JP2009281276A - Fuel injection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection system dispensing with high pressure resistant sealing performance while allowing detection of an actual injection state. <P>SOLUTION: The fuel injection system is provided with: an injector 20 having a high pressure passage 21b formed in an inside of a body 21 and making high pressure fuel flow into an injection hole 21c, a low pressure passage 21g formed in the inside of the body 21 and returning the excess fuel supplied to the high pressure passage 21b to a fuel tank 10, and a nozzle needle 24 for opening and closing the high pressure passage 21b; and low pressure piping 15 connected to the injector 20 and returning low pressure fuel in the low pressure passage 21g to the fuel tank 10. A return pressure sensor 28 for detecting a pressure of the low pressure fuel is disposed in a return passage 21e extended to the fuel tank 10 through the low pressure passage 21g and the low pressure piping 15. The injection state of the fuel injected from the injection hole 21c is detected based on the behavior of a detection value of the return pressure sensor 28. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection system including a fuel injection valve that injects fuel used for combustion of an internal combustion engine.

  In order to accurately control the output torque and the emission state of the internal combustion engine, it is important to accurately control the injection state such as the injection amount of fuel injected from the fuel injection valve and the injection start timing. Thus, conventionally, a technique for detecting the actual injection state by detecting the pressure of the high-pressure fuel has been proposed, focusing on the fact that the pressure of the high-pressure fuel supplied to the fuel injection valve fluctuates with the injection. For example, the actual injection start time can be detected by detecting the time when the fuel pressure starts to decrease along with the injection, or the actual injection amount can be calculated by detecting the amount of decrease in the fuel pressure caused by the injection. I am trying. If the actual injection state can be acquired in this way, the injection state can be accurately controlled based on the acquired value.

When detecting such fluctuations in fuel pressure, the fuel pressure sensor (rail pressure sensor) installed directly on the common rail (accumulation vessel) buffers the fuel pressure fluctuation caused by injection in the common rail. It is impossible to detect the fluctuation of fuel pressure. Therefore, in the invention described in Patent Document 1, a fuel pressure sensor is installed at a connection portion with a common rail in a high-pressure pipe that supplies fuel from the common rail to the fuel injection valve, so that fuel pressure fluctuations caused by injection are buffered in the common rail. It is intended to detect the fluctuation of the fuel pressure before starting.
JP 2000-265892 A

  However, in the structure described in Patent Document 1, since the fuel pressure sensor is attached to the high-pressure pipe, a high pressure-resistant sealing property is required at the attachment portion. Therefore, there are concerns about cost increase due to the high-performance seal structure and fuel leakage from the seal portion.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel injection system that makes it possible to detect an actual injection state and eliminate the need for high pressure-resistant sealability.

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

In invention of Claim 1,
A body formed with an injection hole for injecting fuel used for combustion of an internal combustion engine, a high-pressure passage formed inside the body and allowing high-pressure fuel to flow toward the injection hole, and a high-pressure passage formed inside the body A fuel injection valve having a low pressure passage for returning surplus fuel supplied to the fuel tank, and a valve body housed inside the body and opening and closing a portion near the injection hole in the high pressure passage;
A low pressure pipe connected to the fuel injection valve and returning low pressure fuel in the low pressure passage to a fuel tank;
A fuel injection system comprising:
A return pressure sensor that is disposed in a return path to the fuel tank via the low-pressure passage and the low-pressure pipe, and detects the pressure of the low-pressure fuel in the return path;
Injection state detecting means for detecting an injection state of fuel injected from the nozzle hole based on the behavior of the detection value of the return pressure sensor;
It is characterized by providing.

  In the conventional structure described in Patent Document 1, the fuel pressure sensor is arranged in the high-pressure pipe, paying attention to the fact that the pressure of the high-pressure fuel supplied to the fuel injection valve varies with the injection. On the other hand, the present inventors recall the invention according to claim 1 that detects the injection state based on the pressure behavior of the low-pressure fuel, focusing on the fact that the pressure of the low-pressure fuel in the return path also varies with the injection. did. According to the present invention, the return pressure sensor and the injection state detection means are provided, so that the actual injection state can be detected and the return pressure sensor is arranged in the low pressure path (return path). Can eliminate the need for high pressure-resistant sealing.

  The invention according to claim 2 is applied to a multi-cylinder internal combustion engine having a plurality of cylinders and having the fuel injection valve for each cylinder, and the low-pressure fuel in the low-pressure pipe for each cylinder is gathered in the return path. A collecting pipe returning to the fuel tank is included, and the return pressure sensor is arranged upstream of the collecting pipe.

  Here, if the return pressure sensor is arranged in the collecting pipe, the fluctuation of the fuel pressure caused by the injection in one cylinder interferes with the fluctuation of the fuel pressure caused by the injection in the other cylinder. It becomes difficult to accurately detect the injection state of. According to the second aspect of the invention in view of this point, since the return pressure sensor is arranged on the upstream side of the collecting pipe, the interference can be avoided and the injection state can be detected with high accuracy.

  Here, when the return pressure sensor is attached to the low-pressure pipe, the fuel pressure in a state where the fuel pressure fluctuation caused by the injection is attenuated in the low-pressure pipe is detected, so there is a concern that the detection accuracy of the injection state is lowered. In view of this point, the invention according to claim 3 is characterized in that the return pressure sensor is attached to the fuel injection valve, so that it is possible to detect the fuel pressure in a state where the attenuation is small, and thus improve the detection accuracy of the injection state. Can be achieved.

  According to a fourth aspect of the present invention, a control chamber is formed inside the body and allows a part of the high-pressure fuel in the high-pressure passage to flow in, and biases the valve body in the valve closing direction by the pressure of the high-pressure fuel that flows in. An outlet that is formed in the control chamber and flows out the fuel in the control chamber to the return path; and a low-pressure chamber that is formed by enlarging a part of the low-pressure passage, and opens and closes the outlet. And a control valve for controlling the fuel pressure in the control chamber, and the return pressure sensor is attached to the low pressure chamber.

