JP5267441B2 - Fuel injection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device for an internal combustion that accurately estimates changes in an internal pressure of cylinder without providing a sensor for directly detecting the internal pressure of cylinder. <P>SOLUTION: The device directly supplies fuel in the cylinder of the internal combustion via valve opening drive of a fuel injection valve. The device detects fuel pressure PQ in the fuel injection valve in opening the valve of the fuel injection valve. The device calculates a value equivalent to the fuel pressure PQ as a base pressure PQB while fuel does not burn in the cylinder of the internal combustion. The device calculates pressure difference &Delta;P between the fuel pressure PQ and the base pressure PQB. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a fuel injection device for an internal combustion engine that supplies fuel to an internal combustion engine through drive control of a fuel injection valve.

  Normally, a diesel engine is provided with a fuel injection valve for directly injecting fuel into the cylinder, and the fuel in a state of being pressurized by pumping or the like by a pump is supplied to the fuel injection valve. The fuel injection valve is driven to open, so that fuel is injected into the cylinder of the diesel engine. The fuel injected into the cylinder is ignited and burned by coming into contact with the intake air that has been compressed and heated to a high temperature in the cylinder.

In general, the amount of fuel injected from the fuel injection valve is adjusted by setting the valve opening period of the fuel injection valve in accordance with the operation state of the diesel engine at that time.
In order to accurately adjust the fuel injection amount, a fuel pressure sensor for detecting the pressure of the fuel supplied to the fuel injection valve is provided, and the fuel injection valve is driven based on the fuel pressure detected by the sensor. An apparatus for executing control has been proposed (see, for example, Patent Document 1). In the apparatus described in Patent Document 1, first, a reduction amount of the fuel pressure accompanying fuel injection from the fuel injection valve is obtained, and an actual fuel injection amount is estimated based on the reduction amount. Then, the target fuel injection amount is corrected based on the estimated actual fuel injection amount.

JP 2009-97385 A

  Here, in the case where the combustion injection valve is driven to open in the same manner, the fuel injection amount changes according to the pressure of the fuel supplied to the fuel injection valve, and in addition to the pressure in the cylinder of the internal combustion engine. Also changes. The pressure in the cylinder constantly fluctuates during operation of the internal combustion engine, for example, intermittently suddenly increases with the compression of intake air in the compression stroke and the combustion of fuel in the combustion stroke. Therefore, in order to adjust the fuel injection amount with high accuracy, it is desirable to accurately grasp such a change in the cylinder pressure and execute drive control of the fuel injection valve so as to match the grasped cylinder pressure.

  Such drive control of the fuel injection valve can be realized by newly providing an in-cylinder pressure sensor for directly detecting the in-cylinder pressure. However, it is not preferable to provide a new sensor because the configuration of the fuel injection device is complicated. At present, the in-cylinder pressure sensor is low in reliability and expensive, and it is difficult to provide the sensor in the internal combustion engine.

Such a situation is not limited to diesel engines, but is generally common to other internal combustion engines such as gasoline engines and natural gas engines.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel injection for an internal combustion engine that can accurately estimate a change in the cylinder pressure without providing a sensor that directly detects the cylinder pressure. To provide an apparatus.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
According to the first aspect of the present invention, the pressurized fuel is supplied to the inside of the fuel injection valve, and the fuel is directly injected and supplied into the cylinder of the internal combustion engine through the valve opening drive of the fuel injection valve. In a fuel injection device for an internal combustion engine, a fuel pressure detecting means for detecting a fuel pressure that changes with a change in an actual fuel pressure inside the fuel injection valve when the fuel injection valve is opened, and opening of the fuel injection valve The fuel pressure inside the fuel injection valve at the time of the valve and the base pressure which is the fuel pressure in a predetermined state determined in advance and the fuel pressure detected by the fuel pressure detecting means during the actual operation of the internal combustion engine with the value calculating means for calculating a value indicating the relationship, based on the value indicating the calculated the relationship by the fuel pressure and the value calculating means before the opening of the fuel injection valve detected by said fuel pressure detecting means, wherein As its gist to calculate the estimated in-cylinder pressure in the cylinder.

  Normally, when the fuel injection valve is opened, the pressure of the fuel inside the fuel injection valve temporarily decreases as the fuel is ejected. Even when the fuel injection valve is driven to open in the same manner, the amount of fuel injected per unit time depends on the difference between the fuel pressure inside the fuel injection valve and the pressure inside the cylinder of the internal combustion engine. Different. From this, it can be said that the rate of decrease of the fuel pressure inside the fuel injection valve immediately after the start of the fuel injection valve becomes a value corresponding to the cylinder pressure at that time. Therefore, the fuel pressure inside the fuel injection valve in a predetermined state determined in advance is used as a reference pressure, and the change in the cylinder pressure can be estimated by comparing this reference pressure with the actual fuel pressure. Become.

  According to the above configuration, a value indicating the relationship between the reference pressure (base pressure) and the actual fuel pressure (specifically, the fuel pressure that changes as the fuel pressure inside the fuel injection valve changes) is calculated. In addition, based on the same value, it is possible to accurately estimate the change in the pressure in the cylinder without providing a sensor for directly detecting the pressure in the cylinder of the internal combustion engine.

  As the value indicating the relationship, the difference or ratio between the base pressure and the fuel pressure detected by the fuel pressure detecting means can be adopted. In addition, the predetermined state is a state where the fuel injected into the cylinder is completely burned, a state where the fuel is burned in a state where the fuel efficiency of the internal combustion engine is best, or a case where the fuel injected into the cylinder is burned Including the state that does not.

The invention according to claim 2 is the fuel injection device for an internal combustion engine according to claim 1, wherein the predetermined state is a state in which the fuel injected into the cylinder does not burn.
According to the above configuration, the change in the cylinder pressure accompanying the combustion of the fuel in the cylinder of the internal combustion engine based on the relationship indicated by the value calculated by the value calculation means, that is, the relationship between the actual fuel pressure and the base pressure. Can be estimated with high accuracy.

  According to a third aspect of the present invention, in the fuel injection device for an internal combustion engine according to the second aspect of the present invention, the fuel injection device further comprises ignition detection means for detecting the ignition of fuel in the cylinder based on the value indicating the relationship. The gist.

  The gist of the invention according to claim 4 is the fuel injection device for an internal combustion engine according to claim 3, wherein the ignition detecting means detects the ignition timing of the fuel in the cylinder. .

  When fuel is ignited and burned in the cylinder of the internal combustion engine, the pressure in the cylinder rises rapidly, so that the amount of fuel ejected from the fuel injection valve is reduced compared with the case where fuel does not burn in the cylinder. The rate of decrease of the fuel pressure inside the fuel injection valve is reduced, and the difference between the fuel pressure and the base pressure is increased.

