JPH08326581A - Fuel injection quantity control device for internal combustion engine - Google Patents

Abstract

PURPOSE: To perform high-precise control of an air-fuel ratio according to a fuel injection quantity and to improve exhaust emission and operability by a method wherein a differential pressure between the pressure of a fuel injection part from a fuel injection valve and a fuel feed pressure to a fuel injection valve is detected and based on a differential pressure, a fuel injection quantity is corrected. CONSTITUTION: An ignition plug 9 and a cylinder pressure sensor 10 to detect a pressure in a combustion chamber (in a cylinder) are arranged in a combustion chamber in which a fuel injection valve 8 to inject fuel directly to the interior of a combustion chamber is arranged, and an output signal therefrom is inputted to a control circuit togetherwith detecting values from other sensors. When injection of fuel is controlled, a fuel injection amount corresponding to an area determined by a product of a section between a time after passage through a given section and completion of injection differential pressure at the section is determined, and by adding the result to a fuel injection quantity during the given section, a fuel injection amount during a total period of a fuel injection engine is determined. Thereafter, the fuel injection amount is compared with a reference value, an actual fuel injection period is corrected based on a calculating fuel injection period, and fuel injection quantity is corrected to a proper value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection amount control device for an internal combustion engine such as an automobile, and more particularly to a technique for controlling the fuel injection amount with high accuracy.

[0002]

2. Description of the Related Art As a conventional fuel injection control device for an internal combustion engine, there is one disclosed in Japanese Patent Application Laid-Open No. 62-153513. This means that in a cylinder direct injection internal combustion engine that injects fuel directly into the combustion chamber, knocking is suppressed by injecting fuel at the end of the compression stroke in the full load range, thereby achieving high output and low fuel consumption. It is a thing.

[0003]

However, in such a fuel injection control device for an internal combustion engine, when the operating state is constant even when the pressure in the fuel injection portion varies due to environmental changes or EGR amount. Is always configured to inject fuel within a fixed fuel injection period (injection pulse width), the difference in pressure from the fuel supply pressure (hereinafter referred to as fuel pressure) due to variations in pressure at the fuel injection portion There is a problem that the fuel injection amount fluctuates and the air-fuel ratio fluctuates, which may affect exhaust emission and drivability.

The present invention has been made in view of the above conventional problems, and detects the differential pressure between the pressure of the fuel injection portion from the fuel injection valve and the fuel supply pressure to accurately determine the fuel injection amount. It is an object of the present invention to provide a fuel injection amount control device for an internal combustion engine, which can be controlled in a controlled manner.

[0005]

Therefore, the invention according to claim 1 is, as shown in FIG. 1, in a fuel injection amount control apparatus for an internal combustion engine, in which fuel is injected and supplied by a fuel injection valve,
A differential pressure detecting means for detecting a differential pressure between a pressure of a portion injected from the fuel injection valve and a fuel supply pressure to the fuel injection valve; an operating state detecting means for detecting an operating state of the engine; Fuel injection amount calculation means for calculating the fuel injection amount based on the operating state of the engine detected by the state detection means, and fuel injection calculated by the fuel injection amount calculation means based on the output of the differential pressure detection means. And a fuel injection valve driving means for injecting an amount of fuel corresponding to the fuel injection amount corrected by the fuel injection amount correcting means from the fuel injection valve. It is characterized by

According to a second aspect of the present invention, the fuel injection valve is provided so as to inject fuel into the combustion chamber of the engine, and the differential pressure detecting means is provided for a portion injected from the fuel injection valve. It is characterized in that it includes means for detecting the pressure in the combustion chamber as the pressure. Further, in the invention according to claim 3, the fuel injection valve is provided so as to inject fuel into an intake passage of an engine, and the differential pressure detection means determines a pressure of a portion injected from the fuel injection valve. It is characterized in that it includes means for detecting the pressure in the intake passage.

