state, and as a result, the processing load on the analysis unit can be reduced.

JP 2012-163073 A

  However, in the thing of patent document 1, since the analysis of an injection state is intermittently implemented with respect to the injection of each cylinder, the reduction of an analysis opportunity is unavoidable and it still leaves the room for improvement. ing.

  The present invention has been made to solve the above-described problems, and a main object of the present invention is to provide a fuel injection state analysis apparatus capable of suppressing a decrease in analysis opportunities while reducing the processing load of the analysis unit. There is.

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

  The invention according to claim 1 is provided in each cylinder of the multi-cylinder internal combustion engine, and injects the fuel held in the pressure accumulation state by the pressure accumulation container, and the injection of the fuel injection valve from the discharge port of the pressure accumulation container A fuel pressure sensor for detecting a fuel pressure in a fuel passage leading to a hole, and a fuel injection state analysis device applied to a fuel injection system, wherein a detection value of the fuel pressure sensor is sampled at a set sampling rate Based on the extracted value, the analysis unit that analyzes the fuel injection state by the fuel injection valve and the analysis by the analysis unit is completed between the time when fuel is sequentially injected by the fuel injection valve of each cylinder. And a rate changing unit for changing the sampling rate.

  According to the above configuration, the fuel held in the pressure accumulation state by the pressure accumulation container is injected by the fuel injection valve provided in each cylinder of the multi-cylinder internal combustion engine. Then, the fuel pressure in the fuel passage from the discharge port of the pressure accumulating container to the injection hole of the fuel injection valve is detected by a fuel pressure sensor.

  Here, based on the extracted value obtained by sampling the detection value of the fuel pressure sensor at the set sampling rate, the fuel injection state by the fuel injection valve is analyzed by the analysis unit. At this time, the sampling rate is changed by the rate changing unit so that the analysis by the analyzing unit is completed between the time when fuel is sequentially injected by the fuel injection valve of each cylinder. For this reason, it is possible to reduce the processing load of the analysis unit and finish the analysis between injections between the cylinders, and it is possible to continuously analyze the injection state in the order of injection of each cylinder. Accordingly, it is possible to suppress a decrease in the analysis opportunity of the injection state.

The schematic diagram which shows the outline of a fuel-injection system. The time chart which shows the change of the injection rate and fuel pressure corresponding to an injection command signal. The block diagram which shows the outline | summarys, such as a setting of the injection command signal with respect to a fuel injection valve. The flowchart which shows the whole process of the fuel-injection state analysis including a sampling rate change. The flowchart which shows the calculation procedure of an injection rate parameter. 6 is a flowchart showing subroutine processing of FIG. 5. The figure which shows the injection waveform Wa, the reference waveform Wu, and the injection component Wb. The flowchart which shows the setting procedure of a sampling rate. The time chart which shows the actual pressure fluctuation | variation and sample value of an injection cylinder and a reference cylinder. The time chart which shows the actual pressure fluctuation | variation of a injection cylinder and a reference cylinder, a sample value, and an estimated pressure fluctuation | variation.

  Hereinafter, an embodiment will be described with reference to the drawings. A fuel injection state analysis apparatus described below is mounted on a vehicle engine (internal combustion engine). As this engine, a multi-cylinder diesel engine that injects high-pressure fuel into a plurality of cylinders and performs compression self-ignition combustion. An engine is assumed.

  FIG. 1 shows a fuel injection valve 10 mounted on each cylinder (# 1 to # 4) of the engine, a fuel pressure sensor 20 mounted on each fuel injection valve 10, and an electronic control device mounted on a vehicle. It is a schematic diagram which shows ECU30 grade | etc.,.

  First, an engine fuel injection system including the fuel injection valve 10 will be described. The fuel in the fuel tank 40 is pumped by the fuel pump 41 to the common rail 42 (pressure accumulating vessel) and held in a pressure accumulating state, and is distributed and supplied to the fuel injection valves 10 (# 1 to # 4) of each cylinder through the high pressure pipe 42b. The The plurality of fuel injection valves 10 (# 1 to # 4) sequentially inject fuel in a preset order. In this embodiment, it is assumed that injection is performed in the order of # 1 → # 3 → # 4 → # 2.

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

  The fuel injection valve 10 includes a body 11, a needle-shaped valve body 12, an actuator 13, and the like described below. The body 11 forms a high-pressure passage 11a therein and an injection hole 11b for injecting fuel. The valve body 12 is accommodated in the body 11 and opens and closes the injection 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 11 a and the low pressure passage 11 d and the back pressure chamber 11 c is switched by the control valve 14. When the actuator 13 such as an electromagnetic coil or a piezoelectric element is energized and the control valve 14 is pushed downward in FIG. 1, the back pressure chamber 11c communicates with the low pressure passage 11d and the fuel pressure in the back pressure chamber 11c decreases. To do. As a result, the back pressure applied to the valve body 12 is lowered and the valve body 12 is lifted up (opening operation). Thereby, the seat surface 12a of the valve body 12 is separated from the seat surface 11e of the body 11, and fuel is injected from the injection hole 11b.