  According to the configuration of the third aspect of the present invention, the value calculated by the value calculating means is a value indicating that the difference between the fuel pressure and the base pressure has increased, and therefore, in the cylinder of the internal combustion engine. It is possible to accurately detect that the fuel has ignited.

  According to the configuration of the invention described in claim 4, by obtaining the time when the difference between the fuel pressure and the base pressure starts to increase based on the value calculated by the value calculating means, It can be accurately detected as the time when the fuel is ignited in the cylinder of the engine.

  In addition to using a predetermined value as the base pressure, the base pressure is calculated based on the operating state of the internal combustion engine, and the calculated base pressure is calculated based on the calculated value. It can be used for calculation.

  According to this configuration, the amount of air sucked into the cylinder of the internal combustion engine (intake air amount) is in a device that varies depending on the engine operating state, and the base pressure is accurately adjusted in accordance with the intake air amount. The change in pressure in the cylinder can be accurately estimated based on the base pressure.

  According to a sixth aspect of the present invention, in the fuel injection device for an internal combustion engine according to any one of the first to fifth aspects, the fuel pressure at the start of opening of the fuel injection valve detected by the fuel pressure detecting means The pressure in the cylinder at the start of opening of the fuel injection valve is calculated based on the rate of decrease in fuel pressure immediately after the start of opening of the fuel injection valve calculated based on the fuel pressure detected by the fuel pressure detecting means. Start pressure calculation means further comprising: the value calculation means calculates a base pressure based on the pressure calculated by the start pressure calculation means, and uses the calculated base pressure for the calculation of the value; Is the gist.

  In a device provided with a fuel injection valve of a type that directly injects fuel into a cylinder of an internal combustion engine, fuel injection is performed by the pressure in the cylinder at the start of opening of the fuel injection valve and the fuel pressure inside the fuel injection valve. The rate of decrease in the fuel pressure immediately after the start of valve opening is determined.

  According to the above configuration, based on such a relationship, the fuel injection valve is based on the fuel pressure inside the fuel injection valve at the start of the valve opening and the rate of decrease in the fuel pressure immediately after the start of the fuel injection valve opening. It is possible to accurately estimate the cylinder pressure at the start of valve opening. In addition, the base pressure can be accurately calculated based on the cylinder pressure estimated as described above, and the change in the pressure in the cylinder can be accurately estimated based on the base pressure.

  In addition, as for the calculation of the decreasing speed, as in claim 7, the specific time at which the differential value becomes minimum immediately after the start of driving of the fuel injection valve is obtained from the transition of the differential value of the fuel pressure detected by the fuel pressure detecting means. The slope of the tangent line at a specific time with respect to the time waveform of the fuel pressure detected by the fuel pressure detecting means can be obtained, and the slope can be calculated as the rate of decrease.

  According to an eighth aspect of the present invention, in the fuel injection device for an internal combustion engine according to the sixth or seventh aspect, the value indicating the relationship calculated by the value calculating means and the value of the fuel injection valve detected by the fuel pressure detecting means. Based on the fuel pressure at the start of valve opening and the pressure in the cylinder calculated by the start time pressure calculating means, the valve-opening pressure calculating means for calculating the pressure in the cylinder when the fuel injection valve is opened It is the gist of further comprising.

  According to the above configuration, the in-cylinder pressure in a predetermined state can be accurately grasped based on the in-cylinder pressure at the start of opening of the fuel injection valve. Moreover, as in the configuration described above (the configuration of the invention described in claim 6), the value indicating the relationship calculated based on the cylinder pressure at the start of opening of the fuel injector and the value at the start of opening of the fuel injector From the fuel pressure, it is possible to accurately grasp the change in the actual cylinder pressure with respect to the cylinder pressure in the predetermined state. Therefore, the cylinder pressure at the time of opening of the fuel injection valve is accurately calculated based on the cylinder pressure in the predetermined state and the actual change in cylinder pressure with respect to the same pressure. be able to.

  According to a ninth aspect of the present invention, in the fuel injection device for an internal combustion engine according to any one of the first to fifth aspects, the value indicating the relationship calculated by the value calculating means and the fuel pressure detecting means are detected. The gist of the invention is that it further comprises a valve-opening pressure calculation means for calculating a pressure in the cylinder when the fuel injection valve is opened based on a fuel pressure when the fuel injection valve is opened.

  Under the condition that the fuel pressure inside the fuel injection valve at the start of the valve opening is constant, the manner in which the fuel pressure decreases immediately after the valve opening starts is determined by the pressure in the cylinder of the internal combustion engine. Therefore, when the fuel injection valve is opened, the internal combustion engine at the time of opening of the fuel injection valve is determined by grasping the fuel pressure at the start of the valve opening and the mode of decrease of the fuel pressure after starting the valve opening. It can be said that the pressure in the cylinder can be accurately estimated. Then, the fuel pressure decrease mode after the start of the fuel injection valve can be grasped based on the value indicating the relationship.

  According to the above configuration, the cylinder pressure at the time of opening of the fuel injection valve can be accurately calculated based on the fuel pressure at the start of opening of the fuel injection valve and the value indicating the relationship.

  The invention according to claim 10 is the fuel injection device for an internal combustion engine according to any one of claims 1 to 9, wherein the fuel pressure detecting means is a pressure sensor attached to the fuel injection valve. The gist.

  According to the above configuration, it is possible to detect the fuel pressure at a portion close to the injection hole of the fuel injection valve, as compared with a device that detects the fuel pressure at a position away from the fuel injection valve. Therefore, it is possible to accurately detect a decrease in the fuel pressure inside the fuel injection valve accompanying the opening of the fuel injection valve, and to accurately change the pressure in the cylinder based on the detected fuel pressure. Can be estimated.

  The invention according to claim 11 is the fuel injection device for an internal combustion engine according to any one of claims 1 to 10, wherein the internal combustion engine has a plurality of cylinders and the fuel injection valve. A pressure accumulating container for storing the pressurized fuel in the middle of a fuel supply passage for supplying fuel, and the fuel injection valve is provided for each cylinder of the internal combustion engine and connected to the pressure accumulating container separately; The fuel pressure detecting means is provided for each cylinder of the internal combustion engine, and detects a fuel pressure at a portion between the pressure accumulating container and the injection hole of the fuel injection valve in the fuel supply passage. That is the gist.

  According to the above configuration, in a multi-cylinder internal combustion engine in which the pressure change mode in each cylinder is different for each cylinder, the pressure change in each cylinder is detected by the dedicated fuel pressure detection means provided for each cylinder. It can be estimated accurately based on the fuel pressure.

