JP5182337B2 - Detection deviation judgment device of fuel pressure sensor - Google Patents

Description

  The present invention relates to an apparatus for determining whether or not a detection deviation has occurred in a fuel pressure sensor that detects a change in fuel pressure caused by injecting fuel from a fuel injection valve.

  When fuel is injected from the injection hole of the fuel injection valve, the fuel pressure in the fuel supply path leading to the injection hole changes. Therefore, in Patent Document 1, a fuel pressure sensor is mounted on each fuel injection valve to detect a change in fuel pressure caused by injection. According to this, it is possible to estimate the waveform indicating the change in the injection rate based on the detection value (injection sensor waveform) of the fuel pressure sensor, and it is possible to detect the actual injection state such as the injection start timing, the injection end timing, and the injection amount. By controlling the operation of the fuel injection valve based on the detected injection state, the operating state of the internal combustion engine can be optimized, and exhaust emission reduction and output torque improvement can be achieved.

  However, in the sensor waveform during injection, in addition to the pressure change caused by the injection, the pressure change caused when the fuel pump pumps the fuel, or the pressure in the common rail decreases by the amount of fuel injection. It includes the pressure changes that occur. Therefore, in Patent Document 1, the detection values (non-injection sensor waveforms) of the plurality of fuel pressure sensors corresponding to the cylinders that are not injecting fuel are acquired, and the non-injection sensor waveforms are subtracted from the injecting sensor waveforms. An injection waveform representing a change in fuel pressure due to the above is extracted. And the injection state is detected by estimating the waveform of the injection rate change based on the extracted injection waveform.

JP 2009-97385 A

  However, the detected value of the fuel pressure sensor may deviate from the actual pressure value due to, for example, deterioration of the fuel pressure sensor over time. Then, the detection accuracy of the injection state described above is deteriorated, and the operation state of the internal combustion engine cannot be sufficiently optimized.

  In order to solve this problem, the present inventor studied to determine whether or not a detection error occurred by the following method. In other words, if there is no detection deviation in any fuel pressure sensor, the sensor waveform detected at the same time during non-injection should be the same for all cylinders. The non-injection sensor waveforms of three cylinders or more are acquired, and these non-injection sensor waveforms are compared. For example, if only the non-injection sensor waveform of a predetermined cylinder is different from all other non-injection sensor waveforms, it can be determined that a detection deviation has occurred in the fuel pressure sensor corresponding to the predetermined cylinder.

  However, in the detection deviation determination method, it is required to simultaneously acquire the non-injection sensor waveforms of three or more cylinders detected at the same time, and only the non-injection sensor waveforms can be acquired for two cylinders. When the two non-injection sensor waveforms are different from each other, it is impossible to determine which fuel pressure sensor has a detection deviation.

  Further, in order to extract the injection waveform used for detection of the injection state, it is sufficient to acquire one non-injection sensor waveform in addition to the injection sensor waveform. Therefore, it is sufficient that an ECU (arithmetic unit) that generates a sensor waveform based on the detection value of the fuel pressure sensor can communicate with two fuel pressure sensors at the same time. On the other hand, in the detection deviation determination method, it is necessary to simultaneously detect and acquire the non-injection sensor waveforms of three or more cylinders. It will be high.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel pressure sensor capable of determining the presence or absence of detection deviation without increasing the processing capability required for communication with the fuel pressure sensor. The object is to provide a detection deviation determination device.

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

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

An injection-time sensor waveform acquisition means for acquiring an injection-time sensor waveform detected by a fuel pressure sensor corresponding to a cylinder during fuel injection among the plurality of fuel pressure sensors, and fuel injection is stopped among the plurality of fuel pressure sensors. Non-injection sensor waveform acquisition means for acquiring a non-injection sensor waveform detected by a fuel pressure sensor corresponding to the cylinder of the cylinder, and the injection sensor detected at the same time by different fuel pressure sensors among the plurality of fuel pressure sensors A plurality of injection waveform extracting means for acquiring a waveform and the non-injection sensor waveform, and subtracting the non-injection sensor waveform from the injection sensor waveform to extract an injection waveform representing a change in fuel pressure caused by injection; Of these cylinders, an arbitrary cylinder is a first cylinder, an arbitrary cylinder different from the first cylinder is a second cylinder, and the first cylinder and the second cylinder are different. In the case where the cylinder is defined as a third cylinder, and the injection waveform extracted by the ejection waveform extracting means when the first cylinder injection cylinder and the second cylinder is a non-injection cylinder, if the detected displacement is not generated first-and second deviation calculation means, the ejection waveform extracting means when said third cylinder injection cylinder and the first cylinder is a non-injection cylinder to the calculated difference between the reference injection waveform assuming the ejection waveform The third-first deviation calculating means for calculating a deviation between the injection waveform extracted by the reference injection waveform and the reference injection waveform, the deviation calculated by the first-second deviation calculating means, and the third-first Detection deviation determination means for determining whether a detection deviation has occurred in the fuel pressure sensor corresponding to the first cylinder based on the deviation calculated by the deviation calculation means.