  On the other hand, when the 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 increases and the valve body 12 is lifted down (closed valve operation). Thereby, the seat surface 12a of the valve body 12 is seated on the seat surface 11e of the body 11, and the fuel injection from the injection hole 11b is stopped.

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

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

  Specifically, the pressure sensor element 22 is connected to the mold IC 24. The mold IC 24 includes an amplifier circuit that amplifies the detection signal output from the pressure sensor element 22, a filtering circuit that removes noise superimposed on the detection signal, a circuit that applies a voltage to the pressure sensor element 22, and the like. The pressure sensor element 22 to which a voltage is applied from the voltage application circuit constitutes a bridge circuit in which the resistance value changes according to the magnitude of strain generated in the diaphragm portion 21a. As a result, the output voltage of the bridge circuit changes according to the distortion of the diaphragm portion 21a, and this output voltage is output to the amplification circuit of the mold IC 24 as the pressure detection value of the high-pressure fuel. The amplifier circuit amplifies the analog pressure detection value output from the pressure sensor element 22 (bridge circuit), and outputs the amplified analog signal (continuous value) to the ECU 30.

  The ECU 30 (fuel injection state analysis device) includes a CPU 34a and a microcomputer (microcomputer 34) having a memory 34b such as a RAM and a ROM. The microcomputer 34 operates the accelerator pedal operation amount, the engine load, and the engine speed NE. Based on the above, a target injection state (for example, the number of injection stages, injection start timing, injection end timing, injection amount, etc.) is calculated. For example, the optimal injection state corresponding to the engine load and the engine speed is stored as an injection state map. Based on the current engine load and engine speed, the target injection state is calculated with reference to the injection state map. Then, the injection command signals t1, t2, and Tq (see FIG. 2A) corresponding to the calculated target injection state are set based on the injection rate parameters td, te, Rα, Rβ, and Rmax described in detail later, and the fuel By outputting to the injection valve 10, the operation of the fuel injection valve 10 is controlled.

  Next, a method of injection control when fuel is injected from the fuel injection valve 10 will be described below with reference to FIGS.

  The CPU 34a of the ECU 30 samples (extracts) the analog pressure detection value output from the fuel pressure sensor 20 at a set sampling rate. Then, the CPU 34a converts the sampled extracted value into a digital pressure detection value. Based on this digital pressure detection value, the CPU 34a detects a change in fuel pressure caused by the injection as a fuel pressure waveform (see FIG. 2C). Here, when the sampling rate is low and the interval between the pressure detection values is wide, the fuel pressure waveform is estimated (interpolated between the pressure detection values) using an approximate curve or the like.

  Based on the detected fuel pressure waveform, the CPU 34a calculates an injection rate waveform (see FIG. 2B) representing a change in the injection rate of the fuel and detects the injection state. Then, while learning the injection rate parameters Rα, Rβ, and Rmax that specify the detected injection rate waveform (injection state), the correlation between the injection command signals (pulse-on timing t1, pulse-off timing t2, and pulse-on period Tq) and the injection state. The injection rate parameters td and te for specifying

  FIG. 3 is a block diagram showing an outline of learning of these injection rate parameters, setting of an injection command signal to be output to the fuel injection valve 10 and the like. Explained. The injection rate parameter calculation means 31 (analysis unit) calculates injection rate parameters td, te, Rα, Rβ, Rmax based on the fuel pressure waveform detected by the fuel pressure sensor 20.

  The learning means 32 learns by updating the calculated injection rate parameter in the memory 34b of the ECU 30. Since the injection rate parameter varies depending on the supply fuel pressure (pressure in the common rail 42) at that time, the injection rate parameter can be learned in association with the supply fuel pressure or a reference pressure Pbase (see FIG. 2C) described later. desirable. In the example of FIG. 3, the injection rate parameter value corresponding to the fuel pressure is stored in the injection rate parameter map M.

  The setting means 33 (injection control unit) acquires an injection rate parameter (learned value) corresponding to the current fuel pressure from the injection rate parameter map M. And based on the acquired injection rate parameter, the injection command signals t1, t2, and Tq corresponding to the target injection state are set. Then, the fuel pressure when the fuel injection valve 10 is operated according to the injection command signal set in this way is detected by the fuel pressure sensor 20. The injection rate parameter calculation means 31 samples the detected fuel pressure (analog value) and converts it into a digital value, and detects a fuel pressure waveform based on this digital value. Then, the injection rate parameter calculation means 31 calculates injection rate parameters td, te, Rα, Rβ, Rmax based on the detected fuel pressure waveform.

  In short, an actual injection state (that is, injection rate parameters td, te, Rα, Rβ, Rmax) with respect to the injection command signal is detected and learned, and an injection command signal corresponding to the target injection state is set based on the learned value. . Therefore, the injection command signal is feedback-controlled based on the actual injection state, and the fuel injection state can be controlled with high accuracy so that the actual injection state coincides with the target injection state even when aging or the like progresses. In particular, feedback control is performed so as to set the injection command period Tq based on the injection rate parameter so that the actual injection amount becomes the target injection amount, so that the actual injection amount is compensated to become the target injection amount.