1 is a schematic diagram showing a schematic configuration of a fuel injection device for an internal combustion engine according to an embodiment embodying the present invention. Sectional drawing which shows the cross-section of a fuel injection valve. The graph which shows the relationship between fuel injection quantity and a pressure difference. The time chart which shows an example of the relationship between the fuel pressure inside a fuel injection valve, and the cylinder pressure of an internal combustion engine. The time chart which shows an example of the change aspect of the cylinder pressure of an internal combustion engine. The flowchart which shows the execution procedure of a pressure state estimation process. [A] and [b] A time chart showing the transition of the fuel pressure and the transition of the differential value of the fuel pressure. [A] and [b] A time chart showing an example of a relationship among a base pressure, a fuel pressure, and a pressure difference.

Hereinafter, a fuel injection device for an internal combustion engine according to an embodiment of the present invention will be described.
FIG. 1 shows a schematic configuration of a fuel injection device for an internal combustion engine according to the present embodiment.

  As shown in FIG. 1, an intake passage 12 is connected to the cylinder 11 of the internal combustion engine 10. Air is sucked into the cylinder 11 of the internal combustion engine 10 through the intake passage 12. As the internal combustion engine 10, a diesel engine having a plurality of (four [# 1 to # 4] in the present embodiment) cylinders 11 is employed. A direct injection type fuel injection valve 20 that directly injects fuel into the cylinder 11 is attached to the internal combustion engine 10 for each cylinder 11. The fuel injected by opening the fuel injection valve 20 is ignited and burned in contact with the intake air compressed and heated in the cylinder 11 of the internal combustion engine 10. In the internal combustion engine 10, the piston 13 is pushed down by the energy generated by the combustion of the fuel in the cylinder 11, and the crankshaft 14 is forcibly rotated. The combustion gas combusted in the cylinder 11 of the internal combustion engine 10 is discharged as exhaust gas into the exhaust passage 15 of the internal combustion engine 10.

  Each fuel injection valve 20 is individually connected to a common rail 34 via a branch passage 31a, and the common rail 34 is connected to a fuel tank 32 via a supply passage 31b. A fuel pump 33 that pumps fuel is provided in the supply passage 31b. In the present embodiment, the fuel boosted by the pumping by the fuel pump 33 is stored in the common rail 34 and supplied to each fuel injection valve 20. In the present embodiment, the branch passage 31a and the supply passage 31b function as a fuel supply passage, and the common rail 34 functions as a pressure accumulating container provided in the middle of the fuel supply passage.

  A return passage 35 is connected to each fuel injection valve 20, and each return passage 35 is connected to a fuel tank 32. A part of the fuel inside the fuel injection valve 20 is returned to the fuel tank 32 through the return passage 35.

  The internal combustion engine 10 is provided with various sensors as peripheral devices for detecting an operation state. As these sensors, for example, the intake air amount sensor 41 for detecting the amount of air passing through the intake passage 12 (passage air amount GA), the rotational phase (crank angle CA) of the crankshaft 14 and the rotational speed (engine rotational speed). NE) is provided. Further, a pressure sensor 43 for detecting the fuel pressure (fuel pressure PQ) inside the fuel injection valve 20 and an accelerator for detecting an operation amount (accelerator operation amount ACC) of an accelerator operation member (for example, an accelerator pedal). A sensor 44 and the like are also provided. A pressure sensor 43 is provided for each cylinder 11 of the internal combustion engine 10 (specifically, one for each fuel injection valve 20).

  Further, as peripheral devices of the internal combustion engine 10, for example, an electronic control unit 40 configured with a microcomputer is also provided. The electronic control unit 40 takes in the output signals of various sensors, performs various calculations based on the output signals, and performs internal combustion engine 10 such as drive control (fuel injection control) of the fuel injection valve 20 according to the calculation results. Various controls related to the operation are executed.

  The fuel injection control is basically executed as follows. That is, first, an injection pattern is selected based on the engine operating state such as the passage air amount GA, the engine rotational speed NE, the fuel pressure PQ, and the accelerator operation amount ACC, and various control target values for each injection of the injection pattern are set. Calculated. Then, each fuel injection valve 20 is driven to open individually according to these control target values. As a result, an amount of fuel corresponding to the engine operating state is injected from each fuel injection valve 20 and supplied into each cylinder 11 of the internal combustion engine 10 with an injection pattern suitable for the engine operating state at that time.

  In the present embodiment, a plurality of injection patterns that combine main injection, pilot injection, pre-injection, after-injection, post-injection, and the like are set in advance and stored in the electronic control unit 40. One of these injection patterns is selected. Various control target values include control target values for the fuel injection amount of each injection such as main injection, pilot injection, and after injection, and control for the fuel injection timing of various injections such as the injection timing of the main injection and the pilot interval. A target value is calculated.

Hereinafter, the internal structure of the fuel injection valve 20 and the mounting structure of the pressure sensor 43 will be described.
The fuel injection valve 20 is of an electromagnetic drive type, and a so-called normally closed type that is closed when not energized is employed.

FIG. 2 shows a cross-sectional structure of the fuel injection valve 20.
As shown in FIG. 2, a needle valve 22 is provided inside the housing 21 of the fuel injection valve 20. The needle valve 22 is provided in a state capable of reciprocating in the housing 21 (moving up and down in the figure). Inside the housing 21 is provided a spring 24 that constantly urges the needle valve 22 toward the injection hole 23 (the lower side in the figure). A fuel chamber 25 is formed in the housing 21 at a position on one side (lower side in the figure) with the needle valve 22 interposed therebetween, and on the other side (upper side in the figure). A pressure chamber 26 is formed. High-pressure fuel is supplied to the fuel chamber 25 and the pressure chamber 26 from the branch passage 31a (common rail 34) via the introduction passage 27. The fuel chamber 25 is formed with an injection hole 23 that communicates the inside with the outside of the housing 21, and the pressure chamber 26 is connected to the return passage 35 via a control valve 28. The control valve 28 includes a solenoid coil 28a and a valve body 28b that moves in response to a drive signal input to the solenoid coil 28a.

  In the fuel injection valve 20, when no drive signal is input to the solenoid coil 28a, the control valve 28 is closed, and the pressure difference between the fuel chamber 25 and the pressure chamber 26 becomes very small. Therefore, the needle valve 22 moves to a position where the injection hole 23 is closed by the urging force of the spring 24. At this time, the fuel injection valve 20 is closed and fuel is not injected from the fuel injection valve 20.

