JP5774521B2 - Fuel leak detection device - Google Patents

Description

  The present invention relates to a fuel leak detection device that detects an abnormal fuel leak in a fuel injection system.

  2. Description of the Related Art Conventionally, there is a common rail type fuel injection system that detects an abnormal fuel leakage (see, for example, Patent Document 1). In the device described in Patent Document 1, the discharge amount QT of the fuel pump, the internal leak amount QI of the injector, the switching leak amount QS associated with the switching of the injector, the fuel amount QP corresponding to the change in the common rail pressure, and the target fuel injection amount QF is calculated. Then, the fuel leakage amount QL = QT− (QI + QS + QP + QF) is calculated, and when the fuel leakage amount QL is equal to or greater than a predetermined value, it is determined that an abnormal fuel leakage has occurred.

JP 9-177586 A

  However, in the thing of patent document 1, said QT, QI, QS, QP, and QF are calculated using the preset arithmetic expression and map. For this reason, it is not always possible to accurately calculate these amounts, and it is necessary to set determination values in consideration of calculation errors of these amounts. Therefore, there is a limit to improving the detection accuracy of abnormal fuel leakage.

  The present invention has been made to solve these problems, and an object of the present invention is to provide a fuel leakage detection device capable of improving the detection accuracy of abnormal fuel leakage.

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

A first aspect of the invention is a fuel leak detection device (30, 20a) applied to a fuel injection system (50) in which fuel supplied from a pressure accumulating vessel (12) is injected by a fuel injection valve (20), Based on the fuel pressure sensor (20a) for sequentially detecting the fuel pressure in the fuel passage (22) from the pressure accumulating container to the injection hole (20f) of the fuel injection valve, and the waveform of the fuel pressure sequentially detected by the fuel pressure sensor. An injection period calculating means for calculating an injection period during which the fuel is injected by the fuel injection valve, and the fuel pressure detected by the fuel pressure sensor at the start point of the predetermined period including the injection period, A first calculating means for calculating a first change amount that is a change amount up to the fuel pressure detected by the fuel pressure sensor at the end point of Second calculation means for calculating a second change amount that is a change amount from the fuel pressure detected by the fuel pressure sensor to the fuel pressure detected by the fuel pressure sensor at the end of the injection period; and the predetermined period; Abnormal leakage of the fuel from the fuel passage is detected based on a change amount per unit period calculated from a difference from the injection period and a difference between the first change amount and the second change amount. And a leak detection means.

  According to the above configuration, the fuel pressure in the fuel passage from the pressure accumulating container to the injection hole of the fuel injection valve is sequentially detected by the fuel pressure sensor. For this reason, the fluctuation of the fuel pressure at the injection hole can be accurately detected before the fluctuation of the fuel pressure in the pressure accumulating vessel is attenuated. And since the injection period in which the fuel is injected by the fuel injection valve is calculated based on the waveform of the fuel pressure sequentially detected by the fuel pressure sensor, the actual injection period can be accurately calculated.

  Further, a first change amount that is a change amount from the fuel pressure detected by the fuel pressure sensor at the start point of the predetermined period including the injection period to the fuel pressure detected by the fuel pressure sensor at the end point of the predetermined period is calculated. The first change amount indicates the amount by which the fuel pressure has changed during a predetermined period including the injection period. Further, a second change amount that is a change amount from the fuel pressure detected by the fuel pressure sensor at the start point of the injection period to the fuel pressure detected by the fuel pressure sensor at the end point of the injection period is calculated. The second change amount indicates the amount of change in the fuel pressure during the injection period, that is, the change amount of the fuel pressure due to fuel injection at the fuel injection valve.

  Here, the difference between the predetermined period and the injection period indicates a period excluding the injection period in the predetermined period, that is, a non-injection period in which fuel is not injected by the fuel injection valve. Further, the difference between the first change amount and the second change amount is the difference between the change amount of the fuel pressure during the predetermined period and the change amount of the fuel pressure during the injection period, that is, the change amount of the fuel pressure during the non-injection period. Is shown. The amount of change per unit period calculated from these indicates the rate of change of the fuel pressure after excluding the influence of injection, and is an index that accurately reflects the degree of fuel leakage. Therefore, the detection accuracy of abnormal fuel leakage can be improved by detecting abnormal fuel leakage from the fuel passage based on the amount of change in fuel pressure per unit period in the non-injection period. Moreover, even when fuel is being injected by the fuel injection valve, abnormal fuel leakage can be detected.

In the second invention, the present invention is applied to a fuel injection system in which the fuel is injected a plurality of times by the same fuel injection valve per combustion cycle, and the injection period calculation means is configured to each of a plurality of injections by the fuel injection valve. The first calculation means calculates the first change amount for the predetermined period including a plurality of the injection periods, and the second calculation means calculates each of the plurality of the injection periods. The second change amount is calculated, and the leak detection means calculates the difference between the predetermined period and the sum of the plurality of injection periods, and the first change amount and the sum of the plurality of second change amounts. An abnormal leakage of the fuel from the fuel passage is detected based on the amount of change per unit period calculated from the difference.

  In a fuel injection system, fuel may be injected multiple times by the same fuel injection valve per combustion cycle. In this case, multiple fuel injections affect the fuel pressure in the fuel passage.

  In this regard, according to the above configuration, the injection period is calculated for each of a plurality of injections by the fuel injection valve. Then, the first change amount is calculated for a predetermined period including a plurality of injection periods, and the second change amount is calculated for each of the plurality of injection periods. For this reason, the first change amount indicates the amount by which the fuel pressure has changed in a predetermined period including a plurality of injection periods. Each second change amount indicates an amount of change in fuel pressure during each injection period, that is, a change amount of fuel pressure due to each fuel injection at the fuel injection valve.

  Further, based on the difference between the predetermined period and the sum of the plurality of injection periods and the difference between the first change amount and the sum of the plurality of second change amounts, the fuel passage is based on the change amount per unit period. An abnormal leak of fuel from is detected. For this reason, the calculated amount of change per unit period indicates the rate of change of the fuel pressure after excluding the influence of multiple injections, and is an index that accurately reflects the degree of fuel leakage. Therefore, even in a fuel injection system in which fuel is injected a plurality of times by the same fuel injection valve per combustion cycle, the detection accuracy of abnormal fuel leakage can be improved.