  The operation and effect of the present invention will be described below with reference to FIG. 5 using a four-cylinder (# 1, # 2, # 3, # 4) internal combustion engine as an example.

  First, the operation of the extracting means when # 1 is the first cylinder, # 2 is the second cylinder, and # 3 is the third cylinder will be described. During the injection at # 1, the injection waveform W (# 1-2) obtained by subtracting the non-injection sensor waveform Wb (# 2) from the injection sensor waveform Wa (# 1) is extracted (FIG. 5A). reference). Further, during the injection at # 3, the injection waveform W (# 3-1) obtained by subtracting the non-injection sensor waveform Wb (# 1) from the injection sensor waveform Wa (# 3) is extracted (FIG. 5 ( b)).

  If detection deviation occurs in the fuel pressure sensors corresponding to # 1 among the fuel pressure sensors corresponding to # 1 to # 4, the two extracted injection waveforms W (# 1-2), W In any of (# 3-1), there should be a deviation in comparison with the reference injection waveform Wbase, and there is a deviation in only one of the injection waveforms W (# 1-2) and W (# 3-1). Will not occur.

  The same applies to the operation of the extraction means when # 4 is set as the first cylinder, # 3 is set as the second cylinder, and # 2 is set as the third cylinder. During injection at # 4, the sensor waveform Wa (# 4 during injection) ) Is extracted from the non-injection sensor waveform Wb (# 3) (see FIG. 5C). Further, during the injection at # 2, the injection waveform W (# 2-4) obtained by subtracting the non-injection sensor waveform Wb (# 4) from the injection sensor waveform Wa (# 2) is extracted (FIG. 5 ( d)).

  If detection deviation occurs in the fuel pressure sensors corresponding to # 4 among the fuel pressure sensors corresponding to # 1 to # 4, the two extracted injection waveforms W (# 4-3), W In any of (# 2-4), there should be a deviation in comparison with the reference injection waveform Wbase, and there is a deviation in only one of the injection waveforms W (# 4-3) and W (# 2-4). Will not occur.

  As described above, according to the above-described invention, it is possible to detect any one of the fuel pressure sensors by simply obtaining two of the sensor waveform at the time of injection and the sensor waveform at the time of non-injection detected by different fuel pressure sensors among the plurality of fuel pressure sensors. It can be determined whether or not a deviation has occurred. Therefore, it is possible to determine whether or not there is a detection deviation in the fuel pressure sensor without increasing the processing capacity required for communication with the fuel pressure sensor. The above-described invention can be applied to an internal combustion engine having three or more cylinders. For example, even in a six-cylinder or eight-cylinder internal combustion engine, the first cylinder, the second cylinder, and the third cylinder are set as described above. If you do, the same effect will be demonstrated.

  Further, according to the above invention, it can be determined as described below whether the detected value of the fuel pressure sensor is shifted to the plus side or the minus side.

  For example, when the injection waveform W (# 1-2) shown in FIG. 5 (a) and the injection waveform W (# 3-1) shown in FIG. 5 (b) are extracted, suppose that FIG. ) If the detected value of the fuel pressure sensor corresponding to # 1 is shifted to the minus side as indicated by Wa (# 1) and Wb (# 1), the injection waveform W (# 1-2 for the reference injection waveform Wbase ) Should be a negative value, and the injection waveform W (# 3-1) should have a positive value.

  In the above invention in view of this point, the deviation (Wbase-W (# 1-2)) calculated by the first-second deviation calculating means and the deviation (Wbase) calculated by the third-first deviation calculating means. -W (# 3-1)), it is determined whether there is a detection error in the fuel pressure sensor corresponding to the first cylinder, so which side is determined based on the positive / negative of the two deviations described above it can.

  The invention according to claim 2 is characterized in that the injection-time sensor waveform and the non-injection-time sensor waveform corresponding to the predetermined cylinder are continuously obtained from a fuel pressure sensor corresponding to the predetermined cylinder.

  For example, in a four-cycle internal combustion engine that repeatedly performs a compression stroke, a combustion stroke, an exhaust stroke, and an intake stroke, a sensor waveform during injection is acquired during a period in which a predetermined cylinder is in the combustion stroke, and then the exhaust stroke is continuously acquired. The sensor waveform during non-injection is acquired during the period. Alternatively, the non-injection sensor waveform is acquired during a period in which the predetermined cylinder is in the compression stroke, and then the injection sensor waveform is acquired continuously during the combustion stroke period.

  Thus, according to the above-described invention for continuously acquiring the sensor waveform during injection and the sensor waveform during non-injection from one fuel pressure sensor, the means (ECU) for acquiring the detected value from the fuel pressure sensor by communication includes a plurality of fuel pressures. When communicating to select and switch two sensors out of the sensors, the number of times of switching can be reduced. Therefore, the processing capability required for the means (ECU) to communicate with the fuel pressure sensor can be reduced.