  On the other hand, when a drive signal is input to the solenoid coil 28 a and the valve body 28 b moves to open the control valve 28, a part of the fuel in the pressure chamber 26 passes through the return passage 35 to the fuel tank 32. Returned. For this reason, the pressure of the fuel in the pressure chamber 26 decreases and the pressure difference between the pressure chamber 26 and the fuel chamber 25 increases, and the pressure difference causes the needle valve 22 to move against the urging force of the spring 24 for injection. Leave the hole 23. At this time, the fuel injection valve 20 is opened, and fuel is injected from the fuel injection valve 20.

  The pressure sensor 43 is integrally attached to the fuel injection valve 20 so as to output a signal corresponding to the fuel pressure inside the introduction passage 27. For this reason, for example, the fuel in a portion near the injection hole 23 of the fuel injection valve 20 as compared with a device that detects the fuel pressure at a position away from the fuel injection valve 20 such as the fuel pressure in the common rail 34 (see FIG. 1). The pressure can be detected, and the change in the fuel pressure inside the fuel injection valve 20 accompanying the opening of the fuel injection valve 20 can be detected with high accuracy.

  In the present embodiment, when the internal combustion engine 10 is operated, the change mode of the pressure in each cylinder 11 (# 1 to # 4) is estimated. Specifically, the pressure in the cylinder 11 corresponding to the fuel injection valve 20 is determined based on the fuel pressure PQ detected by the pressure sensor 43 attached to the fuel injection valve 20 when the fuel injection valve 20 is opened. The estimation process (pressure state estimation process described later) is executed for each cylinder 11. As a result, it is possible to accurately estimate changes in the pressure in each cylinder 11 without providing a sensor that directly detects the pressure in the cylinder 11 of the internal combustion engine 10.

The reason will be described below.
Normally, when the fuel injection valve 20 is opened, the fuel pressure inside the fuel injection valve 20 (specifically, in the fuel chamber 25 [see FIG. 2]) decreases temporarily as the fuel is ejected. become. Further, as shown in FIG. 3, the amount of fuel injected from the fuel injection valve 20 per unit time is the same as that of the fuel injection valve 20 even when the fuel injection valve 20 is driven to open in the same manner. It differs according to the difference (pressure difference) between the fuel pressure inside (specifically, in the fuel chamber 25) and the pressure in the cylinder 11 of the internal combustion engine 10. Therefore, as shown in FIG. 4, the rate of decrease in the fuel pressure inside the fuel injection valve 20 immediately after the start of opening of the fuel injection valve 20 is a value corresponding to the pressure in the cylinder 11 of the internal combustion engine 10 at that time. It can be said. FIG. 4 shows the fuel pressure inside the fuel injection valve 20 and the internal combustion engine 10 when the fuel injection timing and the fuel pressure inside the fuel injection valve 20 at the start of fuel injection are the same. An example of the relationship with the pressure in the cylinder 11 is shown.

  Therefore, by monitoring the change in the actual fuel pressure P2 with reference to the fuel pressure (reference pressure P1) inside the fuel injection valve 20 in a predetermined state in the cylinder 11 of the internal combustion engine 10 as a reference. It becomes possible to estimate a change in the pressure in the cylinder 11 of the internal combustion engine 10. That is, a value indicating the relationship between the reference pressure P1 and the actual fuel pressure P2 (for example, the difference [P2-P1] or the ratio [P2 / P1]) is the pressure of the cylinder 11 of the internal combustion engine 10 in the predetermined state. Therefore, a change in the pressure in the cylinder 11 of the internal combustion engine 10 is estimated by calculating and monitoring such a value. Is possible.

  In view of this point, in the present embodiment, when the fuel injection valve 20 is opened, the fuel pressure PQ is detected by the pressure sensor 43 attached to the fuel injection valve 20 and injected into the cylinder 11 of the internal combustion engine 10. A value (base pressure PQB) corresponding to the fuel pressure PQ when it is assumed that the burned fuel does not burn is calculated, and a difference between them (pressure difference ΔP [= PQ−PQB]) is calculated. For this reason, the change in the pressure in the cylinder 11 can be accurately estimated without providing a sensor for directly detecting the pressure in the cylinder 11 of the internal combustion engine 10 based on the pressure difference ΔP. It becomes like this. In the present embodiment, the state in which the fuel injected into the cylinder 11 of the internal combustion engine 10 does not burn corresponds to a predetermined state.

  In the present embodiment, since the value corresponding to the fuel pressure PQ when the fuel injected into the cylinder 11 of the internal combustion engine 10 is assumed not to burn is calculated as the base pressure PQB, When the fuel is not burned, a value having a high correlation with the difference between the pressure in the cylinder 11 of the internal combustion engine 10 and the actual pressure in the cylinder 11 is calculated. Therefore, based on this pressure difference ΔP, it becomes possible to accurately estimate a change in pressure in the cylinder 11 due to fuel combustion in the cylinder 11 of the internal combustion engine 10.

  In the internal combustion engine, as shown in FIG. 5, the result of detecting the pressure in the cylinder a plurality of times is caused by the influence of individual engine operating conditions, individual differences or deterioration of intake system components, and the like. It is inevitable that variations occur in the pressure. In the apparatus according to the present embodiment, the pressure in the cylinder 11 of the internal combustion engine 10 can be accurately estimated without being affected by such various effects.

  Hereinafter, the execution procedure of the process for estimating the pressure state in the cylinder 11 of the internal combustion engine 10 (pressure state estimation process) will be described in detail with reference to the flowchart shown in FIG.

  The series of processing shown in this flowchart conceptually shows a specific execution procedure of the pressure state estimation processing, and the actual processing is executed by the electronic control unit 40 as interruption processing at predetermined intervals. The In the pressure state estimation process, for example, the pressure in the cylinder 11 [# 1] is estimated based on the detection signal of the pressure sensor 43 provided in the cylinder 11 [# 1] of the internal combustion engine 10, or the internal combustion engine 10 The cylinder 11 (# 1 to # 4) of the internal combustion engine 10 is estimated such that the pressure in the cylinder 11 [# 2] is estimated based on the detection signal of the pressure sensor 43 provided in the cylinder 11 [# 2]. ) Is executed based on the output signal of the corresponding pressure sensor 43.

  As shown in FIG. 6, in this process, first, the fuel pressure (pre-injection fuel pressure PQi) before the fuel injection valve 20 is opened is detected (step S101). Specifically, an average value of the fuel pressure PQ detected several times before and after the drive signal is output to the fuel injection valve 20 (a period during which the fuel injection valve 20 is not actually opened) is calculated. The average value is stored as the pre-injection fuel pressure PQi.