  FIG. 4 is a flowchart showing the entire process of fuel injection state analysis including sampling rate change. This series of processing is repeatedly executed by the microcomputer 34 included in the ECU 30.

  First, the injection interval between the analysis cylinders for analyzing the injection state is calculated (S100). Specifically, when the injection state is continuously analyzed in the order of injection of # 1 → # 3 → # 4 → # 2, the next cylinder is injected after being injected by one cylinder based on the rotational speed of the engine. To calculate the time until injection. Further, when the injection state is analyzed intermittently with respect to the injection of each cylinder, the injection interval between the cylinders to be analyzed is calculated based on the rotational speed of the engine. For example, when analyzing the injection state in the cylinder # 4 after the analysis of the injection state in the cylinder # 1, the time from the injection in the cylinder # 1 to the injection in the cylinder # 4 is calculated.

  Subsequently, an analysis time required for analyzing the injection state in one cylinder is calculated (S200). Specifically, the time from the start to the end of the analysis is measured by a timer. When multiple stages of injection are performed in one cylinder, the injection state of each stage is analyzed, and the total analysis time of each stage is taken as the analysis time. Here, the analysis time measured in the previous analysis (last analysis) is used.

  Subsequently, the sampling rate is set so that the analysis of the injection state is completed within the injection interval (between injections in successive cylinders or between injections in intermittent analysis cylinders) (S300). Details of the setting of the sampling rate will be described later.

  Subsequently, it is determined whether or not it is determined that it is necessary to thin out the analysis cylinder (S400). Whether or not it is necessary to thin out the analysis cylinder is determined when the sampling rate is set. This determination will also be described later.

  In the above determination, when it is determined that it is necessary to thin out the analysis cylinder (S400: YES), the analysis state is intermittently set by thinning out the analysis cylinder (S500). For example, the injection order of # 1 → # 3 → # 4 → # 2 is set to analyze in the order of # 1 → # 2 → # 4 → # 3 → # 1 →. That is, after analyzing the injection state for # 1, the injection state for # 3 and # 4 is not analyzed, and thereafter the injection state is analyzed for # 2. In this case, since the order of the fuel injection valves 10 to be analyzed circulates evenly, the cumulative number of analyzes performed on each fuel injection valve 10 in the predetermined period is the same. Thereafter, the processing of S100 to S400 is executed again in a setting in which the analysis cylinder is thinned and the injection state is analyzed intermittently. In that case, the injection interval calculated in S100 becomes longer, and the sampling rate is set accordingly in S300.

  On the other hand, in the above determination, when it is determined that it is not determined that it is necessary to thin out the analysis cylinder (S400: NO), the injection state is analyzed with respect to the set analysis cylinder at the set sampling rate ( S600). Thereafter, this series of processing is temporarily terminated (END).

  In addition, the process of S100 corresponds to the process as an injection interval calculation part, the process of S200 corresponds to the process as an analysis time calculation part, the process of S300 corresponds to the process as a rate change part, and S400 and S500. The process corresponds to the process as the analysis thinning unit, and the process of S600 corresponds to the process as the analysis unit.

  Next, the procedure for analyzing the injection state in S600 of FIG. 4 will be described using the flowchart of FIG. 5 is repeatedly executed by the microcomputer 34 included in the ECU 30.

  First, it is determined whether or not fuel injection has been performed in a preset analysis order cylinder (S605). The cylinders in this analysis order are set in the order of injection from # 1 → # 3 → # 4 → # 2, or the analysis cylinders are thinned out and set intermittently (S400 and S500 in FIG. 4).

  When it is determined that the injection is executed in the analysis order cylinder (S5: YES), the injection component Wb used for the analysis of the injection state is calculated based on the detection value of the fuel pressure sensor 20 (S610).

  FIG. 6 is a flowchart showing the subroutine processing of S610. In the following description, a cylinder during fuel injection is referred to as an injection cylinder, and a cylinder that stops injection when fuel is injected in the injection cylinder is referred to as a reference cylinder. Further, the fuel pressure sensor 20 mounted on the fuel injection valve 10 of the injection cylinder is referred to as an injection time sensor, and the fuel pressure sensor 20 mounted on the fuel injection valve 10 of the reference cylinder is referred to as a non-injection time sensor.

  First, based on the pressure detection value by the injection sensor, an injection waveform Wa (see FIG. 7A) that represents a change in fuel pressure in the injection sensor caused by the injection is generated (S610a). Specifically, a plurality of extracted values are obtained by sampling the analog detection value output from the injection sensor at a sampling rate set for the injection cylinder. These extracted values are converted into digital detection values, and an injection waveform Wa representing a change in fuel pressure is generated based on these digital detection values. Here, when the sampling rate is low and the interval between the detection values is wide, the injection waveform Wa is estimated using an approximate curve or the like. Note that high-frequency noise is removed from the generated ejection waveform Wa using means such as a low-pass filter.