  Here, in continuously acquiring the sensor waveform during injection and the sensor waveform during non-injection as described above, the acquisition start timing is set in advance, such as the timing when the piston of the internal combustion engine reaches top dead center or bottom dead center. What is necessary is just to fix and set to the time (crank angle) set beforehand.

Alternatively, as in the invention described in claim 3, the fuel injection start timing in the predetermined cylinder may be variably set. According to the above-mentioned invention variably set in this way, a change in fuel pressure caused by fuel injection from the nozzle hole can be reliably included in the sensor waveform during injection.
According to a fourth aspect of the present invention, the latest value of the injection waveform extracted by the injection waveform extraction means of a plurality of the cylinders and the storage values of the injection waveforms of all cylinders other than the current injection cylinder calculated in the past, And a reference injection waveform calculating means for calculating the average value thereof as the reference injection waveform.

The figure which shows the outline of the fuel-injection system with which the fuel-injection state detection apparatus concerning one Embodiment of this invention is applied. (A) is an injection command signal to the fuel injection valve shown in FIG. 1, (b) is an injection rate waveform representing a change in fuel injection rate caused by the injection command signal, and (c) is detected by a fuel pressure sensor shown in FIG. The time chart which shows the pressure waveform showing the change of the detected pressure made. The figure which shows the injection waveform W obtained by subtracting the sensor waveform Wb at the time of non-injection from the sensor waveform Wa at the time of injection. The time chart which shows the switching order in switching reception of the detection value output from a some fuel pressure sensor. The figure which shows the sensor waveform Wa at the time of injection acquired by switching of FIG. 4, the sensor waveform Wb at the time of non-injection, etc. The flowchart which shows the procedure which determines the detection shift | offset | difference of a fuel pressure sensor based on the sensor waveform Wa at the time of injection shown in FIG. 5, and the sensor waveform Wb at the time of non-injection. 7 is a determination table used in the determination of FIG.

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

  FIG. 1 shows a fuel injection valve 10 mounted on each cylinder of the engine, a fuel pressure sensor 20 mounted on each fuel injection valve 10, and an ECU 30 (an electronic control device installed in a vehicle). FIG. First, an engine fuel injection system including the fuel injection valve 10 will be described. The fuel in the fuel tank 40 is pumped and stored in the common rail 42 (pressure accumulator) by a high pressure pump 41 (fuel pump), and is distributed and supplied to the fuel injection valves 10 (# 1 to # 4) of each cylinder. The plurality of fuel injection valves 10 (# 1 to # 4) sequentially inject fuel in a preset order. In addition, since the plunger pump is used for the high pressure pump 41, fuel is pumped in synchronism with the reciprocation of the plunger.

  The ECU 30 controls the fuel pressure (rail pressure) in the common rail 42 as follows. That is, the high-pressure pump calculates the target rail pressure based on the engine operating state such as the engine load and the engine speed, and matches the actual rail pressure (corresponding to the pressure of the non-injection sensor waveform Wb described later) with the target rail pressure. 41 (feed amount, for example) is feedback controlled.

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

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

  Therefore, the ECU 30 controls the energization of the actuator 13 so that the opening / closing operation of the needle 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 needle 12. For example, the ECU 30 calculates a target injection state such as an injection start timing, an injection end timing, and an injection amount based on the rotation speed of the engine output shaft, the engine load, and the like, and sends an injection command signal to the actuator 13 so that the calculated target injection state is obtained. Is output to control the operation of the fuel injection valve 10.

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

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

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

  The mold IC 23 is formed by resin-molding electronic components such as an amplification circuit that amplifies the pressure detection signal output from the pressure sensor element 22 and a communication circuit 23a that performs bidirectional communication with the ECU 30. At the same time, it is mounted on the fuel injection valve 10. A connector 15 is provided on the upper portion of the body 11, and the mold IC 23, the actuator 13, and the ECU 30 are electrically connected by a harness 16 connected to the connector 15.

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

  Next, a sensor waveform during injection that represents a change in fuel pressure detected by a fuel pressure sensor 20 mounted on the fuel injection valve 10 during fuel injection, and an injection rate waveform that represents a change in fuel injection rate applied to the fuel injection valve 10. Will be described with reference to FIG.

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

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

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

  As explained above, the correlation between the injection sensor waveform and the injection rate waveform is high. The injection rate waveform shows the injection start time (R1 appearance time), the injection end time (R4 appearance time), and the injection amount (area of the halftone dot portion in FIG. 2B). An injection state can be detected by converting a sensor waveform during injection (or an injection waveform W described in detail later) into an injection rate waveform.