  In a fuel injection valve provided with such a control chamber, an outflow port, and a control valve, the pressure fluctuation of the low-pressure fuel caused by the injection occurs at the outflow port. According to the fourth aspect of the invention in view of this point, since the return pressure sensor is attached to the low pressure chamber, it is possible to detect the fuel pressure with the least attenuation as described above, and further improve the detection accuracy of the injection state. .

  According to a fifth aspect of the present invention, the injection state detecting means is configured to determine an injection start time, an injection end time, and a valve opening operation amount of the valve body when the injection hole is opened and closed by the valve body. At least one of the maximum full lift time points is detected as the injection state.

  In particular, when the internal combustion engine to be applied is a compression self-ignition type such as a diesel engine, the injection start time has a greater influence on the combustion state than an ignition type such as a gasoline engine. By detecting the actual injection start time according to the invention and controlling the operation of the fuel injection valve using the detected value, the desired combustion state can be accurately achieved.

  Further, the present inventors have found that the required time from the injection start point to the full lift point changes depending on the degree of aging deterioration of the fuel injection valve. Therefore, if the actual injection start time and the full lift time are detected and the required time is calculated according to the invention described in claim 5, the degree of aging deterioration can be estimated. Therefore, for example, if the operation of the fuel injection valve is controlled according to the estimation result, the desired combustion state can be accurately achieved. Incidentally, the inclination of the detected value from the injection start time to the full lift time may be calculated, and the degree of aging deterioration may be estimated based on this inclination.

  According to a sixth aspect of the present invention, the injection state detecting means detects at least the injection start time and the injection end time, and performs one time by the valve body based on the detected injection start time and the injection end time. An injection amount calculation means for calculating an injection amount of fuel injected when the valve is opened is provided. The injection time from the injection start time to the injection end time is highly correlated with the injection amount. That is, the injection amount increases as the injection time increases. Therefore, it is preferable to calculate the injection amount based on the injection start time and the injection end time as described in claim 6.

  According to a seventh aspect of the present invention, a high-pressure side sensor that detects the pressure of the high-pressure fuel is provided, and the injection amount calculation means detects the high-pressure side sensor in addition to the detected injection start time and the injection end time. The injection amount is calculated based on the value.

  Here, even if the injection time described above is the same, the injection amount increases as the pressure of the high-pressure fuel supplied to the fuel injection valve increases. In the invention according to claim 7 in view of this point, since the injection amount is calculated based on the detection value of the high-pressure side sensor in addition to the injection start time and the injection end time, the calculation accuracy can be improved. The detection value of the high-pressure sensor used for calculating the injection amount is preferably a detection value before the injection start time.

  In the invention according to claim 8, immediately after the fuel injection valve starts the operation to open the valve body, the injection state detection means increases the detection value of the return pressure sensor and reaches a rising peak. Then, a time point when the vehicle descends and reaches a descending peak is detected, and the descending peak time is detected as the injection start time.

  The present inventors have found that the “falling peak time point” appears in the behavior of the detection value of the return pressure sensor at the injection start time point. Therefore, according to the invention of claim 8 based on this finding, the injection start time can be easily detected. Hereinafter, the reason why the “falling peak time” appears at the injection start time will be described using the simulation results shown in FIG.

  First, when the fuel injection valve starts to open the valve body (that is, the control valve opens the outlet), the fuel in the control chamber flows out from the outlet to the low-pressure chamber. The fuel pressure rises (see symbol A1 in FIG. 6A). When a predetermined amount of fuel in the control chamber flows out, the fuel pressure in the control chamber gradually decreases, and the fuel pressure in the low-pressure chamber gradually decreases with the decrease (see symbol A2 in FIG. 6A). After that, when the valve body starts to open due to the fuel pressure in the control chamber decreasing, the fuel in the control chamber is pushed out from the outlet by the valve opening operating force, and as a result, the fuel pressure in the low pressure chamber increases again. (See reference numeral A3 in FIG. 6A). That is, the pressure of the low-pressure fuel in the return path rises again at the timing when the valve body starts the valve opening operation.

  As described above, after the detection value of the return pressure sensor rises (A1) and reaches the rising peak, the time point t3 (that is, the starting point of the re-raising A3) when the falling (A2) reaches the falling peak is the injection start time. It can be said that there is. FIG. 6A shows the simulation result when the return pressure sensor is attached to the low-pressure chamber in the configuration including the control chamber and the control valve (in the case of the configuration according to claim 4). It is assumed that the same tendency as in FIG.

  In the ninth aspect of the invention, the injection state detecting means increases the detection value of the return pressure sensor and reaches a rising peak immediately after the fuel injection valve starts to open the valve body. Then, a time point at which the vehicle descends once, then rises again, and starts to descend again in a stable state is detected, and the descending start time is detected as the full lift time.

  The present inventors have found that the above-mentioned “fall start time” appears in the behavior of the detection value of the return pressure sensor at the full lift time. Therefore, according to the ninth aspect of the invention based on this finding, the full lift time can be easily detected. Hereinafter, the reason why the “downward start time” appears at the time of full lift will be described with reference to FIG.

  As described above, when the fuel in the control chamber is pushed out, the low-pressure fuel in the return path rises again while pulsating (A3) at the initial stage of pushing out, but the fuel pressure in the low-pressure chamber is stabilized in the later stage of pushing out ( Reference A4). After that, when the valve opening operation amount of the valve body reaches the maximum (full lift), the fuel in the control chamber is not pushed out, so the fuel pressure in the low pressure chamber decreases again (see symbol A5). From the above, it can be said that the time point t4 at which the descent starts again (that is, the start point of the re-decreasing A5) is the full lift time in the state where the detection value of the return pressure sensor is re-raised (A3) and stabilized (A4).