According to a fourth aspect of the invention, the differential pressure detecting means detects the pressure of the portion injected from the fuel injection valve, and the means for detecting the fuel supply pressure to the fuel injection valve. And is provided, and the differential pressure is detected by calculating the difference between the respective detected values. Further, the invention according to claim 5 is characterized in that the differential pressure detecting means directly detects a differential pressure between a pressure of a portion injected from the fuel injection valve and a fuel supply pressure to the fuel injection valve. And

Further, in the invention according to claim 6, the difference between the pressure of the portion injected from the fuel injection valve by the differential pressure detecting means and the supply pressure to the fuel injection valve which is regarded as a substantially constant value. Is calculated to detect the differential pressure. Also,
According to a seventh aspect of the present invention, the fuel injection amount correcting means includes a predetermined section within a fuel injection period corresponding to the fuel injection amount calculated by the fuel injection amount calculating means, and a differential pressure detected by the differential pressure detecting means. It is characterized in that the fuel injection amount is corrected by correcting the actual fuel injection period based on the area obtained by the product of

Further, in the invention according to claim 8, the fuel injection amount correcting means is provided with a difference between a predetermined section in the corresponding fuel injection period calculated by the fuel injection amount calculating means and the differential pressure detecting means. It is characterized in that the fuel injection amount is corrected by correcting the actual fuel injection period based on the area obtained by the product of the pressure and its history over the entire period of the fuel injection period.

The invention according to claim 9 further comprises fuel pressure control means for variably controlling the fuel supply pressure to the fuel injection valve, as shown by the dotted line in FIG. The fuel supply pressure to the fuel injection valve is corrected via the fuel pressure control means based on the differential pressure detected by the differential pressure detection means at a predetermined timing within the corresponding fuel injection period calculated by the injection amount calculation means. It is characterized in that the fuel injection amount is corrected by doing so.

[0011]

According to the first aspect of the present invention, the differential pressure detecting means detects the differential pressure between the pressure of the portion injected from the fuel injection valve and the fuel supply pressure to the fuel injection valve. And
The fuel injection amount correction unit corrects the fuel injection amount calculated by the fuel injection amount calculation unit based on the operating state such as the engine speed and load detected by the operating state detection unit by the fuel injection amount correction unit based on the differential pressure. The injection valve drive means drives the fuel injection valve to inject a quantity of fuel corresponding to the corrected fuel injection quantity from the fuel injection valve.

As described above, since the fuel injection amount is corrected on the basis of the detected differential pressure, it is possible to perform highly accurate fuel injection amount control and therefore air-fuel ratio control, whereby exhaust emission and drivability are achieved. Can be improved. Further, according to the invention of claim 2, since the fuel injection valve injects the fuel into the combustion chamber of the engine, the pressure of the injection portion becomes the pressure in the combustion chamber, and the differential pressure detecting means detects the pressure in the combustion chamber. The pressure of the fuel injection portion is detected by the means.

According to the third aspect of the invention, since the fuel injection valve injects fuel into the intake passage of the engine, the pressure at the injection portion becomes the pressure in the intake passage, and the differential pressure detection means The pressure in the fuel injection portion is detected by the means for detecting the pressure in the intake passage. Further, according to the invention of claim 4, since the differential pressure detecting means is provided with each means for separately detecting the pressure of the fuel injection portion and the fuel supply pressure, the difference between the detected values is calculated. The differential pressure can be detected with high accuracy.

Further, according to the invention of claim 5, the differential pressure detecting means detects the differential pressure with high accuracy by directly detecting the differential pressure between the pressure of the fuel injection portion and the fuel supply pressure. You can Further, according to the invention of claim 6, the differential pressure detecting means detects only the pressure of the fuel injection portion and considers the fuel supply pressure to be substantially constant to calculate the differential pressure. The pressure can be detected.

Further, according to the invention of claim 7, the area obtained by the product of the predetermined section in the fuel injection period calculated corresponding to the fuel injection amount and the detected differential pressure, that is, in the predetermined section The fuel injection amount can be corrected by correcting the actual fuel injection period with respect to the calculated fuel injection period by, for example, comparing the fuel injection amount of 1 with a reference value.

According to the eighth aspect of the present invention, the fuel injection amount in the predetermined section is determined in the same manner as in the seventh section, and the differential pressure at the end of injection is determined by the history of the differential pressure in the predetermined section. Is calculated to obtain the fuel injection amount of the section corresponding to the area obtained by the product of the section up to the end of injection after the passage of the predetermined section and the pressure difference in the section, and added to the fuel injection amount in the predetermined section. By calculating the fuel injection amount in the entire period of the fuel injection period and comparing it with a reference value to correct the actual fuel injection period with respect to the calculated fuel injection period. The amount can be corrected.

