JPH06185381A - Fuel injection device of internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a fuel injection device by which right corrective fuel injection is carried out by means of detected pressure even at the time of high rotational speed of an engine, in an air assisting type fuel injection device for detecting pressure directly downstream from a fuel injection port of a fuel injection valve, and performing fuel correction. CONSTITUTION:A fuel injection valve 8, an air assisting passage 12, a pressure sensor 19 and an ECU 9 are provided in the present fuel injection device, and basic fuel injection quantity TAUbase is corrected by the ECU 9, based on pressure P1 detected by a pressure sensor and correction of a fuel injection quantity guaranteed by the calculated correction quantity is applied to the next fuel injection taking place just after detecting the pressure, and thereby its calculation time is secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an internal combustion engine, and more particularly to a fuel injection device for injecting assist air immediately downstream of an injection port of a fuel injection valve to promote atomization of injected fuel.

[0002]

2. Description of the Related Art In order to improve combustion in an internal combustion engine, an air assist passage is opened in a space immediately downstream of a fuel injection valve, and assist air introduced through an intake passage from the outside or an intake passage upstream of a throttle valve is introduced. A fuel injection device that has already tried to promote atomization of fuel by injecting the fuel injected from a fuel injection valve is already known.

By the way, in the fuel injection device having such an air assist mechanism, the pressure of the assist air,
In particular, the pressure at the tip of the fuel injection valve tends to have a large effect on the fuel injection pressure, and it can be said that the pressure is an important control characteristic for improving the accuracy of the fuel injection amount. Under such circumstances, for example, in Japanese Utility Model Application Laid-Open No. 58-173767, a fuel injection valve is provided in contrast to a pressure adjustment valve provided for adjusting the fuel pressure in a fuel pipe in an air-assisted fuel injection device. There is disclosed a fuel pressure adjusting device which directly takes out the pressure in the space immediately downstream of the injection port and controls the pressure adjusting valve to improve the accuracy of the injected fuel amount. The publication also discloses a device in which a pressure sensor for detecting the assist air pressure is provided in the air assist passage, and the fuel injection amount is corrected based on the pressure difference from the intake pressure.

[0004]

In the air-assisted fuel injection device as described above, the fuel correction is naturally performed by detecting the pressure in the air-assist passage or the pressure immediately downstream of the injection port of the fuel injection valve before starting the fuel injection. The quantity calculation must be completed. However, under an operating condition where the engine speed becomes high, for example, this correction calculation cannot possibly be completed until the fuel injection start timing of the own cylinder,
The fuel injection amount at that time does not reach the calculated value, resulting in a problem that the target air-fuel ratio cannot be achieved.

The present invention is provided in view of the problems of the fuel injection device having such an air assist mechanism.

[0006]

In order to solve the above problems, according to the invention as set forth in claim 1, assist air is supplied directly downstream of the injection port of the fuel injection valve through the air assist passage to perform injection. A fuel injection device for an internal combustion engine, which is configured to promote atomization of the fuel, and a pressure sensor that detects the pressure in the space immediately downstream of the fuel injection valve when the fuel is not injected,
Correction calculation means for calculating a correction amount of fuel injection based on the pressure detected by the pressure sensor, and correction injection of the fuel injection amount based on the correction amount, the fuel injection next to the fuel injection immediately after the pressure is detected. There is provided a fuel injection device for an internal combustion engine, comprising: a fuel injection correction control unit that is executed at times.

In order to solve the same problem, according to the invention as set forth in claim 3, the assist air is supplied immediately downstream of the injection port of the fuel injection valve through the air assist passage, and fine particles of the injected fuel are injected. A fuel injection device for an internal combustion engine, which is designed to accelerate the fuel injection, and operates a fuel injection valve based on a basic fuel injection time and a pressure sensor that detects the pressure in the space immediately downstream of the fuel injection valve when fuel is not injected. The basic fuel injection means for injecting fuel, the correction calculation means for calculating the correction amount of the fuel injection based on the pressure detected by the pressure sensor, and the fuel injection based on the correction amount There is provided a fuel injection device for an internal combustion engine, which is provided with a correction fuel injection means to be performed later.