A third invention is a fuel leak detection device (30, 20a) applied to a fuel injection system (50) in which fuel supplied from a pressure accumulating vessel (12) is injected by a fuel injection valve (20), Based on the fuel pressure sensor (20a) for sequentially detecting the fuel pressure in the fuel passage (22) from the pressure accumulating container to the injection hole (20f) of the fuel injection valve, and the waveform of the fuel pressure sequentially detected by the fuel pressure sensor. A non-injection period calculating means for calculating a non-injection period excluding an injection period in which the fuel is injected by the fuel injection valve in a predetermined period, and a change speed of the fuel pressure in the non-injection period. And a leak detecting means for detecting an abnormal leak of the fuel from the fuel passage.

According to the above configuration, the fuel pressure fluctuation at the injection hole can be accurately detected, as in the first invention. Then, based on the fuel pressure waveform sequentially detected by the fuel pressure sensor, a non-injection period excluding an injection period in which fuel is injected by the fuel injection valve in a predetermined period is calculated. For this reason, the actual non-injection period can be accurately calculated as in the case of calculating the actual injection period. And since the abnormal leak of the fuel from the fuel passage is detected based on the change speed of the fuel pressure in the non-injection period where the influence of the injection does not reach, the detection accuracy of the abnormal fuel leak can be improved. . Moreover, even when fuel is being injected by the fuel injection valve, abnormal fuel leakage can be detected.

The schematic diagram which shows the fuel-injection system in 1st Embodiment. Sectional drawing which shows the injector of FIG. 1 typically. The flowchart which shows the process sequence of fuel-injection control. The flowchart which shows the process sequence of abnormal fuel leak detection. The time chart which shows the relationship between the waveform of the detection pressure at the time of single stage injection execution, and the waveform of an injection rate. The time chart which shows the relationship between the waveform of the detection pressure at the time of multistage injection execution, and the waveform of an injection rate. The time chart which shows the relationship between the pumping component in 2nd Embodiment, and the waveform of detected pressure.

  Each embodiment will be described below with reference to the drawings. Each embodiment is embodied as a common rail fuel injection system for a four-wheeled vehicle engine (internal combustion engine), for example. This system is used when high-pressure fuel (for example, light oil having an injection pressure of “1000 atm” or higher) is directly injected into a combustion chamber (cylinder) of a diesel engine.

(First embodiment)
First, an outline of a common rail fuel injection system will be described with reference to FIG. In this embodiment, a multi-cylinder (for example, inline 4-cylinder) 4-stroke, reciprocating diesel engine is assumed. In this engine, a cylinder discrimination sensor (electromagnetic pickup) provided on the camshaft of the intake / exhaust valve sequentially discriminates the target cylinder at that time, and intake, compression, combustion, and exhaust for each of the four cylinders # 1 to # 4 are performed. One combustion cycle by the four strokes is executed at a period of “720 ° CA”. Specifically, one combustion cycle is sequentially executed in the order of cylinders # 1, # 3, # 4, and # 2, with a shift of “180 ° CA” between the cylinders.

  As shown in the figure, the fuel injection system 50 is roughly configured by each device that an ECU 30 (electronic control unit) takes in sensor outputs from various sensors and constitutes a fuel supply system based on the respective sensor outputs. It is comprised so that the drive of may be controlled. The ECU 30 adjusts the current supply amount to the intake adjustment valve 11c and controls the fuel discharge amount of the fuel pump 11 to a desired value, thereby feedback-controlling the fuel pressure in the common rail 12 (pressure accumulator) to the target value (for example, PID control). Then, based on the fuel pressure, the fuel injection amount to the predetermined cylinder of the target engine, and consequently the output of the engine (the rotational speed and torque of the output shaft) are controlled to a desired magnitude.

  Various devices constituting the fuel supply system are arranged in order of the fuel tank 10, the fuel pump 11 (pump), the common rail 12, and the injector 20 (fuel injection valve) from the upstream side of the fuel. Of these, the fuel tank 10 and the fuel pump 11 are connected by a pipe 10a via a fuel filter 10b.

  The fuel pump 11 has a high-pressure pump 11a and a low-pressure pump 11b that are driven by a drive shaft 11d. The fuel pumped up from the fuel tank 10 by the low pressure pump 11b is pressurized and discharged by the high pressure pump 11a. The amount of fuel pumped to the high-pressure pump 11a, and hence the amount of fuel discharged from the fuel pump 11, is metered by a suction control valve (SCV) 11c provided on the fuel suction side of the fuel pump 11. That is, in the fuel pump 11, the fuel discharge from the pump 11 is adjusted by adjusting the drive current amount (and consequently the valve opening) of the intake adjustment valve 11 c (for example, a normally-on type adjustment valve that opens when not energized). The amount is controlled to the desired value.

  Of the two pumps constituting the fuel pump 11, the low-pressure pump 11b is configured as a trochoid feed pump, for example. On the other hand, the high-pressure pump 11a is composed of, for example, a plunger pump, and fuel sent to the pressurizing chamber by reciprocating predetermined plungers (for example, three plungers) in the axial direction by eccentric cams (not shown). Are sequentially pumped at a predetermined timing. Both pumps are driven by the drive shaft 11d. Incidentally, the drive shaft 11d is interlocked with the crankshaft 41, which is the output shaft of the target engine, and rotates, for example, at a ratio of "1/1" or "1/2" with respect to one rotation of the crankshaft 41. That is, the low pressure pump 11b and the high pressure pump 11a are driven by the output of the target engine.

  The fuel pumped up from the fuel tank 10 through the fuel filter 10 b by the fuel pump 11 is pressurized and supplied (pressure-fed) to the common rail 12. The common rail 12 stores the fuel pumped from the fuel pump 11 in a high pressure state. The common rail 12 distributes and supplies the stored fuel to the injectors 20 of the cylinders # 1 to # 4 through the high-pressure pipe 14 provided for each cylinder. The fuel discharge ports 21 of these injectors 20 (# 1) to (# 4) are connected to a pipe 18 for returning excess fuel to the fuel tank 10, respectively. In addition, an orifice 12 a (fuel pulsation reducing means) is provided between the common rail 12 and the high-pressure pipe 14 to attenuate the pressure pulsation of fuel propagating from the common rail 12 to the high-pressure pipe 14.