  In the invention according to claim 10, the injection state detection means starts the operation so that the fuel injection valve closes the valve body, and after the detection value of the return pressure sensor starts decreasing, A point in time when the descent ends is detected, and a point in time when a predetermined time has passed since the descent end point is detected as the injection end point.

  The present inventors have found that the above-mentioned “falling end point” appears in the behavior of the detection value of the return pressure sensor before a predetermined time before the end point of injection. Therefore, according to the invention described in claim 10 based on this finding, it is possible to easily detect the injection end point. Hereinafter, the reason why the “falling end time point” appears a predetermined time before the injection end time point will be described with reference to FIG.

  When the control valve is operated to stop the injection from the nozzle hole in the stable state where the fuel pressure in the low pressure chamber is lowered again A5 as described above, the fuel pressure in the low pressure chamber is lowered again (see symbol A6), and the outlet is The fuel pressure drop (A6) in the low pressure chamber ends at the timing when the control valve is closed (see t7). Thereafter, the valve body starts the valve closing operation and ends the valve closing operation after a predetermined time (see symbol B2 in FIG. 6E) has elapsed (see symbol t8 in FIG. 6D). As described above, the time point (t8) when the predetermined time (B2) has elapsed from the time point t7 when the detection value of the return pressure sensor is lowered (A6) and the lowering is finished in accordance with the start of the injection stop operation is the time point when the injection is finished. It can be said that.

  The invention according to claim 11 is characterized in that the predetermined time is variably set according to a required rise time from the detected injection start time to the full lift time. Here, the present inventors have found that the required rise time varies depending on the degree of deterioration of the fuel injection valve over time. According to the invention described in claim 11 in view of this point, since the predetermined time used for detection of the injection end time is variably set according to the required rise time, the injection end time can be detected with high accuracy.

  Furthermore, the present inventors have found that the required rise time varies depending on the pressure of the high-pressure fuel supplied to the fuel injection valve. According to the invention described in claim 12 in view of this point, since the predetermined time used for detection of the injection end time is variably set according to the detection value of the high-pressure side sensor, the injection end time can be detected with high accuracy. . The detection value of the high-pressure side sensor used for the variable setting is preferably a detection value before the injection start time.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.

(First embodiment)
First, an outline of an engine (internal combustion engine) on which the fuel injection system according to the present embodiment is mounted will be briefly described.

  In this embodiment, a diesel engine for a four-wheeled vehicle is targeted, and an engine of a system in which high pressure fuel (for example, light oil having an injection pressure of “1000 atm” or more) is directly supplied to the combustion chamber by injection (direct injection supply). is there. Further, the engine is assumed to be a multi-cylinder (for example, in-line four-cylinder) four-stroke, reciprocating diesel engine, and four cylinders # 1 to # 4 are respectively subjected to four strokes of intake, compression, combustion, and exhaust. One combustion cycle is a “720 ° CA” cycle. Specifically, for example, the cylinders are sequentially executed in the order of cylinders # 1, # 3, # 4, and # 2 with a shift of “180 ° CA” between the cylinders.

  Next, the fuel system of the engine will be described with reference to FIGS.

  FIG. 1 is a configuration diagram of a common rail fuel injection system according to the present embodiment. The ECU 30 (electronic control unit) provided in this system adjusts the amount of current supplied to the intake regulating valve 11c and controls the fuel discharge amount of the fuel pump 11 to a desired value, so that the inside of the common rail 12 (pressure accumulating vessel) is adjusted. The fuel pressure (the fuel pressure at times measured by the rail pressure sensor 13) is feedback-controlled (for example, PID control) to the target value (target fuel pressure). Based on the fuel pressure, the fuel injection amount for the predetermined cylinder of the target engine, and hence 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, the common rail 12, and the injector 20 (fuel injection valve) from the upstream side of the fuel. The fuel pump 11 has a high-pressure pump 11a and a low-pressure pump 11b that are driven by the output of the target engine. 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. It is configured. The amount of fuel pumped to the high-pressure pump 11a, and thus 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 amount of fuel discharged from the pump 11 is controlled to a desired value by adjusting the drive current amount (and thus the valve opening degree) of the intake adjustment valve 11c.

  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 is configured to sequentially pump fuel sent to the pressurizing chamber at a predetermined timing by reciprocating the plunger in the axial direction with an eccentric cam (not shown). ing.

  The fuel in the fuel tank 10 is pressurized (supplied) to the common rail 12 by the fuel pump 11 and then stored in the common rail 12 in a high pressure state. Thereafter, the fuel is distributed and supplied to the injectors 20 of the cylinders # 1 to # 4 through the high-pressure pipe 14 provided for each cylinder. The surplus fuel supplied to the injectors 20 (# 1) to (# 4) is returned to the fuel tank 10 through the low pressure pipe 15 and the collecting pipe 16. The low-pressure pipe 15 is connected to each injector 20 for each cylinder, and the low-pressure fuel flowing through each low-pressure pipe 15 is collected by the collecting pipe 16 and then flows to the fuel tank 10.

  FIG. 2 shows a detailed structure of the injector 20. The four injectors 20 (# 1) to (# 4) basically 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 engine fuel for combustion (fuel in the fuel tank 10). Transmission of driving power during fuel injection is transmitted via the fuel in the control chamber Cd. Done. As shown in FIG. 2, the injector 20 is configured as a normally closed type fuel injection valve that is in a closed state when not energized.