  By the way, the pressure of the fuel distributed and supplied from the common rail 42 to the fuel injection valve 10 changes every moment. For example, the solid line in FIG. 3A indicates the injection sensor waveform Wa, while the dotted line Wb in FIG. 3A indicates the change in the distribution supply pressure detected at the same time as the injection sensor waveform. Show. The change in the distribution supply pressure is detected by using the fuel pressure sensor 20 corresponding to the fuel injection valve 10 that is not injecting. Therefore, for example, when the fuel is injected from the fuel injection valve 10 (# 1) of the # 1 cylinder and the injection is stopped from the fuel injection valve 10 (# 2) of the # 2 cylinder, the # 1 cylinder (front cylinder) ) Detected by the fuel pressure sensor 20 corresponds to the injection sensor waveform Wa, and the pressure detected by the # 2 cylinder (back cylinder) fuel pressure sensor 20 corresponds to the non-injection sensor waveform Wb indicating a change in the distribution supply pressure. .

  The reason why the non-injection sensor waveform Wb illustrated in FIG. 3A is a waveform that gradually decreases with the start of injection is the amount that is distributed and supplied from the common rail 42 to the fuel injection valve 10 of the injection cylinder. This is due to a decrease in the distribution supply pressure. Incidentally, when pumping by the high-pressure pump 41 is performed during fuel injection, the distribution supply pressure rises even during fuel injection.

  In short, since the sensor waveform Wa at the time of injection is affected by the change in the distribution supply pressure (sensor waveform Wb at the time of non-injection), if the sensor waveform Wb at the time of non-injection is subtracted from the sensor waveform Wa at the time of injection. The influence of the change in the distribution supply pressure is removed from Wa. The solid line in FIG. 3B shows the sensor waveform at the time of injection after performing the correction to be subtracted in this way, and this waveform corresponds to an injection waveform W representing a change in fuel pressure caused by injection.

  Note that the injection sensor waveform Wa illustrated in FIG. 2C is a waveform when it is assumed that the distribution supply pressure has not changed, and the subtracted injection waveform W and the injection sensor waveform Wa are obtained. It is assumed that the waveforms are the same.

  Next, communication between the fuel pressure sensors 20 (# 1) to 10 (# 4) corresponding to the cylinders # 1 to # 4 and the ECU 30 will be described. Each of the fuel pressure sensors 20 (# 1) to 10 (# 4) is connected to the ECU 30 by harnesses 16 (# 1) to 16 (# 4), and the fuel pressure sensors 20 (# 1) to 10 (# 4) The communication circuit 23a and the communication circuit 31 provided in the ECU 30 allow the fuel pressure sensors 20 (# 1) to 10 (# 4) and the ECU 30 to communicate bidirectionally, provided that the communication circuit 31 can receive simultaneously. The number of fuel pressure sensors 20 is limited to two. That is, the communication circuit 31 receives and acquires detection signals from two fuel pressure sensors 20 selected from the four fuel pressure sensors 20 (# 1) to 10 (# 4).

  The selection is performed so that one of the selected fuel pressure sensors 20 includes the fuel pressure sensor 20 corresponding to the cylinder being injected. Incidentally, the waveform of the detection value acquired from the fuel pressure sensor 20 of the injection cylinder in this way corresponds to the sensor waveform Wa during injection. The waveform of the detection value acquired from the fuel pressure sensor of the non-injection cylinder, which is the remaining one of the selected fuel pressure sensors 20, corresponds to the non-injection sensor waveform Wb.

  Then, the communication circuit 31 selects two fuel pressure sensors 20 to be selected as shown in FIG. 4 so as to continuously acquire the sensor waveform Wa during injection and the sensor waveform Wb during non-injection from the fuel pressure sensor 20 corresponding to the predetermined cylinder. Switch. FIG. 4A is a time chart showing an example of the above switching, where the vertical axis indicates the fuel pressure sensors 20 of # 1, # 3, # 4, and # 2 in order from the top, and the horizontal axis indicates the combustion stroke of # 1. , # 3, # 4, # 2, # 1,...

  In the example of FIG. 4A, in the period A1 where # 1 is the combustion stroke and the period A2 where the exhaust stroke is # 1, the detection value of the fuel pressure sensor 20 of # 1 is continuously acquired, and then # 4 is the combustion stroke. In the period A3 that is and the period A4 that is the exhaust stroke, the switching is performed so that the detection value of the # 4 fuel pressure sensor 20 is continuously acquired. In addition, in period B1 in which # 3 is the combustion stroke and in period B2 in which the exhaust stroke is performed, the detection value of the fuel pressure sensor 20 of # 3 is continuously acquired, and thereafter, period B3 and exhaust stroke in which # 2 is the combustion stroke. In the period B4, the switching is performed so that the detection value of the # 2 fuel pressure sensor 20 is continuously acquired.