  FIG. 2 shows a detailed structure of the injector 20. The four injectors 20 (# 1) to (# 4) have the same structure (for example, the structure shown in FIG. 2). Each of the injectors 20 is a hydraulically driven fuel injection valve that uses combustion fuel (fuel in the fuel tank 10). During fuel injection, driving power is transmitted through the hydraulic chamber Cd (control chamber). As shown in the figure, the injector 20 is configured as a normally closed type fuel injection valve that is in a closed state when not energized.

  High-pressure fuel supplied from the common rail 12 flows into the fuel inlet 22 formed in the housing 20 e of the injector 20. A part of the high-pressure fuel that flows in flows into the hydraulic chamber Cd, and the other flows toward the injection hole 20f. A leak hole 24 that is opened and closed by the control valve 23 is formed in the hydraulic chamber Cd. When the leak hole 24 is opened by the control valve 23, the fuel in the hydraulic chamber Cd is returned to the fuel tank 10 from the leak hole 24 through the fuel discharge port 21.

  When fuel is injected from the injector 20, the control valve 23 is operated according to the energized state (energized / non-energized) for the solenoid 20b constituting the two-way solenoid valve. As a result, the degree of sealing of the hydraulic chamber Cd, and consequently the pressure in the hydraulic chamber Cd (corresponding to the back pressure of the needle valve 20c) is increased or decreased. As the pressure increases or decreases, the needle valve 20c reciprocates (up and down) in the housing 20e according to or against the extension force of the spring 20d (coil spring). Thereby, the internal fuel passage 25 to the injection hole 20f is opened and closed. Specifically, the needle valve 20c is seated or separated from the valve seat portion based on the reciprocating motion.

  Here, drive control of the needle valve 20c is performed through on / off control. That is, a pulse signal (energization signal) for instructing on / off is sent from the ECU 30 to the drive portion (the above-described two-way electromagnetic valve) of the needle valve 20c. Then, the needle valve 20c is lifted up based on the ON signal (or OFF signal), and the injection hole 20f is opened. On the other hand, the needle valve 20c is lifted down based on the off signal (or on signal), and the injection hole 20f is closed.

  Incidentally, the pressure increasing process of the hydraulic chamber Cd is performed by supplying fuel from the common rail 12. On the other hand, the pressure reducing process of the hydraulic chamber Cd is performed by opening the leak hole 24 by operating the control valve 23 by energizing the solenoid 20b. As a result, the fuel in the hydraulic chamber Cd is returned to the fuel tank 10 through the pipe 18 (FIG. 1) connecting the injector 20 and the fuel tank 10. That is, by adjusting the fuel pressure in the hydraulic chamber Cd by the opening / closing operation of the control valve 23, the operation of the needle valve 20c that opens and closes the injection hole 20f is controlled. In the injector 20, even when the injection hole 20 f is closed, an internal leak amount QI is generated due to fuel leaking from a gap between parts.

  In the non-driving state of the injector 20, the needle valve 20c is displaced toward the valve closing side by a constantly applied force toward the valve closing side (extension force by the spring 20d). On the other hand, in the driving state, when the driving force is applied as described above, the needle valve 20c is displaced toward the valve opening side against the extension force of the spring 20d. At this time, the lift amount of the needle valve 20c changes substantially symmetrically between the non-driven state and the driven state.

  A fuel pressure sensor 20a (see also FIG. 1) for detecting the fuel pressure is attached to the injector 20. Specifically, the fuel inlet 22 formed in the housing 20e and the high-pressure pipe 14 are connected by a jig 20j, and the fuel pressure sensor 20a is attached to the jig 20j. By attaching the fuel pressure sensor 20a to the fuel inlet 22 of the injector 20 in this way, it is possible to detect the fuel pressure (inlet pressure) in the fuel inlet 22 at any time. Specifically, the output of the fuel pressure sensor 20a can detect (measure) the fluctuation of the fuel pressure accompanying the injection operation of the injector 20, the fuel pressure level (stable pressure), the fuel injection pressure, and the like.

  The fuel pressure sensor 20a is provided for each of the plurality of injectors 20 (# 1) to (# 4). Based on the output of the fuel pressure sensor 20a, the waveform of the fuel pressure accompanying the injection operation of the injector 20 can be detected with high accuracy for a predetermined injection (details will be described later).

  A vehicle (not shown) (for example, a four-wheel passenger car or a truck) is provided with various sensors for vehicle control in addition to the above sensors. For example, a crank angle sensor 42 (for example, an electromagnetic pickup) that outputs a crank angle signal at every predetermined crank angle (for example, at a cycle of 30 ° CA) is provided on the outer peripheral side of the crankshaft 41 that is the output shaft of the target engine. . The crank angle sensor 42 detects the rotation angle position, rotation speed (engine rotation speed), and the like of the crankshaft 41. The accelerator pedal of the vehicle is provided with an accelerator sensor 44 that outputs an electrical signal corresponding to the state (displacement amount) of the accelerator pedal. The accelerator sensor 44 detects the amount of operation (depression amount) of the accelerator pedal by the driver.

  In such a system, the part that performs engine control is the ECU 30. The ECU 30 includes a known microcomputer, and grasps the operating state of the target engine and the user's request based on the detection signals of the various sensors. Then, by operating various actuators such as the suction adjusting valve 11c and the injector 20 in accordance with them, various controls relating to the engine are performed in an optimum manner according to the situation at that time.

  The microcomputer mounted on the ECU 30 includes a CPU (basic processing unit) that performs various calculations, a RAM as a main memory that temporarily stores data during the calculation, calculation results, and the like, and a ROM as a program memory. And a nonvolatile memory for storing data, a backup RAM, and the like. The ROM stores various programs and control maps related to engine control including a program related to fuel injection control, and the nonvolatile memory for storing data includes various data including design data of the target engine. Control data and the like are stored in advance.

  In the present embodiment, the ECU 30 satisfies the torque (required torque) to be generated on the output shaft (crankshaft 41) at that time, based on various sensor outputs (detection signals) input at any time, and thus satisfies the required torque. The fuel injection amount for calculating is calculated. Thus, by variably setting the fuel injection amount of the injector 20, torque (generated torque) generated through fuel combustion in each cylinder (combustion chamber), and eventually output to the output shaft (crankshaft 41). The shaft torque (output torque) is controlled (matched to the required torque).

