JP2006242091A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reliability of pressure reduction characteristics used for calculation of command value given to a pressure reducing valve in control of operation of the pressure reducing valve reducing actual rail pressure. <P>SOLUTION: A microcomputer and a pressure reducing valve drive circuit are made function as rail pressure control means and the microcomputer is made function as a pressure reduction characteristic correction means. The rail pressure control means calculates the command value given to the pressure reducing valve and outputs the same to the pressure reducing valve to control operation of the pressure reducing valve for making actual rail pressure and target rail pressure roughly consistent based on the pressure reduction characteristics indicating correlation between relief quantity and actual rail pressure. The pressure reduction characteristic correction means corrects the pressure reduction characteristics according to estimated error equivalent to difference between actual pressure reduction quantity indicating actual rail pressure drop quantity accompanying execution of the rail pressure control means and estimated pressure reduction quantity estimated based on pressure reduction characteristics. Consequently, pressure reduction characteristics are corrected for each pressure reducing valve product and changes to what are suitable for control of individual product. Consequently, reliability of pressure reduction characteristics is improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection device that injects and supplies fuel to an engine.

[Conventional technology]
2. Description of the Related Art Conventionally, a pressure accumulation type fuel injection device that includes a common rail that receives fuel supply so that fuel is accumulated at a target pressure according to the state of the engine and that supplies fuel to the engine via the common rail has been publicly known. ing.

  2. Description of the Related Art In recent years, in a pressure accumulation type fuel injection device, the pressure of fuel in the device has been increased for the purpose of improving injection response and promoting atomization of spray. As the pressure increases, there is an increasing demand for improved reliability for pressure reduction control for accurately reducing the actual pressure (actual rail pressure) of fuel accumulated in the common rail.

  The conventional fuel injection device relates to pressure reduction control of the actual rail pressure, and opens a valve to release fuel from the common rail, thereby reducing the actual rail pressure and a command value given to the pressure reduction valve using a predetermined pressure reduction characteristic. Is calculated and output to the pressure reducing valve to provide rail pressure control means for controlling the operation of the pressure reducing valve. This pressure reduction characteristic indicates, for example, the correlation between the amount of fuel escaped from the pressure reducing valve per unit time and the actual rail pressure. The rail pressure control means estimates the escape amount by applying the measured actual rail pressure to the pressure reduction characteristic, and calculates a command value based on this estimation.

[Problems with conventional technology]
However, the amount of relief of the pressure reducing valve varies depending on the individual product and varies within the allowable range of the performance standard. For this reason, the amount of relief etc. is estimated using the decompression characteristics, and even if the command value is calculated based on the estimated amount of relief etc. and given to the decompression valve, due to fluctuation factors such as deterioration over time, within a predetermined time A situation in which a desired amount of reduced pressure cannot be obtained may occur. As a result, for example, when the escape amount is smaller than the standard median value, there is a possibility that fuel is not sufficiently released from the common rail and injection is performed with the actual rail pressure higher than the target pressure. If injection is performed in such a state that the actual rail pressure is higher than the target pressure, the risk of emission deterioration and noise generation increases. In particular, the recent progress in high pressure makes the risk of emission deterioration and noise generation higher and higher.

For the purpose of improving the performance of the pressure reducing valve, a pressure reducing valve having a solenoid for driving the valve body in the valve opening direction and a solenoid for driving the valve body in the valve closing direction has been considered (for example, Patent Documents). 1). However, the purpose of the performance improvement by this pressure reducing valve is to expand the controllable pressure region, and not to improve the reliability with respect to pressure reducing characteristics such as the above-mentioned escape amount.
JP 2004-11448 A

  The present invention has been made to solve the above-described problems, and its purpose is to calculate a command value to be given to the pressure reducing valve when controlling the operation of the pressure reducing valve for reducing the actual rail pressure. The purpose is to improve the reliability of the decompression characteristics to be used.