[0008]

According to the invention described in claim 1, the time required for the calculation is delayed by delaying the correction injection of fuel based on the detected pressure until the fuel injection next to the fuel injection immediately after the detection of the pressure. Can be secured. According to the third aspect of the invention, the basic fuel injection is divided into the basic fuel injection that does not depend on the correction calculation and the corrected fuel injection that reflects the calculated correction amount. It is sufficient to perform the correction calculation before the completion, and the calculation time can be secured similarly.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 1 showing a schematic configuration of an air-assist type fuel injection device common to each embodiment described below, 1 is an engine body, 2 is an intake pipe for supplying intake air to the engine body, 3 is an exhaust pipe, and 4 is a surge. A tank, 5 is an air flow meter, and 6 is an air cleaner.

A fuel injection valve 8 for injecting fuel into an intake passage 7 inside the intake pipe 2 (or engine body 1).
Is installed. The opening / closing operation of the fuel injection valve 8 is controlled by, for example, a control circuit (ECU) 9 such as a computer, and the ECU 9 outputs a drive signal thereof at a predetermined timing according to the detected operating condition.

Although only one cylinder is shown in this figure, a throttle valve 10 for controlling the intake amount is provided upstream of the surge tank 4 in which the intake pipes 2 from each cylinder are combined. still,
The opening degree of the throttle valve 10 is also input to the ECU 9 via a throttle position sensor (not shown) or the like. On the input side of the ECU 9, intake air flowing in the intake passage 7 is also supplied. Signals are input from various sensors such as an air flow meter 5 that detects the amount Q and an intake pressure sensor 11 that detects the intake pipe pressure PM.

An air assist passage 12 for supplying assist air for promoting fuel atomization is connected to the tip of the above-mentioned fuel injection valve 8. The air assist passage 12 has one end open to the intake passage 7 on the intake upstream side of the throttle valve 10. Further, in the middle of the air assist passage 12, the assist air is supercharged to the tip of the fuel injection valve 8. A pressurizing pump 13 for controlling and an air control valve 14 for controlling the amount of assist air are provided.
Its operation is controlled by 10.

A pressure regulator 17 for maintaining a constant fuel pressure (hereinafter referred to as fuel pressure) is provided between the fuel injection valve 8 and the fuel pump 16 which pumps the fuel from the fuel tank 15. FIG. 2 shows an enlarged cross section of the tip portion of the fuel injection valve 8 shown in FIG. As is clear from this figure, the injection port 8a of the fuel injection valve 8 is opened and closed by the valve 8b, but the adapter into which the assist air from the air assist passage 12 described above flows into the tip of the injection port 8a. 18, the injected fuel collides with assist air and is atomized.

Further, in the present injection device, a pressure sensor 19 for detecting the pressure P1 in the adapter internal space 18a immediately downstream of the injection port 8a is attached to the adapter 18, and the pressure P1 immediately below the injection port detected here is detected. Is input to the ECU 9. Therefore, in the present injection device, the injection amount of fuel injected from the fuel injection valve 8 per hour depends on the differential pressure (effective fuel pressure) between the fuel pressure and the pressure P1 immediately below the injection port. (For example, the intake pipe pressure PM) and the air assist amount, and the injection amount per unit time fluctuates.

Therefore, in the apparatus having the configuration shown in the figure, the pressure P1 immediately before the fuel injection is detected, and the intake air amount Q previously detected by the air flow meter 5 and the crank angle sensor 20 (FIG. 1) are detected based on the pressure P1. The fuel injection amount TAUbase calculated based on the detected engine speed N or the like is corrected. In this specification, the corrected fuel injection amount will be referred to as TAU.

FIG. 3 shows a fuel injection operation timing of a specific cylinder as an embodiment corresponding to claim 1, and FIG. 4 is a fuel injection control routine for executing this. However, according to this embodiment, as shown in FIG. 3, the supply (injection) of the assist air accompanying the opening of the air control valve 14 is naturally performed prior to the fuel injection timing of the same cylinder. The pressure P1 immediately downstream of the fuel injection valve is detected by the pressure sensor 19, and the calculation / correction of the fuel injection amount TAU that reflects the pressure value P1 detected here is as follows.
As indicated by the dotted arrow in the figure, the fuel is not injected immediately after pressure detection but for the next fuel injection.