  FIG. 5 is a diagram showing a change in fuel pressure in each cylinder corresponding to the combustion cycle of FIG. 4. When switching is performed as described above, for example, fuel is injected from the fuel injection valve 10 (# 1) of the # 1 cylinder. At the same time, the pressure detected by the fuel pressure sensor 20 for the # 1 cylinder (front cylinder) (sensor waveform Wa (# 1) during injection) is acquired, and at the same time, the pressure detected by the fuel pressure sensor 20 for the # 2 cylinder (back cylinder) (Non-injection sensor waveform Wb (# 2)) is acquired (see FIG. 5A).

  Thereafter, at the time of fuel injection in the # 3 cylinder, the sensor waveform Wa (# 3) at the time of injection at the # 3 cylinder (front cylinder) is acquired, and at the same time, the sensor waveform at the time of non-injection in the # 1 cylinder (back cylinder). Wb (# 1) is acquired (see FIG. 5B). In the same manner, the sensor waveform Wa (# 4) during injection and the sensor waveform Wb (# 3) during non-injection are simultaneously acquired during fuel injection in the # 4 cylinder (see FIG. 5 (c)). During fuel injection, the sensor waveform Wa (# 2) during injection and the sensor waveform Wb (# 4) during non-injection are acquired simultaneously (see FIG. 5 (d)).

  The sensor waveform Wa during injection and the sensor waveform Wb during non-injection acquired in this way are used for extraction of the injection waveform W described above with reference to FIG. 3 (W = Wa−Wb). For example, the injection waveform W (# 1-2) representing the change in fuel pressure caused by injection in the # 1 cylinder is calculated by subtracting the non-injection sensor waveform Wb (# 2) from the injection sensor waveform Wa (# 1). The waveform shown at the bottom in FIG. Similarly, the injection waveforms W (# 3-1), W (# 4-3), and W (# 2-4) representing the change in fuel pressure caused by the injection in each cylinder are shown in FIGS. ) The waveform shown at the bottom in (d).

  Incidentally, in the example of FIG. 4A, in order to continuously obtain the detection value of the fuel pressure sensor 20, after obtaining the sensor waveform Wa at the time of injection of the front cylinder, the sensor waveform Wb at the time of non-injection of the back cylinder is obtained. ing. On the other hand, as shown in FIG. 4B, after acquiring the non-injection sensor waveform Wb of the back cylinder, the injection sensor waveform Wa of the front cylinder may be acquired.

  Here, the detection value of the fuel pressure sensor 20 may deviate from the actual pressure value due to aging degradation of the fuel pressure sensor 20 or the like. For example, when the detected value of the fuel pressure sensor 20 (# 1) of the # 1 cylinder becomes lower than the actual fuel pressure (shifts to the minus side), the sensor waveform Wa (# 1) during injection corresponding to the # 1 cylinder and the non-injection The hour sensor waveform Wb (# 1) is a waveform indicated by a solid line in the uppermost stage of FIG. Note that the waveform indicated by the dotted line in the uppermost stage is a waveform indicating an actual change in fuel pressure.

  When such a detection deviation occurs, the injection waveform W deviates from the actual fuel pressure change caused by the injection, so that the calculation accuracy of the injection rate waveform is deteriorated and the injection state is accurately controlled to the target injection state. I can't do that. As a result, the engine operating state cannot be sufficiently optimized, for example, exhaust emission is deteriorated and output torque is reduced.

  Therefore, in the present embodiment, the presence or absence of detection deviation of the fuel pressure sensor 20 is determined as follows using the sensor waveforms Wa and Wb acquired as described above. FIG. 6 is a flowchart showing a processing procedure of the above determination by the microcomputer of the ECU 30, and the processing is repeatedly executed at a predetermined cycle.

  First, in step S10 shown in FIG. 6 (sensor waveform acquisition unit during injection, sensor waveform acquisition unit during non-injection), the sensor waveform Wa during injection and the sensor waveform Wb during non-injection described above with reference to FIGS. get. In the subsequent step S11 (injection waveform extracting means), the non-injection sensor waveform Wb is subtracted from the injection sensor waveform Wa acquired in step S10 to extract the injection waveform W shown in the lowermost stage in FIG.

  In subsequent step S12, a reference injection waveform Wbase used for detection deviation determination to be performed later is calculated. This reference injection waveform Wbase assumes an injection waveform when no detection deviation occurs. For example, the injection waveforms W (# 1-2), W (# 3-1), An average value of W (# 4-3) and W (# 2-4) is calculated, and a waveform (average injection waveform) including the average value is calculated as a reference injection waveform Wbase.

  In the subsequent step S13 (first-second deviation calculating means, third-first deviation calculating means), the injection waveforms W (# 1-2), W (# 3-1), W (# 4- 3) By subtracting the reference injection waveform Wbase from W (# 2-4), deviations ΔW (# 1-2), ΔW (# 3-1), ΔW (# 4-3) and ΔW (# 2-4) are calculated. In the example of FIG. 5 in which the detected value of the # 1 cylinder fuel pressure sensor 20 (# 1) is shifted to the minus side, W (# 1-2), W (# 3-1), W (# 4- 3) The average value of W (# 2-4) coincides with W (# 4-3) and W (# 2-4). Therefore, the deviations ΔW (# 4-3) and ΔW (# 2-4) are zero. On the other hand, the deviation ΔW (# 1-2) of the injection waveform W (# 1-2) based on the sensor waveform of the fuel pressure sensor 20 (# 1) where the detection deviation has occurred becomes negative, and the injection waveform W (# 3- The deviation ΔW (# 3-1) of 1) is positive.