[Means of Claim 1]
The fuel injection device according to claim 1 includes a common rail that receives the supply of fuel so that the fuel is accumulated at a target pressure corresponding to the state of the engine, and the fuel is injected and supplied to the engine via the common rail. . This fuel injection device opens the valve and releases the fuel from the common rail, thereby reducing the actual pressure of the fuel accumulated in the common rail, and the correlation between the amount of fuel released from the pressure reducing valve and the actual pressure. Rail pressure control means for controlling the operation of the pressure reducing valve so that the actual pressure substantially matches the target pressure by calculating a command value to be given to the pressure reducing valve and outputting the command value to the pressure reducing valve. Pressure reduction characteristic correcting means for correcting the pressure reduction characteristic according to a difference between an actual pressure reduction amount indicating an actual pressure drop amount due to execution of the control means and an estimated pressure reduction amount estimated from the pressure reduction characteristics is provided.
As a result, the pressure reduction characteristics are corrected for each product in accordance with the way in which the amount of relief in each product of the pressure reducing valve is biased, and change to one suitable for control of each product. For this reason, the reliability of the decompression characteristic is improved and the control adaptability is maintained at a high level.
Note that a physical quantity called a reduced pressure quantity such as an actual reduced pressure quantity or a determined reduced pressure quantity can be calculated as a physical quantity having a pressure dimension, but can also be calculated as a physical quantity having a fuel elastic modulus or a viscosity dimension.

[Means of claim 2]
The pressure reducing characteristic in the fuel injection device according to claim 2 is a correlation between the opening command period indicating the period during which the pressure reducing valve is open and the actual pressure.
This means shows one form of the decompression characteristic.

[Means of claim 3]
The decompression characteristic correcting means in the fuel injection device according to claim 3 is executed when it is determined that the absolute value of the difference between the actual decompression amount and the estimated decompression amount is equal to or greater than a predetermined threshold value.
Thereby, only when the difference between the actual decompression amount and the estimated decompression amount is surely enlarged, the decompression characteristic is corrected. For this reason, the possibility of erroneous correction can be reduced, and the frequency of correction can be reduced to reduce the processing load of the microcomputer or the like.

[Means of claim 4]
The decompression characteristic correcting means in the fuel injection device according to claim 4 is executed when the engine is stopped.
When the engine is stopped (so-called ignition off), it is reliably injecting and depressurizing, and the amount of fuel escaped from other than the pressure reducing valve (for example, the amount of fuel leaking from the injector) can be predicted. It is. Therefore, if the decompression characteristic correcting means is executed when the ignition is off, the decompression characteristic can be corrected accurately.

[Means of claim 5]
The decompression characteristic in the fuel injection device according to claim 5 is stored in a non-volatile storage means that can retain data even when the power supply state is released.
A state where the decompression characteristics must be corrected, for example, a state where the difference between the actual decompression amount and the estimated decompression amount is surely widened and the necessity for correction is increased does not occur frequently. Therefore, it is preferable to use a non-volatile storage means in order to store the decompression characteristic data reliably over a long period of time.

[Means of claim 6]
The decompression characteristic correcting means in the fuel injection device according to claim 6 reduces the correction amount of the decompression characteristic and corrects the decompression characteristic with the reduced correction amount.
If the decompression characteristics are changed drastically by one correction, the risk of erroneous correction increases. Therefore, if the correction amount is reduced as described above, the possibility of erroneous correction can be reduced.

[Means of Claim 7]
The decompression characteristic correcting means in the fuel injection device according to claim 7 limits the range to be corrected in the decompression characteristic according to the measured value of the actual pressure.
If the pressure reduction characteristics are changed in the entire range that the actual pressure can take with one correction, the risk of erroneous correction increases. Therefore, if the range to be corrected is limited as described above, the possibility of erroneous correction can be reduced.

  The fuel injection device of the best mode 1 is provided with a common rail that receives the supply of fuel so that the fuel is accumulated at a target pressure corresponding to the state of the engine, and the fuel is injected and supplied to the engine via the common rail. This fuel injection device opens the valve and releases the fuel from the common rail, thereby reducing the actual pressure of the fuel accumulated in the common rail, and the correlation between the amount of fuel released from the pressure reducing valve and the actual pressure. Rail pressure control means for controlling the operation of the pressure reducing valve so that the actual pressure substantially matches the target pressure by calculating a command value to be given to the pressure reducing valve and outputting the command value to the pressure reducing valve. Pressure reduction characteristic correcting means for correcting the pressure reduction characteristic according to a difference between an actual pressure reduction amount indicating an actual pressure drop amount due to execution of the control means and an estimated pressure reduction amount estimated from the pressure reduction characteristics is provided.