Therefore, in the case of such detection / calculation / injection timing, the time from pressure detection to injection is the time a shown in the figure, which is significantly longer than the conventional time b, and as a result, fuel Even during the high engine speed operation in which the injection interval becomes extremely short, a sufficient calculation time is secured. Explaining a program that achieves such fuel injection, first, in step S1 of FIG. 4, it is determined whether or not it is the calculation timing of the fuel injection amount TAU. That is, this TAU calculation timing can be defined in advance by, for example, a crank angle signal, and here it is determined whether or not the crank angle detected by the crank angle sensor 20 has reached the specified angle.

If it is determined at this step S1 that it is the TAU calculation timing (Yes), the routine next proceeds to step S2, where the intake air amount Q, the engine speed N from the air flow meter 5, the crank angle sensor 20 and the like. And the fuel injection amount (time) TAUbase required to achieve the target air-fuel ratio is obtained in step S3. Next, in step S4, the fuel injection amount TAUbase thus calculated is corrected by the pressure P1 currently stored in the predetermined memory of the ECU 9 to calculate the final target fuel injection amount TAU. The corrected fuel injection amount TAU at this time is the actual fuel pressure Pf calculated from the pressure P1 based on the TAUbase calculated based on the constant fuel pressure Pf.
It is obtained by converting into the fuel injection amount at -P1.

On the other hand, if No is determined in step S1, the routine next determines in step S5 whether or not the assist air injection start timing defined in advance is reached. This routine is based on the fuel injection amount TAU described above.
If it is the routine after the calculation and it is the assist air injection start timing, it is determined as Yes here, and in the following step S6, the air control valve 14 is opened to start the assist air injection, and in the following step S7, the assist air injection is performed. Set the end time (or end crank angle) so that the air assist will end automatically when the end time is reached. The assist air injection end time is preferably set after the end of fuel injection from the viewpoint of ensuring atomization of the fuel.

Then, in the next step S8, the pressure P to be reached while the assist air injection is being performed in this manner.
The detection permission flag Fa for 1 detection is set to 1.
On the other hand, if No in step S5, the routine next proceeds to step S9, and it is determined whether or not it is the current fuel injection start timing. Then, if it is not the fuel injection start timing at present, the routine proceeds to step S10, and it is determined whether or not the pressure detection permission flag Fa is set to 1.

If the flag is set in the previous routine (Yes), the routine proceeds to step S11, where the pressure P1 is detected by the pressure sensor 19, and the pressure P1 stored in the ECU 9 up to that point is updated. In the subsequent step S12, the pressure detection permission flag Fa is reset,
This routine ends. In addition, when No is determined in step S10, steps S11 and S12 are skipped and the present routine ends.

Next, the routine comes around and step S9 is executed.
When it is determined that the fuel injection start timing is determined in (Ye
s), the routine outputs a drive signal to the fuel injection valve 8 in step S13 to immediately start fuel injection, and in subsequent step S14, sets the injection end time with the fuel injection amount (time) TAU calculated in the previous routine. Then, this routine is finished.

As described above, in the above-described embodiment, the pressure value P1 stored in the memory at that time is used in the calculation / correction of the fuel injection amount TAU, but the pressure value used for this calculation is the last time. Since it corresponds to the pressure value detected immediately before the fuel injection, sufficient time can be taken from the pressure detection to the fuel injection, and the correction calculation may not be in time even when the engine is rotating at high speed, and the air-fuel ratio may deviate from the target value. There is no.
For comparison, FIG. 5 shows a conventional pressure detection / TAU correction timing chart.

Further, in the above-mentioned flow chart, the fuel injection or assist air injection start timing is fixed and the end time thereof is variably set, but conversely the end timing may be fixed. In the embodiment described above, the correction of the fuel injection amount is performed at the fuel injection timing of the same cylinder next to the fuel injection immediately after the pressure P1 immediately downstream of the injection port is detected, so that the time required for the calculation / correction is secured. However, the correction calculation time can be secured by using it for the fuel injection calculation of the cylinder different from the pressure detection cylinder.