  Thereafter, the decrease rate VP of the fuel pressure PQ immediately after the start of the opening of the fuel injection valve 20 is detected (step S102). Specifically, as shown in an example in FIG. 7, a time waveform (FIG. [A]) of the fuel pressure PQ is formed and stored, and a differential value ([b] in FIG. 7) of the fuel pressure PQ is obtained. Calculated. Then, the timing (specific time T1) at which the differential value becomes minimum immediately after the start of the fuel injection valve 20 is obtained, and the slope ΔPQ of the tangent L of the time waveform of the fuel pressure PQ at the specific time T1 is calculated. Is done. This slope ΔPQ is stored as the decrease speed VP.

  Next, based on the pre-injection fuel pressure PQi (FIG. 6) and the decrease speed VP, the pressure in the cylinder 11 of the internal combustion engine 10 at the start of opening of the fuel injection valve 20 (starting cylinder pressure PSi) is calculated. (Step S103). As is clear from FIG. 4 above, the fuel pressure inside the fuel injection valve 20 before opening the valve (in this embodiment, the fuel pressure PQi before injection) and the inside of the fuel injection valve 20 immediately after the opening of the valve are started. The relationship between the fuel pressure decrease rate (in this embodiment, the decrease rate VP) and the pressure in the cylinder 11 of the internal combustion engine 10 (in this embodiment, the starting cylinder pressure PSi) can be accurately grasped. . In view of this point, in the present embodiment, the relationship between the pre-injection fuel pressure PQi, the decrease speed VP, and the in-cylinder pressure PSi is obtained in advance based on the results of experiments and simulations and stored in the electronic control unit 40. Yes. In the process of step S103 in FIG. 6, the starting in-cylinder pressure PSi is calculated based on the pre-injection fuel pressure PQi and the decrease speed VP based on this relationship. The in-cylinder pressure PSi at the start is used as a value indicating the pressure in the cylinder 11 of the internal combustion engine 10 at the start of the opening of the fuel injection valve 20, and the fuel injected from the fuel injection valve 20 is the internal combustion engine. It can also be used as an index value of the pressure in the cylinder 11 when combustion does not occur in the 10 cylinders 11. In the present embodiment, the process of step S103 functions as a start time pressure calculating unit.

  Thereafter, based on the passage air amount GA and the engine rotational speed NE, a value (base pressure PQB) corresponding to the fuel pressure PQ when the fuel injected from the fuel injection valve 20 into the cylinder 11 of the internal combustion engine 10 is not combusted. A time waveform is calculated (step S104). In the present embodiment, the relationship between the engine operating region determined by the passage air amount GA and the engine rotational speed NE and the base pressure PQB is obtained in advance based on the results of experiments and simulations and stored in the electronic control unit 40. . In the process of step S104, the base pressure PQB is calculated based on the passage air amount GA and the engine speed NE based on this relationship (for example, an arithmetic map or an arithmetic expression). Here, in the internal combustion engine 10, the amount of air sucked into the cylinder 11 (intake air amount) differs depending on the operating state, and the pressure in the cylinder 11 in the compression stroke and the combustion stroke also varies. In the present embodiment, since the base pressure PQB is calculated according to the operating state of the internal combustion engine 10, the base pressure PQB can be accurately calculated in accordance with the intake air amount, and the base pressure PQB can be calculated. Based on this, it is possible to accurately estimate the change in pressure in the cylinder 11.

  After the time waveform of the base pressure PQB is calculated in this way, the time waveform of the difference (the pressure difference ΔP) between the base pressure PQB and the fuel pressure PQ is calculated (step S105). FIG. 8 shows an example of the relationship among the base pressure PQB (solid line in FIG. [A]), the fuel pressure PQ (dotted line in FIG. [A]), and the pressure difference ΔP ([b] in FIG. 8). In the present embodiment, the process of step S105 functions as a calculation unit that calculates a value indicating the relationship.

  Thereafter, based on the time waveform of the pressure difference ΔP, a time T2 when the pressure difference ΔP starts to increase is obtained, and the simultaneous period T2 is a time when the fuel is ignited in the cylinder 11 of the internal combustion engine 10 (ignition time). It is stored (step S106 in FIG. 6). The time T2 (FIG. 8) is obtained based on a time when a predetermined condition such as a large pressure difference ΔP or a high increase rate of the pressure difference ΔP is satisfied. In the present embodiment, the process of step S106 functions as an ignition detection unit.

  Here, when the fuel is ignited and burned in the cylinder 11 of the internal combustion engine 10, the pressure in the cylinder 11 rapidly rises, so that the fuel ejected from the fuel injection valve 20 compared to the case where the fuel does not burn in the cylinder 11. As the fuel pressure PQ decreases, the rate of decrease in the fuel pressure PQ decreases, and the difference between the fuel pressure PQ and the base pressure PQB increases. Therefore, as in the present embodiment, by obtaining the time T2 when the pressure difference ΔP starts to increase, the simultaneous period T2 can be accurately detected as the fuel ignition timing in the cylinder 11 of the internal combustion engine 10. It is determined that the fuel has ignited when the pressure difference ΔP exceeds a predetermined determination value, while it is determined that the fuel has not normally ignited when the pressure difference ΔP does not exceed the predetermined determination value. As described above, it is possible to accurately determine the ignition state of the fuel in the cylinder 11 of the internal combustion engine 10 based on the pressure difference ΔP.

  This ignition timing can be used to calculate the time (so-called ignition delay time) from when the fuel injection by the fuel injection valve 20 is started until the fuel is ignited in the cylinder 11 of the internal combustion engine 10. Further, when the compression ratio in the cylinder 11 of the internal combustion engine 10 changes, the fuel ignition timing in the cylinder 11 also changes. Therefore, the compression ratio can be estimated based on the difference from the timing based on the ignition timing.

  After the ignition timing is detected in this way, the pressure in the cylinder 11 of the internal combustion engine 10 (estimated in-cylinder pressure VPS) is based on the pre-injection fuel pressure PQi (FIG. 6) and the pressure difference ΔP as follows. Is calculated (step S107). In the present embodiment, the process of step S107 functions as valve opening time pressure calculation means.

  As apparent from FIG. 4 above, under the condition that the fuel pressure inside the fuel injection valve 20 at the start of the opening of the fuel injection valve 20 is constant, the subsequent reduction mode of the fuel pressure is the cylinder of the internal combustion engine 10. 11 is determined by the pressure inside. Therefore, the fuel pressure at the start of the opening of the fuel injection valve 20 (in this embodiment, the fuel pressure PQi before injection) and the fuel pressure drop mode immediately after the start of the valve opening (in this embodiment, the time of the pressure difference ΔP) It is possible to accurately estimate the pressure in the cylinder 11 of the internal combustion engine 10 when the fuel injection valve 20 is opened (in-cylinder pressure PSON at the time of injection).

