JPH1054271A - Fuel injection controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply fuel easily and completely, whose amount corresponds to a change in a wall flow amount at the time of starting. SOLUTION: Fuel is supplied to respective cylinders by sequential injection control from the beginning at the time of starting. It is discriminated which of the first fuel injection, or the second fuel injection and thereafter is conducted for the respective cylinders (first injection detection means), and from the discriminated results, targeted air-fuel ratio is changed over to be set (targeted air-fuel ratio changing-over means). based on basic pulse duration and the targeted fuel ratio, final injection pulse duration is calculated (fuel injection amount calculating means). The injection pulse signal of the injection pulse duration is outputted to the fuel injection valve of the cylinder under injection timing (injection control means).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control apparatus for an internal combustion engine, and more particularly to an injection control technique for starting a multi-cylinder internal combustion engine having a fuel injection valve for each cylinder.

[0002]

2. Description of the Related Art Conventional fuel injection control at start-up includes:
For example, there is one disclosed in Japanese Patent Application Laid-Open No. 7-103025. In this system, asynchronous injection is performed once for all cylinders at the same time before the cylinder determination is performed immediately after the start, and after the cylinder determination, the operation is shifted to synchronous injection (sequential injection), and among the fuel injected by the asynchronous injection, There is disclosed a configuration in which the amount of fuel not taken into the cylinder in the first intake stroke is reduced in the first synchronous injection.

[0003]

By the way, since fuel does not adhere to the intake port or the inner wall of the cylinder at the time of start, most of the injected fuel is taken into the intake air in the first fuel injection into each cylinder after the start. It will adhere to the port and the inner wall of the cylinder, but in the second and subsequent injections of each cylinder,
There is a characteristic that the adhesion ratio is rapidly reduced.

Here, in the above-described conventional start-time injection control,
Since the asynchronous injection immediately after the start (simultaneous injection of all cylinders) is the first fuel injection for each cylinder, the injection amount in the asynchronous injection is set to a relatively large amount corresponding to the attached fuel amount, and the sequential injection is performed. In the injection, by setting the injection amount on the assumption that the adhesion amount is substantially satisfied, the injection amount can be set in accordance with the change in the adhesion ratio.

However, in the conventional start-up injection control described above, 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. However, it is necessary to inject more fuel than necessary so that the required amount is sucked into each cylinder as much as possible. Since such a large amount of the initial injection is not always sucked in the first intake stroke of each cylinder, it is determined whether or not the fuel injected by the asynchronous injection remains, and the reduction of the residual is performed. And the control becomes complicated.

Here, if the fuel injection is performed by synchronous injection (sequential injection) from the beginning after the start, the generation of residual fuel can be avoided, and the control contents added for the start can be simplified. Is possible. However, in the related art, the first injection is simultaneously performed in all cylinders at the same time and asynchronously, so that the first fuel injection for each cylinder is substantially distinguished from the second and subsequent injections by synchronous injection. If the fuel injection is performed only by the synchronous injection (sequential injection) from the beginning later, it is not possible to cope with the change in the adhesion ratio, and the fuel required for the intake port or the inner wall of the cylinder is caused to adhere early. However, there is a problem that it is not possible to improve the exhaust properties at the time of starting by avoiding the supply of excessive fuel.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is possible to inject a fuel suitable for the characteristics of fuel adhesion to an intake port and an inner wall of a cylinder with a simple control structure and without generating residual fuel. It is an object of the present invention to provide a fuel injection control device which can be used.

[0008]

According to the present invention, a fuel injection valve is provided for each cylinder, and the fuel injection by the fuel injection valve is performed at the same timing as the intake stroke of each cylinder. In the fuel injection control device for the internal combustion engine, the setting of the fuel injection amount is changed between the first fuel injection at the start of each cylinder and the second or subsequent fuel injection to each cylinder.

With this configuration, in the so-called sequential injection control that is performed from the beginning after the start, the first fuel injection for each cylinder and the second and subsequent fuel injections are clearly separated from each other in terms of control, and the first fuel injection is performed. Injection
It is positioned for the purpose of filling the adhering fuel, and the amount of fuel required for the filling is added to the amount of fuel to be supplied into the cylinder, and the fuel is injected. In addition, it is possible to inject fuel corresponding to the reduction in the required amount of the attached fuel.