  That is, the ECU 30 calculates a fuel injection amount in accordance with, for example, the engine operating state from time to time or the accelerator pedal operation amount by the driver, and injects fuel at that fuel injection amount in synchronization with a desired injection timing. An instructing injection control signal (injection command signal) is output to the injector 20. Thereby, based on the drive amount (for example, valve opening period) of the injector 20, the output torque of the target engine is controlled to the target value.

  As is well known, in a diesel engine, the intake throttle valve (throttle valve) provided in the intake passage of the engine is maintained in a substantially fully open state for the purpose of increasing the amount of fresh air and reducing pumping loss during steady operation. Is done. Therefore, control of the fuel injection amount is mainly used as combustion control during steady operation (particularly combustion control related to torque adjustment).

  Hereinafter, a basic processing procedure of the fuel injection control will be described with reference to FIG. Note that the values of various parameters used in this control are stored as needed in a storage device such as a RAM, a non-volatile memory, or a backup RAM mounted on the ECU 30, and updated as necessary.

  As shown in the figure, in this series of processing, first, in step S11, predetermined parameters, for example, the engine speed at that time (actually measured value by the crank angle sensor 42) and fuel pressure (actually measured value by the fuel pressure sensor 20a), Further, the accelerator operation amount (actual value measured by the accelerator sensor 44) by the driver at that time is read.

  In subsequent step S12, an injection pattern is set based on the various parameters read in step S11. For example, in the case of single-stage injection, the injection amount Q (injection time) of the injection, and in the case of the injection pattern of multi-stage injection, the total injection amount Q (total injection time) of each injection that contributes to torque is described above. It is variably set according to the torque to be generated on the output shaft (crankshaft 41) (requested torque calculated from the accelerator operation amount or the like).

  This injection pattern is acquired based on, for example, a predetermined map (an injection control map, which may be a mathematical expression) stored in the ROM and a correction coefficient. Specifically, for example, an optimal injection pattern (adapted value) is obtained in advance for a range of the predetermined parameter (step S11) that is assumed, and is written in the injection control map.

  This injection pattern is determined by parameters such as the number of injection stages (the number of injections in one combustion cycle), the injection timing (injection timing) and the injection time (corresponding to the injection amount) of each injection. Thus, the injection control map shows the relationship between these parameters and the optimal injection pattern.

  Then, the injection pattern acquired in the map for injection control is corrected based on a separately updated correction coefficient (for example, stored in a nonvolatile memory in the ECU 30) (for example, “set value = value on map / correction”). "Coefficient" is calculated). As a result, an injection command signal for the injector 20 corresponding to the injection pattern of the fuel to be injected at that time, and corresponding to the injection pattern is obtained. The correction coefficient is sequentially updated during operation of the internal combustion engine by a separate process.

  It should be noted that, for the setting of the injection pattern (step S12), each map provided separately for each element of the injection pattern (the number of injection stages, etc.) may be used, or each element of these injection patterns may be used. Several (for example, all) maps created together may be used.

  The injection pattern thus set, and thus the command value (injection command signal) corresponding to the injection pattern, is used in the subsequent step S13. That is, in step S13, the command value is output to the injector 20, and the drive of the injector 20 is controlled. Then, with the drive control of the injector 20, the series of processes in FIG.

  Next, a processing procedure for detecting abnormal fuel leakage in the fuel injection system 50 will be described with reference to FIG. A series of processes shown in FIG. 4 is executed at a predetermined cycle (for example, a calculation cycle performed by the CPU described above) or at predetermined crank angles.

  First, in step S21, the detected pressure (output value) from the fuel pressure sensor 20a is captured. This intake process is executed for each of the plurality of fuel pressure sensors 20a. Hereinafter, the capturing process in step S21 will be described in detail with reference to FIG.

  FIG. 5A shows the injection command signal (pulse signal) output to the injector 20 in step S13 of FIG. 3, and the solenoid 20b is activated by the ON signal of this command signal to release the injection hole 20f. Is done. That is, the start of injection is commanded by the on timing t1 of the injection command signal, and the end of injection is commanded by the off timing t2. Therefore, the injection amount Q is controlled by controlling the release time Tq of the injection hole 20f according to the ON period (injection command period) of the command signal. FIG. 5B shows a change (injection rate waveform) of the fuel injection rate from the injection hole 20f caused by the injection command, and the solid line in FIG. 5C shows the fuel pressure sensor 20a generated by the change of the injection rate. The change in detected pressure due to (detected pressure waveform) is shown.

  Then, the ECU 30 sequentially detects the output value of the fuel pressure sensor 20a by a subroutine process different from the process of FIG. In the subroutine processing, the output value of the fuel pressure sensor 20a is sequentially acquired at intervals that are short enough to draw a pressure waveform (pressure transition) based on the output (interval shorter than the processing cycle of FIG. 4). . Specifically, sensor outputs are sequentially acquired at intervals shorter than 50 μsec (more desirably 20 μsec).

  Since the change in the detected pressure by the fuel pressure sensor 20a and the change in the injection rate have a correlation described below, the waveform of the injection rate can be estimated from the waveform of the detected pressure. That is, first, as shown in FIG. 5 (a), after the time point t1 when the injection start command is made, the injection rate starts increasing at the time point R1, and the injection is started. On the other hand, the detected pressure starts decreasing at the change point P1 as the injection rate starts increasing at the time point R1. Thereafter, as the injection rate reaches the maximum injection rate at the time point R2, the decrease in the detected pressure stops at the change point P2. Next, as the injection rate starts decreasing at the time point R2, the detected pressure starts increasing at the change point P2. Thereafter, as the injection rate becomes zero at the time point R3 and the actual injection is finished, the increase in the detected pressure stops at the change point P3.

  As described above, by detecting the change points P1 and P3 in the waveform of the pressure detected by the fuel pressure sensor 20a, the injection rate increase start time R1 (actual injection start time) and decrease end time R3 (actual injection end time) are calculated. (Estimated). Further, the change in the injection rate can be estimated from the change in the detected pressure based on the correlation between the change in the detected pressure and the change in the injection rate described below.