  In the present embodiment, the relationship between the pre-injection fuel pressure PQi and the time waveform of the pressure difference ΔP and the time waveform of the in-cylinder pressure PSON is obtained in advance from the results of experiments and simulations and stored in the electronic control unit 40. ing. Based on the pre-injection fuel pressure PQi and the pressure difference ΔP, the time waveform of the in-cylinder pressure PSON is calculated from the above relationship.

  Further, by accurately grasping the time waveform of the in-cylinder pressure PSON at the time of injection, based on the waveform, the internal combustion engine 10 before and after that (in detail, immediately before the start of opening of the fuel injection valve 20 and immediately after closing). The transition of pressure in the cylinder 11 can be estimated with high accuracy.

  In the present embodiment, the relationship between the time waveform of the in-cylinder pressure PSON during injection and the time waveform of the pressure in the cylinder 11 of the internal combustion engine 10 immediately before the start of the fuel injection valve 20 (in-cylinder pressure PSB before injection) The relationship between the time waveform of the in-cylinder pressure PSON during injection and the time waveform of the pressure in the cylinder 11 of the internal combustion engine 10 immediately after the fuel injection valve 20 is closed (post-injection in-cylinder pressure PSA) is obtained in advance from the results of experiments and simulations. And stored in the electronic control unit 40. Based on the time waveform of the in-cylinder pressure PSON during injection, the time waveform of the pre-injection cylinder pressure PSB and the time waveform of the post-injection cylinder pressure PSA are calculated from these relationships. A time waveform obtained by combining the time waveform of the pre-injection in-cylinder pressure PSB, the time waveform of the in-cylinder pressure PSON, and the time waveform of the post-injection cylinder pressure PSA is calculated as the time waveform of the estimated in-cylinder pressure VPS.

  The estimated in-cylinder pressure VPS is used as the pressure in the cylinder 11 in the compression stroke and combustion stroke of the internal combustion engine 10, and the amount of fuel actually injected into the cylinder 11 and the fuel burned in the cylinder 11. It can also be used to estimate the amount of

  In the apparatus according to the present embodiment, the pressure state in the cylinder 11 of the internal combustion engine 10 is accurate based on each value (starting in-cylinder pressure PSi, ignition timing, estimated in-cylinder pressure VPS) calculated by the pressure state estimation process described above. It is well understood. Further, since the pressure state estimation process is executed for each cylinder 11 of the internal combustion engine 10, the pressure state in each cylinder 11 that is different for each cylinder 11 is detected by a dedicated pressure sensor 43 provided for each cylinder 11. Is accurately estimated and grasped based on the fuel pressure PQ.

  Further, in the apparatus according to the present embodiment, the fuel injection control is executed in a manner corresponding to the pressure state of each cylinder 11 of the internal combustion engine 10 thus grasped. Specifically, correction values for various control target values for each injection (main injection, pilot injection, after-injection) in accordance with the pressure state (or each value itself) grasped based on each value. Are calculated respectively. In the present embodiment, the relationship between the pressure state in the cylinder 11 and each correction value suitable for the same pressure state is obtained in advance based on the results of experiments and simulations and stored in the electronic control unit 40. From the relationship, the correction value is calculated based on the pressure state. The correction value is calculated for each cylinder 11 of the internal combustion engine 10.

  The process of correcting the various control target values with the correction values and executing the valve opening drive of the fuel injection valve 20 corresponding to the correction term according to the various control target values after correction is performed. It is executed every time. Thereby, the valve opening drive of each fuel injection valve 20 can be appropriately executed in accordance with the actual pressure state in each cylinder 11 so as to match the actual operation state of the internal combustion engine 10. .

As described above, according to the present embodiment, the effects described below can be obtained.
(1) Since the difference between the fuel pressure PQ and the base pressure PQB when the fuel injection valve 20 is opened is calculated as the pressure difference ΔP, the inside of the cylinder 11 of the internal combustion engine 10 is based on the pressure difference ΔP. It is possible to accurately estimate the change in the pressure in the cylinder 11 without providing a sensor for directly detecting the pressure of the cylinder 11.

  (2) Since the value corresponding to the fuel pressure PQ when the fuel injected into the cylinder 11 of the internal combustion engine 10 is assumed not to burn is calculated as the base pressure PQB, the pressure difference calculated based on the base pressure PQB Based on ΔP, it is possible to accurately estimate a change in pressure in the cylinder 11 due to fuel combustion in the cylinder 11 of the internal combustion engine 10.

(3) It is possible to accurately detect that the fuel has ignited in the cylinder 11 of the internal combustion engine 10 based on the pressure difference ΔP.
(4) The ignition timing of the fuel in the cylinder 11 of the internal combustion engine 10 can be accurately detected based on the pressure difference ΔP.

  (5) Since the base pressure PQB is calculated based on the operating state of the internal combustion engine 10, the base pressure PQB can be accurately calculated in accordance with the intake air amount of the internal combustion engine 10. Since the pressure difference ΔP is calculated based on the base pressure PQB, a change in the pressure in the cylinder 11 of the internal combustion engine 10 can be accurately estimated based on the pressure difference ΔP.

  (6) The specific time T1 at which the differential value of the fuel pressure PQ is minimized immediately after the start of the fuel injection valve 20 is obtained, and the slope ΔPQ of the tangent L of the time waveform of the fuel pressure PQ at the specific time T1 is calculated. Thus, the decrease rate VP can be calculated such that the same inclination ΔPQ is stored as the decrease rate VP.

(7) The in-cylinder pressure PSON during injection can be accurately calculated based on the pre-injection fuel pressure PQi and the pressure difference ΔP.
(8) The fuel pressure PQ is detected by the pressure sensor 43 integrally attached to the fuel injection valve 20. Therefore, as compared with a device in which the fuel pressure is detected at a position away from the fuel injection valve 20, the fuel pressure at a portion near the injection hole 23 of the fuel injection valve 20 can be detected. Accordingly, it is possible to accurately detect a decrease in the fuel pressure inside the fuel injection valve 20 due to the valve opening drive of the fuel injection valve 20, and the cylinder 11 of the internal combustion engine 10 based on the detected fuel pressure. The change in the internal pressure can be estimated with high accuracy.

  (9) The pressure states in the cylinders 11 that are different for each cylinder 11 of the internal combustion engine 10 can be accurately estimated based on the fuel pressure PQ detected by the dedicated pressure sensor 43 provided for each cylinder 11. .