  A high-pressure pipe 14 is connected to a fuel supply port 21 a formed in the body 21 of the injector 20, and high-pressure fuel sent from the common rail 12 flows in. Part of the high-pressure fuel that has flowed in from the fuel supply port 21a flows into the control chamber Cd formed in the body 21, and other fuel flows toward the nozzle hole 21c through the high-pressure passage 21b formed in the body 21. Flowing. An outlet 21d that is opened and closed by the control valve 22 is formed in the control chamber Cd. When the outlet 21d is opened by the control valve 22, the fuel in the control chamber Cd flows out from the outlet 21d to the low pressure chamber 21e. Then, the gas is discharged from the low pressure chamber 21e through the fuel discharge port 21f to the low pressure pipe 15 and returned to the fuel tank 10 through the collective pipe 16. Note that orifices are formed at the outlet 21d and the inlet from the high-pressure passage 21b to the control chamber Cd.

  A command piston 23 and a nozzle needle 24 (valve element) are accommodated inside the body 21 so as to be slidable in the axial direction (vertical direction in FIG. 2). One end of the command piston 23 is urged toward the nozzle hole 21c (closed valve side) by the fuel pressure in the control chamber Cd, and the other end of the command piston 23 is the pressure of the low-pressure fuel in the low-pressure passage 21g branched from the control chamber Cd. Therefore, it is urged toward the counter injection hole 21c (opening side).

  In a state where the nozzle needle 24 is seated on the seat portion 21h formed in the body 21 and the high-pressure passage 21b is closed (injection stopped state), one end of the nozzle needle 24 serves as an operating force of the command piston 23, a spring 25 It is biased toward the injection hole 21c (valve closing side) by the elastic force of the (coil spring) and the pressure of the low pressure fuel in the low pressure passage 21g. The other end of the nozzle needle 24 is urged toward the anti-injection hole 21c (opening side) by the pressure of the high-pressure fuel in the high-pressure passage 21b.

  When fuel is injected from the injector 20, the solenoid 26 that constitutes the two-way solenoid valve is energized. Then, the control valve 22 operates to open the outlet 21 d of the control chamber Cd against the elastic force of the spring 27. Then, the fuel pressure in the control chamber Cd (hereinafter referred to as control pressure) is lowered, and the nozzle needle 24 is lifted up together with the command piston 23 so as to open, and the nozzle needle 24 from the seat portion 21h. Sits away. Thereby, the high-pressure fuel in the high-pressure passage 21b is injected from the injection hole 21c.

  In short, the pressure increasing process in the control chamber Cd is performed by supplying high-pressure fuel from the fuel supply port 21a. On the other hand, the decompression process of the control chamber Cd is performed by operating the control valve 22 by energizing the solenoid 26 to open the outlet 21d. That is, by adjusting the fuel pressure in the control chamber Cd by the opening / closing operation of the control valve 22, the operation of the nozzle needle 24 that opens and closes the nozzle hole 21c is controlled.

  The drive control of the nozzle needle 24 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 unit (the above-described two-way electromagnetic valve) of the nozzle needle 24. When the pulse is turned on (or off), the nozzle needle 24 is lifted up to open the nozzle hole 21c, and when the pulse is turned off (or on), the nozzle needle 24 is lifted down to close the nozzle hole 21c.

  A return pressure sensor 28 (see also FIG. 1) for detecting the pressure of the low-pressure fuel discharged from the outlet 21d of the control chamber Cd is attached to the injector 20. Specifically, the return pressure sensor 28 is attached to the low pressure chamber 21e and detects the fuel pressure in the low pressure chamber 21e. Thus, by attaching the return pressure sensor 28 to the low pressure chamber 21e communicating with the outlet 21d, it is possible to detect the pressure of the low pressure fuel discharged from the outlet 21d at any time.

  The return pressure sensor 28 is provided for each of the plurality of injectors 20 (# 1) to (# 4). Based on the output of the return pressure sensor 28, the pressure fluctuation waveform of the low-pressure fuel generated by the injection operation of the injector 20 can be detected with high accuracy for the injection of the predetermined cylinder (details). Will be described later). A specific example of the return pressure sensor 28 includes a stem member that is elastically deformed by receiving a fuel pressure and a strain gauge attached to the stem member.

  A harness (not shown) connected to the return pressure sensor 28 is taken out of the body 21 through an outlet 21 i formed in the body 21 and connected to the ECU 30. A signal detected by the return pressure sensor 28 is input to the ECU 30 through this harness. In order to prevent the low-pressure fuel in the low-pressure chamber 21e from leaking outside through the outlet 21i, the return pressure sensor 28 and the outlet 21i are sealed.

  As a specific example of the seal, when the return pressure sensor 28 is constituted by a sensing element that detects the fuel pressure and a housing that houses the sensing element, a seal member is interposed between the housing and the body 21. The seal may be realized by the above, or the seal may be realized by bringing the housing into surface contact with the body 21 at a predetermined pressure.

  A microcomputer (microcomputer) mounted on the ECU 30 includes a CPU for performing various calculations, a RAM as a main memory for temporarily storing data and calculation results during the calculation, a ROM as a program memory, and a data storage memory. And a backup RAM (a memory that is always powered by a backup power source such as an in-vehicle battery even after the main power supply of the ECU 30 is stopped). The ROM stores various programs related to engine control including a program related to the fuel injection control, a control map, and the like, and the data storage memory (for example, EEPROM) includes design data of the target engine. Various control data and the like are stored in advance.

  Further, the ECU 30 calculates the rotational angle position and rotational speed (engine rotational speed NE) of the output shaft (crankshaft 41) of the target engine based on the detection signal input from the crank angle sensor 42 (see FIG. 1). Further, based on a detection signal input from the accelerator sensor 44, an operation amount (depression amount) of the accelerator pedal by the driver is calculated. The ECU 30 grasps the operating state of the target engine and the user's request based on the detection signals of the various sensors 42 and 44 and various sensors described later, and operates the various actuators such as the intake adjustment valve 11c and the injector 20 accordingly. By doing so, various controls related to the engine are performed in an optimum manner according to the situation at that time.

