JP3692641B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to an injection control technique at the start of a multi-cylinder internal combustion engine provided with a fuel injection valve for each cylinder.
[0002]
[Prior art]
As a conventional fuel injection control at the time of starting, there has been one disclosed in, for example, Japanese Patent Laid-Open No. 7-103025.
This is because all cylinders perform asynchronous injection once before cylinder discrimination immediately after starting, and after cylinder discrimination shifts to synchronous injection (sequential injection), and among the fuel injected by the asynchronous injection, There is a disclosure of a configuration in which the amount of fuel that has not been sucked into the cylinder in the first intake stroke is corrected for reduction in the first synchronous injection.
[0003]
[Problems to be solved by the invention]
By the way, since no fuel adheres to the intake port or the cylinder inner wall at the time of starting, in the first fuel injection to each cylinder after the start, most of the injected fuel adheres to the intake port or the cylinder inner wall. However, in the second and subsequent injections of each cylinder, there is a characteristic that the adhesion rate decreases rapidly.
[0004]
Here, in the above-described conventional start-up injection control, the asynchronous injection immediately after the start (simultaneous injection of all cylinders) is the first fuel injection for each cylinder, so the injection amount in the asynchronous injection is changed to the attached fuel amount. Set a relatively large amount to match, and in sequential injection, setting the injection amount on the assumption that the amount of adhesion is substantially satisfied, the injection amount setting corresponding to the change in the adhesion rate can be set. You can do it.
[0005]
However, in the conventional start-up injection control, since the initial fuel injection for each cylinder is asynchronous injection, a deviation between the intake stroke and the injection timing occurs for each cylinder. It is necessary to inject more fuel than the required amount so that the required amount is sucked into each cylinder. And since such a large amount of initial injection is not necessarily sucked in the initial intake stroke of each cylinder, it is determined whether or not the fuel injected by asynchronous injection remains, and the reduction of the residual is corrected. There is a problem that the control is complicated.
[0006]
Here, if the fuel injection is performed by the synchronous injection (sequential injection) from the beginning after the start, it is possible to avoid the generation of residual fuel and to simplify the control content added for the start. is there.
However, in the past, since the first injection was made asynchronous at the same time for all the cylinders, the initial fuel injection for each cylinder was substantially distinguished from the second and subsequent injections by synchronous injection, so the engine was simply started. Even if the configuration is such that fuel injection is performed by synchronous injection (sequential injection) from the beginning later, it cannot cope with the change in the adhesion ratio, and the required fuel is adhered to the intake port and the cylinder inner wall at an early stage. However, there is a problem that it is not possible to improve the exhaust properties at the start by avoiding excessive fuel supply.
[0007]
The present invention has been made in view of the above problems, and fuel injection capable of injecting fuel suitable for the adhesion characteristics of fuel to the intake port and the inner wall of the cylinder with a simple control configuration and without generating residual fuel. An object is to provide a control device.
[0008]
[Means for Solving the Problems]
Therefore, the invention according to claim 1 is a fuel injection control device for an internal combustion engine, which includes a fuel injection valve for each cylinder, and performs fuel injection by the fuel injection valve in accordance with the intake stroke of each cylinder, respectively. The first fuel injection at the start for each cylinder is detected. In the first fuel injection at the start for each cylinder, the fuel required to satisfy the wall flow fuel is injected, and the second and subsequent times for each cylinder are injected . The fuel injection is configured to inject fuel commensurate with the decrease in the amount of attached fuel .
[0009]
According to such a configuration, in so-called sequential injection control performed from the beginning after the start, the first fuel injection for each cylinder and the second and subsequent fuel injections are clearly divided in terms of control. In order to satisfy the adhering fuel, the amount of fuel required for the addition is added to the amount of fuel to be supplied into the cylinder and injected. After the second time, the adhering fuel is substantially satisfied and only a small amount of adhering fuel is required. Then, the fuel corresponding to the decrease in the required amount of the adhered fuel is injected.
[0011]
The invention described in claim 2 is configured as shown in FIG.
In FIG. 1, the fuel injection amount calculating means calculates the fuel injection amount based on the target fuel / air ratio and the engine operating conditions, and the reference signal output means is an injection timing that is synchronized with the intake stroke of each cylinder. A reference signal is output as a reference.
The injection control means performs fuel injection by driving the fuel injection valve provided for each cylinder according to the fuel injection amount at each injection timing of each cylinder detected based on the reference signal. Make it.
[0012]
On the other hand, the initial injection detecting means detects the initial fuel injection at the start for each cylinder.