According to the invention of claim 9, the fuel injection amount is corrected by correcting the fuel supply pressure by comparing the differential pressure detected at a predetermined timing during the fuel injection period with a reference value. Can be corrected.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows the system configuration of an embodiment of the present invention. To explain the configuration, as means for detecting the operating state of the engine 11, an air flow meter 2 for detecting an intake air flow rate Q and a throttle valve 3 for controlling the intake air flow rate are provided in an intake passage 1 of the engine, and a distributor is provided. A crank angle sensor 4 for detecting the crank angle position and the engine rotation speed is provided internally or close to the cam shaft,
In the exhaust passage 5 of the engine, an air-fuel ratio sensor 6 that detects the concentration of a predetermined component in the exhaust gas, such as oxygen, to detect the air-fuel ratio is provided. A water temperature sensor 7 for detecting the temperature of cooling water of the engine and an electromagnetically driven fuel injection valve 8 for directly injecting fuel into the combustion chamber are provided in the engine body, and a spark plug 9 for performing spark ignition in the combustion chamber and In the combustion chamber to detect the combustion state
(In-cylinder) An in-cylinder pressure sensor 10 that detects pressure is provided.

Regarding the detected value and other external information detected by the sensors, the analog signal is input to the circuit centered on the microcomputer shown in FIG.
A digital signal is directly input from the input port 304 via the A / D converter 305, and the CPU 301 uses the control program and various data stored in the ROM 302 based on these detected values, and temporarily stores them in the RAM 303. Output port 30 by executing various calculations while storing information
The engine control is performed by outputting each control signal from 6. Specifically, the fuel injection amount is calculated, the fuel injection valve 8 is driven to perform fuel injection control, the ignition timing is calculated,
The ignition plug 9 is driven to perform ignition control, and an EGR valve provided in an EGR passage (not shown) is driven to drive the EG.
R control is performed.

Next, the operation will be described. In a cylinder direct injection internal combustion engine, it is possible to inject fuel in the compression stroke.
(See Figure 4). Here, the actual fuel injection amount is determined by the pressure difference between the in-cylinder pressure and the fuel pressure, and the fuel injection period, that is, the fuel injection pulse width, as shown in FIG. Variations such as those shown in FIG. 6 occur due to the EGR amount, cylinder-by-cylinder, etc. As a result, the above-mentioned differential pressure also varies, and even if fuel injection is performed with the same fuel injection pulse width, the amount of fuel actually injected into a cylinder is It can be different.

Therefore, when it can be considered that the detected differential pressure or the fuel pressure is constant, it is possible to correct the fuel injection pulse width or the fuel pressure based on the in-cylinder pressure. here,
The case where the fuel pressure can be regarded as constant means that the fuel pressure is maintained at a substantially constant value by the fuel pump, and whether or not the fuel pressure can be regarded as constant can be confirmed by experiments in advance to confirm the characteristics of the pump and, for example, with respect to the target fuel pressure. ± 2% in steady operation
If it is within the range, it may be regarded as constant. When correcting either the fuel injection pulse width or the fuel pressure, after the fuel injection pulse calculated from the operating state is raised, the differential pressure or the cylinder pressure is A / D converted and taken in,
The timing of the falling edge of the pulse based on the detected value,
Alternatively, the fuel injection pulse width or the differential pressure is corrected by correcting the fuel pressure. This makes it possible to control the air-fuel ratio with high accuracy even if the in-cylinder pressure in the compression stroke varies due to environmental changes, EGR amount, cylinder-by-cylinder, etc. under the same operating conditions.

Also in a normal type fuel injection type internal combustion engine which injects fuel into the intake port, the pressure in the intake pipe may fluctuate due to environmental changes and EGR amount, as in the case of the direct injection type internal combustion engine. There is. Also in this case, if a sensor for detecting the intake pipe pressure is provided, as in the case of the direct injection type internal combustion engine, the differential pressure between the detected intake pipe pressure and the fuel pressure or the fuel pressure can be regarded as constant. Corrects the fuel injection pulse width or the differential pressure based on the intake pipe pressure, so that the environmental change and E
Even if the pressure in the intake pipe varies due to the GR amount or the like, the air-fuel ratio can be controlled with high accuracy.