  Next, an outline of fuel system control executed by the ECU 30 will be described.

  The microcomputer of the ECU 30 calculates the fuel injection amount according to the engine operating state (for example, the engine speed NE) and the amount of operation of the accelerator pedal by the driver, and the fuel injection is synchronized with the desired injection start timing. An injection control signal (injection command signal) for instructing fuel injection in an amount is output to the injector 20. When the injector 20 operates with a drive amount (for example, valve opening time) corresponding to the injection control signal, the output torque of the target engine is controlled to the target value.

  Hereinafter, a basic processing procedure of the fuel system control will be described with reference to FIG. Note that the values of various parameters used in the processing of FIG. 3 are stored as needed in a storage device such as a RAM, EEPROM, or backup RAM mounted in the ECU 30 and updated as necessary. 3 is executed by a program stored in the ROM of the ECU 30.

  As shown in FIG. 3, in this series of processing, first, in step S11, predetermined parameters, for example, the engine speed NE at that time (actual value measured by the crank angle sensor 42) and the supply fuel pressure (based on the rail pressure sensor 13). (Actually measured value), and further, the accelerator operation amount (actually measured value by the accelerator sensor 44) at that time by the driver 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) (required torque calculated from the accelerator operation amount or the like, which corresponds to the engine load at that time).

  This injection pattern is obtained based on, for example, the map M (injection control map, which may be a mathematical expression) shown in FIG. 4 stored and held in the above-mentioned EEPROM, and is optimal for achieving a required torque and a good emission state. Pattern. Specifically, for example, an optimum injection pattern (adapted value) is obtained in advance by testing for an assumed range of the predetermined parameter (step S11), and is written in the injection control map M.

  This injection pattern is determined by parameters such as the number of injection stages (the number of injections in one combustion cycle) and the injection start timing and injection time (corresponding to the injection amount) of each injection. The map M according to the present embodiment defines the relationship between the total injection amount Q and the engine rotation speed NE and the injection pattern, and is provided for each injector 20 of each cylinder # 1 to # 4. Incidentally, you may make it provide the map M for every other parameters, such as engine cooling water temperature.

  A command value (injection command signal) for the injector 20 is set based on the injection pattern acquired using such an injection control map M. As a result, the pilot injection, pre-injection, after-injection, post-injection, etc. in the multi-stage injection described above are appropriately executed together with the main injection in accordance with the situation of the vehicle.

  Further, the injection pattern acquired in this injection control map M is corrected based on a separately updated correction coefficient (for example, stored in the EEPROM in the ECU 30) (for example, “set value = value on the map / correction coefficient”). To obtain an injection command signal for the injector 20 corresponding to the injection pattern to be injected at that time. The correction coefficient is sequentially updated during operation of the internal combustion engine by a separate process.

  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.

  By the way, the actual injection state (for example, the injection amount, the injection start timing, the injection end timing, etc.) with respect to the injection command signal changes due to the deterioration of the injector 20 over time. Therefore, in the present embodiment, focusing on the fact that the pressure of the low-pressure fuel fluctuates with the injection, the actual injection state is detected based on the behavior of the detection value of the return pressure sensor 28. Then, learning is performed by correcting the data (injection pattern) stored in the above-described injection control map M so as to approach the detected injection state.

  Hereinafter, the processing procedure for detecting the actual injection state based on the detection value of the return pressure sensor 28 will be described with reference to FIGS. 5 and 6. 5 is repeatedly executed by the microcomputer of the ECU 30 at a predetermined cycle (for example, a calculation cycle of the microcomputer) or every predetermined crank angle, for example. FIG. 6 is a simulation result showing various changes caused by one valve-opening injection. (A) is a detection value of the return pressure sensor 28 (leak pressure of the low pressure chamber 21e), and (b) is the above step. The injection command signal output to the injector 20 at S13, (c) is the lift amount of the control valve 22, (d) is the lift amount of the nozzle needle 24, and (e) is the injection rate of the fuel injected from the injection hole 21c. (Injection amount per unit time) is shown, and the horizontal axis shows elapsed time.

  In the series of processing shown in FIG. 6, first, in step S21, the detection value of the return pressure sensor 28 is captured. This intake process is executed for each of the plurality of return pressure sensors 28. Hereinafter, the capturing process in step S21 will be described in detail with reference to FIG.

  As shown in FIG. 6 (b), the solenoid 26 is actuated by opening the injection command signal to open the nozzle hole 21c. 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 t5. Therefore, the injection amount Q is controlled by controlling the valve opening time Tq of the injection hole 21c by the pulse-on period (injection command period) of the injection command signal.

  Then, the ECU 30 detects the detection value of the return pressure sensor 28 by a subroutine process different from the process of FIG. 5. In the subroutine process, the detection value of the return pressure sensor 28 is detected and the pressure fluctuation waveform is output from the sensor output. Are sequentially acquired at intervals (shorter than the processing cycle of FIG. 5) such that the locus (trajectory illustrated in FIG. 6A) is drawn. Specifically, sensor outputs are sequentially acquired at intervals shorter than 50 μsec (more desirably 20 μsec).

  In the subsequent step S22 (injection state detection means), the timing at which a descending peak time point t3, a descending start time point t4 and a descending end time point t7 described below appear is detected from the fluctuation waveform of the detected value acquired in step S21. Hereinafter, the correlation between the timing at which these times t3, t4, and t7 appear and the lift amount of the control valve 22, the lift amount of the nozzle needle 24, and the injection rate will be described with reference to FIG.