The target fuel / air ratio setting means sets the target air / fuel ratio required for satisfying the wall flow fuel in the initial fuel injection at the start of each cylinder, and in the second and subsequent fuel injections for each cylinder. Then, a target air-fuel ratio that matches the decrease in the amount of attached fuel is set.
[0013]
According to such a configuration, fuel is injected into each cylinder by so-called sequential injection that is timed immediately after the start in accordance with the intake stroke of each cylinder. Further, it is determined whether the fuel injection by the sequential injection is the first time for each cylinder or the second time or later, the target fuel-air ratio is individually set, and the fuel injection amount at the first time, The fuel injection amount for the second and subsequent times is set based on different target fuel-air ratios. That is, if it is the first injection for each cylinder, a target fuel-air ratio that can secure the amount of fuel necessary to satisfy the almost lost attached fuel is set. Furthermore, since the amount of adhering fuel and the amount of fuel adhering to the cylinder will be balanced, the fuel / air ratio required for the cylinder intake air mixture will be set as the target fuel / air ratio. Let it be set.
[0014]
According to a third aspect of the present invention, the fuel injection amount calculation means includes a first basic injection amount calculation means for calculating a basic fuel injection amount in accordance with an engine temperature detection result within a predetermined period from the start, and the predetermined amount. And a second basic injection amount calculation means for calculating a basic fuel injection amount in accordance with the detection result of the intake air amount of the engine after the elapse of the period, wherein the calculated basic fuel injection amount and the target fuel are calculated. The final fuel injection amount is calculated based on the air ratio.
[0015]
According to such a configuration, during a predetermined period immediately after the start when the intake air amount greatly varies, the detection result of the intake air amount by an air flow meter, an intake pressure sensor, or the like is not used, and the engine represented by the cooling water temperature or the like is used. The basic fuel injection amount is calculated based on the temperature, and after the predetermined period, the basic fuel injection amount is calculated based on the detection result of the intake air amount by an air flow meter, an intake pressure sensor, or the like. Then, a final injection amount is determined based on the basic fuel injection amount and a target fuel / air ratio set individually depending on whether or not the injection is the first time of each cylinder.
[0016]
According to a fourth aspect of the present invention, the predetermined period in the first basic injection amount calculating means is a period until the engine speed reaches a preset speed.
According to this configuration, the basic fuel injection amount is calculated based on the engine temperature until the engine rotational speed reaches a predetermined rotational speed from the start, in other words, until it is considered that a complete explosion has occurred. After that, the basic fuel injection amount of the amount commensurate with the actual intake air amount is normally calculated.
[0017]
According to a fifth aspect of the present invention, the target fuel / air ratio setting means sets the target fuel / air ratio according to the engine temperature in the initial fuel injection at the time of start for each cylinder.
According to such a configuration, the engine temperature correlates with the amount of fuel adhering to the intake port or the like, so the target fuel-air ratio is determined in accordance with the amount of fuel that will be adhering in the first fuel injection to each cylinder. It will be.
[0018]
In a sixth aspect of the present invention, the target fuel / air ratio setting means sets the target fuel / air ratio based on the engine load, the engine speed, and the engine temperature in the second and subsequent fuel injections for each cylinder. It was.
According to such a configuration, in the second and subsequent fuel injections of each cylinder, the target fuel-air ratio is set in consideration of the engine temperature to ensure the combustion stability in the cold state. The target fuel-air ratio can be set in consideration of power performance and fuel efficiency required based on load and rotation.
[0019]
【The invention's effect】
According to the invention of claim 1, wherein, for the fuel injection in response to changes in the adhering fuel amount in the initial injection and the second and subsequent injection, can be realized in a so-called sequential injection control, by a simple control This has the effect of improving startability and exhaust performance.
[0021]
According to the third aspect of the present invention, there is an effect that it is possible to set the injection amount corresponding to the change in the adhering amount while performing the stable injection amount control even in the unstable state immediately after the start. .
According to the invention described in claim 4, there is an effect that the setting of the basic injection amount can be switched by accurately determining that the engine is in a stable state.
[0022]
According to the fifth aspect of the present invention, it is possible to set the target fuel-air ratio in the predetermined injection corresponding to the adhering fuel amount that varies depending on the engine temperature, and it is possible to inject the fuel required for the first injection without excess or deficiency. There is an effect of becoming.