The timing charts shown in FIGS. 6, 7, 8 and 9 show the pressure value P1 immediately downstream of the detected fuel injection valve in a plurality of cylinders (for example, a 4-cylinder or 6-cylinder internal combustion engine). It shows each embodiment in which the calculation time is secured by using it for the fuel injection correction calculation of the cylinder. Explaining the figure, in FIG. 6, in a four-cylinder internal combustion engine in which fuel injection continues with cylinder numbers # 1 → # 3 → # 4 → # 2, the cylinder before one explosion is calculated and corrected for the fuel injection amount TAUbase of that cylinder. The pressure P1 detected in step # 3 is used, and for example, the pressure value P1 detected in cylinder # 1 is used in the TAU calculation for the next cylinder # 3.
The pressure P1 detected in the cylinder # 3 is used in the TAU calculation of the cylinder # 4.

In this case, the previously detected pressure value P of the own cylinder
The interval from the pressure detection to the fuel injection in which this is reflected is shorter than that in the previous embodiment in which the correction is performed by 1, and the reliability of the correction itself is further improved. Further, the timing chart of FIG. 7 shows the pressure when the exhaust system is divided into groups such as cylinders # 1 and 4; cylinders # 2 and 3 in a four-cylinder internal combustion engine having the same fuel injection order. Detection ~ TA
9 illustrates an example of a U operation shift.

That is, the pulsation of the exhaust system and the like also affects the intake system, and naturally has a great effect on the pressure value P1 immediately downstream of the fuel injection valve injection port. As a result, when trying to correct the fuel by using the pressures detected in the cylinders of other groups, there is a possibility that the difference between the actually required fuel injection amount and the calculated fuel injection amount becomes large. Therefore, in this embodiment, the pressure detection to the TAU calculation shift within the same group are performed, and the pressure value P1 detected in the cylinder # 1 is used for the fuel injection amount calculation of the injection of the cylinder # 4 as shown in the figure. The pressure value P1 detected in the cylinder # 2 is used for the calculation of the cylinder # 3. In terms of injection order, the fuel injection correction calculation is performed using the pressure value P1 detected in the cylinder two cylinders before. .

The timing chart shown in FIG. 8 is a V-type 6
This is an example of the case where the intake system is divided into groups in a cylinder engine. In this example, since the cylinders # 1, 3, 4 are in one bank and the cylinders # 2, 4, 6 are in the other bank, the intake system and the air assist passage are divided into two systems, so the assist air amount There is a high possibility that there will be variations among the lines. Therefore, in this embodiment, in order to exclude such a pressure error between the systems, the pressure value P1 detected in the cylinder of the own group is set to the fuel injection amount TAU of the other cylinders in the group.
Used for calculation correction. In terms of injection order, this is also an embodiment in which correction calculation is performed using the pressure value P1 detected in the cylinder two before.

In the timing chart shown in FIG. 9, the pressure value P detected by one pressure sensor 19 for the entire engine is shown.
The fuel injection correction calculation is performed based on 1, and in this embodiment, the pressure value P1 detected during the air assist of the cylinder # 1.
However, the following cylinders # 3 → #
The fuel injection amount TAU of 4 → # 2 → # 1 is used for one cycle of calculation. Therefore, this embodiment has an advantage that the number of pressure sensors can be reduced and the cost can be reduced as compared with the conventional case.

As described above, the timing charts have been used to explain the respective embodiments in which the fuel injection amount is corrected at the fuel injection timing thereafter except for the fuel injection immediately after the pressure P1 immediately downstream of the injection port is detected. The operation routine of the ECU that performs such fuel injection control is basically the same as the flowchart of FIG. 4 described above. For example, the pressure value P1 detected as shown in FIGS. When the fuel injection calculation for the cylinder is performed, the pressure value stored in the predetermined area is read,
Only the number of memory areas for storing pressure values is different.

As for the program when one pressure value is used for the fuel injection calculation of all cylinders as shown in FIG. 9, the number of routines in which the air assist process (step S6) is executed in FIG. 4 is counted. If the number reaches the number of cylinders, the pressure detection permission flag Fa for updating the pressure value may be set. In all the embodiments described so far, the detected pressure value P1 immediately downstream of the injection port is detected.
Is not included in the fuel injection calculation immediately after, and is used in the subsequent fuel injection amount calculation correction, and each fuel injection is continuously performed with the corrected final fuel injection amount TAU.