The pressure reduction characteristic is a correlation between an opening command period indicating a period during which the pressure reducing valve is open and an actual pressure.
The decompression characteristic correcting means is executed when it is determined that the absolute value of the difference between the actual decompression amount and the estimated decompression amount is equal to or greater than a predetermined threshold value.

Further, the decompression characteristic correcting means is executed when the engine is stopped.
Further, the decompression characteristic is stored in a non-volatile storage unit that can retain data even when the power supply state is released.
The decompression characteristic correction means reduces the correction amount of the decompression characteristic and corrects the decompression characteristic with the reduced correction amount.

  The decompression characteristic correcting means in the fuel injection device of the best mode 2 limits the range to be corrected in the decompression characteristic according to the measured value of the actual pressure.

[Configuration of Example 1]
The configuration of the fuel injection device 1 according to the first embodiment will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, the fuel injection device 1 includes a common rail 3 that receives supply of fuel so that fuel is accumulated at a target pressure corresponding to a state of an engine (not shown). The fuel is injected and supplied.

  In addition to the common rail 3, this fuel injection device 1 is mounted on a fuel supply pump 5 that pumps fuel from a fuel tank 4 and supplies the fuel to the common rail 3, and the fuel accumulated in the common rail 3 is injected into the cylinder. An injector 6, a pressure reducing valve 7 for reducing the actual pressure of fuel accumulated in the common rail 3 (actual rail pressure), a command value to be given to the pressure reducing valve 7, etc. based on detection values input from various sensors; The microcomputer 8 that is output as a command signal, and various drive circuits that supply a drive current and an applied voltage to the pressure reducing valve 7 and the like according to the command signal output from the microcomputer 8 are configured.

  Here, the various drive circuits are: a pressure reducing valve driving circuit 12 for supplying a driving current to the pressure reducing valve 7, an injector driving circuit 13 for supplying a driving current and an applied voltage to the injector 6, and a pump driving circuit for supplying a driving current to the fuel supply pump 5. 14 mag. The number of injectors 6 is the same as the number of cylinders (only one is shown in FIG. 1).

  With the above configuration, in the fuel injection device 1, the supply amount from the fuel supply pump 5 is controlled so that the actual rail pressure substantially matches the target pressure (target rail pressure) corresponding to the state of the engine, and the engine The injection timing and the injection period by the injector 6 are controlled so that an amount of fuel corresponding to the state of the engine is injected at the time according to the state. As a result, the actual rail pressure substantially coincides with the target rail pressure, and fuel is injected into each cylinder at an injection pressure corresponding to the actual rail pressure, and an operation corresponding to the state of the engine is performed.

  Next, the part (the common rail 3, the pressure reducing valve 7, the microcomputer 8, the pressure reducing valve drive circuit 12, etc.) related to the pressure reduction control of the actual rail pressure in the fuel injection device 1 will be described in detail.

  The common rail 3 is connected to the discharge port of the fuel supply pump 5 via a high-pressure channel 15, receives the supply of high-pressure fuel, and accumulates fuel in a high-pressure state. The fuel at the actual rail pressure is supplied to each injector 6. That is, the common rail 3 functions as a pressure accumulation container that accumulates high-pressure fuel, and also functions as a distribution container that distributes high-pressure fuel to the injectors 6. The actual rail pressure is detected by a rail pressure sensor 17 attached to one end of the common rail 3, and the detected value is output to the microcomputer 8 as a rail pressure detection signal.