According to the sixth aspect of the invention, in the second and subsequent fuel injections, while ensuring the combustion stability during cold operation, the target fuel-air ratio capable of realizing the power performance and fuel consumption performance required based on the load and rotation. There is an effect that can be set.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 2 is a diagram showing a system configuration of the internal combustion engine in the embodiment. In the internal combustion engine 1, air that has passed through an air cleaner (not shown) is adjusted by the throttle valve 2 and sucked into the cylinder through the intake valve 3. Thus, an air-fuel mixture is formed by the fuel injected from the fuel injection valve 4 provided in the intake port portion of each cylinder.
[0024]
The air-fuel mixture in the cylinder is ignited and burned by spark ignition by the spark plug 5, and the combustion exhaust gas is discharged through the exhaust valve 6 and then purified by a catalyst (not shown) and released into the atmosphere.
The engine 1 includes an air flow meter 11 for detecting the intake air flow rate Q, a throttle sensor 12 for detecting the opening TVO of the throttle valve 2, a water temperature sensor 13 for detecting a cooling water temperature TW representing the temperature of the engine, an engine An oxygen sensor 14 that detects the oxygen concentration in the exhaust gas that is closely related to the fuel-air ratio of the intake air-fuel mixture, a crank angle sensor 15 that outputs a reference angle signal REF for each reference piston position of each cylinder, and the like are provided. .
[0025]
For example, the reference angle signal REF is set so that the pulse width differs between the cylinders so as to be associated with each cylinder, and the pulse width of the reference angle signal REF output from the crank angle sensor 15 is detected. The cylinder can be discriminated by. Further, since the fuel injection (sequential injection) is performed at the timing of the intake stroke of each cylinder with reference to the reference angle signal REF, the crank angle sensor 15 corresponds to the reference signal output means. Furthermore, the engine speed Ne (rpm) can be calculated by measuring the generation period of the reference angle signal REF.
[0026]
Detection signals from the various sensors are input to a control unit 20 including a CPU 21, RAM 22, ROM 23, input interface 24, output interface 25, and the like. In addition to the detection signals from the various sensors, an ON / OFF signal of a start switch (not shown) is input to the control unit 20.
[0027]
The control unit 20 controls fuel injection by the fuel injection valve 4 and ignition by the spark plug 5 based on detection signals from the various sensors.
Specifically, the injection pulse width TI corresponding to the valve opening time of the fuel injection valve 4 is calculated, and the injection pulse is detected when a preset injection timing is detected (for example, when the reference angle signal REF is output). An injection pulse signal having a width TI is output to the fuel injection valve 4. The fuel injection valve 4 is supplied with fuel whose pressure is adjusted so that the differential pressure with respect to the negative suction pressure of the engine 1 is constant, and each fuel is supplied in an amount proportional to the injection pulse width TI. Injection to each cylinder.
[0028]
On the other hand, the control unit 20 determines the ignition timing from the detection result of the engine load and the engine speed Ne, and outputs an ignition signal to the ignition coil 7 based on the determination.
Here, the fuel injection control by the control unit 20 will be described in detail with reference to the functional block diagram shown in FIG.
[0029]
In FIG. 3, the fuel injection amount calculation means A calculates the basic pulse width TP and finally performs injection based on the target fuel / air ratio output from the target fuel / air ratio switching means B and the basic pulse width TP. The pulse width TI is calculated.
On the other hand, the cylinder discrimination means C performs cylinder discrimination based on the reference angle signal REF.
Then, the injection control means D outputs the injection pulse signal of the injection pulse width TI from the fuel injection amount calculation means A to the fuel injection valve 4 of the cylinder at the injection timing based on the result of the cylinder discrimination. . As a result, so-called sequential injection control in which the timing is matched with the intake stroke of each cylinder is performed from the first fuel injection at the start (injection to the cylinder for which cylinder discrimination is first performed) (see FIG. 5). ).
[0030]
Here, the target fuel / air ratio switching means B receives the target fuel / air ratio from the initial target fuel / air ratio calculation means E and the target fuel / air ratio from the target fuel / air ratio calculation means F, respectively. Based on whether or not it is the first fuel injection for each cylinder detected by the injection detecting means G, the target fuel / air ratio of either the calculating means E or the calculating means F is selected and the selected fuel / air ratio is selected. The target fuel / air ratio is output to the fuel injection amount calculation means A.
[0031]
The target fuel / air ratio setting means B, the initial target fuel / air ratio calculation means E, and the target fuel / air ratio calculation means F constitute a target fuel / air ratio setting means.
That is, as shown in the flowchart of FIG. 4, it is determined whether or not the first fuel injection for each cylinder is performed (step 1). The injection pulse width TI is calculated based on the calculated target fuel / air ratio (step 2), and the target fuel / air ratio calculated by the target fuel / air ratio calculating means F is used in the second and subsequent fuel injections for each cylinder. The injection pulse width TI is calculated based on the ratio (step 3).