  In the subsequent step S14 (detection deviation determination means), the deviations ΔW (# 1-2), ΔW (# 3-1), ΔW (# 4-3), ΔW (# 2-4) of each cylinder calculated in step S13. ), Whether or not there is a detection deviation in any of the fuel pressure sensors 20 (# 1), 20 (# 2), 20 (# 3), and 20 (# 4) of each cylinder is determined in FIG. Determine according to the table.

  As illustrated in FIG. 5, when the detected value of the # 1 cylinder fuel pressure sensor 20 (# 1) is shifted to the minus side, ΔW (# 1-2) = minus, ΔW (# 3-1 ) = Plus, ΔW (# 4-3) = 0, ΔW (# 2-4) = 0. Therefore, when these deviations ΔW are the determination pattern J1 shown in FIG. 7, it is determined that the detected value of the fuel pressure sensor 20 (# 1) of the # 1 cylinder is shifted, and the detected shift is on the minus side. Determine that it has occurred. On the other hand, when the detected value of the fuel pressure sensor 20 (# 1) is shifted to the plus side, ΔW (# 1-2) = plus, ΔW (# 3-1) = minus, ΔW (# 4-3) = 0 and ΔW (# 2-4) = 0. Therefore, when the deviation ΔW is the determination pattern J2, it is determined that the detected value of the fuel pressure sensor 20 (# 1) of the # 1 cylinder is shifted to the plus side.

  Similarly, when the determination pattern is J3, the detection value of the # 3 cylinder fuel pressure sensor 20 (# 3) is on the minus side, and when the determination pattern is J4, the detection value of the fuel pressure sensor 20 (# 3) is Judge that it is shifted to the plus side. The determination is similarly performed for the determination patterns J5 to J8.

  In short, if a detection deviation occurs in the fuel pressure sensor 20 in any of the plurality of cylinders, two of the calculated deviations ΔW will deviate from the reference injection waveform Wbase. In this case, it can be determined that a detection deviation has occurred in the fuel pressure sensor 20 of the cylinder involved in any of the two deviations ΔW in which the deviation has occurred. Then, based on the positive and negative of the two deviations ΔW where the deviation occurs, it can be determined according to the determination table of FIG. 7 whether the detected value of the fuel pressure sensor 20 where the detection deviation occurs is shifted between positive and negative.

  Incidentally, when all the deviations ΔW are zero, it is determined that no detection deviation occurs in the fuel pressure sensor 20 of any cylinder. If it is determined that no detection deviation has occurred (S15: NO), the process of FIG. 6 is temporarily terminated.

  On the other hand, if it is determined by the detection deviation determination in step S14 that there is a detection deviation in the fuel pressure sensor 20 of any cylinder (S15: YES), it is determined in step S16 (correction means) that there is a detection deviation. The detected value of the fuel pressure sensor 20 is corrected based on the deviation ΔW corresponding to the cylinder. In the subsequent injection control, the injection waveform W is calculated using the sensor waveform Wa during injection and the sensor waveform Wb during non-injection based on the corrected detection value, and the injection rate waveform is estimated based on the injection waveform W. The injection command signal in the injection map is corrected.

  Note that in step S13, each of the deviation calculated by the “first-second deviation calculating unit” and the deviation calculated by the “third-first deviation calculating unit” is the # 1 cylinder being the injection cylinder. In this case, it corresponds to the deviation ΔW (# 1-2) and the deviation ΔW (# 3-1). In this case, it is possible to determine the detection deviation of the fuel pressure sensor 20 (# 1) corresponding to the # 1 cylinder. In this case, the # 1 cylinder corresponds to the “first cylinder”, the # 2 cylinder corresponds to the “second cylinder”, and the # 3 cylinder corresponds to the “third cylinder”.

  When the # 3 cylinder is an injection cylinder, each of the deviation calculated by the “first-second deviation calculating unit” and the deviation calculated by the “third-first deviation calculating unit” is: This corresponds to the deviation ΔW (# 3-1) and the deviation ΔW (# 4-3). In this case, it is possible to determine the detection deviation of the fuel pressure sensor 20 (# 3) corresponding to the # 3 cylinder. In this case, the # 3 cylinder corresponds to the “first cylinder”, the # 1 cylinder corresponds to the “second cylinder”, and the # 4 cylinder corresponds to the “third cylinder”.