Since this variation is smaller than that in the case where fuel injection is performed in the compression stroke in a direct injection type internal combustion engine, its influence is considered to be small. It is possible to remove the pressure regulator that was used to correct the pressure difference between the intake pipe pressure and the fuel pressure.In particular, the intake pressure sensor is provided in advance to basically determine the fuel injection amount (fuel injection pulse width) based on the intake pressure. In an engine that is set, the effect of cost reduction can be obtained, and even when a new intake pressure sensor is provided, the EGR flow rate is determined from the differential pressure between the intake pressure signal detected by the intake pressure sensor and the exhaust pressure. Can be used for the purpose of measuring. When injecting fuel in the compression stroke in a direct injection type internal combustion engine, the pressure of the fuel pump (5 [M
Pa)), the cylinder pressure is about 5 [ms]
The pressure may change by about 2 [MPa], and a large pressure change that cannot be ignored is assumed in a very short time. Therefore, keep the differential pressure substantially constant regardless of the crank angle by a mechanical pressure regulator. Does not have a pressure regulator because it is practically difficult.

FIG. 7 shows the fuel injection pulse rise timing Tis, the pulse fall timing Tie, and the cylinder pressure reading timing Tcr according to the first embodiment.
The flowchart of the routine which sets (k) is shown. In the figure, a step (denoted by S in the figure, the same applies hereinafter) 70
At 1, the intake air flow rate Qa detected by the air flow meter 1 is read.

In step 702, the crank angle sensor 4
The engine rotation speed N is calculated based on the detection signal from.
In step 703, the fuel injection amount Ti is calculated from the intake air flow rate Qa and the engine rotation speed N. Here, the area S shown in FIG. 8 defined by the product of the pressure difference between the fuel injection atmosphere pressure (cylinder pressure) and the fuel pressure, and the fuel injection pulse width, and the fuel injection amount T
The relationship of FIG. 9 is established between i and i, and each time [T
It is assumed that cr (1) to Tcr (n)] and reference differential pressure data [Cr (1) to Cr (n)] corresponding thereto are provided as map data for each operating condition. Although n = 4 is set here, the number is not limited to this, and the score may be different for each operating condition.

In step 704, the area S corresponding to the fuel injection amount Ti calculated in step 703 is calculated. Ti is calculated from the relationship shown in FIG. In step 705, the area S is calculated based on the time Tcr (k) and the differential pressure reference data Cr (k) of the map corresponding to the current operating condition. A pulse rising timing Tis and a pulse falling timing Tie for realizing Ti are set.

At step 706, each time Tcr (k) of the map corresponding to the operating condition is set as the cylinder pressure reading timing. FIG. 10 shows a flowchart of a routine for outputting a fuel injection pulse, which is executed at each pulse rise timing. In step 1001, a fuel injection pulse rising signal is output.

In step 1002, the reference value Pfuel is set.
(Constant because fuel pressure is considered constant here) and cylinder pressure Pc
The data of the first point of the pressure difference with yl is read. Step 1
At 003, the elapsed time T is counted. Step 10
In 04, it is determined whether or not it is the timing Tcr (2) for reading the in-cylinder pressure set in FIG.

At the cylinder pressure reading timing, the second differential pressure is read in step 1005, and similarly, the cylinder reading timing Tcr (3) is waited for in steps 1006 and 1007. At 1008, the third differential pressure is read. Step 100
In 9, the area S of the shaded area in FIG. 12 is calculated from the differential pressure data at three points and the cylinder pressure reading timing Tcr (k). Here, the larger the area, the larger the amount of fuel injected in that section, and the smaller the area S, the smaller the amount of fuel injected. Further, the processing shown in this flowchart is executed from the time when the last in-cylinder pressure is read to the time when the injection pulse output ends, but from Tcr (3) to Tcr (3)
If the interval of ie is too short, the calculation end time of the area S is set to a time earlier than Tcr (3) by a predetermined time instead of Tcr (3), and the time for executing the processing shown in this flowchart is secured. To do so.

In step 1010, the reference differential pressure data Cr shown in FIG. 8 is obtained in the same section where the area S is calculated.
Target value S of area S from (k) Calculate the tag. In step 1011, the area S and the target value S Based on the difference with the tag, the correction coefficient ADJ of the pulse falling timing
To calculate. In step 1012, the pulse fall timing is corrected by the process shown in FIG. 11, and the pulse falls.

FIG. 11 shows step 1012 of the processing of FIG.
Run on. In step 1101, the pulse correction timing Tie corrected using the correction coefficient ADJ calculated in 1011 is set as Tie ′. In steps 1102 and 1103, the arrival of the pulse falling timing Tie ′ is counted. Step 11
At 04, the fuel injection pulse is lowered.