  Subsequently, based on the pressure detection value by the non-injection sensor, a reference waveform Wu (see FIG. 7B) that represents a change in fuel pressure in the non-injection sensor that occurs with the injection in the injection cylinder is generated (S610b). ). Specifically, the analog detection value output from the non-injection sensor is sampled at a sampling rate set for the reference cylinder to obtain a plurality of extracted values. These extracted values are converted into digital detection values, and a reference waveform Wu representing a change in fuel pressure is generated based on these digital detection values. Here, when the sampling rate is low and the interval between the detection values is wide, the reference waveform Wu is estimated using an approximate curve or the like.

  Incidentally, when the timing for pumping fuel from the fuel pump 41 to the common rail 42 and the injection timing overlap, the reference waveform Wu is a waveform in which the pressure is generally increased as shown by the solid line in FIG. It becomes. On the other hand, when such pump pumping is not performed during fuel injection, immediately after the fuel is injected, the fuel pressure in the common rail 42 is reduced by that amount. For this reason, the reference waveform Wu ′ is a waveform in which the pressure is reduced as a whole, as indicated by the dotted line in FIG.

  Such components of the reference waveforms Wu and Wu 'are also included in the injection waveform Wa generated in S610a. In other words, the injection waveform Wa includes an injection component Wb representing a change in fuel pressure due to injection and components of the reference waveforms Wu and Wu ′.

  Therefore, a process of extracting the injection component Wb is performed by subtracting the reference waveforms Wu, Wu ′ generated in S610b from the injection waveform Wa generated in S610a (W610 = W-Wu) (S610c).

  Here, when performing multi-stage injection, the swell component Wc (see FIG. 2C), which is the pulsation after injection of the fuel pressure waveform for the pre-stage injection, is superimposed on the injection waveform Wa generated in S610a. In particular, when the interval from the preceding injection is short, the injection waveform Wa is greatly affected by the swell component Wc. Therefore, when multi-stage injection is performed (S610d: YES), a swell removal process for subtracting the swell component Wc of the previous stage injection from the injection component Wb is performed (S610e).

  By performing the subroutine processing of FIG. 6 as described above, the injection component Wb used for calculation (injection state analysis) of the injection rate parameters td, te, Rα, Rβ, Rmax is calculated.

  In addition, the process of S610a is equivalent to the process as an injection waveform production | generation part, the process of S610b is equivalent to the process as a reference waveform generation part, and the process of S610c-S610e is equivalent to the process as a calculating part.

  Returning to the description of FIG. 5 (see also FIG. 2), after calculating the injection component Wb in S610, the portion of the injection component Wb corresponding to the period until the fuel pressure starts to decrease with the start of injection. Based on the reference waveform which is a waveform, the average fuel pressure of the reference waveform is calculated as the reference pressure Pbase (S611).

  Subsequently, an approximate straight line Lα of the descending waveform is calculated based on a descending waveform that is a waveform corresponding to a period in which the fuel pressure decreases as the injection rate increases in the injection component Wb (S612).

  Subsequently, an approximate straight line Lβ of the rising waveform is calculated based on the rising waveform that is the waveform corresponding to the period during which the fuel pressure increases as the injection rate decreases in the injection component Wb (S613).

  Subsequently, reference values Bα and Bβ are calculated based on the reference pressure Pbase (S614). For example, values lower than the reference pressure Pbase by a predetermined amount may be calculated as the reference values Bα and Bβ.

  Subsequently, a timing (intersection timing LBα between Lα and Bα) of the approximate straight line Lα that is the reference value Bα is calculated, and an injection start timing R1 is calculated based on the intersection timing LBα (S615). 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.

  Subsequently, a timing (intersection timing LBβ between Lβ and Bβ) that is the reference value Bβ in the approximate straight line Lβ is calculated, and an injection end timing R4 is calculated based on the intersection timing LBβ (S616). 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.

  In the subsequent step S617, the slope of the straight line Rα indicating an increase in the injection rate waveform shown in FIG. 2B is calculated based on the slope of the approximate straight line Lα. For example, the slope of Rα may be calculated by multiplying the slope of Lα by a predetermined coefficient. Note that, based on the injection start timing R1 calculated in S615 and the slope of Rα calculated in S617, the straight line Rα representing the rising portion of the injection rate waveform with respect to the injection command signal can be specified. Further, in S617, the slope of the straight line Rβ indicating the injection reduction in the injection rate waveform is calculated based on the slope of the approximate straight line Lβ. For example, the slope of Rβ may be calculated by multiplying the slope of Lβ by a predetermined coefficient. Note that, based on the injection end timing R4 calculated in S616 and the slope of Rβ calculated in S617, a straight line Rβ that represents the descending portion of the injection rate waveform with respect to the injection command signal can be specified.