  That is, there is a correlation between the pressure decrease rate Pα from the detected pressure change point P1 to P2 and the injection rate increase rate Rα from the injection rate change point R1 to R2. There is a correlation between the pressure increase rate Pγ from the change points P2 to P3 and the injection rate decrease rate Rγ from the change points R2 to R3. There is a correlation between the pressure drop amount Pβ (maximum drop amount) from the change points P1 to P2 and the injection rate increase amount Rβ from the change points R1 to R2. Therefore, the injection rate increase rate Rα, the injection rate decrease rate Rγ, and the injection rate increase amount Rβ are detected by detecting the pressure decrease rate Pα, the pressure increase rate Pγ, and the pressure decrease amount Pβ from the waveform of the pressure detected by the fuel pressure sensor 20a. Can be calculated (estimated). Accordingly, it is possible to calculate (estimate) the waveform of the fuel injection rate (transition of the fuel injection rate) shown in FIG.

  Note that the integral value of the injection rate from the start to the end of actual injection (the area of the portion indicated by the hatched symbol S) corresponds to the injection amount. The integral value of the pressure and the integral value S of the injection rate in the portion corresponding to the change in the injection rate from the start to the end of the actual injection (the change points P1 to P3) in the fluctuation waveform of the detected pressure have a correlation. Therefore, the injection rate integrated value S corresponding to the injection amount Q can be calculated (estimated) based on calculating the pressure integrated value from the waveform of the detected pressure by the fuel pressure sensor 20a.

  Returning to the description of FIG. 4, the processing contents in steps S22 to S28 after step S21 are different between when single-stage injection is executed and when multistage injection is executed. Hereinafter, first, the processing content when the single-stage injection is executed will be described with reference to FIG. 5, and then the processing content when the multi-stage injection is executed will be described with reference to FIG. In subsequent steps S22 to S28, the waveform of the detected pressure by the fuel pressure sensor 20a corresponding to the injection cylinder among the plurality of cylinders in which injection and non-injection are sequentially executed is used.

  Further, during the period in which the fuel is being pumped from the high pressure pump 11a to the common rail 12, the pressure detected by the fuel pressure sensor 20a includes the pressure increase due to the fuel pumping of the high pressure pump 11a. Therefore, in the present embodiment, among the detected pressure waveforms acquired for each of the plurality of fuel pressure sensors 20a, the fuel pumping period from the high pressure pump 11a to the common rail 12 does not overlap with a predetermined period including the injection period by the injector 20. Using the portion, the processes of subsequent steps S22 to S28 are executed.

<When single-stage injection is performed>
In step S22 following step S21 described above, the actual injection start point and the actual injection end point are calculated based on the detected pressure waveform acquired in step S21. Specifically, the appearance times of the change points P1 and P3 are calculated. The first-order differential value of the waveform of the detected pressure is calculated, and the appearance of the change point P1 is detected when the differential value first exceeds the threshold after the on-time t1 of the injection command. In addition, after the appearance of the change point P1, when the stable state where the differential value changes within the threshold value is reached, the appearance of the change point P3 is detected when the differential value finally falls below the threshold value before the stable state.

  In subsequent step S23, an actual injection period (unit: time) in which the fuel is actually injected by the injector 20 is calculated from the actual injection start time and the actual injection end time calculated in step S22. Specifically, the time from the actual injection start time to the actual injection end time is calculated as the actual injection period.

  In subsequent step S24, a first change amount that is a change amount of the detected pressure in a predetermined period including the actual injection period calculated in step S23 is calculated. Specifically, in the piston of the cylinder whose fuel pressure is to be detected, a period from 90 ° CA before compression top dead center to 90 ° CA after compression top dead center is set as the predetermined period (unit is time). Yes. That is, this predetermined period is a period from the compression stroke to the combustion stroke in one combustion cycle and includes the actual injection period. Then, based on the waveform of the detected pressure acquired in step S21, the amount of change from the fuel pressure detected by the fuel pressure sensor 20a at the start point of the predetermined period to the fuel pressure detected by the fuel pressure sensor 20a at the end point of the predetermined period Is calculated as the first change amount.

  In subsequent step S25, a second change amount that is a change amount of the detected pressure in the actual injection period calculated in step S23 is calculated. Specifically, based on the detected pressure waveform acquired in step S21, the fuel detected by the fuel pressure sensor 20a at the end point of the actual injection period from the fuel pressure detected by the fuel pressure sensor 20a at the start point of the actual injection period. A change amount up to the pressure is calculated as the second change amount. The second change amount indicates the amount of change in the fuel pressure during the actual injection period, that is, the change amount of the fuel pressure due to the fuel injection in the injector 20.

  In subsequent step S26, a non-injection period excluding the actual injection period calculated in step S23 in the predetermined period is calculated. Specifically, the non-injection period (unit is time) is calculated by subtracting the actual injection period from the predetermined period. This non-injection period is a period during which fuel is not injected by the injector 20 in the predetermined period.

  In the subsequent step S27, the difference between the first change amount calculated in step S24 and the second change amount calculated in step S25 is calculated. Specifically, the difference between these changes is calculated by subtracting the second change from the first change. The difference between the first change amount and the second change amount is the difference between the change amount of the fuel pressure in the predetermined period and the change amount of the fuel pressure in the actual injection period, that is, the fuel pressure in the non-injection period. The amount of change is shown.

  In the subsequent step S28, a change amount per unit period is calculated from the difference between the non-injection period calculated in step S26 and the first change amount and the second change amount calculated in step S27. Specifically, the difference between the first change amount and the second change amount is divided by the non-injection period to calculate the change amount of the fuel pressure per unit period in the non-injection period.

  The amount of change per unit period indicates the rate of change of fuel pressure after excluding the influence of injection, and is an index that accurately reflects the degree of fuel leakage. That is, when an abnormal fuel leak occurs in the fuel injection system 50, the fuel pressure decreases faster than normal even in the non-injection period (see the dashed line in FIG. 5C). Abnormal fuel leakage includes a case where the high-pressure pipe 14 is cracked or a case where the injection hole 20f of the injector 20 is left open. Note that, in the fuel injection system 50, even when an abnormal fuel leak does not occur (normal state), a leak such as the internal leak amount QI of the injector 20 described above occurs.

  In the following step S29, an abnormal fuel leakage of the fuel injection system 50 is detected based on the change amount of the fuel pressure per unit period in the non-injection period calculated in step S28. Specifically, when the absolute value of the change amount of the fuel pressure per unit period (the change speed of the fuel pressure) is larger than the determination value, the fuel injection system 50 has an abnormal fuel leak. judge. This determination value is set to a value at which it is possible to detect that a fuel pressure drop larger than the fuel pressure drop caused by the internal leak amount QI of the injector 20 occurs in the fuel injection system 50.