In this embodiment, the score of the in-cylinder pressure monitored during fuel injection is set to three, but the score and timing may be different for each operating condition. Further, in the present embodiment, as shown in FIG. 2, the sensor for detecting the in-cylinder pressure is assumed to be a spark plug washer type, but it may be a sensor for directly detecting the in-cylinder pressure. As described above, the pressure difference between the pressure of the fuel injection portion (cylinder pressure in this embodiment) and the fuel supply pressure to the fuel injection valve is detected, and the fuel injection amount is corrected based on the pressure difference. Since the configuration is adopted, the fuel injection amount and thus the air-fuel ratio can be controlled with high accuracy, and thus exhaust emission and drivability can be improved. This basic effect can be obtained similarly in the following embodiments.

Next, a second embodiment will be described. First
In the embodiment, the fuel pressure is considered to be substantially constant and the pressure difference between the cylinder pressure and the cylinder pressure is calculated. However, in the second embodiment, a means (fuel pressure sensor) for detecting the fuel pressure is provided, and the cylinder pressure and the fuel pressure are calculated in each case. Is detected to calculate the differential pressure with high accuracy. In this case, step 1002, step 1005, and step 1008 of FIG.
It is assumed that the detected fuel pressure is read in Pfuel in Fig. 12, and the area of the hatched portion is calculated from the pressure difference between the fuel pressure and the in-cylinder pressure in Fig. 13, instead of Fig. 12, and in comparison with the first embodiment. Although the accuracy of the fuel injection amount is improved, the cost is increased because a sensor for detecting the fuel pressure is required.

Next, a third embodiment will be described. In this embodiment, means for directly detecting the pressure difference between the cylinder pressure and the fuel pressure
(Differential pressure sensor) Specifically, in the case of an in-cylinder direct injection internal combustion engine, the fuel pressure is generally very high, but it is considered that the fuel pipe is embedded in the cylinder head. If a hole for taking out the pressure and the fuel pressure is opened, the pressure of both taken out is applied to both sides of the thin plate, and the displacement of the thin plate is taken out with a strain gauge, it becomes a differential pressure sensor that directly detects the differential pressure. can do.

Then, Pfel-P in steps 1002, 1005 and 1008 of FIG.
The detected differential pressure is substituted into cyl. Also in this embodiment, as in the second embodiment, the accuracy of the fuel injection amount is improved as compared with the first embodiment, and only one sensor is required (there are two pressure outlets), so the cost is increased. It can be kept low.

Next, a fourth embodiment will be described. In this embodiment, the fuel pressure is assumed to be constant as in the first embodiment. In the first embodiment, the pulse fall timing correction value AD
When calculating J, the area S of FIG. 12 is obtained by the processing of FIG.
Was calculated and used. In this case, the area S is a partial area up to the middle [Tcr (3)] of the fuel injection pulse, and is compared with the partial area obtained from the reference differential pressure data in FIG. 8 in the same section as in FIG. However, in this embodiment,
At the time of Tcr (3), the differential pressure [dP (4)] at the end of the set pulse (Tie) is estimated, dS shown in FIG. 15 is calculated from the data, and it is used to calculate the dS of the entire fuel injection pulse. The area S is estimated, and this is referred to as S in FIG. This is to be compared with Ti.

In this embodiment, instead of FIG. 10, FIG.
The flow chart of is used. In steps 1401 to 1408, dP (1) to dP are performed in the same manner as in FIG.
Read (3). In step 1409, dP (1)
~ DP (3) and Tie, Tcr (3) linear approximation,
DP (4) is estimated by quadratic curve approximation or the like, and dS is calculated based on it.

In step 1410, the Tis to Tc are calculated.
The area in the r (3) section and the dS estimated in step 1409 are added, and the area is set to S. Step 14
11, S obtained from Ti in FIG. Ti is the target value S
Substitute as targ. After that, step 141
2. In step 1413, the pulse fall timing is corrected in the same manner as in FIG. 10 to fall the pulse.

In this embodiment, the accuracy is higher than in the first embodiment, but the calculation load is increased accordingly. Next, a fifth embodiment will be described. This embodiment is provided with a means (fuel pressure sensor) for detecting the fuel pressure, detects the fuel pressure, and calculates the differential pressure from the in-cylinder pressure, while performing the same processing as in the fourth embodiment.
(Processing of FIG. 14) is performed.