  The pressure reducing valve 7 is attached to the other end of the common rail 3 and is opened to reduce the actual rail pressure by allowing fuel to escape from the common rail 3 to the low pressure flow path 18. As shown in FIG. 2, the pressure reducing valve 7 includes a ball-shaped valve body 22 and a valve body 22 that open or close by communicating or blocking between the common rail 3 and the low-pressure flow path 18. The movable element 23 that contacts and is displaced toward the valve opening side by receiving a magnetic attraction force is energized by the solenoid 24 and the solenoid 24 that is energized by the drive current and generates a magnetic attraction force that displaces the mover 23 toward the valve opening side. A stator 25 that is excited and magnetically attracts the mover 23, a spring 26 that is disposed between the mover 23 and the stator 25, and biases the mover 23 toward the valve closing side, and the like.

  The low pressure flow path 18 is connected to a low pressure flow path 29 through which fuel is released from the injector 6, and the fuel released from the common rail 3 returns to the fuel tank 4 together with the fuel released from the injector 6.

  The microcomputer 8 is a computer having a known structure including a CPU that performs control processing and arithmetic processing, storage means such as a ROM, RAM, EEPROM, and backup RAM that store various programs and data, an input circuit, an output circuit, and the like.

  Then, the microcomputer 8 and the pressure reducing valve drive circuit 12 determine the command value to be given to the pressure reducing valve 7 based on the pressure reducing characteristic indicating the correlation between the amount of fuel escaped from the pressure reducing valve 7 (referred to as the amount of escape) and the actual rail pressure. By calculating and outputting to the pressure reducing valve 7, it functions as a rail pressure control means for controlling the operation of the pressure reducing valve 7 so that the actual rail pressure substantially matches the target rail pressure. In addition, the microcomputer 8 corrects the decompression characteristic according to the difference between the actual decompression amount indicating the amount of decrease in the actual rail pressure accompanying the execution of the rail pressure control means and the estimated decompression amount estimated from the decompression characteristic. Functions as a means. The actual reduced pressure amount and the estimated reduced pressure amount can be calculated as physical quantities having a pressure dimension, but can also be calculated as physical quantities having a fuel elastic modulus and viscosity dimension.

  That is, the microcomputer 8 stores a pressure reduction characteristic indicating a correlation between the escape amount and the actual rail pressure, and calculates a command value to be given to the pressure reducing valve 7 based on the pressure reduction characteristic. As shown in FIG. 3A, for example, this pressure reduction characteristic is a correlation between an open command period indicating a period during which the pressure reducing valve 7 is open and the actual rail pressure. Further, the open command period is, for example, The actual rail pressure corresponds to the opening time of the pressure reducing valve 7 required for reducing the unit pressure, and corresponds to the escape amount per unit time. The command value in the present embodiment is an open command period, and the microcomputer 8 synthesizes a command signal based on the calculated open command period and outputs it to the pressure reducing valve drive circuit 12. Then, the pressure reducing valve drive circuit 12 energizes the solenoid 24 in accordance with this command signal to open the pressure reducing valve 7. As described above, the microcomputer 8 and the pressure reducing valve drive circuit 12 function as rail pressure control means by outputting an open command period as a command value to the pressure reducing valve 7.

  Further, the microcomputer 8 stores a correction characteristic indicating a correlation between the correction amount of the escape amount and the absolute value of the difference between the actual decompression amount and the estimated decompression amount (hereinafter referred to as an estimation error), and the correction characteristic is stored in the correction characteristic. Based on the correction of the decompression characteristic, it functions as a decompression characteristic correcting means. This correction characteristic is, for example, the correlation between the correction amount and the estimation error for the open command period, and this correction amount indicates, for example, the extension time or shortening time of the open command period as shown in FIG. It is an adjustment time. For example, when the actual decompression amount is lower than the estimated decompression amount, and the microcomputer 8 determines that the decompression characteristic needs to be corrected, the decompression characteristic is modified so as to be raised for an adjustment time corresponding to the estimation error.

  The decompression characteristic correcting means is executed when it is determined that the estimation error is equal to or greater than a predetermined threshold, or when it is determined that there is no injection and the decompression execution state is certain, such as when the ignition is off. The Further, the decompression characteristics are stored in a non-volatile storage means (for example, EEPROM) that can retain data even when the power supply state is released. Further, the decompression characteristic correcting means reduces the addition / subtraction time by a predetermined gain and corrects the decompression characteristic using the reduced addition / subtraction time.