<Correlation between descent peak time t3 and injection start time t3>
First, as the injection command signal is turned on (see t1), the control valve 22 starts to lift up. Then, the fuel in the control chamber Cd starts to flow out from the outlet 21d to the low pressure chamber 21e, and the fuel pressure (leak pressure) in the low pressure chamber 21e increases along with the outflow (see symbol A1). Thereafter, the first rising peak t2 appears in the fluctuation waveform. That is, when a predetermined amount of fuel flows out from the control chamber Cd, the fuel pressure in the control chamber Cd begins to decrease, and the fuel pressure in the low-pressure chamber 21e gradually decreases along with the decrease (see symbol A2).

  Thereafter, when the fuel pressure in the control chamber Cd decreases and the nozzle needle 24 starts the valve opening operation (see symbol t3 in FIG. 6D), the fuel in the control chamber Cd is discharged from the outlet 21d by the valve opening operation force. As a result, the fuel pressure in the low pressure chamber 21e rises again (see symbol A3). That is, at the timing t3 when the nozzle needle 24 starts the valve opening operation, the fuel pressure in the low pressure chamber 21e rises again (see A3). From the above, it can be said that the injection start point is the time point t3 (that is, the start point of the re-rise A3) after the first rise peak t2 appears in the fluctuation waveform after the pulse of the injection command signal is turned on.

<Correlation between descent start time t4 and full lift time t4>
As described above, when the fuel in the control chamber Cd is pushed out, the fluctuation waveform (fuel pressure in the low pressure chamber 21e) rises again while pulsating (see A3) in the initial stage of pushing out, but in the latter stage of pushing out, the fluctuation waveform is Stable (see reference A4). Thereafter, when the valve opening operation amount of the nozzle needle 24 reaches the maximum (full lift) as indicated by reference numeral t4 in FIG. 6D, the fuel in the control chamber Cd is not pushed out, so the fuel pressure in the low pressure chamber 21e is It descends again (see symbol A5). As described above, when the second rise (see A3) appears in the fluctuation waveform and then stabilizes (see A4), the time point t4 at which the descent starts again (that is, the start point of the re-lowering A5) It can be said that it is the time when the lift amount reaches the maximum (full lift time).

<Correlation between descent end time t7 and injection end time t8>
As described above, when the fuel pressure in the low-pressure chamber 21e is lowered again A5 and is stable, when the injection command signal is pulsed off (see t5 in FIG. 6B), the control valve 22 is lifted down (valve closing operation). Is started (see t6). Then, the fuel pressure in the low-pressure chamber 21e is lowered again with the lift-down operation of the control valve 22 (see A6), and the fuel pressure in the low-pressure chamber 21e is lowered (see A6) at the timing when the outlet 21d is closed by the control valve 22. The process ends (see symbol t7). After that, the nozzle needle 24 starts the lift-down operation (valve closing operation), and after a predetermined time (see reference numeral B2 in FIG. 6 (e)) has elapsed, the nozzle needle 24 is seated on the seat portion 21h and ends the valve closing operation. (See symbol t8 in FIG. 6D). As described above, the fluctuation waveform is lowered (A6) as the injection command signal is pulsed off, and the predetermined time (B2) from the time t7 when the end of the lowering appears (that is, when the return pressure returns to the level before the injection starts). It can be said that the time point t8 when) has elapsed is the injection end time point.

  Returning to the description of FIG. 5, in step S23 following step S22 described above, the injection start time point is determined based on the descent peak time point t3 and the descent end time point t7 detected in step S22 using the injection state detection map described below. t3 and the injection end time t8 are calculated. An injection state detection map is stored in the ROM and EEPROM. The map stores the relationship between the descent peak time t3 and descent end time t7, and the injection start time t3 and injection end time t8. The map may be provided for each of various parameters such as rail pressure and fuel temperature detected by the rail pressure sensor 13 (high pressure side sensor).

  In the following step S24, the required rise time (see symbol B4 in FIG. 6E) from the injection start time t3 calculated in step S23 to the full lift time t4 detected in step S22 is calculated.

  Here, the required rise time B4 changes in accordance with the degree of deterioration of the injector 20 over time. And the said predetermined time B2 changes according to the degree of this aged deterioration. Therefore, in subsequent step S25, the injection end time t8 calculated in step S23 is corrected based on the required rise time B4 calculated in step S24. For example, as the aging progresses, the clearance between the command piston 23 and the body 21 increases due to wear, so that the required rise time B4 becomes shorter and the predetermined time B2 becomes longer. Therefore, the predetermined time B2 is corrected to be longer as the required rise time B4 is shorter. That is, a specific example of the correction is to correct the injection end time t8 calculated in step S23 to be delayed.

  Even if the required rise time B4 is the same, the predetermined time B2 changes according to the rail pressure at that time. In view of this point, in step S25, the determination of the degree of aging deterioration is changed according to the rail pressure when the required rise time B4 is detected, and the correction amount at the injection end time t8 is changed.

  In subsequent step S26 (injection amount calculating means), the injection command signal is turned on / off once based on the injection start time t3 calculated in step S23, the injection end time t8 corrected in step S25, and the rail pressure. An injection amount of the injected fuel is calculated. That is, the injection amount increases as the injection period B3 is longer and the rail pressure is higher. Since the injection period B3 (B3 = B1 + B2) can be specified by the injection start time t3 and the injection end time t8, the injection amount can be calculated based on both the time points t3 and t8 and the rail pressure. It should be noted that the relationship between both time points t3 and t8 and the rail pressure and the injection amount may be stored in advance as a map, and the injection amount may be calculated using the map, or the injection may be performed using a pre-stored calculation formula. The amount may be calculated.

  With the above, the series of processes in FIG. 5 is completed, and based on the injection start time t3 detected in step S22, the injection end time t8 calculated in step S25, and the injection amount calculated in step S26, This is used for updating (learning) the above-described injection control map used in step S12 of FIG.