The embodiment described above may be modified as follows.
The method for detecting the decrease rate VP of the fuel pressure PQ immediately after the start of opening of the fuel injection valve 20 can be changed as appropriate. For example, as the rate of decrease in the fuel pressure PQ, a method of detecting the amount of decrease in the fuel pressure PQ in a predetermined period immediately after the start of the fuel injection valve 20 can be employed.

  The method for obtaining the ignition timing based on the pressure difference ΔP can be arbitrarily changed. For example, the timing when the pressure difference ΔP becomes larger than a predetermined determination value may be set as the ignition timing, and the timing when the increase rate of the pressure difference ΔP becomes larger than the predetermined determination value may be set as the ignition timing.

  The fuel injection from the fuel injection valve 20 is executed in a situation where the internal combustion engine 10 is being operated and the fuel injected from the fuel injection valve 20 is not combusted in the cylinder 11 of the internal combustion engine 10; A value (in-cylinder pressure correlation value) and a fuel pressure PQ that are highly correlated with the pressure in the cylinder 11 of the internal combustion engine 10 at that time are detected, and the base pressure PQB is detected based on the in-cylinder pressure correlation value and the fuel pressure PQ. You may make it learn and update the relationship used for calculation. Specifically, the intake stroke of the internal combustion engine 10 can be adopted as the timing for executing the fuel injection from the fuel injection valve 20, and the cylinder pressure correlation value in this case is the pressure in the intake passage 12 (for example, excessive pressure). Supply pressure, etc.) can be employed. In addition, the exhaust stroke of the internal combustion engine 10 can also be adopted as the timing for executing the fuel injection from the fuel injection valve 20, and the in-cylinder pressure correlation value in that case includes the passage air amount GA, the engine rotational speed NE, And the exhaust temperature in the exhaust passage 15 can be adopted.

  The learning / updating of the relationship described above can be executed as follows, for example. That is, first, based on the in-cylinder pressure correlation value and the fuel pressure PQ, a value corresponding to the fuel pressure in the fuel injection valve 20 when the fuel injected from the fuel injection valve 20 does not burn in the cylinder 11 of the internal combustion engine 10 ( Base pressure equivalent value) is calculated. When the base pressure equivalent value is lower than the base pressure PQB of the specific engine operation region stored in the relationship, a predetermined value is subtracted from all the base pressures PQB stored in the relationship. On the other hand, when the base pressure equivalent value is equal to or higher than the base pressure PQB of the specific engine operation region, a predetermined value is added to all the base pressures PQB stored in the relationship.

  Here, for example, when a change with time of the internal combustion engine 10 occurs, such as adhesion of deposits to the intake port or intake valve of the internal combustion engine 10 and the injection hole 23 of the fuel injection valve 20, wear of the piston ring, etc., such a change with time will occur. Compared with the case where it does not occur, the fuel pressure PQ when the fuel injected from the fuel injection valve 20 into the cylinder 11 of the internal combustion engine 10 does not burn may change. In this case, since the relationship between the engine operating region determined by the passage air amount GA and the engine rotational speed NE and the fuel pressure PQ when the fuel injection from the fuel injection valve 20 is not changed, the electronic control unit 40 is simply changed. If the base pressure PQB is calculated based on the stored relationship, the calculation error of the base pressure PQB may increase.

  In this regard, according to the above configuration, the fuel injected from the fuel injection valve 20 does not burn in the cylinder 11 of the internal combustion engine 10 based on the in-cylinder pressure correlation value and the fuel pressure PQ detected as described above. It is possible to grasp the actual fuel pressure inside the fuel injection valve 20 when the fuel injection from the fuel injection valve 20 is executed. Then, the relationship used for calculating the base pressure PQB can be learned and updated based on the actual fuel pressure that has been grasped. Thereby, the calculation mode of the base pressure PQB can be changed in accordance with the change with time of the internal combustion engine 10 described above, and errors due to the change with time can be reduced.

  The starting cylinder pressure PSi may be used as a calculation parameter for the base pressure PQB. According to such a configuration, the base pressure PQB can be accurately calculated in accordance with the in-cylinder pressure PSi at the start, that is, the pressure in the cylinder 11 of the internal combustion engine 10 when the fuel injection valve 20 starts to open. Thus, the change in the pressure in the cylinder 11 can be estimated with higher accuracy based on the base pressure PQB.

  When such a configuration is employed, it is desirable to use the starting cylinder pressure PSi as a calculation parameter for the injection cylinder pressure PSON. According to such a configuration, it is possible to accurately grasp the pressure in the cylinder 11 when it is assumed that the fuel injected into the cylinder 11 of the internal combustion engine 10 does not burn based on the starting cylinder pressure PSi. Moreover, in the cylinder 11 when it is assumed that the fuel injected into the cylinder 11 of the internal combustion engine 10 is not burned by the pressure difference ΔP calculated based on the starting in-cylinder pressure PSi and the fuel pressure PQi before injection as described above. It is possible to accurately grasp the actual pressure change in the cylinder 11 with respect to the pressure. Therefore, the in-cylinder pressure PSON during injection can be accurately calculated based on the pressure in the cylinder 11 thus grasped and the actual change in the pressure in the cylinder 11 with respect to the same pressure.

  As the estimated in-cylinder pressure VPS, a time waveform combining a time waveform of the in-cylinder pressure PSB before injection and a time waveform of the in-cylinder pressure PSON, a time waveform of the in-cylinder pressure PSON and a time waveform of the after-injection cylinder pressure PSA Only the time waveform combining these or the time waveform of the in-cylinder pressure PSON during injection may be calculated.

  In the pressure state estimation process (FIG. 6), the process for calculating the starting cylinder pressure PSi (steps S102 and S103), the process for detecting the ignition timing (step S106), and the process for calculating the estimated cylinder pressure VPS ( Any one or two of step S107) may be omitted.

  If the pressure that is an index of the fuel pressure in the fuel injection valve 20 (specifically, in the fuel chamber 25), in other words, the fuel pressure that changes with the change of the fuel pressure can be detected properly. The pressure sensor 43 is not limited to being directly attached to the fuel injection valve 20, and the attachment mode of the pressure sensor 43 can be arbitrarily changed. Specifically, the pressure sensor 43 may be attached to a portion (branch passage 31 a) between the common rail 34 and the fuel injection valve 20 in the fuel supply passage, or may be attached to the common rail 34.