  Similarly, when the # 4 cylinder is an injection cylinder, it corresponds to the deviation ΔW (# 4-3) and the deviation ΔW (# 2-4), and the detection deviation of the fuel pressure sensor 20 (# 4) is determined. it can. In this case, the # 4 cylinder corresponds to the “first cylinder”, the # 3 cylinder corresponds to the “second cylinder”, and the # 2 cylinder corresponds to the “third cylinder”. When the # 2 cylinder is an injection cylinder, it corresponds to the deviation ΔW (# 2-4) and the deviation ΔW (# 1-2), and the detection deviation of the fuel pressure sensor 20 (# 2) can be determined. In this case, the # 2 cylinder corresponds to the “first cylinder”, the # 4 cylinder corresponds to the “second cylinder”, and the # 1 cylinder corresponds to the “third cylinder”.

  As described above, according to the present embodiment, it is not necessary to simultaneously acquire sensor waveforms from the fuel pressure sensors 20 of all the cylinders, and only two of the sensor waveform Wa during injection and the sensor waveform Wb during non-injection are acquired simultaneously. Thus, it is possible to determine which fuel pressure sensor 20 has a detection deviation and the direction of the detection deviation. Therefore, it is possible to determine the detection deviation without making the communication circuit 31 used for communication with the fuel pressure sensor 20 into a circuit that can receive four simultaneously.

  In addition, since the detection deviation determination described above is performed using the injection waveform W extracted by subtracting the non-injection sensor waveform Wb from the injection sensor waveform Wa, a waveform (injection rate waveform) indicating an injection rate change is estimated. Detection deviation can be determined using the injection waveform W used in the above. Therefore, it is unnecessary to generate a waveform dedicated to detection deviation determination from the detected value of the fuel pressure sensor.

  Further, since the detection value of the fuel pressure sensor 20 in which the detection deviation has occurred is corrected based on the deviation ΔW used for detection deviation determination, the calculation accuracy of the injection rate waveform can be improved, and the injection state can be accurately controlled to the target injection state. Will be able to. Therefore, it is possible to sufficiently optimize the operating state of the engine and promote reduction of exhaust emission and improvement of output torque.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows. Moreover, you may make it combine the characteristic structure of each embodiment arbitrarily, respectively.

  In the above-described embodiment shown in FIG. 4A, a period corresponding to a 360 crank angle from the time when the piston of the engine is located at the top dead center or the bottom dead center, and the symbol M ( During the period indicated by # 3) (acquisition period M (# 3)), the sensor waveform Wa during injection and the sensor waveform Wb during non-injection are continuously acquired. That is, the acquisition start timing of the sensor waveforms Wa and Wb is set as the time point at which the top dead center or the bottom dead center is located. On the other hand, the acquisition start timings of the sensor waveforms Wa and Wb may be variably set according to the fuel injection start timing of the corresponding cylinder. For example, the acquisition period M (# 3) described above may be represented by the symbol M ′ ( As shown in # 3), it may be shifted to the advance side or the retard side from the top dead center position.

  For example, when performing multi-stage injection in which multiple injections are performed from the same fuel injection valve 10 during one combustion cycle, injection is performed in two stages of pilot injection + main injection, and injection is performed in two stages of main injection + post injection. Then, the injection start timing of the main injection changes greatly. Therefore, if the acquisition start timing of the injection sensor waveform Wa for the main injection is variably set according to the fuel injection start timing without being limited to the piston top dead center point, the change in the fuel pressure caused by the fuel injection is injected. The time sensor waveform Wa can be reliably included.

  Even if there is no detection deviation for all the fuel pressure sensors 20, the values of the in-injection sensor waveforms Wa that are successively and sequentially acquired do not coincide with each other during the transition in which the target injection state is changed. Then, each deviation ΔW used for detection deviation determination also does not match, and there is a risk of erroneous determination that a detection deviation has occurred. In view of this point, when the target injection state (or the actual injection state detected from the injection rate estimation waveform) is in a stable state that fluctuates within a predetermined range, the in-injection sensor waveform Wa and the non-injection sensor waveform Wb are It is desirable to sequentially detect and perform detection deviation determination. For example, when the command injection amount of each cylinder is the same (or within a predetermined range), both sensor waveforms Wa and Wb may be sequentially acquired to perform detection deviation determination.

  Even if there is no detection deviation for all the fuel pressure sensors 20, the values of the non-injection sensor waveforms Wb that are successively acquired when the rail pressure is changing abruptly do not match. Then, each deviation ΔW used for detection deviation determination also does not match, and there is a risk of erroneous determination that a detection deviation has occurred. In view of this point, the non-injection sensor waveform Wb and the injection sensor waveform when the target rail pressure (or the actual rail pressure detected from the non-injection sensor waveform Wb) fluctuates within a predetermined range. It is desirable to sequentially detect Wa and perform detection deviation determination.