  Subsequently, based on the straight lines Rα and Rβ of the injection rate waveform calculated in S617, a timing (valve closing operation start timing R23) at which the valve body 12 starts lift-down in response to the command to end injection is calculated (S618). . Specifically, the intersection of both straight lines Rα and Rβ is calculated, and the intersection timing is calculated as the valve closing operation start timing R23.

  In subsequent S619, a delay time (injection start delay time td) of the injection start timing R1 calculated in S615 with respect to the injection start command timing t1 is calculated. Further, in S619, a delay time (injection end delay time te) with respect to the injection end command timing t2 of the valve closing operation start timing R23 calculated in S618 is calculated.

  Subsequently, it is determined whether or not the pressure difference ΔPγ between the reference pressure Pbase and the intersection pressure Pαβ is less than a predetermined value ΔPγth (S620). If it is determined that ΔPγ <ΔPγth (S620: YES), in the subsequent S621, it is assumed that the injection is small injection (injection that ends before the injection rate reaches a certain maximum value), and the maximum injection is based on the pressure difference ΔPγ. The rate Rmax is calculated (Rmax = ΔPγ × Cγ). On the other hand, when it is determined that ΔPγ ≧ ΔPγth (S620: NO), in the subsequent S622, a preset value (set value Rγ) is calculated as the maximum injection rate Rmax.

  Next, the subroutine processing (sampling rate setting) in S300 of FIG. 4 will be described using the flowchart of FIG. This series of processing is executed by the microcomputer 34.

  First, in order to analyze the injection state between injections by the fuel injection valve 10 of each cylinder, it is determined whether or not the processing load of the microcomputer 34 is exceeded (S311). Specifically, it is determined whether or not the analysis time calculated in S200 of FIG. 4 exceeds a predetermined ratio with respect to the injection interval calculated in S100. For example, 100% or 90% can be set as the predetermined ratio.

  If it is determined in S311 that the processing load of the microcomputer 34 has been exceeded (S311: YES), it is determined whether or not the sampling rate set for the pressure detection value in the reference cylinder is the lower limit value. (S314). This lower limit is set according to the required injection accuracy. The required injection accuracy varies depending on the operating state of the fuel injection system (pressure in the common rail 42, required injection amount, injection interval, etc.). For this reason, the said lower limit is set according to the operation state of the fuel injection system.

  If it is determined in S314 that the sampling rate set for the pressure detection value in the reference cylinder is not the lower limit value (S314: NO), the sampling rate for the pressure detection value in the reference cylinder is set to the processing load of the microcomputer 34. Is lowered according to the degree of overshooting (S315). Specifically, based on the injection interval and the analysis time, the sampling rate for the pressure detection value in the reference cylinder is set so that the analysis time does not exceed a predetermined ratio of the injection interval. Specifically, the sampling rate is set in consideration of the number of extracted values to be sampled, the calculation load in AD conversion, the calculation load of the injection component Wb, the calculation load of the injection rate parameter, and the like. Note that the relationship between these conditions and the sampling rate to be set may be obtained in advance through experiments or the like.

  On the other hand, in the determination of S314, when it is determined that the sampling rate set for the pressure detection value in the reference cylinder is the lower limit value (S314: YES), it is set for the pressure detection value in the injection cylinder. It is determined whether the sampling rate is the lower limit value (S316). The lower limit value of the sampling rate in the injection cylinder is also set according to the required injection accuracy, similarly to the lower limit value of the sampling rate in the reference cylinder. Here, since the variation in the fuel pressure in the reference cylinder is smaller than the variation in the fuel pressure in the injection cylinder (see FIG. 7), the generation of the reference waveform Wu is easier than the generation of the injection waveform Wa. Therefore, the lower limit value of the sampling rate in the reference cylinder is set smaller than the lower limit value of the sampling rate in the injection cylinder. Further, on the condition that the sampling rate in the reference cylinder is the lower limit value in S314 (S314: YES), the sampling rate in the injection cylinder is lowered (S316, S317). That is, the sampling rate in the reference cylinder is preferentially lowered over the sampling rate in the injection cylinder.

  If it is determined in S316 that the sampling rate set for the pressure detection value in the injection cylinder is not the lower limit value (S316: NO), the sampling rate for the pressure detection value in the injection cylinder is processed by the microcomputer 34. The load is lowered according to the degree of overload (S317). Specifically, based on the injection interval and the analysis time, a sampling rate for the pressure detection value in the injection cylinder is set so that the analysis time does not exceed a predetermined ratio of the injection interval.

  On the other hand, if it is determined in S316 that the sampling rate set for the detected pressure value in the injection cylinder is the lower limit (S316: YES), it is necessary to perform analysis intermittently by thinning out the analysis cylinder. It is determined that there is (S340). That is, even if the sampling rate in the reference cylinder and the injection illuminating cylinder is lowered to the lower limit value, the analysis of the injection state cannot be completed between the time when fuel is injected by the fuel injection valve 10 of each cylinder. Analysis is intermittently performed for the injection of each cylinder. Note that the determination in S400 in FIG. 4 is performed based on the determination result in S340. Then, after the process of S340, this subroutine process is terminated, and the process proceeds to S400 of FIG.