On the other hand, in the embodiment shown in FIGS. 10 and 11, this fuel injection is divided into a basic fuel injection obtained from the operating condition and a correction fuel injection calculation obtained from the pressure value P1.
The correction amount is calculated at least until the basic fuel injection is completed to secure the time required for the correction calculation. Therefore, according to this embodiment, as shown in FIG.
As shown in the timing chart of 0, since the detected pressure value P1 of the cylinder is reflected in the latter half of the fuel injection immediately after, the correction calculation time secured as compared with each of the above-described embodiments is short, but the reverse. Since the same cylinder is used and the fuel is injected immediately after, the reliability of the corrected fuel injection amount itself is high.

Further, in this embodiment, since the injection is intermittent, the injection speed and injection amount of the fuel for each injection are smaller than those for one continuous fuel injection, and therefore the atomization effect by the assist air is great. As a control routine for executing this embodiment,
As shown in FIGS. 11 and 12, in step S21, it is currently determined whether or not it is the calculation timing of the fuel injection amount TAU, and if it is determined that it is the TAU calculation timing (Yes), then in step S22, the intake air The amount Q and the engine speed N are read, and the fuel injection amount (time) TAUbase is obtained in step S23.

The fuel injection amount TAUbase here
Is calculated on the assumption that the pressure P1 immediately downstream of the injection port is the reference pressure P0, and the fuel injection amount corresponding to each operating condition is set in the predetermined region of the ECU 9 under this pressure value P0. The map is stored. Therefore, the effective fuel pressure of the fuel injection valve 8 calculated here is Pf-P0 when the fuel pressure is Pf.

On the other hand, if No in step S21, the routine next determines in step S24 whether or not it is the assist air injection start timing defined in advance. This routine is based on the fuel injection amount T described above.
If it is the routine after the AUbase calculation and it is the assist air injection start timing, here, it is determined to be Yes, the air control valve 14 is opened to start the assist air injection in the following step S25, and the assist air injection is performed in the following step S26. The injection end time (or the end crank angle) is set so that the air assist is automatically ended when the end time is reached.

In the next step S27, the detection permission flag Fa for detecting the upcoming pressure P1 is set to 1 while the assist air injection is being performed in this way. On the other hand, if No in step S24, the routine next proceeds to step S28, and it is determined whether or not it is the current fuel injection start timing. Then, if it is not the fuel injection start timing at present, the routine proceeds to step S29, and it is determined whether or not the pressure detection permission flag Fa is set to 1.

If the flag is set in the previous routine (Yes), the routine proceeds to step S30, where the pressure P1 is detected by the pressure sensor 19, and the pressure P1 stored in the ECU 9 up to that point is updated. In a succeeding step S31, the pressure detection permission flag Fa is reset,
This routine ends. If No is determined in step S29, steps S30 and S31 are skipped and this routine is finished.

Next, the routine comes around and step S2
When it is determined at 8 that the fuel injection start timing is reached (Yes
s), the routine outputs a drive signal to the fuel injection valve 8 in step S32 to immediately start fuel injection, and in subsequent step S33, sets the injection end time by the fuel injection amount (time) TAUbase calculated in the previous routine. To do.
In step S34 following step S33, TAUbas under the effective fuel pressure Pf-P0 previously calculated with the pressure P1 detected in step S30 immediately before the current injection.
Correct e. That is, the calculation here is such that, if the corrected total fuel injection amount is TAU, the actual effective fuel pressure is Pf-P1.
Therefore, TAU = TAUbase · (Pf−P0) / (Pf−P
1) It becomes base.

When the calculation process of the total fuel injection amount TAU is completed in this way, the routine next proceeds to step S35.
Then, it is determined whether or not the fuel injection based on TAUbase is currently completed. Then, tentatively, step S35
If it is determined No in step S6, and the fuel injection has not yet ended, the injection end time is reset with the total fuel injection amount TAU in step S36 in order to continue the correction injection.