In this case, Pfuel in steps 1402, 1405 and 1408 of FIG.
Assuming that the detected fuel pressure is read, the area of the hatched portion is calculated from the pressure difference between the fuel pressure and the in-cylinder pressure in FIG. 16, and the accuracy of the fuel injection amount is higher than that in the fourth embodiment. Although it can be increased, the cost is increased because a sensor for detecting the fuel pressure is required.

Next, a sixth embodiment will be described. In this embodiment, as in the third embodiment, a means (differential pressure sensor) for directly detecting the pressure difference between the in-cylinder pressure and the fuel pressure is provided, and steps 1402, 1405 and 140 of FIG. 14 are provided.
The detected differential pressure is substituted into Pfeul-Pcyl in 8.

Also in this embodiment, the fourth embodiment is used as in the fifth embodiment.
Compared with the embodiment described above, the accuracy of the fuel injection amount is improved, and since only one sensor is required, the cost increase can be suppressed low. Next, a seventh embodiment will be described. In the first to sixth embodiments, the fuel injection pulse width is corrected based on the pressure difference, but in the present embodiment, the fuel pressure is corrected.

That is, while using a fuel pump capable of variably controlling the discharge pressure (fuel pressure), it is used in FIG. 10, FIG. 11 or the fourth to sixth embodiments used in the first to third embodiments. Instead of the flowcharts of FIGS. 14 and 11, the calculation process is performed using FIGS. 17 and 18. As shown in FIG. 19, a fuel pump provided with such a fuel pressure control means is branched from a fuel discharge passage 23 of a fuel pump 22 driven by a motor 21 and a part of fuel is relieved in a fuel tank 25. The relief passage 24 may be provided with an electromagnetic proportional relief valve 26, and the fuel supply pressure P to the fuel injection valve is proportional to the energizing current to the relief valve 26.
As shown in, the fuel pressure P can be variably controlled by the current value i.

In step 1701, the fuel injection pulse is raised, and in step 1702, the in-cylinder pressure and the reference value Pf.
Read the first data of differential pressure of uel (constant here because it is regarded as constant). In step 1703, the fuel pressure is corrected based on the output of step 1702 by the subroutine shown in FIG. This correction will be described later.

At steps 1704 and 1705, the timing Tc for detecting the in-cylinder pressure set in FIG. 7 is set.
It is determined whether or not r (2) is reached, and when it is determined, the differential pressure at the second point is calculated in step 1706. Step 170
In step 7, the fuel pressure is corrected in the same manner as in step 1703,
In steps 1708 and 1709, it is determined whether or not the timing Tcr (3) for reading the in-cylinder pressure has come, and in step 1710, the third differential pressure is calculated.

In step 1711, the fuel pressure is corrected. In step 1712 and step 1713, wait for the pulse falling timing Tie to arrive, and then execute step 1714.
To lower the fuel injection pulse. Step 170
The subroutine for the fuel pressure correction performed in step 3, step 1707, and step 1711 will be described with reference to the flowchart of FIG.

At step 1801, the read differential pressure d
Reference value Cr of P (k) (k = 1 to 3 in this embodiment)
Read (k) from the map. In step 1802,
A fuel pressure correction value dN is calculated from the read differential pressure and map value. Here, K in the illustrated calculation formula is a gain of integration. In Step 1803, the reference fuel pressure N is set to Step 1
The set fuel pressure Nou is calculated by adding the correction amount dN calculated in 802.
t.

In step 1804, step 1803
The fuel pressure signal set in step 2 is output to the fuel pump. The concept of the timing of monitoring the in-cylinder pressure and the number of points are the same as in the first embodiment. Next, an eighth embodiment will be described. In the present embodiment, a fuel pressure detecting means (fuel pressure sensor) is provided, and while the fuel pressure is detected and the pressure difference with the in-cylinder pressure is calculated, the same processing as that in the seventh embodiment (processing in FIG. 17) is performed. It was done like this.

In this case, Pfuel in steps 1702, 1706 and 1710 of FIG.
Assuming that the fuel pressure detected is read, the accuracy of the fuel injection amount can be further improved as compared with the seventh embodiment, but the cost is increased because a sensor for detecting the fuel pressure is required. Next, a ninth embodiment will be described.