  If it is determined in S311 that the processing load of the microcomputer 34 has not been exceeded (S311: NO), whether or not the sampling rate set for the pressure detection value in the injection cylinder is the upper limit value. Determination is made (S312). This upper limit value is set within a range in which the injection state in all cylinders can be analyzed.

  When it is determined in S312 that the sampling rate set for the pressure detection value in the injection cylinder is not the upper limit value (S312: NO), the sampling rate for the pressure detection value in the injection cylinder is set to the processing load of the microcomputer 34. (S318). Specifically, based on the injection interval and the analysis time, the sampling rate for the pressure detection value in the injection cylinder is set so that the analysis time is equal to or slightly smaller than the predetermined ratio of the injection interval.

  On the other hand, when it is determined in S312 that the sampling rate set for the pressure detection value in the injection cylinder is the upper limit value (S312: YES), the pressure is set for the pressure detection value in the reference cylinder. It is determined whether or not the sampling rate is the upper limit value (S313). This upper limit value is set within a range in which the injection state in all cylinders can be analyzed.

  If it is determined in S313 that the sampling rate set for the pressure detection value in the reference cylinder is not the upper limit value (S313: NO), the sampling rate for the pressure detection value in the reference cylinder is set to the processing load of the microcomputer 34. (S319).

  Then, after the processes of S315, S317, and S319, this subroutine process is terminated, and the process proceeds to the process of S400 of FIG.

  If it is determined in S313 that the sampling rate set for the pressure detection value in the reference cylinder is the upper limit (S313: YES), whether or not the engine speed is higher than the threshold value. Determination is made (S321). This threshold value (predetermined rotational speed) is set to a value for determining whether or not the processing load of the microcomputer 34 is exceeded when the rotational speed increases during engine transient operation.

  Here, as the rotational speed of the engine increases, the injection interval between the cylinders becomes shorter. Therefore, it is necessary to shorten the time required for analyzing the injection state. In this regard, the sampling rate is lowered when the rotational speed of the engine is higher than the threshold value.

  Since the process of S322-S329 is the same as the process of S312-S319 mentioned above, description is abbreviate | omitted.

  If it is determined in S323 that the sampling rate set for the pressure detection value in the reference cylinder is the upper limit value (S323: YES), the number of injection stages by the fuel injection valve 10 in one combustion stroke is threshold. It is determined whether or not the value is greater than the value (S331). This threshold value (predetermined number of stages) is set to a value for determining whether or not the processing load of the microcomputer 34 is exceeded when the number of injection stages increases during the transient operation of the engine.

  Here, the injection state of each stage is analyzed with respect to the plurality of stages of fuel injection by the fuel injection valve 10 in each cylinder. Therefore, since the number of times of analysis increases as the number of fuel injection stages increases, it is necessary to shorten the time required for analysis of the injection state. In this regard, when the number of fuel injection stages by the fuel injection valve 10 is larger than the threshold value, the sampling rate is lowered.

  Since the process of S332-S339 is the same as the process of S312-S319 mentioned above, description is abbreviate | omitted. Then, after the process of S333, this subroutine process is terminated, and the process proceeds to the process of S400 of FIG.

  Note that the processing of S315, S317, S318, S319, S325, S327, S328, S329, S335, S337, S338, and S339 corresponds to the processing as the rate setting unit.

  FIG. 9 is a time chart showing actual pressure fluctuations and sample values of the injection cylinder and the reference cylinder. In the figure, the sampling interval is exaggerated and wide (the sampling rate is exaggerated and low).

  When the injection state in all cylinders can be analyzed, the sampling rate is increased in the injection cylinder and the reference cylinder as shown in FIG. That is, the sampling rate in the injection cylinder and the reference cylinder is set as high as possible without exceeding the processing load of the microcomputer 34.

  FIG. 10 is a time chart showing actual pressure fluctuations, sample values, and estimated pressure fluctuations in the injection cylinder and the reference cylinder. In this figure, the sampling interval is exaggerated and wide (the sampling rate is exaggerated and low).

  When the injection state in all cylinders cannot be analyzed with the current sampling rate, the sampling rate in the reference cylinder is preferentially lowered as shown in FIG. That is, while maintaining the sampling rate in the injection cylinder, the sampling rate in the reference cylinder is lowered so as not to exceed the processing load of the microcomputer 34. Even in this case, since the fluctuation of the fuel pressure in the reference cylinder is smaller than the fluctuation of the fuel pressure in the injection cylinder, the accuracy of the estimated pressure fluctuation (reference waveform Wu) can be ensured as shown by the solid line.

  The embodiment described in detail above has the following advantages.