According to the second aspect of the present invention, the fuel injection amount is set according to the target fuel-air ratio. The first fuel injection at the start of each cylinder and the second and subsequent fuel injections at each cylinder are performed. By setting the target fuel-air ratio individually for fuel injection, the setting of the fuel injection amount is changed. According to such a configuration, for example, in a configuration in which the final fuel injection amount is set based on the basic fuel injection amount and the target fuel-air ratio, the basic fuel injection amount is the first injection or the second or later injection. Whether the target fuel-air ratio is the first time or the second time or later is switched regardless of the target fuel-air ratio, it is possible to cope with the difference in the required fuel amount due to the change in the amount of adhesion.

The invention according to claim 3 is configured as shown in FIG. In FIG. 1, a fuel injection amount calculating means calculates a fuel injection amount based on a target fuel-air ratio and an engine operating condition, and a reference signal output means outputs an injection timing adjusted to an intake stroke of each cylinder. And outputs a reference signal serving as a reference for the. Then, at each injection timing of each cylinder detected based on the reference signal, the injection control means drives a fuel injection valve provided for each cylinder in accordance with the fuel injection amount to perform fuel injection. Let

On the other hand, the first-time injection detecting means detects the first-time fuel injection at the start of each cylinder. Then, the target fuel-air ratio setting means determines whether the first fuel injection at the start of each cylinder detected by the first injection detection means is the first fuel injection or the second or subsequent fuel injection to each cylinder. The target fuel-air ratio is set individually.

According to such a configuration, fuel is injected into each cylinder by so-called sequential injection at a timing synchronized with the intake stroke of each cylinder immediately after the start. Further, it is determined whether the fuel injection by the sequential injection is the first fuel injection for each cylinder or the second or later fuel injection, the target fuel-air ratio is set individually, and the fuel injection amount in the first fuel injection, The fuel injection amount after the second time is
It is set based on different target fuel-air ratios. That is, in the case of the first injection for each cylinder, the target fuel-air ratio that can secure the fuel amount necessary to fill the substantially lost adhered fuel is set. Since the amount of the adhering fuel and the amount of the adhering fuel flowing into the cylinder become balanced, the fuel-air ratio required for the cylinder intake air-fuel mixture assuming that there is almost no adhering fuel is set as the target fuel-air ratio. Can be set.

According to a fourth aspect of the present invention, the fuel injection amount calculating means calculates a basic fuel injection amount according to a detection result of the temperature of the engine within a predetermined period from the start of the engine. A second basic injection amount calculating means for calculating a basic fuel injection amount according to a detection result of the intake air amount of the engine after the predetermined period has elapsed. A final fuel injection amount is calculated based on the target fuel-air ratio.

According to such a configuration, during a predetermined period immediately after the start-up in which the fluctuation of the intake air amount is large, the temperature is represented by the cooling water temperature or the like without using the detection result of the intake air amount by the air flow meter or the intake pressure sensor. The basic fuel injection amount is calculated based on the temperature of the engine, and after the lapse of the predetermined period,
A basic fuel injection amount is calculated based on a detection result of an 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 which is individually set depending on whether or not the injection is for the first time in each cylinder.

According to a fifth aspect of the present invention, the predetermined period in the first basic injection amount calculating means is a period until the rotation speed of the engine reaches a predetermined rotation speed. According to this configuration, the basic fuel injection amount is calculated based on the temperature of the engine until the engine speed reaches the predetermined speed from the start, in other words, until the engine is considered to be almost completely detonated. After that, a basic fuel injection amount is calculated which normally corresponds to the actual intake air amount.

According to a sixth aspect of the present invention, the target fuel / air ratio setting means sets the target fuel / air ratio in accordance with the engine temperature in the first fuel injection at the time of starting each cylinder. According to such a configuration, the temperature of the engine is correlated with the amount of fuel attached to the intake port and the like. Therefore, the target fuel-air ratio is determined according to the amount of fuel that will be attached in the first fuel injection to each cylinder. Will be.