In this embodiment, as in the third embodiment, means for directly detecting the pressure difference between the in-cylinder pressure and the fuel pressure (differential pressure sensor).
17 and step 1702 and step 170 in FIG.
6, Pfer-Pcyl in step 1710,
The detected differential pressure is substituted. In the present embodiment as well, as in the eighth embodiment, the accuracy of the fuel injection amount is improved as compared with the seventh embodiment, and since only one sensor is required, the cost increase can be kept low.

In the above embodiments, the cylinder direct injection type internal combustion engine is shown. However, in the case of the intake port injection type internal combustion engine, an intake pressure sensor for detecting the intake pipe pressure is provided instead of the cylinder pressure sensor. If the in-cylinder pressure reading portion of each embodiment is replaced with the intake pipe pressure reading, the same holds true.

[0052]

As described above, according to the invention of claim 1, the differential pressure between the pressure of the fuel injection portion from the fuel injection valve and the fuel supply pressure to the fuel injection valve is detected, and the difference is detected. Since the fuel injection amount is corrected based on the pressure, the fuel injection amount and thus the air-fuel ratio can be controlled with high accuracy, and exhaust emission and drivability can be improved.

According to the second aspect of the invention, in the in-cylinder linear injection internal combustion engine, the pressure in the combustion chamber where the fuel is injected from the fuel injection valve can be detected as the pressure in the fuel injection portion. Further, according to the third aspect of the invention, in the internal combustion engine in which fuel is injected into the intake passage, the pressure in the intake passage can be detected as the pressure of the fuel injection portion.

Further, according to the invention of claim 4, the differential pressure detecting means separately detects the pressure of the fuel injection portion and the fuel supply pressure by the separate detecting means, and calculates the difference between the detected values. By doing so, the differential pressure can be detected with high accuracy. Further, according to the invention of claim 5, the differential pressure detecting means can detect the differential pressure with high accuracy by directly detecting the differential pressure between the pressure of the fuel injection portion and the fuel supply pressure.

Further, according to the invention of claim 6, the differential pressure detecting means detects only the pressure of the fuel injection portion, and the fuel supply pressure is considered to be substantially constant to calculate the differential pressure.
The differential pressure can be detected with a simple structure. Further, according to the invention of claim 7, the fuel injection period is corrected based on the area obtained by the product of a predetermined section of the fuel injection period calculated corresponding to the fuel injection amount and the detected differential pressure. By doing so, the fuel injection amount can be corrected.

Further, according to the invention of claim 8, the fuel injection amount can be corrected by correcting the fuel injection period based on the area obtained by the product of the entire period of the fuel injection period and the differential pressure. it can. Further, according to the invention of claim 9, the fuel injection amount can be corrected by correcting the fuel supply pressure based on the differential pressure detected at a predetermined timing during the fuel injection period.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a diagram showing a system configuration of the present invention.

FIG. 3 is a diagram showing a control circuit system of the same.

FIG. 4 is a diagram showing a relationship between an injection period and a cylinder pressure value in a cylinder direct injection internal combustion engine.

FIG. 5 is a diagram showing a relationship between a fuel injection pulse width and a fuel injection amount, similarly using a differential pressure as a parameter.

FIG. 6 is a diagram showing a change in in-cylinder pressure with respect to variations such as environmental changes.

FIG. 7 is a flowchart of a routine for setting in-cylinder pressure reading timing used in each embodiment of the present invention.

FIG. 8 is a diagram for calculating a target value of an area obtained by a product of a fuel injection pulse width and a pressure difference used in the first embodiment and the like.

FIG. 9 is a diagram similarly showing a relationship between the target value of the area and the fuel injection amount.

FIG. 10 is a flowchart of a routine for outputting a fuel injection pulse used in the above embodiment and the like.

FIG. 11 is a flowchart of a subroutine for correcting the fuel injection amount in the same routine.

FIG. 12 is a diagram for calculating an area obtained by the product of the fuel injection pulse width and the detected differential pressure used in the above-described embodiment and the like.

FIG. 13 is a diagram for calculating an area obtained by a product of a fuel injection pulse width and a detected pressure difference used in the second embodiment and the like.

FIG. 14 is a flowchart of a routine for outputting a fuel injection pulse used in the fourth embodiment and the like.

FIG. 15 is a diagram for calculating an area similarly obtained by the product of the fuel injection pulse width and the detected differential pressure.