<When performing multi-stage injection>
The waveform of the detected pressure at the time of single-stage injection is as shown in FIG. 5C, whereas at the time of multi-stage injection, the waveform is as shown in FIG. In the example shown in FIG. 6, pilot injection, pre-injection, main injection, and after-injection are sequentially performed during one combustion cycle, and symbols P11, P21, P31, and P41 in FIG. The reference points P13, P23, P33, and P43 indicate the change points that appear in the waveform as the injection ends in each injection stage. Here, in FIG. 6C, the solid line indicates a normal state, and the alternate long and short dash line indicates a state where abnormal fuel leakage occurs in the fuel injection system 50. Even when an abnormal fuel leak occurs, the actual injection start time (change points P11, P21, P31, P41) and the actual injection end time (change points P13, P23, P33, P43) are normal. It is calculated as the same time point (time). Note that areas S1, S2, S3, and S4 indicated by hatching in FIG. 6B correspond to the injection amounts Q1, Q2, Q3, and Q4 of the respective injection stages.

  In the case of the multistage injection shown in FIG. 6, in step S22, the actual injection start time and the actual injection end time are determined for each of the multiple injections based on the waveform of the detected pressure acquired in step S21. It is calculated by the same method as in. In subsequent step S23, an actual injection period (unit: time) is calculated for each of the plurality of injections from the actual injection start time and the actual injection end time of each of the plurality of injections calculated in step S22. In subsequent step S24, a first change amount that is a change amount of the detected pressure in a predetermined period including the plurality of actual injection periods calculated in step S23 is calculated by the same method as in the case of single-stage injection. In subsequent step S25, for each of the plurality of actual injection periods calculated in step S23, a second change amount that is a change amount of the detected pressure in the actual injection period is calculated by the same method as in the case of single-stage injection.

  In subsequent step S26, a non-injection period excluding the plurality of actual injection periods calculated in step S23 in the predetermined period is calculated. That is, the difference between the predetermined period and the total of a plurality of actual injection periods is calculated. This non-injection period is the total of the period during which fuel is not injected by the injector 20 in the predetermined period. In the subsequent step S27, the difference between the first change amount calculated in step S24 and the sum of the plurality of second change amounts calculated in step S25 is calculated. The difference between the first change amount and the sum of the plurality of second change amounts is the difference between the change amount of the fuel pressure during the predetermined period and the sum of the change amounts of the fuel pressure during the plurality of actual injection periods, That is, the change amount of the fuel pressure in the non-injection period is shown.

  In the subsequent step S28, the change amount per unit period is calculated from the difference between the non-injection period calculated in step S26, the first change amount calculated in step S27, and the sum of the plurality of second change amounts. The amount of change per unit period indicates the rate of change of fuel pressure after excluding the influence of multiple injections, and is an index that accurately reflects the degree of fuel leakage. That is, when an abnormal fuel leak occurs in the fuel injection system 50, the fuel pressure is decreased faster than in the normal state even during the non-injection period (see the dashed line in FIG. 6C). In the following step S29, abnormal fuel leakage of the fuel injection system 50 is detected by the same method as in the case of single stage injection based on the amount of change in fuel pressure per unit period in the non-injection period calculated in step S28. To do.

  The fuel pressure sensor 20a and the ECU 30 constitute a fuel leak detection device, and the processing of S22 and S23 corresponds to the processing as the injection period calculation means, the processing of S24 corresponds to the processing as the first calculation means, and the processing of S25 The processing corresponds to processing as the second calculation means, the processing in S26 corresponds to processing as the non-injection period calculation means, and the processing in S27 to S29 corresponds to processing as the leakage detection means.

  The embodiment described in detail above has the following advantages.

  The fuel pressure sensor 20a sequentially detects the fuel pressure in the fuel passage from the common rail 12 to the injection hole 20f of the injector 20, specifically, the fuel inflow port 22. For this reason, the fluctuation of the fuel pressure in the injection hole 20f can be accurately detected before the fluctuation of the fuel pressure in the common rail 12 is attenuated. Since the actual injection period in which the fuel is actually injected by the injector 20 is calculated based on the waveform of the fuel pressure sequentially detected by the fuel pressure sensor 20a, the actual injection period can be calculated accurately.

  Further, a first change amount that is a change amount from the fuel pressure detected by the fuel pressure sensor 20a at the start point of the predetermined period including the actual injection period to the fuel pressure detected by the fuel pressure sensor 20a at the end point of the predetermined period is calculated. The The first change amount indicates the amount by which the fuel pressure has changed in a predetermined period including the actual injection period. Further, a second change amount that is a change amount from the fuel pressure detected by the fuel pressure sensor 20a at the start point of the actual injection period to the fuel pressure detected by the fuel pressure sensor 20a at the end point of the actual injection period is calculated. The second change amount indicates the amount of change in the fuel pressure during the actual injection period, that is, the change amount of the fuel pressure due to the fuel injection in the injector 20.

  Here, the difference between the predetermined period and the actual injection period indicates a period excluding the actual injection period in the predetermined period, that is, a non-injection period in which the fuel is not injected by the injector 20. The difference between the first change amount and the second change amount is the difference between the change amount of the fuel pressure in the predetermined period and the change amount of the fuel pressure in the actual injection period, that is, the change in the fuel pressure in the non-injection period. Indicates the amount. The amount of change per unit period calculated from these indicates the rate of change of the fuel pressure after excluding the influence of injection, and is an index that accurately reflects the degree of fuel leakage. Therefore, the detection accuracy of abnormal fuel leakage can be improved by detecting abnormal fuel leakage from the fuel passage based on the amount of change in fuel pressure per unit period in the non-injection period.

  The actual injection period is calculated for each of the multiple injections by the injector 20. Then, the first change amount is calculated for a predetermined period including a plurality of actual injection periods, and the second change amount is calculated for each of the plurality of actual injection periods. For this reason, the first change amount indicates the amount of change in the fuel pressure in a predetermined period including a plurality of actual injection periods. Each second change amount indicates the amount of change in the fuel pressure during each actual injection period, that is, the change amount of the fuel pressure due to each fuel injection in the injector 20.