  The fuel injection state by the fuel injection valve 10 is analyzed based on the extracted value obtained by sampling the detection value of the fuel pressure sensor 20 at the set sampling rate. At this time, the sampling rate is changed so that the analysis is completed between the time when fuel is sequentially injected by the fuel injection valve 10 of each cylinder. For this reason, the processing load of the microcomputer 34 can be reduced and the analysis can be terminated between the injections between the cylinders, and the analysis of the injection state can be continuously performed in the order of injection of each cylinder. Accordingly, it is possible to suppress a decrease in the analysis opportunity of the injection state.

  An injection interval at which fuel is sequentially injected by the fuel injection valve 10 of each cylinder is calculated. In addition, an analysis time required for the analysis is calculated. Then, the sampling rate is set so that the calculated analysis time does not exceed a predetermined ratio of the calculated injection interval. Therefore, the processing load of the microcomputer 34 can be surely reduced to a processing load that can end the analysis.

  -The sampling rate in the reference cylinder is preferentially lowered over the sampling rate in the injection cylinder. For this reason, the processing load of the microcomputer 34 can be reduced while ensuring the accuracy of analyzing the injection state.

  The sampling rate in the injection cylinder cannot be lowered until the sampling rate in the reference cylinder is lowered to the lower limit value. For this reason, it is possible to reduce the processing load of the microcomputer 34 while suppressing a decrease in the accuracy of generating the injection waveform Wa.

  -The sampling rate in the injection cylinder is preferentially increased over the sampling rate in the reference cylinder. For this reason, when there is a margin in the processing load of the microcomputer 34, the accuracy of analyzing the injection state can be improved.

  -A lower limit value for changing the sampling rate is set according to the operating state of the fuel injection system. Therefore, the processing load on the microcomputer 34 can be reduced according to the required injection accuracy.

  The sampling rate is lowered when the number of fuel injection stages by the fuel injection valve 10 is greater than the threshold value. For this reason, it becomes easy to end the analysis by the microcomputer 34 between the time when fuel is sequentially injected by the fuel injection valve 10 of each cylinder. Note that the sampling rate may be lowered as the number of fuel injection stages by the fuel injection valve 10 increases.

  • The sampling rate is lowered when the engine speed is higher than the threshold value. For this reason, it becomes easy to end the analysis by the microcomputer 34 between the time when fuel is sequentially injected by the fuel injection valve 10 of each cylinder. Note that the sampling rate may be lowered as the engine speed increases.

  When the analysis by the microcomputer 34 cannot be completed between the time when fuel is sequentially injected by the fuel injection valve 10 of each cylinder, the analysis is intermittently performed for the injection of each cylinder. Therefore, it is possible to avoid a situation in which the analysis of the injection state by the microcomputer 34 cannot be performed.

  Note that the present invention is not limited to the above embodiment, and may be modified as follows.

  In S321 of FIG. 8, it is determined whether or not the engine speed is higher than the threshold value. Instead, it is determined whether or not the engine acceleration is higher than the threshold value (predetermined rotation acceleration). Also good.

  That is, the higher the rotational acceleration of the engine, the higher the possibility that the rotational speed of the engine will increase. And it is necessary to shorten the time required for the analysis of an injection state, so that the rotational speed of an engine becomes high. In this regard, the sampling rate is lowered when the rotational acceleration of the engine is higher than the threshold value. For this reason, it is possible to reduce the processing load on the microcomputer 34 by predicting that the engine speed will increase. Note that the sampling rate may be lowered as the rotational acceleration of the engine increases. The rotational acceleration may be detected by an acceleration sensor, or may be estimated from the amount of depression of the accelerator pedal of the vehicle.

  -At least 1 process should just be performed among the 1st process of S311-S319 of FIG. 8, the 2nd process of S321-S329, and the 3rd process of S331-S339. Even in this case, it is possible to suppress a decrease in analysis opportunities while reducing the processing load on the microcomputer 34.

  The sampling rate of the detection value used for calculating the injection rate parameter that has a small influence on the fuel injection state may be lower than the sampling rate of the detection value used for calculating the injection rate parameter having a large influence. For example, the sampling rate of the detection values in other ranges may be lowered with respect to the sampling rate of the detection values near the change point P1 to the change point P2 used for calculating the injection start delay time.

  Here, the magnitude of the influence on the fuel injection accuracy differs depending on the type of injection rate parameter. In this respect, the sampling rate of the detection value used for calculating the injection rate parameter having a small influence on the fuel injection state is lowered than the sampling rate of the detection value used for calculating the injection rate parameter having a large influence. For this reason, it is possible to reduce the processing load of the microcomputer 34 while suppressing a decrease in the injection accuracy.

  In the above embodiment, the lower limit value for changing the sampling rate is set according to the operating state of the fuel injection system, but the lower limit value may be set according to the operating state of the engine. For example, when the engine is idling, the required injection accuracy is increased, and therefore the lower limit value may be increased.

  In the above embodiment, the sampling rate for the pressure detection value is lowered according to the degree to which the processing load of the microcomputer 34 is exceeded, but the sampling rate may be lowered by a predetermined value.