[0032]
In this way, by setting the target fuel-air ratio individually based on whether or not the fuel injection is the first time for each cylinder, sequential injection corresponding to the change in the required injection amount at the time of start is realized. (See FIG. 5).
At the time of the first fuel injection to each cylinder at the time of starting, there is no fuel adhering to the intake port wall and the cylinder inner wall, and most of the fuel injected by the first injection becomes the wall flow, In the first fuel injection for each cylinder, a large amount of fuel is required. On the other hand, in the second and subsequent fuel injections, only a small amount of wall flow adhesion is required by the first injection, there is a part that contributes to combustion by the wall flow flowing into the cylinder, rotation due to the first explosion Since the negative pressure develops due to the rise and the intake air amount decreases, the required fuel amount decreases (see FIG. 6).
[0033]
In order to cope with the difference between the required fuel amount at the time of the first injection and the required fuel amount at the second and subsequent times, the target fuel-air ratio is set individually depending on whether or not it is at the time of the first injection. Thus, at the time of the first injection for each cylinder, it is possible to perform the injection with the injection pulse width TI that can sufficiently secure the wall flow adhesion. In the second and subsequent injections in which the flow deposit is reduced, it is possible to set the injection pulse width TI commensurate with the decrease in the deposit and avoid excessive fuel injection.
[0034]
The initial target fuel / air ratio calculation means E calculates the target fuel / air ratio based on the water temperature TW, while the target fuel / air ratio calculation means F calculates the target fuel / air ratio by calculating the intake air flow rate Q, engine The calculation is based on the rotational speed Ne (rpm) and the water temperature TW.
Specifically, the target fuel / air ratio calculating means F calculates the target fuel / air ratio TFBYA,
TFBYA = KMR + KAS + KTW
Calculate as Here, KMR is a basic fuel-air ratio, and is obtained by referring to a table from the engine speed Ne and the basic pulse width TP representing the engine load. KAS is an increase coefficient after starting, and is obtained from the water temperature TW by referring to a table only for a predetermined time after starting. Furthermore, KTW is a water temperature increase coefficient and is obtained from the water temperature TW by referring to a table.
[0035]
On the other hand, the initial target fuel / air ratio calculation means E obtains the target fuel / air ratio TFBYA from the water temperature TW by referring to a table.
The fuel injection amount calculation means A that inputs the target fuel / air ratio TFBYA calculates the injection pulse width TI according to the following equation.
TI = (TP * TFBYA + KATHOS) * Kconst * (ALPHA + KBLRC-1) + TS + CHOS
Here, TP is the basic pulse width, but the value obtained by referring to the table from the water temperature TW is used until the predetermined rotational speed Ne is reached after the start (first basic injection amount calculating means), and the predetermined rotational speed is used. After the number Ne is reached, calculation is performed based on the intake air flow rate Q and the engine speed Ne (second basic fuel injection amount calculation means).
[0036]
Here, normally, the basic pulse width TP at the first injection of each cylinder and the second basic pulse width TP are substantially the same value, but the same value is obtained by switching the target fuel-air ratio described above. Even with the basic pulse width TP, it is possible to inject a relatively large amount of fuel that meets the satisfaction of the wall flow adhesion during the first injection.
KATHOS is a transient correction pulse width for correcting an error associated with a delay in fuel response at the time of transition, and MKINJ is a constant set according to the characteristics of the fuel injection valve 4 and the like.
[0037]
ALPHA is an air-fuel ratio feedback correction for feedback-correcting the actual fuel-air ratio of the engine intake air-fuel mixture to the target fuel-air ratio based on the oxygen concentration in the exhaust gas detected by the oxygen sensor 14 in a predetermined operating region. The coefficient (initial value = 1.0).
KBLRC is an air-fuel ratio learning correction value obtained by learning the air-fuel ratio feedback correction coefficient ALPHA for each of a plurality of operation regions.
[0038]
TS is an invalid injection pulse width for correcting the valve opening delay of the fuel injection valve 4 accompanying a decrease in the power supply voltage (battery voltage).
CHOS is a cylinder-specific wall flow correction pulse width.
Next, the state of the injection amount control will be described according to the flowchart of FIG.
First, in step 11, the basic pulse width TP is calculated. The basic pulse width TP is set according to the water temperature TW from the start until the predetermined rotational speed (rpm), but after reaching the predetermined rotational speed, the basic pulse width TP is based on the intake air flow rate Q and the rotational speed Ne. Is calculated.