FIG. 16 is a diagram for calculating an area obtained by a product of a fuel injection pulse width and a detected pressure difference used in the fifth embodiment and the like.

FIG. 17 is a flowchart of a routine for outputting a fuel injection pulse used in the seventh embodiment and the like.

FIG. 18 is a flowchart of a subroutine for correcting the fuel injection amount in the same routine.

FIG. 19 is a diagram showing a system configuration of the control unit of the embodiment for variably controlling the fuel supply pressure.

FIG. 20 is a diagram showing operating characteristics of the control unit according to the embodiment.

[Explanation of symbols]

 2 Air flow meter 4 Crank angle sensor 6 Air-fuel ratio sensor 8 Fuel injection valve 10 Cylinder pressure sensor 11 Internal combustion engine 26 Relief valve 301 CPU

Claims (9)

[Claims] 1. A fuel injection amount control device for an internal combustion engine, which supplies fuel by a fuel injection valve, wherein a pressure difference between a pressure of a portion injected from the fuel injection valve and a fuel supply pressure to the fuel injection valve. Differential pressure detecting means for detecting the engine operating state detecting means for detecting the operating state of the engine, and fuel injection amount calculating means for calculating the fuel injection amount based on the operating state of the engine detected by the operating state detecting means. And a fuel injection amount correction unit that corrects the fuel injection amount calculated by the fuel injection amount calculation unit based on the output of the differential pressure detection unit, and a fuel injection amount corrected by the fuel injection amount correction unit. A fuel injection amount control device for an internal combustion engine, comprising: a fuel injection valve drive means for injecting a predetermined amount of fuel from the fuel injection valve. 2. The fuel injection valve is provided so as to inject fuel into a combustion chamber of an engine, and the differential pressure detecting means detects a pressure in the combustion chamber as a pressure of a portion injected from the fuel injection valve. 2. The fuel injection amount control device for an internal combustion engine according to claim 1, further comprising means. 3. The fuel injection valve is provided so as to inject fuel into an intake passage of an engine, and the differential pressure detecting means uses an intake passage internal pressure as a pressure of a portion injected from the fuel injection valve. The fuel injection amount control device for an internal combustion engine according to claim 1, further comprising a detecting unit. 4. The differential pressure detecting means includes means for detecting the pressure of a portion injected from the fuel injection valve, and means for detecting the fuel supply pressure to the fuel injection valve, each of which is detected. The fuel injection amount control device for an internal combustion engine according to any one of claims 1 to 3, wherein a difference between the values is calculated to detect the differential pressure. 5. The differential pressure detecting means directly detects the differential pressure between the pressure of the portion injected from the fuel injection valve and the fuel supply pressure to the fuel injection valve. ~
The fuel injection amount control device for an internal combustion engine according to claim 3. 6. The differential pressure detecting means detects the differential pressure by calculating the difference between the pressure of the portion injected from the fuel injection valve and the supply pressure to the fuel injection valve regarded as a substantially constant value. The fuel injection amount control device for an internal combustion engine according to any one of claims 1 to 3, wherein: 7. The fuel injection amount correction means is a product of a predetermined section in a fuel injection period corresponding to the fuel injection amount calculated by the fuel injection amount calculation means and a differential pressure detected by the differential pressure detection means. The fuel injection amount control device for an internal combustion engine according to any one of claims 1 to 6, wherein the fuel injection amount is corrected by correcting the actual fuel injection period based on the obtained area. 8. The fuel injection amount correction means, a predetermined section in a fuel injection period corresponding to the fuel injection amount calculated by the fuel injection amount calculation means, the differential pressure detected by the differential pressure detection means, and its history. 7. The fuel injection amount is corrected by correcting the actual fuel injection period based on the area obtained by the product of the two from the above in the entire fuel injection period. And a fuel injection amount control device for an internal combustion engine. 9. A fuel pressure control means for variably controlling the fuel supply pressure to the fuel injection valve, wherein the fuel injection amount correction means is for a fuel injection period corresponding to the fuel injection amount calculated by the fuel injection amount calculation means. The fuel injection amount is corrected by correcting the fuel supply pressure to the fuel injection valve via the fuel pressure control means based on the differential pressure detected by the differential pressure detection means at a predetermined timing. The fuel injection amount control device for an internal combustion engine according to any one of claims 1 to 6.