In the invention described in claim 7, the target fuel / air ratio setting means determines 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 configured to be set. With this configuration, even 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 combustion stability in a cold state, and after complete warming, the required power performance and fuel efficiency based on load and rotation are considered. Enables setting of target fuel-air ratio.

[0019]

According to the first aspect of the invention, the fuel injection corresponding to the change in the amount of the attached fuel in the first injection and the second and subsequent injections can be realized by the so-called sequential injection control. Such control has the effect of improving startability and exhaust performance.

According to the second aspect of the present invention, by switching the target fuel-air ratio used for setting the fuel injection amount, it is possible to easily perform the sequential injection control corresponding to the change in the amount of the attached fuel. is there. Claim 3
According to the invention described above, the sequential injection control corresponding to the change in the amount of adhering fuel can be performed by switching the target fuel-air ratio, so that the startability and the exhaust performance can be improved by simple control. There is.

According to the fourth aspect of the invention, even in an unstable state immediately after starting, the injection amount can be set in accordance with a change in the amount of adhesion while performing stable injection amount control. effective. According to the fifth aspect of the invention, 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.

According to the sixth aspect of the present invention, the target fuel-air ratio in the predetermined injection can be set in accordance with the amount of adhering fuel which varies depending on the engine temperature, and the fuel required for the first injection is injected without excess or deficiency. The effect is that it becomes possible. According to the seventh aspect of the present invention, in the second and subsequent fuel injections, the target fuel-air ratio can ensure the combustion stability at the time of cooling and can achieve the required power performance and fuel efficiency based on the load and rotation. There is an effect that can be set.

[0023]

Embodiments of the present invention will be described below. FIG. 2 is a diagram illustrating a system configuration of the internal combustion engine according to the embodiment. In the internal combustion engine 1, air that has passed through an air cleaner (not shown) is adjusted by a throttle valve 2.
The mixture is sucked into the cylinder via the intake valve 3, and a fuel-air mixture is formed by the fuel injected from the fuel injection valves 4 provided at the intake ports of the respective cylinders.

The air-fuel mixture in the cylinder is ignited and burned by spark ignition by a spark plug 5, and the combustion exhaust gas is exhausted by an exhaust valve 6.
And then purified by a catalyst (not shown) and released into the atmosphere. The engine 1 has an intake air flow rate Q
, An air flow meter 11 for detecting the opening degree TVO of the throttle valve 2, a water temperature sensor 13 for detecting a cooling water temperature TW representing a temperature of the engine, and a close relationship with a fuel-air ratio of an engine intake air-fuel mixture. , An oxygen sensor 14 for detecting the oxygen concentration in the exhaust gas, a crank angle sensor 15 for outputting a reference angle signal REF for each reference piston position of each cylinder, and the like.

The reference angle signal REF is set to have a different pulse width between cylinders, for example, so as to be associated with each cylinder. The pulse width of the reference angle signal REF output from the crank angle sensor 15 is determined by the reference angle signal REF. Cylinder discrimination can be performed by detection. Further, since the fuel injection (sequential injection) is performed at the timing corresponding to the intake stroke of each cylinder based on the reference angle signal REF, the crank angle sensor 15 is used.
Corresponds to reference signal output means. Further, by measuring the generation cycle of the reference angle signal REF, the engine speed Ne is measured.
(rpm) can be calculated.

The detection signals from the various sensors are input to a control unit 20 including a CPU 21, a RAM 22, a ROM 23, an input interface 24, an output interface 25 and the like. The control unit 20 receives ON / OFF signals of a start switch (not shown) and the like in addition to the detection signals from the various sensors.

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, an injection pulse width TI corresponding to the valve opening time of the fuel injection valve 4 is calculated, and when a preset injection timing is detected (for example, when the reference angle signal REF is output), the injection pulse An injection pulse signal having a width TI is output to the fuel injection valve 4. Fuel whose pressure has been adjusted so that the differential pressure with respect to the suction negative pressure of the engine 1 is constant is supplied to the fuel injection valve 4, and an amount of fuel proportional to the injection pulse width TI is supplied to each fuel injection valve 4. Inject into each cylinder.

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 state of the fuel injection control by the control unit 20 will be described in detail with reference to the functional block diagram shown in FIG.