  Further, based on the difference between the predetermined period and the total of the plurality of actual injection periods, and the change amount per unit period calculated from the difference between the first change amount and the sum of the plurality of second change amounts, the fuel Abnormal fuel leakage from the passage is detected. For this reason, the calculated amount of change per unit period indicates the rate of change of the fuel pressure after excluding the influence of multiple injections, and is an index that accurately reflects the degree of fuel leakage. Therefore, even in the fuel injection system 50 in which fuel is injected a plurality of times by the same injector 20 per combustion cycle, the detection accuracy of abnormal fuel leakage can be improved.

  The predetermined period is a period from the compression stroke to the combustion stroke in one combustion cycle and includes the actual injection period. Specifically, the predetermined period is a period from 90 ° CA before the compression top dead center to 90 ° CA after the compression top dead center in the piston of the cylinder for which the fuel pressure is detected. Thus, even during the period when fuel injection is performed by the injector 20, it is possible to detect abnormal fuel leakage. Even when fuel injection is not performed by the injector 20 during this predetermined period by executing fuel cut control or the like of the engine, it is possible to detect abnormal fuel leakage of the fuel injection system 50. In this case, since the actual injection period becomes 0, all the predetermined periods become non-injection periods.

  Of the detected pressure waveforms acquired for each of the plurality of fuel pressure sensors 20a, a portion in which the fuel pumping period from the high pressure pump 11a to the common rail 12 does not overlap with a predetermined period including the injection period by the injector 20 is used. The processing of steps S22 to S28 of 4 is executed. Therefore, the first change amount and the second change amount can be calculated based on the detected pressure to which the pressure increase due to fuel pumping is not added, and as a result, the detection accuracy of abnormal fuel leakage can be improved.

  Since the fuel pressure sensor 20a is attached to the injector 20, the attachment position of the fuel pressure sensor 20a is closer to the injection hole 20f than the case where the fuel pressure sensor 20a is attached to the high-pressure pipe 14 connecting the common rail 12 and the injector 20. Become. Therefore, the pressure fluctuation at the injection hole 20f can be detected more accurately as compared with the case where the pressure fluctuation after the pressure fluctuation at the injection hole 20f is attenuated by the high-pressure pipe 14 is detected.

(Second Embodiment)
In the first embodiment, among the detected pressure waveforms acquired for each of the plurality of fuel pressure sensors 20a, the fuel pumping period from the high pressure pump 11a to the common rail 12 does not overlap with a predetermined period including the injection period by the injector 20. The process of steps S22 to S28 in FIG. 4 is executed using the portion. On the other hand, in the present embodiment, an abnormal fuel leak in the fuel injection system 50 can be detected even when the fuel pumping period by the high-pressure pump 11a overlaps with a predetermined period including the injection period by the injector 20. Yes.

  Hereinafter, an abnormal fuel leak detection processing procedure of the fuel injection system 50 according to the present embodiment will be described with reference to FIG. FIG. 7A shows the transition of the injection command signal for the injector 20, FIG. 7B shows the transition of the injection rate, FIG. 7C shows the waveform of the detected pressure of the fuel pressure sensor 20a for the injection cylinder, and FIG. Fig. 4 shows a waveform of the pressure detected by the fuel pressure sensor 20a for a non-injection cylinder, and Fig. 3 (e) shows a pressure waveform corresponding to a pressure increase due to fuel pumping.

  In addition, in (c) and (d), waveforms L11 and L13 indicated by alternate long and short dash lines are fuel pressure waveforms when there is no influence of the pressure increase due to fuel pumping (when the pumping component is zero). And the waveform L12 shown by the solid line in (d) is only the rising component (the component rising in conjunction with the pumping component shown in (e)) caused by fuel pumping because the fuel injection is not performed by the injector 20. It is a waveform in the state where appears. On the other hand, a solid line waveform L10 in (c) is a waveform in the case where the fuel injection by the injector 20 and the fuel pumping by the fuel pump 11 are performed in an overlapping manner. Waveform L11) shown by the alternate long and short dash line and a waveform generated by the fuel pumping (the waveform rising in conjunction with the pumping component shown in (e), that is, the waveform L12 shown by the solid line in (d)) It is.

  In the present embodiment, first, a waveform (a waveform L12 indicated by a solid line in (d)) as a pump pressure component that appears in the detected pressure of the fuel pressure sensor 20a corresponding to the non-injection cylinder is acquired. Next, regarding the injection cylinder when the fuel pumping period overlaps at least a part of the predetermined period and the actual injection period, the waveform of the detected pressure of the corresponding fuel pressure sensor 20a (shown by a solid line in (c)) A waveform L10) is acquired.

  Next, by subtracting the waveform L12 (pump pumping component) of the fuel pressure sensor 20a corresponding to the non-injection cylinder from the acquired waveform L10, a waveform L11 indicated by a one-dot chain line in (c) is calculated. When there are a plurality of fuel pressure sensors 20a corresponding to the non-injection cylinders, an average value is calculated for the waveform of each fuel pressure sensor 20a corresponding to the non-injection cylinder, and the waveform based on this average value is subtracted from the waveform L10. Thus, the waveform L11 may be calculated. Then, using the waveform L11 calculated in this way, the processes of steps S22 to S28 in FIG. 4 are executed. As described above, similarly to the first embodiment, an abnormal fuel leak in the fuel injection system 50 can be detected, and the detection accuracy of the abnormal fuel leak can be improved.

(Other embodiments)
Each of the above embodiments can be implemented with the following modifications.

  In each of the above embodiments, the difference between the first change amount and the second change amount is divided by the non-injection period to calculate the change amount of fuel pressure per unit period (fuel pressure change rate) in the non-injection period. doing. However, the fuel pressure detected sequentially in the non-injection period may be approximated to a curve (or a straight line) by the least square method or the like, and the amount of change in fuel pressure per unit period may be calculated as the slope of this curve. In this case, the amount of change in the fuel pressure per unit period can be calculated for a part of the non-injection period, and abnormal fuel leakage of the fuel injection system 50 can be detected.

  In each of the above embodiments, the unit of the actual injection period and the predetermined period is time. However, if abnormal fuel leakage is detected at a predetermined engine speed, the unit of the actual injection period and the predetermined period is CA ( Crank angle). Alternatively, the unit of the actual injection period and the predetermined period can be CA, and the actual injection period and the predetermined period can be corrected with the engine speed.