  As the base pressure PQB, a value corresponding to the fuel pressure PQ when the fuel injected into the cylinder 11 of the internal combustion engine 10 is completely combusted, or the state where the fuel efficiency of the internal combustion engine 10 is the best A value corresponding to the fuel pressure PQ in the case where it is assumed that the fuel is burned in may be calculated. In short, a value corresponding to the fuel pressure PQ in a predetermined state determined in advance may be calculated as the base pressure PQB. Even with such a configuration, the pressure difference ΔP has a high correlation with the difference between the pressure in the cylinder 11 of the internal combustion engine 10 and the actual pressure in the cylinder 11 in the predetermined state. By monitoring the above, it is possible to estimate a change in pressure in the cylinder 11 of the internal combustion engine 10.

As the base pressure PQB, a predetermined value that is set in advance may be set regardless of the operating state of the internal combustion engine 10.
Not only calculating the pressure difference ΔP (= PQ−PQB), but also accurately grasping the value indicating the relationship between the base pressure PQB and the fuel pressure PQ, in other words, the relationship between the base pressure PQB and the fuel pressure PQ. Any value can be calculated as long as the value can be satisfied. Specifically, a pressure difference (PQB-PQ), a ratio between the base pressure PQB and the fuel pressure PQ ([PQB / PQ] or [PQ / PQB]) may be calculated.

  In place of the fuel injection valve 20 driven by the solenoid coil 28a, a fuel injection valve driven by something other than the solenoid coil 28a (for example, a piezo element) may be employed.

  The present invention is not limited to an internal combustion engine having four cylinders, but also to a single cylinder internal combustion engine, an internal combustion engine having two cylinders, an internal combustion engine having three cylinders, or an internal combustion engine having five or more cylinders. Can be applied.

  The present invention can be applied not only to a diesel engine but also to a gasoline engine using gasoline fuel and a natural gas engine using natural gas fuel.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Cylinder, 12 ... Intake passage, 13 ... Piston, 14 ... Crankshaft, 15 ... Exhaust passage, 20 ... Fuel injection valve, 21 ... Housing, 22 ... Needle valve, 23 ... Injection hole, 24 ... Spring, 25 ... Fuel chamber, 26 ... Pressure chamber, 27 ... Introduction passage, 28 ... Control valve, 28a ... Solenoid coil, 28b ... Valve body, 31a ... Branch passage, 31b ... Supply passage, 32 ... Fuel tank, 33 ... Fuel Pump, 34 ... common rail, 35 ... return passage, 40 ... electronic control unit, 41 ... intake air sensor, 42 ... crank sensor, 43 ... pressure sensor (fuel pressure detecting means), 44 ... accelerator sensor.

Claims (11)

A fuel injection device for an internal combustion engine in which fuel in a pressurized state is supplied to the inside of the fuel injection valve and directly injects fuel into a cylinder of the internal combustion engine through valve opening driving of the fuel injection valve. ,
A fuel pressure detecting means for detecting a fuel pressure that changes in accordance with a change in an actual fuel pressure inside the fuel injection valve when the fuel injection valve is opened, and an internal part of the fuel injection valve when the fuel injection valve is opened. Value calculating means for calculating a value indicating a relationship between a fuel pressure and a base pressure which is a fuel pressure in a predetermined state determined in advance and a fuel pressure detected by the fuel pressure detecting means during actual operation of the internal combustion engine With
An estimated in-cylinder pressure in the cylinder is calculated based on the fuel pressure before opening the fuel injection valve detected by the fuel pressure detecting means and a value indicating the relationship calculated by the value calculating means. A fuel injection device for an internal combustion engine. The fuel injection device for an internal combustion engine according to claim 1,
The fuel injection device for an internal combustion engine, wherein the predetermined state is a state in which the fuel injected into the cylinder does not burn. The fuel injection device for an internal combustion engine according to claim 2, further comprising ignition detection means for detecting ignition of fuel in the cylinder based on a value indicating the relationship. The fuel injection device for an internal combustion engine according to claim 3,
The fuel injection device for an internal combustion engine, wherein the ignition detection means detects an ignition timing of fuel in the cylinder. In the fuel-injection apparatus of the internal combustion engine as described in any one of Claims 1-4,
The fuel injection device for an internal combustion engine, wherein the value calculation means calculates the base pressure based on an operating state of the internal combustion engine, and uses the calculated base pressure for the calculation of the value. In the fuel-injection apparatus of the internal combustion engine as described in any one of Claims 1-5,
The fuel pressure at the start of opening of the fuel injection valve detected by the fuel pressure detecting means and the rate of decrease in the fuel pressure immediately after the start of opening of the fuel injection valve calculated based on the fuel pressure detected by the fuel pressure detecting means. And a starting pressure calculating means for calculating the pressure in the cylinder at the start of opening of the fuel injection valve based on
The value calculation means calculates a base pressure based on the pressure calculated by the start time pressure calculation means, and uses the calculated base pressure for the calculation of the value. apparatus. The fuel injection device for an internal combustion engine according to claim 6,
The start-time pressure calculating means obtains a specific timing at which the differential value becomes minimum immediately after the start of opening of the fuel injection valve from the transition of the differential value of the fuel pressure detected by the fuel pressure detecting means, and the fuel pressure detecting means A fuel injection device for an internal combustion engine, characterized in that an inclination of a tangent line at the specific time of the time waveform of the fuel pressure detected by the step is obtained and the inclination is calculated as the rate of decrease. Based on the value calculated by the value calculation means, the fuel pressure at the start of opening of the fuel injection valve detected by the fuel pressure detection means, and the pressure in the cylinder calculated by the start pressure calculation means. The fuel injection device for an internal combustion engine according to claim 6 or 7, further comprising valve-opening pressure calculation means for calculating a pressure in the cylinder when the fuel injection valve is opened. The pressure in the cylinder when the fuel injector is opened based on the value calculated by the value calculator and the fuel pressure detected by the fuel pressure detector when the fuel injector is opened. The fuel injection device for an internal combustion engine according to any one of claims 1 to 5, further comprising valve-opening pressure calculating means for calculating In the fuel-injection apparatus of the internal combustion engine as described in any one of Claims 1-9,
The fuel injection device for an internal combustion engine, wherein the fuel pressure detection means is a pressure sensor attached to the fuel injection valve. In the fuel-injection apparatus of the internal combustion engine as described in any one of Claims 1-10,
The internal combustion engine has a plurality of cylinders and a pressure accumulating container that stores the pressurized fuel in the middle of a fuel supply passage that supplies fuel to the fuel injection valve.
The fuel injection valve is provided for each cylinder of the internal combustion engine and is separately connected to the pressure accumulating vessel,
The fuel pressure detecting means is provided for each cylinder of the internal combustion engine, and detects a fuel pressure in a portion between the pressure accumulating container and the injection hole of the fuel injection valve in the fuel supply passage. A fuel injection device for an internal combustion engine.

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