In FIG. 3, the fuel injection amount calculating means A comprises:
In addition to calculating the basic pulse width TP, the target fuel-air ratio output from the target fuel-air ratio switching means B and the basic pulse width T
A final injection pulse width TI is calculated based on P.
On the other hand, the cylinder discriminating means C performs cylinder discrimination based on the reference angle signal REF. Then, the injection control means D outputs an 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, the so-called sequential injection control in which the timing is adjusted to the intake stroke of each cylinder is performed from the first fuel injection at the time of starting (injection into the cylinder for which the cylinder is first determined) (see FIG. 5). ).

The target fuel / air ratio switching means B receives the target fuel / air ratio from the first target fuel / air ratio calculating means E and the target fuel / air ratio from the target fuel / air ratio calculating means F. Then, based on whether or not the first fuel injection for each of the cylinders detected by the first injection detection means G is performed, the target fuel-air ratio of one of the calculation means E and the calculation means F is selected, The selected target fuel-air ratio is output to the fuel injection amount calculating means A.

The target fuel / air ratio switching means B, the initial target fuel / air ratio calculating means E, and the target fuel / air ratio calculating means F constitute 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 is performed for each of the cylinders (step 1).
The injection pulse width TI is calculated based on the target fuel-air ratio calculated in (2) (step 2). In the second and subsequent fuel injections for each cylinder, the target fuel-air ratio calculated by the target fuel-air ratio calculation means F is used. Injection pulse width TI based on air ratio
Is calculated (step 3).

As described above, by sequentially setting the target fuel-air ratio based on whether or not the first fuel injection is performed for each cylinder, the sequential injection corresponding to the change in the required injection amount at the time of starting can be performed. (See FIG. 5). At the time of the first fuel injection for each cylinder at the time of starting, there is no fuel adhesion on the intake port wall or the cylinder inner wall, and most of the fuel injected in 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,
The required amount of fuel decreases because there is a portion that contributes to combustion by the wall flow flowing into the cylinder, and the negative pressure develops due to the rotation increase due to the first explosion, and the amount of intake air decreases (see FIG. 6). ).

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 individually set according to whether or not the first injection. (See FIG. 5), whereby during the first injection to each cylinder, it is possible to perform injection with an injection pulse width TI that can sufficiently secure the wall flow adhesion. In the second and subsequent injections in which the amount of the adhering wall flow is reduced, it is possible to set the injection pulse width TI in accordance with the decrease in the amount of the adhering gas, thereby avoiding excessive fuel injection.

The first-time target fuel-air ratio calculating means E calculates the target fuel-air ratio based on the water temperature TW, while the target fuel-air ratio calculating means F calculates the target fuel-air ratio as the intake air flow rate. The calculation is performed based on Q, the engine speed Ne (rpm), and the water temperature TW. Specifically, the target fuel-air ratio calculating means F calculates the target fuel-air ratio TFBYA as TFBYA = KMR + KAS + KTW. Here, KMR is a basic fuel-air ratio, which is determined by referring to a table from the engine speed Ne and the basic pulse width TP representing the load of the engine. Also, KA
S is a post-start increase coefficient, which is obtained from the water temperature TW only for a predetermined time after start by referring to a table. Furthermore, KTW
Is a water temperature increase coefficient, which is obtained from the water temperature TW by referring to a table.

On the other hand, in the first-time target fuel-air ratio calculating means E,
The target fuel-air ratio TFBYA is obtained from the water temperature TW by referring to a table. The fuel injection amount calculating means A which 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 until the predetermined rotational speed Ne is reached after the start is used (first basic injection amount calculation). Means), after the rotation speed reaches the predetermined rotation speed Ne, calculation is performed based on the intake air flow rate Q and the engine rotation speed Ne (second basic fuel injection amount calculation means).

Here, usually, the basic pulse width TP at the time of the first injection of each cylinder and the second basic pulse width TP are substantially the same value, but the above-described switching of the target fuel-air ratio is performed. Accordingly, even at the same basic pulse width TP, it is possible to inject a relatively large amount of fuel that satisfies the sufficient amount of the adhered wall flow at the first injection. KATHOS
Is a transient correction pulse width for correcting an error due to a fuel response delay at the time of transition, and MKINJ is a constant set according to characteristics of the fuel injection valve 4 and the like.