[Control Method of Example 1]
The control method of Example 1 is demonstrated using the flowchart shown in FIG.
First, in step S1, it is determined whether a condition (correction condition) for correcting the decompression characteristic is satisfied. The correction condition is that the estimation error is equal to or greater than a predetermined threshold value, and that the engine is reliably in the non-injection and decompression execution state as in the case of ignition off. If the correction condition is satisfied (YES), the process proceeds to step S2, and if the correction condition is not satisfied (NO), the process is terminated.

  Next, in step S2, the initial value of the actual rail pressure is measured. This measurement is performed by the microcomputer 8 using a rail pressure detection signal input from the rail pressure sensor 17 to the microcomputer 8. Then, when a predetermined time has elapsed in step S3 (YES), the process proceeds to step S4, and the final value of the actual rail pressure is measured in the same manner. In step S3, the process does not proceed while the predetermined time has not elapsed (NO). Note that this predetermined time is at least longer than the time required for the processing by the rail pressure control means to be executed to calculate a new opening command period and to perform valve opening based on the new opening command period. Is set.

  Next, in step S5, the difference between the initial value of the actual rail pressure and the final value of the actual rail pressure, that is, the amount of decrease in the actual rail pressure associated with the execution of the rail pressure control means is obtained. Calculate the amount. Further, in step S6, the initial value of the actual rail pressure is applied to the pressure reduction characteristic to calculate the open command period, and the estimated value is estimated using the calculated open command period and the difference between the initial value of the actual rail pressure and the target rail pressure. Calculate the amount of decompression. In step S7, the difference between the actual decompression amount and the estimated decompression amount is obtained, and the absolute value of this difference is used as the estimation error.

  Next, in step S8, an addition error is calculated by applying an estimation error to the correction characteristic. In step S9, the adjustment time is multiplied by a predetermined gain for reduction, and the reduced pressure characteristic is corrected using the reduced adjustment time.

[Operation of Example 1]
The operation of the first embodiment will be described with reference to FIG.
For example, as shown in FIG. 5A, when the actual rail pressure is lowered from the initial pressure P1 to the final pressure P2 by the pressure reducing valve 7 whose escape amount is smaller than the standard median value (solid line a), the relief amount is the standard median. The time to reach the final pressure P2 is longer than when the actual rail pressure is lowered from the initial pressure P1 to the final pressure P2 by the pressure reducing valve 7 (solid line b). Therefore, when the control for lowering the target rail pressure from the initial pressure P1 to the final pressure P2 is executed based on the pressure reduction characteristic created on the assumption that the escape amount is the standard median value, the actual rail pressure is greater than the final pressure P2. Depressurization ends at a high intermediate pressure P2 '. For this reason, injection is performed in a state where the actual rail pressure is higher than the target rail pressure.

  Accordingly, the time difference between the solid line a and the solid line b until the actual rail pressure reaches the final pressure P2 from the initial pressure P1 is calculated as an addition / subtraction time using the correction characteristic to correct the pressure reduction characteristic, and FIG. ), The open command period in the case of the solid line a is extended by the calculated addition / subtraction time than the open command period in the case of the solid line b. Thus, different open command periods are given to the pressure reducing valve 7 indicated by the solid line a and the pressure reducing valve 7 indicated by the solid line b when the target rail pressure is lowered from the initial pressure P1 to the final pressure P2. For this reason, both the pressure reducing valve 7 (the pressure reducing valve 7 indicated by the solid line b) whose escape amount is the standard median and the pressure reducing valve 7 (the pressure reducing valve 7 indicated by the solid line a) whose escape amount is smaller than the standard median value are required until the next injection. The actual rail pressure can be reliably lowered from the initial pressure P1 to the final pressure P2.