  In the second embodiment, the first change amount and the second change amount are calculated by subtracting the change amount of the fuel pressure in the fuel passage caused by the fuel pumping by the pump 11, that is, the rising component caused by the fuel pumping. Yes. However, instead of calculating the first change amount and the second change amount by subtracting the rising component caused by fuel pumping, a determination value for determining the change amount of the fuel pressure per unit period in the non-injection period, You may make it set in consideration of the rising component which arises with fuel pumping. That is, the determination value may be set by adding a rising component generated by the fuel pumping.

  In the first embodiment, as the waveform used in steps S22 to S28 in FIG. 4, the waveform acquired when the fuel pumping period does not overlap with the predetermined period including the injection period is used. However, in the case where a pressure reducing valve is installed in the high pressure fuel supply path such as the common rail 12, the waveform obtained when the pressure reducing valve is not activated and the fuel pressure is not lowered and the above-described non-overlapping waveform is obtained. You may make it use. According to this, since the first change amount and the second change amount can be calculated based on the detected pressure to which the pressure reducing component due to the pressure reducing valve operation is not added, it is possible to improve the detection accuracy of abnormal fuel leakage. it can.

  In attaching the fuel pressure sensor 20 a to the injector 20, the fuel pressure sensor 20 a is attached to the fuel inlet 22 of the injector 20 in the above embodiment. However, as shown by the one-dot chain line in FIG. 2, a fuel pressure sensor 200a is assembled inside the housing 20e to detect the fuel pressure in the internal fuel passage 25 from the fuel inlet 22 to the injection hole 20f. May be.

  When the fuel pressure sensor 20a is attached to the fuel inlet 22 as described above, the structure of the attachment portion of the fuel pressure sensor 20a can be simplified compared to the case where the fuel pressure sensor 20a is attached to the inside of the housing 20e. On the other hand, in the case of mounting inside the housing 20e, the mounting position of the fuel pressure sensor 20a is closer to the injection hole 20f than in the case of mounting to the fuel inlet 22, so the pressure fluctuation at the injection hole 20f is more accurately detected. Can be detected.

  The fuel pressure sensor 20a may be attached to the high pressure pipe 14. In this case, it is desirable to attach the fuel pressure sensor 20a at a position separated from the common rail 12 by a certain distance.

  The number of fuel pressure sensors 20a is arbitrary, and for example, two or more sensors may be provided for the fuel flow path of one cylinder. In addition to the fuel pressure sensor 20a described in the above embodiment, a rail pressure sensor for measuring the pressure in the common rail 12 may be provided.

  A piezo drive injector may be used instead of the electromagnetic drive injector 20 illustrated in FIG. Further, a fuel injection valve that does not cause pressure leakage from the leak hole 24 or the like, for example, a direct acting injector (for example, a direct acting piezo injector) that does not involve the hydraulic chamber Cd for transmission of driving power can be used.

  -The type and system configuration of the engine to be controlled can be changed as appropriate according to the application. For example, although the case where it applied to the diesel engine was mentioned in the said embodiment, it can apply fundamentally similarly, for example also to a spark ignition type gasoline engine (especially direct injection engine) etc., for example. The fuel injection system of a direct injection type gasoline engine is equipped with a delivery pipe that stores fuel (gasoline) in a high-pressure state. The fuel is pumped from the fuel pump to the delivery pipe, and the high-pressure fuel in the delivery pipe is The fuel is distributed to a plurality of injectors 20 and injected into the engine combustion chamber. In such a system, the delivery pipe corresponds to a pressure accumulating vessel.

  DESCRIPTION OF SYMBOLS 11 ... Fuel pump, 12 ... Common rail, 20 ... Injector, 20a ... Fuel pressure sensor, 20f ... Injection hole, 30 ... ECU, 50 ... Fuel injection system, 200a ... Fuel pressure sensor.

Claims (5)

A fuel leakage detection device (30, 20a, 200a) applied to a fuel injection system (50) for injecting fuel supplied from an accumulator (12) by a fuel injection valve (20),
A fuel pressure sensor (20a, 200a) for sequentially detecting the fuel pressure in the fuel passage (14, 22, 25) from the pressure accumulating container to the injection hole (20f) of the fuel injection valve;
An injection period calculating means for calculating an injection period in which the fuel is injected by the fuel injection valve based on a waveform of the fuel pressure sequentially detected by the fuel pressure sensor;
A first change amount that is a change amount from the fuel pressure detected by the fuel pressure sensor at the start point of the predetermined period including the injection period to the fuel pressure detected by the fuel pressure sensor at the end point of the predetermined period is calculated. First calculating means for
A second calculation that calculates a second change amount that is a change amount from the fuel pressure detected by the fuel pressure sensor at the start point of the injection period to the fuel pressure detected by the fuel pressure sensor at the end point of the injection period. Means,
Based on the change amount per unit period calculated from the difference between the predetermined period and the injection period, and the difference between the first change amount and the second change amount, an abnormal condition of the fuel from the fuel passage is obtained. Leak detection means for detecting leaks;
A fuel leak detection device comprising: Applied to a fuel injection system that injects the fuel multiple times by the same fuel injection valve per combustion cycle;
The injection period calculating means calculates the injection period for each of a plurality of injections by the fuel injection valve,
The first calculation means calculates the first change amount for the predetermined period including a plurality of the injection periods,
The second calculation means calculates the second change amount for each of the plurality of injection periods,
The leak detection means is configured to calculate the difference between the predetermined period and the sum of the plurality of injection periods, and the difference between the first change amount and the sum of the plurality of second change amounts per unit period. The fuel leakage detection device according to claim 1, wherein an abnormal leakage of the fuel from the fuel passage is detected based on a change amount of the fuel. Applied to a fuel injection system in which fuel is pumped from the pump (11) to the pressure accumulating vessel during a period that overlaps at least a part of the predetermined period and the injection period;
The first calculation means calculates the first change amount by subtracting the change amount of the fuel pressure in the fuel passage caused by the pumping of the fuel by the pump,
3. The fuel leak detection device according to claim 1, wherein the second calculation unit calculates the second change amount by subtracting a change amount of the fuel pressure in the fuel passage caused by the pumping of the fuel by the pump. . The predetermined period is a period from the compression stroke toward the combustion stroke of one combustion cycle, and a fuel leakage detection system according to any one of claims 1 to 3, which is a period including the ejection period. The fuel leak detection device according to any one of claims 1 to 4 , wherein the fuel pressure sensor is attached to the fuel injection valve.

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