  Note that the injection amount may be calculated using a map described below instead of steps S23 to S25. For example, a map that specifies the relationship between the descent peak time t3, descent start time t4 and descent end time t7 detected in step S22, and the injection start time, injection end time, and injection amount is stored in advance. The injection start time, the injection end time, and the injection amount may be calculated based on the descending peak time t3, the descending start time t4, and the descending end time t7.

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

  (1) The return pressure sensor 28 is disposed in the low pressure chamber 21e, and the actual injection start time, injection end time, and injection amount are detected based on the pressure fluctuation waveform of the low pressure fuel. Compared to the detection based on the above, it is possible to eliminate the need for a high pressure-resistant sealing property for the seal between the return pressure sensor 28 and the outlet 21i. Therefore, the possibility of fuel leakage at the attachment portion of the return pressure sensor 28 can be suppressed, or an inexpensive seal structure with a low pressure-resistant sealing property can be employed.

  (2) A return pressure sensor 28 for detecting the fuel pressure in the low pressure path is attached to the injector 20. Therefore, it is possible to avoid the following problems that are a concern when the return pressure sensor 28 is arranged in the collecting pipe 16. That is, it is possible to avoid the problem that the fuel pressure fluctuation generated in the other injector 20 interferes with the pressure fluctuation of the low-pressure fuel generated in the injector 20 to be detected. Further, it is possible to avoid such a problem that the fuel pressure in a state where the pressure fluctuation of the low-pressure fuel caused by the injection is attenuated in the low-pressure pipe 15 is detected. As described above, according to the present embodiment, the actual injection start point, injection end point, and injection amount can be accurately detected.

  (3) The return pressure sensor 28 is attached to the low pressure chamber 21e within the injector 20. Therefore, it is possible to detect the fuel pressure in which the above-described attenuation is further reduced as compared with the case where the return pressure sensor 28 is attached to the low pressure passage 21g, the fuel discharge port 21f, and the like located on the downstream side of the low pressure chamber 21e. Therefore, the actual injection start time, injection end time, and injection amount can be detected with high accuracy.

  (4) By detecting the full lift time t4 from the fluctuation waveform by the return pressure sensor 28, the required rise time B4 can be calculated and acquired. Since the injection end time t8 is corrected according to the required rise time B4 having a high correlation with the aging deterioration of the injector 20, the actual injection end time t8 and the injection amount can be accurately detected.

  (5) Since the injection amount is calculated based on the rail pressure in addition to the injection period B3, the injection amount can be calculated with high accuracy. Note that there is a correlation between the leak pressure and the rail pressure, and the higher the rail pressure, the higher the leak pressure. Therefore, the injection amount may be calculated based on the injection period B3 and the leak pressure. In this case, the rail pressure sensor 13 can be eliminated. As a specific example of the leak pressure used for calculating the injection amount as described above, the leak pressure at the following time is used. That is, ascending peak time t2, during a stable period in the latter period when fuel in control chamber Cd is pushed out (see A4), descent start time t4, time t5 when the injection command signal is pulsed off, and control valve 22 is lifted down The time t6 etc. which started is mentioned.

(Second Embodiment)
In the first embodiment, the portion communicating with the outlet 21d in the low pressure path is the low pressure chamber 21e, whereas in the present embodiment shown in FIG. 2, the portion communicating with the outlet 21d is the intermediate back pressure chamber 210e. The orifice 21j is formed in the communication path between the intermediate back pressure chamber 210e and the low pressure chamber 21e. In short, the orifice 21j is provided in the downstream portion of the leak pressure sensor 28 in the low pressure path. By the action of the orifice 21j, the fuel pressure in the intermediate back pressure chamber 210e immediately after the control valve 22 is lifted up becomes an intermediate value between the fuel pressure in the control chamber Cd and the fuel pressure in the low pressure passage 21g.

  Therefore, cavitation at the outlet 21d that occurs when fuel flows out from the outlet 21d can be reduced. Therefore, noise due to cavitation included in the detection value of the leak pressure sensor 28 can be reduced, so that the detection accuracy can be improved when detecting the actual injection state based on the fuel pressure fluctuation. However, according to the first embodiment in which such an orifice 21j is not provided, even a slight fuel pressure fluctuation can be detected, so that the fuel pressure fluctuation detected with high sensitivity can be acquired.

(Other embodiments)
The above embodiments may be implemented with the following modifications. Further, the present invention is not limited to the description of the above embodiment, and the characteristic configurations of the respective embodiments may be arbitrarily combined.

  In the above embodiment, from the fluctuation in fuel pressure detected by the leak pressure sensor 28 (see FIG. 6A), the descent peak time t3, the descent start time t4, and the descent end time t7 are detected as the injection state, and the injection starts. The time point, the end point of injection, and the injection amount are calculated, but other values indicating the injection state include the maximum injection rate arrival point, the injection rate drop start point, the injection rate increase rate, the injection rate decrease rate, and the maximum injection rate. Rate.

  An injection rate calculation unit that calculates the injection rate variation (see FIG. 6E) based on the fuel pressure variation (see FIG. 6A) detected by the leak pressure sensor 28 may be provided. For example, the injection rate fluctuation is calculated based on the descending peak time t3, the descending start time t4, the descending end time t7, the rail pressure, and the like.

  -You may make it provide the aged deterioration estimation means which estimates the aged deterioration degree of the injector 20 based on rise required time B4.

  In the first embodiment, the leak pressure sensor 28 is disposed in the low pressure chamber 21e. However, the present invention is not limited to such an arrangement, and may be any arrangement in the low pressure path. For example, it may be arranged in the low pressure passage 21g, the fuel discharge port 21f, the low pressure pipe 15, the collecting pipe 16, and the like. In the example shown in FIG. 1, the low-pressure chamber 21e, the low-pressure passage 21g, the fuel discharge port 21f, the low-pressure pipe 15, and the collective pipe 16 formed by enlarging the low-pressure passage 21g are described in the claims. It corresponds to “return route”.