ALPHA operates in a predetermined operating range.
An air-fuel ratio feedback correction coefficient (initial value = 1.0) 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. . 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 operating regions.

TS is an invalid injection pulse width for correcting a valve opening delay of the fuel injection valve 4 due to a decrease in power supply voltage (battery voltage). CHOS is a pulse width correction pulse width for each cylinder. Next, the state of the injection amount control will be described with reference to the flowchart of FIG. First, in step 11, the basic pulse width TP is calculated. Predetermined rotation speed (rpm) from start
Until the above, the basic pulse width TP is set according to the water temperature TW, but after the predetermined rotational speed is reached, it is calculated based on the intake air flow rate Q and the rotational speed Ne.

In step 12, a target fuel-air ratio TFBYA is calculated. The target fuel-air ratio TFBYA is individually set depending on whether the first injection is performed for each cylinder or the second or later injection, the first time is set from the water temperature table for the first time, A basic value according to the rotation speed (basic pulse width TP) and the load is corrected and set according to the water temperature.

In steps 13 to 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. . Then, at step 18, the injection pulse width TI is calculated as: TI = (TP × TFBYA + KATHOS) × Kconst
X (ALPHA + KBLRC-1) + TS + CHOS, and outputs an injection pulse signal of the injection pulse width TI to the fuel injection valve 4 of the cylinder at the injection timing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a fuel injection control device according to the invention of claim 3;

FIG. 2 is a system configuration diagram of an 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 a 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 a correlation between the number of cycles, a required pulse width, and a suction negative pressure.

FIG. 7 is a flowchart showing a state of an injection pulse width calculation in the embodiment.

[Explanation of symbols]

 Reference Signs List 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 (7)

[Claims] 1. A fuel injection control device for an internal combustion engine, comprising: a fuel injection valve for each cylinder, wherein fuel injection by the fuel injection valve is performed in synchronization with an intake stroke of each cylinder. A fuel injection control device for an internal combustion engine, wherein the setting of the fuel injection amount is changed between the first fuel injection at the time of starting and the second and subsequent fuel injections for each cylinder. 2. The fuel injection amount is set in accordance with a target fuel-air ratio, wherein the first fuel injection at the start of each cylinder and the second or subsequent fuel injection to each cylinder are performed. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the setting of the fuel injection amount is changed by individually setting the target fuel-air ratio. A fuel injection valve provided for each cylinder; a fuel injection amount calculating means for calculating a fuel injection amount based on a target fuel-air ratio and an engine operating condition; and a timing for an intake stroke of each cylinder. Reference signal output means for outputting a reference signal serving as a reference for the combined injection timing; and for each injection timing of each cylinder detected based on the reference signal, driving the fuel injector in accordance with the fuel injection amount. Injection control means for performing fuel injection, and first-time fuel injection detection means for detecting the first-time fuel injection at the time of starting for each cylinder, and first-time fueling for each cylinder detected by the first time fuel injection detecting means. Target fuel-air ratio setting means for individually setting the target fuel-air ratio depending on whether the fuel injection is performed or the second or subsequent fuel injection for each cylinder. The fuel injection control device for an internal combustion engine characterized by and. 4. A first basic injection amount calculating means for calculating a basic fuel injection amount in accordance with a detection result of an engine temperature within a predetermined period from a start, after the predetermined period has elapsed. And a second basic injection amount calculating means for calculating a basic fuel injection amount in accordance with a detection result of the intake air amount of the engine, and wherein the calculated basic fuel injection amount, the target fuel-air ratio and 4. The fuel injection control device for an internal combustion engine according to claim 3, wherein a final fuel injection amount is calculated based on the following. 5. The fuel for an internal combustion engine according to claim 4, wherein the predetermined period in the first basic injection amount calculating means is a period until the engine speed reaches a preset engine speed. Injection control device. 6. The target fuel-air ratio setting means according to claim 3, wherein said target fuel-air ratio setting means sets a target fuel-air ratio in accordance with an engine temperature in the first fuel injection at the time of starting each cylinder. A fuel injection control device for an internal combustion engine according to any one of the preceding claims. 7. 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 of the cylinders. The fuel injection control device for an internal combustion engine according to any one of claims 3 to 6.