On the other hand, Yes in step S35,
That is, at the end of the correction calculation in step S34, TAUb has already been
If the fuel injection by the asase is completed, the routine proceeds to step S37, and the correction amount TAU-TAUbase
The fuel injection is started, the correction fuel injection end is set in step S38, and this routine is ended.

As described above, according to this embodiment, the fuel injection by TAUbase cannot be started and the time for the correction calculation by the pressure P1 immediately downstream of the injection port is gained. If the calculation cannot be completed by the end of TAUbase injection, ,
Since the TAUbase fuel injection is ended once and the correction amount is then injected again when the correction calculation is completed, the correction amount may be calculated before the TAUbase fuel injection is ended.

Further, in this embodiment, when intermittent injection is performed in this manner, atomization is promoted due to the low injection fuel velocity with respect to the assist air.

[0043]

As described above, according to the first aspect of the present invention, the calculation of the correction amount is completed before the fuel injection immediately after the fuel injection immediately downstream of the injection port is detected. It is sufficient and the calculation time is secured. Further, according to the second aspect of the present invention, the correction amount may be calculated by the time the basic fuel injection corresponding to the engine operating condition is completed, and the fuel is intermittently injected to the assist air flow. The fuel atomization effect is great.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a fuel injection device according to the present invention.

FIG. 2 is an enlarged sectional view of a tip portion of the fuel injection valve of FIG.

FIG. 3 is a timing chart of the embodiment in which the calculation / correction of the fuel injection amount TAU is reflected in the fuel injection next to the fuel injection immediately after the pressure detection.

FIG. 4 is a flowchart illustrating the operation of the ECU that executes the fuel injection timing of FIG.

FIG. 5 is a timing chart showing a conventional fuel injection / calculation timing.

FIG. 6 is a timing chart of the embodiment in which the calculation / correction of the fuel injection amount TAU is executed for the next fuel injection cylinder after the pressure detection.

FIG. 7 is a timing chart showing an example of fuel injection calculation / correction shift when the exhaust system is divided into groups.

FIG. 8 is a timing chart showing an example of fuel injection calculation / correction shift when the intake system is divided into groups.

FIG. 9 is a timing chart diagram in which fuel injection correction for all cylinders is performed based on the pressure value of one cylinder.

FIG. 10 is a timing chart of an embodiment in which the correction amount is intermittently injected with respect to the basic fuel injection.

11 is a diagram showing a fuel injection flowchart for executing the timing chart of FIG. 10 and a diagram showing an upper portion thereof. FIG.

FIG. 12 is a view following the flow chart of FIG. 11.

[Explanation of symbols]

 8 ... Fuel injection valve 9 ... Control circuit 12 ... Air assist passage 19 ... Pressure sensor

Claims (3)

[Claims] 1. A fuel injection device for an internal combustion engine, wherein assist air is supplied immediately downstream of an injection port of a fuel injection valve via an air assist passage to promote atomization of injected fuel. A pressure sensor that detects the pressure in the space immediately downstream of the fuel injection valve when fuel is not injected, a correction calculation unit that calculates a correction amount for fuel injection based on the pressure detected by the pressure sensor, and fuel based on the correction amount. 2. A fuel injection device for an internal combustion engine, comprising: a fuel injection correction control unit that executes the correction injection of the injection amount at the time of the fuel injection subsequent to the fuel injection immediately after the pressure is detected. 2. The internal combustion engine is provided with a plurality of fuel injection valves having different fuel injection timings, and the fuel injection correction control means detects the pressure for the correction injection based on the calculated correction amount. The fuel injection device for an internal combustion engine according to claim 1, which is executed at the time of fuel injection by a fuel injection valve different from the injection valve. 3. A fuel injection device for an internal combustion engine, wherein assist air is supplied immediately downstream of an injection port of a fuel injection valve via an air assist passage to promote atomization of injected fuel. A pressure sensor for detecting the pressure in the space immediately downstream of the fuel injection valve when fuel is not injected, a basic fuel injection means for operating the fuel injection valve to inject fuel based on the basic fuel injection time, and a pressure sensor detected by the pressure sensor. An internal combustion engine, comprising: a correction calculation unit that calculates a correction amount of fuel injection based on pressure; and a correction fuel injection unit that performs fuel injection based on the correction amount after completion of the basic fuel injection. Fuel injector.