  A piezo drive injector may be used instead of the electromagnetic drive injector 20 illustrated in FIG.

  -The type and system configuration of the engine to be controlled can be changed as appropriate according to the application. For example, in the above embodiment, the case where the present invention is applied to a diesel engine has been described. However, for example, the present invention can be basically applied to a spark ignition type gasoline engine (particularly a direct injection engine). it can. The fuel injection system of a direct injection gasoline engine is equipped with a delivery pipe that stores fuel (gasoline) in a high-pressure state. 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 supplied to the engine combustion chamber. Further, the present invention may be applied to a single cylinder engine.

1 is a configuration diagram showing an outline of a fuel system to which a fuel injection system according to a first embodiment of the present invention is applied. The figure which shows typically the internal structure of the fuel injection valve of FIG. The flowchart which shows the basic procedure of the fuel-injection control process which concerns on the system of FIG. The figure which shows the map for injection control used for the process of FIG. The flowchart which shows the process sequence which detects an injection state in the system of FIG. The simulation result which shows the various changes which arise with one valve opening injection in the system of FIG. The figure which shows typically the internal structure of the fuel injection valve which concerns on 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel tank, 13 ... Rail pressure sensor (high pressure side sensor), 15 ... Low pressure piping (return path), 16 ... Collective piping (return path), 20 ... Injector (fuel injection valve), 21 ... Body, 21b ... High pressure Passage, 21c ... nozzle hole, 21d ... outlet, 21e ... low pressure chamber (return path), 210e ... intermediate back pressure chamber (return path), 21f ... fuel outlet (return path), 21g ... low pressure path (return path) , 22 ... control valve, 24 ... nozzle needle (valve element), 28 ... return pressure sensor, Cd ... control chamber, S22 ... injection state detecting means, S26 ... injection amount calculating means.

Claims (12)

A body formed with an injection hole for injecting fuel used for combustion of an internal combustion engine, a high-pressure passage formed inside the body and allowing high-pressure fuel to flow toward the injection hole, and a high-pressure passage formed inside the body A fuel injection valve having a low pressure passage for returning surplus fuel supplied to the fuel tank, and a valve body housed inside the body and opening and closing a portion near the injection hole in the high pressure passage;
A low pressure pipe connected to the fuel injection valve and returning low pressure fuel in the low pressure passage to a fuel tank;
A fuel injection system comprising:
A return pressure sensor that is disposed in a return path to the fuel tank via the low-pressure passage and the low-pressure pipe, and detects the pressure of the low-pressure fuel in the return path;
Injection state detecting means for detecting an injection state of fuel injected from the nozzle hole based on the behavior of the detection value of the return pressure sensor;
A fuel injection system comprising: Applied to a multi-cylinder internal combustion engine having a plurality of cylinders and the fuel injection valve for each cylinder;
The return path includes a collecting pipe that collects the low-pressure fuel of the low-pressure pipe for each cylinder and returns the fuel to the fuel tank,
The fuel injection system according to claim 1, wherein the return pressure sensor is arranged on the upstream side of the collecting pipe.   The fuel injection system according to claim 1, wherein the return pressure sensor is attached to the fuel injection valve. A control chamber formed inside the body, allowing a portion of the high-pressure fuel in the high-pressure passage to flow in, and biasing the valve body in a valve-closing direction by the pressure of the high-pressure fuel that has flowed in;
An outlet that is formed in the control chamber and allows the fuel in the control chamber to flow into the return path;
A control valve that is disposed in a low-pressure chamber formed by enlarging a part of the low-pressure passage, and controls the fuel pressure in the control chamber by opening and closing the outlet.
With
The fuel injection system according to claim 3, wherein the return pressure sensor is attached to the low pressure chamber.   The injection state detecting means is at least one of a start time of injection from the injection hole, an end time of injection, and a full lift time when the valve opening operation amount of the valve body is maximum when the injection hole is opened and closed by the valve body. The fuel injection system according to claim 1, wherein one is detected as the injection state. The injection state detection means detects at least the injection start time and the injection end time,
6. An injection amount calculation means for calculating an injection amount of fuel injected with one valve opening by the valve body based on the detected injection start time and injection end time. The fuel injection system described in 1. A high-pressure side sensor for detecting the pressure of the high-pressure fuel;
The fuel injection according to claim 6, wherein the injection amount calculation means calculates the injection amount based on a detected value of the high-pressure side sensor in addition to the detected injection start time and the injection end time. system.   Immediately after the fuel injection valve starts operation to open the valve body, the injection state detection means decreases after the detection value of the return pressure sensor increases and reaches an increase peak, and then decreases and decreases. The fuel injection system according to any one of claims 5 to 7, wherein a time point at which the pressure reaches is detected and a descending peak time point is detected as the injection start time point.   Immediately after the fuel injection valve starts operating to open the valve body, the injection state detection means rises after the detection value of the return pressure sensor rises and reaches a rise peak, and then drops once. 9. The fuel injection system according to claim 5, wherein a time point at which descent starts again in a stable state is detected, and the descent start time is detected as the full lift time point. 9. .   The injection state detecting means detects when the fuel injection valve starts its operation so as to close the valve body, and after the detection value of the return pressure sensor starts to decrease, the decrease ends. The fuel injection system according to any one of claims 5 to 9, wherein a time point at which a predetermined time has elapsed from the end point of the descent is detected as the injection end time point.   The fuel injection system according to claim 10, wherein the predetermined time is variably set according to a required rise time from the detected injection start time to the full lift time. A high-pressure side sensor for detecting the pressure of the high-pressure fuel;
The fuel injection system according to claim 10 or 11, wherein the predetermined time is variably set according to a detection value of the high-pressure side sensor.

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