  In the above embodiment, in the injection state analysis process, the time from the start to the end of the analysis is measured by the timer and the analysis time is calculated. However, the analysis time under various conditions may be calculated in advance by experiments or the like. Good.

  In each of the above embodiments, the fuel pressure sensor 20 is mounted on the fuel injection valve 10, but the fuel pressure sensor is arranged to detect the fuel pressure in the fuel supply path from the discharge port 42a of the common rail 42 to the injection hole 11b. Any fuel pressure sensor may be used. Therefore, for example, a fuel pressure sensor may be mounted on the high-pressure pipe 42 b that connects the common rail 42 and the fuel injection valve 10. That is, the high-pressure pipe 42b connecting the common rail 42 and the fuel injection valve 10 and the high-pressure passage 11a in the body 11 correspond to a “fuel passage”.

  -Not only a diesel engine but the fuel injection state analysis apparatus mentioned above can also be applied to a gasoline direct-injection engine provided with a delivery pipe.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 11a ... High pressure passage, 11b ... Injection hole, 20 ... Fuel pressure sensor, 30 ... ECU, 34 ... Microcomputer, 42a ... Discharge port, 42b ... High pressure piping.

Claims (10)

A fuel injection valve (10) that is provided in each cylinder (# 1 to # 4) of the multi-cylinder internal combustion engine and injects fuel held in an accumulated state by the accumulator (42);
A fuel pressure sensor (20) for detecting a fuel pressure in the fuel passage (11a) from the discharge port (42a) of the pressure accumulating container to the injection hole (11b) of the fuel injection valve;
A fuel injection state analysis device (30) applied to a fuel injection system comprising:
An analysis unit (34) for analyzing a fuel injection state by the fuel injection valve based on an extracted value obtained by sampling a detection value of the fuel pressure sensor at a set sampling rate;
A rate changing unit (34) for changing the sampling rate so that the analysis by the analyzing unit is completed between the time when fuel is sequentially injected by the fuel injection valve of each cylinder;
A fuel injection state analyzing apparatus comprising: The rate changing unit
An injection interval calculation unit for calculating an injection interval at which fuel is sequentially injected by the fuel injection valve of each cylinder;
An analysis time calculation unit for calculating an analysis time required for the analysis by the analysis unit;
A rate setting unit that sets the sampling rate so that the analysis time calculated by the analysis time calculation unit does not exceed a predetermined ratio of the injection interval calculated by the injection interval calculation unit;
The fuel-injection-state analysis apparatus of Claim 1 provided with. In the case where the cylinder during fuel injection is an injection cylinder, and the cylinder that is stopped when the fuel is injected in the injection cylinder is a reference cylinder,
The analysis unit
An injection waveform generator that generates an injection waveform representing a change in fuel pressure detected by a fuel pressure sensor corresponding to the injection cylinder;
A reference waveform generator that generates a reference waveform representing a change in fuel pressure detected by a fuel pressure sensor corresponding to the reference cylinder;
Based on a waveform obtained by subtracting the reference waveform from the injection waveform, a calculation unit that calculates an injection state in the injection cylinder;
Have
The fuel injection state analysis device according to claim 1 or 2, wherein the rate changing unit preferentially lowers the sampling rate in the reference cylinder over the sampling rate in the injection cylinder.   The fuel injection state analysis device according to claim 3, wherein the rate changing unit lowers the sampling rate in the injection cylinder on condition that the sampling rate in the reference cylinder is a lower limit value.   The fuel injection state analysis device according to any one of claims 1 to 4, wherein the rate changing unit sets a lower limit value when changing the sampling rate in accordance with an operating state of the fuel injection system. The analysis unit calculates a plurality of parameters representing an injection state of the fuel,
The rate changing unit lowers the sampling rate of the detected value used for calculation of the parameter having a small influence on the fuel injection state lower than the sampling rate of the detected value used for calculating the parameter having a large influence. The fuel-injection-state analysis apparatus of any one of Claims 1-5. The analysis unit analyzes an injection state of each stage with respect to a plurality of stages of fuel injection by the fuel injection valve in each cylinder,
The fuel injection state analysis device according to any one of claims 1 to 6, wherein the rate changing unit lowers the sampling rate when the number of fuel injection stages by the fuel injection valve is larger than a predetermined number of stages.   The fuel injection state analysis device according to any one of claims 1 to 7, wherein the rate changing unit lowers the sampling rate when a rotational speed of the engine is higher than a predetermined rotational speed.   The fuel injection state analysis device according to any one of claims 1 to 8, wherein the rate changing unit lowers the sampling rate when a rotational acceleration of the engine is higher than a predetermined rotational acceleration.   When the analysis by the analysis unit cannot be completed between the time when fuel is sequentially injected by the fuel injection valve of each cylinder, the analysis unit performs the analysis intermittently with respect to the injection of each cylinder. The fuel injection state analysis apparatus according to any one of claims 1 to 9, further comprising an analysis thinning unit.

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