[Effect of Example 1]
In the fuel injection device 1 of the first embodiment, the microcomputer 8 and the pressure reducing valve drive circuit 12 set the opening command period as a command value to be given to the pressure reducing valve 7 based on the pressure reducing characteristic that is a correlation between the opening command period and the actual rail pressure. By calculating and outputting to the pressure reducing valve 7, it functions as a rail pressure control means for controlling the operation of the pressure reducing valve 7 so that the actual rail pressure substantially matches the target rail pressure. Further, the microcomputer 8 changes the pressure reduction characteristic according to the estimation error corresponding to the difference between the actual pressure reduction amount indicating the amount of decrease in the actual rail pressure due to the execution of the rail pressure control means and the estimated pressure reduction amount estimated by the pressure reduction characteristic. It functions as a decompression characteristic correcting means for correcting.
As a result, the decompression characteristics are corrected for each product in accordance with how the escape amount of each individual decompression valve 7 is biased, and change to those suitable for control of each individual product. For this reason, the reliability of the decompression characteristic is improved and the control adaptability is maintained at a high level.

The decompression characteristic correcting means is executed when it is determined that the estimation error, which is the absolute value of the difference between the actual decompression amount and the estimated decompression amount, is greater than or equal to a predetermined threshold value.
As a result, the decompression characteristic is corrected only when the estimation error is reliably enlarged. For this reason, the possibility of erroneous correction can be reduced, and the frequency of correction can be reduced to reduce the processing load on the microcomputer 8 and the like.

The decompression characteristic correction means is executed when the ignition is off.
When the ignition is off, there is no injection and the pressure is reduced, and the amount of fuel escaped from other than the pressure reducing valve 7 (for example, the amount of fuel leaked from the injector 6) can be predicted. Therefore, if the decompression characteristic correcting means is executed when the ignition is off, the decompression characteristic can be corrected accurately.

Further, the decompression characteristic is stored in a non-volatile storage unit that can retain data even when the power supply state is released.
A state in which the decompression characteristic must be corrected, for example, a state in which the estimation error is surely enlarged and the necessity for correction is increased does not occur frequently. Therefore, it is preferable to use a non-volatile storage means in order to store the decompression characteristic data reliably over a long period of time.

The decompression characteristic correcting means reduces the addition / subtraction time by a predetermined gain and corrects the decompression characteristic using the reduced addition / subtraction time.
If the decompression characteristics are changed drastically by one correction, the risk of erroneous correction increases. Therefore, if the correction amount is reduced as described above, the possibility of erroneous correction can be reduced.

[Configuration of Example 2]
The decompression characteristic correcting means of the fuel injection device 1 according to the second embodiment limits the range to be corrected in the decompression characteristic according to the initial value of the actual rail pressure. For example, the pressure reducing characteristic correcting means limits the range of the actual rail pressure to be corrected in the pressure reducing characteristic to the range of the actual rail pressure including the initial value. Then, the pressure reduction characteristic correction means corrects the pressure reduction characteristic within the limited range of the actual rail pressure using the addition / subtraction time calculated in the same manner as in the first embodiment.

[Control Method of Example 2]
A control method according to the second embodiment will be described with reference to a flowchart shown in FIG.
In this flowchart, each step from step S11 to step S18 and step S20 are the same as each step from step S1 to step S9 shown in FIG.

  In the flowchart shown in FIG. 6, in step S19, the actual rail pressure range (correction range) to be corrected is determined based on the initial value of the actual rail pressure. Various methods are conceivable for determining the correction range. For example, the entire range that the actual rail pressure can take may be divided into a plurality of actual rail pressure ranges in advance, and the actual rail pressure range including the initial value may be set as the correction range. Further, the correction range may be determined so as to have a predetermined width with the initial value as the center value.

  Further, in order to be careful in applying the corrected decompression characteristic, the corrected decompression characteristic may be applied after correction is made in a plurality of correction ranges.

[Effect of Example 2]
The decompression characteristic correction means in the fuel injection device 1 of the second embodiment limits the correction range of the decompression characteristic according to the initial value of the actual rail pressure.
If the pressure reduction characteristics are changed in the entire range that the actual rail pressure can take with one correction, the possibility of erroneous correction increases. Therefore, if the correction range is limited as described above, the possibility of erroneous correction can be reduced.