  As described above, the high pressure pump 41 pumps fuel in synchronism with the reciprocation of the plunger. Therefore, the fuel pressure in the common rail 42 increases during the fuel pumping period, and the non-injection sensor waveform Wb also increases with the increase. On the other hand, the fuel pressure in the common rail 42 is reduced by the amount of fuel injected in the injection cylinder during the period in which the fuel is not being pumped, and the non-injection sensor waveform Wb is also reduced along with the drop (see FIG. 5). In the embodiment shown in FIG. 5, the deviation ΔW used for detection deviation determination is calculated using the injection waveform W based on the non-injection sensor waveform Wb acquired during the period when the fuel is not being pumped. On the other hand, the deviation ΔW used for detection deviation determination may be calculated using the injection waveform W based on the non-injection sensor waveform Wb acquired during the fuel pumping period.

  In performing the detection deviation determination in step S14, if each deviation ΔW calculated in step S13 is less than a predetermined threshold value TH, the deviation ΔW may be regarded as zero and determined.

  In the above embodiment, the average value of the injection waveforms W (# 1-2), W (# 3-1), W (# 4-3), and W (# 2-4) obtained continuously is calculated. Then, a waveform composed of the average value is calculated as a reference injection waveform Wbase. That is, the average injection waveform representing the average of the first to second injection waveforms and the third to first injection waveforms is set as the reference injection waveform Wbase. On the other hand, the estimated injection waveform W ′ is calculated using a map or the like based on the injection command signal output to the fuel injection valve 10 or the target injection state, and the estimated injection waveform W ′ is used as the reference injection waveform Wbase. May be.

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

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 11b ... Injection hole, 20 ... Fuel pressure sensor, 42 ... Common rail (distribution container), 42a ... Discharge port, S10 ... Sensor waveform acquisition means at the time of injection, Sensor waveform acquisition means at the time of non-injection, S11 ... Injection waveform Extracting means, S13... 1st to 2nd deviation calculating means, 3rd to 1st deviation calculating means, S14... Detection deviation determining means, Wa... Sensor waveform during injection, Wb. .

Claims (4)

A fuel injection valve provided in each cylinder of the multi-cylinder internal combustion engine;
A distribution container for accumulating and supplying fuel supplied from a fuel pump to the plurality of fuel injection valves;
Change in fuel pressure that is provided for each of a plurality of cylinders and that occurs in the fuel supply path from the outlet of the distribution container to the nozzle hole as fuel is injected from the nozzle hole of the fuel injection valve A fuel pressure sensor for detecting
Applied to the fuel injection system with
An in-injection sensor waveform acquisition means for acquiring an in-injection sensor waveform detected by a fuel pressure sensor corresponding to a cylinder during fuel injection among the plurality of fuel pressure sensors;
Non-injection sensor waveform acquisition means for acquiring a non-injection sensor waveform detected by a fuel pressure sensor corresponding to a cylinder in which fuel injection is stopped among the plurality of fuel pressure sensors;
While acquiring the sensor waveform during injection and the sensor waveform during non-injection detected at the same time by different fuel pressure sensors among the plurality of fuel pressure sensors, subtracting the sensor waveform during non-injection from the sensor waveform during injection, An injection waveform extracting means for extracting an injection waveform representing a change in fuel pressure caused by injection;
An arbitrary cylinder among the plurality of cylinders is a first cylinder, an arbitrary cylinder different from the first cylinder is a second cylinder, an arbitrary cylinder different from the first cylinder and the second cylinder is a third cylinder When the first cylinder is an injection cylinder and the second cylinder is a non-injection cylinder, the injection waveform extracted by the injection waveform extraction means and the injection waveform when no detection deviation occurs are assumed. First to second deviation calculating means for calculating a deviation from the reference injection waveform,
Third-first deviation calculating means for calculating a deviation between the injection waveform extracted by the injection waveform extracting means and the reference injection waveform when the third cylinder is an injection cylinder and the first cylinder is a non-injection cylinder. When,
Based on the deviation calculated by the first-second deviation calculating means and the deviation calculated by the third-first deviation calculating means, it is determined whether a detection deviation has occurred in the fuel pressure sensor corresponding to the first cylinder. Detection deviation determination means for determining;
A detection deviation determination device for a fuel pressure sensor, comprising:   The detection of the fuel pressure sensor according to claim 1, wherein the sensor waveform during injection and the sensor waveform during non-injection corresponding to the predetermined cylinder are continuously acquired from a fuel pressure sensor corresponding to the predetermined cylinder. Deviation determination device.   3. The acquisition start timing is variably set according to the fuel injection start timing in the predetermined cylinder when continuously acquiring the injection sensor waveform and the non-injection sensor waveform. The detection deviation determination apparatus of the fuel pressure sensor described in 1. From the latest value of the injection waveform extracted by the injection waveform extraction means of the plurality of cylinders and the stored value of the injection waveform of all cylinders other than the current injection cylinder calculated in the past, the average value thereof is The fuel pressure sensor detection deviation determination device according to any one of claims 1 to 3, further comprising reference injection waveform calculation means for calculating the reference injection waveform.

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