[0039]
In step 12, the target fuel / air ratio TFBYA is calculated. The target fuel / air ratio TFBYA is individually set depending on whether the injection is performed for each cylinder for the first time or for the second and subsequent injections. The first time is set from the water temperature table. The basic value corresponding to the rotation speed (basic pulse width TP) and the load is corrected and set according to the water temperature.
[0040]
In step 13 to step 17, the transient correction pulse width KATHOS, the air-fuel ratio feedback correction coefficient ALPHA, the air-fuel ratio learning correction value KBLRC, the invalid injection pulse width TS, and the cylinder-specific wall flow correction pulse width CHOS are calculated.
In step 18, the injection pulse width TI is set to
TI = (TP * TFBYA + KATHOS) * Kconst * (ALPHA + KBLRC-1) + TS + CHOS
And the injection pulse signal having the injection pulse width TI is output to the fuel injection valve 4 of the cylinder at the injection timing.
[Brief description of the drawings]
FIG. 1 is a basic configuration block diagram of a fuel injection control device according to a second aspect of the present invention;
FIG. 2 is a system configuration diagram of the internal combustion engine in the embodiment.
FIG. 3 is a functional block diagram of fuel injection control in the embodiment.
FIG. 4 is a flowchart showing how the target fuel-air ratio is switched in the embodiment.
FIG. 5 is a time chart showing characteristics of injection control in the embodiment.
FIG. 6 is a diagram showing the correlation between the number of cycles, the required pulse width, and the suction negative pressure.
FIG. 7 is a flowchart showing a state of injection pulse width calculation in the embodiment.
[Explanation of symbols]
1 Internal combustion engine 2 Throttle valve 3 Intake valve 4 Fuel injection valve 5 Spark plug 6 Exhaust valve 7 Ignition coil
11 Air flow meter
12 Throttle sensor
13 Water temperature sensor
14 Oxygen sensor
15 Crank angle sensor
20 Control unit

Claims (6)

In a fuel injection control device for an internal combustion engine, which includes a fuel injection valve for each cylinder, and performs fuel injection by the fuel injection valve in accordance with the intake stroke of each cylinder, respectively.
The first fuel injection at the start for each cylinder is detected. In the first fuel injection at the start for each cylinder, the fuel required to satisfy the wall flow fuel is injected, and the second and subsequent times for each cylinder are injected . In the fuel injection , a fuel injection control device for an internal combustion engine, wherein fuel corresponding to a decrease in the amount of attached fuel is injected . A fuel injection valve provided for each cylinder;
Fuel injection amount calculation means for calculating the fuel injection amount based on the target fuel-air ratio and the engine operating condition;
A reference signal output means for outputting a reference signal serving as a reference of the injection timing that is synchronized with the intake stroke of each cylinder;
Injection control means for driving each fuel injection valve according to the fuel injection amount to perform fuel injection at each injection timing of each cylinder detected based on the reference signal;
Initial injection detecting means for detecting initial fuel injection at the start of each cylinder;
In the initial fuel injection at the start of each cylinder, the target air-fuel ratio required for satisfying the wall flow fuel is set, and in the second and subsequent fuel injections for each cylinder, the target air ratio is commensurate with the decrease in the amount of attached fuel. Target fuel-air ratio setting means for setting the fuel ratio;
A fuel injection control device for an internal combustion engine, comprising: The fuel injection amount calculation means is
First basic injection amount calculation means for calculating a basic fuel injection amount in accordance with the detection result of the engine temperature within a predetermined period from the start;
Second basic injection amount calculation means for calculating a basic fuel injection amount in accordance with a detection result of the intake air amount of the engine after the predetermined period has elapsed;
3. A fuel injection control apparatus for an internal combustion engine according to claim 2 , wherein a final fuel injection amount is calculated based on the calculated basic fuel injection amount and the target fuel-air ratio. . 4. The fuel injection control device for an internal combustion engine according to claim 3, wherein the predetermined period in the first basic injection amount calculating means is a period until the rotational speed of the engine reaches a preset rotational speed. The target air-fuel ratio setting means, in the first fuel injection at the start for each of the cylinders, to any one of claims 2-4, characterized in that the set according to the target air-fuel ratio to the engine temperature A fuel injection control device for an internal combustion engine as described. 3. The target fuel / air ratio setting means sets a target fuel / air ratio based on an engine load, an engine speed, and an engine temperature in the second and subsequent fuel injections for each cylinder . 5. The fuel injection control device for an internal combustion engine according to claim 5 .

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