[Modification]
Although the pressure reducing valve 7 of this embodiment opens or closes by an on / off method according to energization or non-energization of the solenoid 24, it is not limited to such a form. For example, the pressure reducing valve 7 may be a variable opening type that can adjust the valve opening degree by duty control, and the present invention can be applied to this variable opening type pressure reducing valve. In this case, the valve opening degree can be added as a variation factor to the decompression characteristics.

  Further, the pressure reducing valve 7 of this embodiment is opened by the pressure reducing valve drive circuit 12 energizing the solenoid 24 in accordance with a command signal output from the microcomputer 8. It is not limited to such a form. For example, without providing the pressure reducing valve drive circuit 12, a drive current may be directly supplied from a predetermined power source to the solenoid 24.

  Further, in the flowchart of the present embodiment, the actual rail pressure is measured before and after the elapse of a predetermined time, and is calculated as the actual depressurization amount based on the difference (the descending amount). However, the actual rail pressure is reduced by a predetermined amount. It is also possible to measure the time required to calculate the actual decompression amount using this time measurement value.

1 is an overall configuration diagram of a fuel injection device (Example 1). FIG. It is a principal part block diagram of a fuel-injection apparatus (Example 1). (A) is a characteristic diagram which shows a pressure-reduction characteristic, (b) is a characteristic figure which shows a correction characteristic (Example 1). 7 is a flowchart illustrating processing by a decompression characteristic correcting unit (Example 1). (A) is a time chart which shows transition of the actual rail pressure at the time of pressure reduction execution, (b) is explanatory drawing explaining extension of an open command period (Example 1). 10 is a flowchart illustrating processing by a decompression characteristic correcting unit (Example 2).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 3 Common rail 7 Pressure reducing valve 8 Microcomputer (Rail pressure control means, pressure reduction characteristic correction means)
12 Pressure reducing valve drive circuit (rail pressure control means)

Claims (7)

In a fuel injection device that includes a common rail that receives supply of fuel so that fuel is accumulated at a target pressure corresponding to the state of the engine, and that supplies fuel to the engine through the common rail,
A pressure reducing valve for reducing the actual pressure of the fuel accumulated in the common rail by opening the valve and releasing the fuel from the common rail;
Based on the pressure reduction characteristic indicating the correlation between the amount of fuel escaped from the pressure reducing valve and the actual pressure, a command value to be given to the pressure reducing valve is calculated and output to the pressure reducing valve, so that the actual pressure becomes the target pressure. Rail pressure control means for controlling the operation of the pressure reducing valve so as to substantially match,
Pressure reduction characteristic correcting means for correcting the pressure reduction characteristic according to a difference between an actual pressure reduction amount indicating an amount of decrease in the actual pressure due to execution of the rail pressure control means and an estimated pressure reduction amount estimated by the pressure reduction characteristic; A fuel injection device comprising: The fuel injection device according to claim 1,
The fuel injection device according to claim 1, wherein the pressure reducing characteristic is a correlation between an opening command period indicating a period during which the pressure reducing valve is open and the actual pressure. The fuel injection device according to claim 1,
The fuel pressure-injection apparatus is characterized in that the pressure reduction characteristic correcting means is executed when it is determined that an absolute value of a difference between the actual pressure reduction amount and the estimated pressure reduction amount is equal to or greater than a predetermined threshold value. The fuel injection device according to claim 1,
The fuel injection device according to claim 1, wherein the decompression characteristic correcting means is executed when the engine is stopped. The fuel injection device according to claim 1,
The fuel injection device according to claim 1, wherein the decompression characteristic is stored in a non-volatile storage means that can retain data even when the power supply state is released. The fuel injection device according to claim 1,
The fuel pressure-reducing device is characterized in that the pressure reduction characteristic correcting means reduces the correction amount of the pressure reduction characteristic and corrects the pressure reduction characteristic with the reduced correction amount. The fuel injection device according to claim 1,
The fuel pressure-injection apparatus according to claim 1, wherein the pressure-reduction characteristic correcting unit limits a range to be corrected in the pressure-reduction characteristic according to the measured value of the actual pressure.

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